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 /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2796 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as GNU/Linux and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2847 @cindex focus of debugging
2848 @cindex current thread
2849 The @value{GDBN} thread debugging facility allows you to observe all
2850 threads while your program runs---but whenever @value{GDBN} takes
2851 control, one thread in particular is always the focus of debugging.
2852 This thread is called the @dfn{current thread}. Debugging commands show
2853 program information from the perspective of the current thread.
2855 @cindex @code{New} @var{systag} message
2856 @cindex thread identifier (system)
2857 @c FIXME-implementors!! It would be more helpful if the [New...] message
2858 @c included GDB's numeric thread handle, so you could just go to that
2859 @c thread without first checking `info threads'.
2860 Whenever @value{GDBN} detects a new thread in your program, it displays
2861 the target system's identification for the thread with a message in the
2862 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2863 whose form varies depending on the particular system. For example, on
2864 @sc{gnu}/Linux, you might see
2867 [New Thread 0x41e02940 (LWP 25582)]
2871 when @value{GDBN} notices a new thread. In contrast, on other systems,
2872 the @var{systag} is simply something like @samp{process 368}, with no
2875 @c FIXME!! (1) Does the [New...] message appear even for the very first
2876 @c thread of a program, or does it only appear for the
2877 @c second---i.e.@: when it becomes obvious we have a multithread
2879 @c (2) *Is* there necessarily a first thread always? Or do some
2880 @c multithread systems permit starting a program with multiple
2881 @c threads ab initio?
2883 @cindex thread number
2884 @cindex thread identifier (GDB)
2885 For debugging purposes, @value{GDBN} associates its own thread
2886 number---always a single integer---with each thread in your program.
2888 From @value{GDBN}'s perspective, a process always has at least one
2889 thread. In other words, @value{GDBN} assigns a thread number to the
2890 program's ``main thread'' even if the program is not multi-threaded.
2893 @kindex info threads
2894 @item info threads @r{[}@var{id}@dots{}@r{]}
2895 Display a summary of all threads currently in your program. Optional
2896 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2897 means to print information only about the specified thread or threads.
2898 @value{GDBN} displays for each thread (in this order):
2902 the thread number assigned by @value{GDBN}
2905 the target system's thread identifier (@var{systag})
2908 the thread's name, if one is known. A thread can either be named by
2909 the user (see @code{thread name}, below), or, in some cases, by the
2913 the current stack frame summary for that thread
2917 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2918 indicates the current thread.
2922 @c end table here to get a little more width for example
2925 (@value{GDBP}) info threads
2927 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2928 2 process 35 thread 23 0x34e5 in sigpause ()
2929 3 process 35 thread 27 0x34e5 in sigpause ()
2933 On Solaris, you can display more information about user threads with a
2934 Solaris-specific command:
2937 @item maint info sol-threads
2938 @kindex maint info sol-threads
2939 @cindex thread info (Solaris)
2940 Display info on Solaris user threads.
2944 @kindex thread @var{threadno}
2945 @item thread @var{threadno}
2946 Make thread number @var{threadno} the current thread. The command
2947 argument @var{threadno} is the internal @value{GDBN} thread number, as
2948 shown in the first field of the @samp{info threads} display.
2949 @value{GDBN} responds by displaying the system identifier of the thread
2950 you selected, and its current stack frame summary:
2953 (@value{GDBP}) thread 2
2954 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2955 #0 some_function (ignore=0x0) at example.c:8
2956 8 printf ("hello\n");
2960 As with the @samp{[New @dots{}]} message, the form of the text after
2961 @samp{Switching to} depends on your system's conventions for identifying
2964 @vindex $_thread@r{, convenience variable}
2965 The debugger convenience variable @samp{$_thread} contains the number
2966 of the current thread. You may find this useful in writing breakpoint
2967 conditional expressions, command scripts, and so forth. See
2968 @xref{Convenience Vars,, Convenience Variables}, for general
2969 information on convenience variables.
2971 @kindex thread apply
2972 @cindex apply command to several threads
2973 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2974 The @code{thread apply} command allows you to apply the named
2975 @var{command} to one or more threads. Specify the numbers of the
2976 threads that you want affected with the command argument
2977 @var{threadno}. It can be a single thread number, one of the numbers
2978 shown in the first field of the @samp{info threads} display; or it
2979 could be a range of thread numbers, as in @code{2-4}. To apply
2980 a command to all threads in descending order, type @kbd{thread apply all
2981 @var{command}}. To apply a command to all threads in ascending order,
2982 type @kbd{thread apply all -ascending @var{command}}.
2986 @cindex name a thread
2987 @item thread name [@var{name}]
2988 This command assigns a name to the current thread. If no argument is
2989 given, any existing user-specified name is removed. The thread name
2990 appears in the @samp{info threads} display.
2992 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2993 determine the name of the thread as given by the OS. On these
2994 systems, a name specified with @samp{thread name} will override the
2995 system-give name, and removing the user-specified name will cause
2996 @value{GDBN} to once again display the system-specified name.
2999 @cindex search for a thread
3000 @item thread find [@var{regexp}]
3001 Search for and display thread ids whose name or @var{systag}
3002 matches the supplied regular expression.
3004 As well as being the complement to the @samp{thread name} command,
3005 this command also allows you to identify a thread by its target
3006 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3010 (@value{GDBN}) thread find 26688
3011 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3012 (@value{GDBN}) info thread 4
3014 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3017 @kindex set print thread-events
3018 @cindex print messages on thread start and exit
3019 @item set print thread-events
3020 @itemx set print thread-events on
3021 @itemx set print thread-events off
3022 The @code{set print thread-events} command allows you to enable or
3023 disable printing of messages when @value{GDBN} notices that new threads have
3024 started or that threads have exited. By default, these messages will
3025 be printed if detection of these events is supported by the target.
3026 Note that these messages cannot be disabled on all targets.
3028 @kindex show print thread-events
3029 @item show print thread-events
3030 Show whether messages will be printed when @value{GDBN} detects that threads
3031 have started and exited.
3034 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3035 more information about how @value{GDBN} behaves when you stop and start
3036 programs with multiple threads.
3038 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3039 watchpoints in programs with multiple threads.
3041 @anchor{set libthread-db-search-path}
3043 @kindex set libthread-db-search-path
3044 @cindex search path for @code{libthread_db}
3045 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3046 If this variable is set, @var{path} is a colon-separated list of
3047 directories @value{GDBN} will use to search for @code{libthread_db}.
3048 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3049 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3050 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3053 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3054 @code{libthread_db} library to obtain information about threads in the
3055 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3056 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3057 specific thread debugging library loading is enabled
3058 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3060 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3061 refers to the default system directories that are
3062 normally searched for loading shared libraries. The @samp{$sdir} entry
3063 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3064 (@pxref{libthread_db.so.1 file}).
3066 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3067 refers to the directory from which @code{libpthread}
3068 was loaded in the inferior process.
3070 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3071 @value{GDBN} attempts to initialize it with the current inferior process.
3072 If this initialization fails (which could happen because of a version
3073 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3074 will unload @code{libthread_db}, and continue with the next directory.
3075 If none of @code{libthread_db} libraries initialize successfully,
3076 @value{GDBN} will issue a warning and thread debugging will be disabled.
3078 Setting @code{libthread-db-search-path} is currently implemented
3079 only on some platforms.
3081 @kindex show libthread-db-search-path
3082 @item show libthread-db-search-path
3083 Display current libthread_db search path.
3085 @kindex set debug libthread-db
3086 @kindex show debug libthread-db
3087 @cindex debugging @code{libthread_db}
3088 @item set debug libthread-db
3089 @itemx show debug libthread-db
3090 Turns on or off display of @code{libthread_db}-related events.
3091 Use @code{1} to enable, @code{0} to disable.
3095 @section Debugging Forks
3097 @cindex fork, debugging programs which call
3098 @cindex multiple processes
3099 @cindex processes, multiple
3100 On most systems, @value{GDBN} has no special support for debugging
3101 programs which create additional processes using the @code{fork}
3102 function. When a program forks, @value{GDBN} will continue to debug the
3103 parent process and the child process will run unimpeded. If you have
3104 set a breakpoint in any code which the child then executes, the child
3105 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3106 will cause it to terminate.
3108 However, if you want to debug the child process there is a workaround
3109 which isn't too painful. Put a call to @code{sleep} in the code which
3110 the child process executes after the fork. It may be useful to sleep
3111 only if a certain environment variable is set, or a certain file exists,
3112 so that the delay need not occur when you don't want to run @value{GDBN}
3113 on the child. While the child is sleeping, use the @code{ps} program to
3114 get its process ID. Then tell @value{GDBN} (a new invocation of
3115 @value{GDBN} if you are also debugging the parent process) to attach to
3116 the child process (@pxref{Attach}). From that point on you can debug
3117 the child process just like any other process which you attached to.
3119 On some systems, @value{GDBN} provides support for debugging programs
3120 that create additional processes using the @code{fork} or @code{vfork}
3121 functions. On @sc{gnu}/Linux platforms, this feature is supported
3122 with kernel version 2.5.46 and later.
3124 The fork debugging commands are supported in native mode and when
3125 connected to @code{gdbserver} in either @code{target remote} mode or
3126 @code{target extended-remote} mode.
3128 By default, when a program forks, @value{GDBN} will continue to debug
3129 the parent process and the child process will run unimpeded.
3131 If you want to follow the child process instead of the parent process,
3132 use the command @w{@code{set follow-fork-mode}}.
3135 @kindex set follow-fork-mode
3136 @item set follow-fork-mode @var{mode}
3137 Set the debugger response to a program call of @code{fork} or
3138 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3139 process. The @var{mode} argument can be:
3143 The original process is debugged after a fork. The child process runs
3144 unimpeded. This is the default.
3147 The new process is debugged after a fork. The parent process runs
3152 @kindex show follow-fork-mode
3153 @item show follow-fork-mode
3154 Display the current debugger response to a @code{fork} or @code{vfork} call.
3157 @cindex debugging multiple processes
3158 On Linux, if you want to debug both the parent and child processes, use the
3159 command @w{@code{set detach-on-fork}}.
3162 @kindex set detach-on-fork
3163 @item set detach-on-fork @var{mode}
3164 Tells gdb whether to detach one of the processes after a fork, or
3165 retain debugger control over them both.
3169 The child process (or parent process, depending on the value of
3170 @code{follow-fork-mode}) will be detached and allowed to run
3171 independently. This is the default.
3174 Both processes will be held under the control of @value{GDBN}.
3175 One process (child or parent, depending on the value of
3176 @code{follow-fork-mode}) is debugged as usual, while the other
3181 @kindex show detach-on-fork
3182 @item show detach-on-fork
3183 Show whether detach-on-fork mode is on/off.
3186 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3187 will retain control of all forked processes (including nested forks).
3188 You can list the forked processes under the control of @value{GDBN} by
3189 using the @w{@code{info inferiors}} command, and switch from one fork
3190 to another by using the @code{inferior} command (@pxref{Inferiors and
3191 Programs, ,Debugging Multiple Inferiors and Programs}).
3193 To quit debugging one of the forked processes, you can either detach
3194 from it by using the @w{@code{detach inferiors}} command (allowing it
3195 to run independently), or kill it using the @w{@code{kill inferiors}}
3196 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3199 If you ask to debug a child process and a @code{vfork} is followed by an
3200 @code{exec}, @value{GDBN} executes the new target up to the first
3201 breakpoint in the new target. If you have a breakpoint set on
3202 @code{main} in your original program, the breakpoint will also be set on
3203 the child process's @code{main}.
3205 On some systems, when a child process is spawned by @code{vfork}, you
3206 cannot debug the child or parent until an @code{exec} call completes.
3208 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3209 call executes, the new target restarts. To restart the parent
3210 process, use the @code{file} command with the parent executable name
3211 as its argument. By default, after an @code{exec} call executes,
3212 @value{GDBN} discards the symbols of the previous executable image.
3213 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3217 @kindex set follow-exec-mode
3218 @item set follow-exec-mode @var{mode}
3220 Set debugger response to a program call of @code{exec}. An
3221 @code{exec} call replaces the program image of a process.
3223 @code{follow-exec-mode} can be:
3227 @value{GDBN} creates a new inferior and rebinds the process to this
3228 new inferior. The program the process was running before the
3229 @code{exec} call can be restarted afterwards by restarting the
3235 (@value{GDBP}) info inferiors
3237 Id Description Executable
3240 process 12020 is executing new program: prog2
3241 Program exited normally.
3242 (@value{GDBP}) info inferiors
3243 Id Description Executable
3249 @value{GDBN} keeps the process bound to the same inferior. The new
3250 executable image replaces the previous executable loaded in the
3251 inferior. Restarting the inferior after the @code{exec} call, with
3252 e.g., the @code{run} command, restarts the executable the process was
3253 running after the @code{exec} call. This is the default mode.
3258 (@value{GDBP}) info inferiors
3259 Id Description Executable
3262 process 12020 is executing new program: prog2
3263 Program exited normally.
3264 (@value{GDBP}) info inferiors
3265 Id Description Executable
3272 @code{follow-exec-mode} is supported in native mode and
3273 @code{target extended-remote} mode.
3275 You can use the @code{catch} command to make @value{GDBN} stop whenever
3276 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3277 Catchpoints, ,Setting Catchpoints}.
3279 @node Checkpoint/Restart
3280 @section Setting a @emph{Bookmark} to Return to Later
3285 @cindex snapshot of a process
3286 @cindex rewind program state
3288 On certain operating systems@footnote{Currently, only
3289 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3290 program's state, called a @dfn{checkpoint}, and come back to it
3293 Returning to a checkpoint effectively undoes everything that has
3294 happened in the program since the @code{checkpoint} was saved. This
3295 includes changes in memory, registers, and even (within some limits)
3296 system state. Effectively, it is like going back in time to the
3297 moment when the checkpoint was saved.
3299 Thus, if you're stepping thru a program and you think you're
3300 getting close to the point where things go wrong, you can save
3301 a checkpoint. Then, if you accidentally go too far and miss
3302 the critical statement, instead of having to restart your program
3303 from the beginning, you can just go back to the checkpoint and
3304 start again from there.
3306 This can be especially useful if it takes a lot of time or
3307 steps to reach the point where you think the bug occurs.
3309 To use the @code{checkpoint}/@code{restart} method of debugging:
3314 Save a snapshot of the debugged program's current execution state.
3315 The @code{checkpoint} command takes no arguments, but each checkpoint
3316 is assigned a small integer id, similar to a breakpoint id.
3318 @kindex info checkpoints
3319 @item info checkpoints
3320 List the checkpoints that have been saved in the current debugging
3321 session. For each checkpoint, the following information will be
3328 @item Source line, or label
3331 @kindex restart @var{checkpoint-id}
3332 @item restart @var{checkpoint-id}
3333 Restore the program state that was saved as checkpoint number
3334 @var{checkpoint-id}. All program variables, registers, stack frames
3335 etc.@: will be returned to the values that they had when the checkpoint
3336 was saved. In essence, gdb will ``wind back the clock'' to the point
3337 in time when the checkpoint was saved.
3339 Note that breakpoints, @value{GDBN} variables, command history etc.
3340 are not affected by restoring a checkpoint. In general, a checkpoint
3341 only restores things that reside in the program being debugged, not in
3344 @kindex delete checkpoint @var{checkpoint-id}
3345 @item delete checkpoint @var{checkpoint-id}
3346 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3350 Returning to a previously saved checkpoint will restore the user state
3351 of the program being debugged, plus a significant subset of the system
3352 (OS) state, including file pointers. It won't ``un-write'' data from
3353 a file, but it will rewind the file pointer to the previous location,
3354 so that the previously written data can be overwritten. For files
3355 opened in read mode, the pointer will also be restored so that the
3356 previously read data can be read again.
3358 Of course, characters that have been sent to a printer (or other
3359 external device) cannot be ``snatched back'', and characters received
3360 from eg.@: a serial device can be removed from internal program buffers,
3361 but they cannot be ``pushed back'' into the serial pipeline, ready to
3362 be received again. Similarly, the actual contents of files that have
3363 been changed cannot be restored (at this time).
3365 However, within those constraints, you actually can ``rewind'' your
3366 program to a previously saved point in time, and begin debugging it
3367 again --- and you can change the course of events so as to debug a
3368 different execution path this time.
3370 @cindex checkpoints and process id
3371 Finally, there is one bit of internal program state that will be
3372 different when you return to a checkpoint --- the program's process
3373 id. Each checkpoint will have a unique process id (or @var{pid}),
3374 and each will be different from the program's original @var{pid}.
3375 If your program has saved a local copy of its process id, this could
3376 potentially pose a problem.
3378 @subsection A Non-obvious Benefit of Using Checkpoints
3380 On some systems such as @sc{gnu}/Linux, address space randomization
3381 is performed on new processes for security reasons. This makes it
3382 difficult or impossible to set a breakpoint, or watchpoint, on an
3383 absolute address if you have to restart the program, since the
3384 absolute location of a symbol will change from one execution to the
3387 A checkpoint, however, is an @emph{identical} copy of a process.
3388 Therefore if you create a checkpoint at (eg.@:) the start of main,
3389 and simply return to that checkpoint instead of restarting the
3390 process, you can avoid the effects of address randomization and
3391 your symbols will all stay in the same place.
3394 @chapter Stopping and Continuing
3396 The principal purposes of using a debugger are so that you can stop your
3397 program before it terminates; or so that, if your program runs into
3398 trouble, you can investigate and find out why.
3400 Inside @value{GDBN}, your program may stop for any of several reasons,
3401 such as a signal, a breakpoint, or reaching a new line after a
3402 @value{GDBN} command such as @code{step}. You may then examine and
3403 change variables, set new breakpoints or remove old ones, and then
3404 continue execution. Usually, the messages shown by @value{GDBN} provide
3405 ample explanation of the status of your program---but you can also
3406 explicitly request this information at any time.
3409 @kindex info program
3411 Display information about the status of your program: whether it is
3412 running or not, what process it is, and why it stopped.
3416 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3417 * Continuing and Stepping:: Resuming execution
3418 * Skipping Over Functions and Files::
3419 Skipping over functions and files
3421 * Thread Stops:: Stopping and starting multi-thread programs
3425 @section Breakpoints, Watchpoints, and Catchpoints
3428 A @dfn{breakpoint} makes your program stop whenever a certain point in
3429 the program is reached. For each breakpoint, you can add conditions to
3430 control in finer detail whether your program stops. You can set
3431 breakpoints with the @code{break} command and its variants (@pxref{Set
3432 Breaks, ,Setting Breakpoints}), to specify the place where your program
3433 should stop by line number, function name or exact address in the
3436 On some systems, you can set breakpoints in shared libraries before
3437 the executable is run.
3440 @cindex data breakpoints
3441 @cindex memory tracing
3442 @cindex breakpoint on memory address
3443 @cindex breakpoint on variable modification
3444 A @dfn{watchpoint} is a special breakpoint that stops your program
3445 when the value of an expression changes. The expression may be a value
3446 of a variable, or it could involve values of one or more variables
3447 combined by operators, such as @samp{a + b}. This is sometimes called
3448 @dfn{data breakpoints}. You must use a different command to set
3449 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3450 from that, you can manage a watchpoint like any other breakpoint: you
3451 enable, disable, and delete both breakpoints and watchpoints using the
3454 You can arrange to have values from your program displayed automatically
3455 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3459 @cindex breakpoint on events
3460 A @dfn{catchpoint} is another special breakpoint that stops your program
3461 when a certain kind of event occurs, such as the throwing of a C@t{++}
3462 exception or the loading of a library. As with watchpoints, you use a
3463 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3464 Catchpoints}), but aside from that, you can manage a catchpoint like any
3465 other breakpoint. (To stop when your program receives a signal, use the
3466 @code{handle} command; see @ref{Signals, ,Signals}.)
3468 @cindex breakpoint numbers
3469 @cindex numbers for breakpoints
3470 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3471 catchpoint when you create it; these numbers are successive integers
3472 starting with one. In many of the commands for controlling various
3473 features of breakpoints you use the breakpoint number to say which
3474 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3475 @dfn{disabled}; if disabled, it has no effect on your program until you
3478 @cindex breakpoint ranges
3479 @cindex ranges of breakpoints
3480 Some @value{GDBN} commands accept a range of breakpoints on which to
3481 operate. A breakpoint range is either a single breakpoint number, like
3482 @samp{5}, or two such numbers, in increasing order, separated by a
3483 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3484 all breakpoints in that range are operated on.
3487 * Set Breaks:: Setting breakpoints
3488 * Set Watchpoints:: Setting watchpoints
3489 * Set Catchpoints:: Setting catchpoints
3490 * Delete Breaks:: Deleting breakpoints
3491 * Disabling:: Disabling breakpoints
3492 * Conditions:: Break conditions
3493 * Break Commands:: Breakpoint command lists
3494 * Dynamic Printf:: Dynamic printf
3495 * Save Breakpoints:: How to save breakpoints in a file
3496 * Static Probe Points:: Listing static probe points
3497 * Error in Breakpoints:: ``Cannot insert breakpoints''
3498 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3502 @subsection Setting Breakpoints
3504 @c FIXME LMB what does GDB do if no code on line of breakpt?
3505 @c consider in particular declaration with/without initialization.
3507 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3510 @kindex b @r{(@code{break})}
3511 @vindex $bpnum@r{, convenience variable}
3512 @cindex latest breakpoint
3513 Breakpoints are set with the @code{break} command (abbreviated
3514 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3515 number of the breakpoint you've set most recently; see @ref{Convenience
3516 Vars,, Convenience Variables}, for a discussion of what you can do with
3517 convenience variables.
3520 @item break @var{location}
3521 Set a breakpoint at the given @var{location}, which can specify a
3522 function name, a line number, or an address of an instruction.
3523 (@xref{Specify Location}, for a list of all the possible ways to
3524 specify a @var{location}.) The breakpoint will stop your program just
3525 before it executes any of the code in the specified @var{location}.
3527 When using source languages that permit overloading of symbols, such as
3528 C@t{++}, a function name may refer to more than one possible place to break.
3529 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3532 It is also possible to insert a breakpoint that will stop the program
3533 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3534 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3537 When called without any arguments, @code{break} sets a breakpoint at
3538 the next instruction to be executed in the selected stack frame
3539 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3540 innermost, this makes your program stop as soon as control
3541 returns to that frame. This is similar to the effect of a
3542 @code{finish} command in the frame inside the selected frame---except
3543 that @code{finish} does not leave an active breakpoint. If you use
3544 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3545 the next time it reaches the current location; this may be useful
3548 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3549 least one instruction has been executed. If it did not do this, you
3550 would be unable to proceed past a breakpoint without first disabling the
3551 breakpoint. This rule applies whether or not the breakpoint already
3552 existed when your program stopped.
3554 @item break @dots{} if @var{cond}
3555 Set a breakpoint with condition @var{cond}; evaluate the expression
3556 @var{cond} each time the breakpoint is reached, and stop only if the
3557 value is nonzero---that is, if @var{cond} evaluates as true.
3558 @samp{@dots{}} stands for one of the possible arguments described
3559 above (or no argument) specifying where to break. @xref{Conditions,
3560 ,Break Conditions}, for more information on breakpoint conditions.
3563 @item tbreak @var{args}
3564 Set a breakpoint enabled only for one stop. The @var{args} are the
3565 same as for the @code{break} command, and the breakpoint is set in the same
3566 way, but the breakpoint is automatically deleted after the first time your
3567 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3570 @cindex hardware breakpoints
3571 @item hbreak @var{args}
3572 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3573 @code{break} command and the breakpoint is set in the same way, but the
3574 breakpoint requires hardware support and some target hardware may not
3575 have this support. The main purpose of this is EPROM/ROM code
3576 debugging, so you can set a breakpoint at an instruction without
3577 changing the instruction. This can be used with the new trap-generation
3578 provided by SPARClite DSU and most x86-based targets. These targets
3579 will generate traps when a program accesses some data or instruction
3580 address that is assigned to the debug registers. However the hardware
3581 breakpoint registers can take a limited number of breakpoints. For
3582 example, on the DSU, only two data breakpoints can be set at a time, and
3583 @value{GDBN} will reject this command if more than two are used. Delete
3584 or disable unused hardware breakpoints before setting new ones
3585 (@pxref{Disabling, ,Disabling Breakpoints}).
3586 @xref{Conditions, ,Break Conditions}.
3587 For remote targets, you can restrict the number of hardware
3588 breakpoints @value{GDBN} will use, see @ref{set remote
3589 hardware-breakpoint-limit}.
3592 @item thbreak @var{args}
3593 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3594 are the same as for the @code{hbreak} command and the breakpoint is set in
3595 the same way. However, like the @code{tbreak} command,
3596 the breakpoint is automatically deleted after the
3597 first time your program stops there. Also, like the @code{hbreak}
3598 command, the breakpoint requires hardware support and some target hardware
3599 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3600 See also @ref{Conditions, ,Break Conditions}.
3603 @cindex regular expression
3604 @cindex breakpoints at functions matching a regexp
3605 @cindex set breakpoints in many functions
3606 @item rbreak @var{regex}
3607 Set breakpoints on all functions matching the regular expression
3608 @var{regex}. This command sets an unconditional breakpoint on all
3609 matches, printing a list of all breakpoints it set. Once these
3610 breakpoints are set, they are treated just like the breakpoints set with
3611 the @code{break} command. You can delete them, disable them, or make
3612 them conditional the same way as any other breakpoint.
3614 The syntax of the regular expression is the standard one used with tools
3615 like @file{grep}. Note that this is different from the syntax used by
3616 shells, so for instance @code{foo*} matches all functions that include
3617 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3618 @code{.*} leading and trailing the regular expression you supply, so to
3619 match only functions that begin with @code{foo}, use @code{^foo}.
3621 @cindex non-member C@t{++} functions, set breakpoint in
3622 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3623 breakpoints on overloaded functions that are not members of any special
3626 @cindex set breakpoints on all functions
3627 The @code{rbreak} command can be used to set breakpoints in
3628 @strong{all} the functions in a program, like this:
3631 (@value{GDBP}) rbreak .
3634 @item rbreak @var{file}:@var{regex}
3635 If @code{rbreak} is called with a filename qualification, it limits
3636 the search for functions matching the given regular expression to the
3637 specified @var{file}. This can be used, for example, to set breakpoints on
3638 every function in a given file:
3641 (@value{GDBP}) rbreak file.c:.
3644 The colon separating the filename qualifier from the regex may
3645 optionally be surrounded by spaces.
3647 @kindex info breakpoints
3648 @cindex @code{$_} and @code{info breakpoints}
3649 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3650 @itemx info break @r{[}@var{n}@dots{}@r{]}
3651 Print a table of all breakpoints, watchpoints, and catchpoints set and
3652 not deleted. Optional argument @var{n} means print information only
3653 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3654 For each breakpoint, following columns are printed:
3657 @item Breakpoint Numbers
3659 Breakpoint, watchpoint, or catchpoint.
3661 Whether the breakpoint is marked to be disabled or deleted when hit.
3662 @item Enabled or Disabled
3663 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3664 that are not enabled.
3666 Where the breakpoint is in your program, as a memory address. For a
3667 pending breakpoint whose address is not yet known, this field will
3668 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3669 library that has the symbol or line referred by breakpoint is loaded.
3670 See below for details. A breakpoint with several locations will
3671 have @samp{<MULTIPLE>} in this field---see below for details.
3673 Where the breakpoint is in the source for your program, as a file and
3674 line number. For a pending breakpoint, the original string passed to
3675 the breakpoint command will be listed as it cannot be resolved until
3676 the appropriate shared library is loaded in the future.
3680 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3681 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3682 @value{GDBN} on the host's side. If it is ``target'', then the condition
3683 is evaluated by the target. The @code{info break} command shows
3684 the condition on the line following the affected breakpoint, together with
3685 its condition evaluation mode in between parentheses.
3687 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3688 allowed to have a condition specified for it. The condition is not parsed for
3689 validity until a shared library is loaded that allows the pending
3690 breakpoint to resolve to a valid location.
3693 @code{info break} with a breakpoint
3694 number @var{n} as argument lists only that breakpoint. The
3695 convenience variable @code{$_} and the default examining-address for
3696 the @code{x} command are set to the address of the last breakpoint
3697 listed (@pxref{Memory, ,Examining Memory}).
3700 @code{info break} displays a count of the number of times the breakpoint
3701 has been hit. This is especially useful in conjunction with the
3702 @code{ignore} command. You can ignore a large number of breakpoint
3703 hits, look at the breakpoint info to see how many times the breakpoint
3704 was hit, and then run again, ignoring one less than that number. This
3705 will get you quickly to the last hit of that breakpoint.
3708 For a breakpoints with an enable count (xref) greater than 1,
3709 @code{info break} also displays that count.
3713 @value{GDBN} allows you to set any number of breakpoints at the same place in
3714 your program. There is nothing silly or meaningless about this. When
3715 the breakpoints are conditional, this is even useful
3716 (@pxref{Conditions, ,Break Conditions}).
3718 @cindex multiple locations, breakpoints
3719 @cindex breakpoints, multiple locations
3720 It is possible that a breakpoint corresponds to several locations
3721 in your program. Examples of this situation are:
3725 Multiple functions in the program may have the same name.
3728 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3729 instances of the function body, used in different cases.
3732 For a C@t{++} template function, a given line in the function can
3733 correspond to any number of instantiations.
3736 For an inlined function, a given source line can correspond to
3737 several places where that function is inlined.
3740 In all those cases, @value{GDBN} will insert a breakpoint at all
3741 the relevant locations.
3743 A breakpoint with multiple locations is displayed in the breakpoint
3744 table using several rows---one header row, followed by one row for
3745 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3746 address column. The rows for individual locations contain the actual
3747 addresses for locations, and show the functions to which those
3748 locations belong. The number column for a location is of the form
3749 @var{breakpoint-number}.@var{location-number}.
3754 Num Type Disp Enb Address What
3755 1 breakpoint keep y <MULTIPLE>
3757 breakpoint already hit 1 time
3758 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3759 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3762 Each location can be individually enabled or disabled by passing
3763 @var{breakpoint-number}.@var{location-number} as argument to the
3764 @code{enable} and @code{disable} commands. Note that you cannot
3765 delete the individual locations from the list, you can only delete the
3766 entire list of locations that belong to their parent breakpoint (with
3767 the @kbd{delete @var{num}} command, where @var{num} is the number of
3768 the parent breakpoint, 1 in the above example). Disabling or enabling
3769 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3770 that belong to that breakpoint.
3772 @cindex pending breakpoints
3773 It's quite common to have a breakpoint inside a shared library.
3774 Shared libraries can be loaded and unloaded explicitly,
3775 and possibly repeatedly, as the program is executed. To support
3776 this use case, @value{GDBN} updates breakpoint locations whenever
3777 any shared library is loaded or unloaded. Typically, you would
3778 set a breakpoint in a shared library at the beginning of your
3779 debugging session, when the library is not loaded, and when the
3780 symbols from the library are not available. When you try to set
3781 breakpoint, @value{GDBN} will ask you if you want to set
3782 a so called @dfn{pending breakpoint}---breakpoint whose address
3783 is not yet resolved.
3785 After the program is run, whenever a new shared library is loaded,
3786 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3787 shared library contains the symbol or line referred to by some
3788 pending breakpoint, that breakpoint is resolved and becomes an
3789 ordinary breakpoint. When a library is unloaded, all breakpoints
3790 that refer to its symbols or source lines become pending again.
3792 This logic works for breakpoints with multiple locations, too. For
3793 example, if you have a breakpoint in a C@t{++} template function, and
3794 a newly loaded shared library has an instantiation of that template,
3795 a new location is added to the list of locations for the breakpoint.
3797 Except for having unresolved address, pending breakpoints do not
3798 differ from regular breakpoints. You can set conditions or commands,
3799 enable and disable them and perform other breakpoint operations.
3801 @value{GDBN} provides some additional commands for controlling what
3802 happens when the @samp{break} command cannot resolve breakpoint
3803 address specification to an address:
3805 @kindex set breakpoint pending
3806 @kindex show breakpoint pending
3808 @item set breakpoint pending auto
3809 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3810 location, it queries you whether a pending breakpoint should be created.
3812 @item set breakpoint pending on
3813 This indicates that an unrecognized breakpoint location should automatically
3814 result in a pending breakpoint being created.
3816 @item set breakpoint pending off
3817 This indicates that pending breakpoints are not to be created. Any
3818 unrecognized breakpoint location results in an error. This setting does
3819 not affect any pending breakpoints previously created.
3821 @item show breakpoint pending
3822 Show the current behavior setting for creating pending breakpoints.
3825 The settings above only affect the @code{break} command and its
3826 variants. Once breakpoint is set, it will be automatically updated
3827 as shared libraries are loaded and unloaded.
3829 @cindex automatic hardware breakpoints
3830 For some targets, @value{GDBN} can automatically decide if hardware or
3831 software breakpoints should be used, depending on whether the
3832 breakpoint address is read-only or read-write. This applies to
3833 breakpoints set with the @code{break} command as well as to internal
3834 breakpoints set by commands like @code{next} and @code{finish}. For
3835 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3838 You can control this automatic behaviour with the following commands::
3840 @kindex set breakpoint auto-hw
3841 @kindex show breakpoint auto-hw
3843 @item set breakpoint auto-hw on
3844 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3845 will try to use the target memory map to decide if software or hardware
3846 breakpoint must be used.
3848 @item set breakpoint auto-hw off
3849 This indicates @value{GDBN} should not automatically select breakpoint
3850 type. If the target provides a memory map, @value{GDBN} will warn when
3851 trying to set software breakpoint at a read-only address.
3854 @value{GDBN} normally implements breakpoints by replacing the program code
3855 at the breakpoint address with a special instruction, which, when
3856 executed, given control to the debugger. By default, the program
3857 code is so modified only when the program is resumed. As soon as
3858 the program stops, @value{GDBN} restores the original instructions. This
3859 behaviour guards against leaving breakpoints inserted in the
3860 target should gdb abrubptly disconnect. However, with slow remote
3861 targets, inserting and removing breakpoint can reduce the performance.
3862 This behavior can be controlled with the following commands::
3864 @kindex set breakpoint always-inserted
3865 @kindex show breakpoint always-inserted
3867 @item set breakpoint always-inserted off
3868 All breakpoints, including newly added by the user, are inserted in
3869 the target only when the target is resumed. All breakpoints are
3870 removed from the target when it stops. This is the default mode.
3872 @item set breakpoint always-inserted on
3873 Causes all breakpoints to be inserted in the target at all times. If
3874 the user adds a new breakpoint, or changes an existing breakpoint, the
3875 breakpoints in the target are updated immediately. A breakpoint is
3876 removed from the target only when breakpoint itself is deleted.
3879 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3880 when a breakpoint breaks. If the condition is true, then the process being
3881 debugged stops, otherwise the process is resumed.
3883 If the target supports evaluating conditions on its end, @value{GDBN} may
3884 download the breakpoint, together with its conditions, to it.
3886 This feature can be controlled via the following commands:
3888 @kindex set breakpoint condition-evaluation
3889 @kindex show breakpoint condition-evaluation
3891 @item set breakpoint condition-evaluation host
3892 This option commands @value{GDBN} to evaluate the breakpoint
3893 conditions on the host's side. Unconditional breakpoints are sent to
3894 the target which in turn receives the triggers and reports them back to GDB
3895 for condition evaluation. This is the standard evaluation mode.
3897 @item set breakpoint condition-evaluation target
3898 This option commands @value{GDBN} to download breakpoint conditions
3899 to the target at the moment of their insertion. The target
3900 is responsible for evaluating the conditional expression and reporting
3901 breakpoint stop events back to @value{GDBN} whenever the condition
3902 is true. Due to limitations of target-side evaluation, some conditions
3903 cannot be evaluated there, e.g., conditions that depend on local data
3904 that is only known to the host. Examples include
3905 conditional expressions involving convenience variables, complex types
3906 that cannot be handled by the agent expression parser and expressions
3907 that are too long to be sent over to the target, specially when the
3908 target is a remote system. In these cases, the conditions will be
3909 evaluated by @value{GDBN}.
3911 @item set breakpoint condition-evaluation auto
3912 This is the default mode. If the target supports evaluating breakpoint
3913 conditions on its end, @value{GDBN} will download breakpoint conditions to
3914 the target (limitations mentioned previously apply). If the target does
3915 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3916 to evaluating all these conditions on the host's side.
3920 @cindex negative breakpoint numbers
3921 @cindex internal @value{GDBN} breakpoints
3922 @value{GDBN} itself sometimes sets breakpoints in your program for
3923 special purposes, such as proper handling of @code{longjmp} (in C
3924 programs). These internal breakpoints are assigned negative numbers,
3925 starting with @code{-1}; @samp{info breakpoints} does not display them.
3926 You can see these breakpoints with the @value{GDBN} maintenance command
3927 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3930 @node Set Watchpoints
3931 @subsection Setting Watchpoints
3933 @cindex setting watchpoints
3934 You can use a watchpoint to stop execution whenever the value of an
3935 expression changes, without having to predict a particular place where
3936 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3937 The expression may be as simple as the value of a single variable, or
3938 as complex as many variables combined by operators. Examples include:
3942 A reference to the value of a single variable.
3945 An address cast to an appropriate data type. For example,
3946 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3947 address (assuming an @code{int} occupies 4 bytes).
3950 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3951 expression can use any operators valid in the program's native
3952 language (@pxref{Languages}).
3955 You can set a watchpoint on an expression even if the expression can
3956 not be evaluated yet. For instance, you can set a watchpoint on
3957 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3958 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3959 the expression produces a valid value. If the expression becomes
3960 valid in some other way than changing a variable (e.g.@: if the memory
3961 pointed to by @samp{*global_ptr} becomes readable as the result of a
3962 @code{malloc} call), @value{GDBN} may not stop until the next time
3963 the expression changes.
3965 @cindex software watchpoints
3966 @cindex hardware watchpoints
3967 Depending on your system, watchpoints may be implemented in software or
3968 hardware. @value{GDBN} does software watchpointing by single-stepping your
3969 program and testing the variable's value each time, which is hundreds of
3970 times slower than normal execution. (But this may still be worth it, to
3971 catch errors where you have no clue what part of your program is the
3974 On some systems, such as most PowerPC or x86-based targets,
3975 @value{GDBN} includes support for hardware watchpoints, which do not
3976 slow down the running of your program.
3980 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3981 Set a watchpoint for an expression. @value{GDBN} will break when the
3982 expression @var{expr} is written into by the program and its value
3983 changes. The simplest (and the most popular) use of this command is
3984 to watch the value of a single variable:
3987 (@value{GDBP}) watch foo
3990 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3991 argument, @value{GDBN} breaks only when the thread identified by
3992 @var{threadnum} changes the value of @var{expr}. If any other threads
3993 change the value of @var{expr}, @value{GDBN} will not break. Note
3994 that watchpoints restricted to a single thread in this way only work
3995 with Hardware Watchpoints.
3997 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3998 (see below). The @code{-location} argument tells @value{GDBN} to
3999 instead watch the memory referred to by @var{expr}. In this case,
4000 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4001 and watch the memory at that address. The type of the result is used
4002 to determine the size of the watched memory. If the expression's
4003 result does not have an address, then @value{GDBN} will print an
4006 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4007 of masked watchpoints, if the current architecture supports this
4008 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4009 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4010 to an address to watch. The mask specifies that some bits of an address
4011 (the bits which are reset in the mask) should be ignored when matching
4012 the address accessed by the inferior against the watchpoint address.
4013 Thus, a masked watchpoint watches many addresses simultaneously---those
4014 addresses whose unmasked bits are identical to the unmasked bits in the
4015 watchpoint address. The @code{mask} argument implies @code{-location}.
4019 (@value{GDBP}) watch foo mask 0xffff00ff
4020 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4024 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4025 Set a watchpoint that will break when the value of @var{expr} is read
4029 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4030 Set a watchpoint that will break when @var{expr} is either read from
4031 or written into by the program.
4033 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4034 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4035 This command prints a list of watchpoints, using the same format as
4036 @code{info break} (@pxref{Set Breaks}).
4039 If you watch for a change in a numerically entered address you need to
4040 dereference it, as the address itself is just a constant number which will
4041 never change. @value{GDBN} refuses to create a watchpoint that watches
4042 a never-changing value:
4045 (@value{GDBP}) watch 0x600850
4046 Cannot watch constant value 0x600850.
4047 (@value{GDBP}) watch *(int *) 0x600850
4048 Watchpoint 1: *(int *) 6293584
4051 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4052 watchpoints execute very quickly, and the debugger reports a change in
4053 value at the exact instruction where the change occurs. If @value{GDBN}
4054 cannot set a hardware watchpoint, it sets a software watchpoint, which
4055 executes more slowly and reports the change in value at the next
4056 @emph{statement}, not the instruction, after the change occurs.
4058 @cindex use only software watchpoints
4059 You can force @value{GDBN} to use only software watchpoints with the
4060 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4061 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4062 the underlying system supports them. (Note that hardware-assisted
4063 watchpoints that were set @emph{before} setting
4064 @code{can-use-hw-watchpoints} to zero will still use the hardware
4065 mechanism of watching expression values.)
4068 @item set can-use-hw-watchpoints
4069 @kindex set can-use-hw-watchpoints
4070 Set whether or not to use hardware watchpoints.
4072 @item show can-use-hw-watchpoints
4073 @kindex show can-use-hw-watchpoints
4074 Show the current mode of using hardware watchpoints.
4077 For remote targets, you can restrict the number of hardware
4078 watchpoints @value{GDBN} will use, see @ref{set remote
4079 hardware-breakpoint-limit}.
4081 When you issue the @code{watch} command, @value{GDBN} reports
4084 Hardware watchpoint @var{num}: @var{expr}
4088 if it was able to set a hardware watchpoint.
4090 Currently, the @code{awatch} and @code{rwatch} commands can only set
4091 hardware watchpoints, because accesses to data that don't change the
4092 value of the watched expression cannot be detected without examining
4093 every instruction as it is being executed, and @value{GDBN} does not do
4094 that currently. If @value{GDBN} finds that it is unable to set a
4095 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4096 will print a message like this:
4099 Expression cannot be implemented with read/access watchpoint.
4102 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4103 data type of the watched expression is wider than what a hardware
4104 watchpoint on the target machine can handle. For example, some systems
4105 can only watch regions that are up to 4 bytes wide; on such systems you
4106 cannot set hardware watchpoints for an expression that yields a
4107 double-precision floating-point number (which is typically 8 bytes
4108 wide). As a work-around, it might be possible to break the large region
4109 into a series of smaller ones and watch them with separate watchpoints.
4111 If you set too many hardware watchpoints, @value{GDBN} might be unable
4112 to insert all of them when you resume the execution of your program.
4113 Since the precise number of active watchpoints is unknown until such
4114 time as the program is about to be resumed, @value{GDBN} might not be
4115 able to warn you about this when you set the watchpoints, and the
4116 warning will be printed only when the program is resumed:
4119 Hardware watchpoint @var{num}: Could not insert watchpoint
4123 If this happens, delete or disable some of the watchpoints.
4125 Watching complex expressions that reference many variables can also
4126 exhaust the resources available for hardware-assisted watchpoints.
4127 That's because @value{GDBN} needs to watch every variable in the
4128 expression with separately allocated resources.
4130 If you call a function interactively using @code{print} or @code{call},
4131 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4132 kind of breakpoint or the call completes.
4134 @value{GDBN} automatically deletes watchpoints that watch local
4135 (automatic) variables, or expressions that involve such variables, when
4136 they go out of scope, that is, when the execution leaves the block in
4137 which these variables were defined. In particular, when the program
4138 being debugged terminates, @emph{all} local variables go out of scope,
4139 and so only watchpoints that watch global variables remain set. If you
4140 rerun the program, you will need to set all such watchpoints again. One
4141 way of doing that would be to set a code breakpoint at the entry to the
4142 @code{main} function and when it breaks, set all the watchpoints.
4144 @cindex watchpoints and threads
4145 @cindex threads and watchpoints
4146 In multi-threaded programs, watchpoints will detect changes to the
4147 watched expression from every thread.
4150 @emph{Warning:} In multi-threaded programs, software watchpoints
4151 have only limited usefulness. If @value{GDBN} creates a software
4152 watchpoint, it can only watch the value of an expression @emph{in a
4153 single thread}. If you are confident that the expression can only
4154 change due to the current thread's activity (and if you are also
4155 confident that no other thread can become current), then you can use
4156 software watchpoints as usual. However, @value{GDBN} may not notice
4157 when a non-current thread's activity changes the expression. (Hardware
4158 watchpoints, in contrast, watch an expression in all threads.)
4161 @xref{set remote hardware-watchpoint-limit}.
4163 @node Set Catchpoints
4164 @subsection Setting Catchpoints
4165 @cindex catchpoints, setting
4166 @cindex exception handlers
4167 @cindex event handling
4169 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4170 kinds of program events, such as C@t{++} exceptions or the loading of a
4171 shared library. Use the @code{catch} command to set a catchpoint.
4175 @item catch @var{event}
4176 Stop when @var{event} occurs. The @var{event} can be any of the following:
4179 @item throw @r{[}@var{regexp}@r{]}
4180 @itemx rethrow @r{[}@var{regexp}@r{]}
4181 @itemx catch @r{[}@var{regexp}@r{]}
4183 @kindex catch rethrow
4185 @cindex stop on C@t{++} exceptions
4186 The throwing, re-throwing, or catching of a C@t{++} exception.
4188 If @var{regexp} is given, then only exceptions whose type matches the
4189 regular expression will be caught.
4191 @vindex $_exception@r{, convenience variable}
4192 The convenience variable @code{$_exception} is available at an
4193 exception-related catchpoint, on some systems. This holds the
4194 exception being thrown.
4196 There are currently some limitations to C@t{++} exception handling in
4201 The support for these commands is system-dependent. Currently, only
4202 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4206 The regular expression feature and the @code{$_exception} convenience
4207 variable rely on the presence of some SDT probes in @code{libstdc++}.
4208 If these probes are not present, then these features cannot be used.
4209 These probes were first available in the GCC 4.8 release, but whether
4210 or not they are available in your GCC also depends on how it was
4214 The @code{$_exception} convenience variable is only valid at the
4215 instruction at which an exception-related catchpoint is set.
4218 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4219 location in the system library which implements runtime exception
4220 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4221 (@pxref{Selection}) to get to your code.
4224 If you call a function interactively, @value{GDBN} normally returns
4225 control to you when the function has finished executing. If the call
4226 raises an exception, however, the call may bypass the mechanism that
4227 returns control to you and cause your program either to abort or to
4228 simply continue running until it hits a breakpoint, catches a signal
4229 that @value{GDBN} is listening for, or exits. This is the case even if
4230 you set a catchpoint for the exception; catchpoints on exceptions are
4231 disabled within interactive calls. @xref{Calling}, for information on
4232 controlling this with @code{set unwind-on-terminating-exception}.
4235 You cannot raise an exception interactively.
4238 You cannot install an exception handler interactively.
4242 @kindex catch exception
4243 @cindex Ada exception catching
4244 @cindex catch Ada exceptions
4245 An Ada exception being raised. If an exception name is specified
4246 at the end of the command (eg @code{catch exception Program_Error}),
4247 the debugger will stop only when this specific exception is raised.
4248 Otherwise, the debugger stops execution when any Ada exception is raised.
4250 When inserting an exception catchpoint on a user-defined exception whose
4251 name is identical to one of the exceptions defined by the language, the
4252 fully qualified name must be used as the exception name. Otherwise,
4253 @value{GDBN} will assume that it should stop on the pre-defined exception
4254 rather than the user-defined one. For instance, assuming an exception
4255 called @code{Constraint_Error} is defined in package @code{Pck}, then
4256 the command to use to catch such exceptions is @kbd{catch exception
4257 Pck.Constraint_Error}.
4259 @item exception unhandled
4260 @kindex catch exception unhandled
4261 An exception that was raised but is not handled by the program.
4264 @kindex catch assert
4265 A failed Ada assertion.
4269 @cindex break on fork/exec
4270 A call to @code{exec}.
4273 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4274 @kindex catch syscall
4275 @cindex break on a system call.
4276 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4277 syscall is a mechanism for application programs to request a service
4278 from the operating system (OS) or one of the OS system services.
4279 @value{GDBN} can catch some or all of the syscalls issued by the
4280 debuggee, and show the related information for each syscall. If no
4281 argument is specified, calls to and returns from all system calls
4284 @var{name} can be any system call name that is valid for the
4285 underlying OS. Just what syscalls are valid depends on the OS. On
4286 GNU and Unix systems, you can find the full list of valid syscall
4287 names on @file{/usr/include/asm/unistd.h}.
4289 @c For MS-Windows, the syscall names and the corresponding numbers
4290 @c can be found, e.g., on this URL:
4291 @c http://www.metasploit.com/users/opcode/syscalls.html
4292 @c but we don't support Windows syscalls yet.
4294 Normally, @value{GDBN} knows in advance which syscalls are valid for
4295 each OS, so you can use the @value{GDBN} command-line completion
4296 facilities (@pxref{Completion,, command completion}) to list the
4299 You may also specify the system call numerically. A syscall's
4300 number is the value passed to the OS's syscall dispatcher to
4301 identify the requested service. When you specify the syscall by its
4302 name, @value{GDBN} uses its database of syscalls to convert the name
4303 into the corresponding numeric code, but using the number directly
4304 may be useful if @value{GDBN}'s database does not have the complete
4305 list of syscalls on your system (e.g., because @value{GDBN} lags
4306 behind the OS upgrades).
4308 The example below illustrates how this command works if you don't provide
4312 (@value{GDBP}) catch syscall
4313 Catchpoint 1 (syscall)
4315 Starting program: /tmp/catch-syscall
4317 Catchpoint 1 (call to syscall 'close'), \
4318 0xffffe424 in __kernel_vsyscall ()
4322 Catchpoint 1 (returned from syscall 'close'), \
4323 0xffffe424 in __kernel_vsyscall ()
4327 Here is an example of catching a system call by name:
4330 (@value{GDBP}) catch syscall chroot
4331 Catchpoint 1 (syscall 'chroot' [61])
4333 Starting program: /tmp/catch-syscall
4335 Catchpoint 1 (call to syscall 'chroot'), \
4336 0xffffe424 in __kernel_vsyscall ()
4340 Catchpoint 1 (returned from syscall 'chroot'), \
4341 0xffffe424 in __kernel_vsyscall ()
4345 An example of specifying a system call numerically. In the case
4346 below, the syscall number has a corresponding entry in the XML
4347 file, so @value{GDBN} finds its name and prints it:
4350 (@value{GDBP}) catch syscall 252
4351 Catchpoint 1 (syscall(s) 'exit_group')
4353 Starting program: /tmp/catch-syscall
4355 Catchpoint 1 (call to syscall 'exit_group'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 Program exited normally.
4364 However, there can be situations when there is no corresponding name
4365 in XML file for that syscall number. In this case, @value{GDBN} prints
4366 a warning message saying that it was not able to find the syscall name,
4367 but the catchpoint will be set anyway. See the example below:
4370 (@value{GDBP}) catch syscall 764
4371 warning: The number '764' does not represent a known syscall.
4372 Catchpoint 2 (syscall 764)
4376 If you configure @value{GDBN} using the @samp{--without-expat} option,
4377 it will not be able to display syscall names. Also, if your
4378 architecture does not have an XML file describing its system calls,
4379 you will not be able to see the syscall names. It is important to
4380 notice that these two features are used for accessing the syscall
4381 name database. In either case, you will see a warning like this:
4384 (@value{GDBP}) catch syscall
4385 warning: Could not open "syscalls/i386-linux.xml"
4386 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4387 GDB will not be able to display syscall names.
4388 Catchpoint 1 (syscall)
4392 Of course, the file name will change depending on your architecture and system.
4394 Still using the example above, you can also try to catch a syscall by its
4395 number. In this case, you would see something like:
4398 (@value{GDBP}) catch syscall 252
4399 Catchpoint 1 (syscall(s) 252)
4402 Again, in this case @value{GDBN} would not be able to display syscall's names.
4406 A call to @code{fork}.
4410 A call to @code{vfork}.
4412 @item load @r{[}regexp@r{]}
4413 @itemx unload @r{[}regexp@r{]}
4415 @kindex catch unload
4416 The loading or unloading of a shared library. If @var{regexp} is
4417 given, then the catchpoint will stop only if the regular expression
4418 matches one of the affected libraries.
4420 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4421 @kindex catch signal
4422 The delivery of a signal.
4424 With no arguments, this catchpoint will catch any signal that is not
4425 used internally by @value{GDBN}, specifically, all signals except
4426 @samp{SIGTRAP} and @samp{SIGINT}.
4428 With the argument @samp{all}, all signals, including those used by
4429 @value{GDBN}, will be caught. This argument cannot be used with other
4432 Otherwise, the arguments are a list of signal names as given to
4433 @code{handle} (@pxref{Signals}). Only signals specified in this list
4436 One reason that @code{catch signal} can be more useful than
4437 @code{handle} is that you can attach commands and conditions to the
4440 When a signal is caught by a catchpoint, the signal's @code{stop} and
4441 @code{print} settings, as specified by @code{handle}, are ignored.
4442 However, whether the signal is still delivered to the inferior depends
4443 on the @code{pass} setting; this can be changed in the catchpoint's
4448 @item tcatch @var{event}
4450 Set a catchpoint that is enabled only for one stop. The catchpoint is
4451 automatically deleted after the first time the event is caught.
4455 Use the @code{info break} command to list the current catchpoints.
4459 @subsection Deleting Breakpoints
4461 @cindex clearing breakpoints, watchpoints, catchpoints
4462 @cindex deleting breakpoints, watchpoints, catchpoints
4463 It is often necessary to eliminate a breakpoint, watchpoint, or
4464 catchpoint once it has done its job and you no longer want your program
4465 to stop there. This is called @dfn{deleting} the breakpoint. A
4466 breakpoint that has been deleted no longer exists; it is forgotten.
4468 With the @code{clear} command you can delete breakpoints according to
4469 where they are in your program. With the @code{delete} command you can
4470 delete individual breakpoints, watchpoints, or catchpoints by specifying
4471 their breakpoint numbers.
4473 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4474 automatically ignores breakpoints on the first instruction to be executed
4475 when you continue execution without changing the execution address.
4480 Delete any breakpoints at the next instruction to be executed in the
4481 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4482 the innermost frame is selected, this is a good way to delete a
4483 breakpoint where your program just stopped.
4485 @item clear @var{location}
4486 Delete any breakpoints set at the specified @var{location}.
4487 @xref{Specify Location}, for the various forms of @var{location}; the
4488 most useful ones are listed below:
4491 @item clear @var{function}
4492 @itemx clear @var{filename}:@var{function}
4493 Delete any breakpoints set at entry to the named @var{function}.
4495 @item clear @var{linenum}
4496 @itemx clear @var{filename}:@var{linenum}
4497 Delete any breakpoints set at or within the code of the specified
4498 @var{linenum} of the specified @var{filename}.
4501 @cindex delete breakpoints
4503 @kindex d @r{(@code{delete})}
4504 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4505 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4506 ranges specified as arguments. If no argument is specified, delete all
4507 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4508 confirm off}). You can abbreviate this command as @code{d}.
4512 @subsection Disabling Breakpoints
4514 @cindex enable/disable a breakpoint
4515 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4516 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4517 it had been deleted, but remembers the information on the breakpoint so
4518 that you can @dfn{enable} it again later.
4520 You disable and enable breakpoints, watchpoints, and catchpoints with
4521 the @code{enable} and @code{disable} commands, optionally specifying
4522 one or more breakpoint numbers as arguments. Use @code{info break} to
4523 print a list of all breakpoints, watchpoints, and catchpoints if you
4524 do not know which numbers to use.
4526 Disabling and enabling a breakpoint that has multiple locations
4527 affects all of its locations.
4529 A breakpoint, watchpoint, or catchpoint can have any of several
4530 different states of enablement:
4534 Enabled. The breakpoint stops your program. A breakpoint set
4535 with the @code{break} command starts out in this state.
4537 Disabled. The breakpoint has no effect on your program.
4539 Enabled once. The breakpoint stops your program, but then becomes
4542 Enabled for a count. The breakpoint stops your program for the next
4543 N times, then becomes disabled.
4545 Enabled for deletion. The breakpoint stops your program, but
4546 immediately after it does so it is deleted permanently. A breakpoint
4547 set with the @code{tbreak} command starts out in this state.
4550 You can use the following commands to enable or disable breakpoints,
4551 watchpoints, and catchpoints:
4555 @kindex dis @r{(@code{disable})}
4556 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4557 Disable the specified breakpoints---or all breakpoints, if none are
4558 listed. A disabled breakpoint has no effect but is not forgotten. All
4559 options such as ignore-counts, conditions and commands are remembered in
4560 case the breakpoint is enabled again later. You may abbreviate
4561 @code{disable} as @code{dis}.
4564 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4565 Enable the specified breakpoints (or all defined breakpoints). They
4566 become effective once again in stopping your program.
4568 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4569 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4570 of these breakpoints immediately after stopping your program.
4572 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4573 Enable the specified breakpoints temporarily. @value{GDBN} records
4574 @var{count} with each of the specified breakpoints, and decrements a
4575 breakpoint's count when it is hit. When any count reaches 0,
4576 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4577 count (@pxref{Conditions, ,Break Conditions}), that will be
4578 decremented to 0 before @var{count} is affected.
4580 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4581 Enable the specified breakpoints to work once, then die. @value{GDBN}
4582 deletes any of these breakpoints as soon as your program stops there.
4583 Breakpoints set by the @code{tbreak} command start out in this state.
4586 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4587 @c confusing: tbreak is also initially enabled.
4588 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4589 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4590 subsequently, they become disabled or enabled only when you use one of
4591 the commands above. (The command @code{until} can set and delete a
4592 breakpoint of its own, but it does not change the state of your other
4593 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4597 @subsection Break Conditions
4598 @cindex conditional breakpoints
4599 @cindex breakpoint conditions
4601 @c FIXME what is scope of break condition expr? Context where wanted?
4602 @c in particular for a watchpoint?
4603 The simplest sort of breakpoint breaks every time your program reaches a
4604 specified place. You can also specify a @dfn{condition} for a
4605 breakpoint. A condition is just a Boolean expression in your
4606 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4607 a condition evaluates the expression each time your program reaches it,
4608 and your program stops only if the condition is @emph{true}.
4610 This is the converse of using assertions for program validation; in that
4611 situation, you want to stop when the assertion is violated---that is,
4612 when the condition is false. In C, if you want to test an assertion expressed
4613 by the condition @var{assert}, you should set the condition
4614 @samp{! @var{assert}} on the appropriate breakpoint.
4616 Conditions are also accepted for watchpoints; you may not need them,
4617 since a watchpoint is inspecting the value of an expression anyhow---but
4618 it might be simpler, say, to just set a watchpoint on a variable name,
4619 and specify a condition that tests whether the new value is an interesting
4622 Break conditions can have side effects, and may even call functions in
4623 your program. This can be useful, for example, to activate functions
4624 that log program progress, or to use your own print functions to
4625 format special data structures. The effects are completely predictable
4626 unless there is another enabled breakpoint at the same address. (In
4627 that case, @value{GDBN} might see the other breakpoint first and stop your
4628 program without checking the condition of this one.) Note that
4629 breakpoint commands are usually more convenient and flexible than break
4631 purpose of performing side effects when a breakpoint is reached
4632 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4634 Breakpoint conditions can also be evaluated on the target's side if
4635 the target supports it. Instead of evaluating the conditions locally,
4636 @value{GDBN} encodes the expression into an agent expression
4637 (@pxref{Agent Expressions}) suitable for execution on the target,
4638 independently of @value{GDBN}. Global variables become raw memory
4639 locations, locals become stack accesses, and so forth.
4641 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4642 when its condition evaluates to true. This mechanism may provide faster
4643 response times depending on the performance characteristics of the target
4644 since it does not need to keep @value{GDBN} informed about
4645 every breakpoint trigger, even those with false conditions.
4647 Break conditions can be specified when a breakpoint is set, by using
4648 @samp{if} in the arguments to the @code{break} command. @xref{Set
4649 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4650 with the @code{condition} command.
4652 You can also use the @code{if} keyword with the @code{watch} command.
4653 The @code{catch} command does not recognize the @code{if} keyword;
4654 @code{condition} is the only way to impose a further condition on a
4659 @item condition @var{bnum} @var{expression}
4660 Specify @var{expression} as the break condition for breakpoint,
4661 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4662 breakpoint @var{bnum} stops your program only if the value of
4663 @var{expression} is true (nonzero, in C). When you use
4664 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4665 syntactic correctness, and to determine whether symbols in it have
4666 referents in the context of your breakpoint. If @var{expression} uses
4667 symbols not referenced in the context of the breakpoint, @value{GDBN}
4668 prints an error message:
4671 No symbol "foo" in current context.
4676 not actually evaluate @var{expression} at the time the @code{condition}
4677 command (or a command that sets a breakpoint with a condition, like
4678 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4680 @item condition @var{bnum}
4681 Remove the condition from breakpoint number @var{bnum}. It becomes
4682 an ordinary unconditional breakpoint.
4685 @cindex ignore count (of breakpoint)
4686 A special case of a breakpoint condition is to stop only when the
4687 breakpoint has been reached a certain number of times. This is so
4688 useful that there is a special way to do it, using the @dfn{ignore
4689 count} of the breakpoint. Every breakpoint has an ignore count, which
4690 is an integer. Most of the time, the ignore count is zero, and
4691 therefore has no effect. But if your program reaches a breakpoint whose
4692 ignore count is positive, then instead of stopping, it just decrements
4693 the ignore count by one and continues. As a result, if the ignore count
4694 value is @var{n}, the breakpoint does not stop the next @var{n} times
4695 your program reaches it.
4699 @item ignore @var{bnum} @var{count}
4700 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4701 The next @var{count} times the breakpoint is reached, your program's
4702 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4705 To make the breakpoint stop the next time it is reached, specify
4708 When you use @code{continue} to resume execution of your program from a
4709 breakpoint, you can specify an ignore count directly as an argument to
4710 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4711 Stepping,,Continuing and Stepping}.
4713 If a breakpoint has a positive ignore count and a condition, the
4714 condition is not checked. Once the ignore count reaches zero,
4715 @value{GDBN} resumes checking the condition.
4717 You could achieve the effect of the ignore count with a condition such
4718 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4719 is decremented each time. @xref{Convenience Vars, ,Convenience
4723 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4726 @node Break Commands
4727 @subsection Breakpoint Command Lists
4729 @cindex breakpoint commands
4730 You can give any breakpoint (or watchpoint or catchpoint) a series of
4731 commands to execute when your program stops due to that breakpoint. For
4732 example, you might want to print the values of certain expressions, or
4733 enable other breakpoints.
4737 @kindex end@r{ (breakpoint commands)}
4738 @item commands @r{[}@var{range}@dots{}@r{]}
4739 @itemx @dots{} @var{command-list} @dots{}
4741 Specify a list of commands for the given breakpoints. The commands
4742 themselves appear on the following lines. Type a line containing just
4743 @code{end} to terminate the commands.
4745 To remove all commands from a breakpoint, type @code{commands} and
4746 follow it immediately with @code{end}; that is, give no commands.
4748 With no argument, @code{commands} refers to the last breakpoint,
4749 watchpoint, or catchpoint set (not to the breakpoint most recently
4750 encountered). If the most recent breakpoints were set with a single
4751 command, then the @code{commands} will apply to all the breakpoints
4752 set by that command. This applies to breakpoints set by
4753 @code{rbreak}, and also applies when a single @code{break} command
4754 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4758 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4759 disabled within a @var{command-list}.
4761 You can use breakpoint commands to start your program up again. Simply
4762 use the @code{continue} command, or @code{step}, or any other command
4763 that resumes execution.
4765 Any other commands in the command list, after a command that resumes
4766 execution, are ignored. This is because any time you resume execution
4767 (even with a simple @code{next} or @code{step}), you may encounter
4768 another breakpoint---which could have its own command list, leading to
4769 ambiguities about which list to execute.
4772 If the first command you specify in a command list is @code{silent}, the
4773 usual message about stopping at a breakpoint is not printed. This may
4774 be desirable for breakpoints that are to print a specific message and
4775 then continue. If none of the remaining commands print anything, you
4776 see no sign that the breakpoint was reached. @code{silent} is
4777 meaningful only at the beginning of a breakpoint command list.
4779 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4780 print precisely controlled output, and are often useful in silent
4781 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4783 For example, here is how you could use breakpoint commands to print the
4784 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4790 printf "x is %d\n",x
4795 One application for breakpoint commands is to compensate for one bug so
4796 you can test for another. Put a breakpoint just after the erroneous line
4797 of code, give it a condition to detect the case in which something
4798 erroneous has been done, and give it commands to assign correct values
4799 to any variables that need them. End with the @code{continue} command
4800 so that your program does not stop, and start with the @code{silent}
4801 command so that no output is produced. Here is an example:
4812 @node Dynamic Printf
4813 @subsection Dynamic Printf
4815 @cindex dynamic printf
4817 The dynamic printf command @code{dprintf} combines a breakpoint with
4818 formatted printing of your program's data to give you the effect of
4819 inserting @code{printf} calls into your program on-the-fly, without
4820 having to recompile it.
4822 In its most basic form, the output goes to the GDB console. However,
4823 you can set the variable @code{dprintf-style} for alternate handling.
4824 For instance, you can ask to format the output by calling your
4825 program's @code{printf} function. This has the advantage that the
4826 characters go to the program's output device, so they can recorded in
4827 redirects to files and so forth.
4829 If you are doing remote debugging with a stub or agent, you can also
4830 ask to have the printf handled by the remote agent. In addition to
4831 ensuring that the output goes to the remote program's device along
4832 with any other output the program might produce, you can also ask that
4833 the dprintf remain active even after disconnecting from the remote
4834 target. Using the stub/agent is also more efficient, as it can do
4835 everything without needing to communicate with @value{GDBN}.
4839 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4840 Whenever execution reaches @var{location}, print the values of one or
4841 more @var{expressions} under the control of the string @var{template}.
4842 To print several values, separate them with commas.
4844 @item set dprintf-style @var{style}
4845 Set the dprintf output to be handled in one of several different
4846 styles enumerated below. A change of style affects all existing
4847 dynamic printfs immediately. (If you need individual control over the
4848 print commands, simply define normal breakpoints with
4849 explicitly-supplied command lists.)
4852 @kindex dprintf-style gdb
4853 Handle the output using the @value{GDBN} @code{printf} command.
4856 @kindex dprintf-style call
4857 Handle the output by calling a function in your program (normally
4861 @kindex dprintf-style agent
4862 Have the remote debugging agent (such as @code{gdbserver}) handle
4863 the output itself. This style is only available for agents that
4864 support running commands on the target.
4866 @item set dprintf-function @var{function}
4867 Set the function to call if the dprintf style is @code{call}. By
4868 default its value is @code{printf}. You may set it to any expression.
4869 that @value{GDBN} can evaluate to a function, as per the @code{call}
4872 @item set dprintf-channel @var{channel}
4873 Set a ``channel'' for dprintf. If set to a non-empty value,
4874 @value{GDBN} will evaluate it as an expression and pass the result as
4875 a first argument to the @code{dprintf-function}, in the manner of
4876 @code{fprintf} and similar functions. Otherwise, the dprintf format
4877 string will be the first argument, in the manner of @code{printf}.
4879 As an example, if you wanted @code{dprintf} output to go to a logfile
4880 that is a standard I/O stream assigned to the variable @code{mylog},
4881 you could do the following:
4884 (gdb) set dprintf-style call
4885 (gdb) set dprintf-function fprintf
4886 (gdb) set dprintf-channel mylog
4887 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4888 Dprintf 1 at 0x123456: file main.c, line 25.
4890 1 dprintf keep y 0x00123456 in main at main.c:25
4891 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4896 Note that the @code{info break} displays the dynamic printf commands
4897 as normal breakpoint commands; you can thus easily see the effect of
4898 the variable settings.
4900 @item set disconnected-dprintf on
4901 @itemx set disconnected-dprintf off
4902 @kindex set disconnected-dprintf
4903 Choose whether @code{dprintf} commands should continue to run if
4904 @value{GDBN} has disconnected from the target. This only applies
4905 if the @code{dprintf-style} is @code{agent}.
4907 @item show disconnected-dprintf off
4908 @kindex show disconnected-dprintf
4909 Show the current choice for disconnected @code{dprintf}.
4913 @value{GDBN} does not check the validity of function and channel,
4914 relying on you to supply values that are meaningful for the contexts
4915 in which they are being used. For instance, the function and channel
4916 may be the values of local variables, but if that is the case, then
4917 all enabled dynamic prints must be at locations within the scope of
4918 those locals. If evaluation fails, @value{GDBN} will report an error.
4920 @node Save Breakpoints
4921 @subsection How to save breakpoints to a file
4923 To save breakpoint definitions to a file use the @w{@code{save
4924 breakpoints}} command.
4927 @kindex save breakpoints
4928 @cindex save breakpoints to a file for future sessions
4929 @item save breakpoints [@var{filename}]
4930 This command saves all current breakpoint definitions together with
4931 their commands and ignore counts, into a file @file{@var{filename}}
4932 suitable for use in a later debugging session. This includes all
4933 types of breakpoints (breakpoints, watchpoints, catchpoints,
4934 tracepoints). To read the saved breakpoint definitions, use the
4935 @code{source} command (@pxref{Command Files}). Note that watchpoints
4936 with expressions involving local variables may fail to be recreated
4937 because it may not be possible to access the context where the
4938 watchpoint is valid anymore. Because the saved breakpoint definitions
4939 are simply a sequence of @value{GDBN} commands that recreate the
4940 breakpoints, you can edit the file in your favorite editing program,
4941 and remove the breakpoint definitions you're not interested in, or
4942 that can no longer be recreated.
4945 @node Static Probe Points
4946 @subsection Static Probe Points
4948 @cindex static probe point, SystemTap
4949 @cindex static probe point, DTrace
4950 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4951 for Statically Defined Tracing, and the probes are designed to have a tiny
4952 runtime code and data footprint, and no dynamic relocations.
4954 Currently, the following types of probes are supported on
4955 ELF-compatible systems:
4959 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4960 @acronym{SDT} probes@footnote{See
4961 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4962 for more information on how to add @code{SystemTap} @acronym{SDT}
4963 probes in your applications.}. @code{SystemTap} probes are usable
4964 from assembly, C and C@t{++} languages@footnote{See
4965 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4966 for a good reference on how the @acronym{SDT} probes are implemented.}.
4968 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4969 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4973 @cindex semaphores on static probe points
4974 Some @code{SystemTap} probes have an associated semaphore variable;
4975 for instance, this happens automatically if you defined your probe
4976 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4977 @value{GDBN} will automatically enable it when you specify a
4978 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4979 breakpoint at a probe's location by some other method (e.g.,
4980 @code{break file:line}), then @value{GDBN} will not automatically set
4981 the semaphore. @code{DTrace} probes do not support semaphores.
4983 You can examine the available static static probes using @code{info
4984 probes}, with optional arguments:
4988 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4989 If given, @var{type} is either @code{stap} for listing
4990 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
4991 probes. If omitted all probes are listed regardless of their types.
4993 If given, @var{provider} is a regular expression used to match against provider
4994 names when selecting which probes to list. If omitted, probes by all
4995 probes from all providers are listed.
4997 If given, @var{name} is a regular expression to match against probe names
4998 when selecting which probes to list. If omitted, probe names are not
4999 considered when deciding whether to display them.
5001 If given, @var{objfile} is a regular expression used to select which
5002 object files (executable or shared libraries) to examine. If not
5003 given, all object files are considered.
5005 @item info probes all
5006 List the available static probes, from all types.
5009 @cindex enabling and disabling probes
5010 Some probe points can be enabled and/or disabled. The effect of
5011 enabling or disabling a probe depends on the type of probe being
5012 handled. Some @code{DTrace} probes can be enabled or
5013 disabled, but @code{SystemTap} probes cannot be disabled.
5015 You can enable (or disable) one or more probes using the following
5016 commands, with optional arguments:
5019 @kindex enable probes
5020 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5021 If given, @var{provider} is a regular expression used to match against
5022 provider names when selecting which probes to enable. If omitted,
5023 all probes from all providers are enabled.
5025 If given, @var{name} is a regular expression to match against probe
5026 names when selecting which probes to enable. If omitted, probe names
5027 are not considered when deciding whether to enable them.
5029 If given, @var{objfile} is a regular expression used to select which
5030 object files (executable or shared libraries) to examine. If not
5031 given, all object files are considered.
5033 @kindex disable probes
5034 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5035 See the @code{enable probes} command above for a description of the
5036 optional arguments accepted by this command.
5039 @vindex $_probe_arg@r{, convenience variable}
5040 A probe may specify up to twelve arguments. These are available at the
5041 point at which the probe is defined---that is, when the current PC is
5042 at the probe's location. The arguments are available using the
5043 convenience variables (@pxref{Convenience Vars})
5044 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5045 probes each probe argument is an integer of the appropriate size;
5046 types are not preserved. In @code{DTrace} probes types are preserved
5047 provided that they are recognized as such by @value{GDBN}; otherwise
5048 the value of the probe argument will be a long integer. The
5049 convenience variable @code{$_probe_argc} holds the number of arguments
5050 at the current probe point.
5052 These variables are always available, but attempts to access them at
5053 any location other than a probe point will cause @value{GDBN} to give
5057 @c @ifclear BARETARGET
5058 @node Error in Breakpoints
5059 @subsection ``Cannot insert breakpoints''
5061 If you request too many active hardware-assisted breakpoints and
5062 watchpoints, you will see this error message:
5064 @c FIXME: the precise wording of this message may change; the relevant
5065 @c source change is not committed yet (Sep 3, 1999).
5067 Stopped; cannot insert breakpoints.
5068 You may have requested too many hardware breakpoints and watchpoints.
5072 This message is printed when you attempt to resume the program, since
5073 only then @value{GDBN} knows exactly how many hardware breakpoints and
5074 watchpoints it needs to insert.
5076 When this message is printed, you need to disable or remove some of the
5077 hardware-assisted breakpoints and watchpoints, and then continue.
5079 @node Breakpoint-related Warnings
5080 @subsection ``Breakpoint address adjusted...''
5081 @cindex breakpoint address adjusted
5083 Some processor architectures place constraints on the addresses at
5084 which breakpoints may be placed. For architectures thus constrained,
5085 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5086 with the constraints dictated by the architecture.
5088 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5089 a VLIW architecture in which a number of RISC-like instructions may be
5090 bundled together for parallel execution. The FR-V architecture
5091 constrains the location of a breakpoint instruction within such a
5092 bundle to the instruction with the lowest address. @value{GDBN}
5093 honors this constraint by adjusting a breakpoint's address to the
5094 first in the bundle.
5096 It is not uncommon for optimized code to have bundles which contain
5097 instructions from different source statements, thus it may happen that
5098 a breakpoint's address will be adjusted from one source statement to
5099 another. Since this adjustment may significantly alter @value{GDBN}'s
5100 breakpoint related behavior from what the user expects, a warning is
5101 printed when the breakpoint is first set and also when the breakpoint
5104 A warning like the one below is printed when setting a breakpoint
5105 that's been subject to address adjustment:
5108 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5111 Such warnings are printed both for user settable and @value{GDBN}'s
5112 internal breakpoints. If you see one of these warnings, you should
5113 verify that a breakpoint set at the adjusted address will have the
5114 desired affect. If not, the breakpoint in question may be removed and
5115 other breakpoints may be set which will have the desired behavior.
5116 E.g., it may be sufficient to place the breakpoint at a later
5117 instruction. A conditional breakpoint may also be useful in some
5118 cases to prevent the breakpoint from triggering too often.
5120 @value{GDBN} will also issue a warning when stopping at one of these
5121 adjusted breakpoints:
5124 warning: Breakpoint 1 address previously adjusted from 0x00010414
5128 When this warning is encountered, it may be too late to take remedial
5129 action except in cases where the breakpoint is hit earlier or more
5130 frequently than expected.
5132 @node Continuing and Stepping
5133 @section Continuing and Stepping
5137 @cindex resuming execution
5138 @dfn{Continuing} means resuming program execution until your program
5139 completes normally. In contrast, @dfn{stepping} means executing just
5140 one more ``step'' of your program, where ``step'' may mean either one
5141 line of source code, or one machine instruction (depending on what
5142 particular command you use). Either when continuing or when stepping,
5143 your program may stop even sooner, due to a breakpoint or a signal. (If
5144 it stops due to a signal, you may want to use @code{handle}, or use
5145 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5146 or you may step into the signal's handler (@pxref{stepping and signal
5151 @kindex c @r{(@code{continue})}
5152 @kindex fg @r{(resume foreground execution)}
5153 @item continue @r{[}@var{ignore-count}@r{]}
5154 @itemx c @r{[}@var{ignore-count}@r{]}
5155 @itemx fg @r{[}@var{ignore-count}@r{]}
5156 Resume program execution, at the address where your program last stopped;
5157 any breakpoints set at that address are bypassed. The optional argument
5158 @var{ignore-count} allows you to specify a further number of times to
5159 ignore a breakpoint at this location; its effect is like that of
5160 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5162 The argument @var{ignore-count} is meaningful only when your program
5163 stopped due to a breakpoint. At other times, the argument to
5164 @code{continue} is ignored.
5166 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5167 debugged program is deemed to be the foreground program) are provided
5168 purely for convenience, and have exactly the same behavior as
5172 To resume execution at a different place, you can use @code{return}
5173 (@pxref{Returning, ,Returning from a Function}) to go back to the
5174 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5175 Different Address}) to go to an arbitrary location in your program.
5177 A typical technique for using stepping is to set a breakpoint
5178 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5179 beginning of the function or the section of your program where a problem
5180 is believed to lie, run your program until it stops at that breakpoint,
5181 and then step through the suspect area, examining the variables that are
5182 interesting, until you see the problem happen.
5186 @kindex s @r{(@code{step})}
5188 Continue running your program until control reaches a different source
5189 line, then stop it and return control to @value{GDBN}. This command is
5190 abbreviated @code{s}.
5193 @c "without debugging information" is imprecise; actually "without line
5194 @c numbers in the debugging information". (gcc -g1 has debugging info but
5195 @c not line numbers). But it seems complex to try to make that
5196 @c distinction here.
5197 @emph{Warning:} If you use the @code{step} command while control is
5198 within a function that was compiled without debugging information,
5199 execution proceeds until control reaches a function that does have
5200 debugging information. Likewise, it will not step into a function which
5201 is compiled without debugging information. To step through functions
5202 without debugging information, use the @code{stepi} command, described
5206 The @code{step} command only stops at the first instruction of a source
5207 line. This prevents the multiple stops that could otherwise occur in
5208 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5209 to stop if a function that has debugging information is called within
5210 the line. In other words, @code{step} @emph{steps inside} any functions
5211 called within the line.
5213 Also, the @code{step} command only enters a function if there is line
5214 number information for the function. Otherwise it acts like the
5215 @code{next} command. This avoids problems when using @code{cc -gl}
5216 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5217 was any debugging information about the routine.
5219 @item step @var{count}
5220 Continue running as in @code{step}, but do so @var{count} times. If a
5221 breakpoint is reached, or a signal not related to stepping occurs before
5222 @var{count} steps, stepping stops right away.
5225 @kindex n @r{(@code{next})}
5226 @item next @r{[}@var{count}@r{]}
5227 Continue to the next source line in the current (innermost) stack frame.
5228 This is similar to @code{step}, but function calls that appear within
5229 the line of code are executed without stopping. Execution stops when
5230 control reaches a different line of code at the original stack level
5231 that was executing when you gave the @code{next} command. This command
5232 is abbreviated @code{n}.
5234 An argument @var{count} is a repeat count, as for @code{step}.
5237 @c FIX ME!! Do we delete this, or is there a way it fits in with
5238 @c the following paragraph? --- Vctoria
5240 @c @code{next} within a function that lacks debugging information acts like
5241 @c @code{step}, but any function calls appearing within the code of the
5242 @c function are executed without stopping.
5244 The @code{next} command only stops at the first instruction of a
5245 source line. This prevents multiple stops that could otherwise occur in
5246 @code{switch} statements, @code{for} loops, etc.
5248 @kindex set step-mode
5250 @cindex functions without line info, and stepping
5251 @cindex stepping into functions with no line info
5252 @itemx set step-mode on
5253 The @code{set step-mode on} command causes the @code{step} command to
5254 stop at the first instruction of a function which contains no debug line
5255 information rather than stepping over it.
5257 This is useful in cases where you may be interested in inspecting the
5258 machine instructions of a function which has no symbolic info and do not
5259 want @value{GDBN} to automatically skip over this function.
5261 @item set step-mode off
5262 Causes the @code{step} command to step over any functions which contains no
5263 debug information. This is the default.
5265 @item show step-mode
5266 Show whether @value{GDBN} will stop in or step over functions without
5267 source line debug information.
5270 @kindex fin @r{(@code{finish})}
5272 Continue running until just after function in the selected stack frame
5273 returns. Print the returned value (if any). This command can be
5274 abbreviated as @code{fin}.
5276 Contrast this with the @code{return} command (@pxref{Returning,
5277 ,Returning from a Function}).
5280 @kindex u @r{(@code{until})}
5281 @cindex run until specified location
5284 Continue running until a source line past the current line, in the
5285 current stack frame, is reached. This command is used to avoid single
5286 stepping through a loop more than once. It is like the @code{next}
5287 command, except that when @code{until} encounters a jump, it
5288 automatically continues execution until the program counter is greater
5289 than the address of the jump.
5291 This means that when you reach the end of a loop after single stepping
5292 though it, @code{until} makes your program continue execution until it
5293 exits the loop. In contrast, a @code{next} command at the end of a loop
5294 simply steps back to the beginning of the loop, which forces you to step
5295 through the next iteration.
5297 @code{until} always stops your program if it attempts to exit the current
5300 @code{until} may produce somewhat counterintuitive results if the order
5301 of machine code does not match the order of the source lines. For
5302 example, in the following excerpt from a debugging session, the @code{f}
5303 (@code{frame}) command shows that execution is stopped at line
5304 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5308 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5310 (@value{GDBP}) until
5311 195 for ( ; argc > 0; NEXTARG) @{
5314 This happened because, for execution efficiency, the compiler had
5315 generated code for the loop closure test at the end, rather than the
5316 start, of the loop---even though the test in a C @code{for}-loop is
5317 written before the body of the loop. The @code{until} command appeared
5318 to step back to the beginning of the loop when it advanced to this
5319 expression; however, it has not really gone to an earlier
5320 statement---not in terms of the actual machine code.
5322 @code{until} with no argument works by means of single
5323 instruction stepping, and hence is slower than @code{until} with an
5326 @item until @var{location}
5327 @itemx u @var{location}
5328 Continue running your program until either the specified @var{location} is
5329 reached, or the current stack frame returns. The location is any of
5330 the forms described in @ref{Specify Location}.
5331 This form of the command uses temporary breakpoints, and
5332 hence is quicker than @code{until} without an argument. The specified
5333 location is actually reached only if it is in the current frame. This
5334 implies that @code{until} can be used to skip over recursive function
5335 invocations. For instance in the code below, if the current location is
5336 line @code{96}, issuing @code{until 99} will execute the program up to
5337 line @code{99} in the same invocation of factorial, i.e., after the inner
5338 invocations have returned.
5341 94 int factorial (int value)
5343 96 if (value > 1) @{
5344 97 value *= factorial (value - 1);
5351 @kindex advance @var{location}
5352 @item advance @var{location}
5353 Continue running the program up to the given @var{location}. An argument is
5354 required, which should be of one of the forms described in
5355 @ref{Specify Location}.
5356 Execution will also stop upon exit from the current stack
5357 frame. This command is similar to @code{until}, but @code{advance} will
5358 not skip over recursive function calls, and the target location doesn't
5359 have to be in the same frame as the current one.
5363 @kindex si @r{(@code{stepi})}
5365 @itemx stepi @var{arg}
5367 Execute one machine instruction, then stop and return to the debugger.
5369 It is often useful to do @samp{display/i $pc} when stepping by machine
5370 instructions. This makes @value{GDBN} automatically display the next
5371 instruction to be executed, each time your program stops. @xref{Auto
5372 Display,, Automatic Display}.
5374 An argument is a repeat count, as in @code{step}.
5378 @kindex ni @r{(@code{nexti})}
5380 @itemx nexti @var{arg}
5382 Execute one machine instruction, but if it is a function call,
5383 proceed until the function returns.
5385 An argument is a repeat count, as in @code{next}.
5389 @anchor{range stepping}
5390 @cindex range stepping
5391 @cindex target-assisted range stepping
5392 By default, and if available, @value{GDBN} makes use of
5393 target-assisted @dfn{range stepping}. In other words, whenever you
5394 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5395 tells the target to step the corresponding range of instruction
5396 addresses instead of issuing multiple single-steps. This speeds up
5397 line stepping, particularly for remote targets. Ideally, there should
5398 be no reason you would want to turn range stepping off. However, it's
5399 possible that a bug in the debug info, a bug in the remote stub (for
5400 remote targets), or even a bug in @value{GDBN} could make line
5401 stepping behave incorrectly when target-assisted range stepping is
5402 enabled. You can use the following command to turn off range stepping
5406 @kindex set range-stepping
5407 @kindex show range-stepping
5408 @item set range-stepping
5409 @itemx show range-stepping
5410 Control whether range stepping is enabled.
5412 If @code{on}, and the target supports it, @value{GDBN} tells the
5413 target to step a range of addresses itself, instead of issuing
5414 multiple single-steps. If @code{off}, @value{GDBN} always issues
5415 single-steps, even if range stepping is supported by the target. The
5416 default is @code{on}.
5420 @node Skipping Over Functions and Files
5421 @section Skipping Over Functions and Files
5422 @cindex skipping over functions and files
5424 The program you are debugging may contain some functions which are
5425 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5426 skip a function or all functions in a file when stepping.
5428 For example, consider the following C function:
5439 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5440 are not interested in stepping through @code{boring}. If you run @code{step}
5441 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5442 step over both @code{foo} and @code{boring}!
5444 One solution is to @code{step} into @code{boring} and use the @code{finish}
5445 command to immediately exit it. But this can become tedious if @code{boring}
5446 is called from many places.
5448 A more flexible solution is to execute @kbd{skip boring}. This instructs
5449 @value{GDBN} never to step into @code{boring}. Now when you execute
5450 @code{step} at line 103, you'll step over @code{boring} and directly into
5453 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5454 example, @code{skip file boring.c}.
5457 @kindex skip function
5458 @item skip @r{[}@var{linespec}@r{]}
5459 @itemx skip function @r{[}@var{linespec}@r{]}
5460 After running this command, the function named by @var{linespec} or the
5461 function containing the line named by @var{linespec} will be skipped over when
5462 stepping. @xref{Specify Location}.
5464 If you do not specify @var{linespec}, the function you're currently debugging
5467 (If you have a function called @code{file} that you want to skip, use
5468 @kbd{skip function file}.)
5471 @item skip file @r{[}@var{filename}@r{]}
5472 After running this command, any function whose source lives in @var{filename}
5473 will be skipped over when stepping.
5475 If you do not specify @var{filename}, functions whose source lives in the file
5476 you're currently debugging will be skipped.
5479 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5480 These are the commands for managing your list of skips:
5484 @item info skip @r{[}@var{range}@r{]}
5485 Print details about the specified skip(s). If @var{range} is not specified,
5486 print a table with details about all functions and files marked for skipping.
5487 @code{info skip} prints the following information about each skip:
5491 A number identifying this skip.
5493 The type of this skip, either @samp{function} or @samp{file}.
5494 @item Enabled or Disabled
5495 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5497 For function skips, this column indicates the address in memory of the function
5498 being skipped. If you've set a function skip on a function which has not yet
5499 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5500 which has the function is loaded, @code{info skip} will show the function's
5503 For file skips, this field contains the filename being skipped. For functions
5504 skips, this field contains the function name and its line number in the file
5505 where it is defined.
5509 @item skip delete @r{[}@var{range}@r{]}
5510 Delete the specified skip(s). If @var{range} is not specified, delete all
5514 @item skip enable @r{[}@var{range}@r{]}
5515 Enable the specified skip(s). If @var{range} is not specified, enable all
5518 @kindex skip disable
5519 @item skip disable @r{[}@var{range}@r{]}
5520 Disable the specified skip(s). If @var{range} is not specified, disable all
5529 A signal is an asynchronous event that can happen in a program. The
5530 operating system defines the possible kinds of signals, and gives each
5531 kind a name and a number. For example, in Unix @code{SIGINT} is the
5532 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5533 @code{SIGSEGV} is the signal a program gets from referencing a place in
5534 memory far away from all the areas in use; @code{SIGALRM} occurs when
5535 the alarm clock timer goes off (which happens only if your program has
5536 requested an alarm).
5538 @cindex fatal signals
5539 Some signals, including @code{SIGALRM}, are a normal part of the
5540 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5541 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5542 program has not specified in advance some other way to handle the signal.
5543 @code{SIGINT} does not indicate an error in your program, but it is normally
5544 fatal so it can carry out the purpose of the interrupt: to kill the program.
5546 @value{GDBN} has the ability to detect any occurrence of a signal in your
5547 program. You can tell @value{GDBN} in advance what to do for each kind of
5550 @cindex handling signals
5551 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5552 @code{SIGALRM} be silently passed to your program
5553 (so as not to interfere with their role in the program's functioning)
5554 but to stop your program immediately whenever an error signal happens.
5555 You can change these settings with the @code{handle} command.
5558 @kindex info signals
5562 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5563 handle each one. You can use this to see the signal numbers of all
5564 the defined types of signals.
5566 @item info signals @var{sig}
5567 Similar, but print information only about the specified signal number.
5569 @code{info handle} is an alias for @code{info signals}.
5571 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5572 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5573 for details about this command.
5576 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5577 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5578 can be the number of a signal or its name (with or without the
5579 @samp{SIG} at the beginning); a list of signal numbers of the form
5580 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5581 known signals. Optional arguments @var{keywords}, described below,
5582 say what change to make.
5586 The keywords allowed by the @code{handle} command can be abbreviated.
5587 Their full names are:
5591 @value{GDBN} should not stop your program when this signal happens. It may
5592 still print a message telling you that the signal has come in.
5595 @value{GDBN} should stop your program when this signal happens. This implies
5596 the @code{print} keyword as well.
5599 @value{GDBN} should print a message when this signal happens.
5602 @value{GDBN} should not mention the occurrence of the signal at all. This
5603 implies the @code{nostop} keyword as well.
5607 @value{GDBN} should allow your program to see this signal; your program
5608 can handle the signal, or else it may terminate if the signal is fatal
5609 and not handled. @code{pass} and @code{noignore} are synonyms.
5613 @value{GDBN} should not allow your program to see this signal.
5614 @code{nopass} and @code{ignore} are synonyms.
5618 When a signal stops your program, the signal is not visible to the
5620 continue. Your program sees the signal then, if @code{pass} is in
5621 effect for the signal in question @emph{at that time}. In other words,
5622 after @value{GDBN} reports a signal, you can use the @code{handle}
5623 command with @code{pass} or @code{nopass} to control whether your
5624 program sees that signal when you continue.
5626 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5627 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5628 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5631 You can also use the @code{signal} command to prevent your program from
5632 seeing a signal, or cause it to see a signal it normally would not see,
5633 or to give it any signal at any time. For example, if your program stopped
5634 due to some sort of memory reference error, you might store correct
5635 values into the erroneous variables and continue, hoping to see more
5636 execution; but your program would probably terminate immediately as
5637 a result of the fatal signal once it saw the signal. To prevent this,
5638 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5641 @cindex stepping and signal handlers
5642 @anchor{stepping and signal handlers}
5644 @value{GDBN} optimizes for stepping the mainline code. If a signal
5645 that has @code{handle nostop} and @code{handle pass} set arrives while
5646 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5647 in progress, @value{GDBN} lets the signal handler run and then resumes
5648 stepping the mainline code once the signal handler returns. In other
5649 words, @value{GDBN} steps over the signal handler. This prevents
5650 signals that you've specified as not interesting (with @code{handle
5651 nostop}) from changing the focus of debugging unexpectedly. Note that
5652 the signal handler itself may still hit a breakpoint, stop for another
5653 signal that has @code{handle stop} in effect, or for any other event
5654 that normally results in stopping the stepping command sooner. Also
5655 note that @value{GDBN} still informs you that the program received a
5656 signal if @code{handle print} is set.
5658 @anchor{stepping into signal handlers}
5660 If you set @code{handle pass} for a signal, and your program sets up a
5661 handler for it, then issuing a stepping command, such as @code{step}
5662 or @code{stepi}, when your program is stopped due to the signal will
5663 step @emph{into} the signal handler (if the target supports that).
5665 Likewise, if you use the @code{queue-signal} command to queue a signal
5666 to be delivered to the current thread when execution of the thread
5667 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5668 stepping command will step into the signal handler.
5670 Here's an example, using @code{stepi} to step to the first instruction
5671 of @code{SIGUSR1}'s handler:
5674 (@value{GDBP}) handle SIGUSR1
5675 Signal Stop Print Pass to program Description
5676 SIGUSR1 Yes Yes Yes User defined signal 1
5680 Program received signal SIGUSR1, User defined signal 1.
5681 main () sigusr1.c:28
5684 sigusr1_handler () at sigusr1.c:9
5688 The same, but using @code{queue-signal} instead of waiting for the
5689 program to receive the signal first:
5694 (@value{GDBP}) queue-signal SIGUSR1
5696 sigusr1_handler () at sigusr1.c:9
5701 @cindex extra signal information
5702 @anchor{extra signal information}
5704 On some targets, @value{GDBN} can inspect extra signal information
5705 associated with the intercepted signal, before it is actually
5706 delivered to the program being debugged. This information is exported
5707 by the convenience variable @code{$_siginfo}, and consists of data
5708 that is passed by the kernel to the signal handler at the time of the
5709 receipt of a signal. The data type of the information itself is
5710 target dependent. You can see the data type using the @code{ptype
5711 $_siginfo} command. On Unix systems, it typically corresponds to the
5712 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5715 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5716 referenced address that raised a segmentation fault.
5720 (@value{GDBP}) continue
5721 Program received signal SIGSEGV, Segmentation fault.
5722 0x0000000000400766 in main ()
5724 (@value{GDBP}) ptype $_siginfo
5731 struct @{...@} _kill;
5732 struct @{...@} _timer;
5734 struct @{...@} _sigchld;
5735 struct @{...@} _sigfault;
5736 struct @{...@} _sigpoll;
5739 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5743 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5744 $1 = (void *) 0x7ffff7ff7000
5748 Depending on target support, @code{$_siginfo} may also be writable.
5751 @section Stopping and Starting Multi-thread Programs
5753 @cindex stopped threads
5754 @cindex threads, stopped
5756 @cindex continuing threads
5757 @cindex threads, continuing
5759 @value{GDBN} supports debugging programs with multiple threads
5760 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5761 are two modes of controlling execution of your program within the
5762 debugger. In the default mode, referred to as @dfn{all-stop mode},
5763 when any thread in your program stops (for example, at a breakpoint
5764 or while being stepped), all other threads in the program are also stopped by
5765 @value{GDBN}. On some targets, @value{GDBN} also supports
5766 @dfn{non-stop mode}, in which other threads can continue to run freely while
5767 you examine the stopped thread in the debugger.
5770 * All-Stop Mode:: All threads stop when GDB takes control
5771 * Non-Stop Mode:: Other threads continue to execute
5772 * Background Execution:: Running your program asynchronously
5773 * Thread-Specific Breakpoints:: Controlling breakpoints
5774 * Interrupted System Calls:: GDB may interfere with system calls
5775 * Observer Mode:: GDB does not alter program behavior
5779 @subsection All-Stop Mode
5781 @cindex all-stop mode
5783 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5784 @emph{all} threads of execution stop, not just the current thread. This
5785 allows you to examine the overall state of the program, including
5786 switching between threads, without worrying that things may change
5789 Conversely, whenever you restart the program, @emph{all} threads start
5790 executing. @emph{This is true even when single-stepping} with commands
5791 like @code{step} or @code{next}.
5793 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5794 Since thread scheduling is up to your debugging target's operating
5795 system (not controlled by @value{GDBN}), other threads may
5796 execute more than one statement while the current thread completes a
5797 single step. Moreover, in general other threads stop in the middle of a
5798 statement, rather than at a clean statement boundary, when the program
5801 You might even find your program stopped in another thread after
5802 continuing or even single-stepping. This happens whenever some other
5803 thread runs into a breakpoint, a signal, or an exception before the
5804 first thread completes whatever you requested.
5806 @cindex automatic thread selection
5807 @cindex switching threads automatically
5808 @cindex threads, automatic switching
5809 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5810 signal, it automatically selects the thread where that breakpoint or
5811 signal happened. @value{GDBN} alerts you to the context switch with a
5812 message such as @samp{[Switching to Thread @var{n}]} to identify the
5815 On some OSes, you can modify @value{GDBN}'s default behavior by
5816 locking the OS scheduler to allow only a single thread to run.
5819 @item set scheduler-locking @var{mode}
5820 @cindex scheduler locking mode
5821 @cindex lock scheduler
5822 Set the scheduler locking mode. It applies to normal execution,
5823 record mode, and replay mode. If it is @code{off}, then there is no
5824 locking and any thread may run at any time. If @code{on}, then only
5825 the current thread may run when the inferior is resumed. The
5826 @code{step} mode optimizes for single-stepping; it prevents other
5827 threads from preempting the current thread while you are stepping, so
5828 that the focus of debugging does not change unexpectedly. Other
5829 threads never get a chance to run when you step, and they are
5830 completely free to run when you use commands like @samp{continue},
5831 @samp{until}, or @samp{finish}. However, unless another thread hits a
5832 breakpoint during its timeslice, @value{GDBN} does not change the
5833 current thread away from the thread that you are debugging. The
5834 @code{replay} mode behaves like @code{off} in record mode and like
5835 @code{on} in replay mode.
5837 @item show scheduler-locking
5838 Display the current scheduler locking mode.
5841 @cindex resume threads of multiple processes simultaneously
5842 By default, when you issue one of the execution commands such as
5843 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5844 threads of the current inferior to run. For example, if @value{GDBN}
5845 is attached to two inferiors, each with two threads, the
5846 @code{continue} command resumes only the two threads of the current
5847 inferior. This is useful, for example, when you debug a program that
5848 forks and you want to hold the parent stopped (so that, for instance,
5849 it doesn't run to exit), while you debug the child. In other
5850 situations, you may not be interested in inspecting the current state
5851 of any of the processes @value{GDBN} is attached to, and you may want
5852 to resume them all until some breakpoint is hit. In the latter case,
5853 you can instruct @value{GDBN} to allow all threads of all the
5854 inferiors to run with the @w{@code{set schedule-multiple}} command.
5857 @kindex set schedule-multiple
5858 @item set schedule-multiple
5859 Set the mode for allowing threads of multiple processes to be resumed
5860 when an execution command is issued. When @code{on}, all threads of
5861 all processes are allowed to run. When @code{off}, only the threads
5862 of the current process are resumed. The default is @code{off}. The
5863 @code{scheduler-locking} mode takes precedence when set to @code{on},
5864 or while you are stepping and set to @code{step}.
5866 @item show schedule-multiple
5867 Display the current mode for resuming the execution of threads of
5872 @subsection Non-Stop Mode
5874 @cindex non-stop mode
5876 @c This section is really only a place-holder, and needs to be expanded
5877 @c with more details.
5879 For some multi-threaded targets, @value{GDBN} supports an optional
5880 mode of operation in which you can examine stopped program threads in
5881 the debugger while other threads continue to execute freely. This
5882 minimizes intrusion when debugging live systems, such as programs
5883 where some threads have real-time constraints or must continue to
5884 respond to external events. This is referred to as @dfn{non-stop} mode.
5886 In non-stop mode, when a thread stops to report a debugging event,
5887 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5888 threads as well, in contrast to the all-stop mode behavior. Additionally,
5889 execution commands such as @code{continue} and @code{step} apply by default
5890 only to the current thread in non-stop mode, rather than all threads as
5891 in all-stop mode. This allows you to control threads explicitly in
5892 ways that are not possible in all-stop mode --- for example, stepping
5893 one thread while allowing others to run freely, stepping
5894 one thread while holding all others stopped, or stepping several threads
5895 independently and simultaneously.
5897 To enter non-stop mode, use this sequence of commands before you run
5898 or attach to your program:
5901 # If using the CLI, pagination breaks non-stop.
5904 # Finally, turn it on!
5908 You can use these commands to manipulate the non-stop mode setting:
5911 @kindex set non-stop
5912 @item set non-stop on
5913 Enable selection of non-stop mode.
5914 @item set non-stop off
5915 Disable selection of non-stop mode.
5916 @kindex show non-stop
5918 Show the current non-stop enablement setting.
5921 Note these commands only reflect whether non-stop mode is enabled,
5922 not whether the currently-executing program is being run in non-stop mode.
5923 In particular, the @code{set non-stop} preference is only consulted when
5924 @value{GDBN} starts or connects to the target program, and it is generally
5925 not possible to switch modes once debugging has started. Furthermore,
5926 since not all targets support non-stop mode, even when you have enabled
5927 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5930 In non-stop mode, all execution commands apply only to the current thread
5931 by default. That is, @code{continue} only continues one thread.
5932 To continue all threads, issue @code{continue -a} or @code{c -a}.
5934 You can use @value{GDBN}'s background execution commands
5935 (@pxref{Background Execution}) to run some threads in the background
5936 while you continue to examine or step others from @value{GDBN}.
5937 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5938 always executed asynchronously in non-stop mode.
5940 Suspending execution is done with the @code{interrupt} command when
5941 running in the background, or @kbd{Ctrl-c} during foreground execution.
5942 In all-stop mode, this stops the whole process;
5943 but in non-stop mode the interrupt applies only to the current thread.
5944 To stop the whole program, use @code{interrupt -a}.
5946 Other execution commands do not currently support the @code{-a} option.
5948 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5949 that thread current, as it does in all-stop mode. This is because the
5950 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5951 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5952 changed to a different thread just as you entered a command to operate on the
5953 previously current thread.
5955 @node Background Execution
5956 @subsection Background Execution
5958 @cindex foreground execution
5959 @cindex background execution
5960 @cindex asynchronous execution
5961 @cindex execution, foreground, background and asynchronous
5963 @value{GDBN}'s execution commands have two variants: the normal
5964 foreground (synchronous) behavior, and a background
5965 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5966 the program to report that some thread has stopped before prompting for
5967 another command. In background execution, @value{GDBN} immediately gives
5968 a command prompt so that you can issue other commands while your program runs.
5970 If the target doesn't support async mode, @value{GDBN} issues an error
5971 message if you attempt to use the background execution commands.
5973 To specify background execution, add a @code{&} to the command. For example,
5974 the background form of the @code{continue} command is @code{continue&}, or
5975 just @code{c&}. The execution commands that accept background execution
5981 @xref{Starting, , Starting your Program}.
5985 @xref{Attach, , Debugging an Already-running Process}.
5989 @xref{Continuing and Stepping, step}.
5993 @xref{Continuing and Stepping, stepi}.
5997 @xref{Continuing and Stepping, next}.
6001 @xref{Continuing and Stepping, nexti}.
6005 @xref{Continuing and Stepping, continue}.
6009 @xref{Continuing and Stepping, finish}.
6013 @xref{Continuing and Stepping, until}.
6017 Background execution is especially useful in conjunction with non-stop
6018 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6019 However, you can also use these commands in the normal all-stop mode with
6020 the restriction that you cannot issue another execution command until the
6021 previous one finishes. Examples of commands that are valid in all-stop
6022 mode while the program is running include @code{help} and @code{info break}.
6024 You can interrupt your program while it is running in the background by
6025 using the @code{interrupt} command.
6032 Suspend execution of the running program. In all-stop mode,
6033 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6034 only the current thread. To stop the whole program in non-stop mode,
6035 use @code{interrupt -a}.
6038 @node Thread-Specific Breakpoints
6039 @subsection Thread-Specific Breakpoints
6041 When your program has multiple threads (@pxref{Threads,, Debugging
6042 Programs with Multiple Threads}), you can choose whether to set
6043 breakpoints on all threads, or on a particular thread.
6046 @cindex breakpoints and threads
6047 @cindex thread breakpoints
6048 @kindex break @dots{} thread @var{threadno}
6049 @item break @var{location} thread @var{threadno}
6050 @itemx break @var{location} thread @var{threadno} if @dots{}
6051 @var{location} specifies source lines; there are several ways of
6052 writing them (@pxref{Specify Location}), but the effect is always to
6053 specify some source line.
6055 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6056 to specify that you only want @value{GDBN} to stop the program when a
6057 particular thread reaches this breakpoint. The @var{threadno} specifier
6058 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6059 in the first column of the @samp{info threads} display.
6061 If you do not specify @samp{thread @var{threadno}} when you set a
6062 breakpoint, the breakpoint applies to @emph{all} threads of your
6065 You can use the @code{thread} qualifier on conditional breakpoints as
6066 well; in this case, place @samp{thread @var{threadno}} before or
6067 after the breakpoint condition, like this:
6070 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6075 Thread-specific breakpoints are automatically deleted when
6076 @value{GDBN} detects the corresponding thread is no longer in the
6077 thread list. For example:
6081 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6084 There are several ways for a thread to disappear, such as a regular
6085 thread exit, but also when you detach from the process with the
6086 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6087 Process}), or if @value{GDBN} loses the remote connection
6088 (@pxref{Remote Debugging}), etc. Note that with some targets,
6089 @value{GDBN} is only able to detect a thread has exited when the user
6090 explictly asks for the thread list with the @code{info threads}
6093 @node Interrupted System Calls
6094 @subsection Interrupted System Calls
6096 @cindex thread breakpoints and system calls
6097 @cindex system calls and thread breakpoints
6098 @cindex premature return from system calls
6099 There is an unfortunate side effect when using @value{GDBN} to debug
6100 multi-threaded programs. If one thread stops for a
6101 breakpoint, or for some other reason, and another thread is blocked in a
6102 system call, then the system call may return prematurely. This is a
6103 consequence of the interaction between multiple threads and the signals
6104 that @value{GDBN} uses to implement breakpoints and other events that
6107 To handle this problem, your program should check the return value of
6108 each system call and react appropriately. This is good programming
6111 For example, do not write code like this:
6117 The call to @code{sleep} will return early if a different thread stops
6118 at a breakpoint or for some other reason.
6120 Instead, write this:
6125 unslept = sleep (unslept);
6128 A system call is allowed to return early, so the system is still
6129 conforming to its specification. But @value{GDBN} does cause your
6130 multi-threaded program to behave differently than it would without
6133 Also, @value{GDBN} uses internal breakpoints in the thread library to
6134 monitor certain events such as thread creation and thread destruction.
6135 When such an event happens, a system call in another thread may return
6136 prematurely, even though your program does not appear to stop.
6139 @subsection Observer Mode
6141 If you want to build on non-stop mode and observe program behavior
6142 without any chance of disruption by @value{GDBN}, you can set
6143 variables to disable all of the debugger's attempts to modify state,
6144 whether by writing memory, inserting breakpoints, etc. These operate
6145 at a low level, intercepting operations from all commands.
6147 When all of these are set to @code{off}, then @value{GDBN} is said to
6148 be @dfn{observer mode}. As a convenience, the variable
6149 @code{observer} can be set to disable these, plus enable non-stop
6152 Note that @value{GDBN} will not prevent you from making nonsensical
6153 combinations of these settings. For instance, if you have enabled
6154 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6155 then breakpoints that work by writing trap instructions into the code
6156 stream will still not be able to be placed.
6161 @item set observer on
6162 @itemx set observer off
6163 When set to @code{on}, this disables all the permission variables
6164 below (except for @code{insert-fast-tracepoints}), plus enables
6165 non-stop debugging. Setting this to @code{off} switches back to
6166 normal debugging, though remaining in non-stop mode.
6169 Show whether observer mode is on or off.
6171 @kindex may-write-registers
6172 @item set may-write-registers on
6173 @itemx set may-write-registers off
6174 This controls whether @value{GDBN} will attempt to alter the values of
6175 registers, such as with assignment expressions in @code{print}, or the
6176 @code{jump} command. It defaults to @code{on}.
6178 @item show may-write-registers
6179 Show the current permission to write registers.
6181 @kindex may-write-memory
6182 @item set may-write-memory on
6183 @itemx set may-write-memory off
6184 This controls whether @value{GDBN} will attempt to alter the contents
6185 of memory, such as with assignment expressions in @code{print}. It
6186 defaults to @code{on}.
6188 @item show may-write-memory
6189 Show the current permission to write memory.
6191 @kindex may-insert-breakpoints
6192 @item set may-insert-breakpoints on
6193 @itemx set may-insert-breakpoints off
6194 This controls whether @value{GDBN} will attempt to insert breakpoints.
6195 This affects all breakpoints, including internal breakpoints defined
6196 by @value{GDBN}. It defaults to @code{on}.
6198 @item show may-insert-breakpoints
6199 Show the current permission to insert breakpoints.
6201 @kindex may-insert-tracepoints
6202 @item set may-insert-tracepoints on
6203 @itemx set may-insert-tracepoints off
6204 This controls whether @value{GDBN} will attempt to insert (regular)
6205 tracepoints at the beginning of a tracing experiment. It affects only
6206 non-fast tracepoints, fast tracepoints being under the control of
6207 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6209 @item show may-insert-tracepoints
6210 Show the current permission to insert tracepoints.
6212 @kindex may-insert-fast-tracepoints
6213 @item set may-insert-fast-tracepoints on
6214 @itemx set may-insert-fast-tracepoints off
6215 This controls whether @value{GDBN} will attempt to insert fast
6216 tracepoints at the beginning of a tracing experiment. It affects only
6217 fast tracepoints, regular (non-fast) tracepoints being under the
6218 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6220 @item show may-insert-fast-tracepoints
6221 Show the current permission to insert fast tracepoints.
6223 @kindex may-interrupt
6224 @item set may-interrupt on
6225 @itemx set may-interrupt off
6226 This controls whether @value{GDBN} will attempt to interrupt or stop
6227 program execution. When this variable is @code{off}, the
6228 @code{interrupt} command will have no effect, nor will
6229 @kbd{Ctrl-c}. It defaults to @code{on}.
6231 @item show may-interrupt
6232 Show the current permission to interrupt or stop the program.
6236 @node Reverse Execution
6237 @chapter Running programs backward
6238 @cindex reverse execution
6239 @cindex running programs backward
6241 When you are debugging a program, it is not unusual to realize that
6242 you have gone too far, and some event of interest has already happened.
6243 If the target environment supports it, @value{GDBN} can allow you to
6244 ``rewind'' the program by running it backward.
6246 A target environment that supports reverse execution should be able
6247 to ``undo'' the changes in machine state that have taken place as the
6248 program was executing normally. Variables, registers etc.@: should
6249 revert to their previous values. Obviously this requires a great
6250 deal of sophistication on the part of the target environment; not
6251 all target environments can support reverse execution.
6253 When a program is executed in reverse, the instructions that
6254 have most recently been executed are ``un-executed'', in reverse
6255 order. The program counter runs backward, following the previous
6256 thread of execution in reverse. As each instruction is ``un-executed'',
6257 the values of memory and/or registers that were changed by that
6258 instruction are reverted to their previous states. After executing
6259 a piece of source code in reverse, all side effects of that code
6260 should be ``undone'', and all variables should be returned to their
6261 prior values@footnote{
6262 Note that some side effects are easier to undo than others. For instance,
6263 memory and registers are relatively easy, but device I/O is hard. Some
6264 targets may be able undo things like device I/O, and some may not.
6266 The contract between @value{GDBN} and the reverse executing target
6267 requires only that the target do something reasonable when
6268 @value{GDBN} tells it to execute backwards, and then report the
6269 results back to @value{GDBN}. Whatever the target reports back to
6270 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6271 assumes that the memory and registers that the target reports are in a
6272 consistant state, but @value{GDBN} accepts whatever it is given.
6275 If you are debugging in a target environment that supports
6276 reverse execution, @value{GDBN} provides the following commands.
6279 @kindex reverse-continue
6280 @kindex rc @r{(@code{reverse-continue})}
6281 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6282 @itemx rc @r{[}@var{ignore-count}@r{]}
6283 Beginning at the point where your program last stopped, start executing
6284 in reverse. Reverse execution will stop for breakpoints and synchronous
6285 exceptions (signals), just like normal execution. Behavior of
6286 asynchronous signals depends on the target environment.
6288 @kindex reverse-step
6289 @kindex rs @r{(@code{step})}
6290 @item reverse-step @r{[}@var{count}@r{]}
6291 Run the program backward until control reaches the start of a
6292 different source line; then stop it, and return control to @value{GDBN}.
6294 Like the @code{step} command, @code{reverse-step} will only stop
6295 at the beginning of a source line. It ``un-executes'' the previously
6296 executed source line. If the previous source line included calls to
6297 debuggable functions, @code{reverse-step} will step (backward) into
6298 the called function, stopping at the beginning of the @emph{last}
6299 statement in the called function (typically a return statement).
6301 Also, as with the @code{step} command, if non-debuggable functions are
6302 called, @code{reverse-step} will run thru them backward without stopping.
6304 @kindex reverse-stepi
6305 @kindex rsi @r{(@code{reverse-stepi})}
6306 @item reverse-stepi @r{[}@var{count}@r{]}
6307 Reverse-execute one machine instruction. Note that the instruction
6308 to be reverse-executed is @emph{not} the one pointed to by the program
6309 counter, but the instruction executed prior to that one. For instance,
6310 if the last instruction was a jump, @code{reverse-stepi} will take you
6311 back from the destination of the jump to the jump instruction itself.
6313 @kindex reverse-next
6314 @kindex rn @r{(@code{reverse-next})}
6315 @item reverse-next @r{[}@var{count}@r{]}
6316 Run backward to the beginning of the previous line executed in
6317 the current (innermost) stack frame. If the line contains function
6318 calls, they will be ``un-executed'' without stopping. Starting from
6319 the first line of a function, @code{reverse-next} will take you back
6320 to the caller of that function, @emph{before} the function was called,
6321 just as the normal @code{next} command would take you from the last
6322 line of a function back to its return to its caller
6323 @footnote{Unless the code is too heavily optimized.}.
6325 @kindex reverse-nexti
6326 @kindex rni @r{(@code{reverse-nexti})}
6327 @item reverse-nexti @r{[}@var{count}@r{]}
6328 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6329 in reverse, except that called functions are ``un-executed'' atomically.
6330 That is, if the previously executed instruction was a return from
6331 another function, @code{reverse-nexti} will continue to execute
6332 in reverse until the call to that function (from the current stack
6335 @kindex reverse-finish
6336 @item reverse-finish
6337 Just as the @code{finish} command takes you to the point where the
6338 current function returns, @code{reverse-finish} takes you to the point
6339 where it was called. Instead of ending up at the end of the current
6340 function invocation, you end up at the beginning.
6342 @kindex set exec-direction
6343 @item set exec-direction
6344 Set the direction of target execution.
6345 @item set exec-direction reverse
6346 @cindex execute forward or backward in time
6347 @value{GDBN} will perform all execution commands in reverse, until the
6348 exec-direction mode is changed to ``forward''. Affected commands include
6349 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6350 command cannot be used in reverse mode.
6351 @item set exec-direction forward
6352 @value{GDBN} will perform all execution commands in the normal fashion.
6353 This is the default.
6357 @node Process Record and Replay
6358 @chapter Recording Inferior's Execution and Replaying It
6359 @cindex process record and replay
6360 @cindex recording inferior's execution and replaying it
6362 On some platforms, @value{GDBN} provides a special @dfn{process record
6363 and replay} target that can record a log of the process execution, and
6364 replay it later with both forward and reverse execution commands.
6367 When this target is in use, if the execution log includes the record
6368 for the next instruction, @value{GDBN} will debug in @dfn{replay
6369 mode}. In the replay mode, the inferior does not really execute code
6370 instructions. Instead, all the events that normally happen during
6371 code execution are taken from the execution log. While code is not
6372 really executed in replay mode, the values of registers (including the
6373 program counter register) and the memory of the inferior are still
6374 changed as they normally would. Their contents are taken from the
6378 If the record for the next instruction is not in the execution log,
6379 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6380 inferior executes normally, and @value{GDBN} records the execution log
6383 The process record and replay target supports reverse execution
6384 (@pxref{Reverse Execution}), even if the platform on which the
6385 inferior runs does not. However, the reverse execution is limited in
6386 this case by the range of the instructions recorded in the execution
6387 log. In other words, reverse execution on platforms that don't
6388 support it directly can only be done in the replay mode.
6390 When debugging in the reverse direction, @value{GDBN} will work in
6391 replay mode as long as the execution log includes the record for the
6392 previous instruction; otherwise, it will work in record mode, if the
6393 platform supports reverse execution, or stop if not.
6395 For architecture environments that support process record and replay,
6396 @value{GDBN} provides the following commands:
6399 @kindex target record
6400 @kindex target record-full
6401 @kindex target record-btrace
6404 @kindex record btrace
6405 @kindex record btrace bts
6406 @kindex record btrace pt
6412 @kindex rec btrace bts
6413 @kindex rec btrace pt
6416 @item record @var{method}
6417 This command starts the process record and replay target. The
6418 recording method can be specified as parameter. Without a parameter
6419 the command uses the @code{full} recording method. The following
6420 recording methods are available:
6424 Full record/replay recording using @value{GDBN}'s software record and
6425 replay implementation. This method allows replaying and reverse
6428 @item btrace @var{format}
6429 Hardware-supported instruction recording. This method does not record
6430 data. Further, the data is collected in a ring buffer so old data will
6431 be overwritten when the buffer is full. It allows limited reverse
6432 execution. Variables and registers are not available during reverse
6435 The recording format can be specified as parameter. Without a parameter
6436 the command chooses the recording format. The following recording
6437 formats are available:
6441 @cindex branch trace store
6442 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6443 this format, the processor stores a from/to record for each executed
6444 branch in the btrace ring buffer.
6447 @cindex Intel(R) Processor Trace
6448 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6449 format, the processor stores the execution trace in a compressed form
6450 that is afterwards decoded by @value{GDBN}.
6452 The trace can be recorded with very low overhead. The compressed
6453 trace format also allows small trace buffers to already contain a big
6454 number of instructions compared to @acronym{BTS}.
6456 Decoding the recorded execution trace, on the other hand, is more
6457 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6458 increased number of instructions to process. You should increase the
6459 buffer-size with care.
6462 Not all recording formats may be available on all processors.
6465 The process record and replay target can only debug a process that is
6466 already running. Therefore, you need first to start the process with
6467 the @kbd{run} or @kbd{start} commands, and then start the recording
6468 with the @kbd{record @var{method}} command.
6470 @cindex displaced stepping, and process record and replay
6471 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6472 will be automatically disabled when process record and replay target
6473 is started. That's because the process record and replay target
6474 doesn't support displaced stepping.
6476 @cindex non-stop mode, and process record and replay
6477 @cindex asynchronous execution, and process record and replay
6478 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6479 the asynchronous execution mode (@pxref{Background Execution}), not
6480 all recording methods are available. The @code{full} recording method
6481 does not support these two modes.
6486 Stop the process record and replay target. When process record and
6487 replay target stops, the entire execution log will be deleted and the
6488 inferior will either be terminated, or will remain in its final state.
6490 When you stop the process record and replay target in record mode (at
6491 the end of the execution log), the inferior will be stopped at the
6492 next instruction that would have been recorded. In other words, if
6493 you record for a while and then stop recording, the inferior process
6494 will be left in the same state as if the recording never happened.
6496 On the other hand, if the process record and replay target is stopped
6497 while in replay mode (that is, not at the end of the execution log,
6498 but at some earlier point), the inferior process will become ``live''
6499 at that earlier state, and it will then be possible to continue the
6500 usual ``live'' debugging of the process from that state.
6502 When the inferior process exits, or @value{GDBN} detaches from it,
6503 process record and replay target will automatically stop itself.
6507 Go to a specific location in the execution log. There are several
6508 ways to specify the location to go to:
6511 @item record goto begin
6512 @itemx record goto start
6513 Go to the beginning of the execution log.
6515 @item record goto end
6516 Go to the end of the execution log.
6518 @item record goto @var{n}
6519 Go to instruction number @var{n} in the execution log.
6523 @item record save @var{filename}
6524 Save the execution log to a file @file{@var{filename}}.
6525 Default filename is @file{gdb_record.@var{process_id}}, where
6526 @var{process_id} is the process ID of the inferior.
6528 This command may not be available for all recording methods.
6530 @kindex record restore
6531 @item record restore @var{filename}
6532 Restore the execution log from a file @file{@var{filename}}.
6533 File must have been created with @code{record save}.
6535 @kindex set record full
6536 @item set record full insn-number-max @var{limit}
6537 @itemx set record full insn-number-max unlimited
6538 Set the limit of instructions to be recorded for the @code{full}
6539 recording method. Default value is 200000.
6541 If @var{limit} is a positive number, then @value{GDBN} will start
6542 deleting instructions from the log once the number of the record
6543 instructions becomes greater than @var{limit}. For every new recorded
6544 instruction, @value{GDBN} will delete the earliest recorded
6545 instruction to keep the number of recorded instructions at the limit.
6546 (Since deleting recorded instructions loses information, @value{GDBN}
6547 lets you control what happens when the limit is reached, by means of
6548 the @code{stop-at-limit} option, described below.)
6550 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6551 delete recorded instructions from the execution log. The number of
6552 recorded instructions is limited only by the available memory.
6554 @kindex show record full
6555 @item show record full insn-number-max
6556 Show the limit of instructions to be recorded with the @code{full}
6559 @item set record full stop-at-limit
6560 Control the behavior of the @code{full} recording method when the
6561 number of recorded instructions reaches the limit. If ON (the
6562 default), @value{GDBN} will stop when the limit is reached for the
6563 first time and ask you whether you want to stop the inferior or
6564 continue running it and recording the execution log. If you decide
6565 to continue recording, each new recorded instruction will cause the
6566 oldest one to be deleted.
6568 If this option is OFF, @value{GDBN} will automatically delete the
6569 oldest record to make room for each new one, without asking.
6571 @item show record full stop-at-limit
6572 Show the current setting of @code{stop-at-limit}.
6574 @item set record full memory-query
6575 Control the behavior when @value{GDBN} is unable to record memory
6576 changes caused by an instruction for the @code{full} recording method.
6577 If ON, @value{GDBN} will query whether to stop the inferior in that
6580 If this option is OFF (the default), @value{GDBN} will automatically
6581 ignore the effect of such instructions on memory. Later, when
6582 @value{GDBN} replays this execution log, it will mark the log of this
6583 instruction as not accessible, and it will not affect the replay
6586 @item show record full memory-query
6587 Show the current setting of @code{memory-query}.
6589 @kindex set record btrace
6590 The @code{btrace} record target does not trace data. As a
6591 convenience, when replaying, @value{GDBN} reads read-only memory off
6592 the live program directly, assuming that the addresses of the
6593 read-only areas don't change. This for example makes it possible to
6594 disassemble code while replaying, but not to print variables.
6595 In some cases, being able to inspect variables might be useful.
6596 You can use the following command for that:
6598 @item set record btrace replay-memory-access
6599 Control the behavior of the @code{btrace} recording method when
6600 accessing memory during replay. If @code{read-only} (the default),
6601 @value{GDBN} will only allow accesses to read-only memory.
6602 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6603 and to read-write memory. Beware that the accessed memory corresponds
6604 to the live target and not necessarily to the current replay
6607 @kindex show record btrace
6608 @item show record btrace replay-memory-access
6609 Show the current setting of @code{replay-memory-access}.
6611 @kindex set record btrace bts
6612 @item set record btrace bts buffer-size @var{size}
6613 @itemx set record btrace bts buffer-size unlimited
6614 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6615 format. Default is 64KB.
6617 If @var{size} is a positive number, then @value{GDBN} will try to
6618 allocate a buffer of at least @var{size} bytes for each new thread
6619 that uses the btrace recording method and the @acronym{BTS} format.
6620 The actually obtained buffer size may differ from the requested
6621 @var{size}. Use the @code{info record} command to see the actual
6622 buffer size for each thread that uses the btrace recording method and
6623 the @acronym{BTS} format.
6625 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6626 allocate a buffer of 4MB.
6628 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6629 also need longer to process the branch trace data before it can be used.
6631 @item show record btrace bts buffer-size @var{size}
6632 Show the current setting of the requested ring buffer size for branch
6633 tracing in @acronym{BTS} format.
6635 @kindex set record btrace pt
6636 @item set record btrace pt buffer-size @var{size}
6637 @itemx set record btrace pt buffer-size unlimited
6638 Set the requested ring buffer size for branch tracing in Intel(R)
6639 Processor Trace format. Default is 16KB.
6641 If @var{size} is a positive number, then @value{GDBN} will try to
6642 allocate a buffer of at least @var{size} bytes for each new thread
6643 that uses the btrace recording method and the Intel(R) Processor Trace
6644 format. The actually obtained buffer size may differ from the
6645 requested @var{size}. Use the @code{info record} command to see the
6646 actual buffer size for each thread.
6648 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6649 allocate a buffer of 4MB.
6651 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6652 also need longer to process the branch trace data before it can be used.
6654 @item show record btrace pt buffer-size @var{size}
6655 Show the current setting of the requested ring buffer size for branch
6656 tracing in Intel(R) Processor Trace format.
6660 Show various statistics about the recording depending on the recording
6665 For the @code{full} recording method, it shows the state of process
6666 record and its in-memory execution log buffer, including:
6670 Whether in record mode or replay mode.
6672 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6674 Highest recorded instruction number.
6676 Current instruction about to be replayed (if in replay mode).
6678 Number of instructions contained in the execution log.
6680 Maximum number of instructions that may be contained in the execution log.
6684 For the @code{btrace} recording method, it shows:
6690 Number of instructions that have been recorded.
6692 Number of blocks of sequential control-flow formed by the recorded
6695 Whether in record mode or replay mode.
6698 For the @code{bts} recording format, it also shows:
6701 Size of the perf ring buffer.
6704 For the @code{pt} recording format, it also shows:
6707 Size of the perf ring buffer.
6711 @kindex record delete
6714 When record target runs in replay mode (``in the past''), delete the
6715 subsequent execution log and begin to record a new execution log starting
6716 from the current address. This means you will abandon the previously
6717 recorded ``future'' and begin recording a new ``future''.
6719 @kindex record instruction-history
6720 @kindex rec instruction-history
6721 @item record instruction-history
6722 Disassembles instructions from the recorded execution log. By
6723 default, ten instructions are disassembled. This can be changed using
6724 the @code{set record instruction-history-size} command. Instructions
6725 are printed in execution order.
6727 It can also print mixed source+disassembly if you specify the the
6728 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6729 as well as in symbolic form by specifying the @code{/r} modifier.
6731 The current position marker is printed for the instruction at the
6732 current program counter value. This instruction can appear multiple
6733 times in the trace and the current position marker will be printed
6734 every time. To omit the current position marker, specify the
6737 To better align the printed instructions when the trace contains
6738 instructions from more than one function, the function name may be
6739 omitted by specifying the @code{/f} modifier.
6741 Speculatively executed instructions are prefixed with @samp{?}. This
6742 feature is not available for all recording formats.
6744 There are several ways to specify what part of the execution log to
6748 @item record instruction-history @var{insn}
6749 Disassembles ten instructions starting from instruction number
6752 @item record instruction-history @var{insn}, +/-@var{n}
6753 Disassembles @var{n} instructions around instruction number
6754 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6755 @var{n} instructions after instruction number @var{insn}. If
6756 @var{n} is preceded with @code{-}, disassembles @var{n}
6757 instructions before instruction number @var{insn}.
6759 @item record instruction-history
6760 Disassembles ten more instructions after the last disassembly.
6762 @item record instruction-history -
6763 Disassembles ten more instructions before the last disassembly.
6765 @item record instruction-history @var{begin}, @var{end}
6766 Disassembles instructions beginning with instruction number
6767 @var{begin} until instruction number @var{end}. The instruction
6768 number @var{end} is included.
6771 This command may not be available for all recording methods.
6774 @item set record instruction-history-size @var{size}
6775 @itemx set record instruction-history-size unlimited
6776 Define how many instructions to disassemble in the @code{record
6777 instruction-history} command. The default value is 10.
6778 A @var{size} of @code{unlimited} means unlimited instructions.
6781 @item show record instruction-history-size
6782 Show how many instructions to disassemble in the @code{record
6783 instruction-history} command.
6785 @kindex record function-call-history
6786 @kindex rec function-call-history
6787 @item record function-call-history
6788 Prints the execution history at function granularity. It prints one
6789 line for each sequence of instructions that belong to the same
6790 function giving the name of that function, the source lines
6791 for this instruction sequence (if the @code{/l} modifier is
6792 specified), and the instructions numbers that form the sequence (if
6793 the @code{/i} modifier is specified). The function names are indented
6794 to reflect the call stack depth if the @code{/c} modifier is
6795 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6799 (@value{GDBP}) @b{list 1, 10}
6810 (@value{GDBP}) @b{record function-call-history /ilc}
6811 1 bar inst 1,4 at foo.c:6,8
6812 2 foo inst 5,10 at foo.c:2,3
6813 3 bar inst 11,13 at foo.c:9,10
6816 By default, ten lines are printed. This can be changed using the
6817 @code{set record function-call-history-size} command. Functions are
6818 printed in execution order. There are several ways to specify what
6822 @item record function-call-history @var{func}
6823 Prints ten functions starting from function number @var{func}.
6825 @item record function-call-history @var{func}, +/-@var{n}
6826 Prints @var{n} functions around function number @var{func}. If
6827 @var{n} is preceded with @code{+}, prints @var{n} functions after
6828 function number @var{func}. If @var{n} is preceded with @code{-},
6829 prints @var{n} functions before function number @var{func}.
6831 @item record function-call-history
6832 Prints ten more functions after the last ten-line print.
6834 @item record function-call-history -
6835 Prints ten more functions before the last ten-line print.
6837 @item record function-call-history @var{begin}, @var{end}
6838 Prints functions beginning with function number @var{begin} until
6839 function number @var{end}. The function number @var{end} is included.
6842 This command may not be available for all recording methods.
6844 @item set record function-call-history-size @var{size}
6845 @itemx set record function-call-history-size unlimited
6846 Define how many lines to print in the
6847 @code{record function-call-history} command. The default value is 10.
6848 A size of @code{unlimited} means unlimited lines.
6850 @item show record function-call-history-size
6851 Show how many lines to print in the
6852 @code{record function-call-history} command.
6857 @chapter Examining the Stack
6859 When your program has stopped, the first thing you need to know is where it
6860 stopped and how it got there.
6863 Each time your program performs a function call, information about the call
6865 That information includes the location of the call in your program,
6866 the arguments of the call,
6867 and the local variables of the function being called.
6868 The information is saved in a block of data called a @dfn{stack frame}.
6869 The stack frames are allocated in a region of memory called the @dfn{call
6872 When your program stops, the @value{GDBN} commands for examining the
6873 stack allow you to see all of this information.
6875 @cindex selected frame
6876 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6877 @value{GDBN} commands refer implicitly to the selected frame. In
6878 particular, whenever you ask @value{GDBN} for the value of a variable in
6879 your program, the value is found in the selected frame. There are
6880 special @value{GDBN} commands to select whichever frame you are
6881 interested in. @xref{Selection, ,Selecting a Frame}.
6883 When your program stops, @value{GDBN} automatically selects the
6884 currently executing frame and describes it briefly, similar to the
6885 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6888 * Frames:: Stack frames
6889 * Backtrace:: Backtraces
6890 * Selection:: Selecting a frame
6891 * Frame Info:: Information on a frame
6892 * Frame Filter Management:: Managing frame filters
6897 @section Stack Frames
6899 @cindex frame, definition
6901 The call stack is divided up into contiguous pieces called @dfn{stack
6902 frames}, or @dfn{frames} for short; each frame is the data associated
6903 with one call to one function. The frame contains the arguments given
6904 to the function, the function's local variables, and the address at
6905 which the function is executing.
6907 @cindex initial frame
6908 @cindex outermost frame
6909 @cindex innermost frame
6910 When your program is started, the stack has only one frame, that of the
6911 function @code{main}. This is called the @dfn{initial} frame or the
6912 @dfn{outermost} frame. Each time a function is called, a new frame is
6913 made. Each time a function returns, the frame for that function invocation
6914 is eliminated. If a function is recursive, there can be many frames for
6915 the same function. The frame for the function in which execution is
6916 actually occurring is called the @dfn{innermost} frame. This is the most
6917 recently created of all the stack frames that still exist.
6919 @cindex frame pointer
6920 Inside your program, stack frames are identified by their addresses. A
6921 stack frame consists of many bytes, each of which has its own address; each
6922 kind of computer has a convention for choosing one byte whose
6923 address serves as the address of the frame. Usually this address is kept
6924 in a register called the @dfn{frame pointer register}
6925 (@pxref{Registers, $fp}) while execution is going on in that frame.
6927 @cindex frame number
6928 @value{GDBN} assigns numbers to all existing stack frames, starting with
6929 zero for the innermost frame, one for the frame that called it,
6930 and so on upward. These numbers do not really exist in your program;
6931 they are assigned by @value{GDBN} to give you a way of designating stack
6932 frames in @value{GDBN} commands.
6934 @c The -fomit-frame-pointer below perennially causes hbox overflow
6935 @c underflow problems.
6936 @cindex frameless execution
6937 Some compilers provide a way to compile functions so that they operate
6938 without stack frames. (For example, the @value{NGCC} option
6940 @samp{-fomit-frame-pointer}
6942 generates functions without a frame.)
6943 This is occasionally done with heavily used library functions to save
6944 the frame setup time. @value{GDBN} has limited facilities for dealing
6945 with these function invocations. If the innermost function invocation
6946 has no stack frame, @value{GDBN} nevertheless regards it as though
6947 it had a separate frame, which is numbered zero as usual, allowing
6948 correct tracing of the function call chain. However, @value{GDBN} has
6949 no provision for frameless functions elsewhere in the stack.
6955 @cindex call stack traces
6956 A backtrace is a summary of how your program got where it is. It shows one
6957 line per frame, for many frames, starting with the currently executing
6958 frame (frame zero), followed by its caller (frame one), and on up the
6961 @anchor{backtrace-command}
6964 @kindex bt @r{(@code{backtrace})}
6967 Print a backtrace of the entire stack: one line per frame for all
6968 frames in the stack.
6970 You can stop the backtrace at any time by typing the system interrupt
6971 character, normally @kbd{Ctrl-c}.
6973 @item backtrace @var{n}
6975 Similar, but print only the innermost @var{n} frames.
6977 @item backtrace -@var{n}
6979 Similar, but print only the outermost @var{n} frames.
6981 @item backtrace full
6983 @itemx bt full @var{n}
6984 @itemx bt full -@var{n}
6985 Print the values of the local variables also. As described above,
6986 @var{n} specifies the number of frames to print.
6988 @item backtrace no-filters
6989 @itemx bt no-filters
6990 @itemx bt no-filters @var{n}
6991 @itemx bt no-filters -@var{n}
6992 @itemx bt no-filters full
6993 @itemx bt no-filters full @var{n}
6994 @itemx bt no-filters full -@var{n}
6995 Do not run Python frame filters on this backtrace. @xref{Frame
6996 Filter API}, for more information. Additionally use @ref{disable
6997 frame-filter all} to turn off all frame filters. This is only
6998 relevant when @value{GDBN} has been configured with @code{Python}
7004 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7005 are additional aliases for @code{backtrace}.
7007 @cindex multiple threads, backtrace
7008 In a multi-threaded program, @value{GDBN} by default shows the
7009 backtrace only for the current thread. To display the backtrace for
7010 several or all of the threads, use the command @code{thread apply}
7011 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7012 apply all backtrace}, @value{GDBN} will display the backtrace for all
7013 the threads; this is handy when you debug a core dump of a
7014 multi-threaded program.
7016 Each line in the backtrace shows the frame number and the function name.
7017 The program counter value is also shown---unless you use @code{set
7018 print address off}. The backtrace also shows the source file name and
7019 line number, as well as the arguments to the function. The program
7020 counter value is omitted if it is at the beginning of the code for that
7023 Here is an example of a backtrace. It was made with the command
7024 @samp{bt 3}, so it shows the innermost three frames.
7028 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7030 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7031 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7033 (More stack frames follow...)
7038 The display for frame zero does not begin with a program counter
7039 value, indicating that your program has stopped at the beginning of the
7040 code for line @code{993} of @code{builtin.c}.
7043 The value of parameter @code{data} in frame 1 has been replaced by
7044 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7045 only if it is a scalar (integer, pointer, enumeration, etc). See command
7046 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7047 on how to configure the way function parameter values are printed.
7049 @cindex optimized out, in backtrace
7050 @cindex function call arguments, optimized out
7051 If your program was compiled with optimizations, some compilers will
7052 optimize away arguments passed to functions if those arguments are
7053 never used after the call. Such optimizations generate code that
7054 passes arguments through registers, but doesn't store those arguments
7055 in the stack frame. @value{GDBN} has no way of displaying such
7056 arguments in stack frames other than the innermost one. Here's what
7057 such a backtrace might look like:
7061 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7063 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7064 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7066 (More stack frames follow...)
7071 The values of arguments that were not saved in their stack frames are
7072 shown as @samp{<optimized out>}.
7074 If you need to display the values of such optimized-out arguments,
7075 either deduce that from other variables whose values depend on the one
7076 you are interested in, or recompile without optimizations.
7078 @cindex backtrace beyond @code{main} function
7079 @cindex program entry point
7080 @cindex startup code, and backtrace
7081 Most programs have a standard user entry point---a place where system
7082 libraries and startup code transition into user code. For C this is
7083 @code{main}@footnote{
7084 Note that embedded programs (the so-called ``free-standing''
7085 environment) are not required to have a @code{main} function as the
7086 entry point. They could even have multiple entry points.}.
7087 When @value{GDBN} finds the entry function in a backtrace
7088 it will terminate the backtrace, to avoid tracing into highly
7089 system-specific (and generally uninteresting) code.
7091 If you need to examine the startup code, or limit the number of levels
7092 in a backtrace, you can change this behavior:
7095 @item set backtrace past-main
7096 @itemx set backtrace past-main on
7097 @kindex set backtrace
7098 Backtraces will continue past the user entry point.
7100 @item set backtrace past-main off
7101 Backtraces will stop when they encounter the user entry point. This is the
7104 @item show backtrace past-main
7105 @kindex show backtrace
7106 Display the current user entry point backtrace policy.
7108 @item set backtrace past-entry
7109 @itemx set backtrace past-entry on
7110 Backtraces will continue past the internal entry point of an application.
7111 This entry point is encoded by the linker when the application is built,
7112 and is likely before the user entry point @code{main} (or equivalent) is called.
7114 @item set backtrace past-entry off
7115 Backtraces will stop when they encounter the internal entry point of an
7116 application. This is the default.
7118 @item show backtrace past-entry
7119 Display the current internal entry point backtrace policy.
7121 @item set backtrace limit @var{n}
7122 @itemx set backtrace limit 0
7123 @itemx set backtrace limit unlimited
7124 @cindex backtrace limit
7125 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7126 or zero means unlimited levels.
7128 @item show backtrace limit
7129 Display the current limit on backtrace levels.
7132 You can control how file names are displayed.
7135 @item set filename-display
7136 @itemx set filename-display relative
7137 @cindex filename-display
7138 Display file names relative to the compilation directory. This is the default.
7140 @item set filename-display basename
7141 Display only basename of a filename.
7143 @item set filename-display absolute
7144 Display an absolute filename.
7146 @item show filename-display
7147 Show the current way to display filenames.
7151 @section Selecting a Frame
7153 Most commands for examining the stack and other data in your program work on
7154 whichever stack frame is selected at the moment. Here are the commands for
7155 selecting a stack frame; all of them finish by printing a brief description
7156 of the stack frame just selected.
7159 @kindex frame@r{, selecting}
7160 @kindex f @r{(@code{frame})}
7163 Select frame number @var{n}. Recall that frame zero is the innermost
7164 (currently executing) frame, frame one is the frame that called the
7165 innermost one, and so on. The highest-numbered frame is the one for
7168 @item frame @var{stack-addr} [ @var{pc-addr} ]
7169 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7170 Select the frame at address @var{stack-addr}. This is useful mainly if the
7171 chaining of stack frames has been damaged by a bug, making it
7172 impossible for @value{GDBN} to assign numbers properly to all frames. In
7173 addition, this can be useful when your program has multiple stacks and
7174 switches between them. The optional @var{pc-addr} can also be given to
7175 specify the value of PC for the stack frame.
7179 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7180 numbers @var{n}, this advances toward the outermost frame, to higher
7181 frame numbers, to frames that have existed longer.
7184 @kindex do @r{(@code{down})}
7186 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7187 positive numbers @var{n}, this advances toward the innermost frame, to
7188 lower frame numbers, to frames that were created more recently.
7189 You may abbreviate @code{down} as @code{do}.
7192 All of these commands end by printing two lines of output describing the
7193 frame. The first line shows the frame number, the function name, the
7194 arguments, and the source file and line number of execution in that
7195 frame. The second line shows the text of that source line.
7203 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7205 10 read_input_file (argv[i]);
7209 After such a printout, the @code{list} command with no arguments
7210 prints ten lines centered on the point of execution in the frame.
7211 You can also edit the program at the point of execution with your favorite
7212 editing program by typing @code{edit}.
7213 @xref{List, ,Printing Source Lines},
7217 @kindex select-frame
7219 The @code{select-frame} command is a variant of @code{frame} that does
7220 not display the new frame after selecting it. This command is
7221 intended primarily for use in @value{GDBN} command scripts, where the
7222 output might be unnecessary and distracting.
7224 @kindex down-silently
7226 @item up-silently @var{n}
7227 @itemx down-silently @var{n}
7228 These two commands are variants of @code{up} and @code{down},
7229 respectively; they differ in that they do their work silently, without
7230 causing display of the new frame. They are intended primarily for use
7231 in @value{GDBN} command scripts, where the output might be unnecessary and
7236 @section Information About a Frame
7238 There are several other commands to print information about the selected
7244 When used without any argument, this command does not change which
7245 frame is selected, but prints a brief description of the currently
7246 selected stack frame. It can be abbreviated @code{f}. With an
7247 argument, this command is used to select a stack frame.
7248 @xref{Selection, ,Selecting a Frame}.
7251 @kindex info f @r{(@code{info frame})}
7254 This command prints a verbose description of the selected stack frame,
7259 the address of the frame
7261 the address of the next frame down (called by this frame)
7263 the address of the next frame up (caller of this frame)
7265 the language in which the source code corresponding to this frame is written
7267 the address of the frame's arguments
7269 the address of the frame's local variables
7271 the program counter saved in it (the address of execution in the caller frame)
7273 which registers were saved in the frame
7276 @noindent The verbose description is useful when
7277 something has gone wrong that has made the stack format fail to fit
7278 the usual conventions.
7280 @item info frame @var{addr}
7281 @itemx info f @var{addr}
7282 Print a verbose description of the frame at address @var{addr}, without
7283 selecting that frame. The selected frame remains unchanged by this
7284 command. This requires the same kind of address (more than one for some
7285 architectures) that you specify in the @code{frame} command.
7286 @xref{Selection, ,Selecting a Frame}.
7290 Print the arguments of the selected frame, each on a separate line.
7294 Print the local variables of the selected frame, each on a separate
7295 line. These are all variables (declared either static or automatic)
7296 accessible at the point of execution of the selected frame.
7300 @node Frame Filter Management
7301 @section Management of Frame Filters.
7302 @cindex managing frame filters
7304 Frame filters are Python based utilities to manage and decorate the
7305 output of frames. @xref{Frame Filter API}, for further information.
7307 Managing frame filters is performed by several commands available
7308 within @value{GDBN}, detailed here.
7311 @kindex info frame-filter
7312 @item info frame-filter
7313 Print a list of installed frame filters from all dictionaries, showing
7314 their name, priority and enabled status.
7316 @kindex disable frame-filter
7317 @anchor{disable frame-filter all}
7318 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7319 Disable a frame filter in the dictionary matching
7320 @var{filter-dictionary} and @var{filter-name}. The
7321 @var{filter-dictionary} may be @code{all}, @code{global},
7322 @code{progspace}, or the name of the object file where the frame filter
7323 dictionary resides. When @code{all} is specified, all frame filters
7324 across all dictionaries are disabled. The @var{filter-name} is the name
7325 of the frame filter and is used when @code{all} is not the option for
7326 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7327 may be enabled again later.
7329 @kindex enable frame-filter
7330 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7331 Enable a frame filter in the dictionary matching
7332 @var{filter-dictionary} and @var{filter-name}. The
7333 @var{filter-dictionary} may be @code{all}, @code{global},
7334 @code{progspace} or the name of the object file where the frame filter
7335 dictionary resides. When @code{all} is specified, all frame filters across
7336 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7337 filter and is used when @code{all} is not the option for
7338 @var{filter-dictionary}.
7343 (gdb) info frame-filter
7345 global frame-filters:
7346 Priority Enabled Name
7347 1000 No PrimaryFunctionFilter
7350 progspace /build/test frame-filters:
7351 Priority Enabled Name
7352 100 Yes ProgspaceFilter
7354 objfile /build/test frame-filters:
7355 Priority Enabled Name
7356 999 Yes BuildProgra Filter
7358 (gdb) disable frame-filter /build/test BuildProgramFilter
7359 (gdb) info frame-filter
7361 global frame-filters:
7362 Priority Enabled Name
7363 1000 No PrimaryFunctionFilter
7366 progspace /build/test frame-filters:
7367 Priority Enabled Name
7368 100 Yes ProgspaceFilter
7370 objfile /build/test frame-filters:
7371 Priority Enabled Name
7372 999 No BuildProgramFilter
7374 (gdb) enable frame-filter global PrimaryFunctionFilter
7375 (gdb) info frame-filter
7377 global frame-filters:
7378 Priority Enabled Name
7379 1000 Yes PrimaryFunctionFilter
7382 progspace /build/test frame-filters:
7383 Priority Enabled Name
7384 100 Yes ProgspaceFilter
7386 objfile /build/test frame-filters:
7387 Priority Enabled Name
7388 999 No BuildProgramFilter
7391 @kindex set frame-filter priority
7392 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7393 Set the @var{priority} of a frame filter in the dictionary matching
7394 @var{filter-dictionary}, and the frame filter name matching
7395 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7396 @code{progspace} or the name of the object file where the frame filter
7397 dictionary resides. The @var{priority} is an integer.
7399 @kindex show frame-filter priority
7400 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7401 Show the @var{priority} of a frame filter in the dictionary matching
7402 @var{filter-dictionary}, and the frame filter name matching
7403 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7404 @code{progspace} or the name of the object file where the frame filter
7410 (gdb) info frame-filter
7412 global frame-filters:
7413 Priority Enabled Name
7414 1000 Yes PrimaryFunctionFilter
7417 progspace /build/test frame-filters:
7418 Priority Enabled Name
7419 100 Yes ProgspaceFilter
7421 objfile /build/test frame-filters:
7422 Priority Enabled Name
7423 999 No BuildProgramFilter
7425 (gdb) set frame-filter priority global Reverse 50
7426 (gdb) info frame-filter
7428 global frame-filters:
7429 Priority Enabled Name
7430 1000 Yes PrimaryFunctionFilter
7433 progspace /build/test frame-filters:
7434 Priority Enabled Name
7435 100 Yes ProgspaceFilter
7437 objfile /build/test frame-filters:
7438 Priority Enabled Name
7439 999 No BuildProgramFilter
7444 @chapter Examining Source Files
7446 @value{GDBN} can print parts of your program's source, since the debugging
7447 information recorded in the program tells @value{GDBN} what source files were
7448 used to build it. When your program stops, @value{GDBN} spontaneously prints
7449 the line where it stopped. Likewise, when you select a stack frame
7450 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7451 execution in that frame has stopped. You can print other portions of
7452 source files by explicit command.
7454 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7455 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7456 @value{GDBN} under @sc{gnu} Emacs}.
7459 * List:: Printing source lines
7460 * Specify Location:: How to specify code locations
7461 * Edit:: Editing source files
7462 * Search:: Searching source files
7463 * Source Path:: Specifying source directories
7464 * Machine Code:: Source and machine code
7468 @section Printing Source Lines
7471 @kindex l @r{(@code{list})}
7472 To print lines from a source file, use the @code{list} command
7473 (abbreviated @code{l}). By default, ten lines are printed.
7474 There are several ways to specify what part of the file you want to
7475 print; see @ref{Specify Location}, for the full list.
7477 Here are the forms of the @code{list} command most commonly used:
7480 @item list @var{linenum}
7481 Print lines centered around line number @var{linenum} in the
7482 current source file.
7484 @item list @var{function}
7485 Print lines centered around the beginning of function
7489 Print more lines. If the last lines printed were printed with a
7490 @code{list} command, this prints lines following the last lines
7491 printed; however, if the last line printed was a solitary line printed
7492 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7493 Stack}), this prints lines centered around that line.
7496 Print lines just before the lines last printed.
7499 @cindex @code{list}, how many lines to display
7500 By default, @value{GDBN} prints ten source lines with any of these forms of
7501 the @code{list} command. You can change this using @code{set listsize}:
7504 @kindex set listsize
7505 @item set listsize @var{count}
7506 @itemx set listsize unlimited
7507 Make the @code{list} command display @var{count} source lines (unless
7508 the @code{list} argument explicitly specifies some other number).
7509 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7511 @kindex show listsize
7513 Display the number of lines that @code{list} prints.
7516 Repeating a @code{list} command with @key{RET} discards the argument,
7517 so it is equivalent to typing just @code{list}. This is more useful
7518 than listing the same lines again. An exception is made for an
7519 argument of @samp{-}; that argument is preserved in repetition so that
7520 each repetition moves up in the source file.
7522 In general, the @code{list} command expects you to supply zero, one or two
7523 @dfn{locations}. Locations specify source lines; there are several ways
7524 of writing them (@pxref{Specify Location}), but the effect is always
7525 to specify some source line.
7527 Here is a complete description of the possible arguments for @code{list}:
7530 @item list @var{location}
7531 Print lines centered around the line specified by @var{location}.
7533 @item list @var{first},@var{last}
7534 Print lines from @var{first} to @var{last}. Both arguments are
7535 locations. When a @code{list} command has two locations, and the
7536 source file of the second location is omitted, this refers to
7537 the same source file as the first location.
7539 @item list ,@var{last}
7540 Print lines ending with @var{last}.
7542 @item list @var{first},
7543 Print lines starting with @var{first}.
7546 Print lines just after the lines last printed.
7549 Print lines just before the lines last printed.
7552 As described in the preceding table.
7555 @node Specify Location
7556 @section Specifying a Location
7557 @cindex specifying location
7559 @cindex source location
7562 * Linespec Locations:: Linespec locations
7563 * Explicit Locations:: Explicit locations
7564 * Address Locations:: Address locations
7567 Several @value{GDBN} commands accept arguments that specify a location
7568 of your program's code. Since @value{GDBN} is a source-level
7569 debugger, a location usually specifies some line in the source code.
7570 Locations may be specified using three different formats:
7571 linespec locations, explicit locations, or address locations.
7573 @node Linespec Locations
7574 @subsection Linespec Locations
7575 @cindex linespec locations
7577 A @dfn{linespec} is a colon-separated list of source location parameters such
7578 as file name, function name, etc. Here are all the different ways of
7579 specifying a linespec:
7583 Specifies the line number @var{linenum} of the current source file.
7586 @itemx +@var{offset}
7587 Specifies the line @var{offset} lines before or after the @dfn{current
7588 line}. For the @code{list} command, the current line is the last one
7589 printed; for the breakpoint commands, this is the line at which
7590 execution stopped in the currently selected @dfn{stack frame}
7591 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7592 used as the second of the two linespecs in a @code{list} command,
7593 this specifies the line @var{offset} lines up or down from the first
7596 @item @var{filename}:@var{linenum}
7597 Specifies the line @var{linenum} in the source file @var{filename}.
7598 If @var{filename} is a relative file name, then it will match any
7599 source file name with the same trailing components. For example, if
7600 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7601 name of @file{/build/trunk/gcc/expr.c}, but not
7602 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7604 @item @var{function}
7605 Specifies the line that begins the body of the function @var{function}.
7606 For example, in C, this is the line with the open brace.
7608 @item @var{function}:@var{label}
7609 Specifies the line where @var{label} appears in @var{function}.
7611 @item @var{filename}:@var{function}
7612 Specifies the line that begins the body of the function @var{function}
7613 in the file @var{filename}. You only need the file name with a
7614 function name to avoid ambiguity when there are identically named
7615 functions in different source files.
7618 Specifies the line at which the label named @var{label} appears
7619 in the function corresponding to the currently selected stack frame.
7620 If there is no current selected stack frame (for instance, if the inferior
7621 is not running), then @value{GDBN} will not search for a label.
7623 @cindex breakpoint at static probe point
7624 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7625 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7626 applications to embed static probes. @xref{Static Probe Points}, for more
7627 information on finding and using static probes. This form of linespec
7628 specifies the location of such a static probe.
7630 If @var{objfile} is given, only probes coming from that shared library
7631 or executable matching @var{objfile} as a regular expression are considered.
7632 If @var{provider} is given, then only probes from that provider are considered.
7633 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7634 each one of those probes.
7637 @node Explicit Locations
7638 @subsection Explicit Locations
7639 @cindex explicit locations
7641 @dfn{Explicit locations} allow the user to directly specify the source
7642 location's parameters using option-value pairs.
7644 Explicit locations are useful when several functions, labels, or
7645 file names have the same name (base name for files) in the program's
7646 sources. In these cases, explicit locations point to the source
7647 line you meant more accurately and unambiguously. Also, using
7648 explicit locations might be faster in large programs.
7650 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7651 defined in the file named @file{foo} or the label @code{bar} in a function
7652 named @code{foo}. @value{GDBN} must search either the file system or
7653 the symbol table to know.
7655 The list of valid explicit location options is summarized in the
7659 @item -source @var{filename}
7660 The value specifies the source file name. To differentiate between
7661 files with the same base name, prepend as many directories as is necessary
7662 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7663 @value{GDBN} will use the first file it finds with the given base
7664 name. This option requires the use of either @code{-function} or @code{-line}.
7666 @item -function @var{function}
7667 The value specifies the name of a function. Operations
7668 on function locations unmodified by other options (such as @code{-label}
7669 or @code{-line}) refer to the line that begins the body of the function.
7670 In C, for example, this is the line with the open brace.
7672 @item -label @var{label}
7673 The value specifies the name of a label. When the function
7674 name is not specified, the label is searched in the function of the currently
7675 selected stack frame.
7677 @item -line @var{number}
7678 The value specifies a line offset for the location. The offset may either
7679 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7680 the command. When specified without any other options, the line offset is
7681 relative to the current line.
7684 Explicit location options may be abbreviated by omitting any non-unique
7685 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7687 @node Address Locations
7688 @subsection Address Locations
7689 @cindex address locations
7691 @dfn{Address locations} indicate a specific program address. They have
7692 the generalized form *@var{address}.
7694 For line-oriented commands, such as @code{list} and @code{edit}, this
7695 specifies a source line that contains @var{address}. For @code{break} and
7696 other breakpoint-oriented commands, this can be used to set breakpoints in
7697 parts of your program which do not have debugging information or
7700 Here @var{address} may be any expression valid in the current working
7701 language (@pxref{Languages, working language}) that specifies a code
7702 address. In addition, as a convenience, @value{GDBN} extends the
7703 semantics of expressions used in locations to cover several situations
7704 that frequently occur during debugging. Here are the various forms
7708 @item @var{expression}
7709 Any expression valid in the current working language.
7711 @item @var{funcaddr}
7712 An address of a function or procedure derived from its name. In C,
7713 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7714 simply the function's name @var{function} (and actually a special case
7715 of a valid expression). In Pascal and Modula-2, this is
7716 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7717 (although the Pascal form also works).
7719 This form specifies the address of the function's first instruction,
7720 before the stack frame and arguments have been set up.
7722 @item '@var{filename}':@var{funcaddr}
7723 Like @var{funcaddr} above, but also specifies the name of the source
7724 file explicitly. This is useful if the name of the function does not
7725 specify the function unambiguously, e.g., if there are several
7726 functions with identical names in different source files.
7730 @section Editing Source Files
7731 @cindex editing source files
7734 @kindex e @r{(@code{edit})}
7735 To edit the lines in a source file, use the @code{edit} command.
7736 The editing program of your choice
7737 is invoked with the current line set to
7738 the active line in the program.
7739 Alternatively, there are several ways to specify what part of the file you
7740 want to print if you want to see other parts of the program:
7743 @item edit @var{location}
7744 Edit the source file specified by @code{location}. Editing starts at
7745 that @var{location}, e.g., at the specified source line of the
7746 specified file. @xref{Specify Location}, for all the possible forms
7747 of the @var{location} argument; here are the forms of the @code{edit}
7748 command most commonly used:
7751 @item edit @var{number}
7752 Edit the current source file with @var{number} as the active line number.
7754 @item edit @var{function}
7755 Edit the file containing @var{function} at the beginning of its definition.
7760 @subsection Choosing your Editor
7761 You can customize @value{GDBN} to use any editor you want
7763 The only restriction is that your editor (say @code{ex}), recognizes the
7764 following command-line syntax:
7766 ex +@var{number} file
7768 The optional numeric value +@var{number} specifies the number of the line in
7769 the file where to start editing.}.
7770 By default, it is @file{@value{EDITOR}}, but you can change this
7771 by setting the environment variable @code{EDITOR} before using
7772 @value{GDBN}. For example, to configure @value{GDBN} to use the
7773 @code{vi} editor, you could use these commands with the @code{sh} shell:
7779 or in the @code{csh} shell,
7781 setenv EDITOR /usr/bin/vi
7786 @section Searching Source Files
7787 @cindex searching source files
7789 There are two commands for searching through the current source file for a
7794 @kindex forward-search
7795 @kindex fo @r{(@code{forward-search})}
7796 @item forward-search @var{regexp}
7797 @itemx search @var{regexp}
7798 The command @samp{forward-search @var{regexp}} checks each line,
7799 starting with the one following the last line listed, for a match for
7800 @var{regexp}. It lists the line that is found. You can use the
7801 synonym @samp{search @var{regexp}} or abbreviate the command name as
7804 @kindex reverse-search
7805 @item reverse-search @var{regexp}
7806 The command @samp{reverse-search @var{regexp}} checks each line, starting
7807 with the one before the last line listed and going backward, for a match
7808 for @var{regexp}. It lists the line that is found. You can abbreviate
7809 this command as @code{rev}.
7813 @section Specifying Source Directories
7816 @cindex directories for source files
7817 Executable programs sometimes do not record the directories of the source
7818 files from which they were compiled, just the names. Even when they do,
7819 the directories could be moved between the compilation and your debugging
7820 session. @value{GDBN} has a list of directories to search for source files;
7821 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7822 it tries all the directories in the list, in the order they are present
7823 in the list, until it finds a file with the desired name.
7825 For example, suppose an executable references the file
7826 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7827 @file{/mnt/cross}. The file is first looked up literally; if this
7828 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7829 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7830 message is printed. @value{GDBN} does not look up the parts of the
7831 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7832 Likewise, the subdirectories of the source path are not searched: if
7833 the source path is @file{/mnt/cross}, and the binary refers to
7834 @file{foo.c}, @value{GDBN} would not find it under
7835 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7837 Plain file names, relative file names with leading directories, file
7838 names containing dots, etc.@: are all treated as described above; for
7839 instance, if the source path is @file{/mnt/cross}, and the source file
7840 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7841 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7842 that---@file{/mnt/cross/foo.c}.
7844 Note that the executable search path is @emph{not} used to locate the
7847 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7848 any information it has cached about where source files are found and where
7849 each line is in the file.
7853 When you start @value{GDBN}, its source path includes only @samp{cdir}
7854 and @samp{cwd}, in that order.
7855 To add other directories, use the @code{directory} command.
7857 The search path is used to find both program source files and @value{GDBN}
7858 script files (read using the @samp{-command} option and @samp{source} command).
7860 In addition to the source path, @value{GDBN} provides a set of commands
7861 that manage a list of source path substitution rules. A @dfn{substitution
7862 rule} specifies how to rewrite source directories stored in the program's
7863 debug information in case the sources were moved to a different
7864 directory between compilation and debugging. A rule is made of
7865 two strings, the first specifying what needs to be rewritten in
7866 the path, and the second specifying how it should be rewritten.
7867 In @ref{set substitute-path}, we name these two parts @var{from} and
7868 @var{to} respectively. @value{GDBN} does a simple string replacement
7869 of @var{from} with @var{to} at the start of the directory part of the
7870 source file name, and uses that result instead of the original file
7871 name to look up the sources.
7873 Using the previous example, suppose the @file{foo-1.0} tree has been
7874 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7875 @value{GDBN} to replace @file{/usr/src} in all source path names with
7876 @file{/mnt/cross}. The first lookup will then be
7877 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7878 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7879 substitution rule, use the @code{set substitute-path} command
7880 (@pxref{set substitute-path}).
7882 To avoid unexpected substitution results, a rule is applied only if the
7883 @var{from} part of the directory name ends at a directory separator.
7884 For instance, a rule substituting @file{/usr/source} into
7885 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7886 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7887 is applied only at the beginning of the directory name, this rule will
7888 not be applied to @file{/root/usr/source/baz.c} either.
7890 In many cases, you can achieve the same result using the @code{directory}
7891 command. However, @code{set substitute-path} can be more efficient in
7892 the case where the sources are organized in a complex tree with multiple
7893 subdirectories. With the @code{directory} command, you need to add each
7894 subdirectory of your project. If you moved the entire tree while
7895 preserving its internal organization, then @code{set substitute-path}
7896 allows you to direct the debugger to all the sources with one single
7899 @code{set substitute-path} is also more than just a shortcut command.
7900 The source path is only used if the file at the original location no
7901 longer exists. On the other hand, @code{set substitute-path} modifies
7902 the debugger behavior to look at the rewritten location instead. So, if
7903 for any reason a source file that is not relevant to your executable is
7904 located at the original location, a substitution rule is the only
7905 method available to point @value{GDBN} at the new location.
7907 @cindex @samp{--with-relocated-sources}
7908 @cindex default source path substitution
7909 You can configure a default source path substitution rule by
7910 configuring @value{GDBN} with the
7911 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7912 should be the name of a directory under @value{GDBN}'s configured
7913 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7914 directory names in debug information under @var{dir} will be adjusted
7915 automatically if the installed @value{GDBN} is moved to a new
7916 location. This is useful if @value{GDBN}, libraries or executables
7917 with debug information and corresponding source code are being moved
7921 @item directory @var{dirname} @dots{}
7922 @item dir @var{dirname} @dots{}
7923 Add directory @var{dirname} to the front of the source path. Several
7924 directory names may be given to this command, separated by @samp{:}
7925 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7926 part of absolute file names) or
7927 whitespace. You may specify a directory that is already in the source
7928 path; this moves it forward, so @value{GDBN} searches it sooner.
7932 @vindex $cdir@r{, convenience variable}
7933 @vindex $cwd@r{, convenience variable}
7934 @cindex compilation directory
7935 @cindex current directory
7936 @cindex working directory
7937 @cindex directory, current
7938 @cindex directory, compilation
7939 You can use the string @samp{$cdir} to refer to the compilation
7940 directory (if one is recorded), and @samp{$cwd} to refer to the current
7941 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7942 tracks the current working directory as it changes during your @value{GDBN}
7943 session, while the latter is immediately expanded to the current
7944 directory at the time you add an entry to the source path.
7947 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7949 @c RET-repeat for @code{directory} is explicitly disabled, but since
7950 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7952 @item set directories @var{path-list}
7953 @kindex set directories
7954 Set the source path to @var{path-list}.
7955 @samp{$cdir:$cwd} are added if missing.
7957 @item show directories
7958 @kindex show directories
7959 Print the source path: show which directories it contains.
7961 @anchor{set substitute-path}
7962 @item set substitute-path @var{from} @var{to}
7963 @kindex set substitute-path
7964 Define a source path substitution rule, and add it at the end of the
7965 current list of existing substitution rules. If a rule with the same
7966 @var{from} was already defined, then the old rule is also deleted.
7968 For example, if the file @file{/foo/bar/baz.c} was moved to
7969 @file{/mnt/cross/baz.c}, then the command
7972 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
7976 will tell @value{GDBN} to replace @samp{/foo/bar} with
7977 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7978 @file{baz.c} even though it was moved.
7980 In the case when more than one substitution rule have been defined,
7981 the rules are evaluated one by one in the order where they have been
7982 defined. The first one matching, if any, is selected to perform
7985 For instance, if we had entered the following commands:
7988 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7989 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7993 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7994 @file{/mnt/include/defs.h} by using the first rule. However, it would
7995 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7996 @file{/mnt/src/lib/foo.c}.
7999 @item unset substitute-path [path]
8000 @kindex unset substitute-path
8001 If a path is specified, search the current list of substitution rules
8002 for a rule that would rewrite that path. Delete that rule if found.
8003 A warning is emitted by the debugger if no rule could be found.
8005 If no path is specified, then all substitution rules are deleted.
8007 @item show substitute-path [path]
8008 @kindex show substitute-path
8009 If a path is specified, then print the source path substitution rule
8010 which would rewrite that path, if any.
8012 If no path is specified, then print all existing source path substitution
8017 If your source path is cluttered with directories that are no longer of
8018 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8019 versions of source. You can correct the situation as follows:
8023 Use @code{directory} with no argument to reset the source path to its default value.
8026 Use @code{directory} with suitable arguments to reinstall the
8027 directories you want in the source path. You can add all the
8028 directories in one command.
8032 @section Source and Machine Code
8033 @cindex source line and its code address
8035 You can use the command @code{info line} to map source lines to program
8036 addresses (and vice versa), and the command @code{disassemble} to display
8037 a range of addresses as machine instructions. You can use the command
8038 @code{set disassemble-next-line} to set whether to disassemble next
8039 source line when execution stops. When run under @sc{gnu} Emacs
8040 mode, the @code{info line} command causes the arrow to point to the
8041 line specified. Also, @code{info line} prints addresses in symbolic form as
8046 @item info line @var{location}
8047 Print the starting and ending addresses of the compiled code for
8048 source line @var{location}. You can specify source lines in any of
8049 the ways documented in @ref{Specify Location}.
8052 For example, we can use @code{info line} to discover the location of
8053 the object code for the first line of function
8054 @code{m4_changequote}:
8056 @c FIXME: I think this example should also show the addresses in
8057 @c symbolic form, as they usually would be displayed.
8059 (@value{GDBP}) info line m4_changequote
8060 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8064 @cindex code address and its source line
8065 We can also inquire (using @code{*@var{addr}} as the form for
8066 @var{location}) what source line covers a particular address:
8068 (@value{GDBP}) info line *0x63ff
8069 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8072 @cindex @code{$_} and @code{info line}
8073 @cindex @code{x} command, default address
8074 @kindex x@r{(examine), and} info line
8075 After @code{info line}, the default address for the @code{x} command
8076 is changed to the starting address of the line, so that @samp{x/i} is
8077 sufficient to begin examining the machine code (@pxref{Memory,
8078 ,Examining Memory}). Also, this address is saved as the value of the
8079 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8084 @cindex assembly instructions
8085 @cindex instructions, assembly
8086 @cindex machine instructions
8087 @cindex listing machine instructions
8089 @itemx disassemble /m
8090 @itemx disassemble /s
8091 @itemx disassemble /r
8092 This specialized command dumps a range of memory as machine
8093 instructions. It can also print mixed source+disassembly by specifying
8094 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8095 as well as in symbolic form by specifying the @code{/r} modifier.
8096 The default memory range is the function surrounding the
8097 program counter of the selected frame. A single argument to this
8098 command is a program counter value; @value{GDBN} dumps the function
8099 surrounding this value. When two arguments are given, they should
8100 be separated by a comma, possibly surrounded by whitespace. The
8101 arguments specify a range of addresses to dump, in one of two forms:
8104 @item @var{start},@var{end}
8105 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8106 @item @var{start},+@var{length}
8107 the addresses from @var{start} (inclusive) to
8108 @code{@var{start}+@var{length}} (exclusive).
8112 When 2 arguments are specified, the name of the function is also
8113 printed (since there could be several functions in the given range).
8115 The argument(s) can be any expression yielding a numeric value, such as
8116 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8118 If the range of memory being disassembled contains current program counter,
8119 the instruction at that location is shown with a @code{=>} marker.
8122 The following example shows the disassembly of a range of addresses of
8123 HP PA-RISC 2.0 code:
8126 (@value{GDBP}) disas 0x32c4, 0x32e4
8127 Dump of assembler code from 0x32c4 to 0x32e4:
8128 0x32c4 <main+204>: addil 0,dp
8129 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8130 0x32cc <main+212>: ldil 0x3000,r31
8131 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8132 0x32d4 <main+220>: ldo 0(r31),rp
8133 0x32d8 <main+224>: addil -0x800,dp
8134 0x32dc <main+228>: ldo 0x588(r1),r26
8135 0x32e0 <main+232>: ldil 0x3000,r31
8136 End of assembler dump.
8139 Here is an example showing mixed source+assembly for Intel x86
8140 with @code{/m} or @code{/s}, when the program is stopped just after
8141 function prologue in a non-optimized function with no inline code.
8144 (@value{GDBP}) disas /m main
8145 Dump of assembler code for function main:
8147 0x08048330 <+0>: push %ebp
8148 0x08048331 <+1>: mov %esp,%ebp
8149 0x08048333 <+3>: sub $0x8,%esp
8150 0x08048336 <+6>: and $0xfffffff0,%esp
8151 0x08048339 <+9>: sub $0x10,%esp
8153 6 printf ("Hello.\n");
8154 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8155 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8159 0x08048348 <+24>: mov $0x0,%eax
8160 0x0804834d <+29>: leave
8161 0x0804834e <+30>: ret
8163 End of assembler dump.
8166 The @code{/m} option is deprecated as its output is not useful when
8167 there is either inlined code or re-ordered code.
8168 The @code{/s} option is the preferred choice.
8169 Here is an example for AMD x86-64 showing the difference between
8170 @code{/m} output and @code{/s} output.
8171 This example has one inline function defined in a header file,
8172 and the code is compiled with @samp{-O2} optimization.
8173 Note how the @code{/m} output is missing the disassembly of
8174 several instructions that are present in the @code{/s} output.
8204 (@value{GDBP}) disas /m main
8205 Dump of assembler code for function main:
8209 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8210 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8214 0x000000000040041d <+29>: xor %eax,%eax
8215 0x000000000040041f <+31>: retq
8216 0x0000000000400420 <+32>: add %eax,%eax
8217 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8219 End of assembler dump.
8220 (@value{GDBP}) disas /s main
8221 Dump of assembler code for function main:
8225 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8229 0x0000000000400406 <+6>: test %eax,%eax
8230 0x0000000000400408 <+8>: js 0x400420 <main+32>
8235 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8236 0x000000000040040d <+13>: test %eax,%eax
8237 0x000000000040040f <+15>: mov $0x1,%eax
8238 0x0000000000400414 <+20>: cmovne %edx,%eax
8242 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8246 0x000000000040041d <+29>: xor %eax,%eax
8247 0x000000000040041f <+31>: retq
8251 0x0000000000400420 <+32>: add %eax,%eax
8252 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8253 End of assembler dump.
8256 Here is another example showing raw instructions in hex for AMD x86-64,
8259 (gdb) disas /r 0x400281,+10
8260 Dump of assembler code from 0x400281 to 0x40028b:
8261 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8262 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8263 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8264 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8265 End of assembler dump.
8268 Addresses cannot be specified as a location (@pxref{Specify Location}).
8269 So, for example, if you want to disassemble function @code{bar}
8270 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8271 and not @samp{disassemble foo.c:bar}.
8273 Some architectures have more than one commonly-used set of instruction
8274 mnemonics or other syntax.
8276 For programs that were dynamically linked and use shared libraries,
8277 instructions that call functions or branch to locations in the shared
8278 libraries might show a seemingly bogus location---it's actually a
8279 location of the relocation table. On some architectures, @value{GDBN}
8280 might be able to resolve these to actual function names.
8283 @kindex set disassembly-flavor
8284 @cindex Intel disassembly flavor
8285 @cindex AT&T disassembly flavor
8286 @item set disassembly-flavor @var{instruction-set}
8287 Select the instruction set to use when disassembling the
8288 program via the @code{disassemble} or @code{x/i} commands.
8290 Currently this command is only defined for the Intel x86 family. You
8291 can set @var{instruction-set} to either @code{intel} or @code{att}.
8292 The default is @code{att}, the AT&T flavor used by default by Unix
8293 assemblers for x86-based targets.
8295 @kindex show disassembly-flavor
8296 @item show disassembly-flavor
8297 Show the current setting of the disassembly flavor.
8301 @kindex set disassemble-next-line
8302 @kindex show disassemble-next-line
8303 @item set disassemble-next-line
8304 @itemx show disassemble-next-line
8305 Control whether or not @value{GDBN} will disassemble the next source
8306 line or instruction when execution stops. If ON, @value{GDBN} will
8307 display disassembly of the next source line when execution of the
8308 program being debugged stops. This is @emph{in addition} to
8309 displaying the source line itself, which @value{GDBN} always does if
8310 possible. If the next source line cannot be displayed for some reason
8311 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8312 info in the debug info), @value{GDBN} will display disassembly of the
8313 next @emph{instruction} instead of showing the next source line. If
8314 AUTO, @value{GDBN} will display disassembly of next instruction only
8315 if the source line cannot be displayed. This setting causes
8316 @value{GDBN} to display some feedback when you step through a function
8317 with no line info or whose source file is unavailable. The default is
8318 OFF, which means never display the disassembly of the next line or
8324 @chapter Examining Data
8326 @cindex printing data
8327 @cindex examining data
8330 The usual way to examine data in your program is with the @code{print}
8331 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8332 evaluates and prints the value of an expression of the language your
8333 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8334 Different Languages}). It may also print the expression using a
8335 Python-based pretty-printer (@pxref{Pretty Printing}).
8338 @item print @var{expr}
8339 @itemx print /@var{f} @var{expr}
8340 @var{expr} is an expression (in the source language). By default the
8341 value of @var{expr} is printed in a format appropriate to its data type;
8342 you can choose a different format by specifying @samp{/@var{f}}, where
8343 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8347 @itemx print /@var{f}
8348 @cindex reprint the last value
8349 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8350 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8351 conveniently inspect the same value in an alternative format.
8354 A more low-level way of examining data is with the @code{x} command.
8355 It examines data in memory at a specified address and prints it in a
8356 specified format. @xref{Memory, ,Examining Memory}.
8358 If you are interested in information about types, or about how the
8359 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8360 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8363 @cindex exploring hierarchical data structures
8365 Another way of examining values of expressions and type information is
8366 through the Python extension command @code{explore} (available only if
8367 the @value{GDBN} build is configured with @code{--with-python}). It
8368 offers an interactive way to start at the highest level (or, the most
8369 abstract level) of the data type of an expression (or, the data type
8370 itself) and explore all the way down to leaf scalar values/fields
8371 embedded in the higher level data types.
8374 @item explore @var{arg}
8375 @var{arg} is either an expression (in the source language), or a type
8376 visible in the current context of the program being debugged.
8379 The working of the @code{explore} command can be illustrated with an
8380 example. If a data type @code{struct ComplexStruct} is defined in your
8390 struct ComplexStruct
8392 struct SimpleStruct *ss_p;
8398 followed by variable declarations as
8401 struct SimpleStruct ss = @{ 10, 1.11 @};
8402 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8406 then, the value of the variable @code{cs} can be explored using the
8407 @code{explore} command as follows.
8411 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8412 the following fields:
8414 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8415 arr = <Enter 1 to explore this field of type `int [10]'>
8417 Enter the field number of choice:
8421 Since the fields of @code{cs} are not scalar values, you are being
8422 prompted to chose the field you want to explore. Let's say you choose
8423 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8424 pointer, you will be asked if it is pointing to a single value. From
8425 the declaration of @code{cs} above, it is indeed pointing to a single
8426 value, hence you enter @code{y}. If you enter @code{n}, then you will
8427 be asked if it were pointing to an array of values, in which case this
8428 field will be explored as if it were an array.
8431 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8432 Continue exploring it as a pointer to a single value [y/n]: y
8433 The value of `*(cs.ss_p)' is a struct/class of type `struct
8434 SimpleStruct' with the following fields:
8436 i = 10 .. (Value of type `int')
8437 d = 1.1100000000000001 .. (Value of type `double')
8439 Press enter to return to parent value:
8443 If the field @code{arr} of @code{cs} was chosen for exploration by
8444 entering @code{1} earlier, then since it is as array, you will be
8445 prompted to enter the index of the element in the array that you want
8449 `cs.arr' is an array of `int'.
8450 Enter the index of the element you want to explore in `cs.arr': 5
8452 `(cs.arr)[5]' is a scalar value of type `int'.
8456 Press enter to return to parent value:
8459 In general, at any stage of exploration, you can go deeper towards the
8460 leaf values by responding to the prompts appropriately, or hit the
8461 return key to return to the enclosing data structure (the @i{higher}
8462 level data structure).
8464 Similar to exploring values, you can use the @code{explore} command to
8465 explore types. Instead of specifying a value (which is typically a
8466 variable name or an expression valid in the current context of the
8467 program being debugged), you specify a type name. If you consider the
8468 same example as above, your can explore the type
8469 @code{struct ComplexStruct} by passing the argument
8470 @code{struct ComplexStruct} to the @code{explore} command.
8473 (gdb) explore struct ComplexStruct
8477 By responding to the prompts appropriately in the subsequent interactive
8478 session, you can explore the type @code{struct ComplexStruct} in a
8479 manner similar to how the value @code{cs} was explored in the above
8482 The @code{explore} command also has two sub-commands,
8483 @code{explore value} and @code{explore type}. The former sub-command is
8484 a way to explicitly specify that value exploration of the argument is
8485 being invoked, while the latter is a way to explicitly specify that type
8486 exploration of the argument is being invoked.
8489 @item explore value @var{expr}
8490 @cindex explore value
8491 This sub-command of @code{explore} explores the value of the
8492 expression @var{expr} (if @var{expr} is an expression valid in the
8493 current context of the program being debugged). The behavior of this
8494 command is identical to that of the behavior of the @code{explore}
8495 command being passed the argument @var{expr}.
8497 @item explore type @var{arg}
8498 @cindex explore type
8499 This sub-command of @code{explore} explores the type of @var{arg} (if
8500 @var{arg} is a type visible in the current context of program being
8501 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8502 is an expression valid in the current context of the program being
8503 debugged). If @var{arg} is a type, then the behavior of this command is
8504 identical to that of the @code{explore} command being passed the
8505 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8506 this command will be identical to that of the @code{explore} command
8507 being passed the type of @var{arg} as the argument.
8511 * Expressions:: Expressions
8512 * Ambiguous Expressions:: Ambiguous Expressions
8513 * Variables:: Program variables
8514 * Arrays:: Artificial arrays
8515 * Output Formats:: Output formats
8516 * Memory:: Examining memory
8517 * Auto Display:: Automatic display
8518 * Print Settings:: Print settings
8519 * Pretty Printing:: Python pretty printing
8520 * Value History:: Value history
8521 * Convenience Vars:: Convenience variables
8522 * Convenience Funs:: Convenience functions
8523 * Registers:: Registers
8524 * Floating Point Hardware:: Floating point hardware
8525 * Vector Unit:: Vector Unit
8526 * OS Information:: Auxiliary data provided by operating system
8527 * Memory Region Attributes:: Memory region attributes
8528 * Dump/Restore Files:: Copy between memory and a file
8529 * Core File Generation:: Cause a program dump its core
8530 * Character Sets:: Debugging programs that use a different
8531 character set than GDB does
8532 * Caching Target Data:: Data caching for targets
8533 * Searching Memory:: Searching memory for a sequence of bytes
8537 @section Expressions
8540 @code{print} and many other @value{GDBN} commands accept an expression and
8541 compute its value. Any kind of constant, variable or operator defined
8542 by the programming language you are using is valid in an expression in
8543 @value{GDBN}. This includes conditional expressions, function calls,
8544 casts, and string constants. It also includes preprocessor macros, if
8545 you compiled your program to include this information; see
8548 @cindex arrays in expressions
8549 @value{GDBN} supports array constants in expressions input by
8550 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8551 you can use the command @code{print @{1, 2, 3@}} to create an array
8552 of three integers. If you pass an array to a function or assign it
8553 to a program variable, @value{GDBN} copies the array to memory that
8554 is @code{malloc}ed in the target program.
8556 Because C is so widespread, most of the expressions shown in examples in
8557 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8558 Languages}, for information on how to use expressions in other
8561 In this section, we discuss operators that you can use in @value{GDBN}
8562 expressions regardless of your programming language.
8564 @cindex casts, in expressions
8565 Casts are supported in all languages, not just in C, because it is so
8566 useful to cast a number into a pointer in order to examine a structure
8567 at that address in memory.
8568 @c FIXME: casts supported---Mod2 true?
8570 @value{GDBN} supports these operators, in addition to those common
8571 to programming languages:
8575 @samp{@@} is a binary operator for treating parts of memory as arrays.
8576 @xref{Arrays, ,Artificial Arrays}, for more information.
8579 @samp{::} allows you to specify a variable in terms of the file or
8580 function where it is defined. @xref{Variables, ,Program Variables}.
8582 @cindex @{@var{type}@}
8583 @cindex type casting memory
8584 @cindex memory, viewing as typed object
8585 @cindex casts, to view memory
8586 @item @{@var{type}@} @var{addr}
8587 Refers to an object of type @var{type} stored at address @var{addr} in
8588 memory. The address @var{addr} may be any expression whose value is
8589 an integer or pointer (but parentheses are required around binary
8590 operators, just as in a cast). This construct is allowed regardless
8591 of what kind of data is normally supposed to reside at @var{addr}.
8594 @node Ambiguous Expressions
8595 @section Ambiguous Expressions
8596 @cindex ambiguous expressions
8598 Expressions can sometimes contain some ambiguous elements. For instance,
8599 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8600 a single function name to be defined several times, for application in
8601 different contexts. This is called @dfn{overloading}. Another example
8602 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8603 templates and is typically instantiated several times, resulting in
8604 the same function name being defined in different contexts.
8606 In some cases and depending on the language, it is possible to adjust
8607 the expression to remove the ambiguity. For instance in C@t{++}, you
8608 can specify the signature of the function you want to break on, as in
8609 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8610 qualified name of your function often makes the expression unambiguous
8613 When an ambiguity that needs to be resolved is detected, the debugger
8614 has the capability to display a menu of numbered choices for each
8615 possibility, and then waits for the selection with the prompt @samp{>}.
8616 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8617 aborts the current command. If the command in which the expression was
8618 used allows more than one choice to be selected, the next option in the
8619 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8622 For example, the following session excerpt shows an attempt to set a
8623 breakpoint at the overloaded symbol @code{String::after}.
8624 We choose three particular definitions of that function name:
8626 @c FIXME! This is likely to change to show arg type lists, at least
8629 (@value{GDBP}) b String::after
8632 [2] file:String.cc; line number:867
8633 [3] file:String.cc; line number:860
8634 [4] file:String.cc; line number:875
8635 [5] file:String.cc; line number:853
8636 [6] file:String.cc; line number:846
8637 [7] file:String.cc; line number:735
8639 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8640 Breakpoint 2 at 0xb344: file String.cc, line 875.
8641 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8642 Multiple breakpoints were set.
8643 Use the "delete" command to delete unwanted
8650 @kindex set multiple-symbols
8651 @item set multiple-symbols @var{mode}
8652 @cindex multiple-symbols menu
8654 This option allows you to adjust the debugger behavior when an expression
8657 By default, @var{mode} is set to @code{all}. If the command with which
8658 the expression is used allows more than one choice, then @value{GDBN}
8659 automatically selects all possible choices. For instance, inserting
8660 a breakpoint on a function using an ambiguous name results in a breakpoint
8661 inserted on each possible match. However, if a unique choice must be made,
8662 then @value{GDBN} uses the menu to help you disambiguate the expression.
8663 For instance, printing the address of an overloaded function will result
8664 in the use of the menu.
8666 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8667 when an ambiguity is detected.
8669 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8670 an error due to the ambiguity and the command is aborted.
8672 @kindex show multiple-symbols
8673 @item show multiple-symbols
8674 Show the current value of the @code{multiple-symbols} setting.
8678 @section Program Variables
8680 The most common kind of expression to use is the name of a variable
8683 Variables in expressions are understood in the selected stack frame
8684 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8688 global (or file-static)
8695 visible according to the scope rules of the
8696 programming language from the point of execution in that frame
8699 @noindent This means that in the function
8714 you can examine and use the variable @code{a} whenever your program is
8715 executing within the function @code{foo}, but you can only use or
8716 examine the variable @code{b} while your program is executing inside
8717 the block where @code{b} is declared.
8719 @cindex variable name conflict
8720 There is an exception: you can refer to a variable or function whose
8721 scope is a single source file even if the current execution point is not
8722 in this file. But it is possible to have more than one such variable or
8723 function with the same name (in different source files). If that
8724 happens, referring to that name has unpredictable effects. If you wish,
8725 you can specify a static variable in a particular function or file by
8726 using the colon-colon (@code{::}) notation:
8728 @cindex colon-colon, context for variables/functions
8730 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8731 @cindex @code{::}, context for variables/functions
8734 @var{file}::@var{variable}
8735 @var{function}::@var{variable}
8739 Here @var{file} or @var{function} is the name of the context for the
8740 static @var{variable}. In the case of file names, you can use quotes to
8741 make sure @value{GDBN} parses the file name as a single word---for example,
8742 to print a global value of @code{x} defined in @file{f2.c}:
8745 (@value{GDBP}) p 'f2.c'::x
8748 The @code{::} notation is normally used for referring to
8749 static variables, since you typically disambiguate uses of local variables
8750 in functions by selecting the appropriate frame and using the
8751 simple name of the variable. However, you may also use this notation
8752 to refer to local variables in frames enclosing the selected frame:
8761 process (a); /* Stop here */
8772 For example, if there is a breakpoint at the commented line,
8773 here is what you might see
8774 when the program stops after executing the call @code{bar(0)}:
8779 (@value{GDBP}) p bar::a
8782 #2 0x080483d0 in foo (a=5) at foobar.c:12
8785 (@value{GDBP}) p bar::a
8789 @cindex C@t{++} scope resolution
8790 These uses of @samp{::} are very rarely in conflict with the very
8791 similar use of the same notation in C@t{++}. When they are in
8792 conflict, the C@t{++} meaning takes precedence; however, this can be
8793 overridden by quoting the file or function name with single quotes.
8795 For example, suppose the program is stopped in a method of a class
8796 that has a field named @code{includefile}, and there is also an
8797 include file named @file{includefile} that defines a variable,
8801 (@value{GDBP}) p includefile
8803 (@value{GDBP}) p includefile::some_global
8804 A syntax error in expression, near `'.
8805 (@value{GDBP}) p 'includefile'::some_global
8809 @cindex wrong values
8810 @cindex variable values, wrong
8811 @cindex function entry/exit, wrong values of variables
8812 @cindex optimized code, wrong values of variables
8814 @emph{Warning:} Occasionally, a local variable may appear to have the
8815 wrong value at certain points in a function---just after entry to a new
8816 scope, and just before exit.
8818 You may see this problem when you are stepping by machine instructions.
8819 This is because, on most machines, it takes more than one instruction to
8820 set up a stack frame (including local variable definitions); if you are
8821 stepping by machine instructions, variables may appear to have the wrong
8822 values until the stack frame is completely built. On exit, it usually
8823 also takes more than one machine instruction to destroy a stack frame;
8824 after you begin stepping through that group of instructions, local
8825 variable definitions may be gone.
8827 This may also happen when the compiler does significant optimizations.
8828 To be sure of always seeing accurate values, turn off all optimization
8831 @cindex ``No symbol "foo" in current context''
8832 Another possible effect of compiler optimizations is to optimize
8833 unused variables out of existence, or assign variables to registers (as
8834 opposed to memory addresses). Depending on the support for such cases
8835 offered by the debug info format used by the compiler, @value{GDBN}
8836 might not be able to display values for such local variables. If that
8837 happens, @value{GDBN} will print a message like this:
8840 No symbol "foo" in current context.
8843 To solve such problems, either recompile without optimizations, or use a
8844 different debug info format, if the compiler supports several such
8845 formats. @xref{Compilation}, for more information on choosing compiler
8846 options. @xref{C, ,C and C@t{++}}, for more information about debug
8847 info formats that are best suited to C@t{++} programs.
8849 If you ask to print an object whose contents are unknown to
8850 @value{GDBN}, e.g., because its data type is not completely specified
8851 by the debug information, @value{GDBN} will say @samp{<incomplete
8852 type>}. @xref{Symbols, incomplete type}, for more about this.
8854 If you append @kbd{@@entry} string to a function parameter name you get its
8855 value at the time the function got called. If the value is not available an
8856 error message is printed. Entry values are available only with some compilers.
8857 Entry values are normally also printed at the function parameter list according
8858 to @ref{set print entry-values}.
8861 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8867 (gdb) print i@@entry
8871 Strings are identified as arrays of @code{char} values without specified
8872 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8873 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8874 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8875 defines literal string type @code{"char"} as @code{char} without a sign.
8880 signed char var1[] = "A";
8883 You get during debugging
8888 $2 = @{65 'A', 0 '\0'@}
8892 @section Artificial Arrays
8894 @cindex artificial array
8896 @kindex @@@r{, referencing memory as an array}
8897 It is often useful to print out several successive objects of the
8898 same type in memory; a section of an array, or an array of
8899 dynamically determined size for which only a pointer exists in the
8902 You can do this by referring to a contiguous span of memory as an
8903 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8904 operand of @samp{@@} should be the first element of the desired array
8905 and be an individual object. The right operand should be the desired length
8906 of the array. The result is an array value whose elements are all of
8907 the type of the left argument. The first element is actually the left
8908 argument; the second element comes from bytes of memory immediately
8909 following those that hold the first element, and so on. Here is an
8910 example. If a program says
8913 int *array = (int *) malloc (len * sizeof (int));
8917 you can print the contents of @code{array} with
8923 The left operand of @samp{@@} must reside in memory. Array values made
8924 with @samp{@@} in this way behave just like other arrays in terms of
8925 subscripting, and are coerced to pointers when used in expressions.
8926 Artificial arrays most often appear in expressions via the value history
8927 (@pxref{Value History, ,Value History}), after printing one out.
8929 Another way to create an artificial array is to use a cast.
8930 This re-interprets a value as if it were an array.
8931 The value need not be in memory:
8933 (@value{GDBP}) p/x (short[2])0x12345678
8934 $1 = @{0x1234, 0x5678@}
8937 As a convenience, if you leave the array length out (as in
8938 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8939 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8941 (@value{GDBP}) p/x (short[])0x12345678
8942 $2 = @{0x1234, 0x5678@}
8945 Sometimes the artificial array mechanism is not quite enough; in
8946 moderately complex data structures, the elements of interest may not
8947 actually be adjacent---for example, if you are interested in the values
8948 of pointers in an array. One useful work-around in this situation is
8949 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8950 Variables}) as a counter in an expression that prints the first
8951 interesting value, and then repeat that expression via @key{RET}. For
8952 instance, suppose you have an array @code{dtab} of pointers to
8953 structures, and you are interested in the values of a field @code{fv}
8954 in each structure. Here is an example of what you might type:
8964 @node Output Formats
8965 @section Output Formats
8967 @cindex formatted output
8968 @cindex output formats
8969 By default, @value{GDBN} prints a value according to its data type. Sometimes
8970 this is not what you want. For example, you might want to print a number
8971 in hex, or a pointer in decimal. Or you might want to view data in memory
8972 at a certain address as a character string or as an instruction. To do
8973 these things, specify an @dfn{output format} when you print a value.
8975 The simplest use of output formats is to say how to print a value
8976 already computed. This is done by starting the arguments of the
8977 @code{print} command with a slash and a format letter. The format
8978 letters supported are:
8982 Regard the bits of the value as an integer, and print the integer in
8986 Print as integer in signed decimal.
8989 Print as integer in unsigned decimal.
8992 Print as integer in octal.
8995 Print as integer in binary. The letter @samp{t} stands for ``two''.
8996 @footnote{@samp{b} cannot be used because these format letters are also
8997 used with the @code{x} command, where @samp{b} stands for ``byte'';
8998 see @ref{Memory,,Examining Memory}.}
9001 @cindex unknown address, locating
9002 @cindex locate address
9003 Print as an address, both absolute in hexadecimal and as an offset from
9004 the nearest preceding symbol. You can use this format used to discover
9005 where (in what function) an unknown address is located:
9008 (@value{GDBP}) p/a 0x54320
9009 $3 = 0x54320 <_initialize_vx+396>
9013 The command @code{info symbol 0x54320} yields similar results.
9014 @xref{Symbols, info symbol}.
9017 Regard as an integer and print it as a character constant. This
9018 prints both the numerical value and its character representation. The
9019 character representation is replaced with the octal escape @samp{\nnn}
9020 for characters outside the 7-bit @sc{ascii} range.
9022 Without this format, @value{GDBN} displays @code{char},
9023 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9024 constants. Single-byte members of vectors are displayed as integer
9028 Regard the bits of the value as a floating point number and print
9029 using typical floating point syntax.
9032 @cindex printing strings
9033 @cindex printing byte arrays
9034 Regard as a string, if possible. With this format, pointers to single-byte
9035 data are displayed as null-terminated strings and arrays of single-byte data
9036 are displayed as fixed-length strings. Other values are displayed in their
9039 Without this format, @value{GDBN} displays pointers to and arrays of
9040 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9041 strings. Single-byte members of a vector are displayed as an integer
9045 Like @samp{x} formatting, the value is treated as an integer and
9046 printed as hexadecimal, but leading zeros are printed to pad the value
9047 to the size of the integer type.
9050 @cindex raw printing
9051 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9052 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9053 Printing}). This typically results in a higher-level display of the
9054 value's contents. The @samp{r} format bypasses any Python
9055 pretty-printer which might exist.
9058 For example, to print the program counter in hex (@pxref{Registers}), type
9065 Note that no space is required before the slash; this is because command
9066 names in @value{GDBN} cannot contain a slash.
9068 To reprint the last value in the value history with a different format,
9069 you can use the @code{print} command with just a format and no
9070 expression. For example, @samp{p/x} reprints the last value in hex.
9073 @section Examining Memory
9075 You can use the command @code{x} (for ``examine'') to examine memory in
9076 any of several formats, independently of your program's data types.
9078 @cindex examining memory
9080 @kindex x @r{(examine memory)}
9081 @item x/@var{nfu} @var{addr}
9084 Use the @code{x} command to examine memory.
9087 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9088 much memory to display and how to format it; @var{addr} is an
9089 expression giving the address where you want to start displaying memory.
9090 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9091 Several commands set convenient defaults for @var{addr}.
9094 @item @var{n}, the repeat count
9095 The repeat count is a decimal integer; the default is 1. It specifies
9096 how much memory (counting by units @var{u}) to display.
9097 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9100 @item @var{f}, the display format
9101 The display format is one of the formats used by @code{print}
9102 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9103 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9104 The default is @samp{x} (hexadecimal) initially. The default changes
9105 each time you use either @code{x} or @code{print}.
9107 @item @var{u}, the unit size
9108 The unit size is any of
9114 Halfwords (two bytes).
9116 Words (four bytes). This is the initial default.
9118 Giant words (eight bytes).
9121 Each time you specify a unit size with @code{x}, that size becomes the
9122 default unit the next time you use @code{x}. For the @samp{i} format,
9123 the unit size is ignored and is normally not written. For the @samp{s} format,
9124 the unit size defaults to @samp{b}, unless it is explicitly given.
9125 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9126 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9127 Note that the results depend on the programming language of the
9128 current compilation unit. If the language is C, the @samp{s}
9129 modifier will use the UTF-16 encoding while @samp{w} will use
9130 UTF-32. The encoding is set by the programming language and cannot
9133 @item @var{addr}, starting display address
9134 @var{addr} is the address where you want @value{GDBN} to begin displaying
9135 memory. The expression need not have a pointer value (though it may);
9136 it is always interpreted as an integer address of a byte of memory.
9137 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9138 @var{addr} is usually just after the last address examined---but several
9139 other commands also set the default address: @code{info breakpoints} (to
9140 the address of the last breakpoint listed), @code{info line} (to the
9141 starting address of a line), and @code{print} (if you use it to display
9142 a value from memory).
9145 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9146 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9147 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9148 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9149 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9151 Since the letters indicating unit sizes are all distinct from the
9152 letters specifying output formats, you do not have to remember whether
9153 unit size or format comes first; either order works. The output
9154 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9155 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9157 Even though the unit size @var{u} is ignored for the formats @samp{s}
9158 and @samp{i}, you might still want to use a count @var{n}; for example,
9159 @samp{3i} specifies that you want to see three machine instructions,
9160 including any operands. For convenience, especially when used with
9161 the @code{display} command, the @samp{i} format also prints branch delay
9162 slot instructions, if any, beyond the count specified, which immediately
9163 follow the last instruction that is within the count. The command
9164 @code{disassemble} gives an alternative way of inspecting machine
9165 instructions; see @ref{Machine Code,,Source and Machine Code}.
9167 All the defaults for the arguments to @code{x} are designed to make it
9168 easy to continue scanning memory with minimal specifications each time
9169 you use @code{x}. For example, after you have inspected three machine
9170 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9171 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9172 the repeat count @var{n} is used again; the other arguments default as
9173 for successive uses of @code{x}.
9175 When examining machine instructions, the instruction at current program
9176 counter is shown with a @code{=>} marker. For example:
9179 (@value{GDBP}) x/5i $pc-6
9180 0x804837f <main+11>: mov %esp,%ebp
9181 0x8048381 <main+13>: push %ecx
9182 0x8048382 <main+14>: sub $0x4,%esp
9183 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9184 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9187 @cindex @code{$_}, @code{$__}, and value history
9188 The addresses and contents printed by the @code{x} command are not saved
9189 in the value history because there is often too much of them and they
9190 would get in the way. Instead, @value{GDBN} makes these values available for
9191 subsequent use in expressions as values of the convenience variables
9192 @code{$_} and @code{$__}. After an @code{x} command, the last address
9193 examined is available for use in expressions in the convenience variable
9194 @code{$_}. The contents of that address, as examined, are available in
9195 the convenience variable @code{$__}.
9197 If the @code{x} command has a repeat count, the address and contents saved
9198 are from the last memory unit printed; this is not the same as the last
9199 address printed if several units were printed on the last line of output.
9201 @anchor{addressable memory unit}
9202 @cindex addressable memory unit
9203 Most targets have an addressable memory unit size of 8 bits. This means
9204 that to each memory address are associated 8 bits of data. Some
9205 targets, however, have other addressable memory unit sizes.
9206 Within @value{GDBN} and this document, the term
9207 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9208 when explicitly referring to a chunk of data of that size. The word
9209 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9210 the addressable memory unit size of the target. For most systems,
9211 addressable memory unit is a synonym of byte.
9213 @cindex remote memory comparison
9214 @cindex target memory comparison
9215 @cindex verify remote memory image
9216 @cindex verify target memory image
9217 When you are debugging a program running on a remote target machine
9218 (@pxref{Remote Debugging}), you may wish to verify the program's image
9219 in the remote machine's memory against the executable file you
9220 downloaded to the target. Or, on any target, you may want to check
9221 whether the program has corrupted its own read-only sections. The
9222 @code{compare-sections} command is provided for such situations.
9225 @kindex compare-sections
9226 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9227 Compare the data of a loadable section @var{section-name} in the
9228 executable file of the program being debugged with the same section in
9229 the target machine's memory, and report any mismatches. With no
9230 arguments, compares all loadable sections. With an argument of
9231 @code{-r}, compares all loadable read-only sections.
9233 Note: for remote targets, this command can be accelerated if the
9234 target supports computing the CRC checksum of a block of memory
9235 (@pxref{qCRC packet}).
9239 @section Automatic Display
9240 @cindex automatic display
9241 @cindex display of expressions
9243 If you find that you want to print the value of an expression frequently
9244 (to see how it changes), you might want to add it to the @dfn{automatic
9245 display list} so that @value{GDBN} prints its value each time your program stops.
9246 Each expression added to the list is given a number to identify it;
9247 to remove an expression from the list, you specify that number.
9248 The automatic display looks like this:
9252 3: bar[5] = (struct hack *) 0x3804
9256 This display shows item numbers, expressions and their current values. As with
9257 displays you request manually using @code{x} or @code{print}, you can
9258 specify the output format you prefer; in fact, @code{display} decides
9259 whether to use @code{print} or @code{x} depending your format
9260 specification---it uses @code{x} if you specify either the @samp{i}
9261 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9265 @item display @var{expr}
9266 Add the expression @var{expr} to the list of expressions to display
9267 each time your program stops. @xref{Expressions, ,Expressions}.
9269 @code{display} does not repeat if you press @key{RET} again after using it.
9271 @item display/@var{fmt} @var{expr}
9272 For @var{fmt} specifying only a display format and not a size or
9273 count, add the expression @var{expr} to the auto-display list but
9274 arrange to display it each time in the specified format @var{fmt}.
9275 @xref{Output Formats,,Output Formats}.
9277 @item display/@var{fmt} @var{addr}
9278 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9279 number of units, add the expression @var{addr} as a memory address to
9280 be examined each time your program stops. Examining means in effect
9281 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9284 For example, @samp{display/i $pc} can be helpful, to see the machine
9285 instruction about to be executed each time execution stops (@samp{$pc}
9286 is a common name for the program counter; @pxref{Registers, ,Registers}).
9289 @kindex delete display
9291 @item undisplay @var{dnums}@dots{}
9292 @itemx delete display @var{dnums}@dots{}
9293 Remove items from the list of expressions to display. Specify the
9294 numbers of the displays that you want affected with the command
9295 argument @var{dnums}. It can be a single display number, one of the
9296 numbers shown in the first field of the @samp{info display} display;
9297 or it could be a range of display numbers, as in @code{2-4}.
9299 @code{undisplay} does not repeat if you press @key{RET} after using it.
9300 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9302 @kindex disable display
9303 @item disable display @var{dnums}@dots{}
9304 Disable the display of item numbers @var{dnums}. A disabled display
9305 item is not printed automatically, but is not forgotten. It may be
9306 enabled again later. Specify the numbers of the displays that you
9307 want affected with the command argument @var{dnums}. It can be a
9308 single display number, one of the numbers shown in the first field of
9309 the @samp{info display} display; or it could be a range of display
9310 numbers, as in @code{2-4}.
9312 @kindex enable display
9313 @item enable display @var{dnums}@dots{}
9314 Enable display of item numbers @var{dnums}. It becomes effective once
9315 again in auto display of its expression, until you specify otherwise.
9316 Specify the numbers of the displays that you want affected with the
9317 command argument @var{dnums}. It can be a single display number, one
9318 of the numbers shown in the first field of the @samp{info display}
9319 display; or it could be a range of display numbers, as in @code{2-4}.
9322 Display the current values of the expressions on the list, just as is
9323 done when your program stops.
9325 @kindex info display
9327 Print the list of expressions previously set up to display
9328 automatically, each one with its item number, but without showing the
9329 values. This includes disabled expressions, which are marked as such.
9330 It also includes expressions which would not be displayed right now
9331 because they refer to automatic variables not currently available.
9334 @cindex display disabled out of scope
9335 If a display expression refers to local variables, then it does not make
9336 sense outside the lexical context for which it was set up. Such an
9337 expression is disabled when execution enters a context where one of its
9338 variables is not defined. For example, if you give the command
9339 @code{display last_char} while inside a function with an argument
9340 @code{last_char}, @value{GDBN} displays this argument while your program
9341 continues to stop inside that function. When it stops elsewhere---where
9342 there is no variable @code{last_char}---the display is disabled
9343 automatically. The next time your program stops where @code{last_char}
9344 is meaningful, you can enable the display expression once again.
9346 @node Print Settings
9347 @section Print Settings
9349 @cindex format options
9350 @cindex print settings
9351 @value{GDBN} provides the following ways to control how arrays, structures,
9352 and symbols are printed.
9355 These settings are useful for debugging programs in any language:
9359 @item set print address
9360 @itemx set print address on
9361 @cindex print/don't print memory addresses
9362 @value{GDBN} prints memory addresses showing the location of stack
9363 traces, structure values, pointer values, breakpoints, and so forth,
9364 even when it also displays the contents of those addresses. The default
9365 is @code{on}. For example, this is what a stack frame display looks like with
9366 @code{set print address on}:
9371 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9373 530 if (lquote != def_lquote)
9377 @item set print address off
9378 Do not print addresses when displaying their contents. For example,
9379 this is the same stack frame displayed with @code{set print address off}:
9383 (@value{GDBP}) set print addr off
9385 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9386 530 if (lquote != def_lquote)
9390 You can use @samp{set print address off} to eliminate all machine
9391 dependent displays from the @value{GDBN} interface. For example, with
9392 @code{print address off}, you should get the same text for backtraces on
9393 all machines---whether or not they involve pointer arguments.
9396 @item show print address
9397 Show whether or not addresses are to be printed.
9400 When @value{GDBN} prints a symbolic address, it normally prints the
9401 closest earlier symbol plus an offset. If that symbol does not uniquely
9402 identify the address (for example, it is a name whose scope is a single
9403 source file), you may need to clarify. One way to do this is with
9404 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9405 you can set @value{GDBN} to print the source file and line number when
9406 it prints a symbolic address:
9409 @item set print symbol-filename on
9410 @cindex source file and line of a symbol
9411 @cindex symbol, source file and line
9412 Tell @value{GDBN} to print the source file name and line number of a
9413 symbol in the symbolic form of an address.
9415 @item set print symbol-filename off
9416 Do not print source file name and line number of a symbol. This is the
9419 @item show print symbol-filename
9420 Show whether or not @value{GDBN} will print the source file name and
9421 line number of a symbol in the symbolic form of an address.
9424 Another situation where it is helpful to show symbol filenames and line
9425 numbers is when disassembling code; @value{GDBN} shows you the line
9426 number and source file that corresponds to each instruction.
9428 Also, you may wish to see the symbolic form only if the address being
9429 printed is reasonably close to the closest earlier symbol:
9432 @item set print max-symbolic-offset @var{max-offset}
9433 @itemx set print max-symbolic-offset unlimited
9434 @cindex maximum value for offset of closest symbol
9435 Tell @value{GDBN} to only display the symbolic form of an address if the
9436 offset between the closest earlier symbol and the address is less than
9437 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9438 to always print the symbolic form of an address if any symbol precedes
9439 it. Zero is equivalent to @code{unlimited}.
9441 @item show print max-symbolic-offset
9442 Ask how large the maximum offset is that @value{GDBN} prints in a
9446 @cindex wild pointer, interpreting
9447 @cindex pointer, finding referent
9448 If you have a pointer and you are not sure where it points, try
9449 @samp{set print symbol-filename on}. Then you can determine the name
9450 and source file location of the variable where it points, using
9451 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9452 For example, here @value{GDBN} shows that a variable @code{ptt} points
9453 at another variable @code{t}, defined in @file{hi2.c}:
9456 (@value{GDBP}) set print symbol-filename on
9457 (@value{GDBP}) p/a ptt
9458 $4 = 0xe008 <t in hi2.c>
9462 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9463 does not show the symbol name and filename of the referent, even with
9464 the appropriate @code{set print} options turned on.
9467 You can also enable @samp{/a}-like formatting all the time using
9468 @samp{set print symbol on}:
9471 @item set print symbol on
9472 Tell @value{GDBN} to print the symbol corresponding to an address, if
9475 @item set print symbol off
9476 Tell @value{GDBN} not to print the symbol corresponding to an
9477 address. In this mode, @value{GDBN} will still print the symbol
9478 corresponding to pointers to functions. This is the default.
9480 @item show print symbol
9481 Show whether @value{GDBN} will display the symbol corresponding to an
9485 Other settings control how different kinds of objects are printed:
9488 @item set print array
9489 @itemx set print array on
9490 @cindex pretty print arrays
9491 Pretty print arrays. This format is more convenient to read,
9492 but uses more space. The default is off.
9494 @item set print array off
9495 Return to compressed format for arrays.
9497 @item show print array
9498 Show whether compressed or pretty format is selected for displaying
9501 @cindex print array indexes
9502 @item set print array-indexes
9503 @itemx set print array-indexes on
9504 Print the index of each element when displaying arrays. May be more
9505 convenient to locate a given element in the array or quickly find the
9506 index of a given element in that printed array. The default is off.
9508 @item set print array-indexes off
9509 Stop printing element indexes when displaying arrays.
9511 @item show print array-indexes
9512 Show whether the index of each element is printed when displaying
9515 @item set print elements @var{number-of-elements}
9516 @itemx set print elements unlimited
9517 @cindex number of array elements to print
9518 @cindex limit on number of printed array elements
9519 Set a limit on how many elements of an array @value{GDBN} will print.
9520 If @value{GDBN} is printing a large array, it stops printing after it has
9521 printed the number of elements set by the @code{set print elements} command.
9522 This limit also applies to the display of strings.
9523 When @value{GDBN} starts, this limit is set to 200.
9524 Setting @var{number-of-elements} to @code{unlimited} or zero means
9525 that the number of elements to print is unlimited.
9527 @item show print elements
9528 Display the number of elements of a large array that @value{GDBN} will print.
9529 If the number is 0, then the printing is unlimited.
9531 @item set print frame-arguments @var{value}
9532 @kindex set print frame-arguments
9533 @cindex printing frame argument values
9534 @cindex print all frame argument values
9535 @cindex print frame argument values for scalars only
9536 @cindex do not print frame argument values
9537 This command allows to control how the values of arguments are printed
9538 when the debugger prints a frame (@pxref{Frames}). The possible
9543 The values of all arguments are printed.
9546 Print the value of an argument only if it is a scalar. The value of more
9547 complex arguments such as arrays, structures, unions, etc, is replaced
9548 by @code{@dots{}}. This is the default. Here is an example where
9549 only scalar arguments are shown:
9552 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9557 None of the argument values are printed. Instead, the value of each argument
9558 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9561 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9566 By default, only scalar arguments are printed. This command can be used
9567 to configure the debugger to print the value of all arguments, regardless
9568 of their type. However, it is often advantageous to not print the value
9569 of more complex parameters. For instance, it reduces the amount of
9570 information printed in each frame, making the backtrace more readable.
9571 Also, it improves performance when displaying Ada frames, because
9572 the computation of large arguments can sometimes be CPU-intensive,
9573 especially in large applications. Setting @code{print frame-arguments}
9574 to @code{scalars} (the default) or @code{none} avoids this computation,
9575 thus speeding up the display of each Ada frame.
9577 @item show print frame-arguments
9578 Show how the value of arguments should be displayed when printing a frame.
9580 @item set print raw frame-arguments on
9581 Print frame arguments in raw, non pretty-printed, form.
9583 @item set print raw frame-arguments off
9584 Print frame arguments in pretty-printed form, if there is a pretty-printer
9585 for the value (@pxref{Pretty Printing}),
9586 otherwise print the value in raw form.
9587 This is the default.
9589 @item show print raw frame-arguments
9590 Show whether to print frame arguments in raw form.
9592 @anchor{set print entry-values}
9593 @item set print entry-values @var{value}
9594 @kindex set print entry-values
9595 Set printing of frame argument values at function entry. In some cases
9596 @value{GDBN} can determine the value of function argument which was passed by
9597 the function caller, even if the value was modified inside the called function
9598 and therefore is different. With optimized code, the current value could be
9599 unavailable, but the entry value may still be known.
9601 The default value is @code{default} (see below for its description). Older
9602 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9603 this feature will behave in the @code{default} setting the same way as with the
9606 This functionality is currently supported only by DWARF 2 debugging format and
9607 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9608 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9611 The @var{value} parameter can be one of the following:
9615 Print only actual parameter values, never print values from function entry
9619 #0 different (val=6)
9620 #0 lost (val=<optimized out>)
9622 #0 invalid (val=<optimized out>)
9626 Print only parameter values from function entry point. The actual parameter
9627 values are never printed.
9629 #0 equal (val@@entry=5)
9630 #0 different (val@@entry=5)
9631 #0 lost (val@@entry=5)
9632 #0 born (val@@entry=<optimized out>)
9633 #0 invalid (val@@entry=<optimized out>)
9637 Print only parameter values from function entry point. If value from function
9638 entry point is not known while the actual value is known, print the actual
9639 value for such parameter.
9641 #0 equal (val@@entry=5)
9642 #0 different (val@@entry=5)
9643 #0 lost (val@@entry=5)
9645 #0 invalid (val@@entry=<optimized out>)
9649 Print actual parameter values. If actual parameter value is not known while
9650 value from function entry point is known, print the entry point value for such
9654 #0 different (val=6)
9655 #0 lost (val@@entry=5)
9657 #0 invalid (val=<optimized out>)
9661 Always print both the actual parameter value and its value from function entry
9662 point, even if values of one or both are not available due to compiler
9665 #0 equal (val=5, val@@entry=5)
9666 #0 different (val=6, val@@entry=5)
9667 #0 lost (val=<optimized out>, val@@entry=5)
9668 #0 born (val=10, val@@entry=<optimized out>)
9669 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9673 Print the actual parameter value if it is known and also its value from
9674 function entry point if it is known. If neither is known, print for the actual
9675 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9676 values are known and identical, print the shortened
9677 @code{param=param@@entry=VALUE} notation.
9679 #0 equal (val=val@@entry=5)
9680 #0 different (val=6, val@@entry=5)
9681 #0 lost (val@@entry=5)
9683 #0 invalid (val=<optimized out>)
9687 Always print the actual parameter value. Print also its value from function
9688 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9689 if both values are known and identical, print the shortened
9690 @code{param=param@@entry=VALUE} notation.
9692 #0 equal (val=val@@entry=5)
9693 #0 different (val=6, val@@entry=5)
9694 #0 lost (val=<optimized out>, val@@entry=5)
9696 #0 invalid (val=<optimized out>)
9700 For analysis messages on possible failures of frame argument values at function
9701 entry resolution see @ref{set debug entry-values}.
9703 @item show print entry-values
9704 Show the method being used for printing of frame argument values at function
9707 @item set print repeats @var{number-of-repeats}
9708 @itemx set print repeats unlimited
9709 @cindex repeated array elements
9710 Set the threshold for suppressing display of repeated array
9711 elements. When the number of consecutive identical elements of an
9712 array exceeds the threshold, @value{GDBN} prints the string
9713 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9714 identical repetitions, instead of displaying the identical elements
9715 themselves. Setting the threshold to @code{unlimited} or zero will
9716 cause all elements to be individually printed. The default threshold
9719 @item show print repeats
9720 Display the current threshold for printing repeated identical
9723 @item set print null-stop
9724 @cindex @sc{null} elements in arrays
9725 Cause @value{GDBN} to stop printing the characters of an array when the first
9726 @sc{null} is encountered. This is useful when large arrays actually
9727 contain only short strings.
9730 @item show print null-stop
9731 Show whether @value{GDBN} stops printing an array on the first
9732 @sc{null} character.
9734 @item set print pretty on
9735 @cindex print structures in indented form
9736 @cindex indentation in structure display
9737 Cause @value{GDBN} to print structures in an indented format with one member
9738 per line, like this:
9753 @item set print pretty off
9754 Cause @value{GDBN} to print structures in a compact format, like this:
9758 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9759 meat = 0x54 "Pork"@}
9764 This is the default format.
9766 @item show print pretty
9767 Show which format @value{GDBN} is using to print structures.
9769 @item set print sevenbit-strings on
9770 @cindex eight-bit characters in strings
9771 @cindex octal escapes in strings
9772 Print using only seven-bit characters; if this option is set,
9773 @value{GDBN} displays any eight-bit characters (in strings or
9774 character values) using the notation @code{\}@var{nnn}. This setting is
9775 best if you are working in English (@sc{ascii}) and you use the
9776 high-order bit of characters as a marker or ``meta'' bit.
9778 @item set print sevenbit-strings off
9779 Print full eight-bit characters. This allows the use of more
9780 international character sets, and is the default.
9782 @item show print sevenbit-strings
9783 Show whether or not @value{GDBN} is printing only seven-bit characters.
9785 @item set print union on
9786 @cindex unions in structures, printing
9787 Tell @value{GDBN} to print unions which are contained in structures
9788 and other unions. This is the default setting.
9790 @item set print union off
9791 Tell @value{GDBN} not to print unions which are contained in
9792 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9795 @item show print union
9796 Ask @value{GDBN} whether or not it will print unions which are contained in
9797 structures and other unions.
9799 For example, given the declarations
9802 typedef enum @{Tree, Bug@} Species;
9803 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9804 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9815 struct thing foo = @{Tree, @{Acorn@}@};
9819 with @code{set print union on} in effect @samp{p foo} would print
9822 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9826 and with @code{set print union off} in effect it would print
9829 $1 = @{it = Tree, form = @{...@}@}
9833 @code{set print union} affects programs written in C-like languages
9839 These settings are of interest when debugging C@t{++} programs:
9842 @cindex demangling C@t{++} names
9843 @item set print demangle
9844 @itemx set print demangle on
9845 Print C@t{++} names in their source form rather than in the encoded
9846 (``mangled'') form passed to the assembler and linker for type-safe
9847 linkage. The default is on.
9849 @item show print demangle
9850 Show whether C@t{++} names are printed in mangled or demangled form.
9852 @item set print asm-demangle
9853 @itemx set print asm-demangle on
9854 Print C@t{++} names in their source form rather than their mangled form, even
9855 in assembler code printouts such as instruction disassemblies.
9858 @item show print asm-demangle
9859 Show whether C@t{++} names in assembly listings are printed in mangled
9862 @cindex C@t{++} symbol decoding style
9863 @cindex symbol decoding style, C@t{++}
9864 @kindex set demangle-style
9865 @item set demangle-style @var{style}
9866 Choose among several encoding schemes used by different compilers to
9867 represent C@t{++} names. The choices for @var{style} are currently:
9871 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9872 This is the default.
9875 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9878 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9881 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9884 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9885 @strong{Warning:} this setting alone is not sufficient to allow
9886 debugging @code{cfront}-generated executables. @value{GDBN} would
9887 require further enhancement to permit that.
9890 If you omit @var{style}, you will see a list of possible formats.
9892 @item show demangle-style
9893 Display the encoding style currently in use for decoding C@t{++} symbols.
9895 @item set print object
9896 @itemx set print object on
9897 @cindex derived type of an object, printing
9898 @cindex display derived types
9899 When displaying a pointer to an object, identify the @emph{actual}
9900 (derived) type of the object rather than the @emph{declared} type, using
9901 the virtual function table. Note that the virtual function table is
9902 required---this feature can only work for objects that have run-time
9903 type identification; a single virtual method in the object's declared
9904 type is sufficient. Note that this setting is also taken into account when
9905 working with variable objects via MI (@pxref{GDB/MI}).
9907 @item set print object off
9908 Display only the declared type of objects, without reference to the
9909 virtual function table. This is the default setting.
9911 @item show print object
9912 Show whether actual, or declared, object types are displayed.
9914 @item set print static-members
9915 @itemx set print static-members on
9916 @cindex static members of C@t{++} objects
9917 Print static members when displaying a C@t{++} object. The default is on.
9919 @item set print static-members off
9920 Do not print static members when displaying a C@t{++} object.
9922 @item show print static-members
9923 Show whether C@t{++} static members are printed or not.
9925 @item set print pascal_static-members
9926 @itemx set print pascal_static-members on
9927 @cindex static members of Pascal objects
9928 @cindex Pascal objects, static members display
9929 Print static members when displaying a Pascal object. The default is on.
9931 @item set print pascal_static-members off
9932 Do not print static members when displaying a Pascal object.
9934 @item show print pascal_static-members
9935 Show whether Pascal static members are printed or not.
9937 @c These don't work with HP ANSI C++ yet.
9938 @item set print vtbl
9939 @itemx set print vtbl on
9940 @cindex pretty print C@t{++} virtual function tables
9941 @cindex virtual functions (C@t{++}) display
9942 @cindex VTBL display
9943 Pretty print C@t{++} virtual function tables. The default is off.
9944 (The @code{vtbl} commands do not work on programs compiled with the HP
9945 ANSI C@t{++} compiler (@code{aCC}).)
9947 @item set print vtbl off
9948 Do not pretty print C@t{++} virtual function tables.
9950 @item show print vtbl
9951 Show whether C@t{++} virtual function tables are pretty printed, or not.
9954 @node Pretty Printing
9955 @section Pretty Printing
9957 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9958 Python code. It greatly simplifies the display of complex objects. This
9959 mechanism works for both MI and the CLI.
9962 * Pretty-Printer Introduction:: Introduction to pretty-printers
9963 * Pretty-Printer Example:: An example pretty-printer
9964 * Pretty-Printer Commands:: Pretty-printer commands
9967 @node Pretty-Printer Introduction
9968 @subsection Pretty-Printer Introduction
9970 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9971 registered for the value. If there is then @value{GDBN} invokes the
9972 pretty-printer to print the value. Otherwise the value is printed normally.
9974 Pretty-printers are normally named. This makes them easy to manage.
9975 The @samp{info pretty-printer} command will list all the installed
9976 pretty-printers with their names.
9977 If a pretty-printer can handle multiple data types, then its
9978 @dfn{subprinters} are the printers for the individual data types.
9979 Each such subprinter has its own name.
9980 The format of the name is @var{printer-name};@var{subprinter-name}.
9982 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9983 Typically they are automatically loaded and registered when the corresponding
9984 debug information is loaded, thus making them available without having to
9985 do anything special.
9987 There are three places where a pretty-printer can be registered.
9991 Pretty-printers registered globally are available when debugging
9995 Pretty-printers registered with a program space are available only
9996 when debugging that program.
9997 @xref{Progspaces In Python}, for more details on program spaces in Python.
10000 Pretty-printers registered with an objfile are loaded and unloaded
10001 with the corresponding objfile (e.g., shared library).
10002 @xref{Objfiles In Python}, for more details on objfiles in Python.
10005 @xref{Selecting Pretty-Printers}, for further information on how
10006 pretty-printers are selected,
10008 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10011 @node Pretty-Printer Example
10012 @subsection Pretty-Printer Example
10014 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10017 (@value{GDBP}) print s
10019 static npos = 4294967295,
10021 <std::allocator<char>> = @{
10022 <__gnu_cxx::new_allocator<char>> = @{
10023 <No data fields>@}, <No data fields>
10025 members of std::basic_string<char, std::char_traits<char>,
10026 std::allocator<char> >::_Alloc_hider:
10027 _M_p = 0x804a014 "abcd"
10032 With a pretty-printer for @code{std::string} only the contents are printed:
10035 (@value{GDBP}) print s
10039 @node Pretty-Printer Commands
10040 @subsection Pretty-Printer Commands
10041 @cindex pretty-printer commands
10044 @kindex info pretty-printer
10045 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10046 Print the list of installed pretty-printers.
10047 This includes disabled pretty-printers, which are marked as such.
10049 @var{object-regexp} is a regular expression matching the objects
10050 whose pretty-printers to list.
10051 Objects can be @code{global}, the program space's file
10052 (@pxref{Progspaces In Python}),
10053 and the object files within that program space (@pxref{Objfiles In Python}).
10054 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10055 looks up a printer from these three objects.
10057 @var{name-regexp} is a regular expression matching the name of the printers
10060 @kindex disable pretty-printer
10061 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10062 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10063 A disabled pretty-printer is not forgotten, it may be enabled again later.
10065 @kindex enable pretty-printer
10066 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10067 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10072 Suppose we have three pretty-printers installed: one from library1.so
10073 named @code{foo} that prints objects of type @code{foo}, and
10074 another from library2.so named @code{bar} that prints two types of objects,
10075 @code{bar1} and @code{bar2}.
10078 (gdb) info pretty-printer
10085 (gdb) info pretty-printer library2
10090 (gdb) disable pretty-printer library1
10092 2 of 3 printers enabled
10093 (gdb) info pretty-printer
10100 (gdb) disable pretty-printer library2 bar:bar1
10102 1 of 3 printers enabled
10103 (gdb) info pretty-printer library2
10110 (gdb) disable pretty-printer library2 bar
10112 0 of 3 printers enabled
10113 (gdb) info pretty-printer library2
10122 Note that for @code{bar} the entire printer can be disabled,
10123 as can each individual subprinter.
10125 @node Value History
10126 @section Value History
10128 @cindex value history
10129 @cindex history of values printed by @value{GDBN}
10130 Values printed by the @code{print} command are saved in the @value{GDBN}
10131 @dfn{value history}. This allows you to refer to them in other expressions.
10132 Values are kept until the symbol table is re-read or discarded
10133 (for example with the @code{file} or @code{symbol-file} commands).
10134 When the symbol table changes, the value history is discarded,
10135 since the values may contain pointers back to the types defined in the
10140 @cindex history number
10141 The values printed are given @dfn{history numbers} by which you can
10142 refer to them. These are successive integers starting with one.
10143 @code{print} shows you the history number assigned to a value by
10144 printing @samp{$@var{num} = } before the value; here @var{num} is the
10147 To refer to any previous value, use @samp{$} followed by the value's
10148 history number. The way @code{print} labels its output is designed to
10149 remind you of this. Just @code{$} refers to the most recent value in
10150 the history, and @code{$$} refers to the value before that.
10151 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10152 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10153 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10155 For example, suppose you have just printed a pointer to a structure and
10156 want to see the contents of the structure. It suffices to type
10162 If you have a chain of structures where the component @code{next} points
10163 to the next one, you can print the contents of the next one with this:
10170 You can print successive links in the chain by repeating this
10171 command---which you can do by just typing @key{RET}.
10173 Note that the history records values, not expressions. If the value of
10174 @code{x} is 4 and you type these commands:
10182 then the value recorded in the value history by the @code{print} command
10183 remains 4 even though the value of @code{x} has changed.
10186 @kindex show values
10188 Print the last ten values in the value history, with their item numbers.
10189 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10190 values} does not change the history.
10192 @item show values @var{n}
10193 Print ten history values centered on history item number @var{n}.
10195 @item show values +
10196 Print ten history values just after the values last printed. If no more
10197 values are available, @code{show values +} produces no display.
10200 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10201 same effect as @samp{show values +}.
10203 @node Convenience Vars
10204 @section Convenience Variables
10206 @cindex convenience variables
10207 @cindex user-defined variables
10208 @value{GDBN} provides @dfn{convenience variables} that you can use within
10209 @value{GDBN} to hold on to a value and refer to it later. These variables
10210 exist entirely within @value{GDBN}; they are not part of your program, and
10211 setting a convenience variable has no direct effect on further execution
10212 of your program. That is why you can use them freely.
10214 Convenience variables are prefixed with @samp{$}. Any name preceded by
10215 @samp{$} can be used for a convenience variable, unless it is one of
10216 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10217 (Value history references, in contrast, are @emph{numbers} preceded
10218 by @samp{$}. @xref{Value History, ,Value History}.)
10220 You can save a value in a convenience variable with an assignment
10221 expression, just as you would set a variable in your program.
10225 set $foo = *object_ptr
10229 would save in @code{$foo} the value contained in the object pointed to by
10232 Using a convenience variable for the first time creates it, but its
10233 value is @code{void} until you assign a new value. You can alter the
10234 value with another assignment at any time.
10236 Convenience variables have no fixed types. You can assign a convenience
10237 variable any type of value, including structures and arrays, even if
10238 that variable already has a value of a different type. The convenience
10239 variable, when used as an expression, has the type of its current value.
10242 @kindex show convenience
10243 @cindex show all user variables and functions
10244 @item show convenience
10245 Print a list of convenience variables used so far, and their values,
10246 as well as a list of the convenience functions.
10247 Abbreviated @code{show conv}.
10249 @kindex init-if-undefined
10250 @cindex convenience variables, initializing
10251 @item init-if-undefined $@var{variable} = @var{expression}
10252 Set a convenience variable if it has not already been set. This is useful
10253 for user-defined commands that keep some state. It is similar, in concept,
10254 to using local static variables with initializers in C (except that
10255 convenience variables are global). It can also be used to allow users to
10256 override default values used in a command script.
10258 If the variable is already defined then the expression is not evaluated so
10259 any side-effects do not occur.
10262 One of the ways to use a convenience variable is as a counter to be
10263 incremented or a pointer to be advanced. For example, to print
10264 a field from successive elements of an array of structures:
10268 print bar[$i++]->contents
10272 Repeat that command by typing @key{RET}.
10274 Some convenience variables are created automatically by @value{GDBN} and given
10275 values likely to be useful.
10278 @vindex $_@r{, convenience variable}
10280 The variable @code{$_} is automatically set by the @code{x} command to
10281 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10282 commands which provide a default address for @code{x} to examine also
10283 set @code{$_} to that address; these commands include @code{info line}
10284 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10285 except when set by the @code{x} command, in which case it is a pointer
10286 to the type of @code{$__}.
10288 @vindex $__@r{, convenience variable}
10290 The variable @code{$__} is automatically set by the @code{x} command
10291 to the value found in the last address examined. Its type is chosen
10292 to match the format in which the data was printed.
10295 @vindex $_exitcode@r{, convenience variable}
10296 When the program being debugged terminates normally, @value{GDBN}
10297 automatically sets this variable to the exit code of the program, and
10298 resets @code{$_exitsignal} to @code{void}.
10301 @vindex $_exitsignal@r{, convenience variable}
10302 When the program being debugged dies due to an uncaught signal,
10303 @value{GDBN} automatically sets this variable to that signal's number,
10304 and resets @code{$_exitcode} to @code{void}.
10306 To distinguish between whether the program being debugged has exited
10307 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10308 @code{$_exitsignal} is not @code{void}), the convenience function
10309 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10310 Functions}). For example, considering the following source code:
10313 #include <signal.h>
10316 main (int argc, char *argv[])
10323 A valid way of telling whether the program being debugged has exited
10324 or signalled would be:
10327 (@value{GDBP}) define has_exited_or_signalled
10328 Type commands for definition of ``has_exited_or_signalled''.
10329 End with a line saying just ``end''.
10330 >if $_isvoid ($_exitsignal)
10331 >echo The program has exited\n
10333 >echo The program has signalled\n
10339 Program terminated with signal SIGALRM, Alarm clock.
10340 The program no longer exists.
10341 (@value{GDBP}) has_exited_or_signalled
10342 The program has signalled
10345 As can be seen, @value{GDBN} correctly informs that the program being
10346 debugged has signalled, since it calls @code{raise} and raises a
10347 @code{SIGALRM} signal. If the program being debugged had not called
10348 @code{raise}, then @value{GDBN} would report a normal exit:
10351 (@value{GDBP}) has_exited_or_signalled
10352 The program has exited
10356 The variable @code{$_exception} is set to the exception object being
10357 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10360 @itemx $_probe_arg0@dots{}$_probe_arg11
10361 Arguments to a static probe. @xref{Static Probe Points}.
10364 @vindex $_sdata@r{, inspect, convenience variable}
10365 The variable @code{$_sdata} contains extra collected static tracepoint
10366 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10367 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10368 if extra static tracepoint data has not been collected.
10371 @vindex $_siginfo@r{, convenience variable}
10372 The variable @code{$_siginfo} contains extra signal information
10373 (@pxref{extra signal information}). Note that @code{$_siginfo}
10374 could be empty, if the application has not yet received any signals.
10375 For example, it will be empty before you execute the @code{run} command.
10378 @vindex $_tlb@r{, convenience variable}
10379 The variable @code{$_tlb} is automatically set when debugging
10380 applications running on MS-Windows in native mode or connected to
10381 gdbserver that supports the @code{qGetTIBAddr} request.
10382 @xref{General Query Packets}.
10383 This variable contains the address of the thread information block.
10387 @node Convenience Funs
10388 @section Convenience Functions
10390 @cindex convenience functions
10391 @value{GDBN} also supplies some @dfn{convenience functions}. These
10392 have a syntax similar to convenience variables. A convenience
10393 function can be used in an expression just like an ordinary function;
10394 however, a convenience function is implemented internally to
10397 These functions do not require @value{GDBN} to be configured with
10398 @code{Python} support, which means that they are always available.
10402 @item $_isvoid (@var{expr})
10403 @findex $_isvoid@r{, convenience function}
10404 Return one if the expression @var{expr} is @code{void}. Otherwise it
10407 A @code{void} expression is an expression where the type of the result
10408 is @code{void}. For example, you can examine a convenience variable
10409 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10413 (@value{GDBP}) print $_exitcode
10415 (@value{GDBP}) print $_isvoid ($_exitcode)
10418 Starting program: ./a.out
10419 [Inferior 1 (process 29572) exited normally]
10420 (@value{GDBP}) print $_exitcode
10422 (@value{GDBP}) print $_isvoid ($_exitcode)
10426 In the example above, we used @code{$_isvoid} to check whether
10427 @code{$_exitcode} is @code{void} before and after the execution of the
10428 program being debugged. Before the execution there is no exit code to
10429 be examined, therefore @code{$_exitcode} is @code{void}. After the
10430 execution the program being debugged returned zero, therefore
10431 @code{$_exitcode} is zero, which means that it is not @code{void}
10434 The @code{void} expression can also be a call of a function from the
10435 program being debugged. For example, given the following function:
10444 The result of calling it inside @value{GDBN} is @code{void}:
10447 (@value{GDBP}) print foo ()
10449 (@value{GDBP}) print $_isvoid (foo ())
10451 (@value{GDBP}) set $v = foo ()
10452 (@value{GDBP}) print $v
10454 (@value{GDBP}) print $_isvoid ($v)
10460 These functions require @value{GDBN} to be configured with
10461 @code{Python} support.
10465 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10466 @findex $_memeq@r{, convenience function}
10467 Returns one if the @var{length} bytes at the addresses given by
10468 @var{buf1} and @var{buf2} are equal.
10469 Otherwise it returns zero.
10471 @item $_regex(@var{str}, @var{regex})
10472 @findex $_regex@r{, convenience function}
10473 Returns one if the string @var{str} matches the regular expression
10474 @var{regex}. Otherwise it returns zero.
10475 The syntax of the regular expression is that specified by @code{Python}'s
10476 regular expression support.
10478 @item $_streq(@var{str1}, @var{str2})
10479 @findex $_streq@r{, convenience function}
10480 Returns one if the strings @var{str1} and @var{str2} are equal.
10481 Otherwise it returns zero.
10483 @item $_strlen(@var{str})
10484 @findex $_strlen@r{, convenience function}
10485 Returns the length of string @var{str}.
10487 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10488 @findex $_caller_is@r{, convenience function}
10489 Returns one if the calling function's name is equal to @var{name}.
10490 Otherwise it returns zero.
10492 If the optional argument @var{number_of_frames} is provided,
10493 it is the number of frames up in the stack to look.
10501 at testsuite/gdb.python/py-caller-is.c:21
10502 #1 0x00000000004005a0 in middle_func ()
10503 at testsuite/gdb.python/py-caller-is.c:27
10504 #2 0x00000000004005ab in top_func ()
10505 at testsuite/gdb.python/py-caller-is.c:33
10506 #3 0x00000000004005b6 in main ()
10507 at testsuite/gdb.python/py-caller-is.c:39
10508 (gdb) print $_caller_is ("middle_func")
10510 (gdb) print $_caller_is ("top_func", 2)
10514 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10515 @findex $_caller_matches@r{, convenience function}
10516 Returns one if the calling function's name matches the regular expression
10517 @var{regexp}. Otherwise it returns zero.
10519 If the optional argument @var{number_of_frames} is provided,
10520 it is the number of frames up in the stack to look.
10523 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10524 @findex $_any_caller_is@r{, convenience function}
10525 Returns one if any calling function's name is equal to @var{name}.
10526 Otherwise it returns zero.
10528 If the optional argument @var{number_of_frames} is provided,
10529 it is the number of frames up in the stack to look.
10532 This function differs from @code{$_caller_is} in that this function
10533 checks all stack frames from the immediate caller to the frame specified
10534 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10535 frame specified by @var{number_of_frames}.
10537 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10538 @findex $_any_caller_matches@r{, convenience function}
10539 Returns one if any calling function's name matches the regular expression
10540 @var{regexp}. Otherwise it returns zero.
10542 If the optional argument @var{number_of_frames} is provided,
10543 it is the number of frames up in the stack to look.
10546 This function differs from @code{$_caller_matches} in that this function
10547 checks all stack frames from the immediate caller to the frame specified
10548 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10549 frame specified by @var{number_of_frames}.
10553 @value{GDBN} provides the ability to list and get help on
10554 convenience functions.
10557 @item help function
10558 @kindex help function
10559 @cindex show all convenience functions
10560 Print a list of all convenience functions.
10567 You can refer to machine register contents, in expressions, as variables
10568 with names starting with @samp{$}. The names of registers are different
10569 for each machine; use @code{info registers} to see the names used on
10573 @kindex info registers
10574 @item info registers
10575 Print the names and values of all registers except floating-point
10576 and vector registers (in the selected stack frame).
10578 @kindex info all-registers
10579 @cindex floating point registers
10580 @item info all-registers
10581 Print the names and values of all registers, including floating-point
10582 and vector registers (in the selected stack frame).
10584 @item info registers @var{regname} @dots{}
10585 Print the @dfn{relativized} value of each specified register @var{regname}.
10586 As discussed in detail below, register values are normally relative to
10587 the selected stack frame. The @var{regname} may be any register name valid on
10588 the machine you are using, with or without the initial @samp{$}.
10591 @anchor{standard registers}
10592 @cindex stack pointer register
10593 @cindex program counter register
10594 @cindex process status register
10595 @cindex frame pointer register
10596 @cindex standard registers
10597 @value{GDBN} has four ``standard'' register names that are available (in
10598 expressions) on most machines---whenever they do not conflict with an
10599 architecture's canonical mnemonics for registers. The register names
10600 @code{$pc} and @code{$sp} are used for the program counter register and
10601 the stack pointer. @code{$fp} is used for a register that contains a
10602 pointer to the current stack frame, and @code{$ps} is used for a
10603 register that contains the processor status. For example,
10604 you could print the program counter in hex with
10611 or print the instruction to be executed next with
10618 or add four to the stack pointer@footnote{This is a way of removing
10619 one word from the stack, on machines where stacks grow downward in
10620 memory (most machines, nowadays). This assumes that the innermost
10621 stack frame is selected; setting @code{$sp} is not allowed when other
10622 stack frames are selected. To pop entire frames off the stack,
10623 regardless of machine architecture, use @code{return};
10624 see @ref{Returning, ,Returning from a Function}.} with
10630 Whenever possible, these four standard register names are available on
10631 your machine even though the machine has different canonical mnemonics,
10632 so long as there is no conflict. The @code{info registers} command
10633 shows the canonical names. For example, on the SPARC, @code{info
10634 registers} displays the processor status register as @code{$psr} but you
10635 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10636 is an alias for the @sc{eflags} register.
10638 @value{GDBN} always considers the contents of an ordinary register as an
10639 integer when the register is examined in this way. Some machines have
10640 special registers which can hold nothing but floating point; these
10641 registers are considered to have floating point values. There is no way
10642 to refer to the contents of an ordinary register as floating point value
10643 (although you can @emph{print} it as a floating point value with
10644 @samp{print/f $@var{regname}}).
10646 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10647 means that the data format in which the register contents are saved by
10648 the operating system is not the same one that your program normally
10649 sees. For example, the registers of the 68881 floating point
10650 coprocessor are always saved in ``extended'' (raw) format, but all C
10651 programs expect to work with ``double'' (virtual) format. In such
10652 cases, @value{GDBN} normally works with the virtual format only (the format
10653 that makes sense for your program), but the @code{info registers} command
10654 prints the data in both formats.
10656 @cindex SSE registers (x86)
10657 @cindex MMX registers (x86)
10658 Some machines have special registers whose contents can be interpreted
10659 in several different ways. For example, modern x86-based machines
10660 have SSE and MMX registers that can hold several values packed
10661 together in several different formats. @value{GDBN} refers to such
10662 registers in @code{struct} notation:
10665 (@value{GDBP}) print $xmm1
10667 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10668 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10669 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10670 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10671 v4_int32 = @{0, 20657912, 11, 13@},
10672 v2_int64 = @{88725056443645952, 55834574859@},
10673 uint128 = 0x0000000d0000000b013b36f800000000
10678 To set values of such registers, you need to tell @value{GDBN} which
10679 view of the register you wish to change, as if you were assigning
10680 value to a @code{struct} member:
10683 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10686 Normally, register values are relative to the selected stack frame
10687 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10688 value that the register would contain if all stack frames farther in
10689 were exited and their saved registers restored. In order to see the
10690 true contents of hardware registers, you must select the innermost
10691 frame (with @samp{frame 0}).
10693 @cindex caller-saved registers
10694 @cindex call-clobbered registers
10695 @cindex volatile registers
10696 @cindex <not saved> values
10697 Usually ABIs reserve some registers as not needed to be saved by the
10698 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10699 registers). It may therefore not be possible for @value{GDBN} to know
10700 the value a register had before the call (in other words, in the outer
10701 frame), if the register value has since been changed by the callee.
10702 @value{GDBN} tries to deduce where the inner frame saved
10703 (``callee-saved'') registers, from the debug info, unwind info, or the
10704 machine code generated by your compiler. If some register is not
10705 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10706 its own knowledge of the ABI, or because the debug/unwind info
10707 explicitly says the register's value is undefined), @value{GDBN}
10708 displays @w{@samp{<not saved>}} as the register's value. With targets
10709 that @value{GDBN} has no knowledge of the register saving convention,
10710 if a register was not saved by the callee, then its value and location
10711 in the outer frame are assumed to be the same of the inner frame.
10712 This is usually harmless, because if the register is call-clobbered,
10713 the caller either does not care what is in the register after the
10714 call, or has code to restore the value that it does care about. Note,
10715 however, that if you change such a register in the outer frame, you
10716 may also be affecting the inner frame. Also, the more ``outer'' the
10717 frame is you're looking at, the more likely a call-clobbered
10718 register's value is to be wrong, in the sense that it doesn't actually
10719 represent the value the register had just before the call.
10721 @node Floating Point Hardware
10722 @section Floating Point Hardware
10723 @cindex floating point
10725 Depending on the configuration, @value{GDBN} may be able to give
10726 you more information about the status of the floating point hardware.
10731 Display hardware-dependent information about the floating
10732 point unit. The exact contents and layout vary depending on the
10733 floating point chip. Currently, @samp{info float} is supported on
10734 the ARM and x86 machines.
10738 @section Vector Unit
10739 @cindex vector unit
10741 Depending on the configuration, @value{GDBN} may be able to give you
10742 more information about the status of the vector unit.
10745 @kindex info vector
10747 Display information about the vector unit. The exact contents and
10748 layout vary depending on the hardware.
10751 @node OS Information
10752 @section Operating System Auxiliary Information
10753 @cindex OS information
10755 @value{GDBN} provides interfaces to useful OS facilities that can help
10756 you debug your program.
10758 @cindex auxiliary vector
10759 @cindex vector, auxiliary
10760 Some operating systems supply an @dfn{auxiliary vector} to programs at
10761 startup. This is akin to the arguments and environment that you
10762 specify for a program, but contains a system-dependent variety of
10763 binary values that tell system libraries important details about the
10764 hardware, operating system, and process. Each value's purpose is
10765 identified by an integer tag; the meanings are well-known but system-specific.
10766 Depending on the configuration and operating system facilities,
10767 @value{GDBN} may be able to show you this information. For remote
10768 targets, this functionality may further depend on the remote stub's
10769 support of the @samp{qXfer:auxv:read} packet, see
10770 @ref{qXfer auxiliary vector read}.
10775 Display the auxiliary vector of the inferior, which can be either a
10776 live process or a core dump file. @value{GDBN} prints each tag value
10777 numerically, and also shows names and text descriptions for recognized
10778 tags. Some values in the vector are numbers, some bit masks, and some
10779 pointers to strings or other data. @value{GDBN} displays each value in the
10780 most appropriate form for a recognized tag, and in hexadecimal for
10781 an unrecognized tag.
10784 On some targets, @value{GDBN} can access operating system-specific
10785 information and show it to you. The types of information available
10786 will differ depending on the type of operating system running on the
10787 target. The mechanism used to fetch the data is described in
10788 @ref{Operating System Information}. For remote targets, this
10789 functionality depends on the remote stub's support of the
10790 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10794 @item info os @var{infotype}
10796 Display OS information of the requested type.
10798 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10800 @anchor{linux info os infotypes}
10802 @kindex info os cpus
10804 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10805 the available fields from /proc/cpuinfo. For each supported architecture
10806 different fields are available. Two common entries are processor which gives
10807 CPU number and bogomips; a system constant that is calculated during
10808 kernel initialization.
10810 @kindex info os files
10812 Display the list of open file descriptors on the target. For each
10813 file descriptor, @value{GDBN} prints the identifier of the process
10814 owning the descriptor, the command of the owning process, the value
10815 of the descriptor, and the target of the descriptor.
10817 @kindex info os modules
10819 Display the list of all loaded kernel modules on the target. For each
10820 module, @value{GDBN} prints the module name, the size of the module in
10821 bytes, the number of times the module is used, the dependencies of the
10822 module, the status of the module, and the address of the loaded module
10825 @kindex info os msg
10827 Display the list of all System V message queues on the target. For each
10828 message queue, @value{GDBN} prints the message queue key, the message
10829 queue identifier, the access permissions, the current number of bytes
10830 on the queue, the current number of messages on the queue, the processes
10831 that last sent and received a message on the queue, the user and group
10832 of the owner and creator of the message queue, the times at which a
10833 message was last sent and received on the queue, and the time at which
10834 the message queue was last changed.
10836 @kindex info os processes
10838 Display the list of processes on the target. For each process,
10839 @value{GDBN} prints the process identifier, the name of the user, the
10840 command corresponding to the process, and the list of processor cores
10841 that the process is currently running on. (To understand what these
10842 properties mean, for this and the following info types, please consult
10843 the general @sc{gnu}/Linux documentation.)
10845 @kindex info os procgroups
10847 Display the list of process groups on the target. For each process,
10848 @value{GDBN} prints the identifier of the process group that it belongs
10849 to, the command corresponding to the process group leader, the process
10850 identifier, and the command line of the process. The list is sorted
10851 first by the process group identifier, then by the process identifier,
10852 so that processes belonging to the same process group are grouped together
10853 and the process group leader is listed first.
10855 @kindex info os semaphores
10857 Display the list of all System V semaphore sets on the target. For each
10858 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10859 set identifier, the access permissions, the number of semaphores in the
10860 set, the user and group of the owner and creator of the semaphore set,
10861 and the times at which the semaphore set was operated upon and changed.
10863 @kindex info os shm
10865 Display the list of all System V shared-memory regions on the target.
10866 For each shared-memory region, @value{GDBN} prints the region key,
10867 the shared-memory identifier, the access permissions, the size of the
10868 region, the process that created the region, the process that last
10869 attached to or detached from the region, the current number of live
10870 attaches to the region, and the times at which the region was last
10871 attached to, detach from, and changed.
10873 @kindex info os sockets
10875 Display the list of Internet-domain sockets on the target. For each
10876 socket, @value{GDBN} prints the address and port of the local and
10877 remote endpoints, the current state of the connection, the creator of
10878 the socket, the IP address family of the socket, and the type of the
10881 @kindex info os threads
10883 Display the list of threads running on the target. For each thread,
10884 @value{GDBN} prints the identifier of the process that the thread
10885 belongs to, the command of the process, the thread identifier, and the
10886 processor core that it is currently running on. The main thread of a
10887 process is not listed.
10891 If @var{infotype} is omitted, then list the possible values for
10892 @var{infotype} and the kind of OS information available for each
10893 @var{infotype}. If the target does not return a list of possible
10894 types, this command will report an error.
10897 @node Memory Region Attributes
10898 @section Memory Region Attributes
10899 @cindex memory region attributes
10901 @dfn{Memory region attributes} allow you to describe special handling
10902 required by regions of your target's memory. @value{GDBN} uses
10903 attributes to determine whether to allow certain types of memory
10904 accesses; whether to use specific width accesses; and whether to cache
10905 target memory. By default the description of memory regions is
10906 fetched from the target (if the current target supports this), but the
10907 user can override the fetched regions.
10909 Defined memory regions can be individually enabled and disabled. When a
10910 memory region is disabled, @value{GDBN} uses the default attributes when
10911 accessing memory in that region. Similarly, if no memory regions have
10912 been defined, @value{GDBN} uses the default attributes when accessing
10915 When a memory region is defined, it is given a number to identify it;
10916 to enable, disable, or remove a memory region, you specify that number.
10920 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10921 Define a memory region bounded by @var{lower} and @var{upper} with
10922 attributes @var{attributes}@dots{}, and add it to the list of regions
10923 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10924 case: it is treated as the target's maximum memory address.
10925 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10928 Discard any user changes to the memory regions and use target-supplied
10929 regions, if available, or no regions if the target does not support.
10932 @item delete mem @var{nums}@dots{}
10933 Remove memory regions @var{nums}@dots{} from the list of regions
10934 monitored by @value{GDBN}.
10936 @kindex disable mem
10937 @item disable mem @var{nums}@dots{}
10938 Disable monitoring of memory regions @var{nums}@dots{}.
10939 A disabled memory region is not forgotten.
10940 It may be enabled again later.
10943 @item enable mem @var{nums}@dots{}
10944 Enable monitoring of memory regions @var{nums}@dots{}.
10948 Print a table of all defined memory regions, with the following columns
10952 @item Memory Region Number
10953 @item Enabled or Disabled.
10954 Enabled memory regions are marked with @samp{y}.
10955 Disabled memory regions are marked with @samp{n}.
10958 The address defining the inclusive lower bound of the memory region.
10961 The address defining the exclusive upper bound of the memory region.
10964 The list of attributes set for this memory region.
10969 @subsection Attributes
10971 @subsubsection Memory Access Mode
10972 The access mode attributes set whether @value{GDBN} may make read or
10973 write accesses to a memory region.
10975 While these attributes prevent @value{GDBN} from performing invalid
10976 memory accesses, they do nothing to prevent the target system, I/O DMA,
10977 etc.@: from accessing memory.
10981 Memory is read only.
10983 Memory is write only.
10985 Memory is read/write. This is the default.
10988 @subsubsection Memory Access Size
10989 The access size attribute tells @value{GDBN} to use specific sized
10990 accesses in the memory region. Often memory mapped device registers
10991 require specific sized accesses. If no access size attribute is
10992 specified, @value{GDBN} may use accesses of any size.
10996 Use 8 bit memory accesses.
10998 Use 16 bit memory accesses.
11000 Use 32 bit memory accesses.
11002 Use 64 bit memory accesses.
11005 @c @subsubsection Hardware/Software Breakpoints
11006 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11007 @c will use hardware or software breakpoints for the internal breakpoints
11008 @c used by the step, next, finish, until, etc. commands.
11012 @c Always use hardware breakpoints
11013 @c @item swbreak (default)
11016 @subsubsection Data Cache
11017 The data cache attributes set whether @value{GDBN} will cache target
11018 memory. While this generally improves performance by reducing debug
11019 protocol overhead, it can lead to incorrect results because @value{GDBN}
11020 does not know about volatile variables or memory mapped device
11025 Enable @value{GDBN} to cache target memory.
11027 Disable @value{GDBN} from caching target memory. This is the default.
11030 @subsection Memory Access Checking
11031 @value{GDBN} can be instructed to refuse accesses to memory that is
11032 not explicitly described. This can be useful if accessing such
11033 regions has undesired effects for a specific target, or to provide
11034 better error checking. The following commands control this behaviour.
11037 @kindex set mem inaccessible-by-default
11038 @item set mem inaccessible-by-default [on|off]
11039 If @code{on} is specified, make @value{GDBN} treat memory not
11040 explicitly described by the memory ranges as non-existent and refuse accesses
11041 to such memory. The checks are only performed if there's at least one
11042 memory range defined. If @code{off} is specified, make @value{GDBN}
11043 treat the memory not explicitly described by the memory ranges as RAM.
11044 The default value is @code{on}.
11045 @kindex show mem inaccessible-by-default
11046 @item show mem inaccessible-by-default
11047 Show the current handling of accesses to unknown memory.
11051 @c @subsubsection Memory Write Verification
11052 @c The memory write verification attributes set whether @value{GDBN}
11053 @c will re-reads data after each write to verify the write was successful.
11057 @c @item noverify (default)
11060 @node Dump/Restore Files
11061 @section Copy Between Memory and a File
11062 @cindex dump/restore files
11063 @cindex append data to a file
11064 @cindex dump data to a file
11065 @cindex restore data from a file
11067 You can use the commands @code{dump}, @code{append}, and
11068 @code{restore} to copy data between target memory and a file. The
11069 @code{dump} and @code{append} commands write data to a file, and the
11070 @code{restore} command reads data from a file back into the inferior's
11071 memory. Files may be in binary, Motorola S-record, Intel hex,
11072 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11073 append to binary files, and cannot read from Verilog Hex files.
11078 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11079 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11080 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11081 or the value of @var{expr}, to @var{filename} in the given format.
11083 The @var{format} parameter may be any one of:
11090 Motorola S-record format.
11092 Tektronix Hex format.
11094 Verilog Hex format.
11097 @value{GDBN} uses the same definitions of these formats as the
11098 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11099 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11103 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11104 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11105 Append the contents of memory from @var{start_addr} to @var{end_addr},
11106 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11107 (@value{GDBN} can only append data to files in raw binary form.)
11110 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11111 Restore the contents of file @var{filename} into memory. The
11112 @code{restore} command can automatically recognize any known @sc{bfd}
11113 file format, except for raw binary. To restore a raw binary file you
11114 must specify the optional keyword @code{binary} after the filename.
11116 If @var{bias} is non-zero, its value will be added to the addresses
11117 contained in the file. Binary files always start at address zero, so
11118 they will be restored at address @var{bias}. Other bfd files have
11119 a built-in location; they will be restored at offset @var{bias}
11120 from that location.
11122 If @var{start} and/or @var{end} are non-zero, then only data between
11123 file offset @var{start} and file offset @var{end} will be restored.
11124 These offsets are relative to the addresses in the file, before
11125 the @var{bias} argument is applied.
11129 @node Core File Generation
11130 @section How to Produce a Core File from Your Program
11131 @cindex dump core from inferior
11133 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11134 image of a running process and its process status (register values
11135 etc.). Its primary use is post-mortem debugging of a program that
11136 crashed while it ran outside a debugger. A program that crashes
11137 automatically produces a core file, unless this feature is disabled by
11138 the user. @xref{Files}, for information on invoking @value{GDBN} in
11139 the post-mortem debugging mode.
11141 Occasionally, you may wish to produce a core file of the program you
11142 are debugging in order to preserve a snapshot of its state.
11143 @value{GDBN} has a special command for that.
11147 @kindex generate-core-file
11148 @item generate-core-file [@var{file}]
11149 @itemx gcore [@var{file}]
11150 Produce a core dump of the inferior process. The optional argument
11151 @var{file} specifies the file name where to put the core dump. If not
11152 specified, the file name defaults to @file{core.@var{pid}}, where
11153 @var{pid} is the inferior process ID.
11155 Note that this command is implemented only for some systems (as of
11156 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11158 On @sc{gnu}/Linux, this command can take into account the value of the
11159 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11160 dump (@pxref{set use-coredump-filter}).
11162 @kindex set use-coredump-filter
11163 @anchor{set use-coredump-filter}
11164 @item set use-coredump-filter on
11165 @itemx set use-coredump-filter off
11166 Enable or disable the use of the file
11167 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11168 files. This file is used by the Linux kernel to decide what types of
11169 memory mappings will be dumped or ignored when generating a core dump
11170 file. @var{pid} is the process ID of a currently running process.
11172 To make use of this feature, you have to write in the
11173 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11174 which is a bit mask representing the memory mapping types. If a bit
11175 is set in the bit mask, then the memory mappings of the corresponding
11176 types will be dumped; otherwise, they will be ignored. This
11177 configuration is inherited by child processes. For more information
11178 about the bits that can be set in the
11179 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11180 manpage of @code{core(5)}.
11182 By default, this option is @code{on}. If this option is turned
11183 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11184 and instead uses the same default value as the Linux kernel in order
11185 to decide which pages will be dumped in the core dump file. This
11186 value is currently @code{0x33}, which means that bits @code{0}
11187 (anonymous private mappings), @code{1} (anonymous shared mappings),
11188 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11189 This will cause these memory mappings to be dumped automatically.
11192 @node Character Sets
11193 @section Character Sets
11194 @cindex character sets
11196 @cindex translating between character sets
11197 @cindex host character set
11198 @cindex target character set
11200 If the program you are debugging uses a different character set to
11201 represent characters and strings than the one @value{GDBN} uses itself,
11202 @value{GDBN} can automatically translate between the character sets for
11203 you. The character set @value{GDBN} uses we call the @dfn{host
11204 character set}; the one the inferior program uses we call the
11205 @dfn{target character set}.
11207 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11208 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11209 remote protocol (@pxref{Remote Debugging}) to debug a program
11210 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11211 then the host character set is Latin-1, and the target character set is
11212 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11213 target-charset EBCDIC-US}, then @value{GDBN} translates between
11214 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11215 character and string literals in expressions.
11217 @value{GDBN} has no way to automatically recognize which character set
11218 the inferior program uses; you must tell it, using the @code{set
11219 target-charset} command, described below.
11221 Here are the commands for controlling @value{GDBN}'s character set
11225 @item set target-charset @var{charset}
11226 @kindex set target-charset
11227 Set the current target character set to @var{charset}. To display the
11228 list of supported target character sets, type
11229 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11231 @item set host-charset @var{charset}
11232 @kindex set host-charset
11233 Set the current host character set to @var{charset}.
11235 By default, @value{GDBN} uses a host character set appropriate to the
11236 system it is running on; you can override that default using the
11237 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11238 automatically determine the appropriate host character set. In this
11239 case, @value{GDBN} uses @samp{UTF-8}.
11241 @value{GDBN} can only use certain character sets as its host character
11242 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11243 @value{GDBN} will list the host character sets it supports.
11245 @item set charset @var{charset}
11246 @kindex set charset
11247 Set the current host and target character sets to @var{charset}. As
11248 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11249 @value{GDBN} will list the names of the character sets that can be used
11250 for both host and target.
11253 @kindex show charset
11254 Show the names of the current host and target character sets.
11256 @item show host-charset
11257 @kindex show host-charset
11258 Show the name of the current host character set.
11260 @item show target-charset
11261 @kindex show target-charset
11262 Show the name of the current target character set.
11264 @item set target-wide-charset @var{charset}
11265 @kindex set target-wide-charset
11266 Set the current target's wide character set to @var{charset}. This is
11267 the character set used by the target's @code{wchar_t} type. To
11268 display the list of supported wide character sets, type
11269 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11271 @item show target-wide-charset
11272 @kindex show target-wide-charset
11273 Show the name of the current target's wide character set.
11276 Here is an example of @value{GDBN}'s character set support in action.
11277 Assume that the following source code has been placed in the file
11278 @file{charset-test.c}:
11284 = @{72, 101, 108, 108, 111, 44, 32, 119,
11285 111, 114, 108, 100, 33, 10, 0@};
11286 char ibm1047_hello[]
11287 = @{200, 133, 147, 147, 150, 107, 64, 166,
11288 150, 153, 147, 132, 90, 37, 0@};
11292 printf ("Hello, world!\n");
11296 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11297 containing the string @samp{Hello, world!} followed by a newline,
11298 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11300 We compile the program, and invoke the debugger on it:
11303 $ gcc -g charset-test.c -o charset-test
11304 $ gdb -nw charset-test
11305 GNU gdb 2001-12-19-cvs
11306 Copyright 2001 Free Software Foundation, Inc.
11311 We can use the @code{show charset} command to see what character sets
11312 @value{GDBN} is currently using to interpret and display characters and
11316 (@value{GDBP}) show charset
11317 The current host and target character set is `ISO-8859-1'.
11321 For the sake of printing this manual, let's use @sc{ascii} as our
11322 initial character set:
11324 (@value{GDBP}) set charset ASCII
11325 (@value{GDBP}) show charset
11326 The current host and target character set is `ASCII'.
11330 Let's assume that @sc{ascii} is indeed the correct character set for our
11331 host system --- in other words, let's assume that if @value{GDBN} prints
11332 characters using the @sc{ascii} character set, our terminal will display
11333 them properly. Since our current target character set is also
11334 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11337 (@value{GDBP}) print ascii_hello
11338 $1 = 0x401698 "Hello, world!\n"
11339 (@value{GDBP}) print ascii_hello[0]
11344 @value{GDBN} uses the target character set for character and string
11345 literals you use in expressions:
11348 (@value{GDBP}) print '+'
11353 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11356 @value{GDBN} relies on the user to tell it which character set the
11357 target program uses. If we print @code{ibm1047_hello} while our target
11358 character set is still @sc{ascii}, we get jibberish:
11361 (@value{GDBP}) print ibm1047_hello
11362 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11363 (@value{GDBP}) print ibm1047_hello[0]
11368 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11369 @value{GDBN} tells us the character sets it supports:
11372 (@value{GDBP}) set target-charset
11373 ASCII EBCDIC-US IBM1047 ISO-8859-1
11374 (@value{GDBP}) set target-charset
11377 We can select @sc{ibm1047} as our target character set, and examine the
11378 program's strings again. Now the @sc{ascii} string is wrong, but
11379 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11380 target character set, @sc{ibm1047}, to the host character set,
11381 @sc{ascii}, and they display correctly:
11384 (@value{GDBP}) set target-charset IBM1047
11385 (@value{GDBP}) show charset
11386 The current host character set is `ASCII'.
11387 The current target character set is `IBM1047'.
11388 (@value{GDBP}) print ascii_hello
11389 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11390 (@value{GDBP}) print ascii_hello[0]
11392 (@value{GDBP}) print ibm1047_hello
11393 $8 = 0x4016a8 "Hello, world!\n"
11394 (@value{GDBP}) print ibm1047_hello[0]
11399 As above, @value{GDBN} uses the target character set for character and
11400 string literals you use in expressions:
11403 (@value{GDBP}) print '+'
11408 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11411 @node Caching Target Data
11412 @section Caching Data of Targets
11413 @cindex caching data of targets
11415 @value{GDBN} caches data exchanged between the debugger and a target.
11416 Each cache is associated with the address space of the inferior.
11417 @xref{Inferiors and Programs}, about inferior and address space.
11418 Such caching generally improves performance in remote debugging
11419 (@pxref{Remote Debugging}), because it reduces the overhead of the
11420 remote protocol by bundling memory reads and writes into large chunks.
11421 Unfortunately, simply caching everything would lead to incorrect results,
11422 since @value{GDBN} does not necessarily know anything about volatile
11423 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11424 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11426 Therefore, by default, @value{GDBN} only caches data
11427 known to be on the stack@footnote{In non-stop mode, it is moderately
11428 rare for a running thread to modify the stack of a stopped thread
11429 in a way that would interfere with a backtrace, and caching of
11430 stack reads provides a significant speed up of remote backtraces.} or
11431 in the code segment.
11432 Other regions of memory can be explicitly marked as
11433 cacheable; @pxref{Memory Region Attributes}.
11436 @kindex set remotecache
11437 @item set remotecache on
11438 @itemx set remotecache off
11439 This option no longer does anything; it exists for compatibility
11442 @kindex show remotecache
11443 @item show remotecache
11444 Show the current state of the obsolete remotecache flag.
11446 @kindex set stack-cache
11447 @item set stack-cache on
11448 @itemx set stack-cache off
11449 Enable or disable caching of stack accesses. When @code{on}, use
11450 caching. By default, this option is @code{on}.
11452 @kindex show stack-cache
11453 @item show stack-cache
11454 Show the current state of data caching for memory accesses.
11456 @kindex set code-cache
11457 @item set code-cache on
11458 @itemx set code-cache off
11459 Enable or disable caching of code segment accesses. When @code{on},
11460 use caching. By default, this option is @code{on}. This improves
11461 performance of disassembly in remote debugging.
11463 @kindex show code-cache
11464 @item show code-cache
11465 Show the current state of target memory cache for code segment
11468 @kindex info dcache
11469 @item info dcache @r{[}line@r{]}
11470 Print the information about the performance of data cache of the
11471 current inferior's address space. The information displayed
11472 includes the dcache width and depth, and for each cache line, its
11473 number, address, and how many times it was referenced. This
11474 command is useful for debugging the data cache operation.
11476 If a line number is specified, the contents of that line will be
11479 @item set dcache size @var{size}
11480 @cindex dcache size
11481 @kindex set dcache size
11482 Set maximum number of entries in dcache (dcache depth above).
11484 @item set dcache line-size @var{line-size}
11485 @cindex dcache line-size
11486 @kindex set dcache line-size
11487 Set number of bytes each dcache entry caches (dcache width above).
11488 Must be a power of 2.
11490 @item show dcache size
11491 @kindex show dcache size
11492 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11494 @item show dcache line-size
11495 @kindex show dcache line-size
11496 Show default size of dcache lines.
11500 @node Searching Memory
11501 @section Search Memory
11502 @cindex searching memory
11504 Memory can be searched for a particular sequence of bytes with the
11505 @code{find} command.
11509 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11510 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11511 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11512 etc. The search begins at address @var{start_addr} and continues for either
11513 @var{len} bytes or through to @var{end_addr} inclusive.
11516 @var{s} and @var{n} are optional parameters.
11517 They may be specified in either order, apart or together.
11520 @item @var{s}, search query size
11521 The size of each search query value.
11527 halfwords (two bytes)
11531 giant words (eight bytes)
11534 All values are interpreted in the current language.
11535 This means, for example, that if the current source language is C/C@t{++}
11536 then searching for the string ``hello'' includes the trailing '\0'.
11538 If the value size is not specified, it is taken from the
11539 value's type in the current language.
11540 This is useful when one wants to specify the search
11541 pattern as a mixture of types.
11542 Note that this means, for example, that in the case of C-like languages
11543 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11544 which is typically four bytes.
11546 @item @var{n}, maximum number of finds
11547 The maximum number of matches to print. The default is to print all finds.
11550 You can use strings as search values. Quote them with double-quotes
11552 The string value is copied into the search pattern byte by byte,
11553 regardless of the endianness of the target and the size specification.
11555 The address of each match found is printed as well as a count of the
11556 number of matches found.
11558 The address of the last value found is stored in convenience variable
11560 A count of the number of matches is stored in @samp{$numfound}.
11562 For example, if stopped at the @code{printf} in this function:
11568 static char hello[] = "hello-hello";
11569 static struct @{ char c; short s; int i; @}
11570 __attribute__ ((packed)) mixed
11571 = @{ 'c', 0x1234, 0x87654321 @};
11572 printf ("%s\n", hello);
11577 you get during debugging:
11580 (gdb) find &hello[0], +sizeof(hello), "hello"
11581 0x804956d <hello.1620+6>
11583 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11584 0x8049567 <hello.1620>
11585 0x804956d <hello.1620+6>
11587 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11588 0x8049567 <hello.1620>
11590 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11591 0x8049560 <mixed.1625>
11593 (gdb) print $numfound
11596 $2 = (void *) 0x8049560
11599 @node Optimized Code
11600 @chapter Debugging Optimized Code
11601 @cindex optimized code, debugging
11602 @cindex debugging optimized code
11604 Almost all compilers support optimization. With optimization
11605 disabled, the compiler generates assembly code that corresponds
11606 directly to your source code, in a simplistic way. As the compiler
11607 applies more powerful optimizations, the generated assembly code
11608 diverges from your original source code. With help from debugging
11609 information generated by the compiler, @value{GDBN} can map from
11610 the running program back to constructs from your original source.
11612 @value{GDBN} is more accurate with optimization disabled. If you
11613 can recompile without optimization, it is easier to follow the
11614 progress of your program during debugging. But, there are many cases
11615 where you may need to debug an optimized version.
11617 When you debug a program compiled with @samp{-g -O}, remember that the
11618 optimizer has rearranged your code; the debugger shows you what is
11619 really there. Do not be too surprised when the execution path does not
11620 exactly match your source file! An extreme example: if you define a
11621 variable, but never use it, @value{GDBN} never sees that
11622 variable---because the compiler optimizes it out of existence.
11624 Some things do not work as well with @samp{-g -O} as with just
11625 @samp{-g}, particularly on machines with instruction scheduling. If in
11626 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11627 please report it to us as a bug (including a test case!).
11628 @xref{Variables}, for more information about debugging optimized code.
11631 * Inline Functions:: How @value{GDBN} presents inlining
11632 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11635 @node Inline Functions
11636 @section Inline Functions
11637 @cindex inline functions, debugging
11639 @dfn{Inlining} is an optimization that inserts a copy of the function
11640 body directly at each call site, instead of jumping to a shared
11641 routine. @value{GDBN} displays inlined functions just like
11642 non-inlined functions. They appear in backtraces. You can view their
11643 arguments and local variables, step into them with @code{step}, skip
11644 them with @code{next}, and escape from them with @code{finish}.
11645 You can check whether a function was inlined by using the
11646 @code{info frame} command.
11648 For @value{GDBN} to support inlined functions, the compiler must
11649 record information about inlining in the debug information ---
11650 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11651 other compilers do also. @value{GDBN} only supports inlined functions
11652 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11653 do not emit two required attributes (@samp{DW_AT_call_file} and
11654 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11655 function calls with earlier versions of @value{NGCC}. It instead
11656 displays the arguments and local variables of inlined functions as
11657 local variables in the caller.
11659 The body of an inlined function is directly included at its call site;
11660 unlike a non-inlined function, there are no instructions devoted to
11661 the call. @value{GDBN} still pretends that the call site and the
11662 start of the inlined function are different instructions. Stepping to
11663 the call site shows the call site, and then stepping again shows
11664 the first line of the inlined function, even though no additional
11665 instructions are executed.
11667 This makes source-level debugging much clearer; you can see both the
11668 context of the call and then the effect of the call. Only stepping by
11669 a single instruction using @code{stepi} or @code{nexti} does not do
11670 this; single instruction steps always show the inlined body.
11672 There are some ways that @value{GDBN} does not pretend that inlined
11673 function calls are the same as normal calls:
11677 Setting breakpoints at the call site of an inlined function may not
11678 work, because the call site does not contain any code. @value{GDBN}
11679 may incorrectly move the breakpoint to the next line of the enclosing
11680 function, after the call. This limitation will be removed in a future
11681 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11682 or inside the inlined function instead.
11685 @value{GDBN} cannot locate the return value of inlined calls after
11686 using the @code{finish} command. This is a limitation of compiler-generated
11687 debugging information; after @code{finish}, you can step to the next line
11688 and print a variable where your program stored the return value.
11692 @node Tail Call Frames
11693 @section Tail Call Frames
11694 @cindex tail call frames, debugging
11696 Function @code{B} can call function @code{C} in its very last statement. In
11697 unoptimized compilation the call of @code{C} is immediately followed by return
11698 instruction at the end of @code{B} code. Optimizing compiler may replace the
11699 call and return in function @code{B} into one jump to function @code{C}
11700 instead. Such use of a jump instruction is called @dfn{tail call}.
11702 During execution of function @code{C}, there will be no indication in the
11703 function call stack frames that it was tail-called from @code{B}. If function
11704 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11705 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11706 some cases @value{GDBN} can determine that @code{C} was tail-called from
11707 @code{B}, and it will then create fictitious call frame for that, with the
11708 return address set up as if @code{B} called @code{C} normally.
11710 This functionality is currently supported only by DWARF 2 debugging format and
11711 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11712 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11715 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11716 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11720 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11722 Stack level 1, frame at 0x7fffffffda30:
11723 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11724 tail call frame, caller of frame at 0x7fffffffda30
11725 source language c++.
11726 Arglist at unknown address.
11727 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11730 The detection of all the possible code path executions can find them ambiguous.
11731 There is no execution history stored (possible @ref{Reverse Execution} is never
11732 used for this purpose) and the last known caller could have reached the known
11733 callee by multiple different jump sequences. In such case @value{GDBN} still
11734 tries to show at least all the unambiguous top tail callers and all the
11735 unambiguous bottom tail calees, if any.
11738 @anchor{set debug entry-values}
11739 @item set debug entry-values
11740 @kindex set debug entry-values
11741 When set to on, enables printing of analysis messages for both frame argument
11742 values at function entry and tail calls. It will show all the possible valid
11743 tail calls code paths it has considered. It will also print the intersection
11744 of them with the final unambiguous (possibly partial or even empty) code path
11747 @item show debug entry-values
11748 @kindex show debug entry-values
11749 Show the current state of analysis messages printing for both frame argument
11750 values at function entry and tail calls.
11753 The analysis messages for tail calls can for example show why the virtual tail
11754 call frame for function @code{c} has not been recognized (due to the indirect
11755 reference by variable @code{x}):
11758 static void __attribute__((noinline, noclone)) c (void);
11759 void (*x) (void) = c;
11760 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11761 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11762 int main (void) @{ x (); return 0; @}
11764 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11765 DW_TAG_GNU_call_site 0x40039a in main
11767 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11770 #1 0x000000000040039a in main () at t.c:5
11773 Another possibility is an ambiguous virtual tail call frames resolution:
11777 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11778 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11779 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11780 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11781 static void __attribute__((noinline, noclone)) b (void)
11782 @{ if (i) c (); else e (); @}
11783 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11784 int main (void) @{ a (); return 0; @}
11786 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11787 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11788 tailcall: reduced: 0x4004d2(a) |
11791 #1 0x00000000004004d2 in a () at t.c:8
11792 #2 0x0000000000400395 in main () at t.c:9
11795 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11796 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11798 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11799 @ifset HAVE_MAKEINFO_CLICK
11800 @set ARROW @click{}
11801 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11802 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11804 @ifclear HAVE_MAKEINFO_CLICK
11806 @set CALLSEQ1B @value{CALLSEQ1A}
11807 @set CALLSEQ2B @value{CALLSEQ2A}
11810 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11811 The code can have possible execution paths @value{CALLSEQ1B} or
11812 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11814 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11815 has found. It then finds another possible calling sequcen - that one is
11816 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11817 printed as the @code{reduced:} calling sequence. That one could have many
11818 futher @code{compare:} and @code{reduced:} statements as long as there remain
11819 any non-ambiguous sequence entries.
11821 For the frame of function @code{b} in both cases there are different possible
11822 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11823 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11824 therefore this one is displayed to the user while the ambiguous frames are
11827 There can be also reasons why printing of frame argument values at function
11832 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11833 static void __attribute__((noinline, noclone)) a (int i);
11834 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11835 static void __attribute__((noinline, noclone)) a (int i)
11836 @{ if (i) b (i - 1); else c (0); @}
11837 int main (void) @{ a (5); return 0; @}
11840 #0 c (i=i@@entry=0) at t.c:2
11841 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11842 function "a" at 0x400420 can call itself via tail calls
11843 i=<optimized out>) at t.c:6
11844 #2 0x000000000040036e in main () at t.c:7
11847 @value{GDBN} cannot find out from the inferior state if and how many times did
11848 function @code{a} call itself (via function @code{b}) as these calls would be
11849 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11850 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11851 prints @code{<optimized out>} instead.
11854 @chapter C Preprocessor Macros
11856 Some languages, such as C and C@t{++}, provide a way to define and invoke
11857 ``preprocessor macros'' which expand into strings of tokens.
11858 @value{GDBN} can evaluate expressions containing macro invocations, show
11859 the result of macro expansion, and show a macro's definition, including
11860 where it was defined.
11862 You may need to compile your program specially to provide @value{GDBN}
11863 with information about preprocessor macros. Most compilers do not
11864 include macros in their debugging information, even when you compile
11865 with the @option{-g} flag. @xref{Compilation}.
11867 A program may define a macro at one point, remove that definition later,
11868 and then provide a different definition after that. Thus, at different
11869 points in the program, a macro may have different definitions, or have
11870 no definition at all. If there is a current stack frame, @value{GDBN}
11871 uses the macros in scope at that frame's source code line. Otherwise,
11872 @value{GDBN} uses the macros in scope at the current listing location;
11875 Whenever @value{GDBN} evaluates an expression, it always expands any
11876 macro invocations present in the expression. @value{GDBN} also provides
11877 the following commands for working with macros explicitly.
11881 @kindex macro expand
11882 @cindex macro expansion, showing the results of preprocessor
11883 @cindex preprocessor macro expansion, showing the results of
11884 @cindex expanding preprocessor macros
11885 @item macro expand @var{expression}
11886 @itemx macro exp @var{expression}
11887 Show the results of expanding all preprocessor macro invocations in
11888 @var{expression}. Since @value{GDBN} simply expands macros, but does
11889 not parse the result, @var{expression} need not be a valid expression;
11890 it can be any string of tokens.
11893 @item macro expand-once @var{expression}
11894 @itemx macro exp1 @var{expression}
11895 @cindex expand macro once
11896 @i{(This command is not yet implemented.)} Show the results of
11897 expanding those preprocessor macro invocations that appear explicitly in
11898 @var{expression}. Macro invocations appearing in that expansion are
11899 left unchanged. This command allows you to see the effect of a
11900 particular macro more clearly, without being confused by further
11901 expansions. Since @value{GDBN} simply expands macros, but does not
11902 parse the result, @var{expression} need not be a valid expression; it
11903 can be any string of tokens.
11906 @cindex macro definition, showing
11907 @cindex definition of a macro, showing
11908 @cindex macros, from debug info
11909 @item info macro [-a|-all] [--] @var{macro}
11910 Show the current definition or all definitions of the named @var{macro},
11911 and describe the source location or compiler command-line where that
11912 definition was established. The optional double dash is to signify the end of
11913 argument processing and the beginning of @var{macro} for non C-like macros where
11914 the macro may begin with a hyphen.
11916 @kindex info macros
11917 @item info macros @var{location}
11918 Show all macro definitions that are in effect at the location specified
11919 by @var{location}, and describe the source location or compiler
11920 command-line where those definitions were established.
11922 @kindex macro define
11923 @cindex user-defined macros
11924 @cindex defining macros interactively
11925 @cindex macros, user-defined
11926 @item macro define @var{macro} @var{replacement-list}
11927 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11928 Introduce a definition for a preprocessor macro named @var{macro},
11929 invocations of which are replaced by the tokens given in
11930 @var{replacement-list}. The first form of this command defines an
11931 ``object-like'' macro, which takes no arguments; the second form
11932 defines a ``function-like'' macro, which takes the arguments given in
11935 A definition introduced by this command is in scope in every
11936 expression evaluated in @value{GDBN}, until it is removed with the
11937 @code{macro undef} command, described below. The definition overrides
11938 all definitions for @var{macro} present in the program being debugged,
11939 as well as any previous user-supplied definition.
11941 @kindex macro undef
11942 @item macro undef @var{macro}
11943 Remove any user-supplied definition for the macro named @var{macro}.
11944 This command only affects definitions provided with the @code{macro
11945 define} command, described above; it cannot remove definitions present
11946 in the program being debugged.
11950 List all the macros defined using the @code{macro define} command.
11953 @cindex macros, example of debugging with
11954 Here is a transcript showing the above commands in action. First, we
11955 show our source files:
11960 #include "sample.h"
11963 #define ADD(x) (M + x)
11968 printf ("Hello, world!\n");
11970 printf ("We're so creative.\n");
11972 printf ("Goodbye, world!\n");
11979 Now, we compile the program using the @sc{gnu} C compiler,
11980 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11981 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11982 and @option{-gdwarf-4}; we recommend always choosing the most recent
11983 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11984 includes information about preprocessor macros in the debugging
11988 $ gcc -gdwarf-2 -g3 sample.c -o sample
11992 Now, we start @value{GDBN} on our sample program:
11996 GNU gdb 2002-05-06-cvs
11997 Copyright 2002 Free Software Foundation, Inc.
11998 GDB is free software, @dots{}
12002 We can expand macros and examine their definitions, even when the
12003 program is not running. @value{GDBN} uses the current listing position
12004 to decide which macro definitions are in scope:
12007 (@value{GDBP}) list main
12010 5 #define ADD(x) (M + x)
12015 10 printf ("Hello, world!\n");
12017 12 printf ("We're so creative.\n");
12018 (@value{GDBP}) info macro ADD
12019 Defined at /home/jimb/gdb/macros/play/sample.c:5
12020 #define ADD(x) (M + x)
12021 (@value{GDBP}) info macro Q
12022 Defined at /home/jimb/gdb/macros/play/sample.h:1
12023 included at /home/jimb/gdb/macros/play/sample.c:2
12025 (@value{GDBP}) macro expand ADD(1)
12026 expands to: (42 + 1)
12027 (@value{GDBP}) macro expand-once ADD(1)
12028 expands to: once (M + 1)
12032 In the example above, note that @code{macro expand-once} expands only
12033 the macro invocation explicit in the original text --- the invocation of
12034 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12035 which was introduced by @code{ADD}.
12037 Once the program is running, @value{GDBN} uses the macro definitions in
12038 force at the source line of the current stack frame:
12041 (@value{GDBP}) break main
12042 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12044 Starting program: /home/jimb/gdb/macros/play/sample
12046 Breakpoint 1, main () at sample.c:10
12047 10 printf ("Hello, world!\n");
12051 At line 10, the definition of the macro @code{N} at line 9 is in force:
12054 (@value{GDBP}) info macro N
12055 Defined at /home/jimb/gdb/macros/play/sample.c:9
12057 (@value{GDBP}) macro expand N Q M
12058 expands to: 28 < 42
12059 (@value{GDBP}) print N Q M
12064 As we step over directives that remove @code{N}'s definition, and then
12065 give it a new definition, @value{GDBN} finds the definition (or lack
12066 thereof) in force at each point:
12069 (@value{GDBP}) next
12071 12 printf ("We're so creative.\n");
12072 (@value{GDBP}) info macro N
12073 The symbol `N' has no definition as a C/C++ preprocessor macro
12074 at /home/jimb/gdb/macros/play/sample.c:12
12075 (@value{GDBP}) next
12077 14 printf ("Goodbye, world!\n");
12078 (@value{GDBP}) info macro N
12079 Defined at /home/jimb/gdb/macros/play/sample.c:13
12081 (@value{GDBP}) macro expand N Q M
12082 expands to: 1729 < 42
12083 (@value{GDBP}) print N Q M
12088 In addition to source files, macros can be defined on the compilation command
12089 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12090 such a way, @value{GDBN} displays the location of their definition as line zero
12091 of the source file submitted to the compiler.
12094 (@value{GDBP}) info macro __STDC__
12095 Defined at /home/jimb/gdb/macros/play/sample.c:0
12102 @chapter Tracepoints
12103 @c This chapter is based on the documentation written by Michael
12104 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12106 @cindex tracepoints
12107 In some applications, it is not feasible for the debugger to interrupt
12108 the program's execution long enough for the developer to learn
12109 anything helpful about its behavior. If the program's correctness
12110 depends on its real-time behavior, delays introduced by a debugger
12111 might cause the program to change its behavior drastically, or perhaps
12112 fail, even when the code itself is correct. It is useful to be able
12113 to observe the program's behavior without interrupting it.
12115 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12116 specify locations in the program, called @dfn{tracepoints}, and
12117 arbitrary expressions to evaluate when those tracepoints are reached.
12118 Later, using the @code{tfind} command, you can examine the values
12119 those expressions had when the program hit the tracepoints. The
12120 expressions may also denote objects in memory---structures or arrays,
12121 for example---whose values @value{GDBN} should record; while visiting
12122 a particular tracepoint, you may inspect those objects as if they were
12123 in memory at that moment. However, because @value{GDBN} records these
12124 values without interacting with you, it can do so quickly and
12125 unobtrusively, hopefully not disturbing the program's behavior.
12127 The tracepoint facility is currently available only for remote
12128 targets. @xref{Targets}. In addition, your remote target must know
12129 how to collect trace data. This functionality is implemented in the
12130 remote stub; however, none of the stubs distributed with @value{GDBN}
12131 support tracepoints as of this writing. The format of the remote
12132 packets used to implement tracepoints are described in @ref{Tracepoint
12135 It is also possible to get trace data from a file, in a manner reminiscent
12136 of corefiles; you specify the filename, and use @code{tfind} to search
12137 through the file. @xref{Trace Files}, for more details.
12139 This chapter describes the tracepoint commands and features.
12142 * Set Tracepoints::
12143 * Analyze Collected Data::
12144 * Tracepoint Variables::
12148 @node Set Tracepoints
12149 @section Commands to Set Tracepoints
12151 Before running such a @dfn{trace experiment}, an arbitrary number of
12152 tracepoints can be set. A tracepoint is actually a special type of
12153 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12154 standard breakpoint commands. For instance, as with breakpoints,
12155 tracepoint numbers are successive integers starting from one, and many
12156 of the commands associated with tracepoints take the tracepoint number
12157 as their argument, to identify which tracepoint to work on.
12159 For each tracepoint, you can specify, in advance, some arbitrary set
12160 of data that you want the target to collect in the trace buffer when
12161 it hits that tracepoint. The collected data can include registers,
12162 local variables, or global data. Later, you can use @value{GDBN}
12163 commands to examine the values these data had at the time the
12164 tracepoint was hit.
12166 Tracepoints do not support every breakpoint feature. Ignore counts on
12167 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12168 commands when they are hit. Tracepoints may not be thread-specific
12171 @cindex fast tracepoints
12172 Some targets may support @dfn{fast tracepoints}, which are inserted in
12173 a different way (such as with a jump instead of a trap), that is
12174 faster but possibly restricted in where they may be installed.
12176 @cindex static tracepoints
12177 @cindex markers, static tracepoints
12178 @cindex probing markers, static tracepoints
12179 Regular and fast tracepoints are dynamic tracing facilities, meaning
12180 that they can be used to insert tracepoints at (almost) any location
12181 in the target. Some targets may also support controlling @dfn{static
12182 tracepoints} from @value{GDBN}. With static tracing, a set of
12183 instrumentation points, also known as @dfn{markers}, are embedded in
12184 the target program, and can be activated or deactivated by name or
12185 address. These are usually placed at locations which facilitate
12186 investigating what the target is actually doing. @value{GDBN}'s
12187 support for static tracing includes being able to list instrumentation
12188 points, and attach them with @value{GDBN} defined high level
12189 tracepoints that expose the whole range of convenience of
12190 @value{GDBN}'s tracepoints support. Namely, support for collecting
12191 registers values and values of global or local (to the instrumentation
12192 point) variables; tracepoint conditions and trace state variables.
12193 The act of installing a @value{GDBN} static tracepoint on an
12194 instrumentation point, or marker, is referred to as @dfn{probing} a
12195 static tracepoint marker.
12197 @code{gdbserver} supports tracepoints on some target systems.
12198 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12200 This section describes commands to set tracepoints and associated
12201 conditions and actions.
12204 * Create and Delete Tracepoints::
12205 * Enable and Disable Tracepoints::
12206 * Tracepoint Passcounts::
12207 * Tracepoint Conditions::
12208 * Trace State Variables::
12209 * Tracepoint Actions::
12210 * Listing Tracepoints::
12211 * Listing Static Tracepoint Markers::
12212 * Starting and Stopping Trace Experiments::
12213 * Tracepoint Restrictions::
12216 @node Create and Delete Tracepoints
12217 @subsection Create and Delete Tracepoints
12220 @cindex set tracepoint
12222 @item trace @var{location}
12223 The @code{trace} command is very similar to the @code{break} command.
12224 Its argument @var{location} can be any valid location.
12225 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12226 which is a point in the target program where the debugger will briefly stop,
12227 collect some data, and then allow the program to continue. Setting a tracepoint
12228 or changing its actions takes effect immediately if the remote stub
12229 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12231 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12232 these changes don't take effect until the next @code{tstart}
12233 command, and once a trace experiment is running, further changes will
12234 not have any effect until the next trace experiment starts. In addition,
12235 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12236 address is not yet resolved. (This is similar to pending breakpoints.)
12237 Pending tracepoints are not downloaded to the target and not installed
12238 until they are resolved. The resolution of pending tracepoints requires
12239 @value{GDBN} support---when debugging with the remote target, and
12240 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12241 tracing}), pending tracepoints can not be resolved (and downloaded to
12242 the remote stub) while @value{GDBN} is disconnected.
12244 Here are some examples of using the @code{trace} command:
12247 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12249 (@value{GDBP}) @b{trace +2} // 2 lines forward
12251 (@value{GDBP}) @b{trace my_function} // first source line of function
12253 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12255 (@value{GDBP}) @b{trace *0x2117c4} // an address
12259 You can abbreviate @code{trace} as @code{tr}.
12261 @item trace @var{location} if @var{cond}
12262 Set a tracepoint with condition @var{cond}; evaluate the expression
12263 @var{cond} each time the tracepoint is reached, and collect data only
12264 if the value is nonzero---that is, if @var{cond} evaluates as true.
12265 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12266 information on tracepoint conditions.
12268 @item ftrace @var{location} [ if @var{cond} ]
12269 @cindex set fast tracepoint
12270 @cindex fast tracepoints, setting
12272 The @code{ftrace} command sets a fast tracepoint. For targets that
12273 support them, fast tracepoints will use a more efficient but possibly
12274 less general technique to trigger data collection, such as a jump
12275 instruction instead of a trap, or some sort of hardware support. It
12276 may not be possible to create a fast tracepoint at the desired
12277 location, in which case the command will exit with an explanatory
12280 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12283 On 32-bit x86-architecture systems, fast tracepoints normally need to
12284 be placed at an instruction that is 5 bytes or longer, but can be
12285 placed at 4-byte instructions if the low 64K of memory of the target
12286 program is available to install trampolines. Some Unix-type systems,
12287 such as @sc{gnu}/Linux, exclude low addresses from the program's
12288 address space; but for instance with the Linux kernel it is possible
12289 to let @value{GDBN} use this area by doing a @command{sysctl} command
12290 to set the @code{mmap_min_addr} kernel parameter, as in
12293 sudo sysctl -w vm.mmap_min_addr=32768
12297 which sets the low address to 32K, which leaves plenty of room for
12298 trampolines. The minimum address should be set to a page boundary.
12300 @item strace @var{location} [ if @var{cond} ]
12301 @cindex set static tracepoint
12302 @cindex static tracepoints, setting
12303 @cindex probe static tracepoint marker
12305 The @code{strace} command sets a static tracepoint. For targets that
12306 support it, setting a static tracepoint probes a static
12307 instrumentation point, or marker, found at @var{location}. It may not
12308 be possible to set a static tracepoint at the desired location, in
12309 which case the command will exit with an explanatory message.
12311 @value{GDBN} handles arguments to @code{strace} exactly as for
12312 @code{trace}, with the addition that the user can also specify
12313 @code{-m @var{marker}} as @var{location}. This probes the marker
12314 identified by the @var{marker} string identifier. This identifier
12315 depends on the static tracepoint backend library your program is
12316 using. You can find all the marker identifiers in the @samp{ID} field
12317 of the @code{info static-tracepoint-markers} command output.
12318 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12319 Markers}. For example, in the following small program using the UST
12325 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12330 the marker id is composed of joining the first two arguments to the
12331 @code{trace_mark} call with a slash, which translates to:
12334 (@value{GDBP}) info static-tracepoint-markers
12335 Cnt Enb ID Address What
12336 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12342 so you may probe the marker above with:
12345 (@value{GDBP}) strace -m ust/bar33
12348 Static tracepoints accept an extra collect action --- @code{collect
12349 $_sdata}. This collects arbitrary user data passed in the probe point
12350 call to the tracing library. In the UST example above, you'll see
12351 that the third argument to @code{trace_mark} is a printf-like format
12352 string. The user data is then the result of running that formating
12353 string against the following arguments. Note that @code{info
12354 static-tracepoint-markers} command output lists that format string in
12355 the @samp{Data:} field.
12357 You can inspect this data when analyzing the trace buffer, by printing
12358 the $_sdata variable like any other variable available to
12359 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12362 @cindex last tracepoint number
12363 @cindex recent tracepoint number
12364 @cindex tracepoint number
12365 The convenience variable @code{$tpnum} records the tracepoint number
12366 of the most recently set tracepoint.
12368 @kindex delete tracepoint
12369 @cindex tracepoint deletion
12370 @item delete tracepoint @r{[}@var{num}@r{]}
12371 Permanently delete one or more tracepoints. With no argument, the
12372 default is to delete all tracepoints. Note that the regular
12373 @code{delete} command can remove tracepoints also.
12378 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12380 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12384 You can abbreviate this command as @code{del tr}.
12387 @node Enable and Disable Tracepoints
12388 @subsection Enable and Disable Tracepoints
12390 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12393 @kindex disable tracepoint
12394 @item disable tracepoint @r{[}@var{num}@r{]}
12395 Disable tracepoint @var{num}, or all tracepoints if no argument
12396 @var{num} is given. A disabled tracepoint will have no effect during
12397 a trace experiment, but it is not forgotten. You can re-enable
12398 a disabled tracepoint using the @code{enable tracepoint} command.
12399 If the command is issued during a trace experiment and the debug target
12400 has support for disabling tracepoints during a trace experiment, then the
12401 change will be effective immediately. Otherwise, it will be applied to the
12402 next trace experiment.
12404 @kindex enable tracepoint
12405 @item enable tracepoint @r{[}@var{num}@r{]}
12406 Enable tracepoint @var{num}, or all tracepoints. If this command is
12407 issued during a trace experiment and the debug target supports enabling
12408 tracepoints during a trace experiment, then the enabled tracepoints will
12409 become effective immediately. Otherwise, they will become effective the
12410 next time a trace experiment is run.
12413 @node Tracepoint Passcounts
12414 @subsection Tracepoint Passcounts
12418 @cindex tracepoint pass count
12419 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12420 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12421 automatically stop a trace experiment. If a tracepoint's passcount is
12422 @var{n}, then the trace experiment will be automatically stopped on
12423 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12424 @var{num} is not specified, the @code{passcount} command sets the
12425 passcount of the most recently defined tracepoint. If no passcount is
12426 given, the trace experiment will run until stopped explicitly by the
12432 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12433 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12435 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12436 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12437 (@value{GDBP}) @b{trace foo}
12438 (@value{GDBP}) @b{pass 3}
12439 (@value{GDBP}) @b{trace bar}
12440 (@value{GDBP}) @b{pass 2}
12441 (@value{GDBP}) @b{trace baz}
12442 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12443 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12444 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12445 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12449 @node Tracepoint Conditions
12450 @subsection Tracepoint Conditions
12451 @cindex conditional tracepoints
12452 @cindex tracepoint conditions
12454 The simplest sort of tracepoint collects data every time your program
12455 reaches a specified place. You can also specify a @dfn{condition} for
12456 a tracepoint. A condition is just a Boolean expression in your
12457 programming language (@pxref{Expressions, ,Expressions}). A
12458 tracepoint with a condition evaluates the expression each time your
12459 program reaches it, and data collection happens only if the condition
12462 Tracepoint conditions can be specified when a tracepoint is set, by
12463 using @samp{if} in the arguments to the @code{trace} command.
12464 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12465 also be set or changed at any time with the @code{condition} command,
12466 just as with breakpoints.
12468 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12469 the conditional expression itself. Instead, @value{GDBN} encodes the
12470 expression into an agent expression (@pxref{Agent Expressions})
12471 suitable for execution on the target, independently of @value{GDBN}.
12472 Global variables become raw memory locations, locals become stack
12473 accesses, and so forth.
12475 For instance, suppose you have a function that is usually called
12476 frequently, but should not be called after an error has occurred. You
12477 could use the following tracepoint command to collect data about calls
12478 of that function that happen while the error code is propagating
12479 through the program; an unconditional tracepoint could end up
12480 collecting thousands of useless trace frames that you would have to
12484 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12487 @node Trace State Variables
12488 @subsection Trace State Variables
12489 @cindex trace state variables
12491 A @dfn{trace state variable} is a special type of variable that is
12492 created and managed by target-side code. The syntax is the same as
12493 that for GDB's convenience variables (a string prefixed with ``$''),
12494 but they are stored on the target. They must be created explicitly,
12495 using a @code{tvariable} command. They are always 64-bit signed
12498 Trace state variables are remembered by @value{GDBN}, and downloaded
12499 to the target along with tracepoint information when the trace
12500 experiment starts. There are no intrinsic limits on the number of
12501 trace state variables, beyond memory limitations of the target.
12503 @cindex convenience variables, and trace state variables
12504 Although trace state variables are managed by the target, you can use
12505 them in print commands and expressions as if they were convenience
12506 variables; @value{GDBN} will get the current value from the target
12507 while the trace experiment is running. Trace state variables share
12508 the same namespace as other ``$'' variables, which means that you
12509 cannot have trace state variables with names like @code{$23} or
12510 @code{$pc}, nor can you have a trace state variable and a convenience
12511 variable with the same name.
12515 @item tvariable $@var{name} [ = @var{expression} ]
12517 The @code{tvariable} command creates a new trace state variable named
12518 @code{$@var{name}}, and optionally gives it an initial value of
12519 @var{expression}. The @var{expression} is evaluated when this command is
12520 entered; the result will be converted to an integer if possible,
12521 otherwise @value{GDBN} will report an error. A subsequent
12522 @code{tvariable} command specifying the same name does not create a
12523 variable, but instead assigns the supplied initial value to the
12524 existing variable of that name, overwriting any previous initial
12525 value. The default initial value is 0.
12527 @item info tvariables
12528 @kindex info tvariables
12529 List all the trace state variables along with their initial values.
12530 Their current values may also be displayed, if the trace experiment is
12533 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12534 @kindex delete tvariable
12535 Delete the given trace state variables, or all of them if no arguments
12540 @node Tracepoint Actions
12541 @subsection Tracepoint Action Lists
12545 @cindex tracepoint actions
12546 @item actions @r{[}@var{num}@r{]}
12547 This command will prompt for a list of actions to be taken when the
12548 tracepoint is hit. If the tracepoint number @var{num} is not
12549 specified, this command sets the actions for the one that was most
12550 recently defined (so that you can define a tracepoint and then say
12551 @code{actions} without bothering about its number). You specify the
12552 actions themselves on the following lines, one action at a time, and
12553 terminate the actions list with a line containing just @code{end}. So
12554 far, the only defined actions are @code{collect}, @code{teval}, and
12555 @code{while-stepping}.
12557 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12558 Commands, ,Breakpoint Command Lists}), except that only the defined
12559 actions are allowed; any other @value{GDBN} command is rejected.
12561 @cindex remove actions from a tracepoint
12562 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12563 and follow it immediately with @samp{end}.
12566 (@value{GDBP}) @b{collect @var{data}} // collect some data
12568 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12570 (@value{GDBP}) @b{end} // signals the end of actions.
12573 In the following example, the action list begins with @code{collect}
12574 commands indicating the things to be collected when the tracepoint is
12575 hit. Then, in order to single-step and collect additional data
12576 following the tracepoint, a @code{while-stepping} command is used,
12577 followed by the list of things to be collected after each step in a
12578 sequence of single steps. The @code{while-stepping} command is
12579 terminated by its own separate @code{end} command. Lastly, the action
12580 list is terminated by an @code{end} command.
12583 (@value{GDBP}) @b{trace foo}
12584 (@value{GDBP}) @b{actions}
12585 Enter actions for tracepoint 1, one per line:
12588 > while-stepping 12
12589 > collect $pc, arr[i]
12594 @kindex collect @r{(tracepoints)}
12595 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12596 Collect values of the given expressions when the tracepoint is hit.
12597 This command accepts a comma-separated list of any valid expressions.
12598 In addition to global, static, or local variables, the following
12599 special arguments are supported:
12603 Collect all registers.
12606 Collect all function arguments.
12609 Collect all local variables.
12612 Collect the return address. This is helpful if you want to see more
12616 Collects the number of arguments from the static probe at which the
12617 tracepoint is located.
12618 @xref{Static Probe Points}.
12620 @item $_probe_arg@var{n}
12621 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12622 from the static probe at which the tracepoint is located.
12623 @xref{Static Probe Points}.
12626 @vindex $_sdata@r{, collect}
12627 Collect static tracepoint marker specific data. Only available for
12628 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12629 Lists}. On the UST static tracepoints library backend, an
12630 instrumentation point resembles a @code{printf} function call. The
12631 tracing library is able to collect user specified data formatted to a
12632 character string using the format provided by the programmer that
12633 instrumented the program. Other backends have similar mechanisms.
12634 Here's an example of a UST marker call:
12637 const char master_name[] = "$your_name";
12638 trace_mark(channel1, marker1, "hello %s", master_name)
12641 In this case, collecting @code{$_sdata} collects the string
12642 @samp{hello $yourname}. When analyzing the trace buffer, you can
12643 inspect @samp{$_sdata} like any other variable available to
12647 You can give several consecutive @code{collect} commands, each one
12648 with a single argument, or one @code{collect} command with several
12649 arguments separated by commas; the effect is the same.
12651 The optional @var{mods} changes the usual handling of the arguments.
12652 @code{s} requests that pointers to chars be handled as strings, in
12653 particular collecting the contents of the memory being pointed at, up
12654 to the first zero. The upper bound is by default the value of the
12655 @code{print elements} variable; if @code{s} is followed by a decimal
12656 number, that is the upper bound instead. So for instance
12657 @samp{collect/s25 mystr} collects as many as 25 characters at
12660 The command @code{info scope} (@pxref{Symbols, info scope}) is
12661 particularly useful for figuring out what data to collect.
12663 @kindex teval @r{(tracepoints)}
12664 @item teval @var{expr1}, @var{expr2}, @dots{}
12665 Evaluate the given expressions when the tracepoint is hit. This
12666 command accepts a comma-separated list of expressions. The results
12667 are discarded, so this is mainly useful for assigning values to trace
12668 state variables (@pxref{Trace State Variables}) without adding those
12669 values to the trace buffer, as would be the case if the @code{collect}
12672 @kindex while-stepping @r{(tracepoints)}
12673 @item while-stepping @var{n}
12674 Perform @var{n} single-step instruction traces after the tracepoint,
12675 collecting new data after each step. The @code{while-stepping}
12676 command is followed by the list of what to collect while stepping
12677 (followed by its own @code{end} command):
12680 > while-stepping 12
12681 > collect $regs, myglobal
12687 Note that @code{$pc} is not automatically collected by
12688 @code{while-stepping}; you need to explicitly collect that register if
12689 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12692 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12693 @kindex set default-collect
12694 @cindex default collection action
12695 This variable is a list of expressions to collect at each tracepoint
12696 hit. It is effectively an additional @code{collect} action prepended
12697 to every tracepoint action list. The expressions are parsed
12698 individually for each tracepoint, so for instance a variable named
12699 @code{xyz} may be interpreted as a global for one tracepoint, and a
12700 local for another, as appropriate to the tracepoint's location.
12702 @item show default-collect
12703 @kindex show default-collect
12704 Show the list of expressions that are collected by default at each
12709 @node Listing Tracepoints
12710 @subsection Listing Tracepoints
12713 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12714 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12715 @cindex information about tracepoints
12716 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12717 Display information about the tracepoint @var{num}. If you don't
12718 specify a tracepoint number, displays information about all the
12719 tracepoints defined so far. The format is similar to that used for
12720 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12721 command, simply restricting itself to tracepoints.
12723 A tracepoint's listing may include additional information specific to
12728 its passcount as given by the @code{passcount @var{n}} command
12731 the state about installed on target of each location
12735 (@value{GDBP}) @b{info trace}
12736 Num Type Disp Enb Address What
12737 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12739 collect globfoo, $regs
12744 2 tracepoint keep y <MULTIPLE>
12746 2.1 y 0x0804859c in func4 at change-loc.h:35
12747 installed on target
12748 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12749 installed on target
12750 2.3 y <PENDING> set_tracepoint
12751 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12752 not installed on target
12757 This command can be abbreviated @code{info tp}.
12760 @node Listing Static Tracepoint Markers
12761 @subsection Listing Static Tracepoint Markers
12764 @kindex info static-tracepoint-markers
12765 @cindex information about static tracepoint markers
12766 @item info static-tracepoint-markers
12767 Display information about all static tracepoint markers defined in the
12770 For each marker, the following columns are printed:
12774 An incrementing counter, output to help readability. This is not a
12777 The marker ID, as reported by the target.
12778 @item Enabled or Disabled
12779 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12780 that are not enabled.
12782 Where the marker is in your program, as a memory address.
12784 Where the marker is in the source for your program, as a file and line
12785 number. If the debug information included in the program does not
12786 allow @value{GDBN} to locate the source of the marker, this column
12787 will be left blank.
12791 In addition, the following information may be printed for each marker:
12795 User data passed to the tracing library by the marker call. In the
12796 UST backend, this is the format string passed as argument to the
12798 @item Static tracepoints probing the marker
12799 The list of static tracepoints attached to the marker.
12803 (@value{GDBP}) info static-tracepoint-markers
12804 Cnt ID Enb Address What
12805 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12806 Data: number1 %d number2 %d
12807 Probed by static tracepoints: #2
12808 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12814 @node Starting and Stopping Trace Experiments
12815 @subsection Starting and Stopping Trace Experiments
12818 @kindex tstart [ @var{notes} ]
12819 @cindex start a new trace experiment
12820 @cindex collected data discarded
12822 This command starts the trace experiment, and begins collecting data.
12823 It has the side effect of discarding all the data collected in the
12824 trace buffer during the previous trace experiment. If any arguments
12825 are supplied, they are taken as a note and stored with the trace
12826 experiment's state. The notes may be arbitrary text, and are
12827 especially useful with disconnected tracing in a multi-user context;
12828 the notes can explain what the trace is doing, supply user contact
12829 information, and so forth.
12831 @kindex tstop [ @var{notes} ]
12832 @cindex stop a running trace experiment
12834 This command stops the trace experiment. If any arguments are
12835 supplied, they are recorded with the experiment as a note. This is
12836 useful if you are stopping a trace started by someone else, for
12837 instance if the trace is interfering with the system's behavior and
12838 needs to be stopped quickly.
12840 @strong{Note}: a trace experiment and data collection may stop
12841 automatically if any tracepoint's passcount is reached
12842 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12845 @cindex status of trace data collection
12846 @cindex trace experiment, status of
12848 This command displays the status of the current trace data
12852 Here is an example of the commands we described so far:
12855 (@value{GDBP}) @b{trace gdb_c_test}
12856 (@value{GDBP}) @b{actions}
12857 Enter actions for tracepoint #1, one per line.
12858 > collect $regs,$locals,$args
12859 > while-stepping 11
12863 (@value{GDBP}) @b{tstart}
12864 [time passes @dots{}]
12865 (@value{GDBP}) @b{tstop}
12868 @anchor{disconnected tracing}
12869 @cindex disconnected tracing
12870 You can choose to continue running the trace experiment even if
12871 @value{GDBN} disconnects from the target, voluntarily or
12872 involuntarily. For commands such as @code{detach}, the debugger will
12873 ask what you want to do with the trace. But for unexpected
12874 terminations (@value{GDBN} crash, network outage), it would be
12875 unfortunate to lose hard-won trace data, so the variable
12876 @code{disconnected-tracing} lets you decide whether the trace should
12877 continue running without @value{GDBN}.
12880 @item set disconnected-tracing on
12881 @itemx set disconnected-tracing off
12882 @kindex set disconnected-tracing
12883 Choose whether a tracing run should continue to run if @value{GDBN}
12884 has disconnected from the target. Note that @code{detach} or
12885 @code{quit} will ask you directly what to do about a running trace no
12886 matter what this variable's setting, so the variable is mainly useful
12887 for handling unexpected situations, such as loss of the network.
12889 @item show disconnected-tracing
12890 @kindex show disconnected-tracing
12891 Show the current choice for disconnected tracing.
12895 When you reconnect to the target, the trace experiment may or may not
12896 still be running; it might have filled the trace buffer in the
12897 meantime, or stopped for one of the other reasons. If it is running,
12898 it will continue after reconnection.
12900 Upon reconnection, the target will upload information about the
12901 tracepoints in effect. @value{GDBN} will then compare that
12902 information to the set of tracepoints currently defined, and attempt
12903 to match them up, allowing for the possibility that the numbers may
12904 have changed due to creation and deletion in the meantime. If one of
12905 the target's tracepoints does not match any in @value{GDBN}, the
12906 debugger will create a new tracepoint, so that you have a number with
12907 which to specify that tracepoint. This matching-up process is
12908 necessarily heuristic, and it may result in useless tracepoints being
12909 created; you may simply delete them if they are of no use.
12911 @cindex circular trace buffer
12912 If your target agent supports a @dfn{circular trace buffer}, then you
12913 can run a trace experiment indefinitely without filling the trace
12914 buffer; when space runs out, the agent deletes already-collected trace
12915 frames, oldest first, until there is enough room to continue
12916 collecting. This is especially useful if your tracepoints are being
12917 hit too often, and your trace gets terminated prematurely because the
12918 buffer is full. To ask for a circular trace buffer, simply set
12919 @samp{circular-trace-buffer} to on. You can set this at any time,
12920 including during tracing; if the agent can do it, it will change
12921 buffer handling on the fly, otherwise it will not take effect until
12925 @item set circular-trace-buffer on
12926 @itemx set circular-trace-buffer off
12927 @kindex set circular-trace-buffer
12928 Choose whether a tracing run should use a linear or circular buffer
12929 for trace data. A linear buffer will not lose any trace data, but may
12930 fill up prematurely, while a circular buffer will discard old trace
12931 data, but it will have always room for the latest tracepoint hits.
12933 @item show circular-trace-buffer
12934 @kindex show circular-trace-buffer
12935 Show the current choice for the trace buffer. Note that this may not
12936 match the agent's current buffer handling, nor is it guaranteed to
12937 match the setting that might have been in effect during a past run,
12938 for instance if you are looking at frames from a trace file.
12943 @item set trace-buffer-size @var{n}
12944 @itemx set trace-buffer-size unlimited
12945 @kindex set trace-buffer-size
12946 Request that the target use a trace buffer of @var{n} bytes. Not all
12947 targets will honor the request; they may have a compiled-in size for
12948 the trace buffer, or some other limitation. Set to a value of
12949 @code{unlimited} or @code{-1} to let the target use whatever size it
12950 likes. This is also the default.
12952 @item show trace-buffer-size
12953 @kindex show trace-buffer-size
12954 Show the current requested size for the trace buffer. Note that this
12955 will only match the actual size if the target supports size-setting,
12956 and was able to handle the requested size. For instance, if the
12957 target can only change buffer size between runs, this variable will
12958 not reflect the change until the next run starts. Use @code{tstatus}
12959 to get a report of the actual buffer size.
12963 @item set trace-user @var{text}
12964 @kindex set trace-user
12966 @item show trace-user
12967 @kindex show trace-user
12969 @item set trace-notes @var{text}
12970 @kindex set trace-notes
12971 Set the trace run's notes.
12973 @item show trace-notes
12974 @kindex show trace-notes
12975 Show the trace run's notes.
12977 @item set trace-stop-notes @var{text}
12978 @kindex set trace-stop-notes
12979 Set the trace run's stop notes. The handling of the note is as for
12980 @code{tstop} arguments; the set command is convenient way to fix a
12981 stop note that is mistaken or incomplete.
12983 @item show trace-stop-notes
12984 @kindex show trace-stop-notes
12985 Show the trace run's stop notes.
12989 @node Tracepoint Restrictions
12990 @subsection Tracepoint Restrictions
12992 @cindex tracepoint restrictions
12993 There are a number of restrictions on the use of tracepoints. As
12994 described above, tracepoint data gathering occurs on the target
12995 without interaction from @value{GDBN}. Thus the full capabilities of
12996 the debugger are not available during data gathering, and then at data
12997 examination time, you will be limited by only having what was
12998 collected. The following items describe some common problems, but it
12999 is not exhaustive, and you may run into additional difficulties not
13005 Tracepoint expressions are intended to gather objects (lvalues). Thus
13006 the full flexibility of GDB's expression evaluator is not available.
13007 You cannot call functions, cast objects to aggregate types, access
13008 convenience variables or modify values (except by assignment to trace
13009 state variables). Some language features may implicitly call
13010 functions (for instance Objective-C fields with accessors), and therefore
13011 cannot be collected either.
13014 Collection of local variables, either individually or in bulk with
13015 @code{$locals} or @code{$args}, during @code{while-stepping} may
13016 behave erratically. The stepping action may enter a new scope (for
13017 instance by stepping into a function), or the location of the variable
13018 may change (for instance it is loaded into a register). The
13019 tracepoint data recorded uses the location information for the
13020 variables that is correct for the tracepoint location. When the
13021 tracepoint is created, it is not possible, in general, to determine
13022 where the steps of a @code{while-stepping} sequence will advance the
13023 program---particularly if a conditional branch is stepped.
13026 Collection of an incompletely-initialized or partially-destroyed object
13027 may result in something that @value{GDBN} cannot display, or displays
13028 in a misleading way.
13031 When @value{GDBN} displays a pointer to character it automatically
13032 dereferences the pointer to also display characters of the string
13033 being pointed to. However, collecting the pointer during tracing does
13034 not automatically collect the string. You need to explicitly
13035 dereference the pointer and provide size information if you want to
13036 collect not only the pointer, but the memory pointed to. For example,
13037 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13041 It is not possible to collect a complete stack backtrace at a
13042 tracepoint. Instead, you may collect the registers and a few hundred
13043 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13044 (adjust to use the name of the actual stack pointer register on your
13045 target architecture, and the amount of stack you wish to capture).
13046 Then the @code{backtrace} command will show a partial backtrace when
13047 using a trace frame. The number of stack frames that can be examined
13048 depends on the sizes of the frames in the collected stack. Note that
13049 if you ask for a block so large that it goes past the bottom of the
13050 stack, the target agent may report an error trying to read from an
13054 If you do not collect registers at a tracepoint, @value{GDBN} can
13055 infer that the value of @code{$pc} must be the same as the address of
13056 the tracepoint and use that when you are looking at a trace frame
13057 for that tracepoint. However, this cannot work if the tracepoint has
13058 multiple locations (for instance if it was set in a function that was
13059 inlined), or if it has a @code{while-stepping} loop. In those cases
13060 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13065 @node Analyze Collected Data
13066 @section Using the Collected Data
13068 After the tracepoint experiment ends, you use @value{GDBN} commands
13069 for examining the trace data. The basic idea is that each tracepoint
13070 collects a trace @dfn{snapshot} every time it is hit and another
13071 snapshot every time it single-steps. All these snapshots are
13072 consecutively numbered from zero and go into a buffer, and you can
13073 examine them later. The way you examine them is to @dfn{focus} on a
13074 specific trace snapshot. When the remote stub is focused on a trace
13075 snapshot, it will respond to all @value{GDBN} requests for memory and
13076 registers by reading from the buffer which belongs to that snapshot,
13077 rather than from @emph{real} memory or registers of the program being
13078 debugged. This means that @strong{all} @value{GDBN} commands
13079 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13080 behave as if we were currently debugging the program state as it was
13081 when the tracepoint occurred. Any requests for data that are not in
13082 the buffer will fail.
13085 * tfind:: How to select a trace snapshot
13086 * tdump:: How to display all data for a snapshot
13087 * save tracepoints:: How to save tracepoints for a future run
13091 @subsection @code{tfind @var{n}}
13094 @cindex select trace snapshot
13095 @cindex find trace snapshot
13096 The basic command for selecting a trace snapshot from the buffer is
13097 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13098 counting from zero. If no argument @var{n} is given, the next
13099 snapshot is selected.
13101 Here are the various forms of using the @code{tfind} command.
13105 Find the first snapshot in the buffer. This is a synonym for
13106 @code{tfind 0} (since 0 is the number of the first snapshot).
13109 Stop debugging trace snapshots, resume @emph{live} debugging.
13112 Same as @samp{tfind none}.
13115 No argument means find the next trace snapshot.
13118 Find the previous trace snapshot before the current one. This permits
13119 retracing earlier steps.
13121 @item tfind tracepoint @var{num}
13122 Find the next snapshot associated with tracepoint @var{num}. Search
13123 proceeds forward from the last examined trace snapshot. If no
13124 argument @var{num} is given, it means find the next snapshot collected
13125 for the same tracepoint as the current snapshot.
13127 @item tfind pc @var{addr}
13128 Find the next snapshot associated with the value @var{addr} of the
13129 program counter. Search proceeds forward from the last examined trace
13130 snapshot. If no argument @var{addr} is given, it means find the next
13131 snapshot with the same value of PC as the current snapshot.
13133 @item tfind outside @var{addr1}, @var{addr2}
13134 Find the next snapshot whose PC is outside the given range of
13135 addresses (exclusive).
13137 @item tfind range @var{addr1}, @var{addr2}
13138 Find the next snapshot whose PC is between @var{addr1} and
13139 @var{addr2} (inclusive).
13141 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13142 Find the next snapshot associated with the source line @var{n}. If
13143 the optional argument @var{file} is given, refer to line @var{n} in
13144 that source file. Search proceeds forward from the last examined
13145 trace snapshot. If no argument @var{n} is given, it means find the
13146 next line other than the one currently being examined; thus saying
13147 @code{tfind line} repeatedly can appear to have the same effect as
13148 stepping from line to line in a @emph{live} debugging session.
13151 The default arguments for the @code{tfind} commands are specifically
13152 designed to make it easy to scan through the trace buffer. For
13153 instance, @code{tfind} with no argument selects the next trace
13154 snapshot, and @code{tfind -} with no argument selects the previous
13155 trace snapshot. So, by giving one @code{tfind} command, and then
13156 simply hitting @key{RET} repeatedly you can examine all the trace
13157 snapshots in order. Or, by saying @code{tfind -} and then hitting
13158 @key{RET} repeatedly you can examine the snapshots in reverse order.
13159 The @code{tfind line} command with no argument selects the snapshot
13160 for the next source line executed. The @code{tfind pc} command with
13161 no argument selects the next snapshot with the same program counter
13162 (PC) as the current frame. The @code{tfind tracepoint} command with
13163 no argument selects the next trace snapshot collected by the same
13164 tracepoint as the current one.
13166 In addition to letting you scan through the trace buffer manually,
13167 these commands make it easy to construct @value{GDBN} scripts that
13168 scan through the trace buffer and print out whatever collected data
13169 you are interested in. Thus, if we want to examine the PC, FP, and SP
13170 registers from each trace frame in the buffer, we can say this:
13173 (@value{GDBP}) @b{tfind start}
13174 (@value{GDBP}) @b{while ($trace_frame != -1)}
13175 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13176 $trace_frame, $pc, $sp, $fp
13180 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13181 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13182 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13183 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13184 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13185 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13186 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13187 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13188 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13189 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13190 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13193 Or, if we want to examine the variable @code{X} at each source line in
13197 (@value{GDBP}) @b{tfind start}
13198 (@value{GDBP}) @b{while ($trace_frame != -1)}
13199 > printf "Frame %d, X == %d\n", $trace_frame, X
13209 @subsection @code{tdump}
13211 @cindex dump all data collected at tracepoint
13212 @cindex tracepoint data, display
13214 This command takes no arguments. It prints all the data collected at
13215 the current trace snapshot.
13218 (@value{GDBP}) @b{trace 444}
13219 (@value{GDBP}) @b{actions}
13220 Enter actions for tracepoint #2, one per line:
13221 > collect $regs, $locals, $args, gdb_long_test
13224 (@value{GDBP}) @b{tstart}
13226 (@value{GDBP}) @b{tfind line 444}
13227 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13229 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13231 (@value{GDBP}) @b{tdump}
13232 Data collected at tracepoint 2, trace frame 1:
13233 d0 0xc4aa0085 -995491707
13237 d4 0x71aea3d 119204413
13240 d7 0x380035 3670069
13241 a0 0x19e24a 1696330
13242 a1 0x3000668 50333288
13244 a3 0x322000 3284992
13245 a4 0x3000698 50333336
13246 a5 0x1ad3cc 1758156
13247 fp 0x30bf3c 0x30bf3c
13248 sp 0x30bf34 0x30bf34
13250 pc 0x20b2c8 0x20b2c8
13254 p = 0x20e5b4 "gdb-test"
13261 gdb_long_test = 17 '\021'
13266 @code{tdump} works by scanning the tracepoint's current collection
13267 actions and printing the value of each expression listed. So
13268 @code{tdump} can fail, if after a run, you change the tracepoint's
13269 actions to mention variables that were not collected during the run.
13271 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13272 uses the collected value of @code{$pc} to distinguish between trace
13273 frames that were collected at the tracepoint hit, and frames that were
13274 collected while stepping. This allows it to correctly choose whether
13275 to display the basic list of collections, or the collections from the
13276 body of the while-stepping loop. However, if @code{$pc} was not collected,
13277 then @code{tdump} will always attempt to dump using the basic collection
13278 list, and may fail if a while-stepping frame does not include all the
13279 same data that is collected at the tracepoint hit.
13280 @c This is getting pretty arcane, example would be good.
13282 @node save tracepoints
13283 @subsection @code{save tracepoints @var{filename}}
13284 @kindex save tracepoints
13285 @kindex save-tracepoints
13286 @cindex save tracepoints for future sessions
13288 This command saves all current tracepoint definitions together with
13289 their actions and passcounts, into a file @file{@var{filename}}
13290 suitable for use in a later debugging session. To read the saved
13291 tracepoint definitions, use the @code{source} command (@pxref{Command
13292 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13293 alias for @w{@code{save tracepoints}}
13295 @node Tracepoint Variables
13296 @section Convenience Variables for Tracepoints
13297 @cindex tracepoint variables
13298 @cindex convenience variables for tracepoints
13301 @vindex $trace_frame
13302 @item (int) $trace_frame
13303 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13304 snapshot is selected.
13306 @vindex $tracepoint
13307 @item (int) $tracepoint
13308 The tracepoint for the current trace snapshot.
13310 @vindex $trace_line
13311 @item (int) $trace_line
13312 The line number for the current trace snapshot.
13314 @vindex $trace_file
13315 @item (char []) $trace_file
13316 The source file for the current trace snapshot.
13318 @vindex $trace_func
13319 @item (char []) $trace_func
13320 The name of the function containing @code{$tracepoint}.
13323 Note: @code{$trace_file} is not suitable for use in @code{printf},
13324 use @code{output} instead.
13326 Here's a simple example of using these convenience variables for
13327 stepping through all the trace snapshots and printing some of their
13328 data. Note that these are not the same as trace state variables,
13329 which are managed by the target.
13332 (@value{GDBP}) @b{tfind start}
13334 (@value{GDBP}) @b{while $trace_frame != -1}
13335 > output $trace_file
13336 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13342 @section Using Trace Files
13343 @cindex trace files
13345 In some situations, the target running a trace experiment may no
13346 longer be available; perhaps it crashed, or the hardware was needed
13347 for a different activity. To handle these cases, you can arrange to
13348 dump the trace data into a file, and later use that file as a source
13349 of trace data, via the @code{target tfile} command.
13354 @item tsave [ -r ] @var{filename}
13355 @itemx tsave [-ctf] @var{dirname}
13356 Save the trace data to @var{filename}. By default, this command
13357 assumes that @var{filename} refers to the host filesystem, so if
13358 necessary @value{GDBN} will copy raw trace data up from the target and
13359 then save it. If the target supports it, you can also supply the
13360 optional argument @code{-r} (``remote'') to direct the target to save
13361 the data directly into @var{filename} in its own filesystem, which may be
13362 more efficient if the trace buffer is very large. (Note, however, that
13363 @code{target tfile} can only read from files accessible to the host.)
13364 By default, this command will save trace frame in tfile format.
13365 You can supply the optional argument @code{-ctf} to save date in CTF
13366 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13367 that can be shared by multiple debugging and tracing tools. Please go to
13368 @indicateurl{http://www.efficios.com/ctf} to get more information.
13370 @kindex target tfile
13374 @item target tfile @var{filename}
13375 @itemx target ctf @var{dirname}
13376 Use the file named @var{filename} or directory named @var{dirname} as
13377 a source of trace data. Commands that examine data work as they do with
13378 a live target, but it is not possible to run any new trace experiments.
13379 @code{tstatus} will report the state of the trace run at the moment
13380 the data was saved, as well as the current trace frame you are examining.
13381 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13385 (@value{GDBP}) target ctf ctf.ctf
13386 (@value{GDBP}) tfind
13387 Found trace frame 0, tracepoint 2
13388 39 ++a; /* set tracepoint 1 here */
13389 (@value{GDBP}) tdump
13390 Data collected at tracepoint 2, trace frame 0:
13394 c = @{"123", "456", "789", "123", "456", "789"@}
13395 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13403 @chapter Debugging Programs That Use Overlays
13406 If your program is too large to fit completely in your target system's
13407 memory, you can sometimes use @dfn{overlays} to work around this
13408 problem. @value{GDBN} provides some support for debugging programs that
13412 * How Overlays Work:: A general explanation of overlays.
13413 * Overlay Commands:: Managing overlays in @value{GDBN}.
13414 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13415 mapped by asking the inferior.
13416 * Overlay Sample Program:: A sample program using overlays.
13419 @node How Overlays Work
13420 @section How Overlays Work
13421 @cindex mapped overlays
13422 @cindex unmapped overlays
13423 @cindex load address, overlay's
13424 @cindex mapped address
13425 @cindex overlay area
13427 Suppose you have a computer whose instruction address space is only 64
13428 kilobytes long, but which has much more memory which can be accessed by
13429 other means: special instructions, segment registers, or memory
13430 management hardware, for example. Suppose further that you want to
13431 adapt a program which is larger than 64 kilobytes to run on this system.
13433 One solution is to identify modules of your program which are relatively
13434 independent, and need not call each other directly; call these modules
13435 @dfn{overlays}. Separate the overlays from the main program, and place
13436 their machine code in the larger memory. Place your main program in
13437 instruction memory, but leave at least enough space there to hold the
13438 largest overlay as well.
13440 Now, to call a function located in an overlay, you must first copy that
13441 overlay's machine code from the large memory into the space set aside
13442 for it in the instruction memory, and then jump to its entry point
13445 @c NB: In the below the mapped area's size is greater or equal to the
13446 @c size of all overlays. This is intentional to remind the developer
13447 @c that overlays don't necessarily need to be the same size.
13451 Data Instruction Larger
13452 Address Space Address Space Address Space
13453 +-----------+ +-----------+ +-----------+
13455 +-----------+ +-----------+ +-----------+<-- overlay 1
13456 | program | | main | .----| overlay 1 | load address
13457 | variables | | program | | +-----------+
13458 | and heap | | | | | |
13459 +-----------+ | | | +-----------+<-- overlay 2
13460 | | +-----------+ | | | load address
13461 +-----------+ | | | .-| overlay 2 |
13463 mapped --->+-----------+ | | +-----------+
13464 address | | | | | |
13465 | overlay | <-' | | |
13466 | area | <---' +-----------+<-- overlay 3
13467 | | <---. | | load address
13468 +-----------+ `--| overlay 3 |
13475 @anchor{A code overlay}A code overlay
13479 The diagram (@pxref{A code overlay}) shows a system with separate data
13480 and instruction address spaces. To map an overlay, the program copies
13481 its code from the larger address space to the instruction address space.
13482 Since the overlays shown here all use the same mapped address, only one
13483 may be mapped at a time. For a system with a single address space for
13484 data and instructions, the diagram would be similar, except that the
13485 program variables and heap would share an address space with the main
13486 program and the overlay area.
13488 An overlay loaded into instruction memory and ready for use is called a
13489 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13490 instruction memory. An overlay not present (or only partially present)
13491 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13492 is its address in the larger memory. The mapped address is also called
13493 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13494 called the @dfn{load memory address}, or @dfn{LMA}.
13496 Unfortunately, overlays are not a completely transparent way to adapt a
13497 program to limited instruction memory. They introduce a new set of
13498 global constraints you must keep in mind as you design your program:
13503 Before calling or returning to a function in an overlay, your program
13504 must make sure that overlay is actually mapped. Otherwise, the call or
13505 return will transfer control to the right address, but in the wrong
13506 overlay, and your program will probably crash.
13509 If the process of mapping an overlay is expensive on your system, you
13510 will need to choose your overlays carefully to minimize their effect on
13511 your program's performance.
13514 The executable file you load onto your system must contain each
13515 overlay's instructions, appearing at the overlay's load address, not its
13516 mapped address. However, each overlay's instructions must be relocated
13517 and its symbols defined as if the overlay were at its mapped address.
13518 You can use GNU linker scripts to specify different load and relocation
13519 addresses for pieces of your program; see @ref{Overlay Description,,,
13520 ld.info, Using ld: the GNU linker}.
13523 The procedure for loading executable files onto your system must be able
13524 to load their contents into the larger address space as well as the
13525 instruction and data spaces.
13529 The overlay system described above is rather simple, and could be
13530 improved in many ways:
13535 If your system has suitable bank switch registers or memory management
13536 hardware, you could use those facilities to make an overlay's load area
13537 contents simply appear at their mapped address in instruction space.
13538 This would probably be faster than copying the overlay to its mapped
13539 area in the usual way.
13542 If your overlays are small enough, you could set aside more than one
13543 overlay area, and have more than one overlay mapped at a time.
13546 You can use overlays to manage data, as well as instructions. In
13547 general, data overlays are even less transparent to your design than
13548 code overlays: whereas code overlays only require care when you call or
13549 return to functions, data overlays require care every time you access
13550 the data. Also, if you change the contents of a data overlay, you
13551 must copy its contents back out to its load address before you can copy a
13552 different data overlay into the same mapped area.
13557 @node Overlay Commands
13558 @section Overlay Commands
13560 To use @value{GDBN}'s overlay support, each overlay in your program must
13561 correspond to a separate section of the executable file. The section's
13562 virtual memory address and load memory address must be the overlay's
13563 mapped and load addresses. Identifying overlays with sections allows
13564 @value{GDBN} to determine the appropriate address of a function or
13565 variable, depending on whether the overlay is mapped or not.
13567 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13568 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13573 Disable @value{GDBN}'s overlay support. When overlay support is
13574 disabled, @value{GDBN} assumes that all functions and variables are
13575 always present at their mapped addresses. By default, @value{GDBN}'s
13576 overlay support is disabled.
13578 @item overlay manual
13579 @cindex manual overlay debugging
13580 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13581 relies on you to tell it which overlays are mapped, and which are not,
13582 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13583 commands described below.
13585 @item overlay map-overlay @var{overlay}
13586 @itemx overlay map @var{overlay}
13587 @cindex map an overlay
13588 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13589 be the name of the object file section containing the overlay. When an
13590 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13591 functions and variables at their mapped addresses. @value{GDBN} assumes
13592 that any other overlays whose mapped ranges overlap that of
13593 @var{overlay} are now unmapped.
13595 @item overlay unmap-overlay @var{overlay}
13596 @itemx overlay unmap @var{overlay}
13597 @cindex unmap an overlay
13598 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13599 must be the name of the object file section containing the overlay.
13600 When an overlay is unmapped, @value{GDBN} assumes it can find the
13601 overlay's functions and variables at their load addresses.
13604 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13605 consults a data structure the overlay manager maintains in the inferior
13606 to see which overlays are mapped. For details, see @ref{Automatic
13607 Overlay Debugging}.
13609 @item overlay load-target
13610 @itemx overlay load
13611 @cindex reloading the overlay table
13612 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13613 re-reads the table @value{GDBN} automatically each time the inferior
13614 stops, so this command should only be necessary if you have changed the
13615 overlay mapping yourself using @value{GDBN}. This command is only
13616 useful when using automatic overlay debugging.
13618 @item overlay list-overlays
13619 @itemx overlay list
13620 @cindex listing mapped overlays
13621 Display a list of the overlays currently mapped, along with their mapped
13622 addresses, load addresses, and sizes.
13626 Normally, when @value{GDBN} prints a code address, it includes the name
13627 of the function the address falls in:
13630 (@value{GDBP}) print main
13631 $3 = @{int ()@} 0x11a0 <main>
13634 When overlay debugging is enabled, @value{GDBN} recognizes code in
13635 unmapped overlays, and prints the names of unmapped functions with
13636 asterisks around them. For example, if @code{foo} is a function in an
13637 unmapped overlay, @value{GDBN} prints it this way:
13640 (@value{GDBP}) overlay list
13641 No sections are mapped.
13642 (@value{GDBP}) print foo
13643 $5 = @{int (int)@} 0x100000 <*foo*>
13646 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13650 (@value{GDBP}) overlay list
13651 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13652 mapped at 0x1016 - 0x104a
13653 (@value{GDBP}) print foo
13654 $6 = @{int (int)@} 0x1016 <foo>
13657 When overlay debugging is enabled, @value{GDBN} can find the correct
13658 address for functions and variables in an overlay, whether or not the
13659 overlay is mapped. This allows most @value{GDBN} commands, like
13660 @code{break} and @code{disassemble}, to work normally, even on unmapped
13661 code. However, @value{GDBN}'s breakpoint support has some limitations:
13665 @cindex breakpoints in overlays
13666 @cindex overlays, setting breakpoints in
13667 You can set breakpoints in functions in unmapped overlays, as long as
13668 @value{GDBN} can write to the overlay at its load address.
13670 @value{GDBN} can not set hardware or simulator-based breakpoints in
13671 unmapped overlays. However, if you set a breakpoint at the end of your
13672 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13673 you are using manual overlay management), @value{GDBN} will re-set its
13674 breakpoints properly.
13678 @node Automatic Overlay Debugging
13679 @section Automatic Overlay Debugging
13680 @cindex automatic overlay debugging
13682 @value{GDBN} can automatically track which overlays are mapped and which
13683 are not, given some simple co-operation from the overlay manager in the
13684 inferior. If you enable automatic overlay debugging with the
13685 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13686 looks in the inferior's memory for certain variables describing the
13687 current state of the overlays.
13689 Here are the variables your overlay manager must define to support
13690 @value{GDBN}'s automatic overlay debugging:
13694 @item @code{_ovly_table}:
13695 This variable must be an array of the following structures:
13700 /* The overlay's mapped address. */
13703 /* The size of the overlay, in bytes. */
13704 unsigned long size;
13706 /* The overlay's load address. */
13709 /* Non-zero if the overlay is currently mapped;
13711 unsigned long mapped;
13715 @item @code{_novlys}:
13716 This variable must be a four-byte signed integer, holding the total
13717 number of elements in @code{_ovly_table}.
13721 To decide whether a particular overlay is mapped or not, @value{GDBN}
13722 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13723 @code{lma} members equal the VMA and LMA of the overlay's section in the
13724 executable file. When @value{GDBN} finds a matching entry, it consults
13725 the entry's @code{mapped} member to determine whether the overlay is
13728 In addition, your overlay manager may define a function called
13729 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13730 will silently set a breakpoint there. If the overlay manager then
13731 calls this function whenever it has changed the overlay table, this
13732 will enable @value{GDBN} to accurately keep track of which overlays
13733 are in program memory, and update any breakpoints that may be set
13734 in overlays. This will allow breakpoints to work even if the
13735 overlays are kept in ROM or other non-writable memory while they
13736 are not being executed.
13738 @node Overlay Sample Program
13739 @section Overlay Sample Program
13740 @cindex overlay example program
13742 When linking a program which uses overlays, you must place the overlays
13743 at their load addresses, while relocating them to run at their mapped
13744 addresses. To do this, you must write a linker script (@pxref{Overlay
13745 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13746 since linker scripts are specific to a particular host system, target
13747 architecture, and target memory layout, this manual cannot provide
13748 portable sample code demonstrating @value{GDBN}'s overlay support.
13750 However, the @value{GDBN} source distribution does contain an overlaid
13751 program, with linker scripts for a few systems, as part of its test
13752 suite. The program consists of the following files from
13753 @file{gdb/testsuite/gdb.base}:
13757 The main program file.
13759 A simple overlay manager, used by @file{overlays.c}.
13764 Overlay modules, loaded and used by @file{overlays.c}.
13767 Linker scripts for linking the test program on the @code{d10v-elf}
13768 and @code{m32r-elf} targets.
13771 You can build the test program using the @code{d10v-elf} GCC
13772 cross-compiler like this:
13775 $ d10v-elf-gcc -g -c overlays.c
13776 $ d10v-elf-gcc -g -c ovlymgr.c
13777 $ d10v-elf-gcc -g -c foo.c
13778 $ d10v-elf-gcc -g -c bar.c
13779 $ d10v-elf-gcc -g -c baz.c
13780 $ d10v-elf-gcc -g -c grbx.c
13781 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13782 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13785 The build process is identical for any other architecture, except that
13786 you must substitute the appropriate compiler and linker script for the
13787 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13791 @chapter Using @value{GDBN} with Different Languages
13794 Although programming languages generally have common aspects, they are
13795 rarely expressed in the same manner. For instance, in ANSI C,
13796 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13797 Modula-2, it is accomplished by @code{p^}. Values can also be
13798 represented (and displayed) differently. Hex numbers in C appear as
13799 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13801 @cindex working language
13802 Language-specific information is built into @value{GDBN} for some languages,
13803 allowing you to express operations like the above in your program's
13804 native language, and allowing @value{GDBN} to output values in a manner
13805 consistent with the syntax of your program's native language. The
13806 language you use to build expressions is called the @dfn{working
13810 * Setting:: Switching between source languages
13811 * Show:: Displaying the language
13812 * Checks:: Type and range checks
13813 * Supported Languages:: Supported languages
13814 * Unsupported Languages:: Unsupported languages
13818 @section Switching Between Source Languages
13820 There are two ways to control the working language---either have @value{GDBN}
13821 set it automatically, or select it manually yourself. You can use the
13822 @code{set language} command for either purpose. On startup, @value{GDBN}
13823 defaults to setting the language automatically. The working language is
13824 used to determine how expressions you type are interpreted, how values
13827 In addition to the working language, every source file that
13828 @value{GDBN} knows about has its own working language. For some object
13829 file formats, the compiler might indicate which language a particular
13830 source file is in. However, most of the time @value{GDBN} infers the
13831 language from the name of the file. The language of a source file
13832 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13833 show each frame appropriately for its own language. There is no way to
13834 set the language of a source file from within @value{GDBN}, but you can
13835 set the language associated with a filename extension. @xref{Show, ,
13836 Displaying the Language}.
13838 This is most commonly a problem when you use a program, such
13839 as @code{cfront} or @code{f2c}, that generates C but is written in
13840 another language. In that case, make the
13841 program use @code{#line} directives in its C output; that way
13842 @value{GDBN} will know the correct language of the source code of the original
13843 program, and will display that source code, not the generated C code.
13846 * Filenames:: Filename extensions and languages.
13847 * Manually:: Setting the working language manually
13848 * Automatically:: Having @value{GDBN} infer the source language
13852 @subsection List of Filename Extensions and Languages
13854 If a source file name ends in one of the following extensions, then
13855 @value{GDBN} infers that its language is the one indicated.
13873 C@t{++} source file
13879 Objective-C source file
13883 Fortran source file
13886 Modula-2 source file
13890 Assembler source file. This actually behaves almost like C, but
13891 @value{GDBN} does not skip over function prologues when stepping.
13894 In addition, you may set the language associated with a filename
13895 extension. @xref{Show, , Displaying the Language}.
13898 @subsection Setting the Working Language
13900 If you allow @value{GDBN} to set the language automatically,
13901 expressions are interpreted the same way in your debugging session and
13904 @kindex set language
13905 If you wish, you may set the language manually. To do this, issue the
13906 command @samp{set language @var{lang}}, where @var{lang} is the name of
13907 a language, such as
13908 @code{c} or @code{modula-2}.
13909 For a list of the supported languages, type @samp{set language}.
13911 Setting the language manually prevents @value{GDBN} from updating the working
13912 language automatically. This can lead to confusion if you try
13913 to debug a program when the working language is not the same as the
13914 source language, when an expression is acceptable to both
13915 languages---but means different things. For instance, if the current
13916 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13924 might not have the effect you intended. In C, this means to add
13925 @code{b} and @code{c} and place the result in @code{a}. The result
13926 printed would be the value of @code{a}. In Modula-2, this means to compare
13927 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13929 @node Automatically
13930 @subsection Having @value{GDBN} Infer the Source Language
13932 To have @value{GDBN} set the working language automatically, use
13933 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13934 then infers the working language. That is, when your program stops in a
13935 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13936 working language to the language recorded for the function in that
13937 frame. If the language for a frame is unknown (that is, if the function
13938 or block corresponding to the frame was defined in a source file that
13939 does not have a recognized extension), the current working language is
13940 not changed, and @value{GDBN} issues a warning.
13942 This may not seem necessary for most programs, which are written
13943 entirely in one source language. However, program modules and libraries
13944 written in one source language can be used by a main program written in
13945 a different source language. Using @samp{set language auto} in this
13946 case frees you from having to set the working language manually.
13949 @section Displaying the Language
13951 The following commands help you find out which language is the
13952 working language, and also what language source files were written in.
13955 @item show language
13956 @anchor{show language}
13957 @kindex show language
13958 Display the current working language. This is the
13959 language you can use with commands such as @code{print} to
13960 build and compute expressions that may involve variables in your program.
13963 @kindex info frame@r{, show the source language}
13964 Display the source language for this frame. This language becomes the
13965 working language if you use an identifier from this frame.
13966 @xref{Frame Info, ,Information about a Frame}, to identify the other
13967 information listed here.
13970 @kindex info source@r{, show the source language}
13971 Display the source language of this source file.
13972 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13973 information listed here.
13976 In unusual circumstances, you may have source files with extensions
13977 not in the standard list. You can then set the extension associated
13978 with a language explicitly:
13981 @item set extension-language @var{ext} @var{language}
13982 @kindex set extension-language
13983 Tell @value{GDBN} that source files with extension @var{ext} are to be
13984 assumed as written in the source language @var{language}.
13986 @item info extensions
13987 @kindex info extensions
13988 List all the filename extensions and the associated languages.
13992 @section Type and Range Checking
13994 Some languages are designed to guard you against making seemingly common
13995 errors through a series of compile- and run-time checks. These include
13996 checking the type of arguments to functions and operators and making
13997 sure mathematical overflows are caught at run time. Checks such as
13998 these help to ensure a program's correctness once it has been compiled
13999 by eliminating type mismatches and providing active checks for range
14000 errors when your program is running.
14002 By default @value{GDBN} checks for these errors according to the
14003 rules of the current source language. Although @value{GDBN} does not check
14004 the statements in your program, it can check expressions entered directly
14005 into @value{GDBN} for evaluation via the @code{print} command, for example.
14008 * Type Checking:: An overview of type checking
14009 * Range Checking:: An overview of range checking
14012 @cindex type checking
14013 @cindex checks, type
14014 @node Type Checking
14015 @subsection An Overview of Type Checking
14017 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14018 arguments to operators and functions have to be of the correct type,
14019 otherwise an error occurs. These checks prevent type mismatch
14020 errors from ever causing any run-time problems. For example,
14023 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14025 (@value{GDBP}) print obj.my_method (0)
14028 (@value{GDBP}) print obj.my_method (0x1234)
14029 Cannot resolve method klass::my_method to any overloaded instance
14032 The second example fails because in C@t{++} the integer constant
14033 @samp{0x1234} is not type-compatible with the pointer parameter type.
14035 For the expressions you use in @value{GDBN} commands, you can tell
14036 @value{GDBN} to not enforce strict type checking or
14037 to treat any mismatches as errors and abandon the expression;
14038 When type checking is disabled, @value{GDBN} successfully evaluates
14039 expressions like the second example above.
14041 Even if type checking is off, there may be other reasons
14042 related to type that prevent @value{GDBN} from evaluating an expression.
14043 For instance, @value{GDBN} does not know how to add an @code{int} and
14044 a @code{struct foo}. These particular type errors have nothing to do
14045 with the language in use and usually arise from expressions which make
14046 little sense to evaluate anyway.
14048 @value{GDBN} provides some additional commands for controlling type checking:
14050 @kindex set check type
14051 @kindex show check type
14053 @item set check type on
14054 @itemx set check type off
14055 Set strict type checking on or off. If any type mismatches occur in
14056 evaluating an expression while type checking is on, @value{GDBN} prints a
14057 message and aborts evaluation of the expression.
14059 @item show check type
14060 Show the current setting of type checking and whether @value{GDBN}
14061 is enforcing strict type checking rules.
14064 @cindex range checking
14065 @cindex checks, range
14066 @node Range Checking
14067 @subsection An Overview of Range Checking
14069 In some languages (such as Modula-2), it is an error to exceed the
14070 bounds of a type; this is enforced with run-time checks. Such range
14071 checking is meant to ensure program correctness by making sure
14072 computations do not overflow, or indices on an array element access do
14073 not exceed the bounds of the array.
14075 For expressions you use in @value{GDBN} commands, you can tell
14076 @value{GDBN} to treat range errors in one of three ways: ignore them,
14077 always treat them as errors and abandon the expression, or issue
14078 warnings but evaluate the expression anyway.
14080 A range error can result from numerical overflow, from exceeding an
14081 array index bound, or when you type a constant that is not a member
14082 of any type. Some languages, however, do not treat overflows as an
14083 error. In many implementations of C, mathematical overflow causes the
14084 result to ``wrap around'' to lower values---for example, if @var{m} is
14085 the largest integer value, and @var{s} is the smallest, then
14088 @var{m} + 1 @result{} @var{s}
14091 This, too, is specific to individual languages, and in some cases
14092 specific to individual compilers or machines. @xref{Supported Languages, ,
14093 Supported Languages}, for further details on specific languages.
14095 @value{GDBN} provides some additional commands for controlling the range checker:
14097 @kindex set check range
14098 @kindex show check range
14100 @item set check range auto
14101 Set range checking on or off based on the current working language.
14102 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14105 @item set check range on
14106 @itemx set check range off
14107 Set range checking on or off, overriding the default setting for the
14108 current working language. A warning is issued if the setting does not
14109 match the language default. If a range error occurs and range checking is on,
14110 then a message is printed and evaluation of the expression is aborted.
14112 @item set check range warn
14113 Output messages when the @value{GDBN} range checker detects a range error,
14114 but attempt to evaluate the expression anyway. Evaluating the
14115 expression may still be impossible for other reasons, such as accessing
14116 memory that the process does not own (a typical example from many Unix
14120 Show the current setting of the range checker, and whether or not it is
14121 being set automatically by @value{GDBN}.
14124 @node Supported Languages
14125 @section Supported Languages
14127 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14128 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14129 @c This is false ...
14130 Some @value{GDBN} features may be used in expressions regardless of the
14131 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14132 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14133 ,Expressions}) can be used with the constructs of any supported
14136 The following sections detail to what degree each source language is
14137 supported by @value{GDBN}. These sections are not meant to be language
14138 tutorials or references, but serve only as a reference guide to what the
14139 @value{GDBN} expression parser accepts, and what input and output
14140 formats should look like for different languages. There are many good
14141 books written on each of these languages; please look to these for a
14142 language reference or tutorial.
14145 * C:: C and C@t{++}
14148 * Objective-C:: Objective-C
14149 * OpenCL C:: OpenCL C
14150 * Fortran:: Fortran
14152 * Modula-2:: Modula-2
14157 @subsection C and C@t{++}
14159 @cindex C and C@t{++}
14160 @cindex expressions in C or C@t{++}
14162 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14163 to both languages. Whenever this is the case, we discuss those languages
14167 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14168 @cindex @sc{gnu} C@t{++}
14169 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14170 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14171 effectively, you must compile your C@t{++} programs with a supported
14172 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14173 compiler (@code{aCC}).
14176 * C Operators:: C and C@t{++} operators
14177 * C Constants:: C and C@t{++} constants
14178 * C Plus Plus Expressions:: C@t{++} expressions
14179 * C Defaults:: Default settings for C and C@t{++}
14180 * C Checks:: C and C@t{++} type and range checks
14181 * Debugging C:: @value{GDBN} and C
14182 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14183 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14187 @subsubsection C and C@t{++} Operators
14189 @cindex C and C@t{++} operators
14191 Operators must be defined on values of specific types. For instance,
14192 @code{+} is defined on numbers, but not on structures. Operators are
14193 often defined on groups of types.
14195 For the purposes of C and C@t{++}, the following definitions hold:
14200 @emph{Integral types} include @code{int} with any of its storage-class
14201 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14204 @emph{Floating-point types} include @code{float}, @code{double}, and
14205 @code{long double} (if supported by the target platform).
14208 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14211 @emph{Scalar types} include all of the above.
14216 The following operators are supported. They are listed here
14217 in order of increasing precedence:
14221 The comma or sequencing operator. Expressions in a comma-separated list
14222 are evaluated from left to right, with the result of the entire
14223 expression being the last expression evaluated.
14226 Assignment. The value of an assignment expression is the value
14227 assigned. Defined on scalar types.
14230 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14231 and translated to @w{@code{@var{a} = @var{a op b}}}.
14232 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14233 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14234 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14237 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14238 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14239 should be of an integral type.
14242 Logical @sc{or}. Defined on integral types.
14245 Logical @sc{and}. Defined on integral types.
14248 Bitwise @sc{or}. Defined on integral types.
14251 Bitwise exclusive-@sc{or}. Defined on integral types.
14254 Bitwise @sc{and}. Defined on integral types.
14257 Equality and inequality. Defined on scalar types. The value of these
14258 expressions is 0 for false and non-zero for true.
14260 @item <@r{, }>@r{, }<=@r{, }>=
14261 Less than, greater than, less than or equal, greater than or equal.
14262 Defined on scalar types. The value of these expressions is 0 for false
14263 and non-zero for true.
14266 left shift, and right shift. Defined on integral types.
14269 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14272 Addition and subtraction. Defined on integral types, floating-point types and
14275 @item *@r{, }/@r{, }%
14276 Multiplication, division, and modulus. Multiplication and division are
14277 defined on integral and floating-point types. Modulus is defined on
14281 Increment and decrement. When appearing before a variable, the
14282 operation is performed before the variable is used in an expression;
14283 when appearing after it, the variable's value is used before the
14284 operation takes place.
14287 Pointer dereferencing. Defined on pointer types. Same precedence as
14291 Address operator. Defined on variables. Same precedence as @code{++}.
14293 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14294 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14295 to examine the address
14296 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14300 Negative. Defined on integral and floating-point types. Same
14301 precedence as @code{++}.
14304 Logical negation. Defined on integral types. Same precedence as
14308 Bitwise complement operator. Defined on integral types. Same precedence as
14313 Structure member, and pointer-to-structure member. For convenience,
14314 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14315 pointer based on the stored type information.
14316 Defined on @code{struct} and @code{union} data.
14319 Dereferences of pointers to members.
14322 Array indexing. @code{@var{a}[@var{i}]} is defined as
14323 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14326 Function parameter list. Same precedence as @code{->}.
14329 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14330 and @code{class} types.
14333 Doubled colons also represent the @value{GDBN} scope operator
14334 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14338 If an operator is redefined in the user code, @value{GDBN} usually
14339 attempts to invoke the redefined version instead of using the operator's
14340 predefined meaning.
14343 @subsubsection C and C@t{++} Constants
14345 @cindex C and C@t{++} constants
14347 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14352 Integer constants are a sequence of digits. Octal constants are
14353 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14354 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14355 @samp{l}, specifying that the constant should be treated as a
14359 Floating point constants are a sequence of digits, followed by a decimal
14360 point, followed by a sequence of digits, and optionally followed by an
14361 exponent. An exponent is of the form:
14362 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14363 sequence of digits. The @samp{+} is optional for positive exponents.
14364 A floating-point constant may also end with a letter @samp{f} or
14365 @samp{F}, specifying that the constant should be treated as being of
14366 the @code{float} (as opposed to the default @code{double}) type; or with
14367 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14371 Enumerated constants consist of enumerated identifiers, or their
14372 integral equivalents.
14375 Character constants are a single character surrounded by single quotes
14376 (@code{'}), or a number---the ordinal value of the corresponding character
14377 (usually its @sc{ascii} value). Within quotes, the single character may
14378 be represented by a letter or by @dfn{escape sequences}, which are of
14379 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14380 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14381 @samp{@var{x}} is a predefined special character---for example,
14382 @samp{\n} for newline.
14384 Wide character constants can be written by prefixing a character
14385 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14386 form of @samp{x}. The target wide character set is used when
14387 computing the value of this constant (@pxref{Character Sets}).
14390 String constants are a sequence of character constants surrounded by
14391 double quotes (@code{"}). Any valid character constant (as described
14392 above) may appear. Double quotes within the string must be preceded by
14393 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14396 Wide string constants can be written by prefixing a string constant
14397 with @samp{L}, as in C. The target wide character set is used when
14398 computing the value of this constant (@pxref{Character Sets}).
14401 Pointer constants are an integral value. You can also write pointers
14402 to constants using the C operator @samp{&}.
14405 Array constants are comma-separated lists surrounded by braces @samp{@{}
14406 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14407 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14408 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14411 @node C Plus Plus Expressions
14412 @subsubsection C@t{++} Expressions
14414 @cindex expressions in C@t{++}
14415 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14417 @cindex debugging C@t{++} programs
14418 @cindex C@t{++} compilers
14419 @cindex debug formats and C@t{++}
14420 @cindex @value{NGCC} and C@t{++}
14422 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14423 the proper compiler and the proper debug format. Currently,
14424 @value{GDBN} works best when debugging C@t{++} code that is compiled
14425 with the most recent version of @value{NGCC} possible. The DWARF
14426 debugging format is preferred; @value{NGCC} defaults to this on most
14427 popular platforms. Other compilers and/or debug formats are likely to
14428 work badly or not at all when using @value{GDBN} to debug C@t{++}
14429 code. @xref{Compilation}.
14434 @cindex member functions
14436 Member function calls are allowed; you can use expressions like
14439 count = aml->GetOriginal(x, y)
14442 @vindex this@r{, inside C@t{++} member functions}
14443 @cindex namespace in C@t{++}
14445 While a member function is active (in the selected stack frame), your
14446 expressions have the same namespace available as the member function;
14447 that is, @value{GDBN} allows implicit references to the class instance
14448 pointer @code{this} following the same rules as C@t{++}. @code{using}
14449 declarations in the current scope are also respected by @value{GDBN}.
14451 @cindex call overloaded functions
14452 @cindex overloaded functions, calling
14453 @cindex type conversions in C@t{++}
14455 You can call overloaded functions; @value{GDBN} resolves the function
14456 call to the right definition, with some restrictions. @value{GDBN} does not
14457 perform overload resolution involving user-defined type conversions,
14458 calls to constructors, or instantiations of templates that do not exist
14459 in the program. It also cannot handle ellipsis argument lists or
14462 It does perform integral conversions and promotions, floating-point
14463 promotions, arithmetic conversions, pointer conversions, conversions of
14464 class objects to base classes, and standard conversions such as those of
14465 functions or arrays to pointers; it requires an exact match on the
14466 number of function arguments.
14468 Overload resolution is always performed, unless you have specified
14469 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14470 ,@value{GDBN} Features for C@t{++}}.
14472 You must specify @code{set overload-resolution off} in order to use an
14473 explicit function signature to call an overloaded function, as in
14475 p 'foo(char,int)'('x', 13)
14478 The @value{GDBN} command-completion facility can simplify this;
14479 see @ref{Completion, ,Command Completion}.
14481 @cindex reference declarations
14483 @value{GDBN} understands variables declared as C@t{++} references; you can use
14484 them in expressions just as you do in C@t{++} source---they are automatically
14487 In the parameter list shown when @value{GDBN} displays a frame, the values of
14488 reference variables are not displayed (unlike other variables); this
14489 avoids clutter, since references are often used for large structures.
14490 The @emph{address} of a reference variable is always shown, unless
14491 you have specified @samp{set print address off}.
14494 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14495 expressions can use it just as expressions in your program do. Since
14496 one scope may be defined in another, you can use @code{::} repeatedly if
14497 necessary, for example in an expression like
14498 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14499 resolving name scope by reference to source files, in both C and C@t{++}
14500 debugging (@pxref{Variables, ,Program Variables}).
14503 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14508 @subsubsection C and C@t{++} Defaults
14510 @cindex C and C@t{++} defaults
14512 If you allow @value{GDBN} to set range checking automatically, it
14513 defaults to @code{off} whenever the working language changes to
14514 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14515 selects the working language.
14517 If you allow @value{GDBN} to set the language automatically, it
14518 recognizes source files whose names end with @file{.c}, @file{.C}, or
14519 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14520 these files, it sets the working language to C or C@t{++}.
14521 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14522 for further details.
14525 @subsubsection C and C@t{++} Type and Range Checks
14527 @cindex C and C@t{++} checks
14529 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14530 checking is used. However, if you turn type checking off, @value{GDBN}
14531 will allow certain non-standard conversions, such as promoting integer
14532 constants to pointers.
14534 Range checking, if turned on, is done on mathematical operations. Array
14535 indices are not checked, since they are often used to index a pointer
14536 that is not itself an array.
14539 @subsubsection @value{GDBN} and C
14541 The @code{set print union} and @code{show print union} commands apply to
14542 the @code{union} type. When set to @samp{on}, any @code{union} that is
14543 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14544 appears as @samp{@{...@}}.
14546 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14547 with pointers and a memory allocation function. @xref{Expressions,
14550 @node Debugging C Plus Plus
14551 @subsubsection @value{GDBN} Features for C@t{++}
14553 @cindex commands for C@t{++}
14555 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14556 designed specifically for use with C@t{++}. Here is a summary:
14559 @cindex break in overloaded functions
14560 @item @r{breakpoint menus}
14561 When you want a breakpoint in a function whose name is overloaded,
14562 @value{GDBN} has the capability to display a menu of possible breakpoint
14563 locations to help you specify which function definition you want.
14564 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14566 @cindex overloading in C@t{++}
14567 @item rbreak @var{regex}
14568 Setting breakpoints using regular expressions is helpful for setting
14569 breakpoints on overloaded functions that are not members of any special
14571 @xref{Set Breaks, ,Setting Breakpoints}.
14573 @cindex C@t{++} exception handling
14575 @itemx catch rethrow
14577 Debug C@t{++} exception handling using these commands. @xref{Set
14578 Catchpoints, , Setting Catchpoints}.
14580 @cindex inheritance
14581 @item ptype @var{typename}
14582 Print inheritance relationships as well as other information for type
14584 @xref{Symbols, ,Examining the Symbol Table}.
14586 @item info vtbl @var{expression}.
14587 The @code{info vtbl} command can be used to display the virtual
14588 method tables of the object computed by @var{expression}. This shows
14589 one entry per virtual table; there may be multiple virtual tables when
14590 multiple inheritance is in use.
14592 @cindex C@t{++} demangling
14593 @item demangle @var{name}
14594 Demangle @var{name}.
14595 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14597 @cindex C@t{++} symbol display
14598 @item set print demangle
14599 @itemx show print demangle
14600 @itemx set print asm-demangle
14601 @itemx show print asm-demangle
14602 Control whether C@t{++} symbols display in their source form, both when
14603 displaying code as C@t{++} source and when displaying disassemblies.
14604 @xref{Print Settings, ,Print Settings}.
14606 @item set print object
14607 @itemx show print object
14608 Choose whether to print derived (actual) or declared types of objects.
14609 @xref{Print Settings, ,Print Settings}.
14611 @item set print vtbl
14612 @itemx show print vtbl
14613 Control the format for printing virtual function tables.
14614 @xref{Print Settings, ,Print Settings}.
14615 (The @code{vtbl} commands do not work on programs compiled with the HP
14616 ANSI C@t{++} compiler (@code{aCC}).)
14618 @kindex set overload-resolution
14619 @cindex overloaded functions, overload resolution
14620 @item set overload-resolution on
14621 Enable overload resolution for C@t{++} expression evaluation. The default
14622 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14623 and searches for a function whose signature matches the argument types,
14624 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14625 Expressions, ,C@t{++} Expressions}, for details).
14626 If it cannot find a match, it emits a message.
14628 @item set overload-resolution off
14629 Disable overload resolution for C@t{++} expression evaluation. For
14630 overloaded functions that are not class member functions, @value{GDBN}
14631 chooses the first function of the specified name that it finds in the
14632 symbol table, whether or not its arguments are of the correct type. For
14633 overloaded functions that are class member functions, @value{GDBN}
14634 searches for a function whose signature @emph{exactly} matches the
14637 @kindex show overload-resolution
14638 @item show overload-resolution
14639 Show the current setting of overload resolution.
14641 @item @r{Overloaded symbol names}
14642 You can specify a particular definition of an overloaded symbol, using
14643 the same notation that is used to declare such symbols in C@t{++}: type
14644 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14645 also use the @value{GDBN} command-line word completion facilities to list the
14646 available choices, or to finish the type list for you.
14647 @xref{Completion,, Command Completion}, for details on how to do this.
14650 @node Decimal Floating Point
14651 @subsubsection Decimal Floating Point format
14652 @cindex decimal floating point format
14654 @value{GDBN} can examine, set and perform computations with numbers in
14655 decimal floating point format, which in the C language correspond to the
14656 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14657 specified by the extension to support decimal floating-point arithmetic.
14659 There are two encodings in use, depending on the architecture: BID (Binary
14660 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14661 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14664 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14665 to manipulate decimal floating point numbers, it is not possible to convert
14666 (using a cast, for example) integers wider than 32-bit to decimal float.
14668 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14669 point computations, error checking in decimal float operations ignores
14670 underflow, overflow and divide by zero exceptions.
14672 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14673 to inspect @code{_Decimal128} values stored in floating point registers.
14674 See @ref{PowerPC,,PowerPC} for more details.
14680 @value{GDBN} can be used to debug programs written in D and compiled with
14681 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14682 specific feature --- dynamic arrays.
14687 @cindex Go (programming language)
14688 @value{GDBN} can be used to debug programs written in Go and compiled with
14689 @file{gccgo} or @file{6g} compilers.
14691 Here is a summary of the Go-specific features and restrictions:
14694 @cindex current Go package
14695 @item The current Go package
14696 The name of the current package does not need to be specified when
14697 specifying global variables and functions.
14699 For example, given the program:
14703 var myglob = "Shall we?"
14709 When stopped inside @code{main} either of these work:
14713 (gdb) p main.myglob
14716 @cindex builtin Go types
14717 @item Builtin Go types
14718 The @code{string} type is recognized by @value{GDBN} and is printed
14721 @cindex builtin Go functions
14722 @item Builtin Go functions
14723 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14724 function and handles it internally.
14726 @cindex restrictions on Go expressions
14727 @item Restrictions on Go expressions
14728 All Go operators are supported except @code{&^}.
14729 The Go @code{_} ``blank identifier'' is not supported.
14730 Automatic dereferencing of pointers is not supported.
14734 @subsection Objective-C
14736 @cindex Objective-C
14737 This section provides information about some commands and command
14738 options that are useful for debugging Objective-C code. See also
14739 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14740 few more commands specific to Objective-C support.
14743 * Method Names in Commands::
14744 * The Print Command with Objective-C::
14747 @node Method Names in Commands
14748 @subsubsection Method Names in Commands
14750 The following commands have been extended to accept Objective-C method
14751 names as line specifications:
14753 @kindex clear@r{, and Objective-C}
14754 @kindex break@r{, and Objective-C}
14755 @kindex info line@r{, and Objective-C}
14756 @kindex jump@r{, and Objective-C}
14757 @kindex list@r{, and Objective-C}
14761 @item @code{info line}
14766 A fully qualified Objective-C method name is specified as
14769 -[@var{Class} @var{methodName}]
14772 where the minus sign is used to indicate an instance method and a
14773 plus sign (not shown) is used to indicate a class method. The class
14774 name @var{Class} and method name @var{methodName} are enclosed in
14775 brackets, similar to the way messages are specified in Objective-C
14776 source code. For example, to set a breakpoint at the @code{create}
14777 instance method of class @code{Fruit} in the program currently being
14781 break -[Fruit create]
14784 To list ten program lines around the @code{initialize} class method,
14788 list +[NSText initialize]
14791 In the current version of @value{GDBN}, the plus or minus sign is
14792 required. In future versions of @value{GDBN}, the plus or minus
14793 sign will be optional, but you can use it to narrow the search. It
14794 is also possible to specify just a method name:
14800 You must specify the complete method name, including any colons. If
14801 your program's source files contain more than one @code{create} method,
14802 you'll be presented with a numbered list of classes that implement that
14803 method. Indicate your choice by number, or type @samp{0} to exit if
14806 As another example, to clear a breakpoint established at the
14807 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14810 clear -[NSWindow makeKeyAndOrderFront:]
14813 @node The Print Command with Objective-C
14814 @subsubsection The Print Command With Objective-C
14815 @cindex Objective-C, print objects
14816 @kindex print-object
14817 @kindex po @r{(@code{print-object})}
14819 The print command has also been extended to accept methods. For example:
14822 print -[@var{object} hash]
14825 @cindex print an Objective-C object description
14826 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14828 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14829 and print the result. Also, an additional command has been added,
14830 @code{print-object} or @code{po} for short, which is meant to print
14831 the description of an object. However, this command may only work
14832 with certain Objective-C libraries that have a particular hook
14833 function, @code{_NSPrintForDebugger}, defined.
14836 @subsection OpenCL C
14839 This section provides information about @value{GDBN}s OpenCL C support.
14842 * OpenCL C Datatypes::
14843 * OpenCL C Expressions::
14844 * OpenCL C Operators::
14847 @node OpenCL C Datatypes
14848 @subsubsection OpenCL C Datatypes
14850 @cindex OpenCL C Datatypes
14851 @value{GDBN} supports the builtin scalar and vector datatypes specified
14852 by OpenCL 1.1. In addition the half- and double-precision floating point
14853 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14854 extensions are also known to @value{GDBN}.
14856 @node OpenCL C Expressions
14857 @subsubsection OpenCL C Expressions
14859 @cindex OpenCL C Expressions
14860 @value{GDBN} supports accesses to vector components including the access as
14861 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14862 supported by @value{GDBN} can be used as well.
14864 @node OpenCL C Operators
14865 @subsubsection OpenCL C Operators
14867 @cindex OpenCL C Operators
14868 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14872 @subsection Fortran
14873 @cindex Fortran-specific support in @value{GDBN}
14875 @value{GDBN} can be used to debug programs written in Fortran, but it
14876 currently supports only the features of Fortran 77 language.
14878 @cindex trailing underscore, in Fortran symbols
14879 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14880 among them) append an underscore to the names of variables and
14881 functions. When you debug programs compiled by those compilers, you
14882 will need to refer to variables and functions with a trailing
14886 * Fortran Operators:: Fortran operators and expressions
14887 * Fortran Defaults:: Default settings for Fortran
14888 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14891 @node Fortran Operators
14892 @subsubsection Fortran Operators and Expressions
14894 @cindex Fortran operators and expressions
14896 Operators must be defined on values of specific types. For instance,
14897 @code{+} is defined on numbers, but not on characters or other non-
14898 arithmetic types. Operators are often defined on groups of types.
14902 The exponentiation operator. It raises the first operand to the power
14906 The range operator. Normally used in the form of array(low:high) to
14907 represent a section of array.
14910 The access component operator. Normally used to access elements in derived
14911 types. Also suitable for unions. As unions aren't part of regular Fortran,
14912 this can only happen when accessing a register that uses a gdbarch-defined
14916 @node Fortran Defaults
14917 @subsubsection Fortran Defaults
14919 @cindex Fortran Defaults
14921 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14922 default uses case-insensitive matches for Fortran symbols. You can
14923 change that with the @samp{set case-insensitive} command, see
14924 @ref{Symbols}, for the details.
14926 @node Special Fortran Commands
14927 @subsubsection Special Fortran Commands
14929 @cindex Special Fortran commands
14931 @value{GDBN} has some commands to support Fortran-specific features,
14932 such as displaying common blocks.
14935 @cindex @code{COMMON} blocks, Fortran
14936 @kindex info common
14937 @item info common @r{[}@var{common-name}@r{]}
14938 This command prints the values contained in the Fortran @code{COMMON}
14939 block whose name is @var{common-name}. With no argument, the names of
14940 all @code{COMMON} blocks visible at the current program location are
14947 @cindex Pascal support in @value{GDBN}, limitations
14948 Debugging Pascal programs which use sets, subranges, file variables, or
14949 nested functions does not currently work. @value{GDBN} does not support
14950 entering expressions, printing values, or similar features using Pascal
14953 The Pascal-specific command @code{set print pascal_static-members}
14954 controls whether static members of Pascal objects are displayed.
14955 @xref{Print Settings, pascal_static-members}.
14958 @subsection Modula-2
14960 @cindex Modula-2, @value{GDBN} support
14962 The extensions made to @value{GDBN} to support Modula-2 only support
14963 output from the @sc{gnu} Modula-2 compiler (which is currently being
14964 developed). Other Modula-2 compilers are not currently supported, and
14965 attempting to debug executables produced by them is most likely
14966 to give an error as @value{GDBN} reads in the executable's symbol
14969 @cindex expressions in Modula-2
14971 * M2 Operators:: Built-in operators
14972 * Built-In Func/Proc:: Built-in functions and procedures
14973 * M2 Constants:: Modula-2 constants
14974 * M2 Types:: Modula-2 types
14975 * M2 Defaults:: Default settings for Modula-2
14976 * Deviations:: Deviations from standard Modula-2
14977 * M2 Checks:: Modula-2 type and range checks
14978 * M2 Scope:: The scope operators @code{::} and @code{.}
14979 * GDB/M2:: @value{GDBN} and Modula-2
14983 @subsubsection Operators
14984 @cindex Modula-2 operators
14986 Operators must be defined on values of specific types. For instance,
14987 @code{+} is defined on numbers, but not on structures. Operators are
14988 often defined on groups of types. For the purposes of Modula-2, the
14989 following definitions hold:
14994 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14998 @emph{Character types} consist of @code{CHAR} and its subranges.
15001 @emph{Floating-point types} consist of @code{REAL}.
15004 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15008 @emph{Scalar types} consist of all of the above.
15011 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15014 @emph{Boolean types} consist of @code{BOOLEAN}.
15018 The following operators are supported, and appear in order of
15019 increasing precedence:
15023 Function argument or array index separator.
15026 Assignment. The value of @var{var} @code{:=} @var{value} is
15030 Less than, greater than on integral, floating-point, or enumerated
15034 Less than or equal to, greater than or equal to
15035 on integral, floating-point and enumerated types, or set inclusion on
15036 set types. Same precedence as @code{<}.
15038 @item =@r{, }<>@r{, }#
15039 Equality and two ways of expressing inequality, valid on scalar types.
15040 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15041 available for inequality, since @code{#} conflicts with the script
15045 Set membership. Defined on set types and the types of their members.
15046 Same precedence as @code{<}.
15049 Boolean disjunction. Defined on boolean types.
15052 Boolean conjunction. Defined on boolean types.
15055 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15058 Addition and subtraction on integral and floating-point types, or union
15059 and difference on set types.
15062 Multiplication on integral and floating-point types, or set intersection
15066 Division on floating-point types, or symmetric set difference on set
15067 types. Same precedence as @code{*}.
15070 Integer division and remainder. Defined on integral types. Same
15071 precedence as @code{*}.
15074 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15077 Pointer dereferencing. Defined on pointer types.
15080 Boolean negation. Defined on boolean types. Same precedence as
15084 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15085 precedence as @code{^}.
15088 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15091 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15095 @value{GDBN} and Modula-2 scope operators.
15099 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15100 treats the use of the operator @code{IN}, or the use of operators
15101 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15102 @code{<=}, and @code{>=} on sets as an error.
15106 @node Built-In Func/Proc
15107 @subsubsection Built-in Functions and Procedures
15108 @cindex Modula-2 built-ins
15110 Modula-2 also makes available several built-in procedures and functions.
15111 In describing these, the following metavariables are used:
15116 represents an @code{ARRAY} variable.
15119 represents a @code{CHAR} constant or variable.
15122 represents a variable or constant of integral type.
15125 represents an identifier that belongs to a set. Generally used in the
15126 same function with the metavariable @var{s}. The type of @var{s} should
15127 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15130 represents a variable or constant of integral or floating-point type.
15133 represents a variable or constant of floating-point type.
15139 represents a variable.
15142 represents a variable or constant of one of many types. See the
15143 explanation of the function for details.
15146 All Modula-2 built-in procedures also return a result, described below.
15150 Returns the absolute value of @var{n}.
15153 If @var{c} is a lower case letter, it returns its upper case
15154 equivalent, otherwise it returns its argument.
15157 Returns the character whose ordinal value is @var{i}.
15160 Decrements the value in the variable @var{v} by one. Returns the new value.
15162 @item DEC(@var{v},@var{i})
15163 Decrements the value in the variable @var{v} by @var{i}. Returns the
15166 @item EXCL(@var{m},@var{s})
15167 Removes the element @var{m} from the set @var{s}. Returns the new
15170 @item FLOAT(@var{i})
15171 Returns the floating point equivalent of the integer @var{i}.
15173 @item HIGH(@var{a})
15174 Returns the index of the last member of @var{a}.
15177 Increments the value in the variable @var{v} by one. Returns the new value.
15179 @item INC(@var{v},@var{i})
15180 Increments the value in the variable @var{v} by @var{i}. Returns the
15183 @item INCL(@var{m},@var{s})
15184 Adds the element @var{m} to the set @var{s} if it is not already
15185 there. Returns the new set.
15188 Returns the maximum value of the type @var{t}.
15191 Returns the minimum value of the type @var{t}.
15194 Returns boolean TRUE if @var{i} is an odd number.
15197 Returns the ordinal value of its argument. For example, the ordinal
15198 value of a character is its @sc{ascii} value (on machines supporting
15199 the @sc{ascii} character set). The argument @var{x} must be of an
15200 ordered type, which include integral, character and enumerated types.
15202 @item SIZE(@var{x})
15203 Returns the size of its argument. The argument @var{x} can be a
15204 variable or a type.
15206 @item TRUNC(@var{r})
15207 Returns the integral part of @var{r}.
15209 @item TSIZE(@var{x})
15210 Returns the size of its argument. The argument @var{x} can be a
15211 variable or a type.
15213 @item VAL(@var{t},@var{i})
15214 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15218 @emph{Warning:} Sets and their operations are not yet supported, so
15219 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15223 @cindex Modula-2 constants
15225 @subsubsection Constants
15227 @value{GDBN} allows you to express the constants of Modula-2 in the following
15233 Integer constants are simply a sequence of digits. When used in an
15234 expression, a constant is interpreted to be type-compatible with the
15235 rest of the expression. Hexadecimal integers are specified by a
15236 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15239 Floating point constants appear as a sequence of digits, followed by a
15240 decimal point and another sequence of digits. An optional exponent can
15241 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15242 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15243 digits of the floating point constant must be valid decimal (base 10)
15247 Character constants consist of a single character enclosed by a pair of
15248 like quotes, either single (@code{'}) or double (@code{"}). They may
15249 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15250 followed by a @samp{C}.
15253 String constants consist of a sequence of characters enclosed by a
15254 pair of like quotes, either single (@code{'}) or double (@code{"}).
15255 Escape sequences in the style of C are also allowed. @xref{C
15256 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15260 Enumerated constants consist of an enumerated identifier.
15263 Boolean constants consist of the identifiers @code{TRUE} and
15267 Pointer constants consist of integral values only.
15270 Set constants are not yet supported.
15274 @subsubsection Modula-2 Types
15275 @cindex Modula-2 types
15277 Currently @value{GDBN} can print the following data types in Modula-2
15278 syntax: array types, record types, set types, pointer types, procedure
15279 types, enumerated types, subrange types and base types. You can also
15280 print the contents of variables declared using these type.
15281 This section gives a number of simple source code examples together with
15282 sample @value{GDBN} sessions.
15284 The first example contains the following section of code:
15293 and you can request @value{GDBN} to interrogate the type and value of
15294 @code{r} and @code{s}.
15297 (@value{GDBP}) print s
15299 (@value{GDBP}) ptype s
15301 (@value{GDBP}) print r
15303 (@value{GDBP}) ptype r
15308 Likewise if your source code declares @code{s} as:
15312 s: SET ['A'..'Z'] ;
15316 then you may query the type of @code{s} by:
15319 (@value{GDBP}) ptype s
15320 type = SET ['A'..'Z']
15324 Note that at present you cannot interactively manipulate set
15325 expressions using the debugger.
15327 The following example shows how you might declare an array in Modula-2
15328 and how you can interact with @value{GDBN} to print its type and contents:
15332 s: ARRAY [-10..10] OF CHAR ;
15336 (@value{GDBP}) ptype s
15337 ARRAY [-10..10] OF CHAR
15340 Note that the array handling is not yet complete and although the type
15341 is printed correctly, expression handling still assumes that all
15342 arrays have a lower bound of zero and not @code{-10} as in the example
15345 Here are some more type related Modula-2 examples:
15349 colour = (blue, red, yellow, green) ;
15350 t = [blue..yellow] ;
15358 The @value{GDBN} interaction shows how you can query the data type
15359 and value of a variable.
15362 (@value{GDBP}) print s
15364 (@value{GDBP}) ptype t
15365 type = [blue..yellow]
15369 In this example a Modula-2 array is declared and its contents
15370 displayed. Observe that the contents are written in the same way as
15371 their @code{C} counterparts.
15375 s: ARRAY [1..5] OF CARDINAL ;
15381 (@value{GDBP}) print s
15382 $1 = @{1, 0, 0, 0, 0@}
15383 (@value{GDBP}) ptype s
15384 type = ARRAY [1..5] OF CARDINAL
15387 The Modula-2 language interface to @value{GDBN} also understands
15388 pointer types as shown in this example:
15392 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15399 and you can request that @value{GDBN} describes the type of @code{s}.
15402 (@value{GDBP}) ptype s
15403 type = POINTER TO ARRAY [1..5] OF CARDINAL
15406 @value{GDBN} handles compound types as we can see in this example.
15407 Here we combine array types, record types, pointer types and subrange
15418 myarray = ARRAY myrange OF CARDINAL ;
15419 myrange = [-2..2] ;
15421 s: POINTER TO ARRAY myrange OF foo ;
15425 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15429 (@value{GDBP}) ptype s
15430 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15433 f3 : ARRAY [-2..2] OF CARDINAL;
15438 @subsubsection Modula-2 Defaults
15439 @cindex Modula-2 defaults
15441 If type and range checking are set automatically by @value{GDBN}, they
15442 both default to @code{on} whenever the working language changes to
15443 Modula-2. This happens regardless of whether you or @value{GDBN}
15444 selected the working language.
15446 If you allow @value{GDBN} to set the language automatically, then entering
15447 code compiled from a file whose name ends with @file{.mod} sets the
15448 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15449 Infer the Source Language}, for further details.
15452 @subsubsection Deviations from Standard Modula-2
15453 @cindex Modula-2, deviations from
15455 A few changes have been made to make Modula-2 programs easier to debug.
15456 This is done primarily via loosening its type strictness:
15460 Unlike in standard Modula-2, pointer constants can be formed by
15461 integers. This allows you to modify pointer variables during
15462 debugging. (In standard Modula-2, the actual address contained in a
15463 pointer variable is hidden from you; it can only be modified
15464 through direct assignment to another pointer variable or expression that
15465 returned a pointer.)
15468 C escape sequences can be used in strings and characters to represent
15469 non-printable characters. @value{GDBN} prints out strings with these
15470 escape sequences embedded. Single non-printable characters are
15471 printed using the @samp{CHR(@var{nnn})} format.
15474 The assignment operator (@code{:=}) returns the value of its right-hand
15478 All built-in procedures both modify @emph{and} return their argument.
15482 @subsubsection Modula-2 Type and Range Checks
15483 @cindex Modula-2 checks
15486 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15489 @c FIXME remove warning when type/range checks added
15491 @value{GDBN} considers two Modula-2 variables type equivalent if:
15495 They are of types that have been declared equivalent via a @code{TYPE
15496 @var{t1} = @var{t2}} statement
15499 They have been declared on the same line. (Note: This is true of the
15500 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15503 As long as type checking is enabled, any attempt to combine variables
15504 whose types are not equivalent is an error.
15506 Range checking is done on all mathematical operations, assignment, array
15507 index bounds, and all built-in functions and procedures.
15510 @subsubsection The Scope Operators @code{::} and @code{.}
15512 @cindex @code{.}, Modula-2 scope operator
15513 @cindex colon, doubled as scope operator
15515 @vindex colon-colon@r{, in Modula-2}
15516 @c Info cannot handle :: but TeX can.
15519 @vindex ::@r{, in Modula-2}
15522 There are a few subtle differences between the Modula-2 scope operator
15523 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15528 @var{module} . @var{id}
15529 @var{scope} :: @var{id}
15533 where @var{scope} is the name of a module or a procedure,
15534 @var{module} the name of a module, and @var{id} is any declared
15535 identifier within your program, except another module.
15537 Using the @code{::} operator makes @value{GDBN} search the scope
15538 specified by @var{scope} for the identifier @var{id}. If it is not
15539 found in the specified scope, then @value{GDBN} searches all scopes
15540 enclosing the one specified by @var{scope}.
15542 Using the @code{.} operator makes @value{GDBN} search the current scope for
15543 the identifier specified by @var{id} that was imported from the
15544 definition module specified by @var{module}. With this operator, it is
15545 an error if the identifier @var{id} was not imported from definition
15546 module @var{module}, or if @var{id} is not an identifier in
15550 @subsubsection @value{GDBN} and Modula-2
15552 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15553 Five subcommands of @code{set print} and @code{show print} apply
15554 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15555 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15556 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15557 analogue in Modula-2.
15559 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15560 with any language, is not useful with Modula-2. Its
15561 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15562 created in Modula-2 as they can in C or C@t{++}. However, because an
15563 address can be specified by an integral constant, the construct
15564 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15566 @cindex @code{#} in Modula-2
15567 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15568 interpreted as the beginning of a comment. Use @code{<>} instead.
15574 The extensions made to @value{GDBN} for Ada only support
15575 output from the @sc{gnu} Ada (GNAT) compiler.
15576 Other Ada compilers are not currently supported, and
15577 attempting to debug executables produced by them is most likely
15581 @cindex expressions in Ada
15583 * Ada Mode Intro:: General remarks on the Ada syntax
15584 and semantics supported by Ada mode
15586 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15587 * Additions to Ada:: Extensions of the Ada expression syntax.
15588 * Overloading support for Ada:: Support for expressions involving overloaded
15590 * Stopping Before Main Program:: Debugging the program during elaboration.
15591 * Ada Exceptions:: Ada Exceptions
15592 * Ada Tasks:: Listing and setting breakpoints in tasks.
15593 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15594 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15596 * Ada Glitches:: Known peculiarities of Ada mode.
15599 @node Ada Mode Intro
15600 @subsubsection Introduction
15601 @cindex Ada mode, general
15603 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15604 syntax, with some extensions.
15605 The philosophy behind the design of this subset is
15609 That @value{GDBN} should provide basic literals and access to operations for
15610 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15611 leaving more sophisticated computations to subprograms written into the
15612 program (which therefore may be called from @value{GDBN}).
15615 That type safety and strict adherence to Ada language restrictions
15616 are not particularly important to the @value{GDBN} user.
15619 That brevity is important to the @value{GDBN} user.
15622 Thus, for brevity, the debugger acts as if all names declared in
15623 user-written packages are directly visible, even if they are not visible
15624 according to Ada rules, thus making it unnecessary to fully qualify most
15625 names with their packages, regardless of context. Where this causes
15626 ambiguity, @value{GDBN} asks the user's intent.
15628 The debugger will start in Ada mode if it detects an Ada main program.
15629 As for other languages, it will enter Ada mode when stopped in a program that
15630 was translated from an Ada source file.
15632 While in Ada mode, you may use `@t{--}' for comments. This is useful
15633 mostly for documenting command files. The standard @value{GDBN} comment
15634 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15635 middle (to allow based literals).
15637 @node Omissions from Ada
15638 @subsubsection Omissions from Ada
15639 @cindex Ada, omissions from
15641 Here are the notable omissions from the subset:
15645 Only a subset of the attributes are supported:
15649 @t{'First}, @t{'Last}, and @t{'Length}
15650 on array objects (not on types and subtypes).
15653 @t{'Min} and @t{'Max}.
15656 @t{'Pos} and @t{'Val}.
15662 @t{'Range} on array objects (not subtypes), but only as the right
15663 operand of the membership (@code{in}) operator.
15666 @t{'Access}, @t{'Unchecked_Access}, and
15667 @t{'Unrestricted_Access} (a GNAT extension).
15675 @code{Characters.Latin_1} are not available and
15676 concatenation is not implemented. Thus, escape characters in strings are
15677 not currently available.
15680 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15681 equality of representations. They will generally work correctly
15682 for strings and arrays whose elements have integer or enumeration types.
15683 They may not work correctly for arrays whose element
15684 types have user-defined equality, for arrays of real values
15685 (in particular, IEEE-conformant floating point, because of negative
15686 zeroes and NaNs), and for arrays whose elements contain unused bits with
15687 indeterminate values.
15690 The other component-by-component array operations (@code{and}, @code{or},
15691 @code{xor}, @code{not}, and relational tests other than equality)
15692 are not implemented.
15695 @cindex array aggregates (Ada)
15696 @cindex record aggregates (Ada)
15697 @cindex aggregates (Ada)
15698 There is limited support for array and record aggregates. They are
15699 permitted only on the right sides of assignments, as in these examples:
15702 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15703 (@value{GDBP}) set An_Array := (1, others => 0)
15704 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15705 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15706 (@value{GDBP}) set A_Record := (1, "Peter", True);
15707 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15711 discriminant's value by assigning an aggregate has an
15712 undefined effect if that discriminant is used within the record.
15713 However, you can first modify discriminants by directly assigning to
15714 them (which normally would not be allowed in Ada), and then performing an
15715 aggregate assignment. For example, given a variable @code{A_Rec}
15716 declared to have a type such as:
15719 type Rec (Len : Small_Integer := 0) is record
15721 Vals : IntArray (1 .. Len);
15725 you can assign a value with a different size of @code{Vals} with two
15729 (@value{GDBP}) set A_Rec.Len := 4
15730 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15733 As this example also illustrates, @value{GDBN} is very loose about the usual
15734 rules concerning aggregates. You may leave out some of the
15735 components of an array or record aggregate (such as the @code{Len}
15736 component in the assignment to @code{A_Rec} above); they will retain their
15737 original values upon assignment. You may freely use dynamic values as
15738 indices in component associations. You may even use overlapping or
15739 redundant component associations, although which component values are
15740 assigned in such cases is not defined.
15743 Calls to dispatching subprograms are not implemented.
15746 The overloading algorithm is much more limited (i.e., less selective)
15747 than that of real Ada. It makes only limited use of the context in
15748 which a subexpression appears to resolve its meaning, and it is much
15749 looser in its rules for allowing type matches. As a result, some
15750 function calls will be ambiguous, and the user will be asked to choose
15751 the proper resolution.
15754 The @code{new} operator is not implemented.
15757 Entry calls are not implemented.
15760 Aside from printing, arithmetic operations on the native VAX floating-point
15761 formats are not supported.
15764 It is not possible to slice a packed array.
15767 The names @code{True} and @code{False}, when not part of a qualified name,
15768 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15770 Should your program
15771 redefine these names in a package or procedure (at best a dubious practice),
15772 you will have to use fully qualified names to access their new definitions.
15775 @node Additions to Ada
15776 @subsubsection Additions to Ada
15777 @cindex Ada, deviations from
15779 As it does for other languages, @value{GDBN} makes certain generic
15780 extensions to Ada (@pxref{Expressions}):
15784 If the expression @var{E} is a variable residing in memory (typically
15785 a local variable or array element) and @var{N} is a positive integer,
15786 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15787 @var{N}-1 adjacent variables following it in memory as an array. In
15788 Ada, this operator is generally not necessary, since its prime use is
15789 in displaying parts of an array, and slicing will usually do this in
15790 Ada. However, there are occasional uses when debugging programs in
15791 which certain debugging information has been optimized away.
15794 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15795 appears in function or file @var{B}.'' When @var{B} is a file name,
15796 you must typically surround it in single quotes.
15799 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15800 @var{type} that appears at address @var{addr}.''
15803 A name starting with @samp{$} is a convenience variable
15804 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15807 In addition, @value{GDBN} provides a few other shortcuts and outright
15808 additions specific to Ada:
15812 The assignment statement is allowed as an expression, returning
15813 its right-hand operand as its value. Thus, you may enter
15816 (@value{GDBP}) set x := y + 3
15817 (@value{GDBP}) print A(tmp := y + 1)
15821 The semicolon is allowed as an ``operator,'' returning as its value
15822 the value of its right-hand operand.
15823 This allows, for example,
15824 complex conditional breaks:
15827 (@value{GDBP}) break f
15828 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15832 Rather than use catenation and symbolic character names to introduce special
15833 characters into strings, one may instead use a special bracket notation,
15834 which is also used to print strings. A sequence of characters of the form
15835 @samp{["@var{XX}"]} within a string or character literal denotes the
15836 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15837 sequence of characters @samp{["""]} also denotes a single quotation mark
15838 in strings. For example,
15840 "One line.["0a"]Next line.["0a"]"
15843 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15847 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15848 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15852 (@value{GDBP}) print 'max(x, y)
15856 When printing arrays, @value{GDBN} uses positional notation when the
15857 array has a lower bound of 1, and uses a modified named notation otherwise.
15858 For example, a one-dimensional array of three integers with a lower bound
15859 of 3 might print as
15866 That is, in contrast to valid Ada, only the first component has a @code{=>}
15870 You may abbreviate attributes in expressions with any unique,
15871 multi-character subsequence of
15872 their names (an exact match gets preference).
15873 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15874 in place of @t{a'length}.
15877 @cindex quoting Ada internal identifiers
15878 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15879 to lower case. The GNAT compiler uses upper-case characters for
15880 some of its internal identifiers, which are normally of no interest to users.
15881 For the rare occasions when you actually have to look at them,
15882 enclose them in angle brackets to avoid the lower-case mapping.
15885 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15889 Printing an object of class-wide type or dereferencing an
15890 access-to-class-wide value will display all the components of the object's
15891 specific type (as indicated by its run-time tag). Likewise, component
15892 selection on such a value will operate on the specific type of the
15897 @node Overloading support for Ada
15898 @subsubsection Overloading support for Ada
15899 @cindex overloading, Ada
15901 The debugger supports limited overloading. Given a subprogram call in which
15902 the function symbol has multiple definitions, it will use the number of
15903 actual parameters and some information about their types to attempt to narrow
15904 the set of definitions. It also makes very limited use of context, preferring
15905 procedures to functions in the context of the @code{call} command, and
15906 functions to procedures elsewhere.
15908 If, after narrowing, the set of matching definitions still contains more than
15909 one definition, @value{GDBN} will display a menu to query which one it should
15913 (@value{GDBP}) print f(1)
15914 Multiple matches for f
15916 [1] foo.f (integer) return boolean at foo.adb:23
15917 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15921 In this case, just select one menu entry either to cancel expression evaluation
15922 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
15923 instance (type the corresponding number and press @key{RET}).
15925 Here are a couple of commands to customize @value{GDBN}'s behavior in this
15930 @kindex set ada print-signatures
15931 @item set ada print-signatures
15932 Control whether parameter types and return types are displayed in overloads
15933 selection menus. It is @code{on} by default.
15934 @xref{Overloading support for Ada}.
15936 @kindex show ada print-signatures
15937 @item show ada print-signatures
15938 Show the current setting for displaying parameter types and return types in
15939 overloads selection menu.
15940 @xref{Overloading support for Ada}.
15944 @node Stopping Before Main Program
15945 @subsubsection Stopping at the Very Beginning
15947 @cindex breakpointing Ada elaboration code
15948 It is sometimes necessary to debug the program during elaboration, and
15949 before reaching the main procedure.
15950 As defined in the Ada Reference
15951 Manual, the elaboration code is invoked from a procedure called
15952 @code{adainit}. To run your program up to the beginning of
15953 elaboration, simply use the following two commands:
15954 @code{tbreak adainit} and @code{run}.
15956 @node Ada Exceptions
15957 @subsubsection Ada Exceptions
15959 A command is provided to list all Ada exceptions:
15962 @kindex info exceptions
15963 @item info exceptions
15964 @itemx info exceptions @var{regexp}
15965 The @code{info exceptions} command allows you to list all Ada exceptions
15966 defined within the program being debugged, as well as their addresses.
15967 With a regular expression, @var{regexp}, as argument, only those exceptions
15968 whose names match @var{regexp} are listed.
15971 Below is a small example, showing how the command can be used, first
15972 without argument, and next with a regular expression passed as an
15976 (@value{GDBP}) info exceptions
15977 All defined Ada exceptions:
15978 constraint_error: 0x613da0
15979 program_error: 0x613d20
15980 storage_error: 0x613ce0
15981 tasking_error: 0x613ca0
15982 const.aint_global_e: 0x613b00
15983 (@value{GDBP}) info exceptions const.aint
15984 All Ada exceptions matching regular expression "const.aint":
15985 constraint_error: 0x613da0
15986 const.aint_global_e: 0x613b00
15989 It is also possible to ask @value{GDBN} to stop your program's execution
15990 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15993 @subsubsection Extensions for Ada Tasks
15994 @cindex Ada, tasking
15996 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15997 @value{GDBN} provides the following task-related commands:
16002 This command shows a list of current Ada tasks, as in the following example:
16009 (@value{GDBP}) info tasks
16010 ID TID P-ID Pri State Name
16011 1 8088000 0 15 Child Activation Wait main_task
16012 2 80a4000 1 15 Accept Statement b
16013 3 809a800 1 15 Child Activation Wait a
16014 * 4 80ae800 3 15 Runnable c
16019 In this listing, the asterisk before the last task indicates it to be the
16020 task currently being inspected.
16024 Represents @value{GDBN}'s internal task number.
16030 The parent's task ID (@value{GDBN}'s internal task number).
16033 The base priority of the task.
16036 Current state of the task.
16040 The task has been created but has not been activated. It cannot be
16044 The task is not blocked for any reason known to Ada. (It may be waiting
16045 for a mutex, though.) It is conceptually "executing" in normal mode.
16048 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16049 that were waiting on terminate alternatives have been awakened and have
16050 terminated themselves.
16052 @item Child Activation Wait
16053 The task is waiting for created tasks to complete activation.
16055 @item Accept Statement
16056 The task is waiting on an accept or selective wait statement.
16058 @item Waiting on entry call
16059 The task is waiting on an entry call.
16061 @item Async Select Wait
16062 The task is waiting to start the abortable part of an asynchronous
16066 The task is waiting on a select statement with only a delay
16069 @item Child Termination Wait
16070 The task is sleeping having completed a master within itself, and is
16071 waiting for the tasks dependent on that master to become terminated or
16072 waiting on a terminate Phase.
16074 @item Wait Child in Term Alt
16075 The task is sleeping waiting for tasks on terminate alternatives to
16076 finish terminating.
16078 @item Accepting RV with @var{taskno}
16079 The task is accepting a rendez-vous with the task @var{taskno}.
16083 Name of the task in the program.
16087 @kindex info task @var{taskno}
16088 @item info task @var{taskno}
16089 This command shows detailled informations on the specified task, as in
16090 the following example:
16095 (@value{GDBP}) info tasks
16096 ID TID P-ID Pri State Name
16097 1 8077880 0 15 Child Activation Wait main_task
16098 * 2 807c468 1 15 Runnable task_1
16099 (@value{GDBP}) info task 2
16100 Ada Task: 0x807c468
16103 Parent: 1 (main_task)
16109 @kindex task@r{ (Ada)}
16110 @cindex current Ada task ID
16111 This command prints the ID of the current task.
16117 (@value{GDBP}) info tasks
16118 ID TID P-ID Pri State Name
16119 1 8077870 0 15 Child Activation Wait main_task
16120 * 2 807c458 1 15 Runnable t
16121 (@value{GDBP}) task
16122 [Current task is 2]
16125 @item task @var{taskno}
16126 @cindex Ada task switching
16127 This command is like the @code{thread @var{threadno}}
16128 command (@pxref{Threads}). It switches the context of debugging
16129 from the current task to the given task.
16135 (@value{GDBP}) info tasks
16136 ID TID P-ID Pri State Name
16137 1 8077870 0 15 Child Activation Wait main_task
16138 * 2 807c458 1 15 Runnable t
16139 (@value{GDBP}) task 1
16140 [Switching to task 1]
16141 #0 0x8067726 in pthread_cond_wait ()
16143 #0 0x8067726 in pthread_cond_wait ()
16144 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16145 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16146 #3 0x806153e in system.tasking.stages.activate_tasks ()
16147 #4 0x804aacc in un () at un.adb:5
16150 @item break @var{location} task @var{taskno}
16151 @itemx break @var{location} task @var{taskno} if @dots{}
16152 @cindex breakpoints and tasks, in Ada
16153 @cindex task breakpoints, in Ada
16154 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16155 These commands are like the @code{break @dots{} thread @dots{}}
16156 command (@pxref{Thread Stops}). The
16157 @var{location} argument specifies source lines, as described
16158 in @ref{Specify Location}.
16160 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16161 to specify that you only want @value{GDBN} to stop the program when a
16162 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16163 numeric task identifiers assigned by @value{GDBN}, shown in the first
16164 column of the @samp{info tasks} display.
16166 If you do not specify @samp{task @var{taskno}} when you set a
16167 breakpoint, the breakpoint applies to @emph{all} tasks of your
16170 You can use the @code{task} qualifier on conditional breakpoints as
16171 well; in this case, place @samp{task @var{taskno}} before the
16172 breakpoint condition (before the @code{if}).
16180 (@value{GDBP}) info tasks
16181 ID TID P-ID Pri State Name
16182 1 140022020 0 15 Child Activation Wait main_task
16183 2 140045060 1 15 Accept/Select Wait t2
16184 3 140044840 1 15 Runnable t1
16185 * 4 140056040 1 15 Runnable t3
16186 (@value{GDBP}) b 15 task 2
16187 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16188 (@value{GDBP}) cont
16193 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16195 (@value{GDBP}) info tasks
16196 ID TID P-ID Pri State Name
16197 1 140022020 0 15 Child Activation Wait main_task
16198 * 2 140045060 1 15 Runnable t2
16199 3 140044840 1 15 Runnable t1
16200 4 140056040 1 15 Delay Sleep t3
16204 @node Ada Tasks and Core Files
16205 @subsubsection Tasking Support when Debugging Core Files
16206 @cindex Ada tasking and core file debugging
16208 When inspecting a core file, as opposed to debugging a live program,
16209 tasking support may be limited or even unavailable, depending on
16210 the platform being used.
16211 For instance, on x86-linux, the list of tasks is available, but task
16212 switching is not supported.
16214 On certain platforms, the debugger needs to perform some
16215 memory writes in order to provide Ada tasking support. When inspecting
16216 a core file, this means that the core file must be opened with read-write
16217 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16218 Under these circumstances, you should make a backup copy of the core
16219 file before inspecting it with @value{GDBN}.
16221 @node Ravenscar Profile
16222 @subsubsection Tasking Support when using the Ravenscar Profile
16223 @cindex Ravenscar Profile
16225 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16226 specifically designed for systems with safety-critical real-time
16230 @kindex set ravenscar task-switching on
16231 @cindex task switching with program using Ravenscar Profile
16232 @item set ravenscar task-switching on
16233 Allows task switching when debugging a program that uses the Ravenscar
16234 Profile. This is the default.
16236 @kindex set ravenscar task-switching off
16237 @item set ravenscar task-switching off
16238 Turn off task switching when debugging a program that uses the Ravenscar
16239 Profile. This is mostly intended to disable the code that adds support
16240 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16241 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16242 To be effective, this command should be run before the program is started.
16244 @kindex show ravenscar task-switching
16245 @item show ravenscar task-switching
16246 Show whether it is possible to switch from task to task in a program
16247 using the Ravenscar Profile.
16252 @subsubsection Known Peculiarities of Ada Mode
16253 @cindex Ada, problems
16255 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16256 we know of several problems with and limitations of Ada mode in
16258 some of which will be fixed with planned future releases of the debugger
16259 and the GNU Ada compiler.
16263 Static constants that the compiler chooses not to materialize as objects in
16264 storage are invisible to the debugger.
16267 Named parameter associations in function argument lists are ignored (the
16268 argument lists are treated as positional).
16271 Many useful library packages are currently invisible to the debugger.
16274 Fixed-point arithmetic, conversions, input, and output is carried out using
16275 floating-point arithmetic, and may give results that only approximate those on
16279 The GNAT compiler never generates the prefix @code{Standard} for any of
16280 the standard symbols defined by the Ada language. @value{GDBN} knows about
16281 this: it will strip the prefix from names when you use it, and will never
16282 look for a name you have so qualified among local symbols, nor match against
16283 symbols in other packages or subprograms. If you have
16284 defined entities anywhere in your program other than parameters and
16285 local variables whose simple names match names in @code{Standard},
16286 GNAT's lack of qualification here can cause confusion. When this happens,
16287 you can usually resolve the confusion
16288 by qualifying the problematic names with package
16289 @code{Standard} explicitly.
16292 Older versions of the compiler sometimes generate erroneous debugging
16293 information, resulting in the debugger incorrectly printing the value
16294 of affected entities. In some cases, the debugger is able to work
16295 around an issue automatically. In other cases, the debugger is able
16296 to work around the issue, but the work-around has to be specifically
16299 @kindex set ada trust-PAD-over-XVS
16300 @kindex show ada trust-PAD-over-XVS
16303 @item set ada trust-PAD-over-XVS on
16304 Configure GDB to strictly follow the GNAT encoding when computing the
16305 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16306 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16307 a complete description of the encoding used by the GNAT compiler).
16308 This is the default.
16310 @item set ada trust-PAD-over-XVS off
16311 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16312 sometimes prints the wrong value for certain entities, changing @code{ada
16313 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16314 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16315 @code{off}, but this incurs a slight performance penalty, so it is
16316 recommended to leave this setting to @code{on} unless necessary.
16320 @cindex GNAT descriptive types
16321 @cindex GNAT encoding
16322 Internally, the debugger also relies on the compiler following a number
16323 of conventions known as the @samp{GNAT Encoding}, all documented in
16324 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16325 how the debugging information should be generated for certain types.
16326 In particular, this convention makes use of @dfn{descriptive types},
16327 which are artificial types generated purely to help the debugger.
16329 These encodings were defined at a time when the debugging information
16330 format used was not powerful enough to describe some of the more complex
16331 types available in Ada. Since DWARF allows us to express nearly all
16332 Ada features, the long-term goal is to slowly replace these descriptive
16333 types by their pure DWARF equivalent. To facilitate that transition,
16334 a new maintenance option is available to force the debugger to ignore
16335 those descriptive types. It allows the user to quickly evaluate how
16336 well @value{GDBN} works without them.
16340 @kindex maint ada set ignore-descriptive-types
16341 @item maintenance ada set ignore-descriptive-types [on|off]
16342 Control whether the debugger should ignore descriptive types.
16343 The default is not to ignore descriptives types (@code{off}).
16345 @kindex maint ada show ignore-descriptive-types
16346 @item maintenance ada show ignore-descriptive-types
16347 Show if descriptive types are ignored by @value{GDBN}.
16351 @node Unsupported Languages
16352 @section Unsupported Languages
16354 @cindex unsupported languages
16355 @cindex minimal language
16356 In addition to the other fully-supported programming languages,
16357 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16358 It does not represent a real programming language, but provides a set
16359 of capabilities close to what the C or assembly languages provide.
16360 This should allow most simple operations to be performed while debugging
16361 an application that uses a language currently not supported by @value{GDBN}.
16363 If the language is set to @code{auto}, @value{GDBN} will automatically
16364 select this language if the current frame corresponds to an unsupported
16368 @chapter Examining the Symbol Table
16370 The commands described in this chapter allow you to inquire about the
16371 symbols (names of variables, functions and types) defined in your
16372 program. This information is inherent in the text of your program and
16373 does not change as your program executes. @value{GDBN} finds it in your
16374 program's symbol table, in the file indicated when you started @value{GDBN}
16375 (@pxref{File Options, ,Choosing Files}), or by one of the
16376 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16378 @cindex symbol names
16379 @cindex names of symbols
16380 @cindex quoting names
16381 Occasionally, you may need to refer to symbols that contain unusual
16382 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16383 most frequent case is in referring to static variables in other
16384 source files (@pxref{Variables,,Program Variables}). File names
16385 are recorded in object files as debugging symbols, but @value{GDBN} would
16386 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16387 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16388 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16395 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16398 @cindex case-insensitive symbol names
16399 @cindex case sensitivity in symbol names
16400 @kindex set case-sensitive
16401 @item set case-sensitive on
16402 @itemx set case-sensitive off
16403 @itemx set case-sensitive auto
16404 Normally, when @value{GDBN} looks up symbols, it matches their names
16405 with case sensitivity determined by the current source language.
16406 Occasionally, you may wish to control that. The command @code{set
16407 case-sensitive} lets you do that by specifying @code{on} for
16408 case-sensitive matches or @code{off} for case-insensitive ones. If
16409 you specify @code{auto}, case sensitivity is reset to the default
16410 suitable for the source language. The default is case-sensitive
16411 matches for all languages except for Fortran, for which the default is
16412 case-insensitive matches.
16414 @kindex show case-sensitive
16415 @item show case-sensitive
16416 This command shows the current setting of case sensitivity for symbols
16419 @kindex set print type methods
16420 @item set print type methods
16421 @itemx set print type methods on
16422 @itemx set print type methods off
16423 Normally, when @value{GDBN} prints a class, it displays any methods
16424 declared in that class. You can control this behavior either by
16425 passing the appropriate flag to @code{ptype}, or using @command{set
16426 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16427 display the methods; this is the default. Specifying @code{off} will
16428 cause @value{GDBN} to omit the methods.
16430 @kindex show print type methods
16431 @item show print type methods
16432 This command shows the current setting of method display when printing
16435 @kindex set print type typedefs
16436 @item set print type typedefs
16437 @itemx set print type typedefs on
16438 @itemx set print type typedefs off
16440 Normally, when @value{GDBN} prints a class, it displays any typedefs
16441 defined in that class. You can control this behavior either by
16442 passing the appropriate flag to @code{ptype}, or using @command{set
16443 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16444 display the typedef definitions; this is the default. Specifying
16445 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16446 Note that this controls whether the typedef definition itself is
16447 printed, not whether typedef names are substituted when printing other
16450 @kindex show print type typedefs
16451 @item show print type typedefs
16452 This command shows the current setting of typedef display when
16455 @kindex info address
16456 @cindex address of a symbol
16457 @item info address @var{symbol}
16458 Describe where the data for @var{symbol} is stored. For a register
16459 variable, this says which register it is kept in. For a non-register
16460 local variable, this prints the stack-frame offset at which the variable
16463 Note the contrast with @samp{print &@var{symbol}}, which does not work
16464 at all for a register variable, and for a stack local variable prints
16465 the exact address of the current instantiation of the variable.
16467 @kindex info symbol
16468 @cindex symbol from address
16469 @cindex closest symbol and offset for an address
16470 @item info symbol @var{addr}
16471 Print the name of a symbol which is stored at the address @var{addr}.
16472 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16473 nearest symbol and an offset from it:
16476 (@value{GDBP}) info symbol 0x54320
16477 _initialize_vx + 396 in section .text
16481 This is the opposite of the @code{info address} command. You can use
16482 it to find out the name of a variable or a function given its address.
16484 For dynamically linked executables, the name of executable or shared
16485 library containing the symbol is also printed:
16488 (@value{GDBP}) info symbol 0x400225
16489 _start + 5 in section .text of /tmp/a.out
16490 (@value{GDBP}) info symbol 0x2aaaac2811cf
16491 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16496 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16497 Demangle @var{name}.
16498 If @var{language} is provided it is the name of the language to demangle
16499 @var{name} in. Otherwise @var{name} is demangled in the current language.
16501 The @samp{--} option specifies the end of options,
16502 and is useful when @var{name} begins with a dash.
16504 The parameter @code{demangle-style} specifies how to interpret the kind
16505 of mangling used. @xref{Print Settings}.
16508 @item whatis[/@var{flags}] [@var{arg}]
16509 Print the data type of @var{arg}, which can be either an expression
16510 or a name of a data type. With no argument, print the data type of
16511 @code{$}, the last value in the value history.
16513 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16514 is not actually evaluated, and any side-effecting operations (such as
16515 assignments or function calls) inside it do not take place.
16517 If @var{arg} is a variable or an expression, @code{whatis} prints its
16518 literal type as it is used in the source code. If the type was
16519 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16520 the data type underlying the @code{typedef}. If the type of the
16521 variable or the expression is a compound data type, such as
16522 @code{struct} or @code{class}, @code{whatis} never prints their
16523 fields or methods. It just prints the @code{struct}/@code{class}
16524 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16525 such a compound data type, use @code{ptype}.
16527 If @var{arg} is a type name that was defined using @code{typedef},
16528 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16529 Unrolling means that @code{whatis} will show the underlying type used
16530 in the @code{typedef} declaration of @var{arg}. However, if that
16531 underlying type is also a @code{typedef}, @code{whatis} will not
16534 For C code, the type names may also have the form @samp{class
16535 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16536 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16538 @var{flags} can be used to modify how the type is displayed.
16539 Available flags are:
16543 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16544 parameters and typedefs defined in a class when printing the class'
16545 members. The @code{/r} flag disables this.
16548 Do not print methods defined in the class.
16551 Print methods defined in the class. This is the default, but the flag
16552 exists in case you change the default with @command{set print type methods}.
16555 Do not print typedefs defined in the class. Note that this controls
16556 whether the typedef definition itself is printed, not whether typedef
16557 names are substituted when printing other types.
16560 Print typedefs defined in the class. This is the default, but the flag
16561 exists in case you change the default with @command{set print type typedefs}.
16565 @item ptype[/@var{flags}] [@var{arg}]
16566 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16567 detailed description of the type, instead of just the name of the type.
16568 @xref{Expressions, ,Expressions}.
16570 Contrary to @code{whatis}, @code{ptype} always unrolls any
16571 @code{typedef}s in its argument declaration, whether the argument is
16572 a variable, expression, or a data type. This means that @code{ptype}
16573 of a variable or an expression will not print literally its type as
16574 present in the source code---use @code{whatis} for that. @code{typedef}s at
16575 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16576 fields, methods and inner @code{class typedef}s of @code{struct}s,
16577 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16579 For example, for this variable declaration:
16582 typedef double real_t;
16583 struct complex @{ real_t real; double imag; @};
16584 typedef struct complex complex_t;
16586 real_t *real_pointer_var;
16590 the two commands give this output:
16594 (@value{GDBP}) whatis var
16596 (@value{GDBP}) ptype var
16597 type = struct complex @{
16601 (@value{GDBP}) whatis complex_t
16602 type = struct complex
16603 (@value{GDBP}) whatis struct complex
16604 type = struct complex
16605 (@value{GDBP}) ptype struct complex
16606 type = struct complex @{
16610 (@value{GDBP}) whatis real_pointer_var
16612 (@value{GDBP}) ptype real_pointer_var
16618 As with @code{whatis}, using @code{ptype} without an argument refers to
16619 the type of @code{$}, the last value in the value history.
16621 @cindex incomplete type
16622 Sometimes, programs use opaque data types or incomplete specifications
16623 of complex data structure. If the debug information included in the
16624 program does not allow @value{GDBN} to display a full declaration of
16625 the data type, it will say @samp{<incomplete type>}. For example,
16626 given these declarations:
16630 struct foo *fooptr;
16634 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16637 (@value{GDBP}) ptype foo
16638 $1 = <incomplete type>
16642 ``Incomplete type'' is C terminology for data types that are not
16643 completely specified.
16646 @item info types @var{regexp}
16648 Print a brief description of all types whose names match the regular
16649 expression @var{regexp} (or all types in your program, if you supply
16650 no argument). Each complete typename is matched as though it were a
16651 complete line; thus, @samp{i type value} gives information on all
16652 types in your program whose names include the string @code{value}, but
16653 @samp{i type ^value$} gives information only on types whose complete
16654 name is @code{value}.
16656 This command differs from @code{ptype} in two ways: first, like
16657 @code{whatis}, it does not print a detailed description; second, it
16658 lists all source files where a type is defined.
16660 @kindex info type-printers
16661 @item info type-printers
16662 Versions of @value{GDBN} that ship with Python scripting enabled may
16663 have ``type printers'' available. When using @command{ptype} or
16664 @command{whatis}, these printers are consulted when the name of a type
16665 is needed. @xref{Type Printing API}, for more information on writing
16668 @code{info type-printers} displays all the available type printers.
16670 @kindex enable type-printer
16671 @kindex disable type-printer
16672 @item enable type-printer @var{name}@dots{}
16673 @item disable type-printer @var{name}@dots{}
16674 These commands can be used to enable or disable type printers.
16677 @cindex local variables
16678 @item info scope @var{location}
16679 List all the variables local to a particular scope. This command
16680 accepts a @var{location} argument---a function name, a source line, or
16681 an address preceded by a @samp{*}, and prints all the variables local
16682 to the scope defined by that location. (@xref{Specify Location}, for
16683 details about supported forms of @var{location}.) For example:
16686 (@value{GDBP}) @b{info scope command_line_handler}
16687 Scope for command_line_handler:
16688 Symbol rl is an argument at stack/frame offset 8, length 4.
16689 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16690 Symbol linelength is in static storage at address 0x150a1c, length 4.
16691 Symbol p is a local variable in register $esi, length 4.
16692 Symbol p1 is a local variable in register $ebx, length 4.
16693 Symbol nline is a local variable in register $edx, length 4.
16694 Symbol repeat is a local variable at frame offset -8, length 4.
16698 This command is especially useful for determining what data to collect
16699 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16702 @kindex info source
16704 Show information about the current source file---that is, the source file for
16705 the function containing the current point of execution:
16708 the name of the source file, and the directory containing it,
16710 the directory it was compiled in,
16712 its length, in lines,
16714 which programming language it is written in,
16716 if the debug information provides it, the program that compiled the file
16717 (which may include, e.g., the compiler version and command line arguments),
16719 whether the executable includes debugging information for that file, and
16720 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16722 whether the debugging information includes information about
16723 preprocessor macros.
16727 @kindex info sources
16729 Print the names of all source files in your program for which there is
16730 debugging information, organized into two lists: files whose symbols
16731 have already been read, and files whose symbols will be read when needed.
16733 @kindex info functions
16734 @item info functions
16735 Print the names and data types of all defined functions.
16737 @item info functions @var{regexp}
16738 Print the names and data types of all defined functions
16739 whose names contain a match for regular expression @var{regexp}.
16740 Thus, @samp{info fun step} finds all functions whose names
16741 include @code{step}; @samp{info fun ^step} finds those whose names
16742 start with @code{step}. If a function name contains characters
16743 that conflict with the regular expression language (e.g.@:
16744 @samp{operator*()}), they may be quoted with a backslash.
16746 @kindex info variables
16747 @item info variables
16748 Print the names and data types of all variables that are defined
16749 outside of functions (i.e.@: excluding local variables).
16751 @item info variables @var{regexp}
16752 Print the names and data types of all variables (except for local
16753 variables) whose names contain a match for regular expression
16756 @kindex info classes
16757 @cindex Objective-C, classes and selectors
16759 @itemx info classes @var{regexp}
16760 Display all Objective-C classes in your program, or
16761 (with the @var{regexp} argument) all those matching a particular regular
16764 @kindex info selectors
16765 @item info selectors
16766 @itemx info selectors @var{regexp}
16767 Display all Objective-C selectors in your program, or
16768 (with the @var{regexp} argument) all those matching a particular regular
16772 This was never implemented.
16773 @kindex info methods
16775 @itemx info methods @var{regexp}
16776 The @code{info methods} command permits the user to examine all defined
16777 methods within C@t{++} program, or (with the @var{regexp} argument) a
16778 specific set of methods found in the various C@t{++} classes. Many
16779 C@t{++} classes provide a large number of methods. Thus, the output
16780 from the @code{ptype} command can be overwhelming and hard to use. The
16781 @code{info-methods} command filters the methods, printing only those
16782 which match the regular-expression @var{regexp}.
16785 @cindex opaque data types
16786 @kindex set opaque-type-resolution
16787 @item set opaque-type-resolution on
16788 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16789 declared as a pointer to a @code{struct}, @code{class}, or
16790 @code{union}---for example, @code{struct MyType *}---that is used in one
16791 source file although the full declaration of @code{struct MyType} is in
16792 another source file. The default is on.
16794 A change in the setting of this subcommand will not take effect until
16795 the next time symbols for a file are loaded.
16797 @item set opaque-type-resolution off
16798 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16799 is printed as follows:
16801 @{<no data fields>@}
16804 @kindex show opaque-type-resolution
16805 @item show opaque-type-resolution
16806 Show whether opaque types are resolved or not.
16808 @kindex set print symbol-loading
16809 @cindex print messages when symbols are loaded
16810 @item set print symbol-loading
16811 @itemx set print symbol-loading full
16812 @itemx set print symbol-loading brief
16813 @itemx set print symbol-loading off
16814 The @code{set print symbol-loading} command allows you to control the
16815 printing of messages when @value{GDBN} loads symbol information.
16816 By default a message is printed for the executable and one for each
16817 shared library, and normally this is what you want. However, when
16818 debugging apps with large numbers of shared libraries these messages
16820 When set to @code{brief} a message is printed for each executable,
16821 and when @value{GDBN} loads a collection of shared libraries at once
16822 it will only print one message regardless of the number of shared
16823 libraries. When set to @code{off} no messages are printed.
16825 @kindex show print symbol-loading
16826 @item show print symbol-loading
16827 Show whether messages will be printed when a @value{GDBN} command
16828 entered from the keyboard causes symbol information to be loaded.
16830 @kindex maint print symbols
16831 @cindex symbol dump
16832 @kindex maint print psymbols
16833 @cindex partial symbol dump
16834 @kindex maint print msymbols
16835 @cindex minimal symbol dump
16836 @item maint print symbols @var{filename}
16837 @itemx maint print psymbols @var{filename}
16838 @itemx maint print msymbols @var{filename}
16839 Write a dump of debugging symbol data into the file @var{filename}.
16840 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16841 symbols with debugging data are included. If you use @samp{maint print
16842 symbols}, @value{GDBN} includes all the symbols for which it has already
16843 collected full details: that is, @var{filename} reflects symbols for
16844 only those files whose symbols @value{GDBN} has read. You can use the
16845 command @code{info sources} to find out which files these are. If you
16846 use @samp{maint print psymbols} instead, the dump shows information about
16847 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16848 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16849 @samp{maint print msymbols} dumps just the minimal symbol information
16850 required for each object file from which @value{GDBN} has read some symbols.
16851 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16852 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16854 @kindex maint info symtabs
16855 @kindex maint info psymtabs
16856 @cindex listing @value{GDBN}'s internal symbol tables
16857 @cindex symbol tables, listing @value{GDBN}'s internal
16858 @cindex full symbol tables, listing @value{GDBN}'s internal
16859 @cindex partial symbol tables, listing @value{GDBN}'s internal
16860 @item maint info symtabs @r{[} @var{regexp} @r{]}
16861 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16863 List the @code{struct symtab} or @code{struct partial_symtab}
16864 structures whose names match @var{regexp}. If @var{regexp} is not
16865 given, list them all. The output includes expressions which you can
16866 copy into a @value{GDBN} debugging this one to examine a particular
16867 structure in more detail. For example:
16870 (@value{GDBP}) maint info psymtabs dwarf2read
16871 @{ objfile /home/gnu/build/gdb/gdb
16872 ((struct objfile *) 0x82e69d0)
16873 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16874 ((struct partial_symtab *) 0x8474b10)
16877 text addresses 0x814d3c8 -- 0x8158074
16878 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16879 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16880 dependencies (none)
16883 (@value{GDBP}) maint info symtabs
16887 We see that there is one partial symbol table whose filename contains
16888 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16889 and we see that @value{GDBN} has not read in any symtabs yet at all.
16890 If we set a breakpoint on a function, that will cause @value{GDBN} to
16891 read the symtab for the compilation unit containing that function:
16894 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16895 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16897 (@value{GDBP}) maint info symtabs
16898 @{ objfile /home/gnu/build/gdb/gdb
16899 ((struct objfile *) 0x82e69d0)
16900 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16901 ((struct symtab *) 0x86c1f38)
16904 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16905 linetable ((struct linetable *) 0x8370fa0)
16906 debugformat DWARF 2
16912 @kindex maint set symbol-cache-size
16913 @cindex symbol cache size
16914 @item maint set symbol-cache-size @var{size}
16915 Set the size of the symbol cache to @var{size}.
16916 The default size is intended to be good enough for debugging
16917 most applications. This option exists to allow for experimenting
16918 with different sizes.
16920 @kindex maint show symbol-cache-size
16921 @item maint show symbol-cache-size
16922 Show the size of the symbol cache.
16924 @kindex maint print symbol-cache
16925 @cindex symbol cache, printing its contents
16926 @item maint print symbol-cache
16927 Print the contents of the symbol cache.
16928 This is useful when debugging symbol cache issues.
16930 @kindex maint print symbol-cache-statistics
16931 @cindex symbol cache, printing usage statistics
16932 @item maint print symbol-cache-statistics
16933 Print symbol cache usage statistics.
16934 This helps determine how well the cache is being utilized.
16936 @kindex maint flush-symbol-cache
16937 @cindex symbol cache, flushing
16938 @item maint flush-symbol-cache
16939 Flush the contents of the symbol cache, all entries are removed.
16940 This command is useful when debugging the symbol cache.
16941 It is also useful when collecting performance data.
16946 @chapter Altering Execution
16948 Once you think you have found an error in your program, you might want to
16949 find out for certain whether correcting the apparent error would lead to
16950 correct results in the rest of the run. You can find the answer by
16951 experiment, using the @value{GDBN} features for altering execution of the
16954 For example, you can store new values into variables or memory
16955 locations, give your program a signal, restart it at a different
16956 address, or even return prematurely from a function.
16959 * Assignment:: Assignment to variables
16960 * Jumping:: Continuing at a different address
16961 * Signaling:: Giving your program a signal
16962 * Returning:: Returning from a function
16963 * Calling:: Calling your program's functions
16964 * Patching:: Patching your program
16965 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16969 @section Assignment to Variables
16972 @cindex setting variables
16973 To alter the value of a variable, evaluate an assignment expression.
16974 @xref{Expressions, ,Expressions}. For example,
16981 stores the value 4 into the variable @code{x}, and then prints the
16982 value of the assignment expression (which is 4).
16983 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16984 information on operators in supported languages.
16986 @kindex set variable
16987 @cindex variables, setting
16988 If you are not interested in seeing the value of the assignment, use the
16989 @code{set} command instead of the @code{print} command. @code{set} is
16990 really the same as @code{print} except that the expression's value is
16991 not printed and is not put in the value history (@pxref{Value History,
16992 ,Value History}). The expression is evaluated only for its effects.
16994 If the beginning of the argument string of the @code{set} command
16995 appears identical to a @code{set} subcommand, use the @code{set
16996 variable} command instead of just @code{set}. This command is identical
16997 to @code{set} except for its lack of subcommands. For example, if your
16998 program has a variable @code{width}, you get an error if you try to set
16999 a new value with just @samp{set width=13}, because @value{GDBN} has the
17000 command @code{set width}:
17003 (@value{GDBP}) whatis width
17005 (@value{GDBP}) p width
17007 (@value{GDBP}) set width=47
17008 Invalid syntax in expression.
17012 The invalid expression, of course, is @samp{=47}. In
17013 order to actually set the program's variable @code{width}, use
17016 (@value{GDBP}) set var width=47
17019 Because the @code{set} command has many subcommands that can conflict
17020 with the names of program variables, it is a good idea to use the
17021 @code{set variable} command instead of just @code{set}. For example, if
17022 your program has a variable @code{g}, you run into problems if you try
17023 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17024 the command @code{set gnutarget}, abbreviated @code{set g}:
17028 (@value{GDBP}) whatis g
17032 (@value{GDBP}) set g=4
17036 The program being debugged has been started already.
17037 Start it from the beginning? (y or n) y
17038 Starting program: /home/smith/cc_progs/a.out
17039 "/home/smith/cc_progs/a.out": can't open to read symbols:
17040 Invalid bfd target.
17041 (@value{GDBP}) show g
17042 The current BFD target is "=4".
17047 The program variable @code{g} did not change, and you silently set the
17048 @code{gnutarget} to an invalid value. In order to set the variable
17052 (@value{GDBP}) set var g=4
17055 @value{GDBN} allows more implicit conversions in assignments than C; you can
17056 freely store an integer value into a pointer variable or vice versa,
17057 and you can convert any structure to any other structure that is the
17058 same length or shorter.
17059 @comment FIXME: how do structs align/pad in these conversions?
17060 @comment /doc@cygnus.com 18dec1990
17062 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17063 construct to generate a value of specified type at a specified address
17064 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17065 to memory location @code{0x83040} as an integer (which implies a certain size
17066 and representation in memory), and
17069 set @{int@}0x83040 = 4
17073 stores the value 4 into that memory location.
17076 @section Continuing at a Different Address
17078 Ordinarily, when you continue your program, you do so at the place where
17079 it stopped, with the @code{continue} command. You can instead continue at
17080 an address of your own choosing, with the following commands:
17084 @kindex j @r{(@code{jump})}
17085 @item jump @var{location}
17086 @itemx j @var{location}
17087 Resume execution at @var{location}. Execution stops again immediately
17088 if there is a breakpoint there. @xref{Specify Location}, for a description
17089 of the different forms of @var{location}. It is common
17090 practice to use the @code{tbreak} command in conjunction with
17091 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17093 The @code{jump} command does not change the current stack frame, or
17094 the stack pointer, or the contents of any memory location or any
17095 register other than the program counter. If @var{location} is in
17096 a different function from the one currently executing, the results may
17097 be bizarre if the two functions expect different patterns of arguments or
17098 of local variables. For this reason, the @code{jump} command requests
17099 confirmation if the specified line is not in the function currently
17100 executing. However, even bizarre results are predictable if you are
17101 well acquainted with the machine-language code of your program.
17104 On many systems, you can get much the same effect as the @code{jump}
17105 command by storing a new value into the register @code{$pc}. The
17106 difference is that this does not start your program running; it only
17107 changes the address of where it @emph{will} run when you continue. For
17115 makes the next @code{continue} command or stepping command execute at
17116 address @code{0x485}, rather than at the address where your program stopped.
17117 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17119 The most common occasion to use the @code{jump} command is to back
17120 up---perhaps with more breakpoints set---over a portion of a program
17121 that has already executed, in order to examine its execution in more
17126 @section Giving your Program a Signal
17127 @cindex deliver a signal to a program
17131 @item signal @var{signal}
17132 Resume execution where your program is stopped, but immediately give it the
17133 signal @var{signal}. The @var{signal} can be the name or the number of a
17134 signal. For example, on many systems @code{signal 2} and @code{signal
17135 SIGINT} are both ways of sending an interrupt signal.
17137 Alternatively, if @var{signal} is zero, continue execution without
17138 giving a signal. This is useful when your program stopped on account of
17139 a signal and would ordinarily see the signal when resumed with the
17140 @code{continue} command; @samp{signal 0} causes it to resume without a
17143 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17144 delivered to the currently selected thread, not the thread that last
17145 reported a stop. This includes the situation where a thread was
17146 stopped due to a signal. So if you want to continue execution
17147 suppressing the signal that stopped a thread, you should select that
17148 same thread before issuing the @samp{signal 0} command. If you issue
17149 the @samp{signal 0} command with another thread as the selected one,
17150 @value{GDBN} detects that and asks for confirmation.
17152 Invoking the @code{signal} command is not the same as invoking the
17153 @code{kill} utility from the shell. Sending a signal with @code{kill}
17154 causes @value{GDBN} to decide what to do with the signal depending on
17155 the signal handling tables (@pxref{Signals}). The @code{signal} command
17156 passes the signal directly to your program.
17158 @code{signal} does not repeat when you press @key{RET} a second time
17159 after executing the command.
17161 @kindex queue-signal
17162 @item queue-signal @var{signal}
17163 Queue @var{signal} to be delivered immediately to the current thread
17164 when execution of the thread resumes. The @var{signal} can be the name or
17165 the number of a signal. For example, on many systems @code{signal 2} and
17166 @code{signal SIGINT} are both ways of sending an interrupt signal.
17167 The handling of the signal must be set to pass the signal to the program,
17168 otherwise @value{GDBN} will report an error.
17169 You can control the handling of signals from @value{GDBN} with the
17170 @code{handle} command (@pxref{Signals}).
17172 Alternatively, if @var{signal} is zero, any currently queued signal
17173 for the current thread is discarded and when execution resumes no signal
17174 will be delivered. This is useful when your program stopped on account
17175 of a signal and would ordinarily see the signal when resumed with the
17176 @code{continue} command.
17178 This command differs from the @code{signal} command in that the signal
17179 is just queued, execution is not resumed. And @code{queue-signal} cannot
17180 be used to pass a signal whose handling state has been set to @code{nopass}
17185 @xref{stepping into signal handlers}, for information on how stepping
17186 commands behave when the thread has a signal queued.
17189 @section Returning from a Function
17192 @cindex returning from a function
17195 @itemx return @var{expression}
17196 You can cancel execution of a function call with the @code{return}
17197 command. If you give an
17198 @var{expression} argument, its value is used as the function's return
17202 When you use @code{return}, @value{GDBN} discards the selected stack frame
17203 (and all frames within it). You can think of this as making the
17204 discarded frame return prematurely. If you wish to specify a value to
17205 be returned, give that value as the argument to @code{return}.
17207 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17208 Frame}), and any other frames inside of it, leaving its caller as the
17209 innermost remaining frame. That frame becomes selected. The
17210 specified value is stored in the registers used for returning values
17213 The @code{return} command does not resume execution; it leaves the
17214 program stopped in the state that would exist if the function had just
17215 returned. In contrast, the @code{finish} command (@pxref{Continuing
17216 and Stepping, ,Continuing and Stepping}) resumes execution until the
17217 selected stack frame returns naturally.
17219 @value{GDBN} needs to know how the @var{expression} argument should be set for
17220 the inferior. The concrete registers assignment depends on the OS ABI and the
17221 type being returned by the selected stack frame. For example it is common for
17222 OS ABI to return floating point values in FPU registers while integer values in
17223 CPU registers. Still some ABIs return even floating point values in CPU
17224 registers. Larger integer widths (such as @code{long long int}) also have
17225 specific placement rules. @value{GDBN} already knows the OS ABI from its
17226 current target so it needs to find out also the type being returned to make the
17227 assignment into the right register(s).
17229 Normally, the selected stack frame has debug info. @value{GDBN} will always
17230 use the debug info instead of the implicit type of @var{expression} when the
17231 debug info is available. For example, if you type @kbd{return -1}, and the
17232 function in the current stack frame is declared to return a @code{long long
17233 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17234 into a @code{long long int}:
17237 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17239 (@value{GDBP}) return -1
17240 Make func return now? (y or n) y
17241 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17242 43 printf ("result=%lld\n", func ());
17246 However, if the selected stack frame does not have a debug info, e.g., if the
17247 function was compiled without debug info, @value{GDBN} has to find out the type
17248 to return from user. Specifying a different type by mistake may set the value
17249 in different inferior registers than the caller code expects. For example,
17250 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17251 of a @code{long long int} result for a debug info less function (on 32-bit
17252 architectures). Therefore the user is required to specify the return type by
17253 an appropriate cast explicitly:
17256 Breakpoint 2, 0x0040050b in func ()
17257 (@value{GDBP}) return -1
17258 Return value type not available for selected stack frame.
17259 Please use an explicit cast of the value to return.
17260 (@value{GDBP}) return (long long int) -1
17261 Make selected stack frame return now? (y or n) y
17262 #0 0x00400526 in main ()
17267 @section Calling Program Functions
17270 @cindex calling functions
17271 @cindex inferior functions, calling
17272 @item print @var{expr}
17273 Evaluate the expression @var{expr} and display the resulting value.
17274 The expression may include calls to functions in the program being
17278 @item call @var{expr}
17279 Evaluate the expression @var{expr} without displaying @code{void}
17282 You can use this variant of the @code{print} command if you want to
17283 execute a function from your program that does not return anything
17284 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17285 with @code{void} returned values that @value{GDBN} will otherwise
17286 print. If the result is not void, it is printed and saved in the
17290 It is possible for the function you call via the @code{print} or
17291 @code{call} command to generate a signal (e.g., if there's a bug in
17292 the function, or if you passed it incorrect arguments). What happens
17293 in that case is controlled by the @code{set unwindonsignal} command.
17295 Similarly, with a C@t{++} program it is possible for the function you
17296 call via the @code{print} or @code{call} command to generate an
17297 exception that is not handled due to the constraints of the dummy
17298 frame. In this case, any exception that is raised in the frame, but has
17299 an out-of-frame exception handler will not be found. GDB builds a
17300 dummy-frame for the inferior function call, and the unwinder cannot
17301 seek for exception handlers outside of this dummy-frame. What happens
17302 in that case is controlled by the
17303 @code{set unwind-on-terminating-exception} command.
17306 @item set unwindonsignal
17307 @kindex set unwindonsignal
17308 @cindex unwind stack in called functions
17309 @cindex call dummy stack unwinding
17310 Set unwinding of the stack if a signal is received while in a function
17311 that @value{GDBN} called in the program being debugged. If set to on,
17312 @value{GDBN} unwinds the stack it created for the call and restores
17313 the context to what it was before the call. If set to off (the
17314 default), @value{GDBN} stops in the frame where the signal was
17317 @item show unwindonsignal
17318 @kindex show unwindonsignal
17319 Show the current setting of stack unwinding in the functions called by
17322 @item set unwind-on-terminating-exception
17323 @kindex set unwind-on-terminating-exception
17324 @cindex unwind stack in called functions with unhandled exceptions
17325 @cindex call dummy stack unwinding on unhandled exception.
17326 Set unwinding of the stack if a C@t{++} exception is raised, but left
17327 unhandled while in a function that @value{GDBN} called in the program being
17328 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17329 it created for the call and restores the context to what it was before
17330 the call. If set to off, @value{GDBN} the exception is delivered to
17331 the default C@t{++} exception handler and the inferior terminated.
17333 @item show unwind-on-terminating-exception
17334 @kindex show unwind-on-terminating-exception
17335 Show the current setting of stack unwinding in the functions called by
17340 @cindex weak alias functions
17341 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17342 for another function. In such case, @value{GDBN} might not pick up
17343 the type information, including the types of the function arguments,
17344 which causes @value{GDBN} to call the inferior function incorrectly.
17345 As a result, the called function will function erroneously and may
17346 even crash. A solution to that is to use the name of the aliased
17350 @section Patching Programs
17352 @cindex patching binaries
17353 @cindex writing into executables
17354 @cindex writing into corefiles
17356 By default, @value{GDBN} opens the file containing your program's
17357 executable code (or the corefile) read-only. This prevents accidental
17358 alterations to machine code; but it also prevents you from intentionally
17359 patching your program's binary.
17361 If you'd like to be able to patch the binary, you can specify that
17362 explicitly with the @code{set write} command. For example, you might
17363 want to turn on internal debugging flags, or even to make emergency
17369 @itemx set write off
17370 If you specify @samp{set write on}, @value{GDBN} opens executable and
17371 core files for both reading and writing; if you specify @kbd{set write
17372 off} (the default), @value{GDBN} opens them read-only.
17374 If you have already loaded a file, you must load it again (using the
17375 @code{exec-file} or @code{core-file} command) after changing @code{set
17376 write}, for your new setting to take effect.
17380 Display whether executable files and core files are opened for writing
17381 as well as reading.
17384 @node Compiling and Injecting Code
17385 @section Compiling and injecting code in @value{GDBN}
17386 @cindex injecting code
17387 @cindex writing into executables
17388 @cindex compiling code
17390 @value{GDBN} supports on-demand compilation and code injection into
17391 programs running under @value{GDBN}. GCC 5.0 or higher built with
17392 @file{libcc1.so} must be installed for this functionality to be enabled.
17393 This functionality is implemented with the following commands.
17396 @kindex compile code
17397 @item compile code @var{source-code}
17398 @itemx compile code -raw @var{--} @var{source-code}
17399 Compile @var{source-code} with the compiler language found as the current
17400 language in @value{GDBN} (@pxref{Languages}). If compilation and
17401 injection is not supported with the current language specified in
17402 @value{GDBN}, or the compiler does not support this feature, an error
17403 message will be printed. If @var{source-code} compiles and links
17404 successfully, @value{GDBN} will load the object-code emitted,
17405 and execute it within the context of the currently selected inferior.
17406 It is important to note that the compiled code is executed immediately.
17407 After execution, the compiled code is removed from @value{GDBN} and any
17408 new types or variables you have defined will be deleted.
17410 The command allows you to specify @var{source-code} in two ways.
17411 The simplest method is to provide a single line of code to the command.
17415 compile code printf ("hello world\n");
17418 If you specify options on the command line as well as source code, they
17419 may conflict. The @samp{--} delimiter can be used to separate options
17420 from actual source code. E.g.:
17423 compile code -r -- printf ("hello world\n");
17426 Alternatively you can enter source code as multiple lines of text. To
17427 enter this mode, invoke the @samp{compile code} command without any text
17428 following the command. This will start the multiple-line editor and
17429 allow you to type as many lines of source code as required. When you
17430 have completed typing, enter @samp{end} on its own line to exit the
17435 >printf ("hello\n");
17436 >printf ("world\n");
17440 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17441 provided @var{source-code} in a callable scope. In this case, you must
17442 specify the entry point of the code by defining a function named
17443 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17444 inferior. Using @samp{-raw} option may be needed for example when
17445 @var{source-code} requires @samp{#include} lines which may conflict with
17446 inferior symbols otherwise.
17448 @kindex compile file
17449 @item compile file @var{filename}
17450 @itemx compile file -raw @var{filename}
17451 Like @code{compile code}, but take the source code from @var{filename}.
17454 compile file /home/user/example.c
17459 @item compile print @var{expr}
17460 @itemx compile print /@var{f} @var{expr}
17461 Compile and execute @var{expr} with the compiler language found as the
17462 current language in @value{GDBN} (@pxref{Languages}). By default the
17463 value of @var{expr} is printed in a format appropriate to its data type;
17464 you can choose a different format by specifying @samp{/@var{f}}, where
17465 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17468 @item compile print
17469 @itemx compile print /@var{f}
17470 @cindex reprint the last value
17471 Alternatively you can enter the expression (source code producing it) as
17472 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17473 command without any text following the command. This will start the
17474 multiple-line editor.
17478 The process of compiling and injecting the code can be inspected using:
17481 @anchor{set debug compile}
17482 @item set debug compile
17483 @cindex compile command debugging info
17484 Turns on or off display of @value{GDBN} process of compiling and
17485 injecting the code. The default is off.
17487 @item show debug compile
17488 Displays the current state of displaying @value{GDBN} process of
17489 compiling and injecting the code.
17492 @subsection Compilation options for the @code{compile} command
17494 @value{GDBN} needs to specify the right compilation options for the code
17495 to be injected, in part to make its ABI compatible with the inferior
17496 and in part to make the injected code compatible with @value{GDBN}'s
17500 The options used, in increasing precedence:
17503 @item target architecture and OS options (@code{gdbarch})
17504 These options depend on target processor type and target operating
17505 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17506 (@code{-m64}) compilation option.
17508 @item compilation options recorded in the target
17509 @value{NGCC} (since version 4.7) stores the options used for compilation
17510 into @code{DW_AT_producer} part of DWARF debugging information according
17511 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17512 explicitly specify @code{-g} during inferior compilation otherwise
17513 @value{NGCC} produces no DWARF. This feature is only relevant for
17514 platforms where @code{-g} produces DWARF by default, otherwise one may
17515 try to enforce DWARF by using @code{-gdwarf-4}.
17517 @item compilation options set by @code{set compile-args}
17521 You can override compilation options using the following command:
17524 @item set compile-args
17525 @cindex compile command options override
17526 Set compilation options used for compiling and injecting code with the
17527 @code{compile} commands. These options override any conflicting ones
17528 from the target architecture and/or options stored during inferior
17531 @item show compile-args
17532 Displays the current state of compilation options override.
17533 This does not show all the options actually used during compilation,
17534 use @ref{set debug compile} for that.
17537 @subsection Caveats when using the @code{compile} command
17539 There are a few caveats to keep in mind when using the @code{compile}
17540 command. As the caveats are different per language, the table below
17541 highlights specific issues on a per language basis.
17544 @item C code examples and caveats
17545 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17546 attempt to compile the source code with a @samp{C} compiler. The source
17547 code provided to the @code{compile} command will have much the same
17548 access to variables and types as it normally would if it were part of
17549 the program currently being debugged in @value{GDBN}.
17551 Below is a sample program that forms the basis of the examples that
17552 follow. This program has been compiled and loaded into @value{GDBN},
17553 much like any other normal debugging session.
17556 void function1 (void)
17559 printf ("function 1\n");
17562 void function2 (void)
17577 For the purposes of the examples in this section, the program above has
17578 been compiled, loaded into @value{GDBN}, stopped at the function
17579 @code{main}, and @value{GDBN} is awaiting input from the user.
17581 To access variables and types for any program in @value{GDBN}, the
17582 program must be compiled and packaged with debug information. The
17583 @code{compile} command is not an exception to this rule. Without debug
17584 information, you can still use the @code{compile} command, but you will
17585 be very limited in what variables and types you can access.
17587 So with that in mind, the example above has been compiled with debug
17588 information enabled. The @code{compile} command will have access to
17589 all variables and types (except those that may have been optimized
17590 out). Currently, as @value{GDBN} has stopped the program in the
17591 @code{main} function, the @code{compile} command would have access to
17592 the variable @code{k}. You could invoke the @code{compile} command
17593 and type some source code to set the value of @code{k}. You can also
17594 read it, or do anything with that variable you would normally do in
17595 @code{C}. Be aware that changes to inferior variables in the
17596 @code{compile} command are persistent. In the following example:
17599 compile code k = 3;
17603 the variable @code{k} is now 3. It will retain that value until
17604 something else in the example program changes it, or another
17605 @code{compile} command changes it.
17607 Normal scope and access rules apply to source code compiled and
17608 injected by the @code{compile} command. In the example, the variables
17609 @code{j} and @code{k} are not accessible yet, because the program is
17610 currently stopped in the @code{main} function, where these variables
17611 are not in scope. Therefore, the following command
17614 compile code j = 3;
17618 will result in a compilation error message.
17620 Once the program is continued, execution will bring these variables in
17621 scope, and they will become accessible; then the code you specify via
17622 the @code{compile} command will be able to access them.
17624 You can create variables and types with the @code{compile} command as
17625 part of your source code. Variables and types that are created as part
17626 of the @code{compile} command are not visible to the rest of the program for
17627 the duration of its run. This example is valid:
17630 compile code int ff = 5; printf ("ff is %d\n", ff);
17633 However, if you were to type the following into @value{GDBN} after that
17634 command has completed:
17637 compile code printf ("ff is %d\n'', ff);
17641 a compiler error would be raised as the variable @code{ff} no longer
17642 exists. Object code generated and injected by the @code{compile}
17643 command is removed when its execution ends. Caution is advised
17644 when assigning to program variables values of variables created by the
17645 code submitted to the @code{compile} command. This example is valid:
17648 compile code int ff = 5; k = ff;
17651 The value of the variable @code{ff} is assigned to @code{k}. The variable
17652 @code{k} does not require the existence of @code{ff} to maintain the value
17653 it has been assigned. However, pointers require particular care in
17654 assignment. If the source code compiled with the @code{compile} command
17655 changed the address of a pointer in the example program, perhaps to a
17656 variable created in the @code{compile} command, that pointer would point
17657 to an invalid location when the command exits. The following example
17658 would likely cause issues with your debugged program:
17661 compile code int ff = 5; p = &ff;
17664 In this example, @code{p} would point to @code{ff} when the
17665 @code{compile} command is executing the source code provided to it.
17666 However, as variables in the (example) program persist with their
17667 assigned values, the variable @code{p} would point to an invalid
17668 location when the command exists. A general rule should be followed
17669 in that you should either assign @code{NULL} to any assigned pointers,
17670 or restore a valid location to the pointer before the command exits.
17672 Similar caution must be exercised with any structs, unions, and typedefs
17673 defined in @code{compile} command. Types defined in the @code{compile}
17674 command will no longer be available in the next @code{compile} command.
17675 Therefore, if you cast a variable to a type defined in the
17676 @code{compile} command, care must be taken to ensure that any future
17677 need to resolve the type can be achieved.
17680 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17681 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17682 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17683 Compilation failed.
17684 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17688 Variables that have been optimized away by the compiler are not
17689 accessible to the code submitted to the @code{compile} command.
17690 Access to those variables will generate a compiler error which @value{GDBN}
17691 will print to the console.
17694 @subsection Compiler search for the @code{compile} command
17696 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17697 may not be obvious for remote targets of different architecture than where
17698 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17699 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17700 command @code{set environment}). @xref{Environment}. @code{PATH} on
17701 @value{GDBN} host is searched for @value{NGCC} binary matching the
17702 target architecture and operating system.
17704 Specifically @code{PATH} is searched for binaries matching regular expression
17705 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17706 debugged. @var{arch} is processor name --- multiarch is supported, so for
17707 example both @code{i386} and @code{x86_64} targets look for pattern
17708 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17709 for pattern @code{s390x?}. @var{os} is currently supported only for
17710 pattern @code{linux(-gnu)?}.
17713 @chapter @value{GDBN} Files
17715 @value{GDBN} needs to know the file name of the program to be debugged,
17716 both in order to read its symbol table and in order to start your
17717 program. To debug a core dump of a previous run, you must also tell
17718 @value{GDBN} the name of the core dump file.
17721 * Files:: Commands to specify files
17722 * File Caching:: Information about @value{GDBN}'s file caching
17723 * Separate Debug Files:: Debugging information in separate files
17724 * MiniDebugInfo:: Debugging information in a special section
17725 * Index Files:: Index files speed up GDB
17726 * Symbol Errors:: Errors reading symbol files
17727 * Data Files:: GDB data files
17731 @section Commands to Specify Files
17733 @cindex symbol table
17734 @cindex core dump file
17736 You may want to specify executable and core dump file names. The usual
17737 way to do this is at start-up time, using the arguments to
17738 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17739 Out of @value{GDBN}}).
17741 Occasionally it is necessary to change to a different file during a
17742 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17743 specify a file you want to use. Or you are debugging a remote target
17744 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17745 Program}). In these situations the @value{GDBN} commands to specify
17746 new files are useful.
17749 @cindex executable file
17751 @item file @var{filename}
17752 Use @var{filename} as the program to be debugged. It is read for its
17753 symbols and for the contents of pure memory. It is also the program
17754 executed when you use the @code{run} command. If you do not specify a
17755 directory and the file is not found in the @value{GDBN} working directory,
17756 @value{GDBN} uses the environment variable @code{PATH} as a list of
17757 directories to search, just as the shell does when looking for a program
17758 to run. You can change the value of this variable, for both @value{GDBN}
17759 and your program, using the @code{path} command.
17761 @cindex unlinked object files
17762 @cindex patching object files
17763 You can load unlinked object @file{.o} files into @value{GDBN} using
17764 the @code{file} command. You will not be able to ``run'' an object
17765 file, but you can disassemble functions and inspect variables. Also,
17766 if the underlying BFD functionality supports it, you could use
17767 @kbd{gdb -write} to patch object files using this technique. Note
17768 that @value{GDBN} can neither interpret nor modify relocations in this
17769 case, so branches and some initialized variables will appear to go to
17770 the wrong place. But this feature is still handy from time to time.
17773 @code{file} with no argument makes @value{GDBN} discard any information it
17774 has on both executable file and the symbol table.
17777 @item exec-file @r{[} @var{filename} @r{]}
17778 Specify that the program to be run (but not the symbol table) is found
17779 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17780 if necessary to locate your program. Omitting @var{filename} means to
17781 discard information on the executable file.
17783 @kindex symbol-file
17784 @item symbol-file @r{[} @var{filename} @r{]}
17785 Read symbol table information from file @var{filename}. @code{PATH} is
17786 searched when necessary. Use the @code{file} command to get both symbol
17787 table and program to run from the same file.
17789 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17790 program's symbol table.
17792 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17793 some breakpoints and auto-display expressions. This is because they may
17794 contain pointers to the internal data recording symbols and data types,
17795 which are part of the old symbol table data being discarded inside
17798 @code{symbol-file} does not repeat if you press @key{RET} again after
17801 When @value{GDBN} is configured for a particular environment, it
17802 understands debugging information in whatever format is the standard
17803 generated for that environment; you may use either a @sc{gnu} compiler, or
17804 other compilers that adhere to the local conventions.
17805 Best results are usually obtained from @sc{gnu} compilers; for example,
17806 using @code{@value{NGCC}} you can generate debugging information for
17809 For most kinds of object files, with the exception of old SVR3 systems
17810 using COFF, the @code{symbol-file} command does not normally read the
17811 symbol table in full right away. Instead, it scans the symbol table
17812 quickly to find which source files and which symbols are present. The
17813 details are read later, one source file at a time, as they are needed.
17815 The purpose of this two-stage reading strategy is to make @value{GDBN}
17816 start up faster. For the most part, it is invisible except for
17817 occasional pauses while the symbol table details for a particular source
17818 file are being read. (The @code{set verbose} command can turn these
17819 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17820 Warnings and Messages}.)
17822 We have not implemented the two-stage strategy for COFF yet. When the
17823 symbol table is stored in COFF format, @code{symbol-file} reads the
17824 symbol table data in full right away. Note that ``stabs-in-COFF''
17825 still does the two-stage strategy, since the debug info is actually
17829 @cindex reading symbols immediately
17830 @cindex symbols, reading immediately
17831 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17832 @itemx file @r{[} -readnow @r{]} @var{filename}
17833 You can override the @value{GDBN} two-stage strategy for reading symbol
17834 tables by using the @samp{-readnow} option with any of the commands that
17835 load symbol table information, if you want to be sure @value{GDBN} has the
17836 entire symbol table available.
17838 @c FIXME: for now no mention of directories, since this seems to be in
17839 @c flux. 13mar1992 status is that in theory GDB would look either in
17840 @c current dir or in same dir as myprog; but issues like competing
17841 @c GDB's, or clutter in system dirs, mean that in practice right now
17842 @c only current dir is used. FFish says maybe a special GDB hierarchy
17843 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17847 @item core-file @r{[}@var{filename}@r{]}
17849 Specify the whereabouts of a core dump file to be used as the ``contents
17850 of memory''. Traditionally, core files contain only some parts of the
17851 address space of the process that generated them; @value{GDBN} can access the
17852 executable file itself for other parts.
17854 @code{core-file} with no argument specifies that no core file is
17857 Note that the core file is ignored when your program is actually running
17858 under @value{GDBN}. So, if you have been running your program and you
17859 wish to debug a core file instead, you must kill the subprocess in which
17860 the program is running. To do this, use the @code{kill} command
17861 (@pxref{Kill Process, ,Killing the Child Process}).
17863 @kindex add-symbol-file
17864 @cindex dynamic linking
17865 @item add-symbol-file @var{filename} @var{address}
17866 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17867 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17868 The @code{add-symbol-file} command reads additional symbol table
17869 information from the file @var{filename}. You would use this command
17870 when @var{filename} has been dynamically loaded (by some other means)
17871 into the program that is running. The @var{address} should give the memory
17872 address at which the file has been loaded; @value{GDBN} cannot figure
17873 this out for itself. You can additionally specify an arbitrary number
17874 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17875 section name and base address for that section. You can specify any
17876 @var{address} as an expression.
17878 The symbol table of the file @var{filename} is added to the symbol table
17879 originally read with the @code{symbol-file} command. You can use the
17880 @code{add-symbol-file} command any number of times; the new symbol data
17881 thus read is kept in addition to the old.
17883 Changes can be reverted using the command @code{remove-symbol-file}.
17885 @cindex relocatable object files, reading symbols from
17886 @cindex object files, relocatable, reading symbols from
17887 @cindex reading symbols from relocatable object files
17888 @cindex symbols, reading from relocatable object files
17889 @cindex @file{.o} files, reading symbols from
17890 Although @var{filename} is typically a shared library file, an
17891 executable file, or some other object file which has been fully
17892 relocated for loading into a process, you can also load symbolic
17893 information from relocatable @file{.o} files, as long as:
17897 the file's symbolic information refers only to linker symbols defined in
17898 that file, not to symbols defined by other object files,
17900 every section the file's symbolic information refers to has actually
17901 been loaded into the inferior, as it appears in the file, and
17903 you can determine the address at which every section was loaded, and
17904 provide these to the @code{add-symbol-file} command.
17908 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17909 relocatable files into an already running program; such systems
17910 typically make the requirements above easy to meet. However, it's
17911 important to recognize that many native systems use complex link
17912 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17913 assembly, for example) that make the requirements difficult to meet. In
17914 general, one cannot assume that using @code{add-symbol-file} to read a
17915 relocatable object file's symbolic information will have the same effect
17916 as linking the relocatable object file into the program in the normal
17919 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17921 @kindex remove-symbol-file
17922 @item remove-symbol-file @var{filename}
17923 @item remove-symbol-file -a @var{address}
17924 Remove a symbol file added via the @code{add-symbol-file} command. The
17925 file to remove can be identified by its @var{filename} or by an @var{address}
17926 that lies within the boundaries of this symbol file in memory. Example:
17929 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17930 add symbol table from file "/home/user/gdb/mylib.so" at
17931 .text_addr = 0x7ffff7ff9480
17933 Reading symbols from /home/user/gdb/mylib.so...done.
17934 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17935 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17940 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17942 @kindex add-symbol-file-from-memory
17943 @cindex @code{syscall DSO}
17944 @cindex load symbols from memory
17945 @item add-symbol-file-from-memory @var{address}
17946 Load symbols from the given @var{address} in a dynamically loaded
17947 object file whose image is mapped directly into the inferior's memory.
17948 For example, the Linux kernel maps a @code{syscall DSO} into each
17949 process's address space; this DSO provides kernel-specific code for
17950 some system calls. The argument can be any expression whose
17951 evaluation yields the address of the file's shared object file header.
17952 For this command to work, you must have used @code{symbol-file} or
17953 @code{exec-file} commands in advance.
17956 @item section @var{section} @var{addr}
17957 The @code{section} command changes the base address of the named
17958 @var{section} of the exec file to @var{addr}. This can be used if the
17959 exec file does not contain section addresses, (such as in the
17960 @code{a.out} format), or when the addresses specified in the file
17961 itself are wrong. Each section must be changed separately. The
17962 @code{info files} command, described below, lists all the sections and
17966 @kindex info target
17969 @code{info files} and @code{info target} are synonymous; both print the
17970 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17971 including the names of the executable and core dump files currently in
17972 use by @value{GDBN}, and the files from which symbols were loaded. The
17973 command @code{help target} lists all possible targets rather than
17976 @kindex maint info sections
17977 @item maint info sections
17978 Another command that can give you extra information about program sections
17979 is @code{maint info sections}. In addition to the section information
17980 displayed by @code{info files}, this command displays the flags and file
17981 offset of each section in the executable and core dump files. In addition,
17982 @code{maint info sections} provides the following command options (which
17983 may be arbitrarily combined):
17987 Display sections for all loaded object files, including shared libraries.
17988 @item @var{sections}
17989 Display info only for named @var{sections}.
17990 @item @var{section-flags}
17991 Display info only for sections for which @var{section-flags} are true.
17992 The section flags that @value{GDBN} currently knows about are:
17995 Section will have space allocated in the process when loaded.
17996 Set for all sections except those containing debug information.
17998 Section will be loaded from the file into the child process memory.
17999 Set for pre-initialized code and data, clear for @code{.bss} sections.
18001 Section needs to be relocated before loading.
18003 Section cannot be modified by the child process.
18005 Section contains executable code only.
18007 Section contains data only (no executable code).
18009 Section will reside in ROM.
18011 Section contains data for constructor/destructor lists.
18013 Section is not empty.
18015 An instruction to the linker to not output the section.
18016 @item COFF_SHARED_LIBRARY
18017 A notification to the linker that the section contains
18018 COFF shared library information.
18020 Section contains common symbols.
18023 @kindex set trust-readonly-sections
18024 @cindex read-only sections
18025 @item set trust-readonly-sections on
18026 Tell @value{GDBN} that readonly sections in your object file
18027 really are read-only (i.e.@: that their contents will not change).
18028 In that case, @value{GDBN} can fetch values from these sections
18029 out of the object file, rather than from the target program.
18030 For some targets (notably embedded ones), this can be a significant
18031 enhancement to debugging performance.
18033 The default is off.
18035 @item set trust-readonly-sections off
18036 Tell @value{GDBN} not to trust readonly sections. This means that
18037 the contents of the section might change while the program is running,
18038 and must therefore be fetched from the target when needed.
18040 @item show trust-readonly-sections
18041 Show the current setting of trusting readonly sections.
18044 All file-specifying commands allow both absolute and relative file names
18045 as arguments. @value{GDBN} always converts the file name to an absolute file
18046 name and remembers it that way.
18048 @cindex shared libraries
18049 @anchor{Shared Libraries}
18050 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18051 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18052 DSBT (TIC6X) shared libraries.
18054 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18055 shared libraries. @xref{Expat}.
18057 @value{GDBN} automatically loads symbol definitions from shared libraries
18058 when you use the @code{run} command, or when you examine a core file.
18059 (Before you issue the @code{run} command, @value{GDBN} does not understand
18060 references to a function in a shared library, however---unless you are
18061 debugging a core file).
18063 @c FIXME: some @value{GDBN} release may permit some refs to undef
18064 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18065 @c FIXME...lib; check this from time to time when updating manual
18067 There are times, however, when you may wish to not automatically load
18068 symbol definitions from shared libraries, such as when they are
18069 particularly large or there are many of them.
18071 To control the automatic loading of shared library symbols, use the
18075 @kindex set auto-solib-add
18076 @item set auto-solib-add @var{mode}
18077 If @var{mode} is @code{on}, symbols from all shared object libraries
18078 will be loaded automatically when the inferior begins execution, you
18079 attach to an independently started inferior, or when the dynamic linker
18080 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18081 is @code{off}, symbols must be loaded manually, using the
18082 @code{sharedlibrary} command. The default value is @code{on}.
18084 @cindex memory used for symbol tables
18085 If your program uses lots of shared libraries with debug info that
18086 takes large amounts of memory, you can decrease the @value{GDBN}
18087 memory footprint by preventing it from automatically loading the
18088 symbols from shared libraries. To that end, type @kbd{set
18089 auto-solib-add off} before running the inferior, then load each
18090 library whose debug symbols you do need with @kbd{sharedlibrary
18091 @var{regexp}}, where @var{regexp} is a regular expression that matches
18092 the libraries whose symbols you want to be loaded.
18094 @kindex show auto-solib-add
18095 @item show auto-solib-add
18096 Display the current autoloading mode.
18099 @cindex load shared library
18100 To explicitly load shared library symbols, use the @code{sharedlibrary}
18104 @kindex info sharedlibrary
18106 @item info share @var{regex}
18107 @itemx info sharedlibrary @var{regex}
18108 Print the names of the shared libraries which are currently loaded
18109 that match @var{regex}. If @var{regex} is omitted then print
18110 all shared libraries that are loaded.
18113 @item info dll @var{regex}
18114 This is an alias of @code{info sharedlibrary}.
18116 @kindex sharedlibrary
18118 @item sharedlibrary @var{regex}
18119 @itemx share @var{regex}
18120 Load shared object library symbols for files matching a
18121 Unix regular expression.
18122 As with files loaded automatically, it only loads shared libraries
18123 required by your program for a core file or after typing @code{run}. If
18124 @var{regex} is omitted all shared libraries required by your program are
18127 @item nosharedlibrary
18128 @kindex nosharedlibrary
18129 @cindex unload symbols from shared libraries
18130 Unload all shared object library symbols. This discards all symbols
18131 that have been loaded from all shared libraries. Symbols from shared
18132 libraries that were loaded by explicit user requests are not
18136 Sometimes you may wish that @value{GDBN} stops and gives you control
18137 when any of shared library events happen. The best way to do this is
18138 to use @code{catch load} and @code{catch unload} (@pxref{Set
18141 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18142 command for this. This command exists for historical reasons. It is
18143 less useful than setting a catchpoint, because it does not allow for
18144 conditions or commands as a catchpoint does.
18147 @item set stop-on-solib-events
18148 @kindex set stop-on-solib-events
18149 This command controls whether @value{GDBN} should give you control
18150 when the dynamic linker notifies it about some shared library event.
18151 The most common event of interest is loading or unloading of a new
18154 @item show stop-on-solib-events
18155 @kindex show stop-on-solib-events
18156 Show whether @value{GDBN} stops and gives you control when shared
18157 library events happen.
18160 Shared libraries are also supported in many cross or remote debugging
18161 configurations. @value{GDBN} needs to have access to the target's libraries;
18162 this can be accomplished either by providing copies of the libraries
18163 on the host system, or by asking @value{GDBN} to automatically retrieve the
18164 libraries from the target. If copies of the target libraries are
18165 provided, they need to be the same as the target libraries, although the
18166 copies on the target can be stripped as long as the copies on the host are
18169 @cindex where to look for shared libraries
18170 For remote debugging, you need to tell @value{GDBN} where the target
18171 libraries are, so that it can load the correct copies---otherwise, it
18172 may try to load the host's libraries. @value{GDBN} has two variables
18173 to specify the search directories for target libraries.
18176 @cindex prefix for executable and shared library file names
18177 @cindex system root, alternate
18178 @kindex set solib-absolute-prefix
18179 @kindex set sysroot
18180 @item set sysroot @var{path}
18181 Use @var{path} as the system root for the program being debugged. Any
18182 absolute shared library paths will be prefixed with @var{path}; many
18183 runtime loaders store the absolute paths to the shared library in the
18184 target program's memory. When starting processes remotely, and when
18185 attaching to already-running processes (local or remote), their
18186 executable filenames will be prefixed with @var{path} if reported to
18187 @value{GDBN} as absolute by the operating system. If you use
18188 @code{set sysroot} to find executables and shared libraries, they need
18189 to be laid out in the same way that they are on the target, with
18190 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18193 If @var{path} starts with the sequence @file{target:} and the target
18194 system is remote then @value{GDBN} will retrieve the target binaries
18195 from the remote system. This is only supported when using a remote
18196 target that supports the @code{remote get} command (@pxref{File
18197 Transfer,,Sending files to a remote system}). The part of @var{path}
18198 following the initial @file{target:} (if present) is used as system
18199 root prefix on the remote file system. If @var{path} starts with the
18200 sequence @file{remote:} this is converted to the sequence
18201 @file{target:} by @code{set sysroot}@footnote{Historically the
18202 functionality to retrieve binaries from the remote system was
18203 provided by prefixing @var{path} with @file{remote:}}. If you want
18204 to specify a local system root using a directory that happens to be
18205 named @file{target:} or @file{remote:}, you need to use some
18206 equivalent variant of the name like @file{./target:}.
18208 For targets with an MS-DOS based filesystem, such as MS-Windows and
18209 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18210 absolute file name with @var{path}. But first, on Unix hosts,
18211 @value{GDBN} converts all backslash directory separators into forward
18212 slashes, because the backslash is not a directory separator on Unix:
18215 c:\foo\bar.dll @result{} c:/foo/bar.dll
18218 Then, @value{GDBN} attempts prefixing the target file name with
18219 @var{path}, and looks for the resulting file name in the host file
18223 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18226 If that does not find the binary, @value{GDBN} tries removing
18227 the @samp{:} character from the drive spec, both for convenience, and,
18228 for the case of the host file system not supporting file names with
18232 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18235 This makes it possible to have a system root that mirrors a target
18236 with more than one drive. E.g., you may want to setup your local
18237 copies of the target system shared libraries like so (note @samp{c} vs
18241 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18242 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18243 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18247 and point the system root at @file{/path/to/sysroot}, so that
18248 @value{GDBN} can find the correct copies of both
18249 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18251 If that still does not find the binary, @value{GDBN} tries
18252 removing the whole drive spec from the target file name:
18255 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18258 This last lookup makes it possible to not care about the drive name,
18259 if you don't want or need to.
18261 The @code{set solib-absolute-prefix} command is an alias for @code{set
18264 @cindex default system root
18265 @cindex @samp{--with-sysroot}
18266 You can set the default system root by using the configure-time
18267 @samp{--with-sysroot} option. If the system root is inside
18268 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18269 @samp{--exec-prefix}), then the default system root will be updated
18270 automatically if the installed @value{GDBN} is moved to a new
18273 @kindex show sysroot
18275 Display the current executable and shared library prefix.
18277 @kindex set solib-search-path
18278 @item set solib-search-path @var{path}
18279 If this variable is set, @var{path} is a colon-separated list of
18280 directories to search for shared libraries. @samp{solib-search-path}
18281 is used after @samp{sysroot} fails to locate the library, or if the
18282 path to the library is relative instead of absolute. If you want to
18283 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18284 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18285 finding your host's libraries. @samp{sysroot} is preferred; setting
18286 it to a nonexistent directory may interfere with automatic loading
18287 of shared library symbols.
18289 @kindex show solib-search-path
18290 @item show solib-search-path
18291 Display the current shared library search path.
18293 @cindex DOS file-name semantics of file names.
18294 @kindex set target-file-system-kind (unix|dos-based|auto)
18295 @kindex show target-file-system-kind
18296 @item set target-file-system-kind @var{kind}
18297 Set assumed file system kind for target reported file names.
18299 Shared library file names as reported by the target system may not
18300 make sense as is on the system @value{GDBN} is running on. For
18301 example, when remote debugging a target that has MS-DOS based file
18302 system semantics, from a Unix host, the target may be reporting to
18303 @value{GDBN} a list of loaded shared libraries with file names such as
18304 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18305 drive letters, so the @samp{c:\} prefix is not normally understood as
18306 indicating an absolute file name, and neither is the backslash
18307 normally considered a directory separator character. In that case,
18308 the native file system would interpret this whole absolute file name
18309 as a relative file name with no directory components. This would make
18310 it impossible to point @value{GDBN} at a copy of the remote target's
18311 shared libraries on the host using @code{set sysroot}, and impractical
18312 with @code{set solib-search-path}. Setting
18313 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18314 to interpret such file names similarly to how the target would, and to
18315 map them to file names valid on @value{GDBN}'s native file system
18316 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18317 to one of the supported file system kinds. In that case, @value{GDBN}
18318 tries to determine the appropriate file system variant based on the
18319 current target's operating system (@pxref{ABI, ,Configuring the
18320 Current ABI}). The supported file system settings are:
18324 Instruct @value{GDBN} to assume the target file system is of Unix
18325 kind. Only file names starting the forward slash (@samp{/}) character
18326 are considered absolute, and the directory separator character is also
18330 Instruct @value{GDBN} to assume the target file system is DOS based.
18331 File names starting with either a forward slash, or a drive letter
18332 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18333 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18334 considered directory separators.
18337 Instruct @value{GDBN} to use the file system kind associated with the
18338 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18339 This is the default.
18343 @cindex file name canonicalization
18344 @cindex base name differences
18345 When processing file names provided by the user, @value{GDBN}
18346 frequently needs to compare them to the file names recorded in the
18347 program's debug info. Normally, @value{GDBN} compares just the
18348 @dfn{base names} of the files as strings, which is reasonably fast
18349 even for very large programs. (The base name of a file is the last
18350 portion of its name, after stripping all the leading directories.)
18351 This shortcut in comparison is based upon the assumption that files
18352 cannot have more than one base name. This is usually true, but
18353 references to files that use symlinks or similar filesystem
18354 facilities violate that assumption. If your program records files
18355 using such facilities, or if you provide file names to @value{GDBN}
18356 using symlinks etc., you can set @code{basenames-may-differ} to
18357 @code{true} to instruct @value{GDBN} to completely canonicalize each
18358 pair of file names it needs to compare. This will make file-name
18359 comparisons accurate, but at a price of a significant slowdown.
18362 @item set basenames-may-differ
18363 @kindex set basenames-may-differ
18364 Set whether a source file may have multiple base names.
18366 @item show basenames-may-differ
18367 @kindex show basenames-may-differ
18368 Show whether a source file may have multiple base names.
18372 @section File Caching
18373 @cindex caching of opened files
18374 @cindex caching of bfd objects
18376 To speed up file loading, and reduce memory usage, @value{GDBN} will
18377 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18378 BFD, bfd, The Binary File Descriptor Library}. The following commands
18379 allow visibility and control of the caching behavior.
18382 @kindex maint info bfds
18383 @item maint info bfds
18384 This prints information about each @code{bfd} object that is known to
18387 @kindex maint set bfd-sharing
18388 @kindex maint show bfd-sharing
18389 @kindex bfd caching
18390 @item maint set bfd-sharing
18391 @item maint show bfd-sharing
18392 Control whether @code{bfd} objects can be shared. When sharing is
18393 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18394 than reopening the same file. Turning sharing off does not cause
18395 already shared @code{bfd} objects to be unshared, but all future files
18396 that are opened will create a new @code{bfd} object. Similarly,
18397 re-enabling sharing does not cause multiple existing @code{bfd}
18398 objects to be collapsed into a single shared @code{bfd} object.
18400 @kindex set debug bfd-cache @var{level}
18401 @kindex bfd caching
18402 @item set debug bfd-cache @var{level}
18403 Turns on debugging of the bfd cache, setting the level to @var{level}.
18405 @kindex show debug bfd-cache
18406 @kindex bfd caching
18407 @item show debug bfd-cache
18408 Show the current debugging level of the bfd cache.
18411 @node Separate Debug Files
18412 @section Debugging Information in Separate Files
18413 @cindex separate debugging information files
18414 @cindex debugging information in separate files
18415 @cindex @file{.debug} subdirectories
18416 @cindex debugging information directory, global
18417 @cindex global debugging information directories
18418 @cindex build ID, and separate debugging files
18419 @cindex @file{.build-id} directory
18421 @value{GDBN} allows you to put a program's debugging information in a
18422 file separate from the executable itself, in a way that allows
18423 @value{GDBN} to find and load the debugging information automatically.
18424 Since debugging information can be very large---sometimes larger
18425 than the executable code itself---some systems distribute debugging
18426 information for their executables in separate files, which users can
18427 install only when they need to debug a problem.
18429 @value{GDBN} supports two ways of specifying the separate debug info
18434 The executable contains a @dfn{debug link} that specifies the name of
18435 the separate debug info file. The separate debug file's name is
18436 usually @file{@var{executable}.debug}, where @var{executable} is the
18437 name of the corresponding executable file without leading directories
18438 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18439 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18440 checksum for the debug file, which @value{GDBN} uses to validate that
18441 the executable and the debug file came from the same build.
18444 The executable contains a @dfn{build ID}, a unique bit string that is
18445 also present in the corresponding debug info file. (This is supported
18446 only on some operating systems, when using the ELF or PE file formats
18447 for binary files and the @sc{gnu} Binutils.) For more details about
18448 this feature, see the description of the @option{--build-id}
18449 command-line option in @ref{Options, , Command Line Options, ld.info,
18450 The GNU Linker}. The debug info file's name is not specified
18451 explicitly by the build ID, but can be computed from the build ID, see
18455 Depending on the way the debug info file is specified, @value{GDBN}
18456 uses two different methods of looking for the debug file:
18460 For the ``debug link'' method, @value{GDBN} looks up the named file in
18461 the directory of the executable file, then in a subdirectory of that
18462 directory named @file{.debug}, and finally under each one of the global debug
18463 directories, in a subdirectory whose name is identical to the leading
18464 directories of the executable's absolute file name.
18467 For the ``build ID'' method, @value{GDBN} looks in the
18468 @file{.build-id} subdirectory of each one of the global debug directories for
18469 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18470 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18471 are the rest of the bit string. (Real build ID strings are 32 or more
18472 hex characters, not 10.)
18475 So, for example, suppose you ask @value{GDBN} to debug
18476 @file{/usr/bin/ls}, which has a debug link that specifies the
18477 file @file{ls.debug}, and a build ID whose value in hex is
18478 @code{abcdef1234}. If the list of the global debug directories includes
18479 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18480 debug information files, in the indicated order:
18484 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18486 @file{/usr/bin/ls.debug}
18488 @file{/usr/bin/.debug/ls.debug}
18490 @file{/usr/lib/debug/usr/bin/ls.debug}.
18493 @anchor{debug-file-directory}
18494 Global debugging info directories default to what is set by @value{GDBN}
18495 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18496 you can also set the global debugging info directories, and view the list
18497 @value{GDBN} is currently using.
18501 @kindex set debug-file-directory
18502 @item set debug-file-directory @var{directories}
18503 Set the directories which @value{GDBN} searches for separate debugging
18504 information files to @var{directory}. Multiple path components can be set
18505 concatenating them by a path separator.
18507 @kindex show debug-file-directory
18508 @item show debug-file-directory
18509 Show the directories @value{GDBN} searches for separate debugging
18514 @cindex @code{.gnu_debuglink} sections
18515 @cindex debug link sections
18516 A debug link is a special section of the executable file named
18517 @code{.gnu_debuglink}. The section must contain:
18521 A filename, with any leading directory components removed, followed by
18524 zero to three bytes of padding, as needed to reach the next four-byte
18525 boundary within the section, and
18527 a four-byte CRC checksum, stored in the same endianness used for the
18528 executable file itself. The checksum is computed on the debugging
18529 information file's full contents by the function given below, passing
18530 zero as the @var{crc} argument.
18533 Any executable file format can carry a debug link, as long as it can
18534 contain a section named @code{.gnu_debuglink} with the contents
18537 @cindex @code{.note.gnu.build-id} sections
18538 @cindex build ID sections
18539 The build ID is a special section in the executable file (and in other
18540 ELF binary files that @value{GDBN} may consider). This section is
18541 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18542 It contains unique identification for the built files---the ID remains
18543 the same across multiple builds of the same build tree. The default
18544 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18545 content for the build ID string. The same section with an identical
18546 value is present in the original built binary with symbols, in its
18547 stripped variant, and in the separate debugging information file.
18549 The debugging information file itself should be an ordinary
18550 executable, containing a full set of linker symbols, sections, and
18551 debugging information. The sections of the debugging information file
18552 should have the same names, addresses, and sizes as the original file,
18553 but they need not contain any data---much like a @code{.bss} section
18554 in an ordinary executable.
18556 The @sc{gnu} binary utilities (Binutils) package includes the
18557 @samp{objcopy} utility that can produce
18558 the separated executable / debugging information file pairs using the
18559 following commands:
18562 @kbd{objcopy --only-keep-debug foo foo.debug}
18567 These commands remove the debugging
18568 information from the executable file @file{foo} and place it in the file
18569 @file{foo.debug}. You can use the first, second or both methods to link the
18574 The debug link method needs the following additional command to also leave
18575 behind a debug link in @file{foo}:
18578 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18581 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18582 a version of the @code{strip} command such that the command @kbd{strip foo -f
18583 foo.debug} has the same functionality as the two @code{objcopy} commands and
18584 the @code{ln -s} command above, together.
18587 Build ID gets embedded into the main executable using @code{ld --build-id} or
18588 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18589 compatibility fixes for debug files separation are present in @sc{gnu} binary
18590 utilities (Binutils) package since version 2.18.
18595 @cindex CRC algorithm definition
18596 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18597 IEEE 802.3 using the polynomial:
18599 @c TexInfo requires naked braces for multi-digit exponents for Tex
18600 @c output, but this causes HTML output to barf. HTML has to be set using
18601 @c raw commands. So we end up having to specify this equation in 2
18606 <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>
18607 + <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
18613 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18614 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18618 The function is computed byte at a time, taking the least
18619 significant bit of each byte first. The initial pattern
18620 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18621 the final result is inverted to ensure trailing zeros also affect the
18624 @emph{Note:} This is the same CRC polynomial as used in handling the
18625 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18626 However in the case of the Remote Serial Protocol, the CRC is computed
18627 @emph{most} significant bit first, and the result is not inverted, so
18628 trailing zeros have no effect on the CRC value.
18630 To complete the description, we show below the code of the function
18631 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18632 initially supplied @code{crc} argument means that an initial call to
18633 this function passing in zero will start computing the CRC using
18636 @kindex gnu_debuglink_crc32
18639 gnu_debuglink_crc32 (unsigned long crc,
18640 unsigned char *buf, size_t len)
18642 static const unsigned long crc32_table[256] =
18644 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18645 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18646 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18647 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18648 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18649 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18650 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18651 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18652 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18653 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18654 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18655 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18656 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18657 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18658 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18659 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18660 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18661 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18662 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18663 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18664 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18665 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18666 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18667 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18668 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18669 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18670 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18671 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18672 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18673 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18674 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18675 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18676 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18677 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18678 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18679 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18680 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18681 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18682 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18683 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18684 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18685 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18686 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18687 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18688 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18689 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18690 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18691 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18692 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18693 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18694 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18697 unsigned char *end;
18699 crc = ~crc & 0xffffffff;
18700 for (end = buf + len; buf < end; ++buf)
18701 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18702 return ~crc & 0xffffffff;
18707 This computation does not apply to the ``build ID'' method.
18709 @node MiniDebugInfo
18710 @section Debugging information in a special section
18711 @cindex separate debug sections
18712 @cindex @samp{.gnu_debugdata} section
18714 Some systems ship pre-built executables and libraries that have a
18715 special @samp{.gnu_debugdata} section. This feature is called
18716 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18717 is used to supply extra symbols for backtraces.
18719 The intent of this section is to provide extra minimal debugging
18720 information for use in simple backtraces. It is not intended to be a
18721 replacement for full separate debugging information (@pxref{Separate
18722 Debug Files}). The example below shows the intended use; however,
18723 @value{GDBN} does not currently put restrictions on what sort of
18724 debugging information might be included in the section.
18726 @value{GDBN} has support for this extension. If the section exists,
18727 then it is used provided that no other source of debugging information
18728 can be found, and that @value{GDBN} was configured with LZMA support.
18730 This section can be easily created using @command{objcopy} and other
18731 standard utilities:
18734 # Extract the dynamic symbols from the main binary, there is no need
18735 # to also have these in the normal symbol table.
18736 nm -D @var{binary} --format=posix --defined-only \
18737 | awk '@{ print $1 @}' | sort > dynsyms
18739 # Extract all the text (i.e. function) symbols from the debuginfo.
18740 # (Note that we actually also accept "D" symbols, for the benefit
18741 # of platforms like PowerPC64 that use function descriptors.)
18742 nm @var{binary} --format=posix --defined-only \
18743 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18746 # Keep all the function symbols not already in the dynamic symbol
18748 comm -13 dynsyms funcsyms > keep_symbols
18750 # Separate full debug info into debug binary.
18751 objcopy --only-keep-debug @var{binary} debug
18753 # Copy the full debuginfo, keeping only a minimal set of symbols and
18754 # removing some unnecessary sections.
18755 objcopy -S --remove-section .gdb_index --remove-section .comment \
18756 --keep-symbols=keep_symbols debug mini_debuginfo
18758 # Drop the full debug info from the original binary.
18759 strip --strip-all -R .comment @var{binary}
18761 # Inject the compressed data into the .gnu_debugdata section of the
18764 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18768 @section Index Files Speed Up @value{GDBN}
18769 @cindex index files
18770 @cindex @samp{.gdb_index} section
18772 When @value{GDBN} finds a symbol file, it scans the symbols in the
18773 file in order to construct an internal symbol table. This lets most
18774 @value{GDBN} operations work quickly---at the cost of a delay early
18775 on. For large programs, this delay can be quite lengthy, so
18776 @value{GDBN} provides a way to build an index, which speeds up
18779 The index is stored as a section in the symbol file. @value{GDBN} can
18780 write the index to a file, then you can put it into the symbol file
18781 using @command{objcopy}.
18783 To create an index file, use the @code{save gdb-index} command:
18786 @item save gdb-index @var{directory}
18787 @kindex save gdb-index
18788 Create an index file for each symbol file currently known by
18789 @value{GDBN}. Each file is named after its corresponding symbol file,
18790 with @samp{.gdb-index} appended, and is written into the given
18794 Once you have created an index file you can merge it into your symbol
18795 file, here named @file{symfile}, using @command{objcopy}:
18798 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18799 --set-section-flags .gdb_index=readonly symfile symfile
18802 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18803 sections that have been deprecated. Usually they are deprecated because
18804 they are missing a new feature or have performance issues.
18805 To tell @value{GDBN} to use a deprecated index section anyway
18806 specify @code{set use-deprecated-index-sections on}.
18807 The default is @code{off}.
18808 This can speed up startup, but may result in some functionality being lost.
18809 @xref{Index Section Format}.
18811 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18812 must be done before gdb reads the file. The following will not work:
18815 $ gdb -ex "set use-deprecated-index-sections on" <program>
18818 Instead you must do, for example,
18821 $ gdb -iex "set use-deprecated-index-sections on" <program>
18824 There are currently some limitation on indices. They only work when
18825 for DWARF debugging information, not stabs. And, they do not
18826 currently work for programs using Ada.
18828 @node Symbol Errors
18829 @section Errors Reading Symbol Files
18831 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18832 such as symbol types it does not recognize, or known bugs in compiler
18833 output. By default, @value{GDBN} does not notify you of such problems, since
18834 they are relatively common and primarily of interest to people
18835 debugging compilers. If you are interested in seeing information
18836 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18837 only one message about each such type of problem, no matter how many
18838 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18839 to see how many times the problems occur, with the @code{set
18840 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18843 The messages currently printed, and their meanings, include:
18846 @item inner block not inside outer block in @var{symbol}
18848 The symbol information shows where symbol scopes begin and end
18849 (such as at the start of a function or a block of statements). This
18850 error indicates that an inner scope block is not fully contained
18851 in its outer scope blocks.
18853 @value{GDBN} circumvents the problem by treating the inner block as if it had
18854 the same scope as the outer block. In the error message, @var{symbol}
18855 may be shown as ``@code{(don't know)}'' if the outer block is not a
18858 @item block at @var{address} out of order
18860 The symbol information for symbol scope blocks should occur in
18861 order of increasing addresses. This error indicates that it does not
18864 @value{GDBN} does not circumvent this problem, and has trouble
18865 locating symbols in the source file whose symbols it is reading. (You
18866 can often determine what source file is affected by specifying
18867 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18870 @item bad block start address patched
18872 The symbol information for a symbol scope block has a start address
18873 smaller than the address of the preceding source line. This is known
18874 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18876 @value{GDBN} circumvents the problem by treating the symbol scope block as
18877 starting on the previous source line.
18879 @item bad string table offset in symbol @var{n}
18882 Symbol number @var{n} contains a pointer into the string table which is
18883 larger than the size of the string table.
18885 @value{GDBN} circumvents the problem by considering the symbol to have the
18886 name @code{foo}, which may cause other problems if many symbols end up
18889 @item unknown symbol type @code{0x@var{nn}}
18891 The symbol information contains new data types that @value{GDBN} does
18892 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18893 uncomprehended information, in hexadecimal.
18895 @value{GDBN} circumvents the error by ignoring this symbol information.
18896 This usually allows you to debug your program, though certain symbols
18897 are not accessible. If you encounter such a problem and feel like
18898 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18899 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18900 and examine @code{*bufp} to see the symbol.
18902 @item stub type has NULL name
18904 @value{GDBN} could not find the full definition for a struct or class.
18906 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18907 The symbol information for a C@t{++} member function is missing some
18908 information that recent versions of the compiler should have output for
18911 @item info mismatch between compiler and debugger
18913 @value{GDBN} could not parse a type specification output by the compiler.
18918 @section GDB Data Files
18920 @cindex prefix for data files
18921 @value{GDBN} will sometimes read an auxiliary data file. These files
18922 are kept in a directory known as the @dfn{data directory}.
18924 You can set the data directory's name, and view the name @value{GDBN}
18925 is currently using.
18928 @kindex set data-directory
18929 @item set data-directory @var{directory}
18930 Set the directory which @value{GDBN} searches for auxiliary data files
18931 to @var{directory}.
18933 @kindex show data-directory
18934 @item show data-directory
18935 Show the directory @value{GDBN} searches for auxiliary data files.
18938 @cindex default data directory
18939 @cindex @samp{--with-gdb-datadir}
18940 You can set the default data directory by using the configure-time
18941 @samp{--with-gdb-datadir} option. If the data directory is inside
18942 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18943 @samp{--exec-prefix}), then the default data directory will be updated
18944 automatically if the installed @value{GDBN} is moved to a new
18947 The data directory may also be specified with the
18948 @code{--data-directory} command line option.
18949 @xref{Mode Options}.
18952 @chapter Specifying a Debugging Target
18954 @cindex debugging target
18955 A @dfn{target} is the execution environment occupied by your program.
18957 Often, @value{GDBN} runs in the same host environment as your program;
18958 in that case, the debugging target is specified as a side effect when
18959 you use the @code{file} or @code{core} commands. When you need more
18960 flexibility---for example, running @value{GDBN} on a physically separate
18961 host, or controlling a standalone system over a serial port or a
18962 realtime system over a TCP/IP connection---you can use the @code{target}
18963 command to specify one of the target types configured for @value{GDBN}
18964 (@pxref{Target Commands, ,Commands for Managing Targets}).
18966 @cindex target architecture
18967 It is possible to build @value{GDBN} for several different @dfn{target
18968 architectures}. When @value{GDBN} is built like that, you can choose
18969 one of the available architectures with the @kbd{set architecture}
18973 @kindex set architecture
18974 @kindex show architecture
18975 @item set architecture @var{arch}
18976 This command sets the current target architecture to @var{arch}. The
18977 value of @var{arch} can be @code{"auto"}, in addition to one of the
18978 supported architectures.
18980 @item show architecture
18981 Show the current target architecture.
18983 @item set processor
18985 @kindex set processor
18986 @kindex show processor
18987 These are alias commands for, respectively, @code{set architecture}
18988 and @code{show architecture}.
18992 * Active Targets:: Active targets
18993 * Target Commands:: Commands for managing targets
18994 * Byte Order:: Choosing target byte order
18997 @node Active Targets
18998 @section Active Targets
19000 @cindex stacking targets
19001 @cindex active targets
19002 @cindex multiple targets
19004 There are multiple classes of targets such as: processes, executable files or
19005 recording sessions. Core files belong to the process class, making core file
19006 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19007 on multiple active targets, one in each class. This allows you to (for
19008 example) start a process and inspect its activity, while still having access to
19009 the executable file after the process finishes. Or if you start process
19010 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19011 presented a virtual layer of the recording target, while the process target
19012 remains stopped at the chronologically last point of the process execution.
19014 Use the @code{core-file} and @code{exec-file} commands to select a new core
19015 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19016 specify as a target a process that is already running, use the @code{attach}
19017 command (@pxref{Attach, ,Debugging an Already-running Process}).
19019 @node Target Commands
19020 @section Commands for Managing Targets
19023 @item target @var{type} @var{parameters}
19024 Connects the @value{GDBN} host environment to a target machine or
19025 process. A target is typically a protocol for talking to debugging
19026 facilities. You use the argument @var{type} to specify the type or
19027 protocol of the target machine.
19029 Further @var{parameters} are interpreted by the target protocol, but
19030 typically include things like device names or host names to connect
19031 with, process numbers, and baud rates.
19033 The @code{target} command does not repeat if you press @key{RET} again
19034 after executing the command.
19036 @kindex help target
19038 Displays the names of all targets available. To display targets
19039 currently selected, use either @code{info target} or @code{info files}
19040 (@pxref{Files, ,Commands to Specify Files}).
19042 @item help target @var{name}
19043 Describe a particular target, including any parameters necessary to
19046 @kindex set gnutarget
19047 @item set gnutarget @var{args}
19048 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19049 knows whether it is reading an @dfn{executable},
19050 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19051 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19052 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19055 @emph{Warning:} To specify a file format with @code{set gnutarget},
19056 you must know the actual BFD name.
19060 @xref{Files, , Commands to Specify Files}.
19062 @kindex show gnutarget
19063 @item show gnutarget
19064 Use the @code{show gnutarget} command to display what file format
19065 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19066 @value{GDBN} will determine the file format for each file automatically,
19067 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19070 @cindex common targets
19071 Here are some common targets (available, or not, depending on the GDB
19076 @item target exec @var{program}
19077 @cindex executable file target
19078 An executable file. @samp{target exec @var{program}} is the same as
19079 @samp{exec-file @var{program}}.
19081 @item target core @var{filename}
19082 @cindex core dump file target
19083 A core dump file. @samp{target core @var{filename}} is the same as
19084 @samp{core-file @var{filename}}.
19086 @item target remote @var{medium}
19087 @cindex remote target
19088 A remote system connected to @value{GDBN} via a serial line or network
19089 connection. This command tells @value{GDBN} to use its own remote
19090 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19092 For example, if you have a board connected to @file{/dev/ttya} on the
19093 machine running @value{GDBN}, you could say:
19096 target remote /dev/ttya
19099 @code{target remote} supports the @code{load} command. This is only
19100 useful if you have some other way of getting the stub to the target
19101 system, and you can put it somewhere in memory where it won't get
19102 clobbered by the download.
19104 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19105 @cindex built-in simulator target
19106 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19114 works; however, you cannot assume that a specific memory map, device
19115 drivers, or even basic I/O is available, although some simulators do
19116 provide these. For info about any processor-specific simulator details,
19117 see the appropriate section in @ref{Embedded Processors, ,Embedded
19120 @item target native
19121 @cindex native target
19122 Setup for local/native process debugging. Useful to make the
19123 @code{run} command spawn native processes (likewise @code{attach},
19124 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19125 (@pxref{set auto-connect-native-target}).
19129 Different targets are available on different configurations of @value{GDBN};
19130 your configuration may have more or fewer targets.
19132 Many remote targets require you to download the executable's code once
19133 you've successfully established a connection. You may wish to control
19134 various aspects of this process.
19139 @kindex set hash@r{, for remote monitors}
19140 @cindex hash mark while downloading
19141 This command controls whether a hash mark @samp{#} is displayed while
19142 downloading a file to the remote monitor. If on, a hash mark is
19143 displayed after each S-record is successfully downloaded to the
19147 @kindex show hash@r{, for remote monitors}
19148 Show the current status of displaying the hash mark.
19150 @item set debug monitor
19151 @kindex set debug monitor
19152 @cindex display remote monitor communications
19153 Enable or disable display of communications messages between
19154 @value{GDBN} and the remote monitor.
19156 @item show debug monitor
19157 @kindex show debug monitor
19158 Show the current status of displaying communications between
19159 @value{GDBN} and the remote monitor.
19164 @kindex load @var{filename}
19165 @item load @var{filename}
19167 Depending on what remote debugging facilities are configured into
19168 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19169 is meant to make @var{filename} (an executable) available for debugging
19170 on the remote system---by downloading, or dynamic linking, for example.
19171 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19172 the @code{add-symbol-file} command.
19174 If your @value{GDBN} does not have a @code{load} command, attempting to
19175 execute it gets the error message ``@code{You can't do that when your
19176 target is @dots{}}''
19178 The file is loaded at whatever address is specified in the executable.
19179 For some object file formats, you can specify the load address when you
19180 link the program; for other formats, like a.out, the object file format
19181 specifies a fixed address.
19182 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19184 Depending on the remote side capabilities, @value{GDBN} may be able to
19185 load programs into flash memory.
19187 @code{load} does not repeat if you press @key{RET} again after using it.
19191 @section Choosing Target Byte Order
19193 @cindex choosing target byte order
19194 @cindex target byte order
19196 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19197 offer the ability to run either big-endian or little-endian byte
19198 orders. Usually the executable or symbol will include a bit to
19199 designate the endian-ness, and you will not need to worry about
19200 which to use. However, you may still find it useful to adjust
19201 @value{GDBN}'s idea of processor endian-ness manually.
19205 @item set endian big
19206 Instruct @value{GDBN} to assume the target is big-endian.
19208 @item set endian little
19209 Instruct @value{GDBN} to assume the target is little-endian.
19211 @item set endian auto
19212 Instruct @value{GDBN} to use the byte order associated with the
19216 Display @value{GDBN}'s current idea of the target byte order.
19220 Note that these commands merely adjust interpretation of symbolic
19221 data on the host, and that they have absolutely no effect on the
19225 @node Remote Debugging
19226 @chapter Debugging Remote Programs
19227 @cindex remote debugging
19229 If you are trying to debug a program running on a machine that cannot run
19230 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19231 For example, you might use remote debugging on an operating system kernel,
19232 or on a small system which does not have a general purpose operating system
19233 powerful enough to run a full-featured debugger.
19235 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19236 to make this work with particular debugging targets. In addition,
19237 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19238 but not specific to any particular target system) which you can use if you
19239 write the remote stubs---the code that runs on the remote system to
19240 communicate with @value{GDBN}.
19242 Other remote targets may be available in your
19243 configuration of @value{GDBN}; use @code{help target} to list them.
19246 * Connecting:: Connecting to a remote target
19247 * File Transfer:: Sending files to a remote system
19248 * Server:: Using the gdbserver program
19249 * Remote Configuration:: Remote configuration
19250 * Remote Stub:: Implementing a remote stub
19254 @section Connecting to a Remote Target
19255 @cindex remote debugging, connecting
19256 @cindex @code{gdbserver}, connecting
19257 @cindex remote debugging, types of connections
19258 @cindex @code{gdbserver}, types of connections
19259 @cindex @code{gdbserver}, @code{target remote} mode
19260 @cindex @code{gdbserver}, @code{target extended-remote} mode
19262 This section describes how to connect to a remote target, including the
19263 types of connections and their differences, how to set up executable and
19264 symbol files on the host and target, and the commands used for
19265 connecting to and disconnecting from the remote target.
19267 @subsection Types of Remote Connections
19269 @value{GDBN} supports two types of remote connections, @code{target remote}
19270 mode and @code{target extended-remote} mode. Note that many remote targets
19271 support only @code{target remote} mode. There are several major
19272 differences between the two types of connections, enumerated here:
19276 @cindex remote debugging, detach and program exit
19277 @item Result of detach or program exit
19278 @strong{With target remote mode:} When the debugged program exits or you
19279 detach from it, @value{GDBN} disconnects from the target. When using
19280 @code{gdbserver}, @code{gdbserver} will exit.
19282 @strong{With target extended-remote mode:} When the debugged program exits or
19283 you detach from it, @value{GDBN} remains connected to the target, even
19284 though no program is running. You can rerun the program, attach to a
19285 running program, or use @code{monitor} commands specific to the target.
19287 When using @code{gdbserver} in this case, it does not exit unless it was
19288 invoked using the @option{--once} option. If the @option{--once} option
19289 was not used, you can ask @code{gdbserver} to exit using the
19290 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19292 @item Specifying the program to debug
19293 For both connection types you use the @code{file} command to specify the
19294 program on the host system. If you are using @code{gdbserver} there are
19295 some differences in how to specify the location of the program on the
19298 @strong{With target remote mode:} You must either specify the program to debug
19299 on the @code{gdbserver} command line or use the @option{--attach} option
19300 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19302 @cindex @option{--multi}, @code{gdbserver} option
19303 @strong{With target extended-remote mode:} You may specify the program to debug
19304 on the @code{gdbserver} command line, or you can load the program or attach
19305 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19307 @anchor{--multi Option in Types of Remote Connnections}
19308 You can start @code{gdbserver} without supplying an initial command to run
19309 or process ID to attach. To do this, use the @option{--multi} command line
19310 option. Then you can connect using @code{target extended-remote} and start
19311 the program you want to debug (see below for details on using the
19312 @code{run} command in this scenario). Note that the conditions under which
19313 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19314 (@code{target remote} or @code{target extended-remote}). The
19315 @option{--multi} option to @code{gdbserver} has no influence on that.
19317 @item The @code{run} command
19318 @strong{With target remote mode:} The @code{run} command is not
19319 supported. Once a connection has been established, you can use all
19320 the usual @value{GDBN} commands to examine and change data. The
19321 remote program is already running, so you can use commands like
19322 @kbd{step} and @kbd{continue}.
19324 @strong{With target extended-remote mode:} The @code{run} command is
19325 supported. The @code{run} command uses the value set by
19326 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19327 the program to run. Command line arguments are supported, except for
19328 wildcard expansion and I/O redirection (@pxref{Arguments}).
19330 If you specify the program to debug on the command line, then the
19331 @code{run} command is not required to start execution, and you can
19332 resume using commands like @kbd{step} and @kbd{continue} as with
19333 @code{target remote} mode.
19335 @anchor{Attaching in Types of Remote Connections}
19337 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19338 not supported. To attach to a running program using @code{gdbserver}, you
19339 must use the @option{--attach} option (@pxref{Running gdbserver}).
19341 @strong{With target extended-remote mode:} To attach to a running program,
19342 you may use the @code{attach} command after the connection has been
19343 established. If you are using @code{gdbserver}, you may also invoke
19344 @code{gdbserver} using the @option{--attach} option
19345 (@pxref{Running gdbserver}).
19349 @anchor{Host and target files}
19350 @subsection Host and Target Files
19351 @cindex remote debugging, symbol files
19352 @cindex symbol files, remote debugging
19354 @value{GDBN}, running on the host, needs access to symbol and debugging
19355 information for your program running on the target. This requires
19356 access to an unstripped copy of your program, and possibly any associated
19357 symbol files. Note that this section applies equally to both @code{target
19358 remote} mode and @code{target extended-remote} mode.
19360 Some remote targets (@pxref{qXfer executable filename read}, and
19361 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19362 the same connection used to communicate with @value{GDBN}. With such a
19363 target, if the remote program is unstripped, the only command you need is
19364 @code{target remote} (or @code{target extended-remote}).
19366 If the remote program is stripped, or the target does not support remote
19367 program file access, start up @value{GDBN} using the name of the local
19368 unstripped copy of your program as the first argument, or use the
19369 @code{file} command. Use @code{set sysroot} to specify the location (on
19370 the host) of target libraries (unless your @value{GDBN} was compiled with
19371 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19372 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19375 The symbol file and target libraries must exactly match the executable
19376 and libraries on the target, with one exception: the files on the host
19377 system should not be stripped, even if the files on the target system
19378 are. Mismatched or missing files will lead to confusing results
19379 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19380 files may also prevent @code{gdbserver} from debugging multi-threaded
19383 @subsection Remote Connection Commands
19384 @cindex remote connection commands
19385 @value{GDBN} can communicate with the target over a serial line, or
19386 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19387 each case, @value{GDBN} uses the same protocol for debugging your
19388 program; only the medium carrying the debugging packets varies. The
19389 @code{target remote} and @code{target extended-remote} commands
19390 establish a connection to the target. Both commands accept the same
19391 arguments, which indicate the medium to use:
19395 @item target remote @var{serial-device}
19396 @itemx target extended-remote @var{serial-device}
19397 @cindex serial line, @code{target remote}
19398 Use @var{serial-device} to communicate with the target. For example,
19399 to use a serial line connected to the device named @file{/dev/ttyb}:
19402 target remote /dev/ttyb
19405 If you're using a serial line, you may want to give @value{GDBN} the
19406 @samp{--baud} option, or use the @code{set serial baud} command
19407 (@pxref{Remote Configuration, set serial baud}) before the
19408 @code{target} command.
19410 @item target remote @code{@var{host}:@var{port}}
19411 @itemx target remote @code{tcp:@var{host}:@var{port}}
19412 @itemx target extended-remote @code{@var{host}:@var{port}}
19413 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19414 @cindex @acronym{TCP} port, @code{target remote}
19415 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19416 The @var{host} may be either a host name or a numeric @acronym{IP}
19417 address; @var{port} must be a decimal number. The @var{host} could be
19418 the target machine itself, if it is directly connected to the net, or
19419 it might be a terminal server which in turn has a serial line to the
19422 For example, to connect to port 2828 on a terminal server named
19426 target remote manyfarms:2828
19429 If your remote target is actually running on the same machine as your
19430 debugger session (e.g.@: a simulator for your target running on the
19431 same host), you can omit the hostname. For example, to connect to
19432 port 1234 on your local machine:
19435 target remote :1234
19439 Note that the colon is still required here.
19441 @item target remote @code{udp:@var{host}:@var{port}}
19442 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19443 @cindex @acronym{UDP} port, @code{target remote}
19444 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19445 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19448 target remote udp:manyfarms:2828
19451 When using a @acronym{UDP} connection for remote debugging, you should
19452 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19453 can silently drop packets on busy or unreliable networks, which will
19454 cause havoc with your debugging session.
19456 @item target remote | @var{command}
19457 @itemx target extended-remote | @var{command}
19458 @cindex pipe, @code{target remote} to
19459 Run @var{command} in the background and communicate with it using a
19460 pipe. The @var{command} is a shell command, to be parsed and expanded
19461 by the system's command shell, @code{/bin/sh}; it should expect remote
19462 protocol packets on its standard input, and send replies on its
19463 standard output. You could use this to run a stand-alone simulator
19464 that speaks the remote debugging protocol, to make net connections
19465 using programs like @code{ssh}, or for other similar tricks.
19467 If @var{command} closes its standard output (perhaps by exiting),
19468 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19469 program has already exited, this will have no effect.)
19473 @cindex interrupting remote programs
19474 @cindex remote programs, interrupting
19475 Whenever @value{GDBN} is waiting for the remote program, if you type the
19476 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19477 program. This may or may not succeed, depending in part on the hardware
19478 and the serial drivers the remote system uses. If you type the
19479 interrupt character once again, @value{GDBN} displays this prompt:
19482 Interrupted while waiting for the program.
19483 Give up (and stop debugging it)? (y or n)
19486 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19487 the remote debugging session. (If you decide you want to try again later,
19488 you can use @kbd{target remote} again to connect once more.) If you type
19489 @kbd{n}, @value{GDBN} goes back to waiting.
19491 In @code{target extended-remote} mode, typing @kbd{n} will leave
19492 @value{GDBN} connected to the target.
19495 @kindex detach (remote)
19497 When you have finished debugging the remote program, you can use the
19498 @code{detach} command to release it from @value{GDBN} control.
19499 Detaching from the target normally resumes its execution, but the results
19500 will depend on your particular remote stub. After the @code{detach}
19501 command in @code{target remote} mode, @value{GDBN} is free to connect to
19502 another target. In @code{target extended-remote} mode, @value{GDBN} is
19503 still connected to the target.
19507 The @code{disconnect} command closes the connection to the target, and
19508 the target is generally not resumed. It will wait for @value{GDBN}
19509 (this instance or another one) to connect and continue debugging. After
19510 the @code{disconnect} command, @value{GDBN} is again free to connect to
19513 @cindex send command to remote monitor
19514 @cindex extend @value{GDBN} for remote targets
19515 @cindex add new commands for external monitor
19517 @item monitor @var{cmd}
19518 This command allows you to send arbitrary commands directly to the
19519 remote monitor. Since @value{GDBN} doesn't care about the commands it
19520 sends like this, this command is the way to extend @value{GDBN}---you
19521 can add new commands that only the external monitor will understand
19525 @node File Transfer
19526 @section Sending files to a remote system
19527 @cindex remote target, file transfer
19528 @cindex file transfer
19529 @cindex sending files to remote systems
19531 Some remote targets offer the ability to transfer files over the same
19532 connection used to communicate with @value{GDBN}. This is convenient
19533 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19534 running @code{gdbserver} over a network interface. For other targets,
19535 e.g.@: embedded devices with only a single serial port, this may be
19536 the only way to upload or download files.
19538 Not all remote targets support these commands.
19542 @item remote put @var{hostfile} @var{targetfile}
19543 Copy file @var{hostfile} from the host system (the machine running
19544 @value{GDBN}) to @var{targetfile} on the target system.
19547 @item remote get @var{targetfile} @var{hostfile}
19548 Copy file @var{targetfile} from the target system to @var{hostfile}
19549 on the host system.
19551 @kindex remote delete
19552 @item remote delete @var{targetfile}
19553 Delete @var{targetfile} from the target system.
19558 @section Using the @code{gdbserver} Program
19561 @cindex remote connection without stubs
19562 @code{gdbserver} is a control program for Unix-like systems, which
19563 allows you to connect your program with a remote @value{GDBN} via
19564 @code{target remote} or @code{target extended-remote}---but without
19565 linking in the usual debugging stub.
19567 @code{gdbserver} is not a complete replacement for the debugging stubs,
19568 because it requires essentially the same operating-system facilities
19569 that @value{GDBN} itself does. In fact, a system that can run
19570 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19571 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19572 because it is a much smaller program than @value{GDBN} itself. It is
19573 also easier to port than all of @value{GDBN}, so you may be able to get
19574 started more quickly on a new system by using @code{gdbserver}.
19575 Finally, if you develop code for real-time systems, you may find that
19576 the tradeoffs involved in real-time operation make it more convenient to
19577 do as much development work as possible on another system, for example
19578 by cross-compiling. You can use @code{gdbserver} to make a similar
19579 choice for debugging.
19581 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19582 or a TCP connection, using the standard @value{GDBN} remote serial
19586 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19587 Do not run @code{gdbserver} connected to any public network; a
19588 @value{GDBN} connection to @code{gdbserver} provides access to the
19589 target system with the same privileges as the user running
19593 @anchor{Running gdbserver}
19594 @subsection Running @code{gdbserver}
19595 @cindex arguments, to @code{gdbserver}
19596 @cindex @code{gdbserver}, command-line arguments
19598 Run @code{gdbserver} on the target system. You need a copy of the
19599 program you want to debug, including any libraries it requires.
19600 @code{gdbserver} does not need your program's symbol table, so you can
19601 strip the program if necessary to save space. @value{GDBN} on the host
19602 system does all the symbol handling.
19604 To use the server, you must tell it how to communicate with @value{GDBN};
19605 the name of your program; and the arguments for your program. The usual
19609 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19612 @var{comm} is either a device name (to use a serial line), or a TCP
19613 hostname and portnumber, or @code{-} or @code{stdio} to use
19614 stdin/stdout of @code{gdbserver}.
19615 For example, to debug Emacs with the argument
19616 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19620 target> gdbserver /dev/com1 emacs foo.txt
19623 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19626 To use a TCP connection instead of a serial line:
19629 target> gdbserver host:2345 emacs foo.txt
19632 The only difference from the previous example is the first argument,
19633 specifying that you are communicating with the host @value{GDBN} via
19634 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19635 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19636 (Currently, the @samp{host} part is ignored.) You can choose any number
19637 you want for the port number as long as it does not conflict with any
19638 TCP ports already in use on the target system (for example, @code{23} is
19639 reserved for @code{telnet}).@footnote{If you choose a port number that
19640 conflicts with another service, @code{gdbserver} prints an error message
19641 and exits.} You must use the same port number with the host @value{GDBN}
19642 @code{target remote} command.
19644 The @code{stdio} connection is useful when starting @code{gdbserver}
19648 (gdb) target remote | ssh -T hostname gdbserver - hello
19651 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19652 and we don't want escape-character handling. Ssh does this by default when
19653 a command is provided, the flag is provided to make it explicit.
19654 You could elide it if you want to.
19656 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19657 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19658 display through a pipe connected to gdbserver.
19659 Both @code{stdout} and @code{stderr} use the same pipe.
19661 @anchor{Attaching to a program}
19662 @subsubsection Attaching to a Running Program
19663 @cindex attach to a program, @code{gdbserver}
19664 @cindex @option{--attach}, @code{gdbserver} option
19666 On some targets, @code{gdbserver} can also attach to running programs.
19667 This is accomplished via the @code{--attach} argument. The syntax is:
19670 target> gdbserver --attach @var{comm} @var{pid}
19673 @var{pid} is the process ID of a currently running process. It isn't
19674 necessary to point @code{gdbserver} at a binary for the running process.
19676 In @code{target extended-remote} mode, you can also attach using the
19677 @value{GDBN} attach command
19678 (@pxref{Attaching in Types of Remote Connections}).
19681 You can debug processes by name instead of process ID if your target has the
19682 @code{pidof} utility:
19685 target> gdbserver --attach @var{comm} `pidof @var{program}`
19688 In case more than one copy of @var{program} is running, or @var{program}
19689 has multiple threads, most versions of @code{pidof} support the
19690 @code{-s} option to only return the first process ID.
19692 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19694 This section applies only when @code{gdbserver} is run to listen on a TCP
19697 @code{gdbserver} normally terminates after all of its debugged processes have
19698 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19699 extended-remote}, @code{gdbserver} stays running even with no processes left.
19700 @value{GDBN} normally terminates the spawned debugged process on its exit,
19701 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19702 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19703 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19704 stays running even in the @kbd{target remote} mode.
19706 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19707 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19708 completeness, at most one @value{GDBN} can be connected at a time.
19710 @cindex @option{--once}, @code{gdbserver} option
19711 By default, @code{gdbserver} keeps the listening TCP port open, so that
19712 subsequent connections are possible. However, if you start @code{gdbserver}
19713 with the @option{--once} option, it will stop listening for any further
19714 connection attempts after connecting to the first @value{GDBN} session. This
19715 means no further connections to @code{gdbserver} will be possible after the
19716 first one. It also means @code{gdbserver} will terminate after the first
19717 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19718 connections and even in the @kbd{target extended-remote} mode. The
19719 @option{--once} option allows reusing the same port number for connecting to
19720 multiple instances of @code{gdbserver} running on the same host, since each
19721 instance closes its port after the first connection.
19723 @anchor{Other Command-Line Arguments for gdbserver}
19724 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19726 You can use the @option{--multi} option to start @code{gdbserver} without
19727 specifying a program to debug or a process to attach to. Then you can
19728 attach in @code{target extended-remote} mode and run or attach to a
19729 program. For more information,
19730 @pxref{--multi Option in Types of Remote Connnections}.
19732 @cindex @option{--debug}, @code{gdbserver} option
19733 The @option{--debug} option tells @code{gdbserver} to display extra
19734 status information about the debugging process.
19735 @cindex @option{--remote-debug}, @code{gdbserver} option
19736 The @option{--remote-debug} option tells @code{gdbserver} to display
19737 remote protocol debug output. These options are intended for
19738 @code{gdbserver} development and for bug reports to the developers.
19740 @cindex @option{--debug-format}, @code{gdbserver} option
19741 The @option{--debug-format=option1[,option2,...]} option tells
19742 @code{gdbserver} to include additional information in each output.
19743 Possible options are:
19747 Turn off all extra information in debugging output.
19749 Turn on all extra information in debugging output.
19751 Include a timestamp in each line of debugging output.
19754 Options are processed in order. Thus, for example, if @option{none}
19755 appears last then no additional information is added to debugging output.
19757 @cindex @option{--wrapper}, @code{gdbserver} option
19758 The @option{--wrapper} option specifies a wrapper to launch programs
19759 for debugging. The option should be followed by the name of the
19760 wrapper, then any command-line arguments to pass to the wrapper, then
19761 @kbd{--} indicating the end of the wrapper arguments.
19763 @code{gdbserver} runs the specified wrapper program with a combined
19764 command line including the wrapper arguments, then the name of the
19765 program to debug, then any arguments to the program. The wrapper
19766 runs until it executes your program, and then @value{GDBN} gains control.
19768 You can use any program that eventually calls @code{execve} with
19769 its arguments as a wrapper. Several standard Unix utilities do
19770 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19771 with @code{exec "$@@"} will also work.
19773 For example, you can use @code{env} to pass an environment variable to
19774 the debugged program, without setting the variable in @code{gdbserver}'s
19778 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19781 @subsection Connecting to @code{gdbserver}
19783 The basic procedure for connecting to the remote target is:
19787 Run @value{GDBN} on the host system.
19790 Make sure you have the necessary symbol files
19791 (@pxref{Host and target files}).
19792 Load symbols for your application using the @code{file} command before you
19793 connect. Use @code{set sysroot} to locate target libraries (unless your
19794 @value{GDBN} was compiled with the correct sysroot using
19795 @code{--with-sysroot}).
19798 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19799 For TCP connections, you must start up @code{gdbserver} prior to using
19800 the @code{target} command. Otherwise you may get an error whose
19801 text depends on the host system, but which usually looks something like
19802 @samp{Connection refused}. Don't use the @code{load}
19803 command in @value{GDBN} when using @code{target remote} mode, since the
19804 program is already on the target.
19808 @anchor{Monitor Commands for gdbserver}
19809 @subsection Monitor Commands for @code{gdbserver}
19810 @cindex monitor commands, for @code{gdbserver}
19812 During a @value{GDBN} session using @code{gdbserver}, you can use the
19813 @code{monitor} command to send special requests to @code{gdbserver}.
19814 Here are the available commands.
19818 List the available monitor commands.
19820 @item monitor set debug 0
19821 @itemx monitor set debug 1
19822 Disable or enable general debugging messages.
19824 @item monitor set remote-debug 0
19825 @itemx monitor set remote-debug 1
19826 Disable or enable specific debugging messages associated with the remote
19827 protocol (@pxref{Remote Protocol}).
19829 @item monitor set debug-format option1@r{[},option2,...@r{]}
19830 Specify additional text to add to debugging messages.
19831 Possible options are:
19835 Turn off all extra information in debugging output.
19837 Turn on all extra information in debugging output.
19839 Include a timestamp in each line of debugging output.
19842 Options are processed in order. Thus, for example, if @option{none}
19843 appears last then no additional information is added to debugging output.
19845 @item monitor set libthread-db-search-path [PATH]
19846 @cindex gdbserver, search path for @code{libthread_db}
19847 When this command is issued, @var{path} is a colon-separated list of
19848 directories to search for @code{libthread_db} (@pxref{Threads,,set
19849 libthread-db-search-path}). If you omit @var{path},
19850 @samp{libthread-db-search-path} will be reset to its default value.
19852 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19853 not supported in @code{gdbserver}.
19856 Tell gdbserver to exit immediately. This command should be followed by
19857 @code{disconnect} to close the debugging session. @code{gdbserver} will
19858 detach from any attached processes and kill any processes it created.
19859 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19860 of a multi-process mode debug session.
19864 @subsection Tracepoints support in @code{gdbserver}
19865 @cindex tracepoints support in @code{gdbserver}
19867 On some targets, @code{gdbserver} supports tracepoints, fast
19868 tracepoints and static tracepoints.
19870 For fast or static tracepoints to work, a special library called the
19871 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19872 This library is built and distributed as an integral part of
19873 @code{gdbserver}. In addition, support for static tracepoints
19874 requires building the in-process agent library with static tracepoints
19875 support. At present, the UST (LTTng Userspace Tracer,
19876 @url{http://lttng.org/ust}) tracing engine is supported. This support
19877 is automatically available if UST development headers are found in the
19878 standard include path when @code{gdbserver} is built, or if
19879 @code{gdbserver} was explicitly configured using @option{--with-ust}
19880 to point at such headers. You can explicitly disable the support
19881 using @option{--with-ust=no}.
19883 There are several ways to load the in-process agent in your program:
19886 @item Specifying it as dependency at link time
19888 You can link your program dynamically with the in-process agent
19889 library. On most systems, this is accomplished by adding
19890 @code{-linproctrace} to the link command.
19892 @item Using the system's preloading mechanisms
19894 You can force loading the in-process agent at startup time by using
19895 your system's support for preloading shared libraries. Many Unixes
19896 support the concept of preloading user defined libraries. In most
19897 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19898 in the environment. See also the description of @code{gdbserver}'s
19899 @option{--wrapper} command line option.
19901 @item Using @value{GDBN} to force loading the agent at run time
19903 On some systems, you can force the inferior to load a shared library,
19904 by calling a dynamic loader function in the inferior that takes care
19905 of dynamically looking up and loading a shared library. On most Unix
19906 systems, the function is @code{dlopen}. You'll use the @code{call}
19907 command for that. For example:
19910 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19913 Note that on most Unix systems, for the @code{dlopen} function to be
19914 available, the program needs to be linked with @code{-ldl}.
19917 On systems that have a userspace dynamic loader, like most Unix
19918 systems, when you connect to @code{gdbserver} using @code{target
19919 remote}, you'll find that the program is stopped at the dynamic
19920 loader's entry point, and no shared library has been loaded in the
19921 program's address space yet, including the in-process agent. In that
19922 case, before being able to use any of the fast or static tracepoints
19923 features, you need to let the loader run and load the shared
19924 libraries. The simplest way to do that is to run the program to the
19925 main procedure. E.g., if debugging a C or C@t{++} program, start
19926 @code{gdbserver} like so:
19929 $ gdbserver :9999 myprogram
19932 Start GDB and connect to @code{gdbserver} like so, and run to main:
19936 (@value{GDBP}) target remote myhost:9999
19937 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19938 (@value{GDBP}) b main
19939 (@value{GDBP}) continue
19942 The in-process tracing agent library should now be loaded into the
19943 process; you can confirm it with the @code{info sharedlibrary}
19944 command, which will list @file{libinproctrace.so} as loaded in the
19945 process. You are now ready to install fast tracepoints, list static
19946 tracepoint markers, probe static tracepoints markers, and start
19949 @node Remote Configuration
19950 @section Remote Configuration
19953 @kindex show remote
19954 This section documents the configuration options available when
19955 debugging remote programs. For the options related to the File I/O
19956 extensions of the remote protocol, see @ref{system,
19957 system-call-allowed}.
19960 @item set remoteaddresssize @var{bits}
19961 @cindex address size for remote targets
19962 @cindex bits in remote address
19963 Set the maximum size of address in a memory packet to the specified
19964 number of bits. @value{GDBN} will mask off the address bits above
19965 that number, when it passes addresses to the remote target. The
19966 default value is the number of bits in the target's address.
19968 @item show remoteaddresssize
19969 Show the current value of remote address size in bits.
19971 @item set serial baud @var{n}
19972 @cindex baud rate for remote targets
19973 Set the baud rate for the remote serial I/O to @var{n} baud. The
19974 value is used to set the speed of the serial port used for debugging
19977 @item show serial baud
19978 Show the current speed of the remote connection.
19980 @item set serial parity @var{parity}
19981 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19982 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19984 @item show serial parity
19985 Show the current parity of the serial port.
19987 @item set remotebreak
19988 @cindex interrupt remote programs
19989 @cindex BREAK signal instead of Ctrl-C
19990 @anchor{set remotebreak}
19991 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19992 when you type @kbd{Ctrl-c} to interrupt the program running
19993 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19994 character instead. The default is off, since most remote systems
19995 expect to see @samp{Ctrl-C} as the interrupt signal.
19997 @item show remotebreak
19998 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19999 interrupt the remote program.
20001 @item set remoteflow on
20002 @itemx set remoteflow off
20003 @kindex set remoteflow
20004 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20005 on the serial port used to communicate to the remote target.
20007 @item show remoteflow
20008 @kindex show remoteflow
20009 Show the current setting of hardware flow control.
20011 @item set remotelogbase @var{base}
20012 Set the base (a.k.a.@: radix) of logging serial protocol
20013 communications to @var{base}. Supported values of @var{base} are:
20014 @code{ascii}, @code{octal}, and @code{hex}. The default is
20017 @item show remotelogbase
20018 Show the current setting of the radix for logging remote serial
20021 @item set remotelogfile @var{file}
20022 @cindex record serial communications on file
20023 Record remote serial communications on the named @var{file}. The
20024 default is not to record at all.
20026 @item show remotelogfile.
20027 Show the current setting of the file name on which to record the
20028 serial communications.
20030 @item set remotetimeout @var{num}
20031 @cindex timeout for serial communications
20032 @cindex remote timeout
20033 Set the timeout limit to wait for the remote target to respond to
20034 @var{num} seconds. The default is 2 seconds.
20036 @item show remotetimeout
20037 Show the current number of seconds to wait for the remote target
20040 @cindex limit hardware breakpoints and watchpoints
20041 @cindex remote target, limit break- and watchpoints
20042 @anchor{set remote hardware-watchpoint-limit}
20043 @anchor{set remote hardware-breakpoint-limit}
20044 @item set remote hardware-watchpoint-limit @var{limit}
20045 @itemx set remote hardware-breakpoint-limit @var{limit}
20046 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20047 watchpoints. A limit of -1, the default, is treated as unlimited.
20049 @cindex limit hardware watchpoints length
20050 @cindex remote target, limit watchpoints length
20051 @anchor{set remote hardware-watchpoint-length-limit}
20052 @item set remote hardware-watchpoint-length-limit @var{limit}
20053 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20054 a remote hardware watchpoint. A limit of -1, the default, is treated
20057 @item show remote hardware-watchpoint-length-limit
20058 Show the current limit (in bytes) of the maximum length of
20059 a remote hardware watchpoint.
20061 @item set remote exec-file @var{filename}
20062 @itemx show remote exec-file
20063 @anchor{set remote exec-file}
20064 @cindex executable file, for remote target
20065 Select the file used for @code{run} with @code{target
20066 extended-remote}. This should be set to a filename valid on the
20067 target system. If it is not set, the target will use a default
20068 filename (e.g.@: the last program run).
20070 @item set remote interrupt-sequence
20071 @cindex interrupt remote programs
20072 @cindex select Ctrl-C, BREAK or BREAK-g
20073 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20074 @samp{BREAK-g} as the
20075 sequence to the remote target in order to interrupt the execution.
20076 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20077 is high level of serial line for some certain time.
20078 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20079 It is @code{BREAK} signal followed by character @code{g}.
20081 @item show interrupt-sequence
20082 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20083 is sent by @value{GDBN} to interrupt the remote program.
20084 @code{BREAK-g} is BREAK signal followed by @code{g} and
20085 also known as Magic SysRq g.
20087 @item set remote interrupt-on-connect
20088 @cindex send interrupt-sequence on start
20089 Specify whether interrupt-sequence is sent to remote target when
20090 @value{GDBN} connects to it. This is mostly needed when you debug
20091 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20092 which is known as Magic SysRq g in order to connect @value{GDBN}.
20094 @item show interrupt-on-connect
20095 Show whether interrupt-sequence is sent
20096 to remote target when @value{GDBN} connects to it.
20100 @item set tcp auto-retry on
20101 @cindex auto-retry, for remote TCP target
20102 Enable auto-retry for remote TCP connections. This is useful if the remote
20103 debugging agent is launched in parallel with @value{GDBN}; there is a race
20104 condition because the agent may not become ready to accept the connection
20105 before @value{GDBN} attempts to connect. When auto-retry is
20106 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20107 to establish the connection using the timeout specified by
20108 @code{set tcp connect-timeout}.
20110 @item set tcp auto-retry off
20111 Do not auto-retry failed TCP connections.
20113 @item show tcp auto-retry
20114 Show the current auto-retry setting.
20116 @item set tcp connect-timeout @var{seconds}
20117 @itemx set tcp connect-timeout unlimited
20118 @cindex connection timeout, for remote TCP target
20119 @cindex timeout, for remote target connection
20120 Set the timeout for establishing a TCP connection to the remote target to
20121 @var{seconds}. The timeout affects both polling to retry failed connections
20122 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20123 that are merely slow to complete, and represents an approximate cumulative
20124 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20125 @value{GDBN} will keep attempting to establish a connection forever,
20126 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20128 @item show tcp connect-timeout
20129 Show the current connection timeout setting.
20132 @cindex remote packets, enabling and disabling
20133 The @value{GDBN} remote protocol autodetects the packets supported by
20134 your debugging stub. If you need to override the autodetection, you
20135 can use these commands to enable or disable individual packets. Each
20136 packet can be set to @samp{on} (the remote target supports this
20137 packet), @samp{off} (the remote target does not support this packet),
20138 or @samp{auto} (detect remote target support for this packet). They
20139 all default to @samp{auto}. For more information about each packet,
20140 see @ref{Remote Protocol}.
20142 During normal use, you should not have to use any of these commands.
20143 If you do, that may be a bug in your remote debugging stub, or a bug
20144 in @value{GDBN}. You may want to report the problem to the
20145 @value{GDBN} developers.
20147 For each packet @var{name}, the command to enable or disable the
20148 packet is @code{set remote @var{name}-packet}. The available settings
20151 @multitable @columnfractions 0.28 0.32 0.25
20154 @tab Related Features
20156 @item @code{fetch-register}
20158 @tab @code{info registers}
20160 @item @code{set-register}
20164 @item @code{binary-download}
20166 @tab @code{load}, @code{set}
20168 @item @code{read-aux-vector}
20169 @tab @code{qXfer:auxv:read}
20170 @tab @code{info auxv}
20172 @item @code{symbol-lookup}
20173 @tab @code{qSymbol}
20174 @tab Detecting multiple threads
20176 @item @code{attach}
20177 @tab @code{vAttach}
20180 @item @code{verbose-resume}
20182 @tab Stepping or resuming multiple threads
20188 @item @code{software-breakpoint}
20192 @item @code{hardware-breakpoint}
20196 @item @code{write-watchpoint}
20200 @item @code{read-watchpoint}
20204 @item @code{access-watchpoint}
20208 @item @code{pid-to-exec-file}
20209 @tab @code{qXfer:exec-file:read}
20210 @tab @code{attach}, @code{run}
20212 @item @code{target-features}
20213 @tab @code{qXfer:features:read}
20214 @tab @code{set architecture}
20216 @item @code{library-info}
20217 @tab @code{qXfer:libraries:read}
20218 @tab @code{info sharedlibrary}
20220 @item @code{memory-map}
20221 @tab @code{qXfer:memory-map:read}
20222 @tab @code{info mem}
20224 @item @code{read-sdata-object}
20225 @tab @code{qXfer:sdata:read}
20226 @tab @code{print $_sdata}
20228 @item @code{read-spu-object}
20229 @tab @code{qXfer:spu:read}
20230 @tab @code{info spu}
20232 @item @code{write-spu-object}
20233 @tab @code{qXfer:spu:write}
20234 @tab @code{info spu}
20236 @item @code{read-siginfo-object}
20237 @tab @code{qXfer:siginfo:read}
20238 @tab @code{print $_siginfo}
20240 @item @code{write-siginfo-object}
20241 @tab @code{qXfer:siginfo:write}
20242 @tab @code{set $_siginfo}
20244 @item @code{threads}
20245 @tab @code{qXfer:threads:read}
20246 @tab @code{info threads}
20248 @item @code{get-thread-local-@*storage-address}
20249 @tab @code{qGetTLSAddr}
20250 @tab Displaying @code{__thread} variables
20252 @item @code{get-thread-information-block-address}
20253 @tab @code{qGetTIBAddr}
20254 @tab Display MS-Windows Thread Information Block.
20256 @item @code{search-memory}
20257 @tab @code{qSearch:memory}
20260 @item @code{supported-packets}
20261 @tab @code{qSupported}
20262 @tab Remote communications parameters
20264 @item @code{pass-signals}
20265 @tab @code{QPassSignals}
20266 @tab @code{handle @var{signal}}
20268 @item @code{program-signals}
20269 @tab @code{QProgramSignals}
20270 @tab @code{handle @var{signal}}
20272 @item @code{hostio-close-packet}
20273 @tab @code{vFile:close}
20274 @tab @code{remote get}, @code{remote put}
20276 @item @code{hostio-open-packet}
20277 @tab @code{vFile:open}
20278 @tab @code{remote get}, @code{remote put}
20280 @item @code{hostio-pread-packet}
20281 @tab @code{vFile:pread}
20282 @tab @code{remote get}, @code{remote put}
20284 @item @code{hostio-pwrite-packet}
20285 @tab @code{vFile:pwrite}
20286 @tab @code{remote get}, @code{remote put}
20288 @item @code{hostio-unlink-packet}
20289 @tab @code{vFile:unlink}
20290 @tab @code{remote delete}
20292 @item @code{hostio-readlink-packet}
20293 @tab @code{vFile:readlink}
20296 @item @code{hostio-fstat-packet}
20297 @tab @code{vFile:fstat}
20300 @item @code{hostio-setfs-packet}
20301 @tab @code{vFile:setfs}
20304 @item @code{noack-packet}
20305 @tab @code{QStartNoAckMode}
20306 @tab Packet acknowledgment
20308 @item @code{osdata}
20309 @tab @code{qXfer:osdata:read}
20310 @tab @code{info os}
20312 @item @code{query-attached}
20313 @tab @code{qAttached}
20314 @tab Querying remote process attach state.
20316 @item @code{trace-buffer-size}
20317 @tab @code{QTBuffer:size}
20318 @tab @code{set trace-buffer-size}
20320 @item @code{trace-status}
20321 @tab @code{qTStatus}
20322 @tab @code{tstatus}
20324 @item @code{traceframe-info}
20325 @tab @code{qXfer:traceframe-info:read}
20326 @tab Traceframe info
20328 @item @code{install-in-trace}
20329 @tab @code{InstallInTrace}
20330 @tab Install tracepoint in tracing
20332 @item @code{disable-randomization}
20333 @tab @code{QDisableRandomization}
20334 @tab @code{set disable-randomization}
20336 @item @code{conditional-breakpoints-packet}
20337 @tab @code{Z0 and Z1}
20338 @tab @code{Support for target-side breakpoint condition evaluation}
20340 @item @code{multiprocess-extensions}
20341 @tab @code{multiprocess extensions}
20342 @tab Debug multiple processes and remote process PID awareness
20344 @item @code{swbreak-feature}
20345 @tab @code{swbreak stop reason}
20348 @item @code{hwbreak-feature}
20349 @tab @code{hwbreak stop reason}
20352 @item @code{fork-event-feature}
20353 @tab @code{fork stop reason}
20356 @item @code{vfork-event-feature}
20357 @tab @code{vfork stop reason}
20360 @item @code{exec-event-feature}
20361 @tab @code{exec stop reason}
20364 @item @code{thread-events}
20365 @tab @code{QThreadEvents}
20366 @tab Tracking thread lifetime.
20368 @item @code{no-resumed-stop-reply}
20369 @tab @code{no resumed thread left stop reply}
20370 @tab Tracking thread lifetime.
20375 @section Implementing a Remote Stub
20377 @cindex debugging stub, example
20378 @cindex remote stub, example
20379 @cindex stub example, remote debugging
20380 The stub files provided with @value{GDBN} implement the target side of the
20381 communication protocol, and the @value{GDBN} side is implemented in the
20382 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20383 these subroutines to communicate, and ignore the details. (If you're
20384 implementing your own stub file, you can still ignore the details: start
20385 with one of the existing stub files. @file{sparc-stub.c} is the best
20386 organized, and therefore the easiest to read.)
20388 @cindex remote serial debugging, overview
20389 To debug a program running on another machine (the debugging
20390 @dfn{target} machine), you must first arrange for all the usual
20391 prerequisites for the program to run by itself. For example, for a C
20396 A startup routine to set up the C runtime environment; these usually
20397 have a name like @file{crt0}. The startup routine may be supplied by
20398 your hardware supplier, or you may have to write your own.
20401 A C subroutine library to support your program's
20402 subroutine calls, notably managing input and output.
20405 A way of getting your program to the other machine---for example, a
20406 download program. These are often supplied by the hardware
20407 manufacturer, but you may have to write your own from hardware
20411 The next step is to arrange for your program to use a serial port to
20412 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20413 machine). In general terms, the scheme looks like this:
20417 @value{GDBN} already understands how to use this protocol; when everything
20418 else is set up, you can simply use the @samp{target remote} command
20419 (@pxref{Targets,,Specifying a Debugging Target}).
20421 @item On the target,
20422 you must link with your program a few special-purpose subroutines that
20423 implement the @value{GDBN} remote serial protocol. The file containing these
20424 subroutines is called a @dfn{debugging stub}.
20426 On certain remote targets, you can use an auxiliary program
20427 @code{gdbserver} instead of linking a stub into your program.
20428 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20431 The debugging stub is specific to the architecture of the remote
20432 machine; for example, use @file{sparc-stub.c} to debug programs on
20435 @cindex remote serial stub list
20436 These working remote stubs are distributed with @value{GDBN}:
20441 @cindex @file{i386-stub.c}
20444 For Intel 386 and compatible architectures.
20447 @cindex @file{m68k-stub.c}
20448 @cindex Motorola 680x0
20450 For Motorola 680x0 architectures.
20453 @cindex @file{sh-stub.c}
20456 For Renesas SH architectures.
20459 @cindex @file{sparc-stub.c}
20461 For @sc{sparc} architectures.
20463 @item sparcl-stub.c
20464 @cindex @file{sparcl-stub.c}
20467 For Fujitsu @sc{sparclite} architectures.
20471 The @file{README} file in the @value{GDBN} distribution may list other
20472 recently added stubs.
20475 * Stub Contents:: What the stub can do for you
20476 * Bootstrapping:: What you must do for the stub
20477 * Debug Session:: Putting it all together
20480 @node Stub Contents
20481 @subsection What the Stub Can Do for You
20483 @cindex remote serial stub
20484 The debugging stub for your architecture supplies these three
20488 @item set_debug_traps
20489 @findex set_debug_traps
20490 @cindex remote serial stub, initialization
20491 This routine arranges for @code{handle_exception} to run when your
20492 program stops. You must call this subroutine explicitly in your
20493 program's startup code.
20495 @item handle_exception
20496 @findex handle_exception
20497 @cindex remote serial stub, main routine
20498 This is the central workhorse, but your program never calls it
20499 explicitly---the setup code arranges for @code{handle_exception} to
20500 run when a trap is triggered.
20502 @code{handle_exception} takes control when your program stops during
20503 execution (for example, on a breakpoint), and mediates communications
20504 with @value{GDBN} on the host machine. This is where the communications
20505 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20506 representative on the target machine. It begins by sending summary
20507 information on the state of your program, then continues to execute,
20508 retrieving and transmitting any information @value{GDBN} needs, until you
20509 execute a @value{GDBN} command that makes your program resume; at that point,
20510 @code{handle_exception} returns control to your own code on the target
20514 @cindex @code{breakpoint} subroutine, remote
20515 Use this auxiliary subroutine to make your program contain a
20516 breakpoint. Depending on the particular situation, this may be the only
20517 way for @value{GDBN} to get control. For instance, if your target
20518 machine has some sort of interrupt button, you won't need to call this;
20519 pressing the interrupt button transfers control to
20520 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20521 simply receiving characters on the serial port may also trigger a trap;
20522 again, in that situation, you don't need to call @code{breakpoint} from
20523 your own program---simply running @samp{target remote} from the host
20524 @value{GDBN} session gets control.
20526 Call @code{breakpoint} if none of these is true, or if you simply want
20527 to make certain your program stops at a predetermined point for the
20528 start of your debugging session.
20531 @node Bootstrapping
20532 @subsection What You Must Do for the Stub
20534 @cindex remote stub, support routines
20535 The debugging stubs that come with @value{GDBN} are set up for a particular
20536 chip architecture, but they have no information about the rest of your
20537 debugging target machine.
20539 First of all you need to tell the stub how to communicate with the
20543 @item int getDebugChar()
20544 @findex getDebugChar
20545 Write this subroutine to read a single character from the serial port.
20546 It may be identical to @code{getchar} for your target system; a
20547 different name is used to allow you to distinguish the two if you wish.
20549 @item void putDebugChar(int)
20550 @findex putDebugChar
20551 Write this subroutine to write a single character to the serial port.
20552 It may be identical to @code{putchar} for your target system; a
20553 different name is used to allow you to distinguish the two if you wish.
20556 @cindex control C, and remote debugging
20557 @cindex interrupting remote targets
20558 If you want @value{GDBN} to be able to stop your program while it is
20559 running, you need to use an interrupt-driven serial driver, and arrange
20560 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20561 character). That is the character which @value{GDBN} uses to tell the
20562 remote system to stop.
20564 Getting the debugging target to return the proper status to @value{GDBN}
20565 probably requires changes to the standard stub; one quick and dirty way
20566 is to just execute a breakpoint instruction (the ``dirty'' part is that
20567 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20569 Other routines you need to supply are:
20572 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20573 @findex exceptionHandler
20574 Write this function to install @var{exception_address} in the exception
20575 handling tables. You need to do this because the stub does not have any
20576 way of knowing what the exception handling tables on your target system
20577 are like (for example, the processor's table might be in @sc{rom},
20578 containing entries which point to a table in @sc{ram}).
20579 The @var{exception_number} specifies the exception which should be changed;
20580 its meaning is architecture-dependent (for example, different numbers
20581 might represent divide by zero, misaligned access, etc). When this
20582 exception occurs, control should be transferred directly to
20583 @var{exception_address}, and the processor state (stack, registers,
20584 and so on) should be just as it is when a processor exception occurs. So if
20585 you want to use a jump instruction to reach @var{exception_address}, it
20586 should be a simple jump, not a jump to subroutine.
20588 For the 386, @var{exception_address} should be installed as an interrupt
20589 gate so that interrupts are masked while the handler runs. The gate
20590 should be at privilege level 0 (the most privileged level). The
20591 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20592 help from @code{exceptionHandler}.
20594 @item void flush_i_cache()
20595 @findex flush_i_cache
20596 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20597 instruction cache, if any, on your target machine. If there is no
20598 instruction cache, this subroutine may be a no-op.
20600 On target machines that have instruction caches, @value{GDBN} requires this
20601 function to make certain that the state of your program is stable.
20605 You must also make sure this library routine is available:
20608 @item void *memset(void *, int, int)
20610 This is the standard library function @code{memset} that sets an area of
20611 memory to a known value. If you have one of the free versions of
20612 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20613 either obtain it from your hardware manufacturer, or write your own.
20616 If you do not use the GNU C compiler, you may need other standard
20617 library subroutines as well; this varies from one stub to another,
20618 but in general the stubs are likely to use any of the common library
20619 subroutines which @code{@value{NGCC}} generates as inline code.
20622 @node Debug Session
20623 @subsection Putting it All Together
20625 @cindex remote serial debugging summary
20626 In summary, when your program is ready to debug, you must follow these
20631 Make sure you have defined the supporting low-level routines
20632 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20634 @code{getDebugChar}, @code{putDebugChar},
20635 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20639 Insert these lines in your program's startup code, before the main
20640 procedure is called:
20647 On some machines, when a breakpoint trap is raised, the hardware
20648 automatically makes the PC point to the instruction after the
20649 breakpoint. If your machine doesn't do that, you may need to adjust
20650 @code{handle_exception} to arrange for it to return to the instruction
20651 after the breakpoint on this first invocation, so that your program
20652 doesn't keep hitting the initial breakpoint instead of making
20656 For the 680x0 stub only, you need to provide a variable called
20657 @code{exceptionHook}. Normally you just use:
20660 void (*exceptionHook)() = 0;
20664 but if before calling @code{set_debug_traps}, you set it to point to a
20665 function in your program, that function is called when
20666 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20667 error). The function indicated by @code{exceptionHook} is called with
20668 one parameter: an @code{int} which is the exception number.
20671 Compile and link together: your program, the @value{GDBN} debugging stub for
20672 your target architecture, and the supporting subroutines.
20675 Make sure you have a serial connection between your target machine and
20676 the @value{GDBN} host, and identify the serial port on the host.
20679 @c The "remote" target now provides a `load' command, so we should
20680 @c document that. FIXME.
20681 Download your program to your target machine (or get it there by
20682 whatever means the manufacturer provides), and start it.
20685 Start @value{GDBN} on the host, and connect to the target
20686 (@pxref{Connecting,,Connecting to a Remote Target}).
20690 @node Configurations
20691 @chapter Configuration-Specific Information
20693 While nearly all @value{GDBN} commands are available for all native and
20694 cross versions of the debugger, there are some exceptions. This chapter
20695 describes things that are only available in certain configurations.
20697 There are three major categories of configurations: native
20698 configurations, where the host and target are the same, embedded
20699 operating system configurations, which are usually the same for several
20700 different processor architectures, and bare embedded processors, which
20701 are quite different from each other.
20706 * Embedded Processors::
20713 This section describes details specific to particular native
20717 * BSD libkvm Interface:: Debugging BSD kernel memory images
20718 * SVR4 Process Information:: SVR4 process information
20719 * DJGPP Native:: Features specific to the DJGPP port
20720 * Cygwin Native:: Features specific to the Cygwin port
20721 * Hurd Native:: Features specific to @sc{gnu} Hurd
20722 * Darwin:: Features specific to Darwin
20725 @node BSD libkvm Interface
20726 @subsection BSD libkvm Interface
20729 @cindex kernel memory image
20730 @cindex kernel crash dump
20732 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20733 interface that provides a uniform interface for accessing kernel virtual
20734 memory images, including live systems and crash dumps. @value{GDBN}
20735 uses this interface to allow you to debug live kernels and kernel crash
20736 dumps on many native BSD configurations. This is implemented as a
20737 special @code{kvm} debugging target. For debugging a live system, load
20738 the currently running kernel into @value{GDBN} and connect to the
20742 (@value{GDBP}) @b{target kvm}
20745 For debugging crash dumps, provide the file name of the crash dump as an
20749 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20752 Once connected to the @code{kvm} target, the following commands are
20758 Set current context from the @dfn{Process Control Block} (PCB) address.
20761 Set current context from proc address. This command isn't available on
20762 modern FreeBSD systems.
20765 @node SVR4 Process Information
20766 @subsection SVR4 Process Information
20768 @cindex examine process image
20769 @cindex process info via @file{/proc}
20771 Many versions of SVR4 and compatible systems provide a facility called
20772 @samp{/proc} that can be used to examine the image of a running
20773 process using file-system subroutines.
20775 If @value{GDBN} is configured for an operating system with this
20776 facility, the command @code{info proc} is available to report
20777 information about the process running your program, or about any
20778 process running on your system. This includes, as of this writing,
20779 @sc{gnu}/Linux and Solaris, for example.
20781 This command may also work on core files that were created on a system
20782 that has the @samp{/proc} facility.
20788 @itemx info proc @var{process-id}
20789 Summarize available information about any running process. If a
20790 process ID is specified by @var{process-id}, display information about
20791 that process; otherwise display information about the program being
20792 debugged. The summary includes the debugged process ID, the command
20793 line used to invoke it, its current working directory, and its
20794 executable file's absolute file name.
20796 On some systems, @var{process-id} can be of the form
20797 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20798 within a process. If the optional @var{pid} part is missing, it means
20799 a thread from the process being debugged (the leading @samp{/} still
20800 needs to be present, or else @value{GDBN} will interpret the number as
20801 a process ID rather than a thread ID).
20803 @item info proc cmdline
20804 @cindex info proc cmdline
20805 Show the original command line of the process. This command is
20806 specific to @sc{gnu}/Linux.
20808 @item info proc cwd
20809 @cindex info proc cwd
20810 Show the current working directory of the process. This command is
20811 specific to @sc{gnu}/Linux.
20813 @item info proc exe
20814 @cindex info proc exe
20815 Show the name of executable of the process. This command is specific
20818 @item info proc mappings
20819 @cindex memory address space mappings
20820 Report the memory address space ranges accessible in the program, with
20821 information on whether the process has read, write, or execute access
20822 rights to each range. On @sc{gnu}/Linux systems, each memory range
20823 includes the object file which is mapped to that range, instead of the
20824 memory access rights to that range.
20826 @item info proc stat
20827 @itemx info proc status
20828 @cindex process detailed status information
20829 These subcommands are specific to @sc{gnu}/Linux systems. They show
20830 the process-related information, including the user ID and group ID;
20831 how many threads are there in the process; its virtual memory usage;
20832 the signals that are pending, blocked, and ignored; its TTY; its
20833 consumption of system and user time; its stack size; its @samp{nice}
20834 value; etc. For more information, see the @samp{proc} man page
20835 (type @kbd{man 5 proc} from your shell prompt).
20837 @item info proc all
20838 Show all the information about the process described under all of the
20839 above @code{info proc} subcommands.
20842 @comment These sub-options of 'info proc' were not included when
20843 @comment procfs.c was re-written. Keep their descriptions around
20844 @comment against the day when someone finds the time to put them back in.
20845 @kindex info proc times
20846 @item info proc times
20847 Starting time, user CPU time, and system CPU time for your program and
20850 @kindex info proc id
20852 Report on the process IDs related to your program: its own process ID,
20853 the ID of its parent, the process group ID, and the session ID.
20856 @item set procfs-trace
20857 @kindex set procfs-trace
20858 @cindex @code{procfs} API calls
20859 This command enables and disables tracing of @code{procfs} API calls.
20861 @item show procfs-trace
20862 @kindex show procfs-trace
20863 Show the current state of @code{procfs} API call tracing.
20865 @item set procfs-file @var{file}
20866 @kindex set procfs-file
20867 Tell @value{GDBN} to write @code{procfs} API trace to the named
20868 @var{file}. @value{GDBN} appends the trace info to the previous
20869 contents of the file. The default is to display the trace on the
20872 @item show procfs-file
20873 @kindex show procfs-file
20874 Show the file to which @code{procfs} API trace is written.
20876 @item proc-trace-entry
20877 @itemx proc-trace-exit
20878 @itemx proc-untrace-entry
20879 @itemx proc-untrace-exit
20880 @kindex proc-trace-entry
20881 @kindex proc-trace-exit
20882 @kindex proc-untrace-entry
20883 @kindex proc-untrace-exit
20884 These commands enable and disable tracing of entries into and exits
20885 from the @code{syscall} interface.
20888 @kindex info pidlist
20889 @cindex process list, QNX Neutrino
20890 For QNX Neutrino only, this command displays the list of all the
20891 processes and all the threads within each process.
20894 @kindex info meminfo
20895 @cindex mapinfo list, QNX Neutrino
20896 For QNX Neutrino only, this command displays the list of all mapinfos.
20900 @subsection Features for Debugging @sc{djgpp} Programs
20901 @cindex @sc{djgpp} debugging
20902 @cindex native @sc{djgpp} debugging
20903 @cindex MS-DOS-specific commands
20906 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20907 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20908 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20909 top of real-mode DOS systems and their emulations.
20911 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20912 defines a few commands specific to the @sc{djgpp} port. This
20913 subsection describes those commands.
20918 This is a prefix of @sc{djgpp}-specific commands which print
20919 information about the target system and important OS structures.
20922 @cindex MS-DOS system info
20923 @cindex free memory information (MS-DOS)
20924 @item info dos sysinfo
20925 This command displays assorted information about the underlying
20926 platform: the CPU type and features, the OS version and flavor, the
20927 DPMI version, and the available conventional and DPMI memory.
20932 @cindex segment descriptor tables
20933 @cindex descriptor tables display
20935 @itemx info dos ldt
20936 @itemx info dos idt
20937 These 3 commands display entries from, respectively, Global, Local,
20938 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20939 tables are data structures which store a descriptor for each segment
20940 that is currently in use. The segment's selector is an index into a
20941 descriptor table; the table entry for that index holds the
20942 descriptor's base address and limit, and its attributes and access
20945 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20946 segment (used for both data and the stack), and a DOS segment (which
20947 allows access to DOS/BIOS data structures and absolute addresses in
20948 conventional memory). However, the DPMI host will usually define
20949 additional segments in order to support the DPMI environment.
20951 @cindex garbled pointers
20952 These commands allow to display entries from the descriptor tables.
20953 Without an argument, all entries from the specified table are
20954 displayed. An argument, which should be an integer expression, means
20955 display a single entry whose index is given by the argument. For
20956 example, here's a convenient way to display information about the
20957 debugged program's data segment:
20960 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20961 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20965 This comes in handy when you want to see whether a pointer is outside
20966 the data segment's limit (i.e.@: @dfn{garbled}).
20968 @cindex page tables display (MS-DOS)
20970 @itemx info dos pte
20971 These two commands display entries from, respectively, the Page
20972 Directory and the Page Tables. Page Directories and Page Tables are
20973 data structures which control how virtual memory addresses are mapped
20974 into physical addresses. A Page Table includes an entry for every
20975 page of memory that is mapped into the program's address space; there
20976 may be several Page Tables, each one holding up to 4096 entries. A
20977 Page Directory has up to 4096 entries, one each for every Page Table
20978 that is currently in use.
20980 Without an argument, @kbd{info dos pde} displays the entire Page
20981 Directory, and @kbd{info dos pte} displays all the entries in all of
20982 the Page Tables. An argument, an integer expression, given to the
20983 @kbd{info dos pde} command means display only that entry from the Page
20984 Directory table. An argument given to the @kbd{info dos pte} command
20985 means display entries from a single Page Table, the one pointed to by
20986 the specified entry in the Page Directory.
20988 @cindex direct memory access (DMA) on MS-DOS
20989 These commands are useful when your program uses @dfn{DMA} (Direct
20990 Memory Access), which needs physical addresses to program the DMA
20993 These commands are supported only with some DPMI servers.
20995 @cindex physical address from linear address
20996 @item info dos address-pte @var{addr}
20997 This command displays the Page Table entry for a specified linear
20998 address. The argument @var{addr} is a linear address which should
20999 already have the appropriate segment's base address added to it,
21000 because this command accepts addresses which may belong to @emph{any}
21001 segment. For example, here's how to display the Page Table entry for
21002 the page where a variable @code{i} is stored:
21005 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21006 @exdent @code{Page Table entry for address 0x11a00d30:}
21007 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21011 This says that @code{i} is stored at offset @code{0xd30} from the page
21012 whose physical base address is @code{0x02698000}, and shows all the
21013 attributes of that page.
21015 Note that you must cast the addresses of variables to a @code{char *},
21016 since otherwise the value of @code{__djgpp_base_address}, the base
21017 address of all variables and functions in a @sc{djgpp} program, will
21018 be added using the rules of C pointer arithmetics: if @code{i} is
21019 declared an @code{int}, @value{GDBN} will add 4 times the value of
21020 @code{__djgpp_base_address} to the address of @code{i}.
21022 Here's another example, it displays the Page Table entry for the
21026 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21027 @exdent @code{Page Table entry for address 0x29110:}
21028 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21032 (The @code{+ 3} offset is because the transfer buffer's address is the
21033 3rd member of the @code{_go32_info_block} structure.) The output
21034 clearly shows that this DPMI server maps the addresses in conventional
21035 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21036 linear (@code{0x29110}) addresses are identical.
21038 This command is supported only with some DPMI servers.
21041 @cindex DOS serial data link, remote debugging
21042 In addition to native debugging, the DJGPP port supports remote
21043 debugging via a serial data link. The following commands are specific
21044 to remote serial debugging in the DJGPP port of @value{GDBN}.
21047 @kindex set com1base
21048 @kindex set com1irq
21049 @kindex set com2base
21050 @kindex set com2irq
21051 @kindex set com3base
21052 @kindex set com3irq
21053 @kindex set com4base
21054 @kindex set com4irq
21055 @item set com1base @var{addr}
21056 This command sets the base I/O port address of the @file{COM1} serial
21059 @item set com1irq @var{irq}
21060 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21061 for the @file{COM1} serial port.
21063 There are similar commands @samp{set com2base}, @samp{set com3irq},
21064 etc.@: for setting the port address and the @code{IRQ} lines for the
21067 @kindex show com1base
21068 @kindex show com1irq
21069 @kindex show com2base
21070 @kindex show com2irq
21071 @kindex show com3base
21072 @kindex show com3irq
21073 @kindex show com4base
21074 @kindex show com4irq
21075 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21076 display the current settings of the base address and the @code{IRQ}
21077 lines used by the COM ports.
21080 @kindex info serial
21081 @cindex DOS serial port status
21082 This command prints the status of the 4 DOS serial ports. For each
21083 port, it prints whether it's active or not, its I/O base address and
21084 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21085 counts of various errors encountered so far.
21089 @node Cygwin Native
21090 @subsection Features for Debugging MS Windows PE Executables
21091 @cindex MS Windows debugging
21092 @cindex native Cygwin debugging
21093 @cindex Cygwin-specific commands
21095 @value{GDBN} supports native debugging of MS Windows programs, including
21096 DLLs with and without symbolic debugging information.
21098 @cindex Ctrl-BREAK, MS-Windows
21099 @cindex interrupt debuggee on MS-Windows
21100 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21101 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21102 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21103 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21104 sequence, which can be used to interrupt the debuggee even if it
21107 There are various additional Cygwin-specific commands, described in
21108 this section. Working with DLLs that have no debugging symbols is
21109 described in @ref{Non-debug DLL Symbols}.
21114 This is a prefix of MS Windows-specific commands which print
21115 information about the target system and important OS structures.
21117 @item info w32 selector
21118 This command displays information returned by
21119 the Win32 API @code{GetThreadSelectorEntry} function.
21120 It takes an optional argument that is evaluated to
21121 a long value to give the information about this given selector.
21122 Without argument, this command displays information
21123 about the six segment registers.
21125 @item info w32 thread-information-block
21126 This command displays thread specific information stored in the
21127 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21128 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21130 @kindex set cygwin-exceptions
21131 @cindex debugging the Cygwin DLL
21132 @cindex Cygwin DLL, debugging
21133 @item set cygwin-exceptions @var{mode}
21134 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21135 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21136 @value{GDBN} will delay recognition of exceptions, and may ignore some
21137 exceptions which seem to be caused by internal Cygwin DLL
21138 ``bookkeeping''. This option is meant primarily for debugging the
21139 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21140 @value{GDBN} users with false @code{SIGSEGV} signals.
21142 @kindex show cygwin-exceptions
21143 @item show cygwin-exceptions
21144 Displays whether @value{GDBN} will break on exceptions that happen
21145 inside the Cygwin DLL itself.
21147 @kindex set new-console
21148 @item set new-console @var{mode}
21149 If @var{mode} is @code{on} the debuggee will
21150 be started in a new console on next start.
21151 If @var{mode} is @code{off}, the debuggee will
21152 be started in the same console as the debugger.
21154 @kindex show new-console
21155 @item show new-console
21156 Displays whether a new console is used
21157 when the debuggee is started.
21159 @kindex set new-group
21160 @item set new-group @var{mode}
21161 This boolean value controls whether the debuggee should
21162 start a new group or stay in the same group as the debugger.
21163 This affects the way the Windows OS handles
21166 @kindex show new-group
21167 @item show new-group
21168 Displays current value of new-group boolean.
21170 @kindex set debugevents
21171 @item set debugevents
21172 This boolean value adds debug output concerning kernel events related
21173 to the debuggee seen by the debugger. This includes events that
21174 signal thread and process creation and exit, DLL loading and
21175 unloading, console interrupts, and debugging messages produced by the
21176 Windows @code{OutputDebugString} API call.
21178 @kindex set debugexec
21179 @item set debugexec
21180 This boolean value adds debug output concerning execute events
21181 (such as resume thread) seen by the debugger.
21183 @kindex set debugexceptions
21184 @item set debugexceptions
21185 This boolean value adds debug output concerning exceptions in the
21186 debuggee seen by the debugger.
21188 @kindex set debugmemory
21189 @item set debugmemory
21190 This boolean value adds debug output concerning debuggee memory reads
21191 and writes by the debugger.
21195 This boolean values specifies whether the debuggee is called
21196 via a shell or directly (default value is on).
21200 Displays if the debuggee will be started with a shell.
21205 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21208 @node Non-debug DLL Symbols
21209 @subsubsection Support for DLLs without Debugging Symbols
21210 @cindex DLLs with no debugging symbols
21211 @cindex Minimal symbols and DLLs
21213 Very often on windows, some of the DLLs that your program relies on do
21214 not include symbolic debugging information (for example,
21215 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21216 symbols in a DLL, it relies on the minimal amount of symbolic
21217 information contained in the DLL's export table. This section
21218 describes working with such symbols, known internally to @value{GDBN} as
21219 ``minimal symbols''.
21221 Note that before the debugged program has started execution, no DLLs
21222 will have been loaded. The easiest way around this problem is simply to
21223 start the program --- either by setting a breakpoint or letting the
21224 program run once to completion.
21226 @subsubsection DLL Name Prefixes
21228 In keeping with the naming conventions used by the Microsoft debugging
21229 tools, DLL export symbols are made available with a prefix based on the
21230 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21231 also entered into the symbol table, so @code{CreateFileA} is often
21232 sufficient. In some cases there will be name clashes within a program
21233 (particularly if the executable itself includes full debugging symbols)
21234 necessitating the use of the fully qualified name when referring to the
21235 contents of the DLL. Use single-quotes around the name to avoid the
21236 exclamation mark (``!'') being interpreted as a language operator.
21238 Note that the internal name of the DLL may be all upper-case, even
21239 though the file name of the DLL is lower-case, or vice-versa. Since
21240 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21241 some confusion. If in doubt, try the @code{info functions} and
21242 @code{info variables} commands or even @code{maint print msymbols}
21243 (@pxref{Symbols}). Here's an example:
21246 (@value{GDBP}) info function CreateFileA
21247 All functions matching regular expression "CreateFileA":
21249 Non-debugging symbols:
21250 0x77e885f4 CreateFileA
21251 0x77e885f4 KERNEL32!CreateFileA
21255 (@value{GDBP}) info function !
21256 All functions matching regular expression "!":
21258 Non-debugging symbols:
21259 0x6100114c cygwin1!__assert
21260 0x61004034 cygwin1!_dll_crt0@@0
21261 0x61004240 cygwin1!dll_crt0(per_process *)
21265 @subsubsection Working with Minimal Symbols
21267 Symbols extracted from a DLL's export table do not contain very much
21268 type information. All that @value{GDBN} can do is guess whether a symbol
21269 refers to a function or variable depending on the linker section that
21270 contains the symbol. Also note that the actual contents of the memory
21271 contained in a DLL are not available unless the program is running. This
21272 means that you cannot examine the contents of a variable or disassemble
21273 a function within a DLL without a running program.
21275 Variables are generally treated as pointers and dereferenced
21276 automatically. For this reason, it is often necessary to prefix a
21277 variable name with the address-of operator (``&'') and provide explicit
21278 type information in the command. Here's an example of the type of
21282 (@value{GDBP}) print 'cygwin1!__argv'
21287 (@value{GDBP}) x 'cygwin1!__argv'
21288 0x10021610: "\230y\""
21291 And two possible solutions:
21294 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21295 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21299 (@value{GDBP}) x/2x &'cygwin1!__argv'
21300 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21301 (@value{GDBP}) x/x 0x10021608
21302 0x10021608: 0x0022fd98
21303 (@value{GDBP}) x/s 0x0022fd98
21304 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21307 Setting a break point within a DLL is possible even before the program
21308 starts execution. However, under these circumstances, @value{GDBN} can't
21309 examine the initial instructions of the function in order to skip the
21310 function's frame set-up code. You can work around this by using ``*&''
21311 to set the breakpoint at a raw memory address:
21314 (@value{GDBP}) break *&'python22!PyOS_Readline'
21315 Breakpoint 1 at 0x1e04eff0
21318 The author of these extensions is not entirely convinced that setting a
21319 break point within a shared DLL like @file{kernel32.dll} is completely
21323 @subsection Commands Specific to @sc{gnu} Hurd Systems
21324 @cindex @sc{gnu} Hurd debugging
21326 This subsection describes @value{GDBN} commands specific to the
21327 @sc{gnu} Hurd native debugging.
21332 @kindex set signals@r{, Hurd command}
21333 @kindex set sigs@r{, Hurd command}
21334 This command toggles the state of inferior signal interception by
21335 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21336 affected by this command. @code{sigs} is a shorthand alias for
21341 @kindex show signals@r{, Hurd command}
21342 @kindex show sigs@r{, Hurd command}
21343 Show the current state of intercepting inferior's signals.
21345 @item set signal-thread
21346 @itemx set sigthread
21347 @kindex set signal-thread
21348 @kindex set sigthread
21349 This command tells @value{GDBN} which thread is the @code{libc} signal
21350 thread. That thread is run when a signal is delivered to a running
21351 process. @code{set sigthread} is the shorthand alias of @code{set
21354 @item show signal-thread
21355 @itemx show sigthread
21356 @kindex show signal-thread
21357 @kindex show sigthread
21358 These two commands show which thread will run when the inferior is
21359 delivered a signal.
21362 @kindex set stopped@r{, Hurd command}
21363 This commands tells @value{GDBN} that the inferior process is stopped,
21364 as with the @code{SIGSTOP} signal. The stopped process can be
21365 continued by delivering a signal to it.
21368 @kindex show stopped@r{, Hurd command}
21369 This command shows whether @value{GDBN} thinks the debuggee is
21372 @item set exceptions
21373 @kindex set exceptions@r{, Hurd command}
21374 Use this command to turn off trapping of exceptions in the inferior.
21375 When exception trapping is off, neither breakpoints nor
21376 single-stepping will work. To restore the default, set exception
21379 @item show exceptions
21380 @kindex show exceptions@r{, Hurd command}
21381 Show the current state of trapping exceptions in the inferior.
21383 @item set task pause
21384 @kindex set task@r{, Hurd commands}
21385 @cindex task attributes (@sc{gnu} Hurd)
21386 @cindex pause current task (@sc{gnu} Hurd)
21387 This command toggles task suspension when @value{GDBN} has control.
21388 Setting it to on takes effect immediately, and the task is suspended
21389 whenever @value{GDBN} gets control. Setting it to off will take
21390 effect the next time the inferior is continued. If this option is set
21391 to off, you can use @code{set thread default pause on} or @code{set
21392 thread pause on} (see below) to pause individual threads.
21394 @item show task pause
21395 @kindex show task@r{, Hurd commands}
21396 Show the current state of task suspension.
21398 @item set task detach-suspend-count
21399 @cindex task suspend count
21400 @cindex detach from task, @sc{gnu} Hurd
21401 This command sets the suspend count the task will be left with when
21402 @value{GDBN} detaches from it.
21404 @item show task detach-suspend-count
21405 Show the suspend count the task will be left with when detaching.
21407 @item set task exception-port
21408 @itemx set task excp
21409 @cindex task exception port, @sc{gnu} Hurd
21410 This command sets the task exception port to which @value{GDBN} will
21411 forward exceptions. The argument should be the value of the @dfn{send
21412 rights} of the task. @code{set task excp} is a shorthand alias.
21414 @item set noninvasive
21415 @cindex noninvasive task options
21416 This command switches @value{GDBN} to a mode that is the least
21417 invasive as far as interfering with the inferior is concerned. This
21418 is the same as using @code{set task pause}, @code{set exceptions}, and
21419 @code{set signals} to values opposite to the defaults.
21421 @item info send-rights
21422 @itemx info receive-rights
21423 @itemx info port-rights
21424 @itemx info port-sets
21425 @itemx info dead-names
21428 @cindex send rights, @sc{gnu} Hurd
21429 @cindex receive rights, @sc{gnu} Hurd
21430 @cindex port rights, @sc{gnu} Hurd
21431 @cindex port sets, @sc{gnu} Hurd
21432 @cindex dead names, @sc{gnu} Hurd
21433 These commands display information about, respectively, send rights,
21434 receive rights, port rights, port sets, and dead names of a task.
21435 There are also shorthand aliases: @code{info ports} for @code{info
21436 port-rights} and @code{info psets} for @code{info port-sets}.
21438 @item set thread pause
21439 @kindex set thread@r{, Hurd command}
21440 @cindex thread properties, @sc{gnu} Hurd
21441 @cindex pause current thread (@sc{gnu} Hurd)
21442 This command toggles current thread suspension when @value{GDBN} has
21443 control. Setting it to on takes effect immediately, and the current
21444 thread is suspended whenever @value{GDBN} gets control. Setting it to
21445 off will take effect the next time the inferior is continued.
21446 Normally, this command has no effect, since when @value{GDBN} has
21447 control, the whole task is suspended. However, if you used @code{set
21448 task pause off} (see above), this command comes in handy to suspend
21449 only the current thread.
21451 @item show thread pause
21452 @kindex show thread@r{, Hurd command}
21453 This command shows the state of current thread suspension.
21455 @item set thread run
21456 This command sets whether the current thread is allowed to run.
21458 @item show thread run
21459 Show whether the current thread is allowed to run.
21461 @item set thread detach-suspend-count
21462 @cindex thread suspend count, @sc{gnu} Hurd
21463 @cindex detach from thread, @sc{gnu} Hurd
21464 This command sets the suspend count @value{GDBN} will leave on a
21465 thread when detaching. This number is relative to the suspend count
21466 found by @value{GDBN} when it notices the thread; use @code{set thread
21467 takeover-suspend-count} to force it to an absolute value.
21469 @item show thread detach-suspend-count
21470 Show the suspend count @value{GDBN} will leave on the thread when
21473 @item set thread exception-port
21474 @itemx set thread excp
21475 Set the thread exception port to which to forward exceptions. This
21476 overrides the port set by @code{set task exception-port} (see above).
21477 @code{set thread excp} is the shorthand alias.
21479 @item set thread takeover-suspend-count
21480 Normally, @value{GDBN}'s thread suspend counts are relative to the
21481 value @value{GDBN} finds when it notices each thread. This command
21482 changes the suspend counts to be absolute instead.
21484 @item set thread default
21485 @itemx show thread default
21486 @cindex thread default settings, @sc{gnu} Hurd
21487 Each of the above @code{set thread} commands has a @code{set thread
21488 default} counterpart (e.g., @code{set thread default pause}, @code{set
21489 thread default exception-port}, etc.). The @code{thread default}
21490 variety of commands sets the default thread properties for all
21491 threads; you can then change the properties of individual threads with
21492 the non-default commands.
21499 @value{GDBN} provides the following commands specific to the Darwin target:
21502 @item set debug darwin @var{num}
21503 @kindex set debug darwin
21504 When set to a non zero value, enables debugging messages specific to
21505 the Darwin support. Higher values produce more verbose output.
21507 @item show debug darwin
21508 @kindex show debug darwin
21509 Show the current state of Darwin messages.
21511 @item set debug mach-o @var{num}
21512 @kindex set debug mach-o
21513 When set to a non zero value, enables debugging messages while
21514 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21515 file format used on Darwin for object and executable files.) Higher
21516 values produce more verbose output. This is a command to diagnose
21517 problems internal to @value{GDBN} and should not be needed in normal
21520 @item show debug mach-o
21521 @kindex show debug mach-o
21522 Show the current state of Mach-O file messages.
21524 @item set mach-exceptions on
21525 @itemx set mach-exceptions off
21526 @kindex set mach-exceptions
21527 On Darwin, faults are first reported as a Mach exception and are then
21528 mapped to a Posix signal. Use this command to turn on trapping of
21529 Mach exceptions in the inferior. This might be sometimes useful to
21530 better understand the cause of a fault. The default is off.
21532 @item show mach-exceptions
21533 @kindex show mach-exceptions
21534 Show the current state of exceptions trapping.
21539 @section Embedded Operating Systems
21541 This section describes configurations involving the debugging of
21542 embedded operating systems that are available for several different
21545 @value{GDBN} includes the ability to debug programs running on
21546 various real-time operating systems.
21548 @node Embedded Processors
21549 @section Embedded Processors
21551 This section goes into details specific to particular embedded
21554 @cindex send command to simulator
21555 Whenever a specific embedded processor has a simulator, @value{GDBN}
21556 allows to send an arbitrary command to the simulator.
21559 @item sim @var{command}
21560 @kindex sim@r{, a command}
21561 Send an arbitrary @var{command} string to the simulator. Consult the
21562 documentation for the specific simulator in use for information about
21563 acceptable commands.
21569 * M32R/SDI:: Renesas M32R/SDI
21570 * M68K:: Motorola M68K
21571 * MicroBlaze:: Xilinx MicroBlaze
21572 * MIPS Embedded:: MIPS Embedded
21573 * PowerPC Embedded:: PowerPC Embedded
21576 * Super-H:: Renesas Super-H
21582 @value{GDBN} provides the following ARM-specific commands:
21585 @item set arm disassembler
21587 This commands selects from a list of disassembly styles. The
21588 @code{"std"} style is the standard style.
21590 @item show arm disassembler
21592 Show the current disassembly style.
21594 @item set arm apcs32
21595 @cindex ARM 32-bit mode
21596 This command toggles ARM operation mode between 32-bit and 26-bit.
21598 @item show arm apcs32
21599 Display the current usage of the ARM 32-bit mode.
21601 @item set arm fpu @var{fputype}
21602 This command sets the ARM floating-point unit (FPU) type. The
21603 argument @var{fputype} can be one of these:
21607 Determine the FPU type by querying the OS ABI.
21609 Software FPU, with mixed-endian doubles on little-endian ARM
21612 GCC-compiled FPA co-processor.
21614 Software FPU with pure-endian doubles.
21620 Show the current type of the FPU.
21623 This command forces @value{GDBN} to use the specified ABI.
21626 Show the currently used ABI.
21628 @item set arm fallback-mode (arm|thumb|auto)
21629 @value{GDBN} uses the symbol table, when available, to determine
21630 whether instructions are ARM or Thumb. This command controls
21631 @value{GDBN}'s default behavior when the symbol table is not
21632 available. The default is @samp{auto}, which causes @value{GDBN} to
21633 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21636 @item show arm fallback-mode
21637 Show the current fallback instruction mode.
21639 @item set arm force-mode (arm|thumb|auto)
21640 This command overrides use of the symbol table to determine whether
21641 instructions are ARM or Thumb. The default is @samp{auto}, which
21642 causes @value{GDBN} to use the symbol table and then the setting
21643 of @samp{set arm fallback-mode}.
21645 @item show arm force-mode
21646 Show the current forced instruction mode.
21648 @item set debug arm
21649 Toggle whether to display ARM-specific debugging messages from the ARM
21650 target support subsystem.
21652 @item show debug arm
21653 Show whether ARM-specific debugging messages are enabled.
21657 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21658 The @value{GDBN} ARM simulator accepts the following optional arguments.
21661 @item --swi-support=@var{type}
21662 Tell the simulator which SWI interfaces to support. The argument
21663 @var{type} may be a comma separated list of the following values.
21664 The default value is @code{all}.
21677 @subsection Renesas M32R/SDI
21679 The following commands are available for M32R/SDI:
21684 @cindex reset SDI connection, M32R
21685 This command resets the SDI connection.
21689 This command shows the SDI connection status.
21692 @kindex debug_chaos
21693 @cindex M32R/Chaos debugging
21694 Instructs the remote that M32R/Chaos debugging is to be used.
21696 @item use_debug_dma
21697 @kindex use_debug_dma
21698 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21701 @kindex use_mon_code
21702 Instructs the remote to use the MON_CODE method of accessing memory.
21705 @kindex use_ib_break
21706 Instructs the remote to set breakpoints by IB break.
21708 @item use_dbt_break
21709 @kindex use_dbt_break
21710 Instructs the remote to set breakpoints by DBT.
21716 The Motorola m68k configuration includes ColdFire support.
21719 @subsection MicroBlaze
21720 @cindex Xilinx MicroBlaze
21721 @cindex XMD, Xilinx Microprocessor Debugger
21723 The MicroBlaze is a soft-core processor supported on various Xilinx
21724 FPGAs, such as Spartan or Virtex series. Boards with these processors
21725 usually have JTAG ports which connect to a host system running the Xilinx
21726 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21727 This host system is used to download the configuration bitstream to
21728 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21729 communicates with the target board using the JTAG interface and
21730 presents a @code{gdbserver} interface to the board. By default
21731 @code{xmd} uses port @code{1234}. (While it is possible to change
21732 this default port, it requires the use of undocumented @code{xmd}
21733 commands. Contact Xilinx support if you need to do this.)
21735 Use these GDB commands to connect to the MicroBlaze target processor.
21738 @item target remote :1234
21739 Use this command to connect to the target if you are running @value{GDBN}
21740 on the same system as @code{xmd}.
21742 @item target remote @var{xmd-host}:1234
21743 Use this command to connect to the target if it is connected to @code{xmd}
21744 running on a different system named @var{xmd-host}.
21747 Use this command to download a program to the MicroBlaze target.
21749 @item set debug microblaze @var{n}
21750 Enable MicroBlaze-specific debugging messages if non-zero.
21752 @item show debug microblaze @var{n}
21753 Show MicroBlaze-specific debugging level.
21756 @node MIPS Embedded
21757 @subsection @acronym{MIPS} Embedded
21759 @cindex @acronym{MIPS} boards
21760 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21761 @acronym{MIPS} board attached to a serial line. This is available when
21762 you configure @value{GDBN} with @samp{--target=mips-elf}.
21765 Use these @value{GDBN} commands to specify the connection to your target board:
21768 @item target mips @var{port}
21769 @kindex target mips @var{port}
21770 To run a program on the board, start up @code{@value{GDBP}} with the
21771 name of your program as the argument. To connect to the board, use the
21772 command @samp{target mips @var{port}}, where @var{port} is the name of
21773 the serial port connected to the board. If the program has not already
21774 been downloaded to the board, you may use the @code{load} command to
21775 download it. You can then use all the usual @value{GDBN} commands.
21777 For example, this sequence connects to the target board through a serial
21778 port, and loads and runs a program called @var{prog} through the
21782 host$ @value{GDBP} @var{prog}
21783 @value{GDBN} is free software and @dots{}
21784 (@value{GDBP}) target mips /dev/ttyb
21785 (@value{GDBP}) load @var{prog}
21789 @item target mips @var{hostname}:@var{portnumber}
21790 On some @value{GDBN} host configurations, you can specify a TCP
21791 connection (for instance, to a serial line managed by a terminal
21792 concentrator) instead of a serial port, using the syntax
21793 @samp{@var{hostname}:@var{portnumber}}.
21795 @item target pmon @var{port}
21796 @kindex target pmon @var{port}
21799 @item target ddb @var{port}
21800 @kindex target ddb @var{port}
21801 NEC's DDB variant of PMON for Vr4300.
21803 @item target lsi @var{port}
21804 @kindex target lsi @var{port}
21805 LSI variant of PMON.
21811 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21814 @item set mipsfpu double
21815 @itemx set mipsfpu single
21816 @itemx set mipsfpu none
21817 @itemx set mipsfpu auto
21818 @itemx show mipsfpu
21819 @kindex set mipsfpu
21820 @kindex show mipsfpu
21821 @cindex @acronym{MIPS} remote floating point
21822 @cindex floating point, @acronym{MIPS} remote
21823 If your target board does not support the @acronym{MIPS} floating point
21824 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21825 need this, you may wish to put the command in your @value{GDBN} init
21826 file). This tells @value{GDBN} how to find the return value of
21827 functions which return floating point values. It also allows
21828 @value{GDBN} to avoid saving the floating point registers when calling
21829 functions on the board. If you are using a floating point coprocessor
21830 with only single precision floating point support, as on the @sc{r4650}
21831 processor, use the command @samp{set mipsfpu single}. The default
21832 double precision floating point coprocessor may be selected using
21833 @samp{set mipsfpu double}.
21835 In previous versions the only choices were double precision or no
21836 floating point, so @samp{set mipsfpu on} will select double precision
21837 and @samp{set mipsfpu off} will select no floating point.
21839 As usual, you can inquire about the @code{mipsfpu} variable with
21840 @samp{show mipsfpu}.
21842 @item set timeout @var{seconds}
21843 @itemx set retransmit-timeout @var{seconds}
21844 @itemx show timeout
21845 @itemx show retransmit-timeout
21846 @cindex @code{timeout}, @acronym{MIPS} protocol
21847 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21848 @kindex set timeout
21849 @kindex show timeout
21850 @kindex set retransmit-timeout
21851 @kindex show retransmit-timeout
21852 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21853 remote protocol, with the @code{set timeout @var{seconds}} command. The
21854 default is 5 seconds. Similarly, you can control the timeout used while
21855 waiting for an acknowledgment of a packet with the @code{set
21856 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21857 You can inspect both values with @code{show timeout} and @code{show
21858 retransmit-timeout}. (These commands are @emph{only} available when
21859 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21861 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21862 is waiting for your program to stop. In that case, @value{GDBN} waits
21863 forever because it has no way of knowing how long the program is going
21864 to run before stopping.
21866 @item set syn-garbage-limit @var{num}
21867 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21868 @cindex synchronize with remote @acronym{MIPS} target
21869 Limit the maximum number of characters @value{GDBN} should ignore when
21870 it tries to synchronize with the remote target. The default is 10
21871 characters. Setting the limit to -1 means there's no limit.
21873 @item show syn-garbage-limit
21874 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21875 Show the current limit on the number of characters to ignore when
21876 trying to synchronize with the remote system.
21878 @item set monitor-prompt @var{prompt}
21879 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21880 @cindex remote monitor prompt
21881 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21882 remote monitor. The default depends on the target:
21892 @item show monitor-prompt
21893 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21894 Show the current strings @value{GDBN} expects as the prompt from the
21897 @item set monitor-warnings
21898 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21899 Enable or disable monitor warnings about hardware breakpoints. This
21900 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21901 display warning messages whose codes are returned by the @code{lsi}
21902 PMON monitor for breakpoint commands.
21904 @item show monitor-warnings
21905 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21906 Show the current setting of printing monitor warnings.
21908 @item pmon @var{command}
21909 @kindex pmon@r{, @acronym{MIPS} remote}
21910 @cindex send PMON command
21911 This command allows sending an arbitrary @var{command} string to the
21912 monitor. The monitor must be in debug mode for this to work.
21915 @node PowerPC Embedded
21916 @subsection PowerPC Embedded
21918 @cindex DVC register
21919 @value{GDBN} supports using the DVC (Data Value Compare) register to
21920 implement in hardware simple hardware watchpoint conditions of the form:
21923 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21924 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21927 The DVC register will be automatically used when @value{GDBN} detects
21928 such pattern in a condition expression, and the created watchpoint uses one
21929 debug register (either the @code{exact-watchpoints} option is on and the
21930 variable is scalar, or the variable has a length of one byte). This feature
21931 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21934 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21935 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21936 in which case watchpoints using only one debug register are created when
21937 watching variables of scalar types.
21939 You can create an artificial array to watch an arbitrary memory
21940 region using one of the following commands (@pxref{Expressions}):
21943 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21944 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21947 PowerPC embedded processors support masked watchpoints. See the discussion
21948 about the @code{mask} argument in @ref{Set Watchpoints}.
21950 @cindex ranged breakpoint
21951 PowerPC embedded processors support hardware accelerated
21952 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21953 the inferior whenever it executes an instruction at any address within
21954 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21955 use the @code{break-range} command.
21957 @value{GDBN} provides the following PowerPC-specific commands:
21960 @kindex break-range
21961 @item break-range @var{start-location}, @var{end-location}
21962 Set a breakpoint for an address range given by
21963 @var{start-location} and @var{end-location}, which can specify a function name,
21964 a line number, an offset of lines from the current line or from the start
21965 location, or an address of an instruction (see @ref{Specify Location},
21966 for a list of all the possible ways to specify a @var{location}.)
21967 The breakpoint will stop execution of the inferior whenever it
21968 executes an instruction at any address within the specified range,
21969 (including @var{start-location} and @var{end-location}.)
21971 @kindex set powerpc
21972 @item set powerpc soft-float
21973 @itemx show powerpc soft-float
21974 Force @value{GDBN} to use (or not use) a software floating point calling
21975 convention. By default, @value{GDBN} selects the calling convention based
21976 on the selected architecture and the provided executable file.
21978 @item set powerpc vector-abi
21979 @itemx show powerpc vector-abi
21980 Force @value{GDBN} to use the specified calling convention for vector
21981 arguments and return values. The valid options are @samp{auto};
21982 @samp{generic}, to avoid vector registers even if they are present;
21983 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21984 registers. By default, @value{GDBN} selects the calling convention
21985 based on the selected architecture and the provided executable file.
21987 @item set powerpc exact-watchpoints
21988 @itemx show powerpc exact-watchpoints
21989 Allow @value{GDBN} to use only one debug register when watching a variable
21990 of scalar type, thus assuming that the variable is accessed through the
21991 address of its first byte.
21996 @subsection Atmel AVR
21999 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22000 following AVR-specific commands:
22003 @item info io_registers
22004 @kindex info io_registers@r{, AVR}
22005 @cindex I/O registers (Atmel AVR)
22006 This command displays information about the AVR I/O registers. For
22007 each register, @value{GDBN} prints its number and value.
22014 When configured for debugging CRIS, @value{GDBN} provides the
22015 following CRIS-specific commands:
22018 @item set cris-version @var{ver}
22019 @cindex CRIS version
22020 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22021 The CRIS version affects register names and sizes. This command is useful in
22022 case autodetection of the CRIS version fails.
22024 @item show cris-version
22025 Show the current CRIS version.
22027 @item set cris-dwarf2-cfi
22028 @cindex DWARF-2 CFI and CRIS
22029 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22030 Change to @samp{off} when using @code{gcc-cris} whose version is below
22033 @item show cris-dwarf2-cfi
22034 Show the current state of using DWARF-2 CFI.
22036 @item set cris-mode @var{mode}
22038 Set the current CRIS mode to @var{mode}. It should only be changed when
22039 debugging in guru mode, in which case it should be set to
22040 @samp{guru} (the default is @samp{normal}).
22042 @item show cris-mode
22043 Show the current CRIS mode.
22047 @subsection Renesas Super-H
22050 For the Renesas Super-H processor, @value{GDBN} provides these
22054 @item set sh calling-convention @var{convention}
22055 @kindex set sh calling-convention
22056 Set the calling-convention used when calling functions from @value{GDBN}.
22057 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22058 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22059 convention. If the DWARF-2 information of the called function specifies
22060 that the function follows the Renesas calling convention, the function
22061 is called using the Renesas calling convention. If the calling convention
22062 is set to @samp{renesas}, the Renesas calling convention is always used,
22063 regardless of the DWARF-2 information. This can be used to override the
22064 default of @samp{gcc} if debug information is missing, or the compiler
22065 does not emit the DWARF-2 calling convention entry for a function.
22067 @item show sh calling-convention
22068 @kindex show sh calling-convention
22069 Show the current calling convention setting.
22074 @node Architectures
22075 @section Architectures
22077 This section describes characteristics of architectures that affect
22078 all uses of @value{GDBN} with the architecture, both native and cross.
22085 * HPPA:: HP PA architecture
22086 * SPU:: Cell Broadband Engine SPU architecture
22092 @subsection AArch64
22093 @cindex AArch64 support
22095 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22096 following special commands:
22099 @item set debug aarch64
22100 @kindex set debug aarch64
22101 This command determines whether AArch64 architecture-specific debugging
22102 messages are to be displayed.
22104 @item show debug aarch64
22105 Show whether AArch64 debugging messages are displayed.
22110 @subsection x86 Architecture-specific Issues
22113 @item set struct-convention @var{mode}
22114 @kindex set struct-convention
22115 @cindex struct return convention
22116 @cindex struct/union returned in registers
22117 Set the convention used by the inferior to return @code{struct}s and
22118 @code{union}s from functions to @var{mode}. Possible values of
22119 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22120 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22121 are returned on the stack, while @code{"reg"} means that a
22122 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22123 be returned in a register.
22125 @item show struct-convention
22126 @kindex show struct-convention
22127 Show the current setting of the convention to return @code{struct}s
22132 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22133 @cindex Intel(R) Memory Protection Extensions (MPX).
22135 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22136 @footnote{The register named with capital letters represent the architecture
22137 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22138 which are the lower bound and upper bound. Bounds are effective addresses or
22139 memory locations. The upper bounds are architecturally represented in 1's
22140 complement form. A bound having lower bound = 0, and upper bound = 0
22141 (1's complement of all bits set) will allow access to the entire address space.
22143 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22144 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22145 display the upper bound performing the complement of one operation on the
22146 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22147 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22148 can also be noted that the upper bounds are inclusive.
22150 As an example, assume that the register BND0 holds bounds for a pointer having
22151 access allowed for the range between 0x32 and 0x71. The values present on
22152 bnd0raw and bnd registers are presented as follows:
22155 bnd0raw = @{0x32, 0xffffffff8e@}
22156 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22159 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22160 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22161 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22162 Python, the display includes the memory size, in bits, accessible to
22165 Bounds can also be stored in bounds tables, which are stored in
22166 application memory. These tables store bounds for pointers by specifying
22167 the bounds pointer's value along with its bounds. Evaluating and changing
22168 bounds located in bound tables is therefore interesting while investigating
22169 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22172 @item show mpx bound @var{pointer}
22173 @kindex show mpx bound
22174 Display bounds of the given @var{pointer}.
22176 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22177 @kindex set mpx bound
22178 Set the bounds of a pointer in the bound table.
22179 This command takes three parameters: @var{pointer} is the pointers
22180 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22181 for lower and upper bounds respectively.
22187 See the following section.
22190 @subsection @acronym{MIPS}
22192 @cindex stack on Alpha
22193 @cindex stack on @acronym{MIPS}
22194 @cindex Alpha stack
22195 @cindex @acronym{MIPS} stack
22196 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22197 sometimes requires @value{GDBN} to search backward in the object code to
22198 find the beginning of a function.
22200 @cindex response time, @acronym{MIPS} debugging
22201 To improve response time (especially for embedded applications, where
22202 @value{GDBN} may be restricted to a slow serial line for this search)
22203 you may want to limit the size of this search, using one of these
22207 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22208 @item set heuristic-fence-post @var{limit}
22209 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22210 search for the beginning of a function. A value of @var{0} (the
22211 default) means there is no limit. However, except for @var{0}, the
22212 larger the limit the more bytes @code{heuristic-fence-post} must search
22213 and therefore the longer it takes to run. You should only need to use
22214 this command when debugging a stripped executable.
22216 @item show heuristic-fence-post
22217 Display the current limit.
22221 These commands are available @emph{only} when @value{GDBN} is configured
22222 for debugging programs on Alpha or @acronym{MIPS} processors.
22224 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22228 @item set mips abi @var{arg}
22229 @kindex set mips abi
22230 @cindex set ABI for @acronym{MIPS}
22231 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22232 values of @var{arg} are:
22236 The default ABI associated with the current binary (this is the
22246 @item show mips abi
22247 @kindex show mips abi
22248 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22250 @item set mips compression @var{arg}
22251 @kindex set mips compression
22252 @cindex code compression, @acronym{MIPS}
22253 Tell @value{GDBN} which @acronym{MIPS} compressed
22254 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22255 inferior. @value{GDBN} uses this for code disassembly and other
22256 internal interpretation purposes. This setting is only referred to
22257 when no executable has been associated with the debugging session or
22258 the executable does not provide information about the encoding it uses.
22259 Otherwise this setting is automatically updated from information
22260 provided by the executable.
22262 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22263 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22264 executables containing @acronym{MIPS16} code frequently are not
22265 identified as such.
22267 This setting is ``sticky''; that is, it retains its value across
22268 debugging sessions until reset either explicitly with this command or
22269 implicitly from an executable.
22271 The compiler and/or assembler typically add symbol table annotations to
22272 identify functions compiled for the @acronym{MIPS16} or
22273 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22274 are present, @value{GDBN} uses them in preference to the global
22275 compressed @acronym{ISA} encoding setting.
22277 @item show mips compression
22278 @kindex show mips compression
22279 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22280 @value{GDBN} to debug the inferior.
22283 @itemx show mipsfpu
22284 @xref{MIPS Embedded, set mipsfpu}.
22286 @item set mips mask-address @var{arg}
22287 @kindex set mips mask-address
22288 @cindex @acronym{MIPS} addresses, masking
22289 This command determines whether the most-significant 32 bits of 64-bit
22290 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22291 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22292 setting, which lets @value{GDBN} determine the correct value.
22294 @item show mips mask-address
22295 @kindex show mips mask-address
22296 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22299 @item set remote-mips64-transfers-32bit-regs
22300 @kindex set remote-mips64-transfers-32bit-regs
22301 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22302 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22303 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22304 and 64 bits for other registers, set this option to @samp{on}.
22306 @item show remote-mips64-transfers-32bit-regs
22307 @kindex show remote-mips64-transfers-32bit-regs
22308 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22310 @item set debug mips
22311 @kindex set debug mips
22312 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22313 target code in @value{GDBN}.
22315 @item show debug mips
22316 @kindex show debug mips
22317 Show the current setting of @acronym{MIPS} debugging messages.
22323 @cindex HPPA support
22325 When @value{GDBN} is debugging the HP PA architecture, it provides the
22326 following special commands:
22329 @item set debug hppa
22330 @kindex set debug hppa
22331 This command determines whether HPPA architecture-specific debugging
22332 messages are to be displayed.
22334 @item show debug hppa
22335 Show whether HPPA debugging messages are displayed.
22337 @item maint print unwind @var{address}
22338 @kindex maint print unwind@r{, HPPA}
22339 This command displays the contents of the unwind table entry at the
22340 given @var{address}.
22346 @subsection Cell Broadband Engine SPU architecture
22347 @cindex Cell Broadband Engine
22350 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22351 it provides the following special commands:
22354 @item info spu event
22356 Display SPU event facility status. Shows current event mask
22357 and pending event status.
22359 @item info spu signal
22360 Display SPU signal notification facility status. Shows pending
22361 signal-control word and signal notification mode of both signal
22362 notification channels.
22364 @item info spu mailbox
22365 Display SPU mailbox facility status. Shows all pending entries,
22366 in order of processing, in each of the SPU Write Outbound,
22367 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22370 Display MFC DMA status. Shows all pending commands in the MFC
22371 DMA queue. For each entry, opcode, tag, class IDs, effective
22372 and local store addresses and transfer size are shown.
22374 @item info spu proxydma
22375 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22376 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22377 and local store addresses and transfer size are shown.
22381 When @value{GDBN} is debugging a combined PowerPC/SPU application
22382 on the Cell Broadband Engine, it provides in addition the following
22386 @item set spu stop-on-load @var{arg}
22388 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22389 will give control to the user when a new SPE thread enters its @code{main}
22390 function. The default is @code{off}.
22392 @item show spu stop-on-load
22394 Show whether to stop for new SPE threads.
22396 @item set spu auto-flush-cache @var{arg}
22397 Set whether to automatically flush the software-managed cache. When set to
22398 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22399 cache to be flushed whenever SPE execution stops. This provides a consistent
22400 view of PowerPC memory that is accessed via the cache. If an application
22401 does not use the software-managed cache, this option has no effect.
22403 @item show spu auto-flush-cache
22404 Show whether to automatically flush the software-managed cache.
22409 @subsection PowerPC
22410 @cindex PowerPC architecture
22412 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22413 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22414 numbers stored in the floating point registers. These values must be stored
22415 in two consecutive registers, always starting at an even register like
22416 @code{f0} or @code{f2}.
22418 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22419 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22420 @code{f2} and @code{f3} for @code{$dl1} and so on.
22422 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22423 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22426 @subsection Nios II
22427 @cindex Nios II architecture
22429 When @value{GDBN} is debugging the Nios II architecture,
22430 it provides the following special commands:
22434 @item set debug nios2
22435 @kindex set debug nios2
22436 This command turns on and off debugging messages for the Nios II
22437 target code in @value{GDBN}.
22439 @item show debug nios2
22440 @kindex show debug nios2
22441 Show the current setting of Nios II debugging messages.
22444 @node Controlling GDB
22445 @chapter Controlling @value{GDBN}
22447 You can alter the way @value{GDBN} interacts with you by using the
22448 @code{set} command. For commands controlling how @value{GDBN} displays
22449 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22454 * Editing:: Command editing
22455 * Command History:: Command history
22456 * Screen Size:: Screen size
22457 * Numbers:: Numbers
22458 * ABI:: Configuring the current ABI
22459 * Auto-loading:: Automatically loading associated files
22460 * Messages/Warnings:: Optional warnings and messages
22461 * Debugging Output:: Optional messages about internal happenings
22462 * Other Misc Settings:: Other Miscellaneous Settings
22470 @value{GDBN} indicates its readiness to read a command by printing a string
22471 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22472 can change the prompt string with the @code{set prompt} command. For
22473 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22474 the prompt in one of the @value{GDBN} sessions so that you can always tell
22475 which one you are talking to.
22477 @emph{Note:} @code{set prompt} does not add a space for you after the
22478 prompt you set. This allows you to set a prompt which ends in a space
22479 or a prompt that does not.
22483 @item set prompt @var{newprompt}
22484 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22486 @kindex show prompt
22488 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22491 Versions of @value{GDBN} that ship with Python scripting enabled have
22492 prompt extensions. The commands for interacting with these extensions
22496 @kindex set extended-prompt
22497 @item set extended-prompt @var{prompt}
22498 Set an extended prompt that allows for substitutions.
22499 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22500 substitution. Any escape sequences specified as part of the prompt
22501 string are replaced with the corresponding strings each time the prompt
22507 set extended-prompt Current working directory: \w (gdb)
22510 Note that when an extended-prompt is set, it takes control of the
22511 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22513 @kindex show extended-prompt
22514 @item show extended-prompt
22515 Prints the extended prompt. Any escape sequences specified as part of
22516 the prompt string with @code{set extended-prompt}, are replaced with the
22517 corresponding strings each time the prompt is displayed.
22521 @section Command Editing
22523 @cindex command line editing
22525 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22526 @sc{gnu} library provides consistent behavior for programs which provide a
22527 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22528 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22529 substitution, and a storage and recall of command history across
22530 debugging sessions.
22532 You may control the behavior of command line editing in @value{GDBN} with the
22533 command @code{set}.
22536 @kindex set editing
22539 @itemx set editing on
22540 Enable command line editing (enabled by default).
22542 @item set editing off
22543 Disable command line editing.
22545 @kindex show editing
22547 Show whether command line editing is enabled.
22550 @ifset SYSTEM_READLINE
22551 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22553 @ifclear SYSTEM_READLINE
22554 @xref{Command Line Editing},
22556 for more details about the Readline
22557 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22558 encouraged to read that chapter.
22560 @node Command History
22561 @section Command History
22562 @cindex command history
22564 @value{GDBN} can keep track of the commands you type during your
22565 debugging sessions, so that you can be certain of precisely what
22566 happened. Use these commands to manage the @value{GDBN} command
22569 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22570 package, to provide the history facility.
22571 @ifset SYSTEM_READLINE
22572 @xref{Using History Interactively, , , history, GNU History Library},
22574 @ifclear SYSTEM_READLINE
22575 @xref{Using History Interactively},
22577 for the detailed description of the History library.
22579 To issue a command to @value{GDBN} without affecting certain aspects of
22580 the state which is seen by users, prefix it with @samp{server }
22581 (@pxref{Server Prefix}). This
22582 means that this command will not affect the command history, nor will it
22583 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22584 pressed on a line by itself.
22586 @cindex @code{server}, command prefix
22587 The server prefix does not affect the recording of values into the value
22588 history; to print a value without recording it into the value history,
22589 use the @code{output} command instead of the @code{print} command.
22591 Here is the description of @value{GDBN} commands related to command
22595 @cindex history substitution
22596 @cindex history file
22597 @kindex set history filename
22598 @cindex @env{GDBHISTFILE}, environment variable
22599 @item set history filename @var{fname}
22600 Set the name of the @value{GDBN} command history file to @var{fname}.
22601 This is the file where @value{GDBN} reads an initial command history
22602 list, and where it writes the command history from this session when it
22603 exits. You can access this list through history expansion or through
22604 the history command editing characters listed below. This file defaults
22605 to the value of the environment variable @code{GDBHISTFILE}, or to
22606 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22609 @cindex save command history
22610 @kindex set history save
22611 @item set history save
22612 @itemx set history save on
22613 Record command history in a file, whose name may be specified with the
22614 @code{set history filename} command. By default, this option is disabled.
22616 @item set history save off
22617 Stop recording command history in a file.
22619 @cindex history size
22620 @kindex set history size
22621 @cindex @env{GDBHISTSIZE}, environment variable
22622 @item set history size @var{size}
22623 @itemx set history size unlimited
22624 Set the number of commands which @value{GDBN} keeps in its history list.
22625 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22626 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22627 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22628 either a negative number or the empty string, then the number of commands
22629 @value{GDBN} keeps in the history list is unlimited.
22631 @cindex remove duplicate history
22632 @kindex set history remove-duplicates
22633 @item set history remove-duplicates @var{count}
22634 @itemx set history remove-duplicates unlimited
22635 Control the removal of duplicate history entries in the command history list.
22636 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22637 history entries and remove the first entry that is a duplicate of the current
22638 entry being added to the command history list. If @var{count} is
22639 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22640 removal of duplicate history entries is disabled.
22642 Only history entries added during the current session are considered for
22643 removal. This option is set to 0 by default.
22647 History expansion assigns special meaning to the character @kbd{!}.
22648 @ifset SYSTEM_READLINE
22649 @xref{Event Designators, , , history, GNU History Library},
22651 @ifclear SYSTEM_READLINE
22652 @xref{Event Designators},
22656 @cindex history expansion, turn on/off
22657 Since @kbd{!} is also the logical not operator in C, history expansion
22658 is off by default. If you decide to enable history expansion with the
22659 @code{set history expansion on} command, you may sometimes need to
22660 follow @kbd{!} (when it is used as logical not, in an expression) with
22661 a space or a tab to prevent it from being expanded. The readline
22662 history facilities do not attempt substitution on the strings
22663 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22665 The commands to control history expansion are:
22668 @item set history expansion on
22669 @itemx set history expansion
22670 @kindex set history expansion
22671 Enable history expansion. History expansion is off by default.
22673 @item set history expansion off
22674 Disable history expansion.
22677 @kindex show history
22679 @itemx show history filename
22680 @itemx show history save
22681 @itemx show history size
22682 @itemx show history expansion
22683 These commands display the state of the @value{GDBN} history parameters.
22684 @code{show history} by itself displays all four states.
22689 @kindex show commands
22690 @cindex show last commands
22691 @cindex display command history
22692 @item show commands
22693 Display the last ten commands in the command history.
22695 @item show commands @var{n}
22696 Print ten commands centered on command number @var{n}.
22698 @item show commands +
22699 Print ten commands just after the commands last printed.
22703 @section Screen Size
22704 @cindex size of screen
22705 @cindex screen size
22708 @cindex pauses in output
22710 Certain commands to @value{GDBN} may produce large amounts of
22711 information output to the screen. To help you read all of it,
22712 @value{GDBN} pauses and asks you for input at the end of each page of
22713 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22714 to discard the remaining output. Also, the screen width setting
22715 determines when to wrap lines of output. Depending on what is being
22716 printed, @value{GDBN} tries to break the line at a readable place,
22717 rather than simply letting it overflow onto the following line.
22719 Normally @value{GDBN} knows the size of the screen from the terminal
22720 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22721 together with the value of the @code{TERM} environment variable and the
22722 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22723 you can override it with the @code{set height} and @code{set
22730 @kindex show height
22731 @item set height @var{lpp}
22732 @itemx set height unlimited
22734 @itemx set width @var{cpl}
22735 @itemx set width unlimited
22737 These @code{set} commands specify a screen height of @var{lpp} lines and
22738 a screen width of @var{cpl} characters. The associated @code{show}
22739 commands display the current settings.
22741 If you specify a height of either @code{unlimited} or zero lines,
22742 @value{GDBN} does not pause during output no matter how long the
22743 output is. This is useful if output is to a file or to an editor
22746 Likewise, you can specify @samp{set width unlimited} or @samp{set
22747 width 0} to prevent @value{GDBN} from wrapping its output.
22749 @item set pagination on
22750 @itemx set pagination off
22751 @kindex set pagination
22752 Turn the output pagination on or off; the default is on. Turning
22753 pagination off is the alternative to @code{set height unlimited}. Note that
22754 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22755 Options, -batch}) also automatically disables pagination.
22757 @item show pagination
22758 @kindex show pagination
22759 Show the current pagination mode.
22764 @cindex number representation
22765 @cindex entering numbers
22767 You can always enter numbers in octal, decimal, or hexadecimal in
22768 @value{GDBN} by the usual conventions: octal numbers begin with
22769 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22770 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22771 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22772 10; likewise, the default display for numbers---when no particular
22773 format is specified---is base 10. You can change the default base for
22774 both input and output with the commands described below.
22777 @kindex set input-radix
22778 @item set input-radix @var{base}
22779 Set the default base for numeric input. Supported choices
22780 for @var{base} are decimal 8, 10, or 16. The base must itself be
22781 specified either unambiguously or using the current input radix; for
22785 set input-radix 012
22786 set input-radix 10.
22787 set input-radix 0xa
22791 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22792 leaves the input radix unchanged, no matter what it was, since
22793 @samp{10}, being without any leading or trailing signs of its base, is
22794 interpreted in the current radix. Thus, if the current radix is 16,
22795 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22798 @kindex set output-radix
22799 @item set output-radix @var{base}
22800 Set the default base for numeric display. Supported choices
22801 for @var{base} are decimal 8, 10, or 16. The base must itself be
22802 specified either unambiguously or using the current input radix.
22804 @kindex show input-radix
22805 @item show input-radix
22806 Display the current default base for numeric input.
22808 @kindex show output-radix
22809 @item show output-radix
22810 Display the current default base for numeric display.
22812 @item set radix @r{[}@var{base}@r{]}
22816 These commands set and show the default base for both input and output
22817 of numbers. @code{set radix} sets the radix of input and output to
22818 the same base; without an argument, it resets the radix back to its
22819 default value of 10.
22824 @section Configuring the Current ABI
22826 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22827 application automatically. However, sometimes you need to override its
22828 conclusions. Use these commands to manage @value{GDBN}'s view of the
22834 @cindex Newlib OS ABI and its influence on the longjmp handling
22836 One @value{GDBN} configuration can debug binaries for multiple operating
22837 system targets, either via remote debugging or native emulation.
22838 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22839 but you can override its conclusion using the @code{set osabi} command.
22840 One example where this is useful is in debugging of binaries which use
22841 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22842 not have the same identifying marks that the standard C library for your
22845 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22846 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22847 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22848 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22852 Show the OS ABI currently in use.
22855 With no argument, show the list of registered available OS ABI's.
22857 @item set osabi @var{abi}
22858 Set the current OS ABI to @var{abi}.
22861 @cindex float promotion
22863 Generally, the way that an argument of type @code{float} is passed to a
22864 function depends on whether the function is prototyped. For a prototyped
22865 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22866 according to the architecture's convention for @code{float}. For unprototyped
22867 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22868 @code{double} and then passed.
22870 Unfortunately, some forms of debug information do not reliably indicate whether
22871 a function is prototyped. If @value{GDBN} calls a function that is not marked
22872 as prototyped, it consults @kbd{set coerce-float-to-double}.
22875 @kindex set coerce-float-to-double
22876 @item set coerce-float-to-double
22877 @itemx set coerce-float-to-double on
22878 Arguments of type @code{float} will be promoted to @code{double} when passed
22879 to an unprototyped function. This is the default setting.
22881 @item set coerce-float-to-double off
22882 Arguments of type @code{float} will be passed directly to unprototyped
22885 @kindex show coerce-float-to-double
22886 @item show coerce-float-to-double
22887 Show the current setting of promoting @code{float} to @code{double}.
22891 @kindex show cp-abi
22892 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22893 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22894 used to build your application. @value{GDBN} only fully supports
22895 programs with a single C@t{++} ABI; if your program contains code using
22896 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22897 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22898 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22899 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22900 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22901 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22906 Show the C@t{++} ABI currently in use.
22909 With no argument, show the list of supported C@t{++} ABI's.
22911 @item set cp-abi @var{abi}
22912 @itemx set cp-abi auto
22913 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22917 @section Automatically loading associated files
22918 @cindex auto-loading
22920 @value{GDBN} sometimes reads files with commands and settings automatically,
22921 without being explicitly told so by the user. We call this feature
22922 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22923 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22924 results or introduce security risks (e.g., if the file comes from untrusted
22928 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22929 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22931 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22932 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22935 There are various kinds of files @value{GDBN} can automatically load.
22936 In addition to these files, @value{GDBN} supports auto-loading code written
22937 in various extension languages. @xref{Auto-loading extensions}.
22939 Note that loading of these associated files (including the local @file{.gdbinit}
22940 file) requires accordingly configured @code{auto-load safe-path}
22941 (@pxref{Auto-loading safe path}).
22943 For these reasons, @value{GDBN} includes commands and options to let you
22944 control when to auto-load files and which files should be auto-loaded.
22947 @anchor{set auto-load off}
22948 @kindex set auto-load off
22949 @item set auto-load off
22950 Globally disable loading of all auto-loaded files.
22951 You may want to use this command with the @samp{-iex} option
22952 (@pxref{Option -init-eval-command}) such as:
22954 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22957 Be aware that system init file (@pxref{System-wide configuration})
22958 and init files from your home directory (@pxref{Home Directory Init File})
22959 still get read (as they come from generally trusted directories).
22960 To prevent @value{GDBN} from auto-loading even those init files, use the
22961 @option{-nx} option (@pxref{Mode Options}), in addition to
22962 @code{set auto-load no}.
22964 @anchor{show auto-load}
22965 @kindex show auto-load
22966 @item show auto-load
22967 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22971 (gdb) show auto-load
22972 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22973 libthread-db: Auto-loading of inferior specific libthread_db is on.
22974 local-gdbinit: Auto-loading of .gdbinit script from current directory
22976 python-scripts: Auto-loading of Python scripts is on.
22977 safe-path: List of directories from which it is safe to auto-load files
22978 is $debugdir:$datadir/auto-load.
22979 scripts-directory: List of directories from which to load auto-loaded scripts
22980 is $debugdir:$datadir/auto-load.
22983 @anchor{info auto-load}
22984 @kindex info auto-load
22985 @item info auto-load
22986 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22990 (gdb) info auto-load
22993 Yes /home/user/gdb/gdb-gdb.gdb
22994 libthread-db: No auto-loaded libthread-db.
22995 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22999 Yes /home/user/gdb/gdb-gdb.py
23003 These are @value{GDBN} control commands for the auto-loading:
23005 @multitable @columnfractions .5 .5
23006 @item @xref{set auto-load off}.
23007 @tab Disable auto-loading globally.
23008 @item @xref{show auto-load}.
23009 @tab Show setting of all kinds of files.
23010 @item @xref{info auto-load}.
23011 @tab Show state of all kinds of files.
23012 @item @xref{set auto-load gdb-scripts}.
23013 @tab Control for @value{GDBN} command scripts.
23014 @item @xref{show auto-load gdb-scripts}.
23015 @tab Show setting of @value{GDBN} command scripts.
23016 @item @xref{info auto-load gdb-scripts}.
23017 @tab Show state of @value{GDBN} command scripts.
23018 @item @xref{set auto-load python-scripts}.
23019 @tab Control for @value{GDBN} Python scripts.
23020 @item @xref{show auto-load python-scripts}.
23021 @tab Show setting of @value{GDBN} Python scripts.
23022 @item @xref{info auto-load python-scripts}.
23023 @tab Show state of @value{GDBN} Python scripts.
23024 @item @xref{set auto-load guile-scripts}.
23025 @tab Control for @value{GDBN} Guile scripts.
23026 @item @xref{show auto-load guile-scripts}.
23027 @tab Show setting of @value{GDBN} Guile scripts.
23028 @item @xref{info auto-load guile-scripts}.
23029 @tab Show state of @value{GDBN} Guile scripts.
23030 @item @xref{set auto-load scripts-directory}.
23031 @tab Control for @value{GDBN} auto-loaded scripts location.
23032 @item @xref{show auto-load scripts-directory}.
23033 @tab Show @value{GDBN} auto-loaded scripts location.
23034 @item @xref{add-auto-load-scripts-directory}.
23035 @tab Add directory for auto-loaded scripts location list.
23036 @item @xref{set auto-load local-gdbinit}.
23037 @tab Control for init file in the current directory.
23038 @item @xref{show auto-load local-gdbinit}.
23039 @tab Show setting of init file in the current directory.
23040 @item @xref{info auto-load local-gdbinit}.
23041 @tab Show state of init file in the current directory.
23042 @item @xref{set auto-load libthread-db}.
23043 @tab Control for thread debugging library.
23044 @item @xref{show auto-load libthread-db}.
23045 @tab Show setting of thread debugging library.
23046 @item @xref{info auto-load libthread-db}.
23047 @tab Show state of thread debugging library.
23048 @item @xref{set auto-load safe-path}.
23049 @tab Control directories trusted for automatic loading.
23050 @item @xref{show auto-load safe-path}.
23051 @tab Show directories trusted for automatic loading.
23052 @item @xref{add-auto-load-safe-path}.
23053 @tab Add directory trusted for automatic loading.
23056 @node Init File in the Current Directory
23057 @subsection Automatically loading init file in the current directory
23058 @cindex auto-loading init file in the current directory
23060 By default, @value{GDBN} reads and executes the canned sequences of commands
23061 from init file (if any) in the current working directory,
23062 see @ref{Init File in the Current Directory during Startup}.
23064 Note that loading of this local @file{.gdbinit} file also requires accordingly
23065 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23068 @anchor{set auto-load local-gdbinit}
23069 @kindex set auto-load local-gdbinit
23070 @item set auto-load local-gdbinit [on|off]
23071 Enable or disable the auto-loading of canned sequences of commands
23072 (@pxref{Sequences}) found in init file in the current directory.
23074 @anchor{show auto-load local-gdbinit}
23075 @kindex show auto-load local-gdbinit
23076 @item show auto-load local-gdbinit
23077 Show whether auto-loading of canned sequences of commands from init file in the
23078 current directory is enabled or disabled.
23080 @anchor{info auto-load local-gdbinit}
23081 @kindex info auto-load local-gdbinit
23082 @item info auto-load local-gdbinit
23083 Print whether canned sequences of commands from init file in the
23084 current directory have been auto-loaded.
23087 @node libthread_db.so.1 file
23088 @subsection Automatically loading thread debugging library
23089 @cindex auto-loading libthread_db.so.1
23091 This feature is currently present only on @sc{gnu}/Linux native hosts.
23093 @value{GDBN} reads in some cases thread debugging library from places specific
23094 to the inferior (@pxref{set libthread-db-search-path}).
23096 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23097 without checking this @samp{set auto-load libthread-db} switch as system
23098 libraries have to be trusted in general. In all other cases of
23099 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23100 auto-load libthread-db} is enabled before trying to open such thread debugging
23103 Note that loading of this debugging library also requires accordingly configured
23104 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23107 @anchor{set auto-load libthread-db}
23108 @kindex set auto-load libthread-db
23109 @item set auto-load libthread-db [on|off]
23110 Enable or disable the auto-loading of inferior specific thread debugging library.
23112 @anchor{show auto-load libthread-db}
23113 @kindex show auto-load libthread-db
23114 @item show auto-load libthread-db
23115 Show whether auto-loading of inferior specific thread debugging library is
23116 enabled or disabled.
23118 @anchor{info auto-load libthread-db}
23119 @kindex info auto-load libthread-db
23120 @item info auto-load libthread-db
23121 Print the list of all loaded inferior specific thread debugging libraries and
23122 for each such library print list of inferior @var{pid}s using it.
23125 @node Auto-loading safe path
23126 @subsection Security restriction for auto-loading
23127 @cindex auto-loading safe-path
23129 As the files of inferior can come from untrusted source (such as submitted by
23130 an application user) @value{GDBN} does not always load any files automatically.
23131 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23132 directories trusted for loading files not explicitly requested by user.
23133 Each directory can also be a shell wildcard pattern.
23135 If the path is not set properly you will see a warning and the file will not
23140 Reading symbols from /home/user/gdb/gdb...done.
23141 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23142 declined by your `auto-load safe-path' set
23143 to "$debugdir:$datadir/auto-load".
23144 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23145 declined by your `auto-load safe-path' set
23146 to "$debugdir:$datadir/auto-load".
23150 To instruct @value{GDBN} to go ahead and use the init files anyway,
23151 invoke @value{GDBN} like this:
23154 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23157 The list of trusted directories is controlled by the following commands:
23160 @anchor{set auto-load safe-path}
23161 @kindex set auto-load safe-path
23162 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23163 Set the list of directories (and their subdirectories) trusted for automatic
23164 loading and execution of scripts. You can also enter a specific trusted file.
23165 Each directory can also be a shell wildcard pattern; wildcards do not match
23166 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23167 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23168 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23169 its default value as specified during @value{GDBN} compilation.
23171 The list of directories uses path separator (@samp{:} on GNU and Unix
23172 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23173 to the @env{PATH} environment variable.
23175 @anchor{show auto-load safe-path}
23176 @kindex show auto-load safe-path
23177 @item show auto-load safe-path
23178 Show the list of directories trusted for automatic loading and execution of
23181 @anchor{add-auto-load-safe-path}
23182 @kindex add-auto-load-safe-path
23183 @item add-auto-load-safe-path
23184 Add an entry (or list of entries) to the list of directories trusted for
23185 automatic loading and execution of scripts. Multiple entries may be delimited
23186 by the host platform path separator in use.
23189 This variable defaults to what @code{--with-auto-load-dir} has been configured
23190 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23191 substitution applies the same as for @ref{set auto-load scripts-directory}.
23192 The default @code{set auto-load safe-path} value can be also overriden by
23193 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23195 Setting this variable to @file{/} disables this security protection,
23196 corresponding @value{GDBN} configuration option is
23197 @option{--without-auto-load-safe-path}.
23198 This variable is supposed to be set to the system directories writable by the
23199 system superuser only. Users can add their source directories in init files in
23200 their home directories (@pxref{Home Directory Init File}). See also deprecated
23201 init file in the current directory
23202 (@pxref{Init File in the Current Directory during Startup}).
23204 To force @value{GDBN} to load the files it declined to load in the previous
23205 example, you could use one of the following ways:
23208 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23209 Specify this trusted directory (or a file) as additional component of the list.
23210 You have to specify also any existing directories displayed by
23211 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23213 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23214 Specify this directory as in the previous case but just for a single
23215 @value{GDBN} session.
23217 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23218 Disable auto-loading safety for a single @value{GDBN} session.
23219 This assumes all the files you debug during this @value{GDBN} session will come
23220 from trusted sources.
23222 @item @kbd{./configure --without-auto-load-safe-path}
23223 During compilation of @value{GDBN} you may disable any auto-loading safety.
23224 This assumes all the files you will ever debug with this @value{GDBN} come from
23228 On the other hand you can also explicitly forbid automatic files loading which
23229 also suppresses any such warning messages:
23232 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23233 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23235 @item @file{~/.gdbinit}: @samp{set auto-load no}
23236 Disable auto-loading globally for the user
23237 (@pxref{Home Directory Init File}). While it is improbable, you could also
23238 use system init file instead (@pxref{System-wide configuration}).
23241 This setting applies to the file names as entered by user. If no entry matches
23242 @value{GDBN} tries as a last resort to also resolve all the file names into
23243 their canonical form (typically resolving symbolic links) and compare the
23244 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23245 own before starting the comparison so a canonical form of directories is
23246 recommended to be entered.
23248 @node Auto-loading verbose mode
23249 @subsection Displaying files tried for auto-load
23250 @cindex auto-loading verbose mode
23252 For better visibility of all the file locations where you can place scripts to
23253 be auto-loaded with inferior --- or to protect yourself against accidental
23254 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23255 all the files attempted to be loaded. Both existing and non-existing files may
23258 For example the list of directories from which it is safe to auto-load files
23259 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23260 may not be too obvious while setting it up.
23263 (gdb) set debug auto-load on
23264 (gdb) file ~/src/t/true
23265 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23266 for objfile "/tmp/true".
23267 auto-load: Updating directories of "/usr:/opt".
23268 auto-load: Using directory "/usr".
23269 auto-load: Using directory "/opt".
23270 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23271 by your `auto-load safe-path' set to "/usr:/opt".
23275 @anchor{set debug auto-load}
23276 @kindex set debug auto-load
23277 @item set debug auto-load [on|off]
23278 Set whether to print the filenames attempted to be auto-loaded.
23280 @anchor{show debug auto-load}
23281 @kindex show debug auto-load
23282 @item show debug auto-load
23283 Show whether printing of the filenames attempted to be auto-loaded is turned
23287 @node Messages/Warnings
23288 @section Optional Warnings and Messages
23290 @cindex verbose operation
23291 @cindex optional warnings
23292 By default, @value{GDBN} is silent about its inner workings. If you are
23293 running on a slow machine, you may want to use the @code{set verbose}
23294 command. This makes @value{GDBN} tell you when it does a lengthy
23295 internal operation, so you will not think it has crashed.
23297 Currently, the messages controlled by @code{set verbose} are those
23298 which announce that the symbol table for a source file is being read;
23299 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23302 @kindex set verbose
23303 @item set verbose on
23304 Enables @value{GDBN} output of certain informational messages.
23306 @item set verbose off
23307 Disables @value{GDBN} output of certain informational messages.
23309 @kindex show verbose
23311 Displays whether @code{set verbose} is on or off.
23314 By default, if @value{GDBN} encounters bugs in the symbol table of an
23315 object file, it is silent; but if you are debugging a compiler, you may
23316 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23321 @kindex set complaints
23322 @item set complaints @var{limit}
23323 Permits @value{GDBN} to output @var{limit} complaints about each type of
23324 unusual symbols before becoming silent about the problem. Set
23325 @var{limit} to zero to suppress all complaints; set it to a large number
23326 to prevent complaints from being suppressed.
23328 @kindex show complaints
23329 @item show complaints
23330 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23334 @anchor{confirmation requests}
23335 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23336 lot of stupid questions to confirm certain commands. For example, if
23337 you try to run a program which is already running:
23341 The program being debugged has been started already.
23342 Start it from the beginning? (y or n)
23345 If you are willing to unflinchingly face the consequences of your own
23346 commands, you can disable this ``feature'':
23350 @kindex set confirm
23352 @cindex confirmation
23353 @cindex stupid questions
23354 @item set confirm off
23355 Disables confirmation requests. Note that running @value{GDBN} with
23356 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23357 automatically disables confirmation requests.
23359 @item set confirm on
23360 Enables confirmation requests (the default).
23362 @kindex show confirm
23364 Displays state of confirmation requests.
23368 @cindex command tracing
23369 If you need to debug user-defined commands or sourced files you may find it
23370 useful to enable @dfn{command tracing}. In this mode each command will be
23371 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23372 quantity denoting the call depth of each command.
23375 @kindex set trace-commands
23376 @cindex command scripts, debugging
23377 @item set trace-commands on
23378 Enable command tracing.
23379 @item set trace-commands off
23380 Disable command tracing.
23381 @item show trace-commands
23382 Display the current state of command tracing.
23385 @node Debugging Output
23386 @section Optional Messages about Internal Happenings
23387 @cindex optional debugging messages
23389 @value{GDBN} has commands that enable optional debugging messages from
23390 various @value{GDBN} subsystems; normally these commands are of
23391 interest to @value{GDBN} maintainers, or when reporting a bug. This
23392 section documents those commands.
23395 @kindex set exec-done-display
23396 @item set exec-done-display
23397 Turns on or off the notification of asynchronous commands'
23398 completion. When on, @value{GDBN} will print a message when an
23399 asynchronous command finishes its execution. The default is off.
23400 @kindex show exec-done-display
23401 @item show exec-done-display
23402 Displays the current setting of asynchronous command completion
23405 @cindex ARM AArch64
23406 @item set debug aarch64
23407 Turns on or off display of debugging messages related to ARM AArch64.
23408 The default is off.
23410 @item show debug aarch64
23411 Displays the current state of displaying debugging messages related to
23413 @cindex gdbarch debugging info
23414 @cindex architecture debugging info
23415 @item set debug arch
23416 Turns on or off display of gdbarch debugging info. The default is off
23417 @item show debug arch
23418 Displays the current state of displaying gdbarch debugging info.
23419 @item set debug aix-solib
23420 @cindex AIX shared library debugging
23421 Control display of debugging messages from the AIX shared library
23422 support module. The default is off.
23423 @item show debug aix-thread
23424 Show the current state of displaying AIX shared library debugging messages.
23425 @item set debug aix-thread
23426 @cindex AIX threads
23427 Display debugging messages about inner workings of the AIX thread
23429 @item show debug aix-thread
23430 Show the current state of AIX thread debugging info display.
23431 @item set debug check-physname
23433 Check the results of the ``physname'' computation. When reading DWARF
23434 debugging information for C@t{++}, @value{GDBN} attempts to compute
23435 each entity's name. @value{GDBN} can do this computation in two
23436 different ways, depending on exactly what information is present.
23437 When enabled, this setting causes @value{GDBN} to compute the names
23438 both ways and display any discrepancies.
23439 @item show debug check-physname
23440 Show the current state of ``physname'' checking.
23441 @item set debug coff-pe-read
23442 @cindex COFF/PE exported symbols
23443 Control display of debugging messages related to reading of COFF/PE
23444 exported symbols. The default is off.
23445 @item show debug coff-pe-read
23446 Displays the current state of displaying debugging messages related to
23447 reading of COFF/PE exported symbols.
23448 @item set debug dwarf-die
23450 Dump DWARF DIEs after they are read in.
23451 The value is the number of nesting levels to print.
23452 A value of zero turns off the display.
23453 @item show debug dwarf-die
23454 Show the current state of DWARF DIE debugging.
23455 @item set debug dwarf-line
23456 @cindex DWARF Line Tables
23457 Turns on or off display of debugging messages related to reading
23458 DWARF line tables. The default is 0 (off).
23459 A value of 1 provides basic information.
23460 A value greater than 1 provides more verbose information.
23461 @item show debug dwarf-line
23462 Show the current state of DWARF line table debugging.
23463 @item set debug dwarf-read
23464 @cindex DWARF Reading
23465 Turns on or off display of debugging messages related to reading
23466 DWARF debug info. The default is 0 (off).
23467 A value of 1 provides basic information.
23468 A value greater than 1 provides more verbose information.
23469 @item show debug dwarf-read
23470 Show the current state of DWARF reader debugging.
23471 @item set debug displaced
23472 @cindex displaced stepping debugging info
23473 Turns on or off display of @value{GDBN} debugging info for the
23474 displaced stepping support. The default is off.
23475 @item show debug displaced
23476 Displays the current state of displaying @value{GDBN} debugging info
23477 related to displaced stepping.
23478 @item set debug event
23479 @cindex event debugging info
23480 Turns on or off display of @value{GDBN} event debugging info. The
23482 @item show debug event
23483 Displays the current state of displaying @value{GDBN} event debugging
23485 @item set debug expression
23486 @cindex expression debugging info
23487 Turns on or off display of debugging info about @value{GDBN}
23488 expression parsing. The default is off.
23489 @item show debug expression
23490 Displays the current state of displaying debugging info about
23491 @value{GDBN} expression parsing.
23492 @item set debug frame
23493 @cindex frame debugging info
23494 Turns on or off display of @value{GDBN} frame debugging info. The
23496 @item show debug frame
23497 Displays the current state of displaying @value{GDBN} frame debugging
23499 @item set debug gnu-nat
23500 @cindex @sc{gnu}/Hurd debug messages
23501 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23502 @item show debug gnu-nat
23503 Show the current state of @sc{gnu}/Hurd debugging messages.
23504 @item set debug infrun
23505 @cindex inferior debugging info
23506 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23507 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23508 for implementing operations such as single-stepping the inferior.
23509 @item show debug infrun
23510 Displays the current state of @value{GDBN} inferior debugging.
23511 @item set debug jit
23512 @cindex just-in-time compilation, debugging messages
23513 Turns on or off debugging messages from JIT debug support.
23514 @item show debug jit
23515 Displays the current state of @value{GDBN} JIT debugging.
23516 @item set debug lin-lwp
23517 @cindex @sc{gnu}/Linux LWP debug messages
23518 @cindex Linux lightweight processes
23519 Turns on or off debugging messages from the Linux LWP debug support.
23520 @item show debug lin-lwp
23521 Show the current state of Linux LWP debugging messages.
23522 @item set debug linux-namespaces
23523 @cindex @sc{gnu}/Linux namespaces debug messages
23524 Turns on or off debugging messages from the Linux namespaces debug support.
23525 @item show debug linux-namespaces
23526 Show the current state of Linux namespaces debugging messages.
23527 @item set debug mach-o
23528 @cindex Mach-O symbols processing
23529 Control display of debugging messages related to Mach-O symbols
23530 processing. The default is off.
23531 @item show debug mach-o
23532 Displays the current state of displaying debugging messages related to
23533 reading of COFF/PE exported symbols.
23534 @item set debug notification
23535 @cindex remote async notification debugging info
23536 Turns on or off debugging messages about remote async notification.
23537 The default is off.
23538 @item show debug notification
23539 Displays the current state of remote async notification debugging messages.
23540 @item set debug observer
23541 @cindex observer debugging info
23542 Turns on or off display of @value{GDBN} observer debugging. This
23543 includes info such as the notification of observable events.
23544 @item show debug observer
23545 Displays the current state of observer debugging.
23546 @item set debug overload
23547 @cindex C@t{++} overload debugging info
23548 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23549 info. This includes info such as ranking of functions, etc. The default
23551 @item show debug overload
23552 Displays the current state of displaying @value{GDBN} C@t{++} overload
23554 @cindex expression parser, debugging info
23555 @cindex debug expression parser
23556 @item set debug parser
23557 Turns on or off the display of expression parser debugging output.
23558 Internally, this sets the @code{yydebug} variable in the expression
23559 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23560 details. The default is off.
23561 @item show debug parser
23562 Show the current state of expression parser debugging.
23563 @cindex packets, reporting on stdout
23564 @cindex serial connections, debugging
23565 @cindex debug remote protocol
23566 @cindex remote protocol debugging
23567 @cindex display remote packets
23568 @item set debug remote
23569 Turns on or off display of reports on all packets sent back and forth across
23570 the serial line to the remote machine. The info is printed on the
23571 @value{GDBN} standard output stream. The default is off.
23572 @item show debug remote
23573 Displays the state of display of remote packets.
23574 @item set debug serial
23575 Turns on or off display of @value{GDBN} serial debugging info. The
23577 @item show debug serial
23578 Displays the current state of displaying @value{GDBN} serial debugging
23580 @item set debug solib-frv
23581 @cindex FR-V shared-library debugging
23582 Turns on or off debugging messages for FR-V shared-library code.
23583 @item show debug solib-frv
23584 Display the current state of FR-V shared-library code debugging
23586 @item set debug symbol-lookup
23587 @cindex symbol lookup
23588 Turns on or off display of debugging messages related to symbol lookup.
23589 The default is 0 (off).
23590 A value of 1 provides basic information.
23591 A value greater than 1 provides more verbose information.
23592 @item show debug symbol-lookup
23593 Show the current state of symbol lookup debugging messages.
23594 @item set debug symfile
23595 @cindex symbol file functions
23596 Turns on or off display of debugging messages related to symbol file functions.
23597 The default is off. @xref{Files}.
23598 @item show debug symfile
23599 Show the current state of symbol file debugging messages.
23600 @item set debug symtab-create
23601 @cindex symbol table creation
23602 Turns on or off display of debugging messages related to symbol table creation.
23603 The default is 0 (off).
23604 A value of 1 provides basic information.
23605 A value greater than 1 provides more verbose information.
23606 @item show debug symtab-create
23607 Show the current state of symbol table creation debugging.
23608 @item set debug target
23609 @cindex target debugging info
23610 Turns on or off display of @value{GDBN} target debugging info. This info
23611 includes what is going on at the target level of GDB, as it happens. The
23612 default is 0. Set it to 1 to track events, and to 2 to also track the
23613 value of large memory transfers.
23614 @item show debug target
23615 Displays the current state of displaying @value{GDBN} target debugging
23617 @item set debug timestamp
23618 @cindex timestampping debugging info
23619 Turns on or off display of timestamps with @value{GDBN} debugging info.
23620 When enabled, seconds and microseconds are displayed before each debugging
23622 @item show debug timestamp
23623 Displays the current state of displaying timestamps with @value{GDBN}
23625 @item set debug varobj
23626 @cindex variable object debugging info
23627 Turns on or off display of @value{GDBN} variable object debugging
23628 info. The default is off.
23629 @item show debug varobj
23630 Displays the current state of displaying @value{GDBN} variable object
23632 @item set debug xml
23633 @cindex XML parser debugging
23634 Turns on or off debugging messages for built-in XML parsers.
23635 @item show debug xml
23636 Displays the current state of XML debugging messages.
23639 @node Other Misc Settings
23640 @section Other Miscellaneous Settings
23641 @cindex miscellaneous settings
23644 @kindex set interactive-mode
23645 @item set interactive-mode
23646 If @code{on}, forces @value{GDBN} to assume that GDB was started
23647 in a terminal. In practice, this means that @value{GDBN} should wait
23648 for the user to answer queries generated by commands entered at
23649 the command prompt. If @code{off}, forces @value{GDBN} to operate
23650 in the opposite mode, and it uses the default answers to all queries.
23651 If @code{auto} (the default), @value{GDBN} tries to determine whether
23652 its standard input is a terminal, and works in interactive-mode if it
23653 is, non-interactively otherwise.
23655 In the vast majority of cases, the debugger should be able to guess
23656 correctly which mode should be used. But this setting can be useful
23657 in certain specific cases, such as running a MinGW @value{GDBN}
23658 inside a cygwin window.
23660 @kindex show interactive-mode
23661 @item show interactive-mode
23662 Displays whether the debugger is operating in interactive mode or not.
23665 @node Extending GDB
23666 @chapter Extending @value{GDBN}
23667 @cindex extending GDB
23669 @value{GDBN} provides several mechanisms for extension.
23670 @value{GDBN} also provides the ability to automatically load
23671 extensions when it reads a file for debugging. This allows the
23672 user to automatically customize @value{GDBN} for the program
23676 * Sequences:: Canned Sequences of @value{GDBN} Commands
23677 * Python:: Extending @value{GDBN} using Python
23678 * Guile:: Extending @value{GDBN} using Guile
23679 * Auto-loading extensions:: Automatically loading extensions
23680 * Multiple Extension Languages:: Working with multiple extension languages
23681 * Aliases:: Creating new spellings of existing commands
23684 To facilitate the use of extension languages, @value{GDBN} is capable
23685 of evaluating the contents of a file. When doing so, @value{GDBN}
23686 can recognize which extension language is being used by looking at
23687 the filename extension. Files with an unrecognized filename extension
23688 are always treated as a @value{GDBN} Command Files.
23689 @xref{Command Files,, Command files}.
23691 You can control how @value{GDBN} evaluates these files with the following
23695 @kindex set script-extension
23696 @kindex show script-extension
23697 @item set script-extension off
23698 All scripts are always evaluated as @value{GDBN} Command Files.
23700 @item set script-extension soft
23701 The debugger determines the scripting language based on filename
23702 extension. If this scripting language is supported, @value{GDBN}
23703 evaluates the script using that language. Otherwise, it evaluates
23704 the file as a @value{GDBN} Command File.
23706 @item set script-extension strict
23707 The debugger determines the scripting language based on filename
23708 extension, and evaluates the script using that language. If the
23709 language is not supported, then the evaluation fails.
23711 @item show script-extension
23712 Display the current value of the @code{script-extension} option.
23717 @section Canned Sequences of Commands
23719 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23720 Command Lists}), @value{GDBN} provides two ways to store sequences of
23721 commands for execution as a unit: user-defined commands and command
23725 * Define:: How to define your own commands
23726 * Hooks:: Hooks for user-defined commands
23727 * Command Files:: How to write scripts of commands to be stored in a file
23728 * Output:: Commands for controlled output
23729 * Auto-loading sequences:: Controlling auto-loaded command files
23733 @subsection User-defined Commands
23735 @cindex user-defined command
23736 @cindex arguments, to user-defined commands
23737 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23738 which you assign a new name as a command. This is done with the
23739 @code{define} command. User commands may accept up to 10 arguments
23740 separated by whitespace. Arguments are accessed within the user command
23741 via @code{$arg0@dots{}$arg9}. A trivial example:
23745 print $arg0 + $arg1 + $arg2
23750 To execute the command use:
23757 This defines the command @code{adder}, which prints the sum of
23758 its three arguments. Note the arguments are text substitutions, so they may
23759 reference variables, use complex expressions, or even perform inferior
23762 @cindex argument count in user-defined commands
23763 @cindex how many arguments (user-defined commands)
23764 In addition, @code{$argc} may be used to find out how many arguments have
23765 been passed. This expands to a number in the range 0@dots{}10.
23770 print $arg0 + $arg1
23773 print $arg0 + $arg1 + $arg2
23781 @item define @var{commandname}
23782 Define a command named @var{commandname}. If there is already a command
23783 by that name, you are asked to confirm that you want to redefine it.
23784 The argument @var{commandname} may be a bare command name consisting of letters,
23785 numbers, dashes, and underscores. It may also start with any predefined
23786 prefix command. For example, @samp{define target my-target} creates
23787 a user-defined @samp{target my-target} command.
23789 The definition of the command is made up of other @value{GDBN} command lines,
23790 which are given following the @code{define} command. The end of these
23791 commands is marked by a line containing @code{end}.
23794 @kindex end@r{ (user-defined commands)}
23795 @item document @var{commandname}
23796 Document the user-defined command @var{commandname}, so that it can be
23797 accessed by @code{help}. The command @var{commandname} must already be
23798 defined. This command reads lines of documentation just as @code{define}
23799 reads the lines of the command definition, ending with @code{end}.
23800 After the @code{document} command is finished, @code{help} on command
23801 @var{commandname} displays the documentation you have written.
23803 You may use the @code{document} command again to change the
23804 documentation of a command. Redefining the command with @code{define}
23805 does not change the documentation.
23807 @kindex dont-repeat
23808 @cindex don't repeat command
23810 Used inside a user-defined command, this tells @value{GDBN} that this
23811 command should not be repeated when the user hits @key{RET}
23812 (@pxref{Command Syntax, repeat last command}).
23814 @kindex help user-defined
23815 @item help user-defined
23816 List all user-defined commands and all python commands defined in class
23817 COMAND_USER. The first line of the documentation or docstring is
23822 @itemx show user @var{commandname}
23823 Display the @value{GDBN} commands used to define @var{commandname} (but
23824 not its documentation). If no @var{commandname} is given, display the
23825 definitions for all user-defined commands.
23826 This does not work for user-defined python commands.
23828 @cindex infinite recursion in user-defined commands
23829 @kindex show max-user-call-depth
23830 @kindex set max-user-call-depth
23831 @item show max-user-call-depth
23832 @itemx set max-user-call-depth
23833 The value of @code{max-user-call-depth} controls how many recursion
23834 levels are allowed in user-defined commands before @value{GDBN} suspects an
23835 infinite recursion and aborts the command.
23836 This does not apply to user-defined python commands.
23839 In addition to the above commands, user-defined commands frequently
23840 use control flow commands, described in @ref{Command Files}.
23842 When user-defined commands are executed, the
23843 commands of the definition are not printed. An error in any command
23844 stops execution of the user-defined command.
23846 If used interactively, commands that would ask for confirmation proceed
23847 without asking when used inside a user-defined command. Many @value{GDBN}
23848 commands that normally print messages to say what they are doing omit the
23849 messages when used in a user-defined command.
23852 @subsection User-defined Command Hooks
23853 @cindex command hooks
23854 @cindex hooks, for commands
23855 @cindex hooks, pre-command
23858 You may define @dfn{hooks}, which are a special kind of user-defined
23859 command. Whenever you run the command @samp{foo}, if the user-defined
23860 command @samp{hook-foo} exists, it is executed (with no arguments)
23861 before that command.
23863 @cindex hooks, post-command
23865 A hook may also be defined which is run after the command you executed.
23866 Whenever you run the command @samp{foo}, if the user-defined command
23867 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23868 that command. Post-execution hooks may exist simultaneously with
23869 pre-execution hooks, for the same command.
23871 It is valid for a hook to call the command which it hooks. If this
23872 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23874 @c It would be nice if hookpost could be passed a parameter indicating
23875 @c if the command it hooks executed properly or not. FIXME!
23877 @kindex stop@r{, a pseudo-command}
23878 In addition, a pseudo-command, @samp{stop} exists. Defining
23879 (@samp{hook-stop}) makes the associated commands execute every time
23880 execution stops in your program: before breakpoint commands are run,
23881 displays are printed, or the stack frame is printed.
23883 For example, to ignore @code{SIGALRM} signals while
23884 single-stepping, but treat them normally during normal execution,
23889 handle SIGALRM nopass
23893 handle SIGALRM pass
23896 define hook-continue
23897 handle SIGALRM pass
23901 As a further example, to hook at the beginning and end of the @code{echo}
23902 command, and to add extra text to the beginning and end of the message,
23910 define hookpost-echo
23914 (@value{GDBP}) echo Hello World
23915 <<<---Hello World--->>>
23920 You can define a hook for any single-word command in @value{GDBN}, but
23921 not for command aliases; you should define a hook for the basic command
23922 name, e.g.@: @code{backtrace} rather than @code{bt}.
23923 @c FIXME! So how does Joe User discover whether a command is an alias
23925 You can hook a multi-word command by adding @code{hook-} or
23926 @code{hookpost-} to the last word of the command, e.g.@:
23927 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23929 If an error occurs during the execution of your hook, execution of
23930 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23931 (before the command that you actually typed had a chance to run).
23933 If you try to define a hook which does not match any known command, you
23934 get a warning from the @code{define} command.
23936 @node Command Files
23937 @subsection Command Files
23939 @cindex command files
23940 @cindex scripting commands
23941 A command file for @value{GDBN} is a text file made of lines that are
23942 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23943 also be included. An empty line in a command file does nothing; it
23944 does not mean to repeat the last command, as it would from the
23947 You can request the execution of a command file with the @code{source}
23948 command. Note that the @code{source} command is also used to evaluate
23949 scripts that are not Command Files. The exact behavior can be configured
23950 using the @code{script-extension} setting.
23951 @xref{Extending GDB,, Extending GDB}.
23955 @cindex execute commands from a file
23956 @item source [-s] [-v] @var{filename}
23957 Execute the command file @var{filename}.
23960 The lines in a command file are generally executed sequentially,
23961 unless the order of execution is changed by one of the
23962 @emph{flow-control commands} described below. The commands are not
23963 printed as they are executed. An error in any command terminates
23964 execution of the command file and control is returned to the console.
23966 @value{GDBN} first searches for @var{filename} in the current directory.
23967 If the file is not found there, and @var{filename} does not specify a
23968 directory, then @value{GDBN} also looks for the file on the source search path
23969 (specified with the @samp{directory} command);
23970 except that @file{$cdir} is not searched because the compilation directory
23971 is not relevant to scripts.
23973 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23974 on the search path even if @var{filename} specifies a directory.
23975 The search is done by appending @var{filename} to each element of the
23976 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23977 and the search path contains @file{/home/user} then @value{GDBN} will
23978 look for the script @file{/home/user/mylib/myscript}.
23979 The search is also done if @var{filename} is an absolute path.
23980 For example, if @var{filename} is @file{/tmp/myscript} and
23981 the search path contains @file{/home/user} then @value{GDBN} will
23982 look for the script @file{/home/user/tmp/myscript}.
23983 For DOS-like systems, if @var{filename} contains a drive specification,
23984 it is stripped before concatenation. For example, if @var{filename} is
23985 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23986 will look for the script @file{c:/tmp/myscript}.
23988 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23989 each command as it is executed. The option must be given before
23990 @var{filename}, and is interpreted as part of the filename anywhere else.
23992 Commands that would ask for confirmation if used interactively proceed
23993 without asking when used in a command file. Many @value{GDBN} commands that
23994 normally print messages to say what they are doing omit the messages
23995 when called from command files.
23997 @value{GDBN} also accepts command input from standard input. In this
23998 mode, normal output goes to standard output and error output goes to
23999 standard error. Errors in a command file supplied on standard input do
24000 not terminate execution of the command file---execution continues with
24004 gdb < cmds > log 2>&1
24007 (The syntax above will vary depending on the shell used.) This example
24008 will execute commands from the file @file{cmds}. All output and errors
24009 would be directed to @file{log}.
24011 Since commands stored on command files tend to be more general than
24012 commands typed interactively, they frequently need to deal with
24013 complicated situations, such as different or unexpected values of
24014 variables and symbols, changes in how the program being debugged is
24015 built, etc. @value{GDBN} provides a set of flow-control commands to
24016 deal with these complexities. Using these commands, you can write
24017 complex scripts that loop over data structures, execute commands
24018 conditionally, etc.
24025 This command allows to include in your script conditionally executed
24026 commands. The @code{if} command takes a single argument, which is an
24027 expression to evaluate. It is followed by a series of commands that
24028 are executed only if the expression is true (its value is nonzero).
24029 There can then optionally be an @code{else} line, followed by a series
24030 of commands that are only executed if the expression was false. The
24031 end of the list is marked by a line containing @code{end}.
24035 This command allows to write loops. Its syntax is similar to
24036 @code{if}: the command takes a single argument, which is an expression
24037 to evaluate, and must be followed by the commands to execute, one per
24038 line, terminated by an @code{end}. These commands are called the
24039 @dfn{body} of the loop. The commands in the body of @code{while} are
24040 executed repeatedly as long as the expression evaluates to true.
24044 This command exits the @code{while} loop in whose body it is included.
24045 Execution of the script continues after that @code{while}s @code{end}
24048 @kindex loop_continue
24049 @item loop_continue
24050 This command skips the execution of the rest of the body of commands
24051 in the @code{while} loop in whose body it is included. Execution
24052 branches to the beginning of the @code{while} loop, where it evaluates
24053 the controlling expression.
24055 @kindex end@r{ (if/else/while commands)}
24057 Terminate the block of commands that are the body of @code{if},
24058 @code{else}, or @code{while} flow-control commands.
24063 @subsection Commands for Controlled Output
24065 During the execution of a command file or a user-defined command, normal
24066 @value{GDBN} output is suppressed; the only output that appears is what is
24067 explicitly printed by the commands in the definition. This section
24068 describes three commands useful for generating exactly the output you
24073 @item echo @var{text}
24074 @c I do not consider backslash-space a standard C escape sequence
24075 @c because it is not in ANSI.
24076 Print @var{text}. Nonprinting characters can be included in
24077 @var{text} using C escape sequences, such as @samp{\n} to print a
24078 newline. @strong{No newline is printed unless you specify one.}
24079 In addition to the standard C escape sequences, a backslash followed
24080 by a space stands for a space. This is useful for displaying a
24081 string with spaces at the beginning or the end, since leading and
24082 trailing spaces are otherwise trimmed from all arguments.
24083 To print @samp{@w{ }and foo =@w{ }}, use the command
24084 @samp{echo \@w{ }and foo = \@w{ }}.
24086 A backslash at the end of @var{text} can be used, as in C, to continue
24087 the command onto subsequent lines. For example,
24090 echo This is some text\n\
24091 which is continued\n\
24092 onto several lines.\n
24095 produces the same output as
24098 echo This is some text\n
24099 echo which is continued\n
24100 echo onto several lines.\n
24104 @item output @var{expression}
24105 Print the value of @var{expression} and nothing but that value: no
24106 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24107 value history either. @xref{Expressions, ,Expressions}, for more information
24110 @item output/@var{fmt} @var{expression}
24111 Print the value of @var{expression} in format @var{fmt}. You can use
24112 the same formats as for @code{print}. @xref{Output Formats,,Output
24113 Formats}, for more information.
24116 @item printf @var{template}, @var{expressions}@dots{}
24117 Print the values of one or more @var{expressions} under the control of
24118 the string @var{template}. To print several values, make
24119 @var{expressions} be a comma-separated list of individual expressions,
24120 which may be either numbers or pointers. Their values are printed as
24121 specified by @var{template}, exactly as a C program would do by
24122 executing the code below:
24125 printf (@var{template}, @var{expressions}@dots{});
24128 As in @code{C} @code{printf}, ordinary characters in @var{template}
24129 are printed verbatim, while @dfn{conversion specification} introduced
24130 by the @samp{%} character cause subsequent @var{expressions} to be
24131 evaluated, their values converted and formatted according to type and
24132 style information encoded in the conversion specifications, and then
24135 For example, you can print two values in hex like this:
24138 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24141 @code{printf} supports all the standard @code{C} conversion
24142 specifications, including the flags and modifiers between the @samp{%}
24143 character and the conversion letter, with the following exceptions:
24147 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24150 The modifier @samp{*} is not supported for specifying precision or
24154 The @samp{'} flag (for separation of digits into groups according to
24155 @code{LC_NUMERIC'}) is not supported.
24158 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24162 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24165 The conversion letters @samp{a} and @samp{A} are not supported.
24169 Note that the @samp{ll} type modifier is supported only if the
24170 underlying @code{C} implementation used to build @value{GDBN} supports
24171 the @code{long long int} type, and the @samp{L} type modifier is
24172 supported only if @code{long double} type is available.
24174 As in @code{C}, @code{printf} supports simple backslash-escape
24175 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24176 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24177 single character. Octal and hexadecimal escape sequences are not
24180 Additionally, @code{printf} supports conversion specifications for DFP
24181 (@dfn{Decimal Floating Point}) types using the following length modifiers
24182 together with a floating point specifier.
24187 @samp{H} for printing @code{Decimal32} types.
24190 @samp{D} for printing @code{Decimal64} types.
24193 @samp{DD} for printing @code{Decimal128} types.
24196 If the underlying @code{C} implementation used to build @value{GDBN} has
24197 support for the three length modifiers for DFP types, other modifiers
24198 such as width and precision will also be available for @value{GDBN} to use.
24200 In case there is no such @code{C} support, no additional modifiers will be
24201 available and the value will be printed in the standard way.
24203 Here's an example of printing DFP types using the above conversion letters:
24205 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24209 @item eval @var{template}, @var{expressions}@dots{}
24210 Convert the values of one or more @var{expressions} under the control of
24211 the string @var{template} to a command line, and call it.
24215 @node Auto-loading sequences
24216 @subsection Controlling auto-loading native @value{GDBN} scripts
24217 @cindex native script auto-loading
24219 When a new object file is read (for example, due to the @code{file}
24220 command, or because the inferior has loaded a shared library),
24221 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24222 @xref{Auto-loading extensions}.
24224 Auto-loading can be enabled or disabled,
24225 and the list of auto-loaded scripts can be printed.
24228 @anchor{set auto-load gdb-scripts}
24229 @kindex set auto-load gdb-scripts
24230 @item set auto-load gdb-scripts [on|off]
24231 Enable or disable the auto-loading of canned sequences of commands scripts.
24233 @anchor{show auto-load gdb-scripts}
24234 @kindex show auto-load gdb-scripts
24235 @item show auto-load gdb-scripts
24236 Show whether auto-loading of canned sequences of commands scripts is enabled or
24239 @anchor{info auto-load gdb-scripts}
24240 @kindex info auto-load gdb-scripts
24241 @cindex print list of auto-loaded canned sequences of commands scripts
24242 @item info auto-load gdb-scripts [@var{regexp}]
24243 Print the list of all canned sequences of commands scripts that @value{GDBN}
24247 If @var{regexp} is supplied only canned sequences of commands scripts with
24248 matching names are printed.
24250 @c Python docs live in a separate file.
24251 @include python.texi
24253 @c Guile docs live in a separate file.
24254 @include guile.texi
24256 @node Auto-loading extensions
24257 @section Auto-loading extensions
24258 @cindex auto-loading extensions
24260 @value{GDBN} provides two mechanisms for automatically loading extensions
24261 when a new object file is read (for example, due to the @code{file}
24262 command, or because the inferior has loaded a shared library):
24263 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24264 section of modern file formats like ELF.
24267 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24268 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24269 * Which flavor to choose?::
24272 The auto-loading feature is useful for supplying application-specific
24273 debugging commands and features.
24275 Auto-loading can be enabled or disabled,
24276 and the list of auto-loaded scripts can be printed.
24277 See the @samp{auto-loading} section of each extension language
24278 for more information.
24279 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24280 For Python files see @ref{Python Auto-loading}.
24282 Note that loading of this script file also requires accordingly configured
24283 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24285 @node objfile-gdbdotext file
24286 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24287 @cindex @file{@var{objfile}-gdb.gdb}
24288 @cindex @file{@var{objfile}-gdb.py}
24289 @cindex @file{@var{objfile}-gdb.scm}
24291 When a new object file is read, @value{GDBN} looks for a file named
24292 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24293 where @var{objfile} is the object file's name and
24294 where @var{ext} is the file extension for the extension language:
24297 @item @file{@var{objfile}-gdb.gdb}
24298 GDB's own command language
24299 @item @file{@var{objfile}-gdb.py}
24301 @item @file{@var{objfile}-gdb.scm}
24305 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24306 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24307 components, and appending the @file{-gdb.@var{ext}} suffix.
24308 If this file exists and is readable, @value{GDBN} will evaluate it as a
24309 script in the specified extension language.
24311 If this file does not exist, then @value{GDBN} will look for
24312 @var{script-name} file in all of the directories as specified below.
24314 Note that loading of these files requires an accordingly configured
24315 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24317 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24318 scripts normally according to its @file{.exe} filename. But if no scripts are
24319 found @value{GDBN} also tries script filenames matching the object file without
24320 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24321 is attempted on any platform. This makes the script filenames compatible
24322 between Unix and MS-Windows hosts.
24325 @anchor{set auto-load scripts-directory}
24326 @kindex set auto-load scripts-directory
24327 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24328 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24329 may be delimited by the host platform path separator in use
24330 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24332 Each entry here needs to be covered also by the security setting
24333 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24335 @anchor{with-auto-load-dir}
24336 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24337 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24338 configuration option @option{--with-auto-load-dir}.
24340 Any reference to @file{$debugdir} will get replaced by
24341 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24342 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24343 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24344 @file{$datadir} must be placed as a directory component --- either alone or
24345 delimited by @file{/} or @file{\} directory separators, depending on the host
24348 The list of directories uses path separator (@samp{:} on GNU and Unix
24349 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24350 to the @env{PATH} environment variable.
24352 @anchor{show auto-load scripts-directory}
24353 @kindex show auto-load scripts-directory
24354 @item show auto-load scripts-directory
24355 Show @value{GDBN} auto-loaded scripts location.
24357 @anchor{add-auto-load-scripts-directory}
24358 @kindex add-auto-load-scripts-directory
24359 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24360 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24361 Multiple entries may be delimited by the host platform path separator in use.
24364 @value{GDBN} does not track which files it has already auto-loaded this way.
24365 @value{GDBN} will load the associated script every time the corresponding
24366 @var{objfile} is opened.
24367 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24368 is evaluated more than once.
24370 @node dotdebug_gdb_scripts section
24371 @subsection The @code{.debug_gdb_scripts} section
24372 @cindex @code{.debug_gdb_scripts} section
24374 For systems using file formats like ELF and COFF,
24375 when @value{GDBN} loads a new object file
24376 it will look for a special section named @code{.debug_gdb_scripts}.
24377 If this section exists, its contents is a list of null-terminated entries
24378 specifying scripts to load. Each entry begins with a non-null prefix byte that
24379 specifies the kind of entry, typically the extension language and whether the
24380 script is in a file or inlined in @code{.debug_gdb_scripts}.
24382 The following entries are supported:
24385 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24386 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24387 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24388 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24391 @subsubsection Script File Entries
24393 If the entry specifies a file, @value{GDBN} will look for the file first
24394 in the current directory and then along the source search path
24395 (@pxref{Source Path, ,Specifying Source Directories}),
24396 except that @file{$cdir} is not searched, since the compilation
24397 directory is not relevant to scripts.
24399 File entries can be placed in section @code{.debug_gdb_scripts} with,
24400 for example, this GCC macro for Python scripts.
24403 /* Note: The "MS" section flags are to remove duplicates. */
24404 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24406 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24407 .byte 1 /* Python */\n\
24408 .asciz \"" script_name "\"\n\
24414 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24415 Then one can reference the macro in a header or source file like this:
24418 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24421 The script name may include directories if desired.
24423 Note that loading of this script file also requires accordingly configured
24424 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24426 If the macro invocation is put in a header, any application or library
24427 using this header will get a reference to the specified script,
24428 and with the use of @code{"MS"} attributes on the section, the linker
24429 will remove duplicates.
24431 @subsubsection Script Text Entries
24433 Script text entries allow to put the executable script in the entry
24434 itself instead of loading it from a file.
24435 The first line of the entry, everything after the prefix byte and up to
24436 the first newline (@code{0xa}) character, is the script name, and must not
24437 contain any kind of space character, e.g., spaces or tabs.
24438 The rest of the entry, up to the trailing null byte, is the script to
24439 execute in the specified language. The name needs to be unique among
24440 all script names, as @value{GDBN} executes each script only once based
24443 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24447 #include "symcat.h"
24448 #include "gdb/section-scripts.h"
24450 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24451 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24452 ".ascii \"gdb.inlined-script\\n\"\n"
24453 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24454 ".ascii \" def __init__ (self):\\n\"\n"
24455 ".ascii \" super (test_cmd, self).__init__ ("
24456 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24457 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24458 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24459 ".ascii \"test_cmd ()\\n\"\n"
24465 Loading of inlined scripts requires a properly configured
24466 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24467 The path to specify in @code{auto-load safe-path} is the path of the file
24468 containing the @code{.debug_gdb_scripts} section.
24470 @node Which flavor to choose?
24471 @subsection Which flavor to choose?
24473 Given the multiple ways of auto-loading extensions, it might not always
24474 be clear which one to choose. This section provides some guidance.
24477 Benefits of the @file{-gdb.@var{ext}} way:
24481 Can be used with file formats that don't support multiple sections.
24484 Ease of finding scripts for public libraries.
24486 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24487 in the source search path.
24488 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24489 isn't a source directory in which to find the script.
24492 Doesn't require source code additions.
24496 Benefits of the @code{.debug_gdb_scripts} way:
24500 Works with static linking.
24502 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24503 trigger their loading. When an application is statically linked the only
24504 objfile available is the executable, and it is cumbersome to attach all the
24505 scripts from all the input libraries to the executable's
24506 @file{-gdb.@var{ext}} script.
24509 Works with classes that are entirely inlined.
24511 Some classes can be entirely inlined, and thus there may not be an associated
24512 shared library to attach a @file{-gdb.@var{ext}} script to.
24515 Scripts needn't be copied out of the source tree.
24517 In some circumstances, apps can be built out of large collections of internal
24518 libraries, and the build infrastructure necessary to install the
24519 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24520 cumbersome. It may be easier to specify the scripts in the
24521 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24522 top of the source tree to the source search path.
24525 @node Multiple Extension Languages
24526 @section Multiple Extension Languages
24528 The Guile and Python extension languages do not share any state,
24529 and generally do not interfere with each other.
24530 There are some things to be aware of, however.
24532 @subsection Python comes first
24534 Python was @value{GDBN}'s first extension language, and to avoid breaking
24535 existing behaviour Python comes first. This is generally solved by the
24536 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24537 extension languages, and when it makes a call to an extension language,
24538 (say to pretty-print a value), it tries each in turn until an extension
24539 language indicates it has performed the request (e.g., has returned the
24540 pretty-printed form of a value).
24541 This extends to errors while performing such requests: If an error happens
24542 while, for example, trying to pretty-print an object then the error is
24543 reported and any following extension languages are not tried.
24546 @section Creating new spellings of existing commands
24547 @cindex aliases for commands
24549 It is often useful to define alternate spellings of existing commands.
24550 For example, if a new @value{GDBN} command defined in Python has
24551 a long name to type, it is handy to have an abbreviated version of it
24552 that involves less typing.
24554 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24555 of the @samp{step} command even though it is otherwise an ambiguous
24556 abbreviation of other commands like @samp{set} and @samp{show}.
24558 Aliases are also used to provide shortened or more common versions
24559 of multi-word commands. For example, @value{GDBN} provides the
24560 @samp{tty} alias of the @samp{set inferior-tty} command.
24562 You can define a new alias with the @samp{alias} command.
24567 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24571 @var{ALIAS} specifies the name of the new alias.
24572 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24575 @var{COMMAND} specifies the name of an existing command
24576 that is being aliased.
24578 The @samp{-a} option specifies that the new alias is an abbreviation
24579 of the command. Abbreviations are not shown in command
24580 lists displayed by the @samp{help} command.
24582 The @samp{--} option specifies the end of options,
24583 and is useful when @var{ALIAS} begins with a dash.
24585 Here is a simple example showing how to make an abbreviation
24586 of a command so that there is less to type.
24587 Suppose you were tired of typing @samp{disas}, the current
24588 shortest unambiguous abbreviation of the @samp{disassemble} command
24589 and you wanted an even shorter version named @samp{di}.
24590 The following will accomplish this.
24593 (gdb) alias -a di = disas
24596 Note that aliases are different from user-defined commands.
24597 With a user-defined command, you also need to write documentation
24598 for it with the @samp{document} command.
24599 An alias automatically picks up the documentation of the existing command.
24601 Here is an example where we make @samp{elms} an abbreviation of
24602 @samp{elements} in the @samp{set print elements} command.
24603 This is to show that you can make an abbreviation of any part
24607 (gdb) alias -a set print elms = set print elements
24608 (gdb) alias -a show print elms = show print elements
24609 (gdb) set p elms 20
24611 Limit on string chars or array elements to print is 200.
24614 Note that if you are defining an alias of a @samp{set} command,
24615 and you want to have an alias for the corresponding @samp{show}
24616 command, then you need to define the latter separately.
24618 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24619 @var{ALIAS}, just as they are normally.
24622 (gdb) alias -a set pr elms = set p ele
24625 Finally, here is an example showing the creation of a one word
24626 alias for a more complex command.
24627 This creates alias @samp{spe} of the command @samp{set print elements}.
24630 (gdb) alias spe = set print elements
24635 @chapter Command Interpreters
24636 @cindex command interpreters
24638 @value{GDBN} supports multiple command interpreters, and some command
24639 infrastructure to allow users or user interface writers to switch
24640 between interpreters or run commands in other interpreters.
24642 @value{GDBN} currently supports two command interpreters, the console
24643 interpreter (sometimes called the command-line interpreter or @sc{cli})
24644 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24645 describes both of these interfaces in great detail.
24647 By default, @value{GDBN} will start with the console interpreter.
24648 However, the user may choose to start @value{GDBN} with another
24649 interpreter by specifying the @option{-i} or @option{--interpreter}
24650 startup options. Defined interpreters include:
24654 @cindex console interpreter
24655 The traditional console or command-line interpreter. This is the most often
24656 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24657 @value{GDBN} will use this interpreter.
24660 @cindex mi interpreter
24661 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24662 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24663 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24667 @cindex mi2 interpreter
24668 The current @sc{gdb/mi} interface.
24671 @cindex mi1 interpreter
24672 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24676 @cindex invoke another interpreter
24677 The interpreter being used by @value{GDBN} may not be dynamically
24678 switched at runtime. Although possible, this could lead to a very
24679 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24680 enters the command "interpreter-set console" in a console view,
24681 @value{GDBN} would switch to using the console interpreter, rendering
24682 the IDE inoperable!
24684 @kindex interpreter-exec
24685 Although you may only choose a single interpreter at startup, you may execute
24686 commands in any interpreter from the current interpreter using the appropriate
24687 command. If you are running the console interpreter, simply use the
24688 @code{interpreter-exec} command:
24691 interpreter-exec mi "-data-list-register-names"
24694 @sc{gdb/mi} has a similar command, although it is only available in versions of
24695 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24698 @chapter @value{GDBN} Text User Interface
24700 @cindex Text User Interface
24703 * TUI Overview:: TUI overview
24704 * TUI Keys:: TUI key bindings
24705 * TUI Single Key Mode:: TUI single key mode
24706 * TUI Commands:: TUI-specific commands
24707 * TUI Configuration:: TUI configuration variables
24710 The @value{GDBN} Text User Interface (TUI) is a terminal
24711 interface which uses the @code{curses} library to show the source
24712 file, the assembly output, the program registers and @value{GDBN}
24713 commands in separate text windows. The TUI mode is supported only
24714 on platforms where a suitable version of the @code{curses} library
24717 The TUI mode is enabled by default when you invoke @value{GDBN} as
24718 @samp{@value{GDBP} -tui}.
24719 You can also switch in and out of TUI mode while @value{GDBN} runs by
24720 using various TUI commands and key bindings, such as @command{tui
24721 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24722 @ref{TUI Keys, ,TUI Key Bindings}.
24725 @section TUI Overview
24727 In TUI mode, @value{GDBN} can display several text windows:
24731 This window is the @value{GDBN} command window with the @value{GDBN}
24732 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24733 managed using readline.
24736 The source window shows the source file of the program. The current
24737 line and active breakpoints are displayed in this window.
24740 The assembly window shows the disassembly output of the program.
24743 This window shows the processor registers. Registers are highlighted
24744 when their values change.
24747 The source and assembly windows show the current program position
24748 by highlighting the current line and marking it with a @samp{>} marker.
24749 Breakpoints are indicated with two markers. The first marker
24750 indicates the breakpoint type:
24754 Breakpoint which was hit at least once.
24757 Breakpoint which was never hit.
24760 Hardware breakpoint which was hit at least once.
24763 Hardware breakpoint which was never hit.
24766 The second marker indicates whether the breakpoint is enabled or not:
24770 Breakpoint is enabled.
24773 Breakpoint is disabled.
24776 The source, assembly and register windows are updated when the current
24777 thread changes, when the frame changes, or when the program counter
24780 These windows are not all visible at the same time. The command
24781 window is always visible. The others can be arranged in several
24792 source and assembly,
24795 source and registers, or
24798 assembly and registers.
24801 A status line above the command window shows the following information:
24805 Indicates the current @value{GDBN} target.
24806 (@pxref{Targets, ,Specifying a Debugging Target}).
24809 Gives the current process or thread number.
24810 When no process is being debugged, this field is set to @code{No process}.
24813 Gives the current function name for the selected frame.
24814 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24815 When there is no symbol corresponding to the current program counter,
24816 the string @code{??} is displayed.
24819 Indicates the current line number for the selected frame.
24820 When the current line number is not known, the string @code{??} is displayed.
24823 Indicates the current program counter address.
24827 @section TUI Key Bindings
24828 @cindex TUI key bindings
24830 The TUI installs several key bindings in the readline keymaps
24831 @ifset SYSTEM_READLINE
24832 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24834 @ifclear SYSTEM_READLINE
24835 (@pxref{Command Line Editing}).
24837 The following key bindings are installed for both TUI mode and the
24838 @value{GDBN} standard mode.
24847 Enter or leave the TUI mode. When leaving the TUI mode,
24848 the curses window management stops and @value{GDBN} operates using
24849 its standard mode, writing on the terminal directly. When reentering
24850 the TUI mode, control is given back to the curses windows.
24851 The screen is then refreshed.
24855 Use a TUI layout with only one window. The layout will
24856 either be @samp{source} or @samp{assembly}. When the TUI mode
24857 is not active, it will switch to the TUI mode.
24859 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24863 Use a TUI layout with at least two windows. When the current
24864 layout already has two windows, the next layout with two windows is used.
24865 When a new layout is chosen, one window will always be common to the
24866 previous layout and the new one.
24868 Think of it as the Emacs @kbd{C-x 2} binding.
24872 Change the active window. The TUI associates several key bindings
24873 (like scrolling and arrow keys) with the active window. This command
24874 gives the focus to the next TUI window.
24876 Think of it as the Emacs @kbd{C-x o} binding.
24880 Switch in and out of the TUI SingleKey mode that binds single
24881 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24884 The following key bindings only work in the TUI mode:
24889 Scroll the active window one page up.
24893 Scroll the active window one page down.
24897 Scroll the active window one line up.
24901 Scroll the active window one line down.
24905 Scroll the active window one column left.
24909 Scroll the active window one column right.
24913 Refresh the screen.
24916 Because the arrow keys scroll the active window in the TUI mode, they
24917 are not available for their normal use by readline unless the command
24918 window has the focus. When another window is active, you must use
24919 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24920 and @kbd{C-f} to control the command window.
24922 @node TUI Single Key Mode
24923 @section TUI Single Key Mode
24924 @cindex TUI single key mode
24926 The TUI also provides a @dfn{SingleKey} mode, which binds several
24927 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24928 switch into this mode, where the following key bindings are used:
24931 @kindex c @r{(SingleKey TUI key)}
24935 @kindex d @r{(SingleKey TUI key)}
24939 @kindex f @r{(SingleKey TUI key)}
24943 @kindex n @r{(SingleKey TUI key)}
24947 @kindex q @r{(SingleKey TUI key)}
24949 exit the SingleKey mode.
24951 @kindex r @r{(SingleKey TUI key)}
24955 @kindex s @r{(SingleKey TUI key)}
24959 @kindex u @r{(SingleKey TUI key)}
24963 @kindex v @r{(SingleKey TUI key)}
24967 @kindex w @r{(SingleKey TUI key)}
24972 Other keys temporarily switch to the @value{GDBN} command prompt.
24973 The key that was pressed is inserted in the editing buffer so that
24974 it is possible to type most @value{GDBN} commands without interaction
24975 with the TUI SingleKey mode. Once the command is entered the TUI
24976 SingleKey mode is restored. The only way to permanently leave
24977 this mode is by typing @kbd{q} or @kbd{C-x s}.
24981 @section TUI-specific Commands
24982 @cindex TUI commands
24984 The TUI has specific commands to control the text windows.
24985 These commands are always available, even when @value{GDBN} is not in
24986 the TUI mode. When @value{GDBN} is in the standard mode, most
24987 of these commands will automatically switch to the TUI mode.
24989 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24990 terminal, or @value{GDBN} has been started with the machine interface
24991 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24992 these commands will fail with an error, because it would not be
24993 possible or desirable to enable curses window management.
24998 Activate TUI mode. The last active TUI window layout will be used if
24999 TUI mode has prevsiouly been used in the current debugging session,
25000 otherwise a default layout is used.
25003 @kindex tui disable
25004 Disable TUI mode, returning to the console interpreter.
25008 List and give the size of all displayed windows.
25010 @item layout @var{name}
25012 Changes which TUI windows are displayed. In each layout the command
25013 window is always displayed, the @var{name} parameter controls which
25014 additional windows are displayed, and can be any of the following:
25018 Display the next layout.
25021 Display the previous layout.
25024 Display the source and command windows.
25027 Display the assembly and command windows.
25030 Display the source, assembly, and command windows.
25033 When in @code{src} layout display the register, source, and command
25034 windows. When in @code{asm} or @code{split} layout display the
25035 register, assembler, and command windows.
25038 @item focus @var{name}
25040 Changes which TUI window is currently active for scrolling. The
25041 @var{name} parameter can be any of the following:
25045 Make the next window active for scrolling.
25048 Make the previous window active for scrolling.
25051 Make the source window active for scrolling.
25054 Make the assembly window active for scrolling.
25057 Make the register window active for scrolling.
25060 Make the command window active for scrolling.
25065 Refresh the screen. This is similar to typing @kbd{C-L}.
25067 @item tui reg @var{group}
25069 Changes the register group displayed in the tui register window to
25070 @var{group}. If the register window is not currently displayed this
25071 command will cause the register window to be displayed. The list of
25072 register groups, as well as their order is target specific. The
25073 following groups are available on most targets:
25076 Repeatedly selecting this group will cause the display to cycle
25077 through all of the available register groups.
25080 Repeatedly selecting this group will cause the display to cycle
25081 through all of the available register groups in the reverse order to
25085 Display the general registers.
25087 Display the floating point registers.
25089 Display the system registers.
25091 Display the vector registers.
25093 Display all registers.
25098 Update the source window and the current execution point.
25100 @item winheight @var{name} +@var{count}
25101 @itemx winheight @var{name} -@var{count}
25103 Change the height of the window @var{name} by @var{count}
25104 lines. Positive counts increase the height, while negative counts
25105 decrease it. The @var{name} parameter can be one of @code{src} (the
25106 source window), @code{cmd} (the command window), @code{asm} (the
25107 disassembly window), or @code{regs} (the register display window).
25109 @item tabset @var{nchars}
25111 Set the width of tab stops to be @var{nchars} characters. This
25112 setting affects the display of TAB characters in the source and
25116 @node TUI Configuration
25117 @section TUI Configuration Variables
25118 @cindex TUI configuration variables
25120 Several configuration variables control the appearance of TUI windows.
25123 @item set tui border-kind @var{kind}
25124 @kindex set tui border-kind
25125 Select the border appearance for the source, assembly and register windows.
25126 The possible values are the following:
25129 Use a space character to draw the border.
25132 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25135 Use the Alternate Character Set to draw the border. The border is
25136 drawn using character line graphics if the terminal supports them.
25139 @item set tui border-mode @var{mode}
25140 @kindex set tui border-mode
25141 @itemx set tui active-border-mode @var{mode}
25142 @kindex set tui active-border-mode
25143 Select the display attributes for the borders of the inactive windows
25144 or the active window. The @var{mode} can be one of the following:
25147 Use normal attributes to display the border.
25153 Use reverse video mode.
25156 Use half bright mode.
25158 @item half-standout
25159 Use half bright and standout mode.
25162 Use extra bright or bold mode.
25164 @item bold-standout
25165 Use extra bright or bold and standout mode.
25170 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25173 @cindex @sc{gnu} Emacs
25174 A special interface allows you to use @sc{gnu} Emacs to view (and
25175 edit) the source files for the program you are debugging with
25178 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25179 executable file you want to debug as an argument. This command starts
25180 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25181 created Emacs buffer.
25182 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25184 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25189 All ``terminal'' input and output goes through an Emacs buffer, called
25192 This applies both to @value{GDBN} commands and their output, and to the input
25193 and output done by the program you are debugging.
25195 This is useful because it means that you can copy the text of previous
25196 commands and input them again; you can even use parts of the output
25199 All the facilities of Emacs' Shell mode are available for interacting
25200 with your program. In particular, you can send signals the usual
25201 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25205 @value{GDBN} displays source code through Emacs.
25207 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25208 source file for that frame and puts an arrow (@samp{=>}) at the
25209 left margin of the current line. Emacs uses a separate buffer for
25210 source display, and splits the screen to show both your @value{GDBN} session
25213 Explicit @value{GDBN} @code{list} or search commands still produce output as
25214 usual, but you probably have no reason to use them from Emacs.
25217 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25218 a graphical mode, enabled by default, which provides further buffers
25219 that can control the execution and describe the state of your program.
25220 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25222 If you specify an absolute file name when prompted for the @kbd{M-x
25223 gdb} argument, then Emacs sets your current working directory to where
25224 your program resides. If you only specify the file name, then Emacs
25225 sets your current working directory to the directory associated
25226 with the previous buffer. In this case, @value{GDBN} may find your
25227 program by searching your environment's @code{PATH} variable, but on
25228 some operating systems it might not find the source. So, although the
25229 @value{GDBN} input and output session proceeds normally, the auxiliary
25230 buffer does not display the current source and line of execution.
25232 The initial working directory of @value{GDBN} is printed on the top
25233 line of the GUD buffer and this serves as a default for the commands
25234 that specify files for @value{GDBN} to operate on. @xref{Files,
25235 ,Commands to Specify Files}.
25237 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25238 need to call @value{GDBN} by a different name (for example, if you
25239 keep several configurations around, with different names) you can
25240 customize the Emacs variable @code{gud-gdb-command-name} to run the
25243 In the GUD buffer, you can use these special Emacs commands in
25244 addition to the standard Shell mode commands:
25248 Describe the features of Emacs' GUD Mode.
25251 Execute to another source line, like the @value{GDBN} @code{step} command; also
25252 update the display window to show the current file and location.
25255 Execute to next source line in this function, skipping all function
25256 calls, like the @value{GDBN} @code{next} command. Then update the display window
25257 to show the current file and location.
25260 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25261 display window accordingly.
25264 Execute until exit from the selected stack frame, like the @value{GDBN}
25265 @code{finish} command.
25268 Continue execution of your program, like the @value{GDBN} @code{continue}
25272 Go up the number of frames indicated by the numeric argument
25273 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25274 like the @value{GDBN} @code{up} command.
25277 Go down the number of frames indicated by the numeric argument, like the
25278 @value{GDBN} @code{down} command.
25281 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25282 tells @value{GDBN} to set a breakpoint on the source line point is on.
25284 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25285 separate frame which shows a backtrace when the GUD buffer is current.
25286 Move point to any frame in the stack and type @key{RET} to make it
25287 become the current frame and display the associated source in the
25288 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25289 selected frame become the current one. In graphical mode, the
25290 speedbar displays watch expressions.
25292 If you accidentally delete the source-display buffer, an easy way to get
25293 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25294 request a frame display; when you run under Emacs, this recreates
25295 the source buffer if necessary to show you the context of the current
25298 The source files displayed in Emacs are in ordinary Emacs buffers
25299 which are visiting the source files in the usual way. You can edit
25300 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25301 communicates with Emacs in terms of line numbers. If you add or
25302 delete lines from the text, the line numbers that @value{GDBN} knows cease
25303 to correspond properly with the code.
25305 A more detailed description of Emacs' interaction with @value{GDBN} is
25306 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25310 @chapter The @sc{gdb/mi} Interface
25312 @unnumberedsec Function and Purpose
25314 @cindex @sc{gdb/mi}, its purpose
25315 @sc{gdb/mi} is a line based machine oriented text interface to
25316 @value{GDBN} and is activated by specifying using the
25317 @option{--interpreter} command line option (@pxref{Mode Options}). It
25318 is specifically intended to support the development of systems which
25319 use the debugger as just one small component of a larger system.
25321 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25322 in the form of a reference manual.
25324 Note that @sc{gdb/mi} is still under construction, so some of the
25325 features described below are incomplete and subject to change
25326 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25328 @unnumberedsec Notation and Terminology
25330 @cindex notational conventions, for @sc{gdb/mi}
25331 This chapter uses the following notation:
25335 @code{|} separates two alternatives.
25338 @code{[ @var{something} ]} indicates that @var{something} is optional:
25339 it may or may not be given.
25342 @code{( @var{group} )*} means that @var{group} inside the parentheses
25343 may repeat zero or more times.
25346 @code{( @var{group} )+} means that @var{group} inside the parentheses
25347 may repeat one or more times.
25350 @code{"@var{string}"} means a literal @var{string}.
25354 @heading Dependencies
25358 * GDB/MI General Design::
25359 * GDB/MI Command Syntax::
25360 * GDB/MI Compatibility with CLI::
25361 * GDB/MI Development and Front Ends::
25362 * GDB/MI Output Records::
25363 * GDB/MI Simple Examples::
25364 * GDB/MI Command Description Format::
25365 * GDB/MI Breakpoint Commands::
25366 * GDB/MI Catchpoint Commands::
25367 * GDB/MI Program Context::
25368 * GDB/MI Thread Commands::
25369 * GDB/MI Ada Tasking Commands::
25370 * GDB/MI Program Execution::
25371 * GDB/MI Stack Manipulation::
25372 * GDB/MI Variable Objects::
25373 * GDB/MI Data Manipulation::
25374 * GDB/MI Tracepoint Commands::
25375 * GDB/MI Symbol Query::
25376 * GDB/MI File Commands::
25378 * GDB/MI Kod Commands::
25379 * GDB/MI Memory Overlay Commands::
25380 * GDB/MI Signal Handling Commands::
25382 * GDB/MI Target Manipulation::
25383 * GDB/MI File Transfer Commands::
25384 * GDB/MI Ada Exceptions Commands::
25385 * GDB/MI Support Commands::
25386 * GDB/MI Miscellaneous Commands::
25389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25390 @node GDB/MI General Design
25391 @section @sc{gdb/mi} General Design
25392 @cindex GDB/MI General Design
25394 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25395 parts---commands sent to @value{GDBN}, responses to those commands
25396 and notifications. Each command results in exactly one response,
25397 indicating either successful completion of the command, or an error.
25398 For the commands that do not resume the target, the response contains the
25399 requested information. For the commands that resume the target, the
25400 response only indicates whether the target was successfully resumed.
25401 Notifications is the mechanism for reporting changes in the state of the
25402 target, or in @value{GDBN} state, that cannot conveniently be associated with
25403 a command and reported as part of that command response.
25405 The important examples of notifications are:
25409 Exec notifications. These are used to report changes in
25410 target state---when a target is resumed, or stopped. It would not
25411 be feasible to include this information in response of resuming
25412 commands, because one resume commands can result in multiple events in
25413 different threads. Also, quite some time may pass before any event
25414 happens in the target, while a frontend needs to know whether the resuming
25415 command itself was successfully executed.
25418 Console output, and status notifications. Console output
25419 notifications are used to report output of CLI commands, as well as
25420 diagnostics for other commands. Status notifications are used to
25421 report the progress of a long-running operation. Naturally, including
25422 this information in command response would mean no output is produced
25423 until the command is finished, which is undesirable.
25426 General notifications. Commands may have various side effects on
25427 the @value{GDBN} or target state beyond their official purpose. For example,
25428 a command may change the selected thread. Although such changes can
25429 be included in command response, using notification allows for more
25430 orthogonal frontend design.
25434 There's no guarantee that whenever an MI command reports an error,
25435 @value{GDBN} or the target are in any specific state, and especially,
25436 the state is not reverted to the state before the MI command was
25437 processed. Therefore, whenever an MI command results in an error,
25438 we recommend that the frontend refreshes all the information shown in
25439 the user interface.
25443 * Context management::
25444 * Asynchronous and non-stop modes::
25448 @node Context management
25449 @subsection Context management
25451 @subsubsection Threads and Frames
25453 In most cases when @value{GDBN} accesses the target, this access is
25454 done in context of a specific thread and frame (@pxref{Frames}).
25455 Often, even when accessing global data, the target requires that a thread
25456 be specified. The CLI interface maintains the selected thread and frame,
25457 and supplies them to target on each command. This is convenient,
25458 because a command line user would not want to specify that information
25459 explicitly on each command, and because user interacts with
25460 @value{GDBN} via a single terminal, so no confusion is possible as
25461 to what thread and frame are the current ones.
25463 In the case of MI, the concept of selected thread and frame is less
25464 useful. First, a frontend can easily remember this information
25465 itself. Second, a graphical frontend can have more than one window,
25466 each one used for debugging a different thread, and the frontend might
25467 want to access additional threads for internal purposes. This
25468 increases the risk that by relying on implicitly selected thread, the
25469 frontend may be operating on a wrong one. Therefore, each MI command
25470 should explicitly specify which thread and frame to operate on. To
25471 make it possible, each MI command accepts the @samp{--thread} and
25472 @samp{--frame} options, the value to each is @value{GDBN} identifier
25473 for thread and frame to operate on.
25475 Usually, each top-level window in a frontend allows the user to select
25476 a thread and a frame, and remembers the user selection for further
25477 operations. However, in some cases @value{GDBN} may suggest that the
25478 current thread be changed. For example, when stopping on a breakpoint
25479 it is reasonable to switch to the thread where breakpoint is hit. For
25480 another example, if the user issues the CLI @samp{thread} command via
25481 the frontend, it is desirable to change the frontend's selected thread to the
25482 one specified by user. @value{GDBN} communicates the suggestion to
25483 change current thread using the @samp{=thread-selected} notification.
25484 No such notification is available for the selected frame at the moment.
25486 Note that historically, MI shares the selected thread with CLI, so
25487 frontends used the @code{-thread-select} to execute commands in the
25488 right context. However, getting this to work right is cumbersome. The
25489 simplest way is for frontend to emit @code{-thread-select} command
25490 before every command. This doubles the number of commands that need
25491 to be sent. The alternative approach is to suppress @code{-thread-select}
25492 if the selected thread in @value{GDBN} is supposed to be identical to the
25493 thread the frontend wants to operate on. However, getting this
25494 optimization right can be tricky. In particular, if the frontend
25495 sends several commands to @value{GDBN}, and one of the commands changes the
25496 selected thread, then the behaviour of subsequent commands will
25497 change. So, a frontend should either wait for response from such
25498 problematic commands, or explicitly add @code{-thread-select} for
25499 all subsequent commands. No frontend is known to do this exactly
25500 right, so it is suggested to just always pass the @samp{--thread} and
25501 @samp{--frame} options.
25503 @subsubsection Language
25505 The execution of several commands depends on which language is selected.
25506 By default, the current language (@pxref{show language}) is used.
25507 But for commands known to be language-sensitive, it is recommended
25508 to use the @samp{--language} option. This option takes one argument,
25509 which is the name of the language to use while executing the command.
25513 -data-evaluate-expression --language c "sizeof (void*)"
25518 The valid language names are the same names accepted by the
25519 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25520 @samp{local} or @samp{unknown}.
25522 @node Asynchronous and non-stop modes
25523 @subsection Asynchronous command execution and non-stop mode
25525 On some targets, @value{GDBN} is capable of processing MI commands
25526 even while the target is running. This is called @dfn{asynchronous
25527 command execution} (@pxref{Background Execution}). The frontend may
25528 specify a preferrence for asynchronous execution using the
25529 @code{-gdb-set mi-async 1} command, which should be emitted before
25530 either running the executable or attaching to the target. After the
25531 frontend has started the executable or attached to the target, it can
25532 find if asynchronous execution is enabled using the
25533 @code{-list-target-features} command.
25536 @item -gdb-set mi-async on
25537 @item -gdb-set mi-async off
25538 Set whether MI is in asynchronous mode.
25540 When @code{off}, which is the default, MI execution commands (e.g.,
25541 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25542 for the program to stop before processing further commands.
25544 When @code{on}, MI execution commands are background execution
25545 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25546 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25547 MI commands even while the target is running.
25549 @item -gdb-show mi-async
25550 Show whether MI asynchronous mode is enabled.
25553 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25554 @code{target-async} instead of @code{mi-async}, and it had the effect
25555 of both putting MI in asynchronous mode and making CLI background
25556 commands possible. CLI background commands are now always possible
25557 ``out of the box'' if the target supports them. The old spelling is
25558 kept as a deprecated alias for backwards compatibility.
25560 Even if @value{GDBN} can accept a command while target is running,
25561 many commands that access the target do not work when the target is
25562 running. Therefore, asynchronous command execution is most useful
25563 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25564 it is possible to examine the state of one thread, while other threads
25567 When a given thread is running, MI commands that try to access the
25568 target in the context of that thread may not work, or may work only on
25569 some targets. In particular, commands that try to operate on thread's
25570 stack will not work, on any target. Commands that read memory, or
25571 modify breakpoints, may work or not work, depending on the target. Note
25572 that even commands that operate on global state, such as @code{print},
25573 @code{set}, and breakpoint commands, still access the target in the
25574 context of a specific thread, so frontend should try to find a
25575 stopped thread and perform the operation on that thread (using the
25576 @samp{--thread} option).
25578 Which commands will work in the context of a running thread is
25579 highly target dependent. However, the two commands
25580 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25581 to find the state of a thread, will always work.
25583 @node Thread groups
25584 @subsection Thread groups
25585 @value{GDBN} may be used to debug several processes at the same time.
25586 On some platfroms, @value{GDBN} may support debugging of several
25587 hardware systems, each one having several cores with several different
25588 processes running on each core. This section describes the MI
25589 mechanism to support such debugging scenarios.
25591 The key observation is that regardless of the structure of the
25592 target, MI can have a global list of threads, because most commands that
25593 accept the @samp{--thread} option do not need to know what process that
25594 thread belongs to. Therefore, it is not necessary to introduce
25595 neither additional @samp{--process} option, nor an notion of the
25596 current process in the MI interface. The only strictly new feature
25597 that is required is the ability to find how the threads are grouped
25600 To allow the user to discover such grouping, and to support arbitrary
25601 hierarchy of machines/cores/processes, MI introduces the concept of a
25602 @dfn{thread group}. Thread group is a collection of threads and other
25603 thread groups. A thread group always has a string identifier, a type,
25604 and may have additional attributes specific to the type. A new
25605 command, @code{-list-thread-groups}, returns the list of top-level
25606 thread groups, which correspond to processes that @value{GDBN} is
25607 debugging at the moment. By passing an identifier of a thread group
25608 to the @code{-list-thread-groups} command, it is possible to obtain
25609 the members of specific thread group.
25611 To allow the user to easily discover processes, and other objects, he
25612 wishes to debug, a concept of @dfn{available thread group} is
25613 introduced. Available thread group is an thread group that
25614 @value{GDBN} is not debugging, but that can be attached to, using the
25615 @code{-target-attach} command. The list of available top-level thread
25616 groups can be obtained using @samp{-list-thread-groups --available}.
25617 In general, the content of a thread group may be only retrieved only
25618 after attaching to that thread group.
25620 Thread groups are related to inferiors (@pxref{Inferiors and
25621 Programs}). Each inferior corresponds to a thread group of a special
25622 type @samp{process}, and some additional operations are permitted on
25623 such thread groups.
25625 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25626 @node GDB/MI Command Syntax
25627 @section @sc{gdb/mi} Command Syntax
25630 * GDB/MI Input Syntax::
25631 * GDB/MI Output Syntax::
25634 @node GDB/MI Input Syntax
25635 @subsection @sc{gdb/mi} Input Syntax
25637 @cindex input syntax for @sc{gdb/mi}
25638 @cindex @sc{gdb/mi}, input syntax
25640 @item @var{command} @expansion{}
25641 @code{@var{cli-command} | @var{mi-command}}
25643 @item @var{cli-command} @expansion{}
25644 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25645 @var{cli-command} is any existing @value{GDBN} CLI command.
25647 @item @var{mi-command} @expansion{}
25648 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25649 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25651 @item @var{token} @expansion{}
25652 "any sequence of digits"
25654 @item @var{option} @expansion{}
25655 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25657 @item @var{parameter} @expansion{}
25658 @code{@var{non-blank-sequence} | @var{c-string}}
25660 @item @var{operation} @expansion{}
25661 @emph{any of the operations described in this chapter}
25663 @item @var{non-blank-sequence} @expansion{}
25664 @emph{anything, provided it doesn't contain special characters such as
25665 "-", @var{nl}, """ and of course " "}
25667 @item @var{c-string} @expansion{}
25668 @code{""" @var{seven-bit-iso-c-string-content} """}
25670 @item @var{nl} @expansion{}
25679 The CLI commands are still handled by the @sc{mi} interpreter; their
25680 output is described below.
25683 The @code{@var{token}}, when present, is passed back when the command
25687 Some @sc{mi} commands accept optional arguments as part of the parameter
25688 list. Each option is identified by a leading @samp{-} (dash) and may be
25689 followed by an optional argument parameter. Options occur first in the
25690 parameter list and can be delimited from normal parameters using
25691 @samp{--} (this is useful when some parameters begin with a dash).
25698 We want easy access to the existing CLI syntax (for debugging).
25701 We want it to be easy to spot a @sc{mi} operation.
25704 @node GDB/MI Output Syntax
25705 @subsection @sc{gdb/mi} Output Syntax
25707 @cindex output syntax of @sc{gdb/mi}
25708 @cindex @sc{gdb/mi}, output syntax
25709 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25710 followed, optionally, by a single result record. This result record
25711 is for the most recent command. The sequence of output records is
25712 terminated by @samp{(gdb)}.
25714 If an input command was prefixed with a @code{@var{token}} then the
25715 corresponding output for that command will also be prefixed by that same
25719 @item @var{output} @expansion{}
25720 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25722 @item @var{result-record} @expansion{}
25723 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25725 @item @var{out-of-band-record} @expansion{}
25726 @code{@var{async-record} | @var{stream-record}}
25728 @item @var{async-record} @expansion{}
25729 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25731 @item @var{exec-async-output} @expansion{}
25732 @code{[ @var{token} ] "*" @var{async-output nl}}
25734 @item @var{status-async-output} @expansion{}
25735 @code{[ @var{token} ] "+" @var{async-output nl}}
25737 @item @var{notify-async-output} @expansion{}
25738 @code{[ @var{token} ] "=" @var{async-output nl}}
25740 @item @var{async-output} @expansion{}
25741 @code{@var{async-class} ( "," @var{result} )*}
25743 @item @var{result-class} @expansion{}
25744 @code{"done" | "running" | "connected" | "error" | "exit"}
25746 @item @var{async-class} @expansion{}
25747 @code{"stopped" | @var{others}} (where @var{others} will be added
25748 depending on the needs---this is still in development).
25750 @item @var{result} @expansion{}
25751 @code{ @var{variable} "=" @var{value}}
25753 @item @var{variable} @expansion{}
25754 @code{ @var{string} }
25756 @item @var{value} @expansion{}
25757 @code{ @var{const} | @var{tuple} | @var{list} }
25759 @item @var{const} @expansion{}
25760 @code{@var{c-string}}
25762 @item @var{tuple} @expansion{}
25763 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25765 @item @var{list} @expansion{}
25766 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25767 @var{result} ( "," @var{result} )* "]" }
25769 @item @var{stream-record} @expansion{}
25770 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25772 @item @var{console-stream-output} @expansion{}
25773 @code{"~" @var{c-string nl}}
25775 @item @var{target-stream-output} @expansion{}
25776 @code{"@@" @var{c-string nl}}
25778 @item @var{log-stream-output} @expansion{}
25779 @code{"&" @var{c-string nl}}
25781 @item @var{nl} @expansion{}
25784 @item @var{token} @expansion{}
25785 @emph{any sequence of digits}.
25793 All output sequences end in a single line containing a period.
25796 The @code{@var{token}} is from the corresponding request. Note that
25797 for all async output, while the token is allowed by the grammar and
25798 may be output by future versions of @value{GDBN} for select async
25799 output messages, it is generally omitted. Frontends should treat
25800 all async output as reporting general changes in the state of the
25801 target and there should be no need to associate async output to any
25805 @cindex status output in @sc{gdb/mi}
25806 @var{status-async-output} contains on-going status information about the
25807 progress of a slow operation. It can be discarded. All status output is
25808 prefixed by @samp{+}.
25811 @cindex async output in @sc{gdb/mi}
25812 @var{exec-async-output} contains asynchronous state change on the target
25813 (stopped, started, disappeared). All async output is prefixed by
25817 @cindex notify output in @sc{gdb/mi}
25818 @var{notify-async-output} contains supplementary information that the
25819 client should handle (e.g., a new breakpoint information). All notify
25820 output is prefixed by @samp{=}.
25823 @cindex console output in @sc{gdb/mi}
25824 @var{console-stream-output} is output that should be displayed as is in the
25825 console. It is the textual response to a CLI command. All the console
25826 output is prefixed by @samp{~}.
25829 @cindex target output in @sc{gdb/mi}
25830 @var{target-stream-output} is the output produced by the target program.
25831 All the target output is prefixed by @samp{@@}.
25834 @cindex log output in @sc{gdb/mi}
25835 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25836 instance messages that should be displayed as part of an error log. All
25837 the log output is prefixed by @samp{&}.
25840 @cindex list output in @sc{gdb/mi}
25841 New @sc{gdb/mi} commands should only output @var{lists} containing
25847 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25848 details about the various output records.
25850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25851 @node GDB/MI Compatibility with CLI
25852 @section @sc{gdb/mi} Compatibility with CLI
25854 @cindex compatibility, @sc{gdb/mi} and CLI
25855 @cindex @sc{gdb/mi}, compatibility with CLI
25857 For the developers convenience CLI commands can be entered directly,
25858 but there may be some unexpected behaviour. For example, commands
25859 that query the user will behave as if the user replied yes, breakpoint
25860 command lists are not executed and some CLI commands, such as
25861 @code{if}, @code{when} and @code{define}, prompt for further input with
25862 @samp{>}, which is not valid MI output.
25864 This feature may be removed at some stage in the future and it is
25865 recommended that front ends use the @code{-interpreter-exec} command
25866 (@pxref{-interpreter-exec}).
25868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25869 @node GDB/MI Development and Front Ends
25870 @section @sc{gdb/mi} Development and Front Ends
25871 @cindex @sc{gdb/mi} development
25873 The application which takes the MI output and presents the state of the
25874 program being debugged to the user is called a @dfn{front end}.
25876 Although @sc{gdb/mi} is still incomplete, it is currently being used
25877 by a variety of front ends to @value{GDBN}. This makes it difficult
25878 to introduce new functionality without breaking existing usage. This
25879 section tries to minimize the problems by describing how the protocol
25882 Some changes in MI need not break a carefully designed front end, and
25883 for these the MI version will remain unchanged. The following is a
25884 list of changes that may occur within one level, so front ends should
25885 parse MI output in a way that can handle them:
25889 New MI commands may be added.
25892 New fields may be added to the output of any MI command.
25895 The range of values for fields with specified values, e.g.,
25896 @code{in_scope} (@pxref{-var-update}) may be extended.
25898 @c The format of field's content e.g type prefix, may change so parse it
25899 @c at your own risk. Yes, in general?
25901 @c The order of fields may change? Shouldn't really matter but it might
25902 @c resolve inconsistencies.
25905 If the changes are likely to break front ends, the MI version level
25906 will be increased by one. This will allow the front end to parse the
25907 output according to the MI version. Apart from mi0, new versions of
25908 @value{GDBN} will not support old versions of MI and it will be the
25909 responsibility of the front end to work with the new one.
25911 @c Starting with mi3, add a new command -mi-version that prints the MI
25914 The best way to avoid unexpected changes in MI that might break your front
25915 end is to make your project known to @value{GDBN} developers and
25916 follow development on @email{gdb@@sourceware.org} and
25917 @email{gdb-patches@@sourceware.org}.
25918 @cindex mailing lists
25920 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25921 @node GDB/MI Output Records
25922 @section @sc{gdb/mi} Output Records
25925 * GDB/MI Result Records::
25926 * GDB/MI Stream Records::
25927 * GDB/MI Async Records::
25928 * GDB/MI Breakpoint Information::
25929 * GDB/MI Frame Information::
25930 * GDB/MI Thread Information::
25931 * GDB/MI Ada Exception Information::
25934 @node GDB/MI Result Records
25935 @subsection @sc{gdb/mi} Result Records
25937 @cindex result records in @sc{gdb/mi}
25938 @cindex @sc{gdb/mi}, result records
25939 In addition to a number of out-of-band notifications, the response to a
25940 @sc{gdb/mi} command includes one of the following result indications:
25944 @item "^done" [ "," @var{results} ]
25945 The synchronous operation was successful, @code{@var{results}} are the return
25950 This result record is equivalent to @samp{^done}. Historically, it
25951 was output instead of @samp{^done} if the command has resumed the
25952 target. This behaviour is maintained for backward compatibility, but
25953 all frontends should treat @samp{^done} and @samp{^running}
25954 identically and rely on the @samp{*running} output record to determine
25955 which threads are resumed.
25959 @value{GDBN} has connected to a remote target.
25961 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25963 The operation failed. The @code{msg=@var{c-string}} variable contains
25964 the corresponding error message.
25966 If present, the @code{code=@var{c-string}} variable provides an error
25967 code on which consumers can rely on to detect the corresponding
25968 error condition. At present, only one error code is defined:
25971 @item "undefined-command"
25972 Indicates that the command causing the error does not exist.
25977 @value{GDBN} has terminated.
25981 @node GDB/MI Stream Records
25982 @subsection @sc{gdb/mi} Stream Records
25984 @cindex @sc{gdb/mi}, stream records
25985 @cindex stream records in @sc{gdb/mi}
25986 @value{GDBN} internally maintains a number of output streams: the console, the
25987 target, and the log. The output intended for each of these streams is
25988 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25990 Each stream record begins with a unique @dfn{prefix character} which
25991 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25992 Syntax}). In addition to the prefix, each stream record contains a
25993 @code{@var{string-output}}. This is either raw text (with an implicit new
25994 line) or a quoted C string (which does not contain an implicit newline).
25997 @item "~" @var{string-output}
25998 The console output stream contains text that should be displayed in the
25999 CLI console window. It contains the textual responses to CLI commands.
26001 @item "@@" @var{string-output}
26002 The target output stream contains any textual output from the running
26003 target. This is only present when GDB's event loop is truly
26004 asynchronous, which is currently only the case for remote targets.
26006 @item "&" @var{string-output}
26007 The log stream contains debugging messages being produced by @value{GDBN}'s
26011 @node GDB/MI Async Records
26012 @subsection @sc{gdb/mi} Async Records
26014 @cindex async records in @sc{gdb/mi}
26015 @cindex @sc{gdb/mi}, async records
26016 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26017 additional changes that have occurred. Those changes can either be a
26018 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26019 target activity (e.g., target stopped).
26021 The following is the list of possible async records:
26025 @item *running,thread-id="@var{thread}"
26026 The target is now running. The @var{thread} field tells which
26027 specific thread is now running, and can be @samp{all} if all threads
26028 are running. The frontend should assume that no interaction with a
26029 running thread is possible after this notification is produced.
26030 The frontend should not assume that this notification is output
26031 only once for any command. @value{GDBN} may emit this notification
26032 several times, either for different threads, because it cannot resume
26033 all threads together, or even for a single thread, if the thread must
26034 be stepped though some code before letting it run freely.
26036 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26037 The target has stopped. The @var{reason} field can have one of the
26041 @item breakpoint-hit
26042 A breakpoint was reached.
26043 @item watchpoint-trigger
26044 A watchpoint was triggered.
26045 @item read-watchpoint-trigger
26046 A read watchpoint was triggered.
26047 @item access-watchpoint-trigger
26048 An access watchpoint was triggered.
26049 @item function-finished
26050 An -exec-finish or similar CLI command was accomplished.
26051 @item location-reached
26052 An -exec-until or similar CLI command was accomplished.
26053 @item watchpoint-scope
26054 A watchpoint has gone out of scope.
26055 @item end-stepping-range
26056 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26057 similar CLI command was accomplished.
26058 @item exited-signalled
26059 The inferior exited because of a signal.
26061 The inferior exited.
26062 @item exited-normally
26063 The inferior exited normally.
26064 @item signal-received
26065 A signal was received by the inferior.
26067 The inferior has stopped due to a library being loaded or unloaded.
26068 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26069 set or when a @code{catch load} or @code{catch unload} catchpoint is
26070 in use (@pxref{Set Catchpoints}).
26072 The inferior has forked. This is reported when @code{catch fork}
26073 (@pxref{Set Catchpoints}) has been used.
26075 The inferior has vforked. This is reported in when @code{catch vfork}
26076 (@pxref{Set Catchpoints}) has been used.
26077 @item syscall-entry
26078 The inferior entered a system call. This is reported when @code{catch
26079 syscall} (@pxref{Set Catchpoints}) has been used.
26080 @item syscall-return
26081 The inferior returned from a system call. This is reported when
26082 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26084 The inferior called @code{exec}. This is reported when @code{catch exec}
26085 (@pxref{Set Catchpoints}) has been used.
26088 The @var{id} field identifies the thread that directly caused the stop
26089 -- for example by hitting a breakpoint. Depending on whether all-stop
26090 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26091 stop all threads, or only the thread that directly triggered the stop.
26092 If all threads are stopped, the @var{stopped} field will have the
26093 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26094 field will be a list of thread identifiers. Presently, this list will
26095 always include a single thread, but frontend should be prepared to see
26096 several threads in the list. The @var{core} field reports the
26097 processor core on which the stop event has happened. This field may be absent
26098 if such information is not available.
26100 @item =thread-group-added,id="@var{id}"
26101 @itemx =thread-group-removed,id="@var{id}"
26102 A thread group was either added or removed. The @var{id} field
26103 contains the @value{GDBN} identifier of the thread group. When a thread
26104 group is added, it generally might not be associated with a running
26105 process. When a thread group is removed, its id becomes invalid and
26106 cannot be used in any way.
26108 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26109 A thread group became associated with a running program,
26110 either because the program was just started or the thread group
26111 was attached to a program. The @var{id} field contains the
26112 @value{GDBN} identifier of the thread group. The @var{pid} field
26113 contains process identifier, specific to the operating system.
26115 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26116 A thread group is no longer associated with a running program,
26117 either because the program has exited, or because it was detached
26118 from. The @var{id} field contains the @value{GDBN} identifier of the
26119 thread group. The @var{code} field is the exit code of the inferior; it exists
26120 only when the inferior exited with some code.
26122 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26123 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26124 A thread either was created, or has exited. The @var{id} field
26125 contains the @value{GDBN} identifier of the thread. The @var{gid}
26126 field identifies the thread group this thread belongs to.
26128 @item =thread-selected,id="@var{id}"
26129 Informs that the selected thread was changed as result of the last
26130 command. This notification is not emitted as result of @code{-thread-select}
26131 command but is emitted whenever an MI command that is not documented
26132 to change the selected thread actually changes it. In particular,
26133 invoking, directly or indirectly (via user-defined command), the CLI
26134 @code{thread} command, will generate this notification.
26136 We suggest that in response to this notification, front ends
26137 highlight the selected thread and cause subsequent commands to apply to
26140 @item =library-loaded,...
26141 Reports that a new library file was loaded by the program. This
26142 notification has 4 fields---@var{id}, @var{target-name},
26143 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26144 opaque identifier of the library. For remote debugging case,
26145 @var{target-name} and @var{host-name} fields give the name of the
26146 library file on the target, and on the host respectively. For native
26147 debugging, both those fields have the same value. The
26148 @var{symbols-loaded} field is emitted only for backward compatibility
26149 and should not be relied on to convey any useful information. The
26150 @var{thread-group} field, if present, specifies the id of the thread
26151 group in whose context the library was loaded. If the field is
26152 absent, it means the library was loaded in the context of all present
26155 @item =library-unloaded,...
26156 Reports that a library was unloaded by the program. This notification
26157 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26158 the same meaning as for the @code{=library-loaded} notification.
26159 The @var{thread-group} field, if present, specifies the id of the
26160 thread group in whose context the library was unloaded. If the field is
26161 absent, it means the library was unloaded in the context of all present
26164 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26165 @itemx =traceframe-changed,end
26166 Reports that the trace frame was changed and its new number is
26167 @var{tfnum}. The number of the tracepoint associated with this trace
26168 frame is @var{tpnum}.
26170 @item =tsv-created,name=@var{name},initial=@var{initial}
26171 Reports that the new trace state variable @var{name} is created with
26172 initial value @var{initial}.
26174 @item =tsv-deleted,name=@var{name}
26175 @itemx =tsv-deleted
26176 Reports that the trace state variable @var{name} is deleted or all
26177 trace state variables are deleted.
26179 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26180 Reports that the trace state variable @var{name} is modified with
26181 the initial value @var{initial}. The current value @var{current} of
26182 trace state variable is optional and is reported if the current
26183 value of trace state variable is known.
26185 @item =breakpoint-created,bkpt=@{...@}
26186 @itemx =breakpoint-modified,bkpt=@{...@}
26187 @itemx =breakpoint-deleted,id=@var{number}
26188 Reports that a breakpoint was created, modified, or deleted,
26189 respectively. Only user-visible breakpoints are reported to the MI
26192 The @var{bkpt} argument is of the same form as returned by the various
26193 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26194 @var{number} is the ordinal number of the breakpoint.
26196 Note that if a breakpoint is emitted in the result record of a
26197 command, then it will not also be emitted in an async record.
26199 @item =record-started,thread-group="@var{id}"
26200 @itemx =record-stopped,thread-group="@var{id}"
26201 Execution log recording was either started or stopped on an
26202 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26203 group corresponding to the affected inferior.
26205 @item =cmd-param-changed,param=@var{param},value=@var{value}
26206 Reports that a parameter of the command @code{set @var{param}} is
26207 changed to @var{value}. In the multi-word @code{set} command,
26208 the @var{param} is the whole parameter list to @code{set} command.
26209 For example, In command @code{set check type on}, @var{param}
26210 is @code{check type} and @var{value} is @code{on}.
26212 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26213 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26214 written in an inferior. The @var{id} is the identifier of the
26215 thread group corresponding to the affected inferior. The optional
26216 @code{type="code"} part is reported if the memory written to holds
26220 @node GDB/MI Breakpoint Information
26221 @subsection @sc{gdb/mi} Breakpoint Information
26223 When @value{GDBN} reports information about a breakpoint, a
26224 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26229 The breakpoint number. For a breakpoint that represents one location
26230 of a multi-location breakpoint, this will be a dotted pair, like
26234 The type of the breakpoint. For ordinary breakpoints this will be
26235 @samp{breakpoint}, but many values are possible.
26238 If the type of the breakpoint is @samp{catchpoint}, then this
26239 indicates the exact type of catchpoint.
26242 This is the breakpoint disposition---either @samp{del}, meaning that
26243 the breakpoint will be deleted at the next stop, or @samp{keep},
26244 meaning that the breakpoint will not be deleted.
26247 This indicates whether the breakpoint is enabled, in which case the
26248 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26249 Note that this is not the same as the field @code{enable}.
26252 The address of the breakpoint. This may be a hexidecimal number,
26253 giving the address; or the string @samp{<PENDING>}, for a pending
26254 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26255 multiple locations. This field will not be present if no address can
26256 be determined. For example, a watchpoint does not have an address.
26259 If known, the function in which the breakpoint appears.
26260 If not known, this field is not present.
26263 The name of the source file which contains this function, if known.
26264 If not known, this field is not present.
26267 The full file name of the source file which contains this function, if
26268 known. If not known, this field is not present.
26271 The line number at which this breakpoint appears, if known.
26272 If not known, this field is not present.
26275 If the source file is not known, this field may be provided. If
26276 provided, this holds the address of the breakpoint, possibly followed
26280 If this breakpoint is pending, this field is present and holds the
26281 text used to set the breakpoint, as entered by the user.
26284 Where this breakpoint's condition is evaluated, either @samp{host} or
26288 If this is a thread-specific breakpoint, then this identifies the
26289 thread in which the breakpoint can trigger.
26292 If this breakpoint is restricted to a particular Ada task, then this
26293 field will hold the task identifier.
26296 If the breakpoint is conditional, this is the condition expression.
26299 The ignore count of the breakpoint.
26302 The enable count of the breakpoint.
26304 @item traceframe-usage
26307 @item static-tracepoint-marker-string-id
26308 For a static tracepoint, the name of the static tracepoint marker.
26311 For a masked watchpoint, this is the mask.
26314 A tracepoint's pass count.
26316 @item original-location
26317 The location of the breakpoint as originally specified by the user.
26318 This field is optional.
26321 The number of times the breakpoint has been hit.
26324 This field is only given for tracepoints. This is either @samp{y},
26325 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26329 Some extra data, the exact contents of which are type-dependent.
26333 For example, here is what the output of @code{-break-insert}
26334 (@pxref{GDB/MI Breakpoint Commands}) might be:
26337 -> -break-insert main
26338 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26339 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26340 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26345 @node GDB/MI Frame Information
26346 @subsection @sc{gdb/mi} Frame Information
26348 Response from many MI commands includes an information about stack
26349 frame. This information is a tuple that may have the following
26354 The level of the stack frame. The innermost frame has the level of
26355 zero. This field is always present.
26358 The name of the function corresponding to the frame. This field may
26359 be absent if @value{GDBN} is unable to determine the function name.
26362 The code address for the frame. This field is always present.
26365 The name of the source files that correspond to the frame's code
26366 address. This field may be absent.
26369 The source line corresponding to the frames' code address. This field
26373 The name of the binary file (either executable or shared library) the
26374 corresponds to the frame's code address. This field may be absent.
26378 @node GDB/MI Thread Information
26379 @subsection @sc{gdb/mi} Thread Information
26381 Whenever @value{GDBN} has to report an information about a thread, it
26382 uses a tuple with the following fields:
26386 The numeric id assigned to the thread by @value{GDBN}. This field is
26390 Target-specific string identifying the thread. This field is always present.
26393 Additional information about the thread provided by the target.
26394 It is supposed to be human-readable and not interpreted by the
26395 frontend. This field is optional.
26398 Either @samp{stopped} or @samp{running}, depending on whether the
26399 thread is presently running. This field is always present.
26402 The value of this field is an integer number of the processor core the
26403 thread was last seen on. This field is optional.
26406 @node GDB/MI Ada Exception Information
26407 @subsection @sc{gdb/mi} Ada Exception Information
26409 Whenever a @code{*stopped} record is emitted because the program
26410 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26411 @value{GDBN} provides the name of the exception that was raised via
26412 the @code{exception-name} field.
26414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26415 @node GDB/MI Simple Examples
26416 @section Simple Examples of @sc{gdb/mi} Interaction
26417 @cindex @sc{gdb/mi}, simple examples
26419 This subsection presents several simple examples of interaction using
26420 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26421 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26422 the output received from @sc{gdb/mi}.
26424 Note the line breaks shown in the examples are here only for
26425 readability, they don't appear in the real output.
26427 @subheading Setting a Breakpoint
26429 Setting a breakpoint generates synchronous output which contains detailed
26430 information of the breakpoint.
26433 -> -break-insert main
26434 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26435 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26436 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26441 @subheading Program Execution
26443 Program execution generates asynchronous records and MI gives the
26444 reason that execution stopped.
26450 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26451 frame=@{addr="0x08048564",func="main",
26452 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26453 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26458 <- *stopped,reason="exited-normally"
26462 @subheading Quitting @value{GDBN}
26464 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26472 Please note that @samp{^exit} is printed immediately, but it might
26473 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26474 performs necessary cleanups, including killing programs being debugged
26475 or disconnecting from debug hardware, so the frontend should wait till
26476 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26477 fails to exit in reasonable time.
26479 @subheading A Bad Command
26481 Here's what happens if you pass a non-existent command:
26485 <- ^error,msg="Undefined MI command: rubbish"
26490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26491 @node GDB/MI Command Description Format
26492 @section @sc{gdb/mi} Command Description Format
26494 The remaining sections describe blocks of commands. Each block of
26495 commands is laid out in a fashion similar to this section.
26497 @subheading Motivation
26499 The motivation for this collection of commands.
26501 @subheading Introduction
26503 A brief introduction to this collection of commands as a whole.
26505 @subheading Commands
26507 For each command in the block, the following is described:
26509 @subsubheading Synopsis
26512 -command @var{args}@dots{}
26515 @subsubheading Result
26517 @subsubheading @value{GDBN} Command
26519 The corresponding @value{GDBN} CLI command(s), if any.
26521 @subsubheading Example
26523 Example(s) formatted for readability. Some of the described commands have
26524 not been implemented yet and these are labeled N.A.@: (not available).
26527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26528 @node GDB/MI Breakpoint Commands
26529 @section @sc{gdb/mi} Breakpoint Commands
26531 @cindex breakpoint commands for @sc{gdb/mi}
26532 @cindex @sc{gdb/mi}, breakpoint commands
26533 This section documents @sc{gdb/mi} commands for manipulating
26536 @subheading The @code{-break-after} Command
26537 @findex -break-after
26539 @subsubheading Synopsis
26542 -break-after @var{number} @var{count}
26545 The breakpoint number @var{number} is not in effect until it has been
26546 hit @var{count} times. To see how this is reflected in the output of
26547 the @samp{-break-list} command, see the description of the
26548 @samp{-break-list} command below.
26550 @subsubheading @value{GDBN} Command
26552 The corresponding @value{GDBN} command is @samp{ignore}.
26554 @subsubheading Example
26559 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26560 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26561 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26569 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26570 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26571 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26572 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26573 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26574 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26575 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26576 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26577 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26578 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26583 @subheading The @code{-break-catch} Command
26584 @findex -break-catch
26587 @subheading The @code{-break-commands} Command
26588 @findex -break-commands
26590 @subsubheading Synopsis
26593 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26596 Specifies the CLI commands that should be executed when breakpoint
26597 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26598 are the commands. If no command is specified, any previously-set
26599 commands are cleared. @xref{Break Commands}. Typical use of this
26600 functionality is tracing a program, that is, printing of values of
26601 some variables whenever breakpoint is hit and then continuing.
26603 @subsubheading @value{GDBN} Command
26605 The corresponding @value{GDBN} command is @samp{commands}.
26607 @subsubheading Example
26612 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26613 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26614 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26617 -break-commands 1 "print v" "continue"
26622 @subheading The @code{-break-condition} Command
26623 @findex -break-condition
26625 @subsubheading Synopsis
26628 -break-condition @var{number} @var{expr}
26631 Breakpoint @var{number} will stop the program only if the condition in
26632 @var{expr} is true. The condition becomes part of the
26633 @samp{-break-list} output (see the description of the @samp{-break-list}
26636 @subsubheading @value{GDBN} Command
26638 The corresponding @value{GDBN} command is @samp{condition}.
26640 @subsubheading Example
26644 -break-condition 1 1
26648 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26649 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26650 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26651 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26652 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26653 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26654 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26655 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26656 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26657 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26661 @subheading The @code{-break-delete} Command
26662 @findex -break-delete
26664 @subsubheading Synopsis
26667 -break-delete ( @var{breakpoint} )+
26670 Delete the breakpoint(s) whose number(s) are specified in the argument
26671 list. This is obviously reflected in the breakpoint list.
26673 @subsubheading @value{GDBN} Command
26675 The corresponding @value{GDBN} command is @samp{delete}.
26677 @subsubheading Example
26685 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26686 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26687 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26688 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26689 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26690 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26691 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26696 @subheading The @code{-break-disable} Command
26697 @findex -break-disable
26699 @subsubheading Synopsis
26702 -break-disable ( @var{breakpoint} )+
26705 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26706 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26708 @subsubheading @value{GDBN} Command
26710 The corresponding @value{GDBN} command is @samp{disable}.
26712 @subsubheading Example
26720 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26721 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26722 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26723 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26724 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26725 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26726 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26727 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26728 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26729 line="5",thread-groups=["i1"],times="0"@}]@}
26733 @subheading The @code{-break-enable} Command
26734 @findex -break-enable
26736 @subsubheading Synopsis
26739 -break-enable ( @var{breakpoint} )+
26742 Enable (previously disabled) @var{breakpoint}(s).
26744 @subsubheading @value{GDBN} Command
26746 The corresponding @value{GDBN} command is @samp{enable}.
26748 @subsubheading Example
26756 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26757 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26758 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26759 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26760 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26761 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26762 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26763 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26764 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26765 line="5",thread-groups=["i1"],times="0"@}]@}
26769 @subheading The @code{-break-info} Command
26770 @findex -break-info
26772 @subsubheading Synopsis
26775 -break-info @var{breakpoint}
26779 Get information about a single breakpoint.
26781 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26782 Information}, for details on the format of each breakpoint in the
26785 @subsubheading @value{GDBN} Command
26787 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26789 @subsubheading Example
26792 @subheading The @code{-break-insert} Command
26793 @findex -break-insert
26794 @anchor{-break-insert}
26796 @subsubheading Synopsis
26799 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26800 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26801 [ -p @var{thread-id} ] [ @var{location} ]
26805 If specified, @var{location}, can be one of:
26808 @item linespec location
26809 A linespec location. @xref{Linespec Locations}.
26811 @item explicit location
26812 An explicit location. @sc{gdb/mi} explicit locations are
26813 analogous to the CLI's explicit locations using the option names
26814 listed below. @xref{Explicit Locations}.
26817 @item --source @var{filename}
26818 The source file name of the location. This option requires the use
26819 of either @samp{--function} or @samp{--line}.
26821 @item --function @var{function}
26822 The name of a function or method.
26824 @item --label @var{label}
26825 The name of a label.
26827 @item --line @var{lineoffset}
26828 An absolute or relative line offset from the start of the location.
26831 @item address location
26832 An address location, *@var{address}. @xref{Address Locations}.
26836 The possible optional parameters of this command are:
26840 Insert a temporary breakpoint.
26842 Insert a hardware breakpoint.
26844 If @var{location} cannot be parsed (for example if it
26845 refers to unknown files or functions), create a pending
26846 breakpoint. Without this flag, @value{GDBN} will report
26847 an error, and won't create a breakpoint, if @var{location}
26850 Create a disabled breakpoint.
26852 Create a tracepoint. @xref{Tracepoints}. When this parameter
26853 is used together with @samp{-h}, a fast tracepoint is created.
26854 @item -c @var{condition}
26855 Make the breakpoint conditional on @var{condition}.
26856 @item -i @var{ignore-count}
26857 Initialize the @var{ignore-count}.
26858 @item -p @var{thread-id}
26859 Restrict the breakpoint to the specified @var{thread-id}.
26862 @subsubheading Result
26864 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26865 resulting breakpoint.
26867 Note: this format is open to change.
26868 @c An out-of-band breakpoint instead of part of the result?
26870 @subsubheading @value{GDBN} Command
26872 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26873 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26875 @subsubheading Example
26880 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26881 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26884 -break-insert -t foo
26885 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26886 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26890 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26891 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26892 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26893 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26894 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26895 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26896 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26897 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26898 addr="0x0001072c", func="main",file="recursive2.c",
26899 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26901 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26902 addr="0x00010774",func="foo",file="recursive2.c",
26903 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26906 @c -break-insert -r foo.*
26907 @c ~int foo(int, int);
26908 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26909 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26914 @subheading The @code{-dprintf-insert} Command
26915 @findex -dprintf-insert
26917 @subsubheading Synopsis
26920 -dprintf-insert [ -t ] [ -f ] [ -d ]
26921 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26922 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26927 If supplied, @var{location} may be specified the same way as for
26928 the @code{-break-insert} command. @xref{-break-insert}.
26930 The possible optional parameters of this command are:
26934 Insert a temporary breakpoint.
26936 If @var{location} cannot be parsed (for example, if it
26937 refers to unknown files or functions), create a pending
26938 breakpoint. Without this flag, @value{GDBN} will report
26939 an error, and won't create a breakpoint, if @var{location}
26942 Create a disabled breakpoint.
26943 @item -c @var{condition}
26944 Make the breakpoint conditional on @var{condition}.
26945 @item -i @var{ignore-count}
26946 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26947 to @var{ignore-count}.
26948 @item -p @var{thread-id}
26949 Restrict the breakpoint to the specified @var{thread-id}.
26952 @subsubheading Result
26954 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26955 resulting breakpoint.
26957 @c An out-of-band breakpoint instead of part of the result?
26959 @subsubheading @value{GDBN} Command
26961 The corresponding @value{GDBN} command is @samp{dprintf}.
26963 @subsubheading Example
26967 4-dprintf-insert foo "At foo entry\n"
26968 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26969 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26970 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26971 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26972 original-location="foo"@}
26974 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26975 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26976 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26977 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26978 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26979 original-location="mi-dprintf.c:26"@}
26983 @subheading The @code{-break-list} Command
26984 @findex -break-list
26986 @subsubheading Synopsis
26992 Displays the list of inserted breakpoints, showing the following fields:
26996 number of the breakpoint
26998 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27000 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27003 is the breakpoint enabled or no: @samp{y} or @samp{n}
27005 memory location at which the breakpoint is set
27007 logical location of the breakpoint, expressed by function name, file
27009 @item Thread-groups
27010 list of thread groups to which this breakpoint applies
27012 number of times the breakpoint has been hit
27015 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27016 @code{body} field is an empty list.
27018 @subsubheading @value{GDBN} Command
27020 The corresponding @value{GDBN} command is @samp{info break}.
27022 @subsubheading Example
27027 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27028 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27029 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27030 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27031 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27032 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27033 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27034 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27035 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27037 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27038 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27039 line="13",thread-groups=["i1"],times="0"@}]@}
27043 Here's an example of the result when there are no breakpoints:
27048 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27049 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27050 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27051 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27052 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27053 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27054 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27059 @subheading The @code{-break-passcount} Command
27060 @findex -break-passcount
27062 @subsubheading Synopsis
27065 -break-passcount @var{tracepoint-number} @var{passcount}
27068 Set the passcount for tracepoint @var{tracepoint-number} to
27069 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27070 is not a tracepoint, error is emitted. This corresponds to CLI
27071 command @samp{passcount}.
27073 @subheading The @code{-break-watch} Command
27074 @findex -break-watch
27076 @subsubheading Synopsis
27079 -break-watch [ -a | -r ]
27082 Create a watchpoint. With the @samp{-a} option it will create an
27083 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27084 read from or on a write to the memory location. With the @samp{-r}
27085 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27086 trigger only when the memory location is accessed for reading. Without
27087 either of the options, the watchpoint created is a regular watchpoint,
27088 i.e., it will trigger when the memory location is accessed for writing.
27089 @xref{Set Watchpoints, , Setting Watchpoints}.
27091 Note that @samp{-break-list} will report a single list of watchpoints and
27092 breakpoints inserted.
27094 @subsubheading @value{GDBN} Command
27096 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27099 @subsubheading Example
27101 Setting a watchpoint on a variable in the @code{main} function:
27106 ^done,wpt=@{number="2",exp="x"@}
27111 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27112 value=@{old="-268439212",new="55"@},
27113 frame=@{func="main",args=[],file="recursive2.c",
27114 fullname="/home/foo/bar/recursive2.c",line="5"@}
27118 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27119 the program execution twice: first for the variable changing value, then
27120 for the watchpoint going out of scope.
27125 ^done,wpt=@{number="5",exp="C"@}
27130 *stopped,reason="watchpoint-trigger",
27131 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27132 frame=@{func="callee4",args=[],
27133 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27134 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27139 *stopped,reason="watchpoint-scope",wpnum="5",
27140 frame=@{func="callee3",args=[@{name="strarg",
27141 value="0x11940 \"A string argument.\""@}],
27142 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27143 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27147 Listing breakpoints and watchpoints, at different points in the program
27148 execution. Note that once the watchpoint goes out of scope, it is
27154 ^done,wpt=@{number="2",exp="C"@}
27157 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27158 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27159 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27160 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27161 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27162 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27163 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27164 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27165 addr="0x00010734",func="callee4",
27166 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27167 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27169 bkpt=@{number="2",type="watchpoint",disp="keep",
27170 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27175 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27176 value=@{old="-276895068",new="3"@},
27177 frame=@{func="callee4",args=[],
27178 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27179 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27182 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27183 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27184 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27185 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27186 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27187 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27188 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27189 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27190 addr="0x00010734",func="callee4",
27191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27192 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27194 bkpt=@{number="2",type="watchpoint",disp="keep",
27195 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27199 ^done,reason="watchpoint-scope",wpnum="2",
27200 frame=@{func="callee3",args=[@{name="strarg",
27201 value="0x11940 \"A string argument.\""@}],
27202 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27203 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27206 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27207 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27208 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27209 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27210 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27211 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27212 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27213 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27214 addr="0x00010734",func="callee4",
27215 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27216 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27217 thread-groups=["i1"],times="1"@}]@}
27222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27223 @node GDB/MI Catchpoint Commands
27224 @section @sc{gdb/mi} Catchpoint Commands
27226 This section documents @sc{gdb/mi} commands for manipulating
27230 * Shared Library GDB/MI Catchpoint Commands::
27231 * Ada Exception GDB/MI Catchpoint Commands::
27234 @node Shared Library GDB/MI Catchpoint Commands
27235 @subsection Shared Library @sc{gdb/mi} Catchpoints
27237 @subheading The @code{-catch-load} Command
27238 @findex -catch-load
27240 @subsubheading Synopsis
27243 -catch-load [ -t ] [ -d ] @var{regexp}
27246 Add a catchpoint for library load events. If the @samp{-t} option is used,
27247 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27248 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27249 in a disabled state. The @samp{regexp} argument is a regular
27250 expression used to match the name of the loaded library.
27253 @subsubheading @value{GDBN} Command
27255 The corresponding @value{GDBN} command is @samp{catch load}.
27257 @subsubheading Example
27260 -catch-load -t foo.so
27261 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27262 what="load of library matching foo.so",catch-type="load",times="0"@}
27267 @subheading The @code{-catch-unload} Command
27268 @findex -catch-unload
27270 @subsubheading Synopsis
27273 -catch-unload [ -t ] [ -d ] @var{regexp}
27276 Add a catchpoint for library unload events. If the @samp{-t} option is
27277 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27278 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27279 created in a disabled state. The @samp{regexp} argument is a regular
27280 expression used to match the name of the unloaded library.
27282 @subsubheading @value{GDBN} Command
27284 The corresponding @value{GDBN} command is @samp{catch unload}.
27286 @subsubheading Example
27289 -catch-unload -d bar.so
27290 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27291 what="load of library matching bar.so",catch-type="unload",times="0"@}
27295 @node Ada Exception GDB/MI Catchpoint Commands
27296 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27298 The following @sc{gdb/mi} commands can be used to create catchpoints
27299 that stop the execution when Ada exceptions are being raised.
27301 @subheading The @code{-catch-assert} Command
27302 @findex -catch-assert
27304 @subsubheading Synopsis
27307 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27310 Add a catchpoint for failed Ada assertions.
27312 The possible optional parameters for this command are:
27315 @item -c @var{condition}
27316 Make the catchpoint conditional on @var{condition}.
27318 Create a disabled catchpoint.
27320 Create a temporary catchpoint.
27323 @subsubheading @value{GDBN} Command
27325 The corresponding @value{GDBN} command is @samp{catch assert}.
27327 @subsubheading Example
27331 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27332 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27333 thread-groups=["i1"],times="0",
27334 original-location="__gnat_debug_raise_assert_failure"@}
27338 @subheading The @code{-catch-exception} Command
27339 @findex -catch-exception
27341 @subsubheading Synopsis
27344 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27348 Add a catchpoint stopping when Ada exceptions are raised.
27349 By default, the command stops the program when any Ada exception
27350 gets raised. But it is also possible, by using some of the
27351 optional parameters described below, to create more selective
27354 The possible optional parameters for this command are:
27357 @item -c @var{condition}
27358 Make the catchpoint conditional on @var{condition}.
27360 Create a disabled catchpoint.
27361 @item -e @var{exception-name}
27362 Only stop when @var{exception-name} is raised. This option cannot
27363 be used combined with @samp{-u}.
27365 Create a temporary catchpoint.
27367 Stop only when an unhandled exception gets raised. This option
27368 cannot be used combined with @samp{-e}.
27371 @subsubheading @value{GDBN} Command
27373 The corresponding @value{GDBN} commands are @samp{catch exception}
27374 and @samp{catch exception unhandled}.
27376 @subsubheading Example
27379 -catch-exception -e Program_Error
27380 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27381 enabled="y",addr="0x0000000000404874",
27382 what="`Program_Error' Ada exception", thread-groups=["i1"],
27383 times="0",original-location="__gnat_debug_raise_exception"@}
27387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27388 @node GDB/MI Program Context
27389 @section @sc{gdb/mi} Program Context
27391 @subheading The @code{-exec-arguments} Command
27392 @findex -exec-arguments
27395 @subsubheading Synopsis
27398 -exec-arguments @var{args}
27401 Set the inferior program arguments, to be used in the next
27404 @subsubheading @value{GDBN} Command
27406 The corresponding @value{GDBN} command is @samp{set args}.
27408 @subsubheading Example
27412 -exec-arguments -v word
27419 @subheading The @code{-exec-show-arguments} Command
27420 @findex -exec-show-arguments
27422 @subsubheading Synopsis
27425 -exec-show-arguments
27428 Print the arguments of the program.
27430 @subsubheading @value{GDBN} Command
27432 The corresponding @value{GDBN} command is @samp{show args}.
27434 @subsubheading Example
27439 @subheading The @code{-environment-cd} Command
27440 @findex -environment-cd
27442 @subsubheading Synopsis
27445 -environment-cd @var{pathdir}
27448 Set @value{GDBN}'s working directory.
27450 @subsubheading @value{GDBN} Command
27452 The corresponding @value{GDBN} command is @samp{cd}.
27454 @subsubheading Example
27458 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27464 @subheading The @code{-environment-directory} Command
27465 @findex -environment-directory
27467 @subsubheading Synopsis
27470 -environment-directory [ -r ] [ @var{pathdir} ]+
27473 Add directories @var{pathdir} to beginning of search path for source files.
27474 If the @samp{-r} option is used, the search path is reset to the default
27475 search path. If directories @var{pathdir} are supplied in addition to the
27476 @samp{-r} option, the search path is first reset and then addition
27478 Multiple directories may be specified, separated by blanks. Specifying
27479 multiple directories in a single command
27480 results in the directories added to the beginning of the
27481 search path in the same order they were presented in the command.
27482 If blanks are needed as
27483 part of a directory name, double-quotes should be used around
27484 the name. In the command output, the path will show up separated
27485 by the system directory-separator character. The directory-separator
27486 character must not be used
27487 in any directory name.
27488 If no directories are specified, the current search path is displayed.
27490 @subsubheading @value{GDBN} Command
27492 The corresponding @value{GDBN} command is @samp{dir}.
27494 @subsubheading Example
27498 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27499 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27501 -environment-directory ""
27502 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27504 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27505 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27507 -environment-directory -r
27508 ^done,source-path="$cdir:$cwd"
27513 @subheading The @code{-environment-path} Command
27514 @findex -environment-path
27516 @subsubheading Synopsis
27519 -environment-path [ -r ] [ @var{pathdir} ]+
27522 Add directories @var{pathdir} to beginning of search path for object files.
27523 If the @samp{-r} option is used, the search path is reset to the original
27524 search path that existed at gdb start-up. If directories @var{pathdir} are
27525 supplied in addition to the
27526 @samp{-r} option, the search path is first reset and then addition
27528 Multiple directories may be specified, separated by blanks. Specifying
27529 multiple directories in a single command
27530 results in the directories added to the beginning of the
27531 search path in the same order they were presented in the command.
27532 If blanks are needed as
27533 part of a directory name, double-quotes should be used around
27534 the name. In the command output, the path will show up separated
27535 by the system directory-separator character. The directory-separator
27536 character must not be used
27537 in any directory name.
27538 If no directories are specified, the current path is displayed.
27541 @subsubheading @value{GDBN} Command
27543 The corresponding @value{GDBN} command is @samp{path}.
27545 @subsubheading Example
27550 ^done,path="/usr/bin"
27552 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27553 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27555 -environment-path -r /usr/local/bin
27556 ^done,path="/usr/local/bin:/usr/bin"
27561 @subheading The @code{-environment-pwd} Command
27562 @findex -environment-pwd
27564 @subsubheading Synopsis
27570 Show the current working directory.
27572 @subsubheading @value{GDBN} Command
27574 The corresponding @value{GDBN} command is @samp{pwd}.
27576 @subsubheading Example
27581 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27586 @node GDB/MI Thread Commands
27587 @section @sc{gdb/mi} Thread Commands
27590 @subheading The @code{-thread-info} Command
27591 @findex -thread-info
27593 @subsubheading Synopsis
27596 -thread-info [ @var{thread-id} ]
27599 Reports information about either a specific thread, if
27600 the @var{thread-id} parameter is present, or about all
27601 threads. When printing information about all threads,
27602 also reports the current thread.
27604 @subsubheading @value{GDBN} Command
27606 The @samp{info thread} command prints the same information
27609 @subsubheading Result
27611 The result is a list of threads. The following attributes are
27612 defined for a given thread:
27616 This field exists only for the current thread. It has the value @samp{*}.
27619 The identifier that @value{GDBN} uses to refer to the thread.
27622 The identifier that the target uses to refer to the thread.
27625 Extra information about the thread, in a target-specific format. This
27629 The name of the thread. If the user specified a name using the
27630 @code{thread name} command, then this name is given. Otherwise, if
27631 @value{GDBN} can extract the thread name from the target, then that
27632 name is given. If @value{GDBN} cannot find the thread name, then this
27636 The stack frame currently executing in the thread.
27639 The thread's state. The @samp{state} field may have the following
27644 The thread is stopped. Frame information is available for stopped
27648 The thread is running. There's no frame information for running
27654 If @value{GDBN} can find the CPU core on which this thread is running,
27655 then this field is the core identifier. This field is optional.
27659 @subsubheading Example
27664 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27665 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27666 args=[]@},state="running"@},
27667 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27668 frame=@{level="0",addr="0x0804891f",func="foo",
27669 args=[@{name="i",value="10"@}],
27670 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27671 state="running"@}],
27672 current-thread-id="1"
27676 @subheading The @code{-thread-list-ids} Command
27677 @findex -thread-list-ids
27679 @subsubheading Synopsis
27685 Produces a list of the currently known @value{GDBN} thread ids. At the
27686 end of the list it also prints the total number of such threads.
27688 This command is retained for historical reasons, the
27689 @code{-thread-info} command should be used instead.
27691 @subsubheading @value{GDBN} Command
27693 Part of @samp{info threads} supplies the same information.
27695 @subsubheading Example
27700 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27701 current-thread-id="1",number-of-threads="3"
27706 @subheading The @code{-thread-select} Command
27707 @findex -thread-select
27709 @subsubheading Synopsis
27712 -thread-select @var{threadnum}
27715 Make @var{threadnum} the current thread. It prints the number of the new
27716 current thread, and the topmost frame for that thread.
27718 This command is deprecated in favor of explicitly using the
27719 @samp{--thread} option to each command.
27721 @subsubheading @value{GDBN} Command
27723 The corresponding @value{GDBN} command is @samp{thread}.
27725 @subsubheading Example
27732 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27733 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27737 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27738 number-of-threads="3"
27741 ^done,new-thread-id="3",
27742 frame=@{level="0",func="vprintf",
27743 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27744 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27749 @node GDB/MI Ada Tasking Commands
27750 @section @sc{gdb/mi} Ada Tasking Commands
27752 @subheading The @code{-ada-task-info} Command
27753 @findex -ada-task-info
27755 @subsubheading Synopsis
27758 -ada-task-info [ @var{task-id} ]
27761 Reports information about either a specific Ada task, if the
27762 @var{task-id} parameter is present, or about all Ada tasks.
27764 @subsubheading @value{GDBN} Command
27766 The @samp{info tasks} command prints the same information
27767 about all Ada tasks (@pxref{Ada Tasks}).
27769 @subsubheading Result
27771 The result is a table of Ada tasks. The following columns are
27772 defined for each Ada task:
27776 This field exists only for the current thread. It has the value @samp{*}.
27779 The identifier that @value{GDBN} uses to refer to the Ada task.
27782 The identifier that the target uses to refer to the Ada task.
27785 The identifier of the thread corresponding to the Ada task.
27787 This field should always exist, as Ada tasks are always implemented
27788 on top of a thread. But if @value{GDBN} cannot find this corresponding
27789 thread for any reason, the field is omitted.
27792 This field exists only when the task was created by another task.
27793 In this case, it provides the ID of the parent task.
27796 The base priority of the task.
27799 The current state of the task. For a detailed description of the
27800 possible states, see @ref{Ada Tasks}.
27803 The name of the task.
27807 @subsubheading Example
27811 ^done,tasks=@{nr_rows="3",nr_cols="8",
27812 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27813 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27814 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27815 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27816 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27817 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27818 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27819 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27820 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27821 state="Child Termination Wait",name="main_task"@}]@}
27825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27826 @node GDB/MI Program Execution
27827 @section @sc{gdb/mi} Program Execution
27829 These are the asynchronous commands which generate the out-of-band
27830 record @samp{*stopped}. Currently @value{GDBN} only really executes
27831 asynchronously with remote targets and this interaction is mimicked in
27834 @subheading The @code{-exec-continue} Command
27835 @findex -exec-continue
27837 @subsubheading Synopsis
27840 -exec-continue [--reverse] [--all|--thread-group N]
27843 Resumes the execution of the inferior program, which will continue
27844 to execute until it reaches a debugger stop event. If the
27845 @samp{--reverse} option is specified, execution resumes in reverse until
27846 it reaches a stop event. Stop events may include
27849 breakpoints or watchpoints
27851 signals or exceptions
27853 the end of the process (or its beginning under @samp{--reverse})
27855 the end or beginning of a replay log if one is being used.
27857 In all-stop mode (@pxref{All-Stop
27858 Mode}), may resume only one thread, or all threads, depending on the
27859 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27860 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27861 ignored in all-stop mode. If the @samp{--thread-group} options is
27862 specified, then all threads in that thread group are resumed.
27864 @subsubheading @value{GDBN} Command
27866 The corresponding @value{GDBN} corresponding is @samp{continue}.
27868 @subsubheading Example
27875 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27876 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27882 @subheading The @code{-exec-finish} Command
27883 @findex -exec-finish
27885 @subsubheading Synopsis
27888 -exec-finish [--reverse]
27891 Resumes the execution of the inferior program until the current
27892 function is exited. Displays the results returned by the function.
27893 If the @samp{--reverse} option is specified, resumes the reverse
27894 execution of the inferior program until the point where current
27895 function was called.
27897 @subsubheading @value{GDBN} Command
27899 The corresponding @value{GDBN} command is @samp{finish}.
27901 @subsubheading Example
27903 Function returning @code{void}.
27910 *stopped,reason="function-finished",frame=@{func="main",args=[],
27911 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27915 Function returning other than @code{void}. The name of the internal
27916 @value{GDBN} variable storing the result is printed, together with the
27923 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27924 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27925 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27926 gdb-result-var="$1",return-value="0"
27931 @subheading The @code{-exec-interrupt} Command
27932 @findex -exec-interrupt
27934 @subsubheading Synopsis
27937 -exec-interrupt [--all|--thread-group N]
27940 Interrupts the background execution of the target. Note how the token
27941 associated with the stop message is the one for the execution command
27942 that has been interrupted. The token for the interrupt itself only
27943 appears in the @samp{^done} output. If the user is trying to
27944 interrupt a non-running program, an error message will be printed.
27946 Note that when asynchronous execution is enabled, this command is
27947 asynchronous just like other execution commands. That is, first the
27948 @samp{^done} response will be printed, and the target stop will be
27949 reported after that using the @samp{*stopped} notification.
27951 In non-stop mode, only the context thread is interrupted by default.
27952 All threads (in all inferiors) will be interrupted if the
27953 @samp{--all} option is specified. If the @samp{--thread-group}
27954 option is specified, all threads in that group will be interrupted.
27956 @subsubheading @value{GDBN} Command
27958 The corresponding @value{GDBN} command is @samp{interrupt}.
27960 @subsubheading Example
27971 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27972 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27973 fullname="/home/foo/bar/try.c",line="13"@}
27978 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27982 @subheading The @code{-exec-jump} Command
27985 @subsubheading Synopsis
27988 -exec-jump @var{location}
27991 Resumes execution of the inferior program at the location specified by
27992 parameter. @xref{Specify Location}, for a description of the
27993 different forms of @var{location}.
27995 @subsubheading @value{GDBN} Command
27997 The corresponding @value{GDBN} command is @samp{jump}.
27999 @subsubheading Example
28002 -exec-jump foo.c:10
28003 *running,thread-id="all"
28008 @subheading The @code{-exec-next} Command
28011 @subsubheading Synopsis
28014 -exec-next [--reverse]
28017 Resumes execution of the inferior program, stopping when the beginning
28018 of the next source line is reached.
28020 If the @samp{--reverse} option is specified, resumes reverse execution
28021 of the inferior program, stopping at the beginning of the previous
28022 source line. If you issue this command on the first line of a
28023 function, it will take you back to the caller of that function, to the
28024 source line where the function was called.
28027 @subsubheading @value{GDBN} Command
28029 The corresponding @value{GDBN} command is @samp{next}.
28031 @subsubheading Example
28037 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28042 @subheading The @code{-exec-next-instruction} Command
28043 @findex -exec-next-instruction
28045 @subsubheading Synopsis
28048 -exec-next-instruction [--reverse]
28051 Executes one machine instruction. If the instruction is a function
28052 call, continues until the function returns. If the program stops at an
28053 instruction in the middle of a source line, the address will be
28056 If the @samp{--reverse} option is specified, resumes reverse execution
28057 of the inferior program, stopping at the previous instruction. If the
28058 previously executed instruction was a return from another function,
28059 it will continue to execute in reverse until the call to that function
28060 (from the current stack frame) is reached.
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} command is @samp{nexti}.
28066 @subsubheading Example
28070 -exec-next-instruction
28074 *stopped,reason="end-stepping-range",
28075 addr="0x000100d4",line="5",file="hello.c"
28080 @subheading The @code{-exec-return} Command
28081 @findex -exec-return
28083 @subsubheading Synopsis
28089 Makes current function return immediately. Doesn't execute the inferior.
28090 Displays the new current frame.
28092 @subsubheading @value{GDBN} Command
28094 The corresponding @value{GDBN} command is @samp{return}.
28096 @subsubheading Example
28100 200-break-insert callee4
28101 200^done,bkpt=@{number="1",addr="0x00010734",
28102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28107 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28108 frame=@{func="callee4",args=[],
28109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28110 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28116 111^done,frame=@{level="0",func="callee3",
28117 args=[@{name="strarg",
28118 value="0x11940 \"A string argument.\""@}],
28119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28120 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28125 @subheading The @code{-exec-run} Command
28128 @subsubheading Synopsis
28131 -exec-run [ --all | --thread-group N ] [ --start ]
28134 Starts execution of the inferior from the beginning. The inferior
28135 executes until either a breakpoint is encountered or the program
28136 exits. In the latter case the output will include an exit code, if
28137 the program has exited exceptionally.
28139 When neither the @samp{--all} nor the @samp{--thread-group} option
28140 is specified, the current inferior is started. If the
28141 @samp{--thread-group} option is specified, it should refer to a thread
28142 group of type @samp{process}, and that thread group will be started.
28143 If the @samp{--all} option is specified, then all inferiors will be started.
28145 Using the @samp{--start} option instructs the debugger to stop
28146 the execution at the start of the inferior's main subprogram,
28147 following the same behavior as the @code{start} command
28148 (@pxref{Starting}).
28150 @subsubheading @value{GDBN} Command
28152 The corresponding @value{GDBN} command is @samp{run}.
28154 @subsubheading Examples
28159 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28164 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28165 frame=@{func="main",args=[],file="recursive2.c",
28166 fullname="/home/foo/bar/recursive2.c",line="4"@}
28171 Program exited normally:
28179 *stopped,reason="exited-normally"
28184 Program exited exceptionally:
28192 *stopped,reason="exited",exit-code="01"
28196 Another way the program can terminate is if it receives a signal such as
28197 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28201 *stopped,reason="exited-signalled",signal-name="SIGINT",
28202 signal-meaning="Interrupt"
28206 @c @subheading -exec-signal
28209 @subheading The @code{-exec-step} Command
28212 @subsubheading Synopsis
28215 -exec-step [--reverse]
28218 Resumes execution of the inferior program, stopping when the beginning
28219 of the next source line is reached, if the next source line is not a
28220 function call. If it is, stop at the first instruction of the called
28221 function. If the @samp{--reverse} option is specified, resumes reverse
28222 execution of the inferior program, stopping at the beginning of the
28223 previously executed source line.
28225 @subsubheading @value{GDBN} Command
28227 The corresponding @value{GDBN} command is @samp{step}.
28229 @subsubheading Example
28231 Stepping into a function:
28237 *stopped,reason="end-stepping-range",
28238 frame=@{func="foo",args=[@{name="a",value="10"@},
28239 @{name="b",value="0"@}],file="recursive2.c",
28240 fullname="/home/foo/bar/recursive2.c",line="11"@}
28250 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28255 @subheading The @code{-exec-step-instruction} Command
28256 @findex -exec-step-instruction
28258 @subsubheading Synopsis
28261 -exec-step-instruction [--reverse]
28264 Resumes the inferior which executes one machine instruction. If the
28265 @samp{--reverse} option is specified, resumes reverse execution of the
28266 inferior program, stopping at the previously executed instruction.
28267 The output, once @value{GDBN} has stopped, will vary depending on
28268 whether we have stopped in the middle of a source line or not. In the
28269 former case, the address at which the program stopped will be printed
28272 @subsubheading @value{GDBN} Command
28274 The corresponding @value{GDBN} command is @samp{stepi}.
28276 @subsubheading Example
28280 -exec-step-instruction
28284 *stopped,reason="end-stepping-range",
28285 frame=@{func="foo",args=[],file="try.c",
28286 fullname="/home/foo/bar/try.c",line="10"@}
28288 -exec-step-instruction
28292 *stopped,reason="end-stepping-range",
28293 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28294 fullname="/home/foo/bar/try.c",line="10"@}
28299 @subheading The @code{-exec-until} Command
28300 @findex -exec-until
28302 @subsubheading Synopsis
28305 -exec-until [ @var{location} ]
28308 Executes the inferior until the @var{location} specified in the
28309 argument is reached. If there is no argument, the inferior executes
28310 until a source line greater than the current one is reached. The
28311 reason for stopping in this case will be @samp{location-reached}.
28313 @subsubheading @value{GDBN} Command
28315 The corresponding @value{GDBN} command is @samp{until}.
28317 @subsubheading Example
28321 -exec-until recursive2.c:6
28325 *stopped,reason="location-reached",frame=@{func="main",args=[],
28326 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28331 @subheading -file-clear
28332 Is this going away????
28335 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28336 @node GDB/MI Stack Manipulation
28337 @section @sc{gdb/mi} Stack Manipulation Commands
28339 @subheading The @code{-enable-frame-filters} Command
28340 @findex -enable-frame-filters
28343 -enable-frame-filters
28346 @value{GDBN} allows Python-based frame filters to affect the output of
28347 the MI commands relating to stack traces. As there is no way to
28348 implement this in a fully backward-compatible way, a front end must
28349 request that this functionality be enabled.
28351 Once enabled, this feature cannot be disabled.
28353 Note that if Python support has not been compiled into @value{GDBN},
28354 this command will still succeed (and do nothing).
28356 @subheading The @code{-stack-info-frame} Command
28357 @findex -stack-info-frame
28359 @subsubheading Synopsis
28365 Get info on the selected frame.
28367 @subsubheading @value{GDBN} Command
28369 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28370 (without arguments).
28372 @subsubheading Example
28377 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28379 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28383 @subheading The @code{-stack-info-depth} Command
28384 @findex -stack-info-depth
28386 @subsubheading Synopsis
28389 -stack-info-depth [ @var{max-depth} ]
28392 Return the depth of the stack. If the integer argument @var{max-depth}
28393 is specified, do not count beyond @var{max-depth} frames.
28395 @subsubheading @value{GDBN} Command
28397 There's no equivalent @value{GDBN} command.
28399 @subsubheading Example
28401 For a stack with frame levels 0 through 11:
28408 -stack-info-depth 4
28411 -stack-info-depth 12
28414 -stack-info-depth 11
28417 -stack-info-depth 13
28422 @anchor{-stack-list-arguments}
28423 @subheading The @code{-stack-list-arguments} Command
28424 @findex -stack-list-arguments
28426 @subsubheading Synopsis
28429 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28430 [ @var{low-frame} @var{high-frame} ]
28433 Display a list of the arguments for the frames between @var{low-frame}
28434 and @var{high-frame} (inclusive). If @var{low-frame} and
28435 @var{high-frame} are not provided, list the arguments for the whole
28436 call stack. If the two arguments are equal, show the single frame
28437 at the corresponding level. It is an error if @var{low-frame} is
28438 larger than the actual number of frames. On the other hand,
28439 @var{high-frame} may be larger than the actual number of frames, in
28440 which case only existing frames will be returned.
28442 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28443 the variables; if it is 1 or @code{--all-values}, print also their
28444 values; and if it is 2 or @code{--simple-values}, print the name,
28445 type and value for simple data types, and the name and type for arrays,
28446 structures and unions. If the option @code{--no-frame-filters} is
28447 supplied, then Python frame filters will not be executed.
28449 If the @code{--skip-unavailable} option is specified, arguments that
28450 are not available are not listed. Partially available arguments
28451 are still displayed, however.
28453 Use of this command to obtain arguments in a single frame is
28454 deprecated in favor of the @samp{-stack-list-variables} command.
28456 @subsubheading @value{GDBN} Command
28458 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28459 @samp{gdb_get_args} command which partially overlaps with the
28460 functionality of @samp{-stack-list-arguments}.
28462 @subsubheading Example
28469 frame=@{level="0",addr="0x00010734",func="callee4",
28470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28471 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28472 frame=@{level="1",addr="0x0001076c",func="callee3",
28473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28474 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28475 frame=@{level="2",addr="0x0001078c",func="callee2",
28476 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28477 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28478 frame=@{level="3",addr="0x000107b4",func="callee1",
28479 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28480 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28481 frame=@{level="4",addr="0x000107e0",func="main",
28482 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28483 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28485 -stack-list-arguments 0
28488 frame=@{level="0",args=[]@},
28489 frame=@{level="1",args=[name="strarg"]@},
28490 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28491 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28492 frame=@{level="4",args=[]@}]
28494 -stack-list-arguments 1
28497 frame=@{level="0",args=[]@},
28499 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28500 frame=@{level="2",args=[
28501 @{name="intarg",value="2"@},
28502 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28503 @{frame=@{level="3",args=[
28504 @{name="intarg",value="2"@},
28505 @{name="strarg",value="0x11940 \"A string argument.\""@},
28506 @{name="fltarg",value="3.5"@}]@},
28507 frame=@{level="4",args=[]@}]
28509 -stack-list-arguments 0 2 2
28510 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28512 -stack-list-arguments 1 2 2
28513 ^done,stack-args=[frame=@{level="2",
28514 args=[@{name="intarg",value="2"@},
28515 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28519 @c @subheading -stack-list-exception-handlers
28522 @anchor{-stack-list-frames}
28523 @subheading The @code{-stack-list-frames} Command
28524 @findex -stack-list-frames
28526 @subsubheading Synopsis
28529 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28532 List the frames currently on the stack. For each frame it displays the
28537 The frame number, 0 being the topmost frame, i.e., the innermost function.
28539 The @code{$pc} value for that frame.
28543 File name of the source file where the function lives.
28544 @item @var{fullname}
28545 The full file name of the source file where the function lives.
28547 Line number corresponding to the @code{$pc}.
28549 The shared library where this function is defined. This is only given
28550 if the frame's function is not known.
28553 If invoked without arguments, this command prints a backtrace for the
28554 whole stack. If given two integer arguments, it shows the frames whose
28555 levels are between the two arguments (inclusive). If the two arguments
28556 are equal, it shows the single frame at the corresponding level. It is
28557 an error if @var{low-frame} is larger than the actual number of
28558 frames. On the other hand, @var{high-frame} may be larger than the
28559 actual number of frames, in which case only existing frames will be
28560 returned. If the option @code{--no-frame-filters} is supplied, then
28561 Python frame filters will not be executed.
28563 @subsubheading @value{GDBN} Command
28565 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28567 @subsubheading Example
28569 Full stack backtrace:
28575 [frame=@{level="0",addr="0x0001076c",func="foo",
28576 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28577 frame=@{level="1",addr="0x000107a4",func="foo",
28578 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28579 frame=@{level="2",addr="0x000107a4",func="foo",
28580 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28581 frame=@{level="3",addr="0x000107a4",func="foo",
28582 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28583 frame=@{level="4",addr="0x000107a4",func="foo",
28584 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28585 frame=@{level="5",addr="0x000107a4",func="foo",
28586 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28587 frame=@{level="6",addr="0x000107a4",func="foo",
28588 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28589 frame=@{level="7",addr="0x000107a4",func="foo",
28590 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28591 frame=@{level="8",addr="0x000107a4",func="foo",
28592 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28593 frame=@{level="9",addr="0x000107a4",func="foo",
28594 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28595 frame=@{level="10",addr="0x000107a4",func="foo",
28596 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28597 frame=@{level="11",addr="0x00010738",func="main",
28598 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28602 Show frames between @var{low_frame} and @var{high_frame}:
28606 -stack-list-frames 3 5
28608 [frame=@{level="3",addr="0x000107a4",func="foo",
28609 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28610 frame=@{level="4",addr="0x000107a4",func="foo",
28611 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28612 frame=@{level="5",addr="0x000107a4",func="foo",
28613 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28617 Show a single frame:
28621 -stack-list-frames 3 3
28623 [frame=@{level="3",addr="0x000107a4",func="foo",
28624 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28629 @subheading The @code{-stack-list-locals} Command
28630 @findex -stack-list-locals
28631 @anchor{-stack-list-locals}
28633 @subsubheading Synopsis
28636 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28639 Display the local variable names for the selected frame. If
28640 @var{print-values} is 0 or @code{--no-values}, print only the names of
28641 the variables; if it is 1 or @code{--all-values}, print also their
28642 values; and if it is 2 or @code{--simple-values}, print the name,
28643 type and value for simple data types, and the name and type for arrays,
28644 structures and unions. In this last case, a frontend can immediately
28645 display the value of simple data types and create variable objects for
28646 other data types when the user wishes to explore their values in
28647 more detail. If the option @code{--no-frame-filters} is supplied, then
28648 Python frame filters will not be executed.
28650 If the @code{--skip-unavailable} option is specified, local variables
28651 that are not available are not listed. Partially available local
28652 variables are still displayed, however.
28654 This command is deprecated in favor of the
28655 @samp{-stack-list-variables} command.
28657 @subsubheading @value{GDBN} Command
28659 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28661 @subsubheading Example
28665 -stack-list-locals 0
28666 ^done,locals=[name="A",name="B",name="C"]
28668 -stack-list-locals --all-values
28669 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28670 @{name="C",value="@{1, 2, 3@}"@}]
28671 -stack-list-locals --simple-values
28672 ^done,locals=[@{name="A",type="int",value="1"@},
28673 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28677 @anchor{-stack-list-variables}
28678 @subheading The @code{-stack-list-variables} Command
28679 @findex -stack-list-variables
28681 @subsubheading Synopsis
28684 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28687 Display the names of local variables and function arguments for the selected frame. If
28688 @var{print-values} is 0 or @code{--no-values}, print only the names of
28689 the variables; if it is 1 or @code{--all-values}, print also their
28690 values; and if it is 2 or @code{--simple-values}, print the name,
28691 type and value for simple data types, and the name and type for arrays,
28692 structures and unions. If the option @code{--no-frame-filters} is
28693 supplied, then Python frame filters will not be executed.
28695 If the @code{--skip-unavailable} option is specified, local variables
28696 and arguments that are not available are not listed. Partially
28697 available arguments and local variables are still displayed, however.
28699 @subsubheading Example
28703 -stack-list-variables --thread 1 --frame 0 --all-values
28704 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28709 @subheading The @code{-stack-select-frame} Command
28710 @findex -stack-select-frame
28712 @subsubheading Synopsis
28715 -stack-select-frame @var{framenum}
28718 Change the selected frame. Select a different frame @var{framenum} on
28721 This command in deprecated in favor of passing the @samp{--frame}
28722 option to every command.
28724 @subsubheading @value{GDBN} Command
28726 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28727 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28729 @subsubheading Example
28733 -stack-select-frame 2
28738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28739 @node GDB/MI Variable Objects
28740 @section @sc{gdb/mi} Variable Objects
28744 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28746 For the implementation of a variable debugger window (locals, watched
28747 expressions, etc.), we are proposing the adaptation of the existing code
28748 used by @code{Insight}.
28750 The two main reasons for that are:
28754 It has been proven in practice (it is already on its second generation).
28757 It will shorten development time (needless to say how important it is
28761 The original interface was designed to be used by Tcl code, so it was
28762 slightly changed so it could be used through @sc{gdb/mi}. This section
28763 describes the @sc{gdb/mi} operations that will be available and gives some
28764 hints about their use.
28766 @emph{Note}: In addition to the set of operations described here, we
28767 expect the @sc{gui} implementation of a variable window to require, at
28768 least, the following operations:
28771 @item @code{-gdb-show} @code{output-radix}
28772 @item @code{-stack-list-arguments}
28773 @item @code{-stack-list-locals}
28774 @item @code{-stack-select-frame}
28779 @subheading Introduction to Variable Objects
28781 @cindex variable objects in @sc{gdb/mi}
28783 Variable objects are "object-oriented" MI interface for examining and
28784 changing values of expressions. Unlike some other MI interfaces that
28785 work with expressions, variable objects are specifically designed for
28786 simple and efficient presentation in the frontend. A variable object
28787 is identified by string name. When a variable object is created, the
28788 frontend specifies the expression for that variable object. The
28789 expression can be a simple variable, or it can be an arbitrary complex
28790 expression, and can even involve CPU registers. After creating a
28791 variable object, the frontend can invoke other variable object
28792 operations---for example to obtain or change the value of a variable
28793 object, or to change display format.
28795 Variable objects have hierarchical tree structure. Any variable object
28796 that corresponds to a composite type, such as structure in C, has
28797 a number of child variable objects, for example corresponding to each
28798 element of a structure. A child variable object can itself have
28799 children, recursively. Recursion ends when we reach
28800 leaf variable objects, which always have built-in types. Child variable
28801 objects are created only by explicit request, so if a frontend
28802 is not interested in the children of a particular variable object, no
28803 child will be created.
28805 For a leaf variable object it is possible to obtain its value as a
28806 string, or set the value from a string. String value can be also
28807 obtained for a non-leaf variable object, but it's generally a string
28808 that only indicates the type of the object, and does not list its
28809 contents. Assignment to a non-leaf variable object is not allowed.
28811 A frontend does not need to read the values of all variable objects each time
28812 the program stops. Instead, MI provides an update command that lists all
28813 variable objects whose values has changed since the last update
28814 operation. This considerably reduces the amount of data that must
28815 be transferred to the frontend. As noted above, children variable
28816 objects are created on demand, and only leaf variable objects have a
28817 real value. As result, gdb will read target memory only for leaf
28818 variables that frontend has created.
28820 The automatic update is not always desirable. For example, a frontend
28821 might want to keep a value of some expression for future reference,
28822 and never update it. For another example, fetching memory is
28823 relatively slow for embedded targets, so a frontend might want
28824 to disable automatic update for the variables that are either not
28825 visible on the screen, or ``closed''. This is possible using so
28826 called ``frozen variable objects''. Such variable objects are never
28827 implicitly updated.
28829 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28830 fixed variable object, the expression is parsed when the variable
28831 object is created, including associating identifiers to specific
28832 variables. The meaning of expression never changes. For a floating
28833 variable object the values of variables whose names appear in the
28834 expressions are re-evaluated every time in the context of the current
28835 frame. Consider this example:
28840 struct work_state state;
28847 If a fixed variable object for the @code{state} variable is created in
28848 this function, and we enter the recursive call, the variable
28849 object will report the value of @code{state} in the top-level
28850 @code{do_work} invocation. On the other hand, a floating variable
28851 object will report the value of @code{state} in the current frame.
28853 If an expression specified when creating a fixed variable object
28854 refers to a local variable, the variable object becomes bound to the
28855 thread and frame in which the variable object is created. When such
28856 variable object is updated, @value{GDBN} makes sure that the
28857 thread/frame combination the variable object is bound to still exists,
28858 and re-evaluates the variable object in context of that thread/frame.
28860 The following is the complete set of @sc{gdb/mi} operations defined to
28861 access this functionality:
28863 @multitable @columnfractions .4 .6
28864 @item @strong{Operation}
28865 @tab @strong{Description}
28867 @item @code{-enable-pretty-printing}
28868 @tab enable Python-based pretty-printing
28869 @item @code{-var-create}
28870 @tab create a variable object
28871 @item @code{-var-delete}
28872 @tab delete the variable object and/or its children
28873 @item @code{-var-set-format}
28874 @tab set the display format of this variable
28875 @item @code{-var-show-format}
28876 @tab show the display format of this variable
28877 @item @code{-var-info-num-children}
28878 @tab tells how many children this object has
28879 @item @code{-var-list-children}
28880 @tab return a list of the object's children
28881 @item @code{-var-info-type}
28882 @tab show the type of this variable object
28883 @item @code{-var-info-expression}
28884 @tab print parent-relative expression that this variable object represents
28885 @item @code{-var-info-path-expression}
28886 @tab print full expression that this variable object represents
28887 @item @code{-var-show-attributes}
28888 @tab is this variable editable? does it exist here?
28889 @item @code{-var-evaluate-expression}
28890 @tab get the value of this variable
28891 @item @code{-var-assign}
28892 @tab set the value of this variable
28893 @item @code{-var-update}
28894 @tab update the variable and its children
28895 @item @code{-var-set-frozen}
28896 @tab set frozeness attribute
28897 @item @code{-var-set-update-range}
28898 @tab set range of children to display on update
28901 In the next subsection we describe each operation in detail and suggest
28902 how it can be used.
28904 @subheading Description And Use of Operations on Variable Objects
28906 @subheading The @code{-enable-pretty-printing} Command
28907 @findex -enable-pretty-printing
28910 -enable-pretty-printing
28913 @value{GDBN} allows Python-based visualizers to affect the output of the
28914 MI variable object commands. However, because there was no way to
28915 implement this in a fully backward-compatible way, a front end must
28916 request that this functionality be enabled.
28918 Once enabled, this feature cannot be disabled.
28920 Note that if Python support has not been compiled into @value{GDBN},
28921 this command will still succeed (and do nothing).
28923 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28924 may work differently in future versions of @value{GDBN}.
28926 @subheading The @code{-var-create} Command
28927 @findex -var-create
28929 @subsubheading Synopsis
28932 -var-create @{@var{name} | "-"@}
28933 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28936 This operation creates a variable object, which allows the monitoring of
28937 a variable, the result of an expression, a memory cell or a CPU
28940 The @var{name} parameter is the string by which the object can be
28941 referenced. It must be unique. If @samp{-} is specified, the varobj
28942 system will generate a string ``varNNNNNN'' automatically. It will be
28943 unique provided that one does not specify @var{name} of that format.
28944 The command fails if a duplicate name is found.
28946 The frame under which the expression should be evaluated can be
28947 specified by @var{frame-addr}. A @samp{*} indicates that the current
28948 frame should be used. A @samp{@@} indicates that a floating variable
28949 object must be created.
28951 @var{expression} is any expression valid on the current language set (must not
28952 begin with a @samp{*}), or one of the following:
28956 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28959 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28962 @samp{$@var{regname}} --- a CPU register name
28965 @cindex dynamic varobj
28966 A varobj's contents may be provided by a Python-based pretty-printer. In this
28967 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28968 have slightly different semantics in some cases. If the
28969 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28970 will never create a dynamic varobj. This ensures backward
28971 compatibility for existing clients.
28973 @subsubheading Result
28975 This operation returns attributes of the newly-created varobj. These
28980 The name of the varobj.
28983 The number of children of the varobj. This number is not necessarily
28984 reliable for a dynamic varobj. Instead, you must examine the
28985 @samp{has_more} attribute.
28988 The varobj's scalar value. For a varobj whose type is some sort of
28989 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28990 will not be interesting.
28993 The varobj's type. This is a string representation of the type, as
28994 would be printed by the @value{GDBN} CLI. If @samp{print object}
28995 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28996 @emph{actual} (derived) type of the object is shown rather than the
28997 @emph{declared} one.
29000 If a variable object is bound to a specific thread, then this is the
29001 thread's identifier.
29004 For a dynamic varobj, this indicates whether there appear to be any
29005 children available. For a non-dynamic varobj, this will be 0.
29008 This attribute will be present and have the value @samp{1} if the
29009 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29010 then this attribute will not be present.
29013 A dynamic varobj can supply a display hint to the front end. The
29014 value comes directly from the Python pretty-printer object's
29015 @code{display_hint} method. @xref{Pretty Printing API}.
29018 Typical output will look like this:
29021 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29022 has_more="@var{has_more}"
29026 @subheading The @code{-var-delete} Command
29027 @findex -var-delete
29029 @subsubheading Synopsis
29032 -var-delete [ -c ] @var{name}
29035 Deletes a previously created variable object and all of its children.
29036 With the @samp{-c} option, just deletes the children.
29038 Returns an error if the object @var{name} is not found.
29041 @subheading The @code{-var-set-format} Command
29042 @findex -var-set-format
29044 @subsubheading Synopsis
29047 -var-set-format @var{name} @var{format-spec}
29050 Sets the output format for the value of the object @var{name} to be
29053 @anchor{-var-set-format}
29054 The syntax for the @var{format-spec} is as follows:
29057 @var{format-spec} @expansion{}
29058 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29061 The natural format is the default format choosen automatically
29062 based on the variable type (like decimal for an @code{int}, hex
29063 for pointers, etc.).
29065 The zero-hexadecimal format has a representation similar to hexadecimal
29066 but with padding zeroes to the left of the value. For example, a 32-bit
29067 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29068 zero-hexadecimal format.
29070 For a variable with children, the format is set only on the
29071 variable itself, and the children are not affected.
29073 @subheading The @code{-var-show-format} Command
29074 @findex -var-show-format
29076 @subsubheading Synopsis
29079 -var-show-format @var{name}
29082 Returns the format used to display the value of the object @var{name}.
29085 @var{format} @expansion{}
29090 @subheading The @code{-var-info-num-children} Command
29091 @findex -var-info-num-children
29093 @subsubheading Synopsis
29096 -var-info-num-children @var{name}
29099 Returns the number of children of a variable object @var{name}:
29105 Note that this number is not completely reliable for a dynamic varobj.
29106 It will return the current number of children, but more children may
29110 @subheading The @code{-var-list-children} Command
29111 @findex -var-list-children
29113 @subsubheading Synopsis
29116 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29118 @anchor{-var-list-children}
29120 Return a list of the children of the specified variable object and
29121 create variable objects for them, if they do not already exist. With
29122 a single argument or if @var{print-values} has a value of 0 or
29123 @code{--no-values}, print only the names of the variables; if
29124 @var{print-values} is 1 or @code{--all-values}, also print their
29125 values; and if it is 2 or @code{--simple-values} print the name and
29126 value for simple data types and just the name for arrays, structures
29129 @var{from} and @var{to}, if specified, indicate the range of children
29130 to report. If @var{from} or @var{to} is less than zero, the range is
29131 reset and all children will be reported. Otherwise, children starting
29132 at @var{from} (zero-based) and up to and excluding @var{to} will be
29135 If a child range is requested, it will only affect the current call to
29136 @code{-var-list-children}, but not future calls to @code{-var-update}.
29137 For this, you must instead use @code{-var-set-update-range}. The
29138 intent of this approach is to enable a front end to implement any
29139 update approach it likes; for example, scrolling a view may cause the
29140 front end to request more children with @code{-var-list-children}, and
29141 then the front end could call @code{-var-set-update-range} with a
29142 different range to ensure that future updates are restricted to just
29145 For each child the following results are returned:
29150 Name of the variable object created for this child.
29153 The expression to be shown to the user by the front end to designate this child.
29154 For example this may be the name of a structure member.
29156 For a dynamic varobj, this value cannot be used to form an
29157 expression. There is no way to do this at all with a dynamic varobj.
29159 For C/C@t{++} structures there are several pseudo children returned to
29160 designate access qualifiers. For these pseudo children @var{exp} is
29161 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29162 type and value are not present.
29164 A dynamic varobj will not report the access qualifying
29165 pseudo-children, regardless of the language. This information is not
29166 available at all with a dynamic varobj.
29169 Number of children this child has. For a dynamic varobj, this will be
29173 The type of the child. If @samp{print object}
29174 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29175 @emph{actual} (derived) type of the object is shown rather than the
29176 @emph{declared} one.
29179 If values were requested, this is the value.
29182 If this variable object is associated with a thread, this is the thread id.
29183 Otherwise this result is not present.
29186 If the variable object is frozen, this variable will be present with a value of 1.
29189 A dynamic varobj can supply a display hint to the front end. The
29190 value comes directly from the Python pretty-printer object's
29191 @code{display_hint} method. @xref{Pretty Printing API}.
29194 This attribute will be present and have the value @samp{1} if the
29195 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29196 then this attribute will not be present.
29200 The result may have its own attributes:
29204 A dynamic varobj can supply a display hint to the front end. The
29205 value comes directly from the Python pretty-printer object's
29206 @code{display_hint} method. @xref{Pretty Printing API}.
29209 This is an integer attribute which is nonzero if there are children
29210 remaining after the end of the selected range.
29213 @subsubheading Example
29217 -var-list-children n
29218 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29219 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29221 -var-list-children --all-values n
29222 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29223 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29227 @subheading The @code{-var-info-type} Command
29228 @findex -var-info-type
29230 @subsubheading Synopsis
29233 -var-info-type @var{name}
29236 Returns the type of the specified variable @var{name}. The type is
29237 returned as a string in the same format as it is output by the
29241 type=@var{typename}
29245 @subheading The @code{-var-info-expression} Command
29246 @findex -var-info-expression
29248 @subsubheading Synopsis
29251 -var-info-expression @var{name}
29254 Returns a string that is suitable for presenting this
29255 variable object in user interface. The string is generally
29256 not valid expression in the current language, and cannot be evaluated.
29258 For example, if @code{a} is an array, and variable object
29259 @code{A} was created for @code{a}, then we'll get this output:
29262 (gdb) -var-info-expression A.1
29263 ^done,lang="C",exp="1"
29267 Here, the value of @code{lang} is the language name, which can be
29268 found in @ref{Supported Languages}.
29270 Note that the output of the @code{-var-list-children} command also
29271 includes those expressions, so the @code{-var-info-expression} command
29274 @subheading The @code{-var-info-path-expression} Command
29275 @findex -var-info-path-expression
29277 @subsubheading Synopsis
29280 -var-info-path-expression @var{name}
29283 Returns an expression that can be evaluated in the current
29284 context and will yield the same value that a variable object has.
29285 Compare this with the @code{-var-info-expression} command, which
29286 result can be used only for UI presentation. Typical use of
29287 the @code{-var-info-path-expression} command is creating a
29288 watchpoint from a variable object.
29290 This command is currently not valid for children of a dynamic varobj,
29291 and will give an error when invoked on one.
29293 For example, suppose @code{C} is a C@t{++} class, derived from class
29294 @code{Base}, and that the @code{Base} class has a member called
29295 @code{m_size}. Assume a variable @code{c} is has the type of
29296 @code{C} and a variable object @code{C} was created for variable
29297 @code{c}. Then, we'll get this output:
29299 (gdb) -var-info-path-expression C.Base.public.m_size
29300 ^done,path_expr=((Base)c).m_size)
29303 @subheading The @code{-var-show-attributes} Command
29304 @findex -var-show-attributes
29306 @subsubheading Synopsis
29309 -var-show-attributes @var{name}
29312 List attributes of the specified variable object @var{name}:
29315 status=@var{attr} [ ( ,@var{attr} )* ]
29319 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29321 @subheading The @code{-var-evaluate-expression} Command
29322 @findex -var-evaluate-expression
29324 @subsubheading Synopsis
29327 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29330 Evaluates the expression that is represented by the specified variable
29331 object and returns its value as a string. The format of the string
29332 can be specified with the @samp{-f} option. The possible values of
29333 this option are the same as for @code{-var-set-format}
29334 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29335 the current display format will be used. The current display format
29336 can be changed using the @code{-var-set-format} command.
29342 Note that one must invoke @code{-var-list-children} for a variable
29343 before the value of a child variable can be evaluated.
29345 @subheading The @code{-var-assign} Command
29346 @findex -var-assign
29348 @subsubheading Synopsis
29351 -var-assign @var{name} @var{expression}
29354 Assigns the value of @var{expression} to the variable object specified
29355 by @var{name}. The object must be @samp{editable}. If the variable's
29356 value is altered by the assign, the variable will show up in any
29357 subsequent @code{-var-update} list.
29359 @subsubheading Example
29367 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29371 @subheading The @code{-var-update} Command
29372 @findex -var-update
29374 @subsubheading Synopsis
29377 -var-update [@var{print-values}] @{@var{name} | "*"@}
29380 Reevaluate the expressions corresponding to the variable object
29381 @var{name} and all its direct and indirect children, and return the
29382 list of variable objects whose values have changed; @var{name} must
29383 be a root variable object. Here, ``changed'' means that the result of
29384 @code{-var-evaluate-expression} before and after the
29385 @code{-var-update} is different. If @samp{*} is used as the variable
29386 object names, all existing variable objects are updated, except
29387 for frozen ones (@pxref{-var-set-frozen}). The option
29388 @var{print-values} determines whether both names and values, or just
29389 names are printed. The possible values of this option are the same
29390 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29391 recommended to use the @samp{--all-values} option, to reduce the
29392 number of MI commands needed on each program stop.
29394 With the @samp{*} parameter, if a variable object is bound to a
29395 currently running thread, it will not be updated, without any
29398 If @code{-var-set-update-range} was previously used on a varobj, then
29399 only the selected range of children will be reported.
29401 @code{-var-update} reports all the changed varobjs in a tuple named
29404 Each item in the change list is itself a tuple holding:
29408 The name of the varobj.
29411 If values were requested for this update, then this field will be
29412 present and will hold the value of the varobj.
29415 @anchor{-var-update}
29416 This field is a string which may take one of three values:
29420 The variable object's current value is valid.
29423 The variable object does not currently hold a valid value but it may
29424 hold one in the future if its associated expression comes back into
29428 The variable object no longer holds a valid value.
29429 This can occur when the executable file being debugged has changed,
29430 either through recompilation or by using the @value{GDBN} @code{file}
29431 command. The front end should normally choose to delete these variable
29435 In the future new values may be added to this list so the front should
29436 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29439 This is only present if the varobj is still valid. If the type
29440 changed, then this will be the string @samp{true}; otherwise it will
29443 When a varobj's type changes, its children are also likely to have
29444 become incorrect. Therefore, the varobj's children are automatically
29445 deleted when this attribute is @samp{true}. Also, the varobj's update
29446 range, when set using the @code{-var-set-update-range} command, is
29450 If the varobj's type changed, then this field will be present and will
29453 @item new_num_children
29454 For a dynamic varobj, if the number of children changed, or if the
29455 type changed, this will be the new number of children.
29457 The @samp{numchild} field in other varobj responses is generally not
29458 valid for a dynamic varobj -- it will show the number of children that
29459 @value{GDBN} knows about, but because dynamic varobjs lazily
29460 instantiate their children, this will not reflect the number of
29461 children which may be available.
29463 The @samp{new_num_children} attribute only reports changes to the
29464 number of children known by @value{GDBN}. This is the only way to
29465 detect whether an update has removed children (which necessarily can
29466 only happen at the end of the update range).
29469 The display hint, if any.
29472 This is an integer value, which will be 1 if there are more children
29473 available outside the varobj's update range.
29476 This attribute will be present and have the value @samp{1} if the
29477 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29478 then this attribute will not be present.
29481 If new children were added to a dynamic varobj within the selected
29482 update range (as set by @code{-var-set-update-range}), then they will
29483 be listed in this attribute.
29486 @subsubheading Example
29493 -var-update --all-values var1
29494 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29495 type_changed="false"@}]
29499 @subheading The @code{-var-set-frozen} Command
29500 @findex -var-set-frozen
29501 @anchor{-var-set-frozen}
29503 @subsubheading Synopsis
29506 -var-set-frozen @var{name} @var{flag}
29509 Set the frozenness flag on the variable object @var{name}. The
29510 @var{flag} parameter should be either @samp{1} to make the variable
29511 frozen or @samp{0} to make it unfrozen. If a variable object is
29512 frozen, then neither itself, nor any of its children, are
29513 implicitly updated by @code{-var-update} of
29514 a parent variable or by @code{-var-update *}. Only
29515 @code{-var-update} of the variable itself will update its value and
29516 values of its children. After a variable object is unfrozen, it is
29517 implicitly updated by all subsequent @code{-var-update} operations.
29518 Unfreezing a variable does not update it, only subsequent
29519 @code{-var-update} does.
29521 @subsubheading Example
29525 -var-set-frozen V 1
29530 @subheading The @code{-var-set-update-range} command
29531 @findex -var-set-update-range
29532 @anchor{-var-set-update-range}
29534 @subsubheading Synopsis
29537 -var-set-update-range @var{name} @var{from} @var{to}
29540 Set the range of children to be returned by future invocations of
29541 @code{-var-update}.
29543 @var{from} and @var{to} indicate the range of children to report. If
29544 @var{from} or @var{to} is less than zero, the range is reset and all
29545 children will be reported. Otherwise, children starting at @var{from}
29546 (zero-based) and up to and excluding @var{to} will be reported.
29548 @subsubheading Example
29552 -var-set-update-range V 1 2
29556 @subheading The @code{-var-set-visualizer} command
29557 @findex -var-set-visualizer
29558 @anchor{-var-set-visualizer}
29560 @subsubheading Synopsis
29563 -var-set-visualizer @var{name} @var{visualizer}
29566 Set a visualizer for the variable object @var{name}.
29568 @var{visualizer} is the visualizer to use. The special value
29569 @samp{None} means to disable any visualizer in use.
29571 If not @samp{None}, @var{visualizer} must be a Python expression.
29572 This expression must evaluate to a callable object which accepts a
29573 single argument. @value{GDBN} will call this object with the value of
29574 the varobj @var{name} as an argument (this is done so that the same
29575 Python pretty-printing code can be used for both the CLI and MI).
29576 When called, this object must return an object which conforms to the
29577 pretty-printing interface (@pxref{Pretty Printing API}).
29579 The pre-defined function @code{gdb.default_visualizer} may be used to
29580 select a visualizer by following the built-in process
29581 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29582 a varobj is created, and so ordinarily is not needed.
29584 This feature is only available if Python support is enabled. The MI
29585 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29586 can be used to check this.
29588 @subsubheading Example
29590 Resetting the visualizer:
29594 -var-set-visualizer V None
29598 Reselecting the default (type-based) visualizer:
29602 -var-set-visualizer V gdb.default_visualizer
29606 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29607 can be used to instantiate this class for a varobj:
29611 -var-set-visualizer V "lambda val: SomeClass()"
29615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29616 @node GDB/MI Data Manipulation
29617 @section @sc{gdb/mi} Data Manipulation
29619 @cindex data manipulation, in @sc{gdb/mi}
29620 @cindex @sc{gdb/mi}, data manipulation
29621 This section describes the @sc{gdb/mi} commands that manipulate data:
29622 examine memory and registers, evaluate expressions, etc.
29624 For details about what an addressable memory unit is,
29625 @pxref{addressable memory unit}.
29627 @c REMOVED FROM THE INTERFACE.
29628 @c @subheading -data-assign
29629 @c Change the value of a program variable. Plenty of side effects.
29630 @c @subsubheading GDB Command
29632 @c @subsubheading Example
29635 @subheading The @code{-data-disassemble} Command
29636 @findex -data-disassemble
29638 @subsubheading Synopsis
29642 [ -s @var{start-addr} -e @var{end-addr} ]
29643 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29651 @item @var{start-addr}
29652 is the beginning address (or @code{$pc})
29653 @item @var{end-addr}
29655 @item @var{filename}
29656 is the name of the file to disassemble
29657 @item @var{linenum}
29658 is the line number to disassemble around
29660 is the number of disassembly lines to be produced. If it is -1,
29661 the whole function will be disassembled, in case no @var{end-addr} is
29662 specified. If @var{end-addr} is specified as a non-zero value, and
29663 @var{lines} is lower than the number of disassembly lines between
29664 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29665 displayed; if @var{lines} is higher than the number of lines between
29666 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29671 @item 0 disassembly only
29672 @item 1 mixed source and disassembly (deprecated)
29673 @item 2 disassembly with raw opcodes
29674 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29675 @item 4 mixed source and disassembly
29676 @item 5 mixed source and disassembly with raw opcodes
29679 Modes 1 and 3 are deprecated. The output is ``source centric''
29680 which hasn't proved useful in practice.
29681 @xref{Machine Code}, for a discussion of the difference between
29682 @code{/m} and @code{/s} output of the @code{disassemble} command.
29685 @subsubheading Result
29687 The result of the @code{-data-disassemble} command will be a list named
29688 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29689 used with the @code{-data-disassemble} command.
29691 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29696 The address at which this instruction was disassembled.
29699 The name of the function this instruction is within.
29702 The decimal offset in bytes from the start of @samp{func-name}.
29705 The text disassembly for this @samp{address}.
29708 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29709 bytes for the @samp{inst} field.
29713 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29714 @samp{src_and_asm_line}, each of which has the following fields:
29718 The line number within @samp{file}.
29721 The file name from the compilation unit. This might be an absolute
29722 file name or a relative file name depending on the compile command
29726 Absolute file name of @samp{file}. It is converted to a canonical form
29727 using the source file search path
29728 (@pxref{Source Path, ,Specifying Source Directories})
29729 and after resolving all the symbolic links.
29731 If the source file is not found this field will contain the path as
29732 present in the debug information.
29734 @item line_asm_insn
29735 This is a list of tuples containing the disassembly for @samp{line} in
29736 @samp{file}. The fields of each tuple are the same as for
29737 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29738 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29743 Note that whatever included in the @samp{inst} field, is not
29744 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29747 @subsubheading @value{GDBN} Command
29749 The corresponding @value{GDBN} command is @samp{disassemble}.
29751 @subsubheading Example
29753 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29757 -data-disassemble -s $pc -e "$pc + 20" -- 0
29760 @{address="0x000107c0",func-name="main",offset="4",
29761 inst="mov 2, %o0"@},
29762 @{address="0x000107c4",func-name="main",offset="8",
29763 inst="sethi %hi(0x11800), %o2"@},
29764 @{address="0x000107c8",func-name="main",offset="12",
29765 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29766 @{address="0x000107cc",func-name="main",offset="16",
29767 inst="sethi %hi(0x11800), %o2"@},
29768 @{address="0x000107d0",func-name="main",offset="20",
29769 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29773 Disassemble the whole @code{main} function. Line 32 is part of
29777 -data-disassemble -f basics.c -l 32 -- 0
29779 @{address="0x000107bc",func-name="main",offset="0",
29780 inst="save %sp, -112, %sp"@},
29781 @{address="0x000107c0",func-name="main",offset="4",
29782 inst="mov 2, %o0"@},
29783 @{address="0x000107c4",func-name="main",offset="8",
29784 inst="sethi %hi(0x11800), %o2"@},
29786 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29787 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29791 Disassemble 3 instructions from the start of @code{main}:
29795 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29797 @{address="0x000107bc",func-name="main",offset="0",
29798 inst="save %sp, -112, %sp"@},
29799 @{address="0x000107c0",func-name="main",offset="4",
29800 inst="mov 2, %o0"@},
29801 @{address="0x000107c4",func-name="main",offset="8",
29802 inst="sethi %hi(0x11800), %o2"@}]
29806 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29810 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29812 src_and_asm_line=@{line="31",
29813 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29814 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29815 line_asm_insn=[@{address="0x000107bc",
29816 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29817 src_and_asm_line=@{line="32",
29818 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29819 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29820 line_asm_insn=[@{address="0x000107c0",
29821 func-name="main",offset="4",inst="mov 2, %o0"@},
29822 @{address="0x000107c4",func-name="main",offset="8",
29823 inst="sethi %hi(0x11800), %o2"@}]@}]
29828 @subheading The @code{-data-evaluate-expression} Command
29829 @findex -data-evaluate-expression
29831 @subsubheading Synopsis
29834 -data-evaluate-expression @var{expr}
29837 Evaluate @var{expr} as an expression. The expression could contain an
29838 inferior function call. The function call will execute synchronously.
29839 If the expression contains spaces, it must be enclosed in double quotes.
29841 @subsubheading @value{GDBN} Command
29843 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29844 @samp{call}. In @code{gdbtk} only, there's a corresponding
29845 @samp{gdb_eval} command.
29847 @subsubheading Example
29849 In the following example, the numbers that precede the commands are the
29850 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29851 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29855 211-data-evaluate-expression A
29858 311-data-evaluate-expression &A
29859 311^done,value="0xefffeb7c"
29861 411-data-evaluate-expression A+3
29864 511-data-evaluate-expression "A + 3"
29870 @subheading The @code{-data-list-changed-registers} Command
29871 @findex -data-list-changed-registers
29873 @subsubheading Synopsis
29876 -data-list-changed-registers
29879 Display a list of the registers that have changed.
29881 @subsubheading @value{GDBN} Command
29883 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29884 has the corresponding command @samp{gdb_changed_register_list}.
29886 @subsubheading Example
29888 On a PPC MBX board:
29896 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29897 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29900 -data-list-changed-registers
29901 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29902 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29903 "24","25","26","27","28","30","31","64","65","66","67","69"]
29908 @subheading The @code{-data-list-register-names} Command
29909 @findex -data-list-register-names
29911 @subsubheading Synopsis
29914 -data-list-register-names [ ( @var{regno} )+ ]
29917 Show a list of register names for the current target. If no arguments
29918 are given, it shows a list of the names of all the registers. If
29919 integer numbers are given as arguments, it will print a list of the
29920 names of the registers corresponding to the arguments. To ensure
29921 consistency between a register name and its number, the output list may
29922 include empty register names.
29924 @subsubheading @value{GDBN} Command
29926 @value{GDBN} does not have a command which corresponds to
29927 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29928 corresponding command @samp{gdb_regnames}.
29930 @subsubheading Example
29932 For the PPC MBX board:
29935 -data-list-register-names
29936 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29937 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29938 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29939 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29940 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29941 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29942 "", "pc","ps","cr","lr","ctr","xer"]
29944 -data-list-register-names 1 2 3
29945 ^done,register-names=["r1","r2","r3"]
29949 @subheading The @code{-data-list-register-values} Command
29950 @findex -data-list-register-values
29952 @subsubheading Synopsis
29955 -data-list-register-values
29956 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29959 Display the registers' contents. The format according to which the
29960 registers' contents are to be returned is given by @var{fmt}, followed
29961 by an optional list of numbers specifying the registers to display. A
29962 missing list of numbers indicates that the contents of all the
29963 registers must be returned. The @code{--skip-unavailable} option
29964 indicates that only the available registers are to be returned.
29966 Allowed formats for @var{fmt} are:
29983 @subsubheading @value{GDBN} Command
29985 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29986 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29988 @subsubheading Example
29990 For a PPC MBX board (note: line breaks are for readability only, they
29991 don't appear in the actual output):
29995 -data-list-register-values r 64 65
29996 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29997 @{number="65",value="0x00029002"@}]
29999 -data-list-register-values x
30000 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30001 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30002 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30003 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30004 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30005 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30006 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30007 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30008 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30009 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30010 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30011 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30012 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30013 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30014 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30015 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30016 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30017 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30018 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30019 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30020 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30021 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30022 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30023 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30024 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30025 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30026 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30027 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30028 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30029 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30030 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30031 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30032 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30033 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30034 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30035 @{number="69",value="0x20002b03"@}]
30040 @subheading The @code{-data-read-memory} Command
30041 @findex -data-read-memory
30043 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30045 @subsubheading Synopsis
30048 -data-read-memory [ -o @var{byte-offset} ]
30049 @var{address} @var{word-format} @var{word-size}
30050 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30057 @item @var{address}
30058 An expression specifying the address of the first memory word to be
30059 read. Complex expressions containing embedded white space should be
30060 quoted using the C convention.
30062 @item @var{word-format}
30063 The format to be used to print the memory words. The notation is the
30064 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30067 @item @var{word-size}
30068 The size of each memory word in bytes.
30070 @item @var{nr-rows}
30071 The number of rows in the output table.
30073 @item @var{nr-cols}
30074 The number of columns in the output table.
30077 If present, indicates that each row should include an @sc{ascii} dump. The
30078 value of @var{aschar} is used as a padding character when a byte is not a
30079 member of the printable @sc{ascii} character set (printable @sc{ascii}
30080 characters are those whose code is between 32 and 126, inclusively).
30082 @item @var{byte-offset}
30083 An offset to add to the @var{address} before fetching memory.
30086 This command displays memory contents as a table of @var{nr-rows} by
30087 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30088 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30089 (returned as @samp{total-bytes}). Should less than the requested number
30090 of bytes be returned by the target, the missing words are identified
30091 using @samp{N/A}. The number of bytes read from the target is returned
30092 in @samp{nr-bytes} and the starting address used to read memory in
30095 The address of the next/previous row or page is available in
30096 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30099 @subsubheading @value{GDBN} Command
30101 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30102 @samp{gdb_get_mem} memory read command.
30104 @subsubheading Example
30106 Read six bytes of memory starting at @code{bytes+6} but then offset by
30107 @code{-6} bytes. Format as three rows of two columns. One byte per
30108 word. Display each word in hex.
30112 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30113 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30114 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30115 prev-page="0x0000138a",memory=[
30116 @{addr="0x00001390",data=["0x00","0x01"]@},
30117 @{addr="0x00001392",data=["0x02","0x03"]@},
30118 @{addr="0x00001394",data=["0x04","0x05"]@}]
30122 Read two bytes of memory starting at address @code{shorts + 64} and
30123 display as a single word formatted in decimal.
30127 5-data-read-memory shorts+64 d 2 1 1
30128 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30129 next-row="0x00001512",prev-row="0x0000150e",
30130 next-page="0x00001512",prev-page="0x0000150e",memory=[
30131 @{addr="0x00001510",data=["128"]@}]
30135 Read thirty two bytes of memory starting at @code{bytes+16} and format
30136 as eight rows of four columns. Include a string encoding with @samp{x}
30137 used as the non-printable character.
30141 4-data-read-memory bytes+16 x 1 8 4 x
30142 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30143 next-row="0x000013c0",prev-row="0x0000139c",
30144 next-page="0x000013c0",prev-page="0x00001380",memory=[
30145 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30146 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30147 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30148 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30149 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30150 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30151 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30152 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30156 @subheading The @code{-data-read-memory-bytes} Command
30157 @findex -data-read-memory-bytes
30159 @subsubheading Synopsis
30162 -data-read-memory-bytes [ -o @var{offset} ]
30163 @var{address} @var{count}
30170 @item @var{address}
30171 An expression specifying the address of the first addressable memory unit
30172 to be read. Complex expressions containing embedded white space should be
30173 quoted using the C convention.
30176 The number of addressable memory units to read. This should be an integer
30180 The offset relative to @var{address} at which to start reading. This
30181 should be an integer literal. This option is provided so that a frontend
30182 is not required to first evaluate address and then perform address
30183 arithmetics itself.
30187 This command attempts to read all accessible memory regions in the
30188 specified range. First, all regions marked as unreadable in the memory
30189 map (if one is defined) will be skipped. @xref{Memory Region
30190 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30191 regions. For each one, if reading full region results in an errors,
30192 @value{GDBN} will try to read a subset of the region.
30194 In general, every single memory unit in the region may be readable or not,
30195 and the only way to read every readable unit is to try a read at
30196 every address, which is not practical. Therefore, @value{GDBN} will
30197 attempt to read all accessible memory units at either beginning or the end
30198 of the region, using a binary division scheme. This heuristic works
30199 well for reading accross a memory map boundary. Note that if a region
30200 has a readable range that is neither at the beginning or the end,
30201 @value{GDBN} will not read it.
30203 The result record (@pxref{GDB/MI Result Records}) that is output of
30204 the command includes a field named @samp{memory} whose content is a
30205 list of tuples. Each tuple represent a successfully read memory block
30206 and has the following fields:
30210 The start address of the memory block, as hexadecimal literal.
30213 The end address of the memory block, as hexadecimal literal.
30216 The offset of the memory block, as hexadecimal literal, relative to
30217 the start address passed to @code{-data-read-memory-bytes}.
30220 The contents of the memory block, in hex.
30226 @subsubheading @value{GDBN} Command
30228 The corresponding @value{GDBN} command is @samp{x}.
30230 @subsubheading Example
30234 -data-read-memory-bytes &a 10
30235 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30237 contents="01000000020000000300"@}]
30242 @subheading The @code{-data-write-memory-bytes} Command
30243 @findex -data-write-memory-bytes
30245 @subsubheading Synopsis
30248 -data-write-memory-bytes @var{address} @var{contents}
30249 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30256 @item @var{address}
30257 An expression specifying the address of the first addressable memory unit
30258 to be written. Complex expressions containing embedded white space should
30259 be quoted using the C convention.
30261 @item @var{contents}
30262 The hex-encoded data to write. It is an error if @var{contents} does
30263 not represent an integral number of addressable memory units.
30266 Optional argument indicating the number of addressable memory units to be
30267 written. If @var{count} is greater than @var{contents}' length,
30268 @value{GDBN} will repeatedly write @var{contents} until it fills
30269 @var{count} memory units.
30273 @subsubheading @value{GDBN} Command
30275 There's no corresponding @value{GDBN} command.
30277 @subsubheading Example
30281 -data-write-memory-bytes &a "aabbccdd"
30288 -data-write-memory-bytes &a "aabbccdd" 16e
30293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30294 @node GDB/MI Tracepoint Commands
30295 @section @sc{gdb/mi} Tracepoint Commands
30297 The commands defined in this section implement MI support for
30298 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30300 @subheading The @code{-trace-find} Command
30301 @findex -trace-find
30303 @subsubheading Synopsis
30306 -trace-find @var{mode} [@var{parameters}@dots{}]
30309 Find a trace frame using criteria defined by @var{mode} and
30310 @var{parameters}. The following table lists permissible
30311 modes and their parameters. For details of operation, see @ref{tfind}.
30316 No parameters are required. Stops examining trace frames.
30319 An integer is required as parameter. Selects tracepoint frame with
30322 @item tracepoint-number
30323 An integer is required as parameter. Finds next
30324 trace frame that corresponds to tracepoint with the specified number.
30327 An address is required as parameter. Finds
30328 next trace frame that corresponds to any tracepoint at the specified
30331 @item pc-inside-range
30332 Two addresses are required as parameters. Finds next trace
30333 frame that corresponds to a tracepoint at an address inside the
30334 specified range. Both bounds are considered to be inside the range.
30336 @item pc-outside-range
30337 Two addresses are required as parameters. Finds
30338 next trace frame that corresponds to a tracepoint at an address outside
30339 the specified range. Both bounds are considered to be inside the range.
30342 Line specification is required as parameter. @xref{Specify Location}.
30343 Finds next trace frame that corresponds to a tracepoint at
30344 the specified location.
30348 If @samp{none} was passed as @var{mode}, the response does not
30349 have fields. Otherwise, the response may have the following fields:
30353 This field has either @samp{0} or @samp{1} as the value, depending
30354 on whether a matching tracepoint was found.
30357 The index of the found traceframe. This field is present iff
30358 the @samp{found} field has value of @samp{1}.
30361 The index of the found tracepoint. This field is present iff
30362 the @samp{found} field has value of @samp{1}.
30365 The information about the frame corresponding to the found trace
30366 frame. This field is present only if a trace frame was found.
30367 @xref{GDB/MI Frame Information}, for description of this field.
30371 @subsubheading @value{GDBN} Command
30373 The corresponding @value{GDBN} command is @samp{tfind}.
30375 @subheading -trace-define-variable
30376 @findex -trace-define-variable
30378 @subsubheading Synopsis
30381 -trace-define-variable @var{name} [ @var{value} ]
30384 Create trace variable @var{name} if it does not exist. If
30385 @var{value} is specified, sets the initial value of the specified
30386 trace variable to that value. Note that the @var{name} should start
30387 with the @samp{$} character.
30389 @subsubheading @value{GDBN} Command
30391 The corresponding @value{GDBN} command is @samp{tvariable}.
30393 @subheading The @code{-trace-frame-collected} Command
30394 @findex -trace-frame-collected
30396 @subsubheading Synopsis
30399 -trace-frame-collected
30400 [--var-print-values @var{var_pval}]
30401 [--comp-print-values @var{comp_pval}]
30402 [--registers-format @var{regformat}]
30403 [--memory-contents]
30406 This command returns the set of collected objects, register names,
30407 trace state variable names, memory ranges and computed expressions
30408 that have been collected at a particular trace frame. The optional
30409 parameters to the command affect the output format in different ways.
30410 See the output description table below for more details.
30412 The reported names can be used in the normal manner to create
30413 varobjs and inspect the objects themselves. The items returned by
30414 this command are categorized so that it is clear which is a variable,
30415 which is a register, which is a trace state variable, which is a
30416 memory range and which is a computed expression.
30418 For instance, if the actions were
30420 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30421 collect *(int*)0xaf02bef0@@40
30425 the object collected in its entirety would be @code{myVar}. The
30426 object @code{myArray} would be partially collected, because only the
30427 element at index @code{myIndex} would be collected. The remaining
30428 objects would be computed expressions.
30430 An example output would be:
30434 -trace-frame-collected
30436 explicit-variables=[@{name="myVar",value="1"@}],
30437 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30438 @{name="myObj.field",value="0"@},
30439 @{name="myPtr->field",value="1"@},
30440 @{name="myCount + 2",value="3"@},
30441 @{name="$tvar1 + 1",value="43970027"@}],
30442 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30443 @{number="1",value="0x0"@},
30444 @{number="2",value="0x4"@},
30446 @{number="125",value="0x0"@}],
30447 tvars=[@{name="$tvar1",current="43970026"@}],
30448 memory=[@{address="0x0000000000602264",length="4"@},
30449 @{address="0x0000000000615bc0",length="4"@}]
30456 @item explicit-variables
30457 The set of objects that have been collected in their entirety (as
30458 opposed to collecting just a few elements of an array or a few struct
30459 members). For each object, its name and value are printed.
30460 The @code{--var-print-values} option affects how or whether the value
30461 field is output. If @var{var_pval} is 0, then print only the names;
30462 if it is 1, print also their values; and if it is 2, print the name,
30463 type and value for simple data types, and the name and type for
30464 arrays, structures and unions.
30466 @item computed-expressions
30467 The set of computed expressions that have been collected at the
30468 current trace frame. The @code{--comp-print-values} option affects
30469 this set like the @code{--var-print-values} option affects the
30470 @code{explicit-variables} set. See above.
30473 The registers that have been collected at the current trace frame.
30474 For each register collected, the name and current value are returned.
30475 The value is formatted according to the @code{--registers-format}
30476 option. See the @command{-data-list-register-values} command for a
30477 list of the allowed formats. The default is @samp{x}.
30480 The trace state variables that have been collected at the current
30481 trace frame. For each trace state variable collected, the name and
30482 current value are returned.
30485 The set of memory ranges that have been collected at the current trace
30486 frame. Its content is a list of tuples. Each tuple represents a
30487 collected memory range and has the following fields:
30491 The start address of the memory range, as hexadecimal literal.
30494 The length of the memory range, as decimal literal.
30497 The contents of the memory block, in hex. This field is only present
30498 if the @code{--memory-contents} option is specified.
30504 @subsubheading @value{GDBN} Command
30506 There is no corresponding @value{GDBN} command.
30508 @subsubheading Example
30510 @subheading -trace-list-variables
30511 @findex -trace-list-variables
30513 @subsubheading Synopsis
30516 -trace-list-variables
30519 Return a table of all defined trace variables. Each element of the
30520 table has the following fields:
30524 The name of the trace variable. This field is always present.
30527 The initial value. This is a 64-bit signed integer. This
30528 field is always present.
30531 The value the trace variable has at the moment. This is a 64-bit
30532 signed integer. This field is absent iff current value is
30533 not defined, for example if the trace was never run, or is
30538 @subsubheading @value{GDBN} Command
30540 The corresponding @value{GDBN} command is @samp{tvariables}.
30542 @subsubheading Example
30546 -trace-list-variables
30547 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30548 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30549 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30550 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30551 body=[variable=@{name="$trace_timestamp",initial="0"@}
30552 variable=@{name="$foo",initial="10",current="15"@}]@}
30556 @subheading -trace-save
30557 @findex -trace-save
30559 @subsubheading Synopsis
30562 -trace-save [-r ] @var{filename}
30565 Saves the collected trace data to @var{filename}. Without the
30566 @samp{-r} option, the data is downloaded from the target and saved
30567 in a local file. With the @samp{-r} option the target is asked
30568 to perform the save.
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} command is @samp{tsave}.
30575 @subheading -trace-start
30576 @findex -trace-start
30578 @subsubheading Synopsis
30584 Starts a tracing experiments. The result of this command does not
30587 @subsubheading @value{GDBN} Command
30589 The corresponding @value{GDBN} command is @samp{tstart}.
30591 @subheading -trace-status
30592 @findex -trace-status
30594 @subsubheading Synopsis
30600 Obtains the status of a tracing experiment. The result may include
30601 the following fields:
30606 May have a value of either @samp{0}, when no tracing operations are
30607 supported, @samp{1}, when all tracing operations are supported, or
30608 @samp{file} when examining trace file. In the latter case, examining
30609 of trace frame is possible but new tracing experiement cannot be
30610 started. This field is always present.
30613 May have a value of either @samp{0} or @samp{1} depending on whether
30614 tracing experiement is in progress on target. This field is present
30615 if @samp{supported} field is not @samp{0}.
30618 Report the reason why the tracing was stopped last time. This field
30619 may be absent iff tracing was never stopped on target yet. The
30620 value of @samp{request} means the tracing was stopped as result of
30621 the @code{-trace-stop} command. The value of @samp{overflow} means
30622 the tracing buffer is full. The value of @samp{disconnection} means
30623 tracing was automatically stopped when @value{GDBN} has disconnected.
30624 The value of @samp{passcount} means tracing was stopped when a
30625 tracepoint was passed a maximal number of times for that tracepoint.
30626 This field is present if @samp{supported} field is not @samp{0}.
30628 @item stopping-tracepoint
30629 The number of tracepoint whose passcount as exceeded. This field is
30630 present iff the @samp{stop-reason} field has the value of
30634 @itemx frames-created
30635 The @samp{frames} field is a count of the total number of trace frames
30636 in the trace buffer, while @samp{frames-created} is the total created
30637 during the run, including ones that were discarded, such as when a
30638 circular trace buffer filled up. Both fields are optional.
30642 These fields tell the current size of the tracing buffer and the
30643 remaining space. These fields are optional.
30646 The value of the circular trace buffer flag. @code{1} means that the
30647 trace buffer is circular and old trace frames will be discarded if
30648 necessary to make room, @code{0} means that the trace buffer is linear
30652 The value of the disconnected tracing flag. @code{1} means that
30653 tracing will continue after @value{GDBN} disconnects, @code{0} means
30654 that the trace run will stop.
30657 The filename of the trace file being examined. This field is
30658 optional, and only present when examining a trace file.
30662 @subsubheading @value{GDBN} Command
30664 The corresponding @value{GDBN} command is @samp{tstatus}.
30666 @subheading -trace-stop
30667 @findex -trace-stop
30669 @subsubheading Synopsis
30675 Stops a tracing experiment. The result of this command has the same
30676 fields as @code{-trace-status}, except that the @samp{supported} and
30677 @samp{running} fields are not output.
30679 @subsubheading @value{GDBN} Command
30681 The corresponding @value{GDBN} command is @samp{tstop}.
30684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30685 @node GDB/MI Symbol Query
30686 @section @sc{gdb/mi} Symbol Query Commands
30690 @subheading The @code{-symbol-info-address} Command
30691 @findex -symbol-info-address
30693 @subsubheading Synopsis
30696 -symbol-info-address @var{symbol}
30699 Describe where @var{symbol} is stored.
30701 @subsubheading @value{GDBN} Command
30703 The corresponding @value{GDBN} command is @samp{info address}.
30705 @subsubheading Example
30709 @subheading The @code{-symbol-info-file} Command
30710 @findex -symbol-info-file
30712 @subsubheading Synopsis
30718 Show the file for the symbol.
30720 @subsubheading @value{GDBN} Command
30722 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30723 @samp{gdb_find_file}.
30725 @subsubheading Example
30729 @subheading The @code{-symbol-info-function} Command
30730 @findex -symbol-info-function
30732 @subsubheading Synopsis
30735 -symbol-info-function
30738 Show which function the symbol lives in.
30740 @subsubheading @value{GDBN} Command
30742 @samp{gdb_get_function} in @code{gdbtk}.
30744 @subsubheading Example
30748 @subheading The @code{-symbol-info-line} Command
30749 @findex -symbol-info-line
30751 @subsubheading Synopsis
30757 Show the core addresses of the code for a source line.
30759 @subsubheading @value{GDBN} Command
30761 The corresponding @value{GDBN} command is @samp{info line}.
30762 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30764 @subsubheading Example
30768 @subheading The @code{-symbol-info-symbol} Command
30769 @findex -symbol-info-symbol
30771 @subsubheading Synopsis
30774 -symbol-info-symbol @var{addr}
30777 Describe what symbol is at location @var{addr}.
30779 @subsubheading @value{GDBN} Command
30781 The corresponding @value{GDBN} command is @samp{info symbol}.
30783 @subsubheading Example
30787 @subheading The @code{-symbol-list-functions} Command
30788 @findex -symbol-list-functions
30790 @subsubheading Synopsis
30793 -symbol-list-functions
30796 List the functions in the executable.
30798 @subsubheading @value{GDBN} Command
30800 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30801 @samp{gdb_search} in @code{gdbtk}.
30803 @subsubheading Example
30808 @subheading The @code{-symbol-list-lines} Command
30809 @findex -symbol-list-lines
30811 @subsubheading Synopsis
30814 -symbol-list-lines @var{filename}
30817 Print the list of lines that contain code and their associated program
30818 addresses for the given source filename. The entries are sorted in
30819 ascending PC order.
30821 @subsubheading @value{GDBN} Command
30823 There is no corresponding @value{GDBN} command.
30825 @subsubheading Example
30828 -symbol-list-lines basics.c
30829 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30835 @subheading The @code{-symbol-list-types} Command
30836 @findex -symbol-list-types
30838 @subsubheading Synopsis
30844 List all the type names.
30846 @subsubheading @value{GDBN} Command
30848 The corresponding commands are @samp{info types} in @value{GDBN},
30849 @samp{gdb_search} in @code{gdbtk}.
30851 @subsubheading Example
30855 @subheading The @code{-symbol-list-variables} Command
30856 @findex -symbol-list-variables
30858 @subsubheading Synopsis
30861 -symbol-list-variables
30864 List all the global and static variable names.
30866 @subsubheading @value{GDBN} Command
30868 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30870 @subsubheading Example
30874 @subheading The @code{-symbol-locate} Command
30875 @findex -symbol-locate
30877 @subsubheading Synopsis
30883 @subsubheading @value{GDBN} Command
30885 @samp{gdb_loc} in @code{gdbtk}.
30887 @subsubheading Example
30891 @subheading The @code{-symbol-type} Command
30892 @findex -symbol-type
30894 @subsubheading Synopsis
30897 -symbol-type @var{variable}
30900 Show type of @var{variable}.
30902 @subsubheading @value{GDBN} Command
30904 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30905 @samp{gdb_obj_variable}.
30907 @subsubheading Example
30912 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30913 @node GDB/MI File Commands
30914 @section @sc{gdb/mi} File Commands
30916 This section describes the GDB/MI commands to specify executable file names
30917 and to read in and obtain symbol table information.
30919 @subheading The @code{-file-exec-and-symbols} Command
30920 @findex -file-exec-and-symbols
30922 @subsubheading Synopsis
30925 -file-exec-and-symbols @var{file}
30928 Specify the executable file to be debugged. This file is the one from
30929 which the symbol table is also read. If no file is specified, the
30930 command clears the executable and symbol information. If breakpoints
30931 are set when using this command with no arguments, @value{GDBN} will produce
30932 error messages. Otherwise, no output is produced, except a completion
30935 @subsubheading @value{GDBN} Command
30937 The corresponding @value{GDBN} command is @samp{file}.
30939 @subsubheading Example
30943 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30949 @subheading The @code{-file-exec-file} Command
30950 @findex -file-exec-file
30952 @subsubheading Synopsis
30955 -file-exec-file @var{file}
30958 Specify the executable file to be debugged. Unlike
30959 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30960 from this file. If used without argument, @value{GDBN} clears the information
30961 about the executable file. No output is produced, except a completion
30964 @subsubheading @value{GDBN} Command
30966 The corresponding @value{GDBN} command is @samp{exec-file}.
30968 @subsubheading Example
30972 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30979 @subheading The @code{-file-list-exec-sections} Command
30980 @findex -file-list-exec-sections
30982 @subsubheading Synopsis
30985 -file-list-exec-sections
30988 List the sections of the current executable file.
30990 @subsubheading @value{GDBN} Command
30992 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30993 information as this command. @code{gdbtk} has a corresponding command
30994 @samp{gdb_load_info}.
30996 @subsubheading Example
31001 @subheading The @code{-file-list-exec-source-file} Command
31002 @findex -file-list-exec-source-file
31004 @subsubheading Synopsis
31007 -file-list-exec-source-file
31010 List the line number, the current source file, and the absolute path
31011 to the current source file for the current executable. The macro
31012 information field has a value of @samp{1} or @samp{0} depending on
31013 whether or not the file includes preprocessor macro information.
31015 @subsubheading @value{GDBN} Command
31017 The @value{GDBN} equivalent is @samp{info source}
31019 @subsubheading Example
31023 123-file-list-exec-source-file
31024 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31029 @subheading The @code{-file-list-exec-source-files} Command
31030 @findex -file-list-exec-source-files
31032 @subsubheading Synopsis
31035 -file-list-exec-source-files
31038 List the source files for the current executable.
31040 It will always output both the filename and fullname (absolute file
31041 name) of a source file.
31043 @subsubheading @value{GDBN} Command
31045 The @value{GDBN} equivalent is @samp{info sources}.
31046 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31048 @subsubheading Example
31051 -file-list-exec-source-files
31053 @{file=foo.c,fullname=/home/foo.c@},
31054 @{file=/home/bar.c,fullname=/home/bar.c@},
31055 @{file=gdb_could_not_find_fullpath.c@}]
31060 @subheading The @code{-file-list-shared-libraries} Command
31061 @findex -file-list-shared-libraries
31063 @subsubheading Synopsis
31066 -file-list-shared-libraries
31069 List the shared libraries in the program.
31071 @subsubheading @value{GDBN} Command
31073 The corresponding @value{GDBN} command is @samp{info shared}.
31075 @subsubheading Example
31079 @subheading The @code{-file-list-symbol-files} Command
31080 @findex -file-list-symbol-files
31082 @subsubheading Synopsis
31085 -file-list-symbol-files
31090 @subsubheading @value{GDBN} Command
31092 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31094 @subsubheading Example
31099 @subheading The @code{-file-symbol-file} Command
31100 @findex -file-symbol-file
31102 @subsubheading Synopsis
31105 -file-symbol-file @var{file}
31108 Read symbol table info from the specified @var{file} argument. When
31109 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31110 produced, except for a completion notification.
31112 @subsubheading @value{GDBN} Command
31114 The corresponding @value{GDBN} command is @samp{symbol-file}.
31116 @subsubheading Example
31120 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31126 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31127 @node GDB/MI Memory Overlay Commands
31128 @section @sc{gdb/mi} Memory Overlay Commands
31130 The memory overlay commands are not implemented.
31132 @c @subheading -overlay-auto
31134 @c @subheading -overlay-list-mapping-state
31136 @c @subheading -overlay-list-overlays
31138 @c @subheading -overlay-map
31140 @c @subheading -overlay-off
31142 @c @subheading -overlay-on
31144 @c @subheading -overlay-unmap
31146 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31147 @node GDB/MI Signal Handling Commands
31148 @section @sc{gdb/mi} Signal Handling Commands
31150 Signal handling commands are not implemented.
31152 @c @subheading -signal-handle
31154 @c @subheading -signal-list-handle-actions
31156 @c @subheading -signal-list-signal-types
31160 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31161 @node GDB/MI Target Manipulation
31162 @section @sc{gdb/mi} Target Manipulation Commands
31165 @subheading The @code{-target-attach} Command
31166 @findex -target-attach
31168 @subsubheading Synopsis
31171 -target-attach @var{pid} | @var{gid} | @var{file}
31174 Attach to a process @var{pid} or a file @var{file} outside of
31175 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31176 group, the id previously returned by
31177 @samp{-list-thread-groups --available} must be used.
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{attach}.
31183 @subsubheading Example
31187 =thread-created,id="1"
31188 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31194 @subheading The @code{-target-compare-sections} Command
31195 @findex -target-compare-sections
31197 @subsubheading Synopsis
31200 -target-compare-sections [ @var{section} ]
31203 Compare data of section @var{section} on target to the exec file.
31204 Without the argument, all sections are compared.
31206 @subsubheading @value{GDBN} Command
31208 The @value{GDBN} equivalent is @samp{compare-sections}.
31210 @subsubheading Example
31215 @subheading The @code{-target-detach} Command
31216 @findex -target-detach
31218 @subsubheading Synopsis
31221 -target-detach [ @var{pid} | @var{gid} ]
31224 Detach from the remote target which normally resumes its execution.
31225 If either @var{pid} or @var{gid} is specified, detaches from either
31226 the specified process, or specified thread group. There's no output.
31228 @subsubheading @value{GDBN} Command
31230 The corresponding @value{GDBN} command is @samp{detach}.
31232 @subsubheading Example
31242 @subheading The @code{-target-disconnect} Command
31243 @findex -target-disconnect
31245 @subsubheading Synopsis
31251 Disconnect from the remote target. There's no output and the target is
31252 generally not resumed.
31254 @subsubheading @value{GDBN} Command
31256 The corresponding @value{GDBN} command is @samp{disconnect}.
31258 @subsubheading Example
31268 @subheading The @code{-target-download} Command
31269 @findex -target-download
31271 @subsubheading Synopsis
31277 Loads the executable onto the remote target.
31278 It prints out an update message every half second, which includes the fields:
31282 The name of the section.
31284 The size of what has been sent so far for that section.
31286 The size of the section.
31288 The total size of what was sent so far (the current and the previous sections).
31290 The size of the overall executable to download.
31294 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31295 @sc{gdb/mi} Output Syntax}).
31297 In addition, it prints the name and size of the sections, as they are
31298 downloaded. These messages include the following fields:
31302 The name of the section.
31304 The size of the section.
31306 The size of the overall executable to download.
31310 At the end, a summary is printed.
31312 @subsubheading @value{GDBN} Command
31314 The corresponding @value{GDBN} command is @samp{load}.
31316 @subsubheading Example
31318 Note: each status message appears on a single line. Here the messages
31319 have been broken down so that they can fit onto a page.
31324 +download,@{section=".text",section-size="6668",total-size="9880"@}
31325 +download,@{section=".text",section-sent="512",section-size="6668",
31326 total-sent="512",total-size="9880"@}
31327 +download,@{section=".text",section-sent="1024",section-size="6668",
31328 total-sent="1024",total-size="9880"@}
31329 +download,@{section=".text",section-sent="1536",section-size="6668",
31330 total-sent="1536",total-size="9880"@}
31331 +download,@{section=".text",section-sent="2048",section-size="6668",
31332 total-sent="2048",total-size="9880"@}
31333 +download,@{section=".text",section-sent="2560",section-size="6668",
31334 total-sent="2560",total-size="9880"@}
31335 +download,@{section=".text",section-sent="3072",section-size="6668",
31336 total-sent="3072",total-size="9880"@}
31337 +download,@{section=".text",section-sent="3584",section-size="6668",
31338 total-sent="3584",total-size="9880"@}
31339 +download,@{section=".text",section-sent="4096",section-size="6668",
31340 total-sent="4096",total-size="9880"@}
31341 +download,@{section=".text",section-sent="4608",section-size="6668",
31342 total-sent="4608",total-size="9880"@}
31343 +download,@{section=".text",section-sent="5120",section-size="6668",
31344 total-sent="5120",total-size="9880"@}
31345 +download,@{section=".text",section-sent="5632",section-size="6668",
31346 total-sent="5632",total-size="9880"@}
31347 +download,@{section=".text",section-sent="6144",section-size="6668",
31348 total-sent="6144",total-size="9880"@}
31349 +download,@{section=".text",section-sent="6656",section-size="6668",
31350 total-sent="6656",total-size="9880"@}
31351 +download,@{section=".init",section-size="28",total-size="9880"@}
31352 +download,@{section=".fini",section-size="28",total-size="9880"@}
31353 +download,@{section=".data",section-size="3156",total-size="9880"@}
31354 +download,@{section=".data",section-sent="512",section-size="3156",
31355 total-sent="7236",total-size="9880"@}
31356 +download,@{section=".data",section-sent="1024",section-size="3156",
31357 total-sent="7748",total-size="9880"@}
31358 +download,@{section=".data",section-sent="1536",section-size="3156",
31359 total-sent="8260",total-size="9880"@}
31360 +download,@{section=".data",section-sent="2048",section-size="3156",
31361 total-sent="8772",total-size="9880"@}
31362 +download,@{section=".data",section-sent="2560",section-size="3156",
31363 total-sent="9284",total-size="9880"@}
31364 +download,@{section=".data",section-sent="3072",section-size="3156",
31365 total-sent="9796",total-size="9880"@}
31366 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31373 @subheading The @code{-target-exec-status} Command
31374 @findex -target-exec-status
31376 @subsubheading Synopsis
31379 -target-exec-status
31382 Provide information on the state of the target (whether it is running or
31383 not, for instance).
31385 @subsubheading @value{GDBN} Command
31387 There's no equivalent @value{GDBN} command.
31389 @subsubheading Example
31393 @subheading The @code{-target-list-available-targets} Command
31394 @findex -target-list-available-targets
31396 @subsubheading Synopsis
31399 -target-list-available-targets
31402 List the possible targets to connect to.
31404 @subsubheading @value{GDBN} Command
31406 The corresponding @value{GDBN} command is @samp{help target}.
31408 @subsubheading Example
31412 @subheading The @code{-target-list-current-targets} Command
31413 @findex -target-list-current-targets
31415 @subsubheading Synopsis
31418 -target-list-current-targets
31421 Describe the current target.
31423 @subsubheading @value{GDBN} Command
31425 The corresponding information is printed by @samp{info file} (among
31428 @subsubheading Example
31432 @subheading The @code{-target-list-parameters} Command
31433 @findex -target-list-parameters
31435 @subsubheading Synopsis
31438 -target-list-parameters
31444 @subsubheading @value{GDBN} Command
31448 @subsubheading Example
31452 @subheading The @code{-target-select} Command
31453 @findex -target-select
31455 @subsubheading Synopsis
31458 -target-select @var{type} @var{parameters @dots{}}
31461 Connect @value{GDBN} to the remote target. This command takes two args:
31465 The type of target, for instance @samp{remote}, etc.
31466 @item @var{parameters}
31467 Device names, host names and the like. @xref{Target Commands, ,
31468 Commands for Managing Targets}, for more details.
31471 The output is a connection notification, followed by the address at
31472 which the target program is, in the following form:
31475 ^connected,addr="@var{address}",func="@var{function name}",
31476 args=[@var{arg list}]
31479 @subsubheading @value{GDBN} Command
31481 The corresponding @value{GDBN} command is @samp{target}.
31483 @subsubheading Example
31487 -target-select remote /dev/ttya
31488 ^connected,addr="0xfe00a300",func="??",args=[]
31492 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31493 @node GDB/MI File Transfer Commands
31494 @section @sc{gdb/mi} File Transfer Commands
31497 @subheading The @code{-target-file-put} Command
31498 @findex -target-file-put
31500 @subsubheading Synopsis
31503 -target-file-put @var{hostfile} @var{targetfile}
31506 Copy file @var{hostfile} from the host system (the machine running
31507 @value{GDBN}) to @var{targetfile} on the target system.
31509 @subsubheading @value{GDBN} Command
31511 The corresponding @value{GDBN} command is @samp{remote put}.
31513 @subsubheading Example
31517 -target-file-put localfile remotefile
31523 @subheading The @code{-target-file-get} Command
31524 @findex -target-file-get
31526 @subsubheading Synopsis
31529 -target-file-get @var{targetfile} @var{hostfile}
31532 Copy file @var{targetfile} from the target system to @var{hostfile}
31533 on the host system.
31535 @subsubheading @value{GDBN} Command
31537 The corresponding @value{GDBN} command is @samp{remote get}.
31539 @subsubheading Example
31543 -target-file-get remotefile localfile
31549 @subheading The @code{-target-file-delete} Command
31550 @findex -target-file-delete
31552 @subsubheading Synopsis
31555 -target-file-delete @var{targetfile}
31558 Delete @var{targetfile} from the target system.
31560 @subsubheading @value{GDBN} Command
31562 The corresponding @value{GDBN} command is @samp{remote delete}.
31564 @subsubheading Example
31568 -target-file-delete remotefile
31574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31575 @node GDB/MI Ada Exceptions Commands
31576 @section Ada Exceptions @sc{gdb/mi} Commands
31578 @subheading The @code{-info-ada-exceptions} Command
31579 @findex -info-ada-exceptions
31581 @subsubheading Synopsis
31584 -info-ada-exceptions [ @var{regexp}]
31587 List all Ada exceptions defined within the program being debugged.
31588 With a regular expression @var{regexp}, only those exceptions whose
31589 names match @var{regexp} are listed.
31591 @subsubheading @value{GDBN} Command
31593 The corresponding @value{GDBN} command is @samp{info exceptions}.
31595 @subsubheading Result
31597 The result is a table of Ada exceptions. The following columns are
31598 defined for each exception:
31602 The name of the exception.
31605 The address of the exception.
31609 @subsubheading Example
31612 -info-ada-exceptions aint
31613 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31614 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31615 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31616 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31617 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31620 @subheading Catching Ada Exceptions
31622 The commands describing how to ask @value{GDBN} to stop when a program
31623 raises an exception are described at @ref{Ada Exception GDB/MI
31624 Catchpoint Commands}.
31627 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31628 @node GDB/MI Support Commands
31629 @section @sc{gdb/mi} Support Commands
31631 Since new commands and features get regularly added to @sc{gdb/mi},
31632 some commands are available to help front-ends query the debugger
31633 about support for these capabilities. Similarly, it is also possible
31634 to query @value{GDBN} about target support of certain features.
31636 @subheading The @code{-info-gdb-mi-command} Command
31637 @cindex @code{-info-gdb-mi-command}
31638 @findex -info-gdb-mi-command
31640 @subsubheading Synopsis
31643 -info-gdb-mi-command @var{cmd_name}
31646 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31648 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31649 is technically not part of the command name (@pxref{GDB/MI Input
31650 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31651 for ease of use, this command also accepts the form with the leading
31654 @subsubheading @value{GDBN} Command
31656 There is no corresponding @value{GDBN} command.
31658 @subsubheading Result
31660 The result is a tuple. There is currently only one field:
31664 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31665 @code{"false"} otherwise.
31669 @subsubheading Example
31671 Here is an example where the @sc{gdb/mi} command does not exist:
31674 -info-gdb-mi-command unsupported-command
31675 ^done,command=@{exists="false"@}
31679 And here is an example where the @sc{gdb/mi} command is known
31683 -info-gdb-mi-command symbol-list-lines
31684 ^done,command=@{exists="true"@}
31687 @subheading The @code{-list-features} Command
31688 @findex -list-features
31689 @cindex supported @sc{gdb/mi} features, list
31691 Returns a list of particular features of the MI protocol that
31692 this version of gdb implements. A feature can be a command,
31693 or a new field in an output of some command, or even an
31694 important bugfix. While a frontend can sometimes detect presence
31695 of a feature at runtime, it is easier to perform detection at debugger
31698 The command returns a list of strings, with each string naming an
31699 available feature. Each returned string is just a name, it does not
31700 have any internal structure. The list of possible feature names
31706 (gdb) -list-features
31707 ^done,result=["feature1","feature2"]
31710 The current list of features is:
31713 @item frozen-varobjs
31714 Indicates support for the @code{-var-set-frozen} command, as well
31715 as possible presense of the @code{frozen} field in the output
31716 of @code{-varobj-create}.
31717 @item pending-breakpoints
31718 Indicates support for the @option{-f} option to the @code{-break-insert}
31721 Indicates Python scripting support, Python-based
31722 pretty-printing commands, and possible presence of the
31723 @samp{display_hint} field in the output of @code{-var-list-children}
31725 Indicates support for the @code{-thread-info} command.
31726 @item data-read-memory-bytes
31727 Indicates support for the @code{-data-read-memory-bytes} and the
31728 @code{-data-write-memory-bytes} commands.
31729 @item breakpoint-notifications
31730 Indicates that changes to breakpoints and breakpoints created via the
31731 CLI will be announced via async records.
31732 @item ada-task-info
31733 Indicates support for the @code{-ada-task-info} command.
31734 @item language-option
31735 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31736 option (@pxref{Context management}).
31737 @item info-gdb-mi-command
31738 Indicates support for the @code{-info-gdb-mi-command} command.
31739 @item undefined-command-error-code
31740 Indicates support for the "undefined-command" error code in error result
31741 records, produced when trying to execute an undefined @sc{gdb/mi} command
31742 (@pxref{GDB/MI Result Records}).
31743 @item exec-run-start-option
31744 Indicates that the @code{-exec-run} command supports the @option{--start}
31745 option (@pxref{GDB/MI Program Execution}).
31748 @subheading The @code{-list-target-features} Command
31749 @findex -list-target-features
31751 Returns a list of particular features that are supported by the
31752 target. Those features affect the permitted MI commands, but
31753 unlike the features reported by the @code{-list-features} command, the
31754 features depend on which target GDB is using at the moment. Whenever
31755 a target can change, due to commands such as @code{-target-select},
31756 @code{-target-attach} or @code{-exec-run}, the list of target features
31757 may change, and the frontend should obtain it again.
31761 (gdb) -list-target-features
31762 ^done,result=["async"]
31765 The current list of features is:
31769 Indicates that the target is capable of asynchronous command
31770 execution, which means that @value{GDBN} will accept further commands
31771 while the target is running.
31774 Indicates that the target is capable of reverse execution.
31775 @xref{Reverse Execution}, for more information.
31779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31780 @node GDB/MI Miscellaneous Commands
31781 @section Miscellaneous @sc{gdb/mi} Commands
31783 @c @subheading -gdb-complete
31785 @subheading The @code{-gdb-exit} Command
31788 @subsubheading Synopsis
31794 Exit @value{GDBN} immediately.
31796 @subsubheading @value{GDBN} Command
31798 Approximately corresponds to @samp{quit}.
31800 @subsubheading Example
31810 @subheading The @code{-exec-abort} Command
31811 @findex -exec-abort
31813 @subsubheading Synopsis
31819 Kill the inferior running program.
31821 @subsubheading @value{GDBN} Command
31823 The corresponding @value{GDBN} command is @samp{kill}.
31825 @subsubheading Example
31830 @subheading The @code{-gdb-set} Command
31833 @subsubheading Synopsis
31839 Set an internal @value{GDBN} variable.
31840 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31842 @subsubheading @value{GDBN} Command
31844 The corresponding @value{GDBN} command is @samp{set}.
31846 @subsubheading Example
31856 @subheading The @code{-gdb-show} Command
31859 @subsubheading Synopsis
31865 Show the current value of a @value{GDBN} variable.
31867 @subsubheading @value{GDBN} Command
31869 The corresponding @value{GDBN} command is @samp{show}.
31871 @subsubheading Example
31880 @c @subheading -gdb-source
31883 @subheading The @code{-gdb-version} Command
31884 @findex -gdb-version
31886 @subsubheading Synopsis
31892 Show version information for @value{GDBN}. Used mostly in testing.
31894 @subsubheading @value{GDBN} Command
31896 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31897 default shows this information when you start an interactive session.
31899 @subsubheading Example
31901 @c This example modifies the actual output from GDB to avoid overfull
31907 ~Copyright 2000 Free Software Foundation, Inc.
31908 ~GDB is free software, covered by the GNU General Public License, and
31909 ~you are welcome to change it and/or distribute copies of it under
31910 ~ certain conditions.
31911 ~Type "show copying" to see the conditions.
31912 ~There is absolutely no warranty for GDB. Type "show warranty" for
31914 ~This GDB was configured as
31915 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31920 @subheading The @code{-list-thread-groups} Command
31921 @findex -list-thread-groups
31923 @subheading Synopsis
31926 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31929 Lists thread groups (@pxref{Thread groups}). When a single thread
31930 group is passed as the argument, lists the children of that group.
31931 When several thread group are passed, lists information about those
31932 thread groups. Without any parameters, lists information about all
31933 top-level thread groups.
31935 Normally, thread groups that are being debugged are reported.
31936 With the @samp{--available} option, @value{GDBN} reports thread groups
31937 available on the target.
31939 The output of this command may have either a @samp{threads} result or
31940 a @samp{groups} result. The @samp{thread} result has a list of tuples
31941 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31942 Information}). The @samp{groups} result has a list of tuples as value,
31943 each tuple describing a thread group. If top-level groups are
31944 requested (that is, no parameter is passed), or when several groups
31945 are passed, the output always has a @samp{groups} result. The format
31946 of the @samp{group} result is described below.
31948 To reduce the number of roundtrips it's possible to list thread groups
31949 together with their children, by passing the @samp{--recurse} option
31950 and the recursion depth. Presently, only recursion depth of 1 is
31951 permitted. If this option is present, then every reported thread group
31952 will also include its children, either as @samp{group} or
31953 @samp{threads} field.
31955 In general, any combination of option and parameters is permitted, with
31956 the following caveats:
31960 When a single thread group is passed, the output will typically
31961 be the @samp{threads} result. Because threads may not contain
31962 anything, the @samp{recurse} option will be ignored.
31965 When the @samp{--available} option is passed, limited information may
31966 be available. In particular, the list of threads of a process might
31967 be inaccessible. Further, specifying specific thread groups might
31968 not give any performance advantage over listing all thread groups.
31969 The frontend should assume that @samp{-list-thread-groups --available}
31970 is always an expensive operation and cache the results.
31974 The @samp{groups} result is a list of tuples, where each tuple may
31975 have the following fields:
31979 Identifier of the thread group. This field is always present.
31980 The identifier is an opaque string; frontends should not try to
31981 convert it to an integer, even though it might look like one.
31984 The type of the thread group. At present, only @samp{process} is a
31988 The target-specific process identifier. This field is only present
31989 for thread groups of type @samp{process} and only if the process exists.
31992 The exit code of this group's last exited thread, formatted in octal.
31993 This field is only present for thread groups of type @samp{process} and
31994 only if the process is not running.
31997 The number of children this thread group has. This field may be
31998 absent for an available thread group.
32001 This field has a list of tuples as value, each tuple describing a
32002 thread. It may be present if the @samp{--recurse} option is
32003 specified, and it's actually possible to obtain the threads.
32006 This field is a list of integers, each identifying a core that one
32007 thread of the group is running on. This field may be absent if
32008 such information is not available.
32011 The name of the executable file that corresponds to this thread group.
32012 The field is only present for thread groups of type @samp{process},
32013 and only if there is a corresponding executable file.
32017 @subheading Example
32021 -list-thread-groups
32022 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32023 -list-thread-groups 17
32024 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32025 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32026 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32027 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32028 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32029 -list-thread-groups --available
32030 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32031 -list-thread-groups --available --recurse 1
32032 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32033 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32034 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32035 -list-thread-groups --available --recurse 1 17 18
32036 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32037 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32038 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32041 @subheading The @code{-info-os} Command
32044 @subsubheading Synopsis
32047 -info-os [ @var{type} ]
32050 If no argument is supplied, the command returns a table of available
32051 operating-system-specific information types. If one of these types is
32052 supplied as an argument @var{type}, then the command returns a table
32053 of data of that type.
32055 The types of information available depend on the target operating
32058 @subsubheading @value{GDBN} Command
32060 The corresponding @value{GDBN} command is @samp{info os}.
32062 @subsubheading Example
32064 When run on a @sc{gnu}/Linux system, the output will look something
32070 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32071 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32072 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32073 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32074 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32076 item=@{col0="files",col1="Listing of all file descriptors",
32077 col2="File descriptors"@},
32078 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32079 col2="Kernel modules"@},
32080 item=@{col0="msg",col1="Listing of all message queues",
32081 col2="Message queues"@},
32082 item=@{col0="processes",col1="Listing of all processes",
32083 col2="Processes"@},
32084 item=@{col0="procgroups",col1="Listing of all process groups",
32085 col2="Process groups"@},
32086 item=@{col0="semaphores",col1="Listing of all semaphores",
32087 col2="Semaphores"@},
32088 item=@{col0="shm",col1="Listing of all shared-memory regions",
32089 col2="Shared-memory regions"@},
32090 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32092 item=@{col0="threads",col1="Listing of all threads",
32096 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32097 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32098 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32099 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32100 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32101 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32102 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32103 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32105 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32106 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32110 (Note that the MI output here includes a @code{"Title"} column that
32111 does not appear in command-line @code{info os}; this column is useful
32112 for MI clients that want to enumerate the types of data, such as in a
32113 popup menu, but is needless clutter on the command line, and
32114 @code{info os} omits it.)
32116 @subheading The @code{-add-inferior} Command
32117 @findex -add-inferior
32119 @subheading Synopsis
32125 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32126 inferior is not associated with any executable. Such association may
32127 be established with the @samp{-file-exec-and-symbols} command
32128 (@pxref{GDB/MI File Commands}). The command response has a single
32129 field, @samp{inferior}, whose value is the identifier of the
32130 thread group corresponding to the new inferior.
32132 @subheading Example
32137 ^done,inferior="i3"
32140 @subheading The @code{-interpreter-exec} Command
32141 @findex -interpreter-exec
32143 @subheading Synopsis
32146 -interpreter-exec @var{interpreter} @var{command}
32148 @anchor{-interpreter-exec}
32150 Execute the specified @var{command} in the given @var{interpreter}.
32152 @subheading @value{GDBN} Command
32154 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32156 @subheading Example
32160 -interpreter-exec console "break main"
32161 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32162 &"During symbol reading, bad structure-type format.\n"
32163 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32168 @subheading The @code{-inferior-tty-set} Command
32169 @findex -inferior-tty-set
32171 @subheading Synopsis
32174 -inferior-tty-set /dev/pts/1
32177 Set terminal for future runs of the program being debugged.
32179 @subheading @value{GDBN} Command
32181 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32183 @subheading Example
32187 -inferior-tty-set /dev/pts/1
32192 @subheading The @code{-inferior-tty-show} Command
32193 @findex -inferior-tty-show
32195 @subheading Synopsis
32201 Show terminal for future runs of program being debugged.
32203 @subheading @value{GDBN} Command
32205 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32207 @subheading Example
32211 -inferior-tty-set /dev/pts/1
32215 ^done,inferior_tty_terminal="/dev/pts/1"
32219 @subheading The @code{-enable-timings} Command
32220 @findex -enable-timings
32222 @subheading Synopsis
32225 -enable-timings [yes | no]
32228 Toggle the printing of the wallclock, user and system times for an MI
32229 command as a field in its output. This command is to help frontend
32230 developers optimize the performance of their code. No argument is
32231 equivalent to @samp{yes}.
32233 @subheading @value{GDBN} Command
32237 @subheading Example
32245 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32246 addr="0x080484ed",func="main",file="myprog.c",
32247 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32249 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32257 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32258 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32259 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32260 fullname="/home/nickrob/myprog.c",line="73"@}
32265 @chapter @value{GDBN} Annotations
32267 This chapter describes annotations in @value{GDBN}. Annotations were
32268 designed to interface @value{GDBN} to graphical user interfaces or other
32269 similar programs which want to interact with @value{GDBN} at a
32270 relatively high level.
32272 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32276 This is Edition @value{EDITION}, @value{DATE}.
32280 * Annotations Overview:: What annotations are; the general syntax.
32281 * Server Prefix:: Issuing a command without affecting user state.
32282 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32283 * Errors:: Annotations for error messages.
32284 * Invalidation:: Some annotations describe things now invalid.
32285 * Annotations for Running::
32286 Whether the program is running, how it stopped, etc.
32287 * Source Annotations:: Annotations describing source code.
32290 @node Annotations Overview
32291 @section What is an Annotation?
32292 @cindex annotations
32294 Annotations start with a newline character, two @samp{control-z}
32295 characters, and the name of the annotation. If there is no additional
32296 information associated with this annotation, the name of the annotation
32297 is followed immediately by a newline. If there is additional
32298 information, the name of the annotation is followed by a space, the
32299 additional information, and a newline. The additional information
32300 cannot contain newline characters.
32302 Any output not beginning with a newline and two @samp{control-z}
32303 characters denotes literal output from @value{GDBN}. Currently there is
32304 no need for @value{GDBN} to output a newline followed by two
32305 @samp{control-z} characters, but if there was such a need, the
32306 annotations could be extended with an @samp{escape} annotation which
32307 means those three characters as output.
32309 The annotation @var{level}, which is specified using the
32310 @option{--annotate} command line option (@pxref{Mode Options}), controls
32311 how much information @value{GDBN} prints together with its prompt,
32312 values of expressions, source lines, and other types of output. Level 0
32313 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32314 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32315 for programs that control @value{GDBN}, and level 2 annotations have
32316 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32317 Interface, annotate, GDB's Obsolete Annotations}).
32320 @kindex set annotate
32321 @item set annotate @var{level}
32322 The @value{GDBN} command @code{set annotate} sets the level of
32323 annotations to the specified @var{level}.
32325 @item show annotate
32326 @kindex show annotate
32327 Show the current annotation level.
32330 This chapter describes level 3 annotations.
32332 A simple example of starting up @value{GDBN} with annotations is:
32335 $ @kbd{gdb --annotate=3}
32337 Copyright 2003 Free Software Foundation, Inc.
32338 GDB is free software, covered by the GNU General Public License,
32339 and you are welcome to change it and/or distribute copies of it
32340 under certain conditions.
32341 Type "show copying" to see the conditions.
32342 There is absolutely no warranty for GDB. Type "show warranty"
32344 This GDB was configured as "i386-pc-linux-gnu"
32355 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32356 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32357 denotes a @samp{control-z} character) are annotations; the rest is
32358 output from @value{GDBN}.
32360 @node Server Prefix
32361 @section The Server Prefix
32362 @cindex server prefix
32364 If you prefix a command with @samp{server } then it will not affect
32365 the command history, nor will it affect @value{GDBN}'s notion of which
32366 command to repeat if @key{RET} is pressed on a line by itself. This
32367 means that commands can be run behind a user's back by a front-end in
32368 a transparent manner.
32370 The @code{server } prefix does not affect the recording of values into
32371 the value history; to print a value without recording it into the
32372 value history, use the @code{output} command instead of the
32373 @code{print} command.
32375 Using this prefix also disables confirmation requests
32376 (@pxref{confirmation requests}).
32379 @section Annotation for @value{GDBN} Input
32381 @cindex annotations for prompts
32382 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32383 to know when to send output, when the output from a given command is
32386 Different kinds of input each have a different @dfn{input type}. Each
32387 input type has three annotations: a @code{pre-} annotation, which
32388 denotes the beginning of any prompt which is being output, a plain
32389 annotation, which denotes the end of the prompt, and then a @code{post-}
32390 annotation which denotes the end of any echo which may (or may not) be
32391 associated with the input. For example, the @code{prompt} input type
32392 features the following annotations:
32400 The input types are
32403 @findex pre-prompt annotation
32404 @findex prompt annotation
32405 @findex post-prompt annotation
32407 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32409 @findex pre-commands annotation
32410 @findex commands annotation
32411 @findex post-commands annotation
32413 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32414 command. The annotations are repeated for each command which is input.
32416 @findex pre-overload-choice annotation
32417 @findex overload-choice annotation
32418 @findex post-overload-choice annotation
32419 @item overload-choice
32420 When @value{GDBN} wants the user to select between various overloaded functions.
32422 @findex pre-query annotation
32423 @findex query annotation
32424 @findex post-query annotation
32426 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32428 @findex pre-prompt-for-continue annotation
32429 @findex prompt-for-continue annotation
32430 @findex post-prompt-for-continue annotation
32431 @item prompt-for-continue
32432 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32433 expect this to work well; instead use @code{set height 0} to disable
32434 prompting. This is because the counting of lines is buggy in the
32435 presence of annotations.
32440 @cindex annotations for errors, warnings and interrupts
32442 @findex quit annotation
32447 This annotation occurs right before @value{GDBN} responds to an interrupt.
32449 @findex error annotation
32454 This annotation occurs right before @value{GDBN} responds to an error.
32456 Quit and error annotations indicate that any annotations which @value{GDBN} was
32457 in the middle of may end abruptly. For example, if a
32458 @code{value-history-begin} annotation is followed by a @code{error}, one
32459 cannot expect to receive the matching @code{value-history-end}. One
32460 cannot expect not to receive it either, however; an error annotation
32461 does not necessarily mean that @value{GDBN} is immediately returning all the way
32464 @findex error-begin annotation
32465 A quit or error annotation may be preceded by
32471 Any output between that and the quit or error annotation is the error
32474 Warning messages are not yet annotated.
32475 @c If we want to change that, need to fix warning(), type_error(),
32476 @c range_error(), and possibly other places.
32479 @section Invalidation Notices
32481 @cindex annotations for invalidation messages
32482 The following annotations say that certain pieces of state may have
32486 @findex frames-invalid annotation
32487 @item ^Z^Zframes-invalid
32489 The frames (for example, output from the @code{backtrace} command) may
32492 @findex breakpoints-invalid annotation
32493 @item ^Z^Zbreakpoints-invalid
32495 The breakpoints may have changed. For example, the user just added or
32496 deleted a breakpoint.
32499 @node Annotations for Running
32500 @section Running the Program
32501 @cindex annotations for running programs
32503 @findex starting annotation
32504 @findex stopping annotation
32505 When the program starts executing due to a @value{GDBN} command such as
32506 @code{step} or @code{continue},
32512 is output. When the program stops,
32518 is output. Before the @code{stopped} annotation, a variety of
32519 annotations describe how the program stopped.
32522 @findex exited annotation
32523 @item ^Z^Zexited @var{exit-status}
32524 The program exited, and @var{exit-status} is the exit status (zero for
32525 successful exit, otherwise nonzero).
32527 @findex signalled annotation
32528 @findex signal-name annotation
32529 @findex signal-name-end annotation
32530 @findex signal-string annotation
32531 @findex signal-string-end annotation
32532 @item ^Z^Zsignalled
32533 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32534 annotation continues:
32540 ^Z^Zsignal-name-end
32544 ^Z^Zsignal-string-end
32549 where @var{name} is the name of the signal, such as @code{SIGILL} or
32550 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32551 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32552 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32553 user's benefit and have no particular format.
32555 @findex signal annotation
32557 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32558 just saying that the program received the signal, not that it was
32559 terminated with it.
32561 @findex breakpoint annotation
32562 @item ^Z^Zbreakpoint @var{number}
32563 The program hit breakpoint number @var{number}.
32565 @findex watchpoint annotation
32566 @item ^Z^Zwatchpoint @var{number}
32567 The program hit watchpoint number @var{number}.
32570 @node Source Annotations
32571 @section Displaying Source
32572 @cindex annotations for source display
32574 @findex source annotation
32575 The following annotation is used instead of displaying source code:
32578 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32581 where @var{filename} is an absolute file name indicating which source
32582 file, @var{line} is the line number within that file (where 1 is the
32583 first line in the file), @var{character} is the character position
32584 within the file (where 0 is the first character in the file) (for most
32585 debug formats this will necessarily point to the beginning of a line),
32586 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32587 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32588 @var{addr} is the address in the target program associated with the
32589 source which is being displayed. The @var{addr} is in the form @samp{0x}
32590 followed by one or more lowercase hex digits (note that this does not
32591 depend on the language).
32593 @node JIT Interface
32594 @chapter JIT Compilation Interface
32595 @cindex just-in-time compilation
32596 @cindex JIT compilation interface
32598 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32599 interface. A JIT compiler is a program or library that generates native
32600 executable code at runtime and executes it, usually in order to achieve good
32601 performance while maintaining platform independence.
32603 Programs that use JIT compilation are normally difficult to debug because
32604 portions of their code are generated at runtime, instead of being loaded from
32605 object files, which is where @value{GDBN} normally finds the program's symbols
32606 and debug information. In order to debug programs that use JIT compilation,
32607 @value{GDBN} has an interface that allows the program to register in-memory
32608 symbol files with @value{GDBN} at runtime.
32610 If you are using @value{GDBN} to debug a program that uses this interface, then
32611 it should work transparently so long as you have not stripped the binary. If
32612 you are developing a JIT compiler, then the interface is documented in the rest
32613 of this chapter. At this time, the only known client of this interface is the
32616 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32617 JIT compiler communicates with @value{GDBN} by writing data into a global
32618 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32619 attaches, it reads a linked list of symbol files from the global variable to
32620 find existing code, and puts a breakpoint in the function so that it can find
32621 out about additional code.
32624 * Declarations:: Relevant C struct declarations
32625 * Registering Code:: Steps to register code
32626 * Unregistering Code:: Steps to unregister code
32627 * Custom Debug Info:: Emit debug information in a custom format
32631 @section JIT Declarations
32633 These are the relevant struct declarations that a C program should include to
32634 implement the interface:
32644 struct jit_code_entry
32646 struct jit_code_entry *next_entry;
32647 struct jit_code_entry *prev_entry;
32648 const char *symfile_addr;
32649 uint64_t symfile_size;
32652 struct jit_descriptor
32655 /* This type should be jit_actions_t, but we use uint32_t
32656 to be explicit about the bitwidth. */
32657 uint32_t action_flag;
32658 struct jit_code_entry *relevant_entry;
32659 struct jit_code_entry *first_entry;
32662 /* GDB puts a breakpoint in this function. */
32663 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32665 /* Make sure to specify the version statically, because the
32666 debugger may check the version before we can set it. */
32667 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32670 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32671 modifications to this global data properly, which can easily be done by putting
32672 a global mutex around modifications to these structures.
32674 @node Registering Code
32675 @section Registering Code
32677 To register code with @value{GDBN}, the JIT should follow this protocol:
32681 Generate an object file in memory with symbols and other desired debug
32682 information. The file must include the virtual addresses of the sections.
32685 Create a code entry for the file, which gives the start and size of the symbol
32689 Add it to the linked list in the JIT descriptor.
32692 Point the relevant_entry field of the descriptor at the entry.
32695 Set @code{action_flag} to @code{JIT_REGISTER} and call
32696 @code{__jit_debug_register_code}.
32699 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32700 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32701 new code. However, the linked list must still be maintained in order to allow
32702 @value{GDBN} to attach to a running process and still find the symbol files.
32704 @node Unregistering Code
32705 @section Unregistering Code
32707 If code is freed, then the JIT should use the following protocol:
32711 Remove the code entry corresponding to the code from the linked list.
32714 Point the @code{relevant_entry} field of the descriptor at the code entry.
32717 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32718 @code{__jit_debug_register_code}.
32721 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32722 and the JIT will leak the memory used for the associated symbol files.
32724 @node Custom Debug Info
32725 @section Custom Debug Info
32726 @cindex custom JIT debug info
32727 @cindex JIT debug info reader
32729 Generating debug information in platform-native file formats (like ELF
32730 or COFF) may be an overkill for JIT compilers; especially if all the
32731 debug info is used for is displaying a meaningful backtrace. The
32732 issue can be resolved by having the JIT writers decide on a debug info
32733 format and also provide a reader that parses the debug info generated
32734 by the JIT compiler. This section gives a brief overview on writing
32735 such a parser. More specific details can be found in the source file
32736 @file{gdb/jit-reader.in}, which is also installed as a header at
32737 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32739 The reader is implemented as a shared object (so this functionality is
32740 not available on platforms which don't allow loading shared objects at
32741 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32742 @code{jit-reader-unload} are provided, to be used to load and unload
32743 the readers from a preconfigured directory. Once loaded, the shared
32744 object is used the parse the debug information emitted by the JIT
32748 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32749 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32752 @node Using JIT Debug Info Readers
32753 @subsection Using JIT Debug Info Readers
32754 @kindex jit-reader-load
32755 @kindex jit-reader-unload
32757 Readers can be loaded and unloaded using the @code{jit-reader-load}
32758 and @code{jit-reader-unload} commands.
32761 @item jit-reader-load @var{reader}
32762 Load the JIT reader named @var{reader}, which is a shared
32763 object specified as either an absolute or a relative file name. In
32764 the latter case, @value{GDBN} will try to load the reader from a
32765 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32766 system (here @var{libdir} is the system library directory, often
32767 @file{/usr/local/lib}).
32769 Only one reader can be active at a time; trying to load a second
32770 reader when one is already loaded will result in @value{GDBN}
32771 reporting an error. A new JIT reader can be loaded by first unloading
32772 the current one using @code{jit-reader-unload} and then invoking
32773 @code{jit-reader-load}.
32775 @item jit-reader-unload
32776 Unload the currently loaded JIT reader.
32780 @node Writing JIT Debug Info Readers
32781 @subsection Writing JIT Debug Info Readers
32782 @cindex writing JIT debug info readers
32784 As mentioned, a reader is essentially a shared object conforming to a
32785 certain ABI. This ABI is described in @file{jit-reader.h}.
32787 @file{jit-reader.h} defines the structures, macros and functions
32788 required to write a reader. It is installed (along with
32789 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32790 the system include directory.
32792 Readers need to be released under a GPL compatible license. A reader
32793 can be declared as released under such a license by placing the macro
32794 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32796 The entry point for readers is the symbol @code{gdb_init_reader},
32797 which is expected to be a function with the prototype
32799 @findex gdb_init_reader
32801 extern struct gdb_reader_funcs *gdb_init_reader (void);
32804 @cindex @code{struct gdb_reader_funcs}
32806 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32807 functions. These functions are executed to read the debug info
32808 generated by the JIT compiler (@code{read}), to unwind stack frames
32809 (@code{unwind}) and to create canonical frame IDs
32810 (@code{get_Frame_id}). It also has a callback that is called when the
32811 reader is being unloaded (@code{destroy}). The struct looks like this
32814 struct gdb_reader_funcs
32816 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32817 int reader_version;
32819 /* For use by the reader. */
32822 gdb_read_debug_info *read;
32823 gdb_unwind_frame *unwind;
32824 gdb_get_frame_id *get_frame_id;
32825 gdb_destroy_reader *destroy;
32829 @cindex @code{struct gdb_symbol_callbacks}
32830 @cindex @code{struct gdb_unwind_callbacks}
32832 The callbacks are provided with another set of callbacks by
32833 @value{GDBN} to do their job. For @code{read}, these callbacks are
32834 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32835 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32836 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32837 files and new symbol tables inside those object files. @code{struct
32838 gdb_unwind_callbacks} has callbacks to read registers off the current
32839 frame and to write out the values of the registers in the previous
32840 frame. Both have a callback (@code{target_read}) to read bytes off the
32841 target's address space.
32843 @node In-Process Agent
32844 @chapter In-Process Agent
32845 @cindex debugging agent
32846 The traditional debugging model is conceptually low-speed, but works fine,
32847 because most bugs can be reproduced in debugging-mode execution. However,
32848 as multi-core or many-core processors are becoming mainstream, and
32849 multi-threaded programs become more and more popular, there should be more
32850 and more bugs that only manifest themselves at normal-mode execution, for
32851 example, thread races, because debugger's interference with the program's
32852 timing may conceal the bugs. On the other hand, in some applications,
32853 it is not feasible for the debugger to interrupt the program's execution
32854 long enough for the developer to learn anything helpful about its behavior.
32855 If the program's correctness depends on its real-time behavior, delays
32856 introduced by a debugger might cause the program to fail, even when the
32857 code itself is correct. It is useful to be able to observe the program's
32858 behavior without interrupting it.
32860 Therefore, traditional debugging model is too intrusive to reproduce
32861 some bugs. In order to reduce the interference with the program, we can
32862 reduce the number of operations performed by debugger. The
32863 @dfn{In-Process Agent}, a shared library, is running within the same
32864 process with inferior, and is able to perform some debugging operations
32865 itself. As a result, debugger is only involved when necessary, and
32866 performance of debugging can be improved accordingly. Note that
32867 interference with program can be reduced but can't be removed completely,
32868 because the in-process agent will still stop or slow down the program.
32870 The in-process agent can interpret and execute Agent Expressions
32871 (@pxref{Agent Expressions}) during performing debugging operations. The
32872 agent expressions can be used for different purposes, such as collecting
32873 data in tracepoints, and condition evaluation in breakpoints.
32875 @anchor{Control Agent}
32876 You can control whether the in-process agent is used as an aid for
32877 debugging with the following commands:
32880 @kindex set agent on
32882 Causes the in-process agent to perform some operations on behalf of the
32883 debugger. Just which operations requested by the user will be done
32884 by the in-process agent depends on the its capabilities. For example,
32885 if you request to evaluate breakpoint conditions in the in-process agent,
32886 and the in-process agent has such capability as well, then breakpoint
32887 conditions will be evaluated in the in-process agent.
32889 @kindex set agent off
32890 @item set agent off
32891 Disables execution of debugging operations by the in-process agent. All
32892 of the operations will be performed by @value{GDBN}.
32896 Display the current setting of execution of debugging operations by
32897 the in-process agent.
32901 * In-Process Agent Protocol::
32904 @node In-Process Agent Protocol
32905 @section In-Process Agent Protocol
32906 @cindex in-process agent protocol
32908 The in-process agent is able to communicate with both @value{GDBN} and
32909 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32910 used for communications between @value{GDBN} or GDBserver and the IPA.
32911 In general, @value{GDBN} or GDBserver sends commands
32912 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32913 in-process agent replies back with the return result of the command, or
32914 some other information. The data sent to in-process agent is composed
32915 of primitive data types, such as 4-byte or 8-byte type, and composite
32916 types, which are called objects (@pxref{IPA Protocol Objects}).
32919 * IPA Protocol Objects::
32920 * IPA Protocol Commands::
32923 @node IPA Protocol Objects
32924 @subsection IPA Protocol Objects
32925 @cindex ipa protocol objects
32927 The commands sent to and results received from agent may contain some
32928 complex data types called @dfn{objects}.
32930 The in-process agent is running on the same machine with @value{GDBN}
32931 or GDBserver, so it doesn't have to handle as much differences between
32932 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32933 However, there are still some differences of two ends in two processes:
32937 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32938 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32940 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32941 GDBserver is compiled with one, and in-process agent is compiled with
32945 Here are the IPA Protocol Objects:
32949 agent expression object. It represents an agent expression
32950 (@pxref{Agent Expressions}).
32951 @anchor{agent expression object}
32953 tracepoint action object. It represents a tracepoint action
32954 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32955 memory, static trace data and to evaluate expression.
32956 @anchor{tracepoint action object}
32958 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32959 @anchor{tracepoint object}
32963 The following table describes important attributes of each IPA protocol
32966 @multitable @columnfractions .30 .20 .50
32967 @headitem Name @tab Size @tab Description
32968 @item @emph{agent expression object} @tab @tab
32969 @item length @tab 4 @tab length of bytes code
32970 @item byte code @tab @var{length} @tab contents of byte code
32971 @item @emph{tracepoint action for collecting memory} @tab @tab
32972 @item 'M' @tab 1 @tab type of tracepoint action
32973 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32974 address of the lowest byte to collect, otherwise @var{addr} is the offset
32975 of @var{basereg} for memory collecting.
32976 @item len @tab 8 @tab length of memory for collecting
32977 @item basereg @tab 4 @tab the register number containing the starting
32978 memory address for collecting.
32979 @item @emph{tracepoint action for collecting registers} @tab @tab
32980 @item 'R' @tab 1 @tab type of tracepoint action
32981 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32982 @item 'L' @tab 1 @tab type of tracepoint action
32983 @item @emph{tracepoint action for expression evaluation} @tab @tab
32984 @item 'X' @tab 1 @tab type of tracepoint action
32985 @item agent expression @tab length of @tab @ref{agent expression object}
32986 @item @emph{tracepoint object} @tab @tab
32987 @item number @tab 4 @tab number of tracepoint
32988 @item address @tab 8 @tab address of tracepoint inserted on
32989 @item type @tab 4 @tab type of tracepoint
32990 @item enabled @tab 1 @tab enable or disable of tracepoint
32991 @item step_count @tab 8 @tab step
32992 @item pass_count @tab 8 @tab pass
32993 @item numactions @tab 4 @tab number of tracepoint actions
32994 @item hit count @tab 8 @tab hit count
32995 @item trace frame usage @tab 8 @tab trace frame usage
32996 @item compiled_cond @tab 8 @tab compiled condition
32997 @item orig_size @tab 8 @tab orig size
32998 @item condition @tab 4 if condition is NULL otherwise length of
32999 @ref{agent expression object}
33000 @tab zero if condition is NULL, otherwise is
33001 @ref{agent expression object}
33002 @item actions @tab variable
33003 @tab numactions number of @ref{tracepoint action object}
33006 @node IPA Protocol Commands
33007 @subsection IPA Protocol Commands
33008 @cindex ipa protocol commands
33010 The spaces in each command are delimiters to ease reading this commands
33011 specification. They don't exist in real commands.
33015 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33016 Installs a new fast tracepoint described by @var{tracepoint_object}
33017 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33018 head of @dfn{jumppad}, which is used to jump to data collection routine
33023 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33024 @var{target_address} is address of tracepoint in the inferior.
33025 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33026 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33027 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33028 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33035 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33036 is about to kill inferiors.
33044 @item probe_marker_at:@var{address}
33045 Asks in-process agent to probe the marker at @var{address}.
33052 @item unprobe_marker_at:@var{address}
33053 Asks in-process agent to unprobe the marker at @var{address}.
33057 @chapter Reporting Bugs in @value{GDBN}
33058 @cindex bugs in @value{GDBN}
33059 @cindex reporting bugs in @value{GDBN}
33061 Your bug reports play an essential role in making @value{GDBN} reliable.
33063 Reporting a bug may help you by bringing a solution to your problem, or it
33064 may not. But in any case the principal function of a bug report is to help
33065 the entire community by making the next version of @value{GDBN} work better. Bug
33066 reports are your contribution to the maintenance of @value{GDBN}.
33068 In order for a bug report to serve its purpose, you must include the
33069 information that enables us to fix the bug.
33072 * Bug Criteria:: Have you found a bug?
33073 * Bug Reporting:: How to report bugs
33077 @section Have You Found a Bug?
33078 @cindex bug criteria
33080 If you are not sure whether you have found a bug, here are some guidelines:
33083 @cindex fatal signal
33084 @cindex debugger crash
33085 @cindex crash of debugger
33087 If the debugger gets a fatal signal, for any input whatever, that is a
33088 @value{GDBN} bug. Reliable debuggers never crash.
33090 @cindex error on valid input
33092 If @value{GDBN} produces an error message for valid input, that is a
33093 bug. (Note that if you're cross debugging, the problem may also be
33094 somewhere in the connection to the target.)
33096 @cindex invalid input
33098 If @value{GDBN} does not produce an error message for invalid input,
33099 that is a bug. However, you should note that your idea of
33100 ``invalid input'' might be our idea of ``an extension'' or ``support
33101 for traditional practice''.
33104 If you are an experienced user of debugging tools, your suggestions
33105 for improvement of @value{GDBN} are welcome in any case.
33108 @node Bug Reporting
33109 @section How to Report Bugs
33110 @cindex bug reports
33111 @cindex @value{GDBN} bugs, reporting
33113 A number of companies and individuals offer support for @sc{gnu} products.
33114 If you obtained @value{GDBN} from a support organization, we recommend you
33115 contact that organization first.
33117 You can find contact information for many support companies and
33118 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33120 @c should add a web page ref...
33123 @ifset BUGURL_DEFAULT
33124 In any event, we also recommend that you submit bug reports for
33125 @value{GDBN}. The preferred method is to submit them directly using
33126 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33127 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33130 @strong{Do not send bug reports to @samp{info-gdb}, or to
33131 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33132 not want to receive bug reports. Those that do have arranged to receive
33135 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33136 serves as a repeater. The mailing list and the newsgroup carry exactly
33137 the same messages. Often people think of posting bug reports to the
33138 newsgroup instead of mailing them. This appears to work, but it has one
33139 problem which can be crucial: a newsgroup posting often lacks a mail
33140 path back to the sender. Thus, if we need to ask for more information,
33141 we may be unable to reach you. For this reason, it is better to send
33142 bug reports to the mailing list.
33144 @ifclear BUGURL_DEFAULT
33145 In any event, we also recommend that you submit bug reports for
33146 @value{GDBN} to @value{BUGURL}.
33150 The fundamental principle of reporting bugs usefully is this:
33151 @strong{report all the facts}. If you are not sure whether to state a
33152 fact or leave it out, state it!
33154 Often people omit facts because they think they know what causes the
33155 problem and assume that some details do not matter. Thus, you might
33156 assume that the name of the variable you use in an example does not matter.
33157 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33158 stray memory reference which happens to fetch from the location where that
33159 name is stored in memory; perhaps, if the name were different, the contents
33160 of that location would fool the debugger into doing the right thing despite
33161 the bug. Play it safe and give a specific, complete example. That is the
33162 easiest thing for you to do, and the most helpful.
33164 Keep in mind that the purpose of a bug report is to enable us to fix the
33165 bug. It may be that the bug has been reported previously, but neither
33166 you nor we can know that unless your bug report is complete and
33169 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33170 bell?'' Those bug reports are useless, and we urge everyone to
33171 @emph{refuse to respond to them} except to chide the sender to report
33174 To enable us to fix the bug, you should include all these things:
33178 The version of @value{GDBN}. @value{GDBN} announces it if you start
33179 with no arguments; you can also print it at any time using @code{show
33182 Without this, we will not know whether there is any point in looking for
33183 the bug in the current version of @value{GDBN}.
33186 The type of machine you are using, and the operating system name and
33190 The details of the @value{GDBN} build-time configuration.
33191 @value{GDBN} shows these details if you invoke it with the
33192 @option{--configuration} command-line option, or if you type
33193 @code{show configuration} at @value{GDBN}'s prompt.
33196 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33197 ``@value{GCC}--2.8.1''.
33200 What compiler (and its version) was used to compile the program you are
33201 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33202 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33203 to get this information; for other compilers, see the documentation for
33207 The command arguments you gave the compiler to compile your example and
33208 observe the bug. For example, did you use @samp{-O}? To guarantee
33209 you will not omit something important, list them all. A copy of the
33210 Makefile (or the output from make) is sufficient.
33212 If we were to try to guess the arguments, we would probably guess wrong
33213 and then we might not encounter the bug.
33216 A complete input script, and all necessary source files, that will
33220 A description of what behavior you observe that you believe is
33221 incorrect. For example, ``It gets a fatal signal.''
33223 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33224 will certainly notice it. But if the bug is incorrect output, we might
33225 not notice unless it is glaringly wrong. You might as well not give us
33226 a chance to make a mistake.
33228 Even if the problem you experience is a fatal signal, you should still
33229 say so explicitly. Suppose something strange is going on, such as, your
33230 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33231 the C library on your system. (This has happened!) Your copy might
33232 crash and ours would not. If you told us to expect a crash, then when
33233 ours fails to crash, we would know that the bug was not happening for
33234 us. If you had not told us to expect a crash, then we would not be able
33235 to draw any conclusion from our observations.
33238 @cindex recording a session script
33239 To collect all this information, you can use a session recording program
33240 such as @command{script}, which is available on many Unix systems.
33241 Just run your @value{GDBN} session inside @command{script} and then
33242 include the @file{typescript} file with your bug report.
33244 Another way to record a @value{GDBN} session is to run @value{GDBN}
33245 inside Emacs and then save the entire buffer to a file.
33248 If you wish to suggest changes to the @value{GDBN} source, send us context
33249 diffs. If you even discuss something in the @value{GDBN} source, refer to
33250 it by context, not by line number.
33252 The line numbers in our development sources will not match those in your
33253 sources. Your line numbers would convey no useful information to us.
33257 Here are some things that are not necessary:
33261 A description of the envelope of the bug.
33263 Often people who encounter a bug spend a lot of time investigating
33264 which changes to the input file will make the bug go away and which
33265 changes will not affect it.
33267 This is often time consuming and not very useful, because the way we
33268 will find the bug is by running a single example under the debugger
33269 with breakpoints, not by pure deduction from a series of examples.
33270 We recommend that you save your time for something else.
33272 Of course, if you can find a simpler example to report @emph{instead}
33273 of the original one, that is a convenience for us. Errors in the
33274 output will be easier to spot, running under the debugger will take
33275 less time, and so on.
33277 However, simplification is not vital; if you do not want to do this,
33278 report the bug anyway and send us the entire test case you used.
33281 A patch for the bug.
33283 A patch for the bug does help us if it is a good one. But do not omit
33284 the necessary information, such as the test case, on the assumption that
33285 a patch is all we need. We might see problems with your patch and decide
33286 to fix the problem another way, or we might not understand it at all.
33288 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33289 construct an example that will make the program follow a certain path
33290 through the code. If you do not send us the example, we will not be able
33291 to construct one, so we will not be able to verify that the bug is fixed.
33293 And if we cannot understand what bug you are trying to fix, or why your
33294 patch should be an improvement, we will not install it. A test case will
33295 help us to understand.
33298 A guess about what the bug is or what it depends on.
33300 Such guesses are usually wrong. Even we cannot guess right about such
33301 things without first using the debugger to find the facts.
33304 @c The readline documentation is distributed with the readline code
33305 @c and consists of the two following files:
33308 @c Use -I with makeinfo to point to the appropriate directory,
33309 @c environment var TEXINPUTS with TeX.
33310 @ifclear SYSTEM_READLINE
33311 @include rluser.texi
33312 @include hsuser.texi
33316 @appendix In Memoriam
33318 The @value{GDBN} project mourns the loss of the following long-time
33323 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33324 to Free Software in general. Outside of @value{GDBN}, he was known in
33325 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33327 @item Michael Snyder
33328 Michael was one of the Global Maintainers of the @value{GDBN} project,
33329 with contributions recorded as early as 1996, until 2011. In addition
33330 to his day to day participation, he was a large driving force behind
33331 adding Reverse Debugging to @value{GDBN}.
33334 Beyond their technical contributions to the project, they were also
33335 enjoyable members of the Free Software Community. We will miss them.
33337 @node Formatting Documentation
33338 @appendix Formatting Documentation
33340 @cindex @value{GDBN} reference card
33341 @cindex reference card
33342 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33343 for printing with PostScript or Ghostscript, in the @file{gdb}
33344 subdirectory of the main source directory@footnote{In
33345 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33346 release.}. If you can use PostScript or Ghostscript with your printer,
33347 you can print the reference card immediately with @file{refcard.ps}.
33349 The release also includes the source for the reference card. You
33350 can format it, using @TeX{}, by typing:
33356 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33357 mode on US ``letter'' size paper;
33358 that is, on a sheet 11 inches wide by 8.5 inches
33359 high. You will need to specify this form of printing as an option to
33360 your @sc{dvi} output program.
33362 @cindex documentation
33364 All the documentation for @value{GDBN} comes as part of the machine-readable
33365 distribution. The documentation is written in Texinfo format, which is
33366 a documentation system that uses a single source file to produce both
33367 on-line information and a printed manual. You can use one of the Info
33368 formatting commands to create the on-line version of the documentation
33369 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33371 @value{GDBN} includes an already formatted copy of the on-line Info
33372 version of this manual in the @file{gdb} subdirectory. The main Info
33373 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33374 subordinate files matching @samp{gdb.info*} in the same directory. If
33375 necessary, you can print out these files, or read them with any editor;
33376 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33377 Emacs or the standalone @code{info} program, available as part of the
33378 @sc{gnu} Texinfo distribution.
33380 If you want to format these Info files yourself, you need one of the
33381 Info formatting programs, such as @code{texinfo-format-buffer} or
33384 If you have @code{makeinfo} installed, and are in the top level
33385 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33386 version @value{GDBVN}), you can make the Info file by typing:
33393 If you want to typeset and print copies of this manual, you need @TeX{},
33394 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33395 Texinfo definitions file.
33397 @TeX{} is a typesetting program; it does not print files directly, but
33398 produces output files called @sc{dvi} files. To print a typeset
33399 document, you need a program to print @sc{dvi} files. If your system
33400 has @TeX{} installed, chances are it has such a program. The precise
33401 command to use depends on your system; @kbd{lpr -d} is common; another
33402 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33403 require a file name without any extension or a @samp{.dvi} extension.
33405 @TeX{} also requires a macro definitions file called
33406 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33407 written in Texinfo format. On its own, @TeX{} cannot either read or
33408 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33409 and is located in the @file{gdb-@var{version-number}/texinfo}
33412 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33413 typeset and print this manual. First switch to the @file{gdb}
33414 subdirectory of the main source directory (for example, to
33415 @file{gdb-@value{GDBVN}/gdb}) and type:
33421 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33423 @node Installing GDB
33424 @appendix Installing @value{GDBN}
33425 @cindex installation
33428 * Requirements:: Requirements for building @value{GDBN}
33429 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33430 * Separate Objdir:: Compiling @value{GDBN} in another directory
33431 * Config Names:: Specifying names for hosts and targets
33432 * Configure Options:: Summary of options for configure
33433 * System-wide configuration:: Having a system-wide init file
33437 @section Requirements for Building @value{GDBN}
33438 @cindex building @value{GDBN}, requirements for
33440 Building @value{GDBN} requires various tools and packages to be available.
33441 Other packages will be used only if they are found.
33443 @heading Tools/Packages Necessary for Building @value{GDBN}
33445 @item ISO C90 compiler
33446 @value{GDBN} is written in ISO C90. It should be buildable with any
33447 working C90 compiler, e.g.@: GCC.
33451 @heading Tools/Packages Optional for Building @value{GDBN}
33455 @value{GDBN} can use the Expat XML parsing library. This library may be
33456 included with your operating system distribution; if it is not, you
33457 can get the latest version from @url{http://expat.sourceforge.net}.
33458 The @file{configure} script will search for this library in several
33459 standard locations; if it is installed in an unusual path, you can
33460 use the @option{--with-libexpat-prefix} option to specify its location.
33466 Remote protocol memory maps (@pxref{Memory Map Format})
33468 Target descriptions (@pxref{Target Descriptions})
33470 Remote shared library lists (@xref{Library List Format},
33471 or alternatively @pxref{Library List Format for SVR4 Targets})
33473 MS-Windows shared libraries (@pxref{Shared Libraries})
33475 Traceframe info (@pxref{Traceframe Info Format})
33477 Branch trace (@pxref{Branch Trace Format},
33478 @pxref{Branch Trace Configuration Format})
33482 @cindex compressed debug sections
33483 @value{GDBN} will use the @samp{zlib} library, if available, to read
33484 compressed debug sections. Some linkers, such as GNU gold, are capable
33485 of producing binaries with compressed debug sections. If @value{GDBN}
33486 is compiled with @samp{zlib}, it will be able to read the debug
33487 information in such binaries.
33489 The @samp{zlib} library is likely included with your operating system
33490 distribution; if it is not, you can get the latest version from
33491 @url{http://zlib.net}.
33494 @value{GDBN}'s features related to character sets (@pxref{Character
33495 Sets}) require a functioning @code{iconv} implementation. If you are
33496 on a GNU system, then this is provided by the GNU C Library. Some
33497 other systems also provide a working @code{iconv}.
33499 If @value{GDBN} is using the @code{iconv} program which is installed
33500 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33501 This is done with @option{--with-iconv-bin} which specifies the
33502 directory that contains the @code{iconv} program.
33504 On systems without @code{iconv}, you can install GNU Libiconv. If you
33505 have previously installed Libiconv, you can use the
33506 @option{--with-libiconv-prefix} option to configure.
33508 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33509 arrange to build Libiconv if a directory named @file{libiconv} appears
33510 in the top-most source directory. If Libiconv is built this way, and
33511 if the operating system does not provide a suitable @code{iconv}
33512 implementation, then the just-built library will automatically be used
33513 by @value{GDBN}. One easy way to set this up is to download GNU
33514 Libiconv, unpack it, and then rename the directory holding the
33515 Libiconv source code to @samp{libiconv}.
33518 @node Running Configure
33519 @section Invoking the @value{GDBN} @file{configure} Script
33520 @cindex configuring @value{GDBN}
33521 @value{GDBN} comes with a @file{configure} script that automates the process
33522 of preparing @value{GDBN} for installation; you can then use @code{make} to
33523 build the @code{gdb} program.
33525 @c irrelevant in info file; it's as current as the code it lives with.
33526 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33527 look at the @file{README} file in the sources; we may have improved the
33528 installation procedures since publishing this manual.}
33531 The @value{GDBN} distribution includes all the source code you need for
33532 @value{GDBN} in a single directory, whose name is usually composed by
33533 appending the version number to @samp{gdb}.
33535 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33536 @file{gdb-@value{GDBVN}} directory. That directory contains:
33539 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33540 script for configuring @value{GDBN} and all its supporting libraries
33542 @item gdb-@value{GDBVN}/gdb
33543 the source specific to @value{GDBN} itself
33545 @item gdb-@value{GDBVN}/bfd
33546 source for the Binary File Descriptor library
33548 @item gdb-@value{GDBVN}/include
33549 @sc{gnu} include files
33551 @item gdb-@value{GDBVN}/libiberty
33552 source for the @samp{-liberty} free software library
33554 @item gdb-@value{GDBVN}/opcodes
33555 source for the library of opcode tables and disassemblers
33557 @item gdb-@value{GDBVN}/readline
33558 source for the @sc{gnu} command-line interface
33560 @item gdb-@value{GDBVN}/glob
33561 source for the @sc{gnu} filename pattern-matching subroutine
33563 @item gdb-@value{GDBVN}/mmalloc
33564 source for the @sc{gnu} memory-mapped malloc package
33567 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33568 from the @file{gdb-@var{version-number}} source directory, which in
33569 this example is the @file{gdb-@value{GDBVN}} directory.
33571 First switch to the @file{gdb-@var{version-number}} source directory
33572 if you are not already in it; then run @file{configure}. Pass the
33573 identifier for the platform on which @value{GDBN} will run as an
33579 cd gdb-@value{GDBVN}
33580 ./configure @var{host}
33585 where @var{host} is an identifier such as @samp{sun4} or
33586 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33587 (You can often leave off @var{host}; @file{configure} tries to guess the
33588 correct value by examining your system.)
33590 Running @samp{configure @var{host}} and then running @code{make} builds the
33591 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33592 libraries, then @code{gdb} itself. The configured source files, and the
33593 binaries, are left in the corresponding source directories.
33596 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33597 system does not recognize this automatically when you run a different
33598 shell, you may need to run @code{sh} on it explicitly:
33601 sh configure @var{host}
33604 If you run @file{configure} from a directory that contains source
33605 directories for multiple libraries or programs, such as the
33606 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33608 creates configuration files for every directory level underneath (unless
33609 you tell it not to, with the @samp{--norecursion} option).
33611 You should run the @file{configure} script from the top directory in the
33612 source tree, the @file{gdb-@var{version-number}} directory. If you run
33613 @file{configure} from one of the subdirectories, you will configure only
33614 that subdirectory. That is usually not what you want. In particular,
33615 if you run the first @file{configure} from the @file{gdb} subdirectory
33616 of the @file{gdb-@var{version-number}} directory, you will omit the
33617 configuration of @file{bfd}, @file{readline}, and other sibling
33618 directories of the @file{gdb} subdirectory. This leads to build errors
33619 about missing include files such as @file{bfd/bfd.h}.
33621 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33622 However, you should make sure that the shell on your path (named by
33623 the @samp{SHELL} environment variable) is publicly readable. Remember
33624 that @value{GDBN} uses the shell to start your program---some systems refuse to
33625 let @value{GDBN} debug child processes whose programs are not readable.
33627 @node Separate Objdir
33628 @section Compiling @value{GDBN} in Another Directory
33630 If you want to run @value{GDBN} versions for several host or target machines,
33631 you need a different @code{gdb} compiled for each combination of
33632 host and target. @file{configure} is designed to make this easy by
33633 allowing you to generate each configuration in a separate subdirectory,
33634 rather than in the source directory. If your @code{make} program
33635 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33636 @code{make} in each of these directories builds the @code{gdb}
33637 program specified there.
33639 To build @code{gdb} in a separate directory, run @file{configure}
33640 with the @samp{--srcdir} option to specify where to find the source.
33641 (You also need to specify a path to find @file{configure}
33642 itself from your working directory. If the path to @file{configure}
33643 would be the same as the argument to @samp{--srcdir}, you can leave out
33644 the @samp{--srcdir} option; it is assumed.)
33646 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33647 separate directory for a Sun 4 like this:
33651 cd gdb-@value{GDBVN}
33654 ../gdb-@value{GDBVN}/configure sun4
33659 When @file{configure} builds a configuration using a remote source
33660 directory, it creates a tree for the binaries with the same structure
33661 (and using the same names) as the tree under the source directory. In
33662 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33663 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33664 @file{gdb-sun4/gdb}.
33666 Make sure that your path to the @file{configure} script has just one
33667 instance of @file{gdb} in it. If your path to @file{configure} looks
33668 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33669 one subdirectory of @value{GDBN}, not the whole package. This leads to
33670 build errors about missing include files such as @file{bfd/bfd.h}.
33672 One popular reason to build several @value{GDBN} configurations in separate
33673 directories is to configure @value{GDBN} for cross-compiling (where
33674 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33675 programs that run on another machine---the @dfn{target}).
33676 You specify a cross-debugging target by
33677 giving the @samp{--target=@var{target}} option to @file{configure}.
33679 When you run @code{make} to build a program or library, you must run
33680 it in a configured directory---whatever directory you were in when you
33681 called @file{configure} (or one of its subdirectories).
33683 The @code{Makefile} that @file{configure} generates in each source
33684 directory also runs recursively. If you type @code{make} in a source
33685 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33686 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33687 will build all the required libraries, and then build GDB.
33689 When you have multiple hosts or targets configured in separate
33690 directories, you can run @code{make} on them in parallel (for example,
33691 if they are NFS-mounted on each of the hosts); they will not interfere
33695 @section Specifying Names for Hosts and Targets
33697 The specifications used for hosts and targets in the @file{configure}
33698 script are based on a three-part naming scheme, but some short predefined
33699 aliases are also supported. The full naming scheme encodes three pieces
33700 of information in the following pattern:
33703 @var{architecture}-@var{vendor}-@var{os}
33706 For example, you can use the alias @code{sun4} as a @var{host} argument,
33707 or as the value for @var{target} in a @code{--target=@var{target}}
33708 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33710 The @file{configure} script accompanying @value{GDBN} does not provide
33711 any query facility to list all supported host and target names or
33712 aliases. @file{configure} calls the Bourne shell script
33713 @code{config.sub} to map abbreviations to full names; you can read the
33714 script, if you wish, or you can use it to test your guesses on
33715 abbreviations---for example:
33718 % sh config.sub i386-linux
33720 % sh config.sub alpha-linux
33721 alpha-unknown-linux-gnu
33722 % sh config.sub hp9k700
33724 % sh config.sub sun4
33725 sparc-sun-sunos4.1.1
33726 % sh config.sub sun3
33727 m68k-sun-sunos4.1.1
33728 % sh config.sub i986v
33729 Invalid configuration `i986v': machine `i986v' not recognized
33733 @code{config.sub} is also distributed in the @value{GDBN} source
33734 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33736 @node Configure Options
33737 @section @file{configure} Options
33739 Here is a summary of the @file{configure} options and arguments that
33740 are most often useful for building @value{GDBN}. @file{configure} also has
33741 several other options not listed here. @inforef{What Configure
33742 Does,,configure.info}, for a full explanation of @file{configure}.
33745 configure @r{[}--help@r{]}
33746 @r{[}--prefix=@var{dir}@r{]}
33747 @r{[}--exec-prefix=@var{dir}@r{]}
33748 @r{[}--srcdir=@var{dirname}@r{]}
33749 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33750 @r{[}--target=@var{target}@r{]}
33755 You may introduce options with a single @samp{-} rather than
33756 @samp{--} if you prefer; but you may abbreviate option names if you use
33761 Display a quick summary of how to invoke @file{configure}.
33763 @item --prefix=@var{dir}
33764 Configure the source to install programs and files under directory
33767 @item --exec-prefix=@var{dir}
33768 Configure the source to install programs under directory
33771 @c avoid splitting the warning from the explanation:
33773 @item --srcdir=@var{dirname}
33774 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33775 @code{make} that implements the @code{VPATH} feature.}@*
33776 Use this option to make configurations in directories separate from the
33777 @value{GDBN} source directories. Among other things, you can use this to
33778 build (or maintain) several configurations simultaneously, in separate
33779 directories. @file{configure} writes configuration-specific files in
33780 the current directory, but arranges for them to use the source in the
33781 directory @var{dirname}. @file{configure} creates directories under
33782 the working directory in parallel to the source directories below
33785 @item --norecursion
33786 Configure only the directory level where @file{configure} is executed; do not
33787 propagate configuration to subdirectories.
33789 @item --target=@var{target}
33790 Configure @value{GDBN} for cross-debugging programs running on the specified
33791 @var{target}. Without this option, @value{GDBN} is configured to debug
33792 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33794 There is no convenient way to generate a list of all available targets.
33796 @item @var{host} @dots{}
33797 Configure @value{GDBN} to run on the specified @var{host}.
33799 There is no convenient way to generate a list of all available hosts.
33802 There are many other options available as well, but they are generally
33803 needed for special purposes only.
33805 @node System-wide configuration
33806 @section System-wide configuration and settings
33807 @cindex system-wide init file
33809 @value{GDBN} can be configured to have a system-wide init file;
33810 this file will be read and executed at startup (@pxref{Startup, , What
33811 @value{GDBN} does during startup}).
33813 Here is the corresponding configure option:
33816 @item --with-system-gdbinit=@var{file}
33817 Specify that the default location of the system-wide init file is
33821 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33822 it may be subject to relocation. Two possible cases:
33826 If the default location of this init file contains @file{$prefix},
33827 it will be subject to relocation. Suppose that the configure options
33828 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33829 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33830 init file is looked for as @file{$install/etc/gdbinit} instead of
33831 @file{$prefix/etc/gdbinit}.
33834 By contrast, if the default location does not contain the prefix,
33835 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33836 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33837 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33838 wherever @value{GDBN} is installed.
33841 If the configured location of the system-wide init file (as given by the
33842 @option{--with-system-gdbinit} option at configure time) is in the
33843 data-directory (as specified by @option{--with-gdb-datadir} at configure
33844 time) or in one of its subdirectories, then @value{GDBN} will look for the
33845 system-wide init file in the directory specified by the
33846 @option{--data-directory} command-line option.
33847 Note that the system-wide init file is only read once, during @value{GDBN}
33848 initialization. If the data-directory is changed after @value{GDBN} has
33849 started with the @code{set data-directory} command, the file will not be
33853 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33856 @node System-wide Configuration Scripts
33857 @subsection Installed System-wide Configuration Scripts
33858 @cindex system-wide configuration scripts
33860 The @file{system-gdbinit} directory, located inside the data-directory
33861 (as specified by @option{--with-gdb-datadir} at configure time) contains
33862 a number of scripts which can be used as system-wide init files. To
33863 automatically source those scripts at startup, @value{GDBN} should be
33864 configured with @option{--with-system-gdbinit}. Otherwise, any user
33865 should be able to source them by hand as needed.
33867 The following scripts are currently available:
33870 @item @file{elinos.py}
33872 @cindex ELinOS system-wide configuration script
33873 This script is useful when debugging a program on an ELinOS target.
33874 It takes advantage of the environment variables defined in a standard
33875 ELinOS environment in order to determine the location of the system
33876 shared libraries, and then sets the @samp{solib-absolute-prefix}
33877 and @samp{solib-search-path} variables appropriately.
33879 @item @file{wrs-linux.py}
33880 @pindex wrs-linux.py
33881 @cindex Wind River Linux system-wide configuration script
33882 This script is useful when debugging a program on a target running
33883 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33884 the host-side sysroot used by the target system.
33888 @node Maintenance Commands
33889 @appendix Maintenance Commands
33890 @cindex maintenance commands
33891 @cindex internal commands
33893 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33894 includes a number of commands intended for @value{GDBN} developers,
33895 that are not documented elsewhere in this manual. These commands are
33896 provided here for reference. (For commands that turn on debugging
33897 messages, see @ref{Debugging Output}.)
33900 @kindex maint agent
33901 @kindex maint agent-eval
33902 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33903 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33904 Translate the given @var{expression} into remote agent bytecodes.
33905 This command is useful for debugging the Agent Expression mechanism
33906 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33907 expression useful for data collection, such as by tracepoints, while
33908 @samp{maint agent-eval} produces an expression that evaluates directly
33909 to a result. For instance, a collection expression for @code{globa +
33910 globb} will include bytecodes to record four bytes of memory at each
33911 of the addresses of @code{globa} and @code{globb}, while discarding
33912 the result of the addition, while an evaluation expression will do the
33913 addition and return the sum.
33914 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33915 If not, generate remote agent bytecode for current frame PC address.
33917 @kindex maint agent-printf
33918 @item maint agent-printf @var{format},@var{expr},...
33919 Translate the given format string and list of argument expressions
33920 into remote agent bytecodes and display them as a disassembled list.
33921 This command is useful for debugging the agent version of dynamic
33922 printf (@pxref{Dynamic Printf}).
33924 @kindex maint info breakpoints
33925 @item @anchor{maint info breakpoints}maint info breakpoints
33926 Using the same format as @samp{info breakpoints}, display both the
33927 breakpoints you've set explicitly, and those @value{GDBN} is using for
33928 internal purposes. Internal breakpoints are shown with negative
33929 breakpoint numbers. The type column identifies what kind of breakpoint
33934 Normal, explicitly set breakpoint.
33937 Normal, explicitly set watchpoint.
33940 Internal breakpoint, used to handle correctly stepping through
33941 @code{longjmp} calls.
33943 @item longjmp resume
33944 Internal breakpoint at the target of a @code{longjmp}.
33947 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33950 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33953 Shared library events.
33957 @kindex maint info btrace
33958 @item maint info btrace
33959 Pint information about raw branch tracing data.
33961 @kindex maint btrace packet-history
33962 @item maint btrace packet-history
33963 Print the raw branch trace packets that are used to compute the
33964 execution history for the @samp{record btrace} command. Both the
33965 information and the format in which it is printed depend on the btrace
33970 For the BTS recording format, print a list of blocks of sequential
33971 code. For each block, the following information is printed:
33975 Newer blocks have higher numbers. The oldest block has number zero.
33976 @item Lowest @samp{PC}
33977 @item Highest @samp{PC}
33981 For the Intel(R) Processor Trace recording format, print a list of
33982 Intel(R) Processor Trace packets. For each packet, the following
33983 information is printed:
33986 @item Packet number
33987 Newer packets have higher numbers. The oldest packet has number zero.
33989 The packet's offset in the trace stream.
33990 @item Packet opcode and payload
33994 @kindex maint btrace clear-packet-history
33995 @item maint btrace clear-packet-history
33996 Discards the cached packet history printed by the @samp{maint btrace
33997 packet-history} command. The history will be computed again when
34000 @kindex maint btrace clear
34001 @item maint btrace clear
34002 Discard the branch trace data. The data will be fetched anew and the
34003 branch trace will be recomputed when needed.
34005 This implicitly truncates the branch trace to a single branch trace
34006 buffer. When updating branch trace incrementally, the branch trace
34007 available to @value{GDBN} may be bigger than a single branch trace
34010 @kindex maint set btrace pt skip-pad
34011 @item maint set btrace pt skip-pad
34012 @kindex maint show btrace pt skip-pad
34013 @item maint show btrace pt skip-pad
34014 Control whether @value{GDBN} will skip PAD packets when computing the
34017 @kindex set displaced-stepping
34018 @kindex show displaced-stepping
34019 @cindex displaced stepping support
34020 @cindex out-of-line single-stepping
34021 @item set displaced-stepping
34022 @itemx show displaced-stepping
34023 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34024 if the target supports it. Displaced stepping is a way to single-step
34025 over breakpoints without removing them from the inferior, by executing
34026 an out-of-line copy of the instruction that was originally at the
34027 breakpoint location. It is also known as out-of-line single-stepping.
34030 @item set displaced-stepping on
34031 If the target architecture supports it, @value{GDBN} will use
34032 displaced stepping to step over breakpoints.
34034 @item set displaced-stepping off
34035 @value{GDBN} will not use displaced stepping to step over breakpoints,
34036 even if such is supported by the target architecture.
34038 @cindex non-stop mode, and @samp{set displaced-stepping}
34039 @item set displaced-stepping auto
34040 This is the default mode. @value{GDBN} will use displaced stepping
34041 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34042 architecture supports displaced stepping.
34045 @kindex maint check-psymtabs
34046 @item maint check-psymtabs
34047 Check the consistency of currently expanded psymtabs versus symtabs.
34048 Use this to check, for example, whether a symbol is in one but not the other.
34050 @kindex maint check-symtabs
34051 @item maint check-symtabs
34052 Check the consistency of currently expanded symtabs.
34054 @kindex maint expand-symtabs
34055 @item maint expand-symtabs [@var{regexp}]
34056 Expand symbol tables.
34057 If @var{regexp} is specified, only expand symbol tables for file
34058 names matching @var{regexp}.
34060 @kindex maint set catch-demangler-crashes
34061 @kindex maint show catch-demangler-crashes
34062 @cindex demangler crashes
34063 @item maint set catch-demangler-crashes [on|off]
34064 @itemx maint show catch-demangler-crashes
34065 Control whether @value{GDBN} should attempt to catch crashes in the
34066 symbol name demangler. The default is to attempt to catch crashes.
34067 If enabled, the first time a crash is caught, a core file is created,
34068 the offending symbol is displayed and the user is presented with the
34069 option to terminate the current session.
34071 @kindex maint cplus first_component
34072 @item maint cplus first_component @var{name}
34073 Print the first C@t{++} class/namespace component of @var{name}.
34075 @kindex maint cplus namespace
34076 @item maint cplus namespace
34077 Print the list of possible C@t{++} namespaces.
34079 @kindex maint deprecate
34080 @kindex maint undeprecate
34081 @cindex deprecated commands
34082 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34083 @itemx maint undeprecate @var{command}
34084 Deprecate or undeprecate the named @var{command}. Deprecated commands
34085 cause @value{GDBN} to issue a warning when you use them. The optional
34086 argument @var{replacement} says which newer command should be used in
34087 favor of the deprecated one; if it is given, @value{GDBN} will mention
34088 the replacement as part of the warning.
34090 @kindex maint dump-me
34091 @item maint dump-me
34092 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34093 Cause a fatal signal in the debugger and force it to dump its core.
34094 This is supported only on systems which support aborting a program
34095 with the @code{SIGQUIT} signal.
34097 @kindex maint internal-error
34098 @kindex maint internal-warning
34099 @kindex maint demangler-warning
34100 @cindex demangler crashes
34101 @item maint internal-error @r{[}@var{message-text}@r{]}
34102 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34103 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34105 Cause @value{GDBN} to call the internal function @code{internal_error},
34106 @code{internal_warning} or @code{demangler_warning} and hence behave
34107 as though an internal problem has been detected. In addition to
34108 reporting the internal problem, these functions give the user the
34109 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34110 and @code{internal_warning}) create a core file of the current
34111 @value{GDBN} session.
34113 These commands take an optional parameter @var{message-text} that is
34114 used as the text of the error or warning message.
34116 Here's an example of using @code{internal-error}:
34119 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34120 @dots{}/maint.c:121: internal-error: testing, 1, 2
34121 A problem internal to GDB has been detected. Further
34122 debugging may prove unreliable.
34123 Quit this debugging session? (y or n) @kbd{n}
34124 Create a core file? (y or n) @kbd{n}
34128 @cindex @value{GDBN} internal error
34129 @cindex internal errors, control of @value{GDBN} behavior
34130 @cindex demangler crashes
34132 @kindex maint set internal-error
34133 @kindex maint show internal-error
34134 @kindex maint set internal-warning
34135 @kindex maint show internal-warning
34136 @kindex maint set demangler-warning
34137 @kindex maint show demangler-warning
34138 @item maint set internal-error @var{action} [ask|yes|no]
34139 @itemx maint show internal-error @var{action}
34140 @itemx maint set internal-warning @var{action} [ask|yes|no]
34141 @itemx maint show internal-warning @var{action}
34142 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34143 @itemx maint show demangler-warning @var{action}
34144 When @value{GDBN} reports an internal problem (error or warning) it
34145 gives the user the opportunity to both quit @value{GDBN} and create a
34146 core file of the current @value{GDBN} session. These commands let you
34147 override the default behaviour for each particular @var{action},
34148 described in the table below.
34152 You can specify that @value{GDBN} should always (yes) or never (no)
34153 quit. The default is to ask the user what to do.
34156 You can specify that @value{GDBN} should always (yes) or never (no)
34157 create a core file. The default is to ask the user what to do. Note
34158 that there is no @code{corefile} option for @code{demangler-warning}:
34159 demangler warnings always create a core file and this cannot be
34163 @kindex maint packet
34164 @item maint packet @var{text}
34165 If @value{GDBN} is talking to an inferior via the serial protocol,
34166 then this command sends the string @var{text} to the inferior, and
34167 displays the response packet. @value{GDBN} supplies the initial
34168 @samp{$} character, the terminating @samp{#} character, and the
34171 @kindex maint print architecture
34172 @item maint print architecture @r{[}@var{file}@r{]}
34173 Print the entire architecture configuration. The optional argument
34174 @var{file} names the file where the output goes.
34176 @kindex maint print c-tdesc
34177 @item maint print c-tdesc
34178 Print the current target description (@pxref{Target Descriptions}) as
34179 a C source file. The created source file can be used in @value{GDBN}
34180 when an XML parser is not available to parse the description.
34182 @kindex maint print dummy-frames
34183 @item maint print dummy-frames
34184 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34187 (@value{GDBP}) @kbd{b add}
34189 (@value{GDBP}) @kbd{print add(2,3)}
34190 Breakpoint 2, add (a=2, b=3) at @dots{}
34192 The program being debugged stopped while in a function called from GDB.
34194 (@value{GDBP}) @kbd{maint print dummy-frames}
34195 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34199 Takes an optional file parameter.
34201 @kindex maint print registers
34202 @kindex maint print raw-registers
34203 @kindex maint print cooked-registers
34204 @kindex maint print register-groups
34205 @kindex maint print remote-registers
34206 @item maint print registers @r{[}@var{file}@r{]}
34207 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34208 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34209 @itemx maint print register-groups @r{[}@var{file}@r{]}
34210 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34211 Print @value{GDBN}'s internal register data structures.
34213 The command @code{maint print raw-registers} includes the contents of
34214 the raw register cache; the command @code{maint print
34215 cooked-registers} includes the (cooked) value of all registers,
34216 including registers which aren't available on the target nor visible
34217 to user; the command @code{maint print register-groups} includes the
34218 groups that each register is a member of; and the command @code{maint
34219 print remote-registers} includes the remote target's register numbers
34220 and offsets in the `G' packets.
34222 These commands take an optional parameter, a file name to which to
34223 write the information.
34225 @kindex maint print reggroups
34226 @item maint print reggroups @r{[}@var{file}@r{]}
34227 Print @value{GDBN}'s internal register group data structures. The
34228 optional argument @var{file} tells to what file to write the
34231 The register groups info looks like this:
34234 (@value{GDBP}) @kbd{maint print reggroups}
34247 This command forces @value{GDBN} to flush its internal register cache.
34249 @kindex maint print objfiles
34250 @cindex info for known object files
34251 @item maint print objfiles @r{[}@var{regexp}@r{]}
34252 Print a dump of all known object files.
34253 If @var{regexp} is specified, only print object files whose names
34254 match @var{regexp}. For each object file, this command prints its name,
34255 address in memory, and all of its psymtabs and symtabs.
34257 @kindex maint print user-registers
34258 @cindex user registers
34259 @item maint print user-registers
34260 List all currently available @dfn{user registers}. User registers
34261 typically provide alternate names for actual hardware registers. They
34262 include the four ``standard'' registers @code{$fp}, @code{$pc},
34263 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34264 registers can be used in expressions in the same way as the canonical
34265 register names, but only the latter are listed by the @code{info
34266 registers} and @code{maint print registers} commands.
34268 @kindex maint print section-scripts
34269 @cindex info for known .debug_gdb_scripts-loaded scripts
34270 @item maint print section-scripts [@var{regexp}]
34271 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34272 If @var{regexp} is specified, only print scripts loaded by object files
34273 matching @var{regexp}.
34274 For each script, this command prints its name as specified in the objfile,
34275 and the full path if known.
34276 @xref{dotdebug_gdb_scripts section}.
34278 @kindex maint print statistics
34279 @cindex bcache statistics
34280 @item maint print statistics
34281 This command prints, for each object file in the program, various data
34282 about that object file followed by the byte cache (@dfn{bcache})
34283 statistics for the object file. The objfile data includes the number
34284 of minimal, partial, full, and stabs symbols, the number of types
34285 defined by the objfile, the number of as yet unexpanded psym tables,
34286 the number of line tables and string tables, and the amount of memory
34287 used by the various tables. The bcache statistics include the counts,
34288 sizes, and counts of duplicates of all and unique objects, max,
34289 average, and median entry size, total memory used and its overhead and
34290 savings, and various measures of the hash table size and chain
34293 @kindex maint print target-stack
34294 @cindex target stack description
34295 @item maint print target-stack
34296 A @dfn{target} is an interface between the debugger and a particular
34297 kind of file or process. Targets can be stacked in @dfn{strata},
34298 so that more than one target can potentially respond to a request.
34299 In particular, memory accesses will walk down the stack of targets
34300 until they find a target that is interested in handling that particular
34303 This command prints a short description of each layer that was pushed on
34304 the @dfn{target stack}, starting from the top layer down to the bottom one.
34306 @kindex maint print type
34307 @cindex type chain of a data type
34308 @item maint print type @var{expr}
34309 Print the type chain for a type specified by @var{expr}. The argument
34310 can be either a type name or a symbol. If it is a symbol, the type of
34311 that symbol is described. The type chain produced by this command is
34312 a recursive definition of the data type as stored in @value{GDBN}'s
34313 data structures, including its flags and contained types.
34315 @kindex maint set dwarf always-disassemble
34316 @kindex maint show dwarf always-disassemble
34317 @item maint set dwarf always-disassemble
34318 @item maint show dwarf always-disassemble
34319 Control the behavior of @code{info address} when using DWARF debugging
34322 The default is @code{off}, which means that @value{GDBN} should try to
34323 describe a variable's location in an easily readable format. When
34324 @code{on}, @value{GDBN} will instead display the DWARF location
34325 expression in an assembly-like format. Note that some locations are
34326 too complex for @value{GDBN} to describe simply; in this case you will
34327 always see the disassembly form.
34329 Here is an example of the resulting disassembly:
34332 (gdb) info addr argc
34333 Symbol "argc" is a complex DWARF expression:
34337 For more information on these expressions, see
34338 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34340 @kindex maint set dwarf max-cache-age
34341 @kindex maint show dwarf max-cache-age
34342 @item maint set dwarf max-cache-age
34343 @itemx maint show dwarf max-cache-age
34344 Control the DWARF compilation unit cache.
34346 @cindex DWARF compilation units cache
34347 In object files with inter-compilation-unit references, such as those
34348 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34349 reader needs to frequently refer to previously read compilation units.
34350 This setting controls how long a compilation unit will remain in the
34351 cache if it is not referenced. A higher limit means that cached
34352 compilation units will be stored in memory longer, and more total
34353 memory will be used. Setting it to zero disables caching, which will
34354 slow down @value{GDBN} startup, but reduce memory consumption.
34356 @kindex maint set profile
34357 @kindex maint show profile
34358 @cindex profiling GDB
34359 @item maint set profile
34360 @itemx maint show profile
34361 Control profiling of @value{GDBN}.
34363 Profiling will be disabled until you use the @samp{maint set profile}
34364 command to enable it. When you enable profiling, the system will begin
34365 collecting timing and execution count data; when you disable profiling or
34366 exit @value{GDBN}, the results will be written to a log file. Remember that
34367 if you use profiling, @value{GDBN} will overwrite the profiling log file
34368 (often called @file{gmon.out}). If you have a record of important profiling
34369 data in a @file{gmon.out} file, be sure to move it to a safe location.
34371 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34372 compiled with the @samp{-pg} compiler option.
34374 @kindex maint set show-debug-regs
34375 @kindex maint show show-debug-regs
34376 @cindex hardware debug registers
34377 @item maint set show-debug-regs
34378 @itemx maint show show-debug-regs
34379 Control whether to show variables that mirror the hardware debug
34380 registers. Use @code{on} to enable, @code{off} to disable. If
34381 enabled, the debug registers values are shown when @value{GDBN} inserts or
34382 removes a hardware breakpoint or watchpoint, and when the inferior
34383 triggers a hardware-assisted breakpoint or watchpoint.
34385 @kindex maint set show-all-tib
34386 @kindex maint show show-all-tib
34387 @item maint set show-all-tib
34388 @itemx maint show show-all-tib
34389 Control whether to show all non zero areas within a 1k block starting
34390 at thread local base, when using the @samp{info w32 thread-information-block}
34393 @kindex maint set target-async
34394 @kindex maint show target-async
34395 @item maint set target-async
34396 @itemx maint show target-async
34397 This controls whether @value{GDBN} targets operate in synchronous or
34398 asynchronous mode (@pxref{Background Execution}). Normally the
34399 default is asynchronous, if it is available; but this can be changed
34400 to more easily debug problems occurring only in synchronous mode.
34402 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34403 @kindex maint show target-non-stop
34404 @item maint set target-non-stop
34405 @itemx maint show target-non-stop
34407 This controls whether @value{GDBN} targets always operate in non-stop
34408 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34409 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34410 if supported by the target.
34413 @item maint set target-non-stop auto
34414 This is the default mode. @value{GDBN} controls the target in
34415 non-stop mode if the target supports it.
34417 @item maint set target-non-stop on
34418 @value{GDBN} controls the target in non-stop mode even if the target
34419 does not indicate support.
34421 @item maint set target-non-stop off
34422 @value{GDBN} does not control the target in non-stop mode even if the
34423 target supports it.
34426 @kindex maint set per-command
34427 @kindex maint show per-command
34428 @item maint set per-command
34429 @itemx maint show per-command
34430 @cindex resources used by commands
34432 @value{GDBN} can display the resources used by each command.
34433 This is useful in debugging performance problems.
34436 @item maint set per-command space [on|off]
34437 @itemx maint show per-command space
34438 Enable or disable the printing of the memory used by GDB for each command.
34439 If enabled, @value{GDBN} will display how much memory each command
34440 took, following the command's own output.
34441 This can also be requested by invoking @value{GDBN} with the
34442 @option{--statistics} command-line switch (@pxref{Mode Options}).
34444 @item maint set per-command time [on|off]
34445 @itemx maint show per-command time
34446 Enable or disable the printing of the execution time of @value{GDBN}
34448 If enabled, @value{GDBN} will display how much time it
34449 took to execute each command, following the command's own output.
34450 Both CPU time and wallclock time are printed.
34451 Printing both is useful when trying to determine whether the cost is
34452 CPU or, e.g., disk/network latency.
34453 Note that the CPU time printed is for @value{GDBN} only, it does not include
34454 the execution time of the inferior because there's no mechanism currently
34455 to compute how much time was spent by @value{GDBN} and how much time was
34456 spent by the program been debugged.
34457 This can also be requested by invoking @value{GDBN} with the
34458 @option{--statistics} command-line switch (@pxref{Mode Options}).
34460 @item maint set per-command symtab [on|off]
34461 @itemx maint show per-command symtab
34462 Enable or disable the printing of basic symbol table statistics
34464 If enabled, @value{GDBN} will display the following information:
34468 number of symbol tables
34470 number of primary symbol tables
34472 number of blocks in the blockvector
34476 @kindex maint space
34477 @cindex memory used by commands
34478 @item maint space @var{value}
34479 An alias for @code{maint set per-command space}.
34480 A non-zero value enables it, zero disables it.
34483 @cindex time of command execution
34484 @item maint time @var{value}
34485 An alias for @code{maint set per-command time}.
34486 A non-zero value enables it, zero disables it.
34488 @kindex maint translate-address
34489 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34490 Find the symbol stored at the location specified by the address
34491 @var{addr} and an optional section name @var{section}. If found,
34492 @value{GDBN} prints the name of the closest symbol and an offset from
34493 the symbol's location to the specified address. This is similar to
34494 the @code{info address} command (@pxref{Symbols}), except that this
34495 command also allows to find symbols in other sections.
34497 If section was not specified, the section in which the symbol was found
34498 is also printed. For dynamically linked executables, the name of
34499 executable or shared library containing the symbol is printed as well.
34503 The following command is useful for non-interactive invocations of
34504 @value{GDBN}, such as in the test suite.
34507 @item set watchdog @var{nsec}
34508 @kindex set watchdog
34509 @cindex watchdog timer
34510 @cindex timeout for commands
34511 Set the maximum number of seconds @value{GDBN} will wait for the
34512 target operation to finish. If this time expires, @value{GDBN}
34513 reports and error and the command is aborted.
34515 @item show watchdog
34516 Show the current setting of the target wait timeout.
34519 @node Remote Protocol
34520 @appendix @value{GDBN} Remote Serial Protocol
34525 * Stop Reply Packets::
34526 * General Query Packets::
34527 * Architecture-Specific Protocol Details::
34528 * Tracepoint Packets::
34529 * Host I/O Packets::
34531 * Notification Packets::
34532 * Remote Non-Stop::
34533 * Packet Acknowledgment::
34535 * File-I/O Remote Protocol Extension::
34536 * Library List Format::
34537 * Library List Format for SVR4 Targets::
34538 * Memory Map Format::
34539 * Thread List Format::
34540 * Traceframe Info Format::
34541 * Branch Trace Format::
34542 * Branch Trace Configuration Format::
34548 There may be occasions when you need to know something about the
34549 protocol---for example, if there is only one serial port to your target
34550 machine, you might want your program to do something special if it
34551 recognizes a packet meant for @value{GDBN}.
34553 In the examples below, @samp{->} and @samp{<-} are used to indicate
34554 transmitted and received data, respectively.
34556 @cindex protocol, @value{GDBN} remote serial
34557 @cindex serial protocol, @value{GDBN} remote
34558 @cindex remote serial protocol
34559 All @value{GDBN} commands and responses (other than acknowledgments
34560 and notifications, see @ref{Notification Packets}) are sent as a
34561 @var{packet}. A @var{packet} is introduced with the character
34562 @samp{$}, the actual @var{packet-data}, and the terminating character
34563 @samp{#} followed by a two-digit @var{checksum}:
34566 @code{$}@var{packet-data}@code{#}@var{checksum}
34570 @cindex checksum, for @value{GDBN} remote
34572 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34573 characters between the leading @samp{$} and the trailing @samp{#} (an
34574 eight bit unsigned checksum).
34576 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34577 specification also included an optional two-digit @var{sequence-id}:
34580 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34583 @cindex sequence-id, for @value{GDBN} remote
34585 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34586 has never output @var{sequence-id}s. Stubs that handle packets added
34587 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34589 When either the host or the target machine receives a packet, the first
34590 response expected is an acknowledgment: either @samp{+} (to indicate
34591 the package was received correctly) or @samp{-} (to request
34595 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34600 The @samp{+}/@samp{-} acknowledgments can be disabled
34601 once a connection is established.
34602 @xref{Packet Acknowledgment}, for details.
34604 The host (@value{GDBN}) sends @var{command}s, and the target (the
34605 debugging stub incorporated in your program) sends a @var{response}. In
34606 the case of step and continue @var{command}s, the response is only sent
34607 when the operation has completed, and the target has again stopped all
34608 threads in all attached processes. This is the default all-stop mode
34609 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34610 execution mode; see @ref{Remote Non-Stop}, for details.
34612 @var{packet-data} consists of a sequence of characters with the
34613 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34616 @cindex remote protocol, field separator
34617 Fields within the packet should be separated using @samp{,} @samp{;} or
34618 @samp{:}. Except where otherwise noted all numbers are represented in
34619 @sc{hex} with leading zeros suppressed.
34621 Implementors should note that prior to @value{GDBN} 5.0, the character
34622 @samp{:} could not appear as the third character in a packet (as it
34623 would potentially conflict with the @var{sequence-id}).
34625 @cindex remote protocol, binary data
34626 @anchor{Binary Data}
34627 Binary data in most packets is encoded either as two hexadecimal
34628 digits per byte of binary data. This allowed the traditional remote
34629 protocol to work over connections which were only seven-bit clean.
34630 Some packets designed more recently assume an eight-bit clean
34631 connection, and use a more efficient encoding to send and receive
34634 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34635 as an escape character. Any escaped byte is transmitted as the escape
34636 character followed by the original character XORed with @code{0x20}.
34637 For example, the byte @code{0x7d} would be transmitted as the two
34638 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34639 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34640 @samp{@}}) must always be escaped. Responses sent by the stub
34641 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34642 is not interpreted as the start of a run-length encoded sequence
34645 Response @var{data} can be run-length encoded to save space.
34646 Run-length encoding replaces runs of identical characters with one
34647 instance of the repeated character, followed by a @samp{*} and a
34648 repeat count. The repeat count is itself sent encoded, to avoid
34649 binary characters in @var{data}: a value of @var{n} is sent as
34650 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34651 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34652 code 32) for a repeat count of 3. (This is because run-length
34653 encoding starts to win for counts 3 or more.) Thus, for example,
34654 @samp{0* } is a run-length encoding of ``0000'': the space character
34655 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34658 The printable characters @samp{#} and @samp{$} or with a numeric value
34659 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34660 seven repeats (@samp{$}) can be expanded using a repeat count of only
34661 five (@samp{"}). For example, @samp{00000000} can be encoded as
34664 The error response returned for some packets includes a two character
34665 error number. That number is not well defined.
34667 @cindex empty response, for unsupported packets
34668 For any @var{command} not supported by the stub, an empty response
34669 (@samp{$#00}) should be returned. That way it is possible to extend the
34670 protocol. A newer @value{GDBN} can tell if a packet is supported based
34673 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34674 commands for register access, and the @samp{m} and @samp{M} commands
34675 for memory access. Stubs that only control single-threaded targets
34676 can implement run control with the @samp{c} (continue), and @samp{s}
34677 (step) commands. Stubs that support multi-threading targets should
34678 support the @samp{vCont} command. All other commands are optional.
34683 The following table provides a complete list of all currently defined
34684 @var{command}s and their corresponding response @var{data}.
34685 @xref{File-I/O Remote Protocol Extension}, for details about the File
34686 I/O extension of the remote protocol.
34688 Each packet's description has a template showing the packet's overall
34689 syntax, followed by an explanation of the packet's meaning. We
34690 include spaces in some of the templates for clarity; these are not
34691 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34692 separate its components. For example, a template like @samp{foo
34693 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34694 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34695 @var{baz}. @value{GDBN} does not transmit a space character between the
34696 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34699 @cindex @var{thread-id}, in remote protocol
34700 @anchor{thread-id syntax}
34701 Several packets and replies include a @var{thread-id} field to identify
34702 a thread. Normally these are positive numbers with a target-specific
34703 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34704 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34707 In addition, the remote protocol supports a multiprocess feature in
34708 which the @var{thread-id} syntax is extended to optionally include both
34709 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34710 The @var{pid} (process) and @var{tid} (thread) components each have the
34711 format described above: a positive number with target-specific
34712 interpretation formatted as a big-endian hex string, literal @samp{-1}
34713 to indicate all processes or threads (respectively), or @samp{0} to
34714 indicate an arbitrary process or thread. Specifying just a process, as
34715 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34716 error to specify all processes but a specific thread, such as
34717 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34718 for those packets and replies explicitly documented to include a process
34719 ID, rather than a @var{thread-id}.
34721 The multiprocess @var{thread-id} syntax extensions are only used if both
34722 @value{GDBN} and the stub report support for the @samp{multiprocess}
34723 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34726 Note that all packet forms beginning with an upper- or lower-case
34727 letter, other than those described here, are reserved for future use.
34729 Here are the packet descriptions.
34734 @cindex @samp{!} packet
34735 @anchor{extended mode}
34736 Enable extended mode. In extended mode, the remote server is made
34737 persistent. The @samp{R} packet is used to restart the program being
34743 The remote target both supports and has enabled extended mode.
34747 @cindex @samp{?} packet
34749 Indicate the reason the target halted. The reply is the same as for
34750 step and continue. This packet has a special interpretation when the
34751 target is in non-stop mode; see @ref{Remote Non-Stop}.
34754 @xref{Stop Reply Packets}, for the reply specifications.
34756 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34757 @cindex @samp{A} packet
34758 Initialized @code{argv[]} array passed into program. @var{arglen}
34759 specifies the number of bytes in the hex encoded byte stream
34760 @var{arg}. See @code{gdbserver} for more details.
34765 The arguments were set.
34771 @cindex @samp{b} packet
34772 (Don't use this packet; its behavior is not well-defined.)
34773 Change the serial line speed to @var{baud}.
34775 JTC: @emph{When does the transport layer state change? When it's
34776 received, or after the ACK is transmitted. In either case, there are
34777 problems if the command or the acknowledgment packet is dropped.}
34779 Stan: @emph{If people really wanted to add something like this, and get
34780 it working for the first time, they ought to modify ser-unix.c to send
34781 some kind of out-of-band message to a specially-setup stub and have the
34782 switch happen "in between" packets, so that from remote protocol's point
34783 of view, nothing actually happened.}
34785 @item B @var{addr},@var{mode}
34786 @cindex @samp{B} packet
34787 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34788 breakpoint at @var{addr}.
34790 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34791 (@pxref{insert breakpoint or watchpoint packet}).
34793 @cindex @samp{bc} packet
34796 Backward continue. Execute the target system in reverse. No parameter.
34797 @xref{Reverse Execution}, for more information.
34800 @xref{Stop Reply Packets}, for the reply specifications.
34802 @cindex @samp{bs} packet
34805 Backward single step. Execute one instruction in reverse. No parameter.
34806 @xref{Reverse Execution}, for more information.
34809 @xref{Stop Reply Packets}, for the reply specifications.
34811 @item c @r{[}@var{addr}@r{]}
34812 @cindex @samp{c} packet
34813 Continue at @var{addr}, which is the address to resume. If @var{addr}
34814 is omitted, resume at current address.
34816 This packet is deprecated for multi-threading support. @xref{vCont
34820 @xref{Stop Reply Packets}, for the reply specifications.
34822 @item C @var{sig}@r{[};@var{addr}@r{]}
34823 @cindex @samp{C} packet
34824 Continue with signal @var{sig} (hex signal number). If
34825 @samp{;@var{addr}} is omitted, resume at same address.
34827 This packet is deprecated for multi-threading support. @xref{vCont
34831 @xref{Stop Reply Packets}, for the reply specifications.
34834 @cindex @samp{d} packet
34837 Don't use this packet; instead, define a general set packet
34838 (@pxref{General Query Packets}).
34842 @cindex @samp{D} packet
34843 The first form of the packet is used to detach @value{GDBN} from the
34844 remote system. It is sent to the remote target
34845 before @value{GDBN} disconnects via the @code{detach} command.
34847 The second form, including a process ID, is used when multiprocess
34848 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34849 detach only a specific process. The @var{pid} is specified as a
34850 big-endian hex string.
34860 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34861 @cindex @samp{F} packet
34862 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34863 This is part of the File-I/O protocol extension. @xref{File-I/O
34864 Remote Protocol Extension}, for the specification.
34867 @anchor{read registers packet}
34868 @cindex @samp{g} packet
34869 Read general registers.
34873 @item @var{XX@dots{}}
34874 Each byte of register data is described by two hex digits. The bytes
34875 with the register are transmitted in target byte order. The size of
34876 each register and their position within the @samp{g} packet are
34877 determined by the @value{GDBN} internal gdbarch functions
34878 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34879 specification of several standard @samp{g} packets is specified below.
34881 When reading registers from a trace frame (@pxref{Analyze Collected
34882 Data,,Using the Collected Data}), the stub may also return a string of
34883 literal @samp{x}'s in place of the register data digits, to indicate
34884 that the corresponding register has not been collected, thus its value
34885 is unavailable. For example, for an architecture with 4 registers of
34886 4 bytes each, the following reply indicates to @value{GDBN} that
34887 registers 0 and 2 have not been collected, while registers 1 and 3
34888 have been collected, and both have zero value:
34892 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34899 @item G @var{XX@dots{}}
34900 @cindex @samp{G} packet
34901 Write general registers. @xref{read registers packet}, for a
34902 description of the @var{XX@dots{}} data.
34912 @item H @var{op} @var{thread-id}
34913 @cindex @samp{H} packet
34914 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34915 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34916 should be @samp{c} for step and continue operations (note that this
34917 is deprecated, supporting the @samp{vCont} command is a better
34918 option), and @samp{g} for other operations. The thread designator
34919 @var{thread-id} has the format and interpretation described in
34920 @ref{thread-id syntax}.
34931 @c 'H': How restrictive (or permissive) is the thread model. If a
34932 @c thread is selected and stopped, are other threads allowed
34933 @c to continue to execute? As I mentioned above, I think the
34934 @c semantics of each command when a thread is selected must be
34935 @c described. For example:
34937 @c 'g': If the stub supports threads and a specific thread is
34938 @c selected, returns the register block from that thread;
34939 @c otherwise returns current registers.
34941 @c 'G' If the stub supports threads and a specific thread is
34942 @c selected, sets the registers of the register block of
34943 @c that thread; otherwise sets current registers.
34945 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34946 @anchor{cycle step packet}
34947 @cindex @samp{i} packet
34948 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34949 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34950 step starting at that address.
34953 @cindex @samp{I} packet
34954 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34958 @cindex @samp{k} packet
34961 The exact effect of this packet is not specified.
34963 For a bare-metal target, it may power cycle or reset the target
34964 system. For that reason, the @samp{k} packet has no reply.
34966 For a single-process target, it may kill that process if possible.
34968 A multiple-process target may choose to kill just one process, or all
34969 that are under @value{GDBN}'s control. For more precise control, use
34970 the vKill packet (@pxref{vKill packet}).
34972 If the target system immediately closes the connection in response to
34973 @samp{k}, @value{GDBN} does not consider the lack of packet
34974 acknowledgment to be an error, and assumes the kill was successful.
34976 If connected using @kbd{target extended-remote}, and the target does
34977 not close the connection in response to a kill request, @value{GDBN}
34978 probes the target state as if a new connection was opened
34979 (@pxref{? packet}).
34981 @item m @var{addr},@var{length}
34982 @cindex @samp{m} packet
34983 Read @var{length} addressable memory units starting at address @var{addr}
34984 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34985 any particular boundary.
34987 The stub need not use any particular size or alignment when gathering
34988 data from memory for the response; even if @var{addr} is word-aligned
34989 and @var{length} is a multiple of the word size, the stub is free to
34990 use byte accesses, or not. For this reason, this packet may not be
34991 suitable for accessing memory-mapped I/O devices.
34992 @cindex alignment of remote memory accesses
34993 @cindex size of remote memory accesses
34994 @cindex memory, alignment and size of remote accesses
34998 @item @var{XX@dots{}}
34999 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35000 The reply may contain fewer addressable memory units than requested if the
35001 server was able to read only part of the region of memory.
35006 @item M @var{addr},@var{length}:@var{XX@dots{}}
35007 @cindex @samp{M} packet
35008 Write @var{length} addressable memory units starting at address @var{addr}
35009 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35010 byte is transmitted as a two-digit hexadecimal number.
35017 for an error (this includes the case where only part of the data was
35022 @cindex @samp{p} packet
35023 Read the value of register @var{n}; @var{n} is in hex.
35024 @xref{read registers packet}, for a description of how the returned
35025 register value is encoded.
35029 @item @var{XX@dots{}}
35030 the register's value
35034 Indicating an unrecognized @var{query}.
35037 @item P @var{n@dots{}}=@var{r@dots{}}
35038 @anchor{write register packet}
35039 @cindex @samp{P} packet
35040 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35041 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35042 digits for each byte in the register (target byte order).
35052 @item q @var{name} @var{params}@dots{}
35053 @itemx Q @var{name} @var{params}@dots{}
35054 @cindex @samp{q} packet
35055 @cindex @samp{Q} packet
35056 General query (@samp{q}) and set (@samp{Q}). These packets are
35057 described fully in @ref{General Query Packets}.
35060 @cindex @samp{r} packet
35061 Reset the entire system.
35063 Don't use this packet; use the @samp{R} packet instead.
35066 @cindex @samp{R} packet
35067 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35068 This packet is only available in extended mode (@pxref{extended mode}).
35070 The @samp{R} packet has no reply.
35072 @item s @r{[}@var{addr}@r{]}
35073 @cindex @samp{s} packet
35074 Single step, resuming at @var{addr}. If
35075 @var{addr} is omitted, resume at same address.
35077 This packet is deprecated for multi-threading support. @xref{vCont
35081 @xref{Stop Reply Packets}, for the reply specifications.
35083 @item S @var{sig}@r{[};@var{addr}@r{]}
35084 @anchor{step with signal packet}
35085 @cindex @samp{S} packet
35086 Step with signal. This is analogous to the @samp{C} packet, but
35087 requests a single-step, rather than a normal resumption of execution.
35089 This packet is deprecated for multi-threading support. @xref{vCont
35093 @xref{Stop Reply Packets}, for the reply specifications.
35095 @item t @var{addr}:@var{PP},@var{MM}
35096 @cindex @samp{t} packet
35097 Search backwards starting at address @var{addr} for a match with pattern
35098 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35099 There must be at least 3 digits in @var{addr}.
35101 @item T @var{thread-id}
35102 @cindex @samp{T} packet
35103 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35108 thread is still alive
35114 Packets starting with @samp{v} are identified by a multi-letter name,
35115 up to the first @samp{;} or @samp{?} (or the end of the packet).
35117 @item vAttach;@var{pid}
35118 @cindex @samp{vAttach} packet
35119 Attach to a new process with the specified process ID @var{pid}.
35120 The process ID is a
35121 hexadecimal integer identifying the process. In all-stop mode, all
35122 threads in the attached process are stopped; in non-stop mode, it may be
35123 attached without being stopped if that is supported by the target.
35125 @c In non-stop mode, on a successful vAttach, the stub should set the
35126 @c current thread to a thread of the newly-attached process. After
35127 @c attaching, GDB queries for the attached process's thread ID with qC.
35128 @c Also note that, from a user perspective, whether or not the
35129 @c target is stopped on attach in non-stop mode depends on whether you
35130 @c use the foreground or background version of the attach command, not
35131 @c on what vAttach does; GDB does the right thing with respect to either
35132 @c stopping or restarting threads.
35134 This packet is only available in extended mode (@pxref{extended mode}).
35140 @item @r{Any stop packet}
35141 for success in all-stop mode (@pxref{Stop Reply Packets})
35143 for success in non-stop mode (@pxref{Remote Non-Stop})
35146 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35147 @cindex @samp{vCont} packet
35148 @anchor{vCont packet}
35149 Resume the inferior, specifying different actions for each thread.
35150 If an action is specified with no @var{thread-id}, then it is applied to any
35151 threads that don't have a specific action specified; if no default action is
35152 specified then other threads should remain stopped in all-stop mode and
35153 in their current state in non-stop mode.
35154 Specifying multiple
35155 default actions is an error; specifying no actions is also an error.
35156 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35158 Currently supported actions are:
35164 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35168 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35171 @item r @var{start},@var{end}
35172 Step once, and then keep stepping as long as the thread stops at
35173 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35174 The remote stub reports a stop reply when either the thread goes out
35175 of the range or is stopped due to an unrelated reason, such as hitting
35176 a breakpoint. @xref{range stepping}.
35178 If the range is empty (@var{start} == @var{end}), then the action
35179 becomes equivalent to the @samp{s} action. In other words,
35180 single-step once, and report the stop (even if the stepped instruction
35181 jumps to @var{start}).
35183 (A stop reply may be sent at any point even if the PC is still within
35184 the stepping range; for example, it is valid to implement this packet
35185 in a degenerate way as a single instruction step operation.)
35189 The optional argument @var{addr} normally associated with the
35190 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35191 not supported in @samp{vCont}.
35193 The @samp{t} action is only relevant in non-stop mode
35194 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35195 A stop reply should be generated for any affected thread not already stopped.
35196 When a thread is stopped by means of a @samp{t} action,
35197 the corresponding stop reply should indicate that the thread has stopped with
35198 signal @samp{0}, regardless of whether the target uses some other signal
35199 as an implementation detail.
35201 The stub must support @samp{vCont} if it reports support for
35202 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35203 this case @samp{vCont} actions can be specified to apply to all threads
35204 in a process by using the @samp{p@var{pid}.-1} form of the
35208 @xref{Stop Reply Packets}, for the reply specifications.
35211 @cindex @samp{vCont?} packet
35212 Request a list of actions supported by the @samp{vCont} packet.
35216 @item vCont@r{[};@var{action}@dots{}@r{]}
35217 The @samp{vCont} packet is supported. Each @var{action} is a supported
35218 command in the @samp{vCont} packet.
35220 The @samp{vCont} packet is not supported.
35223 @anchor{vCtrlC packet}
35225 @cindex @samp{vCtrlC} packet
35226 Interrupt remote target as if a control-C was pressed on the remote
35227 terminal. This is the equivalent to reacting to the @code{^C}
35228 (@samp{\003}, the control-C character) character in all-stop mode
35229 while the target is running, except this works in non-stop mode.
35230 @xref{interrupting remote targets}, for more info on the all-stop
35241 @item vFile:@var{operation}:@var{parameter}@dots{}
35242 @cindex @samp{vFile} packet
35243 Perform a file operation on the target system. For details,
35244 see @ref{Host I/O Packets}.
35246 @item vFlashErase:@var{addr},@var{length}
35247 @cindex @samp{vFlashErase} packet
35248 Direct the stub to erase @var{length} bytes of flash starting at
35249 @var{addr}. The region may enclose any number of flash blocks, but
35250 its start and end must fall on block boundaries, as indicated by the
35251 flash block size appearing in the memory map (@pxref{Memory Map
35252 Format}). @value{GDBN} groups flash memory programming operations
35253 together, and sends a @samp{vFlashDone} request after each group; the
35254 stub is allowed to delay erase operation until the @samp{vFlashDone}
35255 packet is received.
35265 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35266 @cindex @samp{vFlashWrite} packet
35267 Direct the stub to write data to flash address @var{addr}. The data
35268 is passed in binary form using the same encoding as for the @samp{X}
35269 packet (@pxref{Binary Data}). The memory ranges specified by
35270 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35271 not overlap, and must appear in order of increasing addresses
35272 (although @samp{vFlashErase} packets for higher addresses may already
35273 have been received; the ordering is guaranteed only between
35274 @samp{vFlashWrite} packets). If a packet writes to an address that was
35275 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35276 target-specific method, the results are unpredictable.
35284 for vFlashWrite addressing non-flash memory
35290 @cindex @samp{vFlashDone} packet
35291 Indicate to the stub that flash programming operation is finished.
35292 The stub is permitted to delay or batch the effects of a group of
35293 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35294 @samp{vFlashDone} packet is received. The contents of the affected
35295 regions of flash memory are unpredictable until the @samp{vFlashDone}
35296 request is completed.
35298 @item vKill;@var{pid}
35299 @cindex @samp{vKill} packet
35300 @anchor{vKill packet}
35301 Kill the process with the specified process ID @var{pid}, which is a
35302 hexadecimal integer identifying the process. This packet is used in
35303 preference to @samp{k} when multiprocess protocol extensions are
35304 supported; see @ref{multiprocess extensions}.
35314 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35315 @cindex @samp{vRun} packet
35316 Run the program @var{filename}, passing it each @var{argument} on its
35317 command line. The file and arguments are hex-encoded strings. If
35318 @var{filename} is an empty string, the stub may use a default program
35319 (e.g.@: the last program run). The program is created in the stopped
35322 @c FIXME: What about non-stop mode?
35324 This packet is only available in extended mode (@pxref{extended mode}).
35330 @item @r{Any stop packet}
35331 for success (@pxref{Stop Reply Packets})
35335 @cindex @samp{vStopped} packet
35336 @xref{Notification Packets}.
35338 @item X @var{addr},@var{length}:@var{XX@dots{}}
35340 @cindex @samp{X} packet
35341 Write data to memory, where the data is transmitted in binary.
35342 Memory is specified by its address @var{addr} and number of addressable memory
35343 units @var{length} (@pxref{addressable memory unit});
35344 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35354 @item z @var{type},@var{addr},@var{kind}
35355 @itemx Z @var{type},@var{addr},@var{kind}
35356 @anchor{insert breakpoint or watchpoint packet}
35357 @cindex @samp{z} packet
35358 @cindex @samp{Z} packets
35359 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35360 watchpoint starting at address @var{address} of kind @var{kind}.
35362 Each breakpoint and watchpoint packet @var{type} is documented
35365 @emph{Implementation notes: A remote target shall return an empty string
35366 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35367 remote target shall support either both or neither of a given
35368 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35369 avoid potential problems with duplicate packets, the operations should
35370 be implemented in an idempotent way.}
35372 @item z0,@var{addr},@var{kind}
35373 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35374 @cindex @samp{z0} packet
35375 @cindex @samp{Z0} packet
35376 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35377 @var{addr} of type @var{kind}.
35379 A memory breakpoint is implemented by replacing the instruction at
35380 @var{addr} with a software breakpoint or trap instruction. The
35381 @var{kind} is target-specific and typically indicates the size of
35382 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35383 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35384 architectures have additional meanings for @var{kind};
35385 @var{cond_list} is an optional list of conditional expressions in bytecode
35386 form that should be evaluated on the target's side. These are the
35387 conditions that should be taken into consideration when deciding if
35388 the breakpoint trigger should be reported back to @var{GDBN}.
35390 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35391 for how to best report a memory breakpoint event to @value{GDBN}.
35393 The @var{cond_list} parameter is comprised of a series of expressions,
35394 concatenated without separators. Each expression has the following form:
35398 @item X @var{len},@var{expr}
35399 @var{len} is the length of the bytecode expression and @var{expr} is the
35400 actual conditional expression in bytecode form.
35404 The optional @var{cmd_list} parameter introduces commands that may be
35405 run on the target, rather than being reported back to @value{GDBN}.
35406 The parameter starts with a numeric flag @var{persist}; if the flag is
35407 nonzero, then the breakpoint may remain active and the commands
35408 continue to be run even when @value{GDBN} disconnects from the target.
35409 Following this flag is a series of expressions concatenated with no
35410 separators. Each expression has the following form:
35414 @item X @var{len},@var{expr}
35415 @var{len} is the length of the bytecode expression and @var{expr} is the
35416 actual conditional expression in bytecode form.
35420 see @ref{Architecture-Specific Protocol Details}.
35422 @emph{Implementation note: It is possible for a target to copy or move
35423 code that contains memory breakpoints (e.g., when implementing
35424 overlays). The behavior of this packet, in the presence of such a
35425 target, is not defined.}
35437 @item z1,@var{addr},@var{kind}
35438 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35439 @cindex @samp{z1} packet
35440 @cindex @samp{Z1} packet
35441 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35442 address @var{addr}.
35444 A hardware breakpoint is implemented using a mechanism that is not
35445 dependant on being able to modify the target's memory. The @var{kind}
35446 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35448 @emph{Implementation note: A hardware breakpoint is not affected by code
35461 @item z2,@var{addr},@var{kind}
35462 @itemx Z2,@var{addr},@var{kind}
35463 @cindex @samp{z2} packet
35464 @cindex @samp{Z2} packet
35465 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35466 The number of bytes to watch is specified by @var{kind}.
35478 @item z3,@var{addr},@var{kind}
35479 @itemx Z3,@var{addr},@var{kind}
35480 @cindex @samp{z3} packet
35481 @cindex @samp{Z3} packet
35482 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35483 The number of bytes to watch is specified by @var{kind}.
35495 @item z4,@var{addr},@var{kind}
35496 @itemx Z4,@var{addr},@var{kind}
35497 @cindex @samp{z4} packet
35498 @cindex @samp{Z4} packet
35499 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35500 The number of bytes to watch is specified by @var{kind}.
35514 @node Stop Reply Packets
35515 @section Stop Reply Packets
35516 @cindex stop reply packets
35518 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35519 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35520 receive any of the below as a reply. Except for @samp{?}
35521 and @samp{vStopped}, that reply is only returned
35522 when the target halts. In the below the exact meaning of @dfn{signal
35523 number} is defined by the header @file{include/gdb/signals.h} in the
35524 @value{GDBN} source code.
35526 As in the description of request packets, we include spaces in the
35527 reply templates for clarity; these are not part of the reply packet's
35528 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35534 The program received signal number @var{AA} (a two-digit hexadecimal
35535 number). This is equivalent to a @samp{T} response with no
35536 @var{n}:@var{r} pairs.
35538 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35539 @cindex @samp{T} packet reply
35540 The program received signal number @var{AA} (a two-digit hexadecimal
35541 number). This is equivalent to an @samp{S} response, except that the
35542 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35543 and other information directly in the stop reply packet, reducing
35544 round-trip latency. Single-step and breakpoint traps are reported
35545 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35549 If @var{n} is a hexadecimal number, it is a register number, and the
35550 corresponding @var{r} gives that register's value. The data @var{r} is a
35551 series of bytes in target byte order, with each byte given by a
35552 two-digit hex number.
35555 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35556 the stopped thread, as specified in @ref{thread-id syntax}.
35559 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35560 the core on which the stop event was detected.
35563 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35564 specific event that stopped the target. The currently defined stop
35565 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35566 signal. At most one stop reason should be present.
35569 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35570 and go on to the next; this allows us to extend the protocol in the
35574 The currently defined stop reasons are:
35580 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35583 @cindex shared library events, remote reply
35585 The packet indicates that the loaded libraries have changed.
35586 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35587 list of loaded libraries. The @var{r} part is ignored.
35589 @cindex replay log events, remote reply
35591 The packet indicates that the target cannot continue replaying
35592 logged execution events, because it has reached the end (or the
35593 beginning when executing backward) of the log. The value of @var{r}
35594 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35595 for more information.
35598 @anchor{swbreak stop reason}
35599 The packet indicates a memory breakpoint instruction was executed,
35600 irrespective of whether it was @value{GDBN} that planted the
35601 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35602 part must be left empty.
35604 On some architectures, such as x86, at the architecture level, when a
35605 breakpoint instruction executes the program counter points at the
35606 breakpoint address plus an offset. On such targets, the stub is
35607 responsible for adjusting the PC to point back at the breakpoint
35610 This packet should not be sent by default; older @value{GDBN} versions
35611 did not support it. @value{GDBN} requests it, by supplying an
35612 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35613 remote stub must also supply the appropriate @samp{qSupported} feature
35614 indicating support.
35616 This packet is required for correct non-stop mode operation.
35619 The packet indicates the target stopped for a hardware breakpoint.
35620 The @var{r} part must be left empty.
35622 The same remarks about @samp{qSupported} and non-stop mode above
35625 @cindex fork events, remote reply
35627 The packet indicates that @code{fork} was called, and @var{r}
35628 is the thread ID of the new child process. Refer to
35629 @ref{thread-id syntax} for the format of the @var{thread-id}
35630 field. This packet is only applicable to targets that support
35633 This packet should not be sent by default; older @value{GDBN} versions
35634 did not support it. @value{GDBN} requests it, by supplying an
35635 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35636 remote stub must also supply the appropriate @samp{qSupported} feature
35637 indicating support.
35639 @cindex vfork events, remote reply
35641 The packet indicates that @code{vfork} was called, and @var{r}
35642 is the thread ID of the new child process. Refer to
35643 @ref{thread-id syntax} for the format of the @var{thread-id}
35644 field. This packet is only applicable to targets that support
35647 This packet should not be sent by default; older @value{GDBN} versions
35648 did not support it. @value{GDBN} requests it, by supplying an
35649 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35650 remote stub must also supply the appropriate @samp{qSupported} feature
35651 indicating support.
35653 @cindex vforkdone events, remote reply
35655 The packet indicates that a child process created by a vfork
35656 has either called @code{exec} or terminated, so that the
35657 address spaces of the parent and child process are no longer
35658 shared. The @var{r} part is ignored. This packet is only
35659 applicable to targets that support vforkdone events.
35661 This packet should not be sent by default; older @value{GDBN} versions
35662 did not support it. @value{GDBN} requests it, by supplying an
35663 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35664 remote stub must also supply the appropriate @samp{qSupported} feature
35665 indicating support.
35667 @cindex exec events, remote reply
35669 The packet indicates that @code{execve} was called, and @var{r}
35670 is the absolute pathname of the file that was executed, in hex.
35671 This packet is only applicable to targets that support exec events.
35673 This packet should not be sent by default; older @value{GDBN} versions
35674 did not support it. @value{GDBN} requests it, by supplying an
35675 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35676 remote stub must also supply the appropriate @samp{qSupported} feature
35677 indicating support.
35679 @cindex thread create event, remote reply
35680 @anchor{thread create event}
35682 The packet indicates that the thread was just created. The new thread
35683 is stopped until @value{GDBN} sets it running with a resumption packet
35684 (@pxref{vCont packet}). This packet should not be sent by default;
35685 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35686 also the @samp{w} (@ref{thread exit event}) remote reply below.
35691 @itemx W @var{AA} ; process:@var{pid}
35692 The process exited, and @var{AA} is the exit status. This is only
35693 applicable to certain targets.
35695 The second form of the response, including the process ID of the exited
35696 process, can be used only when @value{GDBN} has reported support for
35697 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35698 The @var{pid} is formatted as a big-endian hex string.
35701 @itemx X @var{AA} ; process:@var{pid}
35702 The process terminated with signal @var{AA}.
35704 The second form of the response, including the process ID of the
35705 terminated process, can be used only when @value{GDBN} has reported
35706 support for multiprocess protocol extensions; see @ref{multiprocess
35707 extensions}. The @var{pid} is formatted as a big-endian hex string.
35709 @anchor{thread exit event}
35710 @cindex thread exit event, remote reply
35711 @item w @var{AA} ; @var{tid}
35713 The thread exited, and @var{AA} is the exit status. This response
35714 should not be sent by default; @value{GDBN} requests it with the
35715 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35718 There are no resumed threads left in the target. In other words, even
35719 though the process is alive, the last resumed thread has exited. For
35720 example, say the target process has two threads: thread 1 and thread
35721 2. The client leaves thread 1 stopped, and resumes thread 2, which
35722 subsequently exits. At this point, even though the process is still
35723 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35724 executing either. The @samp{N} stop reply thus informs the client
35725 that it can stop waiting for stop replies. This packet should not be
35726 sent by default; older @value{GDBN} versions did not support it.
35727 @value{GDBN} requests it, by supplying an appropriate
35728 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35729 also supply the appropriate @samp{qSupported} feature indicating
35732 @item O @var{XX}@dots{}
35733 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35734 written as the program's console output. This can happen at any time
35735 while the program is running and the debugger should continue to wait
35736 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35738 @item F @var{call-id},@var{parameter}@dots{}
35739 @var{call-id} is the identifier which says which host system call should
35740 be called. This is just the name of the function. Translation into the
35741 correct system call is only applicable as it's defined in @value{GDBN}.
35742 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35745 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35746 this very system call.
35748 The target replies with this packet when it expects @value{GDBN} to
35749 call a host system call on behalf of the target. @value{GDBN} replies
35750 with an appropriate @samp{F} packet and keeps up waiting for the next
35751 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35752 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35753 Protocol Extension}, for more details.
35757 @node General Query Packets
35758 @section General Query Packets
35759 @cindex remote query requests
35761 Packets starting with @samp{q} are @dfn{general query packets};
35762 packets starting with @samp{Q} are @dfn{general set packets}. General
35763 query and set packets are a semi-unified form for retrieving and
35764 sending information to and from the stub.
35766 The initial letter of a query or set packet is followed by a name
35767 indicating what sort of thing the packet applies to. For example,
35768 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35769 definitions with the stub. These packet names follow some
35774 The name must not contain commas, colons or semicolons.
35776 Most @value{GDBN} query and set packets have a leading upper case
35779 The names of custom vendor packets should use a company prefix, in
35780 lower case, followed by a period. For example, packets designed at
35781 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35782 foos) or @samp{Qacme.bar} (for setting bars).
35785 The name of a query or set packet should be separated from any
35786 parameters by a @samp{:}; the parameters themselves should be
35787 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35788 full packet name, and check for a separator or the end of the packet,
35789 in case two packet names share a common prefix. New packets should not begin
35790 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35791 packets predate these conventions, and have arguments without any terminator
35792 for the packet name; we suspect they are in widespread use in places that
35793 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35794 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35797 Like the descriptions of the other packets, each description here
35798 has a template showing the packet's overall syntax, followed by an
35799 explanation of the packet's meaning. We include spaces in some of the
35800 templates for clarity; these are not part of the packet's syntax. No
35801 @value{GDBN} packet uses spaces to separate its components.
35803 Here are the currently defined query and set packets:
35809 Turn on or off the agent as a helper to perform some debugging operations
35810 delegated from @value{GDBN} (@pxref{Control Agent}).
35812 @item QAllow:@var{op}:@var{val}@dots{}
35813 @cindex @samp{QAllow} packet
35814 Specify which operations @value{GDBN} expects to request of the
35815 target, as a semicolon-separated list of operation name and value
35816 pairs. Possible values for @var{op} include @samp{WriteReg},
35817 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35818 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35819 indicating that @value{GDBN} will not request the operation, or 1,
35820 indicating that it may. (The target can then use this to set up its
35821 own internals optimally, for instance if the debugger never expects to
35822 insert breakpoints, it may not need to install its own trap handler.)
35825 @cindex current thread, remote request
35826 @cindex @samp{qC} packet
35827 Return the current thread ID.
35831 @item QC @var{thread-id}
35832 Where @var{thread-id} is a thread ID as documented in
35833 @ref{thread-id syntax}.
35834 @item @r{(anything else)}
35835 Any other reply implies the old thread ID.
35838 @item qCRC:@var{addr},@var{length}
35839 @cindex CRC of memory block, remote request
35840 @cindex @samp{qCRC} packet
35841 @anchor{qCRC packet}
35842 Compute the CRC checksum of a block of memory using CRC-32 defined in
35843 IEEE 802.3. The CRC is computed byte at a time, taking the most
35844 significant bit of each byte first. The initial pattern code
35845 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35847 @emph{Note:} This is the same CRC used in validating separate debug
35848 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35849 Files}). However the algorithm is slightly different. When validating
35850 separate debug files, the CRC is computed taking the @emph{least}
35851 significant bit of each byte first, and the final result is inverted to
35852 detect trailing zeros.
35857 An error (such as memory fault)
35858 @item C @var{crc32}
35859 The specified memory region's checksum is @var{crc32}.
35862 @item QDisableRandomization:@var{value}
35863 @cindex disable address space randomization, remote request
35864 @cindex @samp{QDisableRandomization} packet
35865 Some target operating systems will randomize the virtual address space
35866 of the inferior process as a security feature, but provide a feature
35867 to disable such randomization, e.g.@: to allow for a more deterministic
35868 debugging experience. On such systems, this packet with a @var{value}
35869 of 1 directs the target to disable address space randomization for
35870 processes subsequently started via @samp{vRun} packets, while a packet
35871 with a @var{value} of 0 tells the target to enable address space
35874 This packet is only available in extended mode (@pxref{extended mode}).
35879 The request succeeded.
35882 An error occurred. The error number @var{nn} is given as hex digits.
35885 An empty reply indicates that @samp{QDisableRandomization} is not supported
35889 This packet is not probed by default; the remote stub must request it,
35890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35891 This should only be done on targets that actually support disabling
35892 address space randomization.
35895 @itemx qsThreadInfo
35896 @cindex list active threads, remote request
35897 @cindex @samp{qfThreadInfo} packet
35898 @cindex @samp{qsThreadInfo} packet
35899 Obtain a list of all active thread IDs from the target (OS). Since there
35900 may be too many active threads to fit into one reply packet, this query
35901 works iteratively: it may require more than one query/reply sequence to
35902 obtain the entire list of threads. The first query of the sequence will
35903 be the @samp{qfThreadInfo} query; subsequent queries in the
35904 sequence will be the @samp{qsThreadInfo} query.
35906 NOTE: This packet replaces the @samp{qL} query (see below).
35910 @item m @var{thread-id}
35912 @item m @var{thread-id},@var{thread-id}@dots{}
35913 a comma-separated list of thread IDs
35915 (lower case letter @samp{L}) denotes end of list.
35918 In response to each query, the target will reply with a list of one or
35919 more thread IDs, separated by commas.
35920 @value{GDBN} will respond to each reply with a request for more thread
35921 ids (using the @samp{qs} form of the query), until the target responds
35922 with @samp{l} (lower-case ell, for @dfn{last}).
35923 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35926 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35927 initial connection with the remote target, and the very first thread ID
35928 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35929 message. Therefore, the stub should ensure that the first thread ID in
35930 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35932 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35933 @cindex get thread-local storage address, remote request
35934 @cindex @samp{qGetTLSAddr} packet
35935 Fetch the address associated with thread local storage specified
35936 by @var{thread-id}, @var{offset}, and @var{lm}.
35938 @var{thread-id} is the thread ID associated with the
35939 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35941 @var{offset} is the (big endian, hex encoded) offset associated with the
35942 thread local variable. (This offset is obtained from the debug
35943 information associated with the variable.)
35945 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35946 load module associated with the thread local storage. For example,
35947 a @sc{gnu}/Linux system will pass the link map address of the shared
35948 object associated with the thread local storage under consideration.
35949 Other operating environments may choose to represent the load module
35950 differently, so the precise meaning of this parameter will vary.
35954 @item @var{XX}@dots{}
35955 Hex encoded (big endian) bytes representing the address of the thread
35956 local storage requested.
35959 An error occurred. The error number @var{nn} is given as hex digits.
35962 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35965 @item qGetTIBAddr:@var{thread-id}
35966 @cindex get thread information block address
35967 @cindex @samp{qGetTIBAddr} packet
35968 Fetch address of the Windows OS specific Thread Information Block.
35970 @var{thread-id} is the thread ID associated with the thread.
35974 @item @var{XX}@dots{}
35975 Hex encoded (big endian) bytes representing the linear address of the
35976 thread information block.
35979 An error occured. This means that either the thread was not found, or the
35980 address could not be retrieved.
35983 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35986 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35987 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35988 digit) is one to indicate the first query and zero to indicate a
35989 subsequent query; @var{threadcount} (two hex digits) is the maximum
35990 number of threads the response packet can contain; and @var{nextthread}
35991 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35992 returned in the response as @var{argthread}.
35994 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35998 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35999 Where: @var{count} (two hex digits) is the number of threads being
36000 returned; @var{done} (one hex digit) is zero to indicate more threads
36001 and one indicates no further threads; @var{argthreadid} (eight hex
36002 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36003 is a sequence of thread IDs, @var{threadid} (eight hex
36004 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36008 @cindex section offsets, remote request
36009 @cindex @samp{qOffsets} packet
36010 Get section offsets that the target used when relocating the downloaded
36015 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36016 Relocate the @code{Text} section by @var{xxx} from its original address.
36017 Relocate the @code{Data} section by @var{yyy} from its original address.
36018 If the object file format provides segment information (e.g.@: @sc{elf}
36019 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36020 segments by the supplied offsets.
36022 @emph{Note: while a @code{Bss} offset may be included in the response,
36023 @value{GDBN} ignores this and instead applies the @code{Data} offset
36024 to the @code{Bss} section.}
36026 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36027 Relocate the first segment of the object file, which conventionally
36028 contains program code, to a starting address of @var{xxx}. If
36029 @samp{DataSeg} is specified, relocate the second segment, which
36030 conventionally contains modifiable data, to a starting address of
36031 @var{yyy}. @value{GDBN} will report an error if the object file
36032 does not contain segment information, or does not contain at least
36033 as many segments as mentioned in the reply. Extra segments are
36034 kept at fixed offsets relative to the last relocated segment.
36037 @item qP @var{mode} @var{thread-id}
36038 @cindex thread information, remote request
36039 @cindex @samp{qP} packet
36040 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36041 encoded 32 bit mode; @var{thread-id} is a thread ID
36042 (@pxref{thread-id syntax}).
36044 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36047 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36051 @cindex non-stop mode, remote request
36052 @cindex @samp{QNonStop} packet
36054 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36055 @xref{Remote Non-Stop}, for more information.
36060 The request succeeded.
36063 An error occurred. The error number @var{nn} is given as hex digits.
36066 An empty reply indicates that @samp{QNonStop} is not supported by
36070 This packet is not probed by default; the remote stub must request it,
36071 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36072 Use of this packet is controlled by the @code{set non-stop} command;
36073 @pxref{Non-Stop Mode}.
36075 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36076 @cindex pass signals to inferior, remote request
36077 @cindex @samp{QPassSignals} packet
36078 @anchor{QPassSignals}
36079 Each listed @var{signal} should be passed directly to the inferior process.
36080 Signals are numbered identically to continue packets and stop replies
36081 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36082 strictly greater than the previous item. These signals do not need to stop
36083 the inferior, or be reported to @value{GDBN}. All other signals should be
36084 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36085 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36086 new list. This packet improves performance when using @samp{handle
36087 @var{signal} nostop noprint pass}.
36092 The request succeeded.
36095 An error occurred. The error number @var{nn} is given as hex digits.
36098 An empty reply indicates that @samp{QPassSignals} is not supported by
36102 Use of this packet is controlled by the @code{set remote pass-signals}
36103 command (@pxref{Remote Configuration, set remote pass-signals}).
36104 This packet is not probed by default; the remote stub must request it,
36105 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36107 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36108 @cindex signals the inferior may see, remote request
36109 @cindex @samp{QProgramSignals} packet
36110 @anchor{QProgramSignals}
36111 Each listed @var{signal} may be delivered to the inferior process.
36112 Others should be silently discarded.
36114 In some cases, the remote stub may need to decide whether to deliver a
36115 signal to the program or not without @value{GDBN} involvement. One
36116 example of that is while detaching --- the program's threads may have
36117 stopped for signals that haven't yet had a chance of being reported to
36118 @value{GDBN}, and so the remote stub can use the signal list specified
36119 by this packet to know whether to deliver or ignore those pending
36122 This does not influence whether to deliver a signal as requested by a
36123 resumption packet (@pxref{vCont packet}).
36125 Signals are numbered identically to continue packets and stop replies
36126 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36127 strictly greater than the previous item. Multiple
36128 @samp{QProgramSignals} packets do not combine; any earlier
36129 @samp{QProgramSignals} list is completely replaced by the new list.
36134 The request succeeded.
36137 An error occurred. The error number @var{nn} is given as hex digits.
36140 An empty reply indicates that @samp{QProgramSignals} is not supported
36144 Use of this packet is controlled by the @code{set remote program-signals}
36145 command (@pxref{Remote Configuration, set remote program-signals}).
36146 This packet is not probed by default; the remote stub must request it,
36147 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36149 @anchor{QThreadEvents}
36150 @item QThreadEvents:1
36151 @itemx QThreadEvents:0
36152 @cindex thread create/exit events, remote request
36153 @cindex @samp{QThreadEvents} packet
36155 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36156 reporting of thread create and exit events. @xref{thread create
36157 event}, for the reply specifications. For example, this is used in
36158 non-stop mode when @value{GDBN} stops a set of threads and
36159 synchronously waits for the their corresponding stop replies. Without
36160 exit events, if one of the threads exits, @value{GDBN} would hang
36161 forever not knowing that it should no longer expect a stop for that
36162 same thread. @value{GDBN} does not enable this feature unless the
36163 stub reports that it supports it by including @samp{QThreadEvents+} in
36164 its @samp{qSupported} reply.
36169 The request succeeded.
36172 An error occurred. The error number @var{nn} is given as hex digits.
36175 An empty reply indicates that @samp{QThreadEvents} is not supported by
36179 Use of this packet is controlled by the @code{set remote thread-events}
36180 command (@pxref{Remote Configuration, set remote thread-events}).
36182 @item qRcmd,@var{command}
36183 @cindex execute remote command, remote request
36184 @cindex @samp{qRcmd} packet
36185 @var{command} (hex encoded) is passed to the local interpreter for
36186 execution. Invalid commands should be reported using the output
36187 string. Before the final result packet, the target may also respond
36188 with a number of intermediate @samp{O@var{output}} console output
36189 packets. @emph{Implementors should note that providing access to a
36190 stubs's interpreter may have security implications}.
36195 A command response with no output.
36197 A command response with the hex encoded output string @var{OUTPUT}.
36199 Indicate a badly formed request.
36201 An empty reply indicates that @samp{qRcmd} is not recognized.
36204 (Note that the @code{qRcmd} packet's name is separated from the
36205 command by a @samp{,}, not a @samp{:}, contrary to the naming
36206 conventions above. Please don't use this packet as a model for new
36209 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36210 @cindex searching memory, in remote debugging
36212 @cindex @samp{qSearch:memory} packet
36214 @cindex @samp{qSearch memory} packet
36215 @anchor{qSearch memory}
36216 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36217 Both @var{address} and @var{length} are encoded in hex;
36218 @var{search-pattern} is a sequence of bytes, also hex encoded.
36223 The pattern was not found.
36225 The pattern was found at @var{address}.
36227 A badly formed request or an error was encountered while searching memory.
36229 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36232 @item QStartNoAckMode
36233 @cindex @samp{QStartNoAckMode} packet
36234 @anchor{QStartNoAckMode}
36235 Request that the remote stub disable the normal @samp{+}/@samp{-}
36236 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36241 The stub has switched to no-acknowledgment mode.
36242 @value{GDBN} acknowledges this reponse,
36243 but neither the stub nor @value{GDBN} shall send or expect further
36244 @samp{+}/@samp{-} acknowledgments in the current connection.
36246 An empty reply indicates that the stub does not support no-acknowledgment mode.
36249 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36250 @cindex supported packets, remote query
36251 @cindex features of the remote protocol
36252 @cindex @samp{qSupported} packet
36253 @anchor{qSupported}
36254 Tell the remote stub about features supported by @value{GDBN}, and
36255 query the stub for features it supports. This packet allows
36256 @value{GDBN} and the remote stub to take advantage of each others'
36257 features. @samp{qSupported} also consolidates multiple feature probes
36258 at startup, to improve @value{GDBN} performance---a single larger
36259 packet performs better than multiple smaller probe packets on
36260 high-latency links. Some features may enable behavior which must not
36261 be on by default, e.g.@: because it would confuse older clients or
36262 stubs. Other features may describe packets which could be
36263 automatically probed for, but are not. These features must be
36264 reported before @value{GDBN} will use them. This ``default
36265 unsupported'' behavior is not appropriate for all packets, but it
36266 helps to keep the initial connection time under control with new
36267 versions of @value{GDBN} which support increasing numbers of packets.
36271 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36272 The stub supports or does not support each returned @var{stubfeature},
36273 depending on the form of each @var{stubfeature} (see below for the
36276 An empty reply indicates that @samp{qSupported} is not recognized,
36277 or that no features needed to be reported to @value{GDBN}.
36280 The allowed forms for each feature (either a @var{gdbfeature} in the
36281 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36285 @item @var{name}=@var{value}
36286 The remote protocol feature @var{name} is supported, and associated
36287 with the specified @var{value}. The format of @var{value} depends
36288 on the feature, but it must not include a semicolon.
36290 The remote protocol feature @var{name} is supported, and does not
36291 need an associated value.
36293 The remote protocol feature @var{name} is not supported.
36295 The remote protocol feature @var{name} may be supported, and
36296 @value{GDBN} should auto-detect support in some other way when it is
36297 needed. This form will not be used for @var{gdbfeature} notifications,
36298 but may be used for @var{stubfeature} responses.
36301 Whenever the stub receives a @samp{qSupported} request, the
36302 supplied set of @value{GDBN} features should override any previous
36303 request. This allows @value{GDBN} to put the stub in a known
36304 state, even if the stub had previously been communicating with
36305 a different version of @value{GDBN}.
36307 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36312 This feature indicates whether @value{GDBN} supports multiprocess
36313 extensions to the remote protocol. @value{GDBN} does not use such
36314 extensions unless the stub also reports that it supports them by
36315 including @samp{multiprocess+} in its @samp{qSupported} reply.
36316 @xref{multiprocess extensions}, for details.
36319 This feature indicates that @value{GDBN} supports the XML target
36320 description. If the stub sees @samp{xmlRegisters=} with target
36321 specific strings separated by a comma, it will report register
36325 This feature indicates whether @value{GDBN} supports the
36326 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36327 instruction reply packet}).
36330 This feature indicates whether @value{GDBN} supports the swbreak stop
36331 reason in stop replies. @xref{swbreak stop reason}, for details.
36334 This feature indicates whether @value{GDBN} supports the hwbreak stop
36335 reason in stop replies. @xref{swbreak stop reason}, for details.
36338 This feature indicates whether @value{GDBN} supports fork event
36339 extensions to the remote protocol. @value{GDBN} does not use such
36340 extensions unless the stub also reports that it supports them by
36341 including @samp{fork-events+} in its @samp{qSupported} reply.
36344 This feature indicates whether @value{GDBN} supports vfork event
36345 extensions to the remote protocol. @value{GDBN} does not use such
36346 extensions unless the stub also reports that it supports them by
36347 including @samp{vfork-events+} in its @samp{qSupported} reply.
36350 This feature indicates whether @value{GDBN} supports exec event
36351 extensions to the remote protocol. @value{GDBN} does not use such
36352 extensions unless the stub also reports that it supports them by
36353 including @samp{exec-events+} in its @samp{qSupported} reply.
36355 @item vContSupported
36356 This feature indicates whether @value{GDBN} wants to know the
36357 supported actions in the reply to @samp{vCont?} packet.
36360 Stubs should ignore any unknown values for
36361 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36362 packet supports receiving packets of unlimited length (earlier
36363 versions of @value{GDBN} may reject overly long responses). Additional values
36364 for @var{gdbfeature} may be defined in the future to let the stub take
36365 advantage of new features in @value{GDBN}, e.g.@: incompatible
36366 improvements in the remote protocol---the @samp{multiprocess} feature is
36367 an example of such a feature. The stub's reply should be independent
36368 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36369 describes all the features it supports, and then the stub replies with
36370 all the features it supports.
36372 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36373 responses, as long as each response uses one of the standard forms.
36375 Some features are flags. A stub which supports a flag feature
36376 should respond with a @samp{+} form response. Other features
36377 require values, and the stub should respond with an @samp{=}
36380 Each feature has a default value, which @value{GDBN} will use if
36381 @samp{qSupported} is not available or if the feature is not mentioned
36382 in the @samp{qSupported} response. The default values are fixed; a
36383 stub is free to omit any feature responses that match the defaults.
36385 Not all features can be probed, but for those which can, the probing
36386 mechanism is useful: in some cases, a stub's internal
36387 architecture may not allow the protocol layer to know some information
36388 about the underlying target in advance. This is especially common in
36389 stubs which may be configured for multiple targets.
36391 These are the currently defined stub features and their properties:
36393 @multitable @columnfractions 0.35 0.2 0.12 0.2
36394 @c NOTE: The first row should be @headitem, but we do not yet require
36395 @c a new enough version of Texinfo (4.7) to use @headitem.
36397 @tab Value Required
36401 @item @samp{PacketSize}
36406 @item @samp{qXfer:auxv:read}
36411 @item @samp{qXfer:btrace:read}
36416 @item @samp{qXfer:btrace-conf:read}
36421 @item @samp{qXfer:exec-file:read}
36426 @item @samp{qXfer:features:read}
36431 @item @samp{qXfer:libraries:read}
36436 @item @samp{qXfer:libraries-svr4:read}
36441 @item @samp{augmented-libraries-svr4-read}
36446 @item @samp{qXfer:memory-map:read}
36451 @item @samp{qXfer:sdata:read}
36456 @item @samp{qXfer:spu:read}
36461 @item @samp{qXfer:spu:write}
36466 @item @samp{qXfer:siginfo:read}
36471 @item @samp{qXfer:siginfo:write}
36476 @item @samp{qXfer:threads:read}
36481 @item @samp{qXfer:traceframe-info:read}
36486 @item @samp{qXfer:uib:read}
36491 @item @samp{qXfer:fdpic:read}
36496 @item @samp{Qbtrace:off}
36501 @item @samp{Qbtrace:bts}
36506 @item @samp{Qbtrace:pt}
36511 @item @samp{Qbtrace-conf:bts:size}
36516 @item @samp{Qbtrace-conf:pt:size}
36521 @item @samp{QNonStop}
36526 @item @samp{QPassSignals}
36531 @item @samp{QStartNoAckMode}
36536 @item @samp{multiprocess}
36541 @item @samp{ConditionalBreakpoints}
36546 @item @samp{ConditionalTracepoints}
36551 @item @samp{ReverseContinue}
36556 @item @samp{ReverseStep}
36561 @item @samp{TracepointSource}
36566 @item @samp{QAgent}
36571 @item @samp{QAllow}
36576 @item @samp{QDisableRandomization}
36581 @item @samp{EnableDisableTracepoints}
36586 @item @samp{QTBuffer:size}
36591 @item @samp{tracenz}
36596 @item @samp{BreakpointCommands}
36601 @item @samp{swbreak}
36606 @item @samp{hwbreak}
36611 @item @samp{fork-events}
36616 @item @samp{vfork-events}
36621 @item @samp{exec-events}
36626 @item @samp{QThreadEvents}
36631 @item @samp{no-resumed}
36638 These are the currently defined stub features, in more detail:
36641 @cindex packet size, remote protocol
36642 @item PacketSize=@var{bytes}
36643 The remote stub can accept packets up to at least @var{bytes} in
36644 length. @value{GDBN} will send packets up to this size for bulk
36645 transfers, and will never send larger packets. This is a limit on the
36646 data characters in the packet, including the frame and checksum.
36647 There is no trailing NUL byte in a remote protocol packet; if the stub
36648 stores packets in a NUL-terminated format, it should allow an extra
36649 byte in its buffer for the NUL. If this stub feature is not supported,
36650 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36652 @item qXfer:auxv:read
36653 The remote stub understands the @samp{qXfer:auxv:read} packet
36654 (@pxref{qXfer auxiliary vector read}).
36656 @item qXfer:btrace:read
36657 The remote stub understands the @samp{qXfer:btrace:read}
36658 packet (@pxref{qXfer btrace read}).
36660 @item qXfer:btrace-conf:read
36661 The remote stub understands the @samp{qXfer:btrace-conf:read}
36662 packet (@pxref{qXfer btrace-conf read}).
36664 @item qXfer:exec-file:read
36665 The remote stub understands the @samp{qXfer:exec-file:read} packet
36666 (@pxref{qXfer executable filename read}).
36668 @item qXfer:features:read
36669 The remote stub understands the @samp{qXfer:features:read} packet
36670 (@pxref{qXfer target description read}).
36672 @item qXfer:libraries:read
36673 The remote stub understands the @samp{qXfer:libraries:read} packet
36674 (@pxref{qXfer library list read}).
36676 @item qXfer:libraries-svr4:read
36677 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36678 (@pxref{qXfer svr4 library list read}).
36680 @item augmented-libraries-svr4-read
36681 The remote stub understands the augmented form of the
36682 @samp{qXfer:libraries-svr4:read} packet
36683 (@pxref{qXfer svr4 library list read}).
36685 @item qXfer:memory-map:read
36686 The remote stub understands the @samp{qXfer:memory-map:read} packet
36687 (@pxref{qXfer memory map read}).
36689 @item qXfer:sdata:read
36690 The remote stub understands the @samp{qXfer:sdata:read} packet
36691 (@pxref{qXfer sdata read}).
36693 @item qXfer:spu:read
36694 The remote stub understands the @samp{qXfer:spu:read} packet
36695 (@pxref{qXfer spu read}).
36697 @item qXfer:spu:write
36698 The remote stub understands the @samp{qXfer:spu:write} packet
36699 (@pxref{qXfer spu write}).
36701 @item qXfer:siginfo:read
36702 The remote stub understands the @samp{qXfer:siginfo:read} packet
36703 (@pxref{qXfer siginfo read}).
36705 @item qXfer:siginfo:write
36706 The remote stub understands the @samp{qXfer:siginfo:write} packet
36707 (@pxref{qXfer siginfo write}).
36709 @item qXfer:threads:read
36710 The remote stub understands the @samp{qXfer:threads:read} packet
36711 (@pxref{qXfer threads read}).
36713 @item qXfer:traceframe-info:read
36714 The remote stub understands the @samp{qXfer:traceframe-info:read}
36715 packet (@pxref{qXfer traceframe info read}).
36717 @item qXfer:uib:read
36718 The remote stub understands the @samp{qXfer:uib:read}
36719 packet (@pxref{qXfer unwind info block}).
36721 @item qXfer:fdpic:read
36722 The remote stub understands the @samp{qXfer:fdpic:read}
36723 packet (@pxref{qXfer fdpic loadmap read}).
36726 The remote stub understands the @samp{QNonStop} packet
36727 (@pxref{QNonStop}).
36730 The remote stub understands the @samp{QPassSignals} packet
36731 (@pxref{QPassSignals}).
36733 @item QStartNoAckMode
36734 The remote stub understands the @samp{QStartNoAckMode} packet and
36735 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36738 @anchor{multiprocess extensions}
36739 @cindex multiprocess extensions, in remote protocol
36740 The remote stub understands the multiprocess extensions to the remote
36741 protocol syntax. The multiprocess extensions affect the syntax of
36742 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36743 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36744 replies. Note that reporting this feature indicates support for the
36745 syntactic extensions only, not that the stub necessarily supports
36746 debugging of more than one process at a time. The stub must not use
36747 multiprocess extensions in packet replies unless @value{GDBN} has also
36748 indicated it supports them in its @samp{qSupported} request.
36750 @item qXfer:osdata:read
36751 The remote stub understands the @samp{qXfer:osdata:read} packet
36752 ((@pxref{qXfer osdata read}).
36754 @item ConditionalBreakpoints
36755 The target accepts and implements evaluation of conditional expressions
36756 defined for breakpoints. The target will only report breakpoint triggers
36757 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36759 @item ConditionalTracepoints
36760 The remote stub accepts and implements conditional expressions defined
36761 for tracepoints (@pxref{Tracepoint Conditions}).
36763 @item ReverseContinue
36764 The remote stub accepts and implements the reverse continue packet
36768 The remote stub accepts and implements the reverse step packet
36771 @item TracepointSource
36772 The remote stub understands the @samp{QTDPsrc} packet that supplies
36773 the source form of tracepoint definitions.
36776 The remote stub understands the @samp{QAgent} packet.
36779 The remote stub understands the @samp{QAllow} packet.
36781 @item QDisableRandomization
36782 The remote stub understands the @samp{QDisableRandomization} packet.
36784 @item StaticTracepoint
36785 @cindex static tracepoints, in remote protocol
36786 The remote stub supports static tracepoints.
36788 @item InstallInTrace
36789 @anchor{install tracepoint in tracing}
36790 The remote stub supports installing tracepoint in tracing.
36792 @item EnableDisableTracepoints
36793 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36794 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36795 to be enabled and disabled while a trace experiment is running.
36797 @item QTBuffer:size
36798 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36799 packet that allows to change the size of the trace buffer.
36802 @cindex string tracing, in remote protocol
36803 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36804 See @ref{Bytecode Descriptions} for details about the bytecode.
36806 @item BreakpointCommands
36807 @cindex breakpoint commands, in remote protocol
36808 The remote stub supports running a breakpoint's command list itself,
36809 rather than reporting the hit to @value{GDBN}.
36812 The remote stub understands the @samp{Qbtrace:off} packet.
36815 The remote stub understands the @samp{Qbtrace:bts} packet.
36818 The remote stub understands the @samp{Qbtrace:pt} packet.
36820 @item Qbtrace-conf:bts:size
36821 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36823 @item Qbtrace-conf:pt:size
36824 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36827 The remote stub reports the @samp{swbreak} stop reason for memory
36831 The remote stub reports the @samp{hwbreak} stop reason for hardware
36835 The remote stub reports the @samp{fork} stop reason for fork events.
36838 The remote stub reports the @samp{vfork} stop reason for vfork events
36839 and vforkdone events.
36842 The remote stub reports the @samp{exec} stop reason for exec events.
36844 @item vContSupported
36845 The remote stub reports the supported actions in the reply to
36846 @samp{vCont?} packet.
36848 @item QThreadEvents
36849 The remote stub understands the @samp{QThreadEvents} packet.
36852 The remote stub reports the @samp{N} stop reply.
36857 @cindex symbol lookup, remote request
36858 @cindex @samp{qSymbol} packet
36859 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36860 requests. Accept requests from the target for the values of symbols.
36865 The target does not need to look up any (more) symbols.
36866 @item qSymbol:@var{sym_name}
36867 The target requests the value of symbol @var{sym_name} (hex encoded).
36868 @value{GDBN} may provide the value by using the
36869 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36873 @item qSymbol:@var{sym_value}:@var{sym_name}
36874 Set the value of @var{sym_name} to @var{sym_value}.
36876 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36877 target has previously requested.
36879 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36880 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36886 The target does not need to look up any (more) symbols.
36887 @item qSymbol:@var{sym_name}
36888 The target requests the value of a new symbol @var{sym_name} (hex
36889 encoded). @value{GDBN} will continue to supply the values of symbols
36890 (if available), until the target ceases to request them.
36895 @itemx QTDisconnected
36902 @itemx qTMinFTPILen
36904 @xref{Tracepoint Packets}.
36906 @item qThreadExtraInfo,@var{thread-id}
36907 @cindex thread attributes info, remote request
36908 @cindex @samp{qThreadExtraInfo} packet
36909 Obtain from the target OS a printable string description of thread
36910 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36911 for the forms of @var{thread-id}. This
36912 string may contain anything that the target OS thinks is interesting
36913 for @value{GDBN} to tell the user about the thread. The string is
36914 displayed in @value{GDBN}'s @code{info threads} display. Some
36915 examples of possible thread extra info strings are @samp{Runnable}, or
36916 @samp{Blocked on Mutex}.
36920 @item @var{XX}@dots{}
36921 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36922 comprising the printable string containing the extra information about
36923 the thread's attributes.
36926 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36927 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36928 conventions above. Please don't use this packet as a model for new
36947 @xref{Tracepoint Packets}.
36949 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36950 @cindex read special object, remote request
36951 @cindex @samp{qXfer} packet
36952 @anchor{qXfer read}
36953 Read uninterpreted bytes from the target's special data area
36954 identified by the keyword @var{object}. Request @var{length} bytes
36955 starting at @var{offset} bytes into the data. The content and
36956 encoding of @var{annex} is specific to @var{object}; it can supply
36957 additional details about what data to access.
36959 Here are the specific requests of this form defined so far. All
36960 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36961 formats, listed below.
36964 @item qXfer:auxv:read::@var{offset},@var{length}
36965 @anchor{qXfer auxiliary vector read}
36966 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36967 auxiliary vector}. Note @var{annex} must be empty.
36969 This packet is not probed by default; the remote stub must request it,
36970 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36972 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36973 @anchor{qXfer btrace read}
36975 Return a description of the current branch trace.
36976 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36977 packet may have one of the following values:
36981 Returns all available branch trace.
36984 Returns all available branch trace if the branch trace changed since
36985 the last read request.
36988 Returns the new branch trace since the last read request. Adds a new
36989 block to the end of the trace that begins at zero and ends at the source
36990 location of the first branch in the trace buffer. This extra block is
36991 used to stitch traces together.
36993 If the trace buffer overflowed, returns an error indicating the overflow.
36996 This packet is not probed by default; the remote stub must request it
36997 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36999 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37000 @anchor{qXfer btrace-conf read}
37002 Return a description of the current branch trace configuration.
37003 @xref{Branch Trace Configuration Format}.
37005 This packet is not probed by default; the remote stub must request it
37006 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37008 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37009 @anchor{qXfer executable filename read}
37010 Return the full absolute name of the file that was executed to create
37011 a process running on the remote system. The annex specifies the
37012 numeric process ID of the process to query, encoded as a hexadecimal
37013 number. If the annex part is empty the remote stub should return the
37014 filename corresponding to the currently executing process.
37016 This packet is not probed by default; the remote stub must request it,
37017 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37019 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37020 @anchor{qXfer target description read}
37021 Access the @dfn{target description}. @xref{Target Descriptions}. The
37022 annex specifies which XML document to access. The main description is
37023 always loaded from the @samp{target.xml} annex.
37025 This packet is not probed by default; the remote stub must request it,
37026 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37028 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37029 @anchor{qXfer library list read}
37030 Access the target's list of loaded libraries. @xref{Library List Format}.
37031 The annex part of the generic @samp{qXfer} packet must be empty
37032 (@pxref{qXfer read}).
37034 Targets which maintain a list of libraries in the program's memory do
37035 not need to implement this packet; it is designed for platforms where
37036 the operating system manages the list of loaded libraries.
37038 This packet is not probed by default; the remote stub must request it,
37039 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37041 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37042 @anchor{qXfer svr4 library list read}
37043 Access the target's list of loaded libraries when the target is an SVR4
37044 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37045 of the generic @samp{qXfer} packet must be empty unless the remote
37046 stub indicated it supports the augmented form of this packet
37047 by supplying an appropriate @samp{qSupported} response
37048 (@pxref{qXfer read}, @ref{qSupported}).
37050 This packet is optional for better performance on SVR4 targets.
37051 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37053 This packet is not probed by default; the remote stub must request it,
37054 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37056 If the remote stub indicates it supports the augmented form of this
37057 packet then the annex part of the generic @samp{qXfer} packet may
37058 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37059 arguments. The currently supported arguments are:
37062 @item start=@var{address}
37063 A hexadecimal number specifying the address of the @samp{struct
37064 link_map} to start reading the library list from. If unset or zero
37065 then the first @samp{struct link_map} in the library list will be
37066 chosen as the starting point.
37068 @item prev=@var{address}
37069 A hexadecimal number specifying the address of the @samp{struct
37070 link_map} immediately preceding the @samp{struct link_map}
37071 specified by the @samp{start} argument. If unset or zero then
37072 the remote stub will expect that no @samp{struct link_map}
37073 exists prior to the starting point.
37077 Arguments that are not understood by the remote stub will be silently
37080 @item qXfer:memory-map:read::@var{offset},@var{length}
37081 @anchor{qXfer memory map read}
37082 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37083 annex part of the generic @samp{qXfer} packet must be empty
37084 (@pxref{qXfer read}).
37086 This packet is not probed by default; the remote stub must request it,
37087 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37089 @item qXfer:sdata:read::@var{offset},@var{length}
37090 @anchor{qXfer sdata read}
37092 Read contents of the extra collected static tracepoint marker
37093 information. The annex part of the generic @samp{qXfer} packet must
37094 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37097 This packet is not probed by default; the remote stub must request it,
37098 by supplying an appropriate @samp{qSupported} response
37099 (@pxref{qSupported}).
37101 @item qXfer:siginfo:read::@var{offset},@var{length}
37102 @anchor{qXfer siginfo read}
37103 Read contents of the extra signal information on the target
37104 system. The annex part of the generic @samp{qXfer} packet must be
37105 empty (@pxref{qXfer read}).
37107 This packet is not probed by default; the remote stub must request it,
37108 by supplying an appropriate @samp{qSupported} response
37109 (@pxref{qSupported}).
37111 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37112 @anchor{qXfer spu read}
37113 Read contents of an @code{spufs} file on the target system. The
37114 annex specifies which file to read; it must be of the form
37115 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37116 in the target process, and @var{name} identifes the @code{spufs} file
37117 in that context to be accessed.
37119 This packet is not probed by default; the remote stub must request it,
37120 by supplying an appropriate @samp{qSupported} response
37121 (@pxref{qSupported}).
37123 @item qXfer:threads:read::@var{offset},@var{length}
37124 @anchor{qXfer threads read}
37125 Access the list of threads on target. @xref{Thread List Format}. The
37126 annex part of the generic @samp{qXfer} packet must be empty
37127 (@pxref{qXfer read}).
37129 This packet is not probed by default; the remote stub must request it,
37130 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37132 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37133 @anchor{qXfer traceframe info read}
37135 Return a description of the current traceframe's contents.
37136 @xref{Traceframe Info Format}. The annex part of the generic
37137 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37139 This packet is not probed by default; the remote stub must request it,
37140 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37142 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37143 @anchor{qXfer unwind info block}
37145 Return the unwind information block for @var{pc}. This packet is used
37146 on OpenVMS/ia64 to ask the kernel unwind information.
37148 This packet is not probed by default.
37150 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37151 @anchor{qXfer fdpic loadmap read}
37152 Read contents of @code{loadmap}s on the target system. The
37153 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37154 executable @code{loadmap} or interpreter @code{loadmap} to read.
37156 This packet is not probed by default; the remote stub must request it,
37157 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37159 @item qXfer:osdata:read::@var{offset},@var{length}
37160 @anchor{qXfer osdata read}
37161 Access the target's @dfn{operating system information}.
37162 @xref{Operating System Information}.
37169 Data @var{data} (@pxref{Binary Data}) has been read from the
37170 target. There may be more data at a higher address (although
37171 it is permitted to return @samp{m} even for the last valid
37172 block of data, as long as at least one byte of data was read).
37173 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37177 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37178 There is no more data to be read. It is possible for @var{data} to
37179 have fewer bytes than the @var{length} in the request.
37182 The @var{offset} in the request is at the end of the data.
37183 There is no more data to be read.
37186 The request was malformed, or @var{annex} was invalid.
37189 The offset was invalid, or there was an error encountered reading the data.
37190 The @var{nn} part is a hex-encoded @code{errno} value.
37193 An empty reply indicates the @var{object} string was not recognized by
37194 the stub, or that the object does not support reading.
37197 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37198 @cindex write data into object, remote request
37199 @anchor{qXfer write}
37200 Write uninterpreted bytes into the target's special data area
37201 identified by the keyword @var{object}, starting at @var{offset} bytes
37202 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37203 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37204 is specific to @var{object}; it can supply additional details about what data
37207 Here are the specific requests of this form defined so far. All
37208 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37209 formats, listed below.
37212 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37213 @anchor{qXfer siginfo write}
37214 Write @var{data} to the extra signal information on the target system.
37215 The annex part of the generic @samp{qXfer} packet must be
37216 empty (@pxref{qXfer write}).
37218 This packet is not probed by default; the remote stub must request it,
37219 by supplying an appropriate @samp{qSupported} response
37220 (@pxref{qSupported}).
37222 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37223 @anchor{qXfer spu write}
37224 Write @var{data} to an @code{spufs} file on the target system. The
37225 annex specifies which file to write; it must be of the form
37226 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37227 in the target process, and @var{name} identifes the @code{spufs} file
37228 in that context to be accessed.
37230 This packet is not probed by default; the remote stub must request it,
37231 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37237 @var{nn} (hex encoded) is the number of bytes written.
37238 This may be fewer bytes than supplied in the request.
37241 The request was malformed, or @var{annex} was invalid.
37244 The offset was invalid, or there was an error encountered writing the data.
37245 The @var{nn} part is a hex-encoded @code{errno} value.
37248 An empty reply indicates the @var{object} string was not
37249 recognized by the stub, or that the object does not support writing.
37252 @item qXfer:@var{object}:@var{operation}:@dots{}
37253 Requests of this form may be added in the future. When a stub does
37254 not recognize the @var{object} keyword, or its support for
37255 @var{object} does not recognize the @var{operation} keyword, the stub
37256 must respond with an empty packet.
37258 @item qAttached:@var{pid}
37259 @cindex query attached, remote request
37260 @cindex @samp{qAttached} packet
37261 Return an indication of whether the remote server attached to an
37262 existing process or created a new process. When the multiprocess
37263 protocol extensions are supported (@pxref{multiprocess extensions}),
37264 @var{pid} is an integer in hexadecimal format identifying the target
37265 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37266 the query packet will be simplified as @samp{qAttached}.
37268 This query is used, for example, to know whether the remote process
37269 should be detached or killed when a @value{GDBN} session is ended with
37270 the @code{quit} command.
37275 The remote server attached to an existing process.
37277 The remote server created a new process.
37279 A badly formed request or an error was encountered.
37283 Enable branch tracing for the current thread using Branch Trace Store.
37288 Branch tracing has been enabled.
37290 A badly formed request or an error was encountered.
37294 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37299 Branch tracing has been enabled.
37301 A badly formed request or an error was encountered.
37305 Disable branch tracing for the current thread.
37310 Branch tracing has been disabled.
37312 A badly formed request or an error was encountered.
37315 @item Qbtrace-conf:bts:size=@var{value}
37316 Set the requested ring buffer size for new threads that use the
37317 btrace recording method in bts format.
37322 The ring buffer size has been set.
37324 A badly formed request or an error was encountered.
37327 @item Qbtrace-conf:pt:size=@var{value}
37328 Set the requested ring buffer size for new threads that use the
37329 btrace recording method in pt format.
37334 The ring buffer size has been set.
37336 A badly formed request or an error was encountered.
37341 @node Architecture-Specific Protocol Details
37342 @section Architecture-Specific Protocol Details
37344 This section describes how the remote protocol is applied to specific
37345 target architectures. Also see @ref{Standard Target Features}, for
37346 details of XML target descriptions for each architecture.
37349 * ARM-Specific Protocol Details::
37350 * MIPS-Specific Protocol Details::
37353 @node ARM-Specific Protocol Details
37354 @subsection @acronym{ARM}-specific Protocol Details
37357 * ARM Breakpoint Kinds::
37360 @node ARM Breakpoint Kinds
37361 @subsubsection @acronym{ARM} Breakpoint Kinds
37362 @cindex breakpoint kinds, @acronym{ARM}
37364 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37369 16-bit Thumb mode breakpoint.
37372 32-bit Thumb mode (Thumb-2) breakpoint.
37375 32-bit @acronym{ARM} mode breakpoint.
37379 @node MIPS-Specific Protocol Details
37380 @subsection @acronym{MIPS}-specific Protocol Details
37383 * MIPS Register packet Format::
37384 * MIPS Breakpoint Kinds::
37387 @node MIPS Register packet Format
37388 @subsubsection @acronym{MIPS} Register Packet Format
37389 @cindex register packet format, @acronym{MIPS}
37391 The following @code{g}/@code{G} packets have previously been defined.
37392 In the below, some thirty-two bit registers are transferred as
37393 sixty-four bits. Those registers should be zero/sign extended (which?)
37394 to fill the space allocated. Register bytes are transferred in target
37395 byte order. The two nibbles within a register byte are transferred
37396 most-significant -- least-significant.
37401 All registers are transferred as thirty-two bit quantities in the order:
37402 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37403 registers; fsr; fir; fp.
37406 All registers are transferred as sixty-four bit quantities (including
37407 thirty-two bit registers such as @code{sr}). The ordering is the same
37412 @node MIPS Breakpoint Kinds
37413 @subsubsection @acronym{MIPS} Breakpoint Kinds
37414 @cindex breakpoint kinds, @acronym{MIPS}
37416 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37421 16-bit @acronym{MIPS16} mode breakpoint.
37424 16-bit @acronym{microMIPS} mode breakpoint.
37427 32-bit standard @acronym{MIPS} mode breakpoint.
37430 32-bit @acronym{microMIPS} mode breakpoint.
37434 @node Tracepoint Packets
37435 @section Tracepoint Packets
37436 @cindex tracepoint packets
37437 @cindex packets, tracepoint
37439 Here we describe the packets @value{GDBN} uses to implement
37440 tracepoints (@pxref{Tracepoints}).
37444 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37445 @cindex @samp{QTDP} packet
37446 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37447 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37448 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37449 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37450 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37451 the number of bytes that the target should copy elsewhere to make room
37452 for the tracepoint. If an @samp{X} is present, it introduces a
37453 tracepoint condition, which consists of a hexadecimal length, followed
37454 by a comma and hex-encoded bytes, in a manner similar to action
37455 encodings as described below. If the trailing @samp{-} is present,
37456 further @samp{QTDP} packets will follow to specify this tracepoint's
37462 The packet was understood and carried out.
37464 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37466 The packet was not recognized.
37469 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37470 Define actions to be taken when a tracepoint is hit. The @var{n} and
37471 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37472 this tracepoint. This packet may only be sent immediately after
37473 another @samp{QTDP} packet that ended with a @samp{-}. If the
37474 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37475 specifying more actions for this tracepoint.
37477 In the series of action packets for a given tracepoint, at most one
37478 can have an @samp{S} before its first @var{action}. If such a packet
37479 is sent, it and the following packets define ``while-stepping''
37480 actions. Any prior packets define ordinary actions --- that is, those
37481 taken when the tracepoint is first hit. If no action packet has an
37482 @samp{S}, then all the packets in the series specify ordinary
37483 tracepoint actions.
37485 The @samp{@var{action}@dots{}} portion of the packet is a series of
37486 actions, concatenated without separators. Each action has one of the
37492 Collect the registers whose bits are set in @var{mask},
37493 a hexadecimal number whose @var{i}'th bit is set if register number
37494 @var{i} should be collected. (The least significant bit is numbered
37495 zero.) Note that @var{mask} may be any number of digits long; it may
37496 not fit in a 32-bit word.
37498 @item M @var{basereg},@var{offset},@var{len}
37499 Collect @var{len} bytes of memory starting at the address in register
37500 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37501 @samp{-1}, then the range has a fixed address: @var{offset} is the
37502 address of the lowest byte to collect. The @var{basereg},
37503 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37504 values (the @samp{-1} value for @var{basereg} is a special case).
37506 @item X @var{len},@var{expr}
37507 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37508 it directs. The agent expression @var{expr} is as described in
37509 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37510 two-digit hex number in the packet; @var{len} is the number of bytes
37511 in the expression (and thus one-half the number of hex digits in the
37516 Any number of actions may be packed together in a single @samp{QTDP}
37517 packet, as long as the packet does not exceed the maximum packet
37518 length (400 bytes, for many stubs). There may be only one @samp{R}
37519 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37520 actions. Any registers referred to by @samp{M} and @samp{X} actions
37521 must be collected by a preceding @samp{R} action. (The
37522 ``while-stepping'' actions are treated as if they were attached to a
37523 separate tracepoint, as far as these restrictions are concerned.)
37528 The packet was understood and carried out.
37530 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37532 The packet was not recognized.
37535 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37536 @cindex @samp{QTDPsrc} packet
37537 Specify a source string of tracepoint @var{n} at address @var{addr}.
37538 This is useful to get accurate reproduction of the tracepoints
37539 originally downloaded at the beginning of the trace run. The @var{type}
37540 is the name of the tracepoint part, such as @samp{cond} for the
37541 tracepoint's conditional expression (see below for a list of types), while
37542 @var{bytes} is the string, encoded in hexadecimal.
37544 @var{start} is the offset of the @var{bytes} within the overall source
37545 string, while @var{slen} is the total length of the source string.
37546 This is intended for handling source strings that are longer than will
37547 fit in a single packet.
37548 @c Add detailed example when this info is moved into a dedicated
37549 @c tracepoint descriptions section.
37551 The available string types are @samp{at} for the location,
37552 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37553 @value{GDBN} sends a separate packet for each command in the action
37554 list, in the same order in which the commands are stored in the list.
37556 The target does not need to do anything with source strings except
37557 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37560 Although this packet is optional, and @value{GDBN} will only send it
37561 if the target replies with @samp{TracepointSource} @xref{General
37562 Query Packets}, it makes both disconnected tracing and trace files
37563 much easier to use. Otherwise the user must be careful that the
37564 tracepoints in effect while looking at trace frames are identical to
37565 the ones in effect during the trace run; even a small discrepancy
37566 could cause @samp{tdump} not to work, or a particular trace frame not
37569 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37570 @cindex define trace state variable, remote request
37571 @cindex @samp{QTDV} packet
37572 Create a new trace state variable, number @var{n}, with an initial
37573 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37574 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37575 the option of not using this packet for initial values of zero; the
37576 target should simply create the trace state variables as they are
37577 mentioned in expressions. The value @var{builtin} should be 1 (one)
37578 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37579 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37580 @samp{qTsV} packet had it set. The contents of @var{name} is the
37581 hex-encoded name (without the leading @samp{$}) of the trace state
37584 @item QTFrame:@var{n}
37585 @cindex @samp{QTFrame} packet
37586 Select the @var{n}'th tracepoint frame from the buffer, and use the
37587 register and memory contents recorded there to answer subsequent
37588 request packets from @value{GDBN}.
37590 A successful reply from the stub indicates that the stub has found the
37591 requested frame. The response is a series of parts, concatenated
37592 without separators, describing the frame we selected. Each part has
37593 one of the following forms:
37597 The selected frame is number @var{n} in the trace frame buffer;
37598 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37599 was no frame matching the criteria in the request packet.
37602 The selected trace frame records a hit of tracepoint number @var{t};
37603 @var{t} is a hexadecimal number.
37607 @item QTFrame:pc:@var{addr}
37608 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37609 currently selected frame whose PC is @var{addr};
37610 @var{addr} is a hexadecimal number.
37612 @item QTFrame:tdp:@var{t}
37613 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37614 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37615 is a hexadecimal number.
37617 @item QTFrame:range:@var{start}:@var{end}
37618 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37619 currently selected frame whose PC is between @var{start} (inclusive)
37620 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37623 @item QTFrame:outside:@var{start}:@var{end}
37624 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37625 frame @emph{outside} the given range of addresses (exclusive).
37628 @cindex @samp{qTMinFTPILen} packet
37629 This packet requests the minimum length of instruction at which a fast
37630 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37631 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37632 it depends on the target system being able to create trampolines in
37633 the first 64K of memory, which might or might not be possible for that
37634 system. So the reply to this packet will be 4 if it is able to
37641 The minimum instruction length is currently unknown.
37643 The minimum instruction length is @var{length}, where @var{length}
37644 is a hexadecimal number greater or equal to 1. A reply
37645 of 1 means that a fast tracepoint may be placed on any instruction
37646 regardless of size.
37648 An error has occurred.
37650 An empty reply indicates that the request is not supported by the stub.
37654 @cindex @samp{QTStart} packet
37655 Begin the tracepoint experiment. Begin collecting data from
37656 tracepoint hits in the trace frame buffer. This packet supports the
37657 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37658 instruction reply packet}).
37661 @cindex @samp{QTStop} packet
37662 End the tracepoint experiment. Stop collecting trace frames.
37664 @item QTEnable:@var{n}:@var{addr}
37666 @cindex @samp{QTEnable} packet
37667 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37668 experiment. If the tracepoint was previously disabled, then collection
37669 of data from it will resume.
37671 @item QTDisable:@var{n}:@var{addr}
37673 @cindex @samp{QTDisable} packet
37674 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37675 experiment. No more data will be collected from the tracepoint unless
37676 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37679 @cindex @samp{QTinit} packet
37680 Clear the table of tracepoints, and empty the trace frame buffer.
37682 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37683 @cindex @samp{QTro} packet
37684 Establish the given ranges of memory as ``transparent''. The stub
37685 will answer requests for these ranges from memory's current contents,
37686 if they were not collected as part of the tracepoint hit.
37688 @value{GDBN} uses this to mark read-only regions of memory, like those
37689 containing program code. Since these areas never change, they should
37690 still have the same contents they did when the tracepoint was hit, so
37691 there's no reason for the stub to refuse to provide their contents.
37693 @item QTDisconnected:@var{value}
37694 @cindex @samp{QTDisconnected} packet
37695 Set the choice to what to do with the tracing run when @value{GDBN}
37696 disconnects from the target. A @var{value} of 1 directs the target to
37697 continue the tracing run, while 0 tells the target to stop tracing if
37698 @value{GDBN} is no longer in the picture.
37701 @cindex @samp{qTStatus} packet
37702 Ask the stub if there is a trace experiment running right now.
37704 The reply has the form:
37708 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37709 @var{running} is a single digit @code{1} if the trace is presently
37710 running, or @code{0} if not. It is followed by semicolon-separated
37711 optional fields that an agent may use to report additional status.
37715 If the trace is not running, the agent may report any of several
37716 explanations as one of the optional fields:
37721 No trace has been run yet.
37723 @item tstop[:@var{text}]:0
37724 The trace was stopped by a user-originated stop command. The optional
37725 @var{text} field is a user-supplied string supplied as part of the
37726 stop command (for instance, an explanation of why the trace was
37727 stopped manually). It is hex-encoded.
37730 The trace stopped because the trace buffer filled up.
37732 @item tdisconnected:0
37733 The trace stopped because @value{GDBN} disconnected from the target.
37735 @item tpasscount:@var{tpnum}
37736 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37738 @item terror:@var{text}:@var{tpnum}
37739 The trace stopped because tracepoint @var{tpnum} had an error. The
37740 string @var{text} is available to describe the nature of the error
37741 (for instance, a divide by zero in the condition expression); it
37745 The trace stopped for some other reason.
37749 Additional optional fields supply statistical and other information.
37750 Although not required, they are extremely useful for users monitoring
37751 the progress of a trace run. If a trace has stopped, and these
37752 numbers are reported, they must reflect the state of the just-stopped
37757 @item tframes:@var{n}
37758 The number of trace frames in the buffer.
37760 @item tcreated:@var{n}
37761 The total number of trace frames created during the run. This may
37762 be larger than the trace frame count, if the buffer is circular.
37764 @item tsize:@var{n}
37765 The total size of the trace buffer, in bytes.
37767 @item tfree:@var{n}
37768 The number of bytes still unused in the buffer.
37770 @item circular:@var{n}
37771 The value of the circular trace buffer flag. @code{1} means that the
37772 trace buffer is circular and old trace frames will be discarded if
37773 necessary to make room, @code{0} means that the trace buffer is linear
37776 @item disconn:@var{n}
37777 The value of the disconnected tracing flag. @code{1} means that
37778 tracing will continue after @value{GDBN} disconnects, @code{0} means
37779 that the trace run will stop.
37783 @item qTP:@var{tp}:@var{addr}
37784 @cindex tracepoint status, remote request
37785 @cindex @samp{qTP} packet
37786 Ask the stub for the current state of tracepoint number @var{tp} at
37787 address @var{addr}.
37791 @item V@var{hits}:@var{usage}
37792 The tracepoint has been hit @var{hits} times so far during the trace
37793 run, and accounts for @var{usage} in the trace buffer. Note that
37794 @code{while-stepping} steps are not counted as separate hits, but the
37795 steps' space consumption is added into the usage number.
37799 @item qTV:@var{var}
37800 @cindex trace state variable value, remote request
37801 @cindex @samp{qTV} packet
37802 Ask the stub for the value of the trace state variable number @var{var}.
37807 The value of the variable is @var{value}. This will be the current
37808 value of the variable if the user is examining a running target, or a
37809 saved value if the variable was collected in the trace frame that the
37810 user is looking at. Note that multiple requests may result in
37811 different reply values, such as when requesting values while the
37812 program is running.
37815 The value of the variable is unknown. This would occur, for example,
37816 if the user is examining a trace frame in which the requested variable
37821 @cindex @samp{qTfP} packet
37823 @cindex @samp{qTsP} packet
37824 These packets request data about tracepoints that are being used by
37825 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37826 of data, and multiple @code{qTsP} to get additional pieces. Replies
37827 to these packets generally take the form of the @code{QTDP} packets
37828 that define tracepoints. (FIXME add detailed syntax)
37831 @cindex @samp{qTfV} packet
37833 @cindex @samp{qTsV} packet
37834 These packets request data about trace state variables that are on the
37835 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37836 and multiple @code{qTsV} to get additional variables. Replies to
37837 these packets follow the syntax of the @code{QTDV} packets that define
37838 trace state variables.
37844 @cindex @samp{qTfSTM} packet
37845 @cindex @samp{qTsSTM} packet
37846 These packets request data about static tracepoint markers that exist
37847 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37848 first piece of data, and multiple @code{qTsSTM} to get additional
37849 pieces. Replies to these packets take the following form:
37853 @item m @var{address}:@var{id}:@var{extra}
37855 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37856 a comma-separated list of markers
37858 (lower case letter @samp{L}) denotes end of list.
37860 An error occurred. The error number @var{nn} is given as hex digits.
37862 An empty reply indicates that the request is not supported by the
37866 The @var{address} is encoded in hex;
37867 @var{id} and @var{extra} are strings encoded in hex.
37869 In response to each query, the target will reply with a list of one or
37870 more markers, separated by commas. @value{GDBN} will respond to each
37871 reply with a request for more markers (using the @samp{qs} form of the
37872 query), until the target responds with @samp{l} (lower-case ell, for
37875 @item qTSTMat:@var{address}
37877 @cindex @samp{qTSTMat} packet
37878 This packets requests data about static tracepoint markers in the
37879 target program at @var{address}. Replies to this packet follow the
37880 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37881 tracepoint markers.
37883 @item QTSave:@var{filename}
37884 @cindex @samp{QTSave} packet
37885 This packet directs the target to save trace data to the file name
37886 @var{filename} in the target's filesystem. The @var{filename} is encoded
37887 as a hex string; the interpretation of the file name (relative vs
37888 absolute, wild cards, etc) is up to the target.
37890 @item qTBuffer:@var{offset},@var{len}
37891 @cindex @samp{qTBuffer} packet
37892 Return up to @var{len} bytes of the current contents of trace buffer,
37893 starting at @var{offset}. The trace buffer is treated as if it were
37894 a contiguous collection of traceframes, as per the trace file format.
37895 The reply consists as many hex-encoded bytes as the target can deliver
37896 in a packet; it is not an error to return fewer than were asked for.
37897 A reply consisting of just @code{l} indicates that no bytes are
37900 @item QTBuffer:circular:@var{value}
37901 This packet directs the target to use a circular trace buffer if
37902 @var{value} is 1, or a linear buffer if the value is 0.
37904 @item QTBuffer:size:@var{size}
37905 @anchor{QTBuffer-size}
37906 @cindex @samp{QTBuffer size} packet
37907 This packet directs the target to make the trace buffer be of size
37908 @var{size} if possible. A value of @code{-1} tells the target to
37909 use whatever size it prefers.
37911 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37912 @cindex @samp{QTNotes} packet
37913 This packet adds optional textual notes to the trace run. Allowable
37914 types include @code{user}, @code{notes}, and @code{tstop}, the
37915 @var{text} fields are arbitrary strings, hex-encoded.
37919 @subsection Relocate instruction reply packet
37920 When installing fast tracepoints in memory, the target may need to
37921 relocate the instruction currently at the tracepoint address to a
37922 different address in memory. For most instructions, a simple copy is
37923 enough, but, for example, call instructions that implicitly push the
37924 return address on the stack, and relative branches or other
37925 PC-relative instructions require offset adjustment, so that the effect
37926 of executing the instruction at a different address is the same as if
37927 it had executed in the original location.
37929 In response to several of the tracepoint packets, the target may also
37930 respond with a number of intermediate @samp{qRelocInsn} request
37931 packets before the final result packet, to have @value{GDBN} handle
37932 this relocation operation. If a packet supports this mechanism, its
37933 documentation will explicitly say so. See for example the above
37934 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37935 format of the request is:
37938 @item qRelocInsn:@var{from};@var{to}
37940 This requests @value{GDBN} to copy instruction at address @var{from}
37941 to address @var{to}, possibly adjusted so that executing the
37942 instruction at @var{to} has the same effect as executing it at
37943 @var{from}. @value{GDBN} writes the adjusted instruction to target
37944 memory starting at @var{to}.
37949 @item qRelocInsn:@var{adjusted_size}
37950 Informs the stub the relocation is complete. The @var{adjusted_size} is
37951 the length in bytes of resulting relocated instruction sequence.
37953 A badly formed request was detected, or an error was encountered while
37954 relocating the instruction.
37957 @node Host I/O Packets
37958 @section Host I/O Packets
37959 @cindex Host I/O, remote protocol
37960 @cindex file transfer, remote protocol
37962 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37963 operations on the far side of a remote link. For example, Host I/O is
37964 used to upload and download files to a remote target with its own
37965 filesystem. Host I/O uses the same constant values and data structure
37966 layout as the target-initiated File-I/O protocol. However, the
37967 Host I/O packets are structured differently. The target-initiated
37968 protocol relies on target memory to store parameters and buffers.
37969 Host I/O requests are initiated by @value{GDBN}, and the
37970 target's memory is not involved. @xref{File-I/O Remote Protocol
37971 Extension}, for more details on the target-initiated protocol.
37973 The Host I/O request packets all encode a single operation along with
37974 its arguments. They have this format:
37978 @item vFile:@var{operation}: @var{parameter}@dots{}
37979 @var{operation} is the name of the particular request; the target
37980 should compare the entire packet name up to the second colon when checking
37981 for a supported operation. The format of @var{parameter} depends on
37982 the operation. Numbers are always passed in hexadecimal. Negative
37983 numbers have an explicit minus sign (i.e.@: two's complement is not
37984 used). Strings (e.g.@: filenames) are encoded as a series of
37985 hexadecimal bytes. The last argument to a system call may be a
37986 buffer of escaped binary data (@pxref{Binary Data}).
37990 The valid responses to Host I/O packets are:
37994 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37995 @var{result} is the integer value returned by this operation, usually
37996 non-negative for success and -1 for errors. If an error has occured,
37997 @var{errno} will be included in the result specifying a
37998 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37999 operations which return data, @var{attachment} supplies the data as a
38000 binary buffer. Binary buffers in response packets are escaped in the
38001 normal way (@pxref{Binary Data}). See the individual packet
38002 documentation for the interpretation of @var{result} and
38006 An empty response indicates that this operation is not recognized.
38010 These are the supported Host I/O operations:
38013 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38014 Open a file at @var{filename} and return a file descriptor for it, or
38015 return -1 if an error occurs. The @var{filename} is a string,
38016 @var{flags} is an integer indicating a mask of open flags
38017 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38018 of mode bits to use if the file is created (@pxref{mode_t Values}).
38019 @xref{open}, for details of the open flags and mode values.
38021 @item vFile:close: @var{fd}
38022 Close the open file corresponding to @var{fd} and return 0, or
38023 -1 if an error occurs.
38025 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38026 Read data from the open file corresponding to @var{fd}. Up to
38027 @var{count} bytes will be read from the file, starting at @var{offset}
38028 relative to the start of the file. The target may read fewer bytes;
38029 common reasons include packet size limits and an end-of-file
38030 condition. The number of bytes read is returned. Zero should only be
38031 returned for a successful read at the end of the file, or if
38032 @var{count} was zero.
38034 The data read should be returned as a binary attachment on success.
38035 If zero bytes were read, the response should include an empty binary
38036 attachment (i.e.@: a trailing semicolon). The return value is the
38037 number of target bytes read; the binary attachment may be longer if
38038 some characters were escaped.
38040 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38041 Write @var{data} (a binary buffer) to the open file corresponding
38042 to @var{fd}. Start the write at @var{offset} from the start of the
38043 file. Unlike many @code{write} system calls, there is no
38044 separate @var{count} argument; the length of @var{data} in the
38045 packet is used. @samp{vFile:write} returns the number of bytes written,
38046 which may be shorter than the length of @var{data}, or -1 if an
38049 @item vFile:fstat: @var{fd}
38050 Get information about the open file corresponding to @var{fd}.
38051 On success the information is returned as a binary attachment
38052 and the return value is the size of this attachment in bytes.
38053 If an error occurs the return value is -1. The format of the
38054 returned binary attachment is as described in @ref{struct stat}.
38056 @item vFile:unlink: @var{filename}
38057 Delete the file at @var{filename} on the target. Return 0,
38058 or -1 if an error occurs. The @var{filename} is a string.
38060 @item vFile:readlink: @var{filename}
38061 Read value of symbolic link @var{filename} on the target. Return
38062 the number of bytes read, or -1 if an error occurs.
38064 The data read should be returned as a binary attachment on success.
38065 If zero bytes were read, the response should include an empty binary
38066 attachment (i.e.@: a trailing semicolon). The return value is the
38067 number of target bytes read; the binary attachment may be longer if
38068 some characters were escaped.
38070 @item vFile:setfs: @var{pid}
38071 Select the filesystem on which @code{vFile} operations with
38072 @var{filename} arguments will operate. This is required for
38073 @value{GDBN} to be able to access files on remote targets where
38074 the remote stub does not share a common filesystem with the
38077 If @var{pid} is nonzero, select the filesystem as seen by process
38078 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38079 the remote stub. Return 0 on success, or -1 if an error occurs.
38080 If @code{vFile:setfs:} indicates success, the selected filesystem
38081 remains selected until the next successful @code{vFile:setfs:}
38087 @section Interrupts
38088 @cindex interrupts (remote protocol)
38089 @anchor{interrupting remote targets}
38091 In all-stop mode, when a program on the remote target is running,
38092 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38093 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38094 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38096 The precise meaning of @code{BREAK} is defined by the transport
38097 mechanism and may, in fact, be undefined. @value{GDBN} does not
38098 currently define a @code{BREAK} mechanism for any of the network
38099 interfaces except for TCP, in which case @value{GDBN} sends the
38100 @code{telnet} BREAK sequence.
38102 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38103 transport mechanisms. It is represented by sending the single byte
38104 @code{0x03} without any of the usual packet overhead described in
38105 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38106 transmitted as part of a packet, it is considered to be packet data
38107 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38108 (@pxref{X packet}), used for binary downloads, may include an unescaped
38109 @code{0x03} as part of its packet.
38111 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38112 When Linux kernel receives this sequence from serial port,
38113 it stops execution and connects to gdb.
38115 In non-stop mode, because packet resumptions are asynchronous
38116 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38117 command to the remote stub, even when the target is running. For that
38118 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38119 packet}) with the usual packet framing instead of the single byte
38122 Stubs are not required to recognize these interrupt mechanisms and the
38123 precise meaning associated with receipt of the interrupt is
38124 implementation defined. If the target supports debugging of multiple
38125 threads and/or processes, it should attempt to interrupt all
38126 currently-executing threads and processes.
38127 If the stub is successful at interrupting the
38128 running program, it should send one of the stop
38129 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38130 of successfully stopping the program in all-stop mode, and a stop reply
38131 for each stopped thread in non-stop mode.
38132 Interrupts received while the
38133 program is stopped are queued and the program will be interrupted when
38134 it is resumed next time.
38136 @node Notification Packets
38137 @section Notification Packets
38138 @cindex notification packets
38139 @cindex packets, notification
38141 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38142 packets that require no acknowledgment. Both the GDB and the stub
38143 may send notifications (although the only notifications defined at
38144 present are sent by the stub). Notifications carry information
38145 without incurring the round-trip latency of an acknowledgment, and so
38146 are useful for low-impact communications where occasional packet loss
38149 A notification packet has the form @samp{% @var{data} #
38150 @var{checksum}}, where @var{data} is the content of the notification,
38151 and @var{checksum} is a checksum of @var{data}, computed and formatted
38152 as for ordinary @value{GDBN} packets. A notification's @var{data}
38153 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38154 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38155 to acknowledge the notification's receipt or to report its corruption.
38157 Every notification's @var{data} begins with a name, which contains no
38158 colon characters, followed by a colon character.
38160 Recipients should silently ignore corrupted notifications and
38161 notifications they do not understand. Recipients should restart
38162 timeout periods on receipt of a well-formed notification, whether or
38163 not they understand it.
38165 Senders should only send the notifications described here when this
38166 protocol description specifies that they are permitted. In the
38167 future, we may extend the protocol to permit existing notifications in
38168 new contexts; this rule helps older senders avoid confusing newer
38171 (Older versions of @value{GDBN} ignore bytes received until they see
38172 the @samp{$} byte that begins an ordinary packet, so new stubs may
38173 transmit notifications without fear of confusing older clients. There
38174 are no notifications defined for @value{GDBN} to send at the moment, but we
38175 assume that most older stubs would ignore them, as well.)
38177 Each notification is comprised of three parts:
38179 @item @var{name}:@var{event}
38180 The notification packet is sent by the side that initiates the
38181 exchange (currently, only the stub does that), with @var{event}
38182 carrying the specific information about the notification, and
38183 @var{name} specifying the name of the notification.
38185 The acknowledge sent by the other side, usually @value{GDBN}, to
38186 acknowledge the exchange and request the event.
38189 The purpose of an asynchronous notification mechanism is to report to
38190 @value{GDBN} that something interesting happened in the remote stub.
38192 The remote stub may send notification @var{name}:@var{event}
38193 at any time, but @value{GDBN} acknowledges the notification when
38194 appropriate. The notification event is pending before @value{GDBN}
38195 acknowledges. Only one notification at a time may be pending; if
38196 additional events occur before @value{GDBN} has acknowledged the
38197 previous notification, they must be queued by the stub for later
38198 synchronous transmission in response to @var{ack} packets from
38199 @value{GDBN}. Because the notification mechanism is unreliable,
38200 the stub is permitted to resend a notification if it believes
38201 @value{GDBN} may not have received it.
38203 Specifically, notifications may appear when @value{GDBN} is not
38204 otherwise reading input from the stub, or when @value{GDBN} is
38205 expecting to read a normal synchronous response or a
38206 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38207 Notification packets are distinct from any other communication from
38208 the stub so there is no ambiguity.
38210 After receiving a notification, @value{GDBN} shall acknowledge it by
38211 sending a @var{ack} packet as a regular, synchronous request to the
38212 stub. Such acknowledgment is not required to happen immediately, as
38213 @value{GDBN} is permitted to send other, unrelated packets to the
38214 stub first, which the stub should process normally.
38216 Upon receiving a @var{ack} packet, if the stub has other queued
38217 events to report to @value{GDBN}, it shall respond by sending a
38218 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38219 packet to solicit further responses; again, it is permitted to send
38220 other, unrelated packets as well which the stub should process
38223 If the stub receives a @var{ack} packet and there are no additional
38224 @var{event} to report, the stub shall return an @samp{OK} response.
38225 At this point, @value{GDBN} has finished processing a notification
38226 and the stub has completed sending any queued events. @value{GDBN}
38227 won't accept any new notifications until the final @samp{OK} is
38228 received . If further notification events occur, the stub shall send
38229 a new notification, @value{GDBN} shall accept the notification, and
38230 the process shall be repeated.
38232 The process of asynchronous notification can be illustrated by the
38235 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38238 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38240 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38245 The following notifications are defined:
38246 @multitable @columnfractions 0.12 0.12 0.38 0.38
38255 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38256 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38257 for information on how these notifications are acknowledged by
38259 @tab Report an asynchronous stop event in non-stop mode.
38263 @node Remote Non-Stop
38264 @section Remote Protocol Support for Non-Stop Mode
38266 @value{GDBN}'s remote protocol supports non-stop debugging of
38267 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38268 supports non-stop mode, it should report that to @value{GDBN} by including
38269 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38271 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38272 establishing a new connection with the stub. Entering non-stop mode
38273 does not alter the state of any currently-running threads, but targets
38274 must stop all threads in any already-attached processes when entering
38275 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38276 probe the target state after a mode change.
38278 In non-stop mode, when an attached process encounters an event that
38279 would otherwise be reported with a stop reply, it uses the
38280 asynchronous notification mechanism (@pxref{Notification Packets}) to
38281 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38282 in all processes are stopped when a stop reply is sent, in non-stop
38283 mode only the thread reporting the stop event is stopped. That is,
38284 when reporting a @samp{S} or @samp{T} response to indicate completion
38285 of a step operation, hitting a breakpoint, or a fault, only the
38286 affected thread is stopped; any other still-running threads continue
38287 to run. When reporting a @samp{W} or @samp{X} response, all running
38288 threads belonging to other attached processes continue to run.
38290 In non-stop mode, the target shall respond to the @samp{?} packet as
38291 follows. First, any incomplete stop reply notification/@samp{vStopped}
38292 sequence in progress is abandoned. The target must begin a new
38293 sequence reporting stop events for all stopped threads, whether or not
38294 it has previously reported those events to @value{GDBN}. The first
38295 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38296 subsequent stop replies are sent as responses to @samp{vStopped} packets
38297 using the mechanism described above. The target must not send
38298 asynchronous stop reply notifications until the sequence is complete.
38299 If all threads are running when the target receives the @samp{?} packet,
38300 or if the target is not attached to any process, it shall respond
38303 If the stub supports non-stop mode, it should also support the
38304 @samp{swbreak} stop reason if software breakpoints are supported, and
38305 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38306 (@pxref{swbreak stop reason}). This is because given the asynchronous
38307 nature of non-stop mode, between the time a thread hits a breakpoint
38308 and the time the event is finally processed by @value{GDBN}, the
38309 breakpoint may have already been removed from the target. Due to
38310 this, @value{GDBN} needs to be able to tell whether a trap stop was
38311 caused by a delayed breakpoint event, which should be ignored, as
38312 opposed to a random trap signal, which should be reported to the user.
38313 Note the @samp{swbreak} feature implies that the target is responsible
38314 for adjusting the PC when a software breakpoint triggers, if
38315 necessary, such as on the x86 architecture.
38317 @node Packet Acknowledgment
38318 @section Packet Acknowledgment
38320 @cindex acknowledgment, for @value{GDBN} remote
38321 @cindex packet acknowledgment, for @value{GDBN} remote
38322 By default, when either the host or the target machine receives a packet,
38323 the first response expected is an acknowledgment: either @samp{+} (to indicate
38324 the package was received correctly) or @samp{-} (to request retransmission).
38325 This mechanism allows the @value{GDBN} remote protocol to operate over
38326 unreliable transport mechanisms, such as a serial line.
38328 In cases where the transport mechanism is itself reliable (such as a pipe or
38329 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38330 It may be desirable to disable them in that case to reduce communication
38331 overhead, or for other reasons. This can be accomplished by means of the
38332 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38334 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38335 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38336 and response format still includes the normal checksum, as described in
38337 @ref{Overview}, but the checksum may be ignored by the receiver.
38339 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38340 no-acknowledgment mode, it should report that to @value{GDBN}
38341 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38342 @pxref{qSupported}.
38343 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38344 disabled via the @code{set remote noack-packet off} command
38345 (@pxref{Remote Configuration}),
38346 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38347 Only then may the stub actually turn off packet acknowledgments.
38348 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38349 response, which can be safely ignored by the stub.
38351 Note that @code{set remote noack-packet} command only affects negotiation
38352 between @value{GDBN} and the stub when subsequent connections are made;
38353 it does not affect the protocol acknowledgment state for any current
38355 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38356 new connection is established,
38357 there is also no protocol request to re-enable the acknowledgments
38358 for the current connection, once disabled.
38363 Example sequence of a target being re-started. Notice how the restart
38364 does not get any direct output:
38369 @emph{target restarts}
38372 <- @code{T001:1234123412341234}
38376 Example sequence of a target being stepped by a single instruction:
38379 -> @code{G1445@dots{}}
38384 <- @code{T001:1234123412341234}
38388 <- @code{1455@dots{}}
38392 @node File-I/O Remote Protocol Extension
38393 @section File-I/O Remote Protocol Extension
38394 @cindex File-I/O remote protocol extension
38397 * File-I/O Overview::
38398 * Protocol Basics::
38399 * The F Request Packet::
38400 * The F Reply Packet::
38401 * The Ctrl-C Message::
38403 * List of Supported Calls::
38404 * Protocol-specific Representation of Datatypes::
38406 * File-I/O Examples::
38409 @node File-I/O Overview
38410 @subsection File-I/O Overview
38411 @cindex file-i/o overview
38413 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38414 target to use the host's file system and console I/O to perform various
38415 system calls. System calls on the target system are translated into a
38416 remote protocol packet to the host system, which then performs the needed
38417 actions and returns a response packet to the target system.
38418 This simulates file system operations even on targets that lack file systems.
38420 The protocol is defined to be independent of both the host and target systems.
38421 It uses its own internal representation of datatypes and values. Both
38422 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38423 translating the system-dependent value representations into the internal
38424 protocol representations when data is transmitted.
38426 The communication is synchronous. A system call is possible only when
38427 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38428 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38429 the target is stopped to allow deterministic access to the target's
38430 memory. Therefore File-I/O is not interruptible by target signals. On
38431 the other hand, it is possible to interrupt File-I/O by a user interrupt
38432 (@samp{Ctrl-C}) within @value{GDBN}.
38434 The target's request to perform a host system call does not finish
38435 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38436 after finishing the system call, the target returns to continuing the
38437 previous activity (continue, step). No additional continue or step
38438 request from @value{GDBN} is required.
38441 (@value{GDBP}) continue
38442 <- target requests 'system call X'
38443 target is stopped, @value{GDBN} executes system call
38444 -> @value{GDBN} returns result
38445 ... target continues, @value{GDBN} returns to wait for the target
38446 <- target hits breakpoint and sends a Txx packet
38449 The protocol only supports I/O on the console and to regular files on
38450 the host file system. Character or block special devices, pipes,
38451 named pipes, sockets or any other communication method on the host
38452 system are not supported by this protocol.
38454 File I/O is not supported in non-stop mode.
38456 @node Protocol Basics
38457 @subsection Protocol Basics
38458 @cindex protocol basics, file-i/o
38460 The File-I/O protocol uses the @code{F} packet as the request as well
38461 as reply packet. Since a File-I/O system call can only occur when
38462 @value{GDBN} is waiting for a response from the continuing or stepping target,
38463 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38464 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38465 This @code{F} packet contains all information needed to allow @value{GDBN}
38466 to call the appropriate host system call:
38470 A unique identifier for the requested system call.
38473 All parameters to the system call. Pointers are given as addresses
38474 in the target memory address space. Pointers to strings are given as
38475 pointer/length pair. Numerical values are given as they are.
38476 Numerical control flags are given in a protocol-specific representation.
38480 At this point, @value{GDBN} has to perform the following actions.
38484 If the parameters include pointer values to data needed as input to a
38485 system call, @value{GDBN} requests this data from the target with a
38486 standard @code{m} packet request. This additional communication has to be
38487 expected by the target implementation and is handled as any other @code{m}
38491 @value{GDBN} translates all value from protocol representation to host
38492 representation as needed. Datatypes are coerced into the host types.
38495 @value{GDBN} calls the system call.
38498 It then coerces datatypes back to protocol representation.
38501 If the system call is expected to return data in buffer space specified
38502 by pointer parameters to the call, the data is transmitted to the
38503 target using a @code{M} or @code{X} packet. This packet has to be expected
38504 by the target implementation and is handled as any other @code{M} or @code{X}
38509 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38510 necessary information for the target to continue. This at least contains
38517 @code{errno}, if has been changed by the system call.
38524 After having done the needed type and value coercion, the target continues
38525 the latest continue or step action.
38527 @node The F Request Packet
38528 @subsection The @code{F} Request Packet
38529 @cindex file-i/o request packet
38530 @cindex @code{F} request packet
38532 The @code{F} request packet has the following format:
38535 @item F@var{call-id},@var{parameter@dots{}}
38537 @var{call-id} is the identifier to indicate the host system call to be called.
38538 This is just the name of the function.
38540 @var{parameter@dots{}} are the parameters to the system call.
38541 Parameters are hexadecimal integer values, either the actual values in case
38542 of scalar datatypes, pointers to target buffer space in case of compound
38543 datatypes and unspecified memory areas, or pointer/length pairs in case
38544 of string parameters. These are appended to the @var{call-id} as a
38545 comma-delimited list. All values are transmitted in ASCII
38546 string representation, pointer/length pairs separated by a slash.
38552 @node The F Reply Packet
38553 @subsection The @code{F} Reply Packet
38554 @cindex file-i/o reply packet
38555 @cindex @code{F} reply packet
38557 The @code{F} reply packet has the following format:
38561 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38563 @var{retcode} is the return code of the system call as hexadecimal value.
38565 @var{errno} is the @code{errno} set by the call, in protocol-specific
38567 This parameter can be omitted if the call was successful.
38569 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38570 case, @var{errno} must be sent as well, even if the call was successful.
38571 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38578 or, if the call was interrupted before the host call has been performed:
38585 assuming 4 is the protocol-specific representation of @code{EINTR}.
38590 @node The Ctrl-C Message
38591 @subsection The @samp{Ctrl-C} Message
38592 @cindex ctrl-c message, in file-i/o protocol
38594 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38595 reply packet (@pxref{The F Reply Packet}),
38596 the target should behave as if it had
38597 gotten a break message. The meaning for the target is ``system call
38598 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38599 (as with a break message) and return to @value{GDBN} with a @code{T02}
38602 It's important for the target to know in which
38603 state the system call was interrupted. There are two possible cases:
38607 The system call hasn't been performed on the host yet.
38610 The system call on the host has been finished.
38614 These two states can be distinguished by the target by the value of the
38615 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38616 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38617 on POSIX systems. In any other case, the target may presume that the
38618 system call has been finished --- successfully or not --- and should behave
38619 as if the break message arrived right after the system call.
38621 @value{GDBN} must behave reliably. If the system call has not been called
38622 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38623 @code{errno} in the packet. If the system call on the host has been finished
38624 before the user requests a break, the full action must be finished by
38625 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38626 The @code{F} packet may only be sent when either nothing has happened
38627 or the full action has been completed.
38630 @subsection Console I/O
38631 @cindex console i/o as part of file-i/o
38633 By default and if not explicitly closed by the target system, the file
38634 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38635 on the @value{GDBN} console is handled as any other file output operation
38636 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38637 by @value{GDBN} so that after the target read request from file descriptor
38638 0 all following typing is buffered until either one of the following
38643 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38645 system call is treated as finished.
38648 The user presses @key{RET}. This is treated as end of input with a trailing
38652 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38653 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38657 If the user has typed more characters than fit in the buffer given to
38658 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38659 either another @code{read(0, @dots{})} is requested by the target, or debugging
38660 is stopped at the user's request.
38663 @node List of Supported Calls
38664 @subsection List of Supported Calls
38665 @cindex list of supported file-i/o calls
38682 @unnumberedsubsubsec open
38683 @cindex open, file-i/o system call
38688 int open(const char *pathname, int flags);
38689 int open(const char *pathname, int flags, mode_t mode);
38693 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38696 @var{flags} is the bitwise @code{OR} of the following values:
38700 If the file does not exist it will be created. The host
38701 rules apply as far as file ownership and time stamps
38705 When used with @code{O_CREAT}, if the file already exists it is
38706 an error and open() fails.
38709 If the file already exists and the open mode allows
38710 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38711 truncated to zero length.
38714 The file is opened in append mode.
38717 The file is opened for reading only.
38720 The file is opened for writing only.
38723 The file is opened for reading and writing.
38727 Other bits are silently ignored.
38731 @var{mode} is the bitwise @code{OR} of the following values:
38735 User has read permission.
38738 User has write permission.
38741 Group has read permission.
38744 Group has write permission.
38747 Others have read permission.
38750 Others have write permission.
38754 Other bits are silently ignored.
38757 @item Return value:
38758 @code{open} returns the new file descriptor or -1 if an error
38765 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38768 @var{pathname} refers to a directory.
38771 The requested access is not allowed.
38774 @var{pathname} was too long.
38777 A directory component in @var{pathname} does not exist.
38780 @var{pathname} refers to a device, pipe, named pipe or socket.
38783 @var{pathname} refers to a file on a read-only filesystem and
38784 write access was requested.
38787 @var{pathname} is an invalid pointer value.
38790 No space on device to create the file.
38793 The process already has the maximum number of files open.
38796 The limit on the total number of files open on the system
38800 The call was interrupted by the user.
38806 @unnumberedsubsubsec close
38807 @cindex close, file-i/o system call
38816 @samp{Fclose,@var{fd}}
38818 @item Return value:
38819 @code{close} returns zero on success, or -1 if an error occurred.
38825 @var{fd} isn't a valid open file descriptor.
38828 The call was interrupted by the user.
38834 @unnumberedsubsubsec read
38835 @cindex read, file-i/o system call
38840 int read(int fd, void *buf, unsigned int count);
38844 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38846 @item Return value:
38847 On success, the number of bytes read is returned.
38848 Zero indicates end of file. If count is zero, read
38849 returns zero as well. On error, -1 is returned.
38855 @var{fd} is not a valid file descriptor or is not open for
38859 @var{bufptr} is an invalid pointer value.
38862 The call was interrupted by the user.
38868 @unnumberedsubsubsec write
38869 @cindex write, file-i/o system call
38874 int write(int fd, const void *buf, unsigned int count);
38878 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38880 @item Return value:
38881 On success, the number of bytes written are returned.
38882 Zero indicates nothing was written. On error, -1
38889 @var{fd} is not a valid file descriptor or is not open for
38893 @var{bufptr} is an invalid pointer value.
38896 An attempt was made to write a file that exceeds the
38897 host-specific maximum file size allowed.
38900 No space on device to write the data.
38903 The call was interrupted by the user.
38909 @unnumberedsubsubsec lseek
38910 @cindex lseek, file-i/o system call
38915 long lseek (int fd, long offset, int flag);
38919 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38921 @var{flag} is one of:
38925 The offset is set to @var{offset} bytes.
38928 The offset is set to its current location plus @var{offset}
38932 The offset is set to the size of the file plus @var{offset}
38936 @item Return value:
38937 On success, the resulting unsigned offset in bytes from
38938 the beginning of the file is returned. Otherwise, a
38939 value of -1 is returned.
38945 @var{fd} is not a valid open file descriptor.
38948 @var{fd} is associated with the @value{GDBN} console.
38951 @var{flag} is not a proper value.
38954 The call was interrupted by the user.
38960 @unnumberedsubsubsec rename
38961 @cindex rename, file-i/o system call
38966 int rename(const char *oldpath, const char *newpath);
38970 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38972 @item Return value:
38973 On success, zero is returned. On error, -1 is returned.
38979 @var{newpath} is an existing directory, but @var{oldpath} is not a
38983 @var{newpath} is a non-empty directory.
38986 @var{oldpath} or @var{newpath} is a directory that is in use by some
38990 An attempt was made to make a directory a subdirectory
38994 A component used as a directory in @var{oldpath} or new
38995 path is not a directory. Or @var{oldpath} is a directory
38996 and @var{newpath} exists but is not a directory.
38999 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39002 No access to the file or the path of the file.
39006 @var{oldpath} or @var{newpath} was too long.
39009 A directory component in @var{oldpath} or @var{newpath} does not exist.
39012 The file is on a read-only filesystem.
39015 The device containing the file has no room for the new
39019 The call was interrupted by the user.
39025 @unnumberedsubsubsec unlink
39026 @cindex unlink, file-i/o system call
39031 int unlink(const char *pathname);
39035 @samp{Funlink,@var{pathnameptr}/@var{len}}
39037 @item Return value:
39038 On success, zero is returned. On error, -1 is returned.
39044 No access to the file or the path of the file.
39047 The system does not allow unlinking of directories.
39050 The file @var{pathname} cannot be unlinked because it's
39051 being used by another process.
39054 @var{pathnameptr} is an invalid pointer value.
39057 @var{pathname} was too long.
39060 A directory component in @var{pathname} does not exist.
39063 A component of the path is not a directory.
39066 The file is on a read-only filesystem.
39069 The call was interrupted by the user.
39075 @unnumberedsubsubsec stat/fstat
39076 @cindex fstat, file-i/o system call
39077 @cindex stat, file-i/o system call
39082 int stat(const char *pathname, struct stat *buf);
39083 int fstat(int fd, struct stat *buf);
39087 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39088 @samp{Ffstat,@var{fd},@var{bufptr}}
39090 @item Return value:
39091 On success, zero is returned. On error, -1 is returned.
39097 @var{fd} is not a valid open file.
39100 A directory component in @var{pathname} does not exist or the
39101 path is an empty string.
39104 A component of the path is not a directory.
39107 @var{pathnameptr} is an invalid pointer value.
39110 No access to the file or the path of the file.
39113 @var{pathname} was too long.
39116 The call was interrupted by the user.
39122 @unnumberedsubsubsec gettimeofday
39123 @cindex gettimeofday, file-i/o system call
39128 int gettimeofday(struct timeval *tv, void *tz);
39132 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39134 @item Return value:
39135 On success, 0 is returned, -1 otherwise.
39141 @var{tz} is a non-NULL pointer.
39144 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39150 @unnumberedsubsubsec isatty
39151 @cindex isatty, file-i/o system call
39156 int isatty(int fd);
39160 @samp{Fisatty,@var{fd}}
39162 @item Return value:
39163 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39169 The call was interrupted by the user.
39174 Note that the @code{isatty} call is treated as a special case: it returns
39175 1 to the target if the file descriptor is attached
39176 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39177 would require implementing @code{ioctl} and would be more complex than
39182 @unnumberedsubsubsec system
39183 @cindex system, file-i/o system call
39188 int system(const char *command);
39192 @samp{Fsystem,@var{commandptr}/@var{len}}
39194 @item Return value:
39195 If @var{len} is zero, the return value indicates whether a shell is
39196 available. A zero return value indicates a shell is not available.
39197 For non-zero @var{len}, the value returned is -1 on error and the
39198 return status of the command otherwise. Only the exit status of the
39199 command is returned, which is extracted from the host's @code{system}
39200 return value by calling @code{WEXITSTATUS(retval)}. In case
39201 @file{/bin/sh} could not be executed, 127 is returned.
39207 The call was interrupted by the user.
39212 @value{GDBN} takes over the full task of calling the necessary host calls
39213 to perform the @code{system} call. The return value of @code{system} on
39214 the host is simplified before it's returned
39215 to the target. Any termination signal information from the child process
39216 is discarded, and the return value consists
39217 entirely of the exit status of the called command.
39219 Due to security concerns, the @code{system} call is by default refused
39220 by @value{GDBN}. The user has to allow this call explicitly with the
39221 @code{set remote system-call-allowed 1} command.
39224 @item set remote system-call-allowed
39225 @kindex set remote system-call-allowed
39226 Control whether to allow the @code{system} calls in the File I/O
39227 protocol for the remote target. The default is zero (disabled).
39229 @item show remote system-call-allowed
39230 @kindex show remote system-call-allowed
39231 Show whether the @code{system} calls are allowed in the File I/O
39235 @node Protocol-specific Representation of Datatypes
39236 @subsection Protocol-specific Representation of Datatypes
39237 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39240 * Integral Datatypes::
39242 * Memory Transfer::
39247 @node Integral Datatypes
39248 @unnumberedsubsubsec Integral Datatypes
39249 @cindex integral datatypes, in file-i/o protocol
39251 The integral datatypes used in the system calls are @code{int},
39252 @code{unsigned int}, @code{long}, @code{unsigned long},
39253 @code{mode_t}, and @code{time_t}.
39255 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39256 implemented as 32 bit values in this protocol.
39258 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39260 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39261 in @file{limits.h}) to allow range checking on host and target.
39263 @code{time_t} datatypes are defined as seconds since the Epoch.
39265 All integral datatypes transferred as part of a memory read or write of a
39266 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39269 @node Pointer Values
39270 @unnumberedsubsubsec Pointer Values
39271 @cindex pointer values, in file-i/o protocol
39273 Pointers to target data are transmitted as they are. An exception
39274 is made for pointers to buffers for which the length isn't
39275 transmitted as part of the function call, namely strings. Strings
39276 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39283 which is a pointer to data of length 18 bytes at position 0x1aaf.
39284 The length is defined as the full string length in bytes, including
39285 the trailing null byte. For example, the string @code{"hello world"}
39286 at address 0x123456 is transmitted as
39292 @node Memory Transfer
39293 @unnumberedsubsubsec Memory Transfer
39294 @cindex memory transfer, in file-i/o protocol
39296 Structured data which is transferred using a memory read or write (for
39297 example, a @code{struct stat}) is expected to be in a protocol-specific format
39298 with all scalar multibyte datatypes being big endian. Translation to
39299 this representation needs to be done both by the target before the @code{F}
39300 packet is sent, and by @value{GDBN} before
39301 it transfers memory to the target. Transferred pointers to structured
39302 data should point to the already-coerced data at any time.
39306 @unnumberedsubsubsec struct stat
39307 @cindex struct stat, in file-i/o protocol
39309 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39310 is defined as follows:
39314 unsigned int st_dev; /* device */
39315 unsigned int st_ino; /* inode */
39316 mode_t st_mode; /* protection */
39317 unsigned int st_nlink; /* number of hard links */
39318 unsigned int st_uid; /* user ID of owner */
39319 unsigned int st_gid; /* group ID of owner */
39320 unsigned int st_rdev; /* device type (if inode device) */
39321 unsigned long st_size; /* total size, in bytes */
39322 unsigned long st_blksize; /* blocksize for filesystem I/O */
39323 unsigned long st_blocks; /* number of blocks allocated */
39324 time_t st_atime; /* time of last access */
39325 time_t st_mtime; /* time of last modification */
39326 time_t st_ctime; /* time of last change */
39330 The integral datatypes conform to the definitions given in the
39331 appropriate section (see @ref{Integral Datatypes}, for details) so this
39332 structure is of size 64 bytes.
39334 The values of several fields have a restricted meaning and/or
39340 A value of 0 represents a file, 1 the console.
39343 No valid meaning for the target. Transmitted unchanged.
39346 Valid mode bits are described in @ref{Constants}. Any other
39347 bits have currently no meaning for the target.
39352 No valid meaning for the target. Transmitted unchanged.
39357 These values have a host and file system dependent
39358 accuracy. Especially on Windows hosts, the file system may not
39359 support exact timing values.
39362 The target gets a @code{struct stat} of the above representation and is
39363 responsible for coercing it to the target representation before
39366 Note that due to size differences between the host, target, and protocol
39367 representations of @code{struct stat} members, these members could eventually
39368 get truncated on the target.
39370 @node struct timeval
39371 @unnumberedsubsubsec struct timeval
39372 @cindex struct timeval, in file-i/o protocol
39374 The buffer of type @code{struct timeval} used by the File-I/O protocol
39375 is defined as follows:
39379 time_t tv_sec; /* second */
39380 long tv_usec; /* microsecond */
39384 The integral datatypes conform to the definitions given in the
39385 appropriate section (see @ref{Integral Datatypes}, for details) so this
39386 structure is of size 8 bytes.
39389 @subsection Constants
39390 @cindex constants, in file-i/o protocol
39392 The following values are used for the constants inside of the
39393 protocol. @value{GDBN} and target are responsible for translating these
39394 values before and after the call as needed.
39405 @unnumberedsubsubsec Open Flags
39406 @cindex open flags, in file-i/o protocol
39408 All values are given in hexadecimal representation.
39420 @node mode_t Values
39421 @unnumberedsubsubsec mode_t Values
39422 @cindex mode_t values, in file-i/o protocol
39424 All values are given in octal representation.
39441 @unnumberedsubsubsec Errno Values
39442 @cindex errno values, in file-i/o protocol
39444 All values are given in decimal representation.
39469 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39470 any error value not in the list of supported error numbers.
39473 @unnumberedsubsubsec Lseek Flags
39474 @cindex lseek flags, in file-i/o protocol
39483 @unnumberedsubsubsec Limits
39484 @cindex limits, in file-i/o protocol
39486 All values are given in decimal representation.
39489 INT_MIN -2147483648
39491 UINT_MAX 4294967295
39492 LONG_MIN -9223372036854775808
39493 LONG_MAX 9223372036854775807
39494 ULONG_MAX 18446744073709551615
39497 @node File-I/O Examples
39498 @subsection File-I/O Examples
39499 @cindex file-i/o examples
39501 Example sequence of a write call, file descriptor 3, buffer is at target
39502 address 0x1234, 6 bytes should be written:
39505 <- @code{Fwrite,3,1234,6}
39506 @emph{request memory read from target}
39509 @emph{return "6 bytes written"}
39513 Example sequence of a read call, file descriptor 3, buffer is at target
39514 address 0x1234, 6 bytes should be read:
39517 <- @code{Fread,3,1234,6}
39518 @emph{request memory write to target}
39519 -> @code{X1234,6:XXXXXX}
39520 @emph{return "6 bytes read"}
39524 Example sequence of a read call, call fails on the host due to invalid
39525 file descriptor (@code{EBADF}):
39528 <- @code{Fread,3,1234,6}
39532 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39536 <- @code{Fread,3,1234,6}
39541 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39545 <- @code{Fread,3,1234,6}
39546 -> @code{X1234,6:XXXXXX}
39550 @node Library List Format
39551 @section Library List Format
39552 @cindex library list format, remote protocol
39554 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39555 same process as your application to manage libraries. In this case,
39556 @value{GDBN} can use the loader's symbol table and normal memory
39557 operations to maintain a list of shared libraries. On other
39558 platforms, the operating system manages loaded libraries.
39559 @value{GDBN} can not retrieve the list of currently loaded libraries
39560 through memory operations, so it uses the @samp{qXfer:libraries:read}
39561 packet (@pxref{qXfer library list read}) instead. The remote stub
39562 queries the target's operating system and reports which libraries
39565 The @samp{qXfer:libraries:read} packet returns an XML document which
39566 lists loaded libraries and their offsets. Each library has an
39567 associated name and one or more segment or section base addresses,
39568 which report where the library was loaded in memory.
39570 For the common case of libraries that are fully linked binaries, the
39571 library should have a list of segments. If the target supports
39572 dynamic linking of a relocatable object file, its library XML element
39573 should instead include a list of allocated sections. The segment or
39574 section bases are start addresses, not relocation offsets; they do not
39575 depend on the library's link-time base addresses.
39577 @value{GDBN} must be linked with the Expat library to support XML
39578 library lists. @xref{Expat}.
39580 A simple memory map, with one loaded library relocated by a single
39581 offset, looks like this:
39585 <library name="/lib/libc.so.6">
39586 <segment address="0x10000000"/>
39591 Another simple memory map, with one loaded library with three
39592 allocated sections (.text, .data, .bss), looks like this:
39596 <library name="sharedlib.o">
39597 <section address="0x10000000"/>
39598 <section address="0x20000000"/>
39599 <section address="0x30000000"/>
39604 The format of a library list is described by this DTD:
39607 <!-- library-list: Root element with versioning -->
39608 <!ELEMENT library-list (library)*>
39609 <!ATTLIST library-list version CDATA #FIXED "1.0">
39610 <!ELEMENT library (segment*, section*)>
39611 <!ATTLIST library name CDATA #REQUIRED>
39612 <!ELEMENT segment EMPTY>
39613 <!ATTLIST segment address CDATA #REQUIRED>
39614 <!ELEMENT section EMPTY>
39615 <!ATTLIST section address CDATA #REQUIRED>
39618 In addition, segments and section descriptors cannot be mixed within a
39619 single library element, and you must supply at least one segment or
39620 section for each library.
39622 @node Library List Format for SVR4 Targets
39623 @section Library List Format for SVR4 Targets
39624 @cindex library list format, remote protocol
39626 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39627 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39628 shared libraries. Still a special library list provided by this packet is
39629 more efficient for the @value{GDBN} remote protocol.
39631 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39632 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39633 target, the following parameters are reported:
39637 @code{name}, the absolute file name from the @code{l_name} field of
39638 @code{struct link_map}.
39640 @code{lm} with address of @code{struct link_map} used for TLS
39641 (Thread Local Storage) access.
39643 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39644 @code{struct link_map}. For prelinked libraries this is not an absolute
39645 memory address. It is a displacement of absolute memory address against
39646 address the file was prelinked to during the library load.
39648 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39651 Additionally the single @code{main-lm} attribute specifies address of
39652 @code{struct link_map} used for the main executable. This parameter is used
39653 for TLS access and its presence is optional.
39655 @value{GDBN} must be linked with the Expat library to support XML
39656 SVR4 library lists. @xref{Expat}.
39658 A simple memory map, with two loaded libraries (which do not use prelink),
39662 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39663 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39665 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39667 </library-list-svr>
39670 The format of an SVR4 library list is described by this DTD:
39673 <!-- library-list-svr4: Root element with versioning -->
39674 <!ELEMENT library-list-svr4 (library)*>
39675 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39676 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39677 <!ELEMENT library EMPTY>
39678 <!ATTLIST library name CDATA #REQUIRED>
39679 <!ATTLIST library lm CDATA #REQUIRED>
39680 <!ATTLIST library l_addr CDATA #REQUIRED>
39681 <!ATTLIST library l_ld CDATA #REQUIRED>
39684 @node Memory Map Format
39685 @section Memory Map Format
39686 @cindex memory map format
39688 To be able to write into flash memory, @value{GDBN} needs to obtain a
39689 memory map from the target. This section describes the format of the
39692 The memory map is obtained using the @samp{qXfer:memory-map:read}
39693 (@pxref{qXfer memory map read}) packet and is an XML document that
39694 lists memory regions.
39696 @value{GDBN} must be linked with the Expat library to support XML
39697 memory maps. @xref{Expat}.
39699 The top-level structure of the document is shown below:
39702 <?xml version="1.0"?>
39703 <!DOCTYPE memory-map
39704 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39705 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39711 Each region can be either:
39716 A region of RAM starting at @var{addr} and extending for @var{length}
39720 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39725 A region of read-only memory:
39728 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39733 A region of flash memory, with erasure blocks @var{blocksize}
39737 <memory type="flash" start="@var{addr}" length="@var{length}">
39738 <property name="blocksize">@var{blocksize}</property>
39744 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39745 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39746 packets to write to addresses in such ranges.
39748 The formal DTD for memory map format is given below:
39751 <!-- ................................................... -->
39752 <!-- Memory Map XML DTD ................................ -->
39753 <!-- File: memory-map.dtd .............................. -->
39754 <!-- .................................... .............. -->
39755 <!-- memory-map.dtd -->
39756 <!-- memory-map: Root element with versioning -->
39757 <!ELEMENT memory-map (memory | property)>
39758 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39759 <!ELEMENT memory (property)>
39760 <!-- memory: Specifies a memory region,
39761 and its type, or device. -->
39762 <!ATTLIST memory type CDATA #REQUIRED
39763 start CDATA #REQUIRED
39764 length CDATA #REQUIRED
39765 device CDATA #IMPLIED>
39766 <!-- property: Generic attribute tag -->
39767 <!ELEMENT property (#PCDATA | property)*>
39768 <!ATTLIST property name CDATA #REQUIRED>
39771 @node Thread List Format
39772 @section Thread List Format
39773 @cindex thread list format
39775 To efficiently update the list of threads and their attributes,
39776 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39777 (@pxref{qXfer threads read}) and obtains the XML document with
39778 the following structure:
39781 <?xml version="1.0"?>
39783 <thread id="id" core="0" name="name">
39784 ... description ...
39789 Each @samp{thread} element must have the @samp{id} attribute that
39790 identifies the thread (@pxref{thread-id syntax}). The
39791 @samp{core} attribute, if present, specifies which processor core
39792 the thread was last executing on. The @samp{name} attribute, if
39793 present, specifies the human-readable name of the thread. The content
39794 of the of @samp{thread} element is interpreted as human-readable
39795 auxiliary information.
39797 @node Traceframe Info Format
39798 @section Traceframe Info Format
39799 @cindex traceframe info format
39801 To be able to know which objects in the inferior can be examined when
39802 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39803 memory ranges, registers and trace state variables that have been
39804 collected in a traceframe.
39806 This list is obtained using the @samp{qXfer:traceframe-info:read}
39807 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39809 @value{GDBN} must be linked with the Expat library to support XML
39810 traceframe info discovery. @xref{Expat}.
39812 The top-level structure of the document is shown below:
39815 <?xml version="1.0"?>
39816 <!DOCTYPE traceframe-info
39817 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39818 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39824 Each traceframe block can be either:
39829 A region of collected memory starting at @var{addr} and extending for
39830 @var{length} bytes from there:
39833 <memory start="@var{addr}" length="@var{length}"/>
39837 A block indicating trace state variable numbered @var{number} has been
39841 <tvar id="@var{number}"/>
39846 The formal DTD for the traceframe info format is given below:
39849 <!ELEMENT traceframe-info (memory | tvar)* >
39850 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39852 <!ELEMENT memory EMPTY>
39853 <!ATTLIST memory start CDATA #REQUIRED
39854 length CDATA #REQUIRED>
39856 <!ATTLIST tvar id CDATA #REQUIRED>
39859 @node Branch Trace Format
39860 @section Branch Trace Format
39861 @cindex branch trace format
39863 In order to display the branch trace of an inferior thread,
39864 @value{GDBN} needs to obtain the list of branches. This list is
39865 represented as list of sequential code blocks that are connected via
39866 branches. The code in each block has been executed sequentially.
39868 This list is obtained using the @samp{qXfer:btrace:read}
39869 (@pxref{qXfer btrace read}) packet and is an XML document.
39871 @value{GDBN} must be linked with the Expat library to support XML
39872 traceframe info discovery. @xref{Expat}.
39874 The top-level structure of the document is shown below:
39877 <?xml version="1.0"?>
39879 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39880 "http://sourceware.org/gdb/gdb-btrace.dtd">
39889 A block of sequentially executed instructions starting at @var{begin}
39890 and ending at @var{end}:
39893 <block begin="@var{begin}" end="@var{end}"/>
39898 The formal DTD for the branch trace format is given below:
39901 <!ELEMENT btrace (block* | pt) >
39902 <!ATTLIST btrace version CDATA #FIXED "1.0">
39904 <!ELEMENT block EMPTY>
39905 <!ATTLIST block begin CDATA #REQUIRED
39906 end CDATA #REQUIRED>
39908 <!ELEMENT pt (pt-config?, raw?)>
39910 <!ELEMENT pt-config (cpu?)>
39912 <!ELEMENT cpu EMPTY>
39913 <!ATTLIST cpu vendor CDATA #REQUIRED
39914 family CDATA #REQUIRED
39915 model CDATA #REQUIRED
39916 stepping CDATA #REQUIRED>
39918 <!ELEMENT raw (#PCDATA)>
39921 @node Branch Trace Configuration Format
39922 @section Branch Trace Configuration Format
39923 @cindex branch trace configuration format
39925 For each inferior thread, @value{GDBN} can obtain the branch trace
39926 configuration using the @samp{qXfer:btrace-conf:read}
39927 (@pxref{qXfer btrace-conf read}) packet.
39929 The configuration describes the branch trace format and configuration
39930 settings for that format. The following information is described:
39934 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39937 The size of the @acronym{BTS} ring buffer in bytes.
39940 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39944 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39948 @value{GDBN} must be linked with the Expat library to support XML
39949 branch trace configuration discovery. @xref{Expat}.
39951 The formal DTD for the branch trace configuration format is given below:
39954 <!ELEMENT btrace-conf (bts?, pt?)>
39955 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39957 <!ELEMENT bts EMPTY>
39958 <!ATTLIST bts size CDATA #IMPLIED>
39960 <!ELEMENT pt EMPTY>
39961 <!ATTLIST pt size CDATA #IMPLIED>
39964 @include agentexpr.texi
39966 @node Target Descriptions
39967 @appendix Target Descriptions
39968 @cindex target descriptions
39970 One of the challenges of using @value{GDBN} to debug embedded systems
39971 is that there are so many minor variants of each processor
39972 architecture in use. It is common practice for vendors to start with
39973 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39974 and then make changes to adapt it to a particular market niche. Some
39975 architectures have hundreds of variants, available from dozens of
39976 vendors. This leads to a number of problems:
39980 With so many different customized processors, it is difficult for
39981 the @value{GDBN} maintainers to keep up with the changes.
39983 Since individual variants may have short lifetimes or limited
39984 audiences, it may not be worthwhile to carry information about every
39985 variant in the @value{GDBN} source tree.
39987 When @value{GDBN} does support the architecture of the embedded system
39988 at hand, the task of finding the correct architecture name to give the
39989 @command{set architecture} command can be error-prone.
39992 To address these problems, the @value{GDBN} remote protocol allows a
39993 target system to not only identify itself to @value{GDBN}, but to
39994 actually describe its own features. This lets @value{GDBN} support
39995 processor variants it has never seen before --- to the extent that the
39996 descriptions are accurate, and that @value{GDBN} understands them.
39998 @value{GDBN} must be linked with the Expat library to support XML
39999 target descriptions. @xref{Expat}.
40002 * Retrieving Descriptions:: How descriptions are fetched from a target.
40003 * Target Description Format:: The contents of a target description.
40004 * Predefined Target Types:: Standard types available for target
40006 * Standard Target Features:: Features @value{GDBN} knows about.
40009 @node Retrieving Descriptions
40010 @section Retrieving Descriptions
40012 Target descriptions can be read from the target automatically, or
40013 specified by the user manually. The default behavior is to read the
40014 description from the target. @value{GDBN} retrieves it via the remote
40015 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40016 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40017 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40018 XML document, of the form described in @ref{Target Description
40021 Alternatively, you can specify a file to read for the target description.
40022 If a file is set, the target will not be queried. The commands to
40023 specify a file are:
40026 @cindex set tdesc filename
40027 @item set tdesc filename @var{path}
40028 Read the target description from @var{path}.
40030 @cindex unset tdesc filename
40031 @item unset tdesc filename
40032 Do not read the XML target description from a file. @value{GDBN}
40033 will use the description supplied by the current target.
40035 @cindex show tdesc filename
40036 @item show tdesc filename
40037 Show the filename to read for a target description, if any.
40041 @node Target Description Format
40042 @section Target Description Format
40043 @cindex target descriptions, XML format
40045 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40046 document which complies with the Document Type Definition provided in
40047 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40048 means you can use generally available tools like @command{xmllint} to
40049 check that your feature descriptions are well-formed and valid.
40050 However, to help people unfamiliar with XML write descriptions for
40051 their targets, we also describe the grammar here.
40053 Target descriptions can identify the architecture of the remote target
40054 and (for some architectures) provide information about custom register
40055 sets. They can also identify the OS ABI of the remote target.
40056 @value{GDBN} can use this information to autoconfigure for your
40057 target, or to warn you if you connect to an unsupported target.
40059 Here is a simple target description:
40062 <target version="1.0">
40063 <architecture>i386:x86-64</architecture>
40068 This minimal description only says that the target uses
40069 the x86-64 architecture.
40071 A target description has the following overall form, with [ ] marking
40072 optional elements and @dots{} marking repeatable elements. The elements
40073 are explained further below.
40076 <?xml version="1.0"?>
40077 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40078 <target version="1.0">
40079 @r{[}@var{architecture}@r{]}
40080 @r{[}@var{osabi}@r{]}
40081 @r{[}@var{compatible}@r{]}
40082 @r{[}@var{feature}@dots{}@r{]}
40087 The description is generally insensitive to whitespace and line
40088 breaks, under the usual common-sense rules. The XML version
40089 declaration and document type declaration can generally be omitted
40090 (@value{GDBN} does not require them), but specifying them may be
40091 useful for XML validation tools. The @samp{version} attribute for
40092 @samp{<target>} may also be omitted, but we recommend
40093 including it; if future versions of @value{GDBN} use an incompatible
40094 revision of @file{gdb-target.dtd}, they will detect and report
40095 the version mismatch.
40097 @subsection Inclusion
40098 @cindex target descriptions, inclusion
40101 @cindex <xi:include>
40104 It can sometimes be valuable to split a target description up into
40105 several different annexes, either for organizational purposes, or to
40106 share files between different possible target descriptions. You can
40107 divide a description into multiple files by replacing any element of
40108 the target description with an inclusion directive of the form:
40111 <xi:include href="@var{document}"/>
40115 When @value{GDBN} encounters an element of this form, it will retrieve
40116 the named XML @var{document}, and replace the inclusion directive with
40117 the contents of that document. If the current description was read
40118 using @samp{qXfer}, then so will be the included document;
40119 @var{document} will be interpreted as the name of an annex. If the
40120 current description was read from a file, @value{GDBN} will look for
40121 @var{document} as a file in the same directory where it found the
40122 original description.
40124 @subsection Architecture
40125 @cindex <architecture>
40127 An @samp{<architecture>} element has this form:
40130 <architecture>@var{arch}</architecture>
40133 @var{arch} is one of the architectures from the set accepted by
40134 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40137 @cindex @code{<osabi>}
40139 This optional field was introduced in @value{GDBN} version 7.0.
40140 Previous versions of @value{GDBN} ignore it.
40142 An @samp{<osabi>} element has this form:
40145 <osabi>@var{abi-name}</osabi>
40148 @var{abi-name} is an OS ABI name from the same selection accepted by
40149 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40151 @subsection Compatible Architecture
40152 @cindex @code{<compatible>}
40154 This optional field was introduced in @value{GDBN} version 7.0.
40155 Previous versions of @value{GDBN} ignore it.
40157 A @samp{<compatible>} element has this form:
40160 <compatible>@var{arch}</compatible>
40163 @var{arch} is one of the architectures from the set accepted by
40164 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40166 A @samp{<compatible>} element is used to specify that the target
40167 is able to run binaries in some other than the main target architecture
40168 given by the @samp{<architecture>} element. For example, on the
40169 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40170 or @code{powerpc:common64}, but the system is able to run binaries
40171 in the @code{spu} architecture as well. The way to describe this
40172 capability with @samp{<compatible>} is as follows:
40175 <architecture>powerpc:common</architecture>
40176 <compatible>spu</compatible>
40179 @subsection Features
40182 Each @samp{<feature>} describes some logical portion of the target
40183 system. Features are currently used to describe available CPU
40184 registers and the types of their contents. A @samp{<feature>} element
40188 <feature name="@var{name}">
40189 @r{[}@var{type}@dots{}@r{]}
40195 Each feature's name should be unique within the description. The name
40196 of a feature does not matter unless @value{GDBN} has some special
40197 knowledge of the contents of that feature; if it does, the feature
40198 should have its standard name. @xref{Standard Target Features}.
40202 Any register's value is a collection of bits which @value{GDBN} must
40203 interpret. The default interpretation is a two's complement integer,
40204 but other types can be requested by name in the register description.
40205 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40206 Target Types}), and the description can define additional composite types.
40208 Each type element must have an @samp{id} attribute, which gives
40209 a unique (within the containing @samp{<feature>}) name to the type.
40210 Types must be defined before they are used.
40213 Some targets offer vector registers, which can be treated as arrays
40214 of scalar elements. These types are written as @samp{<vector>} elements,
40215 specifying the array element type, @var{type}, and the number of elements,
40219 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40223 If a register's value is usefully viewed in multiple ways, define it
40224 with a union type containing the useful representations. The
40225 @samp{<union>} element contains one or more @samp{<field>} elements,
40226 each of which has a @var{name} and a @var{type}:
40229 <union id="@var{id}">
40230 <field name="@var{name}" type="@var{type}"/>
40236 If a register's value is composed from several separate values, define
40237 it with a structure type. There are two forms of the @samp{<struct>}
40238 element; a @samp{<struct>} element must either contain only bitfields
40239 or contain no bitfields. If the structure contains only bitfields,
40240 its total size in bytes must be specified, each bitfield must have an
40241 explicit start and end, and bitfields are automatically assigned an
40242 integer type. The field's @var{start} should be less than or
40243 equal to its @var{end}, and zero represents the least significant bit.
40246 <struct id="@var{id}" size="@var{size}">
40247 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40252 If the structure contains no bitfields, then each field has an
40253 explicit type, and no implicit padding is added.
40256 <struct id="@var{id}">
40257 <field name="@var{name}" type="@var{type}"/>
40263 If a register's value is a series of single-bit flags, define it with
40264 a flags type. The @samp{<flags>} element has an explicit @var{size}
40265 and contains one or more @samp{<field>} elements. Each field has a
40266 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40270 <flags id="@var{id}" size="@var{size}">
40271 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40276 @subsection Registers
40279 Each register is represented as an element with this form:
40282 <reg name="@var{name}"
40283 bitsize="@var{size}"
40284 @r{[}regnum="@var{num}"@r{]}
40285 @r{[}save-restore="@var{save-restore}"@r{]}
40286 @r{[}type="@var{type}"@r{]}
40287 @r{[}group="@var{group}"@r{]}/>
40291 The components are as follows:
40296 The register's name; it must be unique within the target description.
40299 The register's size, in bits.
40302 The register's number. If omitted, a register's number is one greater
40303 than that of the previous register (either in the current feature or in
40304 a preceding feature); the first register in the target description
40305 defaults to zero. This register number is used to read or write
40306 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40307 packets, and registers appear in the @code{g} and @code{G} packets
40308 in order of increasing register number.
40311 Whether the register should be preserved across inferior function
40312 calls; this must be either @code{yes} or @code{no}. The default is
40313 @code{yes}, which is appropriate for most registers except for
40314 some system control registers; this is not related to the target's
40318 The type of the register. It may be a predefined type, a type
40319 defined in the current feature, or one of the special types @code{int}
40320 and @code{float}. @code{int} is an integer type of the correct size
40321 for @var{bitsize}, and @code{float} is a floating point type (in the
40322 architecture's normal floating point format) of the correct size for
40323 @var{bitsize}. The default is @code{int}.
40326 The register group to which this register belongs. It must
40327 be either @code{general}, @code{float}, or @code{vector}. If no
40328 @var{group} is specified, @value{GDBN} will not display the register
40329 in @code{info registers}.
40333 @node Predefined Target Types
40334 @section Predefined Target Types
40335 @cindex target descriptions, predefined types
40337 Type definitions in the self-description can build up composite types
40338 from basic building blocks, but can not define fundamental types. Instead,
40339 standard identifiers are provided by @value{GDBN} for the fundamental
40340 types. The currently supported types are:
40349 Signed integer types holding the specified number of bits.
40356 Unsigned integer types holding the specified number of bits.
40360 Pointers to unspecified code and data. The program counter and
40361 any dedicated return address register may be marked as code
40362 pointers; printing a code pointer converts it into a symbolic
40363 address. The stack pointer and any dedicated address registers
40364 may be marked as data pointers.
40367 Single precision IEEE floating point.
40370 Double precision IEEE floating point.
40373 The 12-byte extended precision format used by ARM FPA registers.
40376 The 10-byte extended precision format used by x87 registers.
40379 32bit @sc{eflags} register used by x86.
40382 32bit @sc{mxcsr} register used by x86.
40386 @node Standard Target Features
40387 @section Standard Target Features
40388 @cindex target descriptions, standard features
40390 A target description must contain either no registers or all the
40391 target's registers. If the description contains no registers, then
40392 @value{GDBN} will assume a default register layout, selected based on
40393 the architecture. If the description contains any registers, the
40394 default layout will not be used; the standard registers must be
40395 described in the target description, in such a way that @value{GDBN}
40396 can recognize them.
40398 This is accomplished by giving specific names to feature elements
40399 which contain standard registers. @value{GDBN} will look for features
40400 with those names and verify that they contain the expected registers;
40401 if any known feature is missing required registers, or if any required
40402 feature is missing, @value{GDBN} will reject the target
40403 description. You can add additional registers to any of the
40404 standard features --- @value{GDBN} will display them just as if
40405 they were added to an unrecognized feature.
40407 This section lists the known features and their expected contents.
40408 Sample XML documents for these features are included in the
40409 @value{GDBN} source tree, in the directory @file{gdb/features}.
40411 Names recognized by @value{GDBN} should include the name of the
40412 company or organization which selected the name, and the overall
40413 architecture to which the feature applies; so e.g.@: the feature
40414 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40416 The names of registers are not case sensitive for the purpose
40417 of recognizing standard features, but @value{GDBN} will only display
40418 registers using the capitalization used in the description.
40421 * AArch64 Features::
40424 * MicroBlaze Features::
40427 * Nios II Features::
40428 * PowerPC Features::
40429 * S/390 and System z Features::
40434 @node AArch64 Features
40435 @subsection AArch64 Features
40436 @cindex target descriptions, AArch64 features
40438 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40439 targets. It should contain registers @samp{x0} through @samp{x30},
40440 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40442 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40443 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40447 @subsection ARM Features
40448 @cindex target descriptions, ARM features
40450 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40452 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40453 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40455 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40456 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40457 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40460 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40461 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40463 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40464 it should contain at least registers @samp{wR0} through @samp{wR15} and
40465 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40466 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40468 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40469 should contain at least registers @samp{d0} through @samp{d15}. If
40470 they are present, @samp{d16} through @samp{d31} should also be included.
40471 @value{GDBN} will synthesize the single-precision registers from
40472 halves of the double-precision registers.
40474 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40475 need to contain registers; it instructs @value{GDBN} to display the
40476 VFP double-precision registers as vectors and to synthesize the
40477 quad-precision registers from pairs of double-precision registers.
40478 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40479 be present and include 32 double-precision registers.
40481 @node i386 Features
40482 @subsection i386 Features
40483 @cindex target descriptions, i386 features
40485 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40486 targets. It should describe the following registers:
40490 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40492 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40494 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40495 @samp{fs}, @samp{gs}
40497 @samp{st0} through @samp{st7}
40499 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40500 @samp{foseg}, @samp{fooff} and @samp{fop}
40503 The register sets may be different, depending on the target.
40505 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40506 describe registers:
40510 @samp{xmm0} through @samp{xmm7} for i386
40512 @samp{xmm0} through @samp{xmm15} for amd64
40517 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40518 @samp{org.gnu.gdb.i386.sse} feature. It should
40519 describe the upper 128 bits of @sc{ymm} registers:
40523 @samp{ymm0h} through @samp{ymm7h} for i386
40525 @samp{ymm0h} through @samp{ymm15h} for amd64
40528 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40529 Memory Protection Extension (MPX). It should describe the following registers:
40533 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40535 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40538 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40539 describe a single register, @samp{orig_eax}.
40541 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40542 @samp{org.gnu.gdb.i386.avx} feature. It should
40543 describe additional @sc{xmm} registers:
40547 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40550 It should describe the upper 128 bits of additional @sc{ymm} registers:
40554 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40558 describe the upper 256 bits of @sc{zmm} registers:
40562 @samp{zmm0h} through @samp{zmm7h} for i386.
40564 @samp{zmm0h} through @samp{zmm15h} for amd64.
40568 describe the additional @sc{zmm} registers:
40572 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40575 @node MicroBlaze Features
40576 @subsection MicroBlaze Features
40577 @cindex target descriptions, MicroBlaze features
40579 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40580 targets. It should contain registers @samp{r0} through @samp{r31},
40581 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40582 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40583 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40585 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40586 If present, it should contain registers @samp{rshr} and @samp{rslr}
40588 @node MIPS Features
40589 @subsection @acronym{MIPS} Features
40590 @cindex target descriptions, @acronym{MIPS} features
40592 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40593 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40594 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40597 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40598 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40599 registers. They may be 32-bit or 64-bit depending on the target.
40601 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40602 it may be optional in a future version of @value{GDBN}. It should
40603 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40604 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40606 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40607 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40608 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40609 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40611 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40612 contain a single register, @samp{restart}, which is used by the
40613 Linux kernel to control restartable syscalls.
40615 @node M68K Features
40616 @subsection M68K Features
40617 @cindex target descriptions, M68K features
40620 @item @samp{org.gnu.gdb.m68k.core}
40621 @itemx @samp{org.gnu.gdb.coldfire.core}
40622 @itemx @samp{org.gnu.gdb.fido.core}
40623 One of those features must be always present.
40624 The feature that is present determines which flavor of m68k is
40625 used. The feature that is present should contain registers
40626 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40627 @samp{sp}, @samp{ps} and @samp{pc}.
40629 @item @samp{org.gnu.gdb.coldfire.fp}
40630 This feature is optional. If present, it should contain registers
40631 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40635 @node Nios II Features
40636 @subsection Nios II Features
40637 @cindex target descriptions, Nios II features
40639 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40640 targets. It should contain the 32 core registers (@samp{zero},
40641 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40642 @samp{pc}, and the 16 control registers (@samp{status} through
40645 @node PowerPC Features
40646 @subsection PowerPC Features
40647 @cindex target descriptions, PowerPC features
40649 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40650 targets. It should contain registers @samp{r0} through @samp{r31},
40651 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40652 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40654 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40655 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40657 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40658 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40661 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40662 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40663 will combine these registers with the floating point registers
40664 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40665 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40666 through @samp{vs63}, the set of vector registers for POWER7.
40668 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40669 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40670 @samp{spefscr}. SPE targets should provide 32-bit registers in
40671 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40672 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40673 these to present registers @samp{ev0} through @samp{ev31} to the
40676 @node S/390 and System z Features
40677 @subsection S/390 and System z Features
40678 @cindex target descriptions, S/390 features
40679 @cindex target descriptions, System z features
40681 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40682 System z targets. It should contain the PSW and the 16 general
40683 registers. In particular, System z targets should provide the 64-bit
40684 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40685 S/390 targets should provide the 32-bit versions of these registers.
40686 A System z target that runs in 31-bit addressing mode should provide
40687 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40688 register's upper halves @samp{r0h} through @samp{r15h}, and their
40689 lower halves @samp{r0l} through @samp{r15l}.
40691 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40692 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40695 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40696 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40698 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40699 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40700 targets and 32-bit otherwise. In addition, the feature may contain
40701 the @samp{last_break} register, whose width depends on the addressing
40702 mode, as well as the @samp{system_call} register, which is always
40705 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40706 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40707 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40709 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40710 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40711 combined by @value{GDBN} with the floating point registers @samp{f0}
40712 through @samp{f15} to present the 128-bit wide vector registers
40713 @samp{v0} through @samp{v15}. In addition, this feature should
40714 contain the 128-bit wide vector registers @samp{v16} through
40717 @node TIC6x Features
40718 @subsection TMS320C6x Features
40719 @cindex target descriptions, TIC6x features
40720 @cindex target descriptions, TMS320C6x features
40721 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40722 targets. It should contain registers @samp{A0} through @samp{A15},
40723 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40725 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40726 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40727 through @samp{B31}.
40729 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40730 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40732 @node Operating System Information
40733 @appendix Operating System Information
40734 @cindex operating system information
40740 Users of @value{GDBN} often wish to obtain information about the state of
40741 the operating system running on the target---for example the list of
40742 processes, or the list of open files. This section describes the
40743 mechanism that makes it possible. This mechanism is similar to the
40744 target features mechanism (@pxref{Target Descriptions}), but focuses
40745 on a different aspect of target.
40747 Operating system information is retrived from the target via the
40748 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40749 read}). The object name in the request should be @samp{osdata}, and
40750 the @var{annex} identifies the data to be fetched.
40753 @appendixsection Process list
40754 @cindex operating system information, process list
40756 When requesting the process list, the @var{annex} field in the
40757 @samp{qXfer} request should be @samp{processes}. The returned data is
40758 an XML document. The formal syntax of this document is defined in
40759 @file{gdb/features/osdata.dtd}.
40761 An example document is:
40764 <?xml version="1.0"?>
40765 <!DOCTYPE target SYSTEM "osdata.dtd">
40766 <osdata type="processes">
40768 <column name="pid">1</column>
40769 <column name="user">root</column>
40770 <column name="command">/sbin/init</column>
40771 <column name="cores">1,2,3</column>
40776 Each item should include a column whose name is @samp{pid}. The value
40777 of that column should identify the process on the target. The
40778 @samp{user} and @samp{command} columns are optional, and will be
40779 displayed by @value{GDBN}. The @samp{cores} column, if present,
40780 should contain a comma-separated list of cores that this process
40781 is running on. Target may provide additional columns,
40782 which @value{GDBN} currently ignores.
40784 @node Trace File Format
40785 @appendix Trace File Format
40786 @cindex trace file format
40788 The trace file comes in three parts: a header, a textual description
40789 section, and a trace frame section with binary data.
40791 The header has the form @code{\x7fTRACE0\n}. The first byte is
40792 @code{0x7f} so as to indicate that the file contains binary data,
40793 while the @code{0} is a version number that may have different values
40796 The description section consists of multiple lines of @sc{ascii} text
40797 separated by newline characters (@code{0xa}). The lines may include a
40798 variety of optional descriptive or context-setting information, such
40799 as tracepoint definitions or register set size. @value{GDBN} will
40800 ignore any line that it does not recognize. An empty line marks the end
40803 @c FIXME add some specific types of data
40805 The trace frame section consists of a number of consecutive frames.
40806 Each frame begins with a two-byte tracepoint number, followed by a
40807 four-byte size giving the amount of data in the frame. The data in
40808 the frame consists of a number of blocks, each introduced by a
40809 character indicating its type (at least register, memory, and trace
40810 state variable). The data in this section is raw binary, not a
40811 hexadecimal or other encoding; its endianness matches the target's
40814 @c FIXME bi-arch may require endianness/arch info in description section
40817 @item R @var{bytes}
40818 Register block. The number and ordering of bytes matches that of a
40819 @code{g} packet in the remote protocol. Note that these are the
40820 actual bytes, in target order and @value{GDBN} register order, not a
40821 hexadecimal encoding.
40823 @item M @var{address} @var{length} @var{bytes}...
40824 Memory block. This is a contiguous block of memory, at the 8-byte
40825 address @var{address}, with a 2-byte length @var{length}, followed by
40826 @var{length} bytes.
40828 @item V @var{number} @var{value}
40829 Trace state variable block. This records the 8-byte signed value
40830 @var{value} of trace state variable numbered @var{number}.
40834 Future enhancements of the trace file format may include additional types
40837 @node Index Section Format
40838 @appendix @code{.gdb_index} section format
40839 @cindex .gdb_index section format
40840 @cindex index section format
40842 This section documents the index section that is created by @code{save
40843 gdb-index} (@pxref{Index Files}). The index section is
40844 DWARF-specific; some knowledge of DWARF is assumed in this
40847 The mapped index file format is designed to be directly
40848 @code{mmap}able on any architecture. In most cases, a datum is
40849 represented using a little-endian 32-bit integer value, called an
40850 @code{offset_type}. Big endian machines must byte-swap the values
40851 before using them. Exceptions to this rule are noted. The data is
40852 laid out such that alignment is always respected.
40854 A mapped index consists of several areas, laid out in order.
40858 The file header. This is a sequence of values, of @code{offset_type}
40859 unless otherwise noted:
40863 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40864 Version 4 uses a different hashing function from versions 5 and 6.
40865 Version 6 includes symbols for inlined functions, whereas versions 4
40866 and 5 do not. Version 7 adds attributes to the CU indices in the
40867 symbol table. Version 8 specifies that symbols from DWARF type units
40868 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40869 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40871 @value{GDBN} will only read version 4, 5, or 6 indices
40872 by specifying @code{set use-deprecated-index-sections on}.
40873 GDB has a workaround for potentially broken version 7 indices so it is
40874 currently not flagged as deprecated.
40877 The offset, from the start of the file, of the CU list.
40880 The offset, from the start of the file, of the types CU list. Note
40881 that this area can be empty, in which case this offset will be equal
40882 to the next offset.
40885 The offset, from the start of the file, of the address area.
40888 The offset, from the start of the file, of the symbol table.
40891 The offset, from the start of the file, of the constant pool.
40895 The CU list. This is a sequence of pairs of 64-bit little-endian
40896 values, sorted by the CU offset. The first element in each pair is
40897 the offset of a CU in the @code{.debug_info} section. The second
40898 element in each pair is the length of that CU. References to a CU
40899 elsewhere in the map are done using a CU index, which is just the
40900 0-based index into this table. Note that if there are type CUs, then
40901 conceptually CUs and type CUs form a single list for the purposes of
40905 The types CU list. This is a sequence of triplets of 64-bit
40906 little-endian values. In a triplet, the first value is the CU offset,
40907 the second value is the type offset in the CU, and the third value is
40908 the type signature. The types CU list is not sorted.
40911 The address area. The address area consists of a sequence of address
40912 entries. Each address entry has three elements:
40916 The low address. This is a 64-bit little-endian value.
40919 The high address. This is a 64-bit little-endian value. Like
40920 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40923 The CU index. This is an @code{offset_type} value.
40927 The symbol table. This is an open-addressed hash table. The size of
40928 the hash table is always a power of 2.
40930 Each slot in the hash table consists of a pair of @code{offset_type}
40931 values. The first value is the offset of the symbol's name in the
40932 constant pool. The second value is the offset of the CU vector in the
40935 If both values are 0, then this slot in the hash table is empty. This
40936 is ok because while 0 is a valid constant pool index, it cannot be a
40937 valid index for both a string and a CU vector.
40939 The hash value for a table entry is computed by applying an
40940 iterative hash function to the symbol's name. Starting with an
40941 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40942 the string is incorporated into the hash using the formula depending on the
40947 The formula is @code{r = r * 67 + c - 113}.
40949 @item Versions 5 to 7
40950 The formula is @code{r = r * 67 + tolower (c) - 113}.
40953 The terminating @samp{\0} is not incorporated into the hash.
40955 The step size used in the hash table is computed via
40956 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40957 value, and @samp{size} is the size of the hash table. The step size
40958 is used to find the next candidate slot when handling a hash
40961 The names of C@t{++} symbols in the hash table are canonicalized. We
40962 don't currently have a simple description of the canonicalization
40963 algorithm; if you intend to create new index sections, you must read
40967 The constant pool. This is simply a bunch of bytes. It is organized
40968 so that alignment is correct: CU vectors are stored first, followed by
40971 A CU vector in the constant pool is a sequence of @code{offset_type}
40972 values. The first value is the number of CU indices in the vector.
40973 Each subsequent value is the index and symbol attributes of a CU in
40974 the CU list. This element in the hash table is used to indicate which
40975 CUs define the symbol and how the symbol is used.
40976 See below for the format of each CU index+attributes entry.
40978 A string in the constant pool is zero-terminated.
40981 Attributes were added to CU index values in @code{.gdb_index} version 7.
40982 If a symbol has multiple uses within a CU then there is one
40983 CU index+attributes value for each use.
40985 The format of each CU index+attributes entry is as follows
40991 This is the index of the CU in the CU list.
40993 These bits are reserved for future purposes and must be zero.
40995 The kind of the symbol in the CU.
40999 This value is reserved and should not be used.
41000 By reserving zero the full @code{offset_type} value is backwards compatible
41001 with previous versions of the index.
41003 The symbol is a type.
41005 The symbol is a variable or an enum value.
41007 The symbol is a function.
41009 Any other kind of symbol.
41011 These values are reserved.
41015 This bit is zero if the value is global and one if it is static.
41017 The determination of whether a symbol is global or static is complicated.
41018 The authorative reference is the file @file{dwarf2read.c} in
41019 @value{GDBN} sources.
41023 This pseudo-code describes the computation of a symbol's kind and
41024 global/static attributes in the index.
41027 is_external = get_attribute (die, DW_AT_external);
41028 language = get_attribute (cu_die, DW_AT_language);
41031 case DW_TAG_typedef:
41032 case DW_TAG_base_type:
41033 case DW_TAG_subrange_type:
41037 case DW_TAG_enumerator:
41039 is_static = (language != CPLUS && language != JAVA);
41041 case DW_TAG_subprogram:
41043 is_static = ! (is_external || language == ADA);
41045 case DW_TAG_constant:
41047 is_static = ! is_external;
41049 case DW_TAG_variable:
41051 is_static = ! is_external;
41053 case DW_TAG_namespace:
41057 case DW_TAG_class_type:
41058 case DW_TAG_interface_type:
41059 case DW_TAG_structure_type:
41060 case DW_TAG_union_type:
41061 case DW_TAG_enumeration_type:
41063 is_static = (language != CPLUS && language != JAVA);
41071 @appendix Manual pages
41075 * gdb man:: The GNU Debugger man page
41076 * gdbserver man:: Remote Server for the GNU Debugger man page
41077 * gcore man:: Generate a core file of a running program
41078 * gdbinit man:: gdbinit scripts
41084 @c man title gdb The GNU Debugger
41086 @c man begin SYNOPSIS gdb
41087 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41088 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41089 [@option{-b}@w{ }@var{bps}]
41090 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41091 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41092 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41093 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41094 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41097 @c man begin DESCRIPTION gdb
41098 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41099 going on ``inside'' another program while it executes -- or what another
41100 program was doing at the moment it crashed.
41102 @value{GDBN} can do four main kinds of things (plus other things in support of
41103 these) to help you catch bugs in the act:
41107 Start your program, specifying anything that might affect its behavior.
41110 Make your program stop on specified conditions.
41113 Examine what has happened, when your program has stopped.
41116 Change things in your program, so you can experiment with correcting the
41117 effects of one bug and go on to learn about another.
41120 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41123 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41124 commands from the terminal until you tell it to exit with the @value{GDBN}
41125 command @code{quit}. You can get online help from @value{GDBN} itself
41126 by using the command @code{help}.
41128 You can run @code{gdb} with no arguments or options; but the most
41129 usual way to start @value{GDBN} is with one argument or two, specifying an
41130 executable program as the argument:
41136 You can also start with both an executable program and a core file specified:
41142 You can, instead, specify a process ID as a second argument, if you want
41143 to debug a running process:
41151 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41152 named @file{1234}; @value{GDBN} does check for a core file first).
41153 With option @option{-p} you can omit the @var{program} filename.
41155 Here are some of the most frequently needed @value{GDBN} commands:
41157 @c pod2man highlights the right hand side of the @item lines.
41159 @item break [@var{file}:]@var{functiop}
41160 Set a breakpoint at @var{function} (in @var{file}).
41162 @item run [@var{arglist}]
41163 Start your program (with @var{arglist}, if specified).
41166 Backtrace: display the program stack.
41168 @item print @var{expr}
41169 Display the value of an expression.
41172 Continue running your program (after stopping, e.g. at a breakpoint).
41175 Execute next program line (after stopping); step @emph{over} any
41176 function calls in the line.
41178 @item edit [@var{file}:]@var{function}
41179 look at the program line where it is presently stopped.
41181 @item list [@var{file}:]@var{function}
41182 type the text of the program in the vicinity of where it is presently stopped.
41185 Execute next program line (after stopping); step @emph{into} any
41186 function calls in the line.
41188 @item help [@var{name}]
41189 Show information about @value{GDBN} command @var{name}, or general information
41190 about using @value{GDBN}.
41193 Exit from @value{GDBN}.
41197 For full details on @value{GDBN},
41198 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41199 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41200 as the @code{gdb} entry in the @code{info} program.
41204 @c man begin OPTIONS gdb
41205 Any arguments other than options specify an executable
41206 file and core file (or process ID); that is, the first argument
41207 encountered with no
41208 associated option flag is equivalent to a @option{-se} option, and the second,
41209 if any, is equivalent to a @option{-c} option if it's the name of a file.
41211 both long and short forms; both are shown here. The long forms are also
41212 recognized if you truncate them, so long as enough of the option is
41213 present to be unambiguous. (If you prefer, you can flag option
41214 arguments with @option{+} rather than @option{-}, though we illustrate the
41215 more usual convention.)
41217 All the options and command line arguments you give are processed
41218 in sequential order. The order makes a difference when the @option{-x}
41224 List all options, with brief explanations.
41226 @item -symbols=@var{file}
41227 @itemx -s @var{file}
41228 Read symbol table from file @var{file}.
41231 Enable writing into executable and core files.
41233 @item -exec=@var{file}
41234 @itemx -e @var{file}
41235 Use file @var{file} as the executable file to execute when
41236 appropriate, and for examining pure data in conjunction with a core
41239 @item -se=@var{file}
41240 Read symbol table from file @var{file} and use it as the executable
41243 @item -core=@var{file}
41244 @itemx -c @var{file}
41245 Use file @var{file} as a core dump to examine.
41247 @item -command=@var{file}
41248 @itemx -x @var{file}
41249 Execute @value{GDBN} commands from file @var{file}.
41251 @item -ex @var{command}
41252 Execute given @value{GDBN} @var{command}.
41254 @item -directory=@var{directory}
41255 @itemx -d @var{directory}
41256 Add @var{directory} to the path to search for source files.
41259 Do not execute commands from @file{~/.gdbinit}.
41263 Do not execute commands from any @file{.gdbinit} initialization files.
41267 ``Quiet''. Do not print the introductory and copyright messages. These
41268 messages are also suppressed in batch mode.
41271 Run in batch mode. Exit with status @code{0} after processing all the command
41272 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41273 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41274 commands in the command files.
41276 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41277 download and run a program on another computer; in order to make this
41278 more useful, the message
41281 Program exited normally.
41285 (which is ordinarily issued whenever a program running under @value{GDBN} control
41286 terminates) is not issued when running in batch mode.
41288 @item -cd=@var{directory}
41289 Run @value{GDBN} using @var{directory} as its working directory,
41290 instead of the current directory.
41294 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41295 @value{GDBN} to output the full file name and line number in a standard,
41296 recognizable fashion each time a stack frame is displayed (which
41297 includes each time the program stops). This recognizable format looks
41298 like two @samp{\032} characters, followed by the file name, line number
41299 and character position separated by colons, and a newline. The
41300 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41301 characters as a signal to display the source code for the frame.
41304 Set the line speed (baud rate or bits per second) of any serial
41305 interface used by @value{GDBN} for remote debugging.
41307 @item -tty=@var{device}
41308 Run using @var{device} for your program's standard input and output.
41312 @c man begin SEEALSO gdb
41314 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41315 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41316 documentation are properly installed at your site, the command
41323 should give you access to the complete manual.
41325 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41326 Richard M. Stallman and Roland H. Pesch, July 1991.
41330 @node gdbserver man
41331 @heading gdbserver man
41333 @c man title gdbserver Remote Server for the GNU Debugger
41335 @c man begin SYNOPSIS gdbserver
41336 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41338 gdbserver --attach @var{comm} @var{pid}
41340 gdbserver --multi @var{comm}
41344 @c man begin DESCRIPTION gdbserver
41345 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41346 than the one which is running the program being debugged.
41349 @subheading Usage (server (target) side)
41352 Usage (server (target) side):
41355 First, you need to have a copy of the program you want to debug put onto
41356 the target system. The program can be stripped to save space if needed, as
41357 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41358 the @value{GDBN} running on the host system.
41360 To use the server, you log on to the target system, and run the @command{gdbserver}
41361 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41362 your program, and (c) its arguments. The general syntax is:
41365 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41368 For example, using a serial port, you might say:
41372 @c @file would wrap it as F</dev/com1>.
41373 target> gdbserver /dev/com1 emacs foo.txt
41376 target> gdbserver @file{/dev/com1} emacs foo.txt
41380 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41381 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41382 waits patiently for the host @value{GDBN} to communicate with it.
41384 To use a TCP connection, you could say:
41387 target> gdbserver host:2345 emacs foo.txt
41390 This says pretty much the same thing as the last example, except that we are
41391 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41392 that we are expecting to see a TCP connection from @code{host} to local TCP port
41393 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41394 want for the port number as long as it does not conflict with any existing TCP
41395 ports on the target system. This same port number must be used in the host
41396 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41397 you chose a port number that conflicts with another service, @command{gdbserver} will
41398 print an error message and exit.
41400 @command{gdbserver} can also attach to running programs.
41401 This is accomplished via the @option{--attach} argument. The syntax is:
41404 target> gdbserver --attach @var{comm} @var{pid}
41407 @var{pid} is the process ID of a currently running process. It isn't
41408 necessary to point @command{gdbserver} at a binary for the running process.
41410 To start @code{gdbserver} without supplying an initial command to run
41411 or process ID to attach, use the @option{--multi} command line option.
41412 In such case you should connect using @kbd{target extended-remote} to start
41413 the program you want to debug.
41416 target> gdbserver --multi @var{comm}
41420 @subheading Usage (host side)
41426 You need an unstripped copy of the target program on your host system, since
41427 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41428 would, with the target program as the first argument. (You may need to use the
41429 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41430 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41431 new command you need to know about is @code{target remote}
41432 (or @code{target extended-remote}). Its argument is either
41433 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41434 descriptor. For example:
41438 @c @file would wrap it as F</dev/ttyb>.
41439 (gdb) target remote /dev/ttyb
41442 (gdb) target remote @file{/dev/ttyb}
41447 communicates with the server via serial line @file{/dev/ttyb}, and:
41450 (gdb) target remote the-target:2345
41454 communicates via a TCP connection to port 2345 on host `the-target', where
41455 you previously started up @command{gdbserver} with the same port number. Note that for
41456 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41457 command, otherwise you may get an error that looks something like
41458 `Connection refused'.
41460 @command{gdbserver} can also debug multiple inferiors at once,
41463 the @value{GDBN} manual in node @code{Inferiors and Programs}
41464 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41467 @ref{Inferiors and Programs}.
41469 In such case use the @code{extended-remote} @value{GDBN} command variant:
41472 (gdb) target extended-remote the-target:2345
41475 The @command{gdbserver} option @option{--multi} may or may not be used in such
41479 @c man begin OPTIONS gdbserver
41480 There are three different modes for invoking @command{gdbserver}:
41485 Debug a specific program specified by its program name:
41488 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41491 The @var{comm} parameter specifies how should the server communicate
41492 with @value{GDBN}; it is either a device name (to use a serial line),
41493 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41494 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41495 debug in @var{prog}. Any remaining arguments will be passed to the
41496 program verbatim. When the program exits, @value{GDBN} will close the
41497 connection, and @code{gdbserver} will exit.
41500 Debug a specific program by specifying the process ID of a running
41504 gdbserver --attach @var{comm} @var{pid}
41507 The @var{comm} parameter is as described above. Supply the process ID
41508 of a running program in @var{pid}; @value{GDBN} will do everything
41509 else. Like with the previous mode, when the process @var{pid} exits,
41510 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41513 Multi-process mode -- debug more than one program/process:
41516 gdbserver --multi @var{comm}
41519 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41520 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41521 close the connection when a process being debugged exits, so you can
41522 debug several processes in the same session.
41525 In each of the modes you may specify these options:
41530 List all options, with brief explanations.
41533 This option causes @command{gdbserver} to print its version number and exit.
41536 @command{gdbserver} will attach to a running program. The syntax is:
41539 target> gdbserver --attach @var{comm} @var{pid}
41542 @var{pid} is the process ID of a currently running process. It isn't
41543 necessary to point @command{gdbserver} at a binary for the running process.
41546 To start @code{gdbserver} without supplying an initial command to run
41547 or process ID to attach, use this command line option.
41548 Then you can connect using @kbd{target extended-remote} and start
41549 the program you want to debug. The syntax is:
41552 target> gdbserver --multi @var{comm}
41556 Instruct @code{gdbserver} to display extra status information about the debugging
41558 This option is intended for @code{gdbserver} development and for bug reports to
41561 @item --remote-debug
41562 Instruct @code{gdbserver} to display remote protocol debug output.
41563 This option is intended for @code{gdbserver} development and for bug reports to
41566 @item --debug-format=option1@r{[},option2,...@r{]}
41567 Instruct @code{gdbserver} to include extra information in each line
41568 of debugging output.
41569 @xref{Other Command-Line Arguments for gdbserver}.
41572 Specify a wrapper to launch programs
41573 for debugging. The option should be followed by the name of the
41574 wrapper, then any command-line arguments to pass to the wrapper, then
41575 @kbd{--} indicating the end of the wrapper arguments.
41578 By default, @command{gdbserver} keeps the listening TCP port open, so that
41579 additional connections are possible. However, if you start @code{gdbserver}
41580 with the @option{--once} option, it will stop listening for any further
41581 connection attempts after connecting to the first @value{GDBN} session.
41583 @c --disable-packet is not documented for users.
41585 @c --disable-randomization and --no-disable-randomization are superseded by
41586 @c QDisableRandomization.
41591 @c man begin SEEALSO gdbserver
41593 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41594 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41595 documentation are properly installed at your site, the command
41601 should give you access to the complete manual.
41603 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41604 Richard M. Stallman and Roland H. Pesch, July 1991.
41611 @c man title gcore Generate a core file of a running program
41614 @c man begin SYNOPSIS gcore
41615 gcore [-o @var{filename}] @var{pid}
41619 @c man begin DESCRIPTION gcore
41620 Generate a core dump of a running program with process ID @var{pid}.
41621 Produced file is equivalent to a kernel produced core file as if the process
41622 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41623 limit). Unlike after a crash, after @command{gcore} the program remains
41624 running without any change.
41627 @c man begin OPTIONS gcore
41629 @item -o @var{filename}
41630 The optional argument
41631 @var{filename} specifies the file name where to put the core dump.
41632 If not specified, the file name defaults to @file{core.@var{pid}},
41633 where @var{pid} is the running program process ID.
41637 @c man begin SEEALSO gcore
41639 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41640 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41641 documentation are properly installed at your site, the command
41648 should give you access to the complete manual.
41650 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41651 Richard M. Stallman and Roland H. Pesch, July 1991.
41658 @c man title gdbinit GDB initialization scripts
41661 @c man begin SYNOPSIS gdbinit
41662 @ifset SYSTEM_GDBINIT
41663 @value{SYSTEM_GDBINIT}
41672 @c man begin DESCRIPTION gdbinit
41673 These files contain @value{GDBN} commands to automatically execute during
41674 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41677 the @value{GDBN} manual in node @code{Sequences}
41678 -- shell command @code{info -f gdb -n Sequences}.
41684 Please read more in
41686 the @value{GDBN} manual in node @code{Startup}
41687 -- shell command @code{info -f gdb -n Startup}.
41694 @ifset SYSTEM_GDBINIT
41695 @item @value{SYSTEM_GDBINIT}
41697 @ifclear SYSTEM_GDBINIT
41698 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41700 System-wide initialization file. It is executed unless user specified
41701 @value{GDBN} option @code{-nx} or @code{-n}.
41704 the @value{GDBN} manual in node @code{System-wide configuration}
41705 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41708 @ref{System-wide configuration}.
41712 User initialization file. It is executed unless user specified
41713 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41716 Initialization file for current directory. It may need to be enabled with
41717 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41720 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41721 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41724 @ref{Init File in the Current Directory}.
41729 @c man begin SEEALSO gdbinit
41731 gdb(1), @code{info -f gdb -n Startup}
41733 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41734 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41735 documentation are properly installed at your site, the command
41741 should give you access to the complete manual.
41743 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41744 Richard M. Stallman and Roland H. Pesch, July 1991.
41750 @node GNU Free Documentation License
41751 @appendix GNU Free Documentation License
41754 @node Concept Index
41755 @unnumbered Concept Index
41759 @node Command and Variable Index
41760 @unnumbered Command, Variable, and Function Index
41765 % I think something like @@colophon should be in texinfo. In the
41767 \long\def\colophon{\hbox to0pt{}\vfill
41768 \centerline{The body of this manual is set in}
41769 \centerline{\fontname\tenrm,}
41770 \centerline{with headings in {\bf\fontname\tenbf}}
41771 \centerline{and examples in {\tt\fontname\tentt}.}
41772 \centerline{{\it\fontname\tenit\/},}
41773 \centerline{{\bf\fontname\tenbf}, and}
41774 \centerline{{\sl\fontname\tensl\/}}
41775 \centerline{are used for emphasis.}\vfill}
41777 % Blame: doc@@cygnus.com, 1991.