1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2016 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{} 1988-2016 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) 1988-2016 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 @var{filename}
17247 @itemx maint print psymbols @var{filename}
17248 @itemx maint print msymbols @var{filename}
17249 Write a dump of debugging symbol data into the file @var{filename}.
17250 These commands are used to debug the @value{GDBN} symbol-reading code. Only
17251 symbols with debugging data are included. If you use @samp{maint print
17252 symbols}, @value{GDBN} includes all the symbols for which it has already
17253 collected full details: that is, @var{filename} reflects symbols for
17254 only those files whose symbols @value{GDBN} has read. You can use the
17255 command @code{info sources} to find out which files these are. If you
17256 use @samp{maint print psymbols} instead, the dump shows information about
17257 symbols that @value{GDBN} only knows partially---that is, symbols defined in
17258 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
17259 @samp{maint print msymbols} dumps just the minimal symbol information
17260 required for each object file from which @value{GDBN} has read some symbols.
17261 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17262 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17264 @kindex maint info symtabs
17265 @kindex maint info psymtabs
17266 @cindex listing @value{GDBN}'s internal symbol tables
17267 @cindex symbol tables, listing @value{GDBN}'s internal
17268 @cindex full symbol tables, listing @value{GDBN}'s internal
17269 @cindex partial symbol tables, listing @value{GDBN}'s internal
17270 @item maint info symtabs @r{[} @var{regexp} @r{]}
17271 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17273 List the @code{struct symtab} or @code{struct partial_symtab}
17274 structures whose names match @var{regexp}. If @var{regexp} is not
17275 given, list them all. The output includes expressions which you can
17276 copy into a @value{GDBN} debugging this one to examine a particular
17277 structure in more detail. For example:
17280 (@value{GDBP}) maint info psymtabs dwarf2read
17281 @{ objfile /home/gnu/build/gdb/gdb
17282 ((struct objfile *) 0x82e69d0)
17283 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17284 ((struct partial_symtab *) 0x8474b10)
17287 text addresses 0x814d3c8 -- 0x8158074
17288 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17289 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17290 dependencies (none)
17293 (@value{GDBP}) maint info symtabs
17297 We see that there is one partial symbol table whose filename contains
17298 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17299 and we see that @value{GDBN} has not read in any symtabs yet at all.
17300 If we set a breakpoint on a function, that will cause @value{GDBN} to
17301 read the symtab for the compilation unit containing that function:
17304 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17305 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17307 (@value{GDBP}) maint info symtabs
17308 @{ objfile /home/gnu/build/gdb/gdb
17309 ((struct objfile *) 0x82e69d0)
17310 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17311 ((struct symtab *) 0x86c1f38)
17314 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17315 linetable ((struct linetable *) 0x8370fa0)
17316 debugformat DWARF 2
17322 @kindex maint info line-table
17323 @cindex listing @value{GDBN}'s internal line tables
17324 @cindex line tables, listing @value{GDBN}'s internal
17325 @item maint info line-table @r{[} @var{regexp} @r{]}
17327 List the @code{struct linetable} from all @code{struct symtab}
17328 instances whose name matches @var{regexp}. If @var{regexp} is not
17329 given, list the @code{struct linetable} from all @code{struct symtab}.
17331 @kindex maint set symbol-cache-size
17332 @cindex symbol cache size
17333 @item maint set symbol-cache-size @var{size}
17334 Set the size of the symbol cache to @var{size}.
17335 The default size is intended to be good enough for debugging
17336 most applications. This option exists to allow for experimenting
17337 with different sizes.
17339 @kindex maint show symbol-cache-size
17340 @item maint show symbol-cache-size
17341 Show the size of the symbol cache.
17343 @kindex maint print symbol-cache
17344 @cindex symbol cache, printing its contents
17345 @item maint print symbol-cache
17346 Print the contents of the symbol cache.
17347 This is useful when debugging symbol cache issues.
17349 @kindex maint print symbol-cache-statistics
17350 @cindex symbol cache, printing usage statistics
17351 @item maint print symbol-cache-statistics
17352 Print symbol cache usage statistics.
17353 This helps determine how well the cache is being utilized.
17355 @kindex maint flush-symbol-cache
17356 @cindex symbol cache, flushing
17357 @item maint flush-symbol-cache
17358 Flush the contents of the symbol cache, all entries are removed.
17359 This command is useful when debugging the symbol cache.
17360 It is also useful when collecting performance data.
17365 @chapter Altering Execution
17367 Once you think you have found an error in your program, you might want to
17368 find out for certain whether correcting the apparent error would lead to
17369 correct results in the rest of the run. You can find the answer by
17370 experiment, using the @value{GDBN} features for altering execution of the
17373 For example, you can store new values into variables or memory
17374 locations, give your program a signal, restart it at a different
17375 address, or even return prematurely from a function.
17378 * Assignment:: Assignment to variables
17379 * Jumping:: Continuing at a different address
17380 * Signaling:: Giving your program a signal
17381 * Returning:: Returning from a function
17382 * Calling:: Calling your program's functions
17383 * Patching:: Patching your program
17384 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17388 @section Assignment to Variables
17391 @cindex setting variables
17392 To alter the value of a variable, evaluate an assignment expression.
17393 @xref{Expressions, ,Expressions}. For example,
17400 stores the value 4 into the variable @code{x}, and then prints the
17401 value of the assignment expression (which is 4).
17402 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17403 information on operators in supported languages.
17405 @kindex set variable
17406 @cindex variables, setting
17407 If you are not interested in seeing the value of the assignment, use the
17408 @code{set} command instead of the @code{print} command. @code{set} is
17409 really the same as @code{print} except that the expression's value is
17410 not printed and is not put in the value history (@pxref{Value History,
17411 ,Value History}). The expression is evaluated only for its effects.
17413 If the beginning of the argument string of the @code{set} command
17414 appears identical to a @code{set} subcommand, use the @code{set
17415 variable} command instead of just @code{set}. This command is identical
17416 to @code{set} except for its lack of subcommands. For example, if your
17417 program has a variable @code{width}, you get an error if you try to set
17418 a new value with just @samp{set width=13}, because @value{GDBN} has the
17419 command @code{set width}:
17422 (@value{GDBP}) whatis width
17424 (@value{GDBP}) p width
17426 (@value{GDBP}) set width=47
17427 Invalid syntax in expression.
17431 The invalid expression, of course, is @samp{=47}. In
17432 order to actually set the program's variable @code{width}, use
17435 (@value{GDBP}) set var width=47
17438 Because the @code{set} command has many subcommands that can conflict
17439 with the names of program variables, it is a good idea to use the
17440 @code{set variable} command instead of just @code{set}. For example, if
17441 your program has a variable @code{g}, you run into problems if you try
17442 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17443 the command @code{set gnutarget}, abbreviated @code{set g}:
17447 (@value{GDBP}) whatis g
17451 (@value{GDBP}) set g=4
17455 The program being debugged has been started already.
17456 Start it from the beginning? (y or n) y
17457 Starting program: /home/smith/cc_progs/a.out
17458 "/home/smith/cc_progs/a.out": can't open to read symbols:
17459 Invalid bfd target.
17460 (@value{GDBP}) show g
17461 The current BFD target is "=4".
17466 The program variable @code{g} did not change, and you silently set the
17467 @code{gnutarget} to an invalid value. In order to set the variable
17471 (@value{GDBP}) set var g=4
17474 @value{GDBN} allows more implicit conversions in assignments than C; you can
17475 freely store an integer value into a pointer variable or vice versa,
17476 and you can convert any structure to any other structure that is the
17477 same length or shorter.
17478 @comment FIXME: how do structs align/pad in these conversions?
17479 @comment /doc@cygnus.com 18dec1990
17481 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17482 construct to generate a value of specified type at a specified address
17483 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17484 to memory location @code{0x83040} as an integer (which implies a certain size
17485 and representation in memory), and
17488 set @{int@}0x83040 = 4
17492 stores the value 4 into that memory location.
17495 @section Continuing at a Different Address
17497 Ordinarily, when you continue your program, you do so at the place where
17498 it stopped, with the @code{continue} command. You can instead continue at
17499 an address of your own choosing, with the following commands:
17503 @kindex j @r{(@code{jump})}
17504 @item jump @var{location}
17505 @itemx j @var{location}
17506 Resume execution at @var{location}. Execution stops again immediately
17507 if there is a breakpoint there. @xref{Specify Location}, for a description
17508 of the different forms of @var{location}. It is common
17509 practice to use the @code{tbreak} command in conjunction with
17510 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17512 The @code{jump} command does not change the current stack frame, or
17513 the stack pointer, or the contents of any memory location or any
17514 register other than the program counter. If @var{location} is in
17515 a different function from the one currently executing, the results may
17516 be bizarre if the two functions expect different patterns of arguments or
17517 of local variables. For this reason, the @code{jump} command requests
17518 confirmation if the specified line is not in the function currently
17519 executing. However, even bizarre results are predictable if you are
17520 well acquainted with the machine-language code of your program.
17523 On many systems, you can get much the same effect as the @code{jump}
17524 command by storing a new value into the register @code{$pc}. The
17525 difference is that this does not start your program running; it only
17526 changes the address of where it @emph{will} run when you continue. For
17534 makes the next @code{continue} command or stepping command execute at
17535 address @code{0x485}, rather than at the address where your program stopped.
17536 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17538 The most common occasion to use the @code{jump} command is to back
17539 up---perhaps with more breakpoints set---over a portion of a program
17540 that has already executed, in order to examine its execution in more
17545 @section Giving your Program a Signal
17546 @cindex deliver a signal to a program
17550 @item signal @var{signal}
17551 Resume execution where your program is stopped, but immediately give it the
17552 signal @var{signal}. The @var{signal} can be the name or the number of a
17553 signal. For example, on many systems @code{signal 2} and @code{signal
17554 SIGINT} are both ways of sending an interrupt signal.
17556 Alternatively, if @var{signal} is zero, continue execution without
17557 giving a signal. This is useful when your program stopped on account of
17558 a signal and would ordinarily see the signal when resumed with the
17559 @code{continue} command; @samp{signal 0} causes it to resume without a
17562 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17563 delivered to the currently selected thread, not the thread that last
17564 reported a stop. This includes the situation where a thread was
17565 stopped due to a signal. So if you want to continue execution
17566 suppressing the signal that stopped a thread, you should select that
17567 same thread before issuing the @samp{signal 0} command. If you issue
17568 the @samp{signal 0} command with another thread as the selected one,
17569 @value{GDBN} detects that and asks for confirmation.
17571 Invoking the @code{signal} command is not the same as invoking the
17572 @code{kill} utility from the shell. Sending a signal with @code{kill}
17573 causes @value{GDBN} to decide what to do with the signal depending on
17574 the signal handling tables (@pxref{Signals}). The @code{signal} command
17575 passes the signal directly to your program.
17577 @code{signal} does not repeat when you press @key{RET} a second time
17578 after executing the command.
17580 @kindex queue-signal
17581 @item queue-signal @var{signal}
17582 Queue @var{signal} to be delivered immediately to the current thread
17583 when execution of the thread resumes. The @var{signal} can be the name or
17584 the number of a signal. For example, on many systems @code{signal 2} and
17585 @code{signal SIGINT} are both ways of sending an interrupt signal.
17586 The handling of the signal must be set to pass the signal to the program,
17587 otherwise @value{GDBN} will report an error.
17588 You can control the handling of signals from @value{GDBN} with the
17589 @code{handle} command (@pxref{Signals}).
17591 Alternatively, if @var{signal} is zero, any currently queued signal
17592 for the current thread is discarded and when execution resumes no signal
17593 will be delivered. This is useful when your program stopped on account
17594 of a signal and would ordinarily see the signal when resumed with the
17595 @code{continue} command.
17597 This command differs from the @code{signal} command in that the signal
17598 is just queued, execution is not resumed. And @code{queue-signal} cannot
17599 be used to pass a signal whose handling state has been set to @code{nopass}
17604 @xref{stepping into signal handlers}, for information on how stepping
17605 commands behave when the thread has a signal queued.
17608 @section Returning from a Function
17611 @cindex returning from a function
17614 @itemx return @var{expression}
17615 You can cancel execution of a function call with the @code{return}
17616 command. If you give an
17617 @var{expression} argument, its value is used as the function's return
17621 When you use @code{return}, @value{GDBN} discards the selected stack frame
17622 (and all frames within it). You can think of this as making the
17623 discarded frame return prematurely. If you wish to specify a value to
17624 be returned, give that value as the argument to @code{return}.
17626 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17627 Frame}), and any other frames inside of it, leaving its caller as the
17628 innermost remaining frame. That frame becomes selected. The
17629 specified value is stored in the registers used for returning values
17632 The @code{return} command does not resume execution; it leaves the
17633 program stopped in the state that would exist if the function had just
17634 returned. In contrast, the @code{finish} command (@pxref{Continuing
17635 and Stepping, ,Continuing and Stepping}) resumes execution until the
17636 selected stack frame returns naturally.
17638 @value{GDBN} needs to know how the @var{expression} argument should be set for
17639 the inferior. The concrete registers assignment depends on the OS ABI and the
17640 type being returned by the selected stack frame. For example it is common for
17641 OS ABI to return floating point values in FPU registers while integer values in
17642 CPU registers. Still some ABIs return even floating point values in CPU
17643 registers. Larger integer widths (such as @code{long long int}) also have
17644 specific placement rules. @value{GDBN} already knows the OS ABI from its
17645 current target so it needs to find out also the type being returned to make the
17646 assignment into the right register(s).
17648 Normally, the selected stack frame has debug info. @value{GDBN} will always
17649 use the debug info instead of the implicit type of @var{expression} when the
17650 debug info is available. For example, if you type @kbd{return -1}, and the
17651 function in the current stack frame is declared to return a @code{long long
17652 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17653 into a @code{long long int}:
17656 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17658 (@value{GDBP}) return -1
17659 Make func return now? (y or n) y
17660 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17661 43 printf ("result=%lld\n", func ());
17665 However, if the selected stack frame does not have a debug info, e.g., if the
17666 function was compiled without debug info, @value{GDBN} has to find out the type
17667 to return from user. Specifying a different type by mistake may set the value
17668 in different inferior registers than the caller code expects. For example,
17669 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17670 of a @code{long long int} result for a debug info less function (on 32-bit
17671 architectures). Therefore the user is required to specify the return type by
17672 an appropriate cast explicitly:
17675 Breakpoint 2, 0x0040050b in func ()
17676 (@value{GDBP}) return -1
17677 Return value type not available for selected stack frame.
17678 Please use an explicit cast of the value to return.
17679 (@value{GDBP}) return (long long int) -1
17680 Make selected stack frame return now? (y or n) y
17681 #0 0x00400526 in main ()
17686 @section Calling Program Functions
17689 @cindex calling functions
17690 @cindex inferior functions, calling
17691 @item print @var{expr}
17692 Evaluate the expression @var{expr} and display the resulting value.
17693 The expression may include calls to functions in the program being
17697 @item call @var{expr}
17698 Evaluate the expression @var{expr} without displaying @code{void}
17701 You can use this variant of the @code{print} command if you want to
17702 execute a function from your program that does not return anything
17703 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17704 with @code{void} returned values that @value{GDBN} will otherwise
17705 print. If the result is not void, it is printed and saved in the
17709 It is possible for the function you call via the @code{print} or
17710 @code{call} command to generate a signal (e.g., if there's a bug in
17711 the function, or if you passed it incorrect arguments). What happens
17712 in that case is controlled by the @code{set unwindonsignal} command.
17714 Similarly, with a C@t{++} program it is possible for the function you
17715 call via the @code{print} or @code{call} command to generate an
17716 exception that is not handled due to the constraints of the dummy
17717 frame. In this case, any exception that is raised in the frame, but has
17718 an out-of-frame exception handler will not be found. GDB builds a
17719 dummy-frame for the inferior function call, and the unwinder cannot
17720 seek for exception handlers outside of this dummy-frame. What happens
17721 in that case is controlled by the
17722 @code{set unwind-on-terminating-exception} command.
17725 @item set unwindonsignal
17726 @kindex set unwindonsignal
17727 @cindex unwind stack in called functions
17728 @cindex call dummy stack unwinding
17729 Set unwinding of the stack if a signal is received while in a function
17730 that @value{GDBN} called in the program being debugged. If set to on,
17731 @value{GDBN} unwinds the stack it created for the call and restores
17732 the context to what it was before the call. If set to off (the
17733 default), @value{GDBN} stops in the frame where the signal was
17736 @item show unwindonsignal
17737 @kindex show unwindonsignal
17738 Show the current setting of stack unwinding in the functions called by
17741 @item set unwind-on-terminating-exception
17742 @kindex set unwind-on-terminating-exception
17743 @cindex unwind stack in called functions with unhandled exceptions
17744 @cindex call dummy stack unwinding on unhandled exception.
17745 Set unwinding of the stack if a C@t{++} exception is raised, but left
17746 unhandled while in a function that @value{GDBN} called in the program being
17747 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17748 it created for the call and restores the context to what it was before
17749 the call. If set to off, @value{GDBN} the exception is delivered to
17750 the default C@t{++} exception handler and the inferior terminated.
17752 @item show unwind-on-terminating-exception
17753 @kindex show unwind-on-terminating-exception
17754 Show the current setting of stack unwinding in the functions called by
17759 @cindex weak alias functions
17760 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17761 for another function. In such case, @value{GDBN} might not pick up
17762 the type information, including the types of the function arguments,
17763 which causes @value{GDBN} to call the inferior function incorrectly.
17764 As a result, the called function will function erroneously and may
17765 even crash. A solution to that is to use the name of the aliased
17769 @section Patching Programs
17771 @cindex patching binaries
17772 @cindex writing into executables
17773 @cindex writing into corefiles
17775 By default, @value{GDBN} opens the file containing your program's
17776 executable code (or the corefile) read-only. This prevents accidental
17777 alterations to machine code; but it also prevents you from intentionally
17778 patching your program's binary.
17780 If you'd like to be able to patch the binary, you can specify that
17781 explicitly with the @code{set write} command. For example, you might
17782 want to turn on internal debugging flags, or even to make emergency
17788 @itemx set write off
17789 If you specify @samp{set write on}, @value{GDBN} opens executable and
17790 core files for both reading and writing; if you specify @kbd{set write
17791 off} (the default), @value{GDBN} opens them read-only.
17793 If you have already loaded a file, you must load it again (using the
17794 @code{exec-file} or @code{core-file} command) after changing @code{set
17795 write}, for your new setting to take effect.
17799 Display whether executable files and core files are opened for writing
17800 as well as reading.
17803 @node Compiling and Injecting Code
17804 @section Compiling and injecting code in @value{GDBN}
17805 @cindex injecting code
17806 @cindex writing into executables
17807 @cindex compiling code
17809 @value{GDBN} supports on-demand compilation and code injection into
17810 programs running under @value{GDBN}. GCC 5.0 or higher built with
17811 @file{libcc1.so} must be installed for this functionality to be enabled.
17812 This functionality is implemented with the following commands.
17815 @kindex compile code
17816 @item compile code @var{source-code}
17817 @itemx compile code -raw @var{--} @var{source-code}
17818 Compile @var{source-code} with the compiler language found as the current
17819 language in @value{GDBN} (@pxref{Languages}). If compilation and
17820 injection is not supported with the current language specified in
17821 @value{GDBN}, or the compiler does not support this feature, an error
17822 message will be printed. If @var{source-code} compiles and links
17823 successfully, @value{GDBN} will load the object-code emitted,
17824 and execute it within the context of the currently selected inferior.
17825 It is important to note that the compiled code is executed immediately.
17826 After execution, the compiled code is removed from @value{GDBN} and any
17827 new types or variables you have defined will be deleted.
17829 The command allows you to specify @var{source-code} in two ways.
17830 The simplest method is to provide a single line of code to the command.
17834 compile code printf ("hello world\n");
17837 If you specify options on the command line as well as source code, they
17838 may conflict. The @samp{--} delimiter can be used to separate options
17839 from actual source code. E.g.:
17842 compile code -r -- printf ("hello world\n");
17845 Alternatively you can enter source code as multiple lines of text. To
17846 enter this mode, invoke the @samp{compile code} command without any text
17847 following the command. This will start the multiple-line editor and
17848 allow you to type as many lines of source code as required. When you
17849 have completed typing, enter @samp{end} on its own line to exit the
17854 >printf ("hello\n");
17855 >printf ("world\n");
17859 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17860 provided @var{source-code} in a callable scope. In this case, you must
17861 specify the entry point of the code by defining a function named
17862 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17863 inferior. Using @samp{-raw} option may be needed for example when
17864 @var{source-code} requires @samp{#include} lines which may conflict with
17865 inferior symbols otherwise.
17867 @kindex compile file
17868 @item compile file @var{filename}
17869 @itemx compile file -raw @var{filename}
17870 Like @code{compile code}, but take the source code from @var{filename}.
17873 compile file /home/user/example.c
17878 @item compile print @var{expr}
17879 @itemx compile print /@var{f} @var{expr}
17880 Compile and execute @var{expr} with the compiler language found as the
17881 current language in @value{GDBN} (@pxref{Languages}). By default the
17882 value of @var{expr} is printed in a format appropriate to its data type;
17883 you can choose a different format by specifying @samp{/@var{f}}, where
17884 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17887 @item compile print
17888 @itemx compile print /@var{f}
17889 @cindex reprint the last value
17890 Alternatively you can enter the expression (source code producing it) as
17891 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17892 command without any text following the command. This will start the
17893 multiple-line editor.
17897 The process of compiling and injecting the code can be inspected using:
17900 @anchor{set debug compile}
17901 @item set debug compile
17902 @cindex compile command debugging info
17903 Turns on or off display of @value{GDBN} process of compiling and
17904 injecting the code. The default is off.
17906 @item show debug compile
17907 Displays the current state of displaying @value{GDBN} process of
17908 compiling and injecting the code.
17911 @subsection Compilation options for the @code{compile} command
17913 @value{GDBN} needs to specify the right compilation options for the code
17914 to be injected, in part to make its ABI compatible with the inferior
17915 and in part to make the injected code compatible with @value{GDBN}'s
17919 The options used, in increasing precedence:
17922 @item target architecture and OS options (@code{gdbarch})
17923 These options depend on target processor type and target operating
17924 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17925 (@code{-m64}) compilation option.
17927 @item compilation options recorded in the target
17928 @value{NGCC} (since version 4.7) stores the options used for compilation
17929 into @code{DW_AT_producer} part of DWARF debugging information according
17930 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17931 explicitly specify @code{-g} during inferior compilation otherwise
17932 @value{NGCC} produces no DWARF. This feature is only relevant for
17933 platforms where @code{-g} produces DWARF by default, otherwise one may
17934 try to enforce DWARF by using @code{-gdwarf-4}.
17936 @item compilation options set by @code{set compile-args}
17940 You can override compilation options using the following command:
17943 @item set compile-args
17944 @cindex compile command options override
17945 Set compilation options used for compiling and injecting code with the
17946 @code{compile} commands. These options override any conflicting ones
17947 from the target architecture and/or options stored during inferior
17950 @item show compile-args
17951 Displays the current state of compilation options override.
17952 This does not show all the options actually used during compilation,
17953 use @ref{set debug compile} for that.
17956 @subsection Caveats when using the @code{compile} command
17958 There are a few caveats to keep in mind when using the @code{compile}
17959 command. As the caveats are different per language, the table below
17960 highlights specific issues on a per language basis.
17963 @item C code examples and caveats
17964 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17965 attempt to compile the source code with a @samp{C} compiler. The source
17966 code provided to the @code{compile} command will have much the same
17967 access to variables and types as it normally would if it were part of
17968 the program currently being debugged in @value{GDBN}.
17970 Below is a sample program that forms the basis of the examples that
17971 follow. This program has been compiled and loaded into @value{GDBN},
17972 much like any other normal debugging session.
17975 void function1 (void)
17978 printf ("function 1\n");
17981 void function2 (void)
17996 For the purposes of the examples in this section, the program above has
17997 been compiled, loaded into @value{GDBN}, stopped at the function
17998 @code{main}, and @value{GDBN} is awaiting input from the user.
18000 To access variables and types for any program in @value{GDBN}, the
18001 program must be compiled and packaged with debug information. The
18002 @code{compile} command is not an exception to this rule. Without debug
18003 information, you can still use the @code{compile} command, but you will
18004 be very limited in what variables and types you can access.
18006 So with that in mind, the example above has been compiled with debug
18007 information enabled. The @code{compile} command will have access to
18008 all variables and types (except those that may have been optimized
18009 out). Currently, as @value{GDBN} has stopped the program in the
18010 @code{main} function, the @code{compile} command would have access to
18011 the variable @code{k}. You could invoke the @code{compile} command
18012 and type some source code to set the value of @code{k}. You can also
18013 read it, or do anything with that variable you would normally do in
18014 @code{C}. Be aware that changes to inferior variables in the
18015 @code{compile} command are persistent. In the following example:
18018 compile code k = 3;
18022 the variable @code{k} is now 3. It will retain that value until
18023 something else in the example program changes it, or another
18024 @code{compile} command changes it.
18026 Normal scope and access rules apply to source code compiled and
18027 injected by the @code{compile} command. In the example, the variables
18028 @code{j} and @code{k} are not accessible yet, because the program is
18029 currently stopped in the @code{main} function, where these variables
18030 are not in scope. Therefore, the following command
18033 compile code j = 3;
18037 will result in a compilation error message.
18039 Once the program is continued, execution will bring these variables in
18040 scope, and they will become accessible; then the code you specify via
18041 the @code{compile} command will be able to access them.
18043 You can create variables and types with the @code{compile} command as
18044 part of your source code. Variables and types that are created as part
18045 of the @code{compile} command are not visible to the rest of the program for
18046 the duration of its run. This example is valid:
18049 compile code int ff = 5; printf ("ff is %d\n", ff);
18052 However, if you were to type the following into @value{GDBN} after that
18053 command has completed:
18056 compile code printf ("ff is %d\n'', ff);
18060 a compiler error would be raised as the variable @code{ff} no longer
18061 exists. Object code generated and injected by the @code{compile}
18062 command is removed when its execution ends. Caution is advised
18063 when assigning to program variables values of variables created by the
18064 code submitted to the @code{compile} command. This example is valid:
18067 compile code int ff = 5; k = ff;
18070 The value of the variable @code{ff} is assigned to @code{k}. The variable
18071 @code{k} does not require the existence of @code{ff} to maintain the value
18072 it has been assigned. However, pointers require particular care in
18073 assignment. If the source code compiled with the @code{compile} command
18074 changed the address of a pointer in the example program, perhaps to a
18075 variable created in the @code{compile} command, that pointer would point
18076 to an invalid location when the command exits. The following example
18077 would likely cause issues with your debugged program:
18080 compile code int ff = 5; p = &ff;
18083 In this example, @code{p} would point to @code{ff} when the
18084 @code{compile} command is executing the source code provided to it.
18085 However, as variables in the (example) program persist with their
18086 assigned values, the variable @code{p} would point to an invalid
18087 location when the command exists. A general rule should be followed
18088 in that you should either assign @code{NULL} to any assigned pointers,
18089 or restore a valid location to the pointer before the command exits.
18091 Similar caution must be exercised with any structs, unions, and typedefs
18092 defined in @code{compile} command. Types defined in the @code{compile}
18093 command will no longer be available in the next @code{compile} command.
18094 Therefore, if you cast a variable to a type defined in the
18095 @code{compile} command, care must be taken to ensure that any future
18096 need to resolve the type can be achieved.
18099 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18100 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18101 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18102 Compilation failed.
18103 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18107 Variables that have been optimized away by the compiler are not
18108 accessible to the code submitted to the @code{compile} command.
18109 Access to those variables will generate a compiler error which @value{GDBN}
18110 will print to the console.
18113 @subsection Compiler search for the @code{compile} command
18115 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
18116 may not be obvious for remote targets of different architecture than where
18117 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
18118 shell that executed @value{GDBN}, not the one set by @value{GDBN}
18119 command @code{set environment}). @xref{Environment}. @code{PATH} on
18120 @value{GDBN} host is searched for @value{NGCC} binary matching the
18121 target architecture and operating system.
18123 Specifically @code{PATH} is searched for binaries matching regular expression
18124 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18125 debugged. @var{arch} is processor name --- multiarch is supported, so for
18126 example both @code{i386} and @code{x86_64} targets look for pattern
18127 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18128 for pattern @code{s390x?}. @var{os} is currently supported only for
18129 pattern @code{linux(-gnu)?}.
18132 @chapter @value{GDBN} Files
18134 @value{GDBN} needs to know the file name of the program to be debugged,
18135 both in order to read its symbol table and in order to start your
18136 program. To debug a core dump of a previous run, you must also tell
18137 @value{GDBN} the name of the core dump file.
18140 * Files:: Commands to specify files
18141 * File Caching:: Information about @value{GDBN}'s file caching
18142 * Separate Debug Files:: Debugging information in separate files
18143 * MiniDebugInfo:: Debugging information in a special section
18144 * Index Files:: Index files speed up GDB
18145 * Symbol Errors:: Errors reading symbol files
18146 * Data Files:: GDB data files
18150 @section Commands to Specify Files
18152 @cindex symbol table
18153 @cindex core dump file
18155 You may want to specify executable and core dump file names. The usual
18156 way to do this is at start-up time, using the arguments to
18157 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18158 Out of @value{GDBN}}).
18160 Occasionally it is necessary to change to a different file during a
18161 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18162 specify a file you want to use. Or you are debugging a remote target
18163 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18164 Program}). In these situations the @value{GDBN} commands to specify
18165 new files are useful.
18168 @cindex executable file
18170 @item file @var{filename}
18171 Use @var{filename} as the program to be debugged. It is read for its
18172 symbols and for the contents of pure memory. It is also the program
18173 executed when you use the @code{run} command. If you do not specify a
18174 directory and the file is not found in the @value{GDBN} working directory,
18175 @value{GDBN} uses the environment variable @code{PATH} as a list of
18176 directories to search, just as the shell does when looking for a program
18177 to run. You can change the value of this variable, for both @value{GDBN}
18178 and your program, using the @code{path} command.
18180 @cindex unlinked object files
18181 @cindex patching object files
18182 You can load unlinked object @file{.o} files into @value{GDBN} using
18183 the @code{file} command. You will not be able to ``run'' an object
18184 file, but you can disassemble functions and inspect variables. Also,
18185 if the underlying BFD functionality supports it, you could use
18186 @kbd{gdb -write} to patch object files using this technique. Note
18187 that @value{GDBN} can neither interpret nor modify relocations in this
18188 case, so branches and some initialized variables will appear to go to
18189 the wrong place. But this feature is still handy from time to time.
18192 @code{file} with no argument makes @value{GDBN} discard any information it
18193 has on both executable file and the symbol table.
18196 @item exec-file @r{[} @var{filename} @r{]}
18197 Specify that the program to be run (but not the symbol table) is found
18198 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18199 if necessary to locate your program. Omitting @var{filename} means to
18200 discard information on the executable file.
18202 @kindex symbol-file
18203 @item symbol-file @r{[} @var{filename} @r{]}
18204 Read symbol table information from file @var{filename}. @code{PATH} is
18205 searched when necessary. Use the @code{file} command to get both symbol
18206 table and program to run from the same file.
18208 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18209 program's symbol table.
18211 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18212 some breakpoints and auto-display expressions. This is because they may
18213 contain pointers to the internal data recording symbols and data types,
18214 which are part of the old symbol table data being discarded inside
18217 @code{symbol-file} does not repeat if you press @key{RET} again after
18220 When @value{GDBN} is configured for a particular environment, it
18221 understands debugging information in whatever format is the standard
18222 generated for that environment; you may use either a @sc{gnu} compiler, or
18223 other compilers that adhere to the local conventions.
18224 Best results are usually obtained from @sc{gnu} compilers; for example,
18225 using @code{@value{NGCC}} you can generate debugging information for
18228 For most kinds of object files, with the exception of old SVR3 systems
18229 using COFF, the @code{symbol-file} command does not normally read the
18230 symbol table in full right away. Instead, it scans the symbol table
18231 quickly to find which source files and which symbols are present. The
18232 details are read later, one source file at a time, as they are needed.
18234 The purpose of this two-stage reading strategy is to make @value{GDBN}
18235 start up faster. For the most part, it is invisible except for
18236 occasional pauses while the symbol table details for a particular source
18237 file are being read. (The @code{set verbose} command can turn these
18238 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18239 Warnings and Messages}.)
18241 We have not implemented the two-stage strategy for COFF yet. When the
18242 symbol table is stored in COFF format, @code{symbol-file} reads the
18243 symbol table data in full right away. Note that ``stabs-in-COFF''
18244 still does the two-stage strategy, since the debug info is actually
18248 @cindex reading symbols immediately
18249 @cindex symbols, reading immediately
18250 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18251 @itemx file @r{[} -readnow @r{]} @var{filename}
18252 You can override the @value{GDBN} two-stage strategy for reading symbol
18253 tables by using the @samp{-readnow} option with any of the commands that
18254 load symbol table information, if you want to be sure @value{GDBN} has the
18255 entire symbol table available.
18257 @c FIXME: for now no mention of directories, since this seems to be in
18258 @c flux. 13mar1992 status is that in theory GDB would look either in
18259 @c current dir or in same dir as myprog; but issues like competing
18260 @c GDB's, or clutter in system dirs, mean that in practice right now
18261 @c only current dir is used. FFish says maybe a special GDB hierarchy
18262 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18266 @item core-file @r{[}@var{filename}@r{]}
18268 Specify the whereabouts of a core dump file to be used as the ``contents
18269 of memory''. Traditionally, core files contain only some parts of the
18270 address space of the process that generated them; @value{GDBN} can access the
18271 executable file itself for other parts.
18273 @code{core-file} with no argument specifies that no core file is
18276 Note that the core file is ignored when your program is actually running
18277 under @value{GDBN}. So, if you have been running your program and you
18278 wish to debug a core file instead, you must kill the subprocess in which
18279 the program is running. To do this, use the @code{kill} command
18280 (@pxref{Kill Process, ,Killing the Child Process}).
18282 @kindex add-symbol-file
18283 @cindex dynamic linking
18284 @item add-symbol-file @var{filename} @var{address}
18285 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18286 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18287 The @code{add-symbol-file} command reads additional symbol table
18288 information from the file @var{filename}. You would use this command
18289 when @var{filename} has been dynamically loaded (by some other means)
18290 into the program that is running. The @var{address} should give the memory
18291 address at which the file has been loaded; @value{GDBN} cannot figure
18292 this out for itself. You can additionally specify an arbitrary number
18293 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18294 section name and base address for that section. You can specify any
18295 @var{address} as an expression.
18297 The symbol table of the file @var{filename} is added to the symbol table
18298 originally read with the @code{symbol-file} command. You can use the
18299 @code{add-symbol-file} command any number of times; the new symbol data
18300 thus read is kept in addition to the old.
18302 Changes can be reverted using the command @code{remove-symbol-file}.
18304 @cindex relocatable object files, reading symbols from
18305 @cindex object files, relocatable, reading symbols from
18306 @cindex reading symbols from relocatable object files
18307 @cindex symbols, reading from relocatable object files
18308 @cindex @file{.o} files, reading symbols from
18309 Although @var{filename} is typically a shared library file, an
18310 executable file, or some other object file which has been fully
18311 relocated for loading into a process, you can also load symbolic
18312 information from relocatable @file{.o} files, as long as:
18316 the file's symbolic information refers only to linker symbols defined in
18317 that file, not to symbols defined by other object files,
18319 every section the file's symbolic information refers to has actually
18320 been loaded into the inferior, as it appears in the file, and
18322 you can determine the address at which every section was loaded, and
18323 provide these to the @code{add-symbol-file} command.
18327 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18328 relocatable files into an already running program; such systems
18329 typically make the requirements above easy to meet. However, it's
18330 important to recognize that many native systems use complex link
18331 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18332 assembly, for example) that make the requirements difficult to meet. In
18333 general, one cannot assume that using @code{add-symbol-file} to read a
18334 relocatable object file's symbolic information will have the same effect
18335 as linking the relocatable object file into the program in the normal
18338 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18340 @kindex remove-symbol-file
18341 @item remove-symbol-file @var{filename}
18342 @item remove-symbol-file -a @var{address}
18343 Remove a symbol file added via the @code{add-symbol-file} command. The
18344 file to remove can be identified by its @var{filename} or by an @var{address}
18345 that lies within the boundaries of this symbol file in memory. Example:
18348 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18349 add symbol table from file "/home/user/gdb/mylib.so" at
18350 .text_addr = 0x7ffff7ff9480
18352 Reading symbols from /home/user/gdb/mylib.so...done.
18353 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18354 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18359 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18361 @kindex add-symbol-file-from-memory
18362 @cindex @code{syscall DSO}
18363 @cindex load symbols from memory
18364 @item add-symbol-file-from-memory @var{address}
18365 Load symbols from the given @var{address} in a dynamically loaded
18366 object file whose image is mapped directly into the inferior's memory.
18367 For example, the Linux kernel maps a @code{syscall DSO} into each
18368 process's address space; this DSO provides kernel-specific code for
18369 some system calls. The argument can be any expression whose
18370 evaluation yields the address of the file's shared object file header.
18371 For this command to work, you must have used @code{symbol-file} or
18372 @code{exec-file} commands in advance.
18375 @item section @var{section} @var{addr}
18376 The @code{section} command changes the base address of the named
18377 @var{section} of the exec file to @var{addr}. This can be used if the
18378 exec file does not contain section addresses, (such as in the
18379 @code{a.out} format), or when the addresses specified in the file
18380 itself are wrong. Each section must be changed separately. The
18381 @code{info files} command, described below, lists all the sections and
18385 @kindex info target
18388 @code{info files} and @code{info target} are synonymous; both print the
18389 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18390 including the names of the executable and core dump files currently in
18391 use by @value{GDBN}, and the files from which symbols were loaded. The
18392 command @code{help target} lists all possible targets rather than
18395 @kindex maint info sections
18396 @item maint info sections
18397 Another command that can give you extra information about program sections
18398 is @code{maint info sections}. In addition to the section information
18399 displayed by @code{info files}, this command displays the flags and file
18400 offset of each section in the executable and core dump files. In addition,
18401 @code{maint info sections} provides the following command options (which
18402 may be arbitrarily combined):
18406 Display sections for all loaded object files, including shared libraries.
18407 @item @var{sections}
18408 Display info only for named @var{sections}.
18409 @item @var{section-flags}
18410 Display info only for sections for which @var{section-flags} are true.
18411 The section flags that @value{GDBN} currently knows about are:
18414 Section will have space allocated in the process when loaded.
18415 Set for all sections except those containing debug information.
18417 Section will be loaded from the file into the child process memory.
18418 Set for pre-initialized code and data, clear for @code{.bss} sections.
18420 Section needs to be relocated before loading.
18422 Section cannot be modified by the child process.
18424 Section contains executable code only.
18426 Section contains data only (no executable code).
18428 Section will reside in ROM.
18430 Section contains data for constructor/destructor lists.
18432 Section is not empty.
18434 An instruction to the linker to not output the section.
18435 @item COFF_SHARED_LIBRARY
18436 A notification to the linker that the section contains
18437 COFF shared library information.
18439 Section contains common symbols.
18442 @kindex set trust-readonly-sections
18443 @cindex read-only sections
18444 @item set trust-readonly-sections on
18445 Tell @value{GDBN} that readonly sections in your object file
18446 really are read-only (i.e.@: that their contents will not change).
18447 In that case, @value{GDBN} can fetch values from these sections
18448 out of the object file, rather than from the target program.
18449 For some targets (notably embedded ones), this can be a significant
18450 enhancement to debugging performance.
18452 The default is off.
18454 @item set trust-readonly-sections off
18455 Tell @value{GDBN} not to trust readonly sections. This means that
18456 the contents of the section might change while the program is running,
18457 and must therefore be fetched from the target when needed.
18459 @item show trust-readonly-sections
18460 Show the current setting of trusting readonly sections.
18463 All file-specifying commands allow both absolute and relative file names
18464 as arguments. @value{GDBN} always converts the file name to an absolute file
18465 name and remembers it that way.
18467 @cindex shared libraries
18468 @anchor{Shared Libraries}
18469 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18470 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18471 DSBT (TIC6X) shared libraries.
18473 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18474 shared libraries. @xref{Expat}.
18476 @value{GDBN} automatically loads symbol definitions from shared libraries
18477 when you use the @code{run} command, or when you examine a core file.
18478 (Before you issue the @code{run} command, @value{GDBN} does not understand
18479 references to a function in a shared library, however---unless you are
18480 debugging a core file).
18482 @c FIXME: some @value{GDBN} release may permit some refs to undef
18483 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18484 @c FIXME...lib; check this from time to time when updating manual
18486 There are times, however, when you may wish to not automatically load
18487 symbol definitions from shared libraries, such as when they are
18488 particularly large or there are many of them.
18490 To control the automatic loading of shared library symbols, use the
18494 @kindex set auto-solib-add
18495 @item set auto-solib-add @var{mode}
18496 If @var{mode} is @code{on}, symbols from all shared object libraries
18497 will be loaded automatically when the inferior begins execution, you
18498 attach to an independently started inferior, or when the dynamic linker
18499 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18500 is @code{off}, symbols must be loaded manually, using the
18501 @code{sharedlibrary} command. The default value is @code{on}.
18503 @cindex memory used for symbol tables
18504 If your program uses lots of shared libraries with debug info that
18505 takes large amounts of memory, you can decrease the @value{GDBN}
18506 memory footprint by preventing it from automatically loading the
18507 symbols from shared libraries. To that end, type @kbd{set
18508 auto-solib-add off} before running the inferior, then load each
18509 library whose debug symbols you do need with @kbd{sharedlibrary
18510 @var{regexp}}, where @var{regexp} is a regular expression that matches
18511 the libraries whose symbols you want to be loaded.
18513 @kindex show auto-solib-add
18514 @item show auto-solib-add
18515 Display the current autoloading mode.
18518 @cindex load shared library
18519 To explicitly load shared library symbols, use the @code{sharedlibrary}
18523 @kindex info sharedlibrary
18525 @item info share @var{regex}
18526 @itemx info sharedlibrary @var{regex}
18527 Print the names of the shared libraries which are currently loaded
18528 that match @var{regex}. If @var{regex} is omitted then print
18529 all shared libraries that are loaded.
18532 @item info dll @var{regex}
18533 This is an alias of @code{info sharedlibrary}.
18535 @kindex sharedlibrary
18537 @item sharedlibrary @var{regex}
18538 @itemx share @var{regex}
18539 Load shared object library symbols for files matching a
18540 Unix regular expression.
18541 As with files loaded automatically, it only loads shared libraries
18542 required by your program for a core file or after typing @code{run}. If
18543 @var{regex} is omitted all shared libraries required by your program are
18546 @item nosharedlibrary
18547 @kindex nosharedlibrary
18548 @cindex unload symbols from shared libraries
18549 Unload all shared object library symbols. This discards all symbols
18550 that have been loaded from all shared libraries. Symbols from shared
18551 libraries that were loaded by explicit user requests are not
18555 Sometimes you may wish that @value{GDBN} stops and gives you control
18556 when any of shared library events happen. The best way to do this is
18557 to use @code{catch load} and @code{catch unload} (@pxref{Set
18560 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18561 command for this. This command exists for historical reasons. It is
18562 less useful than setting a catchpoint, because it does not allow for
18563 conditions or commands as a catchpoint does.
18566 @item set stop-on-solib-events
18567 @kindex set stop-on-solib-events
18568 This command controls whether @value{GDBN} should give you control
18569 when the dynamic linker notifies it about some shared library event.
18570 The most common event of interest is loading or unloading of a new
18573 @item show stop-on-solib-events
18574 @kindex show stop-on-solib-events
18575 Show whether @value{GDBN} stops and gives you control when shared
18576 library events happen.
18579 Shared libraries are also supported in many cross or remote debugging
18580 configurations. @value{GDBN} needs to have access to the target's libraries;
18581 this can be accomplished either by providing copies of the libraries
18582 on the host system, or by asking @value{GDBN} to automatically retrieve the
18583 libraries from the target. If copies of the target libraries are
18584 provided, they need to be the same as the target libraries, although the
18585 copies on the target can be stripped as long as the copies on the host are
18588 @cindex where to look for shared libraries
18589 For remote debugging, you need to tell @value{GDBN} where the target
18590 libraries are, so that it can load the correct copies---otherwise, it
18591 may try to load the host's libraries. @value{GDBN} has two variables
18592 to specify the search directories for target libraries.
18595 @cindex prefix for executable and shared library file names
18596 @cindex system root, alternate
18597 @kindex set solib-absolute-prefix
18598 @kindex set sysroot
18599 @item set sysroot @var{path}
18600 Use @var{path} as the system root for the program being debugged. Any
18601 absolute shared library paths will be prefixed with @var{path}; many
18602 runtime loaders store the absolute paths to the shared library in the
18603 target program's memory. When starting processes remotely, and when
18604 attaching to already-running processes (local or remote), their
18605 executable filenames will be prefixed with @var{path} if reported to
18606 @value{GDBN} as absolute by the operating system. If you use
18607 @code{set sysroot} to find executables and shared libraries, they need
18608 to be laid out in the same way that they are on the target, with
18609 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18612 If @var{path} starts with the sequence @file{target:} and the target
18613 system is remote then @value{GDBN} will retrieve the target binaries
18614 from the remote system. This is only supported when using a remote
18615 target that supports the @code{remote get} command (@pxref{File
18616 Transfer,,Sending files to a remote system}). The part of @var{path}
18617 following the initial @file{target:} (if present) is used as system
18618 root prefix on the remote file system. If @var{path} starts with the
18619 sequence @file{remote:} this is converted to the sequence
18620 @file{target:} by @code{set sysroot}@footnote{Historically the
18621 functionality to retrieve binaries from the remote system was
18622 provided by prefixing @var{path} with @file{remote:}}. If you want
18623 to specify a local system root using a directory that happens to be
18624 named @file{target:} or @file{remote:}, you need to use some
18625 equivalent variant of the name like @file{./target:}.
18627 For targets with an MS-DOS based filesystem, such as MS-Windows and
18628 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18629 absolute file name with @var{path}. But first, on Unix hosts,
18630 @value{GDBN} converts all backslash directory separators into forward
18631 slashes, because the backslash is not a directory separator on Unix:
18634 c:\foo\bar.dll @result{} c:/foo/bar.dll
18637 Then, @value{GDBN} attempts prefixing the target file name with
18638 @var{path}, and looks for the resulting file name in the host file
18642 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18645 If that does not find the binary, @value{GDBN} tries removing
18646 the @samp{:} character from the drive spec, both for convenience, and,
18647 for the case of the host file system not supporting file names with
18651 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18654 This makes it possible to have a system root that mirrors a target
18655 with more than one drive. E.g., you may want to setup your local
18656 copies of the target system shared libraries like so (note @samp{c} vs
18660 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18661 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18662 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18666 and point the system root at @file{/path/to/sysroot}, so that
18667 @value{GDBN} can find the correct copies of both
18668 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18670 If that still does not find the binary, @value{GDBN} tries
18671 removing the whole drive spec from the target file name:
18674 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18677 This last lookup makes it possible to not care about the drive name,
18678 if you don't want or need to.
18680 The @code{set solib-absolute-prefix} command is an alias for @code{set
18683 @cindex default system root
18684 @cindex @samp{--with-sysroot}
18685 You can set the default system root by using the configure-time
18686 @samp{--with-sysroot} option. If the system root is inside
18687 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18688 @samp{--exec-prefix}), then the default system root will be updated
18689 automatically if the installed @value{GDBN} is moved to a new
18692 @kindex show sysroot
18694 Display the current executable and shared library prefix.
18696 @kindex set solib-search-path
18697 @item set solib-search-path @var{path}
18698 If this variable is set, @var{path} is a colon-separated list of
18699 directories to search for shared libraries. @samp{solib-search-path}
18700 is used after @samp{sysroot} fails to locate the library, or if the
18701 path to the library is relative instead of absolute. If you want to
18702 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18703 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18704 finding your host's libraries. @samp{sysroot} is preferred; setting
18705 it to a nonexistent directory may interfere with automatic loading
18706 of shared library symbols.
18708 @kindex show solib-search-path
18709 @item show solib-search-path
18710 Display the current shared library search path.
18712 @cindex DOS file-name semantics of file names.
18713 @kindex set target-file-system-kind (unix|dos-based|auto)
18714 @kindex show target-file-system-kind
18715 @item set target-file-system-kind @var{kind}
18716 Set assumed file system kind for target reported file names.
18718 Shared library file names as reported by the target system may not
18719 make sense as is on the system @value{GDBN} is running on. For
18720 example, when remote debugging a target that has MS-DOS based file
18721 system semantics, from a Unix host, the target may be reporting to
18722 @value{GDBN} a list of loaded shared libraries with file names such as
18723 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18724 drive letters, so the @samp{c:\} prefix is not normally understood as
18725 indicating an absolute file name, and neither is the backslash
18726 normally considered a directory separator character. In that case,
18727 the native file system would interpret this whole absolute file name
18728 as a relative file name with no directory components. This would make
18729 it impossible to point @value{GDBN} at a copy of the remote target's
18730 shared libraries on the host using @code{set sysroot}, and impractical
18731 with @code{set solib-search-path}. Setting
18732 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18733 to interpret such file names similarly to how the target would, and to
18734 map them to file names valid on @value{GDBN}'s native file system
18735 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18736 to one of the supported file system kinds. In that case, @value{GDBN}
18737 tries to determine the appropriate file system variant based on the
18738 current target's operating system (@pxref{ABI, ,Configuring the
18739 Current ABI}). The supported file system settings are:
18743 Instruct @value{GDBN} to assume the target file system is of Unix
18744 kind. Only file names starting the forward slash (@samp{/}) character
18745 are considered absolute, and the directory separator character is also
18749 Instruct @value{GDBN} to assume the target file system is DOS based.
18750 File names starting with either a forward slash, or a drive letter
18751 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18752 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18753 considered directory separators.
18756 Instruct @value{GDBN} to use the file system kind associated with the
18757 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18758 This is the default.
18762 @cindex file name canonicalization
18763 @cindex base name differences
18764 When processing file names provided by the user, @value{GDBN}
18765 frequently needs to compare them to the file names recorded in the
18766 program's debug info. Normally, @value{GDBN} compares just the
18767 @dfn{base names} of the files as strings, which is reasonably fast
18768 even for very large programs. (The base name of a file is the last
18769 portion of its name, after stripping all the leading directories.)
18770 This shortcut in comparison is based upon the assumption that files
18771 cannot have more than one base name. This is usually true, but
18772 references to files that use symlinks or similar filesystem
18773 facilities violate that assumption. If your program records files
18774 using such facilities, or if you provide file names to @value{GDBN}
18775 using symlinks etc., you can set @code{basenames-may-differ} to
18776 @code{true} to instruct @value{GDBN} to completely canonicalize each
18777 pair of file names it needs to compare. This will make file-name
18778 comparisons accurate, but at a price of a significant slowdown.
18781 @item set basenames-may-differ
18782 @kindex set basenames-may-differ
18783 Set whether a source file may have multiple base names.
18785 @item show basenames-may-differ
18786 @kindex show basenames-may-differ
18787 Show whether a source file may have multiple base names.
18791 @section File Caching
18792 @cindex caching of opened files
18793 @cindex caching of bfd objects
18795 To speed up file loading, and reduce memory usage, @value{GDBN} will
18796 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18797 BFD, bfd, The Binary File Descriptor Library}. The following commands
18798 allow visibility and control of the caching behavior.
18801 @kindex maint info bfds
18802 @item maint info bfds
18803 This prints information about each @code{bfd} object that is known to
18806 @kindex maint set bfd-sharing
18807 @kindex maint show bfd-sharing
18808 @kindex bfd caching
18809 @item maint set bfd-sharing
18810 @item maint show bfd-sharing
18811 Control whether @code{bfd} objects can be shared. When sharing is
18812 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18813 than reopening the same file. Turning sharing off does not cause
18814 already shared @code{bfd} objects to be unshared, but all future files
18815 that are opened will create a new @code{bfd} object. Similarly,
18816 re-enabling sharing does not cause multiple existing @code{bfd}
18817 objects to be collapsed into a single shared @code{bfd} object.
18819 @kindex set debug bfd-cache @var{level}
18820 @kindex bfd caching
18821 @item set debug bfd-cache @var{level}
18822 Turns on debugging of the bfd cache, setting the level to @var{level}.
18824 @kindex show debug bfd-cache
18825 @kindex bfd caching
18826 @item show debug bfd-cache
18827 Show the current debugging level of the bfd cache.
18830 @node Separate Debug Files
18831 @section Debugging Information in Separate Files
18832 @cindex separate debugging information files
18833 @cindex debugging information in separate files
18834 @cindex @file{.debug} subdirectories
18835 @cindex debugging information directory, global
18836 @cindex global debugging information directories
18837 @cindex build ID, and separate debugging files
18838 @cindex @file{.build-id} directory
18840 @value{GDBN} allows you to put a program's debugging information in a
18841 file separate from the executable itself, in a way that allows
18842 @value{GDBN} to find and load the debugging information automatically.
18843 Since debugging information can be very large---sometimes larger
18844 than the executable code itself---some systems distribute debugging
18845 information for their executables in separate files, which users can
18846 install only when they need to debug a problem.
18848 @value{GDBN} supports two ways of specifying the separate debug info
18853 The executable contains a @dfn{debug link} that specifies the name of
18854 the separate debug info file. The separate debug file's name is
18855 usually @file{@var{executable}.debug}, where @var{executable} is the
18856 name of the corresponding executable file without leading directories
18857 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18858 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18859 checksum for the debug file, which @value{GDBN} uses to validate that
18860 the executable and the debug file came from the same build.
18863 The executable contains a @dfn{build ID}, a unique bit string that is
18864 also present in the corresponding debug info file. (This is supported
18865 only on some operating systems, when using the ELF or PE file formats
18866 for binary files and the @sc{gnu} Binutils.) For more details about
18867 this feature, see the description of the @option{--build-id}
18868 command-line option in @ref{Options, , Command Line Options, ld.info,
18869 The GNU Linker}. The debug info file's name is not specified
18870 explicitly by the build ID, but can be computed from the build ID, see
18874 Depending on the way the debug info file is specified, @value{GDBN}
18875 uses two different methods of looking for the debug file:
18879 For the ``debug link'' method, @value{GDBN} looks up the named file in
18880 the directory of the executable file, then in a subdirectory of that
18881 directory named @file{.debug}, and finally under each one of the global debug
18882 directories, in a subdirectory whose name is identical to the leading
18883 directories of the executable's absolute file name.
18886 For the ``build ID'' method, @value{GDBN} looks in the
18887 @file{.build-id} subdirectory of each one of the global debug directories for
18888 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18889 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18890 are the rest of the bit string. (Real build ID strings are 32 or more
18891 hex characters, not 10.)
18894 So, for example, suppose you ask @value{GDBN} to debug
18895 @file{/usr/bin/ls}, which has a debug link that specifies the
18896 file @file{ls.debug}, and a build ID whose value in hex is
18897 @code{abcdef1234}. If the list of the global debug directories includes
18898 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18899 debug information files, in the indicated order:
18903 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18905 @file{/usr/bin/ls.debug}
18907 @file{/usr/bin/.debug/ls.debug}
18909 @file{/usr/lib/debug/usr/bin/ls.debug}.
18912 @anchor{debug-file-directory}
18913 Global debugging info directories default to what is set by @value{GDBN}
18914 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18915 you can also set the global debugging info directories, and view the list
18916 @value{GDBN} is currently using.
18920 @kindex set debug-file-directory
18921 @item set debug-file-directory @var{directories}
18922 Set the directories which @value{GDBN} searches for separate debugging
18923 information files to @var{directory}. Multiple path components can be set
18924 concatenating them by a path separator.
18926 @kindex show debug-file-directory
18927 @item show debug-file-directory
18928 Show the directories @value{GDBN} searches for separate debugging
18933 @cindex @code{.gnu_debuglink} sections
18934 @cindex debug link sections
18935 A debug link is a special section of the executable file named
18936 @code{.gnu_debuglink}. The section must contain:
18940 A filename, with any leading directory components removed, followed by
18943 zero to three bytes of padding, as needed to reach the next four-byte
18944 boundary within the section, and
18946 a four-byte CRC checksum, stored in the same endianness used for the
18947 executable file itself. The checksum is computed on the debugging
18948 information file's full contents by the function given below, passing
18949 zero as the @var{crc} argument.
18952 Any executable file format can carry a debug link, as long as it can
18953 contain a section named @code{.gnu_debuglink} with the contents
18956 @cindex @code{.note.gnu.build-id} sections
18957 @cindex build ID sections
18958 The build ID is a special section in the executable file (and in other
18959 ELF binary files that @value{GDBN} may consider). This section is
18960 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18961 It contains unique identification for the built files---the ID remains
18962 the same across multiple builds of the same build tree. The default
18963 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18964 content for the build ID string. The same section with an identical
18965 value is present in the original built binary with symbols, in its
18966 stripped variant, and in the separate debugging information file.
18968 The debugging information file itself should be an ordinary
18969 executable, containing a full set of linker symbols, sections, and
18970 debugging information. The sections of the debugging information file
18971 should have the same names, addresses, and sizes as the original file,
18972 but they need not contain any data---much like a @code{.bss} section
18973 in an ordinary executable.
18975 The @sc{gnu} binary utilities (Binutils) package includes the
18976 @samp{objcopy} utility that can produce
18977 the separated executable / debugging information file pairs using the
18978 following commands:
18981 @kbd{objcopy --only-keep-debug foo foo.debug}
18986 These commands remove the debugging
18987 information from the executable file @file{foo} and place it in the file
18988 @file{foo.debug}. You can use the first, second or both methods to link the
18993 The debug link method needs the following additional command to also leave
18994 behind a debug link in @file{foo}:
18997 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19000 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19001 a version of the @code{strip} command such that the command @kbd{strip foo -f
19002 foo.debug} has the same functionality as the two @code{objcopy} commands and
19003 the @code{ln -s} command above, together.
19006 Build ID gets embedded into the main executable using @code{ld --build-id} or
19007 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19008 compatibility fixes for debug files separation are present in @sc{gnu} binary
19009 utilities (Binutils) package since version 2.18.
19014 @cindex CRC algorithm definition
19015 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19016 IEEE 802.3 using the polynomial:
19018 @c TexInfo requires naked braces for multi-digit exponents for Tex
19019 @c output, but this causes HTML output to barf. HTML has to be set using
19020 @c raw commands. So we end up having to specify this equation in 2
19025 <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>
19026 + <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
19032 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19033 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19037 The function is computed byte at a time, taking the least
19038 significant bit of each byte first. The initial pattern
19039 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19040 the final result is inverted to ensure trailing zeros also affect the
19043 @emph{Note:} This is the same CRC polynomial as used in handling the
19044 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19045 However in the case of the Remote Serial Protocol, the CRC is computed
19046 @emph{most} significant bit first, and the result is not inverted, so
19047 trailing zeros have no effect on the CRC value.
19049 To complete the description, we show below the code of the function
19050 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19051 initially supplied @code{crc} argument means that an initial call to
19052 this function passing in zero will start computing the CRC using
19055 @kindex gnu_debuglink_crc32
19058 gnu_debuglink_crc32 (unsigned long crc,
19059 unsigned char *buf, size_t len)
19061 static const unsigned long crc32_table[256] =
19063 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19064 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19065 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19066 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19067 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19068 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19069 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19070 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19071 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19072 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19073 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19074 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19075 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19076 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19077 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19078 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19079 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19080 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19081 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19082 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19083 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19084 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19085 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19086 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19087 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19088 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19089 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19090 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19091 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19092 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19093 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19094 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19095 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19096 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19097 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19098 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19099 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19100 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19101 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19102 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19103 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19104 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19105 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19106 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19107 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19108 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19109 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19110 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19111 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19112 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19113 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19116 unsigned char *end;
19118 crc = ~crc & 0xffffffff;
19119 for (end = buf + len; buf < end; ++buf)
19120 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19121 return ~crc & 0xffffffff;
19126 This computation does not apply to the ``build ID'' method.
19128 @node MiniDebugInfo
19129 @section Debugging information in a special section
19130 @cindex separate debug sections
19131 @cindex @samp{.gnu_debugdata} section
19133 Some systems ship pre-built executables and libraries that have a
19134 special @samp{.gnu_debugdata} section. This feature is called
19135 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19136 is used to supply extra symbols for backtraces.
19138 The intent of this section is to provide extra minimal debugging
19139 information for use in simple backtraces. It is not intended to be a
19140 replacement for full separate debugging information (@pxref{Separate
19141 Debug Files}). The example below shows the intended use; however,
19142 @value{GDBN} does not currently put restrictions on what sort of
19143 debugging information might be included in the section.
19145 @value{GDBN} has support for this extension. If the section exists,
19146 then it is used provided that no other source of debugging information
19147 can be found, and that @value{GDBN} was configured with LZMA support.
19149 This section can be easily created using @command{objcopy} and other
19150 standard utilities:
19153 # Extract the dynamic symbols from the main binary, there is no need
19154 # to also have these in the normal symbol table.
19155 nm -D @var{binary} --format=posix --defined-only \
19156 | awk '@{ print $1 @}' | sort > dynsyms
19158 # Extract all the text (i.e. function) symbols from the debuginfo.
19159 # (Note that we actually also accept "D" symbols, for the benefit
19160 # of platforms like PowerPC64 that use function descriptors.)
19161 nm @var{binary} --format=posix --defined-only \
19162 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19165 # Keep all the function symbols not already in the dynamic symbol
19167 comm -13 dynsyms funcsyms > keep_symbols
19169 # Separate full debug info into debug binary.
19170 objcopy --only-keep-debug @var{binary} debug
19172 # Copy the full debuginfo, keeping only a minimal set of symbols and
19173 # removing some unnecessary sections.
19174 objcopy -S --remove-section .gdb_index --remove-section .comment \
19175 --keep-symbols=keep_symbols debug mini_debuginfo
19177 # Drop the full debug info from the original binary.
19178 strip --strip-all -R .comment @var{binary}
19180 # Inject the compressed data into the .gnu_debugdata section of the
19183 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19187 @section Index Files Speed Up @value{GDBN}
19188 @cindex index files
19189 @cindex @samp{.gdb_index} section
19191 When @value{GDBN} finds a symbol file, it scans the symbols in the
19192 file in order to construct an internal symbol table. This lets most
19193 @value{GDBN} operations work quickly---at the cost of a delay early
19194 on. For large programs, this delay can be quite lengthy, so
19195 @value{GDBN} provides a way to build an index, which speeds up
19198 The index is stored as a section in the symbol file. @value{GDBN} can
19199 write the index to a file, then you can put it into the symbol file
19200 using @command{objcopy}.
19202 To create an index file, use the @code{save gdb-index} command:
19205 @item save gdb-index @var{directory}
19206 @kindex save gdb-index
19207 Create an index file for each symbol file currently known by
19208 @value{GDBN}. Each file is named after its corresponding symbol file,
19209 with @samp{.gdb-index} appended, and is written into the given
19213 Once you have created an index file you can merge it into your symbol
19214 file, here named @file{symfile}, using @command{objcopy}:
19217 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19218 --set-section-flags .gdb_index=readonly symfile symfile
19221 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19222 sections that have been deprecated. Usually they are deprecated because
19223 they are missing a new feature or have performance issues.
19224 To tell @value{GDBN} to use a deprecated index section anyway
19225 specify @code{set use-deprecated-index-sections on}.
19226 The default is @code{off}.
19227 This can speed up startup, but may result in some functionality being lost.
19228 @xref{Index Section Format}.
19230 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19231 must be done before gdb reads the file. The following will not work:
19234 $ gdb -ex "set use-deprecated-index-sections on" <program>
19237 Instead you must do, for example,
19240 $ gdb -iex "set use-deprecated-index-sections on" <program>
19243 There are currently some limitation on indices. They only work when
19244 for DWARF debugging information, not stabs. And, they do not
19245 currently work for programs using Ada.
19247 @node Symbol Errors
19248 @section Errors Reading Symbol Files
19250 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19251 such as symbol types it does not recognize, or known bugs in compiler
19252 output. By default, @value{GDBN} does not notify you of such problems, since
19253 they are relatively common and primarily of interest to people
19254 debugging compilers. If you are interested in seeing information
19255 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19256 only one message about each such type of problem, no matter how many
19257 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19258 to see how many times the problems occur, with the @code{set
19259 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19262 The messages currently printed, and their meanings, include:
19265 @item inner block not inside outer block in @var{symbol}
19267 The symbol information shows where symbol scopes begin and end
19268 (such as at the start of a function or a block of statements). This
19269 error indicates that an inner scope block is not fully contained
19270 in its outer scope blocks.
19272 @value{GDBN} circumvents the problem by treating the inner block as if it had
19273 the same scope as the outer block. In the error message, @var{symbol}
19274 may be shown as ``@code{(don't know)}'' if the outer block is not a
19277 @item block at @var{address} out of order
19279 The symbol information for symbol scope blocks should occur in
19280 order of increasing addresses. This error indicates that it does not
19283 @value{GDBN} does not circumvent this problem, and has trouble
19284 locating symbols in the source file whose symbols it is reading. (You
19285 can often determine what source file is affected by specifying
19286 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19289 @item bad block start address patched
19291 The symbol information for a symbol scope block has a start address
19292 smaller than the address of the preceding source line. This is known
19293 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19295 @value{GDBN} circumvents the problem by treating the symbol scope block as
19296 starting on the previous source line.
19298 @item bad string table offset in symbol @var{n}
19301 Symbol number @var{n} contains a pointer into the string table which is
19302 larger than the size of the string table.
19304 @value{GDBN} circumvents the problem by considering the symbol to have the
19305 name @code{foo}, which may cause other problems if many symbols end up
19308 @item unknown symbol type @code{0x@var{nn}}
19310 The symbol information contains new data types that @value{GDBN} does
19311 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19312 uncomprehended information, in hexadecimal.
19314 @value{GDBN} circumvents the error by ignoring this symbol information.
19315 This usually allows you to debug your program, though certain symbols
19316 are not accessible. If you encounter such a problem and feel like
19317 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19318 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19319 and examine @code{*bufp} to see the symbol.
19321 @item stub type has NULL name
19323 @value{GDBN} could not find the full definition for a struct or class.
19325 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19326 The symbol information for a C@t{++} member function is missing some
19327 information that recent versions of the compiler should have output for
19330 @item info mismatch between compiler and debugger
19332 @value{GDBN} could not parse a type specification output by the compiler.
19337 @section GDB Data Files
19339 @cindex prefix for data files
19340 @value{GDBN} will sometimes read an auxiliary data file. These files
19341 are kept in a directory known as the @dfn{data directory}.
19343 You can set the data directory's name, and view the name @value{GDBN}
19344 is currently using.
19347 @kindex set data-directory
19348 @item set data-directory @var{directory}
19349 Set the directory which @value{GDBN} searches for auxiliary data files
19350 to @var{directory}.
19352 @kindex show data-directory
19353 @item show data-directory
19354 Show the directory @value{GDBN} searches for auxiliary data files.
19357 @cindex default data directory
19358 @cindex @samp{--with-gdb-datadir}
19359 You can set the default data directory by using the configure-time
19360 @samp{--with-gdb-datadir} option. If the data directory is inside
19361 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19362 @samp{--exec-prefix}), then the default data directory will be updated
19363 automatically if the installed @value{GDBN} is moved to a new
19366 The data directory may also be specified with the
19367 @code{--data-directory} command line option.
19368 @xref{Mode Options}.
19371 @chapter Specifying a Debugging Target
19373 @cindex debugging target
19374 A @dfn{target} is the execution environment occupied by your program.
19376 Often, @value{GDBN} runs in the same host environment as your program;
19377 in that case, the debugging target is specified as a side effect when
19378 you use the @code{file} or @code{core} commands. When you need more
19379 flexibility---for example, running @value{GDBN} on a physically separate
19380 host, or controlling a standalone system over a serial port or a
19381 realtime system over a TCP/IP connection---you can use the @code{target}
19382 command to specify one of the target types configured for @value{GDBN}
19383 (@pxref{Target Commands, ,Commands for Managing Targets}).
19385 @cindex target architecture
19386 It is possible to build @value{GDBN} for several different @dfn{target
19387 architectures}. When @value{GDBN} is built like that, you can choose
19388 one of the available architectures with the @kbd{set architecture}
19392 @kindex set architecture
19393 @kindex show architecture
19394 @item set architecture @var{arch}
19395 This command sets the current target architecture to @var{arch}. The
19396 value of @var{arch} can be @code{"auto"}, in addition to one of the
19397 supported architectures.
19399 @item show architecture
19400 Show the current target architecture.
19402 @item set processor
19404 @kindex set processor
19405 @kindex show processor
19406 These are alias commands for, respectively, @code{set architecture}
19407 and @code{show architecture}.
19411 * Active Targets:: Active targets
19412 * Target Commands:: Commands for managing targets
19413 * Byte Order:: Choosing target byte order
19416 @node Active Targets
19417 @section Active Targets
19419 @cindex stacking targets
19420 @cindex active targets
19421 @cindex multiple targets
19423 There are multiple classes of targets such as: processes, executable files or
19424 recording sessions. Core files belong to the process class, making core file
19425 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19426 on multiple active targets, one in each class. This allows you to (for
19427 example) start a process and inspect its activity, while still having access to
19428 the executable file after the process finishes. Or if you start process
19429 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19430 presented a virtual layer of the recording target, while the process target
19431 remains stopped at the chronologically last point of the process execution.
19433 Use the @code{core-file} and @code{exec-file} commands to select a new core
19434 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19435 specify as a target a process that is already running, use the @code{attach}
19436 command (@pxref{Attach, ,Debugging an Already-running Process}).
19438 @node Target Commands
19439 @section Commands for Managing Targets
19442 @item target @var{type} @var{parameters}
19443 Connects the @value{GDBN} host environment to a target machine or
19444 process. A target is typically a protocol for talking to debugging
19445 facilities. You use the argument @var{type} to specify the type or
19446 protocol of the target machine.
19448 Further @var{parameters} are interpreted by the target protocol, but
19449 typically include things like device names or host names to connect
19450 with, process numbers, and baud rates.
19452 The @code{target} command does not repeat if you press @key{RET} again
19453 after executing the command.
19455 @kindex help target
19457 Displays the names of all targets available. To display targets
19458 currently selected, use either @code{info target} or @code{info files}
19459 (@pxref{Files, ,Commands to Specify Files}).
19461 @item help target @var{name}
19462 Describe a particular target, including any parameters necessary to
19465 @kindex set gnutarget
19466 @item set gnutarget @var{args}
19467 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19468 knows whether it is reading an @dfn{executable},
19469 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19470 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19471 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19474 @emph{Warning:} To specify a file format with @code{set gnutarget},
19475 you must know the actual BFD name.
19479 @xref{Files, , Commands to Specify Files}.
19481 @kindex show gnutarget
19482 @item show gnutarget
19483 Use the @code{show gnutarget} command to display what file format
19484 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19485 @value{GDBN} will determine the file format for each file automatically,
19486 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19489 @cindex common targets
19490 Here are some common targets (available, or not, depending on the GDB
19495 @item target exec @var{program}
19496 @cindex executable file target
19497 An executable file. @samp{target exec @var{program}} is the same as
19498 @samp{exec-file @var{program}}.
19500 @item target core @var{filename}
19501 @cindex core dump file target
19502 A core dump file. @samp{target core @var{filename}} is the same as
19503 @samp{core-file @var{filename}}.
19505 @item target remote @var{medium}
19506 @cindex remote target
19507 A remote system connected to @value{GDBN} via a serial line or network
19508 connection. This command tells @value{GDBN} to use its own remote
19509 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19511 For example, if you have a board connected to @file{/dev/ttya} on the
19512 machine running @value{GDBN}, you could say:
19515 target remote /dev/ttya
19518 @code{target remote} supports the @code{load} command. This is only
19519 useful if you have some other way of getting the stub to the target
19520 system, and you can put it somewhere in memory where it won't get
19521 clobbered by the download.
19523 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19524 @cindex built-in simulator target
19525 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19533 works; however, you cannot assume that a specific memory map, device
19534 drivers, or even basic I/O is available, although some simulators do
19535 provide these. For info about any processor-specific simulator details,
19536 see the appropriate section in @ref{Embedded Processors, ,Embedded
19539 @item target native
19540 @cindex native target
19541 Setup for local/native process debugging. Useful to make the
19542 @code{run} command spawn native processes (likewise @code{attach},
19543 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19544 (@pxref{set auto-connect-native-target}).
19548 Different targets are available on different configurations of @value{GDBN};
19549 your configuration may have more or fewer targets.
19551 Many remote targets require you to download the executable's code once
19552 you've successfully established a connection. You may wish to control
19553 various aspects of this process.
19558 @kindex set hash@r{, for remote monitors}
19559 @cindex hash mark while downloading
19560 This command controls whether a hash mark @samp{#} is displayed while
19561 downloading a file to the remote monitor. If on, a hash mark is
19562 displayed after each S-record is successfully downloaded to the
19566 @kindex show hash@r{, for remote monitors}
19567 Show the current status of displaying the hash mark.
19569 @item set debug monitor
19570 @kindex set debug monitor
19571 @cindex display remote monitor communications
19572 Enable or disable display of communications messages between
19573 @value{GDBN} and the remote monitor.
19575 @item show debug monitor
19576 @kindex show debug monitor
19577 Show the current status of displaying communications between
19578 @value{GDBN} and the remote monitor.
19583 @kindex load @var{filename}
19584 @item load @var{filename}
19586 Depending on what remote debugging facilities are configured into
19587 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19588 is meant to make @var{filename} (an executable) available for debugging
19589 on the remote system---by downloading, or dynamic linking, for example.
19590 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19591 the @code{add-symbol-file} command.
19593 If your @value{GDBN} does not have a @code{load} command, attempting to
19594 execute it gets the error message ``@code{You can't do that when your
19595 target is @dots{}}''
19597 The file is loaded at whatever address is specified in the executable.
19598 For some object file formats, you can specify the load address when you
19599 link the program; for other formats, like a.out, the object file format
19600 specifies a fixed address.
19601 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19603 Depending on the remote side capabilities, @value{GDBN} may be able to
19604 load programs into flash memory.
19606 @code{load} does not repeat if you press @key{RET} again after using it.
19610 @section Choosing Target Byte Order
19612 @cindex choosing target byte order
19613 @cindex target byte order
19615 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19616 offer the ability to run either big-endian or little-endian byte
19617 orders. Usually the executable or symbol will include a bit to
19618 designate the endian-ness, and you will not need to worry about
19619 which to use. However, you may still find it useful to adjust
19620 @value{GDBN}'s idea of processor endian-ness manually.
19624 @item set endian big
19625 Instruct @value{GDBN} to assume the target is big-endian.
19627 @item set endian little
19628 Instruct @value{GDBN} to assume the target is little-endian.
19630 @item set endian auto
19631 Instruct @value{GDBN} to use the byte order associated with the
19635 Display @value{GDBN}'s current idea of the target byte order.
19639 Note that these commands merely adjust interpretation of symbolic
19640 data on the host, and that they have absolutely no effect on the
19644 @node Remote Debugging
19645 @chapter Debugging Remote Programs
19646 @cindex remote debugging
19648 If you are trying to debug a program running on a machine that cannot run
19649 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19650 For example, you might use remote debugging on an operating system kernel,
19651 or on a small system which does not have a general purpose operating system
19652 powerful enough to run a full-featured debugger.
19654 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19655 to make this work with particular debugging targets. In addition,
19656 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19657 but not specific to any particular target system) which you can use if you
19658 write the remote stubs---the code that runs on the remote system to
19659 communicate with @value{GDBN}.
19661 Other remote targets may be available in your
19662 configuration of @value{GDBN}; use @code{help target} to list them.
19665 * Connecting:: Connecting to a remote target
19666 * File Transfer:: Sending files to a remote system
19667 * Server:: Using the gdbserver program
19668 * Remote Configuration:: Remote configuration
19669 * Remote Stub:: Implementing a remote stub
19673 @section Connecting to a Remote Target
19674 @cindex remote debugging, connecting
19675 @cindex @code{gdbserver}, connecting
19676 @cindex remote debugging, types of connections
19677 @cindex @code{gdbserver}, types of connections
19678 @cindex @code{gdbserver}, @code{target remote} mode
19679 @cindex @code{gdbserver}, @code{target extended-remote} mode
19681 This section describes how to connect to a remote target, including the
19682 types of connections and their differences, how to set up executable and
19683 symbol files on the host and target, and the commands used for
19684 connecting to and disconnecting from the remote target.
19686 @subsection Types of Remote Connections
19688 @value{GDBN} supports two types of remote connections, @code{target remote}
19689 mode and @code{target extended-remote} mode. Note that many remote targets
19690 support only @code{target remote} mode. There are several major
19691 differences between the two types of connections, enumerated here:
19695 @cindex remote debugging, detach and program exit
19696 @item Result of detach or program exit
19697 @strong{With target remote mode:} When the debugged program exits or you
19698 detach from it, @value{GDBN} disconnects from the target. When using
19699 @code{gdbserver}, @code{gdbserver} will exit.
19701 @strong{With target extended-remote mode:} When the debugged program exits or
19702 you detach from it, @value{GDBN} remains connected to the target, even
19703 though no program is running. You can rerun the program, attach to a
19704 running program, or use @code{monitor} commands specific to the target.
19706 When using @code{gdbserver} in this case, it does not exit unless it was
19707 invoked using the @option{--once} option. If the @option{--once} option
19708 was not used, you can ask @code{gdbserver} to exit using the
19709 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19711 @item Specifying the program to debug
19712 For both connection types you use the @code{file} command to specify the
19713 program on the host system. If you are using @code{gdbserver} there are
19714 some differences in how to specify the location of the program on the
19717 @strong{With target remote mode:} You must either specify the program to debug
19718 on the @code{gdbserver} command line or use the @option{--attach} option
19719 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19721 @cindex @option{--multi}, @code{gdbserver} option
19722 @strong{With target extended-remote mode:} You may specify the program to debug
19723 on the @code{gdbserver} command line, or you can load the program or attach
19724 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19726 @anchor{--multi Option in Types of Remote Connnections}
19727 You can start @code{gdbserver} without supplying an initial command to run
19728 or process ID to attach. To do this, use the @option{--multi} command line
19729 option. Then you can connect using @code{target extended-remote} and start
19730 the program you want to debug (see below for details on using the
19731 @code{run} command in this scenario). Note that the conditions under which
19732 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19733 (@code{target remote} or @code{target extended-remote}). The
19734 @option{--multi} option to @code{gdbserver} has no influence on that.
19736 @item The @code{run} command
19737 @strong{With target remote mode:} The @code{run} command is not
19738 supported. Once a connection has been established, you can use all
19739 the usual @value{GDBN} commands to examine and change data. The
19740 remote program is already running, so you can use commands like
19741 @kbd{step} and @kbd{continue}.
19743 @strong{With target extended-remote mode:} The @code{run} command is
19744 supported. The @code{run} command uses the value set by
19745 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19746 the program to run. Command line arguments are supported, except for
19747 wildcard expansion and I/O redirection (@pxref{Arguments}).
19749 If you specify the program to debug on the command line, then the
19750 @code{run} command is not required to start execution, and you can
19751 resume using commands like @kbd{step} and @kbd{continue} as with
19752 @code{target remote} mode.
19754 @anchor{Attaching in Types of Remote Connections}
19756 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19757 not supported. To attach to a running program using @code{gdbserver}, you
19758 must use the @option{--attach} option (@pxref{Running gdbserver}).
19760 @strong{With target extended-remote mode:} To attach to a running program,
19761 you may use the @code{attach} command after the connection has been
19762 established. If you are using @code{gdbserver}, you may also invoke
19763 @code{gdbserver} using the @option{--attach} option
19764 (@pxref{Running gdbserver}).
19768 @anchor{Host and target files}
19769 @subsection Host and Target Files
19770 @cindex remote debugging, symbol files
19771 @cindex symbol files, remote debugging
19773 @value{GDBN}, running on the host, needs access to symbol and debugging
19774 information for your program running on the target. This requires
19775 access to an unstripped copy of your program, and possibly any associated
19776 symbol files. Note that this section applies equally to both @code{target
19777 remote} mode and @code{target extended-remote} mode.
19779 Some remote targets (@pxref{qXfer executable filename read}, and
19780 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19781 the same connection used to communicate with @value{GDBN}. With such a
19782 target, if the remote program is unstripped, the only command you need is
19783 @code{target remote} (or @code{target extended-remote}).
19785 If the remote program is stripped, or the target does not support remote
19786 program file access, start up @value{GDBN} using the name of the local
19787 unstripped copy of your program as the first argument, or use the
19788 @code{file} command. Use @code{set sysroot} to specify the location (on
19789 the host) of target libraries (unless your @value{GDBN} was compiled with
19790 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19791 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19794 The symbol file and target libraries must exactly match the executable
19795 and libraries on the target, with one exception: the files on the host
19796 system should not be stripped, even if the files on the target system
19797 are. Mismatched or missing files will lead to confusing results
19798 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19799 files may also prevent @code{gdbserver} from debugging multi-threaded
19802 @subsection Remote Connection Commands
19803 @cindex remote connection commands
19804 @value{GDBN} can communicate with the target over a serial line, or
19805 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19806 each case, @value{GDBN} uses the same protocol for debugging your
19807 program; only the medium carrying the debugging packets varies. The
19808 @code{target remote} and @code{target extended-remote} commands
19809 establish a connection to the target. Both commands accept the same
19810 arguments, which indicate the medium to use:
19814 @item target remote @var{serial-device}
19815 @itemx target extended-remote @var{serial-device}
19816 @cindex serial line, @code{target remote}
19817 Use @var{serial-device} to communicate with the target. For example,
19818 to use a serial line connected to the device named @file{/dev/ttyb}:
19821 target remote /dev/ttyb
19824 If you're using a serial line, you may want to give @value{GDBN} the
19825 @samp{--baud} option, or use the @code{set serial baud} command
19826 (@pxref{Remote Configuration, set serial baud}) before the
19827 @code{target} command.
19829 @item target remote @code{@var{host}:@var{port}}
19830 @itemx target remote @code{tcp:@var{host}:@var{port}}
19831 @itemx target extended-remote @code{@var{host}:@var{port}}
19832 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19833 @cindex @acronym{TCP} port, @code{target remote}
19834 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19835 The @var{host} may be either a host name or a numeric @acronym{IP}
19836 address; @var{port} must be a decimal number. The @var{host} could be
19837 the target machine itself, if it is directly connected to the net, or
19838 it might be a terminal server which in turn has a serial line to the
19841 For example, to connect to port 2828 on a terminal server named
19845 target remote manyfarms:2828
19848 If your remote target is actually running on the same machine as your
19849 debugger session (e.g.@: a simulator for your target running on the
19850 same host), you can omit the hostname. For example, to connect to
19851 port 1234 on your local machine:
19854 target remote :1234
19858 Note that the colon is still required here.
19860 @item target remote @code{udp:@var{host}:@var{port}}
19861 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19862 @cindex @acronym{UDP} port, @code{target remote}
19863 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19864 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19867 target remote udp:manyfarms:2828
19870 When using a @acronym{UDP} connection for remote debugging, you should
19871 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19872 can silently drop packets on busy or unreliable networks, which will
19873 cause havoc with your debugging session.
19875 @item target remote | @var{command}
19876 @itemx target extended-remote | @var{command}
19877 @cindex pipe, @code{target remote} to
19878 Run @var{command} in the background and communicate with it using a
19879 pipe. The @var{command} is a shell command, to be parsed and expanded
19880 by the system's command shell, @code{/bin/sh}; it should expect remote
19881 protocol packets on its standard input, and send replies on its
19882 standard output. You could use this to run a stand-alone simulator
19883 that speaks the remote debugging protocol, to make net connections
19884 using programs like @code{ssh}, or for other similar tricks.
19886 If @var{command} closes its standard output (perhaps by exiting),
19887 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19888 program has already exited, this will have no effect.)
19892 @cindex interrupting remote programs
19893 @cindex remote programs, interrupting
19894 Whenever @value{GDBN} is waiting for the remote program, if you type the
19895 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19896 program. This may or may not succeed, depending in part on the hardware
19897 and the serial drivers the remote system uses. If you type the
19898 interrupt character once again, @value{GDBN} displays this prompt:
19901 Interrupted while waiting for the program.
19902 Give up (and stop debugging it)? (y or n)
19905 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19906 the remote debugging session. (If you decide you want to try again later,
19907 you can use @kbd{target remote} again to connect once more.) If you type
19908 @kbd{n}, @value{GDBN} goes back to waiting.
19910 In @code{target extended-remote} mode, typing @kbd{n} will leave
19911 @value{GDBN} connected to the target.
19914 @kindex detach (remote)
19916 When you have finished debugging the remote program, you can use the
19917 @code{detach} command to release it from @value{GDBN} control.
19918 Detaching from the target normally resumes its execution, but the results
19919 will depend on your particular remote stub. After the @code{detach}
19920 command in @code{target remote} mode, @value{GDBN} is free to connect to
19921 another target. In @code{target extended-remote} mode, @value{GDBN} is
19922 still connected to the target.
19926 The @code{disconnect} command closes the connection to the target, and
19927 the target is generally not resumed. It will wait for @value{GDBN}
19928 (this instance or another one) to connect and continue debugging. After
19929 the @code{disconnect} command, @value{GDBN} is again free to connect to
19932 @cindex send command to remote monitor
19933 @cindex extend @value{GDBN} for remote targets
19934 @cindex add new commands for external monitor
19936 @item monitor @var{cmd}
19937 This command allows you to send arbitrary commands directly to the
19938 remote monitor. Since @value{GDBN} doesn't care about the commands it
19939 sends like this, this command is the way to extend @value{GDBN}---you
19940 can add new commands that only the external monitor will understand
19944 @node File Transfer
19945 @section Sending files to a remote system
19946 @cindex remote target, file transfer
19947 @cindex file transfer
19948 @cindex sending files to remote systems
19950 Some remote targets offer the ability to transfer files over the same
19951 connection used to communicate with @value{GDBN}. This is convenient
19952 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19953 running @code{gdbserver} over a network interface. For other targets,
19954 e.g.@: embedded devices with only a single serial port, this may be
19955 the only way to upload or download files.
19957 Not all remote targets support these commands.
19961 @item remote put @var{hostfile} @var{targetfile}
19962 Copy file @var{hostfile} from the host system (the machine running
19963 @value{GDBN}) to @var{targetfile} on the target system.
19966 @item remote get @var{targetfile} @var{hostfile}
19967 Copy file @var{targetfile} from the target system to @var{hostfile}
19968 on the host system.
19970 @kindex remote delete
19971 @item remote delete @var{targetfile}
19972 Delete @var{targetfile} from the target system.
19977 @section Using the @code{gdbserver} Program
19980 @cindex remote connection without stubs
19981 @code{gdbserver} is a control program for Unix-like systems, which
19982 allows you to connect your program with a remote @value{GDBN} via
19983 @code{target remote} or @code{target extended-remote}---but without
19984 linking in the usual debugging stub.
19986 @code{gdbserver} is not a complete replacement for the debugging stubs,
19987 because it requires essentially the same operating-system facilities
19988 that @value{GDBN} itself does. In fact, a system that can run
19989 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19990 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19991 because it is a much smaller program than @value{GDBN} itself. It is
19992 also easier to port than all of @value{GDBN}, so you may be able to get
19993 started more quickly on a new system by using @code{gdbserver}.
19994 Finally, if you develop code for real-time systems, you may find that
19995 the tradeoffs involved in real-time operation make it more convenient to
19996 do as much development work as possible on another system, for example
19997 by cross-compiling. You can use @code{gdbserver} to make a similar
19998 choice for debugging.
20000 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20001 or a TCP connection, using the standard @value{GDBN} remote serial
20005 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20006 Do not run @code{gdbserver} connected to any public network; a
20007 @value{GDBN} connection to @code{gdbserver} provides access to the
20008 target system with the same privileges as the user running
20012 @anchor{Running gdbserver}
20013 @subsection Running @code{gdbserver}
20014 @cindex arguments, to @code{gdbserver}
20015 @cindex @code{gdbserver}, command-line arguments
20017 Run @code{gdbserver} on the target system. You need a copy of the
20018 program you want to debug, including any libraries it requires.
20019 @code{gdbserver} does not need your program's symbol table, so you can
20020 strip the program if necessary to save space. @value{GDBN} on the host
20021 system does all the symbol handling.
20023 To use the server, you must tell it how to communicate with @value{GDBN};
20024 the name of your program; and the arguments for your program. The usual
20028 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20031 @var{comm} is either a device name (to use a serial line), or a TCP
20032 hostname and portnumber, or @code{-} or @code{stdio} to use
20033 stdin/stdout of @code{gdbserver}.
20034 For example, to debug Emacs with the argument
20035 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20039 target> gdbserver /dev/com1 emacs foo.txt
20042 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20045 To use a TCP connection instead of a serial line:
20048 target> gdbserver host:2345 emacs foo.txt
20051 The only difference from the previous example is the first argument,
20052 specifying that you are communicating with the host @value{GDBN} via
20053 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20054 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20055 (Currently, the @samp{host} part is ignored.) You can choose any number
20056 you want for the port number as long as it does not conflict with any
20057 TCP ports already in use on the target system (for example, @code{23} is
20058 reserved for @code{telnet}).@footnote{If you choose a port number that
20059 conflicts with another service, @code{gdbserver} prints an error message
20060 and exits.} You must use the same port number with the host @value{GDBN}
20061 @code{target remote} command.
20063 The @code{stdio} connection is useful when starting @code{gdbserver}
20067 (gdb) target remote | ssh -T hostname gdbserver - hello
20070 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20071 and we don't want escape-character handling. Ssh does this by default when
20072 a command is provided, the flag is provided to make it explicit.
20073 You could elide it if you want to.
20075 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20076 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20077 display through a pipe connected to gdbserver.
20078 Both @code{stdout} and @code{stderr} use the same pipe.
20080 @anchor{Attaching to a program}
20081 @subsubsection Attaching to a Running Program
20082 @cindex attach to a program, @code{gdbserver}
20083 @cindex @option{--attach}, @code{gdbserver} option
20085 On some targets, @code{gdbserver} can also attach to running programs.
20086 This is accomplished via the @code{--attach} argument. The syntax is:
20089 target> gdbserver --attach @var{comm} @var{pid}
20092 @var{pid} is the process ID of a currently running process. It isn't
20093 necessary to point @code{gdbserver} at a binary for the running process.
20095 In @code{target extended-remote} mode, you can also attach using the
20096 @value{GDBN} attach command
20097 (@pxref{Attaching in Types of Remote Connections}).
20100 You can debug processes by name instead of process ID if your target has the
20101 @code{pidof} utility:
20104 target> gdbserver --attach @var{comm} `pidof @var{program}`
20107 In case more than one copy of @var{program} is running, or @var{program}
20108 has multiple threads, most versions of @code{pidof} support the
20109 @code{-s} option to only return the first process ID.
20111 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20113 This section applies only when @code{gdbserver} is run to listen on a TCP
20116 @code{gdbserver} normally terminates after all of its debugged processes have
20117 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20118 extended-remote}, @code{gdbserver} stays running even with no processes left.
20119 @value{GDBN} normally terminates the spawned debugged process on its exit,
20120 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20121 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20122 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20123 stays running even in the @kbd{target remote} mode.
20125 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20126 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20127 completeness, at most one @value{GDBN} can be connected at a time.
20129 @cindex @option{--once}, @code{gdbserver} option
20130 By default, @code{gdbserver} keeps the listening TCP port open, so that
20131 subsequent connections are possible. However, if you start @code{gdbserver}
20132 with the @option{--once} option, it will stop listening for any further
20133 connection attempts after connecting to the first @value{GDBN} session. This
20134 means no further connections to @code{gdbserver} will be possible after the
20135 first one. It also means @code{gdbserver} will terminate after the first
20136 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20137 connections and even in the @kbd{target extended-remote} mode. The
20138 @option{--once} option allows reusing the same port number for connecting to
20139 multiple instances of @code{gdbserver} running on the same host, since each
20140 instance closes its port after the first connection.
20142 @anchor{Other Command-Line Arguments for gdbserver}
20143 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20145 You can use the @option{--multi} option to start @code{gdbserver} without
20146 specifying a program to debug or a process to attach to. Then you can
20147 attach in @code{target extended-remote} mode and run or attach to a
20148 program. For more information,
20149 @pxref{--multi Option in Types of Remote Connnections}.
20151 @cindex @option{--debug}, @code{gdbserver} option
20152 The @option{--debug} option tells @code{gdbserver} to display extra
20153 status information about the debugging process.
20154 @cindex @option{--remote-debug}, @code{gdbserver} option
20155 The @option{--remote-debug} option tells @code{gdbserver} to display
20156 remote protocol debug output. These options are intended for
20157 @code{gdbserver} development and for bug reports to the developers.
20159 @cindex @option{--debug-format}, @code{gdbserver} option
20160 The @option{--debug-format=option1[,option2,...]} option tells
20161 @code{gdbserver} to include additional information in each output.
20162 Possible options are:
20166 Turn off all extra information in debugging output.
20168 Turn on all extra information in debugging output.
20170 Include a timestamp in each line of debugging output.
20173 Options are processed in order. Thus, for example, if @option{none}
20174 appears last then no additional information is added to debugging output.
20176 @cindex @option{--wrapper}, @code{gdbserver} option
20177 The @option{--wrapper} option specifies a wrapper to launch programs
20178 for debugging. The option should be followed by the name of the
20179 wrapper, then any command-line arguments to pass to the wrapper, then
20180 @kbd{--} indicating the end of the wrapper arguments.
20182 @code{gdbserver} runs the specified wrapper program with a combined
20183 command line including the wrapper arguments, then the name of the
20184 program to debug, then any arguments to the program. The wrapper
20185 runs until it executes your program, and then @value{GDBN} gains control.
20187 You can use any program that eventually calls @code{execve} with
20188 its arguments as a wrapper. Several standard Unix utilities do
20189 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20190 with @code{exec "$@@"} will also work.
20192 For example, you can use @code{env} to pass an environment variable to
20193 the debugged program, without setting the variable in @code{gdbserver}'s
20197 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20200 @subsection Connecting to @code{gdbserver}
20202 The basic procedure for connecting to the remote target is:
20206 Run @value{GDBN} on the host system.
20209 Make sure you have the necessary symbol files
20210 (@pxref{Host and target files}).
20211 Load symbols for your application using the @code{file} command before you
20212 connect. Use @code{set sysroot} to locate target libraries (unless your
20213 @value{GDBN} was compiled with the correct sysroot using
20214 @code{--with-sysroot}).
20217 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20218 For TCP connections, you must start up @code{gdbserver} prior to using
20219 the @code{target} command. Otherwise you may get an error whose
20220 text depends on the host system, but which usually looks something like
20221 @samp{Connection refused}. Don't use the @code{load}
20222 command in @value{GDBN} when using @code{target remote} mode, since the
20223 program is already on the target.
20227 @anchor{Monitor Commands for gdbserver}
20228 @subsection Monitor Commands for @code{gdbserver}
20229 @cindex monitor commands, for @code{gdbserver}
20231 During a @value{GDBN} session using @code{gdbserver}, you can use the
20232 @code{monitor} command to send special requests to @code{gdbserver}.
20233 Here are the available commands.
20237 List the available monitor commands.
20239 @item monitor set debug 0
20240 @itemx monitor set debug 1
20241 Disable or enable general debugging messages.
20243 @item monitor set remote-debug 0
20244 @itemx monitor set remote-debug 1
20245 Disable or enable specific debugging messages associated with the remote
20246 protocol (@pxref{Remote Protocol}).
20248 @item monitor set debug-format option1@r{[},option2,...@r{]}
20249 Specify additional text to add to debugging messages.
20250 Possible options are:
20254 Turn off all extra information in debugging output.
20256 Turn on all extra information in debugging output.
20258 Include a timestamp in each line of debugging output.
20261 Options are processed in order. Thus, for example, if @option{none}
20262 appears last then no additional information is added to debugging output.
20264 @item monitor set libthread-db-search-path [PATH]
20265 @cindex gdbserver, search path for @code{libthread_db}
20266 When this command is issued, @var{path} is a colon-separated list of
20267 directories to search for @code{libthread_db} (@pxref{Threads,,set
20268 libthread-db-search-path}). If you omit @var{path},
20269 @samp{libthread-db-search-path} will be reset to its default value.
20271 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20272 not supported in @code{gdbserver}.
20275 Tell gdbserver to exit immediately. This command should be followed by
20276 @code{disconnect} to close the debugging session. @code{gdbserver} will
20277 detach from any attached processes and kill any processes it created.
20278 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20279 of a multi-process mode debug session.
20283 @subsection Tracepoints support in @code{gdbserver}
20284 @cindex tracepoints support in @code{gdbserver}
20286 On some targets, @code{gdbserver} supports tracepoints, fast
20287 tracepoints and static tracepoints.
20289 For fast or static tracepoints to work, a special library called the
20290 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20291 This library is built and distributed as an integral part of
20292 @code{gdbserver}. In addition, support for static tracepoints
20293 requires building the in-process agent library with static tracepoints
20294 support. At present, the UST (LTTng Userspace Tracer,
20295 @url{http://lttng.org/ust}) tracing engine is supported. This support
20296 is automatically available if UST development headers are found in the
20297 standard include path when @code{gdbserver} is built, or if
20298 @code{gdbserver} was explicitly configured using @option{--with-ust}
20299 to point at such headers. You can explicitly disable the support
20300 using @option{--with-ust=no}.
20302 There are several ways to load the in-process agent in your program:
20305 @item Specifying it as dependency at link time
20307 You can link your program dynamically with the in-process agent
20308 library. On most systems, this is accomplished by adding
20309 @code{-linproctrace} to the link command.
20311 @item Using the system's preloading mechanisms
20313 You can force loading the in-process agent at startup time by using
20314 your system's support for preloading shared libraries. Many Unixes
20315 support the concept of preloading user defined libraries. In most
20316 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20317 in the environment. See also the description of @code{gdbserver}'s
20318 @option{--wrapper} command line option.
20320 @item Using @value{GDBN} to force loading the agent at run time
20322 On some systems, you can force the inferior to load a shared library,
20323 by calling a dynamic loader function in the inferior that takes care
20324 of dynamically looking up and loading a shared library. On most Unix
20325 systems, the function is @code{dlopen}. You'll use the @code{call}
20326 command for that. For example:
20329 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20332 Note that on most Unix systems, for the @code{dlopen} function to be
20333 available, the program needs to be linked with @code{-ldl}.
20336 On systems that have a userspace dynamic loader, like most Unix
20337 systems, when you connect to @code{gdbserver} using @code{target
20338 remote}, you'll find that the program is stopped at the dynamic
20339 loader's entry point, and no shared library has been loaded in the
20340 program's address space yet, including the in-process agent. In that
20341 case, before being able to use any of the fast or static tracepoints
20342 features, you need to let the loader run and load the shared
20343 libraries. The simplest way to do that is to run the program to the
20344 main procedure. E.g., if debugging a C or C@t{++} program, start
20345 @code{gdbserver} like so:
20348 $ gdbserver :9999 myprogram
20351 Start GDB and connect to @code{gdbserver} like so, and run to main:
20355 (@value{GDBP}) target remote myhost:9999
20356 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20357 (@value{GDBP}) b main
20358 (@value{GDBP}) continue
20361 The in-process tracing agent library should now be loaded into the
20362 process; you can confirm it with the @code{info sharedlibrary}
20363 command, which will list @file{libinproctrace.so} as loaded in the
20364 process. You are now ready to install fast tracepoints, list static
20365 tracepoint markers, probe static tracepoints markers, and start
20368 @node Remote Configuration
20369 @section Remote Configuration
20372 @kindex show remote
20373 This section documents the configuration options available when
20374 debugging remote programs. For the options related to the File I/O
20375 extensions of the remote protocol, see @ref{system,
20376 system-call-allowed}.
20379 @item set remoteaddresssize @var{bits}
20380 @cindex address size for remote targets
20381 @cindex bits in remote address
20382 Set the maximum size of address in a memory packet to the specified
20383 number of bits. @value{GDBN} will mask off the address bits above
20384 that number, when it passes addresses to the remote target. The
20385 default value is the number of bits in the target's address.
20387 @item show remoteaddresssize
20388 Show the current value of remote address size in bits.
20390 @item set serial baud @var{n}
20391 @cindex baud rate for remote targets
20392 Set the baud rate for the remote serial I/O to @var{n} baud. The
20393 value is used to set the speed of the serial port used for debugging
20396 @item show serial baud
20397 Show the current speed of the remote connection.
20399 @item set serial parity @var{parity}
20400 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20401 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20403 @item show serial parity
20404 Show the current parity of the serial port.
20406 @item set remotebreak
20407 @cindex interrupt remote programs
20408 @cindex BREAK signal instead of Ctrl-C
20409 @anchor{set remotebreak}
20410 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20411 when you type @kbd{Ctrl-c} to interrupt the program running
20412 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20413 character instead. The default is off, since most remote systems
20414 expect to see @samp{Ctrl-C} as the interrupt signal.
20416 @item show remotebreak
20417 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20418 interrupt the remote program.
20420 @item set remoteflow on
20421 @itemx set remoteflow off
20422 @kindex set remoteflow
20423 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20424 on the serial port used to communicate to the remote target.
20426 @item show remoteflow
20427 @kindex show remoteflow
20428 Show the current setting of hardware flow control.
20430 @item set remotelogbase @var{base}
20431 Set the base (a.k.a.@: radix) of logging serial protocol
20432 communications to @var{base}. Supported values of @var{base} are:
20433 @code{ascii}, @code{octal}, and @code{hex}. The default is
20436 @item show remotelogbase
20437 Show the current setting of the radix for logging remote serial
20440 @item set remotelogfile @var{file}
20441 @cindex record serial communications on file
20442 Record remote serial communications on the named @var{file}. The
20443 default is not to record at all.
20445 @item show remotelogfile.
20446 Show the current setting of the file name on which to record the
20447 serial communications.
20449 @item set remotetimeout @var{num}
20450 @cindex timeout for serial communications
20451 @cindex remote timeout
20452 Set the timeout limit to wait for the remote target to respond to
20453 @var{num} seconds. The default is 2 seconds.
20455 @item show remotetimeout
20456 Show the current number of seconds to wait for the remote target
20459 @cindex limit hardware breakpoints and watchpoints
20460 @cindex remote target, limit break- and watchpoints
20461 @anchor{set remote hardware-watchpoint-limit}
20462 @anchor{set remote hardware-breakpoint-limit}
20463 @item set remote hardware-watchpoint-limit @var{limit}
20464 @itemx set remote hardware-breakpoint-limit @var{limit}
20465 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20466 watchpoints. A limit of -1, the default, is treated as unlimited.
20468 @cindex limit hardware watchpoints length
20469 @cindex remote target, limit watchpoints length
20470 @anchor{set remote hardware-watchpoint-length-limit}
20471 @item set remote hardware-watchpoint-length-limit @var{limit}
20472 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20473 a remote hardware watchpoint. A limit of -1, the default, is treated
20476 @item show remote hardware-watchpoint-length-limit
20477 Show the current limit (in bytes) of the maximum length of
20478 a remote hardware watchpoint.
20480 @item set remote exec-file @var{filename}
20481 @itemx show remote exec-file
20482 @anchor{set remote exec-file}
20483 @cindex executable file, for remote target
20484 Select the file used for @code{run} with @code{target
20485 extended-remote}. This should be set to a filename valid on the
20486 target system. If it is not set, the target will use a default
20487 filename (e.g.@: the last program run).
20489 @item set remote interrupt-sequence
20490 @cindex interrupt remote programs
20491 @cindex select Ctrl-C, BREAK or BREAK-g
20492 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20493 @samp{BREAK-g} as the
20494 sequence to the remote target in order to interrupt the execution.
20495 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20496 is high level of serial line for some certain time.
20497 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20498 It is @code{BREAK} signal followed by character @code{g}.
20500 @item show interrupt-sequence
20501 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20502 is sent by @value{GDBN} to interrupt the remote program.
20503 @code{BREAK-g} is BREAK signal followed by @code{g} and
20504 also known as Magic SysRq g.
20506 @item set remote interrupt-on-connect
20507 @cindex send interrupt-sequence on start
20508 Specify whether interrupt-sequence is sent to remote target when
20509 @value{GDBN} connects to it. This is mostly needed when you debug
20510 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20511 which is known as Magic SysRq g in order to connect @value{GDBN}.
20513 @item show interrupt-on-connect
20514 Show whether interrupt-sequence is sent
20515 to remote target when @value{GDBN} connects to it.
20519 @item set tcp auto-retry on
20520 @cindex auto-retry, for remote TCP target
20521 Enable auto-retry for remote TCP connections. This is useful if the remote
20522 debugging agent is launched in parallel with @value{GDBN}; there is a race
20523 condition because the agent may not become ready to accept the connection
20524 before @value{GDBN} attempts to connect. When auto-retry is
20525 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20526 to establish the connection using the timeout specified by
20527 @code{set tcp connect-timeout}.
20529 @item set tcp auto-retry off
20530 Do not auto-retry failed TCP connections.
20532 @item show tcp auto-retry
20533 Show the current auto-retry setting.
20535 @item set tcp connect-timeout @var{seconds}
20536 @itemx set tcp connect-timeout unlimited
20537 @cindex connection timeout, for remote TCP target
20538 @cindex timeout, for remote target connection
20539 Set the timeout for establishing a TCP connection to the remote target to
20540 @var{seconds}. The timeout affects both polling to retry failed connections
20541 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20542 that are merely slow to complete, and represents an approximate cumulative
20543 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20544 @value{GDBN} will keep attempting to establish a connection forever,
20545 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20547 @item show tcp connect-timeout
20548 Show the current connection timeout setting.
20551 @cindex remote packets, enabling and disabling
20552 The @value{GDBN} remote protocol autodetects the packets supported by
20553 your debugging stub. If you need to override the autodetection, you
20554 can use these commands to enable or disable individual packets. Each
20555 packet can be set to @samp{on} (the remote target supports this
20556 packet), @samp{off} (the remote target does not support this packet),
20557 or @samp{auto} (detect remote target support for this packet). They
20558 all default to @samp{auto}. For more information about each packet,
20559 see @ref{Remote Protocol}.
20561 During normal use, you should not have to use any of these commands.
20562 If you do, that may be a bug in your remote debugging stub, or a bug
20563 in @value{GDBN}. You may want to report the problem to the
20564 @value{GDBN} developers.
20566 For each packet @var{name}, the command to enable or disable the
20567 packet is @code{set remote @var{name}-packet}. The available settings
20570 @multitable @columnfractions 0.28 0.32 0.25
20573 @tab Related Features
20575 @item @code{fetch-register}
20577 @tab @code{info registers}
20579 @item @code{set-register}
20583 @item @code{binary-download}
20585 @tab @code{load}, @code{set}
20587 @item @code{read-aux-vector}
20588 @tab @code{qXfer:auxv:read}
20589 @tab @code{info auxv}
20591 @item @code{symbol-lookup}
20592 @tab @code{qSymbol}
20593 @tab Detecting multiple threads
20595 @item @code{attach}
20596 @tab @code{vAttach}
20599 @item @code{verbose-resume}
20601 @tab Stepping or resuming multiple threads
20607 @item @code{software-breakpoint}
20611 @item @code{hardware-breakpoint}
20615 @item @code{write-watchpoint}
20619 @item @code{read-watchpoint}
20623 @item @code{access-watchpoint}
20627 @item @code{pid-to-exec-file}
20628 @tab @code{qXfer:exec-file:read}
20629 @tab @code{attach}, @code{run}
20631 @item @code{target-features}
20632 @tab @code{qXfer:features:read}
20633 @tab @code{set architecture}
20635 @item @code{library-info}
20636 @tab @code{qXfer:libraries:read}
20637 @tab @code{info sharedlibrary}
20639 @item @code{memory-map}
20640 @tab @code{qXfer:memory-map:read}
20641 @tab @code{info mem}
20643 @item @code{read-sdata-object}
20644 @tab @code{qXfer:sdata:read}
20645 @tab @code{print $_sdata}
20647 @item @code{read-spu-object}
20648 @tab @code{qXfer:spu:read}
20649 @tab @code{info spu}
20651 @item @code{write-spu-object}
20652 @tab @code{qXfer:spu:write}
20653 @tab @code{info spu}
20655 @item @code{read-siginfo-object}
20656 @tab @code{qXfer:siginfo:read}
20657 @tab @code{print $_siginfo}
20659 @item @code{write-siginfo-object}
20660 @tab @code{qXfer:siginfo:write}
20661 @tab @code{set $_siginfo}
20663 @item @code{threads}
20664 @tab @code{qXfer:threads:read}
20665 @tab @code{info threads}
20667 @item @code{get-thread-local-@*storage-address}
20668 @tab @code{qGetTLSAddr}
20669 @tab Displaying @code{__thread} variables
20671 @item @code{get-thread-information-block-address}
20672 @tab @code{qGetTIBAddr}
20673 @tab Display MS-Windows Thread Information Block.
20675 @item @code{search-memory}
20676 @tab @code{qSearch:memory}
20679 @item @code{supported-packets}
20680 @tab @code{qSupported}
20681 @tab Remote communications parameters
20683 @item @code{catch-syscalls}
20684 @tab @code{QCatchSyscalls}
20685 @tab @code{catch syscall}
20687 @item @code{pass-signals}
20688 @tab @code{QPassSignals}
20689 @tab @code{handle @var{signal}}
20691 @item @code{program-signals}
20692 @tab @code{QProgramSignals}
20693 @tab @code{handle @var{signal}}
20695 @item @code{hostio-close-packet}
20696 @tab @code{vFile:close}
20697 @tab @code{remote get}, @code{remote put}
20699 @item @code{hostio-open-packet}
20700 @tab @code{vFile:open}
20701 @tab @code{remote get}, @code{remote put}
20703 @item @code{hostio-pread-packet}
20704 @tab @code{vFile:pread}
20705 @tab @code{remote get}, @code{remote put}
20707 @item @code{hostio-pwrite-packet}
20708 @tab @code{vFile:pwrite}
20709 @tab @code{remote get}, @code{remote put}
20711 @item @code{hostio-unlink-packet}
20712 @tab @code{vFile:unlink}
20713 @tab @code{remote delete}
20715 @item @code{hostio-readlink-packet}
20716 @tab @code{vFile:readlink}
20719 @item @code{hostio-fstat-packet}
20720 @tab @code{vFile:fstat}
20723 @item @code{hostio-setfs-packet}
20724 @tab @code{vFile:setfs}
20727 @item @code{noack-packet}
20728 @tab @code{QStartNoAckMode}
20729 @tab Packet acknowledgment
20731 @item @code{osdata}
20732 @tab @code{qXfer:osdata:read}
20733 @tab @code{info os}
20735 @item @code{query-attached}
20736 @tab @code{qAttached}
20737 @tab Querying remote process attach state.
20739 @item @code{trace-buffer-size}
20740 @tab @code{QTBuffer:size}
20741 @tab @code{set trace-buffer-size}
20743 @item @code{trace-status}
20744 @tab @code{qTStatus}
20745 @tab @code{tstatus}
20747 @item @code{traceframe-info}
20748 @tab @code{qXfer:traceframe-info:read}
20749 @tab Traceframe info
20751 @item @code{install-in-trace}
20752 @tab @code{InstallInTrace}
20753 @tab Install tracepoint in tracing
20755 @item @code{disable-randomization}
20756 @tab @code{QDisableRandomization}
20757 @tab @code{set disable-randomization}
20759 @item @code{conditional-breakpoints-packet}
20760 @tab @code{Z0 and Z1}
20761 @tab @code{Support for target-side breakpoint condition evaluation}
20763 @item @code{multiprocess-extensions}
20764 @tab @code{multiprocess extensions}
20765 @tab Debug multiple processes and remote process PID awareness
20767 @item @code{swbreak-feature}
20768 @tab @code{swbreak stop reason}
20771 @item @code{hwbreak-feature}
20772 @tab @code{hwbreak stop reason}
20775 @item @code{fork-event-feature}
20776 @tab @code{fork stop reason}
20779 @item @code{vfork-event-feature}
20780 @tab @code{vfork stop reason}
20783 @item @code{exec-event-feature}
20784 @tab @code{exec stop reason}
20787 @item @code{thread-events}
20788 @tab @code{QThreadEvents}
20789 @tab Tracking thread lifetime.
20791 @item @code{no-resumed-stop-reply}
20792 @tab @code{no resumed thread left stop reply}
20793 @tab Tracking thread lifetime.
20798 @section Implementing a Remote Stub
20800 @cindex debugging stub, example
20801 @cindex remote stub, example
20802 @cindex stub example, remote debugging
20803 The stub files provided with @value{GDBN} implement the target side of the
20804 communication protocol, and the @value{GDBN} side is implemented in the
20805 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20806 these subroutines to communicate, and ignore the details. (If you're
20807 implementing your own stub file, you can still ignore the details: start
20808 with one of the existing stub files. @file{sparc-stub.c} is the best
20809 organized, and therefore the easiest to read.)
20811 @cindex remote serial debugging, overview
20812 To debug a program running on another machine (the debugging
20813 @dfn{target} machine), you must first arrange for all the usual
20814 prerequisites for the program to run by itself. For example, for a C
20819 A startup routine to set up the C runtime environment; these usually
20820 have a name like @file{crt0}. The startup routine may be supplied by
20821 your hardware supplier, or you may have to write your own.
20824 A C subroutine library to support your program's
20825 subroutine calls, notably managing input and output.
20828 A way of getting your program to the other machine---for example, a
20829 download program. These are often supplied by the hardware
20830 manufacturer, but you may have to write your own from hardware
20834 The next step is to arrange for your program to use a serial port to
20835 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20836 machine). In general terms, the scheme looks like this:
20840 @value{GDBN} already understands how to use this protocol; when everything
20841 else is set up, you can simply use the @samp{target remote} command
20842 (@pxref{Targets,,Specifying a Debugging Target}).
20844 @item On the target,
20845 you must link with your program a few special-purpose subroutines that
20846 implement the @value{GDBN} remote serial protocol. The file containing these
20847 subroutines is called a @dfn{debugging stub}.
20849 On certain remote targets, you can use an auxiliary program
20850 @code{gdbserver} instead of linking a stub into your program.
20851 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20854 The debugging stub is specific to the architecture of the remote
20855 machine; for example, use @file{sparc-stub.c} to debug programs on
20858 @cindex remote serial stub list
20859 These working remote stubs are distributed with @value{GDBN}:
20864 @cindex @file{i386-stub.c}
20867 For Intel 386 and compatible architectures.
20870 @cindex @file{m68k-stub.c}
20871 @cindex Motorola 680x0
20873 For Motorola 680x0 architectures.
20876 @cindex @file{sh-stub.c}
20879 For Renesas SH architectures.
20882 @cindex @file{sparc-stub.c}
20884 For @sc{sparc} architectures.
20886 @item sparcl-stub.c
20887 @cindex @file{sparcl-stub.c}
20890 For Fujitsu @sc{sparclite} architectures.
20894 The @file{README} file in the @value{GDBN} distribution may list other
20895 recently added stubs.
20898 * Stub Contents:: What the stub can do for you
20899 * Bootstrapping:: What you must do for the stub
20900 * Debug Session:: Putting it all together
20903 @node Stub Contents
20904 @subsection What the Stub Can Do for You
20906 @cindex remote serial stub
20907 The debugging stub for your architecture supplies these three
20911 @item set_debug_traps
20912 @findex set_debug_traps
20913 @cindex remote serial stub, initialization
20914 This routine arranges for @code{handle_exception} to run when your
20915 program stops. You must call this subroutine explicitly in your
20916 program's startup code.
20918 @item handle_exception
20919 @findex handle_exception
20920 @cindex remote serial stub, main routine
20921 This is the central workhorse, but your program never calls it
20922 explicitly---the setup code arranges for @code{handle_exception} to
20923 run when a trap is triggered.
20925 @code{handle_exception} takes control when your program stops during
20926 execution (for example, on a breakpoint), and mediates communications
20927 with @value{GDBN} on the host machine. This is where the communications
20928 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20929 representative on the target machine. It begins by sending summary
20930 information on the state of your program, then continues to execute,
20931 retrieving and transmitting any information @value{GDBN} needs, until you
20932 execute a @value{GDBN} command that makes your program resume; at that point,
20933 @code{handle_exception} returns control to your own code on the target
20937 @cindex @code{breakpoint} subroutine, remote
20938 Use this auxiliary subroutine to make your program contain a
20939 breakpoint. Depending on the particular situation, this may be the only
20940 way for @value{GDBN} to get control. For instance, if your target
20941 machine has some sort of interrupt button, you won't need to call this;
20942 pressing the interrupt button transfers control to
20943 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20944 simply receiving characters on the serial port may also trigger a trap;
20945 again, in that situation, you don't need to call @code{breakpoint} from
20946 your own program---simply running @samp{target remote} from the host
20947 @value{GDBN} session gets control.
20949 Call @code{breakpoint} if none of these is true, or if you simply want
20950 to make certain your program stops at a predetermined point for the
20951 start of your debugging session.
20954 @node Bootstrapping
20955 @subsection What You Must Do for the Stub
20957 @cindex remote stub, support routines
20958 The debugging stubs that come with @value{GDBN} are set up for a particular
20959 chip architecture, but they have no information about the rest of your
20960 debugging target machine.
20962 First of all you need to tell the stub how to communicate with the
20966 @item int getDebugChar()
20967 @findex getDebugChar
20968 Write this subroutine to read a single character from the serial port.
20969 It may be identical to @code{getchar} for your target system; a
20970 different name is used to allow you to distinguish the two if you wish.
20972 @item void putDebugChar(int)
20973 @findex putDebugChar
20974 Write this subroutine to write a single character to the serial port.
20975 It may be identical to @code{putchar} for your target system; a
20976 different name is used to allow you to distinguish the two if you wish.
20979 @cindex control C, and remote debugging
20980 @cindex interrupting remote targets
20981 If you want @value{GDBN} to be able to stop your program while it is
20982 running, you need to use an interrupt-driven serial driver, and arrange
20983 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20984 character). That is the character which @value{GDBN} uses to tell the
20985 remote system to stop.
20987 Getting the debugging target to return the proper status to @value{GDBN}
20988 probably requires changes to the standard stub; one quick and dirty way
20989 is to just execute a breakpoint instruction (the ``dirty'' part is that
20990 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20992 Other routines you need to supply are:
20995 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20996 @findex exceptionHandler
20997 Write this function to install @var{exception_address} in the exception
20998 handling tables. You need to do this because the stub does not have any
20999 way of knowing what the exception handling tables on your target system
21000 are like (for example, the processor's table might be in @sc{rom},
21001 containing entries which point to a table in @sc{ram}).
21002 The @var{exception_number} specifies the exception which should be changed;
21003 its meaning is architecture-dependent (for example, different numbers
21004 might represent divide by zero, misaligned access, etc). When this
21005 exception occurs, control should be transferred directly to
21006 @var{exception_address}, and the processor state (stack, registers,
21007 and so on) should be just as it is when a processor exception occurs. So if
21008 you want to use a jump instruction to reach @var{exception_address}, it
21009 should be a simple jump, not a jump to subroutine.
21011 For the 386, @var{exception_address} should be installed as an interrupt
21012 gate so that interrupts are masked while the handler runs. The gate
21013 should be at privilege level 0 (the most privileged level). The
21014 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21015 help from @code{exceptionHandler}.
21017 @item void flush_i_cache()
21018 @findex flush_i_cache
21019 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21020 instruction cache, if any, on your target machine. If there is no
21021 instruction cache, this subroutine may be a no-op.
21023 On target machines that have instruction caches, @value{GDBN} requires this
21024 function to make certain that the state of your program is stable.
21028 You must also make sure this library routine is available:
21031 @item void *memset(void *, int, int)
21033 This is the standard library function @code{memset} that sets an area of
21034 memory to a known value. If you have one of the free versions of
21035 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21036 either obtain it from your hardware manufacturer, or write your own.
21039 If you do not use the GNU C compiler, you may need other standard
21040 library subroutines as well; this varies from one stub to another,
21041 but in general the stubs are likely to use any of the common library
21042 subroutines which @code{@value{NGCC}} generates as inline code.
21045 @node Debug Session
21046 @subsection Putting it All Together
21048 @cindex remote serial debugging summary
21049 In summary, when your program is ready to debug, you must follow these
21054 Make sure you have defined the supporting low-level routines
21055 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21057 @code{getDebugChar}, @code{putDebugChar},
21058 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21062 Insert these lines in your program's startup code, before the main
21063 procedure is called:
21070 On some machines, when a breakpoint trap is raised, the hardware
21071 automatically makes the PC point to the instruction after the
21072 breakpoint. If your machine doesn't do that, you may need to adjust
21073 @code{handle_exception} to arrange for it to return to the instruction
21074 after the breakpoint on this first invocation, so that your program
21075 doesn't keep hitting the initial breakpoint instead of making
21079 For the 680x0 stub only, you need to provide a variable called
21080 @code{exceptionHook}. Normally you just use:
21083 void (*exceptionHook)() = 0;
21087 but if before calling @code{set_debug_traps}, you set it to point to a
21088 function in your program, that function is called when
21089 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21090 error). The function indicated by @code{exceptionHook} is called with
21091 one parameter: an @code{int} which is the exception number.
21094 Compile and link together: your program, the @value{GDBN} debugging stub for
21095 your target architecture, and the supporting subroutines.
21098 Make sure you have a serial connection between your target machine and
21099 the @value{GDBN} host, and identify the serial port on the host.
21102 @c The "remote" target now provides a `load' command, so we should
21103 @c document that. FIXME.
21104 Download your program to your target machine (or get it there by
21105 whatever means the manufacturer provides), and start it.
21108 Start @value{GDBN} on the host, and connect to the target
21109 (@pxref{Connecting,,Connecting to a Remote Target}).
21113 @node Configurations
21114 @chapter Configuration-Specific Information
21116 While nearly all @value{GDBN} commands are available for all native and
21117 cross versions of the debugger, there are some exceptions. This chapter
21118 describes things that are only available in certain configurations.
21120 There are three major categories of configurations: native
21121 configurations, where the host and target are the same, embedded
21122 operating system configurations, which are usually the same for several
21123 different processor architectures, and bare embedded processors, which
21124 are quite different from each other.
21129 * Embedded Processors::
21136 This section describes details specific to particular native
21140 * BSD libkvm Interface:: Debugging BSD kernel memory images
21141 * SVR4 Process Information:: SVR4 process information
21142 * DJGPP Native:: Features specific to the DJGPP port
21143 * Cygwin Native:: Features specific to the Cygwin port
21144 * Hurd Native:: Features specific to @sc{gnu} Hurd
21145 * Darwin:: Features specific to Darwin
21148 @node BSD libkvm Interface
21149 @subsection BSD libkvm Interface
21152 @cindex kernel memory image
21153 @cindex kernel crash dump
21155 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21156 interface that provides a uniform interface for accessing kernel virtual
21157 memory images, including live systems and crash dumps. @value{GDBN}
21158 uses this interface to allow you to debug live kernels and kernel crash
21159 dumps on many native BSD configurations. This is implemented as a
21160 special @code{kvm} debugging target. For debugging a live system, load
21161 the currently running kernel into @value{GDBN} and connect to the
21165 (@value{GDBP}) @b{target kvm}
21168 For debugging crash dumps, provide the file name of the crash dump as an
21172 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21175 Once connected to the @code{kvm} target, the following commands are
21181 Set current context from the @dfn{Process Control Block} (PCB) address.
21184 Set current context from proc address. This command isn't available on
21185 modern FreeBSD systems.
21188 @node SVR4 Process Information
21189 @subsection SVR4 Process Information
21191 @cindex examine process image
21192 @cindex process info via @file{/proc}
21194 Many versions of SVR4 and compatible systems provide a facility called
21195 @samp{/proc} that can be used to examine the image of a running
21196 process using file-system subroutines.
21198 If @value{GDBN} is configured for an operating system with this
21199 facility, the command @code{info proc} is available to report
21200 information about the process running your program, or about any
21201 process running on your system. This includes, as of this writing,
21202 @sc{gnu}/Linux and Solaris, for example.
21204 This command may also work on core files that were created on a system
21205 that has the @samp{/proc} facility.
21211 @itemx info proc @var{process-id}
21212 Summarize available information about any running process. If a
21213 process ID is specified by @var{process-id}, display information about
21214 that process; otherwise display information about the program being
21215 debugged. The summary includes the debugged process ID, the command
21216 line used to invoke it, its current working directory, and its
21217 executable file's absolute file name.
21219 On some systems, @var{process-id} can be of the form
21220 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21221 within a process. If the optional @var{pid} part is missing, it means
21222 a thread from the process being debugged (the leading @samp{/} still
21223 needs to be present, or else @value{GDBN} will interpret the number as
21224 a process ID rather than a thread ID).
21226 @item info proc cmdline
21227 @cindex info proc cmdline
21228 Show the original command line of the process. This command is
21229 specific to @sc{gnu}/Linux.
21231 @item info proc cwd
21232 @cindex info proc cwd
21233 Show the current working directory of the process. This command is
21234 specific to @sc{gnu}/Linux.
21236 @item info proc exe
21237 @cindex info proc exe
21238 Show the name of executable of the process. This command is specific
21241 @item info proc mappings
21242 @cindex memory address space mappings
21243 Report the memory address space ranges accessible in the program, with
21244 information on whether the process has read, write, or execute access
21245 rights to each range. On @sc{gnu}/Linux systems, each memory range
21246 includes the object file which is mapped to that range, instead of the
21247 memory access rights to that range.
21249 @item info proc stat
21250 @itemx info proc status
21251 @cindex process detailed status information
21252 These subcommands are specific to @sc{gnu}/Linux systems. They show
21253 the process-related information, including the user ID and group ID;
21254 how many threads are there in the process; its virtual memory usage;
21255 the signals that are pending, blocked, and ignored; its TTY; its
21256 consumption of system and user time; its stack size; its @samp{nice}
21257 value; etc. For more information, see the @samp{proc} man page
21258 (type @kbd{man 5 proc} from your shell prompt).
21260 @item info proc all
21261 Show all the information about the process described under all of the
21262 above @code{info proc} subcommands.
21265 @comment These sub-options of 'info proc' were not included when
21266 @comment procfs.c was re-written. Keep their descriptions around
21267 @comment against the day when someone finds the time to put them back in.
21268 @kindex info proc times
21269 @item info proc times
21270 Starting time, user CPU time, and system CPU time for your program and
21273 @kindex info proc id
21275 Report on the process IDs related to your program: its own process ID,
21276 the ID of its parent, the process group ID, and the session ID.
21279 @item set procfs-trace
21280 @kindex set procfs-trace
21281 @cindex @code{procfs} API calls
21282 This command enables and disables tracing of @code{procfs} API calls.
21284 @item show procfs-trace
21285 @kindex show procfs-trace
21286 Show the current state of @code{procfs} API call tracing.
21288 @item set procfs-file @var{file}
21289 @kindex set procfs-file
21290 Tell @value{GDBN} to write @code{procfs} API trace to the named
21291 @var{file}. @value{GDBN} appends the trace info to the previous
21292 contents of the file. The default is to display the trace on the
21295 @item show procfs-file
21296 @kindex show procfs-file
21297 Show the file to which @code{procfs} API trace is written.
21299 @item proc-trace-entry
21300 @itemx proc-trace-exit
21301 @itemx proc-untrace-entry
21302 @itemx proc-untrace-exit
21303 @kindex proc-trace-entry
21304 @kindex proc-trace-exit
21305 @kindex proc-untrace-entry
21306 @kindex proc-untrace-exit
21307 These commands enable and disable tracing of entries into and exits
21308 from the @code{syscall} interface.
21311 @kindex info pidlist
21312 @cindex process list, QNX Neutrino
21313 For QNX Neutrino only, this command displays the list of all the
21314 processes and all the threads within each process.
21317 @kindex info meminfo
21318 @cindex mapinfo list, QNX Neutrino
21319 For QNX Neutrino only, this command displays the list of all mapinfos.
21323 @subsection Features for Debugging @sc{djgpp} Programs
21324 @cindex @sc{djgpp} debugging
21325 @cindex native @sc{djgpp} debugging
21326 @cindex MS-DOS-specific commands
21329 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21330 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21331 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21332 top of real-mode DOS systems and their emulations.
21334 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21335 defines a few commands specific to the @sc{djgpp} port. This
21336 subsection describes those commands.
21341 This is a prefix of @sc{djgpp}-specific commands which print
21342 information about the target system and important OS structures.
21345 @cindex MS-DOS system info
21346 @cindex free memory information (MS-DOS)
21347 @item info dos sysinfo
21348 This command displays assorted information about the underlying
21349 platform: the CPU type and features, the OS version and flavor, the
21350 DPMI version, and the available conventional and DPMI memory.
21355 @cindex segment descriptor tables
21356 @cindex descriptor tables display
21358 @itemx info dos ldt
21359 @itemx info dos idt
21360 These 3 commands display entries from, respectively, Global, Local,
21361 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21362 tables are data structures which store a descriptor for each segment
21363 that is currently in use. The segment's selector is an index into a
21364 descriptor table; the table entry for that index holds the
21365 descriptor's base address and limit, and its attributes and access
21368 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21369 segment (used for both data and the stack), and a DOS segment (which
21370 allows access to DOS/BIOS data structures and absolute addresses in
21371 conventional memory). However, the DPMI host will usually define
21372 additional segments in order to support the DPMI environment.
21374 @cindex garbled pointers
21375 These commands allow to display entries from the descriptor tables.
21376 Without an argument, all entries from the specified table are
21377 displayed. An argument, which should be an integer expression, means
21378 display a single entry whose index is given by the argument. For
21379 example, here's a convenient way to display information about the
21380 debugged program's data segment:
21383 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21384 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21388 This comes in handy when you want to see whether a pointer is outside
21389 the data segment's limit (i.e.@: @dfn{garbled}).
21391 @cindex page tables display (MS-DOS)
21393 @itemx info dos pte
21394 These two commands display entries from, respectively, the Page
21395 Directory and the Page Tables. Page Directories and Page Tables are
21396 data structures which control how virtual memory addresses are mapped
21397 into physical addresses. A Page Table includes an entry for every
21398 page of memory that is mapped into the program's address space; there
21399 may be several Page Tables, each one holding up to 4096 entries. A
21400 Page Directory has up to 4096 entries, one each for every Page Table
21401 that is currently in use.
21403 Without an argument, @kbd{info dos pde} displays the entire Page
21404 Directory, and @kbd{info dos pte} displays all the entries in all of
21405 the Page Tables. An argument, an integer expression, given to the
21406 @kbd{info dos pde} command means display only that entry from the Page
21407 Directory table. An argument given to the @kbd{info dos pte} command
21408 means display entries from a single Page Table, the one pointed to by
21409 the specified entry in the Page Directory.
21411 @cindex direct memory access (DMA) on MS-DOS
21412 These commands are useful when your program uses @dfn{DMA} (Direct
21413 Memory Access), which needs physical addresses to program the DMA
21416 These commands are supported only with some DPMI servers.
21418 @cindex physical address from linear address
21419 @item info dos address-pte @var{addr}
21420 This command displays the Page Table entry for a specified linear
21421 address. The argument @var{addr} is a linear address which should
21422 already have the appropriate segment's base address added to it,
21423 because this command accepts addresses which may belong to @emph{any}
21424 segment. For example, here's how to display the Page Table entry for
21425 the page where a variable @code{i} is stored:
21428 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21429 @exdent @code{Page Table entry for address 0x11a00d30:}
21430 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21434 This says that @code{i} is stored at offset @code{0xd30} from the page
21435 whose physical base address is @code{0x02698000}, and shows all the
21436 attributes of that page.
21438 Note that you must cast the addresses of variables to a @code{char *},
21439 since otherwise the value of @code{__djgpp_base_address}, the base
21440 address of all variables and functions in a @sc{djgpp} program, will
21441 be added using the rules of C pointer arithmetics: if @code{i} is
21442 declared an @code{int}, @value{GDBN} will add 4 times the value of
21443 @code{__djgpp_base_address} to the address of @code{i}.
21445 Here's another example, it displays the Page Table entry for the
21449 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21450 @exdent @code{Page Table entry for address 0x29110:}
21451 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21455 (The @code{+ 3} offset is because the transfer buffer's address is the
21456 3rd member of the @code{_go32_info_block} structure.) The output
21457 clearly shows that this DPMI server maps the addresses in conventional
21458 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21459 linear (@code{0x29110}) addresses are identical.
21461 This command is supported only with some DPMI servers.
21464 @cindex DOS serial data link, remote debugging
21465 In addition to native debugging, the DJGPP port supports remote
21466 debugging via a serial data link. The following commands are specific
21467 to remote serial debugging in the DJGPP port of @value{GDBN}.
21470 @kindex set com1base
21471 @kindex set com1irq
21472 @kindex set com2base
21473 @kindex set com2irq
21474 @kindex set com3base
21475 @kindex set com3irq
21476 @kindex set com4base
21477 @kindex set com4irq
21478 @item set com1base @var{addr}
21479 This command sets the base I/O port address of the @file{COM1} serial
21482 @item set com1irq @var{irq}
21483 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21484 for the @file{COM1} serial port.
21486 There are similar commands @samp{set com2base}, @samp{set com3irq},
21487 etc.@: for setting the port address and the @code{IRQ} lines for the
21490 @kindex show com1base
21491 @kindex show com1irq
21492 @kindex show com2base
21493 @kindex show com2irq
21494 @kindex show com3base
21495 @kindex show com3irq
21496 @kindex show com4base
21497 @kindex show com4irq
21498 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21499 display the current settings of the base address and the @code{IRQ}
21500 lines used by the COM ports.
21503 @kindex info serial
21504 @cindex DOS serial port status
21505 This command prints the status of the 4 DOS serial ports. For each
21506 port, it prints whether it's active or not, its I/O base address and
21507 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21508 counts of various errors encountered so far.
21512 @node Cygwin Native
21513 @subsection Features for Debugging MS Windows PE Executables
21514 @cindex MS Windows debugging
21515 @cindex native Cygwin debugging
21516 @cindex Cygwin-specific commands
21518 @value{GDBN} supports native debugging of MS Windows programs, including
21519 DLLs with and without symbolic debugging information.
21521 @cindex Ctrl-BREAK, MS-Windows
21522 @cindex interrupt debuggee on MS-Windows
21523 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21524 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21525 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21526 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21527 sequence, which can be used to interrupt the debuggee even if it
21530 There are various additional Cygwin-specific commands, described in
21531 this section. Working with DLLs that have no debugging symbols is
21532 described in @ref{Non-debug DLL Symbols}.
21537 This is a prefix of MS Windows-specific commands which print
21538 information about the target system and important OS structures.
21540 @item info w32 selector
21541 This command displays information returned by
21542 the Win32 API @code{GetThreadSelectorEntry} function.
21543 It takes an optional argument that is evaluated to
21544 a long value to give the information about this given selector.
21545 Without argument, this command displays information
21546 about the six segment registers.
21548 @item info w32 thread-information-block
21549 This command displays thread specific information stored in the
21550 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21551 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21553 @kindex signal-event
21554 @item signal-event @var{id}
21555 This command signals an event with user-provided @var{id}. Used to resume
21556 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21558 To use it, create or edit the following keys in
21559 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21560 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21561 (for x86_64 versions):
21565 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21566 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21567 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21569 The first @code{%ld} will be replaced by the process ID of the
21570 crashing process, the second @code{%ld} will be replaced by the ID of
21571 the event that blocks the crashing process, waiting for @value{GDBN}
21575 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21576 make the system run debugger specified by the Debugger key
21577 automatically, @code{0} will cause a dialog box with ``OK'' and
21578 ``Cancel'' buttons to appear, which allows the user to either
21579 terminate the crashing process (OK) or debug it (Cancel).
21582 @kindex set cygwin-exceptions
21583 @cindex debugging the Cygwin DLL
21584 @cindex Cygwin DLL, debugging
21585 @item set cygwin-exceptions @var{mode}
21586 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21587 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21588 @value{GDBN} will delay recognition of exceptions, and may ignore some
21589 exceptions which seem to be caused by internal Cygwin DLL
21590 ``bookkeeping''. This option is meant primarily for debugging the
21591 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21592 @value{GDBN} users with false @code{SIGSEGV} signals.
21594 @kindex show cygwin-exceptions
21595 @item show cygwin-exceptions
21596 Displays whether @value{GDBN} will break on exceptions that happen
21597 inside the Cygwin DLL itself.
21599 @kindex set new-console
21600 @item set new-console @var{mode}
21601 If @var{mode} is @code{on} the debuggee will
21602 be started in a new console on next start.
21603 If @var{mode} is @code{off}, the debuggee will
21604 be started in the same console as the debugger.
21606 @kindex show new-console
21607 @item show new-console
21608 Displays whether a new console is used
21609 when the debuggee is started.
21611 @kindex set new-group
21612 @item set new-group @var{mode}
21613 This boolean value controls whether the debuggee should
21614 start a new group or stay in the same group as the debugger.
21615 This affects the way the Windows OS handles
21618 @kindex show new-group
21619 @item show new-group
21620 Displays current value of new-group boolean.
21622 @kindex set debugevents
21623 @item set debugevents
21624 This boolean value adds debug output concerning kernel events related
21625 to the debuggee seen by the debugger. This includes events that
21626 signal thread and process creation and exit, DLL loading and
21627 unloading, console interrupts, and debugging messages produced by the
21628 Windows @code{OutputDebugString} API call.
21630 @kindex set debugexec
21631 @item set debugexec
21632 This boolean value adds debug output concerning execute events
21633 (such as resume thread) seen by the debugger.
21635 @kindex set debugexceptions
21636 @item set debugexceptions
21637 This boolean value adds debug output concerning exceptions in the
21638 debuggee seen by the debugger.
21640 @kindex set debugmemory
21641 @item set debugmemory
21642 This boolean value adds debug output concerning debuggee memory reads
21643 and writes by the debugger.
21647 This boolean values specifies whether the debuggee is called
21648 via a shell or directly (default value is on).
21652 Displays if the debuggee will be started with a shell.
21657 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21660 @node Non-debug DLL Symbols
21661 @subsubsection Support for DLLs without Debugging Symbols
21662 @cindex DLLs with no debugging symbols
21663 @cindex Minimal symbols and DLLs
21665 Very often on windows, some of the DLLs that your program relies on do
21666 not include symbolic debugging information (for example,
21667 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21668 symbols in a DLL, it relies on the minimal amount of symbolic
21669 information contained in the DLL's export table. This section
21670 describes working with such symbols, known internally to @value{GDBN} as
21671 ``minimal symbols''.
21673 Note that before the debugged program has started execution, no DLLs
21674 will have been loaded. The easiest way around this problem is simply to
21675 start the program --- either by setting a breakpoint or letting the
21676 program run once to completion.
21678 @subsubsection DLL Name Prefixes
21680 In keeping with the naming conventions used by the Microsoft debugging
21681 tools, DLL export symbols are made available with a prefix based on the
21682 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21683 also entered into the symbol table, so @code{CreateFileA} is often
21684 sufficient. In some cases there will be name clashes within a program
21685 (particularly if the executable itself includes full debugging symbols)
21686 necessitating the use of the fully qualified name when referring to the
21687 contents of the DLL. Use single-quotes around the name to avoid the
21688 exclamation mark (``!'') being interpreted as a language operator.
21690 Note that the internal name of the DLL may be all upper-case, even
21691 though the file name of the DLL is lower-case, or vice-versa. Since
21692 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21693 some confusion. If in doubt, try the @code{info functions} and
21694 @code{info variables} commands or even @code{maint print msymbols}
21695 (@pxref{Symbols}). Here's an example:
21698 (@value{GDBP}) info function CreateFileA
21699 All functions matching regular expression "CreateFileA":
21701 Non-debugging symbols:
21702 0x77e885f4 CreateFileA
21703 0x77e885f4 KERNEL32!CreateFileA
21707 (@value{GDBP}) info function !
21708 All functions matching regular expression "!":
21710 Non-debugging symbols:
21711 0x6100114c cygwin1!__assert
21712 0x61004034 cygwin1!_dll_crt0@@0
21713 0x61004240 cygwin1!dll_crt0(per_process *)
21717 @subsubsection Working with Minimal Symbols
21719 Symbols extracted from a DLL's export table do not contain very much
21720 type information. All that @value{GDBN} can do is guess whether a symbol
21721 refers to a function or variable depending on the linker section that
21722 contains the symbol. Also note that the actual contents of the memory
21723 contained in a DLL are not available unless the program is running. This
21724 means that you cannot examine the contents of a variable or disassemble
21725 a function within a DLL without a running program.
21727 Variables are generally treated as pointers and dereferenced
21728 automatically. For this reason, it is often necessary to prefix a
21729 variable name with the address-of operator (``&'') and provide explicit
21730 type information in the command. Here's an example of the type of
21734 (@value{GDBP}) print 'cygwin1!__argv'
21739 (@value{GDBP}) x 'cygwin1!__argv'
21740 0x10021610: "\230y\""
21743 And two possible solutions:
21746 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21747 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21751 (@value{GDBP}) x/2x &'cygwin1!__argv'
21752 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21753 (@value{GDBP}) x/x 0x10021608
21754 0x10021608: 0x0022fd98
21755 (@value{GDBP}) x/s 0x0022fd98
21756 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21759 Setting a break point within a DLL is possible even before the program
21760 starts execution. However, under these circumstances, @value{GDBN} can't
21761 examine the initial instructions of the function in order to skip the
21762 function's frame set-up code. You can work around this by using ``*&''
21763 to set the breakpoint at a raw memory address:
21766 (@value{GDBP}) break *&'python22!PyOS_Readline'
21767 Breakpoint 1 at 0x1e04eff0
21770 The author of these extensions is not entirely convinced that setting a
21771 break point within a shared DLL like @file{kernel32.dll} is completely
21775 @subsection Commands Specific to @sc{gnu} Hurd Systems
21776 @cindex @sc{gnu} Hurd debugging
21778 This subsection describes @value{GDBN} commands specific to the
21779 @sc{gnu} Hurd native debugging.
21784 @kindex set signals@r{, Hurd command}
21785 @kindex set sigs@r{, Hurd command}
21786 This command toggles the state of inferior signal interception by
21787 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21788 affected by this command. @code{sigs} is a shorthand alias for
21793 @kindex show signals@r{, Hurd command}
21794 @kindex show sigs@r{, Hurd command}
21795 Show the current state of intercepting inferior's signals.
21797 @item set signal-thread
21798 @itemx set sigthread
21799 @kindex set signal-thread
21800 @kindex set sigthread
21801 This command tells @value{GDBN} which thread is the @code{libc} signal
21802 thread. That thread is run when a signal is delivered to a running
21803 process. @code{set sigthread} is the shorthand alias of @code{set
21806 @item show signal-thread
21807 @itemx show sigthread
21808 @kindex show signal-thread
21809 @kindex show sigthread
21810 These two commands show which thread will run when the inferior is
21811 delivered a signal.
21814 @kindex set stopped@r{, Hurd command}
21815 This commands tells @value{GDBN} that the inferior process is stopped,
21816 as with the @code{SIGSTOP} signal. The stopped process can be
21817 continued by delivering a signal to it.
21820 @kindex show stopped@r{, Hurd command}
21821 This command shows whether @value{GDBN} thinks the debuggee is
21824 @item set exceptions
21825 @kindex set exceptions@r{, Hurd command}
21826 Use this command to turn off trapping of exceptions in the inferior.
21827 When exception trapping is off, neither breakpoints nor
21828 single-stepping will work. To restore the default, set exception
21831 @item show exceptions
21832 @kindex show exceptions@r{, Hurd command}
21833 Show the current state of trapping exceptions in the inferior.
21835 @item set task pause
21836 @kindex set task@r{, Hurd commands}
21837 @cindex task attributes (@sc{gnu} Hurd)
21838 @cindex pause current task (@sc{gnu} Hurd)
21839 This command toggles task suspension when @value{GDBN} has control.
21840 Setting it to on takes effect immediately, and the task is suspended
21841 whenever @value{GDBN} gets control. Setting it to off will take
21842 effect the next time the inferior is continued. If this option is set
21843 to off, you can use @code{set thread default pause on} or @code{set
21844 thread pause on} (see below) to pause individual threads.
21846 @item show task pause
21847 @kindex show task@r{, Hurd commands}
21848 Show the current state of task suspension.
21850 @item set task detach-suspend-count
21851 @cindex task suspend count
21852 @cindex detach from task, @sc{gnu} Hurd
21853 This command sets the suspend count the task will be left with when
21854 @value{GDBN} detaches from it.
21856 @item show task detach-suspend-count
21857 Show the suspend count the task will be left with when detaching.
21859 @item set task exception-port
21860 @itemx set task excp
21861 @cindex task exception port, @sc{gnu} Hurd
21862 This command sets the task exception port to which @value{GDBN} will
21863 forward exceptions. The argument should be the value of the @dfn{send
21864 rights} of the task. @code{set task excp} is a shorthand alias.
21866 @item set noninvasive
21867 @cindex noninvasive task options
21868 This command switches @value{GDBN} to a mode that is the least
21869 invasive as far as interfering with the inferior is concerned. This
21870 is the same as using @code{set task pause}, @code{set exceptions}, and
21871 @code{set signals} to values opposite to the defaults.
21873 @item info send-rights
21874 @itemx info receive-rights
21875 @itemx info port-rights
21876 @itemx info port-sets
21877 @itemx info dead-names
21880 @cindex send rights, @sc{gnu} Hurd
21881 @cindex receive rights, @sc{gnu} Hurd
21882 @cindex port rights, @sc{gnu} Hurd
21883 @cindex port sets, @sc{gnu} Hurd
21884 @cindex dead names, @sc{gnu} Hurd
21885 These commands display information about, respectively, send rights,
21886 receive rights, port rights, port sets, and dead names of a task.
21887 There are also shorthand aliases: @code{info ports} for @code{info
21888 port-rights} and @code{info psets} for @code{info port-sets}.
21890 @item set thread pause
21891 @kindex set thread@r{, Hurd command}
21892 @cindex thread properties, @sc{gnu} Hurd
21893 @cindex pause current thread (@sc{gnu} Hurd)
21894 This command toggles current thread suspension when @value{GDBN} has
21895 control. Setting it to on takes effect immediately, and the current
21896 thread is suspended whenever @value{GDBN} gets control. Setting it to
21897 off will take effect the next time the inferior is continued.
21898 Normally, this command has no effect, since when @value{GDBN} has
21899 control, the whole task is suspended. However, if you used @code{set
21900 task pause off} (see above), this command comes in handy to suspend
21901 only the current thread.
21903 @item show thread pause
21904 @kindex show thread@r{, Hurd command}
21905 This command shows the state of current thread suspension.
21907 @item set thread run
21908 This command sets whether the current thread is allowed to run.
21910 @item show thread run
21911 Show whether the current thread is allowed to run.
21913 @item set thread detach-suspend-count
21914 @cindex thread suspend count, @sc{gnu} Hurd
21915 @cindex detach from thread, @sc{gnu} Hurd
21916 This command sets the suspend count @value{GDBN} will leave on a
21917 thread when detaching. This number is relative to the suspend count
21918 found by @value{GDBN} when it notices the thread; use @code{set thread
21919 takeover-suspend-count} to force it to an absolute value.
21921 @item show thread detach-suspend-count
21922 Show the suspend count @value{GDBN} will leave on the thread when
21925 @item set thread exception-port
21926 @itemx set thread excp
21927 Set the thread exception port to which to forward exceptions. This
21928 overrides the port set by @code{set task exception-port} (see above).
21929 @code{set thread excp} is the shorthand alias.
21931 @item set thread takeover-suspend-count
21932 Normally, @value{GDBN}'s thread suspend counts are relative to the
21933 value @value{GDBN} finds when it notices each thread. This command
21934 changes the suspend counts to be absolute instead.
21936 @item set thread default
21937 @itemx show thread default
21938 @cindex thread default settings, @sc{gnu} Hurd
21939 Each of the above @code{set thread} commands has a @code{set thread
21940 default} counterpart (e.g., @code{set thread default pause}, @code{set
21941 thread default exception-port}, etc.). The @code{thread default}
21942 variety of commands sets the default thread properties for all
21943 threads; you can then change the properties of individual threads with
21944 the non-default commands.
21951 @value{GDBN} provides the following commands specific to the Darwin target:
21954 @item set debug darwin @var{num}
21955 @kindex set debug darwin
21956 When set to a non zero value, enables debugging messages specific to
21957 the Darwin support. Higher values produce more verbose output.
21959 @item show debug darwin
21960 @kindex show debug darwin
21961 Show the current state of Darwin messages.
21963 @item set debug mach-o @var{num}
21964 @kindex set debug mach-o
21965 When set to a non zero value, enables debugging messages while
21966 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21967 file format used on Darwin for object and executable files.) Higher
21968 values produce more verbose output. This is a command to diagnose
21969 problems internal to @value{GDBN} and should not be needed in normal
21972 @item show debug mach-o
21973 @kindex show debug mach-o
21974 Show the current state of Mach-O file messages.
21976 @item set mach-exceptions on
21977 @itemx set mach-exceptions off
21978 @kindex set mach-exceptions
21979 On Darwin, faults are first reported as a Mach exception and are then
21980 mapped to a Posix signal. Use this command to turn on trapping of
21981 Mach exceptions in the inferior. This might be sometimes useful to
21982 better understand the cause of a fault. The default is off.
21984 @item show mach-exceptions
21985 @kindex show mach-exceptions
21986 Show the current state of exceptions trapping.
21991 @section Embedded Operating Systems
21993 This section describes configurations involving the debugging of
21994 embedded operating systems that are available for several different
21997 @value{GDBN} includes the ability to debug programs running on
21998 various real-time operating systems.
22000 @node Embedded Processors
22001 @section Embedded Processors
22003 This section goes into details specific to particular embedded
22006 @cindex send command to simulator
22007 Whenever a specific embedded processor has a simulator, @value{GDBN}
22008 allows to send an arbitrary command to the simulator.
22011 @item sim @var{command}
22012 @kindex sim@r{, a command}
22013 Send an arbitrary @var{command} string to the simulator. Consult the
22014 documentation for the specific simulator in use for information about
22015 acceptable commands.
22020 * ARC:: Synopsys ARC
22022 * M68K:: Motorola M68K
22023 * MicroBlaze:: Xilinx MicroBlaze
22024 * MIPS Embedded:: MIPS Embedded
22025 * PowerPC Embedded:: PowerPC Embedded
22028 * Super-H:: Renesas Super-H
22032 @subsection Synopsys ARC
22033 @cindex Synopsys ARC
22034 @cindex ARC specific commands
22040 @value{GDBN} provides the following ARC-specific commands:
22043 @item set debug arc
22044 @kindex set debug arc
22045 Control the level of ARC specific debug messages. Use 0 for no messages (the
22046 default) and 1 for debug messages. At present higher values offer no further
22049 @item show debug arc
22050 @kindex show debug arc
22051 Show the level of ARC specific debugging in operation.
22058 @value{GDBN} provides the following ARM-specific commands:
22061 @item set arm disassembler
22063 This commands selects from a list of disassembly styles. The
22064 @code{"std"} style is the standard style.
22066 @item show arm disassembler
22068 Show the current disassembly style.
22070 @item set arm apcs32
22071 @cindex ARM 32-bit mode
22072 This command toggles ARM operation mode between 32-bit and 26-bit.
22074 @item show arm apcs32
22075 Display the current usage of the ARM 32-bit mode.
22077 @item set arm fpu @var{fputype}
22078 This command sets the ARM floating-point unit (FPU) type. The
22079 argument @var{fputype} can be one of these:
22083 Determine the FPU type by querying the OS ABI.
22085 Software FPU, with mixed-endian doubles on little-endian ARM
22088 GCC-compiled FPA co-processor.
22090 Software FPU with pure-endian doubles.
22096 Show the current type of the FPU.
22099 This command forces @value{GDBN} to use the specified ABI.
22102 Show the currently used ABI.
22104 @item set arm fallback-mode (arm|thumb|auto)
22105 @value{GDBN} uses the symbol table, when available, to determine
22106 whether instructions are ARM or Thumb. This command controls
22107 @value{GDBN}'s default behavior when the symbol table is not
22108 available. The default is @samp{auto}, which causes @value{GDBN} to
22109 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22112 @item show arm fallback-mode
22113 Show the current fallback instruction mode.
22115 @item set arm force-mode (arm|thumb|auto)
22116 This command overrides use of the symbol table to determine whether
22117 instructions are ARM or Thumb. The default is @samp{auto}, which
22118 causes @value{GDBN} to use the symbol table and then the setting
22119 of @samp{set arm fallback-mode}.
22121 @item show arm force-mode
22122 Show the current forced instruction mode.
22124 @item set debug arm
22125 Toggle whether to display ARM-specific debugging messages from the ARM
22126 target support subsystem.
22128 @item show debug arm
22129 Show whether ARM-specific debugging messages are enabled.
22133 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22134 The @value{GDBN} ARM simulator accepts the following optional arguments.
22137 @item --swi-support=@var{type}
22138 Tell the simulator which SWI interfaces to support. The argument
22139 @var{type} may be a comma separated list of the following values.
22140 The default value is @code{all}.
22155 The Motorola m68k configuration includes ColdFire support.
22158 @subsection MicroBlaze
22159 @cindex Xilinx MicroBlaze
22160 @cindex XMD, Xilinx Microprocessor Debugger
22162 The MicroBlaze is a soft-core processor supported on various Xilinx
22163 FPGAs, such as Spartan or Virtex series. Boards with these processors
22164 usually have JTAG ports which connect to a host system running the Xilinx
22165 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22166 This host system is used to download the configuration bitstream to
22167 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22168 communicates with the target board using the JTAG interface and
22169 presents a @code{gdbserver} interface to the board. By default
22170 @code{xmd} uses port @code{1234}. (While it is possible to change
22171 this default port, it requires the use of undocumented @code{xmd}
22172 commands. Contact Xilinx support if you need to do this.)
22174 Use these GDB commands to connect to the MicroBlaze target processor.
22177 @item target remote :1234
22178 Use this command to connect to the target if you are running @value{GDBN}
22179 on the same system as @code{xmd}.
22181 @item target remote @var{xmd-host}:1234
22182 Use this command to connect to the target if it is connected to @code{xmd}
22183 running on a different system named @var{xmd-host}.
22186 Use this command to download a program to the MicroBlaze target.
22188 @item set debug microblaze @var{n}
22189 Enable MicroBlaze-specific debugging messages if non-zero.
22191 @item show debug microblaze @var{n}
22192 Show MicroBlaze-specific debugging level.
22195 @node MIPS Embedded
22196 @subsection @acronym{MIPS} Embedded
22199 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22202 @item set mipsfpu double
22203 @itemx set mipsfpu single
22204 @itemx set mipsfpu none
22205 @itemx set mipsfpu auto
22206 @itemx show mipsfpu
22207 @kindex set mipsfpu
22208 @kindex show mipsfpu
22209 @cindex @acronym{MIPS} remote floating point
22210 @cindex floating point, @acronym{MIPS} remote
22211 If your target board does not support the @acronym{MIPS} floating point
22212 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22213 need this, you may wish to put the command in your @value{GDBN} init
22214 file). This tells @value{GDBN} how to find the return value of
22215 functions which return floating point values. It also allows
22216 @value{GDBN} to avoid saving the floating point registers when calling
22217 functions on the board. If you are using a floating point coprocessor
22218 with only single precision floating point support, as on the @sc{r4650}
22219 processor, use the command @samp{set mipsfpu single}. The default
22220 double precision floating point coprocessor may be selected using
22221 @samp{set mipsfpu double}.
22223 In previous versions the only choices were double precision or no
22224 floating point, so @samp{set mipsfpu on} will select double precision
22225 and @samp{set mipsfpu off} will select no floating point.
22227 As usual, you can inquire about the @code{mipsfpu} variable with
22228 @samp{show mipsfpu}.
22231 @node PowerPC Embedded
22232 @subsection PowerPC Embedded
22234 @cindex DVC register
22235 @value{GDBN} supports using the DVC (Data Value Compare) register to
22236 implement in hardware simple hardware watchpoint conditions of the form:
22239 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22240 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22243 The DVC register will be automatically used when @value{GDBN} detects
22244 such pattern in a condition expression, and the created watchpoint uses one
22245 debug register (either the @code{exact-watchpoints} option is on and the
22246 variable is scalar, or the variable has a length of one byte). This feature
22247 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22250 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22251 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22252 in which case watchpoints using only one debug register are created when
22253 watching variables of scalar types.
22255 You can create an artificial array to watch an arbitrary memory
22256 region using one of the following commands (@pxref{Expressions}):
22259 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22260 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22263 PowerPC embedded processors support masked watchpoints. See the discussion
22264 about the @code{mask} argument in @ref{Set Watchpoints}.
22266 @cindex ranged breakpoint
22267 PowerPC embedded processors support hardware accelerated
22268 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22269 the inferior whenever it executes an instruction at any address within
22270 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22271 use the @code{break-range} command.
22273 @value{GDBN} provides the following PowerPC-specific commands:
22276 @kindex break-range
22277 @item break-range @var{start-location}, @var{end-location}
22278 Set a breakpoint for an address range given by
22279 @var{start-location} and @var{end-location}, which can specify a function name,
22280 a line number, an offset of lines from the current line or from the start
22281 location, or an address of an instruction (see @ref{Specify Location},
22282 for a list of all the possible ways to specify a @var{location}.)
22283 The breakpoint will stop execution of the inferior whenever it
22284 executes an instruction at any address within the specified range,
22285 (including @var{start-location} and @var{end-location}.)
22287 @kindex set powerpc
22288 @item set powerpc soft-float
22289 @itemx show powerpc soft-float
22290 Force @value{GDBN} to use (or not use) a software floating point calling
22291 convention. By default, @value{GDBN} selects the calling convention based
22292 on the selected architecture and the provided executable file.
22294 @item set powerpc vector-abi
22295 @itemx show powerpc vector-abi
22296 Force @value{GDBN} to use the specified calling convention for vector
22297 arguments and return values. The valid options are @samp{auto};
22298 @samp{generic}, to avoid vector registers even if they are present;
22299 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22300 registers. By default, @value{GDBN} selects the calling convention
22301 based on the selected architecture and the provided executable file.
22303 @item set powerpc exact-watchpoints
22304 @itemx show powerpc exact-watchpoints
22305 Allow @value{GDBN} to use only one debug register when watching a variable
22306 of scalar type, thus assuming that the variable is accessed through the
22307 address of its first byte.
22312 @subsection Atmel AVR
22315 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22316 following AVR-specific commands:
22319 @item info io_registers
22320 @kindex info io_registers@r{, AVR}
22321 @cindex I/O registers (Atmel AVR)
22322 This command displays information about the AVR I/O registers. For
22323 each register, @value{GDBN} prints its number and value.
22330 When configured for debugging CRIS, @value{GDBN} provides the
22331 following CRIS-specific commands:
22334 @item set cris-version @var{ver}
22335 @cindex CRIS version
22336 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22337 The CRIS version affects register names and sizes. This command is useful in
22338 case autodetection of the CRIS version fails.
22340 @item show cris-version
22341 Show the current CRIS version.
22343 @item set cris-dwarf2-cfi
22344 @cindex DWARF-2 CFI and CRIS
22345 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22346 Change to @samp{off} when using @code{gcc-cris} whose version is below
22349 @item show cris-dwarf2-cfi
22350 Show the current state of using DWARF-2 CFI.
22352 @item set cris-mode @var{mode}
22354 Set the current CRIS mode to @var{mode}. It should only be changed when
22355 debugging in guru mode, in which case it should be set to
22356 @samp{guru} (the default is @samp{normal}).
22358 @item show cris-mode
22359 Show the current CRIS mode.
22363 @subsection Renesas Super-H
22366 For the Renesas Super-H processor, @value{GDBN} provides these
22370 @item set sh calling-convention @var{convention}
22371 @kindex set sh calling-convention
22372 Set the calling-convention used when calling functions from @value{GDBN}.
22373 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22374 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22375 convention. If the DWARF-2 information of the called function specifies
22376 that the function follows the Renesas calling convention, the function
22377 is called using the Renesas calling convention. If the calling convention
22378 is set to @samp{renesas}, the Renesas calling convention is always used,
22379 regardless of the DWARF-2 information. This can be used to override the
22380 default of @samp{gcc} if debug information is missing, or the compiler
22381 does not emit the DWARF-2 calling convention entry for a function.
22383 @item show sh calling-convention
22384 @kindex show sh calling-convention
22385 Show the current calling convention setting.
22390 @node Architectures
22391 @section Architectures
22393 This section describes characteristics of architectures that affect
22394 all uses of @value{GDBN} with the architecture, both native and cross.
22401 * HPPA:: HP PA architecture
22402 * SPU:: Cell Broadband Engine SPU architecture
22408 @subsection AArch64
22409 @cindex AArch64 support
22411 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22412 following special commands:
22415 @item set debug aarch64
22416 @kindex set debug aarch64
22417 This command determines whether AArch64 architecture-specific debugging
22418 messages are to be displayed.
22420 @item show debug aarch64
22421 Show whether AArch64 debugging messages are displayed.
22426 @subsection x86 Architecture-specific Issues
22429 @item set struct-convention @var{mode}
22430 @kindex set struct-convention
22431 @cindex struct return convention
22432 @cindex struct/union returned in registers
22433 Set the convention used by the inferior to return @code{struct}s and
22434 @code{union}s from functions to @var{mode}. Possible values of
22435 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22436 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22437 are returned on the stack, while @code{"reg"} means that a
22438 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22439 be returned in a register.
22441 @item show struct-convention
22442 @kindex show struct-convention
22443 Show the current setting of the convention to return @code{struct}s
22448 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22449 @cindex Intel Memory Protection Extensions (MPX).
22451 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22452 @footnote{The register named with capital letters represent the architecture
22453 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22454 which are the lower bound and upper bound. Bounds are effective addresses or
22455 memory locations. The upper bounds are architecturally represented in 1's
22456 complement form. A bound having lower bound = 0, and upper bound = 0
22457 (1's complement of all bits set) will allow access to the entire address space.
22459 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22460 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22461 display the upper bound performing the complement of one operation on the
22462 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22463 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22464 can also be noted that the upper bounds are inclusive.
22466 As an example, assume that the register BND0 holds bounds for a pointer having
22467 access allowed for the range between 0x32 and 0x71. The values present on
22468 bnd0raw and bnd registers are presented as follows:
22471 bnd0raw = @{0x32, 0xffffffff8e@}
22472 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22475 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22476 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22477 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22478 Python, the display includes the memory size, in bits, accessible to
22481 Bounds can also be stored in bounds tables, which are stored in
22482 application memory. These tables store bounds for pointers by specifying
22483 the bounds pointer's value along with its bounds. Evaluating and changing
22484 bounds located in bound tables is therefore interesting while investigating
22485 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22488 @item show mpx bound @var{pointer}
22489 @kindex show mpx bound
22490 Display bounds of the given @var{pointer}.
22492 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22493 @kindex set mpx bound
22494 Set the bounds of a pointer in the bound table.
22495 This command takes three parameters: @var{pointer} is the pointers
22496 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22497 for lower and upper bounds respectively.
22503 See the following section.
22506 @subsection @acronym{MIPS}
22508 @cindex stack on Alpha
22509 @cindex stack on @acronym{MIPS}
22510 @cindex Alpha stack
22511 @cindex @acronym{MIPS} stack
22512 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22513 sometimes requires @value{GDBN} to search backward in the object code to
22514 find the beginning of a function.
22516 @cindex response time, @acronym{MIPS} debugging
22517 To improve response time (especially for embedded applications, where
22518 @value{GDBN} may be restricted to a slow serial line for this search)
22519 you may want to limit the size of this search, using one of these
22523 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22524 @item set heuristic-fence-post @var{limit}
22525 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22526 search for the beginning of a function. A value of @var{0} (the
22527 default) means there is no limit. However, except for @var{0}, the
22528 larger the limit the more bytes @code{heuristic-fence-post} must search
22529 and therefore the longer it takes to run. You should only need to use
22530 this command when debugging a stripped executable.
22532 @item show heuristic-fence-post
22533 Display the current limit.
22537 These commands are available @emph{only} when @value{GDBN} is configured
22538 for debugging programs on Alpha or @acronym{MIPS} processors.
22540 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22544 @item set mips abi @var{arg}
22545 @kindex set mips abi
22546 @cindex set ABI for @acronym{MIPS}
22547 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22548 values of @var{arg} are:
22552 The default ABI associated with the current binary (this is the
22562 @item show mips abi
22563 @kindex show mips abi
22564 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22566 @item set mips compression @var{arg}
22567 @kindex set mips compression
22568 @cindex code compression, @acronym{MIPS}
22569 Tell @value{GDBN} which @acronym{MIPS} compressed
22570 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22571 inferior. @value{GDBN} uses this for code disassembly and other
22572 internal interpretation purposes. This setting is only referred to
22573 when no executable has been associated with the debugging session or
22574 the executable does not provide information about the encoding it uses.
22575 Otherwise this setting is automatically updated from information
22576 provided by the executable.
22578 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22579 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22580 executables containing @acronym{MIPS16} code frequently are not
22581 identified as such.
22583 This setting is ``sticky''; that is, it retains its value across
22584 debugging sessions until reset either explicitly with this command or
22585 implicitly from an executable.
22587 The compiler and/or assembler typically add symbol table annotations to
22588 identify functions compiled for the @acronym{MIPS16} or
22589 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22590 are present, @value{GDBN} uses them in preference to the global
22591 compressed @acronym{ISA} encoding setting.
22593 @item show mips compression
22594 @kindex show mips compression
22595 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22596 @value{GDBN} to debug the inferior.
22599 @itemx show mipsfpu
22600 @xref{MIPS Embedded, set mipsfpu}.
22602 @item set mips mask-address @var{arg}
22603 @kindex set mips mask-address
22604 @cindex @acronym{MIPS} addresses, masking
22605 This command determines whether the most-significant 32 bits of 64-bit
22606 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22607 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22608 setting, which lets @value{GDBN} determine the correct value.
22610 @item show mips mask-address
22611 @kindex show mips mask-address
22612 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22615 @item set remote-mips64-transfers-32bit-regs
22616 @kindex set remote-mips64-transfers-32bit-regs
22617 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22618 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22619 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22620 and 64 bits for other registers, set this option to @samp{on}.
22622 @item show remote-mips64-transfers-32bit-regs
22623 @kindex show remote-mips64-transfers-32bit-regs
22624 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22626 @item set debug mips
22627 @kindex set debug mips
22628 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22629 target code in @value{GDBN}.
22631 @item show debug mips
22632 @kindex show debug mips
22633 Show the current setting of @acronym{MIPS} debugging messages.
22639 @cindex HPPA support
22641 When @value{GDBN} is debugging the HP PA architecture, it provides the
22642 following special commands:
22645 @item set debug hppa
22646 @kindex set debug hppa
22647 This command determines whether HPPA architecture-specific debugging
22648 messages are to be displayed.
22650 @item show debug hppa
22651 Show whether HPPA debugging messages are displayed.
22653 @item maint print unwind @var{address}
22654 @kindex maint print unwind@r{, HPPA}
22655 This command displays the contents of the unwind table entry at the
22656 given @var{address}.
22662 @subsection Cell Broadband Engine SPU architecture
22663 @cindex Cell Broadband Engine
22666 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22667 it provides the following special commands:
22670 @item info spu event
22672 Display SPU event facility status. Shows current event mask
22673 and pending event status.
22675 @item info spu signal
22676 Display SPU signal notification facility status. Shows pending
22677 signal-control word and signal notification mode of both signal
22678 notification channels.
22680 @item info spu mailbox
22681 Display SPU mailbox facility status. Shows all pending entries,
22682 in order of processing, in each of the SPU Write Outbound,
22683 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22686 Display MFC DMA status. Shows all pending commands in the MFC
22687 DMA queue. For each entry, opcode, tag, class IDs, effective
22688 and local store addresses and transfer size are shown.
22690 @item info spu proxydma
22691 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22692 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22693 and local store addresses and transfer size are shown.
22697 When @value{GDBN} is debugging a combined PowerPC/SPU application
22698 on the Cell Broadband Engine, it provides in addition the following
22702 @item set spu stop-on-load @var{arg}
22704 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22705 will give control to the user when a new SPE thread enters its @code{main}
22706 function. The default is @code{off}.
22708 @item show spu stop-on-load
22710 Show whether to stop for new SPE threads.
22712 @item set spu auto-flush-cache @var{arg}
22713 Set whether to automatically flush the software-managed cache. When set to
22714 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22715 cache to be flushed whenever SPE execution stops. This provides a consistent
22716 view of PowerPC memory that is accessed via the cache. If an application
22717 does not use the software-managed cache, this option has no effect.
22719 @item show spu auto-flush-cache
22720 Show whether to automatically flush the software-managed cache.
22725 @subsection PowerPC
22726 @cindex PowerPC architecture
22728 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22729 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22730 numbers stored in the floating point registers. These values must be stored
22731 in two consecutive registers, always starting at an even register like
22732 @code{f0} or @code{f2}.
22734 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22735 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22736 @code{f2} and @code{f3} for @code{$dl1} and so on.
22738 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22739 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22742 @subsection Nios II
22743 @cindex Nios II architecture
22745 When @value{GDBN} is debugging the Nios II architecture,
22746 it provides the following special commands:
22750 @item set debug nios2
22751 @kindex set debug nios2
22752 This command turns on and off debugging messages for the Nios II
22753 target code in @value{GDBN}.
22755 @item show debug nios2
22756 @kindex show debug nios2
22757 Show the current setting of Nios II debugging messages.
22760 @node Controlling GDB
22761 @chapter Controlling @value{GDBN}
22763 You can alter the way @value{GDBN} interacts with you by using the
22764 @code{set} command. For commands controlling how @value{GDBN} displays
22765 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22770 * Editing:: Command editing
22771 * Command History:: Command history
22772 * Screen Size:: Screen size
22773 * Numbers:: Numbers
22774 * ABI:: Configuring the current ABI
22775 * Auto-loading:: Automatically loading associated files
22776 * Messages/Warnings:: Optional warnings and messages
22777 * Debugging Output:: Optional messages about internal happenings
22778 * Other Misc Settings:: Other Miscellaneous Settings
22786 @value{GDBN} indicates its readiness to read a command by printing a string
22787 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22788 can change the prompt string with the @code{set prompt} command. For
22789 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22790 the prompt in one of the @value{GDBN} sessions so that you can always tell
22791 which one you are talking to.
22793 @emph{Note:} @code{set prompt} does not add a space for you after the
22794 prompt you set. This allows you to set a prompt which ends in a space
22795 or a prompt that does not.
22799 @item set prompt @var{newprompt}
22800 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22802 @kindex show prompt
22804 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22807 Versions of @value{GDBN} that ship with Python scripting enabled have
22808 prompt extensions. The commands for interacting with these extensions
22812 @kindex set extended-prompt
22813 @item set extended-prompt @var{prompt}
22814 Set an extended prompt that allows for substitutions.
22815 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22816 substitution. Any escape sequences specified as part of the prompt
22817 string are replaced with the corresponding strings each time the prompt
22823 set extended-prompt Current working directory: \w (gdb)
22826 Note that when an extended-prompt is set, it takes control of the
22827 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22829 @kindex show extended-prompt
22830 @item show extended-prompt
22831 Prints the extended prompt. Any escape sequences specified as part of
22832 the prompt string with @code{set extended-prompt}, are replaced with the
22833 corresponding strings each time the prompt is displayed.
22837 @section Command Editing
22839 @cindex command line editing
22841 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22842 @sc{gnu} library provides consistent behavior for programs which provide a
22843 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22844 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22845 substitution, and a storage and recall of command history across
22846 debugging sessions.
22848 You may control the behavior of command line editing in @value{GDBN} with the
22849 command @code{set}.
22852 @kindex set editing
22855 @itemx set editing on
22856 Enable command line editing (enabled by default).
22858 @item set editing off
22859 Disable command line editing.
22861 @kindex show editing
22863 Show whether command line editing is enabled.
22866 @ifset SYSTEM_READLINE
22867 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22869 @ifclear SYSTEM_READLINE
22870 @xref{Command Line Editing},
22872 for more details about the Readline
22873 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22874 encouraged to read that chapter.
22876 @node Command History
22877 @section Command History
22878 @cindex command history
22880 @value{GDBN} can keep track of the commands you type during your
22881 debugging sessions, so that you can be certain of precisely what
22882 happened. Use these commands to manage the @value{GDBN} command
22885 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22886 package, to provide the history facility.
22887 @ifset SYSTEM_READLINE
22888 @xref{Using History Interactively, , , history, GNU History Library},
22890 @ifclear SYSTEM_READLINE
22891 @xref{Using History Interactively},
22893 for the detailed description of the History library.
22895 To issue a command to @value{GDBN} without affecting certain aspects of
22896 the state which is seen by users, prefix it with @samp{server }
22897 (@pxref{Server Prefix}). This
22898 means that this command will not affect the command history, nor will it
22899 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22900 pressed on a line by itself.
22902 @cindex @code{server}, command prefix
22903 The server prefix does not affect the recording of values into the value
22904 history; to print a value without recording it into the value history,
22905 use the @code{output} command instead of the @code{print} command.
22907 Here is the description of @value{GDBN} commands related to command
22911 @cindex history substitution
22912 @cindex history file
22913 @kindex set history filename
22914 @cindex @env{GDBHISTFILE}, environment variable
22915 @item set history filename @var{fname}
22916 Set the name of the @value{GDBN} command history file to @var{fname}.
22917 This is the file where @value{GDBN} reads an initial command history
22918 list, and where it writes the command history from this session when it
22919 exits. You can access this list through history expansion or through
22920 the history command editing characters listed below. This file defaults
22921 to the value of the environment variable @code{GDBHISTFILE}, or to
22922 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22925 @cindex save command history
22926 @kindex set history save
22927 @item set history save
22928 @itemx set history save on
22929 Record command history in a file, whose name may be specified with the
22930 @code{set history filename} command. By default, this option is disabled.
22932 @item set history save off
22933 Stop recording command history in a file.
22935 @cindex history size
22936 @kindex set history size
22937 @cindex @env{GDBHISTSIZE}, environment variable
22938 @item set history size @var{size}
22939 @itemx set history size unlimited
22940 Set the number of commands which @value{GDBN} keeps in its history list.
22941 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22942 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22943 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22944 either a negative number or the empty string, then the number of commands
22945 @value{GDBN} keeps in the history list is unlimited.
22947 @cindex remove duplicate history
22948 @kindex set history remove-duplicates
22949 @item set history remove-duplicates @var{count}
22950 @itemx set history remove-duplicates unlimited
22951 Control the removal of duplicate history entries in the command history list.
22952 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22953 history entries and remove the first entry that is a duplicate of the current
22954 entry being added to the command history list. If @var{count} is
22955 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22956 removal of duplicate history entries is disabled.
22958 Only history entries added during the current session are considered for
22959 removal. This option is set to 0 by default.
22963 History expansion assigns special meaning to the character @kbd{!}.
22964 @ifset SYSTEM_READLINE
22965 @xref{Event Designators, , , history, GNU History Library},
22967 @ifclear SYSTEM_READLINE
22968 @xref{Event Designators},
22972 @cindex history expansion, turn on/off
22973 Since @kbd{!} is also the logical not operator in C, history expansion
22974 is off by default. If you decide to enable history expansion with the
22975 @code{set history expansion on} command, you may sometimes need to
22976 follow @kbd{!} (when it is used as logical not, in an expression) with
22977 a space or a tab to prevent it from being expanded. The readline
22978 history facilities do not attempt substitution on the strings
22979 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22981 The commands to control history expansion are:
22984 @item set history expansion on
22985 @itemx set history expansion
22986 @kindex set history expansion
22987 Enable history expansion. History expansion is off by default.
22989 @item set history expansion off
22990 Disable history expansion.
22993 @kindex show history
22995 @itemx show history filename
22996 @itemx show history save
22997 @itemx show history size
22998 @itemx show history expansion
22999 These commands display the state of the @value{GDBN} history parameters.
23000 @code{show history} by itself displays all four states.
23005 @kindex show commands
23006 @cindex show last commands
23007 @cindex display command history
23008 @item show commands
23009 Display the last ten commands in the command history.
23011 @item show commands @var{n}
23012 Print ten commands centered on command number @var{n}.
23014 @item show commands +
23015 Print ten commands just after the commands last printed.
23019 @section Screen Size
23020 @cindex size of screen
23021 @cindex screen size
23024 @cindex pauses in output
23026 Certain commands to @value{GDBN} may produce large amounts of
23027 information output to the screen. To help you read all of it,
23028 @value{GDBN} pauses and asks you for input at the end of each page of
23029 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23030 to discard the remaining output. Also, the screen width setting
23031 determines when to wrap lines of output. Depending on what is being
23032 printed, @value{GDBN} tries to break the line at a readable place,
23033 rather than simply letting it overflow onto the following line.
23035 Normally @value{GDBN} knows the size of the screen from the terminal
23036 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23037 together with the value of the @code{TERM} environment variable and the
23038 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23039 you can override it with the @code{set height} and @code{set
23046 @kindex show height
23047 @item set height @var{lpp}
23048 @itemx set height unlimited
23050 @itemx set width @var{cpl}
23051 @itemx set width unlimited
23053 These @code{set} commands specify a screen height of @var{lpp} lines and
23054 a screen width of @var{cpl} characters. The associated @code{show}
23055 commands display the current settings.
23057 If you specify a height of either @code{unlimited} or zero lines,
23058 @value{GDBN} does not pause during output no matter how long the
23059 output is. This is useful if output is to a file or to an editor
23062 Likewise, you can specify @samp{set width unlimited} or @samp{set
23063 width 0} to prevent @value{GDBN} from wrapping its output.
23065 @item set pagination on
23066 @itemx set pagination off
23067 @kindex set pagination
23068 Turn the output pagination on or off; the default is on. Turning
23069 pagination off is the alternative to @code{set height unlimited}. Note that
23070 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23071 Options, -batch}) also automatically disables pagination.
23073 @item show pagination
23074 @kindex show pagination
23075 Show the current pagination mode.
23080 @cindex number representation
23081 @cindex entering numbers
23083 You can always enter numbers in octal, decimal, or hexadecimal in
23084 @value{GDBN} by the usual conventions: octal numbers begin with
23085 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23086 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23087 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23088 10; likewise, the default display for numbers---when no particular
23089 format is specified---is base 10. You can change the default base for
23090 both input and output with the commands described below.
23093 @kindex set input-radix
23094 @item set input-radix @var{base}
23095 Set the default base for numeric input. Supported choices
23096 for @var{base} are decimal 8, 10, or 16. The base must itself be
23097 specified either unambiguously or using the current input radix; for
23101 set input-radix 012
23102 set input-radix 10.
23103 set input-radix 0xa
23107 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23108 leaves the input radix unchanged, no matter what it was, since
23109 @samp{10}, being without any leading or trailing signs of its base, is
23110 interpreted in the current radix. Thus, if the current radix is 16,
23111 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23114 @kindex set output-radix
23115 @item set output-radix @var{base}
23116 Set the default base for numeric display. Supported choices
23117 for @var{base} are decimal 8, 10, or 16. The base must itself be
23118 specified either unambiguously or using the current input radix.
23120 @kindex show input-radix
23121 @item show input-radix
23122 Display the current default base for numeric input.
23124 @kindex show output-radix
23125 @item show output-radix
23126 Display the current default base for numeric display.
23128 @item set radix @r{[}@var{base}@r{]}
23132 These commands set and show the default base for both input and output
23133 of numbers. @code{set radix} sets the radix of input and output to
23134 the same base; without an argument, it resets the radix back to its
23135 default value of 10.
23140 @section Configuring the Current ABI
23142 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23143 application automatically. However, sometimes you need to override its
23144 conclusions. Use these commands to manage @value{GDBN}'s view of the
23150 @cindex Newlib OS ABI and its influence on the longjmp handling
23152 One @value{GDBN} configuration can debug binaries for multiple operating
23153 system targets, either via remote debugging or native emulation.
23154 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23155 but you can override its conclusion using the @code{set osabi} command.
23156 One example where this is useful is in debugging of binaries which use
23157 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23158 not have the same identifying marks that the standard C library for your
23161 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23162 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23163 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23164 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23168 Show the OS ABI currently in use.
23171 With no argument, show the list of registered available OS ABI's.
23173 @item set osabi @var{abi}
23174 Set the current OS ABI to @var{abi}.
23177 @cindex float promotion
23179 Generally, the way that an argument of type @code{float} is passed to a
23180 function depends on whether the function is prototyped. For a prototyped
23181 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23182 according to the architecture's convention for @code{float}. For unprototyped
23183 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23184 @code{double} and then passed.
23186 Unfortunately, some forms of debug information do not reliably indicate whether
23187 a function is prototyped. If @value{GDBN} calls a function that is not marked
23188 as prototyped, it consults @kbd{set coerce-float-to-double}.
23191 @kindex set coerce-float-to-double
23192 @item set coerce-float-to-double
23193 @itemx set coerce-float-to-double on
23194 Arguments of type @code{float} will be promoted to @code{double} when passed
23195 to an unprototyped function. This is the default setting.
23197 @item set coerce-float-to-double off
23198 Arguments of type @code{float} will be passed directly to unprototyped
23201 @kindex show coerce-float-to-double
23202 @item show coerce-float-to-double
23203 Show the current setting of promoting @code{float} to @code{double}.
23207 @kindex show cp-abi
23208 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23209 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23210 used to build your application. @value{GDBN} only fully supports
23211 programs with a single C@t{++} ABI; if your program contains code using
23212 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23213 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23214 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23215 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23216 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23217 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23222 Show the C@t{++} ABI currently in use.
23225 With no argument, show the list of supported C@t{++} ABI's.
23227 @item set cp-abi @var{abi}
23228 @itemx set cp-abi auto
23229 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23233 @section Automatically loading associated files
23234 @cindex auto-loading
23236 @value{GDBN} sometimes reads files with commands and settings automatically,
23237 without being explicitly told so by the user. We call this feature
23238 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23239 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23240 results or introduce security risks (e.g., if the file comes from untrusted
23244 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23245 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23247 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23248 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23251 There are various kinds of files @value{GDBN} can automatically load.
23252 In addition to these files, @value{GDBN} supports auto-loading code written
23253 in various extension languages. @xref{Auto-loading extensions}.
23255 Note that loading of these associated files (including the local @file{.gdbinit}
23256 file) requires accordingly configured @code{auto-load safe-path}
23257 (@pxref{Auto-loading safe path}).
23259 For these reasons, @value{GDBN} includes commands and options to let you
23260 control when to auto-load files and which files should be auto-loaded.
23263 @anchor{set auto-load off}
23264 @kindex set auto-load off
23265 @item set auto-load off
23266 Globally disable loading of all auto-loaded files.
23267 You may want to use this command with the @samp{-iex} option
23268 (@pxref{Option -init-eval-command}) such as:
23270 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23273 Be aware that system init file (@pxref{System-wide configuration})
23274 and init files from your home directory (@pxref{Home Directory Init File})
23275 still get read (as they come from generally trusted directories).
23276 To prevent @value{GDBN} from auto-loading even those init files, use the
23277 @option{-nx} option (@pxref{Mode Options}), in addition to
23278 @code{set auto-load no}.
23280 @anchor{show auto-load}
23281 @kindex show auto-load
23282 @item show auto-load
23283 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23287 (gdb) show auto-load
23288 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23289 libthread-db: Auto-loading of inferior specific libthread_db is on.
23290 local-gdbinit: Auto-loading of .gdbinit script from current directory
23292 python-scripts: Auto-loading of Python scripts is on.
23293 safe-path: List of directories from which it is safe to auto-load files
23294 is $debugdir:$datadir/auto-load.
23295 scripts-directory: List of directories from which to load auto-loaded scripts
23296 is $debugdir:$datadir/auto-load.
23299 @anchor{info auto-load}
23300 @kindex info auto-load
23301 @item info auto-load
23302 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23306 (gdb) info auto-load
23309 Yes /home/user/gdb/gdb-gdb.gdb
23310 libthread-db: No auto-loaded libthread-db.
23311 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23315 Yes /home/user/gdb/gdb-gdb.py
23319 These are @value{GDBN} control commands for the auto-loading:
23321 @multitable @columnfractions .5 .5
23322 @item @xref{set auto-load off}.
23323 @tab Disable auto-loading globally.
23324 @item @xref{show auto-load}.
23325 @tab Show setting of all kinds of files.
23326 @item @xref{info auto-load}.
23327 @tab Show state of all kinds of files.
23328 @item @xref{set auto-load gdb-scripts}.
23329 @tab Control for @value{GDBN} command scripts.
23330 @item @xref{show auto-load gdb-scripts}.
23331 @tab Show setting of @value{GDBN} command scripts.
23332 @item @xref{info auto-load gdb-scripts}.
23333 @tab Show state of @value{GDBN} command scripts.
23334 @item @xref{set auto-load python-scripts}.
23335 @tab Control for @value{GDBN} Python scripts.
23336 @item @xref{show auto-load python-scripts}.
23337 @tab Show setting of @value{GDBN} Python scripts.
23338 @item @xref{info auto-load python-scripts}.
23339 @tab Show state of @value{GDBN} Python scripts.
23340 @item @xref{set auto-load guile-scripts}.
23341 @tab Control for @value{GDBN} Guile scripts.
23342 @item @xref{show auto-load guile-scripts}.
23343 @tab Show setting of @value{GDBN} Guile scripts.
23344 @item @xref{info auto-load guile-scripts}.
23345 @tab Show state of @value{GDBN} Guile scripts.
23346 @item @xref{set auto-load scripts-directory}.
23347 @tab Control for @value{GDBN} auto-loaded scripts location.
23348 @item @xref{show auto-load scripts-directory}.
23349 @tab Show @value{GDBN} auto-loaded scripts location.
23350 @item @xref{add-auto-load-scripts-directory}.
23351 @tab Add directory for auto-loaded scripts location list.
23352 @item @xref{set auto-load local-gdbinit}.
23353 @tab Control for init file in the current directory.
23354 @item @xref{show auto-load local-gdbinit}.
23355 @tab Show setting of init file in the current directory.
23356 @item @xref{info auto-load local-gdbinit}.
23357 @tab Show state of init file in the current directory.
23358 @item @xref{set auto-load libthread-db}.
23359 @tab Control for thread debugging library.
23360 @item @xref{show auto-load libthread-db}.
23361 @tab Show setting of thread debugging library.
23362 @item @xref{info auto-load libthread-db}.
23363 @tab Show state of thread debugging library.
23364 @item @xref{set auto-load safe-path}.
23365 @tab Control directories trusted for automatic loading.
23366 @item @xref{show auto-load safe-path}.
23367 @tab Show directories trusted for automatic loading.
23368 @item @xref{add-auto-load-safe-path}.
23369 @tab Add directory trusted for automatic loading.
23372 @node Init File in the Current Directory
23373 @subsection Automatically loading init file in the current directory
23374 @cindex auto-loading init file in the current directory
23376 By default, @value{GDBN} reads and executes the canned sequences of commands
23377 from init file (if any) in the current working directory,
23378 see @ref{Init File in the Current Directory during Startup}.
23380 Note that loading of this local @file{.gdbinit} file also requires accordingly
23381 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23384 @anchor{set auto-load local-gdbinit}
23385 @kindex set auto-load local-gdbinit
23386 @item set auto-load local-gdbinit [on|off]
23387 Enable or disable the auto-loading of canned sequences of commands
23388 (@pxref{Sequences}) found in init file in the current directory.
23390 @anchor{show auto-load local-gdbinit}
23391 @kindex show auto-load local-gdbinit
23392 @item show auto-load local-gdbinit
23393 Show whether auto-loading of canned sequences of commands from init file in the
23394 current directory is enabled or disabled.
23396 @anchor{info auto-load local-gdbinit}
23397 @kindex info auto-load local-gdbinit
23398 @item info auto-load local-gdbinit
23399 Print whether canned sequences of commands from init file in the
23400 current directory have been auto-loaded.
23403 @node libthread_db.so.1 file
23404 @subsection Automatically loading thread debugging library
23405 @cindex auto-loading libthread_db.so.1
23407 This feature is currently present only on @sc{gnu}/Linux native hosts.
23409 @value{GDBN} reads in some cases thread debugging library from places specific
23410 to the inferior (@pxref{set libthread-db-search-path}).
23412 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23413 without checking this @samp{set auto-load libthread-db} switch as system
23414 libraries have to be trusted in general. In all other cases of
23415 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23416 auto-load libthread-db} is enabled before trying to open such thread debugging
23419 Note that loading of this debugging library also requires accordingly configured
23420 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23423 @anchor{set auto-load libthread-db}
23424 @kindex set auto-load libthread-db
23425 @item set auto-load libthread-db [on|off]
23426 Enable or disable the auto-loading of inferior specific thread debugging library.
23428 @anchor{show auto-load libthread-db}
23429 @kindex show auto-load libthread-db
23430 @item show auto-load libthread-db
23431 Show whether auto-loading of inferior specific thread debugging library is
23432 enabled or disabled.
23434 @anchor{info auto-load libthread-db}
23435 @kindex info auto-load libthread-db
23436 @item info auto-load libthread-db
23437 Print the list of all loaded inferior specific thread debugging libraries and
23438 for each such library print list of inferior @var{pid}s using it.
23441 @node Auto-loading safe path
23442 @subsection Security restriction for auto-loading
23443 @cindex auto-loading safe-path
23445 As the files of inferior can come from untrusted source (such as submitted by
23446 an application user) @value{GDBN} does not always load any files automatically.
23447 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23448 directories trusted for loading files not explicitly requested by user.
23449 Each directory can also be a shell wildcard pattern.
23451 If the path is not set properly you will see a warning and the file will not
23456 Reading symbols from /home/user/gdb/gdb...done.
23457 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23458 declined by your `auto-load safe-path' set
23459 to "$debugdir:$datadir/auto-load".
23460 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23461 declined by your `auto-load safe-path' set
23462 to "$debugdir:$datadir/auto-load".
23466 To instruct @value{GDBN} to go ahead and use the init files anyway,
23467 invoke @value{GDBN} like this:
23470 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23473 The list of trusted directories is controlled by the following commands:
23476 @anchor{set auto-load safe-path}
23477 @kindex set auto-load safe-path
23478 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23479 Set the list of directories (and their subdirectories) trusted for automatic
23480 loading and execution of scripts. You can also enter a specific trusted file.
23481 Each directory can also be a shell wildcard pattern; wildcards do not match
23482 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23483 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23484 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23485 its default value as specified during @value{GDBN} compilation.
23487 The list of directories uses path separator (@samp{:} on GNU and Unix
23488 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23489 to the @env{PATH} environment variable.
23491 @anchor{show auto-load safe-path}
23492 @kindex show auto-load safe-path
23493 @item show auto-load safe-path
23494 Show the list of directories trusted for automatic loading and execution of
23497 @anchor{add-auto-load-safe-path}
23498 @kindex add-auto-load-safe-path
23499 @item add-auto-load-safe-path
23500 Add an entry (or list of entries) to the list of directories trusted for
23501 automatic loading and execution of scripts. Multiple entries may be delimited
23502 by the host platform path separator in use.
23505 This variable defaults to what @code{--with-auto-load-dir} has been configured
23506 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23507 substitution applies the same as for @ref{set auto-load scripts-directory}.
23508 The default @code{set auto-load safe-path} value can be also overriden by
23509 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23511 Setting this variable to @file{/} disables this security protection,
23512 corresponding @value{GDBN} configuration option is
23513 @option{--without-auto-load-safe-path}.
23514 This variable is supposed to be set to the system directories writable by the
23515 system superuser only. Users can add their source directories in init files in
23516 their home directories (@pxref{Home Directory Init File}). See also deprecated
23517 init file in the current directory
23518 (@pxref{Init File in the Current Directory during Startup}).
23520 To force @value{GDBN} to load the files it declined to load in the previous
23521 example, you could use one of the following ways:
23524 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23525 Specify this trusted directory (or a file) as additional component of the list.
23526 You have to specify also any existing directories displayed by
23527 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23529 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23530 Specify this directory as in the previous case but just for a single
23531 @value{GDBN} session.
23533 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23534 Disable auto-loading safety for a single @value{GDBN} session.
23535 This assumes all the files you debug during this @value{GDBN} session will come
23536 from trusted sources.
23538 @item @kbd{./configure --without-auto-load-safe-path}
23539 During compilation of @value{GDBN} you may disable any auto-loading safety.
23540 This assumes all the files you will ever debug with this @value{GDBN} come from
23544 On the other hand you can also explicitly forbid automatic files loading which
23545 also suppresses any such warning messages:
23548 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23549 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23551 @item @file{~/.gdbinit}: @samp{set auto-load no}
23552 Disable auto-loading globally for the user
23553 (@pxref{Home Directory Init File}). While it is improbable, you could also
23554 use system init file instead (@pxref{System-wide configuration}).
23557 This setting applies to the file names as entered by user. If no entry matches
23558 @value{GDBN} tries as a last resort to also resolve all the file names into
23559 their canonical form (typically resolving symbolic links) and compare the
23560 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23561 own before starting the comparison so a canonical form of directories is
23562 recommended to be entered.
23564 @node Auto-loading verbose mode
23565 @subsection Displaying files tried for auto-load
23566 @cindex auto-loading verbose mode
23568 For better visibility of all the file locations where you can place scripts to
23569 be auto-loaded with inferior --- or to protect yourself against accidental
23570 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23571 all the files attempted to be loaded. Both existing and non-existing files may
23574 For example the list of directories from which it is safe to auto-load files
23575 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23576 may not be too obvious while setting it up.
23579 (gdb) set debug auto-load on
23580 (gdb) file ~/src/t/true
23581 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23582 for objfile "/tmp/true".
23583 auto-load: Updating directories of "/usr:/opt".
23584 auto-load: Using directory "/usr".
23585 auto-load: Using directory "/opt".
23586 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23587 by your `auto-load safe-path' set to "/usr:/opt".
23591 @anchor{set debug auto-load}
23592 @kindex set debug auto-load
23593 @item set debug auto-load [on|off]
23594 Set whether to print the filenames attempted to be auto-loaded.
23596 @anchor{show debug auto-load}
23597 @kindex show debug auto-load
23598 @item show debug auto-load
23599 Show whether printing of the filenames attempted to be auto-loaded is turned
23603 @node Messages/Warnings
23604 @section Optional Warnings and Messages
23606 @cindex verbose operation
23607 @cindex optional warnings
23608 By default, @value{GDBN} is silent about its inner workings. If you are
23609 running on a slow machine, you may want to use the @code{set verbose}
23610 command. This makes @value{GDBN} tell you when it does a lengthy
23611 internal operation, so you will not think it has crashed.
23613 Currently, the messages controlled by @code{set verbose} are those
23614 which announce that the symbol table for a source file is being read;
23615 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23618 @kindex set verbose
23619 @item set verbose on
23620 Enables @value{GDBN} output of certain informational messages.
23622 @item set verbose off
23623 Disables @value{GDBN} output of certain informational messages.
23625 @kindex show verbose
23627 Displays whether @code{set verbose} is on or off.
23630 By default, if @value{GDBN} encounters bugs in the symbol table of an
23631 object file, it is silent; but if you are debugging a compiler, you may
23632 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23637 @kindex set complaints
23638 @item set complaints @var{limit}
23639 Permits @value{GDBN} to output @var{limit} complaints about each type of
23640 unusual symbols before becoming silent about the problem. Set
23641 @var{limit} to zero to suppress all complaints; set it to a large number
23642 to prevent complaints from being suppressed.
23644 @kindex show complaints
23645 @item show complaints
23646 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23650 @anchor{confirmation requests}
23651 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23652 lot of stupid questions to confirm certain commands. For example, if
23653 you try to run a program which is already running:
23657 The program being debugged has been started already.
23658 Start it from the beginning? (y or n)
23661 If you are willing to unflinchingly face the consequences of your own
23662 commands, you can disable this ``feature'':
23666 @kindex set confirm
23668 @cindex confirmation
23669 @cindex stupid questions
23670 @item set confirm off
23671 Disables confirmation requests. Note that running @value{GDBN} with
23672 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23673 automatically disables confirmation requests.
23675 @item set confirm on
23676 Enables confirmation requests (the default).
23678 @kindex show confirm
23680 Displays state of confirmation requests.
23684 @cindex command tracing
23685 If you need to debug user-defined commands or sourced files you may find it
23686 useful to enable @dfn{command tracing}. In this mode each command will be
23687 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23688 quantity denoting the call depth of each command.
23691 @kindex set trace-commands
23692 @cindex command scripts, debugging
23693 @item set trace-commands on
23694 Enable command tracing.
23695 @item set trace-commands off
23696 Disable command tracing.
23697 @item show trace-commands
23698 Display the current state of command tracing.
23701 @node Debugging Output
23702 @section Optional Messages about Internal Happenings
23703 @cindex optional debugging messages
23705 @value{GDBN} has commands that enable optional debugging messages from
23706 various @value{GDBN} subsystems; normally these commands are of
23707 interest to @value{GDBN} maintainers, or when reporting a bug. This
23708 section documents those commands.
23711 @kindex set exec-done-display
23712 @item set exec-done-display
23713 Turns on or off the notification of asynchronous commands'
23714 completion. When on, @value{GDBN} will print a message when an
23715 asynchronous command finishes its execution. The default is off.
23716 @kindex show exec-done-display
23717 @item show exec-done-display
23718 Displays the current setting of asynchronous command completion
23721 @cindex ARM AArch64
23722 @item set debug aarch64
23723 Turns on or off display of debugging messages related to ARM AArch64.
23724 The default is off.
23726 @item show debug aarch64
23727 Displays the current state of displaying debugging messages related to
23729 @cindex gdbarch debugging info
23730 @cindex architecture debugging info
23731 @item set debug arch
23732 Turns on or off display of gdbarch debugging info. The default is off
23733 @item show debug arch
23734 Displays the current state of displaying gdbarch debugging info.
23735 @item set debug aix-solib
23736 @cindex AIX shared library debugging
23737 Control display of debugging messages from the AIX shared library
23738 support module. The default is off.
23739 @item show debug aix-thread
23740 Show the current state of displaying AIX shared library debugging messages.
23741 @item set debug aix-thread
23742 @cindex AIX threads
23743 Display debugging messages about inner workings of the AIX thread
23745 @item show debug aix-thread
23746 Show the current state of AIX thread debugging info display.
23747 @item set debug check-physname
23749 Check the results of the ``physname'' computation. When reading DWARF
23750 debugging information for C@t{++}, @value{GDBN} attempts to compute
23751 each entity's name. @value{GDBN} can do this computation in two
23752 different ways, depending on exactly what information is present.
23753 When enabled, this setting causes @value{GDBN} to compute the names
23754 both ways and display any discrepancies.
23755 @item show debug check-physname
23756 Show the current state of ``physname'' checking.
23757 @item set debug coff-pe-read
23758 @cindex COFF/PE exported symbols
23759 Control display of debugging messages related to reading of COFF/PE
23760 exported symbols. The default is off.
23761 @item show debug coff-pe-read
23762 Displays the current state of displaying debugging messages related to
23763 reading of COFF/PE exported symbols.
23764 @item set debug dwarf-die
23766 Dump DWARF DIEs after they are read in.
23767 The value is the number of nesting levels to print.
23768 A value of zero turns off the display.
23769 @item show debug dwarf-die
23770 Show the current state of DWARF DIE debugging.
23771 @item set debug dwarf-line
23772 @cindex DWARF Line Tables
23773 Turns on or off display of debugging messages related to reading
23774 DWARF line tables. The default is 0 (off).
23775 A value of 1 provides basic information.
23776 A value greater than 1 provides more verbose information.
23777 @item show debug dwarf-line
23778 Show the current state of DWARF line table debugging.
23779 @item set debug dwarf-read
23780 @cindex DWARF Reading
23781 Turns on or off display of debugging messages related to reading
23782 DWARF debug info. The default is 0 (off).
23783 A value of 1 provides basic information.
23784 A value greater than 1 provides more verbose information.
23785 @item show debug dwarf-read
23786 Show the current state of DWARF reader debugging.
23787 @item set debug displaced
23788 @cindex displaced stepping debugging info
23789 Turns on or off display of @value{GDBN} debugging info for the
23790 displaced stepping support. The default is off.
23791 @item show debug displaced
23792 Displays the current state of displaying @value{GDBN} debugging info
23793 related to displaced stepping.
23794 @item set debug event
23795 @cindex event debugging info
23796 Turns on or off display of @value{GDBN} event debugging info. The
23798 @item show debug event
23799 Displays the current state of displaying @value{GDBN} event debugging
23801 @item set debug expression
23802 @cindex expression debugging info
23803 Turns on or off display of debugging info about @value{GDBN}
23804 expression parsing. The default is off.
23805 @item show debug expression
23806 Displays the current state of displaying debugging info about
23807 @value{GDBN} expression parsing.
23808 @item set debug fbsd-lwp
23809 @cindex FreeBSD LWP debug messages
23810 Turns on or off debugging messages from the FreeBSD LWP debug support.
23811 @item show debug fbsd-lwp
23812 Show the current state of FreeBSD LWP debugging messages.
23813 @item set debug frame
23814 @cindex frame debugging info
23815 Turns on or off display of @value{GDBN} frame debugging info. The
23817 @item show debug frame
23818 Displays the current state of displaying @value{GDBN} frame debugging
23820 @item set debug gnu-nat
23821 @cindex @sc{gnu}/Hurd debug messages
23822 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23823 @item show debug gnu-nat
23824 Show the current state of @sc{gnu}/Hurd debugging messages.
23825 @item set debug infrun
23826 @cindex inferior debugging info
23827 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23828 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23829 for implementing operations such as single-stepping the inferior.
23830 @item show debug infrun
23831 Displays the current state of @value{GDBN} inferior debugging.
23832 @item set debug jit
23833 @cindex just-in-time compilation, debugging messages
23834 Turn on or off debugging messages from JIT debug support.
23835 @item show debug jit
23836 Displays the current state of @value{GDBN} JIT debugging.
23837 @item set debug lin-lwp
23838 @cindex @sc{gnu}/Linux LWP debug messages
23839 @cindex Linux lightweight processes
23840 Turn on or off debugging messages from the Linux LWP debug support.
23841 @item show debug lin-lwp
23842 Show the current state of Linux LWP debugging messages.
23843 @item set debug linux-namespaces
23844 @cindex @sc{gnu}/Linux namespaces debug messages
23845 Turn on or off debugging messages from the Linux namespaces debug support.
23846 @item show debug linux-namespaces
23847 Show the current state of Linux namespaces debugging messages.
23848 @item set debug mach-o
23849 @cindex Mach-O symbols processing
23850 Control display of debugging messages related to Mach-O symbols
23851 processing. The default is off.
23852 @item show debug mach-o
23853 Displays the current state of displaying debugging messages related to
23854 reading of COFF/PE exported symbols.
23855 @item set debug notification
23856 @cindex remote async notification debugging info
23857 Turn on or off debugging messages about remote async notification.
23858 The default is off.
23859 @item show debug notification
23860 Displays the current state of remote async notification debugging messages.
23861 @item set debug observer
23862 @cindex observer debugging info
23863 Turns on or off display of @value{GDBN} observer debugging. This
23864 includes info such as the notification of observable events.
23865 @item show debug observer
23866 Displays the current state of observer debugging.
23867 @item set debug overload
23868 @cindex C@t{++} overload debugging info
23869 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23870 info. This includes info such as ranking of functions, etc. The default
23872 @item show debug overload
23873 Displays the current state of displaying @value{GDBN} C@t{++} overload
23875 @cindex expression parser, debugging info
23876 @cindex debug expression parser
23877 @item set debug parser
23878 Turns on or off the display of expression parser debugging output.
23879 Internally, this sets the @code{yydebug} variable in the expression
23880 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23881 details. The default is off.
23882 @item show debug parser
23883 Show the current state of expression parser debugging.
23884 @cindex packets, reporting on stdout
23885 @cindex serial connections, debugging
23886 @cindex debug remote protocol
23887 @cindex remote protocol debugging
23888 @cindex display remote packets
23889 @item set debug remote
23890 Turns on or off display of reports on all packets sent back and forth across
23891 the serial line to the remote machine. The info is printed on the
23892 @value{GDBN} standard output stream. The default is off.
23893 @item show debug remote
23894 Displays the state of display of remote packets.
23895 @item set debug serial
23896 Turns on or off display of @value{GDBN} serial debugging info. The
23898 @item show debug serial
23899 Displays the current state of displaying @value{GDBN} serial debugging
23901 @item set debug solib-frv
23902 @cindex FR-V shared-library debugging
23903 Turn on or off debugging messages for FR-V shared-library code.
23904 @item show debug solib-frv
23905 Display the current state of FR-V shared-library code debugging
23907 @item set debug symbol-lookup
23908 @cindex symbol lookup
23909 Turns on or off display of debugging messages related to symbol lookup.
23910 The default is 0 (off).
23911 A value of 1 provides basic information.
23912 A value greater than 1 provides more verbose information.
23913 @item show debug symbol-lookup
23914 Show the current state of symbol lookup debugging messages.
23915 @item set debug symfile
23916 @cindex symbol file functions
23917 Turns on or off display of debugging messages related to symbol file functions.
23918 The default is off. @xref{Files}.
23919 @item show debug symfile
23920 Show the current state of symbol file debugging messages.
23921 @item set debug symtab-create
23922 @cindex symbol table creation
23923 Turns on or off display of debugging messages related to symbol table creation.
23924 The default is 0 (off).
23925 A value of 1 provides basic information.
23926 A value greater than 1 provides more verbose information.
23927 @item show debug symtab-create
23928 Show the current state of symbol table creation debugging.
23929 @item set debug target
23930 @cindex target debugging info
23931 Turns on or off display of @value{GDBN} target debugging info. This info
23932 includes what is going on at the target level of GDB, as it happens. The
23933 default is 0. Set it to 1 to track events, and to 2 to also track the
23934 value of large memory transfers.
23935 @item show debug target
23936 Displays the current state of displaying @value{GDBN} target debugging
23938 @item set debug timestamp
23939 @cindex timestampping debugging info
23940 Turns on or off display of timestamps with @value{GDBN} debugging info.
23941 When enabled, seconds and microseconds are displayed before each debugging
23943 @item show debug timestamp
23944 Displays the current state of displaying timestamps with @value{GDBN}
23946 @item set debug varobj
23947 @cindex variable object debugging info
23948 Turns on or off display of @value{GDBN} variable object debugging
23949 info. The default is off.
23950 @item show debug varobj
23951 Displays the current state of displaying @value{GDBN} variable object
23953 @item set debug xml
23954 @cindex XML parser debugging
23955 Turn on or off debugging messages for built-in XML parsers.
23956 @item show debug xml
23957 Displays the current state of XML debugging messages.
23960 @node Other Misc Settings
23961 @section Other Miscellaneous Settings
23962 @cindex miscellaneous settings
23965 @kindex set interactive-mode
23966 @item set interactive-mode
23967 If @code{on}, forces @value{GDBN} to assume that GDB was started
23968 in a terminal. In practice, this means that @value{GDBN} should wait
23969 for the user to answer queries generated by commands entered at
23970 the command prompt. If @code{off}, forces @value{GDBN} to operate
23971 in the opposite mode, and it uses the default answers to all queries.
23972 If @code{auto} (the default), @value{GDBN} tries to determine whether
23973 its standard input is a terminal, and works in interactive-mode if it
23974 is, non-interactively otherwise.
23976 In the vast majority of cases, the debugger should be able to guess
23977 correctly which mode should be used. But this setting can be useful
23978 in certain specific cases, such as running a MinGW @value{GDBN}
23979 inside a cygwin window.
23981 @kindex show interactive-mode
23982 @item show interactive-mode
23983 Displays whether the debugger is operating in interactive mode or not.
23986 @node Extending GDB
23987 @chapter Extending @value{GDBN}
23988 @cindex extending GDB
23990 @value{GDBN} provides several mechanisms for extension.
23991 @value{GDBN} also provides the ability to automatically load
23992 extensions when it reads a file for debugging. This allows the
23993 user to automatically customize @value{GDBN} for the program
23997 * Sequences:: Canned Sequences of @value{GDBN} Commands
23998 * Python:: Extending @value{GDBN} using Python
23999 * Guile:: Extending @value{GDBN} using Guile
24000 * Auto-loading extensions:: Automatically loading extensions
24001 * Multiple Extension Languages:: Working with multiple extension languages
24002 * Aliases:: Creating new spellings of existing commands
24005 To facilitate the use of extension languages, @value{GDBN} is capable
24006 of evaluating the contents of a file. When doing so, @value{GDBN}
24007 can recognize which extension language is being used by looking at
24008 the filename extension. Files with an unrecognized filename extension
24009 are always treated as a @value{GDBN} Command Files.
24010 @xref{Command Files,, Command files}.
24012 You can control how @value{GDBN} evaluates these files with the following
24016 @kindex set script-extension
24017 @kindex show script-extension
24018 @item set script-extension off
24019 All scripts are always evaluated as @value{GDBN} Command Files.
24021 @item set script-extension soft
24022 The debugger determines the scripting language based on filename
24023 extension. If this scripting language is supported, @value{GDBN}
24024 evaluates the script using that language. Otherwise, it evaluates
24025 the file as a @value{GDBN} Command File.
24027 @item set script-extension strict
24028 The debugger determines the scripting language based on filename
24029 extension, and evaluates the script using that language. If the
24030 language is not supported, then the evaluation fails.
24032 @item show script-extension
24033 Display the current value of the @code{script-extension} option.
24038 @section Canned Sequences of Commands
24040 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24041 Command Lists}), @value{GDBN} provides two ways to store sequences of
24042 commands for execution as a unit: user-defined commands and command
24046 * Define:: How to define your own commands
24047 * Hooks:: Hooks for user-defined commands
24048 * Command Files:: How to write scripts of commands to be stored in a file
24049 * Output:: Commands for controlled output
24050 * Auto-loading sequences:: Controlling auto-loaded command files
24054 @subsection User-defined Commands
24056 @cindex user-defined command
24057 @cindex arguments, to user-defined commands
24058 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24059 which you assign a new name as a command. This is done with the
24060 @code{define} command. User commands may accept up to 10 arguments
24061 separated by whitespace. Arguments are accessed within the user command
24062 via @code{$arg0@dots{}$arg9}. A trivial example:
24066 print $arg0 + $arg1 + $arg2
24071 To execute the command use:
24078 This defines the command @code{adder}, which prints the sum of
24079 its three arguments. Note the arguments are text substitutions, so they may
24080 reference variables, use complex expressions, or even perform inferior
24083 @cindex argument count in user-defined commands
24084 @cindex how many arguments (user-defined commands)
24085 In addition, @code{$argc} may be used to find out how many arguments have
24086 been passed. This expands to a number in the range 0@dots{}10.
24091 print $arg0 + $arg1
24094 print $arg0 + $arg1 + $arg2
24099 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24100 to process a variable number of arguments:
24107 eval "set $sum = $sum + $arg%d", $i
24117 @item define @var{commandname}
24118 Define a command named @var{commandname}. If there is already a command
24119 by that name, you are asked to confirm that you want to redefine it.
24120 The argument @var{commandname} may be a bare command name consisting of letters,
24121 numbers, dashes, and underscores. It may also start with any predefined
24122 prefix command. For example, @samp{define target my-target} creates
24123 a user-defined @samp{target my-target} command.
24125 The definition of the command is made up of other @value{GDBN} command lines,
24126 which are given following the @code{define} command. The end of these
24127 commands is marked by a line containing @code{end}.
24130 @kindex end@r{ (user-defined commands)}
24131 @item document @var{commandname}
24132 Document the user-defined command @var{commandname}, so that it can be
24133 accessed by @code{help}. The command @var{commandname} must already be
24134 defined. This command reads lines of documentation just as @code{define}
24135 reads the lines of the command definition, ending with @code{end}.
24136 After the @code{document} command is finished, @code{help} on command
24137 @var{commandname} displays the documentation you have written.
24139 You may use the @code{document} command again to change the
24140 documentation of a command. Redefining the command with @code{define}
24141 does not change the documentation.
24143 @kindex dont-repeat
24144 @cindex don't repeat command
24146 Used inside a user-defined command, this tells @value{GDBN} that this
24147 command should not be repeated when the user hits @key{RET}
24148 (@pxref{Command Syntax, repeat last command}).
24150 @kindex help user-defined
24151 @item help user-defined
24152 List all user-defined commands and all python commands defined in class
24153 COMAND_USER. The first line of the documentation or docstring is
24158 @itemx show user @var{commandname}
24159 Display the @value{GDBN} commands used to define @var{commandname} (but
24160 not its documentation). If no @var{commandname} is given, display the
24161 definitions for all user-defined commands.
24162 This does not work for user-defined python commands.
24164 @cindex infinite recursion in user-defined commands
24165 @kindex show max-user-call-depth
24166 @kindex set max-user-call-depth
24167 @item show max-user-call-depth
24168 @itemx set max-user-call-depth
24169 The value of @code{max-user-call-depth} controls how many recursion
24170 levels are allowed in user-defined commands before @value{GDBN} suspects an
24171 infinite recursion and aborts the command.
24172 This does not apply to user-defined python commands.
24175 In addition to the above commands, user-defined commands frequently
24176 use control flow commands, described in @ref{Command Files}.
24178 When user-defined commands are executed, the
24179 commands of the definition are not printed. An error in any command
24180 stops execution of the user-defined command.
24182 If used interactively, commands that would ask for confirmation proceed
24183 without asking when used inside a user-defined command. Many @value{GDBN}
24184 commands that normally print messages to say what they are doing omit the
24185 messages when used in a user-defined command.
24188 @subsection User-defined Command Hooks
24189 @cindex command hooks
24190 @cindex hooks, for commands
24191 @cindex hooks, pre-command
24194 You may define @dfn{hooks}, which are a special kind of user-defined
24195 command. Whenever you run the command @samp{foo}, if the user-defined
24196 command @samp{hook-foo} exists, it is executed (with no arguments)
24197 before that command.
24199 @cindex hooks, post-command
24201 A hook may also be defined which is run after the command you executed.
24202 Whenever you run the command @samp{foo}, if the user-defined command
24203 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24204 that command. Post-execution hooks may exist simultaneously with
24205 pre-execution hooks, for the same command.
24207 It is valid for a hook to call the command which it hooks. If this
24208 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24210 @c It would be nice if hookpost could be passed a parameter indicating
24211 @c if the command it hooks executed properly or not. FIXME!
24213 @kindex stop@r{, a pseudo-command}
24214 In addition, a pseudo-command, @samp{stop} exists. Defining
24215 (@samp{hook-stop}) makes the associated commands execute every time
24216 execution stops in your program: before breakpoint commands are run,
24217 displays are printed, or the stack frame is printed.
24219 For example, to ignore @code{SIGALRM} signals while
24220 single-stepping, but treat them normally during normal execution,
24225 handle SIGALRM nopass
24229 handle SIGALRM pass
24232 define hook-continue
24233 handle SIGALRM pass
24237 As a further example, to hook at the beginning and end of the @code{echo}
24238 command, and to add extra text to the beginning and end of the message,
24246 define hookpost-echo
24250 (@value{GDBP}) echo Hello World
24251 <<<---Hello World--->>>
24256 You can define a hook for any single-word command in @value{GDBN}, but
24257 not for command aliases; you should define a hook for the basic command
24258 name, e.g.@: @code{backtrace} rather than @code{bt}.
24259 @c FIXME! So how does Joe User discover whether a command is an alias
24261 You can hook a multi-word command by adding @code{hook-} or
24262 @code{hookpost-} to the last word of the command, e.g.@:
24263 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24265 If an error occurs during the execution of your hook, execution of
24266 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24267 (before the command that you actually typed had a chance to run).
24269 If you try to define a hook which does not match any known command, you
24270 get a warning from the @code{define} command.
24272 @node Command Files
24273 @subsection Command Files
24275 @cindex command files
24276 @cindex scripting commands
24277 A command file for @value{GDBN} is a text file made of lines that are
24278 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24279 also be included. An empty line in a command file does nothing; it
24280 does not mean to repeat the last command, as it would from the
24283 You can request the execution of a command file with the @code{source}
24284 command. Note that the @code{source} command is also used to evaluate
24285 scripts that are not Command Files. The exact behavior can be configured
24286 using the @code{script-extension} setting.
24287 @xref{Extending GDB,, Extending GDB}.
24291 @cindex execute commands from a file
24292 @item source [-s] [-v] @var{filename}
24293 Execute the command file @var{filename}.
24296 The lines in a command file are generally executed sequentially,
24297 unless the order of execution is changed by one of the
24298 @emph{flow-control commands} described below. The commands are not
24299 printed as they are executed. An error in any command terminates
24300 execution of the command file and control is returned to the console.
24302 @value{GDBN} first searches for @var{filename} in the current directory.
24303 If the file is not found there, and @var{filename} does not specify a
24304 directory, then @value{GDBN} also looks for the file on the source search path
24305 (specified with the @samp{directory} command);
24306 except that @file{$cdir} is not searched because the compilation directory
24307 is not relevant to scripts.
24309 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24310 on the search path even if @var{filename} specifies a directory.
24311 The search is done by appending @var{filename} to each element of the
24312 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24313 and the search path contains @file{/home/user} then @value{GDBN} will
24314 look for the script @file{/home/user/mylib/myscript}.
24315 The search is also done if @var{filename} is an absolute path.
24316 For example, if @var{filename} is @file{/tmp/myscript} and
24317 the search path contains @file{/home/user} then @value{GDBN} will
24318 look for the script @file{/home/user/tmp/myscript}.
24319 For DOS-like systems, if @var{filename} contains a drive specification,
24320 it is stripped before concatenation. For example, if @var{filename} is
24321 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24322 will look for the script @file{c:/tmp/myscript}.
24324 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24325 each command as it is executed. The option must be given before
24326 @var{filename}, and is interpreted as part of the filename anywhere else.
24328 Commands that would ask for confirmation if used interactively proceed
24329 without asking when used in a command file. Many @value{GDBN} commands that
24330 normally print messages to say what they are doing omit the messages
24331 when called from command files.
24333 @value{GDBN} also accepts command input from standard input. In this
24334 mode, normal output goes to standard output and error output goes to
24335 standard error. Errors in a command file supplied on standard input do
24336 not terminate execution of the command file---execution continues with
24340 gdb < cmds > log 2>&1
24343 (The syntax above will vary depending on the shell used.) This example
24344 will execute commands from the file @file{cmds}. All output and errors
24345 would be directed to @file{log}.
24347 Since commands stored on command files tend to be more general than
24348 commands typed interactively, they frequently need to deal with
24349 complicated situations, such as different or unexpected values of
24350 variables and symbols, changes in how the program being debugged is
24351 built, etc. @value{GDBN} provides a set of flow-control commands to
24352 deal with these complexities. Using these commands, you can write
24353 complex scripts that loop over data structures, execute commands
24354 conditionally, etc.
24361 This command allows to include in your script conditionally executed
24362 commands. The @code{if} command takes a single argument, which is an
24363 expression to evaluate. It is followed by a series of commands that
24364 are executed only if the expression is true (its value is nonzero).
24365 There can then optionally be an @code{else} line, followed by a series
24366 of commands that are only executed if the expression was false. The
24367 end of the list is marked by a line containing @code{end}.
24371 This command allows to write loops. Its syntax is similar to
24372 @code{if}: the command takes a single argument, which is an expression
24373 to evaluate, and must be followed by the commands to execute, one per
24374 line, terminated by an @code{end}. These commands are called the
24375 @dfn{body} of the loop. The commands in the body of @code{while} are
24376 executed repeatedly as long as the expression evaluates to true.
24380 This command exits the @code{while} loop in whose body it is included.
24381 Execution of the script continues after that @code{while}s @code{end}
24384 @kindex loop_continue
24385 @item loop_continue
24386 This command skips the execution of the rest of the body of commands
24387 in the @code{while} loop in whose body it is included. Execution
24388 branches to the beginning of the @code{while} loop, where it evaluates
24389 the controlling expression.
24391 @kindex end@r{ (if/else/while commands)}
24393 Terminate the block of commands that are the body of @code{if},
24394 @code{else}, or @code{while} flow-control commands.
24399 @subsection Commands for Controlled Output
24401 During the execution of a command file or a user-defined command, normal
24402 @value{GDBN} output is suppressed; the only output that appears is what is
24403 explicitly printed by the commands in the definition. This section
24404 describes three commands useful for generating exactly the output you
24409 @item echo @var{text}
24410 @c I do not consider backslash-space a standard C escape sequence
24411 @c because it is not in ANSI.
24412 Print @var{text}. Nonprinting characters can be included in
24413 @var{text} using C escape sequences, such as @samp{\n} to print a
24414 newline. @strong{No newline is printed unless you specify one.}
24415 In addition to the standard C escape sequences, a backslash followed
24416 by a space stands for a space. This is useful for displaying a
24417 string with spaces at the beginning or the end, since leading and
24418 trailing spaces are otherwise trimmed from all arguments.
24419 To print @samp{@w{ }and foo =@w{ }}, use the command
24420 @samp{echo \@w{ }and foo = \@w{ }}.
24422 A backslash at the end of @var{text} can be used, as in C, to continue
24423 the command onto subsequent lines. For example,
24426 echo This is some text\n\
24427 which is continued\n\
24428 onto several lines.\n
24431 produces the same output as
24434 echo This is some text\n
24435 echo which is continued\n
24436 echo onto several lines.\n
24440 @item output @var{expression}
24441 Print the value of @var{expression} and nothing but that value: no
24442 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24443 value history either. @xref{Expressions, ,Expressions}, for more information
24446 @item output/@var{fmt} @var{expression}
24447 Print the value of @var{expression} in format @var{fmt}. You can use
24448 the same formats as for @code{print}. @xref{Output Formats,,Output
24449 Formats}, for more information.
24452 @item printf @var{template}, @var{expressions}@dots{}
24453 Print the values of one or more @var{expressions} under the control of
24454 the string @var{template}. To print several values, make
24455 @var{expressions} be a comma-separated list of individual expressions,
24456 which may be either numbers or pointers. Their values are printed as
24457 specified by @var{template}, exactly as a C program would do by
24458 executing the code below:
24461 printf (@var{template}, @var{expressions}@dots{});
24464 As in @code{C} @code{printf}, ordinary characters in @var{template}
24465 are printed verbatim, while @dfn{conversion specification} introduced
24466 by the @samp{%} character cause subsequent @var{expressions} to be
24467 evaluated, their values converted and formatted according to type and
24468 style information encoded in the conversion specifications, and then
24471 For example, you can print two values in hex like this:
24474 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24477 @code{printf} supports all the standard @code{C} conversion
24478 specifications, including the flags and modifiers between the @samp{%}
24479 character and the conversion letter, with the following exceptions:
24483 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24486 The modifier @samp{*} is not supported for specifying precision or
24490 The @samp{'} flag (for separation of digits into groups according to
24491 @code{LC_NUMERIC'}) is not supported.
24494 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24498 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24501 The conversion letters @samp{a} and @samp{A} are not supported.
24505 Note that the @samp{ll} type modifier is supported only if the
24506 underlying @code{C} implementation used to build @value{GDBN} supports
24507 the @code{long long int} type, and the @samp{L} type modifier is
24508 supported only if @code{long double} type is available.
24510 As in @code{C}, @code{printf} supports simple backslash-escape
24511 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24512 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24513 single character. Octal and hexadecimal escape sequences are not
24516 Additionally, @code{printf} supports conversion specifications for DFP
24517 (@dfn{Decimal Floating Point}) types using the following length modifiers
24518 together with a floating point specifier.
24523 @samp{H} for printing @code{Decimal32} types.
24526 @samp{D} for printing @code{Decimal64} types.
24529 @samp{DD} for printing @code{Decimal128} types.
24532 If the underlying @code{C} implementation used to build @value{GDBN} has
24533 support for the three length modifiers for DFP types, other modifiers
24534 such as width and precision will also be available for @value{GDBN} to use.
24536 In case there is no such @code{C} support, no additional modifiers will be
24537 available and the value will be printed in the standard way.
24539 Here's an example of printing DFP types using the above conversion letters:
24541 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24546 @item eval @var{template}, @var{expressions}@dots{}
24547 Convert the values of one or more @var{expressions} under the control of
24548 the string @var{template} to a command line, and call it.
24552 @node Auto-loading sequences
24553 @subsection Controlling auto-loading native @value{GDBN} scripts
24554 @cindex native script auto-loading
24556 When a new object file is read (for example, due to the @code{file}
24557 command, or because the inferior has loaded a shared library),
24558 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24559 @xref{Auto-loading extensions}.
24561 Auto-loading can be enabled or disabled,
24562 and the list of auto-loaded scripts can be printed.
24565 @anchor{set auto-load gdb-scripts}
24566 @kindex set auto-load gdb-scripts
24567 @item set auto-load gdb-scripts [on|off]
24568 Enable or disable the auto-loading of canned sequences of commands scripts.
24570 @anchor{show auto-load gdb-scripts}
24571 @kindex show auto-load gdb-scripts
24572 @item show auto-load gdb-scripts
24573 Show whether auto-loading of canned sequences of commands scripts is enabled or
24576 @anchor{info auto-load gdb-scripts}
24577 @kindex info auto-load gdb-scripts
24578 @cindex print list of auto-loaded canned sequences of commands scripts
24579 @item info auto-load gdb-scripts [@var{regexp}]
24580 Print the list of all canned sequences of commands scripts that @value{GDBN}
24584 If @var{regexp} is supplied only canned sequences of commands scripts with
24585 matching names are printed.
24587 @c Python docs live in a separate file.
24588 @include python.texi
24590 @c Guile docs live in a separate file.
24591 @include guile.texi
24593 @node Auto-loading extensions
24594 @section Auto-loading extensions
24595 @cindex auto-loading extensions
24597 @value{GDBN} provides two mechanisms for automatically loading extensions
24598 when a new object file is read (for example, due to the @code{file}
24599 command, or because the inferior has loaded a shared library):
24600 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24601 section of modern file formats like ELF.
24604 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24605 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24606 * Which flavor to choose?::
24609 The auto-loading feature is useful for supplying application-specific
24610 debugging commands and features.
24612 Auto-loading can be enabled or disabled,
24613 and the list of auto-loaded scripts can be printed.
24614 See the @samp{auto-loading} section of each extension language
24615 for more information.
24616 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24617 For Python files see @ref{Python Auto-loading}.
24619 Note that loading of this script file also requires accordingly configured
24620 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24622 @node objfile-gdbdotext file
24623 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24624 @cindex @file{@var{objfile}-gdb.gdb}
24625 @cindex @file{@var{objfile}-gdb.py}
24626 @cindex @file{@var{objfile}-gdb.scm}
24628 When a new object file is read, @value{GDBN} looks for a file named
24629 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24630 where @var{objfile} is the object file's name and
24631 where @var{ext} is the file extension for the extension language:
24634 @item @file{@var{objfile}-gdb.gdb}
24635 GDB's own command language
24636 @item @file{@var{objfile}-gdb.py}
24638 @item @file{@var{objfile}-gdb.scm}
24642 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24643 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24644 components, and appending the @file{-gdb.@var{ext}} suffix.
24645 If this file exists and is readable, @value{GDBN} will evaluate it as a
24646 script in the specified extension language.
24648 If this file does not exist, then @value{GDBN} will look for
24649 @var{script-name} file in all of the directories as specified below.
24651 Note that loading of these files requires an accordingly configured
24652 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24654 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24655 scripts normally according to its @file{.exe} filename. But if no scripts are
24656 found @value{GDBN} also tries script filenames matching the object file without
24657 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24658 is attempted on any platform. This makes the script filenames compatible
24659 between Unix and MS-Windows hosts.
24662 @anchor{set auto-load scripts-directory}
24663 @kindex set auto-load scripts-directory
24664 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24665 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24666 may be delimited by the host platform path separator in use
24667 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24669 Each entry here needs to be covered also by the security setting
24670 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24672 @anchor{with-auto-load-dir}
24673 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24674 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24675 configuration option @option{--with-auto-load-dir}.
24677 Any reference to @file{$debugdir} will get replaced by
24678 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24679 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24680 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24681 @file{$datadir} must be placed as a directory component --- either alone or
24682 delimited by @file{/} or @file{\} directory separators, depending on the host
24685 The list of directories uses path separator (@samp{:} on GNU and Unix
24686 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24687 to the @env{PATH} environment variable.
24689 @anchor{show auto-load scripts-directory}
24690 @kindex show auto-load scripts-directory
24691 @item show auto-load scripts-directory
24692 Show @value{GDBN} auto-loaded scripts location.
24694 @anchor{add-auto-load-scripts-directory}
24695 @kindex add-auto-load-scripts-directory
24696 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24697 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24698 Multiple entries may be delimited by the host platform path separator in use.
24701 @value{GDBN} does not track which files it has already auto-loaded this way.
24702 @value{GDBN} will load the associated script every time the corresponding
24703 @var{objfile} is opened.
24704 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24705 is evaluated more than once.
24707 @node dotdebug_gdb_scripts section
24708 @subsection The @code{.debug_gdb_scripts} section
24709 @cindex @code{.debug_gdb_scripts} section
24711 For systems using file formats like ELF and COFF,
24712 when @value{GDBN} loads a new object file
24713 it will look for a special section named @code{.debug_gdb_scripts}.
24714 If this section exists, its contents is a list of null-terminated entries
24715 specifying scripts to load. Each entry begins with a non-null prefix byte that
24716 specifies the kind of entry, typically the extension language and whether the
24717 script is in a file or inlined in @code{.debug_gdb_scripts}.
24719 The following entries are supported:
24722 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24723 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24724 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24725 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24728 @subsubsection Script File Entries
24730 If the entry specifies a file, @value{GDBN} will look for the file first
24731 in the current directory and then along the source search path
24732 (@pxref{Source Path, ,Specifying Source Directories}),
24733 except that @file{$cdir} is not searched, since the compilation
24734 directory is not relevant to scripts.
24736 File entries can be placed in section @code{.debug_gdb_scripts} with,
24737 for example, this GCC macro for Python scripts.
24740 /* Note: The "MS" section flags are to remove duplicates. */
24741 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24743 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24744 .byte 1 /* Python */\n\
24745 .asciz \"" script_name "\"\n\
24751 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24752 Then one can reference the macro in a header or source file like this:
24755 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24758 The script name may include directories if desired.
24760 Note that loading of this script file also requires accordingly configured
24761 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24763 If the macro invocation is put in a header, any application or library
24764 using this header will get a reference to the specified script,
24765 and with the use of @code{"MS"} attributes on the section, the linker
24766 will remove duplicates.
24768 @subsubsection Script Text Entries
24770 Script text entries allow to put the executable script in the entry
24771 itself instead of loading it from a file.
24772 The first line of the entry, everything after the prefix byte and up to
24773 the first newline (@code{0xa}) character, is the script name, and must not
24774 contain any kind of space character, e.g., spaces or tabs.
24775 The rest of the entry, up to the trailing null byte, is the script to
24776 execute in the specified language. The name needs to be unique among
24777 all script names, as @value{GDBN} executes each script only once based
24780 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24784 #include "symcat.h"
24785 #include "gdb/section-scripts.h"
24787 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24788 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24789 ".ascii \"gdb.inlined-script\\n\"\n"
24790 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24791 ".ascii \" def __init__ (self):\\n\"\n"
24792 ".ascii \" super (test_cmd, self).__init__ ("
24793 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24794 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24795 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24796 ".ascii \"test_cmd ()\\n\"\n"
24802 Loading of inlined scripts requires a properly configured
24803 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24804 The path to specify in @code{auto-load safe-path} is the path of the file
24805 containing the @code{.debug_gdb_scripts} section.
24807 @node Which flavor to choose?
24808 @subsection Which flavor to choose?
24810 Given the multiple ways of auto-loading extensions, it might not always
24811 be clear which one to choose. This section provides some guidance.
24814 Benefits of the @file{-gdb.@var{ext}} way:
24818 Can be used with file formats that don't support multiple sections.
24821 Ease of finding scripts for public libraries.
24823 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24824 in the source search path.
24825 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24826 isn't a source directory in which to find the script.
24829 Doesn't require source code additions.
24833 Benefits of the @code{.debug_gdb_scripts} way:
24837 Works with static linking.
24839 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24840 trigger their loading. When an application is statically linked the only
24841 objfile available is the executable, and it is cumbersome to attach all the
24842 scripts from all the input libraries to the executable's
24843 @file{-gdb.@var{ext}} script.
24846 Works with classes that are entirely inlined.
24848 Some classes can be entirely inlined, and thus there may not be an associated
24849 shared library to attach a @file{-gdb.@var{ext}} script to.
24852 Scripts needn't be copied out of the source tree.
24854 In some circumstances, apps can be built out of large collections of internal
24855 libraries, and the build infrastructure necessary to install the
24856 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24857 cumbersome. It may be easier to specify the scripts in the
24858 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24859 top of the source tree to the source search path.
24862 @node Multiple Extension Languages
24863 @section Multiple Extension Languages
24865 The Guile and Python extension languages do not share any state,
24866 and generally do not interfere with each other.
24867 There are some things to be aware of, however.
24869 @subsection Python comes first
24871 Python was @value{GDBN}'s first extension language, and to avoid breaking
24872 existing behaviour Python comes first. This is generally solved by the
24873 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24874 extension languages, and when it makes a call to an extension language,
24875 (say to pretty-print a value), it tries each in turn until an extension
24876 language indicates it has performed the request (e.g., has returned the
24877 pretty-printed form of a value).
24878 This extends to errors while performing such requests: If an error happens
24879 while, for example, trying to pretty-print an object then the error is
24880 reported and any following extension languages are not tried.
24883 @section Creating new spellings of existing commands
24884 @cindex aliases for commands
24886 It is often useful to define alternate spellings of existing commands.
24887 For example, if a new @value{GDBN} command defined in Python has
24888 a long name to type, it is handy to have an abbreviated version of it
24889 that involves less typing.
24891 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24892 of the @samp{step} command even though it is otherwise an ambiguous
24893 abbreviation of other commands like @samp{set} and @samp{show}.
24895 Aliases are also used to provide shortened or more common versions
24896 of multi-word commands. For example, @value{GDBN} provides the
24897 @samp{tty} alias of the @samp{set inferior-tty} command.
24899 You can define a new alias with the @samp{alias} command.
24904 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24908 @var{ALIAS} specifies the name of the new alias.
24909 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24912 @var{COMMAND} specifies the name of an existing command
24913 that is being aliased.
24915 The @samp{-a} option specifies that the new alias is an abbreviation
24916 of the command. Abbreviations are not shown in command
24917 lists displayed by the @samp{help} command.
24919 The @samp{--} option specifies the end of options,
24920 and is useful when @var{ALIAS} begins with a dash.
24922 Here is a simple example showing how to make an abbreviation
24923 of a command so that there is less to type.
24924 Suppose you were tired of typing @samp{disas}, the current
24925 shortest unambiguous abbreviation of the @samp{disassemble} command
24926 and you wanted an even shorter version named @samp{di}.
24927 The following will accomplish this.
24930 (gdb) alias -a di = disas
24933 Note that aliases are different from user-defined commands.
24934 With a user-defined command, you also need to write documentation
24935 for it with the @samp{document} command.
24936 An alias automatically picks up the documentation of the existing command.
24938 Here is an example where we make @samp{elms} an abbreviation of
24939 @samp{elements} in the @samp{set print elements} command.
24940 This is to show that you can make an abbreviation of any part
24944 (gdb) alias -a set print elms = set print elements
24945 (gdb) alias -a show print elms = show print elements
24946 (gdb) set p elms 20
24948 Limit on string chars or array elements to print is 200.
24951 Note that if you are defining an alias of a @samp{set} command,
24952 and you want to have an alias for the corresponding @samp{show}
24953 command, then you need to define the latter separately.
24955 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24956 @var{ALIAS}, just as they are normally.
24959 (gdb) alias -a set pr elms = set p ele
24962 Finally, here is an example showing the creation of a one word
24963 alias for a more complex command.
24964 This creates alias @samp{spe} of the command @samp{set print elements}.
24967 (gdb) alias spe = set print elements
24972 @chapter Command Interpreters
24973 @cindex command interpreters
24975 @value{GDBN} supports multiple command interpreters, and some command
24976 infrastructure to allow users or user interface writers to switch
24977 between interpreters or run commands in other interpreters.
24979 @value{GDBN} currently supports two command interpreters, the console
24980 interpreter (sometimes called the command-line interpreter or @sc{cli})
24981 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24982 describes both of these interfaces in great detail.
24984 By default, @value{GDBN} will start with the console interpreter.
24985 However, the user may choose to start @value{GDBN} with another
24986 interpreter by specifying the @option{-i} or @option{--interpreter}
24987 startup options. Defined interpreters include:
24991 @cindex console interpreter
24992 The traditional console or command-line interpreter. This is the most often
24993 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24994 @value{GDBN} will use this interpreter.
24997 @cindex mi interpreter
24998 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24999 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25000 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25004 @cindex mi2 interpreter
25005 The current @sc{gdb/mi} interface.
25008 @cindex mi1 interpreter
25009 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25013 @cindex invoke another interpreter
25015 @kindex interpreter-exec
25016 You may execute commands in any interpreter from the current
25017 interpreter using the appropriate command. If you are running the
25018 console interpreter, simply use the @code{interpreter-exec} command:
25021 interpreter-exec mi "-data-list-register-names"
25024 @sc{gdb/mi} has a similar command, although it is only available in versions of
25025 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25027 Note that @code{interpreter-exec} only changes the interpreter for the
25028 duration of the specified command. It does not change the interpreter
25031 @cindex start a new independent interpreter
25033 Although you may only choose a single interpreter at startup, it is
25034 possible to run an independent interpreter on a specified input/output
25035 device (usually a tty).
25037 For example, consider a debugger GUI or IDE that wants to provide a
25038 @value{GDBN} console view. It may do so by embedding a terminal
25039 emulator widget in its GUI, starting @value{GDBN} in the traditional
25040 command-line mode with stdin/stdout/stderr redirected to that
25041 terminal, and then creating an MI interpreter running on a specified
25042 input/output device. The console interpreter created by @value{GDBN}
25043 at startup handles commands the user types in the terminal widget,
25044 while the GUI controls and synchronizes state with @value{GDBN} using
25045 the separate MI interpreter.
25047 To start a new secondary @dfn{user interface} running MI, use the
25048 @code{new-ui} command:
25051 @cindex new user interface
25053 new-ui @var{interpreter} @var{tty}
25056 The @var{interpreter} parameter specifies the interpreter to run.
25057 This accepts the same values as the @code{interpreter-exec} command.
25058 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25059 @var{tty} parameter specifies the name of the bidirectional file the
25060 interpreter uses for input/output, usually the name of a
25061 pseudoterminal slave on Unix systems. For example:
25064 (@value{GDBP}) new-ui mi /dev/pts/9
25068 runs an MI interpreter on @file{/dev/pts/9}.
25071 @chapter @value{GDBN} Text User Interface
25073 @cindex Text User Interface
25076 * TUI Overview:: TUI overview
25077 * TUI Keys:: TUI key bindings
25078 * TUI Single Key Mode:: TUI single key mode
25079 * TUI Commands:: TUI-specific commands
25080 * TUI Configuration:: TUI configuration variables
25083 The @value{GDBN} Text User Interface (TUI) is a terminal
25084 interface which uses the @code{curses} library to show the source
25085 file, the assembly output, the program registers and @value{GDBN}
25086 commands in separate text windows. The TUI mode is supported only
25087 on platforms where a suitable version of the @code{curses} library
25090 The TUI mode is enabled by default when you invoke @value{GDBN} as
25091 @samp{@value{GDBP} -tui}.
25092 You can also switch in and out of TUI mode while @value{GDBN} runs by
25093 using various TUI commands and key bindings, such as @command{tui
25094 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25095 @ref{TUI Keys, ,TUI Key Bindings}.
25098 @section TUI Overview
25100 In TUI mode, @value{GDBN} can display several text windows:
25104 This window is the @value{GDBN} command window with the @value{GDBN}
25105 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25106 managed using readline.
25109 The source window shows the source file of the program. The current
25110 line and active breakpoints are displayed in this window.
25113 The assembly window shows the disassembly output of the program.
25116 This window shows the processor registers. Registers are highlighted
25117 when their values change.
25120 The source and assembly windows show the current program position
25121 by highlighting the current line and marking it with a @samp{>} marker.
25122 Breakpoints are indicated with two markers. The first marker
25123 indicates the breakpoint type:
25127 Breakpoint which was hit at least once.
25130 Breakpoint which was never hit.
25133 Hardware breakpoint which was hit at least once.
25136 Hardware breakpoint which was never hit.
25139 The second marker indicates whether the breakpoint is enabled or not:
25143 Breakpoint is enabled.
25146 Breakpoint is disabled.
25149 The source, assembly and register windows are updated when the current
25150 thread changes, when the frame changes, or when the program counter
25153 These windows are not all visible at the same time. The command
25154 window is always visible. The others can be arranged in several
25165 source and assembly,
25168 source and registers, or
25171 assembly and registers.
25174 A status line above the command window shows the following information:
25178 Indicates the current @value{GDBN} target.
25179 (@pxref{Targets, ,Specifying a Debugging Target}).
25182 Gives the current process or thread number.
25183 When no process is being debugged, this field is set to @code{No process}.
25186 Gives the current function name for the selected frame.
25187 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25188 When there is no symbol corresponding to the current program counter,
25189 the string @code{??} is displayed.
25192 Indicates the current line number for the selected frame.
25193 When the current line number is not known, the string @code{??} is displayed.
25196 Indicates the current program counter address.
25200 @section TUI Key Bindings
25201 @cindex TUI key bindings
25203 The TUI installs several key bindings in the readline keymaps
25204 @ifset SYSTEM_READLINE
25205 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25207 @ifclear SYSTEM_READLINE
25208 (@pxref{Command Line Editing}).
25210 The following key bindings are installed for both TUI mode and the
25211 @value{GDBN} standard mode.
25220 Enter or leave the TUI mode. When leaving the TUI mode,
25221 the curses window management stops and @value{GDBN} operates using
25222 its standard mode, writing on the terminal directly. When reentering
25223 the TUI mode, control is given back to the curses windows.
25224 The screen is then refreshed.
25228 Use a TUI layout with only one window. The layout will
25229 either be @samp{source} or @samp{assembly}. When the TUI mode
25230 is not active, it will switch to the TUI mode.
25232 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25236 Use a TUI layout with at least two windows. When the current
25237 layout already has two windows, the next layout with two windows is used.
25238 When a new layout is chosen, one window will always be common to the
25239 previous layout and the new one.
25241 Think of it as the Emacs @kbd{C-x 2} binding.
25245 Change the active window. The TUI associates several key bindings
25246 (like scrolling and arrow keys) with the active window. This command
25247 gives the focus to the next TUI window.
25249 Think of it as the Emacs @kbd{C-x o} binding.
25253 Switch in and out of the TUI SingleKey mode that binds single
25254 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25257 The following key bindings only work in the TUI mode:
25262 Scroll the active window one page up.
25266 Scroll the active window one page down.
25270 Scroll the active window one line up.
25274 Scroll the active window one line down.
25278 Scroll the active window one column left.
25282 Scroll the active window one column right.
25286 Refresh the screen.
25289 Because the arrow keys scroll the active window in the TUI mode, they
25290 are not available for their normal use by readline unless the command
25291 window has the focus. When another window is active, you must use
25292 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25293 and @kbd{C-f} to control the command window.
25295 @node TUI Single Key Mode
25296 @section TUI Single Key Mode
25297 @cindex TUI single key mode
25299 The TUI also provides a @dfn{SingleKey} mode, which binds several
25300 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25301 switch into this mode, where the following key bindings are used:
25304 @kindex c @r{(SingleKey TUI key)}
25308 @kindex d @r{(SingleKey TUI key)}
25312 @kindex f @r{(SingleKey TUI key)}
25316 @kindex n @r{(SingleKey TUI key)}
25320 @kindex q @r{(SingleKey TUI key)}
25322 exit the SingleKey mode.
25324 @kindex r @r{(SingleKey TUI key)}
25328 @kindex s @r{(SingleKey TUI key)}
25332 @kindex u @r{(SingleKey TUI key)}
25336 @kindex v @r{(SingleKey TUI key)}
25340 @kindex w @r{(SingleKey TUI key)}
25345 Other keys temporarily switch to the @value{GDBN} command prompt.
25346 The key that was pressed is inserted in the editing buffer so that
25347 it is possible to type most @value{GDBN} commands without interaction
25348 with the TUI SingleKey mode. Once the command is entered the TUI
25349 SingleKey mode is restored. The only way to permanently leave
25350 this mode is by typing @kbd{q} or @kbd{C-x s}.
25354 @section TUI-specific Commands
25355 @cindex TUI commands
25357 The TUI has specific commands to control the text windows.
25358 These commands are always available, even when @value{GDBN} is not in
25359 the TUI mode. When @value{GDBN} is in the standard mode, most
25360 of these commands will automatically switch to the TUI mode.
25362 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25363 terminal, or @value{GDBN} has been started with the machine interface
25364 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25365 these commands will fail with an error, because it would not be
25366 possible or desirable to enable curses window management.
25371 Activate TUI mode. The last active TUI window layout will be used if
25372 TUI mode has prevsiouly been used in the current debugging session,
25373 otherwise a default layout is used.
25376 @kindex tui disable
25377 Disable TUI mode, returning to the console interpreter.
25381 List and give the size of all displayed windows.
25383 @item layout @var{name}
25385 Changes which TUI windows are displayed. In each layout the command
25386 window is always displayed, the @var{name} parameter controls which
25387 additional windows are displayed, and can be any of the following:
25391 Display the next layout.
25394 Display the previous layout.
25397 Display the source and command windows.
25400 Display the assembly and command windows.
25403 Display the source, assembly, and command windows.
25406 When in @code{src} layout display the register, source, and command
25407 windows. When in @code{asm} or @code{split} layout display the
25408 register, assembler, and command windows.
25411 @item focus @var{name}
25413 Changes which TUI window is currently active for scrolling. The
25414 @var{name} parameter can be any of the following:
25418 Make the next window active for scrolling.
25421 Make the previous window active for scrolling.
25424 Make the source window active for scrolling.
25427 Make the assembly window active for scrolling.
25430 Make the register window active for scrolling.
25433 Make the command window active for scrolling.
25438 Refresh the screen. This is similar to typing @kbd{C-L}.
25440 @item tui reg @var{group}
25442 Changes the register group displayed in the tui register window to
25443 @var{group}. If the register window is not currently displayed this
25444 command will cause the register window to be displayed. The list of
25445 register groups, as well as their order is target specific. The
25446 following groups are available on most targets:
25449 Repeatedly selecting this group will cause the display to cycle
25450 through all of the available register groups.
25453 Repeatedly selecting this group will cause the display to cycle
25454 through all of the available register groups in the reverse order to
25458 Display the general registers.
25460 Display the floating point registers.
25462 Display the system registers.
25464 Display the vector registers.
25466 Display all registers.
25471 Update the source window and the current execution point.
25473 @item winheight @var{name} +@var{count}
25474 @itemx winheight @var{name} -@var{count}
25476 Change the height of the window @var{name} by @var{count}
25477 lines. Positive counts increase the height, while negative counts
25478 decrease it. The @var{name} parameter can be one of @code{src} (the
25479 source window), @code{cmd} (the command window), @code{asm} (the
25480 disassembly window), or @code{regs} (the register display window).
25482 @item tabset @var{nchars}
25484 Set the width of tab stops to be @var{nchars} characters. This
25485 setting affects the display of TAB characters in the source and
25489 @node TUI Configuration
25490 @section TUI Configuration Variables
25491 @cindex TUI configuration variables
25493 Several configuration variables control the appearance of TUI windows.
25496 @item set tui border-kind @var{kind}
25497 @kindex set tui border-kind
25498 Select the border appearance for the source, assembly and register windows.
25499 The possible values are the following:
25502 Use a space character to draw the border.
25505 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25508 Use the Alternate Character Set to draw the border. The border is
25509 drawn using character line graphics if the terminal supports them.
25512 @item set tui border-mode @var{mode}
25513 @kindex set tui border-mode
25514 @itemx set tui active-border-mode @var{mode}
25515 @kindex set tui active-border-mode
25516 Select the display attributes for the borders of the inactive windows
25517 or the active window. The @var{mode} can be one of the following:
25520 Use normal attributes to display the border.
25526 Use reverse video mode.
25529 Use half bright mode.
25531 @item half-standout
25532 Use half bright and standout mode.
25535 Use extra bright or bold mode.
25537 @item bold-standout
25538 Use extra bright or bold and standout mode.
25543 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25546 @cindex @sc{gnu} Emacs
25547 A special interface allows you to use @sc{gnu} Emacs to view (and
25548 edit) the source files for the program you are debugging with
25551 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25552 executable file you want to debug as an argument. This command starts
25553 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25554 created Emacs buffer.
25555 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25557 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25562 All ``terminal'' input and output goes through an Emacs buffer, called
25565 This applies both to @value{GDBN} commands and their output, and to the input
25566 and output done by the program you are debugging.
25568 This is useful because it means that you can copy the text of previous
25569 commands and input them again; you can even use parts of the output
25572 All the facilities of Emacs' Shell mode are available for interacting
25573 with your program. In particular, you can send signals the usual
25574 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25578 @value{GDBN} displays source code through Emacs.
25580 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25581 source file for that frame and puts an arrow (@samp{=>}) at the
25582 left margin of the current line. Emacs uses a separate buffer for
25583 source display, and splits the screen to show both your @value{GDBN} session
25586 Explicit @value{GDBN} @code{list} or search commands still produce output as
25587 usual, but you probably have no reason to use them from Emacs.
25590 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25591 a graphical mode, enabled by default, which provides further buffers
25592 that can control the execution and describe the state of your program.
25593 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25595 If you specify an absolute file name when prompted for the @kbd{M-x
25596 gdb} argument, then Emacs sets your current working directory to where
25597 your program resides. If you only specify the file name, then Emacs
25598 sets your current working directory to the directory associated
25599 with the previous buffer. In this case, @value{GDBN} may find your
25600 program by searching your environment's @code{PATH} variable, but on
25601 some operating systems it might not find the source. So, although the
25602 @value{GDBN} input and output session proceeds normally, the auxiliary
25603 buffer does not display the current source and line of execution.
25605 The initial working directory of @value{GDBN} is printed on the top
25606 line of the GUD buffer and this serves as a default for the commands
25607 that specify files for @value{GDBN} to operate on. @xref{Files,
25608 ,Commands to Specify Files}.
25610 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25611 need to call @value{GDBN} by a different name (for example, if you
25612 keep several configurations around, with different names) you can
25613 customize the Emacs variable @code{gud-gdb-command-name} to run the
25616 In the GUD buffer, you can use these special Emacs commands in
25617 addition to the standard Shell mode commands:
25621 Describe the features of Emacs' GUD Mode.
25624 Execute to another source line, like the @value{GDBN} @code{step} command; also
25625 update the display window to show the current file and location.
25628 Execute to next source line in this function, skipping all function
25629 calls, like the @value{GDBN} @code{next} command. Then update the display window
25630 to show the current file and location.
25633 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25634 display window accordingly.
25637 Execute until exit from the selected stack frame, like the @value{GDBN}
25638 @code{finish} command.
25641 Continue execution of your program, like the @value{GDBN} @code{continue}
25645 Go up the number of frames indicated by the numeric argument
25646 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25647 like the @value{GDBN} @code{up} command.
25650 Go down the number of frames indicated by the numeric argument, like the
25651 @value{GDBN} @code{down} command.
25654 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25655 tells @value{GDBN} to set a breakpoint on the source line point is on.
25657 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25658 separate frame which shows a backtrace when the GUD buffer is current.
25659 Move point to any frame in the stack and type @key{RET} to make it
25660 become the current frame and display the associated source in the
25661 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25662 selected frame become the current one. In graphical mode, the
25663 speedbar displays watch expressions.
25665 If you accidentally delete the source-display buffer, an easy way to get
25666 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25667 request a frame display; when you run under Emacs, this recreates
25668 the source buffer if necessary to show you the context of the current
25671 The source files displayed in Emacs are in ordinary Emacs buffers
25672 which are visiting the source files in the usual way. You can edit
25673 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25674 communicates with Emacs in terms of line numbers. If you add or
25675 delete lines from the text, the line numbers that @value{GDBN} knows cease
25676 to correspond properly with the code.
25678 A more detailed description of Emacs' interaction with @value{GDBN} is
25679 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25683 @chapter The @sc{gdb/mi} Interface
25685 @unnumberedsec Function and Purpose
25687 @cindex @sc{gdb/mi}, its purpose
25688 @sc{gdb/mi} is a line based machine oriented text interface to
25689 @value{GDBN} and is activated by specifying using the
25690 @option{--interpreter} command line option (@pxref{Mode Options}). It
25691 is specifically intended to support the development of systems which
25692 use the debugger as just one small component of a larger system.
25694 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25695 in the form of a reference manual.
25697 Note that @sc{gdb/mi} is still under construction, so some of the
25698 features described below are incomplete and subject to change
25699 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25701 @unnumberedsec Notation and Terminology
25703 @cindex notational conventions, for @sc{gdb/mi}
25704 This chapter uses the following notation:
25708 @code{|} separates two alternatives.
25711 @code{[ @var{something} ]} indicates that @var{something} is optional:
25712 it may or may not be given.
25715 @code{( @var{group} )*} means that @var{group} inside the parentheses
25716 may repeat zero or more times.
25719 @code{( @var{group} )+} means that @var{group} inside the parentheses
25720 may repeat one or more times.
25723 @code{"@var{string}"} means a literal @var{string}.
25727 @heading Dependencies
25731 * GDB/MI General Design::
25732 * GDB/MI Command Syntax::
25733 * GDB/MI Compatibility with CLI::
25734 * GDB/MI Development and Front Ends::
25735 * GDB/MI Output Records::
25736 * GDB/MI Simple Examples::
25737 * GDB/MI Command Description Format::
25738 * GDB/MI Breakpoint Commands::
25739 * GDB/MI Catchpoint Commands::
25740 * GDB/MI Program Context::
25741 * GDB/MI Thread Commands::
25742 * GDB/MI Ada Tasking Commands::
25743 * GDB/MI Program Execution::
25744 * GDB/MI Stack Manipulation::
25745 * GDB/MI Variable Objects::
25746 * GDB/MI Data Manipulation::
25747 * GDB/MI Tracepoint Commands::
25748 * GDB/MI Symbol Query::
25749 * GDB/MI File Commands::
25751 * GDB/MI Kod Commands::
25752 * GDB/MI Memory Overlay Commands::
25753 * GDB/MI Signal Handling Commands::
25755 * GDB/MI Target Manipulation::
25756 * GDB/MI File Transfer Commands::
25757 * GDB/MI Ada Exceptions Commands::
25758 * GDB/MI Support Commands::
25759 * GDB/MI Miscellaneous Commands::
25762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25763 @node GDB/MI General Design
25764 @section @sc{gdb/mi} General Design
25765 @cindex GDB/MI General Design
25767 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25768 parts---commands sent to @value{GDBN}, responses to those commands
25769 and notifications. Each command results in exactly one response,
25770 indicating either successful completion of the command, or an error.
25771 For the commands that do not resume the target, the response contains the
25772 requested information. For the commands that resume the target, the
25773 response only indicates whether the target was successfully resumed.
25774 Notifications is the mechanism for reporting changes in the state of the
25775 target, or in @value{GDBN} state, that cannot conveniently be associated with
25776 a command and reported as part of that command response.
25778 The important examples of notifications are:
25782 Exec notifications. These are used to report changes in
25783 target state---when a target is resumed, or stopped. It would not
25784 be feasible to include this information in response of resuming
25785 commands, because one resume commands can result in multiple events in
25786 different threads. Also, quite some time may pass before any event
25787 happens in the target, while a frontend needs to know whether the resuming
25788 command itself was successfully executed.
25791 Console output, and status notifications. Console output
25792 notifications are used to report output of CLI commands, as well as
25793 diagnostics for other commands. Status notifications are used to
25794 report the progress of a long-running operation. Naturally, including
25795 this information in command response would mean no output is produced
25796 until the command is finished, which is undesirable.
25799 General notifications. Commands may have various side effects on
25800 the @value{GDBN} or target state beyond their official purpose. For example,
25801 a command may change the selected thread. Although such changes can
25802 be included in command response, using notification allows for more
25803 orthogonal frontend design.
25807 There's no guarantee that whenever an MI command reports an error,
25808 @value{GDBN} or the target are in any specific state, and especially,
25809 the state is not reverted to the state before the MI command was
25810 processed. Therefore, whenever an MI command results in an error,
25811 we recommend that the frontend refreshes all the information shown in
25812 the user interface.
25816 * Context management::
25817 * Asynchronous and non-stop modes::
25821 @node Context management
25822 @subsection Context management
25824 @subsubsection Threads and Frames
25826 In most cases when @value{GDBN} accesses the target, this access is
25827 done in context of a specific thread and frame (@pxref{Frames}).
25828 Often, even when accessing global data, the target requires that a thread
25829 be specified. The CLI interface maintains the selected thread and frame,
25830 and supplies them to target on each command. This is convenient,
25831 because a command line user would not want to specify that information
25832 explicitly on each command, and because user interacts with
25833 @value{GDBN} via a single terminal, so no confusion is possible as
25834 to what thread and frame are the current ones.
25836 In the case of MI, the concept of selected thread and frame is less
25837 useful. First, a frontend can easily remember this information
25838 itself. Second, a graphical frontend can have more than one window,
25839 each one used for debugging a different thread, and the frontend might
25840 want to access additional threads for internal purposes. This
25841 increases the risk that by relying on implicitly selected thread, the
25842 frontend may be operating on a wrong one. Therefore, each MI command
25843 should explicitly specify which thread and frame to operate on. To
25844 make it possible, each MI command accepts the @samp{--thread} and
25845 @samp{--frame} options, the value to each is @value{GDBN} global
25846 identifier for thread and frame to operate on.
25848 Usually, each top-level window in a frontend allows the user to select
25849 a thread and a frame, and remembers the user selection for further
25850 operations. However, in some cases @value{GDBN} may suggest that the
25851 current thread or frame be changed. For example, when stopping on a
25852 breakpoint it is reasonable to switch to the thread where breakpoint is
25853 hit. For another example, if the user issues the CLI @samp{thread} or
25854 @samp{frame} commands via the frontend, it is desirable to change the
25855 frontend's selection to the one specified by user. @value{GDBN}
25856 communicates the suggestion to change current thread and frame using the
25857 @samp{=thread-selected} notification.
25859 Note that historically, MI shares the selected thread with CLI, so
25860 frontends used the @code{-thread-select} to execute commands in the
25861 right context. However, getting this to work right is cumbersome. The
25862 simplest way is for frontend to emit @code{-thread-select} command
25863 before every command. This doubles the number of commands that need
25864 to be sent. The alternative approach is to suppress @code{-thread-select}
25865 if the selected thread in @value{GDBN} is supposed to be identical to the
25866 thread the frontend wants to operate on. However, getting this
25867 optimization right can be tricky. In particular, if the frontend
25868 sends several commands to @value{GDBN}, and one of the commands changes the
25869 selected thread, then the behaviour of subsequent commands will
25870 change. So, a frontend should either wait for response from such
25871 problematic commands, or explicitly add @code{-thread-select} for
25872 all subsequent commands. No frontend is known to do this exactly
25873 right, so it is suggested to just always pass the @samp{--thread} and
25874 @samp{--frame} options.
25876 @subsubsection Language
25878 The execution of several commands depends on which language is selected.
25879 By default, the current language (@pxref{show language}) is used.
25880 But for commands known to be language-sensitive, it is recommended
25881 to use the @samp{--language} option. This option takes one argument,
25882 which is the name of the language to use while executing the command.
25886 -data-evaluate-expression --language c "sizeof (void*)"
25891 The valid language names are the same names accepted by the
25892 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25893 @samp{local} or @samp{unknown}.
25895 @node Asynchronous and non-stop modes
25896 @subsection Asynchronous command execution and non-stop mode
25898 On some targets, @value{GDBN} is capable of processing MI commands
25899 even while the target is running. This is called @dfn{asynchronous
25900 command execution} (@pxref{Background Execution}). The frontend may
25901 specify a preferrence for asynchronous execution using the
25902 @code{-gdb-set mi-async 1} command, which should be emitted before
25903 either running the executable or attaching to the target. After the
25904 frontend has started the executable or attached to the target, it can
25905 find if asynchronous execution is enabled using the
25906 @code{-list-target-features} command.
25909 @item -gdb-set mi-async on
25910 @item -gdb-set mi-async off
25911 Set whether MI is in asynchronous mode.
25913 When @code{off}, which is the default, MI execution commands (e.g.,
25914 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25915 for the program to stop before processing further commands.
25917 When @code{on}, MI execution commands are background execution
25918 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25919 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25920 MI commands even while the target is running.
25922 @item -gdb-show mi-async
25923 Show whether MI asynchronous mode is enabled.
25926 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25927 @code{target-async} instead of @code{mi-async}, and it had the effect
25928 of both putting MI in asynchronous mode and making CLI background
25929 commands possible. CLI background commands are now always possible
25930 ``out of the box'' if the target supports them. The old spelling is
25931 kept as a deprecated alias for backwards compatibility.
25933 Even if @value{GDBN} can accept a command while target is running,
25934 many commands that access the target do not work when the target is
25935 running. Therefore, asynchronous command execution is most useful
25936 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25937 it is possible to examine the state of one thread, while other threads
25940 When a given thread is running, MI commands that try to access the
25941 target in the context of that thread may not work, or may work only on
25942 some targets. In particular, commands that try to operate on thread's
25943 stack will not work, on any target. Commands that read memory, or
25944 modify breakpoints, may work or not work, depending on the target. Note
25945 that even commands that operate on global state, such as @code{print},
25946 @code{set}, and breakpoint commands, still access the target in the
25947 context of a specific thread, so frontend should try to find a
25948 stopped thread and perform the operation on that thread (using the
25949 @samp{--thread} option).
25951 Which commands will work in the context of a running thread is
25952 highly target dependent. However, the two commands
25953 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25954 to find the state of a thread, will always work.
25956 @node Thread groups
25957 @subsection Thread groups
25958 @value{GDBN} may be used to debug several processes at the same time.
25959 On some platfroms, @value{GDBN} may support debugging of several
25960 hardware systems, each one having several cores with several different
25961 processes running on each core. This section describes the MI
25962 mechanism to support such debugging scenarios.
25964 The key observation is that regardless of the structure of the
25965 target, MI can have a global list of threads, because most commands that
25966 accept the @samp{--thread} option do not need to know what process that
25967 thread belongs to. Therefore, it is not necessary to introduce
25968 neither additional @samp{--process} option, nor an notion of the
25969 current process in the MI interface. The only strictly new feature
25970 that is required is the ability to find how the threads are grouped
25973 To allow the user to discover such grouping, and to support arbitrary
25974 hierarchy of machines/cores/processes, MI introduces the concept of a
25975 @dfn{thread group}. Thread group is a collection of threads and other
25976 thread groups. A thread group always has a string identifier, a type,
25977 and may have additional attributes specific to the type. A new
25978 command, @code{-list-thread-groups}, returns the list of top-level
25979 thread groups, which correspond to processes that @value{GDBN} is
25980 debugging at the moment. By passing an identifier of a thread group
25981 to the @code{-list-thread-groups} command, it is possible to obtain
25982 the members of specific thread group.
25984 To allow the user to easily discover processes, and other objects, he
25985 wishes to debug, a concept of @dfn{available thread group} is
25986 introduced. Available thread group is an thread group that
25987 @value{GDBN} is not debugging, but that can be attached to, using the
25988 @code{-target-attach} command. The list of available top-level thread
25989 groups can be obtained using @samp{-list-thread-groups --available}.
25990 In general, the content of a thread group may be only retrieved only
25991 after attaching to that thread group.
25993 Thread groups are related to inferiors (@pxref{Inferiors and
25994 Programs}). Each inferior corresponds to a thread group of a special
25995 type @samp{process}, and some additional operations are permitted on
25996 such thread groups.
25998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25999 @node GDB/MI Command Syntax
26000 @section @sc{gdb/mi} Command Syntax
26003 * GDB/MI Input Syntax::
26004 * GDB/MI Output Syntax::
26007 @node GDB/MI Input Syntax
26008 @subsection @sc{gdb/mi} Input Syntax
26010 @cindex input syntax for @sc{gdb/mi}
26011 @cindex @sc{gdb/mi}, input syntax
26013 @item @var{command} @expansion{}
26014 @code{@var{cli-command} | @var{mi-command}}
26016 @item @var{cli-command} @expansion{}
26017 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26018 @var{cli-command} is any existing @value{GDBN} CLI command.
26020 @item @var{mi-command} @expansion{}
26021 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26022 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26024 @item @var{token} @expansion{}
26025 "any sequence of digits"
26027 @item @var{option} @expansion{}
26028 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26030 @item @var{parameter} @expansion{}
26031 @code{@var{non-blank-sequence} | @var{c-string}}
26033 @item @var{operation} @expansion{}
26034 @emph{any of the operations described in this chapter}
26036 @item @var{non-blank-sequence} @expansion{}
26037 @emph{anything, provided it doesn't contain special characters such as
26038 "-", @var{nl}, """ and of course " "}
26040 @item @var{c-string} @expansion{}
26041 @code{""" @var{seven-bit-iso-c-string-content} """}
26043 @item @var{nl} @expansion{}
26052 The CLI commands are still handled by the @sc{mi} interpreter; their
26053 output is described below.
26056 The @code{@var{token}}, when present, is passed back when the command
26060 Some @sc{mi} commands accept optional arguments as part of the parameter
26061 list. Each option is identified by a leading @samp{-} (dash) and may be
26062 followed by an optional argument parameter. Options occur first in the
26063 parameter list and can be delimited from normal parameters using
26064 @samp{--} (this is useful when some parameters begin with a dash).
26071 We want easy access to the existing CLI syntax (for debugging).
26074 We want it to be easy to spot a @sc{mi} operation.
26077 @node GDB/MI Output Syntax
26078 @subsection @sc{gdb/mi} Output Syntax
26080 @cindex output syntax of @sc{gdb/mi}
26081 @cindex @sc{gdb/mi}, output syntax
26082 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26083 followed, optionally, by a single result record. This result record
26084 is for the most recent command. The sequence of output records is
26085 terminated by @samp{(gdb)}.
26087 If an input command was prefixed with a @code{@var{token}} then the
26088 corresponding output for that command will also be prefixed by that same
26092 @item @var{output} @expansion{}
26093 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26095 @item @var{result-record} @expansion{}
26096 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26098 @item @var{out-of-band-record} @expansion{}
26099 @code{@var{async-record} | @var{stream-record}}
26101 @item @var{async-record} @expansion{}
26102 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26104 @item @var{exec-async-output} @expansion{}
26105 @code{[ @var{token} ] "*" @var{async-output nl}}
26107 @item @var{status-async-output} @expansion{}
26108 @code{[ @var{token} ] "+" @var{async-output nl}}
26110 @item @var{notify-async-output} @expansion{}
26111 @code{[ @var{token} ] "=" @var{async-output nl}}
26113 @item @var{async-output} @expansion{}
26114 @code{@var{async-class} ( "," @var{result} )*}
26116 @item @var{result-class} @expansion{}
26117 @code{"done" | "running" | "connected" | "error" | "exit"}
26119 @item @var{async-class} @expansion{}
26120 @code{"stopped" | @var{others}} (where @var{others} will be added
26121 depending on the needs---this is still in development).
26123 @item @var{result} @expansion{}
26124 @code{ @var{variable} "=" @var{value}}
26126 @item @var{variable} @expansion{}
26127 @code{ @var{string} }
26129 @item @var{value} @expansion{}
26130 @code{ @var{const} | @var{tuple} | @var{list} }
26132 @item @var{const} @expansion{}
26133 @code{@var{c-string}}
26135 @item @var{tuple} @expansion{}
26136 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26138 @item @var{list} @expansion{}
26139 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26140 @var{result} ( "," @var{result} )* "]" }
26142 @item @var{stream-record} @expansion{}
26143 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26145 @item @var{console-stream-output} @expansion{}
26146 @code{"~" @var{c-string nl}}
26148 @item @var{target-stream-output} @expansion{}
26149 @code{"@@" @var{c-string nl}}
26151 @item @var{log-stream-output} @expansion{}
26152 @code{"&" @var{c-string nl}}
26154 @item @var{nl} @expansion{}
26157 @item @var{token} @expansion{}
26158 @emph{any sequence of digits}.
26166 All output sequences end in a single line containing a period.
26169 The @code{@var{token}} is from the corresponding request. Note that
26170 for all async output, while the token is allowed by the grammar and
26171 may be output by future versions of @value{GDBN} for select async
26172 output messages, it is generally omitted. Frontends should treat
26173 all async output as reporting general changes in the state of the
26174 target and there should be no need to associate async output to any
26178 @cindex status output in @sc{gdb/mi}
26179 @var{status-async-output} contains on-going status information about the
26180 progress of a slow operation. It can be discarded. All status output is
26181 prefixed by @samp{+}.
26184 @cindex async output in @sc{gdb/mi}
26185 @var{exec-async-output} contains asynchronous state change on the target
26186 (stopped, started, disappeared). All async output is prefixed by
26190 @cindex notify output in @sc{gdb/mi}
26191 @var{notify-async-output} contains supplementary information that the
26192 client should handle (e.g., a new breakpoint information). All notify
26193 output is prefixed by @samp{=}.
26196 @cindex console output in @sc{gdb/mi}
26197 @var{console-stream-output} is output that should be displayed as is in the
26198 console. It is the textual response to a CLI command. All the console
26199 output is prefixed by @samp{~}.
26202 @cindex target output in @sc{gdb/mi}
26203 @var{target-stream-output} is the output produced by the target program.
26204 All the target output is prefixed by @samp{@@}.
26207 @cindex log output in @sc{gdb/mi}
26208 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26209 instance messages that should be displayed as part of an error log. All
26210 the log output is prefixed by @samp{&}.
26213 @cindex list output in @sc{gdb/mi}
26214 New @sc{gdb/mi} commands should only output @var{lists} containing
26220 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26221 details about the various output records.
26223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26224 @node GDB/MI Compatibility with CLI
26225 @section @sc{gdb/mi} Compatibility with CLI
26227 @cindex compatibility, @sc{gdb/mi} and CLI
26228 @cindex @sc{gdb/mi}, compatibility with CLI
26230 For the developers convenience CLI commands can be entered directly,
26231 but there may be some unexpected behaviour. For example, commands
26232 that query the user will behave as if the user replied yes, breakpoint
26233 command lists are not executed and some CLI commands, such as
26234 @code{if}, @code{when} and @code{define}, prompt for further input with
26235 @samp{>}, which is not valid MI output.
26237 This feature may be removed at some stage in the future and it is
26238 recommended that front ends use the @code{-interpreter-exec} command
26239 (@pxref{-interpreter-exec}).
26241 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26242 @node GDB/MI Development and Front Ends
26243 @section @sc{gdb/mi} Development and Front Ends
26244 @cindex @sc{gdb/mi} development
26246 The application which takes the MI output and presents the state of the
26247 program being debugged to the user is called a @dfn{front end}.
26249 Although @sc{gdb/mi} is still incomplete, it is currently being used
26250 by a variety of front ends to @value{GDBN}. This makes it difficult
26251 to introduce new functionality without breaking existing usage. This
26252 section tries to minimize the problems by describing how the protocol
26255 Some changes in MI need not break a carefully designed front end, and
26256 for these the MI version will remain unchanged. The following is a
26257 list of changes that may occur within one level, so front ends should
26258 parse MI output in a way that can handle them:
26262 New MI commands may be added.
26265 New fields may be added to the output of any MI command.
26268 The range of values for fields with specified values, e.g.,
26269 @code{in_scope} (@pxref{-var-update}) may be extended.
26271 @c The format of field's content e.g type prefix, may change so parse it
26272 @c at your own risk. Yes, in general?
26274 @c The order of fields may change? Shouldn't really matter but it might
26275 @c resolve inconsistencies.
26278 If the changes are likely to break front ends, the MI version level
26279 will be increased by one. This will allow the front end to parse the
26280 output according to the MI version. Apart from mi0, new versions of
26281 @value{GDBN} will not support old versions of MI and it will be the
26282 responsibility of the front end to work with the new one.
26284 @c Starting with mi3, add a new command -mi-version that prints the MI
26287 The best way to avoid unexpected changes in MI that might break your front
26288 end is to make your project known to @value{GDBN} developers and
26289 follow development on @email{gdb@@sourceware.org} and
26290 @email{gdb-patches@@sourceware.org}.
26291 @cindex mailing lists
26293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26294 @node GDB/MI Output Records
26295 @section @sc{gdb/mi} Output Records
26298 * GDB/MI Result Records::
26299 * GDB/MI Stream Records::
26300 * GDB/MI Async Records::
26301 * GDB/MI Breakpoint Information::
26302 * GDB/MI Frame Information::
26303 * GDB/MI Thread Information::
26304 * GDB/MI Ada Exception Information::
26307 @node GDB/MI Result Records
26308 @subsection @sc{gdb/mi} Result Records
26310 @cindex result records in @sc{gdb/mi}
26311 @cindex @sc{gdb/mi}, result records
26312 In addition to a number of out-of-band notifications, the response to a
26313 @sc{gdb/mi} command includes one of the following result indications:
26317 @item "^done" [ "," @var{results} ]
26318 The synchronous operation was successful, @code{@var{results}} are the return
26323 This result record is equivalent to @samp{^done}. Historically, it
26324 was output instead of @samp{^done} if the command has resumed the
26325 target. This behaviour is maintained for backward compatibility, but
26326 all frontends should treat @samp{^done} and @samp{^running}
26327 identically and rely on the @samp{*running} output record to determine
26328 which threads are resumed.
26332 @value{GDBN} has connected to a remote target.
26334 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26336 The operation failed. The @code{msg=@var{c-string}} variable contains
26337 the corresponding error message.
26339 If present, the @code{code=@var{c-string}} variable provides an error
26340 code on which consumers can rely on to detect the corresponding
26341 error condition. At present, only one error code is defined:
26344 @item "undefined-command"
26345 Indicates that the command causing the error does not exist.
26350 @value{GDBN} has terminated.
26354 @node GDB/MI Stream Records
26355 @subsection @sc{gdb/mi} Stream Records
26357 @cindex @sc{gdb/mi}, stream records
26358 @cindex stream records in @sc{gdb/mi}
26359 @value{GDBN} internally maintains a number of output streams: the console, the
26360 target, and the log. The output intended for each of these streams is
26361 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26363 Each stream record begins with a unique @dfn{prefix character} which
26364 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26365 Syntax}). In addition to the prefix, each stream record contains a
26366 @code{@var{string-output}}. This is either raw text (with an implicit new
26367 line) or a quoted C string (which does not contain an implicit newline).
26370 @item "~" @var{string-output}
26371 The console output stream contains text that should be displayed in the
26372 CLI console window. It contains the textual responses to CLI commands.
26374 @item "@@" @var{string-output}
26375 The target output stream contains any textual output from the running
26376 target. This is only present when GDB's event loop is truly
26377 asynchronous, which is currently only the case for remote targets.
26379 @item "&" @var{string-output}
26380 The log stream contains debugging messages being produced by @value{GDBN}'s
26384 @node GDB/MI Async Records
26385 @subsection @sc{gdb/mi} Async Records
26387 @cindex async records in @sc{gdb/mi}
26388 @cindex @sc{gdb/mi}, async records
26389 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26390 additional changes that have occurred. Those changes can either be a
26391 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26392 target activity (e.g., target stopped).
26394 The following is the list of possible async records:
26398 @item *running,thread-id="@var{thread}"
26399 The target is now running. The @var{thread} field can be the global
26400 thread ID of the the thread that is now running, and it can be
26401 @samp{all} if all threads are running. The frontend should assume
26402 that no interaction with a running thread is possible after this
26403 notification is produced. The frontend should not assume that this
26404 notification is output only once for any command. @value{GDBN} may
26405 emit this notification several times, either for different threads,
26406 because it cannot resume all threads together, or even for a single
26407 thread, if the thread must be stepped though some code before letting
26410 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26411 The target has stopped. The @var{reason} field can have one of the
26415 @item breakpoint-hit
26416 A breakpoint was reached.
26417 @item watchpoint-trigger
26418 A watchpoint was triggered.
26419 @item read-watchpoint-trigger
26420 A read watchpoint was triggered.
26421 @item access-watchpoint-trigger
26422 An access watchpoint was triggered.
26423 @item function-finished
26424 An -exec-finish or similar CLI command was accomplished.
26425 @item location-reached
26426 An -exec-until or similar CLI command was accomplished.
26427 @item watchpoint-scope
26428 A watchpoint has gone out of scope.
26429 @item end-stepping-range
26430 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26431 similar CLI command was accomplished.
26432 @item exited-signalled
26433 The inferior exited because of a signal.
26435 The inferior exited.
26436 @item exited-normally
26437 The inferior exited normally.
26438 @item signal-received
26439 A signal was received by the inferior.
26441 The inferior has stopped due to a library being loaded or unloaded.
26442 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26443 set or when a @code{catch load} or @code{catch unload} catchpoint is
26444 in use (@pxref{Set Catchpoints}).
26446 The inferior has forked. This is reported when @code{catch fork}
26447 (@pxref{Set Catchpoints}) has been used.
26449 The inferior has vforked. This is reported in when @code{catch vfork}
26450 (@pxref{Set Catchpoints}) has been used.
26451 @item syscall-entry
26452 The inferior entered a system call. This is reported when @code{catch
26453 syscall} (@pxref{Set Catchpoints}) has been used.
26454 @item syscall-return
26455 The inferior returned from a system call. This is reported when
26456 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26458 The inferior called @code{exec}. This is reported when @code{catch exec}
26459 (@pxref{Set Catchpoints}) has been used.
26462 The @var{id} field identifies the global thread ID of the thread
26463 that directly caused the stop -- for example by hitting a breakpoint.
26464 Depending on whether all-stop
26465 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26466 stop all threads, or only the thread that directly triggered the stop.
26467 If all threads are stopped, the @var{stopped} field will have the
26468 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26469 field will be a list of thread identifiers. Presently, this list will
26470 always include a single thread, but frontend should be prepared to see
26471 several threads in the list. The @var{core} field reports the
26472 processor core on which the stop event has happened. This field may be absent
26473 if such information is not available.
26475 @item =thread-group-added,id="@var{id}"
26476 @itemx =thread-group-removed,id="@var{id}"
26477 A thread group was either added or removed. The @var{id} field
26478 contains the @value{GDBN} identifier of the thread group. When a thread
26479 group is added, it generally might not be associated with a running
26480 process. When a thread group is removed, its id becomes invalid and
26481 cannot be used in any way.
26483 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26484 A thread group became associated with a running program,
26485 either because the program was just started or the thread group
26486 was attached to a program. The @var{id} field contains the
26487 @value{GDBN} identifier of the thread group. The @var{pid} field
26488 contains process identifier, specific to the operating system.
26490 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26491 A thread group is no longer associated with a running program,
26492 either because the program has exited, or because it was detached
26493 from. The @var{id} field contains the @value{GDBN} identifier of the
26494 thread group. The @var{code} field is the exit code of the inferior; it exists
26495 only when the inferior exited with some code.
26497 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26498 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26499 A thread either was created, or has exited. The @var{id} field
26500 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26501 field identifies the thread group this thread belongs to.
26503 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26504 Informs that the selected thread or frame were changed. This notification
26505 is not emitted as result of the @code{-thread-select} or
26506 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26507 that is not documented to change the selected thread and frame actually
26508 changes them. In particular, invoking, directly or indirectly
26509 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26510 will generate this notification. Changing the thread or frame from another
26511 user interface (see @ref{Interpreters}) will also generate this notification.
26513 The @var{frame} field is only present if the newly selected thread is
26514 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26516 We suggest that in response to this notification, front ends
26517 highlight the selected thread and cause subsequent commands to apply to
26520 @item =library-loaded,...
26521 Reports that a new library file was loaded by the program. This
26522 notification has 4 fields---@var{id}, @var{target-name},
26523 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26524 opaque identifier of the library. For remote debugging case,
26525 @var{target-name} and @var{host-name} fields give the name of the
26526 library file on the target, and on the host respectively. For native
26527 debugging, both those fields have the same value. The
26528 @var{symbols-loaded} field is emitted only for backward compatibility
26529 and should not be relied on to convey any useful information. The
26530 @var{thread-group} field, if present, specifies the id of the thread
26531 group in whose context the library was loaded. If the field is
26532 absent, it means the library was loaded in the context of all present
26535 @item =library-unloaded,...
26536 Reports that a library was unloaded by the program. This notification
26537 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26538 the same meaning as for the @code{=library-loaded} notification.
26539 The @var{thread-group} field, if present, specifies the id of the
26540 thread group in whose context the library was unloaded. If the field is
26541 absent, it means the library was unloaded in the context of all present
26544 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26545 @itemx =traceframe-changed,end
26546 Reports that the trace frame was changed and its new number is
26547 @var{tfnum}. The number of the tracepoint associated with this trace
26548 frame is @var{tpnum}.
26550 @item =tsv-created,name=@var{name},initial=@var{initial}
26551 Reports that the new trace state variable @var{name} is created with
26552 initial value @var{initial}.
26554 @item =tsv-deleted,name=@var{name}
26555 @itemx =tsv-deleted
26556 Reports that the trace state variable @var{name} is deleted or all
26557 trace state variables are deleted.
26559 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26560 Reports that the trace state variable @var{name} is modified with
26561 the initial value @var{initial}. The current value @var{current} of
26562 trace state variable is optional and is reported if the current
26563 value of trace state variable is known.
26565 @item =breakpoint-created,bkpt=@{...@}
26566 @itemx =breakpoint-modified,bkpt=@{...@}
26567 @itemx =breakpoint-deleted,id=@var{number}
26568 Reports that a breakpoint was created, modified, or deleted,
26569 respectively. Only user-visible breakpoints are reported to the MI
26572 The @var{bkpt} argument is of the same form as returned by the various
26573 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26574 @var{number} is the ordinal number of the breakpoint.
26576 Note that if a breakpoint is emitted in the result record of a
26577 command, then it will not also be emitted in an async record.
26579 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26580 @itemx =record-stopped,thread-group="@var{id}"
26581 Execution log recording was either started or stopped on an
26582 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26583 group corresponding to the affected inferior.
26585 The @var{method} field indicates the method used to record execution. If the
26586 method in use supports multiple recording formats, @var{format} will be present
26587 and contain the currently used format. @xref{Process Record and Replay},
26588 for existing method and format values.
26590 @item =cmd-param-changed,param=@var{param},value=@var{value}
26591 Reports that a parameter of the command @code{set @var{param}} is
26592 changed to @var{value}. In the multi-word @code{set} command,
26593 the @var{param} is the whole parameter list to @code{set} command.
26594 For example, In command @code{set check type on}, @var{param}
26595 is @code{check type} and @var{value} is @code{on}.
26597 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26598 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26599 written in an inferior. The @var{id} is the identifier of the
26600 thread group corresponding to the affected inferior. The optional
26601 @code{type="code"} part is reported if the memory written to holds
26605 @node GDB/MI Breakpoint Information
26606 @subsection @sc{gdb/mi} Breakpoint Information
26608 When @value{GDBN} reports information about a breakpoint, a
26609 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26614 The breakpoint number. For a breakpoint that represents one location
26615 of a multi-location breakpoint, this will be a dotted pair, like
26619 The type of the breakpoint. For ordinary breakpoints this will be
26620 @samp{breakpoint}, but many values are possible.
26623 If the type of the breakpoint is @samp{catchpoint}, then this
26624 indicates the exact type of catchpoint.
26627 This is the breakpoint disposition---either @samp{del}, meaning that
26628 the breakpoint will be deleted at the next stop, or @samp{keep},
26629 meaning that the breakpoint will not be deleted.
26632 This indicates whether the breakpoint is enabled, in which case the
26633 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26634 Note that this is not the same as the field @code{enable}.
26637 The address of the breakpoint. This may be a hexidecimal number,
26638 giving the address; or the string @samp{<PENDING>}, for a pending
26639 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26640 multiple locations. This field will not be present if no address can
26641 be determined. For example, a watchpoint does not have an address.
26644 If known, the function in which the breakpoint appears.
26645 If not known, this field is not present.
26648 The name of the source file which contains this function, if known.
26649 If not known, this field is not present.
26652 The full file name of the source file which contains this function, if
26653 known. If not known, this field is not present.
26656 The line number at which this breakpoint appears, if known.
26657 If not known, this field is not present.
26660 If the source file is not known, this field may be provided. If
26661 provided, this holds the address of the breakpoint, possibly followed
26665 If this breakpoint is pending, this field is present and holds the
26666 text used to set the breakpoint, as entered by the user.
26669 Where this breakpoint's condition is evaluated, either @samp{host} or
26673 If this is a thread-specific breakpoint, then this identifies the
26674 thread in which the breakpoint can trigger.
26677 If this breakpoint is restricted to a particular Ada task, then this
26678 field will hold the task identifier.
26681 If the breakpoint is conditional, this is the condition expression.
26684 The ignore count of the breakpoint.
26687 The enable count of the breakpoint.
26689 @item traceframe-usage
26692 @item static-tracepoint-marker-string-id
26693 For a static tracepoint, the name of the static tracepoint marker.
26696 For a masked watchpoint, this is the mask.
26699 A tracepoint's pass count.
26701 @item original-location
26702 The location of the breakpoint as originally specified by the user.
26703 This field is optional.
26706 The number of times the breakpoint has been hit.
26709 This field is only given for tracepoints. This is either @samp{y},
26710 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26714 Some extra data, the exact contents of which are type-dependent.
26718 For example, here is what the output of @code{-break-insert}
26719 (@pxref{GDB/MI Breakpoint Commands}) might be:
26722 -> -break-insert main
26723 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26724 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26725 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26730 @node GDB/MI Frame Information
26731 @subsection @sc{gdb/mi} Frame Information
26733 Response from many MI commands includes an information about stack
26734 frame. This information is a tuple that may have the following
26739 The level of the stack frame. The innermost frame has the level of
26740 zero. This field is always present.
26743 The name of the function corresponding to the frame. This field may
26744 be absent if @value{GDBN} is unable to determine the function name.
26747 The code address for the frame. This field is always present.
26750 The name of the source files that correspond to the frame's code
26751 address. This field may be absent.
26754 The source line corresponding to the frames' code address. This field
26758 The name of the binary file (either executable or shared library) the
26759 corresponds to the frame's code address. This field may be absent.
26763 @node GDB/MI Thread Information
26764 @subsection @sc{gdb/mi} Thread Information
26766 Whenever @value{GDBN} has to report an information about a thread, it
26767 uses a tuple with the following fields:
26771 The global numeric id assigned to the thread by @value{GDBN}. This field is
26775 Target-specific string identifying the thread. This field is always present.
26778 Additional information about the thread provided by the target.
26779 It is supposed to be human-readable and not interpreted by the
26780 frontend. This field is optional.
26783 Either @samp{stopped} or @samp{running}, depending on whether the
26784 thread is presently running. This field is always present.
26787 The value of this field is an integer number of the processor core the
26788 thread was last seen on. This field is optional.
26791 @node GDB/MI Ada Exception Information
26792 @subsection @sc{gdb/mi} Ada Exception Information
26794 Whenever a @code{*stopped} record is emitted because the program
26795 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26796 @value{GDBN} provides the name of the exception that was raised via
26797 the @code{exception-name} field.
26799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26800 @node GDB/MI Simple Examples
26801 @section Simple Examples of @sc{gdb/mi} Interaction
26802 @cindex @sc{gdb/mi}, simple examples
26804 This subsection presents several simple examples of interaction using
26805 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26806 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26807 the output received from @sc{gdb/mi}.
26809 Note the line breaks shown in the examples are here only for
26810 readability, they don't appear in the real output.
26812 @subheading Setting a Breakpoint
26814 Setting a breakpoint generates synchronous output which contains detailed
26815 information of the breakpoint.
26818 -> -break-insert main
26819 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26820 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26821 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26826 @subheading Program Execution
26828 Program execution generates asynchronous records and MI gives the
26829 reason that execution stopped.
26835 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26836 frame=@{addr="0x08048564",func="main",
26837 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26838 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26843 <- *stopped,reason="exited-normally"
26847 @subheading Quitting @value{GDBN}
26849 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26857 Please note that @samp{^exit} is printed immediately, but it might
26858 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26859 performs necessary cleanups, including killing programs being debugged
26860 or disconnecting from debug hardware, so the frontend should wait till
26861 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26862 fails to exit in reasonable time.
26864 @subheading A Bad Command
26866 Here's what happens if you pass a non-existent command:
26870 <- ^error,msg="Undefined MI command: rubbish"
26875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26876 @node GDB/MI Command Description Format
26877 @section @sc{gdb/mi} Command Description Format
26879 The remaining sections describe blocks of commands. Each block of
26880 commands is laid out in a fashion similar to this section.
26882 @subheading Motivation
26884 The motivation for this collection of commands.
26886 @subheading Introduction
26888 A brief introduction to this collection of commands as a whole.
26890 @subheading Commands
26892 For each command in the block, the following is described:
26894 @subsubheading Synopsis
26897 -command @var{args}@dots{}
26900 @subsubheading Result
26902 @subsubheading @value{GDBN} Command
26904 The corresponding @value{GDBN} CLI command(s), if any.
26906 @subsubheading Example
26908 Example(s) formatted for readability. Some of the described commands have
26909 not been implemented yet and these are labeled N.A.@: (not available).
26912 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26913 @node GDB/MI Breakpoint Commands
26914 @section @sc{gdb/mi} Breakpoint Commands
26916 @cindex breakpoint commands for @sc{gdb/mi}
26917 @cindex @sc{gdb/mi}, breakpoint commands
26918 This section documents @sc{gdb/mi} commands for manipulating
26921 @subheading The @code{-break-after} Command
26922 @findex -break-after
26924 @subsubheading Synopsis
26927 -break-after @var{number} @var{count}
26930 The breakpoint number @var{number} is not in effect until it has been
26931 hit @var{count} times. To see how this is reflected in the output of
26932 the @samp{-break-list} command, see the description of the
26933 @samp{-break-list} command below.
26935 @subsubheading @value{GDBN} Command
26937 The corresponding @value{GDBN} command is @samp{ignore}.
26939 @subsubheading Example
26944 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26945 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26946 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26954 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26955 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26956 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26957 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26958 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26959 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26960 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26961 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26962 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26963 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26968 @subheading The @code{-break-catch} Command
26969 @findex -break-catch
26972 @subheading The @code{-break-commands} Command
26973 @findex -break-commands
26975 @subsubheading Synopsis
26978 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26981 Specifies the CLI commands that should be executed when breakpoint
26982 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26983 are the commands. If no command is specified, any previously-set
26984 commands are cleared. @xref{Break Commands}. Typical use of this
26985 functionality is tracing a program, that is, printing of values of
26986 some variables whenever breakpoint is hit and then continuing.
26988 @subsubheading @value{GDBN} Command
26990 The corresponding @value{GDBN} command is @samp{commands}.
26992 @subsubheading Example
26997 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26998 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26999 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27002 -break-commands 1 "print v" "continue"
27007 @subheading The @code{-break-condition} Command
27008 @findex -break-condition
27010 @subsubheading Synopsis
27013 -break-condition @var{number} @var{expr}
27016 Breakpoint @var{number} will stop the program only if the condition in
27017 @var{expr} is true. The condition becomes part of the
27018 @samp{-break-list} output (see the description of the @samp{-break-list}
27021 @subsubheading @value{GDBN} Command
27023 The corresponding @value{GDBN} command is @samp{condition}.
27025 @subsubheading Example
27029 -break-condition 1 1
27033 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27034 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27035 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27036 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27037 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27038 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27039 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27040 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27041 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27042 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27046 @subheading The @code{-break-delete} Command
27047 @findex -break-delete
27049 @subsubheading Synopsis
27052 -break-delete ( @var{breakpoint} )+
27055 Delete the breakpoint(s) whose number(s) are specified in the argument
27056 list. This is obviously reflected in the breakpoint list.
27058 @subsubheading @value{GDBN} Command
27060 The corresponding @value{GDBN} command is @samp{delete}.
27062 @subsubheading Example
27070 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27081 @subheading The @code{-break-disable} Command
27082 @findex -break-disable
27084 @subsubheading Synopsis
27087 -break-disable ( @var{breakpoint} )+
27090 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27091 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27093 @subsubheading @value{GDBN} Command
27095 The corresponding @value{GDBN} command is @samp{disable}.
27097 @subsubheading Example
27105 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27112 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27113 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27114 line="5",thread-groups=["i1"],times="0"@}]@}
27118 @subheading The @code{-break-enable} Command
27119 @findex -break-enable
27121 @subsubheading Synopsis
27124 -break-enable ( @var{breakpoint} )+
27127 Enable (previously disabled) @var{breakpoint}(s).
27129 @subsubheading @value{GDBN} Command
27131 The corresponding @value{GDBN} command is @samp{enable}.
27133 @subsubheading Example
27141 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27142 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27143 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27144 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27145 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27146 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27147 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27148 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27149 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27150 line="5",thread-groups=["i1"],times="0"@}]@}
27154 @subheading The @code{-break-info} Command
27155 @findex -break-info
27157 @subsubheading Synopsis
27160 -break-info @var{breakpoint}
27164 Get information about a single breakpoint.
27166 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27167 Information}, for details on the format of each breakpoint in the
27170 @subsubheading @value{GDBN} Command
27172 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27174 @subsubheading Example
27177 @subheading The @code{-break-insert} Command
27178 @findex -break-insert
27179 @anchor{-break-insert}
27181 @subsubheading Synopsis
27184 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27185 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27186 [ -p @var{thread-id} ] [ @var{location} ]
27190 If specified, @var{location}, can be one of:
27193 @item linespec location
27194 A linespec location. @xref{Linespec Locations}.
27196 @item explicit location
27197 An explicit location. @sc{gdb/mi} explicit locations are
27198 analogous to the CLI's explicit locations using the option names
27199 listed below. @xref{Explicit Locations}.
27202 @item --source @var{filename}
27203 The source file name of the location. This option requires the use
27204 of either @samp{--function} or @samp{--line}.
27206 @item --function @var{function}
27207 The name of a function or method.
27209 @item --label @var{label}
27210 The name of a label.
27212 @item --line @var{lineoffset}
27213 An absolute or relative line offset from the start of the location.
27216 @item address location
27217 An address location, *@var{address}. @xref{Address Locations}.
27221 The possible optional parameters of this command are:
27225 Insert a temporary breakpoint.
27227 Insert a hardware breakpoint.
27229 If @var{location} cannot be parsed (for example if it
27230 refers to unknown files or functions), create a pending
27231 breakpoint. Without this flag, @value{GDBN} will report
27232 an error, and won't create a breakpoint, if @var{location}
27235 Create a disabled breakpoint.
27237 Create a tracepoint. @xref{Tracepoints}. When this parameter
27238 is used together with @samp{-h}, a fast tracepoint is created.
27239 @item -c @var{condition}
27240 Make the breakpoint conditional on @var{condition}.
27241 @item -i @var{ignore-count}
27242 Initialize the @var{ignore-count}.
27243 @item -p @var{thread-id}
27244 Restrict the breakpoint to the thread with the specified global
27248 @subsubheading Result
27250 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27251 resulting breakpoint.
27253 Note: this format is open to change.
27254 @c An out-of-band breakpoint instead of part of the result?
27256 @subsubheading @value{GDBN} Command
27258 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27259 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27261 @subsubheading Example
27266 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27267 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27270 -break-insert -t foo
27271 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27272 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27276 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27277 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27278 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27279 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27280 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27281 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27282 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27283 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27284 addr="0x0001072c", func="main",file="recursive2.c",
27285 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27287 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27288 addr="0x00010774",func="foo",file="recursive2.c",
27289 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27292 @c -break-insert -r foo.*
27293 @c ~int foo(int, int);
27294 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27295 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27300 @subheading The @code{-dprintf-insert} Command
27301 @findex -dprintf-insert
27303 @subsubheading Synopsis
27306 -dprintf-insert [ -t ] [ -f ] [ -d ]
27307 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27308 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27313 If supplied, @var{location} may be specified the same way as for
27314 the @code{-break-insert} command. @xref{-break-insert}.
27316 The possible optional parameters of this command are:
27320 Insert a temporary breakpoint.
27322 If @var{location} cannot be parsed (for example, if it
27323 refers to unknown files or functions), create a pending
27324 breakpoint. Without this flag, @value{GDBN} will report
27325 an error, and won't create a breakpoint, if @var{location}
27328 Create a disabled breakpoint.
27329 @item -c @var{condition}
27330 Make the breakpoint conditional on @var{condition}.
27331 @item -i @var{ignore-count}
27332 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27333 to @var{ignore-count}.
27334 @item -p @var{thread-id}
27335 Restrict the breakpoint to the thread with the specified global
27339 @subsubheading Result
27341 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27342 resulting breakpoint.
27344 @c An out-of-band breakpoint instead of part of the result?
27346 @subsubheading @value{GDBN} Command
27348 The corresponding @value{GDBN} command is @samp{dprintf}.
27350 @subsubheading Example
27354 4-dprintf-insert foo "At foo entry\n"
27355 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27356 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27357 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27358 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27359 original-location="foo"@}
27361 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27362 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27363 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27364 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27365 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27366 original-location="mi-dprintf.c:26"@}
27370 @subheading The @code{-break-list} Command
27371 @findex -break-list
27373 @subsubheading Synopsis
27379 Displays the list of inserted breakpoints, showing the following fields:
27383 number of the breakpoint
27385 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27387 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27390 is the breakpoint enabled or no: @samp{y} or @samp{n}
27392 memory location at which the breakpoint is set
27394 logical location of the breakpoint, expressed by function name, file
27396 @item Thread-groups
27397 list of thread groups to which this breakpoint applies
27399 number of times the breakpoint has been hit
27402 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27403 @code{body} field is an empty list.
27405 @subsubheading @value{GDBN} Command
27407 The corresponding @value{GDBN} command is @samp{info break}.
27409 @subsubheading Example
27414 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27415 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27416 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27417 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27418 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27419 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27420 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27421 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27422 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27424 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27425 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27426 line="13",thread-groups=["i1"],times="0"@}]@}
27430 Here's an example of the result when there are no breakpoints:
27435 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27436 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27437 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27438 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27439 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27440 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27441 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27446 @subheading The @code{-break-passcount} Command
27447 @findex -break-passcount
27449 @subsubheading Synopsis
27452 -break-passcount @var{tracepoint-number} @var{passcount}
27455 Set the passcount for tracepoint @var{tracepoint-number} to
27456 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27457 is not a tracepoint, error is emitted. This corresponds to CLI
27458 command @samp{passcount}.
27460 @subheading The @code{-break-watch} Command
27461 @findex -break-watch
27463 @subsubheading Synopsis
27466 -break-watch [ -a | -r ]
27469 Create a watchpoint. With the @samp{-a} option it will create an
27470 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27471 read from or on a write to the memory location. With the @samp{-r}
27472 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27473 trigger only when the memory location is accessed for reading. Without
27474 either of the options, the watchpoint created is a regular watchpoint,
27475 i.e., it will trigger when the memory location is accessed for writing.
27476 @xref{Set Watchpoints, , Setting Watchpoints}.
27478 Note that @samp{-break-list} will report a single list of watchpoints and
27479 breakpoints inserted.
27481 @subsubheading @value{GDBN} Command
27483 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27486 @subsubheading Example
27488 Setting a watchpoint on a variable in the @code{main} function:
27493 ^done,wpt=@{number="2",exp="x"@}
27498 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27499 value=@{old="-268439212",new="55"@},
27500 frame=@{func="main",args=[],file="recursive2.c",
27501 fullname="/home/foo/bar/recursive2.c",line="5"@}
27505 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27506 the program execution twice: first for the variable changing value, then
27507 for the watchpoint going out of scope.
27512 ^done,wpt=@{number="5",exp="C"@}
27517 *stopped,reason="watchpoint-trigger",
27518 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27519 frame=@{func="callee4",args=[],
27520 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27521 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27526 *stopped,reason="watchpoint-scope",wpnum="5",
27527 frame=@{func="callee3",args=[@{name="strarg",
27528 value="0x11940 \"A string argument.\""@}],
27529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27530 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27534 Listing breakpoints and watchpoints, at different points in the program
27535 execution. Note that once the watchpoint goes out of scope, it is
27541 ^done,wpt=@{number="2",exp="C"@}
27544 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27545 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27546 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27547 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27548 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27549 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27550 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27551 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27552 addr="0x00010734",func="callee4",
27553 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27554 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27556 bkpt=@{number="2",type="watchpoint",disp="keep",
27557 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27562 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27563 value=@{old="-276895068",new="3"@},
27564 frame=@{func="callee4",args=[],
27565 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27566 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27569 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27570 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27571 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27572 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27573 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27574 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27575 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27576 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27577 addr="0x00010734",func="callee4",
27578 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27579 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27581 bkpt=@{number="2",type="watchpoint",disp="keep",
27582 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27586 ^done,reason="watchpoint-scope",wpnum="2",
27587 frame=@{func="callee3",args=[@{name="strarg",
27588 value="0x11940 \"A string argument.\""@}],
27589 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27590 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27593 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27594 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27595 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27596 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27597 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27598 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27599 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27600 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27601 addr="0x00010734",func="callee4",
27602 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27603 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27604 thread-groups=["i1"],times="1"@}]@}
27609 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27610 @node GDB/MI Catchpoint Commands
27611 @section @sc{gdb/mi} Catchpoint Commands
27613 This section documents @sc{gdb/mi} commands for manipulating
27617 * Shared Library GDB/MI Catchpoint Commands::
27618 * Ada Exception GDB/MI Catchpoint Commands::
27621 @node Shared Library GDB/MI Catchpoint Commands
27622 @subsection Shared Library @sc{gdb/mi} Catchpoints
27624 @subheading The @code{-catch-load} Command
27625 @findex -catch-load
27627 @subsubheading Synopsis
27630 -catch-load [ -t ] [ -d ] @var{regexp}
27633 Add a catchpoint for library load events. If the @samp{-t} option is used,
27634 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27635 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27636 in a disabled state. The @samp{regexp} argument is a regular
27637 expression used to match the name of the loaded library.
27640 @subsubheading @value{GDBN} Command
27642 The corresponding @value{GDBN} command is @samp{catch load}.
27644 @subsubheading Example
27647 -catch-load -t foo.so
27648 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27649 what="load of library matching foo.so",catch-type="load",times="0"@}
27654 @subheading The @code{-catch-unload} Command
27655 @findex -catch-unload
27657 @subsubheading Synopsis
27660 -catch-unload [ -t ] [ -d ] @var{regexp}
27663 Add a catchpoint for library unload events. If the @samp{-t} option is
27664 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27665 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27666 created in a disabled state. The @samp{regexp} argument is a regular
27667 expression used to match the name of the unloaded library.
27669 @subsubheading @value{GDBN} Command
27671 The corresponding @value{GDBN} command is @samp{catch unload}.
27673 @subsubheading Example
27676 -catch-unload -d bar.so
27677 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27678 what="load of library matching bar.so",catch-type="unload",times="0"@}
27682 @node Ada Exception GDB/MI Catchpoint Commands
27683 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27685 The following @sc{gdb/mi} commands can be used to create catchpoints
27686 that stop the execution when Ada exceptions are being raised.
27688 @subheading The @code{-catch-assert} Command
27689 @findex -catch-assert
27691 @subsubheading Synopsis
27694 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27697 Add a catchpoint for failed Ada assertions.
27699 The possible optional parameters for this command are:
27702 @item -c @var{condition}
27703 Make the catchpoint conditional on @var{condition}.
27705 Create a disabled catchpoint.
27707 Create a temporary catchpoint.
27710 @subsubheading @value{GDBN} Command
27712 The corresponding @value{GDBN} command is @samp{catch assert}.
27714 @subsubheading Example
27718 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27719 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27720 thread-groups=["i1"],times="0",
27721 original-location="__gnat_debug_raise_assert_failure"@}
27725 @subheading The @code{-catch-exception} Command
27726 @findex -catch-exception
27728 @subsubheading Synopsis
27731 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27735 Add a catchpoint stopping when Ada exceptions are raised.
27736 By default, the command stops the program when any Ada exception
27737 gets raised. But it is also possible, by using some of the
27738 optional parameters described below, to create more selective
27741 The possible optional parameters for this command are:
27744 @item -c @var{condition}
27745 Make the catchpoint conditional on @var{condition}.
27747 Create a disabled catchpoint.
27748 @item -e @var{exception-name}
27749 Only stop when @var{exception-name} is raised. This option cannot
27750 be used combined with @samp{-u}.
27752 Create a temporary catchpoint.
27754 Stop only when an unhandled exception gets raised. This option
27755 cannot be used combined with @samp{-e}.
27758 @subsubheading @value{GDBN} Command
27760 The corresponding @value{GDBN} commands are @samp{catch exception}
27761 and @samp{catch exception unhandled}.
27763 @subsubheading Example
27766 -catch-exception -e Program_Error
27767 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27768 enabled="y",addr="0x0000000000404874",
27769 what="`Program_Error' Ada exception", thread-groups=["i1"],
27770 times="0",original-location="__gnat_debug_raise_exception"@}
27774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27775 @node GDB/MI Program Context
27776 @section @sc{gdb/mi} Program Context
27778 @subheading The @code{-exec-arguments} Command
27779 @findex -exec-arguments
27782 @subsubheading Synopsis
27785 -exec-arguments @var{args}
27788 Set the inferior program arguments, to be used in the next
27791 @subsubheading @value{GDBN} Command
27793 The corresponding @value{GDBN} command is @samp{set args}.
27795 @subsubheading Example
27799 -exec-arguments -v word
27806 @subheading The @code{-exec-show-arguments} Command
27807 @findex -exec-show-arguments
27809 @subsubheading Synopsis
27812 -exec-show-arguments
27815 Print the arguments of the program.
27817 @subsubheading @value{GDBN} Command
27819 The corresponding @value{GDBN} command is @samp{show args}.
27821 @subsubheading Example
27826 @subheading The @code{-environment-cd} Command
27827 @findex -environment-cd
27829 @subsubheading Synopsis
27832 -environment-cd @var{pathdir}
27835 Set @value{GDBN}'s working directory.
27837 @subsubheading @value{GDBN} Command
27839 The corresponding @value{GDBN} command is @samp{cd}.
27841 @subsubheading Example
27845 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27851 @subheading The @code{-environment-directory} Command
27852 @findex -environment-directory
27854 @subsubheading Synopsis
27857 -environment-directory [ -r ] [ @var{pathdir} ]+
27860 Add directories @var{pathdir} to beginning of search path for source files.
27861 If the @samp{-r} option is used, the search path is reset to the default
27862 search path. If directories @var{pathdir} are supplied in addition to the
27863 @samp{-r} option, the search path is first reset and then addition
27865 Multiple directories may be specified, separated by blanks. Specifying
27866 multiple directories in a single command
27867 results in the directories added to the beginning of the
27868 search path in the same order they were presented in the command.
27869 If blanks are needed as
27870 part of a directory name, double-quotes should be used around
27871 the name. In the command output, the path will show up separated
27872 by the system directory-separator character. The directory-separator
27873 character must not be used
27874 in any directory name.
27875 If no directories are specified, the current search path is displayed.
27877 @subsubheading @value{GDBN} Command
27879 The corresponding @value{GDBN} command is @samp{dir}.
27881 @subsubheading Example
27885 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27886 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27888 -environment-directory ""
27889 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27891 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27892 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27894 -environment-directory -r
27895 ^done,source-path="$cdir:$cwd"
27900 @subheading The @code{-environment-path} Command
27901 @findex -environment-path
27903 @subsubheading Synopsis
27906 -environment-path [ -r ] [ @var{pathdir} ]+
27909 Add directories @var{pathdir} to beginning of search path for object files.
27910 If the @samp{-r} option is used, the search path is reset to the original
27911 search path that existed at gdb start-up. If directories @var{pathdir} are
27912 supplied in addition to the
27913 @samp{-r} option, the search path is first reset and then addition
27915 Multiple directories may be specified, separated by blanks. Specifying
27916 multiple directories in a single command
27917 results in the directories added to the beginning of the
27918 search path in the same order they were presented in the command.
27919 If blanks are needed as
27920 part of a directory name, double-quotes should be used around
27921 the name. In the command output, the path will show up separated
27922 by the system directory-separator character. The directory-separator
27923 character must not be used
27924 in any directory name.
27925 If no directories are specified, the current path is displayed.
27928 @subsubheading @value{GDBN} Command
27930 The corresponding @value{GDBN} command is @samp{path}.
27932 @subsubheading Example
27937 ^done,path="/usr/bin"
27939 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27940 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27942 -environment-path -r /usr/local/bin
27943 ^done,path="/usr/local/bin:/usr/bin"
27948 @subheading The @code{-environment-pwd} Command
27949 @findex -environment-pwd
27951 @subsubheading Synopsis
27957 Show the current working directory.
27959 @subsubheading @value{GDBN} Command
27961 The corresponding @value{GDBN} command is @samp{pwd}.
27963 @subsubheading Example
27968 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27973 @node GDB/MI Thread Commands
27974 @section @sc{gdb/mi} Thread Commands
27977 @subheading The @code{-thread-info} Command
27978 @findex -thread-info
27980 @subsubheading Synopsis
27983 -thread-info [ @var{thread-id} ]
27986 Reports information about either a specific thread, if the
27987 @var{thread-id} parameter is present, or about all threads.
27988 @var{thread-id} is the thread's global thread ID. When printing
27989 information about all threads, also reports the global ID of the
27992 @subsubheading @value{GDBN} Command
27994 The @samp{info thread} command prints the same information
27997 @subsubheading Result
27999 The result is a list of threads. The following attributes are
28000 defined for a given thread:
28004 This field exists only for the current thread. It has the value @samp{*}.
28007 The global identifier that @value{GDBN} uses to refer to the thread.
28010 The identifier that the target uses to refer to the thread.
28013 Extra information about the thread, in a target-specific format. This
28017 The name of the thread. If the user specified a name using the
28018 @code{thread name} command, then this name is given. Otherwise, if
28019 @value{GDBN} can extract the thread name from the target, then that
28020 name is given. If @value{GDBN} cannot find the thread name, then this
28024 The stack frame currently executing in the thread.
28027 The thread's state. The @samp{state} field may have the following
28032 The thread is stopped. Frame information is available for stopped
28036 The thread is running. There's no frame information for running
28042 If @value{GDBN} can find the CPU core on which this thread is running,
28043 then this field is the core identifier. This field is optional.
28047 @subsubheading Example
28052 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28053 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28054 args=[]@},state="running"@},
28055 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28056 frame=@{level="0",addr="0x0804891f",func="foo",
28057 args=[@{name="i",value="10"@}],
28058 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28059 state="running"@}],
28060 current-thread-id="1"
28064 @subheading The @code{-thread-list-ids} Command
28065 @findex -thread-list-ids
28067 @subsubheading Synopsis
28073 Produces a list of the currently known global @value{GDBN} thread ids.
28074 At the end of the list it also prints the total number of such
28077 This command is retained for historical reasons, the
28078 @code{-thread-info} command should be used instead.
28080 @subsubheading @value{GDBN} Command
28082 Part of @samp{info threads} supplies the same information.
28084 @subsubheading Example
28089 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28090 current-thread-id="1",number-of-threads="3"
28095 @subheading The @code{-thread-select} Command
28096 @findex -thread-select
28098 @subsubheading Synopsis
28101 -thread-select @var{thread-id}
28104 Make thread with global thread number @var{thread-id} the current
28105 thread. It prints the number of the new current thread, and the
28106 topmost frame for that thread.
28108 This command is deprecated in favor of explicitly using the
28109 @samp{--thread} option to each command.
28111 @subsubheading @value{GDBN} Command
28113 The corresponding @value{GDBN} command is @samp{thread}.
28115 @subsubheading Example
28122 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28123 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28127 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28128 number-of-threads="3"
28131 ^done,new-thread-id="3",
28132 frame=@{level="0",func="vprintf",
28133 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28134 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28139 @node GDB/MI Ada Tasking Commands
28140 @section @sc{gdb/mi} Ada Tasking Commands
28142 @subheading The @code{-ada-task-info} Command
28143 @findex -ada-task-info
28145 @subsubheading Synopsis
28148 -ada-task-info [ @var{task-id} ]
28151 Reports information about either a specific Ada task, if the
28152 @var{task-id} parameter is present, or about all Ada tasks.
28154 @subsubheading @value{GDBN} Command
28156 The @samp{info tasks} command prints the same information
28157 about all Ada tasks (@pxref{Ada Tasks}).
28159 @subsubheading Result
28161 The result is a table of Ada tasks. The following columns are
28162 defined for each Ada task:
28166 This field exists only for the current thread. It has the value @samp{*}.
28169 The identifier that @value{GDBN} uses to refer to the Ada task.
28172 The identifier that the target uses to refer to the Ada task.
28175 The global thread identifier of the thread corresponding to the Ada
28178 This field should always exist, as Ada tasks are always implemented
28179 on top of a thread. But if @value{GDBN} cannot find this corresponding
28180 thread for any reason, the field is omitted.
28183 This field exists only when the task was created by another task.
28184 In this case, it provides the ID of the parent task.
28187 The base priority of the task.
28190 The current state of the task. For a detailed description of the
28191 possible states, see @ref{Ada Tasks}.
28194 The name of the task.
28198 @subsubheading Example
28202 ^done,tasks=@{nr_rows="3",nr_cols="8",
28203 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28204 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28205 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28206 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28207 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28208 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28209 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28210 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28211 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28212 state="Child Termination Wait",name="main_task"@}]@}
28216 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28217 @node GDB/MI Program Execution
28218 @section @sc{gdb/mi} Program Execution
28220 These are the asynchronous commands which generate the out-of-band
28221 record @samp{*stopped}. Currently @value{GDBN} only really executes
28222 asynchronously with remote targets and this interaction is mimicked in
28225 @subheading The @code{-exec-continue} Command
28226 @findex -exec-continue
28228 @subsubheading Synopsis
28231 -exec-continue [--reverse] [--all|--thread-group N]
28234 Resumes the execution of the inferior program, which will continue
28235 to execute until it reaches a debugger stop event. If the
28236 @samp{--reverse} option is specified, execution resumes in reverse until
28237 it reaches a stop event. Stop events may include
28240 breakpoints or watchpoints
28242 signals or exceptions
28244 the end of the process (or its beginning under @samp{--reverse})
28246 the end or beginning of a replay log if one is being used.
28248 In all-stop mode (@pxref{All-Stop
28249 Mode}), may resume only one thread, or all threads, depending on the
28250 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28251 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28252 ignored in all-stop mode. If the @samp{--thread-group} options is
28253 specified, then all threads in that thread group are resumed.
28255 @subsubheading @value{GDBN} Command
28257 The corresponding @value{GDBN} corresponding is @samp{continue}.
28259 @subsubheading Example
28266 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28267 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28273 @subheading The @code{-exec-finish} Command
28274 @findex -exec-finish
28276 @subsubheading Synopsis
28279 -exec-finish [--reverse]
28282 Resumes the execution of the inferior program until the current
28283 function is exited. Displays the results returned by the function.
28284 If the @samp{--reverse} option is specified, resumes the reverse
28285 execution of the inferior program until the point where current
28286 function was called.
28288 @subsubheading @value{GDBN} Command
28290 The corresponding @value{GDBN} command is @samp{finish}.
28292 @subsubheading Example
28294 Function returning @code{void}.
28301 *stopped,reason="function-finished",frame=@{func="main",args=[],
28302 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28306 Function returning other than @code{void}. The name of the internal
28307 @value{GDBN} variable storing the result is printed, together with the
28314 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28315 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28317 gdb-result-var="$1",return-value="0"
28322 @subheading The @code{-exec-interrupt} Command
28323 @findex -exec-interrupt
28325 @subsubheading Synopsis
28328 -exec-interrupt [--all|--thread-group N]
28331 Interrupts the background execution of the target. Note how the token
28332 associated with the stop message is the one for the execution command
28333 that has been interrupted. The token for the interrupt itself only
28334 appears in the @samp{^done} output. If the user is trying to
28335 interrupt a non-running program, an error message will be printed.
28337 Note that when asynchronous execution is enabled, this command is
28338 asynchronous just like other execution commands. That is, first the
28339 @samp{^done} response will be printed, and the target stop will be
28340 reported after that using the @samp{*stopped} notification.
28342 In non-stop mode, only the context thread is interrupted by default.
28343 All threads (in all inferiors) will be interrupted if the
28344 @samp{--all} option is specified. If the @samp{--thread-group}
28345 option is specified, all threads in that group will be interrupted.
28347 @subsubheading @value{GDBN} Command
28349 The corresponding @value{GDBN} command is @samp{interrupt}.
28351 @subsubheading Example
28362 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28363 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28364 fullname="/home/foo/bar/try.c",line="13"@}
28369 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28373 @subheading The @code{-exec-jump} Command
28376 @subsubheading Synopsis
28379 -exec-jump @var{location}
28382 Resumes execution of the inferior program at the location specified by
28383 parameter. @xref{Specify Location}, for a description of the
28384 different forms of @var{location}.
28386 @subsubheading @value{GDBN} Command
28388 The corresponding @value{GDBN} command is @samp{jump}.
28390 @subsubheading Example
28393 -exec-jump foo.c:10
28394 *running,thread-id="all"
28399 @subheading The @code{-exec-next} Command
28402 @subsubheading Synopsis
28405 -exec-next [--reverse]
28408 Resumes execution of the inferior program, stopping when the beginning
28409 of the next source line is reached.
28411 If the @samp{--reverse} option is specified, resumes reverse execution
28412 of the inferior program, stopping at the beginning of the previous
28413 source line. If you issue this command on the first line of a
28414 function, it will take you back to the caller of that function, to the
28415 source line where the function was called.
28418 @subsubheading @value{GDBN} Command
28420 The corresponding @value{GDBN} command is @samp{next}.
28422 @subsubheading Example
28428 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28433 @subheading The @code{-exec-next-instruction} Command
28434 @findex -exec-next-instruction
28436 @subsubheading Synopsis
28439 -exec-next-instruction [--reverse]
28442 Executes one machine instruction. If the instruction is a function
28443 call, continues until the function returns. If the program stops at an
28444 instruction in the middle of a source line, the address will be
28447 If the @samp{--reverse} option is specified, resumes reverse execution
28448 of the inferior program, stopping at the previous instruction. If the
28449 previously executed instruction was a return from another function,
28450 it will continue to execute in reverse until the call to that function
28451 (from the current stack frame) is reached.
28453 @subsubheading @value{GDBN} Command
28455 The corresponding @value{GDBN} command is @samp{nexti}.
28457 @subsubheading Example
28461 -exec-next-instruction
28465 *stopped,reason="end-stepping-range",
28466 addr="0x000100d4",line="5",file="hello.c"
28471 @subheading The @code{-exec-return} Command
28472 @findex -exec-return
28474 @subsubheading Synopsis
28480 Makes current function return immediately. Doesn't execute the inferior.
28481 Displays the new current frame.
28483 @subsubheading @value{GDBN} Command
28485 The corresponding @value{GDBN} command is @samp{return}.
28487 @subsubheading Example
28491 200-break-insert callee4
28492 200^done,bkpt=@{number="1",addr="0x00010734",
28493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28498 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28499 frame=@{func="callee4",args=[],
28500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28501 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28507 111^done,frame=@{level="0",func="callee3",
28508 args=[@{name="strarg",
28509 value="0x11940 \"A string argument.\""@}],
28510 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28511 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28516 @subheading The @code{-exec-run} Command
28519 @subsubheading Synopsis
28522 -exec-run [ --all | --thread-group N ] [ --start ]
28525 Starts execution of the inferior from the beginning. The inferior
28526 executes until either a breakpoint is encountered or the program
28527 exits. In the latter case the output will include an exit code, if
28528 the program has exited exceptionally.
28530 When neither the @samp{--all} nor the @samp{--thread-group} option
28531 is specified, the current inferior is started. If the
28532 @samp{--thread-group} option is specified, it should refer to a thread
28533 group of type @samp{process}, and that thread group will be started.
28534 If the @samp{--all} option is specified, then all inferiors will be started.
28536 Using the @samp{--start} option instructs the debugger to stop
28537 the execution at the start of the inferior's main subprogram,
28538 following the same behavior as the @code{start} command
28539 (@pxref{Starting}).
28541 @subsubheading @value{GDBN} Command
28543 The corresponding @value{GDBN} command is @samp{run}.
28545 @subsubheading Examples
28550 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28555 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28556 frame=@{func="main",args=[],file="recursive2.c",
28557 fullname="/home/foo/bar/recursive2.c",line="4"@}
28562 Program exited normally:
28570 *stopped,reason="exited-normally"
28575 Program exited exceptionally:
28583 *stopped,reason="exited",exit-code="01"
28587 Another way the program can terminate is if it receives a signal such as
28588 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28592 *stopped,reason="exited-signalled",signal-name="SIGINT",
28593 signal-meaning="Interrupt"
28597 @c @subheading -exec-signal
28600 @subheading The @code{-exec-step} Command
28603 @subsubheading Synopsis
28606 -exec-step [--reverse]
28609 Resumes execution of the inferior program, stopping when the beginning
28610 of the next source line is reached, if the next source line is not a
28611 function call. If it is, stop at the first instruction of the called
28612 function. If the @samp{--reverse} option is specified, resumes reverse
28613 execution of the inferior program, stopping at the beginning of the
28614 previously executed source line.
28616 @subsubheading @value{GDBN} Command
28618 The corresponding @value{GDBN} command is @samp{step}.
28620 @subsubheading Example
28622 Stepping into a function:
28628 *stopped,reason="end-stepping-range",
28629 frame=@{func="foo",args=[@{name="a",value="10"@},
28630 @{name="b",value="0"@}],file="recursive2.c",
28631 fullname="/home/foo/bar/recursive2.c",line="11"@}
28641 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28646 @subheading The @code{-exec-step-instruction} Command
28647 @findex -exec-step-instruction
28649 @subsubheading Synopsis
28652 -exec-step-instruction [--reverse]
28655 Resumes the inferior which executes one machine instruction. If the
28656 @samp{--reverse} option is specified, resumes reverse execution of the
28657 inferior program, stopping at the previously executed instruction.
28658 The output, once @value{GDBN} has stopped, will vary depending on
28659 whether we have stopped in the middle of a source line or not. In the
28660 former case, the address at which the program stopped will be printed
28663 @subsubheading @value{GDBN} Command
28665 The corresponding @value{GDBN} command is @samp{stepi}.
28667 @subsubheading Example
28671 -exec-step-instruction
28675 *stopped,reason="end-stepping-range",
28676 frame=@{func="foo",args=[],file="try.c",
28677 fullname="/home/foo/bar/try.c",line="10"@}
28679 -exec-step-instruction
28683 *stopped,reason="end-stepping-range",
28684 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28685 fullname="/home/foo/bar/try.c",line="10"@}
28690 @subheading The @code{-exec-until} Command
28691 @findex -exec-until
28693 @subsubheading Synopsis
28696 -exec-until [ @var{location} ]
28699 Executes the inferior until the @var{location} specified in the
28700 argument is reached. If there is no argument, the inferior executes
28701 until a source line greater than the current one is reached. The
28702 reason for stopping in this case will be @samp{location-reached}.
28704 @subsubheading @value{GDBN} Command
28706 The corresponding @value{GDBN} command is @samp{until}.
28708 @subsubheading Example
28712 -exec-until recursive2.c:6
28716 *stopped,reason="location-reached",frame=@{func="main",args=[],
28717 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28722 @subheading -file-clear
28723 Is this going away????
28726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28727 @node GDB/MI Stack Manipulation
28728 @section @sc{gdb/mi} Stack Manipulation Commands
28730 @subheading The @code{-enable-frame-filters} Command
28731 @findex -enable-frame-filters
28734 -enable-frame-filters
28737 @value{GDBN} allows Python-based frame filters to affect the output of
28738 the MI commands relating to stack traces. As there is no way to
28739 implement this in a fully backward-compatible way, a front end must
28740 request that this functionality be enabled.
28742 Once enabled, this feature cannot be disabled.
28744 Note that if Python support has not been compiled into @value{GDBN},
28745 this command will still succeed (and do nothing).
28747 @subheading The @code{-stack-info-frame} Command
28748 @findex -stack-info-frame
28750 @subsubheading Synopsis
28756 Get info on the selected frame.
28758 @subsubheading @value{GDBN} Command
28760 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28761 (without arguments).
28763 @subsubheading Example
28768 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28769 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28770 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28774 @subheading The @code{-stack-info-depth} Command
28775 @findex -stack-info-depth
28777 @subsubheading Synopsis
28780 -stack-info-depth [ @var{max-depth} ]
28783 Return the depth of the stack. If the integer argument @var{max-depth}
28784 is specified, do not count beyond @var{max-depth} frames.
28786 @subsubheading @value{GDBN} Command
28788 There's no equivalent @value{GDBN} command.
28790 @subsubheading Example
28792 For a stack with frame levels 0 through 11:
28799 -stack-info-depth 4
28802 -stack-info-depth 12
28805 -stack-info-depth 11
28808 -stack-info-depth 13
28813 @anchor{-stack-list-arguments}
28814 @subheading The @code{-stack-list-arguments} Command
28815 @findex -stack-list-arguments
28817 @subsubheading Synopsis
28820 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28821 [ @var{low-frame} @var{high-frame} ]
28824 Display a list of the arguments for the frames between @var{low-frame}
28825 and @var{high-frame} (inclusive). If @var{low-frame} and
28826 @var{high-frame} are not provided, list the arguments for the whole
28827 call stack. If the two arguments are equal, show the single frame
28828 at the corresponding level. It is an error if @var{low-frame} is
28829 larger than the actual number of frames. On the other hand,
28830 @var{high-frame} may be larger than the actual number of frames, in
28831 which case only existing frames will be returned.
28833 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28834 the variables; if it is 1 or @code{--all-values}, print also their
28835 values; and if it is 2 or @code{--simple-values}, print the name,
28836 type and value for simple data types, and the name and type for arrays,
28837 structures and unions. If the option @code{--no-frame-filters} is
28838 supplied, then Python frame filters will not be executed.
28840 If the @code{--skip-unavailable} option is specified, arguments that
28841 are not available are not listed. Partially available arguments
28842 are still displayed, however.
28844 Use of this command to obtain arguments in a single frame is
28845 deprecated in favor of the @samp{-stack-list-variables} command.
28847 @subsubheading @value{GDBN} Command
28849 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28850 @samp{gdb_get_args} command which partially overlaps with the
28851 functionality of @samp{-stack-list-arguments}.
28853 @subsubheading Example
28860 frame=@{level="0",addr="0x00010734",func="callee4",
28861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28863 frame=@{level="1",addr="0x0001076c",func="callee3",
28864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28865 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28866 frame=@{level="2",addr="0x0001078c",func="callee2",
28867 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28868 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28869 frame=@{level="3",addr="0x000107b4",func="callee1",
28870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28871 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28872 frame=@{level="4",addr="0x000107e0",func="main",
28873 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28874 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28876 -stack-list-arguments 0
28879 frame=@{level="0",args=[]@},
28880 frame=@{level="1",args=[name="strarg"]@},
28881 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28882 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28883 frame=@{level="4",args=[]@}]
28885 -stack-list-arguments 1
28888 frame=@{level="0",args=[]@},
28890 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28891 frame=@{level="2",args=[
28892 @{name="intarg",value="2"@},
28893 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28894 @{frame=@{level="3",args=[
28895 @{name="intarg",value="2"@},
28896 @{name="strarg",value="0x11940 \"A string argument.\""@},
28897 @{name="fltarg",value="3.5"@}]@},
28898 frame=@{level="4",args=[]@}]
28900 -stack-list-arguments 0 2 2
28901 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28903 -stack-list-arguments 1 2 2
28904 ^done,stack-args=[frame=@{level="2",
28905 args=[@{name="intarg",value="2"@},
28906 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28910 @c @subheading -stack-list-exception-handlers
28913 @anchor{-stack-list-frames}
28914 @subheading The @code{-stack-list-frames} Command
28915 @findex -stack-list-frames
28917 @subsubheading Synopsis
28920 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28923 List the frames currently on the stack. For each frame it displays the
28928 The frame number, 0 being the topmost frame, i.e., the innermost function.
28930 The @code{$pc} value for that frame.
28934 File name of the source file where the function lives.
28935 @item @var{fullname}
28936 The full file name of the source file where the function lives.
28938 Line number corresponding to the @code{$pc}.
28940 The shared library where this function is defined. This is only given
28941 if the frame's function is not known.
28944 If invoked without arguments, this command prints a backtrace for the
28945 whole stack. If given two integer arguments, it shows the frames whose
28946 levels are between the two arguments (inclusive). If the two arguments
28947 are equal, it shows the single frame at the corresponding level. It is
28948 an error if @var{low-frame} is larger than the actual number of
28949 frames. On the other hand, @var{high-frame} may be larger than the
28950 actual number of frames, in which case only existing frames will be
28951 returned. If the option @code{--no-frame-filters} is supplied, then
28952 Python frame filters will not be executed.
28954 @subsubheading @value{GDBN} Command
28956 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28958 @subsubheading Example
28960 Full stack backtrace:
28966 [frame=@{level="0",addr="0x0001076c",func="foo",
28967 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28968 frame=@{level="1",addr="0x000107a4",func="foo",
28969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28970 frame=@{level="2",addr="0x000107a4",func="foo",
28971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28972 frame=@{level="3",addr="0x000107a4",func="foo",
28973 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28974 frame=@{level="4",addr="0x000107a4",func="foo",
28975 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28976 frame=@{level="5",addr="0x000107a4",func="foo",
28977 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28978 frame=@{level="6",addr="0x000107a4",func="foo",
28979 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28980 frame=@{level="7",addr="0x000107a4",func="foo",
28981 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28982 frame=@{level="8",addr="0x000107a4",func="foo",
28983 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28984 frame=@{level="9",addr="0x000107a4",func="foo",
28985 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28986 frame=@{level="10",addr="0x000107a4",func="foo",
28987 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28988 frame=@{level="11",addr="0x00010738",func="main",
28989 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28993 Show frames between @var{low_frame} and @var{high_frame}:
28997 -stack-list-frames 3 5
28999 [frame=@{level="3",addr="0x000107a4",func="foo",
29000 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29001 frame=@{level="4",addr="0x000107a4",func="foo",
29002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29003 frame=@{level="5",addr="0x000107a4",func="foo",
29004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29008 Show a single frame:
29012 -stack-list-frames 3 3
29014 [frame=@{level="3",addr="0x000107a4",func="foo",
29015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29020 @subheading The @code{-stack-list-locals} Command
29021 @findex -stack-list-locals
29022 @anchor{-stack-list-locals}
29024 @subsubheading Synopsis
29027 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29030 Display the local variable names for the selected frame. If
29031 @var{print-values} is 0 or @code{--no-values}, print only the names of
29032 the variables; if it is 1 or @code{--all-values}, print also their
29033 values; and if it is 2 or @code{--simple-values}, print the name,
29034 type and value for simple data types, and the name and type for arrays,
29035 structures and unions. In this last case, a frontend can immediately
29036 display the value of simple data types and create variable objects for
29037 other data types when the user wishes to explore their values in
29038 more detail. If the option @code{--no-frame-filters} is supplied, then
29039 Python frame filters will not be executed.
29041 If the @code{--skip-unavailable} option is specified, local variables
29042 that are not available are not listed. Partially available local
29043 variables are still displayed, however.
29045 This command is deprecated in favor of the
29046 @samp{-stack-list-variables} command.
29048 @subsubheading @value{GDBN} Command
29050 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29052 @subsubheading Example
29056 -stack-list-locals 0
29057 ^done,locals=[name="A",name="B",name="C"]
29059 -stack-list-locals --all-values
29060 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29061 @{name="C",value="@{1, 2, 3@}"@}]
29062 -stack-list-locals --simple-values
29063 ^done,locals=[@{name="A",type="int",value="1"@},
29064 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29068 @anchor{-stack-list-variables}
29069 @subheading The @code{-stack-list-variables} Command
29070 @findex -stack-list-variables
29072 @subsubheading Synopsis
29075 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29078 Display the names of local variables and function arguments for the selected frame. If
29079 @var{print-values} is 0 or @code{--no-values}, print only the names of
29080 the variables; if it is 1 or @code{--all-values}, print also their
29081 values; and if it is 2 or @code{--simple-values}, print the name,
29082 type and value for simple data types, and the name and type for arrays,
29083 structures and unions. If the option @code{--no-frame-filters} is
29084 supplied, then Python frame filters will not be executed.
29086 If the @code{--skip-unavailable} option is specified, local variables
29087 and arguments that are not available are not listed. Partially
29088 available arguments and local variables are still displayed, however.
29090 @subsubheading Example
29094 -stack-list-variables --thread 1 --frame 0 --all-values
29095 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29100 @subheading The @code{-stack-select-frame} Command
29101 @findex -stack-select-frame
29103 @subsubheading Synopsis
29106 -stack-select-frame @var{framenum}
29109 Change the selected frame. Select a different frame @var{framenum} on
29112 This command in deprecated in favor of passing the @samp{--frame}
29113 option to every command.
29115 @subsubheading @value{GDBN} Command
29117 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29118 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29120 @subsubheading Example
29124 -stack-select-frame 2
29129 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29130 @node GDB/MI Variable Objects
29131 @section @sc{gdb/mi} Variable Objects
29135 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29137 For the implementation of a variable debugger window (locals, watched
29138 expressions, etc.), we are proposing the adaptation of the existing code
29139 used by @code{Insight}.
29141 The two main reasons for that are:
29145 It has been proven in practice (it is already on its second generation).
29148 It will shorten development time (needless to say how important it is
29152 The original interface was designed to be used by Tcl code, so it was
29153 slightly changed so it could be used through @sc{gdb/mi}. This section
29154 describes the @sc{gdb/mi} operations that will be available and gives some
29155 hints about their use.
29157 @emph{Note}: In addition to the set of operations described here, we
29158 expect the @sc{gui} implementation of a variable window to require, at
29159 least, the following operations:
29162 @item @code{-gdb-show} @code{output-radix}
29163 @item @code{-stack-list-arguments}
29164 @item @code{-stack-list-locals}
29165 @item @code{-stack-select-frame}
29170 @subheading Introduction to Variable Objects
29172 @cindex variable objects in @sc{gdb/mi}
29174 Variable objects are "object-oriented" MI interface for examining and
29175 changing values of expressions. Unlike some other MI interfaces that
29176 work with expressions, variable objects are specifically designed for
29177 simple and efficient presentation in the frontend. A variable object
29178 is identified by string name. When a variable object is created, the
29179 frontend specifies the expression for that variable object. The
29180 expression can be a simple variable, or it can be an arbitrary complex
29181 expression, and can even involve CPU registers. After creating a
29182 variable object, the frontend can invoke other variable object
29183 operations---for example to obtain or change the value of a variable
29184 object, or to change display format.
29186 Variable objects have hierarchical tree structure. Any variable object
29187 that corresponds to a composite type, such as structure in C, has
29188 a number of child variable objects, for example corresponding to each
29189 element of a structure. A child variable object can itself have
29190 children, recursively. Recursion ends when we reach
29191 leaf variable objects, which always have built-in types. Child variable
29192 objects are created only by explicit request, so if a frontend
29193 is not interested in the children of a particular variable object, no
29194 child will be created.
29196 For a leaf variable object it is possible to obtain its value as a
29197 string, or set the value from a string. String value can be also
29198 obtained for a non-leaf variable object, but it's generally a string
29199 that only indicates the type of the object, and does not list its
29200 contents. Assignment to a non-leaf variable object is not allowed.
29202 A frontend does not need to read the values of all variable objects each time
29203 the program stops. Instead, MI provides an update command that lists all
29204 variable objects whose values has changed since the last update
29205 operation. This considerably reduces the amount of data that must
29206 be transferred to the frontend. As noted above, children variable
29207 objects are created on demand, and only leaf variable objects have a
29208 real value. As result, gdb will read target memory only for leaf
29209 variables that frontend has created.
29211 The automatic update is not always desirable. For example, a frontend
29212 might want to keep a value of some expression for future reference,
29213 and never update it. For another example, fetching memory is
29214 relatively slow for embedded targets, so a frontend might want
29215 to disable automatic update for the variables that are either not
29216 visible on the screen, or ``closed''. This is possible using so
29217 called ``frozen variable objects''. Such variable objects are never
29218 implicitly updated.
29220 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29221 fixed variable object, the expression is parsed when the variable
29222 object is created, including associating identifiers to specific
29223 variables. The meaning of expression never changes. For a floating
29224 variable object the values of variables whose names appear in the
29225 expressions are re-evaluated every time in the context of the current
29226 frame. Consider this example:
29231 struct work_state state;
29238 If a fixed variable object for the @code{state} variable is created in
29239 this function, and we enter the recursive call, the variable
29240 object will report the value of @code{state} in the top-level
29241 @code{do_work} invocation. On the other hand, a floating variable
29242 object will report the value of @code{state} in the current frame.
29244 If an expression specified when creating a fixed variable object
29245 refers to a local variable, the variable object becomes bound to the
29246 thread and frame in which the variable object is created. When such
29247 variable object is updated, @value{GDBN} makes sure that the
29248 thread/frame combination the variable object is bound to still exists,
29249 and re-evaluates the variable object in context of that thread/frame.
29251 The following is the complete set of @sc{gdb/mi} operations defined to
29252 access this functionality:
29254 @multitable @columnfractions .4 .6
29255 @item @strong{Operation}
29256 @tab @strong{Description}
29258 @item @code{-enable-pretty-printing}
29259 @tab enable Python-based pretty-printing
29260 @item @code{-var-create}
29261 @tab create a variable object
29262 @item @code{-var-delete}
29263 @tab delete the variable object and/or its children
29264 @item @code{-var-set-format}
29265 @tab set the display format of this variable
29266 @item @code{-var-show-format}
29267 @tab show the display format of this variable
29268 @item @code{-var-info-num-children}
29269 @tab tells how many children this object has
29270 @item @code{-var-list-children}
29271 @tab return a list of the object's children
29272 @item @code{-var-info-type}
29273 @tab show the type of this variable object
29274 @item @code{-var-info-expression}
29275 @tab print parent-relative expression that this variable object represents
29276 @item @code{-var-info-path-expression}
29277 @tab print full expression that this variable object represents
29278 @item @code{-var-show-attributes}
29279 @tab is this variable editable? does it exist here?
29280 @item @code{-var-evaluate-expression}
29281 @tab get the value of this variable
29282 @item @code{-var-assign}
29283 @tab set the value of this variable
29284 @item @code{-var-update}
29285 @tab update the variable and its children
29286 @item @code{-var-set-frozen}
29287 @tab set frozeness attribute
29288 @item @code{-var-set-update-range}
29289 @tab set range of children to display on update
29292 In the next subsection we describe each operation in detail and suggest
29293 how it can be used.
29295 @subheading Description And Use of Operations on Variable Objects
29297 @subheading The @code{-enable-pretty-printing} Command
29298 @findex -enable-pretty-printing
29301 -enable-pretty-printing
29304 @value{GDBN} allows Python-based visualizers to affect the output of the
29305 MI variable object commands. However, because there was no way to
29306 implement this in a fully backward-compatible way, a front end must
29307 request that this functionality be enabled.
29309 Once enabled, this feature cannot be disabled.
29311 Note that if Python support has not been compiled into @value{GDBN},
29312 this command will still succeed (and do nothing).
29314 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29315 may work differently in future versions of @value{GDBN}.
29317 @subheading The @code{-var-create} Command
29318 @findex -var-create
29320 @subsubheading Synopsis
29323 -var-create @{@var{name} | "-"@}
29324 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29327 This operation creates a variable object, which allows the monitoring of
29328 a variable, the result of an expression, a memory cell or a CPU
29331 The @var{name} parameter is the string by which the object can be
29332 referenced. It must be unique. If @samp{-} is specified, the varobj
29333 system will generate a string ``varNNNNNN'' automatically. It will be
29334 unique provided that one does not specify @var{name} of that format.
29335 The command fails if a duplicate name is found.
29337 The frame under which the expression should be evaluated can be
29338 specified by @var{frame-addr}. A @samp{*} indicates that the current
29339 frame should be used. A @samp{@@} indicates that a floating variable
29340 object must be created.
29342 @var{expression} is any expression valid on the current language set (must not
29343 begin with a @samp{*}), or one of the following:
29347 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29350 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29353 @samp{$@var{regname}} --- a CPU register name
29356 @cindex dynamic varobj
29357 A varobj's contents may be provided by a Python-based pretty-printer. In this
29358 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29359 have slightly different semantics in some cases. If the
29360 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29361 will never create a dynamic varobj. This ensures backward
29362 compatibility for existing clients.
29364 @subsubheading Result
29366 This operation returns attributes of the newly-created varobj. These
29371 The name of the varobj.
29374 The number of children of the varobj. This number is not necessarily
29375 reliable for a dynamic varobj. Instead, you must examine the
29376 @samp{has_more} attribute.
29379 The varobj's scalar value. For a varobj whose type is some sort of
29380 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29381 will not be interesting.
29384 The varobj's type. This is a string representation of the type, as
29385 would be printed by the @value{GDBN} CLI. If @samp{print object}
29386 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29387 @emph{actual} (derived) type of the object is shown rather than the
29388 @emph{declared} one.
29391 If a variable object is bound to a specific thread, then this is the
29392 thread's global identifier.
29395 For a dynamic varobj, this indicates whether there appear to be any
29396 children available. For a non-dynamic varobj, this will be 0.
29399 This attribute will be present and have the value @samp{1} if the
29400 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29401 then this attribute will not be present.
29404 A dynamic varobj can supply a display hint to the front end. The
29405 value comes directly from the Python pretty-printer object's
29406 @code{display_hint} method. @xref{Pretty Printing API}.
29409 Typical output will look like this:
29412 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29413 has_more="@var{has_more}"
29417 @subheading The @code{-var-delete} Command
29418 @findex -var-delete
29420 @subsubheading Synopsis
29423 -var-delete [ -c ] @var{name}
29426 Deletes a previously created variable object and all of its children.
29427 With the @samp{-c} option, just deletes the children.
29429 Returns an error if the object @var{name} is not found.
29432 @subheading The @code{-var-set-format} Command
29433 @findex -var-set-format
29435 @subsubheading Synopsis
29438 -var-set-format @var{name} @var{format-spec}
29441 Sets the output format for the value of the object @var{name} to be
29444 @anchor{-var-set-format}
29445 The syntax for the @var{format-spec} is as follows:
29448 @var{format-spec} @expansion{}
29449 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29452 The natural format is the default format choosen automatically
29453 based on the variable type (like decimal for an @code{int}, hex
29454 for pointers, etc.).
29456 The zero-hexadecimal format has a representation similar to hexadecimal
29457 but with padding zeroes to the left of the value. For example, a 32-bit
29458 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29459 zero-hexadecimal format.
29461 For a variable with children, the format is set only on the
29462 variable itself, and the children are not affected.
29464 @subheading The @code{-var-show-format} Command
29465 @findex -var-show-format
29467 @subsubheading Synopsis
29470 -var-show-format @var{name}
29473 Returns the format used to display the value of the object @var{name}.
29476 @var{format} @expansion{}
29481 @subheading The @code{-var-info-num-children} Command
29482 @findex -var-info-num-children
29484 @subsubheading Synopsis
29487 -var-info-num-children @var{name}
29490 Returns the number of children of a variable object @var{name}:
29496 Note that this number is not completely reliable for a dynamic varobj.
29497 It will return the current number of children, but more children may
29501 @subheading The @code{-var-list-children} Command
29502 @findex -var-list-children
29504 @subsubheading Synopsis
29507 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29509 @anchor{-var-list-children}
29511 Return a list of the children of the specified variable object and
29512 create variable objects for them, if they do not already exist. With
29513 a single argument or if @var{print-values} has a value of 0 or
29514 @code{--no-values}, print only the names of the variables; if
29515 @var{print-values} is 1 or @code{--all-values}, also print their
29516 values; and if it is 2 or @code{--simple-values} print the name and
29517 value for simple data types and just the name for arrays, structures
29520 @var{from} and @var{to}, if specified, indicate the range of children
29521 to report. If @var{from} or @var{to} is less than zero, the range is
29522 reset and all children will be reported. Otherwise, children starting
29523 at @var{from} (zero-based) and up to and excluding @var{to} will be
29526 If a child range is requested, it will only affect the current call to
29527 @code{-var-list-children}, but not future calls to @code{-var-update}.
29528 For this, you must instead use @code{-var-set-update-range}. The
29529 intent of this approach is to enable a front end to implement any
29530 update approach it likes; for example, scrolling a view may cause the
29531 front end to request more children with @code{-var-list-children}, and
29532 then the front end could call @code{-var-set-update-range} with a
29533 different range to ensure that future updates are restricted to just
29536 For each child the following results are returned:
29541 Name of the variable object created for this child.
29544 The expression to be shown to the user by the front end to designate this child.
29545 For example this may be the name of a structure member.
29547 For a dynamic varobj, this value cannot be used to form an
29548 expression. There is no way to do this at all with a dynamic varobj.
29550 For C/C@t{++} structures there are several pseudo children returned to
29551 designate access qualifiers. For these pseudo children @var{exp} is
29552 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29553 type and value are not present.
29555 A dynamic varobj will not report the access qualifying
29556 pseudo-children, regardless of the language. This information is not
29557 available at all with a dynamic varobj.
29560 Number of children this child has. For a dynamic varobj, this will be
29564 The type of the child. If @samp{print object}
29565 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29566 @emph{actual} (derived) type of the object is shown rather than the
29567 @emph{declared} one.
29570 If values were requested, this is the value.
29573 If this variable object is associated with a thread, this is the
29574 thread's global thread id. Otherwise this result is not present.
29577 If the variable object is frozen, this variable will be present with a value of 1.
29580 A dynamic varobj can supply a display hint to the front end. The
29581 value comes directly from the Python pretty-printer object's
29582 @code{display_hint} method. @xref{Pretty Printing API}.
29585 This attribute will be present and have the value @samp{1} if the
29586 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29587 then this attribute will not be present.
29591 The result may have its own attributes:
29595 A dynamic varobj can supply a display hint to the front end. The
29596 value comes directly from the Python pretty-printer object's
29597 @code{display_hint} method. @xref{Pretty Printing API}.
29600 This is an integer attribute which is nonzero if there are children
29601 remaining after the end of the selected range.
29604 @subsubheading Example
29608 -var-list-children n
29609 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29610 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29612 -var-list-children --all-values n
29613 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29614 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29618 @subheading The @code{-var-info-type} Command
29619 @findex -var-info-type
29621 @subsubheading Synopsis
29624 -var-info-type @var{name}
29627 Returns the type of the specified variable @var{name}. The type is
29628 returned as a string in the same format as it is output by the
29632 type=@var{typename}
29636 @subheading The @code{-var-info-expression} Command
29637 @findex -var-info-expression
29639 @subsubheading Synopsis
29642 -var-info-expression @var{name}
29645 Returns a string that is suitable for presenting this
29646 variable object in user interface. The string is generally
29647 not valid expression in the current language, and cannot be evaluated.
29649 For example, if @code{a} is an array, and variable object
29650 @code{A} was created for @code{a}, then we'll get this output:
29653 (gdb) -var-info-expression A.1
29654 ^done,lang="C",exp="1"
29658 Here, the value of @code{lang} is the language name, which can be
29659 found in @ref{Supported Languages}.
29661 Note that the output of the @code{-var-list-children} command also
29662 includes those expressions, so the @code{-var-info-expression} command
29665 @subheading The @code{-var-info-path-expression} Command
29666 @findex -var-info-path-expression
29668 @subsubheading Synopsis
29671 -var-info-path-expression @var{name}
29674 Returns an expression that can be evaluated in the current
29675 context and will yield the same value that a variable object has.
29676 Compare this with the @code{-var-info-expression} command, which
29677 result can be used only for UI presentation. Typical use of
29678 the @code{-var-info-path-expression} command is creating a
29679 watchpoint from a variable object.
29681 This command is currently not valid for children of a dynamic varobj,
29682 and will give an error when invoked on one.
29684 For example, suppose @code{C} is a C@t{++} class, derived from class
29685 @code{Base}, and that the @code{Base} class has a member called
29686 @code{m_size}. Assume a variable @code{c} is has the type of
29687 @code{C} and a variable object @code{C} was created for variable
29688 @code{c}. Then, we'll get this output:
29690 (gdb) -var-info-path-expression C.Base.public.m_size
29691 ^done,path_expr=((Base)c).m_size)
29694 @subheading The @code{-var-show-attributes} Command
29695 @findex -var-show-attributes
29697 @subsubheading Synopsis
29700 -var-show-attributes @var{name}
29703 List attributes of the specified variable object @var{name}:
29706 status=@var{attr} [ ( ,@var{attr} )* ]
29710 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29712 @subheading The @code{-var-evaluate-expression} Command
29713 @findex -var-evaluate-expression
29715 @subsubheading Synopsis
29718 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29721 Evaluates the expression that is represented by the specified variable
29722 object and returns its value as a string. The format of the string
29723 can be specified with the @samp{-f} option. The possible values of
29724 this option are the same as for @code{-var-set-format}
29725 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29726 the current display format will be used. The current display format
29727 can be changed using the @code{-var-set-format} command.
29733 Note that one must invoke @code{-var-list-children} for a variable
29734 before the value of a child variable can be evaluated.
29736 @subheading The @code{-var-assign} Command
29737 @findex -var-assign
29739 @subsubheading Synopsis
29742 -var-assign @var{name} @var{expression}
29745 Assigns the value of @var{expression} to the variable object specified
29746 by @var{name}. The object must be @samp{editable}. If the variable's
29747 value is altered by the assign, the variable will show up in any
29748 subsequent @code{-var-update} list.
29750 @subsubheading Example
29758 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29762 @subheading The @code{-var-update} Command
29763 @findex -var-update
29765 @subsubheading Synopsis
29768 -var-update [@var{print-values}] @{@var{name} | "*"@}
29771 Reevaluate the expressions corresponding to the variable object
29772 @var{name} and all its direct and indirect children, and return the
29773 list of variable objects whose values have changed; @var{name} must
29774 be a root variable object. Here, ``changed'' means that the result of
29775 @code{-var-evaluate-expression} before and after the
29776 @code{-var-update} is different. If @samp{*} is used as the variable
29777 object names, all existing variable objects are updated, except
29778 for frozen ones (@pxref{-var-set-frozen}). The option
29779 @var{print-values} determines whether both names and values, or just
29780 names are printed. The possible values of this option are the same
29781 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29782 recommended to use the @samp{--all-values} option, to reduce the
29783 number of MI commands needed on each program stop.
29785 With the @samp{*} parameter, if a variable object is bound to a
29786 currently running thread, it will not be updated, without any
29789 If @code{-var-set-update-range} was previously used on a varobj, then
29790 only the selected range of children will be reported.
29792 @code{-var-update} reports all the changed varobjs in a tuple named
29795 Each item in the change list is itself a tuple holding:
29799 The name of the varobj.
29802 If values were requested for this update, then this field will be
29803 present and will hold the value of the varobj.
29806 @anchor{-var-update}
29807 This field is a string which may take one of three values:
29811 The variable object's current value is valid.
29814 The variable object does not currently hold a valid value but it may
29815 hold one in the future if its associated expression comes back into
29819 The variable object no longer holds a valid value.
29820 This can occur when the executable file being debugged has changed,
29821 either through recompilation or by using the @value{GDBN} @code{file}
29822 command. The front end should normally choose to delete these variable
29826 In the future new values may be added to this list so the front should
29827 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29830 This is only present if the varobj is still valid. If the type
29831 changed, then this will be the string @samp{true}; otherwise it will
29834 When a varobj's type changes, its children are also likely to have
29835 become incorrect. Therefore, the varobj's children are automatically
29836 deleted when this attribute is @samp{true}. Also, the varobj's update
29837 range, when set using the @code{-var-set-update-range} command, is
29841 If the varobj's type changed, then this field will be present and will
29844 @item new_num_children
29845 For a dynamic varobj, if the number of children changed, or if the
29846 type changed, this will be the new number of children.
29848 The @samp{numchild} field in other varobj responses is generally not
29849 valid for a dynamic varobj -- it will show the number of children that
29850 @value{GDBN} knows about, but because dynamic varobjs lazily
29851 instantiate their children, this will not reflect the number of
29852 children which may be available.
29854 The @samp{new_num_children} attribute only reports changes to the
29855 number of children known by @value{GDBN}. This is the only way to
29856 detect whether an update has removed children (which necessarily can
29857 only happen at the end of the update range).
29860 The display hint, if any.
29863 This is an integer value, which will be 1 if there are more children
29864 available outside the varobj's update range.
29867 This attribute will be present and have the value @samp{1} if the
29868 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29869 then this attribute will not be present.
29872 If new children were added to a dynamic varobj within the selected
29873 update range (as set by @code{-var-set-update-range}), then they will
29874 be listed in this attribute.
29877 @subsubheading Example
29884 -var-update --all-values var1
29885 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29886 type_changed="false"@}]
29890 @subheading The @code{-var-set-frozen} Command
29891 @findex -var-set-frozen
29892 @anchor{-var-set-frozen}
29894 @subsubheading Synopsis
29897 -var-set-frozen @var{name} @var{flag}
29900 Set the frozenness flag on the variable object @var{name}. The
29901 @var{flag} parameter should be either @samp{1} to make the variable
29902 frozen or @samp{0} to make it unfrozen. If a variable object is
29903 frozen, then neither itself, nor any of its children, are
29904 implicitly updated by @code{-var-update} of
29905 a parent variable or by @code{-var-update *}. Only
29906 @code{-var-update} of the variable itself will update its value and
29907 values of its children. After a variable object is unfrozen, it is
29908 implicitly updated by all subsequent @code{-var-update} operations.
29909 Unfreezing a variable does not update it, only subsequent
29910 @code{-var-update} does.
29912 @subsubheading Example
29916 -var-set-frozen V 1
29921 @subheading The @code{-var-set-update-range} command
29922 @findex -var-set-update-range
29923 @anchor{-var-set-update-range}
29925 @subsubheading Synopsis
29928 -var-set-update-range @var{name} @var{from} @var{to}
29931 Set the range of children to be returned by future invocations of
29932 @code{-var-update}.
29934 @var{from} and @var{to} indicate the range of children to report. If
29935 @var{from} or @var{to} is less than zero, the range is reset and all
29936 children will be reported. Otherwise, children starting at @var{from}
29937 (zero-based) and up to and excluding @var{to} will be reported.
29939 @subsubheading Example
29943 -var-set-update-range V 1 2
29947 @subheading The @code{-var-set-visualizer} command
29948 @findex -var-set-visualizer
29949 @anchor{-var-set-visualizer}
29951 @subsubheading Synopsis
29954 -var-set-visualizer @var{name} @var{visualizer}
29957 Set a visualizer for the variable object @var{name}.
29959 @var{visualizer} is the visualizer to use. The special value
29960 @samp{None} means to disable any visualizer in use.
29962 If not @samp{None}, @var{visualizer} must be a Python expression.
29963 This expression must evaluate to a callable object which accepts a
29964 single argument. @value{GDBN} will call this object with the value of
29965 the varobj @var{name} as an argument (this is done so that the same
29966 Python pretty-printing code can be used for both the CLI and MI).
29967 When called, this object must return an object which conforms to the
29968 pretty-printing interface (@pxref{Pretty Printing API}).
29970 The pre-defined function @code{gdb.default_visualizer} may be used to
29971 select a visualizer by following the built-in process
29972 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29973 a varobj is created, and so ordinarily is not needed.
29975 This feature is only available if Python support is enabled. The MI
29976 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29977 can be used to check this.
29979 @subsubheading Example
29981 Resetting the visualizer:
29985 -var-set-visualizer V None
29989 Reselecting the default (type-based) visualizer:
29993 -var-set-visualizer V gdb.default_visualizer
29997 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29998 can be used to instantiate this class for a varobj:
30002 -var-set-visualizer V "lambda val: SomeClass()"
30006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30007 @node GDB/MI Data Manipulation
30008 @section @sc{gdb/mi} Data Manipulation
30010 @cindex data manipulation, in @sc{gdb/mi}
30011 @cindex @sc{gdb/mi}, data manipulation
30012 This section describes the @sc{gdb/mi} commands that manipulate data:
30013 examine memory and registers, evaluate expressions, etc.
30015 For details about what an addressable memory unit is,
30016 @pxref{addressable memory unit}.
30018 @c REMOVED FROM THE INTERFACE.
30019 @c @subheading -data-assign
30020 @c Change the value of a program variable. Plenty of side effects.
30021 @c @subsubheading GDB Command
30023 @c @subsubheading Example
30026 @subheading The @code{-data-disassemble} Command
30027 @findex -data-disassemble
30029 @subsubheading Synopsis
30033 [ -s @var{start-addr} -e @var{end-addr} ]
30034 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30042 @item @var{start-addr}
30043 is the beginning address (or @code{$pc})
30044 @item @var{end-addr}
30046 @item @var{filename}
30047 is the name of the file to disassemble
30048 @item @var{linenum}
30049 is the line number to disassemble around
30051 is the number of disassembly lines to be produced. If it is -1,
30052 the whole function will be disassembled, in case no @var{end-addr} is
30053 specified. If @var{end-addr} is specified as a non-zero value, and
30054 @var{lines} is lower than the number of disassembly lines between
30055 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30056 displayed; if @var{lines} is higher than the number of lines between
30057 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30062 @item 0 disassembly only
30063 @item 1 mixed source and disassembly (deprecated)
30064 @item 2 disassembly with raw opcodes
30065 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30066 @item 4 mixed source and disassembly
30067 @item 5 mixed source and disassembly with raw opcodes
30070 Modes 1 and 3 are deprecated. The output is ``source centric''
30071 which hasn't proved useful in practice.
30072 @xref{Machine Code}, for a discussion of the difference between
30073 @code{/m} and @code{/s} output of the @code{disassemble} command.
30076 @subsubheading Result
30078 The result of the @code{-data-disassemble} command will be a list named
30079 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30080 used with the @code{-data-disassemble} command.
30082 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30087 The address at which this instruction was disassembled.
30090 The name of the function this instruction is within.
30093 The decimal offset in bytes from the start of @samp{func-name}.
30096 The text disassembly for this @samp{address}.
30099 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30100 bytes for the @samp{inst} field.
30104 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30105 @samp{src_and_asm_line}, each of which has the following fields:
30109 The line number within @samp{file}.
30112 The file name from the compilation unit. This might be an absolute
30113 file name or a relative file name depending on the compile command
30117 Absolute file name of @samp{file}. It is converted to a canonical form
30118 using the source file search path
30119 (@pxref{Source Path, ,Specifying Source Directories})
30120 and after resolving all the symbolic links.
30122 If the source file is not found this field will contain the path as
30123 present in the debug information.
30125 @item line_asm_insn
30126 This is a list of tuples containing the disassembly for @samp{line} in
30127 @samp{file}. The fields of each tuple are the same as for
30128 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30129 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30134 Note that whatever included in the @samp{inst} field, is not
30135 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30138 @subsubheading @value{GDBN} Command
30140 The corresponding @value{GDBN} command is @samp{disassemble}.
30142 @subsubheading Example
30144 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30148 -data-disassemble -s $pc -e "$pc + 20" -- 0
30151 @{address="0x000107c0",func-name="main",offset="4",
30152 inst="mov 2, %o0"@},
30153 @{address="0x000107c4",func-name="main",offset="8",
30154 inst="sethi %hi(0x11800), %o2"@},
30155 @{address="0x000107c8",func-name="main",offset="12",
30156 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30157 @{address="0x000107cc",func-name="main",offset="16",
30158 inst="sethi %hi(0x11800), %o2"@},
30159 @{address="0x000107d0",func-name="main",offset="20",
30160 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30164 Disassemble the whole @code{main} function. Line 32 is part of
30168 -data-disassemble -f basics.c -l 32 -- 0
30170 @{address="0x000107bc",func-name="main",offset="0",
30171 inst="save %sp, -112, %sp"@},
30172 @{address="0x000107c0",func-name="main",offset="4",
30173 inst="mov 2, %o0"@},
30174 @{address="0x000107c4",func-name="main",offset="8",
30175 inst="sethi %hi(0x11800), %o2"@},
30177 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30178 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30182 Disassemble 3 instructions from the start of @code{main}:
30186 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30188 @{address="0x000107bc",func-name="main",offset="0",
30189 inst="save %sp, -112, %sp"@},
30190 @{address="0x000107c0",func-name="main",offset="4",
30191 inst="mov 2, %o0"@},
30192 @{address="0x000107c4",func-name="main",offset="8",
30193 inst="sethi %hi(0x11800), %o2"@}]
30197 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30201 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30203 src_and_asm_line=@{line="31",
30204 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30205 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30206 line_asm_insn=[@{address="0x000107bc",
30207 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30208 src_and_asm_line=@{line="32",
30209 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30210 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30211 line_asm_insn=[@{address="0x000107c0",
30212 func-name="main",offset="4",inst="mov 2, %o0"@},
30213 @{address="0x000107c4",func-name="main",offset="8",
30214 inst="sethi %hi(0x11800), %o2"@}]@}]
30219 @subheading The @code{-data-evaluate-expression} Command
30220 @findex -data-evaluate-expression
30222 @subsubheading Synopsis
30225 -data-evaluate-expression @var{expr}
30228 Evaluate @var{expr} as an expression. The expression could contain an
30229 inferior function call. The function call will execute synchronously.
30230 If the expression contains spaces, it must be enclosed in double quotes.
30232 @subsubheading @value{GDBN} Command
30234 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30235 @samp{call}. In @code{gdbtk} only, there's a corresponding
30236 @samp{gdb_eval} command.
30238 @subsubheading Example
30240 In the following example, the numbers that precede the commands are the
30241 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30242 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30246 211-data-evaluate-expression A
30249 311-data-evaluate-expression &A
30250 311^done,value="0xefffeb7c"
30252 411-data-evaluate-expression A+3
30255 511-data-evaluate-expression "A + 3"
30261 @subheading The @code{-data-list-changed-registers} Command
30262 @findex -data-list-changed-registers
30264 @subsubheading Synopsis
30267 -data-list-changed-registers
30270 Display a list of the registers that have changed.
30272 @subsubheading @value{GDBN} Command
30274 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30275 has the corresponding command @samp{gdb_changed_register_list}.
30277 @subsubheading Example
30279 On a PPC MBX board:
30287 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30288 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30291 -data-list-changed-registers
30292 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30293 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30294 "24","25","26","27","28","30","31","64","65","66","67","69"]
30299 @subheading The @code{-data-list-register-names} Command
30300 @findex -data-list-register-names
30302 @subsubheading Synopsis
30305 -data-list-register-names [ ( @var{regno} )+ ]
30308 Show a list of register names for the current target. If no arguments
30309 are given, it shows a list of the names of all the registers. If
30310 integer numbers are given as arguments, it will print a list of the
30311 names of the registers corresponding to the arguments. To ensure
30312 consistency between a register name and its number, the output list may
30313 include empty register names.
30315 @subsubheading @value{GDBN} Command
30317 @value{GDBN} does not have a command which corresponds to
30318 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30319 corresponding command @samp{gdb_regnames}.
30321 @subsubheading Example
30323 For the PPC MBX board:
30326 -data-list-register-names
30327 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30328 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30329 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30330 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30331 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30332 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30333 "", "pc","ps","cr","lr","ctr","xer"]
30335 -data-list-register-names 1 2 3
30336 ^done,register-names=["r1","r2","r3"]
30340 @subheading The @code{-data-list-register-values} Command
30341 @findex -data-list-register-values
30343 @subsubheading Synopsis
30346 -data-list-register-values
30347 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30350 Display the registers' contents. The format according to which the
30351 registers' contents are to be returned is given by @var{fmt}, followed
30352 by an optional list of numbers specifying the registers to display. A
30353 missing list of numbers indicates that the contents of all the
30354 registers must be returned. The @code{--skip-unavailable} option
30355 indicates that only the available registers are to be returned.
30357 Allowed formats for @var{fmt} are:
30374 @subsubheading @value{GDBN} Command
30376 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30377 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30379 @subsubheading Example
30381 For a PPC MBX board (note: line breaks are for readability only, they
30382 don't appear in the actual output):
30386 -data-list-register-values r 64 65
30387 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30388 @{number="65",value="0x00029002"@}]
30390 -data-list-register-values x
30391 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30392 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30393 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30394 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30395 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30396 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30397 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30398 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30399 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30400 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30401 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30402 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30403 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30404 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30405 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30406 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30407 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30408 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30409 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30410 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30411 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30412 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30413 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30414 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30415 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30416 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30417 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30418 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30419 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30420 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30421 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30422 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30423 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30424 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30425 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30426 @{number="69",value="0x20002b03"@}]
30431 @subheading The @code{-data-read-memory} Command
30432 @findex -data-read-memory
30434 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30436 @subsubheading Synopsis
30439 -data-read-memory [ -o @var{byte-offset} ]
30440 @var{address} @var{word-format} @var{word-size}
30441 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30448 @item @var{address}
30449 An expression specifying the address of the first memory word to be
30450 read. Complex expressions containing embedded white space should be
30451 quoted using the C convention.
30453 @item @var{word-format}
30454 The format to be used to print the memory words. The notation is the
30455 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30458 @item @var{word-size}
30459 The size of each memory word in bytes.
30461 @item @var{nr-rows}
30462 The number of rows in the output table.
30464 @item @var{nr-cols}
30465 The number of columns in the output table.
30468 If present, indicates that each row should include an @sc{ascii} dump. The
30469 value of @var{aschar} is used as a padding character when a byte is not a
30470 member of the printable @sc{ascii} character set (printable @sc{ascii}
30471 characters are those whose code is between 32 and 126, inclusively).
30473 @item @var{byte-offset}
30474 An offset to add to the @var{address} before fetching memory.
30477 This command displays memory contents as a table of @var{nr-rows} by
30478 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30479 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30480 (returned as @samp{total-bytes}). Should less than the requested number
30481 of bytes be returned by the target, the missing words are identified
30482 using @samp{N/A}. The number of bytes read from the target is returned
30483 in @samp{nr-bytes} and the starting address used to read memory in
30486 The address of the next/previous row or page is available in
30487 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30490 @subsubheading @value{GDBN} Command
30492 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30493 @samp{gdb_get_mem} memory read command.
30495 @subsubheading Example
30497 Read six bytes of memory starting at @code{bytes+6} but then offset by
30498 @code{-6} bytes. Format as three rows of two columns. One byte per
30499 word. Display each word in hex.
30503 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30504 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30505 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30506 prev-page="0x0000138a",memory=[
30507 @{addr="0x00001390",data=["0x00","0x01"]@},
30508 @{addr="0x00001392",data=["0x02","0x03"]@},
30509 @{addr="0x00001394",data=["0x04","0x05"]@}]
30513 Read two bytes of memory starting at address @code{shorts + 64} and
30514 display as a single word formatted in decimal.
30518 5-data-read-memory shorts+64 d 2 1 1
30519 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30520 next-row="0x00001512",prev-row="0x0000150e",
30521 next-page="0x00001512",prev-page="0x0000150e",memory=[
30522 @{addr="0x00001510",data=["128"]@}]
30526 Read thirty two bytes of memory starting at @code{bytes+16} and format
30527 as eight rows of four columns. Include a string encoding with @samp{x}
30528 used as the non-printable character.
30532 4-data-read-memory bytes+16 x 1 8 4 x
30533 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30534 next-row="0x000013c0",prev-row="0x0000139c",
30535 next-page="0x000013c0",prev-page="0x00001380",memory=[
30536 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30537 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30538 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30539 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30540 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30541 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30542 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30543 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30547 @subheading The @code{-data-read-memory-bytes} Command
30548 @findex -data-read-memory-bytes
30550 @subsubheading Synopsis
30553 -data-read-memory-bytes [ -o @var{offset} ]
30554 @var{address} @var{count}
30561 @item @var{address}
30562 An expression specifying the address of the first addressable memory unit
30563 to be read. Complex expressions containing embedded white space should be
30564 quoted using the C convention.
30567 The number of addressable memory units to read. This should be an integer
30571 The offset relative to @var{address} at which to start reading. This
30572 should be an integer literal. This option is provided so that a frontend
30573 is not required to first evaluate address and then perform address
30574 arithmetics itself.
30578 This command attempts to read all accessible memory regions in the
30579 specified range. First, all regions marked as unreadable in the memory
30580 map (if one is defined) will be skipped. @xref{Memory Region
30581 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30582 regions. For each one, if reading full region results in an errors,
30583 @value{GDBN} will try to read a subset of the region.
30585 In general, every single memory unit in the region may be readable or not,
30586 and the only way to read every readable unit is to try a read at
30587 every address, which is not practical. Therefore, @value{GDBN} will
30588 attempt to read all accessible memory units at either beginning or the end
30589 of the region, using a binary division scheme. This heuristic works
30590 well for reading accross a memory map boundary. Note that if a region
30591 has a readable range that is neither at the beginning or the end,
30592 @value{GDBN} will not read it.
30594 The result record (@pxref{GDB/MI Result Records}) that is output of
30595 the command includes a field named @samp{memory} whose content is a
30596 list of tuples. Each tuple represent a successfully read memory block
30597 and has the following fields:
30601 The start address of the memory block, as hexadecimal literal.
30604 The end address of the memory block, as hexadecimal literal.
30607 The offset of the memory block, as hexadecimal literal, relative to
30608 the start address passed to @code{-data-read-memory-bytes}.
30611 The contents of the memory block, in hex.
30617 @subsubheading @value{GDBN} Command
30619 The corresponding @value{GDBN} command is @samp{x}.
30621 @subsubheading Example
30625 -data-read-memory-bytes &a 10
30626 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30628 contents="01000000020000000300"@}]
30633 @subheading The @code{-data-write-memory-bytes} Command
30634 @findex -data-write-memory-bytes
30636 @subsubheading Synopsis
30639 -data-write-memory-bytes @var{address} @var{contents}
30640 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30647 @item @var{address}
30648 An expression specifying the address of the first addressable memory unit
30649 to be written. Complex expressions containing embedded white space should
30650 be quoted using the C convention.
30652 @item @var{contents}
30653 The hex-encoded data to write. It is an error if @var{contents} does
30654 not represent an integral number of addressable memory units.
30657 Optional argument indicating the number of addressable memory units to be
30658 written. If @var{count} is greater than @var{contents}' length,
30659 @value{GDBN} will repeatedly write @var{contents} until it fills
30660 @var{count} memory units.
30664 @subsubheading @value{GDBN} Command
30666 There's no corresponding @value{GDBN} command.
30668 @subsubheading Example
30672 -data-write-memory-bytes &a "aabbccdd"
30679 -data-write-memory-bytes &a "aabbccdd" 16e
30684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30685 @node GDB/MI Tracepoint Commands
30686 @section @sc{gdb/mi} Tracepoint Commands
30688 The commands defined in this section implement MI support for
30689 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30691 @subheading The @code{-trace-find} Command
30692 @findex -trace-find
30694 @subsubheading Synopsis
30697 -trace-find @var{mode} [@var{parameters}@dots{}]
30700 Find a trace frame using criteria defined by @var{mode} and
30701 @var{parameters}. The following table lists permissible
30702 modes and their parameters. For details of operation, see @ref{tfind}.
30707 No parameters are required. Stops examining trace frames.
30710 An integer is required as parameter. Selects tracepoint frame with
30713 @item tracepoint-number
30714 An integer is required as parameter. Finds next
30715 trace frame that corresponds to tracepoint with the specified number.
30718 An address is required as parameter. Finds
30719 next trace frame that corresponds to any tracepoint at the specified
30722 @item pc-inside-range
30723 Two addresses are required as parameters. Finds next trace
30724 frame that corresponds to a tracepoint at an address inside the
30725 specified range. Both bounds are considered to be inside the range.
30727 @item pc-outside-range
30728 Two addresses are required as parameters. Finds
30729 next trace frame that corresponds to a tracepoint at an address outside
30730 the specified range. Both bounds are considered to be inside the range.
30733 Line specification is required as parameter. @xref{Specify Location}.
30734 Finds next trace frame that corresponds to a tracepoint at
30735 the specified location.
30739 If @samp{none} was passed as @var{mode}, the response does not
30740 have fields. Otherwise, the response may have the following fields:
30744 This field has either @samp{0} or @samp{1} as the value, depending
30745 on whether a matching tracepoint was found.
30748 The index of the found traceframe. This field is present iff
30749 the @samp{found} field has value of @samp{1}.
30752 The index of the found tracepoint. This field is present iff
30753 the @samp{found} field has value of @samp{1}.
30756 The information about the frame corresponding to the found trace
30757 frame. This field is present only if a trace frame was found.
30758 @xref{GDB/MI Frame Information}, for description of this field.
30762 @subsubheading @value{GDBN} Command
30764 The corresponding @value{GDBN} command is @samp{tfind}.
30766 @subheading -trace-define-variable
30767 @findex -trace-define-variable
30769 @subsubheading Synopsis
30772 -trace-define-variable @var{name} [ @var{value} ]
30775 Create trace variable @var{name} if it does not exist. If
30776 @var{value} is specified, sets the initial value of the specified
30777 trace variable to that value. Note that the @var{name} should start
30778 with the @samp{$} character.
30780 @subsubheading @value{GDBN} Command
30782 The corresponding @value{GDBN} command is @samp{tvariable}.
30784 @subheading The @code{-trace-frame-collected} Command
30785 @findex -trace-frame-collected
30787 @subsubheading Synopsis
30790 -trace-frame-collected
30791 [--var-print-values @var{var_pval}]
30792 [--comp-print-values @var{comp_pval}]
30793 [--registers-format @var{regformat}]
30794 [--memory-contents]
30797 This command returns the set of collected objects, register names,
30798 trace state variable names, memory ranges and computed expressions
30799 that have been collected at a particular trace frame. The optional
30800 parameters to the command affect the output format in different ways.
30801 See the output description table below for more details.
30803 The reported names can be used in the normal manner to create
30804 varobjs and inspect the objects themselves. The items returned by
30805 this command are categorized so that it is clear which is a variable,
30806 which is a register, which is a trace state variable, which is a
30807 memory range and which is a computed expression.
30809 For instance, if the actions were
30811 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30812 collect *(int*)0xaf02bef0@@40
30816 the object collected in its entirety would be @code{myVar}. The
30817 object @code{myArray} would be partially collected, because only the
30818 element at index @code{myIndex} would be collected. The remaining
30819 objects would be computed expressions.
30821 An example output would be:
30825 -trace-frame-collected
30827 explicit-variables=[@{name="myVar",value="1"@}],
30828 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30829 @{name="myObj.field",value="0"@},
30830 @{name="myPtr->field",value="1"@},
30831 @{name="myCount + 2",value="3"@},
30832 @{name="$tvar1 + 1",value="43970027"@}],
30833 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30834 @{number="1",value="0x0"@},
30835 @{number="2",value="0x4"@},
30837 @{number="125",value="0x0"@}],
30838 tvars=[@{name="$tvar1",current="43970026"@}],
30839 memory=[@{address="0x0000000000602264",length="4"@},
30840 @{address="0x0000000000615bc0",length="4"@}]
30847 @item explicit-variables
30848 The set of objects that have been collected in their entirety (as
30849 opposed to collecting just a few elements of an array or a few struct
30850 members). For each object, its name and value are printed.
30851 The @code{--var-print-values} option affects how or whether the value
30852 field is output. If @var{var_pval} is 0, then print only the names;
30853 if it is 1, print also their values; and if it is 2, print the name,
30854 type and value for simple data types, and the name and type for
30855 arrays, structures and unions.
30857 @item computed-expressions
30858 The set of computed expressions that have been collected at the
30859 current trace frame. The @code{--comp-print-values} option affects
30860 this set like the @code{--var-print-values} option affects the
30861 @code{explicit-variables} set. See above.
30864 The registers that have been collected at the current trace frame.
30865 For each register collected, the name and current value are returned.
30866 The value is formatted according to the @code{--registers-format}
30867 option. See the @command{-data-list-register-values} command for a
30868 list of the allowed formats. The default is @samp{x}.
30871 The trace state variables that have been collected at the current
30872 trace frame. For each trace state variable collected, the name and
30873 current value are returned.
30876 The set of memory ranges that have been collected at the current trace
30877 frame. Its content is a list of tuples. Each tuple represents a
30878 collected memory range and has the following fields:
30882 The start address of the memory range, as hexadecimal literal.
30885 The length of the memory range, as decimal literal.
30888 The contents of the memory block, in hex. This field is only present
30889 if the @code{--memory-contents} option is specified.
30895 @subsubheading @value{GDBN} Command
30897 There is no corresponding @value{GDBN} command.
30899 @subsubheading Example
30901 @subheading -trace-list-variables
30902 @findex -trace-list-variables
30904 @subsubheading Synopsis
30907 -trace-list-variables
30910 Return a table of all defined trace variables. Each element of the
30911 table has the following fields:
30915 The name of the trace variable. This field is always present.
30918 The initial value. This is a 64-bit signed integer. This
30919 field is always present.
30922 The value the trace variable has at the moment. This is a 64-bit
30923 signed integer. This field is absent iff current value is
30924 not defined, for example if the trace was never run, or is
30929 @subsubheading @value{GDBN} Command
30931 The corresponding @value{GDBN} command is @samp{tvariables}.
30933 @subsubheading Example
30937 -trace-list-variables
30938 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30939 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30940 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30941 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30942 body=[variable=@{name="$trace_timestamp",initial="0"@}
30943 variable=@{name="$foo",initial="10",current="15"@}]@}
30947 @subheading -trace-save
30948 @findex -trace-save
30950 @subsubheading Synopsis
30953 -trace-save [ -r ] [ -ctf ] @var{filename}
30956 Saves the collected trace data to @var{filename}. Without the
30957 @samp{-r} option, the data is downloaded from the target and saved
30958 in a local file. With the @samp{-r} option the target is asked
30959 to perform the save.
30961 By default, this command will save the trace in the tfile format. You can
30962 supply the optional @samp{-ctf} argument to save it the CTF format. See
30963 @ref{Trace Files} for more information about CTF.
30965 @subsubheading @value{GDBN} Command
30967 The corresponding @value{GDBN} command is @samp{tsave}.
30970 @subheading -trace-start
30971 @findex -trace-start
30973 @subsubheading Synopsis
30979 Starts a tracing experiment. The result of this command does not
30982 @subsubheading @value{GDBN} Command
30984 The corresponding @value{GDBN} command is @samp{tstart}.
30986 @subheading -trace-status
30987 @findex -trace-status
30989 @subsubheading Synopsis
30995 Obtains the status of a tracing experiment. The result may include
30996 the following fields:
31001 May have a value of either @samp{0}, when no tracing operations are
31002 supported, @samp{1}, when all tracing operations are supported, or
31003 @samp{file} when examining trace file. In the latter case, examining
31004 of trace frame is possible but new tracing experiement cannot be
31005 started. This field is always present.
31008 May have a value of either @samp{0} or @samp{1} depending on whether
31009 tracing experiement is in progress on target. This field is present
31010 if @samp{supported} field is not @samp{0}.
31013 Report the reason why the tracing was stopped last time. This field
31014 may be absent iff tracing was never stopped on target yet. The
31015 value of @samp{request} means the tracing was stopped as result of
31016 the @code{-trace-stop} command. The value of @samp{overflow} means
31017 the tracing buffer is full. The value of @samp{disconnection} means
31018 tracing was automatically stopped when @value{GDBN} has disconnected.
31019 The value of @samp{passcount} means tracing was stopped when a
31020 tracepoint was passed a maximal number of times for that tracepoint.
31021 This field is present if @samp{supported} field is not @samp{0}.
31023 @item stopping-tracepoint
31024 The number of tracepoint whose passcount as exceeded. This field is
31025 present iff the @samp{stop-reason} field has the value of
31029 @itemx frames-created
31030 The @samp{frames} field is a count of the total number of trace frames
31031 in the trace buffer, while @samp{frames-created} is the total created
31032 during the run, including ones that were discarded, such as when a
31033 circular trace buffer filled up. Both fields are optional.
31037 These fields tell the current size of the tracing buffer and the
31038 remaining space. These fields are optional.
31041 The value of the circular trace buffer flag. @code{1} means that the
31042 trace buffer is circular and old trace frames will be discarded if
31043 necessary to make room, @code{0} means that the trace buffer is linear
31047 The value of the disconnected tracing flag. @code{1} means that
31048 tracing will continue after @value{GDBN} disconnects, @code{0} means
31049 that the trace run will stop.
31052 The filename of the trace file being examined. This field is
31053 optional, and only present when examining a trace file.
31057 @subsubheading @value{GDBN} Command
31059 The corresponding @value{GDBN} command is @samp{tstatus}.
31061 @subheading -trace-stop
31062 @findex -trace-stop
31064 @subsubheading Synopsis
31070 Stops a tracing experiment. The result of this command has the same
31071 fields as @code{-trace-status}, except that the @samp{supported} and
31072 @samp{running} fields are not output.
31074 @subsubheading @value{GDBN} Command
31076 The corresponding @value{GDBN} command is @samp{tstop}.
31079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31080 @node GDB/MI Symbol Query
31081 @section @sc{gdb/mi} Symbol Query Commands
31085 @subheading The @code{-symbol-info-address} Command
31086 @findex -symbol-info-address
31088 @subsubheading Synopsis
31091 -symbol-info-address @var{symbol}
31094 Describe where @var{symbol} is stored.
31096 @subsubheading @value{GDBN} Command
31098 The corresponding @value{GDBN} command is @samp{info address}.
31100 @subsubheading Example
31104 @subheading The @code{-symbol-info-file} Command
31105 @findex -symbol-info-file
31107 @subsubheading Synopsis
31113 Show the file for the symbol.
31115 @subsubheading @value{GDBN} Command
31117 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31118 @samp{gdb_find_file}.
31120 @subsubheading Example
31124 @subheading The @code{-symbol-info-function} Command
31125 @findex -symbol-info-function
31127 @subsubheading Synopsis
31130 -symbol-info-function
31133 Show which function the symbol lives in.
31135 @subsubheading @value{GDBN} Command
31137 @samp{gdb_get_function} in @code{gdbtk}.
31139 @subsubheading Example
31143 @subheading The @code{-symbol-info-line} Command
31144 @findex -symbol-info-line
31146 @subsubheading Synopsis
31152 Show the core addresses of the code for a source line.
31154 @subsubheading @value{GDBN} Command
31156 The corresponding @value{GDBN} command is @samp{info line}.
31157 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31159 @subsubheading Example
31163 @subheading The @code{-symbol-info-symbol} Command
31164 @findex -symbol-info-symbol
31166 @subsubheading Synopsis
31169 -symbol-info-symbol @var{addr}
31172 Describe what symbol is at location @var{addr}.
31174 @subsubheading @value{GDBN} Command
31176 The corresponding @value{GDBN} command is @samp{info symbol}.
31178 @subsubheading Example
31182 @subheading The @code{-symbol-list-functions} Command
31183 @findex -symbol-list-functions
31185 @subsubheading Synopsis
31188 -symbol-list-functions
31191 List the functions in the executable.
31193 @subsubheading @value{GDBN} Command
31195 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31196 @samp{gdb_search} in @code{gdbtk}.
31198 @subsubheading Example
31203 @subheading The @code{-symbol-list-lines} Command
31204 @findex -symbol-list-lines
31206 @subsubheading Synopsis
31209 -symbol-list-lines @var{filename}
31212 Print the list of lines that contain code and their associated program
31213 addresses for the given source filename. The entries are sorted in
31214 ascending PC order.
31216 @subsubheading @value{GDBN} Command
31218 There is no corresponding @value{GDBN} command.
31220 @subsubheading Example
31223 -symbol-list-lines basics.c
31224 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31230 @subheading The @code{-symbol-list-types} Command
31231 @findex -symbol-list-types
31233 @subsubheading Synopsis
31239 List all the type names.
31241 @subsubheading @value{GDBN} Command
31243 The corresponding commands are @samp{info types} in @value{GDBN},
31244 @samp{gdb_search} in @code{gdbtk}.
31246 @subsubheading Example
31250 @subheading The @code{-symbol-list-variables} Command
31251 @findex -symbol-list-variables
31253 @subsubheading Synopsis
31256 -symbol-list-variables
31259 List all the global and static variable names.
31261 @subsubheading @value{GDBN} Command
31263 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31265 @subsubheading Example
31269 @subheading The @code{-symbol-locate} Command
31270 @findex -symbol-locate
31272 @subsubheading Synopsis
31278 @subsubheading @value{GDBN} Command
31280 @samp{gdb_loc} in @code{gdbtk}.
31282 @subsubheading Example
31286 @subheading The @code{-symbol-type} Command
31287 @findex -symbol-type
31289 @subsubheading Synopsis
31292 -symbol-type @var{variable}
31295 Show type of @var{variable}.
31297 @subsubheading @value{GDBN} Command
31299 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31300 @samp{gdb_obj_variable}.
31302 @subsubheading Example
31307 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31308 @node GDB/MI File Commands
31309 @section @sc{gdb/mi} File Commands
31311 This section describes the GDB/MI commands to specify executable file names
31312 and to read in and obtain symbol table information.
31314 @subheading The @code{-file-exec-and-symbols} Command
31315 @findex -file-exec-and-symbols
31317 @subsubheading Synopsis
31320 -file-exec-and-symbols @var{file}
31323 Specify the executable file to be debugged. This file is the one from
31324 which the symbol table is also read. If no file is specified, the
31325 command clears the executable and symbol information. If breakpoints
31326 are set when using this command with no arguments, @value{GDBN} will produce
31327 error messages. Otherwise, no output is produced, except a completion
31330 @subsubheading @value{GDBN} Command
31332 The corresponding @value{GDBN} command is @samp{file}.
31334 @subsubheading Example
31338 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31344 @subheading The @code{-file-exec-file} Command
31345 @findex -file-exec-file
31347 @subsubheading Synopsis
31350 -file-exec-file @var{file}
31353 Specify the executable file to be debugged. Unlike
31354 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31355 from this file. If used without argument, @value{GDBN} clears the information
31356 about the executable file. No output is produced, except a completion
31359 @subsubheading @value{GDBN} Command
31361 The corresponding @value{GDBN} command is @samp{exec-file}.
31363 @subsubheading Example
31367 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31374 @subheading The @code{-file-list-exec-sections} Command
31375 @findex -file-list-exec-sections
31377 @subsubheading Synopsis
31380 -file-list-exec-sections
31383 List the sections of the current executable file.
31385 @subsubheading @value{GDBN} Command
31387 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31388 information as this command. @code{gdbtk} has a corresponding command
31389 @samp{gdb_load_info}.
31391 @subsubheading Example
31396 @subheading The @code{-file-list-exec-source-file} Command
31397 @findex -file-list-exec-source-file
31399 @subsubheading Synopsis
31402 -file-list-exec-source-file
31405 List the line number, the current source file, and the absolute path
31406 to the current source file for the current executable. The macro
31407 information field has a value of @samp{1} or @samp{0} depending on
31408 whether or not the file includes preprocessor macro information.
31410 @subsubheading @value{GDBN} Command
31412 The @value{GDBN} equivalent is @samp{info source}
31414 @subsubheading Example
31418 123-file-list-exec-source-file
31419 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31424 @subheading The @code{-file-list-exec-source-files} Command
31425 @findex -file-list-exec-source-files
31427 @subsubheading Synopsis
31430 -file-list-exec-source-files
31433 List the source files for the current executable.
31435 It will always output both the filename and fullname (absolute file
31436 name) of a source file.
31438 @subsubheading @value{GDBN} Command
31440 The @value{GDBN} equivalent is @samp{info sources}.
31441 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31443 @subsubheading Example
31446 -file-list-exec-source-files
31448 @{file=foo.c,fullname=/home/foo.c@},
31449 @{file=/home/bar.c,fullname=/home/bar.c@},
31450 @{file=gdb_could_not_find_fullpath.c@}]
31455 @subheading The @code{-file-list-shared-libraries} Command
31456 @findex -file-list-shared-libraries
31458 @subsubheading Synopsis
31461 -file-list-shared-libraries
31464 List the shared libraries in the program.
31466 @subsubheading @value{GDBN} Command
31468 The corresponding @value{GDBN} command is @samp{info shared}.
31470 @subsubheading Example
31474 @subheading The @code{-file-list-symbol-files} Command
31475 @findex -file-list-symbol-files
31477 @subsubheading Synopsis
31480 -file-list-symbol-files
31485 @subsubheading @value{GDBN} Command
31487 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31489 @subsubheading Example
31494 @subheading The @code{-file-symbol-file} Command
31495 @findex -file-symbol-file
31497 @subsubheading Synopsis
31500 -file-symbol-file @var{file}
31503 Read symbol table info from the specified @var{file} argument. When
31504 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31505 produced, except for a completion notification.
31507 @subsubheading @value{GDBN} Command
31509 The corresponding @value{GDBN} command is @samp{symbol-file}.
31511 @subsubheading Example
31515 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31522 @node GDB/MI Memory Overlay Commands
31523 @section @sc{gdb/mi} Memory Overlay Commands
31525 The memory overlay commands are not implemented.
31527 @c @subheading -overlay-auto
31529 @c @subheading -overlay-list-mapping-state
31531 @c @subheading -overlay-list-overlays
31533 @c @subheading -overlay-map
31535 @c @subheading -overlay-off
31537 @c @subheading -overlay-on
31539 @c @subheading -overlay-unmap
31541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31542 @node GDB/MI Signal Handling Commands
31543 @section @sc{gdb/mi} Signal Handling Commands
31545 Signal handling commands are not implemented.
31547 @c @subheading -signal-handle
31549 @c @subheading -signal-list-handle-actions
31551 @c @subheading -signal-list-signal-types
31555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31556 @node GDB/MI Target Manipulation
31557 @section @sc{gdb/mi} Target Manipulation Commands
31560 @subheading The @code{-target-attach} Command
31561 @findex -target-attach
31563 @subsubheading Synopsis
31566 -target-attach @var{pid} | @var{gid} | @var{file}
31569 Attach to a process @var{pid} or a file @var{file} outside of
31570 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31571 group, the id previously returned by
31572 @samp{-list-thread-groups --available} must be used.
31574 @subsubheading @value{GDBN} Command
31576 The corresponding @value{GDBN} command is @samp{attach}.
31578 @subsubheading Example
31582 =thread-created,id="1"
31583 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31589 @subheading The @code{-target-compare-sections} Command
31590 @findex -target-compare-sections
31592 @subsubheading Synopsis
31595 -target-compare-sections [ @var{section} ]
31598 Compare data of section @var{section} on target to the exec file.
31599 Without the argument, all sections are compared.
31601 @subsubheading @value{GDBN} Command
31603 The @value{GDBN} equivalent is @samp{compare-sections}.
31605 @subsubheading Example
31610 @subheading The @code{-target-detach} Command
31611 @findex -target-detach
31613 @subsubheading Synopsis
31616 -target-detach [ @var{pid} | @var{gid} ]
31619 Detach from the remote target which normally resumes its execution.
31620 If either @var{pid} or @var{gid} is specified, detaches from either
31621 the specified process, or specified thread group. There's no output.
31623 @subsubheading @value{GDBN} Command
31625 The corresponding @value{GDBN} command is @samp{detach}.
31627 @subsubheading Example
31637 @subheading The @code{-target-disconnect} Command
31638 @findex -target-disconnect
31640 @subsubheading Synopsis
31646 Disconnect from the remote target. There's no output and the target is
31647 generally not resumed.
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{disconnect}.
31653 @subsubheading Example
31663 @subheading The @code{-target-download} Command
31664 @findex -target-download
31666 @subsubheading Synopsis
31672 Loads the executable onto the remote target.
31673 It prints out an update message every half second, which includes the fields:
31677 The name of the section.
31679 The size of what has been sent so far for that section.
31681 The size of the section.
31683 The total size of what was sent so far (the current and the previous sections).
31685 The size of the overall executable to download.
31689 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31690 @sc{gdb/mi} Output Syntax}).
31692 In addition, it prints the name and size of the sections, as they are
31693 downloaded. These messages include the following fields:
31697 The name of the section.
31699 The size of the section.
31701 The size of the overall executable to download.
31705 At the end, a summary is printed.
31707 @subsubheading @value{GDBN} Command
31709 The corresponding @value{GDBN} command is @samp{load}.
31711 @subsubheading Example
31713 Note: each status message appears on a single line. Here the messages
31714 have been broken down so that they can fit onto a page.
31719 +download,@{section=".text",section-size="6668",total-size="9880"@}
31720 +download,@{section=".text",section-sent="512",section-size="6668",
31721 total-sent="512",total-size="9880"@}
31722 +download,@{section=".text",section-sent="1024",section-size="6668",
31723 total-sent="1024",total-size="9880"@}
31724 +download,@{section=".text",section-sent="1536",section-size="6668",
31725 total-sent="1536",total-size="9880"@}
31726 +download,@{section=".text",section-sent="2048",section-size="6668",
31727 total-sent="2048",total-size="9880"@}
31728 +download,@{section=".text",section-sent="2560",section-size="6668",
31729 total-sent="2560",total-size="9880"@}
31730 +download,@{section=".text",section-sent="3072",section-size="6668",
31731 total-sent="3072",total-size="9880"@}
31732 +download,@{section=".text",section-sent="3584",section-size="6668",
31733 total-sent="3584",total-size="9880"@}
31734 +download,@{section=".text",section-sent="4096",section-size="6668",
31735 total-sent="4096",total-size="9880"@}
31736 +download,@{section=".text",section-sent="4608",section-size="6668",
31737 total-sent="4608",total-size="9880"@}
31738 +download,@{section=".text",section-sent="5120",section-size="6668",
31739 total-sent="5120",total-size="9880"@}
31740 +download,@{section=".text",section-sent="5632",section-size="6668",
31741 total-sent="5632",total-size="9880"@}
31742 +download,@{section=".text",section-sent="6144",section-size="6668",
31743 total-sent="6144",total-size="9880"@}
31744 +download,@{section=".text",section-sent="6656",section-size="6668",
31745 total-sent="6656",total-size="9880"@}
31746 +download,@{section=".init",section-size="28",total-size="9880"@}
31747 +download,@{section=".fini",section-size="28",total-size="9880"@}
31748 +download,@{section=".data",section-size="3156",total-size="9880"@}
31749 +download,@{section=".data",section-sent="512",section-size="3156",
31750 total-sent="7236",total-size="9880"@}
31751 +download,@{section=".data",section-sent="1024",section-size="3156",
31752 total-sent="7748",total-size="9880"@}
31753 +download,@{section=".data",section-sent="1536",section-size="3156",
31754 total-sent="8260",total-size="9880"@}
31755 +download,@{section=".data",section-sent="2048",section-size="3156",
31756 total-sent="8772",total-size="9880"@}
31757 +download,@{section=".data",section-sent="2560",section-size="3156",
31758 total-sent="9284",total-size="9880"@}
31759 +download,@{section=".data",section-sent="3072",section-size="3156",
31760 total-sent="9796",total-size="9880"@}
31761 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31768 @subheading The @code{-target-exec-status} Command
31769 @findex -target-exec-status
31771 @subsubheading Synopsis
31774 -target-exec-status
31777 Provide information on the state of the target (whether it is running or
31778 not, for instance).
31780 @subsubheading @value{GDBN} Command
31782 There's no equivalent @value{GDBN} command.
31784 @subsubheading Example
31788 @subheading The @code{-target-list-available-targets} Command
31789 @findex -target-list-available-targets
31791 @subsubheading Synopsis
31794 -target-list-available-targets
31797 List the possible targets to connect to.
31799 @subsubheading @value{GDBN} Command
31801 The corresponding @value{GDBN} command is @samp{help target}.
31803 @subsubheading Example
31807 @subheading The @code{-target-list-current-targets} Command
31808 @findex -target-list-current-targets
31810 @subsubheading Synopsis
31813 -target-list-current-targets
31816 Describe the current target.
31818 @subsubheading @value{GDBN} Command
31820 The corresponding information is printed by @samp{info file} (among
31823 @subsubheading Example
31827 @subheading The @code{-target-list-parameters} Command
31828 @findex -target-list-parameters
31830 @subsubheading Synopsis
31833 -target-list-parameters
31839 @subsubheading @value{GDBN} Command
31843 @subsubheading Example
31847 @subheading The @code{-target-select} Command
31848 @findex -target-select
31850 @subsubheading Synopsis
31853 -target-select @var{type} @var{parameters @dots{}}
31856 Connect @value{GDBN} to the remote target. This command takes two args:
31860 The type of target, for instance @samp{remote}, etc.
31861 @item @var{parameters}
31862 Device names, host names and the like. @xref{Target Commands, ,
31863 Commands for Managing Targets}, for more details.
31866 The output is a connection notification, followed by the address at
31867 which the target program is, in the following form:
31870 ^connected,addr="@var{address}",func="@var{function name}",
31871 args=[@var{arg list}]
31874 @subsubheading @value{GDBN} Command
31876 The corresponding @value{GDBN} command is @samp{target}.
31878 @subsubheading Example
31882 -target-select remote /dev/ttya
31883 ^connected,addr="0xfe00a300",func="??",args=[]
31887 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31888 @node GDB/MI File Transfer Commands
31889 @section @sc{gdb/mi} File Transfer Commands
31892 @subheading The @code{-target-file-put} Command
31893 @findex -target-file-put
31895 @subsubheading Synopsis
31898 -target-file-put @var{hostfile} @var{targetfile}
31901 Copy file @var{hostfile} from the host system (the machine running
31902 @value{GDBN}) to @var{targetfile} on the target system.
31904 @subsubheading @value{GDBN} Command
31906 The corresponding @value{GDBN} command is @samp{remote put}.
31908 @subsubheading Example
31912 -target-file-put localfile remotefile
31918 @subheading The @code{-target-file-get} Command
31919 @findex -target-file-get
31921 @subsubheading Synopsis
31924 -target-file-get @var{targetfile} @var{hostfile}
31927 Copy file @var{targetfile} from the target system to @var{hostfile}
31928 on the host system.
31930 @subsubheading @value{GDBN} Command
31932 The corresponding @value{GDBN} command is @samp{remote get}.
31934 @subsubheading Example
31938 -target-file-get remotefile localfile
31944 @subheading The @code{-target-file-delete} Command
31945 @findex -target-file-delete
31947 @subsubheading Synopsis
31950 -target-file-delete @var{targetfile}
31953 Delete @var{targetfile} from the target system.
31955 @subsubheading @value{GDBN} Command
31957 The corresponding @value{GDBN} command is @samp{remote delete}.
31959 @subsubheading Example
31963 -target-file-delete remotefile
31969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31970 @node GDB/MI Ada Exceptions Commands
31971 @section Ada Exceptions @sc{gdb/mi} Commands
31973 @subheading The @code{-info-ada-exceptions} Command
31974 @findex -info-ada-exceptions
31976 @subsubheading Synopsis
31979 -info-ada-exceptions [ @var{regexp}]
31982 List all Ada exceptions defined within the program being debugged.
31983 With a regular expression @var{regexp}, only those exceptions whose
31984 names match @var{regexp} are listed.
31986 @subsubheading @value{GDBN} Command
31988 The corresponding @value{GDBN} command is @samp{info exceptions}.
31990 @subsubheading Result
31992 The result is a table of Ada exceptions. The following columns are
31993 defined for each exception:
31997 The name of the exception.
32000 The address of the exception.
32004 @subsubheading Example
32007 -info-ada-exceptions aint
32008 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32009 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32010 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32011 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32012 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32015 @subheading Catching Ada Exceptions
32017 The commands describing how to ask @value{GDBN} to stop when a program
32018 raises an exception are described at @ref{Ada Exception GDB/MI
32019 Catchpoint Commands}.
32022 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32023 @node GDB/MI Support Commands
32024 @section @sc{gdb/mi} Support Commands
32026 Since new commands and features get regularly added to @sc{gdb/mi},
32027 some commands are available to help front-ends query the debugger
32028 about support for these capabilities. Similarly, it is also possible
32029 to query @value{GDBN} about target support of certain features.
32031 @subheading The @code{-info-gdb-mi-command} Command
32032 @cindex @code{-info-gdb-mi-command}
32033 @findex -info-gdb-mi-command
32035 @subsubheading Synopsis
32038 -info-gdb-mi-command @var{cmd_name}
32041 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32043 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32044 is technically not part of the command name (@pxref{GDB/MI Input
32045 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32046 for ease of use, this command also accepts the form with the leading
32049 @subsubheading @value{GDBN} Command
32051 There is no corresponding @value{GDBN} command.
32053 @subsubheading Result
32055 The result is a tuple. There is currently only one field:
32059 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32060 @code{"false"} otherwise.
32064 @subsubheading Example
32066 Here is an example where the @sc{gdb/mi} command does not exist:
32069 -info-gdb-mi-command unsupported-command
32070 ^done,command=@{exists="false"@}
32074 And here is an example where the @sc{gdb/mi} command is known
32078 -info-gdb-mi-command symbol-list-lines
32079 ^done,command=@{exists="true"@}
32082 @subheading The @code{-list-features} Command
32083 @findex -list-features
32084 @cindex supported @sc{gdb/mi} features, list
32086 Returns a list of particular features of the MI protocol that
32087 this version of gdb implements. A feature can be a command,
32088 or a new field in an output of some command, or even an
32089 important bugfix. While a frontend can sometimes detect presence
32090 of a feature at runtime, it is easier to perform detection at debugger
32093 The command returns a list of strings, with each string naming an
32094 available feature. Each returned string is just a name, it does not
32095 have any internal structure. The list of possible feature names
32101 (gdb) -list-features
32102 ^done,result=["feature1","feature2"]
32105 The current list of features is:
32108 @item frozen-varobjs
32109 Indicates support for the @code{-var-set-frozen} command, as well
32110 as possible presense of the @code{frozen} field in the output
32111 of @code{-varobj-create}.
32112 @item pending-breakpoints
32113 Indicates support for the @option{-f} option to the @code{-break-insert}
32116 Indicates Python scripting support, Python-based
32117 pretty-printing commands, and possible presence of the
32118 @samp{display_hint} field in the output of @code{-var-list-children}
32120 Indicates support for the @code{-thread-info} command.
32121 @item data-read-memory-bytes
32122 Indicates support for the @code{-data-read-memory-bytes} and the
32123 @code{-data-write-memory-bytes} commands.
32124 @item breakpoint-notifications
32125 Indicates that changes to breakpoints and breakpoints created via the
32126 CLI will be announced via async records.
32127 @item ada-task-info
32128 Indicates support for the @code{-ada-task-info} command.
32129 @item language-option
32130 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32131 option (@pxref{Context management}).
32132 @item info-gdb-mi-command
32133 Indicates support for the @code{-info-gdb-mi-command} command.
32134 @item undefined-command-error-code
32135 Indicates support for the "undefined-command" error code in error result
32136 records, produced when trying to execute an undefined @sc{gdb/mi} command
32137 (@pxref{GDB/MI Result Records}).
32138 @item exec-run-start-option
32139 Indicates that the @code{-exec-run} command supports the @option{--start}
32140 option (@pxref{GDB/MI Program Execution}).
32143 @subheading The @code{-list-target-features} Command
32144 @findex -list-target-features
32146 Returns a list of particular features that are supported by the
32147 target. Those features affect the permitted MI commands, but
32148 unlike the features reported by the @code{-list-features} command, the
32149 features depend on which target GDB is using at the moment. Whenever
32150 a target can change, due to commands such as @code{-target-select},
32151 @code{-target-attach} or @code{-exec-run}, the list of target features
32152 may change, and the frontend should obtain it again.
32156 (gdb) -list-target-features
32157 ^done,result=["async"]
32160 The current list of features is:
32164 Indicates that the target is capable of asynchronous command
32165 execution, which means that @value{GDBN} will accept further commands
32166 while the target is running.
32169 Indicates that the target is capable of reverse execution.
32170 @xref{Reverse Execution}, for more information.
32174 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32175 @node GDB/MI Miscellaneous Commands
32176 @section Miscellaneous @sc{gdb/mi} Commands
32178 @c @subheading -gdb-complete
32180 @subheading The @code{-gdb-exit} Command
32183 @subsubheading Synopsis
32189 Exit @value{GDBN} immediately.
32191 @subsubheading @value{GDBN} Command
32193 Approximately corresponds to @samp{quit}.
32195 @subsubheading Example
32205 @subheading The @code{-exec-abort} Command
32206 @findex -exec-abort
32208 @subsubheading Synopsis
32214 Kill the inferior running program.
32216 @subsubheading @value{GDBN} Command
32218 The corresponding @value{GDBN} command is @samp{kill}.
32220 @subsubheading Example
32225 @subheading The @code{-gdb-set} Command
32228 @subsubheading Synopsis
32234 Set an internal @value{GDBN} variable.
32235 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32237 @subsubheading @value{GDBN} Command
32239 The corresponding @value{GDBN} command is @samp{set}.
32241 @subsubheading Example
32251 @subheading The @code{-gdb-show} Command
32254 @subsubheading Synopsis
32260 Show the current value of a @value{GDBN} variable.
32262 @subsubheading @value{GDBN} Command
32264 The corresponding @value{GDBN} command is @samp{show}.
32266 @subsubheading Example
32275 @c @subheading -gdb-source
32278 @subheading The @code{-gdb-version} Command
32279 @findex -gdb-version
32281 @subsubheading Synopsis
32287 Show version information for @value{GDBN}. Used mostly in testing.
32289 @subsubheading @value{GDBN} Command
32291 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32292 default shows this information when you start an interactive session.
32294 @subsubheading Example
32296 @c This example modifies the actual output from GDB to avoid overfull
32302 ~Copyright 2000 Free Software Foundation, Inc.
32303 ~GDB is free software, covered by the GNU General Public License, and
32304 ~you are welcome to change it and/or distribute copies of it under
32305 ~ certain conditions.
32306 ~Type "show copying" to see the conditions.
32307 ~There is absolutely no warranty for GDB. Type "show warranty" for
32309 ~This GDB was configured as
32310 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32315 @subheading The @code{-list-thread-groups} Command
32316 @findex -list-thread-groups
32318 @subheading Synopsis
32321 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32324 Lists thread groups (@pxref{Thread groups}). When a single thread
32325 group is passed as the argument, lists the children of that group.
32326 When several thread group are passed, lists information about those
32327 thread groups. Without any parameters, lists information about all
32328 top-level thread groups.
32330 Normally, thread groups that are being debugged are reported.
32331 With the @samp{--available} option, @value{GDBN} reports thread groups
32332 available on the target.
32334 The output of this command may have either a @samp{threads} result or
32335 a @samp{groups} result. The @samp{thread} result has a list of tuples
32336 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32337 Information}). The @samp{groups} result has a list of tuples as value,
32338 each tuple describing a thread group. If top-level groups are
32339 requested (that is, no parameter is passed), or when several groups
32340 are passed, the output always has a @samp{groups} result. The format
32341 of the @samp{group} result is described below.
32343 To reduce the number of roundtrips it's possible to list thread groups
32344 together with their children, by passing the @samp{--recurse} option
32345 and the recursion depth. Presently, only recursion depth of 1 is
32346 permitted. If this option is present, then every reported thread group
32347 will also include its children, either as @samp{group} or
32348 @samp{threads} field.
32350 In general, any combination of option and parameters is permitted, with
32351 the following caveats:
32355 When a single thread group is passed, the output will typically
32356 be the @samp{threads} result. Because threads may not contain
32357 anything, the @samp{recurse} option will be ignored.
32360 When the @samp{--available} option is passed, limited information may
32361 be available. In particular, the list of threads of a process might
32362 be inaccessible. Further, specifying specific thread groups might
32363 not give any performance advantage over listing all thread groups.
32364 The frontend should assume that @samp{-list-thread-groups --available}
32365 is always an expensive operation and cache the results.
32369 The @samp{groups} result is a list of tuples, where each tuple may
32370 have the following fields:
32374 Identifier of the thread group. This field is always present.
32375 The identifier is an opaque string; frontends should not try to
32376 convert it to an integer, even though it might look like one.
32379 The type of the thread group. At present, only @samp{process} is a
32383 The target-specific process identifier. This field is only present
32384 for thread groups of type @samp{process} and only if the process exists.
32387 The exit code of this group's last exited thread, formatted in octal.
32388 This field is only present for thread groups of type @samp{process} and
32389 only if the process is not running.
32392 The number of children this thread group has. This field may be
32393 absent for an available thread group.
32396 This field has a list of tuples as value, each tuple describing a
32397 thread. It may be present if the @samp{--recurse} option is
32398 specified, and it's actually possible to obtain the threads.
32401 This field is a list of integers, each identifying a core that one
32402 thread of the group is running on. This field may be absent if
32403 such information is not available.
32406 The name of the executable file that corresponds to this thread group.
32407 The field is only present for thread groups of type @samp{process},
32408 and only if there is a corresponding executable file.
32412 @subheading Example
32416 -list-thread-groups
32417 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32418 -list-thread-groups 17
32419 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32420 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32421 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32422 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32423 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32424 -list-thread-groups --available
32425 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32426 -list-thread-groups --available --recurse 1
32427 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32428 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32429 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32430 -list-thread-groups --available --recurse 1 17 18
32431 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32432 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32433 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32436 @subheading The @code{-info-os} Command
32439 @subsubheading Synopsis
32442 -info-os [ @var{type} ]
32445 If no argument is supplied, the command returns a table of available
32446 operating-system-specific information types. If one of these types is
32447 supplied as an argument @var{type}, then the command returns a table
32448 of data of that type.
32450 The types of information available depend on the target operating
32453 @subsubheading @value{GDBN} Command
32455 The corresponding @value{GDBN} command is @samp{info os}.
32457 @subsubheading Example
32459 When run on a @sc{gnu}/Linux system, the output will look something
32465 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32466 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32467 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32468 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32469 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32471 item=@{col0="files",col1="Listing of all file descriptors",
32472 col2="File descriptors"@},
32473 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32474 col2="Kernel modules"@},
32475 item=@{col0="msg",col1="Listing of all message queues",
32476 col2="Message queues"@},
32477 item=@{col0="processes",col1="Listing of all processes",
32478 col2="Processes"@},
32479 item=@{col0="procgroups",col1="Listing of all process groups",
32480 col2="Process groups"@},
32481 item=@{col0="semaphores",col1="Listing of all semaphores",
32482 col2="Semaphores"@},
32483 item=@{col0="shm",col1="Listing of all shared-memory regions",
32484 col2="Shared-memory regions"@},
32485 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32487 item=@{col0="threads",col1="Listing of all threads",
32491 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32492 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32493 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32494 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32495 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32496 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32497 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32498 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32500 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32501 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32505 (Note that the MI output here includes a @code{"Title"} column that
32506 does not appear in command-line @code{info os}; this column is useful
32507 for MI clients that want to enumerate the types of data, such as in a
32508 popup menu, but is needless clutter on the command line, and
32509 @code{info os} omits it.)
32511 @subheading The @code{-add-inferior} Command
32512 @findex -add-inferior
32514 @subheading Synopsis
32520 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32521 inferior is not associated with any executable. Such association may
32522 be established with the @samp{-file-exec-and-symbols} command
32523 (@pxref{GDB/MI File Commands}). The command response has a single
32524 field, @samp{inferior}, whose value is the identifier of the
32525 thread group corresponding to the new inferior.
32527 @subheading Example
32532 ^done,inferior="i3"
32535 @subheading The @code{-interpreter-exec} Command
32536 @findex -interpreter-exec
32538 @subheading Synopsis
32541 -interpreter-exec @var{interpreter} @var{command}
32543 @anchor{-interpreter-exec}
32545 Execute the specified @var{command} in the given @var{interpreter}.
32547 @subheading @value{GDBN} Command
32549 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32551 @subheading Example
32555 -interpreter-exec console "break main"
32556 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32557 &"During symbol reading, bad structure-type format.\n"
32558 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32563 @subheading The @code{-inferior-tty-set} Command
32564 @findex -inferior-tty-set
32566 @subheading Synopsis
32569 -inferior-tty-set /dev/pts/1
32572 Set terminal for future runs of the program being debugged.
32574 @subheading @value{GDBN} Command
32576 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32578 @subheading Example
32582 -inferior-tty-set /dev/pts/1
32587 @subheading The @code{-inferior-tty-show} Command
32588 @findex -inferior-tty-show
32590 @subheading Synopsis
32596 Show terminal for future runs of program being debugged.
32598 @subheading @value{GDBN} Command
32600 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32602 @subheading Example
32606 -inferior-tty-set /dev/pts/1
32610 ^done,inferior_tty_terminal="/dev/pts/1"
32614 @subheading The @code{-enable-timings} Command
32615 @findex -enable-timings
32617 @subheading Synopsis
32620 -enable-timings [yes | no]
32623 Toggle the printing of the wallclock, user and system times for an MI
32624 command as a field in its output. This command is to help frontend
32625 developers optimize the performance of their code. No argument is
32626 equivalent to @samp{yes}.
32628 @subheading @value{GDBN} Command
32632 @subheading Example
32640 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32641 addr="0x080484ed",func="main",file="myprog.c",
32642 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32644 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32652 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32653 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32654 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32655 fullname="/home/nickrob/myprog.c",line="73"@}
32660 @chapter @value{GDBN} Annotations
32662 This chapter describes annotations in @value{GDBN}. Annotations were
32663 designed to interface @value{GDBN} to graphical user interfaces or other
32664 similar programs which want to interact with @value{GDBN} at a
32665 relatively high level.
32667 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32671 This is Edition @value{EDITION}, @value{DATE}.
32675 * Annotations Overview:: What annotations are; the general syntax.
32676 * Server Prefix:: Issuing a command without affecting user state.
32677 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32678 * Errors:: Annotations for error messages.
32679 * Invalidation:: Some annotations describe things now invalid.
32680 * Annotations for Running::
32681 Whether the program is running, how it stopped, etc.
32682 * Source Annotations:: Annotations describing source code.
32685 @node Annotations Overview
32686 @section What is an Annotation?
32687 @cindex annotations
32689 Annotations start with a newline character, two @samp{control-z}
32690 characters, and the name of the annotation. If there is no additional
32691 information associated with this annotation, the name of the annotation
32692 is followed immediately by a newline. If there is additional
32693 information, the name of the annotation is followed by a space, the
32694 additional information, and a newline. The additional information
32695 cannot contain newline characters.
32697 Any output not beginning with a newline and two @samp{control-z}
32698 characters denotes literal output from @value{GDBN}. Currently there is
32699 no need for @value{GDBN} to output a newline followed by two
32700 @samp{control-z} characters, but if there was such a need, the
32701 annotations could be extended with an @samp{escape} annotation which
32702 means those three characters as output.
32704 The annotation @var{level}, which is specified using the
32705 @option{--annotate} command line option (@pxref{Mode Options}), controls
32706 how much information @value{GDBN} prints together with its prompt,
32707 values of expressions, source lines, and other types of output. Level 0
32708 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32709 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32710 for programs that control @value{GDBN}, and level 2 annotations have
32711 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32712 Interface, annotate, GDB's Obsolete Annotations}).
32715 @kindex set annotate
32716 @item set annotate @var{level}
32717 The @value{GDBN} command @code{set annotate} sets the level of
32718 annotations to the specified @var{level}.
32720 @item show annotate
32721 @kindex show annotate
32722 Show the current annotation level.
32725 This chapter describes level 3 annotations.
32727 A simple example of starting up @value{GDBN} with annotations is:
32730 $ @kbd{gdb --annotate=3}
32732 Copyright 2003 Free Software Foundation, Inc.
32733 GDB is free software, covered by the GNU General Public License,
32734 and you are welcome to change it and/or distribute copies of it
32735 under certain conditions.
32736 Type "show copying" to see the conditions.
32737 There is absolutely no warranty for GDB. Type "show warranty"
32739 This GDB was configured as "i386-pc-linux-gnu"
32750 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32751 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32752 denotes a @samp{control-z} character) are annotations; the rest is
32753 output from @value{GDBN}.
32755 @node Server Prefix
32756 @section The Server Prefix
32757 @cindex server prefix
32759 If you prefix a command with @samp{server } then it will not affect
32760 the command history, nor will it affect @value{GDBN}'s notion of which
32761 command to repeat if @key{RET} is pressed on a line by itself. This
32762 means that commands can be run behind a user's back by a front-end in
32763 a transparent manner.
32765 The @code{server } prefix does not affect the recording of values into
32766 the value history; to print a value without recording it into the
32767 value history, use the @code{output} command instead of the
32768 @code{print} command.
32770 Using this prefix also disables confirmation requests
32771 (@pxref{confirmation requests}).
32774 @section Annotation for @value{GDBN} Input
32776 @cindex annotations for prompts
32777 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32778 to know when to send output, when the output from a given command is
32781 Different kinds of input each have a different @dfn{input type}. Each
32782 input type has three annotations: a @code{pre-} annotation, which
32783 denotes the beginning of any prompt which is being output, a plain
32784 annotation, which denotes the end of the prompt, and then a @code{post-}
32785 annotation which denotes the end of any echo which may (or may not) be
32786 associated with the input. For example, the @code{prompt} input type
32787 features the following annotations:
32795 The input types are
32798 @findex pre-prompt annotation
32799 @findex prompt annotation
32800 @findex post-prompt annotation
32802 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32804 @findex pre-commands annotation
32805 @findex commands annotation
32806 @findex post-commands annotation
32808 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32809 command. The annotations are repeated for each command which is input.
32811 @findex pre-overload-choice annotation
32812 @findex overload-choice annotation
32813 @findex post-overload-choice annotation
32814 @item overload-choice
32815 When @value{GDBN} wants the user to select between various overloaded functions.
32817 @findex pre-query annotation
32818 @findex query annotation
32819 @findex post-query annotation
32821 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32823 @findex pre-prompt-for-continue annotation
32824 @findex prompt-for-continue annotation
32825 @findex post-prompt-for-continue annotation
32826 @item prompt-for-continue
32827 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32828 expect this to work well; instead use @code{set height 0} to disable
32829 prompting. This is because the counting of lines is buggy in the
32830 presence of annotations.
32835 @cindex annotations for errors, warnings and interrupts
32837 @findex quit annotation
32842 This annotation occurs right before @value{GDBN} responds to an interrupt.
32844 @findex error annotation
32849 This annotation occurs right before @value{GDBN} responds to an error.
32851 Quit and error annotations indicate that any annotations which @value{GDBN} was
32852 in the middle of may end abruptly. For example, if a
32853 @code{value-history-begin} annotation is followed by a @code{error}, one
32854 cannot expect to receive the matching @code{value-history-end}. One
32855 cannot expect not to receive it either, however; an error annotation
32856 does not necessarily mean that @value{GDBN} is immediately returning all the way
32859 @findex error-begin annotation
32860 A quit or error annotation may be preceded by
32866 Any output between that and the quit or error annotation is the error
32869 Warning messages are not yet annotated.
32870 @c If we want to change that, need to fix warning(), type_error(),
32871 @c range_error(), and possibly other places.
32874 @section Invalidation Notices
32876 @cindex annotations for invalidation messages
32877 The following annotations say that certain pieces of state may have
32881 @findex frames-invalid annotation
32882 @item ^Z^Zframes-invalid
32884 The frames (for example, output from the @code{backtrace} command) may
32887 @findex breakpoints-invalid annotation
32888 @item ^Z^Zbreakpoints-invalid
32890 The breakpoints may have changed. For example, the user just added or
32891 deleted a breakpoint.
32894 @node Annotations for Running
32895 @section Running the Program
32896 @cindex annotations for running programs
32898 @findex starting annotation
32899 @findex stopping annotation
32900 When the program starts executing due to a @value{GDBN} command such as
32901 @code{step} or @code{continue},
32907 is output. When the program stops,
32913 is output. Before the @code{stopped} annotation, a variety of
32914 annotations describe how the program stopped.
32917 @findex exited annotation
32918 @item ^Z^Zexited @var{exit-status}
32919 The program exited, and @var{exit-status} is the exit status (zero for
32920 successful exit, otherwise nonzero).
32922 @findex signalled annotation
32923 @findex signal-name annotation
32924 @findex signal-name-end annotation
32925 @findex signal-string annotation
32926 @findex signal-string-end annotation
32927 @item ^Z^Zsignalled
32928 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32929 annotation continues:
32935 ^Z^Zsignal-name-end
32939 ^Z^Zsignal-string-end
32944 where @var{name} is the name of the signal, such as @code{SIGILL} or
32945 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32946 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32947 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32948 user's benefit and have no particular format.
32950 @findex signal annotation
32952 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32953 just saying that the program received the signal, not that it was
32954 terminated with it.
32956 @findex breakpoint annotation
32957 @item ^Z^Zbreakpoint @var{number}
32958 The program hit breakpoint number @var{number}.
32960 @findex watchpoint annotation
32961 @item ^Z^Zwatchpoint @var{number}
32962 The program hit watchpoint number @var{number}.
32965 @node Source Annotations
32966 @section Displaying Source
32967 @cindex annotations for source display
32969 @findex source annotation
32970 The following annotation is used instead of displaying source code:
32973 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32976 where @var{filename} is an absolute file name indicating which source
32977 file, @var{line} is the line number within that file (where 1 is the
32978 first line in the file), @var{character} is the character position
32979 within the file (where 0 is the first character in the file) (for most
32980 debug formats this will necessarily point to the beginning of a line),
32981 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32982 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32983 @var{addr} is the address in the target program associated with the
32984 source which is being displayed. The @var{addr} is in the form @samp{0x}
32985 followed by one or more lowercase hex digits (note that this does not
32986 depend on the language).
32988 @node JIT Interface
32989 @chapter JIT Compilation Interface
32990 @cindex just-in-time compilation
32991 @cindex JIT compilation interface
32993 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32994 interface. A JIT compiler is a program or library that generates native
32995 executable code at runtime and executes it, usually in order to achieve good
32996 performance while maintaining platform independence.
32998 Programs that use JIT compilation are normally difficult to debug because
32999 portions of their code are generated at runtime, instead of being loaded from
33000 object files, which is where @value{GDBN} normally finds the program's symbols
33001 and debug information. In order to debug programs that use JIT compilation,
33002 @value{GDBN} has an interface that allows the program to register in-memory
33003 symbol files with @value{GDBN} at runtime.
33005 If you are using @value{GDBN} to debug a program that uses this interface, then
33006 it should work transparently so long as you have not stripped the binary. If
33007 you are developing a JIT compiler, then the interface is documented in the rest
33008 of this chapter. At this time, the only known client of this interface is the
33011 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33012 JIT compiler communicates with @value{GDBN} by writing data into a global
33013 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33014 attaches, it reads a linked list of symbol files from the global variable to
33015 find existing code, and puts a breakpoint in the function so that it can find
33016 out about additional code.
33019 * Declarations:: Relevant C struct declarations
33020 * Registering Code:: Steps to register code
33021 * Unregistering Code:: Steps to unregister code
33022 * Custom Debug Info:: Emit debug information in a custom format
33026 @section JIT Declarations
33028 These are the relevant struct declarations that a C program should include to
33029 implement the interface:
33039 struct jit_code_entry
33041 struct jit_code_entry *next_entry;
33042 struct jit_code_entry *prev_entry;
33043 const char *symfile_addr;
33044 uint64_t symfile_size;
33047 struct jit_descriptor
33050 /* This type should be jit_actions_t, but we use uint32_t
33051 to be explicit about the bitwidth. */
33052 uint32_t action_flag;
33053 struct jit_code_entry *relevant_entry;
33054 struct jit_code_entry *first_entry;
33057 /* GDB puts a breakpoint in this function. */
33058 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33060 /* Make sure to specify the version statically, because the
33061 debugger may check the version before we can set it. */
33062 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33065 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33066 modifications to this global data properly, which can easily be done by putting
33067 a global mutex around modifications to these structures.
33069 @node Registering Code
33070 @section Registering Code
33072 To register code with @value{GDBN}, the JIT should follow this protocol:
33076 Generate an object file in memory with symbols and other desired debug
33077 information. The file must include the virtual addresses of the sections.
33080 Create a code entry for the file, which gives the start and size of the symbol
33084 Add it to the linked list in the JIT descriptor.
33087 Point the relevant_entry field of the descriptor at the entry.
33090 Set @code{action_flag} to @code{JIT_REGISTER} and call
33091 @code{__jit_debug_register_code}.
33094 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33095 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33096 new code. However, the linked list must still be maintained in order to allow
33097 @value{GDBN} to attach to a running process and still find the symbol files.
33099 @node Unregistering Code
33100 @section Unregistering Code
33102 If code is freed, then the JIT should use the following protocol:
33106 Remove the code entry corresponding to the code from the linked list.
33109 Point the @code{relevant_entry} field of the descriptor at the code entry.
33112 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33113 @code{__jit_debug_register_code}.
33116 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33117 and the JIT will leak the memory used for the associated symbol files.
33119 @node Custom Debug Info
33120 @section Custom Debug Info
33121 @cindex custom JIT debug info
33122 @cindex JIT debug info reader
33124 Generating debug information in platform-native file formats (like ELF
33125 or COFF) may be an overkill for JIT compilers; especially if all the
33126 debug info is used for is displaying a meaningful backtrace. The
33127 issue can be resolved by having the JIT writers decide on a debug info
33128 format and also provide a reader that parses the debug info generated
33129 by the JIT compiler. This section gives a brief overview on writing
33130 such a parser. More specific details can be found in the source file
33131 @file{gdb/jit-reader.in}, which is also installed as a header at
33132 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33134 The reader is implemented as a shared object (so this functionality is
33135 not available on platforms which don't allow loading shared objects at
33136 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33137 @code{jit-reader-unload} are provided, to be used to load and unload
33138 the readers from a preconfigured directory. Once loaded, the shared
33139 object is used the parse the debug information emitted by the JIT
33143 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33144 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33147 @node Using JIT Debug Info Readers
33148 @subsection Using JIT Debug Info Readers
33149 @kindex jit-reader-load
33150 @kindex jit-reader-unload
33152 Readers can be loaded and unloaded using the @code{jit-reader-load}
33153 and @code{jit-reader-unload} commands.
33156 @item jit-reader-load @var{reader}
33157 Load the JIT reader named @var{reader}, which is a shared
33158 object specified as either an absolute or a relative file name. In
33159 the latter case, @value{GDBN} will try to load the reader from a
33160 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33161 system (here @var{libdir} is the system library directory, often
33162 @file{/usr/local/lib}).
33164 Only one reader can be active at a time; trying to load a second
33165 reader when one is already loaded will result in @value{GDBN}
33166 reporting an error. A new JIT reader can be loaded by first unloading
33167 the current one using @code{jit-reader-unload} and then invoking
33168 @code{jit-reader-load}.
33170 @item jit-reader-unload
33171 Unload the currently loaded JIT reader.
33175 @node Writing JIT Debug Info Readers
33176 @subsection Writing JIT Debug Info Readers
33177 @cindex writing JIT debug info readers
33179 As mentioned, a reader is essentially a shared object conforming to a
33180 certain ABI. This ABI is described in @file{jit-reader.h}.
33182 @file{jit-reader.h} defines the structures, macros and functions
33183 required to write a reader. It is installed (along with
33184 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33185 the system include directory.
33187 Readers need to be released under a GPL compatible license. A reader
33188 can be declared as released under such a license by placing the macro
33189 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33191 The entry point for readers is the symbol @code{gdb_init_reader},
33192 which is expected to be a function with the prototype
33194 @findex gdb_init_reader
33196 extern struct gdb_reader_funcs *gdb_init_reader (void);
33199 @cindex @code{struct gdb_reader_funcs}
33201 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33202 functions. These functions are executed to read the debug info
33203 generated by the JIT compiler (@code{read}), to unwind stack frames
33204 (@code{unwind}) and to create canonical frame IDs
33205 (@code{get_Frame_id}). It also has a callback that is called when the
33206 reader is being unloaded (@code{destroy}). The struct looks like this
33209 struct gdb_reader_funcs
33211 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33212 int reader_version;
33214 /* For use by the reader. */
33217 gdb_read_debug_info *read;
33218 gdb_unwind_frame *unwind;
33219 gdb_get_frame_id *get_frame_id;
33220 gdb_destroy_reader *destroy;
33224 @cindex @code{struct gdb_symbol_callbacks}
33225 @cindex @code{struct gdb_unwind_callbacks}
33227 The callbacks are provided with another set of callbacks by
33228 @value{GDBN} to do their job. For @code{read}, these callbacks are
33229 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33230 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33231 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33232 files and new symbol tables inside those object files. @code{struct
33233 gdb_unwind_callbacks} has callbacks to read registers off the current
33234 frame and to write out the values of the registers in the previous
33235 frame. Both have a callback (@code{target_read}) to read bytes off the
33236 target's address space.
33238 @node In-Process Agent
33239 @chapter In-Process Agent
33240 @cindex debugging agent
33241 The traditional debugging model is conceptually low-speed, but works fine,
33242 because most bugs can be reproduced in debugging-mode execution. However,
33243 as multi-core or many-core processors are becoming mainstream, and
33244 multi-threaded programs become more and more popular, there should be more
33245 and more bugs that only manifest themselves at normal-mode execution, for
33246 example, thread races, because debugger's interference with the program's
33247 timing may conceal the bugs. On the other hand, in some applications,
33248 it is not feasible for the debugger to interrupt the program's execution
33249 long enough for the developer to learn anything helpful about its behavior.
33250 If the program's correctness depends on its real-time behavior, delays
33251 introduced by a debugger might cause the program to fail, even when the
33252 code itself is correct. It is useful to be able to observe the program's
33253 behavior without interrupting it.
33255 Therefore, traditional debugging model is too intrusive to reproduce
33256 some bugs. In order to reduce the interference with the program, we can
33257 reduce the number of operations performed by debugger. The
33258 @dfn{In-Process Agent}, a shared library, is running within the same
33259 process with inferior, and is able to perform some debugging operations
33260 itself. As a result, debugger is only involved when necessary, and
33261 performance of debugging can be improved accordingly. Note that
33262 interference with program can be reduced but can't be removed completely,
33263 because the in-process agent will still stop or slow down the program.
33265 The in-process agent can interpret and execute Agent Expressions
33266 (@pxref{Agent Expressions}) during performing debugging operations. The
33267 agent expressions can be used for different purposes, such as collecting
33268 data in tracepoints, and condition evaluation in breakpoints.
33270 @anchor{Control Agent}
33271 You can control whether the in-process agent is used as an aid for
33272 debugging with the following commands:
33275 @kindex set agent on
33277 Causes the in-process agent to perform some operations on behalf of the
33278 debugger. Just which operations requested by the user will be done
33279 by the in-process agent depends on the its capabilities. For example,
33280 if you request to evaluate breakpoint conditions in the in-process agent,
33281 and the in-process agent has such capability as well, then breakpoint
33282 conditions will be evaluated in the in-process agent.
33284 @kindex set agent off
33285 @item set agent off
33286 Disables execution of debugging operations by the in-process agent. All
33287 of the operations will be performed by @value{GDBN}.
33291 Display the current setting of execution of debugging operations by
33292 the in-process agent.
33296 * In-Process Agent Protocol::
33299 @node In-Process Agent Protocol
33300 @section In-Process Agent Protocol
33301 @cindex in-process agent protocol
33303 The in-process agent is able to communicate with both @value{GDBN} and
33304 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33305 used for communications between @value{GDBN} or GDBserver and the IPA.
33306 In general, @value{GDBN} or GDBserver sends commands
33307 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33308 in-process agent replies back with the return result of the command, or
33309 some other information. The data sent to in-process agent is composed
33310 of primitive data types, such as 4-byte or 8-byte type, and composite
33311 types, which are called objects (@pxref{IPA Protocol Objects}).
33314 * IPA Protocol Objects::
33315 * IPA Protocol Commands::
33318 @node IPA Protocol Objects
33319 @subsection IPA Protocol Objects
33320 @cindex ipa protocol objects
33322 The commands sent to and results received from agent may contain some
33323 complex data types called @dfn{objects}.
33325 The in-process agent is running on the same machine with @value{GDBN}
33326 or GDBserver, so it doesn't have to handle as much differences between
33327 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33328 However, there are still some differences of two ends in two processes:
33332 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33333 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33335 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33336 GDBserver is compiled with one, and in-process agent is compiled with
33340 Here are the IPA Protocol Objects:
33344 agent expression object. It represents an agent expression
33345 (@pxref{Agent Expressions}).
33346 @anchor{agent expression object}
33348 tracepoint action object. It represents a tracepoint action
33349 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33350 memory, static trace data and to evaluate expression.
33351 @anchor{tracepoint action object}
33353 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33354 @anchor{tracepoint object}
33358 The following table describes important attributes of each IPA protocol
33361 @multitable @columnfractions .30 .20 .50
33362 @headitem Name @tab Size @tab Description
33363 @item @emph{agent expression object} @tab @tab
33364 @item length @tab 4 @tab length of bytes code
33365 @item byte code @tab @var{length} @tab contents of byte code
33366 @item @emph{tracepoint action for collecting memory} @tab @tab
33367 @item 'M' @tab 1 @tab type of tracepoint action
33368 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33369 address of the lowest byte to collect, otherwise @var{addr} is the offset
33370 of @var{basereg} for memory collecting.
33371 @item len @tab 8 @tab length of memory for collecting
33372 @item basereg @tab 4 @tab the register number containing the starting
33373 memory address for collecting.
33374 @item @emph{tracepoint action for collecting registers} @tab @tab
33375 @item 'R' @tab 1 @tab type of tracepoint action
33376 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33377 @item 'L' @tab 1 @tab type of tracepoint action
33378 @item @emph{tracepoint action for expression evaluation} @tab @tab
33379 @item 'X' @tab 1 @tab type of tracepoint action
33380 @item agent expression @tab length of @tab @ref{agent expression object}
33381 @item @emph{tracepoint object} @tab @tab
33382 @item number @tab 4 @tab number of tracepoint
33383 @item address @tab 8 @tab address of tracepoint inserted on
33384 @item type @tab 4 @tab type of tracepoint
33385 @item enabled @tab 1 @tab enable or disable of tracepoint
33386 @item step_count @tab 8 @tab step
33387 @item pass_count @tab 8 @tab pass
33388 @item numactions @tab 4 @tab number of tracepoint actions
33389 @item hit count @tab 8 @tab hit count
33390 @item trace frame usage @tab 8 @tab trace frame usage
33391 @item compiled_cond @tab 8 @tab compiled condition
33392 @item orig_size @tab 8 @tab orig size
33393 @item condition @tab 4 if condition is NULL otherwise length of
33394 @ref{agent expression object}
33395 @tab zero if condition is NULL, otherwise is
33396 @ref{agent expression object}
33397 @item actions @tab variable
33398 @tab numactions number of @ref{tracepoint action object}
33401 @node IPA Protocol Commands
33402 @subsection IPA Protocol Commands
33403 @cindex ipa protocol commands
33405 The spaces in each command are delimiters to ease reading this commands
33406 specification. They don't exist in real commands.
33410 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33411 Installs a new fast tracepoint described by @var{tracepoint_object}
33412 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33413 head of @dfn{jumppad}, which is used to jump to data collection routine
33418 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33419 @var{target_address} is address of tracepoint in the inferior.
33420 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33421 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33422 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33423 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33430 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33431 is about to kill inferiors.
33439 @item probe_marker_at:@var{address}
33440 Asks in-process agent to probe the marker at @var{address}.
33447 @item unprobe_marker_at:@var{address}
33448 Asks in-process agent to unprobe the marker at @var{address}.
33452 @chapter Reporting Bugs in @value{GDBN}
33453 @cindex bugs in @value{GDBN}
33454 @cindex reporting bugs in @value{GDBN}
33456 Your bug reports play an essential role in making @value{GDBN} reliable.
33458 Reporting a bug may help you by bringing a solution to your problem, or it
33459 may not. But in any case the principal function of a bug report is to help
33460 the entire community by making the next version of @value{GDBN} work better. Bug
33461 reports are your contribution to the maintenance of @value{GDBN}.
33463 In order for a bug report to serve its purpose, you must include the
33464 information that enables us to fix the bug.
33467 * Bug Criteria:: Have you found a bug?
33468 * Bug Reporting:: How to report bugs
33472 @section Have You Found a Bug?
33473 @cindex bug criteria
33475 If you are not sure whether you have found a bug, here are some guidelines:
33478 @cindex fatal signal
33479 @cindex debugger crash
33480 @cindex crash of debugger
33482 If the debugger gets a fatal signal, for any input whatever, that is a
33483 @value{GDBN} bug. Reliable debuggers never crash.
33485 @cindex error on valid input
33487 If @value{GDBN} produces an error message for valid input, that is a
33488 bug. (Note that if you're cross debugging, the problem may also be
33489 somewhere in the connection to the target.)
33491 @cindex invalid input
33493 If @value{GDBN} does not produce an error message for invalid input,
33494 that is a bug. However, you should note that your idea of
33495 ``invalid input'' might be our idea of ``an extension'' or ``support
33496 for traditional practice''.
33499 If you are an experienced user of debugging tools, your suggestions
33500 for improvement of @value{GDBN} are welcome in any case.
33503 @node Bug Reporting
33504 @section How to Report Bugs
33505 @cindex bug reports
33506 @cindex @value{GDBN} bugs, reporting
33508 A number of companies and individuals offer support for @sc{gnu} products.
33509 If you obtained @value{GDBN} from a support organization, we recommend you
33510 contact that organization first.
33512 You can find contact information for many support companies and
33513 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33515 @c should add a web page ref...
33518 @ifset BUGURL_DEFAULT
33519 In any event, we also recommend that you submit bug reports for
33520 @value{GDBN}. The preferred method is to submit them directly using
33521 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33522 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33525 @strong{Do not send bug reports to @samp{info-gdb}, or to
33526 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33527 not want to receive bug reports. Those that do have arranged to receive
33530 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33531 serves as a repeater. The mailing list and the newsgroup carry exactly
33532 the same messages. Often people think of posting bug reports to the
33533 newsgroup instead of mailing them. This appears to work, but it has one
33534 problem which can be crucial: a newsgroup posting often lacks a mail
33535 path back to the sender. Thus, if we need to ask for more information,
33536 we may be unable to reach you. For this reason, it is better to send
33537 bug reports to the mailing list.
33539 @ifclear BUGURL_DEFAULT
33540 In any event, we also recommend that you submit bug reports for
33541 @value{GDBN} to @value{BUGURL}.
33545 The fundamental principle of reporting bugs usefully is this:
33546 @strong{report all the facts}. If you are not sure whether to state a
33547 fact or leave it out, state it!
33549 Often people omit facts because they think they know what causes the
33550 problem and assume that some details do not matter. Thus, you might
33551 assume that the name of the variable you use in an example does not matter.
33552 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33553 stray memory reference which happens to fetch from the location where that
33554 name is stored in memory; perhaps, if the name were different, the contents
33555 of that location would fool the debugger into doing the right thing despite
33556 the bug. Play it safe and give a specific, complete example. That is the
33557 easiest thing for you to do, and the most helpful.
33559 Keep in mind that the purpose of a bug report is to enable us to fix the
33560 bug. It may be that the bug has been reported previously, but neither
33561 you nor we can know that unless your bug report is complete and
33564 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33565 bell?'' Those bug reports are useless, and we urge everyone to
33566 @emph{refuse to respond to them} except to chide the sender to report
33569 To enable us to fix the bug, you should include all these things:
33573 The version of @value{GDBN}. @value{GDBN} announces it if you start
33574 with no arguments; you can also print it at any time using @code{show
33577 Without this, we will not know whether there is any point in looking for
33578 the bug in the current version of @value{GDBN}.
33581 The type of machine you are using, and the operating system name and
33585 The details of the @value{GDBN} build-time configuration.
33586 @value{GDBN} shows these details if you invoke it with the
33587 @option{--configuration} command-line option, or if you type
33588 @code{show configuration} at @value{GDBN}'s prompt.
33591 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33592 ``@value{GCC}--2.8.1''.
33595 What compiler (and its version) was used to compile the program you are
33596 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33597 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33598 to get this information; for other compilers, see the documentation for
33602 The command arguments you gave the compiler to compile your example and
33603 observe the bug. For example, did you use @samp{-O}? To guarantee
33604 you will not omit something important, list them all. A copy of the
33605 Makefile (or the output from make) is sufficient.
33607 If we were to try to guess the arguments, we would probably guess wrong
33608 and then we might not encounter the bug.
33611 A complete input script, and all necessary source files, that will
33615 A description of what behavior you observe that you believe is
33616 incorrect. For example, ``It gets a fatal signal.''
33618 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33619 will certainly notice it. But if the bug is incorrect output, we might
33620 not notice unless it is glaringly wrong. You might as well not give us
33621 a chance to make a mistake.
33623 Even if the problem you experience is a fatal signal, you should still
33624 say so explicitly. Suppose something strange is going on, such as, your
33625 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33626 the C library on your system. (This has happened!) Your copy might
33627 crash and ours would not. If you told us to expect a crash, then when
33628 ours fails to crash, we would know that the bug was not happening for
33629 us. If you had not told us to expect a crash, then we would not be able
33630 to draw any conclusion from our observations.
33633 @cindex recording a session script
33634 To collect all this information, you can use a session recording program
33635 such as @command{script}, which is available on many Unix systems.
33636 Just run your @value{GDBN} session inside @command{script} and then
33637 include the @file{typescript} file with your bug report.
33639 Another way to record a @value{GDBN} session is to run @value{GDBN}
33640 inside Emacs and then save the entire buffer to a file.
33643 If you wish to suggest changes to the @value{GDBN} source, send us context
33644 diffs. If you even discuss something in the @value{GDBN} source, refer to
33645 it by context, not by line number.
33647 The line numbers in our development sources will not match those in your
33648 sources. Your line numbers would convey no useful information to us.
33652 Here are some things that are not necessary:
33656 A description of the envelope of the bug.
33658 Often people who encounter a bug spend a lot of time investigating
33659 which changes to the input file will make the bug go away and which
33660 changes will not affect it.
33662 This is often time consuming and not very useful, because the way we
33663 will find the bug is by running a single example under the debugger
33664 with breakpoints, not by pure deduction from a series of examples.
33665 We recommend that you save your time for something else.
33667 Of course, if you can find a simpler example to report @emph{instead}
33668 of the original one, that is a convenience for us. Errors in the
33669 output will be easier to spot, running under the debugger will take
33670 less time, and so on.
33672 However, simplification is not vital; if you do not want to do this,
33673 report the bug anyway and send us the entire test case you used.
33676 A patch for the bug.
33678 A patch for the bug does help us if it is a good one. But do not omit
33679 the necessary information, such as the test case, on the assumption that
33680 a patch is all we need. We might see problems with your patch and decide
33681 to fix the problem another way, or we might not understand it at all.
33683 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33684 construct an example that will make the program follow a certain path
33685 through the code. If you do not send us the example, we will not be able
33686 to construct one, so we will not be able to verify that the bug is fixed.
33688 And if we cannot understand what bug you are trying to fix, or why your
33689 patch should be an improvement, we will not install it. A test case will
33690 help us to understand.
33693 A guess about what the bug is or what it depends on.
33695 Such guesses are usually wrong. Even we cannot guess right about such
33696 things without first using the debugger to find the facts.
33699 @c The readline documentation is distributed with the readline code
33700 @c and consists of the two following files:
33703 @c Use -I with makeinfo to point to the appropriate directory,
33704 @c environment var TEXINPUTS with TeX.
33705 @ifclear SYSTEM_READLINE
33706 @include rluser.texi
33707 @include hsuser.texi
33711 @appendix In Memoriam
33713 The @value{GDBN} project mourns the loss of the following long-time
33718 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33719 to Free Software in general. Outside of @value{GDBN}, he was known in
33720 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33722 @item Michael Snyder
33723 Michael was one of the Global Maintainers of the @value{GDBN} project,
33724 with contributions recorded as early as 1996, until 2011. In addition
33725 to his day to day participation, he was a large driving force behind
33726 adding Reverse Debugging to @value{GDBN}.
33729 Beyond their technical contributions to the project, they were also
33730 enjoyable members of the Free Software Community. We will miss them.
33732 @node Formatting Documentation
33733 @appendix Formatting Documentation
33735 @cindex @value{GDBN} reference card
33736 @cindex reference card
33737 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33738 for printing with PostScript or Ghostscript, in the @file{gdb}
33739 subdirectory of the main source directory@footnote{In
33740 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33741 release.}. If you can use PostScript or Ghostscript with your printer,
33742 you can print the reference card immediately with @file{refcard.ps}.
33744 The release also includes the source for the reference card. You
33745 can format it, using @TeX{}, by typing:
33751 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33752 mode on US ``letter'' size paper;
33753 that is, on a sheet 11 inches wide by 8.5 inches
33754 high. You will need to specify this form of printing as an option to
33755 your @sc{dvi} output program.
33757 @cindex documentation
33759 All the documentation for @value{GDBN} comes as part of the machine-readable
33760 distribution. The documentation is written in Texinfo format, which is
33761 a documentation system that uses a single source file to produce both
33762 on-line information and a printed manual. You can use one of the Info
33763 formatting commands to create the on-line version of the documentation
33764 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33766 @value{GDBN} includes an already formatted copy of the on-line Info
33767 version of this manual in the @file{gdb} subdirectory. The main Info
33768 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33769 subordinate files matching @samp{gdb.info*} in the same directory. If
33770 necessary, you can print out these files, or read them with any editor;
33771 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33772 Emacs or the standalone @code{info} program, available as part of the
33773 @sc{gnu} Texinfo distribution.
33775 If you want to format these Info files yourself, you need one of the
33776 Info formatting programs, such as @code{texinfo-format-buffer} or
33779 If you have @code{makeinfo} installed, and are in the top level
33780 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33781 version @value{GDBVN}), you can make the Info file by typing:
33788 If you want to typeset and print copies of this manual, you need @TeX{},
33789 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33790 Texinfo definitions file.
33792 @TeX{} is a typesetting program; it does not print files directly, but
33793 produces output files called @sc{dvi} files. To print a typeset
33794 document, you need a program to print @sc{dvi} files. If your system
33795 has @TeX{} installed, chances are it has such a program. The precise
33796 command to use depends on your system; @kbd{lpr -d} is common; another
33797 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33798 require a file name without any extension or a @samp{.dvi} extension.
33800 @TeX{} also requires a macro definitions file called
33801 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33802 written in Texinfo format. On its own, @TeX{} cannot either read or
33803 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33804 and is located in the @file{gdb-@var{version-number}/texinfo}
33807 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33808 typeset and print this manual. First switch to the @file{gdb}
33809 subdirectory of the main source directory (for example, to
33810 @file{gdb-@value{GDBVN}/gdb}) and type:
33816 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33818 @node Installing GDB
33819 @appendix Installing @value{GDBN}
33820 @cindex installation
33823 * Requirements:: Requirements for building @value{GDBN}
33824 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33825 * Separate Objdir:: Compiling @value{GDBN} in another directory
33826 * Config Names:: Specifying names for hosts and targets
33827 * Configure Options:: Summary of options for configure
33828 * System-wide configuration:: Having a system-wide init file
33832 @section Requirements for Building @value{GDBN}
33833 @cindex building @value{GDBN}, requirements for
33835 Building @value{GDBN} requires various tools and packages to be available.
33836 Other packages will be used only if they are found.
33838 @heading Tools/Packages Necessary for Building @value{GDBN}
33840 @item ISO C90 compiler
33841 @value{GDBN} is written in ISO C90. It should be buildable with any
33842 working C90 compiler, e.g.@: GCC.
33846 @heading Tools/Packages Optional for Building @value{GDBN}
33850 @value{GDBN} can use the Expat XML parsing library. This library may be
33851 included with your operating system distribution; if it is not, you
33852 can get the latest version from @url{http://expat.sourceforge.net}.
33853 The @file{configure} script will search for this library in several
33854 standard locations; if it is installed in an unusual path, you can
33855 use the @option{--with-libexpat-prefix} option to specify its location.
33861 Remote protocol memory maps (@pxref{Memory Map Format})
33863 Target descriptions (@pxref{Target Descriptions})
33865 Remote shared library lists (@xref{Library List Format},
33866 or alternatively @pxref{Library List Format for SVR4 Targets})
33868 MS-Windows shared libraries (@pxref{Shared Libraries})
33870 Traceframe info (@pxref{Traceframe Info Format})
33872 Branch trace (@pxref{Branch Trace Format},
33873 @pxref{Branch Trace Configuration Format})
33877 @cindex compressed debug sections
33878 @value{GDBN} will use the @samp{zlib} library, if available, to read
33879 compressed debug sections. Some linkers, such as GNU gold, are capable
33880 of producing binaries with compressed debug sections. If @value{GDBN}
33881 is compiled with @samp{zlib}, it will be able to read the debug
33882 information in such binaries.
33884 The @samp{zlib} library is likely included with your operating system
33885 distribution; if it is not, you can get the latest version from
33886 @url{http://zlib.net}.
33889 @value{GDBN}'s features related to character sets (@pxref{Character
33890 Sets}) require a functioning @code{iconv} implementation. If you are
33891 on a GNU system, then this is provided by the GNU C Library. Some
33892 other systems also provide a working @code{iconv}.
33894 If @value{GDBN} is using the @code{iconv} program which is installed
33895 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33896 This is done with @option{--with-iconv-bin} which specifies the
33897 directory that contains the @code{iconv} program.
33899 On systems without @code{iconv}, you can install GNU Libiconv. If you
33900 have previously installed Libiconv, you can use the
33901 @option{--with-libiconv-prefix} option to configure.
33903 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33904 arrange to build Libiconv if a directory named @file{libiconv} appears
33905 in the top-most source directory. If Libiconv is built this way, and
33906 if the operating system does not provide a suitable @code{iconv}
33907 implementation, then the just-built library will automatically be used
33908 by @value{GDBN}. One easy way to set this up is to download GNU
33909 Libiconv, unpack it, and then rename the directory holding the
33910 Libiconv source code to @samp{libiconv}.
33913 @node Running Configure
33914 @section Invoking the @value{GDBN} @file{configure} Script
33915 @cindex configuring @value{GDBN}
33916 @value{GDBN} comes with a @file{configure} script that automates the process
33917 of preparing @value{GDBN} for installation; you can then use @code{make} to
33918 build the @code{gdb} program.
33920 @c irrelevant in info file; it's as current as the code it lives with.
33921 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33922 look at the @file{README} file in the sources; we may have improved the
33923 installation procedures since publishing this manual.}
33926 The @value{GDBN} distribution includes all the source code you need for
33927 @value{GDBN} in a single directory, whose name is usually composed by
33928 appending the version number to @samp{gdb}.
33930 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33931 @file{gdb-@value{GDBVN}} directory. That directory contains:
33934 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33935 script for configuring @value{GDBN} and all its supporting libraries
33937 @item gdb-@value{GDBVN}/gdb
33938 the source specific to @value{GDBN} itself
33940 @item gdb-@value{GDBVN}/bfd
33941 source for the Binary File Descriptor library
33943 @item gdb-@value{GDBVN}/include
33944 @sc{gnu} include files
33946 @item gdb-@value{GDBVN}/libiberty
33947 source for the @samp{-liberty} free software library
33949 @item gdb-@value{GDBVN}/opcodes
33950 source for the library of opcode tables and disassemblers
33952 @item gdb-@value{GDBVN}/readline
33953 source for the @sc{gnu} command-line interface
33955 @item gdb-@value{GDBVN}/glob
33956 source for the @sc{gnu} filename pattern-matching subroutine
33958 @item gdb-@value{GDBVN}/mmalloc
33959 source for the @sc{gnu} memory-mapped malloc package
33962 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33963 from the @file{gdb-@var{version-number}} source directory, which in
33964 this example is the @file{gdb-@value{GDBVN}} directory.
33966 First switch to the @file{gdb-@var{version-number}} source directory
33967 if you are not already in it; then run @file{configure}. Pass the
33968 identifier for the platform on which @value{GDBN} will run as an
33974 cd gdb-@value{GDBVN}
33975 ./configure @var{host}
33980 where @var{host} is an identifier such as @samp{sun4} or
33981 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33982 (You can often leave off @var{host}; @file{configure} tries to guess the
33983 correct value by examining your system.)
33985 Running @samp{configure @var{host}} and then running @code{make} builds the
33986 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33987 libraries, then @code{gdb} itself. The configured source files, and the
33988 binaries, are left in the corresponding source directories.
33991 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33992 system does not recognize this automatically when you run a different
33993 shell, you may need to run @code{sh} on it explicitly:
33996 sh configure @var{host}
33999 If you run @file{configure} from a directory that contains source
34000 directories for multiple libraries or programs, such as the
34001 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34003 creates configuration files for every directory level underneath (unless
34004 you tell it not to, with the @samp{--norecursion} option).
34006 You should run the @file{configure} script from the top directory in the
34007 source tree, the @file{gdb-@var{version-number}} directory. If you run
34008 @file{configure} from one of the subdirectories, you will configure only
34009 that subdirectory. That is usually not what you want. In particular,
34010 if you run the first @file{configure} from the @file{gdb} subdirectory
34011 of the @file{gdb-@var{version-number}} directory, you will omit the
34012 configuration of @file{bfd}, @file{readline}, and other sibling
34013 directories of the @file{gdb} subdirectory. This leads to build errors
34014 about missing include files such as @file{bfd/bfd.h}.
34016 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34017 However, you should make sure that the shell on your path (named by
34018 the @samp{SHELL} environment variable) is publicly readable. Remember
34019 that @value{GDBN} uses the shell to start your program---some systems refuse to
34020 let @value{GDBN} debug child processes whose programs are not readable.
34022 @node Separate Objdir
34023 @section Compiling @value{GDBN} in Another Directory
34025 If you want to run @value{GDBN} versions for several host or target machines,
34026 you need a different @code{gdb} compiled for each combination of
34027 host and target. @file{configure} is designed to make this easy by
34028 allowing you to generate each configuration in a separate subdirectory,
34029 rather than in the source directory. If your @code{make} program
34030 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34031 @code{make} in each of these directories builds the @code{gdb}
34032 program specified there.
34034 To build @code{gdb} in a separate directory, run @file{configure}
34035 with the @samp{--srcdir} option to specify where to find the source.
34036 (You also need to specify a path to find @file{configure}
34037 itself from your working directory. If the path to @file{configure}
34038 would be the same as the argument to @samp{--srcdir}, you can leave out
34039 the @samp{--srcdir} option; it is assumed.)
34041 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34042 separate directory for a Sun 4 like this:
34046 cd gdb-@value{GDBVN}
34049 ../gdb-@value{GDBVN}/configure sun4
34054 When @file{configure} builds a configuration using a remote source
34055 directory, it creates a tree for the binaries with the same structure
34056 (and using the same names) as the tree under the source directory. In
34057 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34058 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34059 @file{gdb-sun4/gdb}.
34061 Make sure that your path to the @file{configure} script has just one
34062 instance of @file{gdb} in it. If your path to @file{configure} looks
34063 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34064 one subdirectory of @value{GDBN}, not the whole package. This leads to
34065 build errors about missing include files such as @file{bfd/bfd.h}.
34067 One popular reason to build several @value{GDBN} configurations in separate
34068 directories is to configure @value{GDBN} for cross-compiling (where
34069 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34070 programs that run on another machine---the @dfn{target}).
34071 You specify a cross-debugging target by
34072 giving the @samp{--target=@var{target}} option to @file{configure}.
34074 When you run @code{make} to build a program or library, you must run
34075 it in a configured directory---whatever directory you were in when you
34076 called @file{configure} (or one of its subdirectories).
34078 The @code{Makefile} that @file{configure} generates in each source
34079 directory also runs recursively. If you type @code{make} in a source
34080 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34081 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34082 will build all the required libraries, and then build GDB.
34084 When you have multiple hosts or targets configured in separate
34085 directories, you can run @code{make} on them in parallel (for example,
34086 if they are NFS-mounted on each of the hosts); they will not interfere
34090 @section Specifying Names for Hosts and Targets
34092 The specifications used for hosts and targets in the @file{configure}
34093 script are based on a three-part naming scheme, but some short predefined
34094 aliases are also supported. The full naming scheme encodes three pieces
34095 of information in the following pattern:
34098 @var{architecture}-@var{vendor}-@var{os}
34101 For example, you can use the alias @code{sun4} as a @var{host} argument,
34102 or as the value for @var{target} in a @code{--target=@var{target}}
34103 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34105 The @file{configure} script accompanying @value{GDBN} does not provide
34106 any query facility to list all supported host and target names or
34107 aliases. @file{configure} calls the Bourne shell script
34108 @code{config.sub} to map abbreviations to full names; you can read the
34109 script, if you wish, or you can use it to test your guesses on
34110 abbreviations---for example:
34113 % sh config.sub i386-linux
34115 % sh config.sub alpha-linux
34116 alpha-unknown-linux-gnu
34117 % sh config.sub hp9k700
34119 % sh config.sub sun4
34120 sparc-sun-sunos4.1.1
34121 % sh config.sub sun3
34122 m68k-sun-sunos4.1.1
34123 % sh config.sub i986v
34124 Invalid configuration `i986v': machine `i986v' not recognized
34128 @code{config.sub} is also distributed in the @value{GDBN} source
34129 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34131 @node Configure Options
34132 @section @file{configure} Options
34134 Here is a summary of the @file{configure} options and arguments that
34135 are most often useful for building @value{GDBN}. @file{configure} also has
34136 several other options not listed here. @inforef{What Configure
34137 Does,,configure.info}, for a full explanation of @file{configure}.
34140 configure @r{[}--help@r{]}
34141 @r{[}--prefix=@var{dir}@r{]}
34142 @r{[}--exec-prefix=@var{dir}@r{]}
34143 @r{[}--srcdir=@var{dirname}@r{]}
34144 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34145 @r{[}--target=@var{target}@r{]}
34150 You may introduce options with a single @samp{-} rather than
34151 @samp{--} if you prefer; but you may abbreviate option names if you use
34156 Display a quick summary of how to invoke @file{configure}.
34158 @item --prefix=@var{dir}
34159 Configure the source to install programs and files under directory
34162 @item --exec-prefix=@var{dir}
34163 Configure the source to install programs under directory
34166 @c avoid splitting the warning from the explanation:
34168 @item --srcdir=@var{dirname}
34169 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34170 @code{make} that implements the @code{VPATH} feature.}@*
34171 Use this option to make configurations in directories separate from the
34172 @value{GDBN} source directories. Among other things, you can use this to
34173 build (or maintain) several configurations simultaneously, in separate
34174 directories. @file{configure} writes configuration-specific files in
34175 the current directory, but arranges for them to use the source in the
34176 directory @var{dirname}. @file{configure} creates directories under
34177 the working directory in parallel to the source directories below
34180 @item --norecursion
34181 Configure only the directory level where @file{configure} is executed; do not
34182 propagate configuration to subdirectories.
34184 @item --target=@var{target}
34185 Configure @value{GDBN} for cross-debugging programs running on the specified
34186 @var{target}. Without this option, @value{GDBN} is configured to debug
34187 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34189 There is no convenient way to generate a list of all available targets.
34191 @item @var{host} @dots{}
34192 Configure @value{GDBN} to run on the specified @var{host}.
34194 There is no convenient way to generate a list of all available hosts.
34197 There are many other options available as well, but they are generally
34198 needed for special purposes only.
34200 @node System-wide configuration
34201 @section System-wide configuration and settings
34202 @cindex system-wide init file
34204 @value{GDBN} can be configured to have a system-wide init file;
34205 this file will be read and executed at startup (@pxref{Startup, , What
34206 @value{GDBN} does during startup}).
34208 Here is the corresponding configure option:
34211 @item --with-system-gdbinit=@var{file}
34212 Specify that the default location of the system-wide init file is
34216 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34217 it may be subject to relocation. Two possible cases:
34221 If the default location of this init file contains @file{$prefix},
34222 it will be subject to relocation. Suppose that the configure options
34223 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34224 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34225 init file is looked for as @file{$install/etc/gdbinit} instead of
34226 @file{$prefix/etc/gdbinit}.
34229 By contrast, if the default location does not contain the prefix,
34230 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34231 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34232 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34233 wherever @value{GDBN} is installed.
34236 If the configured location of the system-wide init file (as given by the
34237 @option{--with-system-gdbinit} option at configure time) is in the
34238 data-directory (as specified by @option{--with-gdb-datadir} at configure
34239 time) or in one of its subdirectories, then @value{GDBN} will look for the
34240 system-wide init file in the directory specified by the
34241 @option{--data-directory} command-line option.
34242 Note that the system-wide init file is only read once, during @value{GDBN}
34243 initialization. If the data-directory is changed after @value{GDBN} has
34244 started with the @code{set data-directory} command, the file will not be
34248 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34251 @node System-wide Configuration Scripts
34252 @subsection Installed System-wide Configuration Scripts
34253 @cindex system-wide configuration scripts
34255 The @file{system-gdbinit} directory, located inside the data-directory
34256 (as specified by @option{--with-gdb-datadir} at configure time) contains
34257 a number of scripts which can be used as system-wide init files. To
34258 automatically source those scripts at startup, @value{GDBN} should be
34259 configured with @option{--with-system-gdbinit}. Otherwise, any user
34260 should be able to source them by hand as needed.
34262 The following scripts are currently available:
34265 @item @file{elinos.py}
34267 @cindex ELinOS system-wide configuration script
34268 This script is useful when debugging a program on an ELinOS target.
34269 It takes advantage of the environment variables defined in a standard
34270 ELinOS environment in order to determine the location of the system
34271 shared libraries, and then sets the @samp{solib-absolute-prefix}
34272 and @samp{solib-search-path} variables appropriately.
34274 @item @file{wrs-linux.py}
34275 @pindex wrs-linux.py
34276 @cindex Wind River Linux system-wide configuration script
34277 This script is useful when debugging a program on a target running
34278 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34279 the host-side sysroot used by the target system.
34283 @node Maintenance Commands
34284 @appendix Maintenance Commands
34285 @cindex maintenance commands
34286 @cindex internal commands
34288 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34289 includes a number of commands intended for @value{GDBN} developers,
34290 that are not documented elsewhere in this manual. These commands are
34291 provided here for reference. (For commands that turn on debugging
34292 messages, see @ref{Debugging Output}.)
34295 @kindex maint agent
34296 @kindex maint agent-eval
34297 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34298 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34299 Translate the given @var{expression} into remote agent bytecodes.
34300 This command is useful for debugging the Agent Expression mechanism
34301 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34302 expression useful for data collection, such as by tracepoints, while
34303 @samp{maint agent-eval} produces an expression that evaluates directly
34304 to a result. For instance, a collection expression for @code{globa +
34305 globb} will include bytecodes to record four bytes of memory at each
34306 of the addresses of @code{globa} and @code{globb}, while discarding
34307 the result of the addition, while an evaluation expression will do the
34308 addition and return the sum.
34309 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34310 If not, generate remote agent bytecode for current frame PC address.
34312 @kindex maint agent-printf
34313 @item maint agent-printf @var{format},@var{expr},...
34314 Translate the given format string and list of argument expressions
34315 into remote agent bytecodes and display them as a disassembled list.
34316 This command is useful for debugging the agent version of dynamic
34317 printf (@pxref{Dynamic Printf}).
34319 @kindex maint info breakpoints
34320 @item @anchor{maint info breakpoints}maint info breakpoints
34321 Using the same format as @samp{info breakpoints}, display both the
34322 breakpoints you've set explicitly, and those @value{GDBN} is using for
34323 internal purposes. Internal breakpoints are shown with negative
34324 breakpoint numbers. The type column identifies what kind of breakpoint
34329 Normal, explicitly set breakpoint.
34332 Normal, explicitly set watchpoint.
34335 Internal breakpoint, used to handle correctly stepping through
34336 @code{longjmp} calls.
34338 @item longjmp resume
34339 Internal breakpoint at the target of a @code{longjmp}.
34342 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34345 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34348 Shared library events.
34352 @kindex maint info btrace
34353 @item maint info btrace
34354 Pint information about raw branch tracing data.
34356 @kindex maint btrace packet-history
34357 @item maint btrace packet-history
34358 Print the raw branch trace packets that are used to compute the
34359 execution history for the @samp{record btrace} command. Both the
34360 information and the format in which it is printed depend on the btrace
34365 For the BTS recording format, print a list of blocks of sequential
34366 code. For each block, the following information is printed:
34370 Newer blocks have higher numbers. The oldest block has number zero.
34371 @item Lowest @samp{PC}
34372 @item Highest @samp{PC}
34376 For the Intel Processor Trace recording format, print a list of
34377 Intel Processor Trace packets. For each packet, the following
34378 information is printed:
34381 @item Packet number
34382 Newer packets have higher numbers. The oldest packet has number zero.
34384 The packet's offset in the trace stream.
34385 @item Packet opcode and payload
34389 @kindex maint btrace clear-packet-history
34390 @item maint btrace clear-packet-history
34391 Discards the cached packet history printed by the @samp{maint btrace
34392 packet-history} command. The history will be computed again when
34395 @kindex maint btrace clear
34396 @item maint btrace clear
34397 Discard the branch trace data. The data will be fetched anew and the
34398 branch trace will be recomputed when needed.
34400 This implicitly truncates the branch trace to a single branch trace
34401 buffer. When updating branch trace incrementally, the branch trace
34402 available to @value{GDBN} may be bigger than a single branch trace
34405 @kindex maint set btrace pt skip-pad
34406 @item maint set btrace pt skip-pad
34407 @kindex maint show btrace pt skip-pad
34408 @item maint show btrace pt skip-pad
34409 Control whether @value{GDBN} will skip PAD packets when computing the
34412 @kindex set displaced-stepping
34413 @kindex show displaced-stepping
34414 @cindex displaced stepping support
34415 @cindex out-of-line single-stepping
34416 @item set displaced-stepping
34417 @itemx show displaced-stepping
34418 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34419 if the target supports it. Displaced stepping is a way to single-step
34420 over breakpoints without removing them from the inferior, by executing
34421 an out-of-line copy of the instruction that was originally at the
34422 breakpoint location. It is also known as out-of-line single-stepping.
34425 @item set displaced-stepping on
34426 If the target architecture supports it, @value{GDBN} will use
34427 displaced stepping to step over breakpoints.
34429 @item set displaced-stepping off
34430 @value{GDBN} will not use displaced stepping to step over breakpoints,
34431 even if such is supported by the target architecture.
34433 @cindex non-stop mode, and @samp{set displaced-stepping}
34434 @item set displaced-stepping auto
34435 This is the default mode. @value{GDBN} will use displaced stepping
34436 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34437 architecture supports displaced stepping.
34440 @kindex maint check-psymtabs
34441 @item maint check-psymtabs
34442 Check the consistency of currently expanded psymtabs versus symtabs.
34443 Use this to check, for example, whether a symbol is in one but not the other.
34445 @kindex maint check-symtabs
34446 @item maint check-symtabs
34447 Check the consistency of currently expanded symtabs.
34449 @kindex maint expand-symtabs
34450 @item maint expand-symtabs [@var{regexp}]
34451 Expand symbol tables.
34452 If @var{regexp} is specified, only expand symbol tables for file
34453 names matching @var{regexp}.
34455 @kindex maint set catch-demangler-crashes
34456 @kindex maint show catch-demangler-crashes
34457 @cindex demangler crashes
34458 @item maint set catch-demangler-crashes [on|off]
34459 @itemx maint show catch-demangler-crashes
34460 Control whether @value{GDBN} should attempt to catch crashes in the
34461 symbol name demangler. The default is to attempt to catch crashes.
34462 If enabled, the first time a crash is caught, a core file is created,
34463 the offending symbol is displayed and the user is presented with the
34464 option to terminate the current session.
34466 @kindex maint cplus first_component
34467 @item maint cplus first_component @var{name}
34468 Print the first C@t{++} class/namespace component of @var{name}.
34470 @kindex maint cplus namespace
34471 @item maint cplus namespace
34472 Print the list of possible C@t{++} namespaces.
34474 @kindex maint deprecate
34475 @kindex maint undeprecate
34476 @cindex deprecated commands
34477 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34478 @itemx maint undeprecate @var{command}
34479 Deprecate or undeprecate the named @var{command}. Deprecated commands
34480 cause @value{GDBN} to issue a warning when you use them. The optional
34481 argument @var{replacement} says which newer command should be used in
34482 favor of the deprecated one; if it is given, @value{GDBN} will mention
34483 the replacement as part of the warning.
34485 @kindex maint dump-me
34486 @item maint dump-me
34487 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34488 Cause a fatal signal in the debugger and force it to dump its core.
34489 This is supported only on systems which support aborting a program
34490 with the @code{SIGQUIT} signal.
34492 @kindex maint internal-error
34493 @kindex maint internal-warning
34494 @kindex maint demangler-warning
34495 @cindex demangler crashes
34496 @item maint internal-error @r{[}@var{message-text}@r{]}
34497 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34498 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34500 Cause @value{GDBN} to call the internal function @code{internal_error},
34501 @code{internal_warning} or @code{demangler_warning} and hence behave
34502 as though an internal problem has been detected. In addition to
34503 reporting the internal problem, these functions give the user the
34504 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34505 and @code{internal_warning}) create a core file of the current
34506 @value{GDBN} session.
34508 These commands take an optional parameter @var{message-text} that is
34509 used as the text of the error or warning message.
34511 Here's an example of using @code{internal-error}:
34514 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34515 @dots{}/maint.c:121: internal-error: testing, 1, 2
34516 A problem internal to GDB has been detected. Further
34517 debugging may prove unreliable.
34518 Quit this debugging session? (y or n) @kbd{n}
34519 Create a core file? (y or n) @kbd{n}
34523 @cindex @value{GDBN} internal error
34524 @cindex internal errors, control of @value{GDBN} behavior
34525 @cindex demangler crashes
34527 @kindex maint set internal-error
34528 @kindex maint show internal-error
34529 @kindex maint set internal-warning
34530 @kindex maint show internal-warning
34531 @kindex maint set demangler-warning
34532 @kindex maint show demangler-warning
34533 @item maint set internal-error @var{action} [ask|yes|no]
34534 @itemx maint show internal-error @var{action}
34535 @itemx maint set internal-warning @var{action} [ask|yes|no]
34536 @itemx maint show internal-warning @var{action}
34537 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34538 @itemx maint show demangler-warning @var{action}
34539 When @value{GDBN} reports an internal problem (error or warning) it
34540 gives the user the opportunity to both quit @value{GDBN} and create a
34541 core file of the current @value{GDBN} session. These commands let you
34542 override the default behaviour for each particular @var{action},
34543 described in the table below.
34547 You can specify that @value{GDBN} should always (yes) or never (no)
34548 quit. The default is to ask the user what to do.
34551 You can specify that @value{GDBN} should always (yes) or never (no)
34552 create a core file. The default is to ask the user what to do. Note
34553 that there is no @code{corefile} option for @code{demangler-warning}:
34554 demangler warnings always create a core file and this cannot be
34558 @kindex maint packet
34559 @item maint packet @var{text}
34560 If @value{GDBN} is talking to an inferior via the serial protocol,
34561 then this command sends the string @var{text} to the inferior, and
34562 displays the response packet. @value{GDBN} supplies the initial
34563 @samp{$} character, the terminating @samp{#} character, and the
34566 @kindex maint print architecture
34567 @item maint print architecture @r{[}@var{file}@r{]}
34568 Print the entire architecture configuration. The optional argument
34569 @var{file} names the file where the output goes.
34571 @kindex maint print c-tdesc
34572 @item maint print c-tdesc
34573 Print the current target description (@pxref{Target Descriptions}) as
34574 a C source file. The created source file can be used in @value{GDBN}
34575 when an XML parser is not available to parse the description.
34577 @kindex maint print dummy-frames
34578 @item maint print dummy-frames
34579 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34582 (@value{GDBP}) @kbd{b add}
34584 (@value{GDBP}) @kbd{print add(2,3)}
34585 Breakpoint 2, add (a=2, b=3) at @dots{}
34587 The program being debugged stopped while in a function called from GDB.
34589 (@value{GDBP}) @kbd{maint print dummy-frames}
34590 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34594 Takes an optional file parameter.
34596 @kindex maint print registers
34597 @kindex maint print raw-registers
34598 @kindex maint print cooked-registers
34599 @kindex maint print register-groups
34600 @kindex maint print remote-registers
34601 @item maint print registers @r{[}@var{file}@r{]}
34602 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34603 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34604 @itemx maint print register-groups @r{[}@var{file}@r{]}
34605 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34606 Print @value{GDBN}'s internal register data structures.
34608 The command @code{maint print raw-registers} includes the contents of
34609 the raw register cache; the command @code{maint print
34610 cooked-registers} includes the (cooked) value of all registers,
34611 including registers which aren't available on the target nor visible
34612 to user; the command @code{maint print register-groups} includes the
34613 groups that each register is a member of; and the command @code{maint
34614 print remote-registers} includes the remote target's register numbers
34615 and offsets in the `G' packets.
34617 These commands take an optional parameter, a file name to which to
34618 write the information.
34620 @kindex maint print reggroups
34621 @item maint print reggroups @r{[}@var{file}@r{]}
34622 Print @value{GDBN}'s internal register group data structures. The
34623 optional argument @var{file} tells to what file to write the
34626 The register groups info looks like this:
34629 (@value{GDBP}) @kbd{maint print reggroups}
34642 This command forces @value{GDBN} to flush its internal register cache.
34644 @kindex maint print objfiles
34645 @cindex info for known object files
34646 @item maint print objfiles @r{[}@var{regexp}@r{]}
34647 Print a dump of all known object files.
34648 If @var{regexp} is specified, only print object files whose names
34649 match @var{regexp}. For each object file, this command prints its name,
34650 address in memory, and all of its psymtabs and symtabs.
34652 @kindex maint print user-registers
34653 @cindex user registers
34654 @item maint print user-registers
34655 List all currently available @dfn{user registers}. User registers
34656 typically provide alternate names for actual hardware registers. They
34657 include the four ``standard'' registers @code{$fp}, @code{$pc},
34658 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34659 registers can be used in expressions in the same way as the canonical
34660 register names, but only the latter are listed by the @code{info
34661 registers} and @code{maint print registers} commands.
34663 @kindex maint print section-scripts
34664 @cindex info for known .debug_gdb_scripts-loaded scripts
34665 @item maint print section-scripts [@var{regexp}]
34666 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34667 If @var{regexp} is specified, only print scripts loaded by object files
34668 matching @var{regexp}.
34669 For each script, this command prints its name as specified in the objfile,
34670 and the full path if known.
34671 @xref{dotdebug_gdb_scripts section}.
34673 @kindex maint print statistics
34674 @cindex bcache statistics
34675 @item maint print statistics
34676 This command prints, for each object file in the program, various data
34677 about that object file followed by the byte cache (@dfn{bcache})
34678 statistics for the object file. The objfile data includes the number
34679 of minimal, partial, full, and stabs symbols, the number of types
34680 defined by the objfile, the number of as yet unexpanded psym tables,
34681 the number of line tables and string tables, and the amount of memory
34682 used by the various tables. The bcache statistics include the counts,
34683 sizes, and counts of duplicates of all and unique objects, max,
34684 average, and median entry size, total memory used and its overhead and
34685 savings, and various measures of the hash table size and chain
34688 @kindex maint print target-stack
34689 @cindex target stack description
34690 @item maint print target-stack
34691 A @dfn{target} is an interface between the debugger and a particular
34692 kind of file or process. Targets can be stacked in @dfn{strata},
34693 so that more than one target can potentially respond to a request.
34694 In particular, memory accesses will walk down the stack of targets
34695 until they find a target that is interested in handling that particular
34698 This command prints a short description of each layer that was pushed on
34699 the @dfn{target stack}, starting from the top layer down to the bottom one.
34701 @kindex maint print type
34702 @cindex type chain of a data type
34703 @item maint print type @var{expr}
34704 Print the type chain for a type specified by @var{expr}. The argument
34705 can be either a type name or a symbol. If it is a symbol, the type of
34706 that symbol is described. The type chain produced by this command is
34707 a recursive definition of the data type as stored in @value{GDBN}'s
34708 data structures, including its flags and contained types.
34710 @kindex maint selftest
34712 Run any self tests that were compiled in to @value{GDBN}. This will
34713 print a message showing how many tests were run, and how many failed.
34715 @kindex maint set dwarf always-disassemble
34716 @kindex maint show dwarf always-disassemble
34717 @item maint set dwarf always-disassemble
34718 @item maint show dwarf always-disassemble
34719 Control the behavior of @code{info address} when using DWARF debugging
34722 The default is @code{off}, which means that @value{GDBN} should try to
34723 describe a variable's location in an easily readable format. When
34724 @code{on}, @value{GDBN} will instead display the DWARF location
34725 expression in an assembly-like format. Note that some locations are
34726 too complex for @value{GDBN} to describe simply; in this case you will
34727 always see the disassembly form.
34729 Here is an example of the resulting disassembly:
34732 (gdb) info addr argc
34733 Symbol "argc" is a complex DWARF expression:
34737 For more information on these expressions, see
34738 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34740 @kindex maint set dwarf max-cache-age
34741 @kindex maint show dwarf max-cache-age
34742 @item maint set dwarf max-cache-age
34743 @itemx maint show dwarf max-cache-age
34744 Control the DWARF compilation unit cache.
34746 @cindex DWARF compilation units cache
34747 In object files with inter-compilation-unit references, such as those
34748 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34749 reader needs to frequently refer to previously read compilation units.
34750 This setting controls how long a compilation unit will remain in the
34751 cache if it is not referenced. A higher limit means that cached
34752 compilation units will be stored in memory longer, and more total
34753 memory will be used. Setting it to zero disables caching, which will
34754 slow down @value{GDBN} startup, but reduce memory consumption.
34756 @kindex maint set profile
34757 @kindex maint show profile
34758 @cindex profiling GDB
34759 @item maint set profile
34760 @itemx maint show profile
34761 Control profiling of @value{GDBN}.
34763 Profiling will be disabled until you use the @samp{maint set profile}
34764 command to enable it. When you enable profiling, the system will begin
34765 collecting timing and execution count data; when you disable profiling or
34766 exit @value{GDBN}, the results will be written to a log file. Remember that
34767 if you use profiling, @value{GDBN} will overwrite the profiling log file
34768 (often called @file{gmon.out}). If you have a record of important profiling
34769 data in a @file{gmon.out} file, be sure to move it to a safe location.
34771 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34772 compiled with the @samp{-pg} compiler option.
34774 @kindex maint set show-debug-regs
34775 @kindex maint show show-debug-regs
34776 @cindex hardware debug registers
34777 @item maint set show-debug-regs
34778 @itemx maint show show-debug-regs
34779 Control whether to show variables that mirror the hardware debug
34780 registers. Use @code{on} to enable, @code{off} to disable. If
34781 enabled, the debug registers values are shown when @value{GDBN} inserts or
34782 removes a hardware breakpoint or watchpoint, and when the inferior
34783 triggers a hardware-assisted breakpoint or watchpoint.
34785 @kindex maint set show-all-tib
34786 @kindex maint show show-all-tib
34787 @item maint set show-all-tib
34788 @itemx maint show show-all-tib
34789 Control whether to show all non zero areas within a 1k block starting
34790 at thread local base, when using the @samp{info w32 thread-information-block}
34793 @kindex maint set target-async
34794 @kindex maint show target-async
34795 @item maint set target-async
34796 @itemx maint show target-async
34797 This controls whether @value{GDBN} targets operate in synchronous or
34798 asynchronous mode (@pxref{Background Execution}). Normally the
34799 default is asynchronous, if it is available; but this can be changed
34800 to more easily debug problems occurring only in synchronous mode.
34802 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34803 @kindex maint show target-non-stop
34804 @item maint set target-non-stop
34805 @itemx maint show target-non-stop
34807 This controls whether @value{GDBN} targets always operate in non-stop
34808 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34809 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34810 if supported by the target.
34813 @item maint set target-non-stop auto
34814 This is the default mode. @value{GDBN} controls the target in
34815 non-stop mode if the target supports it.
34817 @item maint set target-non-stop on
34818 @value{GDBN} controls the target in non-stop mode even if the target
34819 does not indicate support.
34821 @item maint set target-non-stop off
34822 @value{GDBN} does not control the target in non-stop mode even if the
34823 target supports it.
34826 @kindex maint set per-command
34827 @kindex maint show per-command
34828 @item maint set per-command
34829 @itemx maint show per-command
34830 @cindex resources used by commands
34832 @value{GDBN} can display the resources used by each command.
34833 This is useful in debugging performance problems.
34836 @item maint set per-command space [on|off]
34837 @itemx maint show per-command space
34838 Enable or disable the printing of the memory used by GDB for each command.
34839 If enabled, @value{GDBN} will display how much memory each command
34840 took, following the command's own output.
34841 This can also be requested by invoking @value{GDBN} with the
34842 @option{--statistics} command-line switch (@pxref{Mode Options}).
34844 @item maint set per-command time [on|off]
34845 @itemx maint show per-command time
34846 Enable or disable the printing of the execution time of @value{GDBN}
34848 If enabled, @value{GDBN} will display how much time it
34849 took to execute each command, following the command's own output.
34850 Both CPU time and wallclock time are printed.
34851 Printing both is useful when trying to determine whether the cost is
34852 CPU or, e.g., disk/network latency.
34853 Note that the CPU time printed is for @value{GDBN} only, it does not include
34854 the execution time of the inferior because there's no mechanism currently
34855 to compute how much time was spent by @value{GDBN} and how much time was
34856 spent by the program been debugged.
34857 This can also be requested by invoking @value{GDBN} with the
34858 @option{--statistics} command-line switch (@pxref{Mode Options}).
34860 @item maint set per-command symtab [on|off]
34861 @itemx maint show per-command symtab
34862 Enable or disable the printing of basic symbol table statistics
34864 If enabled, @value{GDBN} will display the following information:
34868 number of symbol tables
34870 number of primary symbol tables
34872 number of blocks in the blockvector
34876 @kindex maint space
34877 @cindex memory used by commands
34878 @item maint space @var{value}
34879 An alias for @code{maint set per-command space}.
34880 A non-zero value enables it, zero disables it.
34883 @cindex time of command execution
34884 @item maint time @var{value}
34885 An alias for @code{maint set per-command time}.
34886 A non-zero value enables it, zero disables it.
34888 @kindex maint translate-address
34889 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34890 Find the symbol stored at the location specified by the address
34891 @var{addr} and an optional section name @var{section}. If found,
34892 @value{GDBN} prints the name of the closest symbol and an offset from
34893 the symbol's location to the specified address. This is similar to
34894 the @code{info address} command (@pxref{Symbols}), except that this
34895 command also allows to find symbols in other sections.
34897 If section was not specified, the section in which the symbol was found
34898 is also printed. For dynamically linked executables, the name of
34899 executable or shared library containing the symbol is printed as well.
34903 The following command is useful for non-interactive invocations of
34904 @value{GDBN}, such as in the test suite.
34907 @item set watchdog @var{nsec}
34908 @kindex set watchdog
34909 @cindex watchdog timer
34910 @cindex timeout for commands
34911 Set the maximum number of seconds @value{GDBN} will wait for the
34912 target operation to finish. If this time expires, @value{GDBN}
34913 reports and error and the command is aborted.
34915 @item show watchdog
34916 Show the current setting of the target wait timeout.
34919 @node Remote Protocol
34920 @appendix @value{GDBN} Remote Serial Protocol
34925 * Stop Reply Packets::
34926 * General Query Packets::
34927 * Architecture-Specific Protocol Details::
34928 * Tracepoint Packets::
34929 * Host I/O Packets::
34931 * Notification Packets::
34932 * Remote Non-Stop::
34933 * Packet Acknowledgment::
34935 * File-I/O Remote Protocol Extension::
34936 * Library List Format::
34937 * Library List Format for SVR4 Targets::
34938 * Memory Map Format::
34939 * Thread List Format::
34940 * Traceframe Info Format::
34941 * Branch Trace Format::
34942 * Branch Trace Configuration Format::
34948 There may be occasions when you need to know something about the
34949 protocol---for example, if there is only one serial port to your target
34950 machine, you might want your program to do something special if it
34951 recognizes a packet meant for @value{GDBN}.
34953 In the examples below, @samp{->} and @samp{<-} are used to indicate
34954 transmitted and received data, respectively.
34956 @cindex protocol, @value{GDBN} remote serial
34957 @cindex serial protocol, @value{GDBN} remote
34958 @cindex remote serial protocol
34959 All @value{GDBN} commands and responses (other than acknowledgments
34960 and notifications, see @ref{Notification Packets}) are sent as a
34961 @var{packet}. A @var{packet} is introduced with the character
34962 @samp{$}, the actual @var{packet-data}, and the terminating character
34963 @samp{#} followed by a two-digit @var{checksum}:
34966 @code{$}@var{packet-data}@code{#}@var{checksum}
34970 @cindex checksum, for @value{GDBN} remote
34972 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34973 characters between the leading @samp{$} and the trailing @samp{#} (an
34974 eight bit unsigned checksum).
34976 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34977 specification also included an optional two-digit @var{sequence-id}:
34980 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34983 @cindex sequence-id, for @value{GDBN} remote
34985 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34986 has never output @var{sequence-id}s. Stubs that handle packets added
34987 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34989 When either the host or the target machine receives a packet, the first
34990 response expected is an acknowledgment: either @samp{+} (to indicate
34991 the package was received correctly) or @samp{-} (to request
34995 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35000 The @samp{+}/@samp{-} acknowledgments can be disabled
35001 once a connection is established.
35002 @xref{Packet Acknowledgment}, for details.
35004 The host (@value{GDBN}) sends @var{command}s, and the target (the
35005 debugging stub incorporated in your program) sends a @var{response}. In
35006 the case of step and continue @var{command}s, the response is only sent
35007 when the operation has completed, and the target has again stopped all
35008 threads in all attached processes. This is the default all-stop mode
35009 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35010 execution mode; see @ref{Remote Non-Stop}, for details.
35012 @var{packet-data} consists of a sequence of characters with the
35013 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35016 @cindex remote protocol, field separator
35017 Fields within the packet should be separated using @samp{,} @samp{;} or
35018 @samp{:}. Except where otherwise noted all numbers are represented in
35019 @sc{hex} with leading zeros suppressed.
35021 Implementors should note that prior to @value{GDBN} 5.0, the character
35022 @samp{:} could not appear as the third character in a packet (as it
35023 would potentially conflict with the @var{sequence-id}).
35025 @cindex remote protocol, binary data
35026 @anchor{Binary Data}
35027 Binary data in most packets is encoded either as two hexadecimal
35028 digits per byte of binary data. This allowed the traditional remote
35029 protocol to work over connections which were only seven-bit clean.
35030 Some packets designed more recently assume an eight-bit clean
35031 connection, and use a more efficient encoding to send and receive
35034 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35035 as an escape character. Any escaped byte is transmitted as the escape
35036 character followed by the original character XORed with @code{0x20}.
35037 For example, the byte @code{0x7d} would be transmitted as the two
35038 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35039 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35040 @samp{@}}) must always be escaped. Responses sent by the stub
35041 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35042 is not interpreted as the start of a run-length encoded sequence
35045 Response @var{data} can be run-length encoded to save space.
35046 Run-length encoding replaces runs of identical characters with one
35047 instance of the repeated character, followed by a @samp{*} and a
35048 repeat count. The repeat count is itself sent encoded, to avoid
35049 binary characters in @var{data}: a value of @var{n} is sent as
35050 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35051 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35052 code 32) for a repeat count of 3. (This is because run-length
35053 encoding starts to win for counts 3 or more.) Thus, for example,
35054 @samp{0* } is a run-length encoding of ``0000'': the space character
35055 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35058 The printable characters @samp{#} and @samp{$} or with a numeric value
35059 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35060 seven repeats (@samp{$}) can be expanded using a repeat count of only
35061 five (@samp{"}). For example, @samp{00000000} can be encoded as
35064 The error response returned for some packets includes a two character
35065 error number. That number is not well defined.
35067 @cindex empty response, for unsupported packets
35068 For any @var{command} not supported by the stub, an empty response
35069 (@samp{$#00}) should be returned. That way it is possible to extend the
35070 protocol. A newer @value{GDBN} can tell if a packet is supported based
35073 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35074 commands for register access, and the @samp{m} and @samp{M} commands
35075 for memory access. Stubs that only control single-threaded targets
35076 can implement run control with the @samp{c} (continue), and @samp{s}
35077 (step) commands. Stubs that support multi-threading targets should
35078 support the @samp{vCont} command. All other commands are optional.
35083 The following table provides a complete list of all currently defined
35084 @var{command}s and their corresponding response @var{data}.
35085 @xref{File-I/O Remote Protocol Extension}, for details about the File
35086 I/O extension of the remote protocol.
35088 Each packet's description has a template showing the packet's overall
35089 syntax, followed by an explanation of the packet's meaning. We
35090 include spaces in some of the templates for clarity; these are not
35091 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35092 separate its components. For example, a template like @samp{foo
35093 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35094 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35095 @var{baz}. @value{GDBN} does not transmit a space character between the
35096 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35099 @cindex @var{thread-id}, in remote protocol
35100 @anchor{thread-id syntax}
35101 Several packets and replies include a @var{thread-id} field to identify
35102 a thread. Normally these are positive numbers with a target-specific
35103 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35104 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35107 In addition, the remote protocol supports a multiprocess feature in
35108 which the @var{thread-id} syntax is extended to optionally include both
35109 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35110 The @var{pid} (process) and @var{tid} (thread) components each have the
35111 format described above: a positive number with target-specific
35112 interpretation formatted as a big-endian hex string, literal @samp{-1}
35113 to indicate all processes or threads (respectively), or @samp{0} to
35114 indicate an arbitrary process or thread. Specifying just a process, as
35115 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35116 error to specify all processes but a specific thread, such as
35117 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35118 for those packets and replies explicitly documented to include a process
35119 ID, rather than a @var{thread-id}.
35121 The multiprocess @var{thread-id} syntax extensions are only used if both
35122 @value{GDBN} and the stub report support for the @samp{multiprocess}
35123 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35126 Note that all packet forms beginning with an upper- or lower-case
35127 letter, other than those described here, are reserved for future use.
35129 Here are the packet descriptions.
35134 @cindex @samp{!} packet
35135 @anchor{extended mode}
35136 Enable extended mode. In extended mode, the remote server is made
35137 persistent. The @samp{R} packet is used to restart the program being
35143 The remote target both supports and has enabled extended mode.
35147 @cindex @samp{?} packet
35149 Indicate the reason the target halted. The reply is the same as for
35150 step and continue. This packet has a special interpretation when the
35151 target is in non-stop mode; see @ref{Remote Non-Stop}.
35154 @xref{Stop Reply Packets}, for the reply specifications.
35156 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35157 @cindex @samp{A} packet
35158 Initialized @code{argv[]} array passed into program. @var{arglen}
35159 specifies the number of bytes in the hex encoded byte stream
35160 @var{arg}. See @code{gdbserver} for more details.
35165 The arguments were set.
35171 @cindex @samp{b} packet
35172 (Don't use this packet; its behavior is not well-defined.)
35173 Change the serial line speed to @var{baud}.
35175 JTC: @emph{When does the transport layer state change? When it's
35176 received, or after the ACK is transmitted. In either case, there are
35177 problems if the command or the acknowledgment packet is dropped.}
35179 Stan: @emph{If people really wanted to add something like this, and get
35180 it working for the first time, they ought to modify ser-unix.c to send
35181 some kind of out-of-band message to a specially-setup stub and have the
35182 switch happen "in between" packets, so that from remote protocol's point
35183 of view, nothing actually happened.}
35185 @item B @var{addr},@var{mode}
35186 @cindex @samp{B} packet
35187 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35188 breakpoint at @var{addr}.
35190 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35191 (@pxref{insert breakpoint or watchpoint packet}).
35193 @cindex @samp{bc} packet
35196 Backward continue. Execute the target system in reverse. No parameter.
35197 @xref{Reverse Execution}, for more information.
35200 @xref{Stop Reply Packets}, for the reply specifications.
35202 @cindex @samp{bs} packet
35205 Backward single step. Execute one instruction in reverse. No parameter.
35206 @xref{Reverse Execution}, for more information.
35209 @xref{Stop Reply Packets}, for the reply specifications.
35211 @item c @r{[}@var{addr}@r{]}
35212 @cindex @samp{c} packet
35213 Continue at @var{addr}, which is the address to resume. If @var{addr}
35214 is omitted, resume at current address.
35216 This packet is deprecated for multi-threading support. @xref{vCont
35220 @xref{Stop Reply Packets}, for the reply specifications.
35222 @item C @var{sig}@r{[};@var{addr}@r{]}
35223 @cindex @samp{C} packet
35224 Continue with signal @var{sig} (hex signal number). If
35225 @samp{;@var{addr}} is omitted, resume at same address.
35227 This packet is deprecated for multi-threading support. @xref{vCont
35231 @xref{Stop Reply Packets}, for the reply specifications.
35234 @cindex @samp{d} packet
35237 Don't use this packet; instead, define a general set packet
35238 (@pxref{General Query Packets}).
35242 @cindex @samp{D} packet
35243 The first form of the packet is used to detach @value{GDBN} from the
35244 remote system. It is sent to the remote target
35245 before @value{GDBN} disconnects via the @code{detach} command.
35247 The second form, including a process ID, is used when multiprocess
35248 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35249 detach only a specific process. The @var{pid} is specified as a
35250 big-endian hex string.
35260 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35261 @cindex @samp{F} packet
35262 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35263 This is part of the File-I/O protocol extension. @xref{File-I/O
35264 Remote Protocol Extension}, for the specification.
35267 @anchor{read registers packet}
35268 @cindex @samp{g} packet
35269 Read general registers.
35273 @item @var{XX@dots{}}
35274 Each byte of register data is described by two hex digits. The bytes
35275 with the register are transmitted in target byte order. The size of
35276 each register and their position within the @samp{g} packet are
35277 determined by the @value{GDBN} internal gdbarch functions
35278 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35280 When reading registers from a trace frame (@pxref{Analyze Collected
35281 Data,,Using the Collected Data}), the stub may also return a string of
35282 literal @samp{x}'s in place of the register data digits, to indicate
35283 that the corresponding register has not been collected, thus its value
35284 is unavailable. For example, for an architecture with 4 registers of
35285 4 bytes each, the following reply indicates to @value{GDBN} that
35286 registers 0 and 2 have not been collected, while registers 1 and 3
35287 have been collected, and both have zero value:
35291 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35298 @item G @var{XX@dots{}}
35299 @cindex @samp{G} packet
35300 Write general registers. @xref{read registers packet}, for a
35301 description of the @var{XX@dots{}} data.
35311 @item H @var{op} @var{thread-id}
35312 @cindex @samp{H} packet
35313 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35314 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35315 should be @samp{c} for step and continue operations (note that this
35316 is deprecated, supporting the @samp{vCont} command is a better
35317 option), and @samp{g} for other operations. The thread designator
35318 @var{thread-id} has the format and interpretation described in
35319 @ref{thread-id syntax}.
35330 @c 'H': How restrictive (or permissive) is the thread model. If a
35331 @c thread is selected and stopped, are other threads allowed
35332 @c to continue to execute? As I mentioned above, I think the
35333 @c semantics of each command when a thread is selected must be
35334 @c described. For example:
35336 @c 'g': If the stub supports threads and a specific thread is
35337 @c selected, returns the register block from that thread;
35338 @c otherwise returns current registers.
35340 @c 'G' If the stub supports threads and a specific thread is
35341 @c selected, sets the registers of the register block of
35342 @c that thread; otherwise sets current registers.
35344 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35345 @anchor{cycle step packet}
35346 @cindex @samp{i} packet
35347 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35348 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35349 step starting at that address.
35352 @cindex @samp{I} packet
35353 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35357 @cindex @samp{k} packet
35360 The exact effect of this packet is not specified.
35362 For a bare-metal target, it may power cycle or reset the target
35363 system. For that reason, the @samp{k} packet has no reply.
35365 For a single-process target, it may kill that process if possible.
35367 A multiple-process target may choose to kill just one process, or all
35368 that are under @value{GDBN}'s control. For more precise control, use
35369 the vKill packet (@pxref{vKill packet}).
35371 If the target system immediately closes the connection in response to
35372 @samp{k}, @value{GDBN} does not consider the lack of packet
35373 acknowledgment to be an error, and assumes the kill was successful.
35375 If connected using @kbd{target extended-remote}, and the target does
35376 not close the connection in response to a kill request, @value{GDBN}
35377 probes the target state as if a new connection was opened
35378 (@pxref{? packet}).
35380 @item m @var{addr},@var{length}
35381 @cindex @samp{m} packet
35382 Read @var{length} addressable memory units starting at address @var{addr}
35383 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35384 any particular boundary.
35386 The stub need not use any particular size or alignment when gathering
35387 data from memory for the response; even if @var{addr} is word-aligned
35388 and @var{length} is a multiple of the word size, the stub is free to
35389 use byte accesses, or not. For this reason, this packet may not be
35390 suitable for accessing memory-mapped I/O devices.
35391 @cindex alignment of remote memory accesses
35392 @cindex size of remote memory accesses
35393 @cindex memory, alignment and size of remote accesses
35397 @item @var{XX@dots{}}
35398 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35399 The reply may contain fewer addressable memory units than requested if the
35400 server was able to read only part of the region of memory.
35405 @item M @var{addr},@var{length}:@var{XX@dots{}}
35406 @cindex @samp{M} packet
35407 Write @var{length} addressable memory units starting at address @var{addr}
35408 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35409 byte is transmitted as a two-digit hexadecimal number.
35416 for an error (this includes the case where only part of the data was
35421 @cindex @samp{p} packet
35422 Read the value of register @var{n}; @var{n} is in hex.
35423 @xref{read registers packet}, for a description of how the returned
35424 register value is encoded.
35428 @item @var{XX@dots{}}
35429 the register's value
35433 Indicating an unrecognized @var{query}.
35436 @item P @var{n@dots{}}=@var{r@dots{}}
35437 @anchor{write register packet}
35438 @cindex @samp{P} packet
35439 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35440 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35441 digits for each byte in the register (target byte order).
35451 @item q @var{name} @var{params}@dots{}
35452 @itemx Q @var{name} @var{params}@dots{}
35453 @cindex @samp{q} packet
35454 @cindex @samp{Q} packet
35455 General query (@samp{q}) and set (@samp{Q}). These packets are
35456 described fully in @ref{General Query Packets}.
35459 @cindex @samp{r} packet
35460 Reset the entire system.
35462 Don't use this packet; use the @samp{R} packet instead.
35465 @cindex @samp{R} packet
35466 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35467 This packet is only available in extended mode (@pxref{extended mode}).
35469 The @samp{R} packet has no reply.
35471 @item s @r{[}@var{addr}@r{]}
35472 @cindex @samp{s} packet
35473 Single step, resuming at @var{addr}. If
35474 @var{addr} is omitted, resume at same address.
35476 This packet is deprecated for multi-threading support. @xref{vCont
35480 @xref{Stop Reply Packets}, for the reply specifications.
35482 @item S @var{sig}@r{[};@var{addr}@r{]}
35483 @anchor{step with signal packet}
35484 @cindex @samp{S} packet
35485 Step with signal. This is analogous to the @samp{C} packet, but
35486 requests a single-step, rather than a normal resumption of execution.
35488 This packet is deprecated for multi-threading support. @xref{vCont
35492 @xref{Stop Reply Packets}, for the reply specifications.
35494 @item t @var{addr}:@var{PP},@var{MM}
35495 @cindex @samp{t} packet
35496 Search backwards starting at address @var{addr} for a match with pattern
35497 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35498 There must be at least 3 digits in @var{addr}.
35500 @item T @var{thread-id}
35501 @cindex @samp{T} packet
35502 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35507 thread is still alive
35513 Packets starting with @samp{v} are identified by a multi-letter name,
35514 up to the first @samp{;} or @samp{?} (or the end of the packet).
35516 @item vAttach;@var{pid}
35517 @cindex @samp{vAttach} packet
35518 Attach to a new process with the specified process ID @var{pid}.
35519 The process ID is a
35520 hexadecimal integer identifying the process. In all-stop mode, all
35521 threads in the attached process are stopped; in non-stop mode, it may be
35522 attached without being stopped if that is supported by the target.
35524 @c In non-stop mode, on a successful vAttach, the stub should set the
35525 @c current thread to a thread of the newly-attached process. After
35526 @c attaching, GDB queries for the attached process's thread ID with qC.
35527 @c Also note that, from a user perspective, whether or not the
35528 @c target is stopped on attach in non-stop mode depends on whether you
35529 @c use the foreground or background version of the attach command, not
35530 @c on what vAttach does; GDB does the right thing with respect to either
35531 @c stopping or restarting threads.
35533 This packet is only available in extended mode (@pxref{extended mode}).
35539 @item @r{Any stop packet}
35540 for success in all-stop mode (@pxref{Stop Reply Packets})
35542 for success in non-stop mode (@pxref{Remote Non-Stop})
35545 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35546 @cindex @samp{vCont} packet
35547 @anchor{vCont packet}
35548 Resume the inferior, specifying different actions for each thread.
35550 For each inferior thread, the leftmost action with a matching
35551 @var{thread-id} is applied. Threads that don't match any action
35552 remain in their current state. Thread IDs are specified using the
35553 syntax described in @ref{thread-id syntax}. If multiprocess
35554 extensions (@pxref{multiprocess extensions}) are supported, actions
35555 can be specified to match all threads in a process by using the
35556 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35557 @var{thread-id} matches all threads. Specifying no actions is an
35560 Currently supported actions are:
35566 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35570 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35573 @item r @var{start},@var{end}
35574 Step once, and then keep stepping as long as the thread stops at
35575 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35576 The remote stub reports a stop reply when either the thread goes out
35577 of the range or is stopped due to an unrelated reason, such as hitting
35578 a breakpoint. @xref{range stepping}.
35580 If the range is empty (@var{start} == @var{end}), then the action
35581 becomes equivalent to the @samp{s} action. In other words,
35582 single-step once, and report the stop (even if the stepped instruction
35583 jumps to @var{start}).
35585 (A stop reply may be sent at any point even if the PC is still within
35586 the stepping range; for example, it is valid to implement this packet
35587 in a degenerate way as a single instruction step operation.)
35591 The optional argument @var{addr} normally associated with the
35592 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35593 not supported in @samp{vCont}.
35595 The @samp{t} action is only relevant in non-stop mode
35596 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35597 A stop reply should be generated for any affected thread not already stopped.
35598 When a thread is stopped by means of a @samp{t} action,
35599 the corresponding stop reply should indicate that the thread has stopped with
35600 signal @samp{0}, regardless of whether the target uses some other signal
35601 as an implementation detail.
35603 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35604 @samp{r} actions for threads that are already running. Conversely,
35605 the server must ignore @samp{t} actions for threads that are already
35608 @emph{Note:} In non-stop mode, a thread is considered running until
35609 @value{GDBN} acknowleges an asynchronous stop notification for it with
35610 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35612 The stub must support @samp{vCont} if it reports support for
35613 multiprocess extensions (@pxref{multiprocess extensions}).
35616 @xref{Stop Reply Packets}, for the reply specifications.
35619 @cindex @samp{vCont?} packet
35620 Request a list of actions supported by the @samp{vCont} packet.
35624 @item vCont@r{[};@var{action}@dots{}@r{]}
35625 The @samp{vCont} packet is supported. Each @var{action} is a supported
35626 command in the @samp{vCont} packet.
35628 The @samp{vCont} packet is not supported.
35631 @anchor{vCtrlC packet}
35633 @cindex @samp{vCtrlC} packet
35634 Interrupt remote target as if a control-C was pressed on the remote
35635 terminal. This is the equivalent to reacting to the @code{^C}
35636 (@samp{\003}, the control-C character) character in all-stop mode
35637 while the target is running, except this works in non-stop mode.
35638 @xref{interrupting remote targets}, for more info on the all-stop
35649 @item vFile:@var{operation}:@var{parameter}@dots{}
35650 @cindex @samp{vFile} packet
35651 Perform a file operation on the target system. For details,
35652 see @ref{Host I/O Packets}.
35654 @item vFlashErase:@var{addr},@var{length}
35655 @cindex @samp{vFlashErase} packet
35656 Direct the stub to erase @var{length} bytes of flash starting at
35657 @var{addr}. The region may enclose any number of flash blocks, but
35658 its start and end must fall on block boundaries, as indicated by the
35659 flash block size appearing in the memory map (@pxref{Memory Map
35660 Format}). @value{GDBN} groups flash memory programming operations
35661 together, and sends a @samp{vFlashDone} request after each group; the
35662 stub is allowed to delay erase operation until the @samp{vFlashDone}
35663 packet is received.
35673 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35674 @cindex @samp{vFlashWrite} packet
35675 Direct the stub to write data to flash address @var{addr}. The data
35676 is passed in binary form using the same encoding as for the @samp{X}
35677 packet (@pxref{Binary Data}). The memory ranges specified by
35678 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35679 not overlap, and must appear in order of increasing addresses
35680 (although @samp{vFlashErase} packets for higher addresses may already
35681 have been received; the ordering is guaranteed only between
35682 @samp{vFlashWrite} packets). If a packet writes to an address that was
35683 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35684 target-specific method, the results are unpredictable.
35692 for vFlashWrite addressing non-flash memory
35698 @cindex @samp{vFlashDone} packet
35699 Indicate to the stub that flash programming operation is finished.
35700 The stub is permitted to delay or batch the effects of a group of
35701 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35702 @samp{vFlashDone} packet is received. The contents of the affected
35703 regions of flash memory are unpredictable until the @samp{vFlashDone}
35704 request is completed.
35706 @item vKill;@var{pid}
35707 @cindex @samp{vKill} packet
35708 @anchor{vKill packet}
35709 Kill the process with the specified process ID @var{pid}, which is a
35710 hexadecimal integer identifying the process. This packet is used in
35711 preference to @samp{k} when multiprocess protocol extensions are
35712 supported; see @ref{multiprocess extensions}.
35722 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35723 @cindex @samp{vRun} packet
35724 Run the program @var{filename}, passing it each @var{argument} on its
35725 command line. The file and arguments are hex-encoded strings. If
35726 @var{filename} is an empty string, the stub may use a default program
35727 (e.g.@: the last program run). The program is created in the stopped
35730 @c FIXME: What about non-stop mode?
35732 This packet is only available in extended mode (@pxref{extended mode}).
35738 @item @r{Any stop packet}
35739 for success (@pxref{Stop Reply Packets})
35743 @cindex @samp{vStopped} packet
35744 @xref{Notification Packets}.
35746 @item X @var{addr},@var{length}:@var{XX@dots{}}
35748 @cindex @samp{X} packet
35749 Write data to memory, where the data is transmitted in binary.
35750 Memory is specified by its address @var{addr} and number of addressable memory
35751 units @var{length} (@pxref{addressable memory unit});
35752 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35762 @item z @var{type},@var{addr},@var{kind}
35763 @itemx Z @var{type},@var{addr},@var{kind}
35764 @anchor{insert breakpoint or watchpoint packet}
35765 @cindex @samp{z} packet
35766 @cindex @samp{Z} packets
35767 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35768 watchpoint starting at address @var{address} of kind @var{kind}.
35770 Each breakpoint and watchpoint packet @var{type} is documented
35773 @emph{Implementation notes: A remote target shall return an empty string
35774 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35775 remote target shall support either both or neither of a given
35776 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35777 avoid potential problems with duplicate packets, the operations should
35778 be implemented in an idempotent way.}
35780 @item z0,@var{addr},@var{kind}
35781 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35782 @cindex @samp{z0} packet
35783 @cindex @samp{Z0} packet
35784 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
35785 @var{addr} of type @var{kind}.
35787 A software breakpoint is implemented by replacing the instruction at
35788 @var{addr} with a software breakpoint or trap instruction. The
35789 @var{kind} is target-specific and typically indicates the size of the
35790 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
35791 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35792 architectures have additional meanings for @var{kind}
35793 (@pxref{Architecture-Specific Protocol Details}); if no
35794 architecture-specific value is being used, it should be @samp{0}.
35795 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
35796 conditional expressions in bytecode form that should be evaluated on
35797 the target's side. These are the conditions that should be taken into
35798 consideration when deciding if the breakpoint trigger should be
35799 reported back to @value{GDBN}.
35801 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35802 for how to best report a software breakpoint event to @value{GDBN}.
35804 The @var{cond_list} parameter is comprised of a series of expressions,
35805 concatenated without separators. Each expression has the following form:
35809 @item X @var{len},@var{expr}
35810 @var{len} is the length of the bytecode expression and @var{expr} is the
35811 actual conditional expression in bytecode form.
35815 The optional @var{cmd_list} parameter introduces commands that may be
35816 run on the target, rather than being reported back to @value{GDBN}.
35817 The parameter starts with a numeric flag @var{persist}; if the flag is
35818 nonzero, then the breakpoint may remain active and the commands
35819 continue to be run even when @value{GDBN} disconnects from the target.
35820 Following this flag is a series of expressions concatenated with no
35821 separators. Each expression has the following form:
35825 @item X @var{len},@var{expr}
35826 @var{len} is the length of the bytecode expression and @var{expr} is the
35827 actual conditional expression in bytecode form.
35831 @emph{Implementation note: It is possible for a target to copy or move
35832 code that contains software breakpoints (e.g., when implementing
35833 overlays). The behavior of this packet, in the presence of such a
35834 target, is not defined.}
35846 @item z1,@var{addr},@var{kind}
35847 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35848 @cindex @samp{z1} packet
35849 @cindex @samp{Z1} packet
35850 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35851 address @var{addr}.
35853 A hardware breakpoint is implemented using a mechanism that is not
35854 dependent on being able to modify the target's memory. The
35855 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
35856 same meaning as in @samp{Z0} packets.
35858 @emph{Implementation note: A hardware breakpoint is not affected by code
35871 @item z2,@var{addr},@var{kind}
35872 @itemx Z2,@var{addr},@var{kind}
35873 @cindex @samp{z2} packet
35874 @cindex @samp{Z2} packet
35875 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35876 The number of bytes to watch is specified by @var{kind}.
35888 @item z3,@var{addr},@var{kind}
35889 @itemx Z3,@var{addr},@var{kind}
35890 @cindex @samp{z3} packet
35891 @cindex @samp{Z3} packet
35892 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35893 The number of bytes to watch is specified by @var{kind}.
35905 @item z4,@var{addr},@var{kind}
35906 @itemx Z4,@var{addr},@var{kind}
35907 @cindex @samp{z4} packet
35908 @cindex @samp{Z4} packet
35909 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35910 The number of bytes to watch is specified by @var{kind}.
35924 @node Stop Reply Packets
35925 @section Stop Reply Packets
35926 @cindex stop reply packets
35928 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35929 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35930 receive any of the below as a reply. Except for @samp{?}
35931 and @samp{vStopped}, that reply is only returned
35932 when the target halts. In the below the exact meaning of @dfn{signal
35933 number} is defined by the header @file{include/gdb/signals.h} in the
35934 @value{GDBN} source code.
35936 In non-stop mode, the server will simply reply @samp{OK} to commands
35937 such as @samp{vCont}; any stop will be the subject of a future
35938 notification. @xref{Remote Non-Stop}.
35940 As in the description of request packets, we include spaces in the
35941 reply templates for clarity; these are not part of the reply packet's
35942 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35948 The program received signal number @var{AA} (a two-digit hexadecimal
35949 number). This is equivalent to a @samp{T} response with no
35950 @var{n}:@var{r} pairs.
35952 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35953 @cindex @samp{T} packet reply
35954 The program received signal number @var{AA} (a two-digit hexadecimal
35955 number). This is equivalent to an @samp{S} response, except that the
35956 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35957 and other information directly in the stop reply packet, reducing
35958 round-trip latency. Single-step and breakpoint traps are reported
35959 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35963 If @var{n} is a hexadecimal number, it is a register number, and the
35964 corresponding @var{r} gives that register's value. The data @var{r} is a
35965 series of bytes in target byte order, with each byte given by a
35966 two-digit hex number.
35969 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35970 the stopped thread, as specified in @ref{thread-id syntax}.
35973 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35974 the core on which the stop event was detected.
35977 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35978 specific event that stopped the target. The currently defined stop
35979 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35980 signal. At most one stop reason should be present.
35983 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35984 and go on to the next; this allows us to extend the protocol in the
35988 The currently defined stop reasons are:
35994 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35997 @item syscall_entry
35998 @itemx syscall_return
35999 The packet indicates a syscall entry or return, and @var{r} is the
36000 syscall number, in hex.
36002 @cindex shared library events, remote reply
36004 The packet indicates that the loaded libraries have changed.
36005 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36006 list of loaded libraries. The @var{r} part is ignored.
36008 @cindex replay log events, remote reply
36010 The packet indicates that the target cannot continue replaying
36011 logged execution events, because it has reached the end (or the
36012 beginning when executing backward) of the log. The value of @var{r}
36013 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36014 for more information.
36017 @anchor{swbreak stop reason}
36018 The packet indicates a software breakpoint instruction was executed,
36019 irrespective of whether it was @value{GDBN} that planted the
36020 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36021 part must be left empty.
36023 On some architectures, such as x86, at the architecture level, when a
36024 breakpoint instruction executes the program counter points at the
36025 breakpoint address plus an offset. On such targets, the stub is
36026 responsible for adjusting the PC to point back at the breakpoint
36029 This packet should not be sent by default; older @value{GDBN} versions
36030 did not support it. @value{GDBN} requests it, by supplying an
36031 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36032 remote stub must also supply the appropriate @samp{qSupported} feature
36033 indicating support.
36035 This packet is required for correct non-stop mode operation.
36038 The packet indicates the target stopped for a hardware breakpoint.
36039 The @var{r} part must be left empty.
36041 The same remarks about @samp{qSupported} and non-stop mode above
36044 @cindex fork events, remote reply
36046 The packet indicates that @code{fork} was called, and @var{r}
36047 is the thread ID of the new child process. Refer to
36048 @ref{thread-id syntax} for the format of the @var{thread-id}
36049 field. This packet is only applicable to targets that support
36052 This packet should not be sent by default; older @value{GDBN} versions
36053 did not support it. @value{GDBN} requests it, by supplying an
36054 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36055 remote stub must also supply the appropriate @samp{qSupported} feature
36056 indicating support.
36058 @cindex vfork events, remote reply
36060 The packet indicates that @code{vfork} was called, and @var{r}
36061 is the thread ID of the new child process. Refer to
36062 @ref{thread-id syntax} for the format of the @var{thread-id}
36063 field. This packet is only applicable to targets that support
36066 This packet should not be sent by default; older @value{GDBN} versions
36067 did not support it. @value{GDBN} requests it, by supplying an
36068 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36069 remote stub must also supply the appropriate @samp{qSupported} feature
36070 indicating support.
36072 @cindex vforkdone events, remote reply
36074 The packet indicates that a child process created by a vfork
36075 has either called @code{exec} or terminated, so that the
36076 address spaces of the parent and child process are no longer
36077 shared. The @var{r} part is ignored. This packet is only
36078 applicable to targets that support vforkdone events.
36080 This packet should not be sent by default; older @value{GDBN} versions
36081 did not support it. @value{GDBN} requests it, by supplying an
36082 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36083 remote stub must also supply the appropriate @samp{qSupported} feature
36084 indicating support.
36086 @cindex exec events, remote reply
36088 The packet indicates that @code{execve} was called, and @var{r}
36089 is the absolute pathname of the file that was executed, in hex.
36090 This packet is only applicable to targets that support exec events.
36092 This packet should not be sent by default; older @value{GDBN} versions
36093 did not support it. @value{GDBN} requests it, by supplying an
36094 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36095 remote stub must also supply the appropriate @samp{qSupported} feature
36096 indicating support.
36098 @cindex thread create event, remote reply
36099 @anchor{thread create event}
36101 The packet indicates that the thread was just created. The new thread
36102 is stopped until @value{GDBN} sets it running with a resumption packet
36103 (@pxref{vCont packet}). This packet should not be sent by default;
36104 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36105 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36106 @var{r} part is ignored.
36111 @itemx W @var{AA} ; process:@var{pid}
36112 The process exited, and @var{AA} is the exit status. This is only
36113 applicable to certain targets.
36115 The second form of the response, including the process ID of the
36116 exited process, can be used only when @value{GDBN} has reported
36117 support for multiprocess protocol extensions; see @ref{multiprocess
36118 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36122 @itemx X @var{AA} ; process:@var{pid}
36123 The process terminated with signal @var{AA}.
36125 The second form of the response, including the process ID of the
36126 terminated process, can be used only when @value{GDBN} has reported
36127 support for multiprocess protocol extensions; see @ref{multiprocess
36128 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36131 @anchor{thread exit event}
36132 @cindex thread exit event, remote reply
36133 @item w @var{AA} ; @var{tid}
36135 The thread exited, and @var{AA} is the exit status. This response
36136 should not be sent by default; @value{GDBN} requests it with the
36137 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36138 @var{AA} is formatted as a big-endian hex string.
36141 There are no resumed threads left in the target. In other words, even
36142 though the process is alive, the last resumed thread has exited. For
36143 example, say the target process has two threads: thread 1 and thread
36144 2. The client leaves thread 1 stopped, and resumes thread 2, which
36145 subsequently exits. At this point, even though the process is still
36146 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36147 executing either. The @samp{N} stop reply thus informs the client
36148 that it can stop waiting for stop replies. This packet should not be
36149 sent by default; older @value{GDBN} versions did not support it.
36150 @value{GDBN} requests it, by supplying an appropriate
36151 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36152 also supply the appropriate @samp{qSupported} feature indicating
36155 @item O @var{XX}@dots{}
36156 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36157 written as the program's console output. This can happen at any time
36158 while the program is running and the debugger should continue to wait
36159 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36161 @item F @var{call-id},@var{parameter}@dots{}
36162 @var{call-id} is the identifier which says which host system call should
36163 be called. This is just the name of the function. Translation into the
36164 correct system call is only applicable as it's defined in @value{GDBN}.
36165 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36168 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36169 this very system call.
36171 The target replies with this packet when it expects @value{GDBN} to
36172 call a host system call on behalf of the target. @value{GDBN} replies
36173 with an appropriate @samp{F} packet and keeps up waiting for the next
36174 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36175 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36176 Protocol Extension}, for more details.
36180 @node General Query Packets
36181 @section General Query Packets
36182 @cindex remote query requests
36184 Packets starting with @samp{q} are @dfn{general query packets};
36185 packets starting with @samp{Q} are @dfn{general set packets}. General
36186 query and set packets are a semi-unified form for retrieving and
36187 sending information to and from the stub.
36189 The initial letter of a query or set packet is followed by a name
36190 indicating what sort of thing the packet applies to. For example,
36191 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36192 definitions with the stub. These packet names follow some
36197 The name must not contain commas, colons or semicolons.
36199 Most @value{GDBN} query and set packets have a leading upper case
36202 The names of custom vendor packets should use a company prefix, in
36203 lower case, followed by a period. For example, packets designed at
36204 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36205 foos) or @samp{Qacme.bar} (for setting bars).
36208 The name of a query or set packet should be separated from any
36209 parameters by a @samp{:}; the parameters themselves should be
36210 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36211 full packet name, and check for a separator or the end of the packet,
36212 in case two packet names share a common prefix. New packets should not begin
36213 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36214 packets predate these conventions, and have arguments without any terminator
36215 for the packet name; we suspect they are in widespread use in places that
36216 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36217 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36220 Like the descriptions of the other packets, each description here
36221 has a template showing the packet's overall syntax, followed by an
36222 explanation of the packet's meaning. We include spaces in some of the
36223 templates for clarity; these are not part of the packet's syntax. No
36224 @value{GDBN} packet uses spaces to separate its components.
36226 Here are the currently defined query and set packets:
36232 Turn on or off the agent as a helper to perform some debugging operations
36233 delegated from @value{GDBN} (@pxref{Control Agent}).
36235 @item QAllow:@var{op}:@var{val}@dots{}
36236 @cindex @samp{QAllow} packet
36237 Specify which operations @value{GDBN} expects to request of the
36238 target, as a semicolon-separated list of operation name and value
36239 pairs. Possible values for @var{op} include @samp{WriteReg},
36240 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36241 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36242 indicating that @value{GDBN} will not request the operation, or 1,
36243 indicating that it may. (The target can then use this to set up its
36244 own internals optimally, for instance if the debugger never expects to
36245 insert breakpoints, it may not need to install its own trap handler.)
36248 @cindex current thread, remote request
36249 @cindex @samp{qC} packet
36250 Return the current thread ID.
36254 @item QC @var{thread-id}
36255 Where @var{thread-id} is a thread ID as documented in
36256 @ref{thread-id syntax}.
36257 @item @r{(anything else)}
36258 Any other reply implies the old thread ID.
36261 @item qCRC:@var{addr},@var{length}
36262 @cindex CRC of memory block, remote request
36263 @cindex @samp{qCRC} packet
36264 @anchor{qCRC packet}
36265 Compute the CRC checksum of a block of memory using CRC-32 defined in
36266 IEEE 802.3. The CRC is computed byte at a time, taking the most
36267 significant bit of each byte first. The initial pattern code
36268 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36270 @emph{Note:} This is the same CRC used in validating separate debug
36271 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36272 Files}). However the algorithm is slightly different. When validating
36273 separate debug files, the CRC is computed taking the @emph{least}
36274 significant bit of each byte first, and the final result is inverted to
36275 detect trailing zeros.
36280 An error (such as memory fault)
36281 @item C @var{crc32}
36282 The specified memory region's checksum is @var{crc32}.
36285 @item QDisableRandomization:@var{value}
36286 @cindex disable address space randomization, remote request
36287 @cindex @samp{QDisableRandomization} packet
36288 Some target operating systems will randomize the virtual address space
36289 of the inferior process as a security feature, but provide a feature
36290 to disable such randomization, e.g.@: to allow for a more deterministic
36291 debugging experience. On such systems, this packet with a @var{value}
36292 of 1 directs the target to disable address space randomization for
36293 processes subsequently started via @samp{vRun} packets, while a packet
36294 with a @var{value} of 0 tells the target to enable address space
36297 This packet is only available in extended mode (@pxref{extended mode}).
36302 The request succeeded.
36305 An error occurred. The error number @var{nn} is given as hex digits.
36308 An empty reply indicates that @samp{QDisableRandomization} is not supported
36312 This packet is not probed by default; the remote stub must request it,
36313 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36314 This should only be done on targets that actually support disabling
36315 address space randomization.
36318 @itemx qsThreadInfo
36319 @cindex list active threads, remote request
36320 @cindex @samp{qfThreadInfo} packet
36321 @cindex @samp{qsThreadInfo} packet
36322 Obtain a list of all active thread IDs from the target (OS). Since there
36323 may be too many active threads to fit into one reply packet, this query
36324 works iteratively: it may require more than one query/reply sequence to
36325 obtain the entire list of threads. The first query of the sequence will
36326 be the @samp{qfThreadInfo} query; subsequent queries in the
36327 sequence will be the @samp{qsThreadInfo} query.
36329 NOTE: This packet replaces the @samp{qL} query (see below).
36333 @item m @var{thread-id}
36335 @item m @var{thread-id},@var{thread-id}@dots{}
36336 a comma-separated list of thread IDs
36338 (lower case letter @samp{L}) denotes end of list.
36341 In response to each query, the target will reply with a list of one or
36342 more thread IDs, separated by commas.
36343 @value{GDBN} will respond to each reply with a request for more thread
36344 ids (using the @samp{qs} form of the query), until the target responds
36345 with @samp{l} (lower-case ell, for @dfn{last}).
36346 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36349 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36350 initial connection with the remote target, and the very first thread ID
36351 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36352 message. Therefore, the stub should ensure that the first thread ID in
36353 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36355 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36356 @cindex get thread-local storage address, remote request
36357 @cindex @samp{qGetTLSAddr} packet
36358 Fetch the address associated with thread local storage specified
36359 by @var{thread-id}, @var{offset}, and @var{lm}.
36361 @var{thread-id} is the thread ID associated with the
36362 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36364 @var{offset} is the (big endian, hex encoded) offset associated with the
36365 thread local variable. (This offset is obtained from the debug
36366 information associated with the variable.)
36368 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36369 load module associated with the thread local storage. For example,
36370 a @sc{gnu}/Linux system will pass the link map address of the shared
36371 object associated with the thread local storage under consideration.
36372 Other operating environments may choose to represent the load module
36373 differently, so the precise meaning of this parameter will vary.
36377 @item @var{XX}@dots{}
36378 Hex encoded (big endian) bytes representing the address of the thread
36379 local storage requested.
36382 An error occurred. The error number @var{nn} is given as hex digits.
36385 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36388 @item qGetTIBAddr:@var{thread-id}
36389 @cindex get thread information block address
36390 @cindex @samp{qGetTIBAddr} packet
36391 Fetch address of the Windows OS specific Thread Information Block.
36393 @var{thread-id} is the thread ID associated with the thread.
36397 @item @var{XX}@dots{}
36398 Hex encoded (big endian) bytes representing the linear address of the
36399 thread information block.
36402 An error occured. This means that either the thread was not found, or the
36403 address could not be retrieved.
36406 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36409 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36410 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36411 digit) is one to indicate the first query and zero to indicate a
36412 subsequent query; @var{threadcount} (two hex digits) is the maximum
36413 number of threads the response packet can contain; and @var{nextthread}
36414 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36415 returned in the response as @var{argthread}.
36417 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36421 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36422 Where: @var{count} (two hex digits) is the number of threads being
36423 returned; @var{done} (one hex digit) is zero to indicate more threads
36424 and one indicates no further threads; @var{argthreadid} (eight hex
36425 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36426 is a sequence of thread IDs, @var{threadid} (eight hex
36427 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36431 @cindex section offsets, remote request
36432 @cindex @samp{qOffsets} packet
36433 Get section offsets that the target used when relocating the downloaded
36438 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36439 Relocate the @code{Text} section by @var{xxx} from its original address.
36440 Relocate the @code{Data} section by @var{yyy} from its original address.
36441 If the object file format provides segment information (e.g.@: @sc{elf}
36442 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36443 segments by the supplied offsets.
36445 @emph{Note: while a @code{Bss} offset may be included in the response,
36446 @value{GDBN} ignores this and instead applies the @code{Data} offset
36447 to the @code{Bss} section.}
36449 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36450 Relocate the first segment of the object file, which conventionally
36451 contains program code, to a starting address of @var{xxx}. If
36452 @samp{DataSeg} is specified, relocate the second segment, which
36453 conventionally contains modifiable data, to a starting address of
36454 @var{yyy}. @value{GDBN} will report an error if the object file
36455 does not contain segment information, or does not contain at least
36456 as many segments as mentioned in the reply. Extra segments are
36457 kept at fixed offsets relative to the last relocated segment.
36460 @item qP @var{mode} @var{thread-id}
36461 @cindex thread information, remote request
36462 @cindex @samp{qP} packet
36463 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36464 encoded 32 bit mode; @var{thread-id} is a thread ID
36465 (@pxref{thread-id syntax}).
36467 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36470 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36474 @cindex non-stop mode, remote request
36475 @cindex @samp{QNonStop} packet
36477 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36478 @xref{Remote Non-Stop}, for more information.
36483 The request succeeded.
36486 An error occurred. The error number @var{nn} is given as hex digits.
36489 An empty reply indicates that @samp{QNonStop} is not supported by
36493 This packet is not probed by default; the remote stub must request it,
36494 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36495 Use of this packet is controlled by the @code{set non-stop} command;
36496 @pxref{Non-Stop Mode}.
36498 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36499 @itemx QCatchSyscalls:0
36500 @cindex catch syscalls from inferior, remote request
36501 @cindex @samp{QCatchSyscalls} packet
36502 @anchor{QCatchSyscalls}
36503 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36504 catching syscalls from the inferior process.
36506 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36507 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36508 is listed, every system call should be reported.
36510 Note that if a syscall not in the list is reported, @value{GDBN} will
36511 still filter the event according to its own list from all corresponding
36512 @code{catch syscall} commands. However, it is more efficient to only
36513 report the requested syscalls.
36515 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36516 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36518 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36519 kept for the new process too. On targets where exec may affect syscall
36520 numbers, for example with exec between 32 and 64-bit processes, the
36521 client should send a new packet with the new syscall list.
36526 The request succeeded.
36529 An error occurred. @var{nn} are hex digits.
36532 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36536 Use of this packet is controlled by the @code{set remote catch-syscalls}
36537 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36538 This packet is not probed by default; the remote stub must request it,
36539 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36541 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36542 @cindex pass signals to inferior, remote request
36543 @cindex @samp{QPassSignals} packet
36544 @anchor{QPassSignals}
36545 Each listed @var{signal} should be passed directly to the inferior process.
36546 Signals are numbered identically to continue packets and stop replies
36547 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36548 strictly greater than the previous item. These signals do not need to stop
36549 the inferior, or be reported to @value{GDBN}. All other signals should be
36550 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36551 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36552 new list. This packet improves performance when using @samp{handle
36553 @var{signal} nostop noprint pass}.
36558 The request succeeded.
36561 An error occurred. The error number @var{nn} is given as hex digits.
36564 An empty reply indicates that @samp{QPassSignals} is not supported by
36568 Use of this packet is controlled by the @code{set remote pass-signals}
36569 command (@pxref{Remote Configuration, set remote pass-signals}).
36570 This packet is not probed by default; the remote stub must request it,
36571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36573 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36574 @cindex signals the inferior may see, remote request
36575 @cindex @samp{QProgramSignals} packet
36576 @anchor{QProgramSignals}
36577 Each listed @var{signal} may be delivered to the inferior process.
36578 Others should be silently discarded.
36580 In some cases, the remote stub may need to decide whether to deliver a
36581 signal to the program or not without @value{GDBN} involvement. One
36582 example of that is while detaching --- the program's threads may have
36583 stopped for signals that haven't yet had a chance of being reported to
36584 @value{GDBN}, and so the remote stub can use the signal list specified
36585 by this packet to know whether to deliver or ignore those pending
36588 This does not influence whether to deliver a signal as requested by a
36589 resumption packet (@pxref{vCont packet}).
36591 Signals are numbered identically to continue packets and stop replies
36592 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36593 strictly greater than the previous item. Multiple
36594 @samp{QProgramSignals} packets do not combine; any earlier
36595 @samp{QProgramSignals} list is completely replaced by the new list.
36600 The request succeeded.
36603 An error occurred. The error number @var{nn} is given as hex digits.
36606 An empty reply indicates that @samp{QProgramSignals} is not supported
36610 Use of this packet is controlled by the @code{set remote program-signals}
36611 command (@pxref{Remote Configuration, set remote program-signals}).
36612 This packet is not probed by default; the remote stub must request it,
36613 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36615 @anchor{QThreadEvents}
36616 @item QThreadEvents:1
36617 @itemx QThreadEvents:0
36618 @cindex thread create/exit events, remote request
36619 @cindex @samp{QThreadEvents} packet
36621 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36622 reporting of thread create and exit events. @xref{thread create
36623 event}, for the reply specifications. For example, this is used in
36624 non-stop mode when @value{GDBN} stops a set of threads and
36625 synchronously waits for the their corresponding stop replies. Without
36626 exit events, if one of the threads exits, @value{GDBN} would hang
36627 forever not knowing that it should no longer expect a stop for that
36628 same thread. @value{GDBN} does not enable this feature unless the
36629 stub reports that it supports it by including @samp{QThreadEvents+} in
36630 its @samp{qSupported} reply.
36635 The request succeeded.
36638 An error occurred. The error number @var{nn} is given as hex digits.
36641 An empty reply indicates that @samp{QThreadEvents} is not supported by
36645 Use of this packet is controlled by the @code{set remote thread-events}
36646 command (@pxref{Remote Configuration, set remote thread-events}).
36648 @item qRcmd,@var{command}
36649 @cindex execute remote command, remote request
36650 @cindex @samp{qRcmd} packet
36651 @var{command} (hex encoded) is passed to the local interpreter for
36652 execution. Invalid commands should be reported using the output
36653 string. Before the final result packet, the target may also respond
36654 with a number of intermediate @samp{O@var{output}} console output
36655 packets. @emph{Implementors should note that providing access to a
36656 stubs's interpreter may have security implications}.
36661 A command response with no output.
36663 A command response with the hex encoded output string @var{OUTPUT}.
36665 Indicate a badly formed request.
36667 An empty reply indicates that @samp{qRcmd} is not recognized.
36670 (Note that the @code{qRcmd} packet's name is separated from the
36671 command by a @samp{,}, not a @samp{:}, contrary to the naming
36672 conventions above. Please don't use this packet as a model for new
36675 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36676 @cindex searching memory, in remote debugging
36678 @cindex @samp{qSearch:memory} packet
36680 @cindex @samp{qSearch memory} packet
36681 @anchor{qSearch memory}
36682 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36683 Both @var{address} and @var{length} are encoded in hex;
36684 @var{search-pattern} is a sequence of bytes, also hex encoded.
36689 The pattern was not found.
36691 The pattern was found at @var{address}.
36693 A badly formed request or an error was encountered while searching memory.
36695 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36698 @item QStartNoAckMode
36699 @cindex @samp{QStartNoAckMode} packet
36700 @anchor{QStartNoAckMode}
36701 Request that the remote stub disable the normal @samp{+}/@samp{-}
36702 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36707 The stub has switched to no-acknowledgment mode.
36708 @value{GDBN} acknowledges this reponse,
36709 but neither the stub nor @value{GDBN} shall send or expect further
36710 @samp{+}/@samp{-} acknowledgments in the current connection.
36712 An empty reply indicates that the stub does not support no-acknowledgment mode.
36715 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36716 @cindex supported packets, remote query
36717 @cindex features of the remote protocol
36718 @cindex @samp{qSupported} packet
36719 @anchor{qSupported}
36720 Tell the remote stub about features supported by @value{GDBN}, and
36721 query the stub for features it supports. This packet allows
36722 @value{GDBN} and the remote stub to take advantage of each others'
36723 features. @samp{qSupported} also consolidates multiple feature probes
36724 at startup, to improve @value{GDBN} performance---a single larger
36725 packet performs better than multiple smaller probe packets on
36726 high-latency links. Some features may enable behavior which must not
36727 be on by default, e.g.@: because it would confuse older clients or
36728 stubs. Other features may describe packets which could be
36729 automatically probed for, but are not. These features must be
36730 reported before @value{GDBN} will use them. This ``default
36731 unsupported'' behavior is not appropriate for all packets, but it
36732 helps to keep the initial connection time under control with new
36733 versions of @value{GDBN} which support increasing numbers of packets.
36737 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36738 The stub supports or does not support each returned @var{stubfeature},
36739 depending on the form of each @var{stubfeature} (see below for the
36742 An empty reply indicates that @samp{qSupported} is not recognized,
36743 or that no features needed to be reported to @value{GDBN}.
36746 The allowed forms for each feature (either a @var{gdbfeature} in the
36747 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36751 @item @var{name}=@var{value}
36752 The remote protocol feature @var{name} is supported, and associated
36753 with the specified @var{value}. The format of @var{value} depends
36754 on the feature, but it must not include a semicolon.
36756 The remote protocol feature @var{name} is supported, and does not
36757 need an associated value.
36759 The remote protocol feature @var{name} is not supported.
36761 The remote protocol feature @var{name} may be supported, and
36762 @value{GDBN} should auto-detect support in some other way when it is
36763 needed. This form will not be used for @var{gdbfeature} notifications,
36764 but may be used for @var{stubfeature} responses.
36767 Whenever the stub receives a @samp{qSupported} request, the
36768 supplied set of @value{GDBN} features should override any previous
36769 request. This allows @value{GDBN} to put the stub in a known
36770 state, even if the stub had previously been communicating with
36771 a different version of @value{GDBN}.
36773 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36778 This feature indicates whether @value{GDBN} supports multiprocess
36779 extensions to the remote protocol. @value{GDBN} does not use such
36780 extensions unless the stub also reports that it supports them by
36781 including @samp{multiprocess+} in its @samp{qSupported} reply.
36782 @xref{multiprocess extensions}, for details.
36785 This feature indicates that @value{GDBN} supports the XML target
36786 description. If the stub sees @samp{xmlRegisters=} with target
36787 specific strings separated by a comma, it will report register
36791 This feature indicates whether @value{GDBN} supports the
36792 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36793 instruction reply packet}).
36796 This feature indicates whether @value{GDBN} supports the swbreak stop
36797 reason in stop replies. @xref{swbreak stop reason}, for details.
36800 This feature indicates whether @value{GDBN} supports the hwbreak stop
36801 reason in stop replies. @xref{swbreak stop reason}, for details.
36804 This feature indicates whether @value{GDBN} supports fork event
36805 extensions to the remote protocol. @value{GDBN} does not use such
36806 extensions unless the stub also reports that it supports them by
36807 including @samp{fork-events+} in its @samp{qSupported} reply.
36810 This feature indicates whether @value{GDBN} supports vfork event
36811 extensions to the remote protocol. @value{GDBN} does not use such
36812 extensions unless the stub also reports that it supports them by
36813 including @samp{vfork-events+} in its @samp{qSupported} reply.
36816 This feature indicates whether @value{GDBN} supports exec event
36817 extensions to the remote protocol. @value{GDBN} does not use such
36818 extensions unless the stub also reports that it supports them by
36819 including @samp{exec-events+} in its @samp{qSupported} reply.
36821 @item vContSupported
36822 This feature indicates whether @value{GDBN} wants to know the
36823 supported actions in the reply to @samp{vCont?} packet.
36826 Stubs should ignore any unknown values for
36827 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36828 packet supports receiving packets of unlimited length (earlier
36829 versions of @value{GDBN} may reject overly long responses). Additional values
36830 for @var{gdbfeature} may be defined in the future to let the stub take
36831 advantage of new features in @value{GDBN}, e.g.@: incompatible
36832 improvements in the remote protocol---the @samp{multiprocess} feature is
36833 an example of such a feature. The stub's reply should be independent
36834 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36835 describes all the features it supports, and then the stub replies with
36836 all the features it supports.
36838 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36839 responses, as long as each response uses one of the standard forms.
36841 Some features are flags. A stub which supports a flag feature
36842 should respond with a @samp{+} form response. Other features
36843 require values, and the stub should respond with an @samp{=}
36846 Each feature has a default value, which @value{GDBN} will use if
36847 @samp{qSupported} is not available or if the feature is not mentioned
36848 in the @samp{qSupported} response. The default values are fixed; a
36849 stub is free to omit any feature responses that match the defaults.
36851 Not all features can be probed, but for those which can, the probing
36852 mechanism is useful: in some cases, a stub's internal
36853 architecture may not allow the protocol layer to know some information
36854 about the underlying target in advance. This is especially common in
36855 stubs which may be configured for multiple targets.
36857 These are the currently defined stub features and their properties:
36859 @multitable @columnfractions 0.35 0.2 0.12 0.2
36860 @c NOTE: The first row should be @headitem, but we do not yet require
36861 @c a new enough version of Texinfo (4.7) to use @headitem.
36863 @tab Value Required
36867 @item @samp{PacketSize}
36872 @item @samp{qXfer:auxv:read}
36877 @item @samp{qXfer:btrace:read}
36882 @item @samp{qXfer:btrace-conf:read}
36887 @item @samp{qXfer:exec-file:read}
36892 @item @samp{qXfer:features:read}
36897 @item @samp{qXfer:libraries:read}
36902 @item @samp{qXfer:libraries-svr4:read}
36907 @item @samp{augmented-libraries-svr4-read}
36912 @item @samp{qXfer:memory-map:read}
36917 @item @samp{qXfer:sdata:read}
36922 @item @samp{qXfer:spu:read}
36927 @item @samp{qXfer:spu:write}
36932 @item @samp{qXfer:siginfo:read}
36937 @item @samp{qXfer:siginfo:write}
36942 @item @samp{qXfer:threads:read}
36947 @item @samp{qXfer:traceframe-info:read}
36952 @item @samp{qXfer:uib:read}
36957 @item @samp{qXfer:fdpic:read}
36962 @item @samp{Qbtrace:off}
36967 @item @samp{Qbtrace:bts}
36972 @item @samp{Qbtrace:pt}
36977 @item @samp{Qbtrace-conf:bts:size}
36982 @item @samp{Qbtrace-conf:pt:size}
36987 @item @samp{QNonStop}
36992 @item @samp{QCatchSyscalls}
36997 @item @samp{QPassSignals}
37002 @item @samp{QStartNoAckMode}
37007 @item @samp{multiprocess}
37012 @item @samp{ConditionalBreakpoints}
37017 @item @samp{ConditionalTracepoints}
37022 @item @samp{ReverseContinue}
37027 @item @samp{ReverseStep}
37032 @item @samp{TracepointSource}
37037 @item @samp{QAgent}
37042 @item @samp{QAllow}
37047 @item @samp{QDisableRandomization}
37052 @item @samp{EnableDisableTracepoints}
37057 @item @samp{QTBuffer:size}
37062 @item @samp{tracenz}
37067 @item @samp{BreakpointCommands}
37072 @item @samp{swbreak}
37077 @item @samp{hwbreak}
37082 @item @samp{fork-events}
37087 @item @samp{vfork-events}
37092 @item @samp{exec-events}
37097 @item @samp{QThreadEvents}
37102 @item @samp{no-resumed}
37109 These are the currently defined stub features, in more detail:
37112 @cindex packet size, remote protocol
37113 @item PacketSize=@var{bytes}
37114 The remote stub can accept packets up to at least @var{bytes} in
37115 length. @value{GDBN} will send packets up to this size for bulk
37116 transfers, and will never send larger packets. This is a limit on the
37117 data characters in the packet, including the frame and checksum.
37118 There is no trailing NUL byte in a remote protocol packet; if the stub
37119 stores packets in a NUL-terminated format, it should allow an extra
37120 byte in its buffer for the NUL. If this stub feature is not supported,
37121 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37123 @item qXfer:auxv:read
37124 The remote stub understands the @samp{qXfer:auxv:read} packet
37125 (@pxref{qXfer auxiliary vector read}).
37127 @item qXfer:btrace:read
37128 The remote stub understands the @samp{qXfer:btrace:read}
37129 packet (@pxref{qXfer btrace read}).
37131 @item qXfer:btrace-conf:read
37132 The remote stub understands the @samp{qXfer:btrace-conf:read}
37133 packet (@pxref{qXfer btrace-conf read}).
37135 @item qXfer:exec-file:read
37136 The remote stub understands the @samp{qXfer:exec-file:read} packet
37137 (@pxref{qXfer executable filename read}).
37139 @item qXfer:features:read
37140 The remote stub understands the @samp{qXfer:features:read} packet
37141 (@pxref{qXfer target description read}).
37143 @item qXfer:libraries:read
37144 The remote stub understands the @samp{qXfer:libraries:read} packet
37145 (@pxref{qXfer library list read}).
37147 @item qXfer:libraries-svr4:read
37148 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37149 (@pxref{qXfer svr4 library list read}).
37151 @item augmented-libraries-svr4-read
37152 The remote stub understands the augmented form of the
37153 @samp{qXfer:libraries-svr4:read} packet
37154 (@pxref{qXfer svr4 library list read}).
37156 @item qXfer:memory-map:read
37157 The remote stub understands the @samp{qXfer:memory-map:read} packet
37158 (@pxref{qXfer memory map read}).
37160 @item qXfer:sdata:read
37161 The remote stub understands the @samp{qXfer:sdata:read} packet
37162 (@pxref{qXfer sdata read}).
37164 @item qXfer:spu:read
37165 The remote stub understands the @samp{qXfer:spu:read} packet
37166 (@pxref{qXfer spu read}).
37168 @item qXfer:spu:write
37169 The remote stub understands the @samp{qXfer:spu:write} packet
37170 (@pxref{qXfer spu write}).
37172 @item qXfer:siginfo:read
37173 The remote stub understands the @samp{qXfer:siginfo:read} packet
37174 (@pxref{qXfer siginfo read}).
37176 @item qXfer:siginfo:write
37177 The remote stub understands the @samp{qXfer:siginfo:write} packet
37178 (@pxref{qXfer siginfo write}).
37180 @item qXfer:threads:read
37181 The remote stub understands the @samp{qXfer:threads:read} packet
37182 (@pxref{qXfer threads read}).
37184 @item qXfer:traceframe-info:read
37185 The remote stub understands the @samp{qXfer:traceframe-info:read}
37186 packet (@pxref{qXfer traceframe info read}).
37188 @item qXfer:uib:read
37189 The remote stub understands the @samp{qXfer:uib:read}
37190 packet (@pxref{qXfer unwind info block}).
37192 @item qXfer:fdpic:read
37193 The remote stub understands the @samp{qXfer:fdpic:read}
37194 packet (@pxref{qXfer fdpic loadmap read}).
37197 The remote stub understands the @samp{QNonStop} packet
37198 (@pxref{QNonStop}).
37200 @item QCatchSyscalls
37201 The remote stub understands the @samp{QCatchSyscalls} packet
37202 (@pxref{QCatchSyscalls}).
37205 The remote stub understands the @samp{QPassSignals} packet
37206 (@pxref{QPassSignals}).
37208 @item QStartNoAckMode
37209 The remote stub understands the @samp{QStartNoAckMode} packet and
37210 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37213 @anchor{multiprocess extensions}
37214 @cindex multiprocess extensions, in remote protocol
37215 The remote stub understands the multiprocess extensions to the remote
37216 protocol syntax. The multiprocess extensions affect the syntax of
37217 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37218 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37219 replies. Note that reporting this feature indicates support for the
37220 syntactic extensions only, not that the stub necessarily supports
37221 debugging of more than one process at a time. The stub must not use
37222 multiprocess extensions in packet replies unless @value{GDBN} has also
37223 indicated it supports them in its @samp{qSupported} request.
37225 @item qXfer:osdata:read
37226 The remote stub understands the @samp{qXfer:osdata:read} packet
37227 ((@pxref{qXfer osdata read}).
37229 @item ConditionalBreakpoints
37230 The target accepts and implements evaluation of conditional expressions
37231 defined for breakpoints. The target will only report breakpoint triggers
37232 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37234 @item ConditionalTracepoints
37235 The remote stub accepts and implements conditional expressions defined
37236 for tracepoints (@pxref{Tracepoint Conditions}).
37238 @item ReverseContinue
37239 The remote stub accepts and implements the reverse continue packet
37243 The remote stub accepts and implements the reverse step packet
37246 @item TracepointSource
37247 The remote stub understands the @samp{QTDPsrc} packet that supplies
37248 the source form of tracepoint definitions.
37251 The remote stub understands the @samp{QAgent} packet.
37254 The remote stub understands the @samp{QAllow} packet.
37256 @item QDisableRandomization
37257 The remote stub understands the @samp{QDisableRandomization} packet.
37259 @item StaticTracepoint
37260 @cindex static tracepoints, in remote protocol
37261 The remote stub supports static tracepoints.
37263 @item InstallInTrace
37264 @anchor{install tracepoint in tracing}
37265 The remote stub supports installing tracepoint in tracing.
37267 @item EnableDisableTracepoints
37268 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37269 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37270 to be enabled and disabled while a trace experiment is running.
37272 @item QTBuffer:size
37273 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37274 packet that allows to change the size of the trace buffer.
37277 @cindex string tracing, in remote protocol
37278 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37279 See @ref{Bytecode Descriptions} for details about the bytecode.
37281 @item BreakpointCommands
37282 @cindex breakpoint commands, in remote protocol
37283 The remote stub supports running a breakpoint's command list itself,
37284 rather than reporting the hit to @value{GDBN}.
37287 The remote stub understands the @samp{Qbtrace:off} packet.
37290 The remote stub understands the @samp{Qbtrace:bts} packet.
37293 The remote stub understands the @samp{Qbtrace:pt} packet.
37295 @item Qbtrace-conf:bts:size
37296 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37298 @item Qbtrace-conf:pt:size
37299 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37302 The remote stub reports the @samp{swbreak} stop reason for memory
37306 The remote stub reports the @samp{hwbreak} stop reason for hardware
37310 The remote stub reports the @samp{fork} stop reason for fork events.
37313 The remote stub reports the @samp{vfork} stop reason for vfork events
37314 and vforkdone events.
37317 The remote stub reports the @samp{exec} stop reason for exec events.
37319 @item vContSupported
37320 The remote stub reports the supported actions in the reply to
37321 @samp{vCont?} packet.
37323 @item QThreadEvents
37324 The remote stub understands the @samp{QThreadEvents} packet.
37327 The remote stub reports the @samp{N} stop reply.
37332 @cindex symbol lookup, remote request
37333 @cindex @samp{qSymbol} packet
37334 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37335 requests. Accept requests from the target for the values of symbols.
37340 The target does not need to look up any (more) symbols.
37341 @item qSymbol:@var{sym_name}
37342 The target requests the value of symbol @var{sym_name} (hex encoded).
37343 @value{GDBN} may provide the value by using the
37344 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37348 @item qSymbol:@var{sym_value}:@var{sym_name}
37349 Set the value of @var{sym_name} to @var{sym_value}.
37351 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37352 target has previously requested.
37354 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37355 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37361 The target does not need to look up any (more) symbols.
37362 @item qSymbol:@var{sym_name}
37363 The target requests the value of a new symbol @var{sym_name} (hex
37364 encoded). @value{GDBN} will continue to supply the values of symbols
37365 (if available), until the target ceases to request them.
37370 @itemx QTDisconnected
37377 @itemx qTMinFTPILen
37379 @xref{Tracepoint Packets}.
37381 @item qThreadExtraInfo,@var{thread-id}
37382 @cindex thread attributes info, remote request
37383 @cindex @samp{qThreadExtraInfo} packet
37384 Obtain from the target OS a printable string description of thread
37385 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37386 for the forms of @var{thread-id}. This
37387 string may contain anything that the target OS thinks is interesting
37388 for @value{GDBN} to tell the user about the thread. The string is
37389 displayed in @value{GDBN}'s @code{info threads} display. Some
37390 examples of possible thread extra info strings are @samp{Runnable}, or
37391 @samp{Blocked on Mutex}.
37395 @item @var{XX}@dots{}
37396 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37397 comprising the printable string containing the extra information about
37398 the thread's attributes.
37401 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37402 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37403 conventions above. Please don't use this packet as a model for new
37422 @xref{Tracepoint Packets}.
37424 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37425 @cindex read special object, remote request
37426 @cindex @samp{qXfer} packet
37427 @anchor{qXfer read}
37428 Read uninterpreted bytes from the target's special data area
37429 identified by the keyword @var{object}. Request @var{length} bytes
37430 starting at @var{offset} bytes into the data. The content and
37431 encoding of @var{annex} is specific to @var{object}; it can supply
37432 additional details about what data to access.
37437 Data @var{data} (@pxref{Binary Data}) has been read from the
37438 target. There may be more data at a higher address (although
37439 it is permitted to return @samp{m} even for the last valid
37440 block of data, as long as at least one byte of data was read).
37441 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37445 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37446 There is no more data to be read. It is possible for @var{data} to
37447 have fewer bytes than the @var{length} in the request.
37450 The @var{offset} in the request is at the end of the data.
37451 There is no more data to be read.
37454 The request was malformed, or @var{annex} was invalid.
37457 The offset was invalid, or there was an error encountered reading the data.
37458 The @var{nn} part is a hex-encoded @code{errno} value.
37461 An empty reply indicates the @var{object} string was not recognized by
37462 the stub, or that the object does not support reading.
37465 Here are the specific requests of this form defined so far. All the
37466 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37467 formats, listed above.
37470 @item qXfer:auxv:read::@var{offset},@var{length}
37471 @anchor{qXfer auxiliary vector read}
37472 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37473 auxiliary vector}. Note @var{annex} must be empty.
37475 This packet is not probed by default; the remote stub must request it,
37476 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37478 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37479 @anchor{qXfer btrace read}
37481 Return a description of the current branch trace.
37482 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37483 packet may have one of the following values:
37487 Returns all available branch trace.
37490 Returns all available branch trace if the branch trace changed since
37491 the last read request.
37494 Returns the new branch trace since the last read request. Adds a new
37495 block to the end of the trace that begins at zero and ends at the source
37496 location of the first branch in the trace buffer. This extra block is
37497 used to stitch traces together.
37499 If the trace buffer overflowed, returns an error indicating the overflow.
37502 This packet is not probed by default; the remote stub must request it
37503 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37505 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37506 @anchor{qXfer btrace-conf read}
37508 Return a description of the current branch trace configuration.
37509 @xref{Branch Trace Configuration Format}.
37511 This packet is not probed by default; the remote stub must request it
37512 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37514 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37515 @anchor{qXfer executable filename read}
37516 Return the full absolute name of the file that was executed to create
37517 a process running on the remote system. The annex specifies the
37518 numeric process ID of the process to query, encoded as a hexadecimal
37519 number. If the annex part is empty the remote stub should return the
37520 filename corresponding to the currently executing process.
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:features:read:@var{annex}:@var{offset},@var{length}
37526 @anchor{qXfer target description read}
37527 Access the @dfn{target description}. @xref{Target Descriptions}. The
37528 annex specifies which XML document to access. The main description is
37529 always loaded from the @samp{target.xml} annex.
37531 This packet is not probed by default; the remote stub must request it,
37532 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37534 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37535 @anchor{qXfer library list read}
37536 Access the target's list of loaded libraries. @xref{Library List Format}.
37537 The annex part of the generic @samp{qXfer} packet must be empty
37538 (@pxref{qXfer read}).
37540 Targets which maintain a list of libraries in the program's memory do
37541 not need to implement this packet; it is designed for platforms where
37542 the operating system manages the list of loaded libraries.
37544 This packet is not probed by default; the remote stub must request it,
37545 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37547 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37548 @anchor{qXfer svr4 library list read}
37549 Access the target's list of loaded libraries when the target is an SVR4
37550 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37551 of the generic @samp{qXfer} packet must be empty unless the remote
37552 stub indicated it supports the augmented form of this packet
37553 by supplying an appropriate @samp{qSupported} response
37554 (@pxref{qXfer read}, @ref{qSupported}).
37556 This packet is optional for better performance on SVR4 targets.
37557 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37559 This packet is not probed by default; the remote stub must request it,
37560 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37562 If the remote stub indicates it supports the augmented form of this
37563 packet then the annex part of the generic @samp{qXfer} packet may
37564 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37565 arguments. The currently supported arguments are:
37568 @item start=@var{address}
37569 A hexadecimal number specifying the address of the @samp{struct
37570 link_map} to start reading the library list from. If unset or zero
37571 then the first @samp{struct link_map} in the library list will be
37572 chosen as the starting point.
37574 @item prev=@var{address}
37575 A hexadecimal number specifying the address of the @samp{struct
37576 link_map} immediately preceding the @samp{struct link_map}
37577 specified by the @samp{start} argument. If unset or zero then
37578 the remote stub will expect that no @samp{struct link_map}
37579 exists prior to the starting point.
37583 Arguments that are not understood by the remote stub will be silently
37586 @item qXfer:memory-map:read::@var{offset},@var{length}
37587 @anchor{qXfer memory map read}
37588 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37589 annex part of the generic @samp{qXfer} packet must be empty
37590 (@pxref{qXfer read}).
37592 This packet is not probed by default; the remote stub must request it,
37593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37595 @item qXfer:sdata:read::@var{offset},@var{length}
37596 @anchor{qXfer sdata read}
37598 Read contents of the extra collected static tracepoint marker
37599 information. The annex part of the generic @samp{qXfer} packet must
37600 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37603 This packet is not probed by default; the remote stub must request it,
37604 by supplying an appropriate @samp{qSupported} response
37605 (@pxref{qSupported}).
37607 @item qXfer:siginfo:read::@var{offset},@var{length}
37608 @anchor{qXfer siginfo read}
37609 Read contents of the extra signal information on the target
37610 system. The annex part of the generic @samp{qXfer} packet must be
37611 empty (@pxref{qXfer read}).
37613 This packet is not probed by default; the remote stub must request it,
37614 by supplying an appropriate @samp{qSupported} response
37615 (@pxref{qSupported}).
37617 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37618 @anchor{qXfer spu read}
37619 Read contents of an @code{spufs} file on the target system. The
37620 annex specifies which file to read; it must be of the form
37621 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37622 in the target process, and @var{name} identifes the @code{spufs} file
37623 in that context to be accessed.
37625 This packet is not probed by default; the remote stub must request it,
37626 by supplying an appropriate @samp{qSupported} response
37627 (@pxref{qSupported}).
37629 @item qXfer:threads:read::@var{offset},@var{length}
37630 @anchor{qXfer threads read}
37631 Access the list of threads on target. @xref{Thread List Format}. The
37632 annex part of the generic @samp{qXfer} packet must be empty
37633 (@pxref{qXfer read}).
37635 This packet is not probed by default; the remote stub must request it,
37636 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37638 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37639 @anchor{qXfer traceframe info read}
37641 Return a description of the current traceframe's contents.
37642 @xref{Traceframe Info Format}. The annex part of the generic
37643 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37645 This packet is not probed by default; the remote stub must request it,
37646 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37648 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37649 @anchor{qXfer unwind info block}
37651 Return the unwind information block for @var{pc}. This packet is used
37652 on OpenVMS/ia64 to ask the kernel unwind information.
37654 This packet is not probed by default.
37656 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37657 @anchor{qXfer fdpic loadmap read}
37658 Read contents of @code{loadmap}s on the target system. The
37659 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37660 executable @code{loadmap} or interpreter @code{loadmap} to read.
37662 This packet is not probed by default; the remote stub must request it,
37663 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37665 @item qXfer:osdata:read::@var{offset},@var{length}
37666 @anchor{qXfer osdata read}
37667 Access the target's @dfn{operating system information}.
37668 @xref{Operating System Information}.
37672 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37673 @cindex write data into object, remote request
37674 @anchor{qXfer write}
37675 Write uninterpreted bytes into the target's special data area
37676 identified by the keyword @var{object}, starting at @var{offset} bytes
37677 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37678 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37679 is specific to @var{object}; it can supply additional details about what data
37685 @var{nn} (hex encoded) is the number of bytes written.
37686 This may be fewer bytes than supplied in the request.
37689 The request was malformed, or @var{annex} was invalid.
37692 The offset was invalid, or there was an error encountered writing the data.
37693 The @var{nn} part is a hex-encoded @code{errno} value.
37696 An empty reply indicates the @var{object} string was not
37697 recognized by the stub, or that the object does not support writing.
37700 Here are the specific requests of this form defined so far. All the
37701 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37702 formats, listed above.
37705 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37706 @anchor{qXfer siginfo write}
37707 Write @var{data} to the extra signal information on the target system.
37708 The annex part of the generic @samp{qXfer} packet must be
37709 empty (@pxref{qXfer write}).
37711 This packet is not probed by default; the remote stub must request it,
37712 by supplying an appropriate @samp{qSupported} response
37713 (@pxref{qSupported}).
37715 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37716 @anchor{qXfer spu write}
37717 Write @var{data} to an @code{spufs} file on the target system. The
37718 annex specifies which file to write; it must be of the form
37719 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37720 in the target process, and @var{name} identifes the @code{spufs} file
37721 in that context to be accessed.
37723 This packet is not probed by default; the remote stub must request it,
37724 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37727 @item qXfer:@var{object}:@var{operation}:@dots{}
37728 Requests of this form may be added in the future. When a stub does
37729 not recognize the @var{object} keyword, or its support for
37730 @var{object} does not recognize the @var{operation} keyword, the stub
37731 must respond with an empty packet.
37733 @item qAttached:@var{pid}
37734 @cindex query attached, remote request
37735 @cindex @samp{qAttached} packet
37736 Return an indication of whether the remote server attached to an
37737 existing process or created a new process. When the multiprocess
37738 protocol extensions are supported (@pxref{multiprocess extensions}),
37739 @var{pid} is an integer in hexadecimal format identifying the target
37740 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37741 the query packet will be simplified as @samp{qAttached}.
37743 This query is used, for example, to know whether the remote process
37744 should be detached or killed when a @value{GDBN} session is ended with
37745 the @code{quit} command.
37750 The remote server attached to an existing process.
37752 The remote server created a new process.
37754 A badly formed request or an error was encountered.
37758 Enable branch tracing for the current thread using Branch Trace Store.
37763 Branch tracing has been enabled.
37765 A badly formed request or an error was encountered.
37769 Enable branch tracing for the current thread using Intel Processor Trace.
37774 Branch tracing has been enabled.
37776 A badly formed request or an error was encountered.
37780 Disable branch tracing for the current thread.
37785 Branch tracing has been disabled.
37787 A badly formed request or an error was encountered.
37790 @item Qbtrace-conf:bts:size=@var{value}
37791 Set the requested ring buffer size for new threads that use the
37792 btrace recording method in bts format.
37797 The ring buffer size has been set.
37799 A badly formed request or an error was encountered.
37802 @item Qbtrace-conf:pt:size=@var{value}
37803 Set the requested ring buffer size for new threads that use the
37804 btrace recording method in pt format.
37809 The ring buffer size has been set.
37811 A badly formed request or an error was encountered.
37816 @node Architecture-Specific Protocol Details
37817 @section Architecture-Specific Protocol Details
37819 This section describes how the remote protocol is applied to specific
37820 target architectures. Also see @ref{Standard Target Features}, for
37821 details of XML target descriptions for each architecture.
37824 * ARM-Specific Protocol Details::
37825 * MIPS-Specific Protocol Details::
37828 @node ARM-Specific Protocol Details
37829 @subsection @acronym{ARM}-specific Protocol Details
37832 * ARM Breakpoint Kinds::
37835 @node ARM Breakpoint Kinds
37836 @subsubsection @acronym{ARM} Breakpoint Kinds
37837 @cindex breakpoint kinds, @acronym{ARM}
37839 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37844 16-bit Thumb mode breakpoint.
37847 32-bit Thumb mode (Thumb-2) breakpoint.
37850 32-bit @acronym{ARM} mode breakpoint.
37854 @node MIPS-Specific Protocol Details
37855 @subsection @acronym{MIPS}-specific Protocol Details
37858 * MIPS Register packet Format::
37859 * MIPS Breakpoint Kinds::
37862 @node MIPS Register packet Format
37863 @subsubsection @acronym{MIPS} Register Packet Format
37864 @cindex register packet format, @acronym{MIPS}
37866 The following @code{g}/@code{G} packets have previously been defined.
37867 In the below, some thirty-two bit registers are transferred as
37868 sixty-four bits. Those registers should be zero/sign extended (which?)
37869 to fill the space allocated. Register bytes are transferred in target
37870 byte order. The two nibbles within a register byte are transferred
37871 most-significant -- least-significant.
37876 All registers are transferred as thirty-two bit quantities in the order:
37877 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37878 registers; fsr; fir; fp.
37881 All registers are transferred as sixty-four bit quantities (including
37882 thirty-two bit registers such as @code{sr}). The ordering is the same
37887 @node MIPS Breakpoint Kinds
37888 @subsubsection @acronym{MIPS} Breakpoint Kinds
37889 @cindex breakpoint kinds, @acronym{MIPS}
37891 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37896 16-bit @acronym{MIPS16} mode breakpoint.
37899 16-bit @acronym{microMIPS} mode breakpoint.
37902 32-bit standard @acronym{MIPS} mode breakpoint.
37905 32-bit @acronym{microMIPS} mode breakpoint.
37909 @node Tracepoint Packets
37910 @section Tracepoint Packets
37911 @cindex tracepoint packets
37912 @cindex packets, tracepoint
37914 Here we describe the packets @value{GDBN} uses to implement
37915 tracepoints (@pxref{Tracepoints}).
37919 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37920 @cindex @samp{QTDP} packet
37921 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37922 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37923 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37924 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37925 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37926 the number of bytes that the target should copy elsewhere to make room
37927 for the tracepoint. If an @samp{X} is present, it introduces a
37928 tracepoint condition, which consists of a hexadecimal length, followed
37929 by a comma and hex-encoded bytes, in a manner similar to action
37930 encodings as described below. If the trailing @samp{-} is present,
37931 further @samp{QTDP} packets will follow to specify this tracepoint's
37937 The packet was understood and carried out.
37939 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37941 The packet was not recognized.
37944 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37945 Define actions to be taken when a tracepoint is hit. The @var{n} and
37946 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37947 this tracepoint. This packet may only be sent immediately after
37948 another @samp{QTDP} packet that ended with a @samp{-}. If the
37949 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37950 specifying more actions for this tracepoint.
37952 In the series of action packets for a given tracepoint, at most one
37953 can have an @samp{S} before its first @var{action}. If such a packet
37954 is sent, it and the following packets define ``while-stepping''
37955 actions. Any prior packets define ordinary actions --- that is, those
37956 taken when the tracepoint is first hit. If no action packet has an
37957 @samp{S}, then all the packets in the series specify ordinary
37958 tracepoint actions.
37960 The @samp{@var{action}@dots{}} portion of the packet is a series of
37961 actions, concatenated without separators. Each action has one of the
37967 Collect the registers whose bits are set in @var{mask},
37968 a hexadecimal number whose @var{i}'th bit is set if register number
37969 @var{i} should be collected. (The least significant bit is numbered
37970 zero.) Note that @var{mask} may be any number of digits long; it may
37971 not fit in a 32-bit word.
37973 @item M @var{basereg},@var{offset},@var{len}
37974 Collect @var{len} bytes of memory starting at the address in register
37975 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37976 @samp{-1}, then the range has a fixed address: @var{offset} is the
37977 address of the lowest byte to collect. The @var{basereg},
37978 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37979 values (the @samp{-1} value for @var{basereg} is a special case).
37981 @item X @var{len},@var{expr}
37982 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37983 it directs. The agent expression @var{expr} is as described in
37984 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37985 two-digit hex number in the packet; @var{len} is the number of bytes
37986 in the expression (and thus one-half the number of hex digits in the
37991 Any number of actions may be packed together in a single @samp{QTDP}
37992 packet, as long as the packet does not exceed the maximum packet
37993 length (400 bytes, for many stubs). There may be only one @samp{R}
37994 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37995 actions. Any registers referred to by @samp{M} and @samp{X} actions
37996 must be collected by a preceding @samp{R} action. (The
37997 ``while-stepping'' actions are treated as if they were attached to a
37998 separate tracepoint, as far as these restrictions are concerned.)
38003 The packet was understood and carried out.
38005 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38007 The packet was not recognized.
38010 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38011 @cindex @samp{QTDPsrc} packet
38012 Specify a source string of tracepoint @var{n} at address @var{addr}.
38013 This is useful to get accurate reproduction of the tracepoints
38014 originally downloaded at the beginning of the trace run. The @var{type}
38015 is the name of the tracepoint part, such as @samp{cond} for the
38016 tracepoint's conditional expression (see below for a list of types), while
38017 @var{bytes} is the string, encoded in hexadecimal.
38019 @var{start} is the offset of the @var{bytes} within the overall source
38020 string, while @var{slen} is the total length of the source string.
38021 This is intended for handling source strings that are longer than will
38022 fit in a single packet.
38023 @c Add detailed example when this info is moved into a dedicated
38024 @c tracepoint descriptions section.
38026 The available string types are @samp{at} for the location,
38027 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38028 @value{GDBN} sends a separate packet for each command in the action
38029 list, in the same order in which the commands are stored in the list.
38031 The target does not need to do anything with source strings except
38032 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38035 Although this packet is optional, and @value{GDBN} will only send it
38036 if the target replies with @samp{TracepointSource} @xref{General
38037 Query Packets}, it makes both disconnected tracing and trace files
38038 much easier to use. Otherwise the user must be careful that the
38039 tracepoints in effect while looking at trace frames are identical to
38040 the ones in effect during the trace run; even a small discrepancy
38041 could cause @samp{tdump} not to work, or a particular trace frame not
38044 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38045 @cindex define trace state variable, remote request
38046 @cindex @samp{QTDV} packet
38047 Create a new trace state variable, number @var{n}, with an initial
38048 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38049 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38050 the option of not using this packet for initial values of zero; the
38051 target should simply create the trace state variables as they are
38052 mentioned in expressions. The value @var{builtin} should be 1 (one)
38053 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38054 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38055 @samp{qTsV} packet had it set. The contents of @var{name} is the
38056 hex-encoded name (without the leading @samp{$}) of the trace state
38059 @item QTFrame:@var{n}
38060 @cindex @samp{QTFrame} packet
38061 Select the @var{n}'th tracepoint frame from the buffer, and use the
38062 register and memory contents recorded there to answer subsequent
38063 request packets from @value{GDBN}.
38065 A successful reply from the stub indicates that the stub has found the
38066 requested frame. The response is a series of parts, concatenated
38067 without separators, describing the frame we selected. Each part has
38068 one of the following forms:
38072 The selected frame is number @var{n} in the trace frame buffer;
38073 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38074 was no frame matching the criteria in the request packet.
38077 The selected trace frame records a hit of tracepoint number @var{t};
38078 @var{t} is a hexadecimal number.
38082 @item QTFrame:pc:@var{addr}
38083 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38084 currently selected frame whose PC is @var{addr};
38085 @var{addr} is a hexadecimal number.
38087 @item QTFrame:tdp:@var{t}
38088 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38089 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38090 is a hexadecimal number.
38092 @item QTFrame:range:@var{start}:@var{end}
38093 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38094 currently selected frame whose PC is between @var{start} (inclusive)
38095 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38098 @item QTFrame:outside:@var{start}:@var{end}
38099 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38100 frame @emph{outside} the given range of addresses (exclusive).
38103 @cindex @samp{qTMinFTPILen} packet
38104 This packet requests the minimum length of instruction at which a fast
38105 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38106 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38107 it depends on the target system being able to create trampolines in
38108 the first 64K of memory, which might or might not be possible for that
38109 system. So the reply to this packet will be 4 if it is able to
38116 The minimum instruction length is currently unknown.
38118 The minimum instruction length is @var{length}, where @var{length}
38119 is a hexadecimal number greater or equal to 1. A reply
38120 of 1 means that a fast tracepoint may be placed on any instruction
38121 regardless of size.
38123 An error has occurred.
38125 An empty reply indicates that the request is not supported by the stub.
38129 @cindex @samp{QTStart} packet
38130 Begin the tracepoint experiment. Begin collecting data from
38131 tracepoint hits in the trace frame buffer. This packet supports the
38132 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38133 instruction reply packet}).
38136 @cindex @samp{QTStop} packet
38137 End the tracepoint experiment. Stop collecting trace frames.
38139 @item QTEnable:@var{n}:@var{addr}
38141 @cindex @samp{QTEnable} packet
38142 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38143 experiment. If the tracepoint was previously disabled, then collection
38144 of data from it will resume.
38146 @item QTDisable:@var{n}:@var{addr}
38148 @cindex @samp{QTDisable} packet
38149 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38150 experiment. No more data will be collected from the tracepoint unless
38151 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38154 @cindex @samp{QTinit} packet
38155 Clear the table of tracepoints, and empty the trace frame buffer.
38157 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38158 @cindex @samp{QTro} packet
38159 Establish the given ranges of memory as ``transparent''. The stub
38160 will answer requests for these ranges from memory's current contents,
38161 if they were not collected as part of the tracepoint hit.
38163 @value{GDBN} uses this to mark read-only regions of memory, like those
38164 containing program code. Since these areas never change, they should
38165 still have the same contents they did when the tracepoint was hit, so
38166 there's no reason for the stub to refuse to provide their contents.
38168 @item QTDisconnected:@var{value}
38169 @cindex @samp{QTDisconnected} packet
38170 Set the choice to what to do with the tracing run when @value{GDBN}
38171 disconnects from the target. A @var{value} of 1 directs the target to
38172 continue the tracing run, while 0 tells the target to stop tracing if
38173 @value{GDBN} is no longer in the picture.
38176 @cindex @samp{qTStatus} packet
38177 Ask the stub if there is a trace experiment running right now.
38179 The reply has the form:
38183 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38184 @var{running} is a single digit @code{1} if the trace is presently
38185 running, or @code{0} if not. It is followed by semicolon-separated
38186 optional fields that an agent may use to report additional status.
38190 If the trace is not running, the agent may report any of several
38191 explanations as one of the optional fields:
38196 No trace has been run yet.
38198 @item tstop[:@var{text}]:0
38199 The trace was stopped by a user-originated stop command. The optional
38200 @var{text} field is a user-supplied string supplied as part of the
38201 stop command (for instance, an explanation of why the trace was
38202 stopped manually). It is hex-encoded.
38205 The trace stopped because the trace buffer filled up.
38207 @item tdisconnected:0
38208 The trace stopped because @value{GDBN} disconnected from the target.
38210 @item tpasscount:@var{tpnum}
38211 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38213 @item terror:@var{text}:@var{tpnum}
38214 The trace stopped because tracepoint @var{tpnum} had an error. The
38215 string @var{text} is available to describe the nature of the error
38216 (for instance, a divide by zero in the condition expression); it
38220 The trace stopped for some other reason.
38224 Additional optional fields supply statistical and other information.
38225 Although not required, they are extremely useful for users monitoring
38226 the progress of a trace run. If a trace has stopped, and these
38227 numbers are reported, they must reflect the state of the just-stopped
38232 @item tframes:@var{n}
38233 The number of trace frames in the buffer.
38235 @item tcreated:@var{n}
38236 The total number of trace frames created during the run. This may
38237 be larger than the trace frame count, if the buffer is circular.
38239 @item tsize:@var{n}
38240 The total size of the trace buffer, in bytes.
38242 @item tfree:@var{n}
38243 The number of bytes still unused in the buffer.
38245 @item circular:@var{n}
38246 The value of the circular trace buffer flag. @code{1} means that the
38247 trace buffer is circular and old trace frames will be discarded if
38248 necessary to make room, @code{0} means that the trace buffer is linear
38251 @item disconn:@var{n}
38252 The value of the disconnected tracing flag. @code{1} means that
38253 tracing will continue after @value{GDBN} disconnects, @code{0} means
38254 that the trace run will stop.
38258 @item qTP:@var{tp}:@var{addr}
38259 @cindex tracepoint status, remote request
38260 @cindex @samp{qTP} packet
38261 Ask the stub for the current state of tracepoint number @var{tp} at
38262 address @var{addr}.
38266 @item V@var{hits}:@var{usage}
38267 The tracepoint has been hit @var{hits} times so far during the trace
38268 run, and accounts for @var{usage} in the trace buffer. Note that
38269 @code{while-stepping} steps are not counted as separate hits, but the
38270 steps' space consumption is added into the usage number.
38274 @item qTV:@var{var}
38275 @cindex trace state variable value, remote request
38276 @cindex @samp{qTV} packet
38277 Ask the stub for the value of the trace state variable number @var{var}.
38282 The value of the variable is @var{value}. This will be the current
38283 value of the variable if the user is examining a running target, or a
38284 saved value if the variable was collected in the trace frame that the
38285 user is looking at. Note that multiple requests may result in
38286 different reply values, such as when requesting values while the
38287 program is running.
38290 The value of the variable is unknown. This would occur, for example,
38291 if the user is examining a trace frame in which the requested variable
38296 @cindex @samp{qTfP} packet
38298 @cindex @samp{qTsP} packet
38299 These packets request data about tracepoints that are being used by
38300 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38301 of data, and multiple @code{qTsP} to get additional pieces. Replies
38302 to these packets generally take the form of the @code{QTDP} packets
38303 that define tracepoints. (FIXME add detailed syntax)
38306 @cindex @samp{qTfV} packet
38308 @cindex @samp{qTsV} packet
38309 These packets request data about trace state variables that are on the
38310 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38311 and multiple @code{qTsV} to get additional variables. Replies to
38312 these packets follow the syntax of the @code{QTDV} packets that define
38313 trace state variables.
38319 @cindex @samp{qTfSTM} packet
38320 @cindex @samp{qTsSTM} packet
38321 These packets request data about static tracepoint markers that exist
38322 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38323 first piece of data, and multiple @code{qTsSTM} to get additional
38324 pieces. Replies to these packets take the following form:
38328 @item m @var{address}:@var{id}:@var{extra}
38330 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38331 a comma-separated list of markers
38333 (lower case letter @samp{L}) denotes end of list.
38335 An error occurred. The error number @var{nn} is given as hex digits.
38337 An empty reply indicates that the request is not supported by the
38341 The @var{address} is encoded in hex;
38342 @var{id} and @var{extra} are strings encoded in hex.
38344 In response to each query, the target will reply with a list of one or
38345 more markers, separated by commas. @value{GDBN} will respond to each
38346 reply with a request for more markers (using the @samp{qs} form of the
38347 query), until the target responds with @samp{l} (lower-case ell, for
38350 @item qTSTMat:@var{address}
38352 @cindex @samp{qTSTMat} packet
38353 This packets requests data about static tracepoint markers in the
38354 target program at @var{address}. Replies to this packet follow the
38355 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38356 tracepoint markers.
38358 @item QTSave:@var{filename}
38359 @cindex @samp{QTSave} packet
38360 This packet directs the target to save trace data to the file name
38361 @var{filename} in the target's filesystem. The @var{filename} is encoded
38362 as a hex string; the interpretation of the file name (relative vs
38363 absolute, wild cards, etc) is up to the target.
38365 @item qTBuffer:@var{offset},@var{len}
38366 @cindex @samp{qTBuffer} packet
38367 Return up to @var{len} bytes of the current contents of trace buffer,
38368 starting at @var{offset}. The trace buffer is treated as if it were
38369 a contiguous collection of traceframes, as per the trace file format.
38370 The reply consists as many hex-encoded bytes as the target can deliver
38371 in a packet; it is not an error to return fewer than were asked for.
38372 A reply consisting of just @code{l} indicates that no bytes are
38375 @item QTBuffer:circular:@var{value}
38376 This packet directs the target to use a circular trace buffer if
38377 @var{value} is 1, or a linear buffer if the value is 0.
38379 @item QTBuffer:size:@var{size}
38380 @anchor{QTBuffer-size}
38381 @cindex @samp{QTBuffer size} packet
38382 This packet directs the target to make the trace buffer be of size
38383 @var{size} if possible. A value of @code{-1} tells the target to
38384 use whatever size it prefers.
38386 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38387 @cindex @samp{QTNotes} packet
38388 This packet adds optional textual notes to the trace run. Allowable
38389 types include @code{user}, @code{notes}, and @code{tstop}, the
38390 @var{text} fields are arbitrary strings, hex-encoded.
38394 @subsection Relocate instruction reply packet
38395 When installing fast tracepoints in memory, the target may need to
38396 relocate the instruction currently at the tracepoint address to a
38397 different address in memory. For most instructions, a simple copy is
38398 enough, but, for example, call instructions that implicitly push the
38399 return address on the stack, and relative branches or other
38400 PC-relative instructions require offset adjustment, so that the effect
38401 of executing the instruction at a different address is the same as if
38402 it had executed in the original location.
38404 In response to several of the tracepoint packets, the target may also
38405 respond with a number of intermediate @samp{qRelocInsn} request
38406 packets before the final result packet, to have @value{GDBN} handle
38407 this relocation operation. If a packet supports this mechanism, its
38408 documentation will explicitly say so. See for example the above
38409 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38410 format of the request is:
38413 @item qRelocInsn:@var{from};@var{to}
38415 This requests @value{GDBN} to copy instruction at address @var{from}
38416 to address @var{to}, possibly adjusted so that executing the
38417 instruction at @var{to} has the same effect as executing it at
38418 @var{from}. @value{GDBN} writes the adjusted instruction to target
38419 memory starting at @var{to}.
38424 @item qRelocInsn:@var{adjusted_size}
38425 Informs the stub the relocation is complete. The @var{adjusted_size} is
38426 the length in bytes of resulting relocated instruction sequence.
38428 A badly formed request was detected, or an error was encountered while
38429 relocating the instruction.
38432 @node Host I/O Packets
38433 @section Host I/O Packets
38434 @cindex Host I/O, remote protocol
38435 @cindex file transfer, remote protocol
38437 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38438 operations on the far side of a remote link. For example, Host I/O is
38439 used to upload and download files to a remote target with its own
38440 filesystem. Host I/O uses the same constant values and data structure
38441 layout as the target-initiated File-I/O protocol. However, the
38442 Host I/O packets are structured differently. The target-initiated
38443 protocol relies on target memory to store parameters and buffers.
38444 Host I/O requests are initiated by @value{GDBN}, and the
38445 target's memory is not involved. @xref{File-I/O Remote Protocol
38446 Extension}, for more details on the target-initiated protocol.
38448 The Host I/O request packets all encode a single operation along with
38449 its arguments. They have this format:
38453 @item vFile:@var{operation}: @var{parameter}@dots{}
38454 @var{operation} is the name of the particular request; the target
38455 should compare the entire packet name up to the second colon when checking
38456 for a supported operation. The format of @var{parameter} depends on
38457 the operation. Numbers are always passed in hexadecimal. Negative
38458 numbers have an explicit minus sign (i.e.@: two's complement is not
38459 used). Strings (e.g.@: filenames) are encoded as a series of
38460 hexadecimal bytes. The last argument to a system call may be a
38461 buffer of escaped binary data (@pxref{Binary Data}).
38465 The valid responses to Host I/O packets are:
38469 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38470 @var{result} is the integer value returned by this operation, usually
38471 non-negative for success and -1 for errors. If an error has occured,
38472 @var{errno} will be included in the result specifying a
38473 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38474 operations which return data, @var{attachment} supplies the data as a
38475 binary buffer. Binary buffers in response packets are escaped in the
38476 normal way (@pxref{Binary Data}). See the individual packet
38477 documentation for the interpretation of @var{result} and
38481 An empty response indicates that this operation is not recognized.
38485 These are the supported Host I/O operations:
38488 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38489 Open a file at @var{filename} and return a file descriptor for it, or
38490 return -1 if an error occurs. The @var{filename} is a string,
38491 @var{flags} is an integer indicating a mask of open flags
38492 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38493 of mode bits to use if the file is created (@pxref{mode_t Values}).
38494 @xref{open}, for details of the open flags and mode values.
38496 @item vFile:close: @var{fd}
38497 Close the open file corresponding to @var{fd} and return 0, or
38498 -1 if an error occurs.
38500 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38501 Read data from the open file corresponding to @var{fd}. Up to
38502 @var{count} bytes will be read from the file, starting at @var{offset}
38503 relative to the start of the file. The target may read fewer bytes;
38504 common reasons include packet size limits and an end-of-file
38505 condition. The number of bytes read is returned. Zero should only be
38506 returned for a successful read at the end of the file, or if
38507 @var{count} was zero.
38509 The data read should be returned as a binary attachment on success.
38510 If zero bytes were read, the response should include an empty binary
38511 attachment (i.e.@: a trailing semicolon). The return value is the
38512 number of target bytes read; the binary attachment may be longer if
38513 some characters were escaped.
38515 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38516 Write @var{data} (a binary buffer) to the open file corresponding
38517 to @var{fd}. Start the write at @var{offset} from the start of the
38518 file. Unlike many @code{write} system calls, there is no
38519 separate @var{count} argument; the length of @var{data} in the
38520 packet is used. @samp{vFile:write} returns the number of bytes written,
38521 which may be shorter than the length of @var{data}, or -1 if an
38524 @item vFile:fstat: @var{fd}
38525 Get information about the open file corresponding to @var{fd}.
38526 On success the information is returned as a binary attachment
38527 and the return value is the size of this attachment in bytes.
38528 If an error occurs the return value is -1. The format of the
38529 returned binary attachment is as described in @ref{struct stat}.
38531 @item vFile:unlink: @var{filename}
38532 Delete the file at @var{filename} on the target. Return 0,
38533 or -1 if an error occurs. The @var{filename} is a string.
38535 @item vFile:readlink: @var{filename}
38536 Read value of symbolic link @var{filename} on the target. Return
38537 the number of bytes read, or -1 if an error occurs.
38539 The data read should be returned as a binary attachment on success.
38540 If zero bytes were read, the response should include an empty binary
38541 attachment (i.e.@: a trailing semicolon). The return value is the
38542 number of target bytes read; the binary attachment may be longer if
38543 some characters were escaped.
38545 @item vFile:setfs: @var{pid}
38546 Select the filesystem on which @code{vFile} operations with
38547 @var{filename} arguments will operate. This is required for
38548 @value{GDBN} to be able to access files on remote targets where
38549 the remote stub does not share a common filesystem with the
38552 If @var{pid} is nonzero, select the filesystem as seen by process
38553 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38554 the remote stub. Return 0 on success, or -1 if an error occurs.
38555 If @code{vFile:setfs:} indicates success, the selected filesystem
38556 remains selected until the next successful @code{vFile:setfs:}
38562 @section Interrupts
38563 @cindex interrupts (remote protocol)
38564 @anchor{interrupting remote targets}
38566 In all-stop mode, when a program on the remote target is running,
38567 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38568 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38569 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38571 The precise meaning of @code{BREAK} is defined by the transport
38572 mechanism and may, in fact, be undefined. @value{GDBN} does not
38573 currently define a @code{BREAK} mechanism for any of the network
38574 interfaces except for TCP, in which case @value{GDBN} sends the
38575 @code{telnet} BREAK sequence.
38577 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38578 transport mechanisms. It is represented by sending the single byte
38579 @code{0x03} without any of the usual packet overhead described in
38580 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38581 transmitted as part of a packet, it is considered to be packet data
38582 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38583 (@pxref{X packet}), used for binary downloads, may include an unescaped
38584 @code{0x03} as part of its packet.
38586 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38587 When Linux kernel receives this sequence from serial port,
38588 it stops execution and connects to gdb.
38590 In non-stop mode, because packet resumptions are asynchronous
38591 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38592 command to the remote stub, even when the target is running. For that
38593 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38594 packet}) with the usual packet framing instead of the single byte
38597 Stubs are not required to recognize these interrupt mechanisms and the
38598 precise meaning associated with receipt of the interrupt is
38599 implementation defined. If the target supports debugging of multiple
38600 threads and/or processes, it should attempt to interrupt all
38601 currently-executing threads and processes.
38602 If the stub is successful at interrupting the
38603 running program, it should send one of the stop
38604 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38605 of successfully stopping the program in all-stop mode, and a stop reply
38606 for each stopped thread in non-stop mode.
38607 Interrupts received while the
38608 program is stopped are queued and the program will be interrupted when
38609 it is resumed next time.
38611 @node Notification Packets
38612 @section Notification Packets
38613 @cindex notification packets
38614 @cindex packets, notification
38616 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38617 packets that require no acknowledgment. Both the GDB and the stub
38618 may send notifications (although the only notifications defined at
38619 present are sent by the stub). Notifications carry information
38620 without incurring the round-trip latency of an acknowledgment, and so
38621 are useful for low-impact communications where occasional packet loss
38624 A notification packet has the form @samp{% @var{data} #
38625 @var{checksum}}, where @var{data} is the content of the notification,
38626 and @var{checksum} is a checksum of @var{data}, computed and formatted
38627 as for ordinary @value{GDBN} packets. A notification's @var{data}
38628 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38629 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38630 to acknowledge the notification's receipt or to report its corruption.
38632 Every notification's @var{data} begins with a name, which contains no
38633 colon characters, followed by a colon character.
38635 Recipients should silently ignore corrupted notifications and
38636 notifications they do not understand. Recipients should restart
38637 timeout periods on receipt of a well-formed notification, whether or
38638 not they understand it.
38640 Senders should only send the notifications described here when this
38641 protocol description specifies that they are permitted. In the
38642 future, we may extend the protocol to permit existing notifications in
38643 new contexts; this rule helps older senders avoid confusing newer
38646 (Older versions of @value{GDBN} ignore bytes received until they see
38647 the @samp{$} byte that begins an ordinary packet, so new stubs may
38648 transmit notifications without fear of confusing older clients. There
38649 are no notifications defined for @value{GDBN} to send at the moment, but we
38650 assume that most older stubs would ignore them, as well.)
38652 Each notification is comprised of three parts:
38654 @item @var{name}:@var{event}
38655 The notification packet is sent by the side that initiates the
38656 exchange (currently, only the stub does that), with @var{event}
38657 carrying the specific information about the notification, and
38658 @var{name} specifying the name of the notification.
38660 The acknowledge sent by the other side, usually @value{GDBN}, to
38661 acknowledge the exchange and request the event.
38664 The purpose of an asynchronous notification mechanism is to report to
38665 @value{GDBN} that something interesting happened in the remote stub.
38667 The remote stub may send notification @var{name}:@var{event}
38668 at any time, but @value{GDBN} acknowledges the notification when
38669 appropriate. The notification event is pending before @value{GDBN}
38670 acknowledges. Only one notification at a time may be pending; if
38671 additional events occur before @value{GDBN} has acknowledged the
38672 previous notification, they must be queued by the stub for later
38673 synchronous transmission in response to @var{ack} packets from
38674 @value{GDBN}. Because the notification mechanism is unreliable,
38675 the stub is permitted to resend a notification if it believes
38676 @value{GDBN} may not have received it.
38678 Specifically, notifications may appear when @value{GDBN} is not
38679 otherwise reading input from the stub, or when @value{GDBN} is
38680 expecting to read a normal synchronous response or a
38681 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38682 Notification packets are distinct from any other communication from
38683 the stub so there is no ambiguity.
38685 After receiving a notification, @value{GDBN} shall acknowledge it by
38686 sending a @var{ack} packet as a regular, synchronous request to the
38687 stub. Such acknowledgment is not required to happen immediately, as
38688 @value{GDBN} is permitted to send other, unrelated packets to the
38689 stub first, which the stub should process normally.
38691 Upon receiving a @var{ack} packet, if the stub has other queued
38692 events to report to @value{GDBN}, it shall respond by sending a
38693 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38694 packet to solicit further responses; again, it is permitted to send
38695 other, unrelated packets as well which the stub should process
38698 If the stub receives a @var{ack} packet and there are no additional
38699 @var{event} to report, the stub shall return an @samp{OK} response.
38700 At this point, @value{GDBN} has finished processing a notification
38701 and the stub has completed sending any queued events. @value{GDBN}
38702 won't accept any new notifications until the final @samp{OK} is
38703 received . If further notification events occur, the stub shall send
38704 a new notification, @value{GDBN} shall accept the notification, and
38705 the process shall be repeated.
38707 The process of asynchronous notification can be illustrated by the
38710 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38713 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38715 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38720 The following notifications are defined:
38721 @multitable @columnfractions 0.12 0.12 0.38 0.38
38730 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38731 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38732 for information on how these notifications are acknowledged by
38734 @tab Report an asynchronous stop event in non-stop mode.
38738 @node Remote Non-Stop
38739 @section Remote Protocol Support for Non-Stop Mode
38741 @value{GDBN}'s remote protocol supports non-stop debugging of
38742 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38743 supports non-stop mode, it should report that to @value{GDBN} by including
38744 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38746 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38747 establishing a new connection with the stub. Entering non-stop mode
38748 does not alter the state of any currently-running threads, but targets
38749 must stop all threads in any already-attached processes when entering
38750 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38751 probe the target state after a mode change.
38753 In non-stop mode, when an attached process encounters an event that
38754 would otherwise be reported with a stop reply, it uses the
38755 asynchronous notification mechanism (@pxref{Notification Packets}) to
38756 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38757 in all processes are stopped when a stop reply is sent, in non-stop
38758 mode only the thread reporting the stop event is stopped. That is,
38759 when reporting a @samp{S} or @samp{T} response to indicate completion
38760 of a step operation, hitting a breakpoint, or a fault, only the
38761 affected thread is stopped; any other still-running threads continue
38762 to run. When reporting a @samp{W} or @samp{X} response, all running
38763 threads belonging to other attached processes continue to run.
38765 In non-stop mode, the target shall respond to the @samp{?} packet as
38766 follows. First, any incomplete stop reply notification/@samp{vStopped}
38767 sequence in progress is abandoned. The target must begin a new
38768 sequence reporting stop events for all stopped threads, whether or not
38769 it has previously reported those events to @value{GDBN}. The first
38770 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38771 subsequent stop replies are sent as responses to @samp{vStopped} packets
38772 using the mechanism described above. The target must not send
38773 asynchronous stop reply notifications until the sequence is complete.
38774 If all threads are running when the target receives the @samp{?} packet,
38775 or if the target is not attached to any process, it shall respond
38778 If the stub supports non-stop mode, it should also support the
38779 @samp{swbreak} stop reason if software breakpoints are supported, and
38780 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38781 (@pxref{swbreak stop reason}). This is because given the asynchronous
38782 nature of non-stop mode, between the time a thread hits a breakpoint
38783 and the time the event is finally processed by @value{GDBN}, the
38784 breakpoint may have already been removed from the target. Due to
38785 this, @value{GDBN} needs to be able to tell whether a trap stop was
38786 caused by a delayed breakpoint event, which should be ignored, as
38787 opposed to a random trap signal, which should be reported to the user.
38788 Note the @samp{swbreak} feature implies that the target is responsible
38789 for adjusting the PC when a software breakpoint triggers, if
38790 necessary, such as on the x86 architecture.
38792 @node Packet Acknowledgment
38793 @section Packet Acknowledgment
38795 @cindex acknowledgment, for @value{GDBN} remote
38796 @cindex packet acknowledgment, for @value{GDBN} remote
38797 By default, when either the host or the target machine receives a packet,
38798 the first response expected is an acknowledgment: either @samp{+} (to indicate
38799 the package was received correctly) or @samp{-} (to request retransmission).
38800 This mechanism allows the @value{GDBN} remote protocol to operate over
38801 unreliable transport mechanisms, such as a serial line.
38803 In cases where the transport mechanism is itself reliable (such as a pipe or
38804 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38805 It may be desirable to disable them in that case to reduce communication
38806 overhead, or for other reasons. This can be accomplished by means of the
38807 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38809 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38810 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38811 and response format still includes the normal checksum, as described in
38812 @ref{Overview}, but the checksum may be ignored by the receiver.
38814 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38815 no-acknowledgment mode, it should report that to @value{GDBN}
38816 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38817 @pxref{qSupported}.
38818 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38819 disabled via the @code{set remote noack-packet off} command
38820 (@pxref{Remote Configuration}),
38821 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38822 Only then may the stub actually turn off packet acknowledgments.
38823 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38824 response, which can be safely ignored by the stub.
38826 Note that @code{set remote noack-packet} command only affects negotiation
38827 between @value{GDBN} and the stub when subsequent connections are made;
38828 it does not affect the protocol acknowledgment state for any current
38830 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38831 new connection is established,
38832 there is also no protocol request to re-enable the acknowledgments
38833 for the current connection, once disabled.
38838 Example sequence of a target being re-started. Notice how the restart
38839 does not get any direct output:
38844 @emph{target restarts}
38847 <- @code{T001:1234123412341234}
38851 Example sequence of a target being stepped by a single instruction:
38854 -> @code{G1445@dots{}}
38859 <- @code{T001:1234123412341234}
38863 <- @code{1455@dots{}}
38867 @node File-I/O Remote Protocol Extension
38868 @section File-I/O Remote Protocol Extension
38869 @cindex File-I/O remote protocol extension
38872 * File-I/O Overview::
38873 * Protocol Basics::
38874 * The F Request Packet::
38875 * The F Reply Packet::
38876 * The Ctrl-C Message::
38878 * List of Supported Calls::
38879 * Protocol-specific Representation of Datatypes::
38881 * File-I/O Examples::
38884 @node File-I/O Overview
38885 @subsection File-I/O Overview
38886 @cindex file-i/o overview
38888 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38889 target to use the host's file system and console I/O to perform various
38890 system calls. System calls on the target system are translated into a
38891 remote protocol packet to the host system, which then performs the needed
38892 actions and returns a response packet to the target system.
38893 This simulates file system operations even on targets that lack file systems.
38895 The protocol is defined to be independent of both the host and target systems.
38896 It uses its own internal representation of datatypes and values. Both
38897 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38898 translating the system-dependent value representations into the internal
38899 protocol representations when data is transmitted.
38901 The communication is synchronous. A system call is possible only when
38902 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38903 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38904 the target is stopped to allow deterministic access to the target's
38905 memory. Therefore File-I/O is not interruptible by target signals. On
38906 the other hand, it is possible to interrupt File-I/O by a user interrupt
38907 (@samp{Ctrl-C}) within @value{GDBN}.
38909 The target's request to perform a host system call does not finish
38910 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38911 after finishing the system call, the target returns to continuing the
38912 previous activity (continue, step). No additional continue or step
38913 request from @value{GDBN} is required.
38916 (@value{GDBP}) continue
38917 <- target requests 'system call X'
38918 target is stopped, @value{GDBN} executes system call
38919 -> @value{GDBN} returns result
38920 ... target continues, @value{GDBN} returns to wait for the target
38921 <- target hits breakpoint and sends a Txx packet
38924 The protocol only supports I/O on the console and to regular files on
38925 the host file system. Character or block special devices, pipes,
38926 named pipes, sockets or any other communication method on the host
38927 system are not supported by this protocol.
38929 File I/O is not supported in non-stop mode.
38931 @node Protocol Basics
38932 @subsection Protocol Basics
38933 @cindex protocol basics, file-i/o
38935 The File-I/O protocol uses the @code{F} packet as the request as well
38936 as reply packet. Since a File-I/O system call can only occur when
38937 @value{GDBN} is waiting for a response from the continuing or stepping target,
38938 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38939 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38940 This @code{F} packet contains all information needed to allow @value{GDBN}
38941 to call the appropriate host system call:
38945 A unique identifier for the requested system call.
38948 All parameters to the system call. Pointers are given as addresses
38949 in the target memory address space. Pointers to strings are given as
38950 pointer/length pair. Numerical values are given as they are.
38951 Numerical control flags are given in a protocol-specific representation.
38955 At this point, @value{GDBN} has to perform the following actions.
38959 If the parameters include pointer values to data needed as input to a
38960 system call, @value{GDBN} requests this data from the target with a
38961 standard @code{m} packet request. This additional communication has to be
38962 expected by the target implementation and is handled as any other @code{m}
38966 @value{GDBN} translates all value from protocol representation to host
38967 representation as needed. Datatypes are coerced into the host types.
38970 @value{GDBN} calls the system call.
38973 It then coerces datatypes back to protocol representation.
38976 If the system call is expected to return data in buffer space specified
38977 by pointer parameters to the call, the data is transmitted to the
38978 target using a @code{M} or @code{X} packet. This packet has to be expected
38979 by the target implementation and is handled as any other @code{M} or @code{X}
38984 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38985 necessary information for the target to continue. This at least contains
38992 @code{errno}, if has been changed by the system call.
38999 After having done the needed type and value coercion, the target continues
39000 the latest continue or step action.
39002 @node The F Request Packet
39003 @subsection The @code{F} Request Packet
39004 @cindex file-i/o request packet
39005 @cindex @code{F} request packet
39007 The @code{F} request packet has the following format:
39010 @item F@var{call-id},@var{parameter@dots{}}
39012 @var{call-id} is the identifier to indicate the host system call to be called.
39013 This is just the name of the function.
39015 @var{parameter@dots{}} are the parameters to the system call.
39016 Parameters are hexadecimal integer values, either the actual values in case
39017 of scalar datatypes, pointers to target buffer space in case of compound
39018 datatypes and unspecified memory areas, or pointer/length pairs in case
39019 of string parameters. These are appended to the @var{call-id} as a
39020 comma-delimited list. All values are transmitted in ASCII
39021 string representation, pointer/length pairs separated by a slash.
39027 @node The F Reply Packet
39028 @subsection The @code{F} Reply Packet
39029 @cindex file-i/o reply packet
39030 @cindex @code{F} reply packet
39032 The @code{F} reply packet has the following format:
39036 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39038 @var{retcode} is the return code of the system call as hexadecimal value.
39040 @var{errno} is the @code{errno} set by the call, in protocol-specific
39042 This parameter can be omitted if the call was successful.
39044 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39045 case, @var{errno} must be sent as well, even if the call was successful.
39046 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39053 or, if the call was interrupted before the host call has been performed:
39060 assuming 4 is the protocol-specific representation of @code{EINTR}.
39065 @node The Ctrl-C Message
39066 @subsection The @samp{Ctrl-C} Message
39067 @cindex ctrl-c message, in file-i/o protocol
39069 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39070 reply packet (@pxref{The F Reply Packet}),
39071 the target should behave as if it had
39072 gotten a break message. The meaning for the target is ``system call
39073 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39074 (as with a break message) and return to @value{GDBN} with a @code{T02}
39077 It's important for the target to know in which
39078 state the system call was interrupted. There are two possible cases:
39082 The system call hasn't been performed on the host yet.
39085 The system call on the host has been finished.
39089 These two states can be distinguished by the target by the value of the
39090 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39091 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39092 on POSIX systems. In any other case, the target may presume that the
39093 system call has been finished --- successfully or not --- and should behave
39094 as if the break message arrived right after the system call.
39096 @value{GDBN} must behave reliably. If the system call has not been called
39097 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39098 @code{errno} in the packet. If the system call on the host has been finished
39099 before the user requests a break, the full action must be finished by
39100 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39101 The @code{F} packet may only be sent when either nothing has happened
39102 or the full action has been completed.
39105 @subsection Console I/O
39106 @cindex console i/o as part of file-i/o
39108 By default and if not explicitly closed by the target system, the file
39109 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39110 on the @value{GDBN} console is handled as any other file output operation
39111 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39112 by @value{GDBN} so that after the target read request from file descriptor
39113 0 all following typing is buffered until either one of the following
39118 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39120 system call is treated as finished.
39123 The user presses @key{RET}. This is treated as end of input with a trailing
39127 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39128 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39132 If the user has typed more characters than fit in the buffer given to
39133 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39134 either another @code{read(0, @dots{})} is requested by the target, or debugging
39135 is stopped at the user's request.
39138 @node List of Supported Calls
39139 @subsection List of Supported Calls
39140 @cindex list of supported file-i/o calls
39157 @unnumberedsubsubsec open
39158 @cindex open, file-i/o system call
39163 int open(const char *pathname, int flags);
39164 int open(const char *pathname, int flags, mode_t mode);
39168 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39171 @var{flags} is the bitwise @code{OR} of the following values:
39175 If the file does not exist it will be created. The host
39176 rules apply as far as file ownership and time stamps
39180 When used with @code{O_CREAT}, if the file already exists it is
39181 an error and open() fails.
39184 If the file already exists and the open mode allows
39185 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39186 truncated to zero length.
39189 The file is opened in append mode.
39192 The file is opened for reading only.
39195 The file is opened for writing only.
39198 The file is opened for reading and writing.
39202 Other bits are silently ignored.
39206 @var{mode} is the bitwise @code{OR} of the following values:
39210 User has read permission.
39213 User has write permission.
39216 Group has read permission.
39219 Group has write permission.
39222 Others have read permission.
39225 Others have write permission.
39229 Other bits are silently ignored.
39232 @item Return value:
39233 @code{open} returns the new file descriptor or -1 if an error
39240 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39243 @var{pathname} refers to a directory.
39246 The requested access is not allowed.
39249 @var{pathname} was too long.
39252 A directory component in @var{pathname} does not exist.
39255 @var{pathname} refers to a device, pipe, named pipe or socket.
39258 @var{pathname} refers to a file on a read-only filesystem and
39259 write access was requested.
39262 @var{pathname} is an invalid pointer value.
39265 No space on device to create the file.
39268 The process already has the maximum number of files open.
39271 The limit on the total number of files open on the system
39275 The call was interrupted by the user.
39281 @unnumberedsubsubsec close
39282 @cindex close, file-i/o system call
39291 @samp{Fclose,@var{fd}}
39293 @item Return value:
39294 @code{close} returns zero on success, or -1 if an error occurred.
39300 @var{fd} isn't a valid open file descriptor.
39303 The call was interrupted by the user.
39309 @unnumberedsubsubsec read
39310 @cindex read, file-i/o system call
39315 int read(int fd, void *buf, unsigned int count);
39319 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39321 @item Return value:
39322 On success, the number of bytes read is returned.
39323 Zero indicates end of file. If count is zero, read
39324 returns zero as well. On error, -1 is returned.
39330 @var{fd} is not a valid file descriptor or is not open for
39334 @var{bufptr} is an invalid pointer value.
39337 The call was interrupted by the user.
39343 @unnumberedsubsubsec write
39344 @cindex write, file-i/o system call
39349 int write(int fd, const void *buf, unsigned int count);
39353 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39355 @item Return value:
39356 On success, the number of bytes written are returned.
39357 Zero indicates nothing was written. On error, -1
39364 @var{fd} is not a valid file descriptor or is not open for
39368 @var{bufptr} is an invalid pointer value.
39371 An attempt was made to write a file that exceeds the
39372 host-specific maximum file size allowed.
39375 No space on device to write the data.
39378 The call was interrupted by the user.
39384 @unnumberedsubsubsec lseek
39385 @cindex lseek, file-i/o system call
39390 long lseek (int fd, long offset, int flag);
39394 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39396 @var{flag} is one of:
39400 The offset is set to @var{offset} bytes.
39403 The offset is set to its current location plus @var{offset}
39407 The offset is set to the size of the file plus @var{offset}
39411 @item Return value:
39412 On success, the resulting unsigned offset in bytes from
39413 the beginning of the file is returned. Otherwise, a
39414 value of -1 is returned.
39420 @var{fd} is not a valid open file descriptor.
39423 @var{fd} is associated with the @value{GDBN} console.
39426 @var{flag} is not a proper value.
39429 The call was interrupted by the user.
39435 @unnumberedsubsubsec rename
39436 @cindex rename, file-i/o system call
39441 int rename(const char *oldpath, const char *newpath);
39445 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39447 @item Return value:
39448 On success, zero is returned. On error, -1 is returned.
39454 @var{newpath} is an existing directory, but @var{oldpath} is not a
39458 @var{newpath} is a non-empty directory.
39461 @var{oldpath} or @var{newpath} is a directory that is in use by some
39465 An attempt was made to make a directory a subdirectory
39469 A component used as a directory in @var{oldpath} or new
39470 path is not a directory. Or @var{oldpath} is a directory
39471 and @var{newpath} exists but is not a directory.
39474 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39477 No access to the file or the path of the file.
39481 @var{oldpath} or @var{newpath} was too long.
39484 A directory component in @var{oldpath} or @var{newpath} does not exist.
39487 The file is on a read-only filesystem.
39490 The device containing the file has no room for the new
39494 The call was interrupted by the user.
39500 @unnumberedsubsubsec unlink
39501 @cindex unlink, file-i/o system call
39506 int unlink(const char *pathname);
39510 @samp{Funlink,@var{pathnameptr}/@var{len}}
39512 @item Return value:
39513 On success, zero is returned. On error, -1 is returned.
39519 No access to the file or the path of the file.
39522 The system does not allow unlinking of directories.
39525 The file @var{pathname} cannot be unlinked because it's
39526 being used by another process.
39529 @var{pathnameptr} is an invalid pointer value.
39532 @var{pathname} was too long.
39535 A directory component in @var{pathname} does not exist.
39538 A component of the path is not a directory.
39541 The file is on a read-only filesystem.
39544 The call was interrupted by the user.
39550 @unnumberedsubsubsec stat/fstat
39551 @cindex fstat, file-i/o system call
39552 @cindex stat, file-i/o system call
39557 int stat(const char *pathname, struct stat *buf);
39558 int fstat(int fd, struct stat *buf);
39562 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39563 @samp{Ffstat,@var{fd},@var{bufptr}}
39565 @item Return value:
39566 On success, zero is returned. On error, -1 is returned.
39572 @var{fd} is not a valid open file.
39575 A directory component in @var{pathname} does not exist or the
39576 path is an empty string.
39579 A component of the path is not a directory.
39582 @var{pathnameptr} is an invalid pointer value.
39585 No access to the file or the path of the file.
39588 @var{pathname} was too long.
39591 The call was interrupted by the user.
39597 @unnumberedsubsubsec gettimeofday
39598 @cindex gettimeofday, file-i/o system call
39603 int gettimeofday(struct timeval *tv, void *tz);
39607 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39609 @item Return value:
39610 On success, 0 is returned, -1 otherwise.
39616 @var{tz} is a non-NULL pointer.
39619 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39625 @unnumberedsubsubsec isatty
39626 @cindex isatty, file-i/o system call
39631 int isatty(int fd);
39635 @samp{Fisatty,@var{fd}}
39637 @item Return value:
39638 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39644 The call was interrupted by the user.
39649 Note that the @code{isatty} call is treated as a special case: it returns
39650 1 to the target if the file descriptor is attached
39651 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39652 would require implementing @code{ioctl} and would be more complex than
39657 @unnumberedsubsubsec system
39658 @cindex system, file-i/o system call
39663 int system(const char *command);
39667 @samp{Fsystem,@var{commandptr}/@var{len}}
39669 @item Return value:
39670 If @var{len} is zero, the return value indicates whether a shell is
39671 available. A zero return value indicates a shell is not available.
39672 For non-zero @var{len}, the value returned is -1 on error and the
39673 return status of the command otherwise. Only the exit status of the
39674 command is returned, which is extracted from the host's @code{system}
39675 return value by calling @code{WEXITSTATUS(retval)}. In case
39676 @file{/bin/sh} could not be executed, 127 is returned.
39682 The call was interrupted by the user.
39687 @value{GDBN} takes over the full task of calling the necessary host calls
39688 to perform the @code{system} call. The return value of @code{system} on
39689 the host is simplified before it's returned
39690 to the target. Any termination signal information from the child process
39691 is discarded, and the return value consists
39692 entirely of the exit status of the called command.
39694 Due to security concerns, the @code{system} call is by default refused
39695 by @value{GDBN}. The user has to allow this call explicitly with the
39696 @code{set remote system-call-allowed 1} command.
39699 @item set remote system-call-allowed
39700 @kindex set remote system-call-allowed
39701 Control whether to allow the @code{system} calls in the File I/O
39702 protocol for the remote target. The default is zero (disabled).
39704 @item show remote system-call-allowed
39705 @kindex show remote system-call-allowed
39706 Show whether the @code{system} calls are allowed in the File I/O
39710 @node Protocol-specific Representation of Datatypes
39711 @subsection Protocol-specific Representation of Datatypes
39712 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39715 * Integral Datatypes::
39717 * Memory Transfer::
39722 @node Integral Datatypes
39723 @unnumberedsubsubsec Integral Datatypes
39724 @cindex integral datatypes, in file-i/o protocol
39726 The integral datatypes used in the system calls are @code{int},
39727 @code{unsigned int}, @code{long}, @code{unsigned long},
39728 @code{mode_t}, and @code{time_t}.
39730 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39731 implemented as 32 bit values in this protocol.
39733 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39735 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39736 in @file{limits.h}) to allow range checking on host and target.
39738 @code{time_t} datatypes are defined as seconds since the Epoch.
39740 All integral datatypes transferred as part of a memory read or write of a
39741 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39744 @node Pointer Values
39745 @unnumberedsubsubsec Pointer Values
39746 @cindex pointer values, in file-i/o protocol
39748 Pointers to target data are transmitted as they are. An exception
39749 is made for pointers to buffers for which the length isn't
39750 transmitted as part of the function call, namely strings. Strings
39751 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39758 which is a pointer to data of length 18 bytes at position 0x1aaf.
39759 The length is defined as the full string length in bytes, including
39760 the trailing null byte. For example, the string @code{"hello world"}
39761 at address 0x123456 is transmitted as
39767 @node Memory Transfer
39768 @unnumberedsubsubsec Memory Transfer
39769 @cindex memory transfer, in file-i/o protocol
39771 Structured data which is transferred using a memory read or write (for
39772 example, a @code{struct stat}) is expected to be in a protocol-specific format
39773 with all scalar multibyte datatypes being big endian. Translation to
39774 this representation needs to be done both by the target before the @code{F}
39775 packet is sent, and by @value{GDBN} before
39776 it transfers memory to the target. Transferred pointers to structured
39777 data should point to the already-coerced data at any time.
39781 @unnumberedsubsubsec struct stat
39782 @cindex struct stat, in file-i/o protocol
39784 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39785 is defined as follows:
39789 unsigned int st_dev; /* device */
39790 unsigned int st_ino; /* inode */
39791 mode_t st_mode; /* protection */
39792 unsigned int st_nlink; /* number of hard links */
39793 unsigned int st_uid; /* user ID of owner */
39794 unsigned int st_gid; /* group ID of owner */
39795 unsigned int st_rdev; /* device type (if inode device) */
39796 unsigned long st_size; /* total size, in bytes */
39797 unsigned long st_blksize; /* blocksize for filesystem I/O */
39798 unsigned long st_blocks; /* number of blocks allocated */
39799 time_t st_atime; /* time of last access */
39800 time_t st_mtime; /* time of last modification */
39801 time_t st_ctime; /* time of last change */
39805 The integral datatypes conform to the definitions given in the
39806 appropriate section (see @ref{Integral Datatypes}, for details) so this
39807 structure is of size 64 bytes.
39809 The values of several fields have a restricted meaning and/or
39815 A value of 0 represents a file, 1 the console.
39818 No valid meaning for the target. Transmitted unchanged.
39821 Valid mode bits are described in @ref{Constants}. Any other
39822 bits have currently no meaning for the target.
39827 No valid meaning for the target. Transmitted unchanged.
39832 These values have a host and file system dependent
39833 accuracy. Especially on Windows hosts, the file system may not
39834 support exact timing values.
39837 The target gets a @code{struct stat} of the above representation and is
39838 responsible for coercing it to the target representation before
39841 Note that due to size differences between the host, target, and protocol
39842 representations of @code{struct stat} members, these members could eventually
39843 get truncated on the target.
39845 @node struct timeval
39846 @unnumberedsubsubsec struct timeval
39847 @cindex struct timeval, in file-i/o protocol
39849 The buffer of type @code{struct timeval} used by the File-I/O protocol
39850 is defined as follows:
39854 time_t tv_sec; /* second */
39855 long tv_usec; /* microsecond */
39859 The integral datatypes conform to the definitions given in the
39860 appropriate section (see @ref{Integral Datatypes}, for details) so this
39861 structure is of size 8 bytes.
39864 @subsection Constants
39865 @cindex constants, in file-i/o protocol
39867 The following values are used for the constants inside of the
39868 protocol. @value{GDBN} and target are responsible for translating these
39869 values before and after the call as needed.
39880 @unnumberedsubsubsec Open Flags
39881 @cindex open flags, in file-i/o protocol
39883 All values are given in hexadecimal representation.
39895 @node mode_t Values
39896 @unnumberedsubsubsec mode_t Values
39897 @cindex mode_t values, in file-i/o protocol
39899 All values are given in octal representation.
39916 @unnumberedsubsubsec Errno Values
39917 @cindex errno values, in file-i/o protocol
39919 All values are given in decimal representation.
39944 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39945 any error value not in the list of supported error numbers.
39948 @unnumberedsubsubsec Lseek Flags
39949 @cindex lseek flags, in file-i/o protocol
39958 @unnumberedsubsubsec Limits
39959 @cindex limits, in file-i/o protocol
39961 All values are given in decimal representation.
39964 INT_MIN -2147483648
39966 UINT_MAX 4294967295
39967 LONG_MIN -9223372036854775808
39968 LONG_MAX 9223372036854775807
39969 ULONG_MAX 18446744073709551615
39972 @node File-I/O Examples
39973 @subsection File-I/O Examples
39974 @cindex file-i/o examples
39976 Example sequence of a write call, file descriptor 3, buffer is at target
39977 address 0x1234, 6 bytes should be written:
39980 <- @code{Fwrite,3,1234,6}
39981 @emph{request memory read from target}
39984 @emph{return "6 bytes written"}
39988 Example sequence of a read call, file descriptor 3, buffer is at target
39989 address 0x1234, 6 bytes should be read:
39992 <- @code{Fread,3,1234,6}
39993 @emph{request memory write to target}
39994 -> @code{X1234,6:XXXXXX}
39995 @emph{return "6 bytes read"}
39999 Example sequence of a read call, call fails on the host due to invalid
40000 file descriptor (@code{EBADF}):
40003 <- @code{Fread,3,1234,6}
40007 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40011 <- @code{Fread,3,1234,6}
40016 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40020 <- @code{Fread,3,1234,6}
40021 -> @code{X1234,6:XXXXXX}
40025 @node Library List Format
40026 @section Library List Format
40027 @cindex library list format, remote protocol
40029 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40030 same process as your application to manage libraries. In this case,
40031 @value{GDBN} can use the loader's symbol table and normal memory
40032 operations to maintain a list of shared libraries. On other
40033 platforms, the operating system manages loaded libraries.
40034 @value{GDBN} can not retrieve the list of currently loaded libraries
40035 through memory operations, so it uses the @samp{qXfer:libraries:read}
40036 packet (@pxref{qXfer library list read}) instead. The remote stub
40037 queries the target's operating system and reports which libraries
40040 The @samp{qXfer:libraries:read} packet returns an XML document which
40041 lists loaded libraries and their offsets. Each library has an
40042 associated name and one or more segment or section base addresses,
40043 which report where the library was loaded in memory.
40045 For the common case of libraries that are fully linked binaries, the
40046 library should have a list of segments. If the target supports
40047 dynamic linking of a relocatable object file, its library XML element
40048 should instead include a list of allocated sections. The segment or
40049 section bases are start addresses, not relocation offsets; they do not
40050 depend on the library's link-time base addresses.
40052 @value{GDBN} must be linked with the Expat library to support XML
40053 library lists. @xref{Expat}.
40055 A simple memory map, with one loaded library relocated by a single
40056 offset, looks like this:
40060 <library name="/lib/libc.so.6">
40061 <segment address="0x10000000"/>
40066 Another simple memory map, with one loaded library with three
40067 allocated sections (.text, .data, .bss), looks like this:
40071 <library name="sharedlib.o">
40072 <section address="0x10000000"/>
40073 <section address="0x20000000"/>
40074 <section address="0x30000000"/>
40079 The format of a library list is described by this DTD:
40082 <!-- library-list: Root element with versioning -->
40083 <!ELEMENT library-list (library)*>
40084 <!ATTLIST library-list version CDATA #FIXED "1.0">
40085 <!ELEMENT library (segment*, section*)>
40086 <!ATTLIST library name CDATA #REQUIRED>
40087 <!ELEMENT segment EMPTY>
40088 <!ATTLIST segment address CDATA #REQUIRED>
40089 <!ELEMENT section EMPTY>
40090 <!ATTLIST section address CDATA #REQUIRED>
40093 In addition, segments and section descriptors cannot be mixed within a
40094 single library element, and you must supply at least one segment or
40095 section for each library.
40097 @node Library List Format for SVR4 Targets
40098 @section Library List Format for SVR4 Targets
40099 @cindex library list format, remote protocol
40101 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40102 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40103 shared libraries. Still a special library list provided by this packet is
40104 more efficient for the @value{GDBN} remote protocol.
40106 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40107 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40108 target, the following parameters are reported:
40112 @code{name}, the absolute file name from the @code{l_name} field of
40113 @code{struct link_map}.
40115 @code{lm} with address of @code{struct link_map} used for TLS
40116 (Thread Local Storage) access.
40118 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40119 @code{struct link_map}. For prelinked libraries this is not an absolute
40120 memory address. It is a displacement of absolute memory address against
40121 address the file was prelinked to during the library load.
40123 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40126 Additionally the single @code{main-lm} attribute specifies address of
40127 @code{struct link_map} used for the main executable. This parameter is used
40128 for TLS access and its presence is optional.
40130 @value{GDBN} must be linked with the Expat library to support XML
40131 SVR4 library lists. @xref{Expat}.
40133 A simple memory map, with two loaded libraries (which do not use prelink),
40137 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40138 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40140 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40142 </library-list-svr>
40145 The format of an SVR4 library list is described by this DTD:
40148 <!-- library-list-svr4: Root element with versioning -->
40149 <!ELEMENT library-list-svr4 (library)*>
40150 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40151 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40152 <!ELEMENT library EMPTY>
40153 <!ATTLIST library name CDATA #REQUIRED>
40154 <!ATTLIST library lm CDATA #REQUIRED>
40155 <!ATTLIST library l_addr CDATA #REQUIRED>
40156 <!ATTLIST library l_ld CDATA #REQUIRED>
40159 @node Memory Map Format
40160 @section Memory Map Format
40161 @cindex memory map format
40163 To be able to write into flash memory, @value{GDBN} needs to obtain a
40164 memory map from the target. This section describes the format of the
40167 The memory map is obtained using the @samp{qXfer:memory-map:read}
40168 (@pxref{qXfer memory map read}) packet and is an XML document that
40169 lists memory regions.
40171 @value{GDBN} must be linked with the Expat library to support XML
40172 memory maps. @xref{Expat}.
40174 The top-level structure of the document is shown below:
40177 <?xml version="1.0"?>
40178 <!DOCTYPE memory-map
40179 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40180 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40186 Each region can be either:
40191 A region of RAM starting at @var{addr} and extending for @var{length}
40195 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40200 A region of read-only memory:
40203 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40208 A region of flash memory, with erasure blocks @var{blocksize}
40212 <memory type="flash" start="@var{addr}" length="@var{length}">
40213 <property name="blocksize">@var{blocksize}</property>
40219 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40220 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40221 packets to write to addresses in such ranges.
40223 The formal DTD for memory map format is given below:
40226 <!-- ................................................... -->
40227 <!-- Memory Map XML DTD ................................ -->
40228 <!-- File: memory-map.dtd .............................. -->
40229 <!-- .................................... .............. -->
40230 <!-- memory-map.dtd -->
40231 <!-- memory-map: Root element with versioning -->
40232 <!ELEMENT memory-map (memory | property)>
40233 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40234 <!ELEMENT memory (property)>
40235 <!-- memory: Specifies a memory region,
40236 and its type, or device. -->
40237 <!ATTLIST memory type CDATA #REQUIRED
40238 start CDATA #REQUIRED
40239 length CDATA #REQUIRED
40240 device CDATA #IMPLIED>
40241 <!-- property: Generic attribute tag -->
40242 <!ELEMENT property (#PCDATA | property)*>
40243 <!ATTLIST property name CDATA #REQUIRED>
40246 @node Thread List Format
40247 @section Thread List Format
40248 @cindex thread list format
40250 To efficiently update the list of threads and their attributes,
40251 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40252 (@pxref{qXfer threads read}) and obtains the XML document with
40253 the following structure:
40256 <?xml version="1.0"?>
40258 <thread id="id" core="0" name="name">
40259 ... description ...
40264 Each @samp{thread} element must have the @samp{id} attribute that
40265 identifies the thread (@pxref{thread-id syntax}). The
40266 @samp{core} attribute, if present, specifies which processor core
40267 the thread was last executing on. The @samp{name} attribute, if
40268 present, specifies the human-readable name of the thread. The content
40269 of the of @samp{thread} element is interpreted as human-readable
40270 auxiliary information.
40272 @node Traceframe Info Format
40273 @section Traceframe Info Format
40274 @cindex traceframe info format
40276 To be able to know which objects in the inferior can be examined when
40277 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40278 memory ranges, registers and trace state variables that have been
40279 collected in a traceframe.
40281 This list is obtained using the @samp{qXfer:traceframe-info:read}
40282 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40284 @value{GDBN} must be linked with the Expat library to support XML
40285 traceframe info discovery. @xref{Expat}.
40287 The top-level structure of the document is shown below:
40290 <?xml version="1.0"?>
40291 <!DOCTYPE traceframe-info
40292 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40293 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40299 Each traceframe block can be either:
40304 A region of collected memory starting at @var{addr} and extending for
40305 @var{length} bytes from there:
40308 <memory start="@var{addr}" length="@var{length}"/>
40312 A block indicating trace state variable numbered @var{number} has been
40316 <tvar id="@var{number}"/>
40321 The formal DTD for the traceframe info format is given below:
40324 <!ELEMENT traceframe-info (memory | tvar)* >
40325 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40327 <!ELEMENT memory EMPTY>
40328 <!ATTLIST memory start CDATA #REQUIRED
40329 length CDATA #REQUIRED>
40331 <!ATTLIST tvar id CDATA #REQUIRED>
40334 @node Branch Trace Format
40335 @section Branch Trace Format
40336 @cindex branch trace format
40338 In order to display the branch trace of an inferior thread,
40339 @value{GDBN} needs to obtain the list of branches. This list is
40340 represented as list of sequential code blocks that are connected via
40341 branches. The code in each block has been executed sequentially.
40343 This list is obtained using the @samp{qXfer:btrace:read}
40344 (@pxref{qXfer btrace read}) packet and is an XML document.
40346 @value{GDBN} must be linked with the Expat library to support XML
40347 traceframe info discovery. @xref{Expat}.
40349 The top-level structure of the document is shown below:
40352 <?xml version="1.0"?>
40354 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40355 "http://sourceware.org/gdb/gdb-btrace.dtd">
40364 A block of sequentially executed instructions starting at @var{begin}
40365 and ending at @var{end}:
40368 <block begin="@var{begin}" end="@var{end}"/>
40373 The formal DTD for the branch trace format is given below:
40376 <!ELEMENT btrace (block* | pt) >
40377 <!ATTLIST btrace version CDATA #FIXED "1.0">
40379 <!ELEMENT block EMPTY>
40380 <!ATTLIST block begin CDATA #REQUIRED
40381 end CDATA #REQUIRED>
40383 <!ELEMENT pt (pt-config?, raw?)>
40385 <!ELEMENT pt-config (cpu?)>
40387 <!ELEMENT cpu EMPTY>
40388 <!ATTLIST cpu vendor CDATA #REQUIRED
40389 family CDATA #REQUIRED
40390 model CDATA #REQUIRED
40391 stepping CDATA #REQUIRED>
40393 <!ELEMENT raw (#PCDATA)>
40396 @node Branch Trace Configuration Format
40397 @section Branch Trace Configuration Format
40398 @cindex branch trace configuration format
40400 For each inferior thread, @value{GDBN} can obtain the branch trace
40401 configuration using the @samp{qXfer:btrace-conf:read}
40402 (@pxref{qXfer btrace-conf read}) packet.
40404 The configuration describes the branch trace format and configuration
40405 settings for that format. The following information is described:
40409 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40412 The size of the @acronym{BTS} ring buffer in bytes.
40415 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40419 The size of the @acronym{Intel PT} ring buffer in bytes.
40423 @value{GDBN} must be linked with the Expat library to support XML
40424 branch trace configuration discovery. @xref{Expat}.
40426 The formal DTD for the branch trace configuration format is given below:
40429 <!ELEMENT btrace-conf (bts?, pt?)>
40430 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40432 <!ELEMENT bts EMPTY>
40433 <!ATTLIST bts size CDATA #IMPLIED>
40435 <!ELEMENT pt EMPTY>
40436 <!ATTLIST pt size CDATA #IMPLIED>
40439 @include agentexpr.texi
40441 @node Target Descriptions
40442 @appendix Target Descriptions
40443 @cindex target descriptions
40445 One of the challenges of using @value{GDBN} to debug embedded systems
40446 is that there are so many minor variants of each processor
40447 architecture in use. It is common practice for vendors to start with
40448 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40449 and then make changes to adapt it to a particular market niche. Some
40450 architectures have hundreds of variants, available from dozens of
40451 vendors. This leads to a number of problems:
40455 With so many different customized processors, it is difficult for
40456 the @value{GDBN} maintainers to keep up with the changes.
40458 Since individual variants may have short lifetimes or limited
40459 audiences, it may not be worthwhile to carry information about every
40460 variant in the @value{GDBN} source tree.
40462 When @value{GDBN} does support the architecture of the embedded system
40463 at hand, the task of finding the correct architecture name to give the
40464 @command{set architecture} command can be error-prone.
40467 To address these problems, the @value{GDBN} remote protocol allows a
40468 target system to not only identify itself to @value{GDBN}, but to
40469 actually describe its own features. This lets @value{GDBN} support
40470 processor variants it has never seen before --- to the extent that the
40471 descriptions are accurate, and that @value{GDBN} understands them.
40473 @value{GDBN} must be linked with the Expat library to support XML
40474 target descriptions. @xref{Expat}.
40477 * Retrieving Descriptions:: How descriptions are fetched from a target.
40478 * Target Description Format:: The contents of a target description.
40479 * Predefined Target Types:: Standard types available for target
40481 * Enum Target Types:: How to define enum target types.
40482 * Standard Target Features:: Features @value{GDBN} knows about.
40485 @node Retrieving Descriptions
40486 @section Retrieving Descriptions
40488 Target descriptions can be read from the target automatically, or
40489 specified by the user manually. The default behavior is to read the
40490 description from the target. @value{GDBN} retrieves it via the remote
40491 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40492 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40493 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40494 XML document, of the form described in @ref{Target Description
40497 Alternatively, you can specify a file to read for the target description.
40498 If a file is set, the target will not be queried. The commands to
40499 specify a file are:
40502 @cindex set tdesc filename
40503 @item set tdesc filename @var{path}
40504 Read the target description from @var{path}.
40506 @cindex unset tdesc filename
40507 @item unset tdesc filename
40508 Do not read the XML target description from a file. @value{GDBN}
40509 will use the description supplied by the current target.
40511 @cindex show tdesc filename
40512 @item show tdesc filename
40513 Show the filename to read for a target description, if any.
40517 @node Target Description Format
40518 @section Target Description Format
40519 @cindex target descriptions, XML format
40521 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40522 document which complies with the Document Type Definition provided in
40523 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40524 means you can use generally available tools like @command{xmllint} to
40525 check that your feature descriptions are well-formed and valid.
40526 However, to help people unfamiliar with XML write descriptions for
40527 their targets, we also describe the grammar here.
40529 Target descriptions can identify the architecture of the remote target
40530 and (for some architectures) provide information about custom register
40531 sets. They can also identify the OS ABI of the remote target.
40532 @value{GDBN} can use this information to autoconfigure for your
40533 target, or to warn you if you connect to an unsupported target.
40535 Here is a simple target description:
40538 <target version="1.0">
40539 <architecture>i386:x86-64</architecture>
40544 This minimal description only says that the target uses
40545 the x86-64 architecture.
40547 A target description has the following overall form, with [ ] marking
40548 optional elements and @dots{} marking repeatable elements. The elements
40549 are explained further below.
40552 <?xml version="1.0"?>
40553 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40554 <target version="1.0">
40555 @r{[}@var{architecture}@r{]}
40556 @r{[}@var{osabi}@r{]}
40557 @r{[}@var{compatible}@r{]}
40558 @r{[}@var{feature}@dots{}@r{]}
40563 The description is generally insensitive to whitespace and line
40564 breaks, under the usual common-sense rules. The XML version
40565 declaration and document type declaration can generally be omitted
40566 (@value{GDBN} does not require them), but specifying them may be
40567 useful for XML validation tools. The @samp{version} attribute for
40568 @samp{<target>} may also be omitted, but we recommend
40569 including it; if future versions of @value{GDBN} use an incompatible
40570 revision of @file{gdb-target.dtd}, they will detect and report
40571 the version mismatch.
40573 @subsection Inclusion
40574 @cindex target descriptions, inclusion
40577 @cindex <xi:include>
40580 It can sometimes be valuable to split a target description up into
40581 several different annexes, either for organizational purposes, or to
40582 share files between different possible target descriptions. You can
40583 divide a description into multiple files by replacing any element of
40584 the target description with an inclusion directive of the form:
40587 <xi:include href="@var{document}"/>
40591 When @value{GDBN} encounters an element of this form, it will retrieve
40592 the named XML @var{document}, and replace the inclusion directive with
40593 the contents of that document. If the current description was read
40594 using @samp{qXfer}, then so will be the included document;
40595 @var{document} will be interpreted as the name of an annex. If the
40596 current description was read from a file, @value{GDBN} will look for
40597 @var{document} as a file in the same directory where it found the
40598 original description.
40600 @subsection Architecture
40601 @cindex <architecture>
40603 An @samp{<architecture>} element has this form:
40606 <architecture>@var{arch}</architecture>
40609 @var{arch} is one of the architectures from the set accepted by
40610 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40613 @cindex @code{<osabi>}
40615 This optional field was introduced in @value{GDBN} version 7.0.
40616 Previous versions of @value{GDBN} ignore it.
40618 An @samp{<osabi>} element has this form:
40621 <osabi>@var{abi-name}</osabi>
40624 @var{abi-name} is an OS ABI name from the same selection accepted by
40625 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40627 @subsection Compatible Architecture
40628 @cindex @code{<compatible>}
40630 This optional field was introduced in @value{GDBN} version 7.0.
40631 Previous versions of @value{GDBN} ignore it.
40633 A @samp{<compatible>} element has this form:
40636 <compatible>@var{arch}</compatible>
40639 @var{arch} is one of the architectures from the set accepted by
40640 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40642 A @samp{<compatible>} element is used to specify that the target
40643 is able to run binaries in some other than the main target architecture
40644 given by the @samp{<architecture>} element. For example, on the
40645 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40646 or @code{powerpc:common64}, but the system is able to run binaries
40647 in the @code{spu} architecture as well. The way to describe this
40648 capability with @samp{<compatible>} is as follows:
40651 <architecture>powerpc:common</architecture>
40652 <compatible>spu</compatible>
40655 @subsection Features
40658 Each @samp{<feature>} describes some logical portion of the target
40659 system. Features are currently used to describe available CPU
40660 registers and the types of their contents. A @samp{<feature>} element
40664 <feature name="@var{name}">
40665 @r{[}@var{type}@dots{}@r{]}
40671 Each feature's name should be unique within the description. The name
40672 of a feature does not matter unless @value{GDBN} has some special
40673 knowledge of the contents of that feature; if it does, the feature
40674 should have its standard name. @xref{Standard Target Features}.
40678 Any register's value is a collection of bits which @value{GDBN} must
40679 interpret. The default interpretation is a two's complement integer,
40680 but other types can be requested by name in the register description.
40681 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40682 Target Types}), and the description can define additional composite
40685 Each type element must have an @samp{id} attribute, which gives
40686 a unique (within the containing @samp{<feature>}) name to the type.
40687 Types must be defined before they are used.
40690 Some targets offer vector registers, which can be treated as arrays
40691 of scalar elements. These types are written as @samp{<vector>} elements,
40692 specifying the array element type, @var{type}, and the number of elements,
40696 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40700 If a register's value is usefully viewed in multiple ways, define it
40701 with a union type containing the useful representations. The
40702 @samp{<union>} element contains one or more @samp{<field>} elements,
40703 each of which has a @var{name} and a @var{type}:
40706 <union id="@var{id}">
40707 <field name="@var{name}" type="@var{type}"/>
40714 If a register's value is composed from several separate values, define
40715 it with either a structure type or a flags type.
40716 A flags type may only contain bitfields.
40717 A structure type may either contain only bitfields or contain no bitfields.
40718 If the value contains only bitfields, its total size in bytes must be
40721 Non-bitfield values have a @var{name} and @var{type}.
40724 <struct id="@var{id}">
40725 <field name="@var{name}" type="@var{type}"/>
40730 Both @var{name} and @var{type} values are required.
40731 No implicit padding is added.
40733 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40736 <struct id="@var{id}" size="@var{size}">
40737 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40743 <flags id="@var{id}" size="@var{size}">
40744 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40749 The @var{name} value is required.
40750 Bitfield values may be named with the empty string, @samp{""},
40751 in which case the field is ``filler'' and its value is not printed.
40752 Not all bits need to be specified, so ``filler'' fields are optional.
40754 The @var{start} and @var{end} values are required, and @var{type}
40756 The field's @var{start} must be less than or equal to its @var{end},
40757 and zero represents the least significant bit.
40759 The default value of @var{type} is @code{bool} for single bit fields,
40760 and an unsigned integer otherwise.
40762 Which to choose? Structures or flags?
40764 Registers defined with @samp{flags} have these advantages over
40765 defining them with @samp{struct}:
40769 Arithmetic may be performed on them as if they were integers.
40771 They are printed in a more readable fashion.
40774 Registers defined with @samp{struct} have one advantage over
40775 defining them with @samp{flags}:
40779 One can fetch individual fields like in @samp{C}.
40782 (gdb) print $my_struct_reg.field3
40788 @subsection Registers
40791 Each register is represented as an element with this form:
40794 <reg name="@var{name}"
40795 bitsize="@var{size}"
40796 @r{[}regnum="@var{num}"@r{]}
40797 @r{[}save-restore="@var{save-restore}"@r{]}
40798 @r{[}type="@var{type}"@r{]}
40799 @r{[}group="@var{group}"@r{]}/>
40803 The components are as follows:
40808 The register's name; it must be unique within the target description.
40811 The register's size, in bits.
40814 The register's number. If omitted, a register's number is one greater
40815 than that of the previous register (either in the current feature or in
40816 a preceding feature); the first register in the target description
40817 defaults to zero. This register number is used to read or write
40818 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40819 packets, and registers appear in the @code{g} and @code{G} packets
40820 in order of increasing register number.
40823 Whether the register should be preserved across inferior function
40824 calls; this must be either @code{yes} or @code{no}. The default is
40825 @code{yes}, which is appropriate for most registers except for
40826 some system control registers; this is not related to the target's
40830 The type of the register. It may be a predefined type, a type
40831 defined in the current feature, or one of the special types @code{int}
40832 and @code{float}. @code{int} is an integer type of the correct size
40833 for @var{bitsize}, and @code{float} is a floating point type (in the
40834 architecture's normal floating point format) of the correct size for
40835 @var{bitsize}. The default is @code{int}.
40838 The register group to which this register belongs. It must
40839 be either @code{general}, @code{float}, or @code{vector}. If no
40840 @var{group} is specified, @value{GDBN} will not display the register
40841 in @code{info registers}.
40845 @node Predefined Target Types
40846 @section Predefined Target Types
40847 @cindex target descriptions, predefined types
40849 Type definitions in the self-description can build up composite types
40850 from basic building blocks, but can not define fundamental types. Instead,
40851 standard identifiers are provided by @value{GDBN} for the fundamental
40852 types. The currently supported types are:
40857 Boolean type, occupying a single bit.
40864 Signed integer types holding the specified number of bits.
40871 Unsigned integer types holding the specified number of bits.
40875 Pointers to unspecified code and data. The program counter and
40876 any dedicated return address register may be marked as code
40877 pointers; printing a code pointer converts it into a symbolic
40878 address. The stack pointer and any dedicated address registers
40879 may be marked as data pointers.
40882 Single precision IEEE floating point.
40885 Double precision IEEE floating point.
40888 The 12-byte extended precision format used by ARM FPA registers.
40891 The 10-byte extended precision format used by x87 registers.
40894 32bit @sc{eflags} register used by x86.
40897 32bit @sc{mxcsr} register used by x86.
40901 @node Enum Target Types
40902 @section Enum Target Types
40903 @cindex target descriptions, enum types
40905 Enum target types are useful in @samp{struct} and @samp{flags}
40906 register descriptions. @xref{Target Description Format}.
40908 Enum types have a name, size and a list of name/value pairs.
40911 <enum id="@var{id}" size="@var{size}">
40912 <evalue name="@var{name}" value="@var{value}"/>
40917 Enums must be defined before they are used.
40920 <enum id="levels_type" size="4">
40921 <evalue name="low" value="0"/>
40922 <evalue name="high" value="1"/>
40924 <flags id="flags_type" size="4">
40925 <field name="X" start="0"/>
40926 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40928 <reg name="flags" bitsize="32" type="flags_type"/>
40931 Given that description, a value of 3 for the @samp{flags} register
40932 would be printed as:
40935 (gdb) info register flags
40936 flags 0x3 [ X LEVEL=high ]
40939 @node Standard Target Features
40940 @section Standard Target Features
40941 @cindex target descriptions, standard features
40943 A target description must contain either no registers or all the
40944 target's registers. If the description contains no registers, then
40945 @value{GDBN} will assume a default register layout, selected based on
40946 the architecture. If the description contains any registers, the
40947 default layout will not be used; the standard registers must be
40948 described in the target description, in such a way that @value{GDBN}
40949 can recognize them.
40951 This is accomplished by giving specific names to feature elements
40952 which contain standard registers. @value{GDBN} will look for features
40953 with those names and verify that they contain the expected registers;
40954 if any known feature is missing required registers, or if any required
40955 feature is missing, @value{GDBN} will reject the target
40956 description. You can add additional registers to any of the
40957 standard features --- @value{GDBN} will display them just as if
40958 they were added to an unrecognized feature.
40960 This section lists the known features and their expected contents.
40961 Sample XML documents for these features are included in the
40962 @value{GDBN} source tree, in the directory @file{gdb/features}.
40964 Names recognized by @value{GDBN} should include the name of the
40965 company or organization which selected the name, and the overall
40966 architecture to which the feature applies; so e.g.@: the feature
40967 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40969 The names of registers are not case sensitive for the purpose
40970 of recognizing standard features, but @value{GDBN} will only display
40971 registers using the capitalization used in the description.
40974 * AArch64 Features::
40978 * MicroBlaze Features::
40982 * Nios II Features::
40983 * PowerPC Features::
40984 * S/390 and System z Features::
40989 @node AArch64 Features
40990 @subsection AArch64 Features
40991 @cindex target descriptions, AArch64 features
40993 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40994 targets. It should contain registers @samp{x0} through @samp{x30},
40995 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40997 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40998 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41002 @subsection ARC Features
41003 @cindex target descriptions, ARC Features
41005 ARC processors are highly configurable, so even core registers and their number
41006 are not completely predetermined. In addition flags and PC registers which are
41007 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41008 that one of the core registers features is present.
41009 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41011 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41012 targets with a normal register file. It should contain registers @samp{r0}
41013 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41014 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41015 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41016 @samp{ilink} and extension core registers are not available to read/write, when
41017 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41019 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41020 ARC HS targets with a reduced register file. It should contain registers
41021 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41022 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41023 This feature may contain register @samp{ilink} and any of extension core
41024 registers @samp{r32} through @samp{r59/acch}.
41026 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41027 targets with a normal register file. It should contain registers @samp{r0}
41028 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41029 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41030 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41031 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41032 registers are not available when debugging GNU/Linux applications. The only
41033 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41034 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41035 ARC v2, but @samp{ilink2} is optional on ARCompact.
41037 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41038 targets. It should contain registers @samp{pc} and @samp{status32}.
41041 @subsection ARM Features
41042 @cindex target descriptions, ARM features
41044 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41046 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41047 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41049 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41050 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41051 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41054 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41055 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41057 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41058 it should contain at least registers @samp{wR0} through @samp{wR15} and
41059 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41060 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41062 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41063 should contain at least registers @samp{d0} through @samp{d15}. If
41064 they are present, @samp{d16} through @samp{d31} should also be included.
41065 @value{GDBN} will synthesize the single-precision registers from
41066 halves of the double-precision registers.
41068 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41069 need to contain registers; it instructs @value{GDBN} to display the
41070 VFP double-precision registers as vectors and to synthesize the
41071 quad-precision registers from pairs of double-precision registers.
41072 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41073 be present and include 32 double-precision registers.
41075 @node i386 Features
41076 @subsection i386 Features
41077 @cindex target descriptions, i386 features
41079 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41080 targets. It should describe the following registers:
41084 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41086 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41088 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41089 @samp{fs}, @samp{gs}
41091 @samp{st0} through @samp{st7}
41093 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41094 @samp{foseg}, @samp{fooff} and @samp{fop}
41097 The register sets may be different, depending on the target.
41099 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41100 describe registers:
41104 @samp{xmm0} through @samp{xmm7} for i386
41106 @samp{xmm0} through @samp{xmm15} for amd64
41111 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41112 @samp{org.gnu.gdb.i386.sse} feature. It should
41113 describe the upper 128 bits of @sc{ymm} registers:
41117 @samp{ymm0h} through @samp{ymm7h} for i386
41119 @samp{ymm0h} through @samp{ymm15h} for amd64
41122 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41123 Memory Protection Extension (MPX). It should describe the following registers:
41127 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41129 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41132 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41133 describe a single register, @samp{orig_eax}.
41135 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41136 @samp{org.gnu.gdb.i386.avx} feature. It should
41137 describe additional @sc{xmm} registers:
41141 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41144 It should describe the upper 128 bits of additional @sc{ymm} registers:
41148 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41152 describe the upper 256 bits of @sc{zmm} registers:
41156 @samp{zmm0h} through @samp{zmm7h} for i386.
41158 @samp{zmm0h} through @samp{zmm15h} for amd64.
41162 describe the additional @sc{zmm} registers:
41166 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41169 @node MicroBlaze Features
41170 @subsection MicroBlaze Features
41171 @cindex target descriptions, MicroBlaze features
41173 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41174 targets. It should contain registers @samp{r0} through @samp{r31},
41175 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41176 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41177 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41179 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41180 If present, it should contain registers @samp{rshr} and @samp{rslr}
41182 @node MIPS Features
41183 @subsection @acronym{MIPS} Features
41184 @cindex target descriptions, @acronym{MIPS} features
41186 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41187 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41188 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41191 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41192 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41193 registers. They may be 32-bit or 64-bit depending on the target.
41195 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41196 it may be optional in a future version of @value{GDBN}. It should
41197 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41198 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41200 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41201 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41202 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41203 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41205 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41206 contain a single register, @samp{restart}, which is used by the
41207 Linux kernel to control restartable syscalls.
41209 @node M68K Features
41210 @subsection M68K Features
41211 @cindex target descriptions, M68K features
41214 @item @samp{org.gnu.gdb.m68k.core}
41215 @itemx @samp{org.gnu.gdb.coldfire.core}
41216 @itemx @samp{org.gnu.gdb.fido.core}
41217 One of those features must be always present.
41218 The feature that is present determines which flavor of m68k is
41219 used. The feature that is present should contain registers
41220 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41221 @samp{sp}, @samp{ps} and @samp{pc}.
41223 @item @samp{org.gnu.gdb.coldfire.fp}
41224 This feature is optional. If present, it should contain registers
41225 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41229 @node NDS32 Features
41230 @subsection NDS32 Features
41231 @cindex target descriptions, NDS32 features
41233 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41234 targets. It should contain at least registers @samp{r0} through
41235 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41238 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41239 it should contain 64-bit double-precision floating-point registers
41240 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41241 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41243 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41244 registers are overlapped with the thirty-two 32-bit single-precision
41245 floating-point registers. The 32-bit single-precision registers, if
41246 not being listed explicitly, will be synthesized from halves of the
41247 overlapping 64-bit double-precision registers. Listing 32-bit
41248 single-precision registers explicitly is deprecated, and the
41249 support to it could be totally removed some day.
41251 @node Nios II Features
41252 @subsection Nios II Features
41253 @cindex target descriptions, Nios II features
41255 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41256 targets. It should contain the 32 core registers (@samp{zero},
41257 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41258 @samp{pc}, and the 16 control registers (@samp{status} through
41261 @node PowerPC Features
41262 @subsection PowerPC Features
41263 @cindex target descriptions, PowerPC features
41265 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41266 targets. It should contain registers @samp{r0} through @samp{r31},
41267 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41268 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41270 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41271 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41273 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41274 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41277 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41278 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41279 will combine these registers with the floating point registers
41280 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41281 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41282 through @samp{vs63}, the set of vector registers for POWER7.
41284 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41285 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41286 @samp{spefscr}. SPE targets should provide 32-bit registers in
41287 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41288 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41289 these to present registers @samp{ev0} through @samp{ev31} to the
41292 @node S/390 and System z Features
41293 @subsection S/390 and System z Features
41294 @cindex target descriptions, S/390 features
41295 @cindex target descriptions, System z features
41297 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41298 System z targets. It should contain the PSW and the 16 general
41299 registers. In particular, System z targets should provide the 64-bit
41300 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41301 S/390 targets should provide the 32-bit versions of these registers.
41302 A System z target that runs in 31-bit addressing mode should provide
41303 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41304 register's upper halves @samp{r0h} through @samp{r15h}, and their
41305 lower halves @samp{r0l} through @samp{r15l}.
41307 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41308 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41311 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41312 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41314 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41315 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41316 targets and 32-bit otherwise. In addition, the feature may contain
41317 the @samp{last_break} register, whose width depends on the addressing
41318 mode, as well as the @samp{system_call} register, which is always
41321 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41322 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41323 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41325 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41326 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41327 combined by @value{GDBN} with the floating point registers @samp{f0}
41328 through @samp{f15} to present the 128-bit wide vector registers
41329 @samp{v0} through @samp{v15}. In addition, this feature should
41330 contain the 128-bit wide vector registers @samp{v16} through
41333 @node TIC6x Features
41334 @subsection TMS320C6x Features
41335 @cindex target descriptions, TIC6x features
41336 @cindex target descriptions, TMS320C6x features
41337 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41338 targets. It should contain registers @samp{A0} through @samp{A15},
41339 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41341 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41342 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41343 through @samp{B31}.
41345 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41346 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41348 @node Operating System Information
41349 @appendix Operating System Information
41350 @cindex operating system information
41356 Users of @value{GDBN} often wish to obtain information about the state of
41357 the operating system running on the target---for example the list of
41358 processes, or the list of open files. This section describes the
41359 mechanism that makes it possible. This mechanism is similar to the
41360 target features mechanism (@pxref{Target Descriptions}), but focuses
41361 on a different aspect of target.
41363 Operating system information is retrived from the target via the
41364 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41365 read}). The object name in the request should be @samp{osdata}, and
41366 the @var{annex} identifies the data to be fetched.
41369 @appendixsection Process list
41370 @cindex operating system information, process list
41372 When requesting the process list, the @var{annex} field in the
41373 @samp{qXfer} request should be @samp{processes}. The returned data is
41374 an XML document. The formal syntax of this document is defined in
41375 @file{gdb/features/osdata.dtd}.
41377 An example document is:
41380 <?xml version="1.0"?>
41381 <!DOCTYPE target SYSTEM "osdata.dtd">
41382 <osdata type="processes">
41384 <column name="pid">1</column>
41385 <column name="user">root</column>
41386 <column name="command">/sbin/init</column>
41387 <column name="cores">1,2,3</column>
41392 Each item should include a column whose name is @samp{pid}. The value
41393 of that column should identify the process on the target. The
41394 @samp{user} and @samp{command} columns are optional, and will be
41395 displayed by @value{GDBN}. The @samp{cores} column, if present,
41396 should contain a comma-separated list of cores that this process
41397 is running on. Target may provide additional columns,
41398 which @value{GDBN} currently ignores.
41400 @node Trace File Format
41401 @appendix Trace File Format
41402 @cindex trace file format
41404 The trace file comes in three parts: a header, a textual description
41405 section, and a trace frame section with binary data.
41407 The header has the form @code{\x7fTRACE0\n}. The first byte is
41408 @code{0x7f} so as to indicate that the file contains binary data,
41409 while the @code{0} is a version number that may have different values
41412 The description section consists of multiple lines of @sc{ascii} text
41413 separated by newline characters (@code{0xa}). The lines may include a
41414 variety of optional descriptive or context-setting information, such
41415 as tracepoint definitions or register set size. @value{GDBN} will
41416 ignore any line that it does not recognize. An empty line marks the end
41421 Specifies the size of a register block in bytes. This is equal to the
41422 size of a @code{g} packet payload in the remote protocol. @var{size}
41423 is an ascii decimal number. There should be only one such line in
41424 a single trace file.
41426 @item status @var{status}
41427 Trace status. @var{status} has the same format as a @code{qTStatus}
41428 remote packet reply. There should be only one such line in a single trace
41431 @item tp @var{payload}
41432 Tracepoint definition. The @var{payload} has the same format as
41433 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41434 may take multiple lines of definition, corresponding to the multiple
41437 @item tsv @var{payload}
41438 Trace state variable definition. The @var{payload} has the same format as
41439 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41440 may take multiple lines of definition, corresponding to the multiple
41443 @item tdesc @var{payload}
41444 Target description in XML format. The @var{payload} is a single line of
41445 the XML file. All such lines should be concatenated together to get
41446 the original XML file. This file is in the same format as @code{qXfer}
41447 @code{features} payload, and corresponds to the main @code{target.xml}
41448 file. Includes are not allowed.
41452 The trace frame section consists of a number of consecutive frames.
41453 Each frame begins with a two-byte tracepoint number, followed by a
41454 four-byte size giving the amount of data in the frame. The data in
41455 the frame consists of a number of blocks, each introduced by a
41456 character indicating its type (at least register, memory, and trace
41457 state variable). The data in this section is raw binary, not a
41458 hexadecimal or other encoding; its endianness matches the target's
41461 @c FIXME bi-arch may require endianness/arch info in description section
41464 @item R @var{bytes}
41465 Register block. The number and ordering of bytes matches that of a
41466 @code{g} packet in the remote protocol. Note that these are the
41467 actual bytes, in target order, not a hexadecimal encoding.
41469 @item M @var{address} @var{length} @var{bytes}...
41470 Memory block. This is a contiguous block of memory, at the 8-byte
41471 address @var{address}, with a 2-byte length @var{length}, followed by
41472 @var{length} bytes.
41474 @item V @var{number} @var{value}
41475 Trace state variable block. This records the 8-byte signed value
41476 @var{value} of trace state variable numbered @var{number}.
41480 Future enhancements of the trace file format may include additional types
41483 @node Index Section Format
41484 @appendix @code{.gdb_index} section format
41485 @cindex .gdb_index section format
41486 @cindex index section format
41488 This section documents the index section that is created by @code{save
41489 gdb-index} (@pxref{Index Files}). The index section is
41490 DWARF-specific; some knowledge of DWARF is assumed in this
41493 The mapped index file format is designed to be directly
41494 @code{mmap}able on any architecture. In most cases, a datum is
41495 represented using a little-endian 32-bit integer value, called an
41496 @code{offset_type}. Big endian machines must byte-swap the values
41497 before using them. Exceptions to this rule are noted. The data is
41498 laid out such that alignment is always respected.
41500 A mapped index consists of several areas, laid out in order.
41504 The file header. This is a sequence of values, of @code{offset_type}
41505 unless otherwise noted:
41509 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41510 Version 4 uses a different hashing function from versions 5 and 6.
41511 Version 6 includes symbols for inlined functions, whereas versions 4
41512 and 5 do not. Version 7 adds attributes to the CU indices in the
41513 symbol table. Version 8 specifies that symbols from DWARF type units
41514 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41515 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41517 @value{GDBN} will only read version 4, 5, or 6 indices
41518 by specifying @code{set use-deprecated-index-sections on}.
41519 GDB has a workaround for potentially broken version 7 indices so it is
41520 currently not flagged as deprecated.
41523 The offset, from the start of the file, of the CU list.
41526 The offset, from the start of the file, of the types CU list. Note
41527 that this area can be empty, in which case this offset will be equal
41528 to the next offset.
41531 The offset, from the start of the file, of the address area.
41534 The offset, from the start of the file, of the symbol table.
41537 The offset, from the start of the file, of the constant pool.
41541 The CU list. This is a sequence of pairs of 64-bit little-endian
41542 values, sorted by the CU offset. The first element in each pair is
41543 the offset of a CU in the @code{.debug_info} section. The second
41544 element in each pair is the length of that CU. References to a CU
41545 elsewhere in the map are done using a CU index, which is just the
41546 0-based index into this table. Note that if there are type CUs, then
41547 conceptually CUs and type CUs form a single list for the purposes of
41551 The types CU list. This is a sequence of triplets of 64-bit
41552 little-endian values. In a triplet, the first value is the CU offset,
41553 the second value is the type offset in the CU, and the third value is
41554 the type signature. The types CU list is not sorted.
41557 The address area. The address area consists of a sequence of address
41558 entries. Each address entry has three elements:
41562 The low address. This is a 64-bit little-endian value.
41565 The high address. This is a 64-bit little-endian value. Like
41566 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41569 The CU index. This is an @code{offset_type} value.
41573 The symbol table. This is an open-addressed hash table. The size of
41574 the hash table is always a power of 2.
41576 Each slot in the hash table consists of a pair of @code{offset_type}
41577 values. The first value is the offset of the symbol's name in the
41578 constant pool. The second value is the offset of the CU vector in the
41581 If both values are 0, then this slot in the hash table is empty. This
41582 is ok because while 0 is a valid constant pool index, it cannot be a
41583 valid index for both a string and a CU vector.
41585 The hash value for a table entry is computed by applying an
41586 iterative hash function to the symbol's name. Starting with an
41587 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41588 the string is incorporated into the hash using the formula depending on the
41593 The formula is @code{r = r * 67 + c - 113}.
41595 @item Versions 5 to 7
41596 The formula is @code{r = r * 67 + tolower (c) - 113}.
41599 The terminating @samp{\0} is not incorporated into the hash.
41601 The step size used in the hash table is computed via
41602 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41603 value, and @samp{size} is the size of the hash table. The step size
41604 is used to find the next candidate slot when handling a hash
41607 The names of C@t{++} symbols in the hash table are canonicalized. We
41608 don't currently have a simple description of the canonicalization
41609 algorithm; if you intend to create new index sections, you must read
41613 The constant pool. This is simply a bunch of bytes. It is organized
41614 so that alignment is correct: CU vectors are stored first, followed by
41617 A CU vector in the constant pool is a sequence of @code{offset_type}
41618 values. The first value is the number of CU indices in the vector.
41619 Each subsequent value is the index and symbol attributes of a CU in
41620 the CU list. This element in the hash table is used to indicate which
41621 CUs define the symbol and how the symbol is used.
41622 See below for the format of each CU index+attributes entry.
41624 A string in the constant pool is zero-terminated.
41627 Attributes were added to CU index values in @code{.gdb_index} version 7.
41628 If a symbol has multiple uses within a CU then there is one
41629 CU index+attributes value for each use.
41631 The format of each CU index+attributes entry is as follows
41637 This is the index of the CU in the CU list.
41639 These bits are reserved for future purposes and must be zero.
41641 The kind of the symbol in the CU.
41645 This value is reserved and should not be used.
41646 By reserving zero the full @code{offset_type} value is backwards compatible
41647 with previous versions of the index.
41649 The symbol is a type.
41651 The symbol is a variable or an enum value.
41653 The symbol is a function.
41655 Any other kind of symbol.
41657 These values are reserved.
41661 This bit is zero if the value is global and one if it is static.
41663 The determination of whether a symbol is global or static is complicated.
41664 The authorative reference is the file @file{dwarf2read.c} in
41665 @value{GDBN} sources.
41669 This pseudo-code describes the computation of a symbol's kind and
41670 global/static attributes in the index.
41673 is_external = get_attribute (die, DW_AT_external);
41674 language = get_attribute (cu_die, DW_AT_language);
41677 case DW_TAG_typedef:
41678 case DW_TAG_base_type:
41679 case DW_TAG_subrange_type:
41683 case DW_TAG_enumerator:
41685 is_static = language != CPLUS;
41687 case DW_TAG_subprogram:
41689 is_static = ! (is_external || language == ADA);
41691 case DW_TAG_constant:
41693 is_static = ! is_external;
41695 case DW_TAG_variable:
41697 is_static = ! is_external;
41699 case DW_TAG_namespace:
41703 case DW_TAG_class_type:
41704 case DW_TAG_interface_type:
41705 case DW_TAG_structure_type:
41706 case DW_TAG_union_type:
41707 case DW_TAG_enumeration_type:
41709 is_static = language != CPLUS;
41717 @appendix Manual pages
41721 * gdb man:: The GNU Debugger man page
41722 * gdbserver man:: Remote Server for the GNU Debugger man page
41723 * gcore man:: Generate a core file of a running program
41724 * gdbinit man:: gdbinit scripts
41730 @c man title gdb The GNU Debugger
41732 @c man begin SYNOPSIS gdb
41733 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41734 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41735 [@option{-b}@w{ }@var{bps}]
41736 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41737 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41738 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41739 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41740 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41743 @c man begin DESCRIPTION gdb
41744 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41745 going on ``inside'' another program while it executes -- or what another
41746 program was doing at the moment it crashed.
41748 @value{GDBN} can do four main kinds of things (plus other things in support of
41749 these) to help you catch bugs in the act:
41753 Start your program, specifying anything that might affect its behavior.
41756 Make your program stop on specified conditions.
41759 Examine what has happened, when your program has stopped.
41762 Change things in your program, so you can experiment with correcting the
41763 effects of one bug and go on to learn about another.
41766 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41769 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41770 commands from the terminal until you tell it to exit with the @value{GDBN}
41771 command @code{quit}. You can get online help from @value{GDBN} itself
41772 by using the command @code{help}.
41774 You can run @code{gdb} with no arguments or options; but the most
41775 usual way to start @value{GDBN} is with one argument or two, specifying an
41776 executable program as the argument:
41782 You can also start with both an executable program and a core file specified:
41788 You can, instead, specify a process ID as a second argument, if you want
41789 to debug a running process:
41797 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41798 named @file{1234}; @value{GDBN} does check for a core file first).
41799 With option @option{-p} you can omit the @var{program} filename.
41801 Here are some of the most frequently needed @value{GDBN} commands:
41803 @c pod2man highlights the right hand side of the @item lines.
41805 @item break [@var{file}:]@var{function}
41806 Set a breakpoint at @var{function} (in @var{file}).
41808 @item run [@var{arglist}]
41809 Start your program (with @var{arglist}, if specified).
41812 Backtrace: display the program stack.
41814 @item print @var{expr}
41815 Display the value of an expression.
41818 Continue running your program (after stopping, e.g. at a breakpoint).
41821 Execute next program line (after stopping); step @emph{over} any
41822 function calls in the line.
41824 @item edit [@var{file}:]@var{function}
41825 look at the program line where it is presently stopped.
41827 @item list [@var{file}:]@var{function}
41828 type the text of the program in the vicinity of where it is presently stopped.
41831 Execute next program line (after stopping); step @emph{into} any
41832 function calls in the line.
41834 @item help [@var{name}]
41835 Show information about @value{GDBN} command @var{name}, or general information
41836 about using @value{GDBN}.
41839 Exit from @value{GDBN}.
41843 For full details on @value{GDBN},
41844 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41845 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41846 as the @code{gdb} entry in the @code{info} program.
41850 @c man begin OPTIONS gdb
41851 Any arguments other than options specify an executable
41852 file and core file (or process ID); that is, the first argument
41853 encountered with no
41854 associated option flag is equivalent to a @option{-se} option, and the second,
41855 if any, is equivalent to a @option{-c} option if it's the name of a file.
41857 both long and short forms; both are shown here. The long forms are also
41858 recognized if you truncate them, so long as enough of the option is
41859 present to be unambiguous. (If you prefer, you can flag option
41860 arguments with @option{+} rather than @option{-}, though we illustrate the
41861 more usual convention.)
41863 All the options and command line arguments you give are processed
41864 in sequential order. The order makes a difference when the @option{-x}
41870 List all options, with brief explanations.
41872 @item -symbols=@var{file}
41873 @itemx -s @var{file}
41874 Read symbol table from file @var{file}.
41877 Enable writing into executable and core files.
41879 @item -exec=@var{file}
41880 @itemx -e @var{file}
41881 Use file @var{file} as the executable file to execute when
41882 appropriate, and for examining pure data in conjunction with a core
41885 @item -se=@var{file}
41886 Read symbol table from file @var{file} and use it as the executable
41889 @item -core=@var{file}
41890 @itemx -c @var{file}
41891 Use file @var{file} as a core dump to examine.
41893 @item -command=@var{file}
41894 @itemx -x @var{file}
41895 Execute @value{GDBN} commands from file @var{file}.
41897 @item -ex @var{command}
41898 Execute given @value{GDBN} @var{command}.
41900 @item -directory=@var{directory}
41901 @itemx -d @var{directory}
41902 Add @var{directory} to the path to search for source files.
41905 Do not execute commands from @file{~/.gdbinit}.
41909 Do not execute commands from any @file{.gdbinit} initialization files.
41913 ``Quiet''. Do not print the introductory and copyright messages. These
41914 messages are also suppressed in batch mode.
41917 Run in batch mode. Exit with status @code{0} after processing all the command
41918 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41919 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41920 commands in the command files.
41922 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41923 download and run a program on another computer; in order to make this
41924 more useful, the message
41927 Program exited normally.
41931 (which is ordinarily issued whenever a program running under @value{GDBN} control
41932 terminates) is not issued when running in batch mode.
41934 @item -cd=@var{directory}
41935 Run @value{GDBN} using @var{directory} as its working directory,
41936 instead of the current directory.
41940 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41941 @value{GDBN} to output the full file name and line number in a standard,
41942 recognizable fashion each time a stack frame is displayed (which
41943 includes each time the program stops). This recognizable format looks
41944 like two @samp{\032} characters, followed by the file name, line number
41945 and character position separated by colons, and a newline. The
41946 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41947 characters as a signal to display the source code for the frame.
41950 Set the line speed (baud rate or bits per second) of any serial
41951 interface used by @value{GDBN} for remote debugging.
41953 @item -tty=@var{device}
41954 Run using @var{device} for your program's standard input and output.
41958 @c man begin SEEALSO gdb
41960 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41961 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41962 documentation are properly installed at your site, the command
41969 should give you access to the complete manual.
41971 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41972 Richard M. Stallman and Roland H. Pesch, July 1991.
41976 @node gdbserver man
41977 @heading gdbserver man
41979 @c man title gdbserver Remote Server for the GNU Debugger
41981 @c man begin SYNOPSIS gdbserver
41982 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41984 gdbserver --attach @var{comm} @var{pid}
41986 gdbserver --multi @var{comm}
41990 @c man begin DESCRIPTION gdbserver
41991 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41992 than the one which is running the program being debugged.
41995 @subheading Usage (server (target) side)
41998 Usage (server (target) side):
42001 First, you need to have a copy of the program you want to debug put onto
42002 the target system. The program can be stripped to save space if needed, as
42003 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42004 the @value{GDBN} running on the host system.
42006 To use the server, you log on to the target system, and run the @command{gdbserver}
42007 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42008 your program, and (c) its arguments. The general syntax is:
42011 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42014 For example, using a serial port, you might say:
42018 @c @file would wrap it as F</dev/com1>.
42019 target> gdbserver /dev/com1 emacs foo.txt
42022 target> gdbserver @file{/dev/com1} emacs foo.txt
42026 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42027 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42028 waits patiently for the host @value{GDBN} to communicate with it.
42030 To use a TCP connection, you could say:
42033 target> gdbserver host:2345 emacs foo.txt
42036 This says pretty much the same thing as the last example, except that we are
42037 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42038 that we are expecting to see a TCP connection from @code{host} to local TCP port
42039 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42040 want for the port number as long as it does not conflict with any existing TCP
42041 ports on the target system. This same port number must be used in the host
42042 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42043 you chose a port number that conflicts with another service, @command{gdbserver} will
42044 print an error message and exit.
42046 @command{gdbserver} can also attach to running programs.
42047 This is accomplished via the @option{--attach} argument. The syntax is:
42050 target> gdbserver --attach @var{comm} @var{pid}
42053 @var{pid} is the process ID of a currently running process. It isn't
42054 necessary to point @command{gdbserver} at a binary for the running process.
42056 To start @code{gdbserver} without supplying an initial command to run
42057 or process ID to attach, use the @option{--multi} command line option.
42058 In such case you should connect using @kbd{target extended-remote} to start
42059 the program you want to debug.
42062 target> gdbserver --multi @var{comm}
42066 @subheading Usage (host side)
42072 You need an unstripped copy of the target program on your host system, since
42073 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42074 would, with the target program as the first argument. (You may need to use the
42075 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42076 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42077 new command you need to know about is @code{target remote}
42078 (or @code{target extended-remote}). Its argument is either
42079 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42080 descriptor. For example:
42084 @c @file would wrap it as F</dev/ttyb>.
42085 (gdb) target remote /dev/ttyb
42088 (gdb) target remote @file{/dev/ttyb}
42093 communicates with the server via serial line @file{/dev/ttyb}, and:
42096 (gdb) target remote the-target:2345
42100 communicates via a TCP connection to port 2345 on host `the-target', where
42101 you previously started up @command{gdbserver} with the same port number. Note that for
42102 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42103 command, otherwise you may get an error that looks something like
42104 `Connection refused'.
42106 @command{gdbserver} can also debug multiple inferiors at once,
42109 the @value{GDBN} manual in node @code{Inferiors and Programs}
42110 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42113 @ref{Inferiors and Programs}.
42115 In such case use the @code{extended-remote} @value{GDBN} command variant:
42118 (gdb) target extended-remote the-target:2345
42121 The @command{gdbserver} option @option{--multi} may or may not be used in such
42125 @c man begin OPTIONS gdbserver
42126 There are three different modes for invoking @command{gdbserver}:
42131 Debug a specific program specified by its program name:
42134 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42137 The @var{comm} parameter specifies how should the server communicate
42138 with @value{GDBN}; it is either a device name (to use a serial line),
42139 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42140 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42141 debug in @var{prog}. Any remaining arguments will be passed to the
42142 program verbatim. When the program exits, @value{GDBN} will close the
42143 connection, and @code{gdbserver} will exit.
42146 Debug a specific program by specifying the process ID of a running
42150 gdbserver --attach @var{comm} @var{pid}
42153 The @var{comm} parameter is as described above. Supply the process ID
42154 of a running program in @var{pid}; @value{GDBN} will do everything
42155 else. Like with the previous mode, when the process @var{pid} exits,
42156 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42159 Multi-process mode -- debug more than one program/process:
42162 gdbserver --multi @var{comm}
42165 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42166 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42167 close the connection when a process being debugged exits, so you can
42168 debug several processes in the same session.
42171 In each of the modes you may specify these options:
42176 List all options, with brief explanations.
42179 This option causes @command{gdbserver} to print its version number and exit.
42182 @command{gdbserver} will attach to a running program. The syntax is:
42185 target> gdbserver --attach @var{comm} @var{pid}
42188 @var{pid} is the process ID of a currently running process. It isn't
42189 necessary to point @command{gdbserver} at a binary for the running process.
42192 To start @code{gdbserver} without supplying an initial command to run
42193 or process ID to attach, use this command line option.
42194 Then you can connect using @kbd{target extended-remote} and start
42195 the program you want to debug. The syntax is:
42198 target> gdbserver --multi @var{comm}
42202 Instruct @code{gdbserver} to display extra status information about the debugging
42204 This option is intended for @code{gdbserver} development and for bug reports to
42207 @item --remote-debug
42208 Instruct @code{gdbserver} to display remote protocol debug output.
42209 This option is intended for @code{gdbserver} development and for bug reports to
42212 @item --debug-format=option1@r{[},option2,...@r{]}
42213 Instruct @code{gdbserver} to include extra information in each line
42214 of debugging output.
42215 @xref{Other Command-Line Arguments for gdbserver}.
42218 Specify a wrapper to launch programs
42219 for debugging. The option should be followed by the name of the
42220 wrapper, then any command-line arguments to pass to the wrapper, then
42221 @kbd{--} indicating the end of the wrapper arguments.
42224 By default, @command{gdbserver} keeps the listening TCP port open, so that
42225 additional connections are possible. However, if you start @code{gdbserver}
42226 with the @option{--once} option, it will stop listening for any further
42227 connection attempts after connecting to the first @value{GDBN} session.
42229 @c --disable-packet is not documented for users.
42231 @c --disable-randomization and --no-disable-randomization are superseded by
42232 @c QDisableRandomization.
42237 @c man begin SEEALSO gdbserver
42239 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42240 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42241 documentation are properly installed at your site, the command
42247 should give you access to the complete manual.
42249 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42250 Richard M. Stallman and Roland H. Pesch, July 1991.
42257 @c man title gcore Generate a core file of a running program
42260 @c man begin SYNOPSIS gcore
42261 gcore [-o @var{filename}] @var{pid}
42265 @c man begin DESCRIPTION gcore
42266 Generate a core dump of a running program with process ID @var{pid}.
42267 Produced file is equivalent to a kernel produced core file as if the process
42268 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42269 limit). Unlike after a crash, after @command{gcore} the program remains
42270 running without any change.
42273 @c man begin OPTIONS gcore
42275 @item -o @var{filename}
42276 The optional argument
42277 @var{filename} specifies the file name where to put the core dump.
42278 If not specified, the file name defaults to @file{core.@var{pid}},
42279 where @var{pid} is the running program process ID.
42283 @c man begin SEEALSO gcore
42285 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42286 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42287 documentation are properly installed at your site, the command
42294 should give you access to the complete manual.
42296 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42297 Richard M. Stallman and Roland H. Pesch, July 1991.
42304 @c man title gdbinit GDB initialization scripts
42307 @c man begin SYNOPSIS gdbinit
42308 @ifset SYSTEM_GDBINIT
42309 @value{SYSTEM_GDBINIT}
42318 @c man begin DESCRIPTION gdbinit
42319 These files contain @value{GDBN} commands to automatically execute during
42320 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42323 the @value{GDBN} manual in node @code{Sequences}
42324 -- shell command @code{info -f gdb -n Sequences}.
42330 Please read more in
42332 the @value{GDBN} manual in node @code{Startup}
42333 -- shell command @code{info -f gdb -n Startup}.
42340 @ifset SYSTEM_GDBINIT
42341 @item @value{SYSTEM_GDBINIT}
42343 @ifclear SYSTEM_GDBINIT
42344 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42346 System-wide initialization file. It is executed unless user specified
42347 @value{GDBN} option @code{-nx} or @code{-n}.
42350 the @value{GDBN} manual in node @code{System-wide configuration}
42351 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42354 @ref{System-wide configuration}.
42358 User initialization file. It is executed unless user specified
42359 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42362 Initialization file for current directory. It may need to be enabled with
42363 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42366 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42367 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42370 @ref{Init File in the Current Directory}.
42375 @c man begin SEEALSO gdbinit
42377 gdb(1), @code{info -f gdb -n Startup}
42379 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42380 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42381 documentation are properly installed at your site, the command
42387 should give you access to the complete manual.
42389 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42390 Richard M. Stallman and Roland H. Pesch, July 1991.
42396 @node GNU Free Documentation License
42397 @appendix GNU Free Documentation License
42400 @node Concept Index
42401 @unnumbered Concept Index
42405 @node Command and Variable Index
42406 @unnumbered Command, Variable, and Function Index
42411 % I think something like @@colophon should be in texinfo. In the
42413 \long\def\colophon{\hbox to0pt{}\vfill
42414 \centerline{The body of this manual is set in}
42415 \centerline{\fontname\tenrm,}
42416 \centerline{with headings in {\bf\fontname\tenbf}}
42417 \centerline{and examples in {\tt\fontname\tentt}.}
42418 \centerline{{\it\fontname\tenit\/},}
42419 \centerline{{\bf\fontname\tenbf}, and}
42420 \centerline{{\sl\fontname\tensl\/}}
42421 \centerline{are used for emphasis.}\vfill}
42423 % Blame: doc@@cygnus.com, 1991.