1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2014 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2014 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
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}).
1239 @c @cindex @code{--xdb}
1240 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1241 @c For information, see the file @file{xdb_trans.html}, which is usually
1242 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1245 @item -interpreter @var{interp}
1246 @cindex @code{--interpreter}
1247 Use the interpreter @var{interp} for interface with the controlling
1248 program or device. This option is meant to be set by programs which
1249 communicate with @value{GDBN} using it as a back end.
1250 @xref{Interpreters, , Command Interpreters}.
1252 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1253 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1254 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1255 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1256 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1257 @sc{gdb/mi} interfaces are no longer supported.
1260 @cindex @code{--write}
1261 Open the executable and core files for both reading and writing. This
1262 is equivalent to the @samp{set write on} command inside @value{GDBN}
1266 @cindex @code{--statistics}
1267 This option causes @value{GDBN} to print statistics about time and
1268 memory usage after it completes each command and returns to the prompt.
1271 @cindex @code{--version}
1272 This option causes @value{GDBN} to print its version number and
1273 no-warranty blurb, and exit.
1275 @item -configuration
1276 @cindex @code{--configuration}
1277 This option causes @value{GDBN} to print details about its build-time
1278 configuration parameters, and then exit. These details can be
1279 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1284 @subsection What @value{GDBN} Does During Startup
1285 @cindex @value{GDBN} startup
1287 Here's the description of what @value{GDBN} does during session startup:
1291 Sets up the command interpreter as specified by the command line
1292 (@pxref{Mode Options, interpreter}).
1296 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1297 used when building @value{GDBN}; @pxref{System-wide configuration,
1298 ,System-wide configuration and settings}) and executes all the commands in
1301 @anchor{Home Directory Init File}
1303 Reads the init file (if any) in your home directory@footnote{On
1304 DOS/Windows systems, the home directory is the one pointed to by the
1305 @code{HOME} environment variable.} and executes all the commands in
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1319 @anchor{Init File in the Current Directory during Startup}
1321 Reads and executes the commands from init file (if any) in the current
1322 working directory as long as @samp{set auto-load local-gdbinit} is set to
1323 @samp{on} (@pxref{Init File in the Current Directory}).
1324 This is only done if the current directory is
1325 different from your home directory. Thus, you can have more than one
1326 init file, one generic in your home directory, and another, specific
1327 to the program you are debugging, in the directory where you invoke
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 Init files use the same syntax as @dfn{command files} (@pxref{Command
1358 Files}) and are processed by @value{GDBN} in the same way. The init
1359 file in your home directory can set options (such as @samp{set
1360 complaints}) that affect subsequent processing of command line options
1361 and operands. Init files are not executed if you use the @samp{-nx}
1362 option (@pxref{Mode Options, ,Choosing Modes}).
1364 To display the list of init files loaded by gdb at startup, you
1365 can use @kbd{gdb --help}.
1367 @cindex init file name
1368 @cindex @file{.gdbinit}
1369 @cindex @file{gdb.ini}
1370 The @value{GDBN} init files are normally called @file{.gdbinit}.
1371 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1372 the limitations of file names imposed by DOS filesystems. The Windows
1373 port of @value{GDBN} uses the standard name, but if it finds a
1374 @file{gdb.ini} file in your home directory, it warns you about that
1375 and suggests to rename the file to the standard name.
1379 @section Quitting @value{GDBN}
1380 @cindex exiting @value{GDBN}
1381 @cindex leaving @value{GDBN}
1384 @kindex quit @r{[}@var{expression}@r{]}
1385 @kindex q @r{(@code{quit})}
1386 @item quit @r{[}@var{expression}@r{]}
1388 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1389 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1390 do not supply @var{expression}, @value{GDBN} will terminate normally;
1391 otherwise it will terminate using the result of @var{expression} as the
1396 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1397 terminates the action of any @value{GDBN} command that is in progress and
1398 returns to @value{GDBN} command level. It is safe to type the interrupt
1399 character at any time because @value{GDBN} does not allow it to take effect
1400 until a time when it is safe.
1402 If you have been using @value{GDBN} to control an attached process or
1403 device, you can release it with the @code{detach} command
1404 (@pxref{Attach, ,Debugging an Already-running Process}).
1406 @node Shell Commands
1407 @section Shell Commands
1409 If you need to execute occasional shell commands during your
1410 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1411 just use the @code{shell} command.
1416 @cindex shell escape
1417 @item shell @var{command-string}
1418 @itemx !@var{command-string}
1419 Invoke a standard shell to execute @var{command-string}.
1420 Note that no space is needed between @code{!} and @var{command-string}.
1421 If it exists, the environment variable @code{SHELL} determines which
1422 shell to run. Otherwise @value{GDBN} uses the default shell
1423 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1426 The utility @code{make} is often needed in development environments.
1427 You do not have to use the @code{shell} command for this purpose in
1432 @cindex calling make
1433 @item make @var{make-args}
1434 Execute the @code{make} program with the specified
1435 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1438 @node Logging Output
1439 @section Logging Output
1440 @cindex logging @value{GDBN} output
1441 @cindex save @value{GDBN} output to a file
1443 You may want to save the output of @value{GDBN} commands to a file.
1444 There are several commands to control @value{GDBN}'s logging.
1448 @item set logging on
1450 @item set logging off
1452 @cindex logging file name
1453 @item set logging file @var{file}
1454 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1455 @item set logging overwrite [on|off]
1456 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1457 you want @code{set logging on} to overwrite the logfile instead.
1458 @item set logging redirect [on|off]
1459 By default, @value{GDBN} output will go to both the terminal and the logfile.
1460 Set @code{redirect} if you want output to go only to the log file.
1461 @kindex show logging
1463 Show the current values of the logging settings.
1467 @chapter @value{GDBN} Commands
1469 You can abbreviate a @value{GDBN} command to the first few letters of the command
1470 name, if that abbreviation is unambiguous; and you can repeat certain
1471 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1472 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1473 show you the alternatives available, if there is more than one possibility).
1476 * Command Syntax:: How to give commands to @value{GDBN}
1477 * Completion:: Command completion
1478 * Help:: How to ask @value{GDBN} for help
1481 @node Command Syntax
1482 @section Command Syntax
1484 A @value{GDBN} command is a single line of input. There is no limit on
1485 how long it can be. It starts with a command name, which is followed by
1486 arguments whose meaning depends on the command name. For example, the
1487 command @code{step} accepts an argument which is the number of times to
1488 step, as in @samp{step 5}. You can also use the @code{step} command
1489 with no arguments. Some commands do not allow any arguments.
1491 @cindex abbreviation
1492 @value{GDBN} command names may always be truncated if that abbreviation is
1493 unambiguous. Other possible command abbreviations are listed in the
1494 documentation for individual commands. In some cases, even ambiguous
1495 abbreviations are allowed; for example, @code{s} is specially defined as
1496 equivalent to @code{step} even though there are other commands whose
1497 names start with @code{s}. You can test abbreviations by using them as
1498 arguments to the @code{help} command.
1500 @cindex repeating commands
1501 @kindex RET @r{(repeat last command)}
1502 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1503 repeat the previous command. Certain commands (for example, @code{run})
1504 will not repeat this way; these are commands whose unintentional
1505 repetition might cause trouble and which you are unlikely to want to
1506 repeat. User-defined commands can disable this feature; see
1507 @ref{Define, dont-repeat}.
1509 The @code{list} and @code{x} commands, when you repeat them with
1510 @key{RET}, construct new arguments rather than repeating
1511 exactly as typed. This permits easy scanning of source or memory.
1513 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1514 output, in a way similar to the common utility @code{more}
1515 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1516 @key{RET} too many in this situation, @value{GDBN} disables command
1517 repetition after any command that generates this sort of display.
1519 @kindex # @r{(a comment)}
1521 Any text from a @kbd{#} to the end of the line is a comment; it does
1522 nothing. This is useful mainly in command files (@pxref{Command
1523 Files,,Command Files}).
1525 @cindex repeating command sequences
1526 @kindex Ctrl-o @r{(operate-and-get-next)}
1527 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1528 commands. This command accepts the current line, like @key{RET}, and
1529 then fetches the next line relative to the current line from the history
1533 @section Command Completion
1536 @cindex word completion
1537 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1538 only one possibility; it can also show you what the valid possibilities
1539 are for the next word in a command, at any time. This works for @value{GDBN}
1540 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1542 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1543 of a word. If there is only one possibility, @value{GDBN} fills in the
1544 word, and waits for you to finish the command (or press @key{RET} to
1545 enter it). For example, if you type
1547 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1548 @c complete accuracy in these examples; space introduced for clarity.
1549 @c If texinfo enhancements make it unnecessary, it would be nice to
1550 @c replace " @key" by "@key" in the following...
1552 (@value{GDBP}) info bre @key{TAB}
1556 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1557 the only @code{info} subcommand beginning with @samp{bre}:
1560 (@value{GDBP}) info breakpoints
1564 You can either press @key{RET} at this point, to run the @code{info
1565 breakpoints} command, or backspace and enter something else, if
1566 @samp{breakpoints} does not look like the command you expected. (If you
1567 were sure you wanted @code{info breakpoints} in the first place, you
1568 might as well just type @key{RET} immediately after @samp{info bre},
1569 to exploit command abbreviations rather than command completion).
1571 If there is more than one possibility for the next word when you press
1572 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1573 characters and try again, or just press @key{TAB} a second time;
1574 @value{GDBN} displays all the possible completions for that word. For
1575 example, you might want to set a breakpoint on a subroutine whose name
1576 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1577 just sounds the bell. Typing @key{TAB} again displays all the
1578 function names in your program that begin with those characters, for
1582 (@value{GDBP}) b make_ @key{TAB}
1583 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1584 make_a_section_from_file make_environ
1585 make_abs_section make_function_type
1586 make_blockvector make_pointer_type
1587 make_cleanup make_reference_type
1588 make_command make_symbol_completion_list
1589 (@value{GDBP}) b make_
1593 After displaying the available possibilities, @value{GDBN} copies your
1594 partial input (@samp{b make_} in the example) so you can finish the
1597 If you just want to see the list of alternatives in the first place, you
1598 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1599 means @kbd{@key{META} ?}. You can type this either by holding down a
1600 key designated as the @key{META} shift on your keyboard (if there is
1601 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1603 @cindex quotes in commands
1604 @cindex completion of quoted strings
1605 Sometimes the string you need, while logically a ``word'', may contain
1606 parentheses or other characters that @value{GDBN} normally excludes from
1607 its notion of a word. To permit word completion to work in this
1608 situation, you may enclose words in @code{'} (single quote marks) in
1609 @value{GDBN} commands.
1611 The most likely situation where you might need this is in typing the
1612 name of a C@t{++} function. This is because C@t{++} allows function
1613 overloading (multiple definitions of the same function, distinguished
1614 by argument type). For example, when you want to set a breakpoint you
1615 may need to distinguish whether you mean the version of @code{name}
1616 that takes an @code{int} parameter, @code{name(int)}, or the version
1617 that takes a @code{float} parameter, @code{name(float)}. To use the
1618 word-completion facilities in this situation, type a single quote
1619 @code{'} at the beginning of the function name. This alerts
1620 @value{GDBN} that it may need to consider more information than usual
1621 when you press @key{TAB} or @kbd{M-?} to request word completion:
1624 (@value{GDBP}) b 'bubble( @kbd{M-?}
1625 bubble(double,double) bubble(int,int)
1626 (@value{GDBP}) b 'bubble(
1629 In some cases, @value{GDBN} can tell that completing a name requires using
1630 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1631 completing as much as it can) if you do not type the quote in the first
1635 (@value{GDBP}) b bub @key{TAB}
1636 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1637 (@value{GDBP}) b 'bubble(
1641 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1642 you have not yet started typing the argument list when you ask for
1643 completion on an overloaded symbol.
1645 For more information about overloaded functions, see @ref{C Plus Plus
1646 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1647 overload-resolution off} to disable overload resolution;
1648 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1650 @cindex completion of structure field names
1651 @cindex structure field name completion
1652 @cindex completion of union field names
1653 @cindex union field name completion
1654 When completing in an expression which looks up a field in a
1655 structure, @value{GDBN} also tries@footnote{The completer can be
1656 confused by certain kinds of invalid expressions. Also, it only
1657 examines the static type of the expression, not the dynamic type.} to
1658 limit completions to the field names available in the type of the
1662 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1663 magic to_fputs to_rewind
1664 to_data to_isatty to_write
1665 to_delete to_put to_write_async_safe
1670 This is because the @code{gdb_stdout} is a variable of the type
1671 @code{struct ui_file} that is defined in @value{GDBN} sources as
1678 ui_file_flush_ftype *to_flush;
1679 ui_file_write_ftype *to_write;
1680 ui_file_write_async_safe_ftype *to_write_async_safe;
1681 ui_file_fputs_ftype *to_fputs;
1682 ui_file_read_ftype *to_read;
1683 ui_file_delete_ftype *to_delete;
1684 ui_file_isatty_ftype *to_isatty;
1685 ui_file_rewind_ftype *to_rewind;
1686 ui_file_put_ftype *to_put;
1693 @section Getting Help
1694 @cindex online documentation
1697 You can always ask @value{GDBN} itself for information on its commands,
1698 using the command @code{help}.
1701 @kindex h @r{(@code{help})}
1704 You can use @code{help} (abbreviated @code{h}) with no arguments to
1705 display a short list of named classes of commands:
1709 List of classes of commands:
1711 aliases -- Aliases of other commands
1712 breakpoints -- Making program stop at certain points
1713 data -- Examining data
1714 files -- Specifying and examining files
1715 internals -- Maintenance commands
1716 obscure -- Obscure features
1717 running -- Running the program
1718 stack -- Examining the stack
1719 status -- Status inquiries
1720 support -- Support facilities
1721 tracepoints -- Tracing of program execution without
1722 stopping the program
1723 user-defined -- User-defined commands
1725 Type "help" followed by a class name for a list of
1726 commands in that class.
1727 Type "help" followed by command name for full
1729 Command name abbreviations are allowed if unambiguous.
1732 @c the above line break eliminates huge line overfull...
1734 @item help @var{class}
1735 Using one of the general help classes as an argument, you can get a
1736 list of the individual commands in that class. For example, here is the
1737 help display for the class @code{status}:
1740 (@value{GDBP}) help status
1745 @c Line break in "show" line falsifies real output, but needed
1746 @c to fit in smallbook page size.
1747 info -- Generic command for showing things
1748 about the program being debugged
1749 show -- Generic command for showing things
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1758 @item help @var{command}
1759 With a command name as @code{help} argument, @value{GDBN} displays a
1760 short paragraph on how to use that command.
1763 @item apropos @var{args}
1764 The @code{apropos} command searches through all of the @value{GDBN}
1765 commands, and their documentation, for the regular expression specified in
1766 @var{args}. It prints out all matches found. For example:
1777 alias -- Define a new command that is an alias of an existing command
1778 aliases -- Aliases of other commands
1779 d -- Delete some breakpoints or auto-display expressions
1780 del -- Delete some breakpoints or auto-display expressions
1781 delete -- Delete some breakpoints or auto-display expressions
1786 @item complete @var{args}
1787 The @code{complete @var{args}} command lists all the possible completions
1788 for the beginning of a command. Use @var{args} to specify the beginning of the
1789 command you want completed. For example:
1795 @noindent results in:
1806 @noindent This is intended for use by @sc{gnu} Emacs.
1809 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1810 and @code{show} to inquire about the state of your program, or the state
1811 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1812 manual introduces each of them in the appropriate context. The listings
1813 under @code{info} and under @code{show} in the Command, Variable, and
1814 Function Index point to all the sub-commands. @xref{Command and Variable
1820 @kindex i @r{(@code{info})}
1822 This command (abbreviated @code{i}) is for describing the state of your
1823 program. For example, you can show the arguments passed to a function
1824 with @code{info args}, list the registers currently in use with @code{info
1825 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1826 You can get a complete list of the @code{info} sub-commands with
1827 @w{@code{help info}}.
1831 You can assign the result of an expression to an environment variable with
1832 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1833 @code{set prompt $}.
1837 In contrast to @code{info}, @code{show} is for describing the state of
1838 @value{GDBN} itself.
1839 You can change most of the things you can @code{show}, by using the
1840 related command @code{set}; for example, you can control what number
1841 system is used for displays with @code{set radix}, or simply inquire
1842 which is currently in use with @code{show radix}.
1845 To display all the settable parameters and their current
1846 values, you can use @code{show} with no arguments; you may also use
1847 @code{info set}. Both commands produce the same display.
1848 @c FIXME: "info set" violates the rule that "info" is for state of
1849 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1850 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1854 Here are several miscellaneous @code{show} subcommands, all of which are
1855 exceptional in lacking corresponding @code{set} commands:
1858 @kindex show version
1859 @cindex @value{GDBN} version number
1861 Show what version of @value{GDBN} is running. You should include this
1862 information in @value{GDBN} bug-reports. If multiple versions of
1863 @value{GDBN} are in use at your site, you may need to determine which
1864 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1865 commands are introduced, and old ones may wither away. Also, many
1866 system vendors ship variant versions of @value{GDBN}, and there are
1867 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1868 The version number is the same as the one announced when you start
1871 @kindex show copying
1872 @kindex info copying
1873 @cindex display @value{GDBN} copyright
1876 Display information about permission for copying @value{GDBN}.
1878 @kindex show warranty
1879 @kindex info warranty
1881 @itemx info warranty
1882 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1883 if your version of @value{GDBN} comes with one.
1885 @kindex show configuration
1886 @item show configuration
1887 Display detailed information about the way @value{GDBN} was configured
1888 when it was built. This displays the optional arguments passed to the
1889 @file{configure} script and also configuration parameters detected
1890 automatically by @command{configure}. When reporting a @value{GDBN}
1891 bug (@pxref{GDB Bugs}), it is important to include this information in
1897 @chapter Running Programs Under @value{GDBN}
1899 When you run a program under @value{GDBN}, you must first generate
1900 debugging information when you compile it.
1902 You may start @value{GDBN} with its arguments, if any, in an environment
1903 of your choice. If you are doing native debugging, you may redirect
1904 your program's input and output, debug an already running process, or
1905 kill a child process.
1908 * Compilation:: Compiling for debugging
1909 * Starting:: Starting your program
1910 * Arguments:: Your program's arguments
1911 * Environment:: Your program's environment
1913 * Working Directory:: Your program's working directory
1914 * Input/Output:: Your program's input and output
1915 * Attach:: Debugging an already-running process
1916 * Kill Process:: Killing the child process
1918 * Inferiors and Programs:: Debugging multiple inferiors and programs
1919 * Threads:: Debugging programs with multiple threads
1920 * Forks:: Debugging forks
1921 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1925 @section Compiling for Debugging
1927 In order to debug a program effectively, you need to generate
1928 debugging information when you compile it. This debugging information
1929 is stored in the object file; it describes the data type of each
1930 variable or function and the correspondence between source line numbers
1931 and addresses in the executable code.
1933 To request debugging information, specify the @samp{-g} option when you run
1936 Programs that are to be shipped to your customers are compiled with
1937 optimizations, using the @samp{-O} compiler option. However, some
1938 compilers are unable to handle the @samp{-g} and @samp{-O} options
1939 together. Using those compilers, you cannot generate optimized
1940 executables containing debugging information.
1942 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1943 without @samp{-O}, making it possible to debug optimized code. We
1944 recommend that you @emph{always} use @samp{-g} whenever you compile a
1945 program. You may think your program is correct, but there is no sense
1946 in pushing your luck. For more information, see @ref{Optimized Code}.
1948 Older versions of the @sc{gnu} C compiler permitted a variant option
1949 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1950 format; if your @sc{gnu} C compiler has this option, do not use it.
1952 @value{GDBN} knows about preprocessor macros and can show you their
1953 expansion (@pxref{Macros}). Most compilers do not include information
1954 about preprocessor macros in the debugging information if you specify
1955 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1956 the @sc{gnu} C compiler, provides macro information if you are using
1957 the DWARF debugging format, and specify the option @option{-g3}.
1959 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1960 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1961 information on @value{NGCC} options affecting debug information.
1963 You will have the best debugging experience if you use the latest
1964 version of the DWARF debugging format that your compiler supports.
1965 DWARF is currently the most expressive and best supported debugging
1966 format in @value{GDBN}.
1970 @section Starting your Program
1976 @kindex r @r{(@code{run})}
1979 Use the @code{run} command to start your program under @value{GDBN}.
1980 You must first specify the program name with an argument to
1981 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1982 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
1983 command (@pxref{Files, ,Commands to Specify Files}).
1987 If you are running your program in an execution environment that
1988 supports processes, @code{run} creates an inferior process and makes
1989 that process run your program. In some environments without processes,
1990 @code{run} jumps to the start of your program. Other targets,
1991 like @samp{remote}, are always running. If you get an error
1992 message like this one:
1995 The "remote" target does not support "run".
1996 Try "help target" or "continue".
2000 then use @code{continue} to run your program. You may need @code{load}
2001 first (@pxref{load}).
2003 The execution of a program is affected by certain information it
2004 receives from its superior. @value{GDBN} provides ways to specify this
2005 information, which you must do @emph{before} starting your program. (You
2006 can change it after starting your program, but such changes only affect
2007 your program the next time you start it.) This information may be
2008 divided into four categories:
2011 @item The @emph{arguments.}
2012 Specify the arguments to give your program as the arguments of the
2013 @code{run} command. If a shell is available on your target, the shell
2014 is used to pass the arguments, so that you may use normal conventions
2015 (such as wildcard expansion or variable substitution) in describing
2017 In Unix systems, you can control which shell is used with the
2018 @code{SHELL} environment variable. If you do not define @code{SHELL},
2019 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2020 use of any shell with the @code{set startup-with-shell} command (see
2023 @item The @emph{environment.}
2024 Your program normally inherits its environment from @value{GDBN}, but you can
2025 use the @value{GDBN} commands @code{set environment} and @code{unset
2026 environment} to change parts of the environment that affect
2027 your program. @xref{Environment, ,Your Program's Environment}.
2029 @item The @emph{working directory.}
2030 Your program inherits its working directory from @value{GDBN}. You can set
2031 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2032 @xref{Working Directory, ,Your Program's Working Directory}.
2034 @item The @emph{standard input and output.}
2035 Your program normally uses the same device for standard input and
2036 standard output as @value{GDBN} is using. You can redirect input and output
2037 in the @code{run} command line, or you can use the @code{tty} command to
2038 set a different device for your program.
2039 @xref{Input/Output, ,Your Program's Input and Output}.
2042 @emph{Warning:} While input and output redirection work, you cannot use
2043 pipes to pass the output of the program you are debugging to another
2044 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2048 When you issue the @code{run} command, your program begins to execute
2049 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2050 of how to arrange for your program to stop. Once your program has
2051 stopped, you may call functions in your program, using the @code{print}
2052 or @code{call} commands. @xref{Data, ,Examining Data}.
2054 If the modification time of your symbol file has changed since the last
2055 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2056 table, and reads it again. When it does this, @value{GDBN} tries to retain
2057 your current breakpoints.
2062 @cindex run to main procedure
2063 The name of the main procedure can vary from language to language.
2064 With C or C@t{++}, the main procedure name is always @code{main}, but
2065 other languages such as Ada do not require a specific name for their
2066 main procedure. The debugger provides a convenient way to start the
2067 execution of the program and to stop at the beginning of the main
2068 procedure, depending on the language used.
2070 The @samp{start} command does the equivalent of setting a temporary
2071 breakpoint at the beginning of the main procedure and then invoking
2072 the @samp{run} command.
2074 @cindex elaboration phase
2075 Some programs contain an @dfn{elaboration} phase where some startup code is
2076 executed before the main procedure is called. This depends on the
2077 languages used to write your program. In C@t{++}, for instance,
2078 constructors for static and global objects are executed before
2079 @code{main} is called. It is therefore possible that the debugger stops
2080 before reaching the main procedure. However, the temporary breakpoint
2081 will remain to halt execution.
2083 Specify the arguments to give to your program as arguments to the
2084 @samp{start} command. These arguments will be given verbatim to the
2085 underlying @samp{run} command. Note that the same arguments will be
2086 reused if no argument is provided during subsequent calls to
2087 @samp{start} or @samp{run}.
2089 It is sometimes necessary to debug the program during elaboration. In
2090 these cases, using the @code{start} command would stop the execution of
2091 your program too late, as the program would have already completed the
2092 elaboration phase. Under these circumstances, insert breakpoints in your
2093 elaboration code before running your program.
2095 @anchor{set exec-wrapper}
2096 @kindex set exec-wrapper
2097 @item set exec-wrapper @var{wrapper}
2098 @itemx show exec-wrapper
2099 @itemx unset exec-wrapper
2100 When @samp{exec-wrapper} is set, the specified wrapper is used to
2101 launch programs for debugging. @value{GDBN} starts your program
2102 with a shell command of the form @kbd{exec @var{wrapper}
2103 @var{program}}. Quoting is added to @var{program} and its
2104 arguments, but not to @var{wrapper}, so you should add quotes if
2105 appropriate for your shell. The wrapper runs until it executes
2106 your program, and then @value{GDBN} takes control.
2108 You can use any program that eventually calls @code{execve} with
2109 its arguments as a wrapper. Several standard Unix utilities do
2110 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2111 with @code{exec "$@@"} will also work.
2113 For example, you can use @code{env} to pass an environment variable to
2114 the debugged program, without setting the variable in your shell's
2118 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2122 This command is available when debugging locally on most targets, excluding
2123 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2125 @kindex set startup-with-shell
2126 @item set startup-with-shell
2127 @itemx set startup-with-shell on
2128 @itemx set startup-with-shell off
2129 @itemx show set startup-with-shell
2130 On Unix systems, by default, if a shell is available on your target,
2131 @value{GDBN}) uses it to start your program. Arguments of the
2132 @code{run} command are passed to the shell, which does variable
2133 substitution, expands wildcard characters and performs redirection of
2134 I/O. In some circumstances, it may be useful to disable such use of a
2135 shell, for example, when debugging the shell itself or diagnosing
2136 startup failures such as:
2140 Starting program: ./a.out
2141 During startup program terminated with signal SIGSEGV, Segmentation fault.
2145 which indicates the shell or the wrapper specified with
2146 @samp{exec-wrapper} crashed, not your program. Most often, this is
2147 caused by something odd in your shell's non-interactive mode
2148 initialization file---such as @file{.cshrc} for C-shell,
2149 $@file{.zshenv} for the Z shell, or the file specified in the
2150 @samp{BASH_ENV} environment variable for BASH.
2152 @anchor{set auto-connect-native-target}
2153 @kindex set auto-connect-native-target
2154 @item set auto-connect-native-target
2155 @itemx set auto-connect-native-target on
2156 @itemx set auto-connect-native-target off
2157 @itemx show auto-connect-native-target
2159 By default, if not connected to any target yet (e.g., with
2160 @code{target remote}), the @code{run} command starts your program as a
2161 native process under @value{GDBN}, on your local machine. If you're
2162 sure you don't want to debug programs on your local machine, you can
2163 tell @value{GDBN} to not connect to the native target automatically
2164 with the @code{set auto-connect-native-target off} command.
2166 If @code{on}, which is the default, and if @value{GDBN} is not
2167 connected to a target already, the @code{run} command automaticaly
2168 connects to the native target, if one is available.
2170 If @code{off}, and if @value{GDBN} is not connected to a target
2171 already, the @code{run} command fails with an error:
2175 Don't know how to run. Try "help target".
2178 If @value{GDBN} is already connected to a target, @value{GDBN} always
2179 uses it with the @code{run} command.
2181 In any case, you can explicitly connect to the native target with the
2182 @code{target native} command. For example,
2185 (@value{GDBP}) set auto-connect-native-target off
2187 Don't know how to run. Try "help target".
2188 (@value{GDBP}) target native
2190 Starting program: ./a.out
2191 [Inferior 1 (process 10421) exited normally]
2194 In case you connected explicitly to the @code{native} target,
2195 @value{GDBN} remains connected even if all inferiors exit, ready for
2196 the next @code{run} command. Use the @code{disconnect} command to
2199 Examples of other commands that likewise respect the
2200 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2201 proc}, @code{info os}.
2203 @kindex set disable-randomization
2204 @item set disable-randomization
2205 @itemx set disable-randomization on
2206 This option (enabled by default in @value{GDBN}) will turn off the native
2207 randomization of the virtual address space of the started program. This option
2208 is useful for multiple debugging sessions to make the execution better
2209 reproducible and memory addresses reusable across debugging sessions.
2211 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2212 On @sc{gnu}/Linux you can get the same behavior using
2215 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2218 @item set disable-randomization off
2219 Leave the behavior of the started executable unchanged. Some bugs rear their
2220 ugly heads only when the program is loaded at certain addresses. If your bug
2221 disappears when you run the program under @value{GDBN}, that might be because
2222 @value{GDBN} by default disables the address randomization on platforms, such
2223 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2224 disable-randomization off} to try to reproduce such elusive bugs.
2226 On targets where it is available, virtual address space randomization
2227 protects the programs against certain kinds of security attacks. In these
2228 cases the attacker needs to know the exact location of a concrete executable
2229 code. Randomizing its location makes it impossible to inject jumps misusing
2230 a code at its expected addresses.
2232 Prelinking shared libraries provides a startup performance advantage but it
2233 makes addresses in these libraries predictable for privileged processes by
2234 having just unprivileged access at the target system. Reading the shared
2235 library binary gives enough information for assembling the malicious code
2236 misusing it. Still even a prelinked shared library can get loaded at a new
2237 random address just requiring the regular relocation process during the
2238 startup. Shared libraries not already prelinked are always loaded at
2239 a randomly chosen address.
2241 Position independent executables (PIE) contain position independent code
2242 similar to the shared libraries and therefore such executables get loaded at
2243 a randomly chosen address upon startup. PIE executables always load even
2244 already prelinked shared libraries at a random address. You can build such
2245 executable using @command{gcc -fPIE -pie}.
2247 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2248 (as long as the randomization is enabled).
2250 @item show disable-randomization
2251 Show the current setting of the explicit disable of the native randomization of
2252 the virtual address space of the started program.
2257 @section Your Program's Arguments
2259 @cindex arguments (to your program)
2260 The arguments to your program can be specified by the arguments of the
2262 They are passed to a shell, which expands wildcard characters and
2263 performs redirection of I/O, and thence to your program. Your
2264 @code{SHELL} environment variable (if it exists) specifies what shell
2265 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2266 the default shell (@file{/bin/sh} on Unix).
2268 On non-Unix systems, the program is usually invoked directly by
2269 @value{GDBN}, which emulates I/O redirection via the appropriate system
2270 calls, and the wildcard characters are expanded by the startup code of
2271 the program, not by the shell.
2273 @code{run} with no arguments uses the same arguments used by the previous
2274 @code{run}, or those set by the @code{set args} command.
2279 Specify the arguments to be used the next time your program is run. If
2280 @code{set args} has no arguments, @code{run} executes your program
2281 with no arguments. Once you have run your program with arguments,
2282 using @code{set args} before the next @code{run} is the only way to run
2283 it again without arguments.
2287 Show the arguments to give your program when it is started.
2291 @section Your Program's Environment
2293 @cindex environment (of your program)
2294 The @dfn{environment} consists of a set of environment variables and
2295 their values. Environment variables conventionally record such things as
2296 your user name, your home directory, your terminal type, and your search
2297 path for programs to run. Usually you set up environment variables with
2298 the shell and they are inherited by all the other programs you run. When
2299 debugging, it can be useful to try running your program with a modified
2300 environment without having to start @value{GDBN} over again.
2304 @item path @var{directory}
2305 Add @var{directory} to the front of the @code{PATH} environment variable
2306 (the search path for executables) that will be passed to your program.
2307 The value of @code{PATH} used by @value{GDBN} does not change.
2308 You may specify several directory names, separated by whitespace or by a
2309 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2310 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2311 is moved to the front, so it is searched sooner.
2313 You can use the string @samp{$cwd} to refer to whatever is the current
2314 working directory at the time @value{GDBN} searches the path. If you
2315 use @samp{.} instead, it refers to the directory where you executed the
2316 @code{path} command. @value{GDBN} replaces @samp{.} in the
2317 @var{directory} argument (with the current path) before adding
2318 @var{directory} to the search path.
2319 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2320 @c document that, since repeating it would be a no-op.
2324 Display the list of search paths for executables (the @code{PATH}
2325 environment variable).
2327 @kindex show environment
2328 @item show environment @r{[}@var{varname}@r{]}
2329 Print the value of environment variable @var{varname} to be given to
2330 your program when it starts. If you do not supply @var{varname},
2331 print the names and values of all environment variables to be given to
2332 your program. You can abbreviate @code{environment} as @code{env}.
2334 @kindex set environment
2335 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2336 Set environment variable @var{varname} to @var{value}. The value
2337 changes for your program (and the shell @value{GDBN} uses to launch
2338 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2339 values of environment variables are just strings, and any
2340 interpretation is supplied by your program itself. The @var{value}
2341 parameter is optional; if it is eliminated, the variable is set to a
2343 @c "any string" here does not include leading, trailing
2344 @c blanks. Gnu asks: does anyone care?
2346 For example, this command:
2353 tells the debugged program, when subsequently run, that its user is named
2354 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2355 are not actually required.)
2357 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2358 which also inherits the environment set with @code{set environment}.
2359 If necessary, you can avoid that by using the @samp{env} program as a
2360 wrapper instead of using @code{set environment}. @xref{set
2361 exec-wrapper}, for an example doing just that.
2363 @kindex unset environment
2364 @item unset environment @var{varname}
2365 Remove variable @var{varname} from the environment to be passed to your
2366 program. This is different from @samp{set env @var{varname} =};
2367 @code{unset environment} removes the variable from the environment,
2368 rather than assigning it an empty value.
2371 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2372 the shell indicated by your @code{SHELL} environment variable if it
2373 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2374 names a shell that runs an initialization file when started
2375 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2376 for the Z shell, or the file specified in the @samp{BASH_ENV}
2377 environment variable for BASH---any variables you set in that file
2378 affect your program. You may wish to move setting of environment
2379 variables to files that are only run when you sign on, such as
2380 @file{.login} or @file{.profile}.
2382 @node Working Directory
2383 @section Your Program's Working Directory
2385 @cindex working directory (of your program)
2386 Each time you start your program with @code{run}, it inherits its
2387 working directory from the current working directory of @value{GDBN}.
2388 The @value{GDBN} working directory is initially whatever it inherited
2389 from its parent process (typically the shell), but you can specify a new
2390 working directory in @value{GDBN} with the @code{cd} command.
2392 The @value{GDBN} working directory also serves as a default for the commands
2393 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2398 @cindex change working directory
2399 @item cd @r{[}@var{directory}@r{]}
2400 Set the @value{GDBN} working directory to @var{directory}. If not
2401 given, @var{directory} uses @file{'~'}.
2405 Print the @value{GDBN} working directory.
2408 It is generally impossible to find the current working directory of
2409 the process being debugged (since a program can change its directory
2410 during its run). If you work on a system where @value{GDBN} is
2411 configured with the @file{/proc} support, you can use the @code{info
2412 proc} command (@pxref{SVR4 Process Information}) to find out the
2413 current working directory of the debuggee.
2416 @section Your Program's Input and Output
2421 By default, the program you run under @value{GDBN} does input and output to
2422 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2423 to its own terminal modes to interact with you, but it records the terminal
2424 modes your program was using and switches back to them when you continue
2425 running your program.
2428 @kindex info terminal
2430 Displays information recorded by @value{GDBN} about the terminal modes your
2434 You can redirect your program's input and/or output using shell
2435 redirection with the @code{run} command. For example,
2442 starts your program, diverting its output to the file @file{outfile}.
2445 @cindex controlling terminal
2446 Another way to specify where your program should do input and output is
2447 with the @code{tty} command. This command accepts a file name as
2448 argument, and causes this file to be the default for future @code{run}
2449 commands. It also resets the controlling terminal for the child
2450 process, for future @code{run} commands. For example,
2457 directs that processes started with subsequent @code{run} commands
2458 default to do input and output on the terminal @file{/dev/ttyb} and have
2459 that as their controlling terminal.
2461 An explicit redirection in @code{run} overrides the @code{tty} command's
2462 effect on the input/output device, but not its effect on the controlling
2465 When you use the @code{tty} command or redirect input in the @code{run}
2466 command, only the input @emph{for your program} is affected. The input
2467 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2468 for @code{set inferior-tty}.
2470 @cindex inferior tty
2471 @cindex set inferior controlling terminal
2472 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2473 display the name of the terminal that will be used for future runs of your
2477 @item set inferior-tty /dev/ttyb
2478 @kindex set inferior-tty
2479 Set the tty for the program being debugged to /dev/ttyb.
2481 @item show inferior-tty
2482 @kindex show inferior-tty
2483 Show the current tty for the program being debugged.
2487 @section Debugging an Already-running Process
2492 @item attach @var{process-id}
2493 This command attaches to a running process---one that was started
2494 outside @value{GDBN}. (@code{info files} shows your active
2495 targets.) The command takes as argument a process ID. The usual way to
2496 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2497 or with the @samp{jobs -l} shell command.
2499 @code{attach} does not repeat if you press @key{RET} a second time after
2500 executing the command.
2503 To use @code{attach}, your program must be running in an environment
2504 which supports processes; for example, @code{attach} does not work for
2505 programs on bare-board targets that lack an operating system. You must
2506 also have permission to send the process a signal.
2508 When you use @code{attach}, the debugger finds the program running in
2509 the process first by looking in the current working directory, then (if
2510 the program is not found) by using the source file search path
2511 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2512 the @code{file} command to load the program. @xref{Files, ,Commands to
2515 The first thing @value{GDBN} does after arranging to debug the specified
2516 process is to stop it. You can examine and modify an attached process
2517 with all the @value{GDBN} commands that are ordinarily available when
2518 you start processes with @code{run}. You can insert breakpoints; you
2519 can step and continue; you can modify storage. If you would rather the
2520 process continue running, you may use the @code{continue} command after
2521 attaching @value{GDBN} to the process.
2526 When you have finished debugging the attached process, you can use the
2527 @code{detach} command to release it from @value{GDBN} control. Detaching
2528 the process continues its execution. After the @code{detach} command,
2529 that process and @value{GDBN} become completely independent once more, and you
2530 are ready to @code{attach} another process or start one with @code{run}.
2531 @code{detach} does not repeat if you press @key{RET} again after
2532 executing the command.
2535 If you exit @value{GDBN} while you have an attached process, you detach
2536 that process. If you use the @code{run} command, you kill that process.
2537 By default, @value{GDBN} asks for confirmation if you try to do either of these
2538 things; you can control whether or not you need to confirm by using the
2539 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2543 @section Killing the Child Process
2548 Kill the child process in which your program is running under @value{GDBN}.
2551 This command is useful if you wish to debug a core dump instead of a
2552 running process. @value{GDBN} ignores any core dump file while your program
2555 On some operating systems, a program cannot be executed outside @value{GDBN}
2556 while you have breakpoints set on it inside @value{GDBN}. You can use the
2557 @code{kill} command in this situation to permit running your program
2558 outside the debugger.
2560 The @code{kill} command is also useful if you wish to recompile and
2561 relink your program, since on many systems it is impossible to modify an
2562 executable file while it is running in a process. In this case, when you
2563 next type @code{run}, @value{GDBN} notices that the file has changed, and
2564 reads the symbol table again (while trying to preserve your current
2565 breakpoint settings).
2567 @node Inferiors and Programs
2568 @section Debugging Multiple Inferiors and Programs
2570 @value{GDBN} lets you run and debug multiple programs in a single
2571 session. In addition, @value{GDBN} on some systems may let you run
2572 several programs simultaneously (otherwise you have to exit from one
2573 before starting another). In the most general case, you can have
2574 multiple threads of execution in each of multiple processes, launched
2575 from multiple executables.
2578 @value{GDBN} represents the state of each program execution with an
2579 object called an @dfn{inferior}. An inferior typically corresponds to
2580 a process, but is more general and applies also to targets that do not
2581 have processes. Inferiors may be created before a process runs, and
2582 may be retained after a process exits. Inferiors have unique
2583 identifiers that are different from process ids. Usually each
2584 inferior will also have its own distinct address space, although some
2585 embedded targets may have several inferiors running in different parts
2586 of a single address space. Each inferior may in turn have multiple
2587 threads running in it.
2589 To find out what inferiors exist at any moment, use @w{@code{info
2593 @kindex info inferiors
2594 @item info inferiors
2595 Print a list of all inferiors currently being managed by @value{GDBN}.
2597 @value{GDBN} displays for each inferior (in this order):
2601 the inferior number assigned by @value{GDBN}
2604 the target system's inferior identifier
2607 the name of the executable the inferior is running.
2612 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2613 indicates the current inferior.
2617 @c end table here to get a little more width for example
2620 (@value{GDBP}) info inferiors
2621 Num Description Executable
2622 2 process 2307 hello
2623 * 1 process 3401 goodbye
2626 To switch focus between inferiors, use the @code{inferior} command:
2629 @kindex inferior @var{infno}
2630 @item inferior @var{infno}
2631 Make inferior number @var{infno} the current inferior. The argument
2632 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2633 in the first field of the @samp{info inferiors} display.
2637 You can get multiple executables into a debugging session via the
2638 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2639 systems @value{GDBN} can add inferiors to the debug session
2640 automatically by following calls to @code{fork} and @code{exec}. To
2641 remove inferiors from the debugging session use the
2642 @w{@code{remove-inferiors}} command.
2645 @kindex add-inferior
2646 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2647 Adds @var{n} inferiors to be run using @var{executable} as the
2648 executable; @var{n} defaults to 1. If no executable is specified,
2649 the inferiors begins empty, with no program. You can still assign or
2650 change the program assigned to the inferior at any time by using the
2651 @code{file} command with the executable name as its argument.
2653 @kindex clone-inferior
2654 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2655 Adds @var{n} inferiors ready to execute the same program as inferior
2656 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2657 number of the current inferior. This is a convenient command when you
2658 want to run another instance of the inferior you are debugging.
2661 (@value{GDBP}) info inferiors
2662 Num Description Executable
2663 * 1 process 29964 helloworld
2664 (@value{GDBP}) clone-inferior
2667 (@value{GDBP}) info inferiors
2668 Num Description Executable
2670 * 1 process 29964 helloworld
2673 You can now simply switch focus to inferior 2 and run it.
2675 @kindex remove-inferiors
2676 @item remove-inferiors @var{infno}@dots{}
2677 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2678 possible to remove an inferior that is running with this command. For
2679 those, use the @code{kill} or @code{detach} command first.
2683 To quit debugging one of the running inferiors that is not the current
2684 inferior, you can either detach from it by using the @w{@code{detach
2685 inferior}} command (allowing it to run independently), or kill it
2686 using the @w{@code{kill inferiors}} command:
2689 @kindex detach inferiors @var{infno}@dots{}
2690 @item detach inferior @var{infno}@dots{}
2691 Detach from the inferior or inferiors identified by @value{GDBN}
2692 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2693 still stays on the list of inferiors shown by @code{info inferiors},
2694 but its Description will show @samp{<null>}.
2696 @kindex kill inferiors @var{infno}@dots{}
2697 @item kill inferiors @var{infno}@dots{}
2698 Kill the inferior or inferiors identified by @value{GDBN} inferior
2699 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2700 stays on the list of inferiors shown by @code{info inferiors}, but its
2701 Description will show @samp{<null>}.
2704 After the successful completion of a command such as @code{detach},
2705 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2706 a normal process exit, the inferior is still valid and listed with
2707 @code{info inferiors}, ready to be restarted.
2710 To be notified when inferiors are started or exit under @value{GDBN}'s
2711 control use @w{@code{set print inferior-events}}:
2714 @kindex set print inferior-events
2715 @cindex print messages on inferior start and exit
2716 @item set print inferior-events
2717 @itemx set print inferior-events on
2718 @itemx set print inferior-events off
2719 The @code{set print inferior-events} command allows you to enable or
2720 disable printing of messages when @value{GDBN} notices that new
2721 inferiors have started or that inferiors have exited or have been
2722 detached. By default, these messages will not be printed.
2724 @kindex show print inferior-events
2725 @item show print inferior-events
2726 Show whether messages will be printed when @value{GDBN} detects that
2727 inferiors have started, exited or have been detached.
2730 Many commands will work the same with multiple programs as with a
2731 single program: e.g., @code{print myglobal} will simply display the
2732 value of @code{myglobal} in the current inferior.
2735 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2736 get more info about the relationship of inferiors, programs, address
2737 spaces in a debug session. You can do that with the @w{@code{maint
2738 info program-spaces}} command.
2741 @kindex maint info program-spaces
2742 @item maint info program-spaces
2743 Print a list of all program spaces currently being managed by
2746 @value{GDBN} displays for each program space (in this order):
2750 the program space number assigned by @value{GDBN}
2753 the name of the executable loaded into the program space, with e.g.,
2754 the @code{file} command.
2759 An asterisk @samp{*} preceding the @value{GDBN} program space number
2760 indicates the current program space.
2762 In addition, below each program space line, @value{GDBN} prints extra
2763 information that isn't suitable to display in tabular form. For
2764 example, the list of inferiors bound to the program space.
2767 (@value{GDBP}) maint info program-spaces
2770 Bound inferiors: ID 1 (process 21561)
2774 Here we can see that no inferior is running the program @code{hello},
2775 while @code{process 21561} is running the program @code{goodbye}. On
2776 some targets, it is possible that multiple inferiors are bound to the
2777 same program space. The most common example is that of debugging both
2778 the parent and child processes of a @code{vfork} call. For example,
2781 (@value{GDBP}) maint info program-spaces
2784 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2787 Here, both inferior 2 and inferior 1 are running in the same program
2788 space as a result of inferior 1 having executed a @code{vfork} call.
2792 @section Debugging Programs with Multiple Threads
2794 @cindex threads of execution
2795 @cindex multiple threads
2796 @cindex switching threads
2797 In some operating systems, such as HP-UX and Solaris, a single program
2798 may have more than one @dfn{thread} of execution. The precise semantics
2799 of threads differ from one operating system to another, but in general
2800 the threads of a single program are akin to multiple processes---except
2801 that they share one address space (that is, they can all examine and
2802 modify the same variables). On the other hand, each thread has its own
2803 registers and execution stack, and perhaps private memory.
2805 @value{GDBN} provides these facilities for debugging multi-thread
2809 @item automatic notification of new threads
2810 @item @samp{thread @var{threadno}}, a command to switch among threads
2811 @item @samp{info threads}, a command to inquire about existing threads
2812 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2813 a command to apply a command to a list of threads
2814 @item thread-specific breakpoints
2815 @item @samp{set print thread-events}, which controls printing of
2816 messages on thread start and exit.
2817 @item @samp{set libthread-db-search-path @var{path}}, which lets
2818 the user specify which @code{libthread_db} to use if the default choice
2819 isn't compatible with the program.
2823 @emph{Warning:} These facilities are not yet available on every
2824 @value{GDBN} configuration where the operating system supports threads.
2825 If your @value{GDBN} does not support threads, these commands have no
2826 effect. For example, a system without thread support shows no output
2827 from @samp{info threads}, and always rejects the @code{thread} command,
2831 (@value{GDBP}) info threads
2832 (@value{GDBP}) thread 1
2833 Thread ID 1 not known. Use the "info threads" command to
2834 see the IDs of currently known threads.
2836 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2837 @c doesn't support threads"?
2840 @cindex focus of debugging
2841 @cindex current thread
2842 The @value{GDBN} thread debugging facility allows you to observe all
2843 threads while your program runs---but whenever @value{GDBN} takes
2844 control, one thread in particular is always the focus of debugging.
2845 This thread is called the @dfn{current thread}. Debugging commands show
2846 program information from the perspective of the current thread.
2848 @cindex @code{New} @var{systag} message
2849 @cindex thread identifier (system)
2850 @c FIXME-implementors!! It would be more helpful if the [New...] message
2851 @c included GDB's numeric thread handle, so you could just go to that
2852 @c thread without first checking `info threads'.
2853 Whenever @value{GDBN} detects a new thread in your program, it displays
2854 the target system's identification for the thread with a message in the
2855 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2856 whose form varies depending on the particular system. For example, on
2857 @sc{gnu}/Linux, you might see
2860 [New Thread 0x41e02940 (LWP 25582)]
2864 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2865 the @var{systag} is simply something like @samp{process 368}, with no
2868 @c FIXME!! (1) Does the [New...] message appear even for the very first
2869 @c thread of a program, or does it only appear for the
2870 @c second---i.e.@: when it becomes obvious we have a multithread
2872 @c (2) *Is* there necessarily a first thread always? Or do some
2873 @c multithread systems permit starting a program with multiple
2874 @c threads ab initio?
2876 @cindex thread number
2877 @cindex thread identifier (GDB)
2878 For debugging purposes, @value{GDBN} associates its own thread
2879 number---always a single integer---with each thread in your program.
2882 @kindex info threads
2883 @item info threads @r{[}@var{id}@dots{}@r{]}
2884 Display a summary of all threads currently in your program. Optional
2885 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2886 means to print information only about the specified thread or threads.
2887 @value{GDBN} displays for each thread (in this order):
2891 the thread number assigned by @value{GDBN}
2894 the target system's thread identifier (@var{systag})
2897 the thread's name, if one is known. A thread can either be named by
2898 the user (see @code{thread name}, below), or, in some cases, by the
2902 the current stack frame summary for that thread
2906 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2907 indicates the current thread.
2911 @c end table here to get a little more width for example
2914 (@value{GDBP}) info threads
2916 3 process 35 thread 27 0x34e5 in sigpause ()
2917 2 process 35 thread 23 0x34e5 in sigpause ()
2918 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2922 On Solaris, you can display more information about user threads with a
2923 Solaris-specific command:
2926 @item maint info sol-threads
2927 @kindex maint info sol-threads
2928 @cindex thread info (Solaris)
2929 Display info on Solaris user threads.
2933 @kindex thread @var{threadno}
2934 @item thread @var{threadno}
2935 Make thread number @var{threadno} the current thread. The command
2936 argument @var{threadno} is the internal @value{GDBN} thread number, as
2937 shown in the first field of the @samp{info threads} display.
2938 @value{GDBN} responds by displaying the system identifier of the thread
2939 you selected, and its current stack frame summary:
2942 (@value{GDBP}) thread 2
2943 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2944 #0 some_function (ignore=0x0) at example.c:8
2945 8 printf ("hello\n");
2949 As with the @samp{[New @dots{}]} message, the form of the text after
2950 @samp{Switching to} depends on your system's conventions for identifying
2953 @vindex $_thread@r{, convenience variable}
2954 The debugger convenience variable @samp{$_thread} contains the number
2955 of the current thread. You may find this useful in writing breakpoint
2956 conditional expressions, command scripts, and so forth. See
2957 @xref{Convenience Vars,, Convenience Variables}, for general
2958 information on convenience variables.
2960 @kindex thread apply
2961 @cindex apply command to several threads
2962 @item thread apply [@var{threadno} | all] @var{command}
2963 The @code{thread apply} command allows you to apply the named
2964 @var{command} to one or more threads. Specify the numbers of the
2965 threads that you want affected with the command argument
2966 @var{threadno}. It can be a single thread number, one of the numbers
2967 shown in the first field of the @samp{info threads} display; or it
2968 could be a range of thread numbers, as in @code{2-4}. To apply a
2969 command to all threads, type @kbd{thread apply all @var{command}}.
2972 @cindex name a thread
2973 @item thread name [@var{name}]
2974 This command assigns a name to the current thread. If no argument is
2975 given, any existing user-specified name is removed. The thread name
2976 appears in the @samp{info threads} display.
2978 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2979 determine the name of the thread as given by the OS. On these
2980 systems, a name specified with @samp{thread name} will override the
2981 system-give name, and removing the user-specified name will cause
2982 @value{GDBN} to once again display the system-specified name.
2985 @cindex search for a thread
2986 @item thread find [@var{regexp}]
2987 Search for and display thread ids whose name or @var{systag}
2988 matches the supplied regular expression.
2990 As well as being the complement to the @samp{thread name} command,
2991 this command also allows you to identify a thread by its target
2992 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2996 (@value{GDBN}) thread find 26688
2997 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2998 (@value{GDBN}) info thread 4
3000 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3003 @kindex set print thread-events
3004 @cindex print messages on thread start and exit
3005 @item set print thread-events
3006 @itemx set print thread-events on
3007 @itemx set print thread-events off
3008 The @code{set print thread-events} command allows you to enable or
3009 disable printing of messages when @value{GDBN} notices that new threads have
3010 started or that threads have exited. By default, these messages will
3011 be printed if detection of these events is supported by the target.
3012 Note that these messages cannot be disabled on all targets.
3014 @kindex show print thread-events
3015 @item show print thread-events
3016 Show whether messages will be printed when @value{GDBN} detects that threads
3017 have started and exited.
3020 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3021 more information about how @value{GDBN} behaves when you stop and start
3022 programs with multiple threads.
3024 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3025 watchpoints in programs with multiple threads.
3027 @anchor{set libthread-db-search-path}
3029 @kindex set libthread-db-search-path
3030 @cindex search path for @code{libthread_db}
3031 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3032 If this variable is set, @var{path} is a colon-separated list of
3033 directories @value{GDBN} will use to search for @code{libthread_db}.
3034 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3035 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3036 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3039 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3040 @code{libthread_db} library to obtain information about threads in the
3041 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3042 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3043 specific thread debugging library loading is enabled
3044 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3046 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3047 refers to the default system directories that are
3048 normally searched for loading shared libraries. The @samp{$sdir} entry
3049 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3050 (@pxref{libthread_db.so.1 file}).
3052 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3053 refers to the directory from which @code{libpthread}
3054 was loaded in the inferior process.
3056 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3057 @value{GDBN} attempts to initialize it with the current inferior process.
3058 If this initialization fails (which could happen because of a version
3059 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3060 will unload @code{libthread_db}, and continue with the next directory.
3061 If none of @code{libthread_db} libraries initialize successfully,
3062 @value{GDBN} will issue a warning and thread debugging will be disabled.
3064 Setting @code{libthread-db-search-path} is currently implemented
3065 only on some platforms.
3067 @kindex show libthread-db-search-path
3068 @item show libthread-db-search-path
3069 Display current libthread_db search path.
3071 @kindex set debug libthread-db
3072 @kindex show debug libthread-db
3073 @cindex debugging @code{libthread_db}
3074 @item set debug libthread-db
3075 @itemx show debug libthread-db
3076 Turns on or off display of @code{libthread_db}-related events.
3077 Use @code{1} to enable, @code{0} to disable.
3081 @section Debugging Forks
3083 @cindex fork, debugging programs which call
3084 @cindex multiple processes
3085 @cindex processes, multiple
3086 On most systems, @value{GDBN} has no special support for debugging
3087 programs which create additional processes using the @code{fork}
3088 function. When a program forks, @value{GDBN} will continue to debug the
3089 parent process and the child process will run unimpeded. If you have
3090 set a breakpoint in any code which the child then executes, the child
3091 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3092 will cause it to terminate.
3094 However, if you want to debug the child process there is a workaround
3095 which isn't too painful. Put a call to @code{sleep} in the code which
3096 the child process executes after the fork. It may be useful to sleep
3097 only if a certain environment variable is set, or a certain file exists,
3098 so that the delay need not occur when you don't want to run @value{GDBN}
3099 on the child. While the child is sleeping, use the @code{ps} program to
3100 get its process ID. Then tell @value{GDBN} (a new invocation of
3101 @value{GDBN} if you are also debugging the parent process) to attach to
3102 the child process (@pxref{Attach}). From that point on you can debug
3103 the child process just like any other process which you attached to.
3105 On some systems, @value{GDBN} provides support for debugging programs that
3106 create additional processes using the @code{fork} or @code{vfork} functions.
3107 Currently, the only platforms with this feature are HP-UX (11.x and later
3108 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3110 By default, when a program forks, @value{GDBN} will continue to debug
3111 the parent process and the child process will run unimpeded.
3113 If you want to follow the child process instead of the parent process,
3114 use the command @w{@code{set follow-fork-mode}}.
3117 @kindex set follow-fork-mode
3118 @item set follow-fork-mode @var{mode}
3119 Set the debugger response to a program call of @code{fork} or
3120 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3121 process. The @var{mode} argument can be:
3125 The original process is debugged after a fork. The child process runs
3126 unimpeded. This is the default.
3129 The new process is debugged after a fork. The parent process runs
3134 @kindex show follow-fork-mode
3135 @item show follow-fork-mode
3136 Display the current debugger response to a @code{fork} or @code{vfork} call.
3139 @cindex debugging multiple processes
3140 On Linux, if you want to debug both the parent and child processes, use the
3141 command @w{@code{set detach-on-fork}}.
3144 @kindex set detach-on-fork
3145 @item set detach-on-fork @var{mode}
3146 Tells gdb whether to detach one of the processes after a fork, or
3147 retain debugger control over them both.
3151 The child process (or parent process, depending on the value of
3152 @code{follow-fork-mode}) will be detached and allowed to run
3153 independently. This is the default.
3156 Both processes will be held under the control of @value{GDBN}.
3157 One process (child or parent, depending on the value of
3158 @code{follow-fork-mode}) is debugged as usual, while the other
3163 @kindex show detach-on-fork
3164 @item show detach-on-fork
3165 Show whether detach-on-fork mode is on/off.
3168 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3169 will retain control of all forked processes (including nested forks).
3170 You can list the forked processes under the control of @value{GDBN} by
3171 using the @w{@code{info inferiors}} command, and switch from one fork
3172 to another by using the @code{inferior} command (@pxref{Inferiors and
3173 Programs, ,Debugging Multiple Inferiors and Programs}).
3175 To quit debugging one of the forked processes, you can either detach
3176 from it by using the @w{@code{detach inferiors}} command (allowing it
3177 to run independently), or kill it using the @w{@code{kill inferiors}}
3178 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3181 If you ask to debug a child process and a @code{vfork} is followed by an
3182 @code{exec}, @value{GDBN} executes the new target up to the first
3183 breakpoint in the new target. If you have a breakpoint set on
3184 @code{main} in your original program, the breakpoint will also be set on
3185 the child process's @code{main}.
3187 On some systems, when a child process is spawned by @code{vfork}, you
3188 cannot debug the child or parent until an @code{exec} call completes.
3190 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3191 call executes, the new target restarts. To restart the parent
3192 process, use the @code{file} command with the parent executable name
3193 as its argument. By default, after an @code{exec} call executes,
3194 @value{GDBN} discards the symbols of the previous executable image.
3195 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3199 @kindex set follow-exec-mode
3200 @item set follow-exec-mode @var{mode}
3202 Set debugger response to a program call of @code{exec}. An
3203 @code{exec} call replaces the program image of a process.
3205 @code{follow-exec-mode} can be:
3209 @value{GDBN} creates a new inferior and rebinds the process to this
3210 new inferior. The program the process was running before the
3211 @code{exec} call can be restarted afterwards by restarting the
3217 (@value{GDBP}) info inferiors
3219 Id Description Executable
3222 process 12020 is executing new program: prog2
3223 Program exited normally.
3224 (@value{GDBP}) info inferiors
3225 Id Description Executable
3231 @value{GDBN} keeps the process bound to the same inferior. The new
3232 executable image replaces the previous executable loaded in the
3233 inferior. Restarting the inferior after the @code{exec} call, with
3234 e.g., the @code{run} command, restarts the executable the process was
3235 running after the @code{exec} call. This is the default mode.
3240 (@value{GDBP}) info inferiors
3241 Id Description Executable
3244 process 12020 is executing new program: prog2
3245 Program exited normally.
3246 (@value{GDBP}) info inferiors
3247 Id Description Executable
3254 You can use the @code{catch} command to make @value{GDBN} stop whenever
3255 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3256 Catchpoints, ,Setting Catchpoints}.
3258 @node Checkpoint/Restart
3259 @section Setting a @emph{Bookmark} to Return to Later
3264 @cindex snapshot of a process
3265 @cindex rewind program state
3267 On certain operating systems@footnote{Currently, only
3268 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3269 program's state, called a @dfn{checkpoint}, and come back to it
3272 Returning to a checkpoint effectively undoes everything that has
3273 happened in the program since the @code{checkpoint} was saved. This
3274 includes changes in memory, registers, and even (within some limits)
3275 system state. Effectively, it is like going back in time to the
3276 moment when the checkpoint was saved.
3278 Thus, if you're stepping thru a program and you think you're
3279 getting close to the point where things go wrong, you can save
3280 a checkpoint. Then, if you accidentally go too far and miss
3281 the critical statement, instead of having to restart your program
3282 from the beginning, you can just go back to the checkpoint and
3283 start again from there.
3285 This can be especially useful if it takes a lot of time or
3286 steps to reach the point where you think the bug occurs.
3288 To use the @code{checkpoint}/@code{restart} method of debugging:
3293 Save a snapshot of the debugged program's current execution state.
3294 The @code{checkpoint} command takes no arguments, but each checkpoint
3295 is assigned a small integer id, similar to a breakpoint id.
3297 @kindex info checkpoints
3298 @item info checkpoints
3299 List the checkpoints that have been saved in the current debugging
3300 session. For each checkpoint, the following information will be
3307 @item Source line, or label
3310 @kindex restart @var{checkpoint-id}
3311 @item restart @var{checkpoint-id}
3312 Restore the program state that was saved as checkpoint number
3313 @var{checkpoint-id}. All program variables, registers, stack frames
3314 etc.@: will be returned to the values that they had when the checkpoint
3315 was saved. In essence, gdb will ``wind back the clock'' to the point
3316 in time when the checkpoint was saved.
3318 Note that breakpoints, @value{GDBN} variables, command history etc.
3319 are not affected by restoring a checkpoint. In general, a checkpoint
3320 only restores things that reside in the program being debugged, not in
3323 @kindex delete checkpoint @var{checkpoint-id}
3324 @item delete checkpoint @var{checkpoint-id}
3325 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3329 Returning to a previously saved checkpoint will restore the user state
3330 of the program being debugged, plus a significant subset of the system
3331 (OS) state, including file pointers. It won't ``un-write'' data from
3332 a file, but it will rewind the file pointer to the previous location,
3333 so that the previously written data can be overwritten. For files
3334 opened in read mode, the pointer will also be restored so that the
3335 previously read data can be read again.
3337 Of course, characters that have been sent to a printer (or other
3338 external device) cannot be ``snatched back'', and characters received
3339 from eg.@: a serial device can be removed from internal program buffers,
3340 but they cannot be ``pushed back'' into the serial pipeline, ready to
3341 be received again. Similarly, the actual contents of files that have
3342 been changed cannot be restored (at this time).
3344 However, within those constraints, you actually can ``rewind'' your
3345 program to a previously saved point in time, and begin debugging it
3346 again --- and you can change the course of events so as to debug a
3347 different execution path this time.
3349 @cindex checkpoints and process id
3350 Finally, there is one bit of internal program state that will be
3351 different when you return to a checkpoint --- the program's process
3352 id. Each checkpoint will have a unique process id (or @var{pid}),
3353 and each will be different from the program's original @var{pid}.
3354 If your program has saved a local copy of its process id, this could
3355 potentially pose a problem.
3357 @subsection A Non-obvious Benefit of Using Checkpoints
3359 On some systems such as @sc{gnu}/Linux, address space randomization
3360 is performed on new processes for security reasons. This makes it
3361 difficult or impossible to set a breakpoint, or watchpoint, on an
3362 absolute address if you have to restart the program, since the
3363 absolute location of a symbol will change from one execution to the
3366 A checkpoint, however, is an @emph{identical} copy of a process.
3367 Therefore if you create a checkpoint at (eg.@:) the start of main,
3368 and simply return to that checkpoint instead of restarting the
3369 process, you can avoid the effects of address randomization and
3370 your symbols will all stay in the same place.
3373 @chapter Stopping and Continuing
3375 The principal purposes of using a debugger are so that you can stop your
3376 program before it terminates; or so that, if your program runs into
3377 trouble, you can investigate and find out why.
3379 Inside @value{GDBN}, your program may stop for any of several reasons,
3380 such as a signal, a breakpoint, or reaching a new line after a
3381 @value{GDBN} command such as @code{step}. You may then examine and
3382 change variables, set new breakpoints or remove old ones, and then
3383 continue execution. Usually, the messages shown by @value{GDBN} provide
3384 ample explanation of the status of your program---but you can also
3385 explicitly request this information at any time.
3388 @kindex info program
3390 Display information about the status of your program: whether it is
3391 running or not, what process it is, and why it stopped.
3395 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3396 * Continuing and Stepping:: Resuming execution
3397 * Skipping Over Functions and Files::
3398 Skipping over functions and files
3400 * Thread Stops:: Stopping and starting multi-thread programs
3404 @section Breakpoints, Watchpoints, and Catchpoints
3407 A @dfn{breakpoint} makes your program stop whenever a certain point in
3408 the program is reached. For each breakpoint, you can add conditions to
3409 control in finer detail whether your program stops. You can set
3410 breakpoints with the @code{break} command and its variants (@pxref{Set
3411 Breaks, ,Setting Breakpoints}), to specify the place where your program
3412 should stop by line number, function name or exact address in the
3415 On some systems, you can set breakpoints in shared libraries before
3416 the executable is run. There is a minor limitation on HP-UX systems:
3417 you must wait until the executable is run in order to set breakpoints
3418 in shared library routines that are not called directly by the program
3419 (for example, routines that are arguments in a @code{pthread_create}
3423 @cindex data breakpoints
3424 @cindex memory tracing
3425 @cindex breakpoint on memory address
3426 @cindex breakpoint on variable modification
3427 A @dfn{watchpoint} is a special breakpoint that stops your program
3428 when the value of an expression changes. The expression may be a value
3429 of a variable, or it could involve values of one or more variables
3430 combined by operators, such as @samp{a + b}. This is sometimes called
3431 @dfn{data breakpoints}. You must use a different command to set
3432 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3433 from that, you can manage a watchpoint like any other breakpoint: you
3434 enable, disable, and delete both breakpoints and watchpoints using the
3437 You can arrange to have values from your program displayed automatically
3438 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3442 @cindex breakpoint on events
3443 A @dfn{catchpoint} is another special breakpoint that stops your program
3444 when a certain kind of event occurs, such as the throwing of a C@t{++}
3445 exception or the loading of a library. As with watchpoints, you use a
3446 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3447 Catchpoints}), but aside from that, you can manage a catchpoint like any
3448 other breakpoint. (To stop when your program receives a signal, use the
3449 @code{handle} command; see @ref{Signals, ,Signals}.)
3451 @cindex breakpoint numbers
3452 @cindex numbers for breakpoints
3453 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3454 catchpoint when you create it; these numbers are successive integers
3455 starting with one. In many of the commands for controlling various
3456 features of breakpoints you use the breakpoint number to say which
3457 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3458 @dfn{disabled}; if disabled, it has no effect on your program until you
3461 @cindex breakpoint ranges
3462 @cindex ranges of breakpoints
3463 Some @value{GDBN} commands accept a range of breakpoints on which to
3464 operate. A breakpoint range is either a single breakpoint number, like
3465 @samp{5}, or two such numbers, in increasing order, separated by a
3466 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3467 all breakpoints in that range are operated on.
3470 * Set Breaks:: Setting breakpoints
3471 * Set Watchpoints:: Setting watchpoints
3472 * Set Catchpoints:: Setting catchpoints
3473 * Delete Breaks:: Deleting breakpoints
3474 * Disabling:: Disabling breakpoints
3475 * Conditions:: Break conditions
3476 * Break Commands:: Breakpoint command lists
3477 * Dynamic Printf:: Dynamic printf
3478 * Save Breakpoints:: How to save breakpoints in a file
3479 * Static Probe Points:: Listing static probe points
3480 * Error in Breakpoints:: ``Cannot insert breakpoints''
3481 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3485 @subsection Setting Breakpoints
3487 @c FIXME LMB what does GDB do if no code on line of breakpt?
3488 @c consider in particular declaration with/without initialization.
3490 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3493 @kindex b @r{(@code{break})}
3494 @vindex $bpnum@r{, convenience variable}
3495 @cindex latest breakpoint
3496 Breakpoints are set with the @code{break} command (abbreviated
3497 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3498 number of the breakpoint you've set most recently; see @ref{Convenience
3499 Vars,, Convenience Variables}, for a discussion of what you can do with
3500 convenience variables.
3503 @item break @var{location}
3504 Set a breakpoint at the given @var{location}, which can specify a
3505 function name, a line number, or an address of an instruction.
3506 (@xref{Specify Location}, for a list of all the possible ways to
3507 specify a @var{location}.) The breakpoint will stop your program just
3508 before it executes any of the code in the specified @var{location}.
3510 When using source languages that permit overloading of symbols, such as
3511 C@t{++}, a function name may refer to more than one possible place to break.
3512 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3515 It is also possible to insert a breakpoint that will stop the program
3516 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3517 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3520 When called without any arguments, @code{break} sets a breakpoint at
3521 the next instruction to be executed in the selected stack frame
3522 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3523 innermost, this makes your program stop as soon as control
3524 returns to that frame. This is similar to the effect of a
3525 @code{finish} command in the frame inside the selected frame---except
3526 that @code{finish} does not leave an active breakpoint. If you use
3527 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3528 the next time it reaches the current location; this may be useful
3531 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3532 least one instruction has been executed. If it did not do this, you
3533 would be unable to proceed past a breakpoint without first disabling the
3534 breakpoint. This rule applies whether or not the breakpoint already
3535 existed when your program stopped.
3537 @item break @dots{} if @var{cond}
3538 Set a breakpoint with condition @var{cond}; evaluate the expression
3539 @var{cond} each time the breakpoint is reached, and stop only if the
3540 value is nonzero---that is, if @var{cond} evaluates as true.
3541 @samp{@dots{}} stands for one of the possible arguments described
3542 above (or no argument) specifying where to break. @xref{Conditions,
3543 ,Break Conditions}, for more information on breakpoint conditions.
3546 @item tbreak @var{args}
3547 Set a breakpoint enabled only for one stop. The @var{args} are the
3548 same as for the @code{break} command, and the breakpoint is set in the same
3549 way, but the breakpoint is automatically deleted after the first time your
3550 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3553 @cindex hardware breakpoints
3554 @item hbreak @var{args}
3555 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3556 @code{break} command and the breakpoint is set in the same way, but the
3557 breakpoint requires hardware support and some target hardware may not
3558 have this support. The main purpose of this is EPROM/ROM code
3559 debugging, so you can set a breakpoint at an instruction without
3560 changing the instruction. This can be used with the new trap-generation
3561 provided by SPARClite DSU and most x86-based targets. These targets
3562 will generate traps when a program accesses some data or instruction
3563 address that is assigned to the debug registers. However the hardware
3564 breakpoint registers can take a limited number of breakpoints. For
3565 example, on the DSU, only two data breakpoints can be set at a time, and
3566 @value{GDBN} will reject this command if more than two are used. Delete
3567 or disable unused hardware breakpoints before setting new ones
3568 (@pxref{Disabling, ,Disabling Breakpoints}).
3569 @xref{Conditions, ,Break Conditions}.
3570 For remote targets, you can restrict the number of hardware
3571 breakpoints @value{GDBN} will use, see @ref{set remote
3572 hardware-breakpoint-limit}.
3575 @item thbreak @var{args}
3576 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3577 are the same as for the @code{hbreak} command and the breakpoint is set in
3578 the same way. However, like the @code{tbreak} command,
3579 the breakpoint is automatically deleted after the
3580 first time your program stops there. Also, like the @code{hbreak}
3581 command, the breakpoint requires hardware support and some target hardware
3582 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3583 See also @ref{Conditions, ,Break Conditions}.
3586 @cindex regular expression
3587 @cindex breakpoints at functions matching a regexp
3588 @cindex set breakpoints in many functions
3589 @item rbreak @var{regex}
3590 Set breakpoints on all functions matching the regular expression
3591 @var{regex}. This command sets an unconditional breakpoint on all
3592 matches, printing a list of all breakpoints it set. Once these
3593 breakpoints are set, they are treated just like the breakpoints set with
3594 the @code{break} command. You can delete them, disable them, or make
3595 them conditional the same way as any other breakpoint.
3597 The syntax of the regular expression is the standard one used with tools
3598 like @file{grep}. Note that this is different from the syntax used by
3599 shells, so for instance @code{foo*} matches all functions that include
3600 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3601 @code{.*} leading and trailing the regular expression you supply, so to
3602 match only functions that begin with @code{foo}, use @code{^foo}.
3604 @cindex non-member C@t{++} functions, set breakpoint in
3605 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3606 breakpoints on overloaded functions that are not members of any special
3609 @cindex set breakpoints on all functions
3610 The @code{rbreak} command can be used to set breakpoints in
3611 @strong{all} the functions in a program, like this:
3614 (@value{GDBP}) rbreak .
3617 @item rbreak @var{file}:@var{regex}
3618 If @code{rbreak} is called with a filename qualification, it limits
3619 the search for functions matching the given regular expression to the
3620 specified @var{file}. This can be used, for example, to set breakpoints on
3621 every function in a given file:
3624 (@value{GDBP}) rbreak file.c:.
3627 The colon separating the filename qualifier from the regex may
3628 optionally be surrounded by spaces.
3630 @kindex info breakpoints
3631 @cindex @code{$_} and @code{info breakpoints}
3632 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3633 @itemx info break @r{[}@var{n}@dots{}@r{]}
3634 Print a table of all breakpoints, watchpoints, and catchpoints set and
3635 not deleted. Optional argument @var{n} means print information only
3636 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3637 For each breakpoint, following columns are printed:
3640 @item Breakpoint Numbers
3642 Breakpoint, watchpoint, or catchpoint.
3644 Whether the breakpoint is marked to be disabled or deleted when hit.
3645 @item Enabled or Disabled
3646 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3647 that are not enabled.
3649 Where the breakpoint is in your program, as a memory address. For a
3650 pending breakpoint whose address is not yet known, this field will
3651 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3652 library that has the symbol or line referred by breakpoint is loaded.
3653 See below for details. A breakpoint with several locations will
3654 have @samp{<MULTIPLE>} in this field---see below for details.
3656 Where the breakpoint is in the source for your program, as a file and
3657 line number. For a pending breakpoint, the original string passed to
3658 the breakpoint command will be listed as it cannot be resolved until
3659 the appropriate shared library is loaded in the future.
3663 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3664 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3665 @value{GDBN} on the host's side. If it is ``target'', then the condition
3666 is evaluated by the target. The @code{info break} command shows
3667 the condition on the line following the affected breakpoint, together with
3668 its condition evaluation mode in between parentheses.
3670 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3671 allowed to have a condition specified for it. The condition is not parsed for
3672 validity until a shared library is loaded that allows the pending
3673 breakpoint to resolve to a valid location.
3676 @code{info break} with a breakpoint
3677 number @var{n} as argument lists only that breakpoint. The
3678 convenience variable @code{$_} and the default examining-address for
3679 the @code{x} command are set to the address of the last breakpoint
3680 listed (@pxref{Memory, ,Examining Memory}).
3683 @code{info break} displays a count of the number of times the breakpoint
3684 has been hit. This is especially useful in conjunction with the
3685 @code{ignore} command. You can ignore a large number of breakpoint
3686 hits, look at the breakpoint info to see how many times the breakpoint
3687 was hit, and then run again, ignoring one less than that number. This
3688 will get you quickly to the last hit of that breakpoint.
3691 For a breakpoints with an enable count (xref) greater than 1,
3692 @code{info break} also displays that count.
3696 @value{GDBN} allows you to set any number of breakpoints at the same place in
3697 your program. There is nothing silly or meaningless about this. When
3698 the breakpoints are conditional, this is even useful
3699 (@pxref{Conditions, ,Break Conditions}).
3701 @cindex multiple locations, breakpoints
3702 @cindex breakpoints, multiple locations
3703 It is possible that a breakpoint corresponds to several locations
3704 in your program. Examples of this situation are:
3708 Multiple functions in the program may have the same name.
3711 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3712 instances of the function body, used in different cases.
3715 For a C@t{++} template function, a given line in the function can
3716 correspond to any number of instantiations.
3719 For an inlined function, a given source line can correspond to
3720 several places where that function is inlined.
3723 In all those cases, @value{GDBN} will insert a breakpoint at all
3724 the relevant locations.
3726 A breakpoint with multiple locations is displayed in the breakpoint
3727 table using several rows---one header row, followed by one row for
3728 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3729 address column. The rows for individual locations contain the actual
3730 addresses for locations, and show the functions to which those
3731 locations belong. The number column for a location is of the form
3732 @var{breakpoint-number}.@var{location-number}.
3737 Num Type Disp Enb Address What
3738 1 breakpoint keep y <MULTIPLE>
3740 breakpoint already hit 1 time
3741 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3742 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3745 Each location can be individually enabled or disabled by passing
3746 @var{breakpoint-number}.@var{location-number} as argument to the
3747 @code{enable} and @code{disable} commands. Note that you cannot
3748 delete the individual locations from the list, you can only delete the
3749 entire list of locations that belong to their parent breakpoint (with
3750 the @kbd{delete @var{num}} command, where @var{num} is the number of
3751 the parent breakpoint, 1 in the above example). Disabling or enabling
3752 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3753 that belong to that breakpoint.
3755 @cindex pending breakpoints
3756 It's quite common to have a breakpoint inside a shared library.
3757 Shared libraries can be loaded and unloaded explicitly,
3758 and possibly repeatedly, as the program is executed. To support
3759 this use case, @value{GDBN} updates breakpoint locations whenever
3760 any shared library is loaded or unloaded. Typically, you would
3761 set a breakpoint in a shared library at the beginning of your
3762 debugging session, when the library is not loaded, and when the
3763 symbols from the library are not available. When you try to set
3764 breakpoint, @value{GDBN} will ask you if you want to set
3765 a so called @dfn{pending breakpoint}---breakpoint whose address
3766 is not yet resolved.
3768 After the program is run, whenever a new shared library is loaded,
3769 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3770 shared library contains the symbol or line referred to by some
3771 pending breakpoint, that breakpoint is resolved and becomes an
3772 ordinary breakpoint. When a library is unloaded, all breakpoints
3773 that refer to its symbols or source lines become pending again.
3775 This logic works for breakpoints with multiple locations, too. For
3776 example, if you have a breakpoint in a C@t{++} template function, and
3777 a newly loaded shared library has an instantiation of that template,
3778 a new location is added to the list of locations for the breakpoint.
3780 Except for having unresolved address, pending breakpoints do not
3781 differ from regular breakpoints. You can set conditions or commands,
3782 enable and disable them and perform other breakpoint operations.
3784 @value{GDBN} provides some additional commands for controlling what
3785 happens when the @samp{break} command cannot resolve breakpoint
3786 address specification to an address:
3788 @kindex set breakpoint pending
3789 @kindex show breakpoint pending
3791 @item set breakpoint pending auto
3792 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3793 location, it queries you whether a pending breakpoint should be created.
3795 @item set breakpoint pending on
3796 This indicates that an unrecognized breakpoint location should automatically
3797 result in a pending breakpoint being created.
3799 @item set breakpoint pending off
3800 This indicates that pending breakpoints are not to be created. Any
3801 unrecognized breakpoint location results in an error. This setting does
3802 not affect any pending breakpoints previously created.
3804 @item show breakpoint pending
3805 Show the current behavior setting for creating pending breakpoints.
3808 The settings above only affect the @code{break} command and its
3809 variants. Once breakpoint is set, it will be automatically updated
3810 as shared libraries are loaded and unloaded.
3812 @cindex automatic hardware breakpoints
3813 For some targets, @value{GDBN} can automatically decide if hardware or
3814 software breakpoints should be used, depending on whether the
3815 breakpoint address is read-only or read-write. This applies to
3816 breakpoints set with the @code{break} command as well as to internal
3817 breakpoints set by commands like @code{next} and @code{finish}. For
3818 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3821 You can control this automatic behaviour with the following commands::
3823 @kindex set breakpoint auto-hw
3824 @kindex show breakpoint auto-hw
3826 @item set breakpoint auto-hw on
3827 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3828 will try to use the target memory map to decide if software or hardware
3829 breakpoint must be used.
3831 @item set breakpoint auto-hw off
3832 This indicates @value{GDBN} should not automatically select breakpoint
3833 type. If the target provides a memory map, @value{GDBN} will warn when
3834 trying to set software breakpoint at a read-only address.
3837 @value{GDBN} normally implements breakpoints by replacing the program code
3838 at the breakpoint address with a special instruction, which, when
3839 executed, given control to the debugger. By default, the program
3840 code is so modified only when the program is resumed. As soon as
3841 the program stops, @value{GDBN} restores the original instructions. This
3842 behaviour guards against leaving breakpoints inserted in the
3843 target should gdb abrubptly disconnect. However, with slow remote
3844 targets, inserting and removing breakpoint can reduce the performance.
3845 This behavior can be controlled with the following commands::
3847 @kindex set breakpoint always-inserted
3848 @kindex show breakpoint always-inserted
3850 @item set breakpoint always-inserted off
3851 All breakpoints, including newly added by the user, are inserted in
3852 the target only when the target is resumed. All breakpoints are
3853 removed from the target when it stops. This is the default mode.
3855 @item set breakpoint always-inserted on
3856 Causes all breakpoints to be inserted in the target at all times. If
3857 the user adds a new breakpoint, or changes an existing breakpoint, the
3858 breakpoints in the target are updated immediately. A breakpoint is
3859 removed from the target only when breakpoint itself is deleted.
3862 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3863 when a breakpoint breaks. If the condition is true, then the process being
3864 debugged stops, otherwise the process is resumed.
3866 If the target supports evaluating conditions on its end, @value{GDBN} may
3867 download the breakpoint, together with its conditions, to it.
3869 This feature can be controlled via the following commands:
3871 @kindex set breakpoint condition-evaluation
3872 @kindex show breakpoint condition-evaluation
3874 @item set breakpoint condition-evaluation host
3875 This option commands @value{GDBN} to evaluate the breakpoint
3876 conditions on the host's side. Unconditional breakpoints are sent to
3877 the target which in turn receives the triggers and reports them back to GDB
3878 for condition evaluation. This is the standard evaluation mode.
3880 @item set breakpoint condition-evaluation target
3881 This option commands @value{GDBN} to download breakpoint conditions
3882 to the target at the moment of their insertion. The target
3883 is responsible for evaluating the conditional expression and reporting
3884 breakpoint stop events back to @value{GDBN} whenever the condition
3885 is true. Due to limitations of target-side evaluation, some conditions
3886 cannot be evaluated there, e.g., conditions that depend on local data
3887 that is only known to the host. Examples include
3888 conditional expressions involving convenience variables, complex types
3889 that cannot be handled by the agent expression parser and expressions
3890 that are too long to be sent over to the target, specially when the
3891 target is a remote system. In these cases, the conditions will be
3892 evaluated by @value{GDBN}.
3894 @item set breakpoint condition-evaluation auto
3895 This is the default mode. If the target supports evaluating breakpoint
3896 conditions on its end, @value{GDBN} will download breakpoint conditions to
3897 the target (limitations mentioned previously apply). If the target does
3898 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3899 to evaluating all these conditions on the host's side.
3903 @cindex negative breakpoint numbers
3904 @cindex internal @value{GDBN} breakpoints
3905 @value{GDBN} itself sometimes sets breakpoints in your program for
3906 special purposes, such as proper handling of @code{longjmp} (in C
3907 programs). These internal breakpoints are assigned negative numbers,
3908 starting with @code{-1}; @samp{info breakpoints} does not display them.
3909 You can see these breakpoints with the @value{GDBN} maintenance command
3910 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3913 @node Set Watchpoints
3914 @subsection Setting Watchpoints
3916 @cindex setting watchpoints
3917 You can use a watchpoint to stop execution whenever the value of an
3918 expression changes, without having to predict a particular place where
3919 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3920 The expression may be as simple as the value of a single variable, or
3921 as complex as many variables combined by operators. Examples include:
3925 A reference to the value of a single variable.
3928 An address cast to an appropriate data type. For example,
3929 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3930 address (assuming an @code{int} occupies 4 bytes).
3933 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3934 expression can use any operators valid in the program's native
3935 language (@pxref{Languages}).
3938 You can set a watchpoint on an expression even if the expression can
3939 not be evaluated yet. For instance, you can set a watchpoint on
3940 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3941 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3942 the expression produces a valid value. If the expression becomes
3943 valid in some other way than changing a variable (e.g.@: if the memory
3944 pointed to by @samp{*global_ptr} becomes readable as the result of a
3945 @code{malloc} call), @value{GDBN} may not stop until the next time
3946 the expression changes.
3948 @cindex software watchpoints
3949 @cindex hardware watchpoints
3950 Depending on your system, watchpoints may be implemented in software or
3951 hardware. @value{GDBN} does software watchpointing by single-stepping your
3952 program and testing the variable's value each time, which is hundreds of
3953 times slower than normal execution. (But this may still be worth it, to
3954 catch errors where you have no clue what part of your program is the
3957 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3958 x86-based targets, @value{GDBN} includes support for hardware
3959 watchpoints, which do not slow down the running of your program.
3963 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3964 Set a watchpoint for an expression. @value{GDBN} will break when the
3965 expression @var{expr} is written into by the program and its value
3966 changes. The simplest (and the most popular) use of this command is
3967 to watch the value of a single variable:
3970 (@value{GDBP}) watch foo
3973 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3974 argument, @value{GDBN} breaks only when the thread identified by
3975 @var{threadnum} changes the value of @var{expr}. If any other threads
3976 change the value of @var{expr}, @value{GDBN} will not break. Note
3977 that watchpoints restricted to a single thread in this way only work
3978 with Hardware Watchpoints.
3980 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3981 (see below). The @code{-location} argument tells @value{GDBN} to
3982 instead watch the memory referred to by @var{expr}. In this case,
3983 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3984 and watch the memory at that address. The type of the result is used
3985 to determine the size of the watched memory. If the expression's
3986 result does not have an address, then @value{GDBN} will print an
3989 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3990 of masked watchpoints, if the current architecture supports this
3991 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3992 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3993 to an address to watch. The mask specifies that some bits of an address
3994 (the bits which are reset in the mask) should be ignored when matching
3995 the address accessed by the inferior against the watchpoint address.
3996 Thus, a masked watchpoint watches many addresses simultaneously---those
3997 addresses whose unmasked bits are identical to the unmasked bits in the
3998 watchpoint address. The @code{mask} argument implies @code{-location}.
4002 (@value{GDBP}) watch foo mask 0xffff00ff
4003 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4007 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4008 Set a watchpoint that will break when the value of @var{expr} is read
4012 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4013 Set a watchpoint that will break when @var{expr} is either read from
4014 or written into by the program.
4016 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4017 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4018 This command prints a list of watchpoints, using the same format as
4019 @code{info break} (@pxref{Set Breaks}).
4022 If you watch for a change in a numerically entered address you need to
4023 dereference it, as the address itself is just a constant number which will
4024 never change. @value{GDBN} refuses to create a watchpoint that watches
4025 a never-changing value:
4028 (@value{GDBP}) watch 0x600850
4029 Cannot watch constant value 0x600850.
4030 (@value{GDBP}) watch *(int *) 0x600850
4031 Watchpoint 1: *(int *) 6293584
4034 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4035 watchpoints execute very quickly, and the debugger reports a change in
4036 value at the exact instruction where the change occurs. If @value{GDBN}
4037 cannot set a hardware watchpoint, it sets a software watchpoint, which
4038 executes more slowly and reports the change in value at the next
4039 @emph{statement}, not the instruction, after the change occurs.
4041 @cindex use only software watchpoints
4042 You can force @value{GDBN} to use only software watchpoints with the
4043 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4044 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4045 the underlying system supports them. (Note that hardware-assisted
4046 watchpoints that were set @emph{before} setting
4047 @code{can-use-hw-watchpoints} to zero will still use the hardware
4048 mechanism of watching expression values.)
4051 @item set can-use-hw-watchpoints
4052 @kindex set can-use-hw-watchpoints
4053 Set whether or not to use hardware watchpoints.
4055 @item show can-use-hw-watchpoints
4056 @kindex show can-use-hw-watchpoints
4057 Show the current mode of using hardware watchpoints.
4060 For remote targets, you can restrict the number of hardware
4061 watchpoints @value{GDBN} will use, see @ref{set remote
4062 hardware-breakpoint-limit}.
4064 When you issue the @code{watch} command, @value{GDBN} reports
4067 Hardware watchpoint @var{num}: @var{expr}
4071 if it was able to set a hardware watchpoint.
4073 Currently, the @code{awatch} and @code{rwatch} commands can only set
4074 hardware watchpoints, because accesses to data that don't change the
4075 value of the watched expression cannot be detected without examining
4076 every instruction as it is being executed, and @value{GDBN} does not do
4077 that currently. If @value{GDBN} finds that it is unable to set a
4078 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4079 will print a message like this:
4082 Expression cannot be implemented with read/access watchpoint.
4085 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4086 data type of the watched expression is wider than what a hardware
4087 watchpoint on the target machine can handle. For example, some systems
4088 can only watch regions that are up to 4 bytes wide; on such systems you
4089 cannot set hardware watchpoints for an expression that yields a
4090 double-precision floating-point number (which is typically 8 bytes
4091 wide). As a work-around, it might be possible to break the large region
4092 into a series of smaller ones and watch them with separate watchpoints.
4094 If you set too many hardware watchpoints, @value{GDBN} might be unable
4095 to insert all of them when you resume the execution of your program.
4096 Since the precise number of active watchpoints is unknown until such
4097 time as the program is about to be resumed, @value{GDBN} might not be
4098 able to warn you about this when you set the watchpoints, and the
4099 warning will be printed only when the program is resumed:
4102 Hardware watchpoint @var{num}: Could not insert watchpoint
4106 If this happens, delete or disable some of the watchpoints.
4108 Watching complex expressions that reference many variables can also
4109 exhaust the resources available for hardware-assisted watchpoints.
4110 That's because @value{GDBN} needs to watch every variable in the
4111 expression with separately allocated resources.
4113 If you call a function interactively using @code{print} or @code{call},
4114 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4115 kind of breakpoint or the call completes.
4117 @value{GDBN} automatically deletes watchpoints that watch local
4118 (automatic) variables, or expressions that involve such variables, when
4119 they go out of scope, that is, when the execution leaves the block in
4120 which these variables were defined. In particular, when the program
4121 being debugged terminates, @emph{all} local variables go out of scope,
4122 and so only watchpoints that watch global variables remain set. If you
4123 rerun the program, you will need to set all such watchpoints again. One
4124 way of doing that would be to set a code breakpoint at the entry to the
4125 @code{main} function and when it breaks, set all the watchpoints.
4127 @cindex watchpoints and threads
4128 @cindex threads and watchpoints
4129 In multi-threaded programs, watchpoints will detect changes to the
4130 watched expression from every thread.
4133 @emph{Warning:} In multi-threaded programs, software watchpoints
4134 have only limited usefulness. If @value{GDBN} creates a software
4135 watchpoint, it can only watch the value of an expression @emph{in a
4136 single thread}. If you are confident that the expression can only
4137 change due to the current thread's activity (and if you are also
4138 confident that no other thread can become current), then you can use
4139 software watchpoints as usual. However, @value{GDBN} may not notice
4140 when a non-current thread's activity changes the expression. (Hardware
4141 watchpoints, in contrast, watch an expression in all threads.)
4144 @xref{set remote hardware-watchpoint-limit}.
4146 @node Set Catchpoints
4147 @subsection Setting Catchpoints
4148 @cindex catchpoints, setting
4149 @cindex exception handlers
4150 @cindex event handling
4152 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4153 kinds of program events, such as C@t{++} exceptions or the loading of a
4154 shared library. Use the @code{catch} command to set a catchpoint.
4158 @item catch @var{event}
4159 Stop when @var{event} occurs. The @var{event} can be any of the following:
4162 @item throw @r{[}@var{regexp}@r{]}
4163 @itemx rethrow @r{[}@var{regexp}@r{]}
4164 @itemx catch @r{[}@var{regexp}@r{]}
4166 @kindex catch rethrow
4168 @cindex stop on C@t{++} exceptions
4169 The throwing, re-throwing, or catching of a C@t{++} exception.
4171 If @var{regexp} is given, then only exceptions whose type matches the
4172 regular expression will be caught.
4174 @vindex $_exception@r{, convenience variable}
4175 The convenience variable @code{$_exception} is available at an
4176 exception-related catchpoint, on some systems. This holds the
4177 exception being thrown.
4179 There are currently some limitations to C@t{++} exception handling in
4184 The support for these commands is system-dependent. Currently, only
4185 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4189 The regular expression feature and the @code{$_exception} convenience
4190 variable rely on the presence of some SDT probes in @code{libstdc++}.
4191 If these probes are not present, then these features cannot be used.
4192 These probes were first available in the GCC 4.8 release, but whether
4193 or not they are available in your GCC also depends on how it was
4197 The @code{$_exception} convenience variable is only valid at the
4198 instruction at which an exception-related catchpoint is set.
4201 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4202 location in the system library which implements runtime exception
4203 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4204 (@pxref{Selection}) to get to your code.
4207 If you call a function interactively, @value{GDBN} normally returns
4208 control to you when the function has finished executing. If the call
4209 raises an exception, however, the call may bypass the mechanism that
4210 returns control to you and cause your program either to abort or to
4211 simply continue running until it hits a breakpoint, catches a signal
4212 that @value{GDBN} is listening for, or exits. This is the case even if
4213 you set a catchpoint for the exception; catchpoints on exceptions are
4214 disabled within interactive calls. @xref{Calling}, for information on
4215 controlling this with @code{set unwind-on-terminating-exception}.
4218 You cannot raise an exception interactively.
4221 You cannot install an exception handler interactively.
4225 @kindex catch exception
4226 @cindex Ada exception catching
4227 @cindex catch Ada exceptions
4228 An Ada exception being raised. If an exception name is specified
4229 at the end of the command (eg @code{catch exception Program_Error}),
4230 the debugger will stop only when this specific exception is raised.
4231 Otherwise, the debugger stops execution when any Ada exception is raised.
4233 When inserting an exception catchpoint on a user-defined exception whose
4234 name is identical to one of the exceptions defined by the language, the
4235 fully qualified name must be used as the exception name. Otherwise,
4236 @value{GDBN} will assume that it should stop on the pre-defined exception
4237 rather than the user-defined one. For instance, assuming an exception
4238 called @code{Constraint_Error} is defined in package @code{Pck}, then
4239 the command to use to catch such exceptions is @kbd{catch exception
4240 Pck.Constraint_Error}.
4242 @item exception unhandled
4243 @kindex catch exception unhandled
4244 An exception that was raised but is not handled by the program.
4247 @kindex catch assert
4248 A failed Ada assertion.
4252 @cindex break on fork/exec
4253 A call to @code{exec}. This is currently only available for HP-UX
4257 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4258 @kindex catch syscall
4259 @cindex break on a system call.
4260 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4261 syscall is a mechanism for application programs to request a service
4262 from the operating system (OS) or one of the OS system services.
4263 @value{GDBN} can catch some or all of the syscalls issued by the
4264 debuggee, and show the related information for each syscall. If no
4265 argument is specified, calls to and returns from all system calls
4268 @var{name} can be any system call name that is valid for the
4269 underlying OS. Just what syscalls are valid depends on the OS. On
4270 GNU and Unix systems, you can find the full list of valid syscall
4271 names on @file{/usr/include/asm/unistd.h}.
4273 @c For MS-Windows, the syscall names and the corresponding numbers
4274 @c can be found, e.g., on this URL:
4275 @c http://www.metasploit.com/users/opcode/syscalls.html
4276 @c but we don't support Windows syscalls yet.
4278 Normally, @value{GDBN} knows in advance which syscalls are valid for
4279 each OS, so you can use the @value{GDBN} command-line completion
4280 facilities (@pxref{Completion,, command completion}) to list the
4283 You may also specify the system call numerically. A syscall's
4284 number is the value passed to the OS's syscall dispatcher to
4285 identify the requested service. When you specify the syscall by its
4286 name, @value{GDBN} uses its database of syscalls to convert the name
4287 into the corresponding numeric code, but using the number directly
4288 may be useful if @value{GDBN}'s database does not have the complete
4289 list of syscalls on your system (e.g., because @value{GDBN} lags
4290 behind the OS upgrades).
4292 The example below illustrates how this command works if you don't provide
4296 (@value{GDBP}) catch syscall
4297 Catchpoint 1 (syscall)
4299 Starting program: /tmp/catch-syscall
4301 Catchpoint 1 (call to syscall 'close'), \
4302 0xffffe424 in __kernel_vsyscall ()
4306 Catchpoint 1 (returned from syscall 'close'), \
4307 0xffffe424 in __kernel_vsyscall ()
4311 Here is an example of catching a system call by name:
4314 (@value{GDBP}) catch syscall chroot
4315 Catchpoint 1 (syscall 'chroot' [61])
4317 Starting program: /tmp/catch-syscall
4319 Catchpoint 1 (call to syscall 'chroot'), \
4320 0xffffe424 in __kernel_vsyscall ()
4324 Catchpoint 1 (returned from syscall 'chroot'), \
4325 0xffffe424 in __kernel_vsyscall ()
4329 An example of specifying a system call numerically. In the case
4330 below, the syscall number has a corresponding entry in the XML
4331 file, so @value{GDBN} finds its name and prints it:
4334 (@value{GDBP}) catch syscall 252
4335 Catchpoint 1 (syscall(s) 'exit_group')
4337 Starting program: /tmp/catch-syscall
4339 Catchpoint 1 (call to syscall 'exit_group'), \
4340 0xffffe424 in __kernel_vsyscall ()
4344 Program exited normally.
4348 However, there can be situations when there is no corresponding name
4349 in XML file for that syscall number. In this case, @value{GDBN} prints
4350 a warning message saying that it was not able to find the syscall name,
4351 but the catchpoint will be set anyway. See the example below:
4354 (@value{GDBP}) catch syscall 764
4355 warning: The number '764' does not represent a known syscall.
4356 Catchpoint 2 (syscall 764)
4360 If you configure @value{GDBN} using the @samp{--without-expat} option,
4361 it will not be able to display syscall names. Also, if your
4362 architecture does not have an XML file describing its system calls,
4363 you will not be able to see the syscall names. It is important to
4364 notice that these two features are used for accessing the syscall
4365 name database. In either case, you will see a warning like this:
4368 (@value{GDBP}) catch syscall
4369 warning: Could not open "syscalls/i386-linux.xml"
4370 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4371 GDB will not be able to display syscall names.
4372 Catchpoint 1 (syscall)
4376 Of course, the file name will change depending on your architecture and system.
4378 Still using the example above, you can also try to catch a syscall by its
4379 number. In this case, you would see something like:
4382 (@value{GDBP}) catch syscall 252
4383 Catchpoint 1 (syscall(s) 252)
4386 Again, in this case @value{GDBN} would not be able to display syscall's names.
4390 A call to @code{fork}. This is currently only available for HP-UX
4395 A call to @code{vfork}. This is currently only available for HP-UX
4398 @item load @r{[}regexp@r{]}
4399 @itemx unload @r{[}regexp@r{]}
4401 @kindex catch unload
4402 The loading or unloading of a shared library. If @var{regexp} is
4403 given, then the catchpoint will stop only if the regular expression
4404 matches one of the affected libraries.
4406 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4407 @kindex catch signal
4408 The delivery of a signal.
4410 With no arguments, this catchpoint will catch any signal that is not
4411 used internally by @value{GDBN}, specifically, all signals except
4412 @samp{SIGTRAP} and @samp{SIGINT}.
4414 With the argument @samp{all}, all signals, including those used by
4415 @value{GDBN}, will be caught. This argument cannot be used with other
4418 Otherwise, the arguments are a list of signal names as given to
4419 @code{handle} (@pxref{Signals}). Only signals specified in this list
4422 One reason that @code{catch signal} can be more useful than
4423 @code{handle} is that you can attach commands and conditions to the
4426 When a signal is caught by a catchpoint, the signal's @code{stop} and
4427 @code{print} settings, as specified by @code{handle}, are ignored.
4428 However, whether the signal is still delivered to the inferior depends
4429 on the @code{pass} setting; this can be changed in the catchpoint's
4434 @item tcatch @var{event}
4436 Set a catchpoint that is enabled only for one stop. The catchpoint is
4437 automatically deleted after the first time the event is caught.
4441 Use the @code{info break} command to list the current catchpoints.
4445 @subsection Deleting Breakpoints
4447 @cindex clearing breakpoints, watchpoints, catchpoints
4448 @cindex deleting breakpoints, watchpoints, catchpoints
4449 It is often necessary to eliminate a breakpoint, watchpoint, or
4450 catchpoint once it has done its job and you no longer want your program
4451 to stop there. This is called @dfn{deleting} the breakpoint. A
4452 breakpoint that has been deleted no longer exists; it is forgotten.
4454 With the @code{clear} command you can delete breakpoints according to
4455 where they are in your program. With the @code{delete} command you can
4456 delete individual breakpoints, watchpoints, or catchpoints by specifying
4457 their breakpoint numbers.
4459 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4460 automatically ignores breakpoints on the first instruction to be executed
4461 when you continue execution without changing the execution address.
4466 Delete any breakpoints at the next instruction to be executed in the
4467 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4468 the innermost frame is selected, this is a good way to delete a
4469 breakpoint where your program just stopped.
4471 @item clear @var{location}
4472 Delete any breakpoints set at the specified @var{location}.
4473 @xref{Specify Location}, for the various forms of @var{location}; the
4474 most useful ones are listed below:
4477 @item clear @var{function}
4478 @itemx clear @var{filename}:@var{function}
4479 Delete any breakpoints set at entry to the named @var{function}.
4481 @item clear @var{linenum}
4482 @itemx clear @var{filename}:@var{linenum}
4483 Delete any breakpoints set at or within the code of the specified
4484 @var{linenum} of the specified @var{filename}.
4487 @cindex delete breakpoints
4489 @kindex d @r{(@code{delete})}
4490 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4491 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4492 ranges specified as arguments. If no argument is specified, delete all
4493 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4494 confirm off}). You can abbreviate this command as @code{d}.
4498 @subsection Disabling Breakpoints
4500 @cindex enable/disable a breakpoint
4501 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4502 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4503 it had been deleted, but remembers the information on the breakpoint so
4504 that you can @dfn{enable} it again later.
4506 You disable and enable breakpoints, watchpoints, and catchpoints with
4507 the @code{enable} and @code{disable} commands, optionally specifying
4508 one or more breakpoint numbers as arguments. Use @code{info break} to
4509 print a list of all breakpoints, watchpoints, and catchpoints if you
4510 do not know which numbers to use.
4512 Disabling and enabling a breakpoint that has multiple locations
4513 affects all of its locations.
4515 A breakpoint, watchpoint, or catchpoint can have any of several
4516 different states of enablement:
4520 Enabled. The breakpoint stops your program. A breakpoint set
4521 with the @code{break} command starts out in this state.
4523 Disabled. The breakpoint has no effect on your program.
4525 Enabled once. The breakpoint stops your program, but then becomes
4528 Enabled for a count. The breakpoint stops your program for the next
4529 N times, then becomes disabled.
4531 Enabled for deletion. The breakpoint stops your program, but
4532 immediately after it does so it is deleted permanently. A breakpoint
4533 set with the @code{tbreak} command starts out in this state.
4536 You can use the following commands to enable or disable breakpoints,
4537 watchpoints, and catchpoints:
4541 @kindex dis @r{(@code{disable})}
4542 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4543 Disable the specified breakpoints---or all breakpoints, if none are
4544 listed. A disabled breakpoint has no effect but is not forgotten. All
4545 options such as ignore-counts, conditions and commands are remembered in
4546 case the breakpoint is enabled again later. You may abbreviate
4547 @code{disable} as @code{dis}.
4550 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4551 Enable the specified breakpoints (or all defined breakpoints). They
4552 become effective once again in stopping your program.
4554 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4555 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4556 of these breakpoints immediately after stopping your program.
4558 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4559 Enable the specified breakpoints temporarily. @value{GDBN} records
4560 @var{count} with each of the specified breakpoints, and decrements a
4561 breakpoint's count when it is hit. When any count reaches 0,
4562 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4563 count (@pxref{Conditions, ,Break Conditions}), that will be
4564 decremented to 0 before @var{count} is affected.
4566 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4567 Enable the specified breakpoints to work once, then die. @value{GDBN}
4568 deletes any of these breakpoints as soon as your program stops there.
4569 Breakpoints set by the @code{tbreak} command start out in this state.
4572 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4573 @c confusing: tbreak is also initially enabled.
4574 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4575 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4576 subsequently, they become disabled or enabled only when you use one of
4577 the commands above. (The command @code{until} can set and delete a
4578 breakpoint of its own, but it does not change the state of your other
4579 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4583 @subsection Break Conditions
4584 @cindex conditional breakpoints
4585 @cindex breakpoint conditions
4587 @c FIXME what is scope of break condition expr? Context where wanted?
4588 @c in particular for a watchpoint?
4589 The simplest sort of breakpoint breaks every time your program reaches a
4590 specified place. You can also specify a @dfn{condition} for a
4591 breakpoint. A condition is just a Boolean expression in your
4592 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4593 a condition evaluates the expression each time your program reaches it,
4594 and your program stops only if the condition is @emph{true}.
4596 This is the converse of using assertions for program validation; in that
4597 situation, you want to stop when the assertion is violated---that is,
4598 when the condition is false. In C, if you want to test an assertion expressed
4599 by the condition @var{assert}, you should set the condition
4600 @samp{! @var{assert}} on the appropriate breakpoint.
4602 Conditions are also accepted for watchpoints; you may not need them,
4603 since a watchpoint is inspecting the value of an expression anyhow---but
4604 it might be simpler, say, to just set a watchpoint on a variable name,
4605 and specify a condition that tests whether the new value is an interesting
4608 Break conditions can have side effects, and may even call functions in
4609 your program. This can be useful, for example, to activate functions
4610 that log program progress, or to use your own print functions to
4611 format special data structures. The effects are completely predictable
4612 unless there is another enabled breakpoint at the same address. (In
4613 that case, @value{GDBN} might see the other breakpoint first and stop your
4614 program without checking the condition of this one.) Note that
4615 breakpoint commands are usually more convenient and flexible than break
4617 purpose of performing side effects when a breakpoint is reached
4618 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4620 Breakpoint conditions can also be evaluated on the target's side if
4621 the target supports it. Instead of evaluating the conditions locally,
4622 @value{GDBN} encodes the expression into an agent expression
4623 (@pxref{Agent Expressions}) suitable for execution on the target,
4624 independently of @value{GDBN}. Global variables become raw memory
4625 locations, locals become stack accesses, and so forth.
4627 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4628 when its condition evaluates to true. This mechanism may provide faster
4629 response times depending on the performance characteristics of the target
4630 since it does not need to keep @value{GDBN} informed about
4631 every breakpoint trigger, even those with false conditions.
4633 Break conditions can be specified when a breakpoint is set, by using
4634 @samp{if} in the arguments to the @code{break} command. @xref{Set
4635 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4636 with the @code{condition} command.
4638 You can also use the @code{if} keyword with the @code{watch} command.
4639 The @code{catch} command does not recognize the @code{if} keyword;
4640 @code{condition} is the only way to impose a further condition on a
4645 @item condition @var{bnum} @var{expression}
4646 Specify @var{expression} as the break condition for breakpoint,
4647 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4648 breakpoint @var{bnum} stops your program only if the value of
4649 @var{expression} is true (nonzero, in C). When you use
4650 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4651 syntactic correctness, and to determine whether symbols in it have
4652 referents in the context of your breakpoint. If @var{expression} uses
4653 symbols not referenced in the context of the breakpoint, @value{GDBN}
4654 prints an error message:
4657 No symbol "foo" in current context.
4662 not actually evaluate @var{expression} at the time the @code{condition}
4663 command (or a command that sets a breakpoint with a condition, like
4664 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4666 @item condition @var{bnum}
4667 Remove the condition from breakpoint number @var{bnum}. It becomes
4668 an ordinary unconditional breakpoint.
4671 @cindex ignore count (of breakpoint)
4672 A special case of a breakpoint condition is to stop only when the
4673 breakpoint has been reached a certain number of times. This is so
4674 useful that there is a special way to do it, using the @dfn{ignore
4675 count} of the breakpoint. Every breakpoint has an ignore count, which
4676 is an integer. Most of the time, the ignore count is zero, and
4677 therefore has no effect. But if your program reaches a breakpoint whose
4678 ignore count is positive, then instead of stopping, it just decrements
4679 the ignore count by one and continues. As a result, if the ignore count
4680 value is @var{n}, the breakpoint does not stop the next @var{n} times
4681 your program reaches it.
4685 @item ignore @var{bnum} @var{count}
4686 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4687 The next @var{count} times the breakpoint is reached, your program's
4688 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4691 To make the breakpoint stop the next time it is reached, specify
4694 When you use @code{continue} to resume execution of your program from a
4695 breakpoint, you can specify an ignore count directly as an argument to
4696 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4697 Stepping,,Continuing and Stepping}.
4699 If a breakpoint has a positive ignore count and a condition, the
4700 condition is not checked. Once the ignore count reaches zero,
4701 @value{GDBN} resumes checking the condition.
4703 You could achieve the effect of the ignore count with a condition such
4704 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4705 is decremented each time. @xref{Convenience Vars, ,Convenience
4709 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4712 @node Break Commands
4713 @subsection Breakpoint Command Lists
4715 @cindex breakpoint commands
4716 You can give any breakpoint (or watchpoint or catchpoint) a series of
4717 commands to execute when your program stops due to that breakpoint. For
4718 example, you might want to print the values of certain expressions, or
4719 enable other breakpoints.
4723 @kindex end@r{ (breakpoint commands)}
4724 @item commands @r{[}@var{range}@dots{}@r{]}
4725 @itemx @dots{} @var{command-list} @dots{}
4727 Specify a list of commands for the given breakpoints. The commands
4728 themselves appear on the following lines. Type a line containing just
4729 @code{end} to terminate the commands.
4731 To remove all commands from a breakpoint, type @code{commands} and
4732 follow it immediately with @code{end}; that is, give no commands.
4734 With no argument, @code{commands} refers to the last breakpoint,
4735 watchpoint, or catchpoint set (not to the breakpoint most recently
4736 encountered). If the most recent breakpoints were set with a single
4737 command, then the @code{commands} will apply to all the breakpoints
4738 set by that command. This applies to breakpoints set by
4739 @code{rbreak}, and also applies when a single @code{break} command
4740 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4744 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4745 disabled within a @var{command-list}.
4747 You can use breakpoint commands to start your program up again. Simply
4748 use the @code{continue} command, or @code{step}, or any other command
4749 that resumes execution.
4751 Any other commands in the command list, after a command that resumes
4752 execution, are ignored. This is because any time you resume execution
4753 (even with a simple @code{next} or @code{step}), you may encounter
4754 another breakpoint---which could have its own command list, leading to
4755 ambiguities about which list to execute.
4758 If the first command you specify in a command list is @code{silent}, the
4759 usual message about stopping at a breakpoint is not printed. This may
4760 be desirable for breakpoints that are to print a specific message and
4761 then continue. If none of the remaining commands print anything, you
4762 see no sign that the breakpoint was reached. @code{silent} is
4763 meaningful only at the beginning of a breakpoint command list.
4765 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4766 print precisely controlled output, and are often useful in silent
4767 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4769 For example, here is how you could use breakpoint commands to print the
4770 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4776 printf "x is %d\n",x
4781 One application for breakpoint commands is to compensate for one bug so
4782 you can test for another. Put a breakpoint just after the erroneous line
4783 of code, give it a condition to detect the case in which something
4784 erroneous has been done, and give it commands to assign correct values
4785 to any variables that need them. End with the @code{continue} command
4786 so that your program does not stop, and start with the @code{silent}
4787 command so that no output is produced. Here is an example:
4798 @node Dynamic Printf
4799 @subsection Dynamic Printf
4801 @cindex dynamic printf
4803 The dynamic printf command @code{dprintf} combines a breakpoint with
4804 formatted printing of your program's data to give you the effect of
4805 inserting @code{printf} calls into your program on-the-fly, without
4806 having to recompile it.
4808 In its most basic form, the output goes to the GDB console. However,
4809 you can set the variable @code{dprintf-style} for alternate handling.
4810 For instance, you can ask to format the output by calling your
4811 program's @code{printf} function. This has the advantage that the
4812 characters go to the program's output device, so they can recorded in
4813 redirects to files and so forth.
4815 If you are doing remote debugging with a stub or agent, you can also
4816 ask to have the printf handled by the remote agent. In addition to
4817 ensuring that the output goes to the remote program's device along
4818 with any other output the program might produce, you can also ask that
4819 the dprintf remain active even after disconnecting from the remote
4820 target. Using the stub/agent is also more efficient, as it can do
4821 everything without needing to communicate with @value{GDBN}.
4825 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4826 Whenever execution reaches @var{location}, print the values of one or
4827 more @var{expressions} under the control of the string @var{template}.
4828 To print several values, separate them with commas.
4830 @item set dprintf-style @var{style}
4831 Set the dprintf output to be handled in one of several different
4832 styles enumerated below. A change of style affects all existing
4833 dynamic printfs immediately. (If you need individual control over the
4834 print commands, simply define normal breakpoints with
4835 explicitly-supplied command lists.)
4838 @kindex dprintf-style gdb
4839 Handle the output using the @value{GDBN} @code{printf} command.
4842 @kindex dprintf-style call
4843 Handle the output by calling a function in your program (normally
4847 @kindex dprintf-style agent
4848 Have the remote debugging agent (such as @code{gdbserver}) handle
4849 the output itself. This style is only available for agents that
4850 support running commands on the target.
4852 @item set dprintf-function @var{function}
4853 Set the function to call if the dprintf style is @code{call}. By
4854 default its value is @code{printf}. You may set it to any expression.
4855 that @value{GDBN} can evaluate to a function, as per the @code{call}
4858 @item set dprintf-channel @var{channel}
4859 Set a ``channel'' for dprintf. If set to a non-empty value,
4860 @value{GDBN} will evaluate it as an expression and pass the result as
4861 a first argument to the @code{dprintf-function}, in the manner of
4862 @code{fprintf} and similar functions. Otherwise, the dprintf format
4863 string will be the first argument, in the manner of @code{printf}.
4865 As an example, if you wanted @code{dprintf} output to go to a logfile
4866 that is a standard I/O stream assigned to the variable @code{mylog},
4867 you could do the following:
4870 (gdb) set dprintf-style call
4871 (gdb) set dprintf-function fprintf
4872 (gdb) set dprintf-channel mylog
4873 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4874 Dprintf 1 at 0x123456: file main.c, line 25.
4876 1 dprintf keep y 0x00123456 in main at main.c:25
4877 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4882 Note that the @code{info break} displays the dynamic printf commands
4883 as normal breakpoint commands; you can thus easily see the effect of
4884 the variable settings.
4886 @item set disconnected-dprintf on
4887 @itemx set disconnected-dprintf off
4888 @kindex set disconnected-dprintf
4889 Choose whether @code{dprintf} commands should continue to run if
4890 @value{GDBN} has disconnected from the target. This only applies
4891 if the @code{dprintf-style} is @code{agent}.
4893 @item show disconnected-dprintf off
4894 @kindex show disconnected-dprintf
4895 Show the current choice for disconnected @code{dprintf}.
4899 @value{GDBN} does not check the validity of function and channel,
4900 relying on you to supply values that are meaningful for the contexts
4901 in which they are being used. For instance, the function and channel
4902 may be the values of local variables, but if that is the case, then
4903 all enabled dynamic prints must be at locations within the scope of
4904 those locals. If evaluation fails, @value{GDBN} will report an error.
4906 @node Save Breakpoints
4907 @subsection How to save breakpoints to a file
4909 To save breakpoint definitions to a file use the @w{@code{save
4910 breakpoints}} command.
4913 @kindex save breakpoints
4914 @cindex save breakpoints to a file for future sessions
4915 @item save breakpoints [@var{filename}]
4916 This command saves all current breakpoint definitions together with
4917 their commands and ignore counts, into a file @file{@var{filename}}
4918 suitable for use in a later debugging session. This includes all
4919 types of breakpoints (breakpoints, watchpoints, catchpoints,
4920 tracepoints). To read the saved breakpoint definitions, use the
4921 @code{source} command (@pxref{Command Files}). Note that watchpoints
4922 with expressions involving local variables may fail to be recreated
4923 because it may not be possible to access the context where the
4924 watchpoint is valid anymore. Because the saved breakpoint definitions
4925 are simply a sequence of @value{GDBN} commands that recreate the
4926 breakpoints, you can edit the file in your favorite editing program,
4927 and remove the breakpoint definitions you're not interested in, or
4928 that can no longer be recreated.
4931 @node Static Probe Points
4932 @subsection Static Probe Points
4934 @cindex static probe point, SystemTap
4935 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4936 for Statically Defined Tracing, and the probes are designed to have a tiny
4937 runtime code and data footprint, and no dynamic relocations. They are
4938 usable from assembly, C and C@t{++} languages. See
4939 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4940 for a good reference on how the @acronym{SDT} probes are implemented.
4942 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4943 @acronym{SDT} probes are supported on ELF-compatible systems. See
4944 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4945 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4946 in your applications.
4948 @cindex semaphores on static probe points
4949 Some probes have an associated semaphore variable; for instance, this
4950 happens automatically if you defined your probe using a DTrace-style
4951 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4952 automatically enable it when you specify a breakpoint using the
4953 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4954 location by some other method (e.g., @code{break file:line}), then
4955 @value{GDBN} will not automatically set the semaphore.
4957 You can examine the available static static probes using @code{info
4958 probes}, with optional arguments:
4962 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4963 If given, @var{provider} is a regular expression used to match against provider
4964 names when selecting which probes to list. If omitted, probes by all
4965 probes from all providers are listed.
4967 If given, @var{name} is a regular expression to match against probe names
4968 when selecting which probes to list. If omitted, probe names are not
4969 considered when deciding whether to display them.
4971 If given, @var{objfile} is a regular expression used to select which
4972 object files (executable or shared libraries) to examine. If not
4973 given, all object files are considered.
4975 @item info probes all
4976 List the available static probes, from all types.
4979 @vindex $_probe_arg@r{, convenience variable}
4980 A probe may specify up to twelve arguments. These are available at the
4981 point at which the probe is defined---that is, when the current PC is
4982 at the probe's location. The arguments are available using the
4983 convenience variables (@pxref{Convenience Vars})
4984 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4985 an integer of the appropriate size; types are not preserved. The
4986 convenience variable @code{$_probe_argc} holds the number of arguments
4987 at the current probe point.
4989 These variables are always available, but attempts to access them at
4990 any location other than a probe point will cause @value{GDBN} to give
4994 @c @ifclear BARETARGET
4995 @node Error in Breakpoints
4996 @subsection ``Cannot insert breakpoints''
4998 If you request too many active hardware-assisted breakpoints and
4999 watchpoints, you will see this error message:
5001 @c FIXME: the precise wording of this message may change; the relevant
5002 @c source change is not committed yet (Sep 3, 1999).
5004 Stopped; cannot insert breakpoints.
5005 You may have requested too many hardware breakpoints and watchpoints.
5009 This message is printed when you attempt to resume the program, since
5010 only then @value{GDBN} knows exactly how many hardware breakpoints and
5011 watchpoints it needs to insert.
5013 When this message is printed, you need to disable or remove some of the
5014 hardware-assisted breakpoints and watchpoints, and then continue.
5016 @node Breakpoint-related Warnings
5017 @subsection ``Breakpoint address adjusted...''
5018 @cindex breakpoint address adjusted
5020 Some processor architectures place constraints on the addresses at
5021 which breakpoints may be placed. For architectures thus constrained,
5022 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5023 with the constraints dictated by the architecture.
5025 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5026 a VLIW architecture in which a number of RISC-like instructions may be
5027 bundled together for parallel execution. The FR-V architecture
5028 constrains the location of a breakpoint instruction within such a
5029 bundle to the instruction with the lowest address. @value{GDBN}
5030 honors this constraint by adjusting a breakpoint's address to the
5031 first in the bundle.
5033 It is not uncommon for optimized code to have bundles which contain
5034 instructions from different source statements, thus it may happen that
5035 a breakpoint's address will be adjusted from one source statement to
5036 another. Since this adjustment may significantly alter @value{GDBN}'s
5037 breakpoint related behavior from what the user expects, a warning is
5038 printed when the breakpoint is first set and also when the breakpoint
5041 A warning like the one below is printed when setting a breakpoint
5042 that's been subject to address adjustment:
5045 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5048 Such warnings are printed both for user settable and @value{GDBN}'s
5049 internal breakpoints. If you see one of these warnings, you should
5050 verify that a breakpoint set at the adjusted address will have the
5051 desired affect. If not, the breakpoint in question may be removed and
5052 other breakpoints may be set which will have the desired behavior.
5053 E.g., it may be sufficient to place the breakpoint at a later
5054 instruction. A conditional breakpoint may also be useful in some
5055 cases to prevent the breakpoint from triggering too often.
5057 @value{GDBN} will also issue a warning when stopping at one of these
5058 adjusted breakpoints:
5061 warning: Breakpoint 1 address previously adjusted from 0x00010414
5065 When this warning is encountered, it may be too late to take remedial
5066 action except in cases where the breakpoint is hit earlier or more
5067 frequently than expected.
5069 @node Continuing and Stepping
5070 @section Continuing and Stepping
5074 @cindex resuming execution
5075 @dfn{Continuing} means resuming program execution until your program
5076 completes normally. In contrast, @dfn{stepping} means executing just
5077 one more ``step'' of your program, where ``step'' may mean either one
5078 line of source code, or one machine instruction (depending on what
5079 particular command you use). Either when continuing or when stepping,
5080 your program may stop even sooner, due to a breakpoint or a signal. (If
5081 it stops due to a signal, you may want to use @code{handle}, or use
5082 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5083 or you may step into the signal's handler (@pxref{stepping and signal
5088 @kindex c @r{(@code{continue})}
5089 @kindex fg @r{(resume foreground execution)}
5090 @item continue @r{[}@var{ignore-count}@r{]}
5091 @itemx c @r{[}@var{ignore-count}@r{]}
5092 @itemx fg @r{[}@var{ignore-count}@r{]}
5093 Resume program execution, at the address where your program last stopped;
5094 any breakpoints set at that address are bypassed. The optional argument
5095 @var{ignore-count} allows you to specify a further number of times to
5096 ignore a breakpoint at this location; its effect is like that of
5097 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5099 The argument @var{ignore-count} is meaningful only when your program
5100 stopped due to a breakpoint. At other times, the argument to
5101 @code{continue} is ignored.
5103 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5104 debugged program is deemed to be the foreground program) are provided
5105 purely for convenience, and have exactly the same behavior as
5109 To resume execution at a different place, you can use @code{return}
5110 (@pxref{Returning, ,Returning from a Function}) to go back to the
5111 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5112 Different Address}) to go to an arbitrary location in your program.
5114 A typical technique for using stepping is to set a breakpoint
5115 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5116 beginning of the function or the section of your program where a problem
5117 is believed to lie, run your program until it stops at that breakpoint,
5118 and then step through the suspect area, examining the variables that are
5119 interesting, until you see the problem happen.
5123 @kindex s @r{(@code{step})}
5125 Continue running your program until control reaches a different source
5126 line, then stop it and return control to @value{GDBN}. This command is
5127 abbreviated @code{s}.
5130 @c "without debugging information" is imprecise; actually "without line
5131 @c numbers in the debugging information". (gcc -g1 has debugging info but
5132 @c not line numbers). But it seems complex to try to make that
5133 @c distinction here.
5134 @emph{Warning:} If you use the @code{step} command while control is
5135 within a function that was compiled without debugging information,
5136 execution proceeds until control reaches a function that does have
5137 debugging information. Likewise, it will not step into a function which
5138 is compiled without debugging information. To step through functions
5139 without debugging information, use the @code{stepi} command, described
5143 The @code{step} command only stops at the first instruction of a source
5144 line. This prevents the multiple stops that could otherwise occur in
5145 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5146 to stop if a function that has debugging information is called within
5147 the line. In other words, @code{step} @emph{steps inside} any functions
5148 called within the line.
5150 Also, the @code{step} command only enters a function if there is line
5151 number information for the function. Otherwise it acts like the
5152 @code{next} command. This avoids problems when using @code{cc -gl}
5153 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5154 was any debugging information about the routine.
5156 @item step @var{count}
5157 Continue running as in @code{step}, but do so @var{count} times. If a
5158 breakpoint is reached, or a signal not related to stepping occurs before
5159 @var{count} steps, stepping stops right away.
5162 @kindex n @r{(@code{next})}
5163 @item next @r{[}@var{count}@r{]}
5164 Continue to the next source line in the current (innermost) stack frame.
5165 This is similar to @code{step}, but function calls that appear within
5166 the line of code are executed without stopping. Execution stops when
5167 control reaches a different line of code at the original stack level
5168 that was executing when you gave the @code{next} command. This command
5169 is abbreviated @code{n}.
5171 An argument @var{count} is a repeat count, as for @code{step}.
5174 @c FIX ME!! Do we delete this, or is there a way it fits in with
5175 @c the following paragraph? --- Vctoria
5177 @c @code{next} within a function that lacks debugging information acts like
5178 @c @code{step}, but any function calls appearing within the code of the
5179 @c function are executed without stopping.
5181 The @code{next} command only stops at the first instruction of a
5182 source line. This prevents multiple stops that could otherwise occur in
5183 @code{switch} statements, @code{for} loops, etc.
5185 @kindex set step-mode
5187 @cindex functions without line info, and stepping
5188 @cindex stepping into functions with no line info
5189 @itemx set step-mode on
5190 The @code{set step-mode on} command causes the @code{step} command to
5191 stop at the first instruction of a function which contains no debug line
5192 information rather than stepping over it.
5194 This is useful in cases where you may be interested in inspecting the
5195 machine instructions of a function which has no symbolic info and do not
5196 want @value{GDBN} to automatically skip over this function.
5198 @item set step-mode off
5199 Causes the @code{step} command to step over any functions which contains no
5200 debug information. This is the default.
5202 @item show step-mode
5203 Show whether @value{GDBN} will stop in or step over functions without
5204 source line debug information.
5207 @kindex fin @r{(@code{finish})}
5209 Continue running until just after function in the selected stack frame
5210 returns. Print the returned value (if any). This command can be
5211 abbreviated as @code{fin}.
5213 Contrast this with the @code{return} command (@pxref{Returning,
5214 ,Returning from a Function}).
5217 @kindex u @r{(@code{until})}
5218 @cindex run until specified location
5221 Continue running until a source line past the current line, in the
5222 current stack frame, is reached. This command is used to avoid single
5223 stepping through a loop more than once. It is like the @code{next}
5224 command, except that when @code{until} encounters a jump, it
5225 automatically continues execution until the program counter is greater
5226 than the address of the jump.
5228 This means that when you reach the end of a loop after single stepping
5229 though it, @code{until} makes your program continue execution until it
5230 exits the loop. In contrast, a @code{next} command at the end of a loop
5231 simply steps back to the beginning of the loop, which forces you to step
5232 through the next iteration.
5234 @code{until} always stops your program if it attempts to exit the current
5237 @code{until} may produce somewhat counterintuitive results if the order
5238 of machine code does not match the order of the source lines. For
5239 example, in the following excerpt from a debugging session, the @code{f}
5240 (@code{frame}) command shows that execution is stopped at line
5241 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5245 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5247 (@value{GDBP}) until
5248 195 for ( ; argc > 0; NEXTARG) @{
5251 This happened because, for execution efficiency, the compiler had
5252 generated code for the loop closure test at the end, rather than the
5253 start, of the loop---even though the test in a C @code{for}-loop is
5254 written before the body of the loop. The @code{until} command appeared
5255 to step back to the beginning of the loop when it advanced to this
5256 expression; however, it has not really gone to an earlier
5257 statement---not in terms of the actual machine code.
5259 @code{until} with no argument works by means of single
5260 instruction stepping, and hence is slower than @code{until} with an
5263 @item until @var{location}
5264 @itemx u @var{location}
5265 Continue running your program until either the specified @var{location} is
5266 reached, or the current stack frame returns. The location is any of
5267 the forms described in @ref{Specify Location}.
5268 This form of the command uses temporary breakpoints, and
5269 hence is quicker than @code{until} without an argument. The specified
5270 location is actually reached only if it is in the current frame. This
5271 implies that @code{until} can be used to skip over recursive function
5272 invocations. For instance in the code below, if the current location is
5273 line @code{96}, issuing @code{until 99} will execute the program up to
5274 line @code{99} in the same invocation of factorial, i.e., after the inner
5275 invocations have returned.
5278 94 int factorial (int value)
5280 96 if (value > 1) @{
5281 97 value *= factorial (value - 1);
5288 @kindex advance @var{location}
5289 @item advance @var{location}
5290 Continue running the program up to the given @var{location}. An argument is
5291 required, which should be of one of the forms described in
5292 @ref{Specify Location}.
5293 Execution will also stop upon exit from the current stack
5294 frame. This command is similar to @code{until}, but @code{advance} will
5295 not skip over recursive function calls, and the target location doesn't
5296 have to be in the same frame as the current one.
5300 @kindex si @r{(@code{stepi})}
5302 @itemx stepi @var{arg}
5304 Execute one machine instruction, then stop and return to the debugger.
5306 It is often useful to do @samp{display/i $pc} when stepping by machine
5307 instructions. This makes @value{GDBN} automatically display the next
5308 instruction to be executed, each time your program stops. @xref{Auto
5309 Display,, Automatic Display}.
5311 An argument is a repeat count, as in @code{step}.
5315 @kindex ni @r{(@code{nexti})}
5317 @itemx nexti @var{arg}
5319 Execute one machine instruction, but if it is a function call,
5320 proceed until the function returns.
5322 An argument is a repeat count, as in @code{next}.
5326 @anchor{range stepping}
5327 @cindex range stepping
5328 @cindex target-assisted range stepping
5329 By default, and if available, @value{GDBN} makes use of
5330 target-assisted @dfn{range stepping}. In other words, whenever you
5331 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5332 tells the target to step the corresponding range of instruction
5333 addresses instead of issuing multiple single-steps. This speeds up
5334 line stepping, particularly for remote targets. Ideally, there should
5335 be no reason you would want to turn range stepping off. However, it's
5336 possible that a bug in the debug info, a bug in the remote stub (for
5337 remote targets), or even a bug in @value{GDBN} could make line
5338 stepping behave incorrectly when target-assisted range stepping is
5339 enabled. You can use the following command to turn off range stepping
5343 @kindex set range-stepping
5344 @kindex show range-stepping
5345 @item set range-stepping
5346 @itemx show range-stepping
5347 Control whether range stepping is enabled.
5349 If @code{on}, and the target supports it, @value{GDBN} tells the
5350 target to step a range of addresses itself, instead of issuing
5351 multiple single-steps. If @code{off}, @value{GDBN} always issues
5352 single-steps, even if range stepping is supported by the target. The
5353 default is @code{on}.
5357 @node Skipping Over Functions and Files
5358 @section Skipping Over Functions and Files
5359 @cindex skipping over functions and files
5361 The program you are debugging may contain some functions which are
5362 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5363 skip a function or all functions in a file when stepping.
5365 For example, consider the following C function:
5376 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5377 are not interested in stepping through @code{boring}. If you run @code{step}
5378 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5379 step over both @code{foo} and @code{boring}!
5381 One solution is to @code{step} into @code{boring} and use the @code{finish}
5382 command to immediately exit it. But this can become tedious if @code{boring}
5383 is called from many places.
5385 A more flexible solution is to execute @kbd{skip boring}. This instructs
5386 @value{GDBN} never to step into @code{boring}. Now when you execute
5387 @code{step} at line 103, you'll step over @code{boring} and directly into
5390 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5391 example, @code{skip file boring.c}.
5394 @kindex skip function
5395 @item skip @r{[}@var{linespec}@r{]}
5396 @itemx skip function @r{[}@var{linespec}@r{]}
5397 After running this command, the function named by @var{linespec} or the
5398 function containing the line named by @var{linespec} will be skipped over when
5399 stepping. @xref{Specify Location}.
5401 If you do not specify @var{linespec}, the function you're currently debugging
5404 (If you have a function called @code{file} that you want to skip, use
5405 @kbd{skip function file}.)
5408 @item skip file @r{[}@var{filename}@r{]}
5409 After running this command, any function whose source lives in @var{filename}
5410 will be skipped over when stepping.
5412 If you do not specify @var{filename}, functions whose source lives in the file
5413 you're currently debugging will be skipped.
5416 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5417 These are the commands for managing your list of skips:
5421 @item info skip @r{[}@var{range}@r{]}
5422 Print details about the specified skip(s). If @var{range} is not specified,
5423 print a table with details about all functions and files marked for skipping.
5424 @code{info skip} prints the following information about each skip:
5428 A number identifying this skip.
5430 The type of this skip, either @samp{function} or @samp{file}.
5431 @item Enabled or Disabled
5432 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5434 For function skips, this column indicates the address in memory of the function
5435 being skipped. If you've set a function skip on a function which has not yet
5436 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5437 which has the function is loaded, @code{info skip} will show the function's
5440 For file skips, this field contains the filename being skipped. For functions
5441 skips, this field contains the function name and its line number in the file
5442 where it is defined.
5446 @item skip delete @r{[}@var{range}@r{]}
5447 Delete the specified skip(s). If @var{range} is not specified, delete all
5451 @item skip enable @r{[}@var{range}@r{]}
5452 Enable the specified skip(s). If @var{range} is not specified, enable all
5455 @kindex skip disable
5456 @item skip disable @r{[}@var{range}@r{]}
5457 Disable the specified skip(s). If @var{range} is not specified, disable all
5466 A signal is an asynchronous event that can happen in a program. The
5467 operating system defines the possible kinds of signals, and gives each
5468 kind a name and a number. For example, in Unix @code{SIGINT} is the
5469 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5470 @code{SIGSEGV} is the signal a program gets from referencing a place in
5471 memory far away from all the areas in use; @code{SIGALRM} occurs when
5472 the alarm clock timer goes off (which happens only if your program has
5473 requested an alarm).
5475 @cindex fatal signals
5476 Some signals, including @code{SIGALRM}, are a normal part of the
5477 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5478 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5479 program has not specified in advance some other way to handle the signal.
5480 @code{SIGINT} does not indicate an error in your program, but it is normally
5481 fatal so it can carry out the purpose of the interrupt: to kill the program.
5483 @value{GDBN} has the ability to detect any occurrence of a signal in your
5484 program. You can tell @value{GDBN} in advance what to do for each kind of
5487 @cindex handling signals
5488 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5489 @code{SIGALRM} be silently passed to your program
5490 (so as not to interfere with their role in the program's functioning)
5491 but to stop your program immediately whenever an error signal happens.
5492 You can change these settings with the @code{handle} command.
5495 @kindex info signals
5499 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5500 handle each one. You can use this to see the signal numbers of all
5501 the defined types of signals.
5503 @item info signals @var{sig}
5504 Similar, but print information only about the specified signal number.
5506 @code{info handle} is an alias for @code{info signals}.
5508 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5509 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5510 for details about this command.
5513 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5514 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5515 can be the number of a signal or its name (with or without the
5516 @samp{SIG} at the beginning); a list of signal numbers of the form
5517 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5518 known signals. Optional arguments @var{keywords}, described below,
5519 say what change to make.
5523 The keywords allowed by the @code{handle} command can be abbreviated.
5524 Their full names are:
5528 @value{GDBN} should not stop your program when this signal happens. It may
5529 still print a message telling you that the signal has come in.
5532 @value{GDBN} should stop your program when this signal happens. This implies
5533 the @code{print} keyword as well.
5536 @value{GDBN} should print a message when this signal happens.
5539 @value{GDBN} should not mention the occurrence of the signal at all. This
5540 implies the @code{nostop} keyword as well.
5544 @value{GDBN} should allow your program to see this signal; your program
5545 can handle the signal, or else it may terminate if the signal is fatal
5546 and not handled. @code{pass} and @code{noignore} are synonyms.
5550 @value{GDBN} should not allow your program to see this signal.
5551 @code{nopass} and @code{ignore} are synonyms.
5555 When a signal stops your program, the signal is not visible to the
5557 continue. Your program sees the signal then, if @code{pass} is in
5558 effect for the signal in question @emph{at that time}. In other words,
5559 after @value{GDBN} reports a signal, you can use the @code{handle}
5560 command with @code{pass} or @code{nopass} to control whether your
5561 program sees that signal when you continue.
5563 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5564 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5565 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5568 You can also use the @code{signal} command to prevent your program from
5569 seeing a signal, or cause it to see a signal it normally would not see,
5570 or to give it any signal at any time. For example, if your program stopped
5571 due to some sort of memory reference error, you might store correct
5572 values into the erroneous variables and continue, hoping to see more
5573 execution; but your program would probably terminate immediately as
5574 a result of the fatal signal once it saw the signal. To prevent this,
5575 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5578 @cindex stepping and signal handlers
5579 @anchor{stepping and signal handlers}
5581 @value{GDBN} optimizes for stepping the mainline code. If a signal
5582 that has @code{handle nostop} and @code{handle pass} set arrives while
5583 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5584 in progress, @value{GDBN} lets the signal handler run and then resumes
5585 stepping the mainline code once the signal handler returns. In other
5586 words, @value{GDBN} steps over the signal handler. This prevents
5587 signals that you've specified as not interesting (with @code{handle
5588 nostop}) from changing the focus of debugging unexpectedly. Note that
5589 the signal handler itself may still hit a breakpoint, stop for another
5590 signal that has @code{handle stop} in effect, or for any other event
5591 that normally results in stopping the stepping command sooner. Also
5592 note that @value{GDBN} still informs you that the program received a
5593 signal if @code{handle print} is set.
5595 @anchor{stepping into signal handlers}
5597 If you set @code{handle pass} for a signal, and your program sets up a
5598 handler for it, then issuing a stepping command, such as @code{step}
5599 or @code{stepi}, when your program is stopped due to the signal will
5600 step @emph{into} the signal handler (if the target supports that).
5602 Likewise, if you use the @code{queue-signal} command to queue a signal
5603 to be delivered to the current thread when execution of the thread
5604 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5605 stepping command will step into the signal handler.
5607 Here's an example, using @code{stepi} to step to the first instruction
5608 of @code{SIGUSR1}'s handler:
5611 (@value{GDBP}) handle SIGUSR1
5612 Signal Stop Print Pass to program Description
5613 SIGUSR1 Yes Yes Yes User defined signal 1
5617 Program received signal SIGUSR1, User defined signal 1.
5618 main () sigusr1.c:28
5621 sigusr1_handler () at sigusr1.c:9
5625 The same, but using @code{queue-signal} instead of waiting for the
5626 program to receive the signal first:
5631 (@value{GDBP}) queue-signal SIGUSR1
5633 sigusr1_handler () at sigusr1.c:9
5638 @cindex extra signal information
5639 @anchor{extra signal information}
5641 On some targets, @value{GDBN} can inspect extra signal information
5642 associated with the intercepted signal, before it is actually
5643 delivered to the program being debugged. This information is exported
5644 by the convenience variable @code{$_siginfo}, and consists of data
5645 that is passed by the kernel to the signal handler at the time of the
5646 receipt of a signal. The data type of the information itself is
5647 target dependent. You can see the data type using the @code{ptype
5648 $_siginfo} command. On Unix systems, it typically corresponds to the
5649 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5652 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5653 referenced address that raised a segmentation fault.
5657 (@value{GDBP}) continue
5658 Program received signal SIGSEGV, Segmentation fault.
5659 0x0000000000400766 in main ()
5661 (@value{GDBP}) ptype $_siginfo
5668 struct @{...@} _kill;
5669 struct @{...@} _timer;
5671 struct @{...@} _sigchld;
5672 struct @{...@} _sigfault;
5673 struct @{...@} _sigpoll;
5676 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5680 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5681 $1 = (void *) 0x7ffff7ff7000
5685 Depending on target support, @code{$_siginfo} may also be writable.
5688 @section Stopping and Starting Multi-thread Programs
5690 @cindex stopped threads
5691 @cindex threads, stopped
5693 @cindex continuing threads
5694 @cindex threads, continuing
5696 @value{GDBN} supports debugging programs with multiple threads
5697 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5698 are two modes of controlling execution of your program within the
5699 debugger. In the default mode, referred to as @dfn{all-stop mode},
5700 when any thread in your program stops (for example, at a breakpoint
5701 or while being stepped), all other threads in the program are also stopped by
5702 @value{GDBN}. On some targets, @value{GDBN} also supports
5703 @dfn{non-stop mode}, in which other threads can continue to run freely while
5704 you examine the stopped thread in the debugger.
5707 * All-Stop Mode:: All threads stop when GDB takes control
5708 * Non-Stop Mode:: Other threads continue to execute
5709 * Background Execution:: Running your program asynchronously
5710 * Thread-Specific Breakpoints:: Controlling breakpoints
5711 * Interrupted System Calls:: GDB may interfere with system calls
5712 * Observer Mode:: GDB does not alter program behavior
5716 @subsection All-Stop Mode
5718 @cindex all-stop mode
5720 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5721 @emph{all} threads of execution stop, not just the current thread. This
5722 allows you to examine the overall state of the program, including
5723 switching between threads, without worrying that things may change
5726 Conversely, whenever you restart the program, @emph{all} threads start
5727 executing. @emph{This is true even when single-stepping} with commands
5728 like @code{step} or @code{next}.
5730 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5731 Since thread scheduling is up to your debugging target's operating
5732 system (not controlled by @value{GDBN}), other threads may
5733 execute more than one statement while the current thread completes a
5734 single step. Moreover, in general other threads stop in the middle of a
5735 statement, rather than at a clean statement boundary, when the program
5738 You might even find your program stopped in another thread after
5739 continuing or even single-stepping. This happens whenever some other
5740 thread runs into a breakpoint, a signal, or an exception before the
5741 first thread completes whatever you requested.
5743 @cindex automatic thread selection
5744 @cindex switching threads automatically
5745 @cindex threads, automatic switching
5746 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5747 signal, it automatically selects the thread where that breakpoint or
5748 signal happened. @value{GDBN} alerts you to the context switch with a
5749 message such as @samp{[Switching to Thread @var{n}]} to identify the
5752 On some OSes, you can modify @value{GDBN}'s default behavior by
5753 locking the OS scheduler to allow only a single thread to run.
5756 @item set scheduler-locking @var{mode}
5757 @cindex scheduler locking mode
5758 @cindex lock scheduler
5759 Set the scheduler locking mode. If it is @code{off}, then there is no
5760 locking and any thread may run at any time. If @code{on}, then only the
5761 current thread may run when the inferior is resumed. The @code{step}
5762 mode optimizes for single-stepping; it prevents other threads
5763 from preempting the current thread while you are stepping, so that
5764 the focus of debugging does not change unexpectedly.
5765 Other threads only rarely (or never) get a chance to run
5766 when you step. They are more likely to run when you @samp{next} over a
5767 function call, and they are completely free to run when you use commands
5768 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5769 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5770 the current thread away from the thread that you are debugging.
5772 @item show scheduler-locking
5773 Display the current scheduler locking mode.
5776 @cindex resume threads of multiple processes simultaneously
5777 By default, when you issue one of the execution commands such as
5778 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5779 threads of the current inferior to run. For example, if @value{GDBN}
5780 is attached to two inferiors, each with two threads, the
5781 @code{continue} command resumes only the two threads of the current
5782 inferior. This is useful, for example, when you debug a program that
5783 forks and you want to hold the parent stopped (so that, for instance,
5784 it doesn't run to exit), while you debug the child. In other
5785 situations, you may not be interested in inspecting the current state
5786 of any of the processes @value{GDBN} is attached to, and you may want
5787 to resume them all until some breakpoint is hit. In the latter case,
5788 you can instruct @value{GDBN} to allow all threads of all the
5789 inferiors to run with the @w{@code{set schedule-multiple}} command.
5792 @kindex set schedule-multiple
5793 @item set schedule-multiple
5794 Set the mode for allowing threads of multiple processes to be resumed
5795 when an execution command is issued. When @code{on}, all threads of
5796 all processes are allowed to run. When @code{off}, only the threads
5797 of the current process are resumed. The default is @code{off}. The
5798 @code{scheduler-locking} mode takes precedence when set to @code{on},
5799 or while you are stepping and set to @code{step}.
5801 @item show schedule-multiple
5802 Display the current mode for resuming the execution of threads of
5807 @subsection Non-Stop Mode
5809 @cindex non-stop mode
5811 @c This section is really only a place-holder, and needs to be expanded
5812 @c with more details.
5814 For some multi-threaded targets, @value{GDBN} supports an optional
5815 mode of operation in which you can examine stopped program threads in
5816 the debugger while other threads continue to execute freely. This
5817 minimizes intrusion when debugging live systems, such as programs
5818 where some threads have real-time constraints or must continue to
5819 respond to external events. This is referred to as @dfn{non-stop} mode.
5821 In non-stop mode, when a thread stops to report a debugging event,
5822 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5823 threads as well, in contrast to the all-stop mode behavior. Additionally,
5824 execution commands such as @code{continue} and @code{step} apply by default
5825 only to the current thread in non-stop mode, rather than all threads as
5826 in all-stop mode. This allows you to control threads explicitly in
5827 ways that are not possible in all-stop mode --- for example, stepping
5828 one thread while allowing others to run freely, stepping
5829 one thread while holding all others stopped, or stepping several threads
5830 independently and simultaneously.
5832 To enter non-stop mode, use this sequence of commands before you run
5833 or attach to your program:
5836 # If using the CLI, pagination breaks non-stop.
5839 # Finally, turn it on!
5843 You can use these commands to manipulate the non-stop mode setting:
5846 @kindex set non-stop
5847 @item set non-stop on
5848 Enable selection of non-stop mode.
5849 @item set non-stop off
5850 Disable selection of non-stop mode.
5851 @kindex show non-stop
5853 Show the current non-stop enablement setting.
5856 Note these commands only reflect whether non-stop mode is enabled,
5857 not whether the currently-executing program is being run in non-stop mode.
5858 In particular, the @code{set non-stop} preference is only consulted when
5859 @value{GDBN} starts or connects to the target program, and it is generally
5860 not possible to switch modes once debugging has started. Furthermore,
5861 since not all targets support non-stop mode, even when you have enabled
5862 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5865 In non-stop mode, all execution commands apply only to the current thread
5866 by default. That is, @code{continue} only continues one thread.
5867 To continue all threads, issue @code{continue -a} or @code{c -a}.
5869 You can use @value{GDBN}'s background execution commands
5870 (@pxref{Background Execution}) to run some threads in the background
5871 while you continue to examine or step others from @value{GDBN}.
5872 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5873 always executed asynchronously in non-stop mode.
5875 Suspending execution is done with the @code{interrupt} command when
5876 running in the background, or @kbd{Ctrl-c} during foreground execution.
5877 In all-stop mode, this stops the whole process;
5878 but in non-stop mode the interrupt applies only to the current thread.
5879 To stop the whole program, use @code{interrupt -a}.
5881 Other execution commands do not currently support the @code{-a} option.
5883 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5884 that thread current, as it does in all-stop mode. This is because the
5885 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5886 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5887 changed to a different thread just as you entered a command to operate on the
5888 previously current thread.
5890 @node Background Execution
5891 @subsection Background Execution
5893 @cindex foreground execution
5894 @cindex background execution
5895 @cindex asynchronous execution
5896 @cindex execution, foreground, background and asynchronous
5898 @value{GDBN}'s execution commands have two variants: the normal
5899 foreground (synchronous) behavior, and a background
5900 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5901 the program to report that some thread has stopped before prompting for
5902 another command. In background execution, @value{GDBN} immediately gives
5903 a command prompt so that you can issue other commands while your program runs.
5905 If the target doesn't support async mode, @value{GDBN} issues an error
5906 message if you attempt to use the background execution commands.
5908 To specify background execution, add a @code{&} to the command. For example,
5909 the background form of the @code{continue} command is @code{continue&}, or
5910 just @code{c&}. The execution commands that accept background execution
5916 @xref{Starting, , Starting your Program}.
5920 @xref{Attach, , Debugging an Already-running Process}.
5924 @xref{Continuing and Stepping, step}.
5928 @xref{Continuing and Stepping, stepi}.
5932 @xref{Continuing and Stepping, next}.
5936 @xref{Continuing and Stepping, nexti}.
5940 @xref{Continuing and Stepping, continue}.
5944 @xref{Continuing and Stepping, finish}.
5948 @xref{Continuing and Stepping, until}.
5952 Background execution is especially useful in conjunction with non-stop
5953 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5954 However, you can also use these commands in the normal all-stop mode with
5955 the restriction that you cannot issue another execution command until the
5956 previous one finishes. Examples of commands that are valid in all-stop
5957 mode while the program is running include @code{help} and @code{info break}.
5959 You can interrupt your program while it is running in the background by
5960 using the @code{interrupt} command.
5967 Suspend execution of the running program. In all-stop mode,
5968 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5969 only the current thread. To stop the whole program in non-stop mode,
5970 use @code{interrupt -a}.
5973 @node Thread-Specific Breakpoints
5974 @subsection Thread-Specific Breakpoints
5976 When your program has multiple threads (@pxref{Threads,, Debugging
5977 Programs with Multiple Threads}), you can choose whether to set
5978 breakpoints on all threads, or on a particular thread.
5981 @cindex breakpoints and threads
5982 @cindex thread breakpoints
5983 @kindex break @dots{} thread @var{threadno}
5984 @item break @var{linespec} thread @var{threadno}
5985 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5986 @var{linespec} specifies source lines; there are several ways of
5987 writing them (@pxref{Specify Location}), but the effect is always to
5988 specify some source line.
5990 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5991 to specify that you only want @value{GDBN} to stop the program when a
5992 particular thread reaches this breakpoint. The @var{threadno} specifier
5993 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
5994 in the first column of the @samp{info threads} display.
5996 If you do not specify @samp{thread @var{threadno}} when you set a
5997 breakpoint, the breakpoint applies to @emph{all} threads of your
6000 You can use the @code{thread} qualifier on conditional breakpoints as
6001 well; in this case, place @samp{thread @var{threadno}} before or
6002 after the breakpoint condition, like this:
6005 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6010 Thread-specific breakpoints are automatically deleted when
6011 @value{GDBN} detects the corresponding thread is no longer in the
6012 thread list. For example:
6016 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6019 There are several ways for a thread to disappear, such as a regular
6020 thread exit, but also when you detach from the process with the
6021 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6022 Process}), or if @value{GDBN} loses the remote connection
6023 (@pxref{Remote Debugging}), etc. Note that with some targets,
6024 @value{GDBN} is only able to detect a thread has exited when the user
6025 explictly asks for the thread list with the @code{info threads}
6028 @node Interrupted System Calls
6029 @subsection Interrupted System Calls
6031 @cindex thread breakpoints and system calls
6032 @cindex system calls and thread breakpoints
6033 @cindex premature return from system calls
6034 There is an unfortunate side effect when using @value{GDBN} to debug
6035 multi-threaded programs. If one thread stops for a
6036 breakpoint, or for some other reason, and another thread is blocked in a
6037 system call, then the system call may return prematurely. This is a
6038 consequence of the interaction between multiple threads and the signals
6039 that @value{GDBN} uses to implement breakpoints and other events that
6042 To handle this problem, your program should check the return value of
6043 each system call and react appropriately. This is good programming
6046 For example, do not write code like this:
6052 The call to @code{sleep} will return early if a different thread stops
6053 at a breakpoint or for some other reason.
6055 Instead, write this:
6060 unslept = sleep (unslept);
6063 A system call is allowed to return early, so the system is still
6064 conforming to its specification. But @value{GDBN} does cause your
6065 multi-threaded program to behave differently than it would without
6068 Also, @value{GDBN} uses internal breakpoints in the thread library to
6069 monitor certain events such as thread creation and thread destruction.
6070 When such an event happens, a system call in another thread may return
6071 prematurely, even though your program does not appear to stop.
6074 @subsection Observer Mode
6076 If you want to build on non-stop mode and observe program behavior
6077 without any chance of disruption by @value{GDBN}, you can set
6078 variables to disable all of the debugger's attempts to modify state,
6079 whether by writing memory, inserting breakpoints, etc. These operate
6080 at a low level, intercepting operations from all commands.
6082 When all of these are set to @code{off}, then @value{GDBN} is said to
6083 be @dfn{observer mode}. As a convenience, the variable
6084 @code{observer} can be set to disable these, plus enable non-stop
6087 Note that @value{GDBN} will not prevent you from making nonsensical
6088 combinations of these settings. For instance, if you have enabled
6089 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6090 then breakpoints that work by writing trap instructions into the code
6091 stream will still not be able to be placed.
6096 @item set observer on
6097 @itemx set observer off
6098 When set to @code{on}, this disables all the permission variables
6099 below (except for @code{insert-fast-tracepoints}), plus enables
6100 non-stop debugging. Setting this to @code{off} switches back to
6101 normal debugging, though remaining in non-stop mode.
6104 Show whether observer mode is on or off.
6106 @kindex may-write-registers
6107 @item set may-write-registers on
6108 @itemx set may-write-registers off
6109 This controls whether @value{GDBN} will attempt to alter the values of
6110 registers, such as with assignment expressions in @code{print}, or the
6111 @code{jump} command. It defaults to @code{on}.
6113 @item show may-write-registers
6114 Show the current permission to write registers.
6116 @kindex may-write-memory
6117 @item set may-write-memory on
6118 @itemx set may-write-memory off
6119 This controls whether @value{GDBN} will attempt to alter the contents
6120 of memory, such as with assignment expressions in @code{print}. It
6121 defaults to @code{on}.
6123 @item show may-write-memory
6124 Show the current permission to write memory.
6126 @kindex may-insert-breakpoints
6127 @item set may-insert-breakpoints on
6128 @itemx set may-insert-breakpoints off
6129 This controls whether @value{GDBN} will attempt to insert breakpoints.
6130 This affects all breakpoints, including internal breakpoints defined
6131 by @value{GDBN}. It defaults to @code{on}.
6133 @item show may-insert-breakpoints
6134 Show the current permission to insert breakpoints.
6136 @kindex may-insert-tracepoints
6137 @item set may-insert-tracepoints on
6138 @itemx set may-insert-tracepoints off
6139 This controls whether @value{GDBN} will attempt to insert (regular)
6140 tracepoints at the beginning of a tracing experiment. It affects only
6141 non-fast tracepoints, fast tracepoints being under the control of
6142 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6144 @item show may-insert-tracepoints
6145 Show the current permission to insert tracepoints.
6147 @kindex may-insert-fast-tracepoints
6148 @item set may-insert-fast-tracepoints on
6149 @itemx set may-insert-fast-tracepoints off
6150 This controls whether @value{GDBN} will attempt to insert fast
6151 tracepoints at the beginning of a tracing experiment. It affects only
6152 fast tracepoints, regular (non-fast) tracepoints being under the
6153 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6155 @item show may-insert-fast-tracepoints
6156 Show the current permission to insert fast tracepoints.
6158 @kindex may-interrupt
6159 @item set may-interrupt on
6160 @itemx set may-interrupt off
6161 This controls whether @value{GDBN} will attempt to interrupt or stop
6162 program execution. When this variable is @code{off}, the
6163 @code{interrupt} command will have no effect, nor will
6164 @kbd{Ctrl-c}. It defaults to @code{on}.
6166 @item show may-interrupt
6167 Show the current permission to interrupt or stop the program.
6171 @node Reverse Execution
6172 @chapter Running programs backward
6173 @cindex reverse execution
6174 @cindex running programs backward
6176 When you are debugging a program, it is not unusual to realize that
6177 you have gone too far, and some event of interest has already happened.
6178 If the target environment supports it, @value{GDBN} can allow you to
6179 ``rewind'' the program by running it backward.
6181 A target environment that supports reverse execution should be able
6182 to ``undo'' the changes in machine state that have taken place as the
6183 program was executing normally. Variables, registers etc.@: should
6184 revert to their previous values. Obviously this requires a great
6185 deal of sophistication on the part of the target environment; not
6186 all target environments can support reverse execution.
6188 When a program is executed in reverse, the instructions that
6189 have most recently been executed are ``un-executed'', in reverse
6190 order. The program counter runs backward, following the previous
6191 thread of execution in reverse. As each instruction is ``un-executed'',
6192 the values of memory and/or registers that were changed by that
6193 instruction are reverted to their previous states. After executing
6194 a piece of source code in reverse, all side effects of that code
6195 should be ``undone'', and all variables should be returned to their
6196 prior values@footnote{
6197 Note that some side effects are easier to undo than others. For instance,
6198 memory and registers are relatively easy, but device I/O is hard. Some
6199 targets may be able undo things like device I/O, and some may not.
6201 The contract between @value{GDBN} and the reverse executing target
6202 requires only that the target do something reasonable when
6203 @value{GDBN} tells it to execute backwards, and then report the
6204 results back to @value{GDBN}. Whatever the target reports back to
6205 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6206 assumes that the memory and registers that the target reports are in a
6207 consistant state, but @value{GDBN} accepts whatever it is given.
6210 If you are debugging in a target environment that supports
6211 reverse execution, @value{GDBN} provides the following commands.
6214 @kindex reverse-continue
6215 @kindex rc @r{(@code{reverse-continue})}
6216 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6217 @itemx rc @r{[}@var{ignore-count}@r{]}
6218 Beginning at the point where your program last stopped, start executing
6219 in reverse. Reverse execution will stop for breakpoints and synchronous
6220 exceptions (signals), just like normal execution. Behavior of
6221 asynchronous signals depends on the target environment.
6223 @kindex reverse-step
6224 @kindex rs @r{(@code{step})}
6225 @item reverse-step @r{[}@var{count}@r{]}
6226 Run the program backward until control reaches the start of a
6227 different source line; then stop it, and return control to @value{GDBN}.
6229 Like the @code{step} command, @code{reverse-step} will only stop
6230 at the beginning of a source line. It ``un-executes'' the previously
6231 executed source line. If the previous source line included calls to
6232 debuggable functions, @code{reverse-step} will step (backward) into
6233 the called function, stopping at the beginning of the @emph{last}
6234 statement in the called function (typically a return statement).
6236 Also, as with the @code{step} command, if non-debuggable functions are
6237 called, @code{reverse-step} will run thru them backward without stopping.
6239 @kindex reverse-stepi
6240 @kindex rsi @r{(@code{reverse-stepi})}
6241 @item reverse-stepi @r{[}@var{count}@r{]}
6242 Reverse-execute one machine instruction. Note that the instruction
6243 to be reverse-executed is @emph{not} the one pointed to by the program
6244 counter, but the instruction executed prior to that one. For instance,
6245 if the last instruction was a jump, @code{reverse-stepi} will take you
6246 back from the destination of the jump to the jump instruction itself.
6248 @kindex reverse-next
6249 @kindex rn @r{(@code{reverse-next})}
6250 @item reverse-next @r{[}@var{count}@r{]}
6251 Run backward to the beginning of the previous line executed in
6252 the current (innermost) stack frame. If the line contains function
6253 calls, they will be ``un-executed'' without stopping. Starting from
6254 the first line of a function, @code{reverse-next} will take you back
6255 to the caller of that function, @emph{before} the function was called,
6256 just as the normal @code{next} command would take you from the last
6257 line of a function back to its return to its caller
6258 @footnote{Unless the code is too heavily optimized.}.
6260 @kindex reverse-nexti
6261 @kindex rni @r{(@code{reverse-nexti})}
6262 @item reverse-nexti @r{[}@var{count}@r{]}
6263 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6264 in reverse, except that called functions are ``un-executed'' atomically.
6265 That is, if the previously executed instruction was a return from
6266 another function, @code{reverse-nexti} will continue to execute
6267 in reverse until the call to that function (from the current stack
6270 @kindex reverse-finish
6271 @item reverse-finish
6272 Just as the @code{finish} command takes you to the point where the
6273 current function returns, @code{reverse-finish} takes you to the point
6274 where it was called. Instead of ending up at the end of the current
6275 function invocation, you end up at the beginning.
6277 @kindex set exec-direction
6278 @item set exec-direction
6279 Set the direction of target execution.
6280 @item set exec-direction reverse
6281 @cindex execute forward or backward in time
6282 @value{GDBN} will perform all execution commands in reverse, until the
6283 exec-direction mode is changed to ``forward''. Affected commands include
6284 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6285 command cannot be used in reverse mode.
6286 @item set exec-direction forward
6287 @value{GDBN} will perform all execution commands in the normal fashion.
6288 This is the default.
6292 @node Process Record and Replay
6293 @chapter Recording Inferior's Execution and Replaying It
6294 @cindex process record and replay
6295 @cindex recording inferior's execution and replaying it
6297 On some platforms, @value{GDBN} provides a special @dfn{process record
6298 and replay} target that can record a log of the process execution, and
6299 replay it later with both forward and reverse execution commands.
6302 When this target is in use, if the execution log includes the record
6303 for the next instruction, @value{GDBN} will debug in @dfn{replay
6304 mode}. In the replay mode, the inferior does not really execute code
6305 instructions. Instead, all the events that normally happen during
6306 code execution are taken from the execution log. While code is not
6307 really executed in replay mode, the values of registers (including the
6308 program counter register) and the memory of the inferior are still
6309 changed as they normally would. Their contents are taken from the
6313 If the record for the next instruction is not in the execution log,
6314 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6315 inferior executes normally, and @value{GDBN} records the execution log
6318 The process record and replay target supports reverse execution
6319 (@pxref{Reverse Execution}), even if the platform on which the
6320 inferior runs does not. However, the reverse execution is limited in
6321 this case by the range of the instructions recorded in the execution
6322 log. In other words, reverse execution on platforms that don't
6323 support it directly can only be done in the replay mode.
6325 When debugging in the reverse direction, @value{GDBN} will work in
6326 replay mode as long as the execution log includes the record for the
6327 previous instruction; otherwise, it will work in record mode, if the
6328 platform supports reverse execution, or stop if not.
6330 For architecture environments that support process record and replay,
6331 @value{GDBN} provides the following commands:
6334 @kindex target record
6335 @kindex target record-full
6336 @kindex target record-btrace
6339 @kindex record btrace
6343 @item record @var{method}
6344 This command starts the process record and replay target. The
6345 recording method can be specified as parameter. Without a parameter
6346 the command uses the @code{full} recording method. The following
6347 recording methods are available:
6351 Full record/replay recording using @value{GDBN}'s software record and
6352 replay implementation. This method allows replaying and reverse
6356 Hardware-supported instruction recording. This method does not record
6357 data. Further, the data is collected in a ring buffer so old data will
6358 be overwritten when the buffer is full. It allows limited replay and
6361 This recording method may not be available on all processors.
6364 The process record and replay target can only debug a process that is
6365 already running. Therefore, you need first to start the process with
6366 the @kbd{run} or @kbd{start} commands, and then start the recording
6367 with the @kbd{record @var{method}} command.
6369 Both @code{record @var{method}} and @code{rec @var{method}} are
6370 aliases of @code{target record-@var{method}}.
6372 @cindex displaced stepping, and process record and replay
6373 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6374 will be automatically disabled when process record and replay target
6375 is started. That's because the process record and replay target
6376 doesn't support displaced stepping.
6378 @cindex non-stop mode, and process record and replay
6379 @cindex asynchronous execution, and process record and replay
6380 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6381 the asynchronous execution mode (@pxref{Background Execution}), not
6382 all recording methods are available. The @code{full} recording method
6383 does not support these two modes.
6388 Stop the process record and replay target. When process record and
6389 replay target stops, the entire execution log will be deleted and the
6390 inferior will either be terminated, or will remain in its final state.
6392 When you stop the process record and replay target in record mode (at
6393 the end of the execution log), the inferior will be stopped at the
6394 next instruction that would have been recorded. In other words, if
6395 you record for a while and then stop recording, the inferior process
6396 will be left in the same state as if the recording never happened.
6398 On the other hand, if the process record and replay target is stopped
6399 while in replay mode (that is, not at the end of the execution log,
6400 but at some earlier point), the inferior process will become ``live''
6401 at that earlier state, and it will then be possible to continue the
6402 usual ``live'' debugging of the process from that state.
6404 When the inferior process exits, or @value{GDBN} detaches from it,
6405 process record and replay target will automatically stop itself.
6409 Go to a specific location in the execution log. There are several
6410 ways to specify the location to go to:
6413 @item record goto begin
6414 @itemx record goto start
6415 Go to the beginning of the execution log.
6417 @item record goto end
6418 Go to the end of the execution log.
6420 @item record goto @var{n}
6421 Go to instruction number @var{n} in the execution log.
6425 @item record save @var{filename}
6426 Save the execution log to a file @file{@var{filename}}.
6427 Default filename is @file{gdb_record.@var{process_id}}, where
6428 @var{process_id} is the process ID of the inferior.
6430 This command may not be available for all recording methods.
6432 @kindex record restore
6433 @item record restore @var{filename}
6434 Restore the execution log from a file @file{@var{filename}}.
6435 File must have been created with @code{record save}.
6437 @kindex set record full
6438 @item set record full insn-number-max @var{limit}
6439 @itemx set record full insn-number-max unlimited
6440 Set the limit of instructions to be recorded for the @code{full}
6441 recording method. Default value is 200000.
6443 If @var{limit} is a positive number, then @value{GDBN} will start
6444 deleting instructions from the log once the number of the record
6445 instructions becomes greater than @var{limit}. For every new recorded
6446 instruction, @value{GDBN} will delete the earliest recorded
6447 instruction to keep the number of recorded instructions at the limit.
6448 (Since deleting recorded instructions loses information, @value{GDBN}
6449 lets you control what happens when the limit is reached, by means of
6450 the @code{stop-at-limit} option, described below.)
6452 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6453 delete recorded instructions from the execution log. The number of
6454 recorded instructions is limited only by the available memory.
6456 @kindex show record full
6457 @item show record full insn-number-max
6458 Show the limit of instructions to be recorded with the @code{full}
6461 @item set record full stop-at-limit
6462 Control the behavior of the @code{full} recording method when the
6463 number of recorded instructions reaches the limit. If ON (the
6464 default), @value{GDBN} will stop when the limit is reached for the
6465 first time and ask you whether you want to stop the inferior or
6466 continue running it and recording the execution log. If you decide
6467 to continue recording, each new recorded instruction will cause the
6468 oldest one to be deleted.
6470 If this option is OFF, @value{GDBN} will automatically delete the
6471 oldest record to make room for each new one, without asking.
6473 @item show record full stop-at-limit
6474 Show the current setting of @code{stop-at-limit}.
6476 @item set record full memory-query
6477 Control the behavior when @value{GDBN} is unable to record memory
6478 changes caused by an instruction for the @code{full} recording method.
6479 If ON, @value{GDBN} will query whether to stop the inferior in that
6482 If this option is OFF (the default), @value{GDBN} will automatically
6483 ignore the effect of such instructions on memory. Later, when
6484 @value{GDBN} replays this execution log, it will mark the log of this
6485 instruction as not accessible, and it will not affect the replay
6488 @item show record full memory-query
6489 Show the current setting of @code{memory-query}.
6491 @kindex set record btrace
6492 The @code{btrace} record target does not trace data. As a
6493 convenience, when replaying, @value{GDBN} reads read-only memory off
6494 the live program directly, assuming that the addresses of the
6495 read-only areas don't change. This for example makes it possible to
6496 disassemble code while replaying, but not to print variables.
6497 In some cases, being able to inspect variables might be useful.
6498 You can use the following command for that:
6500 @item set record btrace replay-memory-access
6501 Control the behavior of the @code{btrace} recording method when
6502 accessing memory during replay. If @code{read-only} (the default),
6503 @value{GDBN} will only allow accesses to read-only memory.
6504 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6505 and to read-write memory. Beware that the accessed memory corresponds
6506 to the live target and not necessarily to the current replay
6509 @kindex show record btrace
6510 @item show record btrace replay-memory-access
6511 Show the current setting of @code{replay-memory-access}.
6515 Show various statistics about the recording depending on the recording
6520 For the @code{full} recording method, it shows the state of process
6521 record and its in-memory execution log buffer, including:
6525 Whether in record mode or replay mode.
6527 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6529 Highest recorded instruction number.
6531 Current instruction about to be replayed (if in replay mode).
6533 Number of instructions contained in the execution log.
6535 Maximum number of instructions that may be contained in the execution log.
6539 For the @code{btrace} recording method, it shows the number of
6540 instructions that have been recorded and the number of blocks of
6541 sequential control-flow that is formed by the recorded instructions.
6544 @kindex record delete
6547 When record target runs in replay mode (``in the past''), delete the
6548 subsequent execution log and begin to record a new execution log starting
6549 from the current address. This means you will abandon the previously
6550 recorded ``future'' and begin recording a new ``future''.
6552 @kindex record instruction-history
6553 @kindex rec instruction-history
6554 @item record instruction-history
6555 Disassembles instructions from the recorded execution log. By
6556 default, ten instructions are disassembled. This can be changed using
6557 the @code{set record instruction-history-size} command. Instructions
6558 are printed in execution order. There are several ways to specify
6559 what part of the execution log to disassemble:
6562 @item record instruction-history @var{insn}
6563 Disassembles ten instructions starting from instruction number
6566 @item record instruction-history @var{insn}, +/-@var{n}
6567 Disassembles @var{n} instructions around instruction number
6568 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6569 @var{n} instructions after instruction number @var{insn}. If
6570 @var{n} is preceded with @code{-}, disassembles @var{n}
6571 instructions before instruction number @var{insn}.
6573 @item record instruction-history
6574 Disassembles ten more instructions after the last disassembly.
6576 @item record instruction-history -
6577 Disassembles ten more instructions before the last disassembly.
6579 @item record instruction-history @var{begin} @var{end}
6580 Disassembles instructions beginning with instruction number
6581 @var{begin} until instruction number @var{end}. The instruction
6582 number @var{end} is included.
6585 This command may not be available for all recording methods.
6588 @item set record instruction-history-size @var{size}
6589 @itemx set record instruction-history-size unlimited
6590 Define how many instructions to disassemble in the @code{record
6591 instruction-history} command. The default value is 10.
6592 A @var{size} of @code{unlimited} means unlimited instructions.
6595 @item show record instruction-history-size
6596 Show how many instructions to disassemble in the @code{record
6597 instruction-history} command.
6599 @kindex record function-call-history
6600 @kindex rec function-call-history
6601 @item record function-call-history
6602 Prints the execution history at function granularity. It prints one
6603 line for each sequence of instructions that belong to the same
6604 function giving the name of that function, the source lines
6605 for this instruction sequence (if the @code{/l} modifier is
6606 specified), and the instructions numbers that form the sequence (if
6607 the @code{/i} modifier is specified). The function names are indented
6608 to reflect the call stack depth if the @code{/c} modifier is
6609 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6613 (@value{GDBP}) @b{list 1, 10}
6624 (@value{GDBP}) @b{record function-call-history /ilc}
6625 1 bar inst 1,4 at foo.c:6,8
6626 2 foo inst 5,10 at foo.c:2,3
6627 3 bar inst 11,13 at foo.c:9,10
6630 By default, ten lines are printed. This can be changed using the
6631 @code{set record function-call-history-size} command. Functions are
6632 printed in execution order. There are several ways to specify what
6636 @item record function-call-history @var{func}
6637 Prints ten functions starting from function number @var{func}.
6639 @item record function-call-history @var{func}, +/-@var{n}
6640 Prints @var{n} functions around function number @var{func}. If
6641 @var{n} is preceded with @code{+}, prints @var{n} functions after
6642 function number @var{func}. If @var{n} is preceded with @code{-},
6643 prints @var{n} functions before function number @var{func}.
6645 @item record function-call-history
6646 Prints ten more functions after the last ten-line print.
6648 @item record function-call-history -
6649 Prints ten more functions before the last ten-line print.
6651 @item record function-call-history @var{begin} @var{end}
6652 Prints functions beginning with function number @var{begin} until
6653 function number @var{end}. The function number @var{end} is included.
6656 This command may not be available for all recording methods.
6658 @item set record function-call-history-size @var{size}
6659 @itemx set record function-call-history-size unlimited
6660 Define how many lines to print in the
6661 @code{record function-call-history} command. The default value is 10.
6662 A size of @code{unlimited} means unlimited lines.
6664 @item show record function-call-history-size
6665 Show how many lines to print in the
6666 @code{record function-call-history} command.
6671 @chapter Examining the Stack
6673 When your program has stopped, the first thing you need to know is where it
6674 stopped and how it got there.
6677 Each time your program performs a function call, information about the call
6679 That information includes the location of the call in your program,
6680 the arguments of the call,
6681 and the local variables of the function being called.
6682 The information is saved in a block of data called a @dfn{stack frame}.
6683 The stack frames are allocated in a region of memory called the @dfn{call
6686 When your program stops, the @value{GDBN} commands for examining the
6687 stack allow you to see all of this information.
6689 @cindex selected frame
6690 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6691 @value{GDBN} commands refer implicitly to the selected frame. In
6692 particular, whenever you ask @value{GDBN} for the value of a variable in
6693 your program, the value is found in the selected frame. There are
6694 special @value{GDBN} commands to select whichever frame you are
6695 interested in. @xref{Selection, ,Selecting a Frame}.
6697 When your program stops, @value{GDBN} automatically selects the
6698 currently executing frame and describes it briefly, similar to the
6699 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6702 * Frames:: Stack frames
6703 * Backtrace:: Backtraces
6704 * Frame Filter Management:: Managing frame filters
6705 * Selection:: Selecting a frame
6706 * Frame Info:: Information on a frame
6711 @section Stack Frames
6713 @cindex frame, definition
6715 The call stack is divided up into contiguous pieces called @dfn{stack
6716 frames}, or @dfn{frames} for short; each frame is the data associated
6717 with one call to one function. The frame contains the arguments given
6718 to the function, the function's local variables, and the address at
6719 which the function is executing.
6721 @cindex initial frame
6722 @cindex outermost frame
6723 @cindex innermost frame
6724 When your program is started, the stack has only one frame, that of the
6725 function @code{main}. This is called the @dfn{initial} frame or the
6726 @dfn{outermost} frame. Each time a function is called, a new frame is
6727 made. Each time a function returns, the frame for that function invocation
6728 is eliminated. If a function is recursive, there can be many frames for
6729 the same function. The frame for the function in which execution is
6730 actually occurring is called the @dfn{innermost} frame. This is the most
6731 recently created of all the stack frames that still exist.
6733 @cindex frame pointer
6734 Inside your program, stack frames are identified by their addresses. A
6735 stack frame consists of many bytes, each of which has its own address; each
6736 kind of computer has a convention for choosing one byte whose
6737 address serves as the address of the frame. Usually this address is kept
6738 in a register called the @dfn{frame pointer register}
6739 (@pxref{Registers, $fp}) while execution is going on in that frame.
6741 @cindex frame number
6742 @value{GDBN} assigns numbers to all existing stack frames, starting with
6743 zero for the innermost frame, one for the frame that called it,
6744 and so on upward. These numbers do not really exist in your program;
6745 they are assigned by @value{GDBN} to give you a way of designating stack
6746 frames in @value{GDBN} commands.
6748 @c The -fomit-frame-pointer below perennially causes hbox overflow
6749 @c underflow problems.
6750 @cindex frameless execution
6751 Some compilers provide a way to compile functions so that they operate
6752 without stack frames. (For example, the @value{NGCC} option
6754 @samp{-fomit-frame-pointer}
6756 generates functions without a frame.)
6757 This is occasionally done with heavily used library functions to save
6758 the frame setup time. @value{GDBN} has limited facilities for dealing
6759 with these function invocations. If the innermost function invocation
6760 has no stack frame, @value{GDBN} nevertheless regards it as though
6761 it had a separate frame, which is numbered zero as usual, allowing
6762 correct tracing of the function call chain. However, @value{GDBN} has
6763 no provision for frameless functions elsewhere in the stack.
6766 @kindex frame@r{, command}
6767 @cindex current stack frame
6768 @item frame @r{[}@var{framespec}@r{]}
6769 The @code{frame} command allows you to move from one stack frame to another,
6770 and to print the stack frame you select. The @var{framespec} may be either the
6771 address of the frame or the stack frame number. Without an argument,
6772 @code{frame} prints the current stack frame.
6774 @kindex select-frame
6775 @cindex selecting frame silently
6777 The @code{select-frame} command allows you to move from one stack frame
6778 to another without printing the frame. This is the silent version of
6786 @cindex call stack traces
6787 A backtrace is a summary of how your program got where it is. It shows one
6788 line per frame, for many frames, starting with the currently executing
6789 frame (frame zero), followed by its caller (frame one), and on up the
6792 @anchor{backtrace-command}
6795 @kindex bt @r{(@code{backtrace})}
6798 Print a backtrace of the entire stack: one line per frame for all
6799 frames in the stack.
6801 You can stop the backtrace at any time by typing the system interrupt
6802 character, normally @kbd{Ctrl-c}.
6804 @item backtrace @var{n}
6806 Similar, but print only the innermost @var{n} frames.
6808 @item backtrace -@var{n}
6810 Similar, but print only the outermost @var{n} frames.
6812 @item backtrace full
6814 @itemx bt full @var{n}
6815 @itemx bt full -@var{n}
6816 Print the values of the local variables also. As described above,
6817 @var{n} specifies the number of frames to print.
6819 @item backtrace no-filters
6820 @itemx bt no-filters
6821 @itemx bt no-filters @var{n}
6822 @itemx bt no-filters -@var{n}
6823 @itemx bt no-filters full
6824 @itemx bt no-filters full @var{n}
6825 @itemx bt no-filters full -@var{n}
6826 Do not run Python frame filters on this backtrace. @xref{Frame
6827 Filter API}, for more information. Additionally use @ref{disable
6828 frame-filter all} to turn off all frame filters. This is only
6829 relevant when @value{GDBN} has been configured with @code{Python}
6835 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6836 are additional aliases for @code{backtrace}.
6838 @cindex multiple threads, backtrace
6839 In a multi-threaded program, @value{GDBN} by default shows the
6840 backtrace only for the current thread. To display the backtrace for
6841 several or all of the threads, use the command @code{thread apply}
6842 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6843 apply all backtrace}, @value{GDBN} will display the backtrace for all
6844 the threads; this is handy when you debug a core dump of a
6845 multi-threaded program.
6847 Each line in the backtrace shows the frame number and the function name.
6848 The program counter value is also shown---unless you use @code{set
6849 print address off}. The backtrace also shows the source file name and
6850 line number, as well as the arguments to the function. The program
6851 counter value is omitted if it is at the beginning of the code for that
6854 Here is an example of a backtrace. It was made with the command
6855 @samp{bt 3}, so it shows the innermost three frames.
6859 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6861 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6862 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6864 (More stack frames follow...)
6869 The display for frame zero does not begin with a program counter
6870 value, indicating that your program has stopped at the beginning of the
6871 code for line @code{993} of @code{builtin.c}.
6874 The value of parameter @code{data} in frame 1 has been replaced by
6875 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6876 only if it is a scalar (integer, pointer, enumeration, etc). See command
6877 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6878 on how to configure the way function parameter values are printed.
6880 @cindex optimized out, in backtrace
6881 @cindex function call arguments, optimized out
6882 If your program was compiled with optimizations, some compilers will
6883 optimize away arguments passed to functions if those arguments are
6884 never used after the call. Such optimizations generate code that
6885 passes arguments through registers, but doesn't store those arguments
6886 in the stack frame. @value{GDBN} has no way of displaying such
6887 arguments in stack frames other than the innermost one. Here's what
6888 such a backtrace might look like:
6892 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6894 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6895 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6897 (More stack frames follow...)
6902 The values of arguments that were not saved in their stack frames are
6903 shown as @samp{<optimized out>}.
6905 If you need to display the values of such optimized-out arguments,
6906 either deduce that from other variables whose values depend on the one
6907 you are interested in, or recompile without optimizations.
6909 @cindex backtrace beyond @code{main} function
6910 @cindex program entry point
6911 @cindex startup code, and backtrace
6912 Most programs have a standard user entry point---a place where system
6913 libraries and startup code transition into user code. For C this is
6914 @code{main}@footnote{
6915 Note that embedded programs (the so-called ``free-standing''
6916 environment) are not required to have a @code{main} function as the
6917 entry point. They could even have multiple entry points.}.
6918 When @value{GDBN} finds the entry function in a backtrace
6919 it will terminate the backtrace, to avoid tracing into highly
6920 system-specific (and generally uninteresting) code.
6922 If you need to examine the startup code, or limit the number of levels
6923 in a backtrace, you can change this behavior:
6926 @item set backtrace past-main
6927 @itemx set backtrace past-main on
6928 @kindex set backtrace
6929 Backtraces will continue past the user entry point.
6931 @item set backtrace past-main off
6932 Backtraces will stop when they encounter the user entry point. This is the
6935 @item show backtrace past-main
6936 @kindex show backtrace
6937 Display the current user entry point backtrace policy.
6939 @item set backtrace past-entry
6940 @itemx set backtrace past-entry on
6941 Backtraces will continue past the internal entry point of an application.
6942 This entry point is encoded by the linker when the application is built,
6943 and is likely before the user entry point @code{main} (or equivalent) is called.
6945 @item set backtrace past-entry off
6946 Backtraces will stop when they encounter the internal entry point of an
6947 application. This is the default.
6949 @item show backtrace past-entry
6950 Display the current internal entry point backtrace policy.
6952 @item set backtrace limit @var{n}
6953 @itemx set backtrace limit 0
6954 @itemx set backtrace limit unlimited
6955 @cindex backtrace limit
6956 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6957 or zero means unlimited levels.
6959 @item show backtrace limit
6960 Display the current limit on backtrace levels.
6963 You can control how file names are displayed.
6966 @item set filename-display
6967 @itemx set filename-display relative
6968 @cindex filename-display
6969 Display file names relative to the compilation directory. This is the default.
6971 @item set filename-display basename
6972 Display only basename of a filename.
6974 @item set filename-display absolute
6975 Display an absolute filename.
6977 @item show filename-display
6978 Show the current way to display filenames.
6981 @node Frame Filter Management
6982 @section Management of Frame Filters.
6983 @cindex managing frame filters
6985 Frame filters are Python based utilities to manage and decorate the
6986 output of frames. @xref{Frame Filter API}, for further information.
6988 Managing frame filters is performed by several commands available
6989 within @value{GDBN}, detailed here.
6992 @kindex info frame-filter
6993 @item info frame-filter
6994 Print a list of installed frame filters from all dictionaries, showing
6995 their name, priority and enabled status.
6997 @kindex disable frame-filter
6998 @anchor{disable frame-filter all}
6999 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7000 Disable a frame filter in the dictionary matching
7001 @var{filter-dictionary} and @var{filter-name}. The
7002 @var{filter-dictionary} may be @code{all}, @code{global},
7003 @code{progspace}, or the name of the object file where the frame filter
7004 dictionary resides. When @code{all} is specified, all frame filters
7005 across all dictionaries are disabled. The @var{filter-name} is the name
7006 of the frame filter and is used when @code{all} is not the option for
7007 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7008 may be enabled again later.
7010 @kindex enable frame-filter
7011 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7012 Enable a frame filter in the dictionary matching
7013 @var{filter-dictionary} and @var{filter-name}. The
7014 @var{filter-dictionary} may be @code{all}, @code{global},
7015 @code{progspace} or the name of the object file where the frame filter
7016 dictionary resides. When @code{all} is specified, all frame filters across
7017 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7018 filter and is used when @code{all} is not the option for
7019 @var{filter-dictionary}.
7024 (gdb) info frame-filter
7026 global frame-filters:
7027 Priority Enabled Name
7028 1000 No PrimaryFunctionFilter
7031 progspace /build/test frame-filters:
7032 Priority Enabled Name
7033 100 Yes ProgspaceFilter
7035 objfile /build/test frame-filters:
7036 Priority Enabled Name
7037 999 Yes BuildProgra Filter
7039 (gdb) disable frame-filter /build/test BuildProgramFilter
7040 (gdb) info frame-filter
7042 global frame-filters:
7043 Priority Enabled Name
7044 1000 No PrimaryFunctionFilter
7047 progspace /build/test frame-filters:
7048 Priority Enabled Name
7049 100 Yes ProgspaceFilter
7051 objfile /build/test frame-filters:
7052 Priority Enabled Name
7053 999 No BuildProgramFilter
7055 (gdb) enable frame-filter global PrimaryFunctionFilter
7056 (gdb) info frame-filter
7058 global frame-filters:
7059 Priority Enabled Name
7060 1000 Yes PrimaryFunctionFilter
7063 progspace /build/test frame-filters:
7064 Priority Enabled Name
7065 100 Yes ProgspaceFilter
7067 objfile /build/test frame-filters:
7068 Priority Enabled Name
7069 999 No BuildProgramFilter
7072 @kindex set frame-filter priority
7073 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7074 Set the @var{priority} of a frame filter in the dictionary matching
7075 @var{filter-dictionary}, and the frame filter name matching
7076 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7077 @code{progspace} or the name of the object file where the frame filter
7078 dictionary resides. The @var{priority} is an integer.
7080 @kindex show frame-filter priority
7081 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7082 Show the @var{priority} of a frame filter in the dictionary matching
7083 @var{filter-dictionary}, and the frame filter name matching
7084 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7085 @code{progspace} or the name of the object file where the frame filter
7091 (gdb) info frame-filter
7093 global frame-filters:
7094 Priority Enabled Name
7095 1000 Yes PrimaryFunctionFilter
7098 progspace /build/test frame-filters:
7099 Priority Enabled Name
7100 100 Yes ProgspaceFilter
7102 objfile /build/test frame-filters:
7103 Priority Enabled Name
7104 999 No BuildProgramFilter
7106 (gdb) set frame-filter priority global Reverse 50
7107 (gdb) info frame-filter
7109 global frame-filters:
7110 Priority Enabled Name
7111 1000 Yes PrimaryFunctionFilter
7114 progspace /build/test frame-filters:
7115 Priority Enabled Name
7116 100 Yes ProgspaceFilter
7118 objfile /build/test frame-filters:
7119 Priority Enabled Name
7120 999 No BuildProgramFilter
7125 @section Selecting a Frame
7127 Most commands for examining the stack and other data in your program work on
7128 whichever stack frame is selected at the moment. Here are the commands for
7129 selecting a stack frame; all of them finish by printing a brief description
7130 of the stack frame just selected.
7133 @kindex frame@r{, selecting}
7134 @kindex f @r{(@code{frame})}
7137 Select frame number @var{n}. Recall that frame zero is the innermost
7138 (currently executing) frame, frame one is the frame that called the
7139 innermost one, and so on. The highest-numbered frame is the one for
7142 @item frame @var{addr}
7144 Select the frame at address @var{addr}. This is useful mainly if the
7145 chaining of stack frames has been damaged by a bug, making it
7146 impossible for @value{GDBN} to assign numbers properly to all frames. In
7147 addition, this can be useful when your program has multiple stacks and
7148 switches between them.
7150 On the SPARC architecture, @code{frame} needs two addresses to
7151 select an arbitrary frame: a frame pointer and a stack pointer.
7153 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7154 pointer and a program counter.
7156 On the 29k architecture, it needs three addresses: a register stack
7157 pointer, a program counter, and a memory stack pointer.
7161 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7162 numbers @var{n}, this advances toward the outermost frame, to higher
7163 frame numbers, to frames that have existed longer.
7166 @kindex do @r{(@code{down})}
7168 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7169 positive numbers @var{n}, this advances toward the innermost frame, to
7170 lower frame numbers, to frames that were created more recently.
7171 You may abbreviate @code{down} as @code{do}.
7174 All of these commands end by printing two lines of output describing the
7175 frame. The first line shows the frame number, the function name, the
7176 arguments, and the source file and line number of execution in that
7177 frame. The second line shows the text of that source line.
7185 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7187 10 read_input_file (argv[i]);
7191 After such a printout, the @code{list} command with no arguments
7192 prints ten lines centered on the point of execution in the frame.
7193 You can also edit the program at the point of execution with your favorite
7194 editing program by typing @code{edit}.
7195 @xref{List, ,Printing Source Lines},
7199 @kindex down-silently
7201 @item up-silently @var{n}
7202 @itemx down-silently @var{n}
7203 These two commands are variants of @code{up} and @code{down},
7204 respectively; they differ in that they do their work silently, without
7205 causing display of the new frame. They are intended primarily for use
7206 in @value{GDBN} command scripts, where the output might be unnecessary and
7211 @section Information About a Frame
7213 There are several other commands to print information about the selected
7219 When used without any argument, this command does not change which
7220 frame is selected, but prints a brief description of the currently
7221 selected stack frame. It can be abbreviated @code{f}. With an
7222 argument, this command is used to select a stack frame.
7223 @xref{Selection, ,Selecting a Frame}.
7226 @kindex info f @r{(@code{info frame})}
7229 This command prints a verbose description of the selected stack frame,
7234 the address of the frame
7236 the address of the next frame down (called by this frame)
7238 the address of the next frame up (caller of this frame)
7240 the language in which the source code corresponding to this frame is written
7242 the address of the frame's arguments
7244 the address of the frame's local variables
7246 the program counter saved in it (the address of execution in the caller frame)
7248 which registers were saved in the frame
7251 @noindent The verbose description is useful when
7252 something has gone wrong that has made the stack format fail to fit
7253 the usual conventions.
7255 @item info frame @var{addr}
7256 @itemx info f @var{addr}
7257 Print a verbose description of the frame at address @var{addr}, without
7258 selecting that frame. The selected frame remains unchanged by this
7259 command. This requires the same kind of address (more than one for some
7260 architectures) that you specify in the @code{frame} command.
7261 @xref{Selection, ,Selecting a Frame}.
7265 Print the arguments of the selected frame, each on a separate line.
7269 Print the local variables of the selected frame, each on a separate
7270 line. These are all variables (declared either static or automatic)
7271 accessible at the point of execution of the selected frame.
7277 @chapter Examining Source Files
7279 @value{GDBN} can print parts of your program's source, since the debugging
7280 information recorded in the program tells @value{GDBN} what source files were
7281 used to build it. When your program stops, @value{GDBN} spontaneously prints
7282 the line where it stopped. Likewise, when you select a stack frame
7283 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7284 execution in that frame has stopped. You can print other portions of
7285 source files by explicit command.
7287 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7288 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7289 @value{GDBN} under @sc{gnu} Emacs}.
7292 * List:: Printing source lines
7293 * Specify Location:: How to specify code locations
7294 * Edit:: Editing source files
7295 * Search:: Searching source files
7296 * Source Path:: Specifying source directories
7297 * Machine Code:: Source and machine code
7301 @section Printing Source Lines
7304 @kindex l @r{(@code{list})}
7305 To print lines from a source file, use the @code{list} command
7306 (abbreviated @code{l}). By default, ten lines are printed.
7307 There are several ways to specify what part of the file you want to
7308 print; see @ref{Specify Location}, for the full list.
7310 Here are the forms of the @code{list} command most commonly used:
7313 @item list @var{linenum}
7314 Print lines centered around line number @var{linenum} in the
7315 current source file.
7317 @item list @var{function}
7318 Print lines centered around the beginning of function
7322 Print more lines. If the last lines printed were printed with a
7323 @code{list} command, this prints lines following the last lines
7324 printed; however, if the last line printed was a solitary line printed
7325 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7326 Stack}), this prints lines centered around that line.
7329 Print lines just before the lines last printed.
7332 @cindex @code{list}, how many lines to display
7333 By default, @value{GDBN} prints ten source lines with any of these forms of
7334 the @code{list} command. You can change this using @code{set listsize}:
7337 @kindex set listsize
7338 @item set listsize @var{count}
7339 @itemx set listsize unlimited
7340 Make the @code{list} command display @var{count} source lines (unless
7341 the @code{list} argument explicitly specifies some other number).
7342 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7344 @kindex show listsize
7346 Display the number of lines that @code{list} prints.
7349 Repeating a @code{list} command with @key{RET} discards the argument,
7350 so it is equivalent to typing just @code{list}. This is more useful
7351 than listing the same lines again. An exception is made for an
7352 argument of @samp{-}; that argument is preserved in repetition so that
7353 each repetition moves up in the source file.
7355 In general, the @code{list} command expects you to supply zero, one or two
7356 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7357 of writing them (@pxref{Specify Location}), but the effect is always
7358 to specify some source line.
7360 Here is a complete description of the possible arguments for @code{list}:
7363 @item list @var{linespec}
7364 Print lines centered around the line specified by @var{linespec}.
7366 @item list @var{first},@var{last}
7367 Print lines from @var{first} to @var{last}. Both arguments are
7368 linespecs. When a @code{list} command has two linespecs, and the
7369 source file of the second linespec is omitted, this refers to
7370 the same source file as the first linespec.
7372 @item list ,@var{last}
7373 Print lines ending with @var{last}.
7375 @item list @var{first},
7376 Print lines starting with @var{first}.
7379 Print lines just after the lines last printed.
7382 Print lines just before the lines last printed.
7385 As described in the preceding table.
7388 @node Specify Location
7389 @section Specifying a Location
7390 @cindex specifying location
7393 Several @value{GDBN} commands accept arguments that specify a location
7394 of your program's code. Since @value{GDBN} is a source-level
7395 debugger, a location usually specifies some line in the source code;
7396 for that reason, locations are also known as @dfn{linespecs}.
7398 Here are all the different ways of specifying a code location that
7399 @value{GDBN} understands:
7403 Specifies the line number @var{linenum} of the current source file.
7406 @itemx +@var{offset}
7407 Specifies the line @var{offset} lines before or after the @dfn{current
7408 line}. For the @code{list} command, the current line is the last one
7409 printed; for the breakpoint commands, this is the line at which
7410 execution stopped in the currently selected @dfn{stack frame}
7411 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7412 used as the second of the two linespecs in a @code{list} command,
7413 this specifies the line @var{offset} lines up or down from the first
7416 @item @var{filename}:@var{linenum}
7417 Specifies the line @var{linenum} in the source file @var{filename}.
7418 If @var{filename} is a relative file name, then it will match any
7419 source file name with the same trailing components. For example, if
7420 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7421 name of @file{/build/trunk/gcc/expr.c}, but not
7422 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7424 @item @var{function}
7425 Specifies the line that begins the body of the function @var{function}.
7426 For example, in C, this is the line with the open brace.
7428 @item @var{function}:@var{label}
7429 Specifies the line where @var{label} appears in @var{function}.
7431 @item @var{filename}:@var{function}
7432 Specifies the line that begins the body of the function @var{function}
7433 in the file @var{filename}. You only need the file name with a
7434 function name to avoid ambiguity when there are identically named
7435 functions in different source files.
7438 Specifies the line at which the label named @var{label} appears.
7439 @value{GDBN} searches for the label in the function corresponding to
7440 the currently selected stack frame. If there is no current selected
7441 stack frame (for instance, if the inferior is not running), then
7442 @value{GDBN} will not search for a label.
7444 @item *@var{address}
7445 Specifies the program address @var{address}. For line-oriented
7446 commands, such as @code{list} and @code{edit}, this specifies a source
7447 line that contains @var{address}. For @code{break} and other
7448 breakpoint oriented commands, this can be used to set breakpoints in
7449 parts of your program which do not have debugging information or
7452 Here @var{address} may be any expression valid in the current working
7453 language (@pxref{Languages, working language}) that specifies a code
7454 address. In addition, as a convenience, @value{GDBN} extends the
7455 semantics of expressions used in locations to cover the situations
7456 that frequently happen during debugging. Here are the various forms
7460 @item @var{expression}
7461 Any expression valid in the current working language.
7463 @item @var{funcaddr}
7464 An address of a function or procedure derived from its name. In C,
7465 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7466 simply the function's name @var{function} (and actually a special case
7467 of a valid expression). In Pascal and Modula-2, this is
7468 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7469 (although the Pascal form also works).
7471 This form specifies the address of the function's first instruction,
7472 before the stack frame and arguments have been set up.
7474 @item '@var{filename}'::@var{funcaddr}
7475 Like @var{funcaddr} above, but also specifies the name of the source
7476 file explicitly. This is useful if the name of the function does not
7477 specify the function unambiguously, e.g., if there are several
7478 functions with identical names in different source files.
7481 @cindex breakpoint at static probe point
7482 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7483 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7484 applications to embed static probes. @xref{Static Probe Points}, for more
7485 information on finding and using static probes. This form of linespec
7486 specifies the location of such a static probe.
7488 If @var{objfile} is given, only probes coming from that shared library
7489 or executable matching @var{objfile} as a regular expression are considered.
7490 If @var{provider} is given, then only probes from that provider are considered.
7491 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7492 each one of those probes.
7498 @section Editing Source Files
7499 @cindex editing source files
7502 @kindex e @r{(@code{edit})}
7503 To edit the lines in a source file, use the @code{edit} command.
7504 The editing program of your choice
7505 is invoked with the current line set to
7506 the active line in the program.
7507 Alternatively, there are several ways to specify what part of the file you
7508 want to print if you want to see other parts of the program:
7511 @item edit @var{location}
7512 Edit the source file specified by @code{location}. Editing starts at
7513 that @var{location}, e.g., at the specified source line of the
7514 specified file. @xref{Specify Location}, for all the possible forms
7515 of the @var{location} argument; here are the forms of the @code{edit}
7516 command most commonly used:
7519 @item edit @var{number}
7520 Edit the current source file with @var{number} as the active line number.
7522 @item edit @var{function}
7523 Edit the file containing @var{function} at the beginning of its definition.
7528 @subsection Choosing your Editor
7529 You can customize @value{GDBN} to use any editor you want
7531 The only restriction is that your editor (say @code{ex}), recognizes the
7532 following command-line syntax:
7534 ex +@var{number} file
7536 The optional numeric value +@var{number} specifies the number of the line in
7537 the file where to start editing.}.
7538 By default, it is @file{@value{EDITOR}}, but you can change this
7539 by setting the environment variable @code{EDITOR} before using
7540 @value{GDBN}. For example, to configure @value{GDBN} to use the
7541 @code{vi} editor, you could use these commands with the @code{sh} shell:
7547 or in the @code{csh} shell,
7549 setenv EDITOR /usr/bin/vi
7554 @section Searching Source Files
7555 @cindex searching source files
7557 There are two commands for searching through the current source file for a
7562 @kindex forward-search
7563 @kindex fo @r{(@code{forward-search})}
7564 @item forward-search @var{regexp}
7565 @itemx search @var{regexp}
7566 The command @samp{forward-search @var{regexp}} checks each line,
7567 starting with the one following the last line listed, for a match for
7568 @var{regexp}. It lists the line that is found. You can use the
7569 synonym @samp{search @var{regexp}} or abbreviate the command name as
7572 @kindex reverse-search
7573 @item reverse-search @var{regexp}
7574 The command @samp{reverse-search @var{regexp}} checks each line, starting
7575 with the one before the last line listed and going backward, for a match
7576 for @var{regexp}. It lists the line that is found. You can abbreviate
7577 this command as @code{rev}.
7581 @section Specifying Source Directories
7584 @cindex directories for source files
7585 Executable programs sometimes do not record the directories of the source
7586 files from which they were compiled, just the names. Even when they do,
7587 the directories could be moved between the compilation and your debugging
7588 session. @value{GDBN} has a list of directories to search for source files;
7589 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7590 it tries all the directories in the list, in the order they are present
7591 in the list, until it finds a file with the desired name.
7593 For example, suppose an executable references the file
7594 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7595 @file{/mnt/cross}. The file is first looked up literally; if this
7596 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7597 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7598 message is printed. @value{GDBN} does not look up the parts of the
7599 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7600 Likewise, the subdirectories of the source path are not searched: if
7601 the source path is @file{/mnt/cross}, and the binary refers to
7602 @file{foo.c}, @value{GDBN} would not find it under
7603 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7605 Plain file names, relative file names with leading directories, file
7606 names containing dots, etc.@: are all treated as described above; for
7607 instance, if the source path is @file{/mnt/cross}, and the source file
7608 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7609 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7610 that---@file{/mnt/cross/foo.c}.
7612 Note that the executable search path is @emph{not} used to locate the
7615 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7616 any information it has cached about where source files are found and where
7617 each line is in the file.
7621 When you start @value{GDBN}, its source path includes only @samp{cdir}
7622 and @samp{cwd}, in that order.
7623 To add other directories, use the @code{directory} command.
7625 The search path is used to find both program source files and @value{GDBN}
7626 script files (read using the @samp{-command} option and @samp{source} command).
7628 In addition to the source path, @value{GDBN} provides a set of commands
7629 that manage a list of source path substitution rules. A @dfn{substitution
7630 rule} specifies how to rewrite source directories stored in the program's
7631 debug information in case the sources were moved to a different
7632 directory between compilation and debugging. A rule is made of
7633 two strings, the first specifying what needs to be rewritten in
7634 the path, and the second specifying how it should be rewritten.
7635 In @ref{set substitute-path}, we name these two parts @var{from} and
7636 @var{to} respectively. @value{GDBN} does a simple string replacement
7637 of @var{from} with @var{to} at the start of the directory part of the
7638 source file name, and uses that result instead of the original file
7639 name to look up the sources.
7641 Using the previous example, suppose the @file{foo-1.0} tree has been
7642 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7643 @value{GDBN} to replace @file{/usr/src} in all source path names with
7644 @file{/mnt/cross}. The first lookup will then be
7645 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7646 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7647 substitution rule, use the @code{set substitute-path} command
7648 (@pxref{set substitute-path}).
7650 To avoid unexpected substitution results, a rule is applied only if the
7651 @var{from} part of the directory name ends at a directory separator.
7652 For instance, a rule substituting @file{/usr/source} into
7653 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7654 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7655 is applied only at the beginning of the directory name, this rule will
7656 not be applied to @file{/root/usr/source/baz.c} either.
7658 In many cases, you can achieve the same result using the @code{directory}
7659 command. However, @code{set substitute-path} can be more efficient in
7660 the case where the sources are organized in a complex tree with multiple
7661 subdirectories. With the @code{directory} command, you need to add each
7662 subdirectory of your project. If you moved the entire tree while
7663 preserving its internal organization, then @code{set substitute-path}
7664 allows you to direct the debugger to all the sources with one single
7667 @code{set substitute-path} is also more than just a shortcut command.
7668 The source path is only used if the file at the original location no
7669 longer exists. On the other hand, @code{set substitute-path} modifies
7670 the debugger behavior to look at the rewritten location instead. So, if
7671 for any reason a source file that is not relevant to your executable is
7672 located at the original location, a substitution rule is the only
7673 method available to point @value{GDBN} at the new location.
7675 @cindex @samp{--with-relocated-sources}
7676 @cindex default source path substitution
7677 You can configure a default source path substitution rule by
7678 configuring @value{GDBN} with the
7679 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7680 should be the name of a directory under @value{GDBN}'s configured
7681 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7682 directory names in debug information under @var{dir} will be adjusted
7683 automatically if the installed @value{GDBN} is moved to a new
7684 location. This is useful if @value{GDBN}, libraries or executables
7685 with debug information and corresponding source code are being moved
7689 @item directory @var{dirname} @dots{}
7690 @item dir @var{dirname} @dots{}
7691 Add directory @var{dirname} to the front of the source path. Several
7692 directory names may be given to this command, separated by @samp{:}
7693 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7694 part of absolute file names) or
7695 whitespace. You may specify a directory that is already in the source
7696 path; this moves it forward, so @value{GDBN} searches it sooner.
7700 @vindex $cdir@r{, convenience variable}
7701 @vindex $cwd@r{, convenience variable}
7702 @cindex compilation directory
7703 @cindex current directory
7704 @cindex working directory
7705 @cindex directory, current
7706 @cindex directory, compilation
7707 You can use the string @samp{$cdir} to refer to the compilation
7708 directory (if one is recorded), and @samp{$cwd} to refer to the current
7709 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7710 tracks the current working directory as it changes during your @value{GDBN}
7711 session, while the latter is immediately expanded to the current
7712 directory at the time you add an entry to the source path.
7715 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7717 @c RET-repeat for @code{directory} is explicitly disabled, but since
7718 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7720 @item set directories @var{path-list}
7721 @kindex set directories
7722 Set the source path to @var{path-list}.
7723 @samp{$cdir:$cwd} are added if missing.
7725 @item show directories
7726 @kindex show directories
7727 Print the source path: show which directories it contains.
7729 @anchor{set substitute-path}
7730 @item set substitute-path @var{from} @var{to}
7731 @kindex set substitute-path
7732 Define a source path substitution rule, and add it at the end of the
7733 current list of existing substitution rules. If a rule with the same
7734 @var{from} was already defined, then the old rule is also deleted.
7736 For example, if the file @file{/foo/bar/baz.c} was moved to
7737 @file{/mnt/cross/baz.c}, then the command
7740 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7744 will tell @value{GDBN} to replace @samp{/usr/src} with
7745 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7746 @file{baz.c} even though it was moved.
7748 In the case when more than one substitution rule have been defined,
7749 the rules are evaluated one by one in the order where they have been
7750 defined. The first one matching, if any, is selected to perform
7753 For instance, if we had entered the following commands:
7756 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7757 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7761 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7762 @file{/mnt/include/defs.h} by using the first rule. However, it would
7763 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7764 @file{/mnt/src/lib/foo.c}.
7767 @item unset substitute-path [path]
7768 @kindex unset substitute-path
7769 If a path is specified, search the current list of substitution rules
7770 for a rule that would rewrite that path. Delete that rule if found.
7771 A warning is emitted by the debugger if no rule could be found.
7773 If no path is specified, then all substitution rules are deleted.
7775 @item show substitute-path [path]
7776 @kindex show substitute-path
7777 If a path is specified, then print the source path substitution rule
7778 which would rewrite that path, if any.
7780 If no path is specified, then print all existing source path substitution
7785 If your source path is cluttered with directories that are no longer of
7786 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7787 versions of source. You can correct the situation as follows:
7791 Use @code{directory} with no argument to reset the source path to its default value.
7794 Use @code{directory} with suitable arguments to reinstall the
7795 directories you want in the source path. You can add all the
7796 directories in one command.
7800 @section Source and Machine Code
7801 @cindex source line and its code address
7803 You can use the command @code{info line} to map source lines to program
7804 addresses (and vice versa), and the command @code{disassemble} to display
7805 a range of addresses as machine instructions. You can use the command
7806 @code{set disassemble-next-line} to set whether to disassemble next
7807 source line when execution stops. When run under @sc{gnu} Emacs
7808 mode, the @code{info line} command causes the arrow to point to the
7809 line specified. Also, @code{info line} prints addresses in symbolic form as
7814 @item info line @var{linespec}
7815 Print the starting and ending addresses of the compiled code for
7816 source line @var{linespec}. You can specify source lines in any of
7817 the ways documented in @ref{Specify Location}.
7820 For example, we can use @code{info line} to discover the location of
7821 the object code for the first line of function
7822 @code{m4_changequote}:
7824 @c FIXME: I think this example should also show the addresses in
7825 @c symbolic form, as they usually would be displayed.
7827 (@value{GDBP}) info line m4_changequote
7828 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7832 @cindex code address and its source line
7833 We can also inquire (using @code{*@var{addr}} as the form for
7834 @var{linespec}) what source line covers a particular address:
7836 (@value{GDBP}) info line *0x63ff
7837 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7840 @cindex @code{$_} and @code{info line}
7841 @cindex @code{x} command, default address
7842 @kindex x@r{(examine), and} info line
7843 After @code{info line}, the default address for the @code{x} command
7844 is changed to the starting address of the line, so that @samp{x/i} is
7845 sufficient to begin examining the machine code (@pxref{Memory,
7846 ,Examining Memory}). Also, this address is saved as the value of the
7847 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7852 @cindex assembly instructions
7853 @cindex instructions, assembly
7854 @cindex machine instructions
7855 @cindex listing machine instructions
7857 @itemx disassemble /m
7858 @itemx disassemble /r
7859 This specialized command dumps a range of memory as machine
7860 instructions. It can also print mixed source+disassembly by specifying
7861 the @code{/m} modifier and print the raw instructions in hex as well as
7862 in symbolic form by specifying the @code{/r}.
7863 The default memory range is the function surrounding the
7864 program counter of the selected frame. A single argument to this
7865 command is a program counter value; @value{GDBN} dumps the function
7866 surrounding this value. When two arguments are given, they should
7867 be separated by a comma, possibly surrounded by whitespace. The
7868 arguments specify a range of addresses to dump, in one of two forms:
7871 @item @var{start},@var{end}
7872 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7873 @item @var{start},+@var{length}
7874 the addresses from @var{start} (inclusive) to
7875 @code{@var{start}+@var{length}} (exclusive).
7879 When 2 arguments are specified, the name of the function is also
7880 printed (since there could be several functions in the given range).
7882 The argument(s) can be any expression yielding a numeric value, such as
7883 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7885 If the range of memory being disassembled contains current program counter,
7886 the instruction at that location is shown with a @code{=>} marker.
7889 The following example shows the disassembly of a range of addresses of
7890 HP PA-RISC 2.0 code:
7893 (@value{GDBP}) disas 0x32c4, 0x32e4
7894 Dump of assembler code from 0x32c4 to 0x32e4:
7895 0x32c4 <main+204>: addil 0,dp
7896 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7897 0x32cc <main+212>: ldil 0x3000,r31
7898 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7899 0x32d4 <main+220>: ldo 0(r31),rp
7900 0x32d8 <main+224>: addil -0x800,dp
7901 0x32dc <main+228>: ldo 0x588(r1),r26
7902 0x32e0 <main+232>: ldil 0x3000,r31
7903 End of assembler dump.
7906 Here is an example showing mixed source+assembly for Intel x86, when the
7907 program is stopped just after function prologue:
7910 (@value{GDBP}) disas /m main
7911 Dump of assembler code for function main:
7913 0x08048330 <+0>: push %ebp
7914 0x08048331 <+1>: mov %esp,%ebp
7915 0x08048333 <+3>: sub $0x8,%esp
7916 0x08048336 <+6>: and $0xfffffff0,%esp
7917 0x08048339 <+9>: sub $0x10,%esp
7919 6 printf ("Hello.\n");
7920 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7921 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7925 0x08048348 <+24>: mov $0x0,%eax
7926 0x0804834d <+29>: leave
7927 0x0804834e <+30>: ret
7929 End of assembler dump.
7932 Here is another example showing raw instructions in hex for AMD x86-64,
7935 (gdb) disas /r 0x400281,+10
7936 Dump of assembler code from 0x400281 to 0x40028b:
7937 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7938 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7939 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7940 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7941 End of assembler dump.
7944 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7945 So, for example, if you want to disassemble function @code{bar}
7946 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7947 and not @samp{disassemble foo.c:bar}.
7949 Some architectures have more than one commonly-used set of instruction
7950 mnemonics or other syntax.
7952 For programs that were dynamically linked and use shared libraries,
7953 instructions that call functions or branch to locations in the shared
7954 libraries might show a seemingly bogus location---it's actually a
7955 location of the relocation table. On some architectures, @value{GDBN}
7956 might be able to resolve these to actual function names.
7959 @kindex set disassembly-flavor
7960 @cindex Intel disassembly flavor
7961 @cindex AT&T disassembly flavor
7962 @item set disassembly-flavor @var{instruction-set}
7963 Select the instruction set to use when disassembling the
7964 program via the @code{disassemble} or @code{x/i} commands.
7966 Currently this command is only defined for the Intel x86 family. You
7967 can set @var{instruction-set} to either @code{intel} or @code{att}.
7968 The default is @code{att}, the AT&T flavor used by default by Unix
7969 assemblers for x86-based targets.
7971 @kindex show disassembly-flavor
7972 @item show disassembly-flavor
7973 Show the current setting of the disassembly flavor.
7977 @kindex set disassemble-next-line
7978 @kindex show disassemble-next-line
7979 @item set disassemble-next-line
7980 @itemx show disassemble-next-line
7981 Control whether or not @value{GDBN} will disassemble the next source
7982 line or instruction when execution stops. If ON, @value{GDBN} will
7983 display disassembly of the next source line when execution of the
7984 program being debugged stops. This is @emph{in addition} to
7985 displaying the source line itself, which @value{GDBN} always does if
7986 possible. If the next source line cannot be displayed for some reason
7987 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7988 info in the debug info), @value{GDBN} will display disassembly of the
7989 next @emph{instruction} instead of showing the next source line. If
7990 AUTO, @value{GDBN} will display disassembly of next instruction only
7991 if the source line cannot be displayed. This setting causes
7992 @value{GDBN} to display some feedback when you step through a function
7993 with no line info or whose source file is unavailable. The default is
7994 OFF, which means never display the disassembly of the next line or
8000 @chapter Examining Data
8002 @cindex printing data
8003 @cindex examining data
8006 The usual way to examine data in your program is with the @code{print}
8007 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8008 evaluates and prints the value of an expression of the language your
8009 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8010 Different Languages}). It may also print the expression using a
8011 Python-based pretty-printer (@pxref{Pretty Printing}).
8014 @item print @var{expr}
8015 @itemx print /@var{f} @var{expr}
8016 @var{expr} is an expression (in the source language). By default the
8017 value of @var{expr} is printed in a format appropriate to its data type;
8018 you can choose a different format by specifying @samp{/@var{f}}, where
8019 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8023 @itemx print /@var{f}
8024 @cindex reprint the last value
8025 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8026 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8027 conveniently inspect the same value in an alternative format.
8030 A more low-level way of examining data is with the @code{x} command.
8031 It examines data in memory at a specified address and prints it in a
8032 specified format. @xref{Memory, ,Examining Memory}.
8034 If you are interested in information about types, or about how the
8035 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8036 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8039 @cindex exploring hierarchical data structures
8041 Another way of examining values of expressions and type information is
8042 through the Python extension command @code{explore} (available only if
8043 the @value{GDBN} build is configured with @code{--with-python}). It
8044 offers an interactive way to start at the highest level (or, the most
8045 abstract level) of the data type of an expression (or, the data type
8046 itself) and explore all the way down to leaf scalar values/fields
8047 embedded in the higher level data types.
8050 @item explore @var{arg}
8051 @var{arg} is either an expression (in the source language), or a type
8052 visible in the current context of the program being debugged.
8055 The working of the @code{explore} command can be illustrated with an
8056 example. If a data type @code{struct ComplexStruct} is defined in your
8066 struct ComplexStruct
8068 struct SimpleStruct *ss_p;
8074 followed by variable declarations as
8077 struct SimpleStruct ss = @{ 10, 1.11 @};
8078 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8082 then, the value of the variable @code{cs} can be explored using the
8083 @code{explore} command as follows.
8087 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8088 the following fields:
8090 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8091 arr = <Enter 1 to explore this field of type `int [10]'>
8093 Enter the field number of choice:
8097 Since the fields of @code{cs} are not scalar values, you are being
8098 prompted to chose the field you want to explore. Let's say you choose
8099 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8100 pointer, you will be asked if it is pointing to a single value. From
8101 the declaration of @code{cs} above, it is indeed pointing to a single
8102 value, hence you enter @code{y}. If you enter @code{n}, then you will
8103 be asked if it were pointing to an array of values, in which case this
8104 field will be explored as if it were an array.
8107 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8108 Continue exploring it as a pointer to a single value [y/n]: y
8109 The value of `*(cs.ss_p)' is a struct/class of type `struct
8110 SimpleStruct' with the following fields:
8112 i = 10 .. (Value of type `int')
8113 d = 1.1100000000000001 .. (Value of type `double')
8115 Press enter to return to parent value:
8119 If the field @code{arr} of @code{cs} was chosen for exploration by
8120 entering @code{1} earlier, then since it is as array, you will be
8121 prompted to enter the index of the element in the array that you want
8125 `cs.arr' is an array of `int'.
8126 Enter the index of the element you want to explore in `cs.arr': 5
8128 `(cs.arr)[5]' is a scalar value of type `int'.
8132 Press enter to return to parent value:
8135 In general, at any stage of exploration, you can go deeper towards the
8136 leaf values by responding to the prompts appropriately, or hit the
8137 return key to return to the enclosing data structure (the @i{higher}
8138 level data structure).
8140 Similar to exploring values, you can use the @code{explore} command to
8141 explore types. Instead of specifying a value (which is typically a
8142 variable name or an expression valid in the current context of the
8143 program being debugged), you specify a type name. If you consider the
8144 same example as above, your can explore the type
8145 @code{struct ComplexStruct} by passing the argument
8146 @code{struct ComplexStruct} to the @code{explore} command.
8149 (gdb) explore struct ComplexStruct
8153 By responding to the prompts appropriately in the subsequent interactive
8154 session, you can explore the type @code{struct ComplexStruct} in a
8155 manner similar to how the value @code{cs} was explored in the above
8158 The @code{explore} command also has two sub-commands,
8159 @code{explore value} and @code{explore type}. The former sub-command is
8160 a way to explicitly specify that value exploration of the argument is
8161 being invoked, while the latter is a way to explicitly specify that type
8162 exploration of the argument is being invoked.
8165 @item explore value @var{expr}
8166 @cindex explore value
8167 This sub-command of @code{explore} explores the value of the
8168 expression @var{expr} (if @var{expr} is an expression valid in the
8169 current context of the program being debugged). The behavior of this
8170 command is identical to that of the behavior of the @code{explore}
8171 command being passed the argument @var{expr}.
8173 @item explore type @var{arg}
8174 @cindex explore type
8175 This sub-command of @code{explore} explores the type of @var{arg} (if
8176 @var{arg} is a type visible in the current context of program being
8177 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8178 is an expression valid in the current context of the program being
8179 debugged). If @var{arg} is a type, then the behavior of this command is
8180 identical to that of the @code{explore} command being passed the
8181 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8182 this command will be identical to that of the @code{explore} command
8183 being passed the type of @var{arg} as the argument.
8187 * Expressions:: Expressions
8188 * Ambiguous Expressions:: Ambiguous Expressions
8189 * Variables:: Program variables
8190 * Arrays:: Artificial arrays
8191 * Output Formats:: Output formats
8192 * Memory:: Examining memory
8193 * Auto Display:: Automatic display
8194 * Print Settings:: Print settings
8195 * Pretty Printing:: Python pretty printing
8196 * Value History:: Value history
8197 * Convenience Vars:: Convenience variables
8198 * Convenience Funs:: Convenience functions
8199 * Registers:: Registers
8200 * Floating Point Hardware:: Floating point hardware
8201 * Vector Unit:: Vector Unit
8202 * OS Information:: Auxiliary data provided by operating system
8203 * Memory Region Attributes:: Memory region attributes
8204 * Dump/Restore Files:: Copy between memory and a file
8205 * Core File Generation:: Cause a program dump its core
8206 * Character Sets:: Debugging programs that use a different
8207 character set than GDB does
8208 * Caching Target Data:: Data caching for targets
8209 * Searching Memory:: Searching memory for a sequence of bytes
8213 @section Expressions
8216 @code{print} and many other @value{GDBN} commands accept an expression and
8217 compute its value. Any kind of constant, variable or operator defined
8218 by the programming language you are using is valid in an expression in
8219 @value{GDBN}. This includes conditional expressions, function calls,
8220 casts, and string constants. It also includes preprocessor macros, if
8221 you compiled your program to include this information; see
8224 @cindex arrays in expressions
8225 @value{GDBN} supports array constants in expressions input by
8226 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8227 you can use the command @code{print @{1, 2, 3@}} to create an array
8228 of three integers. If you pass an array to a function or assign it
8229 to a program variable, @value{GDBN} copies the array to memory that
8230 is @code{malloc}ed in the target program.
8232 Because C is so widespread, most of the expressions shown in examples in
8233 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8234 Languages}, for information on how to use expressions in other
8237 In this section, we discuss operators that you can use in @value{GDBN}
8238 expressions regardless of your programming language.
8240 @cindex casts, in expressions
8241 Casts are supported in all languages, not just in C, because it is so
8242 useful to cast a number into a pointer in order to examine a structure
8243 at that address in memory.
8244 @c FIXME: casts supported---Mod2 true?
8246 @value{GDBN} supports these operators, in addition to those common
8247 to programming languages:
8251 @samp{@@} is a binary operator for treating parts of memory as arrays.
8252 @xref{Arrays, ,Artificial Arrays}, for more information.
8255 @samp{::} allows you to specify a variable in terms of the file or
8256 function where it is defined. @xref{Variables, ,Program Variables}.
8258 @cindex @{@var{type}@}
8259 @cindex type casting memory
8260 @cindex memory, viewing as typed object
8261 @cindex casts, to view memory
8262 @item @{@var{type}@} @var{addr}
8263 Refers to an object of type @var{type} stored at address @var{addr} in
8264 memory. The address @var{addr} may be any expression whose value is
8265 an integer or pointer (but parentheses are required around binary
8266 operators, just as in a cast). This construct is allowed regardless
8267 of what kind of data is normally supposed to reside at @var{addr}.
8270 @node Ambiguous Expressions
8271 @section Ambiguous Expressions
8272 @cindex ambiguous expressions
8274 Expressions can sometimes contain some ambiguous elements. For instance,
8275 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8276 a single function name to be defined several times, for application in
8277 different contexts. This is called @dfn{overloading}. Another example
8278 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8279 templates and is typically instantiated several times, resulting in
8280 the same function name being defined in different contexts.
8282 In some cases and depending on the language, it is possible to adjust
8283 the expression to remove the ambiguity. For instance in C@t{++}, you
8284 can specify the signature of the function you want to break on, as in
8285 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8286 qualified name of your function often makes the expression unambiguous
8289 When an ambiguity that needs to be resolved is detected, the debugger
8290 has the capability to display a menu of numbered choices for each
8291 possibility, and then waits for the selection with the prompt @samp{>}.
8292 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8293 aborts the current command. If the command in which the expression was
8294 used allows more than one choice to be selected, the next option in the
8295 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8298 For example, the following session excerpt shows an attempt to set a
8299 breakpoint at the overloaded symbol @code{String::after}.
8300 We choose three particular definitions of that function name:
8302 @c FIXME! This is likely to change to show arg type lists, at least
8305 (@value{GDBP}) b String::after
8308 [2] file:String.cc; line number:867
8309 [3] file:String.cc; line number:860
8310 [4] file:String.cc; line number:875
8311 [5] file:String.cc; line number:853
8312 [6] file:String.cc; line number:846
8313 [7] file:String.cc; line number:735
8315 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8316 Breakpoint 2 at 0xb344: file String.cc, line 875.
8317 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8318 Multiple breakpoints were set.
8319 Use the "delete" command to delete unwanted
8326 @kindex set multiple-symbols
8327 @item set multiple-symbols @var{mode}
8328 @cindex multiple-symbols menu
8330 This option allows you to adjust the debugger behavior when an expression
8333 By default, @var{mode} is set to @code{all}. If the command with which
8334 the expression is used allows more than one choice, then @value{GDBN}
8335 automatically selects all possible choices. For instance, inserting
8336 a breakpoint on a function using an ambiguous name results in a breakpoint
8337 inserted on each possible match. However, if a unique choice must be made,
8338 then @value{GDBN} uses the menu to help you disambiguate the expression.
8339 For instance, printing the address of an overloaded function will result
8340 in the use of the menu.
8342 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8343 when an ambiguity is detected.
8345 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8346 an error due to the ambiguity and the command is aborted.
8348 @kindex show multiple-symbols
8349 @item show multiple-symbols
8350 Show the current value of the @code{multiple-symbols} setting.
8354 @section Program Variables
8356 The most common kind of expression to use is the name of a variable
8359 Variables in expressions are understood in the selected stack frame
8360 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8364 global (or file-static)
8371 visible according to the scope rules of the
8372 programming language from the point of execution in that frame
8375 @noindent This means that in the function
8390 you can examine and use the variable @code{a} whenever your program is
8391 executing within the function @code{foo}, but you can only use or
8392 examine the variable @code{b} while your program is executing inside
8393 the block where @code{b} is declared.
8395 @cindex variable name conflict
8396 There is an exception: you can refer to a variable or function whose
8397 scope is a single source file even if the current execution point is not
8398 in this file. But it is possible to have more than one such variable or
8399 function with the same name (in different source files). If that
8400 happens, referring to that name has unpredictable effects. If you wish,
8401 you can specify a static variable in a particular function or file by
8402 using the colon-colon (@code{::}) notation:
8404 @cindex colon-colon, context for variables/functions
8406 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8407 @cindex @code{::}, context for variables/functions
8410 @var{file}::@var{variable}
8411 @var{function}::@var{variable}
8415 Here @var{file} or @var{function} is the name of the context for the
8416 static @var{variable}. In the case of file names, you can use quotes to
8417 make sure @value{GDBN} parses the file name as a single word---for example,
8418 to print a global value of @code{x} defined in @file{f2.c}:
8421 (@value{GDBP}) p 'f2.c'::x
8424 The @code{::} notation is normally used for referring to
8425 static variables, since you typically disambiguate uses of local variables
8426 in functions by selecting the appropriate frame and using the
8427 simple name of the variable. However, you may also use this notation
8428 to refer to local variables in frames enclosing the selected frame:
8437 process (a); /* Stop here */
8448 For example, if there is a breakpoint at the commented line,
8449 here is what you might see
8450 when the program stops after executing the call @code{bar(0)}:
8455 (@value{GDBP}) p bar::a
8458 #2 0x080483d0 in foo (a=5) at foobar.c:12
8461 (@value{GDBP}) p bar::a
8465 @cindex C@t{++} scope resolution
8466 These uses of @samp{::} are very rarely in conflict with the very
8467 similar use of the same notation in C@t{++}. When they are in
8468 conflict, the C@t{++} meaning takes precedence; however, this can be
8469 overridden by quoting the file or function name with single quotes.
8471 For example, suppose the program is stopped in a method of a class
8472 that has a field named @code{includefile}, and there is also an
8473 include file named @file{includefile} that defines a variable,
8477 (@value{GDBP}) p includefile
8479 (@value{GDBP}) p includefile::some_global
8480 A syntax error in expression, near `'.
8481 (@value{GDBP}) p 'includefile'::some_global
8485 @cindex wrong values
8486 @cindex variable values, wrong
8487 @cindex function entry/exit, wrong values of variables
8488 @cindex optimized code, wrong values of variables
8490 @emph{Warning:} Occasionally, a local variable may appear to have the
8491 wrong value at certain points in a function---just after entry to a new
8492 scope, and just before exit.
8494 You may see this problem when you are stepping by machine instructions.
8495 This is because, on most machines, it takes more than one instruction to
8496 set up a stack frame (including local variable definitions); if you are
8497 stepping by machine instructions, variables may appear to have the wrong
8498 values until the stack frame is completely built. On exit, it usually
8499 also takes more than one machine instruction to destroy a stack frame;
8500 after you begin stepping through that group of instructions, local
8501 variable definitions may be gone.
8503 This may also happen when the compiler does significant optimizations.
8504 To be sure of always seeing accurate values, turn off all optimization
8507 @cindex ``No symbol "foo" in current context''
8508 Another possible effect of compiler optimizations is to optimize
8509 unused variables out of existence, or assign variables to registers (as
8510 opposed to memory addresses). Depending on the support for such cases
8511 offered by the debug info format used by the compiler, @value{GDBN}
8512 might not be able to display values for such local variables. If that
8513 happens, @value{GDBN} will print a message like this:
8516 No symbol "foo" in current context.
8519 To solve such problems, either recompile without optimizations, or use a
8520 different debug info format, if the compiler supports several such
8521 formats. @xref{Compilation}, for more information on choosing compiler
8522 options. @xref{C, ,C and C@t{++}}, for more information about debug
8523 info formats that are best suited to C@t{++} programs.
8525 If you ask to print an object whose contents are unknown to
8526 @value{GDBN}, e.g., because its data type is not completely specified
8527 by the debug information, @value{GDBN} will say @samp{<incomplete
8528 type>}. @xref{Symbols, incomplete type}, for more about this.
8530 If you append @kbd{@@entry} string to a function parameter name you get its
8531 value at the time the function got called. If the value is not available an
8532 error message is printed. Entry values are available only with some compilers.
8533 Entry values are normally also printed at the function parameter list according
8534 to @ref{set print entry-values}.
8537 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8543 (gdb) print i@@entry
8547 Strings are identified as arrays of @code{char} values without specified
8548 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8549 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8550 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8551 defines literal string type @code{"char"} as @code{char} without a sign.
8556 signed char var1[] = "A";
8559 You get during debugging
8564 $2 = @{65 'A', 0 '\0'@}
8568 @section Artificial Arrays
8570 @cindex artificial array
8572 @kindex @@@r{, referencing memory as an array}
8573 It is often useful to print out several successive objects of the
8574 same type in memory; a section of an array, or an array of
8575 dynamically determined size for which only a pointer exists in the
8578 You can do this by referring to a contiguous span of memory as an
8579 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8580 operand of @samp{@@} should be the first element of the desired array
8581 and be an individual object. The right operand should be the desired length
8582 of the array. The result is an array value whose elements are all of
8583 the type of the left argument. The first element is actually the left
8584 argument; the second element comes from bytes of memory immediately
8585 following those that hold the first element, and so on. Here is an
8586 example. If a program says
8589 int *array = (int *) malloc (len * sizeof (int));
8593 you can print the contents of @code{array} with
8599 The left operand of @samp{@@} must reside in memory. Array values made
8600 with @samp{@@} in this way behave just like other arrays in terms of
8601 subscripting, and are coerced to pointers when used in expressions.
8602 Artificial arrays most often appear in expressions via the value history
8603 (@pxref{Value History, ,Value History}), after printing one out.
8605 Another way to create an artificial array is to use a cast.
8606 This re-interprets a value as if it were an array.
8607 The value need not be in memory:
8609 (@value{GDBP}) p/x (short[2])0x12345678
8610 $1 = @{0x1234, 0x5678@}
8613 As a convenience, if you leave the array length out (as in
8614 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8615 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8617 (@value{GDBP}) p/x (short[])0x12345678
8618 $2 = @{0x1234, 0x5678@}
8621 Sometimes the artificial array mechanism is not quite enough; in
8622 moderately complex data structures, the elements of interest may not
8623 actually be adjacent---for example, if you are interested in the values
8624 of pointers in an array. One useful work-around in this situation is
8625 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8626 Variables}) as a counter in an expression that prints the first
8627 interesting value, and then repeat that expression via @key{RET}. For
8628 instance, suppose you have an array @code{dtab} of pointers to
8629 structures, and you are interested in the values of a field @code{fv}
8630 in each structure. Here is an example of what you might type:
8640 @node Output Formats
8641 @section Output Formats
8643 @cindex formatted output
8644 @cindex output formats
8645 By default, @value{GDBN} prints a value according to its data type. Sometimes
8646 this is not what you want. For example, you might want to print a number
8647 in hex, or a pointer in decimal. Or you might want to view data in memory
8648 at a certain address as a character string or as an instruction. To do
8649 these things, specify an @dfn{output format} when you print a value.
8651 The simplest use of output formats is to say how to print a value
8652 already computed. This is done by starting the arguments of the
8653 @code{print} command with a slash and a format letter. The format
8654 letters supported are:
8658 Regard the bits of the value as an integer, and print the integer in
8662 Print as integer in signed decimal.
8665 Print as integer in unsigned decimal.
8668 Print as integer in octal.
8671 Print as integer in binary. The letter @samp{t} stands for ``two''.
8672 @footnote{@samp{b} cannot be used because these format letters are also
8673 used with the @code{x} command, where @samp{b} stands for ``byte'';
8674 see @ref{Memory,,Examining Memory}.}
8677 @cindex unknown address, locating
8678 @cindex locate address
8679 Print as an address, both absolute in hexadecimal and as an offset from
8680 the nearest preceding symbol. You can use this format used to discover
8681 where (in what function) an unknown address is located:
8684 (@value{GDBP}) p/a 0x54320
8685 $3 = 0x54320 <_initialize_vx+396>
8689 The command @code{info symbol 0x54320} yields similar results.
8690 @xref{Symbols, info symbol}.
8693 Regard as an integer and print it as a character constant. This
8694 prints both the numerical value and its character representation. The
8695 character representation is replaced with the octal escape @samp{\nnn}
8696 for characters outside the 7-bit @sc{ascii} range.
8698 Without this format, @value{GDBN} displays @code{char},
8699 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8700 constants. Single-byte members of vectors are displayed as integer
8704 Regard the bits of the value as a floating point number and print
8705 using typical floating point syntax.
8708 @cindex printing strings
8709 @cindex printing byte arrays
8710 Regard as a string, if possible. With this format, pointers to single-byte
8711 data are displayed as null-terminated strings and arrays of single-byte data
8712 are displayed as fixed-length strings. Other values are displayed in their
8715 Without this format, @value{GDBN} displays pointers to and arrays of
8716 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8717 strings. Single-byte members of a vector are displayed as an integer
8721 Like @samp{x} formatting, the value is treated as an integer and
8722 printed as hexadecimal, but leading zeros are printed to pad the value
8723 to the size of the integer type.
8726 @cindex raw printing
8727 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8728 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8729 Printing}). This typically results in a higher-level display of the
8730 value's contents. The @samp{r} format bypasses any Python
8731 pretty-printer which might exist.
8734 For example, to print the program counter in hex (@pxref{Registers}), type
8741 Note that no space is required before the slash; this is because command
8742 names in @value{GDBN} cannot contain a slash.
8744 To reprint the last value in the value history with a different format,
8745 you can use the @code{print} command with just a format and no
8746 expression. For example, @samp{p/x} reprints the last value in hex.
8749 @section Examining Memory
8751 You can use the command @code{x} (for ``examine'') to examine memory in
8752 any of several formats, independently of your program's data types.
8754 @cindex examining memory
8756 @kindex x @r{(examine memory)}
8757 @item x/@var{nfu} @var{addr}
8760 Use the @code{x} command to examine memory.
8763 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8764 much memory to display and how to format it; @var{addr} is an
8765 expression giving the address where you want to start displaying memory.
8766 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8767 Several commands set convenient defaults for @var{addr}.
8770 @item @var{n}, the repeat count
8771 The repeat count is a decimal integer; the default is 1. It specifies
8772 how much memory (counting by units @var{u}) to display.
8773 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8776 @item @var{f}, the display format
8777 The display format is one of the formats used by @code{print}
8778 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8779 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8780 The default is @samp{x} (hexadecimal) initially. The default changes
8781 each time you use either @code{x} or @code{print}.
8783 @item @var{u}, the unit size
8784 The unit size is any of
8790 Halfwords (two bytes).
8792 Words (four bytes). This is the initial default.
8794 Giant words (eight bytes).
8797 Each time you specify a unit size with @code{x}, that size becomes the
8798 default unit the next time you use @code{x}. For the @samp{i} format,
8799 the unit size is ignored and is normally not written. For the @samp{s} format,
8800 the unit size defaults to @samp{b}, unless it is explicitly given.
8801 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8802 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8803 Note that the results depend on the programming language of the
8804 current compilation unit. If the language is C, the @samp{s}
8805 modifier will use the UTF-16 encoding while @samp{w} will use
8806 UTF-32. The encoding is set by the programming language and cannot
8809 @item @var{addr}, starting display address
8810 @var{addr} is the address where you want @value{GDBN} to begin displaying
8811 memory. The expression need not have a pointer value (though it may);
8812 it is always interpreted as an integer address of a byte of memory.
8813 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8814 @var{addr} is usually just after the last address examined---but several
8815 other commands also set the default address: @code{info breakpoints} (to
8816 the address of the last breakpoint listed), @code{info line} (to the
8817 starting address of a line), and @code{print} (if you use it to display
8818 a value from memory).
8821 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8822 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8823 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8824 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8825 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8827 Since the letters indicating unit sizes are all distinct from the
8828 letters specifying output formats, you do not have to remember whether
8829 unit size or format comes first; either order works. The output
8830 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8831 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8833 Even though the unit size @var{u} is ignored for the formats @samp{s}
8834 and @samp{i}, you might still want to use a count @var{n}; for example,
8835 @samp{3i} specifies that you want to see three machine instructions,
8836 including any operands. For convenience, especially when used with
8837 the @code{display} command, the @samp{i} format also prints branch delay
8838 slot instructions, if any, beyond the count specified, which immediately
8839 follow the last instruction that is within the count. The command
8840 @code{disassemble} gives an alternative way of inspecting machine
8841 instructions; see @ref{Machine Code,,Source and Machine Code}.
8843 All the defaults for the arguments to @code{x} are designed to make it
8844 easy to continue scanning memory with minimal specifications each time
8845 you use @code{x}. For example, after you have inspected three machine
8846 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8847 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8848 the repeat count @var{n} is used again; the other arguments default as
8849 for successive uses of @code{x}.
8851 When examining machine instructions, the instruction at current program
8852 counter is shown with a @code{=>} marker. For example:
8855 (@value{GDBP}) x/5i $pc-6
8856 0x804837f <main+11>: mov %esp,%ebp
8857 0x8048381 <main+13>: push %ecx
8858 0x8048382 <main+14>: sub $0x4,%esp
8859 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8860 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8863 @cindex @code{$_}, @code{$__}, and value history
8864 The addresses and contents printed by the @code{x} command are not saved
8865 in the value history because there is often too much of them and they
8866 would get in the way. Instead, @value{GDBN} makes these values available for
8867 subsequent use in expressions as values of the convenience variables
8868 @code{$_} and @code{$__}. After an @code{x} command, the last address
8869 examined is available for use in expressions in the convenience variable
8870 @code{$_}. The contents of that address, as examined, are available in
8871 the convenience variable @code{$__}.
8873 If the @code{x} command has a repeat count, the address and contents saved
8874 are from the last memory unit printed; this is not the same as the last
8875 address printed if several units were printed on the last line of output.
8877 @cindex remote memory comparison
8878 @cindex target memory comparison
8879 @cindex verify remote memory image
8880 @cindex verify target memory image
8881 When you are debugging a program running on a remote target machine
8882 (@pxref{Remote Debugging}), you may wish to verify the program's image
8883 in the remote machine's memory against the executable file you
8884 downloaded to the target. Or, on any target, you may want to check
8885 whether the program has corrupted its own read-only sections. The
8886 @code{compare-sections} command is provided for such situations.
8889 @kindex compare-sections
8890 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8891 Compare the data of a loadable section @var{section-name} in the
8892 executable file of the program being debugged with the same section in
8893 the target machine's memory, and report any mismatches. With no
8894 arguments, compares all loadable sections. With an argument of
8895 @code{-r}, compares all loadable read-only sections.
8897 Note: for remote targets, this command can be accelerated if the
8898 target supports computing the CRC checksum of a block of memory
8899 (@pxref{qCRC packet}).
8903 @section Automatic Display
8904 @cindex automatic display
8905 @cindex display of expressions
8907 If you find that you want to print the value of an expression frequently
8908 (to see how it changes), you might want to add it to the @dfn{automatic
8909 display list} so that @value{GDBN} prints its value each time your program stops.
8910 Each expression added to the list is given a number to identify it;
8911 to remove an expression from the list, you specify that number.
8912 The automatic display looks like this:
8916 3: bar[5] = (struct hack *) 0x3804
8920 This display shows item numbers, expressions and their current values. As with
8921 displays you request manually using @code{x} or @code{print}, you can
8922 specify the output format you prefer; in fact, @code{display} decides
8923 whether to use @code{print} or @code{x} depending your format
8924 specification---it uses @code{x} if you specify either the @samp{i}
8925 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8929 @item display @var{expr}
8930 Add the expression @var{expr} to the list of expressions to display
8931 each time your program stops. @xref{Expressions, ,Expressions}.
8933 @code{display} does not repeat if you press @key{RET} again after using it.
8935 @item display/@var{fmt} @var{expr}
8936 For @var{fmt} specifying only a display format and not a size or
8937 count, add the expression @var{expr} to the auto-display list but
8938 arrange to display it each time in the specified format @var{fmt}.
8939 @xref{Output Formats,,Output Formats}.
8941 @item display/@var{fmt} @var{addr}
8942 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8943 number of units, add the expression @var{addr} as a memory address to
8944 be examined each time your program stops. Examining means in effect
8945 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8948 For example, @samp{display/i $pc} can be helpful, to see the machine
8949 instruction about to be executed each time execution stops (@samp{$pc}
8950 is a common name for the program counter; @pxref{Registers, ,Registers}).
8953 @kindex delete display
8955 @item undisplay @var{dnums}@dots{}
8956 @itemx delete display @var{dnums}@dots{}
8957 Remove items from the list of expressions to display. Specify the
8958 numbers of the displays that you want affected with the command
8959 argument @var{dnums}. It can be a single display number, one of the
8960 numbers shown in the first field of the @samp{info display} display;
8961 or it could be a range of display numbers, as in @code{2-4}.
8963 @code{undisplay} does not repeat if you press @key{RET} after using it.
8964 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8966 @kindex disable display
8967 @item disable display @var{dnums}@dots{}
8968 Disable the display of item numbers @var{dnums}. A disabled display
8969 item is not printed automatically, but is not forgotten. It may be
8970 enabled again later. Specify the numbers of the displays that you
8971 want affected with the command argument @var{dnums}. It can be a
8972 single display number, one of the numbers shown in the first field of
8973 the @samp{info display} display; or it could be a range of display
8974 numbers, as in @code{2-4}.
8976 @kindex enable display
8977 @item enable display @var{dnums}@dots{}
8978 Enable display of item numbers @var{dnums}. It becomes effective once
8979 again in auto display of its expression, until you specify otherwise.
8980 Specify the numbers of the displays that you want affected with the
8981 command argument @var{dnums}. It can be a single display number, one
8982 of the numbers shown in the first field of the @samp{info display}
8983 display; or it could be a range of display numbers, as in @code{2-4}.
8986 Display the current values of the expressions on the list, just as is
8987 done when your program stops.
8989 @kindex info display
8991 Print the list of expressions previously set up to display
8992 automatically, each one with its item number, but without showing the
8993 values. This includes disabled expressions, which are marked as such.
8994 It also includes expressions which would not be displayed right now
8995 because they refer to automatic variables not currently available.
8998 @cindex display disabled out of scope
8999 If a display expression refers to local variables, then it does not make
9000 sense outside the lexical context for which it was set up. Such an
9001 expression is disabled when execution enters a context where one of its
9002 variables is not defined. For example, if you give the command
9003 @code{display last_char} while inside a function with an argument
9004 @code{last_char}, @value{GDBN} displays this argument while your program
9005 continues to stop inside that function. When it stops elsewhere---where
9006 there is no variable @code{last_char}---the display is disabled
9007 automatically. The next time your program stops where @code{last_char}
9008 is meaningful, you can enable the display expression once again.
9010 @node Print Settings
9011 @section Print Settings
9013 @cindex format options
9014 @cindex print settings
9015 @value{GDBN} provides the following ways to control how arrays, structures,
9016 and symbols are printed.
9019 These settings are useful for debugging programs in any language:
9023 @item set print address
9024 @itemx set print address on
9025 @cindex print/don't print memory addresses
9026 @value{GDBN} prints memory addresses showing the location of stack
9027 traces, structure values, pointer values, breakpoints, and so forth,
9028 even when it also displays the contents of those addresses. The default
9029 is @code{on}. For example, this is what a stack frame display looks like with
9030 @code{set print address on}:
9035 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9037 530 if (lquote != def_lquote)
9041 @item set print address off
9042 Do not print addresses when displaying their contents. For example,
9043 this is the same stack frame displayed with @code{set print address off}:
9047 (@value{GDBP}) set print addr off
9049 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9050 530 if (lquote != def_lquote)
9054 You can use @samp{set print address off} to eliminate all machine
9055 dependent displays from the @value{GDBN} interface. For example, with
9056 @code{print address off}, you should get the same text for backtraces on
9057 all machines---whether or not they involve pointer arguments.
9060 @item show print address
9061 Show whether or not addresses are to be printed.
9064 When @value{GDBN} prints a symbolic address, it normally prints the
9065 closest earlier symbol plus an offset. If that symbol does not uniquely
9066 identify the address (for example, it is a name whose scope is a single
9067 source file), you may need to clarify. One way to do this is with
9068 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9069 you can set @value{GDBN} to print the source file and line number when
9070 it prints a symbolic address:
9073 @item set print symbol-filename on
9074 @cindex source file and line of a symbol
9075 @cindex symbol, source file and line
9076 Tell @value{GDBN} to print the source file name and line number of a
9077 symbol in the symbolic form of an address.
9079 @item set print symbol-filename off
9080 Do not print source file name and line number of a symbol. This is the
9083 @item show print symbol-filename
9084 Show whether or not @value{GDBN} will print the source file name and
9085 line number of a symbol in the symbolic form of an address.
9088 Another situation where it is helpful to show symbol filenames and line
9089 numbers is when disassembling code; @value{GDBN} shows you the line
9090 number and source file that corresponds to each instruction.
9092 Also, you may wish to see the symbolic form only if the address being
9093 printed is reasonably close to the closest earlier symbol:
9096 @item set print max-symbolic-offset @var{max-offset}
9097 @itemx set print max-symbolic-offset unlimited
9098 @cindex maximum value for offset of closest symbol
9099 Tell @value{GDBN} to only display the symbolic form of an address if the
9100 offset between the closest earlier symbol and the address is less than
9101 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9102 to always print the symbolic form of an address if any symbol precedes
9103 it. Zero is equivalent to @code{unlimited}.
9105 @item show print max-symbolic-offset
9106 Ask how large the maximum offset is that @value{GDBN} prints in a
9110 @cindex wild pointer, interpreting
9111 @cindex pointer, finding referent
9112 If you have a pointer and you are not sure where it points, try
9113 @samp{set print symbol-filename on}. Then you can determine the name
9114 and source file location of the variable where it points, using
9115 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9116 For example, here @value{GDBN} shows that a variable @code{ptt} points
9117 at another variable @code{t}, defined in @file{hi2.c}:
9120 (@value{GDBP}) set print symbol-filename on
9121 (@value{GDBP}) p/a ptt
9122 $4 = 0xe008 <t in hi2.c>
9126 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9127 does not show the symbol name and filename of the referent, even with
9128 the appropriate @code{set print} options turned on.
9131 You can also enable @samp{/a}-like formatting all the time using
9132 @samp{set print symbol on}:
9135 @item set print symbol on
9136 Tell @value{GDBN} to print the symbol corresponding to an address, if
9139 @item set print symbol off
9140 Tell @value{GDBN} not to print the symbol corresponding to an
9141 address. In this mode, @value{GDBN} will still print the symbol
9142 corresponding to pointers to functions. This is the default.
9144 @item show print symbol
9145 Show whether @value{GDBN} will display the symbol corresponding to an
9149 Other settings control how different kinds of objects are printed:
9152 @item set print array
9153 @itemx set print array on
9154 @cindex pretty print arrays
9155 Pretty print arrays. This format is more convenient to read,
9156 but uses more space. The default is off.
9158 @item set print array off
9159 Return to compressed format for arrays.
9161 @item show print array
9162 Show whether compressed or pretty format is selected for displaying
9165 @cindex print array indexes
9166 @item set print array-indexes
9167 @itemx set print array-indexes on
9168 Print the index of each element when displaying arrays. May be more
9169 convenient to locate a given element in the array or quickly find the
9170 index of a given element in that printed array. The default is off.
9172 @item set print array-indexes off
9173 Stop printing element indexes when displaying arrays.
9175 @item show print array-indexes
9176 Show whether the index of each element is printed when displaying
9179 @item set print elements @var{number-of-elements}
9180 @itemx set print elements unlimited
9181 @cindex number of array elements to print
9182 @cindex limit on number of printed array elements
9183 Set a limit on how many elements of an array @value{GDBN} will print.
9184 If @value{GDBN} is printing a large array, it stops printing after it has
9185 printed the number of elements set by the @code{set print elements} command.
9186 This limit also applies to the display of strings.
9187 When @value{GDBN} starts, this limit is set to 200.
9188 Setting @var{number-of-elements} to @code{unlimited} or zero means
9189 that the number of elements to print is unlimited.
9191 @item show print elements
9192 Display the number of elements of a large array that @value{GDBN} will print.
9193 If the number is 0, then the printing is unlimited.
9195 @item set print frame-arguments @var{value}
9196 @kindex set print frame-arguments
9197 @cindex printing frame argument values
9198 @cindex print all frame argument values
9199 @cindex print frame argument values for scalars only
9200 @cindex do not print frame argument values
9201 This command allows to control how the values of arguments are printed
9202 when the debugger prints a frame (@pxref{Frames}). The possible
9207 The values of all arguments are printed.
9210 Print the value of an argument only if it is a scalar. The value of more
9211 complex arguments such as arrays, structures, unions, etc, is replaced
9212 by @code{@dots{}}. This is the default. Here is an example where
9213 only scalar arguments are shown:
9216 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9221 None of the argument values are printed. Instead, the value of each argument
9222 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9225 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9230 By default, only scalar arguments are printed. This command can be used
9231 to configure the debugger to print the value of all arguments, regardless
9232 of their type. However, it is often advantageous to not print the value
9233 of more complex parameters. For instance, it reduces the amount of
9234 information printed in each frame, making the backtrace more readable.
9235 Also, it improves performance when displaying Ada frames, because
9236 the computation of large arguments can sometimes be CPU-intensive,
9237 especially in large applications. Setting @code{print frame-arguments}
9238 to @code{scalars} (the default) or @code{none} avoids this computation,
9239 thus speeding up the display of each Ada frame.
9241 @item show print frame-arguments
9242 Show how the value of arguments should be displayed when printing a frame.
9244 @item set print raw frame-arguments on
9245 Print frame arguments in raw, non pretty-printed, form.
9247 @item set print raw frame-arguments off
9248 Print frame arguments in pretty-printed form, if there is a pretty-printer
9249 for the value (@pxref{Pretty Printing}),
9250 otherwise print the value in raw form.
9251 This is the default.
9253 @item show print raw frame-arguments
9254 Show whether to print frame arguments in raw form.
9256 @anchor{set print entry-values}
9257 @item set print entry-values @var{value}
9258 @kindex set print entry-values
9259 Set printing of frame argument values at function entry. In some cases
9260 @value{GDBN} can determine the value of function argument which was passed by
9261 the function caller, even if the value was modified inside the called function
9262 and therefore is different. With optimized code, the current value could be
9263 unavailable, but the entry value may still be known.
9265 The default value is @code{default} (see below for its description). Older
9266 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9267 this feature will behave in the @code{default} setting the same way as with the
9270 This functionality is currently supported only by DWARF 2 debugging format and
9271 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9272 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9275 The @var{value} parameter can be one of the following:
9279 Print only actual parameter values, never print values from function entry
9283 #0 different (val=6)
9284 #0 lost (val=<optimized out>)
9286 #0 invalid (val=<optimized out>)
9290 Print only parameter values from function entry point. The actual parameter
9291 values are never printed.
9293 #0 equal (val@@entry=5)
9294 #0 different (val@@entry=5)
9295 #0 lost (val@@entry=5)
9296 #0 born (val@@entry=<optimized out>)
9297 #0 invalid (val@@entry=<optimized out>)
9301 Print only parameter values from function entry point. If value from function
9302 entry point is not known while the actual value is known, print the actual
9303 value for such parameter.
9305 #0 equal (val@@entry=5)
9306 #0 different (val@@entry=5)
9307 #0 lost (val@@entry=5)
9309 #0 invalid (val@@entry=<optimized out>)
9313 Print actual parameter values. If actual parameter value is not known while
9314 value from function entry point is known, print the entry point value for such
9318 #0 different (val=6)
9319 #0 lost (val@@entry=5)
9321 #0 invalid (val=<optimized out>)
9325 Always print both the actual parameter value and its value from function entry
9326 point, even if values of one or both are not available due to compiler
9329 #0 equal (val=5, val@@entry=5)
9330 #0 different (val=6, val@@entry=5)
9331 #0 lost (val=<optimized out>, val@@entry=5)
9332 #0 born (val=10, val@@entry=<optimized out>)
9333 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9337 Print the actual parameter value if it is known and also its value from
9338 function entry point if it is known. If neither is known, print for the actual
9339 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9340 values are known and identical, print the shortened
9341 @code{param=param@@entry=VALUE} notation.
9343 #0 equal (val=val@@entry=5)
9344 #0 different (val=6, val@@entry=5)
9345 #0 lost (val@@entry=5)
9347 #0 invalid (val=<optimized out>)
9351 Always print the actual parameter value. Print also its value from function
9352 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9353 if both values are known and identical, print the shortened
9354 @code{param=param@@entry=VALUE} notation.
9356 #0 equal (val=val@@entry=5)
9357 #0 different (val=6, val@@entry=5)
9358 #0 lost (val=<optimized out>, val@@entry=5)
9360 #0 invalid (val=<optimized out>)
9364 For analysis messages on possible failures of frame argument values at function
9365 entry resolution see @ref{set debug entry-values}.
9367 @item show print entry-values
9368 Show the method being used for printing of frame argument values at function
9371 @item set print repeats @var{number-of-repeats}
9372 @itemx set print repeats unlimited
9373 @cindex repeated array elements
9374 Set the threshold for suppressing display of repeated array
9375 elements. When the number of consecutive identical elements of an
9376 array exceeds the threshold, @value{GDBN} prints the string
9377 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9378 identical repetitions, instead of displaying the identical elements
9379 themselves. Setting the threshold to @code{unlimited} or zero will
9380 cause all elements to be individually printed. The default threshold
9383 @item show print repeats
9384 Display the current threshold for printing repeated identical
9387 @item set print null-stop
9388 @cindex @sc{null} elements in arrays
9389 Cause @value{GDBN} to stop printing the characters of an array when the first
9390 @sc{null} is encountered. This is useful when large arrays actually
9391 contain only short strings.
9394 @item show print null-stop
9395 Show whether @value{GDBN} stops printing an array on the first
9396 @sc{null} character.
9398 @item set print pretty on
9399 @cindex print structures in indented form
9400 @cindex indentation in structure display
9401 Cause @value{GDBN} to print structures in an indented format with one member
9402 per line, like this:
9417 @item set print pretty off
9418 Cause @value{GDBN} to print structures in a compact format, like this:
9422 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9423 meat = 0x54 "Pork"@}
9428 This is the default format.
9430 @item show print pretty
9431 Show which format @value{GDBN} is using to print structures.
9433 @item set print sevenbit-strings on
9434 @cindex eight-bit characters in strings
9435 @cindex octal escapes in strings
9436 Print using only seven-bit characters; if this option is set,
9437 @value{GDBN} displays any eight-bit characters (in strings or
9438 character values) using the notation @code{\}@var{nnn}. This setting is
9439 best if you are working in English (@sc{ascii}) and you use the
9440 high-order bit of characters as a marker or ``meta'' bit.
9442 @item set print sevenbit-strings off
9443 Print full eight-bit characters. This allows the use of more
9444 international character sets, and is the default.
9446 @item show print sevenbit-strings
9447 Show whether or not @value{GDBN} is printing only seven-bit characters.
9449 @item set print union on
9450 @cindex unions in structures, printing
9451 Tell @value{GDBN} to print unions which are contained in structures
9452 and other unions. This is the default setting.
9454 @item set print union off
9455 Tell @value{GDBN} not to print unions which are contained in
9456 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9459 @item show print union
9460 Ask @value{GDBN} whether or not it will print unions which are contained in
9461 structures and other unions.
9463 For example, given the declarations
9466 typedef enum @{Tree, Bug@} Species;
9467 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9468 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9479 struct thing foo = @{Tree, @{Acorn@}@};
9483 with @code{set print union on} in effect @samp{p foo} would print
9486 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9490 and with @code{set print union off} in effect it would print
9493 $1 = @{it = Tree, form = @{...@}@}
9497 @code{set print union} affects programs written in C-like languages
9503 These settings are of interest when debugging C@t{++} programs:
9506 @cindex demangling C@t{++} names
9507 @item set print demangle
9508 @itemx set print demangle on
9509 Print C@t{++} names in their source form rather than in the encoded
9510 (``mangled'') form passed to the assembler and linker for type-safe
9511 linkage. The default is on.
9513 @item show print demangle
9514 Show whether C@t{++} names are printed in mangled or demangled form.
9516 @item set print asm-demangle
9517 @itemx set print asm-demangle on
9518 Print C@t{++} names in their source form rather than their mangled form, even
9519 in assembler code printouts such as instruction disassemblies.
9522 @item show print asm-demangle
9523 Show whether C@t{++} names in assembly listings are printed in mangled
9526 @cindex C@t{++} symbol decoding style
9527 @cindex symbol decoding style, C@t{++}
9528 @kindex set demangle-style
9529 @item set demangle-style @var{style}
9530 Choose among several encoding schemes used by different compilers to
9531 represent C@t{++} names. The choices for @var{style} are currently:
9535 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9536 This is the default.
9539 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9542 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9545 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9548 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9549 @strong{Warning:} this setting alone is not sufficient to allow
9550 debugging @code{cfront}-generated executables. @value{GDBN} would
9551 require further enhancement to permit that.
9554 If you omit @var{style}, you will see a list of possible formats.
9556 @item show demangle-style
9557 Display the encoding style currently in use for decoding C@t{++} symbols.
9559 @item set print object
9560 @itemx set print object on
9561 @cindex derived type of an object, printing
9562 @cindex display derived types
9563 When displaying a pointer to an object, identify the @emph{actual}
9564 (derived) type of the object rather than the @emph{declared} type, using
9565 the virtual function table. Note that the virtual function table is
9566 required---this feature can only work for objects that have run-time
9567 type identification; a single virtual method in the object's declared
9568 type is sufficient. Note that this setting is also taken into account when
9569 working with variable objects via MI (@pxref{GDB/MI}).
9571 @item set print object off
9572 Display only the declared type of objects, without reference to the
9573 virtual function table. This is the default setting.
9575 @item show print object
9576 Show whether actual, or declared, object types are displayed.
9578 @item set print static-members
9579 @itemx set print static-members on
9580 @cindex static members of C@t{++} objects
9581 Print static members when displaying a C@t{++} object. The default is on.
9583 @item set print static-members off
9584 Do not print static members when displaying a C@t{++} object.
9586 @item show print static-members
9587 Show whether C@t{++} static members are printed or not.
9589 @item set print pascal_static-members
9590 @itemx set print pascal_static-members on
9591 @cindex static members of Pascal objects
9592 @cindex Pascal objects, static members display
9593 Print static members when displaying a Pascal object. The default is on.
9595 @item set print pascal_static-members off
9596 Do not print static members when displaying a Pascal object.
9598 @item show print pascal_static-members
9599 Show whether Pascal static members are printed or not.
9601 @c These don't work with HP ANSI C++ yet.
9602 @item set print vtbl
9603 @itemx set print vtbl on
9604 @cindex pretty print C@t{++} virtual function tables
9605 @cindex virtual functions (C@t{++}) display
9606 @cindex VTBL display
9607 Pretty print C@t{++} virtual function tables. The default is off.
9608 (The @code{vtbl} commands do not work on programs compiled with the HP
9609 ANSI C@t{++} compiler (@code{aCC}).)
9611 @item set print vtbl off
9612 Do not pretty print C@t{++} virtual function tables.
9614 @item show print vtbl
9615 Show whether C@t{++} virtual function tables are pretty printed, or not.
9618 @node Pretty Printing
9619 @section Pretty Printing
9621 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9622 Python code. It greatly simplifies the display of complex objects. This
9623 mechanism works for both MI and the CLI.
9626 * Pretty-Printer Introduction:: Introduction to pretty-printers
9627 * Pretty-Printer Example:: An example pretty-printer
9628 * Pretty-Printer Commands:: Pretty-printer commands
9631 @node Pretty-Printer Introduction
9632 @subsection Pretty-Printer Introduction
9634 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9635 registered for the value. If there is then @value{GDBN} invokes the
9636 pretty-printer to print the value. Otherwise the value is printed normally.
9638 Pretty-printers are normally named. This makes them easy to manage.
9639 The @samp{info pretty-printer} command will list all the installed
9640 pretty-printers with their names.
9641 If a pretty-printer can handle multiple data types, then its
9642 @dfn{subprinters} are the printers for the individual data types.
9643 Each such subprinter has its own name.
9644 The format of the name is @var{printer-name};@var{subprinter-name}.
9646 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9647 Typically they are automatically loaded and registered when the corresponding
9648 debug information is loaded, thus making them available without having to
9649 do anything special.
9651 There are three places where a pretty-printer can be registered.
9655 Pretty-printers registered globally are available when debugging
9659 Pretty-printers registered with a program space are available only
9660 when debugging that program.
9661 @xref{Progspaces In Python}, for more details on program spaces in Python.
9664 Pretty-printers registered with an objfile are loaded and unloaded
9665 with the corresponding objfile (e.g., shared library).
9666 @xref{Objfiles In Python}, for more details on objfiles in Python.
9669 @xref{Selecting Pretty-Printers}, for further information on how
9670 pretty-printers are selected,
9672 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9675 @node Pretty-Printer Example
9676 @subsection Pretty-Printer Example
9678 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9681 (@value{GDBP}) print s
9683 static npos = 4294967295,
9685 <std::allocator<char>> = @{
9686 <__gnu_cxx::new_allocator<char>> = @{
9687 <No data fields>@}, <No data fields>
9689 members of std::basic_string<char, std::char_traits<char>,
9690 std::allocator<char> >::_Alloc_hider:
9691 _M_p = 0x804a014 "abcd"
9696 With a pretty-printer for @code{std::string} only the contents are printed:
9699 (@value{GDBP}) print s
9703 @node Pretty-Printer Commands
9704 @subsection Pretty-Printer Commands
9705 @cindex pretty-printer commands
9708 @kindex info pretty-printer
9709 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9710 Print the list of installed pretty-printers.
9711 This includes disabled pretty-printers, which are marked as such.
9713 @var{object-regexp} is a regular expression matching the objects
9714 whose pretty-printers to list.
9715 Objects can be @code{global}, the program space's file
9716 (@pxref{Progspaces In Python}),
9717 and the object files within that program space (@pxref{Objfiles In Python}).
9718 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9719 looks up a printer from these three objects.
9721 @var{name-regexp} is a regular expression matching the name of the printers
9724 @kindex disable pretty-printer
9725 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9726 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9727 A disabled pretty-printer is not forgotten, it may be enabled again later.
9729 @kindex enable pretty-printer
9730 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9731 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9736 Suppose we have three pretty-printers installed: one from library1.so
9737 named @code{foo} that prints objects of type @code{foo}, and
9738 another from library2.so named @code{bar} that prints two types of objects,
9739 @code{bar1} and @code{bar2}.
9742 (gdb) info pretty-printer
9749 (gdb) info pretty-printer library2
9754 (gdb) disable pretty-printer library1
9756 2 of 3 printers enabled
9757 (gdb) info pretty-printer
9764 (gdb) disable pretty-printer library2 bar:bar1
9766 1 of 3 printers enabled
9767 (gdb) info pretty-printer library2
9774 (gdb) disable pretty-printer library2 bar
9776 0 of 3 printers enabled
9777 (gdb) info pretty-printer library2
9786 Note that for @code{bar} the entire printer can be disabled,
9787 as can each individual subprinter.
9790 @section Value History
9792 @cindex value history
9793 @cindex history of values printed by @value{GDBN}
9794 Values printed by the @code{print} command are saved in the @value{GDBN}
9795 @dfn{value history}. This allows you to refer to them in other expressions.
9796 Values are kept until the symbol table is re-read or discarded
9797 (for example with the @code{file} or @code{symbol-file} commands).
9798 When the symbol table changes, the value history is discarded,
9799 since the values may contain pointers back to the types defined in the
9804 @cindex history number
9805 The values printed are given @dfn{history numbers} by which you can
9806 refer to them. These are successive integers starting with one.
9807 @code{print} shows you the history number assigned to a value by
9808 printing @samp{$@var{num} = } before the value; here @var{num} is the
9811 To refer to any previous value, use @samp{$} followed by the value's
9812 history number. The way @code{print} labels its output is designed to
9813 remind you of this. Just @code{$} refers to the most recent value in
9814 the history, and @code{$$} refers to the value before that.
9815 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9816 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9817 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9819 For example, suppose you have just printed a pointer to a structure and
9820 want to see the contents of the structure. It suffices to type
9826 If you have a chain of structures where the component @code{next} points
9827 to the next one, you can print the contents of the next one with this:
9834 You can print successive links in the chain by repeating this
9835 command---which you can do by just typing @key{RET}.
9837 Note that the history records values, not expressions. If the value of
9838 @code{x} is 4 and you type these commands:
9846 then the value recorded in the value history by the @code{print} command
9847 remains 4 even though the value of @code{x} has changed.
9852 Print the last ten values in the value history, with their item numbers.
9853 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9854 values} does not change the history.
9856 @item show values @var{n}
9857 Print ten history values centered on history item number @var{n}.
9860 Print ten history values just after the values last printed. If no more
9861 values are available, @code{show values +} produces no display.
9864 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9865 same effect as @samp{show values +}.
9867 @node Convenience Vars
9868 @section Convenience Variables
9870 @cindex convenience variables
9871 @cindex user-defined variables
9872 @value{GDBN} provides @dfn{convenience variables} that you can use within
9873 @value{GDBN} to hold on to a value and refer to it later. These variables
9874 exist entirely within @value{GDBN}; they are not part of your program, and
9875 setting a convenience variable has no direct effect on further execution
9876 of your program. That is why you can use them freely.
9878 Convenience variables are prefixed with @samp{$}. Any name preceded by
9879 @samp{$} can be used for a convenience variable, unless it is one of
9880 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9881 (Value history references, in contrast, are @emph{numbers} preceded
9882 by @samp{$}. @xref{Value History, ,Value History}.)
9884 You can save a value in a convenience variable with an assignment
9885 expression, just as you would set a variable in your program.
9889 set $foo = *object_ptr
9893 would save in @code{$foo} the value contained in the object pointed to by
9896 Using a convenience variable for the first time creates it, but its
9897 value is @code{void} until you assign a new value. You can alter the
9898 value with another assignment at any time.
9900 Convenience variables have no fixed types. You can assign a convenience
9901 variable any type of value, including structures and arrays, even if
9902 that variable already has a value of a different type. The convenience
9903 variable, when used as an expression, has the type of its current value.
9906 @kindex show convenience
9907 @cindex show all user variables and functions
9908 @item show convenience
9909 Print a list of convenience variables used so far, and their values,
9910 as well as a list of the convenience functions.
9911 Abbreviated @code{show conv}.
9913 @kindex init-if-undefined
9914 @cindex convenience variables, initializing
9915 @item init-if-undefined $@var{variable} = @var{expression}
9916 Set a convenience variable if it has not already been set. This is useful
9917 for user-defined commands that keep some state. It is similar, in concept,
9918 to using local static variables with initializers in C (except that
9919 convenience variables are global). It can also be used to allow users to
9920 override default values used in a command script.
9922 If the variable is already defined then the expression is not evaluated so
9923 any side-effects do not occur.
9926 One of the ways to use a convenience variable is as a counter to be
9927 incremented or a pointer to be advanced. For example, to print
9928 a field from successive elements of an array of structures:
9932 print bar[$i++]->contents
9936 Repeat that command by typing @key{RET}.
9938 Some convenience variables are created automatically by @value{GDBN} and given
9939 values likely to be useful.
9942 @vindex $_@r{, convenience variable}
9944 The variable @code{$_} is automatically set by the @code{x} command to
9945 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9946 commands which provide a default address for @code{x} to examine also
9947 set @code{$_} to that address; these commands include @code{info line}
9948 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9949 except when set by the @code{x} command, in which case it is a pointer
9950 to the type of @code{$__}.
9952 @vindex $__@r{, convenience variable}
9954 The variable @code{$__} is automatically set by the @code{x} command
9955 to the value found in the last address examined. Its type is chosen
9956 to match the format in which the data was printed.
9959 @vindex $_exitcode@r{, convenience variable}
9960 When the program being debugged terminates normally, @value{GDBN}
9961 automatically sets this variable to the exit code of the program, and
9962 resets @code{$_exitsignal} to @code{void}.
9965 @vindex $_exitsignal@r{, convenience variable}
9966 When the program being debugged dies due to an uncaught signal,
9967 @value{GDBN} automatically sets this variable to that signal's number,
9968 and resets @code{$_exitcode} to @code{void}.
9970 To distinguish between whether the program being debugged has exited
9971 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9972 @code{$_exitsignal} is not @code{void}), the convenience function
9973 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9974 Functions}). For example, considering the following source code:
9980 main (int argc, char *argv[])
9987 A valid way of telling whether the program being debugged has exited
9988 or signalled would be:
9991 (@value{GDBP}) define has_exited_or_signalled
9992 Type commands for definition of ``has_exited_or_signalled''.
9993 End with a line saying just ``end''.
9994 >if $_isvoid ($_exitsignal)
9995 >echo The program has exited\n
9997 >echo The program has signalled\n
10003 Program terminated with signal SIGALRM, Alarm clock.
10004 The program no longer exists.
10005 (@value{GDBP}) has_exited_or_signalled
10006 The program has signalled
10009 As can be seen, @value{GDBN} correctly informs that the program being
10010 debugged has signalled, since it calls @code{raise} and raises a
10011 @code{SIGALRM} signal. If the program being debugged had not called
10012 @code{raise}, then @value{GDBN} would report a normal exit:
10015 (@value{GDBP}) has_exited_or_signalled
10016 The program has exited
10020 The variable @code{$_exception} is set to the exception object being
10021 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10024 @itemx $_probe_arg0@dots{}$_probe_arg11
10025 Arguments to a static probe. @xref{Static Probe Points}.
10028 @vindex $_sdata@r{, inspect, convenience variable}
10029 The variable @code{$_sdata} contains extra collected static tracepoint
10030 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10031 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10032 if extra static tracepoint data has not been collected.
10035 @vindex $_siginfo@r{, convenience variable}
10036 The variable @code{$_siginfo} contains extra signal information
10037 (@pxref{extra signal information}). Note that @code{$_siginfo}
10038 could be empty, if the application has not yet received any signals.
10039 For example, it will be empty before you execute the @code{run} command.
10042 @vindex $_tlb@r{, convenience variable}
10043 The variable @code{$_tlb} is automatically set when debugging
10044 applications running on MS-Windows in native mode or connected to
10045 gdbserver that supports the @code{qGetTIBAddr} request.
10046 @xref{General Query Packets}.
10047 This variable contains the address of the thread information block.
10051 On HP-UX systems, if you refer to a function or variable name that
10052 begins with a dollar sign, @value{GDBN} searches for a user or system
10053 name first, before it searches for a convenience variable.
10055 @node Convenience Funs
10056 @section Convenience Functions
10058 @cindex convenience functions
10059 @value{GDBN} also supplies some @dfn{convenience functions}. These
10060 have a syntax similar to convenience variables. A convenience
10061 function can be used in an expression just like an ordinary function;
10062 however, a convenience function is implemented internally to
10065 These functions do not require @value{GDBN} to be configured with
10066 @code{Python} support, which means that they are always available.
10070 @item $_isvoid (@var{expr})
10071 @findex $_isvoid@r{, convenience function}
10072 Return one if the expression @var{expr} is @code{void}. Otherwise it
10075 A @code{void} expression is an expression where the type of the result
10076 is @code{void}. For example, you can examine a convenience variable
10077 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10081 (@value{GDBP}) print $_exitcode
10083 (@value{GDBP}) print $_isvoid ($_exitcode)
10086 Starting program: ./a.out
10087 [Inferior 1 (process 29572) exited normally]
10088 (@value{GDBP}) print $_exitcode
10090 (@value{GDBP}) print $_isvoid ($_exitcode)
10094 In the example above, we used @code{$_isvoid} to check whether
10095 @code{$_exitcode} is @code{void} before and after the execution of the
10096 program being debugged. Before the execution there is no exit code to
10097 be examined, therefore @code{$_exitcode} is @code{void}. After the
10098 execution the program being debugged returned zero, therefore
10099 @code{$_exitcode} is zero, which means that it is not @code{void}
10102 The @code{void} expression can also be a call of a function from the
10103 program being debugged. For example, given the following function:
10112 The result of calling it inside @value{GDBN} is @code{void}:
10115 (@value{GDBP}) print foo ()
10117 (@value{GDBP}) print $_isvoid (foo ())
10119 (@value{GDBP}) set $v = foo ()
10120 (@value{GDBP}) print $v
10122 (@value{GDBP}) print $_isvoid ($v)
10128 These functions require @value{GDBN} to be configured with
10129 @code{Python} support.
10133 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10134 @findex $_memeq@r{, convenience function}
10135 Returns one if the @var{length} bytes at the addresses given by
10136 @var{buf1} and @var{buf2} are equal.
10137 Otherwise it returns zero.
10139 @item $_regex(@var{str}, @var{regex})
10140 @findex $_regex@r{, convenience function}
10141 Returns one if the string @var{str} matches the regular expression
10142 @var{regex}. Otherwise it returns zero.
10143 The syntax of the regular expression is that specified by @code{Python}'s
10144 regular expression support.
10146 @item $_streq(@var{str1}, @var{str2})
10147 @findex $_streq@r{, convenience function}
10148 Returns one if the strings @var{str1} and @var{str2} are equal.
10149 Otherwise it returns zero.
10151 @item $_strlen(@var{str})
10152 @findex $_strlen@r{, convenience function}
10153 Returns the length of string @var{str}.
10155 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10156 @findex $_caller_is@r{, convenience function}
10157 Returns one if the calling function's name is equal to @var{name}.
10158 Otherwise it returns zero.
10160 If the optional argument @var{number_of_frames} is provided,
10161 it is the number of frames up in the stack to look.
10169 at testsuite/gdb.python/py-caller-is.c:21
10170 #1 0x00000000004005a0 in middle_func ()
10171 at testsuite/gdb.python/py-caller-is.c:27
10172 #2 0x00000000004005ab in top_func ()
10173 at testsuite/gdb.python/py-caller-is.c:33
10174 #3 0x00000000004005b6 in main ()
10175 at testsuite/gdb.python/py-caller-is.c:39
10176 (gdb) print $_caller_is ("middle_func")
10178 (gdb) print $_caller_is ("top_func", 2)
10182 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10183 @findex $_caller_matches@r{, convenience function}
10184 Returns one if the calling function's name matches the regular expression
10185 @var{regexp}. Otherwise it returns zero.
10187 If the optional argument @var{number_of_frames} is provided,
10188 it is the number of frames up in the stack to look.
10191 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10192 @findex $_any_caller_is@r{, convenience function}
10193 Returns one if any calling function's name is equal to @var{name}.
10194 Otherwise it returns zero.
10196 If the optional argument @var{number_of_frames} is provided,
10197 it is the number of frames up in the stack to look.
10200 This function differs from @code{$_caller_is} in that this function
10201 checks all stack frames from the immediate caller to the frame specified
10202 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10203 frame specified by @var{number_of_frames}.
10205 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10206 @findex $_any_caller_matches@r{, convenience function}
10207 Returns one if any calling function's name matches the regular expression
10208 @var{regexp}. Otherwise it returns zero.
10210 If the optional argument @var{number_of_frames} is provided,
10211 it is the number of frames up in the stack to look.
10214 This function differs from @code{$_caller_matches} in that this function
10215 checks all stack frames from the immediate caller to the frame specified
10216 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10217 frame specified by @var{number_of_frames}.
10221 @value{GDBN} provides the ability to list and get help on
10222 convenience functions.
10225 @item help function
10226 @kindex help function
10227 @cindex show all convenience functions
10228 Print a list of all convenience functions.
10235 You can refer to machine register contents, in expressions, as variables
10236 with names starting with @samp{$}. The names of registers are different
10237 for each machine; use @code{info registers} to see the names used on
10241 @kindex info registers
10242 @item info registers
10243 Print the names and values of all registers except floating-point
10244 and vector registers (in the selected stack frame).
10246 @kindex info all-registers
10247 @cindex floating point registers
10248 @item info all-registers
10249 Print the names and values of all registers, including floating-point
10250 and vector registers (in the selected stack frame).
10252 @item info registers @var{regname} @dots{}
10253 Print the @dfn{relativized} value of each specified register @var{regname}.
10254 As discussed in detail below, register values are normally relative to
10255 the selected stack frame. The @var{regname} may be any register name valid on
10256 the machine you are using, with or without the initial @samp{$}.
10259 @cindex stack pointer register
10260 @cindex program counter register
10261 @cindex process status register
10262 @cindex frame pointer register
10263 @cindex standard registers
10264 @value{GDBN} has four ``standard'' register names that are available (in
10265 expressions) on most machines---whenever they do not conflict with an
10266 architecture's canonical mnemonics for registers. The register names
10267 @code{$pc} and @code{$sp} are used for the program counter register and
10268 the stack pointer. @code{$fp} is used for a register that contains a
10269 pointer to the current stack frame, and @code{$ps} is used for a
10270 register that contains the processor status. For example,
10271 you could print the program counter in hex with
10278 or print the instruction to be executed next with
10285 or add four to the stack pointer@footnote{This is a way of removing
10286 one word from the stack, on machines where stacks grow downward in
10287 memory (most machines, nowadays). This assumes that the innermost
10288 stack frame is selected; setting @code{$sp} is not allowed when other
10289 stack frames are selected. To pop entire frames off the stack,
10290 regardless of machine architecture, use @code{return};
10291 see @ref{Returning, ,Returning from a Function}.} with
10297 Whenever possible, these four standard register names are available on
10298 your machine even though the machine has different canonical mnemonics,
10299 so long as there is no conflict. The @code{info registers} command
10300 shows the canonical names. For example, on the SPARC, @code{info
10301 registers} displays the processor status register as @code{$psr} but you
10302 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10303 is an alias for the @sc{eflags} register.
10305 @value{GDBN} always considers the contents of an ordinary register as an
10306 integer when the register is examined in this way. Some machines have
10307 special registers which can hold nothing but floating point; these
10308 registers are considered to have floating point values. There is no way
10309 to refer to the contents of an ordinary register as floating point value
10310 (although you can @emph{print} it as a floating point value with
10311 @samp{print/f $@var{regname}}).
10313 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10314 means that the data format in which the register contents are saved by
10315 the operating system is not the same one that your program normally
10316 sees. For example, the registers of the 68881 floating point
10317 coprocessor are always saved in ``extended'' (raw) format, but all C
10318 programs expect to work with ``double'' (virtual) format. In such
10319 cases, @value{GDBN} normally works with the virtual format only (the format
10320 that makes sense for your program), but the @code{info registers} command
10321 prints the data in both formats.
10323 @cindex SSE registers (x86)
10324 @cindex MMX registers (x86)
10325 Some machines have special registers whose contents can be interpreted
10326 in several different ways. For example, modern x86-based machines
10327 have SSE and MMX registers that can hold several values packed
10328 together in several different formats. @value{GDBN} refers to such
10329 registers in @code{struct} notation:
10332 (@value{GDBP}) print $xmm1
10334 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10335 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10336 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10337 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10338 v4_int32 = @{0, 20657912, 11, 13@},
10339 v2_int64 = @{88725056443645952, 55834574859@},
10340 uint128 = 0x0000000d0000000b013b36f800000000
10345 To set values of such registers, you need to tell @value{GDBN} which
10346 view of the register you wish to change, as if you were assigning
10347 value to a @code{struct} member:
10350 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10353 Normally, register values are relative to the selected stack frame
10354 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10355 value that the register would contain if all stack frames farther in
10356 were exited and their saved registers restored. In order to see the
10357 true contents of hardware registers, you must select the innermost
10358 frame (with @samp{frame 0}).
10360 @cindex caller-saved registers
10361 @cindex call-clobbered registers
10362 @cindex volatile registers
10363 @cindex <not saved> values
10364 Usually ABIs reserve some registers as not needed to be saved by the
10365 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10366 registers). It may therefore not be possible for @value{GDBN} to know
10367 the value a register had before the call (in other words, in the outer
10368 frame), if the register value has since been changed by the callee.
10369 @value{GDBN} tries to deduce where the inner frame saved
10370 (``callee-saved'') registers, from the debug info, unwind info, or the
10371 machine code generated by your compiler. If some register is not
10372 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10373 its own knowledge of the ABI, or because the debug/unwind info
10374 explicitly says the register's value is undefined), @value{GDBN}
10375 displays @w{@samp{<not saved>}} as the register's value. With targets
10376 that @value{GDBN} has no knowledge of the register saving convention,
10377 if a register was not saved by the callee, then its value and location
10378 in the outer frame are assumed to be the same of the inner frame.
10379 This is usually harmless, because if the register is call-clobbered,
10380 the caller either does not care what is in the register after the
10381 call, or has code to restore the value that it does care about. Note,
10382 however, that if you change such a register in the outer frame, you
10383 may also be affecting the inner frame. Also, the more ``outer'' the
10384 frame is you're looking at, the more likely a call-clobbered
10385 register's value is to be wrong, in the sense that it doesn't actually
10386 represent the value the register had just before the call.
10388 @node Floating Point Hardware
10389 @section Floating Point Hardware
10390 @cindex floating point
10392 Depending on the configuration, @value{GDBN} may be able to give
10393 you more information about the status of the floating point hardware.
10398 Display hardware-dependent information about the floating
10399 point unit. The exact contents and layout vary depending on the
10400 floating point chip. Currently, @samp{info float} is supported on
10401 the ARM and x86 machines.
10405 @section Vector Unit
10406 @cindex vector unit
10408 Depending on the configuration, @value{GDBN} may be able to give you
10409 more information about the status of the vector unit.
10412 @kindex info vector
10414 Display information about the vector unit. The exact contents and
10415 layout vary depending on the hardware.
10418 @node OS Information
10419 @section Operating System Auxiliary Information
10420 @cindex OS information
10422 @value{GDBN} provides interfaces to useful OS facilities that can help
10423 you debug your program.
10425 @cindex auxiliary vector
10426 @cindex vector, auxiliary
10427 Some operating systems supply an @dfn{auxiliary vector} to programs at
10428 startup. This is akin to the arguments and environment that you
10429 specify for a program, but contains a system-dependent variety of
10430 binary values that tell system libraries important details about the
10431 hardware, operating system, and process. Each value's purpose is
10432 identified by an integer tag; the meanings are well-known but system-specific.
10433 Depending on the configuration and operating system facilities,
10434 @value{GDBN} may be able to show you this information. For remote
10435 targets, this functionality may further depend on the remote stub's
10436 support of the @samp{qXfer:auxv:read} packet, see
10437 @ref{qXfer auxiliary vector read}.
10442 Display the auxiliary vector of the inferior, which can be either a
10443 live process or a core dump file. @value{GDBN} prints each tag value
10444 numerically, and also shows names and text descriptions for recognized
10445 tags. Some values in the vector are numbers, some bit masks, and some
10446 pointers to strings or other data. @value{GDBN} displays each value in the
10447 most appropriate form for a recognized tag, and in hexadecimal for
10448 an unrecognized tag.
10451 On some targets, @value{GDBN} can access operating system-specific
10452 information and show it to you. The types of information available
10453 will differ depending on the type of operating system running on the
10454 target. The mechanism used to fetch the data is described in
10455 @ref{Operating System Information}. For remote targets, this
10456 functionality depends on the remote stub's support of the
10457 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10461 @item info os @var{infotype}
10463 Display OS information of the requested type.
10465 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10467 @anchor{linux info os infotypes}
10469 @kindex info os processes
10471 Display the list of processes on the target. For each process,
10472 @value{GDBN} prints the process identifier, the name of the user, the
10473 command corresponding to the process, and the list of processor cores
10474 that the process is currently running on. (To understand what these
10475 properties mean, for this and the following info types, please consult
10476 the general @sc{gnu}/Linux documentation.)
10478 @kindex info os procgroups
10480 Display the list of process groups on the target. For each process,
10481 @value{GDBN} prints the identifier of the process group that it belongs
10482 to, the command corresponding to the process group leader, the process
10483 identifier, and the command line of the process. The list is sorted
10484 first by the process group identifier, then by the process identifier,
10485 so that processes belonging to the same process group are grouped together
10486 and the process group leader is listed first.
10488 @kindex info os threads
10490 Display the list of threads running on the target. For each thread,
10491 @value{GDBN} prints the identifier of the process that the thread
10492 belongs to, the command of the process, the thread identifier, and the
10493 processor core that it is currently running on. The main thread of a
10494 process is not listed.
10496 @kindex info os files
10498 Display the list of open file descriptors on the target. For each
10499 file descriptor, @value{GDBN} prints the identifier of the process
10500 owning the descriptor, the command of the owning process, the value
10501 of the descriptor, and the target of the descriptor.
10503 @kindex info os sockets
10505 Display the list of Internet-domain sockets on the target. For each
10506 socket, @value{GDBN} prints the address and port of the local and
10507 remote endpoints, the current state of the connection, the creator of
10508 the socket, the IP address family of the socket, and the type of the
10511 @kindex info os shm
10513 Display the list of all System V shared-memory regions on the target.
10514 For each shared-memory region, @value{GDBN} prints the region key,
10515 the shared-memory identifier, the access permissions, the size of the
10516 region, the process that created the region, the process that last
10517 attached to or detached from the region, the current number of live
10518 attaches to the region, and the times at which the region was last
10519 attached to, detach from, and changed.
10521 @kindex info os semaphores
10523 Display the list of all System V semaphore sets on the target. For each
10524 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10525 set identifier, the access permissions, the number of semaphores in the
10526 set, the user and group of the owner and creator of the semaphore set,
10527 and the times at which the semaphore set was operated upon and changed.
10529 @kindex info os msg
10531 Display the list of all System V message queues on the target. For each
10532 message queue, @value{GDBN} prints the message queue key, the message
10533 queue identifier, the access permissions, the current number of bytes
10534 on the queue, the current number of messages on the queue, the processes
10535 that last sent and received a message on the queue, the user and group
10536 of the owner and creator of the message queue, the times at which a
10537 message was last sent and received on the queue, and the time at which
10538 the message queue was last changed.
10540 @kindex info os modules
10542 Display the list of all loaded kernel modules on the target. For each
10543 module, @value{GDBN} prints the module name, the size of the module in
10544 bytes, the number of times the module is used, the dependencies of the
10545 module, the status of the module, and the address of the loaded module
10550 If @var{infotype} is omitted, then list the possible values for
10551 @var{infotype} and the kind of OS information available for each
10552 @var{infotype}. If the target does not return a list of possible
10553 types, this command will report an error.
10556 @node Memory Region Attributes
10557 @section Memory Region Attributes
10558 @cindex memory region attributes
10560 @dfn{Memory region attributes} allow you to describe special handling
10561 required by regions of your target's memory. @value{GDBN} uses
10562 attributes to determine whether to allow certain types of memory
10563 accesses; whether to use specific width accesses; and whether to cache
10564 target memory. By default the description of memory regions is
10565 fetched from the target (if the current target supports this), but the
10566 user can override the fetched regions.
10568 Defined memory regions can be individually enabled and disabled. When a
10569 memory region is disabled, @value{GDBN} uses the default attributes when
10570 accessing memory in that region. Similarly, if no memory regions have
10571 been defined, @value{GDBN} uses the default attributes when accessing
10574 When a memory region is defined, it is given a number to identify it;
10575 to enable, disable, or remove a memory region, you specify that number.
10579 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10580 Define a memory region bounded by @var{lower} and @var{upper} with
10581 attributes @var{attributes}@dots{}, and add it to the list of regions
10582 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10583 case: it is treated as the target's maximum memory address.
10584 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10587 Discard any user changes to the memory regions and use target-supplied
10588 regions, if available, or no regions if the target does not support.
10591 @item delete mem @var{nums}@dots{}
10592 Remove memory regions @var{nums}@dots{} from the list of regions
10593 monitored by @value{GDBN}.
10595 @kindex disable mem
10596 @item disable mem @var{nums}@dots{}
10597 Disable monitoring of memory regions @var{nums}@dots{}.
10598 A disabled memory region is not forgotten.
10599 It may be enabled again later.
10602 @item enable mem @var{nums}@dots{}
10603 Enable monitoring of memory regions @var{nums}@dots{}.
10607 Print a table of all defined memory regions, with the following columns
10611 @item Memory Region Number
10612 @item Enabled or Disabled.
10613 Enabled memory regions are marked with @samp{y}.
10614 Disabled memory regions are marked with @samp{n}.
10617 The address defining the inclusive lower bound of the memory region.
10620 The address defining the exclusive upper bound of the memory region.
10623 The list of attributes set for this memory region.
10628 @subsection Attributes
10630 @subsubsection Memory Access Mode
10631 The access mode attributes set whether @value{GDBN} may make read or
10632 write accesses to a memory region.
10634 While these attributes prevent @value{GDBN} from performing invalid
10635 memory accesses, they do nothing to prevent the target system, I/O DMA,
10636 etc.@: from accessing memory.
10640 Memory is read only.
10642 Memory is write only.
10644 Memory is read/write. This is the default.
10647 @subsubsection Memory Access Size
10648 The access size attribute tells @value{GDBN} to use specific sized
10649 accesses in the memory region. Often memory mapped device registers
10650 require specific sized accesses. If no access size attribute is
10651 specified, @value{GDBN} may use accesses of any size.
10655 Use 8 bit memory accesses.
10657 Use 16 bit memory accesses.
10659 Use 32 bit memory accesses.
10661 Use 64 bit memory accesses.
10664 @c @subsubsection Hardware/Software Breakpoints
10665 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10666 @c will use hardware or software breakpoints for the internal breakpoints
10667 @c used by the step, next, finish, until, etc. commands.
10671 @c Always use hardware breakpoints
10672 @c @item swbreak (default)
10675 @subsubsection Data Cache
10676 The data cache attributes set whether @value{GDBN} will cache target
10677 memory. While this generally improves performance by reducing debug
10678 protocol overhead, it can lead to incorrect results because @value{GDBN}
10679 does not know about volatile variables or memory mapped device
10684 Enable @value{GDBN} to cache target memory.
10686 Disable @value{GDBN} from caching target memory. This is the default.
10689 @subsection Memory Access Checking
10690 @value{GDBN} can be instructed to refuse accesses to memory that is
10691 not explicitly described. This can be useful if accessing such
10692 regions has undesired effects for a specific target, or to provide
10693 better error checking. The following commands control this behaviour.
10696 @kindex set mem inaccessible-by-default
10697 @item set mem inaccessible-by-default [on|off]
10698 If @code{on} is specified, make @value{GDBN} treat memory not
10699 explicitly described by the memory ranges as non-existent and refuse accesses
10700 to such memory. The checks are only performed if there's at least one
10701 memory range defined. If @code{off} is specified, make @value{GDBN}
10702 treat the memory not explicitly described by the memory ranges as RAM.
10703 The default value is @code{on}.
10704 @kindex show mem inaccessible-by-default
10705 @item show mem inaccessible-by-default
10706 Show the current handling of accesses to unknown memory.
10710 @c @subsubsection Memory Write Verification
10711 @c The memory write verification attributes set whether @value{GDBN}
10712 @c will re-reads data after each write to verify the write was successful.
10716 @c @item noverify (default)
10719 @node Dump/Restore Files
10720 @section Copy Between Memory and a File
10721 @cindex dump/restore files
10722 @cindex append data to a file
10723 @cindex dump data to a file
10724 @cindex restore data from a file
10726 You can use the commands @code{dump}, @code{append}, and
10727 @code{restore} to copy data between target memory and a file. The
10728 @code{dump} and @code{append} commands write data to a file, and the
10729 @code{restore} command reads data from a file back into the inferior's
10730 memory. Files may be in binary, Motorola S-record, Intel hex, or
10731 Tektronix Hex format; however, @value{GDBN} can only append to binary
10737 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10738 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10739 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10740 or the value of @var{expr}, to @var{filename} in the given format.
10742 The @var{format} parameter may be any one of:
10749 Motorola S-record format.
10751 Tektronix Hex format.
10754 @value{GDBN} uses the same definitions of these formats as the
10755 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10756 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10760 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10761 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10762 Append the contents of memory from @var{start_addr} to @var{end_addr},
10763 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10764 (@value{GDBN} can only append data to files in raw binary form.)
10767 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10768 Restore the contents of file @var{filename} into memory. The
10769 @code{restore} command can automatically recognize any known @sc{bfd}
10770 file format, except for raw binary. To restore a raw binary file you
10771 must specify the optional keyword @code{binary} after the filename.
10773 If @var{bias} is non-zero, its value will be added to the addresses
10774 contained in the file. Binary files always start at address zero, so
10775 they will be restored at address @var{bias}. Other bfd files have
10776 a built-in location; they will be restored at offset @var{bias}
10777 from that location.
10779 If @var{start} and/or @var{end} are non-zero, then only data between
10780 file offset @var{start} and file offset @var{end} will be restored.
10781 These offsets are relative to the addresses in the file, before
10782 the @var{bias} argument is applied.
10786 @node Core File Generation
10787 @section How to Produce a Core File from Your Program
10788 @cindex dump core from inferior
10790 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10791 image of a running process and its process status (register values
10792 etc.). Its primary use is post-mortem debugging of a program that
10793 crashed while it ran outside a debugger. A program that crashes
10794 automatically produces a core file, unless this feature is disabled by
10795 the user. @xref{Files}, for information on invoking @value{GDBN} in
10796 the post-mortem debugging mode.
10798 Occasionally, you may wish to produce a core file of the program you
10799 are debugging in order to preserve a snapshot of its state.
10800 @value{GDBN} has a special command for that.
10804 @kindex generate-core-file
10805 @item generate-core-file [@var{file}]
10806 @itemx gcore [@var{file}]
10807 Produce a core dump of the inferior process. The optional argument
10808 @var{file} specifies the file name where to put the core dump. If not
10809 specified, the file name defaults to @file{core.@var{pid}}, where
10810 @var{pid} is the inferior process ID.
10812 Note that this command is implemented only for some systems (as of
10813 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10816 @node Character Sets
10817 @section Character Sets
10818 @cindex character sets
10820 @cindex translating between character sets
10821 @cindex host character set
10822 @cindex target character set
10824 If the program you are debugging uses a different character set to
10825 represent characters and strings than the one @value{GDBN} uses itself,
10826 @value{GDBN} can automatically translate between the character sets for
10827 you. The character set @value{GDBN} uses we call the @dfn{host
10828 character set}; the one the inferior program uses we call the
10829 @dfn{target character set}.
10831 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10832 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10833 remote protocol (@pxref{Remote Debugging}) to debug a program
10834 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10835 then the host character set is Latin-1, and the target character set is
10836 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10837 target-charset EBCDIC-US}, then @value{GDBN} translates between
10838 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10839 character and string literals in expressions.
10841 @value{GDBN} has no way to automatically recognize which character set
10842 the inferior program uses; you must tell it, using the @code{set
10843 target-charset} command, described below.
10845 Here are the commands for controlling @value{GDBN}'s character set
10849 @item set target-charset @var{charset}
10850 @kindex set target-charset
10851 Set the current target character set to @var{charset}. To display the
10852 list of supported target character sets, type
10853 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10855 @item set host-charset @var{charset}
10856 @kindex set host-charset
10857 Set the current host character set to @var{charset}.
10859 By default, @value{GDBN} uses a host character set appropriate to the
10860 system it is running on; you can override that default using the
10861 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10862 automatically determine the appropriate host character set. In this
10863 case, @value{GDBN} uses @samp{UTF-8}.
10865 @value{GDBN} can only use certain character sets as its host character
10866 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10867 @value{GDBN} will list the host character sets it supports.
10869 @item set charset @var{charset}
10870 @kindex set charset
10871 Set the current host and target character sets to @var{charset}. As
10872 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10873 @value{GDBN} will list the names of the character sets that can be used
10874 for both host and target.
10877 @kindex show charset
10878 Show the names of the current host and target character sets.
10880 @item show host-charset
10881 @kindex show host-charset
10882 Show the name of the current host character set.
10884 @item show target-charset
10885 @kindex show target-charset
10886 Show the name of the current target character set.
10888 @item set target-wide-charset @var{charset}
10889 @kindex set target-wide-charset
10890 Set the current target's wide character set to @var{charset}. This is
10891 the character set used by the target's @code{wchar_t} type. To
10892 display the list of supported wide character sets, type
10893 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10895 @item show target-wide-charset
10896 @kindex show target-wide-charset
10897 Show the name of the current target's wide character set.
10900 Here is an example of @value{GDBN}'s character set support in action.
10901 Assume that the following source code has been placed in the file
10902 @file{charset-test.c}:
10908 = @{72, 101, 108, 108, 111, 44, 32, 119,
10909 111, 114, 108, 100, 33, 10, 0@};
10910 char ibm1047_hello[]
10911 = @{200, 133, 147, 147, 150, 107, 64, 166,
10912 150, 153, 147, 132, 90, 37, 0@};
10916 printf ("Hello, world!\n");
10920 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10921 containing the string @samp{Hello, world!} followed by a newline,
10922 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10924 We compile the program, and invoke the debugger on it:
10927 $ gcc -g charset-test.c -o charset-test
10928 $ gdb -nw charset-test
10929 GNU gdb 2001-12-19-cvs
10930 Copyright 2001 Free Software Foundation, Inc.
10935 We can use the @code{show charset} command to see what character sets
10936 @value{GDBN} is currently using to interpret and display characters and
10940 (@value{GDBP}) show charset
10941 The current host and target character set is `ISO-8859-1'.
10945 For the sake of printing this manual, let's use @sc{ascii} as our
10946 initial character set:
10948 (@value{GDBP}) set charset ASCII
10949 (@value{GDBP}) show charset
10950 The current host and target character set is `ASCII'.
10954 Let's assume that @sc{ascii} is indeed the correct character set for our
10955 host system --- in other words, let's assume that if @value{GDBN} prints
10956 characters using the @sc{ascii} character set, our terminal will display
10957 them properly. Since our current target character set is also
10958 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10961 (@value{GDBP}) print ascii_hello
10962 $1 = 0x401698 "Hello, world!\n"
10963 (@value{GDBP}) print ascii_hello[0]
10968 @value{GDBN} uses the target character set for character and string
10969 literals you use in expressions:
10972 (@value{GDBP}) print '+'
10977 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10980 @value{GDBN} relies on the user to tell it which character set the
10981 target program uses. If we print @code{ibm1047_hello} while our target
10982 character set is still @sc{ascii}, we get jibberish:
10985 (@value{GDBP}) print ibm1047_hello
10986 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10987 (@value{GDBP}) print ibm1047_hello[0]
10992 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10993 @value{GDBN} tells us the character sets it supports:
10996 (@value{GDBP}) set target-charset
10997 ASCII EBCDIC-US IBM1047 ISO-8859-1
10998 (@value{GDBP}) set target-charset
11001 We can select @sc{ibm1047} as our target character set, and examine the
11002 program's strings again. Now the @sc{ascii} string is wrong, but
11003 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11004 target character set, @sc{ibm1047}, to the host character set,
11005 @sc{ascii}, and they display correctly:
11008 (@value{GDBP}) set target-charset IBM1047
11009 (@value{GDBP}) show charset
11010 The current host character set is `ASCII'.
11011 The current target character set is `IBM1047'.
11012 (@value{GDBP}) print ascii_hello
11013 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11014 (@value{GDBP}) print ascii_hello[0]
11016 (@value{GDBP}) print ibm1047_hello
11017 $8 = 0x4016a8 "Hello, world!\n"
11018 (@value{GDBP}) print ibm1047_hello[0]
11023 As above, @value{GDBN} uses the target character set for character and
11024 string literals you use in expressions:
11027 (@value{GDBP}) print '+'
11032 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11035 @node Caching Target Data
11036 @section Caching Data of Targets
11037 @cindex caching data of targets
11039 @value{GDBN} caches data exchanged between the debugger and a target.
11040 Each cache is associated with the address space of the inferior.
11041 @xref{Inferiors and Programs}, about inferior and address space.
11042 Such caching generally improves performance in remote debugging
11043 (@pxref{Remote Debugging}), because it reduces the overhead of the
11044 remote protocol by bundling memory reads and writes into large chunks.
11045 Unfortunately, simply caching everything would lead to incorrect results,
11046 since @value{GDBN} does not necessarily know anything about volatile
11047 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11048 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11050 Therefore, by default, @value{GDBN} only caches data
11051 known to be on the stack@footnote{In non-stop mode, it is moderately
11052 rare for a running thread to modify the stack of a stopped thread
11053 in a way that would interfere with a backtrace, and caching of
11054 stack reads provides a significant speed up of remote backtraces.} or
11055 in the code segment.
11056 Other regions of memory can be explicitly marked as
11057 cacheable; @pxref{Memory Region Attributes}.
11060 @kindex set remotecache
11061 @item set remotecache on
11062 @itemx set remotecache off
11063 This option no longer does anything; it exists for compatibility
11066 @kindex show remotecache
11067 @item show remotecache
11068 Show the current state of the obsolete remotecache flag.
11070 @kindex set stack-cache
11071 @item set stack-cache on
11072 @itemx set stack-cache off
11073 Enable or disable caching of stack accesses. When @code{on}, use
11074 caching. By default, this option is @code{on}.
11076 @kindex show stack-cache
11077 @item show stack-cache
11078 Show the current state of data caching for memory accesses.
11080 @kindex set code-cache
11081 @item set code-cache on
11082 @itemx set code-cache off
11083 Enable or disable caching of code segment accesses. When @code{on},
11084 use caching. By default, this option is @code{on}. This improves
11085 performance of disassembly in remote debugging.
11087 @kindex show code-cache
11088 @item show code-cache
11089 Show the current state of target memory cache for code segment
11092 @kindex info dcache
11093 @item info dcache @r{[}line@r{]}
11094 Print the information about the performance of data cache of the
11095 current inferior's address space. The information displayed
11096 includes the dcache width and depth, and for each cache line, its
11097 number, address, and how many times it was referenced. This
11098 command is useful for debugging the data cache operation.
11100 If a line number is specified, the contents of that line will be
11103 @item set dcache size @var{size}
11104 @cindex dcache size
11105 @kindex set dcache size
11106 Set maximum number of entries in dcache (dcache depth above).
11108 @item set dcache line-size @var{line-size}
11109 @cindex dcache line-size
11110 @kindex set dcache line-size
11111 Set number of bytes each dcache entry caches (dcache width above).
11112 Must be a power of 2.
11114 @item show dcache size
11115 @kindex show dcache size
11116 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11118 @item show dcache line-size
11119 @kindex show dcache line-size
11120 Show default size of dcache lines.
11124 @node Searching Memory
11125 @section Search Memory
11126 @cindex searching memory
11128 Memory can be searched for a particular sequence of bytes with the
11129 @code{find} command.
11133 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11134 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11135 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11136 etc. The search begins at address @var{start_addr} and continues for either
11137 @var{len} bytes or through to @var{end_addr} inclusive.
11140 @var{s} and @var{n} are optional parameters.
11141 They may be specified in either order, apart or together.
11144 @item @var{s}, search query size
11145 The size of each search query value.
11151 halfwords (two bytes)
11155 giant words (eight bytes)
11158 All values are interpreted in the current language.
11159 This means, for example, that if the current source language is C/C@t{++}
11160 then searching for the string ``hello'' includes the trailing '\0'.
11162 If the value size is not specified, it is taken from the
11163 value's type in the current language.
11164 This is useful when one wants to specify the search
11165 pattern as a mixture of types.
11166 Note that this means, for example, that in the case of C-like languages
11167 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11168 which is typically four bytes.
11170 @item @var{n}, maximum number of finds
11171 The maximum number of matches to print. The default is to print all finds.
11174 You can use strings as search values. Quote them with double-quotes
11176 The string value is copied into the search pattern byte by byte,
11177 regardless of the endianness of the target and the size specification.
11179 The address of each match found is printed as well as a count of the
11180 number of matches found.
11182 The address of the last value found is stored in convenience variable
11184 A count of the number of matches is stored in @samp{$numfound}.
11186 For example, if stopped at the @code{printf} in this function:
11192 static char hello[] = "hello-hello";
11193 static struct @{ char c; short s; int i; @}
11194 __attribute__ ((packed)) mixed
11195 = @{ 'c', 0x1234, 0x87654321 @};
11196 printf ("%s\n", hello);
11201 you get during debugging:
11204 (gdb) find &hello[0], +sizeof(hello), "hello"
11205 0x804956d <hello.1620+6>
11207 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11208 0x8049567 <hello.1620>
11209 0x804956d <hello.1620+6>
11211 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11212 0x8049567 <hello.1620>
11214 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11215 0x8049560 <mixed.1625>
11217 (gdb) print $numfound
11220 $2 = (void *) 0x8049560
11223 @node Optimized Code
11224 @chapter Debugging Optimized Code
11225 @cindex optimized code, debugging
11226 @cindex debugging optimized code
11228 Almost all compilers support optimization. With optimization
11229 disabled, the compiler generates assembly code that corresponds
11230 directly to your source code, in a simplistic way. As the compiler
11231 applies more powerful optimizations, the generated assembly code
11232 diverges from your original source code. With help from debugging
11233 information generated by the compiler, @value{GDBN} can map from
11234 the running program back to constructs from your original source.
11236 @value{GDBN} is more accurate with optimization disabled. If you
11237 can recompile without optimization, it is easier to follow the
11238 progress of your program during debugging. But, there are many cases
11239 where you may need to debug an optimized version.
11241 When you debug a program compiled with @samp{-g -O}, remember that the
11242 optimizer has rearranged your code; the debugger shows you what is
11243 really there. Do not be too surprised when the execution path does not
11244 exactly match your source file! An extreme example: if you define a
11245 variable, but never use it, @value{GDBN} never sees that
11246 variable---because the compiler optimizes it out of existence.
11248 Some things do not work as well with @samp{-g -O} as with just
11249 @samp{-g}, particularly on machines with instruction scheduling. If in
11250 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11251 please report it to us as a bug (including a test case!).
11252 @xref{Variables}, for more information about debugging optimized code.
11255 * Inline Functions:: How @value{GDBN} presents inlining
11256 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11259 @node Inline Functions
11260 @section Inline Functions
11261 @cindex inline functions, debugging
11263 @dfn{Inlining} is an optimization that inserts a copy of the function
11264 body directly at each call site, instead of jumping to a shared
11265 routine. @value{GDBN} displays inlined functions just like
11266 non-inlined functions. They appear in backtraces. You can view their
11267 arguments and local variables, step into them with @code{step}, skip
11268 them with @code{next}, and escape from them with @code{finish}.
11269 You can check whether a function was inlined by using the
11270 @code{info frame} command.
11272 For @value{GDBN} to support inlined functions, the compiler must
11273 record information about inlining in the debug information ---
11274 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11275 other compilers do also. @value{GDBN} only supports inlined functions
11276 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11277 do not emit two required attributes (@samp{DW_AT_call_file} and
11278 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11279 function calls with earlier versions of @value{NGCC}. It instead
11280 displays the arguments and local variables of inlined functions as
11281 local variables in the caller.
11283 The body of an inlined function is directly included at its call site;
11284 unlike a non-inlined function, there are no instructions devoted to
11285 the call. @value{GDBN} still pretends that the call site and the
11286 start of the inlined function are different instructions. Stepping to
11287 the call site shows the call site, and then stepping again shows
11288 the first line of the inlined function, even though no additional
11289 instructions are executed.
11291 This makes source-level debugging much clearer; you can see both the
11292 context of the call and then the effect of the call. Only stepping by
11293 a single instruction using @code{stepi} or @code{nexti} does not do
11294 this; single instruction steps always show the inlined body.
11296 There are some ways that @value{GDBN} does not pretend that inlined
11297 function calls are the same as normal calls:
11301 Setting breakpoints at the call site of an inlined function may not
11302 work, because the call site does not contain any code. @value{GDBN}
11303 may incorrectly move the breakpoint to the next line of the enclosing
11304 function, after the call. This limitation will be removed in a future
11305 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11306 or inside the inlined function instead.
11309 @value{GDBN} cannot locate the return value of inlined calls after
11310 using the @code{finish} command. This is a limitation of compiler-generated
11311 debugging information; after @code{finish}, you can step to the next line
11312 and print a variable where your program stored the return value.
11316 @node Tail Call Frames
11317 @section Tail Call Frames
11318 @cindex tail call frames, debugging
11320 Function @code{B} can call function @code{C} in its very last statement. In
11321 unoptimized compilation the call of @code{C} is immediately followed by return
11322 instruction at the end of @code{B} code. Optimizing compiler may replace the
11323 call and return in function @code{B} into one jump to function @code{C}
11324 instead. Such use of a jump instruction is called @dfn{tail call}.
11326 During execution of function @code{C}, there will be no indication in the
11327 function call stack frames that it was tail-called from @code{B}. If function
11328 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11329 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11330 some cases @value{GDBN} can determine that @code{C} was tail-called from
11331 @code{B}, and it will then create fictitious call frame for that, with the
11332 return address set up as if @code{B} called @code{C} normally.
11334 This functionality is currently supported only by DWARF 2 debugging format and
11335 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11336 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11339 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11340 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11344 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11346 Stack level 1, frame at 0x7fffffffda30:
11347 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11348 tail call frame, caller of frame at 0x7fffffffda30
11349 source language c++.
11350 Arglist at unknown address.
11351 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11354 The detection of all the possible code path executions can find them ambiguous.
11355 There is no execution history stored (possible @ref{Reverse Execution} is never
11356 used for this purpose) and the last known caller could have reached the known
11357 callee by multiple different jump sequences. In such case @value{GDBN} still
11358 tries to show at least all the unambiguous top tail callers and all the
11359 unambiguous bottom tail calees, if any.
11362 @anchor{set debug entry-values}
11363 @item set debug entry-values
11364 @kindex set debug entry-values
11365 When set to on, enables printing of analysis messages for both frame argument
11366 values at function entry and tail calls. It will show all the possible valid
11367 tail calls code paths it has considered. It will also print the intersection
11368 of them with the final unambiguous (possibly partial or even empty) code path
11371 @item show debug entry-values
11372 @kindex show debug entry-values
11373 Show the current state of analysis messages printing for both frame argument
11374 values at function entry and tail calls.
11377 The analysis messages for tail calls can for example show why the virtual tail
11378 call frame for function @code{c} has not been recognized (due to the indirect
11379 reference by variable @code{x}):
11382 static void __attribute__((noinline, noclone)) c (void);
11383 void (*x) (void) = c;
11384 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11385 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11386 int main (void) @{ x (); return 0; @}
11388 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11389 DW_TAG_GNU_call_site 0x40039a in main
11391 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11394 #1 0x000000000040039a in main () at t.c:5
11397 Another possibility is an ambiguous virtual tail call frames resolution:
11401 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11402 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11403 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11404 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11405 static void __attribute__((noinline, noclone)) b (void)
11406 @{ if (i) c (); else e (); @}
11407 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11408 int main (void) @{ a (); return 0; @}
11410 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11411 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11412 tailcall: reduced: 0x4004d2(a) |
11415 #1 0x00000000004004d2 in a () at t.c:8
11416 #2 0x0000000000400395 in main () at t.c:9
11419 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11420 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11422 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11423 @ifset HAVE_MAKEINFO_CLICK
11424 @set ARROW @click{}
11425 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11426 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11428 @ifclear HAVE_MAKEINFO_CLICK
11430 @set CALLSEQ1B @value{CALLSEQ1A}
11431 @set CALLSEQ2B @value{CALLSEQ2A}
11434 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11435 The code can have possible execution paths @value{CALLSEQ1B} or
11436 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11438 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11439 has found. It then finds another possible calling sequcen - that one is
11440 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11441 printed as the @code{reduced:} calling sequence. That one could have many
11442 futher @code{compare:} and @code{reduced:} statements as long as there remain
11443 any non-ambiguous sequence entries.
11445 For the frame of function @code{b} in both cases there are different possible
11446 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11447 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11448 therefore this one is displayed to the user while the ambiguous frames are
11451 There can be also reasons why printing of frame argument values at function
11456 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11457 static void __attribute__((noinline, noclone)) a (int i);
11458 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11459 static void __attribute__((noinline, noclone)) a (int i)
11460 @{ if (i) b (i - 1); else c (0); @}
11461 int main (void) @{ a (5); return 0; @}
11464 #0 c (i=i@@entry=0) at t.c:2
11465 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11466 function "a" at 0x400420 can call itself via tail calls
11467 i=<optimized out>) at t.c:6
11468 #2 0x000000000040036e in main () at t.c:7
11471 @value{GDBN} cannot find out from the inferior state if and how many times did
11472 function @code{a} call itself (via function @code{b}) as these calls would be
11473 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11474 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11475 prints @code{<optimized out>} instead.
11478 @chapter C Preprocessor Macros
11480 Some languages, such as C and C@t{++}, provide a way to define and invoke
11481 ``preprocessor macros'' which expand into strings of tokens.
11482 @value{GDBN} can evaluate expressions containing macro invocations, show
11483 the result of macro expansion, and show a macro's definition, including
11484 where it was defined.
11486 You may need to compile your program specially to provide @value{GDBN}
11487 with information about preprocessor macros. Most compilers do not
11488 include macros in their debugging information, even when you compile
11489 with the @option{-g} flag. @xref{Compilation}.
11491 A program may define a macro at one point, remove that definition later,
11492 and then provide a different definition after that. Thus, at different
11493 points in the program, a macro may have different definitions, or have
11494 no definition at all. If there is a current stack frame, @value{GDBN}
11495 uses the macros in scope at that frame's source code line. Otherwise,
11496 @value{GDBN} uses the macros in scope at the current listing location;
11499 Whenever @value{GDBN} evaluates an expression, it always expands any
11500 macro invocations present in the expression. @value{GDBN} also provides
11501 the following commands for working with macros explicitly.
11505 @kindex macro expand
11506 @cindex macro expansion, showing the results of preprocessor
11507 @cindex preprocessor macro expansion, showing the results of
11508 @cindex expanding preprocessor macros
11509 @item macro expand @var{expression}
11510 @itemx macro exp @var{expression}
11511 Show the results of expanding all preprocessor macro invocations in
11512 @var{expression}. Since @value{GDBN} simply expands macros, but does
11513 not parse the result, @var{expression} need not be a valid expression;
11514 it can be any string of tokens.
11517 @item macro expand-once @var{expression}
11518 @itemx macro exp1 @var{expression}
11519 @cindex expand macro once
11520 @i{(This command is not yet implemented.)} Show the results of
11521 expanding those preprocessor macro invocations that appear explicitly in
11522 @var{expression}. Macro invocations appearing in that expansion are
11523 left unchanged. This command allows you to see the effect of a
11524 particular macro more clearly, without being confused by further
11525 expansions. Since @value{GDBN} simply expands macros, but does not
11526 parse the result, @var{expression} need not be a valid expression; it
11527 can be any string of tokens.
11530 @cindex macro definition, showing
11531 @cindex definition of a macro, showing
11532 @cindex macros, from debug info
11533 @item info macro [-a|-all] [--] @var{macro}
11534 Show the current definition or all definitions of the named @var{macro},
11535 and describe the source location or compiler command-line where that
11536 definition was established. The optional double dash is to signify the end of
11537 argument processing and the beginning of @var{macro} for non C-like macros where
11538 the macro may begin with a hyphen.
11540 @kindex info macros
11541 @item info macros @var{linespec}
11542 Show all macro definitions that are in effect at the location specified
11543 by @var{linespec}, and describe the source location or compiler
11544 command-line where those definitions were established.
11546 @kindex macro define
11547 @cindex user-defined macros
11548 @cindex defining macros interactively
11549 @cindex macros, user-defined
11550 @item macro define @var{macro} @var{replacement-list}
11551 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11552 Introduce a definition for a preprocessor macro named @var{macro},
11553 invocations of which are replaced by the tokens given in
11554 @var{replacement-list}. The first form of this command defines an
11555 ``object-like'' macro, which takes no arguments; the second form
11556 defines a ``function-like'' macro, which takes the arguments given in
11559 A definition introduced by this command is in scope in every
11560 expression evaluated in @value{GDBN}, until it is removed with the
11561 @code{macro undef} command, described below. The definition overrides
11562 all definitions for @var{macro} present in the program being debugged,
11563 as well as any previous user-supplied definition.
11565 @kindex macro undef
11566 @item macro undef @var{macro}
11567 Remove any user-supplied definition for the macro named @var{macro}.
11568 This command only affects definitions provided with the @code{macro
11569 define} command, described above; it cannot remove definitions present
11570 in the program being debugged.
11574 List all the macros defined using the @code{macro define} command.
11577 @cindex macros, example of debugging with
11578 Here is a transcript showing the above commands in action. First, we
11579 show our source files:
11584 #include "sample.h"
11587 #define ADD(x) (M + x)
11592 printf ("Hello, world!\n");
11594 printf ("We're so creative.\n");
11596 printf ("Goodbye, world!\n");
11603 Now, we compile the program using the @sc{gnu} C compiler,
11604 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11605 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11606 and @option{-gdwarf-4}; we recommend always choosing the most recent
11607 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11608 includes information about preprocessor macros in the debugging
11612 $ gcc -gdwarf-2 -g3 sample.c -o sample
11616 Now, we start @value{GDBN} on our sample program:
11620 GNU gdb 2002-05-06-cvs
11621 Copyright 2002 Free Software Foundation, Inc.
11622 GDB is free software, @dots{}
11626 We can expand macros and examine their definitions, even when the
11627 program is not running. @value{GDBN} uses the current listing position
11628 to decide which macro definitions are in scope:
11631 (@value{GDBP}) list main
11634 5 #define ADD(x) (M + x)
11639 10 printf ("Hello, world!\n");
11641 12 printf ("We're so creative.\n");
11642 (@value{GDBP}) info macro ADD
11643 Defined at /home/jimb/gdb/macros/play/sample.c:5
11644 #define ADD(x) (M + x)
11645 (@value{GDBP}) info macro Q
11646 Defined at /home/jimb/gdb/macros/play/sample.h:1
11647 included at /home/jimb/gdb/macros/play/sample.c:2
11649 (@value{GDBP}) macro expand ADD(1)
11650 expands to: (42 + 1)
11651 (@value{GDBP}) macro expand-once ADD(1)
11652 expands to: once (M + 1)
11656 In the example above, note that @code{macro expand-once} expands only
11657 the macro invocation explicit in the original text --- the invocation of
11658 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11659 which was introduced by @code{ADD}.
11661 Once the program is running, @value{GDBN} uses the macro definitions in
11662 force at the source line of the current stack frame:
11665 (@value{GDBP}) break main
11666 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11668 Starting program: /home/jimb/gdb/macros/play/sample
11670 Breakpoint 1, main () at sample.c:10
11671 10 printf ("Hello, world!\n");
11675 At line 10, the definition of the macro @code{N} at line 9 is in force:
11678 (@value{GDBP}) info macro N
11679 Defined at /home/jimb/gdb/macros/play/sample.c:9
11681 (@value{GDBP}) macro expand N Q M
11682 expands to: 28 < 42
11683 (@value{GDBP}) print N Q M
11688 As we step over directives that remove @code{N}'s definition, and then
11689 give it a new definition, @value{GDBN} finds the definition (or lack
11690 thereof) in force at each point:
11693 (@value{GDBP}) next
11695 12 printf ("We're so creative.\n");
11696 (@value{GDBP}) info macro N
11697 The symbol `N' has no definition as a C/C++ preprocessor macro
11698 at /home/jimb/gdb/macros/play/sample.c:12
11699 (@value{GDBP}) next
11701 14 printf ("Goodbye, world!\n");
11702 (@value{GDBP}) info macro N
11703 Defined at /home/jimb/gdb/macros/play/sample.c:13
11705 (@value{GDBP}) macro expand N Q M
11706 expands to: 1729 < 42
11707 (@value{GDBP}) print N Q M
11712 In addition to source files, macros can be defined on the compilation command
11713 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11714 such a way, @value{GDBN} displays the location of their definition as line zero
11715 of the source file submitted to the compiler.
11718 (@value{GDBP}) info macro __STDC__
11719 Defined at /home/jimb/gdb/macros/play/sample.c:0
11726 @chapter Tracepoints
11727 @c This chapter is based on the documentation written by Michael
11728 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11730 @cindex tracepoints
11731 In some applications, it is not feasible for the debugger to interrupt
11732 the program's execution long enough for the developer to learn
11733 anything helpful about its behavior. If the program's correctness
11734 depends on its real-time behavior, delays introduced by a debugger
11735 might cause the program to change its behavior drastically, or perhaps
11736 fail, even when the code itself is correct. It is useful to be able
11737 to observe the program's behavior without interrupting it.
11739 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11740 specify locations in the program, called @dfn{tracepoints}, and
11741 arbitrary expressions to evaluate when those tracepoints are reached.
11742 Later, using the @code{tfind} command, you can examine the values
11743 those expressions had when the program hit the tracepoints. The
11744 expressions may also denote objects in memory---structures or arrays,
11745 for example---whose values @value{GDBN} should record; while visiting
11746 a particular tracepoint, you may inspect those objects as if they were
11747 in memory at that moment. However, because @value{GDBN} records these
11748 values without interacting with you, it can do so quickly and
11749 unobtrusively, hopefully not disturbing the program's behavior.
11751 The tracepoint facility is currently available only for remote
11752 targets. @xref{Targets}. In addition, your remote target must know
11753 how to collect trace data. This functionality is implemented in the
11754 remote stub; however, none of the stubs distributed with @value{GDBN}
11755 support tracepoints as of this writing. The format of the remote
11756 packets used to implement tracepoints are described in @ref{Tracepoint
11759 It is also possible to get trace data from a file, in a manner reminiscent
11760 of corefiles; you specify the filename, and use @code{tfind} to search
11761 through the file. @xref{Trace Files}, for more details.
11763 This chapter describes the tracepoint commands and features.
11766 * Set Tracepoints::
11767 * Analyze Collected Data::
11768 * Tracepoint Variables::
11772 @node Set Tracepoints
11773 @section Commands to Set Tracepoints
11775 Before running such a @dfn{trace experiment}, an arbitrary number of
11776 tracepoints can be set. A tracepoint is actually a special type of
11777 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11778 standard breakpoint commands. For instance, as with breakpoints,
11779 tracepoint numbers are successive integers starting from one, and many
11780 of the commands associated with tracepoints take the tracepoint number
11781 as their argument, to identify which tracepoint to work on.
11783 For each tracepoint, you can specify, in advance, some arbitrary set
11784 of data that you want the target to collect in the trace buffer when
11785 it hits that tracepoint. The collected data can include registers,
11786 local variables, or global data. Later, you can use @value{GDBN}
11787 commands to examine the values these data had at the time the
11788 tracepoint was hit.
11790 Tracepoints do not support every breakpoint feature. Ignore counts on
11791 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11792 commands when they are hit. Tracepoints may not be thread-specific
11795 @cindex fast tracepoints
11796 Some targets may support @dfn{fast tracepoints}, which are inserted in
11797 a different way (such as with a jump instead of a trap), that is
11798 faster but possibly restricted in where they may be installed.
11800 @cindex static tracepoints
11801 @cindex markers, static tracepoints
11802 @cindex probing markers, static tracepoints
11803 Regular and fast tracepoints are dynamic tracing facilities, meaning
11804 that they can be used to insert tracepoints at (almost) any location
11805 in the target. Some targets may also support controlling @dfn{static
11806 tracepoints} from @value{GDBN}. With static tracing, a set of
11807 instrumentation points, also known as @dfn{markers}, are embedded in
11808 the target program, and can be activated or deactivated by name or
11809 address. These are usually placed at locations which facilitate
11810 investigating what the target is actually doing. @value{GDBN}'s
11811 support for static tracing includes being able to list instrumentation
11812 points, and attach them with @value{GDBN} defined high level
11813 tracepoints that expose the whole range of convenience of
11814 @value{GDBN}'s tracepoints support. Namely, support for collecting
11815 registers values and values of global or local (to the instrumentation
11816 point) variables; tracepoint conditions and trace state variables.
11817 The act of installing a @value{GDBN} static tracepoint on an
11818 instrumentation point, or marker, is referred to as @dfn{probing} a
11819 static tracepoint marker.
11821 @code{gdbserver} supports tracepoints on some target systems.
11822 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11824 This section describes commands to set tracepoints and associated
11825 conditions and actions.
11828 * Create and Delete Tracepoints::
11829 * Enable and Disable Tracepoints::
11830 * Tracepoint Passcounts::
11831 * Tracepoint Conditions::
11832 * Trace State Variables::
11833 * Tracepoint Actions::
11834 * Listing Tracepoints::
11835 * Listing Static Tracepoint Markers::
11836 * Starting and Stopping Trace Experiments::
11837 * Tracepoint Restrictions::
11840 @node Create and Delete Tracepoints
11841 @subsection Create and Delete Tracepoints
11844 @cindex set tracepoint
11846 @item trace @var{location}
11847 The @code{trace} command is very similar to the @code{break} command.
11848 Its argument @var{location} can be a source line, a function name, or
11849 an address in the target program. @xref{Specify Location}. The
11850 @code{trace} command defines a tracepoint, which is a point in the
11851 target program where the debugger will briefly stop, collect some
11852 data, and then allow the program to continue. Setting a tracepoint or
11853 changing its actions takes effect immediately if the remote stub
11854 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11856 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11857 these changes don't take effect until the next @code{tstart}
11858 command, and once a trace experiment is running, further changes will
11859 not have any effect until the next trace experiment starts. In addition,
11860 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11861 address is not yet resolved. (This is similar to pending breakpoints.)
11862 Pending tracepoints are not downloaded to the target and not installed
11863 until they are resolved. The resolution of pending tracepoints requires
11864 @value{GDBN} support---when debugging with the remote target, and
11865 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11866 tracing}), pending tracepoints can not be resolved (and downloaded to
11867 the remote stub) while @value{GDBN} is disconnected.
11869 Here are some examples of using the @code{trace} command:
11872 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11874 (@value{GDBP}) @b{trace +2} // 2 lines forward
11876 (@value{GDBP}) @b{trace my_function} // first source line of function
11878 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11880 (@value{GDBP}) @b{trace *0x2117c4} // an address
11884 You can abbreviate @code{trace} as @code{tr}.
11886 @item trace @var{location} if @var{cond}
11887 Set a tracepoint with condition @var{cond}; evaluate the expression
11888 @var{cond} each time the tracepoint is reached, and collect data only
11889 if the value is nonzero---that is, if @var{cond} evaluates as true.
11890 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11891 information on tracepoint conditions.
11893 @item ftrace @var{location} [ if @var{cond} ]
11894 @cindex set fast tracepoint
11895 @cindex fast tracepoints, setting
11897 The @code{ftrace} command sets a fast tracepoint. For targets that
11898 support them, fast tracepoints will use a more efficient but possibly
11899 less general technique to trigger data collection, such as a jump
11900 instruction instead of a trap, or some sort of hardware support. It
11901 may not be possible to create a fast tracepoint at the desired
11902 location, in which case the command will exit with an explanatory
11905 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11908 On 32-bit x86-architecture systems, fast tracepoints normally need to
11909 be placed at an instruction that is 5 bytes or longer, but can be
11910 placed at 4-byte instructions if the low 64K of memory of the target
11911 program is available to install trampolines. Some Unix-type systems,
11912 such as @sc{gnu}/Linux, exclude low addresses from the program's
11913 address space; but for instance with the Linux kernel it is possible
11914 to let @value{GDBN} use this area by doing a @command{sysctl} command
11915 to set the @code{mmap_min_addr} kernel parameter, as in
11918 sudo sysctl -w vm.mmap_min_addr=32768
11922 which sets the low address to 32K, which leaves plenty of room for
11923 trampolines. The minimum address should be set to a page boundary.
11925 @item strace @var{location} [ if @var{cond} ]
11926 @cindex set static tracepoint
11927 @cindex static tracepoints, setting
11928 @cindex probe static tracepoint marker
11930 The @code{strace} command sets a static tracepoint. For targets that
11931 support it, setting a static tracepoint probes a static
11932 instrumentation point, or marker, found at @var{location}. It may not
11933 be possible to set a static tracepoint at the desired location, in
11934 which case the command will exit with an explanatory message.
11936 @value{GDBN} handles arguments to @code{strace} exactly as for
11937 @code{trace}, with the addition that the user can also specify
11938 @code{-m @var{marker}} as @var{location}. This probes the marker
11939 identified by the @var{marker} string identifier. This identifier
11940 depends on the static tracepoint backend library your program is
11941 using. You can find all the marker identifiers in the @samp{ID} field
11942 of the @code{info static-tracepoint-markers} command output.
11943 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11944 Markers}. For example, in the following small program using the UST
11950 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11955 the marker id is composed of joining the first two arguments to the
11956 @code{trace_mark} call with a slash, which translates to:
11959 (@value{GDBP}) info static-tracepoint-markers
11960 Cnt Enb ID Address What
11961 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11967 so you may probe the marker above with:
11970 (@value{GDBP}) strace -m ust/bar33
11973 Static tracepoints accept an extra collect action --- @code{collect
11974 $_sdata}. This collects arbitrary user data passed in the probe point
11975 call to the tracing library. In the UST example above, you'll see
11976 that the third argument to @code{trace_mark} is a printf-like format
11977 string. The user data is then the result of running that formating
11978 string against the following arguments. Note that @code{info
11979 static-tracepoint-markers} command output lists that format string in
11980 the @samp{Data:} field.
11982 You can inspect this data when analyzing the trace buffer, by printing
11983 the $_sdata variable like any other variable available to
11984 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11987 @cindex last tracepoint number
11988 @cindex recent tracepoint number
11989 @cindex tracepoint number
11990 The convenience variable @code{$tpnum} records the tracepoint number
11991 of the most recently set tracepoint.
11993 @kindex delete tracepoint
11994 @cindex tracepoint deletion
11995 @item delete tracepoint @r{[}@var{num}@r{]}
11996 Permanently delete one or more tracepoints. With no argument, the
11997 default is to delete all tracepoints. Note that the regular
11998 @code{delete} command can remove tracepoints also.
12003 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12005 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12009 You can abbreviate this command as @code{del tr}.
12012 @node Enable and Disable Tracepoints
12013 @subsection Enable and Disable Tracepoints
12015 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12018 @kindex disable tracepoint
12019 @item disable tracepoint @r{[}@var{num}@r{]}
12020 Disable tracepoint @var{num}, or all tracepoints if no argument
12021 @var{num} is given. A disabled tracepoint will have no effect during
12022 a trace experiment, but it is not forgotten. You can re-enable
12023 a disabled tracepoint using the @code{enable tracepoint} command.
12024 If the command is issued during a trace experiment and the debug target
12025 has support for disabling tracepoints during a trace experiment, then the
12026 change will be effective immediately. Otherwise, it will be applied to the
12027 next trace experiment.
12029 @kindex enable tracepoint
12030 @item enable tracepoint @r{[}@var{num}@r{]}
12031 Enable tracepoint @var{num}, or all tracepoints. If this command is
12032 issued during a trace experiment and the debug target supports enabling
12033 tracepoints during a trace experiment, then the enabled tracepoints will
12034 become effective immediately. Otherwise, they will become effective the
12035 next time a trace experiment is run.
12038 @node Tracepoint Passcounts
12039 @subsection Tracepoint Passcounts
12043 @cindex tracepoint pass count
12044 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12045 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12046 automatically stop a trace experiment. If a tracepoint's passcount is
12047 @var{n}, then the trace experiment will be automatically stopped on
12048 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12049 @var{num} is not specified, the @code{passcount} command sets the
12050 passcount of the most recently defined tracepoint. If no passcount is
12051 given, the trace experiment will run until stopped explicitly by the
12057 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12058 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12060 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12061 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12062 (@value{GDBP}) @b{trace foo}
12063 (@value{GDBP}) @b{pass 3}
12064 (@value{GDBP}) @b{trace bar}
12065 (@value{GDBP}) @b{pass 2}
12066 (@value{GDBP}) @b{trace baz}
12067 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12068 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12069 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12070 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12074 @node Tracepoint Conditions
12075 @subsection Tracepoint Conditions
12076 @cindex conditional tracepoints
12077 @cindex tracepoint conditions
12079 The simplest sort of tracepoint collects data every time your program
12080 reaches a specified place. You can also specify a @dfn{condition} for
12081 a tracepoint. A condition is just a Boolean expression in your
12082 programming language (@pxref{Expressions, ,Expressions}). A
12083 tracepoint with a condition evaluates the expression each time your
12084 program reaches it, and data collection happens only if the condition
12087 Tracepoint conditions can be specified when a tracepoint is set, by
12088 using @samp{if} in the arguments to the @code{trace} command.
12089 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12090 also be set or changed at any time with the @code{condition} command,
12091 just as with breakpoints.
12093 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12094 the conditional expression itself. Instead, @value{GDBN} encodes the
12095 expression into an agent expression (@pxref{Agent Expressions})
12096 suitable for execution on the target, independently of @value{GDBN}.
12097 Global variables become raw memory locations, locals become stack
12098 accesses, and so forth.
12100 For instance, suppose you have a function that is usually called
12101 frequently, but should not be called after an error has occurred. You
12102 could use the following tracepoint command to collect data about calls
12103 of that function that happen while the error code is propagating
12104 through the program; an unconditional tracepoint could end up
12105 collecting thousands of useless trace frames that you would have to
12109 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12112 @node Trace State Variables
12113 @subsection Trace State Variables
12114 @cindex trace state variables
12116 A @dfn{trace state variable} is a special type of variable that is
12117 created and managed by target-side code. The syntax is the same as
12118 that for GDB's convenience variables (a string prefixed with ``$''),
12119 but they are stored on the target. They must be created explicitly,
12120 using a @code{tvariable} command. They are always 64-bit signed
12123 Trace state variables are remembered by @value{GDBN}, and downloaded
12124 to the target along with tracepoint information when the trace
12125 experiment starts. There are no intrinsic limits on the number of
12126 trace state variables, beyond memory limitations of the target.
12128 @cindex convenience variables, and trace state variables
12129 Although trace state variables are managed by the target, you can use
12130 them in print commands and expressions as if they were convenience
12131 variables; @value{GDBN} will get the current value from the target
12132 while the trace experiment is running. Trace state variables share
12133 the same namespace as other ``$'' variables, which means that you
12134 cannot have trace state variables with names like @code{$23} or
12135 @code{$pc}, nor can you have a trace state variable and a convenience
12136 variable with the same name.
12140 @item tvariable $@var{name} [ = @var{expression} ]
12142 The @code{tvariable} command creates a new trace state variable named
12143 @code{$@var{name}}, and optionally gives it an initial value of
12144 @var{expression}. The @var{expression} is evaluated when this command is
12145 entered; the result will be converted to an integer if possible,
12146 otherwise @value{GDBN} will report an error. A subsequent
12147 @code{tvariable} command specifying the same name does not create a
12148 variable, but instead assigns the supplied initial value to the
12149 existing variable of that name, overwriting any previous initial
12150 value. The default initial value is 0.
12152 @item info tvariables
12153 @kindex info tvariables
12154 List all the trace state variables along with their initial values.
12155 Their current values may also be displayed, if the trace experiment is
12158 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12159 @kindex delete tvariable
12160 Delete the given trace state variables, or all of them if no arguments
12165 @node Tracepoint Actions
12166 @subsection Tracepoint Action Lists
12170 @cindex tracepoint actions
12171 @item actions @r{[}@var{num}@r{]}
12172 This command will prompt for a list of actions to be taken when the
12173 tracepoint is hit. If the tracepoint number @var{num} is not
12174 specified, this command sets the actions for the one that was most
12175 recently defined (so that you can define a tracepoint and then say
12176 @code{actions} without bothering about its number). You specify the
12177 actions themselves on the following lines, one action at a time, and
12178 terminate the actions list with a line containing just @code{end}. So
12179 far, the only defined actions are @code{collect}, @code{teval}, and
12180 @code{while-stepping}.
12182 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12183 Commands, ,Breakpoint Command Lists}), except that only the defined
12184 actions are allowed; any other @value{GDBN} command is rejected.
12186 @cindex remove actions from a tracepoint
12187 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12188 and follow it immediately with @samp{end}.
12191 (@value{GDBP}) @b{collect @var{data}} // collect some data
12193 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12195 (@value{GDBP}) @b{end} // signals the end of actions.
12198 In the following example, the action list begins with @code{collect}
12199 commands indicating the things to be collected when the tracepoint is
12200 hit. Then, in order to single-step and collect additional data
12201 following the tracepoint, a @code{while-stepping} command is used,
12202 followed by the list of things to be collected after each step in a
12203 sequence of single steps. The @code{while-stepping} command is
12204 terminated by its own separate @code{end} command. Lastly, the action
12205 list is terminated by an @code{end} command.
12208 (@value{GDBP}) @b{trace foo}
12209 (@value{GDBP}) @b{actions}
12210 Enter actions for tracepoint 1, one per line:
12213 > while-stepping 12
12214 > collect $pc, arr[i]
12219 @kindex collect @r{(tracepoints)}
12220 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12221 Collect values of the given expressions when the tracepoint is hit.
12222 This command accepts a comma-separated list of any valid expressions.
12223 In addition to global, static, or local variables, the following
12224 special arguments are supported:
12228 Collect all registers.
12231 Collect all function arguments.
12234 Collect all local variables.
12237 Collect the return address. This is helpful if you want to see more
12241 Collects the number of arguments from the static probe at which the
12242 tracepoint is located.
12243 @xref{Static Probe Points}.
12245 @item $_probe_arg@var{n}
12246 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12247 from the static probe at which the tracepoint is located.
12248 @xref{Static Probe Points}.
12251 @vindex $_sdata@r{, collect}
12252 Collect static tracepoint marker specific data. Only available for
12253 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12254 Lists}. On the UST static tracepoints library backend, an
12255 instrumentation point resembles a @code{printf} function call. The
12256 tracing library is able to collect user specified data formatted to a
12257 character string using the format provided by the programmer that
12258 instrumented the program. Other backends have similar mechanisms.
12259 Here's an example of a UST marker call:
12262 const char master_name[] = "$your_name";
12263 trace_mark(channel1, marker1, "hello %s", master_name)
12266 In this case, collecting @code{$_sdata} collects the string
12267 @samp{hello $yourname}. When analyzing the trace buffer, you can
12268 inspect @samp{$_sdata} like any other variable available to
12272 You can give several consecutive @code{collect} commands, each one
12273 with a single argument, or one @code{collect} command with several
12274 arguments separated by commas; the effect is the same.
12276 The optional @var{mods} changes the usual handling of the arguments.
12277 @code{s} requests that pointers to chars be handled as strings, in
12278 particular collecting the contents of the memory being pointed at, up
12279 to the first zero. The upper bound is by default the value of the
12280 @code{print elements} variable; if @code{s} is followed by a decimal
12281 number, that is the upper bound instead. So for instance
12282 @samp{collect/s25 mystr} collects as many as 25 characters at
12285 The command @code{info scope} (@pxref{Symbols, info scope}) is
12286 particularly useful for figuring out what data to collect.
12288 @kindex teval @r{(tracepoints)}
12289 @item teval @var{expr1}, @var{expr2}, @dots{}
12290 Evaluate the given expressions when the tracepoint is hit. This
12291 command accepts a comma-separated list of expressions. The results
12292 are discarded, so this is mainly useful for assigning values to trace
12293 state variables (@pxref{Trace State Variables}) without adding those
12294 values to the trace buffer, as would be the case if the @code{collect}
12297 @kindex while-stepping @r{(tracepoints)}
12298 @item while-stepping @var{n}
12299 Perform @var{n} single-step instruction traces after the tracepoint,
12300 collecting new data after each step. The @code{while-stepping}
12301 command is followed by the list of what to collect while stepping
12302 (followed by its own @code{end} command):
12305 > while-stepping 12
12306 > collect $regs, myglobal
12312 Note that @code{$pc} is not automatically collected by
12313 @code{while-stepping}; you need to explicitly collect that register if
12314 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12317 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12318 @kindex set default-collect
12319 @cindex default collection action
12320 This variable is a list of expressions to collect at each tracepoint
12321 hit. It is effectively an additional @code{collect} action prepended
12322 to every tracepoint action list. The expressions are parsed
12323 individually for each tracepoint, so for instance a variable named
12324 @code{xyz} may be interpreted as a global for one tracepoint, and a
12325 local for another, as appropriate to the tracepoint's location.
12327 @item show default-collect
12328 @kindex show default-collect
12329 Show the list of expressions that are collected by default at each
12334 @node Listing Tracepoints
12335 @subsection Listing Tracepoints
12338 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12339 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12340 @cindex information about tracepoints
12341 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12342 Display information about the tracepoint @var{num}. If you don't
12343 specify a tracepoint number, displays information about all the
12344 tracepoints defined so far. The format is similar to that used for
12345 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12346 command, simply restricting itself to tracepoints.
12348 A tracepoint's listing may include additional information specific to
12353 its passcount as given by the @code{passcount @var{n}} command
12356 the state about installed on target of each location
12360 (@value{GDBP}) @b{info trace}
12361 Num Type Disp Enb Address What
12362 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12364 collect globfoo, $regs
12369 2 tracepoint keep y <MULTIPLE>
12371 2.1 y 0x0804859c in func4 at change-loc.h:35
12372 installed on target
12373 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12374 installed on target
12375 2.3 y <PENDING> set_tracepoint
12376 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12377 not installed on target
12382 This command can be abbreviated @code{info tp}.
12385 @node Listing Static Tracepoint Markers
12386 @subsection Listing Static Tracepoint Markers
12389 @kindex info static-tracepoint-markers
12390 @cindex information about static tracepoint markers
12391 @item info static-tracepoint-markers
12392 Display information about all static tracepoint markers defined in the
12395 For each marker, the following columns are printed:
12399 An incrementing counter, output to help readability. This is not a
12402 The marker ID, as reported by the target.
12403 @item Enabled or Disabled
12404 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12405 that are not enabled.
12407 Where the marker is in your program, as a memory address.
12409 Where the marker is in the source for your program, as a file and line
12410 number. If the debug information included in the program does not
12411 allow @value{GDBN} to locate the source of the marker, this column
12412 will be left blank.
12416 In addition, the following information may be printed for each marker:
12420 User data passed to the tracing library by the marker call. In the
12421 UST backend, this is the format string passed as argument to the
12423 @item Static tracepoints probing the marker
12424 The list of static tracepoints attached to the marker.
12428 (@value{GDBP}) info static-tracepoint-markers
12429 Cnt ID Enb Address What
12430 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12431 Data: number1 %d number2 %d
12432 Probed by static tracepoints: #2
12433 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12439 @node Starting and Stopping Trace Experiments
12440 @subsection Starting and Stopping Trace Experiments
12443 @kindex tstart [ @var{notes} ]
12444 @cindex start a new trace experiment
12445 @cindex collected data discarded
12447 This command starts the trace experiment, and begins collecting data.
12448 It has the side effect of discarding all the data collected in the
12449 trace buffer during the previous trace experiment. If any arguments
12450 are supplied, they are taken as a note and stored with the trace
12451 experiment's state. The notes may be arbitrary text, and are
12452 especially useful with disconnected tracing in a multi-user context;
12453 the notes can explain what the trace is doing, supply user contact
12454 information, and so forth.
12456 @kindex tstop [ @var{notes} ]
12457 @cindex stop a running trace experiment
12459 This command stops the trace experiment. If any arguments are
12460 supplied, they are recorded with the experiment as a note. This is
12461 useful if you are stopping a trace started by someone else, for
12462 instance if the trace is interfering with the system's behavior and
12463 needs to be stopped quickly.
12465 @strong{Note}: a trace experiment and data collection may stop
12466 automatically if any tracepoint's passcount is reached
12467 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12470 @cindex status of trace data collection
12471 @cindex trace experiment, status of
12473 This command displays the status of the current trace data
12477 Here is an example of the commands we described so far:
12480 (@value{GDBP}) @b{trace gdb_c_test}
12481 (@value{GDBP}) @b{actions}
12482 Enter actions for tracepoint #1, one per line.
12483 > collect $regs,$locals,$args
12484 > while-stepping 11
12488 (@value{GDBP}) @b{tstart}
12489 [time passes @dots{}]
12490 (@value{GDBP}) @b{tstop}
12493 @anchor{disconnected tracing}
12494 @cindex disconnected tracing
12495 You can choose to continue running the trace experiment even if
12496 @value{GDBN} disconnects from the target, voluntarily or
12497 involuntarily. For commands such as @code{detach}, the debugger will
12498 ask what you want to do with the trace. But for unexpected
12499 terminations (@value{GDBN} crash, network outage), it would be
12500 unfortunate to lose hard-won trace data, so the variable
12501 @code{disconnected-tracing} lets you decide whether the trace should
12502 continue running without @value{GDBN}.
12505 @item set disconnected-tracing on
12506 @itemx set disconnected-tracing off
12507 @kindex set disconnected-tracing
12508 Choose whether a tracing run should continue to run if @value{GDBN}
12509 has disconnected from the target. Note that @code{detach} or
12510 @code{quit} will ask you directly what to do about a running trace no
12511 matter what this variable's setting, so the variable is mainly useful
12512 for handling unexpected situations, such as loss of the network.
12514 @item show disconnected-tracing
12515 @kindex show disconnected-tracing
12516 Show the current choice for disconnected tracing.
12520 When you reconnect to the target, the trace experiment may or may not
12521 still be running; it might have filled the trace buffer in the
12522 meantime, or stopped for one of the other reasons. If it is running,
12523 it will continue after reconnection.
12525 Upon reconnection, the target will upload information about the
12526 tracepoints in effect. @value{GDBN} will then compare that
12527 information to the set of tracepoints currently defined, and attempt
12528 to match them up, allowing for the possibility that the numbers may
12529 have changed due to creation and deletion in the meantime. If one of
12530 the target's tracepoints does not match any in @value{GDBN}, the
12531 debugger will create a new tracepoint, so that you have a number with
12532 which to specify that tracepoint. This matching-up process is
12533 necessarily heuristic, and it may result in useless tracepoints being
12534 created; you may simply delete them if they are of no use.
12536 @cindex circular trace buffer
12537 If your target agent supports a @dfn{circular trace buffer}, then you
12538 can run a trace experiment indefinitely without filling the trace
12539 buffer; when space runs out, the agent deletes already-collected trace
12540 frames, oldest first, until there is enough room to continue
12541 collecting. This is especially useful if your tracepoints are being
12542 hit too often, and your trace gets terminated prematurely because the
12543 buffer is full. To ask for a circular trace buffer, simply set
12544 @samp{circular-trace-buffer} to on. You can set this at any time,
12545 including during tracing; if the agent can do it, it will change
12546 buffer handling on the fly, otherwise it will not take effect until
12550 @item set circular-trace-buffer on
12551 @itemx set circular-trace-buffer off
12552 @kindex set circular-trace-buffer
12553 Choose whether a tracing run should use a linear or circular buffer
12554 for trace data. A linear buffer will not lose any trace data, but may
12555 fill up prematurely, while a circular buffer will discard old trace
12556 data, but it will have always room for the latest tracepoint hits.
12558 @item show circular-trace-buffer
12559 @kindex show circular-trace-buffer
12560 Show the current choice for the trace buffer. Note that this may not
12561 match the agent's current buffer handling, nor is it guaranteed to
12562 match the setting that might have been in effect during a past run,
12563 for instance if you are looking at frames from a trace file.
12568 @item set trace-buffer-size @var{n}
12569 @itemx set trace-buffer-size unlimited
12570 @kindex set trace-buffer-size
12571 Request that the target use a trace buffer of @var{n} bytes. Not all
12572 targets will honor the request; they may have a compiled-in size for
12573 the trace buffer, or some other limitation. Set to a value of
12574 @code{unlimited} or @code{-1} to let the target use whatever size it
12575 likes. This is also the default.
12577 @item show trace-buffer-size
12578 @kindex show trace-buffer-size
12579 Show the current requested size for the trace buffer. Note that this
12580 will only match the actual size if the target supports size-setting,
12581 and was able to handle the requested size. For instance, if the
12582 target can only change buffer size between runs, this variable will
12583 not reflect the change until the next run starts. Use @code{tstatus}
12584 to get a report of the actual buffer size.
12588 @item set trace-user @var{text}
12589 @kindex set trace-user
12591 @item show trace-user
12592 @kindex show trace-user
12594 @item set trace-notes @var{text}
12595 @kindex set trace-notes
12596 Set the trace run's notes.
12598 @item show trace-notes
12599 @kindex show trace-notes
12600 Show the trace run's notes.
12602 @item set trace-stop-notes @var{text}
12603 @kindex set trace-stop-notes
12604 Set the trace run's stop notes. The handling of the note is as for
12605 @code{tstop} arguments; the set command is convenient way to fix a
12606 stop note that is mistaken or incomplete.
12608 @item show trace-stop-notes
12609 @kindex show trace-stop-notes
12610 Show the trace run's stop notes.
12614 @node Tracepoint Restrictions
12615 @subsection Tracepoint Restrictions
12617 @cindex tracepoint restrictions
12618 There are a number of restrictions on the use of tracepoints. As
12619 described above, tracepoint data gathering occurs on the target
12620 without interaction from @value{GDBN}. Thus the full capabilities of
12621 the debugger are not available during data gathering, and then at data
12622 examination time, you will be limited by only having what was
12623 collected. The following items describe some common problems, but it
12624 is not exhaustive, and you may run into additional difficulties not
12630 Tracepoint expressions are intended to gather objects (lvalues). Thus
12631 the full flexibility of GDB's expression evaluator is not available.
12632 You cannot call functions, cast objects to aggregate types, access
12633 convenience variables or modify values (except by assignment to trace
12634 state variables). Some language features may implicitly call
12635 functions (for instance Objective-C fields with accessors), and therefore
12636 cannot be collected either.
12639 Collection of local variables, either individually or in bulk with
12640 @code{$locals} or @code{$args}, during @code{while-stepping} may
12641 behave erratically. The stepping action may enter a new scope (for
12642 instance by stepping into a function), or the location of the variable
12643 may change (for instance it is loaded into a register). The
12644 tracepoint data recorded uses the location information for the
12645 variables that is correct for the tracepoint location. When the
12646 tracepoint is created, it is not possible, in general, to determine
12647 where the steps of a @code{while-stepping} sequence will advance the
12648 program---particularly if a conditional branch is stepped.
12651 Collection of an incompletely-initialized or partially-destroyed object
12652 may result in something that @value{GDBN} cannot display, or displays
12653 in a misleading way.
12656 When @value{GDBN} displays a pointer to character it automatically
12657 dereferences the pointer to also display characters of the string
12658 being pointed to. However, collecting the pointer during tracing does
12659 not automatically collect the string. You need to explicitly
12660 dereference the pointer and provide size information if you want to
12661 collect not only the pointer, but the memory pointed to. For example,
12662 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12666 It is not possible to collect a complete stack backtrace at a
12667 tracepoint. Instead, you may collect the registers and a few hundred
12668 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12669 (adjust to use the name of the actual stack pointer register on your
12670 target architecture, and the amount of stack you wish to capture).
12671 Then the @code{backtrace} command will show a partial backtrace when
12672 using a trace frame. The number of stack frames that can be examined
12673 depends on the sizes of the frames in the collected stack. Note that
12674 if you ask for a block so large that it goes past the bottom of the
12675 stack, the target agent may report an error trying to read from an
12679 If you do not collect registers at a tracepoint, @value{GDBN} can
12680 infer that the value of @code{$pc} must be the same as the address of
12681 the tracepoint and use that when you are looking at a trace frame
12682 for that tracepoint. However, this cannot work if the tracepoint has
12683 multiple locations (for instance if it was set in a function that was
12684 inlined), or if it has a @code{while-stepping} loop. In those cases
12685 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12690 @node Analyze Collected Data
12691 @section Using the Collected Data
12693 After the tracepoint experiment ends, you use @value{GDBN} commands
12694 for examining the trace data. The basic idea is that each tracepoint
12695 collects a trace @dfn{snapshot} every time it is hit and another
12696 snapshot every time it single-steps. All these snapshots are
12697 consecutively numbered from zero and go into a buffer, and you can
12698 examine them later. The way you examine them is to @dfn{focus} on a
12699 specific trace snapshot. When the remote stub is focused on a trace
12700 snapshot, it will respond to all @value{GDBN} requests for memory and
12701 registers by reading from the buffer which belongs to that snapshot,
12702 rather than from @emph{real} memory or registers of the program being
12703 debugged. This means that @strong{all} @value{GDBN} commands
12704 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12705 behave as if we were currently debugging the program state as it was
12706 when the tracepoint occurred. Any requests for data that are not in
12707 the buffer will fail.
12710 * tfind:: How to select a trace snapshot
12711 * tdump:: How to display all data for a snapshot
12712 * save tracepoints:: How to save tracepoints for a future run
12716 @subsection @code{tfind @var{n}}
12719 @cindex select trace snapshot
12720 @cindex find trace snapshot
12721 The basic command for selecting a trace snapshot from the buffer is
12722 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12723 counting from zero. If no argument @var{n} is given, the next
12724 snapshot is selected.
12726 Here are the various forms of using the @code{tfind} command.
12730 Find the first snapshot in the buffer. This is a synonym for
12731 @code{tfind 0} (since 0 is the number of the first snapshot).
12734 Stop debugging trace snapshots, resume @emph{live} debugging.
12737 Same as @samp{tfind none}.
12740 No argument means find the next trace snapshot.
12743 Find the previous trace snapshot before the current one. This permits
12744 retracing earlier steps.
12746 @item tfind tracepoint @var{num}
12747 Find the next snapshot associated with tracepoint @var{num}. Search
12748 proceeds forward from the last examined trace snapshot. If no
12749 argument @var{num} is given, it means find the next snapshot collected
12750 for the same tracepoint as the current snapshot.
12752 @item tfind pc @var{addr}
12753 Find the next snapshot associated with the value @var{addr} of the
12754 program counter. Search proceeds forward from the last examined trace
12755 snapshot. If no argument @var{addr} is given, it means find the next
12756 snapshot with the same value of PC as the current snapshot.
12758 @item tfind outside @var{addr1}, @var{addr2}
12759 Find the next snapshot whose PC is outside the given range of
12760 addresses (exclusive).
12762 @item tfind range @var{addr1}, @var{addr2}
12763 Find the next snapshot whose PC is between @var{addr1} and
12764 @var{addr2} (inclusive).
12766 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12767 Find the next snapshot associated with the source line @var{n}. If
12768 the optional argument @var{file} is given, refer to line @var{n} in
12769 that source file. Search proceeds forward from the last examined
12770 trace snapshot. If no argument @var{n} is given, it means find the
12771 next line other than the one currently being examined; thus saying
12772 @code{tfind line} repeatedly can appear to have the same effect as
12773 stepping from line to line in a @emph{live} debugging session.
12776 The default arguments for the @code{tfind} commands are specifically
12777 designed to make it easy to scan through the trace buffer. For
12778 instance, @code{tfind} with no argument selects the next trace
12779 snapshot, and @code{tfind -} with no argument selects the previous
12780 trace snapshot. So, by giving one @code{tfind} command, and then
12781 simply hitting @key{RET} repeatedly you can examine all the trace
12782 snapshots in order. Or, by saying @code{tfind -} and then hitting
12783 @key{RET} repeatedly you can examine the snapshots in reverse order.
12784 The @code{tfind line} command with no argument selects the snapshot
12785 for the next source line executed. The @code{tfind pc} command with
12786 no argument selects the next snapshot with the same program counter
12787 (PC) as the current frame. The @code{tfind tracepoint} command with
12788 no argument selects the next trace snapshot collected by the same
12789 tracepoint as the current one.
12791 In addition to letting you scan through the trace buffer manually,
12792 these commands make it easy to construct @value{GDBN} scripts that
12793 scan through the trace buffer and print out whatever collected data
12794 you are interested in. Thus, if we want to examine the PC, FP, and SP
12795 registers from each trace frame in the buffer, we can say this:
12798 (@value{GDBP}) @b{tfind start}
12799 (@value{GDBP}) @b{while ($trace_frame != -1)}
12800 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12801 $trace_frame, $pc, $sp, $fp
12805 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12806 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12807 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12808 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12809 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12810 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12811 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12812 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12813 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12814 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12815 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12818 Or, if we want to examine the variable @code{X} at each source line in
12822 (@value{GDBP}) @b{tfind start}
12823 (@value{GDBP}) @b{while ($trace_frame != -1)}
12824 > printf "Frame %d, X == %d\n", $trace_frame, X
12834 @subsection @code{tdump}
12836 @cindex dump all data collected at tracepoint
12837 @cindex tracepoint data, display
12839 This command takes no arguments. It prints all the data collected at
12840 the current trace snapshot.
12843 (@value{GDBP}) @b{trace 444}
12844 (@value{GDBP}) @b{actions}
12845 Enter actions for tracepoint #2, one per line:
12846 > collect $regs, $locals, $args, gdb_long_test
12849 (@value{GDBP}) @b{tstart}
12851 (@value{GDBP}) @b{tfind line 444}
12852 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12854 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12856 (@value{GDBP}) @b{tdump}
12857 Data collected at tracepoint 2, trace frame 1:
12858 d0 0xc4aa0085 -995491707
12862 d4 0x71aea3d 119204413
12865 d7 0x380035 3670069
12866 a0 0x19e24a 1696330
12867 a1 0x3000668 50333288
12869 a3 0x322000 3284992
12870 a4 0x3000698 50333336
12871 a5 0x1ad3cc 1758156
12872 fp 0x30bf3c 0x30bf3c
12873 sp 0x30bf34 0x30bf34
12875 pc 0x20b2c8 0x20b2c8
12879 p = 0x20e5b4 "gdb-test"
12886 gdb_long_test = 17 '\021'
12891 @code{tdump} works by scanning the tracepoint's current collection
12892 actions and printing the value of each expression listed. So
12893 @code{tdump} can fail, if after a run, you change the tracepoint's
12894 actions to mention variables that were not collected during the run.
12896 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12897 uses the collected value of @code{$pc} to distinguish between trace
12898 frames that were collected at the tracepoint hit, and frames that were
12899 collected while stepping. This allows it to correctly choose whether
12900 to display the basic list of collections, or the collections from the
12901 body of the while-stepping loop. However, if @code{$pc} was not collected,
12902 then @code{tdump} will always attempt to dump using the basic collection
12903 list, and may fail if a while-stepping frame does not include all the
12904 same data that is collected at the tracepoint hit.
12905 @c This is getting pretty arcane, example would be good.
12907 @node save tracepoints
12908 @subsection @code{save tracepoints @var{filename}}
12909 @kindex save tracepoints
12910 @kindex save-tracepoints
12911 @cindex save tracepoints for future sessions
12913 This command saves all current tracepoint definitions together with
12914 their actions and passcounts, into a file @file{@var{filename}}
12915 suitable for use in a later debugging session. To read the saved
12916 tracepoint definitions, use the @code{source} command (@pxref{Command
12917 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12918 alias for @w{@code{save tracepoints}}
12920 @node Tracepoint Variables
12921 @section Convenience Variables for Tracepoints
12922 @cindex tracepoint variables
12923 @cindex convenience variables for tracepoints
12926 @vindex $trace_frame
12927 @item (int) $trace_frame
12928 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12929 snapshot is selected.
12931 @vindex $tracepoint
12932 @item (int) $tracepoint
12933 The tracepoint for the current trace snapshot.
12935 @vindex $trace_line
12936 @item (int) $trace_line
12937 The line number for the current trace snapshot.
12939 @vindex $trace_file
12940 @item (char []) $trace_file
12941 The source file for the current trace snapshot.
12943 @vindex $trace_func
12944 @item (char []) $trace_func
12945 The name of the function containing @code{$tracepoint}.
12948 Note: @code{$trace_file} is not suitable for use in @code{printf},
12949 use @code{output} instead.
12951 Here's a simple example of using these convenience variables for
12952 stepping through all the trace snapshots and printing some of their
12953 data. Note that these are not the same as trace state variables,
12954 which are managed by the target.
12957 (@value{GDBP}) @b{tfind start}
12959 (@value{GDBP}) @b{while $trace_frame != -1}
12960 > output $trace_file
12961 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12967 @section Using Trace Files
12968 @cindex trace files
12970 In some situations, the target running a trace experiment may no
12971 longer be available; perhaps it crashed, or the hardware was needed
12972 for a different activity. To handle these cases, you can arrange to
12973 dump the trace data into a file, and later use that file as a source
12974 of trace data, via the @code{target tfile} command.
12979 @item tsave [ -r ] @var{filename}
12980 @itemx tsave [-ctf] @var{dirname}
12981 Save the trace data to @var{filename}. By default, this command
12982 assumes that @var{filename} refers to the host filesystem, so if
12983 necessary @value{GDBN} will copy raw trace data up from the target and
12984 then save it. If the target supports it, you can also supply the
12985 optional argument @code{-r} (``remote'') to direct the target to save
12986 the data directly into @var{filename} in its own filesystem, which may be
12987 more efficient if the trace buffer is very large. (Note, however, that
12988 @code{target tfile} can only read from files accessible to the host.)
12989 By default, this command will save trace frame in tfile format.
12990 You can supply the optional argument @code{-ctf} to save date in CTF
12991 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12992 that can be shared by multiple debugging and tracing tools. Please go to
12993 @indicateurl{http://www.efficios.com/ctf} to get more information.
12995 @kindex target tfile
12999 @item target tfile @var{filename}
13000 @itemx target ctf @var{dirname}
13001 Use the file named @var{filename} or directory named @var{dirname} as
13002 a source of trace data. Commands that examine data work as they do with
13003 a live target, but it is not possible to run any new trace experiments.
13004 @code{tstatus} will report the state of the trace run at the moment
13005 the data was saved, as well as the current trace frame you are examining.
13006 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13010 (@value{GDBP}) target ctf ctf.ctf
13011 (@value{GDBP}) tfind
13012 Found trace frame 0, tracepoint 2
13013 39 ++a; /* set tracepoint 1 here */
13014 (@value{GDBP}) tdump
13015 Data collected at tracepoint 2, trace frame 0:
13019 c = @{"123", "456", "789", "123", "456", "789"@}
13020 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13028 @chapter Debugging Programs That Use Overlays
13031 If your program is too large to fit completely in your target system's
13032 memory, you can sometimes use @dfn{overlays} to work around this
13033 problem. @value{GDBN} provides some support for debugging programs that
13037 * How Overlays Work:: A general explanation of overlays.
13038 * Overlay Commands:: Managing overlays in @value{GDBN}.
13039 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13040 mapped by asking the inferior.
13041 * Overlay Sample Program:: A sample program using overlays.
13044 @node How Overlays Work
13045 @section How Overlays Work
13046 @cindex mapped overlays
13047 @cindex unmapped overlays
13048 @cindex load address, overlay's
13049 @cindex mapped address
13050 @cindex overlay area
13052 Suppose you have a computer whose instruction address space is only 64
13053 kilobytes long, but which has much more memory which can be accessed by
13054 other means: special instructions, segment registers, or memory
13055 management hardware, for example. Suppose further that you want to
13056 adapt a program which is larger than 64 kilobytes to run on this system.
13058 One solution is to identify modules of your program which are relatively
13059 independent, and need not call each other directly; call these modules
13060 @dfn{overlays}. Separate the overlays from the main program, and place
13061 their machine code in the larger memory. Place your main program in
13062 instruction memory, but leave at least enough space there to hold the
13063 largest overlay as well.
13065 Now, to call a function located in an overlay, you must first copy that
13066 overlay's machine code from the large memory into the space set aside
13067 for it in the instruction memory, and then jump to its entry point
13070 @c NB: In the below the mapped area's size is greater or equal to the
13071 @c size of all overlays. This is intentional to remind the developer
13072 @c that overlays don't necessarily need to be the same size.
13076 Data Instruction Larger
13077 Address Space Address Space Address Space
13078 +-----------+ +-----------+ +-----------+
13080 +-----------+ +-----------+ +-----------+<-- overlay 1
13081 | program | | main | .----| overlay 1 | load address
13082 | variables | | program | | +-----------+
13083 | and heap | | | | | |
13084 +-----------+ | | | +-----------+<-- overlay 2
13085 | | +-----------+ | | | load address
13086 +-----------+ | | | .-| overlay 2 |
13088 mapped --->+-----------+ | | +-----------+
13089 address | | | | | |
13090 | overlay | <-' | | |
13091 | area | <---' +-----------+<-- overlay 3
13092 | | <---. | | load address
13093 +-----------+ `--| overlay 3 |
13100 @anchor{A code overlay}A code overlay
13104 The diagram (@pxref{A code overlay}) shows a system with separate data
13105 and instruction address spaces. To map an overlay, the program copies
13106 its code from the larger address space to the instruction address space.
13107 Since the overlays shown here all use the same mapped address, only one
13108 may be mapped at a time. For a system with a single address space for
13109 data and instructions, the diagram would be similar, except that the
13110 program variables and heap would share an address space with the main
13111 program and the overlay area.
13113 An overlay loaded into instruction memory and ready for use is called a
13114 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13115 instruction memory. An overlay not present (or only partially present)
13116 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13117 is its address in the larger memory. The mapped address is also called
13118 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13119 called the @dfn{load memory address}, or @dfn{LMA}.
13121 Unfortunately, overlays are not a completely transparent way to adapt a
13122 program to limited instruction memory. They introduce a new set of
13123 global constraints you must keep in mind as you design your program:
13128 Before calling or returning to a function in an overlay, your program
13129 must make sure that overlay is actually mapped. Otherwise, the call or
13130 return will transfer control to the right address, but in the wrong
13131 overlay, and your program will probably crash.
13134 If the process of mapping an overlay is expensive on your system, you
13135 will need to choose your overlays carefully to minimize their effect on
13136 your program's performance.
13139 The executable file you load onto your system must contain each
13140 overlay's instructions, appearing at the overlay's load address, not its
13141 mapped address. However, each overlay's instructions must be relocated
13142 and its symbols defined as if the overlay were at its mapped address.
13143 You can use GNU linker scripts to specify different load and relocation
13144 addresses for pieces of your program; see @ref{Overlay Description,,,
13145 ld.info, Using ld: the GNU linker}.
13148 The procedure for loading executable files onto your system must be able
13149 to load their contents into the larger address space as well as the
13150 instruction and data spaces.
13154 The overlay system described above is rather simple, and could be
13155 improved in many ways:
13160 If your system has suitable bank switch registers or memory management
13161 hardware, you could use those facilities to make an overlay's load area
13162 contents simply appear at their mapped address in instruction space.
13163 This would probably be faster than copying the overlay to its mapped
13164 area in the usual way.
13167 If your overlays are small enough, you could set aside more than one
13168 overlay area, and have more than one overlay mapped at a time.
13171 You can use overlays to manage data, as well as instructions. In
13172 general, data overlays are even less transparent to your design than
13173 code overlays: whereas code overlays only require care when you call or
13174 return to functions, data overlays require care every time you access
13175 the data. Also, if you change the contents of a data overlay, you
13176 must copy its contents back out to its load address before you can copy a
13177 different data overlay into the same mapped area.
13182 @node Overlay Commands
13183 @section Overlay Commands
13185 To use @value{GDBN}'s overlay support, each overlay in your program must
13186 correspond to a separate section of the executable file. The section's
13187 virtual memory address and load memory address must be the overlay's
13188 mapped and load addresses. Identifying overlays with sections allows
13189 @value{GDBN} to determine the appropriate address of a function or
13190 variable, depending on whether the overlay is mapped or not.
13192 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13193 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13198 Disable @value{GDBN}'s overlay support. When overlay support is
13199 disabled, @value{GDBN} assumes that all functions and variables are
13200 always present at their mapped addresses. By default, @value{GDBN}'s
13201 overlay support is disabled.
13203 @item overlay manual
13204 @cindex manual overlay debugging
13205 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13206 relies on you to tell it which overlays are mapped, and which are not,
13207 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13208 commands described below.
13210 @item overlay map-overlay @var{overlay}
13211 @itemx overlay map @var{overlay}
13212 @cindex map an overlay
13213 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13214 be the name of the object file section containing the overlay. When an
13215 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13216 functions and variables at their mapped addresses. @value{GDBN} assumes
13217 that any other overlays whose mapped ranges overlap that of
13218 @var{overlay} are now unmapped.
13220 @item overlay unmap-overlay @var{overlay}
13221 @itemx overlay unmap @var{overlay}
13222 @cindex unmap an overlay
13223 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13224 must be the name of the object file section containing the overlay.
13225 When an overlay is unmapped, @value{GDBN} assumes it can find the
13226 overlay's functions and variables at their load addresses.
13229 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13230 consults a data structure the overlay manager maintains in the inferior
13231 to see which overlays are mapped. For details, see @ref{Automatic
13232 Overlay Debugging}.
13234 @item overlay load-target
13235 @itemx overlay load
13236 @cindex reloading the overlay table
13237 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13238 re-reads the table @value{GDBN} automatically each time the inferior
13239 stops, so this command should only be necessary if you have changed the
13240 overlay mapping yourself using @value{GDBN}. This command is only
13241 useful when using automatic overlay debugging.
13243 @item overlay list-overlays
13244 @itemx overlay list
13245 @cindex listing mapped overlays
13246 Display a list of the overlays currently mapped, along with their mapped
13247 addresses, load addresses, and sizes.
13251 Normally, when @value{GDBN} prints a code address, it includes the name
13252 of the function the address falls in:
13255 (@value{GDBP}) print main
13256 $3 = @{int ()@} 0x11a0 <main>
13259 When overlay debugging is enabled, @value{GDBN} recognizes code in
13260 unmapped overlays, and prints the names of unmapped functions with
13261 asterisks around them. For example, if @code{foo} is a function in an
13262 unmapped overlay, @value{GDBN} prints it this way:
13265 (@value{GDBP}) overlay list
13266 No sections are mapped.
13267 (@value{GDBP}) print foo
13268 $5 = @{int (int)@} 0x100000 <*foo*>
13271 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13275 (@value{GDBP}) overlay list
13276 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13277 mapped at 0x1016 - 0x104a
13278 (@value{GDBP}) print foo
13279 $6 = @{int (int)@} 0x1016 <foo>
13282 When overlay debugging is enabled, @value{GDBN} can find the correct
13283 address for functions and variables in an overlay, whether or not the
13284 overlay is mapped. This allows most @value{GDBN} commands, like
13285 @code{break} and @code{disassemble}, to work normally, even on unmapped
13286 code. However, @value{GDBN}'s breakpoint support has some limitations:
13290 @cindex breakpoints in overlays
13291 @cindex overlays, setting breakpoints in
13292 You can set breakpoints in functions in unmapped overlays, as long as
13293 @value{GDBN} can write to the overlay at its load address.
13295 @value{GDBN} can not set hardware or simulator-based breakpoints in
13296 unmapped overlays. However, if you set a breakpoint at the end of your
13297 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13298 you are using manual overlay management), @value{GDBN} will re-set its
13299 breakpoints properly.
13303 @node Automatic Overlay Debugging
13304 @section Automatic Overlay Debugging
13305 @cindex automatic overlay debugging
13307 @value{GDBN} can automatically track which overlays are mapped and which
13308 are not, given some simple co-operation from the overlay manager in the
13309 inferior. If you enable automatic overlay debugging with the
13310 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13311 looks in the inferior's memory for certain variables describing the
13312 current state of the overlays.
13314 Here are the variables your overlay manager must define to support
13315 @value{GDBN}'s automatic overlay debugging:
13319 @item @code{_ovly_table}:
13320 This variable must be an array of the following structures:
13325 /* The overlay's mapped address. */
13328 /* The size of the overlay, in bytes. */
13329 unsigned long size;
13331 /* The overlay's load address. */
13334 /* Non-zero if the overlay is currently mapped;
13336 unsigned long mapped;
13340 @item @code{_novlys}:
13341 This variable must be a four-byte signed integer, holding the total
13342 number of elements in @code{_ovly_table}.
13346 To decide whether a particular overlay is mapped or not, @value{GDBN}
13347 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13348 @code{lma} members equal the VMA and LMA of the overlay's section in the
13349 executable file. When @value{GDBN} finds a matching entry, it consults
13350 the entry's @code{mapped} member to determine whether the overlay is
13353 In addition, your overlay manager may define a function called
13354 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13355 will silently set a breakpoint there. If the overlay manager then
13356 calls this function whenever it has changed the overlay table, this
13357 will enable @value{GDBN} to accurately keep track of which overlays
13358 are in program memory, and update any breakpoints that may be set
13359 in overlays. This will allow breakpoints to work even if the
13360 overlays are kept in ROM or other non-writable memory while they
13361 are not being executed.
13363 @node Overlay Sample Program
13364 @section Overlay Sample Program
13365 @cindex overlay example program
13367 When linking a program which uses overlays, you must place the overlays
13368 at their load addresses, while relocating them to run at their mapped
13369 addresses. To do this, you must write a linker script (@pxref{Overlay
13370 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13371 since linker scripts are specific to a particular host system, target
13372 architecture, and target memory layout, this manual cannot provide
13373 portable sample code demonstrating @value{GDBN}'s overlay support.
13375 However, the @value{GDBN} source distribution does contain an overlaid
13376 program, with linker scripts for a few systems, as part of its test
13377 suite. The program consists of the following files from
13378 @file{gdb/testsuite/gdb.base}:
13382 The main program file.
13384 A simple overlay manager, used by @file{overlays.c}.
13389 Overlay modules, loaded and used by @file{overlays.c}.
13392 Linker scripts for linking the test program on the @code{d10v-elf}
13393 and @code{m32r-elf} targets.
13396 You can build the test program using the @code{d10v-elf} GCC
13397 cross-compiler like this:
13400 $ d10v-elf-gcc -g -c overlays.c
13401 $ d10v-elf-gcc -g -c ovlymgr.c
13402 $ d10v-elf-gcc -g -c foo.c
13403 $ d10v-elf-gcc -g -c bar.c
13404 $ d10v-elf-gcc -g -c baz.c
13405 $ d10v-elf-gcc -g -c grbx.c
13406 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13407 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13410 The build process is identical for any other architecture, except that
13411 you must substitute the appropriate compiler and linker script for the
13412 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13416 @chapter Using @value{GDBN} with Different Languages
13419 Although programming languages generally have common aspects, they are
13420 rarely expressed in the same manner. For instance, in ANSI C,
13421 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13422 Modula-2, it is accomplished by @code{p^}. Values can also be
13423 represented (and displayed) differently. Hex numbers in C appear as
13424 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13426 @cindex working language
13427 Language-specific information is built into @value{GDBN} for some languages,
13428 allowing you to express operations like the above in your program's
13429 native language, and allowing @value{GDBN} to output values in a manner
13430 consistent with the syntax of your program's native language. The
13431 language you use to build expressions is called the @dfn{working
13435 * Setting:: Switching between source languages
13436 * Show:: Displaying the language
13437 * Checks:: Type and range checks
13438 * Supported Languages:: Supported languages
13439 * Unsupported Languages:: Unsupported languages
13443 @section Switching Between Source Languages
13445 There are two ways to control the working language---either have @value{GDBN}
13446 set it automatically, or select it manually yourself. You can use the
13447 @code{set language} command for either purpose. On startup, @value{GDBN}
13448 defaults to setting the language automatically. The working language is
13449 used to determine how expressions you type are interpreted, how values
13452 In addition to the working language, every source file that
13453 @value{GDBN} knows about has its own working language. For some object
13454 file formats, the compiler might indicate which language a particular
13455 source file is in. However, most of the time @value{GDBN} infers the
13456 language from the name of the file. The language of a source file
13457 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13458 show each frame appropriately for its own language. There is no way to
13459 set the language of a source file from within @value{GDBN}, but you can
13460 set the language associated with a filename extension. @xref{Show, ,
13461 Displaying the Language}.
13463 This is most commonly a problem when you use a program, such
13464 as @code{cfront} or @code{f2c}, that generates C but is written in
13465 another language. In that case, make the
13466 program use @code{#line} directives in its C output; that way
13467 @value{GDBN} will know the correct language of the source code of the original
13468 program, and will display that source code, not the generated C code.
13471 * Filenames:: Filename extensions and languages.
13472 * Manually:: Setting the working language manually
13473 * Automatically:: Having @value{GDBN} infer the source language
13477 @subsection List of Filename Extensions and Languages
13479 If a source file name ends in one of the following extensions, then
13480 @value{GDBN} infers that its language is the one indicated.
13498 C@t{++} source file
13504 Objective-C source file
13508 Fortran source file
13511 Modula-2 source file
13515 Assembler source file. This actually behaves almost like C, but
13516 @value{GDBN} does not skip over function prologues when stepping.
13519 In addition, you may set the language associated with a filename
13520 extension. @xref{Show, , Displaying the Language}.
13523 @subsection Setting the Working Language
13525 If you allow @value{GDBN} to set the language automatically,
13526 expressions are interpreted the same way in your debugging session and
13529 @kindex set language
13530 If you wish, you may set the language manually. To do this, issue the
13531 command @samp{set language @var{lang}}, where @var{lang} is the name of
13532 a language, such as
13533 @code{c} or @code{modula-2}.
13534 For a list of the supported languages, type @samp{set language}.
13536 Setting the language manually prevents @value{GDBN} from updating the working
13537 language automatically. This can lead to confusion if you try
13538 to debug a program when the working language is not the same as the
13539 source language, when an expression is acceptable to both
13540 languages---but means different things. For instance, if the current
13541 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13549 might not have the effect you intended. In C, this means to add
13550 @code{b} and @code{c} and place the result in @code{a}. The result
13551 printed would be the value of @code{a}. In Modula-2, this means to compare
13552 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13554 @node Automatically
13555 @subsection Having @value{GDBN} Infer the Source Language
13557 To have @value{GDBN} set the working language automatically, use
13558 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13559 then infers the working language. That is, when your program stops in a
13560 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13561 working language to the language recorded for the function in that
13562 frame. If the language for a frame is unknown (that is, if the function
13563 or block corresponding to the frame was defined in a source file that
13564 does not have a recognized extension), the current working language is
13565 not changed, and @value{GDBN} issues a warning.
13567 This may not seem necessary for most programs, which are written
13568 entirely in one source language. However, program modules and libraries
13569 written in one source language can be used by a main program written in
13570 a different source language. Using @samp{set language auto} in this
13571 case frees you from having to set the working language manually.
13574 @section Displaying the Language
13576 The following commands help you find out which language is the
13577 working language, and also what language source files were written in.
13580 @item show language
13581 @anchor{show language}
13582 @kindex show language
13583 Display the current working language. This is the
13584 language you can use with commands such as @code{print} to
13585 build and compute expressions that may involve variables in your program.
13588 @kindex info frame@r{, show the source language}
13589 Display the source language for this frame. This language becomes the
13590 working language if you use an identifier from this frame.
13591 @xref{Frame Info, ,Information about a Frame}, to identify the other
13592 information listed here.
13595 @kindex info source@r{, show the source language}
13596 Display the source language of this source file.
13597 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13598 information listed here.
13601 In unusual circumstances, you may have source files with extensions
13602 not in the standard list. You can then set the extension associated
13603 with a language explicitly:
13606 @item set extension-language @var{ext} @var{language}
13607 @kindex set extension-language
13608 Tell @value{GDBN} that source files with extension @var{ext} are to be
13609 assumed as written in the source language @var{language}.
13611 @item info extensions
13612 @kindex info extensions
13613 List all the filename extensions and the associated languages.
13617 @section Type and Range Checking
13619 Some languages are designed to guard you against making seemingly common
13620 errors through a series of compile- and run-time checks. These include
13621 checking the type of arguments to functions and operators and making
13622 sure mathematical overflows are caught at run time. Checks such as
13623 these help to ensure a program's correctness once it has been compiled
13624 by eliminating type mismatches and providing active checks for range
13625 errors when your program is running.
13627 By default @value{GDBN} checks for these errors according to the
13628 rules of the current source language. Although @value{GDBN} does not check
13629 the statements in your program, it can check expressions entered directly
13630 into @value{GDBN} for evaluation via the @code{print} command, for example.
13633 * Type Checking:: An overview of type checking
13634 * Range Checking:: An overview of range checking
13637 @cindex type checking
13638 @cindex checks, type
13639 @node Type Checking
13640 @subsection An Overview of Type Checking
13642 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13643 arguments to operators and functions have to be of the correct type,
13644 otherwise an error occurs. These checks prevent type mismatch
13645 errors from ever causing any run-time problems. For example,
13648 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13650 (@value{GDBP}) print obj.my_method (0)
13653 (@value{GDBP}) print obj.my_method (0x1234)
13654 Cannot resolve method klass::my_method to any overloaded instance
13657 The second example fails because in C@t{++} the integer constant
13658 @samp{0x1234} is not type-compatible with the pointer parameter type.
13660 For the expressions you use in @value{GDBN} commands, you can tell
13661 @value{GDBN} to not enforce strict type checking or
13662 to treat any mismatches as errors and abandon the expression;
13663 When type checking is disabled, @value{GDBN} successfully evaluates
13664 expressions like the second example above.
13666 Even if type checking is off, there may be other reasons
13667 related to type that prevent @value{GDBN} from evaluating an expression.
13668 For instance, @value{GDBN} does not know how to add an @code{int} and
13669 a @code{struct foo}. These particular type errors have nothing to do
13670 with the language in use and usually arise from expressions which make
13671 little sense to evaluate anyway.
13673 @value{GDBN} provides some additional commands for controlling type checking:
13675 @kindex set check type
13676 @kindex show check type
13678 @item set check type on
13679 @itemx set check type off
13680 Set strict type checking on or off. If any type mismatches occur in
13681 evaluating an expression while type checking is on, @value{GDBN} prints a
13682 message and aborts evaluation of the expression.
13684 @item show check type
13685 Show the current setting of type checking and whether @value{GDBN}
13686 is enforcing strict type checking rules.
13689 @cindex range checking
13690 @cindex checks, range
13691 @node Range Checking
13692 @subsection An Overview of Range Checking
13694 In some languages (such as Modula-2), it is an error to exceed the
13695 bounds of a type; this is enforced with run-time checks. Such range
13696 checking is meant to ensure program correctness by making sure
13697 computations do not overflow, or indices on an array element access do
13698 not exceed the bounds of the array.
13700 For expressions you use in @value{GDBN} commands, you can tell
13701 @value{GDBN} to treat range errors in one of three ways: ignore them,
13702 always treat them as errors and abandon the expression, or issue
13703 warnings but evaluate the expression anyway.
13705 A range error can result from numerical overflow, from exceeding an
13706 array index bound, or when you type a constant that is not a member
13707 of any type. Some languages, however, do not treat overflows as an
13708 error. In many implementations of C, mathematical overflow causes the
13709 result to ``wrap around'' to lower values---for example, if @var{m} is
13710 the largest integer value, and @var{s} is the smallest, then
13713 @var{m} + 1 @result{} @var{s}
13716 This, too, is specific to individual languages, and in some cases
13717 specific to individual compilers or machines. @xref{Supported Languages, ,
13718 Supported Languages}, for further details on specific languages.
13720 @value{GDBN} provides some additional commands for controlling the range checker:
13722 @kindex set check range
13723 @kindex show check range
13725 @item set check range auto
13726 Set range checking on or off based on the current working language.
13727 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13730 @item set check range on
13731 @itemx set check range off
13732 Set range checking on or off, overriding the default setting for the
13733 current working language. A warning is issued if the setting does not
13734 match the language default. If a range error occurs and range checking is on,
13735 then a message is printed and evaluation of the expression is aborted.
13737 @item set check range warn
13738 Output messages when the @value{GDBN} range checker detects a range error,
13739 but attempt to evaluate the expression anyway. Evaluating the
13740 expression may still be impossible for other reasons, such as accessing
13741 memory that the process does not own (a typical example from many Unix
13745 Show the current setting of the range checker, and whether or not it is
13746 being set automatically by @value{GDBN}.
13749 @node Supported Languages
13750 @section Supported Languages
13752 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13753 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13754 @c This is false ...
13755 Some @value{GDBN} features may be used in expressions regardless of the
13756 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13757 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13758 ,Expressions}) can be used with the constructs of any supported
13761 The following sections detail to what degree each source language is
13762 supported by @value{GDBN}. These sections are not meant to be language
13763 tutorials or references, but serve only as a reference guide to what the
13764 @value{GDBN} expression parser accepts, and what input and output
13765 formats should look like for different languages. There are many good
13766 books written on each of these languages; please look to these for a
13767 language reference or tutorial.
13770 * C:: C and C@t{++}
13773 * Objective-C:: Objective-C
13774 * OpenCL C:: OpenCL C
13775 * Fortran:: Fortran
13777 * Modula-2:: Modula-2
13782 @subsection C and C@t{++}
13784 @cindex C and C@t{++}
13785 @cindex expressions in C or C@t{++}
13787 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13788 to both languages. Whenever this is the case, we discuss those languages
13792 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13793 @cindex @sc{gnu} C@t{++}
13794 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13795 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13796 effectively, you must compile your C@t{++} programs with a supported
13797 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13798 compiler (@code{aCC}).
13801 * C Operators:: C and C@t{++} operators
13802 * C Constants:: C and C@t{++} constants
13803 * C Plus Plus Expressions:: C@t{++} expressions
13804 * C Defaults:: Default settings for C and C@t{++}
13805 * C Checks:: C and C@t{++} type and range checks
13806 * Debugging C:: @value{GDBN} and C
13807 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13808 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13812 @subsubsection C and C@t{++} Operators
13814 @cindex C and C@t{++} operators
13816 Operators must be defined on values of specific types. For instance,
13817 @code{+} is defined on numbers, but not on structures. Operators are
13818 often defined on groups of types.
13820 For the purposes of C and C@t{++}, the following definitions hold:
13825 @emph{Integral types} include @code{int} with any of its storage-class
13826 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13829 @emph{Floating-point types} include @code{float}, @code{double}, and
13830 @code{long double} (if supported by the target platform).
13833 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13836 @emph{Scalar types} include all of the above.
13841 The following operators are supported. They are listed here
13842 in order of increasing precedence:
13846 The comma or sequencing operator. Expressions in a comma-separated list
13847 are evaluated from left to right, with the result of the entire
13848 expression being the last expression evaluated.
13851 Assignment. The value of an assignment expression is the value
13852 assigned. Defined on scalar types.
13855 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13856 and translated to @w{@code{@var{a} = @var{a op b}}}.
13857 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13858 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13859 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13862 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13863 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13864 should be of an integral type.
13867 Logical @sc{or}. Defined on integral types.
13870 Logical @sc{and}. Defined on integral types.
13873 Bitwise @sc{or}. Defined on integral types.
13876 Bitwise exclusive-@sc{or}. Defined on integral types.
13879 Bitwise @sc{and}. Defined on integral types.
13882 Equality and inequality. Defined on scalar types. The value of these
13883 expressions is 0 for false and non-zero for true.
13885 @item <@r{, }>@r{, }<=@r{, }>=
13886 Less than, greater than, less than or equal, greater than or equal.
13887 Defined on scalar types. The value of these expressions is 0 for false
13888 and non-zero for true.
13891 left shift, and right shift. Defined on integral types.
13894 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13897 Addition and subtraction. Defined on integral types, floating-point types and
13900 @item *@r{, }/@r{, }%
13901 Multiplication, division, and modulus. Multiplication and division are
13902 defined on integral and floating-point types. Modulus is defined on
13906 Increment and decrement. When appearing before a variable, the
13907 operation is performed before the variable is used in an expression;
13908 when appearing after it, the variable's value is used before the
13909 operation takes place.
13912 Pointer dereferencing. Defined on pointer types. Same precedence as
13916 Address operator. Defined on variables. Same precedence as @code{++}.
13918 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13919 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13920 to examine the address
13921 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13925 Negative. Defined on integral and floating-point types. Same
13926 precedence as @code{++}.
13929 Logical negation. Defined on integral types. Same precedence as
13933 Bitwise complement operator. Defined on integral types. Same precedence as
13938 Structure member, and pointer-to-structure member. For convenience,
13939 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13940 pointer based on the stored type information.
13941 Defined on @code{struct} and @code{union} data.
13944 Dereferences of pointers to members.
13947 Array indexing. @code{@var{a}[@var{i}]} is defined as
13948 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13951 Function parameter list. Same precedence as @code{->}.
13954 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13955 and @code{class} types.
13958 Doubled colons also represent the @value{GDBN} scope operator
13959 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13963 If an operator is redefined in the user code, @value{GDBN} usually
13964 attempts to invoke the redefined version instead of using the operator's
13965 predefined meaning.
13968 @subsubsection C and C@t{++} Constants
13970 @cindex C and C@t{++} constants
13972 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13977 Integer constants are a sequence of digits. Octal constants are
13978 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13979 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13980 @samp{l}, specifying that the constant should be treated as a
13984 Floating point constants are a sequence of digits, followed by a decimal
13985 point, followed by a sequence of digits, and optionally followed by an
13986 exponent. An exponent is of the form:
13987 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13988 sequence of digits. The @samp{+} is optional for positive exponents.
13989 A floating-point constant may also end with a letter @samp{f} or
13990 @samp{F}, specifying that the constant should be treated as being of
13991 the @code{float} (as opposed to the default @code{double}) type; or with
13992 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13996 Enumerated constants consist of enumerated identifiers, or their
13997 integral equivalents.
14000 Character constants are a single character surrounded by single quotes
14001 (@code{'}), or a number---the ordinal value of the corresponding character
14002 (usually its @sc{ascii} value). Within quotes, the single character may
14003 be represented by a letter or by @dfn{escape sequences}, which are of
14004 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14005 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14006 @samp{@var{x}} is a predefined special character---for example,
14007 @samp{\n} for newline.
14009 Wide character constants can be written by prefixing a character
14010 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14011 form of @samp{x}. The target wide character set is used when
14012 computing the value of this constant (@pxref{Character Sets}).
14015 String constants are a sequence of character constants surrounded by
14016 double quotes (@code{"}). Any valid character constant (as described
14017 above) may appear. Double quotes within the string must be preceded by
14018 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14021 Wide string constants can be written by prefixing a string constant
14022 with @samp{L}, as in C. The target wide character set is used when
14023 computing the value of this constant (@pxref{Character Sets}).
14026 Pointer constants are an integral value. You can also write pointers
14027 to constants using the C operator @samp{&}.
14030 Array constants are comma-separated lists surrounded by braces @samp{@{}
14031 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14032 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14033 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14036 @node C Plus Plus Expressions
14037 @subsubsection C@t{++} Expressions
14039 @cindex expressions in C@t{++}
14040 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14042 @cindex debugging C@t{++} programs
14043 @cindex C@t{++} compilers
14044 @cindex debug formats and C@t{++}
14045 @cindex @value{NGCC} and C@t{++}
14047 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14048 the proper compiler and the proper debug format. Currently,
14049 @value{GDBN} works best when debugging C@t{++} code that is compiled
14050 with the most recent version of @value{NGCC} possible. The DWARF
14051 debugging format is preferred; @value{NGCC} defaults to this on most
14052 popular platforms. Other compilers and/or debug formats are likely to
14053 work badly or not at all when using @value{GDBN} to debug C@t{++}
14054 code. @xref{Compilation}.
14059 @cindex member functions
14061 Member function calls are allowed; you can use expressions like
14064 count = aml->GetOriginal(x, y)
14067 @vindex this@r{, inside C@t{++} member functions}
14068 @cindex namespace in C@t{++}
14070 While a member function is active (in the selected stack frame), your
14071 expressions have the same namespace available as the member function;
14072 that is, @value{GDBN} allows implicit references to the class instance
14073 pointer @code{this} following the same rules as C@t{++}. @code{using}
14074 declarations in the current scope are also respected by @value{GDBN}.
14076 @cindex call overloaded functions
14077 @cindex overloaded functions, calling
14078 @cindex type conversions in C@t{++}
14080 You can call overloaded functions; @value{GDBN} resolves the function
14081 call to the right definition, with some restrictions. @value{GDBN} does not
14082 perform overload resolution involving user-defined type conversions,
14083 calls to constructors, or instantiations of templates that do not exist
14084 in the program. It also cannot handle ellipsis argument lists or
14087 It does perform integral conversions and promotions, floating-point
14088 promotions, arithmetic conversions, pointer conversions, conversions of
14089 class objects to base classes, and standard conversions such as those of
14090 functions or arrays to pointers; it requires an exact match on the
14091 number of function arguments.
14093 Overload resolution is always performed, unless you have specified
14094 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14095 ,@value{GDBN} Features for C@t{++}}.
14097 You must specify @code{set overload-resolution off} in order to use an
14098 explicit function signature to call an overloaded function, as in
14100 p 'foo(char,int)'('x', 13)
14103 The @value{GDBN} command-completion facility can simplify this;
14104 see @ref{Completion, ,Command Completion}.
14106 @cindex reference declarations
14108 @value{GDBN} understands variables declared as C@t{++} references; you can use
14109 them in expressions just as you do in C@t{++} source---they are automatically
14112 In the parameter list shown when @value{GDBN} displays a frame, the values of
14113 reference variables are not displayed (unlike other variables); this
14114 avoids clutter, since references are often used for large structures.
14115 The @emph{address} of a reference variable is always shown, unless
14116 you have specified @samp{set print address off}.
14119 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14120 expressions can use it just as expressions in your program do. Since
14121 one scope may be defined in another, you can use @code{::} repeatedly if
14122 necessary, for example in an expression like
14123 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14124 resolving name scope by reference to source files, in both C and C@t{++}
14125 debugging (@pxref{Variables, ,Program Variables}).
14128 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14133 @subsubsection C and C@t{++} Defaults
14135 @cindex C and C@t{++} defaults
14137 If you allow @value{GDBN} to set range checking automatically, it
14138 defaults to @code{off} whenever the working language changes to
14139 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14140 selects the working language.
14142 If you allow @value{GDBN} to set the language automatically, it
14143 recognizes source files whose names end with @file{.c}, @file{.C}, or
14144 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14145 these files, it sets the working language to C or C@t{++}.
14146 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14147 for further details.
14150 @subsubsection C and C@t{++} Type and Range Checks
14152 @cindex C and C@t{++} checks
14154 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14155 checking is used. However, if you turn type checking off, @value{GDBN}
14156 will allow certain non-standard conversions, such as promoting integer
14157 constants to pointers.
14159 Range checking, if turned on, is done on mathematical operations. Array
14160 indices are not checked, since they are often used to index a pointer
14161 that is not itself an array.
14164 @subsubsection @value{GDBN} and C
14166 The @code{set print union} and @code{show print union} commands apply to
14167 the @code{union} type. When set to @samp{on}, any @code{union} that is
14168 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14169 appears as @samp{@{...@}}.
14171 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14172 with pointers and a memory allocation function. @xref{Expressions,
14175 @node Debugging C Plus Plus
14176 @subsubsection @value{GDBN} Features for C@t{++}
14178 @cindex commands for C@t{++}
14180 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14181 designed specifically for use with C@t{++}. Here is a summary:
14184 @cindex break in overloaded functions
14185 @item @r{breakpoint menus}
14186 When you want a breakpoint in a function whose name is overloaded,
14187 @value{GDBN} has the capability to display a menu of possible breakpoint
14188 locations to help you specify which function definition you want.
14189 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14191 @cindex overloading in C@t{++}
14192 @item rbreak @var{regex}
14193 Setting breakpoints using regular expressions is helpful for setting
14194 breakpoints on overloaded functions that are not members of any special
14196 @xref{Set Breaks, ,Setting Breakpoints}.
14198 @cindex C@t{++} exception handling
14200 @itemx catch rethrow
14202 Debug C@t{++} exception handling using these commands. @xref{Set
14203 Catchpoints, , Setting Catchpoints}.
14205 @cindex inheritance
14206 @item ptype @var{typename}
14207 Print inheritance relationships as well as other information for type
14209 @xref{Symbols, ,Examining the Symbol Table}.
14211 @item info vtbl @var{expression}.
14212 The @code{info vtbl} command can be used to display the virtual
14213 method tables of the object computed by @var{expression}. This shows
14214 one entry per virtual table; there may be multiple virtual tables when
14215 multiple inheritance is in use.
14217 @cindex C@t{++} symbol display
14218 @item set print demangle
14219 @itemx show print demangle
14220 @itemx set print asm-demangle
14221 @itemx show print asm-demangle
14222 Control whether C@t{++} symbols display in their source form, both when
14223 displaying code as C@t{++} source and when displaying disassemblies.
14224 @xref{Print Settings, ,Print Settings}.
14226 @item set print object
14227 @itemx show print object
14228 Choose whether to print derived (actual) or declared types of objects.
14229 @xref{Print Settings, ,Print Settings}.
14231 @item set print vtbl
14232 @itemx show print vtbl
14233 Control the format for printing virtual function tables.
14234 @xref{Print Settings, ,Print Settings}.
14235 (The @code{vtbl} commands do not work on programs compiled with the HP
14236 ANSI C@t{++} compiler (@code{aCC}).)
14238 @kindex set overload-resolution
14239 @cindex overloaded functions, overload resolution
14240 @item set overload-resolution on
14241 Enable overload resolution for C@t{++} expression evaluation. The default
14242 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14243 and searches for a function whose signature matches the argument types,
14244 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14245 Expressions, ,C@t{++} Expressions}, for details).
14246 If it cannot find a match, it emits a message.
14248 @item set overload-resolution off
14249 Disable overload resolution for C@t{++} expression evaluation. For
14250 overloaded functions that are not class member functions, @value{GDBN}
14251 chooses the first function of the specified name that it finds in the
14252 symbol table, whether or not its arguments are of the correct type. For
14253 overloaded functions that are class member functions, @value{GDBN}
14254 searches for a function whose signature @emph{exactly} matches the
14257 @kindex show overload-resolution
14258 @item show overload-resolution
14259 Show the current setting of overload resolution.
14261 @item @r{Overloaded symbol names}
14262 You can specify a particular definition of an overloaded symbol, using
14263 the same notation that is used to declare such symbols in C@t{++}: type
14264 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14265 also use the @value{GDBN} command-line word completion facilities to list the
14266 available choices, or to finish the type list for you.
14267 @xref{Completion,, Command Completion}, for details on how to do this.
14270 @node Decimal Floating Point
14271 @subsubsection Decimal Floating Point format
14272 @cindex decimal floating point format
14274 @value{GDBN} can examine, set and perform computations with numbers in
14275 decimal floating point format, which in the C language correspond to the
14276 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14277 specified by the extension to support decimal floating-point arithmetic.
14279 There are two encodings in use, depending on the architecture: BID (Binary
14280 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14281 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14284 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14285 to manipulate decimal floating point numbers, it is not possible to convert
14286 (using a cast, for example) integers wider than 32-bit to decimal float.
14288 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14289 point computations, error checking in decimal float operations ignores
14290 underflow, overflow and divide by zero exceptions.
14292 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14293 to inspect @code{_Decimal128} values stored in floating point registers.
14294 See @ref{PowerPC,,PowerPC} for more details.
14300 @value{GDBN} can be used to debug programs written in D and compiled with
14301 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14302 specific feature --- dynamic arrays.
14307 @cindex Go (programming language)
14308 @value{GDBN} can be used to debug programs written in Go and compiled with
14309 @file{gccgo} or @file{6g} compilers.
14311 Here is a summary of the Go-specific features and restrictions:
14314 @cindex current Go package
14315 @item The current Go package
14316 The name of the current package does not need to be specified when
14317 specifying global variables and functions.
14319 For example, given the program:
14323 var myglob = "Shall we?"
14329 When stopped inside @code{main} either of these work:
14333 (gdb) p main.myglob
14336 @cindex builtin Go types
14337 @item Builtin Go types
14338 The @code{string} type is recognized by @value{GDBN} and is printed
14341 @cindex builtin Go functions
14342 @item Builtin Go functions
14343 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14344 function and handles it internally.
14346 @cindex restrictions on Go expressions
14347 @item Restrictions on Go expressions
14348 All Go operators are supported except @code{&^}.
14349 The Go @code{_} ``blank identifier'' is not supported.
14350 Automatic dereferencing of pointers is not supported.
14354 @subsection Objective-C
14356 @cindex Objective-C
14357 This section provides information about some commands and command
14358 options that are useful for debugging Objective-C code. See also
14359 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14360 few more commands specific to Objective-C support.
14363 * Method Names in Commands::
14364 * The Print Command with Objective-C::
14367 @node Method Names in Commands
14368 @subsubsection Method Names in Commands
14370 The following commands have been extended to accept Objective-C method
14371 names as line specifications:
14373 @kindex clear@r{, and Objective-C}
14374 @kindex break@r{, and Objective-C}
14375 @kindex info line@r{, and Objective-C}
14376 @kindex jump@r{, and Objective-C}
14377 @kindex list@r{, and Objective-C}
14381 @item @code{info line}
14386 A fully qualified Objective-C method name is specified as
14389 -[@var{Class} @var{methodName}]
14392 where the minus sign is used to indicate an instance method and a
14393 plus sign (not shown) is used to indicate a class method. The class
14394 name @var{Class} and method name @var{methodName} are enclosed in
14395 brackets, similar to the way messages are specified in Objective-C
14396 source code. For example, to set a breakpoint at the @code{create}
14397 instance method of class @code{Fruit} in the program currently being
14401 break -[Fruit create]
14404 To list ten program lines around the @code{initialize} class method,
14408 list +[NSText initialize]
14411 In the current version of @value{GDBN}, the plus or minus sign is
14412 required. In future versions of @value{GDBN}, the plus or minus
14413 sign will be optional, but you can use it to narrow the search. It
14414 is also possible to specify just a method name:
14420 You must specify the complete method name, including any colons. If
14421 your program's source files contain more than one @code{create} method,
14422 you'll be presented with a numbered list of classes that implement that
14423 method. Indicate your choice by number, or type @samp{0} to exit if
14426 As another example, to clear a breakpoint established at the
14427 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14430 clear -[NSWindow makeKeyAndOrderFront:]
14433 @node The Print Command with Objective-C
14434 @subsubsection The Print Command With Objective-C
14435 @cindex Objective-C, print objects
14436 @kindex print-object
14437 @kindex po @r{(@code{print-object})}
14439 The print command has also been extended to accept methods. For example:
14442 print -[@var{object} hash]
14445 @cindex print an Objective-C object description
14446 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14448 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14449 and print the result. Also, an additional command has been added,
14450 @code{print-object} or @code{po} for short, which is meant to print
14451 the description of an object. However, this command may only work
14452 with certain Objective-C libraries that have a particular hook
14453 function, @code{_NSPrintForDebugger}, defined.
14456 @subsection OpenCL C
14459 This section provides information about @value{GDBN}s OpenCL C support.
14462 * OpenCL C Datatypes::
14463 * OpenCL C Expressions::
14464 * OpenCL C Operators::
14467 @node OpenCL C Datatypes
14468 @subsubsection OpenCL C Datatypes
14470 @cindex OpenCL C Datatypes
14471 @value{GDBN} supports the builtin scalar and vector datatypes specified
14472 by OpenCL 1.1. In addition the half- and double-precision floating point
14473 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14474 extensions are also known to @value{GDBN}.
14476 @node OpenCL C Expressions
14477 @subsubsection OpenCL C Expressions
14479 @cindex OpenCL C Expressions
14480 @value{GDBN} supports accesses to vector components including the access as
14481 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14482 supported by @value{GDBN} can be used as well.
14484 @node OpenCL C Operators
14485 @subsubsection OpenCL C Operators
14487 @cindex OpenCL C Operators
14488 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14492 @subsection Fortran
14493 @cindex Fortran-specific support in @value{GDBN}
14495 @value{GDBN} can be used to debug programs written in Fortran, but it
14496 currently supports only the features of Fortran 77 language.
14498 @cindex trailing underscore, in Fortran symbols
14499 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14500 among them) append an underscore to the names of variables and
14501 functions. When you debug programs compiled by those compilers, you
14502 will need to refer to variables and functions with a trailing
14506 * Fortran Operators:: Fortran operators and expressions
14507 * Fortran Defaults:: Default settings for Fortran
14508 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14511 @node Fortran Operators
14512 @subsubsection Fortran Operators and Expressions
14514 @cindex Fortran operators and expressions
14516 Operators must be defined on values of specific types. For instance,
14517 @code{+} is defined on numbers, but not on characters or other non-
14518 arithmetic types. Operators are often defined on groups of types.
14522 The exponentiation operator. It raises the first operand to the power
14526 The range operator. Normally used in the form of array(low:high) to
14527 represent a section of array.
14530 The access component operator. Normally used to access elements in derived
14531 types. Also suitable for unions. As unions aren't part of regular Fortran,
14532 this can only happen when accessing a register that uses a gdbarch-defined
14536 @node Fortran Defaults
14537 @subsubsection Fortran Defaults
14539 @cindex Fortran Defaults
14541 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14542 default uses case-insensitive matches for Fortran symbols. You can
14543 change that with the @samp{set case-insensitive} command, see
14544 @ref{Symbols}, for the details.
14546 @node Special Fortran Commands
14547 @subsubsection Special Fortran Commands
14549 @cindex Special Fortran commands
14551 @value{GDBN} has some commands to support Fortran-specific features,
14552 such as displaying common blocks.
14555 @cindex @code{COMMON} blocks, Fortran
14556 @kindex info common
14557 @item info common @r{[}@var{common-name}@r{]}
14558 This command prints the values contained in the Fortran @code{COMMON}
14559 block whose name is @var{common-name}. With no argument, the names of
14560 all @code{COMMON} blocks visible at the current program location are
14567 @cindex Pascal support in @value{GDBN}, limitations
14568 Debugging Pascal programs which use sets, subranges, file variables, or
14569 nested functions does not currently work. @value{GDBN} does not support
14570 entering expressions, printing values, or similar features using Pascal
14573 The Pascal-specific command @code{set print pascal_static-members}
14574 controls whether static members of Pascal objects are displayed.
14575 @xref{Print Settings, pascal_static-members}.
14578 @subsection Modula-2
14580 @cindex Modula-2, @value{GDBN} support
14582 The extensions made to @value{GDBN} to support Modula-2 only support
14583 output from the @sc{gnu} Modula-2 compiler (which is currently being
14584 developed). Other Modula-2 compilers are not currently supported, and
14585 attempting to debug executables produced by them is most likely
14586 to give an error as @value{GDBN} reads in the executable's symbol
14589 @cindex expressions in Modula-2
14591 * M2 Operators:: Built-in operators
14592 * Built-In Func/Proc:: Built-in functions and procedures
14593 * M2 Constants:: Modula-2 constants
14594 * M2 Types:: Modula-2 types
14595 * M2 Defaults:: Default settings for Modula-2
14596 * Deviations:: Deviations from standard Modula-2
14597 * M2 Checks:: Modula-2 type and range checks
14598 * M2 Scope:: The scope operators @code{::} and @code{.}
14599 * GDB/M2:: @value{GDBN} and Modula-2
14603 @subsubsection Operators
14604 @cindex Modula-2 operators
14606 Operators must be defined on values of specific types. For instance,
14607 @code{+} is defined on numbers, but not on structures. Operators are
14608 often defined on groups of types. For the purposes of Modula-2, the
14609 following definitions hold:
14614 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14618 @emph{Character types} consist of @code{CHAR} and its subranges.
14621 @emph{Floating-point types} consist of @code{REAL}.
14624 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14628 @emph{Scalar types} consist of all of the above.
14631 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14634 @emph{Boolean types} consist of @code{BOOLEAN}.
14638 The following operators are supported, and appear in order of
14639 increasing precedence:
14643 Function argument or array index separator.
14646 Assignment. The value of @var{var} @code{:=} @var{value} is
14650 Less than, greater than on integral, floating-point, or enumerated
14654 Less than or equal to, greater than or equal to
14655 on integral, floating-point and enumerated types, or set inclusion on
14656 set types. Same precedence as @code{<}.
14658 @item =@r{, }<>@r{, }#
14659 Equality and two ways of expressing inequality, valid on scalar types.
14660 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14661 available for inequality, since @code{#} conflicts with the script
14665 Set membership. Defined on set types and the types of their members.
14666 Same precedence as @code{<}.
14669 Boolean disjunction. Defined on boolean types.
14672 Boolean conjunction. Defined on boolean types.
14675 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14678 Addition and subtraction on integral and floating-point types, or union
14679 and difference on set types.
14682 Multiplication on integral and floating-point types, or set intersection
14686 Division on floating-point types, or symmetric set difference on set
14687 types. Same precedence as @code{*}.
14690 Integer division and remainder. Defined on integral types. Same
14691 precedence as @code{*}.
14694 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14697 Pointer dereferencing. Defined on pointer types.
14700 Boolean negation. Defined on boolean types. Same precedence as
14704 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14705 precedence as @code{^}.
14708 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14711 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14715 @value{GDBN} and Modula-2 scope operators.
14719 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14720 treats the use of the operator @code{IN}, or the use of operators
14721 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14722 @code{<=}, and @code{>=} on sets as an error.
14726 @node Built-In Func/Proc
14727 @subsubsection Built-in Functions and Procedures
14728 @cindex Modula-2 built-ins
14730 Modula-2 also makes available several built-in procedures and functions.
14731 In describing these, the following metavariables are used:
14736 represents an @code{ARRAY} variable.
14739 represents a @code{CHAR} constant or variable.
14742 represents a variable or constant of integral type.
14745 represents an identifier that belongs to a set. Generally used in the
14746 same function with the metavariable @var{s}. The type of @var{s} should
14747 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14750 represents a variable or constant of integral or floating-point type.
14753 represents a variable or constant of floating-point type.
14759 represents a variable.
14762 represents a variable or constant of one of many types. See the
14763 explanation of the function for details.
14766 All Modula-2 built-in procedures also return a result, described below.
14770 Returns the absolute value of @var{n}.
14773 If @var{c} is a lower case letter, it returns its upper case
14774 equivalent, otherwise it returns its argument.
14777 Returns the character whose ordinal value is @var{i}.
14780 Decrements the value in the variable @var{v} by one. Returns the new value.
14782 @item DEC(@var{v},@var{i})
14783 Decrements the value in the variable @var{v} by @var{i}. Returns the
14786 @item EXCL(@var{m},@var{s})
14787 Removes the element @var{m} from the set @var{s}. Returns the new
14790 @item FLOAT(@var{i})
14791 Returns the floating point equivalent of the integer @var{i}.
14793 @item HIGH(@var{a})
14794 Returns the index of the last member of @var{a}.
14797 Increments the value in the variable @var{v} by one. Returns the new value.
14799 @item INC(@var{v},@var{i})
14800 Increments the value in the variable @var{v} by @var{i}. Returns the
14803 @item INCL(@var{m},@var{s})
14804 Adds the element @var{m} to the set @var{s} if it is not already
14805 there. Returns the new set.
14808 Returns the maximum value of the type @var{t}.
14811 Returns the minimum value of the type @var{t}.
14814 Returns boolean TRUE if @var{i} is an odd number.
14817 Returns the ordinal value of its argument. For example, the ordinal
14818 value of a character is its @sc{ascii} value (on machines supporting
14819 the @sc{ascii} character set). The argument @var{x} must be of an
14820 ordered type, which include integral, character and enumerated types.
14822 @item SIZE(@var{x})
14823 Returns the size of its argument. The argument @var{x} can be a
14824 variable or a type.
14826 @item TRUNC(@var{r})
14827 Returns the integral part of @var{r}.
14829 @item TSIZE(@var{x})
14830 Returns the size of its argument. The argument @var{x} can be a
14831 variable or a type.
14833 @item VAL(@var{t},@var{i})
14834 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14838 @emph{Warning:} Sets and their operations are not yet supported, so
14839 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14843 @cindex Modula-2 constants
14845 @subsubsection Constants
14847 @value{GDBN} allows you to express the constants of Modula-2 in the following
14853 Integer constants are simply a sequence of digits. When used in an
14854 expression, a constant is interpreted to be type-compatible with the
14855 rest of the expression. Hexadecimal integers are specified by a
14856 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14859 Floating point constants appear as a sequence of digits, followed by a
14860 decimal point and another sequence of digits. An optional exponent can
14861 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14862 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14863 digits of the floating point constant must be valid decimal (base 10)
14867 Character constants consist of a single character enclosed by a pair of
14868 like quotes, either single (@code{'}) or double (@code{"}). They may
14869 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14870 followed by a @samp{C}.
14873 String constants consist of a sequence of characters enclosed by a
14874 pair of like quotes, either single (@code{'}) or double (@code{"}).
14875 Escape sequences in the style of C are also allowed. @xref{C
14876 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14880 Enumerated constants consist of an enumerated identifier.
14883 Boolean constants consist of the identifiers @code{TRUE} and
14887 Pointer constants consist of integral values only.
14890 Set constants are not yet supported.
14894 @subsubsection Modula-2 Types
14895 @cindex Modula-2 types
14897 Currently @value{GDBN} can print the following data types in Modula-2
14898 syntax: array types, record types, set types, pointer types, procedure
14899 types, enumerated types, subrange types and base types. You can also
14900 print the contents of variables declared using these type.
14901 This section gives a number of simple source code examples together with
14902 sample @value{GDBN} sessions.
14904 The first example contains the following section of code:
14913 and you can request @value{GDBN} to interrogate the type and value of
14914 @code{r} and @code{s}.
14917 (@value{GDBP}) print s
14919 (@value{GDBP}) ptype s
14921 (@value{GDBP}) print r
14923 (@value{GDBP}) ptype r
14928 Likewise if your source code declares @code{s} as:
14932 s: SET ['A'..'Z'] ;
14936 then you may query the type of @code{s} by:
14939 (@value{GDBP}) ptype s
14940 type = SET ['A'..'Z']
14944 Note that at present you cannot interactively manipulate set
14945 expressions using the debugger.
14947 The following example shows how you might declare an array in Modula-2
14948 and how you can interact with @value{GDBN} to print its type and contents:
14952 s: ARRAY [-10..10] OF CHAR ;
14956 (@value{GDBP}) ptype s
14957 ARRAY [-10..10] OF CHAR
14960 Note that the array handling is not yet complete and although the type
14961 is printed correctly, expression handling still assumes that all
14962 arrays have a lower bound of zero and not @code{-10} as in the example
14965 Here are some more type related Modula-2 examples:
14969 colour = (blue, red, yellow, green) ;
14970 t = [blue..yellow] ;
14978 The @value{GDBN} interaction shows how you can query the data type
14979 and value of a variable.
14982 (@value{GDBP}) print s
14984 (@value{GDBP}) ptype t
14985 type = [blue..yellow]
14989 In this example a Modula-2 array is declared and its contents
14990 displayed. Observe that the contents are written in the same way as
14991 their @code{C} counterparts.
14995 s: ARRAY [1..5] OF CARDINAL ;
15001 (@value{GDBP}) print s
15002 $1 = @{1, 0, 0, 0, 0@}
15003 (@value{GDBP}) ptype s
15004 type = ARRAY [1..5] OF CARDINAL
15007 The Modula-2 language interface to @value{GDBN} also understands
15008 pointer types as shown in this example:
15012 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15019 and you can request that @value{GDBN} describes the type of @code{s}.
15022 (@value{GDBP}) ptype s
15023 type = POINTER TO ARRAY [1..5] OF CARDINAL
15026 @value{GDBN} handles compound types as we can see in this example.
15027 Here we combine array types, record types, pointer types and subrange
15038 myarray = ARRAY myrange OF CARDINAL ;
15039 myrange = [-2..2] ;
15041 s: POINTER TO ARRAY myrange OF foo ;
15045 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15049 (@value{GDBP}) ptype s
15050 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15053 f3 : ARRAY [-2..2] OF CARDINAL;
15058 @subsubsection Modula-2 Defaults
15059 @cindex Modula-2 defaults
15061 If type and range checking are set automatically by @value{GDBN}, they
15062 both default to @code{on} whenever the working language changes to
15063 Modula-2. This happens regardless of whether you or @value{GDBN}
15064 selected the working language.
15066 If you allow @value{GDBN} to set the language automatically, then entering
15067 code compiled from a file whose name ends with @file{.mod} sets the
15068 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15069 Infer the Source Language}, for further details.
15072 @subsubsection Deviations from Standard Modula-2
15073 @cindex Modula-2, deviations from
15075 A few changes have been made to make Modula-2 programs easier to debug.
15076 This is done primarily via loosening its type strictness:
15080 Unlike in standard Modula-2, pointer constants can be formed by
15081 integers. This allows you to modify pointer variables during
15082 debugging. (In standard Modula-2, the actual address contained in a
15083 pointer variable is hidden from you; it can only be modified
15084 through direct assignment to another pointer variable or expression that
15085 returned a pointer.)
15088 C escape sequences can be used in strings and characters to represent
15089 non-printable characters. @value{GDBN} prints out strings with these
15090 escape sequences embedded. Single non-printable characters are
15091 printed using the @samp{CHR(@var{nnn})} format.
15094 The assignment operator (@code{:=}) returns the value of its right-hand
15098 All built-in procedures both modify @emph{and} return their argument.
15102 @subsubsection Modula-2 Type and Range Checks
15103 @cindex Modula-2 checks
15106 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15109 @c FIXME remove warning when type/range checks added
15111 @value{GDBN} considers two Modula-2 variables type equivalent if:
15115 They are of types that have been declared equivalent via a @code{TYPE
15116 @var{t1} = @var{t2}} statement
15119 They have been declared on the same line. (Note: This is true of the
15120 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15123 As long as type checking is enabled, any attempt to combine variables
15124 whose types are not equivalent is an error.
15126 Range checking is done on all mathematical operations, assignment, array
15127 index bounds, and all built-in functions and procedures.
15130 @subsubsection The Scope Operators @code{::} and @code{.}
15132 @cindex @code{.}, Modula-2 scope operator
15133 @cindex colon, doubled as scope operator
15135 @vindex colon-colon@r{, in Modula-2}
15136 @c Info cannot handle :: but TeX can.
15139 @vindex ::@r{, in Modula-2}
15142 There are a few subtle differences between the Modula-2 scope operator
15143 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15148 @var{module} . @var{id}
15149 @var{scope} :: @var{id}
15153 where @var{scope} is the name of a module or a procedure,
15154 @var{module} the name of a module, and @var{id} is any declared
15155 identifier within your program, except another module.
15157 Using the @code{::} operator makes @value{GDBN} search the scope
15158 specified by @var{scope} for the identifier @var{id}. If it is not
15159 found in the specified scope, then @value{GDBN} searches all scopes
15160 enclosing the one specified by @var{scope}.
15162 Using the @code{.} operator makes @value{GDBN} search the current scope for
15163 the identifier specified by @var{id} that was imported from the
15164 definition module specified by @var{module}. With this operator, it is
15165 an error if the identifier @var{id} was not imported from definition
15166 module @var{module}, or if @var{id} is not an identifier in
15170 @subsubsection @value{GDBN} and Modula-2
15172 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15173 Five subcommands of @code{set print} and @code{show print} apply
15174 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15175 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15176 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15177 analogue in Modula-2.
15179 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15180 with any language, is not useful with Modula-2. Its
15181 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15182 created in Modula-2 as they can in C or C@t{++}. However, because an
15183 address can be specified by an integral constant, the construct
15184 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15186 @cindex @code{#} in Modula-2
15187 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15188 interpreted as the beginning of a comment. Use @code{<>} instead.
15194 The extensions made to @value{GDBN} for Ada only support
15195 output from the @sc{gnu} Ada (GNAT) compiler.
15196 Other Ada compilers are not currently supported, and
15197 attempting to debug executables produced by them is most likely
15201 @cindex expressions in Ada
15203 * Ada Mode Intro:: General remarks on the Ada syntax
15204 and semantics supported by Ada mode
15206 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15207 * Additions to Ada:: Extensions of the Ada expression syntax.
15208 * Stopping Before Main Program:: Debugging the program during elaboration.
15209 * Ada Exceptions:: Ada Exceptions
15210 * Ada Tasks:: Listing and setting breakpoints in tasks.
15211 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15212 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15214 * Ada Glitches:: Known peculiarities of Ada mode.
15217 @node Ada Mode Intro
15218 @subsubsection Introduction
15219 @cindex Ada mode, general
15221 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15222 syntax, with some extensions.
15223 The philosophy behind the design of this subset is
15227 That @value{GDBN} should provide basic literals and access to operations for
15228 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15229 leaving more sophisticated computations to subprograms written into the
15230 program (which therefore may be called from @value{GDBN}).
15233 That type safety and strict adherence to Ada language restrictions
15234 are not particularly important to the @value{GDBN} user.
15237 That brevity is important to the @value{GDBN} user.
15240 Thus, for brevity, the debugger acts as if all names declared in
15241 user-written packages are directly visible, even if they are not visible
15242 according to Ada rules, thus making it unnecessary to fully qualify most
15243 names with their packages, regardless of context. Where this causes
15244 ambiguity, @value{GDBN} asks the user's intent.
15246 The debugger will start in Ada mode if it detects an Ada main program.
15247 As for other languages, it will enter Ada mode when stopped in a program that
15248 was translated from an Ada source file.
15250 While in Ada mode, you may use `@t{--}' for comments. This is useful
15251 mostly for documenting command files. The standard @value{GDBN} comment
15252 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15253 middle (to allow based literals).
15255 The debugger supports limited overloading. Given a subprogram call in which
15256 the function symbol has multiple definitions, it will use the number of
15257 actual parameters and some information about their types to attempt to narrow
15258 the set of definitions. It also makes very limited use of context, preferring
15259 procedures to functions in the context of the @code{call} command, and
15260 functions to procedures elsewhere.
15262 @node Omissions from Ada
15263 @subsubsection Omissions from Ada
15264 @cindex Ada, omissions from
15266 Here are the notable omissions from the subset:
15270 Only a subset of the attributes are supported:
15274 @t{'First}, @t{'Last}, and @t{'Length}
15275 on array objects (not on types and subtypes).
15278 @t{'Min} and @t{'Max}.
15281 @t{'Pos} and @t{'Val}.
15287 @t{'Range} on array objects (not subtypes), but only as the right
15288 operand of the membership (@code{in}) operator.
15291 @t{'Access}, @t{'Unchecked_Access}, and
15292 @t{'Unrestricted_Access} (a GNAT extension).
15300 @code{Characters.Latin_1} are not available and
15301 concatenation is not implemented. Thus, escape characters in strings are
15302 not currently available.
15305 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15306 equality of representations. They will generally work correctly
15307 for strings and arrays whose elements have integer or enumeration types.
15308 They may not work correctly for arrays whose element
15309 types have user-defined equality, for arrays of real values
15310 (in particular, IEEE-conformant floating point, because of negative
15311 zeroes and NaNs), and for arrays whose elements contain unused bits with
15312 indeterminate values.
15315 The other component-by-component array operations (@code{and}, @code{or},
15316 @code{xor}, @code{not}, and relational tests other than equality)
15317 are not implemented.
15320 @cindex array aggregates (Ada)
15321 @cindex record aggregates (Ada)
15322 @cindex aggregates (Ada)
15323 There is limited support for array and record aggregates. They are
15324 permitted only on the right sides of assignments, as in these examples:
15327 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15328 (@value{GDBP}) set An_Array := (1, others => 0)
15329 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15330 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15331 (@value{GDBP}) set A_Record := (1, "Peter", True);
15332 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15336 discriminant's value by assigning an aggregate has an
15337 undefined effect if that discriminant is used within the record.
15338 However, you can first modify discriminants by directly assigning to
15339 them (which normally would not be allowed in Ada), and then performing an
15340 aggregate assignment. For example, given a variable @code{A_Rec}
15341 declared to have a type such as:
15344 type Rec (Len : Small_Integer := 0) is record
15346 Vals : IntArray (1 .. Len);
15350 you can assign a value with a different size of @code{Vals} with two
15354 (@value{GDBP}) set A_Rec.Len := 4
15355 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15358 As this example also illustrates, @value{GDBN} is very loose about the usual
15359 rules concerning aggregates. You may leave out some of the
15360 components of an array or record aggregate (such as the @code{Len}
15361 component in the assignment to @code{A_Rec} above); they will retain their
15362 original values upon assignment. You may freely use dynamic values as
15363 indices in component associations. You may even use overlapping or
15364 redundant component associations, although which component values are
15365 assigned in such cases is not defined.
15368 Calls to dispatching subprograms are not implemented.
15371 The overloading algorithm is much more limited (i.e., less selective)
15372 than that of real Ada. It makes only limited use of the context in
15373 which a subexpression appears to resolve its meaning, and it is much
15374 looser in its rules for allowing type matches. As a result, some
15375 function calls will be ambiguous, and the user will be asked to choose
15376 the proper resolution.
15379 The @code{new} operator is not implemented.
15382 Entry calls are not implemented.
15385 Aside from printing, arithmetic operations on the native VAX floating-point
15386 formats are not supported.
15389 It is not possible to slice a packed array.
15392 The names @code{True} and @code{False}, when not part of a qualified name,
15393 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15395 Should your program
15396 redefine these names in a package or procedure (at best a dubious practice),
15397 you will have to use fully qualified names to access their new definitions.
15400 @node Additions to Ada
15401 @subsubsection Additions to Ada
15402 @cindex Ada, deviations from
15404 As it does for other languages, @value{GDBN} makes certain generic
15405 extensions to Ada (@pxref{Expressions}):
15409 If the expression @var{E} is a variable residing in memory (typically
15410 a local variable or array element) and @var{N} is a positive integer,
15411 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15412 @var{N}-1 adjacent variables following it in memory as an array. In
15413 Ada, this operator is generally not necessary, since its prime use is
15414 in displaying parts of an array, and slicing will usually do this in
15415 Ada. However, there are occasional uses when debugging programs in
15416 which certain debugging information has been optimized away.
15419 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15420 appears in function or file @var{B}.'' When @var{B} is a file name,
15421 you must typically surround it in single quotes.
15424 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15425 @var{type} that appears at address @var{addr}.''
15428 A name starting with @samp{$} is a convenience variable
15429 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15432 In addition, @value{GDBN} provides a few other shortcuts and outright
15433 additions specific to Ada:
15437 The assignment statement is allowed as an expression, returning
15438 its right-hand operand as its value. Thus, you may enter
15441 (@value{GDBP}) set x := y + 3
15442 (@value{GDBP}) print A(tmp := y + 1)
15446 The semicolon is allowed as an ``operator,'' returning as its value
15447 the value of its right-hand operand.
15448 This allows, for example,
15449 complex conditional breaks:
15452 (@value{GDBP}) break f
15453 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15457 Rather than use catenation and symbolic character names to introduce special
15458 characters into strings, one may instead use a special bracket notation,
15459 which is also used to print strings. A sequence of characters of the form
15460 @samp{["@var{XX}"]} within a string or character literal denotes the
15461 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15462 sequence of characters @samp{["""]} also denotes a single quotation mark
15463 in strings. For example,
15465 "One line.["0a"]Next line.["0a"]"
15468 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15472 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15473 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15477 (@value{GDBP}) print 'max(x, y)
15481 When printing arrays, @value{GDBN} uses positional notation when the
15482 array has a lower bound of 1, and uses a modified named notation otherwise.
15483 For example, a one-dimensional array of three integers with a lower bound
15484 of 3 might print as
15491 That is, in contrast to valid Ada, only the first component has a @code{=>}
15495 You may abbreviate attributes in expressions with any unique,
15496 multi-character subsequence of
15497 their names (an exact match gets preference).
15498 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15499 in place of @t{a'length}.
15502 @cindex quoting Ada internal identifiers
15503 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15504 to lower case. The GNAT compiler uses upper-case characters for
15505 some of its internal identifiers, which are normally of no interest to users.
15506 For the rare occasions when you actually have to look at them,
15507 enclose them in angle brackets to avoid the lower-case mapping.
15510 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15514 Printing an object of class-wide type or dereferencing an
15515 access-to-class-wide value will display all the components of the object's
15516 specific type (as indicated by its run-time tag). Likewise, component
15517 selection on such a value will operate on the specific type of the
15522 @node Stopping Before Main Program
15523 @subsubsection Stopping at the Very Beginning
15525 @cindex breakpointing Ada elaboration code
15526 It is sometimes necessary to debug the program during elaboration, and
15527 before reaching the main procedure.
15528 As defined in the Ada Reference
15529 Manual, the elaboration code is invoked from a procedure called
15530 @code{adainit}. To run your program up to the beginning of
15531 elaboration, simply use the following two commands:
15532 @code{tbreak adainit} and @code{run}.
15534 @node Ada Exceptions
15535 @subsubsection Ada Exceptions
15537 A command is provided to list all Ada exceptions:
15540 @kindex info exceptions
15541 @item info exceptions
15542 @itemx info exceptions @var{regexp}
15543 The @code{info exceptions} command allows you to list all Ada exceptions
15544 defined within the program being debugged, as well as their addresses.
15545 With a regular expression, @var{regexp}, as argument, only those exceptions
15546 whose names match @var{regexp} are listed.
15549 Below is a small example, showing how the command can be used, first
15550 without argument, and next with a regular expression passed as an
15554 (@value{GDBP}) info exceptions
15555 All defined Ada exceptions:
15556 constraint_error: 0x613da0
15557 program_error: 0x613d20
15558 storage_error: 0x613ce0
15559 tasking_error: 0x613ca0
15560 const.aint_global_e: 0x613b00
15561 (@value{GDBP}) info exceptions const.aint
15562 All Ada exceptions matching regular expression "const.aint":
15563 constraint_error: 0x613da0
15564 const.aint_global_e: 0x613b00
15567 It is also possible to ask @value{GDBN} to stop your program's execution
15568 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15571 @subsubsection Extensions for Ada Tasks
15572 @cindex Ada, tasking
15574 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15575 @value{GDBN} provides the following task-related commands:
15580 This command shows a list of current Ada tasks, as in the following example:
15587 (@value{GDBP}) info tasks
15588 ID TID P-ID Pri State Name
15589 1 8088000 0 15 Child Activation Wait main_task
15590 2 80a4000 1 15 Accept Statement b
15591 3 809a800 1 15 Child Activation Wait a
15592 * 4 80ae800 3 15 Runnable c
15597 In this listing, the asterisk before the last task indicates it to be the
15598 task currently being inspected.
15602 Represents @value{GDBN}'s internal task number.
15608 The parent's task ID (@value{GDBN}'s internal task number).
15611 The base priority of the task.
15614 Current state of the task.
15618 The task has been created but has not been activated. It cannot be
15622 The task is not blocked for any reason known to Ada. (It may be waiting
15623 for a mutex, though.) It is conceptually "executing" in normal mode.
15626 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15627 that were waiting on terminate alternatives have been awakened and have
15628 terminated themselves.
15630 @item Child Activation Wait
15631 The task is waiting for created tasks to complete activation.
15633 @item Accept Statement
15634 The task is waiting on an accept or selective wait statement.
15636 @item Waiting on entry call
15637 The task is waiting on an entry call.
15639 @item Async Select Wait
15640 The task is waiting to start the abortable part of an asynchronous
15644 The task is waiting on a select statement with only a delay
15647 @item Child Termination Wait
15648 The task is sleeping having completed a master within itself, and is
15649 waiting for the tasks dependent on that master to become terminated or
15650 waiting on a terminate Phase.
15652 @item Wait Child in Term Alt
15653 The task is sleeping waiting for tasks on terminate alternatives to
15654 finish terminating.
15656 @item Accepting RV with @var{taskno}
15657 The task is accepting a rendez-vous with the task @var{taskno}.
15661 Name of the task in the program.
15665 @kindex info task @var{taskno}
15666 @item info task @var{taskno}
15667 This command shows detailled informations on the specified task, as in
15668 the following example:
15673 (@value{GDBP}) info tasks
15674 ID TID P-ID Pri State Name
15675 1 8077880 0 15 Child Activation Wait main_task
15676 * 2 807c468 1 15 Runnable task_1
15677 (@value{GDBP}) info task 2
15678 Ada Task: 0x807c468
15681 Parent: 1 (main_task)
15687 @kindex task@r{ (Ada)}
15688 @cindex current Ada task ID
15689 This command prints the ID of the current task.
15695 (@value{GDBP}) info tasks
15696 ID TID P-ID Pri State Name
15697 1 8077870 0 15 Child Activation Wait main_task
15698 * 2 807c458 1 15 Runnable t
15699 (@value{GDBP}) task
15700 [Current task is 2]
15703 @item task @var{taskno}
15704 @cindex Ada task switching
15705 This command is like the @code{thread @var{threadno}}
15706 command (@pxref{Threads}). It switches the context of debugging
15707 from the current task to the given task.
15713 (@value{GDBP}) info tasks
15714 ID TID P-ID Pri State Name
15715 1 8077870 0 15 Child Activation Wait main_task
15716 * 2 807c458 1 15 Runnable t
15717 (@value{GDBP}) task 1
15718 [Switching to task 1]
15719 #0 0x8067726 in pthread_cond_wait ()
15721 #0 0x8067726 in pthread_cond_wait ()
15722 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15723 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15724 #3 0x806153e in system.tasking.stages.activate_tasks ()
15725 #4 0x804aacc in un () at un.adb:5
15728 @item break @var{linespec} task @var{taskno}
15729 @itemx break @var{linespec} task @var{taskno} if @dots{}
15730 @cindex breakpoints and tasks, in Ada
15731 @cindex task breakpoints, in Ada
15732 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15733 These commands are like the @code{break @dots{} thread @dots{}}
15734 command (@pxref{Thread Stops}). The
15735 @var{linespec} argument specifies source lines, as described
15736 in @ref{Specify Location}.
15738 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15739 to specify that you only want @value{GDBN} to stop the program when a
15740 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15741 numeric task identifiers assigned by @value{GDBN}, shown in the first
15742 column of the @samp{info tasks} display.
15744 If you do not specify @samp{task @var{taskno}} when you set a
15745 breakpoint, the breakpoint applies to @emph{all} tasks of your
15748 You can use the @code{task} qualifier on conditional breakpoints as
15749 well; in this case, place @samp{task @var{taskno}} before the
15750 breakpoint condition (before the @code{if}).
15758 (@value{GDBP}) info tasks
15759 ID TID P-ID Pri State Name
15760 1 140022020 0 15 Child Activation Wait main_task
15761 2 140045060 1 15 Accept/Select Wait t2
15762 3 140044840 1 15 Runnable t1
15763 * 4 140056040 1 15 Runnable t3
15764 (@value{GDBP}) b 15 task 2
15765 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15766 (@value{GDBP}) cont
15771 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15773 (@value{GDBP}) info tasks
15774 ID TID P-ID Pri State Name
15775 1 140022020 0 15 Child Activation Wait main_task
15776 * 2 140045060 1 15 Runnable t2
15777 3 140044840 1 15 Runnable t1
15778 4 140056040 1 15 Delay Sleep t3
15782 @node Ada Tasks and Core Files
15783 @subsubsection Tasking Support when Debugging Core Files
15784 @cindex Ada tasking and core file debugging
15786 When inspecting a core file, as opposed to debugging a live program,
15787 tasking support may be limited or even unavailable, depending on
15788 the platform being used.
15789 For instance, on x86-linux, the list of tasks is available, but task
15790 switching is not supported.
15792 On certain platforms, the debugger needs to perform some
15793 memory writes in order to provide Ada tasking support. When inspecting
15794 a core file, this means that the core file must be opened with read-write
15795 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15796 Under these circumstances, you should make a backup copy of the core
15797 file before inspecting it with @value{GDBN}.
15799 @node Ravenscar Profile
15800 @subsubsection Tasking Support when using the Ravenscar Profile
15801 @cindex Ravenscar Profile
15803 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15804 specifically designed for systems with safety-critical real-time
15808 @kindex set ravenscar task-switching on
15809 @cindex task switching with program using Ravenscar Profile
15810 @item set ravenscar task-switching on
15811 Allows task switching when debugging a program that uses the Ravenscar
15812 Profile. This is the default.
15814 @kindex set ravenscar task-switching off
15815 @item set ravenscar task-switching off
15816 Turn off task switching when debugging a program that uses the Ravenscar
15817 Profile. This is mostly intended to disable the code that adds support
15818 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15819 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15820 To be effective, this command should be run before the program is started.
15822 @kindex show ravenscar task-switching
15823 @item show ravenscar task-switching
15824 Show whether it is possible to switch from task to task in a program
15825 using the Ravenscar Profile.
15830 @subsubsection Known Peculiarities of Ada Mode
15831 @cindex Ada, problems
15833 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15834 we know of several problems with and limitations of Ada mode in
15836 some of which will be fixed with planned future releases of the debugger
15837 and the GNU Ada compiler.
15841 Static constants that the compiler chooses not to materialize as objects in
15842 storage are invisible to the debugger.
15845 Named parameter associations in function argument lists are ignored (the
15846 argument lists are treated as positional).
15849 Many useful library packages are currently invisible to the debugger.
15852 Fixed-point arithmetic, conversions, input, and output is carried out using
15853 floating-point arithmetic, and may give results that only approximate those on
15857 The GNAT compiler never generates the prefix @code{Standard} for any of
15858 the standard symbols defined by the Ada language. @value{GDBN} knows about
15859 this: it will strip the prefix from names when you use it, and will never
15860 look for a name you have so qualified among local symbols, nor match against
15861 symbols in other packages or subprograms. If you have
15862 defined entities anywhere in your program other than parameters and
15863 local variables whose simple names match names in @code{Standard},
15864 GNAT's lack of qualification here can cause confusion. When this happens,
15865 you can usually resolve the confusion
15866 by qualifying the problematic names with package
15867 @code{Standard} explicitly.
15870 Older versions of the compiler sometimes generate erroneous debugging
15871 information, resulting in the debugger incorrectly printing the value
15872 of affected entities. In some cases, the debugger is able to work
15873 around an issue automatically. In other cases, the debugger is able
15874 to work around the issue, but the work-around has to be specifically
15877 @kindex set ada trust-PAD-over-XVS
15878 @kindex show ada trust-PAD-over-XVS
15881 @item set ada trust-PAD-over-XVS on
15882 Configure GDB to strictly follow the GNAT encoding when computing the
15883 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15884 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15885 a complete description of the encoding used by the GNAT compiler).
15886 This is the default.
15888 @item set ada trust-PAD-over-XVS off
15889 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15890 sometimes prints the wrong value for certain entities, changing @code{ada
15891 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15892 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15893 @code{off}, but this incurs a slight performance penalty, so it is
15894 recommended to leave this setting to @code{on} unless necessary.
15898 @cindex GNAT descriptive types
15899 @cindex GNAT encoding
15900 Internally, the debugger also relies on the compiler following a number
15901 of conventions known as the @samp{GNAT Encoding}, all documented in
15902 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15903 how the debugging information should be generated for certain types.
15904 In particular, this convention makes use of @dfn{descriptive types},
15905 which are artificial types generated purely to help the debugger.
15907 These encodings were defined at a time when the debugging information
15908 format used was not powerful enough to describe some of the more complex
15909 types available in Ada. Since DWARF allows us to express nearly all
15910 Ada features, the long-term goal is to slowly replace these descriptive
15911 types by their pure DWARF equivalent. To facilitate that transition,
15912 a new maintenance option is available to force the debugger to ignore
15913 those descriptive types. It allows the user to quickly evaluate how
15914 well @value{GDBN} works without them.
15918 @kindex maint ada set ignore-descriptive-types
15919 @item maintenance ada set ignore-descriptive-types [on|off]
15920 Control whether the debugger should ignore descriptive types.
15921 The default is not to ignore descriptives types (@code{off}).
15923 @kindex maint ada show ignore-descriptive-types
15924 @item maintenance ada show ignore-descriptive-types
15925 Show if descriptive types are ignored by @value{GDBN}.
15929 @node Unsupported Languages
15930 @section Unsupported Languages
15932 @cindex unsupported languages
15933 @cindex minimal language
15934 In addition to the other fully-supported programming languages,
15935 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15936 It does not represent a real programming language, but provides a set
15937 of capabilities close to what the C or assembly languages provide.
15938 This should allow most simple operations to be performed while debugging
15939 an application that uses a language currently not supported by @value{GDBN}.
15941 If the language is set to @code{auto}, @value{GDBN} will automatically
15942 select this language if the current frame corresponds to an unsupported
15946 @chapter Examining the Symbol Table
15948 The commands described in this chapter allow you to inquire about the
15949 symbols (names of variables, functions and types) defined in your
15950 program. This information is inherent in the text of your program and
15951 does not change as your program executes. @value{GDBN} finds it in your
15952 program's symbol table, in the file indicated when you started @value{GDBN}
15953 (@pxref{File Options, ,Choosing Files}), or by one of the
15954 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15956 @cindex symbol names
15957 @cindex names of symbols
15958 @cindex quoting names
15959 Occasionally, you may need to refer to symbols that contain unusual
15960 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15961 most frequent case is in referring to static variables in other
15962 source files (@pxref{Variables,,Program Variables}). File names
15963 are recorded in object files as debugging symbols, but @value{GDBN} would
15964 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15965 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15966 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15973 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15976 @cindex case-insensitive symbol names
15977 @cindex case sensitivity in symbol names
15978 @kindex set case-sensitive
15979 @item set case-sensitive on
15980 @itemx set case-sensitive off
15981 @itemx set case-sensitive auto
15982 Normally, when @value{GDBN} looks up symbols, it matches their names
15983 with case sensitivity determined by the current source language.
15984 Occasionally, you may wish to control that. The command @code{set
15985 case-sensitive} lets you do that by specifying @code{on} for
15986 case-sensitive matches or @code{off} for case-insensitive ones. If
15987 you specify @code{auto}, case sensitivity is reset to the default
15988 suitable for the source language. The default is case-sensitive
15989 matches for all languages except for Fortran, for which the default is
15990 case-insensitive matches.
15992 @kindex show case-sensitive
15993 @item show case-sensitive
15994 This command shows the current setting of case sensitivity for symbols
15997 @kindex set print type methods
15998 @item set print type methods
15999 @itemx set print type methods on
16000 @itemx set print type methods off
16001 Normally, when @value{GDBN} prints a class, it displays any methods
16002 declared in that class. You can control this behavior either by
16003 passing the appropriate flag to @code{ptype}, or using @command{set
16004 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16005 display the methods; this is the default. Specifying @code{off} will
16006 cause @value{GDBN} to omit the methods.
16008 @kindex show print type methods
16009 @item show print type methods
16010 This command shows the current setting of method display when printing
16013 @kindex set print type typedefs
16014 @item set print type typedefs
16015 @itemx set print type typedefs on
16016 @itemx set print type typedefs off
16018 Normally, when @value{GDBN} prints a class, it displays any typedefs
16019 defined in that class. You can control this behavior either by
16020 passing the appropriate flag to @code{ptype}, or using @command{set
16021 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16022 display the typedef definitions; this is the default. Specifying
16023 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16024 Note that this controls whether the typedef definition itself is
16025 printed, not whether typedef names are substituted when printing other
16028 @kindex show print type typedefs
16029 @item show print type typedefs
16030 This command shows the current setting of typedef display when
16033 @kindex info address
16034 @cindex address of a symbol
16035 @item info address @var{symbol}
16036 Describe where the data for @var{symbol} is stored. For a register
16037 variable, this says which register it is kept in. For a non-register
16038 local variable, this prints the stack-frame offset at which the variable
16041 Note the contrast with @samp{print &@var{symbol}}, which does not work
16042 at all for a register variable, and for a stack local variable prints
16043 the exact address of the current instantiation of the variable.
16045 @kindex info symbol
16046 @cindex symbol from address
16047 @cindex closest symbol and offset for an address
16048 @item info symbol @var{addr}
16049 Print the name of a symbol which is stored at the address @var{addr}.
16050 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16051 nearest symbol and an offset from it:
16054 (@value{GDBP}) info symbol 0x54320
16055 _initialize_vx + 396 in section .text
16059 This is the opposite of the @code{info address} command. You can use
16060 it to find out the name of a variable or a function given its address.
16062 For dynamically linked executables, the name of executable or shared
16063 library containing the symbol is also printed:
16066 (@value{GDBP}) info symbol 0x400225
16067 _start + 5 in section .text of /tmp/a.out
16068 (@value{GDBP}) info symbol 0x2aaaac2811cf
16069 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16073 @item whatis[/@var{flags}] [@var{arg}]
16074 Print the data type of @var{arg}, which can be either an expression
16075 or a name of a data type. With no argument, print the data type of
16076 @code{$}, the last value in the value history.
16078 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16079 is not actually evaluated, and any side-effecting operations (such as
16080 assignments or function calls) inside it do not take place.
16082 If @var{arg} is a variable or an expression, @code{whatis} prints its
16083 literal type as it is used in the source code. If the type was
16084 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16085 the data type underlying the @code{typedef}. If the type of the
16086 variable or the expression is a compound data type, such as
16087 @code{struct} or @code{class}, @code{whatis} never prints their
16088 fields or methods. It just prints the @code{struct}/@code{class}
16089 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16090 such a compound data type, use @code{ptype}.
16092 If @var{arg} is a type name that was defined using @code{typedef},
16093 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16094 Unrolling means that @code{whatis} will show the underlying type used
16095 in the @code{typedef} declaration of @var{arg}. However, if that
16096 underlying type is also a @code{typedef}, @code{whatis} will not
16099 For C code, the type names may also have the form @samp{class
16100 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16101 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16103 @var{flags} can be used to modify how the type is displayed.
16104 Available flags are:
16108 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16109 parameters and typedefs defined in a class when printing the class'
16110 members. The @code{/r} flag disables this.
16113 Do not print methods defined in the class.
16116 Print methods defined in the class. This is the default, but the flag
16117 exists in case you change the default with @command{set print type methods}.
16120 Do not print typedefs defined in the class. Note that this controls
16121 whether the typedef definition itself is printed, not whether typedef
16122 names are substituted when printing other types.
16125 Print typedefs defined in the class. This is the default, but the flag
16126 exists in case you change the default with @command{set print type typedefs}.
16130 @item ptype[/@var{flags}] [@var{arg}]
16131 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16132 detailed description of the type, instead of just the name of the type.
16133 @xref{Expressions, ,Expressions}.
16135 Contrary to @code{whatis}, @code{ptype} always unrolls any
16136 @code{typedef}s in its argument declaration, whether the argument is
16137 a variable, expression, or a data type. This means that @code{ptype}
16138 of a variable or an expression will not print literally its type as
16139 present in the source code---use @code{whatis} for that. @code{typedef}s at
16140 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16141 fields, methods and inner @code{class typedef}s of @code{struct}s,
16142 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16144 For example, for this variable declaration:
16147 typedef double real_t;
16148 struct complex @{ real_t real; double imag; @};
16149 typedef struct complex complex_t;
16151 real_t *real_pointer_var;
16155 the two commands give this output:
16159 (@value{GDBP}) whatis var
16161 (@value{GDBP}) ptype var
16162 type = struct complex @{
16166 (@value{GDBP}) whatis complex_t
16167 type = struct complex
16168 (@value{GDBP}) whatis struct complex
16169 type = struct complex
16170 (@value{GDBP}) ptype struct complex
16171 type = struct complex @{
16175 (@value{GDBP}) whatis real_pointer_var
16177 (@value{GDBP}) ptype real_pointer_var
16183 As with @code{whatis}, using @code{ptype} without an argument refers to
16184 the type of @code{$}, the last value in the value history.
16186 @cindex incomplete type
16187 Sometimes, programs use opaque data types or incomplete specifications
16188 of complex data structure. If the debug information included in the
16189 program does not allow @value{GDBN} to display a full declaration of
16190 the data type, it will say @samp{<incomplete type>}. For example,
16191 given these declarations:
16195 struct foo *fooptr;
16199 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16202 (@value{GDBP}) ptype foo
16203 $1 = <incomplete type>
16207 ``Incomplete type'' is C terminology for data types that are not
16208 completely specified.
16211 @item info types @var{regexp}
16213 Print a brief description of all types whose names match the regular
16214 expression @var{regexp} (or all types in your program, if you supply
16215 no argument). Each complete typename is matched as though it were a
16216 complete line; thus, @samp{i type value} gives information on all
16217 types in your program whose names include the string @code{value}, but
16218 @samp{i type ^value$} gives information only on types whose complete
16219 name is @code{value}.
16221 This command differs from @code{ptype} in two ways: first, like
16222 @code{whatis}, it does not print a detailed description; second, it
16223 lists all source files where a type is defined.
16225 @kindex info type-printers
16226 @item info type-printers
16227 Versions of @value{GDBN} that ship with Python scripting enabled may
16228 have ``type printers'' available. When using @command{ptype} or
16229 @command{whatis}, these printers are consulted when the name of a type
16230 is needed. @xref{Type Printing API}, for more information on writing
16233 @code{info type-printers} displays all the available type printers.
16235 @kindex enable type-printer
16236 @kindex disable type-printer
16237 @item enable type-printer @var{name}@dots{}
16238 @item disable type-printer @var{name}@dots{}
16239 These commands can be used to enable or disable type printers.
16242 @cindex local variables
16243 @item info scope @var{location}
16244 List all the variables local to a particular scope. This command
16245 accepts a @var{location} argument---a function name, a source line, or
16246 an address preceded by a @samp{*}, and prints all the variables local
16247 to the scope defined by that location. (@xref{Specify Location}, for
16248 details about supported forms of @var{location}.) For example:
16251 (@value{GDBP}) @b{info scope command_line_handler}
16252 Scope for command_line_handler:
16253 Symbol rl is an argument at stack/frame offset 8, length 4.
16254 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16255 Symbol linelength is in static storage at address 0x150a1c, length 4.
16256 Symbol p is a local variable in register $esi, length 4.
16257 Symbol p1 is a local variable in register $ebx, length 4.
16258 Symbol nline is a local variable in register $edx, length 4.
16259 Symbol repeat is a local variable at frame offset -8, length 4.
16263 This command is especially useful for determining what data to collect
16264 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16267 @kindex info source
16269 Show information about the current source file---that is, the source file for
16270 the function containing the current point of execution:
16273 the name of the source file, and the directory containing it,
16275 the directory it was compiled in,
16277 its length, in lines,
16279 which programming language it is written in,
16281 whether the executable includes debugging information for that file, and
16282 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16284 whether the debugging information includes information about
16285 preprocessor macros.
16289 @kindex info sources
16291 Print the names of all source files in your program for which there is
16292 debugging information, organized into two lists: files whose symbols
16293 have already been read, and files whose symbols will be read when needed.
16295 @kindex info functions
16296 @item info functions
16297 Print the names and data types of all defined functions.
16299 @item info functions @var{regexp}
16300 Print the names and data types of all defined functions
16301 whose names contain a match for regular expression @var{regexp}.
16302 Thus, @samp{info fun step} finds all functions whose names
16303 include @code{step}; @samp{info fun ^step} finds those whose names
16304 start with @code{step}. If a function name contains characters
16305 that conflict with the regular expression language (e.g.@:
16306 @samp{operator*()}), they may be quoted with a backslash.
16308 @kindex info variables
16309 @item info variables
16310 Print the names and data types of all variables that are defined
16311 outside of functions (i.e.@: excluding local variables).
16313 @item info variables @var{regexp}
16314 Print the names and data types of all variables (except for local
16315 variables) whose names contain a match for regular expression
16318 @kindex info classes
16319 @cindex Objective-C, classes and selectors
16321 @itemx info classes @var{regexp}
16322 Display all Objective-C classes in your program, or
16323 (with the @var{regexp} argument) all those matching a particular regular
16326 @kindex info selectors
16327 @item info selectors
16328 @itemx info selectors @var{regexp}
16329 Display all Objective-C selectors in your program, or
16330 (with the @var{regexp} argument) all those matching a particular regular
16334 This was never implemented.
16335 @kindex info methods
16337 @itemx info methods @var{regexp}
16338 The @code{info methods} command permits the user to examine all defined
16339 methods within C@t{++} program, or (with the @var{regexp} argument) a
16340 specific set of methods found in the various C@t{++} classes. Many
16341 C@t{++} classes provide a large number of methods. Thus, the output
16342 from the @code{ptype} command can be overwhelming and hard to use. The
16343 @code{info-methods} command filters the methods, printing only those
16344 which match the regular-expression @var{regexp}.
16347 @cindex opaque data types
16348 @kindex set opaque-type-resolution
16349 @item set opaque-type-resolution on
16350 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16351 declared as a pointer to a @code{struct}, @code{class}, or
16352 @code{union}---for example, @code{struct MyType *}---that is used in one
16353 source file although the full declaration of @code{struct MyType} is in
16354 another source file. The default is on.
16356 A change in the setting of this subcommand will not take effect until
16357 the next time symbols for a file are loaded.
16359 @item set opaque-type-resolution off
16360 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16361 is printed as follows:
16363 @{<no data fields>@}
16366 @kindex show opaque-type-resolution
16367 @item show opaque-type-resolution
16368 Show whether opaque types are resolved or not.
16370 @kindex set print symbol-loading
16371 @cindex print messages when symbols are loaded
16372 @item set print symbol-loading
16373 @itemx set print symbol-loading full
16374 @itemx set print symbol-loading brief
16375 @itemx set print symbol-loading off
16376 The @code{set print symbol-loading} command allows you to control the
16377 printing of messages when @value{GDBN} loads symbol information.
16378 By default a message is printed for the executable and one for each
16379 shared library, and normally this is what you want. However, when
16380 debugging apps with large numbers of shared libraries these messages
16382 When set to @code{brief} a message is printed for each executable,
16383 and when @value{GDBN} loads a collection of shared libraries at once
16384 it will only print one message regardless of the number of shared
16385 libraries. When set to @code{off} no messages are printed.
16387 @kindex show print symbol-loading
16388 @item show print symbol-loading
16389 Show whether messages will be printed when a @value{GDBN} command
16390 entered from the keyboard causes symbol information to be loaded.
16392 @kindex maint print symbols
16393 @cindex symbol dump
16394 @kindex maint print psymbols
16395 @cindex partial symbol dump
16396 @kindex maint print msymbols
16397 @cindex minimal symbol dump
16398 @item maint print symbols @var{filename}
16399 @itemx maint print psymbols @var{filename}
16400 @itemx maint print msymbols @var{filename}
16401 Write a dump of debugging symbol data into the file @var{filename}.
16402 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16403 symbols with debugging data are included. If you use @samp{maint print
16404 symbols}, @value{GDBN} includes all the symbols for which it has already
16405 collected full details: that is, @var{filename} reflects symbols for
16406 only those files whose symbols @value{GDBN} has read. You can use the
16407 command @code{info sources} to find out which files these are. If you
16408 use @samp{maint print psymbols} instead, the dump shows information about
16409 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16410 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16411 @samp{maint print msymbols} dumps just the minimal symbol information
16412 required for each object file from which @value{GDBN} has read some symbols.
16413 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16414 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16416 @kindex maint info symtabs
16417 @kindex maint info psymtabs
16418 @cindex listing @value{GDBN}'s internal symbol tables
16419 @cindex symbol tables, listing @value{GDBN}'s internal
16420 @cindex full symbol tables, listing @value{GDBN}'s internal
16421 @cindex partial symbol tables, listing @value{GDBN}'s internal
16422 @item maint info symtabs @r{[} @var{regexp} @r{]}
16423 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16425 List the @code{struct symtab} or @code{struct partial_symtab}
16426 structures whose names match @var{regexp}. If @var{regexp} is not
16427 given, list them all. The output includes expressions which you can
16428 copy into a @value{GDBN} debugging this one to examine a particular
16429 structure in more detail. For example:
16432 (@value{GDBP}) maint info psymtabs dwarf2read
16433 @{ objfile /home/gnu/build/gdb/gdb
16434 ((struct objfile *) 0x82e69d0)
16435 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16436 ((struct partial_symtab *) 0x8474b10)
16439 text addresses 0x814d3c8 -- 0x8158074
16440 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16441 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16442 dependencies (none)
16445 (@value{GDBP}) maint info symtabs
16449 We see that there is one partial symbol table whose filename contains
16450 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16451 and we see that @value{GDBN} has not read in any symtabs yet at all.
16452 If we set a breakpoint on a function, that will cause @value{GDBN} to
16453 read the symtab for the compilation unit containing that function:
16456 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16457 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16459 (@value{GDBP}) maint info symtabs
16460 @{ objfile /home/gnu/build/gdb/gdb
16461 ((struct objfile *) 0x82e69d0)
16462 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16463 ((struct symtab *) 0x86c1f38)
16466 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16467 linetable ((struct linetable *) 0x8370fa0)
16468 debugformat DWARF 2
16477 @chapter Altering Execution
16479 Once you think you have found an error in your program, you might want to
16480 find out for certain whether correcting the apparent error would lead to
16481 correct results in the rest of the run. You can find the answer by
16482 experiment, using the @value{GDBN} features for altering execution of the
16485 For example, you can store new values into variables or memory
16486 locations, give your program a signal, restart it at a different
16487 address, or even return prematurely from a function.
16490 * Assignment:: Assignment to variables
16491 * Jumping:: Continuing at a different address
16492 * Signaling:: Giving your program a signal
16493 * Returning:: Returning from a function
16494 * Calling:: Calling your program's functions
16495 * Patching:: Patching your program
16499 @section Assignment to Variables
16502 @cindex setting variables
16503 To alter the value of a variable, evaluate an assignment expression.
16504 @xref{Expressions, ,Expressions}. For example,
16511 stores the value 4 into the variable @code{x}, and then prints the
16512 value of the assignment expression (which is 4).
16513 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16514 information on operators in supported languages.
16516 @kindex set variable
16517 @cindex variables, setting
16518 If you are not interested in seeing the value of the assignment, use the
16519 @code{set} command instead of the @code{print} command. @code{set} is
16520 really the same as @code{print} except that the expression's value is
16521 not printed and is not put in the value history (@pxref{Value History,
16522 ,Value History}). The expression is evaluated only for its effects.
16524 If the beginning of the argument string of the @code{set} command
16525 appears identical to a @code{set} subcommand, use the @code{set
16526 variable} command instead of just @code{set}. This command is identical
16527 to @code{set} except for its lack of subcommands. For example, if your
16528 program has a variable @code{width}, you get an error if you try to set
16529 a new value with just @samp{set width=13}, because @value{GDBN} has the
16530 command @code{set width}:
16533 (@value{GDBP}) whatis width
16535 (@value{GDBP}) p width
16537 (@value{GDBP}) set width=47
16538 Invalid syntax in expression.
16542 The invalid expression, of course, is @samp{=47}. In
16543 order to actually set the program's variable @code{width}, use
16546 (@value{GDBP}) set var width=47
16549 Because the @code{set} command has many subcommands that can conflict
16550 with the names of program variables, it is a good idea to use the
16551 @code{set variable} command instead of just @code{set}. For example, if
16552 your program has a variable @code{g}, you run into problems if you try
16553 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16554 the command @code{set gnutarget}, abbreviated @code{set g}:
16558 (@value{GDBP}) whatis g
16562 (@value{GDBP}) set g=4
16566 The program being debugged has been started already.
16567 Start it from the beginning? (y or n) y
16568 Starting program: /home/smith/cc_progs/a.out
16569 "/home/smith/cc_progs/a.out": can't open to read symbols:
16570 Invalid bfd target.
16571 (@value{GDBP}) show g
16572 The current BFD target is "=4".
16577 The program variable @code{g} did not change, and you silently set the
16578 @code{gnutarget} to an invalid value. In order to set the variable
16582 (@value{GDBP}) set var g=4
16585 @value{GDBN} allows more implicit conversions in assignments than C; you can
16586 freely store an integer value into a pointer variable or vice versa,
16587 and you can convert any structure to any other structure that is the
16588 same length or shorter.
16589 @comment FIXME: how do structs align/pad in these conversions?
16590 @comment /doc@cygnus.com 18dec1990
16592 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16593 construct to generate a value of specified type at a specified address
16594 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16595 to memory location @code{0x83040} as an integer (which implies a certain size
16596 and representation in memory), and
16599 set @{int@}0x83040 = 4
16603 stores the value 4 into that memory location.
16606 @section Continuing at a Different Address
16608 Ordinarily, when you continue your program, you do so at the place where
16609 it stopped, with the @code{continue} command. You can instead continue at
16610 an address of your own choosing, with the following commands:
16614 @kindex j @r{(@code{jump})}
16615 @item jump @var{linespec}
16616 @itemx j @var{linespec}
16617 @itemx jump @var{location}
16618 @itemx j @var{location}
16619 Resume execution at line @var{linespec} or at address given by
16620 @var{location}. Execution stops again immediately if there is a
16621 breakpoint there. @xref{Specify Location}, for a description of the
16622 different forms of @var{linespec} and @var{location}. It is common
16623 practice to use the @code{tbreak} command in conjunction with
16624 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16626 The @code{jump} command does not change the current stack frame, or
16627 the stack pointer, or the contents of any memory location or any
16628 register other than the program counter. If line @var{linespec} is in
16629 a different function from the one currently executing, the results may
16630 be bizarre if the two functions expect different patterns of arguments or
16631 of local variables. For this reason, the @code{jump} command requests
16632 confirmation if the specified line is not in the function currently
16633 executing. However, even bizarre results are predictable if you are
16634 well acquainted with the machine-language code of your program.
16637 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16638 On many systems, you can get much the same effect as the @code{jump}
16639 command by storing a new value into the register @code{$pc}. The
16640 difference is that this does not start your program running; it only
16641 changes the address of where it @emph{will} run when you continue. For
16649 makes the next @code{continue} command or stepping command execute at
16650 address @code{0x485}, rather than at the address where your program stopped.
16651 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16653 The most common occasion to use the @code{jump} command is to back
16654 up---perhaps with more breakpoints set---over a portion of a program
16655 that has already executed, in order to examine its execution in more
16660 @section Giving your Program a Signal
16661 @cindex deliver a signal to a program
16665 @item signal @var{signal}
16666 Resume execution where your program is stopped, but immediately give it the
16667 signal @var{signal}. The @var{signal} can be the name or the number of a
16668 signal. For example, on many systems @code{signal 2} and @code{signal
16669 SIGINT} are both ways of sending an interrupt signal.
16671 Alternatively, if @var{signal} is zero, continue execution without
16672 giving a signal. This is useful when your program stopped on account of
16673 a signal and would ordinarily see the signal when resumed with the
16674 @code{continue} command; @samp{signal 0} causes it to resume without a
16677 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16678 delivered to the currently selected thread, not the thread that last
16679 reported a stop. This includes the situation where a thread was
16680 stopped due to a signal. So if you want to continue execution
16681 suppressing the signal that stopped a thread, you should select that
16682 same thread before issuing the @samp{signal 0} command. If you issue
16683 the @samp{signal 0} command with another thread as the selected one,
16684 @value{GDBN} detects that and asks for confirmation.
16686 Invoking the @code{signal} command is not the same as invoking the
16687 @code{kill} utility from the shell. Sending a signal with @code{kill}
16688 causes @value{GDBN} to decide what to do with the signal depending on
16689 the signal handling tables (@pxref{Signals}). The @code{signal} command
16690 passes the signal directly to your program.
16692 @code{signal} does not repeat when you press @key{RET} a second time
16693 after executing the command.
16695 @kindex queue-signal
16696 @item queue-signal @var{signal}
16697 Queue @var{signal} to be delivered immediately to the current thread
16698 when execution of the thread resumes. The @var{signal} can be the name or
16699 the number of a signal. For example, on many systems @code{signal 2} and
16700 @code{signal SIGINT} are both ways of sending an interrupt signal.
16701 The handling of the signal must be set to pass the signal to the program,
16702 otherwise @value{GDBN} will report an error.
16703 You can control the handling of signals from @value{GDBN} with the
16704 @code{handle} command (@pxref{Signals}).
16706 Alternatively, if @var{signal} is zero, any currently queued signal
16707 for the current thread is discarded and when execution resumes no signal
16708 will be delivered. This is useful when your program stopped on account
16709 of a signal and would ordinarily see the signal when resumed with the
16710 @code{continue} command.
16712 This command differs from the @code{signal} command in that the signal
16713 is just queued, execution is not resumed. And @code{queue-signal} cannot
16714 be used to pass a signal whose handling state has been set to @code{nopass}
16719 @xref{stepping into signal handlers}, for information on how stepping
16720 commands behave when the thread has a signal queued.
16723 @section Returning from a Function
16726 @cindex returning from a function
16729 @itemx return @var{expression}
16730 You can cancel execution of a function call with the @code{return}
16731 command. If you give an
16732 @var{expression} argument, its value is used as the function's return
16736 When you use @code{return}, @value{GDBN} discards the selected stack frame
16737 (and all frames within it). You can think of this as making the
16738 discarded frame return prematurely. If you wish to specify a value to
16739 be returned, give that value as the argument to @code{return}.
16741 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16742 Frame}), and any other frames inside of it, leaving its caller as the
16743 innermost remaining frame. That frame becomes selected. The
16744 specified value is stored in the registers used for returning values
16747 The @code{return} command does not resume execution; it leaves the
16748 program stopped in the state that would exist if the function had just
16749 returned. In contrast, the @code{finish} command (@pxref{Continuing
16750 and Stepping, ,Continuing and Stepping}) resumes execution until the
16751 selected stack frame returns naturally.
16753 @value{GDBN} needs to know how the @var{expression} argument should be set for
16754 the inferior. The concrete registers assignment depends on the OS ABI and the
16755 type being returned by the selected stack frame. For example it is common for
16756 OS ABI to return floating point values in FPU registers while integer values in
16757 CPU registers. Still some ABIs return even floating point values in CPU
16758 registers. Larger integer widths (such as @code{long long int}) also have
16759 specific placement rules. @value{GDBN} already knows the OS ABI from its
16760 current target so it needs to find out also the type being returned to make the
16761 assignment into the right register(s).
16763 Normally, the selected stack frame has debug info. @value{GDBN} will always
16764 use the debug info instead of the implicit type of @var{expression} when the
16765 debug info is available. For example, if you type @kbd{return -1}, and the
16766 function in the current stack frame is declared to return a @code{long long
16767 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16768 into a @code{long long int}:
16771 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16773 (@value{GDBP}) return -1
16774 Make func return now? (y or n) y
16775 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16776 43 printf ("result=%lld\n", func ());
16780 However, if the selected stack frame does not have a debug info, e.g., if the
16781 function was compiled without debug info, @value{GDBN} has to find out the type
16782 to return from user. Specifying a different type by mistake may set the value
16783 in different inferior registers than the caller code expects. For example,
16784 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16785 of a @code{long long int} result for a debug info less function (on 32-bit
16786 architectures). Therefore the user is required to specify the return type by
16787 an appropriate cast explicitly:
16790 Breakpoint 2, 0x0040050b in func ()
16791 (@value{GDBP}) return -1
16792 Return value type not available for selected stack frame.
16793 Please use an explicit cast of the value to return.
16794 (@value{GDBP}) return (long long int) -1
16795 Make selected stack frame return now? (y or n) y
16796 #0 0x00400526 in main ()
16801 @section Calling Program Functions
16804 @cindex calling functions
16805 @cindex inferior functions, calling
16806 @item print @var{expr}
16807 Evaluate the expression @var{expr} and display the resulting value.
16808 The expression may include calls to functions in the program being
16812 @item call @var{expr}
16813 Evaluate the expression @var{expr} without displaying @code{void}
16816 You can use this variant of the @code{print} command if you want to
16817 execute a function from your program that does not return anything
16818 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16819 with @code{void} returned values that @value{GDBN} will otherwise
16820 print. If the result is not void, it is printed and saved in the
16824 It is possible for the function you call via the @code{print} or
16825 @code{call} command to generate a signal (e.g., if there's a bug in
16826 the function, or if you passed it incorrect arguments). What happens
16827 in that case is controlled by the @code{set unwindonsignal} command.
16829 Similarly, with a C@t{++} program it is possible for the function you
16830 call via the @code{print} or @code{call} command to generate an
16831 exception that is not handled due to the constraints of the dummy
16832 frame. In this case, any exception that is raised in the frame, but has
16833 an out-of-frame exception handler will not be found. GDB builds a
16834 dummy-frame for the inferior function call, and the unwinder cannot
16835 seek for exception handlers outside of this dummy-frame. What happens
16836 in that case is controlled by the
16837 @code{set unwind-on-terminating-exception} command.
16840 @item set unwindonsignal
16841 @kindex set unwindonsignal
16842 @cindex unwind stack in called functions
16843 @cindex call dummy stack unwinding
16844 Set unwinding of the stack if a signal is received while in a function
16845 that @value{GDBN} called in the program being debugged. If set to on,
16846 @value{GDBN} unwinds the stack it created for the call and restores
16847 the context to what it was before the call. If set to off (the
16848 default), @value{GDBN} stops in the frame where the signal was
16851 @item show unwindonsignal
16852 @kindex show unwindonsignal
16853 Show the current setting of stack unwinding in the functions called by
16856 @item set unwind-on-terminating-exception
16857 @kindex set unwind-on-terminating-exception
16858 @cindex unwind stack in called functions with unhandled exceptions
16859 @cindex call dummy stack unwinding on unhandled exception.
16860 Set unwinding of the stack if a C@t{++} exception is raised, but left
16861 unhandled while in a function that @value{GDBN} called in the program being
16862 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16863 it created for the call and restores the context to what it was before
16864 the call. If set to off, @value{GDBN} the exception is delivered to
16865 the default C@t{++} exception handler and the inferior terminated.
16867 @item show unwind-on-terminating-exception
16868 @kindex show unwind-on-terminating-exception
16869 Show the current setting of stack unwinding in the functions called by
16874 @cindex weak alias functions
16875 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16876 for another function. In such case, @value{GDBN} might not pick up
16877 the type information, including the types of the function arguments,
16878 which causes @value{GDBN} to call the inferior function incorrectly.
16879 As a result, the called function will function erroneously and may
16880 even crash. A solution to that is to use the name of the aliased
16884 @section Patching Programs
16886 @cindex patching binaries
16887 @cindex writing into executables
16888 @cindex writing into corefiles
16890 By default, @value{GDBN} opens the file containing your program's
16891 executable code (or the corefile) read-only. This prevents accidental
16892 alterations to machine code; but it also prevents you from intentionally
16893 patching your program's binary.
16895 If you'd like to be able to patch the binary, you can specify that
16896 explicitly with the @code{set write} command. For example, you might
16897 want to turn on internal debugging flags, or even to make emergency
16903 @itemx set write off
16904 If you specify @samp{set write on}, @value{GDBN} opens executable and
16905 core files for both reading and writing; if you specify @kbd{set write
16906 off} (the default), @value{GDBN} opens them read-only.
16908 If you have already loaded a file, you must load it again (using the
16909 @code{exec-file} or @code{core-file} command) after changing @code{set
16910 write}, for your new setting to take effect.
16914 Display whether executable files and core files are opened for writing
16915 as well as reading.
16919 @chapter @value{GDBN} Files
16921 @value{GDBN} needs to know the file name of the program to be debugged,
16922 both in order to read its symbol table and in order to start your
16923 program. To debug a core dump of a previous run, you must also tell
16924 @value{GDBN} the name of the core dump file.
16927 * Files:: Commands to specify files
16928 * Separate Debug Files:: Debugging information in separate files
16929 * MiniDebugInfo:: Debugging information in a special section
16930 * Index Files:: Index files speed up GDB
16931 * Symbol Errors:: Errors reading symbol files
16932 * Data Files:: GDB data files
16936 @section Commands to Specify Files
16938 @cindex symbol table
16939 @cindex core dump file
16941 You may want to specify executable and core dump file names. The usual
16942 way to do this is at start-up time, using the arguments to
16943 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16944 Out of @value{GDBN}}).
16946 Occasionally it is necessary to change to a different file during a
16947 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16948 specify a file you want to use. Or you are debugging a remote target
16949 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16950 Program}). In these situations the @value{GDBN} commands to specify
16951 new files are useful.
16954 @cindex executable file
16956 @item file @var{filename}
16957 Use @var{filename} as the program to be debugged. It is read for its
16958 symbols and for the contents of pure memory. It is also the program
16959 executed when you use the @code{run} command. If you do not specify a
16960 directory and the file is not found in the @value{GDBN} working directory,
16961 @value{GDBN} uses the environment variable @code{PATH} as a list of
16962 directories to search, just as the shell does when looking for a program
16963 to run. You can change the value of this variable, for both @value{GDBN}
16964 and your program, using the @code{path} command.
16966 @cindex unlinked object files
16967 @cindex patching object files
16968 You can load unlinked object @file{.o} files into @value{GDBN} using
16969 the @code{file} command. You will not be able to ``run'' an object
16970 file, but you can disassemble functions and inspect variables. Also,
16971 if the underlying BFD functionality supports it, you could use
16972 @kbd{gdb -write} to patch object files using this technique. Note
16973 that @value{GDBN} can neither interpret nor modify relocations in this
16974 case, so branches and some initialized variables will appear to go to
16975 the wrong place. But this feature is still handy from time to time.
16978 @code{file} with no argument makes @value{GDBN} discard any information it
16979 has on both executable file and the symbol table.
16982 @item exec-file @r{[} @var{filename} @r{]}
16983 Specify that the program to be run (but not the symbol table) is found
16984 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16985 if necessary to locate your program. Omitting @var{filename} means to
16986 discard information on the executable file.
16988 @kindex symbol-file
16989 @item symbol-file @r{[} @var{filename} @r{]}
16990 Read symbol table information from file @var{filename}. @code{PATH} is
16991 searched when necessary. Use the @code{file} command to get both symbol
16992 table and program to run from the same file.
16994 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16995 program's symbol table.
16997 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16998 some breakpoints and auto-display expressions. This is because they may
16999 contain pointers to the internal data recording symbols and data types,
17000 which are part of the old symbol table data being discarded inside
17003 @code{symbol-file} does not repeat if you press @key{RET} again after
17006 When @value{GDBN} is configured for a particular environment, it
17007 understands debugging information in whatever format is the standard
17008 generated for that environment; you may use either a @sc{gnu} compiler, or
17009 other compilers that adhere to the local conventions.
17010 Best results are usually obtained from @sc{gnu} compilers; for example,
17011 using @code{@value{NGCC}} you can generate debugging information for
17014 For most kinds of object files, with the exception of old SVR3 systems
17015 using COFF, the @code{symbol-file} command does not normally read the
17016 symbol table in full right away. Instead, it scans the symbol table
17017 quickly to find which source files and which symbols are present. The
17018 details are read later, one source file at a time, as they are needed.
17020 The purpose of this two-stage reading strategy is to make @value{GDBN}
17021 start up faster. For the most part, it is invisible except for
17022 occasional pauses while the symbol table details for a particular source
17023 file are being read. (The @code{set verbose} command can turn these
17024 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17025 Warnings and Messages}.)
17027 We have not implemented the two-stage strategy for COFF yet. When the
17028 symbol table is stored in COFF format, @code{symbol-file} reads the
17029 symbol table data in full right away. Note that ``stabs-in-COFF''
17030 still does the two-stage strategy, since the debug info is actually
17034 @cindex reading symbols immediately
17035 @cindex symbols, reading immediately
17036 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17037 @itemx file @r{[} -readnow @r{]} @var{filename}
17038 You can override the @value{GDBN} two-stage strategy for reading symbol
17039 tables by using the @samp{-readnow} option with any of the commands that
17040 load symbol table information, if you want to be sure @value{GDBN} has the
17041 entire symbol table available.
17043 @c FIXME: for now no mention of directories, since this seems to be in
17044 @c flux. 13mar1992 status is that in theory GDB would look either in
17045 @c current dir or in same dir as myprog; but issues like competing
17046 @c GDB's, or clutter in system dirs, mean that in practice right now
17047 @c only current dir is used. FFish says maybe a special GDB hierarchy
17048 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17052 @item core-file @r{[}@var{filename}@r{]}
17054 Specify the whereabouts of a core dump file to be used as the ``contents
17055 of memory''. Traditionally, core files contain only some parts of the
17056 address space of the process that generated them; @value{GDBN} can access the
17057 executable file itself for other parts.
17059 @code{core-file} with no argument specifies that no core file is
17062 Note that the core file is ignored when your program is actually running
17063 under @value{GDBN}. So, if you have been running your program and you
17064 wish to debug a core file instead, you must kill the subprocess in which
17065 the program is running. To do this, use the @code{kill} command
17066 (@pxref{Kill Process, ,Killing the Child Process}).
17068 @kindex add-symbol-file
17069 @cindex dynamic linking
17070 @item add-symbol-file @var{filename} @var{address}
17071 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17072 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17073 The @code{add-symbol-file} command reads additional symbol table
17074 information from the file @var{filename}. You would use this command
17075 when @var{filename} has been dynamically loaded (by some other means)
17076 into the program that is running. The @var{address} should give the memory
17077 address at which the file has been loaded; @value{GDBN} cannot figure
17078 this out for itself. You can additionally specify an arbitrary number
17079 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17080 section name and base address for that section. You can specify any
17081 @var{address} as an expression.
17083 The symbol table of the file @var{filename} is added to the symbol table
17084 originally read with the @code{symbol-file} command. You can use the
17085 @code{add-symbol-file} command any number of times; the new symbol data
17086 thus read is kept in addition to the old.
17088 Changes can be reverted using the command @code{remove-symbol-file}.
17090 @cindex relocatable object files, reading symbols from
17091 @cindex object files, relocatable, reading symbols from
17092 @cindex reading symbols from relocatable object files
17093 @cindex symbols, reading from relocatable object files
17094 @cindex @file{.o} files, reading symbols from
17095 Although @var{filename} is typically a shared library file, an
17096 executable file, or some other object file which has been fully
17097 relocated for loading into a process, you can also load symbolic
17098 information from relocatable @file{.o} files, as long as:
17102 the file's symbolic information refers only to linker symbols defined in
17103 that file, not to symbols defined by other object files,
17105 every section the file's symbolic information refers to has actually
17106 been loaded into the inferior, as it appears in the file, and
17108 you can determine the address at which every section was loaded, and
17109 provide these to the @code{add-symbol-file} command.
17113 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17114 relocatable files into an already running program; such systems
17115 typically make the requirements above easy to meet. However, it's
17116 important to recognize that many native systems use complex link
17117 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17118 assembly, for example) that make the requirements difficult to meet. In
17119 general, one cannot assume that using @code{add-symbol-file} to read a
17120 relocatable object file's symbolic information will have the same effect
17121 as linking the relocatable object file into the program in the normal
17124 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17126 @kindex remove-symbol-file
17127 @item remove-symbol-file @var{filename}
17128 @item remove-symbol-file -a @var{address}
17129 Remove a symbol file added via the @code{add-symbol-file} command. The
17130 file to remove can be identified by its @var{filename} or by an @var{address}
17131 that lies within the boundaries of this symbol file in memory. Example:
17134 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17135 add symbol table from file "/home/user/gdb/mylib.so" at
17136 .text_addr = 0x7ffff7ff9480
17138 Reading symbols from /home/user/gdb/mylib.so...done.
17139 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17140 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17145 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17147 @kindex add-symbol-file-from-memory
17148 @cindex @code{syscall DSO}
17149 @cindex load symbols from memory
17150 @item add-symbol-file-from-memory @var{address}
17151 Load symbols from the given @var{address} in a dynamically loaded
17152 object file whose image is mapped directly into the inferior's memory.
17153 For example, the Linux kernel maps a @code{syscall DSO} into each
17154 process's address space; this DSO provides kernel-specific code for
17155 some system calls. The argument can be any expression whose
17156 evaluation yields the address of the file's shared object file header.
17157 For this command to work, you must have used @code{symbol-file} or
17158 @code{exec-file} commands in advance.
17160 @kindex add-shared-symbol-files
17162 @item add-shared-symbol-files @var{library-file}
17163 @itemx assf @var{library-file}
17164 This command is deprecated and will be removed in future versions
17165 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
17167 The @code{add-shared-symbol-files} command can currently be used only
17168 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
17169 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
17170 @value{GDBN} automatically looks for shared libraries, however if
17171 @value{GDBN} does not find yours, you can invoke
17172 @code{add-shared-symbol-files}. It takes one argument: the shared
17173 library's file name. @code{assf} is a shorthand alias for
17174 @code{add-shared-symbol-files}.
17177 @item section @var{section} @var{addr}
17178 The @code{section} command changes the base address of the named
17179 @var{section} of the exec file to @var{addr}. This can be used if the
17180 exec file does not contain section addresses, (such as in the
17181 @code{a.out} format), or when the addresses specified in the file
17182 itself are wrong. Each section must be changed separately. The
17183 @code{info files} command, described below, lists all the sections and
17187 @kindex info target
17190 @code{info files} and @code{info target} are synonymous; both print the
17191 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17192 including the names of the executable and core dump files currently in
17193 use by @value{GDBN}, and the files from which symbols were loaded. The
17194 command @code{help target} lists all possible targets rather than
17197 @kindex maint info sections
17198 @item maint info sections
17199 Another command that can give you extra information about program sections
17200 is @code{maint info sections}. In addition to the section information
17201 displayed by @code{info files}, this command displays the flags and file
17202 offset of each section in the executable and core dump files. In addition,
17203 @code{maint info sections} provides the following command options (which
17204 may be arbitrarily combined):
17208 Display sections for all loaded object files, including shared libraries.
17209 @item @var{sections}
17210 Display info only for named @var{sections}.
17211 @item @var{section-flags}
17212 Display info only for sections for which @var{section-flags} are true.
17213 The section flags that @value{GDBN} currently knows about are:
17216 Section will have space allocated in the process when loaded.
17217 Set for all sections except those containing debug information.
17219 Section will be loaded from the file into the child process memory.
17220 Set for pre-initialized code and data, clear for @code{.bss} sections.
17222 Section needs to be relocated before loading.
17224 Section cannot be modified by the child process.
17226 Section contains executable code only.
17228 Section contains data only (no executable code).
17230 Section will reside in ROM.
17232 Section contains data for constructor/destructor lists.
17234 Section is not empty.
17236 An instruction to the linker to not output the section.
17237 @item COFF_SHARED_LIBRARY
17238 A notification to the linker that the section contains
17239 COFF shared library information.
17241 Section contains common symbols.
17244 @kindex set trust-readonly-sections
17245 @cindex read-only sections
17246 @item set trust-readonly-sections on
17247 Tell @value{GDBN} that readonly sections in your object file
17248 really are read-only (i.e.@: that their contents will not change).
17249 In that case, @value{GDBN} can fetch values from these sections
17250 out of the object file, rather than from the target program.
17251 For some targets (notably embedded ones), this can be a significant
17252 enhancement to debugging performance.
17254 The default is off.
17256 @item set trust-readonly-sections off
17257 Tell @value{GDBN} not to trust readonly sections. This means that
17258 the contents of the section might change while the program is running,
17259 and must therefore be fetched from the target when needed.
17261 @item show trust-readonly-sections
17262 Show the current setting of trusting readonly sections.
17265 All file-specifying commands allow both absolute and relative file names
17266 as arguments. @value{GDBN} always converts the file name to an absolute file
17267 name and remembers it that way.
17269 @cindex shared libraries
17270 @anchor{Shared Libraries}
17271 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17272 and IBM RS/6000 AIX shared libraries.
17274 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17275 shared libraries. @xref{Expat}.
17277 @value{GDBN} automatically loads symbol definitions from shared libraries
17278 when you use the @code{run} command, or when you examine a core file.
17279 (Before you issue the @code{run} command, @value{GDBN} does not understand
17280 references to a function in a shared library, however---unless you are
17281 debugging a core file).
17283 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17284 automatically loads the symbols at the time of the @code{shl_load} call.
17286 @c FIXME: some @value{GDBN} release may permit some refs to undef
17287 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17288 @c FIXME...lib; check this from time to time when updating manual
17290 There are times, however, when you may wish to not automatically load
17291 symbol definitions from shared libraries, such as when they are
17292 particularly large or there are many of them.
17294 To control the automatic loading of shared library symbols, use the
17298 @kindex set auto-solib-add
17299 @item set auto-solib-add @var{mode}
17300 If @var{mode} is @code{on}, symbols from all shared object libraries
17301 will be loaded automatically when the inferior begins execution, you
17302 attach to an independently started inferior, or when the dynamic linker
17303 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17304 is @code{off}, symbols must be loaded manually, using the
17305 @code{sharedlibrary} command. The default value is @code{on}.
17307 @cindex memory used for symbol tables
17308 If your program uses lots of shared libraries with debug info that
17309 takes large amounts of memory, you can decrease the @value{GDBN}
17310 memory footprint by preventing it from automatically loading the
17311 symbols from shared libraries. To that end, type @kbd{set
17312 auto-solib-add off} before running the inferior, then load each
17313 library whose debug symbols you do need with @kbd{sharedlibrary
17314 @var{regexp}}, where @var{regexp} is a regular expression that matches
17315 the libraries whose symbols you want to be loaded.
17317 @kindex show auto-solib-add
17318 @item show auto-solib-add
17319 Display the current autoloading mode.
17322 @cindex load shared library
17323 To explicitly load shared library symbols, use the @code{sharedlibrary}
17327 @kindex info sharedlibrary
17329 @item info share @var{regex}
17330 @itemx info sharedlibrary @var{regex}
17331 Print the names of the shared libraries which are currently loaded
17332 that match @var{regex}. If @var{regex} is omitted then print
17333 all shared libraries that are loaded.
17335 @kindex sharedlibrary
17337 @item sharedlibrary @var{regex}
17338 @itemx share @var{regex}
17339 Load shared object library symbols for files matching a
17340 Unix regular expression.
17341 As with files loaded automatically, it only loads shared libraries
17342 required by your program for a core file or after typing @code{run}. If
17343 @var{regex} is omitted all shared libraries required by your program are
17346 @item nosharedlibrary
17347 @kindex nosharedlibrary
17348 @cindex unload symbols from shared libraries
17349 Unload all shared object library symbols. This discards all symbols
17350 that have been loaded from all shared libraries. Symbols from shared
17351 libraries that were loaded by explicit user requests are not
17355 Sometimes you may wish that @value{GDBN} stops and gives you control
17356 when any of shared library events happen. The best way to do this is
17357 to use @code{catch load} and @code{catch unload} (@pxref{Set
17360 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17361 command for this. This command exists for historical reasons. It is
17362 less useful than setting a catchpoint, because it does not allow for
17363 conditions or commands as a catchpoint does.
17366 @item set stop-on-solib-events
17367 @kindex set stop-on-solib-events
17368 This command controls whether @value{GDBN} should give you control
17369 when the dynamic linker notifies it about some shared library event.
17370 The most common event of interest is loading or unloading of a new
17373 @item show stop-on-solib-events
17374 @kindex show stop-on-solib-events
17375 Show whether @value{GDBN} stops and gives you control when shared
17376 library events happen.
17379 Shared libraries are also supported in many cross or remote debugging
17380 configurations. @value{GDBN} needs to have access to the target's libraries;
17381 this can be accomplished either by providing copies of the libraries
17382 on the host system, or by asking @value{GDBN} to automatically retrieve the
17383 libraries from the target. If copies of the target libraries are
17384 provided, they need to be the same as the target libraries, although the
17385 copies on the target can be stripped as long as the copies on the host are
17388 @cindex where to look for shared libraries
17389 For remote debugging, you need to tell @value{GDBN} where the target
17390 libraries are, so that it can load the correct copies---otherwise, it
17391 may try to load the host's libraries. @value{GDBN} has two variables
17392 to specify the search directories for target libraries.
17395 @cindex prefix for shared library file names
17396 @cindex system root, alternate
17397 @kindex set solib-absolute-prefix
17398 @kindex set sysroot
17399 @item set sysroot @var{path}
17400 Use @var{path} as the system root for the program being debugged. Any
17401 absolute shared library paths will be prefixed with @var{path}; many
17402 runtime loaders store the absolute paths to the shared library in the
17403 target program's memory. If you use @code{set sysroot} to find shared
17404 libraries, they need to be laid out in the same way that they are on
17405 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17408 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17409 retrieve the target libraries from the remote system. This is only
17410 supported when using a remote target that supports the @code{remote get}
17411 command (@pxref{File Transfer,,Sending files to a remote system}).
17412 The part of @var{path} following the initial @file{remote:}
17413 (if present) is used as system root prefix on the remote file system.
17414 @footnote{If you want to specify a local system root using a directory
17415 that happens to be named @file{remote:}, you need to use some equivalent
17416 variant of the name like @file{./remote:}.}
17418 For targets with an MS-DOS based filesystem, such as MS-Windows and
17419 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17420 absolute file name with @var{path}. But first, on Unix hosts,
17421 @value{GDBN} converts all backslash directory separators into forward
17422 slashes, because the backslash is not a directory separator on Unix:
17425 c:\foo\bar.dll @result{} c:/foo/bar.dll
17428 Then, @value{GDBN} attempts prefixing the target file name with
17429 @var{path}, and looks for the resulting file name in the host file
17433 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17436 If that does not find the shared library, @value{GDBN} tries removing
17437 the @samp{:} character from the drive spec, both for convenience, and,
17438 for the case of the host file system not supporting file names with
17442 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17445 This makes it possible to have a system root that mirrors a target
17446 with more than one drive. E.g., you may want to setup your local
17447 copies of the target system shared libraries like so (note @samp{c} vs
17451 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17452 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17453 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17457 and point the system root at @file{/path/to/sysroot}, so that
17458 @value{GDBN} can find the correct copies of both
17459 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17461 If that still does not find the shared library, @value{GDBN} tries
17462 removing the whole drive spec from the target file name:
17465 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17468 This last lookup makes it possible to not care about the drive name,
17469 if you don't want or need to.
17471 The @code{set solib-absolute-prefix} command is an alias for @code{set
17474 @cindex default system root
17475 @cindex @samp{--with-sysroot}
17476 You can set the default system root by using the configure-time
17477 @samp{--with-sysroot} option. If the system root is inside
17478 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17479 @samp{--exec-prefix}), then the default system root will be updated
17480 automatically if the installed @value{GDBN} is moved to a new
17483 @kindex show sysroot
17485 Display the current shared library prefix.
17487 @kindex set solib-search-path
17488 @item set solib-search-path @var{path}
17489 If this variable is set, @var{path} is a colon-separated list of
17490 directories to search for shared libraries. @samp{solib-search-path}
17491 is used after @samp{sysroot} fails to locate the library, or if the
17492 path to the library is relative instead of absolute. If you want to
17493 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17494 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17495 finding your host's libraries. @samp{sysroot} is preferred; setting
17496 it to a nonexistent directory may interfere with automatic loading
17497 of shared library symbols.
17499 @kindex show solib-search-path
17500 @item show solib-search-path
17501 Display the current shared library search path.
17503 @cindex DOS file-name semantics of file names.
17504 @kindex set target-file-system-kind (unix|dos-based|auto)
17505 @kindex show target-file-system-kind
17506 @item set target-file-system-kind @var{kind}
17507 Set assumed file system kind for target reported file names.
17509 Shared library file names as reported by the target system may not
17510 make sense as is on the system @value{GDBN} is running on. For
17511 example, when remote debugging a target that has MS-DOS based file
17512 system semantics, from a Unix host, the target may be reporting to
17513 @value{GDBN} a list of loaded shared libraries with file names such as
17514 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17515 drive letters, so the @samp{c:\} prefix is not normally understood as
17516 indicating an absolute file name, and neither is the backslash
17517 normally considered a directory separator character. In that case,
17518 the native file system would interpret this whole absolute file name
17519 as a relative file name with no directory components. This would make
17520 it impossible to point @value{GDBN} at a copy of the remote target's
17521 shared libraries on the host using @code{set sysroot}, and impractical
17522 with @code{set solib-search-path}. Setting
17523 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17524 to interpret such file names similarly to how the target would, and to
17525 map them to file names valid on @value{GDBN}'s native file system
17526 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17527 to one of the supported file system kinds. In that case, @value{GDBN}
17528 tries to determine the appropriate file system variant based on the
17529 current target's operating system (@pxref{ABI, ,Configuring the
17530 Current ABI}). The supported file system settings are:
17534 Instruct @value{GDBN} to assume the target file system is of Unix
17535 kind. Only file names starting the forward slash (@samp{/}) character
17536 are considered absolute, and the directory separator character is also
17540 Instruct @value{GDBN} to assume the target file system is DOS based.
17541 File names starting with either a forward slash, or a drive letter
17542 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17543 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17544 considered directory separators.
17547 Instruct @value{GDBN} to use the file system kind associated with the
17548 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17549 This is the default.
17553 @cindex file name canonicalization
17554 @cindex base name differences
17555 When processing file names provided by the user, @value{GDBN}
17556 frequently needs to compare them to the file names recorded in the
17557 program's debug info. Normally, @value{GDBN} compares just the
17558 @dfn{base names} of the files as strings, which is reasonably fast
17559 even for very large programs. (The base name of a file is the last
17560 portion of its name, after stripping all the leading directories.)
17561 This shortcut in comparison is based upon the assumption that files
17562 cannot have more than one base name. This is usually true, but
17563 references to files that use symlinks or similar filesystem
17564 facilities violate that assumption. If your program records files
17565 using such facilities, or if you provide file names to @value{GDBN}
17566 using symlinks etc., you can set @code{basenames-may-differ} to
17567 @code{true} to instruct @value{GDBN} to completely canonicalize each
17568 pair of file names it needs to compare. This will make file-name
17569 comparisons accurate, but at a price of a significant slowdown.
17572 @item set basenames-may-differ
17573 @kindex set basenames-may-differ
17574 Set whether a source file may have multiple base names.
17576 @item show basenames-may-differ
17577 @kindex show basenames-may-differ
17578 Show whether a source file may have multiple base names.
17581 @node Separate Debug Files
17582 @section Debugging Information in Separate Files
17583 @cindex separate debugging information files
17584 @cindex debugging information in separate files
17585 @cindex @file{.debug} subdirectories
17586 @cindex debugging information directory, global
17587 @cindex global debugging information directories
17588 @cindex build ID, and separate debugging files
17589 @cindex @file{.build-id} directory
17591 @value{GDBN} allows you to put a program's debugging information in a
17592 file separate from the executable itself, in a way that allows
17593 @value{GDBN} to find and load the debugging information automatically.
17594 Since debugging information can be very large---sometimes larger
17595 than the executable code itself---some systems distribute debugging
17596 information for their executables in separate files, which users can
17597 install only when they need to debug a problem.
17599 @value{GDBN} supports two ways of specifying the separate debug info
17604 The executable contains a @dfn{debug link} that specifies the name of
17605 the separate debug info file. The separate debug file's name is
17606 usually @file{@var{executable}.debug}, where @var{executable} is the
17607 name of the corresponding executable file without leading directories
17608 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17609 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17610 checksum for the debug file, which @value{GDBN} uses to validate that
17611 the executable and the debug file came from the same build.
17614 The executable contains a @dfn{build ID}, a unique bit string that is
17615 also present in the corresponding debug info file. (This is supported
17616 only on some operating systems, notably those which use the ELF format
17617 for binary files and the @sc{gnu} Binutils.) For more details about
17618 this feature, see the description of the @option{--build-id}
17619 command-line option in @ref{Options, , Command Line Options, ld.info,
17620 The GNU Linker}. The debug info file's name is not specified
17621 explicitly by the build ID, but can be computed from the build ID, see
17625 Depending on the way the debug info file is specified, @value{GDBN}
17626 uses two different methods of looking for the debug file:
17630 For the ``debug link'' method, @value{GDBN} looks up the named file in
17631 the directory of the executable file, then in a subdirectory of that
17632 directory named @file{.debug}, and finally under each one of the global debug
17633 directories, in a subdirectory whose name is identical to the leading
17634 directories of the executable's absolute file name.
17637 For the ``build ID'' method, @value{GDBN} looks in the
17638 @file{.build-id} subdirectory of each one of the global debug directories for
17639 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17640 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17641 are the rest of the bit string. (Real build ID strings are 32 or more
17642 hex characters, not 10.)
17645 So, for example, suppose you ask @value{GDBN} to debug
17646 @file{/usr/bin/ls}, which has a debug link that specifies the
17647 file @file{ls.debug}, and a build ID whose value in hex is
17648 @code{abcdef1234}. If the list of the global debug directories includes
17649 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17650 debug information files, in the indicated order:
17654 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17656 @file{/usr/bin/ls.debug}
17658 @file{/usr/bin/.debug/ls.debug}
17660 @file{/usr/lib/debug/usr/bin/ls.debug}.
17663 @anchor{debug-file-directory}
17664 Global debugging info directories default to what is set by @value{GDBN}
17665 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17666 you can also set the global debugging info directories, and view the list
17667 @value{GDBN} is currently using.
17671 @kindex set debug-file-directory
17672 @item set debug-file-directory @var{directories}
17673 Set the directories which @value{GDBN} searches for separate debugging
17674 information files to @var{directory}. Multiple path components can be set
17675 concatenating them by a path separator.
17677 @kindex show debug-file-directory
17678 @item show debug-file-directory
17679 Show the directories @value{GDBN} searches for separate debugging
17684 @cindex @code{.gnu_debuglink} sections
17685 @cindex debug link sections
17686 A debug link is a special section of the executable file named
17687 @code{.gnu_debuglink}. The section must contain:
17691 A filename, with any leading directory components removed, followed by
17694 zero to three bytes of padding, as needed to reach the next four-byte
17695 boundary within the section, and
17697 a four-byte CRC checksum, stored in the same endianness used for the
17698 executable file itself. The checksum is computed on the debugging
17699 information file's full contents by the function given below, passing
17700 zero as the @var{crc} argument.
17703 Any executable file format can carry a debug link, as long as it can
17704 contain a section named @code{.gnu_debuglink} with the contents
17707 @cindex @code{.note.gnu.build-id} sections
17708 @cindex build ID sections
17709 The build ID is a special section in the executable file (and in other
17710 ELF binary files that @value{GDBN} may consider). This section is
17711 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17712 It contains unique identification for the built files---the ID remains
17713 the same across multiple builds of the same build tree. The default
17714 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17715 content for the build ID string. The same section with an identical
17716 value is present in the original built binary with symbols, in its
17717 stripped variant, and in the separate debugging information file.
17719 The debugging information file itself should be an ordinary
17720 executable, containing a full set of linker symbols, sections, and
17721 debugging information. The sections of the debugging information file
17722 should have the same names, addresses, and sizes as the original file,
17723 but they need not contain any data---much like a @code{.bss} section
17724 in an ordinary executable.
17726 The @sc{gnu} binary utilities (Binutils) package includes the
17727 @samp{objcopy} utility that can produce
17728 the separated executable / debugging information file pairs using the
17729 following commands:
17732 @kbd{objcopy --only-keep-debug foo foo.debug}
17737 These commands remove the debugging
17738 information from the executable file @file{foo} and place it in the file
17739 @file{foo.debug}. You can use the first, second or both methods to link the
17744 The debug link method needs the following additional command to also leave
17745 behind a debug link in @file{foo}:
17748 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17751 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17752 a version of the @code{strip} command such that the command @kbd{strip foo -f
17753 foo.debug} has the same functionality as the two @code{objcopy} commands and
17754 the @code{ln -s} command above, together.
17757 Build ID gets embedded into the main executable using @code{ld --build-id} or
17758 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17759 compatibility fixes for debug files separation are present in @sc{gnu} binary
17760 utilities (Binutils) package since version 2.18.
17765 @cindex CRC algorithm definition
17766 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17767 IEEE 802.3 using the polynomial:
17769 @c TexInfo requires naked braces for multi-digit exponents for Tex
17770 @c output, but this causes HTML output to barf. HTML has to be set using
17771 @c raw commands. So we end up having to specify this equation in 2
17776 <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>
17777 + <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
17783 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17784 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17788 The function is computed byte at a time, taking the least
17789 significant bit of each byte first. The initial pattern
17790 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17791 the final result is inverted to ensure trailing zeros also affect the
17794 @emph{Note:} This is the same CRC polynomial as used in handling the
17795 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
17796 However in the case of the Remote Serial Protocol, the CRC is computed
17797 @emph{most} significant bit first, and the result is not inverted, so
17798 trailing zeros have no effect on the CRC value.
17800 To complete the description, we show below the code of the function
17801 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17802 initially supplied @code{crc} argument means that an initial call to
17803 this function passing in zero will start computing the CRC using
17806 @kindex gnu_debuglink_crc32
17809 gnu_debuglink_crc32 (unsigned long crc,
17810 unsigned char *buf, size_t len)
17812 static const unsigned long crc32_table[256] =
17814 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17815 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17816 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17817 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17818 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17819 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17820 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17821 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17822 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17823 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17824 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17825 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17826 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17827 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17828 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17829 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17830 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17831 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17832 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17833 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17834 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17835 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17836 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17837 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17838 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17839 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17840 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17841 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17842 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17843 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17844 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17845 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17846 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17847 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17848 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17849 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17850 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17851 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17852 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17853 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17854 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17855 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17856 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17857 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17858 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17859 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17860 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17861 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17862 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17863 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17864 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17867 unsigned char *end;
17869 crc = ~crc & 0xffffffff;
17870 for (end = buf + len; buf < end; ++buf)
17871 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17872 return ~crc & 0xffffffff;
17877 This computation does not apply to the ``build ID'' method.
17879 @node MiniDebugInfo
17880 @section Debugging information in a special section
17881 @cindex separate debug sections
17882 @cindex @samp{.gnu_debugdata} section
17884 Some systems ship pre-built executables and libraries that have a
17885 special @samp{.gnu_debugdata} section. This feature is called
17886 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17887 is used to supply extra symbols for backtraces.
17889 The intent of this section is to provide extra minimal debugging
17890 information for use in simple backtraces. It is not intended to be a
17891 replacement for full separate debugging information (@pxref{Separate
17892 Debug Files}). The example below shows the intended use; however,
17893 @value{GDBN} does not currently put restrictions on what sort of
17894 debugging information might be included in the section.
17896 @value{GDBN} has support for this extension. If the section exists,
17897 then it is used provided that no other source of debugging information
17898 can be found, and that @value{GDBN} was configured with LZMA support.
17900 This section can be easily created using @command{objcopy} and other
17901 standard utilities:
17904 # Extract the dynamic symbols from the main binary, there is no need
17905 # to also have these in the normal symbol table.
17906 nm -D @var{binary} --format=posix --defined-only \
17907 | awk '@{ print $1 @}' | sort > dynsyms
17909 # Extract all the text (i.e. function) symbols from the debuginfo.
17910 # (Note that we actually also accept "D" symbols, for the benefit
17911 # of platforms like PowerPC64 that use function descriptors.)
17912 nm @var{binary} --format=posix --defined-only \
17913 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17916 # Keep all the function symbols not already in the dynamic symbol
17918 comm -13 dynsyms funcsyms > keep_symbols
17920 # Separate full debug info into debug binary.
17921 objcopy --only-keep-debug @var{binary} debug
17923 # Copy the full debuginfo, keeping only a minimal set of symbols and
17924 # removing some unnecessary sections.
17925 objcopy -S --remove-section .gdb_index --remove-section .comment \
17926 --keep-symbols=keep_symbols debug mini_debuginfo
17928 # Drop the full debug info from the original binary.
17929 strip --strip-all -R .comment @var{binary}
17931 # Inject the compressed data into the .gnu_debugdata section of the
17934 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17938 @section Index Files Speed Up @value{GDBN}
17939 @cindex index files
17940 @cindex @samp{.gdb_index} section
17942 When @value{GDBN} finds a symbol file, it scans the symbols in the
17943 file in order to construct an internal symbol table. This lets most
17944 @value{GDBN} operations work quickly---at the cost of a delay early
17945 on. For large programs, this delay can be quite lengthy, so
17946 @value{GDBN} provides a way to build an index, which speeds up
17949 The index is stored as a section in the symbol file. @value{GDBN} can
17950 write the index to a file, then you can put it into the symbol file
17951 using @command{objcopy}.
17953 To create an index file, use the @code{save gdb-index} command:
17956 @item save gdb-index @var{directory}
17957 @kindex save gdb-index
17958 Create an index file for each symbol file currently known by
17959 @value{GDBN}. Each file is named after its corresponding symbol file,
17960 with @samp{.gdb-index} appended, and is written into the given
17964 Once you have created an index file you can merge it into your symbol
17965 file, here named @file{symfile}, using @command{objcopy}:
17968 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17969 --set-section-flags .gdb_index=readonly symfile symfile
17972 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17973 sections that have been deprecated. Usually they are deprecated because
17974 they are missing a new feature or have performance issues.
17975 To tell @value{GDBN} to use a deprecated index section anyway
17976 specify @code{set use-deprecated-index-sections on}.
17977 The default is @code{off}.
17978 This can speed up startup, but may result in some functionality being lost.
17979 @xref{Index Section Format}.
17981 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17982 must be done before gdb reads the file. The following will not work:
17985 $ gdb -ex "set use-deprecated-index-sections on" <program>
17988 Instead you must do, for example,
17991 $ gdb -iex "set use-deprecated-index-sections on" <program>
17994 There are currently some limitation on indices. They only work when
17995 for DWARF debugging information, not stabs. And, they do not
17996 currently work for programs using Ada.
17998 @node Symbol Errors
17999 @section Errors Reading Symbol Files
18001 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18002 such as symbol types it does not recognize, or known bugs in compiler
18003 output. By default, @value{GDBN} does not notify you of such problems, since
18004 they are relatively common and primarily of interest to people
18005 debugging compilers. If you are interested in seeing information
18006 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18007 only one message about each such type of problem, no matter how many
18008 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18009 to see how many times the problems occur, with the @code{set
18010 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18013 The messages currently printed, and their meanings, include:
18016 @item inner block not inside outer block in @var{symbol}
18018 The symbol information shows where symbol scopes begin and end
18019 (such as at the start of a function or a block of statements). This
18020 error indicates that an inner scope block is not fully contained
18021 in its outer scope blocks.
18023 @value{GDBN} circumvents the problem by treating the inner block as if it had
18024 the same scope as the outer block. In the error message, @var{symbol}
18025 may be shown as ``@code{(don't know)}'' if the outer block is not a
18028 @item block at @var{address} out of order
18030 The symbol information for symbol scope blocks should occur in
18031 order of increasing addresses. This error indicates that it does not
18034 @value{GDBN} does not circumvent this problem, and has trouble
18035 locating symbols in the source file whose symbols it is reading. (You
18036 can often determine what source file is affected by specifying
18037 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18040 @item bad block start address patched
18042 The symbol information for a symbol scope block has a start address
18043 smaller than the address of the preceding source line. This is known
18044 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18046 @value{GDBN} circumvents the problem by treating the symbol scope block as
18047 starting on the previous source line.
18049 @item bad string table offset in symbol @var{n}
18052 Symbol number @var{n} contains a pointer into the string table which is
18053 larger than the size of the string table.
18055 @value{GDBN} circumvents the problem by considering the symbol to have the
18056 name @code{foo}, which may cause other problems if many symbols end up
18059 @item unknown symbol type @code{0x@var{nn}}
18061 The symbol information contains new data types that @value{GDBN} does
18062 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18063 uncomprehended information, in hexadecimal.
18065 @value{GDBN} circumvents the error by ignoring this symbol information.
18066 This usually allows you to debug your program, though certain symbols
18067 are not accessible. If you encounter such a problem and feel like
18068 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18069 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18070 and examine @code{*bufp} to see the symbol.
18072 @item stub type has NULL name
18074 @value{GDBN} could not find the full definition for a struct or class.
18076 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18077 The symbol information for a C@t{++} member function is missing some
18078 information that recent versions of the compiler should have output for
18081 @item info mismatch between compiler and debugger
18083 @value{GDBN} could not parse a type specification output by the compiler.
18088 @section GDB Data Files
18090 @cindex prefix for data files
18091 @value{GDBN} will sometimes read an auxiliary data file. These files
18092 are kept in a directory known as the @dfn{data directory}.
18094 You can set the data directory's name, and view the name @value{GDBN}
18095 is currently using.
18098 @kindex set data-directory
18099 @item set data-directory @var{directory}
18100 Set the directory which @value{GDBN} searches for auxiliary data files
18101 to @var{directory}.
18103 @kindex show data-directory
18104 @item show data-directory
18105 Show the directory @value{GDBN} searches for auxiliary data files.
18108 @cindex default data directory
18109 @cindex @samp{--with-gdb-datadir}
18110 You can set the default data directory by using the configure-time
18111 @samp{--with-gdb-datadir} option. If the data directory is inside
18112 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18113 @samp{--exec-prefix}), then the default data directory will be updated
18114 automatically if the installed @value{GDBN} is moved to a new
18117 The data directory may also be specified with the
18118 @code{--data-directory} command line option.
18119 @xref{Mode Options}.
18122 @chapter Specifying a Debugging Target
18124 @cindex debugging target
18125 A @dfn{target} is the execution environment occupied by your program.
18127 Often, @value{GDBN} runs in the same host environment as your program;
18128 in that case, the debugging target is specified as a side effect when
18129 you use the @code{file} or @code{core} commands. When you need more
18130 flexibility---for example, running @value{GDBN} on a physically separate
18131 host, or controlling a standalone system over a serial port or a
18132 realtime system over a TCP/IP connection---you can use the @code{target}
18133 command to specify one of the target types configured for @value{GDBN}
18134 (@pxref{Target Commands, ,Commands for Managing Targets}).
18136 @cindex target architecture
18137 It is possible to build @value{GDBN} for several different @dfn{target
18138 architectures}. When @value{GDBN} is built like that, you can choose
18139 one of the available architectures with the @kbd{set architecture}
18143 @kindex set architecture
18144 @kindex show architecture
18145 @item set architecture @var{arch}
18146 This command sets the current target architecture to @var{arch}. The
18147 value of @var{arch} can be @code{"auto"}, in addition to one of the
18148 supported architectures.
18150 @item show architecture
18151 Show the current target architecture.
18153 @item set processor
18155 @kindex set processor
18156 @kindex show processor
18157 These are alias commands for, respectively, @code{set architecture}
18158 and @code{show architecture}.
18162 * Active Targets:: Active targets
18163 * Target Commands:: Commands for managing targets
18164 * Byte Order:: Choosing target byte order
18167 @node Active Targets
18168 @section Active Targets
18170 @cindex stacking targets
18171 @cindex active targets
18172 @cindex multiple targets
18174 There are multiple classes of targets such as: processes, executable files or
18175 recording sessions. Core files belong to the process class, making core file
18176 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18177 on multiple active targets, one in each class. This allows you to (for
18178 example) start a process and inspect its activity, while still having access to
18179 the executable file after the process finishes. Or if you start process
18180 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18181 presented a virtual layer of the recording target, while the process target
18182 remains stopped at the chronologically last point of the process execution.
18184 Use the @code{core-file} and @code{exec-file} commands to select a new core
18185 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18186 specify as a target a process that is already running, use the @code{attach}
18187 command (@pxref{Attach, ,Debugging an Already-running Process}).
18189 @node Target Commands
18190 @section Commands for Managing Targets
18193 @item target @var{type} @var{parameters}
18194 Connects the @value{GDBN} host environment to a target machine or
18195 process. A target is typically a protocol for talking to debugging
18196 facilities. You use the argument @var{type} to specify the type or
18197 protocol of the target machine.
18199 Further @var{parameters} are interpreted by the target protocol, but
18200 typically include things like device names or host names to connect
18201 with, process numbers, and baud rates.
18203 The @code{target} command does not repeat if you press @key{RET} again
18204 after executing the command.
18206 @kindex help target
18208 Displays the names of all targets available. To display targets
18209 currently selected, use either @code{info target} or @code{info files}
18210 (@pxref{Files, ,Commands to Specify Files}).
18212 @item help target @var{name}
18213 Describe a particular target, including any parameters necessary to
18216 @kindex set gnutarget
18217 @item set gnutarget @var{args}
18218 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18219 knows whether it is reading an @dfn{executable},
18220 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18221 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18222 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18225 @emph{Warning:} To specify a file format with @code{set gnutarget},
18226 you must know the actual BFD name.
18230 @xref{Files, , Commands to Specify Files}.
18232 @kindex show gnutarget
18233 @item show gnutarget
18234 Use the @code{show gnutarget} command to display what file format
18235 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18236 @value{GDBN} will determine the file format for each file automatically,
18237 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18240 @cindex common targets
18241 Here are some common targets (available, or not, depending on the GDB
18246 @item target exec @var{program}
18247 @cindex executable file target
18248 An executable file. @samp{target exec @var{program}} is the same as
18249 @samp{exec-file @var{program}}.
18251 @item target core @var{filename}
18252 @cindex core dump file target
18253 A core dump file. @samp{target core @var{filename}} is the same as
18254 @samp{core-file @var{filename}}.
18256 @item target remote @var{medium}
18257 @cindex remote target
18258 A remote system connected to @value{GDBN} via a serial line or network
18259 connection. This command tells @value{GDBN} to use its own remote
18260 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18262 For example, if you have a board connected to @file{/dev/ttya} on the
18263 machine running @value{GDBN}, you could say:
18266 target remote /dev/ttya
18269 @code{target remote} supports the @code{load} command. This is only
18270 useful if you have some other way of getting the stub to the target
18271 system, and you can put it somewhere in memory where it won't get
18272 clobbered by the download.
18274 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18275 @cindex built-in simulator target
18276 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18284 works; however, you cannot assume that a specific memory map, device
18285 drivers, or even basic I/O is available, although some simulators do
18286 provide these. For info about any processor-specific simulator details,
18287 see the appropriate section in @ref{Embedded Processors, ,Embedded
18290 @item target native
18291 @cindex native target
18292 Setup for local/native process debugging. Useful to make the
18293 @code{run} command spawn native processes (likewise @code{attach},
18294 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18295 (@pxref{set auto-connect-native-target}).
18299 Different targets are available on different configurations of @value{GDBN};
18300 your configuration may have more or fewer targets.
18302 Many remote targets require you to download the executable's code once
18303 you've successfully established a connection. You may wish to control
18304 various aspects of this process.
18309 @kindex set hash@r{, for remote monitors}
18310 @cindex hash mark while downloading
18311 This command controls whether a hash mark @samp{#} is displayed while
18312 downloading a file to the remote monitor. If on, a hash mark is
18313 displayed after each S-record is successfully downloaded to the
18317 @kindex show hash@r{, for remote monitors}
18318 Show the current status of displaying the hash mark.
18320 @item set debug monitor
18321 @kindex set debug monitor
18322 @cindex display remote monitor communications
18323 Enable or disable display of communications messages between
18324 @value{GDBN} and the remote monitor.
18326 @item show debug monitor
18327 @kindex show debug monitor
18328 Show the current status of displaying communications between
18329 @value{GDBN} and the remote monitor.
18334 @kindex load @var{filename}
18335 @item load @var{filename}
18337 Depending on what remote debugging facilities are configured into
18338 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18339 is meant to make @var{filename} (an executable) available for debugging
18340 on the remote system---by downloading, or dynamic linking, for example.
18341 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18342 the @code{add-symbol-file} command.
18344 If your @value{GDBN} does not have a @code{load} command, attempting to
18345 execute it gets the error message ``@code{You can't do that when your
18346 target is @dots{}}''
18348 The file is loaded at whatever address is specified in the executable.
18349 For some object file formats, you can specify the load address when you
18350 link the program; for other formats, like a.out, the object file format
18351 specifies a fixed address.
18352 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18354 Depending on the remote side capabilities, @value{GDBN} may be able to
18355 load programs into flash memory.
18357 @code{load} does not repeat if you press @key{RET} again after using it.
18361 @section Choosing Target Byte Order
18363 @cindex choosing target byte order
18364 @cindex target byte order
18366 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18367 offer the ability to run either big-endian or little-endian byte
18368 orders. Usually the executable or symbol will include a bit to
18369 designate the endian-ness, and you will not need to worry about
18370 which to use. However, you may still find it useful to adjust
18371 @value{GDBN}'s idea of processor endian-ness manually.
18375 @item set endian big
18376 Instruct @value{GDBN} to assume the target is big-endian.
18378 @item set endian little
18379 Instruct @value{GDBN} to assume the target is little-endian.
18381 @item set endian auto
18382 Instruct @value{GDBN} to use the byte order associated with the
18386 Display @value{GDBN}'s current idea of the target byte order.
18390 Note that these commands merely adjust interpretation of symbolic
18391 data on the host, and that they have absolutely no effect on the
18395 @node Remote Debugging
18396 @chapter Debugging Remote Programs
18397 @cindex remote debugging
18399 If you are trying to debug a program running on a machine that cannot run
18400 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18401 For example, you might use remote debugging on an operating system kernel,
18402 or on a small system which does not have a general purpose operating system
18403 powerful enough to run a full-featured debugger.
18405 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18406 to make this work with particular debugging targets. In addition,
18407 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18408 but not specific to any particular target system) which you can use if you
18409 write the remote stubs---the code that runs on the remote system to
18410 communicate with @value{GDBN}.
18412 Other remote targets may be available in your
18413 configuration of @value{GDBN}; use @code{help target} to list them.
18416 * Connecting:: Connecting to a remote target
18417 * File Transfer:: Sending files to a remote system
18418 * Server:: Using the gdbserver program
18419 * Remote Configuration:: Remote configuration
18420 * Remote Stub:: Implementing a remote stub
18424 @section Connecting to a Remote Target
18426 On the @value{GDBN} host machine, you will need an unstripped copy of
18427 your program, since @value{GDBN} needs symbol and debugging information.
18428 Start up @value{GDBN} as usual, using the name of the local copy of your
18429 program as the first argument.
18431 @cindex @code{target remote}
18432 @value{GDBN} can communicate with the target over a serial line, or
18433 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18434 each case, @value{GDBN} uses the same protocol for debugging your
18435 program; only the medium carrying the debugging packets varies. The
18436 @code{target remote} command establishes a connection to the target.
18437 Its arguments indicate which medium to use:
18441 @item target remote @var{serial-device}
18442 @cindex serial line, @code{target remote}
18443 Use @var{serial-device} to communicate with the target. For example,
18444 to use a serial line connected to the device named @file{/dev/ttyb}:
18447 target remote /dev/ttyb
18450 If you're using a serial line, you may want to give @value{GDBN} the
18451 @samp{--baud} option, or use the @code{set serial baud} command
18452 (@pxref{Remote Configuration, set serial baud}) before the
18453 @code{target} command.
18455 @item target remote @code{@var{host}:@var{port}}
18456 @itemx target remote @code{tcp:@var{host}:@var{port}}
18457 @cindex @acronym{TCP} port, @code{target remote}
18458 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18459 The @var{host} may be either a host name or a numeric @acronym{IP}
18460 address; @var{port} must be a decimal number. The @var{host} could be
18461 the target machine itself, if it is directly connected to the net, or
18462 it might be a terminal server which in turn has a serial line to the
18465 For example, to connect to port 2828 on a terminal server named
18469 target remote manyfarms:2828
18472 If your remote target is actually running on the same machine as your
18473 debugger session (e.g.@: a simulator for your target running on the
18474 same host), you can omit the hostname. For example, to connect to
18475 port 1234 on your local machine:
18478 target remote :1234
18482 Note that the colon is still required here.
18484 @item target remote @code{udp:@var{host}:@var{port}}
18485 @cindex @acronym{UDP} port, @code{target remote}
18486 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18487 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18490 target remote udp:manyfarms:2828
18493 When using a @acronym{UDP} connection for remote debugging, you should
18494 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18495 can silently drop packets on busy or unreliable networks, which will
18496 cause havoc with your debugging session.
18498 @item target remote | @var{command}
18499 @cindex pipe, @code{target remote} to
18500 Run @var{command} in the background and communicate with it using a
18501 pipe. The @var{command} is a shell command, to be parsed and expanded
18502 by the system's command shell, @code{/bin/sh}; it should expect remote
18503 protocol packets on its standard input, and send replies on its
18504 standard output. You could use this to run a stand-alone simulator
18505 that speaks the remote debugging protocol, to make net connections
18506 using programs like @code{ssh}, or for other similar tricks.
18508 If @var{command} closes its standard output (perhaps by exiting),
18509 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18510 program has already exited, this will have no effect.)
18514 Once the connection has been established, you can use all the usual
18515 commands to examine and change data. The remote program is already
18516 running; you can use @kbd{step} and @kbd{continue}, and you do not
18517 need to use @kbd{run}.
18519 @cindex interrupting remote programs
18520 @cindex remote programs, interrupting
18521 Whenever @value{GDBN} is waiting for the remote program, if you type the
18522 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18523 program. This may or may not succeed, depending in part on the hardware
18524 and the serial drivers the remote system uses. If you type the
18525 interrupt character once again, @value{GDBN} displays this prompt:
18528 Interrupted while waiting for the program.
18529 Give up (and stop debugging it)? (y or n)
18532 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18533 (If you decide you want to try again later, you can use @samp{target
18534 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18535 goes back to waiting.
18538 @kindex detach (remote)
18540 When you have finished debugging the remote program, you can use the
18541 @code{detach} command to release it from @value{GDBN} control.
18542 Detaching from the target normally resumes its execution, but the results
18543 will depend on your particular remote stub. After the @code{detach}
18544 command, @value{GDBN} is free to connect to another target.
18548 The @code{disconnect} command behaves like @code{detach}, except that
18549 the target is generally not resumed. It will wait for @value{GDBN}
18550 (this instance or another one) to connect and continue debugging. After
18551 the @code{disconnect} command, @value{GDBN} is again free to connect to
18554 @cindex send command to remote monitor
18555 @cindex extend @value{GDBN} for remote targets
18556 @cindex add new commands for external monitor
18558 @item monitor @var{cmd}
18559 This command allows you to send arbitrary commands directly to the
18560 remote monitor. Since @value{GDBN} doesn't care about the commands it
18561 sends like this, this command is the way to extend @value{GDBN}---you
18562 can add new commands that only the external monitor will understand
18566 @node File Transfer
18567 @section Sending files to a remote system
18568 @cindex remote target, file transfer
18569 @cindex file transfer
18570 @cindex sending files to remote systems
18572 Some remote targets offer the ability to transfer files over the same
18573 connection used to communicate with @value{GDBN}. This is convenient
18574 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18575 running @code{gdbserver} over a network interface. For other targets,
18576 e.g.@: embedded devices with only a single serial port, this may be
18577 the only way to upload or download files.
18579 Not all remote targets support these commands.
18583 @item remote put @var{hostfile} @var{targetfile}
18584 Copy file @var{hostfile} from the host system (the machine running
18585 @value{GDBN}) to @var{targetfile} on the target system.
18588 @item remote get @var{targetfile} @var{hostfile}
18589 Copy file @var{targetfile} from the target system to @var{hostfile}
18590 on the host system.
18592 @kindex remote delete
18593 @item remote delete @var{targetfile}
18594 Delete @var{targetfile} from the target system.
18599 @section Using the @code{gdbserver} Program
18602 @cindex remote connection without stubs
18603 @code{gdbserver} is a control program for Unix-like systems, which
18604 allows you to connect your program with a remote @value{GDBN} via
18605 @code{target remote}---but without linking in the usual debugging stub.
18607 @code{gdbserver} is not a complete replacement for the debugging stubs,
18608 because it requires essentially the same operating-system facilities
18609 that @value{GDBN} itself does. In fact, a system that can run
18610 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18611 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18612 because it is a much smaller program than @value{GDBN} itself. It is
18613 also easier to port than all of @value{GDBN}, so you may be able to get
18614 started more quickly on a new system by using @code{gdbserver}.
18615 Finally, if you develop code for real-time systems, you may find that
18616 the tradeoffs involved in real-time operation make it more convenient to
18617 do as much development work as possible on another system, for example
18618 by cross-compiling. You can use @code{gdbserver} to make a similar
18619 choice for debugging.
18621 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18622 or a TCP connection, using the standard @value{GDBN} remote serial
18626 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18627 Do not run @code{gdbserver} connected to any public network; a
18628 @value{GDBN} connection to @code{gdbserver} provides access to the
18629 target system with the same privileges as the user running
18633 @subsection Running @code{gdbserver}
18634 @cindex arguments, to @code{gdbserver}
18635 @cindex @code{gdbserver}, command-line arguments
18637 Run @code{gdbserver} on the target system. You need a copy of the
18638 program you want to debug, including any libraries it requires.
18639 @code{gdbserver} does not need your program's symbol table, so you can
18640 strip the program if necessary to save space. @value{GDBN} on the host
18641 system does all the symbol handling.
18643 To use the server, you must tell it how to communicate with @value{GDBN};
18644 the name of your program; and the arguments for your program. The usual
18648 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18651 @var{comm} is either a device name (to use a serial line), or a TCP
18652 hostname and portnumber, or @code{-} or @code{stdio} to use
18653 stdin/stdout of @code{gdbserver}.
18654 For example, to debug Emacs with the argument
18655 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18659 target> gdbserver /dev/com1 emacs foo.txt
18662 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18665 To use a TCP connection instead of a serial line:
18668 target> gdbserver host:2345 emacs foo.txt
18671 The only difference from the previous example is the first argument,
18672 specifying that you are communicating with the host @value{GDBN} via
18673 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18674 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18675 (Currently, the @samp{host} part is ignored.) You can choose any number
18676 you want for the port number as long as it does not conflict with any
18677 TCP ports already in use on the target system (for example, @code{23} is
18678 reserved for @code{telnet}).@footnote{If you choose a port number that
18679 conflicts with another service, @code{gdbserver} prints an error message
18680 and exits.} You must use the same port number with the host @value{GDBN}
18681 @code{target remote} command.
18683 The @code{stdio} connection is useful when starting @code{gdbserver}
18687 (gdb) target remote | ssh -T hostname gdbserver - hello
18690 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18691 and we don't want escape-character handling. Ssh does this by default when
18692 a command is provided, the flag is provided to make it explicit.
18693 You could elide it if you want to.
18695 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18696 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18697 display through a pipe connected to gdbserver.
18698 Both @code{stdout} and @code{stderr} use the same pipe.
18700 @subsubsection Attaching to a Running Program
18701 @cindex attach to a program, @code{gdbserver}
18702 @cindex @option{--attach}, @code{gdbserver} option
18704 On some targets, @code{gdbserver} can also attach to running programs.
18705 This is accomplished via the @code{--attach} argument. The syntax is:
18708 target> gdbserver --attach @var{comm} @var{pid}
18711 @var{pid} is the process ID of a currently running process. It isn't necessary
18712 to point @code{gdbserver} at a binary for the running process.
18715 You can debug processes by name instead of process ID if your target has the
18716 @code{pidof} utility:
18719 target> gdbserver --attach @var{comm} `pidof @var{program}`
18722 In case more than one copy of @var{program} is running, or @var{program}
18723 has multiple threads, most versions of @code{pidof} support the
18724 @code{-s} option to only return the first process ID.
18726 @subsubsection Multi-Process Mode for @code{gdbserver}
18727 @cindex @code{gdbserver}, multiple processes
18728 @cindex multiple processes with @code{gdbserver}
18730 When you connect to @code{gdbserver} using @code{target remote},
18731 @code{gdbserver} debugs the specified program only once. When the
18732 program exits, or you detach from it, @value{GDBN} closes the connection
18733 and @code{gdbserver} exits.
18735 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18736 enters multi-process mode. When the debugged program exits, or you
18737 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18738 though no program is running. The @code{run} and @code{attach}
18739 commands instruct @code{gdbserver} to run or attach to a new program.
18740 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18741 remote exec-file}) to select the program to run. Command line
18742 arguments are supported, except for wildcard expansion and I/O
18743 redirection (@pxref{Arguments}).
18745 @cindex @option{--multi}, @code{gdbserver} option
18746 To start @code{gdbserver} without supplying an initial command to run
18747 or process ID to attach, use the @option{--multi} command line option.
18748 Then you can connect using @kbd{target extended-remote} and start
18749 the program you want to debug.
18751 In multi-process mode @code{gdbserver} does not automatically exit unless you
18752 use the option @option{--once}. You can terminate it by using
18753 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18754 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18755 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18756 @option{--multi} option to @code{gdbserver} has no influence on that.
18758 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18760 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18762 @code{gdbserver} normally terminates after all of its debugged processes have
18763 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18764 extended-remote}, @code{gdbserver} stays running even with no processes left.
18765 @value{GDBN} normally terminates the spawned debugged process on its exit,
18766 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18767 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18768 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18769 stays running even in the @kbd{target remote} mode.
18771 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18772 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18773 completeness, at most one @value{GDBN} can be connected at a time.
18775 @cindex @option{--once}, @code{gdbserver} option
18776 By default, @code{gdbserver} keeps the listening TCP port open, so that
18777 subsequent connections are possible. However, if you start @code{gdbserver}
18778 with the @option{--once} option, it will stop listening for any further
18779 connection attempts after connecting to the first @value{GDBN} session. This
18780 means no further connections to @code{gdbserver} will be possible after the
18781 first one. It also means @code{gdbserver} will terminate after the first
18782 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18783 connections and even in the @kbd{target extended-remote} mode. The
18784 @option{--once} option allows reusing the same port number for connecting to
18785 multiple instances of @code{gdbserver} running on the same host, since each
18786 instance closes its port after the first connection.
18788 @anchor{Other Command-Line Arguments for gdbserver}
18789 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18791 @cindex @option{--debug}, @code{gdbserver} option
18792 The @option{--debug} option tells @code{gdbserver} to display extra
18793 status information about the debugging process.
18794 @cindex @option{--remote-debug}, @code{gdbserver} option
18795 The @option{--remote-debug} option tells @code{gdbserver} to display
18796 remote protocol debug output. These options are intended for
18797 @code{gdbserver} development and for bug reports to the developers.
18799 @cindex @option{--debug-format}, @code{gdbserver} option
18800 The @option{--debug-format=option1[,option2,...]} option tells
18801 @code{gdbserver} to include additional information in each output.
18802 Possible options are:
18806 Turn off all extra information in debugging output.
18808 Turn on all extra information in debugging output.
18810 Include a timestamp in each line of debugging output.
18813 Options are processed in order. Thus, for example, if @option{none}
18814 appears last then no additional information is added to debugging output.
18816 @cindex @option{--wrapper}, @code{gdbserver} option
18817 The @option{--wrapper} option specifies a wrapper to launch programs
18818 for debugging. The option should be followed by the name of the
18819 wrapper, then any command-line arguments to pass to the wrapper, then
18820 @kbd{--} indicating the end of the wrapper arguments.
18822 @code{gdbserver} runs the specified wrapper program with a combined
18823 command line including the wrapper arguments, then the name of the
18824 program to debug, then any arguments to the program. The wrapper
18825 runs until it executes your program, and then @value{GDBN} gains control.
18827 You can use any program that eventually calls @code{execve} with
18828 its arguments as a wrapper. Several standard Unix utilities do
18829 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18830 with @code{exec "$@@"} will also work.
18832 For example, you can use @code{env} to pass an environment variable to
18833 the debugged program, without setting the variable in @code{gdbserver}'s
18837 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18840 @subsection Connecting to @code{gdbserver}
18842 Run @value{GDBN} on the host system.
18844 First make sure you have the necessary symbol files. Load symbols for
18845 your application using the @code{file} command before you connect. Use
18846 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18847 was compiled with the correct sysroot using @code{--with-sysroot}).
18849 The symbol file and target libraries must exactly match the executable
18850 and libraries on the target, with one exception: the files on the host
18851 system should not be stripped, even if the files on the target system
18852 are. Mismatched or missing files will lead to confusing results
18853 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18854 files may also prevent @code{gdbserver} from debugging multi-threaded
18857 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18858 For TCP connections, you must start up @code{gdbserver} prior to using
18859 the @code{target remote} command. Otherwise you may get an error whose
18860 text depends on the host system, but which usually looks something like
18861 @samp{Connection refused}. Don't use the @code{load}
18862 command in @value{GDBN} when using @code{gdbserver}, since the program is
18863 already on the target.
18865 @subsection Monitor Commands for @code{gdbserver}
18866 @cindex monitor commands, for @code{gdbserver}
18867 @anchor{Monitor Commands for gdbserver}
18869 During a @value{GDBN} session using @code{gdbserver}, you can use the
18870 @code{monitor} command to send special requests to @code{gdbserver}.
18871 Here are the available commands.
18875 List the available monitor commands.
18877 @item monitor set debug 0
18878 @itemx monitor set debug 1
18879 Disable or enable general debugging messages.
18881 @item monitor set remote-debug 0
18882 @itemx monitor set remote-debug 1
18883 Disable or enable specific debugging messages associated with the remote
18884 protocol (@pxref{Remote Protocol}).
18886 @item monitor set debug-format option1@r{[},option2,...@r{]}
18887 Specify additional text to add to debugging messages.
18888 Possible options are:
18892 Turn off all extra information in debugging output.
18894 Turn on all extra information in debugging output.
18896 Include a timestamp in each line of debugging output.
18899 Options are processed in order. Thus, for example, if @option{none}
18900 appears last then no additional information is added to debugging output.
18902 @item monitor set libthread-db-search-path [PATH]
18903 @cindex gdbserver, search path for @code{libthread_db}
18904 When this command is issued, @var{path} is a colon-separated list of
18905 directories to search for @code{libthread_db} (@pxref{Threads,,set
18906 libthread-db-search-path}). If you omit @var{path},
18907 @samp{libthread-db-search-path} will be reset to its default value.
18909 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18910 not supported in @code{gdbserver}.
18913 Tell gdbserver to exit immediately. This command should be followed by
18914 @code{disconnect} to close the debugging session. @code{gdbserver} will
18915 detach from any attached processes and kill any processes it created.
18916 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18917 of a multi-process mode debug session.
18921 @subsection Tracepoints support in @code{gdbserver}
18922 @cindex tracepoints support in @code{gdbserver}
18924 On some targets, @code{gdbserver} supports tracepoints, fast
18925 tracepoints and static tracepoints.
18927 For fast or static tracepoints to work, a special library called the
18928 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18929 This library is built and distributed as an integral part of
18930 @code{gdbserver}. In addition, support for static tracepoints
18931 requires building the in-process agent library with static tracepoints
18932 support. At present, the UST (LTTng Userspace Tracer,
18933 @url{http://lttng.org/ust}) tracing engine is supported. This support
18934 is automatically available if UST development headers are found in the
18935 standard include path when @code{gdbserver} is built, or if
18936 @code{gdbserver} was explicitly configured using @option{--with-ust}
18937 to point at such headers. You can explicitly disable the support
18938 using @option{--with-ust=no}.
18940 There are several ways to load the in-process agent in your program:
18943 @item Specifying it as dependency at link time
18945 You can link your program dynamically with the in-process agent
18946 library. On most systems, this is accomplished by adding
18947 @code{-linproctrace} to the link command.
18949 @item Using the system's preloading mechanisms
18951 You can force loading the in-process agent at startup time by using
18952 your system's support for preloading shared libraries. Many Unixes
18953 support the concept of preloading user defined libraries. In most
18954 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18955 in the environment. See also the description of @code{gdbserver}'s
18956 @option{--wrapper} command line option.
18958 @item Using @value{GDBN} to force loading the agent at run time
18960 On some systems, you can force the inferior to load a shared library,
18961 by calling a dynamic loader function in the inferior that takes care
18962 of dynamically looking up and loading a shared library. On most Unix
18963 systems, the function is @code{dlopen}. You'll use the @code{call}
18964 command for that. For example:
18967 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18970 Note that on most Unix systems, for the @code{dlopen} function to be
18971 available, the program needs to be linked with @code{-ldl}.
18974 On systems that have a userspace dynamic loader, like most Unix
18975 systems, when you connect to @code{gdbserver} using @code{target
18976 remote}, you'll find that the program is stopped at the dynamic
18977 loader's entry point, and no shared library has been loaded in the
18978 program's address space yet, including the in-process agent. In that
18979 case, before being able to use any of the fast or static tracepoints
18980 features, you need to let the loader run and load the shared
18981 libraries. The simplest way to do that is to run the program to the
18982 main procedure. E.g., if debugging a C or C@t{++} program, start
18983 @code{gdbserver} like so:
18986 $ gdbserver :9999 myprogram
18989 Start GDB and connect to @code{gdbserver} like so, and run to main:
18993 (@value{GDBP}) target remote myhost:9999
18994 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18995 (@value{GDBP}) b main
18996 (@value{GDBP}) continue
18999 The in-process tracing agent library should now be loaded into the
19000 process; you can confirm it with the @code{info sharedlibrary}
19001 command, which will list @file{libinproctrace.so} as loaded in the
19002 process. You are now ready to install fast tracepoints, list static
19003 tracepoint markers, probe static tracepoints markers, and start
19006 @node Remote Configuration
19007 @section Remote Configuration
19010 @kindex show remote
19011 This section documents the configuration options available when
19012 debugging remote programs. For the options related to the File I/O
19013 extensions of the remote protocol, see @ref{system,
19014 system-call-allowed}.
19017 @item set remoteaddresssize @var{bits}
19018 @cindex address size for remote targets
19019 @cindex bits in remote address
19020 Set the maximum size of address in a memory packet to the specified
19021 number of bits. @value{GDBN} will mask off the address bits above
19022 that number, when it passes addresses to the remote target. The
19023 default value is the number of bits in the target's address.
19025 @item show remoteaddresssize
19026 Show the current value of remote address size in bits.
19028 @item set serial baud @var{n}
19029 @cindex baud rate for remote targets
19030 Set the baud rate for the remote serial I/O to @var{n} baud. The
19031 value is used to set the speed of the serial port used for debugging
19034 @item show serial baud
19035 Show the current speed of the remote connection.
19037 @item set remotebreak
19038 @cindex interrupt remote programs
19039 @cindex BREAK signal instead of Ctrl-C
19040 @anchor{set remotebreak}
19041 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19042 when you type @kbd{Ctrl-c} to interrupt the program running
19043 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19044 character instead. The default is off, since most remote systems
19045 expect to see @samp{Ctrl-C} as the interrupt signal.
19047 @item show remotebreak
19048 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19049 interrupt the remote program.
19051 @item set remoteflow on
19052 @itemx set remoteflow off
19053 @kindex set remoteflow
19054 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19055 on the serial port used to communicate to the remote target.
19057 @item show remoteflow
19058 @kindex show remoteflow
19059 Show the current setting of hardware flow control.
19061 @item set remotelogbase @var{base}
19062 Set the base (a.k.a.@: radix) of logging serial protocol
19063 communications to @var{base}. Supported values of @var{base} are:
19064 @code{ascii}, @code{octal}, and @code{hex}. The default is
19067 @item show remotelogbase
19068 Show the current setting of the radix for logging remote serial
19071 @item set remotelogfile @var{file}
19072 @cindex record serial communications on file
19073 Record remote serial communications on the named @var{file}. The
19074 default is not to record at all.
19076 @item show remotelogfile.
19077 Show the current setting of the file name on which to record the
19078 serial communications.
19080 @item set remotetimeout @var{num}
19081 @cindex timeout for serial communications
19082 @cindex remote timeout
19083 Set the timeout limit to wait for the remote target to respond to
19084 @var{num} seconds. The default is 2 seconds.
19086 @item show remotetimeout
19087 Show the current number of seconds to wait for the remote target
19090 @cindex limit hardware breakpoints and watchpoints
19091 @cindex remote target, limit break- and watchpoints
19092 @anchor{set remote hardware-watchpoint-limit}
19093 @anchor{set remote hardware-breakpoint-limit}
19094 @item set remote hardware-watchpoint-limit @var{limit}
19095 @itemx set remote hardware-breakpoint-limit @var{limit}
19096 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19097 watchpoints. A limit of -1, the default, is treated as unlimited.
19099 @cindex limit hardware watchpoints length
19100 @cindex remote target, limit watchpoints length
19101 @anchor{set remote hardware-watchpoint-length-limit}
19102 @item set remote hardware-watchpoint-length-limit @var{limit}
19103 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19104 a remote hardware watchpoint. A limit of -1, the default, is treated
19107 @item show remote hardware-watchpoint-length-limit
19108 Show the current limit (in bytes) of the maximum length of
19109 a remote hardware watchpoint.
19111 @item set remote exec-file @var{filename}
19112 @itemx show remote exec-file
19113 @anchor{set remote exec-file}
19114 @cindex executable file, for remote target
19115 Select the file used for @code{run} with @code{target
19116 extended-remote}. This should be set to a filename valid on the
19117 target system. If it is not set, the target will use a default
19118 filename (e.g.@: the last program run).
19120 @item set remote interrupt-sequence
19121 @cindex interrupt remote programs
19122 @cindex select Ctrl-C, BREAK or BREAK-g
19123 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19124 @samp{BREAK-g} as the
19125 sequence to the remote target in order to interrupt the execution.
19126 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19127 is high level of serial line for some certain time.
19128 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19129 It is @code{BREAK} signal followed by character @code{g}.
19131 @item show interrupt-sequence
19132 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19133 is sent by @value{GDBN} to interrupt the remote program.
19134 @code{BREAK-g} is BREAK signal followed by @code{g} and
19135 also known as Magic SysRq g.
19137 @item set remote interrupt-on-connect
19138 @cindex send interrupt-sequence on start
19139 Specify whether interrupt-sequence is sent to remote target when
19140 @value{GDBN} connects to it. This is mostly needed when you debug
19141 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19142 which is known as Magic SysRq g in order to connect @value{GDBN}.
19144 @item show interrupt-on-connect
19145 Show whether interrupt-sequence is sent
19146 to remote target when @value{GDBN} connects to it.
19150 @item set tcp auto-retry on
19151 @cindex auto-retry, for remote TCP target
19152 Enable auto-retry for remote TCP connections. This is useful if the remote
19153 debugging agent is launched in parallel with @value{GDBN}; there is a race
19154 condition because the agent may not become ready to accept the connection
19155 before @value{GDBN} attempts to connect. When auto-retry is
19156 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19157 to establish the connection using the timeout specified by
19158 @code{set tcp connect-timeout}.
19160 @item set tcp auto-retry off
19161 Do not auto-retry failed TCP connections.
19163 @item show tcp auto-retry
19164 Show the current auto-retry setting.
19166 @item set tcp connect-timeout @var{seconds}
19167 @itemx set tcp connect-timeout unlimited
19168 @cindex connection timeout, for remote TCP target
19169 @cindex timeout, for remote target connection
19170 Set the timeout for establishing a TCP connection to the remote target to
19171 @var{seconds}. The timeout affects both polling to retry failed connections
19172 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19173 that are merely slow to complete, and represents an approximate cumulative
19174 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19175 @value{GDBN} will keep attempting to establish a connection forever,
19176 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19178 @item show tcp connect-timeout
19179 Show the current connection timeout setting.
19182 @cindex remote packets, enabling and disabling
19183 The @value{GDBN} remote protocol autodetects the packets supported by
19184 your debugging stub. If you need to override the autodetection, you
19185 can use these commands to enable or disable individual packets. Each
19186 packet can be set to @samp{on} (the remote target supports this
19187 packet), @samp{off} (the remote target does not support this packet),
19188 or @samp{auto} (detect remote target support for this packet). They
19189 all default to @samp{auto}. For more information about each packet,
19190 see @ref{Remote Protocol}.
19192 During normal use, you should not have to use any of these commands.
19193 If you do, that may be a bug in your remote debugging stub, or a bug
19194 in @value{GDBN}. You may want to report the problem to the
19195 @value{GDBN} developers.
19197 For each packet @var{name}, the command to enable or disable the
19198 packet is @code{set remote @var{name}-packet}. The available settings
19201 @multitable @columnfractions 0.28 0.32 0.25
19204 @tab Related Features
19206 @item @code{fetch-register}
19208 @tab @code{info registers}
19210 @item @code{set-register}
19214 @item @code{binary-download}
19216 @tab @code{load}, @code{set}
19218 @item @code{read-aux-vector}
19219 @tab @code{qXfer:auxv:read}
19220 @tab @code{info auxv}
19222 @item @code{symbol-lookup}
19223 @tab @code{qSymbol}
19224 @tab Detecting multiple threads
19226 @item @code{attach}
19227 @tab @code{vAttach}
19230 @item @code{verbose-resume}
19232 @tab Stepping or resuming multiple threads
19238 @item @code{software-breakpoint}
19242 @item @code{hardware-breakpoint}
19246 @item @code{write-watchpoint}
19250 @item @code{read-watchpoint}
19254 @item @code{access-watchpoint}
19258 @item @code{target-features}
19259 @tab @code{qXfer:features:read}
19260 @tab @code{set architecture}
19262 @item @code{library-info}
19263 @tab @code{qXfer:libraries:read}
19264 @tab @code{info sharedlibrary}
19266 @item @code{memory-map}
19267 @tab @code{qXfer:memory-map:read}
19268 @tab @code{info mem}
19270 @item @code{read-sdata-object}
19271 @tab @code{qXfer:sdata:read}
19272 @tab @code{print $_sdata}
19274 @item @code{read-spu-object}
19275 @tab @code{qXfer:spu:read}
19276 @tab @code{info spu}
19278 @item @code{write-spu-object}
19279 @tab @code{qXfer:spu:write}
19280 @tab @code{info spu}
19282 @item @code{read-siginfo-object}
19283 @tab @code{qXfer:siginfo:read}
19284 @tab @code{print $_siginfo}
19286 @item @code{write-siginfo-object}
19287 @tab @code{qXfer:siginfo:write}
19288 @tab @code{set $_siginfo}
19290 @item @code{threads}
19291 @tab @code{qXfer:threads:read}
19292 @tab @code{info threads}
19294 @item @code{get-thread-local-@*storage-address}
19295 @tab @code{qGetTLSAddr}
19296 @tab Displaying @code{__thread} variables
19298 @item @code{get-thread-information-block-address}
19299 @tab @code{qGetTIBAddr}
19300 @tab Display MS-Windows Thread Information Block.
19302 @item @code{search-memory}
19303 @tab @code{qSearch:memory}
19306 @item @code{supported-packets}
19307 @tab @code{qSupported}
19308 @tab Remote communications parameters
19310 @item @code{pass-signals}
19311 @tab @code{QPassSignals}
19312 @tab @code{handle @var{signal}}
19314 @item @code{program-signals}
19315 @tab @code{QProgramSignals}
19316 @tab @code{handle @var{signal}}
19318 @item @code{hostio-close-packet}
19319 @tab @code{vFile:close}
19320 @tab @code{remote get}, @code{remote put}
19322 @item @code{hostio-open-packet}
19323 @tab @code{vFile:open}
19324 @tab @code{remote get}, @code{remote put}
19326 @item @code{hostio-pread-packet}
19327 @tab @code{vFile:pread}
19328 @tab @code{remote get}, @code{remote put}
19330 @item @code{hostio-pwrite-packet}
19331 @tab @code{vFile:pwrite}
19332 @tab @code{remote get}, @code{remote put}
19334 @item @code{hostio-unlink-packet}
19335 @tab @code{vFile:unlink}
19336 @tab @code{remote delete}
19338 @item @code{hostio-readlink-packet}
19339 @tab @code{vFile:readlink}
19342 @item @code{noack-packet}
19343 @tab @code{QStartNoAckMode}
19344 @tab Packet acknowledgment
19346 @item @code{osdata}
19347 @tab @code{qXfer:osdata:read}
19348 @tab @code{info os}
19350 @item @code{query-attached}
19351 @tab @code{qAttached}
19352 @tab Querying remote process attach state.
19354 @item @code{trace-buffer-size}
19355 @tab @code{QTBuffer:size}
19356 @tab @code{set trace-buffer-size}
19358 @item @code{trace-status}
19359 @tab @code{qTStatus}
19360 @tab @code{tstatus}
19362 @item @code{traceframe-info}
19363 @tab @code{qXfer:traceframe-info:read}
19364 @tab Traceframe info
19366 @item @code{install-in-trace}
19367 @tab @code{InstallInTrace}
19368 @tab Install tracepoint in tracing
19370 @item @code{disable-randomization}
19371 @tab @code{QDisableRandomization}
19372 @tab @code{set disable-randomization}
19374 @item @code{conditional-breakpoints-packet}
19375 @tab @code{Z0 and Z1}
19376 @tab @code{Support for target-side breakpoint condition evaluation}
19380 @section Implementing a Remote Stub
19382 @cindex debugging stub, example
19383 @cindex remote stub, example
19384 @cindex stub example, remote debugging
19385 The stub files provided with @value{GDBN} implement the target side of the
19386 communication protocol, and the @value{GDBN} side is implemented in the
19387 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19388 these subroutines to communicate, and ignore the details. (If you're
19389 implementing your own stub file, you can still ignore the details: start
19390 with one of the existing stub files. @file{sparc-stub.c} is the best
19391 organized, and therefore the easiest to read.)
19393 @cindex remote serial debugging, overview
19394 To debug a program running on another machine (the debugging
19395 @dfn{target} machine), you must first arrange for all the usual
19396 prerequisites for the program to run by itself. For example, for a C
19401 A startup routine to set up the C runtime environment; these usually
19402 have a name like @file{crt0}. The startup routine may be supplied by
19403 your hardware supplier, or you may have to write your own.
19406 A C subroutine library to support your program's
19407 subroutine calls, notably managing input and output.
19410 A way of getting your program to the other machine---for example, a
19411 download program. These are often supplied by the hardware
19412 manufacturer, but you may have to write your own from hardware
19416 The next step is to arrange for your program to use a serial port to
19417 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19418 machine). In general terms, the scheme looks like this:
19422 @value{GDBN} already understands how to use this protocol; when everything
19423 else is set up, you can simply use the @samp{target remote} command
19424 (@pxref{Targets,,Specifying a Debugging Target}).
19426 @item On the target,
19427 you must link with your program a few special-purpose subroutines that
19428 implement the @value{GDBN} remote serial protocol. The file containing these
19429 subroutines is called a @dfn{debugging stub}.
19431 On certain remote targets, you can use an auxiliary program
19432 @code{gdbserver} instead of linking a stub into your program.
19433 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19436 The debugging stub is specific to the architecture of the remote
19437 machine; for example, use @file{sparc-stub.c} to debug programs on
19440 @cindex remote serial stub list
19441 These working remote stubs are distributed with @value{GDBN}:
19446 @cindex @file{i386-stub.c}
19449 For Intel 386 and compatible architectures.
19452 @cindex @file{m68k-stub.c}
19453 @cindex Motorola 680x0
19455 For Motorola 680x0 architectures.
19458 @cindex @file{sh-stub.c}
19461 For Renesas SH architectures.
19464 @cindex @file{sparc-stub.c}
19466 For @sc{sparc} architectures.
19468 @item sparcl-stub.c
19469 @cindex @file{sparcl-stub.c}
19472 For Fujitsu @sc{sparclite} architectures.
19476 The @file{README} file in the @value{GDBN} distribution may list other
19477 recently added stubs.
19480 * Stub Contents:: What the stub can do for you
19481 * Bootstrapping:: What you must do for the stub
19482 * Debug Session:: Putting it all together
19485 @node Stub Contents
19486 @subsection What the Stub Can Do for You
19488 @cindex remote serial stub
19489 The debugging stub for your architecture supplies these three
19493 @item set_debug_traps
19494 @findex set_debug_traps
19495 @cindex remote serial stub, initialization
19496 This routine arranges for @code{handle_exception} to run when your
19497 program stops. You must call this subroutine explicitly in your
19498 program's startup code.
19500 @item handle_exception
19501 @findex handle_exception
19502 @cindex remote serial stub, main routine
19503 This is the central workhorse, but your program never calls it
19504 explicitly---the setup code arranges for @code{handle_exception} to
19505 run when a trap is triggered.
19507 @code{handle_exception} takes control when your program stops during
19508 execution (for example, on a breakpoint), and mediates communications
19509 with @value{GDBN} on the host machine. This is where the communications
19510 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19511 representative on the target machine. It begins by sending summary
19512 information on the state of your program, then continues to execute,
19513 retrieving and transmitting any information @value{GDBN} needs, until you
19514 execute a @value{GDBN} command that makes your program resume; at that point,
19515 @code{handle_exception} returns control to your own code on the target
19519 @cindex @code{breakpoint} subroutine, remote
19520 Use this auxiliary subroutine to make your program contain a
19521 breakpoint. Depending on the particular situation, this may be the only
19522 way for @value{GDBN} to get control. For instance, if your target
19523 machine has some sort of interrupt button, you won't need to call this;
19524 pressing the interrupt button transfers control to
19525 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19526 simply receiving characters on the serial port may also trigger a trap;
19527 again, in that situation, you don't need to call @code{breakpoint} from
19528 your own program---simply running @samp{target remote} from the host
19529 @value{GDBN} session gets control.
19531 Call @code{breakpoint} if none of these is true, or if you simply want
19532 to make certain your program stops at a predetermined point for the
19533 start of your debugging session.
19536 @node Bootstrapping
19537 @subsection What You Must Do for the Stub
19539 @cindex remote stub, support routines
19540 The debugging stubs that come with @value{GDBN} are set up for a particular
19541 chip architecture, but they have no information about the rest of your
19542 debugging target machine.
19544 First of all you need to tell the stub how to communicate with the
19548 @item int getDebugChar()
19549 @findex getDebugChar
19550 Write this subroutine to read a single character from the serial port.
19551 It may be identical to @code{getchar} for your target system; a
19552 different name is used to allow you to distinguish the two if you wish.
19554 @item void putDebugChar(int)
19555 @findex putDebugChar
19556 Write this subroutine to write a single character to the serial port.
19557 It may be identical to @code{putchar} for your target system; a
19558 different name is used to allow you to distinguish the two if you wish.
19561 @cindex control C, and remote debugging
19562 @cindex interrupting remote targets
19563 If you want @value{GDBN} to be able to stop your program while it is
19564 running, you need to use an interrupt-driven serial driver, and arrange
19565 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19566 character). That is the character which @value{GDBN} uses to tell the
19567 remote system to stop.
19569 Getting the debugging target to return the proper status to @value{GDBN}
19570 probably requires changes to the standard stub; one quick and dirty way
19571 is to just execute a breakpoint instruction (the ``dirty'' part is that
19572 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19574 Other routines you need to supply are:
19577 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19578 @findex exceptionHandler
19579 Write this function to install @var{exception_address} in the exception
19580 handling tables. You need to do this because the stub does not have any
19581 way of knowing what the exception handling tables on your target system
19582 are like (for example, the processor's table might be in @sc{rom},
19583 containing entries which point to a table in @sc{ram}).
19584 The @var{exception_number} specifies the exception which should be changed;
19585 its meaning is architecture-dependent (for example, different numbers
19586 might represent divide by zero, misaligned access, etc). When this
19587 exception occurs, control should be transferred directly to
19588 @var{exception_address}, and the processor state (stack, registers,
19589 and so on) should be just as it is when a processor exception occurs. So if
19590 you want to use a jump instruction to reach @var{exception_address}, it
19591 should be a simple jump, not a jump to subroutine.
19593 For the 386, @var{exception_address} should be installed as an interrupt
19594 gate so that interrupts are masked while the handler runs. The gate
19595 should be at privilege level 0 (the most privileged level). The
19596 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19597 help from @code{exceptionHandler}.
19599 @item void flush_i_cache()
19600 @findex flush_i_cache
19601 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19602 instruction cache, if any, on your target machine. If there is no
19603 instruction cache, this subroutine may be a no-op.
19605 On target machines that have instruction caches, @value{GDBN} requires this
19606 function to make certain that the state of your program is stable.
19610 You must also make sure this library routine is available:
19613 @item void *memset(void *, int, int)
19615 This is the standard library function @code{memset} that sets an area of
19616 memory to a known value. If you have one of the free versions of
19617 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19618 either obtain it from your hardware manufacturer, or write your own.
19621 If you do not use the GNU C compiler, you may need other standard
19622 library subroutines as well; this varies from one stub to another,
19623 but in general the stubs are likely to use any of the common library
19624 subroutines which @code{@value{NGCC}} generates as inline code.
19627 @node Debug Session
19628 @subsection Putting it All Together
19630 @cindex remote serial debugging summary
19631 In summary, when your program is ready to debug, you must follow these
19636 Make sure you have defined the supporting low-level routines
19637 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19639 @code{getDebugChar}, @code{putDebugChar},
19640 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19644 Insert these lines in your program's startup code, before the main
19645 procedure is called:
19652 On some machines, when a breakpoint trap is raised, the hardware
19653 automatically makes the PC point to the instruction after the
19654 breakpoint. If your machine doesn't do that, you may need to adjust
19655 @code{handle_exception} to arrange for it to return to the instruction
19656 after the breakpoint on this first invocation, so that your program
19657 doesn't keep hitting the initial breakpoint instead of making
19661 For the 680x0 stub only, you need to provide a variable called
19662 @code{exceptionHook}. Normally you just use:
19665 void (*exceptionHook)() = 0;
19669 but if before calling @code{set_debug_traps}, you set it to point to a
19670 function in your program, that function is called when
19671 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19672 error). The function indicated by @code{exceptionHook} is called with
19673 one parameter: an @code{int} which is the exception number.
19676 Compile and link together: your program, the @value{GDBN} debugging stub for
19677 your target architecture, and the supporting subroutines.
19680 Make sure you have a serial connection between your target machine and
19681 the @value{GDBN} host, and identify the serial port on the host.
19684 @c The "remote" target now provides a `load' command, so we should
19685 @c document that. FIXME.
19686 Download your program to your target machine (or get it there by
19687 whatever means the manufacturer provides), and start it.
19690 Start @value{GDBN} on the host, and connect to the target
19691 (@pxref{Connecting,,Connecting to a Remote Target}).
19695 @node Configurations
19696 @chapter Configuration-Specific Information
19698 While nearly all @value{GDBN} commands are available for all native and
19699 cross versions of the debugger, there are some exceptions. This chapter
19700 describes things that are only available in certain configurations.
19702 There are three major categories of configurations: native
19703 configurations, where the host and target are the same, embedded
19704 operating system configurations, which are usually the same for several
19705 different processor architectures, and bare embedded processors, which
19706 are quite different from each other.
19711 * Embedded Processors::
19718 This section describes details specific to particular native
19723 * BSD libkvm Interface:: Debugging BSD kernel memory images
19724 * SVR4 Process Information:: SVR4 process information
19725 * DJGPP Native:: Features specific to the DJGPP port
19726 * Cygwin Native:: Features specific to the Cygwin port
19727 * Hurd Native:: Features specific to @sc{gnu} Hurd
19728 * Darwin:: Features specific to Darwin
19734 On HP-UX systems, if you refer to a function or variable name that
19735 begins with a dollar sign, @value{GDBN} searches for a user or system
19736 name first, before it searches for a convenience variable.
19739 @node BSD libkvm Interface
19740 @subsection BSD libkvm Interface
19743 @cindex kernel memory image
19744 @cindex kernel crash dump
19746 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19747 interface that provides a uniform interface for accessing kernel virtual
19748 memory images, including live systems and crash dumps. @value{GDBN}
19749 uses this interface to allow you to debug live kernels and kernel crash
19750 dumps on many native BSD configurations. This is implemented as a
19751 special @code{kvm} debugging target. For debugging a live system, load
19752 the currently running kernel into @value{GDBN} and connect to the
19756 (@value{GDBP}) @b{target kvm}
19759 For debugging crash dumps, provide the file name of the crash dump as an
19763 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19766 Once connected to the @code{kvm} target, the following commands are
19772 Set current context from the @dfn{Process Control Block} (PCB) address.
19775 Set current context from proc address. This command isn't available on
19776 modern FreeBSD systems.
19779 @node SVR4 Process Information
19780 @subsection SVR4 Process Information
19782 @cindex examine process image
19783 @cindex process info via @file{/proc}
19785 Many versions of SVR4 and compatible systems provide a facility called
19786 @samp{/proc} that can be used to examine the image of a running
19787 process using file-system subroutines.
19789 If @value{GDBN} is configured for an operating system with this
19790 facility, the command @code{info proc} is available to report
19791 information about the process running your program, or about any
19792 process running on your system. This includes, as of this writing,
19793 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
19795 This command may also work on core files that were created on a system
19796 that has the @samp{/proc} facility.
19802 @itemx info proc @var{process-id}
19803 Summarize available information about any running process. If a
19804 process ID is specified by @var{process-id}, display information about
19805 that process; otherwise display information about the program being
19806 debugged. The summary includes the debugged process ID, the command
19807 line used to invoke it, its current working directory, and its
19808 executable file's absolute file name.
19810 On some systems, @var{process-id} can be of the form
19811 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19812 within a process. If the optional @var{pid} part is missing, it means
19813 a thread from the process being debugged (the leading @samp{/} still
19814 needs to be present, or else @value{GDBN} will interpret the number as
19815 a process ID rather than a thread ID).
19817 @item info proc cmdline
19818 @cindex info proc cmdline
19819 Show the original command line of the process. This command is
19820 specific to @sc{gnu}/Linux.
19822 @item info proc cwd
19823 @cindex info proc cwd
19824 Show the current working directory of the process. This command is
19825 specific to @sc{gnu}/Linux.
19827 @item info proc exe
19828 @cindex info proc exe
19829 Show the name of executable of the process. This command is specific
19832 @item info proc mappings
19833 @cindex memory address space mappings
19834 Report the memory address space ranges accessible in the program, with
19835 information on whether the process has read, write, or execute access
19836 rights to each range. On @sc{gnu}/Linux systems, each memory range
19837 includes the object file which is mapped to that range, instead of the
19838 memory access rights to that range.
19840 @item info proc stat
19841 @itemx info proc status
19842 @cindex process detailed status information
19843 These subcommands are specific to @sc{gnu}/Linux systems. They show
19844 the process-related information, including the user ID and group ID;
19845 how many threads are there in the process; its virtual memory usage;
19846 the signals that are pending, blocked, and ignored; its TTY; its
19847 consumption of system and user time; its stack size; its @samp{nice}
19848 value; etc. For more information, see the @samp{proc} man page
19849 (type @kbd{man 5 proc} from your shell prompt).
19851 @item info proc all
19852 Show all the information about the process described under all of the
19853 above @code{info proc} subcommands.
19856 @comment These sub-options of 'info proc' were not included when
19857 @comment procfs.c was re-written. Keep their descriptions around
19858 @comment against the day when someone finds the time to put them back in.
19859 @kindex info proc times
19860 @item info proc times
19861 Starting time, user CPU time, and system CPU time for your program and
19864 @kindex info proc id
19866 Report on the process IDs related to your program: its own process ID,
19867 the ID of its parent, the process group ID, and the session ID.
19870 @item set procfs-trace
19871 @kindex set procfs-trace
19872 @cindex @code{procfs} API calls
19873 This command enables and disables tracing of @code{procfs} API calls.
19875 @item show procfs-trace
19876 @kindex show procfs-trace
19877 Show the current state of @code{procfs} API call tracing.
19879 @item set procfs-file @var{file}
19880 @kindex set procfs-file
19881 Tell @value{GDBN} to write @code{procfs} API trace to the named
19882 @var{file}. @value{GDBN} appends the trace info to the previous
19883 contents of the file. The default is to display the trace on the
19886 @item show procfs-file
19887 @kindex show procfs-file
19888 Show the file to which @code{procfs} API trace is written.
19890 @item proc-trace-entry
19891 @itemx proc-trace-exit
19892 @itemx proc-untrace-entry
19893 @itemx proc-untrace-exit
19894 @kindex proc-trace-entry
19895 @kindex proc-trace-exit
19896 @kindex proc-untrace-entry
19897 @kindex proc-untrace-exit
19898 These commands enable and disable tracing of entries into and exits
19899 from the @code{syscall} interface.
19902 @kindex info pidlist
19903 @cindex process list, QNX Neutrino
19904 For QNX Neutrino only, this command displays the list of all the
19905 processes and all the threads within each process.
19908 @kindex info meminfo
19909 @cindex mapinfo list, QNX Neutrino
19910 For QNX Neutrino only, this command displays the list of all mapinfos.
19914 @subsection Features for Debugging @sc{djgpp} Programs
19915 @cindex @sc{djgpp} debugging
19916 @cindex native @sc{djgpp} debugging
19917 @cindex MS-DOS-specific commands
19920 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19921 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19922 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19923 top of real-mode DOS systems and their emulations.
19925 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19926 defines a few commands specific to the @sc{djgpp} port. This
19927 subsection describes those commands.
19932 This is a prefix of @sc{djgpp}-specific commands which print
19933 information about the target system and important OS structures.
19936 @cindex MS-DOS system info
19937 @cindex free memory information (MS-DOS)
19938 @item info dos sysinfo
19939 This command displays assorted information about the underlying
19940 platform: the CPU type and features, the OS version and flavor, the
19941 DPMI version, and the available conventional and DPMI memory.
19946 @cindex segment descriptor tables
19947 @cindex descriptor tables display
19949 @itemx info dos ldt
19950 @itemx info dos idt
19951 These 3 commands display entries from, respectively, Global, Local,
19952 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19953 tables are data structures which store a descriptor for each segment
19954 that is currently in use. The segment's selector is an index into a
19955 descriptor table; the table entry for that index holds the
19956 descriptor's base address and limit, and its attributes and access
19959 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19960 segment (used for both data and the stack), and a DOS segment (which
19961 allows access to DOS/BIOS data structures and absolute addresses in
19962 conventional memory). However, the DPMI host will usually define
19963 additional segments in order to support the DPMI environment.
19965 @cindex garbled pointers
19966 These commands allow to display entries from the descriptor tables.
19967 Without an argument, all entries from the specified table are
19968 displayed. An argument, which should be an integer expression, means
19969 display a single entry whose index is given by the argument. For
19970 example, here's a convenient way to display information about the
19971 debugged program's data segment:
19974 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19975 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19979 This comes in handy when you want to see whether a pointer is outside
19980 the data segment's limit (i.e.@: @dfn{garbled}).
19982 @cindex page tables display (MS-DOS)
19984 @itemx info dos pte
19985 These two commands display entries from, respectively, the Page
19986 Directory and the Page Tables. Page Directories and Page Tables are
19987 data structures which control how virtual memory addresses are mapped
19988 into physical addresses. A Page Table includes an entry for every
19989 page of memory that is mapped into the program's address space; there
19990 may be several Page Tables, each one holding up to 4096 entries. A
19991 Page Directory has up to 4096 entries, one each for every Page Table
19992 that is currently in use.
19994 Without an argument, @kbd{info dos pde} displays the entire Page
19995 Directory, and @kbd{info dos pte} displays all the entries in all of
19996 the Page Tables. An argument, an integer expression, given to the
19997 @kbd{info dos pde} command means display only that entry from the Page
19998 Directory table. An argument given to the @kbd{info dos pte} command
19999 means display entries from a single Page Table, the one pointed to by
20000 the specified entry in the Page Directory.
20002 @cindex direct memory access (DMA) on MS-DOS
20003 These commands are useful when your program uses @dfn{DMA} (Direct
20004 Memory Access), which needs physical addresses to program the DMA
20007 These commands are supported only with some DPMI servers.
20009 @cindex physical address from linear address
20010 @item info dos address-pte @var{addr}
20011 This command displays the Page Table entry for a specified linear
20012 address. The argument @var{addr} is a linear address which should
20013 already have the appropriate segment's base address added to it,
20014 because this command accepts addresses which may belong to @emph{any}
20015 segment. For example, here's how to display the Page Table entry for
20016 the page where a variable @code{i} is stored:
20019 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20020 @exdent @code{Page Table entry for address 0x11a00d30:}
20021 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20025 This says that @code{i} is stored at offset @code{0xd30} from the page
20026 whose physical base address is @code{0x02698000}, and shows all the
20027 attributes of that page.
20029 Note that you must cast the addresses of variables to a @code{char *},
20030 since otherwise the value of @code{__djgpp_base_address}, the base
20031 address of all variables and functions in a @sc{djgpp} program, will
20032 be added using the rules of C pointer arithmetics: if @code{i} is
20033 declared an @code{int}, @value{GDBN} will add 4 times the value of
20034 @code{__djgpp_base_address} to the address of @code{i}.
20036 Here's another example, it displays the Page Table entry for the
20040 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20041 @exdent @code{Page Table entry for address 0x29110:}
20042 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20046 (The @code{+ 3} offset is because the transfer buffer's address is the
20047 3rd member of the @code{_go32_info_block} structure.) The output
20048 clearly shows that this DPMI server maps the addresses in conventional
20049 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20050 linear (@code{0x29110}) addresses are identical.
20052 This command is supported only with some DPMI servers.
20055 @cindex DOS serial data link, remote debugging
20056 In addition to native debugging, the DJGPP port supports remote
20057 debugging via a serial data link. The following commands are specific
20058 to remote serial debugging in the DJGPP port of @value{GDBN}.
20061 @kindex set com1base
20062 @kindex set com1irq
20063 @kindex set com2base
20064 @kindex set com2irq
20065 @kindex set com3base
20066 @kindex set com3irq
20067 @kindex set com4base
20068 @kindex set com4irq
20069 @item set com1base @var{addr}
20070 This command sets the base I/O port address of the @file{COM1} serial
20073 @item set com1irq @var{irq}
20074 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20075 for the @file{COM1} serial port.
20077 There are similar commands @samp{set com2base}, @samp{set com3irq},
20078 etc.@: for setting the port address and the @code{IRQ} lines for the
20081 @kindex show com1base
20082 @kindex show com1irq
20083 @kindex show com2base
20084 @kindex show com2irq
20085 @kindex show com3base
20086 @kindex show com3irq
20087 @kindex show com4base
20088 @kindex show com4irq
20089 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20090 display the current settings of the base address and the @code{IRQ}
20091 lines used by the COM ports.
20094 @kindex info serial
20095 @cindex DOS serial port status
20096 This command prints the status of the 4 DOS serial ports. For each
20097 port, it prints whether it's active or not, its I/O base address and
20098 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20099 counts of various errors encountered so far.
20103 @node Cygwin Native
20104 @subsection Features for Debugging MS Windows PE Executables
20105 @cindex MS Windows debugging
20106 @cindex native Cygwin debugging
20107 @cindex Cygwin-specific commands
20109 @value{GDBN} supports native debugging of MS Windows programs, including
20110 DLLs with and without symbolic debugging information.
20112 @cindex Ctrl-BREAK, MS-Windows
20113 @cindex interrupt debuggee on MS-Windows
20114 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20115 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20116 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20117 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20118 sequence, which can be used to interrupt the debuggee even if it
20121 There are various additional Cygwin-specific commands, described in
20122 this section. Working with DLLs that have no debugging symbols is
20123 described in @ref{Non-debug DLL Symbols}.
20128 This is a prefix of MS Windows-specific commands which print
20129 information about the target system and important OS structures.
20131 @item info w32 selector
20132 This command displays information returned by
20133 the Win32 API @code{GetThreadSelectorEntry} function.
20134 It takes an optional argument that is evaluated to
20135 a long value to give the information about this given selector.
20136 Without argument, this command displays information
20137 about the six segment registers.
20139 @item info w32 thread-information-block
20140 This command displays thread specific information stored in the
20141 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20142 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20146 This is a Cygwin-specific alias of @code{info shared}.
20148 @kindex dll-symbols
20150 This command is deprecated and will be removed in future versions
20151 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
20153 This command loads symbols from a dll similarly to
20154 add-sym command but without the need to specify a base address.
20156 @kindex set cygwin-exceptions
20157 @cindex debugging the Cygwin DLL
20158 @cindex Cygwin DLL, debugging
20159 @item set cygwin-exceptions @var{mode}
20160 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20161 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20162 @value{GDBN} will delay recognition of exceptions, and may ignore some
20163 exceptions which seem to be caused by internal Cygwin DLL
20164 ``bookkeeping''. This option is meant primarily for debugging the
20165 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20166 @value{GDBN} users with false @code{SIGSEGV} signals.
20168 @kindex show cygwin-exceptions
20169 @item show cygwin-exceptions
20170 Displays whether @value{GDBN} will break on exceptions that happen
20171 inside the Cygwin DLL itself.
20173 @kindex set new-console
20174 @item set new-console @var{mode}
20175 If @var{mode} is @code{on} the debuggee will
20176 be started in a new console on next start.
20177 If @var{mode} is @code{off}, the debuggee will
20178 be started in the same console as the debugger.
20180 @kindex show new-console
20181 @item show new-console
20182 Displays whether a new console is used
20183 when the debuggee is started.
20185 @kindex set new-group
20186 @item set new-group @var{mode}
20187 This boolean value controls whether the debuggee should
20188 start a new group or stay in the same group as the debugger.
20189 This affects the way the Windows OS handles
20192 @kindex show new-group
20193 @item show new-group
20194 Displays current value of new-group boolean.
20196 @kindex set debugevents
20197 @item set debugevents
20198 This boolean value adds debug output concerning kernel events related
20199 to the debuggee seen by the debugger. This includes events that
20200 signal thread and process creation and exit, DLL loading and
20201 unloading, console interrupts, and debugging messages produced by the
20202 Windows @code{OutputDebugString} API call.
20204 @kindex set debugexec
20205 @item set debugexec
20206 This boolean value adds debug output concerning execute events
20207 (such as resume thread) seen by the debugger.
20209 @kindex set debugexceptions
20210 @item set debugexceptions
20211 This boolean value adds debug output concerning exceptions in the
20212 debuggee seen by the debugger.
20214 @kindex set debugmemory
20215 @item set debugmemory
20216 This boolean value adds debug output concerning debuggee memory reads
20217 and writes by the debugger.
20221 This boolean values specifies whether the debuggee is called
20222 via a shell or directly (default value is on).
20226 Displays if the debuggee will be started with a shell.
20231 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20234 @node Non-debug DLL Symbols
20235 @subsubsection Support for DLLs without Debugging Symbols
20236 @cindex DLLs with no debugging symbols
20237 @cindex Minimal symbols and DLLs
20239 Very often on windows, some of the DLLs that your program relies on do
20240 not include symbolic debugging information (for example,
20241 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20242 symbols in a DLL, it relies on the minimal amount of symbolic
20243 information contained in the DLL's export table. This section
20244 describes working with such symbols, known internally to @value{GDBN} as
20245 ``minimal symbols''.
20247 Note that before the debugged program has started execution, no DLLs
20248 will have been loaded. The easiest way around this problem is simply to
20249 start the program --- either by setting a breakpoint or letting the
20250 program run once to completion.
20252 @subsubsection DLL Name Prefixes
20254 In keeping with the naming conventions used by the Microsoft debugging
20255 tools, DLL export symbols are made available with a prefix based on the
20256 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20257 also entered into the symbol table, so @code{CreateFileA} is often
20258 sufficient. In some cases there will be name clashes within a program
20259 (particularly if the executable itself includes full debugging symbols)
20260 necessitating the use of the fully qualified name when referring to the
20261 contents of the DLL. Use single-quotes around the name to avoid the
20262 exclamation mark (``!'') being interpreted as a language operator.
20264 Note that the internal name of the DLL may be all upper-case, even
20265 though the file name of the DLL is lower-case, or vice-versa. Since
20266 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20267 some confusion. If in doubt, try the @code{info functions} and
20268 @code{info variables} commands or even @code{maint print msymbols}
20269 (@pxref{Symbols}). Here's an example:
20272 (@value{GDBP}) info function CreateFileA
20273 All functions matching regular expression "CreateFileA":
20275 Non-debugging symbols:
20276 0x77e885f4 CreateFileA
20277 0x77e885f4 KERNEL32!CreateFileA
20281 (@value{GDBP}) info function !
20282 All functions matching regular expression "!":
20284 Non-debugging symbols:
20285 0x6100114c cygwin1!__assert
20286 0x61004034 cygwin1!_dll_crt0@@0
20287 0x61004240 cygwin1!dll_crt0(per_process *)
20291 @subsubsection Working with Minimal Symbols
20293 Symbols extracted from a DLL's export table do not contain very much
20294 type information. All that @value{GDBN} can do is guess whether a symbol
20295 refers to a function or variable depending on the linker section that
20296 contains the symbol. Also note that the actual contents of the memory
20297 contained in a DLL are not available unless the program is running. This
20298 means that you cannot examine the contents of a variable or disassemble
20299 a function within a DLL without a running program.
20301 Variables are generally treated as pointers and dereferenced
20302 automatically. For this reason, it is often necessary to prefix a
20303 variable name with the address-of operator (``&'') and provide explicit
20304 type information in the command. Here's an example of the type of
20308 (@value{GDBP}) print 'cygwin1!__argv'
20313 (@value{GDBP}) x 'cygwin1!__argv'
20314 0x10021610: "\230y\""
20317 And two possible solutions:
20320 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20321 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20325 (@value{GDBP}) x/2x &'cygwin1!__argv'
20326 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20327 (@value{GDBP}) x/x 0x10021608
20328 0x10021608: 0x0022fd98
20329 (@value{GDBP}) x/s 0x0022fd98
20330 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20333 Setting a break point within a DLL is possible even before the program
20334 starts execution. However, under these circumstances, @value{GDBN} can't
20335 examine the initial instructions of the function in order to skip the
20336 function's frame set-up code. You can work around this by using ``*&''
20337 to set the breakpoint at a raw memory address:
20340 (@value{GDBP}) break *&'python22!PyOS_Readline'
20341 Breakpoint 1 at 0x1e04eff0
20344 The author of these extensions is not entirely convinced that setting a
20345 break point within a shared DLL like @file{kernel32.dll} is completely
20349 @subsection Commands Specific to @sc{gnu} Hurd Systems
20350 @cindex @sc{gnu} Hurd debugging
20352 This subsection describes @value{GDBN} commands specific to the
20353 @sc{gnu} Hurd native debugging.
20358 @kindex set signals@r{, Hurd command}
20359 @kindex set sigs@r{, Hurd command}
20360 This command toggles the state of inferior signal interception by
20361 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20362 affected by this command. @code{sigs} is a shorthand alias for
20367 @kindex show signals@r{, Hurd command}
20368 @kindex show sigs@r{, Hurd command}
20369 Show the current state of intercepting inferior's signals.
20371 @item set signal-thread
20372 @itemx set sigthread
20373 @kindex set signal-thread
20374 @kindex set sigthread
20375 This command tells @value{GDBN} which thread is the @code{libc} signal
20376 thread. That thread is run when a signal is delivered to a running
20377 process. @code{set sigthread} is the shorthand alias of @code{set
20380 @item show signal-thread
20381 @itemx show sigthread
20382 @kindex show signal-thread
20383 @kindex show sigthread
20384 These two commands show which thread will run when the inferior is
20385 delivered a signal.
20388 @kindex set stopped@r{, Hurd command}
20389 This commands tells @value{GDBN} that the inferior process is stopped,
20390 as with the @code{SIGSTOP} signal. The stopped process can be
20391 continued by delivering a signal to it.
20394 @kindex show stopped@r{, Hurd command}
20395 This command shows whether @value{GDBN} thinks the debuggee is
20398 @item set exceptions
20399 @kindex set exceptions@r{, Hurd command}
20400 Use this command to turn off trapping of exceptions in the inferior.
20401 When exception trapping is off, neither breakpoints nor
20402 single-stepping will work. To restore the default, set exception
20405 @item show exceptions
20406 @kindex show exceptions@r{, Hurd command}
20407 Show the current state of trapping exceptions in the inferior.
20409 @item set task pause
20410 @kindex set task@r{, Hurd commands}
20411 @cindex task attributes (@sc{gnu} Hurd)
20412 @cindex pause current task (@sc{gnu} Hurd)
20413 This command toggles task suspension when @value{GDBN} has control.
20414 Setting it to on takes effect immediately, and the task is suspended
20415 whenever @value{GDBN} gets control. Setting it to off will take
20416 effect the next time the inferior is continued. If this option is set
20417 to off, you can use @code{set thread default pause on} or @code{set
20418 thread pause on} (see below) to pause individual threads.
20420 @item show task pause
20421 @kindex show task@r{, Hurd commands}
20422 Show the current state of task suspension.
20424 @item set task detach-suspend-count
20425 @cindex task suspend count
20426 @cindex detach from task, @sc{gnu} Hurd
20427 This command sets the suspend count the task will be left with when
20428 @value{GDBN} detaches from it.
20430 @item show task detach-suspend-count
20431 Show the suspend count the task will be left with when detaching.
20433 @item set task exception-port
20434 @itemx set task excp
20435 @cindex task exception port, @sc{gnu} Hurd
20436 This command sets the task exception port to which @value{GDBN} will
20437 forward exceptions. The argument should be the value of the @dfn{send
20438 rights} of the task. @code{set task excp} is a shorthand alias.
20440 @item set noninvasive
20441 @cindex noninvasive task options
20442 This command switches @value{GDBN} to a mode that is the least
20443 invasive as far as interfering with the inferior is concerned. This
20444 is the same as using @code{set task pause}, @code{set exceptions}, and
20445 @code{set signals} to values opposite to the defaults.
20447 @item info send-rights
20448 @itemx info receive-rights
20449 @itemx info port-rights
20450 @itemx info port-sets
20451 @itemx info dead-names
20454 @cindex send rights, @sc{gnu} Hurd
20455 @cindex receive rights, @sc{gnu} Hurd
20456 @cindex port rights, @sc{gnu} Hurd
20457 @cindex port sets, @sc{gnu} Hurd
20458 @cindex dead names, @sc{gnu} Hurd
20459 These commands display information about, respectively, send rights,
20460 receive rights, port rights, port sets, and dead names of a task.
20461 There are also shorthand aliases: @code{info ports} for @code{info
20462 port-rights} and @code{info psets} for @code{info port-sets}.
20464 @item set thread pause
20465 @kindex set thread@r{, Hurd command}
20466 @cindex thread properties, @sc{gnu} Hurd
20467 @cindex pause current thread (@sc{gnu} Hurd)
20468 This command toggles current thread suspension when @value{GDBN} has
20469 control. Setting it to on takes effect immediately, and the current
20470 thread is suspended whenever @value{GDBN} gets control. Setting it to
20471 off will take effect the next time the inferior is continued.
20472 Normally, this command has no effect, since when @value{GDBN} has
20473 control, the whole task is suspended. However, if you used @code{set
20474 task pause off} (see above), this command comes in handy to suspend
20475 only the current thread.
20477 @item show thread pause
20478 @kindex show thread@r{, Hurd command}
20479 This command shows the state of current thread suspension.
20481 @item set thread run
20482 This command sets whether the current thread is allowed to run.
20484 @item show thread run
20485 Show whether the current thread is allowed to run.
20487 @item set thread detach-suspend-count
20488 @cindex thread suspend count, @sc{gnu} Hurd
20489 @cindex detach from thread, @sc{gnu} Hurd
20490 This command sets the suspend count @value{GDBN} will leave on a
20491 thread when detaching. This number is relative to the suspend count
20492 found by @value{GDBN} when it notices the thread; use @code{set thread
20493 takeover-suspend-count} to force it to an absolute value.
20495 @item show thread detach-suspend-count
20496 Show the suspend count @value{GDBN} will leave on the thread when
20499 @item set thread exception-port
20500 @itemx set thread excp
20501 Set the thread exception port to which to forward exceptions. This
20502 overrides the port set by @code{set task exception-port} (see above).
20503 @code{set thread excp} is the shorthand alias.
20505 @item set thread takeover-suspend-count
20506 Normally, @value{GDBN}'s thread suspend counts are relative to the
20507 value @value{GDBN} finds when it notices each thread. This command
20508 changes the suspend counts to be absolute instead.
20510 @item set thread default
20511 @itemx show thread default
20512 @cindex thread default settings, @sc{gnu} Hurd
20513 Each of the above @code{set thread} commands has a @code{set thread
20514 default} counterpart (e.g., @code{set thread default pause}, @code{set
20515 thread default exception-port}, etc.). The @code{thread default}
20516 variety of commands sets the default thread properties for all
20517 threads; you can then change the properties of individual threads with
20518 the non-default commands.
20525 @value{GDBN} provides the following commands specific to the Darwin target:
20528 @item set debug darwin @var{num}
20529 @kindex set debug darwin
20530 When set to a non zero value, enables debugging messages specific to
20531 the Darwin support. Higher values produce more verbose output.
20533 @item show debug darwin
20534 @kindex show debug darwin
20535 Show the current state of Darwin messages.
20537 @item set debug mach-o @var{num}
20538 @kindex set debug mach-o
20539 When set to a non zero value, enables debugging messages while
20540 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20541 file format used on Darwin for object and executable files.) Higher
20542 values produce more verbose output. This is a command to diagnose
20543 problems internal to @value{GDBN} and should not be needed in normal
20546 @item show debug mach-o
20547 @kindex show debug mach-o
20548 Show the current state of Mach-O file messages.
20550 @item set mach-exceptions on
20551 @itemx set mach-exceptions off
20552 @kindex set mach-exceptions
20553 On Darwin, faults are first reported as a Mach exception and are then
20554 mapped to a Posix signal. Use this command to turn on trapping of
20555 Mach exceptions in the inferior. This might be sometimes useful to
20556 better understand the cause of a fault. The default is off.
20558 @item show mach-exceptions
20559 @kindex show mach-exceptions
20560 Show the current state of exceptions trapping.
20565 @section Embedded Operating Systems
20567 This section describes configurations involving the debugging of
20568 embedded operating systems that are available for several different
20571 @value{GDBN} includes the ability to debug programs running on
20572 various real-time operating systems.
20574 @node Embedded Processors
20575 @section Embedded Processors
20577 This section goes into details specific to particular embedded
20580 @cindex send command to simulator
20581 Whenever a specific embedded processor has a simulator, @value{GDBN}
20582 allows to send an arbitrary command to the simulator.
20585 @item sim @var{command}
20586 @kindex sim@r{, a command}
20587 Send an arbitrary @var{command} string to the simulator. Consult the
20588 documentation for the specific simulator in use for information about
20589 acceptable commands.
20595 * M32R/D:: Renesas M32R/D
20596 * M68K:: Motorola M68K
20597 * MicroBlaze:: Xilinx MicroBlaze
20598 * MIPS Embedded:: MIPS Embedded
20599 * PowerPC Embedded:: PowerPC Embedded
20600 * PA:: HP PA Embedded
20601 * Sparclet:: Tsqware Sparclet
20602 * Sparclite:: Fujitsu Sparclite
20603 * Z8000:: Zilog Z8000
20606 * Super-H:: Renesas Super-H
20615 @item target rdi @var{dev}
20616 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20617 use this target to communicate with both boards running the Angel
20618 monitor, or with the EmbeddedICE JTAG debug device.
20621 @item target rdp @var{dev}
20626 @value{GDBN} provides the following ARM-specific commands:
20629 @item set arm disassembler
20631 This commands selects from a list of disassembly styles. The
20632 @code{"std"} style is the standard style.
20634 @item show arm disassembler
20636 Show the current disassembly style.
20638 @item set arm apcs32
20639 @cindex ARM 32-bit mode
20640 This command toggles ARM operation mode between 32-bit and 26-bit.
20642 @item show arm apcs32
20643 Display the current usage of the ARM 32-bit mode.
20645 @item set arm fpu @var{fputype}
20646 This command sets the ARM floating-point unit (FPU) type. The
20647 argument @var{fputype} can be one of these:
20651 Determine the FPU type by querying the OS ABI.
20653 Software FPU, with mixed-endian doubles on little-endian ARM
20656 GCC-compiled FPA co-processor.
20658 Software FPU with pure-endian doubles.
20664 Show the current type of the FPU.
20667 This command forces @value{GDBN} to use the specified ABI.
20670 Show the currently used ABI.
20672 @item set arm fallback-mode (arm|thumb|auto)
20673 @value{GDBN} uses the symbol table, when available, to determine
20674 whether instructions are ARM or Thumb. This command controls
20675 @value{GDBN}'s default behavior when the symbol table is not
20676 available. The default is @samp{auto}, which causes @value{GDBN} to
20677 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20680 @item show arm fallback-mode
20681 Show the current fallback instruction mode.
20683 @item set arm force-mode (arm|thumb|auto)
20684 This command overrides use of the symbol table to determine whether
20685 instructions are ARM or Thumb. The default is @samp{auto}, which
20686 causes @value{GDBN} to use the symbol table and then the setting
20687 of @samp{set arm fallback-mode}.
20689 @item show arm force-mode
20690 Show the current forced instruction mode.
20692 @item set debug arm
20693 Toggle whether to display ARM-specific debugging messages from the ARM
20694 target support subsystem.
20696 @item show debug arm
20697 Show whether ARM-specific debugging messages are enabled.
20700 The following commands are available when an ARM target is debugged
20701 using the RDI interface:
20704 @item rdilogfile @r{[}@var{file}@r{]}
20706 @cindex ADP (Angel Debugger Protocol) logging
20707 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20708 With an argument, sets the log file to the specified @var{file}. With
20709 no argument, show the current log file name. The default log file is
20712 @item rdilogenable @r{[}@var{arg}@r{]}
20713 @kindex rdilogenable
20714 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20715 enables logging, with an argument 0 or @code{"no"} disables it. With
20716 no arguments displays the current setting. When logging is enabled,
20717 ADP packets exchanged between @value{GDBN} and the RDI target device
20718 are logged to a file.
20720 @item set rdiromatzero
20721 @kindex set rdiromatzero
20722 @cindex ROM at zero address, RDI
20723 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20724 vector catching is disabled, so that zero address can be used. If off
20725 (the default), vector catching is enabled. For this command to take
20726 effect, it needs to be invoked prior to the @code{target rdi} command.
20728 @item show rdiromatzero
20729 @kindex show rdiromatzero
20730 Show the current setting of ROM at zero address.
20732 @item set rdiheartbeat
20733 @kindex set rdiheartbeat
20734 @cindex RDI heartbeat
20735 Enable or disable RDI heartbeat packets. It is not recommended to
20736 turn on this option, since it confuses ARM and EPI JTAG interface, as
20737 well as the Angel monitor.
20739 @item show rdiheartbeat
20740 @kindex show rdiheartbeat
20741 Show the setting of RDI heartbeat packets.
20745 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20746 The @value{GDBN} ARM simulator accepts the following optional arguments.
20749 @item --swi-support=@var{type}
20750 Tell the simulator which SWI interfaces to support. The argument
20751 @var{type} may be a comma separated list of the following values.
20752 The default value is @code{all}.
20765 @subsection Renesas M32R/D and M32R/SDI
20768 @kindex target m32r
20769 @item target m32r @var{dev}
20770 Renesas M32R/D ROM monitor.
20772 @kindex target m32rsdi
20773 @item target m32rsdi @var{dev}
20774 Renesas M32R SDI server, connected via parallel port to the board.
20777 The following @value{GDBN} commands are specific to the M32R monitor:
20780 @item set download-path @var{path}
20781 @kindex set download-path
20782 @cindex find downloadable @sc{srec} files (M32R)
20783 Set the default path for finding downloadable @sc{srec} files.
20785 @item show download-path
20786 @kindex show download-path
20787 Show the default path for downloadable @sc{srec} files.
20789 @item set board-address @var{addr}
20790 @kindex set board-address
20791 @cindex M32-EVA target board address
20792 Set the IP address for the M32R-EVA target board.
20794 @item show board-address
20795 @kindex show board-address
20796 Show the current IP address of the target board.
20798 @item set server-address @var{addr}
20799 @kindex set server-address
20800 @cindex download server address (M32R)
20801 Set the IP address for the download server, which is the @value{GDBN}'s
20804 @item show server-address
20805 @kindex show server-address
20806 Display the IP address of the download server.
20808 @item upload @r{[}@var{file}@r{]}
20809 @kindex upload@r{, M32R}
20810 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20811 upload capability. If no @var{file} argument is given, the current
20812 executable file is uploaded.
20814 @item tload @r{[}@var{file}@r{]}
20815 @kindex tload@r{, M32R}
20816 Test the @code{upload} command.
20819 The following commands are available for M32R/SDI:
20824 @cindex reset SDI connection, M32R
20825 This command resets the SDI connection.
20829 This command shows the SDI connection status.
20832 @kindex debug_chaos
20833 @cindex M32R/Chaos debugging
20834 Instructs the remote that M32R/Chaos debugging is to be used.
20836 @item use_debug_dma
20837 @kindex use_debug_dma
20838 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20841 @kindex use_mon_code
20842 Instructs the remote to use the MON_CODE method of accessing memory.
20845 @kindex use_ib_break
20846 Instructs the remote to set breakpoints by IB break.
20848 @item use_dbt_break
20849 @kindex use_dbt_break
20850 Instructs the remote to set breakpoints by DBT.
20856 The Motorola m68k configuration includes ColdFire support, and a
20857 target command for the following ROM monitor.
20861 @kindex target dbug
20862 @item target dbug @var{dev}
20863 dBUG ROM monitor for Motorola ColdFire.
20868 @subsection MicroBlaze
20869 @cindex Xilinx MicroBlaze
20870 @cindex XMD, Xilinx Microprocessor Debugger
20872 The MicroBlaze is a soft-core processor supported on various Xilinx
20873 FPGAs, such as Spartan or Virtex series. Boards with these processors
20874 usually have JTAG ports which connect to a host system running the Xilinx
20875 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20876 This host system is used to download the configuration bitstream to
20877 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20878 communicates with the target board using the JTAG interface and
20879 presents a @code{gdbserver} interface to the board. By default
20880 @code{xmd} uses port @code{1234}. (While it is possible to change
20881 this default port, it requires the use of undocumented @code{xmd}
20882 commands. Contact Xilinx support if you need to do this.)
20884 Use these GDB commands to connect to the MicroBlaze target processor.
20887 @item target remote :1234
20888 Use this command to connect to the target if you are running @value{GDBN}
20889 on the same system as @code{xmd}.
20891 @item target remote @var{xmd-host}:1234
20892 Use this command to connect to the target if it is connected to @code{xmd}
20893 running on a different system named @var{xmd-host}.
20896 Use this command to download a program to the MicroBlaze target.
20898 @item set debug microblaze @var{n}
20899 Enable MicroBlaze-specific debugging messages if non-zero.
20901 @item show debug microblaze @var{n}
20902 Show MicroBlaze-specific debugging level.
20905 @node MIPS Embedded
20906 @subsection @acronym{MIPS} Embedded
20908 @cindex @acronym{MIPS} boards
20909 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20910 @acronym{MIPS} board attached to a serial line. This is available when
20911 you configure @value{GDBN} with @samp{--target=mips-elf}.
20914 Use these @value{GDBN} commands to specify the connection to your target board:
20917 @item target mips @var{port}
20918 @kindex target mips @var{port}
20919 To run a program on the board, start up @code{@value{GDBP}} with the
20920 name of your program as the argument. To connect to the board, use the
20921 command @samp{target mips @var{port}}, where @var{port} is the name of
20922 the serial port connected to the board. If the program has not already
20923 been downloaded to the board, you may use the @code{load} command to
20924 download it. You can then use all the usual @value{GDBN} commands.
20926 For example, this sequence connects to the target board through a serial
20927 port, and loads and runs a program called @var{prog} through the
20931 host$ @value{GDBP} @var{prog}
20932 @value{GDBN} is free software and @dots{}
20933 (@value{GDBP}) target mips /dev/ttyb
20934 (@value{GDBP}) load @var{prog}
20938 @item target mips @var{hostname}:@var{portnumber}
20939 On some @value{GDBN} host configurations, you can specify a TCP
20940 connection (for instance, to a serial line managed by a terminal
20941 concentrator) instead of a serial port, using the syntax
20942 @samp{@var{hostname}:@var{portnumber}}.
20944 @item target pmon @var{port}
20945 @kindex target pmon @var{port}
20948 @item target ddb @var{port}
20949 @kindex target ddb @var{port}
20950 NEC's DDB variant of PMON for Vr4300.
20952 @item target lsi @var{port}
20953 @kindex target lsi @var{port}
20954 LSI variant of PMON.
20956 @kindex target r3900
20957 @item target r3900 @var{dev}
20958 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20960 @kindex target array
20961 @item target array @var{dev}
20962 Array Tech LSI33K RAID controller board.
20968 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20971 @item set mipsfpu double
20972 @itemx set mipsfpu single
20973 @itemx set mipsfpu none
20974 @itemx set mipsfpu auto
20975 @itemx show mipsfpu
20976 @kindex set mipsfpu
20977 @kindex show mipsfpu
20978 @cindex @acronym{MIPS} remote floating point
20979 @cindex floating point, @acronym{MIPS} remote
20980 If your target board does not support the @acronym{MIPS} floating point
20981 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20982 need this, you may wish to put the command in your @value{GDBN} init
20983 file). This tells @value{GDBN} how to find the return value of
20984 functions which return floating point values. It also allows
20985 @value{GDBN} to avoid saving the floating point registers when calling
20986 functions on the board. If you are using a floating point coprocessor
20987 with only single precision floating point support, as on the @sc{r4650}
20988 processor, use the command @samp{set mipsfpu single}. The default
20989 double precision floating point coprocessor may be selected using
20990 @samp{set mipsfpu double}.
20992 In previous versions the only choices were double precision or no
20993 floating point, so @samp{set mipsfpu on} will select double precision
20994 and @samp{set mipsfpu off} will select no floating point.
20996 As usual, you can inquire about the @code{mipsfpu} variable with
20997 @samp{show mipsfpu}.
20999 @item set timeout @var{seconds}
21000 @itemx set retransmit-timeout @var{seconds}
21001 @itemx show timeout
21002 @itemx show retransmit-timeout
21003 @cindex @code{timeout}, @acronym{MIPS} protocol
21004 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21005 @kindex set timeout
21006 @kindex show timeout
21007 @kindex set retransmit-timeout
21008 @kindex show retransmit-timeout
21009 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21010 remote protocol, with the @code{set timeout @var{seconds}} command. The
21011 default is 5 seconds. Similarly, you can control the timeout used while
21012 waiting for an acknowledgment of a packet with the @code{set
21013 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21014 You can inspect both values with @code{show timeout} and @code{show
21015 retransmit-timeout}. (These commands are @emph{only} available when
21016 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21018 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21019 is waiting for your program to stop. In that case, @value{GDBN} waits
21020 forever because it has no way of knowing how long the program is going
21021 to run before stopping.
21023 @item set syn-garbage-limit @var{num}
21024 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21025 @cindex synchronize with remote @acronym{MIPS} target
21026 Limit the maximum number of characters @value{GDBN} should ignore when
21027 it tries to synchronize with the remote target. The default is 10
21028 characters. Setting the limit to -1 means there's no limit.
21030 @item show syn-garbage-limit
21031 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21032 Show the current limit on the number of characters to ignore when
21033 trying to synchronize with the remote system.
21035 @item set monitor-prompt @var{prompt}
21036 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21037 @cindex remote monitor prompt
21038 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21039 remote monitor. The default depends on the target:
21049 @item show monitor-prompt
21050 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21051 Show the current strings @value{GDBN} expects as the prompt from the
21054 @item set monitor-warnings
21055 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21056 Enable or disable monitor warnings about hardware breakpoints. This
21057 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21058 display warning messages whose codes are returned by the @code{lsi}
21059 PMON monitor for breakpoint commands.
21061 @item show monitor-warnings
21062 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21063 Show the current setting of printing monitor warnings.
21065 @item pmon @var{command}
21066 @kindex pmon@r{, @acronym{MIPS} remote}
21067 @cindex send PMON command
21068 This command allows sending an arbitrary @var{command} string to the
21069 monitor. The monitor must be in debug mode for this to work.
21072 @node PowerPC Embedded
21073 @subsection PowerPC Embedded
21075 @cindex DVC register
21076 @value{GDBN} supports using the DVC (Data Value Compare) register to
21077 implement in hardware simple hardware watchpoint conditions of the form:
21080 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21081 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21084 The DVC register will be automatically used when @value{GDBN} detects
21085 such pattern in a condition expression, and the created watchpoint uses one
21086 debug register (either the @code{exact-watchpoints} option is on and the
21087 variable is scalar, or the variable has a length of one byte). This feature
21088 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21091 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21092 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21093 in which case watchpoints using only one debug register are created when
21094 watching variables of scalar types.
21096 You can create an artificial array to watch an arbitrary memory
21097 region using one of the following commands (@pxref{Expressions}):
21100 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21101 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21104 PowerPC embedded processors support masked watchpoints. See the discussion
21105 about the @code{mask} argument in @ref{Set Watchpoints}.
21107 @cindex ranged breakpoint
21108 PowerPC embedded processors support hardware accelerated
21109 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21110 the inferior whenever it executes an instruction at any address within
21111 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21112 use the @code{break-range} command.
21114 @value{GDBN} provides the following PowerPC-specific commands:
21117 @kindex break-range
21118 @item break-range @var{start-location}, @var{end-location}
21119 Set a breakpoint for an address range given by
21120 @var{start-location} and @var{end-location}, which can specify a function name,
21121 a line number, an offset of lines from the current line or from the start
21122 location, or an address of an instruction (see @ref{Specify Location},
21123 for a list of all the possible ways to specify a @var{location}.)
21124 The breakpoint will stop execution of the inferior whenever it
21125 executes an instruction at any address within the specified range,
21126 (including @var{start-location} and @var{end-location}.)
21128 @kindex set powerpc
21129 @item set powerpc soft-float
21130 @itemx show powerpc soft-float
21131 Force @value{GDBN} to use (or not use) a software floating point calling
21132 convention. By default, @value{GDBN} selects the calling convention based
21133 on the selected architecture and the provided executable file.
21135 @item set powerpc vector-abi
21136 @itemx show powerpc vector-abi
21137 Force @value{GDBN} to use the specified calling convention for vector
21138 arguments and return values. The valid options are @samp{auto};
21139 @samp{generic}, to avoid vector registers even if they are present;
21140 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21141 registers. By default, @value{GDBN} selects the calling convention
21142 based on the selected architecture and the provided executable file.
21144 @item set powerpc exact-watchpoints
21145 @itemx show powerpc exact-watchpoints
21146 Allow @value{GDBN} to use only one debug register when watching a variable
21147 of scalar type, thus assuming that the variable is accessed through the
21148 address of its first byte.
21150 @kindex target dink32
21151 @item target dink32 @var{dev}
21152 DINK32 ROM monitor.
21154 @kindex target ppcbug
21155 @item target ppcbug @var{dev}
21156 @kindex target ppcbug1
21157 @item target ppcbug1 @var{dev}
21158 PPCBUG ROM monitor for PowerPC.
21161 @item target sds @var{dev}
21162 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21165 @cindex SDS protocol
21166 The following commands specific to the SDS protocol are supported
21170 @item set sdstimeout @var{nsec}
21171 @kindex set sdstimeout
21172 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21173 default is 2 seconds.
21175 @item show sdstimeout
21176 @kindex show sdstimeout
21177 Show the current value of the SDS timeout.
21179 @item sds @var{command}
21180 @kindex sds@r{, a command}
21181 Send the specified @var{command} string to the SDS monitor.
21186 @subsection HP PA Embedded
21190 @kindex target op50n
21191 @item target op50n @var{dev}
21192 OP50N monitor, running on an OKI HPPA board.
21194 @kindex target w89k
21195 @item target w89k @var{dev}
21196 W89K monitor, running on a Winbond HPPA board.
21201 @subsection Tsqware Sparclet
21205 @value{GDBN} enables developers to debug tasks running on
21206 Sparclet targets from a Unix host.
21207 @value{GDBN} uses code that runs on
21208 both the Unix host and on the Sparclet target. The program
21209 @code{@value{GDBP}} is installed and executed on the Unix host.
21212 @item remotetimeout @var{args}
21213 @kindex remotetimeout
21214 @value{GDBN} supports the option @code{remotetimeout}.
21215 This option is set by the user, and @var{args} represents the number of
21216 seconds @value{GDBN} waits for responses.
21219 @cindex compiling, on Sparclet
21220 When compiling for debugging, include the options @samp{-g} to get debug
21221 information and @samp{-Ttext} to relocate the program to where you wish to
21222 load it on the target. You may also want to add the options @samp{-n} or
21223 @samp{-N} in order to reduce the size of the sections. Example:
21226 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21229 You can use @code{objdump} to verify that the addresses are what you intended:
21232 sparclet-aout-objdump --headers --syms prog
21235 @cindex running, on Sparclet
21237 your Unix execution search path to find @value{GDBN}, you are ready to
21238 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21239 (or @code{sparclet-aout-gdb}, depending on your installation).
21241 @value{GDBN} comes up showing the prompt:
21248 * Sparclet File:: Setting the file to debug
21249 * Sparclet Connection:: Connecting to Sparclet
21250 * Sparclet Download:: Sparclet download
21251 * Sparclet Execution:: Running and debugging
21254 @node Sparclet File
21255 @subsubsection Setting File to Debug
21257 The @value{GDBN} command @code{file} lets you choose with program to debug.
21260 (gdbslet) file prog
21264 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21265 @value{GDBN} locates
21266 the file by searching the directories listed in the command search
21268 If the file was compiled with debug information (option @samp{-g}), source
21269 files will be searched as well.
21270 @value{GDBN} locates
21271 the source files by searching the directories listed in the directory search
21272 path (@pxref{Environment, ,Your Program's Environment}).
21274 to find a file, it displays a message such as:
21277 prog: No such file or directory.
21280 When this happens, add the appropriate directories to the search paths with
21281 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21282 @code{target} command again.
21284 @node Sparclet Connection
21285 @subsubsection Connecting to Sparclet
21287 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21288 To connect to a target on serial port ``@code{ttya}'', type:
21291 (gdbslet) target sparclet /dev/ttya
21292 Remote target sparclet connected to /dev/ttya
21293 main () at ../prog.c:3
21297 @value{GDBN} displays messages like these:
21303 @node Sparclet Download
21304 @subsubsection Sparclet Download
21306 @cindex download to Sparclet
21307 Once connected to the Sparclet target,
21308 you can use the @value{GDBN}
21309 @code{load} command to download the file from the host to the target.
21310 The file name and load offset should be given as arguments to the @code{load}
21312 Since the file format is aout, the program must be loaded to the starting
21313 address. You can use @code{objdump} to find out what this value is. The load
21314 offset is an offset which is added to the VMA (virtual memory address)
21315 of each of the file's sections.
21316 For instance, if the program
21317 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21318 and bss at 0x12010170, in @value{GDBN}, type:
21321 (gdbslet) load prog 0x12010000
21322 Loading section .text, size 0xdb0 vma 0x12010000
21325 If the code is loaded at a different address then what the program was linked
21326 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21327 to tell @value{GDBN} where to map the symbol table.
21329 @node Sparclet Execution
21330 @subsubsection Running and Debugging
21332 @cindex running and debugging Sparclet programs
21333 You can now begin debugging the task using @value{GDBN}'s execution control
21334 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21335 manual for the list of commands.
21339 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21341 Starting program: prog
21342 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21343 3 char *symarg = 0;
21345 4 char *execarg = "hello!";
21350 @subsection Fujitsu Sparclite
21354 @kindex target sparclite
21355 @item target sparclite @var{dev}
21356 Fujitsu sparclite boards, used only for the purpose of loading.
21357 You must use an additional command to debug the program.
21358 For example: target remote @var{dev} using @value{GDBN} standard
21364 @subsection Zilog Z8000
21367 @cindex simulator, Z8000
21368 @cindex Zilog Z8000 simulator
21370 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21373 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21374 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21375 segmented variant). The simulator recognizes which architecture is
21376 appropriate by inspecting the object code.
21379 @item target sim @var{args}
21381 @kindex target sim@r{, with Z8000}
21382 Debug programs on a simulated CPU. If the simulator supports setup
21383 options, specify them via @var{args}.
21387 After specifying this target, you can debug programs for the simulated
21388 CPU in the same style as programs for your host computer; use the
21389 @code{file} command to load a new program image, the @code{run} command
21390 to run your program, and so on.
21392 As well as making available all the usual machine registers
21393 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21394 additional items of information as specially named registers:
21399 Counts clock-ticks in the simulator.
21402 Counts instructions run in the simulator.
21405 Execution time in 60ths of a second.
21409 You can refer to these values in @value{GDBN} expressions with the usual
21410 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21411 conditional breakpoint that suspends only after at least 5000
21412 simulated clock ticks.
21415 @subsection Atmel AVR
21418 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21419 following AVR-specific commands:
21422 @item info io_registers
21423 @kindex info io_registers@r{, AVR}
21424 @cindex I/O registers (Atmel AVR)
21425 This command displays information about the AVR I/O registers. For
21426 each register, @value{GDBN} prints its number and value.
21433 When configured for debugging CRIS, @value{GDBN} provides the
21434 following CRIS-specific commands:
21437 @item set cris-version @var{ver}
21438 @cindex CRIS version
21439 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21440 The CRIS version affects register names and sizes. This command is useful in
21441 case autodetection of the CRIS version fails.
21443 @item show cris-version
21444 Show the current CRIS version.
21446 @item set cris-dwarf2-cfi
21447 @cindex DWARF-2 CFI and CRIS
21448 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21449 Change to @samp{off} when using @code{gcc-cris} whose version is below
21452 @item show cris-dwarf2-cfi
21453 Show the current state of using DWARF-2 CFI.
21455 @item set cris-mode @var{mode}
21457 Set the current CRIS mode to @var{mode}. It should only be changed when
21458 debugging in guru mode, in which case it should be set to
21459 @samp{guru} (the default is @samp{normal}).
21461 @item show cris-mode
21462 Show the current CRIS mode.
21466 @subsection Renesas Super-H
21469 For the Renesas Super-H processor, @value{GDBN} provides these
21473 @item set sh calling-convention @var{convention}
21474 @kindex set sh calling-convention
21475 Set the calling-convention used when calling functions from @value{GDBN}.
21476 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21477 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21478 convention. If the DWARF-2 information of the called function specifies
21479 that the function follows the Renesas calling convention, the function
21480 is called using the Renesas calling convention. If the calling convention
21481 is set to @samp{renesas}, the Renesas calling convention is always used,
21482 regardless of the DWARF-2 information. This can be used to override the
21483 default of @samp{gcc} if debug information is missing, or the compiler
21484 does not emit the DWARF-2 calling convention entry for a function.
21486 @item show sh calling-convention
21487 @kindex show sh calling-convention
21488 Show the current calling convention setting.
21493 @node Architectures
21494 @section Architectures
21496 This section describes characteristics of architectures that affect
21497 all uses of @value{GDBN} with the architecture, both native and cross.
21504 * HPPA:: HP PA architecture
21505 * SPU:: Cell Broadband Engine SPU architecture
21511 @subsection AArch64
21512 @cindex AArch64 support
21514 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21515 following special commands:
21518 @item set debug aarch64
21519 @kindex set debug aarch64
21520 This command determines whether AArch64 architecture-specific debugging
21521 messages are to be displayed.
21523 @item show debug aarch64
21524 Show whether AArch64 debugging messages are displayed.
21529 @subsection x86 Architecture-specific Issues
21532 @item set struct-convention @var{mode}
21533 @kindex set struct-convention
21534 @cindex struct return convention
21535 @cindex struct/union returned in registers
21536 Set the convention used by the inferior to return @code{struct}s and
21537 @code{union}s from functions to @var{mode}. Possible values of
21538 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21539 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21540 are returned on the stack, while @code{"reg"} means that a
21541 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21542 be returned in a register.
21544 @item show struct-convention
21545 @kindex show struct-convention
21546 Show the current setting of the convention to return @code{struct}s
21550 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21551 @cindex Intel(R) Memory Protection Extensions (MPX).
21553 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21554 @footnote{The register named with capital letters represent the architecture
21555 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21556 which are the lower bound and upper bound. Bounds are effective addresses or
21557 memory locations. The upper bounds are architecturally represented in 1's
21558 complement form. A bound having lower bound = 0, and upper bound = 0
21559 (1's complement of all bits set) will allow access to the entire address space.
21561 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21562 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21563 display the upper bound performing the complement of one operation on the
21564 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21565 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21566 can also be noted that the upper bounds are inclusive.
21568 As an example, assume that the register BND0 holds bounds for a pointer having
21569 access allowed for the range between 0x32 and 0x71. The values present on
21570 bnd0raw and bnd registers are presented as follows:
21573 bnd0raw = @{0x32, 0xffffffff8e@}
21574 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21577 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21578 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21579 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21580 Python, the display includes the memory size, in bits, accessible to
21586 See the following section.
21589 @subsection @acronym{MIPS}
21591 @cindex stack on Alpha
21592 @cindex stack on @acronym{MIPS}
21593 @cindex Alpha stack
21594 @cindex @acronym{MIPS} stack
21595 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21596 sometimes requires @value{GDBN} to search backward in the object code to
21597 find the beginning of a function.
21599 @cindex response time, @acronym{MIPS} debugging
21600 To improve response time (especially for embedded applications, where
21601 @value{GDBN} may be restricted to a slow serial line for this search)
21602 you may want to limit the size of this search, using one of these
21606 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21607 @item set heuristic-fence-post @var{limit}
21608 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21609 search for the beginning of a function. A value of @var{0} (the
21610 default) means there is no limit. However, except for @var{0}, the
21611 larger the limit the more bytes @code{heuristic-fence-post} must search
21612 and therefore the longer it takes to run. You should only need to use
21613 this command when debugging a stripped executable.
21615 @item show heuristic-fence-post
21616 Display the current limit.
21620 These commands are available @emph{only} when @value{GDBN} is configured
21621 for debugging programs on Alpha or @acronym{MIPS} processors.
21623 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21627 @item set mips abi @var{arg}
21628 @kindex set mips abi
21629 @cindex set ABI for @acronym{MIPS}
21630 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21631 values of @var{arg} are:
21635 The default ABI associated with the current binary (this is the
21645 @item show mips abi
21646 @kindex show mips abi
21647 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21649 @item set mips compression @var{arg}
21650 @kindex set mips compression
21651 @cindex code compression, @acronym{MIPS}
21652 Tell @value{GDBN} which @acronym{MIPS} compressed
21653 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21654 inferior. @value{GDBN} uses this for code disassembly and other
21655 internal interpretation purposes. This setting is only referred to
21656 when no executable has been associated with the debugging session or
21657 the executable does not provide information about the encoding it uses.
21658 Otherwise this setting is automatically updated from information
21659 provided by the executable.
21661 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21662 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21663 executables containing @acronym{MIPS16} code frequently are not
21664 identified as such.
21666 This setting is ``sticky''; that is, it retains its value across
21667 debugging sessions until reset either explicitly with this command or
21668 implicitly from an executable.
21670 The compiler and/or assembler typically add symbol table annotations to
21671 identify functions compiled for the @acronym{MIPS16} or
21672 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21673 are present, @value{GDBN} uses them in preference to the global
21674 compressed @acronym{ISA} encoding setting.
21676 @item show mips compression
21677 @kindex show mips compression
21678 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21679 @value{GDBN} to debug the inferior.
21682 @itemx show mipsfpu
21683 @xref{MIPS Embedded, set mipsfpu}.
21685 @item set mips mask-address @var{arg}
21686 @kindex set mips mask-address
21687 @cindex @acronym{MIPS} addresses, masking
21688 This command determines whether the most-significant 32 bits of 64-bit
21689 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21690 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21691 setting, which lets @value{GDBN} determine the correct value.
21693 @item show mips mask-address
21694 @kindex show mips mask-address
21695 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21698 @item set remote-mips64-transfers-32bit-regs
21699 @kindex set remote-mips64-transfers-32bit-regs
21700 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21701 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21702 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21703 and 64 bits for other registers, set this option to @samp{on}.
21705 @item show remote-mips64-transfers-32bit-regs
21706 @kindex show remote-mips64-transfers-32bit-regs
21707 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21709 @item set debug mips
21710 @kindex set debug mips
21711 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21712 target code in @value{GDBN}.
21714 @item show debug mips
21715 @kindex show debug mips
21716 Show the current setting of @acronym{MIPS} debugging messages.
21722 @cindex HPPA support
21724 When @value{GDBN} is debugging the HP PA architecture, it provides the
21725 following special commands:
21728 @item set debug hppa
21729 @kindex set debug hppa
21730 This command determines whether HPPA architecture-specific debugging
21731 messages are to be displayed.
21733 @item show debug hppa
21734 Show whether HPPA debugging messages are displayed.
21736 @item maint print unwind @var{address}
21737 @kindex maint print unwind@r{, HPPA}
21738 This command displays the contents of the unwind table entry at the
21739 given @var{address}.
21745 @subsection Cell Broadband Engine SPU architecture
21746 @cindex Cell Broadband Engine
21749 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21750 it provides the following special commands:
21753 @item info spu event
21755 Display SPU event facility status. Shows current event mask
21756 and pending event status.
21758 @item info spu signal
21759 Display SPU signal notification facility status. Shows pending
21760 signal-control word and signal notification mode of both signal
21761 notification channels.
21763 @item info spu mailbox
21764 Display SPU mailbox facility status. Shows all pending entries,
21765 in order of processing, in each of the SPU Write Outbound,
21766 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21769 Display MFC DMA status. Shows all pending commands in the MFC
21770 DMA queue. For each entry, opcode, tag, class IDs, effective
21771 and local store addresses and transfer size are shown.
21773 @item info spu proxydma
21774 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21775 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21776 and local store addresses and transfer size are shown.
21780 When @value{GDBN} is debugging a combined PowerPC/SPU application
21781 on the Cell Broadband Engine, it provides in addition the following
21785 @item set spu stop-on-load @var{arg}
21787 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21788 will give control to the user when a new SPE thread enters its @code{main}
21789 function. The default is @code{off}.
21791 @item show spu stop-on-load
21793 Show whether to stop for new SPE threads.
21795 @item set spu auto-flush-cache @var{arg}
21796 Set whether to automatically flush the software-managed cache. When set to
21797 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21798 cache to be flushed whenever SPE execution stops. This provides a consistent
21799 view of PowerPC memory that is accessed via the cache. If an application
21800 does not use the software-managed cache, this option has no effect.
21802 @item show spu auto-flush-cache
21803 Show whether to automatically flush the software-managed cache.
21808 @subsection PowerPC
21809 @cindex PowerPC architecture
21811 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21812 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21813 numbers stored in the floating point registers. These values must be stored
21814 in two consecutive registers, always starting at an even register like
21815 @code{f0} or @code{f2}.
21817 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21818 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21819 @code{f2} and @code{f3} for @code{$dl1} and so on.
21821 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21822 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21825 @subsection Nios II
21826 @cindex Nios II architecture
21828 When @value{GDBN} is debugging the Nios II architecture,
21829 it provides the following special commands:
21833 @item set debug nios2
21834 @kindex set debug nios2
21835 This command turns on and off debugging messages for the Nios II
21836 target code in @value{GDBN}.
21838 @item show debug nios2
21839 @kindex show debug nios2
21840 Show the current setting of Nios II debugging messages.
21843 @node Controlling GDB
21844 @chapter Controlling @value{GDBN}
21846 You can alter the way @value{GDBN} interacts with you by using the
21847 @code{set} command. For commands controlling how @value{GDBN} displays
21848 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21853 * Editing:: Command editing
21854 * Command History:: Command history
21855 * Screen Size:: Screen size
21856 * Numbers:: Numbers
21857 * ABI:: Configuring the current ABI
21858 * Auto-loading:: Automatically loading associated files
21859 * Messages/Warnings:: Optional warnings and messages
21860 * Debugging Output:: Optional messages about internal happenings
21861 * Other Misc Settings:: Other Miscellaneous Settings
21869 @value{GDBN} indicates its readiness to read a command by printing a string
21870 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21871 can change the prompt string with the @code{set prompt} command. For
21872 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21873 the prompt in one of the @value{GDBN} sessions so that you can always tell
21874 which one you are talking to.
21876 @emph{Note:} @code{set prompt} does not add a space for you after the
21877 prompt you set. This allows you to set a prompt which ends in a space
21878 or a prompt that does not.
21882 @item set prompt @var{newprompt}
21883 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21885 @kindex show prompt
21887 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21890 Versions of @value{GDBN} that ship with Python scripting enabled have
21891 prompt extensions. The commands for interacting with these extensions
21895 @kindex set extended-prompt
21896 @item set extended-prompt @var{prompt}
21897 Set an extended prompt that allows for substitutions.
21898 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21899 substitution. Any escape sequences specified as part of the prompt
21900 string are replaced with the corresponding strings each time the prompt
21906 set extended-prompt Current working directory: \w (gdb)
21909 Note that when an extended-prompt is set, it takes control of the
21910 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21912 @kindex show extended-prompt
21913 @item show extended-prompt
21914 Prints the extended prompt. Any escape sequences specified as part of
21915 the prompt string with @code{set extended-prompt}, are replaced with the
21916 corresponding strings each time the prompt is displayed.
21920 @section Command Editing
21922 @cindex command line editing
21924 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21925 @sc{gnu} library provides consistent behavior for programs which provide a
21926 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21927 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21928 substitution, and a storage and recall of command history across
21929 debugging sessions.
21931 You may control the behavior of command line editing in @value{GDBN} with the
21932 command @code{set}.
21935 @kindex set editing
21938 @itemx set editing on
21939 Enable command line editing (enabled by default).
21941 @item set editing off
21942 Disable command line editing.
21944 @kindex show editing
21946 Show whether command line editing is enabled.
21949 @ifset SYSTEM_READLINE
21950 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21952 @ifclear SYSTEM_READLINE
21953 @xref{Command Line Editing},
21955 for more details about the Readline
21956 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21957 encouraged to read that chapter.
21959 @node Command History
21960 @section Command History
21961 @cindex command history
21963 @value{GDBN} can keep track of the commands you type during your
21964 debugging sessions, so that you can be certain of precisely what
21965 happened. Use these commands to manage the @value{GDBN} command
21968 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21969 package, to provide the history facility.
21970 @ifset SYSTEM_READLINE
21971 @xref{Using History Interactively, , , history, GNU History Library},
21973 @ifclear SYSTEM_READLINE
21974 @xref{Using History Interactively},
21976 for the detailed description of the History library.
21978 To issue a command to @value{GDBN} without affecting certain aspects of
21979 the state which is seen by users, prefix it with @samp{server }
21980 (@pxref{Server Prefix}). This
21981 means that this command will not affect the command history, nor will it
21982 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21983 pressed on a line by itself.
21985 @cindex @code{server}, command prefix
21986 The server prefix does not affect the recording of values into the value
21987 history; to print a value without recording it into the value history,
21988 use the @code{output} command instead of the @code{print} command.
21990 Here is the description of @value{GDBN} commands related to command
21994 @cindex history substitution
21995 @cindex history file
21996 @kindex set history filename
21997 @cindex @env{GDBHISTFILE}, environment variable
21998 @item set history filename @var{fname}
21999 Set the name of the @value{GDBN} command history file to @var{fname}.
22000 This is the file where @value{GDBN} reads an initial command history
22001 list, and where it writes the command history from this session when it
22002 exits. You can access this list through history expansion or through
22003 the history command editing characters listed below. This file defaults
22004 to the value of the environment variable @code{GDBHISTFILE}, or to
22005 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22008 @cindex save command history
22009 @kindex set history save
22010 @item set history save
22011 @itemx set history save on
22012 Record command history in a file, whose name may be specified with the
22013 @code{set history filename} command. By default, this option is disabled.
22015 @item set history save off
22016 Stop recording command history in a file.
22018 @cindex history size
22019 @kindex set history size
22020 @cindex @env{HISTSIZE}, environment variable
22021 @item set history size @var{size}
22022 @itemx set history size unlimited
22023 Set the number of commands which @value{GDBN} keeps in its history list.
22024 This defaults to the value of the environment variable
22025 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22026 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22027 history list is unlimited.
22030 History expansion assigns special meaning to the character @kbd{!}.
22031 @ifset SYSTEM_READLINE
22032 @xref{Event Designators, , , history, GNU History Library},
22034 @ifclear SYSTEM_READLINE
22035 @xref{Event Designators},
22039 @cindex history expansion, turn on/off
22040 Since @kbd{!} is also the logical not operator in C, history expansion
22041 is off by default. If you decide to enable history expansion with the
22042 @code{set history expansion on} command, you may sometimes need to
22043 follow @kbd{!} (when it is used as logical not, in an expression) with
22044 a space or a tab to prevent it from being expanded. The readline
22045 history facilities do not attempt substitution on the strings
22046 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22048 The commands to control history expansion are:
22051 @item set history expansion on
22052 @itemx set history expansion
22053 @kindex set history expansion
22054 Enable history expansion. History expansion is off by default.
22056 @item set history expansion off
22057 Disable history expansion.
22060 @kindex show history
22062 @itemx show history filename
22063 @itemx show history save
22064 @itemx show history size
22065 @itemx show history expansion
22066 These commands display the state of the @value{GDBN} history parameters.
22067 @code{show history} by itself displays all four states.
22072 @kindex show commands
22073 @cindex show last commands
22074 @cindex display command history
22075 @item show commands
22076 Display the last ten commands in the command history.
22078 @item show commands @var{n}
22079 Print ten commands centered on command number @var{n}.
22081 @item show commands +
22082 Print ten commands just after the commands last printed.
22086 @section Screen Size
22087 @cindex size of screen
22088 @cindex screen size
22091 @cindex pauses in output
22093 Certain commands to @value{GDBN} may produce large amounts of
22094 information output to the screen. To help you read all of it,
22095 @value{GDBN} pauses and asks you for input at the end of each page of
22096 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22097 to discard the remaining output. Also, the screen width setting
22098 determines when to wrap lines of output. Depending on what is being
22099 printed, @value{GDBN} tries to break the line at a readable place,
22100 rather than simply letting it overflow onto the following line.
22102 Normally @value{GDBN} knows the size of the screen from the terminal
22103 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22104 together with the value of the @code{TERM} environment variable and the
22105 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22106 you can override it with the @code{set height} and @code{set
22113 @kindex show height
22114 @item set height @var{lpp}
22115 @itemx set height unlimited
22117 @itemx set width @var{cpl}
22118 @itemx set width unlimited
22120 These @code{set} commands specify a screen height of @var{lpp} lines and
22121 a screen width of @var{cpl} characters. The associated @code{show}
22122 commands display the current settings.
22124 If you specify a height of either @code{unlimited} or zero lines,
22125 @value{GDBN} does not pause during output no matter how long the
22126 output is. This is useful if output is to a file or to an editor
22129 Likewise, you can specify @samp{set width unlimited} or @samp{set
22130 width 0} to prevent @value{GDBN} from wrapping its output.
22132 @item set pagination on
22133 @itemx set pagination off
22134 @kindex set pagination
22135 Turn the output pagination on or off; the default is on. Turning
22136 pagination off is the alternative to @code{set height unlimited}. Note that
22137 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22138 Options, -batch}) also automatically disables pagination.
22140 @item show pagination
22141 @kindex show pagination
22142 Show the current pagination mode.
22147 @cindex number representation
22148 @cindex entering numbers
22150 You can always enter numbers in octal, decimal, or hexadecimal in
22151 @value{GDBN} by the usual conventions: octal numbers begin with
22152 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22153 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22154 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22155 10; likewise, the default display for numbers---when no particular
22156 format is specified---is base 10. You can change the default base for
22157 both input and output with the commands described below.
22160 @kindex set input-radix
22161 @item set input-radix @var{base}
22162 Set the default base for numeric input. Supported choices
22163 for @var{base} are decimal 8, 10, or 16. The base must itself be
22164 specified either unambiguously or using the current input radix; for
22168 set input-radix 012
22169 set input-radix 10.
22170 set input-radix 0xa
22174 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22175 leaves the input radix unchanged, no matter what it was, since
22176 @samp{10}, being without any leading or trailing signs of its base, is
22177 interpreted in the current radix. Thus, if the current radix is 16,
22178 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22181 @kindex set output-radix
22182 @item set output-radix @var{base}
22183 Set the default base for numeric display. Supported choices
22184 for @var{base} are decimal 8, 10, or 16. The base must itself be
22185 specified either unambiguously or using the current input radix.
22187 @kindex show input-radix
22188 @item show input-radix
22189 Display the current default base for numeric input.
22191 @kindex show output-radix
22192 @item show output-radix
22193 Display the current default base for numeric display.
22195 @item set radix @r{[}@var{base}@r{]}
22199 These commands set and show the default base for both input and output
22200 of numbers. @code{set radix} sets the radix of input and output to
22201 the same base; without an argument, it resets the radix back to its
22202 default value of 10.
22207 @section Configuring the Current ABI
22209 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22210 application automatically. However, sometimes you need to override its
22211 conclusions. Use these commands to manage @value{GDBN}'s view of the
22217 @cindex Newlib OS ABI and its influence on the longjmp handling
22219 One @value{GDBN} configuration can debug binaries for multiple operating
22220 system targets, either via remote debugging or native emulation.
22221 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22222 but you can override its conclusion using the @code{set osabi} command.
22223 One example where this is useful is in debugging of binaries which use
22224 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22225 not have the same identifying marks that the standard C library for your
22228 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22229 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22230 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22231 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22235 Show the OS ABI currently in use.
22238 With no argument, show the list of registered available OS ABI's.
22240 @item set osabi @var{abi}
22241 Set the current OS ABI to @var{abi}.
22244 @cindex float promotion
22246 Generally, the way that an argument of type @code{float} is passed to a
22247 function depends on whether the function is prototyped. For a prototyped
22248 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22249 according to the architecture's convention for @code{float}. For unprototyped
22250 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22251 @code{double} and then passed.
22253 Unfortunately, some forms of debug information do not reliably indicate whether
22254 a function is prototyped. If @value{GDBN} calls a function that is not marked
22255 as prototyped, it consults @kbd{set coerce-float-to-double}.
22258 @kindex set coerce-float-to-double
22259 @item set coerce-float-to-double
22260 @itemx set coerce-float-to-double on
22261 Arguments of type @code{float} will be promoted to @code{double} when passed
22262 to an unprototyped function. This is the default setting.
22264 @item set coerce-float-to-double off
22265 Arguments of type @code{float} will be passed directly to unprototyped
22268 @kindex show coerce-float-to-double
22269 @item show coerce-float-to-double
22270 Show the current setting of promoting @code{float} to @code{double}.
22274 @kindex show cp-abi
22275 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22276 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22277 used to build your application. @value{GDBN} only fully supports
22278 programs with a single C@t{++} ABI; if your program contains code using
22279 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22280 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22281 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22282 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22283 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22284 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22289 Show the C@t{++} ABI currently in use.
22292 With no argument, show the list of supported C@t{++} ABI's.
22294 @item set cp-abi @var{abi}
22295 @itemx set cp-abi auto
22296 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22300 @section Automatically loading associated files
22301 @cindex auto-loading
22303 @value{GDBN} sometimes reads files with commands and settings automatically,
22304 without being explicitly told so by the user. We call this feature
22305 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22306 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22307 results or introduce security risks (e.g., if the file comes from untrusted
22311 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22312 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22314 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22315 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22318 There are various kinds of files @value{GDBN} can automatically load.
22319 In addition to these files, @value{GDBN} supports auto-loading code written
22320 in various extension languages. @xref{Auto-loading extensions}.
22322 Note that loading of these associated files (including the local @file{.gdbinit}
22323 file) requires accordingly configured @code{auto-load safe-path}
22324 (@pxref{Auto-loading safe path}).
22326 For these reasons, @value{GDBN} includes commands and options to let you
22327 control when to auto-load files and which files should be auto-loaded.
22330 @anchor{set auto-load off}
22331 @kindex set auto-load off
22332 @item set auto-load off
22333 Globally disable loading of all auto-loaded files.
22334 You may want to use this command with the @samp{-iex} option
22335 (@pxref{Option -init-eval-command}) such as:
22337 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22340 Be aware that system init file (@pxref{System-wide configuration})
22341 and init files from your home directory (@pxref{Home Directory Init File})
22342 still get read (as they come from generally trusted directories).
22343 To prevent @value{GDBN} from auto-loading even those init files, use the
22344 @option{-nx} option (@pxref{Mode Options}), in addition to
22345 @code{set auto-load no}.
22347 @anchor{show auto-load}
22348 @kindex show auto-load
22349 @item show auto-load
22350 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22354 (gdb) show auto-load
22355 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22356 libthread-db: Auto-loading of inferior specific libthread_db is on.
22357 local-gdbinit: Auto-loading of .gdbinit script from current directory
22359 python-scripts: Auto-loading of Python scripts is on.
22360 safe-path: List of directories from which it is safe to auto-load files
22361 is $debugdir:$datadir/auto-load.
22362 scripts-directory: List of directories from which to load auto-loaded scripts
22363 is $debugdir:$datadir/auto-load.
22366 @anchor{info auto-load}
22367 @kindex info auto-load
22368 @item info auto-load
22369 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22373 (gdb) info auto-load
22376 Yes /home/user/gdb/gdb-gdb.gdb
22377 libthread-db: No auto-loaded libthread-db.
22378 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22382 Yes /home/user/gdb/gdb-gdb.py
22386 These are @value{GDBN} control commands for the auto-loading:
22388 @multitable @columnfractions .5 .5
22389 @item @xref{set auto-load off}.
22390 @tab Disable auto-loading globally.
22391 @item @xref{show auto-load}.
22392 @tab Show setting of all kinds of files.
22393 @item @xref{info auto-load}.
22394 @tab Show state of all kinds of files.
22395 @item @xref{set auto-load gdb-scripts}.
22396 @tab Control for @value{GDBN} command scripts.
22397 @item @xref{show auto-load gdb-scripts}.
22398 @tab Show setting of @value{GDBN} command scripts.
22399 @item @xref{info auto-load gdb-scripts}.
22400 @tab Show state of @value{GDBN} command scripts.
22401 @item @xref{set auto-load python-scripts}.
22402 @tab Control for @value{GDBN} Python scripts.
22403 @item @xref{show auto-load python-scripts}.
22404 @tab Show setting of @value{GDBN} Python scripts.
22405 @item @xref{info auto-load python-scripts}.
22406 @tab Show state of @value{GDBN} Python scripts.
22407 @item @xref{set auto-load guile-scripts}.
22408 @tab Control for @value{GDBN} Guile scripts.
22409 @item @xref{show auto-load guile-scripts}.
22410 @tab Show setting of @value{GDBN} Guile scripts.
22411 @item @xref{info auto-load guile-scripts}.
22412 @tab Show state of @value{GDBN} Guile scripts.
22413 @item @xref{set auto-load scripts-directory}.
22414 @tab Control for @value{GDBN} auto-loaded scripts location.
22415 @item @xref{show auto-load scripts-directory}.
22416 @tab Show @value{GDBN} auto-loaded scripts location.
22417 @item @xref{add-auto-load-scripts-directory}.
22418 @tab Add directory for auto-loaded scripts location list.
22419 @item @xref{set auto-load local-gdbinit}.
22420 @tab Control for init file in the current directory.
22421 @item @xref{show auto-load local-gdbinit}.
22422 @tab Show setting of init file in the current directory.
22423 @item @xref{info auto-load local-gdbinit}.
22424 @tab Show state of init file in the current directory.
22425 @item @xref{set auto-load libthread-db}.
22426 @tab Control for thread debugging library.
22427 @item @xref{show auto-load libthread-db}.
22428 @tab Show setting of thread debugging library.
22429 @item @xref{info auto-load libthread-db}.
22430 @tab Show state of thread debugging library.
22431 @item @xref{set auto-load safe-path}.
22432 @tab Control directories trusted for automatic loading.
22433 @item @xref{show auto-load safe-path}.
22434 @tab Show directories trusted for automatic loading.
22435 @item @xref{add-auto-load-safe-path}.
22436 @tab Add directory trusted for automatic loading.
22439 @node Init File in the Current Directory
22440 @subsection Automatically loading init file in the current directory
22441 @cindex auto-loading init file in the current directory
22443 By default, @value{GDBN} reads and executes the canned sequences of commands
22444 from init file (if any) in the current working directory,
22445 see @ref{Init File in the Current Directory during Startup}.
22447 Note that loading of this local @file{.gdbinit} file also requires accordingly
22448 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22451 @anchor{set auto-load local-gdbinit}
22452 @kindex set auto-load local-gdbinit
22453 @item set auto-load local-gdbinit [on|off]
22454 Enable or disable the auto-loading of canned sequences of commands
22455 (@pxref{Sequences}) found in init file in the current directory.
22457 @anchor{show auto-load local-gdbinit}
22458 @kindex show auto-load local-gdbinit
22459 @item show auto-load local-gdbinit
22460 Show whether auto-loading of canned sequences of commands from init file in the
22461 current directory is enabled or disabled.
22463 @anchor{info auto-load local-gdbinit}
22464 @kindex info auto-load local-gdbinit
22465 @item info auto-load local-gdbinit
22466 Print whether canned sequences of commands from init file in the
22467 current directory have been auto-loaded.
22470 @node libthread_db.so.1 file
22471 @subsection Automatically loading thread debugging library
22472 @cindex auto-loading libthread_db.so.1
22474 This feature is currently present only on @sc{gnu}/Linux native hosts.
22476 @value{GDBN} reads in some cases thread debugging library from places specific
22477 to the inferior (@pxref{set libthread-db-search-path}).
22479 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22480 without checking this @samp{set auto-load libthread-db} switch as system
22481 libraries have to be trusted in general. In all other cases of
22482 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22483 auto-load libthread-db} is enabled before trying to open such thread debugging
22486 Note that loading of this debugging library also requires accordingly configured
22487 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22490 @anchor{set auto-load libthread-db}
22491 @kindex set auto-load libthread-db
22492 @item set auto-load libthread-db [on|off]
22493 Enable or disable the auto-loading of inferior specific thread debugging library.
22495 @anchor{show auto-load libthread-db}
22496 @kindex show auto-load libthread-db
22497 @item show auto-load libthread-db
22498 Show whether auto-loading of inferior specific thread debugging library is
22499 enabled or disabled.
22501 @anchor{info auto-load libthread-db}
22502 @kindex info auto-load libthread-db
22503 @item info auto-load libthread-db
22504 Print the list of all loaded inferior specific thread debugging libraries and
22505 for each such library print list of inferior @var{pid}s using it.
22508 @node Auto-loading safe path
22509 @subsection Security restriction for auto-loading
22510 @cindex auto-loading safe-path
22512 As the files of inferior can come from untrusted source (such as submitted by
22513 an application user) @value{GDBN} does not always load any files automatically.
22514 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22515 directories trusted for loading files not explicitly requested by user.
22516 Each directory can also be a shell wildcard pattern.
22518 If the path is not set properly you will see a warning and the file will not
22523 Reading symbols from /home/user/gdb/gdb...done.
22524 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22525 declined by your `auto-load safe-path' set
22526 to "$debugdir:$datadir/auto-load".
22527 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22528 declined by your `auto-load safe-path' set
22529 to "$debugdir:$datadir/auto-load".
22533 To instruct @value{GDBN} to go ahead and use the init files anyway,
22534 invoke @value{GDBN} like this:
22537 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22540 The list of trusted directories is controlled by the following commands:
22543 @anchor{set auto-load safe-path}
22544 @kindex set auto-load safe-path
22545 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22546 Set the list of directories (and their subdirectories) trusted for automatic
22547 loading and execution of scripts. You can also enter a specific trusted file.
22548 Each directory can also be a shell wildcard pattern; wildcards do not match
22549 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22550 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22551 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22552 its default value as specified during @value{GDBN} compilation.
22554 The list of directories uses path separator (@samp{:} on GNU and Unix
22555 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22556 to the @env{PATH} environment variable.
22558 @anchor{show auto-load safe-path}
22559 @kindex show auto-load safe-path
22560 @item show auto-load safe-path
22561 Show the list of directories trusted for automatic loading and execution of
22564 @anchor{add-auto-load-safe-path}
22565 @kindex add-auto-load-safe-path
22566 @item add-auto-load-safe-path
22567 Add an entry (or list of entries) to the list of directories trusted for
22568 automatic loading and execution of scripts. Multiple entries may be delimited
22569 by the host platform path separator in use.
22572 This variable defaults to what @code{--with-auto-load-dir} has been configured
22573 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22574 substitution applies the same as for @ref{set auto-load scripts-directory}.
22575 The default @code{set auto-load safe-path} value can be also overriden by
22576 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22578 Setting this variable to @file{/} disables this security protection,
22579 corresponding @value{GDBN} configuration option is
22580 @option{--without-auto-load-safe-path}.
22581 This variable is supposed to be set to the system directories writable by the
22582 system superuser only. Users can add their source directories in init files in
22583 their home directories (@pxref{Home Directory Init File}). See also deprecated
22584 init file in the current directory
22585 (@pxref{Init File in the Current Directory during Startup}).
22587 To force @value{GDBN} to load the files it declined to load in the previous
22588 example, you could use one of the following ways:
22591 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22592 Specify this trusted directory (or a file) as additional component of the list.
22593 You have to specify also any existing directories displayed by
22594 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22596 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22597 Specify this directory as in the previous case but just for a single
22598 @value{GDBN} session.
22600 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22601 Disable auto-loading safety for a single @value{GDBN} session.
22602 This assumes all the files you debug during this @value{GDBN} session will come
22603 from trusted sources.
22605 @item @kbd{./configure --without-auto-load-safe-path}
22606 During compilation of @value{GDBN} you may disable any auto-loading safety.
22607 This assumes all the files you will ever debug with this @value{GDBN} come from
22611 On the other hand you can also explicitly forbid automatic files loading which
22612 also suppresses any such warning messages:
22615 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22616 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22618 @item @file{~/.gdbinit}: @samp{set auto-load no}
22619 Disable auto-loading globally for the user
22620 (@pxref{Home Directory Init File}). While it is improbable, you could also
22621 use system init file instead (@pxref{System-wide configuration}).
22624 This setting applies to the file names as entered by user. If no entry matches
22625 @value{GDBN} tries as a last resort to also resolve all the file names into
22626 their canonical form (typically resolving symbolic links) and compare the
22627 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22628 own before starting the comparison so a canonical form of directories is
22629 recommended to be entered.
22631 @node Auto-loading verbose mode
22632 @subsection Displaying files tried for auto-load
22633 @cindex auto-loading verbose mode
22635 For better visibility of all the file locations where you can place scripts to
22636 be auto-loaded with inferior --- or to protect yourself against accidental
22637 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22638 all the files attempted to be loaded. Both existing and non-existing files may
22641 For example the list of directories from which it is safe to auto-load files
22642 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22643 may not be too obvious while setting it up.
22646 (gdb) set debug auto-load on
22647 (gdb) file ~/src/t/true
22648 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22649 for objfile "/tmp/true".
22650 auto-load: Updating directories of "/usr:/opt".
22651 auto-load: Using directory "/usr".
22652 auto-load: Using directory "/opt".
22653 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22654 by your `auto-load safe-path' set to "/usr:/opt".
22658 @anchor{set debug auto-load}
22659 @kindex set debug auto-load
22660 @item set debug auto-load [on|off]
22661 Set whether to print the filenames attempted to be auto-loaded.
22663 @anchor{show debug auto-load}
22664 @kindex show debug auto-load
22665 @item show debug auto-load
22666 Show whether printing of the filenames attempted to be auto-loaded is turned
22670 @node Messages/Warnings
22671 @section Optional Warnings and Messages
22673 @cindex verbose operation
22674 @cindex optional warnings
22675 By default, @value{GDBN} is silent about its inner workings. If you are
22676 running on a slow machine, you may want to use the @code{set verbose}
22677 command. This makes @value{GDBN} tell you when it does a lengthy
22678 internal operation, so you will not think it has crashed.
22680 Currently, the messages controlled by @code{set verbose} are those
22681 which announce that the symbol table for a source file is being read;
22682 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22685 @kindex set verbose
22686 @item set verbose on
22687 Enables @value{GDBN} output of certain informational messages.
22689 @item set verbose off
22690 Disables @value{GDBN} output of certain informational messages.
22692 @kindex show verbose
22694 Displays whether @code{set verbose} is on or off.
22697 By default, if @value{GDBN} encounters bugs in the symbol table of an
22698 object file, it is silent; but if you are debugging a compiler, you may
22699 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22704 @kindex set complaints
22705 @item set complaints @var{limit}
22706 Permits @value{GDBN} to output @var{limit} complaints about each type of
22707 unusual symbols before becoming silent about the problem. Set
22708 @var{limit} to zero to suppress all complaints; set it to a large number
22709 to prevent complaints from being suppressed.
22711 @kindex show complaints
22712 @item show complaints
22713 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22717 @anchor{confirmation requests}
22718 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22719 lot of stupid questions to confirm certain commands. For example, if
22720 you try to run a program which is already running:
22724 The program being debugged has been started already.
22725 Start it from the beginning? (y or n)
22728 If you are willing to unflinchingly face the consequences of your own
22729 commands, you can disable this ``feature'':
22733 @kindex set confirm
22735 @cindex confirmation
22736 @cindex stupid questions
22737 @item set confirm off
22738 Disables confirmation requests. Note that running @value{GDBN} with
22739 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22740 automatically disables confirmation requests.
22742 @item set confirm on
22743 Enables confirmation requests (the default).
22745 @kindex show confirm
22747 Displays state of confirmation requests.
22751 @cindex command tracing
22752 If you need to debug user-defined commands or sourced files you may find it
22753 useful to enable @dfn{command tracing}. In this mode each command will be
22754 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22755 quantity denoting the call depth of each command.
22758 @kindex set trace-commands
22759 @cindex command scripts, debugging
22760 @item set trace-commands on
22761 Enable command tracing.
22762 @item set trace-commands off
22763 Disable command tracing.
22764 @item show trace-commands
22765 Display the current state of command tracing.
22768 @node Debugging Output
22769 @section Optional Messages about Internal Happenings
22770 @cindex optional debugging messages
22772 @value{GDBN} has commands that enable optional debugging messages from
22773 various @value{GDBN} subsystems; normally these commands are of
22774 interest to @value{GDBN} maintainers, or when reporting a bug. This
22775 section documents those commands.
22778 @kindex set exec-done-display
22779 @item set exec-done-display
22780 Turns on or off the notification of asynchronous commands'
22781 completion. When on, @value{GDBN} will print a message when an
22782 asynchronous command finishes its execution. The default is off.
22783 @kindex show exec-done-display
22784 @item show exec-done-display
22785 Displays the current setting of asynchronous command completion
22788 @cindex ARM AArch64
22789 @item set debug aarch64
22790 Turns on or off display of debugging messages related to ARM AArch64.
22791 The default is off.
22793 @item show debug aarch64
22794 Displays the current state of displaying debugging messages related to
22796 @cindex gdbarch debugging info
22797 @cindex architecture debugging info
22798 @item set debug arch
22799 Turns on or off display of gdbarch debugging info. The default is off
22800 @item show debug arch
22801 Displays the current state of displaying gdbarch debugging info.
22802 @item set debug aix-solib
22803 @cindex AIX shared library debugging
22804 Control display of debugging messages from the AIX shared library
22805 support module. The default is off.
22806 @item show debug aix-thread
22807 Show the current state of displaying AIX shared library debugging messages.
22808 @item set debug aix-thread
22809 @cindex AIX threads
22810 Display debugging messages about inner workings of the AIX thread
22812 @item show debug aix-thread
22813 Show the current state of AIX thread debugging info display.
22814 @item set debug check-physname
22816 Check the results of the ``physname'' computation. When reading DWARF
22817 debugging information for C@t{++}, @value{GDBN} attempts to compute
22818 each entity's name. @value{GDBN} can do this computation in two
22819 different ways, depending on exactly what information is present.
22820 When enabled, this setting causes @value{GDBN} to compute the names
22821 both ways and display any discrepancies.
22822 @item show debug check-physname
22823 Show the current state of ``physname'' checking.
22824 @item set debug coff-pe-read
22825 @cindex COFF/PE exported symbols
22826 Control display of debugging messages related to reading of COFF/PE
22827 exported symbols. The default is off.
22828 @item show debug coff-pe-read
22829 Displays the current state of displaying debugging messages related to
22830 reading of COFF/PE exported symbols.
22831 @item set debug dwarf2-die
22832 @cindex DWARF2 DIEs
22833 Dump DWARF2 DIEs after they are read in.
22834 The value is the number of nesting levels to print.
22835 A value of zero turns off the display.
22836 @item show debug dwarf2-die
22837 Show the current state of DWARF2 DIE debugging.
22838 @item set debug dwarf2-read
22839 @cindex DWARF2 Reading
22840 Turns on or off display of debugging messages related to reading
22841 DWARF debug info. The default is 0 (off).
22842 A value of 1 provides basic information.
22843 A value greater than 1 provides more verbose information.
22844 @item show debug dwarf2-read
22845 Show the current state of DWARF2 reader debugging.
22846 @item set debug displaced
22847 @cindex displaced stepping debugging info
22848 Turns on or off display of @value{GDBN} debugging info for the
22849 displaced stepping support. The default is off.
22850 @item show debug displaced
22851 Displays the current state of displaying @value{GDBN} debugging info
22852 related to displaced stepping.
22853 @item set debug event
22854 @cindex event debugging info
22855 Turns on or off display of @value{GDBN} event debugging info. The
22857 @item show debug event
22858 Displays the current state of displaying @value{GDBN} event debugging
22860 @item set debug expression
22861 @cindex expression debugging info
22862 Turns on or off display of debugging info about @value{GDBN}
22863 expression parsing. The default is off.
22864 @item show debug expression
22865 Displays the current state of displaying debugging info about
22866 @value{GDBN} expression parsing.
22867 @item set debug frame
22868 @cindex frame debugging info
22869 Turns on or off display of @value{GDBN} frame debugging info. The
22871 @item show debug frame
22872 Displays the current state of displaying @value{GDBN} frame debugging
22874 @item set debug gnu-nat
22875 @cindex @sc{gnu}/Hurd debug messages
22876 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22877 @item show debug gnu-nat
22878 Show the current state of @sc{gnu}/Hurd debugging messages.
22879 @item set debug infrun
22880 @cindex inferior debugging info
22881 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22882 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22883 for implementing operations such as single-stepping the inferior.
22884 @item show debug infrun
22885 Displays the current state of @value{GDBN} inferior debugging.
22886 @item set debug jit
22887 @cindex just-in-time compilation, debugging messages
22888 Turns on or off debugging messages from JIT debug support.
22889 @item show debug jit
22890 Displays the current state of @value{GDBN} JIT debugging.
22891 @item set debug lin-lwp
22892 @cindex @sc{gnu}/Linux LWP debug messages
22893 @cindex Linux lightweight processes
22894 Turns on or off debugging messages from the Linux LWP debug support.
22895 @item show debug lin-lwp
22896 Show the current state of Linux LWP debugging messages.
22897 @item set debug mach-o
22898 @cindex Mach-O symbols processing
22899 Control display of debugging messages related to Mach-O symbols
22900 processing. The default is off.
22901 @item show debug mach-o
22902 Displays the current state of displaying debugging messages related to
22903 reading of COFF/PE exported symbols.
22904 @item set debug notification
22905 @cindex remote async notification debugging info
22906 Turns on or off debugging messages about remote async notification.
22907 The default is off.
22908 @item show debug notification
22909 Displays the current state of remote async notification debugging messages.
22910 @item set debug observer
22911 @cindex observer debugging info
22912 Turns on or off display of @value{GDBN} observer debugging. This
22913 includes info such as the notification of observable events.
22914 @item show debug observer
22915 Displays the current state of observer debugging.
22916 @item set debug overload
22917 @cindex C@t{++} overload debugging info
22918 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22919 info. This includes info such as ranking of functions, etc. The default
22921 @item show debug overload
22922 Displays the current state of displaying @value{GDBN} C@t{++} overload
22924 @cindex expression parser, debugging info
22925 @cindex debug expression parser
22926 @item set debug parser
22927 Turns on or off the display of expression parser debugging output.
22928 Internally, this sets the @code{yydebug} variable in the expression
22929 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22930 details. The default is off.
22931 @item show debug parser
22932 Show the current state of expression parser debugging.
22933 @cindex packets, reporting on stdout
22934 @cindex serial connections, debugging
22935 @cindex debug remote protocol
22936 @cindex remote protocol debugging
22937 @cindex display remote packets
22938 @item set debug remote
22939 Turns on or off display of reports on all packets sent back and forth across
22940 the serial line to the remote machine. The info is printed on the
22941 @value{GDBN} standard output stream. The default is off.
22942 @item show debug remote
22943 Displays the state of display of remote packets.
22944 @item set debug serial
22945 Turns on or off display of @value{GDBN} serial debugging info. The
22947 @item show debug serial
22948 Displays the current state of displaying @value{GDBN} serial debugging
22950 @item set debug solib-frv
22951 @cindex FR-V shared-library debugging
22952 Turns on or off debugging messages for FR-V shared-library code.
22953 @item show debug solib-frv
22954 Display the current state of FR-V shared-library code debugging
22956 @item set debug symfile
22957 @cindex symbol file functions
22958 Turns on or off display of debugging messages related to symbol file functions.
22959 The default is off. @xref{Files}.
22960 @item show debug symfile
22961 Show the current state of symbol file debugging messages.
22962 @item set debug symtab-create
22963 @cindex symbol table creation
22964 Turns on or off display of debugging messages related to symbol table creation.
22965 The default is 0 (off).
22966 A value of 1 provides basic information.
22967 A value greater than 1 provides more verbose information.
22968 @item show debug symtab-create
22969 Show the current state of symbol table creation debugging.
22970 @item set debug target
22971 @cindex target debugging info
22972 Turns on or off display of @value{GDBN} target debugging info. This info
22973 includes what is going on at the target level of GDB, as it happens. The
22974 default is 0. Set it to 1 to track events, and to 2 to also track the
22975 value of large memory transfers.
22976 @item show debug target
22977 Displays the current state of displaying @value{GDBN} target debugging
22979 @item set debug timestamp
22980 @cindex timestampping debugging info
22981 Turns on or off display of timestamps with @value{GDBN} debugging info.
22982 When enabled, seconds and microseconds are displayed before each debugging
22984 @item show debug timestamp
22985 Displays the current state of displaying timestamps with @value{GDBN}
22987 @item set debug varobj
22988 @cindex variable object debugging info
22989 Turns on or off display of @value{GDBN} variable object debugging
22990 info. The default is off.
22991 @item show debug varobj
22992 Displays the current state of displaying @value{GDBN} variable object
22994 @item set debug xml
22995 @cindex XML parser debugging
22996 Turns on or off debugging messages for built-in XML parsers.
22997 @item show debug xml
22998 Displays the current state of XML debugging messages.
23001 @node Other Misc Settings
23002 @section Other Miscellaneous Settings
23003 @cindex miscellaneous settings
23006 @kindex set interactive-mode
23007 @item set interactive-mode
23008 If @code{on}, forces @value{GDBN} to assume that GDB was started
23009 in a terminal. In practice, this means that @value{GDBN} should wait
23010 for the user to answer queries generated by commands entered at
23011 the command prompt. If @code{off}, forces @value{GDBN} to operate
23012 in the opposite mode, and it uses the default answers to all queries.
23013 If @code{auto} (the default), @value{GDBN} tries to determine whether
23014 its standard input is a terminal, and works in interactive-mode if it
23015 is, non-interactively otherwise.
23017 In the vast majority of cases, the debugger should be able to guess
23018 correctly which mode should be used. But this setting can be useful
23019 in certain specific cases, such as running a MinGW @value{GDBN}
23020 inside a cygwin window.
23022 @kindex show interactive-mode
23023 @item show interactive-mode
23024 Displays whether the debugger is operating in interactive mode or not.
23027 @node Extending GDB
23028 @chapter Extending @value{GDBN}
23029 @cindex extending GDB
23031 @value{GDBN} provides several mechanisms for extension.
23032 @value{GDBN} also provides the ability to automatically load
23033 extensions when it reads a file for debugging. This allows the
23034 user to automatically customize @value{GDBN} for the program
23038 * Sequences:: Canned Sequences of @value{GDBN} Commands
23039 * Python:: Extending @value{GDBN} using Python
23040 * Guile:: Extending @value{GDBN} using Guile
23041 * Auto-loading extensions:: Automatically loading extensions
23042 * Multiple Extension Languages:: Working with multiple extension languages
23043 * Aliases:: Creating new spellings of existing commands
23046 To facilitate the use of extension languages, @value{GDBN} is capable
23047 of evaluating the contents of a file. When doing so, @value{GDBN}
23048 can recognize which extension language is being used by looking at
23049 the filename extension. Files with an unrecognized filename extension
23050 are always treated as a @value{GDBN} Command Files.
23051 @xref{Command Files,, Command files}.
23053 You can control how @value{GDBN} evaluates these files with the following
23057 @kindex set script-extension
23058 @kindex show script-extension
23059 @item set script-extension off
23060 All scripts are always evaluated as @value{GDBN} Command Files.
23062 @item set script-extension soft
23063 The debugger determines the scripting language based on filename
23064 extension. If this scripting language is supported, @value{GDBN}
23065 evaluates the script using that language. Otherwise, it evaluates
23066 the file as a @value{GDBN} Command File.
23068 @item set script-extension strict
23069 The debugger determines the scripting language based on filename
23070 extension, and evaluates the script using that language. If the
23071 language is not supported, then the evaluation fails.
23073 @item show script-extension
23074 Display the current value of the @code{script-extension} option.
23079 @section Canned Sequences of Commands
23081 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23082 Command Lists}), @value{GDBN} provides two ways to store sequences of
23083 commands for execution as a unit: user-defined commands and command
23087 * Define:: How to define your own commands
23088 * Hooks:: Hooks for user-defined commands
23089 * Command Files:: How to write scripts of commands to be stored in a file
23090 * Output:: Commands for controlled output
23091 * Auto-loading sequences:: Controlling auto-loaded command files
23095 @subsection User-defined Commands
23097 @cindex user-defined command
23098 @cindex arguments, to user-defined commands
23099 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23100 which you assign a new name as a command. This is done with the
23101 @code{define} command. User commands may accept up to 10 arguments
23102 separated by whitespace. Arguments are accessed within the user command
23103 via @code{$arg0@dots{}$arg9}. A trivial example:
23107 print $arg0 + $arg1 + $arg2
23112 To execute the command use:
23119 This defines the command @code{adder}, which prints the sum of
23120 its three arguments. Note the arguments are text substitutions, so they may
23121 reference variables, use complex expressions, or even perform inferior
23124 @cindex argument count in user-defined commands
23125 @cindex how many arguments (user-defined commands)
23126 In addition, @code{$argc} may be used to find out how many arguments have
23127 been passed. This expands to a number in the range 0@dots{}10.
23132 print $arg0 + $arg1
23135 print $arg0 + $arg1 + $arg2
23143 @item define @var{commandname}
23144 Define a command named @var{commandname}. If there is already a command
23145 by that name, you are asked to confirm that you want to redefine it.
23146 The argument @var{commandname} may be a bare command name consisting of letters,
23147 numbers, dashes, and underscores. It may also start with any predefined
23148 prefix command. For example, @samp{define target my-target} creates
23149 a user-defined @samp{target my-target} command.
23151 The definition of the command is made up of other @value{GDBN} command lines,
23152 which are given following the @code{define} command. The end of these
23153 commands is marked by a line containing @code{end}.
23156 @kindex end@r{ (user-defined commands)}
23157 @item document @var{commandname}
23158 Document the user-defined command @var{commandname}, so that it can be
23159 accessed by @code{help}. The command @var{commandname} must already be
23160 defined. This command reads lines of documentation just as @code{define}
23161 reads the lines of the command definition, ending with @code{end}.
23162 After the @code{document} command is finished, @code{help} on command
23163 @var{commandname} displays the documentation you have written.
23165 You may use the @code{document} command again to change the
23166 documentation of a command. Redefining the command with @code{define}
23167 does not change the documentation.
23169 @kindex dont-repeat
23170 @cindex don't repeat command
23172 Used inside a user-defined command, this tells @value{GDBN} that this
23173 command should not be repeated when the user hits @key{RET}
23174 (@pxref{Command Syntax, repeat last command}).
23176 @kindex help user-defined
23177 @item help user-defined
23178 List all user-defined commands and all python commands defined in class
23179 COMAND_USER. The first line of the documentation or docstring is
23184 @itemx show user @var{commandname}
23185 Display the @value{GDBN} commands used to define @var{commandname} (but
23186 not its documentation). If no @var{commandname} is given, display the
23187 definitions for all user-defined commands.
23188 This does not work for user-defined python commands.
23190 @cindex infinite recursion in user-defined commands
23191 @kindex show max-user-call-depth
23192 @kindex set max-user-call-depth
23193 @item show max-user-call-depth
23194 @itemx set max-user-call-depth
23195 The value of @code{max-user-call-depth} controls how many recursion
23196 levels are allowed in user-defined commands before @value{GDBN} suspects an
23197 infinite recursion and aborts the command.
23198 This does not apply to user-defined python commands.
23201 In addition to the above commands, user-defined commands frequently
23202 use control flow commands, described in @ref{Command Files}.
23204 When user-defined commands are executed, the
23205 commands of the definition are not printed. An error in any command
23206 stops execution of the user-defined command.
23208 If used interactively, commands that would ask for confirmation proceed
23209 without asking when used inside a user-defined command. Many @value{GDBN}
23210 commands that normally print messages to say what they are doing omit the
23211 messages when used in a user-defined command.
23214 @subsection User-defined Command Hooks
23215 @cindex command hooks
23216 @cindex hooks, for commands
23217 @cindex hooks, pre-command
23220 You may define @dfn{hooks}, which are a special kind of user-defined
23221 command. Whenever you run the command @samp{foo}, if the user-defined
23222 command @samp{hook-foo} exists, it is executed (with no arguments)
23223 before that command.
23225 @cindex hooks, post-command
23227 A hook may also be defined which is run after the command you executed.
23228 Whenever you run the command @samp{foo}, if the user-defined command
23229 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23230 that command. Post-execution hooks may exist simultaneously with
23231 pre-execution hooks, for the same command.
23233 It is valid for a hook to call the command which it hooks. If this
23234 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23236 @c It would be nice if hookpost could be passed a parameter indicating
23237 @c if the command it hooks executed properly or not. FIXME!
23239 @kindex stop@r{, a pseudo-command}
23240 In addition, a pseudo-command, @samp{stop} exists. Defining
23241 (@samp{hook-stop}) makes the associated commands execute every time
23242 execution stops in your program: before breakpoint commands are run,
23243 displays are printed, or the stack frame is printed.
23245 For example, to ignore @code{SIGALRM} signals while
23246 single-stepping, but treat them normally during normal execution,
23251 handle SIGALRM nopass
23255 handle SIGALRM pass
23258 define hook-continue
23259 handle SIGALRM pass
23263 As a further example, to hook at the beginning and end of the @code{echo}
23264 command, and to add extra text to the beginning and end of the message,
23272 define hookpost-echo
23276 (@value{GDBP}) echo Hello World
23277 <<<---Hello World--->>>
23282 You can define a hook for any single-word command in @value{GDBN}, but
23283 not for command aliases; you should define a hook for the basic command
23284 name, e.g.@: @code{backtrace} rather than @code{bt}.
23285 @c FIXME! So how does Joe User discover whether a command is an alias
23287 You can hook a multi-word command by adding @code{hook-} or
23288 @code{hookpost-} to the last word of the command, e.g.@:
23289 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23291 If an error occurs during the execution of your hook, execution of
23292 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23293 (before the command that you actually typed had a chance to run).
23295 If you try to define a hook which does not match any known command, you
23296 get a warning from the @code{define} command.
23298 @node Command Files
23299 @subsection Command Files
23301 @cindex command files
23302 @cindex scripting commands
23303 A command file for @value{GDBN} is a text file made of lines that are
23304 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23305 also be included. An empty line in a command file does nothing; it
23306 does not mean to repeat the last command, as it would from the
23309 You can request the execution of a command file with the @code{source}
23310 command. Note that the @code{source} command is also used to evaluate
23311 scripts that are not Command Files. The exact behavior can be configured
23312 using the @code{script-extension} setting.
23313 @xref{Extending GDB,, Extending GDB}.
23317 @cindex execute commands from a file
23318 @item source [-s] [-v] @var{filename}
23319 Execute the command file @var{filename}.
23322 The lines in a command file are generally executed sequentially,
23323 unless the order of execution is changed by one of the
23324 @emph{flow-control commands} described below. The commands are not
23325 printed as they are executed. An error in any command terminates
23326 execution of the command file and control is returned to the console.
23328 @value{GDBN} first searches for @var{filename} in the current directory.
23329 If the file is not found there, and @var{filename} does not specify a
23330 directory, then @value{GDBN} also looks for the file on the source search path
23331 (specified with the @samp{directory} command);
23332 except that @file{$cdir} is not searched because the compilation directory
23333 is not relevant to scripts.
23335 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23336 on the search path even if @var{filename} specifies a directory.
23337 The search is done by appending @var{filename} to each element of the
23338 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23339 and the search path contains @file{/home/user} then @value{GDBN} will
23340 look for the script @file{/home/user/mylib/myscript}.
23341 The search is also done if @var{filename} is an absolute path.
23342 For example, if @var{filename} is @file{/tmp/myscript} and
23343 the search path contains @file{/home/user} then @value{GDBN} will
23344 look for the script @file{/home/user/tmp/myscript}.
23345 For DOS-like systems, if @var{filename} contains a drive specification,
23346 it is stripped before concatenation. For example, if @var{filename} is
23347 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23348 will look for the script @file{c:/tmp/myscript}.
23350 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23351 each command as it is executed. The option must be given before
23352 @var{filename}, and is interpreted as part of the filename anywhere else.
23354 Commands that would ask for confirmation if used interactively proceed
23355 without asking when used in a command file. Many @value{GDBN} commands that
23356 normally print messages to say what they are doing omit the messages
23357 when called from command files.
23359 @value{GDBN} also accepts command input from standard input. In this
23360 mode, normal output goes to standard output and error output goes to
23361 standard error. Errors in a command file supplied on standard input do
23362 not terminate execution of the command file---execution continues with
23366 gdb < cmds > log 2>&1
23369 (The syntax above will vary depending on the shell used.) This example
23370 will execute commands from the file @file{cmds}. All output and errors
23371 would be directed to @file{log}.
23373 Since commands stored on command files tend to be more general than
23374 commands typed interactively, they frequently need to deal with
23375 complicated situations, such as different or unexpected values of
23376 variables and symbols, changes in how the program being debugged is
23377 built, etc. @value{GDBN} provides a set of flow-control commands to
23378 deal with these complexities. Using these commands, you can write
23379 complex scripts that loop over data structures, execute commands
23380 conditionally, etc.
23387 This command allows to include in your script conditionally executed
23388 commands. The @code{if} command takes a single argument, which is an
23389 expression to evaluate. It is followed by a series of commands that
23390 are executed only if the expression is true (its value is nonzero).
23391 There can then optionally be an @code{else} line, followed by a series
23392 of commands that are only executed if the expression was false. The
23393 end of the list is marked by a line containing @code{end}.
23397 This command allows to write loops. Its syntax is similar to
23398 @code{if}: the command takes a single argument, which is an expression
23399 to evaluate, and must be followed by the commands to execute, one per
23400 line, terminated by an @code{end}. These commands are called the
23401 @dfn{body} of the loop. The commands in the body of @code{while} are
23402 executed repeatedly as long as the expression evaluates to true.
23406 This command exits the @code{while} loop in whose body it is included.
23407 Execution of the script continues after that @code{while}s @code{end}
23410 @kindex loop_continue
23411 @item loop_continue
23412 This command skips the execution of the rest of the body of commands
23413 in the @code{while} loop in whose body it is included. Execution
23414 branches to the beginning of the @code{while} loop, where it evaluates
23415 the controlling expression.
23417 @kindex end@r{ (if/else/while commands)}
23419 Terminate the block of commands that are the body of @code{if},
23420 @code{else}, or @code{while} flow-control commands.
23425 @subsection Commands for Controlled Output
23427 During the execution of a command file or a user-defined command, normal
23428 @value{GDBN} output is suppressed; the only output that appears is what is
23429 explicitly printed by the commands in the definition. This section
23430 describes three commands useful for generating exactly the output you
23435 @item echo @var{text}
23436 @c I do not consider backslash-space a standard C escape sequence
23437 @c because it is not in ANSI.
23438 Print @var{text}. Nonprinting characters can be included in
23439 @var{text} using C escape sequences, such as @samp{\n} to print a
23440 newline. @strong{No newline is printed unless you specify one.}
23441 In addition to the standard C escape sequences, a backslash followed
23442 by a space stands for a space. This is useful for displaying a
23443 string with spaces at the beginning or the end, since leading and
23444 trailing spaces are otherwise trimmed from all arguments.
23445 To print @samp{@w{ }and foo =@w{ }}, use the command
23446 @samp{echo \@w{ }and foo = \@w{ }}.
23448 A backslash at the end of @var{text} can be used, as in C, to continue
23449 the command onto subsequent lines. For example,
23452 echo This is some text\n\
23453 which is continued\n\
23454 onto several lines.\n
23457 produces the same output as
23460 echo This is some text\n
23461 echo which is continued\n
23462 echo onto several lines.\n
23466 @item output @var{expression}
23467 Print the value of @var{expression} and nothing but that value: no
23468 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23469 value history either. @xref{Expressions, ,Expressions}, for more information
23472 @item output/@var{fmt} @var{expression}
23473 Print the value of @var{expression} in format @var{fmt}. You can use
23474 the same formats as for @code{print}. @xref{Output Formats,,Output
23475 Formats}, for more information.
23478 @item printf @var{template}, @var{expressions}@dots{}
23479 Print the values of one or more @var{expressions} under the control of
23480 the string @var{template}. To print several values, make
23481 @var{expressions} be a comma-separated list of individual expressions,
23482 which may be either numbers or pointers. Their values are printed as
23483 specified by @var{template}, exactly as a C program would do by
23484 executing the code below:
23487 printf (@var{template}, @var{expressions}@dots{});
23490 As in @code{C} @code{printf}, ordinary characters in @var{template}
23491 are printed verbatim, while @dfn{conversion specification} introduced
23492 by the @samp{%} character cause subsequent @var{expressions} to be
23493 evaluated, their values converted and formatted according to type and
23494 style information encoded in the conversion specifications, and then
23497 For example, you can print two values in hex like this:
23500 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23503 @code{printf} supports all the standard @code{C} conversion
23504 specifications, including the flags and modifiers between the @samp{%}
23505 character and the conversion letter, with the following exceptions:
23509 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23512 The modifier @samp{*} is not supported for specifying precision or
23516 The @samp{'} flag (for separation of digits into groups according to
23517 @code{LC_NUMERIC'}) is not supported.
23520 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23524 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23527 The conversion letters @samp{a} and @samp{A} are not supported.
23531 Note that the @samp{ll} type modifier is supported only if the
23532 underlying @code{C} implementation used to build @value{GDBN} supports
23533 the @code{long long int} type, and the @samp{L} type modifier is
23534 supported only if @code{long double} type is available.
23536 As in @code{C}, @code{printf} supports simple backslash-escape
23537 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23538 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23539 single character. Octal and hexadecimal escape sequences are not
23542 Additionally, @code{printf} supports conversion specifications for DFP
23543 (@dfn{Decimal Floating Point}) types using the following length modifiers
23544 together with a floating point specifier.
23549 @samp{H} for printing @code{Decimal32} types.
23552 @samp{D} for printing @code{Decimal64} types.
23555 @samp{DD} for printing @code{Decimal128} types.
23558 If the underlying @code{C} implementation used to build @value{GDBN} has
23559 support for the three length modifiers for DFP types, other modifiers
23560 such as width and precision will also be available for @value{GDBN} to use.
23562 In case there is no such @code{C} support, no additional modifiers will be
23563 available and the value will be printed in the standard way.
23565 Here's an example of printing DFP types using the above conversion letters:
23567 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23571 @item eval @var{template}, @var{expressions}@dots{}
23572 Convert the values of one or more @var{expressions} under the control of
23573 the string @var{template} to a command line, and call it.
23577 @node Auto-loading sequences
23578 @subsection Controlling auto-loading native @value{GDBN} scripts
23579 @cindex native script auto-loading
23581 When a new object file is read (for example, due to the @code{file}
23582 command, or because the inferior has loaded a shared library),
23583 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23584 @xref{Auto-loading extensions}.
23586 Auto-loading can be enabled or disabled,
23587 and the list of auto-loaded scripts can be printed.
23590 @anchor{set auto-load gdb-scripts}
23591 @kindex set auto-load gdb-scripts
23592 @item set auto-load gdb-scripts [on|off]
23593 Enable or disable the auto-loading of canned sequences of commands scripts.
23595 @anchor{show auto-load gdb-scripts}
23596 @kindex show auto-load gdb-scripts
23597 @item show auto-load gdb-scripts
23598 Show whether auto-loading of canned sequences of commands scripts is enabled or
23601 @anchor{info auto-load gdb-scripts}
23602 @kindex info auto-load gdb-scripts
23603 @cindex print list of auto-loaded canned sequences of commands scripts
23604 @item info auto-load gdb-scripts [@var{regexp}]
23605 Print the list of all canned sequences of commands scripts that @value{GDBN}
23609 If @var{regexp} is supplied only canned sequences of commands scripts with
23610 matching names are printed.
23612 @c Python docs live in a separate file.
23613 @include python.texi
23615 @c Guile docs live in a separate file.
23616 @include guile.texi
23618 @node Auto-loading extensions
23619 @section Auto-loading extensions
23620 @cindex auto-loading extensions
23622 @value{GDBN} provides two mechanisms for automatically loading extensions
23623 when a new object file is read (for example, due to the @code{file}
23624 command, or because the inferior has loaded a shared library):
23625 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23626 section of modern file formats like ELF.
23629 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23630 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23631 * Which flavor to choose?::
23634 The auto-loading feature is useful for supplying application-specific
23635 debugging commands and features.
23637 Auto-loading can be enabled or disabled,
23638 and the list of auto-loaded scripts can be printed.
23639 See the @samp{auto-loading} section of each extension language
23640 for more information.
23641 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23642 For Python files see @ref{Python Auto-loading}.
23644 Note that loading of this script file also requires accordingly configured
23645 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23647 @node objfile-gdbdotext file
23648 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23649 @cindex @file{@var{objfile}-gdb.gdb}
23650 @cindex @file{@var{objfile}-gdb.py}
23651 @cindex @file{@var{objfile}-gdb.scm}
23653 When a new object file is read, @value{GDBN} looks for a file named
23654 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23655 where @var{objfile} is the object file's name and
23656 where @var{ext} is the file extension for the extension language:
23659 @item @file{@var{objfile}-gdb.gdb}
23660 GDB's own command language
23661 @item @file{@var{objfile}-gdb.py}
23663 @item @file{@var{objfile}-gdb.scm}
23667 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23668 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23669 components, and appending the @file{-gdb.@var{ext}} suffix.
23670 If this file exists and is readable, @value{GDBN} will evaluate it as a
23671 script in the specified extension language.
23673 If this file does not exist, then @value{GDBN} will look for
23674 @var{script-name} file in all of the directories as specified below.
23676 Note that loading of these files requires an accordingly configured
23677 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23679 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23680 scripts normally according to its @file{.exe} filename. But if no scripts are
23681 found @value{GDBN} also tries script filenames matching the object file without
23682 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23683 is attempted on any platform. This makes the script filenames compatible
23684 between Unix and MS-Windows hosts.
23687 @anchor{set auto-load scripts-directory}
23688 @kindex set auto-load scripts-directory
23689 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23690 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23691 may be delimited by the host platform path separator in use
23692 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23694 Each entry here needs to be covered also by the security setting
23695 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23697 @anchor{with-auto-load-dir}
23698 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23699 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23700 configuration option @option{--with-auto-load-dir}.
23702 Any reference to @file{$debugdir} will get replaced by
23703 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23704 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23705 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23706 @file{$datadir} must be placed as a directory component --- either alone or
23707 delimited by @file{/} or @file{\} directory separators, depending on the host
23710 The list of directories uses path separator (@samp{:} on GNU and Unix
23711 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23712 to the @env{PATH} environment variable.
23714 @anchor{show auto-load scripts-directory}
23715 @kindex show auto-load scripts-directory
23716 @item show auto-load scripts-directory
23717 Show @value{GDBN} auto-loaded scripts location.
23719 @anchor{add-auto-load-scripts-directory}
23720 @kindex add-auto-load-scripts-directory
23721 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
23722 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
23723 Multiple entries may be delimited by the host platform path separator in use.
23726 @value{GDBN} does not track which files it has already auto-loaded this way.
23727 @value{GDBN} will load the associated script every time the corresponding
23728 @var{objfile} is opened.
23729 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23730 is evaluated more than once.
23732 @node dotdebug_gdb_scripts section
23733 @subsection The @code{.debug_gdb_scripts} section
23734 @cindex @code{.debug_gdb_scripts} section
23736 For systems using file formats like ELF and COFF,
23737 when @value{GDBN} loads a new object file
23738 it will look for a special section named @code{.debug_gdb_scripts}.
23739 If this section exists, its contents is a list of NUL-terminated names
23740 of scripts to load. Each entry begins with a non-NULL prefix byte that
23741 specifies the kind of entry, typically the extension language.
23743 @value{GDBN} will look for each specified script file first in the
23744 current directory and then along the source search path
23745 (@pxref{Source Path, ,Specifying Source Directories}),
23746 except that @file{$cdir} is not searched, since the compilation
23747 directory is not relevant to scripts.
23749 Entries can be placed in section @code{.debug_gdb_scripts} with,
23750 for example, this GCC macro for Python scripts.
23753 /* Note: The "MS" section flags are to remove duplicates. */
23754 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23756 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23757 .byte 1 /* Python */\n\
23758 .asciz \"" script_name "\"\n\
23764 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
23765 Then one can reference the macro in a header or source file like this:
23768 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
23771 The script name may include directories if desired.
23773 Note that loading of this script file also requires accordingly configured
23774 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23776 If the macro invocation is put in a header, any application or library
23777 using this header will get a reference to the specified script,
23778 and with the use of @code{"MS"} attributes on the section, the linker
23779 will remove duplicates.
23781 @node Which flavor to choose?
23782 @subsection Which flavor to choose?
23784 Given the multiple ways of auto-loading extensions, it might not always
23785 be clear which one to choose. This section provides some guidance.
23788 Benefits of the @file{-gdb.@var{ext}} way:
23792 Can be used with file formats that don't support multiple sections.
23795 Ease of finding scripts for public libraries.
23797 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23798 in the source search path.
23799 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23800 isn't a source directory in which to find the script.
23803 Doesn't require source code additions.
23807 Benefits of the @code{.debug_gdb_scripts} way:
23811 Works with static linking.
23813 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
23814 trigger their loading. When an application is statically linked the only
23815 objfile available is the executable, and it is cumbersome to attach all the
23816 scripts from all the input libraries to the executable's
23817 @file{-gdb.@var{ext}} script.
23820 Works with classes that are entirely inlined.
23822 Some classes can be entirely inlined, and thus there may not be an associated
23823 shared library to attach a @file{-gdb.@var{ext}} script to.
23826 Scripts needn't be copied out of the source tree.
23828 In some circumstances, apps can be built out of large collections of internal
23829 libraries, and the build infrastructure necessary to install the
23830 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
23831 cumbersome. It may be easier to specify the scripts in the
23832 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23833 top of the source tree to the source search path.
23836 @node Multiple Extension Languages
23837 @section Multiple Extension Languages
23839 The Guile and Python extension languages do not share any state,
23840 and generally do not interfere with each other.
23841 There are some things to be aware of, however.
23843 @subsection Python comes first
23845 Python was @value{GDBN}'s first extension language, and to avoid breaking
23846 existing behaviour Python comes first. This is generally solved by the
23847 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
23848 extension languages, and when it makes a call to an extension language,
23849 (say to pretty-print a value), it tries each in turn until an extension
23850 language indicates it has performed the request (e.g., has returned the
23851 pretty-printed form of a value).
23852 This extends to errors while performing such requests: If an error happens
23853 while, for example, trying to pretty-print an object then the error is
23854 reported and any following extension languages are not tried.
23857 @section Creating new spellings of existing commands
23858 @cindex aliases for commands
23860 It is often useful to define alternate spellings of existing commands.
23861 For example, if a new @value{GDBN} command defined in Python has
23862 a long name to type, it is handy to have an abbreviated version of it
23863 that involves less typing.
23865 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
23866 of the @samp{step} command even though it is otherwise an ambiguous
23867 abbreviation of other commands like @samp{set} and @samp{show}.
23869 Aliases are also used to provide shortened or more common versions
23870 of multi-word commands. For example, @value{GDBN} provides the
23871 @samp{tty} alias of the @samp{set inferior-tty} command.
23873 You can define a new alias with the @samp{alias} command.
23878 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
23882 @var{ALIAS} specifies the name of the new alias.
23883 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
23886 @var{COMMAND} specifies the name of an existing command
23887 that is being aliased.
23889 The @samp{-a} option specifies that the new alias is an abbreviation
23890 of the command. Abbreviations are not shown in command
23891 lists displayed by the @samp{help} command.
23893 The @samp{--} option specifies the end of options,
23894 and is useful when @var{ALIAS} begins with a dash.
23896 Here is a simple example showing how to make an abbreviation
23897 of a command so that there is less to type.
23898 Suppose you were tired of typing @samp{disas}, the current
23899 shortest unambiguous abbreviation of the @samp{disassemble} command
23900 and you wanted an even shorter version named @samp{di}.
23901 The following will accomplish this.
23904 (gdb) alias -a di = disas
23907 Note that aliases are different from user-defined commands.
23908 With a user-defined command, you also need to write documentation
23909 for it with the @samp{document} command.
23910 An alias automatically picks up the documentation of the existing command.
23912 Here is an example where we make @samp{elms} an abbreviation of
23913 @samp{elements} in the @samp{set print elements} command.
23914 This is to show that you can make an abbreviation of any part
23918 (gdb) alias -a set print elms = set print elements
23919 (gdb) alias -a show print elms = show print elements
23920 (gdb) set p elms 20
23922 Limit on string chars or array elements to print is 200.
23925 Note that if you are defining an alias of a @samp{set} command,
23926 and you want to have an alias for the corresponding @samp{show}
23927 command, then you need to define the latter separately.
23929 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
23930 @var{ALIAS}, just as they are normally.
23933 (gdb) alias -a set pr elms = set p ele
23936 Finally, here is an example showing the creation of a one word
23937 alias for a more complex command.
23938 This creates alias @samp{spe} of the command @samp{set print elements}.
23941 (gdb) alias spe = set print elements
23946 @chapter Command Interpreters
23947 @cindex command interpreters
23949 @value{GDBN} supports multiple command interpreters, and some command
23950 infrastructure to allow users or user interface writers to switch
23951 between interpreters or run commands in other interpreters.
23953 @value{GDBN} currently supports two command interpreters, the console
23954 interpreter (sometimes called the command-line interpreter or @sc{cli})
23955 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23956 describes both of these interfaces in great detail.
23958 By default, @value{GDBN} will start with the console interpreter.
23959 However, the user may choose to start @value{GDBN} with another
23960 interpreter by specifying the @option{-i} or @option{--interpreter}
23961 startup options. Defined interpreters include:
23965 @cindex console interpreter
23966 The traditional console or command-line interpreter. This is the most often
23967 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23968 @value{GDBN} will use this interpreter.
23971 @cindex mi interpreter
23972 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23973 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23974 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23978 @cindex mi2 interpreter
23979 The current @sc{gdb/mi} interface.
23982 @cindex mi1 interpreter
23983 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23987 @cindex invoke another interpreter
23988 The interpreter being used by @value{GDBN} may not be dynamically
23989 switched at runtime. Although possible, this could lead to a very
23990 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23991 enters the command "interpreter-set console" in a console view,
23992 @value{GDBN} would switch to using the console interpreter, rendering
23993 the IDE inoperable!
23995 @kindex interpreter-exec
23996 Although you may only choose a single interpreter at startup, you may execute
23997 commands in any interpreter from the current interpreter using the appropriate
23998 command. If you are running the console interpreter, simply use the
23999 @code{interpreter-exec} command:
24002 interpreter-exec mi "-data-list-register-names"
24005 @sc{gdb/mi} has a similar command, although it is only available in versions of
24006 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24009 @chapter @value{GDBN} Text User Interface
24011 @cindex Text User Interface
24014 * TUI Overview:: TUI overview
24015 * TUI Keys:: TUI key bindings
24016 * TUI Single Key Mode:: TUI single key mode
24017 * TUI Commands:: TUI-specific commands
24018 * TUI Configuration:: TUI configuration variables
24021 The @value{GDBN} Text User Interface (TUI) is a terminal
24022 interface which uses the @code{curses} library to show the source
24023 file, the assembly output, the program registers and @value{GDBN}
24024 commands in separate text windows. The TUI mode is supported only
24025 on platforms where a suitable version of the @code{curses} library
24028 The TUI mode is enabled by default when you invoke @value{GDBN} as
24029 @samp{@value{GDBP} -tui}.
24030 You can also switch in and out of TUI mode while @value{GDBN} runs by
24031 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24032 @xref{TUI Keys, ,TUI Key Bindings}.
24035 @section TUI Overview
24037 In TUI mode, @value{GDBN} can display several text windows:
24041 This window is the @value{GDBN} command window with the @value{GDBN}
24042 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24043 managed using readline.
24046 The source window shows the source file of the program. The current
24047 line and active breakpoints are displayed in this window.
24050 The assembly window shows the disassembly output of the program.
24053 This window shows the processor registers. Registers are highlighted
24054 when their values change.
24057 The source and assembly windows show the current program position
24058 by highlighting the current line and marking it with a @samp{>} marker.
24059 Breakpoints are indicated with two markers. The first marker
24060 indicates the breakpoint type:
24064 Breakpoint which was hit at least once.
24067 Breakpoint which was never hit.
24070 Hardware breakpoint which was hit at least once.
24073 Hardware breakpoint which was never hit.
24076 The second marker indicates whether the breakpoint is enabled or not:
24080 Breakpoint is enabled.
24083 Breakpoint is disabled.
24086 The source, assembly and register windows are updated when the current
24087 thread changes, when the frame changes, or when the program counter
24090 These windows are not all visible at the same time. The command
24091 window is always visible. The others can be arranged in several
24102 source and assembly,
24105 source and registers, or
24108 assembly and registers.
24111 A status line above the command window shows the following information:
24115 Indicates the current @value{GDBN} target.
24116 (@pxref{Targets, ,Specifying a Debugging Target}).
24119 Gives the current process or thread number.
24120 When no process is being debugged, this field is set to @code{No process}.
24123 Gives the current function name for the selected frame.
24124 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24125 When there is no symbol corresponding to the current program counter,
24126 the string @code{??} is displayed.
24129 Indicates the current line number for the selected frame.
24130 When the current line number is not known, the string @code{??} is displayed.
24133 Indicates the current program counter address.
24137 @section TUI Key Bindings
24138 @cindex TUI key bindings
24140 The TUI installs several key bindings in the readline keymaps
24141 @ifset SYSTEM_READLINE
24142 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24144 @ifclear SYSTEM_READLINE
24145 (@pxref{Command Line Editing}).
24147 The following key bindings are installed for both TUI mode and the
24148 @value{GDBN} standard mode.
24157 Enter or leave the TUI mode. When leaving the TUI mode,
24158 the curses window management stops and @value{GDBN} operates using
24159 its standard mode, writing on the terminal directly. When reentering
24160 the TUI mode, control is given back to the curses windows.
24161 The screen is then refreshed.
24165 Use a TUI layout with only one window. The layout will
24166 either be @samp{source} or @samp{assembly}. When the TUI mode
24167 is not active, it will switch to the TUI mode.
24169 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24173 Use a TUI layout with at least two windows. When the current
24174 layout already has two windows, the next layout with two windows is used.
24175 When a new layout is chosen, one window will always be common to the
24176 previous layout and the new one.
24178 Think of it as the Emacs @kbd{C-x 2} binding.
24182 Change the active window. The TUI associates several key bindings
24183 (like scrolling and arrow keys) with the active window. This command
24184 gives the focus to the next TUI window.
24186 Think of it as the Emacs @kbd{C-x o} binding.
24190 Switch in and out of the TUI SingleKey mode that binds single
24191 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24194 The following key bindings only work in the TUI mode:
24199 Scroll the active window one page up.
24203 Scroll the active window one page down.
24207 Scroll the active window one line up.
24211 Scroll the active window one line down.
24215 Scroll the active window one column left.
24219 Scroll the active window one column right.
24223 Refresh the screen.
24226 Because the arrow keys scroll the active window in the TUI mode, they
24227 are not available for their normal use by readline unless the command
24228 window has the focus. When another window is active, you must use
24229 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24230 and @kbd{C-f} to control the command window.
24232 @node TUI Single Key Mode
24233 @section TUI Single Key Mode
24234 @cindex TUI single key mode
24236 The TUI also provides a @dfn{SingleKey} mode, which binds several
24237 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24238 switch into this mode, where the following key bindings are used:
24241 @kindex c @r{(SingleKey TUI key)}
24245 @kindex d @r{(SingleKey TUI key)}
24249 @kindex f @r{(SingleKey TUI key)}
24253 @kindex n @r{(SingleKey TUI key)}
24257 @kindex q @r{(SingleKey TUI key)}
24259 exit the SingleKey mode.
24261 @kindex r @r{(SingleKey TUI key)}
24265 @kindex s @r{(SingleKey TUI key)}
24269 @kindex u @r{(SingleKey TUI key)}
24273 @kindex v @r{(SingleKey TUI key)}
24277 @kindex w @r{(SingleKey TUI key)}
24282 Other keys temporarily switch to the @value{GDBN} command prompt.
24283 The key that was pressed is inserted in the editing buffer so that
24284 it is possible to type most @value{GDBN} commands without interaction
24285 with the TUI SingleKey mode. Once the command is entered the TUI
24286 SingleKey mode is restored. The only way to permanently leave
24287 this mode is by typing @kbd{q} or @kbd{C-x s}.
24291 @section TUI-specific Commands
24292 @cindex TUI commands
24294 The TUI has specific commands to control the text windows.
24295 These commands are always available, even when @value{GDBN} is not in
24296 the TUI mode. When @value{GDBN} is in the standard mode, most
24297 of these commands will automatically switch to the TUI mode.
24299 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24300 terminal, or @value{GDBN} has been started with the machine interface
24301 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24302 these commands will fail with an error, because it would not be
24303 possible or desirable to enable curses window management.
24308 List and give the size of all displayed windows.
24312 Display the next layout.
24315 Display the previous layout.
24318 Display the source window only.
24321 Display the assembly window only.
24324 Display the source and assembly window.
24327 Display the register window together with the source or assembly window.
24331 Make the next window active for scrolling.
24334 Make the previous window active for scrolling.
24337 Make the source window active for scrolling.
24340 Make the assembly window active for scrolling.
24343 Make the register window active for scrolling.
24346 Make the command window active for scrolling.
24350 Refresh the screen. This is similar to typing @kbd{C-L}.
24352 @item tui reg float
24354 Show the floating point registers in the register window.
24356 @item tui reg general
24357 Show the general registers in the register window.
24360 Show the next register group. The list of register groups as well as
24361 their order is target specific. The predefined register groups are the
24362 following: @code{general}, @code{float}, @code{system}, @code{vector},
24363 @code{all}, @code{save}, @code{restore}.
24365 @item tui reg system
24366 Show the system registers in the register window.
24370 Update the source window and the current execution point.
24372 @item winheight @var{name} +@var{count}
24373 @itemx winheight @var{name} -@var{count}
24375 Change the height of the window @var{name} by @var{count}
24376 lines. Positive counts increase the height, while negative counts
24379 @item tabset @var{nchars}
24381 Set the width of tab stops to be @var{nchars} characters.
24384 @node TUI Configuration
24385 @section TUI Configuration Variables
24386 @cindex TUI configuration variables
24388 Several configuration variables control the appearance of TUI windows.
24391 @item set tui border-kind @var{kind}
24392 @kindex set tui border-kind
24393 Select the border appearance for the source, assembly and register windows.
24394 The possible values are the following:
24397 Use a space character to draw the border.
24400 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24403 Use the Alternate Character Set to draw the border. The border is
24404 drawn using character line graphics if the terminal supports them.
24407 @item set tui border-mode @var{mode}
24408 @kindex set tui border-mode
24409 @itemx set tui active-border-mode @var{mode}
24410 @kindex set tui active-border-mode
24411 Select the display attributes for the borders of the inactive windows
24412 or the active window. The @var{mode} can be one of the following:
24415 Use normal attributes to display the border.
24421 Use reverse video mode.
24424 Use half bright mode.
24426 @item half-standout
24427 Use half bright and standout mode.
24430 Use extra bright or bold mode.
24432 @item bold-standout
24433 Use extra bright or bold and standout mode.
24438 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24441 @cindex @sc{gnu} Emacs
24442 A special interface allows you to use @sc{gnu} Emacs to view (and
24443 edit) the source files for the program you are debugging with
24446 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24447 executable file you want to debug as an argument. This command starts
24448 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24449 created Emacs buffer.
24450 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24452 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24457 All ``terminal'' input and output goes through an Emacs buffer, called
24460 This applies both to @value{GDBN} commands and their output, and to the input
24461 and output done by the program you are debugging.
24463 This is useful because it means that you can copy the text of previous
24464 commands and input them again; you can even use parts of the output
24467 All the facilities of Emacs' Shell mode are available for interacting
24468 with your program. In particular, you can send signals the usual
24469 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24473 @value{GDBN} displays source code through Emacs.
24475 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24476 source file for that frame and puts an arrow (@samp{=>}) at the
24477 left margin of the current line. Emacs uses a separate buffer for
24478 source display, and splits the screen to show both your @value{GDBN} session
24481 Explicit @value{GDBN} @code{list} or search commands still produce output as
24482 usual, but you probably have no reason to use them from Emacs.
24485 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24486 a graphical mode, enabled by default, which provides further buffers
24487 that can control the execution and describe the state of your program.
24488 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24490 If you specify an absolute file name when prompted for the @kbd{M-x
24491 gdb} argument, then Emacs sets your current working directory to where
24492 your program resides. If you only specify the file name, then Emacs
24493 sets your current working directory to the directory associated
24494 with the previous buffer. In this case, @value{GDBN} may find your
24495 program by searching your environment's @code{PATH} variable, but on
24496 some operating systems it might not find the source. So, although the
24497 @value{GDBN} input and output session proceeds normally, the auxiliary
24498 buffer does not display the current source and line of execution.
24500 The initial working directory of @value{GDBN} is printed on the top
24501 line of the GUD buffer and this serves as a default for the commands
24502 that specify files for @value{GDBN} to operate on. @xref{Files,
24503 ,Commands to Specify Files}.
24505 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24506 need to call @value{GDBN} by a different name (for example, if you
24507 keep several configurations around, with different names) you can
24508 customize the Emacs variable @code{gud-gdb-command-name} to run the
24511 In the GUD buffer, you can use these special Emacs commands in
24512 addition to the standard Shell mode commands:
24516 Describe the features of Emacs' GUD Mode.
24519 Execute to another source line, like the @value{GDBN} @code{step} command; also
24520 update the display window to show the current file and location.
24523 Execute to next source line in this function, skipping all function
24524 calls, like the @value{GDBN} @code{next} command. Then update the display window
24525 to show the current file and location.
24528 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24529 display window accordingly.
24532 Execute until exit from the selected stack frame, like the @value{GDBN}
24533 @code{finish} command.
24536 Continue execution of your program, like the @value{GDBN} @code{continue}
24540 Go up the number of frames indicated by the numeric argument
24541 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24542 like the @value{GDBN} @code{up} command.
24545 Go down the number of frames indicated by the numeric argument, like the
24546 @value{GDBN} @code{down} command.
24549 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24550 tells @value{GDBN} to set a breakpoint on the source line point is on.
24552 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24553 separate frame which shows a backtrace when the GUD buffer is current.
24554 Move point to any frame in the stack and type @key{RET} to make it
24555 become the current frame and display the associated source in the
24556 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24557 selected frame become the current one. In graphical mode, the
24558 speedbar displays watch expressions.
24560 If you accidentally delete the source-display buffer, an easy way to get
24561 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24562 request a frame display; when you run under Emacs, this recreates
24563 the source buffer if necessary to show you the context of the current
24566 The source files displayed in Emacs are in ordinary Emacs buffers
24567 which are visiting the source files in the usual way. You can edit
24568 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24569 communicates with Emacs in terms of line numbers. If you add or
24570 delete lines from the text, the line numbers that @value{GDBN} knows cease
24571 to correspond properly with the code.
24573 A more detailed description of Emacs' interaction with @value{GDBN} is
24574 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24578 @chapter The @sc{gdb/mi} Interface
24580 @unnumberedsec Function and Purpose
24582 @cindex @sc{gdb/mi}, its purpose
24583 @sc{gdb/mi} is a line based machine oriented text interface to
24584 @value{GDBN} and is activated by specifying using the
24585 @option{--interpreter} command line option (@pxref{Mode Options}). It
24586 is specifically intended to support the development of systems which
24587 use the debugger as just one small component of a larger system.
24589 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24590 in the form of a reference manual.
24592 Note that @sc{gdb/mi} is still under construction, so some of the
24593 features described below are incomplete and subject to change
24594 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24596 @unnumberedsec Notation and Terminology
24598 @cindex notational conventions, for @sc{gdb/mi}
24599 This chapter uses the following notation:
24603 @code{|} separates two alternatives.
24606 @code{[ @var{something} ]} indicates that @var{something} is optional:
24607 it may or may not be given.
24610 @code{( @var{group} )*} means that @var{group} inside the parentheses
24611 may repeat zero or more times.
24614 @code{( @var{group} )+} means that @var{group} inside the parentheses
24615 may repeat one or more times.
24618 @code{"@var{string}"} means a literal @var{string}.
24622 @heading Dependencies
24626 * GDB/MI General Design::
24627 * GDB/MI Command Syntax::
24628 * GDB/MI Compatibility with CLI::
24629 * GDB/MI Development and Front Ends::
24630 * GDB/MI Output Records::
24631 * GDB/MI Simple Examples::
24632 * GDB/MI Command Description Format::
24633 * GDB/MI Breakpoint Commands::
24634 * GDB/MI Catchpoint Commands::
24635 * GDB/MI Program Context::
24636 * GDB/MI Thread Commands::
24637 * GDB/MI Ada Tasking Commands::
24638 * GDB/MI Program Execution::
24639 * GDB/MI Stack Manipulation::
24640 * GDB/MI Variable Objects::
24641 * GDB/MI Data Manipulation::
24642 * GDB/MI Tracepoint Commands::
24643 * GDB/MI Symbol Query::
24644 * GDB/MI File Commands::
24646 * GDB/MI Kod Commands::
24647 * GDB/MI Memory Overlay Commands::
24648 * GDB/MI Signal Handling Commands::
24650 * GDB/MI Target Manipulation::
24651 * GDB/MI File Transfer Commands::
24652 * GDB/MI Ada Exceptions Commands::
24653 * GDB/MI Support Commands::
24654 * GDB/MI Miscellaneous Commands::
24657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24658 @node GDB/MI General Design
24659 @section @sc{gdb/mi} General Design
24660 @cindex GDB/MI General Design
24662 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24663 parts---commands sent to @value{GDBN}, responses to those commands
24664 and notifications. Each command results in exactly one response,
24665 indicating either successful completion of the command, or an error.
24666 For the commands that do not resume the target, the response contains the
24667 requested information. For the commands that resume the target, the
24668 response only indicates whether the target was successfully resumed.
24669 Notifications is the mechanism for reporting changes in the state of the
24670 target, or in @value{GDBN} state, that cannot conveniently be associated with
24671 a command and reported as part of that command response.
24673 The important examples of notifications are:
24677 Exec notifications. These are used to report changes in
24678 target state---when a target is resumed, or stopped. It would not
24679 be feasible to include this information in response of resuming
24680 commands, because one resume commands can result in multiple events in
24681 different threads. Also, quite some time may pass before any event
24682 happens in the target, while a frontend needs to know whether the resuming
24683 command itself was successfully executed.
24686 Console output, and status notifications. Console output
24687 notifications are used to report output of CLI commands, as well as
24688 diagnostics for other commands. Status notifications are used to
24689 report the progress of a long-running operation. Naturally, including
24690 this information in command response would mean no output is produced
24691 until the command is finished, which is undesirable.
24694 General notifications. Commands may have various side effects on
24695 the @value{GDBN} or target state beyond their official purpose. For example,
24696 a command may change the selected thread. Although such changes can
24697 be included in command response, using notification allows for more
24698 orthogonal frontend design.
24702 There's no guarantee that whenever an MI command reports an error,
24703 @value{GDBN} or the target are in any specific state, and especially,
24704 the state is not reverted to the state before the MI command was
24705 processed. Therefore, whenever an MI command results in an error,
24706 we recommend that the frontend refreshes all the information shown in
24707 the user interface.
24711 * Context management::
24712 * Asynchronous and non-stop modes::
24716 @node Context management
24717 @subsection Context management
24719 @subsubsection Threads and Frames
24721 In most cases when @value{GDBN} accesses the target, this access is
24722 done in context of a specific thread and frame (@pxref{Frames}).
24723 Often, even when accessing global data, the target requires that a thread
24724 be specified. The CLI interface maintains the selected thread and frame,
24725 and supplies them to target on each command. This is convenient,
24726 because a command line user would not want to specify that information
24727 explicitly on each command, and because user interacts with
24728 @value{GDBN} via a single terminal, so no confusion is possible as
24729 to what thread and frame are the current ones.
24731 In the case of MI, the concept of selected thread and frame is less
24732 useful. First, a frontend can easily remember this information
24733 itself. Second, a graphical frontend can have more than one window,
24734 each one used for debugging a different thread, and the frontend might
24735 want to access additional threads for internal purposes. This
24736 increases the risk that by relying on implicitly selected thread, the
24737 frontend may be operating on a wrong one. Therefore, each MI command
24738 should explicitly specify which thread and frame to operate on. To
24739 make it possible, each MI command accepts the @samp{--thread} and
24740 @samp{--frame} options, the value to each is @value{GDBN} identifier
24741 for thread and frame to operate on.
24743 Usually, each top-level window in a frontend allows the user to select
24744 a thread and a frame, and remembers the user selection for further
24745 operations. However, in some cases @value{GDBN} may suggest that the
24746 current thread be changed. For example, when stopping on a breakpoint
24747 it is reasonable to switch to the thread where breakpoint is hit. For
24748 another example, if the user issues the CLI @samp{thread} command via
24749 the frontend, it is desirable to change the frontend's selected thread to the
24750 one specified by user. @value{GDBN} communicates the suggestion to
24751 change current thread using the @samp{=thread-selected} notification.
24752 No such notification is available for the selected frame at the moment.
24754 Note that historically, MI shares the selected thread with CLI, so
24755 frontends used the @code{-thread-select} to execute commands in the
24756 right context. However, getting this to work right is cumbersome. The
24757 simplest way is for frontend to emit @code{-thread-select} command
24758 before every command. This doubles the number of commands that need
24759 to be sent. The alternative approach is to suppress @code{-thread-select}
24760 if the selected thread in @value{GDBN} is supposed to be identical to the
24761 thread the frontend wants to operate on. However, getting this
24762 optimization right can be tricky. In particular, if the frontend
24763 sends several commands to @value{GDBN}, and one of the commands changes the
24764 selected thread, then the behaviour of subsequent commands will
24765 change. So, a frontend should either wait for response from such
24766 problematic commands, or explicitly add @code{-thread-select} for
24767 all subsequent commands. No frontend is known to do this exactly
24768 right, so it is suggested to just always pass the @samp{--thread} and
24769 @samp{--frame} options.
24771 @subsubsection Language
24773 The execution of several commands depends on which language is selected.
24774 By default, the current language (@pxref{show language}) is used.
24775 But for commands known to be language-sensitive, it is recommended
24776 to use the @samp{--language} option. This option takes one argument,
24777 which is the name of the language to use while executing the command.
24781 -data-evaluate-expression --language c "sizeof (void*)"
24786 The valid language names are the same names accepted by the
24787 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
24788 @samp{local} or @samp{unknown}.
24790 @node Asynchronous and non-stop modes
24791 @subsection Asynchronous command execution and non-stop mode
24793 On some targets, @value{GDBN} is capable of processing MI commands
24794 even while the target is running. This is called @dfn{asynchronous
24795 command execution} (@pxref{Background Execution}). The frontend may
24796 specify a preferrence for asynchronous execution using the
24797 @code{-gdb-set mi-async 1} command, which should be emitted before
24798 either running the executable or attaching to the target. After the
24799 frontend has started the executable or attached to the target, it can
24800 find if asynchronous execution is enabled using the
24801 @code{-list-target-features} command.
24804 @item -gdb-set mi-async on
24805 @item -gdb-set mi-async off
24806 Set whether MI is in asynchronous mode.
24808 When @code{off}, which is the default, MI execution commands (e.g.,
24809 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
24810 for the program to stop before processing further commands.
24812 When @code{on}, MI execution commands are background execution
24813 commands (e.g., @code{-exec-continue} becomes the equivalent of the
24814 @code{c&} CLI command), and so @value{GDBN} is capable of processing
24815 MI commands even while the target is running.
24817 @item -gdb-show mi-async
24818 Show whether MI asynchronous mode is enabled.
24821 Note: In @value{GDBN} version 7.7 and earlier, this option was called
24822 @code{target-async} instead of @code{mi-async}, and it had the effect
24823 of both putting MI in asynchronous mode and making CLI background
24824 commands possible. CLI background commands are now always possible
24825 ``out of the box'' if the target supports them. The old spelling is
24826 kept as a deprecated alias for backwards compatibility.
24828 Even if @value{GDBN} can accept a command while target is running,
24829 many commands that access the target do not work when the target is
24830 running. Therefore, asynchronous command execution is most useful
24831 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24832 it is possible to examine the state of one thread, while other threads
24835 When a given thread is running, MI commands that try to access the
24836 target in the context of that thread may not work, or may work only on
24837 some targets. In particular, commands that try to operate on thread's
24838 stack will not work, on any target. Commands that read memory, or
24839 modify breakpoints, may work or not work, depending on the target. Note
24840 that even commands that operate on global state, such as @code{print},
24841 @code{set}, and breakpoint commands, still access the target in the
24842 context of a specific thread, so frontend should try to find a
24843 stopped thread and perform the operation on that thread (using the
24844 @samp{--thread} option).
24846 Which commands will work in the context of a running thread is
24847 highly target dependent. However, the two commands
24848 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24849 to find the state of a thread, will always work.
24851 @node Thread groups
24852 @subsection Thread groups
24853 @value{GDBN} may be used to debug several processes at the same time.
24854 On some platfroms, @value{GDBN} may support debugging of several
24855 hardware systems, each one having several cores with several different
24856 processes running on each core. This section describes the MI
24857 mechanism to support such debugging scenarios.
24859 The key observation is that regardless of the structure of the
24860 target, MI can have a global list of threads, because most commands that
24861 accept the @samp{--thread} option do not need to know what process that
24862 thread belongs to. Therefore, it is not necessary to introduce
24863 neither additional @samp{--process} option, nor an notion of the
24864 current process in the MI interface. The only strictly new feature
24865 that is required is the ability to find how the threads are grouped
24868 To allow the user to discover such grouping, and to support arbitrary
24869 hierarchy of machines/cores/processes, MI introduces the concept of a
24870 @dfn{thread group}. Thread group is a collection of threads and other
24871 thread groups. A thread group always has a string identifier, a type,
24872 and may have additional attributes specific to the type. A new
24873 command, @code{-list-thread-groups}, returns the list of top-level
24874 thread groups, which correspond to processes that @value{GDBN} is
24875 debugging at the moment. By passing an identifier of a thread group
24876 to the @code{-list-thread-groups} command, it is possible to obtain
24877 the members of specific thread group.
24879 To allow the user to easily discover processes, and other objects, he
24880 wishes to debug, a concept of @dfn{available thread group} is
24881 introduced. Available thread group is an thread group that
24882 @value{GDBN} is not debugging, but that can be attached to, using the
24883 @code{-target-attach} command. The list of available top-level thread
24884 groups can be obtained using @samp{-list-thread-groups --available}.
24885 In general, the content of a thread group may be only retrieved only
24886 after attaching to that thread group.
24888 Thread groups are related to inferiors (@pxref{Inferiors and
24889 Programs}). Each inferior corresponds to a thread group of a special
24890 type @samp{process}, and some additional operations are permitted on
24891 such thread groups.
24893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24894 @node GDB/MI Command Syntax
24895 @section @sc{gdb/mi} Command Syntax
24898 * GDB/MI Input Syntax::
24899 * GDB/MI Output Syntax::
24902 @node GDB/MI Input Syntax
24903 @subsection @sc{gdb/mi} Input Syntax
24905 @cindex input syntax for @sc{gdb/mi}
24906 @cindex @sc{gdb/mi}, input syntax
24908 @item @var{command} @expansion{}
24909 @code{@var{cli-command} | @var{mi-command}}
24911 @item @var{cli-command} @expansion{}
24912 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24913 @var{cli-command} is any existing @value{GDBN} CLI command.
24915 @item @var{mi-command} @expansion{}
24916 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24917 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24919 @item @var{token} @expansion{}
24920 "any sequence of digits"
24922 @item @var{option} @expansion{}
24923 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24925 @item @var{parameter} @expansion{}
24926 @code{@var{non-blank-sequence} | @var{c-string}}
24928 @item @var{operation} @expansion{}
24929 @emph{any of the operations described in this chapter}
24931 @item @var{non-blank-sequence} @expansion{}
24932 @emph{anything, provided it doesn't contain special characters such as
24933 "-", @var{nl}, """ and of course " "}
24935 @item @var{c-string} @expansion{}
24936 @code{""" @var{seven-bit-iso-c-string-content} """}
24938 @item @var{nl} @expansion{}
24947 The CLI commands are still handled by the @sc{mi} interpreter; their
24948 output is described below.
24951 The @code{@var{token}}, when present, is passed back when the command
24955 Some @sc{mi} commands accept optional arguments as part of the parameter
24956 list. Each option is identified by a leading @samp{-} (dash) and may be
24957 followed by an optional argument parameter. Options occur first in the
24958 parameter list and can be delimited from normal parameters using
24959 @samp{--} (this is useful when some parameters begin with a dash).
24966 We want easy access to the existing CLI syntax (for debugging).
24969 We want it to be easy to spot a @sc{mi} operation.
24972 @node GDB/MI Output Syntax
24973 @subsection @sc{gdb/mi} Output Syntax
24975 @cindex output syntax of @sc{gdb/mi}
24976 @cindex @sc{gdb/mi}, output syntax
24977 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24978 followed, optionally, by a single result record. This result record
24979 is for the most recent command. The sequence of output records is
24980 terminated by @samp{(gdb)}.
24982 If an input command was prefixed with a @code{@var{token}} then the
24983 corresponding output for that command will also be prefixed by that same
24987 @item @var{output} @expansion{}
24988 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24990 @item @var{result-record} @expansion{}
24991 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24993 @item @var{out-of-band-record} @expansion{}
24994 @code{@var{async-record} | @var{stream-record}}
24996 @item @var{async-record} @expansion{}
24997 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24999 @item @var{exec-async-output} @expansion{}
25000 @code{[ @var{token} ] "*" @var{async-output nl}}
25002 @item @var{status-async-output} @expansion{}
25003 @code{[ @var{token} ] "+" @var{async-output nl}}
25005 @item @var{notify-async-output} @expansion{}
25006 @code{[ @var{token} ] "=" @var{async-output nl}}
25008 @item @var{async-output} @expansion{}
25009 @code{@var{async-class} ( "," @var{result} )*}
25011 @item @var{result-class} @expansion{}
25012 @code{"done" | "running" | "connected" | "error" | "exit"}
25014 @item @var{async-class} @expansion{}
25015 @code{"stopped" | @var{others}} (where @var{others} will be added
25016 depending on the needs---this is still in development).
25018 @item @var{result} @expansion{}
25019 @code{ @var{variable} "=" @var{value}}
25021 @item @var{variable} @expansion{}
25022 @code{ @var{string} }
25024 @item @var{value} @expansion{}
25025 @code{ @var{const} | @var{tuple} | @var{list} }
25027 @item @var{const} @expansion{}
25028 @code{@var{c-string}}
25030 @item @var{tuple} @expansion{}
25031 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25033 @item @var{list} @expansion{}
25034 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25035 @var{result} ( "," @var{result} )* "]" }
25037 @item @var{stream-record} @expansion{}
25038 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25040 @item @var{console-stream-output} @expansion{}
25041 @code{"~" @var{c-string nl}}
25043 @item @var{target-stream-output} @expansion{}
25044 @code{"@@" @var{c-string nl}}
25046 @item @var{log-stream-output} @expansion{}
25047 @code{"&" @var{c-string nl}}
25049 @item @var{nl} @expansion{}
25052 @item @var{token} @expansion{}
25053 @emph{any sequence of digits}.
25061 All output sequences end in a single line containing a period.
25064 The @code{@var{token}} is from the corresponding request. Note that
25065 for all async output, while the token is allowed by the grammar and
25066 may be output by future versions of @value{GDBN} for select async
25067 output messages, it is generally omitted. Frontends should treat
25068 all async output as reporting general changes in the state of the
25069 target and there should be no need to associate async output to any
25073 @cindex status output in @sc{gdb/mi}
25074 @var{status-async-output} contains on-going status information about the
25075 progress of a slow operation. It can be discarded. All status output is
25076 prefixed by @samp{+}.
25079 @cindex async output in @sc{gdb/mi}
25080 @var{exec-async-output} contains asynchronous state change on the target
25081 (stopped, started, disappeared). All async output is prefixed by
25085 @cindex notify output in @sc{gdb/mi}
25086 @var{notify-async-output} contains supplementary information that the
25087 client should handle (e.g., a new breakpoint information). All notify
25088 output is prefixed by @samp{=}.
25091 @cindex console output in @sc{gdb/mi}
25092 @var{console-stream-output} is output that should be displayed as is in the
25093 console. It is the textual response to a CLI command. All the console
25094 output is prefixed by @samp{~}.
25097 @cindex target output in @sc{gdb/mi}
25098 @var{target-stream-output} is the output produced by the target program.
25099 All the target output is prefixed by @samp{@@}.
25102 @cindex log output in @sc{gdb/mi}
25103 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25104 instance messages that should be displayed as part of an error log. All
25105 the log output is prefixed by @samp{&}.
25108 @cindex list output in @sc{gdb/mi}
25109 New @sc{gdb/mi} commands should only output @var{lists} containing
25115 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25116 details about the various output records.
25118 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25119 @node GDB/MI Compatibility with CLI
25120 @section @sc{gdb/mi} Compatibility with CLI
25122 @cindex compatibility, @sc{gdb/mi} and CLI
25123 @cindex @sc{gdb/mi}, compatibility with CLI
25125 For the developers convenience CLI commands can be entered directly,
25126 but there may be some unexpected behaviour. For example, commands
25127 that query the user will behave as if the user replied yes, breakpoint
25128 command lists are not executed and some CLI commands, such as
25129 @code{if}, @code{when} and @code{define}, prompt for further input with
25130 @samp{>}, which is not valid MI output.
25132 This feature may be removed at some stage in the future and it is
25133 recommended that front ends use the @code{-interpreter-exec} command
25134 (@pxref{-interpreter-exec}).
25136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25137 @node GDB/MI Development and Front Ends
25138 @section @sc{gdb/mi} Development and Front Ends
25139 @cindex @sc{gdb/mi} development
25141 The application which takes the MI output and presents the state of the
25142 program being debugged to the user is called a @dfn{front end}.
25144 Although @sc{gdb/mi} is still incomplete, it is currently being used
25145 by a variety of front ends to @value{GDBN}. This makes it difficult
25146 to introduce new functionality without breaking existing usage. This
25147 section tries to minimize the problems by describing how the protocol
25150 Some changes in MI need not break a carefully designed front end, and
25151 for these the MI version will remain unchanged. The following is a
25152 list of changes that may occur within one level, so front ends should
25153 parse MI output in a way that can handle them:
25157 New MI commands may be added.
25160 New fields may be added to the output of any MI command.
25163 The range of values for fields with specified values, e.g.,
25164 @code{in_scope} (@pxref{-var-update}) may be extended.
25166 @c The format of field's content e.g type prefix, may change so parse it
25167 @c at your own risk. Yes, in general?
25169 @c The order of fields may change? Shouldn't really matter but it might
25170 @c resolve inconsistencies.
25173 If the changes are likely to break front ends, the MI version level
25174 will be increased by one. This will allow the front end to parse the
25175 output according to the MI version. Apart from mi0, new versions of
25176 @value{GDBN} will not support old versions of MI and it will be the
25177 responsibility of the front end to work with the new one.
25179 @c Starting with mi3, add a new command -mi-version that prints the MI
25182 The best way to avoid unexpected changes in MI that might break your front
25183 end is to make your project known to @value{GDBN} developers and
25184 follow development on @email{gdb@@sourceware.org} and
25185 @email{gdb-patches@@sourceware.org}.
25186 @cindex mailing lists
25188 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25189 @node GDB/MI Output Records
25190 @section @sc{gdb/mi} Output Records
25193 * GDB/MI Result Records::
25194 * GDB/MI Stream Records::
25195 * GDB/MI Async Records::
25196 * GDB/MI Breakpoint Information::
25197 * GDB/MI Frame Information::
25198 * GDB/MI Thread Information::
25199 * GDB/MI Ada Exception Information::
25202 @node GDB/MI Result Records
25203 @subsection @sc{gdb/mi} Result Records
25205 @cindex result records in @sc{gdb/mi}
25206 @cindex @sc{gdb/mi}, result records
25207 In addition to a number of out-of-band notifications, the response to a
25208 @sc{gdb/mi} command includes one of the following result indications:
25212 @item "^done" [ "," @var{results} ]
25213 The synchronous operation was successful, @code{@var{results}} are the return
25218 This result record is equivalent to @samp{^done}. Historically, it
25219 was output instead of @samp{^done} if the command has resumed the
25220 target. This behaviour is maintained for backward compatibility, but
25221 all frontends should treat @samp{^done} and @samp{^running}
25222 identically and rely on the @samp{*running} output record to determine
25223 which threads are resumed.
25227 @value{GDBN} has connected to a remote target.
25229 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25231 The operation failed. The @code{msg=@var{c-string}} variable contains
25232 the corresponding error message.
25234 If present, the @code{code=@var{c-string}} variable provides an error
25235 code on which consumers can rely on to detect the corresponding
25236 error condition. At present, only one error code is defined:
25239 @item "undefined-command"
25240 Indicates that the command causing the error does not exist.
25245 @value{GDBN} has terminated.
25249 @node GDB/MI Stream Records
25250 @subsection @sc{gdb/mi} Stream Records
25252 @cindex @sc{gdb/mi}, stream records
25253 @cindex stream records in @sc{gdb/mi}
25254 @value{GDBN} internally maintains a number of output streams: the console, the
25255 target, and the log. The output intended for each of these streams is
25256 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25258 Each stream record begins with a unique @dfn{prefix character} which
25259 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25260 Syntax}). In addition to the prefix, each stream record contains a
25261 @code{@var{string-output}}. This is either raw text (with an implicit new
25262 line) or a quoted C string (which does not contain an implicit newline).
25265 @item "~" @var{string-output}
25266 The console output stream contains text that should be displayed in the
25267 CLI console window. It contains the textual responses to CLI commands.
25269 @item "@@" @var{string-output}
25270 The target output stream contains any textual output from the running
25271 target. This is only present when GDB's event loop is truly
25272 asynchronous, which is currently only the case for remote targets.
25274 @item "&" @var{string-output}
25275 The log stream contains debugging messages being produced by @value{GDBN}'s
25279 @node GDB/MI Async Records
25280 @subsection @sc{gdb/mi} Async Records
25282 @cindex async records in @sc{gdb/mi}
25283 @cindex @sc{gdb/mi}, async records
25284 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25285 additional changes that have occurred. Those changes can either be a
25286 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25287 target activity (e.g., target stopped).
25289 The following is the list of possible async records:
25293 @item *running,thread-id="@var{thread}"
25294 The target is now running. The @var{thread} field tells which
25295 specific thread is now running, and can be @samp{all} if all threads
25296 are running. The frontend should assume that no interaction with a
25297 running thread is possible after this notification is produced.
25298 The frontend should not assume that this notification is output
25299 only once for any command. @value{GDBN} may emit this notification
25300 several times, either for different threads, because it cannot resume
25301 all threads together, or even for a single thread, if the thread must
25302 be stepped though some code before letting it run freely.
25304 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25305 The target has stopped. The @var{reason} field can have one of the
25309 @item breakpoint-hit
25310 A breakpoint was reached.
25311 @item watchpoint-trigger
25312 A watchpoint was triggered.
25313 @item read-watchpoint-trigger
25314 A read watchpoint was triggered.
25315 @item access-watchpoint-trigger
25316 An access watchpoint was triggered.
25317 @item function-finished
25318 An -exec-finish or similar CLI command was accomplished.
25319 @item location-reached
25320 An -exec-until or similar CLI command was accomplished.
25321 @item watchpoint-scope
25322 A watchpoint has gone out of scope.
25323 @item end-stepping-range
25324 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25325 similar CLI command was accomplished.
25326 @item exited-signalled
25327 The inferior exited because of a signal.
25329 The inferior exited.
25330 @item exited-normally
25331 The inferior exited normally.
25332 @item signal-received
25333 A signal was received by the inferior.
25335 The inferior has stopped due to a library being loaded or unloaded.
25336 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25337 set or when a @code{catch load} or @code{catch unload} catchpoint is
25338 in use (@pxref{Set Catchpoints}).
25340 The inferior has forked. This is reported when @code{catch fork}
25341 (@pxref{Set Catchpoints}) has been used.
25343 The inferior has vforked. This is reported in when @code{catch vfork}
25344 (@pxref{Set Catchpoints}) has been used.
25345 @item syscall-entry
25346 The inferior entered a system call. This is reported when @code{catch
25347 syscall} (@pxref{Set Catchpoints}) has been used.
25348 @item syscall-entry
25349 The inferior returned from a system call. This is reported when
25350 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25352 The inferior called @code{exec}. This is reported when @code{catch exec}
25353 (@pxref{Set Catchpoints}) has been used.
25356 The @var{id} field identifies the thread that directly caused the stop
25357 -- for example by hitting a breakpoint. Depending on whether all-stop
25358 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25359 stop all threads, or only the thread that directly triggered the stop.
25360 If all threads are stopped, the @var{stopped} field will have the
25361 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25362 field will be a list of thread identifiers. Presently, this list will
25363 always include a single thread, but frontend should be prepared to see
25364 several threads in the list. The @var{core} field reports the
25365 processor core on which the stop event has happened. This field may be absent
25366 if such information is not available.
25368 @item =thread-group-added,id="@var{id}"
25369 @itemx =thread-group-removed,id="@var{id}"
25370 A thread group was either added or removed. The @var{id} field
25371 contains the @value{GDBN} identifier of the thread group. When a thread
25372 group is added, it generally might not be associated with a running
25373 process. When a thread group is removed, its id becomes invalid and
25374 cannot be used in any way.
25376 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25377 A thread group became associated with a running program,
25378 either because the program was just started or the thread group
25379 was attached to a program. The @var{id} field contains the
25380 @value{GDBN} identifier of the thread group. The @var{pid} field
25381 contains process identifier, specific to the operating system.
25383 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25384 A thread group is no longer associated with a running program,
25385 either because the program has exited, or because it was detached
25386 from. The @var{id} field contains the @value{GDBN} identifier of the
25387 thread group. The @var{code} field is the exit code of the inferior; it exists
25388 only when the inferior exited with some code.
25390 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25391 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25392 A thread either was created, or has exited. The @var{id} field
25393 contains the @value{GDBN} identifier of the thread. The @var{gid}
25394 field identifies the thread group this thread belongs to.
25396 @item =thread-selected,id="@var{id}"
25397 Informs that the selected thread was changed as result of the last
25398 command. This notification is not emitted as result of @code{-thread-select}
25399 command but is emitted whenever an MI command that is not documented
25400 to change the selected thread actually changes it. In particular,
25401 invoking, directly or indirectly (via user-defined command), the CLI
25402 @code{thread} command, will generate this notification.
25404 We suggest that in response to this notification, front ends
25405 highlight the selected thread and cause subsequent commands to apply to
25408 @item =library-loaded,...
25409 Reports that a new library file was loaded by the program. This
25410 notification has 4 fields---@var{id}, @var{target-name},
25411 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25412 opaque identifier of the library. For remote debugging case,
25413 @var{target-name} and @var{host-name} fields give the name of the
25414 library file on the target, and on the host respectively. For native
25415 debugging, both those fields have the same value. The
25416 @var{symbols-loaded} field is emitted only for backward compatibility
25417 and should not be relied on to convey any useful information. The
25418 @var{thread-group} field, if present, specifies the id of the thread
25419 group in whose context the library was loaded. If the field is
25420 absent, it means the library was loaded in the context of all present
25423 @item =library-unloaded,...
25424 Reports that a library was unloaded by the program. This notification
25425 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25426 the same meaning as for the @code{=library-loaded} notification.
25427 The @var{thread-group} field, if present, specifies the id of the
25428 thread group in whose context the library was unloaded. If the field is
25429 absent, it means the library was unloaded in the context of all present
25432 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25433 @itemx =traceframe-changed,end
25434 Reports that the trace frame was changed and its new number is
25435 @var{tfnum}. The number of the tracepoint associated with this trace
25436 frame is @var{tpnum}.
25438 @item =tsv-created,name=@var{name},initial=@var{initial}
25439 Reports that the new trace state variable @var{name} is created with
25440 initial value @var{initial}.
25442 @item =tsv-deleted,name=@var{name}
25443 @itemx =tsv-deleted
25444 Reports that the trace state variable @var{name} is deleted or all
25445 trace state variables are deleted.
25447 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25448 Reports that the trace state variable @var{name} is modified with
25449 the initial value @var{initial}. The current value @var{current} of
25450 trace state variable is optional and is reported if the current
25451 value of trace state variable is known.
25453 @item =breakpoint-created,bkpt=@{...@}
25454 @itemx =breakpoint-modified,bkpt=@{...@}
25455 @itemx =breakpoint-deleted,id=@var{number}
25456 Reports that a breakpoint was created, modified, or deleted,
25457 respectively. Only user-visible breakpoints are reported to the MI
25460 The @var{bkpt} argument is of the same form as returned by the various
25461 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25462 @var{number} is the ordinal number of the breakpoint.
25464 Note that if a breakpoint is emitted in the result record of a
25465 command, then it will not also be emitted in an async record.
25467 @item =record-started,thread-group="@var{id}"
25468 @itemx =record-stopped,thread-group="@var{id}"
25469 Execution log recording was either started or stopped on an
25470 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25471 group corresponding to the affected inferior.
25473 @item =cmd-param-changed,param=@var{param},value=@var{value}
25474 Reports that a parameter of the command @code{set @var{param}} is
25475 changed to @var{value}. In the multi-word @code{set} command,
25476 the @var{param} is the whole parameter list to @code{set} command.
25477 For example, In command @code{set check type on}, @var{param}
25478 is @code{check type} and @var{value} is @code{on}.
25480 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25481 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25482 written in an inferior. The @var{id} is the identifier of the
25483 thread group corresponding to the affected inferior. The optional
25484 @code{type="code"} part is reported if the memory written to holds
25488 @node GDB/MI Breakpoint Information
25489 @subsection @sc{gdb/mi} Breakpoint Information
25491 When @value{GDBN} reports information about a breakpoint, a
25492 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25497 The breakpoint number. For a breakpoint that represents one location
25498 of a multi-location breakpoint, this will be a dotted pair, like
25502 The type of the breakpoint. For ordinary breakpoints this will be
25503 @samp{breakpoint}, but many values are possible.
25506 If the type of the breakpoint is @samp{catchpoint}, then this
25507 indicates the exact type of catchpoint.
25510 This is the breakpoint disposition---either @samp{del}, meaning that
25511 the breakpoint will be deleted at the next stop, or @samp{keep},
25512 meaning that the breakpoint will not be deleted.
25515 This indicates whether the breakpoint is enabled, in which case the
25516 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25517 Note that this is not the same as the field @code{enable}.
25520 The address of the breakpoint. This may be a hexidecimal number,
25521 giving the address; or the string @samp{<PENDING>}, for a pending
25522 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25523 multiple locations. This field will not be present if no address can
25524 be determined. For example, a watchpoint does not have an address.
25527 If known, the function in which the breakpoint appears.
25528 If not known, this field is not present.
25531 The name of the source file which contains this function, if known.
25532 If not known, this field is not present.
25535 The full file name of the source file which contains this function, if
25536 known. If not known, this field is not present.
25539 The line number at which this breakpoint appears, if known.
25540 If not known, this field is not present.
25543 If the source file is not known, this field may be provided. If
25544 provided, this holds the address of the breakpoint, possibly followed
25548 If this breakpoint is pending, this field is present and holds the
25549 text used to set the breakpoint, as entered by the user.
25552 Where this breakpoint's condition is evaluated, either @samp{host} or
25556 If this is a thread-specific breakpoint, then this identifies the
25557 thread in which the breakpoint can trigger.
25560 If this breakpoint is restricted to a particular Ada task, then this
25561 field will hold the task identifier.
25564 If the breakpoint is conditional, this is the condition expression.
25567 The ignore count of the breakpoint.
25570 The enable count of the breakpoint.
25572 @item traceframe-usage
25575 @item static-tracepoint-marker-string-id
25576 For a static tracepoint, the name of the static tracepoint marker.
25579 For a masked watchpoint, this is the mask.
25582 A tracepoint's pass count.
25584 @item original-location
25585 The location of the breakpoint as originally specified by the user.
25586 This field is optional.
25589 The number of times the breakpoint has been hit.
25592 This field is only given for tracepoints. This is either @samp{y},
25593 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25597 Some extra data, the exact contents of which are type-dependent.
25601 For example, here is what the output of @code{-break-insert}
25602 (@pxref{GDB/MI Breakpoint Commands}) might be:
25605 -> -break-insert main
25606 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25607 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25608 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25613 @node GDB/MI Frame Information
25614 @subsection @sc{gdb/mi} Frame Information
25616 Response from many MI commands includes an information about stack
25617 frame. This information is a tuple that may have the following
25622 The level of the stack frame. The innermost frame has the level of
25623 zero. This field is always present.
25626 The name of the function corresponding to the frame. This field may
25627 be absent if @value{GDBN} is unable to determine the function name.
25630 The code address for the frame. This field is always present.
25633 The name of the source files that correspond to the frame's code
25634 address. This field may be absent.
25637 The source line corresponding to the frames' code address. This field
25641 The name of the binary file (either executable or shared library) the
25642 corresponds to the frame's code address. This field may be absent.
25646 @node GDB/MI Thread Information
25647 @subsection @sc{gdb/mi} Thread Information
25649 Whenever @value{GDBN} has to report an information about a thread, it
25650 uses a tuple with the following fields:
25654 The numeric id assigned to the thread by @value{GDBN}. This field is
25658 Target-specific string identifying the thread. This field is always present.
25661 Additional information about the thread provided by the target.
25662 It is supposed to be human-readable and not interpreted by the
25663 frontend. This field is optional.
25666 Either @samp{stopped} or @samp{running}, depending on whether the
25667 thread is presently running. This field is always present.
25670 The value of this field is an integer number of the processor core the
25671 thread was last seen on. This field is optional.
25674 @node GDB/MI Ada Exception Information
25675 @subsection @sc{gdb/mi} Ada Exception Information
25677 Whenever a @code{*stopped} record is emitted because the program
25678 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25679 @value{GDBN} provides the name of the exception that was raised via
25680 the @code{exception-name} field.
25682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25683 @node GDB/MI Simple Examples
25684 @section Simple Examples of @sc{gdb/mi} Interaction
25685 @cindex @sc{gdb/mi}, simple examples
25687 This subsection presents several simple examples of interaction using
25688 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25689 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25690 the output received from @sc{gdb/mi}.
25692 Note the line breaks shown in the examples are here only for
25693 readability, they don't appear in the real output.
25695 @subheading Setting a Breakpoint
25697 Setting a breakpoint generates synchronous output which contains detailed
25698 information of the breakpoint.
25701 -> -break-insert main
25702 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25703 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25704 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25709 @subheading Program Execution
25711 Program execution generates asynchronous records and MI gives the
25712 reason that execution stopped.
25718 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25719 frame=@{addr="0x08048564",func="main",
25720 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25721 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25726 <- *stopped,reason="exited-normally"
25730 @subheading Quitting @value{GDBN}
25732 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25740 Please note that @samp{^exit} is printed immediately, but it might
25741 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25742 performs necessary cleanups, including killing programs being debugged
25743 or disconnecting from debug hardware, so the frontend should wait till
25744 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25745 fails to exit in reasonable time.
25747 @subheading A Bad Command
25749 Here's what happens if you pass a non-existent command:
25753 <- ^error,msg="Undefined MI command: rubbish"
25758 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25759 @node GDB/MI Command Description Format
25760 @section @sc{gdb/mi} Command Description Format
25762 The remaining sections describe blocks of commands. Each block of
25763 commands is laid out in a fashion similar to this section.
25765 @subheading Motivation
25767 The motivation for this collection of commands.
25769 @subheading Introduction
25771 A brief introduction to this collection of commands as a whole.
25773 @subheading Commands
25775 For each command in the block, the following is described:
25777 @subsubheading Synopsis
25780 -command @var{args}@dots{}
25783 @subsubheading Result
25785 @subsubheading @value{GDBN} Command
25787 The corresponding @value{GDBN} CLI command(s), if any.
25789 @subsubheading Example
25791 Example(s) formatted for readability. Some of the described commands have
25792 not been implemented yet and these are labeled N.A.@: (not available).
25795 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25796 @node GDB/MI Breakpoint Commands
25797 @section @sc{gdb/mi} Breakpoint Commands
25799 @cindex breakpoint commands for @sc{gdb/mi}
25800 @cindex @sc{gdb/mi}, breakpoint commands
25801 This section documents @sc{gdb/mi} commands for manipulating
25804 @subheading The @code{-break-after} Command
25805 @findex -break-after
25807 @subsubheading Synopsis
25810 -break-after @var{number} @var{count}
25813 The breakpoint number @var{number} is not in effect until it has been
25814 hit @var{count} times. To see how this is reflected in the output of
25815 the @samp{-break-list} command, see the description of the
25816 @samp{-break-list} command below.
25818 @subsubheading @value{GDBN} Command
25820 The corresponding @value{GDBN} command is @samp{ignore}.
25822 @subsubheading Example
25827 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25828 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25829 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25837 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25838 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25839 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25840 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25841 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25842 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25843 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25844 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25845 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25846 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
25851 @subheading The @code{-break-catch} Command
25852 @findex -break-catch
25855 @subheading The @code{-break-commands} Command
25856 @findex -break-commands
25858 @subsubheading Synopsis
25861 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25864 Specifies the CLI commands that should be executed when breakpoint
25865 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25866 are the commands. If no command is specified, any previously-set
25867 commands are cleared. @xref{Break Commands}. Typical use of this
25868 functionality is tracing a program, that is, printing of values of
25869 some variables whenever breakpoint is hit and then continuing.
25871 @subsubheading @value{GDBN} Command
25873 The corresponding @value{GDBN} command is @samp{commands}.
25875 @subsubheading Example
25880 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25881 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25882 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25885 -break-commands 1 "print v" "continue"
25890 @subheading The @code{-break-condition} Command
25891 @findex -break-condition
25893 @subsubheading Synopsis
25896 -break-condition @var{number} @var{expr}
25899 Breakpoint @var{number} will stop the program only if the condition in
25900 @var{expr} is true. The condition becomes part of the
25901 @samp{-break-list} output (see the description of the @samp{-break-list}
25904 @subsubheading @value{GDBN} Command
25906 The corresponding @value{GDBN} command is @samp{condition}.
25908 @subsubheading Example
25912 -break-condition 1 1
25916 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25917 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25918 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25919 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25920 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25921 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25922 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25923 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25924 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25925 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
25929 @subheading The @code{-break-delete} Command
25930 @findex -break-delete
25932 @subsubheading Synopsis
25935 -break-delete ( @var{breakpoint} )+
25938 Delete the breakpoint(s) whose number(s) are specified in the argument
25939 list. This is obviously reflected in the breakpoint list.
25941 @subsubheading @value{GDBN} Command
25943 The corresponding @value{GDBN} command is @samp{delete}.
25945 @subsubheading Example
25953 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25954 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25955 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25956 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25957 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25958 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25959 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25964 @subheading The @code{-break-disable} Command
25965 @findex -break-disable
25967 @subsubheading Synopsis
25970 -break-disable ( @var{breakpoint} )+
25973 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25974 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25976 @subsubheading @value{GDBN} Command
25978 The corresponding @value{GDBN} command is @samp{disable}.
25980 @subsubheading Example
25988 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25989 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25990 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25991 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25992 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25993 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25994 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25995 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25996 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25997 line="5",thread-groups=["i1"],times="0"@}]@}
26001 @subheading The @code{-break-enable} Command
26002 @findex -break-enable
26004 @subsubheading Synopsis
26007 -break-enable ( @var{breakpoint} )+
26010 Enable (previously disabled) @var{breakpoint}(s).
26012 @subsubheading @value{GDBN} Command
26014 The corresponding @value{GDBN} command is @samp{enable}.
26016 @subsubheading Example
26024 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26025 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26026 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26027 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26028 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26029 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26030 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26031 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26032 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26033 line="5",thread-groups=["i1"],times="0"@}]@}
26037 @subheading The @code{-break-info} Command
26038 @findex -break-info
26040 @subsubheading Synopsis
26043 -break-info @var{breakpoint}
26047 Get information about a single breakpoint.
26049 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26050 Information}, for details on the format of each breakpoint in the
26053 @subsubheading @value{GDBN} Command
26055 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26057 @subsubheading Example
26060 @subheading The @code{-break-insert} Command
26061 @findex -break-insert
26063 @subsubheading Synopsis
26066 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26067 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26068 [ -p @var{thread-id} ] [ @var{location} ]
26072 If specified, @var{location}, can be one of:
26079 @item filename:linenum
26080 @item filename:function
26084 The possible optional parameters of this command are:
26088 Insert a temporary breakpoint.
26090 Insert a hardware breakpoint.
26092 If @var{location} cannot be parsed (for example if it
26093 refers to unknown files or functions), create a pending
26094 breakpoint. Without this flag, @value{GDBN} will report
26095 an error, and won't create a breakpoint, if @var{location}
26098 Create a disabled breakpoint.
26100 Create a tracepoint. @xref{Tracepoints}. When this parameter
26101 is used together with @samp{-h}, a fast tracepoint is created.
26102 @item -c @var{condition}
26103 Make the breakpoint conditional on @var{condition}.
26104 @item -i @var{ignore-count}
26105 Initialize the @var{ignore-count}.
26106 @item -p @var{thread-id}
26107 Restrict the breakpoint to the specified @var{thread-id}.
26110 @subsubheading Result
26112 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26113 resulting breakpoint.
26115 Note: this format is open to change.
26116 @c An out-of-band breakpoint instead of part of the result?
26118 @subsubheading @value{GDBN} Command
26120 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26121 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26123 @subsubheading Example
26128 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26129 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26132 -break-insert -t foo
26133 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26134 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26138 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26139 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26140 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26141 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26142 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26143 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26144 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26145 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26146 addr="0x0001072c", func="main",file="recursive2.c",
26147 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26149 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26150 addr="0x00010774",func="foo",file="recursive2.c",
26151 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26154 @c -break-insert -r foo.*
26155 @c ~int foo(int, int);
26156 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26157 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26162 @subheading The @code{-dprintf-insert} Command
26163 @findex -dprintf-insert
26165 @subsubheading Synopsis
26168 -dprintf-insert [ -t ] [ -f ] [ -d ]
26169 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26170 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26175 If specified, @var{location}, can be one of:
26178 @item @var{function}
26181 @c @item @var{linenum}
26182 @item @var{filename}:@var{linenum}
26183 @item @var{filename}:function
26184 @item *@var{address}
26187 The possible optional parameters of this command are:
26191 Insert a temporary breakpoint.
26193 If @var{location} cannot be parsed (for example, if it
26194 refers to unknown files or functions), create a pending
26195 breakpoint. Without this flag, @value{GDBN} will report
26196 an error, and won't create a breakpoint, if @var{location}
26199 Create a disabled breakpoint.
26200 @item -c @var{condition}
26201 Make the breakpoint conditional on @var{condition}.
26202 @item -i @var{ignore-count}
26203 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26204 to @var{ignore-count}.
26205 @item -p @var{thread-id}
26206 Restrict the breakpoint to the specified @var{thread-id}.
26209 @subsubheading Result
26211 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26212 resulting breakpoint.
26214 @c An out-of-band breakpoint instead of part of the result?
26216 @subsubheading @value{GDBN} Command
26218 The corresponding @value{GDBN} command is @samp{dprintf}.
26220 @subsubheading Example
26224 4-dprintf-insert foo "At foo entry\n"
26225 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26226 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26227 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26228 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26229 original-location="foo"@}
26231 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26232 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26233 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26234 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26235 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26236 original-location="mi-dprintf.c:26"@}
26240 @subheading The @code{-break-list} Command
26241 @findex -break-list
26243 @subsubheading Synopsis
26249 Displays the list of inserted breakpoints, showing the following fields:
26253 number of the breakpoint
26255 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26257 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26260 is the breakpoint enabled or no: @samp{y} or @samp{n}
26262 memory location at which the breakpoint is set
26264 logical location of the breakpoint, expressed by function name, file
26266 @item Thread-groups
26267 list of thread groups to which this breakpoint applies
26269 number of times the breakpoint has been hit
26272 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26273 @code{body} field is an empty list.
26275 @subsubheading @value{GDBN} Command
26277 The corresponding @value{GDBN} command is @samp{info break}.
26279 @subsubheading Example
26284 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26285 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26286 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26287 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26288 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26289 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26290 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26291 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26292 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26294 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26295 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26296 line="13",thread-groups=["i1"],times="0"@}]@}
26300 Here's an example of the result when there are no breakpoints:
26305 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26306 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26307 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26308 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26309 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26310 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26311 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26316 @subheading The @code{-break-passcount} Command
26317 @findex -break-passcount
26319 @subsubheading Synopsis
26322 -break-passcount @var{tracepoint-number} @var{passcount}
26325 Set the passcount for tracepoint @var{tracepoint-number} to
26326 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26327 is not a tracepoint, error is emitted. This corresponds to CLI
26328 command @samp{passcount}.
26330 @subheading The @code{-break-watch} Command
26331 @findex -break-watch
26333 @subsubheading Synopsis
26336 -break-watch [ -a | -r ]
26339 Create a watchpoint. With the @samp{-a} option it will create an
26340 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26341 read from or on a write to the memory location. With the @samp{-r}
26342 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26343 trigger only when the memory location is accessed for reading. Without
26344 either of the options, the watchpoint created is a regular watchpoint,
26345 i.e., it will trigger when the memory location is accessed for writing.
26346 @xref{Set Watchpoints, , Setting Watchpoints}.
26348 Note that @samp{-break-list} will report a single list of watchpoints and
26349 breakpoints inserted.
26351 @subsubheading @value{GDBN} Command
26353 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26356 @subsubheading Example
26358 Setting a watchpoint on a variable in the @code{main} function:
26363 ^done,wpt=@{number="2",exp="x"@}
26368 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26369 value=@{old="-268439212",new="55"@},
26370 frame=@{func="main",args=[],file="recursive2.c",
26371 fullname="/home/foo/bar/recursive2.c",line="5"@}
26375 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26376 the program execution twice: first for the variable changing value, then
26377 for the watchpoint going out of scope.
26382 ^done,wpt=@{number="5",exp="C"@}
26387 *stopped,reason="watchpoint-trigger",
26388 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26389 frame=@{func="callee4",args=[],
26390 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26391 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26396 *stopped,reason="watchpoint-scope",wpnum="5",
26397 frame=@{func="callee3",args=[@{name="strarg",
26398 value="0x11940 \"A string argument.\""@}],
26399 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26400 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26404 Listing breakpoints and watchpoints, at different points in the program
26405 execution. Note that once the watchpoint goes out of scope, it is
26411 ^done,wpt=@{number="2",exp="C"@}
26414 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26415 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26416 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26417 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26418 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26419 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26420 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26421 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26422 addr="0x00010734",func="callee4",
26423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26424 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26426 bkpt=@{number="2",type="watchpoint",disp="keep",
26427 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26432 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26433 value=@{old="-276895068",new="3"@},
26434 frame=@{func="callee4",args=[],
26435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26436 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26439 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26440 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26441 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26442 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26443 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26444 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26445 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26446 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26447 addr="0x00010734",func="callee4",
26448 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26449 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26451 bkpt=@{number="2",type="watchpoint",disp="keep",
26452 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26456 ^done,reason="watchpoint-scope",wpnum="2",
26457 frame=@{func="callee3",args=[@{name="strarg",
26458 value="0x11940 \"A string argument.\""@}],
26459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26460 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26463 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26464 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26465 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26466 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26467 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26468 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26469 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26470 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26471 addr="0x00010734",func="callee4",
26472 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26473 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26474 thread-groups=["i1"],times="1"@}]@}
26479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26480 @node GDB/MI Catchpoint Commands
26481 @section @sc{gdb/mi} Catchpoint Commands
26483 This section documents @sc{gdb/mi} commands for manipulating
26487 * Shared Library GDB/MI Catchpoint Commands::
26488 * Ada Exception GDB/MI Catchpoint Commands::
26491 @node Shared Library GDB/MI Catchpoint Commands
26492 @subsection Shared Library @sc{gdb/mi} Catchpoints
26494 @subheading The @code{-catch-load} Command
26495 @findex -catch-load
26497 @subsubheading Synopsis
26500 -catch-load [ -t ] [ -d ] @var{regexp}
26503 Add a catchpoint for library load events. If the @samp{-t} option is used,
26504 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26505 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26506 in a disabled state. The @samp{regexp} argument is a regular
26507 expression used to match the name of the loaded library.
26510 @subsubheading @value{GDBN} Command
26512 The corresponding @value{GDBN} command is @samp{catch load}.
26514 @subsubheading Example
26517 -catch-load -t foo.so
26518 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26519 what="load of library matching foo.so",catch-type="load",times="0"@}
26524 @subheading The @code{-catch-unload} Command
26525 @findex -catch-unload
26527 @subsubheading Synopsis
26530 -catch-unload [ -t ] [ -d ] @var{regexp}
26533 Add a catchpoint for library unload events. If the @samp{-t} option is
26534 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26535 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26536 created in a disabled state. The @samp{regexp} argument is a regular
26537 expression used to match the name of the unloaded library.
26539 @subsubheading @value{GDBN} Command
26541 The corresponding @value{GDBN} command is @samp{catch unload}.
26543 @subsubheading Example
26546 -catch-unload -d bar.so
26547 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26548 what="load of library matching bar.so",catch-type="unload",times="0"@}
26552 @node Ada Exception GDB/MI Catchpoint Commands
26553 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26555 The following @sc{gdb/mi} commands can be used to create catchpoints
26556 that stop the execution when Ada exceptions are being raised.
26558 @subheading The @code{-catch-assert} Command
26559 @findex -catch-assert
26561 @subsubheading Synopsis
26564 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26567 Add a catchpoint for failed Ada assertions.
26569 The possible optional parameters for this command are:
26572 @item -c @var{condition}
26573 Make the catchpoint conditional on @var{condition}.
26575 Create a disabled catchpoint.
26577 Create a temporary catchpoint.
26580 @subsubheading @value{GDBN} Command
26582 The corresponding @value{GDBN} command is @samp{catch assert}.
26584 @subsubheading Example
26588 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26589 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26590 thread-groups=["i1"],times="0",
26591 original-location="__gnat_debug_raise_assert_failure"@}
26595 @subheading The @code{-catch-exception} Command
26596 @findex -catch-exception
26598 @subsubheading Synopsis
26601 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26605 Add a catchpoint stopping when Ada exceptions are raised.
26606 By default, the command stops the program when any Ada exception
26607 gets raised. But it is also possible, by using some of the
26608 optional parameters described below, to create more selective
26611 The possible optional parameters for this command are:
26614 @item -c @var{condition}
26615 Make the catchpoint conditional on @var{condition}.
26617 Create a disabled catchpoint.
26618 @item -e @var{exception-name}
26619 Only stop when @var{exception-name} is raised. This option cannot
26620 be used combined with @samp{-u}.
26622 Create a temporary catchpoint.
26624 Stop only when an unhandled exception gets raised. This option
26625 cannot be used combined with @samp{-e}.
26628 @subsubheading @value{GDBN} Command
26630 The corresponding @value{GDBN} commands are @samp{catch exception}
26631 and @samp{catch exception unhandled}.
26633 @subsubheading Example
26636 -catch-exception -e Program_Error
26637 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26638 enabled="y",addr="0x0000000000404874",
26639 what="`Program_Error' Ada exception", thread-groups=["i1"],
26640 times="0",original-location="__gnat_debug_raise_exception"@}
26644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26645 @node GDB/MI Program Context
26646 @section @sc{gdb/mi} Program Context
26648 @subheading The @code{-exec-arguments} Command
26649 @findex -exec-arguments
26652 @subsubheading Synopsis
26655 -exec-arguments @var{args}
26658 Set the inferior program arguments, to be used in the next
26661 @subsubheading @value{GDBN} Command
26663 The corresponding @value{GDBN} command is @samp{set args}.
26665 @subsubheading Example
26669 -exec-arguments -v word
26676 @subheading The @code{-exec-show-arguments} Command
26677 @findex -exec-show-arguments
26679 @subsubheading Synopsis
26682 -exec-show-arguments
26685 Print the arguments of the program.
26687 @subsubheading @value{GDBN} Command
26689 The corresponding @value{GDBN} command is @samp{show args}.
26691 @subsubheading Example
26696 @subheading The @code{-environment-cd} Command
26697 @findex -environment-cd
26699 @subsubheading Synopsis
26702 -environment-cd @var{pathdir}
26705 Set @value{GDBN}'s working directory.
26707 @subsubheading @value{GDBN} Command
26709 The corresponding @value{GDBN} command is @samp{cd}.
26711 @subsubheading Example
26715 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26721 @subheading The @code{-environment-directory} Command
26722 @findex -environment-directory
26724 @subsubheading Synopsis
26727 -environment-directory [ -r ] [ @var{pathdir} ]+
26730 Add directories @var{pathdir} to beginning of search path for source files.
26731 If the @samp{-r} option is used, the search path is reset to the default
26732 search path. If directories @var{pathdir} are supplied in addition to the
26733 @samp{-r} option, the search path is first reset and then addition
26735 Multiple directories may be specified, separated by blanks. Specifying
26736 multiple directories in a single command
26737 results in the directories added to the beginning of the
26738 search path in the same order they were presented in the command.
26739 If blanks are needed as
26740 part of a directory name, double-quotes should be used around
26741 the name. In the command output, the path will show up separated
26742 by the system directory-separator character. The directory-separator
26743 character must not be used
26744 in any directory name.
26745 If no directories are specified, the current search path is displayed.
26747 @subsubheading @value{GDBN} Command
26749 The corresponding @value{GDBN} command is @samp{dir}.
26751 @subsubheading Example
26755 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26756 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26758 -environment-directory ""
26759 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26761 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26762 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26764 -environment-directory -r
26765 ^done,source-path="$cdir:$cwd"
26770 @subheading The @code{-environment-path} Command
26771 @findex -environment-path
26773 @subsubheading Synopsis
26776 -environment-path [ -r ] [ @var{pathdir} ]+
26779 Add directories @var{pathdir} to beginning of search path for object files.
26780 If the @samp{-r} option is used, the search path is reset to the original
26781 search path that existed at gdb start-up. If directories @var{pathdir} are
26782 supplied in addition to the
26783 @samp{-r} option, the search path is first reset and then addition
26785 Multiple directories may be specified, separated by blanks. Specifying
26786 multiple directories in a single command
26787 results in the directories added to the beginning of the
26788 search path in the same order they were presented in the command.
26789 If blanks are needed as
26790 part of a directory name, double-quotes should be used around
26791 the name. In the command output, the path will show up separated
26792 by the system directory-separator character. The directory-separator
26793 character must not be used
26794 in any directory name.
26795 If no directories are specified, the current path is displayed.
26798 @subsubheading @value{GDBN} Command
26800 The corresponding @value{GDBN} command is @samp{path}.
26802 @subsubheading Example
26807 ^done,path="/usr/bin"
26809 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26810 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26812 -environment-path -r /usr/local/bin
26813 ^done,path="/usr/local/bin:/usr/bin"
26818 @subheading The @code{-environment-pwd} Command
26819 @findex -environment-pwd
26821 @subsubheading Synopsis
26827 Show the current working directory.
26829 @subsubheading @value{GDBN} Command
26831 The corresponding @value{GDBN} command is @samp{pwd}.
26833 @subsubheading Example
26838 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26842 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26843 @node GDB/MI Thread Commands
26844 @section @sc{gdb/mi} Thread Commands
26847 @subheading The @code{-thread-info} Command
26848 @findex -thread-info
26850 @subsubheading Synopsis
26853 -thread-info [ @var{thread-id} ]
26856 Reports information about either a specific thread, if
26857 the @var{thread-id} parameter is present, or about all
26858 threads. When printing information about all threads,
26859 also reports the current thread.
26861 @subsubheading @value{GDBN} Command
26863 The @samp{info thread} command prints the same information
26866 @subsubheading Result
26868 The result is a list of threads. The following attributes are
26869 defined for a given thread:
26873 This field exists only for the current thread. It has the value @samp{*}.
26876 The identifier that @value{GDBN} uses to refer to the thread.
26879 The identifier that the target uses to refer to the thread.
26882 Extra information about the thread, in a target-specific format. This
26886 The name of the thread. If the user specified a name using the
26887 @code{thread name} command, then this name is given. Otherwise, if
26888 @value{GDBN} can extract the thread name from the target, then that
26889 name is given. If @value{GDBN} cannot find the thread name, then this
26893 The stack frame currently executing in the thread.
26896 The thread's state. The @samp{state} field may have the following
26901 The thread is stopped. Frame information is available for stopped
26905 The thread is running. There's no frame information for running
26911 If @value{GDBN} can find the CPU core on which this thread is running,
26912 then this field is the core identifier. This field is optional.
26916 @subsubheading Example
26921 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26922 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26923 args=[]@},state="running"@},
26924 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26925 frame=@{level="0",addr="0x0804891f",func="foo",
26926 args=[@{name="i",value="10"@}],
26927 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26928 state="running"@}],
26929 current-thread-id="1"
26933 @subheading The @code{-thread-list-ids} Command
26934 @findex -thread-list-ids
26936 @subsubheading Synopsis
26942 Produces a list of the currently known @value{GDBN} thread ids. At the
26943 end of the list it also prints the total number of such threads.
26945 This command is retained for historical reasons, the
26946 @code{-thread-info} command should be used instead.
26948 @subsubheading @value{GDBN} Command
26950 Part of @samp{info threads} supplies the same information.
26952 @subsubheading Example
26957 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26958 current-thread-id="1",number-of-threads="3"
26963 @subheading The @code{-thread-select} Command
26964 @findex -thread-select
26966 @subsubheading Synopsis
26969 -thread-select @var{threadnum}
26972 Make @var{threadnum} the current thread. It prints the number of the new
26973 current thread, and the topmost frame for that thread.
26975 This command is deprecated in favor of explicitly using the
26976 @samp{--thread} option to each command.
26978 @subsubheading @value{GDBN} Command
26980 The corresponding @value{GDBN} command is @samp{thread}.
26982 @subsubheading Example
26989 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26990 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26994 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26995 number-of-threads="3"
26998 ^done,new-thread-id="3",
26999 frame=@{level="0",func="vprintf",
27000 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27001 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27005 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27006 @node GDB/MI Ada Tasking Commands
27007 @section @sc{gdb/mi} Ada Tasking Commands
27009 @subheading The @code{-ada-task-info} Command
27010 @findex -ada-task-info
27012 @subsubheading Synopsis
27015 -ada-task-info [ @var{task-id} ]
27018 Reports information about either a specific Ada task, if the
27019 @var{task-id} parameter is present, or about all Ada tasks.
27021 @subsubheading @value{GDBN} Command
27023 The @samp{info tasks} command prints the same information
27024 about all Ada tasks (@pxref{Ada Tasks}).
27026 @subsubheading Result
27028 The result is a table of Ada tasks. The following columns are
27029 defined for each Ada task:
27033 This field exists only for the current thread. It has the value @samp{*}.
27036 The identifier that @value{GDBN} uses to refer to the Ada task.
27039 The identifier that the target uses to refer to the Ada task.
27042 The identifier of the thread corresponding to the Ada task.
27044 This field should always exist, as Ada tasks are always implemented
27045 on top of a thread. But if @value{GDBN} cannot find this corresponding
27046 thread for any reason, the field is omitted.
27049 This field exists only when the task was created by another task.
27050 In this case, it provides the ID of the parent task.
27053 The base priority of the task.
27056 The current state of the task. For a detailed description of the
27057 possible states, see @ref{Ada Tasks}.
27060 The name of the task.
27064 @subsubheading Example
27068 ^done,tasks=@{nr_rows="3",nr_cols="8",
27069 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27070 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27071 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27072 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27073 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27074 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27075 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27076 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27077 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27078 state="Child Termination Wait",name="main_task"@}]@}
27082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27083 @node GDB/MI Program Execution
27084 @section @sc{gdb/mi} Program Execution
27086 These are the asynchronous commands which generate the out-of-band
27087 record @samp{*stopped}. Currently @value{GDBN} only really executes
27088 asynchronously with remote targets and this interaction is mimicked in
27091 @subheading The @code{-exec-continue} Command
27092 @findex -exec-continue
27094 @subsubheading Synopsis
27097 -exec-continue [--reverse] [--all|--thread-group N]
27100 Resumes the execution of the inferior program, which will continue
27101 to execute until it reaches a debugger stop event. If the
27102 @samp{--reverse} option is specified, execution resumes in reverse until
27103 it reaches a stop event. Stop events may include
27106 breakpoints or watchpoints
27108 signals or exceptions
27110 the end of the process (or its beginning under @samp{--reverse})
27112 the end or beginning of a replay log if one is being used.
27114 In all-stop mode (@pxref{All-Stop
27115 Mode}), may resume only one thread, or all threads, depending on the
27116 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27117 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27118 ignored in all-stop mode. If the @samp{--thread-group} options is
27119 specified, then all threads in that thread group are resumed.
27121 @subsubheading @value{GDBN} Command
27123 The corresponding @value{GDBN} corresponding is @samp{continue}.
27125 @subsubheading Example
27132 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27133 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27139 @subheading The @code{-exec-finish} Command
27140 @findex -exec-finish
27142 @subsubheading Synopsis
27145 -exec-finish [--reverse]
27148 Resumes the execution of the inferior program until the current
27149 function is exited. Displays the results returned by the function.
27150 If the @samp{--reverse} option is specified, resumes the reverse
27151 execution of the inferior program until the point where current
27152 function was called.
27154 @subsubheading @value{GDBN} Command
27156 The corresponding @value{GDBN} command is @samp{finish}.
27158 @subsubheading Example
27160 Function returning @code{void}.
27167 *stopped,reason="function-finished",frame=@{func="main",args=[],
27168 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27172 Function returning other than @code{void}. The name of the internal
27173 @value{GDBN} variable storing the result is printed, together with the
27180 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27181 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27182 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27183 gdb-result-var="$1",return-value="0"
27188 @subheading The @code{-exec-interrupt} Command
27189 @findex -exec-interrupt
27191 @subsubheading Synopsis
27194 -exec-interrupt [--all|--thread-group N]
27197 Interrupts the background execution of the target. Note how the token
27198 associated with the stop message is the one for the execution command
27199 that has been interrupted. The token for the interrupt itself only
27200 appears in the @samp{^done} output. If the user is trying to
27201 interrupt a non-running program, an error message will be printed.
27203 Note that when asynchronous execution is enabled, this command is
27204 asynchronous just like other execution commands. That is, first the
27205 @samp{^done} response will be printed, and the target stop will be
27206 reported after that using the @samp{*stopped} notification.
27208 In non-stop mode, only the context thread is interrupted by default.
27209 All threads (in all inferiors) will be interrupted if the
27210 @samp{--all} option is specified. If the @samp{--thread-group}
27211 option is specified, all threads in that group will be interrupted.
27213 @subsubheading @value{GDBN} Command
27215 The corresponding @value{GDBN} command is @samp{interrupt}.
27217 @subsubheading Example
27228 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27229 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27230 fullname="/home/foo/bar/try.c",line="13"@}
27235 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27239 @subheading The @code{-exec-jump} Command
27242 @subsubheading Synopsis
27245 -exec-jump @var{location}
27248 Resumes execution of the inferior program at the location specified by
27249 parameter. @xref{Specify Location}, for a description of the
27250 different forms of @var{location}.
27252 @subsubheading @value{GDBN} Command
27254 The corresponding @value{GDBN} command is @samp{jump}.
27256 @subsubheading Example
27259 -exec-jump foo.c:10
27260 *running,thread-id="all"
27265 @subheading The @code{-exec-next} Command
27268 @subsubheading Synopsis
27271 -exec-next [--reverse]
27274 Resumes execution of the inferior program, stopping when the beginning
27275 of the next source line is reached.
27277 If the @samp{--reverse} option is specified, resumes reverse execution
27278 of the inferior program, stopping at the beginning of the previous
27279 source line. If you issue this command on the first line of a
27280 function, it will take you back to the caller of that function, to the
27281 source line where the function was called.
27284 @subsubheading @value{GDBN} Command
27286 The corresponding @value{GDBN} command is @samp{next}.
27288 @subsubheading Example
27294 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27299 @subheading The @code{-exec-next-instruction} Command
27300 @findex -exec-next-instruction
27302 @subsubheading Synopsis
27305 -exec-next-instruction [--reverse]
27308 Executes one machine instruction. If the instruction is a function
27309 call, continues until the function returns. If the program stops at an
27310 instruction in the middle of a source line, the address will be
27313 If the @samp{--reverse} option is specified, resumes reverse execution
27314 of the inferior program, stopping at the previous instruction. If the
27315 previously executed instruction was a return from another function,
27316 it will continue to execute in reverse until the call to that function
27317 (from the current stack frame) is reached.
27319 @subsubheading @value{GDBN} Command
27321 The corresponding @value{GDBN} command is @samp{nexti}.
27323 @subsubheading Example
27327 -exec-next-instruction
27331 *stopped,reason="end-stepping-range",
27332 addr="0x000100d4",line="5",file="hello.c"
27337 @subheading The @code{-exec-return} Command
27338 @findex -exec-return
27340 @subsubheading Synopsis
27346 Makes current function return immediately. Doesn't execute the inferior.
27347 Displays the new current frame.
27349 @subsubheading @value{GDBN} Command
27351 The corresponding @value{GDBN} command is @samp{return}.
27353 @subsubheading Example
27357 200-break-insert callee4
27358 200^done,bkpt=@{number="1",addr="0x00010734",
27359 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27364 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27365 frame=@{func="callee4",args=[],
27366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27373 111^done,frame=@{level="0",func="callee3",
27374 args=[@{name="strarg",
27375 value="0x11940 \"A string argument.\""@}],
27376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27377 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27382 @subheading The @code{-exec-run} Command
27385 @subsubheading Synopsis
27388 -exec-run [ --all | --thread-group N ] [ --start ]
27391 Starts execution of the inferior from the beginning. The inferior
27392 executes until either a breakpoint is encountered or the program
27393 exits. In the latter case the output will include an exit code, if
27394 the program has exited exceptionally.
27396 When neither the @samp{--all} nor the @samp{--thread-group} option
27397 is specified, the current inferior is started. If the
27398 @samp{--thread-group} option is specified, it should refer to a thread
27399 group of type @samp{process}, and that thread group will be started.
27400 If the @samp{--all} option is specified, then all inferiors will be started.
27402 Using the @samp{--start} option instructs the debugger to stop
27403 the execution at the start of the inferior's main subprogram,
27404 following the same behavior as the @code{start} command
27405 (@pxref{Starting}).
27407 @subsubheading @value{GDBN} Command
27409 The corresponding @value{GDBN} command is @samp{run}.
27411 @subsubheading Examples
27416 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27421 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27422 frame=@{func="main",args=[],file="recursive2.c",
27423 fullname="/home/foo/bar/recursive2.c",line="4"@}
27428 Program exited normally:
27436 *stopped,reason="exited-normally"
27441 Program exited exceptionally:
27449 *stopped,reason="exited",exit-code="01"
27453 Another way the program can terminate is if it receives a signal such as
27454 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27458 *stopped,reason="exited-signalled",signal-name="SIGINT",
27459 signal-meaning="Interrupt"
27463 @c @subheading -exec-signal
27466 @subheading The @code{-exec-step} Command
27469 @subsubheading Synopsis
27472 -exec-step [--reverse]
27475 Resumes execution of the inferior program, stopping when the beginning
27476 of the next source line is reached, if the next source line is not a
27477 function call. If it is, stop at the first instruction of the called
27478 function. If the @samp{--reverse} option is specified, resumes reverse
27479 execution of the inferior program, stopping at the beginning of the
27480 previously executed source line.
27482 @subsubheading @value{GDBN} Command
27484 The corresponding @value{GDBN} command is @samp{step}.
27486 @subsubheading Example
27488 Stepping into a function:
27494 *stopped,reason="end-stepping-range",
27495 frame=@{func="foo",args=[@{name="a",value="10"@},
27496 @{name="b",value="0"@}],file="recursive2.c",
27497 fullname="/home/foo/bar/recursive2.c",line="11"@}
27507 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27512 @subheading The @code{-exec-step-instruction} Command
27513 @findex -exec-step-instruction
27515 @subsubheading Synopsis
27518 -exec-step-instruction [--reverse]
27521 Resumes the inferior which executes one machine instruction. If the
27522 @samp{--reverse} option is specified, resumes reverse execution of the
27523 inferior program, stopping at the previously executed instruction.
27524 The output, once @value{GDBN} has stopped, will vary depending on
27525 whether we have stopped in the middle of a source line or not. In the
27526 former case, the address at which the program stopped will be printed
27529 @subsubheading @value{GDBN} Command
27531 The corresponding @value{GDBN} command is @samp{stepi}.
27533 @subsubheading Example
27537 -exec-step-instruction
27541 *stopped,reason="end-stepping-range",
27542 frame=@{func="foo",args=[],file="try.c",
27543 fullname="/home/foo/bar/try.c",line="10"@}
27545 -exec-step-instruction
27549 *stopped,reason="end-stepping-range",
27550 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27551 fullname="/home/foo/bar/try.c",line="10"@}
27556 @subheading The @code{-exec-until} Command
27557 @findex -exec-until
27559 @subsubheading Synopsis
27562 -exec-until [ @var{location} ]
27565 Executes the inferior until the @var{location} specified in the
27566 argument is reached. If there is no argument, the inferior executes
27567 until a source line greater than the current one is reached. The
27568 reason for stopping in this case will be @samp{location-reached}.
27570 @subsubheading @value{GDBN} Command
27572 The corresponding @value{GDBN} command is @samp{until}.
27574 @subsubheading Example
27578 -exec-until recursive2.c:6
27582 *stopped,reason="location-reached",frame=@{func="main",args=[],
27583 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27588 @subheading -file-clear
27589 Is this going away????
27592 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27593 @node GDB/MI Stack Manipulation
27594 @section @sc{gdb/mi} Stack Manipulation Commands
27596 @subheading The @code{-enable-frame-filters} Command
27597 @findex -enable-frame-filters
27600 -enable-frame-filters
27603 @value{GDBN} allows Python-based frame filters to affect the output of
27604 the MI commands relating to stack traces. As there is no way to
27605 implement this in a fully backward-compatible way, a front end must
27606 request that this functionality be enabled.
27608 Once enabled, this feature cannot be disabled.
27610 Note that if Python support has not been compiled into @value{GDBN},
27611 this command will still succeed (and do nothing).
27613 @subheading The @code{-stack-info-frame} Command
27614 @findex -stack-info-frame
27616 @subsubheading Synopsis
27622 Get info on the selected frame.
27624 @subsubheading @value{GDBN} Command
27626 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27627 (without arguments).
27629 @subsubheading Example
27634 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27635 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27636 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27640 @subheading The @code{-stack-info-depth} Command
27641 @findex -stack-info-depth
27643 @subsubheading Synopsis
27646 -stack-info-depth [ @var{max-depth} ]
27649 Return the depth of the stack. If the integer argument @var{max-depth}
27650 is specified, do not count beyond @var{max-depth} frames.
27652 @subsubheading @value{GDBN} Command
27654 There's no equivalent @value{GDBN} command.
27656 @subsubheading Example
27658 For a stack with frame levels 0 through 11:
27665 -stack-info-depth 4
27668 -stack-info-depth 12
27671 -stack-info-depth 11
27674 -stack-info-depth 13
27679 @anchor{-stack-list-arguments}
27680 @subheading The @code{-stack-list-arguments} Command
27681 @findex -stack-list-arguments
27683 @subsubheading Synopsis
27686 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27687 [ @var{low-frame} @var{high-frame} ]
27690 Display a list of the arguments for the frames between @var{low-frame}
27691 and @var{high-frame} (inclusive). If @var{low-frame} and
27692 @var{high-frame} are not provided, list the arguments for the whole
27693 call stack. If the two arguments are equal, show the single frame
27694 at the corresponding level. It is an error if @var{low-frame} is
27695 larger than the actual number of frames. On the other hand,
27696 @var{high-frame} may be larger than the actual number of frames, in
27697 which case only existing frames will be returned.
27699 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27700 the variables; if it is 1 or @code{--all-values}, print also their
27701 values; and if it is 2 or @code{--simple-values}, print the name,
27702 type and value for simple data types, and the name and type for arrays,
27703 structures and unions. If the option @code{--no-frame-filters} is
27704 supplied, then Python frame filters will not be executed.
27706 If the @code{--skip-unavailable} option is specified, arguments that
27707 are not available are not listed. Partially available arguments
27708 are still displayed, however.
27710 Use of this command to obtain arguments in a single frame is
27711 deprecated in favor of the @samp{-stack-list-variables} command.
27713 @subsubheading @value{GDBN} Command
27715 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27716 @samp{gdb_get_args} command which partially overlaps with the
27717 functionality of @samp{-stack-list-arguments}.
27719 @subsubheading Example
27726 frame=@{level="0",addr="0x00010734",func="callee4",
27727 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27728 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27729 frame=@{level="1",addr="0x0001076c",func="callee3",
27730 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27731 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27732 frame=@{level="2",addr="0x0001078c",func="callee2",
27733 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27734 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27735 frame=@{level="3",addr="0x000107b4",func="callee1",
27736 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27737 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27738 frame=@{level="4",addr="0x000107e0",func="main",
27739 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27740 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27742 -stack-list-arguments 0
27745 frame=@{level="0",args=[]@},
27746 frame=@{level="1",args=[name="strarg"]@},
27747 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27748 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27749 frame=@{level="4",args=[]@}]
27751 -stack-list-arguments 1
27754 frame=@{level="0",args=[]@},
27756 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27757 frame=@{level="2",args=[
27758 @{name="intarg",value="2"@},
27759 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27760 @{frame=@{level="3",args=[
27761 @{name="intarg",value="2"@},
27762 @{name="strarg",value="0x11940 \"A string argument.\""@},
27763 @{name="fltarg",value="3.5"@}]@},
27764 frame=@{level="4",args=[]@}]
27766 -stack-list-arguments 0 2 2
27767 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27769 -stack-list-arguments 1 2 2
27770 ^done,stack-args=[frame=@{level="2",
27771 args=[@{name="intarg",value="2"@},
27772 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27776 @c @subheading -stack-list-exception-handlers
27779 @anchor{-stack-list-frames}
27780 @subheading The @code{-stack-list-frames} Command
27781 @findex -stack-list-frames
27783 @subsubheading Synopsis
27786 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
27789 List the frames currently on the stack. For each frame it displays the
27794 The frame number, 0 being the topmost frame, i.e., the innermost function.
27796 The @code{$pc} value for that frame.
27800 File name of the source file where the function lives.
27801 @item @var{fullname}
27802 The full file name of the source file where the function lives.
27804 Line number corresponding to the @code{$pc}.
27806 The shared library where this function is defined. This is only given
27807 if the frame's function is not known.
27810 If invoked without arguments, this command prints a backtrace for the
27811 whole stack. If given two integer arguments, it shows the frames whose
27812 levels are between the two arguments (inclusive). If the two arguments
27813 are equal, it shows the single frame at the corresponding level. It is
27814 an error if @var{low-frame} is larger than the actual number of
27815 frames. On the other hand, @var{high-frame} may be larger than the
27816 actual number of frames, in which case only existing frames will be
27817 returned. If the option @code{--no-frame-filters} is supplied, then
27818 Python frame filters will not be executed.
27820 @subsubheading @value{GDBN} Command
27822 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27824 @subsubheading Example
27826 Full stack backtrace:
27832 [frame=@{level="0",addr="0x0001076c",func="foo",
27833 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27834 frame=@{level="1",addr="0x000107a4",func="foo",
27835 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27836 frame=@{level="2",addr="0x000107a4",func="foo",
27837 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27838 frame=@{level="3",addr="0x000107a4",func="foo",
27839 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27840 frame=@{level="4",addr="0x000107a4",func="foo",
27841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27842 frame=@{level="5",addr="0x000107a4",func="foo",
27843 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27844 frame=@{level="6",addr="0x000107a4",func="foo",
27845 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27846 frame=@{level="7",addr="0x000107a4",func="foo",
27847 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27848 frame=@{level="8",addr="0x000107a4",func="foo",
27849 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27850 frame=@{level="9",addr="0x000107a4",func="foo",
27851 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27852 frame=@{level="10",addr="0x000107a4",func="foo",
27853 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27854 frame=@{level="11",addr="0x00010738",func="main",
27855 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27859 Show frames between @var{low_frame} and @var{high_frame}:
27863 -stack-list-frames 3 5
27865 [frame=@{level="3",addr="0x000107a4",func="foo",
27866 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27867 frame=@{level="4",addr="0x000107a4",func="foo",
27868 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27869 frame=@{level="5",addr="0x000107a4",func="foo",
27870 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27874 Show a single frame:
27878 -stack-list-frames 3 3
27880 [frame=@{level="3",addr="0x000107a4",func="foo",
27881 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27886 @subheading The @code{-stack-list-locals} Command
27887 @findex -stack-list-locals
27888 @anchor{-stack-list-locals}
27890 @subsubheading Synopsis
27893 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27896 Display the local variable names for the selected frame. If
27897 @var{print-values} is 0 or @code{--no-values}, print only the names of
27898 the variables; if it is 1 or @code{--all-values}, print also their
27899 values; and if it is 2 or @code{--simple-values}, print the name,
27900 type and value for simple data types, and the name and type for arrays,
27901 structures and unions. In this last case, a frontend can immediately
27902 display the value of simple data types and create variable objects for
27903 other data types when the user wishes to explore their values in
27904 more detail. If the option @code{--no-frame-filters} is supplied, then
27905 Python frame filters will not be executed.
27907 If the @code{--skip-unavailable} option is specified, local variables
27908 that are not available are not listed. Partially available local
27909 variables are still displayed, however.
27911 This command is deprecated in favor of the
27912 @samp{-stack-list-variables} command.
27914 @subsubheading @value{GDBN} Command
27916 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27918 @subsubheading Example
27922 -stack-list-locals 0
27923 ^done,locals=[name="A",name="B",name="C"]
27925 -stack-list-locals --all-values
27926 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27927 @{name="C",value="@{1, 2, 3@}"@}]
27928 -stack-list-locals --simple-values
27929 ^done,locals=[@{name="A",type="int",value="1"@},
27930 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27934 @anchor{-stack-list-variables}
27935 @subheading The @code{-stack-list-variables} Command
27936 @findex -stack-list-variables
27938 @subsubheading Synopsis
27941 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27944 Display the names of local variables and function arguments for the selected frame. If
27945 @var{print-values} is 0 or @code{--no-values}, print only the names of
27946 the variables; if it is 1 or @code{--all-values}, print also their
27947 values; and if it is 2 or @code{--simple-values}, print the name,
27948 type and value for simple data types, and the name and type for arrays,
27949 structures and unions. If the option @code{--no-frame-filters} is
27950 supplied, then Python frame filters will not be executed.
27952 If the @code{--skip-unavailable} option is specified, local variables
27953 and arguments that are not available are not listed. Partially
27954 available arguments and local variables are still displayed, however.
27956 @subsubheading Example
27960 -stack-list-variables --thread 1 --frame 0 --all-values
27961 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27966 @subheading The @code{-stack-select-frame} Command
27967 @findex -stack-select-frame
27969 @subsubheading Synopsis
27972 -stack-select-frame @var{framenum}
27975 Change the selected frame. Select a different frame @var{framenum} on
27978 This command in deprecated in favor of passing the @samp{--frame}
27979 option to every command.
27981 @subsubheading @value{GDBN} Command
27983 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27984 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27986 @subsubheading Example
27990 -stack-select-frame 2
27995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27996 @node GDB/MI Variable Objects
27997 @section @sc{gdb/mi} Variable Objects
28001 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28003 For the implementation of a variable debugger window (locals, watched
28004 expressions, etc.), we are proposing the adaptation of the existing code
28005 used by @code{Insight}.
28007 The two main reasons for that are:
28011 It has been proven in practice (it is already on its second generation).
28014 It will shorten development time (needless to say how important it is
28018 The original interface was designed to be used by Tcl code, so it was
28019 slightly changed so it could be used through @sc{gdb/mi}. This section
28020 describes the @sc{gdb/mi} operations that will be available and gives some
28021 hints about their use.
28023 @emph{Note}: In addition to the set of operations described here, we
28024 expect the @sc{gui} implementation of a variable window to require, at
28025 least, the following operations:
28028 @item @code{-gdb-show} @code{output-radix}
28029 @item @code{-stack-list-arguments}
28030 @item @code{-stack-list-locals}
28031 @item @code{-stack-select-frame}
28036 @subheading Introduction to Variable Objects
28038 @cindex variable objects in @sc{gdb/mi}
28040 Variable objects are "object-oriented" MI interface for examining and
28041 changing values of expressions. Unlike some other MI interfaces that
28042 work with expressions, variable objects are specifically designed for
28043 simple and efficient presentation in the frontend. A variable object
28044 is identified by string name. When a variable object is created, the
28045 frontend specifies the expression for that variable object. The
28046 expression can be a simple variable, or it can be an arbitrary complex
28047 expression, and can even involve CPU registers. After creating a
28048 variable object, the frontend can invoke other variable object
28049 operations---for example to obtain or change the value of a variable
28050 object, or to change display format.
28052 Variable objects have hierarchical tree structure. Any variable object
28053 that corresponds to a composite type, such as structure in C, has
28054 a number of child variable objects, for example corresponding to each
28055 element of a structure. A child variable object can itself have
28056 children, recursively. Recursion ends when we reach
28057 leaf variable objects, which always have built-in types. Child variable
28058 objects are created only by explicit request, so if a frontend
28059 is not interested in the children of a particular variable object, no
28060 child will be created.
28062 For a leaf variable object it is possible to obtain its value as a
28063 string, or set the value from a string. String value can be also
28064 obtained for a non-leaf variable object, but it's generally a string
28065 that only indicates the type of the object, and does not list its
28066 contents. Assignment to a non-leaf variable object is not allowed.
28068 A frontend does not need to read the values of all variable objects each time
28069 the program stops. Instead, MI provides an update command that lists all
28070 variable objects whose values has changed since the last update
28071 operation. This considerably reduces the amount of data that must
28072 be transferred to the frontend. As noted above, children variable
28073 objects are created on demand, and only leaf variable objects have a
28074 real value. As result, gdb will read target memory only for leaf
28075 variables that frontend has created.
28077 The automatic update is not always desirable. For example, a frontend
28078 might want to keep a value of some expression for future reference,
28079 and never update it. For another example, fetching memory is
28080 relatively slow for embedded targets, so a frontend might want
28081 to disable automatic update for the variables that are either not
28082 visible on the screen, or ``closed''. This is possible using so
28083 called ``frozen variable objects''. Such variable objects are never
28084 implicitly updated.
28086 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28087 fixed variable object, the expression is parsed when the variable
28088 object is created, including associating identifiers to specific
28089 variables. The meaning of expression never changes. For a floating
28090 variable object the values of variables whose names appear in the
28091 expressions are re-evaluated every time in the context of the current
28092 frame. Consider this example:
28097 struct work_state state;
28104 If a fixed variable object for the @code{state} variable is created in
28105 this function, and we enter the recursive call, the variable
28106 object will report the value of @code{state} in the top-level
28107 @code{do_work} invocation. On the other hand, a floating variable
28108 object will report the value of @code{state} in the current frame.
28110 If an expression specified when creating a fixed variable object
28111 refers to a local variable, the variable object becomes bound to the
28112 thread and frame in which the variable object is created. When such
28113 variable object is updated, @value{GDBN} makes sure that the
28114 thread/frame combination the variable object is bound to still exists,
28115 and re-evaluates the variable object in context of that thread/frame.
28117 The following is the complete set of @sc{gdb/mi} operations defined to
28118 access this functionality:
28120 @multitable @columnfractions .4 .6
28121 @item @strong{Operation}
28122 @tab @strong{Description}
28124 @item @code{-enable-pretty-printing}
28125 @tab enable Python-based pretty-printing
28126 @item @code{-var-create}
28127 @tab create a variable object
28128 @item @code{-var-delete}
28129 @tab delete the variable object and/or its children
28130 @item @code{-var-set-format}
28131 @tab set the display format of this variable
28132 @item @code{-var-show-format}
28133 @tab show the display format of this variable
28134 @item @code{-var-info-num-children}
28135 @tab tells how many children this object has
28136 @item @code{-var-list-children}
28137 @tab return a list of the object's children
28138 @item @code{-var-info-type}
28139 @tab show the type of this variable object
28140 @item @code{-var-info-expression}
28141 @tab print parent-relative expression that this variable object represents
28142 @item @code{-var-info-path-expression}
28143 @tab print full expression that this variable object represents
28144 @item @code{-var-show-attributes}
28145 @tab is this variable editable? does it exist here?
28146 @item @code{-var-evaluate-expression}
28147 @tab get the value of this variable
28148 @item @code{-var-assign}
28149 @tab set the value of this variable
28150 @item @code{-var-update}
28151 @tab update the variable and its children
28152 @item @code{-var-set-frozen}
28153 @tab set frozeness attribute
28154 @item @code{-var-set-update-range}
28155 @tab set range of children to display on update
28158 In the next subsection we describe each operation in detail and suggest
28159 how it can be used.
28161 @subheading Description And Use of Operations on Variable Objects
28163 @subheading The @code{-enable-pretty-printing} Command
28164 @findex -enable-pretty-printing
28167 -enable-pretty-printing
28170 @value{GDBN} allows Python-based visualizers to affect the output of the
28171 MI variable object commands. However, because there was no way to
28172 implement this in a fully backward-compatible way, a front end must
28173 request that this functionality be enabled.
28175 Once enabled, this feature cannot be disabled.
28177 Note that if Python support has not been compiled into @value{GDBN},
28178 this command will still succeed (and do nothing).
28180 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28181 may work differently in future versions of @value{GDBN}.
28183 @subheading The @code{-var-create} Command
28184 @findex -var-create
28186 @subsubheading Synopsis
28189 -var-create @{@var{name} | "-"@}
28190 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28193 This operation creates a variable object, which allows the monitoring of
28194 a variable, the result of an expression, a memory cell or a CPU
28197 The @var{name} parameter is the string by which the object can be
28198 referenced. It must be unique. If @samp{-} is specified, the varobj
28199 system will generate a string ``varNNNNNN'' automatically. It will be
28200 unique provided that one does not specify @var{name} of that format.
28201 The command fails if a duplicate name is found.
28203 The frame under which the expression should be evaluated can be
28204 specified by @var{frame-addr}. A @samp{*} indicates that the current
28205 frame should be used. A @samp{@@} indicates that a floating variable
28206 object must be created.
28208 @var{expression} is any expression valid on the current language set (must not
28209 begin with a @samp{*}), or one of the following:
28213 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28216 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28219 @samp{$@var{regname}} --- a CPU register name
28222 @cindex dynamic varobj
28223 A varobj's contents may be provided by a Python-based pretty-printer. In this
28224 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28225 have slightly different semantics in some cases. If the
28226 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28227 will never create a dynamic varobj. This ensures backward
28228 compatibility for existing clients.
28230 @subsubheading Result
28232 This operation returns attributes of the newly-created varobj. These
28237 The name of the varobj.
28240 The number of children of the varobj. This number is not necessarily
28241 reliable for a dynamic varobj. Instead, you must examine the
28242 @samp{has_more} attribute.
28245 The varobj's scalar value. For a varobj whose type is some sort of
28246 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28247 will not be interesting.
28250 The varobj's type. This is a string representation of the type, as
28251 would be printed by the @value{GDBN} CLI. If @samp{print object}
28252 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28253 @emph{actual} (derived) type of the object is shown rather than the
28254 @emph{declared} one.
28257 If a variable object is bound to a specific thread, then this is the
28258 thread's identifier.
28261 For a dynamic varobj, this indicates whether there appear to be any
28262 children available. For a non-dynamic varobj, this will be 0.
28265 This attribute will be present and have the value @samp{1} if the
28266 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28267 then this attribute will not be present.
28270 A dynamic varobj can supply a display hint to the front end. The
28271 value comes directly from the Python pretty-printer object's
28272 @code{display_hint} method. @xref{Pretty Printing API}.
28275 Typical output will look like this:
28278 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28279 has_more="@var{has_more}"
28283 @subheading The @code{-var-delete} Command
28284 @findex -var-delete
28286 @subsubheading Synopsis
28289 -var-delete [ -c ] @var{name}
28292 Deletes a previously created variable object and all of its children.
28293 With the @samp{-c} option, just deletes the children.
28295 Returns an error if the object @var{name} is not found.
28298 @subheading The @code{-var-set-format} Command
28299 @findex -var-set-format
28301 @subsubheading Synopsis
28304 -var-set-format @var{name} @var{format-spec}
28307 Sets the output format for the value of the object @var{name} to be
28310 @anchor{-var-set-format}
28311 The syntax for the @var{format-spec} is as follows:
28314 @var{format-spec} @expansion{}
28315 @{binary | decimal | hexadecimal | octal | natural@}
28318 The natural format is the default format choosen automatically
28319 based on the variable type (like decimal for an @code{int}, hex
28320 for pointers, etc.).
28322 For a variable with children, the format is set only on the
28323 variable itself, and the children are not affected.
28325 @subheading The @code{-var-show-format} Command
28326 @findex -var-show-format
28328 @subsubheading Synopsis
28331 -var-show-format @var{name}
28334 Returns the format used to display the value of the object @var{name}.
28337 @var{format} @expansion{}
28342 @subheading The @code{-var-info-num-children} Command
28343 @findex -var-info-num-children
28345 @subsubheading Synopsis
28348 -var-info-num-children @var{name}
28351 Returns the number of children of a variable object @var{name}:
28357 Note that this number is not completely reliable for a dynamic varobj.
28358 It will return the current number of children, but more children may
28362 @subheading The @code{-var-list-children} Command
28363 @findex -var-list-children
28365 @subsubheading Synopsis
28368 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28370 @anchor{-var-list-children}
28372 Return a list of the children of the specified variable object and
28373 create variable objects for them, if they do not already exist. With
28374 a single argument or if @var{print-values} has a value of 0 or
28375 @code{--no-values}, print only the names of the variables; if
28376 @var{print-values} is 1 or @code{--all-values}, also print their
28377 values; and if it is 2 or @code{--simple-values} print the name and
28378 value for simple data types and just the name for arrays, structures
28381 @var{from} and @var{to}, if specified, indicate the range of children
28382 to report. If @var{from} or @var{to} is less than zero, the range is
28383 reset and all children will be reported. Otherwise, children starting
28384 at @var{from} (zero-based) and up to and excluding @var{to} will be
28387 If a child range is requested, it will only affect the current call to
28388 @code{-var-list-children}, but not future calls to @code{-var-update}.
28389 For this, you must instead use @code{-var-set-update-range}. The
28390 intent of this approach is to enable a front end to implement any
28391 update approach it likes; for example, scrolling a view may cause the
28392 front end to request more children with @code{-var-list-children}, and
28393 then the front end could call @code{-var-set-update-range} with a
28394 different range to ensure that future updates are restricted to just
28397 For each child the following results are returned:
28402 Name of the variable object created for this child.
28405 The expression to be shown to the user by the front end to designate this child.
28406 For example this may be the name of a structure member.
28408 For a dynamic varobj, this value cannot be used to form an
28409 expression. There is no way to do this at all with a dynamic varobj.
28411 For C/C@t{++} structures there are several pseudo children returned to
28412 designate access qualifiers. For these pseudo children @var{exp} is
28413 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28414 type and value are not present.
28416 A dynamic varobj will not report the access qualifying
28417 pseudo-children, regardless of the language. This information is not
28418 available at all with a dynamic varobj.
28421 Number of children this child has. For a dynamic varobj, this will be
28425 The type of the child. If @samp{print object}
28426 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28427 @emph{actual} (derived) type of the object is shown rather than the
28428 @emph{declared} one.
28431 If values were requested, this is the value.
28434 If this variable object is associated with a thread, this is the thread id.
28435 Otherwise this result is not present.
28438 If the variable object is frozen, this variable will be present with a value of 1.
28441 A dynamic varobj can supply a display hint to the front end. The
28442 value comes directly from the Python pretty-printer object's
28443 @code{display_hint} method. @xref{Pretty Printing API}.
28446 This attribute will be present and have the value @samp{1} if the
28447 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28448 then this attribute will not be present.
28452 The result may have its own attributes:
28456 A dynamic varobj can supply a display hint to the front end. The
28457 value comes directly from the Python pretty-printer object's
28458 @code{display_hint} method. @xref{Pretty Printing API}.
28461 This is an integer attribute which is nonzero if there are children
28462 remaining after the end of the selected range.
28465 @subsubheading Example
28469 -var-list-children n
28470 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28471 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28473 -var-list-children --all-values n
28474 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28475 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28479 @subheading The @code{-var-info-type} Command
28480 @findex -var-info-type
28482 @subsubheading Synopsis
28485 -var-info-type @var{name}
28488 Returns the type of the specified variable @var{name}. The type is
28489 returned as a string in the same format as it is output by the
28493 type=@var{typename}
28497 @subheading The @code{-var-info-expression} Command
28498 @findex -var-info-expression
28500 @subsubheading Synopsis
28503 -var-info-expression @var{name}
28506 Returns a string that is suitable for presenting this
28507 variable object in user interface. The string is generally
28508 not valid expression in the current language, and cannot be evaluated.
28510 For example, if @code{a} is an array, and variable object
28511 @code{A} was created for @code{a}, then we'll get this output:
28514 (gdb) -var-info-expression A.1
28515 ^done,lang="C",exp="1"
28519 Here, the value of @code{lang} is the language name, which can be
28520 found in @ref{Supported Languages}.
28522 Note that the output of the @code{-var-list-children} command also
28523 includes those expressions, so the @code{-var-info-expression} command
28526 @subheading The @code{-var-info-path-expression} Command
28527 @findex -var-info-path-expression
28529 @subsubheading Synopsis
28532 -var-info-path-expression @var{name}
28535 Returns an expression that can be evaluated in the current
28536 context and will yield the same value that a variable object has.
28537 Compare this with the @code{-var-info-expression} command, which
28538 result can be used only for UI presentation. Typical use of
28539 the @code{-var-info-path-expression} command is creating a
28540 watchpoint from a variable object.
28542 This command is currently not valid for children of a dynamic varobj,
28543 and will give an error when invoked on one.
28545 For example, suppose @code{C} is a C@t{++} class, derived from class
28546 @code{Base}, and that the @code{Base} class has a member called
28547 @code{m_size}. Assume a variable @code{c} is has the type of
28548 @code{C} and a variable object @code{C} was created for variable
28549 @code{c}. Then, we'll get this output:
28551 (gdb) -var-info-path-expression C.Base.public.m_size
28552 ^done,path_expr=((Base)c).m_size)
28555 @subheading The @code{-var-show-attributes} Command
28556 @findex -var-show-attributes
28558 @subsubheading Synopsis
28561 -var-show-attributes @var{name}
28564 List attributes of the specified variable object @var{name}:
28567 status=@var{attr} [ ( ,@var{attr} )* ]
28571 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28573 @subheading The @code{-var-evaluate-expression} Command
28574 @findex -var-evaluate-expression
28576 @subsubheading Synopsis
28579 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28582 Evaluates the expression that is represented by the specified variable
28583 object and returns its value as a string. The format of the string
28584 can be specified with the @samp{-f} option. The possible values of
28585 this option are the same as for @code{-var-set-format}
28586 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28587 the current display format will be used. The current display format
28588 can be changed using the @code{-var-set-format} command.
28594 Note that one must invoke @code{-var-list-children} for a variable
28595 before the value of a child variable can be evaluated.
28597 @subheading The @code{-var-assign} Command
28598 @findex -var-assign
28600 @subsubheading Synopsis
28603 -var-assign @var{name} @var{expression}
28606 Assigns the value of @var{expression} to the variable object specified
28607 by @var{name}. The object must be @samp{editable}. If the variable's
28608 value is altered by the assign, the variable will show up in any
28609 subsequent @code{-var-update} list.
28611 @subsubheading Example
28619 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28623 @subheading The @code{-var-update} Command
28624 @findex -var-update
28626 @subsubheading Synopsis
28629 -var-update [@var{print-values}] @{@var{name} | "*"@}
28632 Reevaluate the expressions corresponding to the variable object
28633 @var{name} and all its direct and indirect children, and return the
28634 list of variable objects whose values have changed; @var{name} must
28635 be a root variable object. Here, ``changed'' means that the result of
28636 @code{-var-evaluate-expression} before and after the
28637 @code{-var-update} is different. If @samp{*} is used as the variable
28638 object names, all existing variable objects are updated, except
28639 for frozen ones (@pxref{-var-set-frozen}). The option
28640 @var{print-values} determines whether both names and values, or just
28641 names are printed. The possible values of this option are the same
28642 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28643 recommended to use the @samp{--all-values} option, to reduce the
28644 number of MI commands needed on each program stop.
28646 With the @samp{*} parameter, if a variable object is bound to a
28647 currently running thread, it will not be updated, without any
28650 If @code{-var-set-update-range} was previously used on a varobj, then
28651 only the selected range of children will be reported.
28653 @code{-var-update} reports all the changed varobjs in a tuple named
28656 Each item in the change list is itself a tuple holding:
28660 The name of the varobj.
28663 If values were requested for this update, then this field will be
28664 present and will hold the value of the varobj.
28667 @anchor{-var-update}
28668 This field is a string which may take one of three values:
28672 The variable object's current value is valid.
28675 The variable object does not currently hold a valid value but it may
28676 hold one in the future if its associated expression comes back into
28680 The variable object no longer holds a valid value.
28681 This can occur when the executable file being debugged has changed,
28682 either through recompilation or by using the @value{GDBN} @code{file}
28683 command. The front end should normally choose to delete these variable
28687 In the future new values may be added to this list so the front should
28688 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28691 This is only present if the varobj is still valid. If the type
28692 changed, then this will be the string @samp{true}; otherwise it will
28695 When a varobj's type changes, its children are also likely to have
28696 become incorrect. Therefore, the varobj's children are automatically
28697 deleted when this attribute is @samp{true}. Also, the varobj's update
28698 range, when set using the @code{-var-set-update-range} command, is
28702 If the varobj's type changed, then this field will be present and will
28705 @item new_num_children
28706 For a dynamic varobj, if the number of children changed, or if the
28707 type changed, this will be the new number of children.
28709 The @samp{numchild} field in other varobj responses is generally not
28710 valid for a dynamic varobj -- it will show the number of children that
28711 @value{GDBN} knows about, but because dynamic varobjs lazily
28712 instantiate their children, this will not reflect the number of
28713 children which may be available.
28715 The @samp{new_num_children} attribute only reports changes to the
28716 number of children known by @value{GDBN}. This is the only way to
28717 detect whether an update has removed children (which necessarily can
28718 only happen at the end of the update range).
28721 The display hint, if any.
28724 This is an integer value, which will be 1 if there are more children
28725 available outside the varobj's update range.
28728 This attribute will be present and have the value @samp{1} if the
28729 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28730 then this attribute will not be present.
28733 If new children were added to a dynamic varobj within the selected
28734 update range (as set by @code{-var-set-update-range}), then they will
28735 be listed in this attribute.
28738 @subsubheading Example
28745 -var-update --all-values var1
28746 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28747 type_changed="false"@}]
28751 @subheading The @code{-var-set-frozen} Command
28752 @findex -var-set-frozen
28753 @anchor{-var-set-frozen}
28755 @subsubheading Synopsis
28758 -var-set-frozen @var{name} @var{flag}
28761 Set the frozenness flag on the variable object @var{name}. The
28762 @var{flag} parameter should be either @samp{1} to make the variable
28763 frozen or @samp{0} to make it unfrozen. If a variable object is
28764 frozen, then neither itself, nor any of its children, are
28765 implicitly updated by @code{-var-update} of
28766 a parent variable or by @code{-var-update *}. Only
28767 @code{-var-update} of the variable itself will update its value and
28768 values of its children. After a variable object is unfrozen, it is
28769 implicitly updated by all subsequent @code{-var-update} operations.
28770 Unfreezing a variable does not update it, only subsequent
28771 @code{-var-update} does.
28773 @subsubheading Example
28777 -var-set-frozen V 1
28782 @subheading The @code{-var-set-update-range} command
28783 @findex -var-set-update-range
28784 @anchor{-var-set-update-range}
28786 @subsubheading Synopsis
28789 -var-set-update-range @var{name} @var{from} @var{to}
28792 Set the range of children to be returned by future invocations of
28793 @code{-var-update}.
28795 @var{from} and @var{to} indicate the range of children to report. If
28796 @var{from} or @var{to} is less than zero, the range is reset and all
28797 children will be reported. Otherwise, children starting at @var{from}
28798 (zero-based) and up to and excluding @var{to} will be reported.
28800 @subsubheading Example
28804 -var-set-update-range V 1 2
28808 @subheading The @code{-var-set-visualizer} command
28809 @findex -var-set-visualizer
28810 @anchor{-var-set-visualizer}
28812 @subsubheading Synopsis
28815 -var-set-visualizer @var{name} @var{visualizer}
28818 Set a visualizer for the variable object @var{name}.
28820 @var{visualizer} is the visualizer to use. The special value
28821 @samp{None} means to disable any visualizer in use.
28823 If not @samp{None}, @var{visualizer} must be a Python expression.
28824 This expression must evaluate to a callable object which accepts a
28825 single argument. @value{GDBN} will call this object with the value of
28826 the varobj @var{name} as an argument (this is done so that the same
28827 Python pretty-printing code can be used for both the CLI and MI).
28828 When called, this object must return an object which conforms to the
28829 pretty-printing interface (@pxref{Pretty Printing API}).
28831 The pre-defined function @code{gdb.default_visualizer} may be used to
28832 select a visualizer by following the built-in process
28833 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28834 a varobj is created, and so ordinarily is not needed.
28836 This feature is only available if Python support is enabled. The MI
28837 command @code{-list-features} (@pxref{GDB/MI Support Commands})
28838 can be used to check this.
28840 @subsubheading Example
28842 Resetting the visualizer:
28846 -var-set-visualizer V None
28850 Reselecting the default (type-based) visualizer:
28854 -var-set-visualizer V gdb.default_visualizer
28858 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28859 can be used to instantiate this class for a varobj:
28863 -var-set-visualizer V "lambda val: SomeClass()"
28867 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28868 @node GDB/MI Data Manipulation
28869 @section @sc{gdb/mi} Data Manipulation
28871 @cindex data manipulation, in @sc{gdb/mi}
28872 @cindex @sc{gdb/mi}, data manipulation
28873 This section describes the @sc{gdb/mi} commands that manipulate data:
28874 examine memory and registers, evaluate expressions, etc.
28876 @c REMOVED FROM THE INTERFACE.
28877 @c @subheading -data-assign
28878 @c Change the value of a program variable. Plenty of side effects.
28879 @c @subsubheading GDB Command
28881 @c @subsubheading Example
28884 @subheading The @code{-data-disassemble} Command
28885 @findex -data-disassemble
28887 @subsubheading Synopsis
28891 [ -s @var{start-addr} -e @var{end-addr} ]
28892 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28900 @item @var{start-addr}
28901 is the beginning address (or @code{$pc})
28902 @item @var{end-addr}
28904 @item @var{filename}
28905 is the name of the file to disassemble
28906 @item @var{linenum}
28907 is the line number to disassemble around
28909 is the number of disassembly lines to be produced. If it is -1,
28910 the whole function will be disassembled, in case no @var{end-addr} is
28911 specified. If @var{end-addr} is specified as a non-zero value, and
28912 @var{lines} is lower than the number of disassembly lines between
28913 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28914 displayed; if @var{lines} is higher than the number of lines between
28915 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28918 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28919 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28920 mixed source and disassembly with raw opcodes).
28923 @subsubheading Result
28925 The result of the @code{-data-disassemble} command will be a list named
28926 @samp{asm_insns}, the contents of this list depend on the @var{mode}
28927 used with the @code{-data-disassemble} command.
28929 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
28934 The address at which this instruction was disassembled.
28937 The name of the function this instruction is within.
28940 The decimal offset in bytes from the start of @samp{func-name}.
28943 The text disassembly for this @samp{address}.
28946 This field is only present for mode 2. This contains the raw opcode
28947 bytes for the @samp{inst} field.
28951 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
28952 @samp{src_and_asm_line}, each of which has the following fields:
28956 The line number within @samp{file}.
28959 The file name from the compilation unit. This might be an absolute
28960 file name or a relative file name depending on the compile command
28964 Absolute file name of @samp{file}. It is converted to a canonical form
28965 using the source file search path
28966 (@pxref{Source Path, ,Specifying Source Directories})
28967 and after resolving all the symbolic links.
28969 If the source file is not found this field will contain the path as
28970 present in the debug information.
28972 @item line_asm_insn
28973 This is a list of tuples containing the disassembly for @samp{line} in
28974 @samp{file}. The fields of each tuple are the same as for
28975 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
28976 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
28981 Note that whatever included in the @samp{inst} field, is not
28982 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
28985 @subsubheading @value{GDBN} Command
28987 The corresponding @value{GDBN} command is @samp{disassemble}.
28989 @subsubheading Example
28991 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28995 -data-disassemble -s $pc -e "$pc + 20" -- 0
28998 @{address="0x000107c0",func-name="main",offset="4",
28999 inst="mov 2, %o0"@},
29000 @{address="0x000107c4",func-name="main",offset="8",
29001 inst="sethi %hi(0x11800), %o2"@},
29002 @{address="0x000107c8",func-name="main",offset="12",
29003 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29004 @{address="0x000107cc",func-name="main",offset="16",
29005 inst="sethi %hi(0x11800), %o2"@},
29006 @{address="0x000107d0",func-name="main",offset="20",
29007 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29011 Disassemble the whole @code{main} function. Line 32 is part of
29015 -data-disassemble -f basics.c -l 32 -- 0
29017 @{address="0x000107bc",func-name="main",offset="0",
29018 inst="save %sp, -112, %sp"@},
29019 @{address="0x000107c0",func-name="main",offset="4",
29020 inst="mov 2, %o0"@},
29021 @{address="0x000107c4",func-name="main",offset="8",
29022 inst="sethi %hi(0x11800), %o2"@},
29024 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29025 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29029 Disassemble 3 instructions from the start of @code{main}:
29033 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29035 @{address="0x000107bc",func-name="main",offset="0",
29036 inst="save %sp, -112, %sp"@},
29037 @{address="0x000107c0",func-name="main",offset="4",
29038 inst="mov 2, %o0"@},
29039 @{address="0x000107c4",func-name="main",offset="8",
29040 inst="sethi %hi(0x11800), %o2"@}]
29044 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29048 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29050 src_and_asm_line=@{line="31",
29051 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29052 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29053 line_asm_insn=[@{address="0x000107bc",
29054 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29055 src_and_asm_line=@{line="32",
29056 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29057 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29058 line_asm_insn=[@{address="0x000107c0",
29059 func-name="main",offset="4",inst="mov 2, %o0"@},
29060 @{address="0x000107c4",func-name="main",offset="8",
29061 inst="sethi %hi(0x11800), %o2"@}]@}]
29066 @subheading The @code{-data-evaluate-expression} Command
29067 @findex -data-evaluate-expression
29069 @subsubheading Synopsis
29072 -data-evaluate-expression @var{expr}
29075 Evaluate @var{expr} as an expression. The expression could contain an
29076 inferior function call. The function call will execute synchronously.
29077 If the expression contains spaces, it must be enclosed in double quotes.
29079 @subsubheading @value{GDBN} Command
29081 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29082 @samp{call}. In @code{gdbtk} only, there's a corresponding
29083 @samp{gdb_eval} command.
29085 @subsubheading Example
29087 In the following example, the numbers that precede the commands are the
29088 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29089 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29093 211-data-evaluate-expression A
29096 311-data-evaluate-expression &A
29097 311^done,value="0xefffeb7c"
29099 411-data-evaluate-expression A+3
29102 511-data-evaluate-expression "A + 3"
29108 @subheading The @code{-data-list-changed-registers} Command
29109 @findex -data-list-changed-registers
29111 @subsubheading Synopsis
29114 -data-list-changed-registers
29117 Display a list of the registers that have changed.
29119 @subsubheading @value{GDBN} Command
29121 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29122 has the corresponding command @samp{gdb_changed_register_list}.
29124 @subsubheading Example
29126 On a PPC MBX board:
29134 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29135 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29138 -data-list-changed-registers
29139 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29140 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29141 "24","25","26","27","28","30","31","64","65","66","67","69"]
29146 @subheading The @code{-data-list-register-names} Command
29147 @findex -data-list-register-names
29149 @subsubheading Synopsis
29152 -data-list-register-names [ ( @var{regno} )+ ]
29155 Show a list of register names for the current target. If no arguments
29156 are given, it shows a list of the names of all the registers. If
29157 integer numbers are given as arguments, it will print a list of the
29158 names of the registers corresponding to the arguments. To ensure
29159 consistency between a register name and its number, the output list may
29160 include empty register names.
29162 @subsubheading @value{GDBN} Command
29164 @value{GDBN} does not have a command which corresponds to
29165 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29166 corresponding command @samp{gdb_regnames}.
29168 @subsubheading Example
29170 For the PPC MBX board:
29173 -data-list-register-names
29174 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29175 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29176 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29177 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29178 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29179 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29180 "", "pc","ps","cr","lr","ctr","xer"]
29182 -data-list-register-names 1 2 3
29183 ^done,register-names=["r1","r2","r3"]
29187 @subheading The @code{-data-list-register-values} Command
29188 @findex -data-list-register-values
29190 @subsubheading Synopsis
29193 -data-list-register-values
29194 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29197 Display the registers' contents. The format according to which the
29198 registers' contents are to be returned is given by @var{fmt}, followed
29199 by an optional list of numbers specifying the registers to display. A
29200 missing list of numbers indicates that the contents of all the
29201 registers must be returned. The @code{--skip-unavailable} option
29202 indicates that only the available registers are to be returned.
29204 Allowed formats for @var{fmt} are:
29221 @subsubheading @value{GDBN} Command
29223 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29224 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29226 @subsubheading Example
29228 For a PPC MBX board (note: line breaks are for readability only, they
29229 don't appear in the actual output):
29233 -data-list-register-values r 64 65
29234 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29235 @{number="65",value="0x00029002"@}]
29237 -data-list-register-values x
29238 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29239 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29240 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29241 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29242 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29243 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29244 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29245 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29246 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29247 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29248 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29249 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29250 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29251 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29252 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29253 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29254 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29255 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29256 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29257 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29258 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29259 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29260 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29261 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29262 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29263 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29264 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29265 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29266 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29267 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29268 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29269 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29270 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29271 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29272 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29273 @{number="69",value="0x20002b03"@}]
29278 @subheading The @code{-data-read-memory} Command
29279 @findex -data-read-memory
29281 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29283 @subsubheading Synopsis
29286 -data-read-memory [ -o @var{byte-offset} ]
29287 @var{address} @var{word-format} @var{word-size}
29288 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29295 @item @var{address}
29296 An expression specifying the address of the first memory word to be
29297 read. Complex expressions containing embedded white space should be
29298 quoted using the C convention.
29300 @item @var{word-format}
29301 The format to be used to print the memory words. The notation is the
29302 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29305 @item @var{word-size}
29306 The size of each memory word in bytes.
29308 @item @var{nr-rows}
29309 The number of rows in the output table.
29311 @item @var{nr-cols}
29312 The number of columns in the output table.
29315 If present, indicates that each row should include an @sc{ascii} dump. The
29316 value of @var{aschar} is used as a padding character when a byte is not a
29317 member of the printable @sc{ascii} character set (printable @sc{ascii}
29318 characters are those whose code is between 32 and 126, inclusively).
29320 @item @var{byte-offset}
29321 An offset to add to the @var{address} before fetching memory.
29324 This command displays memory contents as a table of @var{nr-rows} by
29325 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29326 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29327 (returned as @samp{total-bytes}). Should less than the requested number
29328 of bytes be returned by the target, the missing words are identified
29329 using @samp{N/A}. The number of bytes read from the target is returned
29330 in @samp{nr-bytes} and the starting address used to read memory in
29333 The address of the next/previous row or page is available in
29334 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29337 @subsubheading @value{GDBN} Command
29339 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29340 @samp{gdb_get_mem} memory read command.
29342 @subsubheading Example
29344 Read six bytes of memory starting at @code{bytes+6} but then offset by
29345 @code{-6} bytes. Format as three rows of two columns. One byte per
29346 word. Display each word in hex.
29350 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29351 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29352 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29353 prev-page="0x0000138a",memory=[
29354 @{addr="0x00001390",data=["0x00","0x01"]@},
29355 @{addr="0x00001392",data=["0x02","0x03"]@},
29356 @{addr="0x00001394",data=["0x04","0x05"]@}]
29360 Read two bytes of memory starting at address @code{shorts + 64} and
29361 display as a single word formatted in decimal.
29365 5-data-read-memory shorts+64 d 2 1 1
29366 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29367 next-row="0x00001512",prev-row="0x0000150e",
29368 next-page="0x00001512",prev-page="0x0000150e",memory=[
29369 @{addr="0x00001510",data=["128"]@}]
29373 Read thirty two bytes of memory starting at @code{bytes+16} and format
29374 as eight rows of four columns. Include a string encoding with @samp{x}
29375 used as the non-printable character.
29379 4-data-read-memory bytes+16 x 1 8 4 x
29380 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29381 next-row="0x000013c0",prev-row="0x0000139c",
29382 next-page="0x000013c0",prev-page="0x00001380",memory=[
29383 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29384 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29385 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29386 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29387 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29388 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29389 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29390 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29394 @subheading The @code{-data-read-memory-bytes} Command
29395 @findex -data-read-memory-bytes
29397 @subsubheading Synopsis
29400 -data-read-memory-bytes [ -o @var{byte-offset} ]
29401 @var{address} @var{count}
29408 @item @var{address}
29409 An expression specifying the address of the first memory word to be
29410 read. Complex expressions containing embedded white space should be
29411 quoted using the C convention.
29414 The number of bytes to read. This should be an integer literal.
29416 @item @var{byte-offset}
29417 The offsets in bytes relative to @var{address} at which to start
29418 reading. This should be an integer literal. This option is provided
29419 so that a frontend is not required to first evaluate address and then
29420 perform address arithmetics itself.
29424 This command attempts to read all accessible memory regions in the
29425 specified range. First, all regions marked as unreadable in the memory
29426 map (if one is defined) will be skipped. @xref{Memory Region
29427 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29428 regions. For each one, if reading full region results in an errors,
29429 @value{GDBN} will try to read a subset of the region.
29431 In general, every single byte in the region may be readable or not,
29432 and the only way to read every readable byte is to try a read at
29433 every address, which is not practical. Therefore, @value{GDBN} will
29434 attempt to read all accessible bytes at either beginning or the end
29435 of the region, using a binary division scheme. This heuristic works
29436 well for reading accross a memory map boundary. Note that if a region
29437 has a readable range that is neither at the beginning or the end,
29438 @value{GDBN} will not read it.
29440 The result record (@pxref{GDB/MI Result Records}) that is output of
29441 the command includes a field named @samp{memory} whose content is a
29442 list of tuples. Each tuple represent a successfully read memory block
29443 and has the following fields:
29447 The start address of the memory block, as hexadecimal literal.
29450 The end address of the memory block, as hexadecimal literal.
29453 The offset of the memory block, as hexadecimal literal, relative to
29454 the start address passed to @code{-data-read-memory-bytes}.
29457 The contents of the memory block, in hex.
29463 @subsubheading @value{GDBN} Command
29465 The corresponding @value{GDBN} command is @samp{x}.
29467 @subsubheading Example
29471 -data-read-memory-bytes &a 10
29472 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29474 contents="01000000020000000300"@}]
29479 @subheading The @code{-data-write-memory-bytes} Command
29480 @findex -data-write-memory-bytes
29482 @subsubheading Synopsis
29485 -data-write-memory-bytes @var{address} @var{contents}
29486 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29493 @item @var{address}
29494 An expression specifying the address of the first memory word to be
29495 read. Complex expressions containing embedded white space should be
29496 quoted using the C convention.
29498 @item @var{contents}
29499 The hex-encoded bytes to write.
29502 Optional argument indicating the number of bytes to be written. If @var{count}
29503 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29504 write @var{contents} until it fills @var{count} bytes.
29508 @subsubheading @value{GDBN} Command
29510 There's no corresponding @value{GDBN} command.
29512 @subsubheading Example
29516 -data-write-memory-bytes &a "aabbccdd"
29523 -data-write-memory-bytes &a "aabbccdd" 16e
29528 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29529 @node GDB/MI Tracepoint Commands
29530 @section @sc{gdb/mi} Tracepoint Commands
29532 The commands defined in this section implement MI support for
29533 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29535 @subheading The @code{-trace-find} Command
29536 @findex -trace-find
29538 @subsubheading Synopsis
29541 -trace-find @var{mode} [@var{parameters}@dots{}]
29544 Find a trace frame using criteria defined by @var{mode} and
29545 @var{parameters}. The following table lists permissible
29546 modes and their parameters. For details of operation, see @ref{tfind}.
29551 No parameters are required. Stops examining trace frames.
29554 An integer is required as parameter. Selects tracepoint frame with
29557 @item tracepoint-number
29558 An integer is required as parameter. Finds next
29559 trace frame that corresponds to tracepoint with the specified number.
29562 An address is required as parameter. Finds
29563 next trace frame that corresponds to any tracepoint at the specified
29566 @item pc-inside-range
29567 Two addresses are required as parameters. Finds next trace
29568 frame that corresponds to a tracepoint at an address inside the
29569 specified range. Both bounds are considered to be inside the range.
29571 @item pc-outside-range
29572 Two addresses are required as parameters. Finds
29573 next trace frame that corresponds to a tracepoint at an address outside
29574 the specified range. Both bounds are considered to be inside the range.
29577 Line specification is required as parameter. @xref{Specify Location}.
29578 Finds next trace frame that corresponds to a tracepoint at
29579 the specified location.
29583 If @samp{none} was passed as @var{mode}, the response does not
29584 have fields. Otherwise, the response may have the following fields:
29588 This field has either @samp{0} or @samp{1} as the value, depending
29589 on whether a matching tracepoint was found.
29592 The index of the found traceframe. This field is present iff
29593 the @samp{found} field has value of @samp{1}.
29596 The index of the found tracepoint. This field is present iff
29597 the @samp{found} field has value of @samp{1}.
29600 The information about the frame corresponding to the found trace
29601 frame. This field is present only if a trace frame was found.
29602 @xref{GDB/MI Frame Information}, for description of this field.
29606 @subsubheading @value{GDBN} Command
29608 The corresponding @value{GDBN} command is @samp{tfind}.
29610 @subheading -trace-define-variable
29611 @findex -trace-define-variable
29613 @subsubheading Synopsis
29616 -trace-define-variable @var{name} [ @var{value} ]
29619 Create trace variable @var{name} if it does not exist. If
29620 @var{value} is specified, sets the initial value of the specified
29621 trace variable to that value. Note that the @var{name} should start
29622 with the @samp{$} character.
29624 @subsubheading @value{GDBN} Command
29626 The corresponding @value{GDBN} command is @samp{tvariable}.
29628 @subheading The @code{-trace-frame-collected} Command
29629 @findex -trace-frame-collected
29631 @subsubheading Synopsis
29634 -trace-frame-collected
29635 [--var-print-values @var{var_pval}]
29636 [--comp-print-values @var{comp_pval}]
29637 [--registers-format @var{regformat}]
29638 [--memory-contents]
29641 This command returns the set of collected objects, register names,
29642 trace state variable names, memory ranges and computed expressions
29643 that have been collected at a particular trace frame. The optional
29644 parameters to the command affect the output format in different ways.
29645 See the output description table below for more details.
29647 The reported names can be used in the normal manner to create
29648 varobjs and inspect the objects themselves. The items returned by
29649 this command are categorized so that it is clear which is a variable,
29650 which is a register, which is a trace state variable, which is a
29651 memory range and which is a computed expression.
29653 For instance, if the actions were
29655 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29656 collect *(int*)0xaf02bef0@@40
29660 the object collected in its entirety would be @code{myVar}. The
29661 object @code{myArray} would be partially collected, because only the
29662 element at index @code{myIndex} would be collected. The remaining
29663 objects would be computed expressions.
29665 An example output would be:
29669 -trace-frame-collected
29671 explicit-variables=[@{name="myVar",value="1"@}],
29672 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29673 @{name="myObj.field",value="0"@},
29674 @{name="myPtr->field",value="1"@},
29675 @{name="myCount + 2",value="3"@},
29676 @{name="$tvar1 + 1",value="43970027"@}],
29677 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29678 @{number="1",value="0x0"@},
29679 @{number="2",value="0x4"@},
29681 @{number="125",value="0x0"@}],
29682 tvars=[@{name="$tvar1",current="43970026"@}],
29683 memory=[@{address="0x0000000000602264",length="4"@},
29684 @{address="0x0000000000615bc0",length="4"@}]
29691 @item explicit-variables
29692 The set of objects that have been collected in their entirety (as
29693 opposed to collecting just a few elements of an array or a few struct
29694 members). For each object, its name and value are printed.
29695 The @code{--var-print-values} option affects how or whether the value
29696 field is output. If @var{var_pval} is 0, then print only the names;
29697 if it is 1, print also their values; and if it is 2, print the name,
29698 type and value for simple data types, and the name and type for
29699 arrays, structures and unions.
29701 @item computed-expressions
29702 The set of computed expressions that have been collected at the
29703 current trace frame. The @code{--comp-print-values} option affects
29704 this set like the @code{--var-print-values} option affects the
29705 @code{explicit-variables} set. See above.
29708 The registers that have been collected at the current trace frame.
29709 For each register collected, the name and current value are returned.
29710 The value is formatted according to the @code{--registers-format}
29711 option. See the @command{-data-list-register-values} command for a
29712 list of the allowed formats. The default is @samp{x}.
29715 The trace state variables that have been collected at the current
29716 trace frame. For each trace state variable collected, the name and
29717 current value are returned.
29720 The set of memory ranges that have been collected at the current trace
29721 frame. Its content is a list of tuples. Each tuple represents a
29722 collected memory range and has the following fields:
29726 The start address of the memory range, as hexadecimal literal.
29729 The length of the memory range, as decimal literal.
29732 The contents of the memory block, in hex. This field is only present
29733 if the @code{--memory-contents} option is specified.
29739 @subsubheading @value{GDBN} Command
29741 There is no corresponding @value{GDBN} command.
29743 @subsubheading Example
29745 @subheading -trace-list-variables
29746 @findex -trace-list-variables
29748 @subsubheading Synopsis
29751 -trace-list-variables
29754 Return a table of all defined trace variables. Each element of the
29755 table has the following fields:
29759 The name of the trace variable. This field is always present.
29762 The initial value. This is a 64-bit signed integer. This
29763 field is always present.
29766 The value the trace variable has at the moment. This is a 64-bit
29767 signed integer. This field is absent iff current value is
29768 not defined, for example if the trace was never run, or is
29773 @subsubheading @value{GDBN} Command
29775 The corresponding @value{GDBN} command is @samp{tvariables}.
29777 @subsubheading Example
29781 -trace-list-variables
29782 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29783 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29784 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29785 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29786 body=[variable=@{name="$trace_timestamp",initial="0"@}
29787 variable=@{name="$foo",initial="10",current="15"@}]@}
29791 @subheading -trace-save
29792 @findex -trace-save
29794 @subsubheading Synopsis
29797 -trace-save [-r ] @var{filename}
29800 Saves the collected trace data to @var{filename}. Without the
29801 @samp{-r} option, the data is downloaded from the target and saved
29802 in a local file. With the @samp{-r} option the target is asked
29803 to perform the save.
29805 @subsubheading @value{GDBN} Command
29807 The corresponding @value{GDBN} command is @samp{tsave}.
29810 @subheading -trace-start
29811 @findex -trace-start
29813 @subsubheading Synopsis
29819 Starts a tracing experiments. The result of this command does not
29822 @subsubheading @value{GDBN} Command
29824 The corresponding @value{GDBN} command is @samp{tstart}.
29826 @subheading -trace-status
29827 @findex -trace-status
29829 @subsubheading Synopsis
29835 Obtains the status of a tracing experiment. The result may include
29836 the following fields:
29841 May have a value of either @samp{0}, when no tracing operations are
29842 supported, @samp{1}, when all tracing operations are supported, or
29843 @samp{file} when examining trace file. In the latter case, examining
29844 of trace frame is possible but new tracing experiement cannot be
29845 started. This field is always present.
29848 May have a value of either @samp{0} or @samp{1} depending on whether
29849 tracing experiement is in progress on target. This field is present
29850 if @samp{supported} field is not @samp{0}.
29853 Report the reason why the tracing was stopped last time. This field
29854 may be absent iff tracing was never stopped on target yet. The
29855 value of @samp{request} means the tracing was stopped as result of
29856 the @code{-trace-stop} command. The value of @samp{overflow} means
29857 the tracing buffer is full. The value of @samp{disconnection} means
29858 tracing was automatically stopped when @value{GDBN} has disconnected.
29859 The value of @samp{passcount} means tracing was stopped when a
29860 tracepoint was passed a maximal number of times for that tracepoint.
29861 This field is present if @samp{supported} field is not @samp{0}.
29863 @item stopping-tracepoint
29864 The number of tracepoint whose passcount as exceeded. This field is
29865 present iff the @samp{stop-reason} field has the value of
29869 @itemx frames-created
29870 The @samp{frames} field is a count of the total number of trace frames
29871 in the trace buffer, while @samp{frames-created} is the total created
29872 during the run, including ones that were discarded, such as when a
29873 circular trace buffer filled up. Both fields are optional.
29877 These fields tell the current size of the tracing buffer and the
29878 remaining space. These fields are optional.
29881 The value of the circular trace buffer flag. @code{1} means that the
29882 trace buffer is circular and old trace frames will be discarded if
29883 necessary to make room, @code{0} means that the trace buffer is linear
29887 The value of the disconnected tracing flag. @code{1} means that
29888 tracing will continue after @value{GDBN} disconnects, @code{0} means
29889 that the trace run will stop.
29892 The filename of the trace file being examined. This field is
29893 optional, and only present when examining a trace file.
29897 @subsubheading @value{GDBN} Command
29899 The corresponding @value{GDBN} command is @samp{tstatus}.
29901 @subheading -trace-stop
29902 @findex -trace-stop
29904 @subsubheading Synopsis
29910 Stops a tracing experiment. The result of this command has the same
29911 fields as @code{-trace-status}, except that the @samp{supported} and
29912 @samp{running} fields are not output.
29914 @subsubheading @value{GDBN} Command
29916 The corresponding @value{GDBN} command is @samp{tstop}.
29919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29920 @node GDB/MI Symbol Query
29921 @section @sc{gdb/mi} Symbol Query Commands
29925 @subheading The @code{-symbol-info-address} Command
29926 @findex -symbol-info-address
29928 @subsubheading Synopsis
29931 -symbol-info-address @var{symbol}
29934 Describe where @var{symbol} is stored.
29936 @subsubheading @value{GDBN} Command
29938 The corresponding @value{GDBN} command is @samp{info address}.
29940 @subsubheading Example
29944 @subheading The @code{-symbol-info-file} Command
29945 @findex -symbol-info-file
29947 @subsubheading Synopsis
29953 Show the file for the symbol.
29955 @subsubheading @value{GDBN} Command
29957 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29958 @samp{gdb_find_file}.
29960 @subsubheading Example
29964 @subheading The @code{-symbol-info-function} Command
29965 @findex -symbol-info-function
29967 @subsubheading Synopsis
29970 -symbol-info-function
29973 Show which function the symbol lives in.
29975 @subsubheading @value{GDBN} Command
29977 @samp{gdb_get_function} in @code{gdbtk}.
29979 @subsubheading Example
29983 @subheading The @code{-symbol-info-line} Command
29984 @findex -symbol-info-line
29986 @subsubheading Synopsis
29992 Show the core addresses of the code for a source line.
29994 @subsubheading @value{GDBN} Command
29996 The corresponding @value{GDBN} command is @samp{info line}.
29997 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29999 @subsubheading Example
30003 @subheading The @code{-symbol-info-symbol} Command
30004 @findex -symbol-info-symbol
30006 @subsubheading Synopsis
30009 -symbol-info-symbol @var{addr}
30012 Describe what symbol is at location @var{addr}.
30014 @subsubheading @value{GDBN} Command
30016 The corresponding @value{GDBN} command is @samp{info symbol}.
30018 @subsubheading Example
30022 @subheading The @code{-symbol-list-functions} Command
30023 @findex -symbol-list-functions
30025 @subsubheading Synopsis
30028 -symbol-list-functions
30031 List the functions in the executable.
30033 @subsubheading @value{GDBN} Command
30035 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30036 @samp{gdb_search} in @code{gdbtk}.
30038 @subsubheading Example
30043 @subheading The @code{-symbol-list-lines} Command
30044 @findex -symbol-list-lines
30046 @subsubheading Synopsis
30049 -symbol-list-lines @var{filename}
30052 Print the list of lines that contain code and their associated program
30053 addresses for the given source filename. The entries are sorted in
30054 ascending PC order.
30056 @subsubheading @value{GDBN} Command
30058 There is no corresponding @value{GDBN} command.
30060 @subsubheading Example
30063 -symbol-list-lines basics.c
30064 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30070 @subheading The @code{-symbol-list-types} Command
30071 @findex -symbol-list-types
30073 @subsubheading Synopsis
30079 List all the type names.
30081 @subsubheading @value{GDBN} Command
30083 The corresponding commands are @samp{info types} in @value{GDBN},
30084 @samp{gdb_search} in @code{gdbtk}.
30086 @subsubheading Example
30090 @subheading The @code{-symbol-list-variables} Command
30091 @findex -symbol-list-variables
30093 @subsubheading Synopsis
30096 -symbol-list-variables
30099 List all the global and static variable names.
30101 @subsubheading @value{GDBN} Command
30103 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30105 @subsubheading Example
30109 @subheading The @code{-symbol-locate} Command
30110 @findex -symbol-locate
30112 @subsubheading Synopsis
30118 @subsubheading @value{GDBN} Command
30120 @samp{gdb_loc} in @code{gdbtk}.
30122 @subsubheading Example
30126 @subheading The @code{-symbol-type} Command
30127 @findex -symbol-type
30129 @subsubheading Synopsis
30132 -symbol-type @var{variable}
30135 Show type of @var{variable}.
30137 @subsubheading @value{GDBN} Command
30139 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30140 @samp{gdb_obj_variable}.
30142 @subsubheading Example
30147 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30148 @node GDB/MI File Commands
30149 @section @sc{gdb/mi} File Commands
30151 This section describes the GDB/MI commands to specify executable file names
30152 and to read in and obtain symbol table information.
30154 @subheading The @code{-file-exec-and-symbols} Command
30155 @findex -file-exec-and-symbols
30157 @subsubheading Synopsis
30160 -file-exec-and-symbols @var{file}
30163 Specify the executable file to be debugged. This file is the one from
30164 which the symbol table is also read. If no file is specified, the
30165 command clears the executable and symbol information. If breakpoints
30166 are set when using this command with no arguments, @value{GDBN} will produce
30167 error messages. Otherwise, no output is produced, except a completion
30170 @subsubheading @value{GDBN} Command
30172 The corresponding @value{GDBN} command is @samp{file}.
30174 @subsubheading Example
30178 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30184 @subheading The @code{-file-exec-file} Command
30185 @findex -file-exec-file
30187 @subsubheading Synopsis
30190 -file-exec-file @var{file}
30193 Specify the executable file to be debugged. Unlike
30194 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30195 from this file. If used without argument, @value{GDBN} clears the information
30196 about the executable file. No output is produced, except a completion
30199 @subsubheading @value{GDBN} Command
30201 The corresponding @value{GDBN} command is @samp{exec-file}.
30203 @subsubheading Example
30207 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30214 @subheading The @code{-file-list-exec-sections} Command
30215 @findex -file-list-exec-sections
30217 @subsubheading Synopsis
30220 -file-list-exec-sections
30223 List the sections of the current executable file.
30225 @subsubheading @value{GDBN} Command
30227 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30228 information as this command. @code{gdbtk} has a corresponding command
30229 @samp{gdb_load_info}.
30231 @subsubheading Example
30236 @subheading The @code{-file-list-exec-source-file} Command
30237 @findex -file-list-exec-source-file
30239 @subsubheading Synopsis
30242 -file-list-exec-source-file
30245 List the line number, the current source file, and the absolute path
30246 to the current source file for the current executable. The macro
30247 information field has a value of @samp{1} or @samp{0} depending on
30248 whether or not the file includes preprocessor macro information.
30250 @subsubheading @value{GDBN} Command
30252 The @value{GDBN} equivalent is @samp{info source}
30254 @subsubheading Example
30258 123-file-list-exec-source-file
30259 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30264 @subheading The @code{-file-list-exec-source-files} Command
30265 @findex -file-list-exec-source-files
30267 @subsubheading Synopsis
30270 -file-list-exec-source-files
30273 List the source files for the current executable.
30275 It will always output both the filename and fullname (absolute file
30276 name) of a source file.
30278 @subsubheading @value{GDBN} Command
30280 The @value{GDBN} equivalent is @samp{info sources}.
30281 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30283 @subsubheading Example
30286 -file-list-exec-source-files
30288 @{file=foo.c,fullname=/home/foo.c@},
30289 @{file=/home/bar.c,fullname=/home/bar.c@},
30290 @{file=gdb_could_not_find_fullpath.c@}]
30295 @subheading The @code{-file-list-shared-libraries} Command
30296 @findex -file-list-shared-libraries
30298 @subsubheading Synopsis
30301 -file-list-shared-libraries
30304 List the shared libraries in the program.
30306 @subsubheading @value{GDBN} Command
30308 The corresponding @value{GDBN} command is @samp{info shared}.
30310 @subsubheading Example
30314 @subheading The @code{-file-list-symbol-files} Command
30315 @findex -file-list-symbol-files
30317 @subsubheading Synopsis
30320 -file-list-symbol-files
30325 @subsubheading @value{GDBN} Command
30327 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30329 @subsubheading Example
30334 @subheading The @code{-file-symbol-file} Command
30335 @findex -file-symbol-file
30337 @subsubheading Synopsis
30340 -file-symbol-file @var{file}
30343 Read symbol table info from the specified @var{file} argument. When
30344 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30345 produced, except for a completion notification.
30347 @subsubheading @value{GDBN} Command
30349 The corresponding @value{GDBN} command is @samp{symbol-file}.
30351 @subsubheading Example
30355 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30361 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30362 @node GDB/MI Memory Overlay Commands
30363 @section @sc{gdb/mi} Memory Overlay Commands
30365 The memory overlay commands are not implemented.
30367 @c @subheading -overlay-auto
30369 @c @subheading -overlay-list-mapping-state
30371 @c @subheading -overlay-list-overlays
30373 @c @subheading -overlay-map
30375 @c @subheading -overlay-off
30377 @c @subheading -overlay-on
30379 @c @subheading -overlay-unmap
30381 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30382 @node GDB/MI Signal Handling Commands
30383 @section @sc{gdb/mi} Signal Handling Commands
30385 Signal handling commands are not implemented.
30387 @c @subheading -signal-handle
30389 @c @subheading -signal-list-handle-actions
30391 @c @subheading -signal-list-signal-types
30395 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30396 @node GDB/MI Target Manipulation
30397 @section @sc{gdb/mi} Target Manipulation Commands
30400 @subheading The @code{-target-attach} Command
30401 @findex -target-attach
30403 @subsubheading Synopsis
30406 -target-attach @var{pid} | @var{gid} | @var{file}
30409 Attach to a process @var{pid} or a file @var{file} outside of
30410 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30411 group, the id previously returned by
30412 @samp{-list-thread-groups --available} must be used.
30414 @subsubheading @value{GDBN} Command
30416 The corresponding @value{GDBN} command is @samp{attach}.
30418 @subsubheading Example
30422 =thread-created,id="1"
30423 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30429 @subheading The @code{-target-compare-sections} Command
30430 @findex -target-compare-sections
30432 @subsubheading Synopsis
30435 -target-compare-sections [ @var{section} ]
30438 Compare data of section @var{section} on target to the exec file.
30439 Without the argument, all sections are compared.
30441 @subsubheading @value{GDBN} Command
30443 The @value{GDBN} equivalent is @samp{compare-sections}.
30445 @subsubheading Example
30450 @subheading The @code{-target-detach} Command
30451 @findex -target-detach
30453 @subsubheading Synopsis
30456 -target-detach [ @var{pid} | @var{gid} ]
30459 Detach from the remote target which normally resumes its execution.
30460 If either @var{pid} or @var{gid} is specified, detaches from either
30461 the specified process, or specified thread group. There's no output.
30463 @subsubheading @value{GDBN} Command
30465 The corresponding @value{GDBN} command is @samp{detach}.
30467 @subsubheading Example
30477 @subheading The @code{-target-disconnect} Command
30478 @findex -target-disconnect
30480 @subsubheading Synopsis
30486 Disconnect from the remote target. There's no output and the target is
30487 generally not resumed.
30489 @subsubheading @value{GDBN} Command
30491 The corresponding @value{GDBN} command is @samp{disconnect}.
30493 @subsubheading Example
30503 @subheading The @code{-target-download} Command
30504 @findex -target-download
30506 @subsubheading Synopsis
30512 Loads the executable onto the remote target.
30513 It prints out an update message every half second, which includes the fields:
30517 The name of the section.
30519 The size of what has been sent so far for that section.
30521 The size of the section.
30523 The total size of what was sent so far (the current and the previous sections).
30525 The size of the overall executable to download.
30529 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30530 @sc{gdb/mi} Output Syntax}).
30532 In addition, it prints the name and size of the sections, as they are
30533 downloaded. These messages include the following fields:
30537 The name of the section.
30539 The size of the section.
30541 The size of the overall executable to download.
30545 At the end, a summary is printed.
30547 @subsubheading @value{GDBN} Command
30549 The corresponding @value{GDBN} command is @samp{load}.
30551 @subsubheading Example
30553 Note: each status message appears on a single line. Here the messages
30554 have been broken down so that they can fit onto a page.
30559 +download,@{section=".text",section-size="6668",total-size="9880"@}
30560 +download,@{section=".text",section-sent="512",section-size="6668",
30561 total-sent="512",total-size="9880"@}
30562 +download,@{section=".text",section-sent="1024",section-size="6668",
30563 total-sent="1024",total-size="9880"@}
30564 +download,@{section=".text",section-sent="1536",section-size="6668",
30565 total-sent="1536",total-size="9880"@}
30566 +download,@{section=".text",section-sent="2048",section-size="6668",
30567 total-sent="2048",total-size="9880"@}
30568 +download,@{section=".text",section-sent="2560",section-size="6668",
30569 total-sent="2560",total-size="9880"@}
30570 +download,@{section=".text",section-sent="3072",section-size="6668",
30571 total-sent="3072",total-size="9880"@}
30572 +download,@{section=".text",section-sent="3584",section-size="6668",
30573 total-sent="3584",total-size="9880"@}
30574 +download,@{section=".text",section-sent="4096",section-size="6668",
30575 total-sent="4096",total-size="9880"@}
30576 +download,@{section=".text",section-sent="4608",section-size="6668",
30577 total-sent="4608",total-size="9880"@}
30578 +download,@{section=".text",section-sent="5120",section-size="6668",
30579 total-sent="5120",total-size="9880"@}
30580 +download,@{section=".text",section-sent="5632",section-size="6668",
30581 total-sent="5632",total-size="9880"@}
30582 +download,@{section=".text",section-sent="6144",section-size="6668",
30583 total-sent="6144",total-size="9880"@}
30584 +download,@{section=".text",section-sent="6656",section-size="6668",
30585 total-sent="6656",total-size="9880"@}
30586 +download,@{section=".init",section-size="28",total-size="9880"@}
30587 +download,@{section=".fini",section-size="28",total-size="9880"@}
30588 +download,@{section=".data",section-size="3156",total-size="9880"@}
30589 +download,@{section=".data",section-sent="512",section-size="3156",
30590 total-sent="7236",total-size="9880"@}
30591 +download,@{section=".data",section-sent="1024",section-size="3156",
30592 total-sent="7748",total-size="9880"@}
30593 +download,@{section=".data",section-sent="1536",section-size="3156",
30594 total-sent="8260",total-size="9880"@}
30595 +download,@{section=".data",section-sent="2048",section-size="3156",
30596 total-sent="8772",total-size="9880"@}
30597 +download,@{section=".data",section-sent="2560",section-size="3156",
30598 total-sent="9284",total-size="9880"@}
30599 +download,@{section=".data",section-sent="3072",section-size="3156",
30600 total-sent="9796",total-size="9880"@}
30601 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30608 @subheading The @code{-target-exec-status} Command
30609 @findex -target-exec-status
30611 @subsubheading Synopsis
30614 -target-exec-status
30617 Provide information on the state of the target (whether it is running or
30618 not, for instance).
30620 @subsubheading @value{GDBN} Command
30622 There's no equivalent @value{GDBN} command.
30624 @subsubheading Example
30628 @subheading The @code{-target-list-available-targets} Command
30629 @findex -target-list-available-targets
30631 @subsubheading Synopsis
30634 -target-list-available-targets
30637 List the possible targets to connect to.
30639 @subsubheading @value{GDBN} Command
30641 The corresponding @value{GDBN} command is @samp{help target}.
30643 @subsubheading Example
30647 @subheading The @code{-target-list-current-targets} Command
30648 @findex -target-list-current-targets
30650 @subsubheading Synopsis
30653 -target-list-current-targets
30656 Describe the current target.
30658 @subsubheading @value{GDBN} Command
30660 The corresponding information is printed by @samp{info file} (among
30663 @subsubheading Example
30667 @subheading The @code{-target-list-parameters} Command
30668 @findex -target-list-parameters
30670 @subsubheading Synopsis
30673 -target-list-parameters
30679 @subsubheading @value{GDBN} Command
30683 @subsubheading Example
30687 @subheading The @code{-target-select} Command
30688 @findex -target-select
30690 @subsubheading Synopsis
30693 -target-select @var{type} @var{parameters @dots{}}
30696 Connect @value{GDBN} to the remote target. This command takes two args:
30700 The type of target, for instance @samp{remote}, etc.
30701 @item @var{parameters}
30702 Device names, host names and the like. @xref{Target Commands, ,
30703 Commands for Managing Targets}, for more details.
30706 The output is a connection notification, followed by the address at
30707 which the target program is, in the following form:
30710 ^connected,addr="@var{address}",func="@var{function name}",
30711 args=[@var{arg list}]
30714 @subsubheading @value{GDBN} Command
30716 The corresponding @value{GDBN} command is @samp{target}.
30718 @subsubheading Example
30722 -target-select remote /dev/ttya
30723 ^connected,addr="0xfe00a300",func="??",args=[]
30727 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30728 @node GDB/MI File Transfer Commands
30729 @section @sc{gdb/mi} File Transfer Commands
30732 @subheading The @code{-target-file-put} Command
30733 @findex -target-file-put
30735 @subsubheading Synopsis
30738 -target-file-put @var{hostfile} @var{targetfile}
30741 Copy file @var{hostfile} from the host system (the machine running
30742 @value{GDBN}) to @var{targetfile} on the target system.
30744 @subsubheading @value{GDBN} Command
30746 The corresponding @value{GDBN} command is @samp{remote put}.
30748 @subsubheading Example
30752 -target-file-put localfile remotefile
30758 @subheading The @code{-target-file-get} Command
30759 @findex -target-file-get
30761 @subsubheading Synopsis
30764 -target-file-get @var{targetfile} @var{hostfile}
30767 Copy file @var{targetfile} from the target system to @var{hostfile}
30768 on the host system.
30770 @subsubheading @value{GDBN} Command
30772 The corresponding @value{GDBN} command is @samp{remote get}.
30774 @subsubheading Example
30778 -target-file-get remotefile localfile
30784 @subheading The @code{-target-file-delete} Command
30785 @findex -target-file-delete
30787 @subsubheading Synopsis
30790 -target-file-delete @var{targetfile}
30793 Delete @var{targetfile} from the target system.
30795 @subsubheading @value{GDBN} Command
30797 The corresponding @value{GDBN} command is @samp{remote delete}.
30799 @subsubheading Example
30803 -target-file-delete remotefile
30809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30810 @node GDB/MI Ada Exceptions Commands
30811 @section Ada Exceptions @sc{gdb/mi} Commands
30813 @subheading The @code{-info-ada-exceptions} Command
30814 @findex -info-ada-exceptions
30816 @subsubheading Synopsis
30819 -info-ada-exceptions [ @var{regexp}]
30822 List all Ada exceptions defined within the program being debugged.
30823 With a regular expression @var{regexp}, only those exceptions whose
30824 names match @var{regexp} are listed.
30826 @subsubheading @value{GDBN} Command
30828 The corresponding @value{GDBN} command is @samp{info exceptions}.
30830 @subsubheading Result
30832 The result is a table of Ada exceptions. The following columns are
30833 defined for each exception:
30837 The name of the exception.
30840 The address of the exception.
30844 @subsubheading Example
30847 -info-ada-exceptions aint
30848 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
30849 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
30850 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
30851 body=[@{name="constraint_error",address="0x0000000000613da0"@},
30852 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
30855 @subheading Catching Ada Exceptions
30857 The commands describing how to ask @value{GDBN} to stop when a program
30858 raises an exception are described at @ref{Ada Exception GDB/MI
30859 Catchpoint Commands}.
30862 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30863 @node GDB/MI Support Commands
30864 @section @sc{gdb/mi} Support Commands
30866 Since new commands and features get regularly added to @sc{gdb/mi},
30867 some commands are available to help front-ends query the debugger
30868 about support for these capabilities. Similarly, it is also possible
30869 to query @value{GDBN} about target support of certain features.
30871 @subheading The @code{-info-gdb-mi-command} Command
30872 @cindex @code{-info-gdb-mi-command}
30873 @findex -info-gdb-mi-command
30875 @subsubheading Synopsis
30878 -info-gdb-mi-command @var{cmd_name}
30881 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
30883 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
30884 is technically not part of the command name (@pxref{GDB/MI Input
30885 Syntax}), and thus should be omitted in @var{cmd_name}. However,
30886 for ease of use, this command also accepts the form with the leading
30889 @subsubheading @value{GDBN} Command
30891 There is no corresponding @value{GDBN} command.
30893 @subsubheading Result
30895 The result is a tuple. There is currently only one field:
30899 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
30900 @code{"false"} otherwise.
30904 @subsubheading Example
30906 Here is an example where the @sc{gdb/mi} command does not exist:
30909 -info-gdb-mi-command unsupported-command
30910 ^done,command=@{exists="false"@}
30914 And here is an example where the @sc{gdb/mi} command is known
30918 -info-gdb-mi-command symbol-list-lines
30919 ^done,command=@{exists="true"@}
30922 @subheading The @code{-list-features} Command
30923 @findex -list-features
30924 @cindex supported @sc{gdb/mi} features, list
30926 Returns a list of particular features of the MI protocol that
30927 this version of gdb implements. A feature can be a command,
30928 or a new field in an output of some command, or even an
30929 important bugfix. While a frontend can sometimes detect presence
30930 of a feature at runtime, it is easier to perform detection at debugger
30933 The command returns a list of strings, with each string naming an
30934 available feature. Each returned string is just a name, it does not
30935 have any internal structure. The list of possible feature names
30941 (gdb) -list-features
30942 ^done,result=["feature1","feature2"]
30945 The current list of features is:
30948 @item frozen-varobjs
30949 Indicates support for the @code{-var-set-frozen} command, as well
30950 as possible presense of the @code{frozen} field in the output
30951 of @code{-varobj-create}.
30952 @item pending-breakpoints
30953 Indicates support for the @option{-f} option to the @code{-break-insert}
30956 Indicates Python scripting support, Python-based
30957 pretty-printing commands, and possible presence of the
30958 @samp{display_hint} field in the output of @code{-var-list-children}
30960 Indicates support for the @code{-thread-info} command.
30961 @item data-read-memory-bytes
30962 Indicates support for the @code{-data-read-memory-bytes} and the
30963 @code{-data-write-memory-bytes} commands.
30964 @item breakpoint-notifications
30965 Indicates that changes to breakpoints and breakpoints created via the
30966 CLI will be announced via async records.
30967 @item ada-task-info
30968 Indicates support for the @code{-ada-task-info} command.
30969 @item language-option
30970 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
30971 option (@pxref{Context management}).
30972 @item info-gdb-mi-command
30973 Indicates support for the @code{-info-gdb-mi-command} command.
30974 @item undefined-command-error-code
30975 Indicates support for the "undefined-command" error code in error result
30976 records, produced when trying to execute an undefined @sc{gdb/mi} command
30977 (@pxref{GDB/MI Result Records}).
30978 @item exec-run-start-option
30979 Indicates that the @code{-exec-run} command supports the @option{--start}
30980 option (@pxref{GDB/MI Program Execution}).
30983 @subheading The @code{-list-target-features} Command
30984 @findex -list-target-features
30986 Returns a list of particular features that are supported by the
30987 target. Those features affect the permitted MI commands, but
30988 unlike the features reported by the @code{-list-features} command, the
30989 features depend on which target GDB is using at the moment. Whenever
30990 a target can change, due to commands such as @code{-target-select},
30991 @code{-target-attach} or @code{-exec-run}, the list of target features
30992 may change, and the frontend should obtain it again.
30996 (gdb) -list-target-features
30997 ^done,result=["async"]
31000 The current list of features is:
31004 Indicates that the target is capable of asynchronous command
31005 execution, which means that @value{GDBN} will accept further commands
31006 while the target is running.
31009 Indicates that the target is capable of reverse execution.
31010 @xref{Reverse Execution}, for more information.
31014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31015 @node GDB/MI Miscellaneous Commands
31016 @section Miscellaneous @sc{gdb/mi} Commands
31018 @c @subheading -gdb-complete
31020 @subheading The @code{-gdb-exit} Command
31023 @subsubheading Synopsis
31029 Exit @value{GDBN} immediately.
31031 @subsubheading @value{GDBN} Command
31033 Approximately corresponds to @samp{quit}.
31035 @subsubheading Example
31045 @subheading The @code{-exec-abort} Command
31046 @findex -exec-abort
31048 @subsubheading Synopsis
31054 Kill the inferior running program.
31056 @subsubheading @value{GDBN} Command
31058 The corresponding @value{GDBN} command is @samp{kill}.
31060 @subsubheading Example
31065 @subheading The @code{-gdb-set} Command
31068 @subsubheading Synopsis
31074 Set an internal @value{GDBN} variable.
31075 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31077 @subsubheading @value{GDBN} Command
31079 The corresponding @value{GDBN} command is @samp{set}.
31081 @subsubheading Example
31091 @subheading The @code{-gdb-show} Command
31094 @subsubheading Synopsis
31100 Show the current value of a @value{GDBN} variable.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{show}.
31106 @subsubheading Example
31115 @c @subheading -gdb-source
31118 @subheading The @code{-gdb-version} Command
31119 @findex -gdb-version
31121 @subsubheading Synopsis
31127 Show version information for @value{GDBN}. Used mostly in testing.
31129 @subsubheading @value{GDBN} Command
31131 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31132 default shows this information when you start an interactive session.
31134 @subsubheading Example
31136 @c This example modifies the actual output from GDB to avoid overfull
31142 ~Copyright 2000 Free Software Foundation, Inc.
31143 ~GDB is free software, covered by the GNU General Public License, and
31144 ~you are welcome to change it and/or distribute copies of it under
31145 ~ certain conditions.
31146 ~Type "show copying" to see the conditions.
31147 ~There is absolutely no warranty for GDB. Type "show warranty" for
31149 ~This GDB was configured as
31150 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31155 @subheading The @code{-list-thread-groups} Command
31156 @findex -list-thread-groups
31158 @subheading Synopsis
31161 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31164 Lists thread groups (@pxref{Thread groups}). When a single thread
31165 group is passed as the argument, lists the children of that group.
31166 When several thread group are passed, lists information about those
31167 thread groups. Without any parameters, lists information about all
31168 top-level thread groups.
31170 Normally, thread groups that are being debugged are reported.
31171 With the @samp{--available} option, @value{GDBN} reports thread groups
31172 available on the target.
31174 The output of this command may have either a @samp{threads} result or
31175 a @samp{groups} result. The @samp{thread} result has a list of tuples
31176 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31177 Information}). The @samp{groups} result has a list of tuples as value,
31178 each tuple describing a thread group. If top-level groups are
31179 requested (that is, no parameter is passed), or when several groups
31180 are passed, the output always has a @samp{groups} result. The format
31181 of the @samp{group} result is described below.
31183 To reduce the number of roundtrips it's possible to list thread groups
31184 together with their children, by passing the @samp{--recurse} option
31185 and the recursion depth. Presently, only recursion depth of 1 is
31186 permitted. If this option is present, then every reported thread group
31187 will also include its children, either as @samp{group} or
31188 @samp{threads} field.
31190 In general, any combination of option and parameters is permitted, with
31191 the following caveats:
31195 When a single thread group is passed, the output will typically
31196 be the @samp{threads} result. Because threads may not contain
31197 anything, the @samp{recurse} option will be ignored.
31200 When the @samp{--available} option is passed, limited information may
31201 be available. In particular, the list of threads of a process might
31202 be inaccessible. Further, specifying specific thread groups might
31203 not give any performance advantage over listing all thread groups.
31204 The frontend should assume that @samp{-list-thread-groups --available}
31205 is always an expensive operation and cache the results.
31209 The @samp{groups} result is a list of tuples, where each tuple may
31210 have the following fields:
31214 Identifier of the thread group. This field is always present.
31215 The identifier is an opaque string; frontends should not try to
31216 convert it to an integer, even though it might look like one.
31219 The type of the thread group. At present, only @samp{process} is a
31223 The target-specific process identifier. This field is only present
31224 for thread groups of type @samp{process} and only if the process exists.
31227 The exit code of this group's last exited thread, formatted in octal.
31228 This field is only present for thread groups of type @samp{process} and
31229 only if the process is not running.
31232 The number of children this thread group has. This field may be
31233 absent for an available thread group.
31236 This field has a list of tuples as value, each tuple describing a
31237 thread. It may be present if the @samp{--recurse} option is
31238 specified, and it's actually possible to obtain the threads.
31241 This field is a list of integers, each identifying a core that one
31242 thread of the group is running on. This field may be absent if
31243 such information is not available.
31246 The name of the executable file that corresponds to this thread group.
31247 The field is only present for thread groups of type @samp{process},
31248 and only if there is a corresponding executable file.
31252 @subheading Example
31256 -list-thread-groups
31257 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31258 -list-thread-groups 17
31259 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31260 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31261 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31262 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31263 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31264 -list-thread-groups --available
31265 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31266 -list-thread-groups --available --recurse 1
31267 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31268 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31269 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31270 -list-thread-groups --available --recurse 1 17 18
31271 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31272 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31273 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31276 @subheading The @code{-info-os} Command
31279 @subsubheading Synopsis
31282 -info-os [ @var{type} ]
31285 If no argument is supplied, the command returns a table of available
31286 operating-system-specific information types. If one of these types is
31287 supplied as an argument @var{type}, then the command returns a table
31288 of data of that type.
31290 The types of information available depend on the target operating
31293 @subsubheading @value{GDBN} Command
31295 The corresponding @value{GDBN} command is @samp{info os}.
31297 @subsubheading Example
31299 When run on a @sc{gnu}/Linux system, the output will look something
31305 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31306 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31307 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31308 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31309 body=[item=@{col0="processes",col1="Listing of all processes",
31310 col2="Processes"@},
31311 item=@{col0="procgroups",col1="Listing of all process groups",
31312 col2="Process groups"@},
31313 item=@{col0="threads",col1="Listing of all threads",
31315 item=@{col0="files",col1="Listing of all file descriptors",
31316 col2="File descriptors"@},
31317 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31319 item=@{col0="shm",col1="Listing of all shared-memory regions",
31320 col2="Shared-memory regions"@},
31321 item=@{col0="semaphores",col1="Listing of all semaphores",
31322 col2="Semaphores"@},
31323 item=@{col0="msg",col1="Listing of all message queues",
31324 col2="Message queues"@},
31325 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31326 col2="Kernel modules"@}]@}
31329 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31330 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31331 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31332 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31333 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31334 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31335 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31336 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31338 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31339 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31343 (Note that the MI output here includes a @code{"Title"} column that
31344 does not appear in command-line @code{info os}; this column is useful
31345 for MI clients that want to enumerate the types of data, such as in a
31346 popup menu, but is needless clutter on the command line, and
31347 @code{info os} omits it.)
31349 @subheading The @code{-add-inferior} Command
31350 @findex -add-inferior
31352 @subheading Synopsis
31358 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31359 inferior is not associated with any executable. Such association may
31360 be established with the @samp{-file-exec-and-symbols} command
31361 (@pxref{GDB/MI File Commands}). The command response has a single
31362 field, @samp{inferior}, whose value is the identifier of the
31363 thread group corresponding to the new inferior.
31365 @subheading Example
31370 ^done,inferior="i3"
31373 @subheading The @code{-interpreter-exec} Command
31374 @findex -interpreter-exec
31376 @subheading Synopsis
31379 -interpreter-exec @var{interpreter} @var{command}
31381 @anchor{-interpreter-exec}
31383 Execute the specified @var{command} in the given @var{interpreter}.
31385 @subheading @value{GDBN} Command
31387 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31389 @subheading Example
31393 -interpreter-exec console "break main"
31394 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31395 &"During symbol reading, bad structure-type format.\n"
31396 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31401 @subheading The @code{-inferior-tty-set} Command
31402 @findex -inferior-tty-set
31404 @subheading Synopsis
31407 -inferior-tty-set /dev/pts/1
31410 Set terminal for future runs of the program being debugged.
31412 @subheading @value{GDBN} Command
31414 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31416 @subheading Example
31420 -inferior-tty-set /dev/pts/1
31425 @subheading The @code{-inferior-tty-show} Command
31426 @findex -inferior-tty-show
31428 @subheading Synopsis
31434 Show terminal for future runs of program being debugged.
31436 @subheading @value{GDBN} Command
31438 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31440 @subheading Example
31444 -inferior-tty-set /dev/pts/1
31448 ^done,inferior_tty_terminal="/dev/pts/1"
31452 @subheading The @code{-enable-timings} Command
31453 @findex -enable-timings
31455 @subheading Synopsis
31458 -enable-timings [yes | no]
31461 Toggle the printing of the wallclock, user and system times for an MI
31462 command as a field in its output. This command is to help frontend
31463 developers optimize the performance of their code. No argument is
31464 equivalent to @samp{yes}.
31466 @subheading @value{GDBN} Command
31470 @subheading Example
31478 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31479 addr="0x080484ed",func="main",file="myprog.c",
31480 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31482 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31490 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31491 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31492 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31493 fullname="/home/nickrob/myprog.c",line="73"@}
31498 @chapter @value{GDBN} Annotations
31500 This chapter describes annotations in @value{GDBN}. Annotations were
31501 designed to interface @value{GDBN} to graphical user interfaces or other
31502 similar programs which want to interact with @value{GDBN} at a
31503 relatively high level.
31505 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31509 This is Edition @value{EDITION}, @value{DATE}.
31513 * Annotations Overview:: What annotations are; the general syntax.
31514 * Server Prefix:: Issuing a command without affecting user state.
31515 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31516 * Errors:: Annotations for error messages.
31517 * Invalidation:: Some annotations describe things now invalid.
31518 * Annotations for Running::
31519 Whether the program is running, how it stopped, etc.
31520 * Source Annotations:: Annotations describing source code.
31523 @node Annotations Overview
31524 @section What is an Annotation?
31525 @cindex annotations
31527 Annotations start with a newline character, two @samp{control-z}
31528 characters, and the name of the annotation. If there is no additional
31529 information associated with this annotation, the name of the annotation
31530 is followed immediately by a newline. If there is additional
31531 information, the name of the annotation is followed by a space, the
31532 additional information, and a newline. The additional information
31533 cannot contain newline characters.
31535 Any output not beginning with a newline and two @samp{control-z}
31536 characters denotes literal output from @value{GDBN}. Currently there is
31537 no need for @value{GDBN} to output a newline followed by two
31538 @samp{control-z} characters, but if there was such a need, the
31539 annotations could be extended with an @samp{escape} annotation which
31540 means those three characters as output.
31542 The annotation @var{level}, which is specified using the
31543 @option{--annotate} command line option (@pxref{Mode Options}), controls
31544 how much information @value{GDBN} prints together with its prompt,
31545 values of expressions, source lines, and other types of output. Level 0
31546 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31547 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31548 for programs that control @value{GDBN}, and level 2 annotations have
31549 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31550 Interface, annotate, GDB's Obsolete Annotations}).
31553 @kindex set annotate
31554 @item set annotate @var{level}
31555 The @value{GDBN} command @code{set annotate} sets the level of
31556 annotations to the specified @var{level}.
31558 @item show annotate
31559 @kindex show annotate
31560 Show the current annotation level.
31563 This chapter describes level 3 annotations.
31565 A simple example of starting up @value{GDBN} with annotations is:
31568 $ @kbd{gdb --annotate=3}
31570 Copyright 2003 Free Software Foundation, Inc.
31571 GDB is free software, covered by the GNU General Public License,
31572 and you are welcome to change it and/or distribute copies of it
31573 under certain conditions.
31574 Type "show copying" to see the conditions.
31575 There is absolutely no warranty for GDB. Type "show warranty"
31577 This GDB was configured as "i386-pc-linux-gnu"
31588 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31589 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31590 denotes a @samp{control-z} character) are annotations; the rest is
31591 output from @value{GDBN}.
31593 @node Server Prefix
31594 @section The Server Prefix
31595 @cindex server prefix
31597 If you prefix a command with @samp{server } then it will not affect
31598 the command history, nor will it affect @value{GDBN}'s notion of which
31599 command to repeat if @key{RET} is pressed on a line by itself. This
31600 means that commands can be run behind a user's back by a front-end in
31601 a transparent manner.
31603 The @code{server } prefix does not affect the recording of values into
31604 the value history; to print a value without recording it into the
31605 value history, use the @code{output} command instead of the
31606 @code{print} command.
31608 Using this prefix also disables confirmation requests
31609 (@pxref{confirmation requests}).
31612 @section Annotation for @value{GDBN} Input
31614 @cindex annotations for prompts
31615 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31616 to know when to send output, when the output from a given command is
31619 Different kinds of input each have a different @dfn{input type}. Each
31620 input type has three annotations: a @code{pre-} annotation, which
31621 denotes the beginning of any prompt which is being output, a plain
31622 annotation, which denotes the end of the prompt, and then a @code{post-}
31623 annotation which denotes the end of any echo which may (or may not) be
31624 associated with the input. For example, the @code{prompt} input type
31625 features the following annotations:
31633 The input types are
31636 @findex pre-prompt annotation
31637 @findex prompt annotation
31638 @findex post-prompt annotation
31640 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31642 @findex pre-commands annotation
31643 @findex commands annotation
31644 @findex post-commands annotation
31646 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31647 command. The annotations are repeated for each command which is input.
31649 @findex pre-overload-choice annotation
31650 @findex overload-choice annotation
31651 @findex post-overload-choice annotation
31652 @item overload-choice
31653 When @value{GDBN} wants the user to select between various overloaded functions.
31655 @findex pre-query annotation
31656 @findex query annotation
31657 @findex post-query annotation
31659 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31661 @findex pre-prompt-for-continue annotation
31662 @findex prompt-for-continue annotation
31663 @findex post-prompt-for-continue annotation
31664 @item prompt-for-continue
31665 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31666 expect this to work well; instead use @code{set height 0} to disable
31667 prompting. This is because the counting of lines is buggy in the
31668 presence of annotations.
31673 @cindex annotations for errors, warnings and interrupts
31675 @findex quit annotation
31680 This annotation occurs right before @value{GDBN} responds to an interrupt.
31682 @findex error annotation
31687 This annotation occurs right before @value{GDBN} responds to an error.
31689 Quit and error annotations indicate that any annotations which @value{GDBN} was
31690 in the middle of may end abruptly. For example, if a
31691 @code{value-history-begin} annotation is followed by a @code{error}, one
31692 cannot expect to receive the matching @code{value-history-end}. One
31693 cannot expect not to receive it either, however; an error annotation
31694 does not necessarily mean that @value{GDBN} is immediately returning all the way
31697 @findex error-begin annotation
31698 A quit or error annotation may be preceded by
31704 Any output between that and the quit or error annotation is the error
31707 Warning messages are not yet annotated.
31708 @c If we want to change that, need to fix warning(), type_error(),
31709 @c range_error(), and possibly other places.
31712 @section Invalidation Notices
31714 @cindex annotations for invalidation messages
31715 The following annotations say that certain pieces of state may have
31719 @findex frames-invalid annotation
31720 @item ^Z^Zframes-invalid
31722 The frames (for example, output from the @code{backtrace} command) may
31725 @findex breakpoints-invalid annotation
31726 @item ^Z^Zbreakpoints-invalid
31728 The breakpoints may have changed. For example, the user just added or
31729 deleted a breakpoint.
31732 @node Annotations for Running
31733 @section Running the Program
31734 @cindex annotations for running programs
31736 @findex starting annotation
31737 @findex stopping annotation
31738 When the program starts executing due to a @value{GDBN} command such as
31739 @code{step} or @code{continue},
31745 is output. When the program stops,
31751 is output. Before the @code{stopped} annotation, a variety of
31752 annotations describe how the program stopped.
31755 @findex exited annotation
31756 @item ^Z^Zexited @var{exit-status}
31757 The program exited, and @var{exit-status} is the exit status (zero for
31758 successful exit, otherwise nonzero).
31760 @findex signalled annotation
31761 @findex signal-name annotation
31762 @findex signal-name-end annotation
31763 @findex signal-string annotation
31764 @findex signal-string-end annotation
31765 @item ^Z^Zsignalled
31766 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31767 annotation continues:
31773 ^Z^Zsignal-name-end
31777 ^Z^Zsignal-string-end
31782 where @var{name} is the name of the signal, such as @code{SIGILL} or
31783 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31784 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
31785 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31786 user's benefit and have no particular format.
31788 @findex signal annotation
31790 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31791 just saying that the program received the signal, not that it was
31792 terminated with it.
31794 @findex breakpoint annotation
31795 @item ^Z^Zbreakpoint @var{number}
31796 The program hit breakpoint number @var{number}.
31798 @findex watchpoint annotation
31799 @item ^Z^Zwatchpoint @var{number}
31800 The program hit watchpoint number @var{number}.
31803 @node Source Annotations
31804 @section Displaying Source
31805 @cindex annotations for source display
31807 @findex source annotation
31808 The following annotation is used instead of displaying source code:
31811 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31814 where @var{filename} is an absolute file name indicating which source
31815 file, @var{line} is the line number within that file (where 1 is the
31816 first line in the file), @var{character} is the character position
31817 within the file (where 0 is the first character in the file) (for most
31818 debug formats this will necessarily point to the beginning of a line),
31819 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31820 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31821 @var{addr} is the address in the target program associated with the
31822 source which is being displayed. The @var{addr} is in the form @samp{0x}
31823 followed by one or more lowercase hex digits (note that this does not
31824 depend on the language).
31826 @node JIT Interface
31827 @chapter JIT Compilation Interface
31828 @cindex just-in-time compilation
31829 @cindex JIT compilation interface
31831 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31832 interface. A JIT compiler is a program or library that generates native
31833 executable code at runtime and executes it, usually in order to achieve good
31834 performance while maintaining platform independence.
31836 Programs that use JIT compilation are normally difficult to debug because
31837 portions of their code are generated at runtime, instead of being loaded from
31838 object files, which is where @value{GDBN} normally finds the program's symbols
31839 and debug information. In order to debug programs that use JIT compilation,
31840 @value{GDBN} has an interface that allows the program to register in-memory
31841 symbol files with @value{GDBN} at runtime.
31843 If you are using @value{GDBN} to debug a program that uses this interface, then
31844 it should work transparently so long as you have not stripped the binary. If
31845 you are developing a JIT compiler, then the interface is documented in the rest
31846 of this chapter. At this time, the only known client of this interface is the
31849 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31850 JIT compiler communicates with @value{GDBN} by writing data into a global
31851 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31852 attaches, it reads a linked list of symbol files from the global variable to
31853 find existing code, and puts a breakpoint in the function so that it can find
31854 out about additional code.
31857 * Declarations:: Relevant C struct declarations
31858 * Registering Code:: Steps to register code
31859 * Unregistering Code:: Steps to unregister code
31860 * Custom Debug Info:: Emit debug information in a custom format
31864 @section JIT Declarations
31866 These are the relevant struct declarations that a C program should include to
31867 implement the interface:
31877 struct jit_code_entry
31879 struct jit_code_entry *next_entry;
31880 struct jit_code_entry *prev_entry;
31881 const char *symfile_addr;
31882 uint64_t symfile_size;
31885 struct jit_descriptor
31888 /* This type should be jit_actions_t, but we use uint32_t
31889 to be explicit about the bitwidth. */
31890 uint32_t action_flag;
31891 struct jit_code_entry *relevant_entry;
31892 struct jit_code_entry *first_entry;
31895 /* GDB puts a breakpoint in this function. */
31896 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31898 /* Make sure to specify the version statically, because the
31899 debugger may check the version before we can set it. */
31900 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31903 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31904 modifications to this global data properly, which can easily be done by putting
31905 a global mutex around modifications to these structures.
31907 @node Registering Code
31908 @section Registering Code
31910 To register code with @value{GDBN}, the JIT should follow this protocol:
31914 Generate an object file in memory with symbols and other desired debug
31915 information. The file must include the virtual addresses of the sections.
31918 Create a code entry for the file, which gives the start and size of the symbol
31922 Add it to the linked list in the JIT descriptor.
31925 Point the relevant_entry field of the descriptor at the entry.
31928 Set @code{action_flag} to @code{JIT_REGISTER} and call
31929 @code{__jit_debug_register_code}.
31932 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31933 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31934 new code. However, the linked list must still be maintained in order to allow
31935 @value{GDBN} to attach to a running process and still find the symbol files.
31937 @node Unregistering Code
31938 @section Unregistering Code
31940 If code is freed, then the JIT should use the following protocol:
31944 Remove the code entry corresponding to the code from the linked list.
31947 Point the @code{relevant_entry} field of the descriptor at the code entry.
31950 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31951 @code{__jit_debug_register_code}.
31954 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31955 and the JIT will leak the memory used for the associated symbol files.
31957 @node Custom Debug Info
31958 @section Custom Debug Info
31959 @cindex custom JIT debug info
31960 @cindex JIT debug info reader
31962 Generating debug information in platform-native file formats (like ELF
31963 or COFF) may be an overkill for JIT compilers; especially if all the
31964 debug info is used for is displaying a meaningful backtrace. The
31965 issue can be resolved by having the JIT writers decide on a debug info
31966 format and also provide a reader that parses the debug info generated
31967 by the JIT compiler. This section gives a brief overview on writing
31968 such a parser. More specific details can be found in the source file
31969 @file{gdb/jit-reader.in}, which is also installed as a header at
31970 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
31972 The reader is implemented as a shared object (so this functionality is
31973 not available on platforms which don't allow loading shared objects at
31974 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
31975 @code{jit-reader-unload} are provided, to be used to load and unload
31976 the readers from a preconfigured directory. Once loaded, the shared
31977 object is used the parse the debug information emitted by the JIT
31981 * Using JIT Debug Info Readers:: How to use supplied readers correctly
31982 * Writing JIT Debug Info Readers:: Creating a debug-info reader
31985 @node Using JIT Debug Info Readers
31986 @subsection Using JIT Debug Info Readers
31987 @kindex jit-reader-load
31988 @kindex jit-reader-unload
31990 Readers can be loaded and unloaded using the @code{jit-reader-load}
31991 and @code{jit-reader-unload} commands.
31994 @item jit-reader-load @var{reader}
31995 Load the JIT reader named @var{reader}, which is a shared
31996 object specified as either an absolute or a relative file name. In
31997 the latter case, @value{GDBN} will try to load the reader from a
31998 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
31999 system (here @var{libdir} is the system library directory, often
32000 @file{/usr/local/lib}).
32002 Only one reader can be active at a time; trying to load a second
32003 reader when one is already loaded will result in @value{GDBN}
32004 reporting an error. A new JIT reader can be loaded by first unloading
32005 the current one using @code{jit-reader-unload} and then invoking
32006 @code{jit-reader-load}.
32008 @item jit-reader-unload
32009 Unload the currently loaded JIT reader.
32013 @node Writing JIT Debug Info Readers
32014 @subsection Writing JIT Debug Info Readers
32015 @cindex writing JIT debug info readers
32017 As mentioned, a reader is essentially a shared object conforming to a
32018 certain ABI. This ABI is described in @file{jit-reader.h}.
32020 @file{jit-reader.h} defines the structures, macros and functions
32021 required to write a reader. It is installed (along with
32022 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32023 the system include directory.
32025 Readers need to be released under a GPL compatible license. A reader
32026 can be declared as released under such a license by placing the macro
32027 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32029 The entry point for readers is the symbol @code{gdb_init_reader},
32030 which is expected to be a function with the prototype
32032 @findex gdb_init_reader
32034 extern struct gdb_reader_funcs *gdb_init_reader (void);
32037 @cindex @code{struct gdb_reader_funcs}
32039 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32040 functions. These functions are executed to read the debug info
32041 generated by the JIT compiler (@code{read}), to unwind stack frames
32042 (@code{unwind}) and to create canonical frame IDs
32043 (@code{get_Frame_id}). It also has a callback that is called when the
32044 reader is being unloaded (@code{destroy}). The struct looks like this
32047 struct gdb_reader_funcs
32049 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32050 int reader_version;
32052 /* For use by the reader. */
32055 gdb_read_debug_info *read;
32056 gdb_unwind_frame *unwind;
32057 gdb_get_frame_id *get_frame_id;
32058 gdb_destroy_reader *destroy;
32062 @cindex @code{struct gdb_symbol_callbacks}
32063 @cindex @code{struct gdb_unwind_callbacks}
32065 The callbacks are provided with another set of callbacks by
32066 @value{GDBN} to do their job. For @code{read}, these callbacks are
32067 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32068 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32069 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32070 files and new symbol tables inside those object files. @code{struct
32071 gdb_unwind_callbacks} has callbacks to read registers off the current
32072 frame and to write out the values of the registers in the previous
32073 frame. Both have a callback (@code{target_read}) to read bytes off the
32074 target's address space.
32076 @node In-Process Agent
32077 @chapter In-Process Agent
32078 @cindex debugging agent
32079 The traditional debugging model is conceptually low-speed, but works fine,
32080 because most bugs can be reproduced in debugging-mode execution. However,
32081 as multi-core or many-core processors are becoming mainstream, and
32082 multi-threaded programs become more and more popular, there should be more
32083 and more bugs that only manifest themselves at normal-mode execution, for
32084 example, thread races, because debugger's interference with the program's
32085 timing may conceal the bugs. On the other hand, in some applications,
32086 it is not feasible for the debugger to interrupt the program's execution
32087 long enough for the developer to learn anything helpful about its behavior.
32088 If the program's correctness depends on its real-time behavior, delays
32089 introduced by a debugger might cause the program to fail, even when the
32090 code itself is correct. It is useful to be able to observe the program's
32091 behavior without interrupting it.
32093 Therefore, traditional debugging model is too intrusive to reproduce
32094 some bugs. In order to reduce the interference with the program, we can
32095 reduce the number of operations performed by debugger. The
32096 @dfn{In-Process Agent}, a shared library, is running within the same
32097 process with inferior, and is able to perform some debugging operations
32098 itself. As a result, debugger is only involved when necessary, and
32099 performance of debugging can be improved accordingly. Note that
32100 interference with program can be reduced but can't be removed completely,
32101 because the in-process agent will still stop or slow down the program.
32103 The in-process agent can interpret and execute Agent Expressions
32104 (@pxref{Agent Expressions}) during performing debugging operations. The
32105 agent expressions can be used for different purposes, such as collecting
32106 data in tracepoints, and condition evaluation in breakpoints.
32108 @anchor{Control Agent}
32109 You can control whether the in-process agent is used as an aid for
32110 debugging with the following commands:
32113 @kindex set agent on
32115 Causes the in-process agent to perform some operations on behalf of the
32116 debugger. Just which operations requested by the user will be done
32117 by the in-process agent depends on the its capabilities. For example,
32118 if you request to evaluate breakpoint conditions in the in-process agent,
32119 and the in-process agent has such capability as well, then breakpoint
32120 conditions will be evaluated in the in-process agent.
32122 @kindex set agent off
32123 @item set agent off
32124 Disables execution of debugging operations by the in-process agent. All
32125 of the operations will be performed by @value{GDBN}.
32129 Display the current setting of execution of debugging operations by
32130 the in-process agent.
32134 * In-Process Agent Protocol::
32137 @node In-Process Agent Protocol
32138 @section In-Process Agent Protocol
32139 @cindex in-process agent protocol
32141 The in-process agent is able to communicate with both @value{GDBN} and
32142 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32143 used for communications between @value{GDBN} or GDBserver and the IPA.
32144 In general, @value{GDBN} or GDBserver sends commands
32145 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32146 in-process agent replies back with the return result of the command, or
32147 some other information. The data sent to in-process agent is composed
32148 of primitive data types, such as 4-byte or 8-byte type, and composite
32149 types, which are called objects (@pxref{IPA Protocol Objects}).
32152 * IPA Protocol Objects::
32153 * IPA Protocol Commands::
32156 @node IPA Protocol Objects
32157 @subsection IPA Protocol Objects
32158 @cindex ipa protocol objects
32160 The commands sent to and results received from agent may contain some
32161 complex data types called @dfn{objects}.
32163 The in-process agent is running on the same machine with @value{GDBN}
32164 or GDBserver, so it doesn't have to handle as much differences between
32165 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32166 However, there are still some differences of two ends in two processes:
32170 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32171 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32173 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32174 GDBserver is compiled with one, and in-process agent is compiled with
32178 Here are the IPA Protocol Objects:
32182 agent expression object. It represents an agent expression
32183 (@pxref{Agent Expressions}).
32184 @anchor{agent expression object}
32186 tracepoint action object. It represents a tracepoint action
32187 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32188 memory, static trace data and to evaluate expression.
32189 @anchor{tracepoint action object}
32191 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32192 @anchor{tracepoint object}
32196 The following table describes important attributes of each IPA protocol
32199 @multitable @columnfractions .30 .20 .50
32200 @headitem Name @tab Size @tab Description
32201 @item @emph{agent expression object} @tab @tab
32202 @item length @tab 4 @tab length of bytes code
32203 @item byte code @tab @var{length} @tab contents of byte code
32204 @item @emph{tracepoint action for collecting memory} @tab @tab
32205 @item 'M' @tab 1 @tab type of tracepoint action
32206 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32207 address of the lowest byte to collect, otherwise @var{addr} is the offset
32208 of @var{basereg} for memory collecting.
32209 @item len @tab 8 @tab length of memory for collecting
32210 @item basereg @tab 4 @tab the register number containing the starting
32211 memory address for collecting.
32212 @item @emph{tracepoint action for collecting registers} @tab @tab
32213 @item 'R' @tab 1 @tab type of tracepoint action
32214 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32215 @item 'L' @tab 1 @tab type of tracepoint action
32216 @item @emph{tracepoint action for expression evaluation} @tab @tab
32217 @item 'X' @tab 1 @tab type of tracepoint action
32218 @item agent expression @tab length of @tab @ref{agent expression object}
32219 @item @emph{tracepoint object} @tab @tab
32220 @item number @tab 4 @tab number of tracepoint
32221 @item address @tab 8 @tab address of tracepoint inserted on
32222 @item type @tab 4 @tab type of tracepoint
32223 @item enabled @tab 1 @tab enable or disable of tracepoint
32224 @item step_count @tab 8 @tab step
32225 @item pass_count @tab 8 @tab pass
32226 @item numactions @tab 4 @tab number of tracepoint actions
32227 @item hit count @tab 8 @tab hit count
32228 @item trace frame usage @tab 8 @tab trace frame usage
32229 @item compiled_cond @tab 8 @tab compiled condition
32230 @item orig_size @tab 8 @tab orig size
32231 @item condition @tab 4 if condition is NULL otherwise length of
32232 @ref{agent expression object}
32233 @tab zero if condition is NULL, otherwise is
32234 @ref{agent expression object}
32235 @item actions @tab variable
32236 @tab numactions number of @ref{tracepoint action object}
32239 @node IPA Protocol Commands
32240 @subsection IPA Protocol Commands
32241 @cindex ipa protocol commands
32243 The spaces in each command are delimiters to ease reading this commands
32244 specification. They don't exist in real commands.
32248 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32249 Installs a new fast tracepoint described by @var{tracepoint_object}
32250 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32251 head of @dfn{jumppad}, which is used to jump to data collection routine
32256 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32257 @var{target_address} is address of tracepoint in the inferior.
32258 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32259 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32260 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32261 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32268 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32269 is about to kill inferiors.
32277 @item probe_marker_at:@var{address}
32278 Asks in-process agent to probe the marker at @var{address}.
32285 @item unprobe_marker_at:@var{address}
32286 Asks in-process agent to unprobe the marker at @var{address}.
32290 @chapter Reporting Bugs in @value{GDBN}
32291 @cindex bugs in @value{GDBN}
32292 @cindex reporting bugs in @value{GDBN}
32294 Your bug reports play an essential role in making @value{GDBN} reliable.
32296 Reporting a bug may help you by bringing a solution to your problem, or it
32297 may not. But in any case the principal function of a bug report is to help
32298 the entire community by making the next version of @value{GDBN} work better. Bug
32299 reports are your contribution to the maintenance of @value{GDBN}.
32301 In order for a bug report to serve its purpose, you must include the
32302 information that enables us to fix the bug.
32305 * Bug Criteria:: Have you found a bug?
32306 * Bug Reporting:: How to report bugs
32310 @section Have You Found a Bug?
32311 @cindex bug criteria
32313 If you are not sure whether you have found a bug, here are some guidelines:
32316 @cindex fatal signal
32317 @cindex debugger crash
32318 @cindex crash of debugger
32320 If the debugger gets a fatal signal, for any input whatever, that is a
32321 @value{GDBN} bug. Reliable debuggers never crash.
32323 @cindex error on valid input
32325 If @value{GDBN} produces an error message for valid input, that is a
32326 bug. (Note that if you're cross debugging, the problem may also be
32327 somewhere in the connection to the target.)
32329 @cindex invalid input
32331 If @value{GDBN} does not produce an error message for invalid input,
32332 that is a bug. However, you should note that your idea of
32333 ``invalid input'' might be our idea of ``an extension'' or ``support
32334 for traditional practice''.
32337 If you are an experienced user of debugging tools, your suggestions
32338 for improvement of @value{GDBN} are welcome in any case.
32341 @node Bug Reporting
32342 @section How to Report Bugs
32343 @cindex bug reports
32344 @cindex @value{GDBN} bugs, reporting
32346 A number of companies and individuals offer support for @sc{gnu} products.
32347 If you obtained @value{GDBN} from a support organization, we recommend you
32348 contact that organization first.
32350 You can find contact information for many support companies and
32351 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32353 @c should add a web page ref...
32356 @ifset BUGURL_DEFAULT
32357 In any event, we also recommend that you submit bug reports for
32358 @value{GDBN}. The preferred method is to submit them directly using
32359 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32360 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32363 @strong{Do not send bug reports to @samp{info-gdb}, or to
32364 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32365 not want to receive bug reports. Those that do have arranged to receive
32368 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32369 serves as a repeater. The mailing list and the newsgroup carry exactly
32370 the same messages. Often people think of posting bug reports to the
32371 newsgroup instead of mailing them. This appears to work, but it has one
32372 problem which can be crucial: a newsgroup posting often lacks a mail
32373 path back to the sender. Thus, if we need to ask for more information,
32374 we may be unable to reach you. For this reason, it is better to send
32375 bug reports to the mailing list.
32377 @ifclear BUGURL_DEFAULT
32378 In any event, we also recommend that you submit bug reports for
32379 @value{GDBN} to @value{BUGURL}.
32383 The fundamental principle of reporting bugs usefully is this:
32384 @strong{report all the facts}. If you are not sure whether to state a
32385 fact or leave it out, state it!
32387 Often people omit facts because they think they know what causes the
32388 problem and assume that some details do not matter. Thus, you might
32389 assume that the name of the variable you use in an example does not matter.
32390 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32391 stray memory reference which happens to fetch from the location where that
32392 name is stored in memory; perhaps, if the name were different, the contents
32393 of that location would fool the debugger into doing the right thing despite
32394 the bug. Play it safe and give a specific, complete example. That is the
32395 easiest thing for you to do, and the most helpful.
32397 Keep in mind that the purpose of a bug report is to enable us to fix the
32398 bug. It may be that the bug has been reported previously, but neither
32399 you nor we can know that unless your bug report is complete and
32402 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32403 bell?'' Those bug reports are useless, and we urge everyone to
32404 @emph{refuse to respond to them} except to chide the sender to report
32407 To enable us to fix the bug, you should include all these things:
32411 The version of @value{GDBN}. @value{GDBN} announces it if you start
32412 with no arguments; you can also print it at any time using @code{show
32415 Without this, we will not know whether there is any point in looking for
32416 the bug in the current version of @value{GDBN}.
32419 The type of machine you are using, and the operating system name and
32423 The details of the @value{GDBN} build-time configuration.
32424 @value{GDBN} shows these details if you invoke it with the
32425 @option{--configuration} command-line option, or if you type
32426 @code{show configuration} at @value{GDBN}'s prompt.
32429 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32430 ``@value{GCC}--2.8.1''.
32433 What compiler (and its version) was used to compile the program you are
32434 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32435 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32436 to get this information; for other compilers, see the documentation for
32440 The command arguments you gave the compiler to compile your example and
32441 observe the bug. For example, did you use @samp{-O}? To guarantee
32442 you will not omit something important, list them all. A copy of the
32443 Makefile (or the output from make) is sufficient.
32445 If we were to try to guess the arguments, we would probably guess wrong
32446 and then we might not encounter the bug.
32449 A complete input script, and all necessary source files, that will
32453 A description of what behavior you observe that you believe is
32454 incorrect. For example, ``It gets a fatal signal.''
32456 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32457 will certainly notice it. But if the bug is incorrect output, we might
32458 not notice unless it is glaringly wrong. You might as well not give us
32459 a chance to make a mistake.
32461 Even if the problem you experience is a fatal signal, you should still
32462 say so explicitly. Suppose something strange is going on, such as, your
32463 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32464 the C library on your system. (This has happened!) Your copy might
32465 crash and ours would not. If you told us to expect a crash, then when
32466 ours fails to crash, we would know that the bug was not happening for
32467 us. If you had not told us to expect a crash, then we would not be able
32468 to draw any conclusion from our observations.
32471 @cindex recording a session script
32472 To collect all this information, you can use a session recording program
32473 such as @command{script}, which is available on many Unix systems.
32474 Just run your @value{GDBN} session inside @command{script} and then
32475 include the @file{typescript} file with your bug report.
32477 Another way to record a @value{GDBN} session is to run @value{GDBN}
32478 inside Emacs and then save the entire buffer to a file.
32481 If you wish to suggest changes to the @value{GDBN} source, send us context
32482 diffs. If you even discuss something in the @value{GDBN} source, refer to
32483 it by context, not by line number.
32485 The line numbers in our development sources will not match those in your
32486 sources. Your line numbers would convey no useful information to us.
32490 Here are some things that are not necessary:
32494 A description of the envelope of the bug.
32496 Often people who encounter a bug spend a lot of time investigating
32497 which changes to the input file will make the bug go away and which
32498 changes will not affect it.
32500 This is often time consuming and not very useful, because the way we
32501 will find the bug is by running a single example under the debugger
32502 with breakpoints, not by pure deduction from a series of examples.
32503 We recommend that you save your time for something else.
32505 Of course, if you can find a simpler example to report @emph{instead}
32506 of the original one, that is a convenience for us. Errors in the
32507 output will be easier to spot, running under the debugger will take
32508 less time, and so on.
32510 However, simplification is not vital; if you do not want to do this,
32511 report the bug anyway and send us the entire test case you used.
32514 A patch for the bug.
32516 A patch for the bug does help us if it is a good one. But do not omit
32517 the necessary information, such as the test case, on the assumption that
32518 a patch is all we need. We might see problems with your patch and decide
32519 to fix the problem another way, or we might not understand it at all.
32521 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32522 construct an example that will make the program follow a certain path
32523 through the code. If you do not send us the example, we will not be able
32524 to construct one, so we will not be able to verify that the bug is fixed.
32526 And if we cannot understand what bug you are trying to fix, or why your
32527 patch should be an improvement, we will not install it. A test case will
32528 help us to understand.
32531 A guess about what the bug is or what it depends on.
32533 Such guesses are usually wrong. Even we cannot guess right about such
32534 things without first using the debugger to find the facts.
32537 @c The readline documentation is distributed with the readline code
32538 @c and consists of the two following files:
32541 @c Use -I with makeinfo to point to the appropriate directory,
32542 @c environment var TEXINPUTS with TeX.
32543 @ifclear SYSTEM_READLINE
32544 @include rluser.texi
32545 @include hsuser.texi
32549 @appendix In Memoriam
32551 The @value{GDBN} project mourns the loss of the following long-time
32556 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32557 to Free Software in general. Outside of @value{GDBN}, he was known in
32558 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32560 @item Michael Snyder
32561 Michael was one of the Global Maintainers of the @value{GDBN} project,
32562 with contributions recorded as early as 1996, until 2011. In addition
32563 to his day to day participation, he was a large driving force behind
32564 adding Reverse Debugging to @value{GDBN}.
32567 Beyond their technical contributions to the project, they were also
32568 enjoyable members of the Free Software Community. We will miss them.
32570 @node Formatting Documentation
32571 @appendix Formatting Documentation
32573 @cindex @value{GDBN} reference card
32574 @cindex reference card
32575 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32576 for printing with PostScript or Ghostscript, in the @file{gdb}
32577 subdirectory of the main source directory@footnote{In
32578 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32579 release.}. If you can use PostScript or Ghostscript with your printer,
32580 you can print the reference card immediately with @file{refcard.ps}.
32582 The release also includes the source for the reference card. You
32583 can format it, using @TeX{}, by typing:
32589 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32590 mode on US ``letter'' size paper;
32591 that is, on a sheet 11 inches wide by 8.5 inches
32592 high. You will need to specify this form of printing as an option to
32593 your @sc{dvi} output program.
32595 @cindex documentation
32597 All the documentation for @value{GDBN} comes as part of the machine-readable
32598 distribution. The documentation is written in Texinfo format, which is
32599 a documentation system that uses a single source file to produce both
32600 on-line information and a printed manual. You can use one of the Info
32601 formatting commands to create the on-line version of the documentation
32602 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32604 @value{GDBN} includes an already formatted copy of the on-line Info
32605 version of this manual in the @file{gdb} subdirectory. The main Info
32606 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32607 subordinate files matching @samp{gdb.info*} in the same directory. If
32608 necessary, you can print out these files, or read them with any editor;
32609 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32610 Emacs or the standalone @code{info} program, available as part of the
32611 @sc{gnu} Texinfo distribution.
32613 If you want to format these Info files yourself, you need one of the
32614 Info formatting programs, such as @code{texinfo-format-buffer} or
32617 If you have @code{makeinfo} installed, and are in the top level
32618 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32619 version @value{GDBVN}), you can make the Info file by typing:
32626 If you want to typeset and print copies of this manual, you need @TeX{},
32627 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32628 Texinfo definitions file.
32630 @TeX{} is a typesetting program; it does not print files directly, but
32631 produces output files called @sc{dvi} files. To print a typeset
32632 document, you need a program to print @sc{dvi} files. If your system
32633 has @TeX{} installed, chances are it has such a program. The precise
32634 command to use depends on your system; @kbd{lpr -d} is common; another
32635 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32636 require a file name without any extension or a @samp{.dvi} extension.
32638 @TeX{} also requires a macro definitions file called
32639 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32640 written in Texinfo format. On its own, @TeX{} cannot either read or
32641 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32642 and is located in the @file{gdb-@var{version-number}/texinfo}
32645 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32646 typeset and print this manual. First switch to the @file{gdb}
32647 subdirectory of the main source directory (for example, to
32648 @file{gdb-@value{GDBVN}/gdb}) and type:
32654 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32656 @node Installing GDB
32657 @appendix Installing @value{GDBN}
32658 @cindex installation
32661 * Requirements:: Requirements for building @value{GDBN}
32662 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32663 * Separate Objdir:: Compiling @value{GDBN} in another directory
32664 * Config Names:: Specifying names for hosts and targets
32665 * Configure Options:: Summary of options for configure
32666 * System-wide configuration:: Having a system-wide init file
32670 @section Requirements for Building @value{GDBN}
32671 @cindex building @value{GDBN}, requirements for
32673 Building @value{GDBN} requires various tools and packages to be available.
32674 Other packages will be used only if they are found.
32676 @heading Tools/Packages Necessary for Building @value{GDBN}
32678 @item ISO C90 compiler
32679 @value{GDBN} is written in ISO C90. It should be buildable with any
32680 working C90 compiler, e.g.@: GCC.
32684 @heading Tools/Packages Optional for Building @value{GDBN}
32688 @value{GDBN} can use the Expat XML parsing library. This library may be
32689 included with your operating system distribution; if it is not, you
32690 can get the latest version from @url{http://expat.sourceforge.net}.
32691 The @file{configure} script will search for this library in several
32692 standard locations; if it is installed in an unusual path, you can
32693 use the @option{--with-libexpat-prefix} option to specify its location.
32699 Remote protocol memory maps (@pxref{Memory Map Format})
32701 Target descriptions (@pxref{Target Descriptions})
32703 Remote shared library lists (@xref{Library List Format},
32704 or alternatively @pxref{Library List Format for SVR4 Targets})
32706 MS-Windows shared libraries (@pxref{Shared Libraries})
32708 Traceframe info (@pxref{Traceframe Info Format})
32710 Branch trace (@pxref{Branch Trace Format})
32714 @cindex compressed debug sections
32715 @value{GDBN} will use the @samp{zlib} library, if available, to read
32716 compressed debug sections. Some linkers, such as GNU gold, are capable
32717 of producing binaries with compressed debug sections. If @value{GDBN}
32718 is compiled with @samp{zlib}, it will be able to read the debug
32719 information in such binaries.
32721 The @samp{zlib} library is likely included with your operating system
32722 distribution; if it is not, you can get the latest version from
32723 @url{http://zlib.net}.
32726 @value{GDBN}'s features related to character sets (@pxref{Character
32727 Sets}) require a functioning @code{iconv} implementation. If you are
32728 on a GNU system, then this is provided by the GNU C Library. Some
32729 other systems also provide a working @code{iconv}.
32731 If @value{GDBN} is using the @code{iconv} program which is installed
32732 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32733 This is done with @option{--with-iconv-bin} which specifies the
32734 directory that contains the @code{iconv} program.
32736 On systems without @code{iconv}, you can install GNU Libiconv. If you
32737 have previously installed Libiconv, you can use the
32738 @option{--with-libiconv-prefix} option to configure.
32740 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32741 arrange to build Libiconv if a directory named @file{libiconv} appears
32742 in the top-most source directory. If Libiconv is built this way, and
32743 if the operating system does not provide a suitable @code{iconv}
32744 implementation, then the just-built library will automatically be used
32745 by @value{GDBN}. One easy way to set this up is to download GNU
32746 Libiconv, unpack it, and then rename the directory holding the
32747 Libiconv source code to @samp{libiconv}.
32750 @node Running Configure
32751 @section Invoking the @value{GDBN} @file{configure} Script
32752 @cindex configuring @value{GDBN}
32753 @value{GDBN} comes with a @file{configure} script that automates the process
32754 of preparing @value{GDBN} for installation; you can then use @code{make} to
32755 build the @code{gdb} program.
32757 @c irrelevant in info file; it's as current as the code it lives with.
32758 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32759 look at the @file{README} file in the sources; we may have improved the
32760 installation procedures since publishing this manual.}
32763 The @value{GDBN} distribution includes all the source code you need for
32764 @value{GDBN} in a single directory, whose name is usually composed by
32765 appending the version number to @samp{gdb}.
32767 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32768 @file{gdb-@value{GDBVN}} directory. That directory contains:
32771 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32772 script for configuring @value{GDBN} and all its supporting libraries
32774 @item gdb-@value{GDBVN}/gdb
32775 the source specific to @value{GDBN} itself
32777 @item gdb-@value{GDBVN}/bfd
32778 source for the Binary File Descriptor library
32780 @item gdb-@value{GDBVN}/include
32781 @sc{gnu} include files
32783 @item gdb-@value{GDBVN}/libiberty
32784 source for the @samp{-liberty} free software library
32786 @item gdb-@value{GDBVN}/opcodes
32787 source for the library of opcode tables and disassemblers
32789 @item gdb-@value{GDBVN}/readline
32790 source for the @sc{gnu} command-line interface
32792 @item gdb-@value{GDBVN}/glob
32793 source for the @sc{gnu} filename pattern-matching subroutine
32795 @item gdb-@value{GDBVN}/mmalloc
32796 source for the @sc{gnu} memory-mapped malloc package
32799 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32800 from the @file{gdb-@var{version-number}} source directory, which in
32801 this example is the @file{gdb-@value{GDBVN}} directory.
32803 First switch to the @file{gdb-@var{version-number}} source directory
32804 if you are not already in it; then run @file{configure}. Pass the
32805 identifier for the platform on which @value{GDBN} will run as an
32811 cd gdb-@value{GDBVN}
32812 ./configure @var{host}
32817 where @var{host} is an identifier such as @samp{sun4} or
32818 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32819 (You can often leave off @var{host}; @file{configure} tries to guess the
32820 correct value by examining your system.)
32822 Running @samp{configure @var{host}} and then running @code{make} builds the
32823 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32824 libraries, then @code{gdb} itself. The configured source files, and the
32825 binaries, are left in the corresponding source directories.
32828 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32829 system does not recognize this automatically when you run a different
32830 shell, you may need to run @code{sh} on it explicitly:
32833 sh configure @var{host}
32836 If you run @file{configure} from a directory that contains source
32837 directories for multiple libraries or programs, such as the
32838 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32840 creates configuration files for every directory level underneath (unless
32841 you tell it not to, with the @samp{--norecursion} option).
32843 You should run the @file{configure} script from the top directory in the
32844 source tree, the @file{gdb-@var{version-number}} directory. If you run
32845 @file{configure} from one of the subdirectories, you will configure only
32846 that subdirectory. That is usually not what you want. In particular,
32847 if you run the first @file{configure} from the @file{gdb} subdirectory
32848 of the @file{gdb-@var{version-number}} directory, you will omit the
32849 configuration of @file{bfd}, @file{readline}, and other sibling
32850 directories of the @file{gdb} subdirectory. This leads to build errors
32851 about missing include files such as @file{bfd/bfd.h}.
32853 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32854 However, you should make sure that the shell on your path (named by
32855 the @samp{SHELL} environment variable) is publicly readable. Remember
32856 that @value{GDBN} uses the shell to start your program---some systems refuse to
32857 let @value{GDBN} debug child processes whose programs are not readable.
32859 @node Separate Objdir
32860 @section Compiling @value{GDBN} in Another Directory
32862 If you want to run @value{GDBN} versions for several host or target machines,
32863 you need a different @code{gdb} compiled for each combination of
32864 host and target. @file{configure} is designed to make this easy by
32865 allowing you to generate each configuration in a separate subdirectory,
32866 rather than in the source directory. If your @code{make} program
32867 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32868 @code{make} in each of these directories builds the @code{gdb}
32869 program specified there.
32871 To build @code{gdb} in a separate directory, run @file{configure}
32872 with the @samp{--srcdir} option to specify where to find the source.
32873 (You also need to specify a path to find @file{configure}
32874 itself from your working directory. If the path to @file{configure}
32875 would be the same as the argument to @samp{--srcdir}, you can leave out
32876 the @samp{--srcdir} option; it is assumed.)
32878 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32879 separate directory for a Sun 4 like this:
32883 cd gdb-@value{GDBVN}
32886 ../gdb-@value{GDBVN}/configure sun4
32891 When @file{configure} builds a configuration using a remote source
32892 directory, it creates a tree for the binaries with the same structure
32893 (and using the same names) as the tree under the source directory. In
32894 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32895 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32896 @file{gdb-sun4/gdb}.
32898 Make sure that your path to the @file{configure} script has just one
32899 instance of @file{gdb} in it. If your path to @file{configure} looks
32900 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32901 one subdirectory of @value{GDBN}, not the whole package. This leads to
32902 build errors about missing include files such as @file{bfd/bfd.h}.
32904 One popular reason to build several @value{GDBN} configurations in separate
32905 directories is to configure @value{GDBN} for cross-compiling (where
32906 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32907 programs that run on another machine---the @dfn{target}).
32908 You specify a cross-debugging target by
32909 giving the @samp{--target=@var{target}} option to @file{configure}.
32911 When you run @code{make} to build a program or library, you must run
32912 it in a configured directory---whatever directory you were in when you
32913 called @file{configure} (or one of its subdirectories).
32915 The @code{Makefile} that @file{configure} generates in each source
32916 directory also runs recursively. If you type @code{make} in a source
32917 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32918 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32919 will build all the required libraries, and then build GDB.
32921 When you have multiple hosts or targets configured in separate
32922 directories, you can run @code{make} on them in parallel (for example,
32923 if they are NFS-mounted on each of the hosts); they will not interfere
32927 @section Specifying Names for Hosts and Targets
32929 The specifications used for hosts and targets in the @file{configure}
32930 script are based on a three-part naming scheme, but some short predefined
32931 aliases are also supported. The full naming scheme encodes three pieces
32932 of information in the following pattern:
32935 @var{architecture}-@var{vendor}-@var{os}
32938 For example, you can use the alias @code{sun4} as a @var{host} argument,
32939 or as the value for @var{target} in a @code{--target=@var{target}}
32940 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32942 The @file{configure} script accompanying @value{GDBN} does not provide
32943 any query facility to list all supported host and target names or
32944 aliases. @file{configure} calls the Bourne shell script
32945 @code{config.sub} to map abbreviations to full names; you can read the
32946 script, if you wish, or you can use it to test your guesses on
32947 abbreviations---for example:
32950 % sh config.sub i386-linux
32952 % sh config.sub alpha-linux
32953 alpha-unknown-linux-gnu
32954 % sh config.sub hp9k700
32956 % sh config.sub sun4
32957 sparc-sun-sunos4.1.1
32958 % sh config.sub sun3
32959 m68k-sun-sunos4.1.1
32960 % sh config.sub i986v
32961 Invalid configuration `i986v': machine `i986v' not recognized
32965 @code{config.sub} is also distributed in the @value{GDBN} source
32966 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32968 @node Configure Options
32969 @section @file{configure} Options
32971 Here is a summary of the @file{configure} options and arguments that
32972 are most often useful for building @value{GDBN}. @file{configure} also has
32973 several other options not listed here. @inforef{What Configure
32974 Does,,configure.info}, for a full explanation of @file{configure}.
32977 configure @r{[}--help@r{]}
32978 @r{[}--prefix=@var{dir}@r{]}
32979 @r{[}--exec-prefix=@var{dir}@r{]}
32980 @r{[}--srcdir=@var{dirname}@r{]}
32981 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32982 @r{[}--target=@var{target}@r{]}
32987 You may introduce options with a single @samp{-} rather than
32988 @samp{--} if you prefer; but you may abbreviate option names if you use
32993 Display a quick summary of how to invoke @file{configure}.
32995 @item --prefix=@var{dir}
32996 Configure the source to install programs and files under directory
32999 @item --exec-prefix=@var{dir}
33000 Configure the source to install programs under directory
33003 @c avoid splitting the warning from the explanation:
33005 @item --srcdir=@var{dirname}
33006 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33007 @code{make} that implements the @code{VPATH} feature.}@*
33008 Use this option to make configurations in directories separate from the
33009 @value{GDBN} source directories. Among other things, you can use this to
33010 build (or maintain) several configurations simultaneously, in separate
33011 directories. @file{configure} writes configuration-specific files in
33012 the current directory, but arranges for them to use the source in the
33013 directory @var{dirname}. @file{configure} creates directories under
33014 the working directory in parallel to the source directories below
33017 @item --norecursion
33018 Configure only the directory level where @file{configure} is executed; do not
33019 propagate configuration to subdirectories.
33021 @item --target=@var{target}
33022 Configure @value{GDBN} for cross-debugging programs running on the specified
33023 @var{target}. Without this option, @value{GDBN} is configured to debug
33024 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33026 There is no convenient way to generate a list of all available targets.
33028 @item @var{host} @dots{}
33029 Configure @value{GDBN} to run on the specified @var{host}.
33031 There is no convenient way to generate a list of all available hosts.
33034 There are many other options available as well, but they are generally
33035 needed for special purposes only.
33037 @node System-wide configuration
33038 @section System-wide configuration and settings
33039 @cindex system-wide init file
33041 @value{GDBN} can be configured to have a system-wide init file;
33042 this file will be read and executed at startup (@pxref{Startup, , What
33043 @value{GDBN} does during startup}).
33045 Here is the corresponding configure option:
33048 @item --with-system-gdbinit=@var{file}
33049 Specify that the default location of the system-wide init file is
33053 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33054 it may be subject to relocation. Two possible cases:
33058 If the default location of this init file contains @file{$prefix},
33059 it will be subject to relocation. Suppose that the configure options
33060 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33061 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33062 init file is looked for as @file{$install/etc/gdbinit} instead of
33063 @file{$prefix/etc/gdbinit}.
33066 By contrast, if the default location does not contain the prefix,
33067 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33068 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33069 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33070 wherever @value{GDBN} is installed.
33073 If the configured location of the system-wide init file (as given by the
33074 @option{--with-system-gdbinit} option at configure time) is in the
33075 data-directory (as specified by @option{--with-gdb-datadir} at configure
33076 time) or in one of its subdirectories, then @value{GDBN} will look for the
33077 system-wide init file in the directory specified by the
33078 @option{--data-directory} command-line option.
33079 Note that the system-wide init file is only read once, during @value{GDBN}
33080 initialization. If the data-directory is changed after @value{GDBN} has
33081 started with the @code{set data-directory} command, the file will not be
33085 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33088 @node System-wide Configuration Scripts
33089 @subsection Installed System-wide Configuration Scripts
33090 @cindex system-wide configuration scripts
33092 The @file{system-gdbinit} directory, located inside the data-directory
33093 (as specified by @option{--with-gdb-datadir} at configure time) contains
33094 a number of scripts which can be used as system-wide init files. To
33095 automatically source those scripts at startup, @value{GDBN} should be
33096 configured with @option{--with-system-gdbinit}. Otherwise, any user
33097 should be able to source them by hand as needed.
33099 The following scripts are currently available:
33102 @item @file{elinos.py}
33104 @cindex ELinOS system-wide configuration script
33105 This script is useful when debugging a program on an ELinOS target.
33106 It takes advantage of the environment variables defined in a standard
33107 ELinOS environment in order to determine the location of the system
33108 shared libraries, and then sets the @samp{solib-absolute-prefix}
33109 and @samp{solib-search-path} variables appropriately.
33111 @item @file{wrs-linux.py}
33112 @pindex wrs-linux.py
33113 @cindex Wind River Linux system-wide configuration script
33114 This script is useful when debugging a program on a target running
33115 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33116 the host-side sysroot used by the target system.
33120 @node Maintenance Commands
33121 @appendix Maintenance Commands
33122 @cindex maintenance commands
33123 @cindex internal commands
33125 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33126 includes a number of commands intended for @value{GDBN} developers,
33127 that are not documented elsewhere in this manual. These commands are
33128 provided here for reference. (For commands that turn on debugging
33129 messages, see @ref{Debugging Output}.)
33132 @kindex maint agent
33133 @kindex maint agent-eval
33134 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33135 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33136 Translate the given @var{expression} into remote agent bytecodes.
33137 This command is useful for debugging the Agent Expression mechanism
33138 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33139 expression useful for data collection, such as by tracepoints, while
33140 @samp{maint agent-eval} produces an expression that evaluates directly
33141 to a result. For instance, a collection expression for @code{globa +
33142 globb} will include bytecodes to record four bytes of memory at each
33143 of the addresses of @code{globa} and @code{globb}, while discarding
33144 the result of the addition, while an evaluation expression will do the
33145 addition and return the sum.
33146 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33147 If not, generate remote agent bytecode for current frame PC address.
33149 @kindex maint agent-printf
33150 @item maint agent-printf @var{format},@var{expr},...
33151 Translate the given format string and list of argument expressions
33152 into remote agent bytecodes and display them as a disassembled list.
33153 This command is useful for debugging the agent version of dynamic
33154 printf (@pxref{Dynamic Printf}).
33156 @kindex maint info breakpoints
33157 @item @anchor{maint info breakpoints}maint info breakpoints
33158 Using the same format as @samp{info breakpoints}, display both the
33159 breakpoints you've set explicitly, and those @value{GDBN} is using for
33160 internal purposes. Internal breakpoints are shown with negative
33161 breakpoint numbers. The type column identifies what kind of breakpoint
33166 Normal, explicitly set breakpoint.
33169 Normal, explicitly set watchpoint.
33172 Internal breakpoint, used to handle correctly stepping through
33173 @code{longjmp} calls.
33175 @item longjmp resume
33176 Internal breakpoint at the target of a @code{longjmp}.
33179 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33182 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33185 Shared library events.
33189 @kindex maint info bfds
33190 @item maint info bfds
33191 This prints information about each @code{bfd} object that is known to
33192 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33194 @kindex set displaced-stepping
33195 @kindex show displaced-stepping
33196 @cindex displaced stepping support
33197 @cindex out-of-line single-stepping
33198 @item set displaced-stepping
33199 @itemx show displaced-stepping
33200 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33201 if the target supports it. Displaced stepping is a way to single-step
33202 over breakpoints without removing them from the inferior, by executing
33203 an out-of-line copy of the instruction that was originally at the
33204 breakpoint location. It is also known as out-of-line single-stepping.
33207 @item set displaced-stepping on
33208 If the target architecture supports it, @value{GDBN} will use
33209 displaced stepping to step over breakpoints.
33211 @item set displaced-stepping off
33212 @value{GDBN} will not use displaced stepping to step over breakpoints,
33213 even if such is supported by the target architecture.
33215 @cindex non-stop mode, and @samp{set displaced-stepping}
33216 @item set displaced-stepping auto
33217 This is the default mode. @value{GDBN} will use displaced stepping
33218 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33219 architecture supports displaced stepping.
33222 @kindex maint check-psymtabs
33223 @item maint check-psymtabs
33224 Check the consistency of currently expanded psymtabs versus symtabs.
33225 Use this to check, for example, whether a symbol is in one but not the other.
33227 @kindex maint check-symtabs
33228 @item maint check-symtabs
33229 Check the consistency of currently expanded symtabs.
33231 @kindex maint expand-symtabs
33232 @item maint expand-symtabs [@var{regexp}]
33233 Expand symbol tables.
33234 If @var{regexp} is specified, only expand symbol tables for file
33235 names matching @var{regexp}.
33237 @kindex maint set catch-demangler-crashes
33238 @kindex maint show catch-demangler-crashes
33239 @cindex demangler crashes
33240 @item maint set catch-demangler-crashes [on|off]
33241 @itemx maint show catch-demangler-crashes
33242 Control whether @value{GDBN} should attempt to catch crashes in the
33243 symbol name demangler. The default is to attempt to catch crashes.
33244 If enabled, the first time a crash is caught, a core file is created,
33245 the offending symbol is displayed and the user is presented with the
33246 option to terminate the current session.
33248 @kindex maint cplus first_component
33249 @item maint cplus first_component @var{name}
33250 Print the first C@t{++} class/namespace component of @var{name}.
33252 @kindex maint cplus namespace
33253 @item maint cplus namespace
33254 Print the list of possible C@t{++} namespaces.
33256 @kindex maint demangle
33257 @item maint demangle @var{name}
33258 Demangle a C@t{++} or Objective-C mangled @var{name}.
33260 @kindex maint deprecate
33261 @kindex maint undeprecate
33262 @cindex deprecated commands
33263 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33264 @itemx maint undeprecate @var{command}
33265 Deprecate or undeprecate the named @var{command}. Deprecated commands
33266 cause @value{GDBN} to issue a warning when you use them. The optional
33267 argument @var{replacement} says which newer command should be used in
33268 favor of the deprecated one; if it is given, @value{GDBN} will mention
33269 the replacement as part of the warning.
33271 @kindex maint dump-me
33272 @item maint dump-me
33273 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33274 Cause a fatal signal in the debugger and force it to dump its core.
33275 This is supported only on systems which support aborting a program
33276 with the @code{SIGQUIT} signal.
33278 @kindex maint internal-error
33279 @kindex maint internal-warning
33280 @kindex maint demangler-warning
33281 @cindex demangler crashes
33282 @item maint internal-error @r{[}@var{message-text}@r{]}
33283 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33284 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33286 Cause @value{GDBN} to call the internal function @code{internal_error},
33287 @code{internal_warning} or @code{demangler_warning} and hence behave
33288 as though an internal problam has been detected. In addition to
33289 reporting the internal problem, these functions give the user the
33290 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33291 and @code{internal_warning}) create a core file of the current
33292 @value{GDBN} session.
33294 These commands take an optional parameter @var{message-text} that is
33295 used as the text of the error or warning message.
33297 Here's an example of using @code{internal-error}:
33300 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33301 @dots{}/maint.c:121: internal-error: testing, 1, 2
33302 A problem internal to GDB has been detected. Further
33303 debugging may prove unreliable.
33304 Quit this debugging session? (y or n) @kbd{n}
33305 Create a core file? (y or n) @kbd{n}
33309 @cindex @value{GDBN} internal error
33310 @cindex internal errors, control of @value{GDBN} behavior
33311 @cindex demangler crashes
33313 @kindex maint set internal-error
33314 @kindex maint show internal-error
33315 @kindex maint set internal-warning
33316 @kindex maint show internal-warning
33317 @kindex maint set demangler-warning
33318 @kindex maint show demangler-warning
33319 @item maint set internal-error @var{action} [ask|yes|no]
33320 @itemx maint show internal-error @var{action}
33321 @itemx maint set internal-warning @var{action} [ask|yes|no]
33322 @itemx maint show internal-warning @var{action}
33323 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33324 @itemx maint show demangler-warning @var{action}
33325 When @value{GDBN} reports an internal problem (error or warning) it
33326 gives the user the opportunity to both quit @value{GDBN} and create a
33327 core file of the current @value{GDBN} session. These commands let you
33328 override the default behaviour for each particular @var{action},
33329 described in the table below.
33333 You can specify that @value{GDBN} should always (yes) or never (no)
33334 quit. The default is to ask the user what to do.
33337 You can specify that @value{GDBN} should always (yes) or never (no)
33338 create a core file. The default is to ask the user what to do. Note
33339 that there is no @code{corefile} option for @code{demangler-warning}:
33340 demangler warnings always create a core file and this cannot be
33344 @kindex maint packet
33345 @item maint packet @var{text}
33346 If @value{GDBN} is talking to an inferior via the serial protocol,
33347 then this command sends the string @var{text} to the inferior, and
33348 displays the response packet. @value{GDBN} supplies the initial
33349 @samp{$} character, the terminating @samp{#} character, and the
33352 @kindex maint print architecture
33353 @item maint print architecture @r{[}@var{file}@r{]}
33354 Print the entire architecture configuration. The optional argument
33355 @var{file} names the file where the output goes.
33357 @kindex maint print c-tdesc
33358 @item maint print c-tdesc
33359 Print the current target description (@pxref{Target Descriptions}) as
33360 a C source file. The created source file can be used in @value{GDBN}
33361 when an XML parser is not available to parse the description.
33363 @kindex maint print dummy-frames
33364 @item maint print dummy-frames
33365 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33368 (@value{GDBP}) @kbd{b add}
33370 (@value{GDBP}) @kbd{print add(2,3)}
33371 Breakpoint 2, add (a=2, b=3) at @dots{}
33373 The program being debugged stopped while in a function called from GDB.
33375 (@value{GDBP}) @kbd{maint print dummy-frames}
33376 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33380 Takes an optional file parameter.
33382 @kindex maint print registers
33383 @kindex maint print raw-registers
33384 @kindex maint print cooked-registers
33385 @kindex maint print register-groups
33386 @kindex maint print remote-registers
33387 @item maint print registers @r{[}@var{file}@r{]}
33388 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33389 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33390 @itemx maint print register-groups @r{[}@var{file}@r{]}
33391 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33392 Print @value{GDBN}'s internal register data structures.
33394 The command @code{maint print raw-registers} includes the contents of
33395 the raw register cache; the command @code{maint print
33396 cooked-registers} includes the (cooked) value of all registers,
33397 including registers which aren't available on the target nor visible
33398 to user; the command @code{maint print register-groups} includes the
33399 groups that each register is a member of; and the command @code{maint
33400 print remote-registers} includes the remote target's register numbers
33401 and offsets in the `G' packets.
33403 These commands take an optional parameter, a file name to which to
33404 write the information.
33406 @kindex maint print reggroups
33407 @item maint print reggroups @r{[}@var{file}@r{]}
33408 Print @value{GDBN}'s internal register group data structures. The
33409 optional argument @var{file} tells to what file to write the
33412 The register groups info looks like this:
33415 (@value{GDBP}) @kbd{maint print reggroups}
33428 This command forces @value{GDBN} to flush its internal register cache.
33430 @kindex maint print objfiles
33431 @cindex info for known object files
33432 @item maint print objfiles @r{[}@var{regexp}@r{]}
33433 Print a dump of all known object files.
33434 If @var{regexp} is specified, only print object files whose names
33435 match @var{regexp}. For each object file, this command prints its name,
33436 address in memory, and all of its psymtabs and symtabs.
33438 @kindex maint print section-scripts
33439 @cindex info for known .debug_gdb_scripts-loaded scripts
33440 @item maint print section-scripts [@var{regexp}]
33441 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33442 If @var{regexp} is specified, only print scripts loaded by object files
33443 matching @var{regexp}.
33444 For each script, this command prints its name as specified in the objfile,
33445 and the full path if known.
33446 @xref{dotdebug_gdb_scripts section}.
33448 @kindex maint print statistics
33449 @cindex bcache statistics
33450 @item maint print statistics
33451 This command prints, for each object file in the program, various data
33452 about that object file followed by the byte cache (@dfn{bcache})
33453 statistics for the object file. The objfile data includes the number
33454 of minimal, partial, full, and stabs symbols, the number of types
33455 defined by the objfile, the number of as yet unexpanded psym tables,
33456 the number of line tables and string tables, and the amount of memory
33457 used by the various tables. The bcache statistics include the counts,
33458 sizes, and counts of duplicates of all and unique objects, max,
33459 average, and median entry size, total memory used and its overhead and
33460 savings, and various measures of the hash table size and chain
33463 @kindex maint print target-stack
33464 @cindex target stack description
33465 @item maint print target-stack
33466 A @dfn{target} is an interface between the debugger and a particular
33467 kind of file or process. Targets can be stacked in @dfn{strata},
33468 so that more than one target can potentially respond to a request.
33469 In particular, memory accesses will walk down the stack of targets
33470 until they find a target that is interested in handling that particular
33473 This command prints a short description of each layer that was pushed on
33474 the @dfn{target stack}, starting from the top layer down to the bottom one.
33476 @kindex maint print type
33477 @cindex type chain of a data type
33478 @item maint print type @var{expr}
33479 Print the type chain for a type specified by @var{expr}. The argument
33480 can be either a type name or a symbol. If it is a symbol, the type of
33481 that symbol is described. The type chain produced by this command is
33482 a recursive definition of the data type as stored in @value{GDBN}'s
33483 data structures, including its flags and contained types.
33485 @kindex maint set dwarf2 always-disassemble
33486 @kindex maint show dwarf2 always-disassemble
33487 @item maint set dwarf2 always-disassemble
33488 @item maint show dwarf2 always-disassemble
33489 Control the behavior of @code{info address} when using DWARF debugging
33492 The default is @code{off}, which means that @value{GDBN} should try to
33493 describe a variable's location in an easily readable format. When
33494 @code{on}, @value{GDBN} will instead display the DWARF location
33495 expression in an assembly-like format. Note that some locations are
33496 too complex for @value{GDBN} to describe simply; in this case you will
33497 always see the disassembly form.
33499 Here is an example of the resulting disassembly:
33502 (gdb) info addr argc
33503 Symbol "argc" is a complex DWARF expression:
33507 For more information on these expressions, see
33508 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33510 @kindex maint set dwarf2 max-cache-age
33511 @kindex maint show dwarf2 max-cache-age
33512 @item maint set dwarf2 max-cache-age
33513 @itemx maint show dwarf2 max-cache-age
33514 Control the DWARF 2 compilation unit cache.
33516 @cindex DWARF 2 compilation units cache
33517 In object files with inter-compilation-unit references, such as those
33518 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33519 reader needs to frequently refer to previously read compilation units.
33520 This setting controls how long a compilation unit will remain in the
33521 cache if it is not referenced. A higher limit means that cached
33522 compilation units will be stored in memory longer, and more total
33523 memory will be used. Setting it to zero disables caching, which will
33524 slow down @value{GDBN} startup, but reduce memory consumption.
33526 @kindex maint set profile
33527 @kindex maint show profile
33528 @cindex profiling GDB
33529 @item maint set profile
33530 @itemx maint show profile
33531 Control profiling of @value{GDBN}.
33533 Profiling will be disabled until you use the @samp{maint set profile}
33534 command to enable it. When you enable profiling, the system will begin
33535 collecting timing and execution count data; when you disable profiling or
33536 exit @value{GDBN}, the results will be written to a log file. Remember that
33537 if you use profiling, @value{GDBN} will overwrite the profiling log file
33538 (often called @file{gmon.out}). If you have a record of important profiling
33539 data in a @file{gmon.out} file, be sure to move it to a safe location.
33541 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33542 compiled with the @samp{-pg} compiler option.
33544 @kindex maint set show-debug-regs
33545 @kindex maint show show-debug-regs
33546 @cindex hardware debug registers
33547 @item maint set show-debug-regs
33548 @itemx maint show show-debug-regs
33549 Control whether to show variables that mirror the hardware debug
33550 registers. Use @code{on} to enable, @code{off} to disable. If
33551 enabled, the debug registers values are shown when @value{GDBN} inserts or
33552 removes a hardware breakpoint or watchpoint, and when the inferior
33553 triggers a hardware-assisted breakpoint or watchpoint.
33555 @kindex maint set show-all-tib
33556 @kindex maint show show-all-tib
33557 @item maint set show-all-tib
33558 @itemx maint show show-all-tib
33559 Control whether to show all non zero areas within a 1k block starting
33560 at thread local base, when using the @samp{info w32 thread-information-block}
33563 @kindex maint set target-async
33564 @kindex maint show target-async
33565 @item maint set target-async
33566 @itemx maint show target-async
33567 This controls whether @value{GDBN} targets operate in synchronous or
33568 asynchronous mode (@pxref{Background Execution}). Normally the
33569 default is asynchronous, if it is available; but this can be changed
33570 to more easily debug problems occurring only in synchronous mode.
33572 @kindex maint set per-command
33573 @kindex maint show per-command
33574 @item maint set per-command
33575 @itemx maint show per-command
33576 @cindex resources used by commands
33578 @value{GDBN} can display the resources used by each command.
33579 This is useful in debugging performance problems.
33582 @item maint set per-command space [on|off]
33583 @itemx maint show per-command space
33584 Enable or disable the printing of the memory used by GDB for each command.
33585 If enabled, @value{GDBN} will display how much memory each command
33586 took, following the command's own output.
33587 This can also be requested by invoking @value{GDBN} with the
33588 @option{--statistics} command-line switch (@pxref{Mode Options}).
33590 @item maint set per-command time [on|off]
33591 @itemx maint show per-command time
33592 Enable or disable the printing of the execution time of @value{GDBN}
33594 If enabled, @value{GDBN} will display how much time it
33595 took to execute each command, following the command's own output.
33596 Both CPU time and wallclock time are printed.
33597 Printing both is useful when trying to determine whether the cost is
33598 CPU or, e.g., disk/network latency.
33599 Note that the CPU time printed is for @value{GDBN} only, it does not include
33600 the execution time of the inferior because there's no mechanism currently
33601 to compute how much time was spent by @value{GDBN} and how much time was
33602 spent by the program been debugged.
33603 This can also be requested by invoking @value{GDBN} with the
33604 @option{--statistics} command-line switch (@pxref{Mode Options}).
33606 @item maint set per-command symtab [on|off]
33607 @itemx maint show per-command symtab
33608 Enable or disable the printing of basic symbol table statistics
33610 If enabled, @value{GDBN} will display the following information:
33614 number of symbol tables
33616 number of primary symbol tables
33618 number of blocks in the blockvector
33622 @kindex maint space
33623 @cindex memory used by commands
33624 @item maint space @var{value}
33625 An alias for @code{maint set per-command space}.
33626 A non-zero value enables it, zero disables it.
33629 @cindex time of command execution
33630 @item maint time @var{value}
33631 An alias for @code{maint set per-command time}.
33632 A non-zero value enables it, zero disables it.
33634 @kindex maint translate-address
33635 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33636 Find the symbol stored at the location specified by the address
33637 @var{addr} and an optional section name @var{section}. If found,
33638 @value{GDBN} prints the name of the closest symbol and an offset from
33639 the symbol's location to the specified address. This is similar to
33640 the @code{info address} command (@pxref{Symbols}), except that this
33641 command also allows to find symbols in other sections.
33643 If section was not specified, the section in which the symbol was found
33644 is also printed. For dynamically linked executables, the name of
33645 executable or shared library containing the symbol is printed as well.
33649 The following command is useful for non-interactive invocations of
33650 @value{GDBN}, such as in the test suite.
33653 @item set watchdog @var{nsec}
33654 @kindex set watchdog
33655 @cindex watchdog timer
33656 @cindex timeout for commands
33657 Set the maximum number of seconds @value{GDBN} will wait for the
33658 target operation to finish. If this time expires, @value{GDBN}
33659 reports and error and the command is aborted.
33661 @item show watchdog
33662 Show the current setting of the target wait timeout.
33665 @node Remote Protocol
33666 @appendix @value{GDBN} Remote Serial Protocol
33671 * Stop Reply Packets::
33672 * General Query Packets::
33673 * Architecture-Specific Protocol Details::
33674 * Tracepoint Packets::
33675 * Host I/O Packets::
33677 * Notification Packets::
33678 * Remote Non-Stop::
33679 * Packet Acknowledgment::
33681 * File-I/O Remote Protocol Extension::
33682 * Library List Format::
33683 * Library List Format for SVR4 Targets::
33684 * Memory Map Format::
33685 * Thread List Format::
33686 * Traceframe Info Format::
33687 * Branch Trace Format::
33693 There may be occasions when you need to know something about the
33694 protocol---for example, if there is only one serial port to your target
33695 machine, you might want your program to do something special if it
33696 recognizes a packet meant for @value{GDBN}.
33698 In the examples below, @samp{->} and @samp{<-} are used to indicate
33699 transmitted and received data, respectively.
33701 @cindex protocol, @value{GDBN} remote serial
33702 @cindex serial protocol, @value{GDBN} remote
33703 @cindex remote serial protocol
33704 All @value{GDBN} commands and responses (other than acknowledgments
33705 and notifications, see @ref{Notification Packets}) are sent as a
33706 @var{packet}. A @var{packet} is introduced with the character
33707 @samp{$}, the actual @var{packet-data}, and the terminating character
33708 @samp{#} followed by a two-digit @var{checksum}:
33711 @code{$}@var{packet-data}@code{#}@var{checksum}
33715 @cindex checksum, for @value{GDBN} remote
33717 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33718 characters between the leading @samp{$} and the trailing @samp{#} (an
33719 eight bit unsigned checksum).
33721 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33722 specification also included an optional two-digit @var{sequence-id}:
33725 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33728 @cindex sequence-id, for @value{GDBN} remote
33730 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33731 has never output @var{sequence-id}s. Stubs that handle packets added
33732 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33734 When either the host or the target machine receives a packet, the first
33735 response expected is an acknowledgment: either @samp{+} (to indicate
33736 the package was received correctly) or @samp{-} (to request
33740 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33745 The @samp{+}/@samp{-} acknowledgments can be disabled
33746 once a connection is established.
33747 @xref{Packet Acknowledgment}, for details.
33749 The host (@value{GDBN}) sends @var{command}s, and the target (the
33750 debugging stub incorporated in your program) sends a @var{response}. In
33751 the case of step and continue @var{command}s, the response is only sent
33752 when the operation has completed, and the target has again stopped all
33753 threads in all attached processes. This is the default all-stop mode
33754 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33755 execution mode; see @ref{Remote Non-Stop}, for details.
33757 @var{packet-data} consists of a sequence of characters with the
33758 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33761 @cindex remote protocol, field separator
33762 Fields within the packet should be separated using @samp{,} @samp{;} or
33763 @samp{:}. Except where otherwise noted all numbers are represented in
33764 @sc{hex} with leading zeros suppressed.
33766 Implementors should note that prior to @value{GDBN} 5.0, the character
33767 @samp{:} could not appear as the third character in a packet (as it
33768 would potentially conflict with the @var{sequence-id}).
33770 @cindex remote protocol, binary data
33771 @anchor{Binary Data}
33772 Binary data in most packets is encoded either as two hexadecimal
33773 digits per byte of binary data. This allowed the traditional remote
33774 protocol to work over connections which were only seven-bit clean.
33775 Some packets designed more recently assume an eight-bit clean
33776 connection, and use a more efficient encoding to send and receive
33779 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33780 as an escape character. Any escaped byte is transmitted as the escape
33781 character followed by the original character XORed with @code{0x20}.
33782 For example, the byte @code{0x7d} would be transmitted as the two
33783 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33784 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33785 @samp{@}}) must always be escaped. Responses sent by the stub
33786 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33787 is not interpreted as the start of a run-length encoded sequence
33790 Response @var{data} can be run-length encoded to save space.
33791 Run-length encoding replaces runs of identical characters with one
33792 instance of the repeated character, followed by a @samp{*} and a
33793 repeat count. The repeat count is itself sent encoded, to avoid
33794 binary characters in @var{data}: a value of @var{n} is sent as
33795 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33796 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33797 code 32) for a repeat count of 3. (This is because run-length
33798 encoding starts to win for counts 3 or more.) Thus, for example,
33799 @samp{0* } is a run-length encoding of ``0000'': the space character
33800 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33803 The printable characters @samp{#} and @samp{$} or with a numeric value
33804 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33805 seven repeats (@samp{$}) can be expanded using a repeat count of only
33806 five (@samp{"}). For example, @samp{00000000} can be encoded as
33809 The error response returned for some packets includes a two character
33810 error number. That number is not well defined.
33812 @cindex empty response, for unsupported packets
33813 For any @var{command} not supported by the stub, an empty response
33814 (@samp{$#00}) should be returned. That way it is possible to extend the
33815 protocol. A newer @value{GDBN} can tell if a packet is supported based
33818 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33819 commands for register access, and the @samp{m} and @samp{M} commands
33820 for memory access. Stubs that only control single-threaded targets
33821 can implement run control with the @samp{c} (continue), and @samp{s}
33822 (step) commands. Stubs that support multi-threading targets should
33823 support the @samp{vCont} command. All other commands are optional.
33828 The following table provides a complete list of all currently defined
33829 @var{command}s and their corresponding response @var{data}.
33830 @xref{File-I/O Remote Protocol Extension}, for details about the File
33831 I/O extension of the remote protocol.
33833 Each packet's description has a template showing the packet's overall
33834 syntax, followed by an explanation of the packet's meaning. We
33835 include spaces in some of the templates for clarity; these are not
33836 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33837 separate its components. For example, a template like @samp{foo
33838 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33839 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33840 @var{baz}. @value{GDBN} does not transmit a space character between the
33841 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33844 @cindex @var{thread-id}, in remote protocol
33845 @anchor{thread-id syntax}
33846 Several packets and replies include a @var{thread-id} field to identify
33847 a thread. Normally these are positive numbers with a target-specific
33848 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33849 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33852 In addition, the remote protocol supports a multiprocess feature in
33853 which the @var{thread-id} syntax is extended to optionally include both
33854 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33855 The @var{pid} (process) and @var{tid} (thread) components each have the
33856 format described above: a positive number with target-specific
33857 interpretation formatted as a big-endian hex string, literal @samp{-1}
33858 to indicate all processes or threads (respectively), or @samp{0} to
33859 indicate an arbitrary process or thread. Specifying just a process, as
33860 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33861 error to specify all processes but a specific thread, such as
33862 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33863 for those packets and replies explicitly documented to include a process
33864 ID, rather than a @var{thread-id}.
33866 The multiprocess @var{thread-id} syntax extensions are only used if both
33867 @value{GDBN} and the stub report support for the @samp{multiprocess}
33868 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33871 Note that all packet forms beginning with an upper- or lower-case
33872 letter, other than those described here, are reserved for future use.
33874 Here are the packet descriptions.
33879 @cindex @samp{!} packet
33880 @anchor{extended mode}
33881 Enable extended mode. In extended mode, the remote server is made
33882 persistent. The @samp{R} packet is used to restart the program being
33888 The remote target both supports and has enabled extended mode.
33892 @cindex @samp{?} packet
33894 Indicate the reason the target halted. The reply is the same as for
33895 step and continue. This packet has a special interpretation when the
33896 target is in non-stop mode; see @ref{Remote Non-Stop}.
33899 @xref{Stop Reply Packets}, for the reply specifications.
33901 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33902 @cindex @samp{A} packet
33903 Initialized @code{argv[]} array passed into program. @var{arglen}
33904 specifies the number of bytes in the hex encoded byte stream
33905 @var{arg}. See @code{gdbserver} for more details.
33910 The arguments were set.
33916 @cindex @samp{b} packet
33917 (Don't use this packet; its behavior is not well-defined.)
33918 Change the serial line speed to @var{baud}.
33920 JTC: @emph{When does the transport layer state change? When it's
33921 received, or after the ACK is transmitted. In either case, there are
33922 problems if the command or the acknowledgment packet is dropped.}
33924 Stan: @emph{If people really wanted to add something like this, and get
33925 it working for the first time, they ought to modify ser-unix.c to send
33926 some kind of out-of-band message to a specially-setup stub and have the
33927 switch happen "in between" packets, so that from remote protocol's point
33928 of view, nothing actually happened.}
33930 @item B @var{addr},@var{mode}
33931 @cindex @samp{B} packet
33932 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33933 breakpoint at @var{addr}.
33935 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33936 (@pxref{insert breakpoint or watchpoint packet}).
33938 @cindex @samp{bc} packet
33941 Backward continue. Execute the target system in reverse. No parameter.
33942 @xref{Reverse Execution}, for more information.
33945 @xref{Stop Reply Packets}, for the reply specifications.
33947 @cindex @samp{bs} packet
33950 Backward single step. Execute one instruction in reverse. No parameter.
33951 @xref{Reverse Execution}, for more information.
33954 @xref{Stop Reply Packets}, for the reply specifications.
33956 @item c @r{[}@var{addr}@r{]}
33957 @cindex @samp{c} packet
33958 Continue at @var{addr}, which is the address to resume. If @var{addr}
33959 is omitted, resume at current address.
33961 This packet is deprecated for multi-threading support. @xref{vCont
33965 @xref{Stop Reply Packets}, for the reply specifications.
33967 @item C @var{sig}@r{[};@var{addr}@r{]}
33968 @cindex @samp{C} packet
33969 Continue with signal @var{sig} (hex signal number). If
33970 @samp{;@var{addr}} is omitted, resume at same address.
33972 This packet is deprecated for multi-threading support. @xref{vCont
33976 @xref{Stop Reply Packets}, for the reply specifications.
33979 @cindex @samp{d} packet
33982 Don't use this packet; instead, define a general set packet
33983 (@pxref{General Query Packets}).
33987 @cindex @samp{D} packet
33988 The first form of the packet is used to detach @value{GDBN} from the
33989 remote system. It is sent to the remote target
33990 before @value{GDBN} disconnects via the @code{detach} command.
33992 The second form, including a process ID, is used when multiprocess
33993 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33994 detach only a specific process. The @var{pid} is specified as a
33995 big-endian hex string.
34005 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34006 @cindex @samp{F} packet
34007 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34008 This is part of the File-I/O protocol extension. @xref{File-I/O
34009 Remote Protocol Extension}, for the specification.
34012 @anchor{read registers packet}
34013 @cindex @samp{g} packet
34014 Read general registers.
34018 @item @var{XX@dots{}}
34019 Each byte of register data is described by two hex digits. The bytes
34020 with the register are transmitted in target byte order. The size of
34021 each register and their position within the @samp{g} packet are
34022 determined by the @value{GDBN} internal gdbarch functions
34023 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34024 specification of several standard @samp{g} packets is specified below.
34026 When reading registers from a trace frame (@pxref{Analyze Collected
34027 Data,,Using the Collected Data}), the stub may also return a string of
34028 literal @samp{x}'s in place of the register data digits, to indicate
34029 that the corresponding register has not been collected, thus its value
34030 is unavailable. For example, for an architecture with 4 registers of
34031 4 bytes each, the following reply indicates to @value{GDBN} that
34032 registers 0 and 2 have not been collected, while registers 1 and 3
34033 have been collected, and both have zero value:
34037 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34044 @item G @var{XX@dots{}}
34045 @cindex @samp{G} packet
34046 Write general registers. @xref{read registers packet}, for a
34047 description of the @var{XX@dots{}} data.
34057 @item H @var{op} @var{thread-id}
34058 @cindex @samp{H} packet
34059 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34060 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34061 should be @samp{c} for step and continue operations (note that this
34062 is deprecated, supporting the @samp{vCont} command is a better
34063 option), and @samp{g} for other operations. The thread designator
34064 @var{thread-id} has the format and interpretation described in
34065 @ref{thread-id syntax}.
34076 @c 'H': How restrictive (or permissive) is the thread model. If a
34077 @c thread is selected and stopped, are other threads allowed
34078 @c to continue to execute? As I mentioned above, I think the
34079 @c semantics of each command when a thread is selected must be
34080 @c described. For example:
34082 @c 'g': If the stub supports threads and a specific thread is
34083 @c selected, returns the register block from that thread;
34084 @c otherwise returns current registers.
34086 @c 'G' If the stub supports threads and a specific thread is
34087 @c selected, sets the registers of the register block of
34088 @c that thread; otherwise sets current registers.
34090 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34091 @anchor{cycle step packet}
34092 @cindex @samp{i} packet
34093 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34094 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34095 step starting at that address.
34098 @cindex @samp{I} packet
34099 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34103 @cindex @samp{k} packet
34106 The exact effect of this packet is not specified.
34108 For a bare-metal target, it may power cycle or reset the target
34109 system. For that reason, the @samp{k} packet has no reply.
34111 For a single-process target, it may kill that process if possible.
34113 A multiple-process target may choose to kill just one process, or all
34114 that are under @value{GDBN}'s control. For more precise control, use
34115 the vKill packet (@pxref{vKill packet}).
34117 If the target system immediately closes the connection in response to
34118 @samp{k}, @value{GDBN} does not consider the lack of packet
34119 acknowledgment to be an error, and assumes the kill was successful.
34121 If connected using @kbd{target extended-remote}, and the target does
34122 not close the connection in response to a kill request, @value{GDBN}
34123 probes the target state as if a new connection was opened
34124 (@pxref{? packet}).
34126 @item m @var{addr},@var{length}
34127 @cindex @samp{m} packet
34128 Read @var{length} bytes of memory starting at address @var{addr}.
34129 Note that @var{addr} may not be aligned to any particular boundary.
34131 The stub need not use any particular size or alignment when gathering
34132 data from memory for the response; even if @var{addr} is word-aligned
34133 and @var{length} is a multiple of the word size, the stub is free to
34134 use byte accesses, or not. For this reason, this packet may not be
34135 suitable for accessing memory-mapped I/O devices.
34136 @cindex alignment of remote memory accesses
34137 @cindex size of remote memory accesses
34138 @cindex memory, alignment and size of remote accesses
34142 @item @var{XX@dots{}}
34143 Memory contents; each byte is transmitted as a two-digit hexadecimal
34144 number. The reply may contain fewer bytes than requested if the
34145 server was able to read only part of the region of memory.
34150 @item M @var{addr},@var{length}:@var{XX@dots{}}
34151 @cindex @samp{M} packet
34152 Write @var{length} bytes of memory starting at address @var{addr}.
34153 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34154 hexadecimal number.
34161 for an error (this includes the case where only part of the data was
34166 @cindex @samp{p} packet
34167 Read the value of register @var{n}; @var{n} is in hex.
34168 @xref{read registers packet}, for a description of how the returned
34169 register value is encoded.
34173 @item @var{XX@dots{}}
34174 the register's value
34178 Indicating an unrecognized @var{query}.
34181 @item P @var{n@dots{}}=@var{r@dots{}}
34182 @anchor{write register packet}
34183 @cindex @samp{P} packet
34184 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34185 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34186 digits for each byte in the register (target byte order).
34196 @item q @var{name} @var{params}@dots{}
34197 @itemx Q @var{name} @var{params}@dots{}
34198 @cindex @samp{q} packet
34199 @cindex @samp{Q} packet
34200 General query (@samp{q}) and set (@samp{Q}). These packets are
34201 described fully in @ref{General Query Packets}.
34204 @cindex @samp{r} packet
34205 Reset the entire system.
34207 Don't use this packet; use the @samp{R} packet instead.
34210 @cindex @samp{R} packet
34211 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34212 This packet is only available in extended mode (@pxref{extended mode}).
34214 The @samp{R} packet has no reply.
34216 @item s @r{[}@var{addr}@r{]}
34217 @cindex @samp{s} packet
34218 Single step, resuming at @var{addr}. If
34219 @var{addr} is omitted, resume at same address.
34221 This packet is deprecated for multi-threading support. @xref{vCont
34225 @xref{Stop Reply Packets}, for the reply specifications.
34227 @item S @var{sig}@r{[};@var{addr}@r{]}
34228 @anchor{step with signal packet}
34229 @cindex @samp{S} packet
34230 Step with signal. This is analogous to the @samp{C} packet, but
34231 requests a single-step, rather than a normal resumption of execution.
34233 This packet is deprecated for multi-threading support. @xref{vCont
34237 @xref{Stop Reply Packets}, for the reply specifications.
34239 @item t @var{addr}:@var{PP},@var{MM}
34240 @cindex @samp{t} packet
34241 Search backwards starting at address @var{addr} for a match with pattern
34242 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34243 There must be at least 3 digits in @var{addr}.
34245 @item T @var{thread-id}
34246 @cindex @samp{T} packet
34247 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34252 thread is still alive
34258 Packets starting with @samp{v} are identified by a multi-letter name,
34259 up to the first @samp{;} or @samp{?} (or the end of the packet).
34261 @item vAttach;@var{pid}
34262 @cindex @samp{vAttach} packet
34263 Attach to a new process with the specified process ID @var{pid}.
34264 The process ID is a
34265 hexadecimal integer identifying the process. In all-stop mode, all
34266 threads in the attached process are stopped; in non-stop mode, it may be
34267 attached without being stopped if that is supported by the target.
34269 @c In non-stop mode, on a successful vAttach, the stub should set the
34270 @c current thread to a thread of the newly-attached process. After
34271 @c attaching, GDB queries for the attached process's thread ID with qC.
34272 @c Also note that, from a user perspective, whether or not the
34273 @c target is stopped on attach in non-stop mode depends on whether you
34274 @c use the foreground or background version of the attach command, not
34275 @c on what vAttach does; GDB does the right thing with respect to either
34276 @c stopping or restarting threads.
34278 This packet is only available in extended mode (@pxref{extended mode}).
34284 @item @r{Any stop packet}
34285 for success in all-stop mode (@pxref{Stop Reply Packets})
34287 for success in non-stop mode (@pxref{Remote Non-Stop})
34290 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34291 @cindex @samp{vCont} packet
34292 @anchor{vCont packet}
34293 Resume the inferior, specifying different actions for each thread.
34294 If an action is specified with no @var{thread-id}, then it is applied to any
34295 threads that don't have a specific action specified; if no default action is
34296 specified then other threads should remain stopped in all-stop mode and
34297 in their current state in non-stop mode.
34298 Specifying multiple
34299 default actions is an error; specifying no actions is also an error.
34300 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34302 Currently supported actions are:
34308 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34312 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34315 @item r @var{start},@var{end}
34316 Step once, and then keep stepping as long as the thread stops at
34317 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34318 The remote stub reports a stop reply when either the thread goes out
34319 of the range or is stopped due to an unrelated reason, such as hitting
34320 a breakpoint. @xref{range stepping}.
34322 If the range is empty (@var{start} == @var{end}), then the action
34323 becomes equivalent to the @samp{s} action. In other words,
34324 single-step once, and report the stop (even if the stepped instruction
34325 jumps to @var{start}).
34327 (A stop reply may be sent at any point even if the PC is still within
34328 the stepping range; for example, it is valid to implement this packet
34329 in a degenerate way as a single instruction step operation.)
34333 The optional argument @var{addr} normally associated with the
34334 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34335 not supported in @samp{vCont}.
34337 The @samp{t} action is only relevant in non-stop mode
34338 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34339 A stop reply should be generated for any affected thread not already stopped.
34340 When a thread is stopped by means of a @samp{t} action,
34341 the corresponding stop reply should indicate that the thread has stopped with
34342 signal @samp{0}, regardless of whether the target uses some other signal
34343 as an implementation detail.
34345 The stub must support @samp{vCont} if it reports support for
34346 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34347 this case @samp{vCont} actions can be specified to apply to all threads
34348 in a process by using the @samp{p@var{pid}.-1} form of the
34352 @xref{Stop Reply Packets}, for the reply specifications.
34355 @cindex @samp{vCont?} packet
34356 Request a list of actions supported by the @samp{vCont} packet.
34360 @item vCont@r{[};@var{action}@dots{}@r{]}
34361 The @samp{vCont} packet is supported. Each @var{action} is a supported
34362 command in the @samp{vCont} packet.
34364 The @samp{vCont} packet is not supported.
34367 @item vFile:@var{operation}:@var{parameter}@dots{}
34368 @cindex @samp{vFile} packet
34369 Perform a file operation on the target system. For details,
34370 see @ref{Host I/O Packets}.
34372 @item vFlashErase:@var{addr},@var{length}
34373 @cindex @samp{vFlashErase} packet
34374 Direct the stub to erase @var{length} bytes of flash starting at
34375 @var{addr}. The region may enclose any number of flash blocks, but
34376 its start and end must fall on block boundaries, as indicated by the
34377 flash block size appearing in the memory map (@pxref{Memory Map
34378 Format}). @value{GDBN} groups flash memory programming operations
34379 together, and sends a @samp{vFlashDone} request after each group; the
34380 stub is allowed to delay erase operation until the @samp{vFlashDone}
34381 packet is received.
34391 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34392 @cindex @samp{vFlashWrite} packet
34393 Direct the stub to write data to flash address @var{addr}. The data
34394 is passed in binary form using the same encoding as for the @samp{X}
34395 packet (@pxref{Binary Data}). The memory ranges specified by
34396 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34397 not overlap, and must appear in order of increasing addresses
34398 (although @samp{vFlashErase} packets for higher addresses may already
34399 have been received; the ordering is guaranteed only between
34400 @samp{vFlashWrite} packets). If a packet writes to an address that was
34401 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34402 target-specific method, the results are unpredictable.
34410 for vFlashWrite addressing non-flash memory
34416 @cindex @samp{vFlashDone} packet
34417 Indicate to the stub that flash programming operation is finished.
34418 The stub is permitted to delay or batch the effects of a group of
34419 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34420 @samp{vFlashDone} packet is received. The contents of the affected
34421 regions of flash memory are unpredictable until the @samp{vFlashDone}
34422 request is completed.
34424 @item vKill;@var{pid}
34425 @cindex @samp{vKill} packet
34426 @anchor{vKill packet}
34427 Kill the process with the specified process ID @var{pid}, which is a
34428 hexadecimal integer identifying the process. This packet is used in
34429 preference to @samp{k} when multiprocess protocol extensions are
34430 supported; see @ref{multiprocess extensions}.
34440 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34441 @cindex @samp{vRun} packet
34442 Run the program @var{filename}, passing it each @var{argument} on its
34443 command line. The file and arguments are hex-encoded strings. If
34444 @var{filename} is an empty string, the stub may use a default program
34445 (e.g.@: the last program run). The program is created in the stopped
34448 @c FIXME: What about non-stop mode?
34450 This packet is only available in extended mode (@pxref{extended mode}).
34456 @item @r{Any stop packet}
34457 for success (@pxref{Stop Reply Packets})
34461 @cindex @samp{vStopped} packet
34462 @xref{Notification Packets}.
34464 @item X @var{addr},@var{length}:@var{XX@dots{}}
34466 @cindex @samp{X} packet
34467 Write data to memory, where the data is transmitted in binary.
34468 Memory is specified by its address @var{addr} and number of bytes @var{length};
34469 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34479 @item z @var{type},@var{addr},@var{kind}
34480 @itemx Z @var{type},@var{addr},@var{kind}
34481 @anchor{insert breakpoint or watchpoint packet}
34482 @cindex @samp{z} packet
34483 @cindex @samp{Z} packets
34484 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34485 watchpoint starting at address @var{address} of kind @var{kind}.
34487 Each breakpoint and watchpoint packet @var{type} is documented
34490 @emph{Implementation notes: A remote target shall return an empty string
34491 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34492 remote target shall support either both or neither of a given
34493 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34494 avoid potential problems with duplicate packets, the operations should
34495 be implemented in an idempotent way.}
34497 @item z0,@var{addr},@var{kind}
34498 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34499 @cindex @samp{z0} packet
34500 @cindex @samp{Z0} packet
34501 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34502 @var{addr} of type @var{kind}.
34504 A memory breakpoint is implemented by replacing the instruction at
34505 @var{addr} with a software breakpoint or trap instruction. The
34506 @var{kind} is target-specific and typically indicates the size of
34507 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34508 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34509 architectures have additional meanings for @var{kind};
34510 @var{cond_list} is an optional list of conditional expressions in bytecode
34511 form that should be evaluated on the target's side. These are the
34512 conditions that should be taken into consideration when deciding if
34513 the breakpoint trigger should be reported back to @var{GDBN}.
34515 The @var{cond_list} parameter is comprised of a series of expressions,
34516 concatenated without separators. Each expression has the following form:
34520 @item X @var{len},@var{expr}
34521 @var{len} is the length of the bytecode expression and @var{expr} is the
34522 actual conditional expression in bytecode form.
34526 The optional @var{cmd_list} parameter introduces commands that may be
34527 run on the target, rather than being reported back to @value{GDBN}.
34528 The parameter starts with a numeric flag @var{persist}; if the flag is
34529 nonzero, then the breakpoint may remain active and the commands
34530 continue to be run even when @value{GDBN} disconnects from the target.
34531 Following this flag is a series of expressions concatenated with no
34532 separators. Each expression has the following form:
34536 @item X @var{len},@var{expr}
34537 @var{len} is the length of the bytecode expression and @var{expr} is the
34538 actual conditional expression in bytecode form.
34542 see @ref{Architecture-Specific Protocol Details}.
34544 @emph{Implementation note: It is possible for a target to copy or move
34545 code that contains memory breakpoints (e.g., when implementing
34546 overlays). The behavior of this packet, in the presence of such a
34547 target, is not defined.}
34559 @item z1,@var{addr},@var{kind}
34560 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34561 @cindex @samp{z1} packet
34562 @cindex @samp{Z1} packet
34563 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34564 address @var{addr}.
34566 A hardware breakpoint is implemented using a mechanism that is not
34567 dependant on being able to modify the target's memory. The @var{kind}
34568 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34570 @emph{Implementation note: A hardware breakpoint is not affected by code
34583 @item z2,@var{addr},@var{kind}
34584 @itemx Z2,@var{addr},@var{kind}
34585 @cindex @samp{z2} packet
34586 @cindex @samp{Z2} packet
34587 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34588 The number of bytes to watch is specified by @var{kind}.
34600 @item z3,@var{addr},@var{kind}
34601 @itemx Z3,@var{addr},@var{kind}
34602 @cindex @samp{z3} packet
34603 @cindex @samp{Z3} packet
34604 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34605 The number of bytes to watch is specified by @var{kind}.
34617 @item z4,@var{addr},@var{kind}
34618 @itemx Z4,@var{addr},@var{kind}
34619 @cindex @samp{z4} packet
34620 @cindex @samp{Z4} packet
34621 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34622 The number of bytes to watch is specified by @var{kind}.
34636 @node Stop Reply Packets
34637 @section Stop Reply Packets
34638 @cindex stop reply packets
34640 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34641 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34642 receive any of the below as a reply. Except for @samp{?}
34643 and @samp{vStopped}, that reply is only returned
34644 when the target halts. In the below the exact meaning of @dfn{signal
34645 number} is defined by the header @file{include/gdb/signals.h} in the
34646 @value{GDBN} source code.
34648 As in the description of request packets, we include spaces in the
34649 reply templates for clarity; these are not part of the reply packet's
34650 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34656 The program received signal number @var{AA} (a two-digit hexadecimal
34657 number). This is equivalent to a @samp{T} response with no
34658 @var{n}:@var{r} pairs.
34660 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34661 @cindex @samp{T} packet reply
34662 The program received signal number @var{AA} (a two-digit hexadecimal
34663 number). This is equivalent to an @samp{S} response, except that the
34664 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34665 and other information directly in the stop reply packet, reducing
34666 round-trip latency. Single-step and breakpoint traps are reported
34667 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34671 If @var{n} is a hexadecimal number, it is a register number, and the
34672 corresponding @var{r} gives that register's value. The data @var{r} is a
34673 series of bytes in target byte order, with each byte given by a
34674 two-digit hex number.
34677 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34678 the stopped thread, as specified in @ref{thread-id syntax}.
34681 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34682 the core on which the stop event was detected.
34685 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34686 specific event that stopped the target. The currently defined stop
34687 reasons are listed below. The @var{aa} should be @samp{05}, the trap
34688 signal. At most one stop reason should be present.
34691 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34692 and go on to the next; this allows us to extend the protocol in the
34696 The currently defined stop reasons are:
34702 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34705 @cindex shared library events, remote reply
34707 The packet indicates that the loaded libraries have changed.
34708 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34709 list of loaded libraries. The @var{r} part is ignored.
34711 @cindex replay log events, remote reply
34713 The packet indicates that the target cannot continue replaying
34714 logged execution events, because it has reached the end (or the
34715 beginning when executing backward) of the log. The value of @var{r}
34716 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34717 for more information.
34721 @itemx W @var{AA} ; process:@var{pid}
34722 The process exited, and @var{AA} is the exit status. This is only
34723 applicable to certain targets.
34725 The second form of the response, including the process ID of the exited
34726 process, can be used only when @value{GDBN} has reported support for
34727 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34728 The @var{pid} is formatted as a big-endian hex string.
34731 @itemx X @var{AA} ; process:@var{pid}
34732 The process terminated with signal @var{AA}.
34734 The second form of the response, including the process ID of the
34735 terminated process, can be used only when @value{GDBN} has reported
34736 support for multiprocess protocol extensions; see @ref{multiprocess
34737 extensions}. The @var{pid} is formatted as a big-endian hex string.
34739 @item O @var{XX}@dots{}
34740 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34741 written as the program's console output. This can happen at any time
34742 while the program is running and the debugger should continue to wait
34743 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34745 @item F @var{call-id},@var{parameter}@dots{}
34746 @var{call-id} is the identifier which says which host system call should
34747 be called. This is just the name of the function. Translation into the
34748 correct system call is only applicable as it's defined in @value{GDBN}.
34749 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34752 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34753 this very system call.
34755 The target replies with this packet when it expects @value{GDBN} to
34756 call a host system call on behalf of the target. @value{GDBN} replies
34757 with an appropriate @samp{F} packet and keeps up waiting for the next
34758 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34759 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34760 Protocol Extension}, for more details.
34764 @node General Query Packets
34765 @section General Query Packets
34766 @cindex remote query requests
34768 Packets starting with @samp{q} are @dfn{general query packets};
34769 packets starting with @samp{Q} are @dfn{general set packets}. General
34770 query and set packets are a semi-unified form for retrieving and
34771 sending information to and from the stub.
34773 The initial letter of a query or set packet is followed by a name
34774 indicating what sort of thing the packet applies to. For example,
34775 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34776 definitions with the stub. These packet names follow some
34781 The name must not contain commas, colons or semicolons.
34783 Most @value{GDBN} query and set packets have a leading upper case
34786 The names of custom vendor packets should use a company prefix, in
34787 lower case, followed by a period. For example, packets designed at
34788 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34789 foos) or @samp{Qacme.bar} (for setting bars).
34792 The name of a query or set packet should be separated from any
34793 parameters by a @samp{:}; the parameters themselves should be
34794 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34795 full packet name, and check for a separator or the end of the packet,
34796 in case two packet names share a common prefix. New packets should not begin
34797 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34798 packets predate these conventions, and have arguments without any terminator
34799 for the packet name; we suspect they are in widespread use in places that
34800 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34801 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34804 Like the descriptions of the other packets, each description here
34805 has a template showing the packet's overall syntax, followed by an
34806 explanation of the packet's meaning. We include spaces in some of the
34807 templates for clarity; these are not part of the packet's syntax. No
34808 @value{GDBN} packet uses spaces to separate its components.
34810 Here are the currently defined query and set packets:
34816 Turn on or off the agent as a helper to perform some debugging operations
34817 delegated from @value{GDBN} (@pxref{Control Agent}).
34819 @item QAllow:@var{op}:@var{val}@dots{}
34820 @cindex @samp{QAllow} packet
34821 Specify which operations @value{GDBN} expects to request of the
34822 target, as a semicolon-separated list of operation name and value
34823 pairs. Possible values for @var{op} include @samp{WriteReg},
34824 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34825 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34826 indicating that @value{GDBN} will not request the operation, or 1,
34827 indicating that it may. (The target can then use this to set up its
34828 own internals optimally, for instance if the debugger never expects to
34829 insert breakpoints, it may not need to install its own trap handler.)
34832 @cindex current thread, remote request
34833 @cindex @samp{qC} packet
34834 Return the current thread ID.
34838 @item QC @var{thread-id}
34839 Where @var{thread-id} is a thread ID as documented in
34840 @ref{thread-id syntax}.
34841 @item @r{(anything else)}
34842 Any other reply implies the old thread ID.
34845 @item qCRC:@var{addr},@var{length}
34846 @cindex CRC of memory block, remote request
34847 @cindex @samp{qCRC} packet
34848 @anchor{qCRC packet}
34849 Compute the CRC checksum of a block of memory using CRC-32 defined in
34850 IEEE 802.3. The CRC is computed byte at a time, taking the most
34851 significant bit of each byte first. The initial pattern code
34852 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34854 @emph{Note:} This is the same CRC used in validating separate debug
34855 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34856 Files}). However the algorithm is slightly different. When validating
34857 separate debug files, the CRC is computed taking the @emph{least}
34858 significant bit of each byte first, and the final result is inverted to
34859 detect trailing zeros.
34864 An error (such as memory fault)
34865 @item C @var{crc32}
34866 The specified memory region's checksum is @var{crc32}.
34869 @item QDisableRandomization:@var{value}
34870 @cindex disable address space randomization, remote request
34871 @cindex @samp{QDisableRandomization} packet
34872 Some target operating systems will randomize the virtual address space
34873 of the inferior process as a security feature, but provide a feature
34874 to disable such randomization, e.g.@: to allow for a more deterministic
34875 debugging experience. On such systems, this packet with a @var{value}
34876 of 1 directs the target to disable address space randomization for
34877 processes subsequently started via @samp{vRun} packets, while a packet
34878 with a @var{value} of 0 tells the target to enable address space
34881 This packet is only available in extended mode (@pxref{extended mode}).
34886 The request succeeded.
34889 An error occurred. The error number @var{nn} is given as hex digits.
34892 An empty reply indicates that @samp{QDisableRandomization} is not supported
34896 This packet is not probed by default; the remote stub must request it,
34897 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34898 This should only be done on targets that actually support disabling
34899 address space randomization.
34902 @itemx qsThreadInfo
34903 @cindex list active threads, remote request
34904 @cindex @samp{qfThreadInfo} packet
34905 @cindex @samp{qsThreadInfo} packet
34906 Obtain a list of all active thread IDs from the target (OS). Since there
34907 may be too many active threads to fit into one reply packet, this query
34908 works iteratively: it may require more than one query/reply sequence to
34909 obtain the entire list of threads. The first query of the sequence will
34910 be the @samp{qfThreadInfo} query; subsequent queries in the
34911 sequence will be the @samp{qsThreadInfo} query.
34913 NOTE: This packet replaces the @samp{qL} query (see below).
34917 @item m @var{thread-id}
34919 @item m @var{thread-id},@var{thread-id}@dots{}
34920 a comma-separated list of thread IDs
34922 (lower case letter @samp{L}) denotes end of list.
34925 In response to each query, the target will reply with a list of one or
34926 more thread IDs, separated by commas.
34927 @value{GDBN} will respond to each reply with a request for more thread
34928 ids (using the @samp{qs} form of the query), until the target responds
34929 with @samp{l} (lower-case ell, for @dfn{last}).
34930 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34933 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
34934 initial connection with the remote target, and the very first thread ID
34935 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
34936 message. Therefore, the stub should ensure that the first thread ID in
34937 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
34939 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34940 @cindex get thread-local storage address, remote request
34941 @cindex @samp{qGetTLSAddr} packet
34942 Fetch the address associated with thread local storage specified
34943 by @var{thread-id}, @var{offset}, and @var{lm}.
34945 @var{thread-id} is the thread ID associated with the
34946 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34948 @var{offset} is the (big endian, hex encoded) offset associated with the
34949 thread local variable. (This offset is obtained from the debug
34950 information associated with the variable.)
34952 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34953 load module associated with the thread local storage. For example,
34954 a @sc{gnu}/Linux system will pass the link map address of the shared
34955 object associated with the thread local storage under consideration.
34956 Other operating environments may choose to represent the load module
34957 differently, so the precise meaning of this parameter will vary.
34961 @item @var{XX}@dots{}
34962 Hex encoded (big endian) bytes representing the address of the thread
34963 local storage requested.
34966 An error occurred. The error number @var{nn} is given as hex digits.
34969 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34972 @item qGetTIBAddr:@var{thread-id}
34973 @cindex get thread information block address
34974 @cindex @samp{qGetTIBAddr} packet
34975 Fetch address of the Windows OS specific Thread Information Block.
34977 @var{thread-id} is the thread ID associated with the thread.
34981 @item @var{XX}@dots{}
34982 Hex encoded (big endian) bytes representing the linear address of the
34983 thread information block.
34986 An error occured. This means that either the thread was not found, or the
34987 address could not be retrieved.
34990 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34993 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34994 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34995 digit) is one to indicate the first query and zero to indicate a
34996 subsequent query; @var{threadcount} (two hex digits) is the maximum
34997 number of threads the response packet can contain; and @var{nextthread}
34998 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34999 returned in the response as @var{argthread}.
35001 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35005 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35006 Where: @var{count} (two hex digits) is the number of threads being
35007 returned; @var{done} (one hex digit) is zero to indicate more threads
35008 and one indicates no further threads; @var{argthreadid} (eight hex
35009 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35010 is a sequence of thread IDs, @var{threadid} (eight hex
35011 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35015 @cindex section offsets, remote request
35016 @cindex @samp{qOffsets} packet
35017 Get section offsets that the target used when relocating the downloaded
35022 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35023 Relocate the @code{Text} section by @var{xxx} from its original address.
35024 Relocate the @code{Data} section by @var{yyy} from its original address.
35025 If the object file format provides segment information (e.g.@: @sc{elf}
35026 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35027 segments by the supplied offsets.
35029 @emph{Note: while a @code{Bss} offset may be included in the response,
35030 @value{GDBN} ignores this and instead applies the @code{Data} offset
35031 to the @code{Bss} section.}
35033 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35034 Relocate the first segment of the object file, which conventionally
35035 contains program code, to a starting address of @var{xxx}. If
35036 @samp{DataSeg} is specified, relocate the second segment, which
35037 conventionally contains modifiable data, to a starting address of
35038 @var{yyy}. @value{GDBN} will report an error if the object file
35039 does not contain segment information, or does not contain at least
35040 as many segments as mentioned in the reply. Extra segments are
35041 kept at fixed offsets relative to the last relocated segment.
35044 @item qP @var{mode} @var{thread-id}
35045 @cindex thread information, remote request
35046 @cindex @samp{qP} packet
35047 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35048 encoded 32 bit mode; @var{thread-id} is a thread ID
35049 (@pxref{thread-id syntax}).
35051 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35054 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35058 @cindex non-stop mode, remote request
35059 @cindex @samp{QNonStop} packet
35061 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35062 @xref{Remote Non-Stop}, for more information.
35067 The request succeeded.
35070 An error occurred. The error number @var{nn} is given as hex digits.
35073 An empty reply indicates that @samp{QNonStop} is not supported by
35077 This packet is not probed by default; the remote stub must request it,
35078 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35079 Use of this packet is controlled by the @code{set non-stop} command;
35080 @pxref{Non-Stop Mode}.
35082 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35083 @cindex pass signals to inferior, remote request
35084 @cindex @samp{QPassSignals} packet
35085 @anchor{QPassSignals}
35086 Each listed @var{signal} should be passed directly to the inferior process.
35087 Signals are numbered identically to continue packets and stop replies
35088 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35089 strictly greater than the previous item. These signals do not need to stop
35090 the inferior, or be reported to @value{GDBN}. All other signals should be
35091 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35092 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35093 new list. This packet improves performance when using @samp{handle
35094 @var{signal} nostop noprint pass}.
35099 The request succeeded.
35102 An error occurred. The error number @var{nn} is given as hex digits.
35105 An empty reply indicates that @samp{QPassSignals} is not supported by
35109 Use of this packet is controlled by the @code{set remote pass-signals}
35110 command (@pxref{Remote Configuration, set remote pass-signals}).
35111 This packet is not probed by default; the remote stub must request it,
35112 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35114 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35115 @cindex signals the inferior may see, remote request
35116 @cindex @samp{QProgramSignals} packet
35117 @anchor{QProgramSignals}
35118 Each listed @var{signal} may be delivered to the inferior process.
35119 Others should be silently discarded.
35121 In some cases, the remote stub may need to decide whether to deliver a
35122 signal to the program or not without @value{GDBN} involvement. One
35123 example of that is while detaching --- the program's threads may have
35124 stopped for signals that haven't yet had a chance of being reported to
35125 @value{GDBN}, and so the remote stub can use the signal list specified
35126 by this packet to know whether to deliver or ignore those pending
35129 This does not influence whether to deliver a signal as requested by a
35130 resumption packet (@pxref{vCont packet}).
35132 Signals are numbered identically to continue packets and stop replies
35133 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35134 strictly greater than the previous item. Multiple
35135 @samp{QProgramSignals} packets do not combine; any earlier
35136 @samp{QProgramSignals} list is completely replaced by the new list.
35141 The request succeeded.
35144 An error occurred. The error number @var{nn} is given as hex digits.
35147 An empty reply indicates that @samp{QProgramSignals} is not supported
35151 Use of this packet is controlled by the @code{set remote program-signals}
35152 command (@pxref{Remote Configuration, set remote program-signals}).
35153 This packet is not probed by default; the remote stub must request it,
35154 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35156 @item qRcmd,@var{command}
35157 @cindex execute remote command, remote request
35158 @cindex @samp{qRcmd} packet
35159 @var{command} (hex encoded) is passed to the local interpreter for
35160 execution. Invalid commands should be reported using the output
35161 string. Before the final result packet, the target may also respond
35162 with a number of intermediate @samp{O@var{output}} console output
35163 packets. @emph{Implementors should note that providing access to a
35164 stubs's interpreter may have security implications}.
35169 A command response with no output.
35171 A command response with the hex encoded output string @var{OUTPUT}.
35173 Indicate a badly formed request.
35175 An empty reply indicates that @samp{qRcmd} is not recognized.
35178 (Note that the @code{qRcmd} packet's name is separated from the
35179 command by a @samp{,}, not a @samp{:}, contrary to the naming
35180 conventions above. Please don't use this packet as a model for new
35183 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35184 @cindex searching memory, in remote debugging
35186 @cindex @samp{qSearch:memory} packet
35188 @cindex @samp{qSearch memory} packet
35189 @anchor{qSearch memory}
35190 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35191 Both @var{address} and @var{length} are encoded in hex;
35192 @var{search-pattern} is a sequence of bytes, also hex encoded.
35197 The pattern was not found.
35199 The pattern was found at @var{address}.
35201 A badly formed request or an error was encountered while searching memory.
35203 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35206 @item QStartNoAckMode
35207 @cindex @samp{QStartNoAckMode} packet
35208 @anchor{QStartNoAckMode}
35209 Request that the remote stub disable the normal @samp{+}/@samp{-}
35210 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35215 The stub has switched to no-acknowledgment mode.
35216 @value{GDBN} acknowledges this reponse,
35217 but neither the stub nor @value{GDBN} shall send or expect further
35218 @samp{+}/@samp{-} acknowledgments in the current connection.
35220 An empty reply indicates that the stub does not support no-acknowledgment mode.
35223 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35224 @cindex supported packets, remote query
35225 @cindex features of the remote protocol
35226 @cindex @samp{qSupported} packet
35227 @anchor{qSupported}
35228 Tell the remote stub about features supported by @value{GDBN}, and
35229 query the stub for features it supports. This packet allows
35230 @value{GDBN} and the remote stub to take advantage of each others'
35231 features. @samp{qSupported} also consolidates multiple feature probes
35232 at startup, to improve @value{GDBN} performance---a single larger
35233 packet performs better than multiple smaller probe packets on
35234 high-latency links. Some features may enable behavior which must not
35235 be on by default, e.g.@: because it would confuse older clients or
35236 stubs. Other features may describe packets which could be
35237 automatically probed for, but are not. These features must be
35238 reported before @value{GDBN} will use them. This ``default
35239 unsupported'' behavior is not appropriate for all packets, but it
35240 helps to keep the initial connection time under control with new
35241 versions of @value{GDBN} which support increasing numbers of packets.
35245 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35246 The stub supports or does not support each returned @var{stubfeature},
35247 depending on the form of each @var{stubfeature} (see below for the
35250 An empty reply indicates that @samp{qSupported} is not recognized,
35251 or that no features needed to be reported to @value{GDBN}.
35254 The allowed forms for each feature (either a @var{gdbfeature} in the
35255 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35259 @item @var{name}=@var{value}
35260 The remote protocol feature @var{name} is supported, and associated
35261 with the specified @var{value}. The format of @var{value} depends
35262 on the feature, but it must not include a semicolon.
35264 The remote protocol feature @var{name} is supported, and does not
35265 need an associated value.
35267 The remote protocol feature @var{name} is not supported.
35269 The remote protocol feature @var{name} may be supported, and
35270 @value{GDBN} should auto-detect support in some other way when it is
35271 needed. This form will not be used for @var{gdbfeature} notifications,
35272 but may be used for @var{stubfeature} responses.
35275 Whenever the stub receives a @samp{qSupported} request, the
35276 supplied set of @value{GDBN} features should override any previous
35277 request. This allows @value{GDBN} to put the stub in a known
35278 state, even if the stub had previously been communicating with
35279 a different version of @value{GDBN}.
35281 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35286 This feature indicates whether @value{GDBN} supports multiprocess
35287 extensions to the remote protocol. @value{GDBN} does not use such
35288 extensions unless the stub also reports that it supports them by
35289 including @samp{multiprocess+} in its @samp{qSupported} reply.
35290 @xref{multiprocess extensions}, for details.
35293 This feature indicates that @value{GDBN} supports the XML target
35294 description. If the stub sees @samp{xmlRegisters=} with target
35295 specific strings separated by a comma, it will report register
35299 This feature indicates whether @value{GDBN} supports the
35300 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35301 instruction reply packet}).
35304 Stubs should ignore any unknown values for
35305 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35306 packet supports receiving packets of unlimited length (earlier
35307 versions of @value{GDBN} may reject overly long responses). Additional values
35308 for @var{gdbfeature} may be defined in the future to let the stub take
35309 advantage of new features in @value{GDBN}, e.g.@: incompatible
35310 improvements in the remote protocol---the @samp{multiprocess} feature is
35311 an example of such a feature. The stub's reply should be independent
35312 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35313 describes all the features it supports, and then the stub replies with
35314 all the features it supports.
35316 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35317 responses, as long as each response uses one of the standard forms.
35319 Some features are flags. A stub which supports a flag feature
35320 should respond with a @samp{+} form response. Other features
35321 require values, and the stub should respond with an @samp{=}
35324 Each feature has a default value, which @value{GDBN} will use if
35325 @samp{qSupported} is not available or if the feature is not mentioned
35326 in the @samp{qSupported} response. The default values are fixed; a
35327 stub is free to omit any feature responses that match the defaults.
35329 Not all features can be probed, but for those which can, the probing
35330 mechanism is useful: in some cases, a stub's internal
35331 architecture may not allow the protocol layer to know some information
35332 about the underlying target in advance. This is especially common in
35333 stubs which may be configured for multiple targets.
35335 These are the currently defined stub features and their properties:
35337 @multitable @columnfractions 0.35 0.2 0.12 0.2
35338 @c NOTE: The first row should be @headitem, but we do not yet require
35339 @c a new enough version of Texinfo (4.7) to use @headitem.
35341 @tab Value Required
35345 @item @samp{PacketSize}
35350 @item @samp{qXfer:auxv:read}
35355 @item @samp{qXfer:btrace:read}
35360 @item @samp{qXfer:features:read}
35365 @item @samp{qXfer:libraries:read}
35370 @item @samp{qXfer:libraries-svr4:read}
35375 @item @samp{augmented-libraries-svr4-read}
35380 @item @samp{qXfer:memory-map:read}
35385 @item @samp{qXfer:sdata:read}
35390 @item @samp{qXfer:spu:read}
35395 @item @samp{qXfer:spu:write}
35400 @item @samp{qXfer:siginfo:read}
35405 @item @samp{qXfer:siginfo:write}
35410 @item @samp{qXfer:threads:read}
35415 @item @samp{qXfer:traceframe-info:read}
35420 @item @samp{qXfer:uib:read}
35425 @item @samp{qXfer:fdpic:read}
35430 @item @samp{Qbtrace:off}
35435 @item @samp{Qbtrace:bts}
35440 @item @samp{QNonStop}
35445 @item @samp{QPassSignals}
35450 @item @samp{QStartNoAckMode}
35455 @item @samp{multiprocess}
35460 @item @samp{ConditionalBreakpoints}
35465 @item @samp{ConditionalTracepoints}
35470 @item @samp{ReverseContinue}
35475 @item @samp{ReverseStep}
35480 @item @samp{TracepointSource}
35485 @item @samp{QAgent}
35490 @item @samp{QAllow}
35495 @item @samp{QDisableRandomization}
35500 @item @samp{EnableDisableTracepoints}
35505 @item @samp{QTBuffer:size}
35510 @item @samp{tracenz}
35515 @item @samp{BreakpointCommands}
35522 These are the currently defined stub features, in more detail:
35525 @cindex packet size, remote protocol
35526 @item PacketSize=@var{bytes}
35527 The remote stub can accept packets up to at least @var{bytes} in
35528 length. @value{GDBN} will send packets up to this size for bulk
35529 transfers, and will never send larger packets. This is a limit on the
35530 data characters in the packet, including the frame and checksum.
35531 There is no trailing NUL byte in a remote protocol packet; if the stub
35532 stores packets in a NUL-terminated format, it should allow an extra
35533 byte in its buffer for the NUL. If this stub feature is not supported,
35534 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35536 @item qXfer:auxv:read
35537 The remote stub understands the @samp{qXfer:auxv:read} packet
35538 (@pxref{qXfer auxiliary vector read}).
35540 @item qXfer:btrace:read
35541 The remote stub understands the @samp{qXfer:btrace:read}
35542 packet (@pxref{qXfer btrace read}).
35544 @item qXfer:features:read
35545 The remote stub understands the @samp{qXfer:features:read} packet
35546 (@pxref{qXfer target description read}).
35548 @item qXfer:libraries:read
35549 The remote stub understands the @samp{qXfer:libraries:read} packet
35550 (@pxref{qXfer library list read}).
35552 @item qXfer:libraries-svr4:read
35553 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35554 (@pxref{qXfer svr4 library list read}).
35556 @item augmented-libraries-svr4-read
35557 The remote stub understands the augmented form of the
35558 @samp{qXfer:libraries-svr4:read} packet
35559 (@pxref{qXfer svr4 library list read}).
35561 @item qXfer:memory-map:read
35562 The remote stub understands the @samp{qXfer:memory-map:read} packet
35563 (@pxref{qXfer memory map read}).
35565 @item qXfer:sdata:read
35566 The remote stub understands the @samp{qXfer:sdata:read} packet
35567 (@pxref{qXfer sdata read}).
35569 @item qXfer:spu:read
35570 The remote stub understands the @samp{qXfer:spu:read} packet
35571 (@pxref{qXfer spu read}).
35573 @item qXfer:spu:write
35574 The remote stub understands the @samp{qXfer:spu:write} packet
35575 (@pxref{qXfer spu write}).
35577 @item qXfer:siginfo:read
35578 The remote stub understands the @samp{qXfer:siginfo:read} packet
35579 (@pxref{qXfer siginfo read}).
35581 @item qXfer:siginfo:write
35582 The remote stub understands the @samp{qXfer:siginfo:write} packet
35583 (@pxref{qXfer siginfo write}).
35585 @item qXfer:threads:read
35586 The remote stub understands the @samp{qXfer:threads:read} packet
35587 (@pxref{qXfer threads read}).
35589 @item qXfer:traceframe-info:read
35590 The remote stub understands the @samp{qXfer:traceframe-info:read}
35591 packet (@pxref{qXfer traceframe info read}).
35593 @item qXfer:uib:read
35594 The remote stub understands the @samp{qXfer:uib:read}
35595 packet (@pxref{qXfer unwind info block}).
35597 @item qXfer:fdpic:read
35598 The remote stub understands the @samp{qXfer:fdpic:read}
35599 packet (@pxref{qXfer fdpic loadmap read}).
35602 The remote stub understands the @samp{QNonStop} packet
35603 (@pxref{QNonStop}).
35606 The remote stub understands the @samp{QPassSignals} packet
35607 (@pxref{QPassSignals}).
35609 @item QStartNoAckMode
35610 The remote stub understands the @samp{QStartNoAckMode} packet and
35611 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35614 @anchor{multiprocess extensions}
35615 @cindex multiprocess extensions, in remote protocol
35616 The remote stub understands the multiprocess extensions to the remote
35617 protocol syntax. The multiprocess extensions affect the syntax of
35618 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35619 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35620 replies. Note that reporting this feature indicates support for the
35621 syntactic extensions only, not that the stub necessarily supports
35622 debugging of more than one process at a time. The stub must not use
35623 multiprocess extensions in packet replies unless @value{GDBN} has also
35624 indicated it supports them in its @samp{qSupported} request.
35626 @item qXfer:osdata:read
35627 The remote stub understands the @samp{qXfer:osdata:read} packet
35628 ((@pxref{qXfer osdata read}).
35630 @item ConditionalBreakpoints
35631 The target accepts and implements evaluation of conditional expressions
35632 defined for breakpoints. The target will only report breakpoint triggers
35633 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35635 @item ConditionalTracepoints
35636 The remote stub accepts and implements conditional expressions defined
35637 for tracepoints (@pxref{Tracepoint Conditions}).
35639 @item ReverseContinue
35640 The remote stub accepts and implements the reverse continue packet
35644 The remote stub accepts and implements the reverse step packet
35647 @item TracepointSource
35648 The remote stub understands the @samp{QTDPsrc} packet that supplies
35649 the source form of tracepoint definitions.
35652 The remote stub understands the @samp{QAgent} packet.
35655 The remote stub understands the @samp{QAllow} packet.
35657 @item QDisableRandomization
35658 The remote stub understands the @samp{QDisableRandomization} packet.
35660 @item StaticTracepoint
35661 @cindex static tracepoints, in remote protocol
35662 The remote stub supports static tracepoints.
35664 @item InstallInTrace
35665 @anchor{install tracepoint in tracing}
35666 The remote stub supports installing tracepoint in tracing.
35668 @item EnableDisableTracepoints
35669 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35670 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35671 to be enabled and disabled while a trace experiment is running.
35673 @item QTBuffer:size
35674 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35675 packet that allows to change the size of the trace buffer.
35678 @cindex string tracing, in remote protocol
35679 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35680 See @ref{Bytecode Descriptions} for details about the bytecode.
35682 @item BreakpointCommands
35683 @cindex breakpoint commands, in remote protocol
35684 The remote stub supports running a breakpoint's command list itself,
35685 rather than reporting the hit to @value{GDBN}.
35688 The remote stub understands the @samp{Qbtrace:off} packet.
35691 The remote stub understands the @samp{Qbtrace:bts} packet.
35696 @cindex symbol lookup, remote request
35697 @cindex @samp{qSymbol} packet
35698 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35699 requests. Accept requests from the target for the values of symbols.
35704 The target does not need to look up any (more) symbols.
35705 @item qSymbol:@var{sym_name}
35706 The target requests the value of symbol @var{sym_name} (hex encoded).
35707 @value{GDBN} may provide the value by using the
35708 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35712 @item qSymbol:@var{sym_value}:@var{sym_name}
35713 Set the value of @var{sym_name} to @var{sym_value}.
35715 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35716 target has previously requested.
35718 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35719 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35725 The target does not need to look up any (more) symbols.
35726 @item qSymbol:@var{sym_name}
35727 The target requests the value of a new symbol @var{sym_name} (hex
35728 encoded). @value{GDBN} will continue to supply the values of symbols
35729 (if available), until the target ceases to request them.
35734 @itemx QTDisconnected
35741 @itemx qTMinFTPILen
35743 @xref{Tracepoint Packets}.
35745 @item qThreadExtraInfo,@var{thread-id}
35746 @cindex thread attributes info, remote request
35747 @cindex @samp{qThreadExtraInfo} packet
35748 Obtain from the target OS a printable string description of thread
35749 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
35750 for the forms of @var{thread-id}. This
35751 string may contain anything that the target OS thinks is interesting
35752 for @value{GDBN} to tell the user about the thread. The string is
35753 displayed in @value{GDBN}'s @code{info threads} display. Some
35754 examples of possible thread extra info strings are @samp{Runnable}, or
35755 @samp{Blocked on Mutex}.
35759 @item @var{XX}@dots{}
35760 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35761 comprising the printable string containing the extra information about
35762 the thread's attributes.
35765 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35766 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35767 conventions above. Please don't use this packet as a model for new
35786 @xref{Tracepoint Packets}.
35788 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35789 @cindex read special object, remote request
35790 @cindex @samp{qXfer} packet
35791 @anchor{qXfer read}
35792 Read uninterpreted bytes from the target's special data area
35793 identified by the keyword @var{object}. Request @var{length} bytes
35794 starting at @var{offset} bytes into the data. The content and
35795 encoding of @var{annex} is specific to @var{object}; it can supply
35796 additional details about what data to access.
35798 Here are the specific requests of this form defined so far. All
35799 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35800 formats, listed below.
35803 @item qXfer:auxv:read::@var{offset},@var{length}
35804 @anchor{qXfer auxiliary vector read}
35805 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35806 auxiliary vector}. Note @var{annex} must be empty.
35808 This packet is not probed by default; the remote stub must request it,
35809 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35811 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
35812 @anchor{qXfer btrace read}
35814 Return a description of the current branch trace.
35815 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
35816 packet may have one of the following values:
35820 Returns all available branch trace.
35823 Returns all available branch trace if the branch trace changed since
35824 the last read request.
35827 Returns the new branch trace since the last read request. Adds a new
35828 block to the end of the trace that begins at zero and ends at the source
35829 location of the first branch in the trace buffer. This extra block is
35830 used to stitch traces together.
35832 If the trace buffer overflowed, returns an error indicating the overflow.
35835 This packet is not probed by default; the remote stub must request it
35836 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35838 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35839 @anchor{qXfer target description read}
35840 Access the @dfn{target description}. @xref{Target Descriptions}. The
35841 annex specifies which XML document to access. The main description is
35842 always loaded from the @samp{target.xml} annex.
35844 This packet is not probed by default; the remote stub must request it,
35845 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35847 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35848 @anchor{qXfer library list read}
35849 Access the target's list of loaded libraries. @xref{Library List Format}.
35850 The annex part of the generic @samp{qXfer} packet must be empty
35851 (@pxref{qXfer read}).
35853 Targets which maintain a list of libraries in the program's memory do
35854 not need to implement this packet; it is designed for platforms where
35855 the operating system manages the list of loaded libraries.
35857 This packet is not probed by default; the remote stub must request it,
35858 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35860 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35861 @anchor{qXfer svr4 library list read}
35862 Access the target's list of loaded libraries when the target is an SVR4
35863 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35864 of the generic @samp{qXfer} packet must be empty unless the remote
35865 stub indicated it supports the augmented form of this packet
35866 by supplying an appropriate @samp{qSupported} response
35867 (@pxref{qXfer read}, @ref{qSupported}).
35869 This packet is optional for better performance on SVR4 targets.
35870 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35872 This packet is not probed by default; the remote stub must request it,
35873 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35875 If the remote stub indicates it supports the augmented form of this
35876 packet then the annex part of the generic @samp{qXfer} packet may
35877 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
35878 arguments. The currently supported arguments are:
35881 @item start=@var{address}
35882 A hexadecimal number specifying the address of the @samp{struct
35883 link_map} to start reading the library list from. If unset or zero
35884 then the first @samp{struct link_map} in the library list will be
35885 chosen as the starting point.
35887 @item prev=@var{address}
35888 A hexadecimal number specifying the address of the @samp{struct
35889 link_map} immediately preceding the @samp{struct link_map}
35890 specified by the @samp{start} argument. If unset or zero then
35891 the remote stub will expect that no @samp{struct link_map}
35892 exists prior to the starting point.
35896 Arguments that are not understood by the remote stub will be silently
35899 @item qXfer:memory-map:read::@var{offset},@var{length}
35900 @anchor{qXfer memory map read}
35901 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35902 annex part of the generic @samp{qXfer} packet must be empty
35903 (@pxref{qXfer read}).
35905 This packet is not probed by default; the remote stub must request it,
35906 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35908 @item qXfer:sdata:read::@var{offset},@var{length}
35909 @anchor{qXfer sdata read}
35911 Read contents of the extra collected static tracepoint marker
35912 information. The annex part of the generic @samp{qXfer} packet must
35913 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35916 This packet is not probed by default; the remote stub must request it,
35917 by supplying an appropriate @samp{qSupported} response
35918 (@pxref{qSupported}).
35920 @item qXfer:siginfo:read::@var{offset},@var{length}
35921 @anchor{qXfer siginfo read}
35922 Read contents of the extra signal information on the target
35923 system. The annex part of the generic @samp{qXfer} packet must be
35924 empty (@pxref{qXfer read}).
35926 This packet is not probed by default; the remote stub must request it,
35927 by supplying an appropriate @samp{qSupported} response
35928 (@pxref{qSupported}).
35930 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35931 @anchor{qXfer spu read}
35932 Read contents of an @code{spufs} file on the target system. The
35933 annex specifies which file to read; it must be of the form
35934 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35935 in the target process, and @var{name} identifes the @code{spufs} file
35936 in that context to be accessed.
35938 This packet is not probed by default; the remote stub must request it,
35939 by supplying an appropriate @samp{qSupported} response
35940 (@pxref{qSupported}).
35942 @item qXfer:threads:read::@var{offset},@var{length}
35943 @anchor{qXfer threads read}
35944 Access the list of threads on target. @xref{Thread List Format}. The
35945 annex part of the generic @samp{qXfer} packet must be empty
35946 (@pxref{qXfer read}).
35948 This packet is not probed by default; the remote stub must request it,
35949 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35951 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35952 @anchor{qXfer traceframe info read}
35954 Return a description of the current traceframe's contents.
35955 @xref{Traceframe Info Format}. The annex part of the generic
35956 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35958 This packet is not probed by default; the remote stub must request it,
35959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35961 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35962 @anchor{qXfer unwind info block}
35964 Return the unwind information block for @var{pc}. This packet is used
35965 on OpenVMS/ia64 to ask the kernel unwind information.
35967 This packet is not probed by default.
35969 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35970 @anchor{qXfer fdpic loadmap read}
35971 Read contents of @code{loadmap}s on the target system. The
35972 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35973 executable @code{loadmap} or interpreter @code{loadmap} to read.
35975 This packet is not probed by default; the remote stub must request it,
35976 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35978 @item qXfer:osdata:read::@var{offset},@var{length}
35979 @anchor{qXfer osdata read}
35980 Access the target's @dfn{operating system information}.
35981 @xref{Operating System Information}.
35988 Data @var{data} (@pxref{Binary Data}) has been read from the
35989 target. There may be more data at a higher address (although
35990 it is permitted to return @samp{m} even for the last valid
35991 block of data, as long as at least one byte of data was read).
35992 It is possible for @var{data} to have fewer bytes than the @var{length} in the
35996 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35997 There is no more data to be read. It is possible for @var{data} to
35998 have fewer bytes than the @var{length} in the request.
36001 The @var{offset} in the request is at the end of the data.
36002 There is no more data to be read.
36005 The request was malformed, or @var{annex} was invalid.
36008 The offset was invalid, or there was an error encountered reading the data.
36009 The @var{nn} part is a hex-encoded @code{errno} value.
36012 An empty reply indicates the @var{object} string was not recognized by
36013 the stub, or that the object does not support reading.
36016 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36017 @cindex write data into object, remote request
36018 @anchor{qXfer write}
36019 Write uninterpreted bytes into the target's special data area
36020 identified by the keyword @var{object}, starting at @var{offset} bytes
36021 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36022 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36023 is specific to @var{object}; it can supply additional details about what data
36026 Here are the specific requests of this form defined so far. All
36027 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36028 formats, listed below.
36031 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36032 @anchor{qXfer siginfo write}
36033 Write @var{data} to the extra signal information on the target system.
36034 The annex part of the generic @samp{qXfer} packet must be
36035 empty (@pxref{qXfer write}).
36037 This packet is not probed by default; the remote stub must request it,
36038 by supplying an appropriate @samp{qSupported} response
36039 (@pxref{qSupported}).
36041 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36042 @anchor{qXfer spu write}
36043 Write @var{data} to an @code{spufs} file on the target system. The
36044 annex specifies which file to write; it must be of the form
36045 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36046 in the target process, and @var{name} identifes the @code{spufs} file
36047 in that context to be accessed.
36049 This packet is not probed by default; the remote stub must request it,
36050 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36056 @var{nn} (hex encoded) is the number of bytes written.
36057 This may be fewer bytes than supplied in the request.
36060 The request was malformed, or @var{annex} was invalid.
36063 The offset was invalid, or there was an error encountered writing the data.
36064 The @var{nn} part is a hex-encoded @code{errno} value.
36067 An empty reply indicates the @var{object} string was not
36068 recognized by the stub, or that the object does not support writing.
36071 @item qXfer:@var{object}:@var{operation}:@dots{}
36072 Requests of this form may be added in the future. When a stub does
36073 not recognize the @var{object} keyword, or its support for
36074 @var{object} does not recognize the @var{operation} keyword, the stub
36075 must respond with an empty packet.
36077 @item qAttached:@var{pid}
36078 @cindex query attached, remote request
36079 @cindex @samp{qAttached} packet
36080 Return an indication of whether the remote server attached to an
36081 existing process or created a new process. When the multiprocess
36082 protocol extensions are supported (@pxref{multiprocess extensions}),
36083 @var{pid} is an integer in hexadecimal format identifying the target
36084 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36085 the query packet will be simplified as @samp{qAttached}.
36087 This query is used, for example, to know whether the remote process
36088 should be detached or killed when a @value{GDBN} session is ended with
36089 the @code{quit} command.
36094 The remote server attached to an existing process.
36096 The remote server created a new process.
36098 A badly formed request or an error was encountered.
36102 Enable branch tracing for the current thread using bts tracing.
36107 Branch tracing has been enabled.
36109 A badly formed request or an error was encountered.
36113 Disable branch tracing for the current thread.
36118 Branch tracing has been disabled.
36120 A badly formed request or an error was encountered.
36125 @node Architecture-Specific Protocol Details
36126 @section Architecture-Specific Protocol Details
36128 This section describes how the remote protocol is applied to specific
36129 target architectures. Also see @ref{Standard Target Features}, for
36130 details of XML target descriptions for each architecture.
36133 * ARM-Specific Protocol Details::
36134 * MIPS-Specific Protocol Details::
36137 @node ARM-Specific Protocol Details
36138 @subsection @acronym{ARM}-specific Protocol Details
36141 * ARM Breakpoint Kinds::
36144 @node ARM Breakpoint Kinds
36145 @subsubsection @acronym{ARM} Breakpoint Kinds
36146 @cindex breakpoint kinds, @acronym{ARM}
36148 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36153 16-bit Thumb mode breakpoint.
36156 32-bit Thumb mode (Thumb-2) breakpoint.
36159 32-bit @acronym{ARM} mode breakpoint.
36163 @node MIPS-Specific Protocol Details
36164 @subsection @acronym{MIPS}-specific Protocol Details
36167 * MIPS Register packet Format::
36168 * MIPS Breakpoint Kinds::
36171 @node MIPS Register packet Format
36172 @subsubsection @acronym{MIPS} Register Packet Format
36173 @cindex register packet format, @acronym{MIPS}
36175 The following @code{g}/@code{G} packets have previously been defined.
36176 In the below, some thirty-two bit registers are transferred as
36177 sixty-four bits. Those registers should be zero/sign extended (which?)
36178 to fill the space allocated. Register bytes are transferred in target
36179 byte order. The two nibbles within a register byte are transferred
36180 most-significant -- least-significant.
36185 All registers are transferred as thirty-two bit quantities in the order:
36186 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36187 registers; fsr; fir; fp.
36190 All registers are transferred as sixty-four bit quantities (including
36191 thirty-two bit registers such as @code{sr}). The ordering is the same
36196 @node MIPS Breakpoint Kinds
36197 @subsubsection @acronym{MIPS} Breakpoint Kinds
36198 @cindex breakpoint kinds, @acronym{MIPS}
36200 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36205 16-bit @acronym{MIPS16} mode breakpoint.
36208 16-bit @acronym{microMIPS} mode breakpoint.
36211 32-bit standard @acronym{MIPS} mode breakpoint.
36214 32-bit @acronym{microMIPS} mode breakpoint.
36218 @node Tracepoint Packets
36219 @section Tracepoint Packets
36220 @cindex tracepoint packets
36221 @cindex packets, tracepoint
36223 Here we describe the packets @value{GDBN} uses to implement
36224 tracepoints (@pxref{Tracepoints}).
36228 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36229 @cindex @samp{QTDP} packet
36230 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36231 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36232 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36233 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36234 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36235 the number of bytes that the target should copy elsewhere to make room
36236 for the tracepoint. If an @samp{X} is present, it introduces a
36237 tracepoint condition, which consists of a hexadecimal length, followed
36238 by a comma and hex-encoded bytes, in a manner similar to action
36239 encodings as described below. If the trailing @samp{-} is present,
36240 further @samp{QTDP} packets will follow to specify this tracepoint's
36246 The packet was understood and carried out.
36248 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36250 The packet was not recognized.
36253 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36254 Define actions to be taken when a tracepoint is hit. The @var{n} and
36255 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36256 this tracepoint. This packet may only be sent immediately after
36257 another @samp{QTDP} packet that ended with a @samp{-}. If the
36258 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36259 specifying more actions for this tracepoint.
36261 In the series of action packets for a given tracepoint, at most one
36262 can have an @samp{S} before its first @var{action}. If such a packet
36263 is sent, it and the following packets define ``while-stepping''
36264 actions. Any prior packets define ordinary actions --- that is, those
36265 taken when the tracepoint is first hit. If no action packet has an
36266 @samp{S}, then all the packets in the series specify ordinary
36267 tracepoint actions.
36269 The @samp{@var{action}@dots{}} portion of the packet is a series of
36270 actions, concatenated without separators. Each action has one of the
36276 Collect the registers whose bits are set in @var{mask},
36277 a hexadecimal number whose @var{i}'th bit is set if register number
36278 @var{i} should be collected. (The least significant bit is numbered
36279 zero.) Note that @var{mask} may be any number of digits long; it may
36280 not fit in a 32-bit word.
36282 @item M @var{basereg},@var{offset},@var{len}
36283 Collect @var{len} bytes of memory starting at the address in register
36284 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36285 @samp{-1}, then the range has a fixed address: @var{offset} is the
36286 address of the lowest byte to collect. The @var{basereg},
36287 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36288 values (the @samp{-1} value for @var{basereg} is a special case).
36290 @item X @var{len},@var{expr}
36291 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36292 it directs. The agent expression @var{expr} is as described in
36293 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36294 two-digit hex number in the packet; @var{len} is the number of bytes
36295 in the expression (and thus one-half the number of hex digits in the
36300 Any number of actions may be packed together in a single @samp{QTDP}
36301 packet, as long as the packet does not exceed the maximum packet
36302 length (400 bytes, for many stubs). There may be only one @samp{R}
36303 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36304 actions. Any registers referred to by @samp{M} and @samp{X} actions
36305 must be collected by a preceding @samp{R} action. (The
36306 ``while-stepping'' actions are treated as if they were attached to a
36307 separate tracepoint, as far as these restrictions are concerned.)
36312 The packet was understood and carried out.
36314 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36316 The packet was not recognized.
36319 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36320 @cindex @samp{QTDPsrc} packet
36321 Specify a source string of tracepoint @var{n} at address @var{addr}.
36322 This is useful to get accurate reproduction of the tracepoints
36323 originally downloaded at the beginning of the trace run. The @var{type}
36324 is the name of the tracepoint part, such as @samp{cond} for the
36325 tracepoint's conditional expression (see below for a list of types), while
36326 @var{bytes} is the string, encoded in hexadecimal.
36328 @var{start} is the offset of the @var{bytes} within the overall source
36329 string, while @var{slen} is the total length of the source string.
36330 This is intended for handling source strings that are longer than will
36331 fit in a single packet.
36332 @c Add detailed example when this info is moved into a dedicated
36333 @c tracepoint descriptions section.
36335 The available string types are @samp{at} for the location,
36336 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36337 @value{GDBN} sends a separate packet for each command in the action
36338 list, in the same order in which the commands are stored in the list.
36340 The target does not need to do anything with source strings except
36341 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36344 Although this packet is optional, and @value{GDBN} will only send it
36345 if the target replies with @samp{TracepointSource} @xref{General
36346 Query Packets}, it makes both disconnected tracing and trace files
36347 much easier to use. Otherwise the user must be careful that the
36348 tracepoints in effect while looking at trace frames are identical to
36349 the ones in effect during the trace run; even a small discrepancy
36350 could cause @samp{tdump} not to work, or a particular trace frame not
36353 @item QTDV:@var{n}:@var{value}
36354 @cindex define trace state variable, remote request
36355 @cindex @samp{QTDV} packet
36356 Create a new trace state variable, number @var{n}, with an initial
36357 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36358 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36359 the option of not using this packet for initial values of zero; the
36360 target should simply create the trace state variables as they are
36361 mentioned in expressions.
36363 @item QTFrame:@var{n}
36364 @cindex @samp{QTFrame} packet
36365 Select the @var{n}'th tracepoint frame from the buffer, and use the
36366 register and memory contents recorded there to answer subsequent
36367 request packets from @value{GDBN}.
36369 A successful reply from the stub indicates that the stub has found the
36370 requested frame. The response is a series of parts, concatenated
36371 without separators, describing the frame we selected. Each part has
36372 one of the following forms:
36376 The selected frame is number @var{n} in the trace frame buffer;
36377 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36378 was no frame matching the criteria in the request packet.
36381 The selected trace frame records a hit of tracepoint number @var{t};
36382 @var{t} is a hexadecimal number.
36386 @item QTFrame:pc:@var{addr}
36387 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36388 currently selected frame whose PC is @var{addr};
36389 @var{addr} is a hexadecimal number.
36391 @item QTFrame:tdp:@var{t}
36392 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36393 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36394 is a hexadecimal number.
36396 @item QTFrame:range:@var{start}:@var{end}
36397 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36398 currently selected frame whose PC is between @var{start} (inclusive)
36399 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36402 @item QTFrame:outside:@var{start}:@var{end}
36403 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36404 frame @emph{outside} the given range of addresses (exclusive).
36407 @cindex @samp{qTMinFTPILen} packet
36408 This packet requests the minimum length of instruction at which a fast
36409 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36410 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36411 it depends on the target system being able to create trampolines in
36412 the first 64K of memory, which might or might not be possible for that
36413 system. So the reply to this packet will be 4 if it is able to
36420 The minimum instruction length is currently unknown.
36422 The minimum instruction length is @var{length}, where @var{length}
36423 is a hexadecimal number greater or equal to 1. A reply
36424 of 1 means that a fast tracepoint may be placed on any instruction
36425 regardless of size.
36427 An error has occurred.
36429 An empty reply indicates that the request is not supported by the stub.
36433 @cindex @samp{QTStart} packet
36434 Begin the tracepoint experiment. Begin collecting data from
36435 tracepoint hits in the trace frame buffer. This packet supports the
36436 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36437 instruction reply packet}).
36440 @cindex @samp{QTStop} packet
36441 End the tracepoint experiment. Stop collecting trace frames.
36443 @item QTEnable:@var{n}:@var{addr}
36445 @cindex @samp{QTEnable} packet
36446 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36447 experiment. If the tracepoint was previously disabled, then collection
36448 of data from it will resume.
36450 @item QTDisable:@var{n}:@var{addr}
36452 @cindex @samp{QTDisable} packet
36453 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36454 experiment. No more data will be collected from the tracepoint unless
36455 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36458 @cindex @samp{QTinit} packet
36459 Clear the table of tracepoints, and empty the trace frame buffer.
36461 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36462 @cindex @samp{QTro} packet
36463 Establish the given ranges of memory as ``transparent''. The stub
36464 will answer requests for these ranges from memory's current contents,
36465 if they were not collected as part of the tracepoint hit.
36467 @value{GDBN} uses this to mark read-only regions of memory, like those
36468 containing program code. Since these areas never change, they should
36469 still have the same contents they did when the tracepoint was hit, so
36470 there's no reason for the stub to refuse to provide their contents.
36472 @item QTDisconnected:@var{value}
36473 @cindex @samp{QTDisconnected} packet
36474 Set the choice to what to do with the tracing run when @value{GDBN}
36475 disconnects from the target. A @var{value} of 1 directs the target to
36476 continue the tracing run, while 0 tells the target to stop tracing if
36477 @value{GDBN} is no longer in the picture.
36480 @cindex @samp{qTStatus} packet
36481 Ask the stub if there is a trace experiment running right now.
36483 The reply has the form:
36487 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36488 @var{running} is a single digit @code{1} if the trace is presently
36489 running, or @code{0} if not. It is followed by semicolon-separated
36490 optional fields that an agent may use to report additional status.
36494 If the trace is not running, the agent may report any of several
36495 explanations as one of the optional fields:
36500 No trace has been run yet.
36502 @item tstop[:@var{text}]:0
36503 The trace was stopped by a user-originated stop command. The optional
36504 @var{text} field is a user-supplied string supplied as part of the
36505 stop command (for instance, an explanation of why the trace was
36506 stopped manually). It is hex-encoded.
36509 The trace stopped because the trace buffer filled up.
36511 @item tdisconnected:0
36512 The trace stopped because @value{GDBN} disconnected from the target.
36514 @item tpasscount:@var{tpnum}
36515 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36517 @item terror:@var{text}:@var{tpnum}
36518 The trace stopped because tracepoint @var{tpnum} had an error. The
36519 string @var{text} is available to describe the nature of the error
36520 (for instance, a divide by zero in the condition expression); it
36524 The trace stopped for some other reason.
36528 Additional optional fields supply statistical and other information.
36529 Although not required, they are extremely useful for users monitoring
36530 the progress of a trace run. If a trace has stopped, and these
36531 numbers are reported, they must reflect the state of the just-stopped
36536 @item tframes:@var{n}
36537 The number of trace frames in the buffer.
36539 @item tcreated:@var{n}
36540 The total number of trace frames created during the run. This may
36541 be larger than the trace frame count, if the buffer is circular.
36543 @item tsize:@var{n}
36544 The total size of the trace buffer, in bytes.
36546 @item tfree:@var{n}
36547 The number of bytes still unused in the buffer.
36549 @item circular:@var{n}
36550 The value of the circular trace buffer flag. @code{1} means that the
36551 trace buffer is circular and old trace frames will be discarded if
36552 necessary to make room, @code{0} means that the trace buffer is linear
36555 @item disconn:@var{n}
36556 The value of the disconnected tracing flag. @code{1} means that
36557 tracing will continue after @value{GDBN} disconnects, @code{0} means
36558 that the trace run will stop.
36562 @item qTP:@var{tp}:@var{addr}
36563 @cindex tracepoint status, remote request
36564 @cindex @samp{qTP} packet
36565 Ask the stub for the current state of tracepoint number @var{tp} at
36566 address @var{addr}.
36570 @item V@var{hits}:@var{usage}
36571 The tracepoint has been hit @var{hits} times so far during the trace
36572 run, and accounts for @var{usage} in the trace buffer. Note that
36573 @code{while-stepping} steps are not counted as separate hits, but the
36574 steps' space consumption is added into the usage number.
36578 @item qTV:@var{var}
36579 @cindex trace state variable value, remote request
36580 @cindex @samp{qTV} packet
36581 Ask the stub for the value of the trace state variable number @var{var}.
36586 The value of the variable is @var{value}. This will be the current
36587 value of the variable if the user is examining a running target, or a
36588 saved value if the variable was collected in the trace frame that the
36589 user is looking at. Note that multiple requests may result in
36590 different reply values, such as when requesting values while the
36591 program is running.
36594 The value of the variable is unknown. This would occur, for example,
36595 if the user is examining a trace frame in which the requested variable
36600 @cindex @samp{qTfP} packet
36602 @cindex @samp{qTsP} packet
36603 These packets request data about tracepoints that are being used by
36604 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36605 of data, and multiple @code{qTsP} to get additional pieces. Replies
36606 to these packets generally take the form of the @code{QTDP} packets
36607 that define tracepoints. (FIXME add detailed syntax)
36610 @cindex @samp{qTfV} packet
36612 @cindex @samp{qTsV} packet
36613 These packets request data about trace state variables that are on the
36614 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36615 and multiple @code{qTsV} to get additional variables. Replies to
36616 these packets follow the syntax of the @code{QTDV} packets that define
36617 trace state variables.
36623 @cindex @samp{qTfSTM} packet
36624 @cindex @samp{qTsSTM} packet
36625 These packets request data about static tracepoint markers that exist
36626 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36627 first piece of data, and multiple @code{qTsSTM} to get additional
36628 pieces. Replies to these packets take the following form:
36632 @item m @var{address}:@var{id}:@var{extra}
36634 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36635 a comma-separated list of markers
36637 (lower case letter @samp{L}) denotes end of list.
36639 An error occurred. The error number @var{nn} is given as hex digits.
36641 An empty reply indicates that the request is not supported by the
36645 The @var{address} is encoded in hex;
36646 @var{id} and @var{extra} are strings encoded in hex.
36648 In response to each query, the target will reply with a list of one or
36649 more markers, separated by commas. @value{GDBN} will respond to each
36650 reply with a request for more markers (using the @samp{qs} form of the
36651 query), until the target responds with @samp{l} (lower-case ell, for
36654 @item qTSTMat:@var{address}
36656 @cindex @samp{qTSTMat} packet
36657 This packets requests data about static tracepoint markers in the
36658 target program at @var{address}. Replies to this packet follow the
36659 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36660 tracepoint markers.
36662 @item QTSave:@var{filename}
36663 @cindex @samp{QTSave} packet
36664 This packet directs the target to save trace data to the file name
36665 @var{filename} in the target's filesystem. The @var{filename} is encoded
36666 as a hex string; the interpretation of the file name (relative vs
36667 absolute, wild cards, etc) is up to the target.
36669 @item qTBuffer:@var{offset},@var{len}
36670 @cindex @samp{qTBuffer} packet
36671 Return up to @var{len} bytes of the current contents of trace buffer,
36672 starting at @var{offset}. The trace buffer is treated as if it were
36673 a contiguous collection of traceframes, as per the trace file format.
36674 The reply consists as many hex-encoded bytes as the target can deliver
36675 in a packet; it is not an error to return fewer than were asked for.
36676 A reply consisting of just @code{l} indicates that no bytes are
36679 @item QTBuffer:circular:@var{value}
36680 This packet directs the target to use a circular trace buffer if
36681 @var{value} is 1, or a linear buffer if the value is 0.
36683 @item QTBuffer:size:@var{size}
36684 @anchor{QTBuffer-size}
36685 @cindex @samp{QTBuffer size} packet
36686 This packet directs the target to make the trace buffer be of size
36687 @var{size} if possible. A value of @code{-1} tells the target to
36688 use whatever size it prefers.
36690 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36691 @cindex @samp{QTNotes} packet
36692 This packet adds optional textual notes to the trace run. Allowable
36693 types include @code{user}, @code{notes}, and @code{tstop}, the
36694 @var{text} fields are arbitrary strings, hex-encoded.
36698 @subsection Relocate instruction reply packet
36699 When installing fast tracepoints in memory, the target may need to
36700 relocate the instruction currently at the tracepoint address to a
36701 different address in memory. For most instructions, a simple copy is
36702 enough, but, for example, call instructions that implicitly push the
36703 return address on the stack, and relative branches or other
36704 PC-relative instructions require offset adjustment, so that the effect
36705 of executing the instruction at a different address is the same as if
36706 it had executed in the original location.
36708 In response to several of the tracepoint packets, the target may also
36709 respond with a number of intermediate @samp{qRelocInsn} request
36710 packets before the final result packet, to have @value{GDBN} handle
36711 this relocation operation. If a packet supports this mechanism, its
36712 documentation will explicitly say so. See for example the above
36713 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36714 format of the request is:
36717 @item qRelocInsn:@var{from};@var{to}
36719 This requests @value{GDBN} to copy instruction at address @var{from}
36720 to address @var{to}, possibly adjusted so that executing the
36721 instruction at @var{to} has the same effect as executing it at
36722 @var{from}. @value{GDBN} writes the adjusted instruction to target
36723 memory starting at @var{to}.
36728 @item qRelocInsn:@var{adjusted_size}
36729 Informs the stub the relocation is complete. The @var{adjusted_size} is
36730 the length in bytes of resulting relocated instruction sequence.
36732 A badly formed request was detected, or an error was encountered while
36733 relocating the instruction.
36736 @node Host I/O Packets
36737 @section Host I/O Packets
36738 @cindex Host I/O, remote protocol
36739 @cindex file transfer, remote protocol
36741 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36742 operations on the far side of a remote link. For example, Host I/O is
36743 used to upload and download files to a remote target with its own
36744 filesystem. Host I/O uses the same constant values and data structure
36745 layout as the target-initiated File-I/O protocol. However, the
36746 Host I/O packets are structured differently. The target-initiated
36747 protocol relies on target memory to store parameters and buffers.
36748 Host I/O requests are initiated by @value{GDBN}, and the
36749 target's memory is not involved. @xref{File-I/O Remote Protocol
36750 Extension}, for more details on the target-initiated protocol.
36752 The Host I/O request packets all encode a single operation along with
36753 its arguments. They have this format:
36757 @item vFile:@var{operation}: @var{parameter}@dots{}
36758 @var{operation} is the name of the particular request; the target
36759 should compare the entire packet name up to the second colon when checking
36760 for a supported operation. The format of @var{parameter} depends on
36761 the operation. Numbers are always passed in hexadecimal. Negative
36762 numbers have an explicit minus sign (i.e.@: two's complement is not
36763 used). Strings (e.g.@: filenames) are encoded as a series of
36764 hexadecimal bytes. The last argument to a system call may be a
36765 buffer of escaped binary data (@pxref{Binary Data}).
36769 The valid responses to Host I/O packets are:
36773 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36774 @var{result} is the integer value returned by this operation, usually
36775 non-negative for success and -1 for errors. If an error has occured,
36776 @var{errno} will be included in the result specifying a
36777 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36778 operations which return data, @var{attachment} supplies the data as a
36779 binary buffer. Binary buffers in response packets are escaped in the
36780 normal way (@pxref{Binary Data}). See the individual packet
36781 documentation for the interpretation of @var{result} and
36785 An empty response indicates that this operation is not recognized.
36789 These are the supported Host I/O operations:
36792 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
36793 Open a file at @var{filename} and return a file descriptor for it, or
36794 return -1 if an error occurs. The @var{filename} is a string,
36795 @var{flags} is an integer indicating a mask of open flags
36796 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36797 of mode bits to use if the file is created (@pxref{mode_t Values}).
36798 @xref{open}, for details of the open flags and mode values.
36800 @item vFile:close: @var{fd}
36801 Close the open file corresponding to @var{fd} and return 0, or
36802 -1 if an error occurs.
36804 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36805 Read data from the open file corresponding to @var{fd}. Up to
36806 @var{count} bytes will be read from the file, starting at @var{offset}
36807 relative to the start of the file. The target may read fewer bytes;
36808 common reasons include packet size limits and an end-of-file
36809 condition. The number of bytes read is returned. Zero should only be
36810 returned for a successful read at the end of the file, or if
36811 @var{count} was zero.
36813 The data read should be returned as a binary attachment on success.
36814 If zero bytes were read, the response should include an empty binary
36815 attachment (i.e.@: a trailing semicolon). The return value is the
36816 number of target bytes read; the binary attachment may be longer if
36817 some characters were escaped.
36819 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36820 Write @var{data} (a binary buffer) to the open file corresponding
36821 to @var{fd}. Start the write at @var{offset} from the start of the
36822 file. Unlike many @code{write} system calls, there is no
36823 separate @var{count} argument; the length of @var{data} in the
36824 packet is used. @samp{vFile:write} returns the number of bytes written,
36825 which may be shorter than the length of @var{data}, or -1 if an
36828 @item vFile:unlink: @var{filename}
36829 Delete the file at @var{filename} on the target. Return 0,
36830 or -1 if an error occurs. The @var{filename} is a string.
36832 @item vFile:readlink: @var{filename}
36833 Read value of symbolic link @var{filename} on the target. Return
36834 the number of bytes read, or -1 if an error occurs.
36836 The data read should be returned as a binary attachment on success.
36837 If zero bytes were read, the response should include an empty binary
36838 attachment (i.e.@: a trailing semicolon). The return value is the
36839 number of target bytes read; the binary attachment may be longer if
36840 some characters were escaped.
36845 @section Interrupts
36846 @cindex interrupts (remote protocol)
36848 When a program on the remote target is running, @value{GDBN} may
36849 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36850 a @code{BREAK} followed by @code{g},
36851 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36853 The precise meaning of @code{BREAK} is defined by the transport
36854 mechanism and may, in fact, be undefined. @value{GDBN} does not
36855 currently define a @code{BREAK} mechanism for any of the network
36856 interfaces except for TCP, in which case @value{GDBN} sends the
36857 @code{telnet} BREAK sequence.
36859 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36860 transport mechanisms. It is represented by sending the single byte
36861 @code{0x03} without any of the usual packet overhead described in
36862 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36863 transmitted as part of a packet, it is considered to be packet data
36864 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36865 (@pxref{X packet}), used for binary downloads, may include an unescaped
36866 @code{0x03} as part of its packet.
36868 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36869 When Linux kernel receives this sequence from serial port,
36870 it stops execution and connects to gdb.
36872 Stubs are not required to recognize these interrupt mechanisms and the
36873 precise meaning associated with receipt of the interrupt is
36874 implementation defined. If the target supports debugging of multiple
36875 threads and/or processes, it should attempt to interrupt all
36876 currently-executing threads and processes.
36877 If the stub is successful at interrupting the
36878 running program, it should send one of the stop
36879 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36880 of successfully stopping the program in all-stop mode, and a stop reply
36881 for each stopped thread in non-stop mode.
36882 Interrupts received while the
36883 program is stopped are discarded.
36885 @node Notification Packets
36886 @section Notification Packets
36887 @cindex notification packets
36888 @cindex packets, notification
36890 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36891 packets that require no acknowledgment. Both the GDB and the stub
36892 may send notifications (although the only notifications defined at
36893 present are sent by the stub). Notifications carry information
36894 without incurring the round-trip latency of an acknowledgment, and so
36895 are useful for low-impact communications where occasional packet loss
36898 A notification packet has the form @samp{% @var{data} #
36899 @var{checksum}}, where @var{data} is the content of the notification,
36900 and @var{checksum} is a checksum of @var{data}, computed and formatted
36901 as for ordinary @value{GDBN} packets. A notification's @var{data}
36902 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36903 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36904 to acknowledge the notification's receipt or to report its corruption.
36906 Every notification's @var{data} begins with a name, which contains no
36907 colon characters, followed by a colon character.
36909 Recipients should silently ignore corrupted notifications and
36910 notifications they do not understand. Recipients should restart
36911 timeout periods on receipt of a well-formed notification, whether or
36912 not they understand it.
36914 Senders should only send the notifications described here when this
36915 protocol description specifies that they are permitted. In the
36916 future, we may extend the protocol to permit existing notifications in
36917 new contexts; this rule helps older senders avoid confusing newer
36920 (Older versions of @value{GDBN} ignore bytes received until they see
36921 the @samp{$} byte that begins an ordinary packet, so new stubs may
36922 transmit notifications without fear of confusing older clients. There
36923 are no notifications defined for @value{GDBN} to send at the moment, but we
36924 assume that most older stubs would ignore them, as well.)
36926 Each notification is comprised of three parts:
36928 @item @var{name}:@var{event}
36929 The notification packet is sent by the side that initiates the
36930 exchange (currently, only the stub does that), with @var{event}
36931 carrying the specific information about the notification, and
36932 @var{name} specifying the name of the notification.
36934 The acknowledge sent by the other side, usually @value{GDBN}, to
36935 acknowledge the exchange and request the event.
36938 The purpose of an asynchronous notification mechanism is to report to
36939 @value{GDBN} that something interesting happened in the remote stub.
36941 The remote stub may send notification @var{name}:@var{event}
36942 at any time, but @value{GDBN} acknowledges the notification when
36943 appropriate. The notification event is pending before @value{GDBN}
36944 acknowledges. Only one notification at a time may be pending; if
36945 additional events occur before @value{GDBN} has acknowledged the
36946 previous notification, they must be queued by the stub for later
36947 synchronous transmission in response to @var{ack} packets from
36948 @value{GDBN}. Because the notification mechanism is unreliable,
36949 the stub is permitted to resend a notification if it believes
36950 @value{GDBN} may not have received it.
36952 Specifically, notifications may appear when @value{GDBN} is not
36953 otherwise reading input from the stub, or when @value{GDBN} is
36954 expecting to read a normal synchronous response or a
36955 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36956 Notification packets are distinct from any other communication from
36957 the stub so there is no ambiguity.
36959 After receiving a notification, @value{GDBN} shall acknowledge it by
36960 sending a @var{ack} packet as a regular, synchronous request to the
36961 stub. Such acknowledgment is not required to happen immediately, as
36962 @value{GDBN} is permitted to send other, unrelated packets to the
36963 stub first, which the stub should process normally.
36965 Upon receiving a @var{ack} packet, if the stub has other queued
36966 events to report to @value{GDBN}, it shall respond by sending a
36967 normal @var{event}. @value{GDBN} shall then send another @var{ack}
36968 packet to solicit further responses; again, it is permitted to send
36969 other, unrelated packets as well which the stub should process
36972 If the stub receives a @var{ack} packet and there are no additional
36973 @var{event} to report, the stub shall return an @samp{OK} response.
36974 At this point, @value{GDBN} has finished processing a notification
36975 and the stub has completed sending any queued events. @value{GDBN}
36976 won't accept any new notifications until the final @samp{OK} is
36977 received . If further notification events occur, the stub shall send
36978 a new notification, @value{GDBN} shall accept the notification, and
36979 the process shall be repeated.
36981 The process of asynchronous notification can be illustrated by the
36984 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
36987 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
36989 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
36994 The following notifications are defined:
36995 @multitable @columnfractions 0.12 0.12 0.38 0.38
37004 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37005 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37006 for information on how these notifications are acknowledged by
37008 @tab Report an asynchronous stop event in non-stop mode.
37012 @node Remote Non-Stop
37013 @section Remote Protocol Support for Non-Stop Mode
37015 @value{GDBN}'s remote protocol supports non-stop debugging of
37016 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37017 supports non-stop mode, it should report that to @value{GDBN} by including
37018 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37020 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37021 establishing a new connection with the stub. Entering non-stop mode
37022 does not alter the state of any currently-running threads, but targets
37023 must stop all threads in any already-attached processes when entering
37024 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37025 probe the target state after a mode change.
37027 In non-stop mode, when an attached process encounters an event that
37028 would otherwise be reported with a stop reply, it uses the
37029 asynchronous notification mechanism (@pxref{Notification Packets}) to
37030 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37031 in all processes are stopped when a stop reply is sent, in non-stop
37032 mode only the thread reporting the stop event is stopped. That is,
37033 when reporting a @samp{S} or @samp{T} response to indicate completion
37034 of a step operation, hitting a breakpoint, or a fault, only the
37035 affected thread is stopped; any other still-running threads continue
37036 to run. When reporting a @samp{W} or @samp{X} response, all running
37037 threads belonging to other attached processes continue to run.
37039 In non-stop mode, the target shall respond to the @samp{?} packet as
37040 follows. First, any incomplete stop reply notification/@samp{vStopped}
37041 sequence in progress is abandoned. The target must begin a new
37042 sequence reporting stop events for all stopped threads, whether or not
37043 it has previously reported those events to @value{GDBN}. The first
37044 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37045 subsequent stop replies are sent as responses to @samp{vStopped} packets
37046 using the mechanism described above. The target must not send
37047 asynchronous stop reply notifications until the sequence is complete.
37048 If all threads are running when the target receives the @samp{?} packet,
37049 or if the target is not attached to any process, it shall respond
37052 @node Packet Acknowledgment
37053 @section Packet Acknowledgment
37055 @cindex acknowledgment, for @value{GDBN} remote
37056 @cindex packet acknowledgment, for @value{GDBN} remote
37057 By default, when either the host or the target machine receives a packet,
37058 the first response expected is an acknowledgment: either @samp{+} (to indicate
37059 the package was received correctly) or @samp{-} (to request retransmission).
37060 This mechanism allows the @value{GDBN} remote protocol to operate over
37061 unreliable transport mechanisms, such as a serial line.
37063 In cases where the transport mechanism is itself reliable (such as a pipe or
37064 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37065 It may be desirable to disable them in that case to reduce communication
37066 overhead, or for other reasons. This can be accomplished by means of the
37067 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37069 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37070 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37071 and response format still includes the normal checksum, as described in
37072 @ref{Overview}, but the checksum may be ignored by the receiver.
37074 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37075 no-acknowledgment mode, it should report that to @value{GDBN}
37076 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37077 @pxref{qSupported}.
37078 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37079 disabled via the @code{set remote noack-packet off} command
37080 (@pxref{Remote Configuration}),
37081 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37082 Only then may the stub actually turn off packet acknowledgments.
37083 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37084 response, which can be safely ignored by the stub.
37086 Note that @code{set remote noack-packet} command only affects negotiation
37087 between @value{GDBN} and the stub when subsequent connections are made;
37088 it does not affect the protocol acknowledgment state for any current
37090 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37091 new connection is established,
37092 there is also no protocol request to re-enable the acknowledgments
37093 for the current connection, once disabled.
37098 Example sequence of a target being re-started. Notice how the restart
37099 does not get any direct output:
37104 @emph{target restarts}
37107 <- @code{T001:1234123412341234}
37111 Example sequence of a target being stepped by a single instruction:
37114 -> @code{G1445@dots{}}
37119 <- @code{T001:1234123412341234}
37123 <- @code{1455@dots{}}
37127 @node File-I/O Remote Protocol Extension
37128 @section File-I/O Remote Protocol Extension
37129 @cindex File-I/O remote protocol extension
37132 * File-I/O Overview::
37133 * Protocol Basics::
37134 * The F Request Packet::
37135 * The F Reply Packet::
37136 * The Ctrl-C Message::
37138 * List of Supported Calls::
37139 * Protocol-specific Representation of Datatypes::
37141 * File-I/O Examples::
37144 @node File-I/O Overview
37145 @subsection File-I/O Overview
37146 @cindex file-i/o overview
37148 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37149 target to use the host's file system and console I/O to perform various
37150 system calls. System calls on the target system are translated into a
37151 remote protocol packet to the host system, which then performs the needed
37152 actions and returns a response packet to the target system.
37153 This simulates file system operations even on targets that lack file systems.
37155 The protocol is defined to be independent of both the host and target systems.
37156 It uses its own internal representation of datatypes and values. Both
37157 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37158 translating the system-dependent value representations into the internal
37159 protocol representations when data is transmitted.
37161 The communication is synchronous. A system call is possible only when
37162 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37163 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37164 the target is stopped to allow deterministic access to the target's
37165 memory. Therefore File-I/O is not interruptible by target signals. On
37166 the other hand, it is possible to interrupt File-I/O by a user interrupt
37167 (@samp{Ctrl-C}) within @value{GDBN}.
37169 The target's request to perform a host system call does not finish
37170 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37171 after finishing the system call, the target returns to continuing the
37172 previous activity (continue, step). No additional continue or step
37173 request from @value{GDBN} is required.
37176 (@value{GDBP}) continue
37177 <- target requests 'system call X'
37178 target is stopped, @value{GDBN} executes system call
37179 -> @value{GDBN} returns result
37180 ... target continues, @value{GDBN} returns to wait for the target
37181 <- target hits breakpoint and sends a Txx packet
37184 The protocol only supports I/O on the console and to regular files on
37185 the host file system. Character or block special devices, pipes,
37186 named pipes, sockets or any other communication method on the host
37187 system are not supported by this protocol.
37189 File I/O is not supported in non-stop mode.
37191 @node Protocol Basics
37192 @subsection Protocol Basics
37193 @cindex protocol basics, file-i/o
37195 The File-I/O protocol uses the @code{F} packet as the request as well
37196 as reply packet. Since a File-I/O system call can only occur when
37197 @value{GDBN} is waiting for a response from the continuing or stepping target,
37198 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37199 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37200 This @code{F} packet contains all information needed to allow @value{GDBN}
37201 to call the appropriate host system call:
37205 A unique identifier for the requested system call.
37208 All parameters to the system call. Pointers are given as addresses
37209 in the target memory address space. Pointers to strings are given as
37210 pointer/length pair. Numerical values are given as they are.
37211 Numerical control flags are given in a protocol-specific representation.
37215 At this point, @value{GDBN} has to perform the following actions.
37219 If the parameters include pointer values to data needed as input to a
37220 system call, @value{GDBN} requests this data from the target with a
37221 standard @code{m} packet request. This additional communication has to be
37222 expected by the target implementation and is handled as any other @code{m}
37226 @value{GDBN} translates all value from protocol representation to host
37227 representation as needed. Datatypes are coerced into the host types.
37230 @value{GDBN} calls the system call.
37233 It then coerces datatypes back to protocol representation.
37236 If the system call is expected to return data in buffer space specified
37237 by pointer parameters to the call, the data is transmitted to the
37238 target using a @code{M} or @code{X} packet. This packet has to be expected
37239 by the target implementation and is handled as any other @code{M} or @code{X}
37244 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37245 necessary information for the target to continue. This at least contains
37252 @code{errno}, if has been changed by the system call.
37259 After having done the needed type and value coercion, the target continues
37260 the latest continue or step action.
37262 @node The F Request Packet
37263 @subsection The @code{F} Request Packet
37264 @cindex file-i/o request packet
37265 @cindex @code{F} request packet
37267 The @code{F} request packet has the following format:
37270 @item F@var{call-id},@var{parameter@dots{}}
37272 @var{call-id} is the identifier to indicate the host system call to be called.
37273 This is just the name of the function.
37275 @var{parameter@dots{}} are the parameters to the system call.
37276 Parameters are hexadecimal integer values, either the actual values in case
37277 of scalar datatypes, pointers to target buffer space in case of compound
37278 datatypes and unspecified memory areas, or pointer/length pairs in case
37279 of string parameters. These are appended to the @var{call-id} as a
37280 comma-delimited list. All values are transmitted in ASCII
37281 string representation, pointer/length pairs separated by a slash.
37287 @node The F Reply Packet
37288 @subsection The @code{F} Reply Packet
37289 @cindex file-i/o reply packet
37290 @cindex @code{F} reply packet
37292 The @code{F} reply packet has the following format:
37296 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37298 @var{retcode} is the return code of the system call as hexadecimal value.
37300 @var{errno} is the @code{errno} set by the call, in protocol-specific
37302 This parameter can be omitted if the call was successful.
37304 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37305 case, @var{errno} must be sent as well, even if the call was successful.
37306 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37313 or, if the call was interrupted before the host call has been performed:
37320 assuming 4 is the protocol-specific representation of @code{EINTR}.
37325 @node The Ctrl-C Message
37326 @subsection The @samp{Ctrl-C} Message
37327 @cindex ctrl-c message, in file-i/o protocol
37329 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37330 reply packet (@pxref{The F Reply Packet}),
37331 the target should behave as if it had
37332 gotten a break message. The meaning for the target is ``system call
37333 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37334 (as with a break message) and return to @value{GDBN} with a @code{T02}
37337 It's important for the target to know in which
37338 state the system call was interrupted. There are two possible cases:
37342 The system call hasn't been performed on the host yet.
37345 The system call on the host has been finished.
37349 These two states can be distinguished by the target by the value of the
37350 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37351 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37352 on POSIX systems. In any other case, the target may presume that the
37353 system call has been finished --- successfully or not --- and should behave
37354 as if the break message arrived right after the system call.
37356 @value{GDBN} must behave reliably. If the system call has not been called
37357 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37358 @code{errno} in the packet. If the system call on the host has been finished
37359 before the user requests a break, the full action must be finished by
37360 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37361 The @code{F} packet may only be sent when either nothing has happened
37362 or the full action has been completed.
37365 @subsection Console I/O
37366 @cindex console i/o as part of file-i/o
37368 By default and if not explicitly closed by the target system, the file
37369 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37370 on the @value{GDBN} console is handled as any other file output operation
37371 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37372 by @value{GDBN} so that after the target read request from file descriptor
37373 0 all following typing is buffered until either one of the following
37378 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37380 system call is treated as finished.
37383 The user presses @key{RET}. This is treated as end of input with a trailing
37387 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37388 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37392 If the user has typed more characters than fit in the buffer given to
37393 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37394 either another @code{read(0, @dots{})} is requested by the target, or debugging
37395 is stopped at the user's request.
37398 @node List of Supported Calls
37399 @subsection List of Supported Calls
37400 @cindex list of supported file-i/o calls
37417 @unnumberedsubsubsec open
37418 @cindex open, file-i/o system call
37423 int open(const char *pathname, int flags);
37424 int open(const char *pathname, int flags, mode_t mode);
37428 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37431 @var{flags} is the bitwise @code{OR} of the following values:
37435 If the file does not exist it will be created. The host
37436 rules apply as far as file ownership and time stamps
37440 When used with @code{O_CREAT}, if the file already exists it is
37441 an error and open() fails.
37444 If the file already exists and the open mode allows
37445 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37446 truncated to zero length.
37449 The file is opened in append mode.
37452 The file is opened for reading only.
37455 The file is opened for writing only.
37458 The file is opened for reading and writing.
37462 Other bits are silently ignored.
37466 @var{mode} is the bitwise @code{OR} of the following values:
37470 User has read permission.
37473 User has write permission.
37476 Group has read permission.
37479 Group has write permission.
37482 Others have read permission.
37485 Others have write permission.
37489 Other bits are silently ignored.
37492 @item Return value:
37493 @code{open} returns the new file descriptor or -1 if an error
37500 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37503 @var{pathname} refers to a directory.
37506 The requested access is not allowed.
37509 @var{pathname} was too long.
37512 A directory component in @var{pathname} does not exist.
37515 @var{pathname} refers to a device, pipe, named pipe or socket.
37518 @var{pathname} refers to a file on a read-only filesystem and
37519 write access was requested.
37522 @var{pathname} is an invalid pointer value.
37525 No space on device to create the file.
37528 The process already has the maximum number of files open.
37531 The limit on the total number of files open on the system
37535 The call was interrupted by the user.
37541 @unnumberedsubsubsec close
37542 @cindex close, file-i/o system call
37551 @samp{Fclose,@var{fd}}
37553 @item Return value:
37554 @code{close} returns zero on success, or -1 if an error occurred.
37560 @var{fd} isn't a valid open file descriptor.
37563 The call was interrupted by the user.
37569 @unnumberedsubsubsec read
37570 @cindex read, file-i/o system call
37575 int read(int fd, void *buf, unsigned int count);
37579 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37581 @item Return value:
37582 On success, the number of bytes read is returned.
37583 Zero indicates end of file. If count is zero, read
37584 returns zero as well. On error, -1 is returned.
37590 @var{fd} is not a valid file descriptor or is not open for
37594 @var{bufptr} is an invalid pointer value.
37597 The call was interrupted by the user.
37603 @unnumberedsubsubsec write
37604 @cindex write, file-i/o system call
37609 int write(int fd, const void *buf, unsigned int count);
37613 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37615 @item Return value:
37616 On success, the number of bytes written are returned.
37617 Zero indicates nothing was written. On error, -1
37624 @var{fd} is not a valid file descriptor or is not open for
37628 @var{bufptr} is an invalid pointer value.
37631 An attempt was made to write a file that exceeds the
37632 host-specific maximum file size allowed.
37635 No space on device to write the data.
37638 The call was interrupted by the user.
37644 @unnumberedsubsubsec lseek
37645 @cindex lseek, file-i/o system call
37650 long lseek (int fd, long offset, int flag);
37654 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37656 @var{flag} is one of:
37660 The offset is set to @var{offset} bytes.
37663 The offset is set to its current location plus @var{offset}
37667 The offset is set to the size of the file plus @var{offset}
37671 @item Return value:
37672 On success, the resulting unsigned offset in bytes from
37673 the beginning of the file is returned. Otherwise, a
37674 value of -1 is returned.
37680 @var{fd} is not a valid open file descriptor.
37683 @var{fd} is associated with the @value{GDBN} console.
37686 @var{flag} is not a proper value.
37689 The call was interrupted by the user.
37695 @unnumberedsubsubsec rename
37696 @cindex rename, file-i/o system call
37701 int rename(const char *oldpath, const char *newpath);
37705 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37707 @item Return value:
37708 On success, zero is returned. On error, -1 is returned.
37714 @var{newpath} is an existing directory, but @var{oldpath} is not a
37718 @var{newpath} is a non-empty directory.
37721 @var{oldpath} or @var{newpath} is a directory that is in use by some
37725 An attempt was made to make a directory a subdirectory
37729 A component used as a directory in @var{oldpath} or new
37730 path is not a directory. Or @var{oldpath} is a directory
37731 and @var{newpath} exists but is not a directory.
37734 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37737 No access to the file or the path of the file.
37741 @var{oldpath} or @var{newpath} was too long.
37744 A directory component in @var{oldpath} or @var{newpath} does not exist.
37747 The file is on a read-only filesystem.
37750 The device containing the file has no room for the new
37754 The call was interrupted by the user.
37760 @unnumberedsubsubsec unlink
37761 @cindex unlink, file-i/o system call
37766 int unlink(const char *pathname);
37770 @samp{Funlink,@var{pathnameptr}/@var{len}}
37772 @item Return value:
37773 On success, zero is returned. On error, -1 is returned.
37779 No access to the file or the path of the file.
37782 The system does not allow unlinking of directories.
37785 The file @var{pathname} cannot be unlinked because it's
37786 being used by another process.
37789 @var{pathnameptr} is an invalid pointer value.
37792 @var{pathname} was too long.
37795 A directory component in @var{pathname} does not exist.
37798 A component of the path is not a directory.
37801 The file is on a read-only filesystem.
37804 The call was interrupted by the user.
37810 @unnumberedsubsubsec stat/fstat
37811 @cindex fstat, file-i/o system call
37812 @cindex stat, file-i/o system call
37817 int stat(const char *pathname, struct stat *buf);
37818 int fstat(int fd, struct stat *buf);
37822 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37823 @samp{Ffstat,@var{fd},@var{bufptr}}
37825 @item Return value:
37826 On success, zero is returned. On error, -1 is returned.
37832 @var{fd} is not a valid open file.
37835 A directory component in @var{pathname} does not exist or the
37836 path is an empty string.
37839 A component of the path is not a directory.
37842 @var{pathnameptr} is an invalid pointer value.
37845 No access to the file or the path of the file.
37848 @var{pathname} was too long.
37851 The call was interrupted by the user.
37857 @unnumberedsubsubsec gettimeofday
37858 @cindex gettimeofday, file-i/o system call
37863 int gettimeofday(struct timeval *tv, void *tz);
37867 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37869 @item Return value:
37870 On success, 0 is returned, -1 otherwise.
37876 @var{tz} is a non-NULL pointer.
37879 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37885 @unnumberedsubsubsec isatty
37886 @cindex isatty, file-i/o system call
37891 int isatty(int fd);
37895 @samp{Fisatty,@var{fd}}
37897 @item Return value:
37898 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37904 The call was interrupted by the user.
37909 Note that the @code{isatty} call is treated as a special case: it returns
37910 1 to the target if the file descriptor is attached
37911 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37912 would require implementing @code{ioctl} and would be more complex than
37917 @unnumberedsubsubsec system
37918 @cindex system, file-i/o system call
37923 int system(const char *command);
37927 @samp{Fsystem,@var{commandptr}/@var{len}}
37929 @item Return value:
37930 If @var{len} is zero, the return value indicates whether a shell is
37931 available. A zero return value indicates a shell is not available.
37932 For non-zero @var{len}, the value returned is -1 on error and the
37933 return status of the command otherwise. Only the exit status of the
37934 command is returned, which is extracted from the host's @code{system}
37935 return value by calling @code{WEXITSTATUS(retval)}. In case
37936 @file{/bin/sh} could not be executed, 127 is returned.
37942 The call was interrupted by the user.
37947 @value{GDBN} takes over the full task of calling the necessary host calls
37948 to perform the @code{system} call. The return value of @code{system} on
37949 the host is simplified before it's returned
37950 to the target. Any termination signal information from the child process
37951 is discarded, and the return value consists
37952 entirely of the exit status of the called command.
37954 Due to security concerns, the @code{system} call is by default refused
37955 by @value{GDBN}. The user has to allow this call explicitly with the
37956 @code{set remote system-call-allowed 1} command.
37959 @item set remote system-call-allowed
37960 @kindex set remote system-call-allowed
37961 Control whether to allow the @code{system} calls in the File I/O
37962 protocol for the remote target. The default is zero (disabled).
37964 @item show remote system-call-allowed
37965 @kindex show remote system-call-allowed
37966 Show whether the @code{system} calls are allowed in the File I/O
37970 @node Protocol-specific Representation of Datatypes
37971 @subsection Protocol-specific Representation of Datatypes
37972 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37975 * Integral Datatypes::
37977 * Memory Transfer::
37982 @node Integral Datatypes
37983 @unnumberedsubsubsec Integral Datatypes
37984 @cindex integral datatypes, in file-i/o protocol
37986 The integral datatypes used in the system calls are @code{int},
37987 @code{unsigned int}, @code{long}, @code{unsigned long},
37988 @code{mode_t}, and @code{time_t}.
37990 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37991 implemented as 32 bit values in this protocol.
37993 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37995 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37996 in @file{limits.h}) to allow range checking on host and target.
37998 @code{time_t} datatypes are defined as seconds since the Epoch.
38000 All integral datatypes transferred as part of a memory read or write of a
38001 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38004 @node Pointer Values
38005 @unnumberedsubsubsec Pointer Values
38006 @cindex pointer values, in file-i/o protocol
38008 Pointers to target data are transmitted as they are. An exception
38009 is made for pointers to buffers for which the length isn't
38010 transmitted as part of the function call, namely strings. Strings
38011 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38018 which is a pointer to data of length 18 bytes at position 0x1aaf.
38019 The length is defined as the full string length in bytes, including
38020 the trailing null byte. For example, the string @code{"hello world"}
38021 at address 0x123456 is transmitted as
38027 @node Memory Transfer
38028 @unnumberedsubsubsec Memory Transfer
38029 @cindex memory transfer, in file-i/o protocol
38031 Structured data which is transferred using a memory read or write (for
38032 example, a @code{struct stat}) is expected to be in a protocol-specific format
38033 with all scalar multibyte datatypes being big endian. Translation to
38034 this representation needs to be done both by the target before the @code{F}
38035 packet is sent, and by @value{GDBN} before
38036 it transfers memory to the target. Transferred pointers to structured
38037 data should point to the already-coerced data at any time.
38041 @unnumberedsubsubsec struct stat
38042 @cindex struct stat, in file-i/o protocol
38044 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38045 is defined as follows:
38049 unsigned int st_dev; /* device */
38050 unsigned int st_ino; /* inode */
38051 mode_t st_mode; /* protection */
38052 unsigned int st_nlink; /* number of hard links */
38053 unsigned int st_uid; /* user ID of owner */
38054 unsigned int st_gid; /* group ID of owner */
38055 unsigned int st_rdev; /* device type (if inode device) */
38056 unsigned long st_size; /* total size, in bytes */
38057 unsigned long st_blksize; /* blocksize for filesystem I/O */
38058 unsigned long st_blocks; /* number of blocks allocated */
38059 time_t st_atime; /* time of last access */
38060 time_t st_mtime; /* time of last modification */
38061 time_t st_ctime; /* time of last change */
38065 The integral datatypes conform to the definitions given in the
38066 appropriate section (see @ref{Integral Datatypes}, for details) so this
38067 structure is of size 64 bytes.
38069 The values of several fields have a restricted meaning and/or
38075 A value of 0 represents a file, 1 the console.
38078 No valid meaning for the target. Transmitted unchanged.
38081 Valid mode bits are described in @ref{Constants}. Any other
38082 bits have currently no meaning for the target.
38087 No valid meaning for the target. Transmitted unchanged.
38092 These values have a host and file system dependent
38093 accuracy. Especially on Windows hosts, the file system may not
38094 support exact timing values.
38097 The target gets a @code{struct stat} of the above representation and is
38098 responsible for coercing it to the target representation before
38101 Note that due to size differences between the host, target, and protocol
38102 representations of @code{struct stat} members, these members could eventually
38103 get truncated on the target.
38105 @node struct timeval
38106 @unnumberedsubsubsec struct timeval
38107 @cindex struct timeval, in file-i/o protocol
38109 The buffer of type @code{struct timeval} used by the File-I/O protocol
38110 is defined as follows:
38114 time_t tv_sec; /* second */
38115 long tv_usec; /* microsecond */
38119 The integral datatypes conform to the definitions given in the
38120 appropriate section (see @ref{Integral Datatypes}, for details) so this
38121 structure is of size 8 bytes.
38124 @subsection Constants
38125 @cindex constants, in file-i/o protocol
38127 The following values are used for the constants inside of the
38128 protocol. @value{GDBN} and target are responsible for translating these
38129 values before and after the call as needed.
38140 @unnumberedsubsubsec Open Flags
38141 @cindex open flags, in file-i/o protocol
38143 All values are given in hexadecimal representation.
38155 @node mode_t Values
38156 @unnumberedsubsubsec mode_t Values
38157 @cindex mode_t values, in file-i/o protocol
38159 All values are given in octal representation.
38176 @unnumberedsubsubsec Errno Values
38177 @cindex errno values, in file-i/o protocol
38179 All values are given in decimal representation.
38204 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38205 any error value not in the list of supported error numbers.
38208 @unnumberedsubsubsec Lseek Flags
38209 @cindex lseek flags, in file-i/o protocol
38218 @unnumberedsubsubsec Limits
38219 @cindex limits, in file-i/o protocol
38221 All values are given in decimal representation.
38224 INT_MIN -2147483648
38226 UINT_MAX 4294967295
38227 LONG_MIN -9223372036854775808
38228 LONG_MAX 9223372036854775807
38229 ULONG_MAX 18446744073709551615
38232 @node File-I/O Examples
38233 @subsection File-I/O Examples
38234 @cindex file-i/o examples
38236 Example sequence of a write call, file descriptor 3, buffer is at target
38237 address 0x1234, 6 bytes should be written:
38240 <- @code{Fwrite,3,1234,6}
38241 @emph{request memory read from target}
38244 @emph{return "6 bytes written"}
38248 Example sequence of a read call, file descriptor 3, buffer is at target
38249 address 0x1234, 6 bytes should be read:
38252 <- @code{Fread,3,1234,6}
38253 @emph{request memory write to target}
38254 -> @code{X1234,6:XXXXXX}
38255 @emph{return "6 bytes read"}
38259 Example sequence of a read call, call fails on the host due to invalid
38260 file descriptor (@code{EBADF}):
38263 <- @code{Fread,3,1234,6}
38267 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38271 <- @code{Fread,3,1234,6}
38276 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38280 <- @code{Fread,3,1234,6}
38281 -> @code{X1234,6:XXXXXX}
38285 @node Library List Format
38286 @section Library List Format
38287 @cindex library list format, remote protocol
38289 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38290 same process as your application to manage libraries. In this case,
38291 @value{GDBN} can use the loader's symbol table and normal memory
38292 operations to maintain a list of shared libraries. On other
38293 platforms, the operating system manages loaded libraries.
38294 @value{GDBN} can not retrieve the list of currently loaded libraries
38295 through memory operations, so it uses the @samp{qXfer:libraries:read}
38296 packet (@pxref{qXfer library list read}) instead. The remote stub
38297 queries the target's operating system and reports which libraries
38300 The @samp{qXfer:libraries:read} packet returns an XML document which
38301 lists loaded libraries and their offsets. Each library has an
38302 associated name and one or more segment or section base addresses,
38303 which report where the library was loaded in memory.
38305 For the common case of libraries that are fully linked binaries, the
38306 library should have a list of segments. If the target supports
38307 dynamic linking of a relocatable object file, its library XML element
38308 should instead include a list of allocated sections. The segment or
38309 section bases are start addresses, not relocation offsets; they do not
38310 depend on the library's link-time base addresses.
38312 @value{GDBN} must be linked with the Expat library to support XML
38313 library lists. @xref{Expat}.
38315 A simple memory map, with one loaded library relocated by a single
38316 offset, looks like this:
38320 <library name="/lib/libc.so.6">
38321 <segment address="0x10000000"/>
38326 Another simple memory map, with one loaded library with three
38327 allocated sections (.text, .data, .bss), looks like this:
38331 <library name="sharedlib.o">
38332 <section address="0x10000000"/>
38333 <section address="0x20000000"/>
38334 <section address="0x30000000"/>
38339 The format of a library list is described by this DTD:
38342 <!-- library-list: Root element with versioning -->
38343 <!ELEMENT library-list (library)*>
38344 <!ATTLIST library-list version CDATA #FIXED "1.0">
38345 <!ELEMENT library (segment*, section*)>
38346 <!ATTLIST library name CDATA #REQUIRED>
38347 <!ELEMENT segment EMPTY>
38348 <!ATTLIST segment address CDATA #REQUIRED>
38349 <!ELEMENT section EMPTY>
38350 <!ATTLIST section address CDATA #REQUIRED>
38353 In addition, segments and section descriptors cannot be mixed within a
38354 single library element, and you must supply at least one segment or
38355 section for each library.
38357 @node Library List Format for SVR4 Targets
38358 @section Library List Format for SVR4 Targets
38359 @cindex library list format, remote protocol
38361 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38362 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38363 shared libraries. Still a special library list provided by this packet is
38364 more efficient for the @value{GDBN} remote protocol.
38366 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38367 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38368 target, the following parameters are reported:
38372 @code{name}, the absolute file name from the @code{l_name} field of
38373 @code{struct link_map}.
38375 @code{lm} with address of @code{struct link_map} used for TLS
38376 (Thread Local Storage) access.
38378 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38379 @code{struct link_map}. For prelinked libraries this is not an absolute
38380 memory address. It is a displacement of absolute memory address against
38381 address the file was prelinked to during the library load.
38383 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38386 Additionally the single @code{main-lm} attribute specifies address of
38387 @code{struct link_map} used for the main executable. This parameter is used
38388 for TLS access and its presence is optional.
38390 @value{GDBN} must be linked with the Expat library to support XML
38391 SVR4 library lists. @xref{Expat}.
38393 A simple memory map, with two loaded libraries (which do not use prelink),
38397 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38398 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38400 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38402 </library-list-svr>
38405 The format of an SVR4 library list is described by this DTD:
38408 <!-- library-list-svr4: Root element with versioning -->
38409 <!ELEMENT library-list-svr4 (library)*>
38410 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38411 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38412 <!ELEMENT library EMPTY>
38413 <!ATTLIST library name CDATA #REQUIRED>
38414 <!ATTLIST library lm CDATA #REQUIRED>
38415 <!ATTLIST library l_addr CDATA #REQUIRED>
38416 <!ATTLIST library l_ld CDATA #REQUIRED>
38419 @node Memory Map Format
38420 @section Memory Map Format
38421 @cindex memory map format
38423 To be able to write into flash memory, @value{GDBN} needs to obtain a
38424 memory map from the target. This section describes the format of the
38427 The memory map is obtained using the @samp{qXfer:memory-map:read}
38428 (@pxref{qXfer memory map read}) packet and is an XML document that
38429 lists memory regions.
38431 @value{GDBN} must be linked with the Expat library to support XML
38432 memory maps. @xref{Expat}.
38434 The top-level structure of the document is shown below:
38437 <?xml version="1.0"?>
38438 <!DOCTYPE memory-map
38439 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38440 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38446 Each region can be either:
38451 A region of RAM starting at @var{addr} and extending for @var{length}
38455 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38460 A region of read-only memory:
38463 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38468 A region of flash memory, with erasure blocks @var{blocksize}
38472 <memory type="flash" start="@var{addr}" length="@var{length}">
38473 <property name="blocksize">@var{blocksize}</property>
38479 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38480 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38481 packets to write to addresses in such ranges.
38483 The formal DTD for memory map format is given below:
38486 <!-- ................................................... -->
38487 <!-- Memory Map XML DTD ................................ -->
38488 <!-- File: memory-map.dtd .............................. -->
38489 <!-- .................................... .............. -->
38490 <!-- memory-map.dtd -->
38491 <!-- memory-map: Root element with versioning -->
38492 <!ELEMENT memory-map (memory | property)>
38493 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38494 <!ELEMENT memory (property)>
38495 <!-- memory: Specifies a memory region,
38496 and its type, or device. -->
38497 <!ATTLIST memory type CDATA #REQUIRED
38498 start CDATA #REQUIRED
38499 length CDATA #REQUIRED
38500 device CDATA #IMPLIED>
38501 <!-- property: Generic attribute tag -->
38502 <!ELEMENT property (#PCDATA | property)*>
38503 <!ATTLIST property name CDATA #REQUIRED>
38506 @node Thread List Format
38507 @section Thread List Format
38508 @cindex thread list format
38510 To efficiently update the list of threads and their attributes,
38511 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38512 (@pxref{qXfer threads read}) and obtains the XML document with
38513 the following structure:
38516 <?xml version="1.0"?>
38518 <thread id="id" core="0">
38519 ... description ...
38524 Each @samp{thread} element must have the @samp{id} attribute that
38525 identifies the thread (@pxref{thread-id syntax}). The
38526 @samp{core} attribute, if present, specifies which processor core
38527 the thread was last executing on. The content of the of @samp{thread}
38528 element is interpreted as human-readable auxilliary information.
38530 @node Traceframe Info Format
38531 @section Traceframe Info Format
38532 @cindex traceframe info format
38534 To be able to know which objects in the inferior can be examined when
38535 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38536 memory ranges, registers and trace state variables that have been
38537 collected in a traceframe.
38539 This list is obtained using the @samp{qXfer:traceframe-info:read}
38540 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38542 @value{GDBN} must be linked with the Expat library to support XML
38543 traceframe info discovery. @xref{Expat}.
38545 The top-level structure of the document is shown below:
38548 <?xml version="1.0"?>
38549 <!DOCTYPE traceframe-info
38550 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38551 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38557 Each traceframe block can be either:
38562 A region of collected memory starting at @var{addr} and extending for
38563 @var{length} bytes from there:
38566 <memory start="@var{addr}" length="@var{length}"/>
38570 A block indicating trace state variable numbered @var{number} has been
38574 <tvar id="@var{number}"/>
38579 The formal DTD for the traceframe info format is given below:
38582 <!ELEMENT traceframe-info (memory | tvar)* >
38583 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38585 <!ELEMENT memory EMPTY>
38586 <!ATTLIST memory start CDATA #REQUIRED
38587 length CDATA #REQUIRED>
38589 <!ATTLIST tvar id CDATA #REQUIRED>
38592 @node Branch Trace Format
38593 @section Branch Trace Format
38594 @cindex branch trace format
38596 In order to display the branch trace of an inferior thread,
38597 @value{GDBN} needs to obtain the list of branches. This list is
38598 represented as list of sequential code blocks that are connected via
38599 branches. The code in each block has been executed sequentially.
38601 This list is obtained using the @samp{qXfer:btrace:read}
38602 (@pxref{qXfer btrace read}) packet and is an XML document.
38604 @value{GDBN} must be linked with the Expat library to support XML
38605 traceframe info discovery. @xref{Expat}.
38607 The top-level structure of the document is shown below:
38610 <?xml version="1.0"?>
38612 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38613 "http://sourceware.org/gdb/gdb-btrace.dtd">
38622 A block of sequentially executed instructions starting at @var{begin}
38623 and ending at @var{end}:
38626 <block begin="@var{begin}" end="@var{end}"/>
38631 The formal DTD for the branch trace format is given below:
38634 <!ELEMENT btrace (block)* >
38635 <!ATTLIST btrace version CDATA #FIXED "1.0">
38637 <!ELEMENT block EMPTY>
38638 <!ATTLIST block begin CDATA #REQUIRED
38639 end CDATA #REQUIRED>
38642 @include agentexpr.texi
38644 @node Target Descriptions
38645 @appendix Target Descriptions
38646 @cindex target descriptions
38648 One of the challenges of using @value{GDBN} to debug embedded systems
38649 is that there are so many minor variants of each processor
38650 architecture in use. It is common practice for vendors to start with
38651 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38652 and then make changes to adapt it to a particular market niche. Some
38653 architectures have hundreds of variants, available from dozens of
38654 vendors. This leads to a number of problems:
38658 With so many different customized processors, it is difficult for
38659 the @value{GDBN} maintainers to keep up with the changes.
38661 Since individual variants may have short lifetimes or limited
38662 audiences, it may not be worthwhile to carry information about every
38663 variant in the @value{GDBN} source tree.
38665 When @value{GDBN} does support the architecture of the embedded system
38666 at hand, the task of finding the correct architecture name to give the
38667 @command{set architecture} command can be error-prone.
38670 To address these problems, the @value{GDBN} remote protocol allows a
38671 target system to not only identify itself to @value{GDBN}, but to
38672 actually describe its own features. This lets @value{GDBN} support
38673 processor variants it has never seen before --- to the extent that the
38674 descriptions are accurate, and that @value{GDBN} understands them.
38676 @value{GDBN} must be linked with the Expat library to support XML
38677 target descriptions. @xref{Expat}.
38680 * Retrieving Descriptions:: How descriptions are fetched from a target.
38681 * Target Description Format:: The contents of a target description.
38682 * Predefined Target Types:: Standard types available for target
38684 * Standard Target Features:: Features @value{GDBN} knows about.
38687 @node Retrieving Descriptions
38688 @section Retrieving Descriptions
38690 Target descriptions can be read from the target automatically, or
38691 specified by the user manually. The default behavior is to read the
38692 description from the target. @value{GDBN} retrieves it via the remote
38693 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38694 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38695 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38696 XML document, of the form described in @ref{Target Description
38699 Alternatively, you can specify a file to read for the target description.
38700 If a file is set, the target will not be queried. The commands to
38701 specify a file are:
38704 @cindex set tdesc filename
38705 @item set tdesc filename @var{path}
38706 Read the target description from @var{path}.
38708 @cindex unset tdesc filename
38709 @item unset tdesc filename
38710 Do not read the XML target description from a file. @value{GDBN}
38711 will use the description supplied by the current target.
38713 @cindex show tdesc filename
38714 @item show tdesc filename
38715 Show the filename to read for a target description, if any.
38719 @node Target Description Format
38720 @section Target Description Format
38721 @cindex target descriptions, XML format
38723 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38724 document which complies with the Document Type Definition provided in
38725 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38726 means you can use generally available tools like @command{xmllint} to
38727 check that your feature descriptions are well-formed and valid.
38728 However, to help people unfamiliar with XML write descriptions for
38729 their targets, we also describe the grammar here.
38731 Target descriptions can identify the architecture of the remote target
38732 and (for some architectures) provide information about custom register
38733 sets. They can also identify the OS ABI of the remote target.
38734 @value{GDBN} can use this information to autoconfigure for your
38735 target, or to warn you if you connect to an unsupported target.
38737 Here is a simple target description:
38740 <target version="1.0">
38741 <architecture>i386:x86-64</architecture>
38746 This minimal description only says that the target uses
38747 the x86-64 architecture.
38749 A target description has the following overall form, with [ ] marking
38750 optional elements and @dots{} marking repeatable elements. The elements
38751 are explained further below.
38754 <?xml version="1.0"?>
38755 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38756 <target version="1.0">
38757 @r{[}@var{architecture}@r{]}
38758 @r{[}@var{osabi}@r{]}
38759 @r{[}@var{compatible}@r{]}
38760 @r{[}@var{feature}@dots{}@r{]}
38765 The description is generally insensitive to whitespace and line
38766 breaks, under the usual common-sense rules. The XML version
38767 declaration and document type declaration can generally be omitted
38768 (@value{GDBN} does not require them), but specifying them may be
38769 useful for XML validation tools. The @samp{version} attribute for
38770 @samp{<target>} may also be omitted, but we recommend
38771 including it; if future versions of @value{GDBN} use an incompatible
38772 revision of @file{gdb-target.dtd}, they will detect and report
38773 the version mismatch.
38775 @subsection Inclusion
38776 @cindex target descriptions, inclusion
38779 @cindex <xi:include>
38782 It can sometimes be valuable to split a target description up into
38783 several different annexes, either for organizational purposes, or to
38784 share files between different possible target descriptions. You can
38785 divide a description into multiple files by replacing any element of
38786 the target description with an inclusion directive of the form:
38789 <xi:include href="@var{document}"/>
38793 When @value{GDBN} encounters an element of this form, it will retrieve
38794 the named XML @var{document}, and replace the inclusion directive with
38795 the contents of that document. If the current description was read
38796 using @samp{qXfer}, then so will be the included document;
38797 @var{document} will be interpreted as the name of an annex. If the
38798 current description was read from a file, @value{GDBN} will look for
38799 @var{document} as a file in the same directory where it found the
38800 original description.
38802 @subsection Architecture
38803 @cindex <architecture>
38805 An @samp{<architecture>} element has this form:
38808 <architecture>@var{arch}</architecture>
38811 @var{arch} is one of the architectures from the set accepted by
38812 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38815 @cindex @code{<osabi>}
38817 This optional field was introduced in @value{GDBN} version 7.0.
38818 Previous versions of @value{GDBN} ignore it.
38820 An @samp{<osabi>} element has this form:
38823 <osabi>@var{abi-name}</osabi>
38826 @var{abi-name} is an OS ABI name from the same selection accepted by
38827 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38829 @subsection Compatible Architecture
38830 @cindex @code{<compatible>}
38832 This optional field was introduced in @value{GDBN} version 7.0.
38833 Previous versions of @value{GDBN} ignore it.
38835 A @samp{<compatible>} element has this form:
38838 <compatible>@var{arch}</compatible>
38841 @var{arch} is one of the architectures from the set accepted by
38842 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38844 A @samp{<compatible>} element is used to specify that the target
38845 is able to run binaries in some other than the main target architecture
38846 given by the @samp{<architecture>} element. For example, on the
38847 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38848 or @code{powerpc:common64}, but the system is able to run binaries
38849 in the @code{spu} architecture as well. The way to describe this
38850 capability with @samp{<compatible>} is as follows:
38853 <architecture>powerpc:common</architecture>
38854 <compatible>spu</compatible>
38857 @subsection Features
38860 Each @samp{<feature>} describes some logical portion of the target
38861 system. Features are currently used to describe available CPU
38862 registers and the types of their contents. A @samp{<feature>} element
38866 <feature name="@var{name}">
38867 @r{[}@var{type}@dots{}@r{]}
38873 Each feature's name should be unique within the description. The name
38874 of a feature does not matter unless @value{GDBN} has some special
38875 knowledge of the contents of that feature; if it does, the feature
38876 should have its standard name. @xref{Standard Target Features}.
38880 Any register's value is a collection of bits which @value{GDBN} must
38881 interpret. The default interpretation is a two's complement integer,
38882 but other types can be requested by name in the register description.
38883 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38884 Target Types}), and the description can define additional composite types.
38886 Each type element must have an @samp{id} attribute, which gives
38887 a unique (within the containing @samp{<feature>}) name to the type.
38888 Types must be defined before they are used.
38891 Some targets offer vector registers, which can be treated as arrays
38892 of scalar elements. These types are written as @samp{<vector>} elements,
38893 specifying the array element type, @var{type}, and the number of elements,
38897 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38901 If a register's value is usefully viewed in multiple ways, define it
38902 with a union type containing the useful representations. The
38903 @samp{<union>} element contains one or more @samp{<field>} elements,
38904 each of which has a @var{name} and a @var{type}:
38907 <union id="@var{id}">
38908 <field name="@var{name}" type="@var{type}"/>
38914 If a register's value is composed from several separate values, define
38915 it with a structure type. There are two forms of the @samp{<struct>}
38916 element; a @samp{<struct>} element must either contain only bitfields
38917 or contain no bitfields. If the structure contains only bitfields,
38918 its total size in bytes must be specified, each bitfield must have an
38919 explicit start and end, and bitfields are automatically assigned an
38920 integer type. The field's @var{start} should be less than or
38921 equal to its @var{end}, and zero represents the least significant bit.
38924 <struct id="@var{id}" size="@var{size}">
38925 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38930 If the structure contains no bitfields, then each field has an
38931 explicit type, and no implicit padding is added.
38934 <struct id="@var{id}">
38935 <field name="@var{name}" type="@var{type}"/>
38941 If a register's value is a series of single-bit flags, define it with
38942 a flags type. The @samp{<flags>} element has an explicit @var{size}
38943 and contains one or more @samp{<field>} elements. Each field has a
38944 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38948 <flags id="@var{id}" size="@var{size}">
38949 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38954 @subsection Registers
38957 Each register is represented as an element with this form:
38960 <reg name="@var{name}"
38961 bitsize="@var{size}"
38962 @r{[}regnum="@var{num}"@r{]}
38963 @r{[}save-restore="@var{save-restore}"@r{]}
38964 @r{[}type="@var{type}"@r{]}
38965 @r{[}group="@var{group}"@r{]}/>
38969 The components are as follows:
38974 The register's name; it must be unique within the target description.
38977 The register's size, in bits.
38980 The register's number. If omitted, a register's number is one greater
38981 than that of the previous register (either in the current feature or in
38982 a preceding feature); the first register in the target description
38983 defaults to zero. This register number is used to read or write
38984 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38985 packets, and registers appear in the @code{g} and @code{G} packets
38986 in order of increasing register number.
38989 Whether the register should be preserved across inferior function
38990 calls; this must be either @code{yes} or @code{no}. The default is
38991 @code{yes}, which is appropriate for most registers except for
38992 some system control registers; this is not related to the target's
38996 The type of the register. It may be a predefined type, a type
38997 defined in the current feature, or one of the special types @code{int}
38998 and @code{float}. @code{int} is an integer type of the correct size
38999 for @var{bitsize}, and @code{float} is a floating point type (in the
39000 architecture's normal floating point format) of the correct size for
39001 @var{bitsize}. The default is @code{int}.
39004 The register group to which this register belongs. It must
39005 be either @code{general}, @code{float}, or @code{vector}. If no
39006 @var{group} is specified, @value{GDBN} will not display the register
39007 in @code{info registers}.
39011 @node Predefined Target Types
39012 @section Predefined Target Types
39013 @cindex target descriptions, predefined types
39015 Type definitions in the self-description can build up composite types
39016 from basic building blocks, but can not define fundamental types. Instead,
39017 standard identifiers are provided by @value{GDBN} for the fundamental
39018 types. The currently supported types are:
39027 Signed integer types holding the specified number of bits.
39034 Unsigned integer types holding the specified number of bits.
39038 Pointers to unspecified code and data. The program counter and
39039 any dedicated return address register may be marked as code
39040 pointers; printing a code pointer converts it into a symbolic
39041 address. The stack pointer and any dedicated address registers
39042 may be marked as data pointers.
39045 Single precision IEEE floating point.
39048 Double precision IEEE floating point.
39051 The 12-byte extended precision format used by ARM FPA registers.
39054 The 10-byte extended precision format used by x87 registers.
39057 32bit @sc{eflags} register used by x86.
39060 32bit @sc{mxcsr} register used by x86.
39064 @node Standard Target Features
39065 @section Standard Target Features
39066 @cindex target descriptions, standard features
39068 A target description must contain either no registers or all the
39069 target's registers. If the description contains no registers, then
39070 @value{GDBN} will assume a default register layout, selected based on
39071 the architecture. If the description contains any registers, the
39072 default layout will not be used; the standard registers must be
39073 described in the target description, in such a way that @value{GDBN}
39074 can recognize them.
39076 This is accomplished by giving specific names to feature elements
39077 which contain standard registers. @value{GDBN} will look for features
39078 with those names and verify that they contain the expected registers;
39079 if any known feature is missing required registers, or if any required
39080 feature is missing, @value{GDBN} will reject the target
39081 description. You can add additional registers to any of the
39082 standard features --- @value{GDBN} will display them just as if
39083 they were added to an unrecognized feature.
39085 This section lists the known features and their expected contents.
39086 Sample XML documents for these features are included in the
39087 @value{GDBN} source tree, in the directory @file{gdb/features}.
39089 Names recognized by @value{GDBN} should include the name of the
39090 company or organization which selected the name, and the overall
39091 architecture to which the feature applies; so e.g.@: the feature
39092 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39094 The names of registers are not case sensitive for the purpose
39095 of recognizing standard features, but @value{GDBN} will only display
39096 registers using the capitalization used in the description.
39099 * AArch64 Features::
39102 * MicroBlaze Features::
39105 * Nios II Features::
39106 * PowerPC Features::
39107 * S/390 and System z Features::
39112 @node AArch64 Features
39113 @subsection AArch64 Features
39114 @cindex target descriptions, AArch64 features
39116 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39117 targets. It should contain registers @samp{x0} through @samp{x30},
39118 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39120 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39121 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39125 @subsection ARM Features
39126 @cindex target descriptions, ARM features
39128 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39130 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39131 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39133 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39134 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39135 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39138 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39139 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39141 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39142 it should contain at least registers @samp{wR0} through @samp{wR15} and
39143 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39144 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39146 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39147 should contain at least registers @samp{d0} through @samp{d15}. If
39148 they are present, @samp{d16} through @samp{d31} should also be included.
39149 @value{GDBN} will synthesize the single-precision registers from
39150 halves of the double-precision registers.
39152 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39153 need to contain registers; it instructs @value{GDBN} to display the
39154 VFP double-precision registers as vectors and to synthesize the
39155 quad-precision registers from pairs of double-precision registers.
39156 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39157 be present and include 32 double-precision registers.
39159 @node i386 Features
39160 @subsection i386 Features
39161 @cindex target descriptions, i386 features
39163 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39164 targets. It should describe the following registers:
39168 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39170 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39172 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39173 @samp{fs}, @samp{gs}
39175 @samp{st0} through @samp{st7}
39177 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39178 @samp{foseg}, @samp{fooff} and @samp{fop}
39181 The register sets may be different, depending on the target.
39183 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39184 describe registers:
39188 @samp{xmm0} through @samp{xmm7} for i386
39190 @samp{xmm0} through @samp{xmm15} for amd64
39195 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39196 @samp{org.gnu.gdb.i386.sse} feature. It should
39197 describe the upper 128 bits of @sc{ymm} registers:
39201 @samp{ymm0h} through @samp{ymm7h} for i386
39203 @samp{ymm0h} through @samp{ymm15h} for amd64
39206 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39207 Memory Protection Extension (MPX). It should describe the following registers:
39211 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39213 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39216 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39217 describe a single register, @samp{orig_eax}.
39219 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39220 @samp{org.gnu.gdb.i386.avx} feature. It should
39221 describe additional @sc{xmm} registers:
39225 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39228 It should describe the upper 128 bits of additional @sc{ymm} registers:
39232 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39236 describe the upper 256 bits of @sc{zmm} registers:
39240 @samp{zmm0h} through @samp{zmm7h} for i386.
39242 @samp{zmm0h} through @samp{zmm15h} for amd64.
39246 describe the additional @sc{zmm} registers:
39250 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39253 @node MicroBlaze Features
39254 @subsection MicroBlaze Features
39255 @cindex target descriptions, MicroBlaze features
39257 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39258 targets. It should contain registers @samp{r0} through @samp{r31},
39259 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39260 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39261 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39263 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39264 If present, it should contain registers @samp{rshr} and @samp{rslr}
39266 @node MIPS Features
39267 @subsection @acronym{MIPS} Features
39268 @cindex target descriptions, @acronym{MIPS} features
39270 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39271 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39272 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39275 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39276 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39277 registers. They may be 32-bit or 64-bit depending on the target.
39279 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39280 it may be optional in a future version of @value{GDBN}. It should
39281 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39282 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39284 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39285 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39286 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39287 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39289 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39290 contain a single register, @samp{restart}, which is used by the
39291 Linux kernel to control restartable syscalls.
39293 @node M68K Features
39294 @subsection M68K Features
39295 @cindex target descriptions, M68K features
39298 @item @samp{org.gnu.gdb.m68k.core}
39299 @itemx @samp{org.gnu.gdb.coldfire.core}
39300 @itemx @samp{org.gnu.gdb.fido.core}
39301 One of those features must be always present.
39302 The feature that is present determines which flavor of m68k is
39303 used. The feature that is present should contain registers
39304 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39305 @samp{sp}, @samp{ps} and @samp{pc}.
39307 @item @samp{org.gnu.gdb.coldfire.fp}
39308 This feature is optional. If present, it should contain registers
39309 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39313 @node Nios II Features
39314 @subsection Nios II Features
39315 @cindex target descriptions, Nios II features
39317 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39318 targets. It should contain the 32 core registers (@samp{zero},
39319 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39320 @samp{pc}, and the 16 control registers (@samp{status} through
39323 @node PowerPC Features
39324 @subsection PowerPC Features
39325 @cindex target descriptions, PowerPC features
39327 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39328 targets. It should contain registers @samp{r0} through @samp{r31},
39329 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39330 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39332 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39333 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39335 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39336 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39339 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39340 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39341 will combine these registers with the floating point registers
39342 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39343 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39344 through @samp{vs63}, the set of vector registers for POWER7.
39346 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39347 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39348 @samp{spefscr}. SPE targets should provide 32-bit registers in
39349 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39350 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39351 these to present registers @samp{ev0} through @samp{ev31} to the
39354 @node S/390 and System z Features
39355 @subsection S/390 and System z Features
39356 @cindex target descriptions, S/390 features
39357 @cindex target descriptions, System z features
39359 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39360 System z targets. It should contain the PSW and the 16 general
39361 registers. In particular, System z targets should provide the 64-bit
39362 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39363 S/390 targets should provide the 32-bit versions of these registers.
39364 A System z target that runs in 31-bit addressing mode should provide
39365 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39366 register's upper halves @samp{r0h} through @samp{r15h}, and their
39367 lower halves @samp{r0l} through @samp{r15l}.
39369 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39370 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39373 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39374 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39376 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39377 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39378 targets and 32-bit otherwise. In addition, the feature may contain
39379 the @samp{last_break} register, whose width depends on the addressing
39380 mode, as well as the @samp{system_call} register, which is always
39383 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39384 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39385 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39387 @node TIC6x Features
39388 @subsection TMS320C6x Features
39389 @cindex target descriptions, TIC6x features
39390 @cindex target descriptions, TMS320C6x features
39391 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39392 targets. It should contain registers @samp{A0} through @samp{A15},
39393 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39395 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39396 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39397 through @samp{B31}.
39399 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39400 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39402 @node Operating System Information
39403 @appendix Operating System Information
39404 @cindex operating system information
39410 Users of @value{GDBN} often wish to obtain information about the state of
39411 the operating system running on the target---for example the list of
39412 processes, or the list of open files. This section describes the
39413 mechanism that makes it possible. This mechanism is similar to the
39414 target features mechanism (@pxref{Target Descriptions}), but focuses
39415 on a different aspect of target.
39417 Operating system information is retrived from the target via the
39418 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39419 read}). The object name in the request should be @samp{osdata}, and
39420 the @var{annex} identifies the data to be fetched.
39423 @appendixsection Process list
39424 @cindex operating system information, process list
39426 When requesting the process list, the @var{annex} field in the
39427 @samp{qXfer} request should be @samp{processes}. The returned data is
39428 an XML document. The formal syntax of this document is defined in
39429 @file{gdb/features/osdata.dtd}.
39431 An example document is:
39434 <?xml version="1.0"?>
39435 <!DOCTYPE target SYSTEM "osdata.dtd">
39436 <osdata type="processes">
39438 <column name="pid">1</column>
39439 <column name="user">root</column>
39440 <column name="command">/sbin/init</column>
39441 <column name="cores">1,2,3</column>
39446 Each item should include a column whose name is @samp{pid}. The value
39447 of that column should identify the process on the target. The
39448 @samp{user} and @samp{command} columns are optional, and will be
39449 displayed by @value{GDBN}. The @samp{cores} column, if present,
39450 should contain a comma-separated list of cores that this process
39451 is running on. Target may provide additional columns,
39452 which @value{GDBN} currently ignores.
39454 @node Trace File Format
39455 @appendix Trace File Format
39456 @cindex trace file format
39458 The trace file comes in three parts: a header, a textual description
39459 section, and a trace frame section with binary data.
39461 The header has the form @code{\x7fTRACE0\n}. The first byte is
39462 @code{0x7f} so as to indicate that the file contains binary data,
39463 while the @code{0} is a version number that may have different values
39466 The description section consists of multiple lines of @sc{ascii} text
39467 separated by newline characters (@code{0xa}). The lines may include a
39468 variety of optional descriptive or context-setting information, such
39469 as tracepoint definitions or register set size. @value{GDBN} will
39470 ignore any line that it does not recognize. An empty line marks the end
39473 @c FIXME add some specific types of data
39475 The trace frame section consists of a number of consecutive frames.
39476 Each frame begins with a two-byte tracepoint number, followed by a
39477 four-byte size giving the amount of data in the frame. The data in
39478 the frame consists of a number of blocks, each introduced by a
39479 character indicating its type (at least register, memory, and trace
39480 state variable). The data in this section is raw binary, not a
39481 hexadecimal or other encoding; its endianness matches the target's
39484 @c FIXME bi-arch may require endianness/arch info in description section
39487 @item R @var{bytes}
39488 Register block. The number and ordering of bytes matches that of a
39489 @code{g} packet in the remote protocol. Note that these are the
39490 actual bytes, in target order and @value{GDBN} register order, not a
39491 hexadecimal encoding.
39493 @item M @var{address} @var{length} @var{bytes}...
39494 Memory block. This is a contiguous block of memory, at the 8-byte
39495 address @var{address}, with a 2-byte length @var{length}, followed by
39496 @var{length} bytes.
39498 @item V @var{number} @var{value}
39499 Trace state variable block. This records the 8-byte signed value
39500 @var{value} of trace state variable numbered @var{number}.
39504 Future enhancements of the trace file format may include additional types
39507 @node Index Section Format
39508 @appendix @code{.gdb_index} section format
39509 @cindex .gdb_index section format
39510 @cindex index section format
39512 This section documents the index section that is created by @code{save
39513 gdb-index} (@pxref{Index Files}). The index section is
39514 DWARF-specific; some knowledge of DWARF is assumed in this
39517 The mapped index file format is designed to be directly
39518 @code{mmap}able on any architecture. In most cases, a datum is
39519 represented using a little-endian 32-bit integer value, called an
39520 @code{offset_type}. Big endian machines must byte-swap the values
39521 before using them. Exceptions to this rule are noted. The data is
39522 laid out such that alignment is always respected.
39524 A mapped index consists of several areas, laid out in order.
39528 The file header. This is a sequence of values, of @code{offset_type}
39529 unless otherwise noted:
39533 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39534 Version 4 uses a different hashing function from versions 5 and 6.
39535 Version 6 includes symbols for inlined functions, whereas versions 4
39536 and 5 do not. Version 7 adds attributes to the CU indices in the
39537 symbol table. Version 8 specifies that symbols from DWARF type units
39538 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39539 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39541 @value{GDBN} will only read version 4, 5, or 6 indices
39542 by specifying @code{set use-deprecated-index-sections on}.
39543 GDB has a workaround for potentially broken version 7 indices so it is
39544 currently not flagged as deprecated.
39547 The offset, from the start of the file, of the CU list.
39550 The offset, from the start of the file, of the types CU list. Note
39551 that this area can be empty, in which case this offset will be equal
39552 to the next offset.
39555 The offset, from the start of the file, of the address area.
39558 The offset, from the start of the file, of the symbol table.
39561 The offset, from the start of the file, of the constant pool.
39565 The CU list. This is a sequence of pairs of 64-bit little-endian
39566 values, sorted by the CU offset. The first element in each pair is
39567 the offset of a CU in the @code{.debug_info} section. The second
39568 element in each pair is the length of that CU. References to a CU
39569 elsewhere in the map are done using a CU index, which is just the
39570 0-based index into this table. Note that if there are type CUs, then
39571 conceptually CUs and type CUs form a single list for the purposes of
39575 The types CU list. This is a sequence of triplets of 64-bit
39576 little-endian values. In a triplet, the first value is the CU offset,
39577 the second value is the type offset in the CU, and the third value is
39578 the type signature. The types CU list is not sorted.
39581 The address area. The address area consists of a sequence of address
39582 entries. Each address entry has three elements:
39586 The low address. This is a 64-bit little-endian value.
39589 The high address. This is a 64-bit little-endian value. Like
39590 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39593 The CU index. This is an @code{offset_type} value.
39597 The symbol table. This is an open-addressed hash table. The size of
39598 the hash table is always a power of 2.
39600 Each slot in the hash table consists of a pair of @code{offset_type}
39601 values. The first value is the offset of the symbol's name in the
39602 constant pool. The second value is the offset of the CU vector in the
39605 If both values are 0, then this slot in the hash table is empty. This
39606 is ok because while 0 is a valid constant pool index, it cannot be a
39607 valid index for both a string and a CU vector.
39609 The hash value for a table entry is computed by applying an
39610 iterative hash function to the symbol's name. Starting with an
39611 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39612 the string is incorporated into the hash using the formula depending on the
39617 The formula is @code{r = r * 67 + c - 113}.
39619 @item Versions 5 to 7
39620 The formula is @code{r = r * 67 + tolower (c) - 113}.
39623 The terminating @samp{\0} is not incorporated into the hash.
39625 The step size used in the hash table is computed via
39626 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39627 value, and @samp{size} is the size of the hash table. The step size
39628 is used to find the next candidate slot when handling a hash
39631 The names of C@t{++} symbols in the hash table are canonicalized. We
39632 don't currently have a simple description of the canonicalization
39633 algorithm; if you intend to create new index sections, you must read
39637 The constant pool. This is simply a bunch of bytes. It is organized
39638 so that alignment is correct: CU vectors are stored first, followed by
39641 A CU vector in the constant pool is a sequence of @code{offset_type}
39642 values. The first value is the number of CU indices in the vector.
39643 Each subsequent value is the index and symbol attributes of a CU in
39644 the CU list. This element in the hash table is used to indicate which
39645 CUs define the symbol and how the symbol is used.
39646 See below for the format of each CU index+attributes entry.
39648 A string in the constant pool is zero-terminated.
39651 Attributes were added to CU index values in @code{.gdb_index} version 7.
39652 If a symbol has multiple uses within a CU then there is one
39653 CU index+attributes value for each use.
39655 The format of each CU index+attributes entry is as follows
39661 This is the index of the CU in the CU list.
39663 These bits are reserved for future purposes and must be zero.
39665 The kind of the symbol in the CU.
39669 This value is reserved and should not be used.
39670 By reserving zero the full @code{offset_type} value is backwards compatible
39671 with previous versions of the index.
39673 The symbol is a type.
39675 The symbol is a variable or an enum value.
39677 The symbol is a function.
39679 Any other kind of symbol.
39681 These values are reserved.
39685 This bit is zero if the value is global and one if it is static.
39687 The determination of whether a symbol is global or static is complicated.
39688 The authorative reference is the file @file{dwarf2read.c} in
39689 @value{GDBN} sources.
39693 This pseudo-code describes the computation of a symbol's kind and
39694 global/static attributes in the index.
39697 is_external = get_attribute (die, DW_AT_external);
39698 language = get_attribute (cu_die, DW_AT_language);
39701 case DW_TAG_typedef:
39702 case DW_TAG_base_type:
39703 case DW_TAG_subrange_type:
39707 case DW_TAG_enumerator:
39709 is_static = (language != CPLUS && language != JAVA);
39711 case DW_TAG_subprogram:
39713 is_static = ! (is_external || language == ADA);
39715 case DW_TAG_constant:
39717 is_static = ! is_external;
39719 case DW_TAG_variable:
39721 is_static = ! is_external;
39723 case DW_TAG_namespace:
39727 case DW_TAG_class_type:
39728 case DW_TAG_interface_type:
39729 case DW_TAG_structure_type:
39730 case DW_TAG_union_type:
39731 case DW_TAG_enumeration_type:
39733 is_static = (language != CPLUS && language != JAVA);
39741 @appendix Manual pages
39745 * gdb man:: The GNU Debugger man page
39746 * gdbserver man:: Remote Server for the GNU Debugger man page
39747 * gcore man:: Generate a core file of a running program
39748 * gdbinit man:: gdbinit scripts
39754 @c man title gdb The GNU Debugger
39756 @c man begin SYNOPSIS gdb
39757 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
39758 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
39759 [@option{-b}@w{ }@var{bps}]
39760 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
39761 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
39762 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
39763 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
39764 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
39767 @c man begin DESCRIPTION gdb
39768 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
39769 going on ``inside'' another program while it executes -- or what another
39770 program was doing at the moment it crashed.
39772 @value{GDBN} can do four main kinds of things (plus other things in support of
39773 these) to help you catch bugs in the act:
39777 Start your program, specifying anything that might affect its behavior.
39780 Make your program stop on specified conditions.
39783 Examine what has happened, when your program has stopped.
39786 Change things in your program, so you can experiment with correcting the
39787 effects of one bug and go on to learn about another.
39790 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
39793 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
39794 commands from the terminal until you tell it to exit with the @value{GDBN}
39795 command @code{quit}. You can get online help from @value{GDBN} itself
39796 by using the command @code{help}.
39798 You can run @code{gdb} with no arguments or options; but the most
39799 usual way to start @value{GDBN} is with one argument or two, specifying an
39800 executable program as the argument:
39806 You can also start with both an executable program and a core file specified:
39812 You can, instead, specify a process ID as a second argument, if you want
39813 to debug a running process:
39821 would attach @value{GDBN} to process @code{1234} (unless you also have a file
39822 named @file{1234}; @value{GDBN} does check for a core file first).
39823 With option @option{-p} you can omit the @var{program} filename.
39825 Here are some of the most frequently needed @value{GDBN} commands:
39827 @c pod2man highlights the right hand side of the @item lines.
39829 @item break [@var{file}:]@var{functiop}
39830 Set a breakpoint at @var{function} (in @var{file}).
39832 @item run [@var{arglist}]
39833 Start your program (with @var{arglist}, if specified).
39836 Backtrace: display the program stack.
39838 @item print @var{expr}
39839 Display the value of an expression.
39842 Continue running your program (after stopping, e.g. at a breakpoint).
39845 Execute next program line (after stopping); step @emph{over} any
39846 function calls in the line.
39848 @item edit [@var{file}:]@var{function}
39849 look at the program line where it is presently stopped.
39851 @item list [@var{file}:]@var{function}
39852 type the text of the program in the vicinity of where it is presently stopped.
39855 Execute next program line (after stopping); step @emph{into} any
39856 function calls in the line.
39858 @item help [@var{name}]
39859 Show information about @value{GDBN} command @var{name}, or general information
39860 about using @value{GDBN}.
39863 Exit from @value{GDBN}.
39867 For full details on @value{GDBN},
39868 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39869 by Richard M. Stallman and Roland H. Pesch. The same text is available online
39870 as the @code{gdb} entry in the @code{info} program.
39874 @c man begin OPTIONS gdb
39875 Any arguments other than options specify an executable
39876 file and core file (or process ID); that is, the first argument
39877 encountered with no
39878 associated option flag is equivalent to a @option{-se} option, and the second,
39879 if any, is equivalent to a @option{-c} option if it's the name of a file.
39881 both long and short forms; both are shown here. The long forms are also
39882 recognized if you truncate them, so long as enough of the option is
39883 present to be unambiguous. (If you prefer, you can flag option
39884 arguments with @option{+} rather than @option{-}, though we illustrate the
39885 more usual convention.)
39887 All the options and command line arguments you give are processed
39888 in sequential order. The order makes a difference when the @option{-x}
39894 List all options, with brief explanations.
39896 @item -symbols=@var{file}
39897 @itemx -s @var{file}
39898 Read symbol table from file @var{file}.
39901 Enable writing into executable and core files.
39903 @item -exec=@var{file}
39904 @itemx -e @var{file}
39905 Use file @var{file} as the executable file to execute when
39906 appropriate, and for examining pure data in conjunction with a core
39909 @item -se=@var{file}
39910 Read symbol table from file @var{file} and use it as the executable
39913 @item -core=@var{file}
39914 @itemx -c @var{file}
39915 Use file @var{file} as a core dump to examine.
39917 @item -command=@var{file}
39918 @itemx -x @var{file}
39919 Execute @value{GDBN} commands from file @var{file}.
39921 @item -ex @var{command}
39922 Execute given @value{GDBN} @var{command}.
39924 @item -directory=@var{directory}
39925 @itemx -d @var{directory}
39926 Add @var{directory} to the path to search for source files.
39929 Do not execute commands from @file{~/.gdbinit}.
39933 Do not execute commands from any @file{.gdbinit} initialization files.
39937 ``Quiet''. Do not print the introductory and copyright messages. These
39938 messages are also suppressed in batch mode.
39941 Run in batch mode. Exit with status @code{0} after processing all the command
39942 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
39943 Exit with nonzero status if an error occurs in executing the @value{GDBN}
39944 commands in the command files.
39946 Batch mode may be useful for running @value{GDBN} as a filter, for example to
39947 download and run a program on another computer; in order to make this
39948 more useful, the message
39951 Program exited normally.
39955 (which is ordinarily issued whenever a program running under @value{GDBN} control
39956 terminates) is not issued when running in batch mode.
39958 @item -cd=@var{directory}
39959 Run @value{GDBN} using @var{directory} as its working directory,
39960 instead of the current directory.
39964 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
39965 @value{GDBN} to output the full file name and line number in a standard,
39966 recognizable fashion each time a stack frame is displayed (which
39967 includes each time the program stops). This recognizable format looks
39968 like two @samp{\032} characters, followed by the file name, line number
39969 and character position separated by colons, and a newline. The
39970 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
39971 characters as a signal to display the source code for the frame.
39974 Set the line speed (baud rate or bits per second) of any serial
39975 interface used by @value{GDBN} for remote debugging.
39977 @item -tty=@var{device}
39978 Run using @var{device} for your program's standard input and output.
39982 @c man begin SEEALSO gdb
39984 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
39985 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
39986 documentation are properly installed at your site, the command
39993 should give you access to the complete manual.
39995 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39996 Richard M. Stallman and Roland H. Pesch, July 1991.
40000 @node gdbserver man
40001 @heading gdbserver man
40003 @c man title gdbserver Remote Server for the GNU Debugger
40005 @c man begin SYNOPSIS gdbserver
40006 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40008 gdbserver --attach @var{comm} @var{pid}
40010 gdbserver --multi @var{comm}
40014 @c man begin DESCRIPTION gdbserver
40015 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40016 than the one which is running the program being debugged.
40019 @subheading Usage (server (target) side)
40022 Usage (server (target) side):
40025 First, you need to have a copy of the program you want to debug put onto
40026 the target system. The program can be stripped to save space if needed, as
40027 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40028 the @value{GDBN} running on the host system.
40030 To use the server, you log on to the target system, and run the @command{gdbserver}
40031 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40032 your program, and (c) its arguments. The general syntax is:
40035 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40038 For example, using a serial port, you might say:
40042 @c @file would wrap it as F</dev/com1>.
40043 target> gdbserver /dev/com1 emacs foo.txt
40046 target> gdbserver @file{/dev/com1} emacs foo.txt
40050 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40051 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40052 waits patiently for the host @value{GDBN} to communicate with it.
40054 To use a TCP connection, you could say:
40057 target> gdbserver host:2345 emacs foo.txt
40060 This says pretty much the same thing as the last example, except that we are
40061 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40062 that we are expecting to see a TCP connection from @code{host} to local TCP port
40063 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40064 want for the port number as long as it does not conflict with any existing TCP
40065 ports on the target system. This same port number must be used in the host
40066 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40067 you chose a port number that conflicts with another service, @command{gdbserver} will
40068 print an error message and exit.
40070 @command{gdbserver} can also attach to running programs.
40071 This is accomplished via the @option{--attach} argument. The syntax is:
40074 target> gdbserver --attach @var{comm} @var{pid}
40077 @var{pid} is the process ID of a currently running process. It isn't
40078 necessary to point @command{gdbserver} at a binary for the running process.
40080 To start @code{gdbserver} without supplying an initial command to run
40081 or process ID to attach, use the @option{--multi} command line option.
40082 In such case you should connect using @kbd{target extended-remote} to start
40083 the program you want to debug.
40086 target> gdbserver --multi @var{comm}
40090 @subheading Usage (host side)
40096 You need an unstripped copy of the target program on your host system, since
40097 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40098 would, with the target program as the first argument. (You may need to use the
40099 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40100 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40101 new command you need to know about is @code{target remote}
40102 (or @code{target extended-remote}). Its argument is either
40103 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40104 descriptor. For example:
40108 @c @file would wrap it as F</dev/ttyb>.
40109 (gdb) target remote /dev/ttyb
40112 (gdb) target remote @file{/dev/ttyb}
40117 communicates with the server via serial line @file{/dev/ttyb}, and:
40120 (gdb) target remote the-target:2345
40124 communicates via a TCP connection to port 2345 on host `the-target', where
40125 you previously started up @command{gdbserver} with the same port number. Note that for
40126 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40127 command, otherwise you may get an error that looks something like
40128 `Connection refused'.
40130 @command{gdbserver} can also debug multiple inferiors at once,
40133 the @value{GDBN} manual in node @code{Inferiors and Programs}
40134 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40137 @ref{Inferiors and Programs}.
40139 In such case use the @code{extended-remote} @value{GDBN} command variant:
40142 (gdb) target extended-remote the-target:2345
40145 The @command{gdbserver} option @option{--multi} may or may not be used in such
40149 @c man begin OPTIONS gdbserver
40150 There are three different modes for invoking @command{gdbserver}:
40155 Debug a specific program specified by its program name:
40158 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40161 The @var{comm} parameter specifies how should the server communicate
40162 with @value{GDBN}; it is either a device name (to use a serial line),
40163 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40164 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40165 debug in @var{prog}. Any remaining arguments will be passed to the
40166 program verbatim. When the program exits, @value{GDBN} will close the
40167 connection, and @code{gdbserver} will exit.
40170 Debug a specific program by specifying the process ID of a running
40174 gdbserver --attach @var{comm} @var{pid}
40177 The @var{comm} parameter is as described above. Supply the process ID
40178 of a running program in @var{pid}; @value{GDBN} will do everything
40179 else. Like with the previous mode, when the process @var{pid} exits,
40180 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40183 Multi-process mode -- debug more than one program/process:
40186 gdbserver --multi @var{comm}
40189 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40190 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40191 close the connection when a process being debugged exits, so you can
40192 debug several processes in the same session.
40195 In each of the modes you may specify these options:
40200 List all options, with brief explanations.
40203 This option causes @command{gdbserver} to print its version number and exit.
40206 @command{gdbserver} will attach to a running program. The syntax is:
40209 target> gdbserver --attach @var{comm} @var{pid}
40212 @var{pid} is the process ID of a currently running process. It isn't
40213 necessary to point @command{gdbserver} at a binary for the running process.
40216 To start @code{gdbserver} without supplying an initial command to run
40217 or process ID to attach, use this command line option.
40218 Then you can connect using @kbd{target extended-remote} and start
40219 the program you want to debug. The syntax is:
40222 target> gdbserver --multi @var{comm}
40226 Instruct @code{gdbserver} to display extra status information about the debugging
40228 This option is intended for @code{gdbserver} development and for bug reports to
40231 @item --remote-debug
40232 Instruct @code{gdbserver} to display remote protocol debug output.
40233 This option is intended for @code{gdbserver} development and for bug reports to
40236 @item --debug-format=option1@r{[},option2,...@r{]}
40237 Instruct @code{gdbserver} to include extra information in each line
40238 of debugging output.
40239 @xref{Other Command-Line Arguments for gdbserver}.
40242 Specify a wrapper to launch programs
40243 for debugging. The option should be followed by the name of the
40244 wrapper, then any command-line arguments to pass to the wrapper, then
40245 @kbd{--} indicating the end of the wrapper arguments.
40248 By default, @command{gdbserver} keeps the listening TCP port open, so that
40249 additional connections are possible. However, if you start @code{gdbserver}
40250 with the @option{--once} option, it will stop listening for any further
40251 connection attempts after connecting to the first @value{GDBN} session.
40253 @c --disable-packet is not documented for users.
40255 @c --disable-randomization and --no-disable-randomization are superseded by
40256 @c QDisableRandomization.
40261 @c man begin SEEALSO gdbserver
40263 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40264 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40265 documentation are properly installed at your site, the command
40271 should give you access to the complete manual.
40273 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40274 Richard M. Stallman and Roland H. Pesch, July 1991.
40281 @c man title gcore Generate a core file of a running program
40284 @c man begin SYNOPSIS gcore
40285 gcore [-o @var{filename}] @var{pid}
40289 @c man begin DESCRIPTION gcore
40290 Generate a core dump of a running program with process ID @var{pid}.
40291 Produced file is equivalent to a kernel produced core file as if the process
40292 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40293 limit). Unlike after a crash, after @command{gcore} the program remains
40294 running without any change.
40297 @c man begin OPTIONS gcore
40299 @item -o @var{filename}
40300 The optional argument
40301 @var{filename} specifies the file name where to put the core dump.
40302 If not specified, the file name defaults to @file{core.@var{pid}},
40303 where @var{pid} is the running program process ID.
40307 @c man begin SEEALSO gcore
40309 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40310 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40311 documentation are properly installed at your site, the command
40318 should give you access to the complete manual.
40320 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40321 Richard M. Stallman and Roland H. Pesch, July 1991.
40328 @c man title gdbinit GDB initialization scripts
40331 @c man begin SYNOPSIS gdbinit
40332 @ifset SYSTEM_GDBINIT
40333 @value{SYSTEM_GDBINIT}
40342 @c man begin DESCRIPTION gdbinit
40343 These files contain @value{GDBN} commands to automatically execute during
40344 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40347 the @value{GDBN} manual in node @code{Sequences}
40348 -- shell command @code{info -f gdb -n Sequences}.
40354 Please read more in
40356 the @value{GDBN} manual in node @code{Startup}
40357 -- shell command @code{info -f gdb -n Startup}.
40364 @ifset SYSTEM_GDBINIT
40365 @item @value{SYSTEM_GDBINIT}
40367 @ifclear SYSTEM_GDBINIT
40368 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40370 System-wide initialization file. It is executed unless user specified
40371 @value{GDBN} option @code{-nx} or @code{-n}.
40374 the @value{GDBN} manual in node @code{System-wide configuration}
40375 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40378 @ref{System-wide configuration}.
40382 User initialization file. It is executed unless user specified
40383 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40386 Initialization file for current directory. It may need to be enabled with
40387 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40390 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40391 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40394 @ref{Init File in the Current Directory}.
40399 @c man begin SEEALSO gdbinit
40401 gdb(1), @code{info -f gdb -n Startup}
40403 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40404 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40405 documentation are properly installed at your site, the command
40411 should give you access to the complete manual.
40413 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40414 Richard M. Stallman and Roland H. Pesch, July 1991.
40420 @node GNU Free Documentation License
40421 @appendix GNU Free Documentation License
40424 @node Concept Index
40425 @unnumbered Concept Index
40429 @node Command and Variable Index
40430 @unnumbered Command, Variable, and Function Index
40435 % I think something like @@colophon should be in texinfo. In the
40437 \long\def\colophon{\hbox to0pt{}\vfill
40438 \centerline{The body of this manual is set in}
40439 \centerline{\fontname\tenrm,}
40440 \centerline{with headings in {\bf\fontname\tenbf}}
40441 \centerline{and examples in {\tt\fontname\tentt}.}
40442 \centerline{{\it\fontname\tenit\/},}
40443 \centerline{{\bf\fontname\tenbf}, and}
40444 \centerline{{\sl\fontname\tensl\/}}
40445 \centerline{are used for emphasis.}\vfill}
40447 % Blame: doc@@cygnus.com, 1991.