1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 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) 1988-2017 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}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty [ @var{tty} ]
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2505 restores the default behavior, which is to use the same terminal as
2508 @item show inferior-tty
2509 @kindex show inferior-tty
2510 Show the current tty for the program being debugged.
2514 @section Debugging an Already-running Process
2519 @item attach @var{process-id}
2520 This command attaches to a running process---one that was started
2521 outside @value{GDBN}. (@code{info files} shows your active
2522 targets.) The command takes as argument a process ID. The usual way to
2523 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2524 or with the @samp{jobs -l} shell command.
2526 @code{attach} does not repeat if you press @key{RET} a second time after
2527 executing the command.
2530 To use @code{attach}, your program must be running in an environment
2531 which supports processes; for example, @code{attach} does not work for
2532 programs on bare-board targets that lack an operating system. You must
2533 also have permission to send the process a signal.
2535 When you use @code{attach}, the debugger finds the program running in
2536 the process first by looking in the current working directory, then (if
2537 the program is not found) by using the source file search path
2538 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2539 the @code{file} command to load the program. @xref{Files, ,Commands to
2542 The first thing @value{GDBN} does after arranging to debug the specified
2543 process is to stop it. You can examine and modify an attached process
2544 with all the @value{GDBN} commands that are ordinarily available when
2545 you start processes with @code{run}. You can insert breakpoints; you
2546 can step and continue; you can modify storage. If you would rather the
2547 process continue running, you may use the @code{continue} command after
2548 attaching @value{GDBN} to the process.
2553 When you have finished debugging the attached process, you can use the
2554 @code{detach} command to release it from @value{GDBN} control. Detaching
2555 the process continues its execution. After the @code{detach} command,
2556 that process and @value{GDBN} become completely independent once more, and you
2557 are ready to @code{attach} another process or start one with @code{run}.
2558 @code{detach} does not repeat if you press @key{RET} again after
2559 executing the command.
2562 If you exit @value{GDBN} while you have an attached process, you detach
2563 that process. If you use the @code{run} command, you kill that process.
2564 By default, @value{GDBN} asks for confirmation if you try to do either of these
2565 things; you can control whether or not you need to confirm by using the
2566 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2570 @section Killing the Child Process
2575 Kill the child process in which your program is running under @value{GDBN}.
2578 This command is useful if you wish to debug a core dump instead of a
2579 running process. @value{GDBN} ignores any core dump file while your program
2582 On some operating systems, a program cannot be executed outside @value{GDBN}
2583 while you have breakpoints set on it inside @value{GDBN}. You can use the
2584 @code{kill} command in this situation to permit running your program
2585 outside the debugger.
2587 The @code{kill} command is also useful if you wish to recompile and
2588 relink your program, since on many systems it is impossible to modify an
2589 executable file while it is running in a process. In this case, when you
2590 next type @code{run}, @value{GDBN} notices that the file has changed, and
2591 reads the symbol table again (while trying to preserve your current
2592 breakpoint settings).
2594 @node Inferiors and Programs
2595 @section Debugging Multiple Inferiors and Programs
2597 @value{GDBN} lets you run and debug multiple programs in a single
2598 session. In addition, @value{GDBN} on some systems may let you run
2599 several programs simultaneously (otherwise you have to exit from one
2600 before starting another). In the most general case, you can have
2601 multiple threads of execution in each of multiple processes, launched
2602 from multiple executables.
2605 @value{GDBN} represents the state of each program execution with an
2606 object called an @dfn{inferior}. An inferior typically corresponds to
2607 a process, but is more general and applies also to targets that do not
2608 have processes. Inferiors may be created before a process runs, and
2609 may be retained after a process exits. Inferiors have unique
2610 identifiers that are different from process ids. Usually each
2611 inferior will also have its own distinct address space, although some
2612 embedded targets may have several inferiors running in different parts
2613 of a single address space. Each inferior may in turn have multiple
2614 threads running in it.
2616 To find out what inferiors exist at any moment, use @w{@code{info
2620 @kindex info inferiors
2621 @item info inferiors
2622 Print a list of all inferiors currently being managed by @value{GDBN}.
2624 @value{GDBN} displays for each inferior (in this order):
2628 the inferior number assigned by @value{GDBN}
2631 the target system's inferior identifier
2634 the name of the executable the inferior is running.
2639 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2640 indicates the current inferior.
2644 @c end table here to get a little more width for example
2647 (@value{GDBP}) info inferiors
2648 Num Description Executable
2649 2 process 2307 hello
2650 * 1 process 3401 goodbye
2653 To switch focus between inferiors, use the @code{inferior} command:
2656 @kindex inferior @var{infno}
2657 @item inferior @var{infno}
2658 Make inferior number @var{infno} the current inferior. The argument
2659 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2660 in the first field of the @samp{info inferiors} display.
2663 @vindex $_inferior@r{, convenience variable}
2664 The debugger convenience variable @samp{$_inferior} contains the
2665 number of the current inferior. You may find this useful in writing
2666 breakpoint conditional expressions, command scripts, and so forth.
2667 @xref{Convenience Vars,, Convenience Variables}, for general
2668 information on convenience variables.
2670 You can get multiple executables into a debugging session via the
2671 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2672 systems @value{GDBN} can add inferiors to the debug session
2673 automatically by following calls to @code{fork} and @code{exec}. To
2674 remove inferiors from the debugging session use the
2675 @w{@code{remove-inferiors}} command.
2678 @kindex add-inferior
2679 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2680 Adds @var{n} inferiors to be run using @var{executable} as the
2681 executable; @var{n} defaults to 1. If no executable is specified,
2682 the inferiors begins empty, with no program. You can still assign or
2683 change the program assigned to the inferior at any time by using the
2684 @code{file} command with the executable name as its argument.
2686 @kindex clone-inferior
2687 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2688 Adds @var{n} inferiors ready to execute the same program as inferior
2689 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2690 number of the current inferior. This is a convenient command when you
2691 want to run another instance of the inferior you are debugging.
2694 (@value{GDBP}) info inferiors
2695 Num Description Executable
2696 * 1 process 29964 helloworld
2697 (@value{GDBP}) clone-inferior
2700 (@value{GDBP}) info inferiors
2701 Num Description Executable
2703 * 1 process 29964 helloworld
2706 You can now simply switch focus to inferior 2 and run it.
2708 @kindex remove-inferiors
2709 @item remove-inferiors @var{infno}@dots{}
2710 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2711 possible to remove an inferior that is running with this command. For
2712 those, use the @code{kill} or @code{detach} command first.
2716 To quit debugging one of the running inferiors that is not the current
2717 inferior, you can either detach from it by using the @w{@code{detach
2718 inferior}} command (allowing it to run independently), or kill it
2719 using the @w{@code{kill inferiors}} command:
2722 @kindex detach inferiors @var{infno}@dots{}
2723 @item detach inferior @var{infno}@dots{}
2724 Detach from the inferior or inferiors identified by @value{GDBN}
2725 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2726 still stays on the list of inferiors shown by @code{info inferiors},
2727 but its Description will show @samp{<null>}.
2729 @kindex kill inferiors @var{infno}@dots{}
2730 @item kill inferiors @var{infno}@dots{}
2731 Kill the inferior or inferiors identified by @value{GDBN} inferior
2732 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2733 stays on the list of inferiors shown by @code{info inferiors}, but its
2734 Description will show @samp{<null>}.
2737 After the successful completion of a command such as @code{detach},
2738 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2739 a normal process exit, the inferior is still valid and listed with
2740 @code{info inferiors}, ready to be restarted.
2743 To be notified when inferiors are started or exit under @value{GDBN}'s
2744 control use @w{@code{set print inferior-events}}:
2747 @kindex set print inferior-events
2748 @cindex print messages on inferior start and exit
2749 @item set print inferior-events
2750 @itemx set print inferior-events on
2751 @itemx set print inferior-events off
2752 The @code{set print inferior-events} command allows you to enable or
2753 disable printing of messages when @value{GDBN} notices that new
2754 inferiors have started or that inferiors have exited or have been
2755 detached. By default, these messages will not be printed.
2757 @kindex show print inferior-events
2758 @item show print inferior-events
2759 Show whether messages will be printed when @value{GDBN} detects that
2760 inferiors have started, exited or have been detached.
2763 Many commands will work the same with multiple programs as with a
2764 single program: e.g., @code{print myglobal} will simply display the
2765 value of @code{myglobal} in the current inferior.
2768 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2769 get more info about the relationship of inferiors, programs, address
2770 spaces in a debug session. You can do that with the @w{@code{maint
2771 info program-spaces}} command.
2774 @kindex maint info program-spaces
2775 @item maint info program-spaces
2776 Print a list of all program spaces currently being managed by
2779 @value{GDBN} displays for each program space (in this order):
2783 the program space number assigned by @value{GDBN}
2786 the name of the executable loaded into the program space, with e.g.,
2787 the @code{file} command.
2792 An asterisk @samp{*} preceding the @value{GDBN} program space number
2793 indicates the current program space.
2795 In addition, below each program space line, @value{GDBN} prints extra
2796 information that isn't suitable to display in tabular form. For
2797 example, the list of inferiors bound to the program space.
2800 (@value{GDBP}) maint info program-spaces
2804 Bound inferiors: ID 1 (process 21561)
2807 Here we can see that no inferior is running the program @code{hello},
2808 while @code{process 21561} is running the program @code{goodbye}. On
2809 some targets, it is possible that multiple inferiors are bound to the
2810 same program space. The most common example is that of debugging both
2811 the parent and child processes of a @code{vfork} call. For example,
2814 (@value{GDBP}) maint info program-spaces
2817 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2820 Here, both inferior 2 and inferior 1 are running in the same program
2821 space as a result of inferior 1 having executed a @code{vfork} call.
2825 @section Debugging Programs with Multiple Threads
2827 @cindex threads of execution
2828 @cindex multiple threads
2829 @cindex switching threads
2830 In some operating systems, such as GNU/Linux and Solaris, a single program
2831 may have more than one @dfn{thread} of execution. The precise semantics
2832 of threads differ from one operating system to another, but in general
2833 the threads of a single program are akin to multiple processes---except
2834 that they share one address space (that is, they can all examine and
2835 modify the same variables). On the other hand, each thread has its own
2836 registers and execution stack, and perhaps private memory.
2838 @value{GDBN} provides these facilities for debugging multi-thread
2842 @item automatic notification of new threads
2843 @item @samp{thread @var{thread-id}}, a command to switch among threads
2844 @item @samp{info threads}, a command to inquire about existing threads
2845 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2846 a command to apply a command to a list of threads
2847 @item thread-specific breakpoints
2848 @item @samp{set print thread-events}, which controls printing of
2849 messages on thread start and exit.
2850 @item @samp{set libthread-db-search-path @var{path}}, which lets
2851 the user specify which @code{libthread_db} to use if the default choice
2852 isn't compatible with the program.
2855 @cindex focus of debugging
2856 @cindex current thread
2857 The @value{GDBN} thread debugging facility allows you to observe all
2858 threads while your program runs---but whenever @value{GDBN} takes
2859 control, one thread in particular is always the focus of debugging.
2860 This thread is called the @dfn{current thread}. Debugging commands show
2861 program information from the perspective of the current thread.
2863 @cindex @code{New} @var{systag} message
2864 @cindex thread identifier (system)
2865 @c FIXME-implementors!! It would be more helpful if the [New...] message
2866 @c included GDB's numeric thread handle, so you could just go to that
2867 @c thread without first checking `info threads'.
2868 Whenever @value{GDBN} detects a new thread in your program, it displays
2869 the target system's identification for the thread with a message in the
2870 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2871 whose form varies depending on the particular system. For example, on
2872 @sc{gnu}/Linux, you might see
2875 [New Thread 0x41e02940 (LWP 25582)]
2879 when @value{GDBN} notices a new thread. In contrast, on other systems,
2880 the @var{systag} is simply something like @samp{process 368}, with no
2883 @c FIXME!! (1) Does the [New...] message appear even for the very first
2884 @c thread of a program, or does it only appear for the
2885 @c second---i.e.@: when it becomes obvious we have a multithread
2887 @c (2) *Is* there necessarily a first thread always? Or do some
2888 @c multithread systems permit starting a program with multiple
2889 @c threads ab initio?
2891 @anchor{thread numbers}
2892 @cindex thread number, per inferior
2893 @cindex thread identifier (GDB)
2894 For debugging purposes, @value{GDBN} associates its own thread number
2895 ---always a single integer---with each thread of an inferior. This
2896 number is unique between all threads of an inferior, but not unique
2897 between threads of different inferiors.
2899 @cindex qualified thread ID
2900 You can refer to a given thread in an inferior using the qualified
2901 @var{inferior-num}.@var{thread-num} syntax, also known as
2902 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2903 number and @var{thread-num} being the thread number of the given
2904 inferior. For example, thread @code{2.3} refers to thread number 3 of
2905 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2906 then @value{GDBN} infers you're referring to a thread of the current
2909 Until you create a second inferior, @value{GDBN} does not show the
2910 @var{inferior-num} part of thread IDs, even though you can always use
2911 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2912 of inferior 1, the initial inferior.
2914 @anchor{thread ID lists}
2915 @cindex thread ID lists
2916 Some commands accept a space-separated @dfn{thread ID list} as
2917 argument. A list element can be:
2921 A thread ID as shown in the first field of the @samp{info threads}
2922 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2926 A range of thread numbers, again with or without an inferior
2927 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2928 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2931 All threads of an inferior, specified with a star wildcard, with or
2932 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2933 @samp{1.*}) or @code{*}. The former refers to all threads of the
2934 given inferior, and the latter form without an inferior qualifier
2935 refers to all threads of the current inferior.
2939 For example, if the current inferior is 1, and inferior 7 has one
2940 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2941 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2942 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2943 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2947 @anchor{global thread numbers}
2948 @cindex global thread number
2949 @cindex global thread identifier (GDB)
2950 In addition to a @emph{per-inferior} number, each thread is also
2951 assigned a unique @emph{global} number, also known as @dfn{global
2952 thread ID}, a single integer. Unlike the thread number component of
2953 the thread ID, no two threads have the same global ID, even when
2954 you're debugging multiple inferiors.
2956 From @value{GDBN}'s perspective, a process always has at least one
2957 thread. In other words, @value{GDBN} assigns a thread number to the
2958 program's ``main thread'' even if the program is not multi-threaded.
2960 @vindex $_thread@r{, convenience variable}
2961 @vindex $_gthread@r{, convenience variable}
2962 The debugger convenience variables @samp{$_thread} and
2963 @samp{$_gthread} contain, respectively, the per-inferior thread number
2964 and the global thread number of the current thread. You may find this
2965 useful in writing breakpoint conditional expressions, command scripts,
2966 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2967 general information on convenience variables.
2969 If @value{GDBN} detects the program is multi-threaded, it augments the
2970 usual message about stopping at a breakpoint with the ID and name of
2971 the thread that hit the breakpoint.
2974 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2977 Likewise when the program receives a signal:
2980 Thread 1 "main" received signal SIGINT, Interrupt.
2984 @kindex info threads
2985 @item info threads @r{[}@var{thread-id-list}@r{]}
2987 Display information about one or more threads. With no arguments
2988 displays information about all threads. You can specify the list of
2989 threads that you want to display using the thread ID list syntax
2990 (@pxref{thread ID lists}).
2992 @value{GDBN} displays for each thread (in this order):
2996 the per-inferior thread number assigned by @value{GDBN}
2999 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3000 option was specified
3003 the target system's thread identifier (@var{systag})
3006 the thread's name, if one is known. A thread can either be named by
3007 the user (see @code{thread name}, below), or, in some cases, by the
3011 the current stack frame summary for that thread
3015 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3016 indicates the current thread.
3020 @c end table here to get a little more width for example
3023 (@value{GDBP}) info threads
3025 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3026 2 process 35 thread 23 0x34e5 in sigpause ()
3027 3 process 35 thread 27 0x34e5 in sigpause ()
3031 If you're debugging multiple inferiors, @value{GDBN} displays thread
3032 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3033 Otherwise, only @var{thread-num} is shown.
3035 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3036 indicating each thread's global thread ID:
3039 (@value{GDBP}) info threads
3040 Id GId Target Id Frame
3041 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3042 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3043 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3044 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3047 On Solaris, you can display more information about user threads with a
3048 Solaris-specific command:
3051 @item maint info sol-threads
3052 @kindex maint info sol-threads
3053 @cindex thread info (Solaris)
3054 Display info on Solaris user threads.
3058 @kindex thread @var{thread-id}
3059 @item thread @var{thread-id}
3060 Make thread ID @var{thread-id} the current thread. The command
3061 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3062 the first field of the @samp{info threads} display, with or without an
3063 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3065 @value{GDBN} responds by displaying the system identifier of the
3066 thread you selected, and its current stack frame summary:
3069 (@value{GDBP}) thread 2
3070 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3071 #0 some_function (ignore=0x0) at example.c:8
3072 8 printf ("hello\n");
3076 As with the @samp{[New @dots{}]} message, the form of the text after
3077 @samp{Switching to} depends on your system's conventions for identifying
3080 @kindex thread apply
3081 @cindex apply command to several threads
3082 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3083 The @code{thread apply} command allows you to apply the named
3084 @var{command} to one or more threads. Specify the threads that you
3085 want affected using the thread ID list syntax (@pxref{thread ID
3086 lists}), or specify @code{all} to apply to all threads. To apply a
3087 command to all threads in descending order, type @kbd{thread apply all
3088 @var{command}}. To apply a command to all threads in ascending order,
3089 type @kbd{thread apply all -ascending @var{command}}.
3093 @cindex name a thread
3094 @item thread name [@var{name}]
3095 This command assigns a name to the current thread. If no argument is
3096 given, any existing user-specified name is removed. The thread name
3097 appears in the @samp{info threads} display.
3099 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3100 determine the name of the thread as given by the OS. On these
3101 systems, a name specified with @samp{thread name} will override the
3102 system-give name, and removing the user-specified name will cause
3103 @value{GDBN} to once again display the system-specified name.
3106 @cindex search for a thread
3107 @item thread find [@var{regexp}]
3108 Search for and display thread ids whose name or @var{systag}
3109 matches the supplied regular expression.
3111 As well as being the complement to the @samp{thread name} command,
3112 this command also allows you to identify a thread by its target
3113 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3117 (@value{GDBN}) thread find 26688
3118 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3119 (@value{GDBN}) info thread 4
3121 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3124 @kindex set print thread-events
3125 @cindex print messages on thread start and exit
3126 @item set print thread-events
3127 @itemx set print thread-events on
3128 @itemx set print thread-events off
3129 The @code{set print thread-events} command allows you to enable or
3130 disable printing of messages when @value{GDBN} notices that new threads have
3131 started or that threads have exited. By default, these messages will
3132 be printed if detection of these events is supported by the target.
3133 Note that these messages cannot be disabled on all targets.
3135 @kindex show print thread-events
3136 @item show print thread-events
3137 Show whether messages will be printed when @value{GDBN} detects that threads
3138 have started and exited.
3141 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3142 more information about how @value{GDBN} behaves when you stop and start
3143 programs with multiple threads.
3145 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3146 watchpoints in programs with multiple threads.
3148 @anchor{set libthread-db-search-path}
3150 @kindex set libthread-db-search-path
3151 @cindex search path for @code{libthread_db}
3152 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3153 If this variable is set, @var{path} is a colon-separated list of
3154 directories @value{GDBN} will use to search for @code{libthread_db}.
3155 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3156 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3157 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3160 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3161 @code{libthread_db} library to obtain information about threads in the
3162 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3163 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3164 specific thread debugging library loading is enabled
3165 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3167 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3168 refers to the default system directories that are
3169 normally searched for loading shared libraries. The @samp{$sdir} entry
3170 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3171 (@pxref{libthread_db.so.1 file}).
3173 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3174 refers to the directory from which @code{libpthread}
3175 was loaded in the inferior process.
3177 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3178 @value{GDBN} attempts to initialize it with the current inferior process.
3179 If this initialization fails (which could happen because of a version
3180 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3181 will unload @code{libthread_db}, and continue with the next directory.
3182 If none of @code{libthread_db} libraries initialize successfully,
3183 @value{GDBN} will issue a warning and thread debugging will be disabled.
3185 Setting @code{libthread-db-search-path} is currently implemented
3186 only on some platforms.
3188 @kindex show libthread-db-search-path
3189 @item show libthread-db-search-path
3190 Display current libthread_db search path.
3192 @kindex set debug libthread-db
3193 @kindex show debug libthread-db
3194 @cindex debugging @code{libthread_db}
3195 @item set debug libthread-db
3196 @itemx show debug libthread-db
3197 Turns on or off display of @code{libthread_db}-related events.
3198 Use @code{1} to enable, @code{0} to disable.
3202 @section Debugging Forks
3204 @cindex fork, debugging programs which call
3205 @cindex multiple processes
3206 @cindex processes, multiple
3207 On most systems, @value{GDBN} has no special support for debugging
3208 programs which create additional processes using the @code{fork}
3209 function. When a program forks, @value{GDBN} will continue to debug the
3210 parent process and the child process will run unimpeded. If you have
3211 set a breakpoint in any code which the child then executes, the child
3212 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3213 will cause it to terminate.
3215 However, if you want to debug the child process there is a workaround
3216 which isn't too painful. Put a call to @code{sleep} in the code which
3217 the child process executes after the fork. It may be useful to sleep
3218 only if a certain environment variable is set, or a certain file exists,
3219 so that the delay need not occur when you don't want to run @value{GDBN}
3220 on the child. While the child is sleeping, use the @code{ps} program to
3221 get its process ID. Then tell @value{GDBN} (a new invocation of
3222 @value{GDBN} if you are also debugging the parent process) to attach to
3223 the child process (@pxref{Attach}). From that point on you can debug
3224 the child process just like any other process which you attached to.
3226 On some systems, @value{GDBN} provides support for debugging programs
3227 that create additional processes using the @code{fork} or @code{vfork}
3228 functions. On @sc{gnu}/Linux platforms, this feature is supported
3229 with kernel version 2.5.46 and later.
3231 The fork debugging commands are supported in native mode and when
3232 connected to @code{gdbserver} in either @code{target remote} mode or
3233 @code{target extended-remote} mode.
3235 By default, when a program forks, @value{GDBN} will continue to debug
3236 the parent process and the child process will run unimpeded.
3238 If you want to follow the child process instead of the parent process,
3239 use the command @w{@code{set follow-fork-mode}}.
3242 @kindex set follow-fork-mode
3243 @item set follow-fork-mode @var{mode}
3244 Set the debugger response to a program call of @code{fork} or
3245 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3246 process. The @var{mode} argument can be:
3250 The original process is debugged after a fork. The child process runs
3251 unimpeded. This is the default.
3254 The new process is debugged after a fork. The parent process runs
3259 @kindex show follow-fork-mode
3260 @item show follow-fork-mode
3261 Display the current debugger response to a @code{fork} or @code{vfork} call.
3264 @cindex debugging multiple processes
3265 On Linux, if you want to debug both the parent and child processes, use the
3266 command @w{@code{set detach-on-fork}}.
3269 @kindex set detach-on-fork
3270 @item set detach-on-fork @var{mode}
3271 Tells gdb whether to detach one of the processes after a fork, or
3272 retain debugger control over them both.
3276 The child process (or parent process, depending on the value of
3277 @code{follow-fork-mode}) will be detached and allowed to run
3278 independently. This is the default.
3281 Both processes will be held under the control of @value{GDBN}.
3282 One process (child or parent, depending on the value of
3283 @code{follow-fork-mode}) is debugged as usual, while the other
3288 @kindex show detach-on-fork
3289 @item show detach-on-fork
3290 Show whether detach-on-fork mode is on/off.
3293 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3294 will retain control of all forked processes (including nested forks).
3295 You can list the forked processes under the control of @value{GDBN} by
3296 using the @w{@code{info inferiors}} command, and switch from one fork
3297 to another by using the @code{inferior} command (@pxref{Inferiors and
3298 Programs, ,Debugging Multiple Inferiors and Programs}).
3300 To quit debugging one of the forked processes, you can either detach
3301 from it by using the @w{@code{detach inferiors}} command (allowing it
3302 to run independently), or kill it using the @w{@code{kill inferiors}}
3303 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3306 If you ask to debug a child process and a @code{vfork} is followed by an
3307 @code{exec}, @value{GDBN} executes the new target up to the first
3308 breakpoint in the new target. If you have a breakpoint set on
3309 @code{main} in your original program, the breakpoint will also be set on
3310 the child process's @code{main}.
3312 On some systems, when a child process is spawned by @code{vfork}, you
3313 cannot debug the child or parent until an @code{exec} call completes.
3315 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3316 call executes, the new target restarts. To restart the parent
3317 process, use the @code{file} command with the parent executable name
3318 as its argument. By default, after an @code{exec} call executes,
3319 @value{GDBN} discards the symbols of the previous executable image.
3320 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3324 @kindex set follow-exec-mode
3325 @item set follow-exec-mode @var{mode}
3327 Set debugger response to a program call of @code{exec}. An
3328 @code{exec} call replaces the program image of a process.
3330 @code{follow-exec-mode} can be:
3334 @value{GDBN} creates a new inferior and rebinds the process to this
3335 new inferior. The program the process was running before the
3336 @code{exec} call can be restarted afterwards by restarting the
3342 (@value{GDBP}) info inferiors
3344 Id Description Executable
3347 process 12020 is executing new program: prog2
3348 Program exited normally.
3349 (@value{GDBP}) info inferiors
3350 Id Description Executable
3356 @value{GDBN} keeps the process bound to the same inferior. The new
3357 executable image replaces the previous executable loaded in the
3358 inferior. Restarting the inferior after the @code{exec} call, with
3359 e.g., the @code{run} command, restarts the executable the process was
3360 running after the @code{exec} call. This is the default mode.
3365 (@value{GDBP}) info inferiors
3366 Id Description Executable
3369 process 12020 is executing new program: prog2
3370 Program exited normally.
3371 (@value{GDBP}) info inferiors
3372 Id Description Executable
3379 @code{follow-exec-mode} is supported in native mode and
3380 @code{target extended-remote} mode.
3382 You can use the @code{catch} command to make @value{GDBN} stop whenever
3383 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3384 Catchpoints, ,Setting Catchpoints}.
3386 @node Checkpoint/Restart
3387 @section Setting a @emph{Bookmark} to Return to Later
3392 @cindex snapshot of a process
3393 @cindex rewind program state
3395 On certain operating systems@footnote{Currently, only
3396 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3397 program's state, called a @dfn{checkpoint}, and come back to it
3400 Returning to a checkpoint effectively undoes everything that has
3401 happened in the program since the @code{checkpoint} was saved. This
3402 includes changes in memory, registers, and even (within some limits)
3403 system state. Effectively, it is like going back in time to the
3404 moment when the checkpoint was saved.
3406 Thus, if you're stepping thru a program and you think you're
3407 getting close to the point where things go wrong, you can save
3408 a checkpoint. Then, if you accidentally go too far and miss
3409 the critical statement, instead of having to restart your program
3410 from the beginning, you can just go back to the checkpoint and
3411 start again from there.
3413 This can be especially useful if it takes a lot of time or
3414 steps to reach the point where you think the bug occurs.
3416 To use the @code{checkpoint}/@code{restart} method of debugging:
3421 Save a snapshot of the debugged program's current execution state.
3422 The @code{checkpoint} command takes no arguments, but each checkpoint
3423 is assigned a small integer id, similar to a breakpoint id.
3425 @kindex info checkpoints
3426 @item info checkpoints
3427 List the checkpoints that have been saved in the current debugging
3428 session. For each checkpoint, the following information will be
3435 @item Source line, or label
3438 @kindex restart @var{checkpoint-id}
3439 @item restart @var{checkpoint-id}
3440 Restore the program state that was saved as checkpoint number
3441 @var{checkpoint-id}. All program variables, registers, stack frames
3442 etc.@: will be returned to the values that they had when the checkpoint
3443 was saved. In essence, gdb will ``wind back the clock'' to the point
3444 in time when the checkpoint was saved.
3446 Note that breakpoints, @value{GDBN} variables, command history etc.
3447 are not affected by restoring a checkpoint. In general, a checkpoint
3448 only restores things that reside in the program being debugged, not in
3451 @kindex delete checkpoint @var{checkpoint-id}
3452 @item delete checkpoint @var{checkpoint-id}
3453 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3457 Returning to a previously saved checkpoint will restore the user state
3458 of the program being debugged, plus a significant subset of the system
3459 (OS) state, including file pointers. It won't ``un-write'' data from
3460 a file, but it will rewind the file pointer to the previous location,
3461 so that the previously written data can be overwritten. For files
3462 opened in read mode, the pointer will also be restored so that the
3463 previously read data can be read again.
3465 Of course, characters that have been sent to a printer (or other
3466 external device) cannot be ``snatched back'', and characters received
3467 from eg.@: a serial device can be removed from internal program buffers,
3468 but they cannot be ``pushed back'' into the serial pipeline, ready to
3469 be received again. Similarly, the actual contents of files that have
3470 been changed cannot be restored (at this time).
3472 However, within those constraints, you actually can ``rewind'' your
3473 program to a previously saved point in time, and begin debugging it
3474 again --- and you can change the course of events so as to debug a
3475 different execution path this time.
3477 @cindex checkpoints and process id
3478 Finally, there is one bit of internal program state that will be
3479 different when you return to a checkpoint --- the program's process
3480 id. Each checkpoint will have a unique process id (or @var{pid}),
3481 and each will be different from the program's original @var{pid}.
3482 If your program has saved a local copy of its process id, this could
3483 potentially pose a problem.
3485 @subsection A Non-obvious Benefit of Using Checkpoints
3487 On some systems such as @sc{gnu}/Linux, address space randomization
3488 is performed on new processes for security reasons. This makes it
3489 difficult or impossible to set a breakpoint, or watchpoint, on an
3490 absolute address if you have to restart the program, since the
3491 absolute location of a symbol will change from one execution to the
3494 A checkpoint, however, is an @emph{identical} copy of a process.
3495 Therefore if you create a checkpoint at (eg.@:) the start of main,
3496 and simply return to that checkpoint instead of restarting the
3497 process, you can avoid the effects of address randomization and
3498 your symbols will all stay in the same place.
3501 @chapter Stopping and Continuing
3503 The principal purposes of using a debugger are so that you can stop your
3504 program before it terminates; or so that, if your program runs into
3505 trouble, you can investigate and find out why.
3507 Inside @value{GDBN}, your program may stop for any of several reasons,
3508 such as a signal, a breakpoint, or reaching a new line after a
3509 @value{GDBN} command such as @code{step}. You may then examine and
3510 change variables, set new breakpoints or remove old ones, and then
3511 continue execution. Usually, the messages shown by @value{GDBN} provide
3512 ample explanation of the status of your program---but you can also
3513 explicitly request this information at any time.
3516 @kindex info program
3518 Display information about the status of your program: whether it is
3519 running or not, what process it is, and why it stopped.
3523 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3524 * Continuing and Stepping:: Resuming execution
3525 * Skipping Over Functions and Files::
3526 Skipping over functions and files
3528 * Thread Stops:: Stopping and starting multi-thread programs
3532 @section Breakpoints, Watchpoints, and Catchpoints
3535 A @dfn{breakpoint} makes your program stop whenever a certain point in
3536 the program is reached. For each breakpoint, you can add conditions to
3537 control in finer detail whether your program stops. You can set
3538 breakpoints with the @code{break} command and its variants (@pxref{Set
3539 Breaks, ,Setting Breakpoints}), to specify the place where your program
3540 should stop by line number, function name or exact address in the
3543 On some systems, you can set breakpoints in shared libraries before
3544 the executable is run.
3547 @cindex data breakpoints
3548 @cindex memory tracing
3549 @cindex breakpoint on memory address
3550 @cindex breakpoint on variable modification
3551 A @dfn{watchpoint} is a special breakpoint that stops your program
3552 when the value of an expression changes. The expression may be a value
3553 of a variable, or it could involve values of one or more variables
3554 combined by operators, such as @samp{a + b}. This is sometimes called
3555 @dfn{data breakpoints}. You must use a different command to set
3556 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3557 from that, you can manage a watchpoint like any other breakpoint: you
3558 enable, disable, and delete both breakpoints and watchpoints using the
3561 You can arrange to have values from your program displayed automatically
3562 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3566 @cindex breakpoint on events
3567 A @dfn{catchpoint} is another special breakpoint that stops your program
3568 when a certain kind of event occurs, such as the throwing of a C@t{++}
3569 exception or the loading of a library. As with watchpoints, you use a
3570 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3571 Catchpoints}), but aside from that, you can manage a catchpoint like any
3572 other breakpoint. (To stop when your program receives a signal, use the
3573 @code{handle} command; see @ref{Signals, ,Signals}.)
3575 @cindex breakpoint numbers
3576 @cindex numbers for breakpoints
3577 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3578 catchpoint when you create it; these numbers are successive integers
3579 starting with one. In many of the commands for controlling various
3580 features of breakpoints you use the breakpoint number to say which
3581 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3582 @dfn{disabled}; if disabled, it has no effect on your program until you
3585 @cindex breakpoint ranges
3586 @cindex ranges of breakpoints
3587 Some @value{GDBN} commands accept a range of breakpoints on which to
3588 operate. A breakpoint range is either a single breakpoint number, like
3589 @samp{5}, or two such numbers, in increasing order, separated by a
3590 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3591 all breakpoints in that range are operated on.
3594 * Set Breaks:: Setting breakpoints
3595 * Set Watchpoints:: Setting watchpoints
3596 * Set Catchpoints:: Setting catchpoints
3597 * Delete Breaks:: Deleting breakpoints
3598 * Disabling:: Disabling breakpoints
3599 * Conditions:: Break conditions
3600 * Break Commands:: Breakpoint command lists
3601 * Dynamic Printf:: Dynamic printf
3602 * Save Breakpoints:: How to save breakpoints in a file
3603 * Static Probe Points:: Listing static probe points
3604 * Error in Breakpoints:: ``Cannot insert breakpoints''
3605 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3609 @subsection Setting Breakpoints
3611 @c FIXME LMB what does GDB do if no code on line of breakpt?
3612 @c consider in particular declaration with/without initialization.
3614 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3617 @kindex b @r{(@code{break})}
3618 @vindex $bpnum@r{, convenience variable}
3619 @cindex latest breakpoint
3620 Breakpoints are set with the @code{break} command (abbreviated
3621 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3622 number of the breakpoint you've set most recently; see @ref{Convenience
3623 Vars,, Convenience Variables}, for a discussion of what you can do with
3624 convenience variables.
3627 @item break @var{location}
3628 Set a breakpoint at the given @var{location}, which can specify a
3629 function name, a line number, or an address of an instruction.
3630 (@xref{Specify Location}, for a list of all the possible ways to
3631 specify a @var{location}.) The breakpoint will stop your program just
3632 before it executes any of the code in the specified @var{location}.
3634 When using source languages that permit overloading of symbols, such as
3635 C@t{++}, a function name may refer to more than one possible place to break.
3636 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3639 It is also possible to insert a breakpoint that will stop the program
3640 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3641 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3644 When called without any arguments, @code{break} sets a breakpoint at
3645 the next instruction to be executed in the selected stack frame
3646 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3647 innermost, this makes your program stop as soon as control
3648 returns to that frame. This is similar to the effect of a
3649 @code{finish} command in the frame inside the selected frame---except
3650 that @code{finish} does not leave an active breakpoint. If you use
3651 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3652 the next time it reaches the current location; this may be useful
3655 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3656 least one instruction has been executed. If it did not do this, you
3657 would be unable to proceed past a breakpoint without first disabling the
3658 breakpoint. This rule applies whether or not the breakpoint already
3659 existed when your program stopped.
3661 @item break @dots{} if @var{cond}
3662 Set a breakpoint with condition @var{cond}; evaluate the expression
3663 @var{cond} each time the breakpoint is reached, and stop only if the
3664 value is nonzero---that is, if @var{cond} evaluates as true.
3665 @samp{@dots{}} stands for one of the possible arguments described
3666 above (or no argument) specifying where to break. @xref{Conditions,
3667 ,Break Conditions}, for more information on breakpoint conditions.
3670 @item tbreak @var{args}
3671 Set a breakpoint enabled only for one stop. The @var{args} are the
3672 same as for the @code{break} command, and the breakpoint is set in the same
3673 way, but the breakpoint is automatically deleted after the first time your
3674 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3677 @cindex hardware breakpoints
3678 @item hbreak @var{args}
3679 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3680 @code{break} command and the breakpoint is set in the same way, but the
3681 breakpoint requires hardware support and some target hardware may not
3682 have this support. The main purpose of this is EPROM/ROM code
3683 debugging, so you can set a breakpoint at an instruction without
3684 changing the instruction. This can be used with the new trap-generation
3685 provided by SPARClite DSU and most x86-based targets. These targets
3686 will generate traps when a program accesses some data or instruction
3687 address that is assigned to the debug registers. However the hardware
3688 breakpoint registers can take a limited number of breakpoints. For
3689 example, on the DSU, only two data breakpoints can be set at a time, and
3690 @value{GDBN} will reject this command if more than two are used. Delete
3691 or disable unused hardware breakpoints before setting new ones
3692 (@pxref{Disabling, ,Disabling Breakpoints}).
3693 @xref{Conditions, ,Break Conditions}.
3694 For remote targets, you can restrict the number of hardware
3695 breakpoints @value{GDBN} will use, see @ref{set remote
3696 hardware-breakpoint-limit}.
3699 @item thbreak @var{args}
3700 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3701 are the same as for the @code{hbreak} command and the breakpoint is set in
3702 the same way. However, like the @code{tbreak} command,
3703 the breakpoint is automatically deleted after the
3704 first time your program stops there. Also, like the @code{hbreak}
3705 command, the breakpoint requires hardware support and some target hardware
3706 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3707 See also @ref{Conditions, ,Break Conditions}.
3710 @cindex regular expression
3711 @cindex breakpoints at functions matching a regexp
3712 @cindex set breakpoints in many functions
3713 @item rbreak @var{regex}
3714 Set breakpoints on all functions matching the regular expression
3715 @var{regex}. This command sets an unconditional breakpoint on all
3716 matches, printing a list of all breakpoints it set. Once these
3717 breakpoints are set, they are treated just like the breakpoints set with
3718 the @code{break} command. You can delete them, disable them, or make
3719 them conditional the same way as any other breakpoint.
3721 The syntax of the regular expression is the standard one used with tools
3722 like @file{grep}. Note that this is different from the syntax used by
3723 shells, so for instance @code{foo*} matches all functions that include
3724 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3725 @code{.*} leading and trailing the regular expression you supply, so to
3726 match only functions that begin with @code{foo}, use @code{^foo}.
3728 @cindex non-member C@t{++} functions, set breakpoint in
3729 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3730 breakpoints on overloaded functions that are not members of any special
3733 @cindex set breakpoints on all functions
3734 The @code{rbreak} command can be used to set breakpoints in
3735 @strong{all} the functions in a program, like this:
3738 (@value{GDBP}) rbreak .
3741 @item rbreak @var{file}:@var{regex}
3742 If @code{rbreak} is called with a filename qualification, it limits
3743 the search for functions matching the given regular expression to the
3744 specified @var{file}. This can be used, for example, to set breakpoints on
3745 every function in a given file:
3748 (@value{GDBP}) rbreak file.c:.
3751 The colon separating the filename qualifier from the regex may
3752 optionally be surrounded by spaces.
3754 @kindex info breakpoints
3755 @cindex @code{$_} and @code{info breakpoints}
3756 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3757 @itemx info break @r{[}@var{n}@dots{}@r{]}
3758 Print a table of all breakpoints, watchpoints, and catchpoints set and
3759 not deleted. Optional argument @var{n} means print information only
3760 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3761 For each breakpoint, following columns are printed:
3764 @item Breakpoint Numbers
3766 Breakpoint, watchpoint, or catchpoint.
3768 Whether the breakpoint is marked to be disabled or deleted when hit.
3769 @item Enabled or Disabled
3770 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3771 that are not enabled.
3773 Where the breakpoint is in your program, as a memory address. For a
3774 pending breakpoint whose address is not yet known, this field will
3775 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3776 library that has the symbol or line referred by breakpoint is loaded.
3777 See below for details. A breakpoint with several locations will
3778 have @samp{<MULTIPLE>} in this field---see below for details.
3780 Where the breakpoint is in the source for your program, as a file and
3781 line number. For a pending breakpoint, the original string passed to
3782 the breakpoint command will be listed as it cannot be resolved until
3783 the appropriate shared library is loaded in the future.
3787 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3788 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3789 @value{GDBN} on the host's side. If it is ``target'', then the condition
3790 is evaluated by the target. The @code{info break} command shows
3791 the condition on the line following the affected breakpoint, together with
3792 its condition evaluation mode in between parentheses.
3794 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3795 allowed to have a condition specified for it. The condition is not parsed for
3796 validity until a shared library is loaded that allows the pending
3797 breakpoint to resolve to a valid location.
3800 @code{info break} with a breakpoint
3801 number @var{n} as argument lists only that breakpoint. The
3802 convenience variable @code{$_} and the default examining-address for
3803 the @code{x} command are set to the address of the last breakpoint
3804 listed (@pxref{Memory, ,Examining Memory}).
3807 @code{info break} displays a count of the number of times the breakpoint
3808 has been hit. This is especially useful in conjunction with the
3809 @code{ignore} command. You can ignore a large number of breakpoint
3810 hits, look at the breakpoint info to see how many times the breakpoint
3811 was hit, and then run again, ignoring one less than that number. This
3812 will get you quickly to the last hit of that breakpoint.
3815 For a breakpoints with an enable count (xref) greater than 1,
3816 @code{info break} also displays that count.
3820 @value{GDBN} allows you to set any number of breakpoints at the same place in
3821 your program. There is nothing silly or meaningless about this. When
3822 the breakpoints are conditional, this is even useful
3823 (@pxref{Conditions, ,Break Conditions}).
3825 @cindex multiple locations, breakpoints
3826 @cindex breakpoints, multiple locations
3827 It is possible that a breakpoint corresponds to several locations
3828 in your program. Examples of this situation are:
3832 Multiple functions in the program may have the same name.
3835 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3836 instances of the function body, used in different cases.
3839 For a C@t{++} template function, a given line in the function can
3840 correspond to any number of instantiations.
3843 For an inlined function, a given source line can correspond to
3844 several places where that function is inlined.
3847 In all those cases, @value{GDBN} will insert a breakpoint at all
3848 the relevant locations.
3850 A breakpoint with multiple locations is displayed in the breakpoint
3851 table using several rows---one header row, followed by one row for
3852 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3853 address column. The rows for individual locations contain the actual
3854 addresses for locations, and show the functions to which those
3855 locations belong. The number column for a location is of the form
3856 @var{breakpoint-number}.@var{location-number}.
3861 Num Type Disp Enb Address What
3862 1 breakpoint keep y <MULTIPLE>
3864 breakpoint already hit 1 time
3865 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3866 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3869 Each location can be individually enabled or disabled by passing
3870 @var{breakpoint-number}.@var{location-number} as argument to the
3871 @code{enable} and @code{disable} commands. Note that you cannot
3872 delete the individual locations from the list, you can only delete the
3873 entire list of locations that belong to their parent breakpoint (with
3874 the @kbd{delete @var{num}} command, where @var{num} is the number of
3875 the parent breakpoint, 1 in the above example). Disabling or enabling
3876 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3877 that belong to that breakpoint.
3879 @cindex pending breakpoints
3880 It's quite common to have a breakpoint inside a shared library.
3881 Shared libraries can be loaded and unloaded explicitly,
3882 and possibly repeatedly, as the program is executed. To support
3883 this use case, @value{GDBN} updates breakpoint locations whenever
3884 any shared library is loaded or unloaded. Typically, you would
3885 set a breakpoint in a shared library at the beginning of your
3886 debugging session, when the library is not loaded, and when the
3887 symbols from the library are not available. When you try to set
3888 breakpoint, @value{GDBN} will ask you if you want to set
3889 a so called @dfn{pending breakpoint}---breakpoint whose address
3890 is not yet resolved.
3892 After the program is run, whenever a new shared library is loaded,
3893 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3894 shared library contains the symbol or line referred to by some
3895 pending breakpoint, that breakpoint is resolved and becomes an
3896 ordinary breakpoint. When a library is unloaded, all breakpoints
3897 that refer to its symbols or source lines become pending again.
3899 This logic works for breakpoints with multiple locations, too. For
3900 example, if you have a breakpoint in a C@t{++} template function, and
3901 a newly loaded shared library has an instantiation of that template,
3902 a new location is added to the list of locations for the breakpoint.
3904 Except for having unresolved address, pending breakpoints do not
3905 differ from regular breakpoints. You can set conditions or commands,
3906 enable and disable them and perform other breakpoint operations.
3908 @value{GDBN} provides some additional commands for controlling what
3909 happens when the @samp{break} command cannot resolve breakpoint
3910 address specification to an address:
3912 @kindex set breakpoint pending
3913 @kindex show breakpoint pending
3915 @item set breakpoint pending auto
3916 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3917 location, it queries you whether a pending breakpoint should be created.
3919 @item set breakpoint pending on
3920 This indicates that an unrecognized breakpoint location should automatically
3921 result in a pending breakpoint being created.
3923 @item set breakpoint pending off
3924 This indicates that pending breakpoints are not to be created. Any
3925 unrecognized breakpoint location results in an error. This setting does
3926 not affect any pending breakpoints previously created.
3928 @item show breakpoint pending
3929 Show the current behavior setting for creating pending breakpoints.
3932 The settings above only affect the @code{break} command and its
3933 variants. Once breakpoint is set, it will be automatically updated
3934 as shared libraries are loaded and unloaded.
3936 @cindex automatic hardware breakpoints
3937 For some targets, @value{GDBN} can automatically decide if hardware or
3938 software breakpoints should be used, depending on whether the
3939 breakpoint address is read-only or read-write. This applies to
3940 breakpoints set with the @code{break} command as well as to internal
3941 breakpoints set by commands like @code{next} and @code{finish}. For
3942 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3945 You can control this automatic behaviour with the following commands::
3947 @kindex set breakpoint auto-hw
3948 @kindex show breakpoint auto-hw
3950 @item set breakpoint auto-hw on
3951 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3952 will try to use the target memory map to decide if software or hardware
3953 breakpoint must be used.
3955 @item set breakpoint auto-hw off
3956 This indicates @value{GDBN} should not automatically select breakpoint
3957 type. If the target provides a memory map, @value{GDBN} will warn when
3958 trying to set software breakpoint at a read-only address.
3961 @value{GDBN} normally implements breakpoints by replacing the program code
3962 at the breakpoint address with a special instruction, which, when
3963 executed, given control to the debugger. By default, the program
3964 code is so modified only when the program is resumed. As soon as
3965 the program stops, @value{GDBN} restores the original instructions. This
3966 behaviour guards against leaving breakpoints inserted in the
3967 target should gdb abrubptly disconnect. However, with slow remote
3968 targets, inserting and removing breakpoint can reduce the performance.
3969 This behavior can be controlled with the following commands::
3971 @kindex set breakpoint always-inserted
3972 @kindex show breakpoint always-inserted
3974 @item set breakpoint always-inserted off
3975 All breakpoints, including newly added by the user, are inserted in
3976 the target only when the target is resumed. All breakpoints are
3977 removed from the target when it stops. This is the default mode.
3979 @item set breakpoint always-inserted on
3980 Causes all breakpoints to be inserted in the target at all times. If
3981 the user adds a new breakpoint, or changes an existing breakpoint, the
3982 breakpoints in the target are updated immediately. A breakpoint is
3983 removed from the target only when breakpoint itself is deleted.
3986 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3987 when a breakpoint breaks. If the condition is true, then the process being
3988 debugged stops, otherwise the process is resumed.
3990 If the target supports evaluating conditions on its end, @value{GDBN} may
3991 download the breakpoint, together with its conditions, to it.
3993 This feature can be controlled via the following commands:
3995 @kindex set breakpoint condition-evaluation
3996 @kindex show breakpoint condition-evaluation
3998 @item set breakpoint condition-evaluation host
3999 This option commands @value{GDBN} to evaluate the breakpoint
4000 conditions on the host's side. Unconditional breakpoints are sent to
4001 the target which in turn receives the triggers and reports them back to GDB
4002 for condition evaluation. This is the standard evaluation mode.
4004 @item set breakpoint condition-evaluation target
4005 This option commands @value{GDBN} to download breakpoint conditions
4006 to the target at the moment of their insertion. The target
4007 is responsible for evaluating the conditional expression and reporting
4008 breakpoint stop events back to @value{GDBN} whenever the condition
4009 is true. Due to limitations of target-side evaluation, some conditions
4010 cannot be evaluated there, e.g., conditions that depend on local data
4011 that is only known to the host. Examples include
4012 conditional expressions involving convenience variables, complex types
4013 that cannot be handled by the agent expression parser and expressions
4014 that are too long to be sent over to the target, specially when the
4015 target is a remote system. In these cases, the conditions will be
4016 evaluated by @value{GDBN}.
4018 @item set breakpoint condition-evaluation auto
4019 This is the default mode. If the target supports evaluating breakpoint
4020 conditions on its end, @value{GDBN} will download breakpoint conditions to
4021 the target (limitations mentioned previously apply). If the target does
4022 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4023 to evaluating all these conditions on the host's side.
4027 @cindex negative breakpoint numbers
4028 @cindex internal @value{GDBN} breakpoints
4029 @value{GDBN} itself sometimes sets breakpoints in your program for
4030 special purposes, such as proper handling of @code{longjmp} (in C
4031 programs). These internal breakpoints are assigned negative numbers,
4032 starting with @code{-1}; @samp{info breakpoints} does not display them.
4033 You can see these breakpoints with the @value{GDBN} maintenance command
4034 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4037 @node Set Watchpoints
4038 @subsection Setting Watchpoints
4040 @cindex setting watchpoints
4041 You can use a watchpoint to stop execution whenever the value of an
4042 expression changes, without having to predict a particular place where
4043 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4044 The expression may be as simple as the value of a single variable, or
4045 as complex as many variables combined by operators. Examples include:
4049 A reference to the value of a single variable.
4052 An address cast to an appropriate data type. For example,
4053 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4054 address (assuming an @code{int} occupies 4 bytes).
4057 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4058 expression can use any operators valid in the program's native
4059 language (@pxref{Languages}).
4062 You can set a watchpoint on an expression even if the expression can
4063 not be evaluated yet. For instance, you can set a watchpoint on
4064 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4065 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4066 the expression produces a valid value. If the expression becomes
4067 valid in some other way than changing a variable (e.g.@: if the memory
4068 pointed to by @samp{*global_ptr} becomes readable as the result of a
4069 @code{malloc} call), @value{GDBN} may not stop until the next time
4070 the expression changes.
4072 @cindex software watchpoints
4073 @cindex hardware watchpoints
4074 Depending on your system, watchpoints may be implemented in software or
4075 hardware. @value{GDBN} does software watchpointing by single-stepping your
4076 program and testing the variable's value each time, which is hundreds of
4077 times slower than normal execution. (But this may still be worth it, to
4078 catch errors where you have no clue what part of your program is the
4081 On some systems, such as most PowerPC or x86-based targets,
4082 @value{GDBN} includes support for hardware watchpoints, which do not
4083 slow down the running of your program.
4087 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4088 Set a watchpoint for an expression. @value{GDBN} will break when the
4089 expression @var{expr} is written into by the program and its value
4090 changes. The simplest (and the most popular) use of this command is
4091 to watch the value of a single variable:
4094 (@value{GDBP}) watch foo
4097 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4098 argument, @value{GDBN} breaks only when the thread identified by
4099 @var{thread-id} changes the value of @var{expr}. If any other threads
4100 change the value of @var{expr}, @value{GDBN} will not break. Note
4101 that watchpoints restricted to a single thread in this way only work
4102 with Hardware Watchpoints.
4104 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4105 (see below). The @code{-location} argument tells @value{GDBN} to
4106 instead watch the memory referred to by @var{expr}. In this case,
4107 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4108 and watch the memory at that address. The type of the result is used
4109 to determine the size of the watched memory. If the expression's
4110 result does not have an address, then @value{GDBN} will print an
4113 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4114 of masked watchpoints, if the current architecture supports this
4115 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4116 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4117 to an address to watch. The mask specifies that some bits of an address
4118 (the bits which are reset in the mask) should be ignored when matching
4119 the address accessed by the inferior against the watchpoint address.
4120 Thus, a masked watchpoint watches many addresses simultaneously---those
4121 addresses whose unmasked bits are identical to the unmasked bits in the
4122 watchpoint address. The @code{mask} argument implies @code{-location}.
4126 (@value{GDBP}) watch foo mask 0xffff00ff
4127 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4131 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4132 Set a watchpoint that will break when the value of @var{expr} is read
4136 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4137 Set a watchpoint that will break when @var{expr} is either read from
4138 or written into by the program.
4140 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4141 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4142 This command prints a list of watchpoints, using the same format as
4143 @code{info break} (@pxref{Set Breaks}).
4146 If you watch for a change in a numerically entered address you need to
4147 dereference it, as the address itself is just a constant number which will
4148 never change. @value{GDBN} refuses to create a watchpoint that watches
4149 a never-changing value:
4152 (@value{GDBP}) watch 0x600850
4153 Cannot watch constant value 0x600850.
4154 (@value{GDBP}) watch *(int *) 0x600850
4155 Watchpoint 1: *(int *) 6293584
4158 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4159 watchpoints execute very quickly, and the debugger reports a change in
4160 value at the exact instruction where the change occurs. If @value{GDBN}
4161 cannot set a hardware watchpoint, it sets a software watchpoint, which
4162 executes more slowly and reports the change in value at the next
4163 @emph{statement}, not the instruction, after the change occurs.
4165 @cindex use only software watchpoints
4166 You can force @value{GDBN} to use only software watchpoints with the
4167 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4168 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4169 the underlying system supports them. (Note that hardware-assisted
4170 watchpoints that were set @emph{before} setting
4171 @code{can-use-hw-watchpoints} to zero will still use the hardware
4172 mechanism of watching expression values.)
4175 @item set can-use-hw-watchpoints
4176 @kindex set can-use-hw-watchpoints
4177 Set whether or not to use hardware watchpoints.
4179 @item show can-use-hw-watchpoints
4180 @kindex show can-use-hw-watchpoints
4181 Show the current mode of using hardware watchpoints.
4184 For remote targets, you can restrict the number of hardware
4185 watchpoints @value{GDBN} will use, see @ref{set remote
4186 hardware-breakpoint-limit}.
4188 When you issue the @code{watch} command, @value{GDBN} reports
4191 Hardware watchpoint @var{num}: @var{expr}
4195 if it was able to set a hardware watchpoint.
4197 Currently, the @code{awatch} and @code{rwatch} commands can only set
4198 hardware watchpoints, because accesses to data that don't change the
4199 value of the watched expression cannot be detected without examining
4200 every instruction as it is being executed, and @value{GDBN} does not do
4201 that currently. If @value{GDBN} finds that it is unable to set a
4202 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4203 will print a message like this:
4206 Expression cannot be implemented with read/access watchpoint.
4209 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4210 data type of the watched expression is wider than what a hardware
4211 watchpoint on the target machine can handle. For example, some systems
4212 can only watch regions that are up to 4 bytes wide; on such systems you
4213 cannot set hardware watchpoints for an expression that yields a
4214 double-precision floating-point number (which is typically 8 bytes
4215 wide). As a work-around, it might be possible to break the large region
4216 into a series of smaller ones and watch them with separate watchpoints.
4218 If you set too many hardware watchpoints, @value{GDBN} might be unable
4219 to insert all of them when you resume the execution of your program.
4220 Since the precise number of active watchpoints is unknown until such
4221 time as the program is about to be resumed, @value{GDBN} might not be
4222 able to warn you about this when you set the watchpoints, and the
4223 warning will be printed only when the program is resumed:
4226 Hardware watchpoint @var{num}: Could not insert watchpoint
4230 If this happens, delete or disable some of the watchpoints.
4232 Watching complex expressions that reference many variables can also
4233 exhaust the resources available for hardware-assisted watchpoints.
4234 That's because @value{GDBN} needs to watch every variable in the
4235 expression with separately allocated resources.
4237 If you call a function interactively using @code{print} or @code{call},
4238 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4239 kind of breakpoint or the call completes.
4241 @value{GDBN} automatically deletes watchpoints that watch local
4242 (automatic) variables, or expressions that involve such variables, when
4243 they go out of scope, that is, when the execution leaves the block in
4244 which these variables were defined. In particular, when the program
4245 being debugged terminates, @emph{all} local variables go out of scope,
4246 and so only watchpoints that watch global variables remain set. If you
4247 rerun the program, you will need to set all such watchpoints again. One
4248 way of doing that would be to set a code breakpoint at the entry to the
4249 @code{main} function and when it breaks, set all the watchpoints.
4251 @cindex watchpoints and threads
4252 @cindex threads and watchpoints
4253 In multi-threaded programs, watchpoints will detect changes to the
4254 watched expression from every thread.
4257 @emph{Warning:} In multi-threaded programs, software watchpoints
4258 have only limited usefulness. If @value{GDBN} creates a software
4259 watchpoint, it can only watch the value of an expression @emph{in a
4260 single thread}. If you are confident that the expression can only
4261 change due to the current thread's activity (and if you are also
4262 confident that no other thread can become current), then you can use
4263 software watchpoints as usual. However, @value{GDBN} may not notice
4264 when a non-current thread's activity changes the expression. (Hardware
4265 watchpoints, in contrast, watch an expression in all threads.)
4268 @xref{set remote hardware-watchpoint-limit}.
4270 @node Set Catchpoints
4271 @subsection Setting Catchpoints
4272 @cindex catchpoints, setting
4273 @cindex exception handlers
4274 @cindex event handling
4276 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4277 kinds of program events, such as C@t{++} exceptions or the loading of a
4278 shared library. Use the @code{catch} command to set a catchpoint.
4282 @item catch @var{event}
4283 Stop when @var{event} occurs. The @var{event} can be any of the following:
4286 @item throw @r{[}@var{regexp}@r{]}
4287 @itemx rethrow @r{[}@var{regexp}@r{]}
4288 @itemx catch @r{[}@var{regexp}@r{]}
4290 @kindex catch rethrow
4292 @cindex stop on C@t{++} exceptions
4293 The throwing, re-throwing, or catching of a C@t{++} exception.
4295 If @var{regexp} is given, then only exceptions whose type matches the
4296 regular expression will be caught.
4298 @vindex $_exception@r{, convenience variable}
4299 The convenience variable @code{$_exception} is available at an
4300 exception-related catchpoint, on some systems. This holds the
4301 exception being thrown.
4303 There are currently some limitations to C@t{++} exception handling in
4308 The support for these commands is system-dependent. Currently, only
4309 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4313 The regular expression feature and the @code{$_exception} convenience
4314 variable rely on the presence of some SDT probes in @code{libstdc++}.
4315 If these probes are not present, then these features cannot be used.
4316 These probes were first available in the GCC 4.8 release, but whether
4317 or not they are available in your GCC also depends on how it was
4321 The @code{$_exception} convenience variable is only valid at the
4322 instruction at which an exception-related catchpoint is set.
4325 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4326 location in the system library which implements runtime exception
4327 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4328 (@pxref{Selection}) to get to your code.
4331 If you call a function interactively, @value{GDBN} normally returns
4332 control to you when the function has finished executing. If the call
4333 raises an exception, however, the call may bypass the mechanism that
4334 returns control to you and cause your program either to abort or to
4335 simply continue running until it hits a breakpoint, catches a signal
4336 that @value{GDBN} is listening for, or exits. This is the case even if
4337 you set a catchpoint for the exception; catchpoints on exceptions are
4338 disabled within interactive calls. @xref{Calling}, for information on
4339 controlling this with @code{set unwind-on-terminating-exception}.
4342 You cannot raise an exception interactively.
4345 You cannot install an exception handler interactively.
4349 @kindex catch exception
4350 @cindex Ada exception catching
4351 @cindex catch Ada exceptions
4352 An Ada exception being raised. If an exception name is specified
4353 at the end of the command (eg @code{catch exception Program_Error}),
4354 the debugger will stop only when this specific exception is raised.
4355 Otherwise, the debugger stops execution when any Ada exception is raised.
4357 When inserting an exception catchpoint on a user-defined exception whose
4358 name is identical to one of the exceptions defined by the language, the
4359 fully qualified name must be used as the exception name. Otherwise,
4360 @value{GDBN} will assume that it should stop on the pre-defined exception
4361 rather than the user-defined one. For instance, assuming an exception
4362 called @code{Constraint_Error} is defined in package @code{Pck}, then
4363 the command to use to catch such exceptions is @kbd{catch exception
4364 Pck.Constraint_Error}.
4366 @item exception unhandled
4367 @kindex catch exception unhandled
4368 An exception that was raised but is not handled by the program.
4371 @kindex catch assert
4372 A failed Ada assertion.
4376 @cindex break on fork/exec
4377 A call to @code{exec}.
4380 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4381 @kindex catch syscall
4382 @cindex break on a system call.
4383 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4384 syscall is a mechanism for application programs to request a service
4385 from the operating system (OS) or one of the OS system services.
4386 @value{GDBN} can catch some or all of the syscalls issued by the
4387 debuggee, and show the related information for each syscall. If no
4388 argument is specified, calls to and returns from all system calls
4391 @var{name} can be any system call name that is valid for the
4392 underlying OS. Just what syscalls are valid depends on the OS. On
4393 GNU and Unix systems, you can find the full list of valid syscall
4394 names on @file{/usr/include/asm/unistd.h}.
4396 @c For MS-Windows, the syscall names and the corresponding numbers
4397 @c can be found, e.g., on this URL:
4398 @c http://www.metasploit.com/users/opcode/syscalls.html
4399 @c but we don't support Windows syscalls yet.
4401 Normally, @value{GDBN} knows in advance which syscalls are valid for
4402 each OS, so you can use the @value{GDBN} command-line completion
4403 facilities (@pxref{Completion,, command completion}) to list the
4406 You may also specify the system call numerically. A syscall's
4407 number is the value passed to the OS's syscall dispatcher to
4408 identify the requested service. When you specify the syscall by its
4409 name, @value{GDBN} uses its database of syscalls to convert the name
4410 into the corresponding numeric code, but using the number directly
4411 may be useful if @value{GDBN}'s database does not have the complete
4412 list of syscalls on your system (e.g., because @value{GDBN} lags
4413 behind the OS upgrades).
4415 You may specify a group of related syscalls to be caught at once using
4416 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4417 instance, on some platforms @value{GDBN} allows you to catch all
4418 network related syscalls, by passing the argument @code{group:network}
4419 to @code{catch syscall}. Note that not all syscall groups are
4420 available in every system. You can use the command completion
4421 facilities (@pxref{Completion,, command completion}) to list the
4422 syscall groups available on your environment.
4424 The example below illustrates how this command works if you don't provide
4428 (@value{GDBP}) catch syscall
4429 Catchpoint 1 (syscall)
4431 Starting program: /tmp/catch-syscall
4433 Catchpoint 1 (call to syscall 'close'), \
4434 0xffffe424 in __kernel_vsyscall ()
4438 Catchpoint 1 (returned from syscall 'close'), \
4439 0xffffe424 in __kernel_vsyscall ()
4443 Here is an example of catching a system call by name:
4446 (@value{GDBP}) catch syscall chroot
4447 Catchpoint 1 (syscall 'chroot' [61])
4449 Starting program: /tmp/catch-syscall
4451 Catchpoint 1 (call to syscall 'chroot'), \
4452 0xffffe424 in __kernel_vsyscall ()
4456 Catchpoint 1 (returned from syscall 'chroot'), \
4457 0xffffe424 in __kernel_vsyscall ()
4461 An example of specifying a system call numerically. In the case
4462 below, the syscall number has a corresponding entry in the XML
4463 file, so @value{GDBN} finds its name and prints it:
4466 (@value{GDBP}) catch syscall 252
4467 Catchpoint 1 (syscall(s) 'exit_group')
4469 Starting program: /tmp/catch-syscall
4471 Catchpoint 1 (call to syscall 'exit_group'), \
4472 0xffffe424 in __kernel_vsyscall ()
4476 Program exited normally.
4480 Here is an example of catching a syscall group:
4483 (@value{GDBP}) catch syscall group:process
4484 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4485 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4486 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4488 Starting program: /tmp/catch-syscall
4490 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4491 from /lib64/ld-linux-x86-64.so.2
4497 However, there can be situations when there is no corresponding name
4498 in XML file for that syscall number. In this case, @value{GDBN} prints
4499 a warning message saying that it was not able to find the syscall name,
4500 but the catchpoint will be set anyway. See the example below:
4503 (@value{GDBP}) catch syscall 764
4504 warning: The number '764' does not represent a known syscall.
4505 Catchpoint 2 (syscall 764)
4509 If you configure @value{GDBN} using the @samp{--without-expat} option,
4510 it will not be able to display syscall names. Also, if your
4511 architecture does not have an XML file describing its system calls,
4512 you will not be able to see the syscall names. It is important to
4513 notice that these two features are used for accessing the syscall
4514 name database. In either case, you will see a warning like this:
4517 (@value{GDBP}) catch syscall
4518 warning: Could not open "syscalls/i386-linux.xml"
4519 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4520 GDB will not be able to display syscall names.
4521 Catchpoint 1 (syscall)
4525 Of course, the file name will change depending on your architecture and system.
4527 Still using the example above, you can also try to catch a syscall by its
4528 number. In this case, you would see something like:
4531 (@value{GDBP}) catch syscall 252
4532 Catchpoint 1 (syscall(s) 252)
4535 Again, in this case @value{GDBN} would not be able to display syscall's names.
4539 A call to @code{fork}.
4543 A call to @code{vfork}.
4545 @item load @r{[}regexp@r{]}
4546 @itemx unload @r{[}regexp@r{]}
4548 @kindex catch unload
4549 The loading or unloading of a shared library. If @var{regexp} is
4550 given, then the catchpoint will stop only if the regular expression
4551 matches one of the affected libraries.
4553 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4554 @kindex catch signal
4555 The delivery of a signal.
4557 With no arguments, this catchpoint will catch any signal that is not
4558 used internally by @value{GDBN}, specifically, all signals except
4559 @samp{SIGTRAP} and @samp{SIGINT}.
4561 With the argument @samp{all}, all signals, including those used by
4562 @value{GDBN}, will be caught. This argument cannot be used with other
4565 Otherwise, the arguments are a list of signal names as given to
4566 @code{handle} (@pxref{Signals}). Only signals specified in this list
4569 One reason that @code{catch signal} can be more useful than
4570 @code{handle} is that you can attach commands and conditions to the
4573 When a signal is caught by a catchpoint, the signal's @code{stop} and
4574 @code{print} settings, as specified by @code{handle}, are ignored.
4575 However, whether the signal is still delivered to the inferior depends
4576 on the @code{pass} setting; this can be changed in the catchpoint's
4581 @item tcatch @var{event}
4583 Set a catchpoint that is enabled only for one stop. The catchpoint is
4584 automatically deleted after the first time the event is caught.
4588 Use the @code{info break} command to list the current catchpoints.
4592 @subsection Deleting Breakpoints
4594 @cindex clearing breakpoints, watchpoints, catchpoints
4595 @cindex deleting breakpoints, watchpoints, catchpoints
4596 It is often necessary to eliminate a breakpoint, watchpoint, or
4597 catchpoint once it has done its job and you no longer want your program
4598 to stop there. This is called @dfn{deleting} the breakpoint. A
4599 breakpoint that has been deleted no longer exists; it is forgotten.
4601 With the @code{clear} command you can delete breakpoints according to
4602 where they are in your program. With the @code{delete} command you can
4603 delete individual breakpoints, watchpoints, or catchpoints by specifying
4604 their breakpoint numbers.
4606 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4607 automatically ignores breakpoints on the first instruction to be executed
4608 when you continue execution without changing the execution address.
4613 Delete any breakpoints at the next instruction to be executed in the
4614 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4615 the innermost frame is selected, this is a good way to delete a
4616 breakpoint where your program just stopped.
4618 @item clear @var{location}
4619 Delete any breakpoints set at the specified @var{location}.
4620 @xref{Specify Location}, for the various forms of @var{location}; the
4621 most useful ones are listed below:
4624 @item clear @var{function}
4625 @itemx clear @var{filename}:@var{function}
4626 Delete any breakpoints set at entry to the named @var{function}.
4628 @item clear @var{linenum}
4629 @itemx clear @var{filename}:@var{linenum}
4630 Delete any breakpoints set at or within the code of the specified
4631 @var{linenum} of the specified @var{filename}.
4634 @cindex delete breakpoints
4636 @kindex d @r{(@code{delete})}
4637 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4638 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4639 ranges specified as arguments. If no argument is specified, delete all
4640 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4641 confirm off}). You can abbreviate this command as @code{d}.
4645 @subsection Disabling Breakpoints
4647 @cindex enable/disable a breakpoint
4648 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4649 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4650 it had been deleted, but remembers the information on the breakpoint so
4651 that you can @dfn{enable} it again later.
4653 You disable and enable breakpoints, watchpoints, and catchpoints with
4654 the @code{enable} and @code{disable} commands, optionally specifying
4655 one or more breakpoint numbers as arguments. Use @code{info break} to
4656 print a list of all breakpoints, watchpoints, and catchpoints if you
4657 do not know which numbers to use.
4659 Disabling and enabling a breakpoint that has multiple locations
4660 affects all of its locations.
4662 A breakpoint, watchpoint, or catchpoint can have any of several
4663 different states of enablement:
4667 Enabled. The breakpoint stops your program. A breakpoint set
4668 with the @code{break} command starts out in this state.
4670 Disabled. The breakpoint has no effect on your program.
4672 Enabled once. The breakpoint stops your program, but then becomes
4675 Enabled for a count. The breakpoint stops your program for the next
4676 N times, then becomes disabled.
4678 Enabled for deletion. The breakpoint stops your program, but
4679 immediately after it does so it is deleted permanently. A breakpoint
4680 set with the @code{tbreak} command starts out in this state.
4683 You can use the following commands to enable or disable breakpoints,
4684 watchpoints, and catchpoints:
4688 @kindex dis @r{(@code{disable})}
4689 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4690 Disable the specified breakpoints---or all breakpoints, if none are
4691 listed. A disabled breakpoint has no effect but is not forgotten. All
4692 options such as ignore-counts, conditions and commands are remembered in
4693 case the breakpoint is enabled again later. You may abbreviate
4694 @code{disable} as @code{dis}.
4697 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4698 Enable the specified breakpoints (or all defined breakpoints). They
4699 become effective once again in stopping your program.
4701 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4702 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4703 of these breakpoints immediately after stopping your program.
4705 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4706 Enable the specified breakpoints temporarily. @value{GDBN} records
4707 @var{count} with each of the specified breakpoints, and decrements a
4708 breakpoint's count when it is hit. When any count reaches 0,
4709 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4710 count (@pxref{Conditions, ,Break Conditions}), that will be
4711 decremented to 0 before @var{count} is affected.
4713 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4714 Enable the specified breakpoints to work once, then die. @value{GDBN}
4715 deletes any of these breakpoints as soon as your program stops there.
4716 Breakpoints set by the @code{tbreak} command start out in this state.
4719 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4720 @c confusing: tbreak is also initially enabled.
4721 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4722 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4723 subsequently, they become disabled or enabled only when you use one of
4724 the commands above. (The command @code{until} can set and delete a
4725 breakpoint of its own, but it does not change the state of your other
4726 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4730 @subsection Break Conditions
4731 @cindex conditional breakpoints
4732 @cindex breakpoint conditions
4734 @c FIXME what is scope of break condition expr? Context where wanted?
4735 @c in particular for a watchpoint?
4736 The simplest sort of breakpoint breaks every time your program reaches a
4737 specified place. You can also specify a @dfn{condition} for a
4738 breakpoint. A condition is just a Boolean expression in your
4739 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4740 a condition evaluates the expression each time your program reaches it,
4741 and your program stops only if the condition is @emph{true}.
4743 This is the converse of using assertions for program validation; in that
4744 situation, you want to stop when the assertion is violated---that is,
4745 when the condition is false. In C, if you want to test an assertion expressed
4746 by the condition @var{assert}, you should set the condition
4747 @samp{! @var{assert}} on the appropriate breakpoint.
4749 Conditions are also accepted for watchpoints; you may not need them,
4750 since a watchpoint is inspecting the value of an expression anyhow---but
4751 it might be simpler, say, to just set a watchpoint on a variable name,
4752 and specify a condition that tests whether the new value is an interesting
4755 Break conditions can have side effects, and may even call functions in
4756 your program. This can be useful, for example, to activate functions
4757 that log program progress, or to use your own print functions to
4758 format special data structures. The effects are completely predictable
4759 unless there is another enabled breakpoint at the same address. (In
4760 that case, @value{GDBN} might see the other breakpoint first and stop your
4761 program without checking the condition of this one.) Note that
4762 breakpoint commands are usually more convenient and flexible than break
4764 purpose of performing side effects when a breakpoint is reached
4765 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4767 Breakpoint conditions can also be evaluated on the target's side if
4768 the target supports it. Instead of evaluating the conditions locally,
4769 @value{GDBN} encodes the expression into an agent expression
4770 (@pxref{Agent Expressions}) suitable for execution on the target,
4771 independently of @value{GDBN}. Global variables become raw memory
4772 locations, locals become stack accesses, and so forth.
4774 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4775 when its condition evaluates to true. This mechanism may provide faster
4776 response times depending on the performance characteristics of the target
4777 since it does not need to keep @value{GDBN} informed about
4778 every breakpoint trigger, even those with false conditions.
4780 Break conditions can be specified when a breakpoint is set, by using
4781 @samp{if} in the arguments to the @code{break} command. @xref{Set
4782 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4783 with the @code{condition} command.
4785 You can also use the @code{if} keyword with the @code{watch} command.
4786 The @code{catch} command does not recognize the @code{if} keyword;
4787 @code{condition} is the only way to impose a further condition on a
4792 @item condition @var{bnum} @var{expression}
4793 Specify @var{expression} as the break condition for breakpoint,
4794 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4795 breakpoint @var{bnum} stops your program only if the value of
4796 @var{expression} is true (nonzero, in C). When you use
4797 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4798 syntactic correctness, and to determine whether symbols in it have
4799 referents in the context of your breakpoint. If @var{expression} uses
4800 symbols not referenced in the context of the breakpoint, @value{GDBN}
4801 prints an error message:
4804 No symbol "foo" in current context.
4809 not actually evaluate @var{expression} at the time the @code{condition}
4810 command (or a command that sets a breakpoint with a condition, like
4811 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4813 @item condition @var{bnum}
4814 Remove the condition from breakpoint number @var{bnum}. It becomes
4815 an ordinary unconditional breakpoint.
4818 @cindex ignore count (of breakpoint)
4819 A special case of a breakpoint condition is to stop only when the
4820 breakpoint has been reached a certain number of times. This is so
4821 useful that there is a special way to do it, using the @dfn{ignore
4822 count} of the breakpoint. Every breakpoint has an ignore count, which
4823 is an integer. Most of the time, the ignore count is zero, and
4824 therefore has no effect. But if your program reaches a breakpoint whose
4825 ignore count is positive, then instead of stopping, it just decrements
4826 the ignore count by one and continues. As a result, if the ignore count
4827 value is @var{n}, the breakpoint does not stop the next @var{n} times
4828 your program reaches it.
4832 @item ignore @var{bnum} @var{count}
4833 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4834 The next @var{count} times the breakpoint is reached, your program's
4835 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4838 To make the breakpoint stop the next time it is reached, specify
4841 When you use @code{continue} to resume execution of your program from a
4842 breakpoint, you can specify an ignore count directly as an argument to
4843 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4844 Stepping,,Continuing and Stepping}.
4846 If a breakpoint has a positive ignore count and a condition, the
4847 condition is not checked. Once the ignore count reaches zero,
4848 @value{GDBN} resumes checking the condition.
4850 You could achieve the effect of the ignore count with a condition such
4851 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4852 is decremented each time. @xref{Convenience Vars, ,Convenience
4856 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4859 @node Break Commands
4860 @subsection Breakpoint Command Lists
4862 @cindex breakpoint commands
4863 You can give any breakpoint (or watchpoint or catchpoint) a series of
4864 commands to execute when your program stops due to that breakpoint. For
4865 example, you might want to print the values of certain expressions, or
4866 enable other breakpoints.
4870 @kindex end@r{ (breakpoint commands)}
4871 @item commands @r{[}@var{range}@dots{}@r{]}
4872 @itemx @dots{} @var{command-list} @dots{}
4874 Specify a list of commands for the given breakpoints. The commands
4875 themselves appear on the following lines. Type a line containing just
4876 @code{end} to terminate the commands.
4878 To remove all commands from a breakpoint, type @code{commands} and
4879 follow it immediately with @code{end}; that is, give no commands.
4881 With no argument, @code{commands} refers to the last breakpoint,
4882 watchpoint, or catchpoint set (not to the breakpoint most recently
4883 encountered). If the most recent breakpoints were set with a single
4884 command, then the @code{commands} will apply to all the breakpoints
4885 set by that command. This applies to breakpoints set by
4886 @code{rbreak}, and also applies when a single @code{break} command
4887 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4891 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4892 disabled within a @var{command-list}.
4894 You can use breakpoint commands to start your program up again. Simply
4895 use the @code{continue} command, or @code{step}, or any other command
4896 that resumes execution.
4898 Any other commands in the command list, after a command that resumes
4899 execution, are ignored. This is because any time you resume execution
4900 (even with a simple @code{next} or @code{step}), you may encounter
4901 another breakpoint---which could have its own command list, leading to
4902 ambiguities about which list to execute.
4905 If the first command you specify in a command list is @code{silent}, the
4906 usual message about stopping at a breakpoint is not printed. This may
4907 be desirable for breakpoints that are to print a specific message and
4908 then continue. If none of the remaining commands print anything, you
4909 see no sign that the breakpoint was reached. @code{silent} is
4910 meaningful only at the beginning of a breakpoint command list.
4912 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4913 print precisely controlled output, and are often useful in silent
4914 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4916 For example, here is how you could use breakpoint commands to print the
4917 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4923 printf "x is %d\n",x
4928 One application for breakpoint commands is to compensate for one bug so
4929 you can test for another. Put a breakpoint just after the erroneous line
4930 of code, give it a condition to detect the case in which something
4931 erroneous has been done, and give it commands to assign correct values
4932 to any variables that need them. End with the @code{continue} command
4933 so that your program does not stop, and start with the @code{silent}
4934 command so that no output is produced. Here is an example:
4945 @node Dynamic Printf
4946 @subsection Dynamic Printf
4948 @cindex dynamic printf
4950 The dynamic printf command @code{dprintf} combines a breakpoint with
4951 formatted printing of your program's data to give you the effect of
4952 inserting @code{printf} calls into your program on-the-fly, without
4953 having to recompile it.
4955 In its most basic form, the output goes to the GDB console. However,
4956 you can set the variable @code{dprintf-style} for alternate handling.
4957 For instance, you can ask to format the output by calling your
4958 program's @code{printf} function. This has the advantage that the
4959 characters go to the program's output device, so they can recorded in
4960 redirects to files and so forth.
4962 If you are doing remote debugging with a stub or agent, you can also
4963 ask to have the printf handled by the remote agent. In addition to
4964 ensuring that the output goes to the remote program's device along
4965 with any other output the program might produce, you can also ask that
4966 the dprintf remain active even after disconnecting from the remote
4967 target. Using the stub/agent is also more efficient, as it can do
4968 everything without needing to communicate with @value{GDBN}.
4972 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4973 Whenever execution reaches @var{location}, print the values of one or
4974 more @var{expressions} under the control of the string @var{template}.
4975 To print several values, separate them with commas.
4977 @item set dprintf-style @var{style}
4978 Set the dprintf output to be handled in one of several different
4979 styles enumerated below. A change of style affects all existing
4980 dynamic printfs immediately. (If you need individual control over the
4981 print commands, simply define normal breakpoints with
4982 explicitly-supplied command lists.)
4985 @kindex dprintf-style gdb
4986 Handle the output using the @value{GDBN} @code{printf} command.
4989 @kindex dprintf-style call
4990 Handle the output by calling a function in your program (normally
4994 @kindex dprintf-style agent
4995 Have the remote debugging agent (such as @code{gdbserver}) handle
4996 the output itself. This style is only available for agents that
4997 support running commands on the target.
4999 @item set dprintf-function @var{function}
5000 Set the function to call if the dprintf style is @code{call}. By
5001 default its value is @code{printf}. You may set it to any expression.
5002 that @value{GDBN} can evaluate to a function, as per the @code{call}
5005 @item set dprintf-channel @var{channel}
5006 Set a ``channel'' for dprintf. If set to a non-empty value,
5007 @value{GDBN} will evaluate it as an expression and pass the result as
5008 a first argument to the @code{dprintf-function}, in the manner of
5009 @code{fprintf} and similar functions. Otherwise, the dprintf format
5010 string will be the first argument, in the manner of @code{printf}.
5012 As an example, if you wanted @code{dprintf} output to go to a logfile
5013 that is a standard I/O stream assigned to the variable @code{mylog},
5014 you could do the following:
5017 (gdb) set dprintf-style call
5018 (gdb) set dprintf-function fprintf
5019 (gdb) set dprintf-channel mylog
5020 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5021 Dprintf 1 at 0x123456: file main.c, line 25.
5023 1 dprintf keep y 0x00123456 in main at main.c:25
5024 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5029 Note that the @code{info break} displays the dynamic printf commands
5030 as normal breakpoint commands; you can thus easily see the effect of
5031 the variable settings.
5033 @item set disconnected-dprintf on
5034 @itemx set disconnected-dprintf off
5035 @kindex set disconnected-dprintf
5036 Choose whether @code{dprintf} commands should continue to run if
5037 @value{GDBN} has disconnected from the target. This only applies
5038 if the @code{dprintf-style} is @code{agent}.
5040 @item show disconnected-dprintf off
5041 @kindex show disconnected-dprintf
5042 Show the current choice for disconnected @code{dprintf}.
5046 @value{GDBN} does not check the validity of function and channel,
5047 relying on you to supply values that are meaningful for the contexts
5048 in which they are being used. For instance, the function and channel
5049 may be the values of local variables, but if that is the case, then
5050 all enabled dynamic prints must be at locations within the scope of
5051 those locals. If evaluation fails, @value{GDBN} will report an error.
5053 @node Save Breakpoints
5054 @subsection How to save breakpoints to a file
5056 To save breakpoint definitions to a file use the @w{@code{save
5057 breakpoints}} command.
5060 @kindex save breakpoints
5061 @cindex save breakpoints to a file for future sessions
5062 @item save breakpoints [@var{filename}]
5063 This command saves all current breakpoint definitions together with
5064 their commands and ignore counts, into a file @file{@var{filename}}
5065 suitable for use in a later debugging session. This includes all
5066 types of breakpoints (breakpoints, watchpoints, catchpoints,
5067 tracepoints). To read the saved breakpoint definitions, use the
5068 @code{source} command (@pxref{Command Files}). Note that watchpoints
5069 with expressions involving local variables may fail to be recreated
5070 because it may not be possible to access the context where the
5071 watchpoint is valid anymore. Because the saved breakpoint definitions
5072 are simply a sequence of @value{GDBN} commands that recreate the
5073 breakpoints, you can edit the file in your favorite editing program,
5074 and remove the breakpoint definitions you're not interested in, or
5075 that can no longer be recreated.
5078 @node Static Probe Points
5079 @subsection Static Probe Points
5081 @cindex static probe point, SystemTap
5082 @cindex static probe point, DTrace
5083 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5084 for Statically Defined Tracing, and the probes are designed to have a tiny
5085 runtime code and data footprint, and no dynamic relocations.
5087 Currently, the following types of probes are supported on
5088 ELF-compatible systems:
5092 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5093 @acronym{SDT} probes@footnote{See
5094 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5095 for more information on how to add @code{SystemTap} @acronym{SDT}
5096 probes in your applications.}. @code{SystemTap} probes are usable
5097 from assembly, C and C@t{++} languages@footnote{See
5098 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5099 for a good reference on how the @acronym{SDT} probes are implemented.}.
5101 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5102 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5106 @cindex semaphores on static probe points
5107 Some @code{SystemTap} probes have an associated semaphore variable;
5108 for instance, this happens automatically if you defined your probe
5109 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5110 @value{GDBN} will automatically enable it when you specify a
5111 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5112 breakpoint at a probe's location by some other method (e.g.,
5113 @code{break file:line}), then @value{GDBN} will not automatically set
5114 the semaphore. @code{DTrace} probes do not support semaphores.
5116 You can examine the available static static probes using @code{info
5117 probes}, with optional arguments:
5121 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5122 If given, @var{type} is either @code{stap} for listing
5123 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5124 probes. If omitted all probes are listed regardless of their types.
5126 If given, @var{provider} is a regular expression used to match against provider
5127 names when selecting which probes to list. If omitted, probes by all
5128 probes from all providers are listed.
5130 If given, @var{name} is a regular expression to match against probe names
5131 when selecting which probes to list. If omitted, probe names are not
5132 considered when deciding whether to display them.
5134 If given, @var{objfile} is a regular expression used to select which
5135 object files (executable or shared libraries) to examine. If not
5136 given, all object files are considered.
5138 @item info probes all
5139 List the available static probes, from all types.
5142 @cindex enabling and disabling probes
5143 Some probe points can be enabled and/or disabled. The effect of
5144 enabling or disabling a probe depends on the type of probe being
5145 handled. Some @code{DTrace} probes can be enabled or
5146 disabled, but @code{SystemTap} probes cannot be disabled.
5148 You can enable (or disable) one or more probes using the following
5149 commands, with optional arguments:
5152 @kindex enable probes
5153 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5154 If given, @var{provider} is a regular expression used to match against
5155 provider names when selecting which probes to enable. If omitted,
5156 all probes from all providers are enabled.
5158 If given, @var{name} is a regular expression to match against probe
5159 names when selecting which probes to enable. If omitted, probe names
5160 are not considered when deciding whether to enable them.
5162 If given, @var{objfile} is a regular expression used to select which
5163 object files (executable or shared libraries) to examine. If not
5164 given, all object files are considered.
5166 @kindex disable probes
5167 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5168 See the @code{enable probes} command above for a description of the
5169 optional arguments accepted by this command.
5172 @vindex $_probe_arg@r{, convenience variable}
5173 A probe may specify up to twelve arguments. These are available at the
5174 point at which the probe is defined---that is, when the current PC is
5175 at the probe's location. The arguments are available using the
5176 convenience variables (@pxref{Convenience Vars})
5177 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5178 probes each probe argument is an integer of the appropriate size;
5179 types are not preserved. In @code{DTrace} probes types are preserved
5180 provided that they are recognized as such by @value{GDBN}; otherwise
5181 the value of the probe argument will be a long integer. The
5182 convenience variable @code{$_probe_argc} holds the number of arguments
5183 at the current probe point.
5185 These variables are always available, but attempts to access them at
5186 any location other than a probe point will cause @value{GDBN} to give
5190 @c @ifclear BARETARGET
5191 @node Error in Breakpoints
5192 @subsection ``Cannot insert breakpoints''
5194 If you request too many active hardware-assisted breakpoints and
5195 watchpoints, you will see this error message:
5197 @c FIXME: the precise wording of this message may change; the relevant
5198 @c source change is not committed yet (Sep 3, 1999).
5200 Stopped; cannot insert breakpoints.
5201 You may have requested too many hardware breakpoints and watchpoints.
5205 This message is printed when you attempt to resume the program, since
5206 only then @value{GDBN} knows exactly how many hardware breakpoints and
5207 watchpoints it needs to insert.
5209 When this message is printed, you need to disable or remove some of the
5210 hardware-assisted breakpoints and watchpoints, and then continue.
5212 @node Breakpoint-related Warnings
5213 @subsection ``Breakpoint address adjusted...''
5214 @cindex breakpoint address adjusted
5216 Some processor architectures place constraints on the addresses at
5217 which breakpoints may be placed. For architectures thus constrained,
5218 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5219 with the constraints dictated by the architecture.
5221 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5222 a VLIW architecture in which a number of RISC-like instructions may be
5223 bundled together for parallel execution. The FR-V architecture
5224 constrains the location of a breakpoint instruction within such a
5225 bundle to the instruction with the lowest address. @value{GDBN}
5226 honors this constraint by adjusting a breakpoint's address to the
5227 first in the bundle.
5229 It is not uncommon for optimized code to have bundles which contain
5230 instructions from different source statements, thus it may happen that
5231 a breakpoint's address will be adjusted from one source statement to
5232 another. Since this adjustment may significantly alter @value{GDBN}'s
5233 breakpoint related behavior from what the user expects, a warning is
5234 printed when the breakpoint is first set and also when the breakpoint
5237 A warning like the one below is printed when setting a breakpoint
5238 that's been subject to address adjustment:
5241 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5244 Such warnings are printed both for user settable and @value{GDBN}'s
5245 internal breakpoints. If you see one of these warnings, you should
5246 verify that a breakpoint set at the adjusted address will have the
5247 desired affect. If not, the breakpoint in question may be removed and
5248 other breakpoints may be set which will have the desired behavior.
5249 E.g., it may be sufficient to place the breakpoint at a later
5250 instruction. A conditional breakpoint may also be useful in some
5251 cases to prevent the breakpoint from triggering too often.
5253 @value{GDBN} will also issue a warning when stopping at one of these
5254 adjusted breakpoints:
5257 warning: Breakpoint 1 address previously adjusted from 0x00010414
5261 When this warning is encountered, it may be too late to take remedial
5262 action except in cases where the breakpoint is hit earlier or more
5263 frequently than expected.
5265 @node Continuing and Stepping
5266 @section Continuing and Stepping
5270 @cindex resuming execution
5271 @dfn{Continuing} means resuming program execution until your program
5272 completes normally. In contrast, @dfn{stepping} means executing just
5273 one more ``step'' of your program, where ``step'' may mean either one
5274 line of source code, or one machine instruction (depending on what
5275 particular command you use). Either when continuing or when stepping,
5276 your program may stop even sooner, due to a breakpoint or a signal. (If
5277 it stops due to a signal, you may want to use @code{handle}, or use
5278 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5279 or you may step into the signal's handler (@pxref{stepping and signal
5284 @kindex c @r{(@code{continue})}
5285 @kindex fg @r{(resume foreground execution)}
5286 @item continue @r{[}@var{ignore-count}@r{]}
5287 @itemx c @r{[}@var{ignore-count}@r{]}
5288 @itemx fg @r{[}@var{ignore-count}@r{]}
5289 Resume program execution, at the address where your program last stopped;
5290 any breakpoints set at that address are bypassed. The optional argument
5291 @var{ignore-count} allows you to specify a further number of times to
5292 ignore a breakpoint at this location; its effect is like that of
5293 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5295 The argument @var{ignore-count} is meaningful only when your program
5296 stopped due to a breakpoint. At other times, the argument to
5297 @code{continue} is ignored.
5299 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5300 debugged program is deemed to be the foreground program) are provided
5301 purely for convenience, and have exactly the same behavior as
5305 To resume execution at a different place, you can use @code{return}
5306 (@pxref{Returning, ,Returning from a Function}) to go back to the
5307 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5308 Different Address}) to go to an arbitrary location in your program.
5310 A typical technique for using stepping is to set a breakpoint
5311 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5312 beginning of the function or the section of your program where a problem
5313 is believed to lie, run your program until it stops at that breakpoint,
5314 and then step through the suspect area, examining the variables that are
5315 interesting, until you see the problem happen.
5319 @kindex s @r{(@code{step})}
5321 Continue running your program until control reaches a different source
5322 line, then stop it and return control to @value{GDBN}. This command is
5323 abbreviated @code{s}.
5326 @c "without debugging information" is imprecise; actually "without line
5327 @c numbers in the debugging information". (gcc -g1 has debugging info but
5328 @c not line numbers). But it seems complex to try to make that
5329 @c distinction here.
5330 @emph{Warning:} If you use the @code{step} command while control is
5331 within a function that was compiled without debugging information,
5332 execution proceeds until control reaches a function that does have
5333 debugging information. Likewise, it will not step into a function which
5334 is compiled without debugging information. To step through functions
5335 without debugging information, use the @code{stepi} command, described
5339 The @code{step} command only stops at the first instruction of a source
5340 line. This prevents the multiple stops that could otherwise occur in
5341 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5342 to stop if a function that has debugging information is called within
5343 the line. In other words, @code{step} @emph{steps inside} any functions
5344 called within the line.
5346 Also, the @code{step} command only enters a function if there is line
5347 number information for the function. Otherwise it acts like the
5348 @code{next} command. This avoids problems when using @code{cc -gl}
5349 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5350 was any debugging information about the routine.
5352 @item step @var{count}
5353 Continue running as in @code{step}, but do so @var{count} times. If a
5354 breakpoint is reached, or a signal not related to stepping occurs before
5355 @var{count} steps, stepping stops right away.
5358 @kindex n @r{(@code{next})}
5359 @item next @r{[}@var{count}@r{]}
5360 Continue to the next source line in the current (innermost) stack frame.
5361 This is similar to @code{step}, but function calls that appear within
5362 the line of code are executed without stopping. Execution stops when
5363 control reaches a different line of code at the original stack level
5364 that was executing when you gave the @code{next} command. This command
5365 is abbreviated @code{n}.
5367 An argument @var{count} is a repeat count, as for @code{step}.
5370 @c FIX ME!! Do we delete this, or is there a way it fits in with
5371 @c the following paragraph? --- Vctoria
5373 @c @code{next} within a function that lacks debugging information acts like
5374 @c @code{step}, but any function calls appearing within the code of the
5375 @c function are executed without stopping.
5377 The @code{next} command only stops at the first instruction of a
5378 source line. This prevents multiple stops that could otherwise occur in
5379 @code{switch} statements, @code{for} loops, etc.
5381 @kindex set step-mode
5383 @cindex functions without line info, and stepping
5384 @cindex stepping into functions with no line info
5385 @itemx set step-mode on
5386 The @code{set step-mode on} command causes the @code{step} command to
5387 stop at the first instruction of a function which contains no debug line
5388 information rather than stepping over it.
5390 This is useful in cases where you may be interested in inspecting the
5391 machine instructions of a function which has no symbolic info and do not
5392 want @value{GDBN} to automatically skip over this function.
5394 @item set step-mode off
5395 Causes the @code{step} command to step over any functions which contains no
5396 debug information. This is the default.
5398 @item show step-mode
5399 Show whether @value{GDBN} will stop in or step over functions without
5400 source line debug information.
5403 @kindex fin @r{(@code{finish})}
5405 Continue running until just after function in the selected stack frame
5406 returns. Print the returned value (if any). This command can be
5407 abbreviated as @code{fin}.
5409 Contrast this with the @code{return} command (@pxref{Returning,
5410 ,Returning from a Function}).
5413 @kindex u @r{(@code{until})}
5414 @cindex run until specified location
5417 Continue running until a source line past the current line, in the
5418 current stack frame, is reached. This command is used to avoid single
5419 stepping through a loop more than once. It is like the @code{next}
5420 command, except that when @code{until} encounters a jump, it
5421 automatically continues execution until the program counter is greater
5422 than the address of the jump.
5424 This means that when you reach the end of a loop after single stepping
5425 though it, @code{until} makes your program continue execution until it
5426 exits the loop. In contrast, a @code{next} command at the end of a loop
5427 simply steps back to the beginning of the loop, which forces you to step
5428 through the next iteration.
5430 @code{until} always stops your program if it attempts to exit the current
5433 @code{until} may produce somewhat counterintuitive results if the order
5434 of machine code does not match the order of the source lines. For
5435 example, in the following excerpt from a debugging session, the @code{f}
5436 (@code{frame}) command shows that execution is stopped at line
5437 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5441 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5443 (@value{GDBP}) until
5444 195 for ( ; argc > 0; NEXTARG) @{
5447 This happened because, for execution efficiency, the compiler had
5448 generated code for the loop closure test at the end, rather than the
5449 start, of the loop---even though the test in a C @code{for}-loop is
5450 written before the body of the loop. The @code{until} command appeared
5451 to step back to the beginning of the loop when it advanced to this
5452 expression; however, it has not really gone to an earlier
5453 statement---not in terms of the actual machine code.
5455 @code{until} with no argument works by means of single
5456 instruction stepping, and hence is slower than @code{until} with an
5459 @item until @var{location}
5460 @itemx u @var{location}
5461 Continue running your program until either the specified @var{location} is
5462 reached, or the current stack frame returns. The location is any of
5463 the forms described in @ref{Specify Location}.
5464 This form of the command uses temporary breakpoints, and
5465 hence is quicker than @code{until} without an argument. The specified
5466 location is actually reached only if it is in the current frame. This
5467 implies that @code{until} can be used to skip over recursive function
5468 invocations. For instance in the code below, if the current location is
5469 line @code{96}, issuing @code{until 99} will execute the program up to
5470 line @code{99} in the same invocation of factorial, i.e., after the inner
5471 invocations have returned.
5474 94 int factorial (int value)
5476 96 if (value > 1) @{
5477 97 value *= factorial (value - 1);
5484 @kindex advance @var{location}
5485 @item advance @var{location}
5486 Continue running the program up to the given @var{location}. An argument is
5487 required, which should be of one of the forms described in
5488 @ref{Specify Location}.
5489 Execution will also stop upon exit from the current stack
5490 frame. This command is similar to @code{until}, but @code{advance} will
5491 not skip over recursive function calls, and the target location doesn't
5492 have to be in the same frame as the current one.
5496 @kindex si @r{(@code{stepi})}
5498 @itemx stepi @var{arg}
5500 Execute one machine instruction, then stop and return to the debugger.
5502 It is often useful to do @samp{display/i $pc} when stepping by machine
5503 instructions. This makes @value{GDBN} automatically display the next
5504 instruction to be executed, each time your program stops. @xref{Auto
5505 Display,, Automatic Display}.
5507 An argument is a repeat count, as in @code{step}.
5511 @kindex ni @r{(@code{nexti})}
5513 @itemx nexti @var{arg}
5515 Execute one machine instruction, but if it is a function call,
5516 proceed until the function returns.
5518 An argument is a repeat count, as in @code{next}.
5522 @anchor{range stepping}
5523 @cindex range stepping
5524 @cindex target-assisted range stepping
5525 By default, and if available, @value{GDBN} makes use of
5526 target-assisted @dfn{range stepping}. In other words, whenever you
5527 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5528 tells the target to step the corresponding range of instruction
5529 addresses instead of issuing multiple single-steps. This speeds up
5530 line stepping, particularly for remote targets. Ideally, there should
5531 be no reason you would want to turn range stepping off. However, it's
5532 possible that a bug in the debug info, a bug in the remote stub (for
5533 remote targets), or even a bug in @value{GDBN} could make line
5534 stepping behave incorrectly when target-assisted range stepping is
5535 enabled. You can use the following command to turn off range stepping
5539 @kindex set range-stepping
5540 @kindex show range-stepping
5541 @item set range-stepping
5542 @itemx show range-stepping
5543 Control whether range stepping is enabled.
5545 If @code{on}, and the target supports it, @value{GDBN} tells the
5546 target to step a range of addresses itself, instead of issuing
5547 multiple single-steps. If @code{off}, @value{GDBN} always issues
5548 single-steps, even if range stepping is supported by the target. The
5549 default is @code{on}.
5553 @node Skipping Over Functions and Files
5554 @section Skipping Over Functions and Files
5555 @cindex skipping over functions and files
5557 The program you are debugging may contain some functions which are
5558 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5559 skip a function, all functions in a file or a particular function in
5560 a particular file when stepping.
5562 For example, consider the following C function:
5573 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5574 are not interested in stepping through @code{boring}. If you run @code{step}
5575 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5576 step over both @code{foo} and @code{boring}!
5578 One solution is to @code{step} into @code{boring} and use the @code{finish}
5579 command to immediately exit it. But this can become tedious if @code{boring}
5580 is called from many places.
5582 A more flexible solution is to execute @kbd{skip boring}. This instructs
5583 @value{GDBN} never to step into @code{boring}. Now when you execute
5584 @code{step} at line 103, you'll step over @code{boring} and directly into
5587 Functions may be skipped by providing either a function name, linespec
5588 (@pxref{Specify Location}), regular expression that matches the function's
5589 name, file name or a @code{glob}-style pattern that matches the file name.
5591 On Posix systems the form of the regular expression is
5592 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5593 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5594 expression is whatever is provided by the @code{regcomp} function of
5595 the underlying system.
5596 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5597 description of @code{glob}-style patterns.
5601 @item skip @r{[}@var{options}@r{]}
5602 The basic form of the @code{skip} command takes zero or more options
5603 that specify what to skip.
5604 The @var{options} argument is any useful combination of the following:
5607 @item -file @var{file}
5608 @itemx -fi @var{file}
5609 Functions in @var{file} will be skipped over when stepping.
5611 @item -gfile @var{file-glob-pattern}
5612 @itemx -gfi @var{file-glob-pattern}
5613 @cindex skipping over files via glob-style patterns
5614 Functions in files matching @var{file-glob-pattern} will be skipped
5618 (gdb) skip -gfi utils/*.c
5621 @item -function @var{linespec}
5622 @itemx -fu @var{linespec}
5623 Functions named by @var{linespec} or the function containing the line
5624 named by @var{linespec} will be skipped over when stepping.
5625 @xref{Specify Location}.
5627 @item -rfunction @var{regexp}
5628 @itemx -rfu @var{regexp}
5629 @cindex skipping over functions via regular expressions
5630 Functions whose name matches @var{regexp} will be skipped over when stepping.
5632 This form is useful for complex function names.
5633 For example, there is generally no need to step into C@t{++} @code{std::string}
5634 constructors or destructors. Plus with C@t{++} templates it can be hard to
5635 write out the full name of the function, and often it doesn't matter what
5636 the template arguments are. Specifying the function to be skipped as a
5637 regular expression makes this easier.
5640 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5643 If you want to skip every templated C@t{++} constructor and destructor
5644 in the @code{std} namespace you can do:
5647 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5651 If no options are specified, the function you're currently debugging
5654 @kindex skip function
5655 @item skip function @r{[}@var{linespec}@r{]}
5656 After running this command, the function named by @var{linespec} or the
5657 function containing the line named by @var{linespec} will be skipped over when
5658 stepping. @xref{Specify Location}.
5660 If you do not specify @var{linespec}, the function you're currently debugging
5663 (If you have a function called @code{file} that you want to skip, use
5664 @kbd{skip function file}.)
5667 @item skip file @r{[}@var{filename}@r{]}
5668 After running this command, any function whose source lives in @var{filename}
5669 will be skipped over when stepping.
5672 (gdb) skip file boring.c
5673 File boring.c will be skipped when stepping.
5676 If you do not specify @var{filename}, functions whose source lives in the file
5677 you're currently debugging will be skipped.
5680 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5681 These are the commands for managing your list of skips:
5685 @item info skip @r{[}@var{range}@r{]}
5686 Print details about the specified skip(s). If @var{range} is not specified,
5687 print a table with details about all functions and files marked for skipping.
5688 @code{info skip} prints the following information about each skip:
5692 A number identifying this skip.
5693 @item Enabled or Disabled
5694 Enabled skips are marked with @samp{y}.
5695 Disabled skips are marked with @samp{n}.
5697 If the file name is a @samp{glob} pattern this is @samp{y}.
5698 Otherwise it is @samp{n}.
5700 The name or @samp{glob} pattern of the file to be skipped.
5701 If no file is specified this is @samp{<none>}.
5703 If the function name is a @samp{regular expression} this is @samp{y}.
5704 Otherwise it is @samp{n}.
5706 The name or regular expression of the function to skip.
5707 If no function is specified this is @samp{<none>}.
5711 @item skip delete @r{[}@var{range}@r{]}
5712 Delete the specified skip(s). If @var{range} is not specified, delete all
5716 @item skip enable @r{[}@var{range}@r{]}
5717 Enable the specified skip(s). If @var{range} is not specified, enable all
5720 @kindex skip disable
5721 @item skip disable @r{[}@var{range}@r{]}
5722 Disable the specified skip(s). If @var{range} is not specified, disable all
5731 A signal is an asynchronous event that can happen in a program. The
5732 operating system defines the possible kinds of signals, and gives each
5733 kind a name and a number. For example, in Unix @code{SIGINT} is the
5734 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5735 @code{SIGSEGV} is the signal a program gets from referencing a place in
5736 memory far away from all the areas in use; @code{SIGALRM} occurs when
5737 the alarm clock timer goes off (which happens only if your program has
5738 requested an alarm).
5740 @cindex fatal signals
5741 Some signals, including @code{SIGALRM}, are a normal part of the
5742 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5743 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5744 program has not specified in advance some other way to handle the signal.
5745 @code{SIGINT} does not indicate an error in your program, but it is normally
5746 fatal so it can carry out the purpose of the interrupt: to kill the program.
5748 @value{GDBN} has the ability to detect any occurrence of a signal in your
5749 program. You can tell @value{GDBN} in advance what to do for each kind of
5752 @cindex handling signals
5753 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5754 @code{SIGALRM} be silently passed to your program
5755 (so as not to interfere with their role in the program's functioning)
5756 but to stop your program immediately whenever an error signal happens.
5757 You can change these settings with the @code{handle} command.
5760 @kindex info signals
5764 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5765 handle each one. You can use this to see the signal numbers of all
5766 the defined types of signals.
5768 @item info signals @var{sig}
5769 Similar, but print information only about the specified signal number.
5771 @code{info handle} is an alias for @code{info signals}.
5773 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5774 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5775 for details about this command.
5778 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5779 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5780 can be the number of a signal or its name (with or without the
5781 @samp{SIG} at the beginning); a list of signal numbers of the form
5782 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5783 known signals. Optional arguments @var{keywords}, described below,
5784 say what change to make.
5788 The keywords allowed by the @code{handle} command can be abbreviated.
5789 Their full names are:
5793 @value{GDBN} should not stop your program when this signal happens. It may
5794 still print a message telling you that the signal has come in.
5797 @value{GDBN} should stop your program when this signal happens. This implies
5798 the @code{print} keyword as well.
5801 @value{GDBN} should print a message when this signal happens.
5804 @value{GDBN} should not mention the occurrence of the signal at all. This
5805 implies the @code{nostop} keyword as well.
5809 @value{GDBN} should allow your program to see this signal; your program
5810 can handle the signal, or else it may terminate if the signal is fatal
5811 and not handled. @code{pass} and @code{noignore} are synonyms.
5815 @value{GDBN} should not allow your program to see this signal.
5816 @code{nopass} and @code{ignore} are synonyms.
5820 When a signal stops your program, the signal is not visible to the
5822 continue. Your program sees the signal then, if @code{pass} is in
5823 effect for the signal in question @emph{at that time}. In other words,
5824 after @value{GDBN} reports a signal, you can use the @code{handle}
5825 command with @code{pass} or @code{nopass} to control whether your
5826 program sees that signal when you continue.
5828 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5829 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5830 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5833 You can also use the @code{signal} command to prevent your program from
5834 seeing a signal, or cause it to see a signal it normally would not see,
5835 or to give it any signal at any time. For example, if your program stopped
5836 due to some sort of memory reference error, you might store correct
5837 values into the erroneous variables and continue, hoping to see more
5838 execution; but your program would probably terminate immediately as
5839 a result of the fatal signal once it saw the signal. To prevent this,
5840 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5843 @cindex stepping and signal handlers
5844 @anchor{stepping and signal handlers}
5846 @value{GDBN} optimizes for stepping the mainline code. If a signal
5847 that has @code{handle nostop} and @code{handle pass} set arrives while
5848 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5849 in progress, @value{GDBN} lets the signal handler run and then resumes
5850 stepping the mainline code once the signal handler returns. In other
5851 words, @value{GDBN} steps over the signal handler. This prevents
5852 signals that you've specified as not interesting (with @code{handle
5853 nostop}) from changing the focus of debugging unexpectedly. Note that
5854 the signal handler itself may still hit a breakpoint, stop for another
5855 signal that has @code{handle stop} in effect, or for any other event
5856 that normally results in stopping the stepping command sooner. Also
5857 note that @value{GDBN} still informs you that the program received a
5858 signal if @code{handle print} is set.
5860 @anchor{stepping into signal handlers}
5862 If you set @code{handle pass} for a signal, and your program sets up a
5863 handler for it, then issuing a stepping command, such as @code{step}
5864 or @code{stepi}, when your program is stopped due to the signal will
5865 step @emph{into} the signal handler (if the target supports that).
5867 Likewise, if you use the @code{queue-signal} command to queue a signal
5868 to be delivered to the current thread when execution of the thread
5869 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5870 stepping command will step into the signal handler.
5872 Here's an example, using @code{stepi} to step to the first instruction
5873 of @code{SIGUSR1}'s handler:
5876 (@value{GDBP}) handle SIGUSR1
5877 Signal Stop Print Pass to program Description
5878 SIGUSR1 Yes Yes Yes User defined signal 1
5882 Program received signal SIGUSR1, User defined signal 1.
5883 main () sigusr1.c:28
5886 sigusr1_handler () at sigusr1.c:9
5890 The same, but using @code{queue-signal} instead of waiting for the
5891 program to receive the signal first:
5896 (@value{GDBP}) queue-signal SIGUSR1
5898 sigusr1_handler () at sigusr1.c:9
5903 @cindex extra signal information
5904 @anchor{extra signal information}
5906 On some targets, @value{GDBN} can inspect extra signal information
5907 associated with the intercepted signal, before it is actually
5908 delivered to the program being debugged. This information is exported
5909 by the convenience variable @code{$_siginfo}, and consists of data
5910 that is passed by the kernel to the signal handler at the time of the
5911 receipt of a signal. The data type of the information itself is
5912 target dependent. You can see the data type using the @code{ptype
5913 $_siginfo} command. On Unix systems, it typically corresponds to the
5914 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5917 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5918 referenced address that raised a segmentation fault.
5922 (@value{GDBP}) continue
5923 Program received signal SIGSEGV, Segmentation fault.
5924 0x0000000000400766 in main ()
5926 (@value{GDBP}) ptype $_siginfo
5933 struct @{...@} _kill;
5934 struct @{...@} _timer;
5936 struct @{...@} _sigchld;
5937 struct @{...@} _sigfault;
5938 struct @{...@} _sigpoll;
5941 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5945 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5946 $1 = (void *) 0x7ffff7ff7000
5950 Depending on target support, @code{$_siginfo} may also be writable.
5952 @cindex Intel MPX boundary violations
5953 @cindex boundary violations, Intel MPX
5954 On some targets, a @code{SIGSEGV} can be caused by a boundary
5955 violation, i.e., accessing an address outside of the allowed range.
5956 In those cases @value{GDBN} may displays additional information,
5957 depending on how @value{GDBN} has been told to handle the signal.
5958 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5959 kind: "Upper" or "Lower", the memory address accessed and the
5960 bounds, while with @code{handle nostop SIGSEGV} no additional
5961 information is displayed.
5963 The usual output of a segfault is:
5965 Program received signal SIGSEGV, Segmentation fault
5966 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5967 68 value = *(p + len);
5970 While a bound violation is presented as:
5972 Program received signal SIGSEGV, Segmentation fault
5973 Upper bound violation while accessing address 0x7fffffffc3b3
5974 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5975 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5976 68 value = *(p + len);
5980 @section Stopping and Starting Multi-thread Programs
5982 @cindex stopped threads
5983 @cindex threads, stopped
5985 @cindex continuing threads
5986 @cindex threads, continuing
5988 @value{GDBN} supports debugging programs with multiple threads
5989 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5990 are two modes of controlling execution of your program within the
5991 debugger. In the default mode, referred to as @dfn{all-stop mode},
5992 when any thread in your program stops (for example, at a breakpoint
5993 or while being stepped), all other threads in the program are also stopped by
5994 @value{GDBN}. On some targets, @value{GDBN} also supports
5995 @dfn{non-stop mode}, in which other threads can continue to run freely while
5996 you examine the stopped thread in the debugger.
5999 * All-Stop Mode:: All threads stop when GDB takes control
6000 * Non-Stop Mode:: Other threads continue to execute
6001 * Background Execution:: Running your program asynchronously
6002 * Thread-Specific Breakpoints:: Controlling breakpoints
6003 * Interrupted System Calls:: GDB may interfere with system calls
6004 * Observer Mode:: GDB does not alter program behavior
6008 @subsection All-Stop Mode
6010 @cindex all-stop mode
6012 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6013 @emph{all} threads of execution stop, not just the current thread. This
6014 allows you to examine the overall state of the program, including
6015 switching between threads, without worrying that things may change
6018 Conversely, whenever you restart the program, @emph{all} threads start
6019 executing. @emph{This is true even when single-stepping} with commands
6020 like @code{step} or @code{next}.
6022 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6023 Since thread scheduling is up to your debugging target's operating
6024 system (not controlled by @value{GDBN}), other threads may
6025 execute more than one statement while the current thread completes a
6026 single step. Moreover, in general other threads stop in the middle of a
6027 statement, rather than at a clean statement boundary, when the program
6030 You might even find your program stopped in another thread after
6031 continuing or even single-stepping. This happens whenever some other
6032 thread runs into a breakpoint, a signal, or an exception before the
6033 first thread completes whatever you requested.
6035 @cindex automatic thread selection
6036 @cindex switching threads automatically
6037 @cindex threads, automatic switching
6038 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6039 signal, it automatically selects the thread where that breakpoint or
6040 signal happened. @value{GDBN} alerts you to the context switch with a
6041 message such as @samp{[Switching to Thread @var{n}]} to identify the
6044 On some OSes, you can modify @value{GDBN}'s default behavior by
6045 locking the OS scheduler to allow only a single thread to run.
6048 @item set scheduler-locking @var{mode}
6049 @cindex scheduler locking mode
6050 @cindex lock scheduler
6051 Set the scheduler locking mode. It applies to normal execution,
6052 record mode, and replay mode. If it is @code{off}, then there is no
6053 locking and any thread may run at any time. If @code{on}, then only
6054 the current thread may run when the inferior is resumed. The
6055 @code{step} mode optimizes for single-stepping; it prevents other
6056 threads from preempting the current thread while you are stepping, so
6057 that the focus of debugging does not change unexpectedly. Other
6058 threads never get a chance to run when you step, and they are
6059 completely free to run when you use commands like @samp{continue},
6060 @samp{until}, or @samp{finish}. However, unless another thread hits a
6061 breakpoint during its timeslice, @value{GDBN} does not change the
6062 current thread away from the thread that you are debugging. The
6063 @code{replay} mode behaves like @code{off} in record mode and like
6064 @code{on} in replay mode.
6066 @item show scheduler-locking
6067 Display the current scheduler locking mode.
6070 @cindex resume threads of multiple processes simultaneously
6071 By default, when you issue one of the execution commands such as
6072 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6073 threads of the current inferior to run. For example, if @value{GDBN}
6074 is attached to two inferiors, each with two threads, the
6075 @code{continue} command resumes only the two threads of the current
6076 inferior. This is useful, for example, when you debug a program that
6077 forks and you want to hold the parent stopped (so that, for instance,
6078 it doesn't run to exit), while you debug the child. In other
6079 situations, you may not be interested in inspecting the current state
6080 of any of the processes @value{GDBN} is attached to, and you may want
6081 to resume them all until some breakpoint is hit. In the latter case,
6082 you can instruct @value{GDBN} to allow all threads of all the
6083 inferiors to run with the @w{@code{set schedule-multiple}} command.
6086 @kindex set schedule-multiple
6087 @item set schedule-multiple
6088 Set the mode for allowing threads of multiple processes to be resumed
6089 when an execution command is issued. When @code{on}, all threads of
6090 all processes are allowed to run. When @code{off}, only the threads
6091 of the current process are resumed. The default is @code{off}. The
6092 @code{scheduler-locking} mode takes precedence when set to @code{on},
6093 or while you are stepping and set to @code{step}.
6095 @item show schedule-multiple
6096 Display the current mode for resuming the execution of threads of
6101 @subsection Non-Stop Mode
6103 @cindex non-stop mode
6105 @c This section is really only a place-holder, and needs to be expanded
6106 @c with more details.
6108 For some multi-threaded targets, @value{GDBN} supports an optional
6109 mode of operation in which you can examine stopped program threads in
6110 the debugger while other threads continue to execute freely. This
6111 minimizes intrusion when debugging live systems, such as programs
6112 where some threads have real-time constraints or must continue to
6113 respond to external events. This is referred to as @dfn{non-stop} mode.
6115 In non-stop mode, when a thread stops to report a debugging event,
6116 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6117 threads as well, in contrast to the all-stop mode behavior. Additionally,
6118 execution commands such as @code{continue} and @code{step} apply by default
6119 only to the current thread in non-stop mode, rather than all threads as
6120 in all-stop mode. This allows you to control threads explicitly in
6121 ways that are not possible in all-stop mode --- for example, stepping
6122 one thread while allowing others to run freely, stepping
6123 one thread while holding all others stopped, or stepping several threads
6124 independently and simultaneously.
6126 To enter non-stop mode, use this sequence of commands before you run
6127 or attach to your program:
6130 # If using the CLI, pagination breaks non-stop.
6133 # Finally, turn it on!
6137 You can use these commands to manipulate the non-stop mode setting:
6140 @kindex set non-stop
6141 @item set non-stop on
6142 Enable selection of non-stop mode.
6143 @item set non-stop off
6144 Disable selection of non-stop mode.
6145 @kindex show non-stop
6147 Show the current non-stop enablement setting.
6150 Note these commands only reflect whether non-stop mode is enabled,
6151 not whether the currently-executing program is being run in non-stop mode.
6152 In particular, the @code{set non-stop} preference is only consulted when
6153 @value{GDBN} starts or connects to the target program, and it is generally
6154 not possible to switch modes once debugging has started. Furthermore,
6155 since not all targets support non-stop mode, even when you have enabled
6156 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6159 In non-stop mode, all execution commands apply only to the current thread
6160 by default. That is, @code{continue} only continues one thread.
6161 To continue all threads, issue @code{continue -a} or @code{c -a}.
6163 You can use @value{GDBN}'s background execution commands
6164 (@pxref{Background Execution}) to run some threads in the background
6165 while you continue to examine or step others from @value{GDBN}.
6166 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6167 always executed asynchronously in non-stop mode.
6169 Suspending execution is done with the @code{interrupt} command when
6170 running in the background, or @kbd{Ctrl-c} during foreground execution.
6171 In all-stop mode, this stops the whole process;
6172 but in non-stop mode the interrupt applies only to the current thread.
6173 To stop the whole program, use @code{interrupt -a}.
6175 Other execution commands do not currently support the @code{-a} option.
6177 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6178 that thread current, as it does in all-stop mode. This is because the
6179 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6180 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6181 changed to a different thread just as you entered a command to operate on the
6182 previously current thread.
6184 @node Background Execution
6185 @subsection Background Execution
6187 @cindex foreground execution
6188 @cindex background execution
6189 @cindex asynchronous execution
6190 @cindex execution, foreground, background and asynchronous
6192 @value{GDBN}'s execution commands have two variants: the normal
6193 foreground (synchronous) behavior, and a background
6194 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6195 the program to report that some thread has stopped before prompting for
6196 another command. In background execution, @value{GDBN} immediately gives
6197 a command prompt so that you can issue other commands while your program runs.
6199 If the target doesn't support async mode, @value{GDBN} issues an error
6200 message if you attempt to use the background execution commands.
6202 To specify background execution, add a @code{&} to the command. For example,
6203 the background form of the @code{continue} command is @code{continue&}, or
6204 just @code{c&}. The execution commands that accept background execution
6210 @xref{Starting, , Starting your Program}.
6214 @xref{Attach, , Debugging an Already-running Process}.
6218 @xref{Continuing and Stepping, step}.
6222 @xref{Continuing and Stepping, stepi}.
6226 @xref{Continuing and Stepping, next}.
6230 @xref{Continuing and Stepping, nexti}.
6234 @xref{Continuing and Stepping, continue}.
6238 @xref{Continuing and Stepping, finish}.
6242 @xref{Continuing and Stepping, until}.
6246 Background execution is especially useful in conjunction with non-stop
6247 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6248 However, you can also use these commands in the normal all-stop mode with
6249 the restriction that you cannot issue another execution command until the
6250 previous one finishes. Examples of commands that are valid in all-stop
6251 mode while the program is running include @code{help} and @code{info break}.
6253 You can interrupt your program while it is running in the background by
6254 using the @code{interrupt} command.
6261 Suspend execution of the running program. In all-stop mode,
6262 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6263 only the current thread. To stop the whole program in non-stop mode,
6264 use @code{interrupt -a}.
6267 @node Thread-Specific Breakpoints
6268 @subsection Thread-Specific Breakpoints
6270 When your program has multiple threads (@pxref{Threads,, Debugging
6271 Programs with Multiple Threads}), you can choose whether to set
6272 breakpoints on all threads, or on a particular thread.
6275 @cindex breakpoints and threads
6276 @cindex thread breakpoints
6277 @kindex break @dots{} thread @var{thread-id}
6278 @item break @var{location} thread @var{thread-id}
6279 @itemx break @var{location} thread @var{thread-id} if @dots{}
6280 @var{location} specifies source lines; there are several ways of
6281 writing them (@pxref{Specify Location}), but the effect is always to
6282 specify some source line.
6284 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6285 to specify that you only want @value{GDBN} to stop the program when a
6286 particular thread reaches this breakpoint. The @var{thread-id} specifier
6287 is one of the thread identifiers assigned by @value{GDBN}, shown
6288 in the first column of the @samp{info threads} display.
6290 If you do not specify @samp{thread @var{thread-id}} when you set a
6291 breakpoint, the breakpoint applies to @emph{all} threads of your
6294 You can use the @code{thread} qualifier on conditional breakpoints as
6295 well; in this case, place @samp{thread @var{thread-id}} before or
6296 after the breakpoint condition, like this:
6299 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6304 Thread-specific breakpoints are automatically deleted when
6305 @value{GDBN} detects the corresponding thread is no longer in the
6306 thread list. For example:
6310 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6313 There are several ways for a thread to disappear, such as a regular
6314 thread exit, but also when you detach from the process with the
6315 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6316 Process}), or if @value{GDBN} loses the remote connection
6317 (@pxref{Remote Debugging}), etc. Note that with some targets,
6318 @value{GDBN} is only able to detect a thread has exited when the user
6319 explictly asks for the thread list with the @code{info threads}
6322 @node Interrupted System Calls
6323 @subsection Interrupted System Calls
6325 @cindex thread breakpoints and system calls
6326 @cindex system calls and thread breakpoints
6327 @cindex premature return from system calls
6328 There is an unfortunate side effect when using @value{GDBN} to debug
6329 multi-threaded programs. If one thread stops for a
6330 breakpoint, or for some other reason, and another thread is blocked in a
6331 system call, then the system call may return prematurely. This is a
6332 consequence of the interaction between multiple threads and the signals
6333 that @value{GDBN} uses to implement breakpoints and other events that
6336 To handle this problem, your program should check the return value of
6337 each system call and react appropriately. This is good programming
6340 For example, do not write code like this:
6346 The call to @code{sleep} will return early if a different thread stops
6347 at a breakpoint or for some other reason.
6349 Instead, write this:
6354 unslept = sleep (unslept);
6357 A system call is allowed to return early, so the system is still
6358 conforming to its specification. But @value{GDBN} does cause your
6359 multi-threaded program to behave differently than it would without
6362 Also, @value{GDBN} uses internal breakpoints in the thread library to
6363 monitor certain events such as thread creation and thread destruction.
6364 When such an event happens, a system call in another thread may return
6365 prematurely, even though your program does not appear to stop.
6368 @subsection Observer Mode
6370 If you want to build on non-stop mode and observe program behavior
6371 without any chance of disruption by @value{GDBN}, you can set
6372 variables to disable all of the debugger's attempts to modify state,
6373 whether by writing memory, inserting breakpoints, etc. These operate
6374 at a low level, intercepting operations from all commands.
6376 When all of these are set to @code{off}, then @value{GDBN} is said to
6377 be @dfn{observer mode}. As a convenience, the variable
6378 @code{observer} can be set to disable these, plus enable non-stop
6381 Note that @value{GDBN} will not prevent you from making nonsensical
6382 combinations of these settings. For instance, if you have enabled
6383 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6384 then breakpoints that work by writing trap instructions into the code
6385 stream will still not be able to be placed.
6390 @item set observer on
6391 @itemx set observer off
6392 When set to @code{on}, this disables all the permission variables
6393 below (except for @code{insert-fast-tracepoints}), plus enables
6394 non-stop debugging. Setting this to @code{off} switches back to
6395 normal debugging, though remaining in non-stop mode.
6398 Show whether observer mode is on or off.
6400 @kindex may-write-registers
6401 @item set may-write-registers on
6402 @itemx set may-write-registers off
6403 This controls whether @value{GDBN} will attempt to alter the values of
6404 registers, such as with assignment expressions in @code{print}, or the
6405 @code{jump} command. It defaults to @code{on}.
6407 @item show may-write-registers
6408 Show the current permission to write registers.
6410 @kindex may-write-memory
6411 @item set may-write-memory on
6412 @itemx set may-write-memory off
6413 This controls whether @value{GDBN} will attempt to alter the contents
6414 of memory, such as with assignment expressions in @code{print}. It
6415 defaults to @code{on}.
6417 @item show may-write-memory
6418 Show the current permission to write memory.
6420 @kindex may-insert-breakpoints
6421 @item set may-insert-breakpoints on
6422 @itemx set may-insert-breakpoints off
6423 This controls whether @value{GDBN} will attempt to insert breakpoints.
6424 This affects all breakpoints, including internal breakpoints defined
6425 by @value{GDBN}. It defaults to @code{on}.
6427 @item show may-insert-breakpoints
6428 Show the current permission to insert breakpoints.
6430 @kindex may-insert-tracepoints
6431 @item set may-insert-tracepoints on
6432 @itemx set may-insert-tracepoints off
6433 This controls whether @value{GDBN} will attempt to insert (regular)
6434 tracepoints at the beginning of a tracing experiment. It affects only
6435 non-fast tracepoints, fast tracepoints being under the control of
6436 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6438 @item show may-insert-tracepoints
6439 Show the current permission to insert tracepoints.
6441 @kindex may-insert-fast-tracepoints
6442 @item set may-insert-fast-tracepoints on
6443 @itemx set may-insert-fast-tracepoints off
6444 This controls whether @value{GDBN} will attempt to insert fast
6445 tracepoints at the beginning of a tracing experiment. It affects only
6446 fast tracepoints, regular (non-fast) tracepoints being under the
6447 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6449 @item show may-insert-fast-tracepoints
6450 Show the current permission to insert fast tracepoints.
6452 @kindex may-interrupt
6453 @item set may-interrupt on
6454 @itemx set may-interrupt off
6455 This controls whether @value{GDBN} will attempt to interrupt or stop
6456 program execution. When this variable is @code{off}, the
6457 @code{interrupt} command will have no effect, nor will
6458 @kbd{Ctrl-c}. It defaults to @code{on}.
6460 @item show may-interrupt
6461 Show the current permission to interrupt or stop the program.
6465 @node Reverse Execution
6466 @chapter Running programs backward
6467 @cindex reverse execution
6468 @cindex running programs backward
6470 When you are debugging a program, it is not unusual to realize that
6471 you have gone too far, and some event of interest has already happened.
6472 If the target environment supports it, @value{GDBN} can allow you to
6473 ``rewind'' the program by running it backward.
6475 A target environment that supports reverse execution should be able
6476 to ``undo'' the changes in machine state that have taken place as the
6477 program was executing normally. Variables, registers etc.@: should
6478 revert to their previous values. Obviously this requires a great
6479 deal of sophistication on the part of the target environment; not
6480 all target environments can support reverse execution.
6482 When a program is executed in reverse, the instructions that
6483 have most recently been executed are ``un-executed'', in reverse
6484 order. The program counter runs backward, following the previous
6485 thread of execution in reverse. As each instruction is ``un-executed'',
6486 the values of memory and/or registers that were changed by that
6487 instruction are reverted to their previous states. After executing
6488 a piece of source code in reverse, all side effects of that code
6489 should be ``undone'', and all variables should be returned to their
6490 prior values@footnote{
6491 Note that some side effects are easier to undo than others. For instance,
6492 memory and registers are relatively easy, but device I/O is hard. Some
6493 targets may be able undo things like device I/O, and some may not.
6495 The contract between @value{GDBN} and the reverse executing target
6496 requires only that the target do something reasonable when
6497 @value{GDBN} tells it to execute backwards, and then report the
6498 results back to @value{GDBN}. Whatever the target reports back to
6499 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6500 assumes that the memory and registers that the target reports are in a
6501 consistant state, but @value{GDBN} accepts whatever it is given.
6504 If you are debugging in a target environment that supports
6505 reverse execution, @value{GDBN} provides the following commands.
6508 @kindex reverse-continue
6509 @kindex rc @r{(@code{reverse-continue})}
6510 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6511 @itemx rc @r{[}@var{ignore-count}@r{]}
6512 Beginning at the point where your program last stopped, start executing
6513 in reverse. Reverse execution will stop for breakpoints and synchronous
6514 exceptions (signals), just like normal execution. Behavior of
6515 asynchronous signals depends on the target environment.
6517 @kindex reverse-step
6518 @kindex rs @r{(@code{step})}
6519 @item reverse-step @r{[}@var{count}@r{]}
6520 Run the program backward until control reaches the start of a
6521 different source line; then stop it, and return control to @value{GDBN}.
6523 Like the @code{step} command, @code{reverse-step} will only stop
6524 at the beginning of a source line. It ``un-executes'' the previously
6525 executed source line. If the previous source line included calls to
6526 debuggable functions, @code{reverse-step} will step (backward) into
6527 the called function, stopping at the beginning of the @emph{last}
6528 statement in the called function (typically a return statement).
6530 Also, as with the @code{step} command, if non-debuggable functions are
6531 called, @code{reverse-step} will run thru them backward without stopping.
6533 @kindex reverse-stepi
6534 @kindex rsi @r{(@code{reverse-stepi})}
6535 @item reverse-stepi @r{[}@var{count}@r{]}
6536 Reverse-execute one machine instruction. Note that the instruction
6537 to be reverse-executed is @emph{not} the one pointed to by the program
6538 counter, but the instruction executed prior to that one. For instance,
6539 if the last instruction was a jump, @code{reverse-stepi} will take you
6540 back from the destination of the jump to the jump instruction itself.
6542 @kindex reverse-next
6543 @kindex rn @r{(@code{reverse-next})}
6544 @item reverse-next @r{[}@var{count}@r{]}
6545 Run backward to the beginning of the previous line executed in
6546 the current (innermost) stack frame. If the line contains function
6547 calls, they will be ``un-executed'' without stopping. Starting from
6548 the first line of a function, @code{reverse-next} will take you back
6549 to the caller of that function, @emph{before} the function was called,
6550 just as the normal @code{next} command would take you from the last
6551 line of a function back to its return to its caller
6552 @footnote{Unless the code is too heavily optimized.}.
6554 @kindex reverse-nexti
6555 @kindex rni @r{(@code{reverse-nexti})}
6556 @item reverse-nexti @r{[}@var{count}@r{]}
6557 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6558 in reverse, except that called functions are ``un-executed'' atomically.
6559 That is, if the previously executed instruction was a return from
6560 another function, @code{reverse-nexti} will continue to execute
6561 in reverse until the call to that function (from the current stack
6564 @kindex reverse-finish
6565 @item reverse-finish
6566 Just as the @code{finish} command takes you to the point where the
6567 current function returns, @code{reverse-finish} takes you to the point
6568 where it was called. Instead of ending up at the end of the current
6569 function invocation, you end up at the beginning.
6571 @kindex set exec-direction
6572 @item set exec-direction
6573 Set the direction of target execution.
6574 @item set exec-direction reverse
6575 @cindex execute forward or backward in time
6576 @value{GDBN} will perform all execution commands in reverse, until the
6577 exec-direction mode is changed to ``forward''. Affected commands include
6578 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6579 command cannot be used in reverse mode.
6580 @item set exec-direction forward
6581 @value{GDBN} will perform all execution commands in the normal fashion.
6582 This is the default.
6586 @node Process Record and Replay
6587 @chapter Recording Inferior's Execution and Replaying It
6588 @cindex process record and replay
6589 @cindex recording inferior's execution and replaying it
6591 On some platforms, @value{GDBN} provides a special @dfn{process record
6592 and replay} target that can record a log of the process execution, and
6593 replay it later with both forward and reverse execution commands.
6596 When this target is in use, if the execution log includes the record
6597 for the next instruction, @value{GDBN} will debug in @dfn{replay
6598 mode}. In the replay mode, the inferior does not really execute code
6599 instructions. Instead, all the events that normally happen during
6600 code execution are taken from the execution log. While code is not
6601 really executed in replay mode, the values of registers (including the
6602 program counter register) and the memory of the inferior are still
6603 changed as they normally would. Their contents are taken from the
6607 If the record for the next instruction is not in the execution log,
6608 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6609 inferior executes normally, and @value{GDBN} records the execution log
6612 The process record and replay target supports reverse execution
6613 (@pxref{Reverse Execution}), even if the platform on which the
6614 inferior runs does not. However, the reverse execution is limited in
6615 this case by the range of the instructions recorded in the execution
6616 log. In other words, reverse execution on platforms that don't
6617 support it directly can only be done in the replay mode.
6619 When debugging in the reverse direction, @value{GDBN} will work in
6620 replay mode as long as the execution log includes the record for the
6621 previous instruction; otherwise, it will work in record mode, if the
6622 platform supports reverse execution, or stop if not.
6624 For architecture environments that support process record and replay,
6625 @value{GDBN} provides the following commands:
6628 @kindex target record
6629 @kindex target record-full
6630 @kindex target record-btrace
6633 @kindex record btrace
6634 @kindex record btrace bts
6635 @kindex record btrace pt
6641 @kindex rec btrace bts
6642 @kindex rec btrace pt
6645 @item record @var{method}
6646 This command starts the process record and replay target. The
6647 recording method can be specified as parameter. Without a parameter
6648 the command uses the @code{full} recording method. The following
6649 recording methods are available:
6653 Full record/replay recording using @value{GDBN}'s software record and
6654 replay implementation. This method allows replaying and reverse
6657 @item btrace @var{format}
6658 Hardware-supported instruction recording. This method does not record
6659 data. Further, the data is collected in a ring buffer so old data will
6660 be overwritten when the buffer is full. It allows limited reverse
6661 execution. Variables and registers are not available during reverse
6662 execution. In remote debugging, recording continues on disconnect.
6663 Recorded data can be inspected after reconnecting. The recording may
6664 be stopped using @code{record stop}.
6666 The recording format can be specified as parameter. Without a parameter
6667 the command chooses the recording format. The following recording
6668 formats are available:
6672 @cindex branch trace store
6673 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6674 this format, the processor stores a from/to record for each executed
6675 branch in the btrace ring buffer.
6678 @cindex Intel Processor Trace
6679 Use the @dfn{Intel Processor Trace} recording format. In this
6680 format, the processor stores the execution trace in a compressed form
6681 that is afterwards decoded by @value{GDBN}.
6683 The trace can be recorded with very low overhead. The compressed
6684 trace format also allows small trace buffers to already contain a big
6685 number of instructions compared to @acronym{BTS}.
6687 Decoding the recorded execution trace, on the other hand, is more
6688 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6689 increased number of instructions to process. You should increase the
6690 buffer-size with care.
6693 Not all recording formats may be available on all processors.
6696 The process record and replay target can only debug a process that is
6697 already running. Therefore, you need first to start the process with
6698 the @kbd{run} or @kbd{start} commands, and then start the recording
6699 with the @kbd{record @var{method}} command.
6701 @cindex displaced stepping, and process record and replay
6702 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6703 will be automatically disabled when process record and replay target
6704 is started. That's because the process record and replay target
6705 doesn't support displaced stepping.
6707 @cindex non-stop mode, and process record and replay
6708 @cindex asynchronous execution, and process record and replay
6709 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6710 the asynchronous execution mode (@pxref{Background Execution}), not
6711 all recording methods are available. The @code{full} recording method
6712 does not support these two modes.
6717 Stop the process record and replay target. When process record and
6718 replay target stops, the entire execution log will be deleted and the
6719 inferior will either be terminated, or will remain in its final state.
6721 When you stop the process record and replay target in record mode (at
6722 the end of the execution log), the inferior will be stopped at the
6723 next instruction that would have been recorded. In other words, if
6724 you record for a while and then stop recording, the inferior process
6725 will be left in the same state as if the recording never happened.
6727 On the other hand, if the process record and replay target is stopped
6728 while in replay mode (that is, not at the end of the execution log,
6729 but at some earlier point), the inferior process will become ``live''
6730 at that earlier state, and it will then be possible to continue the
6731 usual ``live'' debugging of the process from that state.
6733 When the inferior process exits, or @value{GDBN} detaches from it,
6734 process record and replay target will automatically stop itself.
6738 Go to a specific location in the execution log. There are several
6739 ways to specify the location to go to:
6742 @item record goto begin
6743 @itemx record goto start
6744 Go to the beginning of the execution log.
6746 @item record goto end
6747 Go to the end of the execution log.
6749 @item record goto @var{n}
6750 Go to instruction number @var{n} in the execution log.
6754 @item record save @var{filename}
6755 Save the execution log to a file @file{@var{filename}}.
6756 Default filename is @file{gdb_record.@var{process_id}}, where
6757 @var{process_id} is the process ID of the inferior.
6759 This command may not be available for all recording methods.
6761 @kindex record restore
6762 @item record restore @var{filename}
6763 Restore the execution log from a file @file{@var{filename}}.
6764 File must have been created with @code{record save}.
6766 @kindex set record full
6767 @item set record full insn-number-max @var{limit}
6768 @itemx set record full insn-number-max unlimited
6769 Set the limit of instructions to be recorded for the @code{full}
6770 recording method. Default value is 200000.
6772 If @var{limit} is a positive number, then @value{GDBN} will start
6773 deleting instructions from the log once the number of the record
6774 instructions becomes greater than @var{limit}. For every new recorded
6775 instruction, @value{GDBN} will delete the earliest recorded
6776 instruction to keep the number of recorded instructions at the limit.
6777 (Since deleting recorded instructions loses information, @value{GDBN}
6778 lets you control what happens when the limit is reached, by means of
6779 the @code{stop-at-limit} option, described below.)
6781 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6782 delete recorded instructions from the execution log. The number of
6783 recorded instructions is limited only by the available memory.
6785 @kindex show record full
6786 @item show record full insn-number-max
6787 Show the limit of instructions to be recorded with the @code{full}
6790 @item set record full stop-at-limit
6791 Control the behavior of the @code{full} recording method when the
6792 number of recorded instructions reaches the limit. If ON (the
6793 default), @value{GDBN} will stop when the limit is reached for the
6794 first time and ask you whether you want to stop the inferior or
6795 continue running it and recording the execution log. If you decide
6796 to continue recording, each new recorded instruction will cause the
6797 oldest one to be deleted.
6799 If this option is OFF, @value{GDBN} will automatically delete the
6800 oldest record to make room for each new one, without asking.
6802 @item show record full stop-at-limit
6803 Show the current setting of @code{stop-at-limit}.
6805 @item set record full memory-query
6806 Control the behavior when @value{GDBN} is unable to record memory
6807 changes caused by an instruction for the @code{full} recording method.
6808 If ON, @value{GDBN} will query whether to stop the inferior in that
6811 If this option is OFF (the default), @value{GDBN} will automatically
6812 ignore the effect of such instructions on memory. Later, when
6813 @value{GDBN} replays this execution log, it will mark the log of this
6814 instruction as not accessible, and it will not affect the replay
6817 @item show record full memory-query
6818 Show the current setting of @code{memory-query}.
6820 @kindex set record btrace
6821 The @code{btrace} record target does not trace data. As a
6822 convenience, when replaying, @value{GDBN} reads read-only memory off
6823 the live program directly, assuming that the addresses of the
6824 read-only areas don't change. This for example makes it possible to
6825 disassemble code while replaying, but not to print variables.
6826 In some cases, being able to inspect variables might be useful.
6827 You can use the following command for that:
6829 @item set record btrace replay-memory-access
6830 Control the behavior of the @code{btrace} recording method when
6831 accessing memory during replay. If @code{read-only} (the default),
6832 @value{GDBN} will only allow accesses to read-only memory.
6833 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6834 and to read-write memory. Beware that the accessed memory corresponds
6835 to the live target and not necessarily to the current replay
6838 @kindex show record btrace
6839 @item show record btrace replay-memory-access
6840 Show the current setting of @code{replay-memory-access}.
6842 @kindex set record btrace bts
6843 @item set record btrace bts buffer-size @var{size}
6844 @itemx set record btrace bts buffer-size unlimited
6845 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6846 format. Default is 64KB.
6848 If @var{size} is a positive number, then @value{GDBN} will try to
6849 allocate a buffer of at least @var{size} bytes for each new thread
6850 that uses the btrace recording method and the @acronym{BTS} format.
6851 The actually obtained buffer size may differ from the requested
6852 @var{size}. Use the @code{info record} command to see the actual
6853 buffer size for each thread that uses the btrace recording method and
6854 the @acronym{BTS} format.
6856 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6857 allocate a buffer of 4MB.
6859 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6860 also need longer to process the branch trace data before it can be used.
6862 @item show record btrace bts buffer-size @var{size}
6863 Show the current setting of the requested ring buffer size for branch
6864 tracing in @acronym{BTS} format.
6866 @kindex set record btrace pt
6867 @item set record btrace pt buffer-size @var{size}
6868 @itemx set record btrace pt buffer-size unlimited
6869 Set the requested ring buffer size for branch tracing in Intel
6870 Processor Trace format. Default is 16KB.
6872 If @var{size} is a positive number, then @value{GDBN} will try to
6873 allocate a buffer of at least @var{size} bytes for each new thread
6874 that uses the btrace recording method and the Intel Processor Trace
6875 format. The actually obtained buffer size may differ from the
6876 requested @var{size}. Use the @code{info record} command to see the
6877 actual buffer size for each thread.
6879 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6880 allocate a buffer of 4MB.
6882 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6883 also need longer to process the branch trace data before it can be used.
6885 @item show record btrace pt buffer-size @var{size}
6886 Show the current setting of the requested ring buffer size for branch
6887 tracing in Intel Processor Trace format.
6891 Show various statistics about the recording depending on the recording
6896 For the @code{full} recording method, it shows the state of process
6897 record and its in-memory execution log buffer, including:
6901 Whether in record mode or replay mode.
6903 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6905 Highest recorded instruction number.
6907 Current instruction about to be replayed (if in replay mode).
6909 Number of instructions contained in the execution log.
6911 Maximum number of instructions that may be contained in the execution log.
6915 For the @code{btrace} recording method, it shows:
6921 Number of instructions that have been recorded.
6923 Number of blocks of sequential control-flow formed by the recorded
6926 Whether in record mode or replay mode.
6929 For the @code{bts} recording format, it also shows:
6932 Size of the perf ring buffer.
6935 For the @code{pt} recording format, it also shows:
6938 Size of the perf ring buffer.
6942 @kindex record delete
6945 When record target runs in replay mode (``in the past''), delete the
6946 subsequent execution log and begin to record a new execution log starting
6947 from the current address. This means you will abandon the previously
6948 recorded ``future'' and begin recording a new ``future''.
6950 @kindex record instruction-history
6951 @kindex rec instruction-history
6952 @item record instruction-history
6953 Disassembles instructions from the recorded execution log. By
6954 default, ten instructions are disassembled. This can be changed using
6955 the @code{set record instruction-history-size} command. Instructions
6956 are printed in execution order.
6958 It can also print mixed source+disassembly if you specify the the
6959 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6960 as well as in symbolic form by specifying the @code{/r} modifier.
6962 The current position marker is printed for the instruction at the
6963 current program counter value. This instruction can appear multiple
6964 times in the trace and the current position marker will be printed
6965 every time. To omit the current position marker, specify the
6968 To better align the printed instructions when the trace contains
6969 instructions from more than one function, the function name may be
6970 omitted by specifying the @code{/f} modifier.
6972 Speculatively executed instructions are prefixed with @samp{?}. This
6973 feature is not available for all recording formats.
6975 There are several ways to specify what part of the execution log to
6979 @item record instruction-history @var{insn}
6980 Disassembles ten instructions starting from instruction number
6983 @item record instruction-history @var{insn}, +/-@var{n}
6984 Disassembles @var{n} instructions around instruction number
6985 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6986 @var{n} instructions after instruction number @var{insn}. If
6987 @var{n} is preceded with @code{-}, disassembles @var{n}
6988 instructions before instruction number @var{insn}.
6990 @item record instruction-history
6991 Disassembles ten more instructions after the last disassembly.
6993 @item record instruction-history -
6994 Disassembles ten more instructions before the last disassembly.
6996 @item record instruction-history @var{begin}, @var{end}
6997 Disassembles instructions beginning with instruction number
6998 @var{begin} until instruction number @var{end}. The instruction
6999 number @var{end} is included.
7002 This command may not be available for all recording methods.
7005 @item set record instruction-history-size @var{size}
7006 @itemx set record instruction-history-size unlimited
7007 Define how many instructions to disassemble in the @code{record
7008 instruction-history} command. The default value is 10.
7009 A @var{size} of @code{unlimited} means unlimited instructions.
7012 @item show record instruction-history-size
7013 Show how many instructions to disassemble in the @code{record
7014 instruction-history} command.
7016 @kindex record function-call-history
7017 @kindex rec function-call-history
7018 @item record function-call-history
7019 Prints the execution history at function granularity. It prints one
7020 line for each sequence of instructions that belong to the same
7021 function giving the name of that function, the source lines
7022 for this instruction sequence (if the @code{/l} modifier is
7023 specified), and the instructions numbers that form the sequence (if
7024 the @code{/i} modifier is specified). The function names are indented
7025 to reflect the call stack depth if the @code{/c} modifier is
7026 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7030 (@value{GDBP}) @b{list 1, 10}
7041 (@value{GDBP}) @b{record function-call-history /ilc}
7042 1 bar inst 1,4 at foo.c:6,8
7043 2 foo inst 5,10 at foo.c:2,3
7044 3 bar inst 11,13 at foo.c:9,10
7047 By default, ten lines are printed. This can be changed using the
7048 @code{set record function-call-history-size} command. Functions are
7049 printed in execution order. There are several ways to specify what
7053 @item record function-call-history @var{func}
7054 Prints ten functions starting from function number @var{func}.
7056 @item record function-call-history @var{func}, +/-@var{n}
7057 Prints @var{n} functions around function number @var{func}. If
7058 @var{n} is preceded with @code{+}, prints @var{n} functions after
7059 function number @var{func}. If @var{n} is preceded with @code{-},
7060 prints @var{n} functions before function number @var{func}.
7062 @item record function-call-history
7063 Prints ten more functions after the last ten-line print.
7065 @item record function-call-history -
7066 Prints ten more functions before the last ten-line print.
7068 @item record function-call-history @var{begin}, @var{end}
7069 Prints functions beginning with function number @var{begin} until
7070 function number @var{end}. The function number @var{end} is included.
7073 This command may not be available for all recording methods.
7075 @item set record function-call-history-size @var{size}
7076 @itemx set record function-call-history-size unlimited
7077 Define how many lines to print in the
7078 @code{record function-call-history} command. The default value is 10.
7079 A size of @code{unlimited} means unlimited lines.
7081 @item show record function-call-history-size
7082 Show how many lines to print in the
7083 @code{record function-call-history} command.
7088 @chapter Examining the Stack
7090 When your program has stopped, the first thing you need to know is where it
7091 stopped and how it got there.
7094 Each time your program performs a function call, information about the call
7096 That information includes the location of the call in your program,
7097 the arguments of the call,
7098 and the local variables of the function being called.
7099 The information is saved in a block of data called a @dfn{stack frame}.
7100 The stack frames are allocated in a region of memory called the @dfn{call
7103 When your program stops, the @value{GDBN} commands for examining the
7104 stack allow you to see all of this information.
7106 @cindex selected frame
7107 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7108 @value{GDBN} commands refer implicitly to the selected frame. In
7109 particular, whenever you ask @value{GDBN} for the value of a variable in
7110 your program, the value is found in the selected frame. There are
7111 special @value{GDBN} commands to select whichever frame you are
7112 interested in. @xref{Selection, ,Selecting a Frame}.
7114 When your program stops, @value{GDBN} automatically selects the
7115 currently executing frame and describes it briefly, similar to the
7116 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7119 * Frames:: Stack frames
7120 * Backtrace:: Backtraces
7121 * Selection:: Selecting a frame
7122 * Frame Info:: Information on a frame
7123 * Frame Filter Management:: Managing frame filters
7128 @section Stack Frames
7130 @cindex frame, definition
7132 The call stack is divided up into contiguous pieces called @dfn{stack
7133 frames}, or @dfn{frames} for short; each frame is the data associated
7134 with one call to one function. The frame contains the arguments given
7135 to the function, the function's local variables, and the address at
7136 which the function is executing.
7138 @cindex initial frame
7139 @cindex outermost frame
7140 @cindex innermost frame
7141 When your program is started, the stack has only one frame, that of the
7142 function @code{main}. This is called the @dfn{initial} frame or the
7143 @dfn{outermost} frame. Each time a function is called, a new frame is
7144 made. Each time a function returns, the frame for that function invocation
7145 is eliminated. If a function is recursive, there can be many frames for
7146 the same function. The frame for the function in which execution is
7147 actually occurring is called the @dfn{innermost} frame. This is the most
7148 recently created of all the stack frames that still exist.
7150 @cindex frame pointer
7151 Inside your program, stack frames are identified by their addresses. A
7152 stack frame consists of many bytes, each of which has its own address; each
7153 kind of computer has a convention for choosing one byte whose
7154 address serves as the address of the frame. Usually this address is kept
7155 in a register called the @dfn{frame pointer register}
7156 (@pxref{Registers, $fp}) while execution is going on in that frame.
7158 @cindex frame number
7159 @value{GDBN} assigns numbers to all existing stack frames, starting with
7160 zero for the innermost frame, one for the frame that called it,
7161 and so on upward. These numbers do not really exist in your program;
7162 they are assigned by @value{GDBN} to give you a way of designating stack
7163 frames in @value{GDBN} commands.
7165 @c The -fomit-frame-pointer below perennially causes hbox overflow
7166 @c underflow problems.
7167 @cindex frameless execution
7168 Some compilers provide a way to compile functions so that they operate
7169 without stack frames. (For example, the @value{NGCC} option
7171 @samp{-fomit-frame-pointer}
7173 generates functions without a frame.)
7174 This is occasionally done with heavily used library functions to save
7175 the frame setup time. @value{GDBN} has limited facilities for dealing
7176 with these function invocations. If the innermost function invocation
7177 has no stack frame, @value{GDBN} nevertheless regards it as though
7178 it had a separate frame, which is numbered zero as usual, allowing
7179 correct tracing of the function call chain. However, @value{GDBN} has
7180 no provision for frameless functions elsewhere in the stack.
7186 @cindex call stack traces
7187 A backtrace is a summary of how your program got where it is. It shows one
7188 line per frame, for many frames, starting with the currently executing
7189 frame (frame zero), followed by its caller (frame one), and on up the
7192 @anchor{backtrace-command}
7195 @kindex bt @r{(@code{backtrace})}
7198 Print a backtrace of the entire stack: one line per frame for all
7199 frames in the stack.
7201 You can stop the backtrace at any time by typing the system interrupt
7202 character, normally @kbd{Ctrl-c}.
7204 @item backtrace @var{n}
7206 Similar, but print only the innermost @var{n} frames.
7208 @item backtrace -@var{n}
7210 Similar, but print only the outermost @var{n} frames.
7212 @item backtrace full
7214 @itemx bt full @var{n}
7215 @itemx bt full -@var{n}
7216 Print the values of the local variables also. As described above,
7217 @var{n} specifies the number of frames to print.
7219 @item backtrace no-filters
7220 @itemx bt no-filters
7221 @itemx bt no-filters @var{n}
7222 @itemx bt no-filters -@var{n}
7223 @itemx bt no-filters full
7224 @itemx bt no-filters full @var{n}
7225 @itemx bt no-filters full -@var{n}
7226 Do not run Python frame filters on this backtrace. @xref{Frame
7227 Filter API}, for more information. Additionally use @ref{disable
7228 frame-filter all} to turn off all frame filters. This is only
7229 relevant when @value{GDBN} has been configured with @code{Python}
7235 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7236 are additional aliases for @code{backtrace}.
7238 @cindex multiple threads, backtrace
7239 In a multi-threaded program, @value{GDBN} by default shows the
7240 backtrace only for the current thread. To display the backtrace for
7241 several or all of the threads, use the command @code{thread apply}
7242 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7243 apply all backtrace}, @value{GDBN} will display the backtrace for all
7244 the threads; this is handy when you debug a core dump of a
7245 multi-threaded program.
7247 Each line in the backtrace shows the frame number and the function name.
7248 The program counter value is also shown---unless you use @code{set
7249 print address off}. The backtrace also shows the source file name and
7250 line number, as well as the arguments to the function. The program
7251 counter value is omitted if it is at the beginning of the code for that
7254 Here is an example of a backtrace. It was made with the command
7255 @samp{bt 3}, so it shows the innermost three frames.
7259 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7261 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7262 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7264 (More stack frames follow...)
7269 The display for frame zero does not begin with a program counter
7270 value, indicating that your program has stopped at the beginning of the
7271 code for line @code{993} of @code{builtin.c}.
7274 The value of parameter @code{data} in frame 1 has been replaced by
7275 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7276 only if it is a scalar (integer, pointer, enumeration, etc). See command
7277 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7278 on how to configure the way function parameter values are printed.
7280 @cindex optimized out, in backtrace
7281 @cindex function call arguments, optimized out
7282 If your program was compiled with optimizations, some compilers will
7283 optimize away arguments passed to functions if those arguments are
7284 never used after the call. Such optimizations generate code that
7285 passes arguments through registers, but doesn't store those arguments
7286 in the stack frame. @value{GDBN} has no way of displaying such
7287 arguments in stack frames other than the innermost one. Here's what
7288 such a backtrace might look like:
7292 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7294 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7295 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7297 (More stack frames follow...)
7302 The values of arguments that were not saved in their stack frames are
7303 shown as @samp{<optimized out>}.
7305 If you need to display the values of such optimized-out arguments,
7306 either deduce that from other variables whose values depend on the one
7307 you are interested in, or recompile without optimizations.
7309 @cindex backtrace beyond @code{main} function
7310 @cindex program entry point
7311 @cindex startup code, and backtrace
7312 Most programs have a standard user entry point---a place where system
7313 libraries and startup code transition into user code. For C this is
7314 @code{main}@footnote{
7315 Note that embedded programs (the so-called ``free-standing''
7316 environment) are not required to have a @code{main} function as the
7317 entry point. They could even have multiple entry points.}.
7318 When @value{GDBN} finds the entry function in a backtrace
7319 it will terminate the backtrace, to avoid tracing into highly
7320 system-specific (and generally uninteresting) code.
7322 If you need to examine the startup code, or limit the number of levels
7323 in a backtrace, you can change this behavior:
7326 @item set backtrace past-main
7327 @itemx set backtrace past-main on
7328 @kindex set backtrace
7329 Backtraces will continue past the user entry point.
7331 @item set backtrace past-main off
7332 Backtraces will stop when they encounter the user entry point. This is the
7335 @item show backtrace past-main
7336 @kindex show backtrace
7337 Display the current user entry point backtrace policy.
7339 @item set backtrace past-entry
7340 @itemx set backtrace past-entry on
7341 Backtraces will continue past the internal entry point of an application.
7342 This entry point is encoded by the linker when the application is built,
7343 and is likely before the user entry point @code{main} (or equivalent) is called.
7345 @item set backtrace past-entry off
7346 Backtraces will stop when they encounter the internal entry point of an
7347 application. This is the default.
7349 @item show backtrace past-entry
7350 Display the current internal entry point backtrace policy.
7352 @item set backtrace limit @var{n}
7353 @itemx set backtrace limit 0
7354 @itemx set backtrace limit unlimited
7355 @cindex backtrace limit
7356 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7357 or zero means unlimited levels.
7359 @item show backtrace limit
7360 Display the current limit on backtrace levels.
7363 You can control how file names are displayed.
7366 @item set filename-display
7367 @itemx set filename-display relative
7368 @cindex filename-display
7369 Display file names relative to the compilation directory. This is the default.
7371 @item set filename-display basename
7372 Display only basename of a filename.
7374 @item set filename-display absolute
7375 Display an absolute filename.
7377 @item show filename-display
7378 Show the current way to display filenames.
7382 @section Selecting a Frame
7384 Most commands for examining the stack and other data in your program work on
7385 whichever stack frame is selected at the moment. Here are the commands for
7386 selecting a stack frame; all of them finish by printing a brief description
7387 of the stack frame just selected.
7390 @kindex frame@r{, selecting}
7391 @kindex f @r{(@code{frame})}
7394 Select frame number @var{n}. Recall that frame zero is the innermost
7395 (currently executing) frame, frame one is the frame that called the
7396 innermost one, and so on. The highest-numbered frame is the one for
7399 @item frame @var{stack-addr} [ @var{pc-addr} ]
7400 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7401 Select the frame at address @var{stack-addr}. This is useful mainly if the
7402 chaining of stack frames has been damaged by a bug, making it
7403 impossible for @value{GDBN} to assign numbers properly to all frames. In
7404 addition, this can be useful when your program has multiple stacks and
7405 switches between them. The optional @var{pc-addr} can also be given to
7406 specify the value of PC for the stack frame.
7410 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7411 numbers @var{n}, this advances toward the outermost frame, to higher
7412 frame numbers, to frames that have existed longer.
7415 @kindex do @r{(@code{down})}
7417 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7418 positive numbers @var{n}, this advances toward the innermost frame, to
7419 lower frame numbers, to frames that were created more recently.
7420 You may abbreviate @code{down} as @code{do}.
7423 All of these commands end by printing two lines of output describing the
7424 frame. The first line shows the frame number, the function name, the
7425 arguments, and the source file and line number of execution in that
7426 frame. The second line shows the text of that source line.
7434 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7436 10 read_input_file (argv[i]);
7440 After such a printout, the @code{list} command with no arguments
7441 prints ten lines centered on the point of execution in the frame.
7442 You can also edit the program at the point of execution with your favorite
7443 editing program by typing @code{edit}.
7444 @xref{List, ,Printing Source Lines},
7448 @kindex select-frame
7450 The @code{select-frame} command is a variant of @code{frame} that does
7451 not display the new frame after selecting it. This command is
7452 intended primarily for use in @value{GDBN} command scripts, where the
7453 output might be unnecessary and distracting.
7455 @kindex down-silently
7457 @item up-silently @var{n}
7458 @itemx down-silently @var{n}
7459 These two commands are variants of @code{up} and @code{down},
7460 respectively; they differ in that they do their work silently, without
7461 causing display of the new frame. They are intended primarily for use
7462 in @value{GDBN} command scripts, where the output might be unnecessary and
7467 @section Information About a Frame
7469 There are several other commands to print information about the selected
7475 When used without any argument, this command does not change which
7476 frame is selected, but prints a brief description of the currently
7477 selected stack frame. It can be abbreviated @code{f}. With an
7478 argument, this command is used to select a stack frame.
7479 @xref{Selection, ,Selecting a Frame}.
7482 @kindex info f @r{(@code{info frame})}
7485 This command prints a verbose description of the selected stack frame,
7490 the address of the frame
7492 the address of the next frame down (called by this frame)
7494 the address of the next frame up (caller of this frame)
7496 the language in which the source code corresponding to this frame is written
7498 the address of the frame's arguments
7500 the address of the frame's local variables
7502 the program counter saved in it (the address of execution in the caller frame)
7504 which registers were saved in the frame
7507 @noindent The verbose description is useful when
7508 something has gone wrong that has made the stack format fail to fit
7509 the usual conventions.
7511 @item info frame @var{addr}
7512 @itemx info f @var{addr}
7513 Print a verbose description of the frame at address @var{addr}, without
7514 selecting that frame. The selected frame remains unchanged by this
7515 command. This requires the same kind of address (more than one for some
7516 architectures) that you specify in the @code{frame} command.
7517 @xref{Selection, ,Selecting a Frame}.
7521 Print the arguments of the selected frame, each on a separate line.
7525 Print the local variables of the selected frame, each on a separate
7526 line. These are all variables (declared either static or automatic)
7527 accessible at the point of execution of the selected frame.
7531 @node Frame Filter Management
7532 @section Management of Frame Filters.
7533 @cindex managing frame filters
7535 Frame filters are Python based utilities to manage and decorate the
7536 output of frames. @xref{Frame Filter API}, for further information.
7538 Managing frame filters is performed by several commands available
7539 within @value{GDBN}, detailed here.
7542 @kindex info frame-filter
7543 @item info frame-filter
7544 Print a list of installed frame filters from all dictionaries, showing
7545 their name, priority and enabled status.
7547 @kindex disable frame-filter
7548 @anchor{disable frame-filter all}
7549 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7550 Disable a frame filter in the dictionary matching
7551 @var{filter-dictionary} and @var{filter-name}. The
7552 @var{filter-dictionary} may be @code{all}, @code{global},
7553 @code{progspace}, or the name of the object file where the frame filter
7554 dictionary resides. When @code{all} is specified, all frame filters
7555 across all dictionaries are disabled. The @var{filter-name} is the name
7556 of the frame filter and is used when @code{all} is not the option for
7557 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7558 may be enabled again later.
7560 @kindex enable frame-filter
7561 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7562 Enable a frame filter in the dictionary matching
7563 @var{filter-dictionary} and @var{filter-name}. The
7564 @var{filter-dictionary} may be @code{all}, @code{global},
7565 @code{progspace} or the name of the object file where the frame filter
7566 dictionary resides. When @code{all} is specified, all frame filters across
7567 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7568 filter and is used when @code{all} is not the option for
7569 @var{filter-dictionary}.
7574 (gdb) info frame-filter
7576 global frame-filters:
7577 Priority Enabled Name
7578 1000 No PrimaryFunctionFilter
7581 progspace /build/test frame-filters:
7582 Priority Enabled Name
7583 100 Yes ProgspaceFilter
7585 objfile /build/test frame-filters:
7586 Priority Enabled Name
7587 999 Yes BuildProgra Filter
7589 (gdb) disable frame-filter /build/test BuildProgramFilter
7590 (gdb) info frame-filter
7592 global frame-filters:
7593 Priority Enabled Name
7594 1000 No PrimaryFunctionFilter
7597 progspace /build/test frame-filters:
7598 Priority Enabled Name
7599 100 Yes ProgspaceFilter
7601 objfile /build/test frame-filters:
7602 Priority Enabled Name
7603 999 No BuildProgramFilter
7605 (gdb) enable frame-filter global PrimaryFunctionFilter
7606 (gdb) info frame-filter
7608 global frame-filters:
7609 Priority Enabled Name
7610 1000 Yes PrimaryFunctionFilter
7613 progspace /build/test frame-filters:
7614 Priority Enabled Name
7615 100 Yes ProgspaceFilter
7617 objfile /build/test frame-filters:
7618 Priority Enabled Name
7619 999 No BuildProgramFilter
7622 @kindex set frame-filter priority
7623 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7624 Set the @var{priority} of a frame filter in the dictionary matching
7625 @var{filter-dictionary}, and the frame filter name matching
7626 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7627 @code{progspace} or the name of the object file where the frame filter
7628 dictionary resides. The @var{priority} is an integer.
7630 @kindex show frame-filter priority
7631 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7632 Show the @var{priority} of a frame filter in the dictionary matching
7633 @var{filter-dictionary}, and the frame filter name matching
7634 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7635 @code{progspace} or the name of the object file where the frame filter
7641 (gdb) info frame-filter
7643 global frame-filters:
7644 Priority Enabled Name
7645 1000 Yes PrimaryFunctionFilter
7648 progspace /build/test frame-filters:
7649 Priority Enabled Name
7650 100 Yes ProgspaceFilter
7652 objfile /build/test frame-filters:
7653 Priority Enabled Name
7654 999 No BuildProgramFilter
7656 (gdb) set frame-filter priority global Reverse 50
7657 (gdb) info frame-filter
7659 global frame-filters:
7660 Priority Enabled Name
7661 1000 Yes PrimaryFunctionFilter
7664 progspace /build/test frame-filters:
7665 Priority Enabled Name
7666 100 Yes ProgspaceFilter
7668 objfile /build/test frame-filters:
7669 Priority Enabled Name
7670 999 No BuildProgramFilter
7675 @chapter Examining Source Files
7677 @value{GDBN} can print parts of your program's source, since the debugging
7678 information recorded in the program tells @value{GDBN} what source files were
7679 used to build it. When your program stops, @value{GDBN} spontaneously prints
7680 the line where it stopped. Likewise, when you select a stack frame
7681 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7682 execution in that frame has stopped. You can print other portions of
7683 source files by explicit command.
7685 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7686 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7687 @value{GDBN} under @sc{gnu} Emacs}.
7690 * List:: Printing source lines
7691 * Specify Location:: How to specify code locations
7692 * Edit:: Editing source files
7693 * Search:: Searching source files
7694 * Source Path:: Specifying source directories
7695 * Machine Code:: Source and machine code
7699 @section Printing Source Lines
7702 @kindex l @r{(@code{list})}
7703 To print lines from a source file, use the @code{list} command
7704 (abbreviated @code{l}). By default, ten lines are printed.
7705 There are several ways to specify what part of the file you want to
7706 print; see @ref{Specify Location}, for the full list.
7708 Here are the forms of the @code{list} command most commonly used:
7711 @item list @var{linenum}
7712 Print lines centered around line number @var{linenum} in the
7713 current source file.
7715 @item list @var{function}
7716 Print lines centered around the beginning of function
7720 Print more lines. If the last lines printed were printed with a
7721 @code{list} command, this prints lines following the last lines
7722 printed; however, if the last line printed was a solitary line printed
7723 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7724 Stack}), this prints lines centered around that line.
7727 Print lines just before the lines last printed.
7730 @cindex @code{list}, how many lines to display
7731 By default, @value{GDBN} prints ten source lines with any of these forms of
7732 the @code{list} command. You can change this using @code{set listsize}:
7735 @kindex set listsize
7736 @item set listsize @var{count}
7737 @itemx set listsize unlimited
7738 Make the @code{list} command display @var{count} source lines (unless
7739 the @code{list} argument explicitly specifies some other number).
7740 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7742 @kindex show listsize
7744 Display the number of lines that @code{list} prints.
7747 Repeating a @code{list} command with @key{RET} discards the argument,
7748 so it is equivalent to typing just @code{list}. This is more useful
7749 than listing the same lines again. An exception is made for an
7750 argument of @samp{-}; that argument is preserved in repetition so that
7751 each repetition moves up in the source file.
7753 In general, the @code{list} command expects you to supply zero, one or two
7754 @dfn{locations}. Locations specify source lines; there are several ways
7755 of writing them (@pxref{Specify Location}), but the effect is always
7756 to specify some source line.
7758 Here is a complete description of the possible arguments for @code{list}:
7761 @item list @var{location}
7762 Print lines centered around the line specified by @var{location}.
7764 @item list @var{first},@var{last}
7765 Print lines from @var{first} to @var{last}. Both arguments are
7766 locations. When a @code{list} command has two locations, and the
7767 source file of the second location is omitted, this refers to
7768 the same source file as the first location.
7770 @item list ,@var{last}
7771 Print lines ending with @var{last}.
7773 @item list @var{first},
7774 Print lines starting with @var{first}.
7777 Print lines just after the lines last printed.
7780 Print lines just before the lines last printed.
7783 As described in the preceding table.
7786 @node Specify Location
7787 @section Specifying a Location
7788 @cindex specifying location
7790 @cindex source location
7793 * Linespec Locations:: Linespec locations
7794 * Explicit Locations:: Explicit locations
7795 * Address Locations:: Address locations
7798 Several @value{GDBN} commands accept arguments that specify a location
7799 of your program's code. Since @value{GDBN} is a source-level
7800 debugger, a location usually specifies some line in the source code.
7801 Locations may be specified using three different formats:
7802 linespec locations, explicit locations, or address locations.
7804 @node Linespec Locations
7805 @subsection Linespec Locations
7806 @cindex linespec locations
7808 A @dfn{linespec} is a colon-separated list of source location parameters such
7809 as file name, function name, etc. Here are all the different ways of
7810 specifying a linespec:
7814 Specifies the line number @var{linenum} of the current source file.
7817 @itemx +@var{offset}
7818 Specifies the line @var{offset} lines before or after the @dfn{current
7819 line}. For the @code{list} command, the current line is the last one
7820 printed; for the breakpoint commands, this is the line at which
7821 execution stopped in the currently selected @dfn{stack frame}
7822 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7823 used as the second of the two linespecs in a @code{list} command,
7824 this specifies the line @var{offset} lines up or down from the first
7827 @item @var{filename}:@var{linenum}
7828 Specifies the line @var{linenum} in the source file @var{filename}.
7829 If @var{filename} is a relative file name, then it will match any
7830 source file name with the same trailing components. For example, if
7831 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7832 name of @file{/build/trunk/gcc/expr.c}, but not
7833 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7835 @item @var{function}
7836 Specifies the line that begins the body of the function @var{function}.
7837 For example, in C, this is the line with the open brace.
7839 @item @var{function}:@var{label}
7840 Specifies the line where @var{label} appears in @var{function}.
7842 @item @var{filename}:@var{function}
7843 Specifies the line that begins the body of the function @var{function}
7844 in the file @var{filename}. You only need the file name with a
7845 function name to avoid ambiguity when there are identically named
7846 functions in different source files.
7849 Specifies the line at which the label named @var{label} appears
7850 in the function corresponding to the currently selected stack frame.
7851 If there is no current selected stack frame (for instance, if the inferior
7852 is not running), then @value{GDBN} will not search for a label.
7854 @cindex breakpoint at static probe point
7855 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7856 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7857 applications to embed static probes. @xref{Static Probe Points}, for more
7858 information on finding and using static probes. This form of linespec
7859 specifies the location of such a static probe.
7861 If @var{objfile} is given, only probes coming from that shared library
7862 or executable matching @var{objfile} as a regular expression are considered.
7863 If @var{provider} is given, then only probes from that provider are considered.
7864 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7865 each one of those probes.
7868 @node Explicit Locations
7869 @subsection Explicit Locations
7870 @cindex explicit locations
7872 @dfn{Explicit locations} allow the user to directly specify the source
7873 location's parameters using option-value pairs.
7875 Explicit locations are useful when several functions, labels, or
7876 file names have the same name (base name for files) in the program's
7877 sources. In these cases, explicit locations point to the source
7878 line you meant more accurately and unambiguously. Also, using
7879 explicit locations might be faster in large programs.
7881 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7882 defined in the file named @file{foo} or the label @code{bar} in a function
7883 named @code{foo}. @value{GDBN} must search either the file system or
7884 the symbol table to know.
7886 The list of valid explicit location options is summarized in the
7890 @item -source @var{filename}
7891 The value specifies the source file name. To differentiate between
7892 files with the same base name, prepend as many directories as is necessary
7893 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7894 @value{GDBN} will use the first file it finds with the given base
7895 name. This option requires the use of either @code{-function} or @code{-line}.
7897 @item -function @var{function}
7898 The value specifies the name of a function. Operations
7899 on function locations unmodified by other options (such as @code{-label}
7900 or @code{-line}) refer to the line that begins the body of the function.
7901 In C, for example, this is the line with the open brace.
7903 @item -label @var{label}
7904 The value specifies the name of a label. When the function
7905 name is not specified, the label is searched in the function of the currently
7906 selected stack frame.
7908 @item -line @var{number}
7909 The value specifies a line offset for the location. The offset may either
7910 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7911 the command. When specified without any other options, the line offset is
7912 relative to the current line.
7915 Explicit location options may be abbreviated by omitting any non-unique
7916 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7918 @node Address Locations
7919 @subsection Address Locations
7920 @cindex address locations
7922 @dfn{Address locations} indicate a specific program address. They have
7923 the generalized form *@var{address}.
7925 For line-oriented commands, such as @code{list} and @code{edit}, this
7926 specifies a source line that contains @var{address}. For @code{break} and
7927 other breakpoint-oriented commands, this can be used to set breakpoints in
7928 parts of your program which do not have debugging information or
7931 Here @var{address} may be any expression valid in the current working
7932 language (@pxref{Languages, working language}) that specifies a code
7933 address. In addition, as a convenience, @value{GDBN} extends the
7934 semantics of expressions used in locations to cover several situations
7935 that frequently occur during debugging. Here are the various forms
7939 @item @var{expression}
7940 Any expression valid in the current working language.
7942 @item @var{funcaddr}
7943 An address of a function or procedure derived from its name. In C,
7944 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
7945 simply the function's name @var{function} (and actually a special case
7946 of a valid expression). In Pascal and Modula-2, this is
7947 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7948 (although the Pascal form also works).
7950 This form specifies the address of the function's first instruction,
7951 before the stack frame and arguments have been set up.
7953 @item '@var{filename}':@var{funcaddr}
7954 Like @var{funcaddr} above, but also specifies the name of the source
7955 file explicitly. This is useful if the name of the function does not
7956 specify the function unambiguously, e.g., if there are several
7957 functions with identical names in different source files.
7961 @section Editing Source Files
7962 @cindex editing source files
7965 @kindex e @r{(@code{edit})}
7966 To edit the lines in a source file, use the @code{edit} command.
7967 The editing program of your choice
7968 is invoked with the current line set to
7969 the active line in the program.
7970 Alternatively, there are several ways to specify what part of the file you
7971 want to print if you want to see other parts of the program:
7974 @item edit @var{location}
7975 Edit the source file specified by @code{location}. Editing starts at
7976 that @var{location}, e.g., at the specified source line of the
7977 specified file. @xref{Specify Location}, for all the possible forms
7978 of the @var{location} argument; here are the forms of the @code{edit}
7979 command most commonly used:
7982 @item edit @var{number}
7983 Edit the current source file with @var{number} as the active line number.
7985 @item edit @var{function}
7986 Edit the file containing @var{function} at the beginning of its definition.
7991 @subsection Choosing your Editor
7992 You can customize @value{GDBN} to use any editor you want
7994 The only restriction is that your editor (say @code{ex}), recognizes the
7995 following command-line syntax:
7997 ex +@var{number} file
7999 The optional numeric value +@var{number} specifies the number of the line in
8000 the file where to start editing.}.
8001 By default, it is @file{@value{EDITOR}}, but you can change this
8002 by setting the environment variable @code{EDITOR} before using
8003 @value{GDBN}. For example, to configure @value{GDBN} to use the
8004 @code{vi} editor, you could use these commands with the @code{sh} shell:
8010 or in the @code{csh} shell,
8012 setenv EDITOR /usr/bin/vi
8017 @section Searching Source Files
8018 @cindex searching source files
8020 There are two commands for searching through the current source file for a
8025 @kindex forward-search
8026 @kindex fo @r{(@code{forward-search})}
8027 @item forward-search @var{regexp}
8028 @itemx search @var{regexp}
8029 The command @samp{forward-search @var{regexp}} checks each line,
8030 starting with the one following the last line listed, for a match for
8031 @var{regexp}. It lists the line that is found. You can use the
8032 synonym @samp{search @var{regexp}} or abbreviate the command name as
8035 @kindex reverse-search
8036 @item reverse-search @var{regexp}
8037 The command @samp{reverse-search @var{regexp}} checks each line, starting
8038 with the one before the last line listed and going backward, for a match
8039 for @var{regexp}. It lists the line that is found. You can abbreviate
8040 this command as @code{rev}.
8044 @section Specifying Source Directories
8047 @cindex directories for source files
8048 Executable programs sometimes do not record the directories of the source
8049 files from which they were compiled, just the names. Even when they do,
8050 the directories could be moved between the compilation and your debugging
8051 session. @value{GDBN} has a list of directories to search for source files;
8052 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8053 it tries all the directories in the list, in the order they are present
8054 in the list, until it finds a file with the desired name.
8056 For example, suppose an executable references the file
8057 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8058 @file{/mnt/cross}. The file is first looked up literally; if this
8059 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8060 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8061 message is printed. @value{GDBN} does not look up the parts of the
8062 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8063 Likewise, the subdirectories of the source path are not searched: if
8064 the source path is @file{/mnt/cross}, and the binary refers to
8065 @file{foo.c}, @value{GDBN} would not find it under
8066 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8068 Plain file names, relative file names with leading directories, file
8069 names containing dots, etc.@: are all treated as described above; for
8070 instance, if the source path is @file{/mnt/cross}, and the source file
8071 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8072 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8073 that---@file{/mnt/cross/foo.c}.
8075 Note that the executable search path is @emph{not} used to locate the
8078 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8079 any information it has cached about where source files are found and where
8080 each line is in the file.
8084 When you start @value{GDBN}, its source path includes only @samp{cdir}
8085 and @samp{cwd}, in that order.
8086 To add other directories, use the @code{directory} command.
8088 The search path is used to find both program source files and @value{GDBN}
8089 script files (read using the @samp{-command} option and @samp{source} command).
8091 In addition to the source path, @value{GDBN} provides a set of commands
8092 that manage a list of source path substitution rules. A @dfn{substitution
8093 rule} specifies how to rewrite source directories stored in the program's
8094 debug information in case the sources were moved to a different
8095 directory between compilation and debugging. A rule is made of
8096 two strings, the first specifying what needs to be rewritten in
8097 the path, and the second specifying how it should be rewritten.
8098 In @ref{set substitute-path}, we name these two parts @var{from} and
8099 @var{to} respectively. @value{GDBN} does a simple string replacement
8100 of @var{from} with @var{to} at the start of the directory part of the
8101 source file name, and uses that result instead of the original file
8102 name to look up the sources.
8104 Using the previous example, suppose the @file{foo-1.0} tree has been
8105 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8106 @value{GDBN} to replace @file{/usr/src} in all source path names with
8107 @file{/mnt/cross}. The first lookup will then be
8108 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8109 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8110 substitution rule, use the @code{set substitute-path} command
8111 (@pxref{set substitute-path}).
8113 To avoid unexpected substitution results, a rule is applied only if the
8114 @var{from} part of the directory name ends at a directory separator.
8115 For instance, a rule substituting @file{/usr/source} into
8116 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8117 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8118 is applied only at the beginning of the directory name, this rule will
8119 not be applied to @file{/root/usr/source/baz.c} either.
8121 In many cases, you can achieve the same result using the @code{directory}
8122 command. However, @code{set substitute-path} can be more efficient in
8123 the case where the sources are organized in a complex tree with multiple
8124 subdirectories. With the @code{directory} command, you need to add each
8125 subdirectory of your project. If you moved the entire tree while
8126 preserving its internal organization, then @code{set substitute-path}
8127 allows you to direct the debugger to all the sources with one single
8130 @code{set substitute-path} is also more than just a shortcut command.
8131 The source path is only used if the file at the original location no
8132 longer exists. On the other hand, @code{set substitute-path} modifies
8133 the debugger behavior to look at the rewritten location instead. So, if
8134 for any reason a source file that is not relevant to your executable is
8135 located at the original location, a substitution rule is the only
8136 method available to point @value{GDBN} at the new location.
8138 @cindex @samp{--with-relocated-sources}
8139 @cindex default source path substitution
8140 You can configure a default source path substitution rule by
8141 configuring @value{GDBN} with the
8142 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8143 should be the name of a directory under @value{GDBN}'s configured
8144 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8145 directory names in debug information under @var{dir} will be adjusted
8146 automatically if the installed @value{GDBN} is moved to a new
8147 location. This is useful if @value{GDBN}, libraries or executables
8148 with debug information and corresponding source code are being moved
8152 @item directory @var{dirname} @dots{}
8153 @item dir @var{dirname} @dots{}
8154 Add directory @var{dirname} to the front of the source path. Several
8155 directory names may be given to this command, separated by @samp{:}
8156 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8157 part of absolute file names) or
8158 whitespace. You may specify a directory that is already in the source
8159 path; this moves it forward, so @value{GDBN} searches it sooner.
8163 @vindex $cdir@r{, convenience variable}
8164 @vindex $cwd@r{, convenience variable}
8165 @cindex compilation directory
8166 @cindex current directory
8167 @cindex working directory
8168 @cindex directory, current
8169 @cindex directory, compilation
8170 You can use the string @samp{$cdir} to refer to the compilation
8171 directory (if one is recorded), and @samp{$cwd} to refer to the current
8172 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8173 tracks the current working directory as it changes during your @value{GDBN}
8174 session, while the latter is immediately expanded to the current
8175 directory at the time you add an entry to the source path.
8178 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8180 @c RET-repeat for @code{directory} is explicitly disabled, but since
8181 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8183 @item set directories @var{path-list}
8184 @kindex set directories
8185 Set the source path to @var{path-list}.
8186 @samp{$cdir:$cwd} are added if missing.
8188 @item show directories
8189 @kindex show directories
8190 Print the source path: show which directories it contains.
8192 @anchor{set substitute-path}
8193 @item set substitute-path @var{from} @var{to}
8194 @kindex set substitute-path
8195 Define a source path substitution rule, and add it at the end of the
8196 current list of existing substitution rules. If a rule with the same
8197 @var{from} was already defined, then the old rule is also deleted.
8199 For example, if the file @file{/foo/bar/baz.c} was moved to
8200 @file{/mnt/cross/baz.c}, then the command
8203 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8207 will tell @value{GDBN} to replace @samp{/foo/bar} with
8208 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8209 @file{baz.c} even though it was moved.
8211 In the case when more than one substitution rule have been defined,
8212 the rules are evaluated one by one in the order where they have been
8213 defined. The first one matching, if any, is selected to perform
8216 For instance, if we had entered the following commands:
8219 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8220 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8224 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8225 @file{/mnt/include/defs.h} by using the first rule. However, it would
8226 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8227 @file{/mnt/src/lib/foo.c}.
8230 @item unset substitute-path [path]
8231 @kindex unset substitute-path
8232 If a path is specified, search the current list of substitution rules
8233 for a rule that would rewrite that path. Delete that rule if found.
8234 A warning is emitted by the debugger if no rule could be found.
8236 If no path is specified, then all substitution rules are deleted.
8238 @item show substitute-path [path]
8239 @kindex show substitute-path
8240 If a path is specified, then print the source path substitution rule
8241 which would rewrite that path, if any.
8243 If no path is specified, then print all existing source path substitution
8248 If your source path is cluttered with directories that are no longer of
8249 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8250 versions of source. You can correct the situation as follows:
8254 Use @code{directory} with no argument to reset the source path to its default value.
8257 Use @code{directory} with suitable arguments to reinstall the
8258 directories you want in the source path. You can add all the
8259 directories in one command.
8263 @section Source and Machine Code
8264 @cindex source line and its code address
8266 You can use the command @code{info line} to map source lines to program
8267 addresses (and vice versa), and the command @code{disassemble} to display
8268 a range of addresses as machine instructions. You can use the command
8269 @code{set disassemble-next-line} to set whether to disassemble next
8270 source line when execution stops. When run under @sc{gnu} Emacs
8271 mode, the @code{info line} command causes the arrow to point to the
8272 line specified. Also, @code{info line} prints addresses in symbolic form as
8277 @item info line @var{location}
8278 Print the starting and ending addresses of the compiled code for
8279 source line @var{location}. You can specify source lines in any of
8280 the ways documented in @ref{Specify Location}.
8283 For example, we can use @code{info line} to discover the location of
8284 the object code for the first line of function
8285 @code{m4_changequote}:
8287 @c FIXME: I think this example should also show the addresses in
8288 @c symbolic form, as they usually would be displayed.
8290 (@value{GDBP}) info line m4_changequote
8291 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8295 @cindex code address and its source line
8296 We can also inquire (using @code{*@var{addr}} as the form for
8297 @var{location}) what source line covers a particular address:
8299 (@value{GDBP}) info line *0x63ff
8300 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8303 @cindex @code{$_} and @code{info line}
8304 @cindex @code{x} command, default address
8305 @kindex x@r{(examine), and} info line
8306 After @code{info line}, the default address for the @code{x} command
8307 is changed to the starting address of the line, so that @samp{x/i} is
8308 sufficient to begin examining the machine code (@pxref{Memory,
8309 ,Examining Memory}). Also, this address is saved as the value of the
8310 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8315 @cindex assembly instructions
8316 @cindex instructions, assembly
8317 @cindex machine instructions
8318 @cindex listing machine instructions
8320 @itemx disassemble /m
8321 @itemx disassemble /s
8322 @itemx disassemble /r
8323 This specialized command dumps a range of memory as machine
8324 instructions. It can also print mixed source+disassembly by specifying
8325 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8326 as well as in symbolic form by specifying the @code{/r} modifier.
8327 The default memory range is the function surrounding the
8328 program counter of the selected frame. A single argument to this
8329 command is a program counter value; @value{GDBN} dumps the function
8330 surrounding this value. When two arguments are given, they should
8331 be separated by a comma, possibly surrounded by whitespace. The
8332 arguments specify a range of addresses to dump, in one of two forms:
8335 @item @var{start},@var{end}
8336 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8337 @item @var{start},+@var{length}
8338 the addresses from @var{start} (inclusive) to
8339 @code{@var{start}+@var{length}} (exclusive).
8343 When 2 arguments are specified, the name of the function is also
8344 printed (since there could be several functions in the given range).
8346 The argument(s) can be any expression yielding a numeric value, such as
8347 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8349 If the range of memory being disassembled contains current program counter,
8350 the instruction at that location is shown with a @code{=>} marker.
8353 The following example shows the disassembly of a range of addresses of
8354 HP PA-RISC 2.0 code:
8357 (@value{GDBP}) disas 0x32c4, 0x32e4
8358 Dump of assembler code from 0x32c4 to 0x32e4:
8359 0x32c4 <main+204>: addil 0,dp
8360 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8361 0x32cc <main+212>: ldil 0x3000,r31
8362 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8363 0x32d4 <main+220>: ldo 0(r31),rp
8364 0x32d8 <main+224>: addil -0x800,dp
8365 0x32dc <main+228>: ldo 0x588(r1),r26
8366 0x32e0 <main+232>: ldil 0x3000,r31
8367 End of assembler dump.
8370 Here is an example showing mixed source+assembly for Intel x86
8371 with @code{/m} or @code{/s}, when the program is stopped just after
8372 function prologue in a non-optimized function with no inline code.
8375 (@value{GDBP}) disas /m main
8376 Dump of assembler code for function main:
8378 0x08048330 <+0>: push %ebp
8379 0x08048331 <+1>: mov %esp,%ebp
8380 0x08048333 <+3>: sub $0x8,%esp
8381 0x08048336 <+6>: and $0xfffffff0,%esp
8382 0x08048339 <+9>: sub $0x10,%esp
8384 6 printf ("Hello.\n");
8385 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8386 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8390 0x08048348 <+24>: mov $0x0,%eax
8391 0x0804834d <+29>: leave
8392 0x0804834e <+30>: ret
8394 End of assembler dump.
8397 The @code{/m} option is deprecated as its output is not useful when
8398 there is either inlined code or re-ordered code.
8399 The @code{/s} option is the preferred choice.
8400 Here is an example for AMD x86-64 showing the difference between
8401 @code{/m} output and @code{/s} output.
8402 This example has one inline function defined in a header file,
8403 and the code is compiled with @samp{-O2} optimization.
8404 Note how the @code{/m} output is missing the disassembly of
8405 several instructions that are present in the @code{/s} output.
8435 (@value{GDBP}) disas /m main
8436 Dump of assembler code for function main:
8440 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8441 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8445 0x000000000040041d <+29>: xor %eax,%eax
8446 0x000000000040041f <+31>: retq
8447 0x0000000000400420 <+32>: add %eax,%eax
8448 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8450 End of assembler dump.
8451 (@value{GDBP}) disas /s main
8452 Dump of assembler code for function main:
8456 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8460 0x0000000000400406 <+6>: test %eax,%eax
8461 0x0000000000400408 <+8>: js 0x400420 <main+32>
8466 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8467 0x000000000040040d <+13>: test %eax,%eax
8468 0x000000000040040f <+15>: mov $0x1,%eax
8469 0x0000000000400414 <+20>: cmovne %edx,%eax
8473 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8477 0x000000000040041d <+29>: xor %eax,%eax
8478 0x000000000040041f <+31>: retq
8482 0x0000000000400420 <+32>: add %eax,%eax
8483 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8484 End of assembler dump.
8487 Here is another example showing raw instructions in hex for AMD x86-64,
8490 (gdb) disas /r 0x400281,+10
8491 Dump of assembler code from 0x400281 to 0x40028b:
8492 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8493 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8494 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8495 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8496 End of assembler dump.
8499 Addresses cannot be specified as a location (@pxref{Specify Location}).
8500 So, for example, if you want to disassemble function @code{bar}
8501 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8502 and not @samp{disassemble foo.c:bar}.
8504 Some architectures have more than one commonly-used set of instruction
8505 mnemonics or other syntax.
8507 For programs that were dynamically linked and use shared libraries,
8508 instructions that call functions or branch to locations in the shared
8509 libraries might show a seemingly bogus location---it's actually a
8510 location of the relocation table. On some architectures, @value{GDBN}
8511 might be able to resolve these to actual function names.
8514 @kindex set disassembly-flavor
8515 @cindex Intel disassembly flavor
8516 @cindex AT&T disassembly flavor
8517 @item set disassembly-flavor @var{instruction-set}
8518 Select the instruction set to use when disassembling the
8519 program via the @code{disassemble} or @code{x/i} commands.
8521 Currently this command is only defined for the Intel x86 family. You
8522 can set @var{instruction-set} to either @code{intel} or @code{att}.
8523 The default is @code{att}, the AT&T flavor used by default by Unix
8524 assemblers for x86-based targets.
8526 @kindex show disassembly-flavor
8527 @item show disassembly-flavor
8528 Show the current setting of the disassembly flavor.
8532 @kindex set disassemble-next-line
8533 @kindex show disassemble-next-line
8534 @item set disassemble-next-line
8535 @itemx show disassemble-next-line
8536 Control whether or not @value{GDBN} will disassemble the next source
8537 line or instruction when execution stops. If ON, @value{GDBN} will
8538 display disassembly of the next source line when execution of the
8539 program being debugged stops. This is @emph{in addition} to
8540 displaying the source line itself, which @value{GDBN} always does if
8541 possible. If the next source line cannot be displayed for some reason
8542 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8543 info in the debug info), @value{GDBN} will display disassembly of the
8544 next @emph{instruction} instead of showing the next source line. If
8545 AUTO, @value{GDBN} will display disassembly of next instruction only
8546 if the source line cannot be displayed. This setting causes
8547 @value{GDBN} to display some feedback when you step through a function
8548 with no line info or whose source file is unavailable. The default is
8549 OFF, which means never display the disassembly of the next line or
8555 @chapter Examining Data
8557 @cindex printing data
8558 @cindex examining data
8561 The usual way to examine data in your program is with the @code{print}
8562 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8563 evaluates and prints the value of an expression of the language your
8564 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8565 Different Languages}). It may also print the expression using a
8566 Python-based pretty-printer (@pxref{Pretty Printing}).
8569 @item print @var{expr}
8570 @itemx print /@var{f} @var{expr}
8571 @var{expr} is an expression (in the source language). By default the
8572 value of @var{expr} is printed in a format appropriate to its data type;
8573 you can choose a different format by specifying @samp{/@var{f}}, where
8574 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8578 @itemx print /@var{f}
8579 @cindex reprint the last value
8580 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8581 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8582 conveniently inspect the same value in an alternative format.
8585 A more low-level way of examining data is with the @code{x} command.
8586 It examines data in memory at a specified address and prints it in a
8587 specified format. @xref{Memory, ,Examining Memory}.
8589 If you are interested in information about types, or about how the
8590 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8591 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8594 @cindex exploring hierarchical data structures
8596 Another way of examining values of expressions and type information is
8597 through the Python extension command @code{explore} (available only if
8598 the @value{GDBN} build is configured with @code{--with-python}). It
8599 offers an interactive way to start at the highest level (or, the most
8600 abstract level) of the data type of an expression (or, the data type
8601 itself) and explore all the way down to leaf scalar values/fields
8602 embedded in the higher level data types.
8605 @item explore @var{arg}
8606 @var{arg} is either an expression (in the source language), or a type
8607 visible in the current context of the program being debugged.
8610 The working of the @code{explore} command can be illustrated with an
8611 example. If a data type @code{struct ComplexStruct} is defined in your
8621 struct ComplexStruct
8623 struct SimpleStruct *ss_p;
8629 followed by variable declarations as
8632 struct SimpleStruct ss = @{ 10, 1.11 @};
8633 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8637 then, the value of the variable @code{cs} can be explored using the
8638 @code{explore} command as follows.
8642 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8643 the following fields:
8645 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8646 arr = <Enter 1 to explore this field of type `int [10]'>
8648 Enter the field number of choice:
8652 Since the fields of @code{cs} are not scalar values, you are being
8653 prompted to chose the field you want to explore. Let's say you choose
8654 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8655 pointer, you will be asked if it is pointing to a single value. From
8656 the declaration of @code{cs} above, it is indeed pointing to a single
8657 value, hence you enter @code{y}. If you enter @code{n}, then you will
8658 be asked if it were pointing to an array of values, in which case this
8659 field will be explored as if it were an array.
8662 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8663 Continue exploring it as a pointer to a single value [y/n]: y
8664 The value of `*(cs.ss_p)' is a struct/class of type `struct
8665 SimpleStruct' with the following fields:
8667 i = 10 .. (Value of type `int')
8668 d = 1.1100000000000001 .. (Value of type `double')
8670 Press enter to return to parent value:
8674 If the field @code{arr} of @code{cs} was chosen for exploration by
8675 entering @code{1} earlier, then since it is as array, you will be
8676 prompted to enter the index of the element in the array that you want
8680 `cs.arr' is an array of `int'.
8681 Enter the index of the element you want to explore in `cs.arr': 5
8683 `(cs.arr)[5]' is a scalar value of type `int'.
8687 Press enter to return to parent value:
8690 In general, at any stage of exploration, you can go deeper towards the
8691 leaf values by responding to the prompts appropriately, or hit the
8692 return key to return to the enclosing data structure (the @i{higher}
8693 level data structure).
8695 Similar to exploring values, you can use the @code{explore} command to
8696 explore types. Instead of specifying a value (which is typically a
8697 variable name or an expression valid in the current context of the
8698 program being debugged), you specify a type name. If you consider the
8699 same example as above, your can explore the type
8700 @code{struct ComplexStruct} by passing the argument
8701 @code{struct ComplexStruct} to the @code{explore} command.
8704 (gdb) explore struct ComplexStruct
8708 By responding to the prompts appropriately in the subsequent interactive
8709 session, you can explore the type @code{struct ComplexStruct} in a
8710 manner similar to how the value @code{cs} was explored in the above
8713 The @code{explore} command also has two sub-commands,
8714 @code{explore value} and @code{explore type}. The former sub-command is
8715 a way to explicitly specify that value exploration of the argument is
8716 being invoked, while the latter is a way to explicitly specify that type
8717 exploration of the argument is being invoked.
8720 @item explore value @var{expr}
8721 @cindex explore value
8722 This sub-command of @code{explore} explores the value of the
8723 expression @var{expr} (if @var{expr} is an expression valid in the
8724 current context of the program being debugged). The behavior of this
8725 command is identical to that of the behavior of the @code{explore}
8726 command being passed the argument @var{expr}.
8728 @item explore type @var{arg}
8729 @cindex explore type
8730 This sub-command of @code{explore} explores the type of @var{arg} (if
8731 @var{arg} is a type visible in the current context of program being
8732 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8733 is an expression valid in the current context of the program being
8734 debugged). If @var{arg} is a type, then the behavior of this command is
8735 identical to that of the @code{explore} command being passed the
8736 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8737 this command will be identical to that of the @code{explore} command
8738 being passed the type of @var{arg} as the argument.
8742 * Expressions:: Expressions
8743 * Ambiguous Expressions:: Ambiguous Expressions
8744 * Variables:: Program variables
8745 * Arrays:: Artificial arrays
8746 * Output Formats:: Output formats
8747 * Memory:: Examining memory
8748 * Auto Display:: Automatic display
8749 * Print Settings:: Print settings
8750 * Pretty Printing:: Python pretty printing
8751 * Value History:: Value history
8752 * Convenience Vars:: Convenience variables
8753 * Convenience Funs:: Convenience functions
8754 * Registers:: Registers
8755 * Floating Point Hardware:: Floating point hardware
8756 * Vector Unit:: Vector Unit
8757 * OS Information:: Auxiliary data provided by operating system
8758 * Memory Region Attributes:: Memory region attributes
8759 * Dump/Restore Files:: Copy between memory and a file
8760 * Core File Generation:: Cause a program dump its core
8761 * Character Sets:: Debugging programs that use a different
8762 character set than GDB does
8763 * Caching Target Data:: Data caching for targets
8764 * Searching Memory:: Searching memory for a sequence of bytes
8765 * Value Sizes:: Managing memory allocated for values
8769 @section Expressions
8772 @code{print} and many other @value{GDBN} commands accept an expression and
8773 compute its value. Any kind of constant, variable or operator defined
8774 by the programming language you are using is valid in an expression in
8775 @value{GDBN}. This includes conditional expressions, function calls,
8776 casts, and string constants. It also includes preprocessor macros, if
8777 you compiled your program to include this information; see
8780 @cindex arrays in expressions
8781 @value{GDBN} supports array constants in expressions input by
8782 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8783 you can use the command @code{print @{1, 2, 3@}} to create an array
8784 of three integers. If you pass an array to a function or assign it
8785 to a program variable, @value{GDBN} copies the array to memory that
8786 is @code{malloc}ed in the target program.
8788 Because C is so widespread, most of the expressions shown in examples in
8789 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8790 Languages}, for information on how to use expressions in other
8793 In this section, we discuss operators that you can use in @value{GDBN}
8794 expressions regardless of your programming language.
8796 @cindex casts, in expressions
8797 Casts are supported in all languages, not just in C, because it is so
8798 useful to cast a number into a pointer in order to examine a structure
8799 at that address in memory.
8800 @c FIXME: casts supported---Mod2 true?
8802 @value{GDBN} supports these operators, in addition to those common
8803 to programming languages:
8807 @samp{@@} is a binary operator for treating parts of memory as arrays.
8808 @xref{Arrays, ,Artificial Arrays}, for more information.
8811 @samp{::} allows you to specify a variable in terms of the file or
8812 function where it is defined. @xref{Variables, ,Program Variables}.
8814 @cindex @{@var{type}@}
8815 @cindex type casting memory
8816 @cindex memory, viewing as typed object
8817 @cindex casts, to view memory
8818 @item @{@var{type}@} @var{addr}
8819 Refers to an object of type @var{type} stored at address @var{addr} in
8820 memory. The address @var{addr} may be any expression whose value is
8821 an integer or pointer (but parentheses are required around binary
8822 operators, just as in a cast). This construct is allowed regardless
8823 of what kind of data is normally supposed to reside at @var{addr}.
8826 @node Ambiguous Expressions
8827 @section Ambiguous Expressions
8828 @cindex ambiguous expressions
8830 Expressions can sometimes contain some ambiguous elements. For instance,
8831 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8832 a single function name to be defined several times, for application in
8833 different contexts. This is called @dfn{overloading}. Another example
8834 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8835 templates and is typically instantiated several times, resulting in
8836 the same function name being defined in different contexts.
8838 In some cases and depending on the language, it is possible to adjust
8839 the expression to remove the ambiguity. For instance in C@t{++}, you
8840 can specify the signature of the function you want to break on, as in
8841 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8842 qualified name of your function often makes the expression unambiguous
8845 When an ambiguity that needs to be resolved is detected, the debugger
8846 has the capability to display a menu of numbered choices for each
8847 possibility, and then waits for the selection with the prompt @samp{>}.
8848 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8849 aborts the current command. If the command in which the expression was
8850 used allows more than one choice to be selected, the next option in the
8851 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8854 For example, the following session excerpt shows an attempt to set a
8855 breakpoint at the overloaded symbol @code{String::after}.
8856 We choose three particular definitions of that function name:
8858 @c FIXME! This is likely to change to show arg type lists, at least
8861 (@value{GDBP}) b String::after
8864 [2] file:String.cc; line number:867
8865 [3] file:String.cc; line number:860
8866 [4] file:String.cc; line number:875
8867 [5] file:String.cc; line number:853
8868 [6] file:String.cc; line number:846
8869 [7] file:String.cc; line number:735
8871 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8872 Breakpoint 2 at 0xb344: file String.cc, line 875.
8873 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8874 Multiple breakpoints were set.
8875 Use the "delete" command to delete unwanted
8882 @kindex set multiple-symbols
8883 @item set multiple-symbols @var{mode}
8884 @cindex multiple-symbols menu
8886 This option allows you to adjust the debugger behavior when an expression
8889 By default, @var{mode} is set to @code{all}. If the command with which
8890 the expression is used allows more than one choice, then @value{GDBN}
8891 automatically selects all possible choices. For instance, inserting
8892 a breakpoint on a function using an ambiguous name results in a breakpoint
8893 inserted on each possible match. However, if a unique choice must be made,
8894 then @value{GDBN} uses the menu to help you disambiguate the expression.
8895 For instance, printing the address of an overloaded function will result
8896 in the use of the menu.
8898 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8899 when an ambiguity is detected.
8901 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8902 an error due to the ambiguity and the command is aborted.
8904 @kindex show multiple-symbols
8905 @item show multiple-symbols
8906 Show the current value of the @code{multiple-symbols} setting.
8910 @section Program Variables
8912 The most common kind of expression to use is the name of a variable
8915 Variables in expressions are understood in the selected stack frame
8916 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8920 global (or file-static)
8927 visible according to the scope rules of the
8928 programming language from the point of execution in that frame
8931 @noindent This means that in the function
8946 you can examine and use the variable @code{a} whenever your program is
8947 executing within the function @code{foo}, but you can only use or
8948 examine the variable @code{b} while your program is executing inside
8949 the block where @code{b} is declared.
8951 @cindex variable name conflict
8952 There is an exception: you can refer to a variable or function whose
8953 scope is a single source file even if the current execution point is not
8954 in this file. But it is possible to have more than one such variable or
8955 function with the same name (in different source files). If that
8956 happens, referring to that name has unpredictable effects. If you wish,
8957 you can specify a static variable in a particular function or file by
8958 using the colon-colon (@code{::}) notation:
8960 @cindex colon-colon, context for variables/functions
8962 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8963 @cindex @code{::}, context for variables/functions
8966 @var{file}::@var{variable}
8967 @var{function}::@var{variable}
8971 Here @var{file} or @var{function} is the name of the context for the
8972 static @var{variable}. In the case of file names, you can use quotes to
8973 make sure @value{GDBN} parses the file name as a single word---for example,
8974 to print a global value of @code{x} defined in @file{f2.c}:
8977 (@value{GDBP}) p 'f2.c'::x
8980 The @code{::} notation is normally used for referring to
8981 static variables, since you typically disambiguate uses of local variables
8982 in functions by selecting the appropriate frame and using the
8983 simple name of the variable. However, you may also use this notation
8984 to refer to local variables in frames enclosing the selected frame:
8993 process (a); /* Stop here */
9004 For example, if there is a breakpoint at the commented line,
9005 here is what you might see
9006 when the program stops after executing the call @code{bar(0)}:
9011 (@value{GDBP}) p bar::a
9014 #2 0x080483d0 in foo (a=5) at foobar.c:12
9017 (@value{GDBP}) p bar::a
9021 @cindex C@t{++} scope resolution
9022 These uses of @samp{::} are very rarely in conflict with the very
9023 similar use of the same notation in C@t{++}. When they are in
9024 conflict, the C@t{++} meaning takes precedence; however, this can be
9025 overridden by quoting the file or function name with single quotes.
9027 For example, suppose the program is stopped in a method of a class
9028 that has a field named @code{includefile}, and there is also an
9029 include file named @file{includefile} that defines a variable,
9033 (@value{GDBP}) p includefile
9035 (@value{GDBP}) p includefile::some_global
9036 A syntax error in expression, near `'.
9037 (@value{GDBP}) p 'includefile'::some_global
9041 @cindex wrong values
9042 @cindex variable values, wrong
9043 @cindex function entry/exit, wrong values of variables
9044 @cindex optimized code, wrong values of variables
9046 @emph{Warning:} Occasionally, a local variable may appear to have the
9047 wrong value at certain points in a function---just after entry to a new
9048 scope, and just before exit.
9050 You may see this problem when you are stepping by machine instructions.
9051 This is because, on most machines, it takes more than one instruction to
9052 set up a stack frame (including local variable definitions); if you are
9053 stepping by machine instructions, variables may appear to have the wrong
9054 values until the stack frame is completely built. On exit, it usually
9055 also takes more than one machine instruction to destroy a stack frame;
9056 after you begin stepping through that group of instructions, local
9057 variable definitions may be gone.
9059 This may also happen when the compiler does significant optimizations.
9060 To be sure of always seeing accurate values, turn off all optimization
9063 @cindex ``No symbol "foo" in current context''
9064 Another possible effect of compiler optimizations is to optimize
9065 unused variables out of existence, or assign variables to registers (as
9066 opposed to memory addresses). Depending on the support for such cases
9067 offered by the debug info format used by the compiler, @value{GDBN}
9068 might not be able to display values for such local variables. If that
9069 happens, @value{GDBN} will print a message like this:
9072 No symbol "foo" in current context.
9075 To solve such problems, either recompile without optimizations, or use a
9076 different debug info format, if the compiler supports several such
9077 formats. @xref{Compilation}, for more information on choosing compiler
9078 options. @xref{C, ,C and C@t{++}}, for more information about debug
9079 info formats that are best suited to C@t{++} programs.
9081 If you ask to print an object whose contents are unknown to
9082 @value{GDBN}, e.g., because its data type is not completely specified
9083 by the debug information, @value{GDBN} will say @samp{<incomplete
9084 type>}. @xref{Symbols, incomplete type}, for more about this.
9086 If you append @kbd{@@entry} string to a function parameter name you get its
9087 value at the time the function got called. If the value is not available an
9088 error message is printed. Entry values are available only with some compilers.
9089 Entry values are normally also printed at the function parameter list according
9090 to @ref{set print entry-values}.
9093 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9099 (gdb) print i@@entry
9103 Strings are identified as arrays of @code{char} values without specified
9104 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9105 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9106 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9107 defines literal string type @code{"char"} as @code{char} without a sign.
9112 signed char var1[] = "A";
9115 You get during debugging
9120 $2 = @{65 'A', 0 '\0'@}
9124 @section Artificial Arrays
9126 @cindex artificial array
9128 @kindex @@@r{, referencing memory as an array}
9129 It is often useful to print out several successive objects of the
9130 same type in memory; a section of an array, or an array of
9131 dynamically determined size for which only a pointer exists in the
9134 You can do this by referring to a contiguous span of memory as an
9135 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9136 operand of @samp{@@} should be the first element of the desired array
9137 and be an individual object. The right operand should be the desired length
9138 of the array. The result is an array value whose elements are all of
9139 the type of the left argument. The first element is actually the left
9140 argument; the second element comes from bytes of memory immediately
9141 following those that hold the first element, and so on. Here is an
9142 example. If a program says
9145 int *array = (int *) malloc (len * sizeof (int));
9149 you can print the contents of @code{array} with
9155 The left operand of @samp{@@} must reside in memory. Array values made
9156 with @samp{@@} in this way behave just like other arrays in terms of
9157 subscripting, and are coerced to pointers when used in expressions.
9158 Artificial arrays most often appear in expressions via the value history
9159 (@pxref{Value History, ,Value History}), after printing one out.
9161 Another way to create an artificial array is to use a cast.
9162 This re-interprets a value as if it were an array.
9163 The value need not be in memory:
9165 (@value{GDBP}) p/x (short[2])0x12345678
9166 $1 = @{0x1234, 0x5678@}
9169 As a convenience, if you leave the array length out (as in
9170 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9171 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9173 (@value{GDBP}) p/x (short[])0x12345678
9174 $2 = @{0x1234, 0x5678@}
9177 Sometimes the artificial array mechanism is not quite enough; in
9178 moderately complex data structures, the elements of interest may not
9179 actually be adjacent---for example, if you are interested in the values
9180 of pointers in an array. One useful work-around in this situation is
9181 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9182 Variables}) as a counter in an expression that prints the first
9183 interesting value, and then repeat that expression via @key{RET}. For
9184 instance, suppose you have an array @code{dtab} of pointers to
9185 structures, and you are interested in the values of a field @code{fv}
9186 in each structure. Here is an example of what you might type:
9196 @node Output Formats
9197 @section Output Formats
9199 @cindex formatted output
9200 @cindex output formats
9201 By default, @value{GDBN} prints a value according to its data type. Sometimes
9202 this is not what you want. For example, you might want to print a number
9203 in hex, or a pointer in decimal. Or you might want to view data in memory
9204 at a certain address as a character string or as an instruction. To do
9205 these things, specify an @dfn{output format} when you print a value.
9207 The simplest use of output formats is to say how to print a value
9208 already computed. This is done by starting the arguments of the
9209 @code{print} command with a slash and a format letter. The format
9210 letters supported are:
9214 Regard the bits of the value as an integer, and print the integer in
9218 Print as integer in signed decimal.
9221 Print as integer in unsigned decimal.
9224 Print as integer in octal.
9227 Print as integer in binary. The letter @samp{t} stands for ``two''.
9228 @footnote{@samp{b} cannot be used because these format letters are also
9229 used with the @code{x} command, where @samp{b} stands for ``byte'';
9230 see @ref{Memory,,Examining Memory}.}
9233 @cindex unknown address, locating
9234 @cindex locate address
9235 Print as an address, both absolute in hexadecimal and as an offset from
9236 the nearest preceding symbol. You can use this format used to discover
9237 where (in what function) an unknown address is located:
9240 (@value{GDBP}) p/a 0x54320
9241 $3 = 0x54320 <_initialize_vx+396>
9245 The command @code{info symbol 0x54320} yields similar results.
9246 @xref{Symbols, info symbol}.
9249 Regard as an integer and print it as a character constant. This
9250 prints both the numerical value and its character representation. The
9251 character representation is replaced with the octal escape @samp{\nnn}
9252 for characters outside the 7-bit @sc{ascii} range.
9254 Without this format, @value{GDBN} displays @code{char},
9255 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9256 constants. Single-byte members of vectors are displayed as integer
9260 Regard the bits of the value as a floating point number and print
9261 using typical floating point syntax.
9264 @cindex printing strings
9265 @cindex printing byte arrays
9266 Regard as a string, if possible. With this format, pointers to single-byte
9267 data are displayed as null-terminated strings and arrays of single-byte data
9268 are displayed as fixed-length strings. Other values are displayed in their
9271 Without this format, @value{GDBN} displays pointers to and arrays of
9272 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9273 strings. Single-byte members of a vector are displayed as an integer
9277 Like @samp{x} formatting, the value is treated as an integer and
9278 printed as hexadecimal, but leading zeros are printed to pad the value
9279 to the size of the integer type.
9282 @cindex raw printing
9283 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9284 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9285 Printing}). This typically results in a higher-level display of the
9286 value's contents. The @samp{r} format bypasses any Python
9287 pretty-printer which might exist.
9290 For example, to print the program counter in hex (@pxref{Registers}), type
9297 Note that no space is required before the slash; this is because command
9298 names in @value{GDBN} cannot contain a slash.
9300 To reprint the last value in the value history with a different format,
9301 you can use the @code{print} command with just a format and no
9302 expression. For example, @samp{p/x} reprints the last value in hex.
9305 @section Examining Memory
9307 You can use the command @code{x} (for ``examine'') to examine memory in
9308 any of several formats, independently of your program's data types.
9310 @cindex examining memory
9312 @kindex x @r{(examine memory)}
9313 @item x/@var{nfu} @var{addr}
9316 Use the @code{x} command to examine memory.
9319 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9320 much memory to display and how to format it; @var{addr} is an
9321 expression giving the address where you want to start displaying memory.
9322 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9323 Several commands set convenient defaults for @var{addr}.
9326 @item @var{n}, the repeat count
9327 The repeat count is a decimal integer; the default is 1. It specifies
9328 how much memory (counting by units @var{u}) to display. If a negative
9329 number is specified, memory is examined backward from @var{addr}.
9330 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9333 @item @var{f}, the display format
9334 The display format is one of the formats used by @code{print}
9335 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9336 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9337 The default is @samp{x} (hexadecimal) initially. The default changes
9338 each time you use either @code{x} or @code{print}.
9340 @item @var{u}, the unit size
9341 The unit size is any of
9347 Halfwords (two bytes).
9349 Words (four bytes). This is the initial default.
9351 Giant words (eight bytes).
9354 Each time you specify a unit size with @code{x}, that size becomes the
9355 default unit the next time you use @code{x}. For the @samp{i} format,
9356 the unit size is ignored and is normally not written. For the @samp{s} format,
9357 the unit size defaults to @samp{b}, unless it is explicitly given.
9358 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9359 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9360 Note that the results depend on the programming language of the
9361 current compilation unit. If the language is C, the @samp{s}
9362 modifier will use the UTF-16 encoding while @samp{w} will use
9363 UTF-32. The encoding is set by the programming language and cannot
9366 @item @var{addr}, starting display address
9367 @var{addr} is the address where you want @value{GDBN} to begin displaying
9368 memory. The expression need not have a pointer value (though it may);
9369 it is always interpreted as an integer address of a byte of memory.
9370 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9371 @var{addr} is usually just after the last address examined---but several
9372 other commands also set the default address: @code{info breakpoints} (to
9373 the address of the last breakpoint listed), @code{info line} (to the
9374 starting address of a line), and @code{print} (if you use it to display
9375 a value from memory).
9378 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9379 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9380 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9381 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9382 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9384 You can also specify a negative repeat count to examine memory backward
9385 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9386 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9388 Since the letters indicating unit sizes are all distinct from the
9389 letters specifying output formats, you do not have to remember whether
9390 unit size or format comes first; either order works. The output
9391 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9392 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9394 Even though the unit size @var{u} is ignored for the formats @samp{s}
9395 and @samp{i}, you might still want to use a count @var{n}; for example,
9396 @samp{3i} specifies that you want to see three machine instructions,
9397 including any operands. For convenience, especially when used with
9398 the @code{display} command, the @samp{i} format also prints branch delay
9399 slot instructions, if any, beyond the count specified, which immediately
9400 follow the last instruction that is within the count. The command
9401 @code{disassemble} gives an alternative way of inspecting machine
9402 instructions; see @ref{Machine Code,,Source and Machine Code}.
9404 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9405 the command displays null-terminated strings or instructions before the given
9406 address as many as the absolute value of the given number. For the @samp{i}
9407 format, we use line number information in the debug info to accurately locate
9408 instruction boundaries while disassembling backward. If line info is not
9409 available, the command stops examining memory with an error message.
9411 All the defaults for the arguments to @code{x} are designed to make it
9412 easy to continue scanning memory with minimal specifications each time
9413 you use @code{x}. For example, after you have inspected three machine
9414 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9415 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9416 the repeat count @var{n} is used again; the other arguments default as
9417 for successive uses of @code{x}.
9419 When examining machine instructions, the instruction at current program
9420 counter is shown with a @code{=>} marker. For example:
9423 (@value{GDBP}) x/5i $pc-6
9424 0x804837f <main+11>: mov %esp,%ebp
9425 0x8048381 <main+13>: push %ecx
9426 0x8048382 <main+14>: sub $0x4,%esp
9427 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9428 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9431 @cindex @code{$_}, @code{$__}, and value history
9432 The addresses and contents printed by the @code{x} command are not saved
9433 in the value history because there is often too much of them and they
9434 would get in the way. Instead, @value{GDBN} makes these values available for
9435 subsequent use in expressions as values of the convenience variables
9436 @code{$_} and @code{$__}. After an @code{x} command, the last address
9437 examined is available for use in expressions in the convenience variable
9438 @code{$_}. The contents of that address, as examined, are available in
9439 the convenience variable @code{$__}.
9441 If the @code{x} command has a repeat count, the address and contents saved
9442 are from the last memory unit printed; this is not the same as the last
9443 address printed if several units were printed on the last line of output.
9445 @anchor{addressable memory unit}
9446 @cindex addressable memory unit
9447 Most targets have an addressable memory unit size of 8 bits. This means
9448 that to each memory address are associated 8 bits of data. Some
9449 targets, however, have other addressable memory unit sizes.
9450 Within @value{GDBN} and this document, the term
9451 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9452 when explicitly referring to a chunk of data of that size. The word
9453 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9454 the addressable memory unit size of the target. For most systems,
9455 addressable memory unit is a synonym of byte.
9457 @cindex remote memory comparison
9458 @cindex target memory comparison
9459 @cindex verify remote memory image
9460 @cindex verify target memory image
9461 When you are debugging a program running on a remote target machine
9462 (@pxref{Remote Debugging}), you may wish to verify the program's image
9463 in the remote machine's memory against the executable file you
9464 downloaded to the target. Or, on any target, you may want to check
9465 whether the program has corrupted its own read-only sections. The
9466 @code{compare-sections} command is provided for such situations.
9469 @kindex compare-sections
9470 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9471 Compare the data of a loadable section @var{section-name} in the
9472 executable file of the program being debugged with the same section in
9473 the target machine's memory, and report any mismatches. With no
9474 arguments, compares all loadable sections. With an argument of
9475 @code{-r}, compares all loadable read-only sections.
9477 Note: for remote targets, this command can be accelerated if the
9478 target supports computing the CRC checksum of a block of memory
9479 (@pxref{qCRC packet}).
9483 @section Automatic Display
9484 @cindex automatic display
9485 @cindex display of expressions
9487 If you find that you want to print the value of an expression frequently
9488 (to see how it changes), you might want to add it to the @dfn{automatic
9489 display list} so that @value{GDBN} prints its value each time your program stops.
9490 Each expression added to the list is given a number to identify it;
9491 to remove an expression from the list, you specify that number.
9492 The automatic display looks like this:
9496 3: bar[5] = (struct hack *) 0x3804
9500 This display shows item numbers, expressions and their current values. As with
9501 displays you request manually using @code{x} or @code{print}, you can
9502 specify the output format you prefer; in fact, @code{display} decides
9503 whether to use @code{print} or @code{x} depending your format
9504 specification---it uses @code{x} if you specify either the @samp{i}
9505 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9509 @item display @var{expr}
9510 Add the expression @var{expr} to the list of expressions to display
9511 each time your program stops. @xref{Expressions, ,Expressions}.
9513 @code{display} does not repeat if you press @key{RET} again after using it.
9515 @item display/@var{fmt} @var{expr}
9516 For @var{fmt} specifying only a display format and not a size or
9517 count, add the expression @var{expr} to the auto-display list but
9518 arrange to display it each time in the specified format @var{fmt}.
9519 @xref{Output Formats,,Output Formats}.
9521 @item display/@var{fmt} @var{addr}
9522 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9523 number of units, add the expression @var{addr} as a memory address to
9524 be examined each time your program stops. Examining means in effect
9525 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9528 For example, @samp{display/i $pc} can be helpful, to see the machine
9529 instruction about to be executed each time execution stops (@samp{$pc}
9530 is a common name for the program counter; @pxref{Registers, ,Registers}).
9533 @kindex delete display
9535 @item undisplay @var{dnums}@dots{}
9536 @itemx delete display @var{dnums}@dots{}
9537 Remove items from the list of expressions to display. Specify the
9538 numbers of the displays that you want affected with the command
9539 argument @var{dnums}. It can be a single display number, one of the
9540 numbers shown in the first field of the @samp{info display} display;
9541 or it could be a range of display numbers, as in @code{2-4}.
9543 @code{undisplay} does not repeat if you press @key{RET} after using it.
9544 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9546 @kindex disable display
9547 @item disable display @var{dnums}@dots{}
9548 Disable the display of item numbers @var{dnums}. A disabled display
9549 item is not printed automatically, but is not forgotten. It may be
9550 enabled again later. Specify the numbers of the displays that you
9551 want affected with the command argument @var{dnums}. It can be a
9552 single display number, one of the numbers shown in the first field of
9553 the @samp{info display} display; or it could be a range of display
9554 numbers, as in @code{2-4}.
9556 @kindex enable display
9557 @item enable display @var{dnums}@dots{}
9558 Enable display of item numbers @var{dnums}. It becomes effective once
9559 again in auto display of its expression, until you specify otherwise.
9560 Specify the numbers of the displays that you want affected with the
9561 command argument @var{dnums}. It can be a single display number, one
9562 of the numbers shown in the first field of the @samp{info display}
9563 display; or it could be a range of display numbers, as in @code{2-4}.
9566 Display the current values of the expressions on the list, just as is
9567 done when your program stops.
9569 @kindex info display
9571 Print the list of expressions previously set up to display
9572 automatically, each one with its item number, but without showing the
9573 values. This includes disabled expressions, which are marked as such.
9574 It also includes expressions which would not be displayed right now
9575 because they refer to automatic variables not currently available.
9578 @cindex display disabled out of scope
9579 If a display expression refers to local variables, then it does not make
9580 sense outside the lexical context for which it was set up. Such an
9581 expression is disabled when execution enters a context where one of its
9582 variables is not defined. For example, if you give the command
9583 @code{display last_char} while inside a function with an argument
9584 @code{last_char}, @value{GDBN} displays this argument while your program
9585 continues to stop inside that function. When it stops elsewhere---where
9586 there is no variable @code{last_char}---the display is disabled
9587 automatically. The next time your program stops where @code{last_char}
9588 is meaningful, you can enable the display expression once again.
9590 @node Print Settings
9591 @section Print Settings
9593 @cindex format options
9594 @cindex print settings
9595 @value{GDBN} provides the following ways to control how arrays, structures,
9596 and symbols are printed.
9599 These settings are useful for debugging programs in any language:
9603 @item set print address
9604 @itemx set print address on
9605 @cindex print/don't print memory addresses
9606 @value{GDBN} prints memory addresses showing the location of stack
9607 traces, structure values, pointer values, breakpoints, and so forth,
9608 even when it also displays the contents of those addresses. The default
9609 is @code{on}. For example, this is what a stack frame display looks like with
9610 @code{set print address on}:
9615 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9617 530 if (lquote != def_lquote)
9621 @item set print address off
9622 Do not print addresses when displaying their contents. For example,
9623 this is the same stack frame displayed with @code{set print address off}:
9627 (@value{GDBP}) set print addr off
9629 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9630 530 if (lquote != def_lquote)
9634 You can use @samp{set print address off} to eliminate all machine
9635 dependent displays from the @value{GDBN} interface. For example, with
9636 @code{print address off}, you should get the same text for backtraces on
9637 all machines---whether or not they involve pointer arguments.
9640 @item show print address
9641 Show whether or not addresses are to be printed.
9644 When @value{GDBN} prints a symbolic address, it normally prints the
9645 closest earlier symbol plus an offset. If that symbol does not uniquely
9646 identify the address (for example, it is a name whose scope is a single
9647 source file), you may need to clarify. One way to do this is with
9648 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9649 you can set @value{GDBN} to print the source file and line number when
9650 it prints a symbolic address:
9653 @item set print symbol-filename on
9654 @cindex source file and line of a symbol
9655 @cindex symbol, source file and line
9656 Tell @value{GDBN} to print the source file name and line number of a
9657 symbol in the symbolic form of an address.
9659 @item set print symbol-filename off
9660 Do not print source file name and line number of a symbol. This is the
9663 @item show print symbol-filename
9664 Show whether or not @value{GDBN} will print the source file name and
9665 line number of a symbol in the symbolic form of an address.
9668 Another situation where it is helpful to show symbol filenames and line
9669 numbers is when disassembling code; @value{GDBN} shows you the line
9670 number and source file that corresponds to each instruction.
9672 Also, you may wish to see the symbolic form only if the address being
9673 printed is reasonably close to the closest earlier symbol:
9676 @item set print max-symbolic-offset @var{max-offset}
9677 @itemx set print max-symbolic-offset unlimited
9678 @cindex maximum value for offset of closest symbol
9679 Tell @value{GDBN} to only display the symbolic form of an address if the
9680 offset between the closest earlier symbol and the address is less than
9681 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9682 to always print the symbolic form of an address if any symbol precedes
9683 it. Zero is equivalent to @code{unlimited}.
9685 @item show print max-symbolic-offset
9686 Ask how large the maximum offset is that @value{GDBN} prints in a
9690 @cindex wild pointer, interpreting
9691 @cindex pointer, finding referent
9692 If you have a pointer and you are not sure where it points, try
9693 @samp{set print symbol-filename on}. Then you can determine the name
9694 and source file location of the variable where it points, using
9695 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9696 For example, here @value{GDBN} shows that a variable @code{ptt} points
9697 at another variable @code{t}, defined in @file{hi2.c}:
9700 (@value{GDBP}) set print symbol-filename on
9701 (@value{GDBP}) p/a ptt
9702 $4 = 0xe008 <t in hi2.c>
9706 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9707 does not show the symbol name and filename of the referent, even with
9708 the appropriate @code{set print} options turned on.
9711 You can also enable @samp{/a}-like formatting all the time using
9712 @samp{set print symbol on}:
9715 @item set print symbol on
9716 Tell @value{GDBN} to print the symbol corresponding to an address, if
9719 @item set print symbol off
9720 Tell @value{GDBN} not to print the symbol corresponding to an
9721 address. In this mode, @value{GDBN} will still print the symbol
9722 corresponding to pointers to functions. This is the default.
9724 @item show print symbol
9725 Show whether @value{GDBN} will display the symbol corresponding to an
9729 Other settings control how different kinds of objects are printed:
9732 @item set print array
9733 @itemx set print array on
9734 @cindex pretty print arrays
9735 Pretty print arrays. This format is more convenient to read,
9736 but uses more space. The default is off.
9738 @item set print array off
9739 Return to compressed format for arrays.
9741 @item show print array
9742 Show whether compressed or pretty format is selected for displaying
9745 @cindex print array indexes
9746 @item set print array-indexes
9747 @itemx set print array-indexes on
9748 Print the index of each element when displaying arrays. May be more
9749 convenient to locate a given element in the array or quickly find the
9750 index of a given element in that printed array. The default is off.
9752 @item set print array-indexes off
9753 Stop printing element indexes when displaying arrays.
9755 @item show print array-indexes
9756 Show whether the index of each element is printed when displaying
9759 @item set print elements @var{number-of-elements}
9760 @itemx set print elements unlimited
9761 @cindex number of array elements to print
9762 @cindex limit on number of printed array elements
9763 Set a limit on how many elements of an array @value{GDBN} will print.
9764 If @value{GDBN} is printing a large array, it stops printing after it has
9765 printed the number of elements set by the @code{set print elements} command.
9766 This limit also applies to the display of strings.
9767 When @value{GDBN} starts, this limit is set to 200.
9768 Setting @var{number-of-elements} to @code{unlimited} or zero means
9769 that the number of elements to print is unlimited.
9771 @item show print elements
9772 Display the number of elements of a large array that @value{GDBN} will print.
9773 If the number is 0, then the printing is unlimited.
9775 @item set print frame-arguments @var{value}
9776 @kindex set print frame-arguments
9777 @cindex printing frame argument values
9778 @cindex print all frame argument values
9779 @cindex print frame argument values for scalars only
9780 @cindex do not print frame argument values
9781 This command allows to control how the values of arguments are printed
9782 when the debugger prints a frame (@pxref{Frames}). The possible
9787 The values of all arguments are printed.
9790 Print the value of an argument only if it is a scalar. The value of more
9791 complex arguments such as arrays, structures, unions, etc, is replaced
9792 by @code{@dots{}}. This is the default. Here is an example where
9793 only scalar arguments are shown:
9796 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9801 None of the argument values are printed. Instead, the value of each argument
9802 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9805 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9810 By default, only scalar arguments are printed. This command can be used
9811 to configure the debugger to print the value of all arguments, regardless
9812 of their type. However, it is often advantageous to not print the value
9813 of more complex parameters. For instance, it reduces the amount of
9814 information printed in each frame, making the backtrace more readable.
9815 Also, it improves performance when displaying Ada frames, because
9816 the computation of large arguments can sometimes be CPU-intensive,
9817 especially in large applications. Setting @code{print frame-arguments}
9818 to @code{scalars} (the default) or @code{none} avoids this computation,
9819 thus speeding up the display of each Ada frame.
9821 @item show print frame-arguments
9822 Show how the value of arguments should be displayed when printing a frame.
9824 @item set print raw frame-arguments on
9825 Print frame arguments in raw, non pretty-printed, form.
9827 @item set print raw frame-arguments off
9828 Print frame arguments in pretty-printed form, if there is a pretty-printer
9829 for the value (@pxref{Pretty Printing}),
9830 otherwise print the value in raw form.
9831 This is the default.
9833 @item show print raw frame-arguments
9834 Show whether to print frame arguments in raw form.
9836 @anchor{set print entry-values}
9837 @item set print entry-values @var{value}
9838 @kindex set print entry-values
9839 Set printing of frame argument values at function entry. In some cases
9840 @value{GDBN} can determine the value of function argument which was passed by
9841 the function caller, even if the value was modified inside the called function
9842 and therefore is different. With optimized code, the current value could be
9843 unavailable, but the entry value may still be known.
9845 The default value is @code{default} (see below for its description). Older
9846 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9847 this feature will behave in the @code{default} setting the same way as with the
9850 This functionality is currently supported only by DWARF 2 debugging format and
9851 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9852 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9855 The @var{value} parameter can be one of the following:
9859 Print only actual parameter values, never print values from function entry
9863 #0 different (val=6)
9864 #0 lost (val=<optimized out>)
9866 #0 invalid (val=<optimized out>)
9870 Print only parameter values from function entry point. The actual parameter
9871 values are never printed.
9873 #0 equal (val@@entry=5)
9874 #0 different (val@@entry=5)
9875 #0 lost (val@@entry=5)
9876 #0 born (val@@entry=<optimized out>)
9877 #0 invalid (val@@entry=<optimized out>)
9881 Print only parameter values from function entry point. If value from function
9882 entry point is not known while the actual value is known, print the actual
9883 value for such parameter.
9885 #0 equal (val@@entry=5)
9886 #0 different (val@@entry=5)
9887 #0 lost (val@@entry=5)
9889 #0 invalid (val@@entry=<optimized out>)
9893 Print actual parameter values. If actual parameter value is not known while
9894 value from function entry point is known, print the entry point value for such
9898 #0 different (val=6)
9899 #0 lost (val@@entry=5)
9901 #0 invalid (val=<optimized out>)
9905 Always print both the actual parameter value and its value from function entry
9906 point, even if values of one or both are not available due to compiler
9909 #0 equal (val=5, val@@entry=5)
9910 #0 different (val=6, val@@entry=5)
9911 #0 lost (val=<optimized out>, val@@entry=5)
9912 #0 born (val=10, val@@entry=<optimized out>)
9913 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9917 Print the actual parameter value if it is known and also its value from
9918 function entry point if it is known. If neither is known, print for the actual
9919 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9920 values are known and identical, print the shortened
9921 @code{param=param@@entry=VALUE} notation.
9923 #0 equal (val=val@@entry=5)
9924 #0 different (val=6, val@@entry=5)
9925 #0 lost (val@@entry=5)
9927 #0 invalid (val=<optimized out>)
9931 Always print the actual parameter value. Print also its value from function
9932 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9933 if both values are known and identical, print the shortened
9934 @code{param=param@@entry=VALUE} notation.
9936 #0 equal (val=val@@entry=5)
9937 #0 different (val=6, val@@entry=5)
9938 #0 lost (val=<optimized out>, val@@entry=5)
9940 #0 invalid (val=<optimized out>)
9944 For analysis messages on possible failures of frame argument values at function
9945 entry resolution see @ref{set debug entry-values}.
9947 @item show print entry-values
9948 Show the method being used for printing of frame argument values at function
9951 @item set print repeats @var{number-of-repeats}
9952 @itemx set print repeats unlimited
9953 @cindex repeated array elements
9954 Set the threshold for suppressing display of repeated array
9955 elements. When the number of consecutive identical elements of an
9956 array exceeds the threshold, @value{GDBN} prints the string
9957 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9958 identical repetitions, instead of displaying the identical elements
9959 themselves. Setting the threshold to @code{unlimited} or zero will
9960 cause all elements to be individually printed. The default threshold
9963 @item show print repeats
9964 Display the current threshold for printing repeated identical
9967 @item set print null-stop
9968 @cindex @sc{null} elements in arrays
9969 Cause @value{GDBN} to stop printing the characters of an array when the first
9970 @sc{null} is encountered. This is useful when large arrays actually
9971 contain only short strings.
9974 @item show print null-stop
9975 Show whether @value{GDBN} stops printing an array on the first
9976 @sc{null} character.
9978 @item set print pretty on
9979 @cindex print structures in indented form
9980 @cindex indentation in structure display
9981 Cause @value{GDBN} to print structures in an indented format with one member
9982 per line, like this:
9997 @item set print pretty off
9998 Cause @value{GDBN} to print structures in a compact format, like this:
10002 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10003 meat = 0x54 "Pork"@}
10008 This is the default format.
10010 @item show print pretty
10011 Show which format @value{GDBN} is using to print structures.
10013 @item set print sevenbit-strings on
10014 @cindex eight-bit characters in strings
10015 @cindex octal escapes in strings
10016 Print using only seven-bit characters; if this option is set,
10017 @value{GDBN} displays any eight-bit characters (in strings or
10018 character values) using the notation @code{\}@var{nnn}. This setting is
10019 best if you are working in English (@sc{ascii}) and you use the
10020 high-order bit of characters as a marker or ``meta'' bit.
10022 @item set print sevenbit-strings off
10023 Print full eight-bit characters. This allows the use of more
10024 international character sets, and is the default.
10026 @item show print sevenbit-strings
10027 Show whether or not @value{GDBN} is printing only seven-bit characters.
10029 @item set print union on
10030 @cindex unions in structures, printing
10031 Tell @value{GDBN} to print unions which are contained in structures
10032 and other unions. This is the default setting.
10034 @item set print union off
10035 Tell @value{GDBN} not to print unions which are contained in
10036 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10039 @item show print union
10040 Ask @value{GDBN} whether or not it will print unions which are contained in
10041 structures and other unions.
10043 For example, given the declarations
10046 typedef enum @{Tree, Bug@} Species;
10047 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10048 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10059 struct thing foo = @{Tree, @{Acorn@}@};
10063 with @code{set print union on} in effect @samp{p foo} would print
10066 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10070 and with @code{set print union off} in effect it would print
10073 $1 = @{it = Tree, form = @{...@}@}
10077 @code{set print union} affects programs written in C-like languages
10083 These settings are of interest when debugging C@t{++} programs:
10086 @cindex demangling C@t{++} names
10087 @item set print demangle
10088 @itemx set print demangle on
10089 Print C@t{++} names in their source form rather than in the encoded
10090 (``mangled'') form passed to the assembler and linker for type-safe
10091 linkage. The default is on.
10093 @item show print demangle
10094 Show whether C@t{++} names are printed in mangled or demangled form.
10096 @item set print asm-demangle
10097 @itemx set print asm-demangle on
10098 Print C@t{++} names in their source form rather than their mangled form, even
10099 in assembler code printouts such as instruction disassemblies.
10100 The default is off.
10102 @item show print asm-demangle
10103 Show whether C@t{++} names in assembly listings are printed in mangled
10106 @cindex C@t{++} symbol decoding style
10107 @cindex symbol decoding style, C@t{++}
10108 @kindex set demangle-style
10109 @item set demangle-style @var{style}
10110 Choose among several encoding schemes used by different compilers to
10111 represent C@t{++} names. The choices for @var{style} are currently:
10115 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10116 This is the default.
10119 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10122 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10125 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10128 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10129 @strong{Warning:} this setting alone is not sufficient to allow
10130 debugging @code{cfront}-generated executables. @value{GDBN} would
10131 require further enhancement to permit that.
10134 If you omit @var{style}, you will see a list of possible formats.
10136 @item show demangle-style
10137 Display the encoding style currently in use for decoding C@t{++} symbols.
10139 @item set print object
10140 @itemx set print object on
10141 @cindex derived type of an object, printing
10142 @cindex display derived types
10143 When displaying a pointer to an object, identify the @emph{actual}
10144 (derived) type of the object rather than the @emph{declared} type, using
10145 the virtual function table. Note that the virtual function table is
10146 required---this feature can only work for objects that have run-time
10147 type identification; a single virtual method in the object's declared
10148 type is sufficient. Note that this setting is also taken into account when
10149 working with variable objects via MI (@pxref{GDB/MI}).
10151 @item set print object off
10152 Display only the declared type of objects, without reference to the
10153 virtual function table. This is the default setting.
10155 @item show print object
10156 Show whether actual, or declared, object types are displayed.
10158 @item set print static-members
10159 @itemx set print static-members on
10160 @cindex static members of C@t{++} objects
10161 Print static members when displaying a C@t{++} object. The default is on.
10163 @item set print static-members off
10164 Do not print static members when displaying a C@t{++} object.
10166 @item show print static-members
10167 Show whether C@t{++} static members are printed or not.
10169 @item set print pascal_static-members
10170 @itemx set print pascal_static-members on
10171 @cindex static members of Pascal objects
10172 @cindex Pascal objects, static members display
10173 Print static members when displaying a Pascal object. The default is on.
10175 @item set print pascal_static-members off
10176 Do not print static members when displaying a Pascal object.
10178 @item show print pascal_static-members
10179 Show whether Pascal static members are printed or not.
10181 @c These don't work with HP ANSI C++ yet.
10182 @item set print vtbl
10183 @itemx set print vtbl on
10184 @cindex pretty print C@t{++} virtual function tables
10185 @cindex virtual functions (C@t{++}) display
10186 @cindex VTBL display
10187 Pretty print C@t{++} virtual function tables. The default is off.
10188 (The @code{vtbl} commands do not work on programs compiled with the HP
10189 ANSI C@t{++} compiler (@code{aCC}).)
10191 @item set print vtbl off
10192 Do not pretty print C@t{++} virtual function tables.
10194 @item show print vtbl
10195 Show whether C@t{++} virtual function tables are pretty printed, or not.
10198 @node Pretty Printing
10199 @section Pretty Printing
10201 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10202 Python code. It greatly simplifies the display of complex objects. This
10203 mechanism works for both MI and the CLI.
10206 * Pretty-Printer Introduction:: Introduction to pretty-printers
10207 * Pretty-Printer Example:: An example pretty-printer
10208 * Pretty-Printer Commands:: Pretty-printer commands
10211 @node Pretty-Printer Introduction
10212 @subsection Pretty-Printer Introduction
10214 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10215 registered for the value. If there is then @value{GDBN} invokes the
10216 pretty-printer to print the value. Otherwise the value is printed normally.
10218 Pretty-printers are normally named. This makes them easy to manage.
10219 The @samp{info pretty-printer} command will list all the installed
10220 pretty-printers with their names.
10221 If a pretty-printer can handle multiple data types, then its
10222 @dfn{subprinters} are the printers for the individual data types.
10223 Each such subprinter has its own name.
10224 The format of the name is @var{printer-name};@var{subprinter-name}.
10226 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10227 Typically they are automatically loaded and registered when the corresponding
10228 debug information is loaded, thus making them available without having to
10229 do anything special.
10231 There are three places where a pretty-printer can be registered.
10235 Pretty-printers registered globally are available when debugging
10239 Pretty-printers registered with a program space are available only
10240 when debugging that program.
10241 @xref{Progspaces In Python}, for more details on program spaces in Python.
10244 Pretty-printers registered with an objfile are loaded and unloaded
10245 with the corresponding objfile (e.g., shared library).
10246 @xref{Objfiles In Python}, for more details on objfiles in Python.
10249 @xref{Selecting Pretty-Printers}, for further information on how
10250 pretty-printers are selected,
10252 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10255 @node Pretty-Printer Example
10256 @subsection Pretty-Printer Example
10258 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10261 (@value{GDBP}) print s
10263 static npos = 4294967295,
10265 <std::allocator<char>> = @{
10266 <__gnu_cxx::new_allocator<char>> = @{
10267 <No data fields>@}, <No data fields>
10269 members of std::basic_string<char, std::char_traits<char>,
10270 std::allocator<char> >::_Alloc_hider:
10271 _M_p = 0x804a014 "abcd"
10276 With a pretty-printer for @code{std::string} only the contents are printed:
10279 (@value{GDBP}) print s
10283 @node Pretty-Printer Commands
10284 @subsection Pretty-Printer Commands
10285 @cindex pretty-printer commands
10288 @kindex info pretty-printer
10289 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10290 Print the list of installed pretty-printers.
10291 This includes disabled pretty-printers, which are marked as such.
10293 @var{object-regexp} is a regular expression matching the objects
10294 whose pretty-printers to list.
10295 Objects can be @code{global}, the program space's file
10296 (@pxref{Progspaces In Python}),
10297 and the object files within that program space (@pxref{Objfiles In Python}).
10298 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10299 looks up a printer from these three objects.
10301 @var{name-regexp} is a regular expression matching the name of the printers
10304 @kindex disable pretty-printer
10305 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10306 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10307 A disabled pretty-printer is not forgotten, it may be enabled again later.
10309 @kindex enable pretty-printer
10310 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10311 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10316 Suppose we have three pretty-printers installed: one from library1.so
10317 named @code{foo} that prints objects of type @code{foo}, and
10318 another from library2.so named @code{bar} that prints two types of objects,
10319 @code{bar1} and @code{bar2}.
10322 (gdb) info pretty-printer
10329 (gdb) info pretty-printer library2
10334 (gdb) disable pretty-printer library1
10336 2 of 3 printers enabled
10337 (gdb) info pretty-printer
10344 (gdb) disable pretty-printer library2 bar:bar1
10346 1 of 3 printers enabled
10347 (gdb) info pretty-printer library2
10354 (gdb) disable pretty-printer library2 bar
10356 0 of 3 printers enabled
10357 (gdb) info pretty-printer library2
10366 Note that for @code{bar} the entire printer can be disabled,
10367 as can each individual subprinter.
10369 @node Value History
10370 @section Value History
10372 @cindex value history
10373 @cindex history of values printed by @value{GDBN}
10374 Values printed by the @code{print} command are saved in the @value{GDBN}
10375 @dfn{value history}. This allows you to refer to them in other expressions.
10376 Values are kept until the symbol table is re-read or discarded
10377 (for example with the @code{file} or @code{symbol-file} commands).
10378 When the symbol table changes, the value history is discarded,
10379 since the values may contain pointers back to the types defined in the
10384 @cindex history number
10385 The values printed are given @dfn{history numbers} by which you can
10386 refer to them. These are successive integers starting with one.
10387 @code{print} shows you the history number assigned to a value by
10388 printing @samp{$@var{num} = } before the value; here @var{num} is the
10391 To refer to any previous value, use @samp{$} followed by the value's
10392 history number. The way @code{print} labels its output is designed to
10393 remind you of this. Just @code{$} refers to the most recent value in
10394 the history, and @code{$$} refers to the value before that.
10395 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10396 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10397 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10399 For example, suppose you have just printed a pointer to a structure and
10400 want to see the contents of the structure. It suffices to type
10406 If you have a chain of structures where the component @code{next} points
10407 to the next one, you can print the contents of the next one with this:
10414 You can print successive links in the chain by repeating this
10415 command---which you can do by just typing @key{RET}.
10417 Note that the history records values, not expressions. If the value of
10418 @code{x} is 4 and you type these commands:
10426 then the value recorded in the value history by the @code{print} command
10427 remains 4 even though the value of @code{x} has changed.
10430 @kindex show values
10432 Print the last ten values in the value history, with their item numbers.
10433 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10434 values} does not change the history.
10436 @item show values @var{n}
10437 Print ten history values centered on history item number @var{n}.
10439 @item show values +
10440 Print ten history values just after the values last printed. If no more
10441 values are available, @code{show values +} produces no display.
10444 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10445 same effect as @samp{show values +}.
10447 @node Convenience Vars
10448 @section Convenience Variables
10450 @cindex convenience variables
10451 @cindex user-defined variables
10452 @value{GDBN} provides @dfn{convenience variables} that you can use within
10453 @value{GDBN} to hold on to a value and refer to it later. These variables
10454 exist entirely within @value{GDBN}; they are not part of your program, and
10455 setting a convenience variable has no direct effect on further execution
10456 of your program. That is why you can use them freely.
10458 Convenience variables are prefixed with @samp{$}. Any name preceded by
10459 @samp{$} can be used for a convenience variable, unless it is one of
10460 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10461 (Value history references, in contrast, are @emph{numbers} preceded
10462 by @samp{$}. @xref{Value History, ,Value History}.)
10464 You can save a value in a convenience variable with an assignment
10465 expression, just as you would set a variable in your program.
10469 set $foo = *object_ptr
10473 would save in @code{$foo} the value contained in the object pointed to by
10476 Using a convenience variable for the first time creates it, but its
10477 value is @code{void} until you assign a new value. You can alter the
10478 value with another assignment at any time.
10480 Convenience variables have no fixed types. You can assign a convenience
10481 variable any type of value, including structures and arrays, even if
10482 that variable already has a value of a different type. The convenience
10483 variable, when used as an expression, has the type of its current value.
10486 @kindex show convenience
10487 @cindex show all user variables and functions
10488 @item show convenience
10489 Print a list of convenience variables used so far, and their values,
10490 as well as a list of the convenience functions.
10491 Abbreviated @code{show conv}.
10493 @kindex init-if-undefined
10494 @cindex convenience variables, initializing
10495 @item init-if-undefined $@var{variable} = @var{expression}
10496 Set a convenience variable if it has not already been set. This is useful
10497 for user-defined commands that keep some state. It is similar, in concept,
10498 to using local static variables with initializers in C (except that
10499 convenience variables are global). It can also be used to allow users to
10500 override default values used in a command script.
10502 If the variable is already defined then the expression is not evaluated so
10503 any side-effects do not occur.
10506 One of the ways to use a convenience variable is as a counter to be
10507 incremented or a pointer to be advanced. For example, to print
10508 a field from successive elements of an array of structures:
10512 print bar[$i++]->contents
10516 Repeat that command by typing @key{RET}.
10518 Some convenience variables are created automatically by @value{GDBN} and given
10519 values likely to be useful.
10522 @vindex $_@r{, convenience variable}
10524 The variable @code{$_} is automatically set by the @code{x} command to
10525 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10526 commands which provide a default address for @code{x} to examine also
10527 set @code{$_} to that address; these commands include @code{info line}
10528 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10529 except when set by the @code{x} command, in which case it is a pointer
10530 to the type of @code{$__}.
10532 @vindex $__@r{, convenience variable}
10534 The variable @code{$__} is automatically set by the @code{x} command
10535 to the value found in the last address examined. Its type is chosen
10536 to match the format in which the data was printed.
10539 @vindex $_exitcode@r{, convenience variable}
10540 When the program being debugged terminates normally, @value{GDBN}
10541 automatically sets this variable to the exit code of the program, and
10542 resets @code{$_exitsignal} to @code{void}.
10545 @vindex $_exitsignal@r{, convenience variable}
10546 When the program being debugged dies due to an uncaught signal,
10547 @value{GDBN} automatically sets this variable to that signal's number,
10548 and resets @code{$_exitcode} to @code{void}.
10550 To distinguish between whether the program being debugged has exited
10551 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10552 @code{$_exitsignal} is not @code{void}), the convenience function
10553 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10554 Functions}). For example, considering the following source code:
10557 #include <signal.h>
10560 main (int argc, char *argv[])
10567 A valid way of telling whether the program being debugged has exited
10568 or signalled would be:
10571 (@value{GDBP}) define has_exited_or_signalled
10572 Type commands for definition of ``has_exited_or_signalled''.
10573 End with a line saying just ``end''.
10574 >if $_isvoid ($_exitsignal)
10575 >echo The program has exited\n
10577 >echo The program has signalled\n
10583 Program terminated with signal SIGALRM, Alarm clock.
10584 The program no longer exists.
10585 (@value{GDBP}) has_exited_or_signalled
10586 The program has signalled
10589 As can be seen, @value{GDBN} correctly informs that the program being
10590 debugged has signalled, since it calls @code{raise} and raises a
10591 @code{SIGALRM} signal. If the program being debugged had not called
10592 @code{raise}, then @value{GDBN} would report a normal exit:
10595 (@value{GDBP}) has_exited_or_signalled
10596 The program has exited
10600 The variable @code{$_exception} is set to the exception object being
10601 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10604 @itemx $_probe_arg0@dots{}$_probe_arg11
10605 Arguments to a static probe. @xref{Static Probe Points}.
10608 @vindex $_sdata@r{, inspect, convenience variable}
10609 The variable @code{$_sdata} contains extra collected static tracepoint
10610 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10611 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10612 if extra static tracepoint data has not been collected.
10615 @vindex $_siginfo@r{, convenience variable}
10616 The variable @code{$_siginfo} contains extra signal information
10617 (@pxref{extra signal information}). Note that @code{$_siginfo}
10618 could be empty, if the application has not yet received any signals.
10619 For example, it will be empty before you execute the @code{run} command.
10622 @vindex $_tlb@r{, convenience variable}
10623 The variable @code{$_tlb} is automatically set when debugging
10624 applications running on MS-Windows in native mode or connected to
10625 gdbserver that supports the @code{qGetTIBAddr} request.
10626 @xref{General Query Packets}.
10627 This variable contains the address of the thread information block.
10630 The number of the current inferior. @xref{Inferiors and
10631 Programs, ,Debugging Multiple Inferiors and Programs}.
10634 The thread number of the current thread. @xref{thread numbers}.
10637 The global number of the current thread. @xref{global thread numbers}.
10641 @node Convenience Funs
10642 @section Convenience Functions
10644 @cindex convenience functions
10645 @value{GDBN} also supplies some @dfn{convenience functions}. These
10646 have a syntax similar to convenience variables. A convenience
10647 function can be used in an expression just like an ordinary function;
10648 however, a convenience function is implemented internally to
10651 These functions do not require @value{GDBN} to be configured with
10652 @code{Python} support, which means that they are always available.
10656 @item $_isvoid (@var{expr})
10657 @findex $_isvoid@r{, convenience function}
10658 Return one if the expression @var{expr} is @code{void}. Otherwise it
10661 A @code{void} expression is an expression where the type of the result
10662 is @code{void}. For example, you can examine a convenience variable
10663 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10667 (@value{GDBP}) print $_exitcode
10669 (@value{GDBP}) print $_isvoid ($_exitcode)
10672 Starting program: ./a.out
10673 [Inferior 1 (process 29572) exited normally]
10674 (@value{GDBP}) print $_exitcode
10676 (@value{GDBP}) print $_isvoid ($_exitcode)
10680 In the example above, we used @code{$_isvoid} to check whether
10681 @code{$_exitcode} is @code{void} before and after the execution of the
10682 program being debugged. Before the execution there is no exit code to
10683 be examined, therefore @code{$_exitcode} is @code{void}. After the
10684 execution the program being debugged returned zero, therefore
10685 @code{$_exitcode} is zero, which means that it is not @code{void}
10688 The @code{void} expression can also be a call of a function from the
10689 program being debugged. For example, given the following function:
10698 The result of calling it inside @value{GDBN} is @code{void}:
10701 (@value{GDBP}) print foo ()
10703 (@value{GDBP}) print $_isvoid (foo ())
10705 (@value{GDBP}) set $v = foo ()
10706 (@value{GDBP}) print $v
10708 (@value{GDBP}) print $_isvoid ($v)
10714 These functions require @value{GDBN} to be configured with
10715 @code{Python} support.
10719 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10720 @findex $_memeq@r{, convenience function}
10721 Returns one if the @var{length} bytes at the addresses given by
10722 @var{buf1} and @var{buf2} are equal.
10723 Otherwise it returns zero.
10725 @item $_regex(@var{str}, @var{regex})
10726 @findex $_regex@r{, convenience function}
10727 Returns one if the string @var{str} matches the regular expression
10728 @var{regex}. Otherwise it returns zero.
10729 The syntax of the regular expression is that specified by @code{Python}'s
10730 regular expression support.
10732 @item $_streq(@var{str1}, @var{str2})
10733 @findex $_streq@r{, convenience function}
10734 Returns one if the strings @var{str1} and @var{str2} are equal.
10735 Otherwise it returns zero.
10737 @item $_strlen(@var{str})
10738 @findex $_strlen@r{, convenience function}
10739 Returns the length of string @var{str}.
10741 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10742 @findex $_caller_is@r{, convenience function}
10743 Returns one if the calling function's name is equal to @var{name}.
10744 Otherwise it returns zero.
10746 If the optional argument @var{number_of_frames} is provided,
10747 it is the number of frames up in the stack to look.
10755 at testsuite/gdb.python/py-caller-is.c:21
10756 #1 0x00000000004005a0 in middle_func ()
10757 at testsuite/gdb.python/py-caller-is.c:27
10758 #2 0x00000000004005ab in top_func ()
10759 at testsuite/gdb.python/py-caller-is.c:33
10760 #3 0x00000000004005b6 in main ()
10761 at testsuite/gdb.python/py-caller-is.c:39
10762 (gdb) print $_caller_is ("middle_func")
10764 (gdb) print $_caller_is ("top_func", 2)
10768 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10769 @findex $_caller_matches@r{, convenience function}
10770 Returns one if the calling function's name matches the regular expression
10771 @var{regexp}. Otherwise it returns zero.
10773 If the optional argument @var{number_of_frames} is provided,
10774 it is the number of frames up in the stack to look.
10777 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10778 @findex $_any_caller_is@r{, convenience function}
10779 Returns one if any calling function's name is equal to @var{name}.
10780 Otherwise it returns zero.
10782 If the optional argument @var{number_of_frames} is provided,
10783 it is the number of frames up in the stack to look.
10786 This function differs from @code{$_caller_is} in that this function
10787 checks all stack frames from the immediate caller to the frame specified
10788 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10789 frame specified by @var{number_of_frames}.
10791 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10792 @findex $_any_caller_matches@r{, convenience function}
10793 Returns one if any calling function's name matches the regular expression
10794 @var{regexp}. Otherwise it returns zero.
10796 If the optional argument @var{number_of_frames} is provided,
10797 it is the number of frames up in the stack to look.
10800 This function differs from @code{$_caller_matches} in that this function
10801 checks all stack frames from the immediate caller to the frame specified
10802 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10803 frame specified by @var{number_of_frames}.
10805 @item $_as_string(@var{value})
10806 @findex $_as_string@r{, convenience function}
10807 Return the string representation of @var{value}.
10809 This function is useful to obtain the textual label (enumerator) of an
10810 enumeration value. For example, assuming the variable @var{node} is of
10811 an enumerated type:
10814 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10815 Visiting node of type NODE_INTEGER
10820 @value{GDBN} provides the ability to list and get help on
10821 convenience functions.
10824 @item help function
10825 @kindex help function
10826 @cindex show all convenience functions
10827 Print a list of all convenience functions.
10834 You can refer to machine register contents, in expressions, as variables
10835 with names starting with @samp{$}. The names of registers are different
10836 for each machine; use @code{info registers} to see the names used on
10840 @kindex info registers
10841 @item info registers
10842 Print the names and values of all registers except floating-point
10843 and vector registers (in the selected stack frame).
10845 @kindex info all-registers
10846 @cindex floating point registers
10847 @item info all-registers
10848 Print the names and values of all registers, including floating-point
10849 and vector registers (in the selected stack frame).
10851 @item info registers @var{regname} @dots{}
10852 Print the @dfn{relativized} value of each specified register @var{regname}.
10853 As discussed in detail below, register values are normally relative to
10854 the selected stack frame. The @var{regname} may be any register name valid on
10855 the machine you are using, with or without the initial @samp{$}.
10858 @anchor{standard registers}
10859 @cindex stack pointer register
10860 @cindex program counter register
10861 @cindex process status register
10862 @cindex frame pointer register
10863 @cindex standard registers
10864 @value{GDBN} has four ``standard'' register names that are available (in
10865 expressions) on most machines---whenever they do not conflict with an
10866 architecture's canonical mnemonics for registers. The register names
10867 @code{$pc} and @code{$sp} are used for the program counter register and
10868 the stack pointer. @code{$fp} is used for a register that contains a
10869 pointer to the current stack frame, and @code{$ps} is used for a
10870 register that contains the processor status. For example,
10871 you could print the program counter in hex with
10878 or print the instruction to be executed next with
10885 or add four to the stack pointer@footnote{This is a way of removing
10886 one word from the stack, on machines where stacks grow downward in
10887 memory (most machines, nowadays). This assumes that the innermost
10888 stack frame is selected; setting @code{$sp} is not allowed when other
10889 stack frames are selected. To pop entire frames off the stack,
10890 regardless of machine architecture, use @code{return};
10891 see @ref{Returning, ,Returning from a Function}.} with
10897 Whenever possible, these four standard register names are available on
10898 your machine even though the machine has different canonical mnemonics,
10899 so long as there is no conflict. The @code{info registers} command
10900 shows the canonical names. For example, on the SPARC, @code{info
10901 registers} displays the processor status register as @code{$psr} but you
10902 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10903 is an alias for the @sc{eflags} register.
10905 @value{GDBN} always considers the contents of an ordinary register as an
10906 integer when the register is examined in this way. Some machines have
10907 special registers which can hold nothing but floating point; these
10908 registers are considered to have floating point values. There is no way
10909 to refer to the contents of an ordinary register as floating point value
10910 (although you can @emph{print} it as a floating point value with
10911 @samp{print/f $@var{regname}}).
10913 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10914 means that the data format in which the register contents are saved by
10915 the operating system is not the same one that your program normally
10916 sees. For example, the registers of the 68881 floating point
10917 coprocessor are always saved in ``extended'' (raw) format, but all C
10918 programs expect to work with ``double'' (virtual) format. In such
10919 cases, @value{GDBN} normally works with the virtual format only (the format
10920 that makes sense for your program), but the @code{info registers} command
10921 prints the data in both formats.
10923 @cindex SSE registers (x86)
10924 @cindex MMX registers (x86)
10925 Some machines have special registers whose contents can be interpreted
10926 in several different ways. For example, modern x86-based machines
10927 have SSE and MMX registers that can hold several values packed
10928 together in several different formats. @value{GDBN} refers to such
10929 registers in @code{struct} notation:
10932 (@value{GDBP}) print $xmm1
10934 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10935 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10936 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10937 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10938 v4_int32 = @{0, 20657912, 11, 13@},
10939 v2_int64 = @{88725056443645952, 55834574859@},
10940 uint128 = 0x0000000d0000000b013b36f800000000
10945 To set values of such registers, you need to tell @value{GDBN} which
10946 view of the register you wish to change, as if you were assigning
10947 value to a @code{struct} member:
10950 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10953 Normally, register values are relative to the selected stack frame
10954 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10955 value that the register would contain if all stack frames farther in
10956 were exited and their saved registers restored. In order to see the
10957 true contents of hardware registers, you must select the innermost
10958 frame (with @samp{frame 0}).
10960 @cindex caller-saved registers
10961 @cindex call-clobbered registers
10962 @cindex volatile registers
10963 @cindex <not saved> values
10964 Usually ABIs reserve some registers as not needed to be saved by the
10965 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10966 registers). It may therefore not be possible for @value{GDBN} to know
10967 the value a register had before the call (in other words, in the outer
10968 frame), if the register value has since been changed by the callee.
10969 @value{GDBN} tries to deduce where the inner frame saved
10970 (``callee-saved'') registers, from the debug info, unwind info, or the
10971 machine code generated by your compiler. If some register is not
10972 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10973 its own knowledge of the ABI, or because the debug/unwind info
10974 explicitly says the register's value is undefined), @value{GDBN}
10975 displays @w{@samp{<not saved>}} as the register's value. With targets
10976 that @value{GDBN} has no knowledge of the register saving convention,
10977 if a register was not saved by the callee, then its value and location
10978 in the outer frame are assumed to be the same of the inner frame.
10979 This is usually harmless, because if the register is call-clobbered,
10980 the caller either does not care what is in the register after the
10981 call, or has code to restore the value that it does care about. Note,
10982 however, that if you change such a register in the outer frame, you
10983 may also be affecting the inner frame. Also, the more ``outer'' the
10984 frame is you're looking at, the more likely a call-clobbered
10985 register's value is to be wrong, in the sense that it doesn't actually
10986 represent the value the register had just before the call.
10988 @node Floating Point Hardware
10989 @section Floating Point Hardware
10990 @cindex floating point
10992 Depending on the configuration, @value{GDBN} may be able to give
10993 you more information about the status of the floating point hardware.
10998 Display hardware-dependent information about the floating
10999 point unit. The exact contents and layout vary depending on the
11000 floating point chip. Currently, @samp{info float} is supported on
11001 the ARM and x86 machines.
11005 @section Vector Unit
11006 @cindex vector unit
11008 Depending on the configuration, @value{GDBN} may be able to give you
11009 more information about the status of the vector unit.
11012 @kindex info vector
11014 Display information about the vector unit. The exact contents and
11015 layout vary depending on the hardware.
11018 @node OS Information
11019 @section Operating System Auxiliary Information
11020 @cindex OS information
11022 @value{GDBN} provides interfaces to useful OS facilities that can help
11023 you debug your program.
11025 @cindex auxiliary vector
11026 @cindex vector, auxiliary
11027 Some operating systems supply an @dfn{auxiliary vector} to programs at
11028 startup. This is akin to the arguments and environment that you
11029 specify for a program, but contains a system-dependent variety of
11030 binary values that tell system libraries important details about the
11031 hardware, operating system, and process. Each value's purpose is
11032 identified by an integer tag; the meanings are well-known but system-specific.
11033 Depending on the configuration and operating system facilities,
11034 @value{GDBN} may be able to show you this information. For remote
11035 targets, this functionality may further depend on the remote stub's
11036 support of the @samp{qXfer:auxv:read} packet, see
11037 @ref{qXfer auxiliary vector read}.
11042 Display the auxiliary vector of the inferior, which can be either a
11043 live process or a core dump file. @value{GDBN} prints each tag value
11044 numerically, and also shows names and text descriptions for recognized
11045 tags. Some values in the vector are numbers, some bit masks, and some
11046 pointers to strings or other data. @value{GDBN} displays each value in the
11047 most appropriate form for a recognized tag, and in hexadecimal for
11048 an unrecognized tag.
11051 On some targets, @value{GDBN} can access operating system-specific
11052 information and show it to you. The types of information available
11053 will differ depending on the type of operating system running on the
11054 target. The mechanism used to fetch the data is described in
11055 @ref{Operating System Information}. For remote targets, this
11056 functionality depends on the remote stub's support of the
11057 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11061 @item info os @var{infotype}
11063 Display OS information of the requested type.
11065 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11067 @anchor{linux info os infotypes}
11069 @kindex info os cpus
11071 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11072 the available fields from /proc/cpuinfo. For each supported architecture
11073 different fields are available. Two common entries are processor which gives
11074 CPU number and bogomips; a system constant that is calculated during
11075 kernel initialization.
11077 @kindex info os files
11079 Display the list of open file descriptors on the target. For each
11080 file descriptor, @value{GDBN} prints the identifier of the process
11081 owning the descriptor, the command of the owning process, the value
11082 of the descriptor, and the target of the descriptor.
11084 @kindex info os modules
11086 Display the list of all loaded kernel modules on the target. For each
11087 module, @value{GDBN} prints the module name, the size of the module in
11088 bytes, the number of times the module is used, the dependencies of the
11089 module, the status of the module, and the address of the loaded module
11092 @kindex info os msg
11094 Display the list of all System V message queues on the target. For each
11095 message queue, @value{GDBN} prints the message queue key, the message
11096 queue identifier, the access permissions, the current number of bytes
11097 on the queue, the current number of messages on the queue, the processes
11098 that last sent and received a message on the queue, the user and group
11099 of the owner and creator of the message queue, the times at which a
11100 message was last sent and received on the queue, and the time at which
11101 the message queue was last changed.
11103 @kindex info os processes
11105 Display the list of processes on the target. For each process,
11106 @value{GDBN} prints the process identifier, the name of the user, the
11107 command corresponding to the process, and the list of processor cores
11108 that the process is currently running on. (To understand what these
11109 properties mean, for this and the following info types, please consult
11110 the general @sc{gnu}/Linux documentation.)
11112 @kindex info os procgroups
11114 Display the list of process groups on the target. For each process,
11115 @value{GDBN} prints the identifier of the process group that it belongs
11116 to, the command corresponding to the process group leader, the process
11117 identifier, and the command line of the process. The list is sorted
11118 first by the process group identifier, then by the process identifier,
11119 so that processes belonging to the same process group are grouped together
11120 and the process group leader is listed first.
11122 @kindex info os semaphores
11124 Display the list of all System V semaphore sets on the target. For each
11125 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11126 set identifier, the access permissions, the number of semaphores in the
11127 set, the user and group of the owner and creator of the semaphore set,
11128 and the times at which the semaphore set was operated upon and changed.
11130 @kindex info os shm
11132 Display the list of all System V shared-memory regions on the target.
11133 For each shared-memory region, @value{GDBN} prints the region key,
11134 the shared-memory identifier, the access permissions, the size of the
11135 region, the process that created the region, the process that last
11136 attached to or detached from the region, the current number of live
11137 attaches to the region, and the times at which the region was last
11138 attached to, detach from, and changed.
11140 @kindex info os sockets
11142 Display the list of Internet-domain sockets on the target. For each
11143 socket, @value{GDBN} prints the address and port of the local and
11144 remote endpoints, the current state of the connection, the creator of
11145 the socket, the IP address family of the socket, and the type of the
11148 @kindex info os threads
11150 Display the list of threads running on the target. For each thread,
11151 @value{GDBN} prints the identifier of the process that the thread
11152 belongs to, the command of the process, the thread identifier, and the
11153 processor core that it is currently running on. The main thread of a
11154 process is not listed.
11158 If @var{infotype} is omitted, then list the possible values for
11159 @var{infotype} and the kind of OS information available for each
11160 @var{infotype}. If the target does not return a list of possible
11161 types, this command will report an error.
11164 @node Memory Region Attributes
11165 @section Memory Region Attributes
11166 @cindex memory region attributes
11168 @dfn{Memory region attributes} allow you to describe special handling
11169 required by regions of your target's memory. @value{GDBN} uses
11170 attributes to determine whether to allow certain types of memory
11171 accesses; whether to use specific width accesses; and whether to cache
11172 target memory. By default the description of memory regions is
11173 fetched from the target (if the current target supports this), but the
11174 user can override the fetched regions.
11176 Defined memory regions can be individually enabled and disabled. When a
11177 memory region is disabled, @value{GDBN} uses the default attributes when
11178 accessing memory in that region. Similarly, if no memory regions have
11179 been defined, @value{GDBN} uses the default attributes when accessing
11182 When a memory region is defined, it is given a number to identify it;
11183 to enable, disable, or remove a memory region, you specify that number.
11187 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11188 Define a memory region bounded by @var{lower} and @var{upper} with
11189 attributes @var{attributes}@dots{}, and add it to the list of regions
11190 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11191 case: it is treated as the target's maximum memory address.
11192 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11195 Discard any user changes to the memory regions and use target-supplied
11196 regions, if available, or no regions if the target does not support.
11199 @item delete mem @var{nums}@dots{}
11200 Remove memory regions @var{nums}@dots{} from the list of regions
11201 monitored by @value{GDBN}.
11203 @kindex disable mem
11204 @item disable mem @var{nums}@dots{}
11205 Disable monitoring of memory regions @var{nums}@dots{}.
11206 A disabled memory region is not forgotten.
11207 It may be enabled again later.
11210 @item enable mem @var{nums}@dots{}
11211 Enable monitoring of memory regions @var{nums}@dots{}.
11215 Print a table of all defined memory regions, with the following columns
11219 @item Memory Region Number
11220 @item Enabled or Disabled.
11221 Enabled memory regions are marked with @samp{y}.
11222 Disabled memory regions are marked with @samp{n}.
11225 The address defining the inclusive lower bound of the memory region.
11228 The address defining the exclusive upper bound of the memory region.
11231 The list of attributes set for this memory region.
11236 @subsection Attributes
11238 @subsubsection Memory Access Mode
11239 The access mode attributes set whether @value{GDBN} may make read or
11240 write accesses to a memory region.
11242 While these attributes prevent @value{GDBN} from performing invalid
11243 memory accesses, they do nothing to prevent the target system, I/O DMA,
11244 etc.@: from accessing memory.
11248 Memory is read only.
11250 Memory is write only.
11252 Memory is read/write. This is the default.
11255 @subsubsection Memory Access Size
11256 The access size attribute tells @value{GDBN} to use specific sized
11257 accesses in the memory region. Often memory mapped device registers
11258 require specific sized accesses. If no access size attribute is
11259 specified, @value{GDBN} may use accesses of any size.
11263 Use 8 bit memory accesses.
11265 Use 16 bit memory accesses.
11267 Use 32 bit memory accesses.
11269 Use 64 bit memory accesses.
11272 @c @subsubsection Hardware/Software Breakpoints
11273 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11274 @c will use hardware or software breakpoints for the internal breakpoints
11275 @c used by the step, next, finish, until, etc. commands.
11279 @c Always use hardware breakpoints
11280 @c @item swbreak (default)
11283 @subsubsection Data Cache
11284 The data cache attributes set whether @value{GDBN} will cache target
11285 memory. While this generally improves performance by reducing debug
11286 protocol overhead, it can lead to incorrect results because @value{GDBN}
11287 does not know about volatile variables or memory mapped device
11292 Enable @value{GDBN} to cache target memory.
11294 Disable @value{GDBN} from caching target memory. This is the default.
11297 @subsection Memory Access Checking
11298 @value{GDBN} can be instructed to refuse accesses to memory that is
11299 not explicitly described. This can be useful if accessing such
11300 regions has undesired effects for a specific target, or to provide
11301 better error checking. The following commands control this behaviour.
11304 @kindex set mem inaccessible-by-default
11305 @item set mem inaccessible-by-default [on|off]
11306 If @code{on} is specified, make @value{GDBN} treat memory not
11307 explicitly described by the memory ranges as non-existent and refuse accesses
11308 to such memory. The checks are only performed if there's at least one
11309 memory range defined. If @code{off} is specified, make @value{GDBN}
11310 treat the memory not explicitly described by the memory ranges as RAM.
11311 The default value is @code{on}.
11312 @kindex show mem inaccessible-by-default
11313 @item show mem inaccessible-by-default
11314 Show the current handling of accesses to unknown memory.
11318 @c @subsubsection Memory Write Verification
11319 @c The memory write verification attributes set whether @value{GDBN}
11320 @c will re-reads data after each write to verify the write was successful.
11324 @c @item noverify (default)
11327 @node Dump/Restore Files
11328 @section Copy Between Memory and a File
11329 @cindex dump/restore files
11330 @cindex append data to a file
11331 @cindex dump data to a file
11332 @cindex restore data from a file
11334 You can use the commands @code{dump}, @code{append}, and
11335 @code{restore} to copy data between target memory and a file. The
11336 @code{dump} and @code{append} commands write data to a file, and the
11337 @code{restore} command reads data from a file back into the inferior's
11338 memory. Files may be in binary, Motorola S-record, Intel hex,
11339 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11340 append to binary files, and cannot read from Verilog Hex files.
11345 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11346 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11347 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11348 or the value of @var{expr}, to @var{filename} in the given format.
11350 The @var{format} parameter may be any one of:
11357 Motorola S-record format.
11359 Tektronix Hex format.
11361 Verilog Hex format.
11364 @value{GDBN} uses the same definitions of these formats as the
11365 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11366 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11370 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11371 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11372 Append the contents of memory from @var{start_addr} to @var{end_addr},
11373 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11374 (@value{GDBN} can only append data to files in raw binary form.)
11377 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11378 Restore the contents of file @var{filename} into memory. The
11379 @code{restore} command can automatically recognize any known @sc{bfd}
11380 file format, except for raw binary. To restore a raw binary file you
11381 must specify the optional keyword @code{binary} after the filename.
11383 If @var{bias} is non-zero, its value will be added to the addresses
11384 contained in the file. Binary files always start at address zero, so
11385 they will be restored at address @var{bias}. Other bfd files have
11386 a built-in location; they will be restored at offset @var{bias}
11387 from that location.
11389 If @var{start} and/or @var{end} are non-zero, then only data between
11390 file offset @var{start} and file offset @var{end} will be restored.
11391 These offsets are relative to the addresses in the file, before
11392 the @var{bias} argument is applied.
11396 @node Core File Generation
11397 @section How to Produce a Core File from Your Program
11398 @cindex dump core from inferior
11400 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11401 image of a running process and its process status (register values
11402 etc.). Its primary use is post-mortem debugging of a program that
11403 crashed while it ran outside a debugger. A program that crashes
11404 automatically produces a core file, unless this feature is disabled by
11405 the user. @xref{Files}, for information on invoking @value{GDBN} in
11406 the post-mortem debugging mode.
11408 Occasionally, you may wish to produce a core file of the program you
11409 are debugging in order to preserve a snapshot of its state.
11410 @value{GDBN} has a special command for that.
11414 @kindex generate-core-file
11415 @item generate-core-file [@var{file}]
11416 @itemx gcore [@var{file}]
11417 Produce a core dump of the inferior process. The optional argument
11418 @var{file} specifies the file name where to put the core dump. If not
11419 specified, the file name defaults to @file{core.@var{pid}}, where
11420 @var{pid} is the inferior process ID.
11422 Note that this command is implemented only for some systems (as of
11423 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11425 On @sc{gnu}/Linux, this command can take into account the value of the
11426 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11427 dump (@pxref{set use-coredump-filter}).
11429 @kindex set use-coredump-filter
11430 @anchor{set use-coredump-filter}
11431 @item set use-coredump-filter on
11432 @itemx set use-coredump-filter off
11433 Enable or disable the use of the file
11434 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11435 files. This file is used by the Linux kernel to decide what types of
11436 memory mappings will be dumped or ignored when generating a core dump
11437 file. @var{pid} is the process ID of a currently running process.
11439 To make use of this feature, you have to write in the
11440 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11441 which is a bit mask representing the memory mapping types. If a bit
11442 is set in the bit mask, then the memory mappings of the corresponding
11443 types will be dumped; otherwise, they will be ignored. This
11444 configuration is inherited by child processes. For more information
11445 about the bits that can be set in the
11446 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11447 manpage of @code{core(5)}.
11449 By default, this option is @code{on}. If this option is turned
11450 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11451 and instead uses the same default value as the Linux kernel in order
11452 to decide which pages will be dumped in the core dump file. This
11453 value is currently @code{0x33}, which means that bits @code{0}
11454 (anonymous private mappings), @code{1} (anonymous shared mappings),
11455 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11456 This will cause these memory mappings to be dumped automatically.
11459 @node Character Sets
11460 @section Character Sets
11461 @cindex character sets
11463 @cindex translating between character sets
11464 @cindex host character set
11465 @cindex target character set
11467 If the program you are debugging uses a different character set to
11468 represent characters and strings than the one @value{GDBN} uses itself,
11469 @value{GDBN} can automatically translate between the character sets for
11470 you. The character set @value{GDBN} uses we call the @dfn{host
11471 character set}; the one the inferior program uses we call the
11472 @dfn{target character set}.
11474 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11475 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11476 remote protocol (@pxref{Remote Debugging}) to debug a program
11477 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11478 then the host character set is Latin-1, and the target character set is
11479 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11480 target-charset EBCDIC-US}, then @value{GDBN} translates between
11481 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11482 character and string literals in expressions.
11484 @value{GDBN} has no way to automatically recognize which character set
11485 the inferior program uses; you must tell it, using the @code{set
11486 target-charset} command, described below.
11488 Here are the commands for controlling @value{GDBN}'s character set
11492 @item set target-charset @var{charset}
11493 @kindex set target-charset
11494 Set the current target character set to @var{charset}. To display the
11495 list of supported target character sets, type
11496 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11498 @item set host-charset @var{charset}
11499 @kindex set host-charset
11500 Set the current host character set to @var{charset}.
11502 By default, @value{GDBN} uses a host character set appropriate to the
11503 system it is running on; you can override that default using the
11504 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11505 automatically determine the appropriate host character set. In this
11506 case, @value{GDBN} uses @samp{UTF-8}.
11508 @value{GDBN} can only use certain character sets as its host character
11509 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11510 @value{GDBN} will list the host character sets it supports.
11512 @item set charset @var{charset}
11513 @kindex set charset
11514 Set the current host and target character sets to @var{charset}. As
11515 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11516 @value{GDBN} will list the names of the character sets that can be used
11517 for both host and target.
11520 @kindex show charset
11521 Show the names of the current host and target character sets.
11523 @item show host-charset
11524 @kindex show host-charset
11525 Show the name of the current host character set.
11527 @item show target-charset
11528 @kindex show target-charset
11529 Show the name of the current target character set.
11531 @item set target-wide-charset @var{charset}
11532 @kindex set target-wide-charset
11533 Set the current target's wide character set to @var{charset}. This is
11534 the character set used by the target's @code{wchar_t} type. To
11535 display the list of supported wide character sets, type
11536 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11538 @item show target-wide-charset
11539 @kindex show target-wide-charset
11540 Show the name of the current target's wide character set.
11543 Here is an example of @value{GDBN}'s character set support in action.
11544 Assume that the following source code has been placed in the file
11545 @file{charset-test.c}:
11551 = @{72, 101, 108, 108, 111, 44, 32, 119,
11552 111, 114, 108, 100, 33, 10, 0@};
11553 char ibm1047_hello[]
11554 = @{200, 133, 147, 147, 150, 107, 64, 166,
11555 150, 153, 147, 132, 90, 37, 0@};
11559 printf ("Hello, world!\n");
11563 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11564 containing the string @samp{Hello, world!} followed by a newline,
11565 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11567 We compile the program, and invoke the debugger on it:
11570 $ gcc -g charset-test.c -o charset-test
11571 $ gdb -nw charset-test
11572 GNU gdb 2001-12-19-cvs
11573 Copyright 2001 Free Software Foundation, Inc.
11578 We can use the @code{show charset} command to see what character sets
11579 @value{GDBN} is currently using to interpret and display characters and
11583 (@value{GDBP}) show charset
11584 The current host and target character set is `ISO-8859-1'.
11588 For the sake of printing this manual, let's use @sc{ascii} as our
11589 initial character set:
11591 (@value{GDBP}) set charset ASCII
11592 (@value{GDBP}) show charset
11593 The current host and target character set is `ASCII'.
11597 Let's assume that @sc{ascii} is indeed the correct character set for our
11598 host system --- in other words, let's assume that if @value{GDBN} prints
11599 characters using the @sc{ascii} character set, our terminal will display
11600 them properly. Since our current target character set is also
11601 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11604 (@value{GDBP}) print ascii_hello
11605 $1 = 0x401698 "Hello, world!\n"
11606 (@value{GDBP}) print ascii_hello[0]
11611 @value{GDBN} uses the target character set for character and string
11612 literals you use in expressions:
11615 (@value{GDBP}) print '+'
11620 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11623 @value{GDBN} relies on the user to tell it which character set the
11624 target program uses. If we print @code{ibm1047_hello} while our target
11625 character set is still @sc{ascii}, we get jibberish:
11628 (@value{GDBP}) print ibm1047_hello
11629 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11630 (@value{GDBP}) print ibm1047_hello[0]
11635 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11636 @value{GDBN} tells us the character sets it supports:
11639 (@value{GDBP}) set target-charset
11640 ASCII EBCDIC-US IBM1047 ISO-8859-1
11641 (@value{GDBP}) set target-charset
11644 We can select @sc{ibm1047} as our target character set, and examine the
11645 program's strings again. Now the @sc{ascii} string is wrong, but
11646 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11647 target character set, @sc{ibm1047}, to the host character set,
11648 @sc{ascii}, and they display correctly:
11651 (@value{GDBP}) set target-charset IBM1047
11652 (@value{GDBP}) show charset
11653 The current host character set is `ASCII'.
11654 The current target character set is `IBM1047'.
11655 (@value{GDBP}) print ascii_hello
11656 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11657 (@value{GDBP}) print ascii_hello[0]
11659 (@value{GDBP}) print ibm1047_hello
11660 $8 = 0x4016a8 "Hello, world!\n"
11661 (@value{GDBP}) print ibm1047_hello[0]
11666 As above, @value{GDBN} uses the target character set for character and
11667 string literals you use in expressions:
11670 (@value{GDBP}) print '+'
11675 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11678 @node Caching Target Data
11679 @section Caching Data of Targets
11680 @cindex caching data of targets
11682 @value{GDBN} caches data exchanged between the debugger and a target.
11683 Each cache is associated with the address space of the inferior.
11684 @xref{Inferiors and Programs}, about inferior and address space.
11685 Such caching generally improves performance in remote debugging
11686 (@pxref{Remote Debugging}), because it reduces the overhead of the
11687 remote protocol by bundling memory reads and writes into large chunks.
11688 Unfortunately, simply caching everything would lead to incorrect results,
11689 since @value{GDBN} does not necessarily know anything about volatile
11690 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11691 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11693 Therefore, by default, @value{GDBN} only caches data
11694 known to be on the stack@footnote{In non-stop mode, it is moderately
11695 rare for a running thread to modify the stack of a stopped thread
11696 in a way that would interfere with a backtrace, and caching of
11697 stack reads provides a significant speed up of remote backtraces.} or
11698 in the code segment.
11699 Other regions of memory can be explicitly marked as
11700 cacheable; @pxref{Memory Region Attributes}.
11703 @kindex set remotecache
11704 @item set remotecache on
11705 @itemx set remotecache off
11706 This option no longer does anything; it exists for compatibility
11709 @kindex show remotecache
11710 @item show remotecache
11711 Show the current state of the obsolete remotecache flag.
11713 @kindex set stack-cache
11714 @item set stack-cache on
11715 @itemx set stack-cache off
11716 Enable or disable caching of stack accesses. When @code{on}, use
11717 caching. By default, this option is @code{on}.
11719 @kindex show stack-cache
11720 @item show stack-cache
11721 Show the current state of data caching for memory accesses.
11723 @kindex set code-cache
11724 @item set code-cache on
11725 @itemx set code-cache off
11726 Enable or disable caching of code segment accesses. When @code{on},
11727 use caching. By default, this option is @code{on}. This improves
11728 performance of disassembly in remote debugging.
11730 @kindex show code-cache
11731 @item show code-cache
11732 Show the current state of target memory cache for code segment
11735 @kindex info dcache
11736 @item info dcache @r{[}line@r{]}
11737 Print the information about the performance of data cache of the
11738 current inferior's address space. The information displayed
11739 includes the dcache width and depth, and for each cache line, its
11740 number, address, and how many times it was referenced. This
11741 command is useful for debugging the data cache operation.
11743 If a line number is specified, the contents of that line will be
11746 @item set dcache size @var{size}
11747 @cindex dcache size
11748 @kindex set dcache size
11749 Set maximum number of entries in dcache (dcache depth above).
11751 @item set dcache line-size @var{line-size}
11752 @cindex dcache line-size
11753 @kindex set dcache line-size
11754 Set number of bytes each dcache entry caches (dcache width above).
11755 Must be a power of 2.
11757 @item show dcache size
11758 @kindex show dcache size
11759 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11761 @item show dcache line-size
11762 @kindex show dcache line-size
11763 Show default size of dcache lines.
11767 @node Searching Memory
11768 @section Search Memory
11769 @cindex searching memory
11771 Memory can be searched for a particular sequence of bytes with the
11772 @code{find} command.
11776 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11777 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11778 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11779 etc. The search begins at address @var{start_addr} and continues for either
11780 @var{len} bytes or through to @var{end_addr} inclusive.
11783 @var{s} and @var{n} are optional parameters.
11784 They may be specified in either order, apart or together.
11787 @item @var{s}, search query size
11788 The size of each search query value.
11794 halfwords (two bytes)
11798 giant words (eight bytes)
11801 All values are interpreted in the current language.
11802 This means, for example, that if the current source language is C/C@t{++}
11803 then searching for the string ``hello'' includes the trailing '\0'.
11805 If the value size is not specified, it is taken from the
11806 value's type in the current language.
11807 This is useful when one wants to specify the search
11808 pattern as a mixture of types.
11809 Note that this means, for example, that in the case of C-like languages
11810 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11811 which is typically four bytes.
11813 @item @var{n}, maximum number of finds
11814 The maximum number of matches to print. The default is to print all finds.
11817 You can use strings as search values. Quote them with double-quotes
11819 The string value is copied into the search pattern byte by byte,
11820 regardless of the endianness of the target and the size specification.
11822 The address of each match found is printed as well as a count of the
11823 number of matches found.
11825 The address of the last value found is stored in convenience variable
11827 A count of the number of matches is stored in @samp{$numfound}.
11829 For example, if stopped at the @code{printf} in this function:
11835 static char hello[] = "hello-hello";
11836 static struct @{ char c; short s; int i; @}
11837 __attribute__ ((packed)) mixed
11838 = @{ 'c', 0x1234, 0x87654321 @};
11839 printf ("%s\n", hello);
11844 you get during debugging:
11847 (gdb) find &hello[0], +sizeof(hello), "hello"
11848 0x804956d <hello.1620+6>
11850 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11851 0x8049567 <hello.1620>
11852 0x804956d <hello.1620+6>
11854 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11855 0x8049567 <hello.1620>
11857 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11858 0x8049560 <mixed.1625>
11860 (gdb) print $numfound
11863 $2 = (void *) 0x8049560
11867 @section Value Sizes
11869 Whenever @value{GDBN} prints a value memory will be allocated within
11870 @value{GDBN} to hold the contents of the value. It is possible in
11871 some languages with dynamic typing systems, that an invalid program
11872 may indicate a value that is incorrectly large, this in turn may cause
11873 @value{GDBN} to try and allocate an overly large ammount of memory.
11876 @kindex set max-value-size
11877 @item set max-value-size @var{bytes}
11878 @itemx set max-value-size unlimited
11879 Set the maximum size of memory that @value{GDBN} will allocate for the
11880 contents of a value to @var{bytes}, trying to display a value that
11881 requires more memory than that will result in an error.
11883 Setting this variable does not effect values that have already been
11884 allocated within @value{GDBN}, only future allocations.
11886 There's a minimum size that @code{max-value-size} can be set to in
11887 order that @value{GDBN} can still operate correctly, this minimum is
11888 currently 16 bytes.
11890 The limit applies to the results of some subexpressions as well as to
11891 complete expressions. For example, an expression denoting a simple
11892 integer component, such as @code{x.y.z}, may fail if the size of
11893 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11894 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11895 @var{A} is an array variable with non-constant size, will generally
11896 succeed regardless of the bounds on @var{A}, as long as the component
11897 size is less than @var{bytes}.
11899 The default value of @code{max-value-size} is currently 64k.
11901 @kindex show max-value-size
11902 @item show max-value-size
11903 Show the maximum size of memory, in bytes, that @value{GDBN} will
11904 allocate for the contents of a value.
11907 @node Optimized Code
11908 @chapter Debugging Optimized Code
11909 @cindex optimized code, debugging
11910 @cindex debugging optimized code
11912 Almost all compilers support optimization. With optimization
11913 disabled, the compiler generates assembly code that corresponds
11914 directly to your source code, in a simplistic way. As the compiler
11915 applies more powerful optimizations, the generated assembly code
11916 diverges from your original source code. With help from debugging
11917 information generated by the compiler, @value{GDBN} can map from
11918 the running program back to constructs from your original source.
11920 @value{GDBN} is more accurate with optimization disabled. If you
11921 can recompile without optimization, it is easier to follow the
11922 progress of your program during debugging. But, there are many cases
11923 where you may need to debug an optimized version.
11925 When you debug a program compiled with @samp{-g -O}, remember that the
11926 optimizer has rearranged your code; the debugger shows you what is
11927 really there. Do not be too surprised when the execution path does not
11928 exactly match your source file! An extreme example: if you define a
11929 variable, but never use it, @value{GDBN} never sees that
11930 variable---because the compiler optimizes it out of existence.
11932 Some things do not work as well with @samp{-g -O} as with just
11933 @samp{-g}, particularly on machines with instruction scheduling. If in
11934 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11935 please report it to us as a bug (including a test case!).
11936 @xref{Variables}, for more information about debugging optimized code.
11939 * Inline Functions:: How @value{GDBN} presents inlining
11940 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11943 @node Inline Functions
11944 @section Inline Functions
11945 @cindex inline functions, debugging
11947 @dfn{Inlining} is an optimization that inserts a copy of the function
11948 body directly at each call site, instead of jumping to a shared
11949 routine. @value{GDBN} displays inlined functions just like
11950 non-inlined functions. They appear in backtraces. You can view their
11951 arguments and local variables, step into them with @code{step}, skip
11952 them with @code{next}, and escape from them with @code{finish}.
11953 You can check whether a function was inlined by using the
11954 @code{info frame} command.
11956 For @value{GDBN} to support inlined functions, the compiler must
11957 record information about inlining in the debug information ---
11958 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11959 other compilers do also. @value{GDBN} only supports inlined functions
11960 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11961 do not emit two required attributes (@samp{DW_AT_call_file} and
11962 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11963 function calls with earlier versions of @value{NGCC}. It instead
11964 displays the arguments and local variables of inlined functions as
11965 local variables in the caller.
11967 The body of an inlined function is directly included at its call site;
11968 unlike a non-inlined function, there are no instructions devoted to
11969 the call. @value{GDBN} still pretends that the call site and the
11970 start of the inlined function are different instructions. Stepping to
11971 the call site shows the call site, and then stepping again shows
11972 the first line of the inlined function, even though no additional
11973 instructions are executed.
11975 This makes source-level debugging much clearer; you can see both the
11976 context of the call and then the effect of the call. Only stepping by
11977 a single instruction using @code{stepi} or @code{nexti} does not do
11978 this; single instruction steps always show the inlined body.
11980 There are some ways that @value{GDBN} does not pretend that inlined
11981 function calls are the same as normal calls:
11985 Setting breakpoints at the call site of an inlined function may not
11986 work, because the call site does not contain any code. @value{GDBN}
11987 may incorrectly move the breakpoint to the next line of the enclosing
11988 function, after the call. This limitation will be removed in a future
11989 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11990 or inside the inlined function instead.
11993 @value{GDBN} cannot locate the return value of inlined calls after
11994 using the @code{finish} command. This is a limitation of compiler-generated
11995 debugging information; after @code{finish}, you can step to the next line
11996 and print a variable where your program stored the return value.
12000 @node Tail Call Frames
12001 @section Tail Call Frames
12002 @cindex tail call frames, debugging
12004 Function @code{B} can call function @code{C} in its very last statement. In
12005 unoptimized compilation the call of @code{C} is immediately followed by return
12006 instruction at the end of @code{B} code. Optimizing compiler may replace the
12007 call and return in function @code{B} into one jump to function @code{C}
12008 instead. Such use of a jump instruction is called @dfn{tail call}.
12010 During execution of function @code{C}, there will be no indication in the
12011 function call stack frames that it was tail-called from @code{B}. If function
12012 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12013 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12014 some cases @value{GDBN} can determine that @code{C} was tail-called from
12015 @code{B}, and it will then create fictitious call frame for that, with the
12016 return address set up as if @code{B} called @code{C} normally.
12018 This functionality is currently supported only by DWARF 2 debugging format and
12019 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
12020 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12023 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12024 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12028 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12030 Stack level 1, frame at 0x7fffffffda30:
12031 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12032 tail call frame, caller of frame at 0x7fffffffda30
12033 source language c++.
12034 Arglist at unknown address.
12035 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12038 The detection of all the possible code path executions can find them ambiguous.
12039 There is no execution history stored (possible @ref{Reverse Execution} is never
12040 used for this purpose) and the last known caller could have reached the known
12041 callee by multiple different jump sequences. In such case @value{GDBN} still
12042 tries to show at least all the unambiguous top tail callers and all the
12043 unambiguous bottom tail calees, if any.
12046 @anchor{set debug entry-values}
12047 @item set debug entry-values
12048 @kindex set debug entry-values
12049 When set to on, enables printing of analysis messages for both frame argument
12050 values at function entry and tail calls. It will show all the possible valid
12051 tail calls code paths it has considered. It will also print the intersection
12052 of them with the final unambiguous (possibly partial or even empty) code path
12055 @item show debug entry-values
12056 @kindex show debug entry-values
12057 Show the current state of analysis messages printing for both frame argument
12058 values at function entry and tail calls.
12061 The analysis messages for tail calls can for example show why the virtual tail
12062 call frame for function @code{c} has not been recognized (due to the indirect
12063 reference by variable @code{x}):
12066 static void __attribute__((noinline, noclone)) c (void);
12067 void (*x) (void) = c;
12068 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12069 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12070 int main (void) @{ x (); return 0; @}
12072 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12073 DW_TAG_GNU_call_site 0x40039a in main
12075 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12078 #1 0x000000000040039a in main () at t.c:5
12081 Another possibility is an ambiguous virtual tail call frames resolution:
12085 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12086 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12087 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12088 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12089 static void __attribute__((noinline, noclone)) b (void)
12090 @{ if (i) c (); else e (); @}
12091 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12092 int main (void) @{ a (); return 0; @}
12094 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12095 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12096 tailcall: reduced: 0x4004d2(a) |
12099 #1 0x00000000004004d2 in a () at t.c:8
12100 #2 0x0000000000400395 in main () at t.c:9
12103 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12104 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12106 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12107 @ifset HAVE_MAKEINFO_CLICK
12108 @set ARROW @click{}
12109 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12110 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12112 @ifclear HAVE_MAKEINFO_CLICK
12114 @set CALLSEQ1B @value{CALLSEQ1A}
12115 @set CALLSEQ2B @value{CALLSEQ2A}
12118 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12119 The code can have possible execution paths @value{CALLSEQ1B} or
12120 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12122 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12123 has found. It then finds another possible calling sequcen - that one is
12124 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12125 printed as the @code{reduced:} calling sequence. That one could have many
12126 futher @code{compare:} and @code{reduced:} statements as long as there remain
12127 any non-ambiguous sequence entries.
12129 For the frame of function @code{b} in both cases there are different possible
12130 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12131 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12132 therefore this one is displayed to the user while the ambiguous frames are
12135 There can be also reasons why printing of frame argument values at function
12140 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12141 static void __attribute__((noinline, noclone)) a (int i);
12142 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12143 static void __attribute__((noinline, noclone)) a (int i)
12144 @{ if (i) b (i - 1); else c (0); @}
12145 int main (void) @{ a (5); return 0; @}
12148 #0 c (i=i@@entry=0) at t.c:2
12149 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12150 function "a" at 0x400420 can call itself via tail calls
12151 i=<optimized out>) at t.c:6
12152 #2 0x000000000040036e in main () at t.c:7
12155 @value{GDBN} cannot find out from the inferior state if and how many times did
12156 function @code{a} call itself (via function @code{b}) as these calls would be
12157 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12158 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12159 prints @code{<optimized out>} instead.
12162 @chapter C Preprocessor Macros
12164 Some languages, such as C and C@t{++}, provide a way to define and invoke
12165 ``preprocessor macros'' which expand into strings of tokens.
12166 @value{GDBN} can evaluate expressions containing macro invocations, show
12167 the result of macro expansion, and show a macro's definition, including
12168 where it was defined.
12170 You may need to compile your program specially to provide @value{GDBN}
12171 with information about preprocessor macros. Most compilers do not
12172 include macros in their debugging information, even when you compile
12173 with the @option{-g} flag. @xref{Compilation}.
12175 A program may define a macro at one point, remove that definition later,
12176 and then provide a different definition after that. Thus, at different
12177 points in the program, a macro may have different definitions, or have
12178 no definition at all. If there is a current stack frame, @value{GDBN}
12179 uses the macros in scope at that frame's source code line. Otherwise,
12180 @value{GDBN} uses the macros in scope at the current listing location;
12183 Whenever @value{GDBN} evaluates an expression, it always expands any
12184 macro invocations present in the expression. @value{GDBN} also provides
12185 the following commands for working with macros explicitly.
12189 @kindex macro expand
12190 @cindex macro expansion, showing the results of preprocessor
12191 @cindex preprocessor macro expansion, showing the results of
12192 @cindex expanding preprocessor macros
12193 @item macro expand @var{expression}
12194 @itemx macro exp @var{expression}
12195 Show the results of expanding all preprocessor macro invocations in
12196 @var{expression}. Since @value{GDBN} simply expands macros, but does
12197 not parse the result, @var{expression} need not be a valid expression;
12198 it can be any string of tokens.
12201 @item macro expand-once @var{expression}
12202 @itemx macro exp1 @var{expression}
12203 @cindex expand macro once
12204 @i{(This command is not yet implemented.)} Show the results of
12205 expanding those preprocessor macro invocations that appear explicitly in
12206 @var{expression}. Macro invocations appearing in that expansion are
12207 left unchanged. This command allows you to see the effect of a
12208 particular macro more clearly, without being confused by further
12209 expansions. Since @value{GDBN} simply expands macros, but does not
12210 parse the result, @var{expression} need not be a valid expression; it
12211 can be any string of tokens.
12214 @cindex macro definition, showing
12215 @cindex definition of a macro, showing
12216 @cindex macros, from debug info
12217 @item info macro [-a|-all] [--] @var{macro}
12218 Show the current definition or all definitions of the named @var{macro},
12219 and describe the source location or compiler command-line where that
12220 definition was established. The optional double dash is to signify the end of
12221 argument processing and the beginning of @var{macro} for non C-like macros where
12222 the macro may begin with a hyphen.
12224 @kindex info macros
12225 @item info macros @var{location}
12226 Show all macro definitions that are in effect at the location specified
12227 by @var{location}, and describe the source location or compiler
12228 command-line where those definitions were established.
12230 @kindex macro define
12231 @cindex user-defined macros
12232 @cindex defining macros interactively
12233 @cindex macros, user-defined
12234 @item macro define @var{macro} @var{replacement-list}
12235 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12236 Introduce a definition for a preprocessor macro named @var{macro},
12237 invocations of which are replaced by the tokens given in
12238 @var{replacement-list}. The first form of this command defines an
12239 ``object-like'' macro, which takes no arguments; the second form
12240 defines a ``function-like'' macro, which takes the arguments given in
12243 A definition introduced by this command is in scope in every
12244 expression evaluated in @value{GDBN}, until it is removed with the
12245 @code{macro undef} command, described below. The definition overrides
12246 all definitions for @var{macro} present in the program being debugged,
12247 as well as any previous user-supplied definition.
12249 @kindex macro undef
12250 @item macro undef @var{macro}
12251 Remove any user-supplied definition for the macro named @var{macro}.
12252 This command only affects definitions provided with the @code{macro
12253 define} command, described above; it cannot remove definitions present
12254 in the program being debugged.
12258 List all the macros defined using the @code{macro define} command.
12261 @cindex macros, example of debugging with
12262 Here is a transcript showing the above commands in action. First, we
12263 show our source files:
12268 #include "sample.h"
12271 #define ADD(x) (M + x)
12276 printf ("Hello, world!\n");
12278 printf ("We're so creative.\n");
12280 printf ("Goodbye, world!\n");
12287 Now, we compile the program using the @sc{gnu} C compiler,
12288 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12289 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12290 and @option{-gdwarf-4}; we recommend always choosing the most recent
12291 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12292 includes information about preprocessor macros in the debugging
12296 $ gcc -gdwarf-2 -g3 sample.c -o sample
12300 Now, we start @value{GDBN} on our sample program:
12304 GNU gdb 2002-05-06-cvs
12305 Copyright 2002 Free Software Foundation, Inc.
12306 GDB is free software, @dots{}
12310 We can expand macros and examine their definitions, even when the
12311 program is not running. @value{GDBN} uses the current listing position
12312 to decide which macro definitions are in scope:
12315 (@value{GDBP}) list main
12318 5 #define ADD(x) (M + x)
12323 10 printf ("Hello, world!\n");
12325 12 printf ("We're so creative.\n");
12326 (@value{GDBP}) info macro ADD
12327 Defined at /home/jimb/gdb/macros/play/sample.c:5
12328 #define ADD(x) (M + x)
12329 (@value{GDBP}) info macro Q
12330 Defined at /home/jimb/gdb/macros/play/sample.h:1
12331 included at /home/jimb/gdb/macros/play/sample.c:2
12333 (@value{GDBP}) macro expand ADD(1)
12334 expands to: (42 + 1)
12335 (@value{GDBP}) macro expand-once ADD(1)
12336 expands to: once (M + 1)
12340 In the example above, note that @code{macro expand-once} expands only
12341 the macro invocation explicit in the original text --- the invocation of
12342 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12343 which was introduced by @code{ADD}.
12345 Once the program is running, @value{GDBN} uses the macro definitions in
12346 force at the source line of the current stack frame:
12349 (@value{GDBP}) break main
12350 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12352 Starting program: /home/jimb/gdb/macros/play/sample
12354 Breakpoint 1, main () at sample.c:10
12355 10 printf ("Hello, world!\n");
12359 At line 10, the definition of the macro @code{N} at line 9 is in force:
12362 (@value{GDBP}) info macro N
12363 Defined at /home/jimb/gdb/macros/play/sample.c:9
12365 (@value{GDBP}) macro expand N Q M
12366 expands to: 28 < 42
12367 (@value{GDBP}) print N Q M
12372 As we step over directives that remove @code{N}'s definition, and then
12373 give it a new definition, @value{GDBN} finds the definition (or lack
12374 thereof) in force at each point:
12377 (@value{GDBP}) next
12379 12 printf ("We're so creative.\n");
12380 (@value{GDBP}) info macro N
12381 The symbol `N' has no definition as a C/C++ preprocessor macro
12382 at /home/jimb/gdb/macros/play/sample.c:12
12383 (@value{GDBP}) next
12385 14 printf ("Goodbye, world!\n");
12386 (@value{GDBP}) info macro N
12387 Defined at /home/jimb/gdb/macros/play/sample.c:13
12389 (@value{GDBP}) macro expand N Q M
12390 expands to: 1729 < 42
12391 (@value{GDBP}) print N Q M
12396 In addition to source files, macros can be defined on the compilation command
12397 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12398 such a way, @value{GDBN} displays the location of their definition as line zero
12399 of the source file submitted to the compiler.
12402 (@value{GDBP}) info macro __STDC__
12403 Defined at /home/jimb/gdb/macros/play/sample.c:0
12410 @chapter Tracepoints
12411 @c This chapter is based on the documentation written by Michael
12412 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12414 @cindex tracepoints
12415 In some applications, it is not feasible for the debugger to interrupt
12416 the program's execution long enough for the developer to learn
12417 anything helpful about its behavior. If the program's correctness
12418 depends on its real-time behavior, delays introduced by a debugger
12419 might cause the program to change its behavior drastically, or perhaps
12420 fail, even when the code itself is correct. It is useful to be able
12421 to observe the program's behavior without interrupting it.
12423 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12424 specify locations in the program, called @dfn{tracepoints}, and
12425 arbitrary expressions to evaluate when those tracepoints are reached.
12426 Later, using the @code{tfind} command, you can examine the values
12427 those expressions had when the program hit the tracepoints. The
12428 expressions may also denote objects in memory---structures or arrays,
12429 for example---whose values @value{GDBN} should record; while visiting
12430 a particular tracepoint, you may inspect those objects as if they were
12431 in memory at that moment. However, because @value{GDBN} records these
12432 values without interacting with you, it can do so quickly and
12433 unobtrusively, hopefully not disturbing the program's behavior.
12435 The tracepoint facility is currently available only for remote
12436 targets. @xref{Targets}. In addition, your remote target must know
12437 how to collect trace data. This functionality is implemented in the
12438 remote stub; however, none of the stubs distributed with @value{GDBN}
12439 support tracepoints as of this writing. The format of the remote
12440 packets used to implement tracepoints are described in @ref{Tracepoint
12443 It is also possible to get trace data from a file, in a manner reminiscent
12444 of corefiles; you specify the filename, and use @code{tfind} to search
12445 through the file. @xref{Trace Files}, for more details.
12447 This chapter describes the tracepoint commands and features.
12450 * Set Tracepoints::
12451 * Analyze Collected Data::
12452 * Tracepoint Variables::
12456 @node Set Tracepoints
12457 @section Commands to Set Tracepoints
12459 Before running such a @dfn{trace experiment}, an arbitrary number of
12460 tracepoints can be set. A tracepoint is actually a special type of
12461 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12462 standard breakpoint commands. For instance, as with breakpoints,
12463 tracepoint numbers are successive integers starting from one, and many
12464 of the commands associated with tracepoints take the tracepoint number
12465 as their argument, to identify which tracepoint to work on.
12467 For each tracepoint, you can specify, in advance, some arbitrary set
12468 of data that you want the target to collect in the trace buffer when
12469 it hits that tracepoint. The collected data can include registers,
12470 local variables, or global data. Later, you can use @value{GDBN}
12471 commands to examine the values these data had at the time the
12472 tracepoint was hit.
12474 Tracepoints do not support every breakpoint feature. Ignore counts on
12475 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12476 commands when they are hit. Tracepoints may not be thread-specific
12479 @cindex fast tracepoints
12480 Some targets may support @dfn{fast tracepoints}, which are inserted in
12481 a different way (such as with a jump instead of a trap), that is
12482 faster but possibly restricted in where they may be installed.
12484 @cindex static tracepoints
12485 @cindex markers, static tracepoints
12486 @cindex probing markers, static tracepoints
12487 Regular and fast tracepoints are dynamic tracing facilities, meaning
12488 that they can be used to insert tracepoints at (almost) any location
12489 in the target. Some targets may also support controlling @dfn{static
12490 tracepoints} from @value{GDBN}. With static tracing, a set of
12491 instrumentation points, also known as @dfn{markers}, are embedded in
12492 the target program, and can be activated or deactivated by name or
12493 address. These are usually placed at locations which facilitate
12494 investigating what the target is actually doing. @value{GDBN}'s
12495 support for static tracing includes being able to list instrumentation
12496 points, and attach them with @value{GDBN} defined high level
12497 tracepoints that expose the whole range of convenience of
12498 @value{GDBN}'s tracepoints support. Namely, support for collecting
12499 registers values and values of global or local (to the instrumentation
12500 point) variables; tracepoint conditions and trace state variables.
12501 The act of installing a @value{GDBN} static tracepoint on an
12502 instrumentation point, or marker, is referred to as @dfn{probing} a
12503 static tracepoint marker.
12505 @code{gdbserver} supports tracepoints on some target systems.
12506 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12508 This section describes commands to set tracepoints and associated
12509 conditions and actions.
12512 * Create and Delete Tracepoints::
12513 * Enable and Disable Tracepoints::
12514 * Tracepoint Passcounts::
12515 * Tracepoint Conditions::
12516 * Trace State Variables::
12517 * Tracepoint Actions::
12518 * Listing Tracepoints::
12519 * Listing Static Tracepoint Markers::
12520 * Starting and Stopping Trace Experiments::
12521 * Tracepoint Restrictions::
12524 @node Create and Delete Tracepoints
12525 @subsection Create and Delete Tracepoints
12528 @cindex set tracepoint
12530 @item trace @var{location}
12531 The @code{trace} command is very similar to the @code{break} command.
12532 Its argument @var{location} can be any valid location.
12533 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12534 which is a point in the target program where the debugger will briefly stop,
12535 collect some data, and then allow the program to continue. Setting a tracepoint
12536 or changing its actions takes effect immediately if the remote stub
12537 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12539 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12540 these changes don't take effect until the next @code{tstart}
12541 command, and once a trace experiment is running, further changes will
12542 not have any effect until the next trace experiment starts. In addition,
12543 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12544 address is not yet resolved. (This is similar to pending breakpoints.)
12545 Pending tracepoints are not downloaded to the target and not installed
12546 until they are resolved. The resolution of pending tracepoints requires
12547 @value{GDBN} support---when debugging with the remote target, and
12548 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12549 tracing}), pending tracepoints can not be resolved (and downloaded to
12550 the remote stub) while @value{GDBN} is disconnected.
12552 Here are some examples of using the @code{trace} command:
12555 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12557 (@value{GDBP}) @b{trace +2} // 2 lines forward
12559 (@value{GDBP}) @b{trace my_function} // first source line of function
12561 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12563 (@value{GDBP}) @b{trace *0x2117c4} // an address
12567 You can abbreviate @code{trace} as @code{tr}.
12569 @item trace @var{location} if @var{cond}
12570 Set a tracepoint with condition @var{cond}; evaluate the expression
12571 @var{cond} each time the tracepoint is reached, and collect data only
12572 if the value is nonzero---that is, if @var{cond} evaluates as true.
12573 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12574 information on tracepoint conditions.
12576 @item ftrace @var{location} [ if @var{cond} ]
12577 @cindex set fast tracepoint
12578 @cindex fast tracepoints, setting
12580 The @code{ftrace} command sets a fast tracepoint. For targets that
12581 support them, fast tracepoints will use a more efficient but possibly
12582 less general technique to trigger data collection, such as a jump
12583 instruction instead of a trap, or some sort of hardware support. It
12584 may not be possible to create a fast tracepoint at the desired
12585 location, in which case the command will exit with an explanatory
12588 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12591 On 32-bit x86-architecture systems, fast tracepoints normally need to
12592 be placed at an instruction that is 5 bytes or longer, but can be
12593 placed at 4-byte instructions if the low 64K of memory of the target
12594 program is available to install trampolines. Some Unix-type systems,
12595 such as @sc{gnu}/Linux, exclude low addresses from the program's
12596 address space; but for instance with the Linux kernel it is possible
12597 to let @value{GDBN} use this area by doing a @command{sysctl} command
12598 to set the @code{mmap_min_addr} kernel parameter, as in
12601 sudo sysctl -w vm.mmap_min_addr=32768
12605 which sets the low address to 32K, which leaves plenty of room for
12606 trampolines. The minimum address should be set to a page boundary.
12608 @item strace @var{location} [ if @var{cond} ]
12609 @cindex set static tracepoint
12610 @cindex static tracepoints, setting
12611 @cindex probe static tracepoint marker
12613 The @code{strace} command sets a static tracepoint. For targets that
12614 support it, setting a static tracepoint probes a static
12615 instrumentation point, or marker, found at @var{location}. It may not
12616 be possible to set a static tracepoint at the desired location, in
12617 which case the command will exit with an explanatory message.
12619 @value{GDBN} handles arguments to @code{strace} exactly as for
12620 @code{trace}, with the addition that the user can also specify
12621 @code{-m @var{marker}} as @var{location}. This probes the marker
12622 identified by the @var{marker} string identifier. This identifier
12623 depends on the static tracepoint backend library your program is
12624 using. You can find all the marker identifiers in the @samp{ID} field
12625 of the @code{info static-tracepoint-markers} command output.
12626 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12627 Markers}. For example, in the following small program using the UST
12633 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12638 the marker id is composed of joining the first two arguments to the
12639 @code{trace_mark} call with a slash, which translates to:
12642 (@value{GDBP}) info static-tracepoint-markers
12643 Cnt Enb ID Address What
12644 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12650 so you may probe the marker above with:
12653 (@value{GDBP}) strace -m ust/bar33
12656 Static tracepoints accept an extra collect action --- @code{collect
12657 $_sdata}. This collects arbitrary user data passed in the probe point
12658 call to the tracing library. In the UST example above, you'll see
12659 that the third argument to @code{trace_mark} is a printf-like format
12660 string. The user data is then the result of running that formating
12661 string against the following arguments. Note that @code{info
12662 static-tracepoint-markers} command output lists that format string in
12663 the @samp{Data:} field.
12665 You can inspect this data when analyzing the trace buffer, by printing
12666 the $_sdata variable like any other variable available to
12667 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12670 @cindex last tracepoint number
12671 @cindex recent tracepoint number
12672 @cindex tracepoint number
12673 The convenience variable @code{$tpnum} records the tracepoint number
12674 of the most recently set tracepoint.
12676 @kindex delete tracepoint
12677 @cindex tracepoint deletion
12678 @item delete tracepoint @r{[}@var{num}@r{]}
12679 Permanently delete one or more tracepoints. With no argument, the
12680 default is to delete all tracepoints. Note that the regular
12681 @code{delete} command can remove tracepoints also.
12686 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12688 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12692 You can abbreviate this command as @code{del tr}.
12695 @node Enable and Disable Tracepoints
12696 @subsection Enable and Disable Tracepoints
12698 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12701 @kindex disable tracepoint
12702 @item disable tracepoint @r{[}@var{num}@r{]}
12703 Disable tracepoint @var{num}, or all tracepoints if no argument
12704 @var{num} is given. A disabled tracepoint will have no effect during
12705 a trace experiment, but it is not forgotten. You can re-enable
12706 a disabled tracepoint using the @code{enable tracepoint} command.
12707 If the command is issued during a trace experiment and the debug target
12708 has support for disabling tracepoints during a trace experiment, then the
12709 change will be effective immediately. Otherwise, it will be applied to the
12710 next trace experiment.
12712 @kindex enable tracepoint
12713 @item enable tracepoint @r{[}@var{num}@r{]}
12714 Enable tracepoint @var{num}, or all tracepoints. If this command is
12715 issued during a trace experiment and the debug target supports enabling
12716 tracepoints during a trace experiment, then the enabled tracepoints will
12717 become effective immediately. Otherwise, they will become effective the
12718 next time a trace experiment is run.
12721 @node Tracepoint Passcounts
12722 @subsection Tracepoint Passcounts
12726 @cindex tracepoint pass count
12727 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12728 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12729 automatically stop a trace experiment. If a tracepoint's passcount is
12730 @var{n}, then the trace experiment will be automatically stopped on
12731 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12732 @var{num} is not specified, the @code{passcount} command sets the
12733 passcount of the most recently defined tracepoint. If no passcount is
12734 given, the trace experiment will run until stopped explicitly by the
12740 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12741 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12743 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12744 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12745 (@value{GDBP}) @b{trace foo}
12746 (@value{GDBP}) @b{pass 3}
12747 (@value{GDBP}) @b{trace bar}
12748 (@value{GDBP}) @b{pass 2}
12749 (@value{GDBP}) @b{trace baz}
12750 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12751 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12752 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12753 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12757 @node Tracepoint Conditions
12758 @subsection Tracepoint Conditions
12759 @cindex conditional tracepoints
12760 @cindex tracepoint conditions
12762 The simplest sort of tracepoint collects data every time your program
12763 reaches a specified place. You can also specify a @dfn{condition} for
12764 a tracepoint. A condition is just a Boolean expression in your
12765 programming language (@pxref{Expressions, ,Expressions}). A
12766 tracepoint with a condition evaluates the expression each time your
12767 program reaches it, and data collection happens only if the condition
12770 Tracepoint conditions can be specified when a tracepoint is set, by
12771 using @samp{if} in the arguments to the @code{trace} command.
12772 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12773 also be set or changed at any time with the @code{condition} command,
12774 just as with breakpoints.
12776 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12777 the conditional expression itself. Instead, @value{GDBN} encodes the
12778 expression into an agent expression (@pxref{Agent Expressions})
12779 suitable for execution on the target, independently of @value{GDBN}.
12780 Global variables become raw memory locations, locals become stack
12781 accesses, and so forth.
12783 For instance, suppose you have a function that is usually called
12784 frequently, but should not be called after an error has occurred. You
12785 could use the following tracepoint command to collect data about calls
12786 of that function that happen while the error code is propagating
12787 through the program; an unconditional tracepoint could end up
12788 collecting thousands of useless trace frames that you would have to
12792 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12795 @node Trace State Variables
12796 @subsection Trace State Variables
12797 @cindex trace state variables
12799 A @dfn{trace state variable} is a special type of variable that is
12800 created and managed by target-side code. The syntax is the same as
12801 that for GDB's convenience variables (a string prefixed with ``$''),
12802 but they are stored on the target. They must be created explicitly,
12803 using a @code{tvariable} command. They are always 64-bit signed
12806 Trace state variables are remembered by @value{GDBN}, and downloaded
12807 to the target along with tracepoint information when the trace
12808 experiment starts. There are no intrinsic limits on the number of
12809 trace state variables, beyond memory limitations of the target.
12811 @cindex convenience variables, and trace state variables
12812 Although trace state variables are managed by the target, you can use
12813 them in print commands and expressions as if they were convenience
12814 variables; @value{GDBN} will get the current value from the target
12815 while the trace experiment is running. Trace state variables share
12816 the same namespace as other ``$'' variables, which means that you
12817 cannot have trace state variables with names like @code{$23} or
12818 @code{$pc}, nor can you have a trace state variable and a convenience
12819 variable with the same name.
12823 @item tvariable $@var{name} [ = @var{expression} ]
12825 The @code{tvariable} command creates a new trace state variable named
12826 @code{$@var{name}}, and optionally gives it an initial value of
12827 @var{expression}. The @var{expression} is evaluated when this command is
12828 entered; the result will be converted to an integer if possible,
12829 otherwise @value{GDBN} will report an error. A subsequent
12830 @code{tvariable} command specifying the same name does not create a
12831 variable, but instead assigns the supplied initial value to the
12832 existing variable of that name, overwriting any previous initial
12833 value. The default initial value is 0.
12835 @item info tvariables
12836 @kindex info tvariables
12837 List all the trace state variables along with their initial values.
12838 Their current values may also be displayed, if the trace experiment is
12841 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12842 @kindex delete tvariable
12843 Delete the given trace state variables, or all of them if no arguments
12848 @node Tracepoint Actions
12849 @subsection Tracepoint Action Lists
12853 @cindex tracepoint actions
12854 @item actions @r{[}@var{num}@r{]}
12855 This command will prompt for a list of actions to be taken when the
12856 tracepoint is hit. If the tracepoint number @var{num} is not
12857 specified, this command sets the actions for the one that was most
12858 recently defined (so that you can define a tracepoint and then say
12859 @code{actions} without bothering about its number). You specify the
12860 actions themselves on the following lines, one action at a time, and
12861 terminate the actions list with a line containing just @code{end}. So
12862 far, the only defined actions are @code{collect}, @code{teval}, and
12863 @code{while-stepping}.
12865 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12866 Commands, ,Breakpoint Command Lists}), except that only the defined
12867 actions are allowed; any other @value{GDBN} command is rejected.
12869 @cindex remove actions from a tracepoint
12870 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12871 and follow it immediately with @samp{end}.
12874 (@value{GDBP}) @b{collect @var{data}} // collect some data
12876 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12878 (@value{GDBP}) @b{end} // signals the end of actions.
12881 In the following example, the action list begins with @code{collect}
12882 commands indicating the things to be collected when the tracepoint is
12883 hit. Then, in order to single-step and collect additional data
12884 following the tracepoint, a @code{while-stepping} command is used,
12885 followed by the list of things to be collected after each step in a
12886 sequence of single steps. The @code{while-stepping} command is
12887 terminated by its own separate @code{end} command. Lastly, the action
12888 list is terminated by an @code{end} command.
12891 (@value{GDBP}) @b{trace foo}
12892 (@value{GDBP}) @b{actions}
12893 Enter actions for tracepoint 1, one per line:
12896 > while-stepping 12
12897 > collect $pc, arr[i]
12902 @kindex collect @r{(tracepoints)}
12903 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12904 Collect values of the given expressions when the tracepoint is hit.
12905 This command accepts a comma-separated list of any valid expressions.
12906 In addition to global, static, or local variables, the following
12907 special arguments are supported:
12911 Collect all registers.
12914 Collect all function arguments.
12917 Collect all local variables.
12920 Collect the return address. This is helpful if you want to see more
12923 @emph{Note:} The return address location can not always be reliably
12924 determined up front, and the wrong address / registers may end up
12925 collected instead. On some architectures the reliability is higher
12926 for tracepoints at function entry, while on others it's the opposite.
12927 When this happens, backtracing will stop because the return address is
12928 found unavailable (unless another collect rule happened to match it).
12931 Collects the number of arguments from the static probe at which the
12932 tracepoint is located.
12933 @xref{Static Probe Points}.
12935 @item $_probe_arg@var{n}
12936 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12937 from the static probe at which the tracepoint is located.
12938 @xref{Static Probe Points}.
12941 @vindex $_sdata@r{, collect}
12942 Collect static tracepoint marker specific data. Only available for
12943 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12944 Lists}. On the UST static tracepoints library backend, an
12945 instrumentation point resembles a @code{printf} function call. The
12946 tracing library is able to collect user specified data formatted to a
12947 character string using the format provided by the programmer that
12948 instrumented the program. Other backends have similar mechanisms.
12949 Here's an example of a UST marker call:
12952 const char master_name[] = "$your_name";
12953 trace_mark(channel1, marker1, "hello %s", master_name)
12956 In this case, collecting @code{$_sdata} collects the string
12957 @samp{hello $yourname}. When analyzing the trace buffer, you can
12958 inspect @samp{$_sdata} like any other variable available to
12962 You can give several consecutive @code{collect} commands, each one
12963 with a single argument, or one @code{collect} command with several
12964 arguments separated by commas; the effect is the same.
12966 The optional @var{mods} changes the usual handling of the arguments.
12967 @code{s} requests that pointers to chars be handled as strings, in
12968 particular collecting the contents of the memory being pointed at, up
12969 to the first zero. The upper bound is by default the value of the
12970 @code{print elements} variable; if @code{s} is followed by a decimal
12971 number, that is the upper bound instead. So for instance
12972 @samp{collect/s25 mystr} collects as many as 25 characters at
12975 The command @code{info scope} (@pxref{Symbols, info scope}) is
12976 particularly useful for figuring out what data to collect.
12978 @kindex teval @r{(tracepoints)}
12979 @item teval @var{expr1}, @var{expr2}, @dots{}
12980 Evaluate the given expressions when the tracepoint is hit. This
12981 command accepts a comma-separated list of expressions. The results
12982 are discarded, so this is mainly useful for assigning values to trace
12983 state variables (@pxref{Trace State Variables}) without adding those
12984 values to the trace buffer, as would be the case if the @code{collect}
12987 @kindex while-stepping @r{(tracepoints)}
12988 @item while-stepping @var{n}
12989 Perform @var{n} single-step instruction traces after the tracepoint,
12990 collecting new data after each step. The @code{while-stepping}
12991 command is followed by the list of what to collect while stepping
12992 (followed by its own @code{end} command):
12995 > while-stepping 12
12996 > collect $regs, myglobal
13002 Note that @code{$pc} is not automatically collected by
13003 @code{while-stepping}; you need to explicitly collect that register if
13004 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13007 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13008 @kindex set default-collect
13009 @cindex default collection action
13010 This variable is a list of expressions to collect at each tracepoint
13011 hit. It is effectively an additional @code{collect} action prepended
13012 to every tracepoint action list. The expressions are parsed
13013 individually for each tracepoint, so for instance a variable named
13014 @code{xyz} may be interpreted as a global for one tracepoint, and a
13015 local for another, as appropriate to the tracepoint's location.
13017 @item show default-collect
13018 @kindex show default-collect
13019 Show the list of expressions that are collected by default at each
13024 @node Listing Tracepoints
13025 @subsection Listing Tracepoints
13028 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13029 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13030 @cindex information about tracepoints
13031 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13032 Display information about the tracepoint @var{num}. If you don't
13033 specify a tracepoint number, displays information about all the
13034 tracepoints defined so far. The format is similar to that used for
13035 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13036 command, simply restricting itself to tracepoints.
13038 A tracepoint's listing may include additional information specific to
13043 its passcount as given by the @code{passcount @var{n}} command
13046 the state about installed on target of each location
13050 (@value{GDBP}) @b{info trace}
13051 Num Type Disp Enb Address What
13052 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13054 collect globfoo, $regs
13059 2 tracepoint keep y <MULTIPLE>
13061 2.1 y 0x0804859c in func4 at change-loc.h:35
13062 installed on target
13063 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13064 installed on target
13065 2.3 y <PENDING> set_tracepoint
13066 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13067 not installed on target
13072 This command can be abbreviated @code{info tp}.
13075 @node Listing Static Tracepoint Markers
13076 @subsection Listing Static Tracepoint Markers
13079 @kindex info static-tracepoint-markers
13080 @cindex information about static tracepoint markers
13081 @item info static-tracepoint-markers
13082 Display information about all static tracepoint markers defined in the
13085 For each marker, the following columns are printed:
13089 An incrementing counter, output to help readability. This is not a
13092 The marker ID, as reported by the target.
13093 @item Enabled or Disabled
13094 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13095 that are not enabled.
13097 Where the marker is in your program, as a memory address.
13099 Where the marker is in the source for your program, as a file and line
13100 number. If the debug information included in the program does not
13101 allow @value{GDBN} to locate the source of the marker, this column
13102 will be left blank.
13106 In addition, the following information may be printed for each marker:
13110 User data passed to the tracing library by the marker call. In the
13111 UST backend, this is the format string passed as argument to the
13113 @item Static tracepoints probing the marker
13114 The list of static tracepoints attached to the marker.
13118 (@value{GDBP}) info static-tracepoint-markers
13119 Cnt ID Enb Address What
13120 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13121 Data: number1 %d number2 %d
13122 Probed by static tracepoints: #2
13123 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13129 @node Starting and Stopping Trace Experiments
13130 @subsection Starting and Stopping Trace Experiments
13133 @kindex tstart [ @var{notes} ]
13134 @cindex start a new trace experiment
13135 @cindex collected data discarded
13137 This command starts the trace experiment, and begins collecting data.
13138 It has the side effect of discarding all the data collected in the
13139 trace buffer during the previous trace experiment. If any arguments
13140 are supplied, they are taken as a note and stored with the trace
13141 experiment's state. The notes may be arbitrary text, and are
13142 especially useful with disconnected tracing in a multi-user context;
13143 the notes can explain what the trace is doing, supply user contact
13144 information, and so forth.
13146 @kindex tstop [ @var{notes} ]
13147 @cindex stop a running trace experiment
13149 This command stops the trace experiment. If any arguments are
13150 supplied, they are recorded with the experiment as a note. This is
13151 useful if you are stopping a trace started by someone else, for
13152 instance if the trace is interfering with the system's behavior and
13153 needs to be stopped quickly.
13155 @strong{Note}: a trace experiment and data collection may stop
13156 automatically if any tracepoint's passcount is reached
13157 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13160 @cindex status of trace data collection
13161 @cindex trace experiment, status of
13163 This command displays the status of the current trace data
13167 Here is an example of the commands we described so far:
13170 (@value{GDBP}) @b{trace gdb_c_test}
13171 (@value{GDBP}) @b{actions}
13172 Enter actions for tracepoint #1, one per line.
13173 > collect $regs,$locals,$args
13174 > while-stepping 11
13178 (@value{GDBP}) @b{tstart}
13179 [time passes @dots{}]
13180 (@value{GDBP}) @b{tstop}
13183 @anchor{disconnected tracing}
13184 @cindex disconnected tracing
13185 You can choose to continue running the trace experiment even if
13186 @value{GDBN} disconnects from the target, voluntarily or
13187 involuntarily. For commands such as @code{detach}, the debugger will
13188 ask what you want to do with the trace. But for unexpected
13189 terminations (@value{GDBN} crash, network outage), it would be
13190 unfortunate to lose hard-won trace data, so the variable
13191 @code{disconnected-tracing} lets you decide whether the trace should
13192 continue running without @value{GDBN}.
13195 @item set disconnected-tracing on
13196 @itemx set disconnected-tracing off
13197 @kindex set disconnected-tracing
13198 Choose whether a tracing run should continue to run if @value{GDBN}
13199 has disconnected from the target. Note that @code{detach} or
13200 @code{quit} will ask you directly what to do about a running trace no
13201 matter what this variable's setting, so the variable is mainly useful
13202 for handling unexpected situations, such as loss of the network.
13204 @item show disconnected-tracing
13205 @kindex show disconnected-tracing
13206 Show the current choice for disconnected tracing.
13210 When you reconnect to the target, the trace experiment may or may not
13211 still be running; it might have filled the trace buffer in the
13212 meantime, or stopped for one of the other reasons. If it is running,
13213 it will continue after reconnection.
13215 Upon reconnection, the target will upload information about the
13216 tracepoints in effect. @value{GDBN} will then compare that
13217 information to the set of tracepoints currently defined, and attempt
13218 to match them up, allowing for the possibility that the numbers may
13219 have changed due to creation and deletion in the meantime. If one of
13220 the target's tracepoints does not match any in @value{GDBN}, the
13221 debugger will create a new tracepoint, so that you have a number with
13222 which to specify that tracepoint. This matching-up process is
13223 necessarily heuristic, and it may result in useless tracepoints being
13224 created; you may simply delete them if they are of no use.
13226 @cindex circular trace buffer
13227 If your target agent supports a @dfn{circular trace buffer}, then you
13228 can run a trace experiment indefinitely without filling the trace
13229 buffer; when space runs out, the agent deletes already-collected trace
13230 frames, oldest first, until there is enough room to continue
13231 collecting. This is especially useful if your tracepoints are being
13232 hit too often, and your trace gets terminated prematurely because the
13233 buffer is full. To ask for a circular trace buffer, simply set
13234 @samp{circular-trace-buffer} to on. You can set this at any time,
13235 including during tracing; if the agent can do it, it will change
13236 buffer handling on the fly, otherwise it will not take effect until
13240 @item set circular-trace-buffer on
13241 @itemx set circular-trace-buffer off
13242 @kindex set circular-trace-buffer
13243 Choose whether a tracing run should use a linear or circular buffer
13244 for trace data. A linear buffer will not lose any trace data, but may
13245 fill up prematurely, while a circular buffer will discard old trace
13246 data, but it will have always room for the latest tracepoint hits.
13248 @item show circular-trace-buffer
13249 @kindex show circular-trace-buffer
13250 Show the current choice for the trace buffer. Note that this may not
13251 match the agent's current buffer handling, nor is it guaranteed to
13252 match the setting that might have been in effect during a past run,
13253 for instance if you are looking at frames from a trace file.
13258 @item set trace-buffer-size @var{n}
13259 @itemx set trace-buffer-size unlimited
13260 @kindex set trace-buffer-size
13261 Request that the target use a trace buffer of @var{n} bytes. Not all
13262 targets will honor the request; they may have a compiled-in size for
13263 the trace buffer, or some other limitation. Set to a value of
13264 @code{unlimited} or @code{-1} to let the target use whatever size it
13265 likes. This is also the default.
13267 @item show trace-buffer-size
13268 @kindex show trace-buffer-size
13269 Show the current requested size for the trace buffer. Note that this
13270 will only match the actual size if the target supports size-setting,
13271 and was able to handle the requested size. For instance, if the
13272 target can only change buffer size between runs, this variable will
13273 not reflect the change until the next run starts. Use @code{tstatus}
13274 to get a report of the actual buffer size.
13278 @item set trace-user @var{text}
13279 @kindex set trace-user
13281 @item show trace-user
13282 @kindex show trace-user
13284 @item set trace-notes @var{text}
13285 @kindex set trace-notes
13286 Set the trace run's notes.
13288 @item show trace-notes
13289 @kindex show trace-notes
13290 Show the trace run's notes.
13292 @item set trace-stop-notes @var{text}
13293 @kindex set trace-stop-notes
13294 Set the trace run's stop notes. The handling of the note is as for
13295 @code{tstop} arguments; the set command is convenient way to fix a
13296 stop note that is mistaken or incomplete.
13298 @item show trace-stop-notes
13299 @kindex show trace-stop-notes
13300 Show the trace run's stop notes.
13304 @node Tracepoint Restrictions
13305 @subsection Tracepoint Restrictions
13307 @cindex tracepoint restrictions
13308 There are a number of restrictions on the use of tracepoints. As
13309 described above, tracepoint data gathering occurs on the target
13310 without interaction from @value{GDBN}. Thus the full capabilities of
13311 the debugger are not available during data gathering, and then at data
13312 examination time, you will be limited by only having what was
13313 collected. The following items describe some common problems, but it
13314 is not exhaustive, and you may run into additional difficulties not
13320 Tracepoint expressions are intended to gather objects (lvalues). Thus
13321 the full flexibility of GDB's expression evaluator is not available.
13322 You cannot call functions, cast objects to aggregate types, access
13323 convenience variables or modify values (except by assignment to trace
13324 state variables). Some language features may implicitly call
13325 functions (for instance Objective-C fields with accessors), and therefore
13326 cannot be collected either.
13329 Collection of local variables, either individually or in bulk with
13330 @code{$locals} or @code{$args}, during @code{while-stepping} may
13331 behave erratically. The stepping action may enter a new scope (for
13332 instance by stepping into a function), or the location of the variable
13333 may change (for instance it is loaded into a register). The
13334 tracepoint data recorded uses the location information for the
13335 variables that is correct for the tracepoint location. When the
13336 tracepoint is created, it is not possible, in general, to determine
13337 where the steps of a @code{while-stepping} sequence will advance the
13338 program---particularly if a conditional branch is stepped.
13341 Collection of an incompletely-initialized or partially-destroyed object
13342 may result in something that @value{GDBN} cannot display, or displays
13343 in a misleading way.
13346 When @value{GDBN} displays a pointer to character it automatically
13347 dereferences the pointer to also display characters of the string
13348 being pointed to. However, collecting the pointer during tracing does
13349 not automatically collect the string. You need to explicitly
13350 dereference the pointer and provide size information if you want to
13351 collect not only the pointer, but the memory pointed to. For example,
13352 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13356 It is not possible to collect a complete stack backtrace at a
13357 tracepoint. Instead, you may collect the registers and a few hundred
13358 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13359 (adjust to use the name of the actual stack pointer register on your
13360 target architecture, and the amount of stack you wish to capture).
13361 Then the @code{backtrace} command will show a partial backtrace when
13362 using a trace frame. The number of stack frames that can be examined
13363 depends on the sizes of the frames in the collected stack. Note that
13364 if you ask for a block so large that it goes past the bottom of the
13365 stack, the target agent may report an error trying to read from an
13369 If you do not collect registers at a tracepoint, @value{GDBN} can
13370 infer that the value of @code{$pc} must be the same as the address of
13371 the tracepoint and use that when you are looking at a trace frame
13372 for that tracepoint. However, this cannot work if the tracepoint has
13373 multiple locations (for instance if it was set in a function that was
13374 inlined), or if it has a @code{while-stepping} loop. In those cases
13375 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13380 @node Analyze Collected Data
13381 @section Using the Collected Data
13383 After the tracepoint experiment ends, you use @value{GDBN} commands
13384 for examining the trace data. The basic idea is that each tracepoint
13385 collects a trace @dfn{snapshot} every time it is hit and another
13386 snapshot every time it single-steps. All these snapshots are
13387 consecutively numbered from zero and go into a buffer, and you can
13388 examine them later. The way you examine them is to @dfn{focus} on a
13389 specific trace snapshot. When the remote stub is focused on a trace
13390 snapshot, it will respond to all @value{GDBN} requests for memory and
13391 registers by reading from the buffer which belongs to that snapshot,
13392 rather than from @emph{real} memory or registers of the program being
13393 debugged. This means that @strong{all} @value{GDBN} commands
13394 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13395 behave as if we were currently debugging the program state as it was
13396 when the tracepoint occurred. Any requests for data that are not in
13397 the buffer will fail.
13400 * tfind:: How to select a trace snapshot
13401 * tdump:: How to display all data for a snapshot
13402 * save tracepoints:: How to save tracepoints for a future run
13406 @subsection @code{tfind @var{n}}
13409 @cindex select trace snapshot
13410 @cindex find trace snapshot
13411 The basic command for selecting a trace snapshot from the buffer is
13412 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13413 counting from zero. If no argument @var{n} is given, the next
13414 snapshot is selected.
13416 Here are the various forms of using the @code{tfind} command.
13420 Find the first snapshot in the buffer. This is a synonym for
13421 @code{tfind 0} (since 0 is the number of the first snapshot).
13424 Stop debugging trace snapshots, resume @emph{live} debugging.
13427 Same as @samp{tfind none}.
13430 No argument means find the next trace snapshot or find the first
13431 one if no trace snapshot is selected.
13434 Find the previous trace snapshot before the current one. This permits
13435 retracing earlier steps.
13437 @item tfind tracepoint @var{num}
13438 Find the next snapshot associated with tracepoint @var{num}. Search
13439 proceeds forward from the last examined trace snapshot. If no
13440 argument @var{num} is given, it means find the next snapshot collected
13441 for the same tracepoint as the current snapshot.
13443 @item tfind pc @var{addr}
13444 Find the next snapshot associated with the value @var{addr} of the
13445 program counter. Search proceeds forward from the last examined trace
13446 snapshot. If no argument @var{addr} is given, it means find the next
13447 snapshot with the same value of PC as the current snapshot.
13449 @item tfind outside @var{addr1}, @var{addr2}
13450 Find the next snapshot whose PC is outside the given range of
13451 addresses (exclusive).
13453 @item tfind range @var{addr1}, @var{addr2}
13454 Find the next snapshot whose PC is between @var{addr1} and
13455 @var{addr2} (inclusive).
13457 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13458 Find the next snapshot associated with the source line @var{n}. If
13459 the optional argument @var{file} is given, refer to line @var{n} in
13460 that source file. Search proceeds forward from the last examined
13461 trace snapshot. If no argument @var{n} is given, it means find the
13462 next line other than the one currently being examined; thus saying
13463 @code{tfind line} repeatedly can appear to have the same effect as
13464 stepping from line to line in a @emph{live} debugging session.
13467 The default arguments for the @code{tfind} commands are specifically
13468 designed to make it easy to scan through the trace buffer. For
13469 instance, @code{tfind} with no argument selects the next trace
13470 snapshot, and @code{tfind -} with no argument selects the previous
13471 trace snapshot. So, by giving one @code{tfind} command, and then
13472 simply hitting @key{RET} repeatedly you can examine all the trace
13473 snapshots in order. Or, by saying @code{tfind -} and then hitting
13474 @key{RET} repeatedly you can examine the snapshots in reverse order.
13475 The @code{tfind line} command with no argument selects the snapshot
13476 for the next source line executed. The @code{tfind pc} command with
13477 no argument selects the next snapshot with the same program counter
13478 (PC) as the current frame. The @code{tfind tracepoint} command with
13479 no argument selects the next trace snapshot collected by the same
13480 tracepoint as the current one.
13482 In addition to letting you scan through the trace buffer manually,
13483 these commands make it easy to construct @value{GDBN} scripts that
13484 scan through the trace buffer and print out whatever collected data
13485 you are interested in. Thus, if we want to examine the PC, FP, and SP
13486 registers from each trace frame in the buffer, we can say this:
13489 (@value{GDBP}) @b{tfind start}
13490 (@value{GDBP}) @b{while ($trace_frame != -1)}
13491 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13492 $trace_frame, $pc, $sp, $fp
13496 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13497 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13498 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13499 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13500 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13501 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13502 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13503 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13504 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13505 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13506 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13509 Or, if we want to examine the variable @code{X} at each source line in
13513 (@value{GDBP}) @b{tfind start}
13514 (@value{GDBP}) @b{while ($trace_frame != -1)}
13515 > printf "Frame %d, X == %d\n", $trace_frame, X
13525 @subsection @code{tdump}
13527 @cindex dump all data collected at tracepoint
13528 @cindex tracepoint data, display
13530 This command takes no arguments. It prints all the data collected at
13531 the current trace snapshot.
13534 (@value{GDBP}) @b{trace 444}
13535 (@value{GDBP}) @b{actions}
13536 Enter actions for tracepoint #2, one per line:
13537 > collect $regs, $locals, $args, gdb_long_test
13540 (@value{GDBP}) @b{tstart}
13542 (@value{GDBP}) @b{tfind line 444}
13543 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13545 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13547 (@value{GDBP}) @b{tdump}
13548 Data collected at tracepoint 2, trace frame 1:
13549 d0 0xc4aa0085 -995491707
13553 d4 0x71aea3d 119204413
13556 d7 0x380035 3670069
13557 a0 0x19e24a 1696330
13558 a1 0x3000668 50333288
13560 a3 0x322000 3284992
13561 a4 0x3000698 50333336
13562 a5 0x1ad3cc 1758156
13563 fp 0x30bf3c 0x30bf3c
13564 sp 0x30bf34 0x30bf34
13566 pc 0x20b2c8 0x20b2c8
13570 p = 0x20e5b4 "gdb-test"
13577 gdb_long_test = 17 '\021'
13582 @code{tdump} works by scanning the tracepoint's current collection
13583 actions and printing the value of each expression listed. So
13584 @code{tdump} can fail, if after a run, you change the tracepoint's
13585 actions to mention variables that were not collected during the run.
13587 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13588 uses the collected value of @code{$pc} to distinguish between trace
13589 frames that were collected at the tracepoint hit, and frames that were
13590 collected while stepping. This allows it to correctly choose whether
13591 to display the basic list of collections, or the collections from the
13592 body of the while-stepping loop. However, if @code{$pc} was not collected,
13593 then @code{tdump} will always attempt to dump using the basic collection
13594 list, and may fail if a while-stepping frame does not include all the
13595 same data that is collected at the tracepoint hit.
13596 @c This is getting pretty arcane, example would be good.
13598 @node save tracepoints
13599 @subsection @code{save tracepoints @var{filename}}
13600 @kindex save tracepoints
13601 @kindex save-tracepoints
13602 @cindex save tracepoints for future sessions
13604 This command saves all current tracepoint definitions together with
13605 their actions and passcounts, into a file @file{@var{filename}}
13606 suitable for use in a later debugging session. To read the saved
13607 tracepoint definitions, use the @code{source} command (@pxref{Command
13608 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13609 alias for @w{@code{save tracepoints}}
13611 @node Tracepoint Variables
13612 @section Convenience Variables for Tracepoints
13613 @cindex tracepoint variables
13614 @cindex convenience variables for tracepoints
13617 @vindex $trace_frame
13618 @item (int) $trace_frame
13619 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13620 snapshot is selected.
13622 @vindex $tracepoint
13623 @item (int) $tracepoint
13624 The tracepoint for the current trace snapshot.
13626 @vindex $trace_line
13627 @item (int) $trace_line
13628 The line number for the current trace snapshot.
13630 @vindex $trace_file
13631 @item (char []) $trace_file
13632 The source file for the current trace snapshot.
13634 @vindex $trace_func
13635 @item (char []) $trace_func
13636 The name of the function containing @code{$tracepoint}.
13639 Note: @code{$trace_file} is not suitable for use in @code{printf},
13640 use @code{output} instead.
13642 Here's a simple example of using these convenience variables for
13643 stepping through all the trace snapshots and printing some of their
13644 data. Note that these are not the same as trace state variables,
13645 which are managed by the target.
13648 (@value{GDBP}) @b{tfind start}
13650 (@value{GDBP}) @b{while $trace_frame != -1}
13651 > output $trace_file
13652 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13658 @section Using Trace Files
13659 @cindex trace files
13661 In some situations, the target running a trace experiment may no
13662 longer be available; perhaps it crashed, or the hardware was needed
13663 for a different activity. To handle these cases, you can arrange to
13664 dump the trace data into a file, and later use that file as a source
13665 of trace data, via the @code{target tfile} command.
13670 @item tsave [ -r ] @var{filename}
13671 @itemx tsave [-ctf] @var{dirname}
13672 Save the trace data to @var{filename}. By default, this command
13673 assumes that @var{filename} refers to the host filesystem, so if
13674 necessary @value{GDBN} will copy raw trace data up from the target and
13675 then save it. If the target supports it, you can also supply the
13676 optional argument @code{-r} (``remote'') to direct the target to save
13677 the data directly into @var{filename} in its own filesystem, which may be
13678 more efficient if the trace buffer is very large. (Note, however, that
13679 @code{target tfile} can only read from files accessible to the host.)
13680 By default, this command will save trace frame in tfile format.
13681 You can supply the optional argument @code{-ctf} to save data in CTF
13682 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13683 that can be shared by multiple debugging and tracing tools. Please go to
13684 @indicateurl{http://www.efficios.com/ctf} to get more information.
13686 @kindex target tfile
13690 @item target tfile @var{filename}
13691 @itemx target ctf @var{dirname}
13692 Use the file named @var{filename} or directory named @var{dirname} as
13693 a source of trace data. Commands that examine data work as they do with
13694 a live target, but it is not possible to run any new trace experiments.
13695 @code{tstatus} will report the state of the trace run at the moment
13696 the data was saved, as well as the current trace frame you are examining.
13697 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13701 (@value{GDBP}) target ctf ctf.ctf
13702 (@value{GDBP}) tfind
13703 Found trace frame 0, tracepoint 2
13704 39 ++a; /* set tracepoint 1 here */
13705 (@value{GDBP}) tdump
13706 Data collected at tracepoint 2, trace frame 0:
13710 c = @{"123", "456", "789", "123", "456", "789"@}
13711 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13719 @chapter Debugging Programs That Use Overlays
13722 If your program is too large to fit completely in your target system's
13723 memory, you can sometimes use @dfn{overlays} to work around this
13724 problem. @value{GDBN} provides some support for debugging programs that
13728 * How Overlays Work:: A general explanation of overlays.
13729 * Overlay Commands:: Managing overlays in @value{GDBN}.
13730 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13731 mapped by asking the inferior.
13732 * Overlay Sample Program:: A sample program using overlays.
13735 @node How Overlays Work
13736 @section How Overlays Work
13737 @cindex mapped overlays
13738 @cindex unmapped overlays
13739 @cindex load address, overlay's
13740 @cindex mapped address
13741 @cindex overlay area
13743 Suppose you have a computer whose instruction address space is only 64
13744 kilobytes long, but which has much more memory which can be accessed by
13745 other means: special instructions, segment registers, or memory
13746 management hardware, for example. Suppose further that you want to
13747 adapt a program which is larger than 64 kilobytes to run on this system.
13749 One solution is to identify modules of your program which are relatively
13750 independent, and need not call each other directly; call these modules
13751 @dfn{overlays}. Separate the overlays from the main program, and place
13752 their machine code in the larger memory. Place your main program in
13753 instruction memory, but leave at least enough space there to hold the
13754 largest overlay as well.
13756 Now, to call a function located in an overlay, you must first copy that
13757 overlay's machine code from the large memory into the space set aside
13758 for it in the instruction memory, and then jump to its entry point
13761 @c NB: In the below the mapped area's size is greater or equal to the
13762 @c size of all overlays. This is intentional to remind the developer
13763 @c that overlays don't necessarily need to be the same size.
13767 Data Instruction Larger
13768 Address Space Address Space Address Space
13769 +-----------+ +-----------+ +-----------+
13771 +-----------+ +-----------+ +-----------+<-- overlay 1
13772 | program | | main | .----| overlay 1 | load address
13773 | variables | | program | | +-----------+
13774 | and heap | | | | | |
13775 +-----------+ | | | +-----------+<-- overlay 2
13776 | | +-----------+ | | | load address
13777 +-----------+ | | | .-| overlay 2 |
13779 mapped --->+-----------+ | | +-----------+
13780 address | | | | | |
13781 | overlay | <-' | | |
13782 | area | <---' +-----------+<-- overlay 3
13783 | | <---. | | load address
13784 +-----------+ `--| overlay 3 |
13791 @anchor{A code overlay}A code overlay
13795 The diagram (@pxref{A code overlay}) shows a system with separate data
13796 and instruction address spaces. To map an overlay, the program copies
13797 its code from the larger address space to the instruction address space.
13798 Since the overlays shown here all use the same mapped address, only one
13799 may be mapped at a time. For a system with a single address space for
13800 data and instructions, the diagram would be similar, except that the
13801 program variables and heap would share an address space with the main
13802 program and the overlay area.
13804 An overlay loaded into instruction memory and ready for use is called a
13805 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13806 instruction memory. An overlay not present (or only partially present)
13807 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13808 is its address in the larger memory. The mapped address is also called
13809 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13810 called the @dfn{load memory address}, or @dfn{LMA}.
13812 Unfortunately, overlays are not a completely transparent way to adapt a
13813 program to limited instruction memory. They introduce a new set of
13814 global constraints you must keep in mind as you design your program:
13819 Before calling or returning to a function in an overlay, your program
13820 must make sure that overlay is actually mapped. Otherwise, the call or
13821 return will transfer control to the right address, but in the wrong
13822 overlay, and your program will probably crash.
13825 If the process of mapping an overlay is expensive on your system, you
13826 will need to choose your overlays carefully to minimize their effect on
13827 your program's performance.
13830 The executable file you load onto your system must contain each
13831 overlay's instructions, appearing at the overlay's load address, not its
13832 mapped address. However, each overlay's instructions must be relocated
13833 and its symbols defined as if the overlay were at its mapped address.
13834 You can use GNU linker scripts to specify different load and relocation
13835 addresses for pieces of your program; see @ref{Overlay Description,,,
13836 ld.info, Using ld: the GNU linker}.
13839 The procedure for loading executable files onto your system must be able
13840 to load their contents into the larger address space as well as the
13841 instruction and data spaces.
13845 The overlay system described above is rather simple, and could be
13846 improved in many ways:
13851 If your system has suitable bank switch registers or memory management
13852 hardware, you could use those facilities to make an overlay's load area
13853 contents simply appear at their mapped address in instruction space.
13854 This would probably be faster than copying the overlay to its mapped
13855 area in the usual way.
13858 If your overlays are small enough, you could set aside more than one
13859 overlay area, and have more than one overlay mapped at a time.
13862 You can use overlays to manage data, as well as instructions. In
13863 general, data overlays are even less transparent to your design than
13864 code overlays: whereas code overlays only require care when you call or
13865 return to functions, data overlays require care every time you access
13866 the data. Also, if you change the contents of a data overlay, you
13867 must copy its contents back out to its load address before you can copy a
13868 different data overlay into the same mapped area.
13873 @node Overlay Commands
13874 @section Overlay Commands
13876 To use @value{GDBN}'s overlay support, each overlay in your program must
13877 correspond to a separate section of the executable file. The section's
13878 virtual memory address and load memory address must be the overlay's
13879 mapped and load addresses. Identifying overlays with sections allows
13880 @value{GDBN} to determine the appropriate address of a function or
13881 variable, depending on whether the overlay is mapped or not.
13883 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13884 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13889 Disable @value{GDBN}'s overlay support. When overlay support is
13890 disabled, @value{GDBN} assumes that all functions and variables are
13891 always present at their mapped addresses. By default, @value{GDBN}'s
13892 overlay support is disabled.
13894 @item overlay manual
13895 @cindex manual overlay debugging
13896 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13897 relies on you to tell it which overlays are mapped, and which are not,
13898 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13899 commands described below.
13901 @item overlay map-overlay @var{overlay}
13902 @itemx overlay map @var{overlay}
13903 @cindex map an overlay
13904 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13905 be the name of the object file section containing the overlay. When an
13906 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13907 functions and variables at their mapped addresses. @value{GDBN} assumes
13908 that any other overlays whose mapped ranges overlap that of
13909 @var{overlay} are now unmapped.
13911 @item overlay unmap-overlay @var{overlay}
13912 @itemx overlay unmap @var{overlay}
13913 @cindex unmap an overlay
13914 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13915 must be the name of the object file section containing the overlay.
13916 When an overlay is unmapped, @value{GDBN} assumes it can find the
13917 overlay's functions and variables at their load addresses.
13920 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13921 consults a data structure the overlay manager maintains in the inferior
13922 to see which overlays are mapped. For details, see @ref{Automatic
13923 Overlay Debugging}.
13925 @item overlay load-target
13926 @itemx overlay load
13927 @cindex reloading the overlay table
13928 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13929 re-reads the table @value{GDBN} automatically each time the inferior
13930 stops, so this command should only be necessary if you have changed the
13931 overlay mapping yourself using @value{GDBN}. This command is only
13932 useful when using automatic overlay debugging.
13934 @item overlay list-overlays
13935 @itemx overlay list
13936 @cindex listing mapped overlays
13937 Display a list of the overlays currently mapped, along with their mapped
13938 addresses, load addresses, and sizes.
13942 Normally, when @value{GDBN} prints a code address, it includes the name
13943 of the function the address falls in:
13946 (@value{GDBP}) print main
13947 $3 = @{int ()@} 0x11a0 <main>
13950 When overlay debugging is enabled, @value{GDBN} recognizes code in
13951 unmapped overlays, and prints the names of unmapped functions with
13952 asterisks around them. For example, if @code{foo} is a function in an
13953 unmapped overlay, @value{GDBN} prints it this way:
13956 (@value{GDBP}) overlay list
13957 No sections are mapped.
13958 (@value{GDBP}) print foo
13959 $5 = @{int (int)@} 0x100000 <*foo*>
13962 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13966 (@value{GDBP}) overlay list
13967 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13968 mapped at 0x1016 - 0x104a
13969 (@value{GDBP}) print foo
13970 $6 = @{int (int)@} 0x1016 <foo>
13973 When overlay debugging is enabled, @value{GDBN} can find the correct
13974 address for functions and variables in an overlay, whether or not the
13975 overlay is mapped. This allows most @value{GDBN} commands, like
13976 @code{break} and @code{disassemble}, to work normally, even on unmapped
13977 code. However, @value{GDBN}'s breakpoint support has some limitations:
13981 @cindex breakpoints in overlays
13982 @cindex overlays, setting breakpoints in
13983 You can set breakpoints in functions in unmapped overlays, as long as
13984 @value{GDBN} can write to the overlay at its load address.
13986 @value{GDBN} can not set hardware or simulator-based breakpoints in
13987 unmapped overlays. However, if you set a breakpoint at the end of your
13988 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13989 you are using manual overlay management), @value{GDBN} will re-set its
13990 breakpoints properly.
13994 @node Automatic Overlay Debugging
13995 @section Automatic Overlay Debugging
13996 @cindex automatic overlay debugging
13998 @value{GDBN} can automatically track which overlays are mapped and which
13999 are not, given some simple co-operation from the overlay manager in the
14000 inferior. If you enable automatic overlay debugging with the
14001 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14002 looks in the inferior's memory for certain variables describing the
14003 current state of the overlays.
14005 Here are the variables your overlay manager must define to support
14006 @value{GDBN}'s automatic overlay debugging:
14010 @item @code{_ovly_table}:
14011 This variable must be an array of the following structures:
14016 /* The overlay's mapped address. */
14019 /* The size of the overlay, in bytes. */
14020 unsigned long size;
14022 /* The overlay's load address. */
14025 /* Non-zero if the overlay is currently mapped;
14027 unsigned long mapped;
14031 @item @code{_novlys}:
14032 This variable must be a four-byte signed integer, holding the total
14033 number of elements in @code{_ovly_table}.
14037 To decide whether a particular overlay is mapped or not, @value{GDBN}
14038 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14039 @code{lma} members equal the VMA and LMA of the overlay's section in the
14040 executable file. When @value{GDBN} finds a matching entry, it consults
14041 the entry's @code{mapped} member to determine whether the overlay is
14044 In addition, your overlay manager may define a function called
14045 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14046 will silently set a breakpoint there. If the overlay manager then
14047 calls this function whenever it has changed the overlay table, this
14048 will enable @value{GDBN} to accurately keep track of which overlays
14049 are in program memory, and update any breakpoints that may be set
14050 in overlays. This will allow breakpoints to work even if the
14051 overlays are kept in ROM or other non-writable memory while they
14052 are not being executed.
14054 @node Overlay Sample Program
14055 @section Overlay Sample Program
14056 @cindex overlay example program
14058 When linking a program which uses overlays, you must place the overlays
14059 at their load addresses, while relocating them to run at their mapped
14060 addresses. To do this, you must write a linker script (@pxref{Overlay
14061 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14062 since linker scripts are specific to a particular host system, target
14063 architecture, and target memory layout, this manual cannot provide
14064 portable sample code demonstrating @value{GDBN}'s overlay support.
14066 However, the @value{GDBN} source distribution does contain an overlaid
14067 program, with linker scripts for a few systems, as part of its test
14068 suite. The program consists of the following files from
14069 @file{gdb/testsuite/gdb.base}:
14073 The main program file.
14075 A simple overlay manager, used by @file{overlays.c}.
14080 Overlay modules, loaded and used by @file{overlays.c}.
14083 Linker scripts for linking the test program on the @code{d10v-elf}
14084 and @code{m32r-elf} targets.
14087 You can build the test program using the @code{d10v-elf} GCC
14088 cross-compiler like this:
14091 $ d10v-elf-gcc -g -c overlays.c
14092 $ d10v-elf-gcc -g -c ovlymgr.c
14093 $ d10v-elf-gcc -g -c foo.c
14094 $ d10v-elf-gcc -g -c bar.c
14095 $ d10v-elf-gcc -g -c baz.c
14096 $ d10v-elf-gcc -g -c grbx.c
14097 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14098 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14101 The build process is identical for any other architecture, except that
14102 you must substitute the appropriate compiler and linker script for the
14103 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14107 @chapter Using @value{GDBN} with Different Languages
14110 Although programming languages generally have common aspects, they are
14111 rarely expressed in the same manner. For instance, in ANSI C,
14112 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14113 Modula-2, it is accomplished by @code{p^}. Values can also be
14114 represented (and displayed) differently. Hex numbers in C appear as
14115 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14117 @cindex working language
14118 Language-specific information is built into @value{GDBN} for some languages,
14119 allowing you to express operations like the above in your program's
14120 native language, and allowing @value{GDBN} to output values in a manner
14121 consistent with the syntax of your program's native language. The
14122 language you use to build expressions is called the @dfn{working
14126 * Setting:: Switching between source languages
14127 * Show:: Displaying the language
14128 * Checks:: Type and range checks
14129 * Supported Languages:: Supported languages
14130 * Unsupported Languages:: Unsupported languages
14134 @section Switching Between Source Languages
14136 There are two ways to control the working language---either have @value{GDBN}
14137 set it automatically, or select it manually yourself. You can use the
14138 @code{set language} command for either purpose. On startup, @value{GDBN}
14139 defaults to setting the language automatically. The working language is
14140 used to determine how expressions you type are interpreted, how values
14143 In addition to the working language, every source file that
14144 @value{GDBN} knows about has its own working language. For some object
14145 file formats, the compiler might indicate which language a particular
14146 source file is in. However, most of the time @value{GDBN} infers the
14147 language from the name of the file. The language of a source file
14148 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14149 show each frame appropriately for its own language. There is no way to
14150 set the language of a source file from within @value{GDBN}, but you can
14151 set the language associated with a filename extension. @xref{Show, ,
14152 Displaying the Language}.
14154 This is most commonly a problem when you use a program, such
14155 as @code{cfront} or @code{f2c}, that generates C but is written in
14156 another language. In that case, make the
14157 program use @code{#line} directives in its C output; that way
14158 @value{GDBN} will know the correct language of the source code of the original
14159 program, and will display that source code, not the generated C code.
14162 * Filenames:: Filename extensions and languages.
14163 * Manually:: Setting the working language manually
14164 * Automatically:: Having @value{GDBN} infer the source language
14168 @subsection List of Filename Extensions and Languages
14170 If a source file name ends in one of the following extensions, then
14171 @value{GDBN} infers that its language is the one indicated.
14189 C@t{++} source file
14195 Objective-C source file
14199 Fortran source file
14202 Modula-2 source file
14206 Assembler source file. This actually behaves almost like C, but
14207 @value{GDBN} does not skip over function prologues when stepping.
14210 In addition, you may set the language associated with a filename
14211 extension. @xref{Show, , Displaying the Language}.
14214 @subsection Setting the Working Language
14216 If you allow @value{GDBN} to set the language automatically,
14217 expressions are interpreted the same way in your debugging session and
14220 @kindex set language
14221 If you wish, you may set the language manually. To do this, issue the
14222 command @samp{set language @var{lang}}, where @var{lang} is the name of
14223 a language, such as
14224 @code{c} or @code{modula-2}.
14225 For a list of the supported languages, type @samp{set language}.
14227 Setting the language manually prevents @value{GDBN} from updating the working
14228 language automatically. This can lead to confusion if you try
14229 to debug a program when the working language is not the same as the
14230 source language, when an expression is acceptable to both
14231 languages---but means different things. For instance, if the current
14232 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14240 might not have the effect you intended. In C, this means to add
14241 @code{b} and @code{c} and place the result in @code{a}. The result
14242 printed would be the value of @code{a}. In Modula-2, this means to compare
14243 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14245 @node Automatically
14246 @subsection Having @value{GDBN} Infer the Source Language
14248 To have @value{GDBN} set the working language automatically, use
14249 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14250 then infers the working language. That is, when your program stops in a
14251 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14252 working language to the language recorded for the function in that
14253 frame. If the language for a frame is unknown (that is, if the function
14254 or block corresponding to the frame was defined in a source file that
14255 does not have a recognized extension), the current working language is
14256 not changed, and @value{GDBN} issues a warning.
14258 This may not seem necessary for most programs, which are written
14259 entirely in one source language. However, program modules and libraries
14260 written in one source language can be used by a main program written in
14261 a different source language. Using @samp{set language auto} in this
14262 case frees you from having to set the working language manually.
14265 @section Displaying the Language
14267 The following commands help you find out which language is the
14268 working language, and also what language source files were written in.
14271 @item show language
14272 @anchor{show language}
14273 @kindex show language
14274 Display the current working language. This is the
14275 language you can use with commands such as @code{print} to
14276 build and compute expressions that may involve variables in your program.
14279 @kindex info frame@r{, show the source language}
14280 Display the source language for this frame. This language becomes the
14281 working language if you use an identifier from this frame.
14282 @xref{Frame Info, ,Information about a Frame}, to identify the other
14283 information listed here.
14286 @kindex info source@r{, show the source language}
14287 Display the source language of this source file.
14288 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14289 information listed here.
14292 In unusual circumstances, you may have source files with extensions
14293 not in the standard list. You can then set the extension associated
14294 with a language explicitly:
14297 @item set extension-language @var{ext} @var{language}
14298 @kindex set extension-language
14299 Tell @value{GDBN} that source files with extension @var{ext} are to be
14300 assumed as written in the source language @var{language}.
14302 @item info extensions
14303 @kindex info extensions
14304 List all the filename extensions and the associated languages.
14308 @section Type and Range Checking
14310 Some languages are designed to guard you against making seemingly common
14311 errors through a series of compile- and run-time checks. These include
14312 checking the type of arguments to functions and operators and making
14313 sure mathematical overflows are caught at run time. Checks such as
14314 these help to ensure a program's correctness once it has been compiled
14315 by eliminating type mismatches and providing active checks for range
14316 errors when your program is running.
14318 By default @value{GDBN} checks for these errors according to the
14319 rules of the current source language. Although @value{GDBN} does not check
14320 the statements in your program, it can check expressions entered directly
14321 into @value{GDBN} for evaluation via the @code{print} command, for example.
14324 * Type Checking:: An overview of type checking
14325 * Range Checking:: An overview of range checking
14328 @cindex type checking
14329 @cindex checks, type
14330 @node Type Checking
14331 @subsection An Overview of Type Checking
14333 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14334 arguments to operators and functions have to be of the correct type,
14335 otherwise an error occurs. These checks prevent type mismatch
14336 errors from ever causing any run-time problems. For example,
14339 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14341 (@value{GDBP}) print obj.my_method (0)
14344 (@value{GDBP}) print obj.my_method (0x1234)
14345 Cannot resolve method klass::my_method to any overloaded instance
14348 The second example fails because in C@t{++} the integer constant
14349 @samp{0x1234} is not type-compatible with the pointer parameter type.
14351 For the expressions you use in @value{GDBN} commands, you can tell
14352 @value{GDBN} to not enforce strict type checking or
14353 to treat any mismatches as errors and abandon the expression;
14354 When type checking is disabled, @value{GDBN} successfully evaluates
14355 expressions like the second example above.
14357 Even if type checking is off, there may be other reasons
14358 related to type that prevent @value{GDBN} from evaluating an expression.
14359 For instance, @value{GDBN} does not know how to add an @code{int} and
14360 a @code{struct foo}. These particular type errors have nothing to do
14361 with the language in use and usually arise from expressions which make
14362 little sense to evaluate anyway.
14364 @value{GDBN} provides some additional commands for controlling type checking:
14366 @kindex set check type
14367 @kindex show check type
14369 @item set check type on
14370 @itemx set check type off
14371 Set strict type checking on or off. If any type mismatches occur in
14372 evaluating an expression while type checking is on, @value{GDBN} prints a
14373 message and aborts evaluation of the expression.
14375 @item show check type
14376 Show the current setting of type checking and whether @value{GDBN}
14377 is enforcing strict type checking rules.
14380 @cindex range checking
14381 @cindex checks, range
14382 @node Range Checking
14383 @subsection An Overview of Range Checking
14385 In some languages (such as Modula-2), it is an error to exceed the
14386 bounds of a type; this is enforced with run-time checks. Such range
14387 checking is meant to ensure program correctness by making sure
14388 computations do not overflow, or indices on an array element access do
14389 not exceed the bounds of the array.
14391 For expressions you use in @value{GDBN} commands, you can tell
14392 @value{GDBN} to treat range errors in one of three ways: ignore them,
14393 always treat them as errors and abandon the expression, or issue
14394 warnings but evaluate the expression anyway.
14396 A range error can result from numerical overflow, from exceeding an
14397 array index bound, or when you type a constant that is not a member
14398 of any type. Some languages, however, do not treat overflows as an
14399 error. In many implementations of C, mathematical overflow causes the
14400 result to ``wrap around'' to lower values---for example, if @var{m} is
14401 the largest integer value, and @var{s} is the smallest, then
14404 @var{m} + 1 @result{} @var{s}
14407 This, too, is specific to individual languages, and in some cases
14408 specific to individual compilers or machines. @xref{Supported Languages, ,
14409 Supported Languages}, for further details on specific languages.
14411 @value{GDBN} provides some additional commands for controlling the range checker:
14413 @kindex set check range
14414 @kindex show check range
14416 @item set check range auto
14417 Set range checking on or off based on the current working language.
14418 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14421 @item set check range on
14422 @itemx set check range off
14423 Set range checking on or off, overriding the default setting for the
14424 current working language. A warning is issued if the setting does not
14425 match the language default. If a range error occurs and range checking is on,
14426 then a message is printed and evaluation of the expression is aborted.
14428 @item set check range warn
14429 Output messages when the @value{GDBN} range checker detects a range error,
14430 but attempt to evaluate the expression anyway. Evaluating the
14431 expression may still be impossible for other reasons, such as accessing
14432 memory that the process does not own (a typical example from many Unix
14436 Show the current setting of the range checker, and whether or not it is
14437 being set automatically by @value{GDBN}.
14440 @node Supported Languages
14441 @section Supported Languages
14443 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14444 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14445 @c This is false ...
14446 Some @value{GDBN} features may be used in expressions regardless of the
14447 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14448 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14449 ,Expressions}) can be used with the constructs of any supported
14452 The following sections detail to what degree each source language is
14453 supported by @value{GDBN}. These sections are not meant to be language
14454 tutorials or references, but serve only as a reference guide to what the
14455 @value{GDBN} expression parser accepts, and what input and output
14456 formats should look like for different languages. There are many good
14457 books written on each of these languages; please look to these for a
14458 language reference or tutorial.
14461 * C:: C and C@t{++}
14464 * Objective-C:: Objective-C
14465 * OpenCL C:: OpenCL C
14466 * Fortran:: Fortran
14469 * Modula-2:: Modula-2
14474 @subsection C and C@t{++}
14476 @cindex C and C@t{++}
14477 @cindex expressions in C or C@t{++}
14479 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14480 to both languages. Whenever this is the case, we discuss those languages
14484 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14485 @cindex @sc{gnu} C@t{++}
14486 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14487 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14488 effectively, you must compile your C@t{++} programs with a supported
14489 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14490 compiler (@code{aCC}).
14493 * C Operators:: C and C@t{++} operators
14494 * C Constants:: C and C@t{++} constants
14495 * C Plus Plus Expressions:: C@t{++} expressions
14496 * C Defaults:: Default settings for C and C@t{++}
14497 * C Checks:: C and C@t{++} type and range checks
14498 * Debugging C:: @value{GDBN} and C
14499 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14500 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14504 @subsubsection C and C@t{++} Operators
14506 @cindex C and C@t{++} operators
14508 Operators must be defined on values of specific types. For instance,
14509 @code{+} is defined on numbers, but not on structures. Operators are
14510 often defined on groups of types.
14512 For the purposes of C and C@t{++}, the following definitions hold:
14517 @emph{Integral types} include @code{int} with any of its storage-class
14518 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14521 @emph{Floating-point types} include @code{float}, @code{double}, and
14522 @code{long double} (if supported by the target platform).
14525 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14528 @emph{Scalar types} include all of the above.
14533 The following operators are supported. They are listed here
14534 in order of increasing precedence:
14538 The comma or sequencing operator. Expressions in a comma-separated list
14539 are evaluated from left to right, with the result of the entire
14540 expression being the last expression evaluated.
14543 Assignment. The value of an assignment expression is the value
14544 assigned. Defined on scalar types.
14547 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14548 and translated to @w{@code{@var{a} = @var{a op b}}}.
14549 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14550 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14551 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14554 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14555 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14556 should be of an integral type.
14559 Logical @sc{or}. Defined on integral types.
14562 Logical @sc{and}. Defined on integral types.
14565 Bitwise @sc{or}. Defined on integral types.
14568 Bitwise exclusive-@sc{or}. Defined on integral types.
14571 Bitwise @sc{and}. Defined on integral types.
14574 Equality and inequality. Defined on scalar types. The value of these
14575 expressions is 0 for false and non-zero for true.
14577 @item <@r{, }>@r{, }<=@r{, }>=
14578 Less than, greater than, less than or equal, greater than or equal.
14579 Defined on scalar types. The value of these expressions is 0 for false
14580 and non-zero for true.
14583 left shift, and right shift. Defined on integral types.
14586 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14589 Addition and subtraction. Defined on integral types, floating-point types and
14592 @item *@r{, }/@r{, }%
14593 Multiplication, division, and modulus. Multiplication and division are
14594 defined on integral and floating-point types. Modulus is defined on
14598 Increment and decrement. When appearing before a variable, the
14599 operation is performed before the variable is used in an expression;
14600 when appearing after it, the variable's value is used before the
14601 operation takes place.
14604 Pointer dereferencing. Defined on pointer types. Same precedence as
14608 Address operator. Defined on variables. Same precedence as @code{++}.
14610 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14611 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14612 to examine the address
14613 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14617 Negative. Defined on integral and floating-point types. Same
14618 precedence as @code{++}.
14621 Logical negation. Defined on integral types. Same precedence as
14625 Bitwise complement operator. Defined on integral types. Same precedence as
14630 Structure member, and pointer-to-structure member. For convenience,
14631 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14632 pointer based on the stored type information.
14633 Defined on @code{struct} and @code{union} data.
14636 Dereferences of pointers to members.
14639 Array indexing. @code{@var{a}[@var{i}]} is defined as
14640 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14643 Function parameter list. Same precedence as @code{->}.
14646 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14647 and @code{class} types.
14650 Doubled colons also represent the @value{GDBN} scope operator
14651 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14655 If an operator is redefined in the user code, @value{GDBN} usually
14656 attempts to invoke the redefined version instead of using the operator's
14657 predefined meaning.
14660 @subsubsection C and C@t{++} Constants
14662 @cindex C and C@t{++} constants
14664 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14669 Integer constants are a sequence of digits. Octal constants are
14670 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14671 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14672 @samp{l}, specifying that the constant should be treated as a
14676 Floating point constants are a sequence of digits, followed by a decimal
14677 point, followed by a sequence of digits, and optionally followed by an
14678 exponent. An exponent is of the form:
14679 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14680 sequence of digits. The @samp{+} is optional for positive exponents.
14681 A floating-point constant may also end with a letter @samp{f} or
14682 @samp{F}, specifying that the constant should be treated as being of
14683 the @code{float} (as opposed to the default @code{double}) type; or with
14684 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14688 Enumerated constants consist of enumerated identifiers, or their
14689 integral equivalents.
14692 Character constants are a single character surrounded by single quotes
14693 (@code{'}), or a number---the ordinal value of the corresponding character
14694 (usually its @sc{ascii} value). Within quotes, the single character may
14695 be represented by a letter or by @dfn{escape sequences}, which are of
14696 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14697 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14698 @samp{@var{x}} is a predefined special character---for example,
14699 @samp{\n} for newline.
14701 Wide character constants can be written by prefixing a character
14702 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14703 form of @samp{x}. The target wide character set is used when
14704 computing the value of this constant (@pxref{Character Sets}).
14707 String constants are a sequence of character constants surrounded by
14708 double quotes (@code{"}). Any valid character constant (as described
14709 above) may appear. Double quotes within the string must be preceded by
14710 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14713 Wide string constants can be written by prefixing a string constant
14714 with @samp{L}, as in C. The target wide character set is used when
14715 computing the value of this constant (@pxref{Character Sets}).
14718 Pointer constants are an integral value. You can also write pointers
14719 to constants using the C operator @samp{&}.
14722 Array constants are comma-separated lists surrounded by braces @samp{@{}
14723 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14724 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14725 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14728 @node C Plus Plus Expressions
14729 @subsubsection C@t{++} Expressions
14731 @cindex expressions in C@t{++}
14732 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14734 @cindex debugging C@t{++} programs
14735 @cindex C@t{++} compilers
14736 @cindex debug formats and C@t{++}
14737 @cindex @value{NGCC} and C@t{++}
14739 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14740 the proper compiler and the proper debug format. Currently,
14741 @value{GDBN} works best when debugging C@t{++} code that is compiled
14742 with the most recent version of @value{NGCC} possible. The DWARF
14743 debugging format is preferred; @value{NGCC} defaults to this on most
14744 popular platforms. Other compilers and/or debug formats are likely to
14745 work badly or not at all when using @value{GDBN} to debug C@t{++}
14746 code. @xref{Compilation}.
14751 @cindex member functions
14753 Member function calls are allowed; you can use expressions like
14756 count = aml->GetOriginal(x, y)
14759 @vindex this@r{, inside C@t{++} member functions}
14760 @cindex namespace in C@t{++}
14762 While a member function is active (in the selected stack frame), your
14763 expressions have the same namespace available as the member function;
14764 that is, @value{GDBN} allows implicit references to the class instance
14765 pointer @code{this} following the same rules as C@t{++}. @code{using}
14766 declarations in the current scope are also respected by @value{GDBN}.
14768 @cindex call overloaded functions
14769 @cindex overloaded functions, calling
14770 @cindex type conversions in C@t{++}
14772 You can call overloaded functions; @value{GDBN} resolves the function
14773 call to the right definition, with some restrictions. @value{GDBN} does not
14774 perform overload resolution involving user-defined type conversions,
14775 calls to constructors, or instantiations of templates that do not exist
14776 in the program. It also cannot handle ellipsis argument lists or
14779 It does perform integral conversions and promotions, floating-point
14780 promotions, arithmetic conversions, pointer conversions, conversions of
14781 class objects to base classes, and standard conversions such as those of
14782 functions or arrays to pointers; it requires an exact match on the
14783 number of function arguments.
14785 Overload resolution is always performed, unless you have specified
14786 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14787 ,@value{GDBN} Features for C@t{++}}.
14789 You must specify @code{set overload-resolution off} in order to use an
14790 explicit function signature to call an overloaded function, as in
14792 p 'foo(char,int)'('x', 13)
14795 The @value{GDBN} command-completion facility can simplify this;
14796 see @ref{Completion, ,Command Completion}.
14798 @cindex reference declarations
14800 @value{GDBN} understands variables declared as C@t{++} references; you can use
14801 them in expressions just as you do in C@t{++} source---they are automatically
14804 In the parameter list shown when @value{GDBN} displays a frame, the values of
14805 reference variables are not displayed (unlike other variables); this
14806 avoids clutter, since references are often used for large structures.
14807 The @emph{address} of a reference variable is always shown, unless
14808 you have specified @samp{set print address off}.
14811 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14812 expressions can use it just as expressions in your program do. Since
14813 one scope may be defined in another, you can use @code{::} repeatedly if
14814 necessary, for example in an expression like
14815 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14816 resolving name scope by reference to source files, in both C and C@t{++}
14817 debugging (@pxref{Variables, ,Program Variables}).
14820 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14825 @subsubsection C and C@t{++} Defaults
14827 @cindex C and C@t{++} defaults
14829 If you allow @value{GDBN} to set range checking automatically, it
14830 defaults to @code{off} whenever the working language changes to
14831 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14832 selects the working language.
14834 If you allow @value{GDBN} to set the language automatically, it
14835 recognizes source files whose names end with @file{.c}, @file{.C}, or
14836 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14837 these files, it sets the working language to C or C@t{++}.
14838 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14839 for further details.
14842 @subsubsection C and C@t{++} Type and Range Checks
14844 @cindex C and C@t{++} checks
14846 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14847 checking is used. However, if you turn type checking off, @value{GDBN}
14848 will allow certain non-standard conversions, such as promoting integer
14849 constants to pointers.
14851 Range checking, if turned on, is done on mathematical operations. Array
14852 indices are not checked, since they are often used to index a pointer
14853 that is not itself an array.
14856 @subsubsection @value{GDBN} and C
14858 The @code{set print union} and @code{show print union} commands apply to
14859 the @code{union} type. When set to @samp{on}, any @code{union} that is
14860 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14861 appears as @samp{@{...@}}.
14863 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14864 with pointers and a memory allocation function. @xref{Expressions,
14867 @node Debugging C Plus Plus
14868 @subsubsection @value{GDBN} Features for C@t{++}
14870 @cindex commands for C@t{++}
14872 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14873 designed specifically for use with C@t{++}. Here is a summary:
14876 @cindex break in overloaded functions
14877 @item @r{breakpoint menus}
14878 When you want a breakpoint in a function whose name is overloaded,
14879 @value{GDBN} has the capability to display a menu of possible breakpoint
14880 locations to help you specify which function definition you want.
14881 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14883 @cindex overloading in C@t{++}
14884 @item rbreak @var{regex}
14885 Setting breakpoints using regular expressions is helpful for setting
14886 breakpoints on overloaded functions that are not members of any special
14888 @xref{Set Breaks, ,Setting Breakpoints}.
14890 @cindex C@t{++} exception handling
14892 @itemx catch rethrow
14894 Debug C@t{++} exception handling using these commands. @xref{Set
14895 Catchpoints, , Setting Catchpoints}.
14897 @cindex inheritance
14898 @item ptype @var{typename}
14899 Print inheritance relationships as well as other information for type
14901 @xref{Symbols, ,Examining the Symbol Table}.
14903 @item info vtbl @var{expression}.
14904 The @code{info vtbl} command can be used to display the virtual
14905 method tables of the object computed by @var{expression}. This shows
14906 one entry per virtual table; there may be multiple virtual tables when
14907 multiple inheritance is in use.
14909 @cindex C@t{++} demangling
14910 @item demangle @var{name}
14911 Demangle @var{name}.
14912 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14914 @cindex C@t{++} symbol display
14915 @item set print demangle
14916 @itemx show print demangle
14917 @itemx set print asm-demangle
14918 @itemx show print asm-demangle
14919 Control whether C@t{++} symbols display in their source form, both when
14920 displaying code as C@t{++} source and when displaying disassemblies.
14921 @xref{Print Settings, ,Print Settings}.
14923 @item set print object
14924 @itemx show print object
14925 Choose whether to print derived (actual) or declared types of objects.
14926 @xref{Print Settings, ,Print Settings}.
14928 @item set print vtbl
14929 @itemx show print vtbl
14930 Control the format for printing virtual function tables.
14931 @xref{Print Settings, ,Print Settings}.
14932 (The @code{vtbl} commands do not work on programs compiled with the HP
14933 ANSI C@t{++} compiler (@code{aCC}).)
14935 @kindex set overload-resolution
14936 @cindex overloaded functions, overload resolution
14937 @item set overload-resolution on
14938 Enable overload resolution for C@t{++} expression evaluation. The default
14939 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14940 and searches for a function whose signature matches the argument types,
14941 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14942 Expressions, ,C@t{++} Expressions}, for details).
14943 If it cannot find a match, it emits a message.
14945 @item set overload-resolution off
14946 Disable overload resolution for C@t{++} expression evaluation. For
14947 overloaded functions that are not class member functions, @value{GDBN}
14948 chooses the first function of the specified name that it finds in the
14949 symbol table, whether or not its arguments are of the correct type. For
14950 overloaded functions that are class member functions, @value{GDBN}
14951 searches for a function whose signature @emph{exactly} matches the
14954 @kindex show overload-resolution
14955 @item show overload-resolution
14956 Show the current setting of overload resolution.
14958 @item @r{Overloaded symbol names}
14959 You can specify a particular definition of an overloaded symbol, using
14960 the same notation that is used to declare such symbols in C@t{++}: type
14961 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14962 also use the @value{GDBN} command-line word completion facilities to list the
14963 available choices, or to finish the type list for you.
14964 @xref{Completion,, Command Completion}, for details on how to do this.
14967 @node Decimal Floating Point
14968 @subsubsection Decimal Floating Point format
14969 @cindex decimal floating point format
14971 @value{GDBN} can examine, set and perform computations with numbers in
14972 decimal floating point format, which in the C language correspond to the
14973 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14974 specified by the extension to support decimal floating-point arithmetic.
14976 There are two encodings in use, depending on the architecture: BID (Binary
14977 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14978 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14981 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14982 to manipulate decimal floating point numbers, it is not possible to convert
14983 (using a cast, for example) integers wider than 32-bit to decimal float.
14985 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14986 point computations, error checking in decimal float operations ignores
14987 underflow, overflow and divide by zero exceptions.
14989 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14990 to inspect @code{_Decimal128} values stored in floating point registers.
14991 See @ref{PowerPC,,PowerPC} for more details.
14997 @value{GDBN} can be used to debug programs written in D and compiled with
14998 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14999 specific feature --- dynamic arrays.
15004 @cindex Go (programming language)
15005 @value{GDBN} can be used to debug programs written in Go and compiled with
15006 @file{gccgo} or @file{6g} compilers.
15008 Here is a summary of the Go-specific features and restrictions:
15011 @cindex current Go package
15012 @item The current Go package
15013 The name of the current package does not need to be specified when
15014 specifying global variables and functions.
15016 For example, given the program:
15020 var myglob = "Shall we?"
15026 When stopped inside @code{main} either of these work:
15030 (gdb) p main.myglob
15033 @cindex builtin Go types
15034 @item Builtin Go types
15035 The @code{string} type is recognized by @value{GDBN} and is printed
15038 @cindex builtin Go functions
15039 @item Builtin Go functions
15040 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15041 function and handles it internally.
15043 @cindex restrictions on Go expressions
15044 @item Restrictions on Go expressions
15045 All Go operators are supported except @code{&^}.
15046 The Go @code{_} ``blank identifier'' is not supported.
15047 Automatic dereferencing of pointers is not supported.
15051 @subsection Objective-C
15053 @cindex Objective-C
15054 This section provides information about some commands and command
15055 options that are useful for debugging Objective-C code. See also
15056 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15057 few more commands specific to Objective-C support.
15060 * Method Names in Commands::
15061 * The Print Command with Objective-C::
15064 @node Method Names in Commands
15065 @subsubsection Method Names in Commands
15067 The following commands have been extended to accept Objective-C method
15068 names as line specifications:
15070 @kindex clear@r{, and Objective-C}
15071 @kindex break@r{, and Objective-C}
15072 @kindex info line@r{, and Objective-C}
15073 @kindex jump@r{, and Objective-C}
15074 @kindex list@r{, and Objective-C}
15078 @item @code{info line}
15083 A fully qualified Objective-C method name is specified as
15086 -[@var{Class} @var{methodName}]
15089 where the minus sign is used to indicate an instance method and a
15090 plus sign (not shown) is used to indicate a class method. The class
15091 name @var{Class} and method name @var{methodName} are enclosed in
15092 brackets, similar to the way messages are specified in Objective-C
15093 source code. For example, to set a breakpoint at the @code{create}
15094 instance method of class @code{Fruit} in the program currently being
15098 break -[Fruit create]
15101 To list ten program lines around the @code{initialize} class method,
15105 list +[NSText initialize]
15108 In the current version of @value{GDBN}, the plus or minus sign is
15109 required. In future versions of @value{GDBN}, the plus or minus
15110 sign will be optional, but you can use it to narrow the search. It
15111 is also possible to specify just a method name:
15117 You must specify the complete method name, including any colons. If
15118 your program's source files contain more than one @code{create} method,
15119 you'll be presented with a numbered list of classes that implement that
15120 method. Indicate your choice by number, or type @samp{0} to exit if
15123 As another example, to clear a breakpoint established at the
15124 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15127 clear -[NSWindow makeKeyAndOrderFront:]
15130 @node The Print Command with Objective-C
15131 @subsubsection The Print Command With Objective-C
15132 @cindex Objective-C, print objects
15133 @kindex print-object
15134 @kindex po @r{(@code{print-object})}
15136 The print command has also been extended to accept methods. For example:
15139 print -[@var{object} hash]
15142 @cindex print an Objective-C object description
15143 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15145 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15146 and print the result. Also, an additional command has been added,
15147 @code{print-object} or @code{po} for short, which is meant to print
15148 the description of an object. However, this command may only work
15149 with certain Objective-C libraries that have a particular hook
15150 function, @code{_NSPrintForDebugger}, defined.
15153 @subsection OpenCL C
15156 This section provides information about @value{GDBN}s OpenCL C support.
15159 * OpenCL C Datatypes::
15160 * OpenCL C Expressions::
15161 * OpenCL C Operators::
15164 @node OpenCL C Datatypes
15165 @subsubsection OpenCL C Datatypes
15167 @cindex OpenCL C Datatypes
15168 @value{GDBN} supports the builtin scalar and vector datatypes specified
15169 by OpenCL 1.1. In addition the half- and double-precision floating point
15170 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15171 extensions are also known to @value{GDBN}.
15173 @node OpenCL C Expressions
15174 @subsubsection OpenCL C Expressions
15176 @cindex OpenCL C Expressions
15177 @value{GDBN} supports accesses to vector components including the access as
15178 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15179 supported by @value{GDBN} can be used as well.
15181 @node OpenCL C Operators
15182 @subsubsection OpenCL C Operators
15184 @cindex OpenCL C Operators
15185 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15189 @subsection Fortran
15190 @cindex Fortran-specific support in @value{GDBN}
15192 @value{GDBN} can be used to debug programs written in Fortran, but it
15193 currently supports only the features of Fortran 77 language.
15195 @cindex trailing underscore, in Fortran symbols
15196 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15197 among them) append an underscore to the names of variables and
15198 functions. When you debug programs compiled by those compilers, you
15199 will need to refer to variables and functions with a trailing
15203 * Fortran Operators:: Fortran operators and expressions
15204 * Fortran Defaults:: Default settings for Fortran
15205 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15208 @node Fortran Operators
15209 @subsubsection Fortran Operators and Expressions
15211 @cindex Fortran operators and expressions
15213 Operators must be defined on values of specific types. For instance,
15214 @code{+} is defined on numbers, but not on characters or other non-
15215 arithmetic types. Operators are often defined on groups of types.
15219 The exponentiation operator. It raises the first operand to the power
15223 The range operator. Normally used in the form of array(low:high) to
15224 represent a section of array.
15227 The access component operator. Normally used to access elements in derived
15228 types. Also suitable for unions. As unions aren't part of regular Fortran,
15229 this can only happen when accessing a register that uses a gdbarch-defined
15233 @node Fortran Defaults
15234 @subsubsection Fortran Defaults
15236 @cindex Fortran Defaults
15238 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15239 default uses case-insensitive matches for Fortran symbols. You can
15240 change that with the @samp{set case-insensitive} command, see
15241 @ref{Symbols}, for the details.
15243 @node Special Fortran Commands
15244 @subsubsection Special Fortran Commands
15246 @cindex Special Fortran commands
15248 @value{GDBN} has some commands to support Fortran-specific features,
15249 such as displaying common blocks.
15252 @cindex @code{COMMON} blocks, Fortran
15253 @kindex info common
15254 @item info common @r{[}@var{common-name}@r{]}
15255 This command prints the values contained in the Fortran @code{COMMON}
15256 block whose name is @var{common-name}. With no argument, the names of
15257 all @code{COMMON} blocks visible at the current program location are
15264 @cindex Pascal support in @value{GDBN}, limitations
15265 Debugging Pascal programs which use sets, subranges, file variables, or
15266 nested functions does not currently work. @value{GDBN} does not support
15267 entering expressions, printing values, or similar features using Pascal
15270 The Pascal-specific command @code{set print pascal_static-members}
15271 controls whether static members of Pascal objects are displayed.
15272 @xref{Print Settings, pascal_static-members}.
15277 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15278 Programming Language}. Type- and value-printing, and expression
15279 parsing, are reasonably complete. However, there are a few
15280 peculiarities and holes to be aware of.
15284 Linespecs (@pxref{Specify Location}) are never relative to the current
15285 crate. Instead, they act as if there were a global namespace of
15286 crates, somewhat similar to the way @code{extern crate} behaves.
15288 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15289 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15290 to set a breakpoint in a function named @samp{f} in a crate named
15293 As a consequence of this approach, linespecs also cannot refer to
15294 items using @samp{self::} or @samp{super::}.
15297 Because @value{GDBN} implements Rust name-lookup semantics in
15298 expressions, it will sometimes prepend the current crate to a name.
15299 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15300 @samp{K}, then @code{print ::x::y} will try to find the symbol
15303 However, since it is useful to be able to refer to other crates when
15304 debugging, @value{GDBN} provides the @code{extern} extension to
15305 circumvent this. To use the extension, just put @code{extern} before
15306 a path expression to refer to the otherwise unavailable ``global''
15309 In the above example, if you wanted to refer to the symbol @samp{y} in
15310 the crate @samp{x}, you would use @code{print extern x::y}.
15313 The Rust expression evaluator does not support ``statement-like''
15314 expressions such as @code{if} or @code{match}, or lambda expressions.
15317 Tuple expressions are not implemented.
15320 The Rust expression evaluator does not currently implement the
15321 @code{Drop} trait. Objects that may be created by the evaluator will
15322 never be destroyed.
15325 @value{GDBN} does not implement type inference for generics. In order
15326 to call generic functions or otherwise refer to generic items, you
15327 will have to specify the type parameters manually.
15330 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15331 cases this does not cause any problems. However, in an expression
15332 context, completing a generic function name will give syntactically
15333 invalid results. This happens because Rust requires the @samp{::}
15334 operator between the function name and its generic arguments. For
15335 example, @value{GDBN} might provide a completion like
15336 @code{crate::f<u32>}, where the parser would require
15337 @code{crate::f::<u32>}.
15340 As of this writing, the Rust compiler (version 1.8) has a few holes in
15341 the debugging information it generates. These holes prevent certain
15342 features from being implemented by @value{GDBN}:
15346 Method calls cannot be made via traits.
15349 Trait objects cannot be created or inspected.
15352 Operator overloading is not implemented.
15355 When debugging in a monomorphized function, you cannot use the generic
15359 The type @code{Self} is not available.
15362 @code{use} statements are not available, so some names may not be
15363 available in the crate.
15368 @subsection Modula-2
15370 @cindex Modula-2, @value{GDBN} support
15372 The extensions made to @value{GDBN} to support Modula-2 only support
15373 output from the @sc{gnu} Modula-2 compiler (which is currently being
15374 developed). Other Modula-2 compilers are not currently supported, and
15375 attempting to debug executables produced by them is most likely
15376 to give an error as @value{GDBN} reads in the executable's symbol
15379 @cindex expressions in Modula-2
15381 * M2 Operators:: Built-in operators
15382 * Built-In Func/Proc:: Built-in functions and procedures
15383 * M2 Constants:: Modula-2 constants
15384 * M2 Types:: Modula-2 types
15385 * M2 Defaults:: Default settings for Modula-2
15386 * Deviations:: Deviations from standard Modula-2
15387 * M2 Checks:: Modula-2 type and range checks
15388 * M2 Scope:: The scope operators @code{::} and @code{.}
15389 * GDB/M2:: @value{GDBN} and Modula-2
15393 @subsubsection Operators
15394 @cindex Modula-2 operators
15396 Operators must be defined on values of specific types. For instance,
15397 @code{+} is defined on numbers, but not on structures. Operators are
15398 often defined on groups of types. For the purposes of Modula-2, the
15399 following definitions hold:
15404 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15408 @emph{Character types} consist of @code{CHAR} and its subranges.
15411 @emph{Floating-point types} consist of @code{REAL}.
15414 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15418 @emph{Scalar types} consist of all of the above.
15421 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15424 @emph{Boolean types} consist of @code{BOOLEAN}.
15428 The following operators are supported, and appear in order of
15429 increasing precedence:
15433 Function argument or array index separator.
15436 Assignment. The value of @var{var} @code{:=} @var{value} is
15440 Less than, greater than on integral, floating-point, or enumerated
15444 Less than or equal to, greater than or equal to
15445 on integral, floating-point and enumerated types, or set inclusion on
15446 set types. Same precedence as @code{<}.
15448 @item =@r{, }<>@r{, }#
15449 Equality and two ways of expressing inequality, valid on scalar types.
15450 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15451 available for inequality, since @code{#} conflicts with the script
15455 Set membership. Defined on set types and the types of their members.
15456 Same precedence as @code{<}.
15459 Boolean disjunction. Defined on boolean types.
15462 Boolean conjunction. Defined on boolean types.
15465 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15468 Addition and subtraction on integral and floating-point types, or union
15469 and difference on set types.
15472 Multiplication on integral and floating-point types, or set intersection
15476 Division on floating-point types, or symmetric set difference on set
15477 types. Same precedence as @code{*}.
15480 Integer division and remainder. Defined on integral types. Same
15481 precedence as @code{*}.
15484 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15487 Pointer dereferencing. Defined on pointer types.
15490 Boolean negation. Defined on boolean types. Same precedence as
15494 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15495 precedence as @code{^}.
15498 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15501 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15505 @value{GDBN} and Modula-2 scope operators.
15509 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15510 treats the use of the operator @code{IN}, or the use of operators
15511 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15512 @code{<=}, and @code{>=} on sets as an error.
15516 @node Built-In Func/Proc
15517 @subsubsection Built-in Functions and Procedures
15518 @cindex Modula-2 built-ins
15520 Modula-2 also makes available several built-in procedures and functions.
15521 In describing these, the following metavariables are used:
15526 represents an @code{ARRAY} variable.
15529 represents a @code{CHAR} constant or variable.
15532 represents a variable or constant of integral type.
15535 represents an identifier that belongs to a set. Generally used in the
15536 same function with the metavariable @var{s}. The type of @var{s} should
15537 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15540 represents a variable or constant of integral or floating-point type.
15543 represents a variable or constant of floating-point type.
15549 represents a variable.
15552 represents a variable or constant of one of many types. See the
15553 explanation of the function for details.
15556 All Modula-2 built-in procedures also return a result, described below.
15560 Returns the absolute value of @var{n}.
15563 If @var{c} is a lower case letter, it returns its upper case
15564 equivalent, otherwise it returns its argument.
15567 Returns the character whose ordinal value is @var{i}.
15570 Decrements the value in the variable @var{v} by one. Returns the new value.
15572 @item DEC(@var{v},@var{i})
15573 Decrements the value in the variable @var{v} by @var{i}. Returns the
15576 @item EXCL(@var{m},@var{s})
15577 Removes the element @var{m} from the set @var{s}. Returns the new
15580 @item FLOAT(@var{i})
15581 Returns the floating point equivalent of the integer @var{i}.
15583 @item HIGH(@var{a})
15584 Returns the index of the last member of @var{a}.
15587 Increments the value in the variable @var{v} by one. Returns the new value.
15589 @item INC(@var{v},@var{i})
15590 Increments the value in the variable @var{v} by @var{i}. Returns the
15593 @item INCL(@var{m},@var{s})
15594 Adds the element @var{m} to the set @var{s} if it is not already
15595 there. Returns the new set.
15598 Returns the maximum value of the type @var{t}.
15601 Returns the minimum value of the type @var{t}.
15604 Returns boolean TRUE if @var{i} is an odd number.
15607 Returns the ordinal value of its argument. For example, the ordinal
15608 value of a character is its @sc{ascii} value (on machines supporting
15609 the @sc{ascii} character set). The argument @var{x} must be of an
15610 ordered type, which include integral, character and enumerated types.
15612 @item SIZE(@var{x})
15613 Returns the size of its argument. The argument @var{x} can be a
15614 variable or a type.
15616 @item TRUNC(@var{r})
15617 Returns the integral part of @var{r}.
15619 @item TSIZE(@var{x})
15620 Returns the size of its argument. The argument @var{x} can be a
15621 variable or a type.
15623 @item VAL(@var{t},@var{i})
15624 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15628 @emph{Warning:} Sets and their operations are not yet supported, so
15629 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15633 @cindex Modula-2 constants
15635 @subsubsection Constants
15637 @value{GDBN} allows you to express the constants of Modula-2 in the following
15643 Integer constants are simply a sequence of digits. When used in an
15644 expression, a constant is interpreted to be type-compatible with the
15645 rest of the expression. Hexadecimal integers are specified by a
15646 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15649 Floating point constants appear as a sequence of digits, followed by a
15650 decimal point and another sequence of digits. An optional exponent can
15651 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15652 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15653 digits of the floating point constant must be valid decimal (base 10)
15657 Character constants consist of a single character enclosed by a pair of
15658 like quotes, either single (@code{'}) or double (@code{"}). They may
15659 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15660 followed by a @samp{C}.
15663 String constants consist of a sequence of characters enclosed by a
15664 pair of like quotes, either single (@code{'}) or double (@code{"}).
15665 Escape sequences in the style of C are also allowed. @xref{C
15666 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15670 Enumerated constants consist of an enumerated identifier.
15673 Boolean constants consist of the identifiers @code{TRUE} and
15677 Pointer constants consist of integral values only.
15680 Set constants are not yet supported.
15684 @subsubsection Modula-2 Types
15685 @cindex Modula-2 types
15687 Currently @value{GDBN} can print the following data types in Modula-2
15688 syntax: array types, record types, set types, pointer types, procedure
15689 types, enumerated types, subrange types and base types. You can also
15690 print the contents of variables declared using these type.
15691 This section gives a number of simple source code examples together with
15692 sample @value{GDBN} sessions.
15694 The first example contains the following section of code:
15703 and you can request @value{GDBN} to interrogate the type and value of
15704 @code{r} and @code{s}.
15707 (@value{GDBP}) print s
15709 (@value{GDBP}) ptype s
15711 (@value{GDBP}) print r
15713 (@value{GDBP}) ptype r
15718 Likewise if your source code declares @code{s} as:
15722 s: SET ['A'..'Z'] ;
15726 then you may query the type of @code{s} by:
15729 (@value{GDBP}) ptype s
15730 type = SET ['A'..'Z']
15734 Note that at present you cannot interactively manipulate set
15735 expressions using the debugger.
15737 The following example shows how you might declare an array in Modula-2
15738 and how you can interact with @value{GDBN} to print its type and contents:
15742 s: ARRAY [-10..10] OF CHAR ;
15746 (@value{GDBP}) ptype s
15747 ARRAY [-10..10] OF CHAR
15750 Note that the array handling is not yet complete and although the type
15751 is printed correctly, expression handling still assumes that all
15752 arrays have a lower bound of zero and not @code{-10} as in the example
15755 Here are some more type related Modula-2 examples:
15759 colour = (blue, red, yellow, green) ;
15760 t = [blue..yellow] ;
15768 The @value{GDBN} interaction shows how you can query the data type
15769 and value of a variable.
15772 (@value{GDBP}) print s
15774 (@value{GDBP}) ptype t
15775 type = [blue..yellow]
15779 In this example a Modula-2 array is declared and its contents
15780 displayed. Observe that the contents are written in the same way as
15781 their @code{C} counterparts.
15785 s: ARRAY [1..5] OF CARDINAL ;
15791 (@value{GDBP}) print s
15792 $1 = @{1, 0, 0, 0, 0@}
15793 (@value{GDBP}) ptype s
15794 type = ARRAY [1..5] OF CARDINAL
15797 The Modula-2 language interface to @value{GDBN} also understands
15798 pointer types as shown in this example:
15802 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15809 and you can request that @value{GDBN} describes the type of @code{s}.
15812 (@value{GDBP}) ptype s
15813 type = POINTER TO ARRAY [1..5] OF CARDINAL
15816 @value{GDBN} handles compound types as we can see in this example.
15817 Here we combine array types, record types, pointer types and subrange
15828 myarray = ARRAY myrange OF CARDINAL ;
15829 myrange = [-2..2] ;
15831 s: POINTER TO ARRAY myrange OF foo ;
15835 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15839 (@value{GDBP}) ptype s
15840 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15843 f3 : ARRAY [-2..2] OF CARDINAL;
15848 @subsubsection Modula-2 Defaults
15849 @cindex Modula-2 defaults
15851 If type and range checking are set automatically by @value{GDBN}, they
15852 both default to @code{on} whenever the working language changes to
15853 Modula-2. This happens regardless of whether you or @value{GDBN}
15854 selected the working language.
15856 If you allow @value{GDBN} to set the language automatically, then entering
15857 code compiled from a file whose name ends with @file{.mod} sets the
15858 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15859 Infer the Source Language}, for further details.
15862 @subsubsection Deviations from Standard Modula-2
15863 @cindex Modula-2, deviations from
15865 A few changes have been made to make Modula-2 programs easier to debug.
15866 This is done primarily via loosening its type strictness:
15870 Unlike in standard Modula-2, pointer constants can be formed by
15871 integers. This allows you to modify pointer variables during
15872 debugging. (In standard Modula-2, the actual address contained in a
15873 pointer variable is hidden from you; it can only be modified
15874 through direct assignment to another pointer variable or expression that
15875 returned a pointer.)
15878 C escape sequences can be used in strings and characters to represent
15879 non-printable characters. @value{GDBN} prints out strings with these
15880 escape sequences embedded. Single non-printable characters are
15881 printed using the @samp{CHR(@var{nnn})} format.
15884 The assignment operator (@code{:=}) returns the value of its right-hand
15888 All built-in procedures both modify @emph{and} return their argument.
15892 @subsubsection Modula-2 Type and Range Checks
15893 @cindex Modula-2 checks
15896 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15899 @c FIXME remove warning when type/range checks added
15901 @value{GDBN} considers two Modula-2 variables type equivalent if:
15905 They are of types that have been declared equivalent via a @code{TYPE
15906 @var{t1} = @var{t2}} statement
15909 They have been declared on the same line. (Note: This is true of the
15910 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15913 As long as type checking is enabled, any attempt to combine variables
15914 whose types are not equivalent is an error.
15916 Range checking is done on all mathematical operations, assignment, array
15917 index bounds, and all built-in functions and procedures.
15920 @subsubsection The Scope Operators @code{::} and @code{.}
15922 @cindex @code{.}, Modula-2 scope operator
15923 @cindex colon, doubled as scope operator
15925 @vindex colon-colon@r{, in Modula-2}
15926 @c Info cannot handle :: but TeX can.
15929 @vindex ::@r{, in Modula-2}
15932 There are a few subtle differences between the Modula-2 scope operator
15933 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15938 @var{module} . @var{id}
15939 @var{scope} :: @var{id}
15943 where @var{scope} is the name of a module or a procedure,
15944 @var{module} the name of a module, and @var{id} is any declared
15945 identifier within your program, except another module.
15947 Using the @code{::} operator makes @value{GDBN} search the scope
15948 specified by @var{scope} for the identifier @var{id}. If it is not
15949 found in the specified scope, then @value{GDBN} searches all scopes
15950 enclosing the one specified by @var{scope}.
15952 Using the @code{.} operator makes @value{GDBN} search the current scope for
15953 the identifier specified by @var{id} that was imported from the
15954 definition module specified by @var{module}. With this operator, it is
15955 an error if the identifier @var{id} was not imported from definition
15956 module @var{module}, or if @var{id} is not an identifier in
15960 @subsubsection @value{GDBN} and Modula-2
15962 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15963 Five subcommands of @code{set print} and @code{show print} apply
15964 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15965 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15966 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15967 analogue in Modula-2.
15969 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15970 with any language, is not useful with Modula-2. Its
15971 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15972 created in Modula-2 as they can in C or C@t{++}. However, because an
15973 address can be specified by an integral constant, the construct
15974 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15976 @cindex @code{#} in Modula-2
15977 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15978 interpreted as the beginning of a comment. Use @code{<>} instead.
15984 The extensions made to @value{GDBN} for Ada only support
15985 output from the @sc{gnu} Ada (GNAT) compiler.
15986 Other Ada compilers are not currently supported, and
15987 attempting to debug executables produced by them is most likely
15991 @cindex expressions in Ada
15993 * Ada Mode Intro:: General remarks on the Ada syntax
15994 and semantics supported by Ada mode
15996 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15997 * Additions to Ada:: Extensions of the Ada expression syntax.
15998 * Overloading support for Ada:: Support for expressions involving overloaded
16000 * Stopping Before Main Program:: Debugging the program during elaboration.
16001 * Ada Exceptions:: Ada Exceptions
16002 * Ada Tasks:: Listing and setting breakpoints in tasks.
16003 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16004 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16006 * Ada Glitches:: Known peculiarities of Ada mode.
16009 @node Ada Mode Intro
16010 @subsubsection Introduction
16011 @cindex Ada mode, general
16013 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16014 syntax, with some extensions.
16015 The philosophy behind the design of this subset is
16019 That @value{GDBN} should provide basic literals and access to operations for
16020 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16021 leaving more sophisticated computations to subprograms written into the
16022 program (which therefore may be called from @value{GDBN}).
16025 That type safety and strict adherence to Ada language restrictions
16026 are not particularly important to the @value{GDBN} user.
16029 That brevity is important to the @value{GDBN} user.
16032 Thus, for brevity, the debugger acts as if all names declared in
16033 user-written packages are directly visible, even if they are not visible
16034 according to Ada rules, thus making it unnecessary to fully qualify most
16035 names with their packages, regardless of context. Where this causes
16036 ambiguity, @value{GDBN} asks the user's intent.
16038 The debugger will start in Ada mode if it detects an Ada main program.
16039 As for other languages, it will enter Ada mode when stopped in a program that
16040 was translated from an Ada source file.
16042 While in Ada mode, you may use `@t{--}' for comments. This is useful
16043 mostly for documenting command files. The standard @value{GDBN} comment
16044 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16045 middle (to allow based literals).
16047 @node Omissions from Ada
16048 @subsubsection Omissions from Ada
16049 @cindex Ada, omissions from
16051 Here are the notable omissions from the subset:
16055 Only a subset of the attributes are supported:
16059 @t{'First}, @t{'Last}, and @t{'Length}
16060 on array objects (not on types and subtypes).
16063 @t{'Min} and @t{'Max}.
16066 @t{'Pos} and @t{'Val}.
16072 @t{'Range} on array objects (not subtypes), but only as the right
16073 operand of the membership (@code{in}) operator.
16076 @t{'Access}, @t{'Unchecked_Access}, and
16077 @t{'Unrestricted_Access} (a GNAT extension).
16085 @code{Characters.Latin_1} are not available and
16086 concatenation is not implemented. Thus, escape characters in strings are
16087 not currently available.
16090 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16091 equality of representations. They will generally work correctly
16092 for strings and arrays whose elements have integer or enumeration types.
16093 They may not work correctly for arrays whose element
16094 types have user-defined equality, for arrays of real values
16095 (in particular, IEEE-conformant floating point, because of negative
16096 zeroes and NaNs), and for arrays whose elements contain unused bits with
16097 indeterminate values.
16100 The other component-by-component array operations (@code{and}, @code{or},
16101 @code{xor}, @code{not}, and relational tests other than equality)
16102 are not implemented.
16105 @cindex array aggregates (Ada)
16106 @cindex record aggregates (Ada)
16107 @cindex aggregates (Ada)
16108 There is limited support for array and record aggregates. They are
16109 permitted only on the right sides of assignments, as in these examples:
16112 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16113 (@value{GDBP}) set An_Array := (1, others => 0)
16114 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16115 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16116 (@value{GDBP}) set A_Record := (1, "Peter", True);
16117 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16121 discriminant's value by assigning an aggregate has an
16122 undefined effect if that discriminant is used within the record.
16123 However, you can first modify discriminants by directly assigning to
16124 them (which normally would not be allowed in Ada), and then performing an
16125 aggregate assignment. For example, given a variable @code{A_Rec}
16126 declared to have a type such as:
16129 type Rec (Len : Small_Integer := 0) is record
16131 Vals : IntArray (1 .. Len);
16135 you can assign a value with a different size of @code{Vals} with two
16139 (@value{GDBP}) set A_Rec.Len := 4
16140 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16143 As this example also illustrates, @value{GDBN} is very loose about the usual
16144 rules concerning aggregates. You may leave out some of the
16145 components of an array or record aggregate (such as the @code{Len}
16146 component in the assignment to @code{A_Rec} above); they will retain their
16147 original values upon assignment. You may freely use dynamic values as
16148 indices in component associations. You may even use overlapping or
16149 redundant component associations, although which component values are
16150 assigned in such cases is not defined.
16153 Calls to dispatching subprograms are not implemented.
16156 The overloading algorithm is much more limited (i.e., less selective)
16157 than that of real Ada. It makes only limited use of the context in
16158 which a subexpression appears to resolve its meaning, and it is much
16159 looser in its rules for allowing type matches. As a result, some
16160 function calls will be ambiguous, and the user will be asked to choose
16161 the proper resolution.
16164 The @code{new} operator is not implemented.
16167 Entry calls are not implemented.
16170 Aside from printing, arithmetic operations on the native VAX floating-point
16171 formats are not supported.
16174 It is not possible to slice a packed array.
16177 The names @code{True} and @code{False}, when not part of a qualified name,
16178 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16180 Should your program
16181 redefine these names in a package or procedure (at best a dubious practice),
16182 you will have to use fully qualified names to access their new definitions.
16185 @node Additions to Ada
16186 @subsubsection Additions to Ada
16187 @cindex Ada, deviations from
16189 As it does for other languages, @value{GDBN} makes certain generic
16190 extensions to Ada (@pxref{Expressions}):
16194 If the expression @var{E} is a variable residing in memory (typically
16195 a local variable or array element) and @var{N} is a positive integer,
16196 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16197 @var{N}-1 adjacent variables following it in memory as an array. In
16198 Ada, this operator is generally not necessary, since its prime use is
16199 in displaying parts of an array, and slicing will usually do this in
16200 Ada. However, there are occasional uses when debugging programs in
16201 which certain debugging information has been optimized away.
16204 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16205 appears in function or file @var{B}.'' When @var{B} is a file name,
16206 you must typically surround it in single quotes.
16209 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16210 @var{type} that appears at address @var{addr}.''
16213 A name starting with @samp{$} is a convenience variable
16214 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16217 In addition, @value{GDBN} provides a few other shortcuts and outright
16218 additions specific to Ada:
16222 The assignment statement is allowed as an expression, returning
16223 its right-hand operand as its value. Thus, you may enter
16226 (@value{GDBP}) set x := y + 3
16227 (@value{GDBP}) print A(tmp := y + 1)
16231 The semicolon is allowed as an ``operator,'' returning as its value
16232 the value of its right-hand operand.
16233 This allows, for example,
16234 complex conditional breaks:
16237 (@value{GDBP}) break f
16238 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16242 Rather than use catenation and symbolic character names to introduce special
16243 characters into strings, one may instead use a special bracket notation,
16244 which is also used to print strings. A sequence of characters of the form
16245 @samp{["@var{XX}"]} within a string or character literal denotes the
16246 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16247 sequence of characters @samp{["""]} also denotes a single quotation mark
16248 in strings. For example,
16250 "One line.["0a"]Next line.["0a"]"
16253 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16257 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16258 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16262 (@value{GDBP}) print 'max(x, y)
16266 When printing arrays, @value{GDBN} uses positional notation when the
16267 array has a lower bound of 1, and uses a modified named notation otherwise.
16268 For example, a one-dimensional array of three integers with a lower bound
16269 of 3 might print as
16276 That is, in contrast to valid Ada, only the first component has a @code{=>}
16280 You may abbreviate attributes in expressions with any unique,
16281 multi-character subsequence of
16282 their names (an exact match gets preference).
16283 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16284 in place of @t{a'length}.
16287 @cindex quoting Ada internal identifiers
16288 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16289 to lower case. The GNAT compiler uses upper-case characters for
16290 some of its internal identifiers, which are normally of no interest to users.
16291 For the rare occasions when you actually have to look at them,
16292 enclose them in angle brackets to avoid the lower-case mapping.
16295 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16299 Printing an object of class-wide type or dereferencing an
16300 access-to-class-wide value will display all the components of the object's
16301 specific type (as indicated by its run-time tag). Likewise, component
16302 selection on such a value will operate on the specific type of the
16307 @node Overloading support for Ada
16308 @subsubsection Overloading support for Ada
16309 @cindex overloading, Ada
16311 The debugger supports limited overloading. Given a subprogram call in which
16312 the function symbol has multiple definitions, it will use the number of
16313 actual parameters and some information about their types to attempt to narrow
16314 the set of definitions. It also makes very limited use of context, preferring
16315 procedures to functions in the context of the @code{call} command, and
16316 functions to procedures elsewhere.
16318 If, after narrowing, the set of matching definitions still contains more than
16319 one definition, @value{GDBN} will display a menu to query which one it should
16323 (@value{GDBP}) print f(1)
16324 Multiple matches for f
16326 [1] foo.f (integer) return boolean at foo.adb:23
16327 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16331 In this case, just select one menu entry either to cancel expression evaluation
16332 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16333 instance (type the corresponding number and press @key{RET}).
16335 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16340 @kindex set ada print-signatures
16341 @item set ada print-signatures
16342 Control whether parameter types and return types are displayed in overloads
16343 selection menus. It is @code{on} by default.
16344 @xref{Overloading support for Ada}.
16346 @kindex show ada print-signatures
16347 @item show ada print-signatures
16348 Show the current setting for displaying parameter types and return types in
16349 overloads selection menu.
16350 @xref{Overloading support for Ada}.
16354 @node Stopping Before Main Program
16355 @subsubsection Stopping at the Very Beginning
16357 @cindex breakpointing Ada elaboration code
16358 It is sometimes necessary to debug the program during elaboration, and
16359 before reaching the main procedure.
16360 As defined in the Ada Reference
16361 Manual, the elaboration code is invoked from a procedure called
16362 @code{adainit}. To run your program up to the beginning of
16363 elaboration, simply use the following two commands:
16364 @code{tbreak adainit} and @code{run}.
16366 @node Ada Exceptions
16367 @subsubsection Ada Exceptions
16369 A command is provided to list all Ada exceptions:
16372 @kindex info exceptions
16373 @item info exceptions
16374 @itemx info exceptions @var{regexp}
16375 The @code{info exceptions} command allows you to list all Ada exceptions
16376 defined within the program being debugged, as well as their addresses.
16377 With a regular expression, @var{regexp}, as argument, only those exceptions
16378 whose names match @var{regexp} are listed.
16381 Below is a small example, showing how the command can be used, first
16382 without argument, and next with a regular expression passed as an
16386 (@value{GDBP}) info exceptions
16387 All defined Ada exceptions:
16388 constraint_error: 0x613da0
16389 program_error: 0x613d20
16390 storage_error: 0x613ce0
16391 tasking_error: 0x613ca0
16392 const.aint_global_e: 0x613b00
16393 (@value{GDBP}) info exceptions const.aint
16394 All Ada exceptions matching regular expression "const.aint":
16395 constraint_error: 0x613da0
16396 const.aint_global_e: 0x613b00
16399 It is also possible to ask @value{GDBN} to stop your program's execution
16400 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16403 @subsubsection Extensions for Ada Tasks
16404 @cindex Ada, tasking
16406 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16407 @value{GDBN} provides the following task-related commands:
16412 This command shows a list of current Ada tasks, as in the following example:
16419 (@value{GDBP}) info tasks
16420 ID TID P-ID Pri State Name
16421 1 8088000 0 15 Child Activation Wait main_task
16422 2 80a4000 1 15 Accept Statement b
16423 3 809a800 1 15 Child Activation Wait a
16424 * 4 80ae800 3 15 Runnable c
16429 In this listing, the asterisk before the last task indicates it to be the
16430 task currently being inspected.
16434 Represents @value{GDBN}'s internal task number.
16440 The parent's task ID (@value{GDBN}'s internal task number).
16443 The base priority of the task.
16446 Current state of the task.
16450 The task has been created but has not been activated. It cannot be
16454 The task is not blocked for any reason known to Ada. (It may be waiting
16455 for a mutex, though.) It is conceptually "executing" in normal mode.
16458 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16459 that were waiting on terminate alternatives have been awakened and have
16460 terminated themselves.
16462 @item Child Activation Wait
16463 The task is waiting for created tasks to complete activation.
16465 @item Accept Statement
16466 The task is waiting on an accept or selective wait statement.
16468 @item Waiting on entry call
16469 The task is waiting on an entry call.
16471 @item Async Select Wait
16472 The task is waiting to start the abortable part of an asynchronous
16476 The task is waiting on a select statement with only a delay
16479 @item Child Termination Wait
16480 The task is sleeping having completed a master within itself, and is
16481 waiting for the tasks dependent on that master to become terminated or
16482 waiting on a terminate Phase.
16484 @item Wait Child in Term Alt
16485 The task is sleeping waiting for tasks on terminate alternatives to
16486 finish terminating.
16488 @item Accepting RV with @var{taskno}
16489 The task is accepting a rendez-vous with the task @var{taskno}.
16493 Name of the task in the program.
16497 @kindex info task @var{taskno}
16498 @item info task @var{taskno}
16499 This command shows detailled informations on the specified task, as in
16500 the following example:
16505 (@value{GDBP}) info tasks
16506 ID TID P-ID Pri State Name
16507 1 8077880 0 15 Child Activation Wait main_task
16508 * 2 807c468 1 15 Runnable task_1
16509 (@value{GDBP}) info task 2
16510 Ada Task: 0x807c468
16513 Parent: 1 (main_task)
16519 @kindex task@r{ (Ada)}
16520 @cindex current Ada task ID
16521 This command prints the ID of the current task.
16527 (@value{GDBP}) info tasks
16528 ID TID P-ID Pri State Name
16529 1 8077870 0 15 Child Activation Wait main_task
16530 * 2 807c458 1 15 Runnable t
16531 (@value{GDBP}) task
16532 [Current task is 2]
16535 @item task @var{taskno}
16536 @cindex Ada task switching
16537 This command is like the @code{thread @var{thread-id}}
16538 command (@pxref{Threads}). It switches the context of debugging
16539 from the current task to the given task.
16545 (@value{GDBP}) info tasks
16546 ID TID P-ID Pri State Name
16547 1 8077870 0 15 Child Activation Wait main_task
16548 * 2 807c458 1 15 Runnable t
16549 (@value{GDBP}) task 1
16550 [Switching to task 1]
16551 #0 0x8067726 in pthread_cond_wait ()
16553 #0 0x8067726 in pthread_cond_wait ()
16554 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16555 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16556 #3 0x806153e in system.tasking.stages.activate_tasks ()
16557 #4 0x804aacc in un () at un.adb:5
16560 @item break @var{location} task @var{taskno}
16561 @itemx break @var{location} task @var{taskno} if @dots{}
16562 @cindex breakpoints and tasks, in Ada
16563 @cindex task breakpoints, in Ada
16564 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16565 These commands are like the @code{break @dots{} thread @dots{}}
16566 command (@pxref{Thread Stops}). The
16567 @var{location} argument specifies source lines, as described
16568 in @ref{Specify Location}.
16570 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16571 to specify that you only want @value{GDBN} to stop the program when a
16572 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16573 numeric task identifiers assigned by @value{GDBN}, shown in the first
16574 column of the @samp{info tasks} display.
16576 If you do not specify @samp{task @var{taskno}} when you set a
16577 breakpoint, the breakpoint applies to @emph{all} tasks of your
16580 You can use the @code{task} qualifier on conditional breakpoints as
16581 well; in this case, place @samp{task @var{taskno}} before the
16582 breakpoint condition (before the @code{if}).
16590 (@value{GDBP}) info tasks
16591 ID TID P-ID Pri State Name
16592 1 140022020 0 15 Child Activation Wait main_task
16593 2 140045060 1 15 Accept/Select Wait t2
16594 3 140044840 1 15 Runnable t1
16595 * 4 140056040 1 15 Runnable t3
16596 (@value{GDBP}) b 15 task 2
16597 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16598 (@value{GDBP}) cont
16603 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16605 (@value{GDBP}) info tasks
16606 ID TID P-ID Pri State Name
16607 1 140022020 0 15 Child Activation Wait main_task
16608 * 2 140045060 1 15 Runnable t2
16609 3 140044840 1 15 Runnable t1
16610 4 140056040 1 15 Delay Sleep t3
16614 @node Ada Tasks and Core Files
16615 @subsubsection Tasking Support when Debugging Core Files
16616 @cindex Ada tasking and core file debugging
16618 When inspecting a core file, as opposed to debugging a live program,
16619 tasking support may be limited or even unavailable, depending on
16620 the platform being used.
16621 For instance, on x86-linux, the list of tasks is available, but task
16622 switching is not supported.
16624 On certain platforms, the debugger needs to perform some
16625 memory writes in order to provide Ada tasking support. When inspecting
16626 a core file, this means that the core file must be opened with read-write
16627 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16628 Under these circumstances, you should make a backup copy of the core
16629 file before inspecting it with @value{GDBN}.
16631 @node Ravenscar Profile
16632 @subsubsection Tasking Support when using the Ravenscar Profile
16633 @cindex Ravenscar Profile
16635 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16636 specifically designed for systems with safety-critical real-time
16640 @kindex set ravenscar task-switching on
16641 @cindex task switching with program using Ravenscar Profile
16642 @item set ravenscar task-switching on
16643 Allows task switching when debugging a program that uses the Ravenscar
16644 Profile. This is the default.
16646 @kindex set ravenscar task-switching off
16647 @item set ravenscar task-switching off
16648 Turn off task switching when debugging a program that uses the Ravenscar
16649 Profile. This is mostly intended to disable the code that adds support
16650 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16651 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16652 To be effective, this command should be run before the program is started.
16654 @kindex show ravenscar task-switching
16655 @item show ravenscar task-switching
16656 Show whether it is possible to switch from task to task in a program
16657 using the Ravenscar Profile.
16662 @subsubsection Known Peculiarities of Ada Mode
16663 @cindex Ada, problems
16665 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16666 we know of several problems with and limitations of Ada mode in
16668 some of which will be fixed with planned future releases of the debugger
16669 and the GNU Ada compiler.
16673 Static constants that the compiler chooses not to materialize as objects in
16674 storage are invisible to the debugger.
16677 Named parameter associations in function argument lists are ignored (the
16678 argument lists are treated as positional).
16681 Many useful library packages are currently invisible to the debugger.
16684 Fixed-point arithmetic, conversions, input, and output is carried out using
16685 floating-point arithmetic, and may give results that only approximate those on
16689 The GNAT compiler never generates the prefix @code{Standard} for any of
16690 the standard symbols defined by the Ada language. @value{GDBN} knows about
16691 this: it will strip the prefix from names when you use it, and will never
16692 look for a name you have so qualified among local symbols, nor match against
16693 symbols in other packages or subprograms. If you have
16694 defined entities anywhere in your program other than parameters and
16695 local variables whose simple names match names in @code{Standard},
16696 GNAT's lack of qualification here can cause confusion. When this happens,
16697 you can usually resolve the confusion
16698 by qualifying the problematic names with package
16699 @code{Standard} explicitly.
16702 Older versions of the compiler sometimes generate erroneous debugging
16703 information, resulting in the debugger incorrectly printing the value
16704 of affected entities. In some cases, the debugger is able to work
16705 around an issue automatically. In other cases, the debugger is able
16706 to work around the issue, but the work-around has to be specifically
16709 @kindex set ada trust-PAD-over-XVS
16710 @kindex show ada trust-PAD-over-XVS
16713 @item set ada trust-PAD-over-XVS on
16714 Configure GDB to strictly follow the GNAT encoding when computing the
16715 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16716 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16717 a complete description of the encoding used by the GNAT compiler).
16718 This is the default.
16720 @item set ada trust-PAD-over-XVS off
16721 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16722 sometimes prints the wrong value for certain entities, changing @code{ada
16723 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16724 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16725 @code{off}, but this incurs a slight performance penalty, so it is
16726 recommended to leave this setting to @code{on} unless necessary.
16730 @cindex GNAT descriptive types
16731 @cindex GNAT encoding
16732 Internally, the debugger also relies on the compiler following a number
16733 of conventions known as the @samp{GNAT Encoding}, all documented in
16734 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16735 how the debugging information should be generated for certain types.
16736 In particular, this convention makes use of @dfn{descriptive types},
16737 which are artificial types generated purely to help the debugger.
16739 These encodings were defined at a time when the debugging information
16740 format used was not powerful enough to describe some of the more complex
16741 types available in Ada. Since DWARF allows us to express nearly all
16742 Ada features, the long-term goal is to slowly replace these descriptive
16743 types by their pure DWARF equivalent. To facilitate that transition,
16744 a new maintenance option is available to force the debugger to ignore
16745 those descriptive types. It allows the user to quickly evaluate how
16746 well @value{GDBN} works without them.
16750 @kindex maint ada set ignore-descriptive-types
16751 @item maintenance ada set ignore-descriptive-types [on|off]
16752 Control whether the debugger should ignore descriptive types.
16753 The default is not to ignore descriptives types (@code{off}).
16755 @kindex maint ada show ignore-descriptive-types
16756 @item maintenance ada show ignore-descriptive-types
16757 Show if descriptive types are ignored by @value{GDBN}.
16761 @node Unsupported Languages
16762 @section Unsupported Languages
16764 @cindex unsupported languages
16765 @cindex minimal language
16766 In addition to the other fully-supported programming languages,
16767 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16768 It does not represent a real programming language, but provides a set
16769 of capabilities close to what the C or assembly languages provide.
16770 This should allow most simple operations to be performed while debugging
16771 an application that uses a language currently not supported by @value{GDBN}.
16773 If the language is set to @code{auto}, @value{GDBN} will automatically
16774 select this language if the current frame corresponds to an unsupported
16778 @chapter Examining the Symbol Table
16780 The commands described in this chapter allow you to inquire about the
16781 symbols (names of variables, functions and types) defined in your
16782 program. This information is inherent in the text of your program and
16783 does not change as your program executes. @value{GDBN} finds it in your
16784 program's symbol table, in the file indicated when you started @value{GDBN}
16785 (@pxref{File Options, ,Choosing Files}), or by one of the
16786 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16788 @cindex symbol names
16789 @cindex names of symbols
16790 @cindex quoting names
16791 Occasionally, you may need to refer to symbols that contain unusual
16792 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16793 most frequent case is in referring to static variables in other
16794 source files (@pxref{Variables,,Program Variables}). File names
16795 are recorded in object files as debugging symbols, but @value{GDBN} would
16796 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16797 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16798 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16805 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16808 @cindex case-insensitive symbol names
16809 @cindex case sensitivity in symbol names
16810 @kindex set case-sensitive
16811 @item set case-sensitive on
16812 @itemx set case-sensitive off
16813 @itemx set case-sensitive auto
16814 Normally, when @value{GDBN} looks up symbols, it matches their names
16815 with case sensitivity determined by the current source language.
16816 Occasionally, you may wish to control that. The command @code{set
16817 case-sensitive} lets you do that by specifying @code{on} for
16818 case-sensitive matches or @code{off} for case-insensitive ones. If
16819 you specify @code{auto}, case sensitivity is reset to the default
16820 suitable for the source language. The default is case-sensitive
16821 matches for all languages except for Fortran, for which the default is
16822 case-insensitive matches.
16824 @kindex show case-sensitive
16825 @item show case-sensitive
16826 This command shows the current setting of case sensitivity for symbols
16829 @kindex set print type methods
16830 @item set print type methods
16831 @itemx set print type methods on
16832 @itemx set print type methods off
16833 Normally, when @value{GDBN} prints a class, it displays any methods
16834 declared in that class. You can control this behavior either by
16835 passing the appropriate flag to @code{ptype}, or using @command{set
16836 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16837 display the methods; this is the default. Specifying @code{off} will
16838 cause @value{GDBN} to omit the methods.
16840 @kindex show print type methods
16841 @item show print type methods
16842 This command shows the current setting of method display when printing
16845 @kindex set print type typedefs
16846 @item set print type typedefs
16847 @itemx set print type typedefs on
16848 @itemx set print type typedefs off
16850 Normally, when @value{GDBN} prints a class, it displays any typedefs
16851 defined in that class. You can control this behavior either by
16852 passing the appropriate flag to @code{ptype}, or using @command{set
16853 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16854 display the typedef definitions; this is the default. Specifying
16855 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16856 Note that this controls whether the typedef definition itself is
16857 printed, not whether typedef names are substituted when printing other
16860 @kindex show print type typedefs
16861 @item show print type typedefs
16862 This command shows the current setting of typedef display when
16865 @kindex info address
16866 @cindex address of a symbol
16867 @item info address @var{symbol}
16868 Describe where the data for @var{symbol} is stored. For a register
16869 variable, this says which register it is kept in. For a non-register
16870 local variable, this prints the stack-frame offset at which the variable
16873 Note the contrast with @samp{print &@var{symbol}}, which does not work
16874 at all for a register variable, and for a stack local variable prints
16875 the exact address of the current instantiation of the variable.
16877 @kindex info symbol
16878 @cindex symbol from address
16879 @cindex closest symbol and offset for an address
16880 @item info symbol @var{addr}
16881 Print the name of a symbol which is stored at the address @var{addr}.
16882 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16883 nearest symbol and an offset from it:
16886 (@value{GDBP}) info symbol 0x54320
16887 _initialize_vx + 396 in section .text
16891 This is the opposite of the @code{info address} command. You can use
16892 it to find out the name of a variable or a function given its address.
16894 For dynamically linked executables, the name of executable or shared
16895 library containing the symbol is also printed:
16898 (@value{GDBP}) info symbol 0x400225
16899 _start + 5 in section .text of /tmp/a.out
16900 (@value{GDBP}) info symbol 0x2aaaac2811cf
16901 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16906 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16907 Demangle @var{name}.
16908 If @var{language} is provided it is the name of the language to demangle
16909 @var{name} in. Otherwise @var{name} is demangled in the current language.
16911 The @samp{--} option specifies the end of options,
16912 and is useful when @var{name} begins with a dash.
16914 The parameter @code{demangle-style} specifies how to interpret the kind
16915 of mangling used. @xref{Print Settings}.
16918 @item whatis[/@var{flags}] [@var{arg}]
16919 Print the data type of @var{arg}, which can be either an expression
16920 or a name of a data type. With no argument, print the data type of
16921 @code{$}, the last value in the value history.
16923 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16924 is not actually evaluated, and any side-effecting operations (such as
16925 assignments or function calls) inside it do not take place.
16927 If @var{arg} is a variable or an expression, @code{whatis} prints its
16928 literal type as it is used in the source code. If the type was
16929 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16930 the data type underlying the @code{typedef}. If the type of the
16931 variable or the expression is a compound data type, such as
16932 @code{struct} or @code{class}, @code{whatis} never prints their
16933 fields or methods. It just prints the @code{struct}/@code{class}
16934 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16935 such a compound data type, use @code{ptype}.
16937 If @var{arg} is a type name that was defined using @code{typedef},
16938 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16939 Unrolling means that @code{whatis} will show the underlying type used
16940 in the @code{typedef} declaration of @var{arg}. However, if that
16941 underlying type is also a @code{typedef}, @code{whatis} will not
16944 For C code, the type names may also have the form @samp{class
16945 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16946 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16948 @var{flags} can be used to modify how the type is displayed.
16949 Available flags are:
16953 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16954 parameters and typedefs defined in a class when printing the class'
16955 members. The @code{/r} flag disables this.
16958 Do not print methods defined in the class.
16961 Print methods defined in the class. This is the default, but the flag
16962 exists in case you change the default with @command{set print type methods}.
16965 Do not print typedefs defined in the class. Note that this controls
16966 whether the typedef definition itself is printed, not whether typedef
16967 names are substituted when printing other types.
16970 Print typedefs defined in the class. This is the default, but the flag
16971 exists in case you change the default with @command{set print type typedefs}.
16975 @item ptype[/@var{flags}] [@var{arg}]
16976 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16977 detailed description of the type, instead of just the name of the type.
16978 @xref{Expressions, ,Expressions}.
16980 Contrary to @code{whatis}, @code{ptype} always unrolls any
16981 @code{typedef}s in its argument declaration, whether the argument is
16982 a variable, expression, or a data type. This means that @code{ptype}
16983 of a variable or an expression will not print literally its type as
16984 present in the source code---use @code{whatis} for that. @code{typedef}s at
16985 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16986 fields, methods and inner @code{class typedef}s of @code{struct}s,
16987 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16989 For example, for this variable declaration:
16992 typedef double real_t;
16993 struct complex @{ real_t real; double imag; @};
16994 typedef struct complex complex_t;
16996 real_t *real_pointer_var;
17000 the two commands give this output:
17004 (@value{GDBP}) whatis var
17006 (@value{GDBP}) ptype var
17007 type = struct complex @{
17011 (@value{GDBP}) whatis complex_t
17012 type = struct complex
17013 (@value{GDBP}) whatis struct complex
17014 type = struct complex
17015 (@value{GDBP}) ptype struct complex
17016 type = struct complex @{
17020 (@value{GDBP}) whatis real_pointer_var
17022 (@value{GDBP}) ptype real_pointer_var
17028 As with @code{whatis}, using @code{ptype} without an argument refers to
17029 the type of @code{$}, the last value in the value history.
17031 @cindex incomplete type
17032 Sometimes, programs use opaque data types or incomplete specifications
17033 of complex data structure. If the debug information included in the
17034 program does not allow @value{GDBN} to display a full declaration of
17035 the data type, it will say @samp{<incomplete type>}. For example,
17036 given these declarations:
17040 struct foo *fooptr;
17044 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17047 (@value{GDBP}) ptype foo
17048 $1 = <incomplete type>
17052 ``Incomplete type'' is C terminology for data types that are not
17053 completely specified.
17056 @item info types @var{regexp}
17058 Print a brief description of all types whose names match the regular
17059 expression @var{regexp} (or all types in your program, if you supply
17060 no argument). Each complete typename is matched as though it were a
17061 complete line; thus, @samp{i type value} gives information on all
17062 types in your program whose names include the string @code{value}, but
17063 @samp{i type ^value$} gives information only on types whose complete
17064 name is @code{value}.
17066 This command differs from @code{ptype} in two ways: first, like
17067 @code{whatis}, it does not print a detailed description; second, it
17068 lists all source files where a type is defined.
17070 @kindex info type-printers
17071 @item info type-printers
17072 Versions of @value{GDBN} that ship with Python scripting enabled may
17073 have ``type printers'' available. When using @command{ptype} or
17074 @command{whatis}, these printers are consulted when the name of a type
17075 is needed. @xref{Type Printing API}, for more information on writing
17078 @code{info type-printers} displays all the available type printers.
17080 @kindex enable type-printer
17081 @kindex disable type-printer
17082 @item enable type-printer @var{name}@dots{}
17083 @item disable type-printer @var{name}@dots{}
17084 These commands can be used to enable or disable type printers.
17087 @cindex local variables
17088 @item info scope @var{location}
17089 List all the variables local to a particular scope. This command
17090 accepts a @var{location} argument---a function name, a source line, or
17091 an address preceded by a @samp{*}, and prints all the variables local
17092 to the scope defined by that location. (@xref{Specify Location}, for
17093 details about supported forms of @var{location}.) For example:
17096 (@value{GDBP}) @b{info scope command_line_handler}
17097 Scope for command_line_handler:
17098 Symbol rl is an argument at stack/frame offset 8, length 4.
17099 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17100 Symbol linelength is in static storage at address 0x150a1c, length 4.
17101 Symbol p is a local variable in register $esi, length 4.
17102 Symbol p1 is a local variable in register $ebx, length 4.
17103 Symbol nline is a local variable in register $edx, length 4.
17104 Symbol repeat is a local variable at frame offset -8, length 4.
17108 This command is especially useful for determining what data to collect
17109 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17112 @kindex info source
17114 Show information about the current source file---that is, the source file for
17115 the function containing the current point of execution:
17118 the name of the source file, and the directory containing it,
17120 the directory it was compiled in,
17122 its length, in lines,
17124 which programming language it is written in,
17126 if the debug information provides it, the program that compiled the file
17127 (which may include, e.g., the compiler version and command line arguments),
17129 whether the executable includes debugging information for that file, and
17130 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17132 whether the debugging information includes information about
17133 preprocessor macros.
17137 @kindex info sources
17139 Print the names of all source files in your program for which there is
17140 debugging information, organized into two lists: files whose symbols
17141 have already been read, and files whose symbols will be read when needed.
17143 @kindex info functions
17144 @item info functions
17145 Print the names and data types of all defined functions.
17147 @item info functions @var{regexp}
17148 Print the names and data types of all defined functions
17149 whose names contain a match for regular expression @var{regexp}.
17150 Thus, @samp{info fun step} finds all functions whose names
17151 include @code{step}; @samp{info fun ^step} finds those whose names
17152 start with @code{step}. If a function name contains characters
17153 that conflict with the regular expression language (e.g.@:
17154 @samp{operator*()}), they may be quoted with a backslash.
17156 @kindex info variables
17157 @item info variables
17158 Print the names and data types of all variables that are defined
17159 outside of functions (i.e.@: excluding local variables).
17161 @item info variables @var{regexp}
17162 Print the names and data types of all variables (except for local
17163 variables) whose names contain a match for regular expression
17166 @kindex info classes
17167 @cindex Objective-C, classes and selectors
17169 @itemx info classes @var{regexp}
17170 Display all Objective-C classes in your program, or
17171 (with the @var{regexp} argument) all those matching a particular regular
17174 @kindex info selectors
17175 @item info selectors
17176 @itemx info selectors @var{regexp}
17177 Display all Objective-C selectors in your program, or
17178 (with the @var{regexp} argument) all those matching a particular regular
17182 This was never implemented.
17183 @kindex info methods
17185 @itemx info methods @var{regexp}
17186 The @code{info methods} command permits the user to examine all defined
17187 methods within C@t{++} program, or (with the @var{regexp} argument) a
17188 specific set of methods found in the various C@t{++} classes. Many
17189 C@t{++} classes provide a large number of methods. Thus, the output
17190 from the @code{ptype} command can be overwhelming and hard to use. The
17191 @code{info-methods} command filters the methods, printing only those
17192 which match the regular-expression @var{regexp}.
17195 @cindex opaque data types
17196 @kindex set opaque-type-resolution
17197 @item set opaque-type-resolution on
17198 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17199 declared as a pointer to a @code{struct}, @code{class}, or
17200 @code{union}---for example, @code{struct MyType *}---that is used in one
17201 source file although the full declaration of @code{struct MyType} is in
17202 another source file. The default is on.
17204 A change in the setting of this subcommand will not take effect until
17205 the next time symbols for a file are loaded.
17207 @item set opaque-type-resolution off
17208 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17209 is printed as follows:
17211 @{<no data fields>@}
17214 @kindex show opaque-type-resolution
17215 @item show opaque-type-resolution
17216 Show whether opaque types are resolved or not.
17218 @kindex set print symbol-loading
17219 @cindex print messages when symbols are loaded
17220 @item set print symbol-loading
17221 @itemx set print symbol-loading full
17222 @itemx set print symbol-loading brief
17223 @itemx set print symbol-loading off
17224 The @code{set print symbol-loading} command allows you to control the
17225 printing of messages when @value{GDBN} loads symbol information.
17226 By default a message is printed for the executable and one for each
17227 shared library, and normally this is what you want. However, when
17228 debugging apps with large numbers of shared libraries these messages
17230 When set to @code{brief} a message is printed for each executable,
17231 and when @value{GDBN} loads a collection of shared libraries at once
17232 it will only print one message regardless of the number of shared
17233 libraries. When set to @code{off} no messages are printed.
17235 @kindex show print symbol-loading
17236 @item show print symbol-loading
17237 Show whether messages will be printed when a @value{GDBN} command
17238 entered from the keyboard causes symbol information to be loaded.
17240 @kindex maint print symbols
17241 @cindex symbol dump
17242 @kindex maint print psymbols
17243 @cindex partial symbol dump
17244 @kindex maint print msymbols
17245 @cindex minimal symbol dump
17246 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17247 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17248 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17249 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17250 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17251 Write a dump of debugging symbol data into the file @var{filename} or
17252 the terminal if @var{filename} is unspecified.
17253 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17255 If @code{-pc @var{address}} is specified, only dump symbols for the file
17256 with code at that address. Note that @var{address} may be a symbol like
17258 If @code{-source @var{source}} is specified, only dump symbols for that
17261 These commands are used to debug the @value{GDBN} symbol-reading code.
17262 These commands do not modify internal @value{GDBN} state, therefore
17263 @samp{maint print symbols} will only print symbols for already expanded symbol
17265 You can use the command @code{info sources} to find out which files these are.
17266 If you use @samp{maint print psymbols} instead, the dump shows information
17267 about symbols that @value{GDBN} only knows partially---that is, symbols
17268 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17269 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17272 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17273 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17275 @kindex maint info symtabs
17276 @kindex maint info psymtabs
17277 @cindex listing @value{GDBN}'s internal symbol tables
17278 @cindex symbol tables, listing @value{GDBN}'s internal
17279 @cindex full symbol tables, listing @value{GDBN}'s internal
17280 @cindex partial symbol tables, listing @value{GDBN}'s internal
17281 @item maint info symtabs @r{[} @var{regexp} @r{]}
17282 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17284 List the @code{struct symtab} or @code{struct partial_symtab}
17285 structures whose names match @var{regexp}. If @var{regexp} is not
17286 given, list them all. The output includes expressions which you can
17287 copy into a @value{GDBN} debugging this one to examine a particular
17288 structure in more detail. For example:
17291 (@value{GDBP}) maint info psymtabs dwarf2read
17292 @{ objfile /home/gnu/build/gdb/gdb
17293 ((struct objfile *) 0x82e69d0)
17294 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17295 ((struct partial_symtab *) 0x8474b10)
17298 text addresses 0x814d3c8 -- 0x8158074
17299 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17300 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17301 dependencies (none)
17304 (@value{GDBP}) maint info symtabs
17308 We see that there is one partial symbol table whose filename contains
17309 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17310 and we see that @value{GDBN} has not read in any symtabs yet at all.
17311 If we set a breakpoint on a function, that will cause @value{GDBN} to
17312 read the symtab for the compilation unit containing that function:
17315 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17316 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17318 (@value{GDBP}) maint info symtabs
17319 @{ objfile /home/gnu/build/gdb/gdb
17320 ((struct objfile *) 0x82e69d0)
17321 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17322 ((struct symtab *) 0x86c1f38)
17325 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17326 linetable ((struct linetable *) 0x8370fa0)
17327 debugformat DWARF 2
17333 @kindex maint info line-table
17334 @cindex listing @value{GDBN}'s internal line tables
17335 @cindex line tables, listing @value{GDBN}'s internal
17336 @item maint info line-table @r{[} @var{regexp} @r{]}
17338 List the @code{struct linetable} from all @code{struct symtab}
17339 instances whose name matches @var{regexp}. If @var{regexp} is not
17340 given, list the @code{struct linetable} from all @code{struct symtab}.
17342 @kindex maint set symbol-cache-size
17343 @cindex symbol cache size
17344 @item maint set symbol-cache-size @var{size}
17345 Set the size of the symbol cache to @var{size}.
17346 The default size is intended to be good enough for debugging
17347 most applications. This option exists to allow for experimenting
17348 with different sizes.
17350 @kindex maint show symbol-cache-size
17351 @item maint show symbol-cache-size
17352 Show the size of the symbol cache.
17354 @kindex maint print symbol-cache
17355 @cindex symbol cache, printing its contents
17356 @item maint print symbol-cache
17357 Print the contents of the symbol cache.
17358 This is useful when debugging symbol cache issues.
17360 @kindex maint print symbol-cache-statistics
17361 @cindex symbol cache, printing usage statistics
17362 @item maint print symbol-cache-statistics
17363 Print symbol cache usage statistics.
17364 This helps determine how well the cache is being utilized.
17366 @kindex maint flush-symbol-cache
17367 @cindex symbol cache, flushing
17368 @item maint flush-symbol-cache
17369 Flush the contents of the symbol cache, all entries are removed.
17370 This command is useful when debugging the symbol cache.
17371 It is also useful when collecting performance data.
17376 @chapter Altering Execution
17378 Once you think you have found an error in your program, you might want to
17379 find out for certain whether correcting the apparent error would lead to
17380 correct results in the rest of the run. You can find the answer by
17381 experiment, using the @value{GDBN} features for altering execution of the
17384 For example, you can store new values into variables or memory
17385 locations, give your program a signal, restart it at a different
17386 address, or even return prematurely from a function.
17389 * Assignment:: Assignment to variables
17390 * Jumping:: Continuing at a different address
17391 * Signaling:: Giving your program a signal
17392 * Returning:: Returning from a function
17393 * Calling:: Calling your program's functions
17394 * Patching:: Patching your program
17395 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17399 @section Assignment to Variables
17402 @cindex setting variables
17403 To alter the value of a variable, evaluate an assignment expression.
17404 @xref{Expressions, ,Expressions}. For example,
17411 stores the value 4 into the variable @code{x}, and then prints the
17412 value of the assignment expression (which is 4).
17413 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17414 information on operators in supported languages.
17416 @kindex set variable
17417 @cindex variables, setting
17418 If you are not interested in seeing the value of the assignment, use the
17419 @code{set} command instead of the @code{print} command. @code{set} is
17420 really the same as @code{print} except that the expression's value is
17421 not printed and is not put in the value history (@pxref{Value History,
17422 ,Value History}). The expression is evaluated only for its effects.
17424 If the beginning of the argument string of the @code{set} command
17425 appears identical to a @code{set} subcommand, use the @code{set
17426 variable} command instead of just @code{set}. This command is identical
17427 to @code{set} except for its lack of subcommands. For example, if your
17428 program has a variable @code{width}, you get an error if you try to set
17429 a new value with just @samp{set width=13}, because @value{GDBN} has the
17430 command @code{set width}:
17433 (@value{GDBP}) whatis width
17435 (@value{GDBP}) p width
17437 (@value{GDBP}) set width=47
17438 Invalid syntax in expression.
17442 The invalid expression, of course, is @samp{=47}. In
17443 order to actually set the program's variable @code{width}, use
17446 (@value{GDBP}) set var width=47
17449 Because the @code{set} command has many subcommands that can conflict
17450 with the names of program variables, it is a good idea to use the
17451 @code{set variable} command instead of just @code{set}. For example, if
17452 your program has a variable @code{g}, you run into problems if you try
17453 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17454 the command @code{set gnutarget}, abbreviated @code{set g}:
17458 (@value{GDBP}) whatis g
17462 (@value{GDBP}) set g=4
17466 The program being debugged has been started already.
17467 Start it from the beginning? (y or n) y
17468 Starting program: /home/smith/cc_progs/a.out
17469 "/home/smith/cc_progs/a.out": can't open to read symbols:
17470 Invalid bfd target.
17471 (@value{GDBP}) show g
17472 The current BFD target is "=4".
17477 The program variable @code{g} did not change, and you silently set the
17478 @code{gnutarget} to an invalid value. In order to set the variable
17482 (@value{GDBP}) set var g=4
17485 @value{GDBN} allows more implicit conversions in assignments than C; you can
17486 freely store an integer value into a pointer variable or vice versa,
17487 and you can convert any structure to any other structure that is the
17488 same length or shorter.
17489 @comment FIXME: how do structs align/pad in these conversions?
17490 @comment /doc@cygnus.com 18dec1990
17492 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17493 construct to generate a value of specified type at a specified address
17494 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17495 to memory location @code{0x83040} as an integer (which implies a certain size
17496 and representation in memory), and
17499 set @{int@}0x83040 = 4
17503 stores the value 4 into that memory location.
17506 @section Continuing at a Different Address
17508 Ordinarily, when you continue your program, you do so at the place where
17509 it stopped, with the @code{continue} command. You can instead continue at
17510 an address of your own choosing, with the following commands:
17514 @kindex j @r{(@code{jump})}
17515 @item jump @var{location}
17516 @itemx j @var{location}
17517 Resume execution at @var{location}. Execution stops again immediately
17518 if there is a breakpoint there. @xref{Specify Location}, for a description
17519 of the different forms of @var{location}. It is common
17520 practice to use the @code{tbreak} command in conjunction with
17521 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17523 The @code{jump} command does not change the current stack frame, or
17524 the stack pointer, or the contents of any memory location or any
17525 register other than the program counter. If @var{location} is in
17526 a different function from the one currently executing, the results may
17527 be bizarre if the two functions expect different patterns of arguments or
17528 of local variables. For this reason, the @code{jump} command requests
17529 confirmation if the specified line is not in the function currently
17530 executing. However, even bizarre results are predictable if you are
17531 well acquainted with the machine-language code of your program.
17534 On many systems, you can get much the same effect as the @code{jump}
17535 command by storing a new value into the register @code{$pc}. The
17536 difference is that this does not start your program running; it only
17537 changes the address of where it @emph{will} run when you continue. For
17545 makes the next @code{continue} command or stepping command execute at
17546 address @code{0x485}, rather than at the address where your program stopped.
17547 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17549 The most common occasion to use the @code{jump} command is to back
17550 up---perhaps with more breakpoints set---over a portion of a program
17551 that has already executed, in order to examine its execution in more
17556 @section Giving your Program a Signal
17557 @cindex deliver a signal to a program
17561 @item signal @var{signal}
17562 Resume execution where your program is stopped, but immediately give it the
17563 signal @var{signal}. The @var{signal} can be the name or the number of a
17564 signal. For example, on many systems @code{signal 2} and @code{signal
17565 SIGINT} are both ways of sending an interrupt signal.
17567 Alternatively, if @var{signal} is zero, continue execution without
17568 giving a signal. This is useful when your program stopped on account of
17569 a signal and would ordinarily see the signal when resumed with the
17570 @code{continue} command; @samp{signal 0} causes it to resume without a
17573 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17574 delivered to the currently selected thread, not the thread that last
17575 reported a stop. This includes the situation where a thread was
17576 stopped due to a signal. So if you want to continue execution
17577 suppressing the signal that stopped a thread, you should select that
17578 same thread before issuing the @samp{signal 0} command. If you issue
17579 the @samp{signal 0} command with another thread as the selected one,
17580 @value{GDBN} detects that and asks for confirmation.
17582 Invoking the @code{signal} command is not the same as invoking the
17583 @code{kill} utility from the shell. Sending a signal with @code{kill}
17584 causes @value{GDBN} to decide what to do with the signal depending on
17585 the signal handling tables (@pxref{Signals}). The @code{signal} command
17586 passes the signal directly to your program.
17588 @code{signal} does not repeat when you press @key{RET} a second time
17589 after executing the command.
17591 @kindex queue-signal
17592 @item queue-signal @var{signal}
17593 Queue @var{signal} to be delivered immediately to the current thread
17594 when execution of the thread resumes. The @var{signal} can be the name or
17595 the number of a signal. For example, on many systems @code{signal 2} and
17596 @code{signal SIGINT} are both ways of sending an interrupt signal.
17597 The handling of the signal must be set to pass the signal to the program,
17598 otherwise @value{GDBN} will report an error.
17599 You can control the handling of signals from @value{GDBN} with the
17600 @code{handle} command (@pxref{Signals}).
17602 Alternatively, if @var{signal} is zero, any currently queued signal
17603 for the current thread is discarded and when execution resumes no signal
17604 will be delivered. This is useful when your program stopped on account
17605 of a signal and would ordinarily see the signal when resumed with the
17606 @code{continue} command.
17608 This command differs from the @code{signal} command in that the signal
17609 is just queued, execution is not resumed. And @code{queue-signal} cannot
17610 be used to pass a signal whose handling state has been set to @code{nopass}
17615 @xref{stepping into signal handlers}, for information on how stepping
17616 commands behave when the thread has a signal queued.
17619 @section Returning from a Function
17622 @cindex returning from a function
17625 @itemx return @var{expression}
17626 You can cancel execution of a function call with the @code{return}
17627 command. If you give an
17628 @var{expression} argument, its value is used as the function's return
17632 When you use @code{return}, @value{GDBN} discards the selected stack frame
17633 (and all frames within it). You can think of this as making the
17634 discarded frame return prematurely. If you wish to specify a value to
17635 be returned, give that value as the argument to @code{return}.
17637 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17638 Frame}), and any other frames inside of it, leaving its caller as the
17639 innermost remaining frame. That frame becomes selected. The
17640 specified value is stored in the registers used for returning values
17643 The @code{return} command does not resume execution; it leaves the
17644 program stopped in the state that would exist if the function had just
17645 returned. In contrast, the @code{finish} command (@pxref{Continuing
17646 and Stepping, ,Continuing and Stepping}) resumes execution until the
17647 selected stack frame returns naturally.
17649 @value{GDBN} needs to know how the @var{expression} argument should be set for
17650 the inferior. The concrete registers assignment depends on the OS ABI and the
17651 type being returned by the selected stack frame. For example it is common for
17652 OS ABI to return floating point values in FPU registers while integer values in
17653 CPU registers. Still some ABIs return even floating point values in CPU
17654 registers. Larger integer widths (such as @code{long long int}) also have
17655 specific placement rules. @value{GDBN} already knows the OS ABI from its
17656 current target so it needs to find out also the type being returned to make the
17657 assignment into the right register(s).
17659 Normally, the selected stack frame has debug info. @value{GDBN} will always
17660 use the debug info instead of the implicit type of @var{expression} when the
17661 debug info is available. For example, if you type @kbd{return -1}, and the
17662 function in the current stack frame is declared to return a @code{long long
17663 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17664 into a @code{long long int}:
17667 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17669 (@value{GDBP}) return -1
17670 Make func return now? (y or n) y
17671 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17672 43 printf ("result=%lld\n", func ());
17676 However, if the selected stack frame does not have a debug info, e.g., if the
17677 function was compiled without debug info, @value{GDBN} has to find out the type
17678 to return from user. Specifying a different type by mistake may set the value
17679 in different inferior registers than the caller code expects. For example,
17680 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17681 of a @code{long long int} result for a debug info less function (on 32-bit
17682 architectures). Therefore the user is required to specify the return type by
17683 an appropriate cast explicitly:
17686 Breakpoint 2, 0x0040050b in func ()
17687 (@value{GDBP}) return -1
17688 Return value type not available for selected stack frame.
17689 Please use an explicit cast of the value to return.
17690 (@value{GDBP}) return (long long int) -1
17691 Make selected stack frame return now? (y or n) y
17692 #0 0x00400526 in main ()
17697 @section Calling Program Functions
17700 @cindex calling functions
17701 @cindex inferior functions, calling
17702 @item print @var{expr}
17703 Evaluate the expression @var{expr} and display the resulting value.
17704 The expression may include calls to functions in the program being
17708 @item call @var{expr}
17709 Evaluate the expression @var{expr} without displaying @code{void}
17712 You can use this variant of the @code{print} command if you want to
17713 execute a function from your program that does not return anything
17714 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17715 with @code{void} returned values that @value{GDBN} will otherwise
17716 print. If the result is not void, it is printed and saved in the
17720 It is possible for the function you call via the @code{print} or
17721 @code{call} command to generate a signal (e.g., if there's a bug in
17722 the function, or if you passed it incorrect arguments). What happens
17723 in that case is controlled by the @code{set unwindonsignal} command.
17725 Similarly, with a C@t{++} program it is possible for the function you
17726 call via the @code{print} or @code{call} command to generate an
17727 exception that is not handled due to the constraints of the dummy
17728 frame. In this case, any exception that is raised in the frame, but has
17729 an out-of-frame exception handler will not be found. GDB builds a
17730 dummy-frame for the inferior function call, and the unwinder cannot
17731 seek for exception handlers outside of this dummy-frame. What happens
17732 in that case is controlled by the
17733 @code{set unwind-on-terminating-exception} command.
17736 @item set unwindonsignal
17737 @kindex set unwindonsignal
17738 @cindex unwind stack in called functions
17739 @cindex call dummy stack unwinding
17740 Set unwinding of the stack if a signal is received while in a function
17741 that @value{GDBN} called in the program being debugged. If set to on,
17742 @value{GDBN} unwinds the stack it created for the call and restores
17743 the context to what it was before the call. If set to off (the
17744 default), @value{GDBN} stops in the frame where the signal was
17747 @item show unwindonsignal
17748 @kindex show unwindonsignal
17749 Show the current setting of stack unwinding in the functions called by
17752 @item set unwind-on-terminating-exception
17753 @kindex set unwind-on-terminating-exception
17754 @cindex unwind stack in called functions with unhandled exceptions
17755 @cindex call dummy stack unwinding on unhandled exception.
17756 Set unwinding of the stack if a C@t{++} exception is raised, but left
17757 unhandled while in a function that @value{GDBN} called in the program being
17758 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17759 it created for the call and restores the context to what it was before
17760 the call. If set to off, @value{GDBN} the exception is delivered to
17761 the default C@t{++} exception handler and the inferior terminated.
17763 @item show unwind-on-terminating-exception
17764 @kindex show unwind-on-terminating-exception
17765 Show the current setting of stack unwinding in the functions called by
17770 @cindex weak alias functions
17771 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17772 for another function. In such case, @value{GDBN} might not pick up
17773 the type information, including the types of the function arguments,
17774 which causes @value{GDBN} to call the inferior function incorrectly.
17775 As a result, the called function will function erroneously and may
17776 even crash. A solution to that is to use the name of the aliased
17780 @section Patching Programs
17782 @cindex patching binaries
17783 @cindex writing into executables
17784 @cindex writing into corefiles
17786 By default, @value{GDBN} opens the file containing your program's
17787 executable code (or the corefile) read-only. This prevents accidental
17788 alterations to machine code; but it also prevents you from intentionally
17789 patching your program's binary.
17791 If you'd like to be able to patch the binary, you can specify that
17792 explicitly with the @code{set write} command. For example, you might
17793 want to turn on internal debugging flags, or even to make emergency
17799 @itemx set write off
17800 If you specify @samp{set write on}, @value{GDBN} opens executable and
17801 core files for both reading and writing; if you specify @kbd{set write
17802 off} (the default), @value{GDBN} opens them read-only.
17804 If you have already loaded a file, you must load it again (using the
17805 @code{exec-file} or @code{core-file} command) after changing @code{set
17806 write}, for your new setting to take effect.
17810 Display whether executable files and core files are opened for writing
17811 as well as reading.
17814 @node Compiling and Injecting Code
17815 @section Compiling and injecting code in @value{GDBN}
17816 @cindex injecting code
17817 @cindex writing into executables
17818 @cindex compiling code
17820 @value{GDBN} supports on-demand compilation and code injection into
17821 programs running under @value{GDBN}. GCC 5.0 or higher built with
17822 @file{libcc1.so} must be installed for this functionality to be enabled.
17823 This functionality is implemented with the following commands.
17826 @kindex compile code
17827 @item compile code @var{source-code}
17828 @itemx compile code -raw @var{--} @var{source-code}
17829 Compile @var{source-code} with the compiler language found as the current
17830 language in @value{GDBN} (@pxref{Languages}). If compilation and
17831 injection is not supported with the current language specified in
17832 @value{GDBN}, or the compiler does not support this feature, an error
17833 message will be printed. If @var{source-code} compiles and links
17834 successfully, @value{GDBN} will load the object-code emitted,
17835 and execute it within the context of the currently selected inferior.
17836 It is important to note that the compiled code is executed immediately.
17837 After execution, the compiled code is removed from @value{GDBN} and any
17838 new types or variables you have defined will be deleted.
17840 The command allows you to specify @var{source-code} in two ways.
17841 The simplest method is to provide a single line of code to the command.
17845 compile code printf ("hello world\n");
17848 If you specify options on the command line as well as source code, they
17849 may conflict. The @samp{--} delimiter can be used to separate options
17850 from actual source code. E.g.:
17853 compile code -r -- printf ("hello world\n");
17856 Alternatively you can enter source code as multiple lines of text. To
17857 enter this mode, invoke the @samp{compile code} command without any text
17858 following the command. This will start the multiple-line editor and
17859 allow you to type as many lines of source code as required. When you
17860 have completed typing, enter @samp{end} on its own line to exit the
17865 >printf ("hello\n");
17866 >printf ("world\n");
17870 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17871 provided @var{source-code} in a callable scope. In this case, you must
17872 specify the entry point of the code by defining a function named
17873 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17874 inferior. Using @samp{-raw} option may be needed for example when
17875 @var{source-code} requires @samp{#include} lines which may conflict with
17876 inferior symbols otherwise.
17878 @kindex compile file
17879 @item compile file @var{filename}
17880 @itemx compile file -raw @var{filename}
17881 Like @code{compile code}, but take the source code from @var{filename}.
17884 compile file /home/user/example.c
17889 @item compile print @var{expr}
17890 @itemx compile print /@var{f} @var{expr}
17891 Compile and execute @var{expr} with the compiler language found as the
17892 current language in @value{GDBN} (@pxref{Languages}). By default the
17893 value of @var{expr} is printed in a format appropriate to its data type;
17894 you can choose a different format by specifying @samp{/@var{f}}, where
17895 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17898 @item compile print
17899 @itemx compile print /@var{f}
17900 @cindex reprint the last value
17901 Alternatively you can enter the expression (source code producing it) as
17902 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17903 command without any text following the command. This will start the
17904 multiple-line editor.
17908 The process of compiling and injecting the code can be inspected using:
17911 @anchor{set debug compile}
17912 @item set debug compile
17913 @cindex compile command debugging info
17914 Turns on or off display of @value{GDBN} process of compiling and
17915 injecting the code. The default is off.
17917 @item show debug compile
17918 Displays the current state of displaying @value{GDBN} process of
17919 compiling and injecting the code.
17922 @subsection Compilation options for the @code{compile} command
17924 @value{GDBN} needs to specify the right compilation options for the code
17925 to be injected, in part to make its ABI compatible with the inferior
17926 and in part to make the injected code compatible with @value{GDBN}'s
17930 The options used, in increasing precedence:
17933 @item target architecture and OS options (@code{gdbarch})
17934 These options depend on target processor type and target operating
17935 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17936 (@code{-m64}) compilation option.
17938 @item compilation options recorded in the target
17939 @value{NGCC} (since version 4.7) stores the options used for compilation
17940 into @code{DW_AT_producer} part of DWARF debugging information according
17941 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17942 explicitly specify @code{-g} during inferior compilation otherwise
17943 @value{NGCC} produces no DWARF. This feature is only relevant for
17944 platforms where @code{-g} produces DWARF by default, otherwise one may
17945 try to enforce DWARF by using @code{-gdwarf-4}.
17947 @item compilation options set by @code{set compile-args}
17951 You can override compilation options using the following command:
17954 @item set compile-args
17955 @cindex compile command options override
17956 Set compilation options used for compiling and injecting code with the
17957 @code{compile} commands. These options override any conflicting ones
17958 from the target architecture and/or options stored during inferior
17961 @item show compile-args
17962 Displays the current state of compilation options override.
17963 This does not show all the options actually used during compilation,
17964 use @ref{set debug compile} for that.
17967 @subsection Caveats when using the @code{compile} command
17969 There are a few caveats to keep in mind when using the @code{compile}
17970 command. As the caveats are different per language, the table below
17971 highlights specific issues on a per language basis.
17974 @item C code examples and caveats
17975 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17976 attempt to compile the source code with a @samp{C} compiler. The source
17977 code provided to the @code{compile} command will have much the same
17978 access to variables and types as it normally would if it were part of
17979 the program currently being debugged in @value{GDBN}.
17981 Below is a sample program that forms the basis of the examples that
17982 follow. This program has been compiled and loaded into @value{GDBN},
17983 much like any other normal debugging session.
17986 void function1 (void)
17989 printf ("function 1\n");
17992 void function2 (void)
18007 For the purposes of the examples in this section, the program above has
18008 been compiled, loaded into @value{GDBN}, stopped at the function
18009 @code{main}, and @value{GDBN} is awaiting input from the user.
18011 To access variables and types for any program in @value{GDBN}, the
18012 program must be compiled and packaged with debug information. The
18013 @code{compile} command is not an exception to this rule. Without debug
18014 information, you can still use the @code{compile} command, but you will
18015 be very limited in what variables and types you can access.
18017 So with that in mind, the example above has been compiled with debug
18018 information enabled. The @code{compile} command will have access to
18019 all variables and types (except those that may have been optimized
18020 out). Currently, as @value{GDBN} has stopped the program in the
18021 @code{main} function, the @code{compile} command would have access to
18022 the variable @code{k}. You could invoke the @code{compile} command
18023 and type some source code to set the value of @code{k}. You can also
18024 read it, or do anything with that variable you would normally do in
18025 @code{C}. Be aware that changes to inferior variables in the
18026 @code{compile} command are persistent. In the following example:
18029 compile code k = 3;
18033 the variable @code{k} is now 3. It will retain that value until
18034 something else in the example program changes it, or another
18035 @code{compile} command changes it.
18037 Normal scope and access rules apply to source code compiled and
18038 injected by the @code{compile} command. In the example, the variables
18039 @code{j} and @code{k} are not accessible yet, because the program is
18040 currently stopped in the @code{main} function, where these variables
18041 are not in scope. Therefore, the following command
18044 compile code j = 3;
18048 will result in a compilation error message.
18050 Once the program is continued, execution will bring these variables in
18051 scope, and they will become accessible; then the code you specify via
18052 the @code{compile} command will be able to access them.
18054 You can create variables and types with the @code{compile} command as
18055 part of your source code. Variables and types that are created as part
18056 of the @code{compile} command are not visible to the rest of the program for
18057 the duration of its run. This example is valid:
18060 compile code int ff = 5; printf ("ff is %d\n", ff);
18063 However, if you were to type the following into @value{GDBN} after that
18064 command has completed:
18067 compile code printf ("ff is %d\n'', ff);
18071 a compiler error would be raised as the variable @code{ff} no longer
18072 exists. Object code generated and injected by the @code{compile}
18073 command is removed when its execution ends. Caution is advised
18074 when assigning to program variables values of variables created by the
18075 code submitted to the @code{compile} command. This example is valid:
18078 compile code int ff = 5; k = ff;
18081 The value of the variable @code{ff} is assigned to @code{k}. The variable
18082 @code{k} does not require the existence of @code{ff} to maintain the value
18083 it has been assigned. However, pointers require particular care in
18084 assignment. If the source code compiled with the @code{compile} command
18085 changed the address of a pointer in the example program, perhaps to a
18086 variable created in the @code{compile} command, that pointer would point
18087 to an invalid location when the command exits. The following example
18088 would likely cause issues with your debugged program:
18091 compile code int ff = 5; p = &ff;
18094 In this example, @code{p} would point to @code{ff} when the
18095 @code{compile} command is executing the source code provided to it.
18096 However, as variables in the (example) program persist with their
18097 assigned values, the variable @code{p} would point to an invalid
18098 location when the command exists. A general rule should be followed
18099 in that you should either assign @code{NULL} to any assigned pointers,
18100 or restore a valid location to the pointer before the command exits.
18102 Similar caution must be exercised with any structs, unions, and typedefs
18103 defined in @code{compile} command. Types defined in the @code{compile}
18104 command will no longer be available in the next @code{compile} command.
18105 Therefore, if you cast a variable to a type defined in the
18106 @code{compile} command, care must be taken to ensure that any future
18107 need to resolve the type can be achieved.
18110 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18111 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18112 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18113 Compilation failed.
18114 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18118 Variables that have been optimized away by the compiler are not
18119 accessible to the code submitted to the @code{compile} command.
18120 Access to those variables will generate a compiler error which @value{GDBN}
18121 will print to the console.
18124 @subsection Compiler search for the @code{compile} command
18126 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
18127 may not be obvious for remote targets of different architecture than where
18128 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
18129 shell that executed @value{GDBN}, not the one set by @value{GDBN}
18130 command @code{set environment}). @xref{Environment}. @code{PATH} on
18131 @value{GDBN} host is searched for @value{NGCC} binary matching the
18132 target architecture and operating system.
18134 Specifically @code{PATH} is searched for binaries matching regular expression
18135 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18136 debugged. @var{arch} is processor name --- multiarch is supported, so for
18137 example both @code{i386} and @code{x86_64} targets look for pattern
18138 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18139 for pattern @code{s390x?}. @var{os} is currently supported only for
18140 pattern @code{linux(-gnu)?}.
18143 @chapter @value{GDBN} Files
18145 @value{GDBN} needs to know the file name of the program to be debugged,
18146 both in order to read its symbol table and in order to start your
18147 program. To debug a core dump of a previous run, you must also tell
18148 @value{GDBN} the name of the core dump file.
18151 * Files:: Commands to specify files
18152 * File Caching:: Information about @value{GDBN}'s file caching
18153 * Separate Debug Files:: Debugging information in separate files
18154 * MiniDebugInfo:: Debugging information in a special section
18155 * Index Files:: Index files speed up GDB
18156 * Symbol Errors:: Errors reading symbol files
18157 * Data Files:: GDB data files
18161 @section Commands to Specify Files
18163 @cindex symbol table
18164 @cindex core dump file
18166 You may want to specify executable and core dump file names. The usual
18167 way to do this is at start-up time, using the arguments to
18168 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18169 Out of @value{GDBN}}).
18171 Occasionally it is necessary to change to a different file during a
18172 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18173 specify a file you want to use. Or you are debugging a remote target
18174 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18175 Program}). In these situations the @value{GDBN} commands to specify
18176 new files are useful.
18179 @cindex executable file
18181 @item file @var{filename}
18182 Use @var{filename} as the program to be debugged. It is read for its
18183 symbols and for the contents of pure memory. It is also the program
18184 executed when you use the @code{run} command. If you do not specify a
18185 directory and the file is not found in the @value{GDBN} working directory,
18186 @value{GDBN} uses the environment variable @code{PATH} as a list of
18187 directories to search, just as the shell does when looking for a program
18188 to run. You can change the value of this variable, for both @value{GDBN}
18189 and your program, using the @code{path} command.
18191 @cindex unlinked object files
18192 @cindex patching object files
18193 You can load unlinked object @file{.o} files into @value{GDBN} using
18194 the @code{file} command. You will not be able to ``run'' an object
18195 file, but you can disassemble functions and inspect variables. Also,
18196 if the underlying BFD functionality supports it, you could use
18197 @kbd{gdb -write} to patch object files using this technique. Note
18198 that @value{GDBN} can neither interpret nor modify relocations in this
18199 case, so branches and some initialized variables will appear to go to
18200 the wrong place. But this feature is still handy from time to time.
18203 @code{file} with no argument makes @value{GDBN} discard any information it
18204 has on both executable file and the symbol table.
18207 @item exec-file @r{[} @var{filename} @r{]}
18208 Specify that the program to be run (but not the symbol table) is found
18209 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18210 if necessary to locate your program. Omitting @var{filename} means to
18211 discard information on the executable file.
18213 @kindex symbol-file
18214 @item symbol-file @r{[} @var{filename} @r{]}
18215 Read symbol table information from file @var{filename}. @code{PATH} is
18216 searched when necessary. Use the @code{file} command to get both symbol
18217 table and program to run from the same file.
18219 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18220 program's symbol table.
18222 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18223 some breakpoints and auto-display expressions. This is because they may
18224 contain pointers to the internal data recording symbols and data types,
18225 which are part of the old symbol table data being discarded inside
18228 @code{symbol-file} does not repeat if you press @key{RET} again after
18231 When @value{GDBN} is configured for a particular environment, it
18232 understands debugging information in whatever format is the standard
18233 generated for that environment; you may use either a @sc{gnu} compiler, or
18234 other compilers that adhere to the local conventions.
18235 Best results are usually obtained from @sc{gnu} compilers; for example,
18236 using @code{@value{NGCC}} you can generate debugging information for
18239 For most kinds of object files, with the exception of old SVR3 systems
18240 using COFF, the @code{symbol-file} command does not normally read the
18241 symbol table in full right away. Instead, it scans the symbol table
18242 quickly to find which source files and which symbols are present. The
18243 details are read later, one source file at a time, as they are needed.
18245 The purpose of this two-stage reading strategy is to make @value{GDBN}
18246 start up faster. For the most part, it is invisible except for
18247 occasional pauses while the symbol table details for a particular source
18248 file are being read. (The @code{set verbose} command can turn these
18249 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18250 Warnings and Messages}.)
18252 We have not implemented the two-stage strategy for COFF yet. When the
18253 symbol table is stored in COFF format, @code{symbol-file} reads the
18254 symbol table data in full right away. Note that ``stabs-in-COFF''
18255 still does the two-stage strategy, since the debug info is actually
18259 @cindex reading symbols immediately
18260 @cindex symbols, reading immediately
18261 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18262 @itemx file @r{[} -readnow @r{]} @var{filename}
18263 You can override the @value{GDBN} two-stage strategy for reading symbol
18264 tables by using the @samp{-readnow} option with any of the commands that
18265 load symbol table information, if you want to be sure @value{GDBN} has the
18266 entire symbol table available.
18268 @c FIXME: for now no mention of directories, since this seems to be in
18269 @c flux. 13mar1992 status is that in theory GDB would look either in
18270 @c current dir or in same dir as myprog; but issues like competing
18271 @c GDB's, or clutter in system dirs, mean that in practice right now
18272 @c only current dir is used. FFish says maybe a special GDB hierarchy
18273 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18277 @item core-file @r{[}@var{filename}@r{]}
18279 Specify the whereabouts of a core dump file to be used as the ``contents
18280 of memory''. Traditionally, core files contain only some parts of the
18281 address space of the process that generated them; @value{GDBN} can access the
18282 executable file itself for other parts.
18284 @code{core-file} with no argument specifies that no core file is
18287 Note that the core file is ignored when your program is actually running
18288 under @value{GDBN}. So, if you have been running your program and you
18289 wish to debug a core file instead, you must kill the subprocess in which
18290 the program is running. To do this, use the @code{kill} command
18291 (@pxref{Kill Process, ,Killing the Child Process}).
18293 @kindex add-symbol-file
18294 @cindex dynamic linking
18295 @item add-symbol-file @var{filename} @var{address}
18296 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18297 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18298 The @code{add-symbol-file} command reads additional symbol table
18299 information from the file @var{filename}. You would use this command
18300 when @var{filename} has been dynamically loaded (by some other means)
18301 into the program that is running. The @var{address} should give the memory
18302 address at which the file has been loaded; @value{GDBN} cannot figure
18303 this out for itself. You can additionally specify an arbitrary number
18304 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18305 section name and base address for that section. You can specify any
18306 @var{address} as an expression.
18308 The symbol table of the file @var{filename} is added to the symbol table
18309 originally read with the @code{symbol-file} command. You can use the
18310 @code{add-symbol-file} command any number of times; the new symbol data
18311 thus read is kept in addition to the old.
18313 Changes can be reverted using the command @code{remove-symbol-file}.
18315 @cindex relocatable object files, reading symbols from
18316 @cindex object files, relocatable, reading symbols from
18317 @cindex reading symbols from relocatable object files
18318 @cindex symbols, reading from relocatable object files
18319 @cindex @file{.o} files, reading symbols from
18320 Although @var{filename} is typically a shared library file, an
18321 executable file, or some other object file which has been fully
18322 relocated for loading into a process, you can also load symbolic
18323 information from relocatable @file{.o} files, as long as:
18327 the file's symbolic information refers only to linker symbols defined in
18328 that file, not to symbols defined by other object files,
18330 every section the file's symbolic information refers to has actually
18331 been loaded into the inferior, as it appears in the file, and
18333 you can determine the address at which every section was loaded, and
18334 provide these to the @code{add-symbol-file} command.
18338 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18339 relocatable files into an already running program; such systems
18340 typically make the requirements above easy to meet. However, it's
18341 important to recognize that many native systems use complex link
18342 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18343 assembly, for example) that make the requirements difficult to meet. In
18344 general, one cannot assume that using @code{add-symbol-file} to read a
18345 relocatable object file's symbolic information will have the same effect
18346 as linking the relocatable object file into the program in the normal
18349 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18351 @kindex remove-symbol-file
18352 @item remove-symbol-file @var{filename}
18353 @item remove-symbol-file -a @var{address}
18354 Remove a symbol file added via the @code{add-symbol-file} command. The
18355 file to remove can be identified by its @var{filename} or by an @var{address}
18356 that lies within the boundaries of this symbol file in memory. Example:
18359 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18360 add symbol table from file "/home/user/gdb/mylib.so" at
18361 .text_addr = 0x7ffff7ff9480
18363 Reading symbols from /home/user/gdb/mylib.so...done.
18364 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18365 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18370 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18372 @kindex add-symbol-file-from-memory
18373 @cindex @code{syscall DSO}
18374 @cindex load symbols from memory
18375 @item add-symbol-file-from-memory @var{address}
18376 Load symbols from the given @var{address} in a dynamically loaded
18377 object file whose image is mapped directly into the inferior's memory.
18378 For example, the Linux kernel maps a @code{syscall DSO} into each
18379 process's address space; this DSO provides kernel-specific code for
18380 some system calls. The argument can be any expression whose
18381 evaluation yields the address of the file's shared object file header.
18382 For this command to work, you must have used @code{symbol-file} or
18383 @code{exec-file} commands in advance.
18386 @item section @var{section} @var{addr}
18387 The @code{section} command changes the base address of the named
18388 @var{section} of the exec file to @var{addr}. This can be used if the
18389 exec file does not contain section addresses, (such as in the
18390 @code{a.out} format), or when the addresses specified in the file
18391 itself are wrong. Each section must be changed separately. The
18392 @code{info files} command, described below, lists all the sections and
18396 @kindex info target
18399 @code{info files} and @code{info target} are synonymous; both print the
18400 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18401 including the names of the executable and core dump files currently in
18402 use by @value{GDBN}, and the files from which symbols were loaded. The
18403 command @code{help target} lists all possible targets rather than
18406 @kindex maint info sections
18407 @item maint info sections
18408 Another command that can give you extra information about program sections
18409 is @code{maint info sections}. In addition to the section information
18410 displayed by @code{info files}, this command displays the flags and file
18411 offset of each section in the executable and core dump files. In addition,
18412 @code{maint info sections} provides the following command options (which
18413 may be arbitrarily combined):
18417 Display sections for all loaded object files, including shared libraries.
18418 @item @var{sections}
18419 Display info only for named @var{sections}.
18420 @item @var{section-flags}
18421 Display info only for sections for which @var{section-flags} are true.
18422 The section flags that @value{GDBN} currently knows about are:
18425 Section will have space allocated in the process when loaded.
18426 Set for all sections except those containing debug information.
18428 Section will be loaded from the file into the child process memory.
18429 Set for pre-initialized code and data, clear for @code{.bss} sections.
18431 Section needs to be relocated before loading.
18433 Section cannot be modified by the child process.
18435 Section contains executable code only.
18437 Section contains data only (no executable code).
18439 Section will reside in ROM.
18441 Section contains data for constructor/destructor lists.
18443 Section is not empty.
18445 An instruction to the linker to not output the section.
18446 @item COFF_SHARED_LIBRARY
18447 A notification to the linker that the section contains
18448 COFF shared library information.
18450 Section contains common symbols.
18453 @kindex set trust-readonly-sections
18454 @cindex read-only sections
18455 @item set trust-readonly-sections on
18456 Tell @value{GDBN} that readonly sections in your object file
18457 really are read-only (i.e.@: that their contents will not change).
18458 In that case, @value{GDBN} can fetch values from these sections
18459 out of the object file, rather than from the target program.
18460 For some targets (notably embedded ones), this can be a significant
18461 enhancement to debugging performance.
18463 The default is off.
18465 @item set trust-readonly-sections off
18466 Tell @value{GDBN} not to trust readonly sections. This means that
18467 the contents of the section might change while the program is running,
18468 and must therefore be fetched from the target when needed.
18470 @item show trust-readonly-sections
18471 Show the current setting of trusting readonly sections.
18474 All file-specifying commands allow both absolute and relative file names
18475 as arguments. @value{GDBN} always converts the file name to an absolute file
18476 name and remembers it that way.
18478 @cindex shared libraries
18479 @anchor{Shared Libraries}
18480 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18481 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18482 DSBT (TIC6X) shared libraries.
18484 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18485 shared libraries. @xref{Expat}.
18487 @value{GDBN} automatically loads symbol definitions from shared libraries
18488 when you use the @code{run} command, or when you examine a core file.
18489 (Before you issue the @code{run} command, @value{GDBN} does not understand
18490 references to a function in a shared library, however---unless you are
18491 debugging a core file).
18493 @c FIXME: some @value{GDBN} release may permit some refs to undef
18494 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18495 @c FIXME...lib; check this from time to time when updating manual
18497 There are times, however, when you may wish to not automatically load
18498 symbol definitions from shared libraries, such as when they are
18499 particularly large or there are many of them.
18501 To control the automatic loading of shared library symbols, use the
18505 @kindex set auto-solib-add
18506 @item set auto-solib-add @var{mode}
18507 If @var{mode} is @code{on}, symbols from all shared object libraries
18508 will be loaded automatically when the inferior begins execution, you
18509 attach to an independently started inferior, or when the dynamic linker
18510 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18511 is @code{off}, symbols must be loaded manually, using the
18512 @code{sharedlibrary} command. The default value is @code{on}.
18514 @cindex memory used for symbol tables
18515 If your program uses lots of shared libraries with debug info that
18516 takes large amounts of memory, you can decrease the @value{GDBN}
18517 memory footprint by preventing it from automatically loading the
18518 symbols from shared libraries. To that end, type @kbd{set
18519 auto-solib-add off} before running the inferior, then load each
18520 library whose debug symbols you do need with @kbd{sharedlibrary
18521 @var{regexp}}, where @var{regexp} is a regular expression that matches
18522 the libraries whose symbols you want to be loaded.
18524 @kindex show auto-solib-add
18525 @item show auto-solib-add
18526 Display the current autoloading mode.
18529 @cindex load shared library
18530 To explicitly load shared library symbols, use the @code{sharedlibrary}
18534 @kindex info sharedlibrary
18536 @item info share @var{regex}
18537 @itemx info sharedlibrary @var{regex}
18538 Print the names of the shared libraries which are currently loaded
18539 that match @var{regex}. If @var{regex} is omitted then print
18540 all shared libraries that are loaded.
18543 @item info dll @var{regex}
18544 This is an alias of @code{info sharedlibrary}.
18546 @kindex sharedlibrary
18548 @item sharedlibrary @var{regex}
18549 @itemx share @var{regex}
18550 Load shared object library symbols for files matching a
18551 Unix regular expression.
18552 As with files loaded automatically, it only loads shared libraries
18553 required by your program for a core file or after typing @code{run}. If
18554 @var{regex} is omitted all shared libraries required by your program are
18557 @item nosharedlibrary
18558 @kindex nosharedlibrary
18559 @cindex unload symbols from shared libraries
18560 Unload all shared object library symbols. This discards all symbols
18561 that have been loaded from all shared libraries. Symbols from shared
18562 libraries that were loaded by explicit user requests are not
18566 Sometimes you may wish that @value{GDBN} stops and gives you control
18567 when any of shared library events happen. The best way to do this is
18568 to use @code{catch load} and @code{catch unload} (@pxref{Set
18571 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18572 command for this. This command exists for historical reasons. It is
18573 less useful than setting a catchpoint, because it does not allow for
18574 conditions or commands as a catchpoint does.
18577 @item set stop-on-solib-events
18578 @kindex set stop-on-solib-events
18579 This command controls whether @value{GDBN} should give you control
18580 when the dynamic linker notifies it about some shared library event.
18581 The most common event of interest is loading or unloading of a new
18584 @item show stop-on-solib-events
18585 @kindex show stop-on-solib-events
18586 Show whether @value{GDBN} stops and gives you control when shared
18587 library events happen.
18590 Shared libraries are also supported in many cross or remote debugging
18591 configurations. @value{GDBN} needs to have access to the target's libraries;
18592 this can be accomplished either by providing copies of the libraries
18593 on the host system, or by asking @value{GDBN} to automatically retrieve the
18594 libraries from the target. If copies of the target libraries are
18595 provided, they need to be the same as the target libraries, although the
18596 copies on the target can be stripped as long as the copies on the host are
18599 @cindex where to look for shared libraries
18600 For remote debugging, you need to tell @value{GDBN} where the target
18601 libraries are, so that it can load the correct copies---otherwise, it
18602 may try to load the host's libraries. @value{GDBN} has two variables
18603 to specify the search directories for target libraries.
18606 @cindex prefix for executable and shared library file names
18607 @cindex system root, alternate
18608 @kindex set solib-absolute-prefix
18609 @kindex set sysroot
18610 @item set sysroot @var{path}
18611 Use @var{path} as the system root for the program being debugged. Any
18612 absolute shared library paths will be prefixed with @var{path}; many
18613 runtime loaders store the absolute paths to the shared library in the
18614 target program's memory. When starting processes remotely, and when
18615 attaching to already-running processes (local or remote), their
18616 executable filenames will be prefixed with @var{path} if reported to
18617 @value{GDBN} as absolute by the operating system. If you use
18618 @code{set sysroot} to find executables and shared libraries, they need
18619 to be laid out in the same way that they are on the target, with
18620 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18623 If @var{path} starts with the sequence @file{target:} and the target
18624 system is remote then @value{GDBN} will retrieve the target binaries
18625 from the remote system. This is only supported when using a remote
18626 target that supports the @code{remote get} command (@pxref{File
18627 Transfer,,Sending files to a remote system}). The part of @var{path}
18628 following the initial @file{target:} (if present) is used as system
18629 root prefix on the remote file system. If @var{path} starts with the
18630 sequence @file{remote:} this is converted to the sequence
18631 @file{target:} by @code{set sysroot}@footnote{Historically the
18632 functionality to retrieve binaries from the remote system was
18633 provided by prefixing @var{path} with @file{remote:}}. If you want
18634 to specify a local system root using a directory that happens to be
18635 named @file{target:} or @file{remote:}, you need to use some
18636 equivalent variant of the name like @file{./target:}.
18638 For targets with an MS-DOS based filesystem, such as MS-Windows and
18639 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18640 absolute file name with @var{path}. But first, on Unix hosts,
18641 @value{GDBN} converts all backslash directory separators into forward
18642 slashes, because the backslash is not a directory separator on Unix:
18645 c:\foo\bar.dll @result{} c:/foo/bar.dll
18648 Then, @value{GDBN} attempts prefixing the target file name with
18649 @var{path}, and looks for the resulting file name in the host file
18653 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18656 If that does not find the binary, @value{GDBN} tries removing
18657 the @samp{:} character from the drive spec, both for convenience, and,
18658 for the case of the host file system not supporting file names with
18662 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18665 This makes it possible to have a system root that mirrors a target
18666 with more than one drive. E.g., you may want to setup your local
18667 copies of the target system shared libraries like so (note @samp{c} vs
18671 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18672 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18673 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18677 and point the system root at @file{/path/to/sysroot}, so that
18678 @value{GDBN} can find the correct copies of both
18679 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18681 If that still does not find the binary, @value{GDBN} tries
18682 removing the whole drive spec from the target file name:
18685 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18688 This last lookup makes it possible to not care about the drive name,
18689 if you don't want or need to.
18691 The @code{set solib-absolute-prefix} command is an alias for @code{set
18694 @cindex default system root
18695 @cindex @samp{--with-sysroot}
18696 You can set the default system root by using the configure-time
18697 @samp{--with-sysroot} option. If the system root is inside
18698 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18699 @samp{--exec-prefix}), then the default system root will be updated
18700 automatically if the installed @value{GDBN} is moved to a new
18703 @kindex show sysroot
18705 Display the current executable and shared library prefix.
18707 @kindex set solib-search-path
18708 @item set solib-search-path @var{path}
18709 If this variable is set, @var{path} is a colon-separated list of
18710 directories to search for shared libraries. @samp{solib-search-path}
18711 is used after @samp{sysroot} fails to locate the library, or if the
18712 path to the library is relative instead of absolute. If you want to
18713 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18714 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18715 finding your host's libraries. @samp{sysroot} is preferred; setting
18716 it to a nonexistent directory may interfere with automatic loading
18717 of shared library symbols.
18719 @kindex show solib-search-path
18720 @item show solib-search-path
18721 Display the current shared library search path.
18723 @cindex DOS file-name semantics of file names.
18724 @kindex set target-file-system-kind (unix|dos-based|auto)
18725 @kindex show target-file-system-kind
18726 @item set target-file-system-kind @var{kind}
18727 Set assumed file system kind for target reported file names.
18729 Shared library file names as reported by the target system may not
18730 make sense as is on the system @value{GDBN} is running on. For
18731 example, when remote debugging a target that has MS-DOS based file
18732 system semantics, from a Unix host, the target may be reporting to
18733 @value{GDBN} a list of loaded shared libraries with file names such as
18734 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18735 drive letters, so the @samp{c:\} prefix is not normally understood as
18736 indicating an absolute file name, and neither is the backslash
18737 normally considered a directory separator character. In that case,
18738 the native file system would interpret this whole absolute file name
18739 as a relative file name with no directory components. This would make
18740 it impossible to point @value{GDBN} at a copy of the remote target's
18741 shared libraries on the host using @code{set sysroot}, and impractical
18742 with @code{set solib-search-path}. Setting
18743 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18744 to interpret such file names similarly to how the target would, and to
18745 map them to file names valid on @value{GDBN}'s native file system
18746 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18747 to one of the supported file system kinds. In that case, @value{GDBN}
18748 tries to determine the appropriate file system variant based on the
18749 current target's operating system (@pxref{ABI, ,Configuring the
18750 Current ABI}). The supported file system settings are:
18754 Instruct @value{GDBN} to assume the target file system is of Unix
18755 kind. Only file names starting the forward slash (@samp{/}) character
18756 are considered absolute, and the directory separator character is also
18760 Instruct @value{GDBN} to assume the target file system is DOS based.
18761 File names starting with either a forward slash, or a drive letter
18762 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18763 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18764 considered directory separators.
18767 Instruct @value{GDBN} to use the file system kind associated with the
18768 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18769 This is the default.
18773 @cindex file name canonicalization
18774 @cindex base name differences
18775 When processing file names provided by the user, @value{GDBN}
18776 frequently needs to compare them to the file names recorded in the
18777 program's debug info. Normally, @value{GDBN} compares just the
18778 @dfn{base names} of the files as strings, which is reasonably fast
18779 even for very large programs. (The base name of a file is the last
18780 portion of its name, after stripping all the leading directories.)
18781 This shortcut in comparison is based upon the assumption that files
18782 cannot have more than one base name. This is usually true, but
18783 references to files that use symlinks or similar filesystem
18784 facilities violate that assumption. If your program records files
18785 using such facilities, or if you provide file names to @value{GDBN}
18786 using symlinks etc., you can set @code{basenames-may-differ} to
18787 @code{true} to instruct @value{GDBN} to completely canonicalize each
18788 pair of file names it needs to compare. This will make file-name
18789 comparisons accurate, but at a price of a significant slowdown.
18792 @item set basenames-may-differ
18793 @kindex set basenames-may-differ
18794 Set whether a source file may have multiple base names.
18796 @item show basenames-may-differ
18797 @kindex show basenames-may-differ
18798 Show whether a source file may have multiple base names.
18802 @section File Caching
18803 @cindex caching of opened files
18804 @cindex caching of bfd objects
18806 To speed up file loading, and reduce memory usage, @value{GDBN} will
18807 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18808 BFD, bfd, The Binary File Descriptor Library}. The following commands
18809 allow visibility and control of the caching behavior.
18812 @kindex maint info bfds
18813 @item maint info bfds
18814 This prints information about each @code{bfd} object that is known to
18817 @kindex maint set bfd-sharing
18818 @kindex maint show bfd-sharing
18819 @kindex bfd caching
18820 @item maint set bfd-sharing
18821 @item maint show bfd-sharing
18822 Control whether @code{bfd} objects can be shared. When sharing is
18823 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18824 than reopening the same file. Turning sharing off does not cause
18825 already shared @code{bfd} objects to be unshared, but all future files
18826 that are opened will create a new @code{bfd} object. Similarly,
18827 re-enabling sharing does not cause multiple existing @code{bfd}
18828 objects to be collapsed into a single shared @code{bfd} object.
18830 @kindex set debug bfd-cache @var{level}
18831 @kindex bfd caching
18832 @item set debug bfd-cache @var{level}
18833 Turns on debugging of the bfd cache, setting the level to @var{level}.
18835 @kindex show debug bfd-cache
18836 @kindex bfd caching
18837 @item show debug bfd-cache
18838 Show the current debugging level of the bfd cache.
18841 @node Separate Debug Files
18842 @section Debugging Information in Separate Files
18843 @cindex separate debugging information files
18844 @cindex debugging information in separate files
18845 @cindex @file{.debug} subdirectories
18846 @cindex debugging information directory, global
18847 @cindex global debugging information directories
18848 @cindex build ID, and separate debugging files
18849 @cindex @file{.build-id} directory
18851 @value{GDBN} allows you to put a program's debugging information in a
18852 file separate from the executable itself, in a way that allows
18853 @value{GDBN} to find and load the debugging information automatically.
18854 Since debugging information can be very large---sometimes larger
18855 than the executable code itself---some systems distribute debugging
18856 information for their executables in separate files, which users can
18857 install only when they need to debug a problem.
18859 @value{GDBN} supports two ways of specifying the separate debug info
18864 The executable contains a @dfn{debug link} that specifies the name of
18865 the separate debug info file. The separate debug file's name is
18866 usually @file{@var{executable}.debug}, where @var{executable} is the
18867 name of the corresponding executable file without leading directories
18868 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18869 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18870 checksum for the debug file, which @value{GDBN} uses to validate that
18871 the executable and the debug file came from the same build.
18874 The executable contains a @dfn{build ID}, a unique bit string that is
18875 also present in the corresponding debug info file. (This is supported
18876 only on some operating systems, when using the ELF or PE file formats
18877 for binary files and the @sc{gnu} Binutils.) For more details about
18878 this feature, see the description of the @option{--build-id}
18879 command-line option in @ref{Options, , Command Line Options, ld.info,
18880 The GNU Linker}. The debug info file's name is not specified
18881 explicitly by the build ID, but can be computed from the build ID, see
18885 Depending on the way the debug info file is specified, @value{GDBN}
18886 uses two different methods of looking for the debug file:
18890 For the ``debug link'' method, @value{GDBN} looks up the named file in
18891 the directory of the executable file, then in a subdirectory of that
18892 directory named @file{.debug}, and finally under each one of the global debug
18893 directories, in a subdirectory whose name is identical to the leading
18894 directories of the executable's absolute file name.
18897 For the ``build ID'' method, @value{GDBN} looks in the
18898 @file{.build-id} subdirectory of each one of the global debug directories for
18899 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18900 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18901 are the rest of the bit string. (Real build ID strings are 32 or more
18902 hex characters, not 10.)
18905 So, for example, suppose you ask @value{GDBN} to debug
18906 @file{/usr/bin/ls}, which has a debug link that specifies the
18907 file @file{ls.debug}, and a build ID whose value in hex is
18908 @code{abcdef1234}. If the list of the global debug directories includes
18909 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18910 debug information files, in the indicated order:
18914 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18916 @file{/usr/bin/ls.debug}
18918 @file{/usr/bin/.debug/ls.debug}
18920 @file{/usr/lib/debug/usr/bin/ls.debug}.
18923 @anchor{debug-file-directory}
18924 Global debugging info directories default to what is set by @value{GDBN}
18925 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18926 you can also set the global debugging info directories, and view the list
18927 @value{GDBN} is currently using.
18931 @kindex set debug-file-directory
18932 @item set debug-file-directory @var{directories}
18933 Set the directories which @value{GDBN} searches for separate debugging
18934 information files to @var{directory}. Multiple path components can be set
18935 concatenating them by a path separator.
18937 @kindex show debug-file-directory
18938 @item show debug-file-directory
18939 Show the directories @value{GDBN} searches for separate debugging
18944 @cindex @code{.gnu_debuglink} sections
18945 @cindex debug link sections
18946 A debug link is a special section of the executable file named
18947 @code{.gnu_debuglink}. The section must contain:
18951 A filename, with any leading directory components removed, followed by
18954 zero to three bytes of padding, as needed to reach the next four-byte
18955 boundary within the section, and
18957 a four-byte CRC checksum, stored in the same endianness used for the
18958 executable file itself. The checksum is computed on the debugging
18959 information file's full contents by the function given below, passing
18960 zero as the @var{crc} argument.
18963 Any executable file format can carry a debug link, as long as it can
18964 contain a section named @code{.gnu_debuglink} with the contents
18967 @cindex @code{.note.gnu.build-id} sections
18968 @cindex build ID sections
18969 The build ID is a special section in the executable file (and in other
18970 ELF binary files that @value{GDBN} may consider). This section is
18971 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18972 It contains unique identification for the built files---the ID remains
18973 the same across multiple builds of the same build tree. The default
18974 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18975 content for the build ID string. The same section with an identical
18976 value is present in the original built binary with symbols, in its
18977 stripped variant, and in the separate debugging information file.
18979 The debugging information file itself should be an ordinary
18980 executable, containing a full set of linker symbols, sections, and
18981 debugging information. The sections of the debugging information file
18982 should have the same names, addresses, and sizes as the original file,
18983 but they need not contain any data---much like a @code{.bss} section
18984 in an ordinary executable.
18986 The @sc{gnu} binary utilities (Binutils) package includes the
18987 @samp{objcopy} utility that can produce
18988 the separated executable / debugging information file pairs using the
18989 following commands:
18992 @kbd{objcopy --only-keep-debug foo foo.debug}
18997 These commands remove the debugging
18998 information from the executable file @file{foo} and place it in the file
18999 @file{foo.debug}. You can use the first, second or both methods to link the
19004 The debug link method needs the following additional command to also leave
19005 behind a debug link in @file{foo}:
19008 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19011 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19012 a version of the @code{strip} command such that the command @kbd{strip foo -f
19013 foo.debug} has the same functionality as the two @code{objcopy} commands and
19014 the @code{ln -s} command above, together.
19017 Build ID gets embedded into the main executable using @code{ld --build-id} or
19018 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19019 compatibility fixes for debug files separation are present in @sc{gnu} binary
19020 utilities (Binutils) package since version 2.18.
19025 @cindex CRC algorithm definition
19026 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19027 IEEE 802.3 using the polynomial:
19029 @c TexInfo requires naked braces for multi-digit exponents for Tex
19030 @c output, but this causes HTML output to barf. HTML has to be set using
19031 @c raw commands. So we end up having to specify this equation in 2
19036 <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>
19037 + <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
19043 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19044 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19048 The function is computed byte at a time, taking the least
19049 significant bit of each byte first. The initial pattern
19050 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19051 the final result is inverted to ensure trailing zeros also affect the
19054 @emph{Note:} This is the same CRC polynomial as used in handling the
19055 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19056 However in the case of the Remote Serial Protocol, the CRC is computed
19057 @emph{most} significant bit first, and the result is not inverted, so
19058 trailing zeros have no effect on the CRC value.
19060 To complete the description, we show below the code of the function
19061 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19062 initially supplied @code{crc} argument means that an initial call to
19063 this function passing in zero will start computing the CRC using
19066 @kindex gnu_debuglink_crc32
19069 gnu_debuglink_crc32 (unsigned long crc,
19070 unsigned char *buf, size_t len)
19072 static const unsigned long crc32_table[256] =
19074 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19075 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19076 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19077 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19078 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19079 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19080 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19081 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19082 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19083 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19084 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19085 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19086 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19087 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19088 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19089 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19090 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19091 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19092 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19093 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19094 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19095 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19096 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19097 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19098 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19099 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19100 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19101 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19102 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19103 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19104 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19105 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19106 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19107 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19108 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19109 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19110 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19111 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19112 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19113 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19114 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19115 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19116 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19117 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19118 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19119 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19120 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19121 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19122 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19123 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19124 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19127 unsigned char *end;
19129 crc = ~crc & 0xffffffff;
19130 for (end = buf + len; buf < end; ++buf)
19131 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19132 return ~crc & 0xffffffff;
19137 This computation does not apply to the ``build ID'' method.
19139 @node MiniDebugInfo
19140 @section Debugging information in a special section
19141 @cindex separate debug sections
19142 @cindex @samp{.gnu_debugdata} section
19144 Some systems ship pre-built executables and libraries that have a
19145 special @samp{.gnu_debugdata} section. This feature is called
19146 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19147 is used to supply extra symbols for backtraces.
19149 The intent of this section is to provide extra minimal debugging
19150 information for use in simple backtraces. It is not intended to be a
19151 replacement for full separate debugging information (@pxref{Separate
19152 Debug Files}). The example below shows the intended use; however,
19153 @value{GDBN} does not currently put restrictions on what sort of
19154 debugging information might be included in the section.
19156 @value{GDBN} has support for this extension. If the section exists,
19157 then it is used provided that no other source of debugging information
19158 can be found, and that @value{GDBN} was configured with LZMA support.
19160 This section can be easily created using @command{objcopy} and other
19161 standard utilities:
19164 # Extract the dynamic symbols from the main binary, there is no need
19165 # to also have these in the normal symbol table.
19166 nm -D @var{binary} --format=posix --defined-only \
19167 | awk '@{ print $1 @}' | sort > dynsyms
19169 # Extract all the text (i.e. function) symbols from the debuginfo.
19170 # (Note that we actually also accept "D" symbols, for the benefit
19171 # of platforms like PowerPC64 that use function descriptors.)
19172 nm @var{binary} --format=posix --defined-only \
19173 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19176 # Keep all the function symbols not already in the dynamic symbol
19178 comm -13 dynsyms funcsyms > keep_symbols
19180 # Separate full debug info into debug binary.
19181 objcopy --only-keep-debug @var{binary} debug
19183 # Copy the full debuginfo, keeping only a minimal set of symbols and
19184 # removing some unnecessary sections.
19185 objcopy -S --remove-section .gdb_index --remove-section .comment \
19186 --keep-symbols=keep_symbols debug mini_debuginfo
19188 # Drop the full debug info from the original binary.
19189 strip --strip-all -R .comment @var{binary}
19191 # Inject the compressed data into the .gnu_debugdata section of the
19194 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19198 @section Index Files Speed Up @value{GDBN}
19199 @cindex index files
19200 @cindex @samp{.gdb_index} section
19202 When @value{GDBN} finds a symbol file, it scans the symbols in the
19203 file in order to construct an internal symbol table. This lets most
19204 @value{GDBN} operations work quickly---at the cost of a delay early
19205 on. For large programs, this delay can be quite lengthy, so
19206 @value{GDBN} provides a way to build an index, which speeds up
19209 The index is stored as a section in the symbol file. @value{GDBN} can
19210 write the index to a file, then you can put it into the symbol file
19211 using @command{objcopy}.
19213 To create an index file, use the @code{save gdb-index} command:
19216 @item save gdb-index @var{directory}
19217 @kindex save gdb-index
19218 Create an index file for each symbol file currently known by
19219 @value{GDBN}. Each file is named after its corresponding symbol file,
19220 with @samp{.gdb-index} appended, and is written into the given
19224 Once you have created an index file you can merge it into your symbol
19225 file, here named @file{symfile}, using @command{objcopy}:
19228 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19229 --set-section-flags .gdb_index=readonly symfile symfile
19232 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19233 sections that have been deprecated. Usually they are deprecated because
19234 they are missing a new feature or have performance issues.
19235 To tell @value{GDBN} to use a deprecated index section anyway
19236 specify @code{set use-deprecated-index-sections on}.
19237 The default is @code{off}.
19238 This can speed up startup, but may result in some functionality being lost.
19239 @xref{Index Section Format}.
19241 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19242 must be done before gdb reads the file. The following will not work:
19245 $ gdb -ex "set use-deprecated-index-sections on" <program>
19248 Instead you must do, for example,
19251 $ gdb -iex "set use-deprecated-index-sections on" <program>
19254 There are currently some limitation on indices. They only work when
19255 for DWARF debugging information, not stabs. And, they do not
19256 currently work for programs using Ada.
19258 @node Symbol Errors
19259 @section Errors Reading Symbol Files
19261 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19262 such as symbol types it does not recognize, or known bugs in compiler
19263 output. By default, @value{GDBN} does not notify you of such problems, since
19264 they are relatively common and primarily of interest to people
19265 debugging compilers. If you are interested in seeing information
19266 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19267 only one message about each such type of problem, no matter how many
19268 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19269 to see how many times the problems occur, with the @code{set
19270 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19273 The messages currently printed, and their meanings, include:
19276 @item inner block not inside outer block in @var{symbol}
19278 The symbol information shows where symbol scopes begin and end
19279 (such as at the start of a function or a block of statements). This
19280 error indicates that an inner scope block is not fully contained
19281 in its outer scope blocks.
19283 @value{GDBN} circumvents the problem by treating the inner block as if it had
19284 the same scope as the outer block. In the error message, @var{symbol}
19285 may be shown as ``@code{(don't know)}'' if the outer block is not a
19288 @item block at @var{address} out of order
19290 The symbol information for symbol scope blocks should occur in
19291 order of increasing addresses. This error indicates that it does not
19294 @value{GDBN} does not circumvent this problem, and has trouble
19295 locating symbols in the source file whose symbols it is reading. (You
19296 can often determine what source file is affected by specifying
19297 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19300 @item bad block start address patched
19302 The symbol information for a symbol scope block has a start address
19303 smaller than the address of the preceding source line. This is known
19304 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19306 @value{GDBN} circumvents the problem by treating the symbol scope block as
19307 starting on the previous source line.
19309 @item bad string table offset in symbol @var{n}
19312 Symbol number @var{n} contains a pointer into the string table which is
19313 larger than the size of the string table.
19315 @value{GDBN} circumvents the problem by considering the symbol to have the
19316 name @code{foo}, which may cause other problems if many symbols end up
19319 @item unknown symbol type @code{0x@var{nn}}
19321 The symbol information contains new data types that @value{GDBN} does
19322 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19323 uncomprehended information, in hexadecimal.
19325 @value{GDBN} circumvents the error by ignoring this symbol information.
19326 This usually allows you to debug your program, though certain symbols
19327 are not accessible. If you encounter such a problem and feel like
19328 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19329 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19330 and examine @code{*bufp} to see the symbol.
19332 @item stub type has NULL name
19334 @value{GDBN} could not find the full definition for a struct or class.
19336 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19337 The symbol information for a C@t{++} member function is missing some
19338 information that recent versions of the compiler should have output for
19341 @item info mismatch between compiler and debugger
19343 @value{GDBN} could not parse a type specification output by the compiler.
19348 @section GDB Data Files
19350 @cindex prefix for data files
19351 @value{GDBN} will sometimes read an auxiliary data file. These files
19352 are kept in a directory known as the @dfn{data directory}.
19354 You can set the data directory's name, and view the name @value{GDBN}
19355 is currently using.
19358 @kindex set data-directory
19359 @item set data-directory @var{directory}
19360 Set the directory which @value{GDBN} searches for auxiliary data files
19361 to @var{directory}.
19363 @kindex show data-directory
19364 @item show data-directory
19365 Show the directory @value{GDBN} searches for auxiliary data files.
19368 @cindex default data directory
19369 @cindex @samp{--with-gdb-datadir}
19370 You can set the default data directory by using the configure-time
19371 @samp{--with-gdb-datadir} option. If the data directory is inside
19372 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19373 @samp{--exec-prefix}), then the default data directory will be updated
19374 automatically if the installed @value{GDBN} is moved to a new
19377 The data directory may also be specified with the
19378 @code{--data-directory} command line option.
19379 @xref{Mode Options}.
19382 @chapter Specifying a Debugging Target
19384 @cindex debugging target
19385 A @dfn{target} is the execution environment occupied by your program.
19387 Often, @value{GDBN} runs in the same host environment as your program;
19388 in that case, the debugging target is specified as a side effect when
19389 you use the @code{file} or @code{core} commands. When you need more
19390 flexibility---for example, running @value{GDBN} on a physically separate
19391 host, or controlling a standalone system over a serial port or a
19392 realtime system over a TCP/IP connection---you can use the @code{target}
19393 command to specify one of the target types configured for @value{GDBN}
19394 (@pxref{Target Commands, ,Commands for Managing Targets}).
19396 @cindex target architecture
19397 It is possible to build @value{GDBN} for several different @dfn{target
19398 architectures}. When @value{GDBN} is built like that, you can choose
19399 one of the available architectures with the @kbd{set architecture}
19403 @kindex set architecture
19404 @kindex show architecture
19405 @item set architecture @var{arch}
19406 This command sets the current target architecture to @var{arch}. The
19407 value of @var{arch} can be @code{"auto"}, in addition to one of the
19408 supported architectures.
19410 @item show architecture
19411 Show the current target architecture.
19413 @item set processor
19415 @kindex set processor
19416 @kindex show processor
19417 These are alias commands for, respectively, @code{set architecture}
19418 and @code{show architecture}.
19422 * Active Targets:: Active targets
19423 * Target Commands:: Commands for managing targets
19424 * Byte Order:: Choosing target byte order
19427 @node Active Targets
19428 @section Active Targets
19430 @cindex stacking targets
19431 @cindex active targets
19432 @cindex multiple targets
19434 There are multiple classes of targets such as: processes, executable files or
19435 recording sessions. Core files belong to the process class, making core file
19436 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19437 on multiple active targets, one in each class. This allows you to (for
19438 example) start a process and inspect its activity, while still having access to
19439 the executable file after the process finishes. Or if you start process
19440 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19441 presented a virtual layer of the recording target, while the process target
19442 remains stopped at the chronologically last point of the process execution.
19444 Use the @code{core-file} and @code{exec-file} commands to select a new core
19445 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19446 specify as a target a process that is already running, use the @code{attach}
19447 command (@pxref{Attach, ,Debugging an Already-running Process}).
19449 @node Target Commands
19450 @section Commands for Managing Targets
19453 @item target @var{type} @var{parameters}
19454 Connects the @value{GDBN} host environment to a target machine or
19455 process. A target is typically a protocol for talking to debugging
19456 facilities. You use the argument @var{type} to specify the type or
19457 protocol of the target machine.
19459 Further @var{parameters} are interpreted by the target protocol, but
19460 typically include things like device names or host names to connect
19461 with, process numbers, and baud rates.
19463 The @code{target} command does not repeat if you press @key{RET} again
19464 after executing the command.
19466 @kindex help target
19468 Displays the names of all targets available. To display targets
19469 currently selected, use either @code{info target} or @code{info files}
19470 (@pxref{Files, ,Commands to Specify Files}).
19472 @item help target @var{name}
19473 Describe a particular target, including any parameters necessary to
19476 @kindex set gnutarget
19477 @item set gnutarget @var{args}
19478 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19479 knows whether it is reading an @dfn{executable},
19480 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19481 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19482 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19485 @emph{Warning:} To specify a file format with @code{set gnutarget},
19486 you must know the actual BFD name.
19490 @xref{Files, , Commands to Specify Files}.
19492 @kindex show gnutarget
19493 @item show gnutarget
19494 Use the @code{show gnutarget} command to display what file format
19495 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19496 @value{GDBN} will determine the file format for each file automatically,
19497 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19500 @cindex common targets
19501 Here are some common targets (available, or not, depending on the GDB
19506 @item target exec @var{program}
19507 @cindex executable file target
19508 An executable file. @samp{target exec @var{program}} is the same as
19509 @samp{exec-file @var{program}}.
19511 @item target core @var{filename}
19512 @cindex core dump file target
19513 A core dump file. @samp{target core @var{filename}} is the same as
19514 @samp{core-file @var{filename}}.
19516 @item target remote @var{medium}
19517 @cindex remote target
19518 A remote system connected to @value{GDBN} via a serial line or network
19519 connection. This command tells @value{GDBN} to use its own remote
19520 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19522 For example, if you have a board connected to @file{/dev/ttya} on the
19523 machine running @value{GDBN}, you could say:
19526 target remote /dev/ttya
19529 @code{target remote} supports the @code{load} command. This is only
19530 useful if you have some other way of getting the stub to the target
19531 system, and you can put it somewhere in memory where it won't get
19532 clobbered by the download.
19534 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19535 @cindex built-in simulator target
19536 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19544 works; however, you cannot assume that a specific memory map, device
19545 drivers, or even basic I/O is available, although some simulators do
19546 provide these. For info about any processor-specific simulator details,
19547 see the appropriate section in @ref{Embedded Processors, ,Embedded
19550 @item target native
19551 @cindex native target
19552 Setup for local/native process debugging. Useful to make the
19553 @code{run} command spawn native processes (likewise @code{attach},
19554 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19555 (@pxref{set auto-connect-native-target}).
19559 Different targets are available on different configurations of @value{GDBN};
19560 your configuration may have more or fewer targets.
19562 Many remote targets require you to download the executable's code once
19563 you've successfully established a connection. You may wish to control
19564 various aspects of this process.
19569 @kindex set hash@r{, for remote monitors}
19570 @cindex hash mark while downloading
19571 This command controls whether a hash mark @samp{#} is displayed while
19572 downloading a file to the remote monitor. If on, a hash mark is
19573 displayed after each S-record is successfully downloaded to the
19577 @kindex show hash@r{, for remote monitors}
19578 Show the current status of displaying the hash mark.
19580 @item set debug monitor
19581 @kindex set debug monitor
19582 @cindex display remote monitor communications
19583 Enable or disable display of communications messages between
19584 @value{GDBN} and the remote monitor.
19586 @item show debug monitor
19587 @kindex show debug monitor
19588 Show the current status of displaying communications between
19589 @value{GDBN} and the remote monitor.
19594 @kindex load @var{filename}
19595 @item load @var{filename}
19597 Depending on what remote debugging facilities are configured into
19598 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19599 is meant to make @var{filename} (an executable) available for debugging
19600 on the remote system---by downloading, or dynamic linking, for example.
19601 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19602 the @code{add-symbol-file} command.
19604 If your @value{GDBN} does not have a @code{load} command, attempting to
19605 execute it gets the error message ``@code{You can't do that when your
19606 target is @dots{}}''
19608 The file is loaded at whatever address is specified in the executable.
19609 For some object file formats, you can specify the load address when you
19610 link the program; for other formats, like a.out, the object file format
19611 specifies a fixed address.
19612 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19614 Depending on the remote side capabilities, @value{GDBN} may be able to
19615 load programs into flash memory.
19617 @code{load} does not repeat if you press @key{RET} again after using it.
19621 @section Choosing Target Byte Order
19623 @cindex choosing target byte order
19624 @cindex target byte order
19626 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19627 offer the ability to run either big-endian or little-endian byte
19628 orders. Usually the executable or symbol will include a bit to
19629 designate the endian-ness, and you will not need to worry about
19630 which to use. However, you may still find it useful to adjust
19631 @value{GDBN}'s idea of processor endian-ness manually.
19635 @item set endian big
19636 Instruct @value{GDBN} to assume the target is big-endian.
19638 @item set endian little
19639 Instruct @value{GDBN} to assume the target is little-endian.
19641 @item set endian auto
19642 Instruct @value{GDBN} to use the byte order associated with the
19646 Display @value{GDBN}'s current idea of the target byte order.
19650 Note that these commands merely adjust interpretation of symbolic
19651 data on the host, and that they have absolutely no effect on the
19655 @node Remote Debugging
19656 @chapter Debugging Remote Programs
19657 @cindex remote debugging
19659 If you are trying to debug a program running on a machine that cannot run
19660 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19661 For example, you might use remote debugging on an operating system kernel,
19662 or on a small system which does not have a general purpose operating system
19663 powerful enough to run a full-featured debugger.
19665 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19666 to make this work with particular debugging targets. In addition,
19667 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19668 but not specific to any particular target system) which you can use if you
19669 write the remote stubs---the code that runs on the remote system to
19670 communicate with @value{GDBN}.
19672 Other remote targets may be available in your
19673 configuration of @value{GDBN}; use @code{help target} to list them.
19676 * Connecting:: Connecting to a remote target
19677 * File Transfer:: Sending files to a remote system
19678 * Server:: Using the gdbserver program
19679 * Remote Configuration:: Remote configuration
19680 * Remote Stub:: Implementing a remote stub
19684 @section Connecting to a Remote Target
19685 @cindex remote debugging, connecting
19686 @cindex @code{gdbserver}, connecting
19687 @cindex remote debugging, types of connections
19688 @cindex @code{gdbserver}, types of connections
19689 @cindex @code{gdbserver}, @code{target remote} mode
19690 @cindex @code{gdbserver}, @code{target extended-remote} mode
19692 This section describes how to connect to a remote target, including the
19693 types of connections and their differences, how to set up executable and
19694 symbol files on the host and target, and the commands used for
19695 connecting to and disconnecting from the remote target.
19697 @subsection Types of Remote Connections
19699 @value{GDBN} supports two types of remote connections, @code{target remote}
19700 mode and @code{target extended-remote} mode. Note that many remote targets
19701 support only @code{target remote} mode. There are several major
19702 differences between the two types of connections, enumerated here:
19706 @cindex remote debugging, detach and program exit
19707 @item Result of detach or program exit
19708 @strong{With target remote mode:} When the debugged program exits or you
19709 detach from it, @value{GDBN} disconnects from the target. When using
19710 @code{gdbserver}, @code{gdbserver} will exit.
19712 @strong{With target extended-remote mode:} When the debugged program exits or
19713 you detach from it, @value{GDBN} remains connected to the target, even
19714 though no program is running. You can rerun the program, attach to a
19715 running program, or use @code{monitor} commands specific to the target.
19717 When using @code{gdbserver} in this case, it does not exit unless it was
19718 invoked using the @option{--once} option. If the @option{--once} option
19719 was not used, you can ask @code{gdbserver} to exit using the
19720 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19722 @item Specifying the program to debug
19723 For both connection types you use the @code{file} command to specify the
19724 program on the host system. If you are using @code{gdbserver} there are
19725 some differences in how to specify the location of the program on the
19728 @strong{With target remote mode:} You must either specify the program to debug
19729 on the @code{gdbserver} command line or use the @option{--attach} option
19730 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19732 @cindex @option{--multi}, @code{gdbserver} option
19733 @strong{With target extended-remote mode:} You may specify the program to debug
19734 on the @code{gdbserver} command line, or you can load the program or attach
19735 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19737 @anchor{--multi Option in Types of Remote Connnections}
19738 You can start @code{gdbserver} without supplying an initial command to run
19739 or process ID to attach. To do this, use the @option{--multi} command line
19740 option. Then you can connect using @code{target extended-remote} and start
19741 the program you want to debug (see below for details on using the
19742 @code{run} command in this scenario). Note that the conditions under which
19743 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19744 (@code{target remote} or @code{target extended-remote}). The
19745 @option{--multi} option to @code{gdbserver} has no influence on that.
19747 @item The @code{run} command
19748 @strong{With target remote mode:} The @code{run} command is not
19749 supported. Once a connection has been established, you can use all
19750 the usual @value{GDBN} commands to examine and change data. The
19751 remote program is already running, so you can use commands like
19752 @kbd{step} and @kbd{continue}.
19754 @strong{With target extended-remote mode:} The @code{run} command is
19755 supported. The @code{run} command uses the value set by
19756 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19757 the program to run. Command line arguments are supported, except for
19758 wildcard expansion and I/O redirection (@pxref{Arguments}).
19760 If you specify the program to debug on the command line, then the
19761 @code{run} command is not required to start execution, and you can
19762 resume using commands like @kbd{step} and @kbd{continue} as with
19763 @code{target remote} mode.
19765 @anchor{Attaching in Types of Remote Connections}
19767 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19768 not supported. To attach to a running program using @code{gdbserver}, you
19769 must use the @option{--attach} option (@pxref{Running gdbserver}).
19771 @strong{With target extended-remote mode:} To attach to a running program,
19772 you may use the @code{attach} command after the connection has been
19773 established. If you are using @code{gdbserver}, you may also invoke
19774 @code{gdbserver} using the @option{--attach} option
19775 (@pxref{Running gdbserver}).
19779 @anchor{Host and target files}
19780 @subsection Host and Target Files
19781 @cindex remote debugging, symbol files
19782 @cindex symbol files, remote debugging
19784 @value{GDBN}, running on the host, needs access to symbol and debugging
19785 information for your program running on the target. This requires
19786 access to an unstripped copy of your program, and possibly any associated
19787 symbol files. Note that this section applies equally to both @code{target
19788 remote} mode and @code{target extended-remote} mode.
19790 Some remote targets (@pxref{qXfer executable filename read}, and
19791 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19792 the same connection used to communicate with @value{GDBN}. With such a
19793 target, if the remote program is unstripped, the only command you need is
19794 @code{target remote} (or @code{target extended-remote}).
19796 If the remote program is stripped, or the target does not support remote
19797 program file access, start up @value{GDBN} using the name of the local
19798 unstripped copy of your program as the first argument, or use the
19799 @code{file} command. Use @code{set sysroot} to specify the location (on
19800 the host) of target libraries (unless your @value{GDBN} was compiled with
19801 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19802 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19805 The symbol file and target libraries must exactly match the executable
19806 and libraries on the target, with one exception: the files on the host
19807 system should not be stripped, even if the files on the target system
19808 are. Mismatched or missing files will lead to confusing results
19809 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19810 files may also prevent @code{gdbserver} from debugging multi-threaded
19813 @subsection Remote Connection Commands
19814 @cindex remote connection commands
19815 @value{GDBN} can communicate with the target over a serial line, or
19816 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19817 each case, @value{GDBN} uses the same protocol for debugging your
19818 program; only the medium carrying the debugging packets varies. The
19819 @code{target remote} and @code{target extended-remote} commands
19820 establish a connection to the target. Both commands accept the same
19821 arguments, which indicate the medium to use:
19825 @item target remote @var{serial-device}
19826 @itemx target extended-remote @var{serial-device}
19827 @cindex serial line, @code{target remote}
19828 Use @var{serial-device} to communicate with the target. For example,
19829 to use a serial line connected to the device named @file{/dev/ttyb}:
19832 target remote /dev/ttyb
19835 If you're using a serial line, you may want to give @value{GDBN} the
19836 @samp{--baud} option, or use the @code{set serial baud} command
19837 (@pxref{Remote Configuration, set serial baud}) before the
19838 @code{target} command.
19840 @item target remote @code{@var{host}:@var{port}}
19841 @itemx target remote @code{tcp:@var{host}:@var{port}}
19842 @itemx target extended-remote @code{@var{host}:@var{port}}
19843 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19844 @cindex @acronym{TCP} port, @code{target remote}
19845 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19846 The @var{host} may be either a host name or a numeric @acronym{IP}
19847 address; @var{port} must be a decimal number. The @var{host} could be
19848 the target machine itself, if it is directly connected to the net, or
19849 it might be a terminal server which in turn has a serial line to the
19852 For example, to connect to port 2828 on a terminal server named
19856 target remote manyfarms:2828
19859 If your remote target is actually running on the same machine as your
19860 debugger session (e.g.@: a simulator for your target running on the
19861 same host), you can omit the hostname. For example, to connect to
19862 port 1234 on your local machine:
19865 target remote :1234
19869 Note that the colon is still required here.
19871 @item target remote @code{udp:@var{host}:@var{port}}
19872 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19873 @cindex @acronym{UDP} port, @code{target remote}
19874 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19875 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19878 target remote udp:manyfarms:2828
19881 When using a @acronym{UDP} connection for remote debugging, you should
19882 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19883 can silently drop packets on busy or unreliable networks, which will
19884 cause havoc with your debugging session.
19886 @item target remote | @var{command}
19887 @itemx target extended-remote | @var{command}
19888 @cindex pipe, @code{target remote} to
19889 Run @var{command} in the background and communicate with it using a
19890 pipe. The @var{command} is a shell command, to be parsed and expanded
19891 by the system's command shell, @code{/bin/sh}; it should expect remote
19892 protocol packets on its standard input, and send replies on its
19893 standard output. You could use this to run a stand-alone simulator
19894 that speaks the remote debugging protocol, to make net connections
19895 using programs like @code{ssh}, or for other similar tricks.
19897 If @var{command} closes its standard output (perhaps by exiting),
19898 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19899 program has already exited, this will have no effect.)
19903 @cindex interrupting remote programs
19904 @cindex remote programs, interrupting
19905 Whenever @value{GDBN} is waiting for the remote program, if you type the
19906 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19907 program. This may or may not succeed, depending in part on the hardware
19908 and the serial drivers the remote system uses. If you type the
19909 interrupt character once again, @value{GDBN} displays this prompt:
19912 Interrupted while waiting for the program.
19913 Give up (and stop debugging it)? (y or n)
19916 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19917 the remote debugging session. (If you decide you want to try again later,
19918 you can use @kbd{target remote} again to connect once more.) If you type
19919 @kbd{n}, @value{GDBN} goes back to waiting.
19921 In @code{target extended-remote} mode, typing @kbd{n} will leave
19922 @value{GDBN} connected to the target.
19925 @kindex detach (remote)
19927 When you have finished debugging the remote program, you can use the
19928 @code{detach} command to release it from @value{GDBN} control.
19929 Detaching from the target normally resumes its execution, but the results
19930 will depend on your particular remote stub. After the @code{detach}
19931 command in @code{target remote} mode, @value{GDBN} is free to connect to
19932 another target. In @code{target extended-remote} mode, @value{GDBN} is
19933 still connected to the target.
19937 The @code{disconnect} command closes the connection to the target, and
19938 the target is generally not resumed. It will wait for @value{GDBN}
19939 (this instance or another one) to connect and continue debugging. After
19940 the @code{disconnect} command, @value{GDBN} is again free to connect to
19943 @cindex send command to remote monitor
19944 @cindex extend @value{GDBN} for remote targets
19945 @cindex add new commands for external monitor
19947 @item monitor @var{cmd}
19948 This command allows you to send arbitrary commands directly to the
19949 remote monitor. Since @value{GDBN} doesn't care about the commands it
19950 sends like this, this command is the way to extend @value{GDBN}---you
19951 can add new commands that only the external monitor will understand
19955 @node File Transfer
19956 @section Sending files to a remote system
19957 @cindex remote target, file transfer
19958 @cindex file transfer
19959 @cindex sending files to remote systems
19961 Some remote targets offer the ability to transfer files over the same
19962 connection used to communicate with @value{GDBN}. This is convenient
19963 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19964 running @code{gdbserver} over a network interface. For other targets,
19965 e.g.@: embedded devices with only a single serial port, this may be
19966 the only way to upload or download files.
19968 Not all remote targets support these commands.
19972 @item remote put @var{hostfile} @var{targetfile}
19973 Copy file @var{hostfile} from the host system (the machine running
19974 @value{GDBN}) to @var{targetfile} on the target system.
19977 @item remote get @var{targetfile} @var{hostfile}
19978 Copy file @var{targetfile} from the target system to @var{hostfile}
19979 on the host system.
19981 @kindex remote delete
19982 @item remote delete @var{targetfile}
19983 Delete @var{targetfile} from the target system.
19988 @section Using the @code{gdbserver} Program
19991 @cindex remote connection without stubs
19992 @code{gdbserver} is a control program for Unix-like systems, which
19993 allows you to connect your program with a remote @value{GDBN} via
19994 @code{target remote} or @code{target extended-remote}---but without
19995 linking in the usual debugging stub.
19997 @code{gdbserver} is not a complete replacement for the debugging stubs,
19998 because it requires essentially the same operating-system facilities
19999 that @value{GDBN} itself does. In fact, a system that can run
20000 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20001 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20002 because it is a much smaller program than @value{GDBN} itself. It is
20003 also easier to port than all of @value{GDBN}, so you may be able to get
20004 started more quickly on a new system by using @code{gdbserver}.
20005 Finally, if you develop code for real-time systems, you may find that
20006 the tradeoffs involved in real-time operation make it more convenient to
20007 do as much development work as possible on another system, for example
20008 by cross-compiling. You can use @code{gdbserver} to make a similar
20009 choice for debugging.
20011 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20012 or a TCP connection, using the standard @value{GDBN} remote serial
20016 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20017 Do not run @code{gdbserver} connected to any public network; a
20018 @value{GDBN} connection to @code{gdbserver} provides access to the
20019 target system with the same privileges as the user running
20023 @anchor{Running gdbserver}
20024 @subsection Running @code{gdbserver}
20025 @cindex arguments, to @code{gdbserver}
20026 @cindex @code{gdbserver}, command-line arguments
20028 Run @code{gdbserver} on the target system. You need a copy of the
20029 program you want to debug, including any libraries it requires.
20030 @code{gdbserver} does not need your program's symbol table, so you can
20031 strip the program if necessary to save space. @value{GDBN} on the host
20032 system does all the symbol handling.
20034 To use the server, you must tell it how to communicate with @value{GDBN};
20035 the name of your program; and the arguments for your program. The usual
20039 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20042 @var{comm} is either a device name (to use a serial line), or a TCP
20043 hostname and portnumber, or @code{-} or @code{stdio} to use
20044 stdin/stdout of @code{gdbserver}.
20045 For example, to debug Emacs with the argument
20046 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20050 target> gdbserver /dev/com1 emacs foo.txt
20053 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20056 To use a TCP connection instead of a serial line:
20059 target> gdbserver host:2345 emacs foo.txt
20062 The only difference from the previous example is the first argument,
20063 specifying that you are communicating with the host @value{GDBN} via
20064 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20065 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20066 (Currently, the @samp{host} part is ignored.) You can choose any number
20067 you want for the port number as long as it does not conflict with any
20068 TCP ports already in use on the target system (for example, @code{23} is
20069 reserved for @code{telnet}).@footnote{If you choose a port number that
20070 conflicts with another service, @code{gdbserver} prints an error message
20071 and exits.} You must use the same port number with the host @value{GDBN}
20072 @code{target remote} command.
20074 The @code{stdio} connection is useful when starting @code{gdbserver}
20078 (gdb) target remote | ssh -T hostname gdbserver - hello
20081 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20082 and we don't want escape-character handling. Ssh does this by default when
20083 a command is provided, the flag is provided to make it explicit.
20084 You could elide it if you want to.
20086 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20087 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20088 display through a pipe connected to gdbserver.
20089 Both @code{stdout} and @code{stderr} use the same pipe.
20091 @anchor{Attaching to a program}
20092 @subsubsection Attaching to a Running Program
20093 @cindex attach to a program, @code{gdbserver}
20094 @cindex @option{--attach}, @code{gdbserver} option
20096 On some targets, @code{gdbserver} can also attach to running programs.
20097 This is accomplished via the @code{--attach} argument. The syntax is:
20100 target> gdbserver --attach @var{comm} @var{pid}
20103 @var{pid} is the process ID of a currently running process. It isn't
20104 necessary to point @code{gdbserver} at a binary for the running process.
20106 In @code{target extended-remote} mode, you can also attach using the
20107 @value{GDBN} attach command
20108 (@pxref{Attaching in Types of Remote Connections}).
20111 You can debug processes by name instead of process ID if your target has the
20112 @code{pidof} utility:
20115 target> gdbserver --attach @var{comm} `pidof @var{program}`
20118 In case more than one copy of @var{program} is running, or @var{program}
20119 has multiple threads, most versions of @code{pidof} support the
20120 @code{-s} option to only return the first process ID.
20122 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20124 This section applies only when @code{gdbserver} is run to listen on a TCP
20127 @code{gdbserver} normally terminates after all of its debugged processes have
20128 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20129 extended-remote}, @code{gdbserver} stays running even with no processes left.
20130 @value{GDBN} normally terminates the spawned debugged process on its exit,
20131 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20132 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20133 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20134 stays running even in the @kbd{target remote} mode.
20136 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20137 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20138 completeness, at most one @value{GDBN} can be connected at a time.
20140 @cindex @option{--once}, @code{gdbserver} option
20141 By default, @code{gdbserver} keeps the listening TCP port open, so that
20142 subsequent connections are possible. However, if you start @code{gdbserver}
20143 with the @option{--once} option, it will stop listening for any further
20144 connection attempts after connecting to the first @value{GDBN} session. This
20145 means no further connections to @code{gdbserver} will be possible after the
20146 first one. It also means @code{gdbserver} will terminate after the first
20147 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20148 connections and even in the @kbd{target extended-remote} mode. The
20149 @option{--once} option allows reusing the same port number for connecting to
20150 multiple instances of @code{gdbserver} running on the same host, since each
20151 instance closes its port after the first connection.
20153 @anchor{Other Command-Line Arguments for gdbserver}
20154 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20156 You can use the @option{--multi} option to start @code{gdbserver} without
20157 specifying a program to debug or a process to attach to. Then you can
20158 attach in @code{target extended-remote} mode and run or attach to a
20159 program. For more information,
20160 @pxref{--multi Option in Types of Remote Connnections}.
20162 @cindex @option{--debug}, @code{gdbserver} option
20163 The @option{--debug} option tells @code{gdbserver} to display extra
20164 status information about the debugging process.
20165 @cindex @option{--remote-debug}, @code{gdbserver} option
20166 The @option{--remote-debug} option tells @code{gdbserver} to display
20167 remote protocol debug output. These options are intended for
20168 @code{gdbserver} development and for bug reports to the developers.
20170 @cindex @option{--debug-format}, @code{gdbserver} option
20171 The @option{--debug-format=option1[,option2,...]} option tells
20172 @code{gdbserver} to include additional information in each output.
20173 Possible options are:
20177 Turn off all extra information in debugging output.
20179 Turn on all extra information in debugging output.
20181 Include a timestamp in each line of debugging output.
20184 Options are processed in order. Thus, for example, if @option{none}
20185 appears last then no additional information is added to debugging output.
20187 @cindex @option{--wrapper}, @code{gdbserver} option
20188 The @option{--wrapper} option specifies a wrapper to launch programs
20189 for debugging. The option should be followed by the name of the
20190 wrapper, then any command-line arguments to pass to the wrapper, then
20191 @kbd{--} indicating the end of the wrapper arguments.
20193 @code{gdbserver} runs the specified wrapper program with a combined
20194 command line including the wrapper arguments, then the name of the
20195 program to debug, then any arguments to the program. The wrapper
20196 runs until it executes your program, and then @value{GDBN} gains control.
20198 You can use any program that eventually calls @code{execve} with
20199 its arguments as a wrapper. Several standard Unix utilities do
20200 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20201 with @code{exec "$@@"} will also work.
20203 For example, you can use @code{env} to pass an environment variable to
20204 the debugged program, without setting the variable in @code{gdbserver}'s
20208 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20211 @subsection Connecting to @code{gdbserver}
20213 The basic procedure for connecting to the remote target is:
20217 Run @value{GDBN} on the host system.
20220 Make sure you have the necessary symbol files
20221 (@pxref{Host and target files}).
20222 Load symbols for your application using the @code{file} command before you
20223 connect. Use @code{set sysroot} to locate target libraries (unless your
20224 @value{GDBN} was compiled with the correct sysroot using
20225 @code{--with-sysroot}).
20228 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20229 For TCP connections, you must start up @code{gdbserver} prior to using
20230 the @code{target} command. Otherwise you may get an error whose
20231 text depends on the host system, but which usually looks something like
20232 @samp{Connection refused}. Don't use the @code{load}
20233 command in @value{GDBN} when using @code{target remote} mode, since the
20234 program is already on the target.
20238 @anchor{Monitor Commands for gdbserver}
20239 @subsection Monitor Commands for @code{gdbserver}
20240 @cindex monitor commands, for @code{gdbserver}
20242 During a @value{GDBN} session using @code{gdbserver}, you can use the
20243 @code{monitor} command to send special requests to @code{gdbserver}.
20244 Here are the available commands.
20248 List the available monitor commands.
20250 @item monitor set debug 0
20251 @itemx monitor set debug 1
20252 Disable or enable general debugging messages.
20254 @item monitor set remote-debug 0
20255 @itemx monitor set remote-debug 1
20256 Disable or enable specific debugging messages associated with the remote
20257 protocol (@pxref{Remote Protocol}).
20259 @item monitor set debug-format option1@r{[},option2,...@r{]}
20260 Specify additional text to add to debugging messages.
20261 Possible options are:
20265 Turn off all extra information in debugging output.
20267 Turn on all extra information in debugging output.
20269 Include a timestamp in each line of debugging output.
20272 Options are processed in order. Thus, for example, if @option{none}
20273 appears last then no additional information is added to debugging output.
20275 @item monitor set libthread-db-search-path [PATH]
20276 @cindex gdbserver, search path for @code{libthread_db}
20277 When this command is issued, @var{path} is a colon-separated list of
20278 directories to search for @code{libthread_db} (@pxref{Threads,,set
20279 libthread-db-search-path}). If you omit @var{path},
20280 @samp{libthread-db-search-path} will be reset to its default value.
20282 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20283 not supported in @code{gdbserver}.
20286 Tell gdbserver to exit immediately. This command should be followed by
20287 @code{disconnect} to close the debugging session. @code{gdbserver} will
20288 detach from any attached processes and kill any processes it created.
20289 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20290 of a multi-process mode debug session.
20294 @subsection Tracepoints support in @code{gdbserver}
20295 @cindex tracepoints support in @code{gdbserver}
20297 On some targets, @code{gdbserver} supports tracepoints, fast
20298 tracepoints and static tracepoints.
20300 For fast or static tracepoints to work, a special library called the
20301 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20302 This library is built and distributed as an integral part of
20303 @code{gdbserver}. In addition, support for static tracepoints
20304 requires building the in-process agent library with static tracepoints
20305 support. At present, the UST (LTTng Userspace Tracer,
20306 @url{http://lttng.org/ust}) tracing engine is supported. This support
20307 is automatically available if UST development headers are found in the
20308 standard include path when @code{gdbserver} is built, or if
20309 @code{gdbserver} was explicitly configured using @option{--with-ust}
20310 to point at such headers. You can explicitly disable the support
20311 using @option{--with-ust=no}.
20313 There are several ways to load the in-process agent in your program:
20316 @item Specifying it as dependency at link time
20318 You can link your program dynamically with the in-process agent
20319 library. On most systems, this is accomplished by adding
20320 @code{-linproctrace} to the link command.
20322 @item Using the system's preloading mechanisms
20324 You can force loading the in-process agent at startup time by using
20325 your system's support for preloading shared libraries. Many Unixes
20326 support the concept of preloading user defined libraries. In most
20327 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20328 in the environment. See also the description of @code{gdbserver}'s
20329 @option{--wrapper} command line option.
20331 @item Using @value{GDBN} to force loading the agent at run time
20333 On some systems, you can force the inferior to load a shared library,
20334 by calling a dynamic loader function in the inferior that takes care
20335 of dynamically looking up and loading a shared library. On most Unix
20336 systems, the function is @code{dlopen}. You'll use the @code{call}
20337 command for that. For example:
20340 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20343 Note that on most Unix systems, for the @code{dlopen} function to be
20344 available, the program needs to be linked with @code{-ldl}.
20347 On systems that have a userspace dynamic loader, like most Unix
20348 systems, when you connect to @code{gdbserver} using @code{target
20349 remote}, you'll find that the program is stopped at the dynamic
20350 loader's entry point, and no shared library has been loaded in the
20351 program's address space yet, including the in-process agent. In that
20352 case, before being able to use any of the fast or static tracepoints
20353 features, you need to let the loader run and load the shared
20354 libraries. The simplest way to do that is to run the program to the
20355 main procedure. E.g., if debugging a C or C@t{++} program, start
20356 @code{gdbserver} like so:
20359 $ gdbserver :9999 myprogram
20362 Start GDB and connect to @code{gdbserver} like so, and run to main:
20366 (@value{GDBP}) target remote myhost:9999
20367 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20368 (@value{GDBP}) b main
20369 (@value{GDBP}) continue
20372 The in-process tracing agent library should now be loaded into the
20373 process; you can confirm it with the @code{info sharedlibrary}
20374 command, which will list @file{libinproctrace.so} as loaded in the
20375 process. You are now ready to install fast tracepoints, list static
20376 tracepoint markers, probe static tracepoints markers, and start
20379 @node Remote Configuration
20380 @section Remote Configuration
20383 @kindex show remote
20384 This section documents the configuration options available when
20385 debugging remote programs. For the options related to the File I/O
20386 extensions of the remote protocol, see @ref{system,
20387 system-call-allowed}.
20390 @item set remoteaddresssize @var{bits}
20391 @cindex address size for remote targets
20392 @cindex bits in remote address
20393 Set the maximum size of address in a memory packet to the specified
20394 number of bits. @value{GDBN} will mask off the address bits above
20395 that number, when it passes addresses to the remote target. The
20396 default value is the number of bits in the target's address.
20398 @item show remoteaddresssize
20399 Show the current value of remote address size in bits.
20401 @item set serial baud @var{n}
20402 @cindex baud rate for remote targets
20403 Set the baud rate for the remote serial I/O to @var{n} baud. The
20404 value is used to set the speed of the serial port used for debugging
20407 @item show serial baud
20408 Show the current speed of the remote connection.
20410 @item set serial parity @var{parity}
20411 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20412 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20414 @item show serial parity
20415 Show the current parity of the serial port.
20417 @item set remotebreak
20418 @cindex interrupt remote programs
20419 @cindex BREAK signal instead of Ctrl-C
20420 @anchor{set remotebreak}
20421 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20422 when you type @kbd{Ctrl-c} to interrupt the program running
20423 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20424 character instead. The default is off, since most remote systems
20425 expect to see @samp{Ctrl-C} as the interrupt signal.
20427 @item show remotebreak
20428 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20429 interrupt the remote program.
20431 @item set remoteflow on
20432 @itemx set remoteflow off
20433 @kindex set remoteflow
20434 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20435 on the serial port used to communicate to the remote target.
20437 @item show remoteflow
20438 @kindex show remoteflow
20439 Show the current setting of hardware flow control.
20441 @item set remotelogbase @var{base}
20442 Set the base (a.k.a.@: radix) of logging serial protocol
20443 communications to @var{base}. Supported values of @var{base} are:
20444 @code{ascii}, @code{octal}, and @code{hex}. The default is
20447 @item show remotelogbase
20448 Show the current setting of the radix for logging remote serial
20451 @item set remotelogfile @var{file}
20452 @cindex record serial communications on file
20453 Record remote serial communications on the named @var{file}. The
20454 default is not to record at all.
20456 @item show remotelogfile.
20457 Show the current setting of the file name on which to record the
20458 serial communications.
20460 @item set remotetimeout @var{num}
20461 @cindex timeout for serial communications
20462 @cindex remote timeout
20463 Set the timeout limit to wait for the remote target to respond to
20464 @var{num} seconds. The default is 2 seconds.
20466 @item show remotetimeout
20467 Show the current number of seconds to wait for the remote target
20470 @cindex limit hardware breakpoints and watchpoints
20471 @cindex remote target, limit break- and watchpoints
20472 @anchor{set remote hardware-watchpoint-limit}
20473 @anchor{set remote hardware-breakpoint-limit}
20474 @item set remote hardware-watchpoint-limit @var{limit}
20475 @itemx set remote hardware-breakpoint-limit @var{limit}
20476 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20477 watchpoints. A limit of -1, the default, is treated as unlimited.
20479 @cindex limit hardware watchpoints length
20480 @cindex remote target, limit watchpoints length
20481 @anchor{set remote hardware-watchpoint-length-limit}
20482 @item set remote hardware-watchpoint-length-limit @var{limit}
20483 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20484 a remote hardware watchpoint. A limit of -1, the default, is treated
20487 @item show remote hardware-watchpoint-length-limit
20488 Show the current limit (in bytes) of the maximum length of
20489 a remote hardware watchpoint.
20491 @item set remote exec-file @var{filename}
20492 @itemx show remote exec-file
20493 @anchor{set remote exec-file}
20494 @cindex executable file, for remote target
20495 Select the file used for @code{run} with @code{target
20496 extended-remote}. This should be set to a filename valid on the
20497 target system. If it is not set, the target will use a default
20498 filename (e.g.@: the last program run).
20500 @item set remote interrupt-sequence
20501 @cindex interrupt remote programs
20502 @cindex select Ctrl-C, BREAK or BREAK-g
20503 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20504 @samp{BREAK-g} as the
20505 sequence to the remote target in order to interrupt the execution.
20506 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20507 is high level of serial line for some certain time.
20508 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20509 It is @code{BREAK} signal followed by character @code{g}.
20511 @item show interrupt-sequence
20512 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20513 is sent by @value{GDBN} to interrupt the remote program.
20514 @code{BREAK-g} is BREAK signal followed by @code{g} and
20515 also known as Magic SysRq g.
20517 @item set remote interrupt-on-connect
20518 @cindex send interrupt-sequence on start
20519 Specify whether interrupt-sequence is sent to remote target when
20520 @value{GDBN} connects to it. This is mostly needed when you debug
20521 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20522 which is known as Magic SysRq g in order to connect @value{GDBN}.
20524 @item show interrupt-on-connect
20525 Show whether interrupt-sequence is sent
20526 to remote target when @value{GDBN} connects to it.
20530 @item set tcp auto-retry on
20531 @cindex auto-retry, for remote TCP target
20532 Enable auto-retry for remote TCP connections. This is useful if the remote
20533 debugging agent is launched in parallel with @value{GDBN}; there is a race
20534 condition because the agent may not become ready to accept the connection
20535 before @value{GDBN} attempts to connect. When auto-retry is
20536 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20537 to establish the connection using the timeout specified by
20538 @code{set tcp connect-timeout}.
20540 @item set tcp auto-retry off
20541 Do not auto-retry failed TCP connections.
20543 @item show tcp auto-retry
20544 Show the current auto-retry setting.
20546 @item set tcp connect-timeout @var{seconds}
20547 @itemx set tcp connect-timeout unlimited
20548 @cindex connection timeout, for remote TCP target
20549 @cindex timeout, for remote target connection
20550 Set the timeout for establishing a TCP connection to the remote target to
20551 @var{seconds}. The timeout affects both polling to retry failed connections
20552 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20553 that are merely slow to complete, and represents an approximate cumulative
20554 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20555 @value{GDBN} will keep attempting to establish a connection forever,
20556 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20558 @item show tcp connect-timeout
20559 Show the current connection timeout setting.
20562 @cindex remote packets, enabling and disabling
20563 The @value{GDBN} remote protocol autodetects the packets supported by
20564 your debugging stub. If you need to override the autodetection, you
20565 can use these commands to enable or disable individual packets. Each
20566 packet can be set to @samp{on} (the remote target supports this
20567 packet), @samp{off} (the remote target does not support this packet),
20568 or @samp{auto} (detect remote target support for this packet). They
20569 all default to @samp{auto}. For more information about each packet,
20570 see @ref{Remote Protocol}.
20572 During normal use, you should not have to use any of these commands.
20573 If you do, that may be a bug in your remote debugging stub, or a bug
20574 in @value{GDBN}. You may want to report the problem to the
20575 @value{GDBN} developers.
20577 For each packet @var{name}, the command to enable or disable the
20578 packet is @code{set remote @var{name}-packet}. The available settings
20581 @multitable @columnfractions 0.28 0.32 0.25
20584 @tab Related Features
20586 @item @code{fetch-register}
20588 @tab @code{info registers}
20590 @item @code{set-register}
20594 @item @code{binary-download}
20596 @tab @code{load}, @code{set}
20598 @item @code{read-aux-vector}
20599 @tab @code{qXfer:auxv:read}
20600 @tab @code{info auxv}
20602 @item @code{symbol-lookup}
20603 @tab @code{qSymbol}
20604 @tab Detecting multiple threads
20606 @item @code{attach}
20607 @tab @code{vAttach}
20610 @item @code{verbose-resume}
20612 @tab Stepping or resuming multiple threads
20618 @item @code{software-breakpoint}
20622 @item @code{hardware-breakpoint}
20626 @item @code{write-watchpoint}
20630 @item @code{read-watchpoint}
20634 @item @code{access-watchpoint}
20638 @item @code{pid-to-exec-file}
20639 @tab @code{qXfer:exec-file:read}
20640 @tab @code{attach}, @code{run}
20642 @item @code{target-features}
20643 @tab @code{qXfer:features:read}
20644 @tab @code{set architecture}
20646 @item @code{library-info}
20647 @tab @code{qXfer:libraries:read}
20648 @tab @code{info sharedlibrary}
20650 @item @code{memory-map}
20651 @tab @code{qXfer:memory-map:read}
20652 @tab @code{info mem}
20654 @item @code{read-sdata-object}
20655 @tab @code{qXfer:sdata:read}
20656 @tab @code{print $_sdata}
20658 @item @code{read-spu-object}
20659 @tab @code{qXfer:spu:read}
20660 @tab @code{info spu}
20662 @item @code{write-spu-object}
20663 @tab @code{qXfer:spu:write}
20664 @tab @code{info spu}
20666 @item @code{read-siginfo-object}
20667 @tab @code{qXfer:siginfo:read}
20668 @tab @code{print $_siginfo}
20670 @item @code{write-siginfo-object}
20671 @tab @code{qXfer:siginfo:write}
20672 @tab @code{set $_siginfo}
20674 @item @code{threads}
20675 @tab @code{qXfer:threads:read}
20676 @tab @code{info threads}
20678 @item @code{get-thread-local-@*storage-address}
20679 @tab @code{qGetTLSAddr}
20680 @tab Displaying @code{__thread} variables
20682 @item @code{get-thread-information-block-address}
20683 @tab @code{qGetTIBAddr}
20684 @tab Display MS-Windows Thread Information Block.
20686 @item @code{search-memory}
20687 @tab @code{qSearch:memory}
20690 @item @code{supported-packets}
20691 @tab @code{qSupported}
20692 @tab Remote communications parameters
20694 @item @code{catch-syscalls}
20695 @tab @code{QCatchSyscalls}
20696 @tab @code{catch syscall}
20698 @item @code{pass-signals}
20699 @tab @code{QPassSignals}
20700 @tab @code{handle @var{signal}}
20702 @item @code{program-signals}
20703 @tab @code{QProgramSignals}
20704 @tab @code{handle @var{signal}}
20706 @item @code{hostio-close-packet}
20707 @tab @code{vFile:close}
20708 @tab @code{remote get}, @code{remote put}
20710 @item @code{hostio-open-packet}
20711 @tab @code{vFile:open}
20712 @tab @code{remote get}, @code{remote put}
20714 @item @code{hostio-pread-packet}
20715 @tab @code{vFile:pread}
20716 @tab @code{remote get}, @code{remote put}
20718 @item @code{hostio-pwrite-packet}
20719 @tab @code{vFile:pwrite}
20720 @tab @code{remote get}, @code{remote put}
20722 @item @code{hostio-unlink-packet}
20723 @tab @code{vFile:unlink}
20724 @tab @code{remote delete}
20726 @item @code{hostio-readlink-packet}
20727 @tab @code{vFile:readlink}
20730 @item @code{hostio-fstat-packet}
20731 @tab @code{vFile:fstat}
20734 @item @code{hostio-setfs-packet}
20735 @tab @code{vFile:setfs}
20738 @item @code{noack-packet}
20739 @tab @code{QStartNoAckMode}
20740 @tab Packet acknowledgment
20742 @item @code{osdata}
20743 @tab @code{qXfer:osdata:read}
20744 @tab @code{info os}
20746 @item @code{query-attached}
20747 @tab @code{qAttached}
20748 @tab Querying remote process attach state.
20750 @item @code{trace-buffer-size}
20751 @tab @code{QTBuffer:size}
20752 @tab @code{set trace-buffer-size}
20754 @item @code{trace-status}
20755 @tab @code{qTStatus}
20756 @tab @code{tstatus}
20758 @item @code{traceframe-info}
20759 @tab @code{qXfer:traceframe-info:read}
20760 @tab Traceframe info
20762 @item @code{install-in-trace}
20763 @tab @code{InstallInTrace}
20764 @tab Install tracepoint in tracing
20766 @item @code{disable-randomization}
20767 @tab @code{QDisableRandomization}
20768 @tab @code{set disable-randomization}
20770 @item @code{conditional-breakpoints-packet}
20771 @tab @code{Z0 and Z1}
20772 @tab @code{Support for target-side breakpoint condition evaluation}
20774 @item @code{multiprocess-extensions}
20775 @tab @code{multiprocess extensions}
20776 @tab Debug multiple processes and remote process PID awareness
20778 @item @code{swbreak-feature}
20779 @tab @code{swbreak stop reason}
20782 @item @code{hwbreak-feature}
20783 @tab @code{hwbreak stop reason}
20786 @item @code{fork-event-feature}
20787 @tab @code{fork stop reason}
20790 @item @code{vfork-event-feature}
20791 @tab @code{vfork stop reason}
20794 @item @code{exec-event-feature}
20795 @tab @code{exec stop reason}
20798 @item @code{thread-events}
20799 @tab @code{QThreadEvents}
20800 @tab Tracking thread lifetime.
20802 @item @code{no-resumed-stop-reply}
20803 @tab @code{no resumed thread left stop reply}
20804 @tab Tracking thread lifetime.
20809 @section Implementing a Remote Stub
20811 @cindex debugging stub, example
20812 @cindex remote stub, example
20813 @cindex stub example, remote debugging
20814 The stub files provided with @value{GDBN} implement the target side of the
20815 communication protocol, and the @value{GDBN} side is implemented in the
20816 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20817 these subroutines to communicate, and ignore the details. (If you're
20818 implementing your own stub file, you can still ignore the details: start
20819 with one of the existing stub files. @file{sparc-stub.c} is the best
20820 organized, and therefore the easiest to read.)
20822 @cindex remote serial debugging, overview
20823 To debug a program running on another machine (the debugging
20824 @dfn{target} machine), you must first arrange for all the usual
20825 prerequisites for the program to run by itself. For example, for a C
20830 A startup routine to set up the C runtime environment; these usually
20831 have a name like @file{crt0}. The startup routine may be supplied by
20832 your hardware supplier, or you may have to write your own.
20835 A C subroutine library to support your program's
20836 subroutine calls, notably managing input and output.
20839 A way of getting your program to the other machine---for example, a
20840 download program. These are often supplied by the hardware
20841 manufacturer, but you may have to write your own from hardware
20845 The next step is to arrange for your program to use a serial port to
20846 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20847 machine). In general terms, the scheme looks like this:
20851 @value{GDBN} already understands how to use this protocol; when everything
20852 else is set up, you can simply use the @samp{target remote} command
20853 (@pxref{Targets,,Specifying a Debugging Target}).
20855 @item On the target,
20856 you must link with your program a few special-purpose subroutines that
20857 implement the @value{GDBN} remote serial protocol. The file containing these
20858 subroutines is called a @dfn{debugging stub}.
20860 On certain remote targets, you can use an auxiliary program
20861 @code{gdbserver} instead of linking a stub into your program.
20862 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20865 The debugging stub is specific to the architecture of the remote
20866 machine; for example, use @file{sparc-stub.c} to debug programs on
20869 @cindex remote serial stub list
20870 These working remote stubs are distributed with @value{GDBN}:
20875 @cindex @file{i386-stub.c}
20878 For Intel 386 and compatible architectures.
20881 @cindex @file{m68k-stub.c}
20882 @cindex Motorola 680x0
20884 For Motorola 680x0 architectures.
20887 @cindex @file{sh-stub.c}
20890 For Renesas SH architectures.
20893 @cindex @file{sparc-stub.c}
20895 For @sc{sparc} architectures.
20897 @item sparcl-stub.c
20898 @cindex @file{sparcl-stub.c}
20901 For Fujitsu @sc{sparclite} architectures.
20905 The @file{README} file in the @value{GDBN} distribution may list other
20906 recently added stubs.
20909 * Stub Contents:: What the stub can do for you
20910 * Bootstrapping:: What you must do for the stub
20911 * Debug Session:: Putting it all together
20914 @node Stub Contents
20915 @subsection What the Stub Can Do for You
20917 @cindex remote serial stub
20918 The debugging stub for your architecture supplies these three
20922 @item set_debug_traps
20923 @findex set_debug_traps
20924 @cindex remote serial stub, initialization
20925 This routine arranges for @code{handle_exception} to run when your
20926 program stops. You must call this subroutine explicitly in your
20927 program's startup code.
20929 @item handle_exception
20930 @findex handle_exception
20931 @cindex remote serial stub, main routine
20932 This is the central workhorse, but your program never calls it
20933 explicitly---the setup code arranges for @code{handle_exception} to
20934 run when a trap is triggered.
20936 @code{handle_exception} takes control when your program stops during
20937 execution (for example, on a breakpoint), and mediates communications
20938 with @value{GDBN} on the host machine. This is where the communications
20939 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20940 representative on the target machine. It begins by sending summary
20941 information on the state of your program, then continues to execute,
20942 retrieving and transmitting any information @value{GDBN} needs, until you
20943 execute a @value{GDBN} command that makes your program resume; at that point,
20944 @code{handle_exception} returns control to your own code on the target
20948 @cindex @code{breakpoint} subroutine, remote
20949 Use this auxiliary subroutine to make your program contain a
20950 breakpoint. Depending on the particular situation, this may be the only
20951 way for @value{GDBN} to get control. For instance, if your target
20952 machine has some sort of interrupt button, you won't need to call this;
20953 pressing the interrupt button transfers control to
20954 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20955 simply receiving characters on the serial port may also trigger a trap;
20956 again, in that situation, you don't need to call @code{breakpoint} from
20957 your own program---simply running @samp{target remote} from the host
20958 @value{GDBN} session gets control.
20960 Call @code{breakpoint} if none of these is true, or if you simply want
20961 to make certain your program stops at a predetermined point for the
20962 start of your debugging session.
20965 @node Bootstrapping
20966 @subsection What You Must Do for the Stub
20968 @cindex remote stub, support routines
20969 The debugging stubs that come with @value{GDBN} are set up for a particular
20970 chip architecture, but they have no information about the rest of your
20971 debugging target machine.
20973 First of all you need to tell the stub how to communicate with the
20977 @item int getDebugChar()
20978 @findex getDebugChar
20979 Write this subroutine to read a single character from the serial port.
20980 It may be identical to @code{getchar} for your target system; a
20981 different name is used to allow you to distinguish the two if you wish.
20983 @item void putDebugChar(int)
20984 @findex putDebugChar
20985 Write this subroutine to write a single character to the serial port.
20986 It may be identical to @code{putchar} for your target system; a
20987 different name is used to allow you to distinguish the two if you wish.
20990 @cindex control C, and remote debugging
20991 @cindex interrupting remote targets
20992 If you want @value{GDBN} to be able to stop your program while it is
20993 running, you need to use an interrupt-driven serial driver, and arrange
20994 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20995 character). That is the character which @value{GDBN} uses to tell the
20996 remote system to stop.
20998 Getting the debugging target to return the proper status to @value{GDBN}
20999 probably requires changes to the standard stub; one quick and dirty way
21000 is to just execute a breakpoint instruction (the ``dirty'' part is that
21001 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21003 Other routines you need to supply are:
21006 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21007 @findex exceptionHandler
21008 Write this function to install @var{exception_address} in the exception
21009 handling tables. You need to do this because the stub does not have any
21010 way of knowing what the exception handling tables on your target system
21011 are like (for example, the processor's table might be in @sc{rom},
21012 containing entries which point to a table in @sc{ram}).
21013 The @var{exception_number} specifies the exception which should be changed;
21014 its meaning is architecture-dependent (for example, different numbers
21015 might represent divide by zero, misaligned access, etc). When this
21016 exception occurs, control should be transferred directly to
21017 @var{exception_address}, and the processor state (stack, registers,
21018 and so on) should be just as it is when a processor exception occurs. So if
21019 you want to use a jump instruction to reach @var{exception_address}, it
21020 should be a simple jump, not a jump to subroutine.
21022 For the 386, @var{exception_address} should be installed as an interrupt
21023 gate so that interrupts are masked while the handler runs. The gate
21024 should be at privilege level 0 (the most privileged level). The
21025 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21026 help from @code{exceptionHandler}.
21028 @item void flush_i_cache()
21029 @findex flush_i_cache
21030 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21031 instruction cache, if any, on your target machine. If there is no
21032 instruction cache, this subroutine may be a no-op.
21034 On target machines that have instruction caches, @value{GDBN} requires this
21035 function to make certain that the state of your program is stable.
21039 You must also make sure this library routine is available:
21042 @item void *memset(void *, int, int)
21044 This is the standard library function @code{memset} that sets an area of
21045 memory to a known value. If you have one of the free versions of
21046 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21047 either obtain it from your hardware manufacturer, or write your own.
21050 If you do not use the GNU C compiler, you may need other standard
21051 library subroutines as well; this varies from one stub to another,
21052 but in general the stubs are likely to use any of the common library
21053 subroutines which @code{@value{NGCC}} generates as inline code.
21056 @node Debug Session
21057 @subsection Putting it All Together
21059 @cindex remote serial debugging summary
21060 In summary, when your program is ready to debug, you must follow these
21065 Make sure you have defined the supporting low-level routines
21066 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21068 @code{getDebugChar}, @code{putDebugChar},
21069 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21073 Insert these lines in your program's startup code, before the main
21074 procedure is called:
21081 On some machines, when a breakpoint trap is raised, the hardware
21082 automatically makes the PC point to the instruction after the
21083 breakpoint. If your machine doesn't do that, you may need to adjust
21084 @code{handle_exception} to arrange for it to return to the instruction
21085 after the breakpoint on this first invocation, so that your program
21086 doesn't keep hitting the initial breakpoint instead of making
21090 For the 680x0 stub only, you need to provide a variable called
21091 @code{exceptionHook}. Normally you just use:
21094 void (*exceptionHook)() = 0;
21098 but if before calling @code{set_debug_traps}, you set it to point to a
21099 function in your program, that function is called when
21100 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21101 error). The function indicated by @code{exceptionHook} is called with
21102 one parameter: an @code{int} which is the exception number.
21105 Compile and link together: your program, the @value{GDBN} debugging stub for
21106 your target architecture, and the supporting subroutines.
21109 Make sure you have a serial connection between your target machine and
21110 the @value{GDBN} host, and identify the serial port on the host.
21113 @c The "remote" target now provides a `load' command, so we should
21114 @c document that. FIXME.
21115 Download your program to your target machine (or get it there by
21116 whatever means the manufacturer provides), and start it.
21119 Start @value{GDBN} on the host, and connect to the target
21120 (@pxref{Connecting,,Connecting to a Remote Target}).
21124 @node Configurations
21125 @chapter Configuration-Specific Information
21127 While nearly all @value{GDBN} commands are available for all native and
21128 cross versions of the debugger, there are some exceptions. This chapter
21129 describes things that are only available in certain configurations.
21131 There are three major categories of configurations: native
21132 configurations, where the host and target are the same, embedded
21133 operating system configurations, which are usually the same for several
21134 different processor architectures, and bare embedded processors, which
21135 are quite different from each other.
21140 * Embedded Processors::
21147 This section describes details specific to particular native
21151 * BSD libkvm Interface:: Debugging BSD kernel memory images
21152 * SVR4 Process Information:: SVR4 process information
21153 * DJGPP Native:: Features specific to the DJGPP port
21154 * Cygwin Native:: Features specific to the Cygwin port
21155 * Hurd Native:: Features specific to @sc{gnu} Hurd
21156 * Darwin:: Features specific to Darwin
21159 @node BSD libkvm Interface
21160 @subsection BSD libkvm Interface
21163 @cindex kernel memory image
21164 @cindex kernel crash dump
21166 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21167 interface that provides a uniform interface for accessing kernel virtual
21168 memory images, including live systems and crash dumps. @value{GDBN}
21169 uses this interface to allow you to debug live kernels and kernel crash
21170 dumps on many native BSD configurations. This is implemented as a
21171 special @code{kvm} debugging target. For debugging a live system, load
21172 the currently running kernel into @value{GDBN} and connect to the
21176 (@value{GDBP}) @b{target kvm}
21179 For debugging crash dumps, provide the file name of the crash dump as an
21183 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21186 Once connected to the @code{kvm} target, the following commands are
21192 Set current context from the @dfn{Process Control Block} (PCB) address.
21195 Set current context from proc address. This command isn't available on
21196 modern FreeBSD systems.
21199 @node SVR4 Process Information
21200 @subsection SVR4 Process Information
21202 @cindex examine process image
21203 @cindex process info via @file{/proc}
21205 Many versions of SVR4 and compatible systems provide a facility called
21206 @samp{/proc} that can be used to examine the image of a running
21207 process using file-system subroutines.
21209 If @value{GDBN} is configured for an operating system with this
21210 facility, the command @code{info proc} is available to report
21211 information about the process running your program, or about any
21212 process running on your system. This includes, as of this writing,
21213 @sc{gnu}/Linux and Solaris, for example.
21215 This command may also work on core files that were created on a system
21216 that has the @samp{/proc} facility.
21222 @itemx info proc @var{process-id}
21223 Summarize available information about any running process. If a
21224 process ID is specified by @var{process-id}, display information about
21225 that process; otherwise display information about the program being
21226 debugged. The summary includes the debugged process ID, the command
21227 line used to invoke it, its current working directory, and its
21228 executable file's absolute file name.
21230 On some systems, @var{process-id} can be of the form
21231 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21232 within a process. If the optional @var{pid} part is missing, it means
21233 a thread from the process being debugged (the leading @samp{/} still
21234 needs to be present, or else @value{GDBN} will interpret the number as
21235 a process ID rather than a thread ID).
21237 @item info proc cmdline
21238 @cindex info proc cmdline
21239 Show the original command line of the process. This command is
21240 specific to @sc{gnu}/Linux.
21242 @item info proc cwd
21243 @cindex info proc cwd
21244 Show the current working directory of the process. This command is
21245 specific to @sc{gnu}/Linux.
21247 @item info proc exe
21248 @cindex info proc exe
21249 Show the name of executable of the process. This command is specific
21252 @item info proc mappings
21253 @cindex memory address space mappings
21254 Report the memory address space ranges accessible in the program, with
21255 information on whether the process has read, write, or execute access
21256 rights to each range. On @sc{gnu}/Linux systems, each memory range
21257 includes the object file which is mapped to that range, instead of the
21258 memory access rights to that range.
21260 @item info proc stat
21261 @itemx info proc status
21262 @cindex process detailed status information
21263 These subcommands are specific to @sc{gnu}/Linux systems. They show
21264 the process-related information, including the user ID and group ID;
21265 how many threads are there in the process; its virtual memory usage;
21266 the signals that are pending, blocked, and ignored; its TTY; its
21267 consumption of system and user time; its stack size; its @samp{nice}
21268 value; etc. For more information, see the @samp{proc} man page
21269 (type @kbd{man 5 proc} from your shell prompt).
21271 @item info proc all
21272 Show all the information about the process described under all of the
21273 above @code{info proc} subcommands.
21276 @comment These sub-options of 'info proc' were not included when
21277 @comment procfs.c was re-written. Keep their descriptions around
21278 @comment against the day when someone finds the time to put them back in.
21279 @kindex info proc times
21280 @item info proc times
21281 Starting time, user CPU time, and system CPU time for your program and
21284 @kindex info proc id
21286 Report on the process IDs related to your program: its own process ID,
21287 the ID of its parent, the process group ID, and the session ID.
21290 @item set procfs-trace
21291 @kindex set procfs-trace
21292 @cindex @code{procfs} API calls
21293 This command enables and disables tracing of @code{procfs} API calls.
21295 @item show procfs-trace
21296 @kindex show procfs-trace
21297 Show the current state of @code{procfs} API call tracing.
21299 @item set procfs-file @var{file}
21300 @kindex set procfs-file
21301 Tell @value{GDBN} to write @code{procfs} API trace to the named
21302 @var{file}. @value{GDBN} appends the trace info to the previous
21303 contents of the file. The default is to display the trace on the
21306 @item show procfs-file
21307 @kindex show procfs-file
21308 Show the file to which @code{procfs} API trace is written.
21310 @item proc-trace-entry
21311 @itemx proc-trace-exit
21312 @itemx proc-untrace-entry
21313 @itemx proc-untrace-exit
21314 @kindex proc-trace-entry
21315 @kindex proc-trace-exit
21316 @kindex proc-untrace-entry
21317 @kindex proc-untrace-exit
21318 These commands enable and disable tracing of entries into and exits
21319 from the @code{syscall} interface.
21322 @kindex info pidlist
21323 @cindex process list, QNX Neutrino
21324 For QNX Neutrino only, this command displays the list of all the
21325 processes and all the threads within each process.
21328 @kindex info meminfo
21329 @cindex mapinfo list, QNX Neutrino
21330 For QNX Neutrino only, this command displays the list of all mapinfos.
21334 @subsection Features for Debugging @sc{djgpp} Programs
21335 @cindex @sc{djgpp} debugging
21336 @cindex native @sc{djgpp} debugging
21337 @cindex MS-DOS-specific commands
21340 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21341 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21342 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21343 top of real-mode DOS systems and their emulations.
21345 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21346 defines a few commands specific to the @sc{djgpp} port. This
21347 subsection describes those commands.
21352 This is a prefix of @sc{djgpp}-specific commands which print
21353 information about the target system and important OS structures.
21356 @cindex MS-DOS system info
21357 @cindex free memory information (MS-DOS)
21358 @item info dos sysinfo
21359 This command displays assorted information about the underlying
21360 platform: the CPU type and features, the OS version and flavor, the
21361 DPMI version, and the available conventional and DPMI memory.
21366 @cindex segment descriptor tables
21367 @cindex descriptor tables display
21369 @itemx info dos ldt
21370 @itemx info dos idt
21371 These 3 commands display entries from, respectively, Global, Local,
21372 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21373 tables are data structures which store a descriptor for each segment
21374 that is currently in use. The segment's selector is an index into a
21375 descriptor table; the table entry for that index holds the
21376 descriptor's base address and limit, and its attributes and access
21379 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21380 segment (used for both data and the stack), and a DOS segment (which
21381 allows access to DOS/BIOS data structures and absolute addresses in
21382 conventional memory). However, the DPMI host will usually define
21383 additional segments in order to support the DPMI environment.
21385 @cindex garbled pointers
21386 These commands allow to display entries from the descriptor tables.
21387 Without an argument, all entries from the specified table are
21388 displayed. An argument, which should be an integer expression, means
21389 display a single entry whose index is given by the argument. For
21390 example, here's a convenient way to display information about the
21391 debugged program's data segment:
21394 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21395 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21399 This comes in handy when you want to see whether a pointer is outside
21400 the data segment's limit (i.e.@: @dfn{garbled}).
21402 @cindex page tables display (MS-DOS)
21404 @itemx info dos pte
21405 These two commands display entries from, respectively, the Page
21406 Directory and the Page Tables. Page Directories and Page Tables are
21407 data structures which control how virtual memory addresses are mapped
21408 into physical addresses. A Page Table includes an entry for every
21409 page of memory that is mapped into the program's address space; there
21410 may be several Page Tables, each one holding up to 4096 entries. A
21411 Page Directory has up to 4096 entries, one each for every Page Table
21412 that is currently in use.
21414 Without an argument, @kbd{info dos pde} displays the entire Page
21415 Directory, and @kbd{info dos pte} displays all the entries in all of
21416 the Page Tables. An argument, an integer expression, given to the
21417 @kbd{info dos pde} command means display only that entry from the Page
21418 Directory table. An argument given to the @kbd{info dos pte} command
21419 means display entries from a single Page Table, the one pointed to by
21420 the specified entry in the Page Directory.
21422 @cindex direct memory access (DMA) on MS-DOS
21423 These commands are useful when your program uses @dfn{DMA} (Direct
21424 Memory Access), which needs physical addresses to program the DMA
21427 These commands are supported only with some DPMI servers.
21429 @cindex physical address from linear address
21430 @item info dos address-pte @var{addr}
21431 This command displays the Page Table entry for a specified linear
21432 address. The argument @var{addr} is a linear address which should
21433 already have the appropriate segment's base address added to it,
21434 because this command accepts addresses which may belong to @emph{any}
21435 segment. For example, here's how to display the Page Table entry for
21436 the page where a variable @code{i} is stored:
21439 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21440 @exdent @code{Page Table entry for address 0x11a00d30:}
21441 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21445 This says that @code{i} is stored at offset @code{0xd30} from the page
21446 whose physical base address is @code{0x02698000}, and shows all the
21447 attributes of that page.
21449 Note that you must cast the addresses of variables to a @code{char *},
21450 since otherwise the value of @code{__djgpp_base_address}, the base
21451 address of all variables and functions in a @sc{djgpp} program, will
21452 be added using the rules of C pointer arithmetics: if @code{i} is
21453 declared an @code{int}, @value{GDBN} will add 4 times the value of
21454 @code{__djgpp_base_address} to the address of @code{i}.
21456 Here's another example, it displays the Page Table entry for the
21460 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21461 @exdent @code{Page Table entry for address 0x29110:}
21462 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21466 (The @code{+ 3} offset is because the transfer buffer's address is the
21467 3rd member of the @code{_go32_info_block} structure.) The output
21468 clearly shows that this DPMI server maps the addresses in conventional
21469 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21470 linear (@code{0x29110}) addresses are identical.
21472 This command is supported only with some DPMI servers.
21475 @cindex DOS serial data link, remote debugging
21476 In addition to native debugging, the DJGPP port supports remote
21477 debugging via a serial data link. The following commands are specific
21478 to remote serial debugging in the DJGPP port of @value{GDBN}.
21481 @kindex set com1base
21482 @kindex set com1irq
21483 @kindex set com2base
21484 @kindex set com2irq
21485 @kindex set com3base
21486 @kindex set com3irq
21487 @kindex set com4base
21488 @kindex set com4irq
21489 @item set com1base @var{addr}
21490 This command sets the base I/O port address of the @file{COM1} serial
21493 @item set com1irq @var{irq}
21494 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21495 for the @file{COM1} serial port.
21497 There are similar commands @samp{set com2base}, @samp{set com3irq},
21498 etc.@: for setting the port address and the @code{IRQ} lines for the
21501 @kindex show com1base
21502 @kindex show com1irq
21503 @kindex show com2base
21504 @kindex show com2irq
21505 @kindex show com3base
21506 @kindex show com3irq
21507 @kindex show com4base
21508 @kindex show com4irq
21509 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21510 display the current settings of the base address and the @code{IRQ}
21511 lines used by the COM ports.
21514 @kindex info serial
21515 @cindex DOS serial port status
21516 This command prints the status of the 4 DOS serial ports. For each
21517 port, it prints whether it's active or not, its I/O base address and
21518 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21519 counts of various errors encountered so far.
21523 @node Cygwin Native
21524 @subsection Features for Debugging MS Windows PE Executables
21525 @cindex MS Windows debugging
21526 @cindex native Cygwin debugging
21527 @cindex Cygwin-specific commands
21529 @value{GDBN} supports native debugging of MS Windows programs, including
21530 DLLs with and without symbolic debugging information.
21532 @cindex Ctrl-BREAK, MS-Windows
21533 @cindex interrupt debuggee on MS-Windows
21534 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21535 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21536 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21537 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21538 sequence, which can be used to interrupt the debuggee even if it
21541 There are various additional Cygwin-specific commands, described in
21542 this section. Working with DLLs that have no debugging symbols is
21543 described in @ref{Non-debug DLL Symbols}.
21548 This is a prefix of MS Windows-specific commands which print
21549 information about the target system and important OS structures.
21551 @item info w32 selector
21552 This command displays information returned by
21553 the Win32 API @code{GetThreadSelectorEntry} function.
21554 It takes an optional argument that is evaluated to
21555 a long value to give the information about this given selector.
21556 Without argument, this command displays information
21557 about the six segment registers.
21559 @item info w32 thread-information-block
21560 This command displays thread specific information stored in the
21561 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21562 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21564 @kindex signal-event
21565 @item signal-event @var{id}
21566 This command signals an event with user-provided @var{id}. Used to resume
21567 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21569 To use it, create or edit the following keys in
21570 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21571 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21572 (for x86_64 versions):
21576 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21577 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21578 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21580 The first @code{%ld} will be replaced by the process ID of the
21581 crashing process, the second @code{%ld} will be replaced by the ID of
21582 the event that blocks the crashing process, waiting for @value{GDBN}
21586 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21587 make the system run debugger specified by the Debugger key
21588 automatically, @code{0} will cause a dialog box with ``OK'' and
21589 ``Cancel'' buttons to appear, which allows the user to either
21590 terminate the crashing process (OK) or debug it (Cancel).
21593 @kindex set cygwin-exceptions
21594 @cindex debugging the Cygwin DLL
21595 @cindex Cygwin DLL, debugging
21596 @item set cygwin-exceptions @var{mode}
21597 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21598 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21599 @value{GDBN} will delay recognition of exceptions, and may ignore some
21600 exceptions which seem to be caused by internal Cygwin DLL
21601 ``bookkeeping''. This option is meant primarily for debugging the
21602 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21603 @value{GDBN} users with false @code{SIGSEGV} signals.
21605 @kindex show cygwin-exceptions
21606 @item show cygwin-exceptions
21607 Displays whether @value{GDBN} will break on exceptions that happen
21608 inside the Cygwin DLL itself.
21610 @kindex set new-console
21611 @item set new-console @var{mode}
21612 If @var{mode} is @code{on} the debuggee will
21613 be started in a new console on next start.
21614 If @var{mode} is @code{off}, the debuggee will
21615 be started in the same console as the debugger.
21617 @kindex show new-console
21618 @item show new-console
21619 Displays whether a new console is used
21620 when the debuggee is started.
21622 @kindex set new-group
21623 @item set new-group @var{mode}
21624 This boolean value controls whether the debuggee should
21625 start a new group or stay in the same group as the debugger.
21626 This affects the way the Windows OS handles
21629 @kindex show new-group
21630 @item show new-group
21631 Displays current value of new-group boolean.
21633 @kindex set debugevents
21634 @item set debugevents
21635 This boolean value adds debug output concerning kernel events related
21636 to the debuggee seen by the debugger. This includes events that
21637 signal thread and process creation and exit, DLL loading and
21638 unloading, console interrupts, and debugging messages produced by the
21639 Windows @code{OutputDebugString} API call.
21641 @kindex set debugexec
21642 @item set debugexec
21643 This boolean value adds debug output concerning execute events
21644 (such as resume thread) seen by the debugger.
21646 @kindex set debugexceptions
21647 @item set debugexceptions
21648 This boolean value adds debug output concerning exceptions in the
21649 debuggee seen by the debugger.
21651 @kindex set debugmemory
21652 @item set debugmemory
21653 This boolean value adds debug output concerning debuggee memory reads
21654 and writes by the debugger.
21658 This boolean values specifies whether the debuggee is called
21659 via a shell or directly (default value is on).
21663 Displays if the debuggee will be started with a shell.
21668 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21671 @node Non-debug DLL Symbols
21672 @subsubsection Support for DLLs without Debugging Symbols
21673 @cindex DLLs with no debugging symbols
21674 @cindex Minimal symbols and DLLs
21676 Very often on windows, some of the DLLs that your program relies on do
21677 not include symbolic debugging information (for example,
21678 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21679 symbols in a DLL, it relies on the minimal amount of symbolic
21680 information contained in the DLL's export table. This section
21681 describes working with such symbols, known internally to @value{GDBN} as
21682 ``minimal symbols''.
21684 Note that before the debugged program has started execution, no DLLs
21685 will have been loaded. The easiest way around this problem is simply to
21686 start the program --- either by setting a breakpoint or letting the
21687 program run once to completion.
21689 @subsubsection DLL Name Prefixes
21691 In keeping with the naming conventions used by the Microsoft debugging
21692 tools, DLL export symbols are made available with a prefix based on the
21693 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21694 also entered into the symbol table, so @code{CreateFileA} is often
21695 sufficient. In some cases there will be name clashes within a program
21696 (particularly if the executable itself includes full debugging symbols)
21697 necessitating the use of the fully qualified name when referring to the
21698 contents of the DLL. Use single-quotes around the name to avoid the
21699 exclamation mark (``!'') being interpreted as a language operator.
21701 Note that the internal name of the DLL may be all upper-case, even
21702 though the file name of the DLL is lower-case, or vice-versa. Since
21703 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21704 some confusion. If in doubt, try the @code{info functions} and
21705 @code{info variables} commands or even @code{maint print msymbols}
21706 (@pxref{Symbols}). Here's an example:
21709 (@value{GDBP}) info function CreateFileA
21710 All functions matching regular expression "CreateFileA":
21712 Non-debugging symbols:
21713 0x77e885f4 CreateFileA
21714 0x77e885f4 KERNEL32!CreateFileA
21718 (@value{GDBP}) info function !
21719 All functions matching regular expression "!":
21721 Non-debugging symbols:
21722 0x6100114c cygwin1!__assert
21723 0x61004034 cygwin1!_dll_crt0@@0
21724 0x61004240 cygwin1!dll_crt0(per_process *)
21728 @subsubsection Working with Minimal Symbols
21730 Symbols extracted from a DLL's export table do not contain very much
21731 type information. All that @value{GDBN} can do is guess whether a symbol
21732 refers to a function or variable depending on the linker section that
21733 contains the symbol. Also note that the actual contents of the memory
21734 contained in a DLL are not available unless the program is running. This
21735 means that you cannot examine the contents of a variable or disassemble
21736 a function within a DLL without a running program.
21738 Variables are generally treated as pointers and dereferenced
21739 automatically. For this reason, it is often necessary to prefix a
21740 variable name with the address-of operator (``&'') and provide explicit
21741 type information in the command. Here's an example of the type of
21745 (@value{GDBP}) print 'cygwin1!__argv'
21750 (@value{GDBP}) x 'cygwin1!__argv'
21751 0x10021610: "\230y\""
21754 And two possible solutions:
21757 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21758 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21762 (@value{GDBP}) x/2x &'cygwin1!__argv'
21763 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21764 (@value{GDBP}) x/x 0x10021608
21765 0x10021608: 0x0022fd98
21766 (@value{GDBP}) x/s 0x0022fd98
21767 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21770 Setting a break point within a DLL is possible even before the program
21771 starts execution. However, under these circumstances, @value{GDBN} can't
21772 examine the initial instructions of the function in order to skip the
21773 function's frame set-up code. You can work around this by using ``*&''
21774 to set the breakpoint at a raw memory address:
21777 (@value{GDBP}) break *&'python22!PyOS_Readline'
21778 Breakpoint 1 at 0x1e04eff0
21781 The author of these extensions is not entirely convinced that setting a
21782 break point within a shared DLL like @file{kernel32.dll} is completely
21786 @subsection Commands Specific to @sc{gnu} Hurd Systems
21787 @cindex @sc{gnu} Hurd debugging
21789 This subsection describes @value{GDBN} commands specific to the
21790 @sc{gnu} Hurd native debugging.
21795 @kindex set signals@r{, Hurd command}
21796 @kindex set sigs@r{, Hurd command}
21797 This command toggles the state of inferior signal interception by
21798 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21799 affected by this command. @code{sigs} is a shorthand alias for
21804 @kindex show signals@r{, Hurd command}
21805 @kindex show sigs@r{, Hurd command}
21806 Show the current state of intercepting inferior's signals.
21808 @item set signal-thread
21809 @itemx set sigthread
21810 @kindex set signal-thread
21811 @kindex set sigthread
21812 This command tells @value{GDBN} which thread is the @code{libc} signal
21813 thread. That thread is run when a signal is delivered to a running
21814 process. @code{set sigthread} is the shorthand alias of @code{set
21817 @item show signal-thread
21818 @itemx show sigthread
21819 @kindex show signal-thread
21820 @kindex show sigthread
21821 These two commands show which thread will run when the inferior is
21822 delivered a signal.
21825 @kindex set stopped@r{, Hurd command}
21826 This commands tells @value{GDBN} that the inferior process is stopped,
21827 as with the @code{SIGSTOP} signal. The stopped process can be
21828 continued by delivering a signal to it.
21831 @kindex show stopped@r{, Hurd command}
21832 This command shows whether @value{GDBN} thinks the debuggee is
21835 @item set exceptions
21836 @kindex set exceptions@r{, Hurd command}
21837 Use this command to turn off trapping of exceptions in the inferior.
21838 When exception trapping is off, neither breakpoints nor
21839 single-stepping will work. To restore the default, set exception
21842 @item show exceptions
21843 @kindex show exceptions@r{, Hurd command}
21844 Show the current state of trapping exceptions in the inferior.
21846 @item set task pause
21847 @kindex set task@r{, Hurd commands}
21848 @cindex task attributes (@sc{gnu} Hurd)
21849 @cindex pause current task (@sc{gnu} Hurd)
21850 This command toggles task suspension when @value{GDBN} has control.
21851 Setting it to on takes effect immediately, and the task is suspended
21852 whenever @value{GDBN} gets control. Setting it to off will take
21853 effect the next time the inferior is continued. If this option is set
21854 to off, you can use @code{set thread default pause on} or @code{set
21855 thread pause on} (see below) to pause individual threads.
21857 @item show task pause
21858 @kindex show task@r{, Hurd commands}
21859 Show the current state of task suspension.
21861 @item set task detach-suspend-count
21862 @cindex task suspend count
21863 @cindex detach from task, @sc{gnu} Hurd
21864 This command sets the suspend count the task will be left with when
21865 @value{GDBN} detaches from it.
21867 @item show task detach-suspend-count
21868 Show the suspend count the task will be left with when detaching.
21870 @item set task exception-port
21871 @itemx set task excp
21872 @cindex task exception port, @sc{gnu} Hurd
21873 This command sets the task exception port to which @value{GDBN} will
21874 forward exceptions. The argument should be the value of the @dfn{send
21875 rights} of the task. @code{set task excp} is a shorthand alias.
21877 @item set noninvasive
21878 @cindex noninvasive task options
21879 This command switches @value{GDBN} to a mode that is the least
21880 invasive as far as interfering with the inferior is concerned. This
21881 is the same as using @code{set task pause}, @code{set exceptions}, and
21882 @code{set signals} to values opposite to the defaults.
21884 @item info send-rights
21885 @itemx info receive-rights
21886 @itemx info port-rights
21887 @itemx info port-sets
21888 @itemx info dead-names
21891 @cindex send rights, @sc{gnu} Hurd
21892 @cindex receive rights, @sc{gnu} Hurd
21893 @cindex port rights, @sc{gnu} Hurd
21894 @cindex port sets, @sc{gnu} Hurd
21895 @cindex dead names, @sc{gnu} Hurd
21896 These commands display information about, respectively, send rights,
21897 receive rights, port rights, port sets, and dead names of a task.
21898 There are also shorthand aliases: @code{info ports} for @code{info
21899 port-rights} and @code{info psets} for @code{info port-sets}.
21901 @item set thread pause
21902 @kindex set thread@r{, Hurd command}
21903 @cindex thread properties, @sc{gnu} Hurd
21904 @cindex pause current thread (@sc{gnu} Hurd)
21905 This command toggles current thread suspension when @value{GDBN} has
21906 control. Setting it to on takes effect immediately, and the current
21907 thread is suspended whenever @value{GDBN} gets control. Setting it to
21908 off will take effect the next time the inferior is continued.
21909 Normally, this command has no effect, since when @value{GDBN} has
21910 control, the whole task is suspended. However, if you used @code{set
21911 task pause off} (see above), this command comes in handy to suspend
21912 only the current thread.
21914 @item show thread pause
21915 @kindex show thread@r{, Hurd command}
21916 This command shows the state of current thread suspension.
21918 @item set thread run
21919 This command sets whether the current thread is allowed to run.
21921 @item show thread run
21922 Show whether the current thread is allowed to run.
21924 @item set thread detach-suspend-count
21925 @cindex thread suspend count, @sc{gnu} Hurd
21926 @cindex detach from thread, @sc{gnu} Hurd
21927 This command sets the suspend count @value{GDBN} will leave on a
21928 thread when detaching. This number is relative to the suspend count
21929 found by @value{GDBN} when it notices the thread; use @code{set thread
21930 takeover-suspend-count} to force it to an absolute value.
21932 @item show thread detach-suspend-count
21933 Show the suspend count @value{GDBN} will leave on the thread when
21936 @item set thread exception-port
21937 @itemx set thread excp
21938 Set the thread exception port to which to forward exceptions. This
21939 overrides the port set by @code{set task exception-port} (see above).
21940 @code{set thread excp} is the shorthand alias.
21942 @item set thread takeover-suspend-count
21943 Normally, @value{GDBN}'s thread suspend counts are relative to the
21944 value @value{GDBN} finds when it notices each thread. This command
21945 changes the suspend counts to be absolute instead.
21947 @item set thread default
21948 @itemx show thread default
21949 @cindex thread default settings, @sc{gnu} Hurd
21950 Each of the above @code{set thread} commands has a @code{set thread
21951 default} counterpart (e.g., @code{set thread default pause}, @code{set
21952 thread default exception-port}, etc.). The @code{thread default}
21953 variety of commands sets the default thread properties for all
21954 threads; you can then change the properties of individual threads with
21955 the non-default commands.
21962 @value{GDBN} provides the following commands specific to the Darwin target:
21965 @item set debug darwin @var{num}
21966 @kindex set debug darwin
21967 When set to a non zero value, enables debugging messages specific to
21968 the Darwin support. Higher values produce more verbose output.
21970 @item show debug darwin
21971 @kindex show debug darwin
21972 Show the current state of Darwin messages.
21974 @item set debug mach-o @var{num}
21975 @kindex set debug mach-o
21976 When set to a non zero value, enables debugging messages while
21977 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21978 file format used on Darwin for object and executable files.) Higher
21979 values produce more verbose output. This is a command to diagnose
21980 problems internal to @value{GDBN} and should not be needed in normal
21983 @item show debug mach-o
21984 @kindex show debug mach-o
21985 Show the current state of Mach-O file messages.
21987 @item set mach-exceptions on
21988 @itemx set mach-exceptions off
21989 @kindex set mach-exceptions
21990 On Darwin, faults are first reported as a Mach exception and are then
21991 mapped to a Posix signal. Use this command to turn on trapping of
21992 Mach exceptions in the inferior. This might be sometimes useful to
21993 better understand the cause of a fault. The default is off.
21995 @item show mach-exceptions
21996 @kindex show mach-exceptions
21997 Show the current state of exceptions trapping.
22002 @section Embedded Operating Systems
22004 This section describes configurations involving the debugging of
22005 embedded operating systems that are available for several different
22008 @value{GDBN} includes the ability to debug programs running on
22009 various real-time operating systems.
22011 @node Embedded Processors
22012 @section Embedded Processors
22014 This section goes into details specific to particular embedded
22017 @cindex send command to simulator
22018 Whenever a specific embedded processor has a simulator, @value{GDBN}
22019 allows to send an arbitrary command to the simulator.
22022 @item sim @var{command}
22023 @kindex sim@r{, a command}
22024 Send an arbitrary @var{command} string to the simulator. Consult the
22025 documentation for the specific simulator in use for information about
22026 acceptable commands.
22031 * ARC:: Synopsys ARC
22033 * M68K:: Motorola M68K
22034 * MicroBlaze:: Xilinx MicroBlaze
22035 * MIPS Embedded:: MIPS Embedded
22036 * PowerPC Embedded:: PowerPC Embedded
22039 * Super-H:: Renesas Super-H
22043 @subsection Synopsys ARC
22044 @cindex Synopsys ARC
22045 @cindex ARC specific commands
22051 @value{GDBN} provides the following ARC-specific commands:
22054 @item set debug arc
22055 @kindex set debug arc
22056 Control the level of ARC specific debug messages. Use 0 for no messages (the
22057 default) and 1 for debug messages. At present higher values offer no further
22060 @item show debug arc
22061 @kindex show debug arc
22062 Show the level of ARC specific debugging in operation.
22069 @value{GDBN} provides the following ARM-specific commands:
22072 @item set arm disassembler
22074 This commands selects from a list of disassembly styles. The
22075 @code{"std"} style is the standard style.
22077 @item show arm disassembler
22079 Show the current disassembly style.
22081 @item set arm apcs32
22082 @cindex ARM 32-bit mode
22083 This command toggles ARM operation mode between 32-bit and 26-bit.
22085 @item show arm apcs32
22086 Display the current usage of the ARM 32-bit mode.
22088 @item set arm fpu @var{fputype}
22089 This command sets the ARM floating-point unit (FPU) type. The
22090 argument @var{fputype} can be one of these:
22094 Determine the FPU type by querying the OS ABI.
22096 Software FPU, with mixed-endian doubles on little-endian ARM
22099 GCC-compiled FPA co-processor.
22101 Software FPU with pure-endian doubles.
22107 Show the current type of the FPU.
22110 This command forces @value{GDBN} to use the specified ABI.
22113 Show the currently used ABI.
22115 @item set arm fallback-mode (arm|thumb|auto)
22116 @value{GDBN} uses the symbol table, when available, to determine
22117 whether instructions are ARM or Thumb. This command controls
22118 @value{GDBN}'s default behavior when the symbol table is not
22119 available. The default is @samp{auto}, which causes @value{GDBN} to
22120 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22123 @item show arm fallback-mode
22124 Show the current fallback instruction mode.
22126 @item set arm force-mode (arm|thumb|auto)
22127 This command overrides use of the symbol table to determine whether
22128 instructions are ARM or Thumb. The default is @samp{auto}, which
22129 causes @value{GDBN} to use the symbol table and then the setting
22130 of @samp{set arm fallback-mode}.
22132 @item show arm force-mode
22133 Show the current forced instruction mode.
22135 @item set debug arm
22136 Toggle whether to display ARM-specific debugging messages from the ARM
22137 target support subsystem.
22139 @item show debug arm
22140 Show whether ARM-specific debugging messages are enabled.
22144 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22145 The @value{GDBN} ARM simulator accepts the following optional arguments.
22148 @item --swi-support=@var{type}
22149 Tell the simulator which SWI interfaces to support. The argument
22150 @var{type} may be a comma separated list of the following values.
22151 The default value is @code{all}.
22166 The Motorola m68k configuration includes ColdFire support.
22169 @subsection MicroBlaze
22170 @cindex Xilinx MicroBlaze
22171 @cindex XMD, Xilinx Microprocessor Debugger
22173 The MicroBlaze is a soft-core processor supported on various Xilinx
22174 FPGAs, such as Spartan or Virtex series. Boards with these processors
22175 usually have JTAG ports which connect to a host system running the Xilinx
22176 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22177 This host system is used to download the configuration bitstream to
22178 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22179 communicates with the target board using the JTAG interface and
22180 presents a @code{gdbserver} interface to the board. By default
22181 @code{xmd} uses port @code{1234}. (While it is possible to change
22182 this default port, it requires the use of undocumented @code{xmd}
22183 commands. Contact Xilinx support if you need to do this.)
22185 Use these GDB commands to connect to the MicroBlaze target processor.
22188 @item target remote :1234
22189 Use this command to connect to the target if you are running @value{GDBN}
22190 on the same system as @code{xmd}.
22192 @item target remote @var{xmd-host}:1234
22193 Use this command to connect to the target if it is connected to @code{xmd}
22194 running on a different system named @var{xmd-host}.
22197 Use this command to download a program to the MicroBlaze target.
22199 @item set debug microblaze @var{n}
22200 Enable MicroBlaze-specific debugging messages if non-zero.
22202 @item show debug microblaze @var{n}
22203 Show MicroBlaze-specific debugging level.
22206 @node MIPS Embedded
22207 @subsection @acronym{MIPS} Embedded
22210 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22213 @item set mipsfpu double
22214 @itemx set mipsfpu single
22215 @itemx set mipsfpu none
22216 @itemx set mipsfpu auto
22217 @itemx show mipsfpu
22218 @kindex set mipsfpu
22219 @kindex show mipsfpu
22220 @cindex @acronym{MIPS} remote floating point
22221 @cindex floating point, @acronym{MIPS} remote
22222 If your target board does not support the @acronym{MIPS} floating point
22223 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22224 need this, you may wish to put the command in your @value{GDBN} init
22225 file). This tells @value{GDBN} how to find the return value of
22226 functions which return floating point values. It also allows
22227 @value{GDBN} to avoid saving the floating point registers when calling
22228 functions on the board. If you are using a floating point coprocessor
22229 with only single precision floating point support, as on the @sc{r4650}
22230 processor, use the command @samp{set mipsfpu single}. The default
22231 double precision floating point coprocessor may be selected using
22232 @samp{set mipsfpu double}.
22234 In previous versions the only choices were double precision or no
22235 floating point, so @samp{set mipsfpu on} will select double precision
22236 and @samp{set mipsfpu off} will select no floating point.
22238 As usual, you can inquire about the @code{mipsfpu} variable with
22239 @samp{show mipsfpu}.
22242 @node PowerPC Embedded
22243 @subsection PowerPC Embedded
22245 @cindex DVC register
22246 @value{GDBN} supports using the DVC (Data Value Compare) register to
22247 implement in hardware simple hardware watchpoint conditions of the form:
22250 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22251 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22254 The DVC register will be automatically used when @value{GDBN} detects
22255 such pattern in a condition expression, and the created watchpoint uses one
22256 debug register (either the @code{exact-watchpoints} option is on and the
22257 variable is scalar, or the variable has a length of one byte). This feature
22258 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22261 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22262 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22263 in which case watchpoints using only one debug register are created when
22264 watching variables of scalar types.
22266 You can create an artificial array to watch an arbitrary memory
22267 region using one of the following commands (@pxref{Expressions}):
22270 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22271 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22274 PowerPC embedded processors support masked watchpoints. See the discussion
22275 about the @code{mask} argument in @ref{Set Watchpoints}.
22277 @cindex ranged breakpoint
22278 PowerPC embedded processors support hardware accelerated
22279 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22280 the inferior whenever it executes an instruction at any address within
22281 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22282 use the @code{break-range} command.
22284 @value{GDBN} provides the following PowerPC-specific commands:
22287 @kindex break-range
22288 @item break-range @var{start-location}, @var{end-location}
22289 Set a breakpoint for an address range given by
22290 @var{start-location} and @var{end-location}, which can specify a function name,
22291 a line number, an offset of lines from the current line or from the start
22292 location, or an address of an instruction (see @ref{Specify Location},
22293 for a list of all the possible ways to specify a @var{location}.)
22294 The breakpoint will stop execution of the inferior whenever it
22295 executes an instruction at any address within the specified range,
22296 (including @var{start-location} and @var{end-location}.)
22298 @kindex set powerpc
22299 @item set powerpc soft-float
22300 @itemx show powerpc soft-float
22301 Force @value{GDBN} to use (or not use) a software floating point calling
22302 convention. By default, @value{GDBN} selects the calling convention based
22303 on the selected architecture and the provided executable file.
22305 @item set powerpc vector-abi
22306 @itemx show powerpc vector-abi
22307 Force @value{GDBN} to use the specified calling convention for vector
22308 arguments and return values. The valid options are @samp{auto};
22309 @samp{generic}, to avoid vector registers even if they are present;
22310 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22311 registers. By default, @value{GDBN} selects the calling convention
22312 based on the selected architecture and the provided executable file.
22314 @item set powerpc exact-watchpoints
22315 @itemx show powerpc exact-watchpoints
22316 Allow @value{GDBN} to use only one debug register when watching a variable
22317 of scalar type, thus assuming that the variable is accessed through the
22318 address of its first byte.
22323 @subsection Atmel AVR
22326 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22327 following AVR-specific commands:
22330 @item info io_registers
22331 @kindex info io_registers@r{, AVR}
22332 @cindex I/O registers (Atmel AVR)
22333 This command displays information about the AVR I/O registers. For
22334 each register, @value{GDBN} prints its number and value.
22341 When configured for debugging CRIS, @value{GDBN} provides the
22342 following CRIS-specific commands:
22345 @item set cris-version @var{ver}
22346 @cindex CRIS version
22347 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22348 The CRIS version affects register names and sizes. This command is useful in
22349 case autodetection of the CRIS version fails.
22351 @item show cris-version
22352 Show the current CRIS version.
22354 @item set cris-dwarf2-cfi
22355 @cindex DWARF-2 CFI and CRIS
22356 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22357 Change to @samp{off} when using @code{gcc-cris} whose version is below
22360 @item show cris-dwarf2-cfi
22361 Show the current state of using DWARF-2 CFI.
22363 @item set cris-mode @var{mode}
22365 Set the current CRIS mode to @var{mode}. It should only be changed when
22366 debugging in guru mode, in which case it should be set to
22367 @samp{guru} (the default is @samp{normal}).
22369 @item show cris-mode
22370 Show the current CRIS mode.
22374 @subsection Renesas Super-H
22377 For the Renesas Super-H processor, @value{GDBN} provides these
22381 @item set sh calling-convention @var{convention}
22382 @kindex set sh calling-convention
22383 Set the calling-convention used when calling functions from @value{GDBN}.
22384 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22385 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22386 convention. If the DWARF-2 information of the called function specifies
22387 that the function follows the Renesas calling convention, the function
22388 is called using the Renesas calling convention. If the calling convention
22389 is set to @samp{renesas}, the Renesas calling convention is always used,
22390 regardless of the DWARF-2 information. This can be used to override the
22391 default of @samp{gcc} if debug information is missing, or the compiler
22392 does not emit the DWARF-2 calling convention entry for a function.
22394 @item show sh calling-convention
22395 @kindex show sh calling-convention
22396 Show the current calling convention setting.
22401 @node Architectures
22402 @section Architectures
22404 This section describes characteristics of architectures that affect
22405 all uses of @value{GDBN} with the architecture, both native and cross.
22412 * HPPA:: HP PA architecture
22413 * SPU:: Cell Broadband Engine SPU architecture
22419 @subsection AArch64
22420 @cindex AArch64 support
22422 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22423 following special commands:
22426 @item set debug aarch64
22427 @kindex set debug aarch64
22428 This command determines whether AArch64 architecture-specific debugging
22429 messages are to be displayed.
22431 @item show debug aarch64
22432 Show whether AArch64 debugging messages are displayed.
22437 @subsection x86 Architecture-specific Issues
22440 @item set struct-convention @var{mode}
22441 @kindex set struct-convention
22442 @cindex struct return convention
22443 @cindex struct/union returned in registers
22444 Set the convention used by the inferior to return @code{struct}s and
22445 @code{union}s from functions to @var{mode}. Possible values of
22446 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22447 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22448 are returned on the stack, while @code{"reg"} means that a
22449 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22450 be returned in a register.
22452 @item show struct-convention
22453 @kindex show struct-convention
22454 Show the current setting of the convention to return @code{struct}s
22459 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22460 @cindex Intel Memory Protection Extensions (MPX).
22462 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22463 @footnote{The register named with capital letters represent the architecture
22464 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22465 which are the lower bound and upper bound. Bounds are effective addresses or
22466 memory locations. The upper bounds are architecturally represented in 1's
22467 complement form. A bound having lower bound = 0, and upper bound = 0
22468 (1's complement of all bits set) will allow access to the entire address space.
22470 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22471 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22472 display the upper bound performing the complement of one operation on the
22473 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22474 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22475 can also be noted that the upper bounds are inclusive.
22477 As an example, assume that the register BND0 holds bounds for a pointer having
22478 access allowed for the range between 0x32 and 0x71. The values present on
22479 bnd0raw and bnd registers are presented as follows:
22482 bnd0raw = @{0x32, 0xffffffff8e@}
22483 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22486 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22487 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22488 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22489 Python, the display includes the memory size, in bits, accessible to
22492 Bounds can also be stored in bounds tables, which are stored in
22493 application memory. These tables store bounds for pointers by specifying
22494 the bounds pointer's value along with its bounds. Evaluating and changing
22495 bounds located in bound tables is therefore interesting while investigating
22496 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22499 @item show mpx bound @var{pointer}
22500 @kindex show mpx bound
22501 Display bounds of the given @var{pointer}.
22503 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22504 @kindex set mpx bound
22505 Set the bounds of a pointer in the bound table.
22506 This command takes three parameters: @var{pointer} is the pointers
22507 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22508 for lower and upper bounds respectively.
22514 See the following section.
22517 @subsection @acronym{MIPS}
22519 @cindex stack on Alpha
22520 @cindex stack on @acronym{MIPS}
22521 @cindex Alpha stack
22522 @cindex @acronym{MIPS} stack
22523 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22524 sometimes requires @value{GDBN} to search backward in the object code to
22525 find the beginning of a function.
22527 @cindex response time, @acronym{MIPS} debugging
22528 To improve response time (especially for embedded applications, where
22529 @value{GDBN} may be restricted to a slow serial line for this search)
22530 you may want to limit the size of this search, using one of these
22534 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22535 @item set heuristic-fence-post @var{limit}
22536 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22537 search for the beginning of a function. A value of @var{0} (the
22538 default) means there is no limit. However, except for @var{0}, the
22539 larger the limit the more bytes @code{heuristic-fence-post} must search
22540 and therefore the longer it takes to run. You should only need to use
22541 this command when debugging a stripped executable.
22543 @item show heuristic-fence-post
22544 Display the current limit.
22548 These commands are available @emph{only} when @value{GDBN} is configured
22549 for debugging programs on Alpha or @acronym{MIPS} processors.
22551 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22555 @item set mips abi @var{arg}
22556 @kindex set mips abi
22557 @cindex set ABI for @acronym{MIPS}
22558 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22559 values of @var{arg} are:
22563 The default ABI associated with the current binary (this is the
22573 @item show mips abi
22574 @kindex show mips abi
22575 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22577 @item set mips compression @var{arg}
22578 @kindex set mips compression
22579 @cindex code compression, @acronym{MIPS}
22580 Tell @value{GDBN} which @acronym{MIPS} compressed
22581 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22582 inferior. @value{GDBN} uses this for code disassembly and other
22583 internal interpretation purposes. This setting is only referred to
22584 when no executable has been associated with the debugging session or
22585 the executable does not provide information about the encoding it uses.
22586 Otherwise this setting is automatically updated from information
22587 provided by the executable.
22589 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22590 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22591 executables containing @acronym{MIPS16} code frequently are not
22592 identified as such.
22594 This setting is ``sticky''; that is, it retains its value across
22595 debugging sessions until reset either explicitly with this command or
22596 implicitly from an executable.
22598 The compiler and/or assembler typically add symbol table annotations to
22599 identify functions compiled for the @acronym{MIPS16} or
22600 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22601 are present, @value{GDBN} uses them in preference to the global
22602 compressed @acronym{ISA} encoding setting.
22604 @item show mips compression
22605 @kindex show mips compression
22606 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22607 @value{GDBN} to debug the inferior.
22610 @itemx show mipsfpu
22611 @xref{MIPS Embedded, set mipsfpu}.
22613 @item set mips mask-address @var{arg}
22614 @kindex set mips mask-address
22615 @cindex @acronym{MIPS} addresses, masking
22616 This command determines whether the most-significant 32 bits of 64-bit
22617 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22618 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22619 setting, which lets @value{GDBN} determine the correct value.
22621 @item show mips mask-address
22622 @kindex show mips mask-address
22623 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22626 @item set remote-mips64-transfers-32bit-regs
22627 @kindex set remote-mips64-transfers-32bit-regs
22628 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22629 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22630 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22631 and 64 bits for other registers, set this option to @samp{on}.
22633 @item show remote-mips64-transfers-32bit-regs
22634 @kindex show remote-mips64-transfers-32bit-regs
22635 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22637 @item set debug mips
22638 @kindex set debug mips
22639 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22640 target code in @value{GDBN}.
22642 @item show debug mips
22643 @kindex show debug mips
22644 Show the current setting of @acronym{MIPS} debugging messages.
22650 @cindex HPPA support
22652 When @value{GDBN} is debugging the HP PA architecture, it provides the
22653 following special commands:
22656 @item set debug hppa
22657 @kindex set debug hppa
22658 This command determines whether HPPA architecture-specific debugging
22659 messages are to be displayed.
22661 @item show debug hppa
22662 Show whether HPPA debugging messages are displayed.
22664 @item maint print unwind @var{address}
22665 @kindex maint print unwind@r{, HPPA}
22666 This command displays the contents of the unwind table entry at the
22667 given @var{address}.
22673 @subsection Cell Broadband Engine SPU architecture
22674 @cindex Cell Broadband Engine
22677 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22678 it provides the following special commands:
22681 @item info spu event
22683 Display SPU event facility status. Shows current event mask
22684 and pending event status.
22686 @item info spu signal
22687 Display SPU signal notification facility status. Shows pending
22688 signal-control word and signal notification mode of both signal
22689 notification channels.
22691 @item info spu mailbox
22692 Display SPU mailbox facility status. Shows all pending entries,
22693 in order of processing, in each of the SPU Write Outbound,
22694 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22697 Display MFC DMA status. Shows all pending commands in the MFC
22698 DMA queue. For each entry, opcode, tag, class IDs, effective
22699 and local store addresses and transfer size are shown.
22701 @item info spu proxydma
22702 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22703 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22704 and local store addresses and transfer size are shown.
22708 When @value{GDBN} is debugging a combined PowerPC/SPU application
22709 on the Cell Broadband Engine, it provides in addition the following
22713 @item set spu stop-on-load @var{arg}
22715 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22716 will give control to the user when a new SPE thread enters its @code{main}
22717 function. The default is @code{off}.
22719 @item show spu stop-on-load
22721 Show whether to stop for new SPE threads.
22723 @item set spu auto-flush-cache @var{arg}
22724 Set whether to automatically flush the software-managed cache. When set to
22725 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22726 cache to be flushed whenever SPE execution stops. This provides a consistent
22727 view of PowerPC memory that is accessed via the cache. If an application
22728 does not use the software-managed cache, this option has no effect.
22730 @item show spu auto-flush-cache
22731 Show whether to automatically flush the software-managed cache.
22736 @subsection PowerPC
22737 @cindex PowerPC architecture
22739 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22740 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22741 numbers stored in the floating point registers. These values must be stored
22742 in two consecutive registers, always starting at an even register like
22743 @code{f0} or @code{f2}.
22745 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22746 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22747 @code{f2} and @code{f3} for @code{$dl1} and so on.
22749 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22750 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22753 @subsection Nios II
22754 @cindex Nios II architecture
22756 When @value{GDBN} is debugging the Nios II architecture,
22757 it provides the following special commands:
22761 @item set debug nios2
22762 @kindex set debug nios2
22763 This command turns on and off debugging messages for the Nios II
22764 target code in @value{GDBN}.
22766 @item show debug nios2
22767 @kindex show debug nios2
22768 Show the current setting of Nios II debugging messages.
22771 @node Controlling GDB
22772 @chapter Controlling @value{GDBN}
22774 You can alter the way @value{GDBN} interacts with you by using the
22775 @code{set} command. For commands controlling how @value{GDBN} displays
22776 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22781 * Editing:: Command editing
22782 * Command History:: Command history
22783 * Screen Size:: Screen size
22784 * Numbers:: Numbers
22785 * ABI:: Configuring the current ABI
22786 * Auto-loading:: Automatically loading associated files
22787 * Messages/Warnings:: Optional warnings and messages
22788 * Debugging Output:: Optional messages about internal happenings
22789 * Other Misc Settings:: Other Miscellaneous Settings
22797 @value{GDBN} indicates its readiness to read a command by printing a string
22798 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22799 can change the prompt string with the @code{set prompt} command. For
22800 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22801 the prompt in one of the @value{GDBN} sessions so that you can always tell
22802 which one you are talking to.
22804 @emph{Note:} @code{set prompt} does not add a space for you after the
22805 prompt you set. This allows you to set a prompt which ends in a space
22806 or a prompt that does not.
22810 @item set prompt @var{newprompt}
22811 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22813 @kindex show prompt
22815 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22818 Versions of @value{GDBN} that ship with Python scripting enabled have
22819 prompt extensions. The commands for interacting with these extensions
22823 @kindex set extended-prompt
22824 @item set extended-prompt @var{prompt}
22825 Set an extended prompt that allows for substitutions.
22826 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22827 substitution. Any escape sequences specified as part of the prompt
22828 string are replaced with the corresponding strings each time the prompt
22834 set extended-prompt Current working directory: \w (gdb)
22837 Note that when an extended-prompt is set, it takes control of the
22838 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22840 @kindex show extended-prompt
22841 @item show extended-prompt
22842 Prints the extended prompt. Any escape sequences specified as part of
22843 the prompt string with @code{set extended-prompt}, are replaced with the
22844 corresponding strings each time the prompt is displayed.
22848 @section Command Editing
22850 @cindex command line editing
22852 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22853 @sc{gnu} library provides consistent behavior for programs which provide a
22854 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22855 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22856 substitution, and a storage and recall of command history across
22857 debugging sessions.
22859 You may control the behavior of command line editing in @value{GDBN} with the
22860 command @code{set}.
22863 @kindex set editing
22866 @itemx set editing on
22867 Enable command line editing (enabled by default).
22869 @item set editing off
22870 Disable command line editing.
22872 @kindex show editing
22874 Show whether command line editing is enabled.
22877 @ifset SYSTEM_READLINE
22878 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22880 @ifclear SYSTEM_READLINE
22881 @xref{Command Line Editing},
22883 for more details about the Readline
22884 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22885 encouraged to read that chapter.
22887 @node Command History
22888 @section Command History
22889 @cindex command history
22891 @value{GDBN} can keep track of the commands you type during your
22892 debugging sessions, so that you can be certain of precisely what
22893 happened. Use these commands to manage the @value{GDBN} command
22896 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22897 package, to provide the history facility.
22898 @ifset SYSTEM_READLINE
22899 @xref{Using History Interactively, , , history, GNU History Library},
22901 @ifclear SYSTEM_READLINE
22902 @xref{Using History Interactively},
22904 for the detailed description of the History library.
22906 To issue a command to @value{GDBN} without affecting certain aspects of
22907 the state which is seen by users, prefix it with @samp{server }
22908 (@pxref{Server Prefix}). This
22909 means that this command will not affect the command history, nor will it
22910 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22911 pressed on a line by itself.
22913 @cindex @code{server}, command prefix
22914 The server prefix does not affect the recording of values into the value
22915 history; to print a value without recording it into the value history,
22916 use the @code{output} command instead of the @code{print} command.
22918 Here is the description of @value{GDBN} commands related to command
22922 @cindex history substitution
22923 @cindex history file
22924 @kindex set history filename
22925 @cindex @env{GDBHISTFILE}, environment variable
22926 @item set history filename @var{fname}
22927 Set the name of the @value{GDBN} command history file to @var{fname}.
22928 This is the file where @value{GDBN} reads an initial command history
22929 list, and where it writes the command history from this session when it
22930 exits. You can access this list through history expansion or through
22931 the history command editing characters listed below. This file defaults
22932 to the value of the environment variable @code{GDBHISTFILE}, or to
22933 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22936 @cindex save command history
22937 @kindex set history save
22938 @item set history save
22939 @itemx set history save on
22940 Record command history in a file, whose name may be specified with the
22941 @code{set history filename} command. By default, this option is disabled.
22943 @item set history save off
22944 Stop recording command history in a file.
22946 @cindex history size
22947 @kindex set history size
22948 @cindex @env{GDBHISTSIZE}, environment variable
22949 @item set history size @var{size}
22950 @itemx set history size unlimited
22951 Set the number of commands which @value{GDBN} keeps in its history list.
22952 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22953 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22954 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22955 either a negative number or the empty string, then the number of commands
22956 @value{GDBN} keeps in the history list is unlimited.
22958 @cindex remove duplicate history
22959 @kindex set history remove-duplicates
22960 @item set history remove-duplicates @var{count}
22961 @itemx set history remove-duplicates unlimited
22962 Control the removal of duplicate history entries in the command history list.
22963 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22964 history entries and remove the first entry that is a duplicate of the current
22965 entry being added to the command history list. If @var{count} is
22966 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22967 removal of duplicate history entries is disabled.
22969 Only history entries added during the current session are considered for
22970 removal. This option is set to 0 by default.
22974 History expansion assigns special meaning to the character @kbd{!}.
22975 @ifset SYSTEM_READLINE
22976 @xref{Event Designators, , , history, GNU History Library},
22978 @ifclear SYSTEM_READLINE
22979 @xref{Event Designators},
22983 @cindex history expansion, turn on/off
22984 Since @kbd{!} is also the logical not operator in C, history expansion
22985 is off by default. If you decide to enable history expansion with the
22986 @code{set history expansion on} command, you may sometimes need to
22987 follow @kbd{!} (when it is used as logical not, in an expression) with
22988 a space or a tab to prevent it from being expanded. The readline
22989 history facilities do not attempt substitution on the strings
22990 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22992 The commands to control history expansion are:
22995 @item set history expansion on
22996 @itemx set history expansion
22997 @kindex set history expansion
22998 Enable history expansion. History expansion is off by default.
23000 @item set history expansion off
23001 Disable history expansion.
23004 @kindex show history
23006 @itemx show history filename
23007 @itemx show history save
23008 @itemx show history size
23009 @itemx show history expansion
23010 These commands display the state of the @value{GDBN} history parameters.
23011 @code{show history} by itself displays all four states.
23016 @kindex show commands
23017 @cindex show last commands
23018 @cindex display command history
23019 @item show commands
23020 Display the last ten commands in the command history.
23022 @item show commands @var{n}
23023 Print ten commands centered on command number @var{n}.
23025 @item show commands +
23026 Print ten commands just after the commands last printed.
23030 @section Screen Size
23031 @cindex size of screen
23032 @cindex screen size
23035 @cindex pauses in output
23037 Certain commands to @value{GDBN} may produce large amounts of
23038 information output to the screen. To help you read all of it,
23039 @value{GDBN} pauses and asks you for input at the end of each page of
23040 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23041 to discard the remaining output. Also, the screen width setting
23042 determines when to wrap lines of output. Depending on what is being
23043 printed, @value{GDBN} tries to break the line at a readable place,
23044 rather than simply letting it overflow onto the following line.
23046 Normally @value{GDBN} knows the size of the screen from the terminal
23047 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23048 together with the value of the @code{TERM} environment variable and the
23049 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23050 you can override it with the @code{set height} and @code{set
23057 @kindex show height
23058 @item set height @var{lpp}
23059 @itemx set height unlimited
23061 @itemx set width @var{cpl}
23062 @itemx set width unlimited
23064 These @code{set} commands specify a screen height of @var{lpp} lines and
23065 a screen width of @var{cpl} characters. The associated @code{show}
23066 commands display the current settings.
23068 If you specify a height of either @code{unlimited} or zero lines,
23069 @value{GDBN} does not pause during output no matter how long the
23070 output is. This is useful if output is to a file or to an editor
23073 Likewise, you can specify @samp{set width unlimited} or @samp{set
23074 width 0} to prevent @value{GDBN} from wrapping its output.
23076 @item set pagination on
23077 @itemx set pagination off
23078 @kindex set pagination
23079 Turn the output pagination on or off; the default is on. Turning
23080 pagination off is the alternative to @code{set height unlimited}. Note that
23081 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23082 Options, -batch}) also automatically disables pagination.
23084 @item show pagination
23085 @kindex show pagination
23086 Show the current pagination mode.
23091 @cindex number representation
23092 @cindex entering numbers
23094 You can always enter numbers in octal, decimal, or hexadecimal in
23095 @value{GDBN} by the usual conventions: octal numbers begin with
23096 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23097 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23098 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23099 10; likewise, the default display for numbers---when no particular
23100 format is specified---is base 10. You can change the default base for
23101 both input and output with the commands described below.
23104 @kindex set input-radix
23105 @item set input-radix @var{base}
23106 Set the default base for numeric input. Supported choices
23107 for @var{base} are decimal 8, 10, or 16. The base must itself be
23108 specified either unambiguously or using the current input radix; for
23112 set input-radix 012
23113 set input-radix 10.
23114 set input-radix 0xa
23118 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23119 leaves the input radix unchanged, no matter what it was, since
23120 @samp{10}, being without any leading or trailing signs of its base, is
23121 interpreted in the current radix. Thus, if the current radix is 16,
23122 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23125 @kindex set output-radix
23126 @item set output-radix @var{base}
23127 Set the default base for numeric display. Supported choices
23128 for @var{base} are decimal 8, 10, or 16. The base must itself be
23129 specified either unambiguously or using the current input radix.
23131 @kindex show input-radix
23132 @item show input-radix
23133 Display the current default base for numeric input.
23135 @kindex show output-radix
23136 @item show output-radix
23137 Display the current default base for numeric display.
23139 @item set radix @r{[}@var{base}@r{]}
23143 These commands set and show the default base for both input and output
23144 of numbers. @code{set radix} sets the radix of input and output to
23145 the same base; without an argument, it resets the radix back to its
23146 default value of 10.
23151 @section Configuring the Current ABI
23153 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23154 application automatically. However, sometimes you need to override its
23155 conclusions. Use these commands to manage @value{GDBN}'s view of the
23161 @cindex Newlib OS ABI and its influence on the longjmp handling
23163 One @value{GDBN} configuration can debug binaries for multiple operating
23164 system targets, either via remote debugging or native emulation.
23165 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23166 but you can override its conclusion using the @code{set osabi} command.
23167 One example where this is useful is in debugging of binaries which use
23168 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23169 not have the same identifying marks that the standard C library for your
23172 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23173 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23174 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23175 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23179 Show the OS ABI currently in use.
23182 With no argument, show the list of registered available OS ABI's.
23184 @item set osabi @var{abi}
23185 Set the current OS ABI to @var{abi}.
23188 @cindex float promotion
23190 Generally, the way that an argument of type @code{float} is passed to a
23191 function depends on whether the function is prototyped. For a prototyped
23192 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23193 according to the architecture's convention for @code{float}. For unprototyped
23194 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23195 @code{double} and then passed.
23197 Unfortunately, some forms of debug information do not reliably indicate whether
23198 a function is prototyped. If @value{GDBN} calls a function that is not marked
23199 as prototyped, it consults @kbd{set coerce-float-to-double}.
23202 @kindex set coerce-float-to-double
23203 @item set coerce-float-to-double
23204 @itemx set coerce-float-to-double on
23205 Arguments of type @code{float} will be promoted to @code{double} when passed
23206 to an unprototyped function. This is the default setting.
23208 @item set coerce-float-to-double off
23209 Arguments of type @code{float} will be passed directly to unprototyped
23212 @kindex show coerce-float-to-double
23213 @item show coerce-float-to-double
23214 Show the current setting of promoting @code{float} to @code{double}.
23218 @kindex show cp-abi
23219 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23220 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23221 used to build your application. @value{GDBN} only fully supports
23222 programs with a single C@t{++} ABI; if your program contains code using
23223 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23224 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23225 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23226 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23227 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23228 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23233 Show the C@t{++} ABI currently in use.
23236 With no argument, show the list of supported C@t{++} ABI's.
23238 @item set cp-abi @var{abi}
23239 @itemx set cp-abi auto
23240 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23244 @section Automatically loading associated files
23245 @cindex auto-loading
23247 @value{GDBN} sometimes reads files with commands and settings automatically,
23248 without being explicitly told so by the user. We call this feature
23249 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23250 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23251 results or introduce security risks (e.g., if the file comes from untrusted
23255 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23256 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23258 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23259 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23262 There are various kinds of files @value{GDBN} can automatically load.
23263 In addition to these files, @value{GDBN} supports auto-loading code written
23264 in various extension languages. @xref{Auto-loading extensions}.
23266 Note that loading of these associated files (including the local @file{.gdbinit}
23267 file) requires accordingly configured @code{auto-load safe-path}
23268 (@pxref{Auto-loading safe path}).
23270 For these reasons, @value{GDBN} includes commands and options to let you
23271 control when to auto-load files and which files should be auto-loaded.
23274 @anchor{set auto-load off}
23275 @kindex set auto-load off
23276 @item set auto-load off
23277 Globally disable loading of all auto-loaded files.
23278 You may want to use this command with the @samp{-iex} option
23279 (@pxref{Option -init-eval-command}) such as:
23281 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23284 Be aware that system init file (@pxref{System-wide configuration})
23285 and init files from your home directory (@pxref{Home Directory Init File})
23286 still get read (as they come from generally trusted directories).
23287 To prevent @value{GDBN} from auto-loading even those init files, use the
23288 @option{-nx} option (@pxref{Mode Options}), in addition to
23289 @code{set auto-load no}.
23291 @anchor{show auto-load}
23292 @kindex show auto-load
23293 @item show auto-load
23294 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23298 (gdb) show auto-load
23299 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23300 libthread-db: Auto-loading of inferior specific libthread_db is on.
23301 local-gdbinit: Auto-loading of .gdbinit script from current directory
23303 python-scripts: Auto-loading of Python scripts is on.
23304 safe-path: List of directories from which it is safe to auto-load files
23305 is $debugdir:$datadir/auto-load.
23306 scripts-directory: List of directories from which to load auto-loaded scripts
23307 is $debugdir:$datadir/auto-load.
23310 @anchor{info auto-load}
23311 @kindex info auto-load
23312 @item info auto-load
23313 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23317 (gdb) info auto-load
23320 Yes /home/user/gdb/gdb-gdb.gdb
23321 libthread-db: No auto-loaded libthread-db.
23322 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23326 Yes /home/user/gdb/gdb-gdb.py
23330 These are @value{GDBN} control commands for the auto-loading:
23332 @multitable @columnfractions .5 .5
23333 @item @xref{set auto-load off}.
23334 @tab Disable auto-loading globally.
23335 @item @xref{show auto-load}.
23336 @tab Show setting of all kinds of files.
23337 @item @xref{info auto-load}.
23338 @tab Show state of all kinds of files.
23339 @item @xref{set auto-load gdb-scripts}.
23340 @tab Control for @value{GDBN} command scripts.
23341 @item @xref{show auto-load gdb-scripts}.
23342 @tab Show setting of @value{GDBN} command scripts.
23343 @item @xref{info auto-load gdb-scripts}.
23344 @tab Show state of @value{GDBN} command scripts.
23345 @item @xref{set auto-load python-scripts}.
23346 @tab Control for @value{GDBN} Python scripts.
23347 @item @xref{show auto-load python-scripts}.
23348 @tab Show setting of @value{GDBN} Python scripts.
23349 @item @xref{info auto-load python-scripts}.
23350 @tab Show state of @value{GDBN} Python scripts.
23351 @item @xref{set auto-load guile-scripts}.
23352 @tab Control for @value{GDBN} Guile scripts.
23353 @item @xref{show auto-load guile-scripts}.
23354 @tab Show setting of @value{GDBN} Guile scripts.
23355 @item @xref{info auto-load guile-scripts}.
23356 @tab Show state of @value{GDBN} Guile scripts.
23357 @item @xref{set auto-load scripts-directory}.
23358 @tab Control for @value{GDBN} auto-loaded scripts location.
23359 @item @xref{show auto-load scripts-directory}.
23360 @tab Show @value{GDBN} auto-loaded scripts location.
23361 @item @xref{add-auto-load-scripts-directory}.
23362 @tab Add directory for auto-loaded scripts location list.
23363 @item @xref{set auto-load local-gdbinit}.
23364 @tab Control for init file in the current directory.
23365 @item @xref{show auto-load local-gdbinit}.
23366 @tab Show setting of init file in the current directory.
23367 @item @xref{info auto-load local-gdbinit}.
23368 @tab Show state of init file in the current directory.
23369 @item @xref{set auto-load libthread-db}.
23370 @tab Control for thread debugging library.
23371 @item @xref{show auto-load libthread-db}.
23372 @tab Show setting of thread debugging library.
23373 @item @xref{info auto-load libthread-db}.
23374 @tab Show state of thread debugging library.
23375 @item @xref{set auto-load safe-path}.
23376 @tab Control directories trusted for automatic loading.
23377 @item @xref{show auto-load safe-path}.
23378 @tab Show directories trusted for automatic loading.
23379 @item @xref{add-auto-load-safe-path}.
23380 @tab Add directory trusted for automatic loading.
23383 @node Init File in the Current Directory
23384 @subsection Automatically loading init file in the current directory
23385 @cindex auto-loading init file in the current directory
23387 By default, @value{GDBN} reads and executes the canned sequences of commands
23388 from init file (if any) in the current working directory,
23389 see @ref{Init File in the Current Directory during Startup}.
23391 Note that loading of this local @file{.gdbinit} file also requires accordingly
23392 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23395 @anchor{set auto-load local-gdbinit}
23396 @kindex set auto-load local-gdbinit
23397 @item set auto-load local-gdbinit [on|off]
23398 Enable or disable the auto-loading of canned sequences of commands
23399 (@pxref{Sequences}) found in init file in the current directory.
23401 @anchor{show auto-load local-gdbinit}
23402 @kindex show auto-load local-gdbinit
23403 @item show auto-load local-gdbinit
23404 Show whether auto-loading of canned sequences of commands from init file in the
23405 current directory is enabled or disabled.
23407 @anchor{info auto-load local-gdbinit}
23408 @kindex info auto-load local-gdbinit
23409 @item info auto-load local-gdbinit
23410 Print whether canned sequences of commands from init file in the
23411 current directory have been auto-loaded.
23414 @node libthread_db.so.1 file
23415 @subsection Automatically loading thread debugging library
23416 @cindex auto-loading libthread_db.so.1
23418 This feature is currently present only on @sc{gnu}/Linux native hosts.
23420 @value{GDBN} reads in some cases thread debugging library from places specific
23421 to the inferior (@pxref{set libthread-db-search-path}).
23423 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23424 without checking this @samp{set auto-load libthread-db} switch as system
23425 libraries have to be trusted in general. In all other cases of
23426 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23427 auto-load libthread-db} is enabled before trying to open such thread debugging
23430 Note that loading of this debugging library also requires accordingly configured
23431 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23434 @anchor{set auto-load libthread-db}
23435 @kindex set auto-load libthread-db
23436 @item set auto-load libthread-db [on|off]
23437 Enable or disable the auto-loading of inferior specific thread debugging library.
23439 @anchor{show auto-load libthread-db}
23440 @kindex show auto-load libthread-db
23441 @item show auto-load libthread-db
23442 Show whether auto-loading of inferior specific thread debugging library is
23443 enabled or disabled.
23445 @anchor{info auto-load libthread-db}
23446 @kindex info auto-load libthread-db
23447 @item info auto-load libthread-db
23448 Print the list of all loaded inferior specific thread debugging libraries and
23449 for each such library print list of inferior @var{pid}s using it.
23452 @node Auto-loading safe path
23453 @subsection Security restriction for auto-loading
23454 @cindex auto-loading safe-path
23456 As the files of inferior can come from untrusted source (such as submitted by
23457 an application user) @value{GDBN} does not always load any files automatically.
23458 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23459 directories trusted for loading files not explicitly requested by user.
23460 Each directory can also be a shell wildcard pattern.
23462 If the path is not set properly you will see a warning and the file will not
23467 Reading symbols from /home/user/gdb/gdb...done.
23468 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23469 declined by your `auto-load safe-path' set
23470 to "$debugdir:$datadir/auto-load".
23471 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23472 declined by your `auto-load safe-path' set
23473 to "$debugdir:$datadir/auto-load".
23477 To instruct @value{GDBN} to go ahead and use the init files anyway,
23478 invoke @value{GDBN} like this:
23481 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23484 The list of trusted directories is controlled by the following commands:
23487 @anchor{set auto-load safe-path}
23488 @kindex set auto-load safe-path
23489 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23490 Set the list of directories (and their subdirectories) trusted for automatic
23491 loading and execution of scripts. You can also enter a specific trusted file.
23492 Each directory can also be a shell wildcard pattern; wildcards do not match
23493 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23494 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23495 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23496 its default value as specified during @value{GDBN} compilation.
23498 The list of directories uses path separator (@samp{:} on GNU and Unix
23499 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23500 to the @env{PATH} environment variable.
23502 @anchor{show auto-load safe-path}
23503 @kindex show auto-load safe-path
23504 @item show auto-load safe-path
23505 Show the list of directories trusted for automatic loading and execution of
23508 @anchor{add-auto-load-safe-path}
23509 @kindex add-auto-load-safe-path
23510 @item add-auto-load-safe-path
23511 Add an entry (or list of entries) to the list of directories trusted for
23512 automatic loading and execution of scripts. Multiple entries may be delimited
23513 by the host platform path separator in use.
23516 This variable defaults to what @code{--with-auto-load-dir} has been configured
23517 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23518 substitution applies the same as for @ref{set auto-load scripts-directory}.
23519 The default @code{set auto-load safe-path} value can be also overriden by
23520 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23522 Setting this variable to @file{/} disables this security protection,
23523 corresponding @value{GDBN} configuration option is
23524 @option{--without-auto-load-safe-path}.
23525 This variable is supposed to be set to the system directories writable by the
23526 system superuser only. Users can add their source directories in init files in
23527 their home directories (@pxref{Home Directory Init File}). See also deprecated
23528 init file in the current directory
23529 (@pxref{Init File in the Current Directory during Startup}).
23531 To force @value{GDBN} to load the files it declined to load in the previous
23532 example, you could use one of the following ways:
23535 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23536 Specify this trusted directory (or a file) as additional component of the list.
23537 You have to specify also any existing directories displayed by
23538 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23540 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23541 Specify this directory as in the previous case but just for a single
23542 @value{GDBN} session.
23544 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23545 Disable auto-loading safety for a single @value{GDBN} session.
23546 This assumes all the files you debug during this @value{GDBN} session will come
23547 from trusted sources.
23549 @item @kbd{./configure --without-auto-load-safe-path}
23550 During compilation of @value{GDBN} you may disable any auto-loading safety.
23551 This assumes all the files you will ever debug with this @value{GDBN} come from
23555 On the other hand you can also explicitly forbid automatic files loading which
23556 also suppresses any such warning messages:
23559 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23560 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23562 @item @file{~/.gdbinit}: @samp{set auto-load no}
23563 Disable auto-loading globally for the user
23564 (@pxref{Home Directory Init File}). While it is improbable, you could also
23565 use system init file instead (@pxref{System-wide configuration}).
23568 This setting applies to the file names as entered by user. If no entry matches
23569 @value{GDBN} tries as a last resort to also resolve all the file names into
23570 their canonical form (typically resolving symbolic links) and compare the
23571 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23572 own before starting the comparison so a canonical form of directories is
23573 recommended to be entered.
23575 @node Auto-loading verbose mode
23576 @subsection Displaying files tried for auto-load
23577 @cindex auto-loading verbose mode
23579 For better visibility of all the file locations where you can place scripts to
23580 be auto-loaded with inferior --- or to protect yourself against accidental
23581 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23582 all the files attempted to be loaded. Both existing and non-existing files may
23585 For example the list of directories from which it is safe to auto-load files
23586 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23587 may not be too obvious while setting it up.
23590 (gdb) set debug auto-load on
23591 (gdb) file ~/src/t/true
23592 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23593 for objfile "/tmp/true".
23594 auto-load: Updating directories of "/usr:/opt".
23595 auto-load: Using directory "/usr".
23596 auto-load: Using directory "/opt".
23597 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23598 by your `auto-load safe-path' set to "/usr:/opt".
23602 @anchor{set debug auto-load}
23603 @kindex set debug auto-load
23604 @item set debug auto-load [on|off]
23605 Set whether to print the filenames attempted to be auto-loaded.
23607 @anchor{show debug auto-load}
23608 @kindex show debug auto-load
23609 @item show debug auto-load
23610 Show whether printing of the filenames attempted to be auto-loaded is turned
23614 @node Messages/Warnings
23615 @section Optional Warnings and Messages
23617 @cindex verbose operation
23618 @cindex optional warnings
23619 By default, @value{GDBN} is silent about its inner workings. If you are
23620 running on a slow machine, you may want to use the @code{set verbose}
23621 command. This makes @value{GDBN} tell you when it does a lengthy
23622 internal operation, so you will not think it has crashed.
23624 Currently, the messages controlled by @code{set verbose} are those
23625 which announce that the symbol table for a source file is being read;
23626 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23629 @kindex set verbose
23630 @item set verbose on
23631 Enables @value{GDBN} output of certain informational messages.
23633 @item set verbose off
23634 Disables @value{GDBN} output of certain informational messages.
23636 @kindex show verbose
23638 Displays whether @code{set verbose} is on or off.
23641 By default, if @value{GDBN} encounters bugs in the symbol table of an
23642 object file, it is silent; but if you are debugging a compiler, you may
23643 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23648 @kindex set complaints
23649 @item set complaints @var{limit}
23650 Permits @value{GDBN} to output @var{limit} complaints about each type of
23651 unusual symbols before becoming silent about the problem. Set
23652 @var{limit} to zero to suppress all complaints; set it to a large number
23653 to prevent complaints from being suppressed.
23655 @kindex show complaints
23656 @item show complaints
23657 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23661 @anchor{confirmation requests}
23662 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23663 lot of stupid questions to confirm certain commands. For example, if
23664 you try to run a program which is already running:
23668 The program being debugged has been started already.
23669 Start it from the beginning? (y or n)
23672 If you are willing to unflinchingly face the consequences of your own
23673 commands, you can disable this ``feature'':
23677 @kindex set confirm
23679 @cindex confirmation
23680 @cindex stupid questions
23681 @item set confirm off
23682 Disables confirmation requests. Note that running @value{GDBN} with
23683 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23684 automatically disables confirmation requests.
23686 @item set confirm on
23687 Enables confirmation requests (the default).
23689 @kindex show confirm
23691 Displays state of confirmation requests.
23695 @cindex command tracing
23696 If you need to debug user-defined commands or sourced files you may find it
23697 useful to enable @dfn{command tracing}. In this mode each command will be
23698 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23699 quantity denoting the call depth of each command.
23702 @kindex set trace-commands
23703 @cindex command scripts, debugging
23704 @item set trace-commands on
23705 Enable command tracing.
23706 @item set trace-commands off
23707 Disable command tracing.
23708 @item show trace-commands
23709 Display the current state of command tracing.
23712 @node Debugging Output
23713 @section Optional Messages about Internal Happenings
23714 @cindex optional debugging messages
23716 @value{GDBN} has commands that enable optional debugging messages from
23717 various @value{GDBN} subsystems; normally these commands are of
23718 interest to @value{GDBN} maintainers, or when reporting a bug. This
23719 section documents those commands.
23722 @kindex set exec-done-display
23723 @item set exec-done-display
23724 Turns on or off the notification of asynchronous commands'
23725 completion. When on, @value{GDBN} will print a message when an
23726 asynchronous command finishes its execution. The default is off.
23727 @kindex show exec-done-display
23728 @item show exec-done-display
23729 Displays the current setting of asynchronous command completion
23732 @cindex ARM AArch64
23733 @item set debug aarch64
23734 Turns on or off display of debugging messages related to ARM AArch64.
23735 The default is off.
23737 @item show debug aarch64
23738 Displays the current state of displaying debugging messages related to
23740 @cindex gdbarch debugging info
23741 @cindex architecture debugging info
23742 @item set debug arch
23743 Turns on or off display of gdbarch debugging info. The default is off
23744 @item show debug arch
23745 Displays the current state of displaying gdbarch debugging info.
23746 @item set debug aix-solib
23747 @cindex AIX shared library debugging
23748 Control display of debugging messages from the AIX shared library
23749 support module. The default is off.
23750 @item show debug aix-thread
23751 Show the current state of displaying AIX shared library debugging messages.
23752 @item set debug aix-thread
23753 @cindex AIX threads
23754 Display debugging messages about inner workings of the AIX thread
23756 @item show debug aix-thread
23757 Show the current state of AIX thread debugging info display.
23758 @item set debug check-physname
23760 Check the results of the ``physname'' computation. When reading DWARF
23761 debugging information for C@t{++}, @value{GDBN} attempts to compute
23762 each entity's name. @value{GDBN} can do this computation in two
23763 different ways, depending on exactly what information is present.
23764 When enabled, this setting causes @value{GDBN} to compute the names
23765 both ways and display any discrepancies.
23766 @item show debug check-physname
23767 Show the current state of ``physname'' checking.
23768 @item set debug coff-pe-read
23769 @cindex COFF/PE exported symbols
23770 Control display of debugging messages related to reading of COFF/PE
23771 exported symbols. The default is off.
23772 @item show debug coff-pe-read
23773 Displays the current state of displaying debugging messages related to
23774 reading of COFF/PE exported symbols.
23775 @item set debug dwarf-die
23777 Dump DWARF DIEs after they are read in.
23778 The value is the number of nesting levels to print.
23779 A value of zero turns off the display.
23780 @item show debug dwarf-die
23781 Show the current state of DWARF DIE debugging.
23782 @item set debug dwarf-line
23783 @cindex DWARF Line Tables
23784 Turns on or off display of debugging messages related to reading
23785 DWARF line tables. The default is 0 (off).
23786 A value of 1 provides basic information.
23787 A value greater than 1 provides more verbose information.
23788 @item show debug dwarf-line
23789 Show the current state of DWARF line table debugging.
23790 @item set debug dwarf-read
23791 @cindex DWARF Reading
23792 Turns on or off display of debugging messages related to reading
23793 DWARF debug info. The default is 0 (off).
23794 A value of 1 provides basic information.
23795 A value greater than 1 provides more verbose information.
23796 @item show debug dwarf-read
23797 Show the current state of DWARF reader debugging.
23798 @item set debug displaced
23799 @cindex displaced stepping debugging info
23800 Turns on or off display of @value{GDBN} debugging info for the
23801 displaced stepping support. The default is off.
23802 @item show debug displaced
23803 Displays the current state of displaying @value{GDBN} debugging info
23804 related to displaced stepping.
23805 @item set debug event
23806 @cindex event debugging info
23807 Turns on or off display of @value{GDBN} event debugging info. The
23809 @item show debug event
23810 Displays the current state of displaying @value{GDBN} event debugging
23812 @item set debug expression
23813 @cindex expression debugging info
23814 Turns on or off display of debugging info about @value{GDBN}
23815 expression parsing. The default is off.
23816 @item show debug expression
23817 Displays the current state of displaying debugging info about
23818 @value{GDBN} expression parsing.
23819 @item set debug fbsd-lwp
23820 @cindex FreeBSD LWP debug messages
23821 Turns on or off debugging messages from the FreeBSD LWP debug support.
23822 @item show debug fbsd-lwp
23823 Show the current state of FreeBSD LWP debugging messages.
23824 @item set debug frame
23825 @cindex frame debugging info
23826 Turns on or off display of @value{GDBN} frame debugging info. The
23828 @item show debug frame
23829 Displays the current state of displaying @value{GDBN} frame debugging
23831 @item set debug gnu-nat
23832 @cindex @sc{gnu}/Hurd debug messages
23833 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23834 @item show debug gnu-nat
23835 Show the current state of @sc{gnu}/Hurd debugging messages.
23836 @item set debug infrun
23837 @cindex inferior debugging info
23838 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23839 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23840 for implementing operations such as single-stepping the inferior.
23841 @item show debug infrun
23842 Displays the current state of @value{GDBN} inferior debugging.
23843 @item set debug jit
23844 @cindex just-in-time compilation, debugging messages
23845 Turn on or off debugging messages from JIT debug support.
23846 @item show debug jit
23847 Displays the current state of @value{GDBN} JIT debugging.
23848 @item set debug lin-lwp
23849 @cindex @sc{gnu}/Linux LWP debug messages
23850 @cindex Linux lightweight processes
23851 Turn on or off debugging messages from the Linux LWP debug support.
23852 @item show debug lin-lwp
23853 Show the current state of Linux LWP debugging messages.
23854 @item set debug linux-namespaces
23855 @cindex @sc{gnu}/Linux namespaces debug messages
23856 Turn on or off debugging messages from the Linux namespaces debug support.
23857 @item show debug linux-namespaces
23858 Show the current state of Linux namespaces debugging messages.
23859 @item set debug mach-o
23860 @cindex Mach-O symbols processing
23861 Control display of debugging messages related to Mach-O symbols
23862 processing. The default is off.
23863 @item show debug mach-o
23864 Displays the current state of displaying debugging messages related to
23865 reading of COFF/PE exported symbols.
23866 @item set debug notification
23867 @cindex remote async notification debugging info
23868 Turn on or off debugging messages about remote async notification.
23869 The default is off.
23870 @item show debug notification
23871 Displays the current state of remote async notification debugging messages.
23872 @item set debug observer
23873 @cindex observer debugging info
23874 Turns on or off display of @value{GDBN} observer debugging. This
23875 includes info such as the notification of observable events.
23876 @item show debug observer
23877 Displays the current state of observer debugging.
23878 @item set debug overload
23879 @cindex C@t{++} overload debugging info
23880 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23881 info. This includes info such as ranking of functions, etc. The default
23883 @item show debug overload
23884 Displays the current state of displaying @value{GDBN} C@t{++} overload
23886 @cindex expression parser, debugging info
23887 @cindex debug expression parser
23888 @item set debug parser
23889 Turns on or off the display of expression parser debugging output.
23890 Internally, this sets the @code{yydebug} variable in the expression
23891 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23892 details. The default is off.
23893 @item show debug parser
23894 Show the current state of expression parser debugging.
23895 @cindex packets, reporting on stdout
23896 @cindex serial connections, debugging
23897 @cindex debug remote protocol
23898 @cindex remote protocol debugging
23899 @cindex display remote packets
23900 @item set debug remote
23901 Turns on or off display of reports on all packets sent back and forth across
23902 the serial line to the remote machine. The info is printed on the
23903 @value{GDBN} standard output stream. The default is off.
23904 @item show debug remote
23905 Displays the state of display of remote packets.
23906 @item set debug serial
23907 Turns on or off display of @value{GDBN} serial debugging info. The
23909 @item show debug serial
23910 Displays the current state of displaying @value{GDBN} serial debugging
23912 @item set debug solib-frv
23913 @cindex FR-V shared-library debugging
23914 Turn on or off debugging messages for FR-V shared-library code.
23915 @item show debug solib-frv
23916 Display the current state of FR-V shared-library code debugging
23918 @item set debug symbol-lookup
23919 @cindex symbol lookup
23920 Turns on or off display of debugging messages related to symbol lookup.
23921 The default is 0 (off).
23922 A value of 1 provides basic information.
23923 A value greater than 1 provides more verbose information.
23924 @item show debug symbol-lookup
23925 Show the current state of symbol lookup debugging messages.
23926 @item set debug symfile
23927 @cindex symbol file functions
23928 Turns on or off display of debugging messages related to symbol file functions.
23929 The default is off. @xref{Files}.
23930 @item show debug symfile
23931 Show the current state of symbol file debugging messages.
23932 @item set debug symtab-create
23933 @cindex symbol table creation
23934 Turns on or off display of debugging messages related to symbol table creation.
23935 The default is 0 (off).
23936 A value of 1 provides basic information.
23937 A value greater than 1 provides more verbose information.
23938 @item show debug symtab-create
23939 Show the current state of symbol table creation debugging.
23940 @item set debug target
23941 @cindex target debugging info
23942 Turns on or off display of @value{GDBN} target debugging info. This info
23943 includes what is going on at the target level of GDB, as it happens. The
23944 default is 0. Set it to 1 to track events, and to 2 to also track the
23945 value of large memory transfers.
23946 @item show debug target
23947 Displays the current state of displaying @value{GDBN} target debugging
23949 @item set debug timestamp
23950 @cindex timestampping debugging info
23951 Turns on or off display of timestamps with @value{GDBN} debugging info.
23952 When enabled, seconds and microseconds are displayed before each debugging
23954 @item show debug timestamp
23955 Displays the current state of displaying timestamps with @value{GDBN}
23957 @item set debug varobj
23958 @cindex variable object debugging info
23959 Turns on or off display of @value{GDBN} variable object debugging
23960 info. The default is off.
23961 @item show debug varobj
23962 Displays the current state of displaying @value{GDBN} variable object
23964 @item set debug xml
23965 @cindex XML parser debugging
23966 Turn on or off debugging messages for built-in XML parsers.
23967 @item show debug xml
23968 Displays the current state of XML debugging messages.
23971 @node Other Misc Settings
23972 @section Other Miscellaneous Settings
23973 @cindex miscellaneous settings
23976 @kindex set interactive-mode
23977 @item set interactive-mode
23978 If @code{on}, forces @value{GDBN} to assume that GDB was started
23979 in a terminal. In practice, this means that @value{GDBN} should wait
23980 for the user to answer queries generated by commands entered at
23981 the command prompt. If @code{off}, forces @value{GDBN} to operate
23982 in the opposite mode, and it uses the default answers to all queries.
23983 If @code{auto} (the default), @value{GDBN} tries to determine whether
23984 its standard input is a terminal, and works in interactive-mode if it
23985 is, non-interactively otherwise.
23987 In the vast majority of cases, the debugger should be able to guess
23988 correctly which mode should be used. But this setting can be useful
23989 in certain specific cases, such as running a MinGW @value{GDBN}
23990 inside a cygwin window.
23992 @kindex show interactive-mode
23993 @item show interactive-mode
23994 Displays whether the debugger is operating in interactive mode or not.
23997 @node Extending GDB
23998 @chapter Extending @value{GDBN}
23999 @cindex extending GDB
24001 @value{GDBN} provides several mechanisms for extension.
24002 @value{GDBN} also provides the ability to automatically load
24003 extensions when it reads a file for debugging. This allows the
24004 user to automatically customize @value{GDBN} for the program
24008 * Sequences:: Canned Sequences of @value{GDBN} Commands
24009 * Python:: Extending @value{GDBN} using Python
24010 * Guile:: Extending @value{GDBN} using Guile
24011 * Auto-loading extensions:: Automatically loading extensions
24012 * Multiple Extension Languages:: Working with multiple extension languages
24013 * Aliases:: Creating new spellings of existing commands
24016 To facilitate the use of extension languages, @value{GDBN} is capable
24017 of evaluating the contents of a file. When doing so, @value{GDBN}
24018 can recognize which extension language is being used by looking at
24019 the filename extension. Files with an unrecognized filename extension
24020 are always treated as a @value{GDBN} Command Files.
24021 @xref{Command Files,, Command files}.
24023 You can control how @value{GDBN} evaluates these files with the following
24027 @kindex set script-extension
24028 @kindex show script-extension
24029 @item set script-extension off
24030 All scripts are always evaluated as @value{GDBN} Command Files.
24032 @item set script-extension soft
24033 The debugger determines the scripting language based on filename
24034 extension. If this scripting language is supported, @value{GDBN}
24035 evaluates the script using that language. Otherwise, it evaluates
24036 the file as a @value{GDBN} Command File.
24038 @item set script-extension strict
24039 The debugger determines the scripting language based on filename
24040 extension, and evaluates the script using that language. If the
24041 language is not supported, then the evaluation fails.
24043 @item show script-extension
24044 Display the current value of the @code{script-extension} option.
24049 @section Canned Sequences of Commands
24051 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24052 Command Lists}), @value{GDBN} provides two ways to store sequences of
24053 commands for execution as a unit: user-defined commands and command
24057 * Define:: How to define your own commands
24058 * Hooks:: Hooks for user-defined commands
24059 * Command Files:: How to write scripts of commands to be stored in a file
24060 * Output:: Commands for controlled output
24061 * Auto-loading sequences:: Controlling auto-loaded command files
24065 @subsection User-defined Commands
24067 @cindex user-defined command
24068 @cindex arguments, to user-defined commands
24069 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24070 which you assign a new name as a command. This is done with the
24071 @code{define} command. User commands may accept an unlimited number of arguments
24072 separated by whitespace. Arguments are accessed within the user command
24073 via @code{$arg0@dots{}$argN}. A trivial example:
24077 print $arg0 + $arg1 + $arg2
24082 To execute the command use:
24089 This defines the command @code{adder}, which prints the sum of
24090 its three arguments. Note the arguments are text substitutions, so they may
24091 reference variables, use complex expressions, or even perform inferior
24094 @cindex argument count in user-defined commands
24095 @cindex how many arguments (user-defined commands)
24096 In addition, @code{$argc} may be used to find out how many arguments have
24102 print $arg0 + $arg1
24105 print $arg0 + $arg1 + $arg2
24110 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24111 to process a variable number of arguments:
24118 eval "set $sum = $sum + $arg%d", $i
24128 @item define @var{commandname}
24129 Define a command named @var{commandname}. If there is already a command
24130 by that name, you are asked to confirm that you want to redefine it.
24131 The argument @var{commandname} may be a bare command name consisting of letters,
24132 numbers, dashes, and underscores. It may also start with any predefined
24133 prefix command. For example, @samp{define target my-target} creates
24134 a user-defined @samp{target my-target} command.
24136 The definition of the command is made up of other @value{GDBN} command lines,
24137 which are given following the @code{define} command. The end of these
24138 commands is marked by a line containing @code{end}.
24141 @kindex end@r{ (user-defined commands)}
24142 @item document @var{commandname}
24143 Document the user-defined command @var{commandname}, so that it can be
24144 accessed by @code{help}. The command @var{commandname} must already be
24145 defined. This command reads lines of documentation just as @code{define}
24146 reads the lines of the command definition, ending with @code{end}.
24147 After the @code{document} command is finished, @code{help} on command
24148 @var{commandname} displays the documentation you have written.
24150 You may use the @code{document} command again to change the
24151 documentation of a command. Redefining the command with @code{define}
24152 does not change the documentation.
24154 @kindex dont-repeat
24155 @cindex don't repeat command
24157 Used inside a user-defined command, this tells @value{GDBN} that this
24158 command should not be repeated when the user hits @key{RET}
24159 (@pxref{Command Syntax, repeat last command}).
24161 @kindex help user-defined
24162 @item help user-defined
24163 List all user-defined commands and all python commands defined in class
24164 COMAND_USER. The first line of the documentation or docstring is
24169 @itemx show user @var{commandname}
24170 Display the @value{GDBN} commands used to define @var{commandname} (but
24171 not its documentation). If no @var{commandname} is given, display the
24172 definitions for all user-defined commands.
24173 This does not work for user-defined python commands.
24175 @cindex infinite recursion in user-defined commands
24176 @kindex show max-user-call-depth
24177 @kindex set max-user-call-depth
24178 @item show max-user-call-depth
24179 @itemx set max-user-call-depth
24180 The value of @code{max-user-call-depth} controls how many recursion
24181 levels are allowed in user-defined commands before @value{GDBN} suspects an
24182 infinite recursion and aborts the command.
24183 This does not apply to user-defined python commands.
24186 In addition to the above commands, user-defined commands frequently
24187 use control flow commands, described in @ref{Command Files}.
24189 When user-defined commands are executed, the
24190 commands of the definition are not printed. An error in any command
24191 stops execution of the user-defined command.
24193 If used interactively, commands that would ask for confirmation proceed
24194 without asking when used inside a user-defined command. Many @value{GDBN}
24195 commands that normally print messages to say what they are doing omit the
24196 messages when used in a user-defined command.
24199 @subsection User-defined Command Hooks
24200 @cindex command hooks
24201 @cindex hooks, for commands
24202 @cindex hooks, pre-command
24205 You may define @dfn{hooks}, which are a special kind of user-defined
24206 command. Whenever you run the command @samp{foo}, if the user-defined
24207 command @samp{hook-foo} exists, it is executed (with no arguments)
24208 before that command.
24210 @cindex hooks, post-command
24212 A hook may also be defined which is run after the command you executed.
24213 Whenever you run the command @samp{foo}, if the user-defined command
24214 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24215 that command. Post-execution hooks may exist simultaneously with
24216 pre-execution hooks, for the same command.
24218 It is valid for a hook to call the command which it hooks. If this
24219 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24221 @c It would be nice if hookpost could be passed a parameter indicating
24222 @c if the command it hooks executed properly or not. FIXME!
24224 @kindex stop@r{, a pseudo-command}
24225 In addition, a pseudo-command, @samp{stop} exists. Defining
24226 (@samp{hook-stop}) makes the associated commands execute every time
24227 execution stops in your program: before breakpoint commands are run,
24228 displays are printed, or the stack frame is printed.
24230 For example, to ignore @code{SIGALRM} signals while
24231 single-stepping, but treat them normally during normal execution,
24236 handle SIGALRM nopass
24240 handle SIGALRM pass
24243 define hook-continue
24244 handle SIGALRM pass
24248 As a further example, to hook at the beginning and end of the @code{echo}
24249 command, and to add extra text to the beginning and end of the message,
24257 define hookpost-echo
24261 (@value{GDBP}) echo Hello World
24262 <<<---Hello World--->>>
24267 You can define a hook for any single-word command in @value{GDBN}, but
24268 not for command aliases; you should define a hook for the basic command
24269 name, e.g.@: @code{backtrace} rather than @code{bt}.
24270 @c FIXME! So how does Joe User discover whether a command is an alias
24272 You can hook a multi-word command by adding @code{hook-} or
24273 @code{hookpost-} to the last word of the command, e.g.@:
24274 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24276 If an error occurs during the execution of your hook, execution of
24277 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24278 (before the command that you actually typed had a chance to run).
24280 If you try to define a hook which does not match any known command, you
24281 get a warning from the @code{define} command.
24283 @node Command Files
24284 @subsection Command Files
24286 @cindex command files
24287 @cindex scripting commands
24288 A command file for @value{GDBN} is a text file made of lines that are
24289 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24290 also be included. An empty line in a command file does nothing; it
24291 does not mean to repeat the last command, as it would from the
24294 You can request the execution of a command file with the @code{source}
24295 command. Note that the @code{source} command is also used to evaluate
24296 scripts that are not Command Files. The exact behavior can be configured
24297 using the @code{script-extension} setting.
24298 @xref{Extending GDB,, Extending GDB}.
24302 @cindex execute commands from a file
24303 @item source [-s] [-v] @var{filename}
24304 Execute the command file @var{filename}.
24307 The lines in a command file are generally executed sequentially,
24308 unless the order of execution is changed by one of the
24309 @emph{flow-control commands} described below. The commands are not
24310 printed as they are executed. An error in any command terminates
24311 execution of the command file and control is returned to the console.
24313 @value{GDBN} first searches for @var{filename} in the current directory.
24314 If the file is not found there, and @var{filename} does not specify a
24315 directory, then @value{GDBN} also looks for the file on the source search path
24316 (specified with the @samp{directory} command);
24317 except that @file{$cdir} is not searched because the compilation directory
24318 is not relevant to scripts.
24320 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24321 on the search path even if @var{filename} specifies a directory.
24322 The search is done by appending @var{filename} to each element of the
24323 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24324 and the search path contains @file{/home/user} then @value{GDBN} will
24325 look for the script @file{/home/user/mylib/myscript}.
24326 The search is also done if @var{filename} is an absolute path.
24327 For example, if @var{filename} is @file{/tmp/myscript} and
24328 the search path contains @file{/home/user} then @value{GDBN} will
24329 look for the script @file{/home/user/tmp/myscript}.
24330 For DOS-like systems, if @var{filename} contains a drive specification,
24331 it is stripped before concatenation. For example, if @var{filename} is
24332 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24333 will look for the script @file{c:/tmp/myscript}.
24335 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24336 each command as it is executed. The option must be given before
24337 @var{filename}, and is interpreted as part of the filename anywhere else.
24339 Commands that would ask for confirmation if used interactively proceed
24340 without asking when used in a command file. Many @value{GDBN} commands that
24341 normally print messages to say what they are doing omit the messages
24342 when called from command files.
24344 @value{GDBN} also accepts command input from standard input. In this
24345 mode, normal output goes to standard output and error output goes to
24346 standard error. Errors in a command file supplied on standard input do
24347 not terminate execution of the command file---execution continues with
24351 gdb < cmds > log 2>&1
24354 (The syntax above will vary depending on the shell used.) This example
24355 will execute commands from the file @file{cmds}. All output and errors
24356 would be directed to @file{log}.
24358 Since commands stored on command files tend to be more general than
24359 commands typed interactively, they frequently need to deal with
24360 complicated situations, such as different or unexpected values of
24361 variables and symbols, changes in how the program being debugged is
24362 built, etc. @value{GDBN} provides a set of flow-control commands to
24363 deal with these complexities. Using these commands, you can write
24364 complex scripts that loop over data structures, execute commands
24365 conditionally, etc.
24372 This command allows to include in your script conditionally executed
24373 commands. The @code{if} command takes a single argument, which is an
24374 expression to evaluate. It is followed by a series of commands that
24375 are executed only if the expression is true (its value is nonzero).
24376 There can then optionally be an @code{else} line, followed by a series
24377 of commands that are only executed if the expression was false. The
24378 end of the list is marked by a line containing @code{end}.
24382 This command allows to write loops. Its syntax is similar to
24383 @code{if}: the command takes a single argument, which is an expression
24384 to evaluate, and must be followed by the commands to execute, one per
24385 line, terminated by an @code{end}. These commands are called the
24386 @dfn{body} of the loop. The commands in the body of @code{while} are
24387 executed repeatedly as long as the expression evaluates to true.
24391 This command exits the @code{while} loop in whose body it is included.
24392 Execution of the script continues after that @code{while}s @code{end}
24395 @kindex loop_continue
24396 @item loop_continue
24397 This command skips the execution of the rest of the body of commands
24398 in the @code{while} loop in whose body it is included. Execution
24399 branches to the beginning of the @code{while} loop, where it evaluates
24400 the controlling expression.
24402 @kindex end@r{ (if/else/while commands)}
24404 Terminate the block of commands that are the body of @code{if},
24405 @code{else}, or @code{while} flow-control commands.
24410 @subsection Commands for Controlled Output
24412 During the execution of a command file or a user-defined command, normal
24413 @value{GDBN} output is suppressed; the only output that appears is what is
24414 explicitly printed by the commands in the definition. This section
24415 describes three commands useful for generating exactly the output you
24420 @item echo @var{text}
24421 @c I do not consider backslash-space a standard C escape sequence
24422 @c because it is not in ANSI.
24423 Print @var{text}. Nonprinting characters can be included in
24424 @var{text} using C escape sequences, such as @samp{\n} to print a
24425 newline. @strong{No newline is printed unless you specify one.}
24426 In addition to the standard C escape sequences, a backslash followed
24427 by a space stands for a space. This is useful for displaying a
24428 string with spaces at the beginning or the end, since leading and
24429 trailing spaces are otherwise trimmed from all arguments.
24430 To print @samp{@w{ }and foo =@w{ }}, use the command
24431 @samp{echo \@w{ }and foo = \@w{ }}.
24433 A backslash at the end of @var{text} can be used, as in C, to continue
24434 the command onto subsequent lines. For example,
24437 echo This is some text\n\
24438 which is continued\n\
24439 onto several lines.\n
24442 produces the same output as
24445 echo This is some text\n
24446 echo which is continued\n
24447 echo onto several lines.\n
24451 @item output @var{expression}
24452 Print the value of @var{expression} and nothing but that value: no
24453 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24454 value history either. @xref{Expressions, ,Expressions}, for more information
24457 @item output/@var{fmt} @var{expression}
24458 Print the value of @var{expression} in format @var{fmt}. You can use
24459 the same formats as for @code{print}. @xref{Output Formats,,Output
24460 Formats}, for more information.
24463 @item printf @var{template}, @var{expressions}@dots{}
24464 Print the values of one or more @var{expressions} under the control of
24465 the string @var{template}. To print several values, make
24466 @var{expressions} be a comma-separated list of individual expressions,
24467 which may be either numbers or pointers. Their values are printed as
24468 specified by @var{template}, exactly as a C program would do by
24469 executing the code below:
24472 printf (@var{template}, @var{expressions}@dots{});
24475 As in @code{C} @code{printf}, ordinary characters in @var{template}
24476 are printed verbatim, while @dfn{conversion specification} introduced
24477 by the @samp{%} character cause subsequent @var{expressions} to be
24478 evaluated, their values converted and formatted according to type and
24479 style information encoded in the conversion specifications, and then
24482 For example, you can print two values in hex like this:
24485 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24488 @code{printf} supports all the standard @code{C} conversion
24489 specifications, including the flags and modifiers between the @samp{%}
24490 character and the conversion letter, with the following exceptions:
24494 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24497 The modifier @samp{*} is not supported for specifying precision or
24501 The @samp{'} flag (for separation of digits into groups according to
24502 @code{LC_NUMERIC'}) is not supported.
24505 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24509 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24512 The conversion letters @samp{a} and @samp{A} are not supported.
24516 Note that the @samp{ll} type modifier is supported only if the
24517 underlying @code{C} implementation used to build @value{GDBN} supports
24518 the @code{long long int} type, and the @samp{L} type modifier is
24519 supported only if @code{long double} type is available.
24521 As in @code{C}, @code{printf} supports simple backslash-escape
24522 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24523 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24524 single character. Octal and hexadecimal escape sequences are not
24527 Additionally, @code{printf} supports conversion specifications for DFP
24528 (@dfn{Decimal Floating Point}) types using the following length modifiers
24529 together with a floating point specifier.
24534 @samp{H} for printing @code{Decimal32} types.
24537 @samp{D} for printing @code{Decimal64} types.
24540 @samp{DD} for printing @code{Decimal128} types.
24543 If the underlying @code{C} implementation used to build @value{GDBN} has
24544 support for the three length modifiers for DFP types, other modifiers
24545 such as width and precision will also be available for @value{GDBN} to use.
24547 In case there is no such @code{C} support, no additional modifiers will be
24548 available and the value will be printed in the standard way.
24550 Here's an example of printing DFP types using the above conversion letters:
24552 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24557 @item eval @var{template}, @var{expressions}@dots{}
24558 Convert the values of one or more @var{expressions} under the control of
24559 the string @var{template} to a command line, and call it.
24563 @node Auto-loading sequences
24564 @subsection Controlling auto-loading native @value{GDBN} scripts
24565 @cindex native script auto-loading
24567 When a new object file is read (for example, due to the @code{file}
24568 command, or because the inferior has loaded a shared library),
24569 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24570 @xref{Auto-loading extensions}.
24572 Auto-loading can be enabled or disabled,
24573 and the list of auto-loaded scripts can be printed.
24576 @anchor{set auto-load gdb-scripts}
24577 @kindex set auto-load gdb-scripts
24578 @item set auto-load gdb-scripts [on|off]
24579 Enable or disable the auto-loading of canned sequences of commands scripts.
24581 @anchor{show auto-load gdb-scripts}
24582 @kindex show auto-load gdb-scripts
24583 @item show auto-load gdb-scripts
24584 Show whether auto-loading of canned sequences of commands scripts is enabled or
24587 @anchor{info auto-load gdb-scripts}
24588 @kindex info auto-load gdb-scripts
24589 @cindex print list of auto-loaded canned sequences of commands scripts
24590 @item info auto-load gdb-scripts [@var{regexp}]
24591 Print the list of all canned sequences of commands scripts that @value{GDBN}
24595 If @var{regexp} is supplied only canned sequences of commands scripts with
24596 matching names are printed.
24598 @c Python docs live in a separate file.
24599 @include python.texi
24601 @c Guile docs live in a separate file.
24602 @include guile.texi
24604 @node Auto-loading extensions
24605 @section Auto-loading extensions
24606 @cindex auto-loading extensions
24608 @value{GDBN} provides two mechanisms for automatically loading extensions
24609 when a new object file is read (for example, due to the @code{file}
24610 command, or because the inferior has loaded a shared library):
24611 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24612 section of modern file formats like ELF.
24615 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24616 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24617 * Which flavor to choose?::
24620 The auto-loading feature is useful for supplying application-specific
24621 debugging commands and features.
24623 Auto-loading can be enabled or disabled,
24624 and the list of auto-loaded scripts can be printed.
24625 See the @samp{auto-loading} section of each extension language
24626 for more information.
24627 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24628 For Python files see @ref{Python Auto-loading}.
24630 Note that loading of this script file also requires accordingly configured
24631 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24633 @node objfile-gdbdotext file
24634 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24635 @cindex @file{@var{objfile}-gdb.gdb}
24636 @cindex @file{@var{objfile}-gdb.py}
24637 @cindex @file{@var{objfile}-gdb.scm}
24639 When a new object file is read, @value{GDBN} looks for a file named
24640 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24641 where @var{objfile} is the object file's name and
24642 where @var{ext} is the file extension for the extension language:
24645 @item @file{@var{objfile}-gdb.gdb}
24646 GDB's own command language
24647 @item @file{@var{objfile}-gdb.py}
24649 @item @file{@var{objfile}-gdb.scm}
24653 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24654 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24655 components, and appending the @file{-gdb.@var{ext}} suffix.
24656 If this file exists and is readable, @value{GDBN} will evaluate it as a
24657 script in the specified extension language.
24659 If this file does not exist, then @value{GDBN} will look for
24660 @var{script-name} file in all of the directories as specified below.
24662 Note that loading of these files requires an accordingly configured
24663 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24665 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24666 scripts normally according to its @file{.exe} filename. But if no scripts are
24667 found @value{GDBN} also tries script filenames matching the object file without
24668 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24669 is attempted on any platform. This makes the script filenames compatible
24670 between Unix and MS-Windows hosts.
24673 @anchor{set auto-load scripts-directory}
24674 @kindex set auto-load scripts-directory
24675 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24676 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24677 may be delimited by the host platform path separator in use
24678 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24680 Each entry here needs to be covered also by the security setting
24681 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24683 @anchor{with-auto-load-dir}
24684 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24685 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24686 configuration option @option{--with-auto-load-dir}.
24688 Any reference to @file{$debugdir} will get replaced by
24689 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24690 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24691 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24692 @file{$datadir} must be placed as a directory component --- either alone or
24693 delimited by @file{/} or @file{\} directory separators, depending on the host
24696 The list of directories uses path separator (@samp{:} on GNU and Unix
24697 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24698 to the @env{PATH} environment variable.
24700 @anchor{show auto-load scripts-directory}
24701 @kindex show auto-load scripts-directory
24702 @item show auto-load scripts-directory
24703 Show @value{GDBN} auto-loaded scripts location.
24705 @anchor{add-auto-load-scripts-directory}
24706 @kindex add-auto-load-scripts-directory
24707 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24708 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24709 Multiple entries may be delimited by the host platform path separator in use.
24712 @value{GDBN} does not track which files it has already auto-loaded this way.
24713 @value{GDBN} will load the associated script every time the corresponding
24714 @var{objfile} is opened.
24715 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24716 is evaluated more than once.
24718 @node dotdebug_gdb_scripts section
24719 @subsection The @code{.debug_gdb_scripts} section
24720 @cindex @code{.debug_gdb_scripts} section
24722 For systems using file formats like ELF and COFF,
24723 when @value{GDBN} loads a new object file
24724 it will look for a special section named @code{.debug_gdb_scripts}.
24725 If this section exists, its contents is a list of null-terminated entries
24726 specifying scripts to load. Each entry begins with a non-null prefix byte that
24727 specifies the kind of entry, typically the extension language and whether the
24728 script is in a file or inlined in @code{.debug_gdb_scripts}.
24730 The following entries are supported:
24733 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24734 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24735 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24736 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24739 @subsubsection Script File Entries
24741 If the entry specifies a file, @value{GDBN} will look for the file first
24742 in the current directory and then along the source search path
24743 (@pxref{Source Path, ,Specifying Source Directories}),
24744 except that @file{$cdir} is not searched, since the compilation
24745 directory is not relevant to scripts.
24747 File entries can be placed in section @code{.debug_gdb_scripts} with,
24748 for example, this GCC macro for Python scripts.
24751 /* Note: The "MS" section flags are to remove duplicates. */
24752 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24754 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24755 .byte 1 /* Python */\n\
24756 .asciz \"" script_name "\"\n\
24762 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24763 Then one can reference the macro in a header or source file like this:
24766 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24769 The script name may include directories if desired.
24771 Note that loading of this script file also requires accordingly configured
24772 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24774 If the macro invocation is put in a header, any application or library
24775 using this header will get a reference to the specified script,
24776 and with the use of @code{"MS"} attributes on the section, the linker
24777 will remove duplicates.
24779 @subsubsection Script Text Entries
24781 Script text entries allow to put the executable script in the entry
24782 itself instead of loading it from a file.
24783 The first line of the entry, everything after the prefix byte and up to
24784 the first newline (@code{0xa}) character, is the script name, and must not
24785 contain any kind of space character, e.g., spaces or tabs.
24786 The rest of the entry, up to the trailing null byte, is the script to
24787 execute in the specified language. The name needs to be unique among
24788 all script names, as @value{GDBN} executes each script only once based
24791 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24795 #include "symcat.h"
24796 #include "gdb/section-scripts.h"
24798 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24799 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24800 ".ascii \"gdb.inlined-script\\n\"\n"
24801 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24802 ".ascii \" def __init__ (self):\\n\"\n"
24803 ".ascii \" super (test_cmd, self).__init__ ("
24804 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24805 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24806 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24807 ".ascii \"test_cmd ()\\n\"\n"
24813 Loading of inlined scripts requires a properly configured
24814 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24815 The path to specify in @code{auto-load safe-path} is the path of the file
24816 containing the @code{.debug_gdb_scripts} section.
24818 @node Which flavor to choose?
24819 @subsection Which flavor to choose?
24821 Given the multiple ways of auto-loading extensions, it might not always
24822 be clear which one to choose. This section provides some guidance.
24825 Benefits of the @file{-gdb.@var{ext}} way:
24829 Can be used with file formats that don't support multiple sections.
24832 Ease of finding scripts for public libraries.
24834 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24835 in the source search path.
24836 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24837 isn't a source directory in which to find the script.
24840 Doesn't require source code additions.
24844 Benefits of the @code{.debug_gdb_scripts} way:
24848 Works with static linking.
24850 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24851 trigger their loading. When an application is statically linked the only
24852 objfile available is the executable, and it is cumbersome to attach all the
24853 scripts from all the input libraries to the executable's
24854 @file{-gdb.@var{ext}} script.
24857 Works with classes that are entirely inlined.
24859 Some classes can be entirely inlined, and thus there may not be an associated
24860 shared library to attach a @file{-gdb.@var{ext}} script to.
24863 Scripts needn't be copied out of the source tree.
24865 In some circumstances, apps can be built out of large collections of internal
24866 libraries, and the build infrastructure necessary to install the
24867 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24868 cumbersome. It may be easier to specify the scripts in the
24869 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24870 top of the source tree to the source search path.
24873 @node Multiple Extension Languages
24874 @section Multiple Extension Languages
24876 The Guile and Python extension languages do not share any state,
24877 and generally do not interfere with each other.
24878 There are some things to be aware of, however.
24880 @subsection Python comes first
24882 Python was @value{GDBN}'s first extension language, and to avoid breaking
24883 existing behaviour Python comes first. This is generally solved by the
24884 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24885 extension languages, and when it makes a call to an extension language,
24886 (say to pretty-print a value), it tries each in turn until an extension
24887 language indicates it has performed the request (e.g., has returned the
24888 pretty-printed form of a value).
24889 This extends to errors while performing such requests: If an error happens
24890 while, for example, trying to pretty-print an object then the error is
24891 reported and any following extension languages are not tried.
24894 @section Creating new spellings of existing commands
24895 @cindex aliases for commands
24897 It is often useful to define alternate spellings of existing commands.
24898 For example, if a new @value{GDBN} command defined in Python has
24899 a long name to type, it is handy to have an abbreviated version of it
24900 that involves less typing.
24902 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24903 of the @samp{step} command even though it is otherwise an ambiguous
24904 abbreviation of other commands like @samp{set} and @samp{show}.
24906 Aliases are also used to provide shortened or more common versions
24907 of multi-word commands. For example, @value{GDBN} provides the
24908 @samp{tty} alias of the @samp{set inferior-tty} command.
24910 You can define a new alias with the @samp{alias} command.
24915 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24919 @var{ALIAS} specifies the name of the new alias.
24920 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24923 @var{COMMAND} specifies the name of an existing command
24924 that is being aliased.
24926 The @samp{-a} option specifies that the new alias is an abbreviation
24927 of the command. Abbreviations are not shown in command
24928 lists displayed by the @samp{help} command.
24930 The @samp{--} option specifies the end of options,
24931 and is useful when @var{ALIAS} begins with a dash.
24933 Here is a simple example showing how to make an abbreviation
24934 of a command so that there is less to type.
24935 Suppose you were tired of typing @samp{disas}, the current
24936 shortest unambiguous abbreviation of the @samp{disassemble} command
24937 and you wanted an even shorter version named @samp{di}.
24938 The following will accomplish this.
24941 (gdb) alias -a di = disas
24944 Note that aliases are different from user-defined commands.
24945 With a user-defined command, you also need to write documentation
24946 for it with the @samp{document} command.
24947 An alias automatically picks up the documentation of the existing command.
24949 Here is an example where we make @samp{elms} an abbreviation of
24950 @samp{elements} in the @samp{set print elements} command.
24951 This is to show that you can make an abbreviation of any part
24955 (gdb) alias -a set print elms = set print elements
24956 (gdb) alias -a show print elms = show print elements
24957 (gdb) set p elms 20
24959 Limit on string chars or array elements to print is 200.
24962 Note that if you are defining an alias of a @samp{set} command,
24963 and you want to have an alias for the corresponding @samp{show}
24964 command, then you need to define the latter separately.
24966 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24967 @var{ALIAS}, just as they are normally.
24970 (gdb) alias -a set pr elms = set p ele
24973 Finally, here is an example showing the creation of a one word
24974 alias for a more complex command.
24975 This creates alias @samp{spe} of the command @samp{set print elements}.
24978 (gdb) alias spe = set print elements
24983 @chapter Command Interpreters
24984 @cindex command interpreters
24986 @value{GDBN} supports multiple command interpreters, and some command
24987 infrastructure to allow users or user interface writers to switch
24988 between interpreters or run commands in other interpreters.
24990 @value{GDBN} currently supports two command interpreters, the console
24991 interpreter (sometimes called the command-line interpreter or @sc{cli})
24992 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24993 describes both of these interfaces in great detail.
24995 By default, @value{GDBN} will start with the console interpreter.
24996 However, the user may choose to start @value{GDBN} with another
24997 interpreter by specifying the @option{-i} or @option{--interpreter}
24998 startup options. Defined interpreters include:
25002 @cindex console interpreter
25003 The traditional console or command-line interpreter. This is the most often
25004 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25005 @value{GDBN} will use this interpreter.
25008 @cindex mi interpreter
25009 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25010 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25011 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25015 @cindex mi2 interpreter
25016 The current @sc{gdb/mi} interface.
25019 @cindex mi1 interpreter
25020 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25024 @cindex invoke another interpreter
25026 @kindex interpreter-exec
25027 You may execute commands in any interpreter from the current
25028 interpreter using the appropriate command. If you are running the
25029 console interpreter, simply use the @code{interpreter-exec} command:
25032 interpreter-exec mi "-data-list-register-names"
25035 @sc{gdb/mi} has a similar command, although it is only available in versions of
25036 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25038 Note that @code{interpreter-exec} only changes the interpreter for the
25039 duration of the specified command. It does not change the interpreter
25042 @cindex start a new independent interpreter
25044 Although you may only choose a single interpreter at startup, it is
25045 possible to run an independent interpreter on a specified input/output
25046 device (usually a tty).
25048 For example, consider a debugger GUI or IDE that wants to provide a
25049 @value{GDBN} console view. It may do so by embedding a terminal
25050 emulator widget in its GUI, starting @value{GDBN} in the traditional
25051 command-line mode with stdin/stdout/stderr redirected to that
25052 terminal, and then creating an MI interpreter running on a specified
25053 input/output device. The console interpreter created by @value{GDBN}
25054 at startup handles commands the user types in the terminal widget,
25055 while the GUI controls and synchronizes state with @value{GDBN} using
25056 the separate MI interpreter.
25058 To start a new secondary @dfn{user interface} running MI, use the
25059 @code{new-ui} command:
25062 @cindex new user interface
25064 new-ui @var{interpreter} @var{tty}
25067 The @var{interpreter} parameter specifies the interpreter to run.
25068 This accepts the same values as the @code{interpreter-exec} command.
25069 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25070 @var{tty} parameter specifies the name of the bidirectional file the
25071 interpreter uses for input/output, usually the name of a
25072 pseudoterminal slave on Unix systems. For example:
25075 (@value{GDBP}) new-ui mi /dev/pts/9
25079 runs an MI interpreter on @file{/dev/pts/9}.
25082 @chapter @value{GDBN} Text User Interface
25084 @cindex Text User Interface
25087 * TUI Overview:: TUI overview
25088 * TUI Keys:: TUI key bindings
25089 * TUI Single Key Mode:: TUI single key mode
25090 * TUI Commands:: TUI-specific commands
25091 * TUI Configuration:: TUI configuration variables
25094 The @value{GDBN} Text User Interface (TUI) is a terminal
25095 interface which uses the @code{curses} library to show the source
25096 file, the assembly output, the program registers and @value{GDBN}
25097 commands in separate text windows. The TUI mode is supported only
25098 on platforms where a suitable version of the @code{curses} library
25101 The TUI mode is enabled by default when you invoke @value{GDBN} as
25102 @samp{@value{GDBP} -tui}.
25103 You can also switch in and out of TUI mode while @value{GDBN} runs by
25104 using various TUI commands and key bindings, such as @command{tui
25105 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25106 @ref{TUI Keys, ,TUI Key Bindings}.
25109 @section TUI Overview
25111 In TUI mode, @value{GDBN} can display several text windows:
25115 This window is the @value{GDBN} command window with the @value{GDBN}
25116 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25117 managed using readline.
25120 The source window shows the source file of the program. The current
25121 line and active breakpoints are displayed in this window.
25124 The assembly window shows the disassembly output of the program.
25127 This window shows the processor registers. Registers are highlighted
25128 when their values change.
25131 The source and assembly windows show the current program position
25132 by highlighting the current line and marking it with a @samp{>} marker.
25133 Breakpoints are indicated with two markers. The first marker
25134 indicates the breakpoint type:
25138 Breakpoint which was hit at least once.
25141 Breakpoint which was never hit.
25144 Hardware breakpoint which was hit at least once.
25147 Hardware breakpoint which was never hit.
25150 The second marker indicates whether the breakpoint is enabled or not:
25154 Breakpoint is enabled.
25157 Breakpoint is disabled.
25160 The source, assembly and register windows are updated when the current
25161 thread changes, when the frame changes, or when the program counter
25164 These windows are not all visible at the same time. The command
25165 window is always visible. The others can be arranged in several
25176 source and assembly,
25179 source and registers, or
25182 assembly and registers.
25185 A status line above the command window shows the following information:
25189 Indicates the current @value{GDBN} target.
25190 (@pxref{Targets, ,Specifying a Debugging Target}).
25193 Gives the current process or thread number.
25194 When no process is being debugged, this field is set to @code{No process}.
25197 Gives the current function name for the selected frame.
25198 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25199 When there is no symbol corresponding to the current program counter,
25200 the string @code{??} is displayed.
25203 Indicates the current line number for the selected frame.
25204 When the current line number is not known, the string @code{??} is displayed.
25207 Indicates the current program counter address.
25211 @section TUI Key Bindings
25212 @cindex TUI key bindings
25214 The TUI installs several key bindings in the readline keymaps
25215 @ifset SYSTEM_READLINE
25216 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25218 @ifclear SYSTEM_READLINE
25219 (@pxref{Command Line Editing}).
25221 The following key bindings are installed for both TUI mode and the
25222 @value{GDBN} standard mode.
25231 Enter or leave the TUI mode. When leaving the TUI mode,
25232 the curses window management stops and @value{GDBN} operates using
25233 its standard mode, writing on the terminal directly. When reentering
25234 the TUI mode, control is given back to the curses windows.
25235 The screen is then refreshed.
25239 Use a TUI layout with only one window. The layout will
25240 either be @samp{source} or @samp{assembly}. When the TUI mode
25241 is not active, it will switch to the TUI mode.
25243 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25247 Use a TUI layout with at least two windows. When the current
25248 layout already has two windows, the next layout with two windows is used.
25249 When a new layout is chosen, one window will always be common to the
25250 previous layout and the new one.
25252 Think of it as the Emacs @kbd{C-x 2} binding.
25256 Change the active window. The TUI associates several key bindings
25257 (like scrolling and arrow keys) with the active window. This command
25258 gives the focus to the next TUI window.
25260 Think of it as the Emacs @kbd{C-x o} binding.
25264 Switch in and out of the TUI SingleKey mode that binds single
25265 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25268 The following key bindings only work in the TUI mode:
25273 Scroll the active window one page up.
25277 Scroll the active window one page down.
25281 Scroll the active window one line up.
25285 Scroll the active window one line down.
25289 Scroll the active window one column left.
25293 Scroll the active window one column right.
25297 Refresh the screen.
25300 Because the arrow keys scroll the active window in the TUI mode, they
25301 are not available for their normal use by readline unless the command
25302 window has the focus. When another window is active, you must use
25303 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25304 and @kbd{C-f} to control the command window.
25306 @node TUI Single Key Mode
25307 @section TUI Single Key Mode
25308 @cindex TUI single key mode
25310 The TUI also provides a @dfn{SingleKey} mode, which binds several
25311 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25312 switch into this mode, where the following key bindings are used:
25315 @kindex c @r{(SingleKey TUI key)}
25319 @kindex d @r{(SingleKey TUI key)}
25323 @kindex f @r{(SingleKey TUI key)}
25327 @kindex n @r{(SingleKey TUI key)}
25331 @kindex q @r{(SingleKey TUI key)}
25333 exit the SingleKey mode.
25335 @kindex r @r{(SingleKey TUI key)}
25339 @kindex s @r{(SingleKey TUI key)}
25343 @kindex u @r{(SingleKey TUI key)}
25347 @kindex v @r{(SingleKey TUI key)}
25351 @kindex w @r{(SingleKey TUI key)}
25356 Other keys temporarily switch to the @value{GDBN} command prompt.
25357 The key that was pressed is inserted in the editing buffer so that
25358 it is possible to type most @value{GDBN} commands without interaction
25359 with the TUI SingleKey mode. Once the command is entered the TUI
25360 SingleKey mode is restored. The only way to permanently leave
25361 this mode is by typing @kbd{q} or @kbd{C-x s}.
25365 @section TUI-specific Commands
25366 @cindex TUI commands
25368 The TUI has specific commands to control the text windows.
25369 These commands are always available, even when @value{GDBN} is not in
25370 the TUI mode. When @value{GDBN} is in the standard mode, most
25371 of these commands will automatically switch to the TUI mode.
25373 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25374 terminal, or @value{GDBN} has been started with the machine interface
25375 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25376 these commands will fail with an error, because it would not be
25377 possible or desirable to enable curses window management.
25382 Activate TUI mode. The last active TUI window layout will be used if
25383 TUI mode has prevsiouly been used in the current debugging session,
25384 otherwise a default layout is used.
25387 @kindex tui disable
25388 Disable TUI mode, returning to the console interpreter.
25392 List and give the size of all displayed windows.
25394 @item layout @var{name}
25396 Changes which TUI windows are displayed. In each layout the command
25397 window is always displayed, the @var{name} parameter controls which
25398 additional windows are displayed, and can be any of the following:
25402 Display the next layout.
25405 Display the previous layout.
25408 Display the source and command windows.
25411 Display the assembly and command windows.
25414 Display the source, assembly, and command windows.
25417 When in @code{src} layout display the register, source, and command
25418 windows. When in @code{asm} or @code{split} layout display the
25419 register, assembler, and command windows.
25422 @item focus @var{name}
25424 Changes which TUI window is currently active for scrolling. The
25425 @var{name} parameter can be any of the following:
25429 Make the next window active for scrolling.
25432 Make the previous window active for scrolling.
25435 Make the source window active for scrolling.
25438 Make the assembly window active for scrolling.
25441 Make the register window active for scrolling.
25444 Make the command window active for scrolling.
25449 Refresh the screen. This is similar to typing @kbd{C-L}.
25451 @item tui reg @var{group}
25453 Changes the register group displayed in the tui register window to
25454 @var{group}. If the register window is not currently displayed this
25455 command will cause the register window to be displayed. The list of
25456 register groups, as well as their order is target specific. The
25457 following groups are available on most targets:
25460 Repeatedly selecting this group will cause the display to cycle
25461 through all of the available register groups.
25464 Repeatedly selecting this group will cause the display to cycle
25465 through all of the available register groups in the reverse order to
25469 Display the general registers.
25471 Display the floating point registers.
25473 Display the system registers.
25475 Display the vector registers.
25477 Display all registers.
25482 Update the source window and the current execution point.
25484 @item winheight @var{name} +@var{count}
25485 @itemx winheight @var{name} -@var{count}
25487 Change the height of the window @var{name} by @var{count}
25488 lines. Positive counts increase the height, while negative counts
25489 decrease it. The @var{name} parameter can be one of @code{src} (the
25490 source window), @code{cmd} (the command window), @code{asm} (the
25491 disassembly window), or @code{regs} (the register display window).
25493 @item tabset @var{nchars}
25495 Set the width of tab stops to be @var{nchars} characters. This
25496 setting affects the display of TAB characters in the source and
25500 @node TUI Configuration
25501 @section TUI Configuration Variables
25502 @cindex TUI configuration variables
25504 Several configuration variables control the appearance of TUI windows.
25507 @item set tui border-kind @var{kind}
25508 @kindex set tui border-kind
25509 Select the border appearance for the source, assembly and register windows.
25510 The possible values are the following:
25513 Use a space character to draw the border.
25516 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25519 Use the Alternate Character Set to draw the border. The border is
25520 drawn using character line graphics if the terminal supports them.
25523 @item set tui border-mode @var{mode}
25524 @kindex set tui border-mode
25525 @itemx set tui active-border-mode @var{mode}
25526 @kindex set tui active-border-mode
25527 Select the display attributes for the borders of the inactive windows
25528 or the active window. The @var{mode} can be one of the following:
25531 Use normal attributes to display the border.
25537 Use reverse video mode.
25540 Use half bright mode.
25542 @item half-standout
25543 Use half bright and standout mode.
25546 Use extra bright or bold mode.
25548 @item bold-standout
25549 Use extra bright or bold and standout mode.
25554 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25557 @cindex @sc{gnu} Emacs
25558 A special interface allows you to use @sc{gnu} Emacs to view (and
25559 edit) the source files for the program you are debugging with
25562 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25563 executable file you want to debug as an argument. This command starts
25564 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25565 created Emacs buffer.
25566 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25568 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25573 All ``terminal'' input and output goes through an Emacs buffer, called
25576 This applies both to @value{GDBN} commands and their output, and to the input
25577 and output done by the program you are debugging.
25579 This is useful because it means that you can copy the text of previous
25580 commands and input them again; you can even use parts of the output
25583 All the facilities of Emacs' Shell mode are available for interacting
25584 with your program. In particular, you can send signals the usual
25585 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25589 @value{GDBN} displays source code through Emacs.
25591 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25592 source file for that frame and puts an arrow (@samp{=>}) at the
25593 left margin of the current line. Emacs uses a separate buffer for
25594 source display, and splits the screen to show both your @value{GDBN} session
25597 Explicit @value{GDBN} @code{list} or search commands still produce output as
25598 usual, but you probably have no reason to use them from Emacs.
25601 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25602 a graphical mode, enabled by default, which provides further buffers
25603 that can control the execution and describe the state of your program.
25604 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25606 If you specify an absolute file name when prompted for the @kbd{M-x
25607 gdb} argument, then Emacs sets your current working directory to where
25608 your program resides. If you only specify the file name, then Emacs
25609 sets your current working directory to the directory associated
25610 with the previous buffer. In this case, @value{GDBN} may find your
25611 program by searching your environment's @code{PATH} variable, but on
25612 some operating systems it might not find the source. So, although the
25613 @value{GDBN} input and output session proceeds normally, the auxiliary
25614 buffer does not display the current source and line of execution.
25616 The initial working directory of @value{GDBN} is printed on the top
25617 line of the GUD buffer and this serves as a default for the commands
25618 that specify files for @value{GDBN} to operate on. @xref{Files,
25619 ,Commands to Specify Files}.
25621 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25622 need to call @value{GDBN} by a different name (for example, if you
25623 keep several configurations around, with different names) you can
25624 customize the Emacs variable @code{gud-gdb-command-name} to run the
25627 In the GUD buffer, you can use these special Emacs commands in
25628 addition to the standard Shell mode commands:
25632 Describe the features of Emacs' GUD Mode.
25635 Execute to another source line, like the @value{GDBN} @code{step} command; also
25636 update the display window to show the current file and location.
25639 Execute to next source line in this function, skipping all function
25640 calls, like the @value{GDBN} @code{next} command. Then update the display window
25641 to show the current file and location.
25644 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25645 display window accordingly.
25648 Execute until exit from the selected stack frame, like the @value{GDBN}
25649 @code{finish} command.
25652 Continue execution of your program, like the @value{GDBN} @code{continue}
25656 Go up the number of frames indicated by the numeric argument
25657 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25658 like the @value{GDBN} @code{up} command.
25661 Go down the number of frames indicated by the numeric argument, like the
25662 @value{GDBN} @code{down} command.
25665 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25666 tells @value{GDBN} to set a breakpoint on the source line point is on.
25668 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25669 separate frame which shows a backtrace when the GUD buffer is current.
25670 Move point to any frame in the stack and type @key{RET} to make it
25671 become the current frame and display the associated source in the
25672 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25673 selected frame become the current one. In graphical mode, the
25674 speedbar displays watch expressions.
25676 If you accidentally delete the source-display buffer, an easy way to get
25677 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25678 request a frame display; when you run under Emacs, this recreates
25679 the source buffer if necessary to show you the context of the current
25682 The source files displayed in Emacs are in ordinary Emacs buffers
25683 which are visiting the source files in the usual way. You can edit
25684 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25685 communicates with Emacs in terms of line numbers. If you add or
25686 delete lines from the text, the line numbers that @value{GDBN} knows cease
25687 to correspond properly with the code.
25689 A more detailed description of Emacs' interaction with @value{GDBN} is
25690 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25694 @chapter The @sc{gdb/mi} Interface
25696 @unnumberedsec Function and Purpose
25698 @cindex @sc{gdb/mi}, its purpose
25699 @sc{gdb/mi} is a line based machine oriented text interface to
25700 @value{GDBN} and is activated by specifying using the
25701 @option{--interpreter} command line option (@pxref{Mode Options}). It
25702 is specifically intended to support the development of systems which
25703 use the debugger as just one small component of a larger system.
25705 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25706 in the form of a reference manual.
25708 Note that @sc{gdb/mi} is still under construction, so some of the
25709 features described below are incomplete and subject to change
25710 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25712 @unnumberedsec Notation and Terminology
25714 @cindex notational conventions, for @sc{gdb/mi}
25715 This chapter uses the following notation:
25719 @code{|} separates two alternatives.
25722 @code{[ @var{something} ]} indicates that @var{something} is optional:
25723 it may or may not be given.
25726 @code{( @var{group} )*} means that @var{group} inside the parentheses
25727 may repeat zero or more times.
25730 @code{( @var{group} )+} means that @var{group} inside the parentheses
25731 may repeat one or more times.
25734 @code{"@var{string}"} means a literal @var{string}.
25738 @heading Dependencies
25742 * GDB/MI General Design::
25743 * GDB/MI Command Syntax::
25744 * GDB/MI Compatibility with CLI::
25745 * GDB/MI Development and Front Ends::
25746 * GDB/MI Output Records::
25747 * GDB/MI Simple Examples::
25748 * GDB/MI Command Description Format::
25749 * GDB/MI Breakpoint Commands::
25750 * GDB/MI Catchpoint Commands::
25751 * GDB/MI Program Context::
25752 * GDB/MI Thread Commands::
25753 * GDB/MI Ada Tasking Commands::
25754 * GDB/MI Program Execution::
25755 * GDB/MI Stack Manipulation::
25756 * GDB/MI Variable Objects::
25757 * GDB/MI Data Manipulation::
25758 * GDB/MI Tracepoint Commands::
25759 * GDB/MI Symbol Query::
25760 * GDB/MI File Commands::
25762 * GDB/MI Kod Commands::
25763 * GDB/MI Memory Overlay Commands::
25764 * GDB/MI Signal Handling Commands::
25766 * GDB/MI Target Manipulation::
25767 * GDB/MI File Transfer Commands::
25768 * GDB/MI Ada Exceptions Commands::
25769 * GDB/MI Support Commands::
25770 * GDB/MI Miscellaneous Commands::
25773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25774 @node GDB/MI General Design
25775 @section @sc{gdb/mi} General Design
25776 @cindex GDB/MI General Design
25778 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25779 parts---commands sent to @value{GDBN}, responses to those commands
25780 and notifications. Each command results in exactly one response,
25781 indicating either successful completion of the command, or an error.
25782 For the commands that do not resume the target, the response contains the
25783 requested information. For the commands that resume the target, the
25784 response only indicates whether the target was successfully resumed.
25785 Notifications is the mechanism for reporting changes in the state of the
25786 target, or in @value{GDBN} state, that cannot conveniently be associated with
25787 a command and reported as part of that command response.
25789 The important examples of notifications are:
25793 Exec notifications. These are used to report changes in
25794 target state---when a target is resumed, or stopped. It would not
25795 be feasible to include this information in response of resuming
25796 commands, because one resume commands can result in multiple events in
25797 different threads. Also, quite some time may pass before any event
25798 happens in the target, while a frontend needs to know whether the resuming
25799 command itself was successfully executed.
25802 Console output, and status notifications. Console output
25803 notifications are used to report output of CLI commands, as well as
25804 diagnostics for other commands. Status notifications are used to
25805 report the progress of a long-running operation. Naturally, including
25806 this information in command response would mean no output is produced
25807 until the command is finished, which is undesirable.
25810 General notifications. Commands may have various side effects on
25811 the @value{GDBN} or target state beyond their official purpose. For example,
25812 a command may change the selected thread. Although such changes can
25813 be included in command response, using notification allows for more
25814 orthogonal frontend design.
25818 There's no guarantee that whenever an MI command reports an error,
25819 @value{GDBN} or the target are in any specific state, and especially,
25820 the state is not reverted to the state before the MI command was
25821 processed. Therefore, whenever an MI command results in an error,
25822 we recommend that the frontend refreshes all the information shown in
25823 the user interface.
25827 * Context management::
25828 * Asynchronous and non-stop modes::
25832 @node Context management
25833 @subsection Context management
25835 @subsubsection Threads and Frames
25837 In most cases when @value{GDBN} accesses the target, this access is
25838 done in context of a specific thread and frame (@pxref{Frames}).
25839 Often, even when accessing global data, the target requires that a thread
25840 be specified. The CLI interface maintains the selected thread and frame,
25841 and supplies them to target on each command. This is convenient,
25842 because a command line user would not want to specify that information
25843 explicitly on each command, and because user interacts with
25844 @value{GDBN} via a single terminal, so no confusion is possible as
25845 to what thread and frame are the current ones.
25847 In the case of MI, the concept of selected thread and frame is less
25848 useful. First, a frontend can easily remember this information
25849 itself. Second, a graphical frontend can have more than one window,
25850 each one used for debugging a different thread, and the frontend might
25851 want to access additional threads for internal purposes. This
25852 increases the risk that by relying on implicitly selected thread, the
25853 frontend may be operating on a wrong one. Therefore, each MI command
25854 should explicitly specify which thread and frame to operate on. To
25855 make it possible, each MI command accepts the @samp{--thread} and
25856 @samp{--frame} options, the value to each is @value{GDBN} global
25857 identifier for thread and frame to operate on.
25859 Usually, each top-level window in a frontend allows the user to select
25860 a thread and a frame, and remembers the user selection for further
25861 operations. However, in some cases @value{GDBN} may suggest that the
25862 current thread or frame be changed. For example, when stopping on a
25863 breakpoint it is reasonable to switch to the thread where breakpoint is
25864 hit. For another example, if the user issues the CLI @samp{thread} or
25865 @samp{frame} commands via the frontend, it is desirable to change the
25866 frontend's selection to the one specified by user. @value{GDBN}
25867 communicates the suggestion to change current thread and frame using the
25868 @samp{=thread-selected} notification.
25870 Note that historically, MI shares the selected thread with CLI, so
25871 frontends used the @code{-thread-select} to execute commands in the
25872 right context. However, getting this to work right is cumbersome. The
25873 simplest way is for frontend to emit @code{-thread-select} command
25874 before every command. This doubles the number of commands that need
25875 to be sent. The alternative approach is to suppress @code{-thread-select}
25876 if the selected thread in @value{GDBN} is supposed to be identical to the
25877 thread the frontend wants to operate on. However, getting this
25878 optimization right can be tricky. In particular, if the frontend
25879 sends several commands to @value{GDBN}, and one of the commands changes the
25880 selected thread, then the behaviour of subsequent commands will
25881 change. So, a frontend should either wait for response from such
25882 problematic commands, or explicitly add @code{-thread-select} for
25883 all subsequent commands. No frontend is known to do this exactly
25884 right, so it is suggested to just always pass the @samp{--thread} and
25885 @samp{--frame} options.
25887 @subsubsection Language
25889 The execution of several commands depends on which language is selected.
25890 By default, the current language (@pxref{show language}) is used.
25891 But for commands known to be language-sensitive, it is recommended
25892 to use the @samp{--language} option. This option takes one argument,
25893 which is the name of the language to use while executing the command.
25897 -data-evaluate-expression --language c "sizeof (void*)"
25902 The valid language names are the same names accepted by the
25903 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25904 @samp{local} or @samp{unknown}.
25906 @node Asynchronous and non-stop modes
25907 @subsection Asynchronous command execution and non-stop mode
25909 On some targets, @value{GDBN} is capable of processing MI commands
25910 even while the target is running. This is called @dfn{asynchronous
25911 command execution} (@pxref{Background Execution}). The frontend may
25912 specify a preferrence for asynchronous execution using the
25913 @code{-gdb-set mi-async 1} command, which should be emitted before
25914 either running the executable or attaching to the target. After the
25915 frontend has started the executable or attached to the target, it can
25916 find if asynchronous execution is enabled using the
25917 @code{-list-target-features} command.
25920 @item -gdb-set mi-async on
25921 @item -gdb-set mi-async off
25922 Set whether MI is in asynchronous mode.
25924 When @code{off}, which is the default, MI execution commands (e.g.,
25925 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25926 for the program to stop before processing further commands.
25928 When @code{on}, MI execution commands are background execution
25929 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25930 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25931 MI commands even while the target is running.
25933 @item -gdb-show mi-async
25934 Show whether MI asynchronous mode is enabled.
25937 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25938 @code{target-async} instead of @code{mi-async}, and it had the effect
25939 of both putting MI in asynchronous mode and making CLI background
25940 commands possible. CLI background commands are now always possible
25941 ``out of the box'' if the target supports them. The old spelling is
25942 kept as a deprecated alias for backwards compatibility.
25944 Even if @value{GDBN} can accept a command while target is running,
25945 many commands that access the target do not work when the target is
25946 running. Therefore, asynchronous command execution is most useful
25947 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25948 it is possible to examine the state of one thread, while other threads
25951 When a given thread is running, MI commands that try to access the
25952 target in the context of that thread may not work, or may work only on
25953 some targets. In particular, commands that try to operate on thread's
25954 stack will not work, on any target. Commands that read memory, or
25955 modify breakpoints, may work or not work, depending on the target. Note
25956 that even commands that operate on global state, such as @code{print},
25957 @code{set}, and breakpoint commands, still access the target in the
25958 context of a specific thread, so frontend should try to find a
25959 stopped thread and perform the operation on that thread (using the
25960 @samp{--thread} option).
25962 Which commands will work in the context of a running thread is
25963 highly target dependent. However, the two commands
25964 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25965 to find the state of a thread, will always work.
25967 @node Thread groups
25968 @subsection Thread groups
25969 @value{GDBN} may be used to debug several processes at the same time.
25970 On some platfroms, @value{GDBN} may support debugging of several
25971 hardware systems, each one having several cores with several different
25972 processes running on each core. This section describes the MI
25973 mechanism to support such debugging scenarios.
25975 The key observation is that regardless of the structure of the
25976 target, MI can have a global list of threads, because most commands that
25977 accept the @samp{--thread} option do not need to know what process that
25978 thread belongs to. Therefore, it is not necessary to introduce
25979 neither additional @samp{--process} option, nor an notion of the
25980 current process in the MI interface. The only strictly new feature
25981 that is required is the ability to find how the threads are grouped
25984 To allow the user to discover such grouping, and to support arbitrary
25985 hierarchy of machines/cores/processes, MI introduces the concept of a
25986 @dfn{thread group}. Thread group is a collection of threads and other
25987 thread groups. A thread group always has a string identifier, a type,
25988 and may have additional attributes specific to the type. A new
25989 command, @code{-list-thread-groups}, returns the list of top-level
25990 thread groups, which correspond to processes that @value{GDBN} is
25991 debugging at the moment. By passing an identifier of a thread group
25992 to the @code{-list-thread-groups} command, it is possible to obtain
25993 the members of specific thread group.
25995 To allow the user to easily discover processes, and other objects, he
25996 wishes to debug, a concept of @dfn{available thread group} is
25997 introduced. Available thread group is an thread group that
25998 @value{GDBN} is not debugging, but that can be attached to, using the
25999 @code{-target-attach} command. The list of available top-level thread
26000 groups can be obtained using @samp{-list-thread-groups --available}.
26001 In general, the content of a thread group may be only retrieved only
26002 after attaching to that thread group.
26004 Thread groups are related to inferiors (@pxref{Inferiors and
26005 Programs}). Each inferior corresponds to a thread group of a special
26006 type @samp{process}, and some additional operations are permitted on
26007 such thread groups.
26009 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26010 @node GDB/MI Command Syntax
26011 @section @sc{gdb/mi} Command Syntax
26014 * GDB/MI Input Syntax::
26015 * GDB/MI Output Syntax::
26018 @node GDB/MI Input Syntax
26019 @subsection @sc{gdb/mi} Input Syntax
26021 @cindex input syntax for @sc{gdb/mi}
26022 @cindex @sc{gdb/mi}, input syntax
26024 @item @var{command} @expansion{}
26025 @code{@var{cli-command} | @var{mi-command}}
26027 @item @var{cli-command} @expansion{}
26028 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26029 @var{cli-command} is any existing @value{GDBN} CLI command.
26031 @item @var{mi-command} @expansion{}
26032 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26033 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26035 @item @var{token} @expansion{}
26036 "any sequence of digits"
26038 @item @var{option} @expansion{}
26039 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26041 @item @var{parameter} @expansion{}
26042 @code{@var{non-blank-sequence} | @var{c-string}}
26044 @item @var{operation} @expansion{}
26045 @emph{any of the operations described in this chapter}
26047 @item @var{non-blank-sequence} @expansion{}
26048 @emph{anything, provided it doesn't contain special characters such as
26049 "-", @var{nl}, """ and of course " "}
26051 @item @var{c-string} @expansion{}
26052 @code{""" @var{seven-bit-iso-c-string-content} """}
26054 @item @var{nl} @expansion{}
26063 The CLI commands are still handled by the @sc{mi} interpreter; their
26064 output is described below.
26067 The @code{@var{token}}, when present, is passed back when the command
26071 Some @sc{mi} commands accept optional arguments as part of the parameter
26072 list. Each option is identified by a leading @samp{-} (dash) and may be
26073 followed by an optional argument parameter. Options occur first in the
26074 parameter list and can be delimited from normal parameters using
26075 @samp{--} (this is useful when some parameters begin with a dash).
26082 We want easy access to the existing CLI syntax (for debugging).
26085 We want it to be easy to spot a @sc{mi} operation.
26088 @node GDB/MI Output Syntax
26089 @subsection @sc{gdb/mi} Output Syntax
26091 @cindex output syntax of @sc{gdb/mi}
26092 @cindex @sc{gdb/mi}, output syntax
26093 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26094 followed, optionally, by a single result record. This result record
26095 is for the most recent command. The sequence of output records is
26096 terminated by @samp{(gdb)}.
26098 If an input command was prefixed with a @code{@var{token}} then the
26099 corresponding output for that command will also be prefixed by that same
26103 @item @var{output} @expansion{}
26104 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26106 @item @var{result-record} @expansion{}
26107 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26109 @item @var{out-of-band-record} @expansion{}
26110 @code{@var{async-record} | @var{stream-record}}
26112 @item @var{async-record} @expansion{}
26113 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26115 @item @var{exec-async-output} @expansion{}
26116 @code{[ @var{token} ] "*" @var{async-output nl}}
26118 @item @var{status-async-output} @expansion{}
26119 @code{[ @var{token} ] "+" @var{async-output nl}}
26121 @item @var{notify-async-output} @expansion{}
26122 @code{[ @var{token} ] "=" @var{async-output nl}}
26124 @item @var{async-output} @expansion{}
26125 @code{@var{async-class} ( "," @var{result} )*}
26127 @item @var{result-class} @expansion{}
26128 @code{"done" | "running" | "connected" | "error" | "exit"}
26130 @item @var{async-class} @expansion{}
26131 @code{"stopped" | @var{others}} (where @var{others} will be added
26132 depending on the needs---this is still in development).
26134 @item @var{result} @expansion{}
26135 @code{ @var{variable} "=" @var{value}}
26137 @item @var{variable} @expansion{}
26138 @code{ @var{string} }
26140 @item @var{value} @expansion{}
26141 @code{ @var{const} | @var{tuple} | @var{list} }
26143 @item @var{const} @expansion{}
26144 @code{@var{c-string}}
26146 @item @var{tuple} @expansion{}
26147 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26149 @item @var{list} @expansion{}
26150 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26151 @var{result} ( "," @var{result} )* "]" }
26153 @item @var{stream-record} @expansion{}
26154 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26156 @item @var{console-stream-output} @expansion{}
26157 @code{"~" @var{c-string nl}}
26159 @item @var{target-stream-output} @expansion{}
26160 @code{"@@" @var{c-string nl}}
26162 @item @var{log-stream-output} @expansion{}
26163 @code{"&" @var{c-string nl}}
26165 @item @var{nl} @expansion{}
26168 @item @var{token} @expansion{}
26169 @emph{any sequence of digits}.
26177 All output sequences end in a single line containing a period.
26180 The @code{@var{token}} is from the corresponding request. Note that
26181 for all async output, while the token is allowed by the grammar and
26182 may be output by future versions of @value{GDBN} for select async
26183 output messages, it is generally omitted. Frontends should treat
26184 all async output as reporting general changes in the state of the
26185 target and there should be no need to associate async output to any
26189 @cindex status output in @sc{gdb/mi}
26190 @var{status-async-output} contains on-going status information about the
26191 progress of a slow operation. It can be discarded. All status output is
26192 prefixed by @samp{+}.
26195 @cindex async output in @sc{gdb/mi}
26196 @var{exec-async-output} contains asynchronous state change on the target
26197 (stopped, started, disappeared). All async output is prefixed by
26201 @cindex notify output in @sc{gdb/mi}
26202 @var{notify-async-output} contains supplementary information that the
26203 client should handle (e.g., a new breakpoint information). All notify
26204 output is prefixed by @samp{=}.
26207 @cindex console output in @sc{gdb/mi}
26208 @var{console-stream-output} is output that should be displayed as is in the
26209 console. It is the textual response to a CLI command. All the console
26210 output is prefixed by @samp{~}.
26213 @cindex target output in @sc{gdb/mi}
26214 @var{target-stream-output} is the output produced by the target program.
26215 All the target output is prefixed by @samp{@@}.
26218 @cindex log output in @sc{gdb/mi}
26219 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26220 instance messages that should be displayed as part of an error log. All
26221 the log output is prefixed by @samp{&}.
26224 @cindex list output in @sc{gdb/mi}
26225 New @sc{gdb/mi} commands should only output @var{lists} containing
26231 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26232 details about the various output records.
26234 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26235 @node GDB/MI Compatibility with CLI
26236 @section @sc{gdb/mi} Compatibility with CLI
26238 @cindex compatibility, @sc{gdb/mi} and CLI
26239 @cindex @sc{gdb/mi}, compatibility with CLI
26241 For the developers convenience CLI commands can be entered directly,
26242 but there may be some unexpected behaviour. For example, commands
26243 that query the user will behave as if the user replied yes, breakpoint
26244 command lists are not executed and some CLI commands, such as
26245 @code{if}, @code{when} and @code{define}, prompt for further input with
26246 @samp{>}, which is not valid MI output.
26248 This feature may be removed at some stage in the future and it is
26249 recommended that front ends use the @code{-interpreter-exec} command
26250 (@pxref{-interpreter-exec}).
26252 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26253 @node GDB/MI Development and Front Ends
26254 @section @sc{gdb/mi} Development and Front Ends
26255 @cindex @sc{gdb/mi} development
26257 The application which takes the MI output and presents the state of the
26258 program being debugged to the user is called a @dfn{front end}.
26260 Although @sc{gdb/mi} is still incomplete, it is currently being used
26261 by a variety of front ends to @value{GDBN}. This makes it difficult
26262 to introduce new functionality without breaking existing usage. This
26263 section tries to minimize the problems by describing how the protocol
26266 Some changes in MI need not break a carefully designed front end, and
26267 for these the MI version will remain unchanged. The following is a
26268 list of changes that may occur within one level, so front ends should
26269 parse MI output in a way that can handle them:
26273 New MI commands may be added.
26276 New fields may be added to the output of any MI command.
26279 The range of values for fields with specified values, e.g.,
26280 @code{in_scope} (@pxref{-var-update}) may be extended.
26282 @c The format of field's content e.g type prefix, may change so parse it
26283 @c at your own risk. Yes, in general?
26285 @c The order of fields may change? Shouldn't really matter but it might
26286 @c resolve inconsistencies.
26289 If the changes are likely to break front ends, the MI version level
26290 will be increased by one. This will allow the front end to parse the
26291 output according to the MI version. Apart from mi0, new versions of
26292 @value{GDBN} will not support old versions of MI and it will be the
26293 responsibility of the front end to work with the new one.
26295 @c Starting with mi3, add a new command -mi-version that prints the MI
26298 The best way to avoid unexpected changes in MI that might break your front
26299 end is to make your project known to @value{GDBN} developers and
26300 follow development on @email{gdb@@sourceware.org} and
26301 @email{gdb-patches@@sourceware.org}.
26302 @cindex mailing lists
26304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26305 @node GDB/MI Output Records
26306 @section @sc{gdb/mi} Output Records
26309 * GDB/MI Result Records::
26310 * GDB/MI Stream Records::
26311 * GDB/MI Async Records::
26312 * GDB/MI Breakpoint Information::
26313 * GDB/MI Frame Information::
26314 * GDB/MI Thread Information::
26315 * GDB/MI Ada Exception Information::
26318 @node GDB/MI Result Records
26319 @subsection @sc{gdb/mi} Result Records
26321 @cindex result records in @sc{gdb/mi}
26322 @cindex @sc{gdb/mi}, result records
26323 In addition to a number of out-of-band notifications, the response to a
26324 @sc{gdb/mi} command includes one of the following result indications:
26328 @item "^done" [ "," @var{results} ]
26329 The synchronous operation was successful, @code{@var{results}} are the return
26334 This result record is equivalent to @samp{^done}. Historically, it
26335 was output instead of @samp{^done} if the command has resumed the
26336 target. This behaviour is maintained for backward compatibility, but
26337 all frontends should treat @samp{^done} and @samp{^running}
26338 identically and rely on the @samp{*running} output record to determine
26339 which threads are resumed.
26343 @value{GDBN} has connected to a remote target.
26345 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26347 The operation failed. The @code{msg=@var{c-string}} variable contains
26348 the corresponding error message.
26350 If present, the @code{code=@var{c-string}} variable provides an error
26351 code on which consumers can rely on to detect the corresponding
26352 error condition. At present, only one error code is defined:
26355 @item "undefined-command"
26356 Indicates that the command causing the error does not exist.
26361 @value{GDBN} has terminated.
26365 @node GDB/MI Stream Records
26366 @subsection @sc{gdb/mi} Stream Records
26368 @cindex @sc{gdb/mi}, stream records
26369 @cindex stream records in @sc{gdb/mi}
26370 @value{GDBN} internally maintains a number of output streams: the console, the
26371 target, and the log. The output intended for each of these streams is
26372 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26374 Each stream record begins with a unique @dfn{prefix character} which
26375 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26376 Syntax}). In addition to the prefix, each stream record contains a
26377 @code{@var{string-output}}. This is either raw text (with an implicit new
26378 line) or a quoted C string (which does not contain an implicit newline).
26381 @item "~" @var{string-output}
26382 The console output stream contains text that should be displayed in the
26383 CLI console window. It contains the textual responses to CLI commands.
26385 @item "@@" @var{string-output}
26386 The target output stream contains any textual output from the running
26387 target. This is only present when GDB's event loop is truly
26388 asynchronous, which is currently only the case for remote targets.
26390 @item "&" @var{string-output}
26391 The log stream contains debugging messages being produced by @value{GDBN}'s
26395 @node GDB/MI Async Records
26396 @subsection @sc{gdb/mi} Async Records
26398 @cindex async records in @sc{gdb/mi}
26399 @cindex @sc{gdb/mi}, async records
26400 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26401 additional changes that have occurred. Those changes can either be a
26402 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26403 target activity (e.g., target stopped).
26405 The following is the list of possible async records:
26409 @item *running,thread-id="@var{thread}"
26410 The target is now running. The @var{thread} field can be the global
26411 thread ID of the the thread that is now running, and it can be
26412 @samp{all} if all threads are running. The frontend should assume
26413 that no interaction with a running thread is possible after this
26414 notification is produced. The frontend should not assume that this
26415 notification is output only once for any command. @value{GDBN} may
26416 emit this notification several times, either for different threads,
26417 because it cannot resume all threads together, or even for a single
26418 thread, if the thread must be stepped though some code before letting
26421 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26422 The target has stopped. The @var{reason} field can have one of the
26426 @item breakpoint-hit
26427 A breakpoint was reached.
26428 @item watchpoint-trigger
26429 A watchpoint was triggered.
26430 @item read-watchpoint-trigger
26431 A read watchpoint was triggered.
26432 @item access-watchpoint-trigger
26433 An access watchpoint was triggered.
26434 @item function-finished
26435 An -exec-finish or similar CLI command was accomplished.
26436 @item location-reached
26437 An -exec-until or similar CLI command was accomplished.
26438 @item watchpoint-scope
26439 A watchpoint has gone out of scope.
26440 @item end-stepping-range
26441 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26442 similar CLI command was accomplished.
26443 @item exited-signalled
26444 The inferior exited because of a signal.
26446 The inferior exited.
26447 @item exited-normally
26448 The inferior exited normally.
26449 @item signal-received
26450 A signal was received by the inferior.
26452 The inferior has stopped due to a library being loaded or unloaded.
26453 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26454 set or when a @code{catch load} or @code{catch unload} catchpoint is
26455 in use (@pxref{Set Catchpoints}).
26457 The inferior has forked. This is reported when @code{catch fork}
26458 (@pxref{Set Catchpoints}) has been used.
26460 The inferior has vforked. This is reported in when @code{catch vfork}
26461 (@pxref{Set Catchpoints}) has been used.
26462 @item syscall-entry
26463 The inferior entered a system call. This is reported when @code{catch
26464 syscall} (@pxref{Set Catchpoints}) has been used.
26465 @item syscall-return
26466 The inferior returned from a system call. This is reported when
26467 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26469 The inferior called @code{exec}. This is reported when @code{catch exec}
26470 (@pxref{Set Catchpoints}) has been used.
26473 The @var{id} field identifies the global thread ID of the thread
26474 that directly caused the stop -- for example by hitting a breakpoint.
26475 Depending on whether all-stop
26476 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26477 stop all threads, or only the thread that directly triggered the stop.
26478 If all threads are stopped, the @var{stopped} field will have the
26479 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26480 field will be a list of thread identifiers. Presently, this list will
26481 always include a single thread, but frontend should be prepared to see
26482 several threads in the list. The @var{core} field reports the
26483 processor core on which the stop event has happened. This field may be absent
26484 if such information is not available.
26486 @item =thread-group-added,id="@var{id}"
26487 @itemx =thread-group-removed,id="@var{id}"
26488 A thread group was either added or removed. The @var{id} field
26489 contains the @value{GDBN} identifier of the thread group. When a thread
26490 group is added, it generally might not be associated with a running
26491 process. When a thread group is removed, its id becomes invalid and
26492 cannot be used in any way.
26494 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26495 A thread group became associated with a running program,
26496 either because the program was just started or the thread group
26497 was attached to a program. The @var{id} field contains the
26498 @value{GDBN} identifier of the thread group. The @var{pid} field
26499 contains process identifier, specific to the operating system.
26501 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26502 A thread group is no longer associated with a running program,
26503 either because the program has exited, or because it was detached
26504 from. The @var{id} field contains the @value{GDBN} identifier of the
26505 thread group. The @var{code} field is the exit code of the inferior; it exists
26506 only when the inferior exited with some code.
26508 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26509 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26510 A thread either was created, or has exited. The @var{id} field
26511 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26512 field identifies the thread group this thread belongs to.
26514 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26515 Informs that the selected thread or frame were changed. This notification
26516 is not emitted as result of the @code{-thread-select} or
26517 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26518 that is not documented to change the selected thread and frame actually
26519 changes them. In particular, invoking, directly or indirectly
26520 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26521 will generate this notification. Changing the thread or frame from another
26522 user interface (see @ref{Interpreters}) will also generate this notification.
26524 The @var{frame} field is only present if the newly selected thread is
26525 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26527 We suggest that in response to this notification, front ends
26528 highlight the selected thread and cause subsequent commands to apply to
26531 @item =library-loaded,...
26532 Reports that a new library file was loaded by the program. This
26533 notification has 4 fields---@var{id}, @var{target-name},
26534 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26535 opaque identifier of the library. For remote debugging case,
26536 @var{target-name} and @var{host-name} fields give the name of the
26537 library file on the target, and on the host respectively. For native
26538 debugging, both those fields have the same value. The
26539 @var{symbols-loaded} field is emitted only for backward compatibility
26540 and should not be relied on to convey any useful information. The
26541 @var{thread-group} field, if present, specifies the id of the thread
26542 group in whose context the library was loaded. If the field is
26543 absent, it means the library was loaded in the context of all present
26546 @item =library-unloaded,...
26547 Reports that a library was unloaded by the program. This notification
26548 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26549 the same meaning as for the @code{=library-loaded} notification.
26550 The @var{thread-group} field, if present, specifies the id of the
26551 thread group in whose context the library was unloaded. If the field is
26552 absent, it means the library was unloaded in the context of all present
26555 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26556 @itemx =traceframe-changed,end
26557 Reports that the trace frame was changed and its new number is
26558 @var{tfnum}. The number of the tracepoint associated with this trace
26559 frame is @var{tpnum}.
26561 @item =tsv-created,name=@var{name},initial=@var{initial}
26562 Reports that the new trace state variable @var{name} is created with
26563 initial value @var{initial}.
26565 @item =tsv-deleted,name=@var{name}
26566 @itemx =tsv-deleted
26567 Reports that the trace state variable @var{name} is deleted or all
26568 trace state variables are deleted.
26570 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26571 Reports that the trace state variable @var{name} is modified with
26572 the initial value @var{initial}. The current value @var{current} of
26573 trace state variable is optional and is reported if the current
26574 value of trace state variable is known.
26576 @item =breakpoint-created,bkpt=@{...@}
26577 @itemx =breakpoint-modified,bkpt=@{...@}
26578 @itemx =breakpoint-deleted,id=@var{number}
26579 Reports that a breakpoint was created, modified, or deleted,
26580 respectively. Only user-visible breakpoints are reported to the MI
26583 The @var{bkpt} argument is of the same form as returned by the various
26584 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26585 @var{number} is the ordinal number of the breakpoint.
26587 Note that if a breakpoint is emitted in the result record of a
26588 command, then it will not also be emitted in an async record.
26590 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26591 @itemx =record-stopped,thread-group="@var{id}"
26592 Execution log recording was either started or stopped on an
26593 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26594 group corresponding to the affected inferior.
26596 The @var{method} field indicates the method used to record execution. If the
26597 method in use supports multiple recording formats, @var{format} will be present
26598 and contain the currently used format. @xref{Process Record and Replay},
26599 for existing method and format values.
26601 @item =cmd-param-changed,param=@var{param},value=@var{value}
26602 Reports that a parameter of the command @code{set @var{param}} is
26603 changed to @var{value}. In the multi-word @code{set} command,
26604 the @var{param} is the whole parameter list to @code{set} command.
26605 For example, In command @code{set check type on}, @var{param}
26606 is @code{check type} and @var{value} is @code{on}.
26608 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26609 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26610 written in an inferior. The @var{id} is the identifier of the
26611 thread group corresponding to the affected inferior. The optional
26612 @code{type="code"} part is reported if the memory written to holds
26616 @node GDB/MI Breakpoint Information
26617 @subsection @sc{gdb/mi} Breakpoint Information
26619 When @value{GDBN} reports information about a breakpoint, a
26620 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26625 The breakpoint number. For a breakpoint that represents one location
26626 of a multi-location breakpoint, this will be a dotted pair, like
26630 The type of the breakpoint. For ordinary breakpoints this will be
26631 @samp{breakpoint}, but many values are possible.
26634 If the type of the breakpoint is @samp{catchpoint}, then this
26635 indicates the exact type of catchpoint.
26638 This is the breakpoint disposition---either @samp{del}, meaning that
26639 the breakpoint will be deleted at the next stop, or @samp{keep},
26640 meaning that the breakpoint will not be deleted.
26643 This indicates whether the breakpoint is enabled, in which case the
26644 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26645 Note that this is not the same as the field @code{enable}.
26648 The address of the breakpoint. This may be a hexidecimal number,
26649 giving the address; or the string @samp{<PENDING>}, for a pending
26650 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26651 multiple locations. This field will not be present if no address can
26652 be determined. For example, a watchpoint does not have an address.
26655 If known, the function in which the breakpoint appears.
26656 If not known, this field is not present.
26659 The name of the source file which contains this function, if known.
26660 If not known, this field is not present.
26663 The full file name of the source file which contains this function, if
26664 known. If not known, this field is not present.
26667 The line number at which this breakpoint appears, if known.
26668 If not known, this field is not present.
26671 If the source file is not known, this field may be provided. If
26672 provided, this holds the address of the breakpoint, possibly followed
26676 If this breakpoint is pending, this field is present and holds the
26677 text used to set the breakpoint, as entered by the user.
26680 Where this breakpoint's condition is evaluated, either @samp{host} or
26684 If this is a thread-specific breakpoint, then this identifies the
26685 thread in which the breakpoint can trigger.
26688 If this breakpoint is restricted to a particular Ada task, then this
26689 field will hold the task identifier.
26692 If the breakpoint is conditional, this is the condition expression.
26695 The ignore count of the breakpoint.
26698 The enable count of the breakpoint.
26700 @item traceframe-usage
26703 @item static-tracepoint-marker-string-id
26704 For a static tracepoint, the name of the static tracepoint marker.
26707 For a masked watchpoint, this is the mask.
26710 A tracepoint's pass count.
26712 @item original-location
26713 The location of the breakpoint as originally specified by the user.
26714 This field is optional.
26717 The number of times the breakpoint has been hit.
26720 This field is only given for tracepoints. This is either @samp{y},
26721 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26725 Some extra data, the exact contents of which are type-dependent.
26729 For example, here is what the output of @code{-break-insert}
26730 (@pxref{GDB/MI Breakpoint Commands}) might be:
26733 -> -break-insert main
26734 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26735 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26736 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26741 @node GDB/MI Frame Information
26742 @subsection @sc{gdb/mi} Frame Information
26744 Response from many MI commands includes an information about stack
26745 frame. This information is a tuple that may have the following
26750 The level of the stack frame. The innermost frame has the level of
26751 zero. This field is always present.
26754 The name of the function corresponding to the frame. This field may
26755 be absent if @value{GDBN} is unable to determine the function name.
26758 The code address for the frame. This field is always present.
26761 The name of the source files that correspond to the frame's code
26762 address. This field may be absent.
26765 The source line corresponding to the frames' code address. This field
26769 The name of the binary file (either executable or shared library) the
26770 corresponds to the frame's code address. This field may be absent.
26774 @node GDB/MI Thread Information
26775 @subsection @sc{gdb/mi} Thread Information
26777 Whenever @value{GDBN} has to report an information about a thread, it
26778 uses a tuple with the following fields:
26782 The global numeric id assigned to the thread by @value{GDBN}. This field is
26786 Target-specific string identifying the thread. This field is always present.
26789 Additional information about the thread provided by the target.
26790 It is supposed to be human-readable and not interpreted by the
26791 frontend. This field is optional.
26794 Either @samp{stopped} or @samp{running}, depending on whether the
26795 thread is presently running. This field is always present.
26798 The value of this field is an integer number of the processor core the
26799 thread was last seen on. This field is optional.
26802 @node GDB/MI Ada Exception Information
26803 @subsection @sc{gdb/mi} Ada Exception Information
26805 Whenever a @code{*stopped} record is emitted because the program
26806 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26807 @value{GDBN} provides the name of the exception that was raised via
26808 the @code{exception-name} field.
26810 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26811 @node GDB/MI Simple Examples
26812 @section Simple Examples of @sc{gdb/mi} Interaction
26813 @cindex @sc{gdb/mi}, simple examples
26815 This subsection presents several simple examples of interaction using
26816 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26817 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26818 the output received from @sc{gdb/mi}.
26820 Note the line breaks shown in the examples are here only for
26821 readability, they don't appear in the real output.
26823 @subheading Setting a Breakpoint
26825 Setting a breakpoint generates synchronous output which contains detailed
26826 information of the breakpoint.
26829 -> -break-insert main
26830 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26831 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26832 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26837 @subheading Program Execution
26839 Program execution generates asynchronous records and MI gives the
26840 reason that execution stopped.
26846 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26847 frame=@{addr="0x08048564",func="main",
26848 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26849 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26854 <- *stopped,reason="exited-normally"
26858 @subheading Quitting @value{GDBN}
26860 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26868 Please note that @samp{^exit} is printed immediately, but it might
26869 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26870 performs necessary cleanups, including killing programs being debugged
26871 or disconnecting from debug hardware, so the frontend should wait till
26872 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26873 fails to exit in reasonable time.
26875 @subheading A Bad Command
26877 Here's what happens if you pass a non-existent command:
26881 <- ^error,msg="Undefined MI command: rubbish"
26886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26887 @node GDB/MI Command Description Format
26888 @section @sc{gdb/mi} Command Description Format
26890 The remaining sections describe blocks of commands. Each block of
26891 commands is laid out in a fashion similar to this section.
26893 @subheading Motivation
26895 The motivation for this collection of commands.
26897 @subheading Introduction
26899 A brief introduction to this collection of commands as a whole.
26901 @subheading Commands
26903 For each command in the block, the following is described:
26905 @subsubheading Synopsis
26908 -command @var{args}@dots{}
26911 @subsubheading Result
26913 @subsubheading @value{GDBN} Command
26915 The corresponding @value{GDBN} CLI command(s), if any.
26917 @subsubheading Example
26919 Example(s) formatted for readability. Some of the described commands have
26920 not been implemented yet and these are labeled N.A.@: (not available).
26923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26924 @node GDB/MI Breakpoint Commands
26925 @section @sc{gdb/mi} Breakpoint Commands
26927 @cindex breakpoint commands for @sc{gdb/mi}
26928 @cindex @sc{gdb/mi}, breakpoint commands
26929 This section documents @sc{gdb/mi} commands for manipulating
26932 @subheading The @code{-break-after} Command
26933 @findex -break-after
26935 @subsubheading Synopsis
26938 -break-after @var{number} @var{count}
26941 The breakpoint number @var{number} is not in effect until it has been
26942 hit @var{count} times. To see how this is reflected in the output of
26943 the @samp{-break-list} command, see the description of the
26944 @samp{-break-list} command below.
26946 @subsubheading @value{GDBN} Command
26948 The corresponding @value{GDBN} command is @samp{ignore}.
26950 @subsubheading Example
26955 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26956 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26957 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26965 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26966 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26967 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26968 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26969 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26970 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26971 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26972 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26973 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26974 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26979 @subheading The @code{-break-catch} Command
26980 @findex -break-catch
26983 @subheading The @code{-break-commands} Command
26984 @findex -break-commands
26986 @subsubheading Synopsis
26989 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26992 Specifies the CLI commands that should be executed when breakpoint
26993 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26994 are the commands. If no command is specified, any previously-set
26995 commands are cleared. @xref{Break Commands}. Typical use of this
26996 functionality is tracing a program, that is, printing of values of
26997 some variables whenever breakpoint is hit and then continuing.
26999 @subsubheading @value{GDBN} Command
27001 The corresponding @value{GDBN} command is @samp{commands}.
27003 @subsubheading Example
27008 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27009 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27010 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27013 -break-commands 1 "print v" "continue"
27018 @subheading The @code{-break-condition} Command
27019 @findex -break-condition
27021 @subsubheading Synopsis
27024 -break-condition @var{number} @var{expr}
27027 Breakpoint @var{number} will stop the program only if the condition in
27028 @var{expr} is true. The condition becomes part of the
27029 @samp{-break-list} output (see the description of the @samp{-break-list}
27032 @subsubheading @value{GDBN} Command
27034 The corresponding @value{GDBN} command is @samp{condition}.
27036 @subsubheading Example
27040 -break-condition 1 1
27044 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27045 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27046 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27047 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27048 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27049 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27050 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27051 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27052 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27053 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27057 @subheading The @code{-break-delete} Command
27058 @findex -break-delete
27060 @subsubheading Synopsis
27063 -break-delete ( @var{breakpoint} )+
27066 Delete the breakpoint(s) whose number(s) are specified in the argument
27067 list. This is obviously reflected in the breakpoint list.
27069 @subsubheading @value{GDBN} Command
27071 The corresponding @value{GDBN} command is @samp{delete}.
27073 @subsubheading Example
27081 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27082 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27083 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27084 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27085 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27086 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27087 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27092 @subheading The @code{-break-disable} Command
27093 @findex -break-disable
27095 @subsubheading Synopsis
27098 -break-disable ( @var{breakpoint} )+
27101 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27102 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27104 @subsubheading @value{GDBN} Command
27106 The corresponding @value{GDBN} command is @samp{disable}.
27108 @subsubheading Example
27116 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27117 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27118 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27119 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27120 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27121 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27122 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27123 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27124 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27125 line="5",thread-groups=["i1"],times="0"@}]@}
27129 @subheading The @code{-break-enable} Command
27130 @findex -break-enable
27132 @subsubheading Synopsis
27135 -break-enable ( @var{breakpoint} )+
27138 Enable (previously disabled) @var{breakpoint}(s).
27140 @subsubheading @value{GDBN} Command
27142 The corresponding @value{GDBN} command is @samp{enable}.
27144 @subsubheading Example
27152 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27153 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27154 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27155 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27156 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27157 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27158 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27159 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27160 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27161 line="5",thread-groups=["i1"],times="0"@}]@}
27165 @subheading The @code{-break-info} Command
27166 @findex -break-info
27168 @subsubheading Synopsis
27171 -break-info @var{breakpoint}
27175 Get information about a single breakpoint.
27177 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27178 Information}, for details on the format of each breakpoint in the
27181 @subsubheading @value{GDBN} Command
27183 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27185 @subsubheading Example
27188 @subheading The @code{-break-insert} Command
27189 @findex -break-insert
27190 @anchor{-break-insert}
27192 @subsubheading Synopsis
27195 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27196 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27197 [ -p @var{thread-id} ] [ @var{location} ]
27201 If specified, @var{location}, can be one of:
27204 @item linespec location
27205 A linespec location. @xref{Linespec Locations}.
27207 @item explicit location
27208 An explicit location. @sc{gdb/mi} explicit locations are
27209 analogous to the CLI's explicit locations using the option names
27210 listed below. @xref{Explicit Locations}.
27213 @item --source @var{filename}
27214 The source file name of the location. This option requires the use
27215 of either @samp{--function} or @samp{--line}.
27217 @item --function @var{function}
27218 The name of a function or method.
27220 @item --label @var{label}
27221 The name of a label.
27223 @item --line @var{lineoffset}
27224 An absolute or relative line offset from the start of the location.
27227 @item address location
27228 An address location, *@var{address}. @xref{Address Locations}.
27232 The possible optional parameters of this command are:
27236 Insert a temporary breakpoint.
27238 Insert a hardware breakpoint.
27240 If @var{location} cannot be parsed (for example if it
27241 refers to unknown files or functions), create a pending
27242 breakpoint. Without this flag, @value{GDBN} will report
27243 an error, and won't create a breakpoint, if @var{location}
27246 Create a disabled breakpoint.
27248 Create a tracepoint. @xref{Tracepoints}. When this parameter
27249 is used together with @samp{-h}, a fast tracepoint is created.
27250 @item -c @var{condition}
27251 Make the breakpoint conditional on @var{condition}.
27252 @item -i @var{ignore-count}
27253 Initialize the @var{ignore-count}.
27254 @item -p @var{thread-id}
27255 Restrict the breakpoint to the thread with the specified global
27259 @subsubheading Result
27261 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27262 resulting breakpoint.
27264 Note: this format is open to change.
27265 @c An out-of-band breakpoint instead of part of the result?
27267 @subsubheading @value{GDBN} Command
27269 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27270 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27272 @subsubheading Example
27277 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27278 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27281 -break-insert -t foo
27282 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27283 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27287 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27288 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27289 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27290 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27291 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27292 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27293 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27294 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27295 addr="0x0001072c", func="main",file="recursive2.c",
27296 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27298 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27299 addr="0x00010774",func="foo",file="recursive2.c",
27300 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27303 @c -break-insert -r foo.*
27304 @c ~int foo(int, int);
27305 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27306 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27311 @subheading The @code{-dprintf-insert} Command
27312 @findex -dprintf-insert
27314 @subsubheading Synopsis
27317 -dprintf-insert [ -t ] [ -f ] [ -d ]
27318 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27319 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27324 If supplied, @var{location} may be specified the same way as for
27325 the @code{-break-insert} command. @xref{-break-insert}.
27327 The possible optional parameters of this command are:
27331 Insert a temporary breakpoint.
27333 If @var{location} cannot be parsed (for example, if it
27334 refers to unknown files or functions), create a pending
27335 breakpoint. Without this flag, @value{GDBN} will report
27336 an error, and won't create a breakpoint, if @var{location}
27339 Create a disabled breakpoint.
27340 @item -c @var{condition}
27341 Make the breakpoint conditional on @var{condition}.
27342 @item -i @var{ignore-count}
27343 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27344 to @var{ignore-count}.
27345 @item -p @var{thread-id}
27346 Restrict the breakpoint to the thread with the specified global
27350 @subsubheading Result
27352 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27353 resulting breakpoint.
27355 @c An out-of-band breakpoint instead of part of the result?
27357 @subsubheading @value{GDBN} Command
27359 The corresponding @value{GDBN} command is @samp{dprintf}.
27361 @subsubheading Example
27365 4-dprintf-insert foo "At foo entry\n"
27366 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27367 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27368 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27369 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27370 original-location="foo"@}
27372 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27373 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27374 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27375 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27376 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27377 original-location="mi-dprintf.c:26"@}
27381 @subheading The @code{-break-list} Command
27382 @findex -break-list
27384 @subsubheading Synopsis
27390 Displays the list of inserted breakpoints, showing the following fields:
27394 number of the breakpoint
27396 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27398 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27401 is the breakpoint enabled or no: @samp{y} or @samp{n}
27403 memory location at which the breakpoint is set
27405 logical location of the breakpoint, expressed by function name, file
27407 @item Thread-groups
27408 list of thread groups to which this breakpoint applies
27410 number of times the breakpoint has been hit
27413 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27414 @code{body} field is an empty list.
27416 @subsubheading @value{GDBN} Command
27418 The corresponding @value{GDBN} command is @samp{info break}.
27420 @subsubheading Example
27425 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27426 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27427 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27428 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27429 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27430 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27431 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27432 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27433 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27435 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27436 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27437 line="13",thread-groups=["i1"],times="0"@}]@}
27441 Here's an example of the result when there are no breakpoints:
27446 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27447 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27448 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27449 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27450 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27451 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27452 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27457 @subheading The @code{-break-passcount} Command
27458 @findex -break-passcount
27460 @subsubheading Synopsis
27463 -break-passcount @var{tracepoint-number} @var{passcount}
27466 Set the passcount for tracepoint @var{tracepoint-number} to
27467 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27468 is not a tracepoint, error is emitted. This corresponds to CLI
27469 command @samp{passcount}.
27471 @subheading The @code{-break-watch} Command
27472 @findex -break-watch
27474 @subsubheading Synopsis
27477 -break-watch [ -a | -r ]
27480 Create a watchpoint. With the @samp{-a} option it will create an
27481 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27482 read from or on a write to the memory location. With the @samp{-r}
27483 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27484 trigger only when the memory location is accessed for reading. Without
27485 either of the options, the watchpoint created is a regular watchpoint,
27486 i.e., it will trigger when the memory location is accessed for writing.
27487 @xref{Set Watchpoints, , Setting Watchpoints}.
27489 Note that @samp{-break-list} will report a single list of watchpoints and
27490 breakpoints inserted.
27492 @subsubheading @value{GDBN} Command
27494 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27497 @subsubheading Example
27499 Setting a watchpoint on a variable in the @code{main} function:
27504 ^done,wpt=@{number="2",exp="x"@}
27509 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27510 value=@{old="-268439212",new="55"@},
27511 frame=@{func="main",args=[],file="recursive2.c",
27512 fullname="/home/foo/bar/recursive2.c",line="5"@}
27516 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27517 the program execution twice: first for the variable changing value, then
27518 for the watchpoint going out of scope.
27523 ^done,wpt=@{number="5",exp="C"@}
27528 *stopped,reason="watchpoint-trigger",
27529 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27530 frame=@{func="callee4",args=[],
27531 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27532 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27537 *stopped,reason="watchpoint-scope",wpnum="5",
27538 frame=@{func="callee3",args=[@{name="strarg",
27539 value="0x11940 \"A string argument.\""@}],
27540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27541 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27545 Listing breakpoints and watchpoints, at different points in the program
27546 execution. Note that once the watchpoint goes out of scope, it is
27552 ^done,wpt=@{number="2",exp="C"@}
27555 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27556 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27557 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27558 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27559 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27560 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27561 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27562 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27563 addr="0x00010734",func="callee4",
27564 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27565 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27567 bkpt=@{number="2",type="watchpoint",disp="keep",
27568 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27573 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27574 value=@{old="-276895068",new="3"@},
27575 frame=@{func="callee4",args=[],
27576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27577 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27580 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27581 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27582 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27583 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27584 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27585 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27586 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27587 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27588 addr="0x00010734",func="callee4",
27589 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27590 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27592 bkpt=@{number="2",type="watchpoint",disp="keep",
27593 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27597 ^done,reason="watchpoint-scope",wpnum="2",
27598 frame=@{func="callee3",args=[@{name="strarg",
27599 value="0x11940 \"A string argument.\""@}],
27600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27611 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27612 addr="0x00010734",func="callee4",
27613 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27614 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27615 thread-groups=["i1"],times="1"@}]@}
27620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27621 @node GDB/MI Catchpoint Commands
27622 @section @sc{gdb/mi} Catchpoint Commands
27624 This section documents @sc{gdb/mi} commands for manipulating
27628 * Shared Library GDB/MI Catchpoint Commands::
27629 * Ada Exception GDB/MI Catchpoint Commands::
27632 @node Shared Library GDB/MI Catchpoint Commands
27633 @subsection Shared Library @sc{gdb/mi} Catchpoints
27635 @subheading The @code{-catch-load} Command
27636 @findex -catch-load
27638 @subsubheading Synopsis
27641 -catch-load [ -t ] [ -d ] @var{regexp}
27644 Add a catchpoint for library load events. If the @samp{-t} option is used,
27645 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27646 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27647 in a disabled state. The @samp{regexp} argument is a regular
27648 expression used to match the name of the loaded library.
27651 @subsubheading @value{GDBN} Command
27653 The corresponding @value{GDBN} command is @samp{catch load}.
27655 @subsubheading Example
27658 -catch-load -t foo.so
27659 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27660 what="load of library matching foo.so",catch-type="load",times="0"@}
27665 @subheading The @code{-catch-unload} Command
27666 @findex -catch-unload
27668 @subsubheading Synopsis
27671 -catch-unload [ -t ] [ -d ] @var{regexp}
27674 Add a catchpoint for library unload events. If the @samp{-t} option is
27675 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27676 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27677 created in a disabled state. The @samp{regexp} argument is a regular
27678 expression used to match the name of the unloaded library.
27680 @subsubheading @value{GDBN} Command
27682 The corresponding @value{GDBN} command is @samp{catch unload}.
27684 @subsubheading Example
27687 -catch-unload -d bar.so
27688 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27689 what="load of library matching bar.so",catch-type="unload",times="0"@}
27693 @node Ada Exception GDB/MI Catchpoint Commands
27694 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27696 The following @sc{gdb/mi} commands can be used to create catchpoints
27697 that stop the execution when Ada exceptions are being raised.
27699 @subheading The @code{-catch-assert} Command
27700 @findex -catch-assert
27702 @subsubheading Synopsis
27705 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27708 Add a catchpoint for failed Ada assertions.
27710 The possible optional parameters for this command are:
27713 @item -c @var{condition}
27714 Make the catchpoint conditional on @var{condition}.
27716 Create a disabled catchpoint.
27718 Create a temporary catchpoint.
27721 @subsubheading @value{GDBN} Command
27723 The corresponding @value{GDBN} command is @samp{catch assert}.
27725 @subsubheading Example
27729 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27730 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27731 thread-groups=["i1"],times="0",
27732 original-location="__gnat_debug_raise_assert_failure"@}
27736 @subheading The @code{-catch-exception} Command
27737 @findex -catch-exception
27739 @subsubheading Synopsis
27742 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27746 Add a catchpoint stopping when Ada exceptions are raised.
27747 By default, the command stops the program when any Ada exception
27748 gets raised. But it is also possible, by using some of the
27749 optional parameters described below, to create more selective
27752 The possible optional parameters for this command are:
27755 @item -c @var{condition}
27756 Make the catchpoint conditional on @var{condition}.
27758 Create a disabled catchpoint.
27759 @item -e @var{exception-name}
27760 Only stop when @var{exception-name} is raised. This option cannot
27761 be used combined with @samp{-u}.
27763 Create a temporary catchpoint.
27765 Stop only when an unhandled exception gets raised. This option
27766 cannot be used combined with @samp{-e}.
27769 @subsubheading @value{GDBN} Command
27771 The corresponding @value{GDBN} commands are @samp{catch exception}
27772 and @samp{catch exception unhandled}.
27774 @subsubheading Example
27777 -catch-exception -e Program_Error
27778 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27779 enabled="y",addr="0x0000000000404874",
27780 what="`Program_Error' Ada exception", thread-groups=["i1"],
27781 times="0",original-location="__gnat_debug_raise_exception"@}
27785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27786 @node GDB/MI Program Context
27787 @section @sc{gdb/mi} Program Context
27789 @subheading The @code{-exec-arguments} Command
27790 @findex -exec-arguments
27793 @subsubheading Synopsis
27796 -exec-arguments @var{args}
27799 Set the inferior program arguments, to be used in the next
27802 @subsubheading @value{GDBN} Command
27804 The corresponding @value{GDBN} command is @samp{set args}.
27806 @subsubheading Example
27810 -exec-arguments -v word
27817 @subheading The @code{-exec-show-arguments} Command
27818 @findex -exec-show-arguments
27820 @subsubheading Synopsis
27823 -exec-show-arguments
27826 Print the arguments of the program.
27828 @subsubheading @value{GDBN} Command
27830 The corresponding @value{GDBN} command is @samp{show args}.
27832 @subsubheading Example
27837 @subheading The @code{-environment-cd} Command
27838 @findex -environment-cd
27840 @subsubheading Synopsis
27843 -environment-cd @var{pathdir}
27846 Set @value{GDBN}'s working directory.
27848 @subsubheading @value{GDBN} Command
27850 The corresponding @value{GDBN} command is @samp{cd}.
27852 @subsubheading Example
27856 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27862 @subheading The @code{-environment-directory} Command
27863 @findex -environment-directory
27865 @subsubheading Synopsis
27868 -environment-directory [ -r ] [ @var{pathdir} ]+
27871 Add directories @var{pathdir} to beginning of search path for source files.
27872 If the @samp{-r} option is used, the search path is reset to the default
27873 search path. If directories @var{pathdir} are supplied in addition to the
27874 @samp{-r} option, the search path is first reset and then addition
27876 Multiple directories may be specified, separated by blanks. Specifying
27877 multiple directories in a single command
27878 results in the directories added to the beginning of the
27879 search path in the same order they were presented in the command.
27880 If blanks are needed as
27881 part of a directory name, double-quotes should be used around
27882 the name. In the command output, the path will show up separated
27883 by the system directory-separator character. The directory-separator
27884 character must not be used
27885 in any directory name.
27886 If no directories are specified, the current search path is displayed.
27888 @subsubheading @value{GDBN} Command
27890 The corresponding @value{GDBN} command is @samp{dir}.
27892 @subsubheading Example
27896 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27897 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27899 -environment-directory ""
27900 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27902 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27903 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27905 -environment-directory -r
27906 ^done,source-path="$cdir:$cwd"
27911 @subheading The @code{-environment-path} Command
27912 @findex -environment-path
27914 @subsubheading Synopsis
27917 -environment-path [ -r ] [ @var{pathdir} ]+
27920 Add directories @var{pathdir} to beginning of search path for object files.
27921 If the @samp{-r} option is used, the search path is reset to the original
27922 search path that existed at gdb start-up. If directories @var{pathdir} are
27923 supplied in addition to the
27924 @samp{-r} option, the search path is first reset and then addition
27926 Multiple directories may be specified, separated by blanks. Specifying
27927 multiple directories in a single command
27928 results in the directories added to the beginning of the
27929 search path in the same order they were presented in the command.
27930 If blanks are needed as
27931 part of a directory name, double-quotes should be used around
27932 the name. In the command output, the path will show up separated
27933 by the system directory-separator character. The directory-separator
27934 character must not be used
27935 in any directory name.
27936 If no directories are specified, the current path is displayed.
27939 @subsubheading @value{GDBN} Command
27941 The corresponding @value{GDBN} command is @samp{path}.
27943 @subsubheading Example
27948 ^done,path="/usr/bin"
27950 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27951 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27953 -environment-path -r /usr/local/bin
27954 ^done,path="/usr/local/bin:/usr/bin"
27959 @subheading The @code{-environment-pwd} Command
27960 @findex -environment-pwd
27962 @subsubheading Synopsis
27968 Show the current working directory.
27970 @subsubheading @value{GDBN} Command
27972 The corresponding @value{GDBN} command is @samp{pwd}.
27974 @subsubheading Example
27979 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27984 @node GDB/MI Thread Commands
27985 @section @sc{gdb/mi} Thread Commands
27988 @subheading The @code{-thread-info} Command
27989 @findex -thread-info
27991 @subsubheading Synopsis
27994 -thread-info [ @var{thread-id} ]
27997 Reports information about either a specific thread, if the
27998 @var{thread-id} parameter is present, or about all threads.
27999 @var{thread-id} is the thread's global thread ID. When printing
28000 information about all threads, also reports the global ID of the
28003 @subsubheading @value{GDBN} Command
28005 The @samp{info thread} command prints the same information
28008 @subsubheading Result
28010 The result is a list of threads. The following attributes are
28011 defined for a given thread:
28015 This field exists only for the current thread. It has the value @samp{*}.
28018 The global identifier that @value{GDBN} uses to refer to the thread.
28021 The identifier that the target uses to refer to the thread.
28024 Extra information about the thread, in a target-specific format. This
28028 The name of the thread. If the user specified a name using the
28029 @code{thread name} command, then this name is given. Otherwise, if
28030 @value{GDBN} can extract the thread name from the target, then that
28031 name is given. If @value{GDBN} cannot find the thread name, then this
28035 The stack frame currently executing in the thread.
28038 The thread's state. The @samp{state} field may have the following
28043 The thread is stopped. Frame information is available for stopped
28047 The thread is running. There's no frame information for running
28053 If @value{GDBN} can find the CPU core on which this thread is running,
28054 then this field is the core identifier. This field is optional.
28058 @subsubheading Example
28063 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28064 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28065 args=[]@},state="running"@},
28066 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28067 frame=@{level="0",addr="0x0804891f",func="foo",
28068 args=[@{name="i",value="10"@}],
28069 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28070 state="running"@}],
28071 current-thread-id="1"
28075 @subheading The @code{-thread-list-ids} Command
28076 @findex -thread-list-ids
28078 @subsubheading Synopsis
28084 Produces a list of the currently known global @value{GDBN} thread ids.
28085 At the end of the list it also prints the total number of such
28088 This command is retained for historical reasons, the
28089 @code{-thread-info} command should be used instead.
28091 @subsubheading @value{GDBN} Command
28093 Part of @samp{info threads} supplies the same information.
28095 @subsubheading Example
28100 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28101 current-thread-id="1",number-of-threads="3"
28106 @subheading The @code{-thread-select} Command
28107 @findex -thread-select
28109 @subsubheading Synopsis
28112 -thread-select @var{thread-id}
28115 Make thread with global thread number @var{thread-id} the current
28116 thread. It prints the number of the new current thread, and the
28117 topmost frame for that thread.
28119 This command is deprecated in favor of explicitly using the
28120 @samp{--thread} option to each command.
28122 @subsubheading @value{GDBN} Command
28124 The corresponding @value{GDBN} command is @samp{thread}.
28126 @subsubheading Example
28133 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28134 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28138 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28139 number-of-threads="3"
28142 ^done,new-thread-id="3",
28143 frame=@{level="0",func="vprintf",
28144 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28145 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28149 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28150 @node GDB/MI Ada Tasking Commands
28151 @section @sc{gdb/mi} Ada Tasking Commands
28153 @subheading The @code{-ada-task-info} Command
28154 @findex -ada-task-info
28156 @subsubheading Synopsis
28159 -ada-task-info [ @var{task-id} ]
28162 Reports information about either a specific Ada task, if the
28163 @var{task-id} parameter is present, or about all Ada tasks.
28165 @subsubheading @value{GDBN} Command
28167 The @samp{info tasks} command prints the same information
28168 about all Ada tasks (@pxref{Ada Tasks}).
28170 @subsubheading Result
28172 The result is a table of Ada tasks. The following columns are
28173 defined for each Ada task:
28177 This field exists only for the current thread. It has the value @samp{*}.
28180 The identifier that @value{GDBN} uses to refer to the Ada task.
28183 The identifier that the target uses to refer to the Ada task.
28186 The global thread identifier of the thread corresponding to the Ada
28189 This field should always exist, as Ada tasks are always implemented
28190 on top of a thread. But if @value{GDBN} cannot find this corresponding
28191 thread for any reason, the field is omitted.
28194 This field exists only when the task was created by another task.
28195 In this case, it provides the ID of the parent task.
28198 The base priority of the task.
28201 The current state of the task. For a detailed description of the
28202 possible states, see @ref{Ada Tasks}.
28205 The name of the task.
28209 @subsubheading Example
28213 ^done,tasks=@{nr_rows="3",nr_cols="8",
28214 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28215 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28216 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28217 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28218 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28219 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28220 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28221 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28222 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28223 state="Child Termination Wait",name="main_task"@}]@}
28227 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28228 @node GDB/MI Program Execution
28229 @section @sc{gdb/mi} Program Execution
28231 These are the asynchronous commands which generate the out-of-band
28232 record @samp{*stopped}. Currently @value{GDBN} only really executes
28233 asynchronously with remote targets and this interaction is mimicked in
28236 @subheading The @code{-exec-continue} Command
28237 @findex -exec-continue
28239 @subsubheading Synopsis
28242 -exec-continue [--reverse] [--all|--thread-group N]
28245 Resumes the execution of the inferior program, which will continue
28246 to execute until it reaches a debugger stop event. If the
28247 @samp{--reverse} option is specified, execution resumes in reverse until
28248 it reaches a stop event. Stop events may include
28251 breakpoints or watchpoints
28253 signals or exceptions
28255 the end of the process (or its beginning under @samp{--reverse})
28257 the end or beginning of a replay log if one is being used.
28259 In all-stop mode (@pxref{All-Stop
28260 Mode}), may resume only one thread, or all threads, depending on the
28261 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28262 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28263 ignored in all-stop mode. If the @samp{--thread-group} options is
28264 specified, then all threads in that thread group are resumed.
28266 @subsubheading @value{GDBN} Command
28268 The corresponding @value{GDBN} corresponding is @samp{continue}.
28270 @subsubheading Example
28277 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28278 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28284 @subheading The @code{-exec-finish} Command
28285 @findex -exec-finish
28287 @subsubheading Synopsis
28290 -exec-finish [--reverse]
28293 Resumes the execution of the inferior program until the current
28294 function is exited. Displays the results returned by the function.
28295 If the @samp{--reverse} option is specified, resumes the reverse
28296 execution of the inferior program until the point where current
28297 function was called.
28299 @subsubheading @value{GDBN} Command
28301 The corresponding @value{GDBN} command is @samp{finish}.
28303 @subsubheading Example
28305 Function returning @code{void}.
28312 *stopped,reason="function-finished",frame=@{func="main",args=[],
28313 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28317 Function returning other than @code{void}. The name of the internal
28318 @value{GDBN} variable storing the result is printed, together with the
28325 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28326 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28327 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28328 gdb-result-var="$1",return-value="0"
28333 @subheading The @code{-exec-interrupt} Command
28334 @findex -exec-interrupt
28336 @subsubheading Synopsis
28339 -exec-interrupt [--all|--thread-group N]
28342 Interrupts the background execution of the target. Note how the token
28343 associated with the stop message is the one for the execution command
28344 that has been interrupted. The token for the interrupt itself only
28345 appears in the @samp{^done} output. If the user is trying to
28346 interrupt a non-running program, an error message will be printed.
28348 Note that when asynchronous execution is enabled, this command is
28349 asynchronous just like other execution commands. That is, first the
28350 @samp{^done} response will be printed, and the target stop will be
28351 reported after that using the @samp{*stopped} notification.
28353 In non-stop mode, only the context thread is interrupted by default.
28354 All threads (in all inferiors) will be interrupted if the
28355 @samp{--all} option is specified. If the @samp{--thread-group}
28356 option is specified, all threads in that group will be interrupted.
28358 @subsubheading @value{GDBN} Command
28360 The corresponding @value{GDBN} command is @samp{interrupt}.
28362 @subsubheading Example
28373 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28374 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28375 fullname="/home/foo/bar/try.c",line="13"@}
28380 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28384 @subheading The @code{-exec-jump} Command
28387 @subsubheading Synopsis
28390 -exec-jump @var{location}
28393 Resumes execution of the inferior program at the location specified by
28394 parameter. @xref{Specify Location}, for a description of the
28395 different forms of @var{location}.
28397 @subsubheading @value{GDBN} Command
28399 The corresponding @value{GDBN} command is @samp{jump}.
28401 @subsubheading Example
28404 -exec-jump foo.c:10
28405 *running,thread-id="all"
28410 @subheading The @code{-exec-next} Command
28413 @subsubheading Synopsis
28416 -exec-next [--reverse]
28419 Resumes execution of the inferior program, stopping when the beginning
28420 of the next source line is reached.
28422 If the @samp{--reverse} option is specified, resumes reverse execution
28423 of the inferior program, stopping at the beginning of the previous
28424 source line. If you issue this command on the first line of a
28425 function, it will take you back to the caller of that function, to the
28426 source line where the function was called.
28429 @subsubheading @value{GDBN} Command
28431 The corresponding @value{GDBN} command is @samp{next}.
28433 @subsubheading Example
28439 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28444 @subheading The @code{-exec-next-instruction} Command
28445 @findex -exec-next-instruction
28447 @subsubheading Synopsis
28450 -exec-next-instruction [--reverse]
28453 Executes one machine instruction. If the instruction is a function
28454 call, continues until the function returns. If the program stops at an
28455 instruction in the middle of a source line, the address will be
28458 If the @samp{--reverse} option is specified, resumes reverse execution
28459 of the inferior program, stopping at the previous instruction. If the
28460 previously executed instruction was a return from another function,
28461 it will continue to execute in reverse until the call to that function
28462 (from the current stack frame) is reached.
28464 @subsubheading @value{GDBN} Command
28466 The corresponding @value{GDBN} command is @samp{nexti}.
28468 @subsubheading Example
28472 -exec-next-instruction
28476 *stopped,reason="end-stepping-range",
28477 addr="0x000100d4",line="5",file="hello.c"
28482 @subheading The @code{-exec-return} Command
28483 @findex -exec-return
28485 @subsubheading Synopsis
28491 Makes current function return immediately. Doesn't execute the inferior.
28492 Displays the new current frame.
28494 @subsubheading @value{GDBN} Command
28496 The corresponding @value{GDBN} command is @samp{return}.
28498 @subsubheading Example
28502 200-break-insert callee4
28503 200^done,bkpt=@{number="1",addr="0x00010734",
28504 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28509 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28510 frame=@{func="callee4",args=[],
28511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28512 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28518 111^done,frame=@{level="0",func="callee3",
28519 args=[@{name="strarg",
28520 value="0x11940 \"A string argument.\""@}],
28521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28527 @subheading The @code{-exec-run} Command
28530 @subsubheading Synopsis
28533 -exec-run [ --all | --thread-group N ] [ --start ]
28536 Starts execution of the inferior from the beginning. The inferior
28537 executes until either a breakpoint is encountered or the program
28538 exits. In the latter case the output will include an exit code, if
28539 the program has exited exceptionally.
28541 When neither the @samp{--all} nor the @samp{--thread-group} option
28542 is specified, the current inferior is started. If the
28543 @samp{--thread-group} option is specified, it should refer to a thread
28544 group of type @samp{process}, and that thread group will be started.
28545 If the @samp{--all} option is specified, then all inferiors will be started.
28547 Using the @samp{--start} option instructs the debugger to stop
28548 the execution at the start of the inferior's main subprogram,
28549 following the same behavior as the @code{start} command
28550 (@pxref{Starting}).
28552 @subsubheading @value{GDBN} Command
28554 The corresponding @value{GDBN} command is @samp{run}.
28556 @subsubheading Examples
28561 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28566 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28567 frame=@{func="main",args=[],file="recursive2.c",
28568 fullname="/home/foo/bar/recursive2.c",line="4"@}
28573 Program exited normally:
28581 *stopped,reason="exited-normally"
28586 Program exited exceptionally:
28594 *stopped,reason="exited",exit-code="01"
28598 Another way the program can terminate is if it receives a signal such as
28599 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28603 *stopped,reason="exited-signalled",signal-name="SIGINT",
28604 signal-meaning="Interrupt"
28608 @c @subheading -exec-signal
28611 @subheading The @code{-exec-step} Command
28614 @subsubheading Synopsis
28617 -exec-step [--reverse]
28620 Resumes execution of the inferior program, stopping when the beginning
28621 of the next source line is reached, if the next source line is not a
28622 function call. If it is, stop at the first instruction of the called
28623 function. If the @samp{--reverse} option is specified, resumes reverse
28624 execution of the inferior program, stopping at the beginning of the
28625 previously executed source line.
28627 @subsubheading @value{GDBN} Command
28629 The corresponding @value{GDBN} command is @samp{step}.
28631 @subsubheading Example
28633 Stepping into a function:
28639 *stopped,reason="end-stepping-range",
28640 frame=@{func="foo",args=[@{name="a",value="10"@},
28641 @{name="b",value="0"@}],file="recursive2.c",
28642 fullname="/home/foo/bar/recursive2.c",line="11"@}
28652 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28657 @subheading The @code{-exec-step-instruction} Command
28658 @findex -exec-step-instruction
28660 @subsubheading Synopsis
28663 -exec-step-instruction [--reverse]
28666 Resumes the inferior which executes one machine instruction. If the
28667 @samp{--reverse} option is specified, resumes reverse execution of the
28668 inferior program, stopping at the previously executed instruction.
28669 The output, once @value{GDBN} has stopped, will vary depending on
28670 whether we have stopped in the middle of a source line or not. In the
28671 former case, the address at which the program stopped will be printed
28674 @subsubheading @value{GDBN} Command
28676 The corresponding @value{GDBN} command is @samp{stepi}.
28678 @subsubheading Example
28682 -exec-step-instruction
28686 *stopped,reason="end-stepping-range",
28687 frame=@{func="foo",args=[],file="try.c",
28688 fullname="/home/foo/bar/try.c",line="10"@}
28690 -exec-step-instruction
28694 *stopped,reason="end-stepping-range",
28695 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28696 fullname="/home/foo/bar/try.c",line="10"@}
28701 @subheading The @code{-exec-until} Command
28702 @findex -exec-until
28704 @subsubheading Synopsis
28707 -exec-until [ @var{location} ]
28710 Executes the inferior until the @var{location} specified in the
28711 argument is reached. If there is no argument, the inferior executes
28712 until a source line greater than the current one is reached. The
28713 reason for stopping in this case will be @samp{location-reached}.
28715 @subsubheading @value{GDBN} Command
28717 The corresponding @value{GDBN} command is @samp{until}.
28719 @subsubheading Example
28723 -exec-until recursive2.c:6
28727 *stopped,reason="location-reached",frame=@{func="main",args=[],
28728 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28733 @subheading -file-clear
28734 Is this going away????
28737 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28738 @node GDB/MI Stack Manipulation
28739 @section @sc{gdb/mi} Stack Manipulation Commands
28741 @subheading The @code{-enable-frame-filters} Command
28742 @findex -enable-frame-filters
28745 -enable-frame-filters
28748 @value{GDBN} allows Python-based frame filters to affect the output of
28749 the MI commands relating to stack traces. As there is no way to
28750 implement this in a fully backward-compatible way, a front end must
28751 request that this functionality be enabled.
28753 Once enabled, this feature cannot be disabled.
28755 Note that if Python support has not been compiled into @value{GDBN},
28756 this command will still succeed (and do nothing).
28758 @subheading The @code{-stack-info-frame} Command
28759 @findex -stack-info-frame
28761 @subsubheading Synopsis
28767 Get info on the selected frame.
28769 @subsubheading @value{GDBN} Command
28771 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28772 (without arguments).
28774 @subsubheading Example
28779 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28780 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28781 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28785 @subheading The @code{-stack-info-depth} Command
28786 @findex -stack-info-depth
28788 @subsubheading Synopsis
28791 -stack-info-depth [ @var{max-depth} ]
28794 Return the depth of the stack. If the integer argument @var{max-depth}
28795 is specified, do not count beyond @var{max-depth} frames.
28797 @subsubheading @value{GDBN} Command
28799 There's no equivalent @value{GDBN} command.
28801 @subsubheading Example
28803 For a stack with frame levels 0 through 11:
28810 -stack-info-depth 4
28813 -stack-info-depth 12
28816 -stack-info-depth 11
28819 -stack-info-depth 13
28824 @anchor{-stack-list-arguments}
28825 @subheading The @code{-stack-list-arguments} Command
28826 @findex -stack-list-arguments
28828 @subsubheading Synopsis
28831 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28832 [ @var{low-frame} @var{high-frame} ]
28835 Display a list of the arguments for the frames between @var{low-frame}
28836 and @var{high-frame} (inclusive). If @var{low-frame} and
28837 @var{high-frame} are not provided, list the arguments for the whole
28838 call stack. If the two arguments are equal, show the single frame
28839 at the corresponding level. It is an error if @var{low-frame} is
28840 larger than the actual number of frames. On the other hand,
28841 @var{high-frame} may be larger than the actual number of frames, in
28842 which case only existing frames will be returned.
28844 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28845 the variables; if it is 1 or @code{--all-values}, print also their
28846 values; and if it is 2 or @code{--simple-values}, print the name,
28847 type and value for simple data types, and the name and type for arrays,
28848 structures and unions. If the option @code{--no-frame-filters} is
28849 supplied, then Python frame filters will not be executed.
28851 If the @code{--skip-unavailable} option is specified, arguments that
28852 are not available are not listed. Partially available arguments
28853 are still displayed, however.
28855 Use of this command to obtain arguments in a single frame is
28856 deprecated in favor of the @samp{-stack-list-variables} command.
28858 @subsubheading @value{GDBN} Command
28860 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28861 @samp{gdb_get_args} command which partially overlaps with the
28862 functionality of @samp{-stack-list-arguments}.
28864 @subsubheading Example
28871 frame=@{level="0",addr="0x00010734",func="callee4",
28872 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28873 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28874 frame=@{level="1",addr="0x0001076c",func="callee3",
28875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28876 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28877 frame=@{level="2",addr="0x0001078c",func="callee2",
28878 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28879 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28880 frame=@{level="3",addr="0x000107b4",func="callee1",
28881 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28882 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28883 frame=@{level="4",addr="0x000107e0",func="main",
28884 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28885 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28887 -stack-list-arguments 0
28890 frame=@{level="0",args=[]@},
28891 frame=@{level="1",args=[name="strarg"]@},
28892 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28893 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28894 frame=@{level="4",args=[]@}]
28896 -stack-list-arguments 1
28899 frame=@{level="0",args=[]@},
28901 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28902 frame=@{level="2",args=[
28903 @{name="intarg",value="2"@},
28904 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28905 @{frame=@{level="3",args=[
28906 @{name="intarg",value="2"@},
28907 @{name="strarg",value="0x11940 \"A string argument.\""@},
28908 @{name="fltarg",value="3.5"@}]@},
28909 frame=@{level="4",args=[]@}]
28911 -stack-list-arguments 0 2 2
28912 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28914 -stack-list-arguments 1 2 2
28915 ^done,stack-args=[frame=@{level="2",
28916 args=[@{name="intarg",value="2"@},
28917 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28921 @c @subheading -stack-list-exception-handlers
28924 @anchor{-stack-list-frames}
28925 @subheading The @code{-stack-list-frames} Command
28926 @findex -stack-list-frames
28928 @subsubheading Synopsis
28931 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28934 List the frames currently on the stack. For each frame it displays the
28939 The frame number, 0 being the topmost frame, i.e., the innermost function.
28941 The @code{$pc} value for that frame.
28945 File name of the source file where the function lives.
28946 @item @var{fullname}
28947 The full file name of the source file where the function lives.
28949 Line number corresponding to the @code{$pc}.
28951 The shared library where this function is defined. This is only given
28952 if the frame's function is not known.
28955 If invoked without arguments, this command prints a backtrace for the
28956 whole stack. If given two integer arguments, it shows the frames whose
28957 levels are between the two arguments (inclusive). If the two arguments
28958 are equal, it shows the single frame at the corresponding level. It is
28959 an error if @var{low-frame} is larger than the actual number of
28960 frames. On the other hand, @var{high-frame} may be larger than the
28961 actual number of frames, in which case only existing frames will be
28962 returned. If the option @code{--no-frame-filters} is supplied, then
28963 Python frame filters will not be executed.
28965 @subsubheading @value{GDBN} Command
28967 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28969 @subsubheading Example
28971 Full stack backtrace:
28977 [frame=@{level="0",addr="0x0001076c",func="foo",
28978 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28979 frame=@{level="1",addr="0x000107a4",func="foo",
28980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28981 frame=@{level="2",addr="0x000107a4",func="foo",
28982 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28983 frame=@{level="3",addr="0x000107a4",func="foo",
28984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28985 frame=@{level="4",addr="0x000107a4",func="foo",
28986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28987 frame=@{level="5",addr="0x000107a4",func="foo",
28988 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28989 frame=@{level="6",addr="0x000107a4",func="foo",
28990 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28991 frame=@{level="7",addr="0x000107a4",func="foo",
28992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28993 frame=@{level="8",addr="0x000107a4",func="foo",
28994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28995 frame=@{level="9",addr="0x000107a4",func="foo",
28996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28997 frame=@{level="10",addr="0x000107a4",func="foo",
28998 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28999 frame=@{level="11",addr="0x00010738",func="main",
29000 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29004 Show frames between @var{low_frame} and @var{high_frame}:
29008 -stack-list-frames 3 5
29010 [frame=@{level="3",addr="0x000107a4",func="foo",
29011 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29012 frame=@{level="4",addr="0x000107a4",func="foo",
29013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29014 frame=@{level="5",addr="0x000107a4",func="foo",
29015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29019 Show a single frame:
29023 -stack-list-frames 3 3
29025 [frame=@{level="3",addr="0x000107a4",func="foo",
29026 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29031 @subheading The @code{-stack-list-locals} Command
29032 @findex -stack-list-locals
29033 @anchor{-stack-list-locals}
29035 @subsubheading Synopsis
29038 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29041 Display the local variable names for the selected frame. If
29042 @var{print-values} is 0 or @code{--no-values}, print only the names of
29043 the variables; if it is 1 or @code{--all-values}, print also their
29044 values; and if it is 2 or @code{--simple-values}, print the name,
29045 type and value for simple data types, and the name and type for arrays,
29046 structures and unions. In this last case, a frontend can immediately
29047 display the value of simple data types and create variable objects for
29048 other data types when the user wishes to explore their values in
29049 more detail. If the option @code{--no-frame-filters} is supplied, then
29050 Python frame filters will not be executed.
29052 If the @code{--skip-unavailable} option is specified, local variables
29053 that are not available are not listed. Partially available local
29054 variables are still displayed, however.
29056 This command is deprecated in favor of the
29057 @samp{-stack-list-variables} command.
29059 @subsubheading @value{GDBN} Command
29061 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29063 @subsubheading Example
29067 -stack-list-locals 0
29068 ^done,locals=[name="A",name="B",name="C"]
29070 -stack-list-locals --all-values
29071 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29072 @{name="C",value="@{1, 2, 3@}"@}]
29073 -stack-list-locals --simple-values
29074 ^done,locals=[@{name="A",type="int",value="1"@},
29075 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29079 @anchor{-stack-list-variables}
29080 @subheading The @code{-stack-list-variables} Command
29081 @findex -stack-list-variables
29083 @subsubheading Synopsis
29086 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29089 Display the names of local variables and function arguments for the selected frame. If
29090 @var{print-values} is 0 or @code{--no-values}, print only the names of
29091 the variables; if it is 1 or @code{--all-values}, print also their
29092 values; and if it is 2 or @code{--simple-values}, print the name,
29093 type and value for simple data types, and the name and type for arrays,
29094 structures and unions. If the option @code{--no-frame-filters} is
29095 supplied, then Python frame filters will not be executed.
29097 If the @code{--skip-unavailable} option is specified, local variables
29098 and arguments that are not available are not listed. Partially
29099 available arguments and local variables are still displayed, however.
29101 @subsubheading Example
29105 -stack-list-variables --thread 1 --frame 0 --all-values
29106 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29111 @subheading The @code{-stack-select-frame} Command
29112 @findex -stack-select-frame
29114 @subsubheading Synopsis
29117 -stack-select-frame @var{framenum}
29120 Change the selected frame. Select a different frame @var{framenum} on
29123 This command in deprecated in favor of passing the @samp{--frame}
29124 option to every command.
29126 @subsubheading @value{GDBN} Command
29128 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29129 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29131 @subsubheading Example
29135 -stack-select-frame 2
29140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29141 @node GDB/MI Variable Objects
29142 @section @sc{gdb/mi} Variable Objects
29146 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29148 For the implementation of a variable debugger window (locals, watched
29149 expressions, etc.), we are proposing the adaptation of the existing code
29150 used by @code{Insight}.
29152 The two main reasons for that are:
29156 It has been proven in practice (it is already on its second generation).
29159 It will shorten development time (needless to say how important it is
29163 The original interface was designed to be used by Tcl code, so it was
29164 slightly changed so it could be used through @sc{gdb/mi}. This section
29165 describes the @sc{gdb/mi} operations that will be available and gives some
29166 hints about their use.
29168 @emph{Note}: In addition to the set of operations described here, we
29169 expect the @sc{gui} implementation of a variable window to require, at
29170 least, the following operations:
29173 @item @code{-gdb-show} @code{output-radix}
29174 @item @code{-stack-list-arguments}
29175 @item @code{-stack-list-locals}
29176 @item @code{-stack-select-frame}
29181 @subheading Introduction to Variable Objects
29183 @cindex variable objects in @sc{gdb/mi}
29185 Variable objects are "object-oriented" MI interface for examining and
29186 changing values of expressions. Unlike some other MI interfaces that
29187 work with expressions, variable objects are specifically designed for
29188 simple and efficient presentation in the frontend. A variable object
29189 is identified by string name. When a variable object is created, the
29190 frontend specifies the expression for that variable object. The
29191 expression can be a simple variable, or it can be an arbitrary complex
29192 expression, and can even involve CPU registers. After creating a
29193 variable object, the frontend can invoke other variable object
29194 operations---for example to obtain or change the value of a variable
29195 object, or to change display format.
29197 Variable objects have hierarchical tree structure. Any variable object
29198 that corresponds to a composite type, such as structure in C, has
29199 a number of child variable objects, for example corresponding to each
29200 element of a structure. A child variable object can itself have
29201 children, recursively. Recursion ends when we reach
29202 leaf variable objects, which always have built-in types. Child variable
29203 objects are created only by explicit request, so if a frontend
29204 is not interested in the children of a particular variable object, no
29205 child will be created.
29207 For a leaf variable object it is possible to obtain its value as a
29208 string, or set the value from a string. String value can be also
29209 obtained for a non-leaf variable object, but it's generally a string
29210 that only indicates the type of the object, and does not list its
29211 contents. Assignment to a non-leaf variable object is not allowed.
29213 A frontend does not need to read the values of all variable objects each time
29214 the program stops. Instead, MI provides an update command that lists all
29215 variable objects whose values has changed since the last update
29216 operation. This considerably reduces the amount of data that must
29217 be transferred to the frontend. As noted above, children variable
29218 objects are created on demand, and only leaf variable objects have a
29219 real value. As result, gdb will read target memory only for leaf
29220 variables that frontend has created.
29222 The automatic update is not always desirable. For example, a frontend
29223 might want to keep a value of some expression for future reference,
29224 and never update it. For another example, fetching memory is
29225 relatively slow for embedded targets, so a frontend might want
29226 to disable automatic update for the variables that are either not
29227 visible on the screen, or ``closed''. This is possible using so
29228 called ``frozen variable objects''. Such variable objects are never
29229 implicitly updated.
29231 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29232 fixed variable object, the expression is parsed when the variable
29233 object is created, including associating identifiers to specific
29234 variables. The meaning of expression never changes. For a floating
29235 variable object the values of variables whose names appear in the
29236 expressions are re-evaluated every time in the context of the current
29237 frame. Consider this example:
29242 struct work_state state;
29249 If a fixed variable object for the @code{state} variable is created in
29250 this function, and we enter the recursive call, the variable
29251 object will report the value of @code{state} in the top-level
29252 @code{do_work} invocation. On the other hand, a floating variable
29253 object will report the value of @code{state} in the current frame.
29255 If an expression specified when creating a fixed variable object
29256 refers to a local variable, the variable object becomes bound to the
29257 thread and frame in which the variable object is created. When such
29258 variable object is updated, @value{GDBN} makes sure that the
29259 thread/frame combination the variable object is bound to still exists,
29260 and re-evaluates the variable object in context of that thread/frame.
29262 The following is the complete set of @sc{gdb/mi} operations defined to
29263 access this functionality:
29265 @multitable @columnfractions .4 .6
29266 @item @strong{Operation}
29267 @tab @strong{Description}
29269 @item @code{-enable-pretty-printing}
29270 @tab enable Python-based pretty-printing
29271 @item @code{-var-create}
29272 @tab create a variable object
29273 @item @code{-var-delete}
29274 @tab delete the variable object and/or its children
29275 @item @code{-var-set-format}
29276 @tab set the display format of this variable
29277 @item @code{-var-show-format}
29278 @tab show the display format of this variable
29279 @item @code{-var-info-num-children}
29280 @tab tells how many children this object has
29281 @item @code{-var-list-children}
29282 @tab return a list of the object's children
29283 @item @code{-var-info-type}
29284 @tab show the type of this variable object
29285 @item @code{-var-info-expression}
29286 @tab print parent-relative expression that this variable object represents
29287 @item @code{-var-info-path-expression}
29288 @tab print full expression that this variable object represents
29289 @item @code{-var-show-attributes}
29290 @tab is this variable editable? does it exist here?
29291 @item @code{-var-evaluate-expression}
29292 @tab get the value of this variable
29293 @item @code{-var-assign}
29294 @tab set the value of this variable
29295 @item @code{-var-update}
29296 @tab update the variable and its children
29297 @item @code{-var-set-frozen}
29298 @tab set frozeness attribute
29299 @item @code{-var-set-update-range}
29300 @tab set range of children to display on update
29303 In the next subsection we describe each operation in detail and suggest
29304 how it can be used.
29306 @subheading Description And Use of Operations on Variable Objects
29308 @subheading The @code{-enable-pretty-printing} Command
29309 @findex -enable-pretty-printing
29312 -enable-pretty-printing
29315 @value{GDBN} allows Python-based visualizers to affect the output of the
29316 MI variable object commands. However, because there was no way to
29317 implement this in a fully backward-compatible way, a front end must
29318 request that this functionality be enabled.
29320 Once enabled, this feature cannot be disabled.
29322 Note that if Python support has not been compiled into @value{GDBN},
29323 this command will still succeed (and do nothing).
29325 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29326 may work differently in future versions of @value{GDBN}.
29328 @subheading The @code{-var-create} Command
29329 @findex -var-create
29331 @subsubheading Synopsis
29334 -var-create @{@var{name} | "-"@}
29335 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29338 This operation creates a variable object, which allows the monitoring of
29339 a variable, the result of an expression, a memory cell or a CPU
29342 The @var{name} parameter is the string by which the object can be
29343 referenced. It must be unique. If @samp{-} is specified, the varobj
29344 system will generate a string ``varNNNNNN'' automatically. It will be
29345 unique provided that one does not specify @var{name} of that format.
29346 The command fails if a duplicate name is found.
29348 The frame under which the expression should be evaluated can be
29349 specified by @var{frame-addr}. A @samp{*} indicates that the current
29350 frame should be used. A @samp{@@} indicates that a floating variable
29351 object must be created.
29353 @var{expression} is any expression valid on the current language set (must not
29354 begin with a @samp{*}), or one of the following:
29358 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29361 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29364 @samp{$@var{regname}} --- a CPU register name
29367 @cindex dynamic varobj
29368 A varobj's contents may be provided by a Python-based pretty-printer. In this
29369 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29370 have slightly different semantics in some cases. If the
29371 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29372 will never create a dynamic varobj. This ensures backward
29373 compatibility for existing clients.
29375 @subsubheading Result
29377 This operation returns attributes of the newly-created varobj. These
29382 The name of the varobj.
29385 The number of children of the varobj. This number is not necessarily
29386 reliable for a dynamic varobj. Instead, you must examine the
29387 @samp{has_more} attribute.
29390 The varobj's scalar value. For a varobj whose type is some sort of
29391 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29392 will not be interesting.
29395 The varobj's type. This is a string representation of the type, as
29396 would be printed by the @value{GDBN} CLI. If @samp{print object}
29397 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29398 @emph{actual} (derived) type of the object is shown rather than the
29399 @emph{declared} one.
29402 If a variable object is bound to a specific thread, then this is the
29403 thread's global identifier.
29406 For a dynamic varobj, this indicates whether there appear to be any
29407 children available. For a non-dynamic varobj, this will be 0.
29410 This attribute will be present and have the value @samp{1} if the
29411 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29412 then this attribute will not be present.
29415 A dynamic varobj can supply a display hint to the front end. The
29416 value comes directly from the Python pretty-printer object's
29417 @code{display_hint} method. @xref{Pretty Printing API}.
29420 Typical output will look like this:
29423 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29424 has_more="@var{has_more}"
29428 @subheading The @code{-var-delete} Command
29429 @findex -var-delete
29431 @subsubheading Synopsis
29434 -var-delete [ -c ] @var{name}
29437 Deletes a previously created variable object and all of its children.
29438 With the @samp{-c} option, just deletes the children.
29440 Returns an error if the object @var{name} is not found.
29443 @subheading The @code{-var-set-format} Command
29444 @findex -var-set-format
29446 @subsubheading Synopsis
29449 -var-set-format @var{name} @var{format-spec}
29452 Sets the output format for the value of the object @var{name} to be
29455 @anchor{-var-set-format}
29456 The syntax for the @var{format-spec} is as follows:
29459 @var{format-spec} @expansion{}
29460 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29463 The natural format is the default format choosen automatically
29464 based on the variable type (like decimal for an @code{int}, hex
29465 for pointers, etc.).
29467 The zero-hexadecimal format has a representation similar to hexadecimal
29468 but with padding zeroes to the left of the value. For example, a 32-bit
29469 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29470 zero-hexadecimal format.
29472 For a variable with children, the format is set only on the
29473 variable itself, and the children are not affected.
29475 @subheading The @code{-var-show-format} Command
29476 @findex -var-show-format
29478 @subsubheading Synopsis
29481 -var-show-format @var{name}
29484 Returns the format used to display the value of the object @var{name}.
29487 @var{format} @expansion{}
29492 @subheading The @code{-var-info-num-children} Command
29493 @findex -var-info-num-children
29495 @subsubheading Synopsis
29498 -var-info-num-children @var{name}
29501 Returns the number of children of a variable object @var{name}:
29507 Note that this number is not completely reliable for a dynamic varobj.
29508 It will return the current number of children, but more children may
29512 @subheading The @code{-var-list-children} Command
29513 @findex -var-list-children
29515 @subsubheading Synopsis
29518 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29520 @anchor{-var-list-children}
29522 Return a list of the children of the specified variable object and
29523 create variable objects for them, if they do not already exist. With
29524 a single argument or if @var{print-values} has a value of 0 or
29525 @code{--no-values}, print only the names of the variables; if
29526 @var{print-values} is 1 or @code{--all-values}, also print their
29527 values; and if it is 2 or @code{--simple-values} print the name and
29528 value for simple data types and just the name for arrays, structures
29531 @var{from} and @var{to}, if specified, indicate the range of children
29532 to report. If @var{from} or @var{to} is less than zero, the range is
29533 reset and all children will be reported. Otherwise, children starting
29534 at @var{from} (zero-based) and up to and excluding @var{to} will be
29537 If a child range is requested, it will only affect the current call to
29538 @code{-var-list-children}, but not future calls to @code{-var-update}.
29539 For this, you must instead use @code{-var-set-update-range}. The
29540 intent of this approach is to enable a front end to implement any
29541 update approach it likes; for example, scrolling a view may cause the
29542 front end to request more children with @code{-var-list-children}, and
29543 then the front end could call @code{-var-set-update-range} with a
29544 different range to ensure that future updates are restricted to just
29547 For each child the following results are returned:
29552 Name of the variable object created for this child.
29555 The expression to be shown to the user by the front end to designate this child.
29556 For example this may be the name of a structure member.
29558 For a dynamic varobj, this value cannot be used to form an
29559 expression. There is no way to do this at all with a dynamic varobj.
29561 For C/C@t{++} structures there are several pseudo children returned to
29562 designate access qualifiers. For these pseudo children @var{exp} is
29563 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29564 type and value are not present.
29566 A dynamic varobj will not report the access qualifying
29567 pseudo-children, regardless of the language. This information is not
29568 available at all with a dynamic varobj.
29571 Number of children this child has. For a dynamic varobj, this will be
29575 The type of the child. If @samp{print object}
29576 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29577 @emph{actual} (derived) type of the object is shown rather than the
29578 @emph{declared} one.
29581 If values were requested, this is the value.
29584 If this variable object is associated with a thread, this is the
29585 thread's global thread id. Otherwise this result is not present.
29588 If the variable object is frozen, this variable will be present with a value of 1.
29591 A dynamic varobj can supply a display hint to the front end. The
29592 value comes directly from the Python pretty-printer object's
29593 @code{display_hint} method. @xref{Pretty Printing API}.
29596 This attribute will be present and have the value @samp{1} if the
29597 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29598 then this attribute will not be present.
29602 The result may have its own attributes:
29606 A dynamic varobj can supply a display hint to the front end. The
29607 value comes directly from the Python pretty-printer object's
29608 @code{display_hint} method. @xref{Pretty Printing API}.
29611 This is an integer attribute which is nonzero if there are children
29612 remaining after the end of the selected range.
29615 @subsubheading Example
29619 -var-list-children n
29620 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29621 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29623 -var-list-children --all-values n
29624 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29625 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29629 @subheading The @code{-var-info-type} Command
29630 @findex -var-info-type
29632 @subsubheading Synopsis
29635 -var-info-type @var{name}
29638 Returns the type of the specified variable @var{name}. The type is
29639 returned as a string in the same format as it is output by the
29643 type=@var{typename}
29647 @subheading The @code{-var-info-expression} Command
29648 @findex -var-info-expression
29650 @subsubheading Synopsis
29653 -var-info-expression @var{name}
29656 Returns a string that is suitable for presenting this
29657 variable object in user interface. The string is generally
29658 not valid expression in the current language, and cannot be evaluated.
29660 For example, if @code{a} is an array, and variable object
29661 @code{A} was created for @code{a}, then we'll get this output:
29664 (gdb) -var-info-expression A.1
29665 ^done,lang="C",exp="1"
29669 Here, the value of @code{lang} is the language name, which can be
29670 found in @ref{Supported Languages}.
29672 Note that the output of the @code{-var-list-children} command also
29673 includes those expressions, so the @code{-var-info-expression} command
29676 @subheading The @code{-var-info-path-expression} Command
29677 @findex -var-info-path-expression
29679 @subsubheading Synopsis
29682 -var-info-path-expression @var{name}
29685 Returns an expression that can be evaluated in the current
29686 context and will yield the same value that a variable object has.
29687 Compare this with the @code{-var-info-expression} command, which
29688 result can be used only for UI presentation. Typical use of
29689 the @code{-var-info-path-expression} command is creating a
29690 watchpoint from a variable object.
29692 This command is currently not valid for children of a dynamic varobj,
29693 and will give an error when invoked on one.
29695 For example, suppose @code{C} is a C@t{++} class, derived from class
29696 @code{Base}, and that the @code{Base} class has a member called
29697 @code{m_size}. Assume a variable @code{c} is has the type of
29698 @code{C} and a variable object @code{C} was created for variable
29699 @code{c}. Then, we'll get this output:
29701 (gdb) -var-info-path-expression C.Base.public.m_size
29702 ^done,path_expr=((Base)c).m_size)
29705 @subheading The @code{-var-show-attributes} Command
29706 @findex -var-show-attributes
29708 @subsubheading Synopsis
29711 -var-show-attributes @var{name}
29714 List attributes of the specified variable object @var{name}:
29717 status=@var{attr} [ ( ,@var{attr} )* ]
29721 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29723 @subheading The @code{-var-evaluate-expression} Command
29724 @findex -var-evaluate-expression
29726 @subsubheading Synopsis
29729 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29732 Evaluates the expression that is represented by the specified variable
29733 object and returns its value as a string. The format of the string
29734 can be specified with the @samp{-f} option. The possible values of
29735 this option are the same as for @code{-var-set-format}
29736 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29737 the current display format will be used. The current display format
29738 can be changed using the @code{-var-set-format} command.
29744 Note that one must invoke @code{-var-list-children} for a variable
29745 before the value of a child variable can be evaluated.
29747 @subheading The @code{-var-assign} Command
29748 @findex -var-assign
29750 @subsubheading Synopsis
29753 -var-assign @var{name} @var{expression}
29756 Assigns the value of @var{expression} to the variable object specified
29757 by @var{name}. The object must be @samp{editable}. If the variable's
29758 value is altered by the assign, the variable will show up in any
29759 subsequent @code{-var-update} list.
29761 @subsubheading Example
29769 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29773 @subheading The @code{-var-update} Command
29774 @findex -var-update
29776 @subsubheading Synopsis
29779 -var-update [@var{print-values}] @{@var{name} | "*"@}
29782 Reevaluate the expressions corresponding to the variable object
29783 @var{name} and all its direct and indirect children, and return the
29784 list of variable objects whose values have changed; @var{name} must
29785 be a root variable object. Here, ``changed'' means that the result of
29786 @code{-var-evaluate-expression} before and after the
29787 @code{-var-update} is different. If @samp{*} is used as the variable
29788 object names, all existing variable objects are updated, except
29789 for frozen ones (@pxref{-var-set-frozen}). The option
29790 @var{print-values} determines whether both names and values, or just
29791 names are printed. The possible values of this option are the same
29792 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29793 recommended to use the @samp{--all-values} option, to reduce the
29794 number of MI commands needed on each program stop.
29796 With the @samp{*} parameter, if a variable object is bound to a
29797 currently running thread, it will not be updated, without any
29800 If @code{-var-set-update-range} was previously used on a varobj, then
29801 only the selected range of children will be reported.
29803 @code{-var-update} reports all the changed varobjs in a tuple named
29806 Each item in the change list is itself a tuple holding:
29810 The name of the varobj.
29813 If values were requested for this update, then this field will be
29814 present and will hold the value of the varobj.
29817 @anchor{-var-update}
29818 This field is a string which may take one of three values:
29822 The variable object's current value is valid.
29825 The variable object does not currently hold a valid value but it may
29826 hold one in the future if its associated expression comes back into
29830 The variable object no longer holds a valid value.
29831 This can occur when the executable file being debugged has changed,
29832 either through recompilation or by using the @value{GDBN} @code{file}
29833 command. The front end should normally choose to delete these variable
29837 In the future new values may be added to this list so the front should
29838 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29841 This is only present if the varobj is still valid. If the type
29842 changed, then this will be the string @samp{true}; otherwise it will
29845 When a varobj's type changes, its children are also likely to have
29846 become incorrect. Therefore, the varobj's children are automatically
29847 deleted when this attribute is @samp{true}. Also, the varobj's update
29848 range, when set using the @code{-var-set-update-range} command, is
29852 If the varobj's type changed, then this field will be present and will
29855 @item new_num_children
29856 For a dynamic varobj, if the number of children changed, or if the
29857 type changed, this will be the new number of children.
29859 The @samp{numchild} field in other varobj responses is generally not
29860 valid for a dynamic varobj -- it will show the number of children that
29861 @value{GDBN} knows about, but because dynamic varobjs lazily
29862 instantiate their children, this will not reflect the number of
29863 children which may be available.
29865 The @samp{new_num_children} attribute only reports changes to the
29866 number of children known by @value{GDBN}. This is the only way to
29867 detect whether an update has removed children (which necessarily can
29868 only happen at the end of the update range).
29871 The display hint, if any.
29874 This is an integer value, which will be 1 if there are more children
29875 available outside the varobj's update range.
29878 This attribute will be present and have the value @samp{1} if the
29879 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29880 then this attribute will not be present.
29883 If new children were added to a dynamic varobj within the selected
29884 update range (as set by @code{-var-set-update-range}), then they will
29885 be listed in this attribute.
29888 @subsubheading Example
29895 -var-update --all-values var1
29896 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29897 type_changed="false"@}]
29901 @subheading The @code{-var-set-frozen} Command
29902 @findex -var-set-frozen
29903 @anchor{-var-set-frozen}
29905 @subsubheading Synopsis
29908 -var-set-frozen @var{name} @var{flag}
29911 Set the frozenness flag on the variable object @var{name}. The
29912 @var{flag} parameter should be either @samp{1} to make the variable
29913 frozen or @samp{0} to make it unfrozen. If a variable object is
29914 frozen, then neither itself, nor any of its children, are
29915 implicitly updated by @code{-var-update} of
29916 a parent variable or by @code{-var-update *}. Only
29917 @code{-var-update} of the variable itself will update its value and
29918 values of its children. After a variable object is unfrozen, it is
29919 implicitly updated by all subsequent @code{-var-update} operations.
29920 Unfreezing a variable does not update it, only subsequent
29921 @code{-var-update} does.
29923 @subsubheading Example
29927 -var-set-frozen V 1
29932 @subheading The @code{-var-set-update-range} command
29933 @findex -var-set-update-range
29934 @anchor{-var-set-update-range}
29936 @subsubheading Synopsis
29939 -var-set-update-range @var{name} @var{from} @var{to}
29942 Set the range of children to be returned by future invocations of
29943 @code{-var-update}.
29945 @var{from} and @var{to} indicate the range of children to report. If
29946 @var{from} or @var{to} is less than zero, the range is reset and all
29947 children will be reported. Otherwise, children starting at @var{from}
29948 (zero-based) and up to and excluding @var{to} will be reported.
29950 @subsubheading Example
29954 -var-set-update-range V 1 2
29958 @subheading The @code{-var-set-visualizer} command
29959 @findex -var-set-visualizer
29960 @anchor{-var-set-visualizer}
29962 @subsubheading Synopsis
29965 -var-set-visualizer @var{name} @var{visualizer}
29968 Set a visualizer for the variable object @var{name}.
29970 @var{visualizer} is the visualizer to use. The special value
29971 @samp{None} means to disable any visualizer in use.
29973 If not @samp{None}, @var{visualizer} must be a Python expression.
29974 This expression must evaluate to a callable object which accepts a
29975 single argument. @value{GDBN} will call this object with the value of
29976 the varobj @var{name} as an argument (this is done so that the same
29977 Python pretty-printing code can be used for both the CLI and MI).
29978 When called, this object must return an object which conforms to the
29979 pretty-printing interface (@pxref{Pretty Printing API}).
29981 The pre-defined function @code{gdb.default_visualizer} may be used to
29982 select a visualizer by following the built-in process
29983 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29984 a varobj is created, and so ordinarily is not needed.
29986 This feature is only available if Python support is enabled. The MI
29987 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29988 can be used to check this.
29990 @subsubheading Example
29992 Resetting the visualizer:
29996 -var-set-visualizer V None
30000 Reselecting the default (type-based) visualizer:
30004 -var-set-visualizer V gdb.default_visualizer
30008 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30009 can be used to instantiate this class for a varobj:
30013 -var-set-visualizer V "lambda val: SomeClass()"
30017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30018 @node GDB/MI Data Manipulation
30019 @section @sc{gdb/mi} Data Manipulation
30021 @cindex data manipulation, in @sc{gdb/mi}
30022 @cindex @sc{gdb/mi}, data manipulation
30023 This section describes the @sc{gdb/mi} commands that manipulate data:
30024 examine memory and registers, evaluate expressions, etc.
30026 For details about what an addressable memory unit is,
30027 @pxref{addressable memory unit}.
30029 @c REMOVED FROM THE INTERFACE.
30030 @c @subheading -data-assign
30031 @c Change the value of a program variable. Plenty of side effects.
30032 @c @subsubheading GDB Command
30034 @c @subsubheading Example
30037 @subheading The @code{-data-disassemble} Command
30038 @findex -data-disassemble
30040 @subsubheading Synopsis
30044 [ -s @var{start-addr} -e @var{end-addr} ]
30045 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30053 @item @var{start-addr}
30054 is the beginning address (or @code{$pc})
30055 @item @var{end-addr}
30057 @item @var{filename}
30058 is the name of the file to disassemble
30059 @item @var{linenum}
30060 is the line number to disassemble around
30062 is the number of disassembly lines to be produced. If it is -1,
30063 the whole function will be disassembled, in case no @var{end-addr} is
30064 specified. If @var{end-addr} is specified as a non-zero value, and
30065 @var{lines} is lower than the number of disassembly lines between
30066 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30067 displayed; if @var{lines} is higher than the number of lines between
30068 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30073 @item 0 disassembly only
30074 @item 1 mixed source and disassembly (deprecated)
30075 @item 2 disassembly with raw opcodes
30076 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30077 @item 4 mixed source and disassembly
30078 @item 5 mixed source and disassembly with raw opcodes
30081 Modes 1 and 3 are deprecated. The output is ``source centric''
30082 which hasn't proved useful in practice.
30083 @xref{Machine Code}, for a discussion of the difference between
30084 @code{/m} and @code{/s} output of the @code{disassemble} command.
30087 @subsubheading Result
30089 The result of the @code{-data-disassemble} command will be a list named
30090 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30091 used with the @code{-data-disassemble} command.
30093 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30098 The address at which this instruction was disassembled.
30101 The name of the function this instruction is within.
30104 The decimal offset in bytes from the start of @samp{func-name}.
30107 The text disassembly for this @samp{address}.
30110 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30111 bytes for the @samp{inst} field.
30115 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30116 @samp{src_and_asm_line}, each of which has the following fields:
30120 The line number within @samp{file}.
30123 The file name from the compilation unit. This might be an absolute
30124 file name or a relative file name depending on the compile command
30128 Absolute file name of @samp{file}. It is converted to a canonical form
30129 using the source file search path
30130 (@pxref{Source Path, ,Specifying Source Directories})
30131 and after resolving all the symbolic links.
30133 If the source file is not found this field will contain the path as
30134 present in the debug information.
30136 @item line_asm_insn
30137 This is a list of tuples containing the disassembly for @samp{line} in
30138 @samp{file}. The fields of each tuple are the same as for
30139 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30140 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30145 Note that whatever included in the @samp{inst} field, is not
30146 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30149 @subsubheading @value{GDBN} Command
30151 The corresponding @value{GDBN} command is @samp{disassemble}.
30153 @subsubheading Example
30155 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30159 -data-disassemble -s $pc -e "$pc + 20" -- 0
30162 @{address="0x000107c0",func-name="main",offset="4",
30163 inst="mov 2, %o0"@},
30164 @{address="0x000107c4",func-name="main",offset="8",
30165 inst="sethi %hi(0x11800), %o2"@},
30166 @{address="0x000107c8",func-name="main",offset="12",
30167 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30168 @{address="0x000107cc",func-name="main",offset="16",
30169 inst="sethi %hi(0x11800), %o2"@},
30170 @{address="0x000107d0",func-name="main",offset="20",
30171 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30175 Disassemble the whole @code{main} function. Line 32 is part of
30179 -data-disassemble -f basics.c -l 32 -- 0
30181 @{address="0x000107bc",func-name="main",offset="0",
30182 inst="save %sp, -112, %sp"@},
30183 @{address="0x000107c0",func-name="main",offset="4",
30184 inst="mov 2, %o0"@},
30185 @{address="0x000107c4",func-name="main",offset="8",
30186 inst="sethi %hi(0x11800), %o2"@},
30188 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30189 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30193 Disassemble 3 instructions from the start of @code{main}:
30197 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30199 @{address="0x000107bc",func-name="main",offset="0",
30200 inst="save %sp, -112, %sp"@},
30201 @{address="0x000107c0",func-name="main",offset="4",
30202 inst="mov 2, %o0"@},
30203 @{address="0x000107c4",func-name="main",offset="8",
30204 inst="sethi %hi(0x11800), %o2"@}]
30208 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30212 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30214 src_and_asm_line=@{line="31",
30215 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30216 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30217 line_asm_insn=[@{address="0x000107bc",
30218 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30219 src_and_asm_line=@{line="32",
30220 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30221 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30222 line_asm_insn=[@{address="0x000107c0",
30223 func-name="main",offset="4",inst="mov 2, %o0"@},
30224 @{address="0x000107c4",func-name="main",offset="8",
30225 inst="sethi %hi(0x11800), %o2"@}]@}]
30230 @subheading The @code{-data-evaluate-expression} Command
30231 @findex -data-evaluate-expression
30233 @subsubheading Synopsis
30236 -data-evaluate-expression @var{expr}
30239 Evaluate @var{expr} as an expression. The expression could contain an
30240 inferior function call. The function call will execute synchronously.
30241 If the expression contains spaces, it must be enclosed in double quotes.
30243 @subsubheading @value{GDBN} Command
30245 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30246 @samp{call}. In @code{gdbtk} only, there's a corresponding
30247 @samp{gdb_eval} command.
30249 @subsubheading Example
30251 In the following example, the numbers that precede the commands are the
30252 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30253 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30257 211-data-evaluate-expression A
30260 311-data-evaluate-expression &A
30261 311^done,value="0xefffeb7c"
30263 411-data-evaluate-expression A+3
30266 511-data-evaluate-expression "A + 3"
30272 @subheading The @code{-data-list-changed-registers} Command
30273 @findex -data-list-changed-registers
30275 @subsubheading Synopsis
30278 -data-list-changed-registers
30281 Display a list of the registers that have changed.
30283 @subsubheading @value{GDBN} Command
30285 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30286 has the corresponding command @samp{gdb_changed_register_list}.
30288 @subsubheading Example
30290 On a PPC MBX board:
30298 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30299 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30302 -data-list-changed-registers
30303 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30304 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30305 "24","25","26","27","28","30","31","64","65","66","67","69"]
30310 @subheading The @code{-data-list-register-names} Command
30311 @findex -data-list-register-names
30313 @subsubheading Synopsis
30316 -data-list-register-names [ ( @var{regno} )+ ]
30319 Show a list of register names for the current target. If no arguments
30320 are given, it shows a list of the names of all the registers. If
30321 integer numbers are given as arguments, it will print a list of the
30322 names of the registers corresponding to the arguments. To ensure
30323 consistency between a register name and its number, the output list may
30324 include empty register names.
30326 @subsubheading @value{GDBN} Command
30328 @value{GDBN} does not have a command which corresponds to
30329 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30330 corresponding command @samp{gdb_regnames}.
30332 @subsubheading Example
30334 For the PPC MBX board:
30337 -data-list-register-names
30338 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30339 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30340 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30341 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30342 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30343 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30344 "", "pc","ps","cr","lr","ctr","xer"]
30346 -data-list-register-names 1 2 3
30347 ^done,register-names=["r1","r2","r3"]
30351 @subheading The @code{-data-list-register-values} Command
30352 @findex -data-list-register-values
30354 @subsubheading Synopsis
30357 -data-list-register-values
30358 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30361 Display the registers' contents. The format according to which the
30362 registers' contents are to be returned is given by @var{fmt}, followed
30363 by an optional list of numbers specifying the registers to display. A
30364 missing list of numbers indicates that the contents of all the
30365 registers must be returned. The @code{--skip-unavailable} option
30366 indicates that only the available registers are to be returned.
30368 Allowed formats for @var{fmt} are:
30385 @subsubheading @value{GDBN} Command
30387 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30388 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30390 @subsubheading Example
30392 For a PPC MBX board (note: line breaks are for readability only, they
30393 don't appear in the actual output):
30397 -data-list-register-values r 64 65
30398 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30399 @{number="65",value="0x00029002"@}]
30401 -data-list-register-values x
30402 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30403 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30404 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30405 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30406 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30407 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30408 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30409 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30410 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30411 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30412 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30413 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30414 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30415 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30416 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30417 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30418 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30419 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30420 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30421 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30422 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30423 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30424 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30425 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30426 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30427 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30428 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30429 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30430 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30431 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30432 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30433 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30434 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30435 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30436 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30437 @{number="69",value="0x20002b03"@}]
30442 @subheading The @code{-data-read-memory} Command
30443 @findex -data-read-memory
30445 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30447 @subsubheading Synopsis
30450 -data-read-memory [ -o @var{byte-offset} ]
30451 @var{address} @var{word-format} @var{word-size}
30452 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30459 @item @var{address}
30460 An expression specifying the address of the first memory word to be
30461 read. Complex expressions containing embedded white space should be
30462 quoted using the C convention.
30464 @item @var{word-format}
30465 The format to be used to print the memory words. The notation is the
30466 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30469 @item @var{word-size}
30470 The size of each memory word in bytes.
30472 @item @var{nr-rows}
30473 The number of rows in the output table.
30475 @item @var{nr-cols}
30476 The number of columns in the output table.
30479 If present, indicates that each row should include an @sc{ascii} dump. The
30480 value of @var{aschar} is used as a padding character when a byte is not a
30481 member of the printable @sc{ascii} character set (printable @sc{ascii}
30482 characters are those whose code is between 32 and 126, inclusively).
30484 @item @var{byte-offset}
30485 An offset to add to the @var{address} before fetching memory.
30488 This command displays memory contents as a table of @var{nr-rows} by
30489 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30490 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30491 (returned as @samp{total-bytes}). Should less than the requested number
30492 of bytes be returned by the target, the missing words are identified
30493 using @samp{N/A}. The number of bytes read from the target is returned
30494 in @samp{nr-bytes} and the starting address used to read memory in
30497 The address of the next/previous row or page is available in
30498 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30501 @subsubheading @value{GDBN} Command
30503 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30504 @samp{gdb_get_mem} memory read command.
30506 @subsubheading Example
30508 Read six bytes of memory starting at @code{bytes+6} but then offset by
30509 @code{-6} bytes. Format as three rows of two columns. One byte per
30510 word. Display each word in hex.
30514 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30515 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30516 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30517 prev-page="0x0000138a",memory=[
30518 @{addr="0x00001390",data=["0x00","0x01"]@},
30519 @{addr="0x00001392",data=["0x02","0x03"]@},
30520 @{addr="0x00001394",data=["0x04","0x05"]@}]
30524 Read two bytes of memory starting at address @code{shorts + 64} and
30525 display as a single word formatted in decimal.
30529 5-data-read-memory shorts+64 d 2 1 1
30530 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30531 next-row="0x00001512",prev-row="0x0000150e",
30532 next-page="0x00001512",prev-page="0x0000150e",memory=[
30533 @{addr="0x00001510",data=["128"]@}]
30537 Read thirty two bytes of memory starting at @code{bytes+16} and format
30538 as eight rows of four columns. Include a string encoding with @samp{x}
30539 used as the non-printable character.
30543 4-data-read-memory bytes+16 x 1 8 4 x
30544 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30545 next-row="0x000013c0",prev-row="0x0000139c",
30546 next-page="0x000013c0",prev-page="0x00001380",memory=[
30547 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30548 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30549 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30550 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30551 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30552 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30553 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30554 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30558 @subheading The @code{-data-read-memory-bytes} Command
30559 @findex -data-read-memory-bytes
30561 @subsubheading Synopsis
30564 -data-read-memory-bytes [ -o @var{offset} ]
30565 @var{address} @var{count}
30572 @item @var{address}
30573 An expression specifying the address of the first addressable memory unit
30574 to be read. Complex expressions containing embedded white space should be
30575 quoted using the C convention.
30578 The number of addressable memory units to read. This should be an integer
30582 The offset relative to @var{address} at which to start reading. This
30583 should be an integer literal. This option is provided so that a frontend
30584 is not required to first evaluate address and then perform address
30585 arithmetics itself.
30589 This command attempts to read all accessible memory regions in the
30590 specified range. First, all regions marked as unreadable in the memory
30591 map (if one is defined) will be skipped. @xref{Memory Region
30592 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30593 regions. For each one, if reading full region results in an errors,
30594 @value{GDBN} will try to read a subset of the region.
30596 In general, every single memory unit in the region may be readable or not,
30597 and the only way to read every readable unit is to try a read at
30598 every address, which is not practical. Therefore, @value{GDBN} will
30599 attempt to read all accessible memory units at either beginning or the end
30600 of the region, using a binary division scheme. This heuristic works
30601 well for reading accross a memory map boundary. Note that if a region
30602 has a readable range that is neither at the beginning or the end,
30603 @value{GDBN} will not read it.
30605 The result record (@pxref{GDB/MI Result Records}) that is output of
30606 the command includes a field named @samp{memory} whose content is a
30607 list of tuples. Each tuple represent a successfully read memory block
30608 and has the following fields:
30612 The start address of the memory block, as hexadecimal literal.
30615 The end address of the memory block, as hexadecimal literal.
30618 The offset of the memory block, as hexadecimal literal, relative to
30619 the start address passed to @code{-data-read-memory-bytes}.
30622 The contents of the memory block, in hex.
30628 @subsubheading @value{GDBN} Command
30630 The corresponding @value{GDBN} command is @samp{x}.
30632 @subsubheading Example
30636 -data-read-memory-bytes &a 10
30637 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30639 contents="01000000020000000300"@}]
30644 @subheading The @code{-data-write-memory-bytes} Command
30645 @findex -data-write-memory-bytes
30647 @subsubheading Synopsis
30650 -data-write-memory-bytes @var{address} @var{contents}
30651 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30658 @item @var{address}
30659 An expression specifying the address of the first addressable memory unit
30660 to be written. Complex expressions containing embedded white space should
30661 be quoted using the C convention.
30663 @item @var{contents}
30664 The hex-encoded data to write. It is an error if @var{contents} does
30665 not represent an integral number of addressable memory units.
30668 Optional argument indicating the number of addressable memory units to be
30669 written. If @var{count} is greater than @var{contents}' length,
30670 @value{GDBN} will repeatedly write @var{contents} until it fills
30671 @var{count} memory units.
30675 @subsubheading @value{GDBN} Command
30677 There's no corresponding @value{GDBN} command.
30679 @subsubheading Example
30683 -data-write-memory-bytes &a "aabbccdd"
30690 -data-write-memory-bytes &a "aabbccdd" 16e
30695 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30696 @node GDB/MI Tracepoint Commands
30697 @section @sc{gdb/mi} Tracepoint Commands
30699 The commands defined in this section implement MI support for
30700 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30702 @subheading The @code{-trace-find} Command
30703 @findex -trace-find
30705 @subsubheading Synopsis
30708 -trace-find @var{mode} [@var{parameters}@dots{}]
30711 Find a trace frame using criteria defined by @var{mode} and
30712 @var{parameters}. The following table lists permissible
30713 modes and their parameters. For details of operation, see @ref{tfind}.
30718 No parameters are required. Stops examining trace frames.
30721 An integer is required as parameter. Selects tracepoint frame with
30724 @item tracepoint-number
30725 An integer is required as parameter. Finds next
30726 trace frame that corresponds to tracepoint with the specified number.
30729 An address is required as parameter. Finds
30730 next trace frame that corresponds to any tracepoint at the specified
30733 @item pc-inside-range
30734 Two addresses are required as parameters. Finds next trace
30735 frame that corresponds to a tracepoint at an address inside the
30736 specified range. Both bounds are considered to be inside the range.
30738 @item pc-outside-range
30739 Two addresses are required as parameters. Finds
30740 next trace frame that corresponds to a tracepoint at an address outside
30741 the specified range. Both bounds are considered to be inside the range.
30744 Line specification is required as parameter. @xref{Specify Location}.
30745 Finds next trace frame that corresponds to a tracepoint at
30746 the specified location.
30750 If @samp{none} was passed as @var{mode}, the response does not
30751 have fields. Otherwise, the response may have the following fields:
30755 This field has either @samp{0} or @samp{1} as the value, depending
30756 on whether a matching tracepoint was found.
30759 The index of the found traceframe. This field is present iff
30760 the @samp{found} field has value of @samp{1}.
30763 The index of the found tracepoint. This field is present iff
30764 the @samp{found} field has value of @samp{1}.
30767 The information about the frame corresponding to the found trace
30768 frame. This field is present only if a trace frame was found.
30769 @xref{GDB/MI Frame Information}, for description of this field.
30773 @subsubheading @value{GDBN} Command
30775 The corresponding @value{GDBN} command is @samp{tfind}.
30777 @subheading -trace-define-variable
30778 @findex -trace-define-variable
30780 @subsubheading Synopsis
30783 -trace-define-variable @var{name} [ @var{value} ]
30786 Create trace variable @var{name} if it does not exist. If
30787 @var{value} is specified, sets the initial value of the specified
30788 trace variable to that value. Note that the @var{name} should start
30789 with the @samp{$} character.
30791 @subsubheading @value{GDBN} Command
30793 The corresponding @value{GDBN} command is @samp{tvariable}.
30795 @subheading The @code{-trace-frame-collected} Command
30796 @findex -trace-frame-collected
30798 @subsubheading Synopsis
30801 -trace-frame-collected
30802 [--var-print-values @var{var_pval}]
30803 [--comp-print-values @var{comp_pval}]
30804 [--registers-format @var{regformat}]
30805 [--memory-contents]
30808 This command returns the set of collected objects, register names,
30809 trace state variable names, memory ranges and computed expressions
30810 that have been collected at a particular trace frame. The optional
30811 parameters to the command affect the output format in different ways.
30812 See the output description table below for more details.
30814 The reported names can be used in the normal manner to create
30815 varobjs and inspect the objects themselves. The items returned by
30816 this command are categorized so that it is clear which is a variable,
30817 which is a register, which is a trace state variable, which is a
30818 memory range and which is a computed expression.
30820 For instance, if the actions were
30822 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30823 collect *(int*)0xaf02bef0@@40
30827 the object collected in its entirety would be @code{myVar}. The
30828 object @code{myArray} would be partially collected, because only the
30829 element at index @code{myIndex} would be collected. The remaining
30830 objects would be computed expressions.
30832 An example output would be:
30836 -trace-frame-collected
30838 explicit-variables=[@{name="myVar",value="1"@}],
30839 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30840 @{name="myObj.field",value="0"@},
30841 @{name="myPtr->field",value="1"@},
30842 @{name="myCount + 2",value="3"@},
30843 @{name="$tvar1 + 1",value="43970027"@}],
30844 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30845 @{number="1",value="0x0"@},
30846 @{number="2",value="0x4"@},
30848 @{number="125",value="0x0"@}],
30849 tvars=[@{name="$tvar1",current="43970026"@}],
30850 memory=[@{address="0x0000000000602264",length="4"@},
30851 @{address="0x0000000000615bc0",length="4"@}]
30858 @item explicit-variables
30859 The set of objects that have been collected in their entirety (as
30860 opposed to collecting just a few elements of an array or a few struct
30861 members). For each object, its name and value are printed.
30862 The @code{--var-print-values} option affects how or whether the value
30863 field is output. If @var{var_pval} is 0, then print only the names;
30864 if it is 1, print also their values; and if it is 2, print the name,
30865 type and value for simple data types, and the name and type for
30866 arrays, structures and unions.
30868 @item computed-expressions
30869 The set of computed expressions that have been collected at the
30870 current trace frame. The @code{--comp-print-values} option affects
30871 this set like the @code{--var-print-values} option affects the
30872 @code{explicit-variables} set. See above.
30875 The registers that have been collected at the current trace frame.
30876 For each register collected, the name and current value are returned.
30877 The value is formatted according to the @code{--registers-format}
30878 option. See the @command{-data-list-register-values} command for a
30879 list of the allowed formats. The default is @samp{x}.
30882 The trace state variables that have been collected at the current
30883 trace frame. For each trace state variable collected, the name and
30884 current value are returned.
30887 The set of memory ranges that have been collected at the current trace
30888 frame. Its content is a list of tuples. Each tuple represents a
30889 collected memory range and has the following fields:
30893 The start address of the memory range, as hexadecimal literal.
30896 The length of the memory range, as decimal literal.
30899 The contents of the memory block, in hex. This field is only present
30900 if the @code{--memory-contents} option is specified.
30906 @subsubheading @value{GDBN} Command
30908 There is no corresponding @value{GDBN} command.
30910 @subsubheading Example
30912 @subheading -trace-list-variables
30913 @findex -trace-list-variables
30915 @subsubheading Synopsis
30918 -trace-list-variables
30921 Return a table of all defined trace variables. Each element of the
30922 table has the following fields:
30926 The name of the trace variable. This field is always present.
30929 The initial value. This is a 64-bit signed integer. This
30930 field is always present.
30933 The value the trace variable has at the moment. This is a 64-bit
30934 signed integer. This field is absent iff current value is
30935 not defined, for example if the trace was never run, or is
30940 @subsubheading @value{GDBN} Command
30942 The corresponding @value{GDBN} command is @samp{tvariables}.
30944 @subsubheading Example
30948 -trace-list-variables
30949 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30950 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30951 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30952 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30953 body=[variable=@{name="$trace_timestamp",initial="0"@}
30954 variable=@{name="$foo",initial="10",current="15"@}]@}
30958 @subheading -trace-save
30959 @findex -trace-save
30961 @subsubheading Synopsis
30964 -trace-save [ -r ] [ -ctf ] @var{filename}
30967 Saves the collected trace data to @var{filename}. Without the
30968 @samp{-r} option, the data is downloaded from the target and saved
30969 in a local file. With the @samp{-r} option the target is asked
30970 to perform the save.
30972 By default, this command will save the trace in the tfile format. You can
30973 supply the optional @samp{-ctf} argument to save it the CTF format. See
30974 @ref{Trace Files} for more information about CTF.
30976 @subsubheading @value{GDBN} Command
30978 The corresponding @value{GDBN} command is @samp{tsave}.
30981 @subheading -trace-start
30982 @findex -trace-start
30984 @subsubheading Synopsis
30990 Starts a tracing experiment. The result of this command does not
30993 @subsubheading @value{GDBN} Command
30995 The corresponding @value{GDBN} command is @samp{tstart}.
30997 @subheading -trace-status
30998 @findex -trace-status
31000 @subsubheading Synopsis
31006 Obtains the status of a tracing experiment. The result may include
31007 the following fields:
31012 May have a value of either @samp{0}, when no tracing operations are
31013 supported, @samp{1}, when all tracing operations are supported, or
31014 @samp{file} when examining trace file. In the latter case, examining
31015 of trace frame is possible but new tracing experiement cannot be
31016 started. This field is always present.
31019 May have a value of either @samp{0} or @samp{1} depending on whether
31020 tracing experiement is in progress on target. This field is present
31021 if @samp{supported} field is not @samp{0}.
31024 Report the reason why the tracing was stopped last time. This field
31025 may be absent iff tracing was never stopped on target yet. The
31026 value of @samp{request} means the tracing was stopped as result of
31027 the @code{-trace-stop} command. The value of @samp{overflow} means
31028 the tracing buffer is full. The value of @samp{disconnection} means
31029 tracing was automatically stopped when @value{GDBN} has disconnected.
31030 The value of @samp{passcount} means tracing was stopped when a
31031 tracepoint was passed a maximal number of times for that tracepoint.
31032 This field is present if @samp{supported} field is not @samp{0}.
31034 @item stopping-tracepoint
31035 The number of tracepoint whose passcount as exceeded. This field is
31036 present iff the @samp{stop-reason} field has the value of
31040 @itemx frames-created
31041 The @samp{frames} field is a count of the total number of trace frames
31042 in the trace buffer, while @samp{frames-created} is the total created
31043 during the run, including ones that were discarded, such as when a
31044 circular trace buffer filled up. Both fields are optional.
31048 These fields tell the current size of the tracing buffer and the
31049 remaining space. These fields are optional.
31052 The value of the circular trace buffer flag. @code{1} means that the
31053 trace buffer is circular and old trace frames will be discarded if
31054 necessary to make room, @code{0} means that the trace buffer is linear
31058 The value of the disconnected tracing flag. @code{1} means that
31059 tracing will continue after @value{GDBN} disconnects, @code{0} means
31060 that the trace run will stop.
31063 The filename of the trace file being examined. This field is
31064 optional, and only present when examining a trace file.
31068 @subsubheading @value{GDBN} Command
31070 The corresponding @value{GDBN} command is @samp{tstatus}.
31072 @subheading -trace-stop
31073 @findex -trace-stop
31075 @subsubheading Synopsis
31081 Stops a tracing experiment. The result of this command has the same
31082 fields as @code{-trace-status}, except that the @samp{supported} and
31083 @samp{running} fields are not output.
31085 @subsubheading @value{GDBN} Command
31087 The corresponding @value{GDBN} command is @samp{tstop}.
31090 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31091 @node GDB/MI Symbol Query
31092 @section @sc{gdb/mi} Symbol Query Commands
31096 @subheading The @code{-symbol-info-address} Command
31097 @findex -symbol-info-address
31099 @subsubheading Synopsis
31102 -symbol-info-address @var{symbol}
31105 Describe where @var{symbol} is stored.
31107 @subsubheading @value{GDBN} Command
31109 The corresponding @value{GDBN} command is @samp{info address}.
31111 @subsubheading Example
31115 @subheading The @code{-symbol-info-file} Command
31116 @findex -symbol-info-file
31118 @subsubheading Synopsis
31124 Show the file for the symbol.
31126 @subsubheading @value{GDBN} Command
31128 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31129 @samp{gdb_find_file}.
31131 @subsubheading Example
31135 @subheading The @code{-symbol-info-function} Command
31136 @findex -symbol-info-function
31138 @subsubheading Synopsis
31141 -symbol-info-function
31144 Show which function the symbol lives in.
31146 @subsubheading @value{GDBN} Command
31148 @samp{gdb_get_function} in @code{gdbtk}.
31150 @subsubheading Example
31154 @subheading The @code{-symbol-info-line} Command
31155 @findex -symbol-info-line
31157 @subsubheading Synopsis
31163 Show the core addresses of the code for a source line.
31165 @subsubheading @value{GDBN} Command
31167 The corresponding @value{GDBN} command is @samp{info line}.
31168 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31170 @subsubheading Example
31174 @subheading The @code{-symbol-info-symbol} Command
31175 @findex -symbol-info-symbol
31177 @subsubheading Synopsis
31180 -symbol-info-symbol @var{addr}
31183 Describe what symbol is at location @var{addr}.
31185 @subsubheading @value{GDBN} Command
31187 The corresponding @value{GDBN} command is @samp{info symbol}.
31189 @subsubheading Example
31193 @subheading The @code{-symbol-list-functions} Command
31194 @findex -symbol-list-functions
31196 @subsubheading Synopsis
31199 -symbol-list-functions
31202 List the functions in the executable.
31204 @subsubheading @value{GDBN} Command
31206 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31207 @samp{gdb_search} in @code{gdbtk}.
31209 @subsubheading Example
31214 @subheading The @code{-symbol-list-lines} Command
31215 @findex -symbol-list-lines
31217 @subsubheading Synopsis
31220 -symbol-list-lines @var{filename}
31223 Print the list of lines that contain code and their associated program
31224 addresses for the given source filename. The entries are sorted in
31225 ascending PC order.
31227 @subsubheading @value{GDBN} Command
31229 There is no corresponding @value{GDBN} command.
31231 @subsubheading Example
31234 -symbol-list-lines basics.c
31235 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31241 @subheading The @code{-symbol-list-types} Command
31242 @findex -symbol-list-types
31244 @subsubheading Synopsis
31250 List all the type names.
31252 @subsubheading @value{GDBN} Command
31254 The corresponding commands are @samp{info types} in @value{GDBN},
31255 @samp{gdb_search} in @code{gdbtk}.
31257 @subsubheading Example
31261 @subheading The @code{-symbol-list-variables} Command
31262 @findex -symbol-list-variables
31264 @subsubheading Synopsis
31267 -symbol-list-variables
31270 List all the global and static variable names.
31272 @subsubheading @value{GDBN} Command
31274 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31276 @subsubheading Example
31280 @subheading The @code{-symbol-locate} Command
31281 @findex -symbol-locate
31283 @subsubheading Synopsis
31289 @subsubheading @value{GDBN} Command
31291 @samp{gdb_loc} in @code{gdbtk}.
31293 @subsubheading Example
31297 @subheading The @code{-symbol-type} Command
31298 @findex -symbol-type
31300 @subsubheading Synopsis
31303 -symbol-type @var{variable}
31306 Show type of @var{variable}.
31308 @subsubheading @value{GDBN} Command
31310 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31311 @samp{gdb_obj_variable}.
31313 @subsubheading Example
31318 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31319 @node GDB/MI File Commands
31320 @section @sc{gdb/mi} File Commands
31322 This section describes the GDB/MI commands to specify executable file names
31323 and to read in and obtain symbol table information.
31325 @subheading The @code{-file-exec-and-symbols} Command
31326 @findex -file-exec-and-symbols
31328 @subsubheading Synopsis
31331 -file-exec-and-symbols @var{file}
31334 Specify the executable file to be debugged. This file is the one from
31335 which the symbol table is also read. If no file is specified, the
31336 command clears the executable and symbol information. If breakpoints
31337 are set when using this command with no arguments, @value{GDBN} will produce
31338 error messages. Otherwise, no output is produced, except a completion
31341 @subsubheading @value{GDBN} Command
31343 The corresponding @value{GDBN} command is @samp{file}.
31345 @subsubheading Example
31349 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31355 @subheading The @code{-file-exec-file} Command
31356 @findex -file-exec-file
31358 @subsubheading Synopsis
31361 -file-exec-file @var{file}
31364 Specify the executable file to be debugged. Unlike
31365 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31366 from this file. If used without argument, @value{GDBN} clears the information
31367 about the executable file. No output is produced, except a completion
31370 @subsubheading @value{GDBN} Command
31372 The corresponding @value{GDBN} command is @samp{exec-file}.
31374 @subsubheading Example
31378 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31385 @subheading The @code{-file-list-exec-sections} Command
31386 @findex -file-list-exec-sections
31388 @subsubheading Synopsis
31391 -file-list-exec-sections
31394 List the sections of the current executable file.
31396 @subsubheading @value{GDBN} Command
31398 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31399 information as this command. @code{gdbtk} has a corresponding command
31400 @samp{gdb_load_info}.
31402 @subsubheading Example
31407 @subheading The @code{-file-list-exec-source-file} Command
31408 @findex -file-list-exec-source-file
31410 @subsubheading Synopsis
31413 -file-list-exec-source-file
31416 List the line number, the current source file, and the absolute path
31417 to the current source file for the current executable. The macro
31418 information field has a value of @samp{1} or @samp{0} depending on
31419 whether or not the file includes preprocessor macro information.
31421 @subsubheading @value{GDBN} Command
31423 The @value{GDBN} equivalent is @samp{info source}
31425 @subsubheading Example
31429 123-file-list-exec-source-file
31430 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31435 @subheading The @code{-file-list-exec-source-files} Command
31436 @findex -file-list-exec-source-files
31438 @subsubheading Synopsis
31441 -file-list-exec-source-files
31444 List the source files for the current executable.
31446 It will always output both the filename and fullname (absolute file
31447 name) of a source file.
31449 @subsubheading @value{GDBN} Command
31451 The @value{GDBN} equivalent is @samp{info sources}.
31452 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31454 @subsubheading Example
31457 -file-list-exec-source-files
31459 @{file=foo.c,fullname=/home/foo.c@},
31460 @{file=/home/bar.c,fullname=/home/bar.c@},
31461 @{file=gdb_could_not_find_fullpath.c@}]
31466 @subheading The @code{-file-list-shared-libraries} Command
31467 @findex -file-list-shared-libraries
31469 @subsubheading Synopsis
31472 -file-list-shared-libraries
31475 List the shared libraries in the program.
31477 @subsubheading @value{GDBN} Command
31479 The corresponding @value{GDBN} command is @samp{info shared}.
31481 @subsubheading Example
31485 @subheading The @code{-file-list-symbol-files} Command
31486 @findex -file-list-symbol-files
31488 @subsubheading Synopsis
31491 -file-list-symbol-files
31496 @subsubheading @value{GDBN} Command
31498 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31500 @subsubheading Example
31505 @subheading The @code{-file-symbol-file} Command
31506 @findex -file-symbol-file
31508 @subsubheading Synopsis
31511 -file-symbol-file @var{file}
31514 Read symbol table info from the specified @var{file} argument. When
31515 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31516 produced, except for a completion notification.
31518 @subsubheading @value{GDBN} Command
31520 The corresponding @value{GDBN} command is @samp{symbol-file}.
31522 @subsubheading Example
31526 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31533 @node GDB/MI Memory Overlay Commands
31534 @section @sc{gdb/mi} Memory Overlay Commands
31536 The memory overlay commands are not implemented.
31538 @c @subheading -overlay-auto
31540 @c @subheading -overlay-list-mapping-state
31542 @c @subheading -overlay-list-overlays
31544 @c @subheading -overlay-map
31546 @c @subheading -overlay-off
31548 @c @subheading -overlay-on
31550 @c @subheading -overlay-unmap
31552 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31553 @node GDB/MI Signal Handling Commands
31554 @section @sc{gdb/mi} Signal Handling Commands
31556 Signal handling commands are not implemented.
31558 @c @subheading -signal-handle
31560 @c @subheading -signal-list-handle-actions
31562 @c @subheading -signal-list-signal-types
31566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31567 @node GDB/MI Target Manipulation
31568 @section @sc{gdb/mi} Target Manipulation Commands
31571 @subheading The @code{-target-attach} Command
31572 @findex -target-attach
31574 @subsubheading Synopsis
31577 -target-attach @var{pid} | @var{gid} | @var{file}
31580 Attach to a process @var{pid} or a file @var{file} outside of
31581 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31582 group, the id previously returned by
31583 @samp{-list-thread-groups --available} must be used.
31585 @subsubheading @value{GDBN} Command
31587 The corresponding @value{GDBN} command is @samp{attach}.
31589 @subsubheading Example
31593 =thread-created,id="1"
31594 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31600 @subheading The @code{-target-compare-sections} Command
31601 @findex -target-compare-sections
31603 @subsubheading Synopsis
31606 -target-compare-sections [ @var{section} ]
31609 Compare data of section @var{section} on target to the exec file.
31610 Without the argument, all sections are compared.
31612 @subsubheading @value{GDBN} Command
31614 The @value{GDBN} equivalent is @samp{compare-sections}.
31616 @subsubheading Example
31621 @subheading The @code{-target-detach} Command
31622 @findex -target-detach
31624 @subsubheading Synopsis
31627 -target-detach [ @var{pid} | @var{gid} ]
31630 Detach from the remote target which normally resumes its execution.
31631 If either @var{pid} or @var{gid} is specified, detaches from either
31632 the specified process, or specified thread group. There's no output.
31634 @subsubheading @value{GDBN} Command
31636 The corresponding @value{GDBN} command is @samp{detach}.
31638 @subsubheading Example
31648 @subheading The @code{-target-disconnect} Command
31649 @findex -target-disconnect
31651 @subsubheading Synopsis
31657 Disconnect from the remote target. There's no output and the target is
31658 generally not resumed.
31660 @subsubheading @value{GDBN} Command
31662 The corresponding @value{GDBN} command is @samp{disconnect}.
31664 @subsubheading Example
31674 @subheading The @code{-target-download} Command
31675 @findex -target-download
31677 @subsubheading Synopsis
31683 Loads the executable onto the remote target.
31684 It prints out an update message every half second, which includes the fields:
31688 The name of the section.
31690 The size of what has been sent so far for that section.
31692 The size of the section.
31694 The total size of what was sent so far (the current and the previous sections).
31696 The size of the overall executable to download.
31700 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31701 @sc{gdb/mi} Output Syntax}).
31703 In addition, it prints the name and size of the sections, as they are
31704 downloaded. These messages include the following fields:
31708 The name of the section.
31710 The size of the section.
31712 The size of the overall executable to download.
31716 At the end, a summary is printed.
31718 @subsubheading @value{GDBN} Command
31720 The corresponding @value{GDBN} command is @samp{load}.
31722 @subsubheading Example
31724 Note: each status message appears on a single line. Here the messages
31725 have been broken down so that they can fit onto a page.
31730 +download,@{section=".text",section-size="6668",total-size="9880"@}
31731 +download,@{section=".text",section-sent="512",section-size="6668",
31732 total-sent="512",total-size="9880"@}
31733 +download,@{section=".text",section-sent="1024",section-size="6668",
31734 total-sent="1024",total-size="9880"@}
31735 +download,@{section=".text",section-sent="1536",section-size="6668",
31736 total-sent="1536",total-size="9880"@}
31737 +download,@{section=".text",section-sent="2048",section-size="6668",
31738 total-sent="2048",total-size="9880"@}
31739 +download,@{section=".text",section-sent="2560",section-size="6668",
31740 total-sent="2560",total-size="9880"@}
31741 +download,@{section=".text",section-sent="3072",section-size="6668",
31742 total-sent="3072",total-size="9880"@}
31743 +download,@{section=".text",section-sent="3584",section-size="6668",
31744 total-sent="3584",total-size="9880"@}
31745 +download,@{section=".text",section-sent="4096",section-size="6668",
31746 total-sent="4096",total-size="9880"@}
31747 +download,@{section=".text",section-sent="4608",section-size="6668",
31748 total-sent="4608",total-size="9880"@}
31749 +download,@{section=".text",section-sent="5120",section-size="6668",
31750 total-sent="5120",total-size="9880"@}
31751 +download,@{section=".text",section-sent="5632",section-size="6668",
31752 total-sent="5632",total-size="9880"@}
31753 +download,@{section=".text",section-sent="6144",section-size="6668",
31754 total-sent="6144",total-size="9880"@}
31755 +download,@{section=".text",section-sent="6656",section-size="6668",
31756 total-sent="6656",total-size="9880"@}
31757 +download,@{section=".init",section-size="28",total-size="9880"@}
31758 +download,@{section=".fini",section-size="28",total-size="9880"@}
31759 +download,@{section=".data",section-size="3156",total-size="9880"@}
31760 +download,@{section=".data",section-sent="512",section-size="3156",
31761 total-sent="7236",total-size="9880"@}
31762 +download,@{section=".data",section-sent="1024",section-size="3156",
31763 total-sent="7748",total-size="9880"@}
31764 +download,@{section=".data",section-sent="1536",section-size="3156",
31765 total-sent="8260",total-size="9880"@}
31766 +download,@{section=".data",section-sent="2048",section-size="3156",
31767 total-sent="8772",total-size="9880"@}
31768 +download,@{section=".data",section-sent="2560",section-size="3156",
31769 total-sent="9284",total-size="9880"@}
31770 +download,@{section=".data",section-sent="3072",section-size="3156",
31771 total-sent="9796",total-size="9880"@}
31772 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31779 @subheading The @code{-target-exec-status} Command
31780 @findex -target-exec-status
31782 @subsubheading Synopsis
31785 -target-exec-status
31788 Provide information on the state of the target (whether it is running or
31789 not, for instance).
31791 @subsubheading @value{GDBN} Command
31793 There's no equivalent @value{GDBN} command.
31795 @subsubheading Example
31799 @subheading The @code{-target-list-available-targets} Command
31800 @findex -target-list-available-targets
31802 @subsubheading Synopsis
31805 -target-list-available-targets
31808 List the possible targets to connect to.
31810 @subsubheading @value{GDBN} Command
31812 The corresponding @value{GDBN} command is @samp{help target}.
31814 @subsubheading Example
31818 @subheading The @code{-target-list-current-targets} Command
31819 @findex -target-list-current-targets
31821 @subsubheading Synopsis
31824 -target-list-current-targets
31827 Describe the current target.
31829 @subsubheading @value{GDBN} Command
31831 The corresponding information is printed by @samp{info file} (among
31834 @subsubheading Example
31838 @subheading The @code{-target-list-parameters} Command
31839 @findex -target-list-parameters
31841 @subsubheading Synopsis
31844 -target-list-parameters
31850 @subsubheading @value{GDBN} Command
31854 @subsubheading Example
31858 @subheading The @code{-target-select} Command
31859 @findex -target-select
31861 @subsubheading Synopsis
31864 -target-select @var{type} @var{parameters @dots{}}
31867 Connect @value{GDBN} to the remote target. This command takes two args:
31871 The type of target, for instance @samp{remote}, etc.
31872 @item @var{parameters}
31873 Device names, host names and the like. @xref{Target Commands, ,
31874 Commands for Managing Targets}, for more details.
31877 The output is a connection notification, followed by the address at
31878 which the target program is, in the following form:
31881 ^connected,addr="@var{address}",func="@var{function name}",
31882 args=[@var{arg list}]
31885 @subsubheading @value{GDBN} Command
31887 The corresponding @value{GDBN} command is @samp{target}.
31889 @subsubheading Example
31893 -target-select remote /dev/ttya
31894 ^connected,addr="0xfe00a300",func="??",args=[]
31898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31899 @node GDB/MI File Transfer Commands
31900 @section @sc{gdb/mi} File Transfer Commands
31903 @subheading The @code{-target-file-put} Command
31904 @findex -target-file-put
31906 @subsubheading Synopsis
31909 -target-file-put @var{hostfile} @var{targetfile}
31912 Copy file @var{hostfile} from the host system (the machine running
31913 @value{GDBN}) to @var{targetfile} on the target system.
31915 @subsubheading @value{GDBN} Command
31917 The corresponding @value{GDBN} command is @samp{remote put}.
31919 @subsubheading Example
31923 -target-file-put localfile remotefile
31929 @subheading The @code{-target-file-get} Command
31930 @findex -target-file-get
31932 @subsubheading Synopsis
31935 -target-file-get @var{targetfile} @var{hostfile}
31938 Copy file @var{targetfile} from the target system to @var{hostfile}
31939 on the host system.
31941 @subsubheading @value{GDBN} Command
31943 The corresponding @value{GDBN} command is @samp{remote get}.
31945 @subsubheading Example
31949 -target-file-get remotefile localfile
31955 @subheading The @code{-target-file-delete} Command
31956 @findex -target-file-delete
31958 @subsubheading Synopsis
31961 -target-file-delete @var{targetfile}
31964 Delete @var{targetfile} from the target system.
31966 @subsubheading @value{GDBN} Command
31968 The corresponding @value{GDBN} command is @samp{remote delete}.
31970 @subsubheading Example
31974 -target-file-delete remotefile
31980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31981 @node GDB/MI Ada Exceptions Commands
31982 @section Ada Exceptions @sc{gdb/mi} Commands
31984 @subheading The @code{-info-ada-exceptions} Command
31985 @findex -info-ada-exceptions
31987 @subsubheading Synopsis
31990 -info-ada-exceptions [ @var{regexp}]
31993 List all Ada exceptions defined within the program being debugged.
31994 With a regular expression @var{regexp}, only those exceptions whose
31995 names match @var{regexp} are listed.
31997 @subsubheading @value{GDBN} Command
31999 The corresponding @value{GDBN} command is @samp{info exceptions}.
32001 @subsubheading Result
32003 The result is a table of Ada exceptions. The following columns are
32004 defined for each exception:
32008 The name of the exception.
32011 The address of the exception.
32015 @subsubheading Example
32018 -info-ada-exceptions aint
32019 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32020 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32021 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32022 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32023 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32026 @subheading Catching Ada Exceptions
32028 The commands describing how to ask @value{GDBN} to stop when a program
32029 raises an exception are described at @ref{Ada Exception GDB/MI
32030 Catchpoint Commands}.
32033 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32034 @node GDB/MI Support Commands
32035 @section @sc{gdb/mi} Support Commands
32037 Since new commands and features get regularly added to @sc{gdb/mi},
32038 some commands are available to help front-ends query the debugger
32039 about support for these capabilities. Similarly, it is also possible
32040 to query @value{GDBN} about target support of certain features.
32042 @subheading The @code{-info-gdb-mi-command} Command
32043 @cindex @code{-info-gdb-mi-command}
32044 @findex -info-gdb-mi-command
32046 @subsubheading Synopsis
32049 -info-gdb-mi-command @var{cmd_name}
32052 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32054 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32055 is technically not part of the command name (@pxref{GDB/MI Input
32056 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32057 for ease of use, this command also accepts the form with the leading
32060 @subsubheading @value{GDBN} Command
32062 There is no corresponding @value{GDBN} command.
32064 @subsubheading Result
32066 The result is a tuple. There is currently only one field:
32070 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32071 @code{"false"} otherwise.
32075 @subsubheading Example
32077 Here is an example where the @sc{gdb/mi} command does not exist:
32080 -info-gdb-mi-command unsupported-command
32081 ^done,command=@{exists="false"@}
32085 And here is an example where the @sc{gdb/mi} command is known
32089 -info-gdb-mi-command symbol-list-lines
32090 ^done,command=@{exists="true"@}
32093 @subheading The @code{-list-features} Command
32094 @findex -list-features
32095 @cindex supported @sc{gdb/mi} features, list
32097 Returns a list of particular features of the MI protocol that
32098 this version of gdb implements. A feature can be a command,
32099 or a new field in an output of some command, or even an
32100 important bugfix. While a frontend can sometimes detect presence
32101 of a feature at runtime, it is easier to perform detection at debugger
32104 The command returns a list of strings, with each string naming an
32105 available feature. Each returned string is just a name, it does not
32106 have any internal structure. The list of possible feature names
32112 (gdb) -list-features
32113 ^done,result=["feature1","feature2"]
32116 The current list of features is:
32119 @item frozen-varobjs
32120 Indicates support for the @code{-var-set-frozen} command, as well
32121 as possible presense of the @code{frozen} field in the output
32122 of @code{-varobj-create}.
32123 @item pending-breakpoints
32124 Indicates support for the @option{-f} option to the @code{-break-insert}
32127 Indicates Python scripting support, Python-based
32128 pretty-printing commands, and possible presence of the
32129 @samp{display_hint} field in the output of @code{-var-list-children}
32131 Indicates support for the @code{-thread-info} command.
32132 @item data-read-memory-bytes
32133 Indicates support for the @code{-data-read-memory-bytes} and the
32134 @code{-data-write-memory-bytes} commands.
32135 @item breakpoint-notifications
32136 Indicates that changes to breakpoints and breakpoints created via the
32137 CLI will be announced via async records.
32138 @item ada-task-info
32139 Indicates support for the @code{-ada-task-info} command.
32140 @item language-option
32141 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32142 option (@pxref{Context management}).
32143 @item info-gdb-mi-command
32144 Indicates support for the @code{-info-gdb-mi-command} command.
32145 @item undefined-command-error-code
32146 Indicates support for the "undefined-command" error code in error result
32147 records, produced when trying to execute an undefined @sc{gdb/mi} command
32148 (@pxref{GDB/MI Result Records}).
32149 @item exec-run-start-option
32150 Indicates that the @code{-exec-run} command supports the @option{--start}
32151 option (@pxref{GDB/MI Program Execution}).
32154 @subheading The @code{-list-target-features} Command
32155 @findex -list-target-features
32157 Returns a list of particular features that are supported by the
32158 target. Those features affect the permitted MI commands, but
32159 unlike the features reported by the @code{-list-features} command, the
32160 features depend on which target GDB is using at the moment. Whenever
32161 a target can change, due to commands such as @code{-target-select},
32162 @code{-target-attach} or @code{-exec-run}, the list of target features
32163 may change, and the frontend should obtain it again.
32167 (gdb) -list-target-features
32168 ^done,result=["async"]
32171 The current list of features is:
32175 Indicates that the target is capable of asynchronous command
32176 execution, which means that @value{GDBN} will accept further commands
32177 while the target is running.
32180 Indicates that the target is capable of reverse execution.
32181 @xref{Reverse Execution}, for more information.
32185 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32186 @node GDB/MI Miscellaneous Commands
32187 @section Miscellaneous @sc{gdb/mi} Commands
32189 @c @subheading -gdb-complete
32191 @subheading The @code{-gdb-exit} Command
32194 @subsubheading Synopsis
32200 Exit @value{GDBN} immediately.
32202 @subsubheading @value{GDBN} Command
32204 Approximately corresponds to @samp{quit}.
32206 @subsubheading Example
32216 @subheading The @code{-exec-abort} Command
32217 @findex -exec-abort
32219 @subsubheading Synopsis
32225 Kill the inferior running program.
32227 @subsubheading @value{GDBN} Command
32229 The corresponding @value{GDBN} command is @samp{kill}.
32231 @subsubheading Example
32236 @subheading The @code{-gdb-set} Command
32239 @subsubheading Synopsis
32245 Set an internal @value{GDBN} variable.
32246 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32248 @subsubheading @value{GDBN} Command
32250 The corresponding @value{GDBN} command is @samp{set}.
32252 @subsubheading Example
32262 @subheading The @code{-gdb-show} Command
32265 @subsubheading Synopsis
32271 Show the current value of a @value{GDBN} variable.
32273 @subsubheading @value{GDBN} Command
32275 The corresponding @value{GDBN} command is @samp{show}.
32277 @subsubheading Example
32286 @c @subheading -gdb-source
32289 @subheading The @code{-gdb-version} Command
32290 @findex -gdb-version
32292 @subsubheading Synopsis
32298 Show version information for @value{GDBN}. Used mostly in testing.
32300 @subsubheading @value{GDBN} Command
32302 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32303 default shows this information when you start an interactive session.
32305 @subsubheading Example
32307 @c This example modifies the actual output from GDB to avoid overfull
32313 ~Copyright 2000 Free Software Foundation, Inc.
32314 ~GDB is free software, covered by the GNU General Public License, and
32315 ~you are welcome to change it and/or distribute copies of it under
32316 ~ certain conditions.
32317 ~Type "show copying" to see the conditions.
32318 ~There is absolutely no warranty for GDB. Type "show warranty" for
32320 ~This GDB was configured as
32321 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32326 @subheading The @code{-list-thread-groups} Command
32327 @findex -list-thread-groups
32329 @subheading Synopsis
32332 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32335 Lists thread groups (@pxref{Thread groups}). When a single thread
32336 group is passed as the argument, lists the children of that group.
32337 When several thread group are passed, lists information about those
32338 thread groups. Without any parameters, lists information about all
32339 top-level thread groups.
32341 Normally, thread groups that are being debugged are reported.
32342 With the @samp{--available} option, @value{GDBN} reports thread groups
32343 available on the target.
32345 The output of this command may have either a @samp{threads} result or
32346 a @samp{groups} result. The @samp{thread} result has a list of tuples
32347 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32348 Information}). The @samp{groups} result has a list of tuples as value,
32349 each tuple describing a thread group. If top-level groups are
32350 requested (that is, no parameter is passed), or when several groups
32351 are passed, the output always has a @samp{groups} result. The format
32352 of the @samp{group} result is described below.
32354 To reduce the number of roundtrips it's possible to list thread groups
32355 together with their children, by passing the @samp{--recurse} option
32356 and the recursion depth. Presently, only recursion depth of 1 is
32357 permitted. If this option is present, then every reported thread group
32358 will also include its children, either as @samp{group} or
32359 @samp{threads} field.
32361 In general, any combination of option and parameters is permitted, with
32362 the following caveats:
32366 When a single thread group is passed, the output will typically
32367 be the @samp{threads} result. Because threads may not contain
32368 anything, the @samp{recurse} option will be ignored.
32371 When the @samp{--available} option is passed, limited information may
32372 be available. In particular, the list of threads of a process might
32373 be inaccessible. Further, specifying specific thread groups might
32374 not give any performance advantage over listing all thread groups.
32375 The frontend should assume that @samp{-list-thread-groups --available}
32376 is always an expensive operation and cache the results.
32380 The @samp{groups} result is a list of tuples, where each tuple may
32381 have the following fields:
32385 Identifier of the thread group. This field is always present.
32386 The identifier is an opaque string; frontends should not try to
32387 convert it to an integer, even though it might look like one.
32390 The type of the thread group. At present, only @samp{process} is a
32394 The target-specific process identifier. This field is only present
32395 for thread groups of type @samp{process} and only if the process exists.
32398 The exit code of this group's last exited thread, formatted in octal.
32399 This field is only present for thread groups of type @samp{process} and
32400 only if the process is not running.
32403 The number of children this thread group has. This field may be
32404 absent for an available thread group.
32407 This field has a list of tuples as value, each tuple describing a
32408 thread. It may be present if the @samp{--recurse} option is
32409 specified, and it's actually possible to obtain the threads.
32412 This field is a list of integers, each identifying a core that one
32413 thread of the group is running on. This field may be absent if
32414 such information is not available.
32417 The name of the executable file that corresponds to this thread group.
32418 The field is only present for thread groups of type @samp{process},
32419 and only if there is a corresponding executable file.
32423 @subheading Example
32427 -list-thread-groups
32428 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32429 -list-thread-groups 17
32430 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32431 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32432 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32433 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32434 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32435 -list-thread-groups --available
32436 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32437 -list-thread-groups --available --recurse 1
32438 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32439 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32440 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32441 -list-thread-groups --available --recurse 1 17 18
32442 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32443 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32444 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32447 @subheading The @code{-info-os} Command
32450 @subsubheading Synopsis
32453 -info-os [ @var{type} ]
32456 If no argument is supplied, the command returns a table of available
32457 operating-system-specific information types. If one of these types is
32458 supplied as an argument @var{type}, then the command returns a table
32459 of data of that type.
32461 The types of information available depend on the target operating
32464 @subsubheading @value{GDBN} Command
32466 The corresponding @value{GDBN} command is @samp{info os}.
32468 @subsubheading Example
32470 When run on a @sc{gnu}/Linux system, the output will look something
32476 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32477 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32478 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32479 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32480 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32482 item=@{col0="files",col1="Listing of all file descriptors",
32483 col2="File descriptors"@},
32484 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32485 col2="Kernel modules"@},
32486 item=@{col0="msg",col1="Listing of all message queues",
32487 col2="Message queues"@},
32488 item=@{col0="processes",col1="Listing of all processes",
32489 col2="Processes"@},
32490 item=@{col0="procgroups",col1="Listing of all process groups",
32491 col2="Process groups"@},
32492 item=@{col0="semaphores",col1="Listing of all semaphores",
32493 col2="Semaphores"@},
32494 item=@{col0="shm",col1="Listing of all shared-memory regions",
32495 col2="Shared-memory regions"@},
32496 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32498 item=@{col0="threads",col1="Listing of all threads",
32502 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32503 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32504 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32505 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32506 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32507 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32508 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32509 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32511 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32512 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32516 (Note that the MI output here includes a @code{"Title"} column that
32517 does not appear in command-line @code{info os}; this column is useful
32518 for MI clients that want to enumerate the types of data, such as in a
32519 popup menu, but is needless clutter on the command line, and
32520 @code{info os} omits it.)
32522 @subheading The @code{-add-inferior} Command
32523 @findex -add-inferior
32525 @subheading Synopsis
32531 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32532 inferior is not associated with any executable. Such association may
32533 be established with the @samp{-file-exec-and-symbols} command
32534 (@pxref{GDB/MI File Commands}). The command response has a single
32535 field, @samp{inferior}, whose value is the identifier of the
32536 thread group corresponding to the new inferior.
32538 @subheading Example
32543 ^done,inferior="i3"
32546 @subheading The @code{-interpreter-exec} Command
32547 @findex -interpreter-exec
32549 @subheading Synopsis
32552 -interpreter-exec @var{interpreter} @var{command}
32554 @anchor{-interpreter-exec}
32556 Execute the specified @var{command} in the given @var{interpreter}.
32558 @subheading @value{GDBN} Command
32560 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32562 @subheading Example
32566 -interpreter-exec console "break main"
32567 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32568 &"During symbol reading, bad structure-type format.\n"
32569 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32574 @subheading The @code{-inferior-tty-set} Command
32575 @findex -inferior-tty-set
32577 @subheading Synopsis
32580 -inferior-tty-set /dev/pts/1
32583 Set terminal for future runs of the program being debugged.
32585 @subheading @value{GDBN} Command
32587 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32589 @subheading Example
32593 -inferior-tty-set /dev/pts/1
32598 @subheading The @code{-inferior-tty-show} Command
32599 @findex -inferior-tty-show
32601 @subheading Synopsis
32607 Show terminal for future runs of program being debugged.
32609 @subheading @value{GDBN} Command
32611 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32613 @subheading Example
32617 -inferior-tty-set /dev/pts/1
32621 ^done,inferior_tty_terminal="/dev/pts/1"
32625 @subheading The @code{-enable-timings} Command
32626 @findex -enable-timings
32628 @subheading Synopsis
32631 -enable-timings [yes | no]
32634 Toggle the printing of the wallclock, user and system times for an MI
32635 command as a field in its output. This command is to help frontend
32636 developers optimize the performance of their code. No argument is
32637 equivalent to @samp{yes}.
32639 @subheading @value{GDBN} Command
32643 @subheading Example
32651 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32652 addr="0x080484ed",func="main",file="myprog.c",
32653 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32655 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32663 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32664 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32665 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32666 fullname="/home/nickrob/myprog.c",line="73"@}
32671 @chapter @value{GDBN} Annotations
32673 This chapter describes annotations in @value{GDBN}. Annotations were
32674 designed to interface @value{GDBN} to graphical user interfaces or other
32675 similar programs which want to interact with @value{GDBN} at a
32676 relatively high level.
32678 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32682 This is Edition @value{EDITION}, @value{DATE}.
32686 * Annotations Overview:: What annotations are; the general syntax.
32687 * Server Prefix:: Issuing a command without affecting user state.
32688 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32689 * Errors:: Annotations for error messages.
32690 * Invalidation:: Some annotations describe things now invalid.
32691 * Annotations for Running::
32692 Whether the program is running, how it stopped, etc.
32693 * Source Annotations:: Annotations describing source code.
32696 @node Annotations Overview
32697 @section What is an Annotation?
32698 @cindex annotations
32700 Annotations start with a newline character, two @samp{control-z}
32701 characters, and the name of the annotation. If there is no additional
32702 information associated with this annotation, the name of the annotation
32703 is followed immediately by a newline. If there is additional
32704 information, the name of the annotation is followed by a space, the
32705 additional information, and a newline. The additional information
32706 cannot contain newline characters.
32708 Any output not beginning with a newline and two @samp{control-z}
32709 characters denotes literal output from @value{GDBN}. Currently there is
32710 no need for @value{GDBN} to output a newline followed by two
32711 @samp{control-z} characters, but if there was such a need, the
32712 annotations could be extended with an @samp{escape} annotation which
32713 means those three characters as output.
32715 The annotation @var{level}, which is specified using the
32716 @option{--annotate} command line option (@pxref{Mode Options}), controls
32717 how much information @value{GDBN} prints together with its prompt,
32718 values of expressions, source lines, and other types of output. Level 0
32719 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32720 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32721 for programs that control @value{GDBN}, and level 2 annotations have
32722 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32723 Interface, annotate, GDB's Obsolete Annotations}).
32726 @kindex set annotate
32727 @item set annotate @var{level}
32728 The @value{GDBN} command @code{set annotate} sets the level of
32729 annotations to the specified @var{level}.
32731 @item show annotate
32732 @kindex show annotate
32733 Show the current annotation level.
32736 This chapter describes level 3 annotations.
32738 A simple example of starting up @value{GDBN} with annotations is:
32741 $ @kbd{gdb --annotate=3}
32743 Copyright 2003 Free Software Foundation, Inc.
32744 GDB is free software, covered by the GNU General Public License,
32745 and you are welcome to change it and/or distribute copies of it
32746 under certain conditions.
32747 Type "show copying" to see the conditions.
32748 There is absolutely no warranty for GDB. Type "show warranty"
32750 This GDB was configured as "i386-pc-linux-gnu"
32761 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32762 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32763 denotes a @samp{control-z} character) are annotations; the rest is
32764 output from @value{GDBN}.
32766 @node Server Prefix
32767 @section The Server Prefix
32768 @cindex server prefix
32770 If you prefix a command with @samp{server } then it will not affect
32771 the command history, nor will it affect @value{GDBN}'s notion of which
32772 command to repeat if @key{RET} is pressed on a line by itself. This
32773 means that commands can be run behind a user's back by a front-end in
32774 a transparent manner.
32776 The @code{server } prefix does not affect the recording of values into
32777 the value history; to print a value without recording it into the
32778 value history, use the @code{output} command instead of the
32779 @code{print} command.
32781 Using this prefix also disables confirmation requests
32782 (@pxref{confirmation requests}).
32785 @section Annotation for @value{GDBN} Input
32787 @cindex annotations for prompts
32788 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32789 to know when to send output, when the output from a given command is
32792 Different kinds of input each have a different @dfn{input type}. Each
32793 input type has three annotations: a @code{pre-} annotation, which
32794 denotes the beginning of any prompt which is being output, a plain
32795 annotation, which denotes the end of the prompt, and then a @code{post-}
32796 annotation which denotes the end of any echo which may (or may not) be
32797 associated with the input. For example, the @code{prompt} input type
32798 features the following annotations:
32806 The input types are
32809 @findex pre-prompt annotation
32810 @findex prompt annotation
32811 @findex post-prompt annotation
32813 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32815 @findex pre-commands annotation
32816 @findex commands annotation
32817 @findex post-commands annotation
32819 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32820 command. The annotations are repeated for each command which is input.
32822 @findex pre-overload-choice annotation
32823 @findex overload-choice annotation
32824 @findex post-overload-choice annotation
32825 @item overload-choice
32826 When @value{GDBN} wants the user to select between various overloaded functions.
32828 @findex pre-query annotation
32829 @findex query annotation
32830 @findex post-query annotation
32832 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32834 @findex pre-prompt-for-continue annotation
32835 @findex prompt-for-continue annotation
32836 @findex post-prompt-for-continue annotation
32837 @item prompt-for-continue
32838 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32839 expect this to work well; instead use @code{set height 0} to disable
32840 prompting. This is because the counting of lines is buggy in the
32841 presence of annotations.
32846 @cindex annotations for errors, warnings and interrupts
32848 @findex quit annotation
32853 This annotation occurs right before @value{GDBN} responds to an interrupt.
32855 @findex error annotation
32860 This annotation occurs right before @value{GDBN} responds to an error.
32862 Quit and error annotations indicate that any annotations which @value{GDBN} was
32863 in the middle of may end abruptly. For example, if a
32864 @code{value-history-begin} annotation is followed by a @code{error}, one
32865 cannot expect to receive the matching @code{value-history-end}. One
32866 cannot expect not to receive it either, however; an error annotation
32867 does not necessarily mean that @value{GDBN} is immediately returning all the way
32870 @findex error-begin annotation
32871 A quit or error annotation may be preceded by
32877 Any output between that and the quit or error annotation is the error
32880 Warning messages are not yet annotated.
32881 @c If we want to change that, need to fix warning(), type_error(),
32882 @c range_error(), and possibly other places.
32885 @section Invalidation Notices
32887 @cindex annotations for invalidation messages
32888 The following annotations say that certain pieces of state may have
32892 @findex frames-invalid annotation
32893 @item ^Z^Zframes-invalid
32895 The frames (for example, output from the @code{backtrace} command) may
32898 @findex breakpoints-invalid annotation
32899 @item ^Z^Zbreakpoints-invalid
32901 The breakpoints may have changed. For example, the user just added or
32902 deleted a breakpoint.
32905 @node Annotations for Running
32906 @section Running the Program
32907 @cindex annotations for running programs
32909 @findex starting annotation
32910 @findex stopping annotation
32911 When the program starts executing due to a @value{GDBN} command such as
32912 @code{step} or @code{continue},
32918 is output. When the program stops,
32924 is output. Before the @code{stopped} annotation, a variety of
32925 annotations describe how the program stopped.
32928 @findex exited annotation
32929 @item ^Z^Zexited @var{exit-status}
32930 The program exited, and @var{exit-status} is the exit status (zero for
32931 successful exit, otherwise nonzero).
32933 @findex signalled annotation
32934 @findex signal-name annotation
32935 @findex signal-name-end annotation
32936 @findex signal-string annotation
32937 @findex signal-string-end annotation
32938 @item ^Z^Zsignalled
32939 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32940 annotation continues:
32946 ^Z^Zsignal-name-end
32950 ^Z^Zsignal-string-end
32955 where @var{name} is the name of the signal, such as @code{SIGILL} or
32956 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32957 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32958 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32959 user's benefit and have no particular format.
32961 @findex signal annotation
32963 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32964 just saying that the program received the signal, not that it was
32965 terminated with it.
32967 @findex breakpoint annotation
32968 @item ^Z^Zbreakpoint @var{number}
32969 The program hit breakpoint number @var{number}.
32971 @findex watchpoint annotation
32972 @item ^Z^Zwatchpoint @var{number}
32973 The program hit watchpoint number @var{number}.
32976 @node Source Annotations
32977 @section Displaying Source
32978 @cindex annotations for source display
32980 @findex source annotation
32981 The following annotation is used instead of displaying source code:
32984 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32987 where @var{filename} is an absolute file name indicating which source
32988 file, @var{line} is the line number within that file (where 1 is the
32989 first line in the file), @var{character} is the character position
32990 within the file (where 0 is the first character in the file) (for most
32991 debug formats this will necessarily point to the beginning of a line),
32992 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32993 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32994 @var{addr} is the address in the target program associated with the
32995 source which is being displayed. The @var{addr} is in the form @samp{0x}
32996 followed by one or more lowercase hex digits (note that this does not
32997 depend on the language).
32999 @node JIT Interface
33000 @chapter JIT Compilation Interface
33001 @cindex just-in-time compilation
33002 @cindex JIT compilation interface
33004 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33005 interface. A JIT compiler is a program or library that generates native
33006 executable code at runtime and executes it, usually in order to achieve good
33007 performance while maintaining platform independence.
33009 Programs that use JIT compilation are normally difficult to debug because
33010 portions of their code are generated at runtime, instead of being loaded from
33011 object files, which is where @value{GDBN} normally finds the program's symbols
33012 and debug information. In order to debug programs that use JIT compilation,
33013 @value{GDBN} has an interface that allows the program to register in-memory
33014 symbol files with @value{GDBN} at runtime.
33016 If you are using @value{GDBN} to debug a program that uses this interface, then
33017 it should work transparently so long as you have not stripped the binary. If
33018 you are developing a JIT compiler, then the interface is documented in the rest
33019 of this chapter. At this time, the only known client of this interface is the
33022 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33023 JIT compiler communicates with @value{GDBN} by writing data into a global
33024 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33025 attaches, it reads a linked list of symbol files from the global variable to
33026 find existing code, and puts a breakpoint in the function so that it can find
33027 out about additional code.
33030 * Declarations:: Relevant C struct declarations
33031 * Registering Code:: Steps to register code
33032 * Unregistering Code:: Steps to unregister code
33033 * Custom Debug Info:: Emit debug information in a custom format
33037 @section JIT Declarations
33039 These are the relevant struct declarations that a C program should include to
33040 implement the interface:
33050 struct jit_code_entry
33052 struct jit_code_entry *next_entry;
33053 struct jit_code_entry *prev_entry;
33054 const char *symfile_addr;
33055 uint64_t symfile_size;
33058 struct jit_descriptor
33061 /* This type should be jit_actions_t, but we use uint32_t
33062 to be explicit about the bitwidth. */
33063 uint32_t action_flag;
33064 struct jit_code_entry *relevant_entry;
33065 struct jit_code_entry *first_entry;
33068 /* GDB puts a breakpoint in this function. */
33069 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33071 /* Make sure to specify the version statically, because the
33072 debugger may check the version before we can set it. */
33073 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33076 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33077 modifications to this global data properly, which can easily be done by putting
33078 a global mutex around modifications to these structures.
33080 @node Registering Code
33081 @section Registering Code
33083 To register code with @value{GDBN}, the JIT should follow this protocol:
33087 Generate an object file in memory with symbols and other desired debug
33088 information. The file must include the virtual addresses of the sections.
33091 Create a code entry for the file, which gives the start and size of the symbol
33095 Add it to the linked list in the JIT descriptor.
33098 Point the relevant_entry field of the descriptor at the entry.
33101 Set @code{action_flag} to @code{JIT_REGISTER} and call
33102 @code{__jit_debug_register_code}.
33105 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33106 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33107 new code. However, the linked list must still be maintained in order to allow
33108 @value{GDBN} to attach to a running process and still find the symbol files.
33110 @node Unregistering Code
33111 @section Unregistering Code
33113 If code is freed, then the JIT should use the following protocol:
33117 Remove the code entry corresponding to the code from the linked list.
33120 Point the @code{relevant_entry} field of the descriptor at the code entry.
33123 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33124 @code{__jit_debug_register_code}.
33127 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33128 and the JIT will leak the memory used for the associated symbol files.
33130 @node Custom Debug Info
33131 @section Custom Debug Info
33132 @cindex custom JIT debug info
33133 @cindex JIT debug info reader
33135 Generating debug information in platform-native file formats (like ELF
33136 or COFF) may be an overkill for JIT compilers; especially if all the
33137 debug info is used for is displaying a meaningful backtrace. The
33138 issue can be resolved by having the JIT writers decide on a debug info
33139 format and also provide a reader that parses the debug info generated
33140 by the JIT compiler. This section gives a brief overview on writing
33141 such a parser. More specific details can be found in the source file
33142 @file{gdb/jit-reader.in}, which is also installed as a header at
33143 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33145 The reader is implemented as a shared object (so this functionality is
33146 not available on platforms which don't allow loading shared objects at
33147 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33148 @code{jit-reader-unload} are provided, to be used to load and unload
33149 the readers from a preconfigured directory. Once loaded, the shared
33150 object is used the parse the debug information emitted by the JIT
33154 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33155 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33158 @node Using JIT Debug Info Readers
33159 @subsection Using JIT Debug Info Readers
33160 @kindex jit-reader-load
33161 @kindex jit-reader-unload
33163 Readers can be loaded and unloaded using the @code{jit-reader-load}
33164 and @code{jit-reader-unload} commands.
33167 @item jit-reader-load @var{reader}
33168 Load the JIT reader named @var{reader}, which is a shared
33169 object specified as either an absolute or a relative file name. In
33170 the latter case, @value{GDBN} will try to load the reader from a
33171 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33172 system (here @var{libdir} is the system library directory, often
33173 @file{/usr/local/lib}).
33175 Only one reader can be active at a time; trying to load a second
33176 reader when one is already loaded will result in @value{GDBN}
33177 reporting an error. A new JIT reader can be loaded by first unloading
33178 the current one using @code{jit-reader-unload} and then invoking
33179 @code{jit-reader-load}.
33181 @item jit-reader-unload
33182 Unload the currently loaded JIT reader.
33186 @node Writing JIT Debug Info Readers
33187 @subsection Writing JIT Debug Info Readers
33188 @cindex writing JIT debug info readers
33190 As mentioned, a reader is essentially a shared object conforming to a
33191 certain ABI. This ABI is described in @file{jit-reader.h}.
33193 @file{jit-reader.h} defines the structures, macros and functions
33194 required to write a reader. It is installed (along with
33195 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33196 the system include directory.
33198 Readers need to be released under a GPL compatible license. A reader
33199 can be declared as released under such a license by placing the macro
33200 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33202 The entry point for readers is the symbol @code{gdb_init_reader},
33203 which is expected to be a function with the prototype
33205 @findex gdb_init_reader
33207 extern struct gdb_reader_funcs *gdb_init_reader (void);
33210 @cindex @code{struct gdb_reader_funcs}
33212 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33213 functions. These functions are executed to read the debug info
33214 generated by the JIT compiler (@code{read}), to unwind stack frames
33215 (@code{unwind}) and to create canonical frame IDs
33216 (@code{get_Frame_id}). It also has a callback that is called when the
33217 reader is being unloaded (@code{destroy}). The struct looks like this
33220 struct gdb_reader_funcs
33222 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33223 int reader_version;
33225 /* For use by the reader. */
33228 gdb_read_debug_info *read;
33229 gdb_unwind_frame *unwind;
33230 gdb_get_frame_id *get_frame_id;
33231 gdb_destroy_reader *destroy;
33235 @cindex @code{struct gdb_symbol_callbacks}
33236 @cindex @code{struct gdb_unwind_callbacks}
33238 The callbacks are provided with another set of callbacks by
33239 @value{GDBN} to do their job. For @code{read}, these callbacks are
33240 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33241 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33242 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33243 files and new symbol tables inside those object files. @code{struct
33244 gdb_unwind_callbacks} has callbacks to read registers off the current
33245 frame and to write out the values of the registers in the previous
33246 frame. Both have a callback (@code{target_read}) to read bytes off the
33247 target's address space.
33249 @node In-Process Agent
33250 @chapter In-Process Agent
33251 @cindex debugging agent
33252 The traditional debugging model is conceptually low-speed, but works fine,
33253 because most bugs can be reproduced in debugging-mode execution. However,
33254 as multi-core or many-core processors are becoming mainstream, and
33255 multi-threaded programs become more and more popular, there should be more
33256 and more bugs that only manifest themselves at normal-mode execution, for
33257 example, thread races, because debugger's interference with the program's
33258 timing may conceal the bugs. On the other hand, in some applications,
33259 it is not feasible for the debugger to interrupt the program's execution
33260 long enough for the developer to learn anything helpful about its behavior.
33261 If the program's correctness depends on its real-time behavior, delays
33262 introduced by a debugger might cause the program to fail, even when the
33263 code itself is correct. It is useful to be able to observe the program's
33264 behavior without interrupting it.
33266 Therefore, traditional debugging model is too intrusive to reproduce
33267 some bugs. In order to reduce the interference with the program, we can
33268 reduce the number of operations performed by debugger. The
33269 @dfn{In-Process Agent}, a shared library, is running within the same
33270 process with inferior, and is able to perform some debugging operations
33271 itself. As a result, debugger is only involved when necessary, and
33272 performance of debugging can be improved accordingly. Note that
33273 interference with program can be reduced but can't be removed completely,
33274 because the in-process agent will still stop or slow down the program.
33276 The in-process agent can interpret and execute Agent Expressions
33277 (@pxref{Agent Expressions}) during performing debugging operations. The
33278 agent expressions can be used for different purposes, such as collecting
33279 data in tracepoints, and condition evaluation in breakpoints.
33281 @anchor{Control Agent}
33282 You can control whether the in-process agent is used as an aid for
33283 debugging with the following commands:
33286 @kindex set agent on
33288 Causes the in-process agent to perform some operations on behalf of the
33289 debugger. Just which operations requested by the user will be done
33290 by the in-process agent depends on the its capabilities. For example,
33291 if you request to evaluate breakpoint conditions in the in-process agent,
33292 and the in-process agent has such capability as well, then breakpoint
33293 conditions will be evaluated in the in-process agent.
33295 @kindex set agent off
33296 @item set agent off
33297 Disables execution of debugging operations by the in-process agent. All
33298 of the operations will be performed by @value{GDBN}.
33302 Display the current setting of execution of debugging operations by
33303 the in-process agent.
33307 * In-Process Agent Protocol::
33310 @node In-Process Agent Protocol
33311 @section In-Process Agent Protocol
33312 @cindex in-process agent protocol
33314 The in-process agent is able to communicate with both @value{GDBN} and
33315 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33316 used for communications between @value{GDBN} or GDBserver and the IPA.
33317 In general, @value{GDBN} or GDBserver sends commands
33318 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33319 in-process agent replies back with the return result of the command, or
33320 some other information. The data sent to in-process agent is composed
33321 of primitive data types, such as 4-byte or 8-byte type, and composite
33322 types, which are called objects (@pxref{IPA Protocol Objects}).
33325 * IPA Protocol Objects::
33326 * IPA Protocol Commands::
33329 @node IPA Protocol Objects
33330 @subsection IPA Protocol Objects
33331 @cindex ipa protocol objects
33333 The commands sent to and results received from agent may contain some
33334 complex data types called @dfn{objects}.
33336 The in-process agent is running on the same machine with @value{GDBN}
33337 or GDBserver, so it doesn't have to handle as much differences between
33338 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33339 However, there are still some differences of two ends in two processes:
33343 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33344 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33346 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33347 GDBserver is compiled with one, and in-process agent is compiled with
33351 Here are the IPA Protocol Objects:
33355 agent expression object. It represents an agent expression
33356 (@pxref{Agent Expressions}).
33357 @anchor{agent expression object}
33359 tracepoint action object. It represents a tracepoint action
33360 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33361 memory, static trace data and to evaluate expression.
33362 @anchor{tracepoint action object}
33364 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33365 @anchor{tracepoint object}
33369 The following table describes important attributes of each IPA protocol
33372 @multitable @columnfractions .30 .20 .50
33373 @headitem Name @tab Size @tab Description
33374 @item @emph{agent expression object} @tab @tab
33375 @item length @tab 4 @tab length of bytes code
33376 @item byte code @tab @var{length} @tab contents of byte code
33377 @item @emph{tracepoint action for collecting memory} @tab @tab
33378 @item 'M' @tab 1 @tab type of tracepoint action
33379 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33380 address of the lowest byte to collect, otherwise @var{addr} is the offset
33381 of @var{basereg} for memory collecting.
33382 @item len @tab 8 @tab length of memory for collecting
33383 @item basereg @tab 4 @tab the register number containing the starting
33384 memory address for collecting.
33385 @item @emph{tracepoint action for collecting registers} @tab @tab
33386 @item 'R' @tab 1 @tab type of tracepoint action
33387 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33388 @item 'L' @tab 1 @tab type of tracepoint action
33389 @item @emph{tracepoint action for expression evaluation} @tab @tab
33390 @item 'X' @tab 1 @tab type of tracepoint action
33391 @item agent expression @tab length of @tab @ref{agent expression object}
33392 @item @emph{tracepoint object} @tab @tab
33393 @item number @tab 4 @tab number of tracepoint
33394 @item address @tab 8 @tab address of tracepoint inserted on
33395 @item type @tab 4 @tab type of tracepoint
33396 @item enabled @tab 1 @tab enable or disable of tracepoint
33397 @item step_count @tab 8 @tab step
33398 @item pass_count @tab 8 @tab pass
33399 @item numactions @tab 4 @tab number of tracepoint actions
33400 @item hit count @tab 8 @tab hit count
33401 @item trace frame usage @tab 8 @tab trace frame usage
33402 @item compiled_cond @tab 8 @tab compiled condition
33403 @item orig_size @tab 8 @tab orig size
33404 @item condition @tab 4 if condition is NULL otherwise length of
33405 @ref{agent expression object}
33406 @tab zero if condition is NULL, otherwise is
33407 @ref{agent expression object}
33408 @item actions @tab variable
33409 @tab numactions number of @ref{tracepoint action object}
33412 @node IPA Protocol Commands
33413 @subsection IPA Protocol Commands
33414 @cindex ipa protocol commands
33416 The spaces in each command are delimiters to ease reading this commands
33417 specification. They don't exist in real commands.
33421 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33422 Installs a new fast tracepoint described by @var{tracepoint_object}
33423 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33424 head of @dfn{jumppad}, which is used to jump to data collection routine
33429 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33430 @var{target_address} is address of tracepoint in the inferior.
33431 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33432 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33433 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33434 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33441 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33442 is about to kill inferiors.
33450 @item probe_marker_at:@var{address}
33451 Asks in-process agent to probe the marker at @var{address}.
33458 @item unprobe_marker_at:@var{address}
33459 Asks in-process agent to unprobe the marker at @var{address}.
33463 @chapter Reporting Bugs in @value{GDBN}
33464 @cindex bugs in @value{GDBN}
33465 @cindex reporting bugs in @value{GDBN}
33467 Your bug reports play an essential role in making @value{GDBN} reliable.
33469 Reporting a bug may help you by bringing a solution to your problem, or it
33470 may not. But in any case the principal function of a bug report is to help
33471 the entire community by making the next version of @value{GDBN} work better. Bug
33472 reports are your contribution to the maintenance of @value{GDBN}.
33474 In order for a bug report to serve its purpose, you must include the
33475 information that enables us to fix the bug.
33478 * Bug Criteria:: Have you found a bug?
33479 * Bug Reporting:: How to report bugs
33483 @section Have You Found a Bug?
33484 @cindex bug criteria
33486 If you are not sure whether you have found a bug, here are some guidelines:
33489 @cindex fatal signal
33490 @cindex debugger crash
33491 @cindex crash of debugger
33493 If the debugger gets a fatal signal, for any input whatever, that is a
33494 @value{GDBN} bug. Reliable debuggers never crash.
33496 @cindex error on valid input
33498 If @value{GDBN} produces an error message for valid input, that is a
33499 bug. (Note that if you're cross debugging, the problem may also be
33500 somewhere in the connection to the target.)
33502 @cindex invalid input
33504 If @value{GDBN} does not produce an error message for invalid input,
33505 that is a bug. However, you should note that your idea of
33506 ``invalid input'' might be our idea of ``an extension'' or ``support
33507 for traditional practice''.
33510 If you are an experienced user of debugging tools, your suggestions
33511 for improvement of @value{GDBN} are welcome in any case.
33514 @node Bug Reporting
33515 @section How to Report Bugs
33516 @cindex bug reports
33517 @cindex @value{GDBN} bugs, reporting
33519 A number of companies and individuals offer support for @sc{gnu} products.
33520 If you obtained @value{GDBN} from a support organization, we recommend you
33521 contact that organization first.
33523 You can find contact information for many support companies and
33524 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33526 @c should add a web page ref...
33529 @ifset BUGURL_DEFAULT
33530 In any event, we also recommend that you submit bug reports for
33531 @value{GDBN}. The preferred method is to submit them directly using
33532 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33533 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33536 @strong{Do not send bug reports to @samp{info-gdb}, or to
33537 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33538 not want to receive bug reports. Those that do have arranged to receive
33541 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33542 serves as a repeater. The mailing list and the newsgroup carry exactly
33543 the same messages. Often people think of posting bug reports to the
33544 newsgroup instead of mailing them. This appears to work, but it has one
33545 problem which can be crucial: a newsgroup posting often lacks a mail
33546 path back to the sender. Thus, if we need to ask for more information,
33547 we may be unable to reach you. For this reason, it is better to send
33548 bug reports to the mailing list.
33550 @ifclear BUGURL_DEFAULT
33551 In any event, we also recommend that you submit bug reports for
33552 @value{GDBN} to @value{BUGURL}.
33556 The fundamental principle of reporting bugs usefully is this:
33557 @strong{report all the facts}. If you are not sure whether to state a
33558 fact or leave it out, state it!
33560 Often people omit facts because they think they know what causes the
33561 problem and assume that some details do not matter. Thus, you might
33562 assume that the name of the variable you use in an example does not matter.
33563 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33564 stray memory reference which happens to fetch from the location where that
33565 name is stored in memory; perhaps, if the name were different, the contents
33566 of that location would fool the debugger into doing the right thing despite
33567 the bug. Play it safe and give a specific, complete example. That is the
33568 easiest thing for you to do, and the most helpful.
33570 Keep in mind that the purpose of a bug report is to enable us to fix the
33571 bug. It may be that the bug has been reported previously, but neither
33572 you nor we can know that unless your bug report is complete and
33575 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33576 bell?'' Those bug reports are useless, and we urge everyone to
33577 @emph{refuse to respond to them} except to chide the sender to report
33580 To enable us to fix the bug, you should include all these things:
33584 The version of @value{GDBN}. @value{GDBN} announces it if you start
33585 with no arguments; you can also print it at any time using @code{show
33588 Without this, we will not know whether there is any point in looking for
33589 the bug in the current version of @value{GDBN}.
33592 The type of machine you are using, and the operating system name and
33596 The details of the @value{GDBN} build-time configuration.
33597 @value{GDBN} shows these details if you invoke it with the
33598 @option{--configuration} command-line option, or if you type
33599 @code{show configuration} at @value{GDBN}'s prompt.
33602 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33603 ``@value{GCC}--2.8.1''.
33606 What compiler (and its version) was used to compile the program you are
33607 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33608 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33609 to get this information; for other compilers, see the documentation for
33613 The command arguments you gave the compiler to compile your example and
33614 observe the bug. For example, did you use @samp{-O}? To guarantee
33615 you will not omit something important, list them all. A copy of the
33616 Makefile (or the output from make) is sufficient.
33618 If we were to try to guess the arguments, we would probably guess wrong
33619 and then we might not encounter the bug.
33622 A complete input script, and all necessary source files, that will
33626 A description of what behavior you observe that you believe is
33627 incorrect. For example, ``It gets a fatal signal.''
33629 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33630 will certainly notice it. But if the bug is incorrect output, we might
33631 not notice unless it is glaringly wrong. You might as well not give us
33632 a chance to make a mistake.
33634 Even if the problem you experience is a fatal signal, you should still
33635 say so explicitly. Suppose something strange is going on, such as, your
33636 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33637 the C library on your system. (This has happened!) Your copy might
33638 crash and ours would not. If you told us to expect a crash, then when
33639 ours fails to crash, we would know that the bug was not happening for
33640 us. If you had not told us to expect a crash, then we would not be able
33641 to draw any conclusion from our observations.
33644 @cindex recording a session script
33645 To collect all this information, you can use a session recording program
33646 such as @command{script}, which is available on many Unix systems.
33647 Just run your @value{GDBN} session inside @command{script} and then
33648 include the @file{typescript} file with your bug report.
33650 Another way to record a @value{GDBN} session is to run @value{GDBN}
33651 inside Emacs and then save the entire buffer to a file.
33654 If you wish to suggest changes to the @value{GDBN} source, send us context
33655 diffs. If you even discuss something in the @value{GDBN} source, refer to
33656 it by context, not by line number.
33658 The line numbers in our development sources will not match those in your
33659 sources. Your line numbers would convey no useful information to us.
33663 Here are some things that are not necessary:
33667 A description of the envelope of the bug.
33669 Often people who encounter a bug spend a lot of time investigating
33670 which changes to the input file will make the bug go away and which
33671 changes will not affect it.
33673 This is often time consuming and not very useful, because the way we
33674 will find the bug is by running a single example under the debugger
33675 with breakpoints, not by pure deduction from a series of examples.
33676 We recommend that you save your time for something else.
33678 Of course, if you can find a simpler example to report @emph{instead}
33679 of the original one, that is a convenience for us. Errors in the
33680 output will be easier to spot, running under the debugger will take
33681 less time, and so on.
33683 However, simplification is not vital; if you do not want to do this,
33684 report the bug anyway and send us the entire test case you used.
33687 A patch for the bug.
33689 A patch for the bug does help us if it is a good one. But do not omit
33690 the necessary information, such as the test case, on the assumption that
33691 a patch is all we need. We might see problems with your patch and decide
33692 to fix the problem another way, or we might not understand it at all.
33694 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33695 construct an example that will make the program follow a certain path
33696 through the code. If you do not send us the example, we will not be able
33697 to construct one, so we will not be able to verify that the bug is fixed.
33699 And if we cannot understand what bug you are trying to fix, or why your
33700 patch should be an improvement, we will not install it. A test case will
33701 help us to understand.
33704 A guess about what the bug is or what it depends on.
33706 Such guesses are usually wrong. Even we cannot guess right about such
33707 things without first using the debugger to find the facts.
33710 @c The readline documentation is distributed with the readline code
33711 @c and consists of the two following files:
33714 @c Use -I with makeinfo to point to the appropriate directory,
33715 @c environment var TEXINPUTS with TeX.
33716 @ifclear SYSTEM_READLINE
33717 @include rluser.texi
33718 @include hsuser.texi
33722 @appendix In Memoriam
33724 The @value{GDBN} project mourns the loss of the following long-time
33729 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33730 to Free Software in general. Outside of @value{GDBN}, he was known in
33731 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33733 @item Michael Snyder
33734 Michael was one of the Global Maintainers of the @value{GDBN} project,
33735 with contributions recorded as early as 1996, until 2011. In addition
33736 to his day to day participation, he was a large driving force behind
33737 adding Reverse Debugging to @value{GDBN}.
33740 Beyond their technical contributions to the project, they were also
33741 enjoyable members of the Free Software Community. We will miss them.
33743 @node Formatting Documentation
33744 @appendix Formatting Documentation
33746 @cindex @value{GDBN} reference card
33747 @cindex reference card
33748 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33749 for printing with PostScript or Ghostscript, in the @file{gdb}
33750 subdirectory of the main source directory@footnote{In
33751 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33752 release.}. If you can use PostScript or Ghostscript with your printer,
33753 you can print the reference card immediately with @file{refcard.ps}.
33755 The release also includes the source for the reference card. You
33756 can format it, using @TeX{}, by typing:
33762 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33763 mode on US ``letter'' size paper;
33764 that is, on a sheet 11 inches wide by 8.5 inches
33765 high. You will need to specify this form of printing as an option to
33766 your @sc{dvi} output program.
33768 @cindex documentation
33770 All the documentation for @value{GDBN} comes as part of the machine-readable
33771 distribution. The documentation is written in Texinfo format, which is
33772 a documentation system that uses a single source file to produce both
33773 on-line information and a printed manual. You can use one of the Info
33774 formatting commands to create the on-line version of the documentation
33775 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33777 @value{GDBN} includes an already formatted copy of the on-line Info
33778 version of this manual in the @file{gdb} subdirectory. The main Info
33779 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33780 subordinate files matching @samp{gdb.info*} in the same directory. If
33781 necessary, you can print out these files, or read them with any editor;
33782 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33783 Emacs or the standalone @code{info} program, available as part of the
33784 @sc{gnu} Texinfo distribution.
33786 If you want to format these Info files yourself, you need one of the
33787 Info formatting programs, such as @code{texinfo-format-buffer} or
33790 If you have @code{makeinfo} installed, and are in the top level
33791 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33792 version @value{GDBVN}), you can make the Info file by typing:
33799 If you want to typeset and print copies of this manual, you need @TeX{},
33800 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33801 Texinfo definitions file.
33803 @TeX{} is a typesetting program; it does not print files directly, but
33804 produces output files called @sc{dvi} files. To print a typeset
33805 document, you need a program to print @sc{dvi} files. If your system
33806 has @TeX{} installed, chances are it has such a program. The precise
33807 command to use depends on your system; @kbd{lpr -d} is common; another
33808 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33809 require a file name without any extension or a @samp{.dvi} extension.
33811 @TeX{} also requires a macro definitions file called
33812 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33813 written in Texinfo format. On its own, @TeX{} cannot either read or
33814 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33815 and is located in the @file{gdb-@var{version-number}/texinfo}
33818 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33819 typeset and print this manual. First switch to the @file{gdb}
33820 subdirectory of the main source directory (for example, to
33821 @file{gdb-@value{GDBVN}/gdb}) and type:
33827 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33829 @node Installing GDB
33830 @appendix Installing @value{GDBN}
33831 @cindex installation
33834 * Requirements:: Requirements for building @value{GDBN}
33835 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33836 * Separate Objdir:: Compiling @value{GDBN} in another directory
33837 * Config Names:: Specifying names for hosts and targets
33838 * Configure Options:: Summary of options for configure
33839 * System-wide configuration:: Having a system-wide init file
33843 @section Requirements for Building @value{GDBN}
33844 @cindex building @value{GDBN}, requirements for
33846 Building @value{GDBN} requires various tools and packages to be available.
33847 Other packages will be used only if they are found.
33849 @heading Tools/Packages Necessary for Building @value{GDBN}
33851 @item ISO C90 compiler
33852 @value{GDBN} is written in ISO C90. It should be buildable with any
33853 working C90 compiler, e.g.@: GCC.
33857 @heading Tools/Packages Optional for Building @value{GDBN}
33861 @value{GDBN} can use the Expat XML parsing library. This library may be
33862 included with your operating system distribution; if it is not, you
33863 can get the latest version from @url{http://expat.sourceforge.net}.
33864 The @file{configure} script will search for this library in several
33865 standard locations; if it is installed in an unusual path, you can
33866 use the @option{--with-libexpat-prefix} option to specify its location.
33872 Remote protocol memory maps (@pxref{Memory Map Format})
33874 Target descriptions (@pxref{Target Descriptions})
33876 Remote shared library lists (@xref{Library List Format},
33877 or alternatively @pxref{Library List Format for SVR4 Targets})
33879 MS-Windows shared libraries (@pxref{Shared Libraries})
33881 Traceframe info (@pxref{Traceframe Info Format})
33883 Branch trace (@pxref{Branch Trace Format},
33884 @pxref{Branch Trace Configuration Format})
33888 @cindex compressed debug sections
33889 @value{GDBN} will use the @samp{zlib} library, if available, to read
33890 compressed debug sections. Some linkers, such as GNU gold, are capable
33891 of producing binaries with compressed debug sections. If @value{GDBN}
33892 is compiled with @samp{zlib}, it will be able to read the debug
33893 information in such binaries.
33895 The @samp{zlib} library is likely included with your operating system
33896 distribution; if it is not, you can get the latest version from
33897 @url{http://zlib.net}.
33900 @value{GDBN}'s features related to character sets (@pxref{Character
33901 Sets}) require a functioning @code{iconv} implementation. If you are
33902 on a GNU system, then this is provided by the GNU C Library. Some
33903 other systems also provide a working @code{iconv}.
33905 If @value{GDBN} is using the @code{iconv} program which is installed
33906 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33907 This is done with @option{--with-iconv-bin} which specifies the
33908 directory that contains the @code{iconv} program.
33910 On systems without @code{iconv}, you can install GNU Libiconv. If you
33911 have previously installed Libiconv, you can use the
33912 @option{--with-libiconv-prefix} option to configure.
33914 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33915 arrange to build Libiconv if a directory named @file{libiconv} appears
33916 in the top-most source directory. If Libiconv is built this way, and
33917 if the operating system does not provide a suitable @code{iconv}
33918 implementation, then the just-built library will automatically be used
33919 by @value{GDBN}. One easy way to set this up is to download GNU
33920 Libiconv, unpack it, and then rename the directory holding the
33921 Libiconv source code to @samp{libiconv}.
33924 @node Running Configure
33925 @section Invoking the @value{GDBN} @file{configure} Script
33926 @cindex configuring @value{GDBN}
33927 @value{GDBN} comes with a @file{configure} script that automates the process
33928 of preparing @value{GDBN} for installation; you can then use @code{make} to
33929 build the @code{gdb} program.
33931 @c irrelevant in info file; it's as current as the code it lives with.
33932 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33933 look at the @file{README} file in the sources; we may have improved the
33934 installation procedures since publishing this manual.}
33937 The @value{GDBN} distribution includes all the source code you need for
33938 @value{GDBN} in a single directory, whose name is usually composed by
33939 appending the version number to @samp{gdb}.
33941 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33942 @file{gdb-@value{GDBVN}} directory. That directory contains:
33945 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33946 script for configuring @value{GDBN} and all its supporting libraries
33948 @item gdb-@value{GDBVN}/gdb
33949 the source specific to @value{GDBN} itself
33951 @item gdb-@value{GDBVN}/bfd
33952 source for the Binary File Descriptor library
33954 @item gdb-@value{GDBVN}/include
33955 @sc{gnu} include files
33957 @item gdb-@value{GDBVN}/libiberty
33958 source for the @samp{-liberty} free software library
33960 @item gdb-@value{GDBVN}/opcodes
33961 source for the library of opcode tables and disassemblers
33963 @item gdb-@value{GDBVN}/readline
33964 source for the @sc{gnu} command-line interface
33966 @item gdb-@value{GDBVN}/glob
33967 source for the @sc{gnu} filename pattern-matching subroutine
33969 @item gdb-@value{GDBVN}/mmalloc
33970 source for the @sc{gnu} memory-mapped malloc package
33973 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33974 from the @file{gdb-@var{version-number}} source directory, which in
33975 this example is the @file{gdb-@value{GDBVN}} directory.
33977 First switch to the @file{gdb-@var{version-number}} source directory
33978 if you are not already in it; then run @file{configure}. Pass the
33979 identifier for the platform on which @value{GDBN} will run as an
33985 cd gdb-@value{GDBVN}
33986 ./configure @var{host}
33991 where @var{host} is an identifier such as @samp{sun4} or
33992 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33993 (You can often leave off @var{host}; @file{configure} tries to guess the
33994 correct value by examining your system.)
33996 Running @samp{configure @var{host}} and then running @code{make} builds the
33997 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33998 libraries, then @code{gdb} itself. The configured source files, and the
33999 binaries, are left in the corresponding source directories.
34002 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34003 system does not recognize this automatically when you run a different
34004 shell, you may need to run @code{sh} on it explicitly:
34007 sh configure @var{host}
34010 If you run @file{configure} from a directory that contains source
34011 directories for multiple libraries or programs, such as the
34012 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34014 creates configuration files for every directory level underneath (unless
34015 you tell it not to, with the @samp{--norecursion} option).
34017 You should run the @file{configure} script from the top directory in the
34018 source tree, the @file{gdb-@var{version-number}} directory. If you run
34019 @file{configure} from one of the subdirectories, you will configure only
34020 that subdirectory. That is usually not what you want. In particular,
34021 if you run the first @file{configure} from the @file{gdb} subdirectory
34022 of the @file{gdb-@var{version-number}} directory, you will omit the
34023 configuration of @file{bfd}, @file{readline}, and other sibling
34024 directories of the @file{gdb} subdirectory. This leads to build errors
34025 about missing include files such as @file{bfd/bfd.h}.
34027 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34028 However, you should make sure that the shell on your path (named by
34029 the @samp{SHELL} environment variable) is publicly readable. Remember
34030 that @value{GDBN} uses the shell to start your program---some systems refuse to
34031 let @value{GDBN} debug child processes whose programs are not readable.
34033 @node Separate Objdir
34034 @section Compiling @value{GDBN} in Another Directory
34036 If you want to run @value{GDBN} versions for several host or target machines,
34037 you need a different @code{gdb} compiled for each combination of
34038 host and target. @file{configure} is designed to make this easy by
34039 allowing you to generate each configuration in a separate subdirectory,
34040 rather than in the source directory. If your @code{make} program
34041 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34042 @code{make} in each of these directories builds the @code{gdb}
34043 program specified there.
34045 To build @code{gdb} in a separate directory, run @file{configure}
34046 with the @samp{--srcdir} option to specify where to find the source.
34047 (You also need to specify a path to find @file{configure}
34048 itself from your working directory. If the path to @file{configure}
34049 would be the same as the argument to @samp{--srcdir}, you can leave out
34050 the @samp{--srcdir} option; it is assumed.)
34052 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34053 separate directory for a Sun 4 like this:
34057 cd gdb-@value{GDBVN}
34060 ../gdb-@value{GDBVN}/configure sun4
34065 When @file{configure} builds a configuration using a remote source
34066 directory, it creates a tree for the binaries with the same structure
34067 (and using the same names) as the tree under the source directory. In
34068 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34069 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34070 @file{gdb-sun4/gdb}.
34072 Make sure that your path to the @file{configure} script has just one
34073 instance of @file{gdb} in it. If your path to @file{configure} looks
34074 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34075 one subdirectory of @value{GDBN}, not the whole package. This leads to
34076 build errors about missing include files such as @file{bfd/bfd.h}.
34078 One popular reason to build several @value{GDBN} configurations in separate
34079 directories is to configure @value{GDBN} for cross-compiling (where
34080 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34081 programs that run on another machine---the @dfn{target}).
34082 You specify a cross-debugging target by
34083 giving the @samp{--target=@var{target}} option to @file{configure}.
34085 When you run @code{make} to build a program or library, you must run
34086 it in a configured directory---whatever directory you were in when you
34087 called @file{configure} (or one of its subdirectories).
34089 The @code{Makefile} that @file{configure} generates in each source
34090 directory also runs recursively. If you type @code{make} in a source
34091 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34092 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34093 will build all the required libraries, and then build GDB.
34095 When you have multiple hosts or targets configured in separate
34096 directories, you can run @code{make} on them in parallel (for example,
34097 if they are NFS-mounted on each of the hosts); they will not interfere
34101 @section Specifying Names for Hosts and Targets
34103 The specifications used for hosts and targets in the @file{configure}
34104 script are based on a three-part naming scheme, but some short predefined
34105 aliases are also supported. The full naming scheme encodes three pieces
34106 of information in the following pattern:
34109 @var{architecture}-@var{vendor}-@var{os}
34112 For example, you can use the alias @code{sun4} as a @var{host} argument,
34113 or as the value for @var{target} in a @code{--target=@var{target}}
34114 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34116 The @file{configure} script accompanying @value{GDBN} does not provide
34117 any query facility to list all supported host and target names or
34118 aliases. @file{configure} calls the Bourne shell script
34119 @code{config.sub} to map abbreviations to full names; you can read the
34120 script, if you wish, or you can use it to test your guesses on
34121 abbreviations---for example:
34124 % sh config.sub i386-linux
34126 % sh config.sub alpha-linux
34127 alpha-unknown-linux-gnu
34128 % sh config.sub hp9k700
34130 % sh config.sub sun4
34131 sparc-sun-sunos4.1.1
34132 % sh config.sub sun3
34133 m68k-sun-sunos4.1.1
34134 % sh config.sub i986v
34135 Invalid configuration `i986v': machine `i986v' not recognized
34139 @code{config.sub} is also distributed in the @value{GDBN} source
34140 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34142 @node Configure Options
34143 @section @file{configure} Options
34145 Here is a summary of the @file{configure} options and arguments that
34146 are most often useful for building @value{GDBN}. @file{configure} also has
34147 several other options not listed here. @inforef{What Configure
34148 Does,,configure.info}, for a full explanation of @file{configure}.
34151 configure @r{[}--help@r{]}
34152 @r{[}--prefix=@var{dir}@r{]}
34153 @r{[}--exec-prefix=@var{dir}@r{]}
34154 @r{[}--srcdir=@var{dirname}@r{]}
34155 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34156 @r{[}--target=@var{target}@r{]}
34161 You may introduce options with a single @samp{-} rather than
34162 @samp{--} if you prefer; but you may abbreviate option names if you use
34167 Display a quick summary of how to invoke @file{configure}.
34169 @item --prefix=@var{dir}
34170 Configure the source to install programs and files under directory
34173 @item --exec-prefix=@var{dir}
34174 Configure the source to install programs under directory
34177 @c avoid splitting the warning from the explanation:
34179 @item --srcdir=@var{dirname}
34180 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34181 @code{make} that implements the @code{VPATH} feature.}@*
34182 Use this option to make configurations in directories separate from the
34183 @value{GDBN} source directories. Among other things, you can use this to
34184 build (or maintain) several configurations simultaneously, in separate
34185 directories. @file{configure} writes configuration-specific files in
34186 the current directory, but arranges for them to use the source in the
34187 directory @var{dirname}. @file{configure} creates directories under
34188 the working directory in parallel to the source directories below
34191 @item --norecursion
34192 Configure only the directory level where @file{configure} is executed; do not
34193 propagate configuration to subdirectories.
34195 @item --target=@var{target}
34196 Configure @value{GDBN} for cross-debugging programs running on the specified
34197 @var{target}. Without this option, @value{GDBN} is configured to debug
34198 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34200 There is no convenient way to generate a list of all available targets.
34202 @item @var{host} @dots{}
34203 Configure @value{GDBN} to run on the specified @var{host}.
34205 There is no convenient way to generate a list of all available hosts.
34208 There are many other options available as well, but they are generally
34209 needed for special purposes only.
34211 @node System-wide configuration
34212 @section System-wide configuration and settings
34213 @cindex system-wide init file
34215 @value{GDBN} can be configured to have a system-wide init file;
34216 this file will be read and executed at startup (@pxref{Startup, , What
34217 @value{GDBN} does during startup}).
34219 Here is the corresponding configure option:
34222 @item --with-system-gdbinit=@var{file}
34223 Specify that the default location of the system-wide init file is
34227 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34228 it may be subject to relocation. Two possible cases:
34232 If the default location of this init file contains @file{$prefix},
34233 it will be subject to relocation. Suppose that the configure options
34234 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34235 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34236 init file is looked for as @file{$install/etc/gdbinit} instead of
34237 @file{$prefix/etc/gdbinit}.
34240 By contrast, if the default location does not contain the prefix,
34241 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34242 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34243 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34244 wherever @value{GDBN} is installed.
34247 If the configured location of the system-wide init file (as given by the
34248 @option{--with-system-gdbinit} option at configure time) is in the
34249 data-directory (as specified by @option{--with-gdb-datadir} at configure
34250 time) or in one of its subdirectories, then @value{GDBN} will look for the
34251 system-wide init file in the directory specified by the
34252 @option{--data-directory} command-line option.
34253 Note that the system-wide init file is only read once, during @value{GDBN}
34254 initialization. If the data-directory is changed after @value{GDBN} has
34255 started with the @code{set data-directory} command, the file will not be
34259 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34262 @node System-wide Configuration Scripts
34263 @subsection Installed System-wide Configuration Scripts
34264 @cindex system-wide configuration scripts
34266 The @file{system-gdbinit} directory, located inside the data-directory
34267 (as specified by @option{--with-gdb-datadir} at configure time) contains
34268 a number of scripts which can be used as system-wide init files. To
34269 automatically source those scripts at startup, @value{GDBN} should be
34270 configured with @option{--with-system-gdbinit}. Otherwise, any user
34271 should be able to source them by hand as needed.
34273 The following scripts are currently available:
34276 @item @file{elinos.py}
34278 @cindex ELinOS system-wide configuration script
34279 This script is useful when debugging a program on an ELinOS target.
34280 It takes advantage of the environment variables defined in a standard
34281 ELinOS environment in order to determine the location of the system
34282 shared libraries, and then sets the @samp{solib-absolute-prefix}
34283 and @samp{solib-search-path} variables appropriately.
34285 @item @file{wrs-linux.py}
34286 @pindex wrs-linux.py
34287 @cindex Wind River Linux system-wide configuration script
34288 This script is useful when debugging a program on a target running
34289 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34290 the host-side sysroot used by the target system.
34294 @node Maintenance Commands
34295 @appendix Maintenance Commands
34296 @cindex maintenance commands
34297 @cindex internal commands
34299 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34300 includes a number of commands intended for @value{GDBN} developers,
34301 that are not documented elsewhere in this manual. These commands are
34302 provided here for reference. (For commands that turn on debugging
34303 messages, see @ref{Debugging Output}.)
34306 @kindex maint agent
34307 @kindex maint agent-eval
34308 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34309 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34310 Translate the given @var{expression} into remote agent bytecodes.
34311 This command is useful for debugging the Agent Expression mechanism
34312 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34313 expression useful for data collection, such as by tracepoints, while
34314 @samp{maint agent-eval} produces an expression that evaluates directly
34315 to a result. For instance, a collection expression for @code{globa +
34316 globb} will include bytecodes to record four bytes of memory at each
34317 of the addresses of @code{globa} and @code{globb}, while discarding
34318 the result of the addition, while an evaluation expression will do the
34319 addition and return the sum.
34320 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34321 If not, generate remote agent bytecode for current frame PC address.
34323 @kindex maint agent-printf
34324 @item maint agent-printf @var{format},@var{expr},...
34325 Translate the given format string and list of argument expressions
34326 into remote agent bytecodes and display them as a disassembled list.
34327 This command is useful for debugging the agent version of dynamic
34328 printf (@pxref{Dynamic Printf}).
34330 @kindex maint info breakpoints
34331 @item @anchor{maint info breakpoints}maint info breakpoints
34332 Using the same format as @samp{info breakpoints}, display both the
34333 breakpoints you've set explicitly, and those @value{GDBN} is using for
34334 internal purposes. Internal breakpoints are shown with negative
34335 breakpoint numbers. The type column identifies what kind of breakpoint
34340 Normal, explicitly set breakpoint.
34343 Normal, explicitly set watchpoint.
34346 Internal breakpoint, used to handle correctly stepping through
34347 @code{longjmp} calls.
34349 @item longjmp resume
34350 Internal breakpoint at the target of a @code{longjmp}.
34353 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34356 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34359 Shared library events.
34363 @kindex maint info btrace
34364 @item maint info btrace
34365 Pint information about raw branch tracing data.
34367 @kindex maint btrace packet-history
34368 @item maint btrace packet-history
34369 Print the raw branch trace packets that are used to compute the
34370 execution history for the @samp{record btrace} command. Both the
34371 information and the format in which it is printed depend on the btrace
34376 For the BTS recording format, print a list of blocks of sequential
34377 code. For each block, the following information is printed:
34381 Newer blocks have higher numbers. The oldest block has number zero.
34382 @item Lowest @samp{PC}
34383 @item Highest @samp{PC}
34387 For the Intel Processor Trace recording format, print a list of
34388 Intel Processor Trace packets. For each packet, the following
34389 information is printed:
34392 @item Packet number
34393 Newer packets have higher numbers. The oldest packet has number zero.
34395 The packet's offset in the trace stream.
34396 @item Packet opcode and payload
34400 @kindex maint btrace clear-packet-history
34401 @item maint btrace clear-packet-history
34402 Discards the cached packet history printed by the @samp{maint btrace
34403 packet-history} command. The history will be computed again when
34406 @kindex maint btrace clear
34407 @item maint btrace clear
34408 Discard the branch trace data. The data will be fetched anew and the
34409 branch trace will be recomputed when needed.
34411 This implicitly truncates the branch trace to a single branch trace
34412 buffer. When updating branch trace incrementally, the branch trace
34413 available to @value{GDBN} may be bigger than a single branch trace
34416 @kindex maint set btrace pt skip-pad
34417 @item maint set btrace pt skip-pad
34418 @kindex maint show btrace pt skip-pad
34419 @item maint show btrace pt skip-pad
34420 Control whether @value{GDBN} will skip PAD packets when computing the
34423 @kindex set displaced-stepping
34424 @kindex show displaced-stepping
34425 @cindex displaced stepping support
34426 @cindex out-of-line single-stepping
34427 @item set displaced-stepping
34428 @itemx show displaced-stepping
34429 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34430 if the target supports it. Displaced stepping is a way to single-step
34431 over breakpoints without removing them from the inferior, by executing
34432 an out-of-line copy of the instruction that was originally at the
34433 breakpoint location. It is also known as out-of-line single-stepping.
34436 @item set displaced-stepping on
34437 If the target architecture supports it, @value{GDBN} will use
34438 displaced stepping to step over breakpoints.
34440 @item set displaced-stepping off
34441 @value{GDBN} will not use displaced stepping to step over breakpoints,
34442 even if such is supported by the target architecture.
34444 @cindex non-stop mode, and @samp{set displaced-stepping}
34445 @item set displaced-stepping auto
34446 This is the default mode. @value{GDBN} will use displaced stepping
34447 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34448 architecture supports displaced stepping.
34451 @kindex maint check-psymtabs
34452 @item maint check-psymtabs
34453 Check the consistency of currently expanded psymtabs versus symtabs.
34454 Use this to check, for example, whether a symbol is in one but not the other.
34456 @kindex maint check-symtabs
34457 @item maint check-symtabs
34458 Check the consistency of currently expanded symtabs.
34460 @kindex maint expand-symtabs
34461 @item maint expand-symtabs [@var{regexp}]
34462 Expand symbol tables.
34463 If @var{regexp} is specified, only expand symbol tables for file
34464 names matching @var{regexp}.
34466 @kindex maint set catch-demangler-crashes
34467 @kindex maint show catch-demangler-crashes
34468 @cindex demangler crashes
34469 @item maint set catch-demangler-crashes [on|off]
34470 @itemx maint show catch-demangler-crashes
34471 Control whether @value{GDBN} should attempt to catch crashes in the
34472 symbol name demangler. The default is to attempt to catch crashes.
34473 If enabled, the first time a crash is caught, a core file is created,
34474 the offending symbol is displayed and the user is presented with the
34475 option to terminate the current session.
34477 @kindex maint cplus first_component
34478 @item maint cplus first_component @var{name}
34479 Print the first C@t{++} class/namespace component of @var{name}.
34481 @kindex maint cplus namespace
34482 @item maint cplus namespace
34483 Print the list of possible C@t{++} namespaces.
34485 @kindex maint deprecate
34486 @kindex maint undeprecate
34487 @cindex deprecated commands
34488 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34489 @itemx maint undeprecate @var{command}
34490 Deprecate or undeprecate the named @var{command}. Deprecated commands
34491 cause @value{GDBN} to issue a warning when you use them. The optional
34492 argument @var{replacement} says which newer command should be used in
34493 favor of the deprecated one; if it is given, @value{GDBN} will mention
34494 the replacement as part of the warning.
34496 @kindex maint dump-me
34497 @item maint dump-me
34498 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34499 Cause a fatal signal in the debugger and force it to dump its core.
34500 This is supported only on systems which support aborting a program
34501 with the @code{SIGQUIT} signal.
34503 @kindex maint internal-error
34504 @kindex maint internal-warning
34505 @kindex maint demangler-warning
34506 @cindex demangler crashes
34507 @item maint internal-error @r{[}@var{message-text}@r{]}
34508 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34509 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34511 Cause @value{GDBN} to call the internal function @code{internal_error},
34512 @code{internal_warning} or @code{demangler_warning} and hence behave
34513 as though an internal problem has been detected. In addition to
34514 reporting the internal problem, these functions give the user the
34515 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34516 and @code{internal_warning}) create a core file of the current
34517 @value{GDBN} session.
34519 These commands take an optional parameter @var{message-text} that is
34520 used as the text of the error or warning message.
34522 Here's an example of using @code{internal-error}:
34525 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34526 @dots{}/maint.c:121: internal-error: testing, 1, 2
34527 A problem internal to GDB has been detected. Further
34528 debugging may prove unreliable.
34529 Quit this debugging session? (y or n) @kbd{n}
34530 Create a core file? (y or n) @kbd{n}
34534 @cindex @value{GDBN} internal error
34535 @cindex internal errors, control of @value{GDBN} behavior
34536 @cindex demangler crashes
34538 @kindex maint set internal-error
34539 @kindex maint show internal-error
34540 @kindex maint set internal-warning
34541 @kindex maint show internal-warning
34542 @kindex maint set demangler-warning
34543 @kindex maint show demangler-warning
34544 @item maint set internal-error @var{action} [ask|yes|no]
34545 @itemx maint show internal-error @var{action}
34546 @itemx maint set internal-warning @var{action} [ask|yes|no]
34547 @itemx maint show internal-warning @var{action}
34548 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34549 @itemx maint show demangler-warning @var{action}
34550 When @value{GDBN} reports an internal problem (error or warning) it
34551 gives the user the opportunity to both quit @value{GDBN} and create a
34552 core file of the current @value{GDBN} session. These commands let you
34553 override the default behaviour for each particular @var{action},
34554 described in the table below.
34558 You can specify that @value{GDBN} should always (yes) or never (no)
34559 quit. The default is to ask the user what to do.
34562 You can specify that @value{GDBN} should always (yes) or never (no)
34563 create a core file. The default is to ask the user what to do. Note
34564 that there is no @code{corefile} option for @code{demangler-warning}:
34565 demangler warnings always create a core file and this cannot be
34569 @kindex maint packet
34570 @item maint packet @var{text}
34571 If @value{GDBN} is talking to an inferior via the serial protocol,
34572 then this command sends the string @var{text} to the inferior, and
34573 displays the response packet. @value{GDBN} supplies the initial
34574 @samp{$} character, the terminating @samp{#} character, and the
34577 @kindex maint print architecture
34578 @item maint print architecture @r{[}@var{file}@r{]}
34579 Print the entire architecture configuration. The optional argument
34580 @var{file} names the file where the output goes.
34582 @kindex maint print c-tdesc
34583 @item maint print c-tdesc
34584 Print the current target description (@pxref{Target Descriptions}) as
34585 a C source file. The created source file can be used in @value{GDBN}
34586 when an XML parser is not available to parse the description.
34588 @kindex maint print dummy-frames
34589 @item maint print dummy-frames
34590 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34593 (@value{GDBP}) @kbd{b add}
34595 (@value{GDBP}) @kbd{print add(2,3)}
34596 Breakpoint 2, add (a=2, b=3) at @dots{}
34598 The program being debugged stopped while in a function called from GDB.
34600 (@value{GDBP}) @kbd{maint print dummy-frames}
34601 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34605 Takes an optional file parameter.
34607 @kindex maint print registers
34608 @kindex maint print raw-registers
34609 @kindex maint print cooked-registers
34610 @kindex maint print register-groups
34611 @kindex maint print remote-registers
34612 @item maint print registers @r{[}@var{file}@r{]}
34613 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34614 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34615 @itemx maint print register-groups @r{[}@var{file}@r{]}
34616 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34617 Print @value{GDBN}'s internal register data structures.
34619 The command @code{maint print raw-registers} includes the contents of
34620 the raw register cache; the command @code{maint print
34621 cooked-registers} includes the (cooked) value of all registers,
34622 including registers which aren't available on the target nor visible
34623 to user; the command @code{maint print register-groups} includes the
34624 groups that each register is a member of; and the command @code{maint
34625 print remote-registers} includes the remote target's register numbers
34626 and offsets in the `G' packets.
34628 These commands take an optional parameter, a file name to which to
34629 write the information.
34631 @kindex maint print reggroups
34632 @item maint print reggroups @r{[}@var{file}@r{]}
34633 Print @value{GDBN}'s internal register group data structures. The
34634 optional argument @var{file} tells to what file to write the
34637 The register groups info looks like this:
34640 (@value{GDBP}) @kbd{maint print reggroups}
34653 This command forces @value{GDBN} to flush its internal register cache.
34655 @kindex maint print objfiles
34656 @cindex info for known object files
34657 @item maint print objfiles @r{[}@var{regexp}@r{]}
34658 Print a dump of all known object files.
34659 If @var{regexp} is specified, only print object files whose names
34660 match @var{regexp}. For each object file, this command prints its name,
34661 address in memory, and all of its psymtabs and symtabs.
34663 @kindex maint print user-registers
34664 @cindex user registers
34665 @item maint print user-registers
34666 List all currently available @dfn{user registers}. User registers
34667 typically provide alternate names for actual hardware registers. They
34668 include the four ``standard'' registers @code{$fp}, @code{$pc},
34669 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34670 registers can be used in expressions in the same way as the canonical
34671 register names, but only the latter are listed by the @code{info
34672 registers} and @code{maint print registers} commands.
34674 @kindex maint print section-scripts
34675 @cindex info for known .debug_gdb_scripts-loaded scripts
34676 @item maint print section-scripts [@var{regexp}]
34677 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34678 If @var{regexp} is specified, only print scripts loaded by object files
34679 matching @var{regexp}.
34680 For each script, this command prints its name as specified in the objfile,
34681 and the full path if known.
34682 @xref{dotdebug_gdb_scripts section}.
34684 @kindex maint print statistics
34685 @cindex bcache statistics
34686 @item maint print statistics
34687 This command prints, for each object file in the program, various data
34688 about that object file followed by the byte cache (@dfn{bcache})
34689 statistics for the object file. The objfile data includes the number
34690 of minimal, partial, full, and stabs symbols, the number of types
34691 defined by the objfile, the number of as yet unexpanded psym tables,
34692 the number of line tables and string tables, and the amount of memory
34693 used by the various tables. The bcache statistics include the counts,
34694 sizes, and counts of duplicates of all and unique objects, max,
34695 average, and median entry size, total memory used and its overhead and
34696 savings, and various measures of the hash table size and chain
34699 @kindex maint print target-stack
34700 @cindex target stack description
34701 @item maint print target-stack
34702 A @dfn{target} is an interface between the debugger and a particular
34703 kind of file or process. Targets can be stacked in @dfn{strata},
34704 so that more than one target can potentially respond to a request.
34705 In particular, memory accesses will walk down the stack of targets
34706 until they find a target that is interested in handling that particular
34709 This command prints a short description of each layer that was pushed on
34710 the @dfn{target stack}, starting from the top layer down to the bottom one.
34712 @kindex maint print type
34713 @cindex type chain of a data type
34714 @item maint print type @var{expr}
34715 Print the type chain for a type specified by @var{expr}. The argument
34716 can be either a type name or a symbol. If it is a symbol, the type of
34717 that symbol is described. The type chain produced by this command is
34718 a recursive definition of the data type as stored in @value{GDBN}'s
34719 data structures, including its flags and contained types.
34721 @kindex maint selftest
34723 Run any self tests that were compiled in to @value{GDBN}. This will
34724 print a message showing how many tests were run, and how many failed.
34726 @kindex maint set dwarf always-disassemble
34727 @kindex maint show dwarf always-disassemble
34728 @item maint set dwarf always-disassemble
34729 @item maint show dwarf always-disassemble
34730 Control the behavior of @code{info address} when using DWARF debugging
34733 The default is @code{off}, which means that @value{GDBN} should try to
34734 describe a variable's location in an easily readable format. When
34735 @code{on}, @value{GDBN} will instead display the DWARF location
34736 expression in an assembly-like format. Note that some locations are
34737 too complex for @value{GDBN} to describe simply; in this case you will
34738 always see the disassembly form.
34740 Here is an example of the resulting disassembly:
34743 (gdb) info addr argc
34744 Symbol "argc" is a complex DWARF expression:
34748 For more information on these expressions, see
34749 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34751 @kindex maint set dwarf max-cache-age
34752 @kindex maint show dwarf max-cache-age
34753 @item maint set dwarf max-cache-age
34754 @itemx maint show dwarf max-cache-age
34755 Control the DWARF compilation unit cache.
34757 @cindex DWARF compilation units cache
34758 In object files with inter-compilation-unit references, such as those
34759 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34760 reader needs to frequently refer to previously read compilation units.
34761 This setting controls how long a compilation unit will remain in the
34762 cache if it is not referenced. A higher limit means that cached
34763 compilation units will be stored in memory longer, and more total
34764 memory will be used. Setting it to zero disables caching, which will
34765 slow down @value{GDBN} startup, but reduce memory consumption.
34767 @kindex maint set profile
34768 @kindex maint show profile
34769 @cindex profiling GDB
34770 @item maint set profile
34771 @itemx maint show profile
34772 Control profiling of @value{GDBN}.
34774 Profiling will be disabled until you use the @samp{maint set profile}
34775 command to enable it. When you enable profiling, the system will begin
34776 collecting timing and execution count data; when you disable profiling or
34777 exit @value{GDBN}, the results will be written to a log file. Remember that
34778 if you use profiling, @value{GDBN} will overwrite the profiling log file
34779 (often called @file{gmon.out}). If you have a record of important profiling
34780 data in a @file{gmon.out} file, be sure to move it to a safe location.
34782 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34783 compiled with the @samp{-pg} compiler option.
34785 @kindex maint set show-debug-regs
34786 @kindex maint show show-debug-regs
34787 @cindex hardware debug registers
34788 @item maint set show-debug-regs
34789 @itemx maint show show-debug-regs
34790 Control whether to show variables that mirror the hardware debug
34791 registers. Use @code{on} to enable, @code{off} to disable. If
34792 enabled, the debug registers values are shown when @value{GDBN} inserts or
34793 removes a hardware breakpoint or watchpoint, and when the inferior
34794 triggers a hardware-assisted breakpoint or watchpoint.
34796 @kindex maint set show-all-tib
34797 @kindex maint show show-all-tib
34798 @item maint set show-all-tib
34799 @itemx maint show show-all-tib
34800 Control whether to show all non zero areas within a 1k block starting
34801 at thread local base, when using the @samp{info w32 thread-information-block}
34804 @kindex maint set target-async
34805 @kindex maint show target-async
34806 @item maint set target-async
34807 @itemx maint show target-async
34808 This controls whether @value{GDBN} targets operate in synchronous or
34809 asynchronous mode (@pxref{Background Execution}). Normally the
34810 default is asynchronous, if it is available; but this can be changed
34811 to more easily debug problems occurring only in synchronous mode.
34813 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34814 @kindex maint show target-non-stop
34815 @item maint set target-non-stop
34816 @itemx maint show target-non-stop
34818 This controls whether @value{GDBN} targets always operate in non-stop
34819 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34820 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34821 if supported by the target.
34824 @item maint set target-non-stop auto
34825 This is the default mode. @value{GDBN} controls the target in
34826 non-stop mode if the target supports it.
34828 @item maint set target-non-stop on
34829 @value{GDBN} controls the target in non-stop mode even if the target
34830 does not indicate support.
34832 @item maint set target-non-stop off
34833 @value{GDBN} does not control the target in non-stop mode even if the
34834 target supports it.
34837 @kindex maint set per-command
34838 @kindex maint show per-command
34839 @item maint set per-command
34840 @itemx maint show per-command
34841 @cindex resources used by commands
34843 @value{GDBN} can display the resources used by each command.
34844 This is useful in debugging performance problems.
34847 @item maint set per-command space [on|off]
34848 @itemx maint show per-command space
34849 Enable or disable the printing of the memory used by GDB for each command.
34850 If enabled, @value{GDBN} will display how much memory each command
34851 took, following the command's own output.
34852 This can also be requested by invoking @value{GDBN} with the
34853 @option{--statistics} command-line switch (@pxref{Mode Options}).
34855 @item maint set per-command time [on|off]
34856 @itemx maint show per-command time
34857 Enable or disable the printing of the execution time of @value{GDBN}
34859 If enabled, @value{GDBN} will display how much time it
34860 took to execute each command, following the command's own output.
34861 Both CPU time and wallclock time are printed.
34862 Printing both is useful when trying to determine whether the cost is
34863 CPU or, e.g., disk/network latency.
34864 Note that the CPU time printed is for @value{GDBN} only, it does not include
34865 the execution time of the inferior because there's no mechanism currently
34866 to compute how much time was spent by @value{GDBN} and how much time was
34867 spent by the program been debugged.
34868 This can also be requested by invoking @value{GDBN} with the
34869 @option{--statistics} command-line switch (@pxref{Mode Options}).
34871 @item maint set per-command symtab [on|off]
34872 @itemx maint show per-command symtab
34873 Enable or disable the printing of basic symbol table statistics
34875 If enabled, @value{GDBN} will display the following information:
34879 number of symbol tables
34881 number of primary symbol tables
34883 number of blocks in the blockvector
34887 @kindex maint space
34888 @cindex memory used by commands
34889 @item maint space @var{value}
34890 An alias for @code{maint set per-command space}.
34891 A non-zero value enables it, zero disables it.
34894 @cindex time of command execution
34895 @item maint time @var{value}
34896 An alias for @code{maint set per-command time}.
34897 A non-zero value enables it, zero disables it.
34899 @kindex maint translate-address
34900 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34901 Find the symbol stored at the location specified by the address
34902 @var{addr} and an optional section name @var{section}. If found,
34903 @value{GDBN} prints the name of the closest symbol and an offset from
34904 the symbol's location to the specified address. This is similar to
34905 the @code{info address} command (@pxref{Symbols}), except that this
34906 command also allows to find symbols in other sections.
34908 If section was not specified, the section in which the symbol was found
34909 is also printed. For dynamically linked executables, the name of
34910 executable or shared library containing the symbol is printed as well.
34914 The following command is useful for non-interactive invocations of
34915 @value{GDBN}, such as in the test suite.
34918 @item set watchdog @var{nsec}
34919 @kindex set watchdog
34920 @cindex watchdog timer
34921 @cindex timeout for commands
34922 Set the maximum number of seconds @value{GDBN} will wait for the
34923 target operation to finish. If this time expires, @value{GDBN}
34924 reports and error and the command is aborted.
34926 @item show watchdog
34927 Show the current setting of the target wait timeout.
34930 @node Remote Protocol
34931 @appendix @value{GDBN} Remote Serial Protocol
34936 * Stop Reply Packets::
34937 * General Query Packets::
34938 * Architecture-Specific Protocol Details::
34939 * Tracepoint Packets::
34940 * Host I/O Packets::
34942 * Notification Packets::
34943 * Remote Non-Stop::
34944 * Packet Acknowledgment::
34946 * File-I/O Remote Protocol Extension::
34947 * Library List Format::
34948 * Library List Format for SVR4 Targets::
34949 * Memory Map Format::
34950 * Thread List Format::
34951 * Traceframe Info Format::
34952 * Branch Trace Format::
34953 * Branch Trace Configuration Format::
34959 There may be occasions when you need to know something about the
34960 protocol---for example, if there is only one serial port to your target
34961 machine, you might want your program to do something special if it
34962 recognizes a packet meant for @value{GDBN}.
34964 In the examples below, @samp{->} and @samp{<-} are used to indicate
34965 transmitted and received data, respectively.
34967 @cindex protocol, @value{GDBN} remote serial
34968 @cindex serial protocol, @value{GDBN} remote
34969 @cindex remote serial protocol
34970 All @value{GDBN} commands and responses (other than acknowledgments
34971 and notifications, see @ref{Notification Packets}) are sent as a
34972 @var{packet}. A @var{packet} is introduced with the character
34973 @samp{$}, the actual @var{packet-data}, and the terminating character
34974 @samp{#} followed by a two-digit @var{checksum}:
34977 @code{$}@var{packet-data}@code{#}@var{checksum}
34981 @cindex checksum, for @value{GDBN} remote
34983 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34984 characters between the leading @samp{$} and the trailing @samp{#} (an
34985 eight bit unsigned checksum).
34987 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34988 specification also included an optional two-digit @var{sequence-id}:
34991 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34994 @cindex sequence-id, for @value{GDBN} remote
34996 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34997 has never output @var{sequence-id}s. Stubs that handle packets added
34998 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35000 When either the host or the target machine receives a packet, the first
35001 response expected is an acknowledgment: either @samp{+} (to indicate
35002 the package was received correctly) or @samp{-} (to request
35006 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35011 The @samp{+}/@samp{-} acknowledgments can be disabled
35012 once a connection is established.
35013 @xref{Packet Acknowledgment}, for details.
35015 The host (@value{GDBN}) sends @var{command}s, and the target (the
35016 debugging stub incorporated in your program) sends a @var{response}. In
35017 the case of step and continue @var{command}s, the response is only sent
35018 when the operation has completed, and the target has again stopped all
35019 threads in all attached processes. This is the default all-stop mode
35020 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35021 execution mode; see @ref{Remote Non-Stop}, for details.
35023 @var{packet-data} consists of a sequence of characters with the
35024 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35027 @cindex remote protocol, field separator
35028 Fields within the packet should be separated using @samp{,} @samp{;} or
35029 @samp{:}. Except where otherwise noted all numbers are represented in
35030 @sc{hex} with leading zeros suppressed.
35032 Implementors should note that prior to @value{GDBN} 5.0, the character
35033 @samp{:} could not appear as the third character in a packet (as it
35034 would potentially conflict with the @var{sequence-id}).
35036 @cindex remote protocol, binary data
35037 @anchor{Binary Data}
35038 Binary data in most packets is encoded either as two hexadecimal
35039 digits per byte of binary data. This allowed the traditional remote
35040 protocol to work over connections which were only seven-bit clean.
35041 Some packets designed more recently assume an eight-bit clean
35042 connection, and use a more efficient encoding to send and receive
35045 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35046 as an escape character. Any escaped byte is transmitted as the escape
35047 character followed by the original character XORed with @code{0x20}.
35048 For example, the byte @code{0x7d} would be transmitted as the two
35049 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35050 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35051 @samp{@}}) must always be escaped. Responses sent by the stub
35052 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35053 is not interpreted as the start of a run-length encoded sequence
35056 Response @var{data} can be run-length encoded to save space.
35057 Run-length encoding replaces runs of identical characters with one
35058 instance of the repeated character, followed by a @samp{*} and a
35059 repeat count. The repeat count is itself sent encoded, to avoid
35060 binary characters in @var{data}: a value of @var{n} is sent as
35061 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35062 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35063 code 32) for a repeat count of 3. (This is because run-length
35064 encoding starts to win for counts 3 or more.) Thus, for example,
35065 @samp{0* } is a run-length encoding of ``0000'': the space character
35066 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35069 The printable characters @samp{#} and @samp{$} or with a numeric value
35070 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35071 seven repeats (@samp{$}) can be expanded using a repeat count of only
35072 five (@samp{"}). For example, @samp{00000000} can be encoded as
35075 The error response returned for some packets includes a two character
35076 error number. That number is not well defined.
35078 @cindex empty response, for unsupported packets
35079 For any @var{command} not supported by the stub, an empty response
35080 (@samp{$#00}) should be returned. That way it is possible to extend the
35081 protocol. A newer @value{GDBN} can tell if a packet is supported based
35084 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35085 commands for register access, and the @samp{m} and @samp{M} commands
35086 for memory access. Stubs that only control single-threaded targets
35087 can implement run control with the @samp{c} (continue), and @samp{s}
35088 (step) commands. Stubs that support multi-threading targets should
35089 support the @samp{vCont} command. All other commands are optional.
35094 The following table provides a complete list of all currently defined
35095 @var{command}s and their corresponding response @var{data}.
35096 @xref{File-I/O Remote Protocol Extension}, for details about the File
35097 I/O extension of the remote protocol.
35099 Each packet's description has a template showing the packet's overall
35100 syntax, followed by an explanation of the packet's meaning. We
35101 include spaces in some of the templates for clarity; these are not
35102 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35103 separate its components. For example, a template like @samp{foo
35104 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35105 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35106 @var{baz}. @value{GDBN} does not transmit a space character between the
35107 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35110 @cindex @var{thread-id}, in remote protocol
35111 @anchor{thread-id syntax}
35112 Several packets and replies include a @var{thread-id} field to identify
35113 a thread. Normally these are positive numbers with a target-specific
35114 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35115 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35118 In addition, the remote protocol supports a multiprocess feature in
35119 which the @var{thread-id} syntax is extended to optionally include both
35120 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35121 The @var{pid} (process) and @var{tid} (thread) components each have the
35122 format described above: a positive number with target-specific
35123 interpretation formatted as a big-endian hex string, literal @samp{-1}
35124 to indicate all processes or threads (respectively), or @samp{0} to
35125 indicate an arbitrary process or thread. Specifying just a process, as
35126 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35127 error to specify all processes but a specific thread, such as
35128 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35129 for those packets and replies explicitly documented to include a process
35130 ID, rather than a @var{thread-id}.
35132 The multiprocess @var{thread-id} syntax extensions are only used if both
35133 @value{GDBN} and the stub report support for the @samp{multiprocess}
35134 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35137 Note that all packet forms beginning with an upper- or lower-case
35138 letter, other than those described here, are reserved for future use.
35140 Here are the packet descriptions.
35145 @cindex @samp{!} packet
35146 @anchor{extended mode}
35147 Enable extended mode. In extended mode, the remote server is made
35148 persistent. The @samp{R} packet is used to restart the program being
35154 The remote target both supports and has enabled extended mode.
35158 @cindex @samp{?} packet
35160 Indicate the reason the target halted. The reply is the same as for
35161 step and continue. This packet has a special interpretation when the
35162 target is in non-stop mode; see @ref{Remote Non-Stop}.
35165 @xref{Stop Reply Packets}, for the reply specifications.
35167 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35168 @cindex @samp{A} packet
35169 Initialized @code{argv[]} array passed into program. @var{arglen}
35170 specifies the number of bytes in the hex encoded byte stream
35171 @var{arg}. See @code{gdbserver} for more details.
35176 The arguments were set.
35182 @cindex @samp{b} packet
35183 (Don't use this packet; its behavior is not well-defined.)
35184 Change the serial line speed to @var{baud}.
35186 JTC: @emph{When does the transport layer state change? When it's
35187 received, or after the ACK is transmitted. In either case, there are
35188 problems if the command or the acknowledgment packet is dropped.}
35190 Stan: @emph{If people really wanted to add something like this, and get
35191 it working for the first time, they ought to modify ser-unix.c to send
35192 some kind of out-of-band message to a specially-setup stub and have the
35193 switch happen "in between" packets, so that from remote protocol's point
35194 of view, nothing actually happened.}
35196 @item B @var{addr},@var{mode}
35197 @cindex @samp{B} packet
35198 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35199 breakpoint at @var{addr}.
35201 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35202 (@pxref{insert breakpoint or watchpoint packet}).
35204 @cindex @samp{bc} packet
35207 Backward continue. Execute the target system in reverse. No parameter.
35208 @xref{Reverse Execution}, for more information.
35211 @xref{Stop Reply Packets}, for the reply specifications.
35213 @cindex @samp{bs} packet
35216 Backward single step. Execute one instruction in reverse. No parameter.
35217 @xref{Reverse Execution}, for more information.
35220 @xref{Stop Reply Packets}, for the reply specifications.
35222 @item c @r{[}@var{addr}@r{]}
35223 @cindex @samp{c} packet
35224 Continue at @var{addr}, which is the address to resume. If @var{addr}
35225 is omitted, resume at current address.
35227 This packet is deprecated for multi-threading support. @xref{vCont
35231 @xref{Stop Reply Packets}, for the reply specifications.
35233 @item C @var{sig}@r{[};@var{addr}@r{]}
35234 @cindex @samp{C} packet
35235 Continue with signal @var{sig} (hex signal number). If
35236 @samp{;@var{addr}} is omitted, resume at same address.
35238 This packet is deprecated for multi-threading support. @xref{vCont
35242 @xref{Stop Reply Packets}, for the reply specifications.
35245 @cindex @samp{d} packet
35248 Don't use this packet; instead, define a general set packet
35249 (@pxref{General Query Packets}).
35253 @cindex @samp{D} packet
35254 The first form of the packet is used to detach @value{GDBN} from the
35255 remote system. It is sent to the remote target
35256 before @value{GDBN} disconnects via the @code{detach} command.
35258 The second form, including a process ID, is used when multiprocess
35259 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35260 detach only a specific process. The @var{pid} is specified as a
35261 big-endian hex string.
35271 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35272 @cindex @samp{F} packet
35273 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35274 This is part of the File-I/O protocol extension. @xref{File-I/O
35275 Remote Protocol Extension}, for the specification.
35278 @anchor{read registers packet}
35279 @cindex @samp{g} packet
35280 Read general registers.
35284 @item @var{XX@dots{}}
35285 Each byte of register data is described by two hex digits. The bytes
35286 with the register are transmitted in target byte order. The size of
35287 each register and their position within the @samp{g} packet are
35288 determined by the @value{GDBN} internal gdbarch functions
35289 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35291 When reading registers from a trace frame (@pxref{Analyze Collected
35292 Data,,Using the Collected Data}), the stub may also return a string of
35293 literal @samp{x}'s in place of the register data digits, to indicate
35294 that the corresponding register has not been collected, thus its value
35295 is unavailable. For example, for an architecture with 4 registers of
35296 4 bytes each, the following reply indicates to @value{GDBN} that
35297 registers 0 and 2 have not been collected, while registers 1 and 3
35298 have been collected, and both have zero value:
35302 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35309 @item G @var{XX@dots{}}
35310 @cindex @samp{G} packet
35311 Write general registers. @xref{read registers packet}, for a
35312 description of the @var{XX@dots{}} data.
35322 @item H @var{op} @var{thread-id}
35323 @cindex @samp{H} packet
35324 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35325 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35326 should be @samp{c} for step and continue operations (note that this
35327 is deprecated, supporting the @samp{vCont} command is a better
35328 option), and @samp{g} for other operations. The thread designator
35329 @var{thread-id} has the format and interpretation described in
35330 @ref{thread-id syntax}.
35341 @c 'H': How restrictive (or permissive) is the thread model. If a
35342 @c thread is selected and stopped, are other threads allowed
35343 @c to continue to execute? As I mentioned above, I think the
35344 @c semantics of each command when a thread is selected must be
35345 @c described. For example:
35347 @c 'g': If the stub supports threads and a specific thread is
35348 @c selected, returns the register block from that thread;
35349 @c otherwise returns current registers.
35351 @c 'G' If the stub supports threads and a specific thread is
35352 @c selected, sets the registers of the register block of
35353 @c that thread; otherwise sets current registers.
35355 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35356 @anchor{cycle step packet}
35357 @cindex @samp{i} packet
35358 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35359 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35360 step starting at that address.
35363 @cindex @samp{I} packet
35364 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35368 @cindex @samp{k} packet
35371 The exact effect of this packet is not specified.
35373 For a bare-metal target, it may power cycle or reset the target
35374 system. For that reason, the @samp{k} packet has no reply.
35376 For a single-process target, it may kill that process if possible.
35378 A multiple-process target may choose to kill just one process, or all
35379 that are under @value{GDBN}'s control. For more precise control, use
35380 the vKill packet (@pxref{vKill packet}).
35382 If the target system immediately closes the connection in response to
35383 @samp{k}, @value{GDBN} does not consider the lack of packet
35384 acknowledgment to be an error, and assumes the kill was successful.
35386 If connected using @kbd{target extended-remote}, and the target does
35387 not close the connection in response to a kill request, @value{GDBN}
35388 probes the target state as if a new connection was opened
35389 (@pxref{? packet}).
35391 @item m @var{addr},@var{length}
35392 @cindex @samp{m} packet
35393 Read @var{length} addressable memory units starting at address @var{addr}
35394 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35395 any particular boundary.
35397 The stub need not use any particular size or alignment when gathering
35398 data from memory for the response; even if @var{addr} is word-aligned
35399 and @var{length} is a multiple of the word size, the stub is free to
35400 use byte accesses, or not. For this reason, this packet may not be
35401 suitable for accessing memory-mapped I/O devices.
35402 @cindex alignment of remote memory accesses
35403 @cindex size of remote memory accesses
35404 @cindex memory, alignment and size of remote accesses
35408 @item @var{XX@dots{}}
35409 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35410 The reply may contain fewer addressable memory units than requested if the
35411 server was able to read only part of the region of memory.
35416 @item M @var{addr},@var{length}:@var{XX@dots{}}
35417 @cindex @samp{M} packet
35418 Write @var{length} addressable memory units starting at address @var{addr}
35419 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35420 byte is transmitted as a two-digit hexadecimal number.
35427 for an error (this includes the case where only part of the data was
35432 @cindex @samp{p} packet
35433 Read the value of register @var{n}; @var{n} is in hex.
35434 @xref{read registers packet}, for a description of how the returned
35435 register value is encoded.
35439 @item @var{XX@dots{}}
35440 the register's value
35444 Indicating an unrecognized @var{query}.
35447 @item P @var{n@dots{}}=@var{r@dots{}}
35448 @anchor{write register packet}
35449 @cindex @samp{P} packet
35450 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35451 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35452 digits for each byte in the register (target byte order).
35462 @item q @var{name} @var{params}@dots{}
35463 @itemx Q @var{name} @var{params}@dots{}
35464 @cindex @samp{q} packet
35465 @cindex @samp{Q} packet
35466 General query (@samp{q}) and set (@samp{Q}). These packets are
35467 described fully in @ref{General Query Packets}.
35470 @cindex @samp{r} packet
35471 Reset the entire system.
35473 Don't use this packet; use the @samp{R} packet instead.
35476 @cindex @samp{R} packet
35477 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35478 This packet is only available in extended mode (@pxref{extended mode}).
35480 The @samp{R} packet has no reply.
35482 @item s @r{[}@var{addr}@r{]}
35483 @cindex @samp{s} packet
35484 Single step, resuming at @var{addr}. If
35485 @var{addr} is omitted, resume at same address.
35487 This packet is deprecated for multi-threading support. @xref{vCont
35491 @xref{Stop Reply Packets}, for the reply specifications.
35493 @item S @var{sig}@r{[};@var{addr}@r{]}
35494 @anchor{step with signal packet}
35495 @cindex @samp{S} packet
35496 Step with signal. This is analogous to the @samp{C} packet, but
35497 requests a single-step, rather than a normal resumption of execution.
35499 This packet is deprecated for multi-threading support. @xref{vCont
35503 @xref{Stop Reply Packets}, for the reply specifications.
35505 @item t @var{addr}:@var{PP},@var{MM}
35506 @cindex @samp{t} packet
35507 Search backwards starting at address @var{addr} for a match with pattern
35508 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35509 There must be at least 3 digits in @var{addr}.
35511 @item T @var{thread-id}
35512 @cindex @samp{T} packet
35513 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35518 thread is still alive
35524 Packets starting with @samp{v} are identified by a multi-letter name,
35525 up to the first @samp{;} or @samp{?} (or the end of the packet).
35527 @item vAttach;@var{pid}
35528 @cindex @samp{vAttach} packet
35529 Attach to a new process with the specified process ID @var{pid}.
35530 The process ID is a
35531 hexadecimal integer identifying the process. In all-stop mode, all
35532 threads in the attached process are stopped; in non-stop mode, it may be
35533 attached without being stopped if that is supported by the target.
35535 @c In non-stop mode, on a successful vAttach, the stub should set the
35536 @c current thread to a thread of the newly-attached process. After
35537 @c attaching, GDB queries for the attached process's thread ID with qC.
35538 @c Also note that, from a user perspective, whether or not the
35539 @c target is stopped on attach in non-stop mode depends on whether you
35540 @c use the foreground or background version of the attach command, not
35541 @c on what vAttach does; GDB does the right thing with respect to either
35542 @c stopping or restarting threads.
35544 This packet is only available in extended mode (@pxref{extended mode}).
35550 @item @r{Any stop packet}
35551 for success in all-stop mode (@pxref{Stop Reply Packets})
35553 for success in non-stop mode (@pxref{Remote Non-Stop})
35556 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35557 @cindex @samp{vCont} packet
35558 @anchor{vCont packet}
35559 Resume the inferior, specifying different actions for each thread.
35561 For each inferior thread, the leftmost action with a matching
35562 @var{thread-id} is applied. Threads that don't match any action
35563 remain in their current state. Thread IDs are specified using the
35564 syntax described in @ref{thread-id syntax}. If multiprocess
35565 extensions (@pxref{multiprocess extensions}) are supported, actions
35566 can be specified to match all threads in a process by using the
35567 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35568 @var{thread-id} matches all threads. Specifying no actions is an
35571 Currently supported actions are:
35577 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35581 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35584 @item r @var{start},@var{end}
35585 Step once, and then keep stepping as long as the thread stops at
35586 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35587 The remote stub reports a stop reply when either the thread goes out
35588 of the range or is stopped due to an unrelated reason, such as hitting
35589 a breakpoint. @xref{range stepping}.
35591 If the range is empty (@var{start} == @var{end}), then the action
35592 becomes equivalent to the @samp{s} action. In other words,
35593 single-step once, and report the stop (even if the stepped instruction
35594 jumps to @var{start}).
35596 (A stop reply may be sent at any point even if the PC is still within
35597 the stepping range; for example, it is valid to implement this packet
35598 in a degenerate way as a single instruction step operation.)
35602 The optional argument @var{addr} normally associated with the
35603 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35604 not supported in @samp{vCont}.
35606 The @samp{t} action is only relevant in non-stop mode
35607 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35608 A stop reply should be generated for any affected thread not already stopped.
35609 When a thread is stopped by means of a @samp{t} action,
35610 the corresponding stop reply should indicate that the thread has stopped with
35611 signal @samp{0}, regardless of whether the target uses some other signal
35612 as an implementation detail.
35614 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35615 @samp{r} actions for threads that are already running. Conversely,
35616 the server must ignore @samp{t} actions for threads that are already
35619 @emph{Note:} In non-stop mode, a thread is considered running until
35620 @value{GDBN} acknowleges an asynchronous stop notification for it with
35621 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35623 The stub must support @samp{vCont} if it reports support for
35624 multiprocess extensions (@pxref{multiprocess extensions}).
35627 @xref{Stop Reply Packets}, for the reply specifications.
35630 @cindex @samp{vCont?} packet
35631 Request a list of actions supported by the @samp{vCont} packet.
35635 @item vCont@r{[};@var{action}@dots{}@r{]}
35636 The @samp{vCont} packet is supported. Each @var{action} is a supported
35637 command in the @samp{vCont} packet.
35639 The @samp{vCont} packet is not supported.
35642 @anchor{vCtrlC packet}
35644 @cindex @samp{vCtrlC} packet
35645 Interrupt remote target as if a control-C was pressed on the remote
35646 terminal. This is the equivalent to reacting to the @code{^C}
35647 (@samp{\003}, the control-C character) character in all-stop mode
35648 while the target is running, except this works in non-stop mode.
35649 @xref{interrupting remote targets}, for more info on the all-stop
35660 @item vFile:@var{operation}:@var{parameter}@dots{}
35661 @cindex @samp{vFile} packet
35662 Perform a file operation on the target system. For details,
35663 see @ref{Host I/O Packets}.
35665 @item vFlashErase:@var{addr},@var{length}
35666 @cindex @samp{vFlashErase} packet
35667 Direct the stub to erase @var{length} bytes of flash starting at
35668 @var{addr}. The region may enclose any number of flash blocks, but
35669 its start and end must fall on block boundaries, as indicated by the
35670 flash block size appearing in the memory map (@pxref{Memory Map
35671 Format}). @value{GDBN} groups flash memory programming operations
35672 together, and sends a @samp{vFlashDone} request after each group; the
35673 stub is allowed to delay erase operation until the @samp{vFlashDone}
35674 packet is received.
35684 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35685 @cindex @samp{vFlashWrite} packet
35686 Direct the stub to write data to flash address @var{addr}. The data
35687 is passed in binary form using the same encoding as for the @samp{X}
35688 packet (@pxref{Binary Data}). The memory ranges specified by
35689 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35690 not overlap, and must appear in order of increasing addresses
35691 (although @samp{vFlashErase} packets for higher addresses may already
35692 have been received; the ordering is guaranteed only between
35693 @samp{vFlashWrite} packets). If a packet writes to an address that was
35694 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35695 target-specific method, the results are unpredictable.
35703 for vFlashWrite addressing non-flash memory
35709 @cindex @samp{vFlashDone} packet
35710 Indicate to the stub that flash programming operation is finished.
35711 The stub is permitted to delay or batch the effects of a group of
35712 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35713 @samp{vFlashDone} packet is received. The contents of the affected
35714 regions of flash memory are unpredictable until the @samp{vFlashDone}
35715 request is completed.
35717 @item vKill;@var{pid}
35718 @cindex @samp{vKill} packet
35719 @anchor{vKill packet}
35720 Kill the process with the specified process ID @var{pid}, which is a
35721 hexadecimal integer identifying the process. This packet is used in
35722 preference to @samp{k} when multiprocess protocol extensions are
35723 supported; see @ref{multiprocess extensions}.
35733 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35734 @cindex @samp{vRun} packet
35735 Run the program @var{filename}, passing it each @var{argument} on its
35736 command line. The file and arguments are hex-encoded strings. If
35737 @var{filename} is an empty string, the stub may use a default program
35738 (e.g.@: the last program run). The program is created in the stopped
35741 @c FIXME: What about non-stop mode?
35743 This packet is only available in extended mode (@pxref{extended mode}).
35749 @item @r{Any stop packet}
35750 for success (@pxref{Stop Reply Packets})
35754 @cindex @samp{vStopped} packet
35755 @xref{Notification Packets}.
35757 @item X @var{addr},@var{length}:@var{XX@dots{}}
35759 @cindex @samp{X} packet
35760 Write data to memory, where the data is transmitted in binary.
35761 Memory is specified by its address @var{addr} and number of addressable memory
35762 units @var{length} (@pxref{addressable memory unit});
35763 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35773 @item z @var{type},@var{addr},@var{kind}
35774 @itemx Z @var{type},@var{addr},@var{kind}
35775 @anchor{insert breakpoint or watchpoint packet}
35776 @cindex @samp{z} packet
35777 @cindex @samp{Z} packets
35778 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35779 watchpoint starting at address @var{address} of kind @var{kind}.
35781 Each breakpoint and watchpoint packet @var{type} is documented
35784 @emph{Implementation notes: A remote target shall return an empty string
35785 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35786 remote target shall support either both or neither of a given
35787 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35788 avoid potential problems with duplicate packets, the operations should
35789 be implemented in an idempotent way.}
35791 @item z0,@var{addr},@var{kind}
35792 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35793 @cindex @samp{z0} packet
35794 @cindex @samp{Z0} packet
35795 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
35796 @var{addr} of type @var{kind}.
35798 A software breakpoint is implemented by replacing the instruction at
35799 @var{addr} with a software breakpoint or trap instruction. The
35800 @var{kind} is target-specific and typically indicates the size of the
35801 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
35802 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35803 architectures have additional meanings for @var{kind}
35804 (@pxref{Architecture-Specific Protocol Details}); if no
35805 architecture-specific value is being used, it should be @samp{0}.
35806 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
35807 conditional expressions in bytecode form that should be evaluated on
35808 the target's side. These are the conditions that should be taken into
35809 consideration when deciding if the breakpoint trigger should be
35810 reported back to @value{GDBN}.
35812 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35813 for how to best report a software breakpoint event to @value{GDBN}.
35815 The @var{cond_list} parameter is comprised of a series of expressions,
35816 concatenated without separators. Each expression has the following form:
35820 @item X @var{len},@var{expr}
35821 @var{len} is the length of the bytecode expression and @var{expr} is the
35822 actual conditional expression in bytecode form.
35826 The optional @var{cmd_list} parameter introduces commands that may be
35827 run on the target, rather than being reported back to @value{GDBN}.
35828 The parameter starts with a numeric flag @var{persist}; if the flag is
35829 nonzero, then the breakpoint may remain active and the commands
35830 continue to be run even when @value{GDBN} disconnects from the target.
35831 Following this flag is a series of expressions concatenated with no
35832 separators. Each expression has the following form:
35836 @item X @var{len},@var{expr}
35837 @var{len} is the length of the bytecode expression and @var{expr} is the
35838 actual conditional expression in bytecode form.
35842 @emph{Implementation note: It is possible for a target to copy or move
35843 code that contains software breakpoints (e.g., when implementing
35844 overlays). The behavior of this packet, in the presence of such a
35845 target, is not defined.}
35857 @item z1,@var{addr},@var{kind}
35858 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35859 @cindex @samp{z1} packet
35860 @cindex @samp{Z1} packet
35861 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35862 address @var{addr}.
35864 A hardware breakpoint is implemented using a mechanism that is not
35865 dependent on being able to modify the target's memory. The
35866 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
35867 same meaning as in @samp{Z0} packets.
35869 @emph{Implementation note: A hardware breakpoint is not affected by code
35882 @item z2,@var{addr},@var{kind}
35883 @itemx Z2,@var{addr},@var{kind}
35884 @cindex @samp{z2} packet
35885 @cindex @samp{Z2} packet
35886 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35887 The number of bytes to watch is specified by @var{kind}.
35899 @item z3,@var{addr},@var{kind}
35900 @itemx Z3,@var{addr},@var{kind}
35901 @cindex @samp{z3} packet
35902 @cindex @samp{Z3} packet
35903 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35904 The number of bytes to watch is specified by @var{kind}.
35916 @item z4,@var{addr},@var{kind}
35917 @itemx Z4,@var{addr},@var{kind}
35918 @cindex @samp{z4} packet
35919 @cindex @samp{Z4} packet
35920 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35921 The number of bytes to watch is specified by @var{kind}.
35935 @node Stop Reply Packets
35936 @section Stop Reply Packets
35937 @cindex stop reply packets
35939 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35940 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35941 receive any of the below as a reply. Except for @samp{?}
35942 and @samp{vStopped}, that reply is only returned
35943 when the target halts. In the below the exact meaning of @dfn{signal
35944 number} is defined by the header @file{include/gdb/signals.h} in the
35945 @value{GDBN} source code.
35947 In non-stop mode, the server will simply reply @samp{OK} to commands
35948 such as @samp{vCont}; any stop will be the subject of a future
35949 notification. @xref{Remote Non-Stop}.
35951 As in the description of request packets, we include spaces in the
35952 reply templates for clarity; these are not part of the reply packet's
35953 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35959 The program received signal number @var{AA} (a two-digit hexadecimal
35960 number). This is equivalent to a @samp{T} response with no
35961 @var{n}:@var{r} pairs.
35963 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35964 @cindex @samp{T} packet reply
35965 The program received signal number @var{AA} (a two-digit hexadecimal
35966 number). This is equivalent to an @samp{S} response, except that the
35967 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35968 and other information directly in the stop reply packet, reducing
35969 round-trip latency. Single-step and breakpoint traps are reported
35970 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35974 If @var{n} is a hexadecimal number, it is a register number, and the
35975 corresponding @var{r} gives that register's value. The data @var{r} is a
35976 series of bytes in target byte order, with each byte given by a
35977 two-digit hex number.
35980 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35981 the stopped thread, as specified in @ref{thread-id syntax}.
35984 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35985 the core on which the stop event was detected.
35988 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35989 specific event that stopped the target. The currently defined stop
35990 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35991 signal. At most one stop reason should be present.
35994 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35995 and go on to the next; this allows us to extend the protocol in the
35999 The currently defined stop reasons are:
36005 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36008 @item syscall_entry
36009 @itemx syscall_return
36010 The packet indicates a syscall entry or return, and @var{r} is the
36011 syscall number, in hex.
36013 @cindex shared library events, remote reply
36015 The packet indicates that the loaded libraries have changed.
36016 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36017 list of loaded libraries. The @var{r} part is ignored.
36019 @cindex replay log events, remote reply
36021 The packet indicates that the target cannot continue replaying
36022 logged execution events, because it has reached the end (or the
36023 beginning when executing backward) of the log. The value of @var{r}
36024 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36025 for more information.
36028 @anchor{swbreak stop reason}
36029 The packet indicates a software breakpoint instruction was executed,
36030 irrespective of whether it was @value{GDBN} that planted the
36031 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36032 part must be left empty.
36034 On some architectures, such as x86, at the architecture level, when a
36035 breakpoint instruction executes the program counter points at the
36036 breakpoint address plus an offset. On such targets, the stub is
36037 responsible for adjusting the PC to point back at the breakpoint
36040 This packet should not be sent by default; older @value{GDBN} versions
36041 did not support it. @value{GDBN} requests it, by supplying an
36042 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36043 remote stub must also supply the appropriate @samp{qSupported} feature
36044 indicating support.
36046 This packet is required for correct non-stop mode operation.
36049 The packet indicates the target stopped for a hardware breakpoint.
36050 The @var{r} part must be left empty.
36052 The same remarks about @samp{qSupported} and non-stop mode above
36055 @cindex fork events, remote reply
36057 The packet indicates that @code{fork} was called, and @var{r}
36058 is the thread ID of the new child process. Refer to
36059 @ref{thread-id syntax} for the format of the @var{thread-id}
36060 field. This packet is only applicable to targets that support
36063 This packet should not be sent by default; older @value{GDBN} versions
36064 did not support it. @value{GDBN} requests it, by supplying an
36065 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36066 remote stub must also supply the appropriate @samp{qSupported} feature
36067 indicating support.
36069 @cindex vfork events, remote reply
36071 The packet indicates that @code{vfork} was called, and @var{r}
36072 is the thread ID of the new child process. Refer to
36073 @ref{thread-id syntax} for the format of the @var{thread-id}
36074 field. This packet is only applicable to targets that support
36077 This packet should not be sent by default; older @value{GDBN} versions
36078 did not support it. @value{GDBN} requests it, by supplying an
36079 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36080 remote stub must also supply the appropriate @samp{qSupported} feature
36081 indicating support.
36083 @cindex vforkdone events, remote reply
36085 The packet indicates that a child process created by a vfork
36086 has either called @code{exec} or terminated, so that the
36087 address spaces of the parent and child process are no longer
36088 shared. The @var{r} part is ignored. This packet is only
36089 applicable to targets that support vforkdone events.
36091 This packet should not be sent by default; older @value{GDBN} versions
36092 did not support it. @value{GDBN} requests it, by supplying an
36093 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36094 remote stub must also supply the appropriate @samp{qSupported} feature
36095 indicating support.
36097 @cindex exec events, remote reply
36099 The packet indicates that @code{execve} was called, and @var{r}
36100 is the absolute pathname of the file that was executed, in hex.
36101 This packet is only applicable to targets that support exec events.
36103 This packet should not be sent by default; older @value{GDBN} versions
36104 did not support it. @value{GDBN} requests it, by supplying an
36105 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36106 remote stub must also supply the appropriate @samp{qSupported} feature
36107 indicating support.
36109 @cindex thread create event, remote reply
36110 @anchor{thread create event}
36112 The packet indicates that the thread was just created. The new thread
36113 is stopped until @value{GDBN} sets it running with a resumption packet
36114 (@pxref{vCont packet}). This packet should not be sent by default;
36115 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36116 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36117 @var{r} part is ignored.
36122 @itemx W @var{AA} ; process:@var{pid}
36123 The process exited, and @var{AA} is the exit status. This is only
36124 applicable to certain targets.
36126 The second form of the response, including the process ID of the
36127 exited process, can be used only when @value{GDBN} has reported
36128 support for multiprocess protocol extensions; see @ref{multiprocess
36129 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36133 @itemx X @var{AA} ; process:@var{pid}
36134 The process terminated with signal @var{AA}.
36136 The second form of the response, including the process ID of the
36137 terminated process, can be used only when @value{GDBN} has reported
36138 support for multiprocess protocol extensions; see @ref{multiprocess
36139 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36142 @anchor{thread exit event}
36143 @cindex thread exit event, remote reply
36144 @item w @var{AA} ; @var{tid}
36146 The thread exited, and @var{AA} is the exit status. This response
36147 should not be sent by default; @value{GDBN} requests it with the
36148 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36149 @var{AA} is formatted as a big-endian hex string.
36152 There are no resumed threads left in the target. In other words, even
36153 though the process is alive, the last resumed thread has exited. For
36154 example, say the target process has two threads: thread 1 and thread
36155 2. The client leaves thread 1 stopped, and resumes thread 2, which
36156 subsequently exits. At this point, even though the process is still
36157 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36158 executing either. The @samp{N} stop reply thus informs the client
36159 that it can stop waiting for stop replies. This packet should not be
36160 sent by default; older @value{GDBN} versions did not support it.
36161 @value{GDBN} requests it, by supplying an appropriate
36162 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36163 also supply the appropriate @samp{qSupported} feature indicating
36166 @item O @var{XX}@dots{}
36167 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36168 written as the program's console output. This can happen at any time
36169 while the program is running and the debugger should continue to wait
36170 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36172 @item F @var{call-id},@var{parameter}@dots{}
36173 @var{call-id} is the identifier which says which host system call should
36174 be called. This is just the name of the function. Translation into the
36175 correct system call is only applicable as it's defined in @value{GDBN}.
36176 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36179 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36180 this very system call.
36182 The target replies with this packet when it expects @value{GDBN} to
36183 call a host system call on behalf of the target. @value{GDBN} replies
36184 with an appropriate @samp{F} packet and keeps up waiting for the next
36185 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36186 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36187 Protocol Extension}, for more details.
36191 @node General Query Packets
36192 @section General Query Packets
36193 @cindex remote query requests
36195 Packets starting with @samp{q} are @dfn{general query packets};
36196 packets starting with @samp{Q} are @dfn{general set packets}. General
36197 query and set packets are a semi-unified form for retrieving and
36198 sending information to and from the stub.
36200 The initial letter of a query or set packet is followed by a name
36201 indicating what sort of thing the packet applies to. For example,
36202 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36203 definitions with the stub. These packet names follow some
36208 The name must not contain commas, colons or semicolons.
36210 Most @value{GDBN} query and set packets have a leading upper case
36213 The names of custom vendor packets should use a company prefix, in
36214 lower case, followed by a period. For example, packets designed at
36215 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36216 foos) or @samp{Qacme.bar} (for setting bars).
36219 The name of a query or set packet should be separated from any
36220 parameters by a @samp{:}; the parameters themselves should be
36221 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36222 full packet name, and check for a separator or the end of the packet,
36223 in case two packet names share a common prefix. New packets should not begin
36224 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36225 packets predate these conventions, and have arguments without any terminator
36226 for the packet name; we suspect they are in widespread use in places that
36227 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36228 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36231 Like the descriptions of the other packets, each description here
36232 has a template showing the packet's overall syntax, followed by an
36233 explanation of the packet's meaning. We include spaces in some of the
36234 templates for clarity; these are not part of the packet's syntax. No
36235 @value{GDBN} packet uses spaces to separate its components.
36237 Here are the currently defined query and set packets:
36243 Turn on or off the agent as a helper to perform some debugging operations
36244 delegated from @value{GDBN} (@pxref{Control Agent}).
36246 @item QAllow:@var{op}:@var{val}@dots{}
36247 @cindex @samp{QAllow} packet
36248 Specify which operations @value{GDBN} expects to request of the
36249 target, as a semicolon-separated list of operation name and value
36250 pairs. Possible values for @var{op} include @samp{WriteReg},
36251 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36252 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36253 indicating that @value{GDBN} will not request the operation, or 1,
36254 indicating that it may. (The target can then use this to set up its
36255 own internals optimally, for instance if the debugger never expects to
36256 insert breakpoints, it may not need to install its own trap handler.)
36259 @cindex current thread, remote request
36260 @cindex @samp{qC} packet
36261 Return the current thread ID.
36265 @item QC @var{thread-id}
36266 Where @var{thread-id} is a thread ID as documented in
36267 @ref{thread-id syntax}.
36268 @item @r{(anything else)}
36269 Any other reply implies the old thread ID.
36272 @item qCRC:@var{addr},@var{length}
36273 @cindex CRC of memory block, remote request
36274 @cindex @samp{qCRC} packet
36275 @anchor{qCRC packet}
36276 Compute the CRC checksum of a block of memory using CRC-32 defined in
36277 IEEE 802.3. The CRC is computed byte at a time, taking the most
36278 significant bit of each byte first. The initial pattern code
36279 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36281 @emph{Note:} This is the same CRC used in validating separate debug
36282 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36283 Files}). However the algorithm is slightly different. When validating
36284 separate debug files, the CRC is computed taking the @emph{least}
36285 significant bit of each byte first, and the final result is inverted to
36286 detect trailing zeros.
36291 An error (such as memory fault)
36292 @item C @var{crc32}
36293 The specified memory region's checksum is @var{crc32}.
36296 @item QDisableRandomization:@var{value}
36297 @cindex disable address space randomization, remote request
36298 @cindex @samp{QDisableRandomization} packet
36299 Some target operating systems will randomize the virtual address space
36300 of the inferior process as a security feature, but provide a feature
36301 to disable such randomization, e.g.@: to allow for a more deterministic
36302 debugging experience. On such systems, this packet with a @var{value}
36303 of 1 directs the target to disable address space randomization for
36304 processes subsequently started via @samp{vRun} packets, while a packet
36305 with a @var{value} of 0 tells the target to enable address space
36308 This packet is only available in extended mode (@pxref{extended mode}).
36313 The request succeeded.
36316 An error occurred. The error number @var{nn} is given as hex digits.
36319 An empty reply indicates that @samp{QDisableRandomization} is not supported
36323 This packet is not probed by default; the remote stub must request it,
36324 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36325 This should only be done on targets that actually support disabling
36326 address space randomization.
36329 @itemx qsThreadInfo
36330 @cindex list active threads, remote request
36331 @cindex @samp{qfThreadInfo} packet
36332 @cindex @samp{qsThreadInfo} packet
36333 Obtain a list of all active thread IDs from the target (OS). Since there
36334 may be too many active threads to fit into one reply packet, this query
36335 works iteratively: it may require more than one query/reply sequence to
36336 obtain the entire list of threads. The first query of the sequence will
36337 be the @samp{qfThreadInfo} query; subsequent queries in the
36338 sequence will be the @samp{qsThreadInfo} query.
36340 NOTE: This packet replaces the @samp{qL} query (see below).
36344 @item m @var{thread-id}
36346 @item m @var{thread-id},@var{thread-id}@dots{}
36347 a comma-separated list of thread IDs
36349 (lower case letter @samp{L}) denotes end of list.
36352 In response to each query, the target will reply with a list of one or
36353 more thread IDs, separated by commas.
36354 @value{GDBN} will respond to each reply with a request for more thread
36355 ids (using the @samp{qs} form of the query), until the target responds
36356 with @samp{l} (lower-case ell, for @dfn{last}).
36357 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36360 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36361 initial connection with the remote target, and the very first thread ID
36362 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36363 message. Therefore, the stub should ensure that the first thread ID in
36364 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36366 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36367 @cindex get thread-local storage address, remote request
36368 @cindex @samp{qGetTLSAddr} packet
36369 Fetch the address associated with thread local storage specified
36370 by @var{thread-id}, @var{offset}, and @var{lm}.
36372 @var{thread-id} is the thread ID associated with the
36373 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36375 @var{offset} is the (big endian, hex encoded) offset associated with the
36376 thread local variable. (This offset is obtained from the debug
36377 information associated with the variable.)
36379 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36380 load module associated with the thread local storage. For example,
36381 a @sc{gnu}/Linux system will pass the link map address of the shared
36382 object associated with the thread local storage under consideration.
36383 Other operating environments may choose to represent the load module
36384 differently, so the precise meaning of this parameter will vary.
36388 @item @var{XX}@dots{}
36389 Hex encoded (big endian) bytes representing the address of the thread
36390 local storage requested.
36393 An error occurred. The error number @var{nn} is given as hex digits.
36396 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36399 @item qGetTIBAddr:@var{thread-id}
36400 @cindex get thread information block address
36401 @cindex @samp{qGetTIBAddr} packet
36402 Fetch address of the Windows OS specific Thread Information Block.
36404 @var{thread-id} is the thread ID associated with the thread.
36408 @item @var{XX}@dots{}
36409 Hex encoded (big endian) bytes representing the linear address of the
36410 thread information block.
36413 An error occured. This means that either the thread was not found, or the
36414 address could not be retrieved.
36417 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36420 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36421 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36422 digit) is one to indicate the first query and zero to indicate a
36423 subsequent query; @var{threadcount} (two hex digits) is the maximum
36424 number of threads the response packet can contain; and @var{nextthread}
36425 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36426 returned in the response as @var{argthread}.
36428 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36432 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36433 Where: @var{count} (two hex digits) is the number of threads being
36434 returned; @var{done} (one hex digit) is zero to indicate more threads
36435 and one indicates no further threads; @var{argthreadid} (eight hex
36436 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36437 is a sequence of thread IDs, @var{threadid} (eight hex
36438 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36442 @cindex section offsets, remote request
36443 @cindex @samp{qOffsets} packet
36444 Get section offsets that the target used when relocating the downloaded
36449 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36450 Relocate the @code{Text} section by @var{xxx} from its original address.
36451 Relocate the @code{Data} section by @var{yyy} from its original address.
36452 If the object file format provides segment information (e.g.@: @sc{elf}
36453 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36454 segments by the supplied offsets.
36456 @emph{Note: while a @code{Bss} offset may be included in the response,
36457 @value{GDBN} ignores this and instead applies the @code{Data} offset
36458 to the @code{Bss} section.}
36460 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36461 Relocate the first segment of the object file, which conventionally
36462 contains program code, to a starting address of @var{xxx}. If
36463 @samp{DataSeg} is specified, relocate the second segment, which
36464 conventionally contains modifiable data, to a starting address of
36465 @var{yyy}. @value{GDBN} will report an error if the object file
36466 does not contain segment information, or does not contain at least
36467 as many segments as mentioned in the reply. Extra segments are
36468 kept at fixed offsets relative to the last relocated segment.
36471 @item qP @var{mode} @var{thread-id}
36472 @cindex thread information, remote request
36473 @cindex @samp{qP} packet
36474 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36475 encoded 32 bit mode; @var{thread-id} is a thread ID
36476 (@pxref{thread-id syntax}).
36478 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36481 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36485 @cindex non-stop mode, remote request
36486 @cindex @samp{QNonStop} packet
36488 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36489 @xref{Remote Non-Stop}, for more information.
36494 The request succeeded.
36497 An error occurred. The error number @var{nn} is given as hex digits.
36500 An empty reply indicates that @samp{QNonStop} is not supported by
36504 This packet is not probed by default; the remote stub must request it,
36505 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36506 Use of this packet is controlled by the @code{set non-stop} command;
36507 @pxref{Non-Stop Mode}.
36509 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36510 @itemx QCatchSyscalls:0
36511 @cindex catch syscalls from inferior, remote request
36512 @cindex @samp{QCatchSyscalls} packet
36513 @anchor{QCatchSyscalls}
36514 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36515 catching syscalls from the inferior process.
36517 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36518 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36519 is listed, every system call should be reported.
36521 Note that if a syscall not in the list is reported, @value{GDBN} will
36522 still filter the event according to its own list from all corresponding
36523 @code{catch syscall} commands. However, it is more efficient to only
36524 report the requested syscalls.
36526 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36527 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36529 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36530 kept for the new process too. On targets where exec may affect syscall
36531 numbers, for example with exec between 32 and 64-bit processes, the
36532 client should send a new packet with the new syscall list.
36537 The request succeeded.
36540 An error occurred. @var{nn} are hex digits.
36543 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36547 Use of this packet is controlled by the @code{set remote catch-syscalls}
36548 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36549 This packet is not probed by default; the remote stub must request it,
36550 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36552 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36553 @cindex pass signals to inferior, remote request
36554 @cindex @samp{QPassSignals} packet
36555 @anchor{QPassSignals}
36556 Each listed @var{signal} should be passed directly to the inferior process.
36557 Signals are numbered identically to continue packets and stop replies
36558 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36559 strictly greater than the previous item. These signals do not need to stop
36560 the inferior, or be reported to @value{GDBN}. All other signals should be
36561 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36562 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36563 new list. This packet improves performance when using @samp{handle
36564 @var{signal} nostop noprint pass}.
36569 The request succeeded.
36572 An error occurred. The error number @var{nn} is given as hex digits.
36575 An empty reply indicates that @samp{QPassSignals} is not supported by
36579 Use of this packet is controlled by the @code{set remote pass-signals}
36580 command (@pxref{Remote Configuration, set remote pass-signals}).
36581 This packet is not probed by default; the remote stub must request it,
36582 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36584 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36585 @cindex signals the inferior may see, remote request
36586 @cindex @samp{QProgramSignals} packet
36587 @anchor{QProgramSignals}
36588 Each listed @var{signal} may be delivered to the inferior process.
36589 Others should be silently discarded.
36591 In some cases, the remote stub may need to decide whether to deliver a
36592 signal to the program or not without @value{GDBN} involvement. One
36593 example of that is while detaching --- the program's threads may have
36594 stopped for signals that haven't yet had a chance of being reported to
36595 @value{GDBN}, and so the remote stub can use the signal list specified
36596 by this packet to know whether to deliver or ignore those pending
36599 This does not influence whether to deliver a signal as requested by a
36600 resumption packet (@pxref{vCont packet}).
36602 Signals are numbered identically to continue packets and stop replies
36603 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36604 strictly greater than the previous item. Multiple
36605 @samp{QProgramSignals} packets do not combine; any earlier
36606 @samp{QProgramSignals} list is completely replaced by the new list.
36611 The request succeeded.
36614 An error occurred. The error number @var{nn} is given as hex digits.
36617 An empty reply indicates that @samp{QProgramSignals} is not supported
36621 Use of this packet is controlled by the @code{set remote program-signals}
36622 command (@pxref{Remote Configuration, set remote program-signals}).
36623 This packet is not probed by default; the remote stub must request it,
36624 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36626 @anchor{QThreadEvents}
36627 @item QThreadEvents:1
36628 @itemx QThreadEvents:0
36629 @cindex thread create/exit events, remote request
36630 @cindex @samp{QThreadEvents} packet
36632 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36633 reporting of thread create and exit events. @xref{thread create
36634 event}, for the reply specifications. For example, this is used in
36635 non-stop mode when @value{GDBN} stops a set of threads and
36636 synchronously waits for the their corresponding stop replies. Without
36637 exit events, if one of the threads exits, @value{GDBN} would hang
36638 forever not knowing that it should no longer expect a stop for that
36639 same thread. @value{GDBN} does not enable this feature unless the
36640 stub reports that it supports it by including @samp{QThreadEvents+} in
36641 its @samp{qSupported} reply.
36646 The request succeeded.
36649 An error occurred. The error number @var{nn} is given as hex digits.
36652 An empty reply indicates that @samp{QThreadEvents} is not supported by
36656 Use of this packet is controlled by the @code{set remote thread-events}
36657 command (@pxref{Remote Configuration, set remote thread-events}).
36659 @item qRcmd,@var{command}
36660 @cindex execute remote command, remote request
36661 @cindex @samp{qRcmd} packet
36662 @var{command} (hex encoded) is passed to the local interpreter for
36663 execution. Invalid commands should be reported using the output
36664 string. Before the final result packet, the target may also respond
36665 with a number of intermediate @samp{O@var{output}} console output
36666 packets. @emph{Implementors should note that providing access to a
36667 stubs's interpreter may have security implications}.
36672 A command response with no output.
36674 A command response with the hex encoded output string @var{OUTPUT}.
36676 Indicate a badly formed request.
36678 An empty reply indicates that @samp{qRcmd} is not recognized.
36681 (Note that the @code{qRcmd} packet's name is separated from the
36682 command by a @samp{,}, not a @samp{:}, contrary to the naming
36683 conventions above. Please don't use this packet as a model for new
36686 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36687 @cindex searching memory, in remote debugging
36689 @cindex @samp{qSearch:memory} packet
36691 @cindex @samp{qSearch memory} packet
36692 @anchor{qSearch memory}
36693 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36694 Both @var{address} and @var{length} are encoded in hex;
36695 @var{search-pattern} is a sequence of bytes, also hex encoded.
36700 The pattern was not found.
36702 The pattern was found at @var{address}.
36704 A badly formed request or an error was encountered while searching memory.
36706 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36709 @item QStartNoAckMode
36710 @cindex @samp{QStartNoAckMode} packet
36711 @anchor{QStartNoAckMode}
36712 Request that the remote stub disable the normal @samp{+}/@samp{-}
36713 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36718 The stub has switched to no-acknowledgment mode.
36719 @value{GDBN} acknowledges this reponse,
36720 but neither the stub nor @value{GDBN} shall send or expect further
36721 @samp{+}/@samp{-} acknowledgments in the current connection.
36723 An empty reply indicates that the stub does not support no-acknowledgment mode.
36726 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36727 @cindex supported packets, remote query
36728 @cindex features of the remote protocol
36729 @cindex @samp{qSupported} packet
36730 @anchor{qSupported}
36731 Tell the remote stub about features supported by @value{GDBN}, and
36732 query the stub for features it supports. This packet allows
36733 @value{GDBN} and the remote stub to take advantage of each others'
36734 features. @samp{qSupported} also consolidates multiple feature probes
36735 at startup, to improve @value{GDBN} performance---a single larger
36736 packet performs better than multiple smaller probe packets on
36737 high-latency links. Some features may enable behavior which must not
36738 be on by default, e.g.@: because it would confuse older clients or
36739 stubs. Other features may describe packets which could be
36740 automatically probed for, but are not. These features must be
36741 reported before @value{GDBN} will use them. This ``default
36742 unsupported'' behavior is not appropriate for all packets, but it
36743 helps to keep the initial connection time under control with new
36744 versions of @value{GDBN} which support increasing numbers of packets.
36748 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36749 The stub supports or does not support each returned @var{stubfeature},
36750 depending on the form of each @var{stubfeature} (see below for the
36753 An empty reply indicates that @samp{qSupported} is not recognized,
36754 or that no features needed to be reported to @value{GDBN}.
36757 The allowed forms for each feature (either a @var{gdbfeature} in the
36758 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36762 @item @var{name}=@var{value}
36763 The remote protocol feature @var{name} is supported, and associated
36764 with the specified @var{value}. The format of @var{value} depends
36765 on the feature, but it must not include a semicolon.
36767 The remote protocol feature @var{name} is supported, and does not
36768 need an associated value.
36770 The remote protocol feature @var{name} is not supported.
36772 The remote protocol feature @var{name} may be supported, and
36773 @value{GDBN} should auto-detect support in some other way when it is
36774 needed. This form will not be used for @var{gdbfeature} notifications,
36775 but may be used for @var{stubfeature} responses.
36778 Whenever the stub receives a @samp{qSupported} request, the
36779 supplied set of @value{GDBN} features should override any previous
36780 request. This allows @value{GDBN} to put the stub in a known
36781 state, even if the stub had previously been communicating with
36782 a different version of @value{GDBN}.
36784 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36789 This feature indicates whether @value{GDBN} supports multiprocess
36790 extensions to the remote protocol. @value{GDBN} does not use such
36791 extensions unless the stub also reports that it supports them by
36792 including @samp{multiprocess+} in its @samp{qSupported} reply.
36793 @xref{multiprocess extensions}, for details.
36796 This feature indicates that @value{GDBN} supports the XML target
36797 description. If the stub sees @samp{xmlRegisters=} with target
36798 specific strings separated by a comma, it will report register
36802 This feature indicates whether @value{GDBN} supports the
36803 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36804 instruction reply packet}).
36807 This feature indicates whether @value{GDBN} supports the swbreak stop
36808 reason in stop replies. @xref{swbreak stop reason}, for details.
36811 This feature indicates whether @value{GDBN} supports the hwbreak stop
36812 reason in stop replies. @xref{swbreak stop reason}, for details.
36815 This feature indicates whether @value{GDBN} supports fork event
36816 extensions to the remote protocol. @value{GDBN} does not use such
36817 extensions unless the stub also reports that it supports them by
36818 including @samp{fork-events+} in its @samp{qSupported} reply.
36821 This feature indicates whether @value{GDBN} supports vfork event
36822 extensions to the remote protocol. @value{GDBN} does not use such
36823 extensions unless the stub also reports that it supports them by
36824 including @samp{vfork-events+} in its @samp{qSupported} reply.
36827 This feature indicates whether @value{GDBN} supports exec event
36828 extensions to the remote protocol. @value{GDBN} does not use such
36829 extensions unless the stub also reports that it supports them by
36830 including @samp{exec-events+} in its @samp{qSupported} reply.
36832 @item vContSupported
36833 This feature indicates whether @value{GDBN} wants to know the
36834 supported actions in the reply to @samp{vCont?} packet.
36837 Stubs should ignore any unknown values for
36838 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36839 packet supports receiving packets of unlimited length (earlier
36840 versions of @value{GDBN} may reject overly long responses). Additional values
36841 for @var{gdbfeature} may be defined in the future to let the stub take
36842 advantage of new features in @value{GDBN}, e.g.@: incompatible
36843 improvements in the remote protocol---the @samp{multiprocess} feature is
36844 an example of such a feature. The stub's reply should be independent
36845 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36846 describes all the features it supports, and then the stub replies with
36847 all the features it supports.
36849 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36850 responses, as long as each response uses one of the standard forms.
36852 Some features are flags. A stub which supports a flag feature
36853 should respond with a @samp{+} form response. Other features
36854 require values, and the stub should respond with an @samp{=}
36857 Each feature has a default value, which @value{GDBN} will use if
36858 @samp{qSupported} is not available or if the feature is not mentioned
36859 in the @samp{qSupported} response. The default values are fixed; a
36860 stub is free to omit any feature responses that match the defaults.
36862 Not all features can be probed, but for those which can, the probing
36863 mechanism is useful: in some cases, a stub's internal
36864 architecture may not allow the protocol layer to know some information
36865 about the underlying target in advance. This is especially common in
36866 stubs which may be configured for multiple targets.
36868 These are the currently defined stub features and their properties:
36870 @multitable @columnfractions 0.35 0.2 0.12 0.2
36871 @c NOTE: The first row should be @headitem, but we do not yet require
36872 @c a new enough version of Texinfo (4.7) to use @headitem.
36874 @tab Value Required
36878 @item @samp{PacketSize}
36883 @item @samp{qXfer:auxv:read}
36888 @item @samp{qXfer:btrace:read}
36893 @item @samp{qXfer:btrace-conf:read}
36898 @item @samp{qXfer:exec-file:read}
36903 @item @samp{qXfer:features:read}
36908 @item @samp{qXfer:libraries:read}
36913 @item @samp{qXfer:libraries-svr4:read}
36918 @item @samp{augmented-libraries-svr4-read}
36923 @item @samp{qXfer:memory-map:read}
36928 @item @samp{qXfer:sdata:read}
36933 @item @samp{qXfer:spu:read}
36938 @item @samp{qXfer:spu:write}
36943 @item @samp{qXfer:siginfo:read}
36948 @item @samp{qXfer:siginfo:write}
36953 @item @samp{qXfer:threads:read}
36958 @item @samp{qXfer:traceframe-info:read}
36963 @item @samp{qXfer:uib:read}
36968 @item @samp{qXfer:fdpic:read}
36973 @item @samp{Qbtrace:off}
36978 @item @samp{Qbtrace:bts}
36983 @item @samp{Qbtrace:pt}
36988 @item @samp{Qbtrace-conf:bts:size}
36993 @item @samp{Qbtrace-conf:pt:size}
36998 @item @samp{QNonStop}
37003 @item @samp{QCatchSyscalls}
37008 @item @samp{QPassSignals}
37013 @item @samp{QStartNoAckMode}
37018 @item @samp{multiprocess}
37023 @item @samp{ConditionalBreakpoints}
37028 @item @samp{ConditionalTracepoints}
37033 @item @samp{ReverseContinue}
37038 @item @samp{ReverseStep}
37043 @item @samp{TracepointSource}
37048 @item @samp{QAgent}
37053 @item @samp{QAllow}
37058 @item @samp{QDisableRandomization}
37063 @item @samp{EnableDisableTracepoints}
37068 @item @samp{QTBuffer:size}
37073 @item @samp{tracenz}
37078 @item @samp{BreakpointCommands}
37083 @item @samp{swbreak}
37088 @item @samp{hwbreak}
37093 @item @samp{fork-events}
37098 @item @samp{vfork-events}
37103 @item @samp{exec-events}
37108 @item @samp{QThreadEvents}
37113 @item @samp{no-resumed}
37120 These are the currently defined stub features, in more detail:
37123 @cindex packet size, remote protocol
37124 @item PacketSize=@var{bytes}
37125 The remote stub can accept packets up to at least @var{bytes} in
37126 length. @value{GDBN} will send packets up to this size for bulk
37127 transfers, and will never send larger packets. This is a limit on the
37128 data characters in the packet, including the frame and checksum.
37129 There is no trailing NUL byte in a remote protocol packet; if the stub
37130 stores packets in a NUL-terminated format, it should allow an extra
37131 byte in its buffer for the NUL. If this stub feature is not supported,
37132 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37134 @item qXfer:auxv:read
37135 The remote stub understands the @samp{qXfer:auxv:read} packet
37136 (@pxref{qXfer auxiliary vector read}).
37138 @item qXfer:btrace:read
37139 The remote stub understands the @samp{qXfer:btrace:read}
37140 packet (@pxref{qXfer btrace read}).
37142 @item qXfer:btrace-conf:read
37143 The remote stub understands the @samp{qXfer:btrace-conf:read}
37144 packet (@pxref{qXfer btrace-conf read}).
37146 @item qXfer:exec-file:read
37147 The remote stub understands the @samp{qXfer:exec-file:read} packet
37148 (@pxref{qXfer executable filename read}).
37150 @item qXfer:features:read
37151 The remote stub understands the @samp{qXfer:features:read} packet
37152 (@pxref{qXfer target description read}).
37154 @item qXfer:libraries:read
37155 The remote stub understands the @samp{qXfer:libraries:read} packet
37156 (@pxref{qXfer library list read}).
37158 @item qXfer:libraries-svr4:read
37159 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37160 (@pxref{qXfer svr4 library list read}).
37162 @item augmented-libraries-svr4-read
37163 The remote stub understands the augmented form of the
37164 @samp{qXfer:libraries-svr4:read} packet
37165 (@pxref{qXfer svr4 library list read}).
37167 @item qXfer:memory-map:read
37168 The remote stub understands the @samp{qXfer:memory-map:read} packet
37169 (@pxref{qXfer memory map read}).
37171 @item qXfer:sdata:read
37172 The remote stub understands the @samp{qXfer:sdata:read} packet
37173 (@pxref{qXfer sdata read}).
37175 @item qXfer:spu:read
37176 The remote stub understands the @samp{qXfer:spu:read} packet
37177 (@pxref{qXfer spu read}).
37179 @item qXfer:spu:write
37180 The remote stub understands the @samp{qXfer:spu:write} packet
37181 (@pxref{qXfer spu write}).
37183 @item qXfer:siginfo:read
37184 The remote stub understands the @samp{qXfer:siginfo:read} packet
37185 (@pxref{qXfer siginfo read}).
37187 @item qXfer:siginfo:write
37188 The remote stub understands the @samp{qXfer:siginfo:write} packet
37189 (@pxref{qXfer siginfo write}).
37191 @item qXfer:threads:read
37192 The remote stub understands the @samp{qXfer:threads:read} packet
37193 (@pxref{qXfer threads read}).
37195 @item qXfer:traceframe-info:read
37196 The remote stub understands the @samp{qXfer:traceframe-info:read}
37197 packet (@pxref{qXfer traceframe info read}).
37199 @item qXfer:uib:read
37200 The remote stub understands the @samp{qXfer:uib:read}
37201 packet (@pxref{qXfer unwind info block}).
37203 @item qXfer:fdpic:read
37204 The remote stub understands the @samp{qXfer:fdpic:read}
37205 packet (@pxref{qXfer fdpic loadmap read}).
37208 The remote stub understands the @samp{QNonStop} packet
37209 (@pxref{QNonStop}).
37211 @item QCatchSyscalls
37212 The remote stub understands the @samp{QCatchSyscalls} packet
37213 (@pxref{QCatchSyscalls}).
37216 The remote stub understands the @samp{QPassSignals} packet
37217 (@pxref{QPassSignals}).
37219 @item QStartNoAckMode
37220 The remote stub understands the @samp{QStartNoAckMode} packet and
37221 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37224 @anchor{multiprocess extensions}
37225 @cindex multiprocess extensions, in remote protocol
37226 The remote stub understands the multiprocess extensions to the remote
37227 protocol syntax. The multiprocess extensions affect the syntax of
37228 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37229 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37230 replies. Note that reporting this feature indicates support for the
37231 syntactic extensions only, not that the stub necessarily supports
37232 debugging of more than one process at a time. The stub must not use
37233 multiprocess extensions in packet replies unless @value{GDBN} has also
37234 indicated it supports them in its @samp{qSupported} request.
37236 @item qXfer:osdata:read
37237 The remote stub understands the @samp{qXfer:osdata:read} packet
37238 ((@pxref{qXfer osdata read}).
37240 @item ConditionalBreakpoints
37241 The target accepts and implements evaluation of conditional expressions
37242 defined for breakpoints. The target will only report breakpoint triggers
37243 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37245 @item ConditionalTracepoints
37246 The remote stub accepts and implements conditional expressions defined
37247 for tracepoints (@pxref{Tracepoint Conditions}).
37249 @item ReverseContinue
37250 The remote stub accepts and implements the reverse continue packet
37254 The remote stub accepts and implements the reverse step packet
37257 @item TracepointSource
37258 The remote stub understands the @samp{QTDPsrc} packet that supplies
37259 the source form of tracepoint definitions.
37262 The remote stub understands the @samp{QAgent} packet.
37265 The remote stub understands the @samp{QAllow} packet.
37267 @item QDisableRandomization
37268 The remote stub understands the @samp{QDisableRandomization} packet.
37270 @item StaticTracepoint
37271 @cindex static tracepoints, in remote protocol
37272 The remote stub supports static tracepoints.
37274 @item InstallInTrace
37275 @anchor{install tracepoint in tracing}
37276 The remote stub supports installing tracepoint in tracing.
37278 @item EnableDisableTracepoints
37279 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37280 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37281 to be enabled and disabled while a trace experiment is running.
37283 @item QTBuffer:size
37284 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37285 packet that allows to change the size of the trace buffer.
37288 @cindex string tracing, in remote protocol
37289 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37290 See @ref{Bytecode Descriptions} for details about the bytecode.
37292 @item BreakpointCommands
37293 @cindex breakpoint commands, in remote protocol
37294 The remote stub supports running a breakpoint's command list itself,
37295 rather than reporting the hit to @value{GDBN}.
37298 The remote stub understands the @samp{Qbtrace:off} packet.
37301 The remote stub understands the @samp{Qbtrace:bts} packet.
37304 The remote stub understands the @samp{Qbtrace:pt} packet.
37306 @item Qbtrace-conf:bts:size
37307 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37309 @item Qbtrace-conf:pt:size
37310 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37313 The remote stub reports the @samp{swbreak} stop reason for memory
37317 The remote stub reports the @samp{hwbreak} stop reason for hardware
37321 The remote stub reports the @samp{fork} stop reason for fork events.
37324 The remote stub reports the @samp{vfork} stop reason for vfork events
37325 and vforkdone events.
37328 The remote stub reports the @samp{exec} stop reason for exec events.
37330 @item vContSupported
37331 The remote stub reports the supported actions in the reply to
37332 @samp{vCont?} packet.
37334 @item QThreadEvents
37335 The remote stub understands the @samp{QThreadEvents} packet.
37338 The remote stub reports the @samp{N} stop reply.
37343 @cindex symbol lookup, remote request
37344 @cindex @samp{qSymbol} packet
37345 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37346 requests. Accept requests from the target for the values of symbols.
37351 The target does not need to look up any (more) symbols.
37352 @item qSymbol:@var{sym_name}
37353 The target requests the value of symbol @var{sym_name} (hex encoded).
37354 @value{GDBN} may provide the value by using the
37355 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37359 @item qSymbol:@var{sym_value}:@var{sym_name}
37360 Set the value of @var{sym_name} to @var{sym_value}.
37362 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37363 target has previously requested.
37365 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37366 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37372 The target does not need to look up any (more) symbols.
37373 @item qSymbol:@var{sym_name}
37374 The target requests the value of a new symbol @var{sym_name} (hex
37375 encoded). @value{GDBN} will continue to supply the values of symbols
37376 (if available), until the target ceases to request them.
37381 @itemx QTDisconnected
37388 @itemx qTMinFTPILen
37390 @xref{Tracepoint Packets}.
37392 @item qThreadExtraInfo,@var{thread-id}
37393 @cindex thread attributes info, remote request
37394 @cindex @samp{qThreadExtraInfo} packet
37395 Obtain from the target OS a printable string description of thread
37396 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37397 for the forms of @var{thread-id}. This
37398 string may contain anything that the target OS thinks is interesting
37399 for @value{GDBN} to tell the user about the thread. The string is
37400 displayed in @value{GDBN}'s @code{info threads} display. Some
37401 examples of possible thread extra info strings are @samp{Runnable}, or
37402 @samp{Blocked on Mutex}.
37406 @item @var{XX}@dots{}
37407 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37408 comprising the printable string containing the extra information about
37409 the thread's attributes.
37412 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37413 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37414 conventions above. Please don't use this packet as a model for new
37433 @xref{Tracepoint Packets}.
37435 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37436 @cindex read special object, remote request
37437 @cindex @samp{qXfer} packet
37438 @anchor{qXfer read}
37439 Read uninterpreted bytes from the target's special data area
37440 identified by the keyword @var{object}. Request @var{length} bytes
37441 starting at @var{offset} bytes into the data. The content and
37442 encoding of @var{annex} is specific to @var{object}; it can supply
37443 additional details about what data to access.
37448 Data @var{data} (@pxref{Binary Data}) has been read from the
37449 target. There may be more data at a higher address (although
37450 it is permitted to return @samp{m} even for the last valid
37451 block of data, as long as at least one byte of data was read).
37452 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37456 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37457 There is no more data to be read. It is possible for @var{data} to
37458 have fewer bytes than the @var{length} in the request.
37461 The @var{offset} in the request is at the end of the data.
37462 There is no more data to be read.
37465 The request was malformed, or @var{annex} was invalid.
37468 The offset was invalid, or there was an error encountered reading the data.
37469 The @var{nn} part is a hex-encoded @code{errno} value.
37472 An empty reply indicates the @var{object} string was not recognized by
37473 the stub, or that the object does not support reading.
37476 Here are the specific requests of this form defined so far. All the
37477 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37478 formats, listed above.
37481 @item qXfer:auxv:read::@var{offset},@var{length}
37482 @anchor{qXfer auxiliary vector read}
37483 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37484 auxiliary vector}. Note @var{annex} must be empty.
37486 This packet is not probed by default; the remote stub must request it,
37487 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37489 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37490 @anchor{qXfer btrace read}
37492 Return a description of the current branch trace.
37493 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37494 packet may have one of the following values:
37498 Returns all available branch trace.
37501 Returns all available branch trace if the branch trace changed since
37502 the last read request.
37505 Returns the new branch trace since the last read request. Adds a new
37506 block to the end of the trace that begins at zero and ends at the source
37507 location of the first branch in the trace buffer. This extra block is
37508 used to stitch traces together.
37510 If the trace buffer overflowed, returns an error indicating the overflow.
37513 This packet is not probed by default; the remote stub must request it
37514 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37516 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37517 @anchor{qXfer btrace-conf read}
37519 Return a description of the current branch trace configuration.
37520 @xref{Branch Trace Configuration Format}.
37522 This packet is not probed by default; the remote stub must request it
37523 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37525 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37526 @anchor{qXfer executable filename read}
37527 Return the full absolute name of the file that was executed to create
37528 a process running on the remote system. The annex specifies the
37529 numeric process ID of the process to query, encoded as a hexadecimal
37530 number. If the annex part is empty the remote stub should return the
37531 filename corresponding to the currently executing process.
37533 This packet is not probed by default; the remote stub must request it,
37534 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37536 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37537 @anchor{qXfer target description read}
37538 Access the @dfn{target description}. @xref{Target Descriptions}. The
37539 annex specifies which XML document to access. The main description is
37540 always loaded from the @samp{target.xml} annex.
37542 This packet is not probed by default; the remote stub must request it,
37543 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37545 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37546 @anchor{qXfer library list read}
37547 Access the target's list of loaded libraries. @xref{Library List Format}.
37548 The annex part of the generic @samp{qXfer} packet must be empty
37549 (@pxref{qXfer read}).
37551 Targets which maintain a list of libraries in the program's memory do
37552 not need to implement this packet; it is designed for platforms where
37553 the operating system manages the list of loaded libraries.
37555 This packet is not probed by default; the remote stub must request it,
37556 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37558 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37559 @anchor{qXfer svr4 library list read}
37560 Access the target's list of loaded libraries when the target is an SVR4
37561 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37562 of the generic @samp{qXfer} packet must be empty unless the remote
37563 stub indicated it supports the augmented form of this packet
37564 by supplying an appropriate @samp{qSupported} response
37565 (@pxref{qXfer read}, @ref{qSupported}).
37567 This packet is optional for better performance on SVR4 targets.
37568 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37570 This packet is not probed by default; the remote stub must request it,
37571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37573 If the remote stub indicates it supports the augmented form of this
37574 packet then the annex part of the generic @samp{qXfer} packet may
37575 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37576 arguments. The currently supported arguments are:
37579 @item start=@var{address}
37580 A hexadecimal number specifying the address of the @samp{struct
37581 link_map} to start reading the library list from. If unset or zero
37582 then the first @samp{struct link_map} in the library list will be
37583 chosen as the starting point.
37585 @item prev=@var{address}
37586 A hexadecimal number specifying the address of the @samp{struct
37587 link_map} immediately preceding the @samp{struct link_map}
37588 specified by the @samp{start} argument. If unset or zero then
37589 the remote stub will expect that no @samp{struct link_map}
37590 exists prior to the starting point.
37594 Arguments that are not understood by the remote stub will be silently
37597 @item qXfer:memory-map:read::@var{offset},@var{length}
37598 @anchor{qXfer memory map read}
37599 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37600 annex part of the generic @samp{qXfer} packet must be empty
37601 (@pxref{qXfer read}).
37603 This packet is not probed by default; the remote stub must request it,
37604 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37606 @item qXfer:sdata:read::@var{offset},@var{length}
37607 @anchor{qXfer sdata read}
37609 Read contents of the extra collected static tracepoint marker
37610 information. The annex part of the generic @samp{qXfer} packet must
37611 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37614 This packet is not probed by default; the remote stub must request it,
37615 by supplying an appropriate @samp{qSupported} response
37616 (@pxref{qSupported}).
37618 @item qXfer:siginfo:read::@var{offset},@var{length}
37619 @anchor{qXfer siginfo read}
37620 Read contents of the extra signal information on the target
37621 system. The annex part of the generic @samp{qXfer} packet must be
37622 empty (@pxref{qXfer read}).
37624 This packet is not probed by default; the remote stub must request it,
37625 by supplying an appropriate @samp{qSupported} response
37626 (@pxref{qSupported}).
37628 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37629 @anchor{qXfer spu read}
37630 Read contents of an @code{spufs} file on the target system. The
37631 annex specifies which file to read; it must be of the form
37632 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37633 in the target process, and @var{name} identifes the @code{spufs} file
37634 in that context to be accessed.
37636 This packet is not probed by default; the remote stub must request it,
37637 by supplying an appropriate @samp{qSupported} response
37638 (@pxref{qSupported}).
37640 @item qXfer:threads:read::@var{offset},@var{length}
37641 @anchor{qXfer threads read}
37642 Access the list of threads on target. @xref{Thread List Format}. The
37643 annex part of the generic @samp{qXfer} packet must be empty
37644 (@pxref{qXfer read}).
37646 This packet is not probed by default; the remote stub must request it,
37647 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37649 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37650 @anchor{qXfer traceframe info read}
37652 Return a description of the current traceframe's contents.
37653 @xref{Traceframe Info Format}. The annex part of the generic
37654 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37656 This packet is not probed by default; the remote stub must request it,
37657 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37659 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37660 @anchor{qXfer unwind info block}
37662 Return the unwind information block for @var{pc}. This packet is used
37663 on OpenVMS/ia64 to ask the kernel unwind information.
37665 This packet is not probed by default.
37667 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37668 @anchor{qXfer fdpic loadmap read}
37669 Read contents of @code{loadmap}s on the target system. The
37670 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37671 executable @code{loadmap} or interpreter @code{loadmap} to read.
37673 This packet is not probed by default; the remote stub must request it,
37674 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37676 @item qXfer:osdata:read::@var{offset},@var{length}
37677 @anchor{qXfer osdata read}
37678 Access the target's @dfn{operating system information}.
37679 @xref{Operating System Information}.
37683 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37684 @cindex write data into object, remote request
37685 @anchor{qXfer write}
37686 Write uninterpreted bytes into the target's special data area
37687 identified by the keyword @var{object}, starting at @var{offset} bytes
37688 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37689 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37690 is specific to @var{object}; it can supply additional details about what data
37696 @var{nn} (hex encoded) is the number of bytes written.
37697 This may be fewer bytes than supplied in the request.
37700 The request was malformed, or @var{annex} was invalid.
37703 The offset was invalid, or there was an error encountered writing the data.
37704 The @var{nn} part is a hex-encoded @code{errno} value.
37707 An empty reply indicates the @var{object} string was not
37708 recognized by the stub, or that the object does not support writing.
37711 Here are the specific requests of this form defined so far. All the
37712 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37713 formats, listed above.
37716 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37717 @anchor{qXfer siginfo write}
37718 Write @var{data} to the extra signal information on the target system.
37719 The annex part of the generic @samp{qXfer} packet must be
37720 empty (@pxref{qXfer write}).
37722 This packet is not probed by default; the remote stub must request it,
37723 by supplying an appropriate @samp{qSupported} response
37724 (@pxref{qSupported}).
37726 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37727 @anchor{qXfer spu write}
37728 Write @var{data} to an @code{spufs} file on the target system. The
37729 annex specifies which file to write; it must be of the form
37730 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37731 in the target process, and @var{name} identifes the @code{spufs} file
37732 in that context to be accessed.
37734 This packet is not probed by default; the remote stub must request it,
37735 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37738 @item qXfer:@var{object}:@var{operation}:@dots{}
37739 Requests of this form may be added in the future. When a stub does
37740 not recognize the @var{object} keyword, or its support for
37741 @var{object} does not recognize the @var{operation} keyword, the stub
37742 must respond with an empty packet.
37744 @item qAttached:@var{pid}
37745 @cindex query attached, remote request
37746 @cindex @samp{qAttached} packet
37747 Return an indication of whether the remote server attached to an
37748 existing process or created a new process. When the multiprocess
37749 protocol extensions are supported (@pxref{multiprocess extensions}),
37750 @var{pid} is an integer in hexadecimal format identifying the target
37751 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37752 the query packet will be simplified as @samp{qAttached}.
37754 This query is used, for example, to know whether the remote process
37755 should be detached or killed when a @value{GDBN} session is ended with
37756 the @code{quit} command.
37761 The remote server attached to an existing process.
37763 The remote server created a new process.
37765 A badly formed request or an error was encountered.
37769 Enable branch tracing for the current thread using Branch Trace Store.
37774 Branch tracing has been enabled.
37776 A badly formed request or an error was encountered.
37780 Enable branch tracing for the current thread using Intel Processor Trace.
37785 Branch tracing has been enabled.
37787 A badly formed request or an error was encountered.
37791 Disable branch tracing for the current thread.
37796 Branch tracing has been disabled.
37798 A badly formed request or an error was encountered.
37801 @item Qbtrace-conf:bts:size=@var{value}
37802 Set the requested ring buffer size for new threads that use the
37803 btrace recording method in bts format.
37808 The ring buffer size has been set.
37810 A badly formed request or an error was encountered.
37813 @item Qbtrace-conf:pt:size=@var{value}
37814 Set the requested ring buffer size for new threads that use the
37815 btrace recording method in pt format.
37820 The ring buffer size has been set.
37822 A badly formed request or an error was encountered.
37827 @node Architecture-Specific Protocol Details
37828 @section Architecture-Specific Protocol Details
37830 This section describes how the remote protocol is applied to specific
37831 target architectures. Also see @ref{Standard Target Features}, for
37832 details of XML target descriptions for each architecture.
37835 * ARM-Specific Protocol Details::
37836 * MIPS-Specific Protocol Details::
37839 @node ARM-Specific Protocol Details
37840 @subsection @acronym{ARM}-specific Protocol Details
37843 * ARM Breakpoint Kinds::
37846 @node ARM Breakpoint Kinds
37847 @subsubsection @acronym{ARM} Breakpoint Kinds
37848 @cindex breakpoint kinds, @acronym{ARM}
37850 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37855 16-bit Thumb mode breakpoint.
37858 32-bit Thumb mode (Thumb-2) breakpoint.
37861 32-bit @acronym{ARM} mode breakpoint.
37865 @node MIPS-Specific Protocol Details
37866 @subsection @acronym{MIPS}-specific Protocol Details
37869 * MIPS Register packet Format::
37870 * MIPS Breakpoint Kinds::
37873 @node MIPS Register packet Format
37874 @subsubsection @acronym{MIPS} Register Packet Format
37875 @cindex register packet format, @acronym{MIPS}
37877 The following @code{g}/@code{G} packets have previously been defined.
37878 In the below, some thirty-two bit registers are transferred as
37879 sixty-four bits. Those registers should be zero/sign extended (which?)
37880 to fill the space allocated. Register bytes are transferred in target
37881 byte order. The two nibbles within a register byte are transferred
37882 most-significant -- least-significant.
37887 All registers are transferred as thirty-two bit quantities in the order:
37888 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37889 registers; fsr; fir; fp.
37892 All registers are transferred as sixty-four bit quantities (including
37893 thirty-two bit registers such as @code{sr}). The ordering is the same
37898 @node MIPS Breakpoint Kinds
37899 @subsubsection @acronym{MIPS} Breakpoint Kinds
37900 @cindex breakpoint kinds, @acronym{MIPS}
37902 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37907 16-bit @acronym{MIPS16} mode breakpoint.
37910 16-bit @acronym{microMIPS} mode breakpoint.
37913 32-bit standard @acronym{MIPS} mode breakpoint.
37916 32-bit @acronym{microMIPS} mode breakpoint.
37920 @node Tracepoint Packets
37921 @section Tracepoint Packets
37922 @cindex tracepoint packets
37923 @cindex packets, tracepoint
37925 Here we describe the packets @value{GDBN} uses to implement
37926 tracepoints (@pxref{Tracepoints}).
37930 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37931 @cindex @samp{QTDP} packet
37932 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37933 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37934 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37935 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37936 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37937 the number of bytes that the target should copy elsewhere to make room
37938 for the tracepoint. If an @samp{X} is present, it introduces a
37939 tracepoint condition, which consists of a hexadecimal length, followed
37940 by a comma and hex-encoded bytes, in a manner similar to action
37941 encodings as described below. If the trailing @samp{-} is present,
37942 further @samp{QTDP} packets will follow to specify this tracepoint's
37948 The packet was understood and carried out.
37950 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37952 The packet was not recognized.
37955 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37956 Define actions to be taken when a tracepoint is hit. The @var{n} and
37957 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37958 this tracepoint. This packet may only be sent immediately after
37959 another @samp{QTDP} packet that ended with a @samp{-}. If the
37960 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37961 specifying more actions for this tracepoint.
37963 In the series of action packets for a given tracepoint, at most one
37964 can have an @samp{S} before its first @var{action}. If such a packet
37965 is sent, it and the following packets define ``while-stepping''
37966 actions. Any prior packets define ordinary actions --- that is, those
37967 taken when the tracepoint is first hit. If no action packet has an
37968 @samp{S}, then all the packets in the series specify ordinary
37969 tracepoint actions.
37971 The @samp{@var{action}@dots{}} portion of the packet is a series of
37972 actions, concatenated without separators. Each action has one of the
37978 Collect the registers whose bits are set in @var{mask},
37979 a hexadecimal number whose @var{i}'th bit is set if register number
37980 @var{i} should be collected. (The least significant bit is numbered
37981 zero.) Note that @var{mask} may be any number of digits long; it may
37982 not fit in a 32-bit word.
37984 @item M @var{basereg},@var{offset},@var{len}
37985 Collect @var{len} bytes of memory starting at the address in register
37986 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37987 @samp{-1}, then the range has a fixed address: @var{offset} is the
37988 address of the lowest byte to collect. The @var{basereg},
37989 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37990 values (the @samp{-1} value for @var{basereg} is a special case).
37992 @item X @var{len},@var{expr}
37993 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37994 it directs. The agent expression @var{expr} is as described in
37995 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37996 two-digit hex number in the packet; @var{len} is the number of bytes
37997 in the expression (and thus one-half the number of hex digits in the
38002 Any number of actions may be packed together in a single @samp{QTDP}
38003 packet, as long as the packet does not exceed the maximum packet
38004 length (400 bytes, for many stubs). There may be only one @samp{R}
38005 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38006 actions. Any registers referred to by @samp{M} and @samp{X} actions
38007 must be collected by a preceding @samp{R} action. (The
38008 ``while-stepping'' actions are treated as if they were attached to a
38009 separate tracepoint, as far as these restrictions are concerned.)
38014 The packet was understood and carried out.
38016 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38018 The packet was not recognized.
38021 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38022 @cindex @samp{QTDPsrc} packet
38023 Specify a source string of tracepoint @var{n} at address @var{addr}.
38024 This is useful to get accurate reproduction of the tracepoints
38025 originally downloaded at the beginning of the trace run. The @var{type}
38026 is the name of the tracepoint part, such as @samp{cond} for the
38027 tracepoint's conditional expression (see below for a list of types), while
38028 @var{bytes} is the string, encoded in hexadecimal.
38030 @var{start} is the offset of the @var{bytes} within the overall source
38031 string, while @var{slen} is the total length of the source string.
38032 This is intended for handling source strings that are longer than will
38033 fit in a single packet.
38034 @c Add detailed example when this info is moved into a dedicated
38035 @c tracepoint descriptions section.
38037 The available string types are @samp{at} for the location,
38038 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38039 @value{GDBN} sends a separate packet for each command in the action
38040 list, in the same order in which the commands are stored in the list.
38042 The target does not need to do anything with source strings except
38043 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38046 Although this packet is optional, and @value{GDBN} will only send it
38047 if the target replies with @samp{TracepointSource} @xref{General
38048 Query Packets}, it makes both disconnected tracing and trace files
38049 much easier to use. Otherwise the user must be careful that the
38050 tracepoints in effect while looking at trace frames are identical to
38051 the ones in effect during the trace run; even a small discrepancy
38052 could cause @samp{tdump} not to work, or a particular trace frame not
38055 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38056 @cindex define trace state variable, remote request
38057 @cindex @samp{QTDV} packet
38058 Create a new trace state variable, number @var{n}, with an initial
38059 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38060 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38061 the option of not using this packet for initial values of zero; the
38062 target should simply create the trace state variables as they are
38063 mentioned in expressions. The value @var{builtin} should be 1 (one)
38064 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38065 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38066 @samp{qTsV} packet had it set. The contents of @var{name} is the
38067 hex-encoded name (without the leading @samp{$}) of the trace state
38070 @item QTFrame:@var{n}
38071 @cindex @samp{QTFrame} packet
38072 Select the @var{n}'th tracepoint frame from the buffer, and use the
38073 register and memory contents recorded there to answer subsequent
38074 request packets from @value{GDBN}.
38076 A successful reply from the stub indicates that the stub has found the
38077 requested frame. The response is a series of parts, concatenated
38078 without separators, describing the frame we selected. Each part has
38079 one of the following forms:
38083 The selected frame is number @var{n} in the trace frame buffer;
38084 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38085 was no frame matching the criteria in the request packet.
38088 The selected trace frame records a hit of tracepoint number @var{t};
38089 @var{t} is a hexadecimal number.
38093 @item QTFrame:pc:@var{addr}
38094 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38095 currently selected frame whose PC is @var{addr};
38096 @var{addr} is a hexadecimal number.
38098 @item QTFrame:tdp:@var{t}
38099 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38100 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38101 is a hexadecimal number.
38103 @item QTFrame:range:@var{start}:@var{end}
38104 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38105 currently selected frame whose PC is between @var{start} (inclusive)
38106 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38109 @item QTFrame:outside:@var{start}:@var{end}
38110 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38111 frame @emph{outside} the given range of addresses (exclusive).
38114 @cindex @samp{qTMinFTPILen} packet
38115 This packet requests the minimum length of instruction at which a fast
38116 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38117 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38118 it depends on the target system being able to create trampolines in
38119 the first 64K of memory, which might or might not be possible for that
38120 system. So the reply to this packet will be 4 if it is able to
38127 The minimum instruction length is currently unknown.
38129 The minimum instruction length is @var{length}, where @var{length}
38130 is a hexadecimal number greater or equal to 1. A reply
38131 of 1 means that a fast tracepoint may be placed on any instruction
38132 regardless of size.
38134 An error has occurred.
38136 An empty reply indicates that the request is not supported by the stub.
38140 @cindex @samp{QTStart} packet
38141 Begin the tracepoint experiment. Begin collecting data from
38142 tracepoint hits in the trace frame buffer. This packet supports the
38143 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38144 instruction reply packet}).
38147 @cindex @samp{QTStop} packet
38148 End the tracepoint experiment. Stop collecting trace frames.
38150 @item QTEnable:@var{n}:@var{addr}
38152 @cindex @samp{QTEnable} packet
38153 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38154 experiment. If the tracepoint was previously disabled, then collection
38155 of data from it will resume.
38157 @item QTDisable:@var{n}:@var{addr}
38159 @cindex @samp{QTDisable} packet
38160 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38161 experiment. No more data will be collected from the tracepoint unless
38162 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38165 @cindex @samp{QTinit} packet
38166 Clear the table of tracepoints, and empty the trace frame buffer.
38168 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38169 @cindex @samp{QTro} packet
38170 Establish the given ranges of memory as ``transparent''. The stub
38171 will answer requests for these ranges from memory's current contents,
38172 if they were not collected as part of the tracepoint hit.
38174 @value{GDBN} uses this to mark read-only regions of memory, like those
38175 containing program code. Since these areas never change, they should
38176 still have the same contents they did when the tracepoint was hit, so
38177 there's no reason for the stub to refuse to provide their contents.
38179 @item QTDisconnected:@var{value}
38180 @cindex @samp{QTDisconnected} packet
38181 Set the choice to what to do with the tracing run when @value{GDBN}
38182 disconnects from the target. A @var{value} of 1 directs the target to
38183 continue the tracing run, while 0 tells the target to stop tracing if
38184 @value{GDBN} is no longer in the picture.
38187 @cindex @samp{qTStatus} packet
38188 Ask the stub if there is a trace experiment running right now.
38190 The reply has the form:
38194 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38195 @var{running} is a single digit @code{1} if the trace is presently
38196 running, or @code{0} if not. It is followed by semicolon-separated
38197 optional fields that an agent may use to report additional status.
38201 If the trace is not running, the agent may report any of several
38202 explanations as one of the optional fields:
38207 No trace has been run yet.
38209 @item tstop[:@var{text}]:0
38210 The trace was stopped by a user-originated stop command. The optional
38211 @var{text} field is a user-supplied string supplied as part of the
38212 stop command (for instance, an explanation of why the trace was
38213 stopped manually). It is hex-encoded.
38216 The trace stopped because the trace buffer filled up.
38218 @item tdisconnected:0
38219 The trace stopped because @value{GDBN} disconnected from the target.
38221 @item tpasscount:@var{tpnum}
38222 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38224 @item terror:@var{text}:@var{tpnum}
38225 The trace stopped because tracepoint @var{tpnum} had an error. The
38226 string @var{text} is available to describe the nature of the error
38227 (for instance, a divide by zero in the condition expression); it
38231 The trace stopped for some other reason.
38235 Additional optional fields supply statistical and other information.
38236 Although not required, they are extremely useful for users monitoring
38237 the progress of a trace run. If a trace has stopped, and these
38238 numbers are reported, they must reflect the state of the just-stopped
38243 @item tframes:@var{n}
38244 The number of trace frames in the buffer.
38246 @item tcreated:@var{n}
38247 The total number of trace frames created during the run. This may
38248 be larger than the trace frame count, if the buffer is circular.
38250 @item tsize:@var{n}
38251 The total size of the trace buffer, in bytes.
38253 @item tfree:@var{n}
38254 The number of bytes still unused in the buffer.
38256 @item circular:@var{n}
38257 The value of the circular trace buffer flag. @code{1} means that the
38258 trace buffer is circular and old trace frames will be discarded if
38259 necessary to make room, @code{0} means that the trace buffer is linear
38262 @item disconn:@var{n}
38263 The value of the disconnected tracing flag. @code{1} means that
38264 tracing will continue after @value{GDBN} disconnects, @code{0} means
38265 that the trace run will stop.
38269 @item qTP:@var{tp}:@var{addr}
38270 @cindex tracepoint status, remote request
38271 @cindex @samp{qTP} packet
38272 Ask the stub for the current state of tracepoint number @var{tp} at
38273 address @var{addr}.
38277 @item V@var{hits}:@var{usage}
38278 The tracepoint has been hit @var{hits} times so far during the trace
38279 run, and accounts for @var{usage} in the trace buffer. Note that
38280 @code{while-stepping} steps are not counted as separate hits, but the
38281 steps' space consumption is added into the usage number.
38285 @item qTV:@var{var}
38286 @cindex trace state variable value, remote request
38287 @cindex @samp{qTV} packet
38288 Ask the stub for the value of the trace state variable number @var{var}.
38293 The value of the variable is @var{value}. This will be the current
38294 value of the variable if the user is examining a running target, or a
38295 saved value if the variable was collected in the trace frame that the
38296 user is looking at. Note that multiple requests may result in
38297 different reply values, such as when requesting values while the
38298 program is running.
38301 The value of the variable is unknown. This would occur, for example,
38302 if the user is examining a trace frame in which the requested variable
38307 @cindex @samp{qTfP} packet
38309 @cindex @samp{qTsP} packet
38310 These packets request data about tracepoints that are being used by
38311 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38312 of data, and multiple @code{qTsP} to get additional pieces. Replies
38313 to these packets generally take the form of the @code{QTDP} packets
38314 that define tracepoints. (FIXME add detailed syntax)
38317 @cindex @samp{qTfV} packet
38319 @cindex @samp{qTsV} packet
38320 These packets request data about trace state variables that are on the
38321 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38322 and multiple @code{qTsV} to get additional variables. Replies to
38323 these packets follow the syntax of the @code{QTDV} packets that define
38324 trace state variables.
38330 @cindex @samp{qTfSTM} packet
38331 @cindex @samp{qTsSTM} packet
38332 These packets request data about static tracepoint markers that exist
38333 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38334 first piece of data, and multiple @code{qTsSTM} to get additional
38335 pieces. Replies to these packets take the following form:
38339 @item m @var{address}:@var{id}:@var{extra}
38341 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38342 a comma-separated list of markers
38344 (lower case letter @samp{L}) denotes end of list.
38346 An error occurred. The error number @var{nn} is given as hex digits.
38348 An empty reply indicates that the request is not supported by the
38352 The @var{address} is encoded in hex;
38353 @var{id} and @var{extra} are strings encoded in hex.
38355 In response to each query, the target will reply with a list of one or
38356 more markers, separated by commas. @value{GDBN} will respond to each
38357 reply with a request for more markers (using the @samp{qs} form of the
38358 query), until the target responds with @samp{l} (lower-case ell, for
38361 @item qTSTMat:@var{address}
38363 @cindex @samp{qTSTMat} packet
38364 This packets requests data about static tracepoint markers in the
38365 target program at @var{address}. Replies to this packet follow the
38366 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38367 tracepoint markers.
38369 @item QTSave:@var{filename}
38370 @cindex @samp{QTSave} packet
38371 This packet directs the target to save trace data to the file name
38372 @var{filename} in the target's filesystem. The @var{filename} is encoded
38373 as a hex string; the interpretation of the file name (relative vs
38374 absolute, wild cards, etc) is up to the target.
38376 @item qTBuffer:@var{offset},@var{len}
38377 @cindex @samp{qTBuffer} packet
38378 Return up to @var{len} bytes of the current contents of trace buffer,
38379 starting at @var{offset}. The trace buffer is treated as if it were
38380 a contiguous collection of traceframes, as per the trace file format.
38381 The reply consists as many hex-encoded bytes as the target can deliver
38382 in a packet; it is not an error to return fewer than were asked for.
38383 A reply consisting of just @code{l} indicates that no bytes are
38386 @item QTBuffer:circular:@var{value}
38387 This packet directs the target to use a circular trace buffer if
38388 @var{value} is 1, or a linear buffer if the value is 0.
38390 @item QTBuffer:size:@var{size}
38391 @anchor{QTBuffer-size}
38392 @cindex @samp{QTBuffer size} packet
38393 This packet directs the target to make the trace buffer be of size
38394 @var{size} if possible. A value of @code{-1} tells the target to
38395 use whatever size it prefers.
38397 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38398 @cindex @samp{QTNotes} packet
38399 This packet adds optional textual notes to the trace run. Allowable
38400 types include @code{user}, @code{notes}, and @code{tstop}, the
38401 @var{text} fields are arbitrary strings, hex-encoded.
38405 @subsection Relocate instruction reply packet
38406 When installing fast tracepoints in memory, the target may need to
38407 relocate the instruction currently at the tracepoint address to a
38408 different address in memory. For most instructions, a simple copy is
38409 enough, but, for example, call instructions that implicitly push the
38410 return address on the stack, and relative branches or other
38411 PC-relative instructions require offset adjustment, so that the effect
38412 of executing the instruction at a different address is the same as if
38413 it had executed in the original location.
38415 In response to several of the tracepoint packets, the target may also
38416 respond with a number of intermediate @samp{qRelocInsn} request
38417 packets before the final result packet, to have @value{GDBN} handle
38418 this relocation operation. If a packet supports this mechanism, its
38419 documentation will explicitly say so. See for example the above
38420 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38421 format of the request is:
38424 @item qRelocInsn:@var{from};@var{to}
38426 This requests @value{GDBN} to copy instruction at address @var{from}
38427 to address @var{to}, possibly adjusted so that executing the
38428 instruction at @var{to} has the same effect as executing it at
38429 @var{from}. @value{GDBN} writes the adjusted instruction to target
38430 memory starting at @var{to}.
38435 @item qRelocInsn:@var{adjusted_size}
38436 Informs the stub the relocation is complete. The @var{adjusted_size} is
38437 the length in bytes of resulting relocated instruction sequence.
38439 A badly formed request was detected, or an error was encountered while
38440 relocating the instruction.
38443 @node Host I/O Packets
38444 @section Host I/O Packets
38445 @cindex Host I/O, remote protocol
38446 @cindex file transfer, remote protocol
38448 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38449 operations on the far side of a remote link. For example, Host I/O is
38450 used to upload and download files to a remote target with its own
38451 filesystem. Host I/O uses the same constant values and data structure
38452 layout as the target-initiated File-I/O protocol. However, the
38453 Host I/O packets are structured differently. The target-initiated
38454 protocol relies on target memory to store parameters and buffers.
38455 Host I/O requests are initiated by @value{GDBN}, and the
38456 target's memory is not involved. @xref{File-I/O Remote Protocol
38457 Extension}, for more details on the target-initiated protocol.
38459 The Host I/O request packets all encode a single operation along with
38460 its arguments. They have this format:
38464 @item vFile:@var{operation}: @var{parameter}@dots{}
38465 @var{operation} is the name of the particular request; the target
38466 should compare the entire packet name up to the second colon when checking
38467 for a supported operation. The format of @var{parameter} depends on
38468 the operation. Numbers are always passed in hexadecimal. Negative
38469 numbers have an explicit minus sign (i.e.@: two's complement is not
38470 used). Strings (e.g.@: filenames) are encoded as a series of
38471 hexadecimal bytes. The last argument to a system call may be a
38472 buffer of escaped binary data (@pxref{Binary Data}).
38476 The valid responses to Host I/O packets are:
38480 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38481 @var{result} is the integer value returned by this operation, usually
38482 non-negative for success and -1 for errors. If an error has occured,
38483 @var{errno} will be included in the result specifying a
38484 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38485 operations which return data, @var{attachment} supplies the data as a
38486 binary buffer. Binary buffers in response packets are escaped in the
38487 normal way (@pxref{Binary Data}). See the individual packet
38488 documentation for the interpretation of @var{result} and
38492 An empty response indicates that this operation is not recognized.
38496 These are the supported Host I/O operations:
38499 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38500 Open a file at @var{filename} and return a file descriptor for it, or
38501 return -1 if an error occurs. The @var{filename} is a string,
38502 @var{flags} is an integer indicating a mask of open flags
38503 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38504 of mode bits to use if the file is created (@pxref{mode_t Values}).
38505 @xref{open}, for details of the open flags and mode values.
38507 @item vFile:close: @var{fd}
38508 Close the open file corresponding to @var{fd} and return 0, or
38509 -1 if an error occurs.
38511 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38512 Read data from the open file corresponding to @var{fd}. Up to
38513 @var{count} bytes will be read from the file, starting at @var{offset}
38514 relative to the start of the file. The target may read fewer bytes;
38515 common reasons include packet size limits and an end-of-file
38516 condition. The number of bytes read is returned. Zero should only be
38517 returned for a successful read at the end of the file, or if
38518 @var{count} was zero.
38520 The data read should be returned as a binary attachment on success.
38521 If zero bytes were read, the response should include an empty binary
38522 attachment (i.e.@: a trailing semicolon). The return value is the
38523 number of target bytes read; the binary attachment may be longer if
38524 some characters were escaped.
38526 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38527 Write @var{data} (a binary buffer) to the open file corresponding
38528 to @var{fd}. Start the write at @var{offset} from the start of the
38529 file. Unlike many @code{write} system calls, there is no
38530 separate @var{count} argument; the length of @var{data} in the
38531 packet is used. @samp{vFile:write} returns the number of bytes written,
38532 which may be shorter than the length of @var{data}, or -1 if an
38535 @item vFile:fstat: @var{fd}
38536 Get information about the open file corresponding to @var{fd}.
38537 On success the information is returned as a binary attachment
38538 and the return value is the size of this attachment in bytes.
38539 If an error occurs the return value is -1. The format of the
38540 returned binary attachment is as described in @ref{struct stat}.
38542 @item vFile:unlink: @var{filename}
38543 Delete the file at @var{filename} on the target. Return 0,
38544 or -1 if an error occurs. The @var{filename} is a string.
38546 @item vFile:readlink: @var{filename}
38547 Read value of symbolic link @var{filename} on the target. Return
38548 the number of bytes read, or -1 if an error occurs.
38550 The data read should be returned as a binary attachment on success.
38551 If zero bytes were read, the response should include an empty binary
38552 attachment (i.e.@: a trailing semicolon). The return value is the
38553 number of target bytes read; the binary attachment may be longer if
38554 some characters were escaped.
38556 @item vFile:setfs: @var{pid}
38557 Select the filesystem on which @code{vFile} operations with
38558 @var{filename} arguments will operate. This is required for
38559 @value{GDBN} to be able to access files on remote targets where
38560 the remote stub does not share a common filesystem with the
38563 If @var{pid} is nonzero, select the filesystem as seen by process
38564 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38565 the remote stub. Return 0 on success, or -1 if an error occurs.
38566 If @code{vFile:setfs:} indicates success, the selected filesystem
38567 remains selected until the next successful @code{vFile:setfs:}
38573 @section Interrupts
38574 @cindex interrupts (remote protocol)
38575 @anchor{interrupting remote targets}
38577 In all-stop mode, when a program on the remote target is running,
38578 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38579 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38580 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38582 The precise meaning of @code{BREAK} is defined by the transport
38583 mechanism and may, in fact, be undefined. @value{GDBN} does not
38584 currently define a @code{BREAK} mechanism for any of the network
38585 interfaces except for TCP, in which case @value{GDBN} sends the
38586 @code{telnet} BREAK sequence.
38588 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38589 transport mechanisms. It is represented by sending the single byte
38590 @code{0x03} without any of the usual packet overhead described in
38591 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38592 transmitted as part of a packet, it is considered to be packet data
38593 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38594 (@pxref{X packet}), used for binary downloads, may include an unescaped
38595 @code{0x03} as part of its packet.
38597 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38598 When Linux kernel receives this sequence from serial port,
38599 it stops execution and connects to gdb.
38601 In non-stop mode, because packet resumptions are asynchronous
38602 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38603 command to the remote stub, even when the target is running. For that
38604 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38605 packet}) with the usual packet framing instead of the single byte
38608 Stubs are not required to recognize these interrupt mechanisms and the
38609 precise meaning associated with receipt of the interrupt is
38610 implementation defined. If the target supports debugging of multiple
38611 threads and/or processes, it should attempt to interrupt all
38612 currently-executing threads and processes.
38613 If the stub is successful at interrupting the
38614 running program, it should send one of the stop
38615 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38616 of successfully stopping the program in all-stop mode, and a stop reply
38617 for each stopped thread in non-stop mode.
38618 Interrupts received while the
38619 program is stopped are queued and the program will be interrupted when
38620 it is resumed next time.
38622 @node Notification Packets
38623 @section Notification Packets
38624 @cindex notification packets
38625 @cindex packets, notification
38627 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38628 packets that require no acknowledgment. Both the GDB and the stub
38629 may send notifications (although the only notifications defined at
38630 present are sent by the stub). Notifications carry information
38631 without incurring the round-trip latency of an acknowledgment, and so
38632 are useful for low-impact communications where occasional packet loss
38635 A notification packet has the form @samp{% @var{data} #
38636 @var{checksum}}, where @var{data} is the content of the notification,
38637 and @var{checksum} is a checksum of @var{data}, computed and formatted
38638 as for ordinary @value{GDBN} packets. A notification's @var{data}
38639 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38640 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38641 to acknowledge the notification's receipt or to report its corruption.
38643 Every notification's @var{data} begins with a name, which contains no
38644 colon characters, followed by a colon character.
38646 Recipients should silently ignore corrupted notifications and
38647 notifications they do not understand. Recipients should restart
38648 timeout periods on receipt of a well-formed notification, whether or
38649 not they understand it.
38651 Senders should only send the notifications described here when this
38652 protocol description specifies that they are permitted. In the
38653 future, we may extend the protocol to permit existing notifications in
38654 new contexts; this rule helps older senders avoid confusing newer
38657 (Older versions of @value{GDBN} ignore bytes received until they see
38658 the @samp{$} byte that begins an ordinary packet, so new stubs may
38659 transmit notifications without fear of confusing older clients. There
38660 are no notifications defined for @value{GDBN} to send at the moment, but we
38661 assume that most older stubs would ignore them, as well.)
38663 Each notification is comprised of three parts:
38665 @item @var{name}:@var{event}
38666 The notification packet is sent by the side that initiates the
38667 exchange (currently, only the stub does that), with @var{event}
38668 carrying the specific information about the notification, and
38669 @var{name} specifying the name of the notification.
38671 The acknowledge sent by the other side, usually @value{GDBN}, to
38672 acknowledge the exchange and request the event.
38675 The purpose of an asynchronous notification mechanism is to report to
38676 @value{GDBN} that something interesting happened in the remote stub.
38678 The remote stub may send notification @var{name}:@var{event}
38679 at any time, but @value{GDBN} acknowledges the notification when
38680 appropriate. The notification event is pending before @value{GDBN}
38681 acknowledges. Only one notification at a time may be pending; if
38682 additional events occur before @value{GDBN} has acknowledged the
38683 previous notification, they must be queued by the stub for later
38684 synchronous transmission in response to @var{ack} packets from
38685 @value{GDBN}. Because the notification mechanism is unreliable,
38686 the stub is permitted to resend a notification if it believes
38687 @value{GDBN} may not have received it.
38689 Specifically, notifications may appear when @value{GDBN} is not
38690 otherwise reading input from the stub, or when @value{GDBN} is
38691 expecting to read a normal synchronous response or a
38692 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38693 Notification packets are distinct from any other communication from
38694 the stub so there is no ambiguity.
38696 After receiving a notification, @value{GDBN} shall acknowledge it by
38697 sending a @var{ack} packet as a regular, synchronous request to the
38698 stub. Such acknowledgment is not required to happen immediately, as
38699 @value{GDBN} is permitted to send other, unrelated packets to the
38700 stub first, which the stub should process normally.
38702 Upon receiving a @var{ack} packet, if the stub has other queued
38703 events to report to @value{GDBN}, it shall respond by sending a
38704 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38705 packet to solicit further responses; again, it is permitted to send
38706 other, unrelated packets as well which the stub should process
38709 If the stub receives a @var{ack} packet and there are no additional
38710 @var{event} to report, the stub shall return an @samp{OK} response.
38711 At this point, @value{GDBN} has finished processing a notification
38712 and the stub has completed sending any queued events. @value{GDBN}
38713 won't accept any new notifications until the final @samp{OK} is
38714 received . If further notification events occur, the stub shall send
38715 a new notification, @value{GDBN} shall accept the notification, and
38716 the process shall be repeated.
38718 The process of asynchronous notification can be illustrated by the
38721 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38724 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38726 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38731 The following notifications are defined:
38732 @multitable @columnfractions 0.12 0.12 0.38 0.38
38741 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38742 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38743 for information on how these notifications are acknowledged by
38745 @tab Report an asynchronous stop event in non-stop mode.
38749 @node Remote Non-Stop
38750 @section Remote Protocol Support for Non-Stop Mode
38752 @value{GDBN}'s remote protocol supports non-stop debugging of
38753 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38754 supports non-stop mode, it should report that to @value{GDBN} by including
38755 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38757 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38758 establishing a new connection with the stub. Entering non-stop mode
38759 does not alter the state of any currently-running threads, but targets
38760 must stop all threads in any already-attached processes when entering
38761 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38762 probe the target state after a mode change.
38764 In non-stop mode, when an attached process encounters an event that
38765 would otherwise be reported with a stop reply, it uses the
38766 asynchronous notification mechanism (@pxref{Notification Packets}) to
38767 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38768 in all processes are stopped when a stop reply is sent, in non-stop
38769 mode only the thread reporting the stop event is stopped. That is,
38770 when reporting a @samp{S} or @samp{T} response to indicate completion
38771 of a step operation, hitting a breakpoint, or a fault, only the
38772 affected thread is stopped; any other still-running threads continue
38773 to run. When reporting a @samp{W} or @samp{X} response, all running
38774 threads belonging to other attached processes continue to run.
38776 In non-stop mode, the target shall respond to the @samp{?} packet as
38777 follows. First, any incomplete stop reply notification/@samp{vStopped}
38778 sequence in progress is abandoned. The target must begin a new
38779 sequence reporting stop events for all stopped threads, whether or not
38780 it has previously reported those events to @value{GDBN}. The first
38781 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38782 subsequent stop replies are sent as responses to @samp{vStopped} packets
38783 using the mechanism described above. The target must not send
38784 asynchronous stop reply notifications until the sequence is complete.
38785 If all threads are running when the target receives the @samp{?} packet,
38786 or if the target is not attached to any process, it shall respond
38789 If the stub supports non-stop mode, it should also support the
38790 @samp{swbreak} stop reason if software breakpoints are supported, and
38791 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38792 (@pxref{swbreak stop reason}). This is because given the asynchronous
38793 nature of non-stop mode, between the time a thread hits a breakpoint
38794 and the time the event is finally processed by @value{GDBN}, the
38795 breakpoint may have already been removed from the target. Due to
38796 this, @value{GDBN} needs to be able to tell whether a trap stop was
38797 caused by a delayed breakpoint event, which should be ignored, as
38798 opposed to a random trap signal, which should be reported to the user.
38799 Note the @samp{swbreak} feature implies that the target is responsible
38800 for adjusting the PC when a software breakpoint triggers, if
38801 necessary, such as on the x86 architecture.
38803 @node Packet Acknowledgment
38804 @section Packet Acknowledgment
38806 @cindex acknowledgment, for @value{GDBN} remote
38807 @cindex packet acknowledgment, for @value{GDBN} remote
38808 By default, when either the host or the target machine receives a packet,
38809 the first response expected is an acknowledgment: either @samp{+} (to indicate
38810 the package was received correctly) or @samp{-} (to request retransmission).
38811 This mechanism allows the @value{GDBN} remote protocol to operate over
38812 unreliable transport mechanisms, such as a serial line.
38814 In cases where the transport mechanism is itself reliable (such as a pipe or
38815 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38816 It may be desirable to disable them in that case to reduce communication
38817 overhead, or for other reasons. This can be accomplished by means of the
38818 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38820 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38821 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38822 and response format still includes the normal checksum, as described in
38823 @ref{Overview}, but the checksum may be ignored by the receiver.
38825 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38826 no-acknowledgment mode, it should report that to @value{GDBN}
38827 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38828 @pxref{qSupported}.
38829 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38830 disabled via the @code{set remote noack-packet off} command
38831 (@pxref{Remote Configuration}),
38832 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38833 Only then may the stub actually turn off packet acknowledgments.
38834 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38835 response, which can be safely ignored by the stub.
38837 Note that @code{set remote noack-packet} command only affects negotiation
38838 between @value{GDBN} and the stub when subsequent connections are made;
38839 it does not affect the protocol acknowledgment state for any current
38841 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38842 new connection is established,
38843 there is also no protocol request to re-enable the acknowledgments
38844 for the current connection, once disabled.
38849 Example sequence of a target being re-started. Notice how the restart
38850 does not get any direct output:
38855 @emph{target restarts}
38858 <- @code{T001:1234123412341234}
38862 Example sequence of a target being stepped by a single instruction:
38865 -> @code{G1445@dots{}}
38870 <- @code{T001:1234123412341234}
38874 <- @code{1455@dots{}}
38878 @node File-I/O Remote Protocol Extension
38879 @section File-I/O Remote Protocol Extension
38880 @cindex File-I/O remote protocol extension
38883 * File-I/O Overview::
38884 * Protocol Basics::
38885 * The F Request Packet::
38886 * The F Reply Packet::
38887 * The Ctrl-C Message::
38889 * List of Supported Calls::
38890 * Protocol-specific Representation of Datatypes::
38892 * File-I/O Examples::
38895 @node File-I/O Overview
38896 @subsection File-I/O Overview
38897 @cindex file-i/o overview
38899 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38900 target to use the host's file system and console I/O to perform various
38901 system calls. System calls on the target system are translated into a
38902 remote protocol packet to the host system, which then performs the needed
38903 actions and returns a response packet to the target system.
38904 This simulates file system operations even on targets that lack file systems.
38906 The protocol is defined to be independent of both the host and target systems.
38907 It uses its own internal representation of datatypes and values. Both
38908 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38909 translating the system-dependent value representations into the internal
38910 protocol representations when data is transmitted.
38912 The communication is synchronous. A system call is possible only when
38913 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38914 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38915 the target is stopped to allow deterministic access to the target's
38916 memory. Therefore File-I/O is not interruptible by target signals. On
38917 the other hand, it is possible to interrupt File-I/O by a user interrupt
38918 (@samp{Ctrl-C}) within @value{GDBN}.
38920 The target's request to perform a host system call does not finish
38921 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38922 after finishing the system call, the target returns to continuing the
38923 previous activity (continue, step). No additional continue or step
38924 request from @value{GDBN} is required.
38927 (@value{GDBP}) continue
38928 <- target requests 'system call X'
38929 target is stopped, @value{GDBN} executes system call
38930 -> @value{GDBN} returns result
38931 ... target continues, @value{GDBN} returns to wait for the target
38932 <- target hits breakpoint and sends a Txx packet
38935 The protocol only supports I/O on the console and to regular files on
38936 the host file system. Character or block special devices, pipes,
38937 named pipes, sockets or any other communication method on the host
38938 system are not supported by this protocol.
38940 File I/O is not supported in non-stop mode.
38942 @node Protocol Basics
38943 @subsection Protocol Basics
38944 @cindex protocol basics, file-i/o
38946 The File-I/O protocol uses the @code{F} packet as the request as well
38947 as reply packet. Since a File-I/O system call can only occur when
38948 @value{GDBN} is waiting for a response from the continuing or stepping target,
38949 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38950 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38951 This @code{F} packet contains all information needed to allow @value{GDBN}
38952 to call the appropriate host system call:
38956 A unique identifier for the requested system call.
38959 All parameters to the system call. Pointers are given as addresses
38960 in the target memory address space. Pointers to strings are given as
38961 pointer/length pair. Numerical values are given as they are.
38962 Numerical control flags are given in a protocol-specific representation.
38966 At this point, @value{GDBN} has to perform the following actions.
38970 If the parameters include pointer values to data needed as input to a
38971 system call, @value{GDBN} requests this data from the target with a
38972 standard @code{m} packet request. This additional communication has to be
38973 expected by the target implementation and is handled as any other @code{m}
38977 @value{GDBN} translates all value from protocol representation to host
38978 representation as needed. Datatypes are coerced into the host types.
38981 @value{GDBN} calls the system call.
38984 It then coerces datatypes back to protocol representation.
38987 If the system call is expected to return data in buffer space specified
38988 by pointer parameters to the call, the data is transmitted to the
38989 target using a @code{M} or @code{X} packet. This packet has to be expected
38990 by the target implementation and is handled as any other @code{M} or @code{X}
38995 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38996 necessary information for the target to continue. This at least contains
39003 @code{errno}, if has been changed by the system call.
39010 After having done the needed type and value coercion, the target continues
39011 the latest continue or step action.
39013 @node The F Request Packet
39014 @subsection The @code{F} Request Packet
39015 @cindex file-i/o request packet
39016 @cindex @code{F} request packet
39018 The @code{F} request packet has the following format:
39021 @item F@var{call-id},@var{parameter@dots{}}
39023 @var{call-id} is the identifier to indicate the host system call to be called.
39024 This is just the name of the function.
39026 @var{parameter@dots{}} are the parameters to the system call.
39027 Parameters are hexadecimal integer values, either the actual values in case
39028 of scalar datatypes, pointers to target buffer space in case of compound
39029 datatypes and unspecified memory areas, or pointer/length pairs in case
39030 of string parameters. These are appended to the @var{call-id} as a
39031 comma-delimited list. All values are transmitted in ASCII
39032 string representation, pointer/length pairs separated by a slash.
39038 @node The F Reply Packet
39039 @subsection The @code{F} Reply Packet
39040 @cindex file-i/o reply packet
39041 @cindex @code{F} reply packet
39043 The @code{F} reply packet has the following format:
39047 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39049 @var{retcode} is the return code of the system call as hexadecimal value.
39051 @var{errno} is the @code{errno} set by the call, in protocol-specific
39053 This parameter can be omitted if the call was successful.
39055 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39056 case, @var{errno} must be sent as well, even if the call was successful.
39057 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39064 or, if the call was interrupted before the host call has been performed:
39071 assuming 4 is the protocol-specific representation of @code{EINTR}.
39076 @node The Ctrl-C Message
39077 @subsection The @samp{Ctrl-C} Message
39078 @cindex ctrl-c message, in file-i/o protocol
39080 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39081 reply packet (@pxref{The F Reply Packet}),
39082 the target should behave as if it had
39083 gotten a break message. The meaning for the target is ``system call
39084 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39085 (as with a break message) and return to @value{GDBN} with a @code{T02}
39088 It's important for the target to know in which
39089 state the system call was interrupted. There are two possible cases:
39093 The system call hasn't been performed on the host yet.
39096 The system call on the host has been finished.
39100 These two states can be distinguished by the target by the value of the
39101 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39102 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39103 on POSIX systems. In any other case, the target may presume that the
39104 system call has been finished --- successfully or not --- and should behave
39105 as if the break message arrived right after the system call.
39107 @value{GDBN} must behave reliably. If the system call has not been called
39108 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39109 @code{errno} in the packet. If the system call on the host has been finished
39110 before the user requests a break, the full action must be finished by
39111 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39112 The @code{F} packet may only be sent when either nothing has happened
39113 or the full action has been completed.
39116 @subsection Console I/O
39117 @cindex console i/o as part of file-i/o
39119 By default and if not explicitly closed by the target system, the file
39120 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39121 on the @value{GDBN} console is handled as any other file output operation
39122 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39123 by @value{GDBN} so that after the target read request from file descriptor
39124 0 all following typing is buffered until either one of the following
39129 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39131 system call is treated as finished.
39134 The user presses @key{RET}. This is treated as end of input with a trailing
39138 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39139 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39143 If the user has typed more characters than fit in the buffer given to
39144 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39145 either another @code{read(0, @dots{})} is requested by the target, or debugging
39146 is stopped at the user's request.
39149 @node List of Supported Calls
39150 @subsection List of Supported Calls
39151 @cindex list of supported file-i/o calls
39168 @unnumberedsubsubsec open
39169 @cindex open, file-i/o system call
39174 int open(const char *pathname, int flags);
39175 int open(const char *pathname, int flags, mode_t mode);
39179 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39182 @var{flags} is the bitwise @code{OR} of the following values:
39186 If the file does not exist it will be created. The host
39187 rules apply as far as file ownership and time stamps
39191 When used with @code{O_CREAT}, if the file already exists it is
39192 an error and open() fails.
39195 If the file already exists and the open mode allows
39196 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39197 truncated to zero length.
39200 The file is opened in append mode.
39203 The file is opened for reading only.
39206 The file is opened for writing only.
39209 The file is opened for reading and writing.
39213 Other bits are silently ignored.
39217 @var{mode} is the bitwise @code{OR} of the following values:
39221 User has read permission.
39224 User has write permission.
39227 Group has read permission.
39230 Group has write permission.
39233 Others have read permission.
39236 Others have write permission.
39240 Other bits are silently ignored.
39243 @item Return value:
39244 @code{open} returns the new file descriptor or -1 if an error
39251 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39254 @var{pathname} refers to a directory.
39257 The requested access is not allowed.
39260 @var{pathname} was too long.
39263 A directory component in @var{pathname} does not exist.
39266 @var{pathname} refers to a device, pipe, named pipe or socket.
39269 @var{pathname} refers to a file on a read-only filesystem and
39270 write access was requested.
39273 @var{pathname} is an invalid pointer value.
39276 No space on device to create the file.
39279 The process already has the maximum number of files open.
39282 The limit on the total number of files open on the system
39286 The call was interrupted by the user.
39292 @unnumberedsubsubsec close
39293 @cindex close, file-i/o system call
39302 @samp{Fclose,@var{fd}}
39304 @item Return value:
39305 @code{close} returns zero on success, or -1 if an error occurred.
39311 @var{fd} isn't a valid open file descriptor.
39314 The call was interrupted by the user.
39320 @unnumberedsubsubsec read
39321 @cindex read, file-i/o system call
39326 int read(int fd, void *buf, unsigned int count);
39330 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39332 @item Return value:
39333 On success, the number of bytes read is returned.
39334 Zero indicates end of file. If count is zero, read
39335 returns zero as well. On error, -1 is returned.
39341 @var{fd} is not a valid file descriptor or is not open for
39345 @var{bufptr} is an invalid pointer value.
39348 The call was interrupted by the user.
39354 @unnumberedsubsubsec write
39355 @cindex write, file-i/o system call
39360 int write(int fd, const void *buf, unsigned int count);
39364 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39366 @item Return value:
39367 On success, the number of bytes written are returned.
39368 Zero indicates nothing was written. On error, -1
39375 @var{fd} is not a valid file descriptor or is not open for
39379 @var{bufptr} is an invalid pointer value.
39382 An attempt was made to write a file that exceeds the
39383 host-specific maximum file size allowed.
39386 No space on device to write the data.
39389 The call was interrupted by the user.
39395 @unnumberedsubsubsec lseek
39396 @cindex lseek, file-i/o system call
39401 long lseek (int fd, long offset, int flag);
39405 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39407 @var{flag} is one of:
39411 The offset is set to @var{offset} bytes.
39414 The offset is set to its current location plus @var{offset}
39418 The offset is set to the size of the file plus @var{offset}
39422 @item Return value:
39423 On success, the resulting unsigned offset in bytes from
39424 the beginning of the file is returned. Otherwise, a
39425 value of -1 is returned.
39431 @var{fd} is not a valid open file descriptor.
39434 @var{fd} is associated with the @value{GDBN} console.
39437 @var{flag} is not a proper value.
39440 The call was interrupted by the user.
39446 @unnumberedsubsubsec rename
39447 @cindex rename, file-i/o system call
39452 int rename(const char *oldpath, const char *newpath);
39456 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39458 @item Return value:
39459 On success, zero is returned. On error, -1 is returned.
39465 @var{newpath} is an existing directory, but @var{oldpath} is not a
39469 @var{newpath} is a non-empty directory.
39472 @var{oldpath} or @var{newpath} is a directory that is in use by some
39476 An attempt was made to make a directory a subdirectory
39480 A component used as a directory in @var{oldpath} or new
39481 path is not a directory. Or @var{oldpath} is a directory
39482 and @var{newpath} exists but is not a directory.
39485 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39488 No access to the file or the path of the file.
39492 @var{oldpath} or @var{newpath} was too long.
39495 A directory component in @var{oldpath} or @var{newpath} does not exist.
39498 The file is on a read-only filesystem.
39501 The device containing the file has no room for the new
39505 The call was interrupted by the user.
39511 @unnumberedsubsubsec unlink
39512 @cindex unlink, file-i/o system call
39517 int unlink(const char *pathname);
39521 @samp{Funlink,@var{pathnameptr}/@var{len}}
39523 @item Return value:
39524 On success, zero is returned. On error, -1 is returned.
39530 No access to the file or the path of the file.
39533 The system does not allow unlinking of directories.
39536 The file @var{pathname} cannot be unlinked because it's
39537 being used by another process.
39540 @var{pathnameptr} is an invalid pointer value.
39543 @var{pathname} was too long.
39546 A directory component in @var{pathname} does not exist.
39549 A component of the path is not a directory.
39552 The file is on a read-only filesystem.
39555 The call was interrupted by the user.
39561 @unnumberedsubsubsec stat/fstat
39562 @cindex fstat, file-i/o system call
39563 @cindex stat, file-i/o system call
39568 int stat(const char *pathname, struct stat *buf);
39569 int fstat(int fd, struct stat *buf);
39573 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39574 @samp{Ffstat,@var{fd},@var{bufptr}}
39576 @item Return value:
39577 On success, zero is returned. On error, -1 is returned.
39583 @var{fd} is not a valid open file.
39586 A directory component in @var{pathname} does not exist or the
39587 path is an empty string.
39590 A component of the path is not a directory.
39593 @var{pathnameptr} is an invalid pointer value.
39596 No access to the file or the path of the file.
39599 @var{pathname} was too long.
39602 The call was interrupted by the user.
39608 @unnumberedsubsubsec gettimeofday
39609 @cindex gettimeofday, file-i/o system call
39614 int gettimeofday(struct timeval *tv, void *tz);
39618 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39620 @item Return value:
39621 On success, 0 is returned, -1 otherwise.
39627 @var{tz} is a non-NULL pointer.
39630 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39636 @unnumberedsubsubsec isatty
39637 @cindex isatty, file-i/o system call
39642 int isatty(int fd);
39646 @samp{Fisatty,@var{fd}}
39648 @item Return value:
39649 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39655 The call was interrupted by the user.
39660 Note that the @code{isatty} call is treated as a special case: it returns
39661 1 to the target if the file descriptor is attached
39662 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39663 would require implementing @code{ioctl} and would be more complex than
39668 @unnumberedsubsubsec system
39669 @cindex system, file-i/o system call
39674 int system(const char *command);
39678 @samp{Fsystem,@var{commandptr}/@var{len}}
39680 @item Return value:
39681 If @var{len} is zero, the return value indicates whether a shell is
39682 available. A zero return value indicates a shell is not available.
39683 For non-zero @var{len}, the value returned is -1 on error and the
39684 return status of the command otherwise. Only the exit status of the
39685 command is returned, which is extracted from the host's @code{system}
39686 return value by calling @code{WEXITSTATUS(retval)}. In case
39687 @file{/bin/sh} could not be executed, 127 is returned.
39693 The call was interrupted by the user.
39698 @value{GDBN} takes over the full task of calling the necessary host calls
39699 to perform the @code{system} call. The return value of @code{system} on
39700 the host is simplified before it's returned
39701 to the target. Any termination signal information from the child process
39702 is discarded, and the return value consists
39703 entirely of the exit status of the called command.
39705 Due to security concerns, the @code{system} call is by default refused
39706 by @value{GDBN}. The user has to allow this call explicitly with the
39707 @code{set remote system-call-allowed 1} command.
39710 @item set remote system-call-allowed
39711 @kindex set remote system-call-allowed
39712 Control whether to allow the @code{system} calls in the File I/O
39713 protocol for the remote target. The default is zero (disabled).
39715 @item show remote system-call-allowed
39716 @kindex show remote system-call-allowed
39717 Show whether the @code{system} calls are allowed in the File I/O
39721 @node Protocol-specific Representation of Datatypes
39722 @subsection Protocol-specific Representation of Datatypes
39723 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39726 * Integral Datatypes::
39728 * Memory Transfer::
39733 @node Integral Datatypes
39734 @unnumberedsubsubsec Integral Datatypes
39735 @cindex integral datatypes, in file-i/o protocol
39737 The integral datatypes used in the system calls are @code{int},
39738 @code{unsigned int}, @code{long}, @code{unsigned long},
39739 @code{mode_t}, and @code{time_t}.
39741 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39742 implemented as 32 bit values in this protocol.
39744 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39746 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39747 in @file{limits.h}) to allow range checking on host and target.
39749 @code{time_t} datatypes are defined as seconds since the Epoch.
39751 All integral datatypes transferred as part of a memory read or write of a
39752 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39755 @node Pointer Values
39756 @unnumberedsubsubsec Pointer Values
39757 @cindex pointer values, in file-i/o protocol
39759 Pointers to target data are transmitted as they are. An exception
39760 is made for pointers to buffers for which the length isn't
39761 transmitted as part of the function call, namely strings. Strings
39762 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39769 which is a pointer to data of length 18 bytes at position 0x1aaf.
39770 The length is defined as the full string length in bytes, including
39771 the trailing null byte. For example, the string @code{"hello world"}
39772 at address 0x123456 is transmitted as
39778 @node Memory Transfer
39779 @unnumberedsubsubsec Memory Transfer
39780 @cindex memory transfer, in file-i/o protocol
39782 Structured data which is transferred using a memory read or write (for
39783 example, a @code{struct stat}) is expected to be in a protocol-specific format
39784 with all scalar multibyte datatypes being big endian. Translation to
39785 this representation needs to be done both by the target before the @code{F}
39786 packet is sent, and by @value{GDBN} before
39787 it transfers memory to the target. Transferred pointers to structured
39788 data should point to the already-coerced data at any time.
39792 @unnumberedsubsubsec struct stat
39793 @cindex struct stat, in file-i/o protocol
39795 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39796 is defined as follows:
39800 unsigned int st_dev; /* device */
39801 unsigned int st_ino; /* inode */
39802 mode_t st_mode; /* protection */
39803 unsigned int st_nlink; /* number of hard links */
39804 unsigned int st_uid; /* user ID of owner */
39805 unsigned int st_gid; /* group ID of owner */
39806 unsigned int st_rdev; /* device type (if inode device) */
39807 unsigned long st_size; /* total size, in bytes */
39808 unsigned long st_blksize; /* blocksize for filesystem I/O */
39809 unsigned long st_blocks; /* number of blocks allocated */
39810 time_t st_atime; /* time of last access */
39811 time_t st_mtime; /* time of last modification */
39812 time_t st_ctime; /* time of last change */
39816 The integral datatypes conform to the definitions given in the
39817 appropriate section (see @ref{Integral Datatypes}, for details) so this
39818 structure is of size 64 bytes.
39820 The values of several fields have a restricted meaning and/or
39826 A value of 0 represents a file, 1 the console.
39829 No valid meaning for the target. Transmitted unchanged.
39832 Valid mode bits are described in @ref{Constants}. Any other
39833 bits have currently no meaning for the target.
39838 No valid meaning for the target. Transmitted unchanged.
39843 These values have a host and file system dependent
39844 accuracy. Especially on Windows hosts, the file system may not
39845 support exact timing values.
39848 The target gets a @code{struct stat} of the above representation and is
39849 responsible for coercing it to the target representation before
39852 Note that due to size differences between the host, target, and protocol
39853 representations of @code{struct stat} members, these members could eventually
39854 get truncated on the target.
39856 @node struct timeval
39857 @unnumberedsubsubsec struct timeval
39858 @cindex struct timeval, in file-i/o protocol
39860 The buffer of type @code{struct timeval} used by the File-I/O protocol
39861 is defined as follows:
39865 time_t tv_sec; /* second */
39866 long tv_usec; /* microsecond */
39870 The integral datatypes conform to the definitions given in the
39871 appropriate section (see @ref{Integral Datatypes}, for details) so this
39872 structure is of size 8 bytes.
39875 @subsection Constants
39876 @cindex constants, in file-i/o protocol
39878 The following values are used for the constants inside of the
39879 protocol. @value{GDBN} and target are responsible for translating these
39880 values before and after the call as needed.
39891 @unnumberedsubsubsec Open Flags
39892 @cindex open flags, in file-i/o protocol
39894 All values are given in hexadecimal representation.
39906 @node mode_t Values
39907 @unnumberedsubsubsec mode_t Values
39908 @cindex mode_t values, in file-i/o protocol
39910 All values are given in octal representation.
39927 @unnumberedsubsubsec Errno Values
39928 @cindex errno values, in file-i/o protocol
39930 All values are given in decimal representation.
39955 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39956 any error value not in the list of supported error numbers.
39959 @unnumberedsubsubsec Lseek Flags
39960 @cindex lseek flags, in file-i/o protocol
39969 @unnumberedsubsubsec Limits
39970 @cindex limits, in file-i/o protocol
39972 All values are given in decimal representation.
39975 INT_MIN -2147483648
39977 UINT_MAX 4294967295
39978 LONG_MIN -9223372036854775808
39979 LONG_MAX 9223372036854775807
39980 ULONG_MAX 18446744073709551615
39983 @node File-I/O Examples
39984 @subsection File-I/O Examples
39985 @cindex file-i/o examples
39987 Example sequence of a write call, file descriptor 3, buffer is at target
39988 address 0x1234, 6 bytes should be written:
39991 <- @code{Fwrite,3,1234,6}
39992 @emph{request memory read from target}
39995 @emph{return "6 bytes written"}
39999 Example sequence of a read call, file descriptor 3, buffer is at target
40000 address 0x1234, 6 bytes should be read:
40003 <- @code{Fread,3,1234,6}
40004 @emph{request memory write to target}
40005 -> @code{X1234,6:XXXXXX}
40006 @emph{return "6 bytes read"}
40010 Example sequence of a read call, call fails on the host due to invalid
40011 file descriptor (@code{EBADF}):
40014 <- @code{Fread,3,1234,6}
40018 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40022 <- @code{Fread,3,1234,6}
40027 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40031 <- @code{Fread,3,1234,6}
40032 -> @code{X1234,6:XXXXXX}
40036 @node Library List Format
40037 @section Library List Format
40038 @cindex library list format, remote protocol
40040 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40041 same process as your application to manage libraries. In this case,
40042 @value{GDBN} can use the loader's symbol table and normal memory
40043 operations to maintain a list of shared libraries. On other
40044 platforms, the operating system manages loaded libraries.
40045 @value{GDBN} can not retrieve the list of currently loaded libraries
40046 through memory operations, so it uses the @samp{qXfer:libraries:read}
40047 packet (@pxref{qXfer library list read}) instead. The remote stub
40048 queries the target's operating system and reports which libraries
40051 The @samp{qXfer:libraries:read} packet returns an XML document which
40052 lists loaded libraries and their offsets. Each library has an
40053 associated name and one or more segment or section base addresses,
40054 which report where the library was loaded in memory.
40056 For the common case of libraries that are fully linked binaries, the
40057 library should have a list of segments. If the target supports
40058 dynamic linking of a relocatable object file, its library XML element
40059 should instead include a list of allocated sections. The segment or
40060 section bases are start addresses, not relocation offsets; they do not
40061 depend on the library's link-time base addresses.
40063 @value{GDBN} must be linked with the Expat library to support XML
40064 library lists. @xref{Expat}.
40066 A simple memory map, with one loaded library relocated by a single
40067 offset, looks like this:
40071 <library name="/lib/libc.so.6">
40072 <segment address="0x10000000"/>
40077 Another simple memory map, with one loaded library with three
40078 allocated sections (.text, .data, .bss), looks like this:
40082 <library name="sharedlib.o">
40083 <section address="0x10000000"/>
40084 <section address="0x20000000"/>
40085 <section address="0x30000000"/>
40090 The format of a library list is described by this DTD:
40093 <!-- library-list: Root element with versioning -->
40094 <!ELEMENT library-list (library)*>
40095 <!ATTLIST library-list version CDATA #FIXED "1.0">
40096 <!ELEMENT library (segment*, section*)>
40097 <!ATTLIST library name CDATA #REQUIRED>
40098 <!ELEMENT segment EMPTY>
40099 <!ATTLIST segment address CDATA #REQUIRED>
40100 <!ELEMENT section EMPTY>
40101 <!ATTLIST section address CDATA #REQUIRED>
40104 In addition, segments and section descriptors cannot be mixed within a
40105 single library element, and you must supply at least one segment or
40106 section for each library.
40108 @node Library List Format for SVR4 Targets
40109 @section Library List Format for SVR4 Targets
40110 @cindex library list format, remote protocol
40112 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40113 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40114 shared libraries. Still a special library list provided by this packet is
40115 more efficient for the @value{GDBN} remote protocol.
40117 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40118 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40119 target, the following parameters are reported:
40123 @code{name}, the absolute file name from the @code{l_name} field of
40124 @code{struct link_map}.
40126 @code{lm} with address of @code{struct link_map} used for TLS
40127 (Thread Local Storage) access.
40129 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40130 @code{struct link_map}. For prelinked libraries this is not an absolute
40131 memory address. It is a displacement of absolute memory address against
40132 address the file was prelinked to during the library load.
40134 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40137 Additionally the single @code{main-lm} attribute specifies address of
40138 @code{struct link_map} used for the main executable. This parameter is used
40139 for TLS access and its presence is optional.
40141 @value{GDBN} must be linked with the Expat library to support XML
40142 SVR4 library lists. @xref{Expat}.
40144 A simple memory map, with two loaded libraries (which do not use prelink),
40148 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40149 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40151 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40153 </library-list-svr>
40156 The format of an SVR4 library list is described by this DTD:
40159 <!-- library-list-svr4: Root element with versioning -->
40160 <!ELEMENT library-list-svr4 (library)*>
40161 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40162 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40163 <!ELEMENT library EMPTY>
40164 <!ATTLIST library name CDATA #REQUIRED>
40165 <!ATTLIST library lm CDATA #REQUIRED>
40166 <!ATTLIST library l_addr CDATA #REQUIRED>
40167 <!ATTLIST library l_ld CDATA #REQUIRED>
40170 @node Memory Map Format
40171 @section Memory Map Format
40172 @cindex memory map format
40174 To be able to write into flash memory, @value{GDBN} needs to obtain a
40175 memory map from the target. This section describes the format of the
40178 The memory map is obtained using the @samp{qXfer:memory-map:read}
40179 (@pxref{qXfer memory map read}) packet and is an XML document that
40180 lists memory regions.
40182 @value{GDBN} must be linked with the Expat library to support XML
40183 memory maps. @xref{Expat}.
40185 The top-level structure of the document is shown below:
40188 <?xml version="1.0"?>
40189 <!DOCTYPE memory-map
40190 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40191 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40197 Each region can be either:
40202 A region of RAM starting at @var{addr} and extending for @var{length}
40206 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40211 A region of read-only memory:
40214 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40219 A region of flash memory, with erasure blocks @var{blocksize}
40223 <memory type="flash" start="@var{addr}" length="@var{length}">
40224 <property name="blocksize">@var{blocksize}</property>
40230 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40231 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40232 packets to write to addresses in such ranges.
40234 The formal DTD for memory map format is given below:
40237 <!-- ................................................... -->
40238 <!-- Memory Map XML DTD ................................ -->
40239 <!-- File: memory-map.dtd .............................. -->
40240 <!-- .................................... .............. -->
40241 <!-- memory-map.dtd -->
40242 <!-- memory-map: Root element with versioning -->
40243 <!ELEMENT memory-map (memory | property)>
40244 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40245 <!ELEMENT memory (property)>
40246 <!-- memory: Specifies a memory region,
40247 and its type, or device. -->
40248 <!ATTLIST memory type CDATA #REQUIRED
40249 start CDATA #REQUIRED
40250 length CDATA #REQUIRED
40251 device CDATA #IMPLIED>
40252 <!-- property: Generic attribute tag -->
40253 <!ELEMENT property (#PCDATA | property)*>
40254 <!ATTLIST property name CDATA #REQUIRED>
40257 @node Thread List Format
40258 @section Thread List Format
40259 @cindex thread list format
40261 To efficiently update the list of threads and their attributes,
40262 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40263 (@pxref{qXfer threads read}) and obtains the XML document with
40264 the following structure:
40267 <?xml version="1.0"?>
40269 <thread id="id" core="0" name="name">
40270 ... description ...
40275 Each @samp{thread} element must have the @samp{id} attribute that
40276 identifies the thread (@pxref{thread-id syntax}). The
40277 @samp{core} attribute, if present, specifies which processor core
40278 the thread was last executing on. The @samp{name} attribute, if
40279 present, specifies the human-readable name of the thread. The content
40280 of the of @samp{thread} element is interpreted as human-readable
40281 auxiliary information.
40283 @node Traceframe Info Format
40284 @section Traceframe Info Format
40285 @cindex traceframe info format
40287 To be able to know which objects in the inferior can be examined when
40288 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40289 memory ranges, registers and trace state variables that have been
40290 collected in a traceframe.
40292 This list is obtained using the @samp{qXfer:traceframe-info:read}
40293 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40295 @value{GDBN} must be linked with the Expat library to support XML
40296 traceframe info discovery. @xref{Expat}.
40298 The top-level structure of the document is shown below:
40301 <?xml version="1.0"?>
40302 <!DOCTYPE traceframe-info
40303 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40304 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40310 Each traceframe block can be either:
40315 A region of collected memory starting at @var{addr} and extending for
40316 @var{length} bytes from there:
40319 <memory start="@var{addr}" length="@var{length}"/>
40323 A block indicating trace state variable numbered @var{number} has been
40327 <tvar id="@var{number}"/>
40332 The formal DTD for the traceframe info format is given below:
40335 <!ELEMENT traceframe-info (memory | tvar)* >
40336 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40338 <!ELEMENT memory EMPTY>
40339 <!ATTLIST memory start CDATA #REQUIRED
40340 length CDATA #REQUIRED>
40342 <!ATTLIST tvar id CDATA #REQUIRED>
40345 @node Branch Trace Format
40346 @section Branch Trace Format
40347 @cindex branch trace format
40349 In order to display the branch trace of an inferior thread,
40350 @value{GDBN} needs to obtain the list of branches. This list is
40351 represented as list of sequential code blocks that are connected via
40352 branches. The code in each block has been executed sequentially.
40354 This list is obtained using the @samp{qXfer:btrace:read}
40355 (@pxref{qXfer btrace read}) packet and is an XML document.
40357 @value{GDBN} must be linked with the Expat library to support XML
40358 traceframe info discovery. @xref{Expat}.
40360 The top-level structure of the document is shown below:
40363 <?xml version="1.0"?>
40365 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40366 "http://sourceware.org/gdb/gdb-btrace.dtd">
40375 A block of sequentially executed instructions starting at @var{begin}
40376 and ending at @var{end}:
40379 <block begin="@var{begin}" end="@var{end}"/>
40384 The formal DTD for the branch trace format is given below:
40387 <!ELEMENT btrace (block* | pt) >
40388 <!ATTLIST btrace version CDATA #FIXED "1.0">
40390 <!ELEMENT block EMPTY>
40391 <!ATTLIST block begin CDATA #REQUIRED
40392 end CDATA #REQUIRED>
40394 <!ELEMENT pt (pt-config?, raw?)>
40396 <!ELEMENT pt-config (cpu?)>
40398 <!ELEMENT cpu EMPTY>
40399 <!ATTLIST cpu vendor CDATA #REQUIRED
40400 family CDATA #REQUIRED
40401 model CDATA #REQUIRED
40402 stepping CDATA #REQUIRED>
40404 <!ELEMENT raw (#PCDATA)>
40407 @node Branch Trace Configuration Format
40408 @section Branch Trace Configuration Format
40409 @cindex branch trace configuration format
40411 For each inferior thread, @value{GDBN} can obtain the branch trace
40412 configuration using the @samp{qXfer:btrace-conf:read}
40413 (@pxref{qXfer btrace-conf read}) packet.
40415 The configuration describes the branch trace format and configuration
40416 settings for that format. The following information is described:
40420 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40423 The size of the @acronym{BTS} ring buffer in bytes.
40426 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40430 The size of the @acronym{Intel PT} ring buffer in bytes.
40434 @value{GDBN} must be linked with the Expat library to support XML
40435 branch trace configuration discovery. @xref{Expat}.
40437 The formal DTD for the branch trace configuration format is given below:
40440 <!ELEMENT btrace-conf (bts?, pt?)>
40441 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40443 <!ELEMENT bts EMPTY>
40444 <!ATTLIST bts size CDATA #IMPLIED>
40446 <!ELEMENT pt EMPTY>
40447 <!ATTLIST pt size CDATA #IMPLIED>
40450 @include agentexpr.texi
40452 @node Target Descriptions
40453 @appendix Target Descriptions
40454 @cindex target descriptions
40456 One of the challenges of using @value{GDBN} to debug embedded systems
40457 is that there are so many minor variants of each processor
40458 architecture in use. It is common practice for vendors to start with
40459 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40460 and then make changes to adapt it to a particular market niche. Some
40461 architectures have hundreds of variants, available from dozens of
40462 vendors. This leads to a number of problems:
40466 With so many different customized processors, it is difficult for
40467 the @value{GDBN} maintainers to keep up with the changes.
40469 Since individual variants may have short lifetimes or limited
40470 audiences, it may not be worthwhile to carry information about every
40471 variant in the @value{GDBN} source tree.
40473 When @value{GDBN} does support the architecture of the embedded system
40474 at hand, the task of finding the correct architecture name to give the
40475 @command{set architecture} command can be error-prone.
40478 To address these problems, the @value{GDBN} remote protocol allows a
40479 target system to not only identify itself to @value{GDBN}, but to
40480 actually describe its own features. This lets @value{GDBN} support
40481 processor variants it has never seen before --- to the extent that the
40482 descriptions are accurate, and that @value{GDBN} understands them.
40484 @value{GDBN} must be linked with the Expat library to support XML
40485 target descriptions. @xref{Expat}.
40488 * Retrieving Descriptions:: How descriptions are fetched from a target.
40489 * Target Description Format:: The contents of a target description.
40490 * Predefined Target Types:: Standard types available for target
40492 * Enum Target Types:: How to define enum target types.
40493 * Standard Target Features:: Features @value{GDBN} knows about.
40496 @node Retrieving Descriptions
40497 @section Retrieving Descriptions
40499 Target descriptions can be read from the target automatically, or
40500 specified by the user manually. The default behavior is to read the
40501 description from the target. @value{GDBN} retrieves it via the remote
40502 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40503 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40504 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40505 XML document, of the form described in @ref{Target Description
40508 Alternatively, you can specify a file to read for the target description.
40509 If a file is set, the target will not be queried. The commands to
40510 specify a file are:
40513 @cindex set tdesc filename
40514 @item set tdesc filename @var{path}
40515 Read the target description from @var{path}.
40517 @cindex unset tdesc filename
40518 @item unset tdesc filename
40519 Do not read the XML target description from a file. @value{GDBN}
40520 will use the description supplied by the current target.
40522 @cindex show tdesc filename
40523 @item show tdesc filename
40524 Show the filename to read for a target description, if any.
40528 @node Target Description Format
40529 @section Target Description Format
40530 @cindex target descriptions, XML format
40532 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40533 document which complies with the Document Type Definition provided in
40534 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40535 means you can use generally available tools like @command{xmllint} to
40536 check that your feature descriptions are well-formed and valid.
40537 However, to help people unfamiliar with XML write descriptions for
40538 their targets, we also describe the grammar here.
40540 Target descriptions can identify the architecture of the remote target
40541 and (for some architectures) provide information about custom register
40542 sets. They can also identify the OS ABI of the remote target.
40543 @value{GDBN} can use this information to autoconfigure for your
40544 target, or to warn you if you connect to an unsupported target.
40546 Here is a simple target description:
40549 <target version="1.0">
40550 <architecture>i386:x86-64</architecture>
40555 This minimal description only says that the target uses
40556 the x86-64 architecture.
40558 A target description has the following overall form, with [ ] marking
40559 optional elements and @dots{} marking repeatable elements. The elements
40560 are explained further below.
40563 <?xml version="1.0"?>
40564 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40565 <target version="1.0">
40566 @r{[}@var{architecture}@r{]}
40567 @r{[}@var{osabi}@r{]}
40568 @r{[}@var{compatible}@r{]}
40569 @r{[}@var{feature}@dots{}@r{]}
40574 The description is generally insensitive to whitespace and line
40575 breaks, under the usual common-sense rules. The XML version
40576 declaration and document type declaration can generally be omitted
40577 (@value{GDBN} does not require them), but specifying them may be
40578 useful for XML validation tools. The @samp{version} attribute for
40579 @samp{<target>} may also be omitted, but we recommend
40580 including it; if future versions of @value{GDBN} use an incompatible
40581 revision of @file{gdb-target.dtd}, they will detect and report
40582 the version mismatch.
40584 @subsection Inclusion
40585 @cindex target descriptions, inclusion
40588 @cindex <xi:include>
40591 It can sometimes be valuable to split a target description up into
40592 several different annexes, either for organizational purposes, or to
40593 share files between different possible target descriptions. You can
40594 divide a description into multiple files by replacing any element of
40595 the target description with an inclusion directive of the form:
40598 <xi:include href="@var{document}"/>
40602 When @value{GDBN} encounters an element of this form, it will retrieve
40603 the named XML @var{document}, and replace the inclusion directive with
40604 the contents of that document. If the current description was read
40605 using @samp{qXfer}, then so will be the included document;
40606 @var{document} will be interpreted as the name of an annex. If the
40607 current description was read from a file, @value{GDBN} will look for
40608 @var{document} as a file in the same directory where it found the
40609 original description.
40611 @subsection Architecture
40612 @cindex <architecture>
40614 An @samp{<architecture>} element has this form:
40617 <architecture>@var{arch}</architecture>
40620 @var{arch} is one of the architectures from the set accepted by
40621 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40624 @cindex @code{<osabi>}
40626 This optional field was introduced in @value{GDBN} version 7.0.
40627 Previous versions of @value{GDBN} ignore it.
40629 An @samp{<osabi>} element has this form:
40632 <osabi>@var{abi-name}</osabi>
40635 @var{abi-name} is an OS ABI name from the same selection accepted by
40636 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40638 @subsection Compatible Architecture
40639 @cindex @code{<compatible>}
40641 This optional field was introduced in @value{GDBN} version 7.0.
40642 Previous versions of @value{GDBN} ignore it.
40644 A @samp{<compatible>} element has this form:
40647 <compatible>@var{arch}</compatible>
40650 @var{arch} is one of the architectures from the set accepted by
40651 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40653 A @samp{<compatible>} element is used to specify that the target
40654 is able to run binaries in some other than the main target architecture
40655 given by the @samp{<architecture>} element. For example, on the
40656 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40657 or @code{powerpc:common64}, but the system is able to run binaries
40658 in the @code{spu} architecture as well. The way to describe this
40659 capability with @samp{<compatible>} is as follows:
40662 <architecture>powerpc:common</architecture>
40663 <compatible>spu</compatible>
40666 @subsection Features
40669 Each @samp{<feature>} describes some logical portion of the target
40670 system. Features are currently used to describe available CPU
40671 registers and the types of their contents. A @samp{<feature>} element
40675 <feature name="@var{name}">
40676 @r{[}@var{type}@dots{}@r{]}
40682 Each feature's name should be unique within the description. The name
40683 of a feature does not matter unless @value{GDBN} has some special
40684 knowledge of the contents of that feature; if it does, the feature
40685 should have its standard name. @xref{Standard Target Features}.
40689 Any register's value is a collection of bits which @value{GDBN} must
40690 interpret. The default interpretation is a two's complement integer,
40691 but other types can be requested by name in the register description.
40692 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40693 Target Types}), and the description can define additional composite
40696 Each type element must have an @samp{id} attribute, which gives
40697 a unique (within the containing @samp{<feature>}) name to the type.
40698 Types must be defined before they are used.
40701 Some targets offer vector registers, which can be treated as arrays
40702 of scalar elements. These types are written as @samp{<vector>} elements,
40703 specifying the array element type, @var{type}, and the number of elements,
40707 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40711 If a register's value is usefully viewed in multiple ways, define it
40712 with a union type containing the useful representations. The
40713 @samp{<union>} element contains one or more @samp{<field>} elements,
40714 each of which has a @var{name} and a @var{type}:
40717 <union id="@var{id}">
40718 <field name="@var{name}" type="@var{type}"/>
40725 If a register's value is composed from several separate values, define
40726 it with either a structure type or a flags type.
40727 A flags type may only contain bitfields.
40728 A structure type may either contain only bitfields or contain no bitfields.
40729 If the value contains only bitfields, its total size in bytes must be
40732 Non-bitfield values have a @var{name} and @var{type}.
40735 <struct id="@var{id}">
40736 <field name="@var{name}" type="@var{type}"/>
40741 Both @var{name} and @var{type} values are required.
40742 No implicit padding is added.
40744 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40747 <struct id="@var{id}" size="@var{size}">
40748 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40754 <flags id="@var{id}" size="@var{size}">
40755 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40760 The @var{name} value is required.
40761 Bitfield values may be named with the empty string, @samp{""},
40762 in which case the field is ``filler'' and its value is not printed.
40763 Not all bits need to be specified, so ``filler'' fields are optional.
40765 The @var{start} and @var{end} values are required, and @var{type}
40767 The field's @var{start} must be less than or equal to its @var{end},
40768 and zero represents the least significant bit.
40770 The default value of @var{type} is @code{bool} for single bit fields,
40771 and an unsigned integer otherwise.
40773 Which to choose? Structures or flags?
40775 Registers defined with @samp{flags} have these advantages over
40776 defining them with @samp{struct}:
40780 Arithmetic may be performed on them as if they were integers.
40782 They are printed in a more readable fashion.
40785 Registers defined with @samp{struct} have one advantage over
40786 defining them with @samp{flags}:
40790 One can fetch individual fields like in @samp{C}.
40793 (gdb) print $my_struct_reg.field3
40799 @subsection Registers
40802 Each register is represented as an element with this form:
40805 <reg name="@var{name}"
40806 bitsize="@var{size}"
40807 @r{[}regnum="@var{num}"@r{]}
40808 @r{[}save-restore="@var{save-restore}"@r{]}
40809 @r{[}type="@var{type}"@r{]}
40810 @r{[}group="@var{group}"@r{]}/>
40814 The components are as follows:
40819 The register's name; it must be unique within the target description.
40822 The register's size, in bits.
40825 The register's number. If omitted, a register's number is one greater
40826 than that of the previous register (either in the current feature or in
40827 a preceding feature); the first register in the target description
40828 defaults to zero. This register number is used to read or write
40829 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40830 packets, and registers appear in the @code{g} and @code{G} packets
40831 in order of increasing register number.
40834 Whether the register should be preserved across inferior function
40835 calls; this must be either @code{yes} or @code{no}. The default is
40836 @code{yes}, which is appropriate for most registers except for
40837 some system control registers; this is not related to the target's
40841 The type of the register. It may be a predefined type, a type
40842 defined in the current feature, or one of the special types @code{int}
40843 and @code{float}. @code{int} is an integer type of the correct size
40844 for @var{bitsize}, and @code{float} is a floating point type (in the
40845 architecture's normal floating point format) of the correct size for
40846 @var{bitsize}. The default is @code{int}.
40849 The register group to which this register belongs. It must
40850 be either @code{general}, @code{float}, or @code{vector}. If no
40851 @var{group} is specified, @value{GDBN} will not display the register
40852 in @code{info registers}.
40856 @node Predefined Target Types
40857 @section Predefined Target Types
40858 @cindex target descriptions, predefined types
40860 Type definitions in the self-description can build up composite types
40861 from basic building blocks, but can not define fundamental types. Instead,
40862 standard identifiers are provided by @value{GDBN} for the fundamental
40863 types. The currently supported types are:
40868 Boolean type, occupying a single bit.
40875 Signed integer types holding the specified number of bits.
40882 Unsigned integer types holding the specified number of bits.
40886 Pointers to unspecified code and data. The program counter and
40887 any dedicated return address register may be marked as code
40888 pointers; printing a code pointer converts it into a symbolic
40889 address. The stack pointer and any dedicated address registers
40890 may be marked as data pointers.
40893 Single precision IEEE floating point.
40896 Double precision IEEE floating point.
40899 The 12-byte extended precision format used by ARM FPA registers.
40902 The 10-byte extended precision format used by x87 registers.
40905 32bit @sc{eflags} register used by x86.
40908 32bit @sc{mxcsr} register used by x86.
40912 @node Enum Target Types
40913 @section Enum Target Types
40914 @cindex target descriptions, enum types
40916 Enum target types are useful in @samp{struct} and @samp{flags}
40917 register descriptions. @xref{Target Description Format}.
40919 Enum types have a name, size and a list of name/value pairs.
40922 <enum id="@var{id}" size="@var{size}">
40923 <evalue name="@var{name}" value="@var{value}"/>
40928 Enums must be defined before they are used.
40931 <enum id="levels_type" size="4">
40932 <evalue name="low" value="0"/>
40933 <evalue name="high" value="1"/>
40935 <flags id="flags_type" size="4">
40936 <field name="X" start="0"/>
40937 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40939 <reg name="flags" bitsize="32" type="flags_type"/>
40942 Given that description, a value of 3 for the @samp{flags} register
40943 would be printed as:
40946 (gdb) info register flags
40947 flags 0x3 [ X LEVEL=high ]
40950 @node Standard Target Features
40951 @section Standard Target Features
40952 @cindex target descriptions, standard features
40954 A target description must contain either no registers or all the
40955 target's registers. If the description contains no registers, then
40956 @value{GDBN} will assume a default register layout, selected based on
40957 the architecture. If the description contains any registers, the
40958 default layout will not be used; the standard registers must be
40959 described in the target description, in such a way that @value{GDBN}
40960 can recognize them.
40962 This is accomplished by giving specific names to feature elements
40963 which contain standard registers. @value{GDBN} will look for features
40964 with those names and verify that they contain the expected registers;
40965 if any known feature is missing required registers, or if any required
40966 feature is missing, @value{GDBN} will reject the target
40967 description. You can add additional registers to any of the
40968 standard features --- @value{GDBN} will display them just as if
40969 they were added to an unrecognized feature.
40971 This section lists the known features and their expected contents.
40972 Sample XML documents for these features are included in the
40973 @value{GDBN} source tree, in the directory @file{gdb/features}.
40975 Names recognized by @value{GDBN} should include the name of the
40976 company or organization which selected the name, and the overall
40977 architecture to which the feature applies; so e.g.@: the feature
40978 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40980 The names of registers are not case sensitive for the purpose
40981 of recognizing standard features, but @value{GDBN} will only display
40982 registers using the capitalization used in the description.
40985 * AArch64 Features::
40989 * MicroBlaze Features::
40993 * Nios II Features::
40994 * PowerPC Features::
40995 * S/390 and System z Features::
41000 @node AArch64 Features
41001 @subsection AArch64 Features
41002 @cindex target descriptions, AArch64 features
41004 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41005 targets. It should contain registers @samp{x0} through @samp{x30},
41006 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41008 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41009 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41013 @subsection ARC Features
41014 @cindex target descriptions, ARC Features
41016 ARC processors are highly configurable, so even core registers and their number
41017 are not completely predetermined. In addition flags and PC registers which are
41018 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41019 that one of the core registers features is present.
41020 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41022 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41023 targets with a normal register file. It should contain registers @samp{r0}
41024 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41025 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41026 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41027 @samp{ilink} and extension core registers are not available to read/write, when
41028 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41030 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41031 ARC HS targets with a reduced register file. It should contain registers
41032 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41033 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41034 This feature may contain register @samp{ilink} and any of extension core
41035 registers @samp{r32} through @samp{r59/acch}.
41037 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41038 targets with a normal register file. It should contain registers @samp{r0}
41039 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41040 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41041 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41042 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41043 registers are not available when debugging GNU/Linux applications. The only
41044 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41045 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41046 ARC v2, but @samp{ilink2} is optional on ARCompact.
41048 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41049 targets. It should contain registers @samp{pc} and @samp{status32}.
41052 @subsection ARM Features
41053 @cindex target descriptions, ARM features
41055 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41057 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41058 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41060 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41061 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41062 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41065 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41066 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41068 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41069 it should contain at least registers @samp{wR0} through @samp{wR15} and
41070 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41071 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41073 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41074 should contain at least registers @samp{d0} through @samp{d15}. If
41075 they are present, @samp{d16} through @samp{d31} should also be included.
41076 @value{GDBN} will synthesize the single-precision registers from
41077 halves of the double-precision registers.
41079 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41080 need to contain registers; it instructs @value{GDBN} to display the
41081 VFP double-precision registers as vectors and to synthesize the
41082 quad-precision registers from pairs of double-precision registers.
41083 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41084 be present and include 32 double-precision registers.
41086 @node i386 Features
41087 @subsection i386 Features
41088 @cindex target descriptions, i386 features
41090 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41091 targets. It should describe the following registers:
41095 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41097 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41099 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41100 @samp{fs}, @samp{gs}
41102 @samp{st0} through @samp{st7}
41104 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41105 @samp{foseg}, @samp{fooff} and @samp{fop}
41108 The register sets may be different, depending on the target.
41110 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41111 describe registers:
41115 @samp{xmm0} through @samp{xmm7} for i386
41117 @samp{xmm0} through @samp{xmm15} for amd64
41122 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41123 @samp{org.gnu.gdb.i386.sse} feature. It should
41124 describe the upper 128 bits of @sc{ymm} registers:
41128 @samp{ymm0h} through @samp{ymm7h} for i386
41130 @samp{ymm0h} through @samp{ymm15h} for amd64
41133 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41134 Memory Protection Extension (MPX). It should describe the following registers:
41138 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41140 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41143 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41144 describe a single register, @samp{orig_eax}.
41146 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41147 @samp{org.gnu.gdb.i386.avx} feature. It should
41148 describe additional @sc{xmm} registers:
41152 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41155 It should describe the upper 128 bits of additional @sc{ymm} registers:
41159 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41163 describe the upper 256 bits of @sc{zmm} registers:
41167 @samp{zmm0h} through @samp{zmm7h} for i386.
41169 @samp{zmm0h} through @samp{zmm15h} for amd64.
41173 describe the additional @sc{zmm} registers:
41177 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41180 @node MicroBlaze Features
41181 @subsection MicroBlaze Features
41182 @cindex target descriptions, MicroBlaze features
41184 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41185 targets. It should contain registers @samp{r0} through @samp{r31},
41186 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41187 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41188 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41190 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41191 If present, it should contain registers @samp{rshr} and @samp{rslr}
41193 @node MIPS Features
41194 @subsection @acronym{MIPS} Features
41195 @cindex target descriptions, @acronym{MIPS} features
41197 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41198 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41199 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41202 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41203 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41204 registers. They may be 32-bit or 64-bit depending on the target.
41206 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41207 it may be optional in a future version of @value{GDBN}. It should
41208 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41209 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41211 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41212 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41213 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41214 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41216 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41217 contain a single register, @samp{restart}, which is used by the
41218 Linux kernel to control restartable syscalls.
41220 @node M68K Features
41221 @subsection M68K Features
41222 @cindex target descriptions, M68K features
41225 @item @samp{org.gnu.gdb.m68k.core}
41226 @itemx @samp{org.gnu.gdb.coldfire.core}
41227 @itemx @samp{org.gnu.gdb.fido.core}
41228 One of those features must be always present.
41229 The feature that is present determines which flavor of m68k is
41230 used. The feature that is present should contain registers
41231 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41232 @samp{sp}, @samp{ps} and @samp{pc}.
41234 @item @samp{org.gnu.gdb.coldfire.fp}
41235 This feature is optional. If present, it should contain registers
41236 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41240 @node NDS32 Features
41241 @subsection NDS32 Features
41242 @cindex target descriptions, NDS32 features
41244 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41245 targets. It should contain at least registers @samp{r0} through
41246 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41249 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41250 it should contain 64-bit double-precision floating-point registers
41251 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41252 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41254 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41255 registers are overlapped with the thirty-two 32-bit single-precision
41256 floating-point registers. The 32-bit single-precision registers, if
41257 not being listed explicitly, will be synthesized from halves of the
41258 overlapping 64-bit double-precision registers. Listing 32-bit
41259 single-precision registers explicitly is deprecated, and the
41260 support to it could be totally removed some day.
41262 @node Nios II Features
41263 @subsection Nios II Features
41264 @cindex target descriptions, Nios II features
41266 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41267 targets. It should contain the 32 core registers (@samp{zero},
41268 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41269 @samp{pc}, and the 16 control registers (@samp{status} through
41272 @node PowerPC Features
41273 @subsection PowerPC Features
41274 @cindex target descriptions, PowerPC features
41276 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41277 targets. It should contain registers @samp{r0} through @samp{r31},
41278 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41279 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41281 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41282 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41284 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41285 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41288 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41289 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41290 will combine these registers with the floating point registers
41291 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41292 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41293 through @samp{vs63}, the set of vector registers for POWER7.
41295 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41296 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41297 @samp{spefscr}. SPE targets should provide 32-bit registers in
41298 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41299 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41300 these to present registers @samp{ev0} through @samp{ev31} to the
41303 @node S/390 and System z Features
41304 @subsection S/390 and System z Features
41305 @cindex target descriptions, S/390 features
41306 @cindex target descriptions, System z features
41308 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41309 System z targets. It should contain the PSW and the 16 general
41310 registers. In particular, System z targets should provide the 64-bit
41311 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41312 S/390 targets should provide the 32-bit versions of these registers.
41313 A System z target that runs in 31-bit addressing mode should provide
41314 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41315 register's upper halves @samp{r0h} through @samp{r15h}, and their
41316 lower halves @samp{r0l} through @samp{r15l}.
41318 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41319 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41322 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41323 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41325 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41326 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41327 targets and 32-bit otherwise. In addition, the feature may contain
41328 the @samp{last_break} register, whose width depends on the addressing
41329 mode, as well as the @samp{system_call} register, which is always
41332 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41333 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41334 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41336 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41337 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41338 combined by @value{GDBN} with the floating point registers @samp{f0}
41339 through @samp{f15} to present the 128-bit wide vector registers
41340 @samp{v0} through @samp{v15}. In addition, this feature should
41341 contain the 128-bit wide vector registers @samp{v16} through
41344 @node TIC6x Features
41345 @subsection TMS320C6x Features
41346 @cindex target descriptions, TIC6x features
41347 @cindex target descriptions, TMS320C6x features
41348 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41349 targets. It should contain registers @samp{A0} through @samp{A15},
41350 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41352 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41353 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41354 through @samp{B31}.
41356 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41357 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41359 @node Operating System Information
41360 @appendix Operating System Information
41361 @cindex operating system information
41367 Users of @value{GDBN} often wish to obtain information about the state of
41368 the operating system running on the target---for example the list of
41369 processes, or the list of open files. This section describes the
41370 mechanism that makes it possible. This mechanism is similar to the
41371 target features mechanism (@pxref{Target Descriptions}), but focuses
41372 on a different aspect of target.
41374 Operating system information is retrived from the target via the
41375 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41376 read}). The object name in the request should be @samp{osdata}, and
41377 the @var{annex} identifies the data to be fetched.
41380 @appendixsection Process list
41381 @cindex operating system information, process list
41383 When requesting the process list, the @var{annex} field in the
41384 @samp{qXfer} request should be @samp{processes}. The returned data is
41385 an XML document. The formal syntax of this document is defined in
41386 @file{gdb/features/osdata.dtd}.
41388 An example document is:
41391 <?xml version="1.0"?>
41392 <!DOCTYPE target SYSTEM "osdata.dtd">
41393 <osdata type="processes">
41395 <column name="pid">1</column>
41396 <column name="user">root</column>
41397 <column name="command">/sbin/init</column>
41398 <column name="cores">1,2,3</column>
41403 Each item should include a column whose name is @samp{pid}. The value
41404 of that column should identify the process on the target. The
41405 @samp{user} and @samp{command} columns are optional, and will be
41406 displayed by @value{GDBN}. The @samp{cores} column, if present,
41407 should contain a comma-separated list of cores that this process
41408 is running on. Target may provide additional columns,
41409 which @value{GDBN} currently ignores.
41411 @node Trace File Format
41412 @appendix Trace File Format
41413 @cindex trace file format
41415 The trace file comes in three parts: a header, a textual description
41416 section, and a trace frame section with binary data.
41418 The header has the form @code{\x7fTRACE0\n}. The first byte is
41419 @code{0x7f} so as to indicate that the file contains binary data,
41420 while the @code{0} is a version number that may have different values
41423 The description section consists of multiple lines of @sc{ascii} text
41424 separated by newline characters (@code{0xa}). The lines may include a
41425 variety of optional descriptive or context-setting information, such
41426 as tracepoint definitions or register set size. @value{GDBN} will
41427 ignore any line that it does not recognize. An empty line marks the end
41432 Specifies the size of a register block in bytes. This is equal to the
41433 size of a @code{g} packet payload in the remote protocol. @var{size}
41434 is an ascii decimal number. There should be only one such line in
41435 a single trace file.
41437 @item status @var{status}
41438 Trace status. @var{status} has the same format as a @code{qTStatus}
41439 remote packet reply. There should be only one such line in a single trace
41442 @item tp @var{payload}
41443 Tracepoint definition. The @var{payload} has the same format as
41444 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41445 may take multiple lines of definition, corresponding to the multiple
41448 @item tsv @var{payload}
41449 Trace state variable definition. The @var{payload} has the same format as
41450 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41451 may take multiple lines of definition, corresponding to the multiple
41454 @item tdesc @var{payload}
41455 Target description in XML format. The @var{payload} is a single line of
41456 the XML file. All such lines should be concatenated together to get
41457 the original XML file. This file is in the same format as @code{qXfer}
41458 @code{features} payload, and corresponds to the main @code{target.xml}
41459 file. Includes are not allowed.
41463 The trace frame section consists of a number of consecutive frames.
41464 Each frame begins with a two-byte tracepoint number, followed by a
41465 four-byte size giving the amount of data in the frame. The data in
41466 the frame consists of a number of blocks, each introduced by a
41467 character indicating its type (at least register, memory, and trace
41468 state variable). The data in this section is raw binary, not a
41469 hexadecimal or other encoding; its endianness matches the target's
41472 @c FIXME bi-arch may require endianness/arch info in description section
41475 @item R @var{bytes}
41476 Register block. The number and ordering of bytes matches that of a
41477 @code{g} packet in the remote protocol. Note that these are the
41478 actual bytes, in target order, not a hexadecimal encoding.
41480 @item M @var{address} @var{length} @var{bytes}...
41481 Memory block. This is a contiguous block of memory, at the 8-byte
41482 address @var{address}, with a 2-byte length @var{length}, followed by
41483 @var{length} bytes.
41485 @item V @var{number} @var{value}
41486 Trace state variable block. This records the 8-byte signed value
41487 @var{value} of trace state variable numbered @var{number}.
41491 Future enhancements of the trace file format may include additional types
41494 @node Index Section Format
41495 @appendix @code{.gdb_index} section format
41496 @cindex .gdb_index section format
41497 @cindex index section format
41499 This section documents the index section that is created by @code{save
41500 gdb-index} (@pxref{Index Files}). The index section is
41501 DWARF-specific; some knowledge of DWARF is assumed in this
41504 The mapped index file format is designed to be directly
41505 @code{mmap}able on any architecture. In most cases, a datum is
41506 represented using a little-endian 32-bit integer value, called an
41507 @code{offset_type}. Big endian machines must byte-swap the values
41508 before using them. Exceptions to this rule are noted. The data is
41509 laid out such that alignment is always respected.
41511 A mapped index consists of several areas, laid out in order.
41515 The file header. This is a sequence of values, of @code{offset_type}
41516 unless otherwise noted:
41520 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41521 Version 4 uses a different hashing function from versions 5 and 6.
41522 Version 6 includes symbols for inlined functions, whereas versions 4
41523 and 5 do not. Version 7 adds attributes to the CU indices in the
41524 symbol table. Version 8 specifies that symbols from DWARF type units
41525 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41526 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41528 @value{GDBN} will only read version 4, 5, or 6 indices
41529 by specifying @code{set use-deprecated-index-sections on}.
41530 GDB has a workaround for potentially broken version 7 indices so it is
41531 currently not flagged as deprecated.
41534 The offset, from the start of the file, of the CU list.
41537 The offset, from the start of the file, of the types CU list. Note
41538 that this area can be empty, in which case this offset will be equal
41539 to the next offset.
41542 The offset, from the start of the file, of the address area.
41545 The offset, from the start of the file, of the symbol table.
41548 The offset, from the start of the file, of the constant pool.
41552 The CU list. This is a sequence of pairs of 64-bit little-endian
41553 values, sorted by the CU offset. The first element in each pair is
41554 the offset of a CU in the @code{.debug_info} section. The second
41555 element in each pair is the length of that CU. References to a CU
41556 elsewhere in the map are done using a CU index, which is just the
41557 0-based index into this table. Note that if there are type CUs, then
41558 conceptually CUs and type CUs form a single list for the purposes of
41562 The types CU list. This is a sequence of triplets of 64-bit
41563 little-endian values. In a triplet, the first value is the CU offset,
41564 the second value is the type offset in the CU, and the third value is
41565 the type signature. The types CU list is not sorted.
41568 The address area. The address area consists of a sequence of address
41569 entries. Each address entry has three elements:
41573 The low address. This is a 64-bit little-endian value.
41576 The high address. This is a 64-bit little-endian value. Like
41577 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41580 The CU index. This is an @code{offset_type} value.
41584 The symbol table. This is an open-addressed hash table. The size of
41585 the hash table is always a power of 2.
41587 Each slot in the hash table consists of a pair of @code{offset_type}
41588 values. The first value is the offset of the symbol's name in the
41589 constant pool. The second value is the offset of the CU vector in the
41592 If both values are 0, then this slot in the hash table is empty. This
41593 is ok because while 0 is a valid constant pool index, it cannot be a
41594 valid index for both a string and a CU vector.
41596 The hash value for a table entry is computed by applying an
41597 iterative hash function to the symbol's name. Starting with an
41598 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41599 the string is incorporated into the hash using the formula depending on the
41604 The formula is @code{r = r * 67 + c - 113}.
41606 @item Versions 5 to 7
41607 The formula is @code{r = r * 67 + tolower (c) - 113}.
41610 The terminating @samp{\0} is not incorporated into the hash.
41612 The step size used in the hash table is computed via
41613 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41614 value, and @samp{size} is the size of the hash table. The step size
41615 is used to find the next candidate slot when handling a hash
41618 The names of C@t{++} symbols in the hash table are canonicalized. We
41619 don't currently have a simple description of the canonicalization
41620 algorithm; if you intend to create new index sections, you must read
41624 The constant pool. This is simply a bunch of bytes. It is organized
41625 so that alignment is correct: CU vectors are stored first, followed by
41628 A CU vector in the constant pool is a sequence of @code{offset_type}
41629 values. The first value is the number of CU indices in the vector.
41630 Each subsequent value is the index and symbol attributes of a CU in
41631 the CU list. This element in the hash table is used to indicate which
41632 CUs define the symbol and how the symbol is used.
41633 See below for the format of each CU index+attributes entry.
41635 A string in the constant pool is zero-terminated.
41638 Attributes were added to CU index values in @code{.gdb_index} version 7.
41639 If a symbol has multiple uses within a CU then there is one
41640 CU index+attributes value for each use.
41642 The format of each CU index+attributes entry is as follows
41648 This is the index of the CU in the CU list.
41650 These bits are reserved for future purposes and must be zero.
41652 The kind of the symbol in the CU.
41656 This value is reserved and should not be used.
41657 By reserving zero the full @code{offset_type} value is backwards compatible
41658 with previous versions of the index.
41660 The symbol is a type.
41662 The symbol is a variable or an enum value.
41664 The symbol is a function.
41666 Any other kind of symbol.
41668 These values are reserved.
41672 This bit is zero if the value is global and one if it is static.
41674 The determination of whether a symbol is global or static is complicated.
41675 The authorative reference is the file @file{dwarf2read.c} in
41676 @value{GDBN} sources.
41680 This pseudo-code describes the computation of a symbol's kind and
41681 global/static attributes in the index.
41684 is_external = get_attribute (die, DW_AT_external);
41685 language = get_attribute (cu_die, DW_AT_language);
41688 case DW_TAG_typedef:
41689 case DW_TAG_base_type:
41690 case DW_TAG_subrange_type:
41694 case DW_TAG_enumerator:
41696 is_static = language != CPLUS;
41698 case DW_TAG_subprogram:
41700 is_static = ! (is_external || language == ADA);
41702 case DW_TAG_constant:
41704 is_static = ! is_external;
41706 case DW_TAG_variable:
41708 is_static = ! is_external;
41710 case DW_TAG_namespace:
41714 case DW_TAG_class_type:
41715 case DW_TAG_interface_type:
41716 case DW_TAG_structure_type:
41717 case DW_TAG_union_type:
41718 case DW_TAG_enumeration_type:
41720 is_static = language != CPLUS;
41728 @appendix Manual pages
41732 * gdb man:: The GNU Debugger man page
41733 * gdbserver man:: Remote Server for the GNU Debugger man page
41734 * gcore man:: Generate a core file of a running program
41735 * gdbinit man:: gdbinit scripts
41741 @c man title gdb The GNU Debugger
41743 @c man begin SYNOPSIS gdb
41744 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41745 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41746 [@option{-b}@w{ }@var{bps}]
41747 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41748 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41749 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41750 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41751 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41754 @c man begin DESCRIPTION gdb
41755 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41756 going on ``inside'' another program while it executes -- or what another
41757 program was doing at the moment it crashed.
41759 @value{GDBN} can do four main kinds of things (plus other things in support of
41760 these) to help you catch bugs in the act:
41764 Start your program, specifying anything that might affect its behavior.
41767 Make your program stop on specified conditions.
41770 Examine what has happened, when your program has stopped.
41773 Change things in your program, so you can experiment with correcting the
41774 effects of one bug and go on to learn about another.
41777 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41780 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41781 commands from the terminal until you tell it to exit with the @value{GDBN}
41782 command @code{quit}. You can get online help from @value{GDBN} itself
41783 by using the command @code{help}.
41785 You can run @code{gdb} with no arguments or options; but the most
41786 usual way to start @value{GDBN} is with one argument or two, specifying an
41787 executable program as the argument:
41793 You can also start with both an executable program and a core file specified:
41799 You can, instead, specify a process ID as a second argument, if you want
41800 to debug a running process:
41808 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41809 named @file{1234}; @value{GDBN} does check for a core file first).
41810 With option @option{-p} you can omit the @var{program} filename.
41812 Here are some of the most frequently needed @value{GDBN} commands:
41814 @c pod2man highlights the right hand side of the @item lines.
41816 @item break [@var{file}:]@var{function}
41817 Set a breakpoint at @var{function} (in @var{file}).
41819 @item run [@var{arglist}]
41820 Start your program (with @var{arglist}, if specified).
41823 Backtrace: display the program stack.
41825 @item print @var{expr}
41826 Display the value of an expression.
41829 Continue running your program (after stopping, e.g. at a breakpoint).
41832 Execute next program line (after stopping); step @emph{over} any
41833 function calls in the line.
41835 @item edit [@var{file}:]@var{function}
41836 look at the program line where it is presently stopped.
41838 @item list [@var{file}:]@var{function}
41839 type the text of the program in the vicinity of where it is presently stopped.
41842 Execute next program line (after stopping); step @emph{into} any
41843 function calls in the line.
41845 @item help [@var{name}]
41846 Show information about @value{GDBN} command @var{name}, or general information
41847 about using @value{GDBN}.
41850 Exit from @value{GDBN}.
41854 For full details on @value{GDBN},
41855 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41856 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41857 as the @code{gdb} entry in the @code{info} program.
41861 @c man begin OPTIONS gdb
41862 Any arguments other than options specify an executable
41863 file and core file (or process ID); that is, the first argument
41864 encountered with no
41865 associated option flag is equivalent to a @option{-se} option, and the second,
41866 if any, is equivalent to a @option{-c} option if it's the name of a file.
41868 both long and short forms; both are shown here. The long forms are also
41869 recognized if you truncate them, so long as enough of the option is
41870 present to be unambiguous. (If you prefer, you can flag option
41871 arguments with @option{+} rather than @option{-}, though we illustrate the
41872 more usual convention.)
41874 All the options and command line arguments you give are processed
41875 in sequential order. The order makes a difference when the @option{-x}
41881 List all options, with brief explanations.
41883 @item -symbols=@var{file}
41884 @itemx -s @var{file}
41885 Read symbol table from file @var{file}.
41888 Enable writing into executable and core files.
41890 @item -exec=@var{file}
41891 @itemx -e @var{file}
41892 Use file @var{file} as the executable file to execute when
41893 appropriate, and for examining pure data in conjunction with a core
41896 @item -se=@var{file}
41897 Read symbol table from file @var{file} and use it as the executable
41900 @item -core=@var{file}
41901 @itemx -c @var{file}
41902 Use file @var{file} as a core dump to examine.
41904 @item -command=@var{file}
41905 @itemx -x @var{file}
41906 Execute @value{GDBN} commands from file @var{file}.
41908 @item -ex @var{command}
41909 Execute given @value{GDBN} @var{command}.
41911 @item -directory=@var{directory}
41912 @itemx -d @var{directory}
41913 Add @var{directory} to the path to search for source files.
41916 Do not execute commands from @file{~/.gdbinit}.
41920 Do not execute commands from any @file{.gdbinit} initialization files.
41924 ``Quiet''. Do not print the introductory and copyright messages. These
41925 messages are also suppressed in batch mode.
41928 Run in batch mode. Exit with status @code{0} after processing all the command
41929 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41930 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41931 commands in the command files.
41933 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41934 download and run a program on another computer; in order to make this
41935 more useful, the message
41938 Program exited normally.
41942 (which is ordinarily issued whenever a program running under @value{GDBN} control
41943 terminates) is not issued when running in batch mode.
41945 @item -cd=@var{directory}
41946 Run @value{GDBN} using @var{directory} as its working directory,
41947 instead of the current directory.
41951 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41952 @value{GDBN} to output the full file name and line number in a standard,
41953 recognizable fashion each time a stack frame is displayed (which
41954 includes each time the program stops). This recognizable format looks
41955 like two @samp{\032} characters, followed by the file name, line number
41956 and character position separated by colons, and a newline. The
41957 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41958 characters as a signal to display the source code for the frame.
41961 Set the line speed (baud rate or bits per second) of any serial
41962 interface used by @value{GDBN} for remote debugging.
41964 @item -tty=@var{device}
41965 Run using @var{device} for your program's standard input and output.
41969 @c man begin SEEALSO gdb
41971 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41972 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41973 documentation are properly installed at your site, the command
41980 should give you access to the complete manual.
41982 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41983 Richard M. Stallman and Roland H. Pesch, July 1991.
41987 @node gdbserver man
41988 @heading gdbserver man
41990 @c man title gdbserver Remote Server for the GNU Debugger
41992 @c man begin SYNOPSIS gdbserver
41993 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41995 gdbserver --attach @var{comm} @var{pid}
41997 gdbserver --multi @var{comm}
42001 @c man begin DESCRIPTION gdbserver
42002 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42003 than the one which is running the program being debugged.
42006 @subheading Usage (server (target) side)
42009 Usage (server (target) side):
42012 First, you need to have a copy of the program you want to debug put onto
42013 the target system. The program can be stripped to save space if needed, as
42014 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42015 the @value{GDBN} running on the host system.
42017 To use the server, you log on to the target system, and run the @command{gdbserver}
42018 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42019 your program, and (c) its arguments. The general syntax is:
42022 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42025 For example, using a serial port, you might say:
42029 @c @file would wrap it as F</dev/com1>.
42030 target> gdbserver /dev/com1 emacs foo.txt
42033 target> gdbserver @file{/dev/com1} emacs foo.txt
42037 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42038 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42039 waits patiently for the host @value{GDBN} to communicate with it.
42041 To use a TCP connection, you could say:
42044 target> gdbserver host:2345 emacs foo.txt
42047 This says pretty much the same thing as the last example, except that we are
42048 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42049 that we are expecting to see a TCP connection from @code{host} to local TCP port
42050 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42051 want for the port number as long as it does not conflict with any existing TCP
42052 ports on the target system. This same port number must be used in the host
42053 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42054 you chose a port number that conflicts with another service, @command{gdbserver} will
42055 print an error message and exit.
42057 @command{gdbserver} can also attach to running programs.
42058 This is accomplished via the @option{--attach} argument. The syntax is:
42061 target> gdbserver --attach @var{comm} @var{pid}
42064 @var{pid} is the process ID of a currently running process. It isn't
42065 necessary to point @command{gdbserver} at a binary for the running process.
42067 To start @code{gdbserver} without supplying an initial command to run
42068 or process ID to attach, use the @option{--multi} command line option.
42069 In such case you should connect using @kbd{target extended-remote} to start
42070 the program you want to debug.
42073 target> gdbserver --multi @var{comm}
42077 @subheading Usage (host side)
42083 You need an unstripped copy of the target program on your host system, since
42084 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42085 would, with the target program as the first argument. (You may need to use the
42086 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42087 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42088 new command you need to know about is @code{target remote}
42089 (or @code{target extended-remote}). Its argument is either
42090 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42091 descriptor. For example:
42095 @c @file would wrap it as F</dev/ttyb>.
42096 (gdb) target remote /dev/ttyb
42099 (gdb) target remote @file{/dev/ttyb}
42104 communicates with the server via serial line @file{/dev/ttyb}, and:
42107 (gdb) target remote the-target:2345
42111 communicates via a TCP connection to port 2345 on host `the-target', where
42112 you previously started up @command{gdbserver} with the same port number. Note that for
42113 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42114 command, otherwise you may get an error that looks something like
42115 `Connection refused'.
42117 @command{gdbserver} can also debug multiple inferiors at once,
42120 the @value{GDBN} manual in node @code{Inferiors and Programs}
42121 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42124 @ref{Inferiors and Programs}.
42126 In such case use the @code{extended-remote} @value{GDBN} command variant:
42129 (gdb) target extended-remote the-target:2345
42132 The @command{gdbserver} option @option{--multi} may or may not be used in such
42136 @c man begin OPTIONS gdbserver
42137 There are three different modes for invoking @command{gdbserver}:
42142 Debug a specific program specified by its program name:
42145 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42148 The @var{comm} parameter specifies how should the server communicate
42149 with @value{GDBN}; it is either a device name (to use a serial line),
42150 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42151 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42152 debug in @var{prog}. Any remaining arguments will be passed to the
42153 program verbatim. When the program exits, @value{GDBN} will close the
42154 connection, and @code{gdbserver} will exit.
42157 Debug a specific program by specifying the process ID of a running
42161 gdbserver --attach @var{comm} @var{pid}
42164 The @var{comm} parameter is as described above. Supply the process ID
42165 of a running program in @var{pid}; @value{GDBN} will do everything
42166 else. Like with the previous mode, when the process @var{pid} exits,
42167 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42170 Multi-process mode -- debug more than one program/process:
42173 gdbserver --multi @var{comm}
42176 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42177 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42178 close the connection when a process being debugged exits, so you can
42179 debug several processes in the same session.
42182 In each of the modes you may specify these options:
42187 List all options, with brief explanations.
42190 This option causes @command{gdbserver} to print its version number and exit.
42193 @command{gdbserver} will attach to a running program. The syntax is:
42196 target> gdbserver --attach @var{comm} @var{pid}
42199 @var{pid} is the process ID of a currently running process. It isn't
42200 necessary to point @command{gdbserver} at a binary for the running process.
42203 To start @code{gdbserver} without supplying an initial command to run
42204 or process ID to attach, use this command line option.
42205 Then you can connect using @kbd{target extended-remote} and start
42206 the program you want to debug. The syntax is:
42209 target> gdbserver --multi @var{comm}
42213 Instruct @code{gdbserver} to display extra status information about the debugging
42215 This option is intended for @code{gdbserver} development and for bug reports to
42218 @item --remote-debug
42219 Instruct @code{gdbserver} to display remote protocol debug output.
42220 This option is intended for @code{gdbserver} development and for bug reports to
42223 @item --debug-format=option1@r{[},option2,...@r{]}
42224 Instruct @code{gdbserver} to include extra information in each line
42225 of debugging output.
42226 @xref{Other Command-Line Arguments for gdbserver}.
42229 Specify a wrapper to launch programs
42230 for debugging. The option should be followed by the name of the
42231 wrapper, then any command-line arguments to pass to the wrapper, then
42232 @kbd{--} indicating the end of the wrapper arguments.
42235 By default, @command{gdbserver} keeps the listening TCP port open, so that
42236 additional connections are possible. However, if you start @code{gdbserver}
42237 with the @option{--once} option, it will stop listening for any further
42238 connection attempts after connecting to the first @value{GDBN} session.
42240 @c --disable-packet is not documented for users.
42242 @c --disable-randomization and --no-disable-randomization are superseded by
42243 @c QDisableRandomization.
42248 @c man begin SEEALSO gdbserver
42250 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42251 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42252 documentation are properly installed at your site, the command
42258 should give you access to the complete manual.
42260 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42261 Richard M. Stallman and Roland H. Pesch, July 1991.
42268 @c man title gcore Generate a core file of a running program
42271 @c man begin SYNOPSIS gcore
42272 gcore [-o @var{filename}] @var{pid}
42276 @c man begin DESCRIPTION gcore
42277 Generate a core dump of a running program with process ID @var{pid}.
42278 Produced file is equivalent to a kernel produced core file as if the process
42279 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42280 limit). Unlike after a crash, after @command{gcore} the program remains
42281 running without any change.
42284 @c man begin OPTIONS gcore
42286 @item -o @var{filename}
42287 The optional argument
42288 @var{filename} specifies the file name where to put the core dump.
42289 If not specified, the file name defaults to @file{core.@var{pid}},
42290 where @var{pid} is the running program process ID.
42294 @c man begin SEEALSO gcore
42296 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42297 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42298 documentation are properly installed at your site, the command
42305 should give you access to the complete manual.
42307 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42308 Richard M. Stallman and Roland H. Pesch, July 1991.
42315 @c man title gdbinit GDB initialization scripts
42318 @c man begin SYNOPSIS gdbinit
42319 @ifset SYSTEM_GDBINIT
42320 @value{SYSTEM_GDBINIT}
42329 @c man begin DESCRIPTION gdbinit
42330 These files contain @value{GDBN} commands to automatically execute during
42331 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42334 the @value{GDBN} manual in node @code{Sequences}
42335 -- shell command @code{info -f gdb -n Sequences}.
42341 Please read more in
42343 the @value{GDBN} manual in node @code{Startup}
42344 -- shell command @code{info -f gdb -n Startup}.
42351 @ifset SYSTEM_GDBINIT
42352 @item @value{SYSTEM_GDBINIT}
42354 @ifclear SYSTEM_GDBINIT
42355 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42357 System-wide initialization file. It is executed unless user specified
42358 @value{GDBN} option @code{-nx} or @code{-n}.
42361 the @value{GDBN} manual in node @code{System-wide configuration}
42362 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42365 @ref{System-wide configuration}.
42369 User initialization file. It is executed unless user specified
42370 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42373 Initialization file for current directory. It may need to be enabled with
42374 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42377 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42378 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42381 @ref{Init File in the Current Directory}.
42386 @c man begin SEEALSO gdbinit
42388 gdb(1), @code{info -f gdb -n Startup}
42390 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42391 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42392 documentation are properly installed at your site, the command
42398 should give you access to the complete manual.
42400 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42401 Richard M. Stallman and Roland H. Pesch, July 1991.
42407 @node GNU Free Documentation License
42408 @appendix GNU Free Documentation License
42411 @node Concept Index
42412 @unnumbered Concept Index
42416 @node Command and Variable Index
42417 @unnumbered Command, Variable, and Function Index
42422 % I think something like @@colophon should be in texinfo. In the
42424 \long\def\colophon{\hbox to0pt{}\vfill
42425 \centerline{The body of this manual is set in}
42426 \centerline{\fontname\tenrm,}
42427 \centerline{with headings in {\bf\fontname\tenbf}}
42428 \centerline{and examples in {\tt\fontname\tentt}.}
42429 \centerline{{\it\fontname\tenit\/},}
42430 \centerline{{\bf\fontname\tenbf}, and}
42431 \centerline{{\sl\fontname\tensl\/}}
42432 \centerline{are used for emphasis.}\vfill}
42434 % Blame: doc@@cygnus.com, 1991.