1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 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{} 1988-2015 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) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2796 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 3 process 35 thread 27 0x34e5 in sigpause ()
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. It applies to normal execution,
5840 record mode, and replay mode. If it is @code{off}, then there is no
5841 locking and any thread may run at any time. If @code{on}, then only
5842 the current thread may run when the inferior is resumed. The
5843 @code{step} mode optimizes for single-stepping; it prevents other
5844 threads from preempting the current thread while you are stepping, so
5845 that the focus of debugging does not change unexpectedly. Other
5846 threads never get a chance to run when you step, and they are
5847 completely free to run when you use commands like @samp{continue},
5848 @samp{until}, or @samp{finish}. However, unless another thread hits a
5849 breakpoint during its timeslice, @value{GDBN} does not change the
5850 current thread away from the thread that you are debugging. The
5851 @code{replay} mode behaves like @code{off} in record mode and like
5852 @code{on} in replay mode.
5854 @item show scheduler-locking
5855 Display the current scheduler locking mode.
5858 @cindex resume threads of multiple processes simultaneously
5859 By default, when you issue one of the execution commands such as
5860 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5861 threads of the current inferior to run. For example, if @value{GDBN}
5862 is attached to two inferiors, each with two threads, the
5863 @code{continue} command resumes only the two threads of the current
5864 inferior. This is useful, for example, when you debug a program that
5865 forks and you want to hold the parent stopped (so that, for instance,
5866 it doesn't run to exit), while you debug the child. In other
5867 situations, you may not be interested in inspecting the current state
5868 of any of the processes @value{GDBN} is attached to, and you may want
5869 to resume them all until some breakpoint is hit. In the latter case,
5870 you can instruct @value{GDBN} to allow all threads of all the
5871 inferiors to run with the @w{@code{set schedule-multiple}} command.
5874 @kindex set schedule-multiple
5875 @item set schedule-multiple
5876 Set the mode for allowing threads of multiple processes to be resumed
5877 when an execution command is issued. When @code{on}, all threads of
5878 all processes are allowed to run. When @code{off}, only the threads
5879 of the current process are resumed. The default is @code{off}. The
5880 @code{scheduler-locking} mode takes precedence when set to @code{on},
5881 or while you are stepping and set to @code{step}.
5883 @item show schedule-multiple
5884 Display the current mode for resuming the execution of threads of
5889 @subsection Non-Stop Mode
5891 @cindex non-stop mode
5893 @c This section is really only a place-holder, and needs to be expanded
5894 @c with more details.
5896 For some multi-threaded targets, @value{GDBN} supports an optional
5897 mode of operation in which you can examine stopped program threads in
5898 the debugger while other threads continue to execute freely. This
5899 minimizes intrusion when debugging live systems, such as programs
5900 where some threads have real-time constraints or must continue to
5901 respond to external events. This is referred to as @dfn{non-stop} mode.
5903 In non-stop mode, when a thread stops to report a debugging event,
5904 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5905 threads as well, in contrast to the all-stop mode behavior. Additionally,
5906 execution commands such as @code{continue} and @code{step} apply by default
5907 only to the current thread in non-stop mode, rather than all threads as
5908 in all-stop mode. This allows you to control threads explicitly in
5909 ways that are not possible in all-stop mode --- for example, stepping
5910 one thread while allowing others to run freely, stepping
5911 one thread while holding all others stopped, or stepping several threads
5912 independently and simultaneously.
5914 To enter non-stop mode, use this sequence of commands before you run
5915 or attach to your program:
5918 # If using the CLI, pagination breaks non-stop.
5921 # Finally, turn it on!
5925 You can use these commands to manipulate the non-stop mode setting:
5928 @kindex set non-stop
5929 @item set non-stop on
5930 Enable selection of non-stop mode.
5931 @item set non-stop off
5932 Disable selection of non-stop mode.
5933 @kindex show non-stop
5935 Show the current non-stop enablement setting.
5938 Note these commands only reflect whether non-stop mode is enabled,
5939 not whether the currently-executing program is being run in non-stop mode.
5940 In particular, the @code{set non-stop} preference is only consulted when
5941 @value{GDBN} starts or connects to the target program, and it is generally
5942 not possible to switch modes once debugging has started. Furthermore,
5943 since not all targets support non-stop mode, even when you have enabled
5944 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5947 In non-stop mode, all execution commands apply only to the current thread
5948 by default. That is, @code{continue} only continues one thread.
5949 To continue all threads, issue @code{continue -a} or @code{c -a}.
5951 You can use @value{GDBN}'s background execution commands
5952 (@pxref{Background Execution}) to run some threads in the background
5953 while you continue to examine or step others from @value{GDBN}.
5954 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5955 always executed asynchronously in non-stop mode.
5957 Suspending execution is done with the @code{interrupt} command when
5958 running in the background, or @kbd{Ctrl-c} during foreground execution.
5959 In all-stop mode, this stops the whole process;
5960 but in non-stop mode the interrupt applies only to the current thread.
5961 To stop the whole program, use @code{interrupt -a}.
5963 Other execution commands do not currently support the @code{-a} option.
5965 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5966 that thread current, as it does in all-stop mode. This is because the
5967 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5968 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5969 changed to a different thread just as you entered a command to operate on the
5970 previously current thread.
5972 @node Background Execution
5973 @subsection Background Execution
5975 @cindex foreground execution
5976 @cindex background execution
5977 @cindex asynchronous execution
5978 @cindex execution, foreground, background and asynchronous
5980 @value{GDBN}'s execution commands have two variants: the normal
5981 foreground (synchronous) behavior, and a background
5982 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5983 the program to report that some thread has stopped before prompting for
5984 another command. In background execution, @value{GDBN} immediately gives
5985 a command prompt so that you can issue other commands while your program runs.
5987 If the target doesn't support async mode, @value{GDBN} issues an error
5988 message if you attempt to use the background execution commands.
5990 To specify background execution, add a @code{&} to the command. For example,
5991 the background form of the @code{continue} command is @code{continue&}, or
5992 just @code{c&}. The execution commands that accept background execution
5998 @xref{Starting, , Starting your Program}.
6002 @xref{Attach, , Debugging an Already-running Process}.
6006 @xref{Continuing and Stepping, step}.
6010 @xref{Continuing and Stepping, stepi}.
6014 @xref{Continuing and Stepping, next}.
6018 @xref{Continuing and Stepping, nexti}.
6022 @xref{Continuing and Stepping, continue}.
6026 @xref{Continuing and Stepping, finish}.
6030 @xref{Continuing and Stepping, until}.
6034 Background execution is especially useful in conjunction with non-stop
6035 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6036 However, you can also use these commands in the normal all-stop mode with
6037 the restriction that you cannot issue another execution command until the
6038 previous one finishes. Examples of commands that are valid in all-stop
6039 mode while the program is running include @code{help} and @code{info break}.
6041 You can interrupt your program while it is running in the background by
6042 using the @code{interrupt} command.
6049 Suspend execution of the running program. In all-stop mode,
6050 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6051 only the current thread. To stop the whole program in non-stop mode,
6052 use @code{interrupt -a}.
6055 @node Thread-Specific Breakpoints
6056 @subsection Thread-Specific Breakpoints
6058 When your program has multiple threads (@pxref{Threads,, Debugging
6059 Programs with Multiple Threads}), you can choose whether to set
6060 breakpoints on all threads, or on a particular thread.
6063 @cindex breakpoints and threads
6064 @cindex thread breakpoints
6065 @kindex break @dots{} thread @var{threadno}
6066 @item break @var{location} thread @var{threadno}
6067 @itemx break @var{location} thread @var{threadno} if @dots{}
6068 @var{location} specifies source lines; there are several ways of
6069 writing them (@pxref{Specify Location}), but the effect is always to
6070 specify some source line.
6072 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6073 to specify that you only want @value{GDBN} to stop the program when a
6074 particular thread reaches this breakpoint. The @var{threadno} specifier
6075 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6076 in the first column of the @samp{info threads} display.
6078 If you do not specify @samp{thread @var{threadno}} when you set a
6079 breakpoint, the breakpoint applies to @emph{all} threads of your
6082 You can use the @code{thread} qualifier on conditional breakpoints as
6083 well; in this case, place @samp{thread @var{threadno}} before or
6084 after the breakpoint condition, like this:
6087 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6092 Thread-specific breakpoints are automatically deleted when
6093 @value{GDBN} detects the corresponding thread is no longer in the
6094 thread list. For example:
6098 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6101 There are several ways for a thread to disappear, such as a regular
6102 thread exit, but also when you detach from the process with the
6103 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6104 Process}), or if @value{GDBN} loses the remote connection
6105 (@pxref{Remote Debugging}), etc. Note that with some targets,
6106 @value{GDBN} is only able to detect a thread has exited when the user
6107 explictly asks for the thread list with the @code{info threads}
6110 @node Interrupted System Calls
6111 @subsection Interrupted System Calls
6113 @cindex thread breakpoints and system calls
6114 @cindex system calls and thread breakpoints
6115 @cindex premature return from system calls
6116 There is an unfortunate side effect when using @value{GDBN} to debug
6117 multi-threaded programs. If one thread stops for a
6118 breakpoint, or for some other reason, and another thread is blocked in a
6119 system call, then the system call may return prematurely. This is a
6120 consequence of the interaction between multiple threads and the signals
6121 that @value{GDBN} uses to implement breakpoints and other events that
6124 To handle this problem, your program should check the return value of
6125 each system call and react appropriately. This is good programming
6128 For example, do not write code like this:
6134 The call to @code{sleep} will return early if a different thread stops
6135 at a breakpoint or for some other reason.
6137 Instead, write this:
6142 unslept = sleep (unslept);
6145 A system call is allowed to return early, so the system is still
6146 conforming to its specification. But @value{GDBN} does cause your
6147 multi-threaded program to behave differently than it would without
6150 Also, @value{GDBN} uses internal breakpoints in the thread library to
6151 monitor certain events such as thread creation and thread destruction.
6152 When such an event happens, a system call in another thread may return
6153 prematurely, even though your program does not appear to stop.
6156 @subsection Observer Mode
6158 If you want to build on non-stop mode and observe program behavior
6159 without any chance of disruption by @value{GDBN}, you can set
6160 variables to disable all of the debugger's attempts to modify state,
6161 whether by writing memory, inserting breakpoints, etc. These operate
6162 at a low level, intercepting operations from all commands.
6164 When all of these are set to @code{off}, then @value{GDBN} is said to
6165 be @dfn{observer mode}. As a convenience, the variable
6166 @code{observer} can be set to disable these, plus enable non-stop
6169 Note that @value{GDBN} will not prevent you from making nonsensical
6170 combinations of these settings. For instance, if you have enabled
6171 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6172 then breakpoints that work by writing trap instructions into the code
6173 stream will still not be able to be placed.
6178 @item set observer on
6179 @itemx set observer off
6180 When set to @code{on}, this disables all the permission variables
6181 below (except for @code{insert-fast-tracepoints}), plus enables
6182 non-stop debugging. Setting this to @code{off} switches back to
6183 normal debugging, though remaining in non-stop mode.
6186 Show whether observer mode is on or off.
6188 @kindex may-write-registers
6189 @item set may-write-registers on
6190 @itemx set may-write-registers off
6191 This controls whether @value{GDBN} will attempt to alter the values of
6192 registers, such as with assignment expressions in @code{print}, or the
6193 @code{jump} command. It defaults to @code{on}.
6195 @item show may-write-registers
6196 Show the current permission to write registers.
6198 @kindex may-write-memory
6199 @item set may-write-memory on
6200 @itemx set may-write-memory off
6201 This controls whether @value{GDBN} will attempt to alter the contents
6202 of memory, such as with assignment expressions in @code{print}. It
6203 defaults to @code{on}.
6205 @item show may-write-memory
6206 Show the current permission to write memory.
6208 @kindex may-insert-breakpoints
6209 @item set may-insert-breakpoints on
6210 @itemx set may-insert-breakpoints off
6211 This controls whether @value{GDBN} will attempt to insert breakpoints.
6212 This affects all breakpoints, including internal breakpoints defined
6213 by @value{GDBN}. It defaults to @code{on}.
6215 @item show may-insert-breakpoints
6216 Show the current permission to insert breakpoints.
6218 @kindex may-insert-tracepoints
6219 @item set may-insert-tracepoints on
6220 @itemx set may-insert-tracepoints off
6221 This controls whether @value{GDBN} will attempt to insert (regular)
6222 tracepoints at the beginning of a tracing experiment. It affects only
6223 non-fast tracepoints, fast tracepoints being under the control of
6224 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6226 @item show may-insert-tracepoints
6227 Show the current permission to insert tracepoints.
6229 @kindex may-insert-fast-tracepoints
6230 @item set may-insert-fast-tracepoints on
6231 @itemx set may-insert-fast-tracepoints off
6232 This controls whether @value{GDBN} will attempt to insert fast
6233 tracepoints at the beginning of a tracing experiment. It affects only
6234 fast tracepoints, regular (non-fast) tracepoints being under the
6235 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6237 @item show may-insert-fast-tracepoints
6238 Show the current permission to insert fast tracepoints.
6240 @kindex may-interrupt
6241 @item set may-interrupt on
6242 @itemx set may-interrupt off
6243 This controls whether @value{GDBN} will attempt to interrupt or stop
6244 program execution. When this variable is @code{off}, the
6245 @code{interrupt} command will have no effect, nor will
6246 @kbd{Ctrl-c}. It defaults to @code{on}.
6248 @item show may-interrupt
6249 Show the current permission to interrupt or stop the program.
6253 @node Reverse Execution
6254 @chapter Running programs backward
6255 @cindex reverse execution
6256 @cindex running programs backward
6258 When you are debugging a program, it is not unusual to realize that
6259 you have gone too far, and some event of interest has already happened.
6260 If the target environment supports it, @value{GDBN} can allow you to
6261 ``rewind'' the program by running it backward.
6263 A target environment that supports reverse execution should be able
6264 to ``undo'' the changes in machine state that have taken place as the
6265 program was executing normally. Variables, registers etc.@: should
6266 revert to their previous values. Obviously this requires a great
6267 deal of sophistication on the part of the target environment; not
6268 all target environments can support reverse execution.
6270 When a program is executed in reverse, the instructions that
6271 have most recently been executed are ``un-executed'', in reverse
6272 order. The program counter runs backward, following the previous
6273 thread of execution in reverse. As each instruction is ``un-executed'',
6274 the values of memory and/or registers that were changed by that
6275 instruction are reverted to their previous states. After executing
6276 a piece of source code in reverse, all side effects of that code
6277 should be ``undone'', and all variables should be returned to their
6278 prior values@footnote{
6279 Note that some side effects are easier to undo than others. For instance,
6280 memory and registers are relatively easy, but device I/O is hard. Some
6281 targets may be able undo things like device I/O, and some may not.
6283 The contract between @value{GDBN} and the reverse executing target
6284 requires only that the target do something reasonable when
6285 @value{GDBN} tells it to execute backwards, and then report the
6286 results back to @value{GDBN}. Whatever the target reports back to
6287 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6288 assumes that the memory and registers that the target reports are in a
6289 consistant state, but @value{GDBN} accepts whatever it is given.
6292 If you are debugging in a target environment that supports
6293 reverse execution, @value{GDBN} provides the following commands.
6296 @kindex reverse-continue
6297 @kindex rc @r{(@code{reverse-continue})}
6298 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6299 @itemx rc @r{[}@var{ignore-count}@r{]}
6300 Beginning at the point where your program last stopped, start executing
6301 in reverse. Reverse execution will stop for breakpoints and synchronous
6302 exceptions (signals), just like normal execution. Behavior of
6303 asynchronous signals depends on the target environment.
6305 @kindex reverse-step
6306 @kindex rs @r{(@code{step})}
6307 @item reverse-step @r{[}@var{count}@r{]}
6308 Run the program backward until control reaches the start of a
6309 different source line; then stop it, and return control to @value{GDBN}.
6311 Like the @code{step} command, @code{reverse-step} will only stop
6312 at the beginning of a source line. It ``un-executes'' the previously
6313 executed source line. If the previous source line included calls to
6314 debuggable functions, @code{reverse-step} will step (backward) into
6315 the called function, stopping at the beginning of the @emph{last}
6316 statement in the called function (typically a return statement).
6318 Also, as with the @code{step} command, if non-debuggable functions are
6319 called, @code{reverse-step} will run thru them backward without stopping.
6321 @kindex reverse-stepi
6322 @kindex rsi @r{(@code{reverse-stepi})}
6323 @item reverse-stepi @r{[}@var{count}@r{]}
6324 Reverse-execute one machine instruction. Note that the instruction
6325 to be reverse-executed is @emph{not} the one pointed to by the program
6326 counter, but the instruction executed prior to that one. For instance,
6327 if the last instruction was a jump, @code{reverse-stepi} will take you
6328 back from the destination of the jump to the jump instruction itself.
6330 @kindex reverse-next
6331 @kindex rn @r{(@code{reverse-next})}
6332 @item reverse-next @r{[}@var{count}@r{]}
6333 Run backward to the beginning of the previous line executed in
6334 the current (innermost) stack frame. If the line contains function
6335 calls, they will be ``un-executed'' without stopping. Starting from
6336 the first line of a function, @code{reverse-next} will take you back
6337 to the caller of that function, @emph{before} the function was called,
6338 just as the normal @code{next} command would take you from the last
6339 line of a function back to its return to its caller
6340 @footnote{Unless the code is too heavily optimized.}.
6342 @kindex reverse-nexti
6343 @kindex rni @r{(@code{reverse-nexti})}
6344 @item reverse-nexti @r{[}@var{count}@r{]}
6345 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6346 in reverse, except that called functions are ``un-executed'' atomically.
6347 That is, if the previously executed instruction was a return from
6348 another function, @code{reverse-nexti} will continue to execute
6349 in reverse until the call to that function (from the current stack
6352 @kindex reverse-finish
6353 @item reverse-finish
6354 Just as the @code{finish} command takes you to the point where the
6355 current function returns, @code{reverse-finish} takes you to the point
6356 where it was called. Instead of ending up at the end of the current
6357 function invocation, you end up at the beginning.
6359 @kindex set exec-direction
6360 @item set exec-direction
6361 Set the direction of target execution.
6362 @item set exec-direction reverse
6363 @cindex execute forward or backward in time
6364 @value{GDBN} will perform all execution commands in reverse, until the
6365 exec-direction mode is changed to ``forward''. Affected commands include
6366 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6367 command cannot be used in reverse mode.
6368 @item set exec-direction forward
6369 @value{GDBN} will perform all execution commands in the normal fashion.
6370 This is the default.
6374 @node Process Record and Replay
6375 @chapter Recording Inferior's Execution and Replaying It
6376 @cindex process record and replay
6377 @cindex recording inferior's execution and replaying it
6379 On some platforms, @value{GDBN} provides a special @dfn{process record
6380 and replay} target that can record a log of the process execution, and
6381 replay it later with both forward and reverse execution commands.
6384 When this target is in use, if the execution log includes the record
6385 for the next instruction, @value{GDBN} will debug in @dfn{replay
6386 mode}. In the replay mode, the inferior does not really execute code
6387 instructions. Instead, all the events that normally happen during
6388 code execution are taken from the execution log. While code is not
6389 really executed in replay mode, the values of registers (including the
6390 program counter register) and the memory of the inferior are still
6391 changed as they normally would. Their contents are taken from the
6395 If the record for the next instruction is not in the execution log,
6396 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6397 inferior executes normally, and @value{GDBN} records the execution log
6400 The process record and replay target supports reverse execution
6401 (@pxref{Reverse Execution}), even if the platform on which the
6402 inferior runs does not. However, the reverse execution is limited in
6403 this case by the range of the instructions recorded in the execution
6404 log. In other words, reverse execution on platforms that don't
6405 support it directly can only be done in the replay mode.
6407 When debugging in the reverse direction, @value{GDBN} will work in
6408 replay mode as long as the execution log includes the record for the
6409 previous instruction; otherwise, it will work in record mode, if the
6410 platform supports reverse execution, or stop if not.
6412 For architecture environments that support process record and replay,
6413 @value{GDBN} provides the following commands:
6416 @kindex target record
6417 @kindex target record-full
6418 @kindex target record-btrace
6421 @kindex record btrace
6422 @kindex record btrace bts
6423 @kindex record btrace pt
6429 @kindex rec btrace bts
6430 @kindex rec btrace pt
6433 @item record @var{method}
6434 This command starts the process record and replay target. The
6435 recording method can be specified as parameter. Without a parameter
6436 the command uses the @code{full} recording method. The following
6437 recording methods are available:
6441 Full record/replay recording using @value{GDBN}'s software record and
6442 replay implementation. This method allows replaying and reverse
6445 @item btrace @var{format}
6446 Hardware-supported instruction recording. This method does not record
6447 data. Further, the data is collected in a ring buffer so old data will
6448 be overwritten when the buffer is full. It allows limited reverse
6449 execution. Variables and registers are not available during reverse
6452 The recording format can be specified as parameter. Without a parameter
6453 the command chooses the recording format. The following recording
6454 formats are available:
6458 @cindex branch trace store
6459 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6460 this format, the processor stores a from/to record for each executed
6461 branch in the btrace ring buffer.
6464 @cindex Intel(R) Processor Trace
6465 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6466 format, the processor stores the execution trace in a compressed form
6467 that is afterwards decoded by @value{GDBN}.
6469 The trace can be recorded with very low overhead. The compressed
6470 trace format also allows small trace buffers to already contain a big
6471 number of instructions compared to @acronym{BTS}.
6473 Decoding the recorded execution trace, on the other hand, is more
6474 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6475 increased number of instructions to process. You should increase the
6476 buffer-size with care.
6479 Not all recording formats may be available on all processors.
6482 The process record and replay target can only debug a process that is
6483 already running. Therefore, you need first to start the process with
6484 the @kbd{run} or @kbd{start} commands, and then start the recording
6485 with the @kbd{record @var{method}} command.
6487 @cindex displaced stepping, and process record and replay
6488 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6489 will be automatically disabled when process record and replay target
6490 is started. That's because the process record and replay target
6491 doesn't support displaced stepping.
6493 @cindex non-stop mode, and process record and replay
6494 @cindex asynchronous execution, and process record and replay
6495 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6496 the asynchronous execution mode (@pxref{Background Execution}), not
6497 all recording methods are available. The @code{full} recording method
6498 does not support these two modes.
6503 Stop the process record and replay target. When process record and
6504 replay target stops, the entire execution log will be deleted and the
6505 inferior will either be terminated, or will remain in its final state.
6507 When you stop the process record and replay target in record mode (at
6508 the end of the execution log), the inferior will be stopped at the
6509 next instruction that would have been recorded. In other words, if
6510 you record for a while and then stop recording, the inferior process
6511 will be left in the same state as if the recording never happened.
6513 On the other hand, if the process record and replay target is stopped
6514 while in replay mode (that is, not at the end of the execution log,
6515 but at some earlier point), the inferior process will become ``live''
6516 at that earlier state, and it will then be possible to continue the
6517 usual ``live'' debugging of the process from that state.
6519 When the inferior process exits, or @value{GDBN} detaches from it,
6520 process record and replay target will automatically stop itself.
6524 Go to a specific location in the execution log. There are several
6525 ways to specify the location to go to:
6528 @item record goto begin
6529 @itemx record goto start
6530 Go to the beginning of the execution log.
6532 @item record goto end
6533 Go to the end of the execution log.
6535 @item record goto @var{n}
6536 Go to instruction number @var{n} in the execution log.
6540 @item record save @var{filename}
6541 Save the execution log to a file @file{@var{filename}}.
6542 Default filename is @file{gdb_record.@var{process_id}}, where
6543 @var{process_id} is the process ID of the inferior.
6545 This command may not be available for all recording methods.
6547 @kindex record restore
6548 @item record restore @var{filename}
6549 Restore the execution log from a file @file{@var{filename}}.
6550 File must have been created with @code{record save}.
6552 @kindex set record full
6553 @item set record full insn-number-max @var{limit}
6554 @itemx set record full insn-number-max unlimited
6555 Set the limit of instructions to be recorded for the @code{full}
6556 recording method. Default value is 200000.
6558 If @var{limit} is a positive number, then @value{GDBN} will start
6559 deleting instructions from the log once the number of the record
6560 instructions becomes greater than @var{limit}. For every new recorded
6561 instruction, @value{GDBN} will delete the earliest recorded
6562 instruction to keep the number of recorded instructions at the limit.
6563 (Since deleting recorded instructions loses information, @value{GDBN}
6564 lets you control what happens when the limit is reached, by means of
6565 the @code{stop-at-limit} option, described below.)
6567 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6568 delete recorded instructions from the execution log. The number of
6569 recorded instructions is limited only by the available memory.
6571 @kindex show record full
6572 @item show record full insn-number-max
6573 Show the limit of instructions to be recorded with the @code{full}
6576 @item set record full stop-at-limit
6577 Control the behavior of the @code{full} recording method when the
6578 number of recorded instructions reaches the limit. If ON (the
6579 default), @value{GDBN} will stop when the limit is reached for the
6580 first time and ask you whether you want to stop the inferior or
6581 continue running it and recording the execution log. If you decide
6582 to continue recording, each new recorded instruction will cause the
6583 oldest one to be deleted.
6585 If this option is OFF, @value{GDBN} will automatically delete the
6586 oldest record to make room for each new one, without asking.
6588 @item show record full stop-at-limit
6589 Show the current setting of @code{stop-at-limit}.
6591 @item set record full memory-query
6592 Control the behavior when @value{GDBN} is unable to record memory
6593 changes caused by an instruction for the @code{full} recording method.
6594 If ON, @value{GDBN} will query whether to stop the inferior in that
6597 If this option is OFF (the default), @value{GDBN} will automatically
6598 ignore the effect of such instructions on memory. Later, when
6599 @value{GDBN} replays this execution log, it will mark the log of this
6600 instruction as not accessible, and it will not affect the replay
6603 @item show record full memory-query
6604 Show the current setting of @code{memory-query}.
6606 @kindex set record btrace
6607 The @code{btrace} record target does not trace data. As a
6608 convenience, when replaying, @value{GDBN} reads read-only memory off
6609 the live program directly, assuming that the addresses of the
6610 read-only areas don't change. This for example makes it possible to
6611 disassemble code while replaying, but not to print variables.
6612 In some cases, being able to inspect variables might be useful.
6613 You can use the following command for that:
6615 @item set record btrace replay-memory-access
6616 Control the behavior of the @code{btrace} recording method when
6617 accessing memory during replay. If @code{read-only} (the default),
6618 @value{GDBN} will only allow accesses to read-only memory.
6619 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6620 and to read-write memory. Beware that the accessed memory corresponds
6621 to the live target and not necessarily to the current replay
6624 @kindex show record btrace
6625 @item show record btrace replay-memory-access
6626 Show the current setting of @code{replay-memory-access}.
6628 @kindex set record btrace bts
6629 @item set record btrace bts buffer-size @var{size}
6630 @itemx set record btrace bts buffer-size unlimited
6631 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6632 format. Default is 64KB.
6634 If @var{size} is a positive number, then @value{GDBN} will try to
6635 allocate a buffer of at least @var{size} bytes for each new thread
6636 that uses the btrace recording method and the @acronym{BTS} format.
6637 The actually obtained buffer size may differ from the requested
6638 @var{size}. Use the @code{info record} command to see the actual
6639 buffer size for each thread that uses the btrace recording method and
6640 the @acronym{BTS} format.
6642 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6643 allocate a buffer of 4MB.
6645 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6646 also need longer to process the branch trace data before it can be used.
6648 @item show record btrace bts buffer-size @var{size}
6649 Show the current setting of the requested ring buffer size for branch
6650 tracing in @acronym{BTS} format.
6652 @kindex set record btrace pt
6653 @item set record btrace pt buffer-size @var{size}
6654 @itemx set record btrace pt buffer-size unlimited
6655 Set the requested ring buffer size for branch tracing in Intel(R)
6656 Processor Trace format. Default is 16KB.
6658 If @var{size} is a positive number, then @value{GDBN} will try to
6659 allocate a buffer of at least @var{size} bytes for each new thread
6660 that uses the btrace recording method and the Intel(R) Processor Trace
6661 format. The actually obtained buffer size may differ from the
6662 requested @var{size}. Use the @code{info record} command to see the
6663 actual buffer size for each thread.
6665 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6666 allocate a buffer of 4MB.
6668 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6669 also need longer to process the branch trace data before it can be used.
6671 @item show record btrace pt buffer-size @var{size}
6672 Show the current setting of the requested ring buffer size for branch
6673 tracing in Intel(R) Processor Trace format.
6677 Show various statistics about the recording depending on the recording
6682 For the @code{full} recording method, it shows the state of process
6683 record and its in-memory execution log buffer, including:
6687 Whether in record mode or replay mode.
6689 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6691 Highest recorded instruction number.
6693 Current instruction about to be replayed (if in replay mode).
6695 Number of instructions contained in the execution log.
6697 Maximum number of instructions that may be contained in the execution log.
6701 For the @code{btrace} recording method, it shows:
6707 Number of instructions that have been recorded.
6709 Number of blocks of sequential control-flow formed by the recorded
6712 Whether in record mode or replay mode.
6715 For the @code{bts} recording format, it also shows:
6718 Size of the perf ring buffer.
6721 For the @code{pt} recording format, it also shows:
6724 Size of the perf ring buffer.
6728 @kindex record delete
6731 When record target runs in replay mode (``in the past''), delete the
6732 subsequent execution log and begin to record a new execution log starting
6733 from the current address. This means you will abandon the previously
6734 recorded ``future'' and begin recording a new ``future''.
6736 @kindex record instruction-history
6737 @kindex rec instruction-history
6738 @item record instruction-history
6739 Disassembles instructions from the recorded execution log. By
6740 default, ten instructions are disassembled. This can be changed using
6741 the @code{set record instruction-history-size} command. Instructions
6742 are printed in execution order.
6744 It can also print mixed source+disassembly if you specify the the
6745 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6746 as well as in symbolic form by specifying the @code{/r} modifier.
6748 The current position marker is printed for the instruction at the
6749 current program counter value. This instruction can appear multiple
6750 times in the trace and the current position marker will be printed
6751 every time. To omit the current position marker, specify the
6754 To better align the printed instructions when the trace contains
6755 instructions from more than one function, the function name may be
6756 omitted by specifying the @code{/f} modifier.
6758 Speculatively executed instructions are prefixed with @samp{?}. This
6759 feature is not available for all recording formats.
6761 There are several ways to specify what part of the execution log to
6765 @item record instruction-history @var{insn}
6766 Disassembles ten instructions starting from instruction number
6769 @item record instruction-history @var{insn}, +/-@var{n}
6770 Disassembles @var{n} instructions around instruction number
6771 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6772 @var{n} instructions after instruction number @var{insn}. If
6773 @var{n} is preceded with @code{-}, disassembles @var{n}
6774 instructions before instruction number @var{insn}.
6776 @item record instruction-history
6777 Disassembles ten more instructions after the last disassembly.
6779 @item record instruction-history -
6780 Disassembles ten more instructions before the last disassembly.
6782 @item record instruction-history @var{begin}, @var{end}
6783 Disassembles instructions beginning with instruction number
6784 @var{begin} until instruction number @var{end}. The instruction
6785 number @var{end} is included.
6788 This command may not be available for all recording methods.
6791 @item set record instruction-history-size @var{size}
6792 @itemx set record instruction-history-size unlimited
6793 Define how many instructions to disassemble in the @code{record
6794 instruction-history} command. The default value is 10.
6795 A @var{size} of @code{unlimited} means unlimited instructions.
6798 @item show record instruction-history-size
6799 Show how many instructions to disassemble in the @code{record
6800 instruction-history} command.
6802 @kindex record function-call-history
6803 @kindex rec function-call-history
6804 @item record function-call-history
6805 Prints the execution history at function granularity. It prints one
6806 line for each sequence of instructions that belong to the same
6807 function giving the name of that function, the source lines
6808 for this instruction sequence (if the @code{/l} modifier is
6809 specified), and the instructions numbers that form the sequence (if
6810 the @code{/i} modifier is specified). The function names are indented
6811 to reflect the call stack depth if the @code{/c} modifier is
6812 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6816 (@value{GDBP}) @b{list 1, 10}
6827 (@value{GDBP}) @b{record function-call-history /ilc}
6828 1 bar inst 1,4 at foo.c:6,8
6829 2 foo inst 5,10 at foo.c:2,3
6830 3 bar inst 11,13 at foo.c:9,10
6833 By default, ten lines are printed. This can be changed using the
6834 @code{set record function-call-history-size} command. Functions are
6835 printed in execution order. There are several ways to specify what
6839 @item record function-call-history @var{func}
6840 Prints ten functions starting from function number @var{func}.
6842 @item record function-call-history @var{func}, +/-@var{n}
6843 Prints @var{n} functions around function number @var{func}. If
6844 @var{n} is preceded with @code{+}, prints @var{n} functions after
6845 function number @var{func}. If @var{n} is preceded with @code{-},
6846 prints @var{n} functions before function number @var{func}.
6848 @item record function-call-history
6849 Prints ten more functions after the last ten-line print.
6851 @item record function-call-history -
6852 Prints ten more functions before the last ten-line print.
6854 @item record function-call-history @var{begin}, @var{end}
6855 Prints functions beginning with function number @var{begin} until
6856 function number @var{end}. The function number @var{end} is included.
6859 This command may not be available for all recording methods.
6861 @item set record function-call-history-size @var{size}
6862 @itemx set record function-call-history-size unlimited
6863 Define how many lines to print in the
6864 @code{record function-call-history} command. The default value is 10.
6865 A size of @code{unlimited} means unlimited lines.
6867 @item show record function-call-history-size
6868 Show how many lines to print in the
6869 @code{record function-call-history} command.
6874 @chapter Examining the Stack
6876 When your program has stopped, the first thing you need to know is where it
6877 stopped and how it got there.
6880 Each time your program performs a function call, information about the call
6882 That information includes the location of the call in your program,
6883 the arguments of the call,
6884 and the local variables of the function being called.
6885 The information is saved in a block of data called a @dfn{stack frame}.
6886 The stack frames are allocated in a region of memory called the @dfn{call
6889 When your program stops, the @value{GDBN} commands for examining the
6890 stack allow you to see all of this information.
6892 @cindex selected frame
6893 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6894 @value{GDBN} commands refer implicitly to the selected frame. In
6895 particular, whenever you ask @value{GDBN} for the value of a variable in
6896 your program, the value is found in the selected frame. There are
6897 special @value{GDBN} commands to select whichever frame you are
6898 interested in. @xref{Selection, ,Selecting a Frame}.
6900 When your program stops, @value{GDBN} automatically selects the
6901 currently executing frame and describes it briefly, similar to the
6902 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6905 * Frames:: Stack frames
6906 * Backtrace:: Backtraces
6907 * Frame Filter Management:: Managing frame filters
6908 * Selection:: Selecting a frame
6909 * Frame Info:: Information on a frame
6914 @section Stack Frames
6916 @cindex frame, definition
6918 The call stack is divided up into contiguous pieces called @dfn{stack
6919 frames}, or @dfn{frames} for short; each frame is the data associated
6920 with one call to one function. The frame contains the arguments given
6921 to the function, the function's local variables, and the address at
6922 which the function is executing.
6924 @cindex initial frame
6925 @cindex outermost frame
6926 @cindex innermost frame
6927 When your program is started, the stack has only one frame, that of the
6928 function @code{main}. This is called the @dfn{initial} frame or the
6929 @dfn{outermost} frame. Each time a function is called, a new frame is
6930 made. Each time a function returns, the frame for that function invocation
6931 is eliminated. If a function is recursive, there can be many frames for
6932 the same function. The frame for the function in which execution is
6933 actually occurring is called the @dfn{innermost} frame. This is the most
6934 recently created of all the stack frames that still exist.
6936 @cindex frame pointer
6937 Inside your program, stack frames are identified by their addresses. A
6938 stack frame consists of many bytes, each of which has its own address; each
6939 kind of computer has a convention for choosing one byte whose
6940 address serves as the address of the frame. Usually this address is kept
6941 in a register called the @dfn{frame pointer register}
6942 (@pxref{Registers, $fp}) while execution is going on in that frame.
6944 @cindex frame number
6945 @value{GDBN} assigns numbers to all existing stack frames, starting with
6946 zero for the innermost frame, one for the frame that called it,
6947 and so on upward. These numbers do not really exist in your program;
6948 they are assigned by @value{GDBN} to give you a way of designating stack
6949 frames in @value{GDBN} commands.
6951 @c The -fomit-frame-pointer below perennially causes hbox overflow
6952 @c underflow problems.
6953 @cindex frameless execution
6954 Some compilers provide a way to compile functions so that they operate
6955 without stack frames. (For example, the @value{NGCC} option
6957 @samp{-fomit-frame-pointer}
6959 generates functions without a frame.)
6960 This is occasionally done with heavily used library functions to save
6961 the frame setup time. @value{GDBN} has limited facilities for dealing
6962 with these function invocations. If the innermost function invocation
6963 has no stack frame, @value{GDBN} nevertheless regards it as though
6964 it had a separate frame, which is numbered zero as usual, allowing
6965 correct tracing of the function call chain. However, @value{GDBN} has
6966 no provision for frameless functions elsewhere in the stack.
6972 @cindex call stack traces
6973 A backtrace is a summary of how your program got where it is. It shows one
6974 line per frame, for many frames, starting with the currently executing
6975 frame (frame zero), followed by its caller (frame one), and on up the
6978 @anchor{backtrace-command}
6981 @kindex bt @r{(@code{backtrace})}
6984 Print a backtrace of the entire stack: one line per frame for all
6985 frames in the stack.
6987 You can stop the backtrace at any time by typing the system interrupt
6988 character, normally @kbd{Ctrl-c}.
6990 @item backtrace @var{n}
6992 Similar, but print only the innermost @var{n} frames.
6994 @item backtrace -@var{n}
6996 Similar, but print only the outermost @var{n} frames.
6998 @item backtrace full
7000 @itemx bt full @var{n}
7001 @itemx bt full -@var{n}
7002 Print the values of the local variables also. As described above,
7003 @var{n} specifies the number of frames to print.
7005 @item backtrace no-filters
7006 @itemx bt no-filters
7007 @itemx bt no-filters @var{n}
7008 @itemx bt no-filters -@var{n}
7009 @itemx bt no-filters full
7010 @itemx bt no-filters full @var{n}
7011 @itemx bt no-filters full -@var{n}
7012 Do not run Python frame filters on this backtrace. @xref{Frame
7013 Filter API}, for more information. Additionally use @ref{disable
7014 frame-filter all} to turn off all frame filters. This is only
7015 relevant when @value{GDBN} has been configured with @code{Python}
7021 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7022 are additional aliases for @code{backtrace}.
7024 @cindex multiple threads, backtrace
7025 In a multi-threaded program, @value{GDBN} by default shows the
7026 backtrace only for the current thread. To display the backtrace for
7027 several or all of the threads, use the command @code{thread apply}
7028 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7029 apply all backtrace}, @value{GDBN} will display the backtrace for all
7030 the threads; this is handy when you debug a core dump of a
7031 multi-threaded program.
7033 Each line in the backtrace shows the frame number and the function name.
7034 The program counter value is also shown---unless you use @code{set
7035 print address off}. The backtrace also shows the source file name and
7036 line number, as well as the arguments to the function. The program
7037 counter value is omitted if it is at the beginning of the code for that
7040 Here is an example of a backtrace. It was made with the command
7041 @samp{bt 3}, so it shows the innermost three frames.
7045 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7047 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7048 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7050 (More stack frames follow...)
7055 The display for frame zero does not begin with a program counter
7056 value, indicating that your program has stopped at the beginning of the
7057 code for line @code{993} of @code{builtin.c}.
7060 The value of parameter @code{data} in frame 1 has been replaced by
7061 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7062 only if it is a scalar (integer, pointer, enumeration, etc). See command
7063 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7064 on how to configure the way function parameter values are printed.
7066 @cindex optimized out, in backtrace
7067 @cindex function call arguments, optimized out
7068 If your program was compiled with optimizations, some compilers will
7069 optimize away arguments passed to functions if those arguments are
7070 never used after the call. Such optimizations generate code that
7071 passes arguments through registers, but doesn't store those arguments
7072 in the stack frame. @value{GDBN} has no way of displaying such
7073 arguments in stack frames other than the innermost one. Here's what
7074 such a backtrace might look like:
7078 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7080 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7081 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7083 (More stack frames follow...)
7088 The values of arguments that were not saved in their stack frames are
7089 shown as @samp{<optimized out>}.
7091 If you need to display the values of such optimized-out arguments,
7092 either deduce that from other variables whose values depend on the one
7093 you are interested in, or recompile without optimizations.
7095 @cindex backtrace beyond @code{main} function
7096 @cindex program entry point
7097 @cindex startup code, and backtrace
7098 Most programs have a standard user entry point---a place where system
7099 libraries and startup code transition into user code. For C this is
7100 @code{main}@footnote{
7101 Note that embedded programs (the so-called ``free-standing''
7102 environment) are not required to have a @code{main} function as the
7103 entry point. They could even have multiple entry points.}.
7104 When @value{GDBN} finds the entry function in a backtrace
7105 it will terminate the backtrace, to avoid tracing into highly
7106 system-specific (and generally uninteresting) code.
7108 If you need to examine the startup code, or limit the number of levels
7109 in a backtrace, you can change this behavior:
7112 @item set backtrace past-main
7113 @itemx set backtrace past-main on
7114 @kindex set backtrace
7115 Backtraces will continue past the user entry point.
7117 @item set backtrace past-main off
7118 Backtraces will stop when they encounter the user entry point. This is the
7121 @item show backtrace past-main
7122 @kindex show backtrace
7123 Display the current user entry point backtrace policy.
7125 @item set backtrace past-entry
7126 @itemx set backtrace past-entry on
7127 Backtraces will continue past the internal entry point of an application.
7128 This entry point is encoded by the linker when the application is built,
7129 and is likely before the user entry point @code{main} (or equivalent) is called.
7131 @item set backtrace past-entry off
7132 Backtraces will stop when they encounter the internal entry point of an
7133 application. This is the default.
7135 @item show backtrace past-entry
7136 Display the current internal entry point backtrace policy.
7138 @item set backtrace limit @var{n}
7139 @itemx set backtrace limit 0
7140 @itemx set backtrace limit unlimited
7141 @cindex backtrace limit
7142 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7143 or zero means unlimited levels.
7145 @item show backtrace limit
7146 Display the current limit on backtrace levels.
7149 You can control how file names are displayed.
7152 @item set filename-display
7153 @itemx set filename-display relative
7154 @cindex filename-display
7155 Display file names relative to the compilation directory. This is the default.
7157 @item set filename-display basename
7158 Display only basename of a filename.
7160 @item set filename-display absolute
7161 Display an absolute filename.
7163 @item show filename-display
7164 Show the current way to display filenames.
7168 @section Selecting a Frame
7170 Most commands for examining the stack and other data in your program work on
7171 whichever stack frame is selected at the moment. Here are the commands for
7172 selecting a stack frame; all of them finish by printing a brief description
7173 of the stack frame just selected.
7176 @kindex frame@r{, selecting}
7177 @kindex f @r{(@code{frame})}
7180 Select frame number @var{n}. Recall that frame zero is the innermost
7181 (currently executing) frame, frame one is the frame that called the
7182 innermost one, and so on. The highest-numbered frame is the one for
7185 @item frame @var{stack-addr} [ @var{pc-addr} ]
7186 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7187 Select the frame at address @var{stack-addr}. This is useful mainly if the
7188 chaining of stack frames has been damaged by a bug, making it
7189 impossible for @value{GDBN} to assign numbers properly to all frames. In
7190 addition, this can be useful when your program has multiple stacks and
7191 switches between them. The optional @var{pc-addr} can also be given to
7192 specify the value of PC for the stack frame.
7196 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7197 numbers @var{n}, this advances toward the outermost frame, to higher
7198 frame numbers, to frames that have existed longer.
7201 @kindex do @r{(@code{down})}
7203 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7204 positive numbers @var{n}, this advances toward the innermost frame, to
7205 lower frame numbers, to frames that were created more recently.
7206 You may abbreviate @code{down} as @code{do}.
7209 All of these commands end by printing two lines of output describing the
7210 frame. The first line shows the frame number, the function name, the
7211 arguments, and the source file and line number of execution in that
7212 frame. The second line shows the text of that source line.
7220 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7222 10 read_input_file (argv[i]);
7226 After such a printout, the @code{list} command with no arguments
7227 prints ten lines centered on the point of execution in the frame.
7228 You can also edit the program at the point of execution with your favorite
7229 editing program by typing @code{edit}.
7230 @xref{List, ,Printing Source Lines},
7234 @kindex select-frame
7236 The @code{select-frame} command is a variant of @code{frame} that does
7237 not display the new frame after selecting it. This command is
7238 intended primarily for use in @value{GDBN} command scripts, where the
7239 output might be unnecessary and distracting.
7241 @kindex down-silently
7243 @item up-silently @var{n}
7244 @itemx down-silently @var{n}
7245 These two commands are variants of @code{up} and @code{down},
7246 respectively; they differ in that they do their work silently, without
7247 causing display of the new frame. They are intended primarily for use
7248 in @value{GDBN} command scripts, where the output might be unnecessary and
7253 @section Information About a Frame
7255 There are several other commands to print information about the selected
7261 When used without any argument, this command does not change which
7262 frame is selected, but prints a brief description of the currently
7263 selected stack frame. It can be abbreviated @code{f}. With an
7264 argument, this command is used to select a stack frame.
7265 @xref{Selection, ,Selecting a Frame}.
7268 @kindex info f @r{(@code{info frame})}
7271 This command prints a verbose description of the selected stack frame,
7276 the address of the frame
7278 the address of the next frame down (called by this frame)
7280 the address of the next frame up (caller of this frame)
7282 the language in which the source code corresponding to this frame is written
7284 the address of the frame's arguments
7286 the address of the frame's local variables
7288 the program counter saved in it (the address of execution in the caller frame)
7290 which registers were saved in the frame
7293 @noindent The verbose description is useful when
7294 something has gone wrong that has made the stack format fail to fit
7295 the usual conventions.
7297 @item info frame @var{addr}
7298 @itemx info f @var{addr}
7299 Print a verbose description of the frame at address @var{addr}, without
7300 selecting that frame. The selected frame remains unchanged by this
7301 command. This requires the same kind of address (more than one for some
7302 architectures) that you specify in the @code{frame} command.
7303 @xref{Selection, ,Selecting a Frame}.
7307 Print the arguments of the selected frame, each on a separate line.
7311 Print the local variables of the selected frame, each on a separate
7312 line. These are all variables (declared either static or automatic)
7313 accessible at the point of execution of the selected frame.
7317 @node Frame Filter Management
7318 @section Management of Frame Filters.
7319 @cindex managing frame filters
7321 Frame filters are Python based utilities to manage and decorate the
7322 output of frames. @xref{Frame Filter API}, for further information.
7324 Managing frame filters is performed by several commands available
7325 within @value{GDBN}, detailed here.
7328 @kindex info frame-filter
7329 @item info frame-filter
7330 Print a list of installed frame filters from all dictionaries, showing
7331 their name, priority and enabled status.
7333 @kindex disable frame-filter
7334 @anchor{disable frame-filter all}
7335 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7336 Disable a frame filter in the dictionary matching
7337 @var{filter-dictionary} and @var{filter-name}. The
7338 @var{filter-dictionary} may be @code{all}, @code{global},
7339 @code{progspace}, or the name of the object file where the frame filter
7340 dictionary resides. When @code{all} is specified, all frame filters
7341 across all dictionaries are disabled. The @var{filter-name} is the name
7342 of the frame filter and is used when @code{all} is not the option for
7343 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7344 may be enabled again later.
7346 @kindex enable frame-filter
7347 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7348 Enable a frame filter in the dictionary matching
7349 @var{filter-dictionary} and @var{filter-name}. The
7350 @var{filter-dictionary} may be @code{all}, @code{global},
7351 @code{progspace} or the name of the object file where the frame filter
7352 dictionary resides. When @code{all} is specified, all frame filters across
7353 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7354 filter and is used when @code{all} is not the option for
7355 @var{filter-dictionary}.
7360 (gdb) info frame-filter
7362 global frame-filters:
7363 Priority Enabled Name
7364 1000 No PrimaryFunctionFilter
7367 progspace /build/test frame-filters:
7368 Priority Enabled Name
7369 100 Yes ProgspaceFilter
7371 objfile /build/test frame-filters:
7372 Priority Enabled Name
7373 999 Yes BuildProgra Filter
7375 (gdb) disable frame-filter /build/test BuildProgramFilter
7376 (gdb) info frame-filter
7378 global frame-filters:
7379 Priority Enabled Name
7380 1000 No PrimaryFunctionFilter
7383 progspace /build/test frame-filters:
7384 Priority Enabled Name
7385 100 Yes ProgspaceFilter
7387 objfile /build/test frame-filters:
7388 Priority Enabled Name
7389 999 No BuildProgramFilter
7391 (gdb) enable frame-filter global PrimaryFunctionFilter
7392 (gdb) info frame-filter
7394 global frame-filters:
7395 Priority Enabled Name
7396 1000 Yes PrimaryFunctionFilter
7399 progspace /build/test frame-filters:
7400 Priority Enabled Name
7401 100 Yes ProgspaceFilter
7403 objfile /build/test frame-filters:
7404 Priority Enabled Name
7405 999 No BuildProgramFilter
7408 @kindex set frame-filter priority
7409 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7410 Set the @var{priority} of a frame filter in the dictionary matching
7411 @var{filter-dictionary}, and the frame filter name matching
7412 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7413 @code{progspace} or the name of the object file where the frame filter
7414 dictionary resides. The @var{priority} is an integer.
7416 @kindex show frame-filter priority
7417 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7418 Show the @var{priority} of a frame filter in the dictionary matching
7419 @var{filter-dictionary}, and the frame filter name matching
7420 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7421 @code{progspace} or the name of the object file where the frame filter
7427 (gdb) info frame-filter
7429 global frame-filters:
7430 Priority Enabled Name
7431 1000 Yes PrimaryFunctionFilter
7434 progspace /build/test frame-filters:
7435 Priority Enabled Name
7436 100 Yes ProgspaceFilter
7438 objfile /build/test frame-filters:
7439 Priority Enabled Name
7440 999 No BuildProgramFilter
7442 (gdb) set frame-filter priority global Reverse 50
7443 (gdb) info frame-filter
7445 global frame-filters:
7446 Priority Enabled Name
7447 1000 Yes PrimaryFunctionFilter
7450 progspace /build/test frame-filters:
7451 Priority Enabled Name
7452 100 Yes ProgspaceFilter
7454 objfile /build/test frame-filters:
7455 Priority Enabled Name
7456 999 No BuildProgramFilter
7461 @chapter Examining Source Files
7463 @value{GDBN} can print parts of your program's source, since the debugging
7464 information recorded in the program tells @value{GDBN} what source files were
7465 used to build it. When your program stops, @value{GDBN} spontaneously prints
7466 the line where it stopped. Likewise, when you select a stack frame
7467 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7468 execution in that frame has stopped. You can print other portions of
7469 source files by explicit command.
7471 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7472 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7473 @value{GDBN} under @sc{gnu} Emacs}.
7476 * List:: Printing source lines
7477 * Specify Location:: How to specify code locations
7478 * Edit:: Editing source files
7479 * Search:: Searching source files
7480 * Source Path:: Specifying source directories
7481 * Machine Code:: Source and machine code
7485 @section Printing Source Lines
7488 @kindex l @r{(@code{list})}
7489 To print lines from a source file, use the @code{list} command
7490 (abbreviated @code{l}). By default, ten lines are printed.
7491 There are several ways to specify what part of the file you want to
7492 print; see @ref{Specify Location}, for the full list.
7494 Here are the forms of the @code{list} command most commonly used:
7497 @item list @var{linenum}
7498 Print lines centered around line number @var{linenum} in the
7499 current source file.
7501 @item list @var{function}
7502 Print lines centered around the beginning of function
7506 Print more lines. If the last lines printed were printed with a
7507 @code{list} command, this prints lines following the last lines
7508 printed; however, if the last line printed was a solitary line printed
7509 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7510 Stack}), this prints lines centered around that line.
7513 Print lines just before the lines last printed.
7516 @cindex @code{list}, how many lines to display
7517 By default, @value{GDBN} prints ten source lines with any of these forms of
7518 the @code{list} command. You can change this using @code{set listsize}:
7521 @kindex set listsize
7522 @item set listsize @var{count}
7523 @itemx set listsize unlimited
7524 Make the @code{list} command display @var{count} source lines (unless
7525 the @code{list} argument explicitly specifies some other number).
7526 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7528 @kindex show listsize
7530 Display the number of lines that @code{list} prints.
7533 Repeating a @code{list} command with @key{RET} discards the argument,
7534 so it is equivalent to typing just @code{list}. This is more useful
7535 than listing the same lines again. An exception is made for an
7536 argument of @samp{-}; that argument is preserved in repetition so that
7537 each repetition moves up in the source file.
7539 In general, the @code{list} command expects you to supply zero, one or two
7540 @dfn{locations}. Locations specify source lines; there are several ways
7541 of writing them (@pxref{Specify Location}), but the effect is always
7542 to specify some source line.
7544 Here is a complete description of the possible arguments for @code{list}:
7547 @item list @var{location}
7548 Print lines centered around the line specified by @var{location}.
7550 @item list @var{first},@var{last}
7551 Print lines from @var{first} to @var{last}. Both arguments are
7552 locations. When a @code{list} command has two locations, and the
7553 source file of the second location is omitted, this refers to
7554 the same source file as the first location.
7556 @item list ,@var{last}
7557 Print lines ending with @var{last}.
7559 @item list @var{first},
7560 Print lines starting with @var{first}.
7563 Print lines just after the lines last printed.
7566 Print lines just before the lines last printed.
7569 As described in the preceding table.
7572 @node Specify Location
7573 @section Specifying a Location
7574 @cindex specifying location
7576 @cindex source location
7579 * Linespec Locations:: Linespec locations
7580 * Explicit Locations:: Explicit locations
7581 * Address Locations:: Address locations
7584 Several @value{GDBN} commands accept arguments that specify a location
7585 of your program's code. Since @value{GDBN} is a source-level
7586 debugger, a location usually specifies some line in the source code.
7587 Locations may be specified using three different formats:
7588 linespec locations, explicit locations, or address locations.
7590 @node Linespec Locations
7591 @subsection Linespec Locations
7592 @cindex linespec locations
7594 A @dfn{linespec} is a colon-separated list of source location parameters such
7595 as file name, function name, etc. Here are all the different ways of
7596 specifying a linespec:
7600 Specifies the line number @var{linenum} of the current source file.
7603 @itemx +@var{offset}
7604 Specifies the line @var{offset} lines before or after the @dfn{current
7605 line}. For the @code{list} command, the current line is the last one
7606 printed; for the breakpoint commands, this is the line at which
7607 execution stopped in the currently selected @dfn{stack frame}
7608 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7609 used as the second of the two linespecs in a @code{list} command,
7610 this specifies the line @var{offset} lines up or down from the first
7613 @item @var{filename}:@var{linenum}
7614 Specifies the line @var{linenum} in the source file @var{filename}.
7615 If @var{filename} is a relative file name, then it will match any
7616 source file name with the same trailing components. For example, if
7617 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7618 name of @file{/build/trunk/gcc/expr.c}, but not
7619 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7621 @item @var{function}
7622 Specifies the line that begins the body of the function @var{function}.
7623 For example, in C, this is the line with the open brace.
7625 @item @var{function}:@var{label}
7626 Specifies the line where @var{label} appears in @var{function}.
7628 @item @var{filename}:@var{function}
7629 Specifies the line that begins the body of the function @var{function}
7630 in the file @var{filename}. You only need the file name with a
7631 function name to avoid ambiguity when there are identically named
7632 functions in different source files.
7635 Specifies the line at which the label named @var{label} appears
7636 in the function corresponding to the currently selected stack frame.
7637 If there is no current selected stack frame (for instance, if the inferior
7638 is not running), then @value{GDBN} will not search for a label.
7640 @cindex breakpoint at static probe point
7641 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7642 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7643 applications to embed static probes. @xref{Static Probe Points}, for more
7644 information on finding and using static probes. This form of linespec
7645 specifies the location of such a static probe.
7647 If @var{objfile} is given, only probes coming from that shared library
7648 or executable matching @var{objfile} as a regular expression are considered.
7649 If @var{provider} is given, then only probes from that provider are considered.
7650 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7651 each one of those probes.
7654 @node Explicit Locations
7655 @subsection Explicit Locations
7656 @cindex explicit locations
7658 @dfn{Explicit locations} allow the user to directly specify the source
7659 location's parameters using option-value pairs.
7661 Explicit locations are useful when several functions, labels, or
7662 file names have the same name (base name for files) in the program's
7663 sources. In these cases, explicit locations point to the source
7664 line you meant more accurately and unambiguously. Also, using
7665 explicit locations might be faster in large programs.
7667 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7668 defined in the file named @file{foo} or the label @code{bar} in a function
7669 named @code{foo}. @value{GDBN} must search either the file system or
7670 the symbol table to know.
7672 The list of valid explicit location options is summarized in the
7676 @item -source @var{filename}
7677 The value specifies the source file name. To differentiate between
7678 files with the same base name, prepend as many directories as is necessary
7679 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7680 @value{GDBN} will use the first file it finds with the given base
7681 name. This option requires the use of either @code{-function} or @code{-line}.
7683 @item -function @var{function}
7684 The value specifies the name of a function. Operations
7685 on function locations unmodified by other options (such as @code{-label}
7686 or @code{-line}) refer to the line that begins the body of the function.
7687 In C, for example, this is the line with the open brace.
7689 @item -label @var{label}
7690 The value specifies the name of a label. When the function
7691 name is not specified, the label is searched in the function of the currently
7692 selected stack frame.
7694 @item -line @var{number}
7695 The value specifies a line offset for the location. The offset may either
7696 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7697 the command. When specified without any other options, the line offset is
7698 relative to the current line.
7701 Explicit location options may be abbreviated by omitting any non-unique
7702 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7704 @node Address Locations
7705 @subsection Address Locations
7706 @cindex address locations
7708 @dfn{Address locations} indicate a specific program address. They have
7709 the generalized form *@var{address}.
7711 For line-oriented commands, such as @code{list} and @code{edit}, this
7712 specifies a source line that contains @var{address}. For @code{break} and
7713 other breakpoint-oriented commands, this can be used to set breakpoints in
7714 parts of your program which do not have debugging information or
7717 Here @var{address} may be any expression valid in the current working
7718 language (@pxref{Languages, working language}) that specifies a code
7719 address. In addition, as a convenience, @value{GDBN} extends the
7720 semantics of expressions used in locations to cover several situations
7721 that frequently occur during debugging. Here are the various forms
7725 @item @var{expression}
7726 Any expression valid in the current working language.
7728 @item @var{funcaddr}
7729 An address of a function or procedure derived from its name. In C,
7730 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7731 simply the function's name @var{function} (and actually a special case
7732 of a valid expression). In Pascal and Modula-2, this is
7733 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7734 (although the Pascal form also works).
7736 This form specifies the address of the function's first instruction,
7737 before the stack frame and arguments have been set up.
7739 @item '@var{filename}':@var{funcaddr}
7740 Like @var{funcaddr} above, but also specifies the name of the source
7741 file explicitly. This is useful if the name of the function does not
7742 specify the function unambiguously, e.g., if there are several
7743 functions with identical names in different source files.
7747 @section Editing Source Files
7748 @cindex editing source files
7751 @kindex e @r{(@code{edit})}
7752 To edit the lines in a source file, use the @code{edit} command.
7753 The editing program of your choice
7754 is invoked with the current line set to
7755 the active line in the program.
7756 Alternatively, there are several ways to specify what part of the file you
7757 want to print if you want to see other parts of the program:
7760 @item edit @var{location}
7761 Edit the source file specified by @code{location}. Editing starts at
7762 that @var{location}, e.g., at the specified source line of the
7763 specified file. @xref{Specify Location}, for all the possible forms
7764 of the @var{location} argument; here are the forms of the @code{edit}
7765 command most commonly used:
7768 @item edit @var{number}
7769 Edit the current source file with @var{number} as the active line number.
7771 @item edit @var{function}
7772 Edit the file containing @var{function} at the beginning of its definition.
7777 @subsection Choosing your Editor
7778 You can customize @value{GDBN} to use any editor you want
7780 The only restriction is that your editor (say @code{ex}), recognizes the
7781 following command-line syntax:
7783 ex +@var{number} file
7785 The optional numeric value +@var{number} specifies the number of the line in
7786 the file where to start editing.}.
7787 By default, it is @file{@value{EDITOR}}, but you can change this
7788 by setting the environment variable @code{EDITOR} before using
7789 @value{GDBN}. For example, to configure @value{GDBN} to use the
7790 @code{vi} editor, you could use these commands with the @code{sh} shell:
7796 or in the @code{csh} shell,
7798 setenv EDITOR /usr/bin/vi
7803 @section Searching Source Files
7804 @cindex searching source files
7806 There are two commands for searching through the current source file for a
7811 @kindex forward-search
7812 @kindex fo @r{(@code{forward-search})}
7813 @item forward-search @var{regexp}
7814 @itemx search @var{regexp}
7815 The command @samp{forward-search @var{regexp}} checks each line,
7816 starting with the one following the last line listed, for a match for
7817 @var{regexp}. It lists the line that is found. You can use the
7818 synonym @samp{search @var{regexp}} or abbreviate the command name as
7821 @kindex reverse-search
7822 @item reverse-search @var{regexp}
7823 The command @samp{reverse-search @var{regexp}} checks each line, starting
7824 with the one before the last line listed and going backward, for a match
7825 for @var{regexp}. It lists the line that is found. You can abbreviate
7826 this command as @code{rev}.
7830 @section Specifying Source Directories
7833 @cindex directories for source files
7834 Executable programs sometimes do not record the directories of the source
7835 files from which they were compiled, just the names. Even when they do,
7836 the directories could be moved between the compilation and your debugging
7837 session. @value{GDBN} has a list of directories to search for source files;
7838 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7839 it tries all the directories in the list, in the order they are present
7840 in the list, until it finds a file with the desired name.
7842 For example, suppose an executable references the file
7843 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7844 @file{/mnt/cross}. The file is first looked up literally; if this
7845 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7846 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7847 message is printed. @value{GDBN} does not look up the parts of the
7848 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7849 Likewise, the subdirectories of the source path are not searched: if
7850 the source path is @file{/mnt/cross}, and the binary refers to
7851 @file{foo.c}, @value{GDBN} would not find it under
7852 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7854 Plain file names, relative file names with leading directories, file
7855 names containing dots, etc.@: are all treated as described above; for
7856 instance, if the source path is @file{/mnt/cross}, and the source file
7857 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7858 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7859 that---@file{/mnt/cross/foo.c}.
7861 Note that the executable search path is @emph{not} used to locate the
7864 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7865 any information it has cached about where source files are found and where
7866 each line is in the file.
7870 When you start @value{GDBN}, its source path includes only @samp{cdir}
7871 and @samp{cwd}, in that order.
7872 To add other directories, use the @code{directory} command.
7874 The search path is used to find both program source files and @value{GDBN}
7875 script files (read using the @samp{-command} option and @samp{source} command).
7877 In addition to the source path, @value{GDBN} provides a set of commands
7878 that manage a list of source path substitution rules. A @dfn{substitution
7879 rule} specifies how to rewrite source directories stored in the program's
7880 debug information in case the sources were moved to a different
7881 directory between compilation and debugging. A rule is made of
7882 two strings, the first specifying what needs to be rewritten in
7883 the path, and the second specifying how it should be rewritten.
7884 In @ref{set substitute-path}, we name these two parts @var{from} and
7885 @var{to} respectively. @value{GDBN} does a simple string replacement
7886 of @var{from} with @var{to} at the start of the directory part of the
7887 source file name, and uses that result instead of the original file
7888 name to look up the sources.
7890 Using the previous example, suppose the @file{foo-1.0} tree has been
7891 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7892 @value{GDBN} to replace @file{/usr/src} in all source path names with
7893 @file{/mnt/cross}. The first lookup will then be
7894 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7895 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7896 substitution rule, use the @code{set substitute-path} command
7897 (@pxref{set substitute-path}).
7899 To avoid unexpected substitution results, a rule is applied only if the
7900 @var{from} part of the directory name ends at a directory separator.
7901 For instance, a rule substituting @file{/usr/source} into
7902 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7903 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7904 is applied only at the beginning of the directory name, this rule will
7905 not be applied to @file{/root/usr/source/baz.c} either.
7907 In many cases, you can achieve the same result using the @code{directory}
7908 command. However, @code{set substitute-path} can be more efficient in
7909 the case where the sources are organized in a complex tree with multiple
7910 subdirectories. With the @code{directory} command, you need to add each
7911 subdirectory of your project. If you moved the entire tree while
7912 preserving its internal organization, then @code{set substitute-path}
7913 allows you to direct the debugger to all the sources with one single
7916 @code{set substitute-path} is also more than just a shortcut command.
7917 The source path is only used if the file at the original location no
7918 longer exists. On the other hand, @code{set substitute-path} modifies
7919 the debugger behavior to look at the rewritten location instead. So, if
7920 for any reason a source file that is not relevant to your executable is
7921 located at the original location, a substitution rule is the only
7922 method available to point @value{GDBN} at the new location.
7924 @cindex @samp{--with-relocated-sources}
7925 @cindex default source path substitution
7926 You can configure a default source path substitution rule by
7927 configuring @value{GDBN} with the
7928 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7929 should be the name of a directory under @value{GDBN}'s configured
7930 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7931 directory names in debug information under @var{dir} will be adjusted
7932 automatically if the installed @value{GDBN} is moved to a new
7933 location. This is useful if @value{GDBN}, libraries or executables
7934 with debug information and corresponding source code are being moved
7938 @item directory @var{dirname} @dots{}
7939 @item dir @var{dirname} @dots{}
7940 Add directory @var{dirname} to the front of the source path. Several
7941 directory names may be given to this command, separated by @samp{:}
7942 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7943 part of absolute file names) or
7944 whitespace. You may specify a directory that is already in the source
7945 path; this moves it forward, so @value{GDBN} searches it sooner.
7949 @vindex $cdir@r{, convenience variable}
7950 @vindex $cwd@r{, convenience variable}
7951 @cindex compilation directory
7952 @cindex current directory
7953 @cindex working directory
7954 @cindex directory, current
7955 @cindex directory, compilation
7956 You can use the string @samp{$cdir} to refer to the compilation
7957 directory (if one is recorded), and @samp{$cwd} to refer to the current
7958 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7959 tracks the current working directory as it changes during your @value{GDBN}
7960 session, while the latter is immediately expanded to the current
7961 directory at the time you add an entry to the source path.
7964 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7966 @c RET-repeat for @code{directory} is explicitly disabled, but since
7967 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7969 @item set directories @var{path-list}
7970 @kindex set directories
7971 Set the source path to @var{path-list}.
7972 @samp{$cdir:$cwd} are added if missing.
7974 @item show directories
7975 @kindex show directories
7976 Print the source path: show which directories it contains.
7978 @anchor{set substitute-path}
7979 @item set substitute-path @var{from} @var{to}
7980 @kindex set substitute-path
7981 Define a source path substitution rule, and add it at the end of the
7982 current list of existing substitution rules. If a rule with the same
7983 @var{from} was already defined, then the old rule is also deleted.
7985 For example, if the file @file{/foo/bar/baz.c} was moved to
7986 @file{/mnt/cross/baz.c}, then the command
7989 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
7993 will tell @value{GDBN} to replace @samp{/foo/bar} with
7994 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7995 @file{baz.c} even though it was moved.
7997 In the case when more than one substitution rule have been defined,
7998 the rules are evaluated one by one in the order where they have been
7999 defined. The first one matching, if any, is selected to perform
8002 For instance, if we had entered the following commands:
8005 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8006 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8010 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8011 @file{/mnt/include/defs.h} by using the first rule. However, it would
8012 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8013 @file{/mnt/src/lib/foo.c}.
8016 @item unset substitute-path [path]
8017 @kindex unset substitute-path
8018 If a path is specified, search the current list of substitution rules
8019 for a rule that would rewrite that path. Delete that rule if found.
8020 A warning is emitted by the debugger if no rule could be found.
8022 If no path is specified, then all substitution rules are deleted.
8024 @item show substitute-path [path]
8025 @kindex show substitute-path
8026 If a path is specified, then print the source path substitution rule
8027 which would rewrite that path, if any.
8029 If no path is specified, then print all existing source path substitution
8034 If your source path is cluttered with directories that are no longer of
8035 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8036 versions of source. You can correct the situation as follows:
8040 Use @code{directory} with no argument to reset the source path to its default value.
8043 Use @code{directory} with suitable arguments to reinstall the
8044 directories you want in the source path. You can add all the
8045 directories in one command.
8049 @section Source and Machine Code
8050 @cindex source line and its code address
8052 You can use the command @code{info line} to map source lines to program
8053 addresses (and vice versa), and the command @code{disassemble} to display
8054 a range of addresses as machine instructions. You can use the command
8055 @code{set disassemble-next-line} to set whether to disassemble next
8056 source line when execution stops. When run under @sc{gnu} Emacs
8057 mode, the @code{info line} command causes the arrow to point to the
8058 line specified. Also, @code{info line} prints addresses in symbolic form as
8063 @item info line @var{location}
8064 Print the starting and ending addresses of the compiled code for
8065 source line @var{location}. You can specify source lines in any of
8066 the ways documented in @ref{Specify Location}.
8069 For example, we can use @code{info line} to discover the location of
8070 the object code for the first line of function
8071 @code{m4_changequote}:
8073 @c FIXME: I think this example should also show the addresses in
8074 @c symbolic form, as they usually would be displayed.
8076 (@value{GDBP}) info line m4_changequote
8077 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8081 @cindex code address and its source line
8082 We can also inquire (using @code{*@var{addr}} as the form for
8083 @var{location}) what source line covers a particular address:
8085 (@value{GDBP}) info line *0x63ff
8086 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8089 @cindex @code{$_} and @code{info line}
8090 @cindex @code{x} command, default address
8091 @kindex x@r{(examine), and} info line
8092 After @code{info line}, the default address for the @code{x} command
8093 is changed to the starting address of the line, so that @samp{x/i} is
8094 sufficient to begin examining the machine code (@pxref{Memory,
8095 ,Examining Memory}). Also, this address is saved as the value of the
8096 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8101 @cindex assembly instructions
8102 @cindex instructions, assembly
8103 @cindex machine instructions
8104 @cindex listing machine instructions
8106 @itemx disassemble /m
8107 @itemx disassemble /s
8108 @itemx disassemble /r
8109 This specialized command dumps a range of memory as machine
8110 instructions. It can also print mixed source+disassembly by specifying
8111 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8112 as well as in symbolic form by specifying the @code{/r} modifier.
8113 The default memory range is the function surrounding the
8114 program counter of the selected frame. A single argument to this
8115 command is a program counter value; @value{GDBN} dumps the function
8116 surrounding this value. When two arguments are given, they should
8117 be separated by a comma, possibly surrounded by whitespace. The
8118 arguments specify a range of addresses to dump, in one of two forms:
8121 @item @var{start},@var{end}
8122 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8123 @item @var{start},+@var{length}
8124 the addresses from @var{start} (inclusive) to
8125 @code{@var{start}+@var{length}} (exclusive).
8129 When 2 arguments are specified, the name of the function is also
8130 printed (since there could be several functions in the given range).
8132 The argument(s) can be any expression yielding a numeric value, such as
8133 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8135 If the range of memory being disassembled contains current program counter,
8136 the instruction at that location is shown with a @code{=>} marker.
8139 The following example shows the disassembly of a range of addresses of
8140 HP PA-RISC 2.0 code:
8143 (@value{GDBP}) disas 0x32c4, 0x32e4
8144 Dump of assembler code from 0x32c4 to 0x32e4:
8145 0x32c4 <main+204>: addil 0,dp
8146 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8147 0x32cc <main+212>: ldil 0x3000,r31
8148 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8149 0x32d4 <main+220>: ldo 0(r31),rp
8150 0x32d8 <main+224>: addil -0x800,dp
8151 0x32dc <main+228>: ldo 0x588(r1),r26
8152 0x32e0 <main+232>: ldil 0x3000,r31
8153 End of assembler dump.
8156 Here is an example showing mixed source+assembly for Intel x86
8157 with @code{/m} or @code{/s}, when the program is stopped just after
8158 function prologue in a non-optimized function with no inline code.
8161 (@value{GDBP}) disas /m main
8162 Dump of assembler code for function main:
8164 0x08048330 <+0>: push %ebp
8165 0x08048331 <+1>: mov %esp,%ebp
8166 0x08048333 <+3>: sub $0x8,%esp
8167 0x08048336 <+6>: and $0xfffffff0,%esp
8168 0x08048339 <+9>: sub $0x10,%esp
8170 6 printf ("Hello.\n");
8171 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8172 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8176 0x08048348 <+24>: mov $0x0,%eax
8177 0x0804834d <+29>: leave
8178 0x0804834e <+30>: ret
8180 End of assembler dump.
8183 The @code{/m} option is deprecated as its output is not useful when
8184 there is either inlined code or re-ordered code.
8185 The @code{/s} option is the preferred choice.
8186 Here is an example for AMD x86-64 showing the difference between
8187 @code{/m} output and @code{/s} output.
8188 This example has one inline function defined in a header file,
8189 and the code is compiled with @samp{-O2} optimization.
8190 Note how the @code{/m} output is missing the disassembly of
8191 several instructions that are present in the @code{/s} output.
8221 (@value{GDBP}) disas /m main
8222 Dump of assembler code for function main:
8226 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8227 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8231 0x000000000040041d <+29>: xor %eax,%eax
8232 0x000000000040041f <+31>: retq
8233 0x0000000000400420 <+32>: add %eax,%eax
8234 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8236 End of assembler dump.
8237 (@value{GDBP}) disas /s main
8238 Dump of assembler code for function main:
8242 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8246 0x0000000000400406 <+6>: test %eax,%eax
8247 0x0000000000400408 <+8>: js 0x400420 <main+32>
8252 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8253 0x000000000040040d <+13>: test %eax,%eax
8254 0x000000000040040f <+15>: mov $0x1,%eax
8255 0x0000000000400414 <+20>: cmovne %edx,%eax
8259 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8263 0x000000000040041d <+29>: xor %eax,%eax
8264 0x000000000040041f <+31>: retq
8268 0x0000000000400420 <+32>: add %eax,%eax
8269 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8270 End of assembler dump.
8273 Here is another example showing raw instructions in hex for AMD x86-64,
8276 (gdb) disas /r 0x400281,+10
8277 Dump of assembler code from 0x400281 to 0x40028b:
8278 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8279 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8280 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8281 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8282 End of assembler dump.
8285 Addresses cannot be specified as a location (@pxref{Specify Location}).
8286 So, for example, if you want to disassemble function @code{bar}
8287 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8288 and not @samp{disassemble foo.c:bar}.
8290 Some architectures have more than one commonly-used set of instruction
8291 mnemonics or other syntax.
8293 For programs that were dynamically linked and use shared libraries,
8294 instructions that call functions or branch to locations in the shared
8295 libraries might show a seemingly bogus location---it's actually a
8296 location of the relocation table. On some architectures, @value{GDBN}
8297 might be able to resolve these to actual function names.
8300 @kindex set disassembly-flavor
8301 @cindex Intel disassembly flavor
8302 @cindex AT&T disassembly flavor
8303 @item set disassembly-flavor @var{instruction-set}
8304 Select the instruction set to use when disassembling the
8305 program via the @code{disassemble} or @code{x/i} commands.
8307 Currently this command is only defined for the Intel x86 family. You
8308 can set @var{instruction-set} to either @code{intel} or @code{att}.
8309 The default is @code{att}, the AT&T flavor used by default by Unix
8310 assemblers for x86-based targets.
8312 @kindex show disassembly-flavor
8313 @item show disassembly-flavor
8314 Show the current setting of the disassembly flavor.
8318 @kindex set disassemble-next-line
8319 @kindex show disassemble-next-line
8320 @item set disassemble-next-line
8321 @itemx show disassemble-next-line
8322 Control whether or not @value{GDBN} will disassemble the next source
8323 line or instruction when execution stops. If ON, @value{GDBN} will
8324 display disassembly of the next source line when execution of the
8325 program being debugged stops. This is @emph{in addition} to
8326 displaying the source line itself, which @value{GDBN} always does if
8327 possible. If the next source line cannot be displayed for some reason
8328 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8329 info in the debug info), @value{GDBN} will display disassembly of the
8330 next @emph{instruction} instead of showing the next source line. If
8331 AUTO, @value{GDBN} will display disassembly of next instruction only
8332 if the source line cannot be displayed. This setting causes
8333 @value{GDBN} to display some feedback when you step through a function
8334 with no line info or whose source file is unavailable. The default is
8335 OFF, which means never display the disassembly of the next line or
8341 @chapter Examining Data
8343 @cindex printing data
8344 @cindex examining data
8347 The usual way to examine data in your program is with the @code{print}
8348 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8349 evaluates and prints the value of an expression of the language your
8350 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8351 Different Languages}). It may also print the expression using a
8352 Python-based pretty-printer (@pxref{Pretty Printing}).
8355 @item print @var{expr}
8356 @itemx print /@var{f} @var{expr}
8357 @var{expr} is an expression (in the source language). By default the
8358 value of @var{expr} is printed in a format appropriate to its data type;
8359 you can choose a different format by specifying @samp{/@var{f}}, where
8360 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8364 @itemx print /@var{f}
8365 @cindex reprint the last value
8366 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8367 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8368 conveniently inspect the same value in an alternative format.
8371 A more low-level way of examining data is with the @code{x} command.
8372 It examines data in memory at a specified address and prints it in a
8373 specified format. @xref{Memory, ,Examining Memory}.
8375 If you are interested in information about types, or about how the
8376 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8377 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8380 @cindex exploring hierarchical data structures
8382 Another way of examining values of expressions and type information is
8383 through the Python extension command @code{explore} (available only if
8384 the @value{GDBN} build is configured with @code{--with-python}). It
8385 offers an interactive way to start at the highest level (or, the most
8386 abstract level) of the data type of an expression (or, the data type
8387 itself) and explore all the way down to leaf scalar values/fields
8388 embedded in the higher level data types.
8391 @item explore @var{arg}
8392 @var{arg} is either an expression (in the source language), or a type
8393 visible in the current context of the program being debugged.
8396 The working of the @code{explore} command can be illustrated with an
8397 example. If a data type @code{struct ComplexStruct} is defined in your
8407 struct ComplexStruct
8409 struct SimpleStruct *ss_p;
8415 followed by variable declarations as
8418 struct SimpleStruct ss = @{ 10, 1.11 @};
8419 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8423 then, the value of the variable @code{cs} can be explored using the
8424 @code{explore} command as follows.
8428 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8429 the following fields:
8431 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8432 arr = <Enter 1 to explore this field of type `int [10]'>
8434 Enter the field number of choice:
8438 Since the fields of @code{cs} are not scalar values, you are being
8439 prompted to chose the field you want to explore. Let's say you choose
8440 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8441 pointer, you will be asked if it is pointing to a single value. From
8442 the declaration of @code{cs} above, it is indeed pointing to a single
8443 value, hence you enter @code{y}. If you enter @code{n}, then you will
8444 be asked if it were pointing to an array of values, in which case this
8445 field will be explored as if it were an array.
8448 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8449 Continue exploring it as a pointer to a single value [y/n]: y
8450 The value of `*(cs.ss_p)' is a struct/class of type `struct
8451 SimpleStruct' with the following fields:
8453 i = 10 .. (Value of type `int')
8454 d = 1.1100000000000001 .. (Value of type `double')
8456 Press enter to return to parent value:
8460 If the field @code{arr} of @code{cs} was chosen for exploration by
8461 entering @code{1} earlier, then since it is as array, you will be
8462 prompted to enter the index of the element in the array that you want
8466 `cs.arr' is an array of `int'.
8467 Enter the index of the element you want to explore in `cs.arr': 5
8469 `(cs.arr)[5]' is a scalar value of type `int'.
8473 Press enter to return to parent value:
8476 In general, at any stage of exploration, you can go deeper towards the
8477 leaf values by responding to the prompts appropriately, or hit the
8478 return key to return to the enclosing data structure (the @i{higher}
8479 level data structure).
8481 Similar to exploring values, you can use the @code{explore} command to
8482 explore types. Instead of specifying a value (which is typically a
8483 variable name or an expression valid in the current context of the
8484 program being debugged), you specify a type name. If you consider the
8485 same example as above, your can explore the type
8486 @code{struct ComplexStruct} by passing the argument
8487 @code{struct ComplexStruct} to the @code{explore} command.
8490 (gdb) explore struct ComplexStruct
8494 By responding to the prompts appropriately in the subsequent interactive
8495 session, you can explore the type @code{struct ComplexStruct} in a
8496 manner similar to how the value @code{cs} was explored in the above
8499 The @code{explore} command also has two sub-commands,
8500 @code{explore value} and @code{explore type}. The former sub-command is
8501 a way to explicitly specify that value exploration of the argument is
8502 being invoked, while the latter is a way to explicitly specify that type
8503 exploration of the argument is being invoked.
8506 @item explore value @var{expr}
8507 @cindex explore value
8508 This sub-command of @code{explore} explores the value of the
8509 expression @var{expr} (if @var{expr} is an expression valid in the
8510 current context of the program being debugged). The behavior of this
8511 command is identical to that of the behavior of the @code{explore}
8512 command being passed the argument @var{expr}.
8514 @item explore type @var{arg}
8515 @cindex explore type
8516 This sub-command of @code{explore} explores the type of @var{arg} (if
8517 @var{arg} is a type visible in the current context of program being
8518 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8519 is an expression valid in the current context of the program being
8520 debugged). If @var{arg} is a type, then the behavior of this command is
8521 identical to that of the @code{explore} command being passed the
8522 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8523 this command will be identical to that of the @code{explore} command
8524 being passed the type of @var{arg} as the argument.
8528 * Expressions:: Expressions
8529 * Ambiguous Expressions:: Ambiguous Expressions
8530 * Variables:: Program variables
8531 * Arrays:: Artificial arrays
8532 * Output Formats:: Output formats
8533 * Memory:: Examining memory
8534 * Auto Display:: Automatic display
8535 * Print Settings:: Print settings
8536 * Pretty Printing:: Python pretty printing
8537 * Value History:: Value history
8538 * Convenience Vars:: Convenience variables
8539 * Convenience Funs:: Convenience functions
8540 * Registers:: Registers
8541 * Floating Point Hardware:: Floating point hardware
8542 * Vector Unit:: Vector Unit
8543 * OS Information:: Auxiliary data provided by operating system
8544 * Memory Region Attributes:: Memory region attributes
8545 * Dump/Restore Files:: Copy between memory and a file
8546 * Core File Generation:: Cause a program dump its core
8547 * Character Sets:: Debugging programs that use a different
8548 character set than GDB does
8549 * Caching Target Data:: Data caching for targets
8550 * Searching Memory:: Searching memory for a sequence of bytes
8554 @section Expressions
8557 @code{print} and many other @value{GDBN} commands accept an expression and
8558 compute its value. Any kind of constant, variable or operator defined
8559 by the programming language you are using is valid in an expression in
8560 @value{GDBN}. This includes conditional expressions, function calls,
8561 casts, and string constants. It also includes preprocessor macros, if
8562 you compiled your program to include this information; see
8565 @cindex arrays in expressions
8566 @value{GDBN} supports array constants in expressions input by
8567 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8568 you can use the command @code{print @{1, 2, 3@}} to create an array
8569 of three integers. If you pass an array to a function or assign it
8570 to a program variable, @value{GDBN} copies the array to memory that
8571 is @code{malloc}ed in the target program.
8573 Because C is so widespread, most of the expressions shown in examples in
8574 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8575 Languages}, for information on how to use expressions in other
8578 In this section, we discuss operators that you can use in @value{GDBN}
8579 expressions regardless of your programming language.
8581 @cindex casts, in expressions
8582 Casts are supported in all languages, not just in C, because it is so
8583 useful to cast a number into a pointer in order to examine a structure
8584 at that address in memory.
8585 @c FIXME: casts supported---Mod2 true?
8587 @value{GDBN} supports these operators, in addition to those common
8588 to programming languages:
8592 @samp{@@} is a binary operator for treating parts of memory as arrays.
8593 @xref{Arrays, ,Artificial Arrays}, for more information.
8596 @samp{::} allows you to specify a variable in terms of the file or
8597 function where it is defined. @xref{Variables, ,Program Variables}.
8599 @cindex @{@var{type}@}
8600 @cindex type casting memory
8601 @cindex memory, viewing as typed object
8602 @cindex casts, to view memory
8603 @item @{@var{type}@} @var{addr}
8604 Refers to an object of type @var{type} stored at address @var{addr} in
8605 memory. The address @var{addr} may be any expression whose value is
8606 an integer or pointer (but parentheses are required around binary
8607 operators, just as in a cast). This construct is allowed regardless
8608 of what kind of data is normally supposed to reside at @var{addr}.
8611 @node Ambiguous Expressions
8612 @section Ambiguous Expressions
8613 @cindex ambiguous expressions
8615 Expressions can sometimes contain some ambiguous elements. For instance,
8616 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8617 a single function name to be defined several times, for application in
8618 different contexts. This is called @dfn{overloading}. Another example
8619 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8620 templates and is typically instantiated several times, resulting in
8621 the same function name being defined in different contexts.
8623 In some cases and depending on the language, it is possible to adjust
8624 the expression to remove the ambiguity. For instance in C@t{++}, you
8625 can specify the signature of the function you want to break on, as in
8626 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8627 qualified name of your function often makes the expression unambiguous
8630 When an ambiguity that needs to be resolved is detected, the debugger
8631 has the capability to display a menu of numbered choices for each
8632 possibility, and then waits for the selection with the prompt @samp{>}.
8633 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8634 aborts the current command. If the command in which the expression was
8635 used allows more than one choice to be selected, the next option in the
8636 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8639 For example, the following session excerpt shows an attempt to set a
8640 breakpoint at the overloaded symbol @code{String::after}.
8641 We choose three particular definitions of that function name:
8643 @c FIXME! This is likely to change to show arg type lists, at least
8646 (@value{GDBP}) b String::after
8649 [2] file:String.cc; line number:867
8650 [3] file:String.cc; line number:860
8651 [4] file:String.cc; line number:875
8652 [5] file:String.cc; line number:853
8653 [6] file:String.cc; line number:846
8654 [7] file:String.cc; line number:735
8656 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8657 Breakpoint 2 at 0xb344: file String.cc, line 875.
8658 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8659 Multiple breakpoints were set.
8660 Use the "delete" command to delete unwanted
8667 @kindex set multiple-symbols
8668 @item set multiple-symbols @var{mode}
8669 @cindex multiple-symbols menu
8671 This option allows you to adjust the debugger behavior when an expression
8674 By default, @var{mode} is set to @code{all}. If the command with which
8675 the expression is used allows more than one choice, then @value{GDBN}
8676 automatically selects all possible choices. For instance, inserting
8677 a breakpoint on a function using an ambiguous name results in a breakpoint
8678 inserted on each possible match. However, if a unique choice must be made,
8679 then @value{GDBN} uses the menu to help you disambiguate the expression.
8680 For instance, printing the address of an overloaded function will result
8681 in the use of the menu.
8683 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8684 when an ambiguity is detected.
8686 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8687 an error due to the ambiguity and the command is aborted.
8689 @kindex show multiple-symbols
8690 @item show multiple-symbols
8691 Show the current value of the @code{multiple-symbols} setting.
8695 @section Program Variables
8697 The most common kind of expression to use is the name of a variable
8700 Variables in expressions are understood in the selected stack frame
8701 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8705 global (or file-static)
8712 visible according to the scope rules of the
8713 programming language from the point of execution in that frame
8716 @noindent This means that in the function
8731 you can examine and use the variable @code{a} whenever your program is
8732 executing within the function @code{foo}, but you can only use or
8733 examine the variable @code{b} while your program is executing inside
8734 the block where @code{b} is declared.
8736 @cindex variable name conflict
8737 There is an exception: you can refer to a variable or function whose
8738 scope is a single source file even if the current execution point is not
8739 in this file. But it is possible to have more than one such variable or
8740 function with the same name (in different source files). If that
8741 happens, referring to that name has unpredictable effects. If you wish,
8742 you can specify a static variable in a particular function or file by
8743 using the colon-colon (@code{::}) notation:
8745 @cindex colon-colon, context for variables/functions
8747 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8748 @cindex @code{::}, context for variables/functions
8751 @var{file}::@var{variable}
8752 @var{function}::@var{variable}
8756 Here @var{file} or @var{function} is the name of the context for the
8757 static @var{variable}. In the case of file names, you can use quotes to
8758 make sure @value{GDBN} parses the file name as a single word---for example,
8759 to print a global value of @code{x} defined in @file{f2.c}:
8762 (@value{GDBP}) p 'f2.c'::x
8765 The @code{::} notation is normally used for referring to
8766 static variables, since you typically disambiguate uses of local variables
8767 in functions by selecting the appropriate frame and using the
8768 simple name of the variable. However, you may also use this notation
8769 to refer to local variables in frames enclosing the selected frame:
8778 process (a); /* Stop here */
8789 For example, if there is a breakpoint at the commented line,
8790 here is what you might see
8791 when the program stops after executing the call @code{bar(0)}:
8796 (@value{GDBP}) p bar::a
8799 #2 0x080483d0 in foo (a=5) at foobar.c:12
8802 (@value{GDBP}) p bar::a
8806 @cindex C@t{++} scope resolution
8807 These uses of @samp{::} are very rarely in conflict with the very
8808 similar use of the same notation in C@t{++}. When they are in
8809 conflict, the C@t{++} meaning takes precedence; however, this can be
8810 overridden by quoting the file or function name with single quotes.
8812 For example, suppose the program is stopped in a method of a class
8813 that has a field named @code{includefile}, and there is also an
8814 include file named @file{includefile} that defines a variable,
8818 (@value{GDBP}) p includefile
8820 (@value{GDBP}) p includefile::some_global
8821 A syntax error in expression, near `'.
8822 (@value{GDBP}) p 'includefile'::some_global
8826 @cindex wrong values
8827 @cindex variable values, wrong
8828 @cindex function entry/exit, wrong values of variables
8829 @cindex optimized code, wrong values of variables
8831 @emph{Warning:} Occasionally, a local variable may appear to have the
8832 wrong value at certain points in a function---just after entry to a new
8833 scope, and just before exit.
8835 You may see this problem when you are stepping by machine instructions.
8836 This is because, on most machines, it takes more than one instruction to
8837 set up a stack frame (including local variable definitions); if you are
8838 stepping by machine instructions, variables may appear to have the wrong
8839 values until the stack frame is completely built. On exit, it usually
8840 also takes more than one machine instruction to destroy a stack frame;
8841 after you begin stepping through that group of instructions, local
8842 variable definitions may be gone.
8844 This may also happen when the compiler does significant optimizations.
8845 To be sure of always seeing accurate values, turn off all optimization
8848 @cindex ``No symbol "foo" in current context''
8849 Another possible effect of compiler optimizations is to optimize
8850 unused variables out of existence, or assign variables to registers (as
8851 opposed to memory addresses). Depending on the support for such cases
8852 offered by the debug info format used by the compiler, @value{GDBN}
8853 might not be able to display values for such local variables. If that
8854 happens, @value{GDBN} will print a message like this:
8857 No symbol "foo" in current context.
8860 To solve such problems, either recompile without optimizations, or use a
8861 different debug info format, if the compiler supports several such
8862 formats. @xref{Compilation}, for more information on choosing compiler
8863 options. @xref{C, ,C and C@t{++}}, for more information about debug
8864 info formats that are best suited to C@t{++} programs.
8866 If you ask to print an object whose contents are unknown to
8867 @value{GDBN}, e.g., because its data type is not completely specified
8868 by the debug information, @value{GDBN} will say @samp{<incomplete
8869 type>}. @xref{Symbols, incomplete type}, for more about this.
8871 If you append @kbd{@@entry} string to a function parameter name you get its
8872 value at the time the function got called. If the value is not available an
8873 error message is printed. Entry values are available only with some compilers.
8874 Entry values are normally also printed at the function parameter list according
8875 to @ref{set print entry-values}.
8878 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8884 (gdb) print i@@entry
8888 Strings are identified as arrays of @code{char} values without specified
8889 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8890 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8891 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8892 defines literal string type @code{"char"} as @code{char} without a sign.
8897 signed char var1[] = "A";
8900 You get during debugging
8905 $2 = @{65 'A', 0 '\0'@}
8909 @section Artificial Arrays
8911 @cindex artificial array
8913 @kindex @@@r{, referencing memory as an array}
8914 It is often useful to print out several successive objects of the
8915 same type in memory; a section of an array, or an array of
8916 dynamically determined size for which only a pointer exists in the
8919 You can do this by referring to a contiguous span of memory as an
8920 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8921 operand of @samp{@@} should be the first element of the desired array
8922 and be an individual object. The right operand should be the desired length
8923 of the array. The result is an array value whose elements are all of
8924 the type of the left argument. The first element is actually the left
8925 argument; the second element comes from bytes of memory immediately
8926 following those that hold the first element, and so on. Here is an
8927 example. If a program says
8930 int *array = (int *) malloc (len * sizeof (int));
8934 you can print the contents of @code{array} with
8940 The left operand of @samp{@@} must reside in memory. Array values made
8941 with @samp{@@} in this way behave just like other arrays in terms of
8942 subscripting, and are coerced to pointers when used in expressions.
8943 Artificial arrays most often appear in expressions via the value history
8944 (@pxref{Value History, ,Value History}), after printing one out.
8946 Another way to create an artificial array is to use a cast.
8947 This re-interprets a value as if it were an array.
8948 The value need not be in memory:
8950 (@value{GDBP}) p/x (short[2])0x12345678
8951 $1 = @{0x1234, 0x5678@}
8954 As a convenience, if you leave the array length out (as in
8955 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8956 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8958 (@value{GDBP}) p/x (short[])0x12345678
8959 $2 = @{0x1234, 0x5678@}
8962 Sometimes the artificial array mechanism is not quite enough; in
8963 moderately complex data structures, the elements of interest may not
8964 actually be adjacent---for example, if you are interested in the values
8965 of pointers in an array. One useful work-around in this situation is
8966 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8967 Variables}) as a counter in an expression that prints the first
8968 interesting value, and then repeat that expression via @key{RET}. For
8969 instance, suppose you have an array @code{dtab} of pointers to
8970 structures, and you are interested in the values of a field @code{fv}
8971 in each structure. Here is an example of what you might type:
8981 @node Output Formats
8982 @section Output Formats
8984 @cindex formatted output
8985 @cindex output formats
8986 By default, @value{GDBN} prints a value according to its data type. Sometimes
8987 this is not what you want. For example, you might want to print a number
8988 in hex, or a pointer in decimal. Or you might want to view data in memory
8989 at a certain address as a character string or as an instruction. To do
8990 these things, specify an @dfn{output format} when you print a value.
8992 The simplest use of output formats is to say how to print a value
8993 already computed. This is done by starting the arguments of the
8994 @code{print} command with a slash and a format letter. The format
8995 letters supported are:
8999 Regard the bits of the value as an integer, and print the integer in
9003 Print as integer in signed decimal.
9006 Print as integer in unsigned decimal.
9009 Print as integer in octal.
9012 Print as integer in binary. The letter @samp{t} stands for ``two''.
9013 @footnote{@samp{b} cannot be used because these format letters are also
9014 used with the @code{x} command, where @samp{b} stands for ``byte'';
9015 see @ref{Memory,,Examining Memory}.}
9018 @cindex unknown address, locating
9019 @cindex locate address
9020 Print as an address, both absolute in hexadecimal and as an offset from
9021 the nearest preceding symbol. You can use this format used to discover
9022 where (in what function) an unknown address is located:
9025 (@value{GDBP}) p/a 0x54320
9026 $3 = 0x54320 <_initialize_vx+396>
9030 The command @code{info symbol 0x54320} yields similar results.
9031 @xref{Symbols, info symbol}.
9034 Regard as an integer and print it as a character constant. This
9035 prints both the numerical value and its character representation. The
9036 character representation is replaced with the octal escape @samp{\nnn}
9037 for characters outside the 7-bit @sc{ascii} range.
9039 Without this format, @value{GDBN} displays @code{char},
9040 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9041 constants. Single-byte members of vectors are displayed as integer
9045 Regard the bits of the value as a floating point number and print
9046 using typical floating point syntax.
9049 @cindex printing strings
9050 @cindex printing byte arrays
9051 Regard as a string, if possible. With this format, pointers to single-byte
9052 data are displayed as null-terminated strings and arrays of single-byte data
9053 are displayed as fixed-length strings. Other values are displayed in their
9056 Without this format, @value{GDBN} displays pointers to and arrays of
9057 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9058 strings. Single-byte members of a vector are displayed as an integer
9062 Like @samp{x} formatting, the value is treated as an integer and
9063 printed as hexadecimal, but leading zeros are printed to pad the value
9064 to the size of the integer type.
9067 @cindex raw printing
9068 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9069 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9070 Printing}). This typically results in a higher-level display of the
9071 value's contents. The @samp{r} format bypasses any Python
9072 pretty-printer which might exist.
9075 For example, to print the program counter in hex (@pxref{Registers}), type
9082 Note that no space is required before the slash; this is because command
9083 names in @value{GDBN} cannot contain a slash.
9085 To reprint the last value in the value history with a different format,
9086 you can use the @code{print} command with just a format and no
9087 expression. For example, @samp{p/x} reprints the last value in hex.
9090 @section Examining Memory
9092 You can use the command @code{x} (for ``examine'') to examine memory in
9093 any of several formats, independently of your program's data types.
9095 @cindex examining memory
9097 @kindex x @r{(examine memory)}
9098 @item x/@var{nfu} @var{addr}
9101 Use the @code{x} command to examine memory.
9104 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9105 much memory to display and how to format it; @var{addr} is an
9106 expression giving the address where you want to start displaying memory.
9107 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9108 Several commands set convenient defaults for @var{addr}.
9111 @item @var{n}, the repeat count
9112 The repeat count is a decimal integer; the default is 1. It specifies
9113 how much memory (counting by units @var{u}) to display.
9114 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9117 @item @var{f}, the display format
9118 The display format is one of the formats used by @code{print}
9119 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9120 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9121 The default is @samp{x} (hexadecimal) initially. The default changes
9122 each time you use either @code{x} or @code{print}.
9124 @item @var{u}, the unit size
9125 The unit size is any of
9131 Halfwords (two bytes).
9133 Words (four bytes). This is the initial default.
9135 Giant words (eight bytes).
9138 Each time you specify a unit size with @code{x}, that size becomes the
9139 default unit the next time you use @code{x}. For the @samp{i} format,
9140 the unit size is ignored and is normally not written. For the @samp{s} format,
9141 the unit size defaults to @samp{b}, unless it is explicitly given.
9142 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9143 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9144 Note that the results depend on the programming language of the
9145 current compilation unit. If the language is C, the @samp{s}
9146 modifier will use the UTF-16 encoding while @samp{w} will use
9147 UTF-32. The encoding is set by the programming language and cannot
9150 @item @var{addr}, starting display address
9151 @var{addr} is the address where you want @value{GDBN} to begin displaying
9152 memory. The expression need not have a pointer value (though it may);
9153 it is always interpreted as an integer address of a byte of memory.
9154 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9155 @var{addr} is usually just after the last address examined---but several
9156 other commands also set the default address: @code{info breakpoints} (to
9157 the address of the last breakpoint listed), @code{info line} (to the
9158 starting address of a line), and @code{print} (if you use it to display
9159 a value from memory).
9162 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9163 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9164 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9165 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9166 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9168 Since the letters indicating unit sizes are all distinct from the
9169 letters specifying output formats, you do not have to remember whether
9170 unit size or format comes first; either order works. The output
9171 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9172 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9174 Even though the unit size @var{u} is ignored for the formats @samp{s}
9175 and @samp{i}, you might still want to use a count @var{n}; for example,
9176 @samp{3i} specifies that you want to see three machine instructions,
9177 including any operands. For convenience, especially when used with
9178 the @code{display} command, the @samp{i} format also prints branch delay
9179 slot instructions, if any, beyond the count specified, which immediately
9180 follow the last instruction that is within the count. The command
9181 @code{disassemble} gives an alternative way of inspecting machine
9182 instructions; see @ref{Machine Code,,Source and Machine Code}.
9184 All the defaults for the arguments to @code{x} are designed to make it
9185 easy to continue scanning memory with minimal specifications each time
9186 you use @code{x}. For example, after you have inspected three machine
9187 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9188 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9189 the repeat count @var{n} is used again; the other arguments default as
9190 for successive uses of @code{x}.
9192 When examining machine instructions, the instruction at current program
9193 counter is shown with a @code{=>} marker. For example:
9196 (@value{GDBP}) x/5i $pc-6
9197 0x804837f <main+11>: mov %esp,%ebp
9198 0x8048381 <main+13>: push %ecx
9199 0x8048382 <main+14>: sub $0x4,%esp
9200 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9201 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9204 @cindex @code{$_}, @code{$__}, and value history
9205 The addresses and contents printed by the @code{x} command are not saved
9206 in the value history because there is often too much of them and they
9207 would get in the way. Instead, @value{GDBN} makes these values available for
9208 subsequent use in expressions as values of the convenience variables
9209 @code{$_} and @code{$__}. After an @code{x} command, the last address
9210 examined is available for use in expressions in the convenience variable
9211 @code{$_}. The contents of that address, as examined, are available in
9212 the convenience variable @code{$__}.
9214 If the @code{x} command has a repeat count, the address and contents saved
9215 are from the last memory unit printed; this is not the same as the last
9216 address printed if several units were printed on the last line of output.
9218 @anchor{addressable memory unit}
9219 @cindex addressable memory unit
9220 Most targets have an addressable memory unit size of 8 bits. This means
9221 that to each memory address are associated 8 bits of data. Some
9222 targets, however, have other addressable memory unit sizes.
9223 Within @value{GDBN} and this document, the term
9224 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9225 when explicitly referring to a chunk of data of that size. The word
9226 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9227 the addressable memory unit size of the target. For most systems,
9228 addressable memory unit is a synonym of byte.
9230 @cindex remote memory comparison
9231 @cindex target memory comparison
9232 @cindex verify remote memory image
9233 @cindex verify target memory image
9234 When you are debugging a program running on a remote target machine
9235 (@pxref{Remote Debugging}), you may wish to verify the program's image
9236 in the remote machine's memory against the executable file you
9237 downloaded to the target. Or, on any target, you may want to check
9238 whether the program has corrupted its own read-only sections. The
9239 @code{compare-sections} command is provided for such situations.
9242 @kindex compare-sections
9243 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9244 Compare the data of a loadable section @var{section-name} in the
9245 executable file of the program being debugged with the same section in
9246 the target machine's memory, and report any mismatches. With no
9247 arguments, compares all loadable sections. With an argument of
9248 @code{-r}, compares all loadable read-only sections.
9250 Note: for remote targets, this command can be accelerated if the
9251 target supports computing the CRC checksum of a block of memory
9252 (@pxref{qCRC packet}).
9256 @section Automatic Display
9257 @cindex automatic display
9258 @cindex display of expressions
9260 If you find that you want to print the value of an expression frequently
9261 (to see how it changes), you might want to add it to the @dfn{automatic
9262 display list} so that @value{GDBN} prints its value each time your program stops.
9263 Each expression added to the list is given a number to identify it;
9264 to remove an expression from the list, you specify that number.
9265 The automatic display looks like this:
9269 3: bar[5] = (struct hack *) 0x3804
9273 This display shows item numbers, expressions and their current values. As with
9274 displays you request manually using @code{x} or @code{print}, you can
9275 specify the output format you prefer; in fact, @code{display} decides
9276 whether to use @code{print} or @code{x} depending your format
9277 specification---it uses @code{x} if you specify either the @samp{i}
9278 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9282 @item display @var{expr}
9283 Add the expression @var{expr} to the list of expressions to display
9284 each time your program stops. @xref{Expressions, ,Expressions}.
9286 @code{display} does not repeat if you press @key{RET} again after using it.
9288 @item display/@var{fmt} @var{expr}
9289 For @var{fmt} specifying only a display format and not a size or
9290 count, add the expression @var{expr} to the auto-display list but
9291 arrange to display it each time in the specified format @var{fmt}.
9292 @xref{Output Formats,,Output Formats}.
9294 @item display/@var{fmt} @var{addr}
9295 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9296 number of units, add the expression @var{addr} as a memory address to
9297 be examined each time your program stops. Examining means in effect
9298 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9301 For example, @samp{display/i $pc} can be helpful, to see the machine
9302 instruction about to be executed each time execution stops (@samp{$pc}
9303 is a common name for the program counter; @pxref{Registers, ,Registers}).
9306 @kindex delete display
9308 @item undisplay @var{dnums}@dots{}
9309 @itemx delete display @var{dnums}@dots{}
9310 Remove items from the list of expressions to display. Specify the
9311 numbers of the displays that you want affected with the command
9312 argument @var{dnums}. It can be a single display number, one of the
9313 numbers shown in the first field of the @samp{info display} display;
9314 or it could be a range of display numbers, as in @code{2-4}.
9316 @code{undisplay} does not repeat if you press @key{RET} after using it.
9317 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9319 @kindex disable display
9320 @item disable display @var{dnums}@dots{}
9321 Disable the display of item numbers @var{dnums}. A disabled display
9322 item is not printed automatically, but is not forgotten. It may be
9323 enabled again later. Specify the numbers of the displays that you
9324 want affected with the command argument @var{dnums}. It can be a
9325 single display number, one of the numbers shown in the first field of
9326 the @samp{info display} display; or it could be a range of display
9327 numbers, as in @code{2-4}.
9329 @kindex enable display
9330 @item enable display @var{dnums}@dots{}
9331 Enable display of item numbers @var{dnums}. It becomes effective once
9332 again in auto display of its expression, until you specify otherwise.
9333 Specify the numbers of the displays that you want affected with the
9334 command argument @var{dnums}. It can be a single display number, one
9335 of the numbers shown in the first field of the @samp{info display}
9336 display; or it could be a range of display numbers, as in @code{2-4}.
9339 Display the current values of the expressions on the list, just as is
9340 done when your program stops.
9342 @kindex info display
9344 Print the list of expressions previously set up to display
9345 automatically, each one with its item number, but without showing the
9346 values. This includes disabled expressions, which are marked as such.
9347 It also includes expressions which would not be displayed right now
9348 because they refer to automatic variables not currently available.
9351 @cindex display disabled out of scope
9352 If a display expression refers to local variables, then it does not make
9353 sense outside the lexical context for which it was set up. Such an
9354 expression is disabled when execution enters a context where one of its
9355 variables is not defined. For example, if you give the command
9356 @code{display last_char} while inside a function with an argument
9357 @code{last_char}, @value{GDBN} displays this argument while your program
9358 continues to stop inside that function. When it stops elsewhere---where
9359 there is no variable @code{last_char}---the display is disabled
9360 automatically. The next time your program stops where @code{last_char}
9361 is meaningful, you can enable the display expression once again.
9363 @node Print Settings
9364 @section Print Settings
9366 @cindex format options
9367 @cindex print settings
9368 @value{GDBN} provides the following ways to control how arrays, structures,
9369 and symbols are printed.
9372 These settings are useful for debugging programs in any language:
9376 @item set print address
9377 @itemx set print address on
9378 @cindex print/don't print memory addresses
9379 @value{GDBN} prints memory addresses showing the location of stack
9380 traces, structure values, pointer values, breakpoints, and so forth,
9381 even when it also displays the contents of those addresses. The default
9382 is @code{on}. For example, this is what a stack frame display looks like with
9383 @code{set print address on}:
9388 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9390 530 if (lquote != def_lquote)
9394 @item set print address off
9395 Do not print addresses when displaying their contents. For example,
9396 this is the same stack frame displayed with @code{set print address off}:
9400 (@value{GDBP}) set print addr off
9402 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9403 530 if (lquote != def_lquote)
9407 You can use @samp{set print address off} to eliminate all machine
9408 dependent displays from the @value{GDBN} interface. For example, with
9409 @code{print address off}, you should get the same text for backtraces on
9410 all machines---whether or not they involve pointer arguments.
9413 @item show print address
9414 Show whether or not addresses are to be printed.
9417 When @value{GDBN} prints a symbolic address, it normally prints the
9418 closest earlier symbol plus an offset. If that symbol does not uniquely
9419 identify the address (for example, it is a name whose scope is a single
9420 source file), you may need to clarify. One way to do this is with
9421 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9422 you can set @value{GDBN} to print the source file and line number when
9423 it prints a symbolic address:
9426 @item set print symbol-filename on
9427 @cindex source file and line of a symbol
9428 @cindex symbol, source file and line
9429 Tell @value{GDBN} to print the source file name and line number of a
9430 symbol in the symbolic form of an address.
9432 @item set print symbol-filename off
9433 Do not print source file name and line number of a symbol. This is the
9436 @item show print symbol-filename
9437 Show whether or not @value{GDBN} will print the source file name and
9438 line number of a symbol in the symbolic form of an address.
9441 Another situation where it is helpful to show symbol filenames and line
9442 numbers is when disassembling code; @value{GDBN} shows you the line
9443 number and source file that corresponds to each instruction.
9445 Also, you may wish to see the symbolic form only if the address being
9446 printed is reasonably close to the closest earlier symbol:
9449 @item set print max-symbolic-offset @var{max-offset}
9450 @itemx set print max-symbolic-offset unlimited
9451 @cindex maximum value for offset of closest symbol
9452 Tell @value{GDBN} to only display the symbolic form of an address if the
9453 offset between the closest earlier symbol and the address is less than
9454 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9455 to always print the symbolic form of an address if any symbol precedes
9456 it. Zero is equivalent to @code{unlimited}.
9458 @item show print max-symbolic-offset
9459 Ask how large the maximum offset is that @value{GDBN} prints in a
9463 @cindex wild pointer, interpreting
9464 @cindex pointer, finding referent
9465 If you have a pointer and you are not sure where it points, try
9466 @samp{set print symbol-filename on}. Then you can determine the name
9467 and source file location of the variable where it points, using
9468 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9469 For example, here @value{GDBN} shows that a variable @code{ptt} points
9470 at another variable @code{t}, defined in @file{hi2.c}:
9473 (@value{GDBP}) set print symbol-filename on
9474 (@value{GDBP}) p/a ptt
9475 $4 = 0xe008 <t in hi2.c>
9479 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9480 does not show the symbol name and filename of the referent, even with
9481 the appropriate @code{set print} options turned on.
9484 You can also enable @samp{/a}-like formatting all the time using
9485 @samp{set print symbol on}:
9488 @item set print symbol on
9489 Tell @value{GDBN} to print the symbol corresponding to an address, if
9492 @item set print symbol off
9493 Tell @value{GDBN} not to print the symbol corresponding to an
9494 address. In this mode, @value{GDBN} will still print the symbol
9495 corresponding to pointers to functions. This is the default.
9497 @item show print symbol
9498 Show whether @value{GDBN} will display the symbol corresponding to an
9502 Other settings control how different kinds of objects are printed:
9505 @item set print array
9506 @itemx set print array on
9507 @cindex pretty print arrays
9508 Pretty print arrays. This format is more convenient to read,
9509 but uses more space. The default is off.
9511 @item set print array off
9512 Return to compressed format for arrays.
9514 @item show print array
9515 Show whether compressed or pretty format is selected for displaying
9518 @cindex print array indexes
9519 @item set print array-indexes
9520 @itemx set print array-indexes on
9521 Print the index of each element when displaying arrays. May be more
9522 convenient to locate a given element in the array or quickly find the
9523 index of a given element in that printed array. The default is off.
9525 @item set print array-indexes off
9526 Stop printing element indexes when displaying arrays.
9528 @item show print array-indexes
9529 Show whether the index of each element is printed when displaying
9532 @item set print elements @var{number-of-elements}
9533 @itemx set print elements unlimited
9534 @cindex number of array elements to print
9535 @cindex limit on number of printed array elements
9536 Set a limit on how many elements of an array @value{GDBN} will print.
9537 If @value{GDBN} is printing a large array, it stops printing after it has
9538 printed the number of elements set by the @code{set print elements} command.
9539 This limit also applies to the display of strings.
9540 When @value{GDBN} starts, this limit is set to 200.
9541 Setting @var{number-of-elements} to @code{unlimited} or zero means
9542 that the number of elements to print is unlimited.
9544 @item show print elements
9545 Display the number of elements of a large array that @value{GDBN} will print.
9546 If the number is 0, then the printing is unlimited.
9548 @item set print frame-arguments @var{value}
9549 @kindex set print frame-arguments
9550 @cindex printing frame argument values
9551 @cindex print all frame argument values
9552 @cindex print frame argument values for scalars only
9553 @cindex do not print frame argument values
9554 This command allows to control how the values of arguments are printed
9555 when the debugger prints a frame (@pxref{Frames}). The possible
9560 The values of all arguments are printed.
9563 Print the value of an argument only if it is a scalar. The value of more
9564 complex arguments such as arrays, structures, unions, etc, is replaced
9565 by @code{@dots{}}. This is the default. Here is an example where
9566 only scalar arguments are shown:
9569 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9574 None of the argument values are printed. Instead, the value of each argument
9575 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9578 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9583 By default, only scalar arguments are printed. This command can be used
9584 to configure the debugger to print the value of all arguments, regardless
9585 of their type. However, it is often advantageous to not print the value
9586 of more complex parameters. For instance, it reduces the amount of
9587 information printed in each frame, making the backtrace more readable.
9588 Also, it improves performance when displaying Ada frames, because
9589 the computation of large arguments can sometimes be CPU-intensive,
9590 especially in large applications. Setting @code{print frame-arguments}
9591 to @code{scalars} (the default) or @code{none} avoids this computation,
9592 thus speeding up the display of each Ada frame.
9594 @item show print frame-arguments
9595 Show how the value of arguments should be displayed when printing a frame.
9597 @item set print raw frame-arguments on
9598 Print frame arguments in raw, non pretty-printed, form.
9600 @item set print raw frame-arguments off
9601 Print frame arguments in pretty-printed form, if there is a pretty-printer
9602 for the value (@pxref{Pretty Printing}),
9603 otherwise print the value in raw form.
9604 This is the default.
9606 @item show print raw frame-arguments
9607 Show whether to print frame arguments in raw form.
9609 @anchor{set print entry-values}
9610 @item set print entry-values @var{value}
9611 @kindex set print entry-values
9612 Set printing of frame argument values at function entry. In some cases
9613 @value{GDBN} can determine the value of function argument which was passed by
9614 the function caller, even if the value was modified inside the called function
9615 and therefore is different. With optimized code, the current value could be
9616 unavailable, but the entry value may still be known.
9618 The default value is @code{default} (see below for its description). Older
9619 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9620 this feature will behave in the @code{default} setting the same way as with the
9623 This functionality is currently supported only by DWARF 2 debugging format and
9624 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9625 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9628 The @var{value} parameter can be one of the following:
9632 Print only actual parameter values, never print values from function entry
9636 #0 different (val=6)
9637 #0 lost (val=<optimized out>)
9639 #0 invalid (val=<optimized out>)
9643 Print only parameter values from function entry point. The actual parameter
9644 values are never printed.
9646 #0 equal (val@@entry=5)
9647 #0 different (val@@entry=5)
9648 #0 lost (val@@entry=5)
9649 #0 born (val@@entry=<optimized out>)
9650 #0 invalid (val@@entry=<optimized out>)
9654 Print only parameter values from function entry point. If value from function
9655 entry point is not known while the actual value is known, print the actual
9656 value for such parameter.
9658 #0 equal (val@@entry=5)
9659 #0 different (val@@entry=5)
9660 #0 lost (val@@entry=5)
9662 #0 invalid (val@@entry=<optimized out>)
9666 Print actual parameter values. If actual parameter value is not known while
9667 value from function entry point is known, print the entry point value for such
9671 #0 different (val=6)
9672 #0 lost (val@@entry=5)
9674 #0 invalid (val=<optimized out>)
9678 Always print both the actual parameter value and its value from function entry
9679 point, even if values of one or both are not available due to compiler
9682 #0 equal (val=5, val@@entry=5)
9683 #0 different (val=6, val@@entry=5)
9684 #0 lost (val=<optimized out>, val@@entry=5)
9685 #0 born (val=10, val@@entry=<optimized out>)
9686 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9690 Print the actual parameter value if it is known and also its value from
9691 function entry point if it is known. If neither is known, print for the actual
9692 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9693 values are known and identical, print the shortened
9694 @code{param=param@@entry=VALUE} notation.
9696 #0 equal (val=val@@entry=5)
9697 #0 different (val=6, val@@entry=5)
9698 #0 lost (val@@entry=5)
9700 #0 invalid (val=<optimized out>)
9704 Always print the actual parameter value. Print also its value from function
9705 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9706 if both values are known and identical, print the shortened
9707 @code{param=param@@entry=VALUE} notation.
9709 #0 equal (val=val@@entry=5)
9710 #0 different (val=6, val@@entry=5)
9711 #0 lost (val=<optimized out>, val@@entry=5)
9713 #0 invalid (val=<optimized out>)
9717 For analysis messages on possible failures of frame argument values at function
9718 entry resolution see @ref{set debug entry-values}.
9720 @item show print entry-values
9721 Show the method being used for printing of frame argument values at function
9724 @item set print repeats @var{number-of-repeats}
9725 @itemx set print repeats unlimited
9726 @cindex repeated array elements
9727 Set the threshold for suppressing display of repeated array
9728 elements. When the number of consecutive identical elements of an
9729 array exceeds the threshold, @value{GDBN} prints the string
9730 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9731 identical repetitions, instead of displaying the identical elements
9732 themselves. Setting the threshold to @code{unlimited} or zero will
9733 cause all elements to be individually printed. The default threshold
9736 @item show print repeats
9737 Display the current threshold for printing repeated identical
9740 @item set print null-stop
9741 @cindex @sc{null} elements in arrays
9742 Cause @value{GDBN} to stop printing the characters of an array when the first
9743 @sc{null} is encountered. This is useful when large arrays actually
9744 contain only short strings.
9747 @item show print null-stop
9748 Show whether @value{GDBN} stops printing an array on the first
9749 @sc{null} character.
9751 @item set print pretty on
9752 @cindex print structures in indented form
9753 @cindex indentation in structure display
9754 Cause @value{GDBN} to print structures in an indented format with one member
9755 per line, like this:
9770 @item set print pretty off
9771 Cause @value{GDBN} to print structures in a compact format, like this:
9775 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9776 meat = 0x54 "Pork"@}
9781 This is the default format.
9783 @item show print pretty
9784 Show which format @value{GDBN} is using to print structures.
9786 @item set print sevenbit-strings on
9787 @cindex eight-bit characters in strings
9788 @cindex octal escapes in strings
9789 Print using only seven-bit characters; if this option is set,
9790 @value{GDBN} displays any eight-bit characters (in strings or
9791 character values) using the notation @code{\}@var{nnn}. This setting is
9792 best if you are working in English (@sc{ascii}) and you use the
9793 high-order bit of characters as a marker or ``meta'' bit.
9795 @item set print sevenbit-strings off
9796 Print full eight-bit characters. This allows the use of more
9797 international character sets, and is the default.
9799 @item show print sevenbit-strings
9800 Show whether or not @value{GDBN} is printing only seven-bit characters.
9802 @item set print union on
9803 @cindex unions in structures, printing
9804 Tell @value{GDBN} to print unions which are contained in structures
9805 and other unions. This is the default setting.
9807 @item set print union off
9808 Tell @value{GDBN} not to print unions which are contained in
9809 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9812 @item show print union
9813 Ask @value{GDBN} whether or not it will print unions which are contained in
9814 structures and other unions.
9816 For example, given the declarations
9819 typedef enum @{Tree, Bug@} Species;
9820 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9821 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9832 struct thing foo = @{Tree, @{Acorn@}@};
9836 with @code{set print union on} in effect @samp{p foo} would print
9839 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9843 and with @code{set print union off} in effect it would print
9846 $1 = @{it = Tree, form = @{...@}@}
9850 @code{set print union} affects programs written in C-like languages
9856 These settings are of interest when debugging C@t{++} programs:
9859 @cindex demangling C@t{++} names
9860 @item set print demangle
9861 @itemx set print demangle on
9862 Print C@t{++} names in their source form rather than in the encoded
9863 (``mangled'') form passed to the assembler and linker for type-safe
9864 linkage. The default is on.
9866 @item show print demangle
9867 Show whether C@t{++} names are printed in mangled or demangled form.
9869 @item set print asm-demangle
9870 @itemx set print asm-demangle on
9871 Print C@t{++} names in their source form rather than their mangled form, even
9872 in assembler code printouts such as instruction disassemblies.
9875 @item show print asm-demangle
9876 Show whether C@t{++} names in assembly listings are printed in mangled
9879 @cindex C@t{++} symbol decoding style
9880 @cindex symbol decoding style, C@t{++}
9881 @kindex set demangle-style
9882 @item set demangle-style @var{style}
9883 Choose among several encoding schemes used by different compilers to
9884 represent C@t{++} names. The choices for @var{style} are currently:
9888 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9889 This is the default.
9892 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9895 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9898 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9901 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9902 @strong{Warning:} this setting alone is not sufficient to allow
9903 debugging @code{cfront}-generated executables. @value{GDBN} would
9904 require further enhancement to permit that.
9907 If you omit @var{style}, you will see a list of possible formats.
9909 @item show demangle-style
9910 Display the encoding style currently in use for decoding C@t{++} symbols.
9912 @item set print object
9913 @itemx set print object on
9914 @cindex derived type of an object, printing
9915 @cindex display derived types
9916 When displaying a pointer to an object, identify the @emph{actual}
9917 (derived) type of the object rather than the @emph{declared} type, using
9918 the virtual function table. Note that the virtual function table is
9919 required---this feature can only work for objects that have run-time
9920 type identification; a single virtual method in the object's declared
9921 type is sufficient. Note that this setting is also taken into account when
9922 working with variable objects via MI (@pxref{GDB/MI}).
9924 @item set print object off
9925 Display only the declared type of objects, without reference to the
9926 virtual function table. This is the default setting.
9928 @item show print object
9929 Show whether actual, or declared, object types are displayed.
9931 @item set print static-members
9932 @itemx set print static-members on
9933 @cindex static members of C@t{++} objects
9934 Print static members when displaying a C@t{++} object. The default is on.
9936 @item set print static-members off
9937 Do not print static members when displaying a C@t{++} object.
9939 @item show print static-members
9940 Show whether C@t{++} static members are printed or not.
9942 @item set print pascal_static-members
9943 @itemx set print pascal_static-members on
9944 @cindex static members of Pascal objects
9945 @cindex Pascal objects, static members display
9946 Print static members when displaying a Pascal object. The default is on.
9948 @item set print pascal_static-members off
9949 Do not print static members when displaying a Pascal object.
9951 @item show print pascal_static-members
9952 Show whether Pascal static members are printed or not.
9954 @c These don't work with HP ANSI C++ yet.
9955 @item set print vtbl
9956 @itemx set print vtbl on
9957 @cindex pretty print C@t{++} virtual function tables
9958 @cindex virtual functions (C@t{++}) display
9959 @cindex VTBL display
9960 Pretty print C@t{++} virtual function tables. The default is off.
9961 (The @code{vtbl} commands do not work on programs compiled with the HP
9962 ANSI C@t{++} compiler (@code{aCC}).)
9964 @item set print vtbl off
9965 Do not pretty print C@t{++} virtual function tables.
9967 @item show print vtbl
9968 Show whether C@t{++} virtual function tables are pretty printed, or not.
9971 @node Pretty Printing
9972 @section Pretty Printing
9974 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9975 Python code. It greatly simplifies the display of complex objects. This
9976 mechanism works for both MI and the CLI.
9979 * Pretty-Printer Introduction:: Introduction to pretty-printers
9980 * Pretty-Printer Example:: An example pretty-printer
9981 * Pretty-Printer Commands:: Pretty-printer commands
9984 @node Pretty-Printer Introduction
9985 @subsection Pretty-Printer Introduction
9987 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9988 registered for the value. If there is then @value{GDBN} invokes the
9989 pretty-printer to print the value. Otherwise the value is printed normally.
9991 Pretty-printers are normally named. This makes them easy to manage.
9992 The @samp{info pretty-printer} command will list all the installed
9993 pretty-printers with their names.
9994 If a pretty-printer can handle multiple data types, then its
9995 @dfn{subprinters} are the printers for the individual data types.
9996 Each such subprinter has its own name.
9997 The format of the name is @var{printer-name};@var{subprinter-name}.
9999 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10000 Typically they are automatically loaded and registered when the corresponding
10001 debug information is loaded, thus making them available without having to
10002 do anything special.
10004 There are three places where a pretty-printer can be registered.
10008 Pretty-printers registered globally are available when debugging
10012 Pretty-printers registered with a program space are available only
10013 when debugging that program.
10014 @xref{Progspaces In Python}, for more details on program spaces in Python.
10017 Pretty-printers registered with an objfile are loaded and unloaded
10018 with the corresponding objfile (e.g., shared library).
10019 @xref{Objfiles In Python}, for more details on objfiles in Python.
10022 @xref{Selecting Pretty-Printers}, for further information on how
10023 pretty-printers are selected,
10025 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10028 @node Pretty-Printer Example
10029 @subsection Pretty-Printer Example
10031 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10034 (@value{GDBP}) print s
10036 static npos = 4294967295,
10038 <std::allocator<char>> = @{
10039 <__gnu_cxx::new_allocator<char>> = @{
10040 <No data fields>@}, <No data fields>
10042 members of std::basic_string<char, std::char_traits<char>,
10043 std::allocator<char> >::_Alloc_hider:
10044 _M_p = 0x804a014 "abcd"
10049 With a pretty-printer for @code{std::string} only the contents are printed:
10052 (@value{GDBP}) print s
10056 @node Pretty-Printer Commands
10057 @subsection Pretty-Printer Commands
10058 @cindex pretty-printer commands
10061 @kindex info pretty-printer
10062 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10063 Print the list of installed pretty-printers.
10064 This includes disabled pretty-printers, which are marked as such.
10066 @var{object-regexp} is a regular expression matching the objects
10067 whose pretty-printers to list.
10068 Objects can be @code{global}, the program space's file
10069 (@pxref{Progspaces In Python}),
10070 and the object files within that program space (@pxref{Objfiles In Python}).
10071 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10072 looks up a printer from these three objects.
10074 @var{name-regexp} is a regular expression matching the name of the printers
10077 @kindex disable pretty-printer
10078 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10079 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10080 A disabled pretty-printer is not forgotten, it may be enabled again later.
10082 @kindex enable pretty-printer
10083 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10084 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10089 Suppose we have three pretty-printers installed: one from library1.so
10090 named @code{foo} that prints objects of type @code{foo}, and
10091 another from library2.so named @code{bar} that prints two types of objects,
10092 @code{bar1} and @code{bar2}.
10095 (gdb) info pretty-printer
10102 (gdb) info pretty-printer library2
10107 (gdb) disable pretty-printer library1
10109 2 of 3 printers enabled
10110 (gdb) info pretty-printer
10117 (gdb) disable pretty-printer library2 bar:bar1
10119 1 of 3 printers enabled
10120 (gdb) info pretty-printer library2
10127 (gdb) disable pretty-printer library2 bar
10129 0 of 3 printers enabled
10130 (gdb) info pretty-printer library2
10139 Note that for @code{bar} the entire printer can be disabled,
10140 as can each individual subprinter.
10142 @node Value History
10143 @section Value History
10145 @cindex value history
10146 @cindex history of values printed by @value{GDBN}
10147 Values printed by the @code{print} command are saved in the @value{GDBN}
10148 @dfn{value history}. This allows you to refer to them in other expressions.
10149 Values are kept until the symbol table is re-read or discarded
10150 (for example with the @code{file} or @code{symbol-file} commands).
10151 When the symbol table changes, the value history is discarded,
10152 since the values may contain pointers back to the types defined in the
10157 @cindex history number
10158 The values printed are given @dfn{history numbers} by which you can
10159 refer to them. These are successive integers starting with one.
10160 @code{print} shows you the history number assigned to a value by
10161 printing @samp{$@var{num} = } before the value; here @var{num} is the
10164 To refer to any previous value, use @samp{$} followed by the value's
10165 history number. The way @code{print} labels its output is designed to
10166 remind you of this. Just @code{$} refers to the most recent value in
10167 the history, and @code{$$} refers to the value before that.
10168 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10169 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10170 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10172 For example, suppose you have just printed a pointer to a structure and
10173 want to see the contents of the structure. It suffices to type
10179 If you have a chain of structures where the component @code{next} points
10180 to the next one, you can print the contents of the next one with this:
10187 You can print successive links in the chain by repeating this
10188 command---which you can do by just typing @key{RET}.
10190 Note that the history records values, not expressions. If the value of
10191 @code{x} is 4 and you type these commands:
10199 then the value recorded in the value history by the @code{print} command
10200 remains 4 even though the value of @code{x} has changed.
10203 @kindex show values
10205 Print the last ten values in the value history, with their item numbers.
10206 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10207 values} does not change the history.
10209 @item show values @var{n}
10210 Print ten history values centered on history item number @var{n}.
10212 @item show values +
10213 Print ten history values just after the values last printed. If no more
10214 values are available, @code{show values +} produces no display.
10217 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10218 same effect as @samp{show values +}.
10220 @node Convenience Vars
10221 @section Convenience Variables
10223 @cindex convenience variables
10224 @cindex user-defined variables
10225 @value{GDBN} provides @dfn{convenience variables} that you can use within
10226 @value{GDBN} to hold on to a value and refer to it later. These variables
10227 exist entirely within @value{GDBN}; they are not part of your program, and
10228 setting a convenience variable has no direct effect on further execution
10229 of your program. That is why you can use them freely.
10231 Convenience variables are prefixed with @samp{$}. Any name preceded by
10232 @samp{$} can be used for a convenience variable, unless it is one of
10233 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10234 (Value history references, in contrast, are @emph{numbers} preceded
10235 by @samp{$}. @xref{Value History, ,Value History}.)
10237 You can save a value in a convenience variable with an assignment
10238 expression, just as you would set a variable in your program.
10242 set $foo = *object_ptr
10246 would save in @code{$foo} the value contained in the object pointed to by
10249 Using a convenience variable for the first time creates it, but its
10250 value is @code{void} until you assign a new value. You can alter the
10251 value with another assignment at any time.
10253 Convenience variables have no fixed types. You can assign a convenience
10254 variable any type of value, including structures and arrays, even if
10255 that variable already has a value of a different type. The convenience
10256 variable, when used as an expression, has the type of its current value.
10259 @kindex show convenience
10260 @cindex show all user variables and functions
10261 @item show convenience
10262 Print a list of convenience variables used so far, and their values,
10263 as well as a list of the convenience functions.
10264 Abbreviated @code{show conv}.
10266 @kindex init-if-undefined
10267 @cindex convenience variables, initializing
10268 @item init-if-undefined $@var{variable} = @var{expression}
10269 Set a convenience variable if it has not already been set. This is useful
10270 for user-defined commands that keep some state. It is similar, in concept,
10271 to using local static variables with initializers in C (except that
10272 convenience variables are global). It can also be used to allow users to
10273 override default values used in a command script.
10275 If the variable is already defined then the expression is not evaluated so
10276 any side-effects do not occur.
10279 One of the ways to use a convenience variable is as a counter to be
10280 incremented or a pointer to be advanced. For example, to print
10281 a field from successive elements of an array of structures:
10285 print bar[$i++]->contents
10289 Repeat that command by typing @key{RET}.
10291 Some convenience variables are created automatically by @value{GDBN} and given
10292 values likely to be useful.
10295 @vindex $_@r{, convenience variable}
10297 The variable @code{$_} is automatically set by the @code{x} command to
10298 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10299 commands which provide a default address for @code{x} to examine also
10300 set @code{$_} to that address; these commands include @code{info line}
10301 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10302 except when set by the @code{x} command, in which case it is a pointer
10303 to the type of @code{$__}.
10305 @vindex $__@r{, convenience variable}
10307 The variable @code{$__} is automatically set by the @code{x} command
10308 to the value found in the last address examined. Its type is chosen
10309 to match the format in which the data was printed.
10312 @vindex $_exitcode@r{, convenience variable}
10313 When the program being debugged terminates normally, @value{GDBN}
10314 automatically sets this variable to the exit code of the program, and
10315 resets @code{$_exitsignal} to @code{void}.
10318 @vindex $_exitsignal@r{, convenience variable}
10319 When the program being debugged dies due to an uncaught signal,
10320 @value{GDBN} automatically sets this variable to that signal's number,
10321 and resets @code{$_exitcode} to @code{void}.
10323 To distinguish between whether the program being debugged has exited
10324 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10325 @code{$_exitsignal} is not @code{void}), the convenience function
10326 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10327 Functions}). For example, considering the following source code:
10330 #include <signal.h>
10333 main (int argc, char *argv[])
10340 A valid way of telling whether the program being debugged has exited
10341 or signalled would be:
10344 (@value{GDBP}) define has_exited_or_signalled
10345 Type commands for definition of ``has_exited_or_signalled''.
10346 End with a line saying just ``end''.
10347 >if $_isvoid ($_exitsignal)
10348 >echo The program has exited\n
10350 >echo The program has signalled\n
10356 Program terminated with signal SIGALRM, Alarm clock.
10357 The program no longer exists.
10358 (@value{GDBP}) has_exited_or_signalled
10359 The program has signalled
10362 As can be seen, @value{GDBN} correctly informs that the program being
10363 debugged has signalled, since it calls @code{raise} and raises a
10364 @code{SIGALRM} signal. If the program being debugged had not called
10365 @code{raise}, then @value{GDBN} would report a normal exit:
10368 (@value{GDBP}) has_exited_or_signalled
10369 The program has exited
10373 The variable @code{$_exception} is set to the exception object being
10374 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10377 @itemx $_probe_arg0@dots{}$_probe_arg11
10378 Arguments to a static probe. @xref{Static Probe Points}.
10381 @vindex $_sdata@r{, inspect, convenience variable}
10382 The variable @code{$_sdata} contains extra collected static tracepoint
10383 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10384 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10385 if extra static tracepoint data has not been collected.
10388 @vindex $_siginfo@r{, convenience variable}
10389 The variable @code{$_siginfo} contains extra signal information
10390 (@pxref{extra signal information}). Note that @code{$_siginfo}
10391 could be empty, if the application has not yet received any signals.
10392 For example, it will be empty before you execute the @code{run} command.
10395 @vindex $_tlb@r{, convenience variable}
10396 The variable @code{$_tlb} is automatically set when debugging
10397 applications running on MS-Windows in native mode or connected to
10398 gdbserver that supports the @code{qGetTIBAddr} request.
10399 @xref{General Query Packets}.
10400 This variable contains the address of the thread information block.
10404 On HP-UX systems, if you refer to a function or variable name that
10405 begins with a dollar sign, @value{GDBN} searches for a user or system
10406 name first, before it searches for a convenience variable.
10408 @node Convenience Funs
10409 @section Convenience Functions
10411 @cindex convenience functions
10412 @value{GDBN} also supplies some @dfn{convenience functions}. These
10413 have a syntax similar to convenience variables. A convenience
10414 function can be used in an expression just like an ordinary function;
10415 however, a convenience function is implemented internally to
10418 These functions do not require @value{GDBN} to be configured with
10419 @code{Python} support, which means that they are always available.
10423 @item $_isvoid (@var{expr})
10424 @findex $_isvoid@r{, convenience function}
10425 Return one if the expression @var{expr} is @code{void}. Otherwise it
10428 A @code{void} expression is an expression where the type of the result
10429 is @code{void}. For example, you can examine a convenience variable
10430 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10434 (@value{GDBP}) print $_exitcode
10436 (@value{GDBP}) print $_isvoid ($_exitcode)
10439 Starting program: ./a.out
10440 [Inferior 1 (process 29572) exited normally]
10441 (@value{GDBP}) print $_exitcode
10443 (@value{GDBP}) print $_isvoid ($_exitcode)
10447 In the example above, we used @code{$_isvoid} to check whether
10448 @code{$_exitcode} is @code{void} before and after the execution of the
10449 program being debugged. Before the execution there is no exit code to
10450 be examined, therefore @code{$_exitcode} is @code{void}. After the
10451 execution the program being debugged returned zero, therefore
10452 @code{$_exitcode} is zero, which means that it is not @code{void}
10455 The @code{void} expression can also be a call of a function from the
10456 program being debugged. For example, given the following function:
10465 The result of calling it inside @value{GDBN} is @code{void}:
10468 (@value{GDBP}) print foo ()
10470 (@value{GDBP}) print $_isvoid (foo ())
10472 (@value{GDBP}) set $v = foo ()
10473 (@value{GDBP}) print $v
10475 (@value{GDBP}) print $_isvoid ($v)
10481 These functions require @value{GDBN} to be configured with
10482 @code{Python} support.
10486 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10487 @findex $_memeq@r{, convenience function}
10488 Returns one if the @var{length} bytes at the addresses given by
10489 @var{buf1} and @var{buf2} are equal.
10490 Otherwise it returns zero.
10492 @item $_regex(@var{str}, @var{regex})
10493 @findex $_regex@r{, convenience function}
10494 Returns one if the string @var{str} matches the regular expression
10495 @var{regex}. Otherwise it returns zero.
10496 The syntax of the regular expression is that specified by @code{Python}'s
10497 regular expression support.
10499 @item $_streq(@var{str1}, @var{str2})
10500 @findex $_streq@r{, convenience function}
10501 Returns one if the strings @var{str1} and @var{str2} are equal.
10502 Otherwise it returns zero.
10504 @item $_strlen(@var{str})
10505 @findex $_strlen@r{, convenience function}
10506 Returns the length of string @var{str}.
10508 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10509 @findex $_caller_is@r{, convenience function}
10510 Returns one if the calling function's name is equal to @var{name}.
10511 Otherwise it returns zero.
10513 If the optional argument @var{number_of_frames} is provided,
10514 it is the number of frames up in the stack to look.
10522 at testsuite/gdb.python/py-caller-is.c:21
10523 #1 0x00000000004005a0 in middle_func ()
10524 at testsuite/gdb.python/py-caller-is.c:27
10525 #2 0x00000000004005ab in top_func ()
10526 at testsuite/gdb.python/py-caller-is.c:33
10527 #3 0x00000000004005b6 in main ()
10528 at testsuite/gdb.python/py-caller-is.c:39
10529 (gdb) print $_caller_is ("middle_func")
10531 (gdb) print $_caller_is ("top_func", 2)
10535 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10536 @findex $_caller_matches@r{, convenience function}
10537 Returns one if the calling function's name matches the regular expression
10538 @var{regexp}. Otherwise it returns zero.
10540 If the optional argument @var{number_of_frames} is provided,
10541 it is the number of frames up in the stack to look.
10544 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10545 @findex $_any_caller_is@r{, convenience function}
10546 Returns one if any calling function's name is equal to @var{name}.
10547 Otherwise it returns zero.
10549 If the optional argument @var{number_of_frames} is provided,
10550 it is the number of frames up in the stack to look.
10553 This function differs from @code{$_caller_is} in that this function
10554 checks all stack frames from the immediate caller to the frame specified
10555 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10556 frame specified by @var{number_of_frames}.
10558 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10559 @findex $_any_caller_matches@r{, convenience function}
10560 Returns one if any calling function's name matches the regular expression
10561 @var{regexp}. Otherwise it returns zero.
10563 If the optional argument @var{number_of_frames} is provided,
10564 it is the number of frames up in the stack to look.
10567 This function differs from @code{$_caller_matches} in that this function
10568 checks all stack frames from the immediate caller to the frame specified
10569 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10570 frame specified by @var{number_of_frames}.
10574 @value{GDBN} provides the ability to list and get help on
10575 convenience functions.
10578 @item help function
10579 @kindex help function
10580 @cindex show all convenience functions
10581 Print a list of all convenience functions.
10588 You can refer to machine register contents, in expressions, as variables
10589 with names starting with @samp{$}. The names of registers are different
10590 for each machine; use @code{info registers} to see the names used on
10594 @kindex info registers
10595 @item info registers
10596 Print the names and values of all registers except floating-point
10597 and vector registers (in the selected stack frame).
10599 @kindex info all-registers
10600 @cindex floating point registers
10601 @item info all-registers
10602 Print the names and values of all registers, including floating-point
10603 and vector registers (in the selected stack frame).
10605 @item info registers @var{regname} @dots{}
10606 Print the @dfn{relativized} value of each specified register @var{regname}.
10607 As discussed in detail below, register values are normally relative to
10608 the selected stack frame. The @var{regname} may be any register name valid on
10609 the machine you are using, with or without the initial @samp{$}.
10612 @anchor{standard registers}
10613 @cindex stack pointer register
10614 @cindex program counter register
10615 @cindex process status register
10616 @cindex frame pointer register
10617 @cindex standard registers
10618 @value{GDBN} has four ``standard'' register names that are available (in
10619 expressions) on most machines---whenever they do not conflict with an
10620 architecture's canonical mnemonics for registers. The register names
10621 @code{$pc} and @code{$sp} are used for the program counter register and
10622 the stack pointer. @code{$fp} is used for a register that contains a
10623 pointer to the current stack frame, and @code{$ps} is used for a
10624 register that contains the processor status. For example,
10625 you could print the program counter in hex with
10632 or print the instruction to be executed next with
10639 or add four to the stack pointer@footnote{This is a way of removing
10640 one word from the stack, on machines where stacks grow downward in
10641 memory (most machines, nowadays). This assumes that the innermost
10642 stack frame is selected; setting @code{$sp} is not allowed when other
10643 stack frames are selected. To pop entire frames off the stack,
10644 regardless of machine architecture, use @code{return};
10645 see @ref{Returning, ,Returning from a Function}.} with
10651 Whenever possible, these four standard register names are available on
10652 your machine even though the machine has different canonical mnemonics,
10653 so long as there is no conflict. The @code{info registers} command
10654 shows the canonical names. For example, on the SPARC, @code{info
10655 registers} displays the processor status register as @code{$psr} but you
10656 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10657 is an alias for the @sc{eflags} register.
10659 @value{GDBN} always considers the contents of an ordinary register as an
10660 integer when the register is examined in this way. Some machines have
10661 special registers which can hold nothing but floating point; these
10662 registers are considered to have floating point values. There is no way
10663 to refer to the contents of an ordinary register as floating point value
10664 (although you can @emph{print} it as a floating point value with
10665 @samp{print/f $@var{regname}}).
10667 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10668 means that the data format in which the register contents are saved by
10669 the operating system is not the same one that your program normally
10670 sees. For example, the registers of the 68881 floating point
10671 coprocessor are always saved in ``extended'' (raw) format, but all C
10672 programs expect to work with ``double'' (virtual) format. In such
10673 cases, @value{GDBN} normally works with the virtual format only (the format
10674 that makes sense for your program), but the @code{info registers} command
10675 prints the data in both formats.
10677 @cindex SSE registers (x86)
10678 @cindex MMX registers (x86)
10679 Some machines have special registers whose contents can be interpreted
10680 in several different ways. For example, modern x86-based machines
10681 have SSE and MMX registers that can hold several values packed
10682 together in several different formats. @value{GDBN} refers to such
10683 registers in @code{struct} notation:
10686 (@value{GDBP}) print $xmm1
10688 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10689 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10690 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10691 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10692 v4_int32 = @{0, 20657912, 11, 13@},
10693 v2_int64 = @{88725056443645952, 55834574859@},
10694 uint128 = 0x0000000d0000000b013b36f800000000
10699 To set values of such registers, you need to tell @value{GDBN} which
10700 view of the register you wish to change, as if you were assigning
10701 value to a @code{struct} member:
10704 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10707 Normally, register values are relative to the selected stack frame
10708 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10709 value that the register would contain if all stack frames farther in
10710 were exited and their saved registers restored. In order to see the
10711 true contents of hardware registers, you must select the innermost
10712 frame (with @samp{frame 0}).
10714 @cindex caller-saved registers
10715 @cindex call-clobbered registers
10716 @cindex volatile registers
10717 @cindex <not saved> values
10718 Usually ABIs reserve some registers as not needed to be saved by the
10719 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10720 registers). It may therefore not be possible for @value{GDBN} to know
10721 the value a register had before the call (in other words, in the outer
10722 frame), if the register value has since been changed by the callee.
10723 @value{GDBN} tries to deduce where the inner frame saved
10724 (``callee-saved'') registers, from the debug info, unwind info, or the
10725 machine code generated by your compiler. If some register is not
10726 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10727 its own knowledge of the ABI, or because the debug/unwind info
10728 explicitly says the register's value is undefined), @value{GDBN}
10729 displays @w{@samp{<not saved>}} as the register's value. With targets
10730 that @value{GDBN} has no knowledge of the register saving convention,
10731 if a register was not saved by the callee, then its value and location
10732 in the outer frame are assumed to be the same of the inner frame.
10733 This is usually harmless, because if the register is call-clobbered,
10734 the caller either does not care what is in the register after the
10735 call, or has code to restore the value that it does care about. Note,
10736 however, that if you change such a register in the outer frame, you
10737 may also be affecting the inner frame. Also, the more ``outer'' the
10738 frame is you're looking at, the more likely a call-clobbered
10739 register's value is to be wrong, in the sense that it doesn't actually
10740 represent the value the register had just before the call.
10742 @node Floating Point Hardware
10743 @section Floating Point Hardware
10744 @cindex floating point
10746 Depending on the configuration, @value{GDBN} may be able to give
10747 you more information about the status of the floating point hardware.
10752 Display hardware-dependent information about the floating
10753 point unit. The exact contents and layout vary depending on the
10754 floating point chip. Currently, @samp{info float} is supported on
10755 the ARM and x86 machines.
10759 @section Vector Unit
10760 @cindex vector unit
10762 Depending on the configuration, @value{GDBN} may be able to give you
10763 more information about the status of the vector unit.
10766 @kindex info vector
10768 Display information about the vector unit. The exact contents and
10769 layout vary depending on the hardware.
10772 @node OS Information
10773 @section Operating System Auxiliary Information
10774 @cindex OS information
10776 @value{GDBN} provides interfaces to useful OS facilities that can help
10777 you debug your program.
10779 @cindex auxiliary vector
10780 @cindex vector, auxiliary
10781 Some operating systems supply an @dfn{auxiliary vector} to programs at
10782 startup. This is akin to the arguments and environment that you
10783 specify for a program, but contains a system-dependent variety of
10784 binary values that tell system libraries important details about the
10785 hardware, operating system, and process. Each value's purpose is
10786 identified by an integer tag; the meanings are well-known but system-specific.
10787 Depending on the configuration and operating system facilities,
10788 @value{GDBN} may be able to show you this information. For remote
10789 targets, this functionality may further depend on the remote stub's
10790 support of the @samp{qXfer:auxv:read} packet, see
10791 @ref{qXfer auxiliary vector read}.
10796 Display the auxiliary vector of the inferior, which can be either a
10797 live process or a core dump file. @value{GDBN} prints each tag value
10798 numerically, and also shows names and text descriptions for recognized
10799 tags. Some values in the vector are numbers, some bit masks, and some
10800 pointers to strings or other data. @value{GDBN} displays each value in the
10801 most appropriate form for a recognized tag, and in hexadecimal for
10802 an unrecognized tag.
10805 On some targets, @value{GDBN} can access operating system-specific
10806 information and show it to you. The types of information available
10807 will differ depending on the type of operating system running on the
10808 target. The mechanism used to fetch the data is described in
10809 @ref{Operating System Information}. For remote targets, this
10810 functionality depends on the remote stub's support of the
10811 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10815 @item info os @var{infotype}
10817 Display OS information of the requested type.
10819 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10821 @anchor{linux info os infotypes}
10823 @kindex info os cpus
10825 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10826 the available fields from /proc/cpuinfo. For each supported architecture
10827 different fields are available. Two common entries are processor which gives
10828 CPU number and bogomips; a system constant that is calculated during
10829 kernel initialization.
10831 @kindex info os files
10833 Display the list of open file descriptors on the target. For each
10834 file descriptor, @value{GDBN} prints the identifier of the process
10835 owning the descriptor, the command of the owning process, the value
10836 of the descriptor, and the target of the descriptor.
10838 @kindex info os modules
10840 Display the list of all loaded kernel modules on the target. For each
10841 module, @value{GDBN} prints the module name, the size of the module in
10842 bytes, the number of times the module is used, the dependencies of the
10843 module, the status of the module, and the address of the loaded module
10846 @kindex info os msg
10848 Display the list of all System V message queues on the target. For each
10849 message queue, @value{GDBN} prints the message queue key, the message
10850 queue identifier, the access permissions, the current number of bytes
10851 on the queue, the current number of messages on the queue, the processes
10852 that last sent and received a message on the queue, the user and group
10853 of the owner and creator of the message queue, the times at which a
10854 message was last sent and received on the queue, and the time at which
10855 the message queue was last changed.
10857 @kindex info os processes
10859 Display the list of processes on the target. For each process,
10860 @value{GDBN} prints the process identifier, the name of the user, the
10861 command corresponding to the process, and the list of processor cores
10862 that the process is currently running on. (To understand what these
10863 properties mean, for this and the following info types, please consult
10864 the general @sc{gnu}/Linux documentation.)
10866 @kindex info os procgroups
10868 Display the list of process groups on the target. For each process,
10869 @value{GDBN} prints the identifier of the process group that it belongs
10870 to, the command corresponding to the process group leader, the process
10871 identifier, and the command line of the process. The list is sorted
10872 first by the process group identifier, then by the process identifier,
10873 so that processes belonging to the same process group are grouped together
10874 and the process group leader is listed first.
10876 @kindex info os semaphores
10878 Display the list of all System V semaphore sets on the target. For each
10879 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10880 set identifier, the access permissions, the number of semaphores in the
10881 set, the user and group of the owner and creator of the semaphore set,
10882 and the times at which the semaphore set was operated upon and changed.
10884 @kindex info os shm
10886 Display the list of all System V shared-memory regions on the target.
10887 For each shared-memory region, @value{GDBN} prints the region key,
10888 the shared-memory identifier, the access permissions, the size of the
10889 region, the process that created the region, the process that last
10890 attached to or detached from the region, the current number of live
10891 attaches to the region, and the times at which the region was last
10892 attached to, detach from, and changed.
10894 @kindex info os sockets
10896 Display the list of Internet-domain sockets on the target. For each
10897 socket, @value{GDBN} prints the address and port of the local and
10898 remote endpoints, the current state of the connection, the creator of
10899 the socket, the IP address family of the socket, and the type of the
10902 @kindex info os threads
10904 Display the list of threads running on the target. For each thread,
10905 @value{GDBN} prints the identifier of the process that the thread
10906 belongs to, the command of the process, the thread identifier, and the
10907 processor core that it is currently running on. The main thread of a
10908 process is not listed.
10912 If @var{infotype} is omitted, then list the possible values for
10913 @var{infotype} and the kind of OS information available for each
10914 @var{infotype}. If the target does not return a list of possible
10915 types, this command will report an error.
10918 @node Memory Region Attributes
10919 @section Memory Region Attributes
10920 @cindex memory region attributes
10922 @dfn{Memory region attributes} allow you to describe special handling
10923 required by regions of your target's memory. @value{GDBN} uses
10924 attributes to determine whether to allow certain types of memory
10925 accesses; whether to use specific width accesses; and whether to cache
10926 target memory. By default the description of memory regions is
10927 fetched from the target (if the current target supports this), but the
10928 user can override the fetched regions.
10930 Defined memory regions can be individually enabled and disabled. When a
10931 memory region is disabled, @value{GDBN} uses the default attributes when
10932 accessing memory in that region. Similarly, if no memory regions have
10933 been defined, @value{GDBN} uses the default attributes when accessing
10936 When a memory region is defined, it is given a number to identify it;
10937 to enable, disable, or remove a memory region, you specify that number.
10941 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10942 Define a memory region bounded by @var{lower} and @var{upper} with
10943 attributes @var{attributes}@dots{}, and add it to the list of regions
10944 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10945 case: it is treated as the target's maximum memory address.
10946 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10949 Discard any user changes to the memory regions and use target-supplied
10950 regions, if available, or no regions if the target does not support.
10953 @item delete mem @var{nums}@dots{}
10954 Remove memory regions @var{nums}@dots{} from the list of regions
10955 monitored by @value{GDBN}.
10957 @kindex disable mem
10958 @item disable mem @var{nums}@dots{}
10959 Disable monitoring of memory regions @var{nums}@dots{}.
10960 A disabled memory region is not forgotten.
10961 It may be enabled again later.
10964 @item enable mem @var{nums}@dots{}
10965 Enable monitoring of memory regions @var{nums}@dots{}.
10969 Print a table of all defined memory regions, with the following columns
10973 @item Memory Region Number
10974 @item Enabled or Disabled.
10975 Enabled memory regions are marked with @samp{y}.
10976 Disabled memory regions are marked with @samp{n}.
10979 The address defining the inclusive lower bound of the memory region.
10982 The address defining the exclusive upper bound of the memory region.
10985 The list of attributes set for this memory region.
10990 @subsection Attributes
10992 @subsubsection Memory Access Mode
10993 The access mode attributes set whether @value{GDBN} may make read or
10994 write accesses to a memory region.
10996 While these attributes prevent @value{GDBN} from performing invalid
10997 memory accesses, they do nothing to prevent the target system, I/O DMA,
10998 etc.@: from accessing memory.
11002 Memory is read only.
11004 Memory is write only.
11006 Memory is read/write. This is the default.
11009 @subsubsection Memory Access Size
11010 The access size attribute tells @value{GDBN} to use specific sized
11011 accesses in the memory region. Often memory mapped device registers
11012 require specific sized accesses. If no access size attribute is
11013 specified, @value{GDBN} may use accesses of any size.
11017 Use 8 bit memory accesses.
11019 Use 16 bit memory accesses.
11021 Use 32 bit memory accesses.
11023 Use 64 bit memory accesses.
11026 @c @subsubsection Hardware/Software Breakpoints
11027 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11028 @c will use hardware or software breakpoints for the internal breakpoints
11029 @c used by the step, next, finish, until, etc. commands.
11033 @c Always use hardware breakpoints
11034 @c @item swbreak (default)
11037 @subsubsection Data Cache
11038 The data cache attributes set whether @value{GDBN} will cache target
11039 memory. While this generally improves performance by reducing debug
11040 protocol overhead, it can lead to incorrect results because @value{GDBN}
11041 does not know about volatile variables or memory mapped device
11046 Enable @value{GDBN} to cache target memory.
11048 Disable @value{GDBN} from caching target memory. This is the default.
11051 @subsection Memory Access Checking
11052 @value{GDBN} can be instructed to refuse accesses to memory that is
11053 not explicitly described. This can be useful if accessing such
11054 regions has undesired effects for a specific target, or to provide
11055 better error checking. The following commands control this behaviour.
11058 @kindex set mem inaccessible-by-default
11059 @item set mem inaccessible-by-default [on|off]
11060 If @code{on} is specified, make @value{GDBN} treat memory not
11061 explicitly described by the memory ranges as non-existent and refuse accesses
11062 to such memory. The checks are only performed if there's at least one
11063 memory range defined. If @code{off} is specified, make @value{GDBN}
11064 treat the memory not explicitly described by the memory ranges as RAM.
11065 The default value is @code{on}.
11066 @kindex show mem inaccessible-by-default
11067 @item show mem inaccessible-by-default
11068 Show the current handling of accesses to unknown memory.
11072 @c @subsubsection Memory Write Verification
11073 @c The memory write verification attributes set whether @value{GDBN}
11074 @c will re-reads data after each write to verify the write was successful.
11078 @c @item noverify (default)
11081 @node Dump/Restore Files
11082 @section Copy Between Memory and a File
11083 @cindex dump/restore files
11084 @cindex append data to a file
11085 @cindex dump data to a file
11086 @cindex restore data from a file
11088 You can use the commands @code{dump}, @code{append}, and
11089 @code{restore} to copy data between target memory and a file. The
11090 @code{dump} and @code{append} commands write data to a file, and the
11091 @code{restore} command reads data from a file back into the inferior's
11092 memory. Files may be in binary, Motorola S-record, Intel hex,
11093 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11094 append to binary files, and cannot read from Verilog Hex files.
11099 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11100 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11101 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11102 or the value of @var{expr}, to @var{filename} in the given format.
11104 The @var{format} parameter may be any one of:
11111 Motorola S-record format.
11113 Tektronix Hex format.
11115 Verilog Hex format.
11118 @value{GDBN} uses the same definitions of these formats as the
11119 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11120 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11124 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11125 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11126 Append the contents of memory from @var{start_addr} to @var{end_addr},
11127 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11128 (@value{GDBN} can only append data to files in raw binary form.)
11131 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11132 Restore the contents of file @var{filename} into memory. The
11133 @code{restore} command can automatically recognize any known @sc{bfd}
11134 file format, except for raw binary. To restore a raw binary file you
11135 must specify the optional keyword @code{binary} after the filename.
11137 If @var{bias} is non-zero, its value will be added to the addresses
11138 contained in the file. Binary files always start at address zero, so
11139 they will be restored at address @var{bias}. Other bfd files have
11140 a built-in location; they will be restored at offset @var{bias}
11141 from that location.
11143 If @var{start} and/or @var{end} are non-zero, then only data between
11144 file offset @var{start} and file offset @var{end} will be restored.
11145 These offsets are relative to the addresses in the file, before
11146 the @var{bias} argument is applied.
11150 @node Core File Generation
11151 @section How to Produce a Core File from Your Program
11152 @cindex dump core from inferior
11154 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11155 image of a running process and its process status (register values
11156 etc.). Its primary use is post-mortem debugging of a program that
11157 crashed while it ran outside a debugger. A program that crashes
11158 automatically produces a core file, unless this feature is disabled by
11159 the user. @xref{Files}, for information on invoking @value{GDBN} in
11160 the post-mortem debugging mode.
11162 Occasionally, you may wish to produce a core file of the program you
11163 are debugging in order to preserve a snapshot of its state.
11164 @value{GDBN} has a special command for that.
11168 @kindex generate-core-file
11169 @item generate-core-file [@var{file}]
11170 @itemx gcore [@var{file}]
11171 Produce a core dump of the inferior process. The optional argument
11172 @var{file} specifies the file name where to put the core dump. If not
11173 specified, the file name defaults to @file{core.@var{pid}}, where
11174 @var{pid} is the inferior process ID.
11176 Note that this command is implemented only for some systems (as of
11177 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11179 On @sc{gnu}/Linux, this command can take into account the value of the
11180 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11181 dump (@pxref{set use-coredump-filter}).
11183 @kindex set use-coredump-filter
11184 @anchor{set use-coredump-filter}
11185 @item set use-coredump-filter on
11186 @itemx set use-coredump-filter off
11187 Enable or disable the use of the file
11188 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11189 files. This file is used by the Linux kernel to decide what types of
11190 memory mappings will be dumped or ignored when generating a core dump
11191 file. @var{pid} is the process ID of a currently running process.
11193 To make use of this feature, you have to write in the
11194 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11195 which is a bit mask representing the memory mapping types. If a bit
11196 is set in the bit mask, then the memory mappings of the corresponding
11197 types will be dumped; otherwise, they will be ignored. This
11198 configuration is inherited by child processes. For more information
11199 about the bits that can be set in the
11200 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11201 manpage of @code{core(5)}.
11203 By default, this option is @code{on}. If this option is turned
11204 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11205 and instead uses the same default value as the Linux kernel in order
11206 to decide which pages will be dumped in the core dump file. This
11207 value is currently @code{0x33}, which means that bits @code{0}
11208 (anonymous private mappings), @code{1} (anonymous shared mappings),
11209 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11210 This will cause these memory mappings to be dumped automatically.
11213 @node Character Sets
11214 @section Character Sets
11215 @cindex character sets
11217 @cindex translating between character sets
11218 @cindex host character set
11219 @cindex target character set
11221 If the program you are debugging uses a different character set to
11222 represent characters and strings than the one @value{GDBN} uses itself,
11223 @value{GDBN} can automatically translate between the character sets for
11224 you. The character set @value{GDBN} uses we call the @dfn{host
11225 character set}; the one the inferior program uses we call the
11226 @dfn{target character set}.
11228 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11229 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11230 remote protocol (@pxref{Remote Debugging}) to debug a program
11231 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11232 then the host character set is Latin-1, and the target character set is
11233 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11234 target-charset EBCDIC-US}, then @value{GDBN} translates between
11235 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11236 character and string literals in expressions.
11238 @value{GDBN} has no way to automatically recognize which character set
11239 the inferior program uses; you must tell it, using the @code{set
11240 target-charset} command, described below.
11242 Here are the commands for controlling @value{GDBN}'s character set
11246 @item set target-charset @var{charset}
11247 @kindex set target-charset
11248 Set the current target character set to @var{charset}. To display the
11249 list of supported target character sets, type
11250 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11252 @item set host-charset @var{charset}
11253 @kindex set host-charset
11254 Set the current host character set to @var{charset}.
11256 By default, @value{GDBN} uses a host character set appropriate to the
11257 system it is running on; you can override that default using the
11258 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11259 automatically determine the appropriate host character set. In this
11260 case, @value{GDBN} uses @samp{UTF-8}.
11262 @value{GDBN} can only use certain character sets as its host character
11263 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11264 @value{GDBN} will list the host character sets it supports.
11266 @item set charset @var{charset}
11267 @kindex set charset
11268 Set the current host and target character sets to @var{charset}. As
11269 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11270 @value{GDBN} will list the names of the character sets that can be used
11271 for both host and target.
11274 @kindex show charset
11275 Show the names of the current host and target character sets.
11277 @item show host-charset
11278 @kindex show host-charset
11279 Show the name of the current host character set.
11281 @item show target-charset
11282 @kindex show target-charset
11283 Show the name of the current target character set.
11285 @item set target-wide-charset @var{charset}
11286 @kindex set target-wide-charset
11287 Set the current target's wide character set to @var{charset}. This is
11288 the character set used by the target's @code{wchar_t} type. To
11289 display the list of supported wide character sets, type
11290 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11292 @item show target-wide-charset
11293 @kindex show target-wide-charset
11294 Show the name of the current target's wide character set.
11297 Here is an example of @value{GDBN}'s character set support in action.
11298 Assume that the following source code has been placed in the file
11299 @file{charset-test.c}:
11305 = @{72, 101, 108, 108, 111, 44, 32, 119,
11306 111, 114, 108, 100, 33, 10, 0@};
11307 char ibm1047_hello[]
11308 = @{200, 133, 147, 147, 150, 107, 64, 166,
11309 150, 153, 147, 132, 90, 37, 0@};
11313 printf ("Hello, world!\n");
11317 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11318 containing the string @samp{Hello, world!} followed by a newline,
11319 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11321 We compile the program, and invoke the debugger on it:
11324 $ gcc -g charset-test.c -o charset-test
11325 $ gdb -nw charset-test
11326 GNU gdb 2001-12-19-cvs
11327 Copyright 2001 Free Software Foundation, Inc.
11332 We can use the @code{show charset} command to see what character sets
11333 @value{GDBN} is currently using to interpret and display characters and
11337 (@value{GDBP}) show charset
11338 The current host and target character set is `ISO-8859-1'.
11342 For the sake of printing this manual, let's use @sc{ascii} as our
11343 initial character set:
11345 (@value{GDBP}) set charset ASCII
11346 (@value{GDBP}) show charset
11347 The current host and target character set is `ASCII'.
11351 Let's assume that @sc{ascii} is indeed the correct character set for our
11352 host system --- in other words, let's assume that if @value{GDBN} prints
11353 characters using the @sc{ascii} character set, our terminal will display
11354 them properly. Since our current target character set is also
11355 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11358 (@value{GDBP}) print ascii_hello
11359 $1 = 0x401698 "Hello, world!\n"
11360 (@value{GDBP}) print ascii_hello[0]
11365 @value{GDBN} uses the target character set for character and string
11366 literals you use in expressions:
11369 (@value{GDBP}) print '+'
11374 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11377 @value{GDBN} relies on the user to tell it which character set the
11378 target program uses. If we print @code{ibm1047_hello} while our target
11379 character set is still @sc{ascii}, we get jibberish:
11382 (@value{GDBP}) print ibm1047_hello
11383 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11384 (@value{GDBP}) print ibm1047_hello[0]
11389 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11390 @value{GDBN} tells us the character sets it supports:
11393 (@value{GDBP}) set target-charset
11394 ASCII EBCDIC-US IBM1047 ISO-8859-1
11395 (@value{GDBP}) set target-charset
11398 We can select @sc{ibm1047} as our target character set, and examine the
11399 program's strings again. Now the @sc{ascii} string is wrong, but
11400 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11401 target character set, @sc{ibm1047}, to the host character set,
11402 @sc{ascii}, and they display correctly:
11405 (@value{GDBP}) set target-charset IBM1047
11406 (@value{GDBP}) show charset
11407 The current host character set is `ASCII'.
11408 The current target character set is `IBM1047'.
11409 (@value{GDBP}) print ascii_hello
11410 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11411 (@value{GDBP}) print ascii_hello[0]
11413 (@value{GDBP}) print ibm1047_hello
11414 $8 = 0x4016a8 "Hello, world!\n"
11415 (@value{GDBP}) print ibm1047_hello[0]
11420 As above, @value{GDBN} uses the target character set for character and
11421 string literals you use in expressions:
11424 (@value{GDBP}) print '+'
11429 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11432 @node Caching Target Data
11433 @section Caching Data of Targets
11434 @cindex caching data of targets
11436 @value{GDBN} caches data exchanged between the debugger and a target.
11437 Each cache is associated with the address space of the inferior.
11438 @xref{Inferiors and Programs}, about inferior and address space.
11439 Such caching generally improves performance in remote debugging
11440 (@pxref{Remote Debugging}), because it reduces the overhead of the
11441 remote protocol by bundling memory reads and writes into large chunks.
11442 Unfortunately, simply caching everything would lead to incorrect results,
11443 since @value{GDBN} does not necessarily know anything about volatile
11444 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11445 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11447 Therefore, by default, @value{GDBN} only caches data
11448 known to be on the stack@footnote{In non-stop mode, it is moderately
11449 rare for a running thread to modify the stack of a stopped thread
11450 in a way that would interfere with a backtrace, and caching of
11451 stack reads provides a significant speed up of remote backtraces.} or
11452 in the code segment.
11453 Other regions of memory can be explicitly marked as
11454 cacheable; @pxref{Memory Region Attributes}.
11457 @kindex set remotecache
11458 @item set remotecache on
11459 @itemx set remotecache off
11460 This option no longer does anything; it exists for compatibility
11463 @kindex show remotecache
11464 @item show remotecache
11465 Show the current state of the obsolete remotecache flag.
11467 @kindex set stack-cache
11468 @item set stack-cache on
11469 @itemx set stack-cache off
11470 Enable or disable caching of stack accesses. When @code{on}, use
11471 caching. By default, this option is @code{on}.
11473 @kindex show stack-cache
11474 @item show stack-cache
11475 Show the current state of data caching for memory accesses.
11477 @kindex set code-cache
11478 @item set code-cache on
11479 @itemx set code-cache off
11480 Enable or disable caching of code segment accesses. When @code{on},
11481 use caching. By default, this option is @code{on}. This improves
11482 performance of disassembly in remote debugging.
11484 @kindex show code-cache
11485 @item show code-cache
11486 Show the current state of target memory cache for code segment
11489 @kindex info dcache
11490 @item info dcache @r{[}line@r{]}
11491 Print the information about the performance of data cache of the
11492 current inferior's address space. The information displayed
11493 includes the dcache width and depth, and for each cache line, its
11494 number, address, and how many times it was referenced. This
11495 command is useful for debugging the data cache operation.
11497 If a line number is specified, the contents of that line will be
11500 @item set dcache size @var{size}
11501 @cindex dcache size
11502 @kindex set dcache size
11503 Set maximum number of entries in dcache (dcache depth above).
11505 @item set dcache line-size @var{line-size}
11506 @cindex dcache line-size
11507 @kindex set dcache line-size
11508 Set number of bytes each dcache entry caches (dcache width above).
11509 Must be a power of 2.
11511 @item show dcache size
11512 @kindex show dcache size
11513 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11515 @item show dcache line-size
11516 @kindex show dcache line-size
11517 Show default size of dcache lines.
11521 @node Searching Memory
11522 @section Search Memory
11523 @cindex searching memory
11525 Memory can be searched for a particular sequence of bytes with the
11526 @code{find} command.
11530 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11531 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11532 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11533 etc. The search begins at address @var{start_addr} and continues for either
11534 @var{len} bytes or through to @var{end_addr} inclusive.
11537 @var{s} and @var{n} are optional parameters.
11538 They may be specified in either order, apart or together.
11541 @item @var{s}, search query size
11542 The size of each search query value.
11548 halfwords (two bytes)
11552 giant words (eight bytes)
11555 All values are interpreted in the current language.
11556 This means, for example, that if the current source language is C/C@t{++}
11557 then searching for the string ``hello'' includes the trailing '\0'.
11559 If the value size is not specified, it is taken from the
11560 value's type in the current language.
11561 This is useful when one wants to specify the search
11562 pattern as a mixture of types.
11563 Note that this means, for example, that in the case of C-like languages
11564 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11565 which is typically four bytes.
11567 @item @var{n}, maximum number of finds
11568 The maximum number of matches to print. The default is to print all finds.
11571 You can use strings as search values. Quote them with double-quotes
11573 The string value is copied into the search pattern byte by byte,
11574 regardless of the endianness of the target and the size specification.
11576 The address of each match found is printed as well as a count of the
11577 number of matches found.
11579 The address of the last value found is stored in convenience variable
11581 A count of the number of matches is stored in @samp{$numfound}.
11583 For example, if stopped at the @code{printf} in this function:
11589 static char hello[] = "hello-hello";
11590 static struct @{ char c; short s; int i; @}
11591 __attribute__ ((packed)) mixed
11592 = @{ 'c', 0x1234, 0x87654321 @};
11593 printf ("%s\n", hello);
11598 you get during debugging:
11601 (gdb) find &hello[0], +sizeof(hello), "hello"
11602 0x804956d <hello.1620+6>
11604 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11605 0x8049567 <hello.1620>
11606 0x804956d <hello.1620+6>
11608 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11609 0x8049567 <hello.1620>
11611 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11612 0x8049560 <mixed.1625>
11614 (gdb) print $numfound
11617 $2 = (void *) 0x8049560
11620 @node Optimized Code
11621 @chapter Debugging Optimized Code
11622 @cindex optimized code, debugging
11623 @cindex debugging optimized code
11625 Almost all compilers support optimization. With optimization
11626 disabled, the compiler generates assembly code that corresponds
11627 directly to your source code, in a simplistic way. As the compiler
11628 applies more powerful optimizations, the generated assembly code
11629 diverges from your original source code. With help from debugging
11630 information generated by the compiler, @value{GDBN} can map from
11631 the running program back to constructs from your original source.
11633 @value{GDBN} is more accurate with optimization disabled. If you
11634 can recompile without optimization, it is easier to follow the
11635 progress of your program during debugging. But, there are many cases
11636 where you may need to debug an optimized version.
11638 When you debug a program compiled with @samp{-g -O}, remember that the
11639 optimizer has rearranged your code; the debugger shows you what is
11640 really there. Do not be too surprised when the execution path does not
11641 exactly match your source file! An extreme example: if you define a
11642 variable, but never use it, @value{GDBN} never sees that
11643 variable---because the compiler optimizes it out of existence.
11645 Some things do not work as well with @samp{-g -O} as with just
11646 @samp{-g}, particularly on machines with instruction scheduling. If in
11647 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11648 please report it to us as a bug (including a test case!).
11649 @xref{Variables}, for more information about debugging optimized code.
11652 * Inline Functions:: How @value{GDBN} presents inlining
11653 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11656 @node Inline Functions
11657 @section Inline Functions
11658 @cindex inline functions, debugging
11660 @dfn{Inlining} is an optimization that inserts a copy of the function
11661 body directly at each call site, instead of jumping to a shared
11662 routine. @value{GDBN} displays inlined functions just like
11663 non-inlined functions. They appear in backtraces. You can view their
11664 arguments and local variables, step into them with @code{step}, skip
11665 them with @code{next}, and escape from them with @code{finish}.
11666 You can check whether a function was inlined by using the
11667 @code{info frame} command.
11669 For @value{GDBN} to support inlined functions, the compiler must
11670 record information about inlining in the debug information ---
11671 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11672 other compilers do also. @value{GDBN} only supports inlined functions
11673 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11674 do not emit two required attributes (@samp{DW_AT_call_file} and
11675 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11676 function calls with earlier versions of @value{NGCC}. It instead
11677 displays the arguments and local variables of inlined functions as
11678 local variables in the caller.
11680 The body of an inlined function is directly included at its call site;
11681 unlike a non-inlined function, there are no instructions devoted to
11682 the call. @value{GDBN} still pretends that the call site and the
11683 start of the inlined function are different instructions. Stepping to
11684 the call site shows the call site, and then stepping again shows
11685 the first line of the inlined function, even though no additional
11686 instructions are executed.
11688 This makes source-level debugging much clearer; you can see both the
11689 context of the call and then the effect of the call. Only stepping by
11690 a single instruction using @code{stepi} or @code{nexti} does not do
11691 this; single instruction steps always show the inlined body.
11693 There are some ways that @value{GDBN} does not pretend that inlined
11694 function calls are the same as normal calls:
11698 Setting breakpoints at the call site of an inlined function may not
11699 work, because the call site does not contain any code. @value{GDBN}
11700 may incorrectly move the breakpoint to the next line of the enclosing
11701 function, after the call. This limitation will be removed in a future
11702 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11703 or inside the inlined function instead.
11706 @value{GDBN} cannot locate the return value of inlined calls after
11707 using the @code{finish} command. This is a limitation of compiler-generated
11708 debugging information; after @code{finish}, you can step to the next line
11709 and print a variable where your program stored the return value.
11713 @node Tail Call Frames
11714 @section Tail Call Frames
11715 @cindex tail call frames, debugging
11717 Function @code{B} can call function @code{C} in its very last statement. In
11718 unoptimized compilation the call of @code{C} is immediately followed by return
11719 instruction at the end of @code{B} code. Optimizing compiler may replace the
11720 call and return in function @code{B} into one jump to function @code{C}
11721 instead. Such use of a jump instruction is called @dfn{tail call}.
11723 During execution of function @code{C}, there will be no indication in the
11724 function call stack frames that it was tail-called from @code{B}. If function
11725 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11726 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11727 some cases @value{GDBN} can determine that @code{C} was tail-called from
11728 @code{B}, and it will then create fictitious call frame for that, with the
11729 return address set up as if @code{B} called @code{C} normally.
11731 This functionality is currently supported only by DWARF 2 debugging format and
11732 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11733 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11736 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11737 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11741 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11743 Stack level 1, frame at 0x7fffffffda30:
11744 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11745 tail call frame, caller of frame at 0x7fffffffda30
11746 source language c++.
11747 Arglist at unknown address.
11748 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11751 The detection of all the possible code path executions can find them ambiguous.
11752 There is no execution history stored (possible @ref{Reverse Execution} is never
11753 used for this purpose) and the last known caller could have reached the known
11754 callee by multiple different jump sequences. In such case @value{GDBN} still
11755 tries to show at least all the unambiguous top tail callers and all the
11756 unambiguous bottom tail calees, if any.
11759 @anchor{set debug entry-values}
11760 @item set debug entry-values
11761 @kindex set debug entry-values
11762 When set to on, enables printing of analysis messages for both frame argument
11763 values at function entry and tail calls. It will show all the possible valid
11764 tail calls code paths it has considered. It will also print the intersection
11765 of them with the final unambiguous (possibly partial or even empty) code path
11768 @item show debug entry-values
11769 @kindex show debug entry-values
11770 Show the current state of analysis messages printing for both frame argument
11771 values at function entry and tail calls.
11774 The analysis messages for tail calls can for example show why the virtual tail
11775 call frame for function @code{c} has not been recognized (due to the indirect
11776 reference by variable @code{x}):
11779 static void __attribute__((noinline, noclone)) c (void);
11780 void (*x) (void) = c;
11781 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11782 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11783 int main (void) @{ x (); return 0; @}
11785 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11786 DW_TAG_GNU_call_site 0x40039a in main
11788 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11791 #1 0x000000000040039a in main () at t.c:5
11794 Another possibility is an ambiguous virtual tail call frames resolution:
11798 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11799 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11800 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11801 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11802 static void __attribute__((noinline, noclone)) b (void)
11803 @{ if (i) c (); else e (); @}
11804 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11805 int main (void) @{ a (); return 0; @}
11807 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11808 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11809 tailcall: reduced: 0x4004d2(a) |
11812 #1 0x00000000004004d2 in a () at t.c:8
11813 #2 0x0000000000400395 in main () at t.c:9
11816 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11817 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11819 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11820 @ifset HAVE_MAKEINFO_CLICK
11821 @set ARROW @click{}
11822 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11823 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11825 @ifclear HAVE_MAKEINFO_CLICK
11827 @set CALLSEQ1B @value{CALLSEQ1A}
11828 @set CALLSEQ2B @value{CALLSEQ2A}
11831 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11832 The code can have possible execution paths @value{CALLSEQ1B} or
11833 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11835 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11836 has found. It then finds another possible calling sequcen - that one is
11837 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11838 printed as the @code{reduced:} calling sequence. That one could have many
11839 futher @code{compare:} and @code{reduced:} statements as long as there remain
11840 any non-ambiguous sequence entries.
11842 For the frame of function @code{b} in both cases there are different possible
11843 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11844 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11845 therefore this one is displayed to the user while the ambiguous frames are
11848 There can be also reasons why printing of frame argument values at function
11853 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11854 static void __attribute__((noinline, noclone)) a (int i);
11855 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11856 static void __attribute__((noinline, noclone)) a (int i)
11857 @{ if (i) b (i - 1); else c (0); @}
11858 int main (void) @{ a (5); return 0; @}
11861 #0 c (i=i@@entry=0) at t.c:2
11862 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11863 function "a" at 0x400420 can call itself via tail calls
11864 i=<optimized out>) at t.c:6
11865 #2 0x000000000040036e in main () at t.c:7
11868 @value{GDBN} cannot find out from the inferior state if and how many times did
11869 function @code{a} call itself (via function @code{b}) as these calls would be
11870 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11871 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11872 prints @code{<optimized out>} instead.
11875 @chapter C Preprocessor Macros
11877 Some languages, such as C and C@t{++}, provide a way to define and invoke
11878 ``preprocessor macros'' which expand into strings of tokens.
11879 @value{GDBN} can evaluate expressions containing macro invocations, show
11880 the result of macro expansion, and show a macro's definition, including
11881 where it was defined.
11883 You may need to compile your program specially to provide @value{GDBN}
11884 with information about preprocessor macros. Most compilers do not
11885 include macros in their debugging information, even when you compile
11886 with the @option{-g} flag. @xref{Compilation}.
11888 A program may define a macro at one point, remove that definition later,
11889 and then provide a different definition after that. Thus, at different
11890 points in the program, a macro may have different definitions, or have
11891 no definition at all. If there is a current stack frame, @value{GDBN}
11892 uses the macros in scope at that frame's source code line. Otherwise,
11893 @value{GDBN} uses the macros in scope at the current listing location;
11896 Whenever @value{GDBN} evaluates an expression, it always expands any
11897 macro invocations present in the expression. @value{GDBN} also provides
11898 the following commands for working with macros explicitly.
11902 @kindex macro expand
11903 @cindex macro expansion, showing the results of preprocessor
11904 @cindex preprocessor macro expansion, showing the results of
11905 @cindex expanding preprocessor macros
11906 @item macro expand @var{expression}
11907 @itemx macro exp @var{expression}
11908 Show the results of expanding all preprocessor macro invocations in
11909 @var{expression}. Since @value{GDBN} simply expands macros, but does
11910 not parse the result, @var{expression} need not be a valid expression;
11911 it can be any string of tokens.
11914 @item macro expand-once @var{expression}
11915 @itemx macro exp1 @var{expression}
11916 @cindex expand macro once
11917 @i{(This command is not yet implemented.)} Show the results of
11918 expanding those preprocessor macro invocations that appear explicitly in
11919 @var{expression}. Macro invocations appearing in that expansion are
11920 left unchanged. This command allows you to see the effect of a
11921 particular macro more clearly, without being confused by further
11922 expansions. Since @value{GDBN} simply expands macros, but does not
11923 parse the result, @var{expression} need not be a valid expression; it
11924 can be any string of tokens.
11927 @cindex macro definition, showing
11928 @cindex definition of a macro, showing
11929 @cindex macros, from debug info
11930 @item info macro [-a|-all] [--] @var{macro}
11931 Show the current definition or all definitions of the named @var{macro},
11932 and describe the source location or compiler command-line where that
11933 definition was established. The optional double dash is to signify the end of
11934 argument processing and the beginning of @var{macro} for non C-like macros where
11935 the macro may begin with a hyphen.
11937 @kindex info macros
11938 @item info macros @var{location}
11939 Show all macro definitions that are in effect at the location specified
11940 by @var{location}, and describe the source location or compiler
11941 command-line where those definitions were established.
11943 @kindex macro define
11944 @cindex user-defined macros
11945 @cindex defining macros interactively
11946 @cindex macros, user-defined
11947 @item macro define @var{macro} @var{replacement-list}
11948 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11949 Introduce a definition for a preprocessor macro named @var{macro},
11950 invocations of which are replaced by the tokens given in
11951 @var{replacement-list}. The first form of this command defines an
11952 ``object-like'' macro, which takes no arguments; the second form
11953 defines a ``function-like'' macro, which takes the arguments given in
11956 A definition introduced by this command is in scope in every
11957 expression evaluated in @value{GDBN}, until it is removed with the
11958 @code{macro undef} command, described below. The definition overrides
11959 all definitions for @var{macro} present in the program being debugged,
11960 as well as any previous user-supplied definition.
11962 @kindex macro undef
11963 @item macro undef @var{macro}
11964 Remove any user-supplied definition for the macro named @var{macro}.
11965 This command only affects definitions provided with the @code{macro
11966 define} command, described above; it cannot remove definitions present
11967 in the program being debugged.
11971 List all the macros defined using the @code{macro define} command.
11974 @cindex macros, example of debugging with
11975 Here is a transcript showing the above commands in action. First, we
11976 show our source files:
11981 #include "sample.h"
11984 #define ADD(x) (M + x)
11989 printf ("Hello, world!\n");
11991 printf ("We're so creative.\n");
11993 printf ("Goodbye, world!\n");
12000 Now, we compile the program using the @sc{gnu} C compiler,
12001 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12002 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12003 and @option{-gdwarf-4}; we recommend always choosing the most recent
12004 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12005 includes information about preprocessor macros in the debugging
12009 $ gcc -gdwarf-2 -g3 sample.c -o sample
12013 Now, we start @value{GDBN} on our sample program:
12017 GNU gdb 2002-05-06-cvs
12018 Copyright 2002 Free Software Foundation, Inc.
12019 GDB is free software, @dots{}
12023 We can expand macros and examine their definitions, even when the
12024 program is not running. @value{GDBN} uses the current listing position
12025 to decide which macro definitions are in scope:
12028 (@value{GDBP}) list main
12031 5 #define ADD(x) (M + x)
12036 10 printf ("Hello, world!\n");
12038 12 printf ("We're so creative.\n");
12039 (@value{GDBP}) info macro ADD
12040 Defined at /home/jimb/gdb/macros/play/sample.c:5
12041 #define ADD(x) (M + x)
12042 (@value{GDBP}) info macro Q
12043 Defined at /home/jimb/gdb/macros/play/sample.h:1
12044 included at /home/jimb/gdb/macros/play/sample.c:2
12046 (@value{GDBP}) macro expand ADD(1)
12047 expands to: (42 + 1)
12048 (@value{GDBP}) macro expand-once ADD(1)
12049 expands to: once (M + 1)
12053 In the example above, note that @code{macro expand-once} expands only
12054 the macro invocation explicit in the original text --- the invocation of
12055 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12056 which was introduced by @code{ADD}.
12058 Once the program is running, @value{GDBN} uses the macro definitions in
12059 force at the source line of the current stack frame:
12062 (@value{GDBP}) break main
12063 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12065 Starting program: /home/jimb/gdb/macros/play/sample
12067 Breakpoint 1, main () at sample.c:10
12068 10 printf ("Hello, world!\n");
12072 At line 10, the definition of the macro @code{N} at line 9 is in force:
12075 (@value{GDBP}) info macro N
12076 Defined at /home/jimb/gdb/macros/play/sample.c:9
12078 (@value{GDBP}) macro expand N Q M
12079 expands to: 28 < 42
12080 (@value{GDBP}) print N Q M
12085 As we step over directives that remove @code{N}'s definition, and then
12086 give it a new definition, @value{GDBN} finds the definition (or lack
12087 thereof) in force at each point:
12090 (@value{GDBP}) next
12092 12 printf ("We're so creative.\n");
12093 (@value{GDBP}) info macro N
12094 The symbol `N' has no definition as a C/C++ preprocessor macro
12095 at /home/jimb/gdb/macros/play/sample.c:12
12096 (@value{GDBP}) next
12098 14 printf ("Goodbye, world!\n");
12099 (@value{GDBP}) info macro N
12100 Defined at /home/jimb/gdb/macros/play/sample.c:13
12102 (@value{GDBP}) macro expand N Q M
12103 expands to: 1729 < 42
12104 (@value{GDBP}) print N Q M
12109 In addition to source files, macros can be defined on the compilation command
12110 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12111 such a way, @value{GDBN} displays the location of their definition as line zero
12112 of the source file submitted to the compiler.
12115 (@value{GDBP}) info macro __STDC__
12116 Defined at /home/jimb/gdb/macros/play/sample.c:0
12123 @chapter Tracepoints
12124 @c This chapter is based on the documentation written by Michael
12125 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12127 @cindex tracepoints
12128 In some applications, it is not feasible for the debugger to interrupt
12129 the program's execution long enough for the developer to learn
12130 anything helpful about its behavior. If the program's correctness
12131 depends on its real-time behavior, delays introduced by a debugger
12132 might cause the program to change its behavior drastically, or perhaps
12133 fail, even when the code itself is correct. It is useful to be able
12134 to observe the program's behavior without interrupting it.
12136 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12137 specify locations in the program, called @dfn{tracepoints}, and
12138 arbitrary expressions to evaluate when those tracepoints are reached.
12139 Later, using the @code{tfind} command, you can examine the values
12140 those expressions had when the program hit the tracepoints. The
12141 expressions may also denote objects in memory---structures or arrays,
12142 for example---whose values @value{GDBN} should record; while visiting
12143 a particular tracepoint, you may inspect those objects as if they were
12144 in memory at that moment. However, because @value{GDBN} records these
12145 values without interacting with you, it can do so quickly and
12146 unobtrusively, hopefully not disturbing the program's behavior.
12148 The tracepoint facility is currently available only for remote
12149 targets. @xref{Targets}. In addition, your remote target must know
12150 how to collect trace data. This functionality is implemented in the
12151 remote stub; however, none of the stubs distributed with @value{GDBN}
12152 support tracepoints as of this writing. The format of the remote
12153 packets used to implement tracepoints are described in @ref{Tracepoint
12156 It is also possible to get trace data from a file, in a manner reminiscent
12157 of corefiles; you specify the filename, and use @code{tfind} to search
12158 through the file. @xref{Trace Files}, for more details.
12160 This chapter describes the tracepoint commands and features.
12163 * Set Tracepoints::
12164 * Analyze Collected Data::
12165 * Tracepoint Variables::
12169 @node Set Tracepoints
12170 @section Commands to Set Tracepoints
12172 Before running such a @dfn{trace experiment}, an arbitrary number of
12173 tracepoints can be set. A tracepoint is actually a special type of
12174 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12175 standard breakpoint commands. For instance, as with breakpoints,
12176 tracepoint numbers are successive integers starting from one, and many
12177 of the commands associated with tracepoints take the tracepoint number
12178 as their argument, to identify which tracepoint to work on.
12180 For each tracepoint, you can specify, in advance, some arbitrary set
12181 of data that you want the target to collect in the trace buffer when
12182 it hits that tracepoint. The collected data can include registers,
12183 local variables, or global data. Later, you can use @value{GDBN}
12184 commands to examine the values these data had at the time the
12185 tracepoint was hit.
12187 Tracepoints do not support every breakpoint feature. Ignore counts on
12188 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12189 commands when they are hit. Tracepoints may not be thread-specific
12192 @cindex fast tracepoints
12193 Some targets may support @dfn{fast tracepoints}, which are inserted in
12194 a different way (such as with a jump instead of a trap), that is
12195 faster but possibly restricted in where they may be installed.
12197 @cindex static tracepoints
12198 @cindex markers, static tracepoints
12199 @cindex probing markers, static tracepoints
12200 Regular and fast tracepoints are dynamic tracing facilities, meaning
12201 that they can be used to insert tracepoints at (almost) any location
12202 in the target. Some targets may also support controlling @dfn{static
12203 tracepoints} from @value{GDBN}. With static tracing, a set of
12204 instrumentation points, also known as @dfn{markers}, are embedded in
12205 the target program, and can be activated or deactivated by name or
12206 address. These are usually placed at locations which facilitate
12207 investigating what the target is actually doing. @value{GDBN}'s
12208 support for static tracing includes being able to list instrumentation
12209 points, and attach them with @value{GDBN} defined high level
12210 tracepoints that expose the whole range of convenience of
12211 @value{GDBN}'s tracepoints support. Namely, support for collecting
12212 registers values and values of global or local (to the instrumentation
12213 point) variables; tracepoint conditions and trace state variables.
12214 The act of installing a @value{GDBN} static tracepoint on an
12215 instrumentation point, or marker, is referred to as @dfn{probing} a
12216 static tracepoint marker.
12218 @code{gdbserver} supports tracepoints on some target systems.
12219 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12221 This section describes commands to set tracepoints and associated
12222 conditions and actions.
12225 * Create and Delete Tracepoints::
12226 * Enable and Disable Tracepoints::
12227 * Tracepoint Passcounts::
12228 * Tracepoint Conditions::
12229 * Trace State Variables::
12230 * Tracepoint Actions::
12231 * Listing Tracepoints::
12232 * Listing Static Tracepoint Markers::
12233 * Starting and Stopping Trace Experiments::
12234 * Tracepoint Restrictions::
12237 @node Create and Delete Tracepoints
12238 @subsection Create and Delete Tracepoints
12241 @cindex set tracepoint
12243 @item trace @var{location}
12244 The @code{trace} command is very similar to the @code{break} command.
12245 Its argument @var{location} can be any valid location.
12246 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12247 which is a point in the target program where the debugger will briefly stop,
12248 collect some data, and then allow the program to continue. Setting a tracepoint
12249 or changing its actions takes effect immediately if the remote stub
12250 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12252 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12253 these changes don't take effect until the next @code{tstart}
12254 command, and once a trace experiment is running, further changes will
12255 not have any effect until the next trace experiment starts. In addition,
12256 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12257 address is not yet resolved. (This is similar to pending breakpoints.)
12258 Pending tracepoints are not downloaded to the target and not installed
12259 until they are resolved. The resolution of pending tracepoints requires
12260 @value{GDBN} support---when debugging with the remote target, and
12261 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12262 tracing}), pending tracepoints can not be resolved (and downloaded to
12263 the remote stub) while @value{GDBN} is disconnected.
12265 Here are some examples of using the @code{trace} command:
12268 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12270 (@value{GDBP}) @b{trace +2} // 2 lines forward
12272 (@value{GDBP}) @b{trace my_function} // first source line of function
12274 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12276 (@value{GDBP}) @b{trace *0x2117c4} // an address
12280 You can abbreviate @code{trace} as @code{tr}.
12282 @item trace @var{location} if @var{cond}
12283 Set a tracepoint with condition @var{cond}; evaluate the expression
12284 @var{cond} each time the tracepoint is reached, and collect data only
12285 if the value is nonzero---that is, if @var{cond} evaluates as true.
12286 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12287 information on tracepoint conditions.
12289 @item ftrace @var{location} [ if @var{cond} ]
12290 @cindex set fast tracepoint
12291 @cindex fast tracepoints, setting
12293 The @code{ftrace} command sets a fast tracepoint. For targets that
12294 support them, fast tracepoints will use a more efficient but possibly
12295 less general technique to trigger data collection, such as a jump
12296 instruction instead of a trap, or some sort of hardware support. It
12297 may not be possible to create a fast tracepoint at the desired
12298 location, in which case the command will exit with an explanatory
12301 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12304 On 32-bit x86-architecture systems, fast tracepoints normally need to
12305 be placed at an instruction that is 5 bytes or longer, but can be
12306 placed at 4-byte instructions if the low 64K of memory of the target
12307 program is available to install trampolines. Some Unix-type systems,
12308 such as @sc{gnu}/Linux, exclude low addresses from the program's
12309 address space; but for instance with the Linux kernel it is possible
12310 to let @value{GDBN} use this area by doing a @command{sysctl} command
12311 to set the @code{mmap_min_addr} kernel parameter, as in
12314 sudo sysctl -w vm.mmap_min_addr=32768
12318 which sets the low address to 32K, which leaves plenty of room for
12319 trampolines. The minimum address should be set to a page boundary.
12321 @item strace @var{location} [ if @var{cond} ]
12322 @cindex set static tracepoint
12323 @cindex static tracepoints, setting
12324 @cindex probe static tracepoint marker
12326 The @code{strace} command sets a static tracepoint. For targets that
12327 support it, setting a static tracepoint probes a static
12328 instrumentation point, or marker, found at @var{location}. It may not
12329 be possible to set a static tracepoint at the desired location, in
12330 which case the command will exit with an explanatory message.
12332 @value{GDBN} handles arguments to @code{strace} exactly as for
12333 @code{trace}, with the addition that the user can also specify
12334 @code{-m @var{marker}} as @var{location}. This probes the marker
12335 identified by the @var{marker} string identifier. This identifier
12336 depends on the static tracepoint backend library your program is
12337 using. You can find all the marker identifiers in the @samp{ID} field
12338 of the @code{info static-tracepoint-markers} command output.
12339 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12340 Markers}. For example, in the following small program using the UST
12346 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12351 the marker id is composed of joining the first two arguments to the
12352 @code{trace_mark} call with a slash, which translates to:
12355 (@value{GDBP}) info static-tracepoint-markers
12356 Cnt Enb ID Address What
12357 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12363 so you may probe the marker above with:
12366 (@value{GDBP}) strace -m ust/bar33
12369 Static tracepoints accept an extra collect action --- @code{collect
12370 $_sdata}. This collects arbitrary user data passed in the probe point
12371 call to the tracing library. In the UST example above, you'll see
12372 that the third argument to @code{trace_mark} is a printf-like format
12373 string. The user data is then the result of running that formating
12374 string against the following arguments. Note that @code{info
12375 static-tracepoint-markers} command output lists that format string in
12376 the @samp{Data:} field.
12378 You can inspect this data when analyzing the trace buffer, by printing
12379 the $_sdata variable like any other variable available to
12380 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12383 @cindex last tracepoint number
12384 @cindex recent tracepoint number
12385 @cindex tracepoint number
12386 The convenience variable @code{$tpnum} records the tracepoint number
12387 of the most recently set tracepoint.
12389 @kindex delete tracepoint
12390 @cindex tracepoint deletion
12391 @item delete tracepoint @r{[}@var{num}@r{]}
12392 Permanently delete one or more tracepoints. With no argument, the
12393 default is to delete all tracepoints. Note that the regular
12394 @code{delete} command can remove tracepoints also.
12399 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12401 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12405 You can abbreviate this command as @code{del tr}.
12408 @node Enable and Disable Tracepoints
12409 @subsection Enable and Disable Tracepoints
12411 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12414 @kindex disable tracepoint
12415 @item disable tracepoint @r{[}@var{num}@r{]}
12416 Disable tracepoint @var{num}, or all tracepoints if no argument
12417 @var{num} is given. A disabled tracepoint will have no effect during
12418 a trace experiment, but it is not forgotten. You can re-enable
12419 a disabled tracepoint using the @code{enable tracepoint} command.
12420 If the command is issued during a trace experiment and the debug target
12421 has support for disabling tracepoints during a trace experiment, then the
12422 change will be effective immediately. Otherwise, it will be applied to the
12423 next trace experiment.
12425 @kindex enable tracepoint
12426 @item enable tracepoint @r{[}@var{num}@r{]}
12427 Enable tracepoint @var{num}, or all tracepoints. If this command is
12428 issued during a trace experiment and the debug target supports enabling
12429 tracepoints during a trace experiment, then the enabled tracepoints will
12430 become effective immediately. Otherwise, they will become effective the
12431 next time a trace experiment is run.
12434 @node Tracepoint Passcounts
12435 @subsection Tracepoint Passcounts
12439 @cindex tracepoint pass count
12440 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12441 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12442 automatically stop a trace experiment. If a tracepoint's passcount is
12443 @var{n}, then the trace experiment will be automatically stopped on
12444 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12445 @var{num} is not specified, the @code{passcount} command sets the
12446 passcount of the most recently defined tracepoint. If no passcount is
12447 given, the trace experiment will run until stopped explicitly by the
12453 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12454 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12456 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12457 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12458 (@value{GDBP}) @b{trace foo}
12459 (@value{GDBP}) @b{pass 3}
12460 (@value{GDBP}) @b{trace bar}
12461 (@value{GDBP}) @b{pass 2}
12462 (@value{GDBP}) @b{trace baz}
12463 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12464 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12465 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12466 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12470 @node Tracepoint Conditions
12471 @subsection Tracepoint Conditions
12472 @cindex conditional tracepoints
12473 @cindex tracepoint conditions
12475 The simplest sort of tracepoint collects data every time your program
12476 reaches a specified place. You can also specify a @dfn{condition} for
12477 a tracepoint. A condition is just a Boolean expression in your
12478 programming language (@pxref{Expressions, ,Expressions}). A
12479 tracepoint with a condition evaluates the expression each time your
12480 program reaches it, and data collection happens only if the condition
12483 Tracepoint conditions can be specified when a tracepoint is set, by
12484 using @samp{if} in the arguments to the @code{trace} command.
12485 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12486 also be set or changed at any time with the @code{condition} command,
12487 just as with breakpoints.
12489 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12490 the conditional expression itself. Instead, @value{GDBN} encodes the
12491 expression into an agent expression (@pxref{Agent Expressions})
12492 suitable for execution on the target, independently of @value{GDBN}.
12493 Global variables become raw memory locations, locals become stack
12494 accesses, and so forth.
12496 For instance, suppose you have a function that is usually called
12497 frequently, but should not be called after an error has occurred. You
12498 could use the following tracepoint command to collect data about calls
12499 of that function that happen while the error code is propagating
12500 through the program; an unconditional tracepoint could end up
12501 collecting thousands of useless trace frames that you would have to
12505 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12508 @node Trace State Variables
12509 @subsection Trace State Variables
12510 @cindex trace state variables
12512 A @dfn{trace state variable} is a special type of variable that is
12513 created and managed by target-side code. The syntax is the same as
12514 that for GDB's convenience variables (a string prefixed with ``$''),
12515 but they are stored on the target. They must be created explicitly,
12516 using a @code{tvariable} command. They are always 64-bit signed
12519 Trace state variables are remembered by @value{GDBN}, and downloaded
12520 to the target along with tracepoint information when the trace
12521 experiment starts. There are no intrinsic limits on the number of
12522 trace state variables, beyond memory limitations of the target.
12524 @cindex convenience variables, and trace state variables
12525 Although trace state variables are managed by the target, you can use
12526 them in print commands and expressions as if they were convenience
12527 variables; @value{GDBN} will get the current value from the target
12528 while the trace experiment is running. Trace state variables share
12529 the same namespace as other ``$'' variables, which means that you
12530 cannot have trace state variables with names like @code{$23} or
12531 @code{$pc}, nor can you have a trace state variable and a convenience
12532 variable with the same name.
12536 @item tvariable $@var{name} [ = @var{expression} ]
12538 The @code{tvariable} command creates a new trace state variable named
12539 @code{$@var{name}}, and optionally gives it an initial value of
12540 @var{expression}. The @var{expression} is evaluated when this command is
12541 entered; the result will be converted to an integer if possible,
12542 otherwise @value{GDBN} will report an error. A subsequent
12543 @code{tvariable} command specifying the same name does not create a
12544 variable, but instead assigns the supplied initial value to the
12545 existing variable of that name, overwriting any previous initial
12546 value. The default initial value is 0.
12548 @item info tvariables
12549 @kindex info tvariables
12550 List all the trace state variables along with their initial values.
12551 Their current values may also be displayed, if the trace experiment is
12554 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12555 @kindex delete tvariable
12556 Delete the given trace state variables, or all of them if no arguments
12561 @node Tracepoint Actions
12562 @subsection Tracepoint Action Lists
12566 @cindex tracepoint actions
12567 @item actions @r{[}@var{num}@r{]}
12568 This command will prompt for a list of actions to be taken when the
12569 tracepoint is hit. If the tracepoint number @var{num} is not
12570 specified, this command sets the actions for the one that was most
12571 recently defined (so that you can define a tracepoint and then say
12572 @code{actions} without bothering about its number). You specify the
12573 actions themselves on the following lines, one action at a time, and
12574 terminate the actions list with a line containing just @code{end}. So
12575 far, the only defined actions are @code{collect}, @code{teval}, and
12576 @code{while-stepping}.
12578 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12579 Commands, ,Breakpoint Command Lists}), except that only the defined
12580 actions are allowed; any other @value{GDBN} command is rejected.
12582 @cindex remove actions from a tracepoint
12583 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12584 and follow it immediately with @samp{end}.
12587 (@value{GDBP}) @b{collect @var{data}} // collect some data
12589 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12591 (@value{GDBP}) @b{end} // signals the end of actions.
12594 In the following example, the action list begins with @code{collect}
12595 commands indicating the things to be collected when the tracepoint is
12596 hit. Then, in order to single-step and collect additional data
12597 following the tracepoint, a @code{while-stepping} command is used,
12598 followed by the list of things to be collected after each step in a
12599 sequence of single steps. The @code{while-stepping} command is
12600 terminated by its own separate @code{end} command. Lastly, the action
12601 list is terminated by an @code{end} command.
12604 (@value{GDBP}) @b{trace foo}
12605 (@value{GDBP}) @b{actions}
12606 Enter actions for tracepoint 1, one per line:
12609 > while-stepping 12
12610 > collect $pc, arr[i]
12615 @kindex collect @r{(tracepoints)}
12616 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12617 Collect values of the given expressions when the tracepoint is hit.
12618 This command accepts a comma-separated list of any valid expressions.
12619 In addition to global, static, or local variables, the following
12620 special arguments are supported:
12624 Collect all registers.
12627 Collect all function arguments.
12630 Collect all local variables.
12633 Collect the return address. This is helpful if you want to see more
12637 Collects the number of arguments from the static probe at which the
12638 tracepoint is located.
12639 @xref{Static Probe Points}.
12641 @item $_probe_arg@var{n}
12642 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12643 from the static probe at which the tracepoint is located.
12644 @xref{Static Probe Points}.
12647 @vindex $_sdata@r{, collect}
12648 Collect static tracepoint marker specific data. Only available for
12649 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12650 Lists}. On the UST static tracepoints library backend, an
12651 instrumentation point resembles a @code{printf} function call. The
12652 tracing library is able to collect user specified data formatted to a
12653 character string using the format provided by the programmer that
12654 instrumented the program. Other backends have similar mechanisms.
12655 Here's an example of a UST marker call:
12658 const char master_name[] = "$your_name";
12659 trace_mark(channel1, marker1, "hello %s", master_name)
12662 In this case, collecting @code{$_sdata} collects the string
12663 @samp{hello $yourname}. When analyzing the trace buffer, you can
12664 inspect @samp{$_sdata} like any other variable available to
12668 You can give several consecutive @code{collect} commands, each one
12669 with a single argument, or one @code{collect} command with several
12670 arguments separated by commas; the effect is the same.
12672 The optional @var{mods} changes the usual handling of the arguments.
12673 @code{s} requests that pointers to chars be handled as strings, in
12674 particular collecting the contents of the memory being pointed at, up
12675 to the first zero. The upper bound is by default the value of the
12676 @code{print elements} variable; if @code{s} is followed by a decimal
12677 number, that is the upper bound instead. So for instance
12678 @samp{collect/s25 mystr} collects as many as 25 characters at
12681 The command @code{info scope} (@pxref{Symbols, info scope}) is
12682 particularly useful for figuring out what data to collect.
12684 @kindex teval @r{(tracepoints)}
12685 @item teval @var{expr1}, @var{expr2}, @dots{}
12686 Evaluate the given expressions when the tracepoint is hit. This
12687 command accepts a comma-separated list of expressions. The results
12688 are discarded, so this is mainly useful for assigning values to trace
12689 state variables (@pxref{Trace State Variables}) without adding those
12690 values to the trace buffer, as would be the case if the @code{collect}
12693 @kindex while-stepping @r{(tracepoints)}
12694 @item while-stepping @var{n}
12695 Perform @var{n} single-step instruction traces after the tracepoint,
12696 collecting new data after each step. The @code{while-stepping}
12697 command is followed by the list of what to collect while stepping
12698 (followed by its own @code{end} command):
12701 > while-stepping 12
12702 > collect $regs, myglobal
12708 Note that @code{$pc} is not automatically collected by
12709 @code{while-stepping}; you need to explicitly collect that register if
12710 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12713 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12714 @kindex set default-collect
12715 @cindex default collection action
12716 This variable is a list of expressions to collect at each tracepoint
12717 hit. It is effectively an additional @code{collect} action prepended
12718 to every tracepoint action list. The expressions are parsed
12719 individually for each tracepoint, so for instance a variable named
12720 @code{xyz} may be interpreted as a global for one tracepoint, and a
12721 local for another, as appropriate to the tracepoint's location.
12723 @item show default-collect
12724 @kindex show default-collect
12725 Show the list of expressions that are collected by default at each
12730 @node Listing Tracepoints
12731 @subsection Listing Tracepoints
12734 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12735 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12736 @cindex information about tracepoints
12737 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12738 Display information about the tracepoint @var{num}. If you don't
12739 specify a tracepoint number, displays information about all the
12740 tracepoints defined so far. The format is similar to that used for
12741 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12742 command, simply restricting itself to tracepoints.
12744 A tracepoint's listing may include additional information specific to
12749 its passcount as given by the @code{passcount @var{n}} command
12752 the state about installed on target of each location
12756 (@value{GDBP}) @b{info trace}
12757 Num Type Disp Enb Address What
12758 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12760 collect globfoo, $regs
12765 2 tracepoint keep y <MULTIPLE>
12767 2.1 y 0x0804859c in func4 at change-loc.h:35
12768 installed on target
12769 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12770 installed on target
12771 2.3 y <PENDING> set_tracepoint
12772 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12773 not installed on target
12778 This command can be abbreviated @code{info tp}.
12781 @node Listing Static Tracepoint Markers
12782 @subsection Listing Static Tracepoint Markers
12785 @kindex info static-tracepoint-markers
12786 @cindex information about static tracepoint markers
12787 @item info static-tracepoint-markers
12788 Display information about all static tracepoint markers defined in the
12791 For each marker, the following columns are printed:
12795 An incrementing counter, output to help readability. This is not a
12798 The marker ID, as reported by the target.
12799 @item Enabled or Disabled
12800 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12801 that are not enabled.
12803 Where the marker is in your program, as a memory address.
12805 Where the marker is in the source for your program, as a file and line
12806 number. If the debug information included in the program does not
12807 allow @value{GDBN} to locate the source of the marker, this column
12808 will be left blank.
12812 In addition, the following information may be printed for each marker:
12816 User data passed to the tracing library by the marker call. In the
12817 UST backend, this is the format string passed as argument to the
12819 @item Static tracepoints probing the marker
12820 The list of static tracepoints attached to the marker.
12824 (@value{GDBP}) info static-tracepoint-markers
12825 Cnt ID Enb Address What
12826 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12827 Data: number1 %d number2 %d
12828 Probed by static tracepoints: #2
12829 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12835 @node Starting and Stopping Trace Experiments
12836 @subsection Starting and Stopping Trace Experiments
12839 @kindex tstart [ @var{notes} ]
12840 @cindex start a new trace experiment
12841 @cindex collected data discarded
12843 This command starts the trace experiment, and begins collecting data.
12844 It has the side effect of discarding all the data collected in the
12845 trace buffer during the previous trace experiment. If any arguments
12846 are supplied, they are taken as a note and stored with the trace
12847 experiment's state. The notes may be arbitrary text, and are
12848 especially useful with disconnected tracing in a multi-user context;
12849 the notes can explain what the trace is doing, supply user contact
12850 information, and so forth.
12852 @kindex tstop [ @var{notes} ]
12853 @cindex stop a running trace experiment
12855 This command stops the trace experiment. If any arguments are
12856 supplied, they are recorded with the experiment as a note. This is
12857 useful if you are stopping a trace started by someone else, for
12858 instance if the trace is interfering with the system's behavior and
12859 needs to be stopped quickly.
12861 @strong{Note}: a trace experiment and data collection may stop
12862 automatically if any tracepoint's passcount is reached
12863 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12866 @cindex status of trace data collection
12867 @cindex trace experiment, status of
12869 This command displays the status of the current trace data
12873 Here is an example of the commands we described so far:
12876 (@value{GDBP}) @b{trace gdb_c_test}
12877 (@value{GDBP}) @b{actions}
12878 Enter actions for tracepoint #1, one per line.
12879 > collect $regs,$locals,$args
12880 > while-stepping 11
12884 (@value{GDBP}) @b{tstart}
12885 [time passes @dots{}]
12886 (@value{GDBP}) @b{tstop}
12889 @anchor{disconnected tracing}
12890 @cindex disconnected tracing
12891 You can choose to continue running the trace experiment even if
12892 @value{GDBN} disconnects from the target, voluntarily or
12893 involuntarily. For commands such as @code{detach}, the debugger will
12894 ask what you want to do with the trace. But for unexpected
12895 terminations (@value{GDBN} crash, network outage), it would be
12896 unfortunate to lose hard-won trace data, so the variable
12897 @code{disconnected-tracing} lets you decide whether the trace should
12898 continue running without @value{GDBN}.
12901 @item set disconnected-tracing on
12902 @itemx set disconnected-tracing off
12903 @kindex set disconnected-tracing
12904 Choose whether a tracing run should continue to run if @value{GDBN}
12905 has disconnected from the target. Note that @code{detach} or
12906 @code{quit} will ask you directly what to do about a running trace no
12907 matter what this variable's setting, so the variable is mainly useful
12908 for handling unexpected situations, such as loss of the network.
12910 @item show disconnected-tracing
12911 @kindex show disconnected-tracing
12912 Show the current choice for disconnected tracing.
12916 When you reconnect to the target, the trace experiment may or may not
12917 still be running; it might have filled the trace buffer in the
12918 meantime, or stopped for one of the other reasons. If it is running,
12919 it will continue after reconnection.
12921 Upon reconnection, the target will upload information about the
12922 tracepoints in effect. @value{GDBN} will then compare that
12923 information to the set of tracepoints currently defined, and attempt
12924 to match them up, allowing for the possibility that the numbers may
12925 have changed due to creation and deletion in the meantime. If one of
12926 the target's tracepoints does not match any in @value{GDBN}, the
12927 debugger will create a new tracepoint, so that you have a number with
12928 which to specify that tracepoint. This matching-up process is
12929 necessarily heuristic, and it may result in useless tracepoints being
12930 created; you may simply delete them if they are of no use.
12932 @cindex circular trace buffer
12933 If your target agent supports a @dfn{circular trace buffer}, then you
12934 can run a trace experiment indefinitely without filling the trace
12935 buffer; when space runs out, the agent deletes already-collected trace
12936 frames, oldest first, until there is enough room to continue
12937 collecting. This is especially useful if your tracepoints are being
12938 hit too often, and your trace gets terminated prematurely because the
12939 buffer is full. To ask for a circular trace buffer, simply set
12940 @samp{circular-trace-buffer} to on. You can set this at any time,
12941 including during tracing; if the agent can do it, it will change
12942 buffer handling on the fly, otherwise it will not take effect until
12946 @item set circular-trace-buffer on
12947 @itemx set circular-trace-buffer off
12948 @kindex set circular-trace-buffer
12949 Choose whether a tracing run should use a linear or circular buffer
12950 for trace data. A linear buffer will not lose any trace data, but may
12951 fill up prematurely, while a circular buffer will discard old trace
12952 data, but it will have always room for the latest tracepoint hits.
12954 @item show circular-trace-buffer
12955 @kindex show circular-trace-buffer
12956 Show the current choice for the trace buffer. Note that this may not
12957 match the agent's current buffer handling, nor is it guaranteed to
12958 match the setting that might have been in effect during a past run,
12959 for instance if you are looking at frames from a trace file.
12964 @item set trace-buffer-size @var{n}
12965 @itemx set trace-buffer-size unlimited
12966 @kindex set trace-buffer-size
12967 Request that the target use a trace buffer of @var{n} bytes. Not all
12968 targets will honor the request; they may have a compiled-in size for
12969 the trace buffer, or some other limitation. Set to a value of
12970 @code{unlimited} or @code{-1} to let the target use whatever size it
12971 likes. This is also the default.
12973 @item show trace-buffer-size
12974 @kindex show trace-buffer-size
12975 Show the current requested size for the trace buffer. Note that this
12976 will only match the actual size if the target supports size-setting,
12977 and was able to handle the requested size. For instance, if the
12978 target can only change buffer size between runs, this variable will
12979 not reflect the change until the next run starts. Use @code{tstatus}
12980 to get a report of the actual buffer size.
12984 @item set trace-user @var{text}
12985 @kindex set trace-user
12987 @item show trace-user
12988 @kindex show trace-user
12990 @item set trace-notes @var{text}
12991 @kindex set trace-notes
12992 Set the trace run's notes.
12994 @item show trace-notes
12995 @kindex show trace-notes
12996 Show the trace run's notes.
12998 @item set trace-stop-notes @var{text}
12999 @kindex set trace-stop-notes
13000 Set the trace run's stop notes. The handling of the note is as for
13001 @code{tstop} arguments; the set command is convenient way to fix a
13002 stop note that is mistaken or incomplete.
13004 @item show trace-stop-notes
13005 @kindex show trace-stop-notes
13006 Show the trace run's stop notes.
13010 @node Tracepoint Restrictions
13011 @subsection Tracepoint Restrictions
13013 @cindex tracepoint restrictions
13014 There are a number of restrictions on the use of tracepoints. As
13015 described above, tracepoint data gathering occurs on the target
13016 without interaction from @value{GDBN}. Thus the full capabilities of
13017 the debugger are not available during data gathering, and then at data
13018 examination time, you will be limited by only having what was
13019 collected. The following items describe some common problems, but it
13020 is not exhaustive, and you may run into additional difficulties not
13026 Tracepoint expressions are intended to gather objects (lvalues). Thus
13027 the full flexibility of GDB's expression evaluator is not available.
13028 You cannot call functions, cast objects to aggregate types, access
13029 convenience variables or modify values (except by assignment to trace
13030 state variables). Some language features may implicitly call
13031 functions (for instance Objective-C fields with accessors), and therefore
13032 cannot be collected either.
13035 Collection of local variables, either individually or in bulk with
13036 @code{$locals} or @code{$args}, during @code{while-stepping} may
13037 behave erratically. The stepping action may enter a new scope (for
13038 instance by stepping into a function), or the location of the variable
13039 may change (for instance it is loaded into a register). The
13040 tracepoint data recorded uses the location information for the
13041 variables that is correct for the tracepoint location. When the
13042 tracepoint is created, it is not possible, in general, to determine
13043 where the steps of a @code{while-stepping} sequence will advance the
13044 program---particularly if a conditional branch is stepped.
13047 Collection of an incompletely-initialized or partially-destroyed object
13048 may result in something that @value{GDBN} cannot display, or displays
13049 in a misleading way.
13052 When @value{GDBN} displays a pointer to character it automatically
13053 dereferences the pointer to also display characters of the string
13054 being pointed to. However, collecting the pointer during tracing does
13055 not automatically collect the string. You need to explicitly
13056 dereference the pointer and provide size information if you want to
13057 collect not only the pointer, but the memory pointed to. For example,
13058 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13062 It is not possible to collect a complete stack backtrace at a
13063 tracepoint. Instead, you may collect the registers and a few hundred
13064 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13065 (adjust to use the name of the actual stack pointer register on your
13066 target architecture, and the amount of stack you wish to capture).
13067 Then the @code{backtrace} command will show a partial backtrace when
13068 using a trace frame. The number of stack frames that can be examined
13069 depends on the sizes of the frames in the collected stack. Note that
13070 if you ask for a block so large that it goes past the bottom of the
13071 stack, the target agent may report an error trying to read from an
13075 If you do not collect registers at a tracepoint, @value{GDBN} can
13076 infer that the value of @code{$pc} must be the same as the address of
13077 the tracepoint and use that when you are looking at a trace frame
13078 for that tracepoint. However, this cannot work if the tracepoint has
13079 multiple locations (for instance if it was set in a function that was
13080 inlined), or if it has a @code{while-stepping} loop. In those cases
13081 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13086 @node Analyze Collected Data
13087 @section Using the Collected Data
13089 After the tracepoint experiment ends, you use @value{GDBN} commands
13090 for examining the trace data. The basic idea is that each tracepoint
13091 collects a trace @dfn{snapshot} every time it is hit and another
13092 snapshot every time it single-steps. All these snapshots are
13093 consecutively numbered from zero and go into a buffer, and you can
13094 examine them later. The way you examine them is to @dfn{focus} on a
13095 specific trace snapshot. When the remote stub is focused on a trace
13096 snapshot, it will respond to all @value{GDBN} requests for memory and
13097 registers by reading from the buffer which belongs to that snapshot,
13098 rather than from @emph{real} memory or registers of the program being
13099 debugged. This means that @strong{all} @value{GDBN} commands
13100 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13101 behave as if we were currently debugging the program state as it was
13102 when the tracepoint occurred. Any requests for data that are not in
13103 the buffer will fail.
13106 * tfind:: How to select a trace snapshot
13107 * tdump:: How to display all data for a snapshot
13108 * save tracepoints:: How to save tracepoints for a future run
13112 @subsection @code{tfind @var{n}}
13115 @cindex select trace snapshot
13116 @cindex find trace snapshot
13117 The basic command for selecting a trace snapshot from the buffer is
13118 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13119 counting from zero. If no argument @var{n} is given, the next
13120 snapshot is selected.
13122 Here are the various forms of using the @code{tfind} command.
13126 Find the first snapshot in the buffer. This is a synonym for
13127 @code{tfind 0} (since 0 is the number of the first snapshot).
13130 Stop debugging trace snapshots, resume @emph{live} debugging.
13133 Same as @samp{tfind none}.
13136 No argument means find the next trace snapshot.
13139 Find the previous trace snapshot before the current one. This permits
13140 retracing earlier steps.
13142 @item tfind tracepoint @var{num}
13143 Find the next snapshot associated with tracepoint @var{num}. Search
13144 proceeds forward from the last examined trace snapshot. If no
13145 argument @var{num} is given, it means find the next snapshot collected
13146 for the same tracepoint as the current snapshot.
13148 @item tfind pc @var{addr}
13149 Find the next snapshot associated with the value @var{addr} of the
13150 program counter. Search proceeds forward from the last examined trace
13151 snapshot. If no argument @var{addr} is given, it means find the next
13152 snapshot with the same value of PC as the current snapshot.
13154 @item tfind outside @var{addr1}, @var{addr2}
13155 Find the next snapshot whose PC is outside the given range of
13156 addresses (exclusive).
13158 @item tfind range @var{addr1}, @var{addr2}
13159 Find the next snapshot whose PC is between @var{addr1} and
13160 @var{addr2} (inclusive).
13162 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13163 Find the next snapshot associated with the source line @var{n}. If
13164 the optional argument @var{file} is given, refer to line @var{n} in
13165 that source file. Search proceeds forward from the last examined
13166 trace snapshot. If no argument @var{n} is given, it means find the
13167 next line other than the one currently being examined; thus saying
13168 @code{tfind line} repeatedly can appear to have the same effect as
13169 stepping from line to line in a @emph{live} debugging session.
13172 The default arguments for the @code{tfind} commands are specifically
13173 designed to make it easy to scan through the trace buffer. For
13174 instance, @code{tfind} with no argument selects the next trace
13175 snapshot, and @code{tfind -} with no argument selects the previous
13176 trace snapshot. So, by giving one @code{tfind} command, and then
13177 simply hitting @key{RET} repeatedly you can examine all the trace
13178 snapshots in order. Or, by saying @code{tfind -} and then hitting
13179 @key{RET} repeatedly you can examine the snapshots in reverse order.
13180 The @code{tfind line} command with no argument selects the snapshot
13181 for the next source line executed. The @code{tfind pc} command with
13182 no argument selects the next snapshot with the same program counter
13183 (PC) as the current frame. The @code{tfind tracepoint} command with
13184 no argument selects the next trace snapshot collected by the same
13185 tracepoint as the current one.
13187 In addition to letting you scan through the trace buffer manually,
13188 these commands make it easy to construct @value{GDBN} scripts that
13189 scan through the trace buffer and print out whatever collected data
13190 you are interested in. Thus, if we want to examine the PC, FP, and SP
13191 registers from each trace frame in the buffer, we can say this:
13194 (@value{GDBP}) @b{tfind start}
13195 (@value{GDBP}) @b{while ($trace_frame != -1)}
13196 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13197 $trace_frame, $pc, $sp, $fp
13201 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13202 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13203 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13204 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13205 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13206 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13207 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13208 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13209 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13210 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13211 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13214 Or, if we want to examine the variable @code{X} at each source line in
13218 (@value{GDBP}) @b{tfind start}
13219 (@value{GDBP}) @b{while ($trace_frame != -1)}
13220 > printf "Frame %d, X == %d\n", $trace_frame, X
13230 @subsection @code{tdump}
13232 @cindex dump all data collected at tracepoint
13233 @cindex tracepoint data, display
13235 This command takes no arguments. It prints all the data collected at
13236 the current trace snapshot.
13239 (@value{GDBP}) @b{trace 444}
13240 (@value{GDBP}) @b{actions}
13241 Enter actions for tracepoint #2, one per line:
13242 > collect $regs, $locals, $args, gdb_long_test
13245 (@value{GDBP}) @b{tstart}
13247 (@value{GDBP}) @b{tfind line 444}
13248 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13250 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13252 (@value{GDBP}) @b{tdump}
13253 Data collected at tracepoint 2, trace frame 1:
13254 d0 0xc4aa0085 -995491707
13258 d4 0x71aea3d 119204413
13261 d7 0x380035 3670069
13262 a0 0x19e24a 1696330
13263 a1 0x3000668 50333288
13265 a3 0x322000 3284992
13266 a4 0x3000698 50333336
13267 a5 0x1ad3cc 1758156
13268 fp 0x30bf3c 0x30bf3c
13269 sp 0x30bf34 0x30bf34
13271 pc 0x20b2c8 0x20b2c8
13275 p = 0x20e5b4 "gdb-test"
13282 gdb_long_test = 17 '\021'
13287 @code{tdump} works by scanning the tracepoint's current collection
13288 actions and printing the value of each expression listed. So
13289 @code{tdump} can fail, if after a run, you change the tracepoint's
13290 actions to mention variables that were not collected during the run.
13292 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13293 uses the collected value of @code{$pc} to distinguish between trace
13294 frames that were collected at the tracepoint hit, and frames that were
13295 collected while stepping. This allows it to correctly choose whether
13296 to display the basic list of collections, or the collections from the
13297 body of the while-stepping loop. However, if @code{$pc} was not collected,
13298 then @code{tdump} will always attempt to dump using the basic collection
13299 list, and may fail if a while-stepping frame does not include all the
13300 same data that is collected at the tracepoint hit.
13301 @c This is getting pretty arcane, example would be good.
13303 @node save tracepoints
13304 @subsection @code{save tracepoints @var{filename}}
13305 @kindex save tracepoints
13306 @kindex save-tracepoints
13307 @cindex save tracepoints for future sessions
13309 This command saves all current tracepoint definitions together with
13310 their actions and passcounts, into a file @file{@var{filename}}
13311 suitable for use in a later debugging session. To read the saved
13312 tracepoint definitions, use the @code{source} command (@pxref{Command
13313 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13314 alias for @w{@code{save tracepoints}}
13316 @node Tracepoint Variables
13317 @section Convenience Variables for Tracepoints
13318 @cindex tracepoint variables
13319 @cindex convenience variables for tracepoints
13322 @vindex $trace_frame
13323 @item (int) $trace_frame
13324 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13325 snapshot is selected.
13327 @vindex $tracepoint
13328 @item (int) $tracepoint
13329 The tracepoint for the current trace snapshot.
13331 @vindex $trace_line
13332 @item (int) $trace_line
13333 The line number for the current trace snapshot.
13335 @vindex $trace_file
13336 @item (char []) $trace_file
13337 The source file for the current trace snapshot.
13339 @vindex $trace_func
13340 @item (char []) $trace_func
13341 The name of the function containing @code{$tracepoint}.
13344 Note: @code{$trace_file} is not suitable for use in @code{printf},
13345 use @code{output} instead.
13347 Here's a simple example of using these convenience variables for
13348 stepping through all the trace snapshots and printing some of their
13349 data. Note that these are not the same as trace state variables,
13350 which are managed by the target.
13353 (@value{GDBP}) @b{tfind start}
13355 (@value{GDBP}) @b{while $trace_frame != -1}
13356 > output $trace_file
13357 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13363 @section Using Trace Files
13364 @cindex trace files
13366 In some situations, the target running a trace experiment may no
13367 longer be available; perhaps it crashed, or the hardware was needed
13368 for a different activity. To handle these cases, you can arrange to
13369 dump the trace data into a file, and later use that file as a source
13370 of trace data, via the @code{target tfile} command.
13375 @item tsave [ -r ] @var{filename}
13376 @itemx tsave [-ctf] @var{dirname}
13377 Save the trace data to @var{filename}. By default, this command
13378 assumes that @var{filename} refers to the host filesystem, so if
13379 necessary @value{GDBN} will copy raw trace data up from the target and
13380 then save it. If the target supports it, you can also supply the
13381 optional argument @code{-r} (``remote'') to direct the target to save
13382 the data directly into @var{filename} in its own filesystem, which may be
13383 more efficient if the trace buffer is very large. (Note, however, that
13384 @code{target tfile} can only read from files accessible to the host.)
13385 By default, this command will save trace frame in tfile format.
13386 You can supply the optional argument @code{-ctf} to save date in CTF
13387 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13388 that can be shared by multiple debugging and tracing tools. Please go to
13389 @indicateurl{http://www.efficios.com/ctf} to get more information.
13391 @kindex target tfile
13395 @item target tfile @var{filename}
13396 @itemx target ctf @var{dirname}
13397 Use the file named @var{filename} or directory named @var{dirname} as
13398 a source of trace data. Commands that examine data work as they do with
13399 a live target, but it is not possible to run any new trace experiments.
13400 @code{tstatus} will report the state of the trace run at the moment
13401 the data was saved, as well as the current trace frame you are examining.
13402 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13406 (@value{GDBP}) target ctf ctf.ctf
13407 (@value{GDBP}) tfind
13408 Found trace frame 0, tracepoint 2
13409 39 ++a; /* set tracepoint 1 here */
13410 (@value{GDBP}) tdump
13411 Data collected at tracepoint 2, trace frame 0:
13415 c = @{"123", "456", "789", "123", "456", "789"@}
13416 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13424 @chapter Debugging Programs That Use Overlays
13427 If your program is too large to fit completely in your target system's
13428 memory, you can sometimes use @dfn{overlays} to work around this
13429 problem. @value{GDBN} provides some support for debugging programs that
13433 * How Overlays Work:: A general explanation of overlays.
13434 * Overlay Commands:: Managing overlays in @value{GDBN}.
13435 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13436 mapped by asking the inferior.
13437 * Overlay Sample Program:: A sample program using overlays.
13440 @node How Overlays Work
13441 @section How Overlays Work
13442 @cindex mapped overlays
13443 @cindex unmapped overlays
13444 @cindex load address, overlay's
13445 @cindex mapped address
13446 @cindex overlay area
13448 Suppose you have a computer whose instruction address space is only 64
13449 kilobytes long, but which has much more memory which can be accessed by
13450 other means: special instructions, segment registers, or memory
13451 management hardware, for example. Suppose further that you want to
13452 adapt a program which is larger than 64 kilobytes to run on this system.
13454 One solution is to identify modules of your program which are relatively
13455 independent, and need not call each other directly; call these modules
13456 @dfn{overlays}. Separate the overlays from the main program, and place
13457 their machine code in the larger memory. Place your main program in
13458 instruction memory, but leave at least enough space there to hold the
13459 largest overlay as well.
13461 Now, to call a function located in an overlay, you must first copy that
13462 overlay's machine code from the large memory into the space set aside
13463 for it in the instruction memory, and then jump to its entry point
13466 @c NB: In the below the mapped area's size is greater or equal to the
13467 @c size of all overlays. This is intentional to remind the developer
13468 @c that overlays don't necessarily need to be the same size.
13472 Data Instruction Larger
13473 Address Space Address Space Address Space
13474 +-----------+ +-----------+ +-----------+
13476 +-----------+ +-----------+ +-----------+<-- overlay 1
13477 | program | | main | .----| overlay 1 | load address
13478 | variables | | program | | +-----------+
13479 | and heap | | | | | |
13480 +-----------+ | | | +-----------+<-- overlay 2
13481 | | +-----------+ | | | load address
13482 +-----------+ | | | .-| overlay 2 |
13484 mapped --->+-----------+ | | +-----------+
13485 address | | | | | |
13486 | overlay | <-' | | |
13487 | area | <---' +-----------+<-- overlay 3
13488 | | <---. | | load address
13489 +-----------+ `--| overlay 3 |
13496 @anchor{A code overlay}A code overlay
13500 The diagram (@pxref{A code overlay}) shows a system with separate data
13501 and instruction address spaces. To map an overlay, the program copies
13502 its code from the larger address space to the instruction address space.
13503 Since the overlays shown here all use the same mapped address, only one
13504 may be mapped at a time. For a system with a single address space for
13505 data and instructions, the diagram would be similar, except that the
13506 program variables and heap would share an address space with the main
13507 program and the overlay area.
13509 An overlay loaded into instruction memory and ready for use is called a
13510 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13511 instruction memory. An overlay not present (or only partially present)
13512 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13513 is its address in the larger memory. The mapped address is also called
13514 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13515 called the @dfn{load memory address}, or @dfn{LMA}.
13517 Unfortunately, overlays are not a completely transparent way to adapt a
13518 program to limited instruction memory. They introduce a new set of
13519 global constraints you must keep in mind as you design your program:
13524 Before calling or returning to a function in an overlay, your program
13525 must make sure that overlay is actually mapped. Otherwise, the call or
13526 return will transfer control to the right address, but in the wrong
13527 overlay, and your program will probably crash.
13530 If the process of mapping an overlay is expensive on your system, you
13531 will need to choose your overlays carefully to minimize their effect on
13532 your program's performance.
13535 The executable file you load onto your system must contain each
13536 overlay's instructions, appearing at the overlay's load address, not its
13537 mapped address. However, each overlay's instructions must be relocated
13538 and its symbols defined as if the overlay were at its mapped address.
13539 You can use GNU linker scripts to specify different load and relocation
13540 addresses for pieces of your program; see @ref{Overlay Description,,,
13541 ld.info, Using ld: the GNU linker}.
13544 The procedure for loading executable files onto your system must be able
13545 to load their contents into the larger address space as well as the
13546 instruction and data spaces.
13550 The overlay system described above is rather simple, and could be
13551 improved in many ways:
13556 If your system has suitable bank switch registers or memory management
13557 hardware, you could use those facilities to make an overlay's load area
13558 contents simply appear at their mapped address in instruction space.
13559 This would probably be faster than copying the overlay to its mapped
13560 area in the usual way.
13563 If your overlays are small enough, you could set aside more than one
13564 overlay area, and have more than one overlay mapped at a time.
13567 You can use overlays to manage data, as well as instructions. In
13568 general, data overlays are even less transparent to your design than
13569 code overlays: whereas code overlays only require care when you call or
13570 return to functions, data overlays require care every time you access
13571 the data. Also, if you change the contents of a data overlay, you
13572 must copy its contents back out to its load address before you can copy a
13573 different data overlay into the same mapped area.
13578 @node Overlay Commands
13579 @section Overlay Commands
13581 To use @value{GDBN}'s overlay support, each overlay in your program must
13582 correspond to a separate section of the executable file. The section's
13583 virtual memory address and load memory address must be the overlay's
13584 mapped and load addresses. Identifying overlays with sections allows
13585 @value{GDBN} to determine the appropriate address of a function or
13586 variable, depending on whether the overlay is mapped or not.
13588 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13589 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13594 Disable @value{GDBN}'s overlay support. When overlay support is
13595 disabled, @value{GDBN} assumes that all functions and variables are
13596 always present at their mapped addresses. By default, @value{GDBN}'s
13597 overlay support is disabled.
13599 @item overlay manual
13600 @cindex manual overlay debugging
13601 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13602 relies on you to tell it which overlays are mapped, and which are not,
13603 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13604 commands described below.
13606 @item overlay map-overlay @var{overlay}
13607 @itemx overlay map @var{overlay}
13608 @cindex map an overlay
13609 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13610 be the name of the object file section containing the overlay. When an
13611 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13612 functions and variables at their mapped addresses. @value{GDBN} assumes
13613 that any other overlays whose mapped ranges overlap that of
13614 @var{overlay} are now unmapped.
13616 @item overlay unmap-overlay @var{overlay}
13617 @itemx overlay unmap @var{overlay}
13618 @cindex unmap an overlay
13619 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13620 must be the name of the object file section containing the overlay.
13621 When an overlay is unmapped, @value{GDBN} assumes it can find the
13622 overlay's functions and variables at their load addresses.
13625 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13626 consults a data structure the overlay manager maintains in the inferior
13627 to see which overlays are mapped. For details, see @ref{Automatic
13628 Overlay Debugging}.
13630 @item overlay load-target
13631 @itemx overlay load
13632 @cindex reloading the overlay table
13633 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13634 re-reads the table @value{GDBN} automatically each time the inferior
13635 stops, so this command should only be necessary if you have changed the
13636 overlay mapping yourself using @value{GDBN}. This command is only
13637 useful when using automatic overlay debugging.
13639 @item overlay list-overlays
13640 @itemx overlay list
13641 @cindex listing mapped overlays
13642 Display a list of the overlays currently mapped, along with their mapped
13643 addresses, load addresses, and sizes.
13647 Normally, when @value{GDBN} prints a code address, it includes the name
13648 of the function the address falls in:
13651 (@value{GDBP}) print main
13652 $3 = @{int ()@} 0x11a0 <main>
13655 When overlay debugging is enabled, @value{GDBN} recognizes code in
13656 unmapped overlays, and prints the names of unmapped functions with
13657 asterisks around them. For example, if @code{foo} is a function in an
13658 unmapped overlay, @value{GDBN} prints it this way:
13661 (@value{GDBP}) overlay list
13662 No sections are mapped.
13663 (@value{GDBP}) print foo
13664 $5 = @{int (int)@} 0x100000 <*foo*>
13667 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13671 (@value{GDBP}) overlay list
13672 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13673 mapped at 0x1016 - 0x104a
13674 (@value{GDBP}) print foo
13675 $6 = @{int (int)@} 0x1016 <foo>
13678 When overlay debugging is enabled, @value{GDBN} can find the correct
13679 address for functions and variables in an overlay, whether or not the
13680 overlay is mapped. This allows most @value{GDBN} commands, like
13681 @code{break} and @code{disassemble}, to work normally, even on unmapped
13682 code. However, @value{GDBN}'s breakpoint support has some limitations:
13686 @cindex breakpoints in overlays
13687 @cindex overlays, setting breakpoints in
13688 You can set breakpoints in functions in unmapped overlays, as long as
13689 @value{GDBN} can write to the overlay at its load address.
13691 @value{GDBN} can not set hardware or simulator-based breakpoints in
13692 unmapped overlays. However, if you set a breakpoint at the end of your
13693 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13694 you are using manual overlay management), @value{GDBN} will re-set its
13695 breakpoints properly.
13699 @node Automatic Overlay Debugging
13700 @section Automatic Overlay Debugging
13701 @cindex automatic overlay debugging
13703 @value{GDBN} can automatically track which overlays are mapped and which
13704 are not, given some simple co-operation from the overlay manager in the
13705 inferior. If you enable automatic overlay debugging with the
13706 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13707 looks in the inferior's memory for certain variables describing the
13708 current state of the overlays.
13710 Here are the variables your overlay manager must define to support
13711 @value{GDBN}'s automatic overlay debugging:
13715 @item @code{_ovly_table}:
13716 This variable must be an array of the following structures:
13721 /* The overlay's mapped address. */
13724 /* The size of the overlay, in bytes. */
13725 unsigned long size;
13727 /* The overlay's load address. */
13730 /* Non-zero if the overlay is currently mapped;
13732 unsigned long mapped;
13736 @item @code{_novlys}:
13737 This variable must be a four-byte signed integer, holding the total
13738 number of elements in @code{_ovly_table}.
13742 To decide whether a particular overlay is mapped or not, @value{GDBN}
13743 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13744 @code{lma} members equal the VMA and LMA of the overlay's section in the
13745 executable file. When @value{GDBN} finds a matching entry, it consults
13746 the entry's @code{mapped} member to determine whether the overlay is
13749 In addition, your overlay manager may define a function called
13750 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13751 will silently set a breakpoint there. If the overlay manager then
13752 calls this function whenever it has changed the overlay table, this
13753 will enable @value{GDBN} to accurately keep track of which overlays
13754 are in program memory, and update any breakpoints that may be set
13755 in overlays. This will allow breakpoints to work even if the
13756 overlays are kept in ROM or other non-writable memory while they
13757 are not being executed.
13759 @node Overlay Sample Program
13760 @section Overlay Sample Program
13761 @cindex overlay example program
13763 When linking a program which uses overlays, you must place the overlays
13764 at their load addresses, while relocating them to run at their mapped
13765 addresses. To do this, you must write a linker script (@pxref{Overlay
13766 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13767 since linker scripts are specific to a particular host system, target
13768 architecture, and target memory layout, this manual cannot provide
13769 portable sample code demonstrating @value{GDBN}'s overlay support.
13771 However, the @value{GDBN} source distribution does contain an overlaid
13772 program, with linker scripts for a few systems, as part of its test
13773 suite. The program consists of the following files from
13774 @file{gdb/testsuite/gdb.base}:
13778 The main program file.
13780 A simple overlay manager, used by @file{overlays.c}.
13785 Overlay modules, loaded and used by @file{overlays.c}.
13788 Linker scripts for linking the test program on the @code{d10v-elf}
13789 and @code{m32r-elf} targets.
13792 You can build the test program using the @code{d10v-elf} GCC
13793 cross-compiler like this:
13796 $ d10v-elf-gcc -g -c overlays.c
13797 $ d10v-elf-gcc -g -c ovlymgr.c
13798 $ d10v-elf-gcc -g -c foo.c
13799 $ d10v-elf-gcc -g -c bar.c
13800 $ d10v-elf-gcc -g -c baz.c
13801 $ d10v-elf-gcc -g -c grbx.c
13802 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13803 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13806 The build process is identical for any other architecture, except that
13807 you must substitute the appropriate compiler and linker script for the
13808 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13812 @chapter Using @value{GDBN} with Different Languages
13815 Although programming languages generally have common aspects, they are
13816 rarely expressed in the same manner. For instance, in ANSI C,
13817 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13818 Modula-2, it is accomplished by @code{p^}. Values can also be
13819 represented (and displayed) differently. Hex numbers in C appear as
13820 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13822 @cindex working language
13823 Language-specific information is built into @value{GDBN} for some languages,
13824 allowing you to express operations like the above in your program's
13825 native language, and allowing @value{GDBN} to output values in a manner
13826 consistent with the syntax of your program's native language. The
13827 language you use to build expressions is called the @dfn{working
13831 * Setting:: Switching between source languages
13832 * Show:: Displaying the language
13833 * Checks:: Type and range checks
13834 * Supported Languages:: Supported languages
13835 * Unsupported Languages:: Unsupported languages
13839 @section Switching Between Source Languages
13841 There are two ways to control the working language---either have @value{GDBN}
13842 set it automatically, or select it manually yourself. You can use the
13843 @code{set language} command for either purpose. On startup, @value{GDBN}
13844 defaults to setting the language automatically. The working language is
13845 used to determine how expressions you type are interpreted, how values
13848 In addition to the working language, every source file that
13849 @value{GDBN} knows about has its own working language. For some object
13850 file formats, the compiler might indicate which language a particular
13851 source file is in. However, most of the time @value{GDBN} infers the
13852 language from the name of the file. The language of a source file
13853 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13854 show each frame appropriately for its own language. There is no way to
13855 set the language of a source file from within @value{GDBN}, but you can
13856 set the language associated with a filename extension. @xref{Show, ,
13857 Displaying the Language}.
13859 This is most commonly a problem when you use a program, such
13860 as @code{cfront} or @code{f2c}, that generates C but is written in
13861 another language. In that case, make the
13862 program use @code{#line} directives in its C output; that way
13863 @value{GDBN} will know the correct language of the source code of the original
13864 program, and will display that source code, not the generated C code.
13867 * Filenames:: Filename extensions and languages.
13868 * Manually:: Setting the working language manually
13869 * Automatically:: Having @value{GDBN} infer the source language
13873 @subsection List of Filename Extensions and Languages
13875 If a source file name ends in one of the following extensions, then
13876 @value{GDBN} infers that its language is the one indicated.
13894 C@t{++} source file
13900 Objective-C source file
13904 Fortran source file
13907 Modula-2 source file
13911 Assembler source file. This actually behaves almost like C, but
13912 @value{GDBN} does not skip over function prologues when stepping.
13915 In addition, you may set the language associated with a filename
13916 extension. @xref{Show, , Displaying the Language}.
13919 @subsection Setting the Working Language
13921 If you allow @value{GDBN} to set the language automatically,
13922 expressions are interpreted the same way in your debugging session and
13925 @kindex set language
13926 If you wish, you may set the language manually. To do this, issue the
13927 command @samp{set language @var{lang}}, where @var{lang} is the name of
13928 a language, such as
13929 @code{c} or @code{modula-2}.
13930 For a list of the supported languages, type @samp{set language}.
13932 Setting the language manually prevents @value{GDBN} from updating the working
13933 language automatically. This can lead to confusion if you try
13934 to debug a program when the working language is not the same as the
13935 source language, when an expression is acceptable to both
13936 languages---but means different things. For instance, if the current
13937 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13945 might not have the effect you intended. In C, this means to add
13946 @code{b} and @code{c} and place the result in @code{a}. The result
13947 printed would be the value of @code{a}. In Modula-2, this means to compare
13948 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13950 @node Automatically
13951 @subsection Having @value{GDBN} Infer the Source Language
13953 To have @value{GDBN} set the working language automatically, use
13954 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13955 then infers the working language. That is, when your program stops in a
13956 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13957 working language to the language recorded for the function in that
13958 frame. If the language for a frame is unknown (that is, if the function
13959 or block corresponding to the frame was defined in a source file that
13960 does not have a recognized extension), the current working language is
13961 not changed, and @value{GDBN} issues a warning.
13963 This may not seem necessary for most programs, which are written
13964 entirely in one source language. However, program modules and libraries
13965 written in one source language can be used by a main program written in
13966 a different source language. Using @samp{set language auto} in this
13967 case frees you from having to set the working language manually.
13970 @section Displaying the Language
13972 The following commands help you find out which language is the
13973 working language, and also what language source files were written in.
13976 @item show language
13977 @anchor{show language}
13978 @kindex show language
13979 Display the current working language. This is the
13980 language you can use with commands such as @code{print} to
13981 build and compute expressions that may involve variables in your program.
13984 @kindex info frame@r{, show the source language}
13985 Display the source language for this frame. This language becomes the
13986 working language if you use an identifier from this frame.
13987 @xref{Frame Info, ,Information about a Frame}, to identify the other
13988 information listed here.
13991 @kindex info source@r{, show the source language}
13992 Display the source language of this source file.
13993 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13994 information listed here.
13997 In unusual circumstances, you may have source files with extensions
13998 not in the standard list. You can then set the extension associated
13999 with a language explicitly:
14002 @item set extension-language @var{ext} @var{language}
14003 @kindex set extension-language
14004 Tell @value{GDBN} that source files with extension @var{ext} are to be
14005 assumed as written in the source language @var{language}.
14007 @item info extensions
14008 @kindex info extensions
14009 List all the filename extensions and the associated languages.
14013 @section Type and Range Checking
14015 Some languages are designed to guard you against making seemingly common
14016 errors through a series of compile- and run-time checks. These include
14017 checking the type of arguments to functions and operators and making
14018 sure mathematical overflows are caught at run time. Checks such as
14019 these help to ensure a program's correctness once it has been compiled
14020 by eliminating type mismatches and providing active checks for range
14021 errors when your program is running.
14023 By default @value{GDBN} checks for these errors according to the
14024 rules of the current source language. Although @value{GDBN} does not check
14025 the statements in your program, it can check expressions entered directly
14026 into @value{GDBN} for evaluation via the @code{print} command, for example.
14029 * Type Checking:: An overview of type checking
14030 * Range Checking:: An overview of range checking
14033 @cindex type checking
14034 @cindex checks, type
14035 @node Type Checking
14036 @subsection An Overview of Type Checking
14038 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14039 arguments to operators and functions have to be of the correct type,
14040 otherwise an error occurs. These checks prevent type mismatch
14041 errors from ever causing any run-time problems. For example,
14044 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14046 (@value{GDBP}) print obj.my_method (0)
14049 (@value{GDBP}) print obj.my_method (0x1234)
14050 Cannot resolve method klass::my_method to any overloaded instance
14053 The second example fails because in C@t{++} the integer constant
14054 @samp{0x1234} is not type-compatible with the pointer parameter type.
14056 For the expressions you use in @value{GDBN} commands, you can tell
14057 @value{GDBN} to not enforce strict type checking or
14058 to treat any mismatches as errors and abandon the expression;
14059 When type checking is disabled, @value{GDBN} successfully evaluates
14060 expressions like the second example above.
14062 Even if type checking is off, there may be other reasons
14063 related to type that prevent @value{GDBN} from evaluating an expression.
14064 For instance, @value{GDBN} does not know how to add an @code{int} and
14065 a @code{struct foo}. These particular type errors have nothing to do
14066 with the language in use and usually arise from expressions which make
14067 little sense to evaluate anyway.
14069 @value{GDBN} provides some additional commands for controlling type checking:
14071 @kindex set check type
14072 @kindex show check type
14074 @item set check type on
14075 @itemx set check type off
14076 Set strict type checking on or off. If any type mismatches occur in
14077 evaluating an expression while type checking is on, @value{GDBN} prints a
14078 message and aborts evaluation of the expression.
14080 @item show check type
14081 Show the current setting of type checking and whether @value{GDBN}
14082 is enforcing strict type checking rules.
14085 @cindex range checking
14086 @cindex checks, range
14087 @node Range Checking
14088 @subsection An Overview of Range Checking
14090 In some languages (such as Modula-2), it is an error to exceed the
14091 bounds of a type; this is enforced with run-time checks. Such range
14092 checking is meant to ensure program correctness by making sure
14093 computations do not overflow, or indices on an array element access do
14094 not exceed the bounds of the array.
14096 For expressions you use in @value{GDBN} commands, you can tell
14097 @value{GDBN} to treat range errors in one of three ways: ignore them,
14098 always treat them as errors and abandon the expression, or issue
14099 warnings but evaluate the expression anyway.
14101 A range error can result from numerical overflow, from exceeding an
14102 array index bound, or when you type a constant that is not a member
14103 of any type. Some languages, however, do not treat overflows as an
14104 error. In many implementations of C, mathematical overflow causes the
14105 result to ``wrap around'' to lower values---for example, if @var{m} is
14106 the largest integer value, and @var{s} is the smallest, then
14109 @var{m} + 1 @result{} @var{s}
14112 This, too, is specific to individual languages, and in some cases
14113 specific to individual compilers or machines. @xref{Supported Languages, ,
14114 Supported Languages}, for further details on specific languages.
14116 @value{GDBN} provides some additional commands for controlling the range checker:
14118 @kindex set check range
14119 @kindex show check range
14121 @item set check range auto
14122 Set range checking on or off based on the current working language.
14123 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14126 @item set check range on
14127 @itemx set check range off
14128 Set range checking on or off, overriding the default setting for the
14129 current working language. A warning is issued if the setting does not
14130 match the language default. If a range error occurs and range checking is on,
14131 then a message is printed and evaluation of the expression is aborted.
14133 @item set check range warn
14134 Output messages when the @value{GDBN} range checker detects a range error,
14135 but attempt to evaluate the expression anyway. Evaluating the
14136 expression may still be impossible for other reasons, such as accessing
14137 memory that the process does not own (a typical example from many Unix
14141 Show the current setting of the range checker, and whether or not it is
14142 being set automatically by @value{GDBN}.
14145 @node Supported Languages
14146 @section Supported Languages
14148 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14149 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14150 @c This is false ...
14151 Some @value{GDBN} features may be used in expressions regardless of the
14152 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14153 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14154 ,Expressions}) can be used with the constructs of any supported
14157 The following sections detail to what degree each source language is
14158 supported by @value{GDBN}. These sections are not meant to be language
14159 tutorials or references, but serve only as a reference guide to what the
14160 @value{GDBN} expression parser accepts, and what input and output
14161 formats should look like for different languages. There are many good
14162 books written on each of these languages; please look to these for a
14163 language reference or tutorial.
14166 * C:: C and C@t{++}
14169 * Objective-C:: Objective-C
14170 * OpenCL C:: OpenCL C
14171 * Fortran:: Fortran
14173 * Modula-2:: Modula-2
14178 @subsection C and C@t{++}
14180 @cindex C and C@t{++}
14181 @cindex expressions in C or C@t{++}
14183 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14184 to both languages. Whenever this is the case, we discuss those languages
14188 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14189 @cindex @sc{gnu} C@t{++}
14190 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14191 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14192 effectively, you must compile your C@t{++} programs with a supported
14193 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14194 compiler (@code{aCC}).
14197 * C Operators:: C and C@t{++} operators
14198 * C Constants:: C and C@t{++} constants
14199 * C Plus Plus Expressions:: C@t{++} expressions
14200 * C Defaults:: Default settings for C and C@t{++}
14201 * C Checks:: C and C@t{++} type and range checks
14202 * Debugging C:: @value{GDBN} and C
14203 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14204 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14208 @subsubsection C and C@t{++} Operators
14210 @cindex C and C@t{++} operators
14212 Operators must be defined on values of specific types. For instance,
14213 @code{+} is defined on numbers, but not on structures. Operators are
14214 often defined on groups of types.
14216 For the purposes of C and C@t{++}, the following definitions hold:
14221 @emph{Integral types} include @code{int} with any of its storage-class
14222 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14225 @emph{Floating-point types} include @code{float}, @code{double}, and
14226 @code{long double} (if supported by the target platform).
14229 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14232 @emph{Scalar types} include all of the above.
14237 The following operators are supported. They are listed here
14238 in order of increasing precedence:
14242 The comma or sequencing operator. Expressions in a comma-separated list
14243 are evaluated from left to right, with the result of the entire
14244 expression being the last expression evaluated.
14247 Assignment. The value of an assignment expression is the value
14248 assigned. Defined on scalar types.
14251 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14252 and translated to @w{@code{@var{a} = @var{a op b}}}.
14253 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14254 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14255 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14258 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14259 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14260 should be of an integral type.
14263 Logical @sc{or}. Defined on integral types.
14266 Logical @sc{and}. Defined on integral types.
14269 Bitwise @sc{or}. Defined on integral types.
14272 Bitwise exclusive-@sc{or}. Defined on integral types.
14275 Bitwise @sc{and}. Defined on integral types.
14278 Equality and inequality. Defined on scalar types. The value of these
14279 expressions is 0 for false and non-zero for true.
14281 @item <@r{, }>@r{, }<=@r{, }>=
14282 Less than, greater than, less than or equal, greater than or equal.
14283 Defined on scalar types. The value of these expressions is 0 for false
14284 and non-zero for true.
14287 left shift, and right shift. Defined on integral types.
14290 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14293 Addition and subtraction. Defined on integral types, floating-point types and
14296 @item *@r{, }/@r{, }%
14297 Multiplication, division, and modulus. Multiplication and division are
14298 defined on integral and floating-point types. Modulus is defined on
14302 Increment and decrement. When appearing before a variable, the
14303 operation is performed before the variable is used in an expression;
14304 when appearing after it, the variable's value is used before the
14305 operation takes place.
14308 Pointer dereferencing. Defined on pointer types. Same precedence as
14312 Address operator. Defined on variables. Same precedence as @code{++}.
14314 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14315 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14316 to examine the address
14317 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14321 Negative. Defined on integral and floating-point types. Same
14322 precedence as @code{++}.
14325 Logical negation. Defined on integral types. Same precedence as
14329 Bitwise complement operator. Defined on integral types. Same precedence as
14334 Structure member, and pointer-to-structure member. For convenience,
14335 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14336 pointer based on the stored type information.
14337 Defined on @code{struct} and @code{union} data.
14340 Dereferences of pointers to members.
14343 Array indexing. @code{@var{a}[@var{i}]} is defined as
14344 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14347 Function parameter list. Same precedence as @code{->}.
14350 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14351 and @code{class} types.
14354 Doubled colons also represent the @value{GDBN} scope operator
14355 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14359 If an operator is redefined in the user code, @value{GDBN} usually
14360 attempts to invoke the redefined version instead of using the operator's
14361 predefined meaning.
14364 @subsubsection C and C@t{++} Constants
14366 @cindex C and C@t{++} constants
14368 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14373 Integer constants are a sequence of digits. Octal constants are
14374 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14375 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14376 @samp{l}, specifying that the constant should be treated as a
14380 Floating point constants are a sequence of digits, followed by a decimal
14381 point, followed by a sequence of digits, and optionally followed by an
14382 exponent. An exponent is of the form:
14383 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14384 sequence of digits. The @samp{+} is optional for positive exponents.
14385 A floating-point constant may also end with a letter @samp{f} or
14386 @samp{F}, specifying that the constant should be treated as being of
14387 the @code{float} (as opposed to the default @code{double}) type; or with
14388 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14392 Enumerated constants consist of enumerated identifiers, or their
14393 integral equivalents.
14396 Character constants are a single character surrounded by single quotes
14397 (@code{'}), or a number---the ordinal value of the corresponding character
14398 (usually its @sc{ascii} value). Within quotes, the single character may
14399 be represented by a letter or by @dfn{escape sequences}, which are of
14400 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14401 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14402 @samp{@var{x}} is a predefined special character---for example,
14403 @samp{\n} for newline.
14405 Wide character constants can be written by prefixing a character
14406 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14407 form of @samp{x}. The target wide character set is used when
14408 computing the value of this constant (@pxref{Character Sets}).
14411 String constants are a sequence of character constants surrounded by
14412 double quotes (@code{"}). Any valid character constant (as described
14413 above) may appear. Double quotes within the string must be preceded by
14414 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14417 Wide string constants can be written by prefixing a string constant
14418 with @samp{L}, as in C. The target wide character set is used when
14419 computing the value of this constant (@pxref{Character Sets}).
14422 Pointer constants are an integral value. You can also write pointers
14423 to constants using the C operator @samp{&}.
14426 Array constants are comma-separated lists surrounded by braces @samp{@{}
14427 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14428 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14429 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14432 @node C Plus Plus Expressions
14433 @subsubsection C@t{++} Expressions
14435 @cindex expressions in C@t{++}
14436 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14438 @cindex debugging C@t{++} programs
14439 @cindex C@t{++} compilers
14440 @cindex debug formats and C@t{++}
14441 @cindex @value{NGCC} and C@t{++}
14443 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14444 the proper compiler and the proper debug format. Currently,
14445 @value{GDBN} works best when debugging C@t{++} code that is compiled
14446 with the most recent version of @value{NGCC} possible. The DWARF
14447 debugging format is preferred; @value{NGCC} defaults to this on most
14448 popular platforms. Other compilers and/or debug formats are likely to
14449 work badly or not at all when using @value{GDBN} to debug C@t{++}
14450 code. @xref{Compilation}.
14455 @cindex member functions
14457 Member function calls are allowed; you can use expressions like
14460 count = aml->GetOriginal(x, y)
14463 @vindex this@r{, inside C@t{++} member functions}
14464 @cindex namespace in C@t{++}
14466 While a member function is active (in the selected stack frame), your
14467 expressions have the same namespace available as the member function;
14468 that is, @value{GDBN} allows implicit references to the class instance
14469 pointer @code{this} following the same rules as C@t{++}. @code{using}
14470 declarations in the current scope are also respected by @value{GDBN}.
14472 @cindex call overloaded functions
14473 @cindex overloaded functions, calling
14474 @cindex type conversions in C@t{++}
14476 You can call overloaded functions; @value{GDBN} resolves the function
14477 call to the right definition, with some restrictions. @value{GDBN} does not
14478 perform overload resolution involving user-defined type conversions,
14479 calls to constructors, or instantiations of templates that do not exist
14480 in the program. It also cannot handle ellipsis argument lists or
14483 It does perform integral conversions and promotions, floating-point
14484 promotions, arithmetic conversions, pointer conversions, conversions of
14485 class objects to base classes, and standard conversions such as those of
14486 functions or arrays to pointers; it requires an exact match on the
14487 number of function arguments.
14489 Overload resolution is always performed, unless you have specified
14490 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14491 ,@value{GDBN} Features for C@t{++}}.
14493 You must specify @code{set overload-resolution off} in order to use an
14494 explicit function signature to call an overloaded function, as in
14496 p 'foo(char,int)'('x', 13)
14499 The @value{GDBN} command-completion facility can simplify this;
14500 see @ref{Completion, ,Command Completion}.
14502 @cindex reference declarations
14504 @value{GDBN} understands variables declared as C@t{++} references; you can use
14505 them in expressions just as you do in C@t{++} source---they are automatically
14508 In the parameter list shown when @value{GDBN} displays a frame, the values of
14509 reference variables are not displayed (unlike other variables); this
14510 avoids clutter, since references are often used for large structures.
14511 The @emph{address} of a reference variable is always shown, unless
14512 you have specified @samp{set print address off}.
14515 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14516 expressions can use it just as expressions in your program do. Since
14517 one scope may be defined in another, you can use @code{::} repeatedly if
14518 necessary, for example in an expression like
14519 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14520 resolving name scope by reference to source files, in both C and C@t{++}
14521 debugging (@pxref{Variables, ,Program Variables}).
14524 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14529 @subsubsection C and C@t{++} Defaults
14531 @cindex C and C@t{++} defaults
14533 If you allow @value{GDBN} to set range checking automatically, it
14534 defaults to @code{off} whenever the working language changes to
14535 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14536 selects the working language.
14538 If you allow @value{GDBN} to set the language automatically, it
14539 recognizes source files whose names end with @file{.c}, @file{.C}, or
14540 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14541 these files, it sets the working language to C or C@t{++}.
14542 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14543 for further details.
14546 @subsubsection C and C@t{++} Type and Range Checks
14548 @cindex C and C@t{++} checks
14550 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14551 checking is used. However, if you turn type checking off, @value{GDBN}
14552 will allow certain non-standard conversions, such as promoting integer
14553 constants to pointers.
14555 Range checking, if turned on, is done on mathematical operations. Array
14556 indices are not checked, since they are often used to index a pointer
14557 that is not itself an array.
14560 @subsubsection @value{GDBN} and C
14562 The @code{set print union} and @code{show print union} commands apply to
14563 the @code{union} type. When set to @samp{on}, any @code{union} that is
14564 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14565 appears as @samp{@{...@}}.
14567 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14568 with pointers and a memory allocation function. @xref{Expressions,
14571 @node Debugging C Plus Plus
14572 @subsubsection @value{GDBN} Features for C@t{++}
14574 @cindex commands for C@t{++}
14576 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14577 designed specifically for use with C@t{++}. Here is a summary:
14580 @cindex break in overloaded functions
14581 @item @r{breakpoint menus}
14582 When you want a breakpoint in a function whose name is overloaded,
14583 @value{GDBN} has the capability to display a menu of possible breakpoint
14584 locations to help you specify which function definition you want.
14585 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14587 @cindex overloading in C@t{++}
14588 @item rbreak @var{regex}
14589 Setting breakpoints using regular expressions is helpful for setting
14590 breakpoints on overloaded functions that are not members of any special
14592 @xref{Set Breaks, ,Setting Breakpoints}.
14594 @cindex C@t{++} exception handling
14596 @itemx catch rethrow
14598 Debug C@t{++} exception handling using these commands. @xref{Set
14599 Catchpoints, , Setting Catchpoints}.
14601 @cindex inheritance
14602 @item ptype @var{typename}
14603 Print inheritance relationships as well as other information for type
14605 @xref{Symbols, ,Examining the Symbol Table}.
14607 @item info vtbl @var{expression}.
14608 The @code{info vtbl} command can be used to display the virtual
14609 method tables of the object computed by @var{expression}. This shows
14610 one entry per virtual table; there may be multiple virtual tables when
14611 multiple inheritance is in use.
14613 @cindex C@t{++} demangling
14614 @item demangle @var{name}
14615 Demangle @var{name}.
14616 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14618 @cindex C@t{++} symbol display
14619 @item set print demangle
14620 @itemx show print demangle
14621 @itemx set print asm-demangle
14622 @itemx show print asm-demangle
14623 Control whether C@t{++} symbols display in their source form, both when
14624 displaying code as C@t{++} source and when displaying disassemblies.
14625 @xref{Print Settings, ,Print Settings}.
14627 @item set print object
14628 @itemx show print object
14629 Choose whether to print derived (actual) or declared types of objects.
14630 @xref{Print Settings, ,Print Settings}.
14632 @item set print vtbl
14633 @itemx show print vtbl
14634 Control the format for printing virtual function tables.
14635 @xref{Print Settings, ,Print Settings}.
14636 (The @code{vtbl} commands do not work on programs compiled with the HP
14637 ANSI C@t{++} compiler (@code{aCC}).)
14639 @kindex set overload-resolution
14640 @cindex overloaded functions, overload resolution
14641 @item set overload-resolution on
14642 Enable overload resolution for C@t{++} expression evaluation. The default
14643 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14644 and searches for a function whose signature matches the argument types,
14645 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14646 Expressions, ,C@t{++} Expressions}, for details).
14647 If it cannot find a match, it emits a message.
14649 @item set overload-resolution off
14650 Disable overload resolution for C@t{++} expression evaluation. For
14651 overloaded functions that are not class member functions, @value{GDBN}
14652 chooses the first function of the specified name that it finds in the
14653 symbol table, whether or not its arguments are of the correct type. For
14654 overloaded functions that are class member functions, @value{GDBN}
14655 searches for a function whose signature @emph{exactly} matches the
14658 @kindex show overload-resolution
14659 @item show overload-resolution
14660 Show the current setting of overload resolution.
14662 @item @r{Overloaded symbol names}
14663 You can specify a particular definition of an overloaded symbol, using
14664 the same notation that is used to declare such symbols in C@t{++}: type
14665 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14666 also use the @value{GDBN} command-line word completion facilities to list the
14667 available choices, or to finish the type list for you.
14668 @xref{Completion,, Command Completion}, for details on how to do this.
14671 @node Decimal Floating Point
14672 @subsubsection Decimal Floating Point format
14673 @cindex decimal floating point format
14675 @value{GDBN} can examine, set and perform computations with numbers in
14676 decimal floating point format, which in the C language correspond to the
14677 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14678 specified by the extension to support decimal floating-point arithmetic.
14680 There are two encodings in use, depending on the architecture: BID (Binary
14681 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14682 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14685 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14686 to manipulate decimal floating point numbers, it is not possible to convert
14687 (using a cast, for example) integers wider than 32-bit to decimal float.
14689 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14690 point computations, error checking in decimal float operations ignores
14691 underflow, overflow and divide by zero exceptions.
14693 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14694 to inspect @code{_Decimal128} values stored in floating point registers.
14695 See @ref{PowerPC,,PowerPC} for more details.
14701 @value{GDBN} can be used to debug programs written in D and compiled with
14702 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14703 specific feature --- dynamic arrays.
14708 @cindex Go (programming language)
14709 @value{GDBN} can be used to debug programs written in Go and compiled with
14710 @file{gccgo} or @file{6g} compilers.
14712 Here is a summary of the Go-specific features and restrictions:
14715 @cindex current Go package
14716 @item The current Go package
14717 The name of the current package does not need to be specified when
14718 specifying global variables and functions.
14720 For example, given the program:
14724 var myglob = "Shall we?"
14730 When stopped inside @code{main} either of these work:
14734 (gdb) p main.myglob
14737 @cindex builtin Go types
14738 @item Builtin Go types
14739 The @code{string} type is recognized by @value{GDBN} and is printed
14742 @cindex builtin Go functions
14743 @item Builtin Go functions
14744 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14745 function and handles it internally.
14747 @cindex restrictions on Go expressions
14748 @item Restrictions on Go expressions
14749 All Go operators are supported except @code{&^}.
14750 The Go @code{_} ``blank identifier'' is not supported.
14751 Automatic dereferencing of pointers is not supported.
14755 @subsection Objective-C
14757 @cindex Objective-C
14758 This section provides information about some commands and command
14759 options that are useful for debugging Objective-C code. See also
14760 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14761 few more commands specific to Objective-C support.
14764 * Method Names in Commands::
14765 * The Print Command with Objective-C::
14768 @node Method Names in Commands
14769 @subsubsection Method Names in Commands
14771 The following commands have been extended to accept Objective-C method
14772 names as line specifications:
14774 @kindex clear@r{, and Objective-C}
14775 @kindex break@r{, and Objective-C}
14776 @kindex info line@r{, and Objective-C}
14777 @kindex jump@r{, and Objective-C}
14778 @kindex list@r{, and Objective-C}
14782 @item @code{info line}
14787 A fully qualified Objective-C method name is specified as
14790 -[@var{Class} @var{methodName}]
14793 where the minus sign is used to indicate an instance method and a
14794 plus sign (not shown) is used to indicate a class method. The class
14795 name @var{Class} and method name @var{methodName} are enclosed in
14796 brackets, similar to the way messages are specified in Objective-C
14797 source code. For example, to set a breakpoint at the @code{create}
14798 instance method of class @code{Fruit} in the program currently being
14802 break -[Fruit create]
14805 To list ten program lines around the @code{initialize} class method,
14809 list +[NSText initialize]
14812 In the current version of @value{GDBN}, the plus or minus sign is
14813 required. In future versions of @value{GDBN}, the plus or minus
14814 sign will be optional, but you can use it to narrow the search. It
14815 is also possible to specify just a method name:
14821 You must specify the complete method name, including any colons. If
14822 your program's source files contain more than one @code{create} method,
14823 you'll be presented with a numbered list of classes that implement that
14824 method. Indicate your choice by number, or type @samp{0} to exit if
14827 As another example, to clear a breakpoint established at the
14828 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14831 clear -[NSWindow makeKeyAndOrderFront:]
14834 @node The Print Command with Objective-C
14835 @subsubsection The Print Command With Objective-C
14836 @cindex Objective-C, print objects
14837 @kindex print-object
14838 @kindex po @r{(@code{print-object})}
14840 The print command has also been extended to accept methods. For example:
14843 print -[@var{object} hash]
14846 @cindex print an Objective-C object description
14847 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14849 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14850 and print the result. Also, an additional command has been added,
14851 @code{print-object} or @code{po} for short, which is meant to print
14852 the description of an object. However, this command may only work
14853 with certain Objective-C libraries that have a particular hook
14854 function, @code{_NSPrintForDebugger}, defined.
14857 @subsection OpenCL C
14860 This section provides information about @value{GDBN}s OpenCL C support.
14863 * OpenCL C Datatypes::
14864 * OpenCL C Expressions::
14865 * OpenCL C Operators::
14868 @node OpenCL C Datatypes
14869 @subsubsection OpenCL C Datatypes
14871 @cindex OpenCL C Datatypes
14872 @value{GDBN} supports the builtin scalar and vector datatypes specified
14873 by OpenCL 1.1. In addition the half- and double-precision floating point
14874 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14875 extensions are also known to @value{GDBN}.
14877 @node OpenCL C Expressions
14878 @subsubsection OpenCL C Expressions
14880 @cindex OpenCL C Expressions
14881 @value{GDBN} supports accesses to vector components including the access as
14882 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14883 supported by @value{GDBN} can be used as well.
14885 @node OpenCL C Operators
14886 @subsubsection OpenCL C Operators
14888 @cindex OpenCL C Operators
14889 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14893 @subsection Fortran
14894 @cindex Fortran-specific support in @value{GDBN}
14896 @value{GDBN} can be used to debug programs written in Fortran, but it
14897 currently supports only the features of Fortran 77 language.
14899 @cindex trailing underscore, in Fortran symbols
14900 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14901 among them) append an underscore to the names of variables and
14902 functions. When you debug programs compiled by those compilers, you
14903 will need to refer to variables and functions with a trailing
14907 * Fortran Operators:: Fortran operators and expressions
14908 * Fortran Defaults:: Default settings for Fortran
14909 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14912 @node Fortran Operators
14913 @subsubsection Fortran Operators and Expressions
14915 @cindex Fortran operators and expressions
14917 Operators must be defined on values of specific types. For instance,
14918 @code{+} is defined on numbers, but not on characters or other non-
14919 arithmetic types. Operators are often defined on groups of types.
14923 The exponentiation operator. It raises the first operand to the power
14927 The range operator. Normally used in the form of array(low:high) to
14928 represent a section of array.
14931 The access component operator. Normally used to access elements in derived
14932 types. Also suitable for unions. As unions aren't part of regular Fortran,
14933 this can only happen when accessing a register that uses a gdbarch-defined
14937 @node Fortran Defaults
14938 @subsubsection Fortran Defaults
14940 @cindex Fortran Defaults
14942 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14943 default uses case-insensitive matches for Fortran symbols. You can
14944 change that with the @samp{set case-insensitive} command, see
14945 @ref{Symbols}, for the details.
14947 @node Special Fortran Commands
14948 @subsubsection Special Fortran Commands
14950 @cindex Special Fortran commands
14952 @value{GDBN} has some commands to support Fortran-specific features,
14953 such as displaying common blocks.
14956 @cindex @code{COMMON} blocks, Fortran
14957 @kindex info common
14958 @item info common @r{[}@var{common-name}@r{]}
14959 This command prints the values contained in the Fortran @code{COMMON}
14960 block whose name is @var{common-name}. With no argument, the names of
14961 all @code{COMMON} blocks visible at the current program location are
14968 @cindex Pascal support in @value{GDBN}, limitations
14969 Debugging Pascal programs which use sets, subranges, file variables, or
14970 nested functions does not currently work. @value{GDBN} does not support
14971 entering expressions, printing values, or similar features using Pascal
14974 The Pascal-specific command @code{set print pascal_static-members}
14975 controls whether static members of Pascal objects are displayed.
14976 @xref{Print Settings, pascal_static-members}.
14979 @subsection Modula-2
14981 @cindex Modula-2, @value{GDBN} support
14983 The extensions made to @value{GDBN} to support Modula-2 only support
14984 output from the @sc{gnu} Modula-2 compiler (which is currently being
14985 developed). Other Modula-2 compilers are not currently supported, and
14986 attempting to debug executables produced by them is most likely
14987 to give an error as @value{GDBN} reads in the executable's symbol
14990 @cindex expressions in Modula-2
14992 * M2 Operators:: Built-in operators
14993 * Built-In Func/Proc:: Built-in functions and procedures
14994 * M2 Constants:: Modula-2 constants
14995 * M2 Types:: Modula-2 types
14996 * M2 Defaults:: Default settings for Modula-2
14997 * Deviations:: Deviations from standard Modula-2
14998 * M2 Checks:: Modula-2 type and range checks
14999 * M2 Scope:: The scope operators @code{::} and @code{.}
15000 * GDB/M2:: @value{GDBN} and Modula-2
15004 @subsubsection Operators
15005 @cindex Modula-2 operators
15007 Operators must be defined on values of specific types. For instance,
15008 @code{+} is defined on numbers, but not on structures. Operators are
15009 often defined on groups of types. For the purposes of Modula-2, the
15010 following definitions hold:
15015 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15019 @emph{Character types} consist of @code{CHAR} and its subranges.
15022 @emph{Floating-point types} consist of @code{REAL}.
15025 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15029 @emph{Scalar types} consist of all of the above.
15032 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15035 @emph{Boolean types} consist of @code{BOOLEAN}.
15039 The following operators are supported, and appear in order of
15040 increasing precedence:
15044 Function argument or array index separator.
15047 Assignment. The value of @var{var} @code{:=} @var{value} is
15051 Less than, greater than on integral, floating-point, or enumerated
15055 Less than or equal to, greater than or equal to
15056 on integral, floating-point and enumerated types, or set inclusion on
15057 set types. Same precedence as @code{<}.
15059 @item =@r{, }<>@r{, }#
15060 Equality and two ways of expressing inequality, valid on scalar types.
15061 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15062 available for inequality, since @code{#} conflicts with the script
15066 Set membership. Defined on set types and the types of their members.
15067 Same precedence as @code{<}.
15070 Boolean disjunction. Defined on boolean types.
15073 Boolean conjunction. Defined on boolean types.
15076 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15079 Addition and subtraction on integral and floating-point types, or union
15080 and difference on set types.
15083 Multiplication on integral and floating-point types, or set intersection
15087 Division on floating-point types, or symmetric set difference on set
15088 types. Same precedence as @code{*}.
15091 Integer division and remainder. Defined on integral types. Same
15092 precedence as @code{*}.
15095 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15098 Pointer dereferencing. Defined on pointer types.
15101 Boolean negation. Defined on boolean types. Same precedence as
15105 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15106 precedence as @code{^}.
15109 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15112 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15116 @value{GDBN} and Modula-2 scope operators.
15120 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15121 treats the use of the operator @code{IN}, or the use of operators
15122 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15123 @code{<=}, and @code{>=} on sets as an error.
15127 @node Built-In Func/Proc
15128 @subsubsection Built-in Functions and Procedures
15129 @cindex Modula-2 built-ins
15131 Modula-2 also makes available several built-in procedures and functions.
15132 In describing these, the following metavariables are used:
15137 represents an @code{ARRAY} variable.
15140 represents a @code{CHAR} constant or variable.
15143 represents a variable or constant of integral type.
15146 represents an identifier that belongs to a set. Generally used in the
15147 same function with the metavariable @var{s}. The type of @var{s} should
15148 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15151 represents a variable or constant of integral or floating-point type.
15154 represents a variable or constant of floating-point type.
15160 represents a variable.
15163 represents a variable or constant of one of many types. See the
15164 explanation of the function for details.
15167 All Modula-2 built-in procedures also return a result, described below.
15171 Returns the absolute value of @var{n}.
15174 If @var{c} is a lower case letter, it returns its upper case
15175 equivalent, otherwise it returns its argument.
15178 Returns the character whose ordinal value is @var{i}.
15181 Decrements the value in the variable @var{v} by one. Returns the new value.
15183 @item DEC(@var{v},@var{i})
15184 Decrements the value in the variable @var{v} by @var{i}. Returns the
15187 @item EXCL(@var{m},@var{s})
15188 Removes the element @var{m} from the set @var{s}. Returns the new
15191 @item FLOAT(@var{i})
15192 Returns the floating point equivalent of the integer @var{i}.
15194 @item HIGH(@var{a})
15195 Returns the index of the last member of @var{a}.
15198 Increments the value in the variable @var{v} by one. Returns the new value.
15200 @item INC(@var{v},@var{i})
15201 Increments the value in the variable @var{v} by @var{i}. Returns the
15204 @item INCL(@var{m},@var{s})
15205 Adds the element @var{m} to the set @var{s} if it is not already
15206 there. Returns the new set.
15209 Returns the maximum value of the type @var{t}.
15212 Returns the minimum value of the type @var{t}.
15215 Returns boolean TRUE if @var{i} is an odd number.
15218 Returns the ordinal value of its argument. For example, the ordinal
15219 value of a character is its @sc{ascii} value (on machines supporting
15220 the @sc{ascii} character set). The argument @var{x} must be of an
15221 ordered type, which include integral, character and enumerated types.
15223 @item SIZE(@var{x})
15224 Returns the size of its argument. The argument @var{x} can be a
15225 variable or a type.
15227 @item TRUNC(@var{r})
15228 Returns the integral part of @var{r}.
15230 @item TSIZE(@var{x})
15231 Returns the size of its argument. The argument @var{x} can be a
15232 variable or a type.
15234 @item VAL(@var{t},@var{i})
15235 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15239 @emph{Warning:} Sets and their operations are not yet supported, so
15240 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15244 @cindex Modula-2 constants
15246 @subsubsection Constants
15248 @value{GDBN} allows you to express the constants of Modula-2 in the following
15254 Integer constants are simply a sequence of digits. When used in an
15255 expression, a constant is interpreted to be type-compatible with the
15256 rest of the expression. Hexadecimal integers are specified by a
15257 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15260 Floating point constants appear as a sequence of digits, followed by a
15261 decimal point and another sequence of digits. An optional exponent can
15262 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15263 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15264 digits of the floating point constant must be valid decimal (base 10)
15268 Character constants consist of a single character enclosed by a pair of
15269 like quotes, either single (@code{'}) or double (@code{"}). They may
15270 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15271 followed by a @samp{C}.
15274 String constants consist of a sequence of characters enclosed by a
15275 pair of like quotes, either single (@code{'}) or double (@code{"}).
15276 Escape sequences in the style of C are also allowed. @xref{C
15277 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15281 Enumerated constants consist of an enumerated identifier.
15284 Boolean constants consist of the identifiers @code{TRUE} and
15288 Pointer constants consist of integral values only.
15291 Set constants are not yet supported.
15295 @subsubsection Modula-2 Types
15296 @cindex Modula-2 types
15298 Currently @value{GDBN} can print the following data types in Modula-2
15299 syntax: array types, record types, set types, pointer types, procedure
15300 types, enumerated types, subrange types and base types. You can also
15301 print the contents of variables declared using these type.
15302 This section gives a number of simple source code examples together with
15303 sample @value{GDBN} sessions.
15305 The first example contains the following section of code:
15314 and you can request @value{GDBN} to interrogate the type and value of
15315 @code{r} and @code{s}.
15318 (@value{GDBP}) print s
15320 (@value{GDBP}) ptype s
15322 (@value{GDBP}) print r
15324 (@value{GDBP}) ptype r
15329 Likewise if your source code declares @code{s} as:
15333 s: SET ['A'..'Z'] ;
15337 then you may query the type of @code{s} by:
15340 (@value{GDBP}) ptype s
15341 type = SET ['A'..'Z']
15345 Note that at present you cannot interactively manipulate set
15346 expressions using the debugger.
15348 The following example shows how you might declare an array in Modula-2
15349 and how you can interact with @value{GDBN} to print its type and contents:
15353 s: ARRAY [-10..10] OF CHAR ;
15357 (@value{GDBP}) ptype s
15358 ARRAY [-10..10] OF CHAR
15361 Note that the array handling is not yet complete and although the type
15362 is printed correctly, expression handling still assumes that all
15363 arrays have a lower bound of zero and not @code{-10} as in the example
15366 Here are some more type related Modula-2 examples:
15370 colour = (blue, red, yellow, green) ;
15371 t = [blue..yellow] ;
15379 The @value{GDBN} interaction shows how you can query the data type
15380 and value of a variable.
15383 (@value{GDBP}) print s
15385 (@value{GDBP}) ptype t
15386 type = [blue..yellow]
15390 In this example a Modula-2 array is declared and its contents
15391 displayed. Observe that the contents are written in the same way as
15392 their @code{C} counterparts.
15396 s: ARRAY [1..5] OF CARDINAL ;
15402 (@value{GDBP}) print s
15403 $1 = @{1, 0, 0, 0, 0@}
15404 (@value{GDBP}) ptype s
15405 type = ARRAY [1..5] OF CARDINAL
15408 The Modula-2 language interface to @value{GDBN} also understands
15409 pointer types as shown in this example:
15413 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15420 and you can request that @value{GDBN} describes the type of @code{s}.
15423 (@value{GDBP}) ptype s
15424 type = POINTER TO ARRAY [1..5] OF CARDINAL
15427 @value{GDBN} handles compound types as we can see in this example.
15428 Here we combine array types, record types, pointer types and subrange
15439 myarray = ARRAY myrange OF CARDINAL ;
15440 myrange = [-2..2] ;
15442 s: POINTER TO ARRAY myrange OF foo ;
15446 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15450 (@value{GDBP}) ptype s
15451 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15454 f3 : ARRAY [-2..2] OF CARDINAL;
15459 @subsubsection Modula-2 Defaults
15460 @cindex Modula-2 defaults
15462 If type and range checking are set automatically by @value{GDBN}, they
15463 both default to @code{on} whenever the working language changes to
15464 Modula-2. This happens regardless of whether you or @value{GDBN}
15465 selected the working language.
15467 If you allow @value{GDBN} to set the language automatically, then entering
15468 code compiled from a file whose name ends with @file{.mod} sets the
15469 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15470 Infer the Source Language}, for further details.
15473 @subsubsection Deviations from Standard Modula-2
15474 @cindex Modula-2, deviations from
15476 A few changes have been made to make Modula-2 programs easier to debug.
15477 This is done primarily via loosening its type strictness:
15481 Unlike in standard Modula-2, pointer constants can be formed by
15482 integers. This allows you to modify pointer variables during
15483 debugging. (In standard Modula-2, the actual address contained in a
15484 pointer variable is hidden from you; it can only be modified
15485 through direct assignment to another pointer variable or expression that
15486 returned a pointer.)
15489 C escape sequences can be used in strings and characters to represent
15490 non-printable characters. @value{GDBN} prints out strings with these
15491 escape sequences embedded. Single non-printable characters are
15492 printed using the @samp{CHR(@var{nnn})} format.
15495 The assignment operator (@code{:=}) returns the value of its right-hand
15499 All built-in procedures both modify @emph{and} return their argument.
15503 @subsubsection Modula-2 Type and Range Checks
15504 @cindex Modula-2 checks
15507 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15510 @c FIXME remove warning when type/range checks added
15512 @value{GDBN} considers two Modula-2 variables type equivalent if:
15516 They are of types that have been declared equivalent via a @code{TYPE
15517 @var{t1} = @var{t2}} statement
15520 They have been declared on the same line. (Note: This is true of the
15521 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15524 As long as type checking is enabled, any attempt to combine variables
15525 whose types are not equivalent is an error.
15527 Range checking is done on all mathematical operations, assignment, array
15528 index bounds, and all built-in functions and procedures.
15531 @subsubsection The Scope Operators @code{::} and @code{.}
15533 @cindex @code{.}, Modula-2 scope operator
15534 @cindex colon, doubled as scope operator
15536 @vindex colon-colon@r{, in Modula-2}
15537 @c Info cannot handle :: but TeX can.
15540 @vindex ::@r{, in Modula-2}
15543 There are a few subtle differences between the Modula-2 scope operator
15544 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15549 @var{module} . @var{id}
15550 @var{scope} :: @var{id}
15554 where @var{scope} is the name of a module or a procedure,
15555 @var{module} the name of a module, and @var{id} is any declared
15556 identifier within your program, except another module.
15558 Using the @code{::} operator makes @value{GDBN} search the scope
15559 specified by @var{scope} for the identifier @var{id}. If it is not
15560 found in the specified scope, then @value{GDBN} searches all scopes
15561 enclosing the one specified by @var{scope}.
15563 Using the @code{.} operator makes @value{GDBN} search the current scope for
15564 the identifier specified by @var{id} that was imported from the
15565 definition module specified by @var{module}. With this operator, it is
15566 an error if the identifier @var{id} was not imported from definition
15567 module @var{module}, or if @var{id} is not an identifier in
15571 @subsubsection @value{GDBN} and Modula-2
15573 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15574 Five subcommands of @code{set print} and @code{show print} apply
15575 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15576 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15577 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15578 analogue in Modula-2.
15580 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15581 with any language, is not useful with Modula-2. Its
15582 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15583 created in Modula-2 as they can in C or C@t{++}. However, because an
15584 address can be specified by an integral constant, the construct
15585 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15587 @cindex @code{#} in Modula-2
15588 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15589 interpreted as the beginning of a comment. Use @code{<>} instead.
15595 The extensions made to @value{GDBN} for Ada only support
15596 output from the @sc{gnu} Ada (GNAT) compiler.
15597 Other Ada compilers are not currently supported, and
15598 attempting to debug executables produced by them is most likely
15602 @cindex expressions in Ada
15604 * Ada Mode Intro:: General remarks on the Ada syntax
15605 and semantics supported by Ada mode
15607 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15608 * Additions to Ada:: Extensions of the Ada expression syntax.
15609 * Overloading support for Ada:: Support for expressions involving overloaded
15611 * Stopping Before Main Program:: Debugging the program during elaboration.
15612 * Ada Exceptions:: Ada Exceptions
15613 * Ada Tasks:: Listing and setting breakpoints in tasks.
15614 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15615 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15617 * Ada Glitches:: Known peculiarities of Ada mode.
15620 @node Ada Mode Intro
15621 @subsubsection Introduction
15622 @cindex Ada mode, general
15624 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15625 syntax, with some extensions.
15626 The philosophy behind the design of this subset is
15630 That @value{GDBN} should provide basic literals and access to operations for
15631 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15632 leaving more sophisticated computations to subprograms written into the
15633 program (which therefore may be called from @value{GDBN}).
15636 That type safety and strict adherence to Ada language restrictions
15637 are not particularly important to the @value{GDBN} user.
15640 That brevity is important to the @value{GDBN} user.
15643 Thus, for brevity, the debugger acts as if all names declared in
15644 user-written packages are directly visible, even if they are not visible
15645 according to Ada rules, thus making it unnecessary to fully qualify most
15646 names with their packages, regardless of context. Where this causes
15647 ambiguity, @value{GDBN} asks the user's intent.
15649 The debugger will start in Ada mode if it detects an Ada main program.
15650 As for other languages, it will enter Ada mode when stopped in a program that
15651 was translated from an Ada source file.
15653 While in Ada mode, you may use `@t{--}' for comments. This is useful
15654 mostly for documenting command files. The standard @value{GDBN} comment
15655 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15656 middle (to allow based literals).
15658 @node Omissions from Ada
15659 @subsubsection Omissions from Ada
15660 @cindex Ada, omissions from
15662 Here are the notable omissions from the subset:
15666 Only a subset of the attributes are supported:
15670 @t{'First}, @t{'Last}, and @t{'Length}
15671 on array objects (not on types and subtypes).
15674 @t{'Min} and @t{'Max}.
15677 @t{'Pos} and @t{'Val}.
15683 @t{'Range} on array objects (not subtypes), but only as the right
15684 operand of the membership (@code{in}) operator.
15687 @t{'Access}, @t{'Unchecked_Access}, and
15688 @t{'Unrestricted_Access} (a GNAT extension).
15696 @code{Characters.Latin_1} are not available and
15697 concatenation is not implemented. Thus, escape characters in strings are
15698 not currently available.
15701 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15702 equality of representations. They will generally work correctly
15703 for strings and arrays whose elements have integer or enumeration types.
15704 They may not work correctly for arrays whose element
15705 types have user-defined equality, for arrays of real values
15706 (in particular, IEEE-conformant floating point, because of negative
15707 zeroes and NaNs), and for arrays whose elements contain unused bits with
15708 indeterminate values.
15711 The other component-by-component array operations (@code{and}, @code{or},
15712 @code{xor}, @code{not}, and relational tests other than equality)
15713 are not implemented.
15716 @cindex array aggregates (Ada)
15717 @cindex record aggregates (Ada)
15718 @cindex aggregates (Ada)
15719 There is limited support for array and record aggregates. They are
15720 permitted only on the right sides of assignments, as in these examples:
15723 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15724 (@value{GDBP}) set An_Array := (1, others => 0)
15725 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15726 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15727 (@value{GDBP}) set A_Record := (1, "Peter", True);
15728 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15732 discriminant's value by assigning an aggregate has an
15733 undefined effect if that discriminant is used within the record.
15734 However, you can first modify discriminants by directly assigning to
15735 them (which normally would not be allowed in Ada), and then performing an
15736 aggregate assignment. For example, given a variable @code{A_Rec}
15737 declared to have a type such as:
15740 type Rec (Len : Small_Integer := 0) is record
15742 Vals : IntArray (1 .. Len);
15746 you can assign a value with a different size of @code{Vals} with two
15750 (@value{GDBP}) set A_Rec.Len := 4
15751 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15754 As this example also illustrates, @value{GDBN} is very loose about the usual
15755 rules concerning aggregates. You may leave out some of the
15756 components of an array or record aggregate (such as the @code{Len}
15757 component in the assignment to @code{A_Rec} above); they will retain their
15758 original values upon assignment. You may freely use dynamic values as
15759 indices in component associations. You may even use overlapping or
15760 redundant component associations, although which component values are
15761 assigned in such cases is not defined.
15764 Calls to dispatching subprograms are not implemented.
15767 The overloading algorithm is much more limited (i.e., less selective)
15768 than that of real Ada. It makes only limited use of the context in
15769 which a subexpression appears to resolve its meaning, and it is much
15770 looser in its rules for allowing type matches. As a result, some
15771 function calls will be ambiguous, and the user will be asked to choose
15772 the proper resolution.
15775 The @code{new} operator is not implemented.
15778 Entry calls are not implemented.
15781 Aside from printing, arithmetic operations on the native VAX floating-point
15782 formats are not supported.
15785 It is not possible to slice a packed array.
15788 The names @code{True} and @code{False}, when not part of a qualified name,
15789 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15791 Should your program
15792 redefine these names in a package or procedure (at best a dubious practice),
15793 you will have to use fully qualified names to access their new definitions.
15796 @node Additions to Ada
15797 @subsubsection Additions to Ada
15798 @cindex Ada, deviations from
15800 As it does for other languages, @value{GDBN} makes certain generic
15801 extensions to Ada (@pxref{Expressions}):
15805 If the expression @var{E} is a variable residing in memory (typically
15806 a local variable or array element) and @var{N} is a positive integer,
15807 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15808 @var{N}-1 adjacent variables following it in memory as an array. In
15809 Ada, this operator is generally not necessary, since its prime use is
15810 in displaying parts of an array, and slicing will usually do this in
15811 Ada. However, there are occasional uses when debugging programs in
15812 which certain debugging information has been optimized away.
15815 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15816 appears in function or file @var{B}.'' When @var{B} is a file name,
15817 you must typically surround it in single quotes.
15820 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15821 @var{type} that appears at address @var{addr}.''
15824 A name starting with @samp{$} is a convenience variable
15825 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15828 In addition, @value{GDBN} provides a few other shortcuts and outright
15829 additions specific to Ada:
15833 The assignment statement is allowed as an expression, returning
15834 its right-hand operand as its value. Thus, you may enter
15837 (@value{GDBP}) set x := y + 3
15838 (@value{GDBP}) print A(tmp := y + 1)
15842 The semicolon is allowed as an ``operator,'' returning as its value
15843 the value of its right-hand operand.
15844 This allows, for example,
15845 complex conditional breaks:
15848 (@value{GDBP}) break f
15849 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15853 Rather than use catenation and symbolic character names to introduce special
15854 characters into strings, one may instead use a special bracket notation,
15855 which is also used to print strings. A sequence of characters of the form
15856 @samp{["@var{XX}"]} within a string or character literal denotes the
15857 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15858 sequence of characters @samp{["""]} also denotes a single quotation mark
15859 in strings. For example,
15861 "One line.["0a"]Next line.["0a"]"
15864 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15868 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15869 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15873 (@value{GDBP}) print 'max(x, y)
15877 When printing arrays, @value{GDBN} uses positional notation when the
15878 array has a lower bound of 1, and uses a modified named notation otherwise.
15879 For example, a one-dimensional array of three integers with a lower bound
15880 of 3 might print as
15887 That is, in contrast to valid Ada, only the first component has a @code{=>}
15891 You may abbreviate attributes in expressions with any unique,
15892 multi-character subsequence of
15893 their names (an exact match gets preference).
15894 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15895 in place of @t{a'length}.
15898 @cindex quoting Ada internal identifiers
15899 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15900 to lower case. The GNAT compiler uses upper-case characters for
15901 some of its internal identifiers, which are normally of no interest to users.
15902 For the rare occasions when you actually have to look at them,
15903 enclose them in angle brackets to avoid the lower-case mapping.
15906 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15910 Printing an object of class-wide type or dereferencing an
15911 access-to-class-wide value will display all the components of the object's
15912 specific type (as indicated by its run-time tag). Likewise, component
15913 selection on such a value will operate on the specific type of the
15918 @node Overloading support for Ada
15919 @subsubsection Overloading support for Ada
15920 @cindex overloading, Ada
15922 The debugger supports limited overloading. Given a subprogram call in which
15923 the function symbol has multiple definitions, it will use the number of
15924 actual parameters and some information about their types to attempt to narrow
15925 the set of definitions. It also makes very limited use of context, preferring
15926 procedures to functions in the context of the @code{call} command, and
15927 functions to procedures elsewhere.
15929 If, after narrowing, the set of matching definitions still contains more than
15930 one definition, @value{GDBN} will display a menu to query which one it should
15934 (@value{GDBP}) print f(1)
15935 Multiple matches for f
15937 [1] foo.f (integer) return boolean at foo.adb:23
15938 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15942 In this case, just select one menu entry either to cancel expression evaluation
15943 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
15944 instance (type the corresponding number and press @key{RET}).
15946 Here are a couple of commands to customize @value{GDBN}'s behavior in this
15951 @kindex set ada print-signatures
15952 @item set ada print-signatures
15953 Control whether parameter types and return types are displayed in overloads
15954 selection menus. It is @code{on} by default.
15955 @xref{Overloading support for Ada}.
15957 @kindex show ada print-signatures
15958 @item show ada print-signatures
15959 Show the current setting for displaying parameter types and return types in
15960 overloads selection menu.
15961 @xref{Overloading support for Ada}.
15965 @node Stopping Before Main Program
15966 @subsubsection Stopping at the Very Beginning
15968 @cindex breakpointing Ada elaboration code
15969 It is sometimes necessary to debug the program during elaboration, and
15970 before reaching the main procedure.
15971 As defined in the Ada Reference
15972 Manual, the elaboration code is invoked from a procedure called
15973 @code{adainit}. To run your program up to the beginning of
15974 elaboration, simply use the following two commands:
15975 @code{tbreak adainit} and @code{run}.
15977 @node Ada Exceptions
15978 @subsubsection Ada Exceptions
15980 A command is provided to list all Ada exceptions:
15983 @kindex info exceptions
15984 @item info exceptions
15985 @itemx info exceptions @var{regexp}
15986 The @code{info exceptions} command allows you to list all Ada exceptions
15987 defined within the program being debugged, as well as their addresses.
15988 With a regular expression, @var{regexp}, as argument, only those exceptions
15989 whose names match @var{regexp} are listed.
15992 Below is a small example, showing how the command can be used, first
15993 without argument, and next with a regular expression passed as an
15997 (@value{GDBP}) info exceptions
15998 All defined Ada exceptions:
15999 constraint_error: 0x613da0
16000 program_error: 0x613d20
16001 storage_error: 0x613ce0
16002 tasking_error: 0x613ca0
16003 const.aint_global_e: 0x613b00
16004 (@value{GDBP}) info exceptions const.aint
16005 All Ada exceptions matching regular expression "const.aint":
16006 constraint_error: 0x613da0
16007 const.aint_global_e: 0x613b00
16010 It is also possible to ask @value{GDBN} to stop your program's execution
16011 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16014 @subsubsection Extensions for Ada Tasks
16015 @cindex Ada, tasking
16017 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16018 @value{GDBN} provides the following task-related commands:
16023 This command shows a list of current Ada tasks, as in the following example:
16030 (@value{GDBP}) info tasks
16031 ID TID P-ID Pri State Name
16032 1 8088000 0 15 Child Activation Wait main_task
16033 2 80a4000 1 15 Accept Statement b
16034 3 809a800 1 15 Child Activation Wait a
16035 * 4 80ae800 3 15 Runnable c
16040 In this listing, the asterisk before the last task indicates it to be the
16041 task currently being inspected.
16045 Represents @value{GDBN}'s internal task number.
16051 The parent's task ID (@value{GDBN}'s internal task number).
16054 The base priority of the task.
16057 Current state of the task.
16061 The task has been created but has not been activated. It cannot be
16065 The task is not blocked for any reason known to Ada. (It may be waiting
16066 for a mutex, though.) It is conceptually "executing" in normal mode.
16069 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16070 that were waiting on terminate alternatives have been awakened and have
16071 terminated themselves.
16073 @item Child Activation Wait
16074 The task is waiting for created tasks to complete activation.
16076 @item Accept Statement
16077 The task is waiting on an accept or selective wait statement.
16079 @item Waiting on entry call
16080 The task is waiting on an entry call.
16082 @item Async Select Wait
16083 The task is waiting to start the abortable part of an asynchronous
16087 The task is waiting on a select statement with only a delay
16090 @item Child Termination Wait
16091 The task is sleeping having completed a master within itself, and is
16092 waiting for the tasks dependent on that master to become terminated or
16093 waiting on a terminate Phase.
16095 @item Wait Child in Term Alt
16096 The task is sleeping waiting for tasks on terminate alternatives to
16097 finish terminating.
16099 @item Accepting RV with @var{taskno}
16100 The task is accepting a rendez-vous with the task @var{taskno}.
16104 Name of the task in the program.
16108 @kindex info task @var{taskno}
16109 @item info task @var{taskno}
16110 This command shows detailled informations on the specified task, as in
16111 the following example:
16116 (@value{GDBP}) info tasks
16117 ID TID P-ID Pri State Name
16118 1 8077880 0 15 Child Activation Wait main_task
16119 * 2 807c468 1 15 Runnable task_1
16120 (@value{GDBP}) info task 2
16121 Ada Task: 0x807c468
16124 Parent: 1 (main_task)
16130 @kindex task@r{ (Ada)}
16131 @cindex current Ada task ID
16132 This command prints the ID of the current task.
16138 (@value{GDBP}) info tasks
16139 ID TID P-ID Pri State Name
16140 1 8077870 0 15 Child Activation Wait main_task
16141 * 2 807c458 1 15 Runnable t
16142 (@value{GDBP}) task
16143 [Current task is 2]
16146 @item task @var{taskno}
16147 @cindex Ada task switching
16148 This command is like the @code{thread @var{threadno}}
16149 command (@pxref{Threads}). It switches the context of debugging
16150 from the current task to the given task.
16156 (@value{GDBP}) info tasks
16157 ID TID P-ID Pri State Name
16158 1 8077870 0 15 Child Activation Wait main_task
16159 * 2 807c458 1 15 Runnable t
16160 (@value{GDBP}) task 1
16161 [Switching to task 1]
16162 #0 0x8067726 in pthread_cond_wait ()
16164 #0 0x8067726 in pthread_cond_wait ()
16165 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16166 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16167 #3 0x806153e in system.tasking.stages.activate_tasks ()
16168 #4 0x804aacc in un () at un.adb:5
16171 @item break @var{location} task @var{taskno}
16172 @itemx break @var{location} task @var{taskno} if @dots{}
16173 @cindex breakpoints and tasks, in Ada
16174 @cindex task breakpoints, in Ada
16175 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16176 These commands are like the @code{break @dots{} thread @dots{}}
16177 command (@pxref{Thread Stops}). The
16178 @var{location} argument specifies source lines, as described
16179 in @ref{Specify Location}.
16181 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16182 to specify that you only want @value{GDBN} to stop the program when a
16183 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16184 numeric task identifiers assigned by @value{GDBN}, shown in the first
16185 column of the @samp{info tasks} display.
16187 If you do not specify @samp{task @var{taskno}} when you set a
16188 breakpoint, the breakpoint applies to @emph{all} tasks of your
16191 You can use the @code{task} qualifier on conditional breakpoints as
16192 well; in this case, place @samp{task @var{taskno}} before the
16193 breakpoint condition (before the @code{if}).
16201 (@value{GDBP}) info tasks
16202 ID TID P-ID Pri State Name
16203 1 140022020 0 15 Child Activation Wait main_task
16204 2 140045060 1 15 Accept/Select Wait t2
16205 3 140044840 1 15 Runnable t1
16206 * 4 140056040 1 15 Runnable t3
16207 (@value{GDBP}) b 15 task 2
16208 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16209 (@value{GDBP}) cont
16214 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16216 (@value{GDBP}) info tasks
16217 ID TID P-ID Pri State Name
16218 1 140022020 0 15 Child Activation Wait main_task
16219 * 2 140045060 1 15 Runnable t2
16220 3 140044840 1 15 Runnable t1
16221 4 140056040 1 15 Delay Sleep t3
16225 @node Ada Tasks and Core Files
16226 @subsubsection Tasking Support when Debugging Core Files
16227 @cindex Ada tasking and core file debugging
16229 When inspecting a core file, as opposed to debugging a live program,
16230 tasking support may be limited or even unavailable, depending on
16231 the platform being used.
16232 For instance, on x86-linux, the list of tasks is available, but task
16233 switching is not supported.
16235 On certain platforms, the debugger needs to perform some
16236 memory writes in order to provide Ada tasking support. When inspecting
16237 a core file, this means that the core file must be opened with read-write
16238 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16239 Under these circumstances, you should make a backup copy of the core
16240 file before inspecting it with @value{GDBN}.
16242 @node Ravenscar Profile
16243 @subsubsection Tasking Support when using the Ravenscar Profile
16244 @cindex Ravenscar Profile
16246 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16247 specifically designed for systems with safety-critical real-time
16251 @kindex set ravenscar task-switching on
16252 @cindex task switching with program using Ravenscar Profile
16253 @item set ravenscar task-switching on
16254 Allows task switching when debugging a program that uses the Ravenscar
16255 Profile. This is the default.
16257 @kindex set ravenscar task-switching off
16258 @item set ravenscar task-switching off
16259 Turn off task switching when debugging a program that uses the Ravenscar
16260 Profile. This is mostly intended to disable the code that adds support
16261 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16262 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16263 To be effective, this command should be run before the program is started.
16265 @kindex show ravenscar task-switching
16266 @item show ravenscar task-switching
16267 Show whether it is possible to switch from task to task in a program
16268 using the Ravenscar Profile.
16273 @subsubsection Known Peculiarities of Ada Mode
16274 @cindex Ada, problems
16276 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16277 we know of several problems with and limitations of Ada mode in
16279 some of which will be fixed with planned future releases of the debugger
16280 and the GNU Ada compiler.
16284 Static constants that the compiler chooses not to materialize as objects in
16285 storage are invisible to the debugger.
16288 Named parameter associations in function argument lists are ignored (the
16289 argument lists are treated as positional).
16292 Many useful library packages are currently invisible to the debugger.
16295 Fixed-point arithmetic, conversions, input, and output is carried out using
16296 floating-point arithmetic, and may give results that only approximate those on
16300 The GNAT compiler never generates the prefix @code{Standard} for any of
16301 the standard symbols defined by the Ada language. @value{GDBN} knows about
16302 this: it will strip the prefix from names when you use it, and will never
16303 look for a name you have so qualified among local symbols, nor match against
16304 symbols in other packages or subprograms. If you have
16305 defined entities anywhere in your program other than parameters and
16306 local variables whose simple names match names in @code{Standard},
16307 GNAT's lack of qualification here can cause confusion. When this happens,
16308 you can usually resolve the confusion
16309 by qualifying the problematic names with package
16310 @code{Standard} explicitly.
16313 Older versions of the compiler sometimes generate erroneous debugging
16314 information, resulting in the debugger incorrectly printing the value
16315 of affected entities. In some cases, the debugger is able to work
16316 around an issue automatically. In other cases, the debugger is able
16317 to work around the issue, but the work-around has to be specifically
16320 @kindex set ada trust-PAD-over-XVS
16321 @kindex show ada trust-PAD-over-XVS
16324 @item set ada trust-PAD-over-XVS on
16325 Configure GDB to strictly follow the GNAT encoding when computing the
16326 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16327 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16328 a complete description of the encoding used by the GNAT compiler).
16329 This is the default.
16331 @item set ada trust-PAD-over-XVS off
16332 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16333 sometimes prints the wrong value for certain entities, changing @code{ada
16334 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16335 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16336 @code{off}, but this incurs a slight performance penalty, so it is
16337 recommended to leave this setting to @code{on} unless necessary.
16341 @cindex GNAT descriptive types
16342 @cindex GNAT encoding
16343 Internally, the debugger also relies on the compiler following a number
16344 of conventions known as the @samp{GNAT Encoding}, all documented in
16345 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16346 how the debugging information should be generated for certain types.
16347 In particular, this convention makes use of @dfn{descriptive types},
16348 which are artificial types generated purely to help the debugger.
16350 These encodings were defined at a time when the debugging information
16351 format used was not powerful enough to describe some of the more complex
16352 types available in Ada. Since DWARF allows us to express nearly all
16353 Ada features, the long-term goal is to slowly replace these descriptive
16354 types by their pure DWARF equivalent. To facilitate that transition,
16355 a new maintenance option is available to force the debugger to ignore
16356 those descriptive types. It allows the user to quickly evaluate how
16357 well @value{GDBN} works without them.
16361 @kindex maint ada set ignore-descriptive-types
16362 @item maintenance ada set ignore-descriptive-types [on|off]
16363 Control whether the debugger should ignore descriptive types.
16364 The default is not to ignore descriptives types (@code{off}).
16366 @kindex maint ada show ignore-descriptive-types
16367 @item maintenance ada show ignore-descriptive-types
16368 Show if descriptive types are ignored by @value{GDBN}.
16372 @node Unsupported Languages
16373 @section Unsupported Languages
16375 @cindex unsupported languages
16376 @cindex minimal language
16377 In addition to the other fully-supported programming languages,
16378 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16379 It does not represent a real programming language, but provides a set
16380 of capabilities close to what the C or assembly languages provide.
16381 This should allow most simple operations to be performed while debugging
16382 an application that uses a language currently not supported by @value{GDBN}.
16384 If the language is set to @code{auto}, @value{GDBN} will automatically
16385 select this language if the current frame corresponds to an unsupported
16389 @chapter Examining the Symbol Table
16391 The commands described in this chapter allow you to inquire about the
16392 symbols (names of variables, functions and types) defined in your
16393 program. This information is inherent in the text of your program and
16394 does not change as your program executes. @value{GDBN} finds it in your
16395 program's symbol table, in the file indicated when you started @value{GDBN}
16396 (@pxref{File Options, ,Choosing Files}), or by one of the
16397 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16399 @cindex symbol names
16400 @cindex names of symbols
16401 @cindex quoting names
16402 Occasionally, you may need to refer to symbols that contain unusual
16403 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16404 most frequent case is in referring to static variables in other
16405 source files (@pxref{Variables,,Program Variables}). File names
16406 are recorded in object files as debugging symbols, but @value{GDBN} would
16407 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16408 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16409 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16416 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16419 @cindex case-insensitive symbol names
16420 @cindex case sensitivity in symbol names
16421 @kindex set case-sensitive
16422 @item set case-sensitive on
16423 @itemx set case-sensitive off
16424 @itemx set case-sensitive auto
16425 Normally, when @value{GDBN} looks up symbols, it matches their names
16426 with case sensitivity determined by the current source language.
16427 Occasionally, you may wish to control that. The command @code{set
16428 case-sensitive} lets you do that by specifying @code{on} for
16429 case-sensitive matches or @code{off} for case-insensitive ones. If
16430 you specify @code{auto}, case sensitivity is reset to the default
16431 suitable for the source language. The default is case-sensitive
16432 matches for all languages except for Fortran, for which the default is
16433 case-insensitive matches.
16435 @kindex show case-sensitive
16436 @item show case-sensitive
16437 This command shows the current setting of case sensitivity for symbols
16440 @kindex set print type methods
16441 @item set print type methods
16442 @itemx set print type methods on
16443 @itemx set print type methods off
16444 Normally, when @value{GDBN} prints a class, it displays any methods
16445 declared in that class. You can control this behavior either by
16446 passing the appropriate flag to @code{ptype}, or using @command{set
16447 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16448 display the methods; this is the default. Specifying @code{off} will
16449 cause @value{GDBN} to omit the methods.
16451 @kindex show print type methods
16452 @item show print type methods
16453 This command shows the current setting of method display when printing
16456 @kindex set print type typedefs
16457 @item set print type typedefs
16458 @itemx set print type typedefs on
16459 @itemx set print type typedefs off
16461 Normally, when @value{GDBN} prints a class, it displays any typedefs
16462 defined in that class. You can control this behavior either by
16463 passing the appropriate flag to @code{ptype}, or using @command{set
16464 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16465 display the typedef definitions; this is the default. Specifying
16466 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16467 Note that this controls whether the typedef definition itself is
16468 printed, not whether typedef names are substituted when printing other
16471 @kindex show print type typedefs
16472 @item show print type typedefs
16473 This command shows the current setting of typedef display when
16476 @kindex info address
16477 @cindex address of a symbol
16478 @item info address @var{symbol}
16479 Describe where the data for @var{symbol} is stored. For a register
16480 variable, this says which register it is kept in. For a non-register
16481 local variable, this prints the stack-frame offset at which the variable
16484 Note the contrast with @samp{print &@var{symbol}}, which does not work
16485 at all for a register variable, and for a stack local variable prints
16486 the exact address of the current instantiation of the variable.
16488 @kindex info symbol
16489 @cindex symbol from address
16490 @cindex closest symbol and offset for an address
16491 @item info symbol @var{addr}
16492 Print the name of a symbol which is stored at the address @var{addr}.
16493 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16494 nearest symbol and an offset from it:
16497 (@value{GDBP}) info symbol 0x54320
16498 _initialize_vx + 396 in section .text
16502 This is the opposite of the @code{info address} command. You can use
16503 it to find out the name of a variable or a function given its address.
16505 For dynamically linked executables, the name of executable or shared
16506 library containing the symbol is also printed:
16509 (@value{GDBP}) info symbol 0x400225
16510 _start + 5 in section .text of /tmp/a.out
16511 (@value{GDBP}) info symbol 0x2aaaac2811cf
16512 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16517 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16518 Demangle @var{name}.
16519 If @var{language} is provided it is the name of the language to demangle
16520 @var{name} in. Otherwise @var{name} is demangled in the current language.
16522 The @samp{--} option specifies the end of options,
16523 and is useful when @var{name} begins with a dash.
16525 The parameter @code{demangle-style} specifies how to interpret the kind
16526 of mangling used. @xref{Print Settings}.
16529 @item whatis[/@var{flags}] [@var{arg}]
16530 Print the data type of @var{arg}, which can be either an expression
16531 or a name of a data type. With no argument, print the data type of
16532 @code{$}, the last value in the value history.
16534 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16535 is not actually evaluated, and any side-effecting operations (such as
16536 assignments or function calls) inside it do not take place.
16538 If @var{arg} is a variable or an expression, @code{whatis} prints its
16539 literal type as it is used in the source code. If the type was
16540 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16541 the data type underlying the @code{typedef}. If the type of the
16542 variable or the expression is a compound data type, such as
16543 @code{struct} or @code{class}, @code{whatis} never prints their
16544 fields or methods. It just prints the @code{struct}/@code{class}
16545 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16546 such a compound data type, use @code{ptype}.
16548 If @var{arg} is a type name that was defined using @code{typedef},
16549 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16550 Unrolling means that @code{whatis} will show the underlying type used
16551 in the @code{typedef} declaration of @var{arg}. However, if that
16552 underlying type is also a @code{typedef}, @code{whatis} will not
16555 For C code, the type names may also have the form @samp{class
16556 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16557 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16559 @var{flags} can be used to modify how the type is displayed.
16560 Available flags are:
16564 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16565 parameters and typedefs defined in a class when printing the class'
16566 members. The @code{/r} flag disables this.
16569 Do not print methods defined in the class.
16572 Print methods defined in the class. This is the default, but the flag
16573 exists in case you change the default with @command{set print type methods}.
16576 Do not print typedefs defined in the class. Note that this controls
16577 whether the typedef definition itself is printed, not whether typedef
16578 names are substituted when printing other types.
16581 Print typedefs defined in the class. This is the default, but the flag
16582 exists in case you change the default with @command{set print type typedefs}.
16586 @item ptype[/@var{flags}] [@var{arg}]
16587 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16588 detailed description of the type, instead of just the name of the type.
16589 @xref{Expressions, ,Expressions}.
16591 Contrary to @code{whatis}, @code{ptype} always unrolls any
16592 @code{typedef}s in its argument declaration, whether the argument is
16593 a variable, expression, or a data type. This means that @code{ptype}
16594 of a variable or an expression will not print literally its type as
16595 present in the source code---use @code{whatis} for that. @code{typedef}s at
16596 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16597 fields, methods and inner @code{class typedef}s of @code{struct}s,
16598 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16600 For example, for this variable declaration:
16603 typedef double real_t;
16604 struct complex @{ real_t real; double imag; @};
16605 typedef struct complex complex_t;
16607 real_t *real_pointer_var;
16611 the two commands give this output:
16615 (@value{GDBP}) whatis var
16617 (@value{GDBP}) ptype var
16618 type = struct complex @{
16622 (@value{GDBP}) whatis complex_t
16623 type = struct complex
16624 (@value{GDBP}) whatis struct complex
16625 type = struct complex
16626 (@value{GDBP}) ptype struct complex
16627 type = struct complex @{
16631 (@value{GDBP}) whatis real_pointer_var
16633 (@value{GDBP}) ptype real_pointer_var
16639 As with @code{whatis}, using @code{ptype} without an argument refers to
16640 the type of @code{$}, the last value in the value history.
16642 @cindex incomplete type
16643 Sometimes, programs use opaque data types or incomplete specifications
16644 of complex data structure. If the debug information included in the
16645 program does not allow @value{GDBN} to display a full declaration of
16646 the data type, it will say @samp{<incomplete type>}. For example,
16647 given these declarations:
16651 struct foo *fooptr;
16655 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16658 (@value{GDBP}) ptype foo
16659 $1 = <incomplete type>
16663 ``Incomplete type'' is C terminology for data types that are not
16664 completely specified.
16667 @item info types @var{regexp}
16669 Print a brief description of all types whose names match the regular
16670 expression @var{regexp} (or all types in your program, if you supply
16671 no argument). Each complete typename is matched as though it were a
16672 complete line; thus, @samp{i type value} gives information on all
16673 types in your program whose names include the string @code{value}, but
16674 @samp{i type ^value$} gives information only on types whose complete
16675 name is @code{value}.
16677 This command differs from @code{ptype} in two ways: first, like
16678 @code{whatis}, it does not print a detailed description; second, it
16679 lists all source files where a type is defined.
16681 @kindex info type-printers
16682 @item info type-printers
16683 Versions of @value{GDBN} that ship with Python scripting enabled may
16684 have ``type printers'' available. When using @command{ptype} or
16685 @command{whatis}, these printers are consulted when the name of a type
16686 is needed. @xref{Type Printing API}, for more information on writing
16689 @code{info type-printers} displays all the available type printers.
16691 @kindex enable type-printer
16692 @kindex disable type-printer
16693 @item enable type-printer @var{name}@dots{}
16694 @item disable type-printer @var{name}@dots{}
16695 These commands can be used to enable or disable type printers.
16698 @cindex local variables
16699 @item info scope @var{location}
16700 List all the variables local to a particular scope. This command
16701 accepts a @var{location} argument---a function name, a source line, or
16702 an address preceded by a @samp{*}, and prints all the variables local
16703 to the scope defined by that location. (@xref{Specify Location}, for
16704 details about supported forms of @var{location}.) For example:
16707 (@value{GDBP}) @b{info scope command_line_handler}
16708 Scope for command_line_handler:
16709 Symbol rl is an argument at stack/frame offset 8, length 4.
16710 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16711 Symbol linelength is in static storage at address 0x150a1c, length 4.
16712 Symbol p is a local variable in register $esi, length 4.
16713 Symbol p1 is a local variable in register $ebx, length 4.
16714 Symbol nline is a local variable in register $edx, length 4.
16715 Symbol repeat is a local variable at frame offset -8, length 4.
16719 This command is especially useful for determining what data to collect
16720 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16723 @kindex info source
16725 Show information about the current source file---that is, the source file for
16726 the function containing the current point of execution:
16729 the name of the source file, and the directory containing it,
16731 the directory it was compiled in,
16733 its length, in lines,
16735 which programming language it is written in,
16737 if the debug information provides it, the program that compiled the file
16738 (which may include, e.g., the compiler version and command line arguments),
16740 whether the executable includes debugging information for that file, and
16741 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16743 whether the debugging information includes information about
16744 preprocessor macros.
16748 @kindex info sources
16750 Print the names of all source files in your program for which there is
16751 debugging information, organized into two lists: files whose symbols
16752 have already been read, and files whose symbols will be read when needed.
16754 @kindex info functions
16755 @item info functions
16756 Print the names and data types of all defined functions.
16758 @item info functions @var{regexp}
16759 Print the names and data types of all defined functions
16760 whose names contain a match for regular expression @var{regexp}.
16761 Thus, @samp{info fun step} finds all functions whose names
16762 include @code{step}; @samp{info fun ^step} finds those whose names
16763 start with @code{step}. If a function name contains characters
16764 that conflict with the regular expression language (e.g.@:
16765 @samp{operator*()}), they may be quoted with a backslash.
16767 @kindex info variables
16768 @item info variables
16769 Print the names and data types of all variables that are defined
16770 outside of functions (i.e.@: excluding local variables).
16772 @item info variables @var{regexp}
16773 Print the names and data types of all variables (except for local
16774 variables) whose names contain a match for regular expression
16777 @kindex info classes
16778 @cindex Objective-C, classes and selectors
16780 @itemx info classes @var{regexp}
16781 Display all Objective-C classes in your program, or
16782 (with the @var{regexp} argument) all those matching a particular regular
16785 @kindex info selectors
16786 @item info selectors
16787 @itemx info selectors @var{regexp}
16788 Display all Objective-C selectors in your program, or
16789 (with the @var{regexp} argument) all those matching a particular regular
16793 This was never implemented.
16794 @kindex info methods
16796 @itemx info methods @var{regexp}
16797 The @code{info methods} command permits the user to examine all defined
16798 methods within C@t{++} program, or (with the @var{regexp} argument) a
16799 specific set of methods found in the various C@t{++} classes. Many
16800 C@t{++} classes provide a large number of methods. Thus, the output
16801 from the @code{ptype} command can be overwhelming and hard to use. The
16802 @code{info-methods} command filters the methods, printing only those
16803 which match the regular-expression @var{regexp}.
16806 @cindex opaque data types
16807 @kindex set opaque-type-resolution
16808 @item set opaque-type-resolution on
16809 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16810 declared as a pointer to a @code{struct}, @code{class}, or
16811 @code{union}---for example, @code{struct MyType *}---that is used in one
16812 source file although the full declaration of @code{struct MyType} is in
16813 another source file. The default is on.
16815 A change in the setting of this subcommand will not take effect until
16816 the next time symbols for a file are loaded.
16818 @item set opaque-type-resolution off
16819 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16820 is printed as follows:
16822 @{<no data fields>@}
16825 @kindex show opaque-type-resolution
16826 @item show opaque-type-resolution
16827 Show whether opaque types are resolved or not.
16829 @kindex set print symbol-loading
16830 @cindex print messages when symbols are loaded
16831 @item set print symbol-loading
16832 @itemx set print symbol-loading full
16833 @itemx set print symbol-loading brief
16834 @itemx set print symbol-loading off
16835 The @code{set print symbol-loading} command allows you to control the
16836 printing of messages when @value{GDBN} loads symbol information.
16837 By default a message is printed for the executable and one for each
16838 shared library, and normally this is what you want. However, when
16839 debugging apps with large numbers of shared libraries these messages
16841 When set to @code{brief} a message is printed for each executable,
16842 and when @value{GDBN} loads a collection of shared libraries at once
16843 it will only print one message regardless of the number of shared
16844 libraries. When set to @code{off} no messages are printed.
16846 @kindex show print symbol-loading
16847 @item show print symbol-loading
16848 Show whether messages will be printed when a @value{GDBN} command
16849 entered from the keyboard causes symbol information to be loaded.
16851 @kindex maint print symbols
16852 @cindex symbol dump
16853 @kindex maint print psymbols
16854 @cindex partial symbol dump
16855 @kindex maint print msymbols
16856 @cindex minimal symbol dump
16857 @item maint print symbols @var{filename}
16858 @itemx maint print psymbols @var{filename}
16859 @itemx maint print msymbols @var{filename}
16860 Write a dump of debugging symbol data into the file @var{filename}.
16861 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16862 symbols with debugging data are included. If you use @samp{maint print
16863 symbols}, @value{GDBN} includes all the symbols for which it has already
16864 collected full details: that is, @var{filename} reflects symbols for
16865 only those files whose symbols @value{GDBN} has read. You can use the
16866 command @code{info sources} to find out which files these are. If you
16867 use @samp{maint print psymbols} instead, the dump shows information about
16868 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16869 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16870 @samp{maint print msymbols} dumps just the minimal symbol information
16871 required for each object file from which @value{GDBN} has read some symbols.
16872 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16873 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16875 @kindex maint info symtabs
16876 @kindex maint info psymtabs
16877 @cindex listing @value{GDBN}'s internal symbol tables
16878 @cindex symbol tables, listing @value{GDBN}'s internal
16879 @cindex full symbol tables, listing @value{GDBN}'s internal
16880 @cindex partial symbol tables, listing @value{GDBN}'s internal
16881 @item maint info symtabs @r{[} @var{regexp} @r{]}
16882 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16884 List the @code{struct symtab} or @code{struct partial_symtab}
16885 structures whose names match @var{regexp}. If @var{regexp} is not
16886 given, list them all. The output includes expressions which you can
16887 copy into a @value{GDBN} debugging this one to examine a particular
16888 structure in more detail. For example:
16891 (@value{GDBP}) maint info psymtabs dwarf2read
16892 @{ objfile /home/gnu/build/gdb/gdb
16893 ((struct objfile *) 0x82e69d0)
16894 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16895 ((struct partial_symtab *) 0x8474b10)
16898 text addresses 0x814d3c8 -- 0x8158074
16899 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16900 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16901 dependencies (none)
16904 (@value{GDBP}) maint info symtabs
16908 We see that there is one partial symbol table whose filename contains
16909 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16910 and we see that @value{GDBN} has not read in any symtabs yet at all.
16911 If we set a breakpoint on a function, that will cause @value{GDBN} to
16912 read the symtab for the compilation unit containing that function:
16915 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16916 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16918 (@value{GDBP}) maint info symtabs
16919 @{ objfile /home/gnu/build/gdb/gdb
16920 ((struct objfile *) 0x82e69d0)
16921 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16922 ((struct symtab *) 0x86c1f38)
16925 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16926 linetable ((struct linetable *) 0x8370fa0)
16927 debugformat DWARF 2
16933 @kindex maint set symbol-cache-size
16934 @cindex symbol cache size
16935 @item maint set symbol-cache-size @var{size}
16936 Set the size of the symbol cache to @var{size}.
16937 The default size is intended to be good enough for debugging
16938 most applications. This option exists to allow for experimenting
16939 with different sizes.
16941 @kindex maint show symbol-cache-size
16942 @item maint show symbol-cache-size
16943 Show the size of the symbol cache.
16945 @kindex maint print symbol-cache
16946 @cindex symbol cache, printing its contents
16947 @item maint print symbol-cache
16948 Print the contents of the symbol cache.
16949 This is useful when debugging symbol cache issues.
16951 @kindex maint print symbol-cache-statistics
16952 @cindex symbol cache, printing usage statistics
16953 @item maint print symbol-cache-statistics
16954 Print symbol cache usage statistics.
16955 This helps determine how well the cache is being utilized.
16957 @kindex maint flush-symbol-cache
16958 @cindex symbol cache, flushing
16959 @item maint flush-symbol-cache
16960 Flush the contents of the symbol cache, all entries are removed.
16961 This command is useful when debugging the symbol cache.
16962 It is also useful when collecting performance data.
16967 @chapter Altering Execution
16969 Once you think you have found an error in your program, you might want to
16970 find out for certain whether correcting the apparent error would lead to
16971 correct results in the rest of the run. You can find the answer by
16972 experiment, using the @value{GDBN} features for altering execution of the
16975 For example, you can store new values into variables or memory
16976 locations, give your program a signal, restart it at a different
16977 address, or even return prematurely from a function.
16980 * Assignment:: Assignment to variables
16981 * Jumping:: Continuing at a different address
16982 * Signaling:: Giving your program a signal
16983 * Returning:: Returning from a function
16984 * Calling:: Calling your program's functions
16985 * Patching:: Patching your program
16986 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16990 @section Assignment to Variables
16993 @cindex setting variables
16994 To alter the value of a variable, evaluate an assignment expression.
16995 @xref{Expressions, ,Expressions}. For example,
17002 stores the value 4 into the variable @code{x}, and then prints the
17003 value of the assignment expression (which is 4).
17004 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17005 information on operators in supported languages.
17007 @kindex set variable
17008 @cindex variables, setting
17009 If you are not interested in seeing the value of the assignment, use the
17010 @code{set} command instead of the @code{print} command. @code{set} is
17011 really the same as @code{print} except that the expression's value is
17012 not printed and is not put in the value history (@pxref{Value History,
17013 ,Value History}). The expression is evaluated only for its effects.
17015 If the beginning of the argument string of the @code{set} command
17016 appears identical to a @code{set} subcommand, use the @code{set
17017 variable} command instead of just @code{set}. This command is identical
17018 to @code{set} except for its lack of subcommands. For example, if your
17019 program has a variable @code{width}, you get an error if you try to set
17020 a new value with just @samp{set width=13}, because @value{GDBN} has the
17021 command @code{set width}:
17024 (@value{GDBP}) whatis width
17026 (@value{GDBP}) p width
17028 (@value{GDBP}) set width=47
17029 Invalid syntax in expression.
17033 The invalid expression, of course, is @samp{=47}. In
17034 order to actually set the program's variable @code{width}, use
17037 (@value{GDBP}) set var width=47
17040 Because the @code{set} command has many subcommands that can conflict
17041 with the names of program variables, it is a good idea to use the
17042 @code{set variable} command instead of just @code{set}. For example, if
17043 your program has a variable @code{g}, you run into problems if you try
17044 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17045 the command @code{set gnutarget}, abbreviated @code{set g}:
17049 (@value{GDBP}) whatis g
17053 (@value{GDBP}) set g=4
17057 The program being debugged has been started already.
17058 Start it from the beginning? (y or n) y
17059 Starting program: /home/smith/cc_progs/a.out
17060 "/home/smith/cc_progs/a.out": can't open to read symbols:
17061 Invalid bfd target.
17062 (@value{GDBP}) show g
17063 The current BFD target is "=4".
17068 The program variable @code{g} did not change, and you silently set the
17069 @code{gnutarget} to an invalid value. In order to set the variable
17073 (@value{GDBP}) set var g=4
17076 @value{GDBN} allows more implicit conversions in assignments than C; you can
17077 freely store an integer value into a pointer variable or vice versa,
17078 and you can convert any structure to any other structure that is the
17079 same length or shorter.
17080 @comment FIXME: how do structs align/pad in these conversions?
17081 @comment /doc@cygnus.com 18dec1990
17083 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17084 construct to generate a value of specified type at a specified address
17085 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17086 to memory location @code{0x83040} as an integer (which implies a certain size
17087 and representation in memory), and
17090 set @{int@}0x83040 = 4
17094 stores the value 4 into that memory location.
17097 @section Continuing at a Different Address
17099 Ordinarily, when you continue your program, you do so at the place where
17100 it stopped, with the @code{continue} command. You can instead continue at
17101 an address of your own choosing, with the following commands:
17105 @kindex j @r{(@code{jump})}
17106 @item jump @var{location}
17107 @itemx j @var{location}
17108 Resume execution at @var{location}. Execution stops again immediately
17109 if there is a breakpoint there. @xref{Specify Location}, for a description
17110 of the different forms of @var{location}. It is common
17111 practice to use the @code{tbreak} command in conjunction with
17112 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17114 The @code{jump} command does not change the current stack frame, or
17115 the stack pointer, or the contents of any memory location or any
17116 register other than the program counter. If @var{location} is in
17117 a different function from the one currently executing, the results may
17118 be bizarre if the two functions expect different patterns of arguments or
17119 of local variables. For this reason, the @code{jump} command requests
17120 confirmation if the specified line is not in the function currently
17121 executing. However, even bizarre results are predictable if you are
17122 well acquainted with the machine-language code of your program.
17125 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
17126 On many systems, you can get much the same effect as the @code{jump}
17127 command by storing a new value into the register @code{$pc}. The
17128 difference is that this does not start your program running; it only
17129 changes the address of where it @emph{will} run when you continue. For
17137 makes the next @code{continue} command or stepping command execute at
17138 address @code{0x485}, rather than at the address where your program stopped.
17139 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17141 The most common occasion to use the @code{jump} command is to back
17142 up---perhaps with more breakpoints set---over a portion of a program
17143 that has already executed, in order to examine its execution in more
17148 @section Giving your Program a Signal
17149 @cindex deliver a signal to a program
17153 @item signal @var{signal}
17154 Resume execution where your program is stopped, but immediately give it the
17155 signal @var{signal}. The @var{signal} can be the name or the number of a
17156 signal. For example, on many systems @code{signal 2} and @code{signal
17157 SIGINT} are both ways of sending an interrupt signal.
17159 Alternatively, if @var{signal} is zero, continue execution without
17160 giving a signal. This is useful when your program stopped on account of
17161 a signal and would ordinarily see the signal when resumed with the
17162 @code{continue} command; @samp{signal 0} causes it to resume without a
17165 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17166 delivered to the currently selected thread, not the thread that last
17167 reported a stop. This includes the situation where a thread was
17168 stopped due to a signal. So if you want to continue execution
17169 suppressing the signal that stopped a thread, you should select that
17170 same thread before issuing the @samp{signal 0} command. If you issue
17171 the @samp{signal 0} command with another thread as the selected one,
17172 @value{GDBN} detects that and asks for confirmation.
17174 Invoking the @code{signal} command is not the same as invoking the
17175 @code{kill} utility from the shell. Sending a signal with @code{kill}
17176 causes @value{GDBN} to decide what to do with the signal depending on
17177 the signal handling tables (@pxref{Signals}). The @code{signal} command
17178 passes the signal directly to your program.
17180 @code{signal} does not repeat when you press @key{RET} a second time
17181 after executing the command.
17183 @kindex queue-signal
17184 @item queue-signal @var{signal}
17185 Queue @var{signal} to be delivered immediately to the current thread
17186 when execution of the thread resumes. The @var{signal} can be the name or
17187 the number of a signal. For example, on many systems @code{signal 2} and
17188 @code{signal SIGINT} are both ways of sending an interrupt signal.
17189 The handling of the signal must be set to pass the signal to the program,
17190 otherwise @value{GDBN} will report an error.
17191 You can control the handling of signals from @value{GDBN} with the
17192 @code{handle} command (@pxref{Signals}).
17194 Alternatively, if @var{signal} is zero, any currently queued signal
17195 for the current thread is discarded and when execution resumes no signal
17196 will be delivered. This is useful when your program stopped on account
17197 of a signal and would ordinarily see the signal when resumed with the
17198 @code{continue} command.
17200 This command differs from the @code{signal} command in that the signal
17201 is just queued, execution is not resumed. And @code{queue-signal} cannot
17202 be used to pass a signal whose handling state has been set to @code{nopass}
17207 @xref{stepping into signal handlers}, for information on how stepping
17208 commands behave when the thread has a signal queued.
17211 @section Returning from a Function
17214 @cindex returning from a function
17217 @itemx return @var{expression}
17218 You can cancel execution of a function call with the @code{return}
17219 command. If you give an
17220 @var{expression} argument, its value is used as the function's return
17224 When you use @code{return}, @value{GDBN} discards the selected stack frame
17225 (and all frames within it). You can think of this as making the
17226 discarded frame return prematurely. If you wish to specify a value to
17227 be returned, give that value as the argument to @code{return}.
17229 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17230 Frame}), and any other frames inside of it, leaving its caller as the
17231 innermost remaining frame. That frame becomes selected. The
17232 specified value is stored in the registers used for returning values
17235 The @code{return} command does not resume execution; it leaves the
17236 program stopped in the state that would exist if the function had just
17237 returned. In contrast, the @code{finish} command (@pxref{Continuing
17238 and Stepping, ,Continuing and Stepping}) resumes execution until the
17239 selected stack frame returns naturally.
17241 @value{GDBN} needs to know how the @var{expression} argument should be set for
17242 the inferior. The concrete registers assignment depends on the OS ABI and the
17243 type being returned by the selected stack frame. For example it is common for
17244 OS ABI to return floating point values in FPU registers while integer values in
17245 CPU registers. Still some ABIs return even floating point values in CPU
17246 registers. Larger integer widths (such as @code{long long int}) also have
17247 specific placement rules. @value{GDBN} already knows the OS ABI from its
17248 current target so it needs to find out also the type being returned to make the
17249 assignment into the right register(s).
17251 Normally, the selected stack frame has debug info. @value{GDBN} will always
17252 use the debug info instead of the implicit type of @var{expression} when the
17253 debug info is available. For example, if you type @kbd{return -1}, and the
17254 function in the current stack frame is declared to return a @code{long long
17255 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17256 into a @code{long long int}:
17259 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17261 (@value{GDBP}) return -1
17262 Make func return now? (y or n) y
17263 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17264 43 printf ("result=%lld\n", func ());
17268 However, if the selected stack frame does not have a debug info, e.g., if the
17269 function was compiled without debug info, @value{GDBN} has to find out the type
17270 to return from user. Specifying a different type by mistake may set the value
17271 in different inferior registers than the caller code expects. For example,
17272 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17273 of a @code{long long int} result for a debug info less function (on 32-bit
17274 architectures). Therefore the user is required to specify the return type by
17275 an appropriate cast explicitly:
17278 Breakpoint 2, 0x0040050b in func ()
17279 (@value{GDBP}) return -1
17280 Return value type not available for selected stack frame.
17281 Please use an explicit cast of the value to return.
17282 (@value{GDBP}) return (long long int) -1
17283 Make selected stack frame return now? (y or n) y
17284 #0 0x00400526 in main ()
17289 @section Calling Program Functions
17292 @cindex calling functions
17293 @cindex inferior functions, calling
17294 @item print @var{expr}
17295 Evaluate the expression @var{expr} and display the resulting value.
17296 The expression may include calls to functions in the program being
17300 @item call @var{expr}
17301 Evaluate the expression @var{expr} without displaying @code{void}
17304 You can use this variant of the @code{print} command if you want to
17305 execute a function from your program that does not return anything
17306 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17307 with @code{void} returned values that @value{GDBN} will otherwise
17308 print. If the result is not void, it is printed and saved in the
17312 It is possible for the function you call via the @code{print} or
17313 @code{call} command to generate a signal (e.g., if there's a bug in
17314 the function, or if you passed it incorrect arguments). What happens
17315 in that case is controlled by the @code{set unwindonsignal} command.
17317 Similarly, with a C@t{++} program it is possible for the function you
17318 call via the @code{print} or @code{call} command to generate an
17319 exception that is not handled due to the constraints of the dummy
17320 frame. In this case, any exception that is raised in the frame, but has
17321 an out-of-frame exception handler will not be found. GDB builds a
17322 dummy-frame for the inferior function call, and the unwinder cannot
17323 seek for exception handlers outside of this dummy-frame. What happens
17324 in that case is controlled by the
17325 @code{set unwind-on-terminating-exception} command.
17328 @item set unwindonsignal
17329 @kindex set unwindonsignal
17330 @cindex unwind stack in called functions
17331 @cindex call dummy stack unwinding
17332 Set unwinding of the stack if a signal is received while in a function
17333 that @value{GDBN} called in the program being debugged. If set to on,
17334 @value{GDBN} unwinds the stack it created for the call and restores
17335 the context to what it was before the call. If set to off (the
17336 default), @value{GDBN} stops in the frame where the signal was
17339 @item show unwindonsignal
17340 @kindex show unwindonsignal
17341 Show the current setting of stack unwinding in the functions called by
17344 @item set unwind-on-terminating-exception
17345 @kindex set unwind-on-terminating-exception
17346 @cindex unwind stack in called functions with unhandled exceptions
17347 @cindex call dummy stack unwinding on unhandled exception.
17348 Set unwinding of the stack if a C@t{++} exception is raised, but left
17349 unhandled while in a function that @value{GDBN} called in the program being
17350 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17351 it created for the call and restores the context to what it was before
17352 the call. If set to off, @value{GDBN} the exception is delivered to
17353 the default C@t{++} exception handler and the inferior terminated.
17355 @item show unwind-on-terminating-exception
17356 @kindex show unwind-on-terminating-exception
17357 Show the current setting of stack unwinding in the functions called by
17362 @cindex weak alias functions
17363 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17364 for another function. In such case, @value{GDBN} might not pick up
17365 the type information, including the types of the function arguments,
17366 which causes @value{GDBN} to call the inferior function incorrectly.
17367 As a result, the called function will function erroneously and may
17368 even crash. A solution to that is to use the name of the aliased
17372 @section Patching Programs
17374 @cindex patching binaries
17375 @cindex writing into executables
17376 @cindex writing into corefiles
17378 By default, @value{GDBN} opens the file containing your program's
17379 executable code (or the corefile) read-only. This prevents accidental
17380 alterations to machine code; but it also prevents you from intentionally
17381 patching your program's binary.
17383 If you'd like to be able to patch the binary, you can specify that
17384 explicitly with the @code{set write} command. For example, you might
17385 want to turn on internal debugging flags, or even to make emergency
17391 @itemx set write off
17392 If you specify @samp{set write on}, @value{GDBN} opens executable and
17393 core files for both reading and writing; if you specify @kbd{set write
17394 off} (the default), @value{GDBN} opens them read-only.
17396 If you have already loaded a file, you must load it again (using the
17397 @code{exec-file} or @code{core-file} command) after changing @code{set
17398 write}, for your new setting to take effect.
17402 Display whether executable files and core files are opened for writing
17403 as well as reading.
17406 @node Compiling and Injecting Code
17407 @section Compiling and injecting code in @value{GDBN}
17408 @cindex injecting code
17409 @cindex writing into executables
17410 @cindex compiling code
17412 @value{GDBN} supports on-demand compilation and code injection into
17413 programs running under @value{GDBN}. GCC 5.0 or higher built with
17414 @file{libcc1.so} must be installed for this functionality to be enabled.
17415 This functionality is implemented with the following commands.
17418 @kindex compile code
17419 @item compile code @var{source-code}
17420 @itemx compile code -raw @var{--} @var{source-code}
17421 Compile @var{source-code} with the compiler language found as the current
17422 language in @value{GDBN} (@pxref{Languages}). If compilation and
17423 injection is not supported with the current language specified in
17424 @value{GDBN}, or the compiler does not support this feature, an error
17425 message will be printed. If @var{source-code} compiles and links
17426 successfully, @value{GDBN} will load the object-code emitted,
17427 and execute it within the context of the currently selected inferior.
17428 It is important to note that the compiled code is executed immediately.
17429 After execution, the compiled code is removed from @value{GDBN} and any
17430 new types or variables you have defined will be deleted.
17432 The command allows you to specify @var{source-code} in two ways.
17433 The simplest method is to provide a single line of code to the command.
17437 compile code printf ("hello world\n");
17440 If you specify options on the command line as well as source code, they
17441 may conflict. The @samp{--} delimiter can be used to separate options
17442 from actual source code. E.g.:
17445 compile code -r -- printf ("hello world\n");
17448 Alternatively you can enter source code as multiple lines of text. To
17449 enter this mode, invoke the @samp{compile code} command without any text
17450 following the command. This will start the multiple-line editor and
17451 allow you to type as many lines of source code as required. When you
17452 have completed typing, enter @samp{end} on its own line to exit the
17457 >printf ("hello\n");
17458 >printf ("world\n");
17462 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17463 provided @var{source-code} in a callable scope. In this case, you must
17464 specify the entry point of the code by defining a function named
17465 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17466 inferior. Using @samp{-raw} option may be needed for example when
17467 @var{source-code} requires @samp{#include} lines which may conflict with
17468 inferior symbols otherwise.
17470 @kindex compile file
17471 @item compile file @var{filename}
17472 @itemx compile file -raw @var{filename}
17473 Like @code{compile code}, but take the source code from @var{filename}.
17476 compile file /home/user/example.c
17481 @item compile print @var{expr}
17482 @itemx compile print /@var{f} @var{expr}
17483 Compile and execute @var{expr} with the compiler language found as the
17484 current language in @value{GDBN} (@pxref{Languages}). By default the
17485 value of @var{expr} is printed in a format appropriate to its data type;
17486 you can choose a different format by specifying @samp{/@var{f}}, where
17487 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17490 @item compile print
17491 @itemx compile print /@var{f}
17492 @cindex reprint the last value
17493 Alternatively you can enter the expression (source code producing it) as
17494 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17495 command without any text following the command. This will start the
17496 multiple-line editor.
17500 The process of compiling and injecting the code can be inspected using:
17503 @anchor{set debug compile}
17504 @item set debug compile
17505 @cindex compile command debugging info
17506 Turns on or off display of @value{GDBN} process of compiling and
17507 injecting the code. The default is off.
17509 @item show debug compile
17510 Displays the current state of displaying @value{GDBN} process of
17511 compiling and injecting the code.
17514 @subsection Compilation options for the @code{compile} command
17516 @value{GDBN} needs to specify the right compilation options for the code
17517 to be injected, in part to make its ABI compatible with the inferior
17518 and in part to make the injected code compatible with @value{GDBN}'s
17522 The options used, in increasing precedence:
17525 @item target architecture and OS options (@code{gdbarch})
17526 These options depend on target processor type and target operating
17527 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17528 (@code{-m64}) compilation option.
17530 @item compilation options recorded in the target
17531 @value{NGCC} (since version 4.7) stores the options used for compilation
17532 into @code{DW_AT_producer} part of DWARF debugging information according
17533 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17534 explicitly specify @code{-g} during inferior compilation otherwise
17535 @value{NGCC} produces no DWARF. This feature is only relevant for
17536 platforms where @code{-g} produces DWARF by default, otherwise one may
17537 try to enforce DWARF by using @code{-gdwarf-4}.
17539 @item compilation options set by @code{set compile-args}
17543 You can override compilation options using the following command:
17546 @item set compile-args
17547 @cindex compile command options override
17548 Set compilation options used for compiling and injecting code with the
17549 @code{compile} commands. These options override any conflicting ones
17550 from the target architecture and/or options stored during inferior
17553 @item show compile-args
17554 Displays the current state of compilation options override.
17555 This does not show all the options actually used during compilation,
17556 use @ref{set debug compile} for that.
17559 @subsection Caveats when using the @code{compile} command
17561 There are a few caveats to keep in mind when using the @code{compile}
17562 command. As the caveats are different per language, the table below
17563 highlights specific issues on a per language basis.
17566 @item C code examples and caveats
17567 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17568 attempt to compile the source code with a @samp{C} compiler. The source
17569 code provided to the @code{compile} command will have much the same
17570 access to variables and types as it normally would if it were part of
17571 the program currently being debugged in @value{GDBN}.
17573 Below is a sample program that forms the basis of the examples that
17574 follow. This program has been compiled and loaded into @value{GDBN},
17575 much like any other normal debugging session.
17578 void function1 (void)
17581 printf ("function 1\n");
17584 void function2 (void)
17599 For the purposes of the examples in this section, the program above has
17600 been compiled, loaded into @value{GDBN}, stopped at the function
17601 @code{main}, and @value{GDBN} is awaiting input from the user.
17603 To access variables and types for any program in @value{GDBN}, the
17604 program must be compiled and packaged with debug information. The
17605 @code{compile} command is not an exception to this rule. Without debug
17606 information, you can still use the @code{compile} command, but you will
17607 be very limited in what variables and types you can access.
17609 So with that in mind, the example above has been compiled with debug
17610 information enabled. The @code{compile} command will have access to
17611 all variables and types (except those that may have been optimized
17612 out). Currently, as @value{GDBN} has stopped the program in the
17613 @code{main} function, the @code{compile} command would have access to
17614 the variable @code{k}. You could invoke the @code{compile} command
17615 and type some source code to set the value of @code{k}. You can also
17616 read it, or do anything with that variable you would normally do in
17617 @code{C}. Be aware that changes to inferior variables in the
17618 @code{compile} command are persistent. In the following example:
17621 compile code k = 3;
17625 the variable @code{k} is now 3. It will retain that value until
17626 something else in the example program changes it, or another
17627 @code{compile} command changes it.
17629 Normal scope and access rules apply to source code compiled and
17630 injected by the @code{compile} command. In the example, the variables
17631 @code{j} and @code{k} are not accessible yet, because the program is
17632 currently stopped in the @code{main} function, where these variables
17633 are not in scope. Therefore, the following command
17636 compile code j = 3;
17640 will result in a compilation error message.
17642 Once the program is continued, execution will bring these variables in
17643 scope, and they will become accessible; then the code you specify via
17644 the @code{compile} command will be able to access them.
17646 You can create variables and types with the @code{compile} command as
17647 part of your source code. Variables and types that are created as part
17648 of the @code{compile} command are not visible to the rest of the program for
17649 the duration of its run. This example is valid:
17652 compile code int ff = 5; printf ("ff is %d\n", ff);
17655 However, if you were to type the following into @value{GDBN} after that
17656 command has completed:
17659 compile code printf ("ff is %d\n'', ff);
17663 a compiler error would be raised as the variable @code{ff} no longer
17664 exists. Object code generated and injected by the @code{compile}
17665 command is removed when its execution ends. Caution is advised
17666 when assigning to program variables values of variables created by the
17667 code submitted to the @code{compile} command. This example is valid:
17670 compile code int ff = 5; k = ff;
17673 The value of the variable @code{ff} is assigned to @code{k}. The variable
17674 @code{k} does not require the existence of @code{ff} to maintain the value
17675 it has been assigned. However, pointers require particular care in
17676 assignment. If the source code compiled with the @code{compile} command
17677 changed the address of a pointer in the example program, perhaps to a
17678 variable created in the @code{compile} command, that pointer would point
17679 to an invalid location when the command exits. The following example
17680 would likely cause issues with your debugged program:
17683 compile code int ff = 5; p = &ff;
17686 In this example, @code{p} would point to @code{ff} when the
17687 @code{compile} command is executing the source code provided to it.
17688 However, as variables in the (example) program persist with their
17689 assigned values, the variable @code{p} would point to an invalid
17690 location when the command exists. A general rule should be followed
17691 in that you should either assign @code{NULL} to any assigned pointers,
17692 or restore a valid location to the pointer before the command exits.
17694 Similar caution must be exercised with any structs, unions, and typedefs
17695 defined in @code{compile} command. Types defined in the @code{compile}
17696 command will no longer be available in the next @code{compile} command.
17697 Therefore, if you cast a variable to a type defined in the
17698 @code{compile} command, care must be taken to ensure that any future
17699 need to resolve the type can be achieved.
17702 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17703 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17704 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17705 Compilation failed.
17706 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17710 Variables that have been optimized away by the compiler are not
17711 accessible to the code submitted to the @code{compile} command.
17712 Access to those variables will generate a compiler error which @value{GDBN}
17713 will print to the console.
17716 @subsection Compiler search for the @code{compile} command
17718 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17719 may not be obvious for remote targets of different architecture than where
17720 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17721 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17722 command @code{set environment}). @xref{Environment}. @code{PATH} on
17723 @value{GDBN} host is searched for @value{NGCC} binary matching the
17724 target architecture and operating system.
17726 Specifically @code{PATH} is searched for binaries matching regular expression
17727 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17728 debugged. @var{arch} is processor name --- multiarch is supported, so for
17729 example both @code{i386} and @code{x86_64} targets look for pattern
17730 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17731 for pattern @code{s390x?}. @var{os} is currently supported only for
17732 pattern @code{linux(-gnu)?}.
17735 @chapter @value{GDBN} Files
17737 @value{GDBN} needs to know the file name of the program to be debugged,
17738 both in order to read its symbol table and in order to start your
17739 program. To debug a core dump of a previous run, you must also tell
17740 @value{GDBN} the name of the core dump file.
17743 * Files:: Commands to specify files
17744 * File Caching:: Information about @value{GDBN}'s file caching
17745 * Separate Debug Files:: Debugging information in separate files
17746 * MiniDebugInfo:: Debugging information in a special section
17747 * Index Files:: Index files speed up GDB
17748 * Symbol Errors:: Errors reading symbol files
17749 * Data Files:: GDB data files
17753 @section Commands to Specify Files
17755 @cindex symbol table
17756 @cindex core dump file
17758 You may want to specify executable and core dump file names. The usual
17759 way to do this is at start-up time, using the arguments to
17760 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17761 Out of @value{GDBN}}).
17763 Occasionally it is necessary to change to a different file during a
17764 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17765 specify a file you want to use. Or you are debugging a remote target
17766 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17767 Program}). In these situations the @value{GDBN} commands to specify
17768 new files are useful.
17771 @cindex executable file
17773 @item file @var{filename}
17774 Use @var{filename} as the program to be debugged. It is read for its
17775 symbols and for the contents of pure memory. It is also the program
17776 executed when you use the @code{run} command. If you do not specify a
17777 directory and the file is not found in the @value{GDBN} working directory,
17778 @value{GDBN} uses the environment variable @code{PATH} as a list of
17779 directories to search, just as the shell does when looking for a program
17780 to run. You can change the value of this variable, for both @value{GDBN}
17781 and your program, using the @code{path} command.
17783 @cindex unlinked object files
17784 @cindex patching object files
17785 You can load unlinked object @file{.o} files into @value{GDBN} using
17786 the @code{file} command. You will not be able to ``run'' an object
17787 file, but you can disassemble functions and inspect variables. Also,
17788 if the underlying BFD functionality supports it, you could use
17789 @kbd{gdb -write} to patch object files using this technique. Note
17790 that @value{GDBN} can neither interpret nor modify relocations in this
17791 case, so branches and some initialized variables will appear to go to
17792 the wrong place. But this feature is still handy from time to time.
17795 @code{file} with no argument makes @value{GDBN} discard any information it
17796 has on both executable file and the symbol table.
17799 @item exec-file @r{[} @var{filename} @r{]}
17800 Specify that the program to be run (but not the symbol table) is found
17801 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17802 if necessary to locate your program. Omitting @var{filename} means to
17803 discard information on the executable file.
17805 @kindex symbol-file
17806 @item symbol-file @r{[} @var{filename} @r{]}
17807 Read symbol table information from file @var{filename}. @code{PATH} is
17808 searched when necessary. Use the @code{file} command to get both symbol
17809 table and program to run from the same file.
17811 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17812 program's symbol table.
17814 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17815 some breakpoints and auto-display expressions. This is because they may
17816 contain pointers to the internal data recording symbols and data types,
17817 which are part of the old symbol table data being discarded inside
17820 @code{symbol-file} does not repeat if you press @key{RET} again after
17823 When @value{GDBN} is configured for a particular environment, it
17824 understands debugging information in whatever format is the standard
17825 generated for that environment; you may use either a @sc{gnu} compiler, or
17826 other compilers that adhere to the local conventions.
17827 Best results are usually obtained from @sc{gnu} compilers; for example,
17828 using @code{@value{NGCC}} you can generate debugging information for
17831 For most kinds of object files, with the exception of old SVR3 systems
17832 using COFF, the @code{symbol-file} command does not normally read the
17833 symbol table in full right away. Instead, it scans the symbol table
17834 quickly to find which source files and which symbols are present. The
17835 details are read later, one source file at a time, as they are needed.
17837 The purpose of this two-stage reading strategy is to make @value{GDBN}
17838 start up faster. For the most part, it is invisible except for
17839 occasional pauses while the symbol table details for a particular source
17840 file are being read. (The @code{set verbose} command can turn these
17841 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17842 Warnings and Messages}.)
17844 We have not implemented the two-stage strategy for COFF yet. When the
17845 symbol table is stored in COFF format, @code{symbol-file} reads the
17846 symbol table data in full right away. Note that ``stabs-in-COFF''
17847 still does the two-stage strategy, since the debug info is actually
17851 @cindex reading symbols immediately
17852 @cindex symbols, reading immediately
17853 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17854 @itemx file @r{[} -readnow @r{]} @var{filename}
17855 You can override the @value{GDBN} two-stage strategy for reading symbol
17856 tables by using the @samp{-readnow} option with any of the commands that
17857 load symbol table information, if you want to be sure @value{GDBN} has the
17858 entire symbol table available.
17860 @c FIXME: for now no mention of directories, since this seems to be in
17861 @c flux. 13mar1992 status is that in theory GDB would look either in
17862 @c current dir or in same dir as myprog; but issues like competing
17863 @c GDB's, or clutter in system dirs, mean that in practice right now
17864 @c only current dir is used. FFish says maybe a special GDB hierarchy
17865 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17869 @item core-file @r{[}@var{filename}@r{]}
17871 Specify the whereabouts of a core dump file to be used as the ``contents
17872 of memory''. Traditionally, core files contain only some parts of the
17873 address space of the process that generated them; @value{GDBN} can access the
17874 executable file itself for other parts.
17876 @code{core-file} with no argument specifies that no core file is
17879 Note that the core file is ignored when your program is actually running
17880 under @value{GDBN}. So, if you have been running your program and you
17881 wish to debug a core file instead, you must kill the subprocess in which
17882 the program is running. To do this, use the @code{kill} command
17883 (@pxref{Kill Process, ,Killing the Child Process}).
17885 @kindex add-symbol-file
17886 @cindex dynamic linking
17887 @item add-symbol-file @var{filename} @var{address}
17888 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17889 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17890 The @code{add-symbol-file} command reads additional symbol table
17891 information from the file @var{filename}. You would use this command
17892 when @var{filename} has been dynamically loaded (by some other means)
17893 into the program that is running. The @var{address} should give the memory
17894 address at which the file has been loaded; @value{GDBN} cannot figure
17895 this out for itself. You can additionally specify an arbitrary number
17896 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17897 section name and base address for that section. You can specify any
17898 @var{address} as an expression.
17900 The symbol table of the file @var{filename} is added to the symbol table
17901 originally read with the @code{symbol-file} command. You can use the
17902 @code{add-symbol-file} command any number of times; the new symbol data
17903 thus read is kept in addition to the old.
17905 Changes can be reverted using the command @code{remove-symbol-file}.
17907 @cindex relocatable object files, reading symbols from
17908 @cindex object files, relocatable, reading symbols from
17909 @cindex reading symbols from relocatable object files
17910 @cindex symbols, reading from relocatable object files
17911 @cindex @file{.o} files, reading symbols from
17912 Although @var{filename} is typically a shared library file, an
17913 executable file, or some other object file which has been fully
17914 relocated for loading into a process, you can also load symbolic
17915 information from relocatable @file{.o} files, as long as:
17919 the file's symbolic information refers only to linker symbols defined in
17920 that file, not to symbols defined by other object files,
17922 every section the file's symbolic information refers to has actually
17923 been loaded into the inferior, as it appears in the file, and
17925 you can determine the address at which every section was loaded, and
17926 provide these to the @code{add-symbol-file} command.
17930 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17931 relocatable files into an already running program; such systems
17932 typically make the requirements above easy to meet. However, it's
17933 important to recognize that many native systems use complex link
17934 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17935 assembly, for example) that make the requirements difficult to meet. In
17936 general, one cannot assume that using @code{add-symbol-file} to read a
17937 relocatable object file's symbolic information will have the same effect
17938 as linking the relocatable object file into the program in the normal
17941 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17943 @kindex remove-symbol-file
17944 @item remove-symbol-file @var{filename}
17945 @item remove-symbol-file -a @var{address}
17946 Remove a symbol file added via the @code{add-symbol-file} command. The
17947 file to remove can be identified by its @var{filename} or by an @var{address}
17948 that lies within the boundaries of this symbol file in memory. Example:
17951 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17952 add symbol table from file "/home/user/gdb/mylib.so" at
17953 .text_addr = 0x7ffff7ff9480
17955 Reading symbols from /home/user/gdb/mylib.so...done.
17956 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17957 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17962 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17964 @kindex add-symbol-file-from-memory
17965 @cindex @code{syscall DSO}
17966 @cindex load symbols from memory
17967 @item add-symbol-file-from-memory @var{address}
17968 Load symbols from the given @var{address} in a dynamically loaded
17969 object file whose image is mapped directly into the inferior's memory.
17970 For example, the Linux kernel maps a @code{syscall DSO} into each
17971 process's address space; this DSO provides kernel-specific code for
17972 some system calls. The argument can be any expression whose
17973 evaluation yields the address of the file's shared object file header.
17974 For this command to work, you must have used @code{symbol-file} or
17975 @code{exec-file} commands in advance.
17978 @item section @var{section} @var{addr}
17979 The @code{section} command changes the base address of the named
17980 @var{section} of the exec file to @var{addr}. This can be used if the
17981 exec file does not contain section addresses, (such as in the
17982 @code{a.out} format), or when the addresses specified in the file
17983 itself are wrong. Each section must be changed separately. The
17984 @code{info files} command, described below, lists all the sections and
17988 @kindex info target
17991 @code{info files} and @code{info target} are synonymous; both print the
17992 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17993 including the names of the executable and core dump files currently in
17994 use by @value{GDBN}, and the files from which symbols were loaded. The
17995 command @code{help target} lists all possible targets rather than
17998 @kindex maint info sections
17999 @item maint info sections
18000 Another command that can give you extra information about program sections
18001 is @code{maint info sections}. In addition to the section information
18002 displayed by @code{info files}, this command displays the flags and file
18003 offset of each section in the executable and core dump files. In addition,
18004 @code{maint info sections} provides the following command options (which
18005 may be arbitrarily combined):
18009 Display sections for all loaded object files, including shared libraries.
18010 @item @var{sections}
18011 Display info only for named @var{sections}.
18012 @item @var{section-flags}
18013 Display info only for sections for which @var{section-flags} are true.
18014 The section flags that @value{GDBN} currently knows about are:
18017 Section will have space allocated in the process when loaded.
18018 Set for all sections except those containing debug information.
18020 Section will be loaded from the file into the child process memory.
18021 Set for pre-initialized code and data, clear for @code{.bss} sections.
18023 Section needs to be relocated before loading.
18025 Section cannot be modified by the child process.
18027 Section contains executable code only.
18029 Section contains data only (no executable code).
18031 Section will reside in ROM.
18033 Section contains data for constructor/destructor lists.
18035 Section is not empty.
18037 An instruction to the linker to not output the section.
18038 @item COFF_SHARED_LIBRARY
18039 A notification to the linker that the section contains
18040 COFF shared library information.
18042 Section contains common symbols.
18045 @kindex set trust-readonly-sections
18046 @cindex read-only sections
18047 @item set trust-readonly-sections on
18048 Tell @value{GDBN} that readonly sections in your object file
18049 really are read-only (i.e.@: that their contents will not change).
18050 In that case, @value{GDBN} can fetch values from these sections
18051 out of the object file, rather than from the target program.
18052 For some targets (notably embedded ones), this can be a significant
18053 enhancement to debugging performance.
18055 The default is off.
18057 @item set trust-readonly-sections off
18058 Tell @value{GDBN} not to trust readonly sections. This means that
18059 the contents of the section might change while the program is running,
18060 and must therefore be fetched from the target when needed.
18062 @item show trust-readonly-sections
18063 Show the current setting of trusting readonly sections.
18066 All file-specifying commands allow both absolute and relative file names
18067 as arguments. @value{GDBN} always converts the file name to an absolute file
18068 name and remembers it that way.
18070 @cindex shared libraries
18071 @anchor{Shared Libraries}
18072 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
18073 and IBM RS/6000 AIX shared libraries.
18075 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18076 shared libraries. @xref{Expat}.
18078 @value{GDBN} automatically loads symbol definitions from shared libraries
18079 when you use the @code{run} command, or when you examine a core file.
18080 (Before you issue the @code{run} command, @value{GDBN} does not understand
18081 references to a function in a shared library, however---unless you are
18082 debugging a core file).
18084 On HP-UX, if the program loads a library explicitly, @value{GDBN}
18085 automatically loads the symbols at the time of the @code{shl_load} call.
18087 @c FIXME: some @value{GDBN} release may permit some refs to undef
18088 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18089 @c FIXME...lib; check this from time to time when updating manual
18091 There are times, however, when you may wish to not automatically load
18092 symbol definitions from shared libraries, such as when they are
18093 particularly large or there are many of them.
18095 To control the automatic loading of shared library symbols, use the
18099 @kindex set auto-solib-add
18100 @item set auto-solib-add @var{mode}
18101 If @var{mode} is @code{on}, symbols from all shared object libraries
18102 will be loaded automatically when the inferior begins execution, you
18103 attach to an independently started inferior, or when the dynamic linker
18104 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18105 is @code{off}, symbols must be loaded manually, using the
18106 @code{sharedlibrary} command. The default value is @code{on}.
18108 @cindex memory used for symbol tables
18109 If your program uses lots of shared libraries with debug info that
18110 takes large amounts of memory, you can decrease the @value{GDBN}
18111 memory footprint by preventing it from automatically loading the
18112 symbols from shared libraries. To that end, type @kbd{set
18113 auto-solib-add off} before running the inferior, then load each
18114 library whose debug symbols you do need with @kbd{sharedlibrary
18115 @var{regexp}}, where @var{regexp} is a regular expression that matches
18116 the libraries whose symbols you want to be loaded.
18118 @kindex show auto-solib-add
18119 @item show auto-solib-add
18120 Display the current autoloading mode.
18123 @cindex load shared library
18124 To explicitly load shared library symbols, use the @code{sharedlibrary}
18128 @kindex info sharedlibrary
18130 @item info share @var{regex}
18131 @itemx info sharedlibrary @var{regex}
18132 Print the names of the shared libraries which are currently loaded
18133 that match @var{regex}. If @var{regex} is omitted then print
18134 all shared libraries that are loaded.
18137 @item info dll @var{regex}
18138 This is an alias of @code{info sharedlibrary}.
18140 @kindex sharedlibrary
18142 @item sharedlibrary @var{regex}
18143 @itemx share @var{regex}
18144 Load shared object library symbols for files matching a
18145 Unix regular expression.
18146 As with files loaded automatically, it only loads shared libraries
18147 required by your program for a core file or after typing @code{run}. If
18148 @var{regex} is omitted all shared libraries required by your program are
18151 @item nosharedlibrary
18152 @kindex nosharedlibrary
18153 @cindex unload symbols from shared libraries
18154 Unload all shared object library symbols. This discards all symbols
18155 that have been loaded from all shared libraries. Symbols from shared
18156 libraries that were loaded by explicit user requests are not
18160 Sometimes you may wish that @value{GDBN} stops and gives you control
18161 when any of shared library events happen. The best way to do this is
18162 to use @code{catch load} and @code{catch unload} (@pxref{Set
18165 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18166 command for this. This command exists for historical reasons. It is
18167 less useful than setting a catchpoint, because it does not allow for
18168 conditions or commands as a catchpoint does.
18171 @item set stop-on-solib-events
18172 @kindex set stop-on-solib-events
18173 This command controls whether @value{GDBN} should give you control
18174 when the dynamic linker notifies it about some shared library event.
18175 The most common event of interest is loading or unloading of a new
18178 @item show stop-on-solib-events
18179 @kindex show stop-on-solib-events
18180 Show whether @value{GDBN} stops and gives you control when shared
18181 library events happen.
18184 Shared libraries are also supported in many cross or remote debugging
18185 configurations. @value{GDBN} needs to have access to the target's libraries;
18186 this can be accomplished either by providing copies of the libraries
18187 on the host system, or by asking @value{GDBN} to automatically retrieve the
18188 libraries from the target. If copies of the target libraries are
18189 provided, they need to be the same as the target libraries, although the
18190 copies on the target can be stripped as long as the copies on the host are
18193 @cindex where to look for shared libraries
18194 For remote debugging, you need to tell @value{GDBN} where the target
18195 libraries are, so that it can load the correct copies---otherwise, it
18196 may try to load the host's libraries. @value{GDBN} has two variables
18197 to specify the search directories for target libraries.
18200 @cindex prefix for executable and shared library file names
18201 @cindex system root, alternate
18202 @kindex set solib-absolute-prefix
18203 @kindex set sysroot
18204 @item set sysroot @var{path}
18205 Use @var{path} as the system root for the program being debugged. Any
18206 absolute shared library paths will be prefixed with @var{path}; many
18207 runtime loaders store the absolute paths to the shared library in the
18208 target program's memory. When starting processes remotely, and when
18209 attaching to already-running processes (local or remote), their
18210 executable filenames will be prefixed with @var{path} if reported to
18211 @value{GDBN} as absolute by the operating system. If you use
18212 @code{set sysroot} to find executables and shared libraries, they need
18213 to be laid out in the same way that they are on the target, with
18214 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18217 If @var{path} starts with the sequence @file{target:} and the target
18218 system is remote then @value{GDBN} will retrieve the target binaries
18219 from the remote system. This is only supported when using a remote
18220 target that supports the @code{remote get} command (@pxref{File
18221 Transfer,,Sending files to a remote system}). The part of @var{path}
18222 following the initial @file{target:} (if present) is used as system
18223 root prefix on the remote file system. If @var{path} starts with the
18224 sequence @file{remote:} this is converted to the sequence
18225 @file{target:} by @code{set sysroot}@footnote{Historically the
18226 functionality to retrieve binaries from the remote system was
18227 provided by prefixing @var{path} with @file{remote:}}. If you want
18228 to specify a local system root using a directory that happens to be
18229 named @file{target:} or @file{remote:}, you need to use some
18230 equivalent variant of the name like @file{./target:}.
18232 For targets with an MS-DOS based filesystem, such as MS-Windows and
18233 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18234 absolute file name with @var{path}. But first, on Unix hosts,
18235 @value{GDBN} converts all backslash directory separators into forward
18236 slashes, because the backslash is not a directory separator on Unix:
18239 c:\foo\bar.dll @result{} c:/foo/bar.dll
18242 Then, @value{GDBN} attempts prefixing the target file name with
18243 @var{path}, and looks for the resulting file name in the host file
18247 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18250 If that does not find the binary, @value{GDBN} tries removing
18251 the @samp{:} character from the drive spec, both for convenience, and,
18252 for the case of the host file system not supporting file names with
18256 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18259 This makes it possible to have a system root that mirrors a target
18260 with more than one drive. E.g., you may want to setup your local
18261 copies of the target system shared libraries like so (note @samp{c} vs
18265 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18266 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18267 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18271 and point the system root at @file{/path/to/sysroot}, so that
18272 @value{GDBN} can find the correct copies of both
18273 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18275 If that still does not find the binary, @value{GDBN} tries
18276 removing the whole drive spec from the target file name:
18279 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18282 This last lookup makes it possible to not care about the drive name,
18283 if you don't want or need to.
18285 The @code{set solib-absolute-prefix} command is an alias for @code{set
18288 @cindex default system root
18289 @cindex @samp{--with-sysroot}
18290 You can set the default system root by using the configure-time
18291 @samp{--with-sysroot} option. If the system root is inside
18292 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18293 @samp{--exec-prefix}), then the default system root will be updated
18294 automatically if the installed @value{GDBN} is moved to a new
18297 @kindex show sysroot
18299 Display the current executable and shared library prefix.
18301 @kindex set solib-search-path
18302 @item set solib-search-path @var{path}
18303 If this variable is set, @var{path} is a colon-separated list of
18304 directories to search for shared libraries. @samp{solib-search-path}
18305 is used after @samp{sysroot} fails to locate the library, or if the
18306 path to the library is relative instead of absolute. If you want to
18307 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18308 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18309 finding your host's libraries. @samp{sysroot} is preferred; setting
18310 it to a nonexistent directory may interfere with automatic loading
18311 of shared library symbols.
18313 @kindex show solib-search-path
18314 @item show solib-search-path
18315 Display the current shared library search path.
18317 @cindex DOS file-name semantics of file names.
18318 @kindex set target-file-system-kind (unix|dos-based|auto)
18319 @kindex show target-file-system-kind
18320 @item set target-file-system-kind @var{kind}
18321 Set assumed file system kind for target reported file names.
18323 Shared library file names as reported by the target system may not
18324 make sense as is on the system @value{GDBN} is running on. For
18325 example, when remote debugging a target that has MS-DOS based file
18326 system semantics, from a Unix host, the target may be reporting to
18327 @value{GDBN} a list of loaded shared libraries with file names such as
18328 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18329 drive letters, so the @samp{c:\} prefix is not normally understood as
18330 indicating an absolute file name, and neither is the backslash
18331 normally considered a directory separator character. In that case,
18332 the native file system would interpret this whole absolute file name
18333 as a relative file name with no directory components. This would make
18334 it impossible to point @value{GDBN} at a copy of the remote target's
18335 shared libraries on the host using @code{set sysroot}, and impractical
18336 with @code{set solib-search-path}. Setting
18337 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18338 to interpret such file names similarly to how the target would, and to
18339 map them to file names valid on @value{GDBN}'s native file system
18340 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18341 to one of the supported file system kinds. In that case, @value{GDBN}
18342 tries to determine the appropriate file system variant based on the
18343 current target's operating system (@pxref{ABI, ,Configuring the
18344 Current ABI}). The supported file system settings are:
18348 Instruct @value{GDBN} to assume the target file system is of Unix
18349 kind. Only file names starting the forward slash (@samp{/}) character
18350 are considered absolute, and the directory separator character is also
18354 Instruct @value{GDBN} to assume the target file system is DOS based.
18355 File names starting with either a forward slash, or a drive letter
18356 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18357 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18358 considered directory separators.
18361 Instruct @value{GDBN} to use the file system kind associated with the
18362 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18363 This is the default.
18367 @cindex file name canonicalization
18368 @cindex base name differences
18369 When processing file names provided by the user, @value{GDBN}
18370 frequently needs to compare them to the file names recorded in the
18371 program's debug info. Normally, @value{GDBN} compares just the
18372 @dfn{base names} of the files as strings, which is reasonably fast
18373 even for very large programs. (The base name of a file is the last
18374 portion of its name, after stripping all the leading directories.)
18375 This shortcut in comparison is based upon the assumption that files
18376 cannot have more than one base name. This is usually true, but
18377 references to files that use symlinks or similar filesystem
18378 facilities violate that assumption. If your program records files
18379 using such facilities, or if you provide file names to @value{GDBN}
18380 using symlinks etc., you can set @code{basenames-may-differ} to
18381 @code{true} to instruct @value{GDBN} to completely canonicalize each
18382 pair of file names it needs to compare. This will make file-name
18383 comparisons accurate, but at a price of a significant slowdown.
18386 @item set basenames-may-differ
18387 @kindex set basenames-may-differ
18388 Set whether a source file may have multiple base names.
18390 @item show basenames-may-differ
18391 @kindex show basenames-may-differ
18392 Show whether a source file may have multiple base names.
18396 @section File Caching
18397 @cindex caching of opened files
18398 @cindex caching of bfd objects
18400 To speed up file loading, and reduce memory usage, @value{GDBN} will
18401 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18402 BFD, bfd, The Binary File Descriptor Library}. The following commands
18403 allow visibility and control of the caching behavior.
18406 @kindex maint info bfds
18407 @item maint info bfds
18408 This prints information about each @code{bfd} object that is known to
18411 @kindex maint set bfd-sharing
18412 @kindex maint show bfd-sharing
18413 @kindex bfd caching
18414 @item maint set bfd-sharing
18415 @item maint show bfd-sharing
18416 Control whether @code{bfd} objects can be shared. When sharing is
18417 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18418 than reopening the same file. Turning sharing off does not cause
18419 already shared @code{bfd} objects to be unshared, but all future files
18420 that are opened will create a new @code{bfd} object. Similarly,
18421 re-enabling sharing does not cause multiple existing @code{bfd}
18422 objects to be collapsed into a single shared @code{bfd} object.
18424 @kindex set debug bfd-cache @var{level}
18425 @kindex bfd caching
18426 @item set debug bfd-cache @var{level}
18427 Turns on debugging of the bfd cache, setting the level to @var{level}.
18429 @kindex show debug bfd-cache
18430 @kindex bfd caching
18431 @item show debug bfd-cache
18432 Show the current debugging level of the bfd cache.
18435 @node Separate Debug Files
18436 @section Debugging Information in Separate Files
18437 @cindex separate debugging information files
18438 @cindex debugging information in separate files
18439 @cindex @file{.debug} subdirectories
18440 @cindex debugging information directory, global
18441 @cindex global debugging information directories
18442 @cindex build ID, and separate debugging files
18443 @cindex @file{.build-id} directory
18445 @value{GDBN} allows you to put a program's debugging information in a
18446 file separate from the executable itself, in a way that allows
18447 @value{GDBN} to find and load the debugging information automatically.
18448 Since debugging information can be very large---sometimes larger
18449 than the executable code itself---some systems distribute debugging
18450 information for their executables in separate files, which users can
18451 install only when they need to debug a problem.
18453 @value{GDBN} supports two ways of specifying the separate debug info
18458 The executable contains a @dfn{debug link} that specifies the name of
18459 the separate debug info file. The separate debug file's name is
18460 usually @file{@var{executable}.debug}, where @var{executable} is the
18461 name of the corresponding executable file without leading directories
18462 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18463 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18464 checksum for the debug file, which @value{GDBN} uses to validate that
18465 the executable and the debug file came from the same build.
18468 The executable contains a @dfn{build ID}, a unique bit string that is
18469 also present in the corresponding debug info file. (This is supported
18470 only on some operating systems, when using the ELF or PE file formats
18471 for binary files and the @sc{gnu} Binutils.) For more details about
18472 this feature, see the description of the @option{--build-id}
18473 command-line option in @ref{Options, , Command Line Options, ld.info,
18474 The GNU Linker}. The debug info file's name is not specified
18475 explicitly by the build ID, but can be computed from the build ID, see
18479 Depending on the way the debug info file is specified, @value{GDBN}
18480 uses two different methods of looking for the debug file:
18484 For the ``debug link'' method, @value{GDBN} looks up the named file in
18485 the directory of the executable file, then in a subdirectory of that
18486 directory named @file{.debug}, and finally under each one of the global debug
18487 directories, in a subdirectory whose name is identical to the leading
18488 directories of the executable's absolute file name.
18491 For the ``build ID'' method, @value{GDBN} looks in the
18492 @file{.build-id} subdirectory of each one of the global debug directories for
18493 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18494 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18495 are the rest of the bit string. (Real build ID strings are 32 or more
18496 hex characters, not 10.)
18499 So, for example, suppose you ask @value{GDBN} to debug
18500 @file{/usr/bin/ls}, which has a debug link that specifies the
18501 file @file{ls.debug}, and a build ID whose value in hex is
18502 @code{abcdef1234}. If the list of the global debug directories includes
18503 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18504 debug information files, in the indicated order:
18508 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18510 @file{/usr/bin/ls.debug}
18512 @file{/usr/bin/.debug/ls.debug}
18514 @file{/usr/lib/debug/usr/bin/ls.debug}.
18517 @anchor{debug-file-directory}
18518 Global debugging info directories default to what is set by @value{GDBN}
18519 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18520 you can also set the global debugging info directories, and view the list
18521 @value{GDBN} is currently using.
18525 @kindex set debug-file-directory
18526 @item set debug-file-directory @var{directories}
18527 Set the directories which @value{GDBN} searches for separate debugging
18528 information files to @var{directory}. Multiple path components can be set
18529 concatenating them by a path separator.
18531 @kindex show debug-file-directory
18532 @item show debug-file-directory
18533 Show the directories @value{GDBN} searches for separate debugging
18538 @cindex @code{.gnu_debuglink} sections
18539 @cindex debug link sections
18540 A debug link is a special section of the executable file named
18541 @code{.gnu_debuglink}. The section must contain:
18545 A filename, with any leading directory components removed, followed by
18548 zero to three bytes of padding, as needed to reach the next four-byte
18549 boundary within the section, and
18551 a four-byte CRC checksum, stored in the same endianness used for the
18552 executable file itself. The checksum is computed on the debugging
18553 information file's full contents by the function given below, passing
18554 zero as the @var{crc} argument.
18557 Any executable file format can carry a debug link, as long as it can
18558 contain a section named @code{.gnu_debuglink} with the contents
18561 @cindex @code{.note.gnu.build-id} sections
18562 @cindex build ID sections
18563 The build ID is a special section in the executable file (and in other
18564 ELF binary files that @value{GDBN} may consider). This section is
18565 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18566 It contains unique identification for the built files---the ID remains
18567 the same across multiple builds of the same build tree. The default
18568 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18569 content for the build ID string. The same section with an identical
18570 value is present in the original built binary with symbols, in its
18571 stripped variant, and in the separate debugging information file.
18573 The debugging information file itself should be an ordinary
18574 executable, containing a full set of linker symbols, sections, and
18575 debugging information. The sections of the debugging information file
18576 should have the same names, addresses, and sizes as the original file,
18577 but they need not contain any data---much like a @code{.bss} section
18578 in an ordinary executable.
18580 The @sc{gnu} binary utilities (Binutils) package includes the
18581 @samp{objcopy} utility that can produce
18582 the separated executable / debugging information file pairs using the
18583 following commands:
18586 @kbd{objcopy --only-keep-debug foo foo.debug}
18591 These commands remove the debugging
18592 information from the executable file @file{foo} and place it in the file
18593 @file{foo.debug}. You can use the first, second or both methods to link the
18598 The debug link method needs the following additional command to also leave
18599 behind a debug link in @file{foo}:
18602 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18605 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18606 a version of the @code{strip} command such that the command @kbd{strip foo -f
18607 foo.debug} has the same functionality as the two @code{objcopy} commands and
18608 the @code{ln -s} command above, together.
18611 Build ID gets embedded into the main executable using @code{ld --build-id} or
18612 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18613 compatibility fixes for debug files separation are present in @sc{gnu} binary
18614 utilities (Binutils) package since version 2.18.
18619 @cindex CRC algorithm definition
18620 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18621 IEEE 802.3 using the polynomial:
18623 @c TexInfo requires naked braces for multi-digit exponents for Tex
18624 @c output, but this causes HTML output to barf. HTML has to be set using
18625 @c raw commands. So we end up having to specify this equation in 2
18630 <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>
18631 + <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
18637 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18638 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18642 The function is computed byte at a time, taking the least
18643 significant bit of each byte first. The initial pattern
18644 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18645 the final result is inverted to ensure trailing zeros also affect the
18648 @emph{Note:} This is the same CRC polynomial as used in handling the
18649 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18650 However in the case of the Remote Serial Protocol, the CRC is computed
18651 @emph{most} significant bit first, and the result is not inverted, so
18652 trailing zeros have no effect on the CRC value.
18654 To complete the description, we show below the code of the function
18655 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18656 initially supplied @code{crc} argument means that an initial call to
18657 this function passing in zero will start computing the CRC using
18660 @kindex gnu_debuglink_crc32
18663 gnu_debuglink_crc32 (unsigned long crc,
18664 unsigned char *buf, size_t len)
18666 static const unsigned long crc32_table[256] =
18668 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18669 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18670 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18671 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18672 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18673 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18674 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18675 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18676 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18677 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18678 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18679 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18680 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18681 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18682 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18683 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18684 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18685 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18686 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18687 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18688 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18689 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18690 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18691 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18692 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18693 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18694 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18695 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18696 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18697 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18698 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18699 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18700 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18701 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18702 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18703 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18704 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18705 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18706 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18707 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18708 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18709 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18710 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18711 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18712 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18713 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18714 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18715 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18716 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18717 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18718 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18721 unsigned char *end;
18723 crc = ~crc & 0xffffffff;
18724 for (end = buf + len; buf < end; ++buf)
18725 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18726 return ~crc & 0xffffffff;
18731 This computation does not apply to the ``build ID'' method.
18733 @node MiniDebugInfo
18734 @section Debugging information in a special section
18735 @cindex separate debug sections
18736 @cindex @samp{.gnu_debugdata} section
18738 Some systems ship pre-built executables and libraries that have a
18739 special @samp{.gnu_debugdata} section. This feature is called
18740 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18741 is used to supply extra symbols for backtraces.
18743 The intent of this section is to provide extra minimal debugging
18744 information for use in simple backtraces. It is not intended to be a
18745 replacement for full separate debugging information (@pxref{Separate
18746 Debug Files}). The example below shows the intended use; however,
18747 @value{GDBN} does not currently put restrictions on what sort of
18748 debugging information might be included in the section.
18750 @value{GDBN} has support for this extension. If the section exists,
18751 then it is used provided that no other source of debugging information
18752 can be found, and that @value{GDBN} was configured with LZMA support.
18754 This section can be easily created using @command{objcopy} and other
18755 standard utilities:
18758 # Extract the dynamic symbols from the main binary, there is no need
18759 # to also have these in the normal symbol table.
18760 nm -D @var{binary} --format=posix --defined-only \
18761 | awk '@{ print $1 @}' | sort > dynsyms
18763 # Extract all the text (i.e. function) symbols from the debuginfo.
18764 # (Note that we actually also accept "D" symbols, for the benefit
18765 # of platforms like PowerPC64 that use function descriptors.)
18766 nm @var{binary} --format=posix --defined-only \
18767 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18770 # Keep all the function symbols not already in the dynamic symbol
18772 comm -13 dynsyms funcsyms > keep_symbols
18774 # Separate full debug info into debug binary.
18775 objcopy --only-keep-debug @var{binary} debug
18777 # Copy the full debuginfo, keeping only a minimal set of symbols and
18778 # removing some unnecessary sections.
18779 objcopy -S --remove-section .gdb_index --remove-section .comment \
18780 --keep-symbols=keep_symbols debug mini_debuginfo
18782 # Drop the full debug info from the original binary.
18783 strip --strip-all -R .comment @var{binary}
18785 # Inject the compressed data into the .gnu_debugdata section of the
18788 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18792 @section Index Files Speed Up @value{GDBN}
18793 @cindex index files
18794 @cindex @samp{.gdb_index} section
18796 When @value{GDBN} finds a symbol file, it scans the symbols in the
18797 file in order to construct an internal symbol table. This lets most
18798 @value{GDBN} operations work quickly---at the cost of a delay early
18799 on. For large programs, this delay can be quite lengthy, so
18800 @value{GDBN} provides a way to build an index, which speeds up
18803 The index is stored as a section in the symbol file. @value{GDBN} can
18804 write the index to a file, then you can put it into the symbol file
18805 using @command{objcopy}.
18807 To create an index file, use the @code{save gdb-index} command:
18810 @item save gdb-index @var{directory}
18811 @kindex save gdb-index
18812 Create an index file for each symbol file currently known by
18813 @value{GDBN}. Each file is named after its corresponding symbol file,
18814 with @samp{.gdb-index} appended, and is written into the given
18818 Once you have created an index file you can merge it into your symbol
18819 file, here named @file{symfile}, using @command{objcopy}:
18822 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18823 --set-section-flags .gdb_index=readonly symfile symfile
18826 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18827 sections that have been deprecated. Usually they are deprecated because
18828 they are missing a new feature or have performance issues.
18829 To tell @value{GDBN} to use a deprecated index section anyway
18830 specify @code{set use-deprecated-index-sections on}.
18831 The default is @code{off}.
18832 This can speed up startup, but may result in some functionality being lost.
18833 @xref{Index Section Format}.
18835 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18836 must be done before gdb reads the file. The following will not work:
18839 $ gdb -ex "set use-deprecated-index-sections on" <program>
18842 Instead you must do, for example,
18845 $ gdb -iex "set use-deprecated-index-sections on" <program>
18848 There are currently some limitation on indices. They only work when
18849 for DWARF debugging information, not stabs. And, they do not
18850 currently work for programs using Ada.
18852 @node Symbol Errors
18853 @section Errors Reading Symbol Files
18855 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18856 such as symbol types it does not recognize, or known bugs in compiler
18857 output. By default, @value{GDBN} does not notify you of such problems, since
18858 they are relatively common and primarily of interest to people
18859 debugging compilers. If you are interested in seeing information
18860 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18861 only one message about each such type of problem, no matter how many
18862 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18863 to see how many times the problems occur, with the @code{set
18864 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18867 The messages currently printed, and their meanings, include:
18870 @item inner block not inside outer block in @var{symbol}
18872 The symbol information shows where symbol scopes begin and end
18873 (such as at the start of a function or a block of statements). This
18874 error indicates that an inner scope block is not fully contained
18875 in its outer scope blocks.
18877 @value{GDBN} circumvents the problem by treating the inner block as if it had
18878 the same scope as the outer block. In the error message, @var{symbol}
18879 may be shown as ``@code{(don't know)}'' if the outer block is not a
18882 @item block at @var{address} out of order
18884 The symbol information for symbol scope blocks should occur in
18885 order of increasing addresses. This error indicates that it does not
18888 @value{GDBN} does not circumvent this problem, and has trouble
18889 locating symbols in the source file whose symbols it is reading. (You
18890 can often determine what source file is affected by specifying
18891 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18894 @item bad block start address patched
18896 The symbol information for a symbol scope block has a start address
18897 smaller than the address of the preceding source line. This is known
18898 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18900 @value{GDBN} circumvents the problem by treating the symbol scope block as
18901 starting on the previous source line.
18903 @item bad string table offset in symbol @var{n}
18906 Symbol number @var{n} contains a pointer into the string table which is
18907 larger than the size of the string table.
18909 @value{GDBN} circumvents the problem by considering the symbol to have the
18910 name @code{foo}, which may cause other problems if many symbols end up
18913 @item unknown symbol type @code{0x@var{nn}}
18915 The symbol information contains new data types that @value{GDBN} does
18916 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18917 uncomprehended information, in hexadecimal.
18919 @value{GDBN} circumvents the error by ignoring this symbol information.
18920 This usually allows you to debug your program, though certain symbols
18921 are not accessible. If you encounter such a problem and feel like
18922 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18923 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18924 and examine @code{*bufp} to see the symbol.
18926 @item stub type has NULL name
18928 @value{GDBN} could not find the full definition for a struct or class.
18930 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18931 The symbol information for a C@t{++} member function is missing some
18932 information that recent versions of the compiler should have output for
18935 @item info mismatch between compiler and debugger
18937 @value{GDBN} could not parse a type specification output by the compiler.
18942 @section GDB Data Files
18944 @cindex prefix for data files
18945 @value{GDBN} will sometimes read an auxiliary data file. These files
18946 are kept in a directory known as the @dfn{data directory}.
18948 You can set the data directory's name, and view the name @value{GDBN}
18949 is currently using.
18952 @kindex set data-directory
18953 @item set data-directory @var{directory}
18954 Set the directory which @value{GDBN} searches for auxiliary data files
18955 to @var{directory}.
18957 @kindex show data-directory
18958 @item show data-directory
18959 Show the directory @value{GDBN} searches for auxiliary data files.
18962 @cindex default data directory
18963 @cindex @samp{--with-gdb-datadir}
18964 You can set the default data directory by using the configure-time
18965 @samp{--with-gdb-datadir} option. If the data directory is inside
18966 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18967 @samp{--exec-prefix}), then the default data directory will be updated
18968 automatically if the installed @value{GDBN} is moved to a new
18971 The data directory may also be specified with the
18972 @code{--data-directory} command line option.
18973 @xref{Mode Options}.
18976 @chapter Specifying a Debugging Target
18978 @cindex debugging target
18979 A @dfn{target} is the execution environment occupied by your program.
18981 Often, @value{GDBN} runs in the same host environment as your program;
18982 in that case, the debugging target is specified as a side effect when
18983 you use the @code{file} or @code{core} commands. When you need more
18984 flexibility---for example, running @value{GDBN} on a physically separate
18985 host, or controlling a standalone system over a serial port or a
18986 realtime system over a TCP/IP connection---you can use the @code{target}
18987 command to specify one of the target types configured for @value{GDBN}
18988 (@pxref{Target Commands, ,Commands for Managing Targets}).
18990 @cindex target architecture
18991 It is possible to build @value{GDBN} for several different @dfn{target
18992 architectures}. When @value{GDBN} is built like that, you can choose
18993 one of the available architectures with the @kbd{set architecture}
18997 @kindex set architecture
18998 @kindex show architecture
18999 @item set architecture @var{arch}
19000 This command sets the current target architecture to @var{arch}. The
19001 value of @var{arch} can be @code{"auto"}, in addition to one of the
19002 supported architectures.
19004 @item show architecture
19005 Show the current target architecture.
19007 @item set processor
19009 @kindex set processor
19010 @kindex show processor
19011 These are alias commands for, respectively, @code{set architecture}
19012 and @code{show architecture}.
19016 * Active Targets:: Active targets
19017 * Target Commands:: Commands for managing targets
19018 * Byte Order:: Choosing target byte order
19021 @node Active Targets
19022 @section Active Targets
19024 @cindex stacking targets
19025 @cindex active targets
19026 @cindex multiple targets
19028 There are multiple classes of targets such as: processes, executable files or
19029 recording sessions. Core files belong to the process class, making core file
19030 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19031 on multiple active targets, one in each class. This allows you to (for
19032 example) start a process and inspect its activity, while still having access to
19033 the executable file after the process finishes. Or if you start process
19034 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19035 presented a virtual layer of the recording target, while the process target
19036 remains stopped at the chronologically last point of the process execution.
19038 Use the @code{core-file} and @code{exec-file} commands to select a new core
19039 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19040 specify as a target a process that is already running, use the @code{attach}
19041 command (@pxref{Attach, ,Debugging an Already-running Process}).
19043 @node Target Commands
19044 @section Commands for Managing Targets
19047 @item target @var{type} @var{parameters}
19048 Connects the @value{GDBN} host environment to a target machine or
19049 process. A target is typically a protocol for talking to debugging
19050 facilities. You use the argument @var{type} to specify the type or
19051 protocol of the target machine.
19053 Further @var{parameters} are interpreted by the target protocol, but
19054 typically include things like device names or host names to connect
19055 with, process numbers, and baud rates.
19057 The @code{target} command does not repeat if you press @key{RET} again
19058 after executing the command.
19060 @kindex help target
19062 Displays the names of all targets available. To display targets
19063 currently selected, use either @code{info target} or @code{info files}
19064 (@pxref{Files, ,Commands to Specify Files}).
19066 @item help target @var{name}
19067 Describe a particular target, including any parameters necessary to
19070 @kindex set gnutarget
19071 @item set gnutarget @var{args}
19072 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19073 knows whether it is reading an @dfn{executable},
19074 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19075 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19076 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19079 @emph{Warning:} To specify a file format with @code{set gnutarget},
19080 you must know the actual BFD name.
19084 @xref{Files, , Commands to Specify Files}.
19086 @kindex show gnutarget
19087 @item show gnutarget
19088 Use the @code{show gnutarget} command to display what file format
19089 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19090 @value{GDBN} will determine the file format for each file automatically,
19091 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19094 @cindex common targets
19095 Here are some common targets (available, or not, depending on the GDB
19100 @item target exec @var{program}
19101 @cindex executable file target
19102 An executable file. @samp{target exec @var{program}} is the same as
19103 @samp{exec-file @var{program}}.
19105 @item target core @var{filename}
19106 @cindex core dump file target
19107 A core dump file. @samp{target core @var{filename}} is the same as
19108 @samp{core-file @var{filename}}.
19110 @item target remote @var{medium}
19111 @cindex remote target
19112 A remote system connected to @value{GDBN} via a serial line or network
19113 connection. This command tells @value{GDBN} to use its own remote
19114 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19116 For example, if you have a board connected to @file{/dev/ttya} on the
19117 machine running @value{GDBN}, you could say:
19120 target remote /dev/ttya
19123 @code{target remote} supports the @code{load} command. This is only
19124 useful if you have some other way of getting the stub to the target
19125 system, and you can put it somewhere in memory where it won't get
19126 clobbered by the download.
19128 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19129 @cindex built-in simulator target
19130 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19138 works; however, you cannot assume that a specific memory map, device
19139 drivers, or even basic I/O is available, although some simulators do
19140 provide these. For info about any processor-specific simulator details,
19141 see the appropriate section in @ref{Embedded Processors, ,Embedded
19144 @item target native
19145 @cindex native target
19146 Setup for local/native process debugging. Useful to make the
19147 @code{run} command spawn native processes (likewise @code{attach},
19148 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19149 (@pxref{set auto-connect-native-target}).
19153 Different targets are available on different configurations of @value{GDBN};
19154 your configuration may have more or fewer targets.
19156 Many remote targets require you to download the executable's code once
19157 you've successfully established a connection. You may wish to control
19158 various aspects of this process.
19163 @kindex set hash@r{, for remote monitors}
19164 @cindex hash mark while downloading
19165 This command controls whether a hash mark @samp{#} is displayed while
19166 downloading a file to the remote monitor. If on, a hash mark is
19167 displayed after each S-record is successfully downloaded to the
19171 @kindex show hash@r{, for remote monitors}
19172 Show the current status of displaying the hash mark.
19174 @item set debug monitor
19175 @kindex set debug monitor
19176 @cindex display remote monitor communications
19177 Enable or disable display of communications messages between
19178 @value{GDBN} and the remote monitor.
19180 @item show debug monitor
19181 @kindex show debug monitor
19182 Show the current status of displaying communications between
19183 @value{GDBN} and the remote monitor.
19188 @kindex load @var{filename}
19189 @item load @var{filename}
19191 Depending on what remote debugging facilities are configured into
19192 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19193 is meant to make @var{filename} (an executable) available for debugging
19194 on the remote system---by downloading, or dynamic linking, for example.
19195 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19196 the @code{add-symbol-file} command.
19198 If your @value{GDBN} does not have a @code{load} command, attempting to
19199 execute it gets the error message ``@code{You can't do that when your
19200 target is @dots{}}''
19202 The file is loaded at whatever address is specified in the executable.
19203 For some object file formats, you can specify the load address when you
19204 link the program; for other formats, like a.out, the object file format
19205 specifies a fixed address.
19206 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19208 Depending on the remote side capabilities, @value{GDBN} may be able to
19209 load programs into flash memory.
19211 @code{load} does not repeat if you press @key{RET} again after using it.
19215 @section Choosing Target Byte Order
19217 @cindex choosing target byte order
19218 @cindex target byte order
19220 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19221 offer the ability to run either big-endian or little-endian byte
19222 orders. Usually the executable or symbol will include a bit to
19223 designate the endian-ness, and you will not need to worry about
19224 which to use. However, you may still find it useful to adjust
19225 @value{GDBN}'s idea of processor endian-ness manually.
19229 @item set endian big
19230 Instruct @value{GDBN} to assume the target is big-endian.
19232 @item set endian little
19233 Instruct @value{GDBN} to assume the target is little-endian.
19235 @item set endian auto
19236 Instruct @value{GDBN} to use the byte order associated with the
19240 Display @value{GDBN}'s current idea of the target byte order.
19244 Note that these commands merely adjust interpretation of symbolic
19245 data on the host, and that they have absolutely no effect on the
19249 @node Remote Debugging
19250 @chapter Debugging Remote Programs
19251 @cindex remote debugging
19253 If you are trying to debug a program running on a machine that cannot run
19254 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19255 For example, you might use remote debugging on an operating system kernel,
19256 or on a small system which does not have a general purpose operating system
19257 powerful enough to run a full-featured debugger.
19259 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19260 to make this work with particular debugging targets. In addition,
19261 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19262 but not specific to any particular target system) which you can use if you
19263 write the remote stubs---the code that runs on the remote system to
19264 communicate with @value{GDBN}.
19266 Other remote targets may be available in your
19267 configuration of @value{GDBN}; use @code{help target} to list them.
19270 * Connecting:: Connecting to a remote target
19271 * File Transfer:: Sending files to a remote system
19272 * Server:: Using the gdbserver program
19273 * Remote Configuration:: Remote configuration
19274 * Remote Stub:: Implementing a remote stub
19278 @section Connecting to a Remote Target
19280 @value{GDBN} needs an unstripped copy of your program to access symbol
19281 and debugging information. Some remote targets (@pxref{qXfer
19282 executable filename read}, and @pxref{Host I/O Packets}) allow
19283 @value{GDBN} to access program files over the same connection used to
19284 communicate with @value{GDBN}. With such a target, if the remote
19285 program is unstripped, the only command you need is @code{target
19286 remote}. Otherwise, start up @value{GDBN} using the name of the local
19287 unstripped copy of your program as the first argument, or use the
19288 @code{file} command.
19290 @cindex @code{target remote}
19291 @value{GDBN} can communicate with the target over a serial line, or
19292 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19293 each case, @value{GDBN} uses the same protocol for debugging your
19294 program; only the medium carrying the debugging packets varies. The
19295 @code{target remote} command establishes a connection to the target.
19296 Its arguments indicate which medium to use:
19300 @item target remote @var{serial-device}
19301 @cindex serial line, @code{target remote}
19302 Use @var{serial-device} to communicate with the target. For example,
19303 to use a serial line connected to the device named @file{/dev/ttyb}:
19306 target remote /dev/ttyb
19309 If you're using a serial line, you may want to give @value{GDBN} the
19310 @samp{--baud} option, or use the @code{set serial baud} command
19311 (@pxref{Remote Configuration, set serial baud}) before the
19312 @code{target} command.
19314 @item target remote @code{@var{host}:@var{port}}
19315 @itemx target remote @code{tcp:@var{host}:@var{port}}
19316 @cindex @acronym{TCP} port, @code{target remote}
19317 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19318 The @var{host} may be either a host name or a numeric @acronym{IP}
19319 address; @var{port} must be a decimal number. The @var{host} could be
19320 the target machine itself, if it is directly connected to the net, or
19321 it might be a terminal server which in turn has a serial line to the
19324 For example, to connect to port 2828 on a terminal server named
19328 target remote manyfarms:2828
19331 If your remote target is actually running on the same machine as your
19332 debugger session (e.g.@: a simulator for your target running on the
19333 same host), you can omit the hostname. For example, to connect to
19334 port 1234 on your local machine:
19337 target remote :1234
19341 Note that the colon is still required here.
19343 @item target remote @code{udp:@var{host}:@var{port}}
19344 @cindex @acronym{UDP} port, @code{target remote}
19345 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19346 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19349 target remote udp:manyfarms:2828
19352 When using a @acronym{UDP} connection for remote debugging, you should
19353 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19354 can silently drop packets on busy or unreliable networks, which will
19355 cause havoc with your debugging session.
19357 @item target remote | @var{command}
19358 @cindex pipe, @code{target remote} to
19359 Run @var{command} in the background and communicate with it using a
19360 pipe. The @var{command} is a shell command, to be parsed and expanded
19361 by the system's command shell, @code{/bin/sh}; it should expect remote
19362 protocol packets on its standard input, and send replies on its
19363 standard output. You could use this to run a stand-alone simulator
19364 that speaks the remote debugging protocol, to make net connections
19365 using programs like @code{ssh}, or for other similar tricks.
19367 If @var{command} closes its standard output (perhaps by exiting),
19368 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19369 program has already exited, this will have no effect.)
19373 Once the connection has been established, you can use all the usual
19374 commands to examine and change data. The remote program is already
19375 running; you can use @kbd{step} and @kbd{continue}, and you do not
19376 need to use @kbd{run}.
19378 @cindex interrupting remote programs
19379 @cindex remote programs, interrupting
19380 Whenever @value{GDBN} is waiting for the remote program, if you type the
19381 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19382 program. This may or may not succeed, depending in part on the hardware
19383 and the serial drivers the remote system uses. If you type the
19384 interrupt character once again, @value{GDBN} displays this prompt:
19387 Interrupted while waiting for the program.
19388 Give up (and stop debugging it)? (y or n)
19391 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19392 (If you decide you want to try again later, you can use @samp{target
19393 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19394 goes back to waiting.
19397 @kindex detach (remote)
19399 When you have finished debugging the remote program, you can use the
19400 @code{detach} command to release it from @value{GDBN} control.
19401 Detaching from the target normally resumes its execution, but the results
19402 will depend on your particular remote stub. After the @code{detach}
19403 command, @value{GDBN} is free to connect to another target.
19407 The @code{disconnect} command behaves like @code{detach}, except that
19408 the target is generally not resumed. It will wait for @value{GDBN}
19409 (this instance or another one) to connect and continue debugging. After
19410 the @code{disconnect} command, @value{GDBN} is again free to connect to
19413 @cindex send command to remote monitor
19414 @cindex extend @value{GDBN} for remote targets
19415 @cindex add new commands for external monitor
19417 @item monitor @var{cmd}
19418 This command allows you to send arbitrary commands directly to the
19419 remote monitor. Since @value{GDBN} doesn't care about the commands it
19420 sends like this, this command is the way to extend @value{GDBN}---you
19421 can add new commands that only the external monitor will understand
19425 @node File Transfer
19426 @section Sending files to a remote system
19427 @cindex remote target, file transfer
19428 @cindex file transfer
19429 @cindex sending files to remote systems
19431 Some remote targets offer the ability to transfer files over the same
19432 connection used to communicate with @value{GDBN}. This is convenient
19433 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19434 running @code{gdbserver} over a network interface. For other targets,
19435 e.g.@: embedded devices with only a single serial port, this may be
19436 the only way to upload or download files.
19438 Not all remote targets support these commands.
19442 @item remote put @var{hostfile} @var{targetfile}
19443 Copy file @var{hostfile} from the host system (the machine running
19444 @value{GDBN}) to @var{targetfile} on the target system.
19447 @item remote get @var{targetfile} @var{hostfile}
19448 Copy file @var{targetfile} from the target system to @var{hostfile}
19449 on the host system.
19451 @kindex remote delete
19452 @item remote delete @var{targetfile}
19453 Delete @var{targetfile} from the target system.
19458 @section Using the @code{gdbserver} Program
19461 @cindex remote connection without stubs
19462 @code{gdbserver} is a control program for Unix-like systems, which
19463 allows you to connect your program with a remote @value{GDBN} via
19464 @code{target remote}---but without linking in the usual debugging stub.
19466 @code{gdbserver} is not a complete replacement for the debugging stubs,
19467 because it requires essentially the same operating-system facilities
19468 that @value{GDBN} itself does. In fact, a system that can run
19469 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19470 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19471 because it is a much smaller program than @value{GDBN} itself. It is
19472 also easier to port than all of @value{GDBN}, so you may be able to get
19473 started more quickly on a new system by using @code{gdbserver}.
19474 Finally, if you develop code for real-time systems, you may find that
19475 the tradeoffs involved in real-time operation make it more convenient to
19476 do as much development work as possible on another system, for example
19477 by cross-compiling. You can use @code{gdbserver} to make a similar
19478 choice for debugging.
19480 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19481 or a TCP connection, using the standard @value{GDBN} remote serial
19485 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19486 Do not run @code{gdbserver} connected to any public network; a
19487 @value{GDBN} connection to @code{gdbserver} provides access to the
19488 target system with the same privileges as the user running
19492 @subsection Running @code{gdbserver}
19493 @cindex arguments, to @code{gdbserver}
19494 @cindex @code{gdbserver}, command-line arguments
19496 Run @code{gdbserver} on the target system. You need a copy of the
19497 program you want to debug, including any libraries it requires.
19498 @code{gdbserver} does not need your program's symbol table, so you can
19499 strip the program if necessary to save space. @value{GDBN} on the host
19500 system does all the symbol handling.
19502 To use the server, you must tell it how to communicate with @value{GDBN};
19503 the name of your program; and the arguments for your program. The usual
19507 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19510 @var{comm} is either a device name (to use a serial line), or a TCP
19511 hostname and portnumber, or @code{-} or @code{stdio} to use
19512 stdin/stdout of @code{gdbserver}.
19513 For example, to debug Emacs with the argument
19514 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19518 target> gdbserver /dev/com1 emacs foo.txt
19521 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19524 To use a TCP connection instead of a serial line:
19527 target> gdbserver host:2345 emacs foo.txt
19530 The only difference from the previous example is the first argument,
19531 specifying that you are communicating with the host @value{GDBN} via
19532 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19533 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19534 (Currently, the @samp{host} part is ignored.) You can choose any number
19535 you want for the port number as long as it does not conflict with any
19536 TCP ports already in use on the target system (for example, @code{23} is
19537 reserved for @code{telnet}).@footnote{If you choose a port number that
19538 conflicts with another service, @code{gdbserver} prints an error message
19539 and exits.} You must use the same port number with the host @value{GDBN}
19540 @code{target remote} command.
19542 The @code{stdio} connection is useful when starting @code{gdbserver}
19546 (gdb) target remote | ssh -T hostname gdbserver - hello
19549 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19550 and we don't want escape-character handling. Ssh does this by default when
19551 a command is provided, the flag is provided to make it explicit.
19552 You could elide it if you want to.
19554 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19555 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19556 display through a pipe connected to gdbserver.
19557 Both @code{stdout} and @code{stderr} use the same pipe.
19559 @subsubsection Attaching to a Running Program
19560 @cindex attach to a program, @code{gdbserver}
19561 @cindex @option{--attach}, @code{gdbserver} option
19563 On some targets, @code{gdbserver} can also attach to running programs.
19564 This is accomplished via the @code{--attach} argument. The syntax is:
19567 target> gdbserver --attach @var{comm} @var{pid}
19570 @var{pid} is the process ID of a currently running process. It isn't necessary
19571 to point @code{gdbserver} at a binary for the running process.
19574 You can debug processes by name instead of process ID if your target has the
19575 @code{pidof} utility:
19578 target> gdbserver --attach @var{comm} `pidof @var{program}`
19581 In case more than one copy of @var{program} is running, or @var{program}
19582 has multiple threads, most versions of @code{pidof} support the
19583 @code{-s} option to only return the first process ID.
19585 @subsubsection Multi-Process Mode for @code{gdbserver}
19586 @cindex @code{gdbserver}, multiple processes
19587 @cindex multiple processes with @code{gdbserver}
19589 When you connect to @code{gdbserver} using @code{target remote},
19590 @code{gdbserver} debugs the specified program only once. When the
19591 program exits, or you detach from it, @value{GDBN} closes the connection
19592 and @code{gdbserver} exits.
19594 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19595 enters multi-process mode. When the debugged program exits, or you
19596 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19597 though no program is running. The @code{run} and @code{attach}
19598 commands instruct @code{gdbserver} to run or attach to a new program.
19599 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19600 remote exec-file}) to select the program to run. Command line
19601 arguments are supported, except for wildcard expansion and I/O
19602 redirection (@pxref{Arguments}).
19604 @cindex @option{--multi}, @code{gdbserver} option
19605 To start @code{gdbserver} without supplying an initial command to run
19606 or process ID to attach, use the @option{--multi} command line option.
19607 Then you can connect using @kbd{target extended-remote} and start
19608 the program you want to debug.
19610 In multi-process mode @code{gdbserver} does not automatically exit unless you
19611 use the option @option{--once}. You can terminate it by using
19612 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19613 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19614 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19615 @option{--multi} option to @code{gdbserver} has no influence on that.
19617 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19619 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19621 @code{gdbserver} normally terminates after all of its debugged processes have
19622 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19623 extended-remote}, @code{gdbserver} stays running even with no processes left.
19624 @value{GDBN} normally terminates the spawned debugged process on its exit,
19625 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19626 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19627 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19628 stays running even in the @kbd{target remote} mode.
19630 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19631 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19632 completeness, at most one @value{GDBN} can be connected at a time.
19634 @cindex @option{--once}, @code{gdbserver} option
19635 By default, @code{gdbserver} keeps the listening TCP port open, so that
19636 subsequent connections are possible. However, if you start @code{gdbserver}
19637 with the @option{--once} option, it will stop listening for any further
19638 connection attempts after connecting to the first @value{GDBN} session. This
19639 means no further connections to @code{gdbserver} will be possible after the
19640 first one. It also means @code{gdbserver} will terminate after the first
19641 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19642 connections and even in the @kbd{target extended-remote} mode. The
19643 @option{--once} option allows reusing the same port number for connecting to
19644 multiple instances of @code{gdbserver} running on the same host, since each
19645 instance closes its port after the first connection.
19647 @anchor{Other Command-Line Arguments for gdbserver}
19648 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19650 @cindex @option{--debug}, @code{gdbserver} option
19651 The @option{--debug} option tells @code{gdbserver} to display extra
19652 status information about the debugging process.
19653 @cindex @option{--remote-debug}, @code{gdbserver} option
19654 The @option{--remote-debug} option tells @code{gdbserver} to display
19655 remote protocol debug output. These options are intended for
19656 @code{gdbserver} development and for bug reports to the developers.
19658 @cindex @option{--debug-format}, @code{gdbserver} option
19659 The @option{--debug-format=option1[,option2,...]} option tells
19660 @code{gdbserver} to include additional information in each output.
19661 Possible options are:
19665 Turn off all extra information in debugging output.
19667 Turn on all extra information in debugging output.
19669 Include a timestamp in each line of debugging output.
19672 Options are processed in order. Thus, for example, if @option{none}
19673 appears last then no additional information is added to debugging output.
19675 @cindex @option{--wrapper}, @code{gdbserver} option
19676 The @option{--wrapper} option specifies a wrapper to launch programs
19677 for debugging. The option should be followed by the name of the
19678 wrapper, then any command-line arguments to pass to the wrapper, then
19679 @kbd{--} indicating the end of the wrapper arguments.
19681 @code{gdbserver} runs the specified wrapper program with a combined
19682 command line including the wrapper arguments, then the name of the
19683 program to debug, then any arguments to the program. The wrapper
19684 runs until it executes your program, and then @value{GDBN} gains control.
19686 You can use any program that eventually calls @code{execve} with
19687 its arguments as a wrapper. Several standard Unix utilities do
19688 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19689 with @code{exec "$@@"} will also work.
19691 For example, you can use @code{env} to pass an environment variable to
19692 the debugged program, without setting the variable in @code{gdbserver}'s
19696 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19699 @subsection Connecting to @code{gdbserver}
19701 Run @value{GDBN} on the host system.
19703 First make sure you have the necessary symbol files. Load symbols for
19704 your application using the @code{file} command before you connect. Use
19705 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19706 was compiled with the correct sysroot using @code{--with-sysroot}).
19708 The symbol file and target libraries must exactly match the executable
19709 and libraries on the target, with one exception: the files on the host
19710 system should not be stripped, even if the files on the target system
19711 are. Mismatched or missing files will lead to confusing results
19712 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19713 files may also prevent @code{gdbserver} from debugging multi-threaded
19716 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19717 For TCP connections, you must start up @code{gdbserver} prior to using
19718 the @code{target remote} command. Otherwise you may get an error whose
19719 text depends on the host system, but which usually looks something like
19720 @samp{Connection refused}. Don't use the @code{load}
19721 command in @value{GDBN} when using @code{gdbserver}, since the program is
19722 already on the target.
19724 @subsection Monitor Commands for @code{gdbserver}
19725 @cindex monitor commands, for @code{gdbserver}
19726 @anchor{Monitor Commands for gdbserver}
19728 During a @value{GDBN} session using @code{gdbserver}, you can use the
19729 @code{monitor} command to send special requests to @code{gdbserver}.
19730 Here are the available commands.
19734 List the available monitor commands.
19736 @item monitor set debug 0
19737 @itemx monitor set debug 1
19738 Disable or enable general debugging messages.
19740 @item monitor set remote-debug 0
19741 @itemx monitor set remote-debug 1
19742 Disable or enable specific debugging messages associated with the remote
19743 protocol (@pxref{Remote Protocol}).
19745 @item monitor set debug-format option1@r{[},option2,...@r{]}
19746 Specify additional text to add to debugging messages.
19747 Possible options are:
19751 Turn off all extra information in debugging output.
19753 Turn on all extra information in debugging output.
19755 Include a timestamp in each line of debugging output.
19758 Options are processed in order. Thus, for example, if @option{none}
19759 appears last then no additional information is added to debugging output.
19761 @item monitor set libthread-db-search-path [PATH]
19762 @cindex gdbserver, search path for @code{libthread_db}
19763 When this command is issued, @var{path} is a colon-separated list of
19764 directories to search for @code{libthread_db} (@pxref{Threads,,set
19765 libthread-db-search-path}). If you omit @var{path},
19766 @samp{libthread-db-search-path} will be reset to its default value.
19768 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19769 not supported in @code{gdbserver}.
19772 Tell gdbserver to exit immediately. This command should be followed by
19773 @code{disconnect} to close the debugging session. @code{gdbserver} will
19774 detach from any attached processes and kill any processes it created.
19775 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19776 of a multi-process mode debug session.
19780 @subsection Tracepoints support in @code{gdbserver}
19781 @cindex tracepoints support in @code{gdbserver}
19783 On some targets, @code{gdbserver} supports tracepoints, fast
19784 tracepoints and static tracepoints.
19786 For fast or static tracepoints to work, a special library called the
19787 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19788 This library is built and distributed as an integral part of
19789 @code{gdbserver}. In addition, support for static tracepoints
19790 requires building the in-process agent library with static tracepoints
19791 support. At present, the UST (LTTng Userspace Tracer,
19792 @url{http://lttng.org/ust}) tracing engine is supported. This support
19793 is automatically available if UST development headers are found in the
19794 standard include path when @code{gdbserver} is built, or if
19795 @code{gdbserver} was explicitly configured using @option{--with-ust}
19796 to point at such headers. You can explicitly disable the support
19797 using @option{--with-ust=no}.
19799 There are several ways to load the in-process agent in your program:
19802 @item Specifying it as dependency at link time
19804 You can link your program dynamically with the in-process agent
19805 library. On most systems, this is accomplished by adding
19806 @code{-linproctrace} to the link command.
19808 @item Using the system's preloading mechanisms
19810 You can force loading the in-process agent at startup time by using
19811 your system's support for preloading shared libraries. Many Unixes
19812 support the concept of preloading user defined libraries. In most
19813 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19814 in the environment. See also the description of @code{gdbserver}'s
19815 @option{--wrapper} command line option.
19817 @item Using @value{GDBN} to force loading the agent at run time
19819 On some systems, you can force the inferior to load a shared library,
19820 by calling a dynamic loader function in the inferior that takes care
19821 of dynamically looking up and loading a shared library. On most Unix
19822 systems, the function is @code{dlopen}. You'll use the @code{call}
19823 command for that. For example:
19826 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19829 Note that on most Unix systems, for the @code{dlopen} function to be
19830 available, the program needs to be linked with @code{-ldl}.
19833 On systems that have a userspace dynamic loader, like most Unix
19834 systems, when you connect to @code{gdbserver} using @code{target
19835 remote}, you'll find that the program is stopped at the dynamic
19836 loader's entry point, and no shared library has been loaded in the
19837 program's address space yet, including the in-process agent. In that
19838 case, before being able to use any of the fast or static tracepoints
19839 features, you need to let the loader run and load the shared
19840 libraries. The simplest way to do that is to run the program to the
19841 main procedure. E.g., if debugging a C or C@t{++} program, start
19842 @code{gdbserver} like so:
19845 $ gdbserver :9999 myprogram
19848 Start GDB and connect to @code{gdbserver} like so, and run to main:
19852 (@value{GDBP}) target remote myhost:9999
19853 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19854 (@value{GDBP}) b main
19855 (@value{GDBP}) continue
19858 The in-process tracing agent library should now be loaded into the
19859 process; you can confirm it with the @code{info sharedlibrary}
19860 command, which will list @file{libinproctrace.so} as loaded in the
19861 process. You are now ready to install fast tracepoints, list static
19862 tracepoint markers, probe static tracepoints markers, and start
19865 @node Remote Configuration
19866 @section Remote Configuration
19869 @kindex show remote
19870 This section documents the configuration options available when
19871 debugging remote programs. For the options related to the File I/O
19872 extensions of the remote protocol, see @ref{system,
19873 system-call-allowed}.
19876 @item set remoteaddresssize @var{bits}
19877 @cindex address size for remote targets
19878 @cindex bits in remote address
19879 Set the maximum size of address in a memory packet to the specified
19880 number of bits. @value{GDBN} will mask off the address bits above
19881 that number, when it passes addresses to the remote target. The
19882 default value is the number of bits in the target's address.
19884 @item show remoteaddresssize
19885 Show the current value of remote address size in bits.
19887 @item set serial baud @var{n}
19888 @cindex baud rate for remote targets
19889 Set the baud rate for the remote serial I/O to @var{n} baud. The
19890 value is used to set the speed of the serial port used for debugging
19893 @item show serial baud
19894 Show the current speed of the remote connection.
19896 @item set serial parity @var{parity}
19897 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19898 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19900 @item show serial parity
19901 Show the current parity of the serial port.
19903 @item set remotebreak
19904 @cindex interrupt remote programs
19905 @cindex BREAK signal instead of Ctrl-C
19906 @anchor{set remotebreak}
19907 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19908 when you type @kbd{Ctrl-c} to interrupt the program running
19909 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19910 character instead. The default is off, since most remote systems
19911 expect to see @samp{Ctrl-C} as the interrupt signal.
19913 @item show remotebreak
19914 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19915 interrupt the remote program.
19917 @item set remoteflow on
19918 @itemx set remoteflow off
19919 @kindex set remoteflow
19920 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19921 on the serial port used to communicate to the remote target.
19923 @item show remoteflow
19924 @kindex show remoteflow
19925 Show the current setting of hardware flow control.
19927 @item set remotelogbase @var{base}
19928 Set the base (a.k.a.@: radix) of logging serial protocol
19929 communications to @var{base}. Supported values of @var{base} are:
19930 @code{ascii}, @code{octal}, and @code{hex}. The default is
19933 @item show remotelogbase
19934 Show the current setting of the radix for logging remote serial
19937 @item set remotelogfile @var{file}
19938 @cindex record serial communications on file
19939 Record remote serial communications on the named @var{file}. The
19940 default is not to record at all.
19942 @item show remotelogfile.
19943 Show the current setting of the file name on which to record the
19944 serial communications.
19946 @item set remotetimeout @var{num}
19947 @cindex timeout for serial communications
19948 @cindex remote timeout
19949 Set the timeout limit to wait for the remote target to respond to
19950 @var{num} seconds. The default is 2 seconds.
19952 @item show remotetimeout
19953 Show the current number of seconds to wait for the remote target
19956 @cindex limit hardware breakpoints and watchpoints
19957 @cindex remote target, limit break- and watchpoints
19958 @anchor{set remote hardware-watchpoint-limit}
19959 @anchor{set remote hardware-breakpoint-limit}
19960 @item set remote hardware-watchpoint-limit @var{limit}
19961 @itemx set remote hardware-breakpoint-limit @var{limit}
19962 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19963 watchpoints. A limit of -1, the default, is treated as unlimited.
19965 @cindex limit hardware watchpoints length
19966 @cindex remote target, limit watchpoints length
19967 @anchor{set remote hardware-watchpoint-length-limit}
19968 @item set remote hardware-watchpoint-length-limit @var{limit}
19969 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19970 a remote hardware watchpoint. A limit of -1, the default, is treated
19973 @item show remote hardware-watchpoint-length-limit
19974 Show the current limit (in bytes) of the maximum length of
19975 a remote hardware watchpoint.
19977 @item set remote exec-file @var{filename}
19978 @itemx show remote exec-file
19979 @anchor{set remote exec-file}
19980 @cindex executable file, for remote target
19981 Select the file used for @code{run} with @code{target
19982 extended-remote}. This should be set to a filename valid on the
19983 target system. If it is not set, the target will use a default
19984 filename (e.g.@: the last program run).
19986 @item set remote interrupt-sequence
19987 @cindex interrupt remote programs
19988 @cindex select Ctrl-C, BREAK or BREAK-g
19989 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19990 @samp{BREAK-g} as the
19991 sequence to the remote target in order to interrupt the execution.
19992 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19993 is high level of serial line for some certain time.
19994 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19995 It is @code{BREAK} signal followed by character @code{g}.
19997 @item show interrupt-sequence
19998 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19999 is sent by @value{GDBN} to interrupt the remote program.
20000 @code{BREAK-g} is BREAK signal followed by @code{g} and
20001 also known as Magic SysRq g.
20003 @item set remote interrupt-on-connect
20004 @cindex send interrupt-sequence on start
20005 Specify whether interrupt-sequence is sent to remote target when
20006 @value{GDBN} connects to it. This is mostly needed when you debug
20007 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20008 which is known as Magic SysRq g in order to connect @value{GDBN}.
20010 @item show interrupt-on-connect
20011 Show whether interrupt-sequence is sent
20012 to remote target when @value{GDBN} connects to it.
20016 @item set tcp auto-retry on
20017 @cindex auto-retry, for remote TCP target
20018 Enable auto-retry for remote TCP connections. This is useful if the remote
20019 debugging agent is launched in parallel with @value{GDBN}; there is a race
20020 condition because the agent may not become ready to accept the connection
20021 before @value{GDBN} attempts to connect. When auto-retry is
20022 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20023 to establish the connection using the timeout specified by
20024 @code{set tcp connect-timeout}.
20026 @item set tcp auto-retry off
20027 Do not auto-retry failed TCP connections.
20029 @item show tcp auto-retry
20030 Show the current auto-retry setting.
20032 @item set tcp connect-timeout @var{seconds}
20033 @itemx set tcp connect-timeout unlimited
20034 @cindex connection timeout, for remote TCP target
20035 @cindex timeout, for remote target connection
20036 Set the timeout for establishing a TCP connection to the remote target to
20037 @var{seconds}. The timeout affects both polling to retry failed connections
20038 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20039 that are merely slow to complete, and represents an approximate cumulative
20040 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20041 @value{GDBN} will keep attempting to establish a connection forever,
20042 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20044 @item show tcp connect-timeout
20045 Show the current connection timeout setting.
20048 @cindex remote packets, enabling and disabling
20049 The @value{GDBN} remote protocol autodetects the packets supported by
20050 your debugging stub. If you need to override the autodetection, you
20051 can use these commands to enable or disable individual packets. Each
20052 packet can be set to @samp{on} (the remote target supports this
20053 packet), @samp{off} (the remote target does not support this packet),
20054 or @samp{auto} (detect remote target support for this packet). They
20055 all default to @samp{auto}. For more information about each packet,
20056 see @ref{Remote Protocol}.
20058 During normal use, you should not have to use any of these commands.
20059 If you do, that may be a bug in your remote debugging stub, or a bug
20060 in @value{GDBN}. You may want to report the problem to the
20061 @value{GDBN} developers.
20063 For each packet @var{name}, the command to enable or disable the
20064 packet is @code{set remote @var{name}-packet}. The available settings
20067 @multitable @columnfractions 0.28 0.32 0.25
20070 @tab Related Features
20072 @item @code{fetch-register}
20074 @tab @code{info registers}
20076 @item @code{set-register}
20080 @item @code{binary-download}
20082 @tab @code{load}, @code{set}
20084 @item @code{read-aux-vector}
20085 @tab @code{qXfer:auxv:read}
20086 @tab @code{info auxv}
20088 @item @code{symbol-lookup}
20089 @tab @code{qSymbol}
20090 @tab Detecting multiple threads
20092 @item @code{attach}
20093 @tab @code{vAttach}
20096 @item @code{verbose-resume}
20098 @tab Stepping or resuming multiple threads
20104 @item @code{software-breakpoint}
20108 @item @code{hardware-breakpoint}
20112 @item @code{write-watchpoint}
20116 @item @code{read-watchpoint}
20120 @item @code{access-watchpoint}
20124 @item @code{pid-to-exec-file}
20125 @tab @code{qXfer:exec-file:read}
20126 @tab @code{attach}, @code{run}
20128 @item @code{target-features}
20129 @tab @code{qXfer:features:read}
20130 @tab @code{set architecture}
20132 @item @code{library-info}
20133 @tab @code{qXfer:libraries:read}
20134 @tab @code{info sharedlibrary}
20136 @item @code{memory-map}
20137 @tab @code{qXfer:memory-map:read}
20138 @tab @code{info mem}
20140 @item @code{read-sdata-object}
20141 @tab @code{qXfer:sdata:read}
20142 @tab @code{print $_sdata}
20144 @item @code{read-spu-object}
20145 @tab @code{qXfer:spu:read}
20146 @tab @code{info spu}
20148 @item @code{write-spu-object}
20149 @tab @code{qXfer:spu:write}
20150 @tab @code{info spu}
20152 @item @code{read-siginfo-object}
20153 @tab @code{qXfer:siginfo:read}
20154 @tab @code{print $_siginfo}
20156 @item @code{write-siginfo-object}
20157 @tab @code{qXfer:siginfo:write}
20158 @tab @code{set $_siginfo}
20160 @item @code{threads}
20161 @tab @code{qXfer:threads:read}
20162 @tab @code{info threads}
20164 @item @code{get-thread-local-@*storage-address}
20165 @tab @code{qGetTLSAddr}
20166 @tab Displaying @code{__thread} variables
20168 @item @code{get-thread-information-block-address}
20169 @tab @code{qGetTIBAddr}
20170 @tab Display MS-Windows Thread Information Block.
20172 @item @code{search-memory}
20173 @tab @code{qSearch:memory}
20176 @item @code{supported-packets}
20177 @tab @code{qSupported}
20178 @tab Remote communications parameters
20180 @item @code{pass-signals}
20181 @tab @code{QPassSignals}
20182 @tab @code{handle @var{signal}}
20184 @item @code{program-signals}
20185 @tab @code{QProgramSignals}
20186 @tab @code{handle @var{signal}}
20188 @item @code{hostio-close-packet}
20189 @tab @code{vFile:close}
20190 @tab @code{remote get}, @code{remote put}
20192 @item @code{hostio-open-packet}
20193 @tab @code{vFile:open}
20194 @tab @code{remote get}, @code{remote put}
20196 @item @code{hostio-pread-packet}
20197 @tab @code{vFile:pread}
20198 @tab @code{remote get}, @code{remote put}
20200 @item @code{hostio-pwrite-packet}
20201 @tab @code{vFile:pwrite}
20202 @tab @code{remote get}, @code{remote put}
20204 @item @code{hostio-unlink-packet}
20205 @tab @code{vFile:unlink}
20206 @tab @code{remote delete}
20208 @item @code{hostio-readlink-packet}
20209 @tab @code{vFile:readlink}
20212 @item @code{hostio-fstat-packet}
20213 @tab @code{vFile:fstat}
20216 @item @code{hostio-setfs-packet}
20217 @tab @code{vFile:setfs}
20220 @item @code{noack-packet}
20221 @tab @code{QStartNoAckMode}
20222 @tab Packet acknowledgment
20224 @item @code{osdata}
20225 @tab @code{qXfer:osdata:read}
20226 @tab @code{info os}
20228 @item @code{query-attached}
20229 @tab @code{qAttached}
20230 @tab Querying remote process attach state.
20232 @item @code{trace-buffer-size}
20233 @tab @code{QTBuffer:size}
20234 @tab @code{set trace-buffer-size}
20236 @item @code{trace-status}
20237 @tab @code{qTStatus}
20238 @tab @code{tstatus}
20240 @item @code{traceframe-info}
20241 @tab @code{qXfer:traceframe-info:read}
20242 @tab Traceframe info
20244 @item @code{install-in-trace}
20245 @tab @code{InstallInTrace}
20246 @tab Install tracepoint in tracing
20248 @item @code{disable-randomization}
20249 @tab @code{QDisableRandomization}
20250 @tab @code{set disable-randomization}
20252 @item @code{conditional-breakpoints-packet}
20253 @tab @code{Z0 and Z1}
20254 @tab @code{Support for target-side breakpoint condition evaluation}
20256 @item @code{multiprocess-extensions}
20257 @tab @code{multiprocess extensions}
20258 @tab Debug multiple processes and remote process PID awareness
20260 @item @code{swbreak-feature}
20261 @tab @code{swbreak stop reason}
20264 @item @code{hwbreak-feature}
20265 @tab @code{hwbreak stop reason}
20268 @item @code{fork-event-feature}
20269 @tab @code{fork stop reason}
20272 @item @code{vfork-event-feature}
20273 @tab @code{vfork stop reason}
20276 @item @code{exec-event-feature}
20277 @tab @code{exec stop reason}
20280 @item @code{thread-events}
20281 @tab @code{QThreadEvents}
20282 @tab Tracking thread lifetime.
20284 @item @code{no-resumed-stop-reply}
20285 @tab @code{no resumed thread left stop reply}
20286 @tab Tracking thread lifetime.
20291 @section Implementing a Remote Stub
20293 @cindex debugging stub, example
20294 @cindex remote stub, example
20295 @cindex stub example, remote debugging
20296 The stub files provided with @value{GDBN} implement the target side of the
20297 communication protocol, and the @value{GDBN} side is implemented in the
20298 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20299 these subroutines to communicate, and ignore the details. (If you're
20300 implementing your own stub file, you can still ignore the details: start
20301 with one of the existing stub files. @file{sparc-stub.c} is the best
20302 organized, and therefore the easiest to read.)
20304 @cindex remote serial debugging, overview
20305 To debug a program running on another machine (the debugging
20306 @dfn{target} machine), you must first arrange for all the usual
20307 prerequisites for the program to run by itself. For example, for a C
20312 A startup routine to set up the C runtime environment; these usually
20313 have a name like @file{crt0}. The startup routine may be supplied by
20314 your hardware supplier, or you may have to write your own.
20317 A C subroutine library to support your program's
20318 subroutine calls, notably managing input and output.
20321 A way of getting your program to the other machine---for example, a
20322 download program. These are often supplied by the hardware
20323 manufacturer, but you may have to write your own from hardware
20327 The next step is to arrange for your program to use a serial port to
20328 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20329 machine). In general terms, the scheme looks like this:
20333 @value{GDBN} already understands how to use this protocol; when everything
20334 else is set up, you can simply use the @samp{target remote} command
20335 (@pxref{Targets,,Specifying a Debugging Target}).
20337 @item On the target,
20338 you must link with your program a few special-purpose subroutines that
20339 implement the @value{GDBN} remote serial protocol. The file containing these
20340 subroutines is called a @dfn{debugging stub}.
20342 On certain remote targets, you can use an auxiliary program
20343 @code{gdbserver} instead of linking a stub into your program.
20344 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20347 The debugging stub is specific to the architecture of the remote
20348 machine; for example, use @file{sparc-stub.c} to debug programs on
20351 @cindex remote serial stub list
20352 These working remote stubs are distributed with @value{GDBN}:
20357 @cindex @file{i386-stub.c}
20360 For Intel 386 and compatible architectures.
20363 @cindex @file{m68k-stub.c}
20364 @cindex Motorola 680x0
20366 For Motorola 680x0 architectures.
20369 @cindex @file{sh-stub.c}
20372 For Renesas SH architectures.
20375 @cindex @file{sparc-stub.c}
20377 For @sc{sparc} architectures.
20379 @item sparcl-stub.c
20380 @cindex @file{sparcl-stub.c}
20383 For Fujitsu @sc{sparclite} architectures.
20387 The @file{README} file in the @value{GDBN} distribution may list other
20388 recently added stubs.
20391 * Stub Contents:: What the stub can do for you
20392 * Bootstrapping:: What you must do for the stub
20393 * Debug Session:: Putting it all together
20396 @node Stub Contents
20397 @subsection What the Stub Can Do for You
20399 @cindex remote serial stub
20400 The debugging stub for your architecture supplies these three
20404 @item set_debug_traps
20405 @findex set_debug_traps
20406 @cindex remote serial stub, initialization
20407 This routine arranges for @code{handle_exception} to run when your
20408 program stops. You must call this subroutine explicitly in your
20409 program's startup code.
20411 @item handle_exception
20412 @findex handle_exception
20413 @cindex remote serial stub, main routine
20414 This is the central workhorse, but your program never calls it
20415 explicitly---the setup code arranges for @code{handle_exception} to
20416 run when a trap is triggered.
20418 @code{handle_exception} takes control when your program stops during
20419 execution (for example, on a breakpoint), and mediates communications
20420 with @value{GDBN} on the host machine. This is where the communications
20421 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20422 representative on the target machine. It begins by sending summary
20423 information on the state of your program, then continues to execute,
20424 retrieving and transmitting any information @value{GDBN} needs, until you
20425 execute a @value{GDBN} command that makes your program resume; at that point,
20426 @code{handle_exception} returns control to your own code on the target
20430 @cindex @code{breakpoint} subroutine, remote
20431 Use this auxiliary subroutine to make your program contain a
20432 breakpoint. Depending on the particular situation, this may be the only
20433 way for @value{GDBN} to get control. For instance, if your target
20434 machine has some sort of interrupt button, you won't need to call this;
20435 pressing the interrupt button transfers control to
20436 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20437 simply receiving characters on the serial port may also trigger a trap;
20438 again, in that situation, you don't need to call @code{breakpoint} from
20439 your own program---simply running @samp{target remote} from the host
20440 @value{GDBN} session gets control.
20442 Call @code{breakpoint} if none of these is true, or if you simply want
20443 to make certain your program stops at a predetermined point for the
20444 start of your debugging session.
20447 @node Bootstrapping
20448 @subsection What You Must Do for the Stub
20450 @cindex remote stub, support routines
20451 The debugging stubs that come with @value{GDBN} are set up for a particular
20452 chip architecture, but they have no information about the rest of your
20453 debugging target machine.
20455 First of all you need to tell the stub how to communicate with the
20459 @item int getDebugChar()
20460 @findex getDebugChar
20461 Write this subroutine to read a single character from the serial port.
20462 It may be identical to @code{getchar} for your target system; a
20463 different name is used to allow you to distinguish the two if you wish.
20465 @item void putDebugChar(int)
20466 @findex putDebugChar
20467 Write this subroutine to write a single character to the serial port.
20468 It may be identical to @code{putchar} for your target system; a
20469 different name is used to allow you to distinguish the two if you wish.
20472 @cindex control C, and remote debugging
20473 @cindex interrupting remote targets
20474 If you want @value{GDBN} to be able to stop your program while it is
20475 running, you need to use an interrupt-driven serial driver, and arrange
20476 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20477 character). That is the character which @value{GDBN} uses to tell the
20478 remote system to stop.
20480 Getting the debugging target to return the proper status to @value{GDBN}
20481 probably requires changes to the standard stub; one quick and dirty way
20482 is to just execute a breakpoint instruction (the ``dirty'' part is that
20483 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20485 Other routines you need to supply are:
20488 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20489 @findex exceptionHandler
20490 Write this function to install @var{exception_address} in the exception
20491 handling tables. You need to do this because the stub does not have any
20492 way of knowing what the exception handling tables on your target system
20493 are like (for example, the processor's table might be in @sc{rom},
20494 containing entries which point to a table in @sc{ram}).
20495 The @var{exception_number} specifies the exception which should be changed;
20496 its meaning is architecture-dependent (for example, different numbers
20497 might represent divide by zero, misaligned access, etc). When this
20498 exception occurs, control should be transferred directly to
20499 @var{exception_address}, and the processor state (stack, registers,
20500 and so on) should be just as it is when a processor exception occurs. So if
20501 you want to use a jump instruction to reach @var{exception_address}, it
20502 should be a simple jump, not a jump to subroutine.
20504 For the 386, @var{exception_address} should be installed as an interrupt
20505 gate so that interrupts are masked while the handler runs. The gate
20506 should be at privilege level 0 (the most privileged level). The
20507 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20508 help from @code{exceptionHandler}.
20510 @item void flush_i_cache()
20511 @findex flush_i_cache
20512 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20513 instruction cache, if any, on your target machine. If there is no
20514 instruction cache, this subroutine may be a no-op.
20516 On target machines that have instruction caches, @value{GDBN} requires this
20517 function to make certain that the state of your program is stable.
20521 You must also make sure this library routine is available:
20524 @item void *memset(void *, int, int)
20526 This is the standard library function @code{memset} that sets an area of
20527 memory to a known value. If you have one of the free versions of
20528 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20529 either obtain it from your hardware manufacturer, or write your own.
20532 If you do not use the GNU C compiler, you may need other standard
20533 library subroutines as well; this varies from one stub to another,
20534 but in general the stubs are likely to use any of the common library
20535 subroutines which @code{@value{NGCC}} generates as inline code.
20538 @node Debug Session
20539 @subsection Putting it All Together
20541 @cindex remote serial debugging summary
20542 In summary, when your program is ready to debug, you must follow these
20547 Make sure you have defined the supporting low-level routines
20548 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20550 @code{getDebugChar}, @code{putDebugChar},
20551 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20555 Insert these lines in your program's startup code, before the main
20556 procedure is called:
20563 On some machines, when a breakpoint trap is raised, the hardware
20564 automatically makes the PC point to the instruction after the
20565 breakpoint. If your machine doesn't do that, you may need to adjust
20566 @code{handle_exception} to arrange for it to return to the instruction
20567 after the breakpoint on this first invocation, so that your program
20568 doesn't keep hitting the initial breakpoint instead of making
20572 For the 680x0 stub only, you need to provide a variable called
20573 @code{exceptionHook}. Normally you just use:
20576 void (*exceptionHook)() = 0;
20580 but if before calling @code{set_debug_traps}, you set it to point to a
20581 function in your program, that function is called when
20582 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20583 error). The function indicated by @code{exceptionHook} is called with
20584 one parameter: an @code{int} which is the exception number.
20587 Compile and link together: your program, the @value{GDBN} debugging stub for
20588 your target architecture, and the supporting subroutines.
20591 Make sure you have a serial connection between your target machine and
20592 the @value{GDBN} host, and identify the serial port on the host.
20595 @c The "remote" target now provides a `load' command, so we should
20596 @c document that. FIXME.
20597 Download your program to your target machine (or get it there by
20598 whatever means the manufacturer provides), and start it.
20601 Start @value{GDBN} on the host, and connect to the target
20602 (@pxref{Connecting,,Connecting to a Remote Target}).
20606 @node Configurations
20607 @chapter Configuration-Specific Information
20609 While nearly all @value{GDBN} commands are available for all native and
20610 cross versions of the debugger, there are some exceptions. This chapter
20611 describes things that are only available in certain configurations.
20613 There are three major categories of configurations: native
20614 configurations, where the host and target are the same, embedded
20615 operating system configurations, which are usually the same for several
20616 different processor architectures, and bare embedded processors, which
20617 are quite different from each other.
20622 * Embedded Processors::
20629 This section describes details specific to particular native
20634 * BSD libkvm Interface:: Debugging BSD kernel memory images
20635 * SVR4 Process Information:: SVR4 process information
20636 * DJGPP Native:: Features specific to the DJGPP port
20637 * Cygwin Native:: Features specific to the Cygwin port
20638 * Hurd Native:: Features specific to @sc{gnu} Hurd
20639 * Darwin:: Features specific to Darwin
20645 On HP-UX systems, if you refer to a function or variable name that
20646 begins with a dollar sign, @value{GDBN} searches for a user or system
20647 name first, before it searches for a convenience variable.
20650 @node BSD libkvm Interface
20651 @subsection BSD libkvm Interface
20654 @cindex kernel memory image
20655 @cindex kernel crash dump
20657 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20658 interface that provides a uniform interface for accessing kernel virtual
20659 memory images, including live systems and crash dumps. @value{GDBN}
20660 uses this interface to allow you to debug live kernels and kernel crash
20661 dumps on many native BSD configurations. This is implemented as a
20662 special @code{kvm} debugging target. For debugging a live system, load
20663 the currently running kernel into @value{GDBN} and connect to the
20667 (@value{GDBP}) @b{target kvm}
20670 For debugging crash dumps, provide the file name of the crash dump as an
20674 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20677 Once connected to the @code{kvm} target, the following commands are
20683 Set current context from the @dfn{Process Control Block} (PCB) address.
20686 Set current context from proc address. This command isn't available on
20687 modern FreeBSD systems.
20690 @node SVR4 Process Information
20691 @subsection SVR4 Process Information
20693 @cindex examine process image
20694 @cindex process info via @file{/proc}
20696 Many versions of SVR4 and compatible systems provide a facility called
20697 @samp{/proc} that can be used to examine the image of a running
20698 process using file-system subroutines.
20700 If @value{GDBN} is configured for an operating system with this
20701 facility, the command @code{info proc} is available to report
20702 information about the process running your program, or about any
20703 process running on your system. This includes, as of this writing,
20704 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20706 This command may also work on core files that were created on a system
20707 that has the @samp{/proc} facility.
20713 @itemx info proc @var{process-id}
20714 Summarize available information about any running process. If a
20715 process ID is specified by @var{process-id}, display information about
20716 that process; otherwise display information about the program being
20717 debugged. The summary includes the debugged process ID, the command
20718 line used to invoke it, its current working directory, and its
20719 executable file's absolute file name.
20721 On some systems, @var{process-id} can be of the form
20722 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20723 within a process. If the optional @var{pid} part is missing, it means
20724 a thread from the process being debugged (the leading @samp{/} still
20725 needs to be present, or else @value{GDBN} will interpret the number as
20726 a process ID rather than a thread ID).
20728 @item info proc cmdline
20729 @cindex info proc cmdline
20730 Show the original command line of the process. This command is
20731 specific to @sc{gnu}/Linux.
20733 @item info proc cwd
20734 @cindex info proc cwd
20735 Show the current working directory of the process. This command is
20736 specific to @sc{gnu}/Linux.
20738 @item info proc exe
20739 @cindex info proc exe
20740 Show the name of executable of the process. This command is specific
20743 @item info proc mappings
20744 @cindex memory address space mappings
20745 Report the memory address space ranges accessible in the program, with
20746 information on whether the process has read, write, or execute access
20747 rights to each range. On @sc{gnu}/Linux systems, each memory range
20748 includes the object file which is mapped to that range, instead of the
20749 memory access rights to that range.
20751 @item info proc stat
20752 @itemx info proc status
20753 @cindex process detailed status information
20754 These subcommands are specific to @sc{gnu}/Linux systems. They show
20755 the process-related information, including the user ID and group ID;
20756 how many threads are there in the process; its virtual memory usage;
20757 the signals that are pending, blocked, and ignored; its TTY; its
20758 consumption of system and user time; its stack size; its @samp{nice}
20759 value; etc. For more information, see the @samp{proc} man page
20760 (type @kbd{man 5 proc} from your shell prompt).
20762 @item info proc all
20763 Show all the information about the process described under all of the
20764 above @code{info proc} subcommands.
20767 @comment These sub-options of 'info proc' were not included when
20768 @comment procfs.c was re-written. Keep their descriptions around
20769 @comment against the day when someone finds the time to put them back in.
20770 @kindex info proc times
20771 @item info proc times
20772 Starting time, user CPU time, and system CPU time for your program and
20775 @kindex info proc id
20777 Report on the process IDs related to your program: its own process ID,
20778 the ID of its parent, the process group ID, and the session ID.
20781 @item set procfs-trace
20782 @kindex set procfs-trace
20783 @cindex @code{procfs} API calls
20784 This command enables and disables tracing of @code{procfs} API calls.
20786 @item show procfs-trace
20787 @kindex show procfs-trace
20788 Show the current state of @code{procfs} API call tracing.
20790 @item set procfs-file @var{file}
20791 @kindex set procfs-file
20792 Tell @value{GDBN} to write @code{procfs} API trace to the named
20793 @var{file}. @value{GDBN} appends the trace info to the previous
20794 contents of the file. The default is to display the trace on the
20797 @item show procfs-file
20798 @kindex show procfs-file
20799 Show the file to which @code{procfs} API trace is written.
20801 @item proc-trace-entry
20802 @itemx proc-trace-exit
20803 @itemx proc-untrace-entry
20804 @itemx proc-untrace-exit
20805 @kindex proc-trace-entry
20806 @kindex proc-trace-exit
20807 @kindex proc-untrace-entry
20808 @kindex proc-untrace-exit
20809 These commands enable and disable tracing of entries into and exits
20810 from the @code{syscall} interface.
20813 @kindex info pidlist
20814 @cindex process list, QNX Neutrino
20815 For QNX Neutrino only, this command displays the list of all the
20816 processes and all the threads within each process.
20819 @kindex info meminfo
20820 @cindex mapinfo list, QNX Neutrino
20821 For QNX Neutrino only, this command displays the list of all mapinfos.
20825 @subsection Features for Debugging @sc{djgpp} Programs
20826 @cindex @sc{djgpp} debugging
20827 @cindex native @sc{djgpp} debugging
20828 @cindex MS-DOS-specific commands
20831 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20832 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20833 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20834 top of real-mode DOS systems and their emulations.
20836 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20837 defines a few commands specific to the @sc{djgpp} port. This
20838 subsection describes those commands.
20843 This is a prefix of @sc{djgpp}-specific commands which print
20844 information about the target system and important OS structures.
20847 @cindex MS-DOS system info
20848 @cindex free memory information (MS-DOS)
20849 @item info dos sysinfo
20850 This command displays assorted information about the underlying
20851 platform: the CPU type and features, the OS version and flavor, the
20852 DPMI version, and the available conventional and DPMI memory.
20857 @cindex segment descriptor tables
20858 @cindex descriptor tables display
20860 @itemx info dos ldt
20861 @itemx info dos idt
20862 These 3 commands display entries from, respectively, Global, Local,
20863 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20864 tables are data structures which store a descriptor for each segment
20865 that is currently in use. The segment's selector is an index into a
20866 descriptor table; the table entry for that index holds the
20867 descriptor's base address and limit, and its attributes and access
20870 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20871 segment (used for both data and the stack), and a DOS segment (which
20872 allows access to DOS/BIOS data structures and absolute addresses in
20873 conventional memory). However, the DPMI host will usually define
20874 additional segments in order to support the DPMI environment.
20876 @cindex garbled pointers
20877 These commands allow to display entries from the descriptor tables.
20878 Without an argument, all entries from the specified table are
20879 displayed. An argument, which should be an integer expression, means
20880 display a single entry whose index is given by the argument. For
20881 example, here's a convenient way to display information about the
20882 debugged program's data segment:
20885 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20886 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20890 This comes in handy when you want to see whether a pointer is outside
20891 the data segment's limit (i.e.@: @dfn{garbled}).
20893 @cindex page tables display (MS-DOS)
20895 @itemx info dos pte
20896 These two commands display entries from, respectively, the Page
20897 Directory and the Page Tables. Page Directories and Page Tables are
20898 data structures which control how virtual memory addresses are mapped
20899 into physical addresses. A Page Table includes an entry for every
20900 page of memory that is mapped into the program's address space; there
20901 may be several Page Tables, each one holding up to 4096 entries. A
20902 Page Directory has up to 4096 entries, one each for every Page Table
20903 that is currently in use.
20905 Without an argument, @kbd{info dos pde} displays the entire Page
20906 Directory, and @kbd{info dos pte} displays all the entries in all of
20907 the Page Tables. An argument, an integer expression, given to the
20908 @kbd{info dos pde} command means display only that entry from the Page
20909 Directory table. An argument given to the @kbd{info dos pte} command
20910 means display entries from a single Page Table, the one pointed to by
20911 the specified entry in the Page Directory.
20913 @cindex direct memory access (DMA) on MS-DOS
20914 These commands are useful when your program uses @dfn{DMA} (Direct
20915 Memory Access), which needs physical addresses to program the DMA
20918 These commands are supported only with some DPMI servers.
20920 @cindex physical address from linear address
20921 @item info dos address-pte @var{addr}
20922 This command displays the Page Table entry for a specified linear
20923 address. The argument @var{addr} is a linear address which should
20924 already have the appropriate segment's base address added to it,
20925 because this command accepts addresses which may belong to @emph{any}
20926 segment. For example, here's how to display the Page Table entry for
20927 the page where a variable @code{i} is stored:
20930 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20931 @exdent @code{Page Table entry for address 0x11a00d30:}
20932 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20936 This says that @code{i} is stored at offset @code{0xd30} from the page
20937 whose physical base address is @code{0x02698000}, and shows all the
20938 attributes of that page.
20940 Note that you must cast the addresses of variables to a @code{char *},
20941 since otherwise the value of @code{__djgpp_base_address}, the base
20942 address of all variables and functions in a @sc{djgpp} program, will
20943 be added using the rules of C pointer arithmetics: if @code{i} is
20944 declared an @code{int}, @value{GDBN} will add 4 times the value of
20945 @code{__djgpp_base_address} to the address of @code{i}.
20947 Here's another example, it displays the Page Table entry for the
20951 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20952 @exdent @code{Page Table entry for address 0x29110:}
20953 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20957 (The @code{+ 3} offset is because the transfer buffer's address is the
20958 3rd member of the @code{_go32_info_block} structure.) The output
20959 clearly shows that this DPMI server maps the addresses in conventional
20960 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20961 linear (@code{0x29110}) addresses are identical.
20963 This command is supported only with some DPMI servers.
20966 @cindex DOS serial data link, remote debugging
20967 In addition to native debugging, the DJGPP port supports remote
20968 debugging via a serial data link. The following commands are specific
20969 to remote serial debugging in the DJGPP port of @value{GDBN}.
20972 @kindex set com1base
20973 @kindex set com1irq
20974 @kindex set com2base
20975 @kindex set com2irq
20976 @kindex set com3base
20977 @kindex set com3irq
20978 @kindex set com4base
20979 @kindex set com4irq
20980 @item set com1base @var{addr}
20981 This command sets the base I/O port address of the @file{COM1} serial
20984 @item set com1irq @var{irq}
20985 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20986 for the @file{COM1} serial port.
20988 There are similar commands @samp{set com2base}, @samp{set com3irq},
20989 etc.@: for setting the port address and the @code{IRQ} lines for the
20992 @kindex show com1base
20993 @kindex show com1irq
20994 @kindex show com2base
20995 @kindex show com2irq
20996 @kindex show com3base
20997 @kindex show com3irq
20998 @kindex show com4base
20999 @kindex show com4irq
21000 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21001 display the current settings of the base address and the @code{IRQ}
21002 lines used by the COM ports.
21005 @kindex info serial
21006 @cindex DOS serial port status
21007 This command prints the status of the 4 DOS serial ports. For each
21008 port, it prints whether it's active or not, its I/O base address and
21009 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21010 counts of various errors encountered so far.
21014 @node Cygwin Native
21015 @subsection Features for Debugging MS Windows PE Executables
21016 @cindex MS Windows debugging
21017 @cindex native Cygwin debugging
21018 @cindex Cygwin-specific commands
21020 @value{GDBN} supports native debugging of MS Windows programs, including
21021 DLLs with and without symbolic debugging information.
21023 @cindex Ctrl-BREAK, MS-Windows
21024 @cindex interrupt debuggee on MS-Windows
21025 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21026 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21027 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21028 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21029 sequence, which can be used to interrupt the debuggee even if it
21032 There are various additional Cygwin-specific commands, described in
21033 this section. Working with DLLs that have no debugging symbols is
21034 described in @ref{Non-debug DLL Symbols}.
21039 This is a prefix of MS Windows-specific commands which print
21040 information about the target system and important OS structures.
21042 @item info w32 selector
21043 This command displays information returned by
21044 the Win32 API @code{GetThreadSelectorEntry} function.
21045 It takes an optional argument that is evaluated to
21046 a long value to give the information about this given selector.
21047 Without argument, this command displays information
21048 about the six segment registers.
21050 @item info w32 thread-information-block
21051 This command displays thread specific information stored in the
21052 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21053 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21055 @kindex set cygwin-exceptions
21056 @cindex debugging the Cygwin DLL
21057 @cindex Cygwin DLL, debugging
21058 @item set cygwin-exceptions @var{mode}
21059 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21060 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21061 @value{GDBN} will delay recognition of exceptions, and may ignore some
21062 exceptions which seem to be caused by internal Cygwin DLL
21063 ``bookkeeping''. This option is meant primarily for debugging the
21064 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21065 @value{GDBN} users with false @code{SIGSEGV} signals.
21067 @kindex show cygwin-exceptions
21068 @item show cygwin-exceptions
21069 Displays whether @value{GDBN} will break on exceptions that happen
21070 inside the Cygwin DLL itself.
21072 @kindex set new-console
21073 @item set new-console @var{mode}
21074 If @var{mode} is @code{on} the debuggee will
21075 be started in a new console on next start.
21076 If @var{mode} is @code{off}, the debuggee will
21077 be started in the same console as the debugger.
21079 @kindex show new-console
21080 @item show new-console
21081 Displays whether a new console is used
21082 when the debuggee is started.
21084 @kindex set new-group
21085 @item set new-group @var{mode}
21086 This boolean value controls whether the debuggee should
21087 start a new group or stay in the same group as the debugger.
21088 This affects the way the Windows OS handles
21091 @kindex show new-group
21092 @item show new-group
21093 Displays current value of new-group boolean.
21095 @kindex set debugevents
21096 @item set debugevents
21097 This boolean value adds debug output concerning kernel events related
21098 to the debuggee seen by the debugger. This includes events that
21099 signal thread and process creation and exit, DLL loading and
21100 unloading, console interrupts, and debugging messages produced by the
21101 Windows @code{OutputDebugString} API call.
21103 @kindex set debugexec
21104 @item set debugexec
21105 This boolean value adds debug output concerning execute events
21106 (such as resume thread) seen by the debugger.
21108 @kindex set debugexceptions
21109 @item set debugexceptions
21110 This boolean value adds debug output concerning exceptions in the
21111 debuggee seen by the debugger.
21113 @kindex set debugmemory
21114 @item set debugmemory
21115 This boolean value adds debug output concerning debuggee memory reads
21116 and writes by the debugger.
21120 This boolean values specifies whether the debuggee is called
21121 via a shell or directly (default value is on).
21125 Displays if the debuggee will be started with a shell.
21130 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21133 @node Non-debug DLL Symbols
21134 @subsubsection Support for DLLs without Debugging Symbols
21135 @cindex DLLs with no debugging symbols
21136 @cindex Minimal symbols and DLLs
21138 Very often on windows, some of the DLLs that your program relies on do
21139 not include symbolic debugging information (for example,
21140 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21141 symbols in a DLL, it relies on the minimal amount of symbolic
21142 information contained in the DLL's export table. This section
21143 describes working with such symbols, known internally to @value{GDBN} as
21144 ``minimal symbols''.
21146 Note that before the debugged program has started execution, no DLLs
21147 will have been loaded. The easiest way around this problem is simply to
21148 start the program --- either by setting a breakpoint or letting the
21149 program run once to completion.
21151 @subsubsection DLL Name Prefixes
21153 In keeping with the naming conventions used by the Microsoft debugging
21154 tools, DLL export symbols are made available with a prefix based on the
21155 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21156 also entered into the symbol table, so @code{CreateFileA} is often
21157 sufficient. In some cases there will be name clashes within a program
21158 (particularly if the executable itself includes full debugging symbols)
21159 necessitating the use of the fully qualified name when referring to the
21160 contents of the DLL. Use single-quotes around the name to avoid the
21161 exclamation mark (``!'') being interpreted as a language operator.
21163 Note that the internal name of the DLL may be all upper-case, even
21164 though the file name of the DLL is lower-case, or vice-versa. Since
21165 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21166 some confusion. If in doubt, try the @code{info functions} and
21167 @code{info variables} commands or even @code{maint print msymbols}
21168 (@pxref{Symbols}). Here's an example:
21171 (@value{GDBP}) info function CreateFileA
21172 All functions matching regular expression "CreateFileA":
21174 Non-debugging symbols:
21175 0x77e885f4 CreateFileA
21176 0x77e885f4 KERNEL32!CreateFileA
21180 (@value{GDBP}) info function !
21181 All functions matching regular expression "!":
21183 Non-debugging symbols:
21184 0x6100114c cygwin1!__assert
21185 0x61004034 cygwin1!_dll_crt0@@0
21186 0x61004240 cygwin1!dll_crt0(per_process *)
21190 @subsubsection Working with Minimal Symbols
21192 Symbols extracted from a DLL's export table do not contain very much
21193 type information. All that @value{GDBN} can do is guess whether a symbol
21194 refers to a function or variable depending on the linker section that
21195 contains the symbol. Also note that the actual contents of the memory
21196 contained in a DLL are not available unless the program is running. This
21197 means that you cannot examine the contents of a variable or disassemble
21198 a function within a DLL without a running program.
21200 Variables are generally treated as pointers and dereferenced
21201 automatically. For this reason, it is often necessary to prefix a
21202 variable name with the address-of operator (``&'') and provide explicit
21203 type information in the command. Here's an example of the type of
21207 (@value{GDBP}) print 'cygwin1!__argv'
21212 (@value{GDBP}) x 'cygwin1!__argv'
21213 0x10021610: "\230y\""
21216 And two possible solutions:
21219 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21220 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21224 (@value{GDBP}) x/2x &'cygwin1!__argv'
21225 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21226 (@value{GDBP}) x/x 0x10021608
21227 0x10021608: 0x0022fd98
21228 (@value{GDBP}) x/s 0x0022fd98
21229 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21232 Setting a break point within a DLL is possible even before the program
21233 starts execution. However, under these circumstances, @value{GDBN} can't
21234 examine the initial instructions of the function in order to skip the
21235 function's frame set-up code. You can work around this by using ``*&''
21236 to set the breakpoint at a raw memory address:
21239 (@value{GDBP}) break *&'python22!PyOS_Readline'
21240 Breakpoint 1 at 0x1e04eff0
21243 The author of these extensions is not entirely convinced that setting a
21244 break point within a shared DLL like @file{kernel32.dll} is completely
21248 @subsection Commands Specific to @sc{gnu} Hurd Systems
21249 @cindex @sc{gnu} Hurd debugging
21251 This subsection describes @value{GDBN} commands specific to the
21252 @sc{gnu} Hurd native debugging.
21257 @kindex set signals@r{, Hurd command}
21258 @kindex set sigs@r{, Hurd command}
21259 This command toggles the state of inferior signal interception by
21260 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21261 affected by this command. @code{sigs} is a shorthand alias for
21266 @kindex show signals@r{, Hurd command}
21267 @kindex show sigs@r{, Hurd command}
21268 Show the current state of intercepting inferior's signals.
21270 @item set signal-thread
21271 @itemx set sigthread
21272 @kindex set signal-thread
21273 @kindex set sigthread
21274 This command tells @value{GDBN} which thread is the @code{libc} signal
21275 thread. That thread is run when a signal is delivered to a running
21276 process. @code{set sigthread} is the shorthand alias of @code{set
21279 @item show signal-thread
21280 @itemx show sigthread
21281 @kindex show signal-thread
21282 @kindex show sigthread
21283 These two commands show which thread will run when the inferior is
21284 delivered a signal.
21287 @kindex set stopped@r{, Hurd command}
21288 This commands tells @value{GDBN} that the inferior process is stopped,
21289 as with the @code{SIGSTOP} signal. The stopped process can be
21290 continued by delivering a signal to it.
21293 @kindex show stopped@r{, Hurd command}
21294 This command shows whether @value{GDBN} thinks the debuggee is
21297 @item set exceptions
21298 @kindex set exceptions@r{, Hurd command}
21299 Use this command to turn off trapping of exceptions in the inferior.
21300 When exception trapping is off, neither breakpoints nor
21301 single-stepping will work. To restore the default, set exception
21304 @item show exceptions
21305 @kindex show exceptions@r{, Hurd command}
21306 Show the current state of trapping exceptions in the inferior.
21308 @item set task pause
21309 @kindex set task@r{, Hurd commands}
21310 @cindex task attributes (@sc{gnu} Hurd)
21311 @cindex pause current task (@sc{gnu} Hurd)
21312 This command toggles task suspension when @value{GDBN} has control.
21313 Setting it to on takes effect immediately, and the task is suspended
21314 whenever @value{GDBN} gets control. Setting it to off will take
21315 effect the next time the inferior is continued. If this option is set
21316 to off, you can use @code{set thread default pause on} or @code{set
21317 thread pause on} (see below) to pause individual threads.
21319 @item show task pause
21320 @kindex show task@r{, Hurd commands}
21321 Show the current state of task suspension.
21323 @item set task detach-suspend-count
21324 @cindex task suspend count
21325 @cindex detach from task, @sc{gnu} Hurd
21326 This command sets the suspend count the task will be left with when
21327 @value{GDBN} detaches from it.
21329 @item show task detach-suspend-count
21330 Show the suspend count the task will be left with when detaching.
21332 @item set task exception-port
21333 @itemx set task excp
21334 @cindex task exception port, @sc{gnu} Hurd
21335 This command sets the task exception port to which @value{GDBN} will
21336 forward exceptions. The argument should be the value of the @dfn{send
21337 rights} of the task. @code{set task excp} is a shorthand alias.
21339 @item set noninvasive
21340 @cindex noninvasive task options
21341 This command switches @value{GDBN} to a mode that is the least
21342 invasive as far as interfering with the inferior is concerned. This
21343 is the same as using @code{set task pause}, @code{set exceptions}, and
21344 @code{set signals} to values opposite to the defaults.
21346 @item info send-rights
21347 @itemx info receive-rights
21348 @itemx info port-rights
21349 @itemx info port-sets
21350 @itemx info dead-names
21353 @cindex send rights, @sc{gnu} Hurd
21354 @cindex receive rights, @sc{gnu} Hurd
21355 @cindex port rights, @sc{gnu} Hurd
21356 @cindex port sets, @sc{gnu} Hurd
21357 @cindex dead names, @sc{gnu} Hurd
21358 These commands display information about, respectively, send rights,
21359 receive rights, port rights, port sets, and dead names of a task.
21360 There are also shorthand aliases: @code{info ports} for @code{info
21361 port-rights} and @code{info psets} for @code{info port-sets}.
21363 @item set thread pause
21364 @kindex set thread@r{, Hurd command}
21365 @cindex thread properties, @sc{gnu} Hurd
21366 @cindex pause current thread (@sc{gnu} Hurd)
21367 This command toggles current thread suspension when @value{GDBN} has
21368 control. Setting it to on takes effect immediately, and the current
21369 thread is suspended whenever @value{GDBN} gets control. Setting it to
21370 off will take effect the next time the inferior is continued.
21371 Normally, this command has no effect, since when @value{GDBN} has
21372 control, the whole task is suspended. However, if you used @code{set
21373 task pause off} (see above), this command comes in handy to suspend
21374 only the current thread.
21376 @item show thread pause
21377 @kindex show thread@r{, Hurd command}
21378 This command shows the state of current thread suspension.
21380 @item set thread run
21381 This command sets whether the current thread is allowed to run.
21383 @item show thread run
21384 Show whether the current thread is allowed to run.
21386 @item set thread detach-suspend-count
21387 @cindex thread suspend count, @sc{gnu} Hurd
21388 @cindex detach from thread, @sc{gnu} Hurd
21389 This command sets the suspend count @value{GDBN} will leave on a
21390 thread when detaching. This number is relative to the suspend count
21391 found by @value{GDBN} when it notices the thread; use @code{set thread
21392 takeover-suspend-count} to force it to an absolute value.
21394 @item show thread detach-suspend-count
21395 Show the suspend count @value{GDBN} will leave on the thread when
21398 @item set thread exception-port
21399 @itemx set thread excp
21400 Set the thread exception port to which to forward exceptions. This
21401 overrides the port set by @code{set task exception-port} (see above).
21402 @code{set thread excp} is the shorthand alias.
21404 @item set thread takeover-suspend-count
21405 Normally, @value{GDBN}'s thread suspend counts are relative to the
21406 value @value{GDBN} finds when it notices each thread. This command
21407 changes the suspend counts to be absolute instead.
21409 @item set thread default
21410 @itemx show thread default
21411 @cindex thread default settings, @sc{gnu} Hurd
21412 Each of the above @code{set thread} commands has a @code{set thread
21413 default} counterpart (e.g., @code{set thread default pause}, @code{set
21414 thread default exception-port}, etc.). The @code{thread default}
21415 variety of commands sets the default thread properties for all
21416 threads; you can then change the properties of individual threads with
21417 the non-default commands.
21424 @value{GDBN} provides the following commands specific to the Darwin target:
21427 @item set debug darwin @var{num}
21428 @kindex set debug darwin
21429 When set to a non zero value, enables debugging messages specific to
21430 the Darwin support. Higher values produce more verbose output.
21432 @item show debug darwin
21433 @kindex show debug darwin
21434 Show the current state of Darwin messages.
21436 @item set debug mach-o @var{num}
21437 @kindex set debug mach-o
21438 When set to a non zero value, enables debugging messages while
21439 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21440 file format used on Darwin for object and executable files.) Higher
21441 values produce more verbose output. This is a command to diagnose
21442 problems internal to @value{GDBN} and should not be needed in normal
21445 @item show debug mach-o
21446 @kindex show debug mach-o
21447 Show the current state of Mach-O file messages.
21449 @item set mach-exceptions on
21450 @itemx set mach-exceptions off
21451 @kindex set mach-exceptions
21452 On Darwin, faults are first reported as a Mach exception and are then
21453 mapped to a Posix signal. Use this command to turn on trapping of
21454 Mach exceptions in the inferior. This might be sometimes useful to
21455 better understand the cause of a fault. The default is off.
21457 @item show mach-exceptions
21458 @kindex show mach-exceptions
21459 Show the current state of exceptions trapping.
21464 @section Embedded Operating Systems
21466 This section describes configurations involving the debugging of
21467 embedded operating systems that are available for several different
21470 @value{GDBN} includes the ability to debug programs running on
21471 various real-time operating systems.
21473 @node Embedded Processors
21474 @section Embedded Processors
21476 This section goes into details specific to particular embedded
21479 @cindex send command to simulator
21480 Whenever a specific embedded processor has a simulator, @value{GDBN}
21481 allows to send an arbitrary command to the simulator.
21484 @item sim @var{command}
21485 @kindex sim@r{, a command}
21486 Send an arbitrary @var{command} string to the simulator. Consult the
21487 documentation for the specific simulator in use for information about
21488 acceptable commands.
21494 * M32R/SDI:: Renesas M32R/SDI
21495 * M68K:: Motorola M68K
21496 * MicroBlaze:: Xilinx MicroBlaze
21497 * MIPS Embedded:: MIPS Embedded
21498 * PowerPC Embedded:: PowerPC Embedded
21501 * Super-H:: Renesas Super-H
21507 @value{GDBN} provides the following ARM-specific commands:
21510 @item set arm disassembler
21512 This commands selects from a list of disassembly styles. The
21513 @code{"std"} style is the standard style.
21515 @item show arm disassembler
21517 Show the current disassembly style.
21519 @item set arm apcs32
21520 @cindex ARM 32-bit mode
21521 This command toggles ARM operation mode between 32-bit and 26-bit.
21523 @item show arm apcs32
21524 Display the current usage of the ARM 32-bit mode.
21526 @item set arm fpu @var{fputype}
21527 This command sets the ARM floating-point unit (FPU) type. The
21528 argument @var{fputype} can be one of these:
21532 Determine the FPU type by querying the OS ABI.
21534 Software FPU, with mixed-endian doubles on little-endian ARM
21537 GCC-compiled FPA co-processor.
21539 Software FPU with pure-endian doubles.
21545 Show the current type of the FPU.
21548 This command forces @value{GDBN} to use the specified ABI.
21551 Show the currently used ABI.
21553 @item set arm fallback-mode (arm|thumb|auto)
21554 @value{GDBN} uses the symbol table, when available, to determine
21555 whether instructions are ARM or Thumb. This command controls
21556 @value{GDBN}'s default behavior when the symbol table is not
21557 available. The default is @samp{auto}, which causes @value{GDBN} to
21558 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21561 @item show arm fallback-mode
21562 Show the current fallback instruction mode.
21564 @item set arm force-mode (arm|thumb|auto)
21565 This command overrides use of the symbol table to determine whether
21566 instructions are ARM or Thumb. The default is @samp{auto}, which
21567 causes @value{GDBN} to use the symbol table and then the setting
21568 of @samp{set arm fallback-mode}.
21570 @item show arm force-mode
21571 Show the current forced instruction mode.
21573 @item set debug arm
21574 Toggle whether to display ARM-specific debugging messages from the ARM
21575 target support subsystem.
21577 @item show debug arm
21578 Show whether ARM-specific debugging messages are enabled.
21582 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21583 The @value{GDBN} ARM simulator accepts the following optional arguments.
21586 @item --swi-support=@var{type}
21587 Tell the simulator which SWI interfaces to support. The argument
21588 @var{type} may be a comma separated list of the following values.
21589 The default value is @code{all}.
21602 @subsection Renesas M32R/SDI
21604 The following commands are available for M32R/SDI:
21609 @cindex reset SDI connection, M32R
21610 This command resets the SDI connection.
21614 This command shows the SDI connection status.
21617 @kindex debug_chaos
21618 @cindex M32R/Chaos debugging
21619 Instructs the remote that M32R/Chaos debugging is to be used.
21621 @item use_debug_dma
21622 @kindex use_debug_dma
21623 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21626 @kindex use_mon_code
21627 Instructs the remote to use the MON_CODE method of accessing memory.
21630 @kindex use_ib_break
21631 Instructs the remote to set breakpoints by IB break.
21633 @item use_dbt_break
21634 @kindex use_dbt_break
21635 Instructs the remote to set breakpoints by DBT.
21641 The Motorola m68k configuration includes ColdFire support.
21644 @subsection MicroBlaze
21645 @cindex Xilinx MicroBlaze
21646 @cindex XMD, Xilinx Microprocessor Debugger
21648 The MicroBlaze is a soft-core processor supported on various Xilinx
21649 FPGAs, such as Spartan or Virtex series. Boards with these processors
21650 usually have JTAG ports which connect to a host system running the Xilinx
21651 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21652 This host system is used to download the configuration bitstream to
21653 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21654 communicates with the target board using the JTAG interface and
21655 presents a @code{gdbserver} interface to the board. By default
21656 @code{xmd} uses port @code{1234}. (While it is possible to change
21657 this default port, it requires the use of undocumented @code{xmd}
21658 commands. Contact Xilinx support if you need to do this.)
21660 Use these GDB commands to connect to the MicroBlaze target processor.
21663 @item target remote :1234
21664 Use this command to connect to the target if you are running @value{GDBN}
21665 on the same system as @code{xmd}.
21667 @item target remote @var{xmd-host}:1234
21668 Use this command to connect to the target if it is connected to @code{xmd}
21669 running on a different system named @var{xmd-host}.
21672 Use this command to download a program to the MicroBlaze target.
21674 @item set debug microblaze @var{n}
21675 Enable MicroBlaze-specific debugging messages if non-zero.
21677 @item show debug microblaze @var{n}
21678 Show MicroBlaze-specific debugging level.
21681 @node MIPS Embedded
21682 @subsection @acronym{MIPS} Embedded
21684 @cindex @acronym{MIPS} boards
21685 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21686 @acronym{MIPS} board attached to a serial line. This is available when
21687 you configure @value{GDBN} with @samp{--target=mips-elf}.
21690 Use these @value{GDBN} commands to specify the connection to your target board:
21693 @item target mips @var{port}
21694 @kindex target mips @var{port}
21695 To run a program on the board, start up @code{@value{GDBP}} with the
21696 name of your program as the argument. To connect to the board, use the
21697 command @samp{target mips @var{port}}, where @var{port} is the name of
21698 the serial port connected to the board. If the program has not already
21699 been downloaded to the board, you may use the @code{load} command to
21700 download it. You can then use all the usual @value{GDBN} commands.
21702 For example, this sequence connects to the target board through a serial
21703 port, and loads and runs a program called @var{prog} through the
21707 host$ @value{GDBP} @var{prog}
21708 @value{GDBN} is free software and @dots{}
21709 (@value{GDBP}) target mips /dev/ttyb
21710 (@value{GDBP}) load @var{prog}
21714 @item target mips @var{hostname}:@var{portnumber}
21715 On some @value{GDBN} host configurations, you can specify a TCP
21716 connection (for instance, to a serial line managed by a terminal
21717 concentrator) instead of a serial port, using the syntax
21718 @samp{@var{hostname}:@var{portnumber}}.
21720 @item target pmon @var{port}
21721 @kindex target pmon @var{port}
21724 @item target ddb @var{port}
21725 @kindex target ddb @var{port}
21726 NEC's DDB variant of PMON for Vr4300.
21728 @item target lsi @var{port}
21729 @kindex target lsi @var{port}
21730 LSI variant of PMON.
21736 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21739 @item set mipsfpu double
21740 @itemx set mipsfpu single
21741 @itemx set mipsfpu none
21742 @itemx set mipsfpu auto
21743 @itemx show mipsfpu
21744 @kindex set mipsfpu
21745 @kindex show mipsfpu
21746 @cindex @acronym{MIPS} remote floating point
21747 @cindex floating point, @acronym{MIPS} remote
21748 If your target board does not support the @acronym{MIPS} floating point
21749 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21750 need this, you may wish to put the command in your @value{GDBN} init
21751 file). This tells @value{GDBN} how to find the return value of
21752 functions which return floating point values. It also allows
21753 @value{GDBN} to avoid saving the floating point registers when calling
21754 functions on the board. If you are using a floating point coprocessor
21755 with only single precision floating point support, as on the @sc{r4650}
21756 processor, use the command @samp{set mipsfpu single}. The default
21757 double precision floating point coprocessor may be selected using
21758 @samp{set mipsfpu double}.
21760 In previous versions the only choices were double precision or no
21761 floating point, so @samp{set mipsfpu on} will select double precision
21762 and @samp{set mipsfpu off} will select no floating point.
21764 As usual, you can inquire about the @code{mipsfpu} variable with
21765 @samp{show mipsfpu}.
21767 @item set timeout @var{seconds}
21768 @itemx set retransmit-timeout @var{seconds}
21769 @itemx show timeout
21770 @itemx show retransmit-timeout
21771 @cindex @code{timeout}, @acronym{MIPS} protocol
21772 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21773 @kindex set timeout
21774 @kindex show timeout
21775 @kindex set retransmit-timeout
21776 @kindex show retransmit-timeout
21777 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21778 remote protocol, with the @code{set timeout @var{seconds}} command. The
21779 default is 5 seconds. Similarly, you can control the timeout used while
21780 waiting for an acknowledgment of a packet with the @code{set
21781 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21782 You can inspect both values with @code{show timeout} and @code{show
21783 retransmit-timeout}. (These commands are @emph{only} available when
21784 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21786 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21787 is waiting for your program to stop. In that case, @value{GDBN} waits
21788 forever because it has no way of knowing how long the program is going
21789 to run before stopping.
21791 @item set syn-garbage-limit @var{num}
21792 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21793 @cindex synchronize with remote @acronym{MIPS} target
21794 Limit the maximum number of characters @value{GDBN} should ignore when
21795 it tries to synchronize with the remote target. The default is 10
21796 characters. Setting the limit to -1 means there's no limit.
21798 @item show syn-garbage-limit
21799 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21800 Show the current limit on the number of characters to ignore when
21801 trying to synchronize with the remote system.
21803 @item set monitor-prompt @var{prompt}
21804 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21805 @cindex remote monitor prompt
21806 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21807 remote monitor. The default depends on the target:
21817 @item show monitor-prompt
21818 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21819 Show the current strings @value{GDBN} expects as the prompt from the
21822 @item set monitor-warnings
21823 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21824 Enable or disable monitor warnings about hardware breakpoints. This
21825 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21826 display warning messages whose codes are returned by the @code{lsi}
21827 PMON monitor for breakpoint commands.
21829 @item show monitor-warnings
21830 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21831 Show the current setting of printing monitor warnings.
21833 @item pmon @var{command}
21834 @kindex pmon@r{, @acronym{MIPS} remote}
21835 @cindex send PMON command
21836 This command allows sending an arbitrary @var{command} string to the
21837 monitor. The monitor must be in debug mode for this to work.
21840 @node PowerPC Embedded
21841 @subsection PowerPC Embedded
21843 @cindex DVC register
21844 @value{GDBN} supports using the DVC (Data Value Compare) register to
21845 implement in hardware simple hardware watchpoint conditions of the form:
21848 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21849 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21852 The DVC register will be automatically used when @value{GDBN} detects
21853 such pattern in a condition expression, and the created watchpoint uses one
21854 debug register (either the @code{exact-watchpoints} option is on and the
21855 variable is scalar, or the variable has a length of one byte). This feature
21856 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21859 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21860 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21861 in which case watchpoints using only one debug register are created when
21862 watching variables of scalar types.
21864 You can create an artificial array to watch an arbitrary memory
21865 region using one of the following commands (@pxref{Expressions}):
21868 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21869 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21872 PowerPC embedded processors support masked watchpoints. See the discussion
21873 about the @code{mask} argument in @ref{Set Watchpoints}.
21875 @cindex ranged breakpoint
21876 PowerPC embedded processors support hardware accelerated
21877 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21878 the inferior whenever it executes an instruction at any address within
21879 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21880 use the @code{break-range} command.
21882 @value{GDBN} provides the following PowerPC-specific commands:
21885 @kindex break-range
21886 @item break-range @var{start-location}, @var{end-location}
21887 Set a breakpoint for an address range given by
21888 @var{start-location} and @var{end-location}, which can specify a function name,
21889 a line number, an offset of lines from the current line or from the start
21890 location, or an address of an instruction (see @ref{Specify Location},
21891 for a list of all the possible ways to specify a @var{location}.)
21892 The breakpoint will stop execution of the inferior whenever it
21893 executes an instruction at any address within the specified range,
21894 (including @var{start-location} and @var{end-location}.)
21896 @kindex set powerpc
21897 @item set powerpc soft-float
21898 @itemx show powerpc soft-float
21899 Force @value{GDBN} to use (or not use) a software floating point calling
21900 convention. By default, @value{GDBN} selects the calling convention based
21901 on the selected architecture and the provided executable file.
21903 @item set powerpc vector-abi
21904 @itemx show powerpc vector-abi
21905 Force @value{GDBN} to use the specified calling convention for vector
21906 arguments and return values. The valid options are @samp{auto};
21907 @samp{generic}, to avoid vector registers even if they are present;
21908 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21909 registers. By default, @value{GDBN} selects the calling convention
21910 based on the selected architecture and the provided executable file.
21912 @item set powerpc exact-watchpoints
21913 @itemx show powerpc exact-watchpoints
21914 Allow @value{GDBN} to use only one debug register when watching a variable
21915 of scalar type, thus assuming that the variable is accessed through the
21916 address of its first byte.
21921 @subsection Atmel AVR
21924 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21925 following AVR-specific commands:
21928 @item info io_registers
21929 @kindex info io_registers@r{, AVR}
21930 @cindex I/O registers (Atmel AVR)
21931 This command displays information about the AVR I/O registers. For
21932 each register, @value{GDBN} prints its number and value.
21939 When configured for debugging CRIS, @value{GDBN} provides the
21940 following CRIS-specific commands:
21943 @item set cris-version @var{ver}
21944 @cindex CRIS version
21945 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21946 The CRIS version affects register names and sizes. This command is useful in
21947 case autodetection of the CRIS version fails.
21949 @item show cris-version
21950 Show the current CRIS version.
21952 @item set cris-dwarf2-cfi
21953 @cindex DWARF-2 CFI and CRIS
21954 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21955 Change to @samp{off} when using @code{gcc-cris} whose version is below
21958 @item show cris-dwarf2-cfi
21959 Show the current state of using DWARF-2 CFI.
21961 @item set cris-mode @var{mode}
21963 Set the current CRIS mode to @var{mode}. It should only be changed when
21964 debugging in guru mode, in which case it should be set to
21965 @samp{guru} (the default is @samp{normal}).
21967 @item show cris-mode
21968 Show the current CRIS mode.
21972 @subsection Renesas Super-H
21975 For the Renesas Super-H processor, @value{GDBN} provides these
21979 @item set sh calling-convention @var{convention}
21980 @kindex set sh calling-convention
21981 Set the calling-convention used when calling functions from @value{GDBN}.
21982 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21983 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21984 convention. If the DWARF-2 information of the called function specifies
21985 that the function follows the Renesas calling convention, the function
21986 is called using the Renesas calling convention. If the calling convention
21987 is set to @samp{renesas}, the Renesas calling convention is always used,
21988 regardless of the DWARF-2 information. This can be used to override the
21989 default of @samp{gcc} if debug information is missing, or the compiler
21990 does not emit the DWARF-2 calling convention entry for a function.
21992 @item show sh calling-convention
21993 @kindex show sh calling-convention
21994 Show the current calling convention setting.
21999 @node Architectures
22000 @section Architectures
22002 This section describes characteristics of architectures that affect
22003 all uses of @value{GDBN} with the architecture, both native and cross.
22010 * HPPA:: HP PA architecture
22011 * SPU:: Cell Broadband Engine SPU architecture
22017 @subsection AArch64
22018 @cindex AArch64 support
22020 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22021 following special commands:
22024 @item set debug aarch64
22025 @kindex set debug aarch64
22026 This command determines whether AArch64 architecture-specific debugging
22027 messages are to be displayed.
22029 @item show debug aarch64
22030 Show whether AArch64 debugging messages are displayed.
22035 @subsection x86 Architecture-specific Issues
22038 @item set struct-convention @var{mode}
22039 @kindex set struct-convention
22040 @cindex struct return convention
22041 @cindex struct/union returned in registers
22042 Set the convention used by the inferior to return @code{struct}s and
22043 @code{union}s from functions to @var{mode}. Possible values of
22044 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22045 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22046 are returned on the stack, while @code{"reg"} means that a
22047 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22048 be returned in a register.
22050 @item show struct-convention
22051 @kindex show struct-convention
22052 Show the current setting of the convention to return @code{struct}s
22057 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22058 @cindex Intel(R) Memory Protection Extensions (MPX).
22060 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22061 @footnote{The register named with capital letters represent the architecture
22062 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22063 which are the lower bound and upper bound. Bounds are effective addresses or
22064 memory locations. The upper bounds are architecturally represented in 1's
22065 complement form. A bound having lower bound = 0, and upper bound = 0
22066 (1's complement of all bits set) will allow access to the entire address space.
22068 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22069 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22070 display the upper bound performing the complement of one operation on the
22071 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22072 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22073 can also be noted that the upper bounds are inclusive.
22075 As an example, assume that the register BND0 holds bounds for a pointer having
22076 access allowed for the range between 0x32 and 0x71. The values present on
22077 bnd0raw and bnd registers are presented as follows:
22080 bnd0raw = @{0x32, 0xffffffff8e@}
22081 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22084 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22085 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22086 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22087 Python, the display includes the memory size, in bits, accessible to
22090 Bounds can also be stored in bounds tables, which are stored in
22091 application memory. These tables store bounds for pointers by specifying
22092 the bounds pointer's value along with its bounds. Evaluating and changing
22093 bounds located in bound tables is therefore interesting while investigating
22094 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22097 @item show mpx bound @var{pointer}
22098 @kindex show mpx bound
22099 Display bounds of the given @var{pointer}.
22101 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22102 @kindex set mpx bound
22103 Set the bounds of a pointer in the bound table.
22104 This command takes three parameters: @var{pointer} is the pointers
22105 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22106 for lower and upper bounds respectively.
22112 See the following section.
22115 @subsection @acronym{MIPS}
22117 @cindex stack on Alpha
22118 @cindex stack on @acronym{MIPS}
22119 @cindex Alpha stack
22120 @cindex @acronym{MIPS} stack
22121 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22122 sometimes requires @value{GDBN} to search backward in the object code to
22123 find the beginning of a function.
22125 @cindex response time, @acronym{MIPS} debugging
22126 To improve response time (especially for embedded applications, where
22127 @value{GDBN} may be restricted to a slow serial line for this search)
22128 you may want to limit the size of this search, using one of these
22132 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22133 @item set heuristic-fence-post @var{limit}
22134 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22135 search for the beginning of a function. A value of @var{0} (the
22136 default) means there is no limit. However, except for @var{0}, the
22137 larger the limit the more bytes @code{heuristic-fence-post} must search
22138 and therefore the longer it takes to run. You should only need to use
22139 this command when debugging a stripped executable.
22141 @item show heuristic-fence-post
22142 Display the current limit.
22146 These commands are available @emph{only} when @value{GDBN} is configured
22147 for debugging programs on Alpha or @acronym{MIPS} processors.
22149 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22153 @item set mips abi @var{arg}
22154 @kindex set mips abi
22155 @cindex set ABI for @acronym{MIPS}
22156 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22157 values of @var{arg} are:
22161 The default ABI associated with the current binary (this is the
22171 @item show mips abi
22172 @kindex show mips abi
22173 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22175 @item set mips compression @var{arg}
22176 @kindex set mips compression
22177 @cindex code compression, @acronym{MIPS}
22178 Tell @value{GDBN} which @acronym{MIPS} compressed
22179 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22180 inferior. @value{GDBN} uses this for code disassembly and other
22181 internal interpretation purposes. This setting is only referred to
22182 when no executable has been associated with the debugging session or
22183 the executable does not provide information about the encoding it uses.
22184 Otherwise this setting is automatically updated from information
22185 provided by the executable.
22187 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22188 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22189 executables containing @acronym{MIPS16} code frequently are not
22190 identified as such.
22192 This setting is ``sticky''; that is, it retains its value across
22193 debugging sessions until reset either explicitly with this command or
22194 implicitly from an executable.
22196 The compiler and/or assembler typically add symbol table annotations to
22197 identify functions compiled for the @acronym{MIPS16} or
22198 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22199 are present, @value{GDBN} uses them in preference to the global
22200 compressed @acronym{ISA} encoding setting.
22202 @item show mips compression
22203 @kindex show mips compression
22204 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22205 @value{GDBN} to debug the inferior.
22208 @itemx show mipsfpu
22209 @xref{MIPS Embedded, set mipsfpu}.
22211 @item set mips mask-address @var{arg}
22212 @kindex set mips mask-address
22213 @cindex @acronym{MIPS} addresses, masking
22214 This command determines whether the most-significant 32 bits of 64-bit
22215 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22216 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22217 setting, which lets @value{GDBN} determine the correct value.
22219 @item show mips mask-address
22220 @kindex show mips mask-address
22221 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22224 @item set remote-mips64-transfers-32bit-regs
22225 @kindex set remote-mips64-transfers-32bit-regs
22226 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22227 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22228 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22229 and 64 bits for other registers, set this option to @samp{on}.
22231 @item show remote-mips64-transfers-32bit-regs
22232 @kindex show remote-mips64-transfers-32bit-regs
22233 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22235 @item set debug mips
22236 @kindex set debug mips
22237 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22238 target code in @value{GDBN}.
22240 @item show debug mips
22241 @kindex show debug mips
22242 Show the current setting of @acronym{MIPS} debugging messages.
22248 @cindex HPPA support
22250 When @value{GDBN} is debugging the HP PA architecture, it provides the
22251 following special commands:
22254 @item set debug hppa
22255 @kindex set debug hppa
22256 This command determines whether HPPA architecture-specific debugging
22257 messages are to be displayed.
22259 @item show debug hppa
22260 Show whether HPPA debugging messages are displayed.
22262 @item maint print unwind @var{address}
22263 @kindex maint print unwind@r{, HPPA}
22264 This command displays the contents of the unwind table entry at the
22265 given @var{address}.
22271 @subsection Cell Broadband Engine SPU architecture
22272 @cindex Cell Broadband Engine
22275 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22276 it provides the following special commands:
22279 @item info spu event
22281 Display SPU event facility status. Shows current event mask
22282 and pending event status.
22284 @item info spu signal
22285 Display SPU signal notification facility status. Shows pending
22286 signal-control word and signal notification mode of both signal
22287 notification channels.
22289 @item info spu mailbox
22290 Display SPU mailbox facility status. Shows all pending entries,
22291 in order of processing, in each of the SPU Write Outbound,
22292 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22295 Display MFC DMA status. Shows all pending commands in the MFC
22296 DMA queue. For each entry, opcode, tag, class IDs, effective
22297 and local store addresses and transfer size are shown.
22299 @item info spu proxydma
22300 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22301 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22302 and local store addresses and transfer size are shown.
22306 When @value{GDBN} is debugging a combined PowerPC/SPU application
22307 on the Cell Broadband Engine, it provides in addition the following
22311 @item set spu stop-on-load @var{arg}
22313 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22314 will give control to the user when a new SPE thread enters its @code{main}
22315 function. The default is @code{off}.
22317 @item show spu stop-on-load
22319 Show whether to stop for new SPE threads.
22321 @item set spu auto-flush-cache @var{arg}
22322 Set whether to automatically flush the software-managed cache. When set to
22323 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22324 cache to be flushed whenever SPE execution stops. This provides a consistent
22325 view of PowerPC memory that is accessed via the cache. If an application
22326 does not use the software-managed cache, this option has no effect.
22328 @item show spu auto-flush-cache
22329 Show whether to automatically flush the software-managed cache.
22334 @subsection PowerPC
22335 @cindex PowerPC architecture
22337 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22338 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22339 numbers stored in the floating point registers. These values must be stored
22340 in two consecutive registers, always starting at an even register like
22341 @code{f0} or @code{f2}.
22343 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22344 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22345 @code{f2} and @code{f3} for @code{$dl1} and so on.
22347 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22348 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22351 @subsection Nios II
22352 @cindex Nios II architecture
22354 When @value{GDBN} is debugging the Nios II architecture,
22355 it provides the following special commands:
22359 @item set debug nios2
22360 @kindex set debug nios2
22361 This command turns on and off debugging messages for the Nios II
22362 target code in @value{GDBN}.
22364 @item show debug nios2
22365 @kindex show debug nios2
22366 Show the current setting of Nios II debugging messages.
22369 @node Controlling GDB
22370 @chapter Controlling @value{GDBN}
22372 You can alter the way @value{GDBN} interacts with you by using the
22373 @code{set} command. For commands controlling how @value{GDBN} displays
22374 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22379 * Editing:: Command editing
22380 * Command History:: Command history
22381 * Screen Size:: Screen size
22382 * Numbers:: Numbers
22383 * ABI:: Configuring the current ABI
22384 * Auto-loading:: Automatically loading associated files
22385 * Messages/Warnings:: Optional warnings and messages
22386 * Debugging Output:: Optional messages about internal happenings
22387 * Other Misc Settings:: Other Miscellaneous Settings
22395 @value{GDBN} indicates its readiness to read a command by printing a string
22396 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22397 can change the prompt string with the @code{set prompt} command. For
22398 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22399 the prompt in one of the @value{GDBN} sessions so that you can always tell
22400 which one you are talking to.
22402 @emph{Note:} @code{set prompt} does not add a space for you after the
22403 prompt you set. This allows you to set a prompt which ends in a space
22404 or a prompt that does not.
22408 @item set prompt @var{newprompt}
22409 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22411 @kindex show prompt
22413 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22416 Versions of @value{GDBN} that ship with Python scripting enabled have
22417 prompt extensions. The commands for interacting with these extensions
22421 @kindex set extended-prompt
22422 @item set extended-prompt @var{prompt}
22423 Set an extended prompt that allows for substitutions.
22424 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22425 substitution. Any escape sequences specified as part of the prompt
22426 string are replaced with the corresponding strings each time the prompt
22432 set extended-prompt Current working directory: \w (gdb)
22435 Note that when an extended-prompt is set, it takes control of the
22436 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22438 @kindex show extended-prompt
22439 @item show extended-prompt
22440 Prints the extended prompt. Any escape sequences specified as part of
22441 the prompt string with @code{set extended-prompt}, are replaced with the
22442 corresponding strings each time the prompt is displayed.
22446 @section Command Editing
22448 @cindex command line editing
22450 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22451 @sc{gnu} library provides consistent behavior for programs which provide a
22452 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22453 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22454 substitution, and a storage and recall of command history across
22455 debugging sessions.
22457 You may control the behavior of command line editing in @value{GDBN} with the
22458 command @code{set}.
22461 @kindex set editing
22464 @itemx set editing on
22465 Enable command line editing (enabled by default).
22467 @item set editing off
22468 Disable command line editing.
22470 @kindex show editing
22472 Show whether command line editing is enabled.
22475 @ifset SYSTEM_READLINE
22476 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22478 @ifclear SYSTEM_READLINE
22479 @xref{Command Line Editing},
22481 for more details about the Readline
22482 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22483 encouraged to read that chapter.
22485 @node Command History
22486 @section Command History
22487 @cindex command history
22489 @value{GDBN} can keep track of the commands you type during your
22490 debugging sessions, so that you can be certain of precisely what
22491 happened. Use these commands to manage the @value{GDBN} command
22494 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22495 package, to provide the history facility.
22496 @ifset SYSTEM_READLINE
22497 @xref{Using History Interactively, , , history, GNU History Library},
22499 @ifclear SYSTEM_READLINE
22500 @xref{Using History Interactively},
22502 for the detailed description of the History library.
22504 To issue a command to @value{GDBN} without affecting certain aspects of
22505 the state which is seen by users, prefix it with @samp{server }
22506 (@pxref{Server Prefix}). This
22507 means that this command will not affect the command history, nor will it
22508 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22509 pressed on a line by itself.
22511 @cindex @code{server}, command prefix
22512 The server prefix does not affect the recording of values into the value
22513 history; to print a value without recording it into the value history,
22514 use the @code{output} command instead of the @code{print} command.
22516 Here is the description of @value{GDBN} commands related to command
22520 @cindex history substitution
22521 @cindex history file
22522 @kindex set history filename
22523 @cindex @env{GDBHISTFILE}, environment variable
22524 @item set history filename @var{fname}
22525 Set the name of the @value{GDBN} command history file to @var{fname}.
22526 This is the file where @value{GDBN} reads an initial command history
22527 list, and where it writes the command history from this session when it
22528 exits. You can access this list through history expansion or through
22529 the history command editing characters listed below. This file defaults
22530 to the value of the environment variable @code{GDBHISTFILE}, or to
22531 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22534 @cindex save command history
22535 @kindex set history save
22536 @item set history save
22537 @itemx set history save on
22538 Record command history in a file, whose name may be specified with the
22539 @code{set history filename} command. By default, this option is disabled.
22541 @item set history save off
22542 Stop recording command history in a file.
22544 @cindex history size
22545 @kindex set history size
22546 @cindex @env{GDBHISTSIZE}, environment variable
22547 @item set history size @var{size}
22548 @itemx set history size unlimited
22549 Set the number of commands which @value{GDBN} keeps in its history list.
22550 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22551 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22552 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22553 either a negative number or the empty string, then the number of commands
22554 @value{GDBN} keeps in the history list is unlimited.
22556 @cindex remove duplicate history
22557 @kindex set history remove-duplicates
22558 @item set history remove-duplicates @var{count}
22559 @itemx set history remove-duplicates unlimited
22560 Control the removal of duplicate history entries in the command history list.
22561 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22562 history entries and remove the first entry that is a duplicate of the current
22563 entry being added to the command history list. If @var{count} is
22564 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22565 removal of duplicate history entries is disabled.
22567 Only history entries added during the current session are considered for
22568 removal. This option is set to 0 by default.
22572 History expansion assigns special meaning to the character @kbd{!}.
22573 @ifset SYSTEM_READLINE
22574 @xref{Event Designators, , , history, GNU History Library},
22576 @ifclear SYSTEM_READLINE
22577 @xref{Event Designators},
22581 @cindex history expansion, turn on/off
22582 Since @kbd{!} is also the logical not operator in C, history expansion
22583 is off by default. If you decide to enable history expansion with the
22584 @code{set history expansion on} command, you may sometimes need to
22585 follow @kbd{!} (when it is used as logical not, in an expression) with
22586 a space or a tab to prevent it from being expanded. The readline
22587 history facilities do not attempt substitution on the strings
22588 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22590 The commands to control history expansion are:
22593 @item set history expansion on
22594 @itemx set history expansion
22595 @kindex set history expansion
22596 Enable history expansion. History expansion is off by default.
22598 @item set history expansion off
22599 Disable history expansion.
22602 @kindex show history
22604 @itemx show history filename
22605 @itemx show history save
22606 @itemx show history size
22607 @itemx show history expansion
22608 These commands display the state of the @value{GDBN} history parameters.
22609 @code{show history} by itself displays all four states.
22614 @kindex show commands
22615 @cindex show last commands
22616 @cindex display command history
22617 @item show commands
22618 Display the last ten commands in the command history.
22620 @item show commands @var{n}
22621 Print ten commands centered on command number @var{n}.
22623 @item show commands +
22624 Print ten commands just after the commands last printed.
22628 @section Screen Size
22629 @cindex size of screen
22630 @cindex screen size
22633 @cindex pauses in output
22635 Certain commands to @value{GDBN} may produce large amounts of
22636 information output to the screen. To help you read all of it,
22637 @value{GDBN} pauses and asks you for input at the end of each page of
22638 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22639 to discard the remaining output. Also, the screen width setting
22640 determines when to wrap lines of output. Depending on what is being
22641 printed, @value{GDBN} tries to break the line at a readable place,
22642 rather than simply letting it overflow onto the following line.
22644 Normally @value{GDBN} knows the size of the screen from the terminal
22645 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22646 together with the value of the @code{TERM} environment variable and the
22647 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22648 you can override it with the @code{set height} and @code{set
22655 @kindex show height
22656 @item set height @var{lpp}
22657 @itemx set height unlimited
22659 @itemx set width @var{cpl}
22660 @itemx set width unlimited
22662 These @code{set} commands specify a screen height of @var{lpp} lines and
22663 a screen width of @var{cpl} characters. The associated @code{show}
22664 commands display the current settings.
22666 If you specify a height of either @code{unlimited} or zero lines,
22667 @value{GDBN} does not pause during output no matter how long the
22668 output is. This is useful if output is to a file or to an editor
22671 Likewise, you can specify @samp{set width unlimited} or @samp{set
22672 width 0} to prevent @value{GDBN} from wrapping its output.
22674 @item set pagination on
22675 @itemx set pagination off
22676 @kindex set pagination
22677 Turn the output pagination on or off; the default is on. Turning
22678 pagination off is the alternative to @code{set height unlimited}. Note that
22679 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22680 Options, -batch}) also automatically disables pagination.
22682 @item show pagination
22683 @kindex show pagination
22684 Show the current pagination mode.
22689 @cindex number representation
22690 @cindex entering numbers
22692 You can always enter numbers in octal, decimal, or hexadecimal in
22693 @value{GDBN} by the usual conventions: octal numbers begin with
22694 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22695 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22696 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22697 10; likewise, the default display for numbers---when no particular
22698 format is specified---is base 10. You can change the default base for
22699 both input and output with the commands described below.
22702 @kindex set input-radix
22703 @item set input-radix @var{base}
22704 Set the default base for numeric input. Supported choices
22705 for @var{base} are decimal 8, 10, or 16. The base must itself be
22706 specified either unambiguously or using the current input radix; for
22710 set input-radix 012
22711 set input-radix 10.
22712 set input-radix 0xa
22716 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22717 leaves the input radix unchanged, no matter what it was, since
22718 @samp{10}, being without any leading or trailing signs of its base, is
22719 interpreted in the current radix. Thus, if the current radix is 16,
22720 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22723 @kindex set output-radix
22724 @item set output-radix @var{base}
22725 Set the default base for numeric display. Supported choices
22726 for @var{base} are decimal 8, 10, or 16. The base must itself be
22727 specified either unambiguously or using the current input radix.
22729 @kindex show input-radix
22730 @item show input-radix
22731 Display the current default base for numeric input.
22733 @kindex show output-radix
22734 @item show output-radix
22735 Display the current default base for numeric display.
22737 @item set radix @r{[}@var{base}@r{]}
22741 These commands set and show the default base for both input and output
22742 of numbers. @code{set radix} sets the radix of input and output to
22743 the same base; without an argument, it resets the radix back to its
22744 default value of 10.
22749 @section Configuring the Current ABI
22751 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22752 application automatically. However, sometimes you need to override its
22753 conclusions. Use these commands to manage @value{GDBN}'s view of the
22759 @cindex Newlib OS ABI and its influence on the longjmp handling
22761 One @value{GDBN} configuration can debug binaries for multiple operating
22762 system targets, either via remote debugging or native emulation.
22763 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22764 but you can override its conclusion using the @code{set osabi} command.
22765 One example where this is useful is in debugging of binaries which use
22766 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22767 not have the same identifying marks that the standard C library for your
22770 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22771 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22772 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22773 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22777 Show the OS ABI currently in use.
22780 With no argument, show the list of registered available OS ABI's.
22782 @item set osabi @var{abi}
22783 Set the current OS ABI to @var{abi}.
22786 @cindex float promotion
22788 Generally, the way that an argument of type @code{float} is passed to a
22789 function depends on whether the function is prototyped. For a prototyped
22790 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22791 according to the architecture's convention for @code{float}. For unprototyped
22792 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22793 @code{double} and then passed.
22795 Unfortunately, some forms of debug information do not reliably indicate whether
22796 a function is prototyped. If @value{GDBN} calls a function that is not marked
22797 as prototyped, it consults @kbd{set coerce-float-to-double}.
22800 @kindex set coerce-float-to-double
22801 @item set coerce-float-to-double
22802 @itemx set coerce-float-to-double on
22803 Arguments of type @code{float} will be promoted to @code{double} when passed
22804 to an unprototyped function. This is the default setting.
22806 @item set coerce-float-to-double off
22807 Arguments of type @code{float} will be passed directly to unprototyped
22810 @kindex show coerce-float-to-double
22811 @item show coerce-float-to-double
22812 Show the current setting of promoting @code{float} to @code{double}.
22816 @kindex show cp-abi
22817 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22818 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22819 used to build your application. @value{GDBN} only fully supports
22820 programs with a single C@t{++} ABI; if your program contains code using
22821 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22822 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22823 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22824 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22825 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22826 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22831 Show the C@t{++} ABI currently in use.
22834 With no argument, show the list of supported C@t{++} ABI's.
22836 @item set cp-abi @var{abi}
22837 @itemx set cp-abi auto
22838 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22842 @section Automatically loading associated files
22843 @cindex auto-loading
22845 @value{GDBN} sometimes reads files with commands and settings automatically,
22846 without being explicitly told so by the user. We call this feature
22847 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22848 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22849 results or introduce security risks (e.g., if the file comes from untrusted
22853 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22854 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22856 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22857 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22860 There are various kinds of files @value{GDBN} can automatically load.
22861 In addition to these files, @value{GDBN} supports auto-loading code written
22862 in various extension languages. @xref{Auto-loading extensions}.
22864 Note that loading of these associated files (including the local @file{.gdbinit}
22865 file) requires accordingly configured @code{auto-load safe-path}
22866 (@pxref{Auto-loading safe path}).
22868 For these reasons, @value{GDBN} includes commands and options to let you
22869 control when to auto-load files and which files should be auto-loaded.
22872 @anchor{set auto-load off}
22873 @kindex set auto-load off
22874 @item set auto-load off
22875 Globally disable loading of all auto-loaded files.
22876 You may want to use this command with the @samp{-iex} option
22877 (@pxref{Option -init-eval-command}) such as:
22879 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22882 Be aware that system init file (@pxref{System-wide configuration})
22883 and init files from your home directory (@pxref{Home Directory Init File})
22884 still get read (as they come from generally trusted directories).
22885 To prevent @value{GDBN} from auto-loading even those init files, use the
22886 @option{-nx} option (@pxref{Mode Options}), in addition to
22887 @code{set auto-load no}.
22889 @anchor{show auto-load}
22890 @kindex show auto-load
22891 @item show auto-load
22892 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22896 (gdb) show auto-load
22897 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22898 libthread-db: Auto-loading of inferior specific libthread_db is on.
22899 local-gdbinit: Auto-loading of .gdbinit script from current directory
22901 python-scripts: Auto-loading of Python scripts is on.
22902 safe-path: List of directories from which it is safe to auto-load files
22903 is $debugdir:$datadir/auto-load.
22904 scripts-directory: List of directories from which to load auto-loaded scripts
22905 is $debugdir:$datadir/auto-load.
22908 @anchor{info auto-load}
22909 @kindex info auto-load
22910 @item info auto-load
22911 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22915 (gdb) info auto-load
22918 Yes /home/user/gdb/gdb-gdb.gdb
22919 libthread-db: No auto-loaded libthread-db.
22920 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22924 Yes /home/user/gdb/gdb-gdb.py
22928 These are @value{GDBN} control commands for the auto-loading:
22930 @multitable @columnfractions .5 .5
22931 @item @xref{set auto-load off}.
22932 @tab Disable auto-loading globally.
22933 @item @xref{show auto-load}.
22934 @tab Show setting of all kinds of files.
22935 @item @xref{info auto-load}.
22936 @tab Show state of all kinds of files.
22937 @item @xref{set auto-load gdb-scripts}.
22938 @tab Control for @value{GDBN} command scripts.
22939 @item @xref{show auto-load gdb-scripts}.
22940 @tab Show setting of @value{GDBN} command scripts.
22941 @item @xref{info auto-load gdb-scripts}.
22942 @tab Show state of @value{GDBN} command scripts.
22943 @item @xref{set auto-load python-scripts}.
22944 @tab Control for @value{GDBN} Python scripts.
22945 @item @xref{show auto-load python-scripts}.
22946 @tab Show setting of @value{GDBN} Python scripts.
22947 @item @xref{info auto-load python-scripts}.
22948 @tab Show state of @value{GDBN} Python scripts.
22949 @item @xref{set auto-load guile-scripts}.
22950 @tab Control for @value{GDBN} Guile scripts.
22951 @item @xref{show auto-load guile-scripts}.
22952 @tab Show setting of @value{GDBN} Guile scripts.
22953 @item @xref{info auto-load guile-scripts}.
22954 @tab Show state of @value{GDBN} Guile scripts.
22955 @item @xref{set auto-load scripts-directory}.
22956 @tab Control for @value{GDBN} auto-loaded scripts location.
22957 @item @xref{show auto-load scripts-directory}.
22958 @tab Show @value{GDBN} auto-loaded scripts location.
22959 @item @xref{add-auto-load-scripts-directory}.
22960 @tab Add directory for auto-loaded scripts location list.
22961 @item @xref{set auto-load local-gdbinit}.
22962 @tab Control for init file in the current directory.
22963 @item @xref{show auto-load local-gdbinit}.
22964 @tab Show setting of init file in the current directory.
22965 @item @xref{info auto-load local-gdbinit}.
22966 @tab Show state of init file in the current directory.
22967 @item @xref{set auto-load libthread-db}.
22968 @tab Control for thread debugging library.
22969 @item @xref{show auto-load libthread-db}.
22970 @tab Show setting of thread debugging library.
22971 @item @xref{info auto-load libthread-db}.
22972 @tab Show state of thread debugging library.
22973 @item @xref{set auto-load safe-path}.
22974 @tab Control directories trusted for automatic loading.
22975 @item @xref{show auto-load safe-path}.
22976 @tab Show directories trusted for automatic loading.
22977 @item @xref{add-auto-load-safe-path}.
22978 @tab Add directory trusted for automatic loading.
22981 @node Init File in the Current Directory
22982 @subsection Automatically loading init file in the current directory
22983 @cindex auto-loading init file in the current directory
22985 By default, @value{GDBN} reads and executes the canned sequences of commands
22986 from init file (if any) in the current working directory,
22987 see @ref{Init File in the Current Directory during Startup}.
22989 Note that loading of this local @file{.gdbinit} file also requires accordingly
22990 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22993 @anchor{set auto-load local-gdbinit}
22994 @kindex set auto-load local-gdbinit
22995 @item set auto-load local-gdbinit [on|off]
22996 Enable or disable the auto-loading of canned sequences of commands
22997 (@pxref{Sequences}) found in init file in the current directory.
22999 @anchor{show auto-load local-gdbinit}
23000 @kindex show auto-load local-gdbinit
23001 @item show auto-load local-gdbinit
23002 Show whether auto-loading of canned sequences of commands from init file in the
23003 current directory is enabled or disabled.
23005 @anchor{info auto-load local-gdbinit}
23006 @kindex info auto-load local-gdbinit
23007 @item info auto-load local-gdbinit
23008 Print whether canned sequences of commands from init file in the
23009 current directory have been auto-loaded.
23012 @node libthread_db.so.1 file
23013 @subsection Automatically loading thread debugging library
23014 @cindex auto-loading libthread_db.so.1
23016 This feature is currently present only on @sc{gnu}/Linux native hosts.
23018 @value{GDBN} reads in some cases thread debugging library from places specific
23019 to the inferior (@pxref{set libthread-db-search-path}).
23021 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23022 without checking this @samp{set auto-load libthread-db} switch as system
23023 libraries have to be trusted in general. In all other cases of
23024 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23025 auto-load libthread-db} is enabled before trying to open such thread debugging
23028 Note that loading of this debugging library also requires accordingly configured
23029 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23032 @anchor{set auto-load libthread-db}
23033 @kindex set auto-load libthread-db
23034 @item set auto-load libthread-db [on|off]
23035 Enable or disable the auto-loading of inferior specific thread debugging library.
23037 @anchor{show auto-load libthread-db}
23038 @kindex show auto-load libthread-db
23039 @item show auto-load libthread-db
23040 Show whether auto-loading of inferior specific thread debugging library is
23041 enabled or disabled.
23043 @anchor{info auto-load libthread-db}
23044 @kindex info auto-load libthread-db
23045 @item info auto-load libthread-db
23046 Print the list of all loaded inferior specific thread debugging libraries and
23047 for each such library print list of inferior @var{pid}s using it.
23050 @node Auto-loading safe path
23051 @subsection Security restriction for auto-loading
23052 @cindex auto-loading safe-path
23054 As the files of inferior can come from untrusted source (such as submitted by
23055 an application user) @value{GDBN} does not always load any files automatically.
23056 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23057 directories trusted for loading files not explicitly requested by user.
23058 Each directory can also be a shell wildcard pattern.
23060 If the path is not set properly you will see a warning and the file will not
23065 Reading symbols from /home/user/gdb/gdb...done.
23066 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23067 declined by your `auto-load safe-path' set
23068 to "$debugdir:$datadir/auto-load".
23069 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23070 declined by your `auto-load safe-path' set
23071 to "$debugdir:$datadir/auto-load".
23075 To instruct @value{GDBN} to go ahead and use the init files anyway,
23076 invoke @value{GDBN} like this:
23079 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23082 The list of trusted directories is controlled by the following commands:
23085 @anchor{set auto-load safe-path}
23086 @kindex set auto-load safe-path
23087 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23088 Set the list of directories (and their subdirectories) trusted for automatic
23089 loading and execution of scripts. You can also enter a specific trusted file.
23090 Each directory can also be a shell wildcard pattern; wildcards do not match
23091 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23092 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23093 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23094 its default value as specified during @value{GDBN} compilation.
23096 The list of directories uses path separator (@samp{:} on GNU and Unix
23097 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23098 to the @env{PATH} environment variable.
23100 @anchor{show auto-load safe-path}
23101 @kindex show auto-load safe-path
23102 @item show auto-load safe-path
23103 Show the list of directories trusted for automatic loading and execution of
23106 @anchor{add-auto-load-safe-path}
23107 @kindex add-auto-load-safe-path
23108 @item add-auto-load-safe-path
23109 Add an entry (or list of entries) to the list of directories trusted for
23110 automatic loading and execution of scripts. Multiple entries may be delimited
23111 by the host platform path separator in use.
23114 This variable defaults to what @code{--with-auto-load-dir} has been configured
23115 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23116 substitution applies the same as for @ref{set auto-load scripts-directory}.
23117 The default @code{set auto-load safe-path} value can be also overriden by
23118 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23120 Setting this variable to @file{/} disables this security protection,
23121 corresponding @value{GDBN} configuration option is
23122 @option{--without-auto-load-safe-path}.
23123 This variable is supposed to be set to the system directories writable by the
23124 system superuser only. Users can add their source directories in init files in
23125 their home directories (@pxref{Home Directory Init File}). See also deprecated
23126 init file in the current directory
23127 (@pxref{Init File in the Current Directory during Startup}).
23129 To force @value{GDBN} to load the files it declined to load in the previous
23130 example, you could use one of the following ways:
23133 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23134 Specify this trusted directory (or a file) as additional component of the list.
23135 You have to specify also any existing directories displayed by
23136 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23138 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23139 Specify this directory as in the previous case but just for a single
23140 @value{GDBN} session.
23142 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23143 Disable auto-loading safety for a single @value{GDBN} session.
23144 This assumes all the files you debug during this @value{GDBN} session will come
23145 from trusted sources.
23147 @item @kbd{./configure --without-auto-load-safe-path}
23148 During compilation of @value{GDBN} you may disable any auto-loading safety.
23149 This assumes all the files you will ever debug with this @value{GDBN} come from
23153 On the other hand you can also explicitly forbid automatic files loading which
23154 also suppresses any such warning messages:
23157 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23158 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23160 @item @file{~/.gdbinit}: @samp{set auto-load no}
23161 Disable auto-loading globally for the user
23162 (@pxref{Home Directory Init File}). While it is improbable, you could also
23163 use system init file instead (@pxref{System-wide configuration}).
23166 This setting applies to the file names as entered by user. If no entry matches
23167 @value{GDBN} tries as a last resort to also resolve all the file names into
23168 their canonical form (typically resolving symbolic links) and compare the
23169 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23170 own before starting the comparison so a canonical form of directories is
23171 recommended to be entered.
23173 @node Auto-loading verbose mode
23174 @subsection Displaying files tried for auto-load
23175 @cindex auto-loading verbose mode
23177 For better visibility of all the file locations where you can place scripts to
23178 be auto-loaded with inferior --- or to protect yourself against accidental
23179 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23180 all the files attempted to be loaded. Both existing and non-existing files may
23183 For example the list of directories from which it is safe to auto-load files
23184 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23185 may not be too obvious while setting it up.
23188 (gdb) set debug auto-load on
23189 (gdb) file ~/src/t/true
23190 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23191 for objfile "/tmp/true".
23192 auto-load: Updating directories of "/usr:/opt".
23193 auto-load: Using directory "/usr".
23194 auto-load: Using directory "/opt".
23195 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23196 by your `auto-load safe-path' set to "/usr:/opt".
23200 @anchor{set debug auto-load}
23201 @kindex set debug auto-load
23202 @item set debug auto-load [on|off]
23203 Set whether to print the filenames attempted to be auto-loaded.
23205 @anchor{show debug auto-load}
23206 @kindex show debug auto-load
23207 @item show debug auto-load
23208 Show whether printing of the filenames attempted to be auto-loaded is turned
23212 @node Messages/Warnings
23213 @section Optional Warnings and Messages
23215 @cindex verbose operation
23216 @cindex optional warnings
23217 By default, @value{GDBN} is silent about its inner workings. If you are
23218 running on a slow machine, you may want to use the @code{set verbose}
23219 command. This makes @value{GDBN} tell you when it does a lengthy
23220 internal operation, so you will not think it has crashed.
23222 Currently, the messages controlled by @code{set verbose} are those
23223 which announce that the symbol table for a source file is being read;
23224 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23227 @kindex set verbose
23228 @item set verbose on
23229 Enables @value{GDBN} output of certain informational messages.
23231 @item set verbose off
23232 Disables @value{GDBN} output of certain informational messages.
23234 @kindex show verbose
23236 Displays whether @code{set verbose} is on or off.
23239 By default, if @value{GDBN} encounters bugs in the symbol table of an
23240 object file, it is silent; but if you are debugging a compiler, you may
23241 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23246 @kindex set complaints
23247 @item set complaints @var{limit}
23248 Permits @value{GDBN} to output @var{limit} complaints about each type of
23249 unusual symbols before becoming silent about the problem. Set
23250 @var{limit} to zero to suppress all complaints; set it to a large number
23251 to prevent complaints from being suppressed.
23253 @kindex show complaints
23254 @item show complaints
23255 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23259 @anchor{confirmation requests}
23260 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23261 lot of stupid questions to confirm certain commands. For example, if
23262 you try to run a program which is already running:
23266 The program being debugged has been started already.
23267 Start it from the beginning? (y or n)
23270 If you are willing to unflinchingly face the consequences of your own
23271 commands, you can disable this ``feature'':
23275 @kindex set confirm
23277 @cindex confirmation
23278 @cindex stupid questions
23279 @item set confirm off
23280 Disables confirmation requests. Note that running @value{GDBN} with
23281 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23282 automatically disables confirmation requests.
23284 @item set confirm on
23285 Enables confirmation requests (the default).
23287 @kindex show confirm
23289 Displays state of confirmation requests.
23293 @cindex command tracing
23294 If you need to debug user-defined commands or sourced files you may find it
23295 useful to enable @dfn{command tracing}. In this mode each command will be
23296 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23297 quantity denoting the call depth of each command.
23300 @kindex set trace-commands
23301 @cindex command scripts, debugging
23302 @item set trace-commands on
23303 Enable command tracing.
23304 @item set trace-commands off
23305 Disable command tracing.
23306 @item show trace-commands
23307 Display the current state of command tracing.
23310 @node Debugging Output
23311 @section Optional Messages about Internal Happenings
23312 @cindex optional debugging messages
23314 @value{GDBN} has commands that enable optional debugging messages from
23315 various @value{GDBN} subsystems; normally these commands are of
23316 interest to @value{GDBN} maintainers, or when reporting a bug. This
23317 section documents those commands.
23320 @kindex set exec-done-display
23321 @item set exec-done-display
23322 Turns on or off the notification of asynchronous commands'
23323 completion. When on, @value{GDBN} will print a message when an
23324 asynchronous command finishes its execution. The default is off.
23325 @kindex show exec-done-display
23326 @item show exec-done-display
23327 Displays the current setting of asynchronous command completion
23330 @cindex ARM AArch64
23331 @item set debug aarch64
23332 Turns on or off display of debugging messages related to ARM AArch64.
23333 The default is off.
23335 @item show debug aarch64
23336 Displays the current state of displaying debugging messages related to
23338 @cindex gdbarch debugging info
23339 @cindex architecture debugging info
23340 @item set debug arch
23341 Turns on or off display of gdbarch debugging info. The default is off
23342 @item show debug arch
23343 Displays the current state of displaying gdbarch debugging info.
23344 @item set debug aix-solib
23345 @cindex AIX shared library debugging
23346 Control display of debugging messages from the AIX shared library
23347 support module. The default is off.
23348 @item show debug aix-thread
23349 Show the current state of displaying AIX shared library debugging messages.
23350 @item set debug aix-thread
23351 @cindex AIX threads
23352 Display debugging messages about inner workings of the AIX thread
23354 @item show debug aix-thread
23355 Show the current state of AIX thread debugging info display.
23356 @item set debug check-physname
23358 Check the results of the ``physname'' computation. When reading DWARF
23359 debugging information for C@t{++}, @value{GDBN} attempts to compute
23360 each entity's name. @value{GDBN} can do this computation in two
23361 different ways, depending on exactly what information is present.
23362 When enabled, this setting causes @value{GDBN} to compute the names
23363 both ways and display any discrepancies.
23364 @item show debug check-physname
23365 Show the current state of ``physname'' checking.
23366 @item set debug coff-pe-read
23367 @cindex COFF/PE exported symbols
23368 Control display of debugging messages related to reading of COFF/PE
23369 exported symbols. The default is off.
23370 @item show debug coff-pe-read
23371 Displays the current state of displaying debugging messages related to
23372 reading of COFF/PE exported symbols.
23373 @item set debug dwarf-die
23375 Dump DWARF DIEs after they are read in.
23376 The value is the number of nesting levels to print.
23377 A value of zero turns off the display.
23378 @item show debug dwarf-die
23379 Show the current state of DWARF DIE debugging.
23380 @item set debug dwarf-line
23381 @cindex DWARF Line Tables
23382 Turns on or off display of debugging messages related to reading
23383 DWARF line tables. The default is 0 (off).
23384 A value of 1 provides basic information.
23385 A value greater than 1 provides more verbose information.
23386 @item show debug dwarf-line
23387 Show the current state of DWARF line table debugging.
23388 @item set debug dwarf-read
23389 @cindex DWARF Reading
23390 Turns on or off display of debugging messages related to reading
23391 DWARF debug info. The default is 0 (off).
23392 A value of 1 provides basic information.
23393 A value greater than 1 provides more verbose information.
23394 @item show debug dwarf-read
23395 Show the current state of DWARF reader debugging.
23396 @item set debug displaced
23397 @cindex displaced stepping debugging info
23398 Turns on or off display of @value{GDBN} debugging info for the
23399 displaced stepping support. The default is off.
23400 @item show debug displaced
23401 Displays the current state of displaying @value{GDBN} debugging info
23402 related to displaced stepping.
23403 @item set debug event
23404 @cindex event debugging info
23405 Turns on or off display of @value{GDBN} event debugging info. The
23407 @item show debug event
23408 Displays the current state of displaying @value{GDBN} event debugging
23410 @item set debug expression
23411 @cindex expression debugging info
23412 Turns on or off display of debugging info about @value{GDBN}
23413 expression parsing. The default is off.
23414 @item show debug expression
23415 Displays the current state of displaying debugging info about
23416 @value{GDBN} expression parsing.
23417 @item set debug frame
23418 @cindex frame debugging info
23419 Turns on or off display of @value{GDBN} frame debugging info. The
23421 @item show debug frame
23422 Displays the current state of displaying @value{GDBN} frame debugging
23424 @item set debug gnu-nat
23425 @cindex @sc{gnu}/Hurd debug messages
23426 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23427 @item show debug gnu-nat
23428 Show the current state of @sc{gnu}/Hurd debugging messages.
23429 @item set debug infrun
23430 @cindex inferior debugging info
23431 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23432 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23433 for implementing operations such as single-stepping the inferior.
23434 @item show debug infrun
23435 Displays the current state of @value{GDBN} inferior debugging.
23436 @item set debug jit
23437 @cindex just-in-time compilation, debugging messages
23438 Turns on or off debugging messages from JIT debug support.
23439 @item show debug jit
23440 Displays the current state of @value{GDBN} JIT debugging.
23441 @item set debug lin-lwp
23442 @cindex @sc{gnu}/Linux LWP debug messages
23443 @cindex Linux lightweight processes
23444 Turns on or off debugging messages from the Linux LWP debug support.
23445 @item show debug lin-lwp
23446 Show the current state of Linux LWP debugging messages.
23447 @item set debug linux-namespaces
23448 @cindex @sc{gnu}/Linux namespaces debug messages
23449 Turns on or off debugging messages from the Linux namespaces debug support.
23450 @item show debug linux-namespaces
23451 Show the current state of Linux namespaces debugging messages.
23452 @item set debug mach-o
23453 @cindex Mach-O symbols processing
23454 Control display of debugging messages related to Mach-O symbols
23455 processing. The default is off.
23456 @item show debug mach-o
23457 Displays the current state of displaying debugging messages related to
23458 reading of COFF/PE exported symbols.
23459 @item set debug notification
23460 @cindex remote async notification debugging info
23461 Turns on or off debugging messages about remote async notification.
23462 The default is off.
23463 @item show debug notification
23464 Displays the current state of remote async notification debugging messages.
23465 @item set debug observer
23466 @cindex observer debugging info
23467 Turns on or off display of @value{GDBN} observer debugging. This
23468 includes info such as the notification of observable events.
23469 @item show debug observer
23470 Displays the current state of observer debugging.
23471 @item set debug overload
23472 @cindex C@t{++} overload debugging info
23473 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23474 info. This includes info such as ranking of functions, etc. The default
23476 @item show debug overload
23477 Displays the current state of displaying @value{GDBN} C@t{++} overload
23479 @cindex expression parser, debugging info
23480 @cindex debug expression parser
23481 @item set debug parser
23482 Turns on or off the display of expression parser debugging output.
23483 Internally, this sets the @code{yydebug} variable in the expression
23484 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23485 details. The default is off.
23486 @item show debug parser
23487 Show the current state of expression parser debugging.
23488 @cindex packets, reporting on stdout
23489 @cindex serial connections, debugging
23490 @cindex debug remote protocol
23491 @cindex remote protocol debugging
23492 @cindex display remote packets
23493 @item set debug remote
23494 Turns on or off display of reports on all packets sent back and forth across
23495 the serial line to the remote machine. The info is printed on the
23496 @value{GDBN} standard output stream. The default is off.
23497 @item show debug remote
23498 Displays the state of display of remote packets.
23499 @item set debug serial
23500 Turns on or off display of @value{GDBN} serial debugging info. The
23502 @item show debug serial
23503 Displays the current state of displaying @value{GDBN} serial debugging
23505 @item set debug solib-frv
23506 @cindex FR-V shared-library debugging
23507 Turns on or off debugging messages for FR-V shared-library code.
23508 @item show debug solib-frv
23509 Display the current state of FR-V shared-library code debugging
23511 @item set debug symbol-lookup
23512 @cindex symbol lookup
23513 Turns on or off display of debugging messages related to symbol lookup.
23514 The default is 0 (off).
23515 A value of 1 provides basic information.
23516 A value greater than 1 provides more verbose information.
23517 @item show debug symbol-lookup
23518 Show the current state of symbol lookup debugging messages.
23519 @item set debug symfile
23520 @cindex symbol file functions
23521 Turns on or off display of debugging messages related to symbol file functions.
23522 The default is off. @xref{Files}.
23523 @item show debug symfile
23524 Show the current state of symbol file debugging messages.
23525 @item set debug symtab-create
23526 @cindex symbol table creation
23527 Turns on or off display of debugging messages related to symbol table creation.
23528 The default is 0 (off).
23529 A value of 1 provides basic information.
23530 A value greater than 1 provides more verbose information.
23531 @item show debug symtab-create
23532 Show the current state of symbol table creation debugging.
23533 @item set debug target
23534 @cindex target debugging info
23535 Turns on or off display of @value{GDBN} target debugging info. This info
23536 includes what is going on at the target level of GDB, as it happens. The
23537 default is 0. Set it to 1 to track events, and to 2 to also track the
23538 value of large memory transfers.
23539 @item show debug target
23540 Displays the current state of displaying @value{GDBN} target debugging
23542 @item set debug timestamp
23543 @cindex timestampping debugging info
23544 Turns on or off display of timestamps with @value{GDBN} debugging info.
23545 When enabled, seconds and microseconds are displayed before each debugging
23547 @item show debug timestamp
23548 Displays the current state of displaying timestamps with @value{GDBN}
23550 @item set debug varobj
23551 @cindex variable object debugging info
23552 Turns on or off display of @value{GDBN} variable object debugging
23553 info. The default is off.
23554 @item show debug varobj
23555 Displays the current state of displaying @value{GDBN} variable object
23557 @item set debug xml
23558 @cindex XML parser debugging
23559 Turns on or off debugging messages for built-in XML parsers.
23560 @item show debug xml
23561 Displays the current state of XML debugging messages.
23564 @node Other Misc Settings
23565 @section Other Miscellaneous Settings
23566 @cindex miscellaneous settings
23569 @kindex set interactive-mode
23570 @item set interactive-mode
23571 If @code{on}, forces @value{GDBN} to assume that GDB was started
23572 in a terminal. In practice, this means that @value{GDBN} should wait
23573 for the user to answer queries generated by commands entered at
23574 the command prompt. If @code{off}, forces @value{GDBN} to operate
23575 in the opposite mode, and it uses the default answers to all queries.
23576 If @code{auto} (the default), @value{GDBN} tries to determine whether
23577 its standard input is a terminal, and works in interactive-mode if it
23578 is, non-interactively otherwise.
23580 In the vast majority of cases, the debugger should be able to guess
23581 correctly which mode should be used. But this setting can be useful
23582 in certain specific cases, such as running a MinGW @value{GDBN}
23583 inside a cygwin window.
23585 @kindex show interactive-mode
23586 @item show interactive-mode
23587 Displays whether the debugger is operating in interactive mode or not.
23590 @node Extending GDB
23591 @chapter Extending @value{GDBN}
23592 @cindex extending GDB
23594 @value{GDBN} provides several mechanisms for extension.
23595 @value{GDBN} also provides the ability to automatically load
23596 extensions when it reads a file for debugging. This allows the
23597 user to automatically customize @value{GDBN} for the program
23601 * Sequences:: Canned Sequences of @value{GDBN} Commands
23602 * Python:: Extending @value{GDBN} using Python
23603 * Guile:: Extending @value{GDBN} using Guile
23604 * Auto-loading extensions:: Automatically loading extensions
23605 * Multiple Extension Languages:: Working with multiple extension languages
23606 * Aliases:: Creating new spellings of existing commands
23609 To facilitate the use of extension languages, @value{GDBN} is capable
23610 of evaluating the contents of a file. When doing so, @value{GDBN}
23611 can recognize which extension language is being used by looking at
23612 the filename extension. Files with an unrecognized filename extension
23613 are always treated as a @value{GDBN} Command Files.
23614 @xref{Command Files,, Command files}.
23616 You can control how @value{GDBN} evaluates these files with the following
23620 @kindex set script-extension
23621 @kindex show script-extension
23622 @item set script-extension off
23623 All scripts are always evaluated as @value{GDBN} Command Files.
23625 @item set script-extension soft
23626 The debugger determines the scripting language based on filename
23627 extension. If this scripting language is supported, @value{GDBN}
23628 evaluates the script using that language. Otherwise, it evaluates
23629 the file as a @value{GDBN} Command File.
23631 @item set script-extension strict
23632 The debugger determines the scripting language based on filename
23633 extension, and evaluates the script using that language. If the
23634 language is not supported, then the evaluation fails.
23636 @item show script-extension
23637 Display the current value of the @code{script-extension} option.
23642 @section Canned Sequences of Commands
23644 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23645 Command Lists}), @value{GDBN} provides two ways to store sequences of
23646 commands for execution as a unit: user-defined commands and command
23650 * Define:: How to define your own commands
23651 * Hooks:: Hooks for user-defined commands
23652 * Command Files:: How to write scripts of commands to be stored in a file
23653 * Output:: Commands for controlled output
23654 * Auto-loading sequences:: Controlling auto-loaded command files
23658 @subsection User-defined Commands
23660 @cindex user-defined command
23661 @cindex arguments, to user-defined commands
23662 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23663 which you assign a new name as a command. This is done with the
23664 @code{define} command. User commands may accept up to 10 arguments
23665 separated by whitespace. Arguments are accessed within the user command
23666 via @code{$arg0@dots{}$arg9}. A trivial example:
23670 print $arg0 + $arg1 + $arg2
23675 To execute the command use:
23682 This defines the command @code{adder}, which prints the sum of
23683 its three arguments. Note the arguments are text substitutions, so they may
23684 reference variables, use complex expressions, or even perform inferior
23687 @cindex argument count in user-defined commands
23688 @cindex how many arguments (user-defined commands)
23689 In addition, @code{$argc} may be used to find out how many arguments have
23690 been passed. This expands to a number in the range 0@dots{}10.
23695 print $arg0 + $arg1
23698 print $arg0 + $arg1 + $arg2
23706 @item define @var{commandname}
23707 Define a command named @var{commandname}. If there is already a command
23708 by that name, you are asked to confirm that you want to redefine it.
23709 The argument @var{commandname} may be a bare command name consisting of letters,
23710 numbers, dashes, and underscores. It may also start with any predefined
23711 prefix command. For example, @samp{define target my-target} creates
23712 a user-defined @samp{target my-target} command.
23714 The definition of the command is made up of other @value{GDBN} command lines,
23715 which are given following the @code{define} command. The end of these
23716 commands is marked by a line containing @code{end}.
23719 @kindex end@r{ (user-defined commands)}
23720 @item document @var{commandname}
23721 Document the user-defined command @var{commandname}, so that it can be
23722 accessed by @code{help}. The command @var{commandname} must already be
23723 defined. This command reads lines of documentation just as @code{define}
23724 reads the lines of the command definition, ending with @code{end}.
23725 After the @code{document} command is finished, @code{help} on command
23726 @var{commandname} displays the documentation you have written.
23728 You may use the @code{document} command again to change the
23729 documentation of a command. Redefining the command with @code{define}
23730 does not change the documentation.
23732 @kindex dont-repeat
23733 @cindex don't repeat command
23735 Used inside a user-defined command, this tells @value{GDBN} that this
23736 command should not be repeated when the user hits @key{RET}
23737 (@pxref{Command Syntax, repeat last command}).
23739 @kindex help user-defined
23740 @item help user-defined
23741 List all user-defined commands and all python commands defined in class
23742 COMAND_USER. The first line of the documentation or docstring is
23747 @itemx show user @var{commandname}
23748 Display the @value{GDBN} commands used to define @var{commandname} (but
23749 not its documentation). If no @var{commandname} is given, display the
23750 definitions for all user-defined commands.
23751 This does not work for user-defined python commands.
23753 @cindex infinite recursion in user-defined commands
23754 @kindex show max-user-call-depth
23755 @kindex set max-user-call-depth
23756 @item show max-user-call-depth
23757 @itemx set max-user-call-depth
23758 The value of @code{max-user-call-depth} controls how many recursion
23759 levels are allowed in user-defined commands before @value{GDBN} suspects an
23760 infinite recursion and aborts the command.
23761 This does not apply to user-defined python commands.
23764 In addition to the above commands, user-defined commands frequently
23765 use control flow commands, described in @ref{Command Files}.
23767 When user-defined commands are executed, the
23768 commands of the definition are not printed. An error in any command
23769 stops execution of the user-defined command.
23771 If used interactively, commands that would ask for confirmation proceed
23772 without asking when used inside a user-defined command. Many @value{GDBN}
23773 commands that normally print messages to say what they are doing omit the
23774 messages when used in a user-defined command.
23777 @subsection User-defined Command Hooks
23778 @cindex command hooks
23779 @cindex hooks, for commands
23780 @cindex hooks, pre-command
23783 You may define @dfn{hooks}, which are a special kind of user-defined
23784 command. Whenever you run the command @samp{foo}, if the user-defined
23785 command @samp{hook-foo} exists, it is executed (with no arguments)
23786 before that command.
23788 @cindex hooks, post-command
23790 A hook may also be defined which is run after the command you executed.
23791 Whenever you run the command @samp{foo}, if the user-defined command
23792 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23793 that command. Post-execution hooks may exist simultaneously with
23794 pre-execution hooks, for the same command.
23796 It is valid for a hook to call the command which it hooks. If this
23797 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23799 @c It would be nice if hookpost could be passed a parameter indicating
23800 @c if the command it hooks executed properly or not. FIXME!
23802 @kindex stop@r{, a pseudo-command}
23803 In addition, a pseudo-command, @samp{stop} exists. Defining
23804 (@samp{hook-stop}) makes the associated commands execute every time
23805 execution stops in your program: before breakpoint commands are run,
23806 displays are printed, or the stack frame is printed.
23808 For example, to ignore @code{SIGALRM} signals while
23809 single-stepping, but treat them normally during normal execution,
23814 handle SIGALRM nopass
23818 handle SIGALRM pass
23821 define hook-continue
23822 handle SIGALRM pass
23826 As a further example, to hook at the beginning and end of the @code{echo}
23827 command, and to add extra text to the beginning and end of the message,
23835 define hookpost-echo
23839 (@value{GDBP}) echo Hello World
23840 <<<---Hello World--->>>
23845 You can define a hook for any single-word command in @value{GDBN}, but
23846 not for command aliases; you should define a hook for the basic command
23847 name, e.g.@: @code{backtrace} rather than @code{bt}.
23848 @c FIXME! So how does Joe User discover whether a command is an alias
23850 You can hook a multi-word command by adding @code{hook-} or
23851 @code{hookpost-} to the last word of the command, e.g.@:
23852 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23854 If an error occurs during the execution of your hook, execution of
23855 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23856 (before the command that you actually typed had a chance to run).
23858 If you try to define a hook which does not match any known command, you
23859 get a warning from the @code{define} command.
23861 @node Command Files
23862 @subsection Command Files
23864 @cindex command files
23865 @cindex scripting commands
23866 A command file for @value{GDBN} is a text file made of lines that are
23867 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23868 also be included. An empty line in a command file does nothing; it
23869 does not mean to repeat the last command, as it would from the
23872 You can request the execution of a command file with the @code{source}
23873 command. Note that the @code{source} command is also used to evaluate
23874 scripts that are not Command Files. The exact behavior can be configured
23875 using the @code{script-extension} setting.
23876 @xref{Extending GDB,, Extending GDB}.
23880 @cindex execute commands from a file
23881 @item source [-s] [-v] @var{filename}
23882 Execute the command file @var{filename}.
23885 The lines in a command file are generally executed sequentially,
23886 unless the order of execution is changed by one of the
23887 @emph{flow-control commands} described below. The commands are not
23888 printed as they are executed. An error in any command terminates
23889 execution of the command file and control is returned to the console.
23891 @value{GDBN} first searches for @var{filename} in the current directory.
23892 If the file is not found there, and @var{filename} does not specify a
23893 directory, then @value{GDBN} also looks for the file on the source search path
23894 (specified with the @samp{directory} command);
23895 except that @file{$cdir} is not searched because the compilation directory
23896 is not relevant to scripts.
23898 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23899 on the search path even if @var{filename} specifies a directory.
23900 The search is done by appending @var{filename} to each element of the
23901 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23902 and the search path contains @file{/home/user} then @value{GDBN} will
23903 look for the script @file{/home/user/mylib/myscript}.
23904 The search is also done if @var{filename} is an absolute path.
23905 For example, if @var{filename} is @file{/tmp/myscript} and
23906 the search path contains @file{/home/user} then @value{GDBN} will
23907 look for the script @file{/home/user/tmp/myscript}.
23908 For DOS-like systems, if @var{filename} contains a drive specification,
23909 it is stripped before concatenation. For example, if @var{filename} is
23910 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23911 will look for the script @file{c:/tmp/myscript}.
23913 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23914 each command as it is executed. The option must be given before
23915 @var{filename}, and is interpreted as part of the filename anywhere else.
23917 Commands that would ask for confirmation if used interactively proceed
23918 without asking when used in a command file. Many @value{GDBN} commands that
23919 normally print messages to say what they are doing omit the messages
23920 when called from command files.
23922 @value{GDBN} also accepts command input from standard input. In this
23923 mode, normal output goes to standard output and error output goes to
23924 standard error. Errors in a command file supplied on standard input do
23925 not terminate execution of the command file---execution continues with
23929 gdb < cmds > log 2>&1
23932 (The syntax above will vary depending on the shell used.) This example
23933 will execute commands from the file @file{cmds}. All output and errors
23934 would be directed to @file{log}.
23936 Since commands stored on command files tend to be more general than
23937 commands typed interactively, they frequently need to deal with
23938 complicated situations, such as different or unexpected values of
23939 variables and symbols, changes in how the program being debugged is
23940 built, etc. @value{GDBN} provides a set of flow-control commands to
23941 deal with these complexities. Using these commands, you can write
23942 complex scripts that loop over data structures, execute commands
23943 conditionally, etc.
23950 This command allows to include in your script conditionally executed
23951 commands. The @code{if} command takes a single argument, which is an
23952 expression to evaluate. It is followed by a series of commands that
23953 are executed only if the expression is true (its value is nonzero).
23954 There can then optionally be an @code{else} line, followed by a series
23955 of commands that are only executed if the expression was false. The
23956 end of the list is marked by a line containing @code{end}.
23960 This command allows to write loops. Its syntax is similar to
23961 @code{if}: the command takes a single argument, which is an expression
23962 to evaluate, and must be followed by the commands to execute, one per
23963 line, terminated by an @code{end}. These commands are called the
23964 @dfn{body} of the loop. The commands in the body of @code{while} are
23965 executed repeatedly as long as the expression evaluates to true.
23969 This command exits the @code{while} loop in whose body it is included.
23970 Execution of the script continues after that @code{while}s @code{end}
23973 @kindex loop_continue
23974 @item loop_continue
23975 This command skips the execution of the rest of the body of commands
23976 in the @code{while} loop in whose body it is included. Execution
23977 branches to the beginning of the @code{while} loop, where it evaluates
23978 the controlling expression.
23980 @kindex end@r{ (if/else/while commands)}
23982 Terminate the block of commands that are the body of @code{if},
23983 @code{else}, or @code{while} flow-control commands.
23988 @subsection Commands for Controlled Output
23990 During the execution of a command file or a user-defined command, normal
23991 @value{GDBN} output is suppressed; the only output that appears is what is
23992 explicitly printed by the commands in the definition. This section
23993 describes three commands useful for generating exactly the output you
23998 @item echo @var{text}
23999 @c I do not consider backslash-space a standard C escape sequence
24000 @c because it is not in ANSI.
24001 Print @var{text}. Nonprinting characters can be included in
24002 @var{text} using C escape sequences, such as @samp{\n} to print a
24003 newline. @strong{No newline is printed unless you specify one.}
24004 In addition to the standard C escape sequences, a backslash followed
24005 by a space stands for a space. This is useful for displaying a
24006 string with spaces at the beginning or the end, since leading and
24007 trailing spaces are otherwise trimmed from all arguments.
24008 To print @samp{@w{ }and foo =@w{ }}, use the command
24009 @samp{echo \@w{ }and foo = \@w{ }}.
24011 A backslash at the end of @var{text} can be used, as in C, to continue
24012 the command onto subsequent lines. For example,
24015 echo This is some text\n\
24016 which is continued\n\
24017 onto several lines.\n
24020 produces the same output as
24023 echo This is some text\n
24024 echo which is continued\n
24025 echo onto several lines.\n
24029 @item output @var{expression}
24030 Print the value of @var{expression} and nothing but that value: no
24031 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24032 value history either. @xref{Expressions, ,Expressions}, for more information
24035 @item output/@var{fmt} @var{expression}
24036 Print the value of @var{expression} in format @var{fmt}. You can use
24037 the same formats as for @code{print}. @xref{Output Formats,,Output
24038 Formats}, for more information.
24041 @item printf @var{template}, @var{expressions}@dots{}
24042 Print the values of one or more @var{expressions} under the control of
24043 the string @var{template}. To print several values, make
24044 @var{expressions} be a comma-separated list of individual expressions,
24045 which may be either numbers or pointers. Their values are printed as
24046 specified by @var{template}, exactly as a C program would do by
24047 executing the code below:
24050 printf (@var{template}, @var{expressions}@dots{});
24053 As in @code{C} @code{printf}, ordinary characters in @var{template}
24054 are printed verbatim, while @dfn{conversion specification} introduced
24055 by the @samp{%} character cause subsequent @var{expressions} to be
24056 evaluated, their values converted and formatted according to type and
24057 style information encoded in the conversion specifications, and then
24060 For example, you can print two values in hex like this:
24063 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24066 @code{printf} supports all the standard @code{C} conversion
24067 specifications, including the flags and modifiers between the @samp{%}
24068 character and the conversion letter, with the following exceptions:
24072 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24075 The modifier @samp{*} is not supported for specifying precision or
24079 The @samp{'} flag (for separation of digits into groups according to
24080 @code{LC_NUMERIC'}) is not supported.
24083 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24087 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24090 The conversion letters @samp{a} and @samp{A} are not supported.
24094 Note that the @samp{ll} type modifier is supported only if the
24095 underlying @code{C} implementation used to build @value{GDBN} supports
24096 the @code{long long int} type, and the @samp{L} type modifier is
24097 supported only if @code{long double} type is available.
24099 As in @code{C}, @code{printf} supports simple backslash-escape
24100 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24101 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24102 single character. Octal and hexadecimal escape sequences are not
24105 Additionally, @code{printf} supports conversion specifications for DFP
24106 (@dfn{Decimal Floating Point}) types using the following length modifiers
24107 together with a floating point specifier.
24112 @samp{H} for printing @code{Decimal32} types.
24115 @samp{D} for printing @code{Decimal64} types.
24118 @samp{DD} for printing @code{Decimal128} types.
24121 If the underlying @code{C} implementation used to build @value{GDBN} has
24122 support for the three length modifiers for DFP types, other modifiers
24123 such as width and precision will also be available for @value{GDBN} to use.
24125 In case there is no such @code{C} support, no additional modifiers will be
24126 available and the value will be printed in the standard way.
24128 Here's an example of printing DFP types using the above conversion letters:
24130 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24134 @item eval @var{template}, @var{expressions}@dots{}
24135 Convert the values of one or more @var{expressions} under the control of
24136 the string @var{template} to a command line, and call it.
24140 @node Auto-loading sequences
24141 @subsection Controlling auto-loading native @value{GDBN} scripts
24142 @cindex native script auto-loading
24144 When a new object file is read (for example, due to the @code{file}
24145 command, or because the inferior has loaded a shared library),
24146 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24147 @xref{Auto-loading extensions}.
24149 Auto-loading can be enabled or disabled,
24150 and the list of auto-loaded scripts can be printed.
24153 @anchor{set auto-load gdb-scripts}
24154 @kindex set auto-load gdb-scripts
24155 @item set auto-load gdb-scripts [on|off]
24156 Enable or disable the auto-loading of canned sequences of commands scripts.
24158 @anchor{show auto-load gdb-scripts}
24159 @kindex show auto-load gdb-scripts
24160 @item show auto-load gdb-scripts
24161 Show whether auto-loading of canned sequences of commands scripts is enabled or
24164 @anchor{info auto-load gdb-scripts}
24165 @kindex info auto-load gdb-scripts
24166 @cindex print list of auto-loaded canned sequences of commands scripts
24167 @item info auto-load gdb-scripts [@var{regexp}]
24168 Print the list of all canned sequences of commands scripts that @value{GDBN}
24172 If @var{regexp} is supplied only canned sequences of commands scripts with
24173 matching names are printed.
24175 @c Python docs live in a separate file.
24176 @include python.texi
24178 @c Guile docs live in a separate file.
24179 @include guile.texi
24181 @node Auto-loading extensions
24182 @section Auto-loading extensions
24183 @cindex auto-loading extensions
24185 @value{GDBN} provides two mechanisms for automatically loading extensions
24186 when a new object file is read (for example, due to the @code{file}
24187 command, or because the inferior has loaded a shared library):
24188 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24189 section of modern file formats like ELF.
24192 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24193 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24194 * Which flavor to choose?::
24197 The auto-loading feature is useful for supplying application-specific
24198 debugging commands and features.
24200 Auto-loading can be enabled or disabled,
24201 and the list of auto-loaded scripts can be printed.
24202 See the @samp{auto-loading} section of each extension language
24203 for more information.
24204 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24205 For Python files see @ref{Python Auto-loading}.
24207 Note that loading of this script file also requires accordingly configured
24208 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24210 @node objfile-gdbdotext file
24211 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24212 @cindex @file{@var{objfile}-gdb.gdb}
24213 @cindex @file{@var{objfile}-gdb.py}
24214 @cindex @file{@var{objfile}-gdb.scm}
24216 When a new object file is read, @value{GDBN} looks for a file named
24217 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24218 where @var{objfile} is the object file's name and
24219 where @var{ext} is the file extension for the extension language:
24222 @item @file{@var{objfile}-gdb.gdb}
24223 GDB's own command language
24224 @item @file{@var{objfile}-gdb.py}
24226 @item @file{@var{objfile}-gdb.scm}
24230 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24231 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24232 components, and appending the @file{-gdb.@var{ext}} suffix.
24233 If this file exists and is readable, @value{GDBN} will evaluate it as a
24234 script in the specified extension language.
24236 If this file does not exist, then @value{GDBN} will look for
24237 @var{script-name} file in all of the directories as specified below.
24239 Note that loading of these files requires an accordingly configured
24240 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24242 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24243 scripts normally according to its @file{.exe} filename. But if no scripts are
24244 found @value{GDBN} also tries script filenames matching the object file without
24245 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24246 is attempted on any platform. This makes the script filenames compatible
24247 between Unix and MS-Windows hosts.
24250 @anchor{set auto-load scripts-directory}
24251 @kindex set auto-load scripts-directory
24252 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24253 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24254 may be delimited by the host platform path separator in use
24255 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24257 Each entry here needs to be covered also by the security setting
24258 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24260 @anchor{with-auto-load-dir}
24261 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24262 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24263 configuration option @option{--with-auto-load-dir}.
24265 Any reference to @file{$debugdir} will get replaced by
24266 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24267 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24268 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24269 @file{$datadir} must be placed as a directory component --- either alone or
24270 delimited by @file{/} or @file{\} directory separators, depending on the host
24273 The list of directories uses path separator (@samp{:} on GNU and Unix
24274 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24275 to the @env{PATH} environment variable.
24277 @anchor{show auto-load scripts-directory}
24278 @kindex show auto-load scripts-directory
24279 @item show auto-load scripts-directory
24280 Show @value{GDBN} auto-loaded scripts location.
24282 @anchor{add-auto-load-scripts-directory}
24283 @kindex add-auto-load-scripts-directory
24284 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24285 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24286 Multiple entries may be delimited by the host platform path separator in use.
24289 @value{GDBN} does not track which files it has already auto-loaded this way.
24290 @value{GDBN} will load the associated script every time the corresponding
24291 @var{objfile} is opened.
24292 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24293 is evaluated more than once.
24295 @node dotdebug_gdb_scripts section
24296 @subsection The @code{.debug_gdb_scripts} section
24297 @cindex @code{.debug_gdb_scripts} section
24299 For systems using file formats like ELF and COFF,
24300 when @value{GDBN} loads a new object file
24301 it will look for a special section named @code{.debug_gdb_scripts}.
24302 If this section exists, its contents is a list of null-terminated entries
24303 specifying scripts to load. Each entry begins with a non-null prefix byte that
24304 specifies the kind of entry, typically the extension language and whether the
24305 script is in a file or inlined in @code{.debug_gdb_scripts}.
24307 The following entries are supported:
24310 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24311 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24312 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24313 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24316 @subsubsection Script File Entries
24318 If the entry specifies a file, @value{GDBN} will look for the file first
24319 in the current directory and then along the source search path
24320 (@pxref{Source Path, ,Specifying Source Directories}),
24321 except that @file{$cdir} is not searched, since the compilation
24322 directory is not relevant to scripts.
24324 File entries can be placed in section @code{.debug_gdb_scripts} with,
24325 for example, this GCC macro for Python scripts.
24328 /* Note: The "MS" section flags are to remove duplicates. */
24329 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24331 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24332 .byte 1 /* Python */\n\
24333 .asciz \"" script_name "\"\n\
24339 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24340 Then one can reference the macro in a header or source file like this:
24343 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24346 The script name may include directories if desired.
24348 Note that loading of this script file also requires accordingly configured
24349 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24351 If the macro invocation is put in a header, any application or library
24352 using this header will get a reference to the specified script,
24353 and with the use of @code{"MS"} attributes on the section, the linker
24354 will remove duplicates.
24356 @subsubsection Script Text Entries
24358 Script text entries allow to put the executable script in the entry
24359 itself instead of loading it from a file.
24360 The first line of the entry, everything after the prefix byte and up to
24361 the first newline (@code{0xa}) character, is the script name, and must not
24362 contain any kind of space character, e.g., spaces or tabs.
24363 The rest of the entry, up to the trailing null byte, is the script to
24364 execute in the specified language. The name needs to be unique among
24365 all script names, as @value{GDBN} executes each script only once based
24368 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24372 #include "symcat.h"
24373 #include "gdb/section-scripts.h"
24375 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24376 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24377 ".ascii \"gdb.inlined-script\\n\"\n"
24378 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24379 ".ascii \" def __init__ (self):\\n\"\n"
24380 ".ascii \" super (test_cmd, self).__init__ ("
24381 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24382 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24383 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24384 ".ascii \"test_cmd ()\\n\"\n"
24390 Loading of inlined scripts requires a properly configured
24391 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24392 The path to specify in @code{auto-load safe-path} is the path of the file
24393 containing the @code{.debug_gdb_scripts} section.
24395 @node Which flavor to choose?
24396 @subsection Which flavor to choose?
24398 Given the multiple ways of auto-loading extensions, it might not always
24399 be clear which one to choose. This section provides some guidance.
24402 Benefits of the @file{-gdb.@var{ext}} way:
24406 Can be used with file formats that don't support multiple sections.
24409 Ease of finding scripts for public libraries.
24411 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24412 in the source search path.
24413 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24414 isn't a source directory in which to find the script.
24417 Doesn't require source code additions.
24421 Benefits of the @code{.debug_gdb_scripts} way:
24425 Works with static linking.
24427 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24428 trigger their loading. When an application is statically linked the only
24429 objfile available is the executable, and it is cumbersome to attach all the
24430 scripts from all the input libraries to the executable's
24431 @file{-gdb.@var{ext}} script.
24434 Works with classes that are entirely inlined.
24436 Some classes can be entirely inlined, and thus there may not be an associated
24437 shared library to attach a @file{-gdb.@var{ext}} script to.
24440 Scripts needn't be copied out of the source tree.
24442 In some circumstances, apps can be built out of large collections of internal
24443 libraries, and the build infrastructure necessary to install the
24444 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24445 cumbersome. It may be easier to specify the scripts in the
24446 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24447 top of the source tree to the source search path.
24450 @node Multiple Extension Languages
24451 @section Multiple Extension Languages
24453 The Guile and Python extension languages do not share any state,
24454 and generally do not interfere with each other.
24455 There are some things to be aware of, however.
24457 @subsection Python comes first
24459 Python was @value{GDBN}'s first extension language, and to avoid breaking
24460 existing behaviour Python comes first. This is generally solved by the
24461 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24462 extension languages, and when it makes a call to an extension language,
24463 (say to pretty-print a value), it tries each in turn until an extension
24464 language indicates it has performed the request (e.g., has returned the
24465 pretty-printed form of a value).
24466 This extends to errors while performing such requests: If an error happens
24467 while, for example, trying to pretty-print an object then the error is
24468 reported and any following extension languages are not tried.
24471 @section Creating new spellings of existing commands
24472 @cindex aliases for commands
24474 It is often useful to define alternate spellings of existing commands.
24475 For example, if a new @value{GDBN} command defined in Python has
24476 a long name to type, it is handy to have an abbreviated version of it
24477 that involves less typing.
24479 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24480 of the @samp{step} command even though it is otherwise an ambiguous
24481 abbreviation of other commands like @samp{set} and @samp{show}.
24483 Aliases are also used to provide shortened or more common versions
24484 of multi-word commands. For example, @value{GDBN} provides the
24485 @samp{tty} alias of the @samp{set inferior-tty} command.
24487 You can define a new alias with the @samp{alias} command.
24492 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24496 @var{ALIAS} specifies the name of the new alias.
24497 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24500 @var{COMMAND} specifies the name of an existing command
24501 that is being aliased.
24503 The @samp{-a} option specifies that the new alias is an abbreviation
24504 of the command. Abbreviations are not shown in command
24505 lists displayed by the @samp{help} command.
24507 The @samp{--} option specifies the end of options,
24508 and is useful when @var{ALIAS} begins with a dash.
24510 Here is a simple example showing how to make an abbreviation
24511 of a command so that there is less to type.
24512 Suppose you were tired of typing @samp{disas}, the current
24513 shortest unambiguous abbreviation of the @samp{disassemble} command
24514 and you wanted an even shorter version named @samp{di}.
24515 The following will accomplish this.
24518 (gdb) alias -a di = disas
24521 Note that aliases are different from user-defined commands.
24522 With a user-defined command, you also need to write documentation
24523 for it with the @samp{document} command.
24524 An alias automatically picks up the documentation of the existing command.
24526 Here is an example where we make @samp{elms} an abbreviation of
24527 @samp{elements} in the @samp{set print elements} command.
24528 This is to show that you can make an abbreviation of any part
24532 (gdb) alias -a set print elms = set print elements
24533 (gdb) alias -a show print elms = show print elements
24534 (gdb) set p elms 20
24536 Limit on string chars or array elements to print is 200.
24539 Note that if you are defining an alias of a @samp{set} command,
24540 and you want to have an alias for the corresponding @samp{show}
24541 command, then you need to define the latter separately.
24543 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24544 @var{ALIAS}, just as they are normally.
24547 (gdb) alias -a set pr elms = set p ele
24550 Finally, here is an example showing the creation of a one word
24551 alias for a more complex command.
24552 This creates alias @samp{spe} of the command @samp{set print elements}.
24555 (gdb) alias spe = set print elements
24560 @chapter Command Interpreters
24561 @cindex command interpreters
24563 @value{GDBN} supports multiple command interpreters, and some command
24564 infrastructure to allow users or user interface writers to switch
24565 between interpreters or run commands in other interpreters.
24567 @value{GDBN} currently supports two command interpreters, the console
24568 interpreter (sometimes called the command-line interpreter or @sc{cli})
24569 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24570 describes both of these interfaces in great detail.
24572 By default, @value{GDBN} will start with the console interpreter.
24573 However, the user may choose to start @value{GDBN} with another
24574 interpreter by specifying the @option{-i} or @option{--interpreter}
24575 startup options. Defined interpreters include:
24579 @cindex console interpreter
24580 The traditional console or command-line interpreter. This is the most often
24581 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24582 @value{GDBN} will use this interpreter.
24585 @cindex mi interpreter
24586 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24587 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24588 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24592 @cindex mi2 interpreter
24593 The current @sc{gdb/mi} interface.
24596 @cindex mi1 interpreter
24597 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24601 @cindex invoke another interpreter
24602 The interpreter being used by @value{GDBN} may not be dynamically
24603 switched at runtime. Although possible, this could lead to a very
24604 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24605 enters the command "interpreter-set console" in a console view,
24606 @value{GDBN} would switch to using the console interpreter, rendering
24607 the IDE inoperable!
24609 @kindex interpreter-exec
24610 Although you may only choose a single interpreter at startup, you may execute
24611 commands in any interpreter from the current interpreter using the appropriate
24612 command. If you are running the console interpreter, simply use the
24613 @code{interpreter-exec} command:
24616 interpreter-exec mi "-data-list-register-names"
24619 @sc{gdb/mi} has a similar command, although it is only available in versions of
24620 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24623 @chapter @value{GDBN} Text User Interface
24625 @cindex Text User Interface
24628 * TUI Overview:: TUI overview
24629 * TUI Keys:: TUI key bindings
24630 * TUI Single Key Mode:: TUI single key mode
24631 * TUI Commands:: TUI-specific commands
24632 * TUI Configuration:: TUI configuration variables
24635 The @value{GDBN} Text User Interface (TUI) is a terminal
24636 interface which uses the @code{curses} library to show the source
24637 file, the assembly output, the program registers and @value{GDBN}
24638 commands in separate text windows. The TUI mode is supported only
24639 on platforms where a suitable version of the @code{curses} library
24642 The TUI mode is enabled by default when you invoke @value{GDBN} as
24643 @samp{@value{GDBP} -tui}.
24644 You can also switch in and out of TUI mode while @value{GDBN} runs by
24645 using various TUI commands and key bindings, such as @command{tui
24646 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24647 @ref{TUI Keys, ,TUI Key Bindings}.
24650 @section TUI Overview
24652 In TUI mode, @value{GDBN} can display several text windows:
24656 This window is the @value{GDBN} command window with the @value{GDBN}
24657 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24658 managed using readline.
24661 The source window shows the source file of the program. The current
24662 line and active breakpoints are displayed in this window.
24665 The assembly window shows the disassembly output of the program.
24668 This window shows the processor registers. Registers are highlighted
24669 when their values change.
24672 The source and assembly windows show the current program position
24673 by highlighting the current line and marking it with a @samp{>} marker.
24674 Breakpoints are indicated with two markers. The first marker
24675 indicates the breakpoint type:
24679 Breakpoint which was hit at least once.
24682 Breakpoint which was never hit.
24685 Hardware breakpoint which was hit at least once.
24688 Hardware breakpoint which was never hit.
24691 The second marker indicates whether the breakpoint is enabled or not:
24695 Breakpoint is enabled.
24698 Breakpoint is disabled.
24701 The source, assembly and register windows are updated when the current
24702 thread changes, when the frame changes, or when the program counter
24705 These windows are not all visible at the same time. The command
24706 window is always visible. The others can be arranged in several
24717 source and assembly,
24720 source and registers, or
24723 assembly and registers.
24726 A status line above the command window shows the following information:
24730 Indicates the current @value{GDBN} target.
24731 (@pxref{Targets, ,Specifying a Debugging Target}).
24734 Gives the current process or thread number.
24735 When no process is being debugged, this field is set to @code{No process}.
24738 Gives the current function name for the selected frame.
24739 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24740 When there is no symbol corresponding to the current program counter,
24741 the string @code{??} is displayed.
24744 Indicates the current line number for the selected frame.
24745 When the current line number is not known, the string @code{??} is displayed.
24748 Indicates the current program counter address.
24752 @section TUI Key Bindings
24753 @cindex TUI key bindings
24755 The TUI installs several key bindings in the readline keymaps
24756 @ifset SYSTEM_READLINE
24757 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24759 @ifclear SYSTEM_READLINE
24760 (@pxref{Command Line Editing}).
24762 The following key bindings are installed for both TUI mode and the
24763 @value{GDBN} standard mode.
24772 Enter or leave the TUI mode. When leaving the TUI mode,
24773 the curses window management stops and @value{GDBN} operates using
24774 its standard mode, writing on the terminal directly. When reentering
24775 the TUI mode, control is given back to the curses windows.
24776 The screen is then refreshed.
24780 Use a TUI layout with only one window. The layout will
24781 either be @samp{source} or @samp{assembly}. When the TUI mode
24782 is not active, it will switch to the TUI mode.
24784 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24788 Use a TUI layout with at least two windows. When the current
24789 layout already has two windows, the next layout with two windows is used.
24790 When a new layout is chosen, one window will always be common to the
24791 previous layout and the new one.
24793 Think of it as the Emacs @kbd{C-x 2} binding.
24797 Change the active window. The TUI associates several key bindings
24798 (like scrolling and arrow keys) with the active window. This command
24799 gives the focus to the next TUI window.
24801 Think of it as the Emacs @kbd{C-x o} binding.
24805 Switch in and out of the TUI SingleKey mode that binds single
24806 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24809 The following key bindings only work in the TUI mode:
24814 Scroll the active window one page up.
24818 Scroll the active window one page down.
24822 Scroll the active window one line up.
24826 Scroll the active window one line down.
24830 Scroll the active window one column left.
24834 Scroll the active window one column right.
24838 Refresh the screen.
24841 Because the arrow keys scroll the active window in the TUI mode, they
24842 are not available for their normal use by readline unless the command
24843 window has the focus. When another window is active, you must use
24844 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24845 and @kbd{C-f} to control the command window.
24847 @node TUI Single Key Mode
24848 @section TUI Single Key Mode
24849 @cindex TUI single key mode
24851 The TUI also provides a @dfn{SingleKey} mode, which binds several
24852 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24853 switch into this mode, where the following key bindings are used:
24856 @kindex c @r{(SingleKey TUI key)}
24860 @kindex d @r{(SingleKey TUI key)}
24864 @kindex f @r{(SingleKey TUI key)}
24868 @kindex n @r{(SingleKey TUI key)}
24872 @kindex q @r{(SingleKey TUI key)}
24874 exit the SingleKey mode.
24876 @kindex r @r{(SingleKey TUI key)}
24880 @kindex s @r{(SingleKey TUI key)}
24884 @kindex u @r{(SingleKey TUI key)}
24888 @kindex v @r{(SingleKey TUI key)}
24892 @kindex w @r{(SingleKey TUI key)}
24897 Other keys temporarily switch to the @value{GDBN} command prompt.
24898 The key that was pressed is inserted in the editing buffer so that
24899 it is possible to type most @value{GDBN} commands without interaction
24900 with the TUI SingleKey mode. Once the command is entered the TUI
24901 SingleKey mode is restored. The only way to permanently leave
24902 this mode is by typing @kbd{q} or @kbd{C-x s}.
24906 @section TUI-specific Commands
24907 @cindex TUI commands
24909 The TUI has specific commands to control the text windows.
24910 These commands are always available, even when @value{GDBN} is not in
24911 the TUI mode. When @value{GDBN} is in the standard mode, most
24912 of these commands will automatically switch to the TUI mode.
24914 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24915 terminal, or @value{GDBN} has been started with the machine interface
24916 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24917 these commands will fail with an error, because it would not be
24918 possible or desirable to enable curses window management.
24923 Activate TUI mode. The last active TUI window layout will be used if
24924 TUI mode has prevsiouly been used in the current debugging session,
24925 otherwise a default layout is used.
24928 @kindex tui disable
24929 Disable TUI mode, returning to the console interpreter.
24933 List and give the size of all displayed windows.
24935 @item layout @var{name}
24937 Changes which TUI windows are displayed. In each layout the command
24938 window is always displayed, the @var{name} parameter controls which
24939 additional windows are displayed, and can be any of the following:
24943 Display the next layout.
24946 Display the previous layout.
24949 Display the source and command windows.
24952 Display the assembly and command windows.
24955 Display the source, assembly, and command windows.
24958 When in @code{src} layout display the register, source, and command
24959 windows. When in @code{asm} or @code{split} layout display the
24960 register, assembler, and command windows.
24963 @item focus @var{name}
24965 Changes which TUI window is currently active for scrolling. The
24966 @var{name} parameter can be any of the following:
24970 Make the next window active for scrolling.
24973 Make the previous window active for scrolling.
24976 Make the source window active for scrolling.
24979 Make the assembly window active for scrolling.
24982 Make the register window active for scrolling.
24985 Make the command window active for scrolling.
24990 Refresh the screen. This is similar to typing @kbd{C-L}.
24992 @item tui reg @var{group}
24994 Changes the register group displayed in the tui register window to
24995 @var{group}. If the register window is not currently displayed this
24996 command will cause the register window to be displayed. The list of
24997 register groups, as well as their order is target specific. The
24998 following groups are available on most targets:
25001 Repeatedly selecting this group will cause the display to cycle
25002 through all of the available register groups.
25005 Repeatedly selecting this group will cause the display to cycle
25006 through all of the available register groups in the reverse order to
25010 Display the general registers.
25012 Display the floating point registers.
25014 Display the system registers.
25016 Display the vector registers.
25018 Display all registers.
25023 Update the source window and the current execution point.
25025 @item winheight @var{name} +@var{count}
25026 @itemx winheight @var{name} -@var{count}
25028 Change the height of the window @var{name} by @var{count}
25029 lines. Positive counts increase the height, while negative counts
25030 decrease it. The @var{name} parameter can be one of @code{src} (the
25031 source window), @code{cmd} (the command window), @code{asm} (the
25032 disassembly window), or @code{regs} (the register display window).
25034 @item tabset @var{nchars}
25036 Set the width of tab stops to be @var{nchars} characters. This
25037 setting affects the display of TAB characters in the source and
25041 @node TUI Configuration
25042 @section TUI Configuration Variables
25043 @cindex TUI configuration variables
25045 Several configuration variables control the appearance of TUI windows.
25048 @item set tui border-kind @var{kind}
25049 @kindex set tui border-kind
25050 Select the border appearance for the source, assembly and register windows.
25051 The possible values are the following:
25054 Use a space character to draw the border.
25057 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25060 Use the Alternate Character Set to draw the border. The border is
25061 drawn using character line graphics if the terminal supports them.
25064 @item set tui border-mode @var{mode}
25065 @kindex set tui border-mode
25066 @itemx set tui active-border-mode @var{mode}
25067 @kindex set tui active-border-mode
25068 Select the display attributes for the borders of the inactive windows
25069 or the active window. The @var{mode} can be one of the following:
25072 Use normal attributes to display the border.
25078 Use reverse video mode.
25081 Use half bright mode.
25083 @item half-standout
25084 Use half bright and standout mode.
25087 Use extra bright or bold mode.
25089 @item bold-standout
25090 Use extra bright or bold and standout mode.
25095 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25098 @cindex @sc{gnu} Emacs
25099 A special interface allows you to use @sc{gnu} Emacs to view (and
25100 edit) the source files for the program you are debugging with
25103 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25104 executable file you want to debug as an argument. This command starts
25105 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25106 created Emacs buffer.
25107 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25109 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25114 All ``terminal'' input and output goes through an Emacs buffer, called
25117 This applies both to @value{GDBN} commands and their output, and to the input
25118 and output done by the program you are debugging.
25120 This is useful because it means that you can copy the text of previous
25121 commands and input them again; you can even use parts of the output
25124 All the facilities of Emacs' Shell mode are available for interacting
25125 with your program. In particular, you can send signals the usual
25126 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25130 @value{GDBN} displays source code through Emacs.
25132 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25133 source file for that frame and puts an arrow (@samp{=>}) at the
25134 left margin of the current line. Emacs uses a separate buffer for
25135 source display, and splits the screen to show both your @value{GDBN} session
25138 Explicit @value{GDBN} @code{list} or search commands still produce output as
25139 usual, but you probably have no reason to use them from Emacs.
25142 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25143 a graphical mode, enabled by default, which provides further buffers
25144 that can control the execution and describe the state of your program.
25145 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25147 If you specify an absolute file name when prompted for the @kbd{M-x
25148 gdb} argument, then Emacs sets your current working directory to where
25149 your program resides. If you only specify the file name, then Emacs
25150 sets your current working directory to the directory associated
25151 with the previous buffer. In this case, @value{GDBN} may find your
25152 program by searching your environment's @code{PATH} variable, but on
25153 some operating systems it might not find the source. So, although the
25154 @value{GDBN} input and output session proceeds normally, the auxiliary
25155 buffer does not display the current source and line of execution.
25157 The initial working directory of @value{GDBN} is printed on the top
25158 line of the GUD buffer and this serves as a default for the commands
25159 that specify files for @value{GDBN} to operate on. @xref{Files,
25160 ,Commands to Specify Files}.
25162 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25163 need to call @value{GDBN} by a different name (for example, if you
25164 keep several configurations around, with different names) you can
25165 customize the Emacs variable @code{gud-gdb-command-name} to run the
25168 In the GUD buffer, you can use these special Emacs commands in
25169 addition to the standard Shell mode commands:
25173 Describe the features of Emacs' GUD Mode.
25176 Execute to another source line, like the @value{GDBN} @code{step} command; also
25177 update the display window to show the current file and location.
25180 Execute to next source line in this function, skipping all function
25181 calls, like the @value{GDBN} @code{next} command. Then update the display window
25182 to show the current file and location.
25185 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25186 display window accordingly.
25189 Execute until exit from the selected stack frame, like the @value{GDBN}
25190 @code{finish} command.
25193 Continue execution of your program, like the @value{GDBN} @code{continue}
25197 Go up the number of frames indicated by the numeric argument
25198 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25199 like the @value{GDBN} @code{up} command.
25202 Go down the number of frames indicated by the numeric argument, like the
25203 @value{GDBN} @code{down} command.
25206 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25207 tells @value{GDBN} to set a breakpoint on the source line point is on.
25209 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25210 separate frame which shows a backtrace when the GUD buffer is current.
25211 Move point to any frame in the stack and type @key{RET} to make it
25212 become the current frame and display the associated source in the
25213 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25214 selected frame become the current one. In graphical mode, the
25215 speedbar displays watch expressions.
25217 If you accidentally delete the source-display buffer, an easy way to get
25218 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25219 request a frame display; when you run under Emacs, this recreates
25220 the source buffer if necessary to show you the context of the current
25223 The source files displayed in Emacs are in ordinary Emacs buffers
25224 which are visiting the source files in the usual way. You can edit
25225 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25226 communicates with Emacs in terms of line numbers. If you add or
25227 delete lines from the text, the line numbers that @value{GDBN} knows cease
25228 to correspond properly with the code.
25230 A more detailed description of Emacs' interaction with @value{GDBN} is
25231 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25235 @chapter The @sc{gdb/mi} Interface
25237 @unnumberedsec Function and Purpose
25239 @cindex @sc{gdb/mi}, its purpose
25240 @sc{gdb/mi} is a line based machine oriented text interface to
25241 @value{GDBN} and is activated by specifying using the
25242 @option{--interpreter} command line option (@pxref{Mode Options}). It
25243 is specifically intended to support the development of systems which
25244 use the debugger as just one small component of a larger system.
25246 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25247 in the form of a reference manual.
25249 Note that @sc{gdb/mi} is still under construction, so some of the
25250 features described below are incomplete and subject to change
25251 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25253 @unnumberedsec Notation and Terminology
25255 @cindex notational conventions, for @sc{gdb/mi}
25256 This chapter uses the following notation:
25260 @code{|} separates two alternatives.
25263 @code{[ @var{something} ]} indicates that @var{something} is optional:
25264 it may or may not be given.
25267 @code{( @var{group} )*} means that @var{group} inside the parentheses
25268 may repeat zero or more times.
25271 @code{( @var{group} )+} means that @var{group} inside the parentheses
25272 may repeat one or more times.
25275 @code{"@var{string}"} means a literal @var{string}.
25279 @heading Dependencies
25283 * GDB/MI General Design::
25284 * GDB/MI Command Syntax::
25285 * GDB/MI Compatibility with CLI::
25286 * GDB/MI Development and Front Ends::
25287 * GDB/MI Output Records::
25288 * GDB/MI Simple Examples::
25289 * GDB/MI Command Description Format::
25290 * GDB/MI Breakpoint Commands::
25291 * GDB/MI Catchpoint Commands::
25292 * GDB/MI Program Context::
25293 * GDB/MI Thread Commands::
25294 * GDB/MI Ada Tasking Commands::
25295 * GDB/MI Program Execution::
25296 * GDB/MI Stack Manipulation::
25297 * GDB/MI Variable Objects::
25298 * GDB/MI Data Manipulation::
25299 * GDB/MI Tracepoint Commands::
25300 * GDB/MI Symbol Query::
25301 * GDB/MI File Commands::
25303 * GDB/MI Kod Commands::
25304 * GDB/MI Memory Overlay Commands::
25305 * GDB/MI Signal Handling Commands::
25307 * GDB/MI Target Manipulation::
25308 * GDB/MI File Transfer Commands::
25309 * GDB/MI Ada Exceptions Commands::
25310 * GDB/MI Support Commands::
25311 * GDB/MI Miscellaneous Commands::
25314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25315 @node GDB/MI General Design
25316 @section @sc{gdb/mi} General Design
25317 @cindex GDB/MI General Design
25319 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25320 parts---commands sent to @value{GDBN}, responses to those commands
25321 and notifications. Each command results in exactly one response,
25322 indicating either successful completion of the command, or an error.
25323 For the commands that do not resume the target, the response contains the
25324 requested information. For the commands that resume the target, the
25325 response only indicates whether the target was successfully resumed.
25326 Notifications is the mechanism for reporting changes in the state of the
25327 target, or in @value{GDBN} state, that cannot conveniently be associated with
25328 a command and reported as part of that command response.
25330 The important examples of notifications are:
25334 Exec notifications. These are used to report changes in
25335 target state---when a target is resumed, or stopped. It would not
25336 be feasible to include this information in response of resuming
25337 commands, because one resume commands can result in multiple events in
25338 different threads. Also, quite some time may pass before any event
25339 happens in the target, while a frontend needs to know whether the resuming
25340 command itself was successfully executed.
25343 Console output, and status notifications. Console output
25344 notifications are used to report output of CLI commands, as well as
25345 diagnostics for other commands. Status notifications are used to
25346 report the progress of a long-running operation. Naturally, including
25347 this information in command response would mean no output is produced
25348 until the command is finished, which is undesirable.
25351 General notifications. Commands may have various side effects on
25352 the @value{GDBN} or target state beyond their official purpose. For example,
25353 a command may change the selected thread. Although such changes can
25354 be included in command response, using notification allows for more
25355 orthogonal frontend design.
25359 There's no guarantee that whenever an MI command reports an error,
25360 @value{GDBN} or the target are in any specific state, and especially,
25361 the state is not reverted to the state before the MI command was
25362 processed. Therefore, whenever an MI command results in an error,
25363 we recommend that the frontend refreshes all the information shown in
25364 the user interface.
25368 * Context management::
25369 * Asynchronous and non-stop modes::
25373 @node Context management
25374 @subsection Context management
25376 @subsubsection Threads and Frames
25378 In most cases when @value{GDBN} accesses the target, this access is
25379 done in context of a specific thread and frame (@pxref{Frames}).
25380 Often, even when accessing global data, the target requires that a thread
25381 be specified. The CLI interface maintains the selected thread and frame,
25382 and supplies them to target on each command. This is convenient,
25383 because a command line user would not want to specify that information
25384 explicitly on each command, and because user interacts with
25385 @value{GDBN} via a single terminal, so no confusion is possible as
25386 to what thread and frame are the current ones.
25388 In the case of MI, the concept of selected thread and frame is less
25389 useful. First, a frontend can easily remember this information
25390 itself. Second, a graphical frontend can have more than one window,
25391 each one used for debugging a different thread, and the frontend might
25392 want to access additional threads for internal purposes. This
25393 increases the risk that by relying on implicitly selected thread, the
25394 frontend may be operating on a wrong one. Therefore, each MI command
25395 should explicitly specify which thread and frame to operate on. To
25396 make it possible, each MI command accepts the @samp{--thread} and
25397 @samp{--frame} options, the value to each is @value{GDBN} identifier
25398 for thread and frame to operate on.
25400 Usually, each top-level window in a frontend allows the user to select
25401 a thread and a frame, and remembers the user selection for further
25402 operations. However, in some cases @value{GDBN} may suggest that the
25403 current thread be changed. For example, when stopping on a breakpoint
25404 it is reasonable to switch to the thread where breakpoint is hit. For
25405 another example, if the user issues the CLI @samp{thread} command via
25406 the frontend, it is desirable to change the frontend's selected thread to the
25407 one specified by user. @value{GDBN} communicates the suggestion to
25408 change current thread using the @samp{=thread-selected} notification.
25409 No such notification is available for the selected frame at the moment.
25411 Note that historically, MI shares the selected thread with CLI, so
25412 frontends used the @code{-thread-select} to execute commands in the
25413 right context. However, getting this to work right is cumbersome. The
25414 simplest way is for frontend to emit @code{-thread-select} command
25415 before every command. This doubles the number of commands that need
25416 to be sent. The alternative approach is to suppress @code{-thread-select}
25417 if the selected thread in @value{GDBN} is supposed to be identical to the
25418 thread the frontend wants to operate on. However, getting this
25419 optimization right can be tricky. In particular, if the frontend
25420 sends several commands to @value{GDBN}, and one of the commands changes the
25421 selected thread, then the behaviour of subsequent commands will
25422 change. So, a frontend should either wait for response from such
25423 problematic commands, or explicitly add @code{-thread-select} for
25424 all subsequent commands. No frontend is known to do this exactly
25425 right, so it is suggested to just always pass the @samp{--thread} and
25426 @samp{--frame} options.
25428 @subsubsection Language
25430 The execution of several commands depends on which language is selected.
25431 By default, the current language (@pxref{show language}) is used.
25432 But for commands known to be language-sensitive, it is recommended
25433 to use the @samp{--language} option. This option takes one argument,
25434 which is the name of the language to use while executing the command.
25438 -data-evaluate-expression --language c "sizeof (void*)"
25443 The valid language names are the same names accepted by the
25444 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25445 @samp{local} or @samp{unknown}.
25447 @node Asynchronous and non-stop modes
25448 @subsection Asynchronous command execution and non-stop mode
25450 On some targets, @value{GDBN} is capable of processing MI commands
25451 even while the target is running. This is called @dfn{asynchronous
25452 command execution} (@pxref{Background Execution}). The frontend may
25453 specify a preferrence for asynchronous execution using the
25454 @code{-gdb-set mi-async 1} command, which should be emitted before
25455 either running the executable or attaching to the target. After the
25456 frontend has started the executable or attached to the target, it can
25457 find if asynchronous execution is enabled using the
25458 @code{-list-target-features} command.
25461 @item -gdb-set mi-async on
25462 @item -gdb-set mi-async off
25463 Set whether MI is in asynchronous mode.
25465 When @code{off}, which is the default, MI execution commands (e.g.,
25466 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25467 for the program to stop before processing further commands.
25469 When @code{on}, MI execution commands are background execution
25470 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25471 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25472 MI commands even while the target is running.
25474 @item -gdb-show mi-async
25475 Show whether MI asynchronous mode is enabled.
25478 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25479 @code{target-async} instead of @code{mi-async}, and it had the effect
25480 of both putting MI in asynchronous mode and making CLI background
25481 commands possible. CLI background commands are now always possible
25482 ``out of the box'' if the target supports them. The old spelling is
25483 kept as a deprecated alias for backwards compatibility.
25485 Even if @value{GDBN} can accept a command while target is running,
25486 many commands that access the target do not work when the target is
25487 running. Therefore, asynchronous command execution is most useful
25488 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25489 it is possible to examine the state of one thread, while other threads
25492 When a given thread is running, MI commands that try to access the
25493 target in the context of that thread may not work, or may work only on
25494 some targets. In particular, commands that try to operate on thread's
25495 stack will not work, on any target. Commands that read memory, or
25496 modify breakpoints, may work or not work, depending on the target. Note
25497 that even commands that operate on global state, such as @code{print},
25498 @code{set}, and breakpoint commands, still access the target in the
25499 context of a specific thread, so frontend should try to find a
25500 stopped thread and perform the operation on that thread (using the
25501 @samp{--thread} option).
25503 Which commands will work in the context of a running thread is
25504 highly target dependent. However, the two commands
25505 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25506 to find the state of a thread, will always work.
25508 @node Thread groups
25509 @subsection Thread groups
25510 @value{GDBN} may be used to debug several processes at the same time.
25511 On some platfroms, @value{GDBN} may support debugging of several
25512 hardware systems, each one having several cores with several different
25513 processes running on each core. This section describes the MI
25514 mechanism to support such debugging scenarios.
25516 The key observation is that regardless of the structure of the
25517 target, MI can have a global list of threads, because most commands that
25518 accept the @samp{--thread} option do not need to know what process that
25519 thread belongs to. Therefore, it is not necessary to introduce
25520 neither additional @samp{--process} option, nor an notion of the
25521 current process in the MI interface. The only strictly new feature
25522 that is required is the ability to find how the threads are grouped
25525 To allow the user to discover such grouping, and to support arbitrary
25526 hierarchy of machines/cores/processes, MI introduces the concept of a
25527 @dfn{thread group}. Thread group is a collection of threads and other
25528 thread groups. A thread group always has a string identifier, a type,
25529 and may have additional attributes specific to the type. A new
25530 command, @code{-list-thread-groups}, returns the list of top-level
25531 thread groups, which correspond to processes that @value{GDBN} is
25532 debugging at the moment. By passing an identifier of a thread group
25533 to the @code{-list-thread-groups} command, it is possible to obtain
25534 the members of specific thread group.
25536 To allow the user to easily discover processes, and other objects, he
25537 wishes to debug, a concept of @dfn{available thread group} is
25538 introduced. Available thread group is an thread group that
25539 @value{GDBN} is not debugging, but that can be attached to, using the
25540 @code{-target-attach} command. The list of available top-level thread
25541 groups can be obtained using @samp{-list-thread-groups --available}.
25542 In general, the content of a thread group may be only retrieved only
25543 after attaching to that thread group.
25545 Thread groups are related to inferiors (@pxref{Inferiors and
25546 Programs}). Each inferior corresponds to a thread group of a special
25547 type @samp{process}, and some additional operations are permitted on
25548 such thread groups.
25550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25551 @node GDB/MI Command Syntax
25552 @section @sc{gdb/mi} Command Syntax
25555 * GDB/MI Input Syntax::
25556 * GDB/MI Output Syntax::
25559 @node GDB/MI Input Syntax
25560 @subsection @sc{gdb/mi} Input Syntax
25562 @cindex input syntax for @sc{gdb/mi}
25563 @cindex @sc{gdb/mi}, input syntax
25565 @item @var{command} @expansion{}
25566 @code{@var{cli-command} | @var{mi-command}}
25568 @item @var{cli-command} @expansion{}
25569 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25570 @var{cli-command} is any existing @value{GDBN} CLI command.
25572 @item @var{mi-command} @expansion{}
25573 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25574 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25576 @item @var{token} @expansion{}
25577 "any sequence of digits"
25579 @item @var{option} @expansion{}
25580 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25582 @item @var{parameter} @expansion{}
25583 @code{@var{non-blank-sequence} | @var{c-string}}
25585 @item @var{operation} @expansion{}
25586 @emph{any of the operations described in this chapter}
25588 @item @var{non-blank-sequence} @expansion{}
25589 @emph{anything, provided it doesn't contain special characters such as
25590 "-", @var{nl}, """ and of course " "}
25592 @item @var{c-string} @expansion{}
25593 @code{""" @var{seven-bit-iso-c-string-content} """}
25595 @item @var{nl} @expansion{}
25604 The CLI commands are still handled by the @sc{mi} interpreter; their
25605 output is described below.
25608 The @code{@var{token}}, when present, is passed back when the command
25612 Some @sc{mi} commands accept optional arguments as part of the parameter
25613 list. Each option is identified by a leading @samp{-} (dash) and may be
25614 followed by an optional argument parameter. Options occur first in the
25615 parameter list and can be delimited from normal parameters using
25616 @samp{--} (this is useful when some parameters begin with a dash).
25623 We want easy access to the existing CLI syntax (for debugging).
25626 We want it to be easy to spot a @sc{mi} operation.
25629 @node GDB/MI Output Syntax
25630 @subsection @sc{gdb/mi} Output Syntax
25632 @cindex output syntax of @sc{gdb/mi}
25633 @cindex @sc{gdb/mi}, output syntax
25634 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25635 followed, optionally, by a single result record. This result record
25636 is for the most recent command. The sequence of output records is
25637 terminated by @samp{(gdb)}.
25639 If an input command was prefixed with a @code{@var{token}} then the
25640 corresponding output for that command will also be prefixed by that same
25644 @item @var{output} @expansion{}
25645 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25647 @item @var{result-record} @expansion{}
25648 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25650 @item @var{out-of-band-record} @expansion{}
25651 @code{@var{async-record} | @var{stream-record}}
25653 @item @var{async-record} @expansion{}
25654 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25656 @item @var{exec-async-output} @expansion{}
25657 @code{[ @var{token} ] "*" @var{async-output nl}}
25659 @item @var{status-async-output} @expansion{}
25660 @code{[ @var{token} ] "+" @var{async-output nl}}
25662 @item @var{notify-async-output} @expansion{}
25663 @code{[ @var{token} ] "=" @var{async-output nl}}
25665 @item @var{async-output} @expansion{}
25666 @code{@var{async-class} ( "," @var{result} )*}
25668 @item @var{result-class} @expansion{}
25669 @code{"done" | "running" | "connected" | "error" | "exit"}
25671 @item @var{async-class} @expansion{}
25672 @code{"stopped" | @var{others}} (where @var{others} will be added
25673 depending on the needs---this is still in development).
25675 @item @var{result} @expansion{}
25676 @code{ @var{variable} "=" @var{value}}
25678 @item @var{variable} @expansion{}
25679 @code{ @var{string} }
25681 @item @var{value} @expansion{}
25682 @code{ @var{const} | @var{tuple} | @var{list} }
25684 @item @var{const} @expansion{}
25685 @code{@var{c-string}}
25687 @item @var{tuple} @expansion{}
25688 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25690 @item @var{list} @expansion{}
25691 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25692 @var{result} ( "," @var{result} )* "]" }
25694 @item @var{stream-record} @expansion{}
25695 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25697 @item @var{console-stream-output} @expansion{}
25698 @code{"~" @var{c-string nl}}
25700 @item @var{target-stream-output} @expansion{}
25701 @code{"@@" @var{c-string nl}}
25703 @item @var{log-stream-output} @expansion{}
25704 @code{"&" @var{c-string nl}}
25706 @item @var{nl} @expansion{}
25709 @item @var{token} @expansion{}
25710 @emph{any sequence of digits}.
25718 All output sequences end in a single line containing a period.
25721 The @code{@var{token}} is from the corresponding request. Note that
25722 for all async output, while the token is allowed by the grammar and
25723 may be output by future versions of @value{GDBN} for select async
25724 output messages, it is generally omitted. Frontends should treat
25725 all async output as reporting general changes in the state of the
25726 target and there should be no need to associate async output to any
25730 @cindex status output in @sc{gdb/mi}
25731 @var{status-async-output} contains on-going status information about the
25732 progress of a slow operation. It can be discarded. All status output is
25733 prefixed by @samp{+}.
25736 @cindex async output in @sc{gdb/mi}
25737 @var{exec-async-output} contains asynchronous state change on the target
25738 (stopped, started, disappeared). All async output is prefixed by
25742 @cindex notify output in @sc{gdb/mi}
25743 @var{notify-async-output} contains supplementary information that the
25744 client should handle (e.g., a new breakpoint information). All notify
25745 output is prefixed by @samp{=}.
25748 @cindex console output in @sc{gdb/mi}
25749 @var{console-stream-output} is output that should be displayed as is in the
25750 console. It is the textual response to a CLI command. All the console
25751 output is prefixed by @samp{~}.
25754 @cindex target output in @sc{gdb/mi}
25755 @var{target-stream-output} is the output produced by the target program.
25756 All the target output is prefixed by @samp{@@}.
25759 @cindex log output in @sc{gdb/mi}
25760 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25761 instance messages that should be displayed as part of an error log. All
25762 the log output is prefixed by @samp{&}.
25765 @cindex list output in @sc{gdb/mi}
25766 New @sc{gdb/mi} commands should only output @var{lists} containing
25772 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25773 details about the various output records.
25775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25776 @node GDB/MI Compatibility with CLI
25777 @section @sc{gdb/mi} Compatibility with CLI
25779 @cindex compatibility, @sc{gdb/mi} and CLI
25780 @cindex @sc{gdb/mi}, compatibility with CLI
25782 For the developers convenience CLI commands can be entered directly,
25783 but there may be some unexpected behaviour. For example, commands
25784 that query the user will behave as if the user replied yes, breakpoint
25785 command lists are not executed and some CLI commands, such as
25786 @code{if}, @code{when} and @code{define}, prompt for further input with
25787 @samp{>}, which is not valid MI output.
25789 This feature may be removed at some stage in the future and it is
25790 recommended that front ends use the @code{-interpreter-exec} command
25791 (@pxref{-interpreter-exec}).
25793 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25794 @node GDB/MI Development and Front Ends
25795 @section @sc{gdb/mi} Development and Front Ends
25796 @cindex @sc{gdb/mi} development
25798 The application which takes the MI output and presents the state of the
25799 program being debugged to the user is called a @dfn{front end}.
25801 Although @sc{gdb/mi} is still incomplete, it is currently being used
25802 by a variety of front ends to @value{GDBN}. This makes it difficult
25803 to introduce new functionality without breaking existing usage. This
25804 section tries to minimize the problems by describing how the protocol
25807 Some changes in MI need not break a carefully designed front end, and
25808 for these the MI version will remain unchanged. The following is a
25809 list of changes that may occur within one level, so front ends should
25810 parse MI output in a way that can handle them:
25814 New MI commands may be added.
25817 New fields may be added to the output of any MI command.
25820 The range of values for fields with specified values, e.g.,
25821 @code{in_scope} (@pxref{-var-update}) may be extended.
25823 @c The format of field's content e.g type prefix, may change so parse it
25824 @c at your own risk. Yes, in general?
25826 @c The order of fields may change? Shouldn't really matter but it might
25827 @c resolve inconsistencies.
25830 If the changes are likely to break front ends, the MI version level
25831 will be increased by one. This will allow the front end to parse the
25832 output according to the MI version. Apart from mi0, new versions of
25833 @value{GDBN} will not support old versions of MI and it will be the
25834 responsibility of the front end to work with the new one.
25836 @c Starting with mi3, add a new command -mi-version that prints the MI
25839 The best way to avoid unexpected changes in MI that might break your front
25840 end is to make your project known to @value{GDBN} developers and
25841 follow development on @email{gdb@@sourceware.org} and
25842 @email{gdb-patches@@sourceware.org}.
25843 @cindex mailing lists
25845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25846 @node GDB/MI Output Records
25847 @section @sc{gdb/mi} Output Records
25850 * GDB/MI Result Records::
25851 * GDB/MI Stream Records::
25852 * GDB/MI Async Records::
25853 * GDB/MI Breakpoint Information::
25854 * GDB/MI Frame Information::
25855 * GDB/MI Thread Information::
25856 * GDB/MI Ada Exception Information::
25859 @node GDB/MI Result Records
25860 @subsection @sc{gdb/mi} Result Records
25862 @cindex result records in @sc{gdb/mi}
25863 @cindex @sc{gdb/mi}, result records
25864 In addition to a number of out-of-band notifications, the response to a
25865 @sc{gdb/mi} command includes one of the following result indications:
25869 @item "^done" [ "," @var{results} ]
25870 The synchronous operation was successful, @code{@var{results}} are the return
25875 This result record is equivalent to @samp{^done}. Historically, it
25876 was output instead of @samp{^done} if the command has resumed the
25877 target. This behaviour is maintained for backward compatibility, but
25878 all frontends should treat @samp{^done} and @samp{^running}
25879 identically and rely on the @samp{*running} output record to determine
25880 which threads are resumed.
25884 @value{GDBN} has connected to a remote target.
25886 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25888 The operation failed. The @code{msg=@var{c-string}} variable contains
25889 the corresponding error message.
25891 If present, the @code{code=@var{c-string}} variable provides an error
25892 code on which consumers can rely on to detect the corresponding
25893 error condition. At present, only one error code is defined:
25896 @item "undefined-command"
25897 Indicates that the command causing the error does not exist.
25902 @value{GDBN} has terminated.
25906 @node GDB/MI Stream Records
25907 @subsection @sc{gdb/mi} Stream Records
25909 @cindex @sc{gdb/mi}, stream records
25910 @cindex stream records in @sc{gdb/mi}
25911 @value{GDBN} internally maintains a number of output streams: the console, the
25912 target, and the log. The output intended for each of these streams is
25913 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25915 Each stream record begins with a unique @dfn{prefix character} which
25916 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25917 Syntax}). In addition to the prefix, each stream record contains a
25918 @code{@var{string-output}}. This is either raw text (with an implicit new
25919 line) or a quoted C string (which does not contain an implicit newline).
25922 @item "~" @var{string-output}
25923 The console output stream contains text that should be displayed in the
25924 CLI console window. It contains the textual responses to CLI commands.
25926 @item "@@" @var{string-output}
25927 The target output stream contains any textual output from the running
25928 target. This is only present when GDB's event loop is truly
25929 asynchronous, which is currently only the case for remote targets.
25931 @item "&" @var{string-output}
25932 The log stream contains debugging messages being produced by @value{GDBN}'s
25936 @node GDB/MI Async Records
25937 @subsection @sc{gdb/mi} Async Records
25939 @cindex async records in @sc{gdb/mi}
25940 @cindex @sc{gdb/mi}, async records
25941 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25942 additional changes that have occurred. Those changes can either be a
25943 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25944 target activity (e.g., target stopped).
25946 The following is the list of possible async records:
25950 @item *running,thread-id="@var{thread}"
25951 The target is now running. The @var{thread} field tells which
25952 specific thread is now running, and can be @samp{all} if all threads
25953 are running. The frontend should assume that no interaction with a
25954 running thread is possible after this notification is produced.
25955 The frontend should not assume that this notification is output
25956 only once for any command. @value{GDBN} may emit this notification
25957 several times, either for different threads, because it cannot resume
25958 all threads together, or even for a single thread, if the thread must
25959 be stepped though some code before letting it run freely.
25961 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25962 The target has stopped. The @var{reason} field can have one of the
25966 @item breakpoint-hit
25967 A breakpoint was reached.
25968 @item watchpoint-trigger
25969 A watchpoint was triggered.
25970 @item read-watchpoint-trigger
25971 A read watchpoint was triggered.
25972 @item access-watchpoint-trigger
25973 An access watchpoint was triggered.
25974 @item function-finished
25975 An -exec-finish or similar CLI command was accomplished.
25976 @item location-reached
25977 An -exec-until or similar CLI command was accomplished.
25978 @item watchpoint-scope
25979 A watchpoint has gone out of scope.
25980 @item end-stepping-range
25981 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25982 similar CLI command was accomplished.
25983 @item exited-signalled
25984 The inferior exited because of a signal.
25986 The inferior exited.
25987 @item exited-normally
25988 The inferior exited normally.
25989 @item signal-received
25990 A signal was received by the inferior.
25992 The inferior has stopped due to a library being loaded or unloaded.
25993 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25994 set or when a @code{catch load} or @code{catch unload} catchpoint is
25995 in use (@pxref{Set Catchpoints}).
25997 The inferior has forked. This is reported when @code{catch fork}
25998 (@pxref{Set Catchpoints}) has been used.
26000 The inferior has vforked. This is reported in when @code{catch vfork}
26001 (@pxref{Set Catchpoints}) has been used.
26002 @item syscall-entry
26003 The inferior entered a system call. This is reported when @code{catch
26004 syscall} (@pxref{Set Catchpoints}) has been used.
26005 @item syscall-return
26006 The inferior returned from a system call. This is reported when
26007 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26009 The inferior called @code{exec}. This is reported when @code{catch exec}
26010 (@pxref{Set Catchpoints}) has been used.
26013 The @var{id} field identifies the thread that directly caused the stop
26014 -- for example by hitting a breakpoint. Depending on whether all-stop
26015 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26016 stop all threads, or only the thread that directly triggered the stop.
26017 If all threads are stopped, the @var{stopped} field will have the
26018 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26019 field will be a list of thread identifiers. Presently, this list will
26020 always include a single thread, but frontend should be prepared to see
26021 several threads in the list. The @var{core} field reports the
26022 processor core on which the stop event has happened. This field may be absent
26023 if such information is not available.
26025 @item =thread-group-added,id="@var{id}"
26026 @itemx =thread-group-removed,id="@var{id}"
26027 A thread group was either added or removed. The @var{id} field
26028 contains the @value{GDBN} identifier of the thread group. When a thread
26029 group is added, it generally might not be associated with a running
26030 process. When a thread group is removed, its id becomes invalid and
26031 cannot be used in any way.
26033 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26034 A thread group became associated with a running program,
26035 either because the program was just started or the thread group
26036 was attached to a program. The @var{id} field contains the
26037 @value{GDBN} identifier of the thread group. The @var{pid} field
26038 contains process identifier, specific to the operating system.
26040 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26041 A thread group is no longer associated with a running program,
26042 either because the program has exited, or because it was detached
26043 from. The @var{id} field contains the @value{GDBN} identifier of the
26044 thread group. The @var{code} field is the exit code of the inferior; it exists
26045 only when the inferior exited with some code.
26047 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26048 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26049 A thread either was created, or has exited. The @var{id} field
26050 contains the @value{GDBN} identifier of the thread. The @var{gid}
26051 field identifies the thread group this thread belongs to.
26053 @item =thread-selected,id="@var{id}"
26054 Informs that the selected thread was changed as result of the last
26055 command. This notification is not emitted as result of @code{-thread-select}
26056 command but is emitted whenever an MI command that is not documented
26057 to change the selected thread actually changes it. In particular,
26058 invoking, directly or indirectly (via user-defined command), the CLI
26059 @code{thread} command, will generate this notification.
26061 We suggest that in response to this notification, front ends
26062 highlight the selected thread and cause subsequent commands to apply to
26065 @item =library-loaded,...
26066 Reports that a new library file was loaded by the program. This
26067 notification has 4 fields---@var{id}, @var{target-name},
26068 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26069 opaque identifier of the library. For remote debugging case,
26070 @var{target-name} and @var{host-name} fields give the name of the
26071 library file on the target, and on the host respectively. For native
26072 debugging, both those fields have the same value. The
26073 @var{symbols-loaded} field is emitted only for backward compatibility
26074 and should not be relied on to convey any useful information. The
26075 @var{thread-group} field, if present, specifies the id of the thread
26076 group in whose context the library was loaded. If the field is
26077 absent, it means the library was loaded in the context of all present
26080 @item =library-unloaded,...
26081 Reports that a library was unloaded by the program. This notification
26082 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26083 the same meaning as for the @code{=library-loaded} notification.
26084 The @var{thread-group} field, if present, specifies the id of the
26085 thread group in whose context the library was unloaded. If the field is
26086 absent, it means the library was unloaded in the context of all present
26089 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26090 @itemx =traceframe-changed,end
26091 Reports that the trace frame was changed and its new number is
26092 @var{tfnum}. The number of the tracepoint associated with this trace
26093 frame is @var{tpnum}.
26095 @item =tsv-created,name=@var{name},initial=@var{initial}
26096 Reports that the new trace state variable @var{name} is created with
26097 initial value @var{initial}.
26099 @item =tsv-deleted,name=@var{name}
26100 @itemx =tsv-deleted
26101 Reports that the trace state variable @var{name} is deleted or all
26102 trace state variables are deleted.
26104 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26105 Reports that the trace state variable @var{name} is modified with
26106 the initial value @var{initial}. The current value @var{current} of
26107 trace state variable is optional and is reported if the current
26108 value of trace state variable is known.
26110 @item =breakpoint-created,bkpt=@{...@}
26111 @itemx =breakpoint-modified,bkpt=@{...@}
26112 @itemx =breakpoint-deleted,id=@var{number}
26113 Reports that a breakpoint was created, modified, or deleted,
26114 respectively. Only user-visible breakpoints are reported to the MI
26117 The @var{bkpt} argument is of the same form as returned by the various
26118 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26119 @var{number} is the ordinal number of the breakpoint.
26121 Note that if a breakpoint is emitted in the result record of a
26122 command, then it will not also be emitted in an async record.
26124 @item =record-started,thread-group="@var{id}"
26125 @itemx =record-stopped,thread-group="@var{id}"
26126 Execution log recording was either started or stopped on an
26127 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26128 group corresponding to the affected inferior.
26130 @item =cmd-param-changed,param=@var{param},value=@var{value}
26131 Reports that a parameter of the command @code{set @var{param}} is
26132 changed to @var{value}. In the multi-word @code{set} command,
26133 the @var{param} is the whole parameter list to @code{set} command.
26134 For example, In command @code{set check type on}, @var{param}
26135 is @code{check type} and @var{value} is @code{on}.
26137 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26138 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26139 written in an inferior. The @var{id} is the identifier of the
26140 thread group corresponding to the affected inferior. The optional
26141 @code{type="code"} part is reported if the memory written to holds
26145 @node GDB/MI Breakpoint Information
26146 @subsection @sc{gdb/mi} Breakpoint Information
26148 When @value{GDBN} reports information about a breakpoint, a
26149 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26154 The breakpoint number. For a breakpoint that represents one location
26155 of a multi-location breakpoint, this will be a dotted pair, like
26159 The type of the breakpoint. For ordinary breakpoints this will be
26160 @samp{breakpoint}, but many values are possible.
26163 If the type of the breakpoint is @samp{catchpoint}, then this
26164 indicates the exact type of catchpoint.
26167 This is the breakpoint disposition---either @samp{del}, meaning that
26168 the breakpoint will be deleted at the next stop, or @samp{keep},
26169 meaning that the breakpoint will not be deleted.
26172 This indicates whether the breakpoint is enabled, in which case the
26173 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26174 Note that this is not the same as the field @code{enable}.
26177 The address of the breakpoint. This may be a hexidecimal number,
26178 giving the address; or the string @samp{<PENDING>}, for a pending
26179 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26180 multiple locations. This field will not be present if no address can
26181 be determined. For example, a watchpoint does not have an address.
26184 If known, the function in which the breakpoint appears.
26185 If not known, this field is not present.
26188 The name of the source file which contains this function, if known.
26189 If not known, this field is not present.
26192 The full file name of the source file which contains this function, if
26193 known. If not known, this field is not present.
26196 The line number at which this breakpoint appears, if known.
26197 If not known, this field is not present.
26200 If the source file is not known, this field may be provided. If
26201 provided, this holds the address of the breakpoint, possibly followed
26205 If this breakpoint is pending, this field is present and holds the
26206 text used to set the breakpoint, as entered by the user.
26209 Where this breakpoint's condition is evaluated, either @samp{host} or
26213 If this is a thread-specific breakpoint, then this identifies the
26214 thread in which the breakpoint can trigger.
26217 If this breakpoint is restricted to a particular Ada task, then this
26218 field will hold the task identifier.
26221 If the breakpoint is conditional, this is the condition expression.
26224 The ignore count of the breakpoint.
26227 The enable count of the breakpoint.
26229 @item traceframe-usage
26232 @item static-tracepoint-marker-string-id
26233 For a static tracepoint, the name of the static tracepoint marker.
26236 For a masked watchpoint, this is the mask.
26239 A tracepoint's pass count.
26241 @item original-location
26242 The location of the breakpoint as originally specified by the user.
26243 This field is optional.
26246 The number of times the breakpoint has been hit.
26249 This field is only given for tracepoints. This is either @samp{y},
26250 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26254 Some extra data, the exact contents of which are type-dependent.
26258 For example, here is what the output of @code{-break-insert}
26259 (@pxref{GDB/MI Breakpoint Commands}) might be:
26262 -> -break-insert main
26263 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26264 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26265 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26270 @node GDB/MI Frame Information
26271 @subsection @sc{gdb/mi} Frame Information
26273 Response from many MI commands includes an information about stack
26274 frame. This information is a tuple that may have the following
26279 The level of the stack frame. The innermost frame has the level of
26280 zero. This field is always present.
26283 The name of the function corresponding to the frame. This field may
26284 be absent if @value{GDBN} is unable to determine the function name.
26287 The code address for the frame. This field is always present.
26290 The name of the source files that correspond to the frame's code
26291 address. This field may be absent.
26294 The source line corresponding to the frames' code address. This field
26298 The name of the binary file (either executable or shared library) the
26299 corresponds to the frame's code address. This field may be absent.
26303 @node GDB/MI Thread Information
26304 @subsection @sc{gdb/mi} Thread Information
26306 Whenever @value{GDBN} has to report an information about a thread, it
26307 uses a tuple with the following fields:
26311 The numeric id assigned to the thread by @value{GDBN}. This field is
26315 Target-specific string identifying the thread. This field is always present.
26318 Additional information about the thread provided by the target.
26319 It is supposed to be human-readable and not interpreted by the
26320 frontend. This field is optional.
26323 Either @samp{stopped} or @samp{running}, depending on whether the
26324 thread is presently running. This field is always present.
26327 The value of this field is an integer number of the processor core the
26328 thread was last seen on. This field is optional.
26331 @node GDB/MI Ada Exception Information
26332 @subsection @sc{gdb/mi} Ada Exception Information
26334 Whenever a @code{*stopped} record is emitted because the program
26335 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26336 @value{GDBN} provides the name of the exception that was raised via
26337 the @code{exception-name} field.
26339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26340 @node GDB/MI Simple Examples
26341 @section Simple Examples of @sc{gdb/mi} Interaction
26342 @cindex @sc{gdb/mi}, simple examples
26344 This subsection presents several simple examples of interaction using
26345 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26346 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26347 the output received from @sc{gdb/mi}.
26349 Note the line breaks shown in the examples are here only for
26350 readability, they don't appear in the real output.
26352 @subheading Setting a Breakpoint
26354 Setting a breakpoint generates synchronous output which contains detailed
26355 information of the breakpoint.
26358 -> -break-insert main
26359 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26360 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26361 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26366 @subheading Program Execution
26368 Program execution generates asynchronous records and MI gives the
26369 reason that execution stopped.
26375 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26376 frame=@{addr="0x08048564",func="main",
26377 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26378 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26383 <- *stopped,reason="exited-normally"
26387 @subheading Quitting @value{GDBN}
26389 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26397 Please note that @samp{^exit} is printed immediately, but it might
26398 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26399 performs necessary cleanups, including killing programs being debugged
26400 or disconnecting from debug hardware, so the frontend should wait till
26401 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26402 fails to exit in reasonable time.
26404 @subheading A Bad Command
26406 Here's what happens if you pass a non-existent command:
26410 <- ^error,msg="Undefined MI command: rubbish"
26415 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26416 @node GDB/MI Command Description Format
26417 @section @sc{gdb/mi} Command Description Format
26419 The remaining sections describe blocks of commands. Each block of
26420 commands is laid out in a fashion similar to this section.
26422 @subheading Motivation
26424 The motivation for this collection of commands.
26426 @subheading Introduction
26428 A brief introduction to this collection of commands as a whole.
26430 @subheading Commands
26432 For each command in the block, the following is described:
26434 @subsubheading Synopsis
26437 -command @var{args}@dots{}
26440 @subsubheading Result
26442 @subsubheading @value{GDBN} Command
26444 The corresponding @value{GDBN} CLI command(s), if any.
26446 @subsubheading Example
26448 Example(s) formatted for readability. Some of the described commands have
26449 not been implemented yet and these are labeled N.A.@: (not available).
26452 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26453 @node GDB/MI Breakpoint Commands
26454 @section @sc{gdb/mi} Breakpoint Commands
26456 @cindex breakpoint commands for @sc{gdb/mi}
26457 @cindex @sc{gdb/mi}, breakpoint commands
26458 This section documents @sc{gdb/mi} commands for manipulating
26461 @subheading The @code{-break-after} Command
26462 @findex -break-after
26464 @subsubheading Synopsis
26467 -break-after @var{number} @var{count}
26470 The breakpoint number @var{number} is not in effect until it has been
26471 hit @var{count} times. To see how this is reflected in the output of
26472 the @samp{-break-list} command, see the description of the
26473 @samp{-break-list} command below.
26475 @subsubheading @value{GDBN} Command
26477 The corresponding @value{GDBN} command is @samp{ignore}.
26479 @subsubheading Example
26484 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26485 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26486 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26494 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26495 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26496 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26497 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26498 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26499 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26500 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26501 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26502 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26503 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26508 @subheading The @code{-break-catch} Command
26509 @findex -break-catch
26512 @subheading The @code{-break-commands} Command
26513 @findex -break-commands
26515 @subsubheading Synopsis
26518 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26521 Specifies the CLI commands that should be executed when breakpoint
26522 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26523 are the commands. If no command is specified, any previously-set
26524 commands are cleared. @xref{Break Commands}. Typical use of this
26525 functionality is tracing a program, that is, printing of values of
26526 some variables whenever breakpoint is hit and then continuing.
26528 @subsubheading @value{GDBN} Command
26530 The corresponding @value{GDBN} command is @samp{commands}.
26532 @subsubheading Example
26537 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26538 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26539 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26542 -break-commands 1 "print v" "continue"
26547 @subheading The @code{-break-condition} Command
26548 @findex -break-condition
26550 @subsubheading Synopsis
26553 -break-condition @var{number} @var{expr}
26556 Breakpoint @var{number} will stop the program only if the condition in
26557 @var{expr} is true. The condition becomes part of the
26558 @samp{-break-list} output (see the description of the @samp{-break-list}
26561 @subsubheading @value{GDBN} Command
26563 The corresponding @value{GDBN} command is @samp{condition}.
26565 @subsubheading Example
26569 -break-condition 1 1
26573 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26574 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26575 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26576 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26577 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26578 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26579 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26580 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26581 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26582 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26586 @subheading The @code{-break-delete} Command
26587 @findex -break-delete
26589 @subsubheading Synopsis
26592 -break-delete ( @var{breakpoint} )+
26595 Delete the breakpoint(s) whose number(s) are specified in the argument
26596 list. This is obviously reflected in the breakpoint list.
26598 @subsubheading @value{GDBN} Command
26600 The corresponding @value{GDBN} command is @samp{delete}.
26602 @subsubheading Example
26610 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26611 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26612 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26613 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26614 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26615 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26616 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26621 @subheading The @code{-break-disable} Command
26622 @findex -break-disable
26624 @subsubheading Synopsis
26627 -break-disable ( @var{breakpoint} )+
26630 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26631 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26633 @subsubheading @value{GDBN} Command
26635 The corresponding @value{GDBN} command is @samp{disable}.
26637 @subsubheading Example
26645 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26646 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26647 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26648 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26649 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26650 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26651 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26652 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26653 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26654 line="5",thread-groups=["i1"],times="0"@}]@}
26658 @subheading The @code{-break-enable} Command
26659 @findex -break-enable
26661 @subsubheading Synopsis
26664 -break-enable ( @var{breakpoint} )+
26667 Enable (previously disabled) @var{breakpoint}(s).
26669 @subsubheading @value{GDBN} Command
26671 The corresponding @value{GDBN} command is @samp{enable}.
26673 @subsubheading Example
26681 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26682 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26683 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26684 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26685 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26686 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26687 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26688 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26689 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26690 line="5",thread-groups=["i1"],times="0"@}]@}
26694 @subheading The @code{-break-info} Command
26695 @findex -break-info
26697 @subsubheading Synopsis
26700 -break-info @var{breakpoint}
26704 Get information about a single breakpoint.
26706 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26707 Information}, for details on the format of each breakpoint in the
26710 @subsubheading @value{GDBN} Command
26712 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26714 @subsubheading Example
26717 @subheading The @code{-break-insert} Command
26718 @findex -break-insert
26719 @anchor{-break-insert}
26721 @subsubheading Synopsis
26724 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26725 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26726 [ -p @var{thread-id} ] [ @var{location} ]
26730 If specified, @var{location}, can be one of:
26733 @item linespec location
26734 A linespec location. @xref{Linespec Locations}.
26736 @item explicit location
26737 An explicit location. @sc{gdb/mi} explicit locations are
26738 analogous to the CLI's explicit locations using the option names
26739 listed below. @xref{Explicit Locations}.
26742 @item --source @var{filename}
26743 The source file name of the location. This option requires the use
26744 of either @samp{--function} or @samp{--line}.
26746 @item --function @var{function}
26747 The name of a function or method.
26749 @item --label @var{label}
26750 The name of a label.
26752 @item --line @var{lineoffset}
26753 An absolute or relative line offset from the start of the location.
26756 @item address location
26757 An address location, *@var{address}. @xref{Address Locations}.
26761 The possible optional parameters of this command are:
26765 Insert a temporary breakpoint.
26767 Insert a hardware breakpoint.
26769 If @var{location} cannot be parsed (for example if it
26770 refers to unknown files or functions), create a pending
26771 breakpoint. Without this flag, @value{GDBN} will report
26772 an error, and won't create a breakpoint, if @var{location}
26775 Create a disabled breakpoint.
26777 Create a tracepoint. @xref{Tracepoints}. When this parameter
26778 is used together with @samp{-h}, a fast tracepoint is created.
26779 @item -c @var{condition}
26780 Make the breakpoint conditional on @var{condition}.
26781 @item -i @var{ignore-count}
26782 Initialize the @var{ignore-count}.
26783 @item -p @var{thread-id}
26784 Restrict the breakpoint to the specified @var{thread-id}.
26787 @subsubheading Result
26789 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26790 resulting breakpoint.
26792 Note: this format is open to change.
26793 @c An out-of-band breakpoint instead of part of the result?
26795 @subsubheading @value{GDBN} Command
26797 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26798 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26800 @subsubheading Example
26805 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26806 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26809 -break-insert -t foo
26810 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26811 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26815 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26816 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26817 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26818 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26819 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26820 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26821 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26822 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26823 addr="0x0001072c", func="main",file="recursive2.c",
26824 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26826 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26827 addr="0x00010774",func="foo",file="recursive2.c",
26828 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26831 @c -break-insert -r foo.*
26832 @c ~int foo(int, int);
26833 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26834 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26839 @subheading The @code{-dprintf-insert} Command
26840 @findex -dprintf-insert
26842 @subsubheading Synopsis
26845 -dprintf-insert [ -t ] [ -f ] [ -d ]
26846 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26847 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26852 If supplied, @var{location} may be specified the same way as for
26853 the @code{-break-insert} command. @xref{-break-insert}.
26855 The possible optional parameters of this command are:
26859 Insert a temporary breakpoint.
26861 If @var{location} cannot be parsed (for example, if it
26862 refers to unknown files or functions), create a pending
26863 breakpoint. Without this flag, @value{GDBN} will report
26864 an error, and won't create a breakpoint, if @var{location}
26867 Create a disabled breakpoint.
26868 @item -c @var{condition}
26869 Make the breakpoint conditional on @var{condition}.
26870 @item -i @var{ignore-count}
26871 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26872 to @var{ignore-count}.
26873 @item -p @var{thread-id}
26874 Restrict the breakpoint to the specified @var{thread-id}.
26877 @subsubheading Result
26879 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26880 resulting breakpoint.
26882 @c An out-of-band breakpoint instead of part of the result?
26884 @subsubheading @value{GDBN} Command
26886 The corresponding @value{GDBN} command is @samp{dprintf}.
26888 @subsubheading Example
26892 4-dprintf-insert foo "At foo entry\n"
26893 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26894 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26895 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26896 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26897 original-location="foo"@}
26899 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26900 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26901 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26902 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26903 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26904 original-location="mi-dprintf.c:26"@}
26908 @subheading The @code{-break-list} Command
26909 @findex -break-list
26911 @subsubheading Synopsis
26917 Displays the list of inserted breakpoints, showing the following fields:
26921 number of the breakpoint
26923 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26925 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26928 is the breakpoint enabled or no: @samp{y} or @samp{n}
26930 memory location at which the breakpoint is set
26932 logical location of the breakpoint, expressed by function name, file
26934 @item Thread-groups
26935 list of thread groups to which this breakpoint applies
26937 number of times the breakpoint has been hit
26940 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26941 @code{body} field is an empty list.
26943 @subsubheading @value{GDBN} Command
26945 The corresponding @value{GDBN} command is @samp{info break}.
26947 @subsubheading Example
26952 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26953 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26954 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26955 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26956 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26957 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26958 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26959 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26960 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26962 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26963 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26964 line="13",thread-groups=["i1"],times="0"@}]@}
26968 Here's an example of the result when there are no breakpoints:
26973 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26974 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26975 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26976 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26977 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26978 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26979 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26984 @subheading The @code{-break-passcount} Command
26985 @findex -break-passcount
26987 @subsubheading Synopsis
26990 -break-passcount @var{tracepoint-number} @var{passcount}
26993 Set the passcount for tracepoint @var{tracepoint-number} to
26994 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26995 is not a tracepoint, error is emitted. This corresponds to CLI
26996 command @samp{passcount}.
26998 @subheading The @code{-break-watch} Command
26999 @findex -break-watch
27001 @subsubheading Synopsis
27004 -break-watch [ -a | -r ]
27007 Create a watchpoint. With the @samp{-a} option it will create an
27008 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27009 read from or on a write to the memory location. With the @samp{-r}
27010 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27011 trigger only when the memory location is accessed for reading. Without
27012 either of the options, the watchpoint created is a regular watchpoint,
27013 i.e., it will trigger when the memory location is accessed for writing.
27014 @xref{Set Watchpoints, , Setting Watchpoints}.
27016 Note that @samp{-break-list} will report a single list of watchpoints and
27017 breakpoints inserted.
27019 @subsubheading @value{GDBN} Command
27021 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27024 @subsubheading Example
27026 Setting a watchpoint on a variable in the @code{main} function:
27031 ^done,wpt=@{number="2",exp="x"@}
27036 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27037 value=@{old="-268439212",new="55"@},
27038 frame=@{func="main",args=[],file="recursive2.c",
27039 fullname="/home/foo/bar/recursive2.c",line="5"@}
27043 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27044 the program execution twice: first for the variable changing value, then
27045 for the watchpoint going out of scope.
27050 ^done,wpt=@{number="5",exp="C"@}
27055 *stopped,reason="watchpoint-trigger",
27056 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27057 frame=@{func="callee4",args=[],
27058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27064 *stopped,reason="watchpoint-scope",wpnum="5",
27065 frame=@{func="callee3",args=[@{name="strarg",
27066 value="0x11940 \"A string argument.\""@}],
27067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27068 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27072 Listing breakpoints and watchpoints, at different points in the program
27073 execution. Note that once the watchpoint goes out of scope, it is
27079 ^done,wpt=@{number="2",exp="C"@}
27082 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27083 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27084 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27085 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27086 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27087 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27088 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27089 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27090 addr="0x00010734",func="callee4",
27091 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27092 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27094 bkpt=@{number="2",type="watchpoint",disp="keep",
27095 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27100 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27101 value=@{old="-276895068",new="3"@},
27102 frame=@{func="callee4",args=[],
27103 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27104 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27107 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27108 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27109 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27110 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27111 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27112 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27113 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27114 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27115 addr="0x00010734",func="callee4",
27116 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27117 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27119 bkpt=@{number="2",type="watchpoint",disp="keep",
27120 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27124 ^done,reason="watchpoint-scope",wpnum="2",
27125 frame=@{func="callee3",args=[@{name="strarg",
27126 value="0x11940 \"A string argument.\""@}],
27127 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27128 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27131 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27132 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27133 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27134 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27135 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27136 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27137 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27138 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27139 addr="0x00010734",func="callee4",
27140 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27141 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27142 thread-groups=["i1"],times="1"@}]@}
27147 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27148 @node GDB/MI Catchpoint Commands
27149 @section @sc{gdb/mi} Catchpoint Commands
27151 This section documents @sc{gdb/mi} commands for manipulating
27155 * Shared Library GDB/MI Catchpoint Commands::
27156 * Ada Exception GDB/MI Catchpoint Commands::
27159 @node Shared Library GDB/MI Catchpoint Commands
27160 @subsection Shared Library @sc{gdb/mi} Catchpoints
27162 @subheading The @code{-catch-load} Command
27163 @findex -catch-load
27165 @subsubheading Synopsis
27168 -catch-load [ -t ] [ -d ] @var{regexp}
27171 Add a catchpoint for library load events. If the @samp{-t} option is used,
27172 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27173 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27174 in a disabled state. The @samp{regexp} argument is a regular
27175 expression used to match the name of the loaded library.
27178 @subsubheading @value{GDBN} Command
27180 The corresponding @value{GDBN} command is @samp{catch load}.
27182 @subsubheading Example
27185 -catch-load -t foo.so
27186 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27187 what="load of library matching foo.so",catch-type="load",times="0"@}
27192 @subheading The @code{-catch-unload} Command
27193 @findex -catch-unload
27195 @subsubheading Synopsis
27198 -catch-unload [ -t ] [ -d ] @var{regexp}
27201 Add a catchpoint for library unload events. If the @samp{-t} option is
27202 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27203 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27204 created in a disabled state. The @samp{regexp} argument is a regular
27205 expression used to match the name of the unloaded library.
27207 @subsubheading @value{GDBN} Command
27209 The corresponding @value{GDBN} command is @samp{catch unload}.
27211 @subsubheading Example
27214 -catch-unload -d bar.so
27215 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27216 what="load of library matching bar.so",catch-type="unload",times="0"@}
27220 @node Ada Exception GDB/MI Catchpoint Commands
27221 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27223 The following @sc{gdb/mi} commands can be used to create catchpoints
27224 that stop the execution when Ada exceptions are being raised.
27226 @subheading The @code{-catch-assert} Command
27227 @findex -catch-assert
27229 @subsubheading Synopsis
27232 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27235 Add a catchpoint for failed Ada assertions.
27237 The possible optional parameters for this command are:
27240 @item -c @var{condition}
27241 Make the catchpoint conditional on @var{condition}.
27243 Create a disabled catchpoint.
27245 Create a temporary catchpoint.
27248 @subsubheading @value{GDBN} Command
27250 The corresponding @value{GDBN} command is @samp{catch assert}.
27252 @subsubheading Example
27256 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27257 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27258 thread-groups=["i1"],times="0",
27259 original-location="__gnat_debug_raise_assert_failure"@}
27263 @subheading The @code{-catch-exception} Command
27264 @findex -catch-exception
27266 @subsubheading Synopsis
27269 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27273 Add a catchpoint stopping when Ada exceptions are raised.
27274 By default, the command stops the program when any Ada exception
27275 gets raised. But it is also possible, by using some of the
27276 optional parameters described below, to create more selective
27279 The possible optional parameters for this command are:
27282 @item -c @var{condition}
27283 Make the catchpoint conditional on @var{condition}.
27285 Create a disabled catchpoint.
27286 @item -e @var{exception-name}
27287 Only stop when @var{exception-name} is raised. This option cannot
27288 be used combined with @samp{-u}.
27290 Create a temporary catchpoint.
27292 Stop only when an unhandled exception gets raised. This option
27293 cannot be used combined with @samp{-e}.
27296 @subsubheading @value{GDBN} Command
27298 The corresponding @value{GDBN} commands are @samp{catch exception}
27299 and @samp{catch exception unhandled}.
27301 @subsubheading Example
27304 -catch-exception -e Program_Error
27305 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27306 enabled="y",addr="0x0000000000404874",
27307 what="`Program_Error' Ada exception", thread-groups=["i1"],
27308 times="0",original-location="__gnat_debug_raise_exception"@}
27312 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27313 @node GDB/MI Program Context
27314 @section @sc{gdb/mi} Program Context
27316 @subheading The @code{-exec-arguments} Command
27317 @findex -exec-arguments
27320 @subsubheading Synopsis
27323 -exec-arguments @var{args}
27326 Set the inferior program arguments, to be used in the next
27329 @subsubheading @value{GDBN} Command
27331 The corresponding @value{GDBN} command is @samp{set args}.
27333 @subsubheading Example
27337 -exec-arguments -v word
27344 @subheading The @code{-exec-show-arguments} Command
27345 @findex -exec-show-arguments
27347 @subsubheading Synopsis
27350 -exec-show-arguments
27353 Print the arguments of the program.
27355 @subsubheading @value{GDBN} Command
27357 The corresponding @value{GDBN} command is @samp{show args}.
27359 @subsubheading Example
27364 @subheading The @code{-environment-cd} Command
27365 @findex -environment-cd
27367 @subsubheading Synopsis
27370 -environment-cd @var{pathdir}
27373 Set @value{GDBN}'s working directory.
27375 @subsubheading @value{GDBN} Command
27377 The corresponding @value{GDBN} command is @samp{cd}.
27379 @subsubheading Example
27383 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27389 @subheading The @code{-environment-directory} Command
27390 @findex -environment-directory
27392 @subsubheading Synopsis
27395 -environment-directory [ -r ] [ @var{pathdir} ]+
27398 Add directories @var{pathdir} to beginning of search path for source files.
27399 If the @samp{-r} option is used, the search path is reset to the default
27400 search path. If directories @var{pathdir} are supplied in addition to the
27401 @samp{-r} option, the search path is first reset and then addition
27403 Multiple directories may be specified, separated by blanks. Specifying
27404 multiple directories in a single command
27405 results in the directories added to the beginning of the
27406 search path in the same order they were presented in the command.
27407 If blanks are needed as
27408 part of a directory name, double-quotes should be used around
27409 the name. In the command output, the path will show up separated
27410 by the system directory-separator character. The directory-separator
27411 character must not be used
27412 in any directory name.
27413 If no directories are specified, the current search path is displayed.
27415 @subsubheading @value{GDBN} Command
27417 The corresponding @value{GDBN} command is @samp{dir}.
27419 @subsubheading Example
27423 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27424 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27426 -environment-directory ""
27427 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27429 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27430 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27432 -environment-directory -r
27433 ^done,source-path="$cdir:$cwd"
27438 @subheading The @code{-environment-path} Command
27439 @findex -environment-path
27441 @subsubheading Synopsis
27444 -environment-path [ -r ] [ @var{pathdir} ]+
27447 Add directories @var{pathdir} to beginning of search path for object files.
27448 If the @samp{-r} option is used, the search path is reset to the original
27449 search path that existed at gdb start-up. If directories @var{pathdir} are
27450 supplied in addition to the
27451 @samp{-r} option, the search path is first reset and then addition
27453 Multiple directories may be specified, separated by blanks. Specifying
27454 multiple directories in a single command
27455 results in the directories added to the beginning of the
27456 search path in the same order they were presented in the command.
27457 If blanks are needed as
27458 part of a directory name, double-quotes should be used around
27459 the name. In the command output, the path will show up separated
27460 by the system directory-separator character. The directory-separator
27461 character must not be used
27462 in any directory name.
27463 If no directories are specified, the current path is displayed.
27466 @subsubheading @value{GDBN} Command
27468 The corresponding @value{GDBN} command is @samp{path}.
27470 @subsubheading Example
27475 ^done,path="/usr/bin"
27477 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27478 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27480 -environment-path -r /usr/local/bin
27481 ^done,path="/usr/local/bin:/usr/bin"
27486 @subheading The @code{-environment-pwd} Command
27487 @findex -environment-pwd
27489 @subsubheading Synopsis
27495 Show the current working directory.
27497 @subsubheading @value{GDBN} Command
27499 The corresponding @value{GDBN} command is @samp{pwd}.
27501 @subsubheading Example
27506 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27510 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27511 @node GDB/MI Thread Commands
27512 @section @sc{gdb/mi} Thread Commands
27515 @subheading The @code{-thread-info} Command
27516 @findex -thread-info
27518 @subsubheading Synopsis
27521 -thread-info [ @var{thread-id} ]
27524 Reports information about either a specific thread, if
27525 the @var{thread-id} parameter is present, or about all
27526 threads. When printing information about all threads,
27527 also reports the current thread.
27529 @subsubheading @value{GDBN} Command
27531 The @samp{info thread} command prints the same information
27534 @subsubheading Result
27536 The result is a list of threads. The following attributes are
27537 defined for a given thread:
27541 This field exists only for the current thread. It has the value @samp{*}.
27544 The identifier that @value{GDBN} uses to refer to the thread.
27547 The identifier that the target uses to refer to the thread.
27550 Extra information about the thread, in a target-specific format. This
27554 The name of the thread. If the user specified a name using the
27555 @code{thread name} command, then this name is given. Otherwise, if
27556 @value{GDBN} can extract the thread name from the target, then that
27557 name is given. If @value{GDBN} cannot find the thread name, then this
27561 The stack frame currently executing in the thread.
27564 The thread's state. The @samp{state} field may have the following
27569 The thread is stopped. Frame information is available for stopped
27573 The thread is running. There's no frame information for running
27579 If @value{GDBN} can find the CPU core on which this thread is running,
27580 then this field is the core identifier. This field is optional.
27584 @subsubheading Example
27589 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27590 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27591 args=[]@},state="running"@},
27592 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27593 frame=@{level="0",addr="0x0804891f",func="foo",
27594 args=[@{name="i",value="10"@}],
27595 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27596 state="running"@}],
27597 current-thread-id="1"
27601 @subheading The @code{-thread-list-ids} Command
27602 @findex -thread-list-ids
27604 @subsubheading Synopsis
27610 Produces a list of the currently known @value{GDBN} thread ids. At the
27611 end of the list it also prints the total number of such threads.
27613 This command is retained for historical reasons, the
27614 @code{-thread-info} command should be used instead.
27616 @subsubheading @value{GDBN} Command
27618 Part of @samp{info threads} supplies the same information.
27620 @subsubheading Example
27625 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27626 current-thread-id="1",number-of-threads="3"
27631 @subheading The @code{-thread-select} Command
27632 @findex -thread-select
27634 @subsubheading Synopsis
27637 -thread-select @var{threadnum}
27640 Make @var{threadnum} the current thread. It prints the number of the new
27641 current thread, and the topmost frame for that thread.
27643 This command is deprecated in favor of explicitly using the
27644 @samp{--thread} option to each command.
27646 @subsubheading @value{GDBN} Command
27648 The corresponding @value{GDBN} command is @samp{thread}.
27650 @subsubheading Example
27657 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27658 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27662 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27663 number-of-threads="3"
27666 ^done,new-thread-id="3",
27667 frame=@{level="0",func="vprintf",
27668 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27669 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27673 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27674 @node GDB/MI Ada Tasking Commands
27675 @section @sc{gdb/mi} Ada Tasking Commands
27677 @subheading The @code{-ada-task-info} Command
27678 @findex -ada-task-info
27680 @subsubheading Synopsis
27683 -ada-task-info [ @var{task-id} ]
27686 Reports information about either a specific Ada task, if the
27687 @var{task-id} parameter is present, or about all Ada tasks.
27689 @subsubheading @value{GDBN} Command
27691 The @samp{info tasks} command prints the same information
27692 about all Ada tasks (@pxref{Ada Tasks}).
27694 @subsubheading Result
27696 The result is a table of Ada tasks. The following columns are
27697 defined for each Ada task:
27701 This field exists only for the current thread. It has the value @samp{*}.
27704 The identifier that @value{GDBN} uses to refer to the Ada task.
27707 The identifier that the target uses to refer to the Ada task.
27710 The identifier of the thread corresponding to the Ada task.
27712 This field should always exist, as Ada tasks are always implemented
27713 on top of a thread. But if @value{GDBN} cannot find this corresponding
27714 thread for any reason, the field is omitted.
27717 This field exists only when the task was created by another task.
27718 In this case, it provides the ID of the parent task.
27721 The base priority of the task.
27724 The current state of the task. For a detailed description of the
27725 possible states, see @ref{Ada Tasks}.
27728 The name of the task.
27732 @subsubheading Example
27736 ^done,tasks=@{nr_rows="3",nr_cols="8",
27737 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27738 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27739 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27740 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27741 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27742 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27743 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27744 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27745 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27746 state="Child Termination Wait",name="main_task"@}]@}
27750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27751 @node GDB/MI Program Execution
27752 @section @sc{gdb/mi} Program Execution
27754 These are the asynchronous commands which generate the out-of-band
27755 record @samp{*stopped}. Currently @value{GDBN} only really executes
27756 asynchronously with remote targets and this interaction is mimicked in
27759 @subheading The @code{-exec-continue} Command
27760 @findex -exec-continue
27762 @subsubheading Synopsis
27765 -exec-continue [--reverse] [--all|--thread-group N]
27768 Resumes the execution of the inferior program, which will continue
27769 to execute until it reaches a debugger stop event. If the
27770 @samp{--reverse} option is specified, execution resumes in reverse until
27771 it reaches a stop event. Stop events may include
27774 breakpoints or watchpoints
27776 signals or exceptions
27778 the end of the process (or its beginning under @samp{--reverse})
27780 the end or beginning of a replay log if one is being used.
27782 In all-stop mode (@pxref{All-Stop
27783 Mode}), may resume only one thread, or all threads, depending on the
27784 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27785 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27786 ignored in all-stop mode. If the @samp{--thread-group} options is
27787 specified, then all threads in that thread group are resumed.
27789 @subsubheading @value{GDBN} Command
27791 The corresponding @value{GDBN} corresponding is @samp{continue}.
27793 @subsubheading Example
27800 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27801 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27807 @subheading The @code{-exec-finish} Command
27808 @findex -exec-finish
27810 @subsubheading Synopsis
27813 -exec-finish [--reverse]
27816 Resumes the execution of the inferior program until the current
27817 function is exited. Displays the results returned by the function.
27818 If the @samp{--reverse} option is specified, resumes the reverse
27819 execution of the inferior program until the point where current
27820 function was called.
27822 @subsubheading @value{GDBN} Command
27824 The corresponding @value{GDBN} command is @samp{finish}.
27826 @subsubheading Example
27828 Function returning @code{void}.
27835 *stopped,reason="function-finished",frame=@{func="main",args=[],
27836 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27840 Function returning other than @code{void}. The name of the internal
27841 @value{GDBN} variable storing the result is printed, together with the
27848 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27849 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27850 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27851 gdb-result-var="$1",return-value="0"
27856 @subheading The @code{-exec-interrupt} Command
27857 @findex -exec-interrupt
27859 @subsubheading Synopsis
27862 -exec-interrupt [--all|--thread-group N]
27865 Interrupts the background execution of the target. Note how the token
27866 associated with the stop message is the one for the execution command
27867 that has been interrupted. The token for the interrupt itself only
27868 appears in the @samp{^done} output. If the user is trying to
27869 interrupt a non-running program, an error message will be printed.
27871 Note that when asynchronous execution is enabled, this command is
27872 asynchronous just like other execution commands. That is, first the
27873 @samp{^done} response will be printed, and the target stop will be
27874 reported after that using the @samp{*stopped} notification.
27876 In non-stop mode, only the context thread is interrupted by default.
27877 All threads (in all inferiors) will be interrupted if the
27878 @samp{--all} option is specified. If the @samp{--thread-group}
27879 option is specified, all threads in that group will be interrupted.
27881 @subsubheading @value{GDBN} Command
27883 The corresponding @value{GDBN} command is @samp{interrupt}.
27885 @subsubheading Example
27896 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27897 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27898 fullname="/home/foo/bar/try.c",line="13"@}
27903 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27907 @subheading The @code{-exec-jump} Command
27910 @subsubheading Synopsis
27913 -exec-jump @var{location}
27916 Resumes execution of the inferior program at the location specified by
27917 parameter. @xref{Specify Location}, for a description of the
27918 different forms of @var{location}.
27920 @subsubheading @value{GDBN} Command
27922 The corresponding @value{GDBN} command is @samp{jump}.
27924 @subsubheading Example
27927 -exec-jump foo.c:10
27928 *running,thread-id="all"
27933 @subheading The @code{-exec-next} Command
27936 @subsubheading Synopsis
27939 -exec-next [--reverse]
27942 Resumes execution of the inferior program, stopping when the beginning
27943 of the next source line is reached.
27945 If the @samp{--reverse} option is specified, resumes reverse execution
27946 of the inferior program, stopping at the beginning of the previous
27947 source line. If you issue this command on the first line of a
27948 function, it will take you back to the caller of that function, to the
27949 source line where the function was called.
27952 @subsubheading @value{GDBN} Command
27954 The corresponding @value{GDBN} command is @samp{next}.
27956 @subsubheading Example
27962 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27967 @subheading The @code{-exec-next-instruction} Command
27968 @findex -exec-next-instruction
27970 @subsubheading Synopsis
27973 -exec-next-instruction [--reverse]
27976 Executes one machine instruction. If the instruction is a function
27977 call, continues until the function returns. If the program stops at an
27978 instruction in the middle of a source line, the address will be
27981 If the @samp{--reverse} option is specified, resumes reverse execution
27982 of the inferior program, stopping at the previous instruction. If the
27983 previously executed instruction was a return from another function,
27984 it will continue to execute in reverse until the call to that function
27985 (from the current stack frame) is reached.
27987 @subsubheading @value{GDBN} Command
27989 The corresponding @value{GDBN} command is @samp{nexti}.
27991 @subsubheading Example
27995 -exec-next-instruction
27999 *stopped,reason="end-stepping-range",
28000 addr="0x000100d4",line="5",file="hello.c"
28005 @subheading The @code{-exec-return} Command
28006 @findex -exec-return
28008 @subsubheading Synopsis
28014 Makes current function return immediately. Doesn't execute the inferior.
28015 Displays the new current frame.
28017 @subsubheading @value{GDBN} Command
28019 The corresponding @value{GDBN} command is @samp{return}.
28021 @subsubheading Example
28025 200-break-insert callee4
28026 200^done,bkpt=@{number="1",addr="0x00010734",
28027 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28032 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28033 frame=@{func="callee4",args=[],
28034 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28035 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28041 111^done,frame=@{level="0",func="callee3",
28042 args=[@{name="strarg",
28043 value="0x11940 \"A string argument.\""@}],
28044 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28045 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28050 @subheading The @code{-exec-run} Command
28053 @subsubheading Synopsis
28056 -exec-run [ --all | --thread-group N ] [ --start ]
28059 Starts execution of the inferior from the beginning. The inferior
28060 executes until either a breakpoint is encountered or the program
28061 exits. In the latter case the output will include an exit code, if
28062 the program has exited exceptionally.
28064 When neither the @samp{--all} nor the @samp{--thread-group} option
28065 is specified, the current inferior is started. If the
28066 @samp{--thread-group} option is specified, it should refer to a thread
28067 group of type @samp{process}, and that thread group will be started.
28068 If the @samp{--all} option is specified, then all inferiors will be started.
28070 Using the @samp{--start} option instructs the debugger to stop
28071 the execution at the start of the inferior's main subprogram,
28072 following the same behavior as the @code{start} command
28073 (@pxref{Starting}).
28075 @subsubheading @value{GDBN} Command
28077 The corresponding @value{GDBN} command is @samp{run}.
28079 @subsubheading Examples
28084 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28089 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28090 frame=@{func="main",args=[],file="recursive2.c",
28091 fullname="/home/foo/bar/recursive2.c",line="4"@}
28096 Program exited normally:
28104 *stopped,reason="exited-normally"
28109 Program exited exceptionally:
28117 *stopped,reason="exited",exit-code="01"
28121 Another way the program can terminate is if it receives a signal such as
28122 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28126 *stopped,reason="exited-signalled",signal-name="SIGINT",
28127 signal-meaning="Interrupt"
28131 @c @subheading -exec-signal
28134 @subheading The @code{-exec-step} Command
28137 @subsubheading Synopsis
28140 -exec-step [--reverse]
28143 Resumes execution of the inferior program, stopping when the beginning
28144 of the next source line is reached, if the next source line is not a
28145 function call. If it is, stop at the first instruction of the called
28146 function. If the @samp{--reverse} option is specified, resumes reverse
28147 execution of the inferior program, stopping at the beginning of the
28148 previously executed source line.
28150 @subsubheading @value{GDBN} Command
28152 The corresponding @value{GDBN} command is @samp{step}.
28154 @subsubheading Example
28156 Stepping into a function:
28162 *stopped,reason="end-stepping-range",
28163 frame=@{func="foo",args=[@{name="a",value="10"@},
28164 @{name="b",value="0"@}],file="recursive2.c",
28165 fullname="/home/foo/bar/recursive2.c",line="11"@}
28175 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28180 @subheading The @code{-exec-step-instruction} Command
28181 @findex -exec-step-instruction
28183 @subsubheading Synopsis
28186 -exec-step-instruction [--reverse]
28189 Resumes the inferior which executes one machine instruction. If the
28190 @samp{--reverse} option is specified, resumes reverse execution of the
28191 inferior program, stopping at the previously executed instruction.
28192 The output, once @value{GDBN} has stopped, will vary depending on
28193 whether we have stopped in the middle of a source line or not. In the
28194 former case, the address at which the program stopped will be printed
28197 @subsubheading @value{GDBN} Command
28199 The corresponding @value{GDBN} command is @samp{stepi}.
28201 @subsubheading Example
28205 -exec-step-instruction
28209 *stopped,reason="end-stepping-range",
28210 frame=@{func="foo",args=[],file="try.c",
28211 fullname="/home/foo/bar/try.c",line="10"@}
28213 -exec-step-instruction
28217 *stopped,reason="end-stepping-range",
28218 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28219 fullname="/home/foo/bar/try.c",line="10"@}
28224 @subheading The @code{-exec-until} Command
28225 @findex -exec-until
28227 @subsubheading Synopsis
28230 -exec-until [ @var{location} ]
28233 Executes the inferior until the @var{location} specified in the
28234 argument is reached. If there is no argument, the inferior executes
28235 until a source line greater than the current one is reached. The
28236 reason for stopping in this case will be @samp{location-reached}.
28238 @subsubheading @value{GDBN} Command
28240 The corresponding @value{GDBN} command is @samp{until}.
28242 @subsubheading Example
28246 -exec-until recursive2.c:6
28250 *stopped,reason="location-reached",frame=@{func="main",args=[],
28251 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28256 @subheading -file-clear
28257 Is this going away????
28260 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28261 @node GDB/MI Stack Manipulation
28262 @section @sc{gdb/mi} Stack Manipulation Commands
28264 @subheading The @code{-enable-frame-filters} Command
28265 @findex -enable-frame-filters
28268 -enable-frame-filters
28271 @value{GDBN} allows Python-based frame filters to affect the output of
28272 the MI commands relating to stack traces. As there is no way to
28273 implement this in a fully backward-compatible way, a front end must
28274 request that this functionality be enabled.
28276 Once enabled, this feature cannot be disabled.
28278 Note that if Python support has not been compiled into @value{GDBN},
28279 this command will still succeed (and do nothing).
28281 @subheading The @code{-stack-info-frame} Command
28282 @findex -stack-info-frame
28284 @subsubheading Synopsis
28290 Get info on the selected frame.
28292 @subsubheading @value{GDBN} Command
28294 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28295 (without arguments).
28297 @subsubheading Example
28302 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28303 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28304 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28308 @subheading The @code{-stack-info-depth} Command
28309 @findex -stack-info-depth
28311 @subsubheading Synopsis
28314 -stack-info-depth [ @var{max-depth} ]
28317 Return the depth of the stack. If the integer argument @var{max-depth}
28318 is specified, do not count beyond @var{max-depth} frames.
28320 @subsubheading @value{GDBN} Command
28322 There's no equivalent @value{GDBN} command.
28324 @subsubheading Example
28326 For a stack with frame levels 0 through 11:
28333 -stack-info-depth 4
28336 -stack-info-depth 12
28339 -stack-info-depth 11
28342 -stack-info-depth 13
28347 @anchor{-stack-list-arguments}
28348 @subheading The @code{-stack-list-arguments} Command
28349 @findex -stack-list-arguments
28351 @subsubheading Synopsis
28354 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28355 [ @var{low-frame} @var{high-frame} ]
28358 Display a list of the arguments for the frames between @var{low-frame}
28359 and @var{high-frame} (inclusive). If @var{low-frame} and
28360 @var{high-frame} are not provided, list the arguments for the whole
28361 call stack. If the two arguments are equal, show the single frame
28362 at the corresponding level. It is an error if @var{low-frame} is
28363 larger than the actual number of frames. On the other hand,
28364 @var{high-frame} may be larger than the actual number of frames, in
28365 which case only existing frames will be returned.
28367 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28368 the variables; if it is 1 or @code{--all-values}, print also their
28369 values; and if it is 2 or @code{--simple-values}, print the name,
28370 type and value for simple data types, and the name and type for arrays,
28371 structures and unions. If the option @code{--no-frame-filters} is
28372 supplied, then Python frame filters will not be executed.
28374 If the @code{--skip-unavailable} option is specified, arguments that
28375 are not available are not listed. Partially available arguments
28376 are still displayed, however.
28378 Use of this command to obtain arguments in a single frame is
28379 deprecated in favor of the @samp{-stack-list-variables} command.
28381 @subsubheading @value{GDBN} Command
28383 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28384 @samp{gdb_get_args} command which partially overlaps with the
28385 functionality of @samp{-stack-list-arguments}.
28387 @subsubheading Example
28394 frame=@{level="0",addr="0x00010734",func="callee4",
28395 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28396 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28397 frame=@{level="1",addr="0x0001076c",func="callee3",
28398 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28399 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28400 frame=@{level="2",addr="0x0001078c",func="callee2",
28401 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28402 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28403 frame=@{level="3",addr="0x000107b4",func="callee1",
28404 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28405 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28406 frame=@{level="4",addr="0x000107e0",func="main",
28407 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28408 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28410 -stack-list-arguments 0
28413 frame=@{level="0",args=[]@},
28414 frame=@{level="1",args=[name="strarg"]@},
28415 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28416 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28417 frame=@{level="4",args=[]@}]
28419 -stack-list-arguments 1
28422 frame=@{level="0",args=[]@},
28424 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28425 frame=@{level="2",args=[
28426 @{name="intarg",value="2"@},
28427 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28428 @{frame=@{level="3",args=[
28429 @{name="intarg",value="2"@},
28430 @{name="strarg",value="0x11940 \"A string argument.\""@},
28431 @{name="fltarg",value="3.5"@}]@},
28432 frame=@{level="4",args=[]@}]
28434 -stack-list-arguments 0 2 2
28435 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28437 -stack-list-arguments 1 2 2
28438 ^done,stack-args=[frame=@{level="2",
28439 args=[@{name="intarg",value="2"@},
28440 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28444 @c @subheading -stack-list-exception-handlers
28447 @anchor{-stack-list-frames}
28448 @subheading The @code{-stack-list-frames} Command
28449 @findex -stack-list-frames
28451 @subsubheading Synopsis
28454 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28457 List the frames currently on the stack. For each frame it displays the
28462 The frame number, 0 being the topmost frame, i.e., the innermost function.
28464 The @code{$pc} value for that frame.
28468 File name of the source file where the function lives.
28469 @item @var{fullname}
28470 The full file name of the source file where the function lives.
28472 Line number corresponding to the @code{$pc}.
28474 The shared library where this function is defined. This is only given
28475 if the frame's function is not known.
28478 If invoked without arguments, this command prints a backtrace for the
28479 whole stack. If given two integer arguments, it shows the frames whose
28480 levels are between the two arguments (inclusive). If the two arguments
28481 are equal, it shows the single frame at the corresponding level. It is
28482 an error if @var{low-frame} is larger than the actual number of
28483 frames. On the other hand, @var{high-frame} may be larger than the
28484 actual number of frames, in which case only existing frames will be
28485 returned. If the option @code{--no-frame-filters} is supplied, then
28486 Python frame filters will not be executed.
28488 @subsubheading @value{GDBN} Command
28490 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28492 @subsubheading Example
28494 Full stack backtrace:
28500 [frame=@{level="0",addr="0x0001076c",func="foo",
28501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28502 frame=@{level="1",addr="0x000107a4",func="foo",
28503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28504 frame=@{level="2",addr="0x000107a4",func="foo",
28505 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28506 frame=@{level="3",addr="0x000107a4",func="foo",
28507 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28508 frame=@{level="4",addr="0x000107a4",func="foo",
28509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28510 frame=@{level="5",addr="0x000107a4",func="foo",
28511 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28512 frame=@{level="6",addr="0x000107a4",func="foo",
28513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28514 frame=@{level="7",addr="0x000107a4",func="foo",
28515 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28516 frame=@{level="8",addr="0x000107a4",func="foo",
28517 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28518 frame=@{level="9",addr="0x000107a4",func="foo",
28519 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28520 frame=@{level="10",addr="0x000107a4",func="foo",
28521 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28522 frame=@{level="11",addr="0x00010738",func="main",
28523 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28527 Show frames between @var{low_frame} and @var{high_frame}:
28531 -stack-list-frames 3 5
28533 [frame=@{level="3",addr="0x000107a4",func="foo",
28534 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28535 frame=@{level="4",addr="0x000107a4",func="foo",
28536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28537 frame=@{level="5",addr="0x000107a4",func="foo",
28538 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28542 Show a single frame:
28546 -stack-list-frames 3 3
28548 [frame=@{level="3",addr="0x000107a4",func="foo",
28549 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28554 @subheading The @code{-stack-list-locals} Command
28555 @findex -stack-list-locals
28556 @anchor{-stack-list-locals}
28558 @subsubheading Synopsis
28561 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28564 Display the local variable names for the selected frame. If
28565 @var{print-values} is 0 or @code{--no-values}, print only the names of
28566 the variables; if it is 1 or @code{--all-values}, print also their
28567 values; and if it is 2 or @code{--simple-values}, print the name,
28568 type and value for simple data types, and the name and type for arrays,
28569 structures and unions. In this last case, a frontend can immediately
28570 display the value of simple data types and create variable objects for
28571 other data types when the user wishes to explore their values in
28572 more detail. If the option @code{--no-frame-filters} is supplied, then
28573 Python frame filters will not be executed.
28575 If the @code{--skip-unavailable} option is specified, local variables
28576 that are not available are not listed. Partially available local
28577 variables are still displayed, however.
28579 This command is deprecated in favor of the
28580 @samp{-stack-list-variables} command.
28582 @subsubheading @value{GDBN} Command
28584 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28586 @subsubheading Example
28590 -stack-list-locals 0
28591 ^done,locals=[name="A",name="B",name="C"]
28593 -stack-list-locals --all-values
28594 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28595 @{name="C",value="@{1, 2, 3@}"@}]
28596 -stack-list-locals --simple-values
28597 ^done,locals=[@{name="A",type="int",value="1"@},
28598 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28602 @anchor{-stack-list-variables}
28603 @subheading The @code{-stack-list-variables} Command
28604 @findex -stack-list-variables
28606 @subsubheading Synopsis
28609 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28612 Display the names of local variables and function arguments for the selected frame. If
28613 @var{print-values} is 0 or @code{--no-values}, print only the names of
28614 the variables; if it is 1 or @code{--all-values}, print also their
28615 values; and if it is 2 or @code{--simple-values}, print the name,
28616 type and value for simple data types, and the name and type for arrays,
28617 structures and unions. If the option @code{--no-frame-filters} is
28618 supplied, then Python frame filters will not be executed.
28620 If the @code{--skip-unavailable} option is specified, local variables
28621 and arguments that are not available are not listed. Partially
28622 available arguments and local variables are still displayed, however.
28624 @subsubheading Example
28628 -stack-list-variables --thread 1 --frame 0 --all-values
28629 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28634 @subheading The @code{-stack-select-frame} Command
28635 @findex -stack-select-frame
28637 @subsubheading Synopsis
28640 -stack-select-frame @var{framenum}
28643 Change the selected frame. Select a different frame @var{framenum} on
28646 This command in deprecated in favor of passing the @samp{--frame}
28647 option to every command.
28649 @subsubheading @value{GDBN} Command
28651 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28652 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28654 @subsubheading Example
28658 -stack-select-frame 2
28663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28664 @node GDB/MI Variable Objects
28665 @section @sc{gdb/mi} Variable Objects
28669 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28671 For the implementation of a variable debugger window (locals, watched
28672 expressions, etc.), we are proposing the adaptation of the existing code
28673 used by @code{Insight}.
28675 The two main reasons for that are:
28679 It has been proven in practice (it is already on its second generation).
28682 It will shorten development time (needless to say how important it is
28686 The original interface was designed to be used by Tcl code, so it was
28687 slightly changed so it could be used through @sc{gdb/mi}. This section
28688 describes the @sc{gdb/mi} operations that will be available and gives some
28689 hints about their use.
28691 @emph{Note}: In addition to the set of operations described here, we
28692 expect the @sc{gui} implementation of a variable window to require, at
28693 least, the following operations:
28696 @item @code{-gdb-show} @code{output-radix}
28697 @item @code{-stack-list-arguments}
28698 @item @code{-stack-list-locals}
28699 @item @code{-stack-select-frame}
28704 @subheading Introduction to Variable Objects
28706 @cindex variable objects in @sc{gdb/mi}
28708 Variable objects are "object-oriented" MI interface for examining and
28709 changing values of expressions. Unlike some other MI interfaces that
28710 work with expressions, variable objects are specifically designed for
28711 simple and efficient presentation in the frontend. A variable object
28712 is identified by string name. When a variable object is created, the
28713 frontend specifies the expression for that variable object. The
28714 expression can be a simple variable, or it can be an arbitrary complex
28715 expression, and can even involve CPU registers. After creating a
28716 variable object, the frontend can invoke other variable object
28717 operations---for example to obtain or change the value of a variable
28718 object, or to change display format.
28720 Variable objects have hierarchical tree structure. Any variable object
28721 that corresponds to a composite type, such as structure in C, has
28722 a number of child variable objects, for example corresponding to each
28723 element of a structure. A child variable object can itself have
28724 children, recursively. Recursion ends when we reach
28725 leaf variable objects, which always have built-in types. Child variable
28726 objects are created only by explicit request, so if a frontend
28727 is not interested in the children of a particular variable object, no
28728 child will be created.
28730 For a leaf variable object it is possible to obtain its value as a
28731 string, or set the value from a string. String value can be also
28732 obtained for a non-leaf variable object, but it's generally a string
28733 that only indicates the type of the object, and does not list its
28734 contents. Assignment to a non-leaf variable object is not allowed.
28736 A frontend does not need to read the values of all variable objects each time
28737 the program stops. Instead, MI provides an update command that lists all
28738 variable objects whose values has changed since the last update
28739 operation. This considerably reduces the amount of data that must
28740 be transferred to the frontend. As noted above, children variable
28741 objects are created on demand, and only leaf variable objects have a
28742 real value. As result, gdb will read target memory only for leaf
28743 variables that frontend has created.
28745 The automatic update is not always desirable. For example, a frontend
28746 might want to keep a value of some expression for future reference,
28747 and never update it. For another example, fetching memory is
28748 relatively slow for embedded targets, so a frontend might want
28749 to disable automatic update for the variables that are either not
28750 visible on the screen, or ``closed''. This is possible using so
28751 called ``frozen variable objects''. Such variable objects are never
28752 implicitly updated.
28754 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28755 fixed variable object, the expression is parsed when the variable
28756 object is created, including associating identifiers to specific
28757 variables. The meaning of expression never changes. For a floating
28758 variable object the values of variables whose names appear in the
28759 expressions are re-evaluated every time in the context of the current
28760 frame. Consider this example:
28765 struct work_state state;
28772 If a fixed variable object for the @code{state} variable is created in
28773 this function, and we enter the recursive call, the variable
28774 object will report the value of @code{state} in the top-level
28775 @code{do_work} invocation. On the other hand, a floating variable
28776 object will report the value of @code{state} in the current frame.
28778 If an expression specified when creating a fixed variable object
28779 refers to a local variable, the variable object becomes bound to the
28780 thread and frame in which the variable object is created. When such
28781 variable object is updated, @value{GDBN} makes sure that the
28782 thread/frame combination the variable object is bound to still exists,
28783 and re-evaluates the variable object in context of that thread/frame.
28785 The following is the complete set of @sc{gdb/mi} operations defined to
28786 access this functionality:
28788 @multitable @columnfractions .4 .6
28789 @item @strong{Operation}
28790 @tab @strong{Description}
28792 @item @code{-enable-pretty-printing}
28793 @tab enable Python-based pretty-printing
28794 @item @code{-var-create}
28795 @tab create a variable object
28796 @item @code{-var-delete}
28797 @tab delete the variable object and/or its children
28798 @item @code{-var-set-format}
28799 @tab set the display format of this variable
28800 @item @code{-var-show-format}
28801 @tab show the display format of this variable
28802 @item @code{-var-info-num-children}
28803 @tab tells how many children this object has
28804 @item @code{-var-list-children}
28805 @tab return a list of the object's children
28806 @item @code{-var-info-type}
28807 @tab show the type of this variable object
28808 @item @code{-var-info-expression}
28809 @tab print parent-relative expression that this variable object represents
28810 @item @code{-var-info-path-expression}
28811 @tab print full expression that this variable object represents
28812 @item @code{-var-show-attributes}
28813 @tab is this variable editable? does it exist here?
28814 @item @code{-var-evaluate-expression}
28815 @tab get the value of this variable
28816 @item @code{-var-assign}
28817 @tab set the value of this variable
28818 @item @code{-var-update}
28819 @tab update the variable and its children
28820 @item @code{-var-set-frozen}
28821 @tab set frozeness attribute
28822 @item @code{-var-set-update-range}
28823 @tab set range of children to display on update
28826 In the next subsection we describe each operation in detail and suggest
28827 how it can be used.
28829 @subheading Description And Use of Operations on Variable Objects
28831 @subheading The @code{-enable-pretty-printing} Command
28832 @findex -enable-pretty-printing
28835 -enable-pretty-printing
28838 @value{GDBN} allows Python-based visualizers to affect the output of the
28839 MI variable object commands. However, because there was no way to
28840 implement this in a fully backward-compatible way, a front end must
28841 request that this functionality be enabled.
28843 Once enabled, this feature cannot be disabled.
28845 Note that if Python support has not been compiled into @value{GDBN},
28846 this command will still succeed (and do nothing).
28848 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28849 may work differently in future versions of @value{GDBN}.
28851 @subheading The @code{-var-create} Command
28852 @findex -var-create
28854 @subsubheading Synopsis
28857 -var-create @{@var{name} | "-"@}
28858 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28861 This operation creates a variable object, which allows the monitoring of
28862 a variable, the result of an expression, a memory cell or a CPU
28865 The @var{name} parameter is the string by which the object can be
28866 referenced. It must be unique. If @samp{-} is specified, the varobj
28867 system will generate a string ``varNNNNNN'' automatically. It will be
28868 unique provided that one does not specify @var{name} of that format.
28869 The command fails if a duplicate name is found.
28871 The frame under which the expression should be evaluated can be
28872 specified by @var{frame-addr}. A @samp{*} indicates that the current
28873 frame should be used. A @samp{@@} indicates that a floating variable
28874 object must be created.
28876 @var{expression} is any expression valid on the current language set (must not
28877 begin with a @samp{*}), or one of the following:
28881 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28884 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28887 @samp{$@var{regname}} --- a CPU register name
28890 @cindex dynamic varobj
28891 A varobj's contents may be provided by a Python-based pretty-printer. In this
28892 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28893 have slightly different semantics in some cases. If the
28894 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28895 will never create a dynamic varobj. This ensures backward
28896 compatibility for existing clients.
28898 @subsubheading Result
28900 This operation returns attributes of the newly-created varobj. These
28905 The name of the varobj.
28908 The number of children of the varobj. This number is not necessarily
28909 reliable for a dynamic varobj. Instead, you must examine the
28910 @samp{has_more} attribute.
28913 The varobj's scalar value. For a varobj whose type is some sort of
28914 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28915 will not be interesting.
28918 The varobj's type. This is a string representation of the type, as
28919 would be printed by the @value{GDBN} CLI. If @samp{print object}
28920 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28921 @emph{actual} (derived) type of the object is shown rather than the
28922 @emph{declared} one.
28925 If a variable object is bound to a specific thread, then this is the
28926 thread's identifier.
28929 For a dynamic varobj, this indicates whether there appear to be any
28930 children available. For a non-dynamic varobj, this will be 0.
28933 This attribute will be present and have the value @samp{1} if the
28934 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28935 then this attribute will not be present.
28938 A dynamic varobj can supply a display hint to the front end. The
28939 value comes directly from the Python pretty-printer object's
28940 @code{display_hint} method. @xref{Pretty Printing API}.
28943 Typical output will look like this:
28946 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28947 has_more="@var{has_more}"
28951 @subheading The @code{-var-delete} Command
28952 @findex -var-delete
28954 @subsubheading Synopsis
28957 -var-delete [ -c ] @var{name}
28960 Deletes a previously created variable object and all of its children.
28961 With the @samp{-c} option, just deletes the children.
28963 Returns an error if the object @var{name} is not found.
28966 @subheading The @code{-var-set-format} Command
28967 @findex -var-set-format
28969 @subsubheading Synopsis
28972 -var-set-format @var{name} @var{format-spec}
28975 Sets the output format for the value of the object @var{name} to be
28978 @anchor{-var-set-format}
28979 The syntax for the @var{format-spec} is as follows:
28982 @var{format-spec} @expansion{}
28983 @{binary | decimal | hexadecimal | octal | natural@}
28986 The natural format is the default format choosen automatically
28987 based on the variable type (like decimal for an @code{int}, hex
28988 for pointers, etc.).
28990 For a variable with children, the format is set only on the
28991 variable itself, and the children are not affected.
28993 @subheading The @code{-var-show-format} Command
28994 @findex -var-show-format
28996 @subsubheading Synopsis
28999 -var-show-format @var{name}
29002 Returns the format used to display the value of the object @var{name}.
29005 @var{format} @expansion{}
29010 @subheading The @code{-var-info-num-children} Command
29011 @findex -var-info-num-children
29013 @subsubheading Synopsis
29016 -var-info-num-children @var{name}
29019 Returns the number of children of a variable object @var{name}:
29025 Note that this number is not completely reliable for a dynamic varobj.
29026 It will return the current number of children, but more children may
29030 @subheading The @code{-var-list-children} Command
29031 @findex -var-list-children
29033 @subsubheading Synopsis
29036 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29038 @anchor{-var-list-children}
29040 Return a list of the children of the specified variable object and
29041 create variable objects for them, if they do not already exist. With
29042 a single argument or if @var{print-values} has a value of 0 or
29043 @code{--no-values}, print only the names of the variables; if
29044 @var{print-values} is 1 or @code{--all-values}, also print their
29045 values; and if it is 2 or @code{--simple-values} print the name and
29046 value for simple data types and just the name for arrays, structures
29049 @var{from} and @var{to}, if specified, indicate the range of children
29050 to report. If @var{from} or @var{to} is less than zero, the range is
29051 reset and all children will be reported. Otherwise, children starting
29052 at @var{from} (zero-based) and up to and excluding @var{to} will be
29055 If a child range is requested, it will only affect the current call to
29056 @code{-var-list-children}, but not future calls to @code{-var-update}.
29057 For this, you must instead use @code{-var-set-update-range}. The
29058 intent of this approach is to enable a front end to implement any
29059 update approach it likes; for example, scrolling a view may cause the
29060 front end to request more children with @code{-var-list-children}, and
29061 then the front end could call @code{-var-set-update-range} with a
29062 different range to ensure that future updates are restricted to just
29065 For each child the following results are returned:
29070 Name of the variable object created for this child.
29073 The expression to be shown to the user by the front end to designate this child.
29074 For example this may be the name of a structure member.
29076 For a dynamic varobj, this value cannot be used to form an
29077 expression. There is no way to do this at all with a dynamic varobj.
29079 For C/C@t{++} structures there are several pseudo children returned to
29080 designate access qualifiers. For these pseudo children @var{exp} is
29081 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29082 type and value are not present.
29084 A dynamic varobj will not report the access qualifying
29085 pseudo-children, regardless of the language. This information is not
29086 available at all with a dynamic varobj.
29089 Number of children this child has. For a dynamic varobj, this will be
29093 The type of the child. If @samp{print object}
29094 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29095 @emph{actual} (derived) type of the object is shown rather than the
29096 @emph{declared} one.
29099 If values were requested, this is the value.
29102 If this variable object is associated with a thread, this is the thread id.
29103 Otherwise this result is not present.
29106 If the variable object is frozen, this variable will be present with a value of 1.
29109 A dynamic varobj can supply a display hint to the front end. The
29110 value comes directly from the Python pretty-printer object's
29111 @code{display_hint} method. @xref{Pretty Printing API}.
29114 This attribute will be present and have the value @samp{1} if the
29115 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29116 then this attribute will not be present.
29120 The result may have its own attributes:
29124 A dynamic varobj can supply a display hint to the front end. The
29125 value comes directly from the Python pretty-printer object's
29126 @code{display_hint} method. @xref{Pretty Printing API}.
29129 This is an integer attribute which is nonzero if there are children
29130 remaining after the end of the selected range.
29133 @subsubheading Example
29137 -var-list-children n
29138 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29139 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29141 -var-list-children --all-values n
29142 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29143 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29147 @subheading The @code{-var-info-type} Command
29148 @findex -var-info-type
29150 @subsubheading Synopsis
29153 -var-info-type @var{name}
29156 Returns the type of the specified variable @var{name}. The type is
29157 returned as a string in the same format as it is output by the
29161 type=@var{typename}
29165 @subheading The @code{-var-info-expression} Command
29166 @findex -var-info-expression
29168 @subsubheading Synopsis
29171 -var-info-expression @var{name}
29174 Returns a string that is suitable for presenting this
29175 variable object in user interface. The string is generally
29176 not valid expression in the current language, and cannot be evaluated.
29178 For example, if @code{a} is an array, and variable object
29179 @code{A} was created for @code{a}, then we'll get this output:
29182 (gdb) -var-info-expression A.1
29183 ^done,lang="C",exp="1"
29187 Here, the value of @code{lang} is the language name, which can be
29188 found in @ref{Supported Languages}.
29190 Note that the output of the @code{-var-list-children} command also
29191 includes those expressions, so the @code{-var-info-expression} command
29194 @subheading The @code{-var-info-path-expression} Command
29195 @findex -var-info-path-expression
29197 @subsubheading Synopsis
29200 -var-info-path-expression @var{name}
29203 Returns an expression that can be evaluated in the current
29204 context and will yield the same value that a variable object has.
29205 Compare this with the @code{-var-info-expression} command, which
29206 result can be used only for UI presentation. Typical use of
29207 the @code{-var-info-path-expression} command is creating a
29208 watchpoint from a variable object.
29210 This command is currently not valid for children of a dynamic varobj,
29211 and will give an error when invoked on one.
29213 For example, suppose @code{C} is a C@t{++} class, derived from class
29214 @code{Base}, and that the @code{Base} class has a member called
29215 @code{m_size}. Assume a variable @code{c} is has the type of
29216 @code{C} and a variable object @code{C} was created for variable
29217 @code{c}. Then, we'll get this output:
29219 (gdb) -var-info-path-expression C.Base.public.m_size
29220 ^done,path_expr=((Base)c).m_size)
29223 @subheading The @code{-var-show-attributes} Command
29224 @findex -var-show-attributes
29226 @subsubheading Synopsis
29229 -var-show-attributes @var{name}
29232 List attributes of the specified variable object @var{name}:
29235 status=@var{attr} [ ( ,@var{attr} )* ]
29239 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29241 @subheading The @code{-var-evaluate-expression} Command
29242 @findex -var-evaluate-expression
29244 @subsubheading Synopsis
29247 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29250 Evaluates the expression that is represented by the specified variable
29251 object and returns its value as a string. The format of the string
29252 can be specified with the @samp{-f} option. The possible values of
29253 this option are the same as for @code{-var-set-format}
29254 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29255 the current display format will be used. The current display format
29256 can be changed using the @code{-var-set-format} command.
29262 Note that one must invoke @code{-var-list-children} for a variable
29263 before the value of a child variable can be evaluated.
29265 @subheading The @code{-var-assign} Command
29266 @findex -var-assign
29268 @subsubheading Synopsis
29271 -var-assign @var{name} @var{expression}
29274 Assigns the value of @var{expression} to the variable object specified
29275 by @var{name}. The object must be @samp{editable}. If the variable's
29276 value is altered by the assign, the variable will show up in any
29277 subsequent @code{-var-update} list.
29279 @subsubheading Example
29287 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29291 @subheading The @code{-var-update} Command
29292 @findex -var-update
29294 @subsubheading Synopsis
29297 -var-update [@var{print-values}] @{@var{name} | "*"@}
29300 Reevaluate the expressions corresponding to the variable object
29301 @var{name} and all its direct and indirect children, and return the
29302 list of variable objects whose values have changed; @var{name} must
29303 be a root variable object. Here, ``changed'' means that the result of
29304 @code{-var-evaluate-expression} before and after the
29305 @code{-var-update} is different. If @samp{*} is used as the variable
29306 object names, all existing variable objects are updated, except
29307 for frozen ones (@pxref{-var-set-frozen}). The option
29308 @var{print-values} determines whether both names and values, or just
29309 names are printed. The possible values of this option are the same
29310 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29311 recommended to use the @samp{--all-values} option, to reduce the
29312 number of MI commands needed on each program stop.
29314 With the @samp{*} parameter, if a variable object is bound to a
29315 currently running thread, it will not be updated, without any
29318 If @code{-var-set-update-range} was previously used on a varobj, then
29319 only the selected range of children will be reported.
29321 @code{-var-update} reports all the changed varobjs in a tuple named
29324 Each item in the change list is itself a tuple holding:
29328 The name of the varobj.
29331 If values were requested for this update, then this field will be
29332 present and will hold the value of the varobj.
29335 @anchor{-var-update}
29336 This field is a string which may take one of three values:
29340 The variable object's current value is valid.
29343 The variable object does not currently hold a valid value but it may
29344 hold one in the future if its associated expression comes back into
29348 The variable object no longer holds a valid value.
29349 This can occur when the executable file being debugged has changed,
29350 either through recompilation or by using the @value{GDBN} @code{file}
29351 command. The front end should normally choose to delete these variable
29355 In the future new values may be added to this list so the front should
29356 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29359 This is only present if the varobj is still valid. If the type
29360 changed, then this will be the string @samp{true}; otherwise it will
29363 When a varobj's type changes, its children are also likely to have
29364 become incorrect. Therefore, the varobj's children are automatically
29365 deleted when this attribute is @samp{true}. Also, the varobj's update
29366 range, when set using the @code{-var-set-update-range} command, is
29370 If the varobj's type changed, then this field will be present and will
29373 @item new_num_children
29374 For a dynamic varobj, if the number of children changed, or if the
29375 type changed, this will be the new number of children.
29377 The @samp{numchild} field in other varobj responses is generally not
29378 valid for a dynamic varobj -- it will show the number of children that
29379 @value{GDBN} knows about, but because dynamic varobjs lazily
29380 instantiate their children, this will not reflect the number of
29381 children which may be available.
29383 The @samp{new_num_children} attribute only reports changes to the
29384 number of children known by @value{GDBN}. This is the only way to
29385 detect whether an update has removed children (which necessarily can
29386 only happen at the end of the update range).
29389 The display hint, if any.
29392 This is an integer value, which will be 1 if there are more children
29393 available outside the varobj's update range.
29396 This attribute will be present and have the value @samp{1} if the
29397 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29398 then this attribute will not be present.
29401 If new children were added to a dynamic varobj within the selected
29402 update range (as set by @code{-var-set-update-range}), then they will
29403 be listed in this attribute.
29406 @subsubheading Example
29413 -var-update --all-values var1
29414 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29415 type_changed="false"@}]
29419 @subheading The @code{-var-set-frozen} Command
29420 @findex -var-set-frozen
29421 @anchor{-var-set-frozen}
29423 @subsubheading Synopsis
29426 -var-set-frozen @var{name} @var{flag}
29429 Set the frozenness flag on the variable object @var{name}. The
29430 @var{flag} parameter should be either @samp{1} to make the variable
29431 frozen or @samp{0} to make it unfrozen. If a variable object is
29432 frozen, then neither itself, nor any of its children, are
29433 implicitly updated by @code{-var-update} of
29434 a parent variable or by @code{-var-update *}. Only
29435 @code{-var-update} of the variable itself will update its value and
29436 values of its children. After a variable object is unfrozen, it is
29437 implicitly updated by all subsequent @code{-var-update} operations.
29438 Unfreezing a variable does not update it, only subsequent
29439 @code{-var-update} does.
29441 @subsubheading Example
29445 -var-set-frozen V 1
29450 @subheading The @code{-var-set-update-range} command
29451 @findex -var-set-update-range
29452 @anchor{-var-set-update-range}
29454 @subsubheading Synopsis
29457 -var-set-update-range @var{name} @var{from} @var{to}
29460 Set the range of children to be returned by future invocations of
29461 @code{-var-update}.
29463 @var{from} and @var{to} indicate the range of children to report. If
29464 @var{from} or @var{to} is less than zero, the range is reset and all
29465 children will be reported. Otherwise, children starting at @var{from}
29466 (zero-based) and up to and excluding @var{to} will be reported.
29468 @subsubheading Example
29472 -var-set-update-range V 1 2
29476 @subheading The @code{-var-set-visualizer} command
29477 @findex -var-set-visualizer
29478 @anchor{-var-set-visualizer}
29480 @subsubheading Synopsis
29483 -var-set-visualizer @var{name} @var{visualizer}
29486 Set a visualizer for the variable object @var{name}.
29488 @var{visualizer} is the visualizer to use. The special value
29489 @samp{None} means to disable any visualizer in use.
29491 If not @samp{None}, @var{visualizer} must be a Python expression.
29492 This expression must evaluate to a callable object which accepts a
29493 single argument. @value{GDBN} will call this object with the value of
29494 the varobj @var{name} as an argument (this is done so that the same
29495 Python pretty-printing code can be used for both the CLI and MI).
29496 When called, this object must return an object which conforms to the
29497 pretty-printing interface (@pxref{Pretty Printing API}).
29499 The pre-defined function @code{gdb.default_visualizer} may be used to
29500 select a visualizer by following the built-in process
29501 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29502 a varobj is created, and so ordinarily is not needed.
29504 This feature is only available if Python support is enabled. The MI
29505 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29506 can be used to check this.
29508 @subsubheading Example
29510 Resetting the visualizer:
29514 -var-set-visualizer V None
29518 Reselecting the default (type-based) visualizer:
29522 -var-set-visualizer V gdb.default_visualizer
29526 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29527 can be used to instantiate this class for a varobj:
29531 -var-set-visualizer V "lambda val: SomeClass()"
29535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29536 @node GDB/MI Data Manipulation
29537 @section @sc{gdb/mi} Data Manipulation
29539 @cindex data manipulation, in @sc{gdb/mi}
29540 @cindex @sc{gdb/mi}, data manipulation
29541 This section describes the @sc{gdb/mi} commands that manipulate data:
29542 examine memory and registers, evaluate expressions, etc.
29544 For details about what an addressable memory unit is,
29545 @pxref{addressable memory unit}.
29547 @c REMOVED FROM THE INTERFACE.
29548 @c @subheading -data-assign
29549 @c Change the value of a program variable. Plenty of side effects.
29550 @c @subsubheading GDB Command
29552 @c @subsubheading Example
29555 @subheading The @code{-data-disassemble} Command
29556 @findex -data-disassemble
29558 @subsubheading Synopsis
29562 [ -s @var{start-addr} -e @var{end-addr} ]
29563 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29571 @item @var{start-addr}
29572 is the beginning address (or @code{$pc})
29573 @item @var{end-addr}
29575 @item @var{filename}
29576 is the name of the file to disassemble
29577 @item @var{linenum}
29578 is the line number to disassemble around
29580 is the number of disassembly lines to be produced. If it is -1,
29581 the whole function will be disassembled, in case no @var{end-addr} is
29582 specified. If @var{end-addr} is specified as a non-zero value, and
29583 @var{lines} is lower than the number of disassembly lines between
29584 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29585 displayed; if @var{lines} is higher than the number of lines between
29586 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29591 @item 0 disassembly only
29592 @item 1 mixed source and disassembly (deprecated)
29593 @item 2 disassembly with raw opcodes
29594 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29595 @item 4 mixed source and disassembly
29596 @item 5 mixed source and disassembly with raw opcodes
29599 Modes 1 and 3 are deprecated. The output is ``source centric''
29600 which hasn't proved useful in practice.
29601 @xref{Machine Code}, for a discussion of the difference between
29602 @code{/m} and @code{/s} output of the @code{disassemble} command.
29605 @subsubheading Result
29607 The result of the @code{-data-disassemble} command will be a list named
29608 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29609 used with the @code{-data-disassemble} command.
29611 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29616 The address at which this instruction was disassembled.
29619 The name of the function this instruction is within.
29622 The decimal offset in bytes from the start of @samp{func-name}.
29625 The text disassembly for this @samp{address}.
29628 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29629 bytes for the @samp{inst} field.
29633 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29634 @samp{src_and_asm_line}, each of which has the following fields:
29638 The line number within @samp{file}.
29641 The file name from the compilation unit. This might be an absolute
29642 file name or a relative file name depending on the compile command
29646 Absolute file name of @samp{file}. It is converted to a canonical form
29647 using the source file search path
29648 (@pxref{Source Path, ,Specifying Source Directories})
29649 and after resolving all the symbolic links.
29651 If the source file is not found this field will contain the path as
29652 present in the debug information.
29654 @item line_asm_insn
29655 This is a list of tuples containing the disassembly for @samp{line} in
29656 @samp{file}. The fields of each tuple are the same as for
29657 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29658 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29663 Note that whatever included in the @samp{inst} field, is not
29664 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29667 @subsubheading @value{GDBN} Command
29669 The corresponding @value{GDBN} command is @samp{disassemble}.
29671 @subsubheading Example
29673 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29677 -data-disassemble -s $pc -e "$pc + 20" -- 0
29680 @{address="0x000107c0",func-name="main",offset="4",
29681 inst="mov 2, %o0"@},
29682 @{address="0x000107c4",func-name="main",offset="8",
29683 inst="sethi %hi(0x11800), %o2"@},
29684 @{address="0x000107c8",func-name="main",offset="12",
29685 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29686 @{address="0x000107cc",func-name="main",offset="16",
29687 inst="sethi %hi(0x11800), %o2"@},
29688 @{address="0x000107d0",func-name="main",offset="20",
29689 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29693 Disassemble the whole @code{main} function. Line 32 is part of
29697 -data-disassemble -f basics.c -l 32 -- 0
29699 @{address="0x000107bc",func-name="main",offset="0",
29700 inst="save %sp, -112, %sp"@},
29701 @{address="0x000107c0",func-name="main",offset="4",
29702 inst="mov 2, %o0"@},
29703 @{address="0x000107c4",func-name="main",offset="8",
29704 inst="sethi %hi(0x11800), %o2"@},
29706 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29707 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29711 Disassemble 3 instructions from the start of @code{main}:
29715 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29717 @{address="0x000107bc",func-name="main",offset="0",
29718 inst="save %sp, -112, %sp"@},
29719 @{address="0x000107c0",func-name="main",offset="4",
29720 inst="mov 2, %o0"@},
29721 @{address="0x000107c4",func-name="main",offset="8",
29722 inst="sethi %hi(0x11800), %o2"@}]
29726 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29730 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29732 src_and_asm_line=@{line="31",
29733 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29734 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29735 line_asm_insn=[@{address="0x000107bc",
29736 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29737 src_and_asm_line=@{line="32",
29738 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29739 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29740 line_asm_insn=[@{address="0x000107c0",
29741 func-name="main",offset="4",inst="mov 2, %o0"@},
29742 @{address="0x000107c4",func-name="main",offset="8",
29743 inst="sethi %hi(0x11800), %o2"@}]@}]
29748 @subheading The @code{-data-evaluate-expression} Command
29749 @findex -data-evaluate-expression
29751 @subsubheading Synopsis
29754 -data-evaluate-expression @var{expr}
29757 Evaluate @var{expr} as an expression. The expression could contain an
29758 inferior function call. The function call will execute synchronously.
29759 If the expression contains spaces, it must be enclosed in double quotes.
29761 @subsubheading @value{GDBN} Command
29763 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29764 @samp{call}. In @code{gdbtk} only, there's a corresponding
29765 @samp{gdb_eval} command.
29767 @subsubheading Example
29769 In the following example, the numbers that precede the commands are the
29770 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29771 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29775 211-data-evaluate-expression A
29778 311-data-evaluate-expression &A
29779 311^done,value="0xefffeb7c"
29781 411-data-evaluate-expression A+3
29784 511-data-evaluate-expression "A + 3"
29790 @subheading The @code{-data-list-changed-registers} Command
29791 @findex -data-list-changed-registers
29793 @subsubheading Synopsis
29796 -data-list-changed-registers
29799 Display a list of the registers that have changed.
29801 @subsubheading @value{GDBN} Command
29803 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29804 has the corresponding command @samp{gdb_changed_register_list}.
29806 @subsubheading Example
29808 On a PPC MBX board:
29816 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29817 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29820 -data-list-changed-registers
29821 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29822 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29823 "24","25","26","27","28","30","31","64","65","66","67","69"]
29828 @subheading The @code{-data-list-register-names} Command
29829 @findex -data-list-register-names
29831 @subsubheading Synopsis
29834 -data-list-register-names [ ( @var{regno} )+ ]
29837 Show a list of register names for the current target. If no arguments
29838 are given, it shows a list of the names of all the registers. If
29839 integer numbers are given as arguments, it will print a list of the
29840 names of the registers corresponding to the arguments. To ensure
29841 consistency between a register name and its number, the output list may
29842 include empty register names.
29844 @subsubheading @value{GDBN} Command
29846 @value{GDBN} does not have a command which corresponds to
29847 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29848 corresponding command @samp{gdb_regnames}.
29850 @subsubheading Example
29852 For the PPC MBX board:
29855 -data-list-register-names
29856 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29857 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29858 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29859 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29860 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29861 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29862 "", "pc","ps","cr","lr","ctr","xer"]
29864 -data-list-register-names 1 2 3
29865 ^done,register-names=["r1","r2","r3"]
29869 @subheading The @code{-data-list-register-values} Command
29870 @findex -data-list-register-values
29872 @subsubheading Synopsis
29875 -data-list-register-values
29876 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29879 Display the registers' contents. The format according to which the
29880 registers' contents are to be returned is given by @var{fmt}, followed
29881 by an optional list of numbers specifying the registers to display. A
29882 missing list of numbers indicates that the contents of all the
29883 registers must be returned. The @code{--skip-unavailable} option
29884 indicates that only the available registers are to be returned.
29886 Allowed formats for @var{fmt} are:
29903 @subsubheading @value{GDBN} Command
29905 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29906 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29908 @subsubheading Example
29910 For a PPC MBX board (note: line breaks are for readability only, they
29911 don't appear in the actual output):
29915 -data-list-register-values r 64 65
29916 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29917 @{number="65",value="0x00029002"@}]
29919 -data-list-register-values x
29920 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29921 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29922 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29923 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29924 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29925 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29926 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29927 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29928 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29929 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29930 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29931 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29932 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29933 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29934 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29935 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29936 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29937 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29938 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29939 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29940 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29941 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29942 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29943 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29944 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29945 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29946 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29947 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29948 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29949 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29950 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29951 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29952 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29953 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29954 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29955 @{number="69",value="0x20002b03"@}]
29960 @subheading The @code{-data-read-memory} Command
29961 @findex -data-read-memory
29963 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29965 @subsubheading Synopsis
29968 -data-read-memory [ -o @var{byte-offset} ]
29969 @var{address} @var{word-format} @var{word-size}
29970 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29977 @item @var{address}
29978 An expression specifying the address of the first memory word to be
29979 read. Complex expressions containing embedded white space should be
29980 quoted using the C convention.
29982 @item @var{word-format}
29983 The format to be used to print the memory words. The notation is the
29984 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29987 @item @var{word-size}
29988 The size of each memory word in bytes.
29990 @item @var{nr-rows}
29991 The number of rows in the output table.
29993 @item @var{nr-cols}
29994 The number of columns in the output table.
29997 If present, indicates that each row should include an @sc{ascii} dump. The
29998 value of @var{aschar} is used as a padding character when a byte is not a
29999 member of the printable @sc{ascii} character set (printable @sc{ascii}
30000 characters are those whose code is between 32 and 126, inclusively).
30002 @item @var{byte-offset}
30003 An offset to add to the @var{address} before fetching memory.
30006 This command displays memory contents as a table of @var{nr-rows} by
30007 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30008 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30009 (returned as @samp{total-bytes}). Should less than the requested number
30010 of bytes be returned by the target, the missing words are identified
30011 using @samp{N/A}. The number of bytes read from the target is returned
30012 in @samp{nr-bytes} and the starting address used to read memory in
30015 The address of the next/previous row or page is available in
30016 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30019 @subsubheading @value{GDBN} Command
30021 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30022 @samp{gdb_get_mem} memory read command.
30024 @subsubheading Example
30026 Read six bytes of memory starting at @code{bytes+6} but then offset by
30027 @code{-6} bytes. Format as three rows of two columns. One byte per
30028 word. Display each word in hex.
30032 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30033 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30034 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30035 prev-page="0x0000138a",memory=[
30036 @{addr="0x00001390",data=["0x00","0x01"]@},
30037 @{addr="0x00001392",data=["0x02","0x03"]@},
30038 @{addr="0x00001394",data=["0x04","0x05"]@}]
30042 Read two bytes of memory starting at address @code{shorts + 64} and
30043 display as a single word formatted in decimal.
30047 5-data-read-memory shorts+64 d 2 1 1
30048 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30049 next-row="0x00001512",prev-row="0x0000150e",
30050 next-page="0x00001512",prev-page="0x0000150e",memory=[
30051 @{addr="0x00001510",data=["128"]@}]
30055 Read thirty two bytes of memory starting at @code{bytes+16} and format
30056 as eight rows of four columns. Include a string encoding with @samp{x}
30057 used as the non-printable character.
30061 4-data-read-memory bytes+16 x 1 8 4 x
30062 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30063 next-row="0x000013c0",prev-row="0x0000139c",
30064 next-page="0x000013c0",prev-page="0x00001380",memory=[
30065 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30066 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30067 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30068 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30069 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30070 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30071 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30072 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30076 @subheading The @code{-data-read-memory-bytes} Command
30077 @findex -data-read-memory-bytes
30079 @subsubheading Synopsis
30082 -data-read-memory-bytes [ -o @var{offset} ]
30083 @var{address} @var{count}
30090 @item @var{address}
30091 An expression specifying the address of the first addressable memory unit
30092 to be read. Complex expressions containing embedded white space should be
30093 quoted using the C convention.
30096 The number of addressable memory units to read. This should be an integer
30100 The offset relative to @var{address} at which to start reading. This
30101 should be an integer literal. This option is provided so that a frontend
30102 is not required to first evaluate address and then perform address
30103 arithmetics itself.
30107 This command attempts to read all accessible memory regions in the
30108 specified range. First, all regions marked as unreadable in the memory
30109 map (if one is defined) will be skipped. @xref{Memory Region
30110 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30111 regions. For each one, if reading full region results in an errors,
30112 @value{GDBN} will try to read a subset of the region.
30114 In general, every single memory unit in the region may be readable or not,
30115 and the only way to read every readable unit is to try a read at
30116 every address, which is not practical. Therefore, @value{GDBN} will
30117 attempt to read all accessible memory units at either beginning or the end
30118 of the region, using a binary division scheme. This heuristic works
30119 well for reading accross a memory map boundary. Note that if a region
30120 has a readable range that is neither at the beginning or the end,
30121 @value{GDBN} will not read it.
30123 The result record (@pxref{GDB/MI Result Records}) that is output of
30124 the command includes a field named @samp{memory} whose content is a
30125 list of tuples. Each tuple represent a successfully read memory block
30126 and has the following fields:
30130 The start address of the memory block, as hexadecimal literal.
30133 The end address of the memory block, as hexadecimal literal.
30136 The offset of the memory block, as hexadecimal literal, relative to
30137 the start address passed to @code{-data-read-memory-bytes}.
30140 The contents of the memory block, in hex.
30146 @subsubheading @value{GDBN} Command
30148 The corresponding @value{GDBN} command is @samp{x}.
30150 @subsubheading Example
30154 -data-read-memory-bytes &a 10
30155 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30157 contents="01000000020000000300"@}]
30162 @subheading The @code{-data-write-memory-bytes} Command
30163 @findex -data-write-memory-bytes
30165 @subsubheading Synopsis
30168 -data-write-memory-bytes @var{address} @var{contents}
30169 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30176 @item @var{address}
30177 An expression specifying the address of the first addressable memory unit
30178 to be written. Complex expressions containing embedded white space should
30179 be quoted using the C convention.
30181 @item @var{contents}
30182 The hex-encoded data to write. It is an error if @var{contents} does
30183 not represent an integral number of addressable memory units.
30186 Optional argument indicating the number of addressable memory units to be
30187 written. If @var{count} is greater than @var{contents}' length,
30188 @value{GDBN} will repeatedly write @var{contents} until it fills
30189 @var{count} memory units.
30193 @subsubheading @value{GDBN} Command
30195 There's no corresponding @value{GDBN} command.
30197 @subsubheading Example
30201 -data-write-memory-bytes &a "aabbccdd"
30208 -data-write-memory-bytes &a "aabbccdd" 16e
30213 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30214 @node GDB/MI Tracepoint Commands
30215 @section @sc{gdb/mi} Tracepoint Commands
30217 The commands defined in this section implement MI support for
30218 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30220 @subheading The @code{-trace-find} Command
30221 @findex -trace-find
30223 @subsubheading Synopsis
30226 -trace-find @var{mode} [@var{parameters}@dots{}]
30229 Find a trace frame using criteria defined by @var{mode} and
30230 @var{parameters}. The following table lists permissible
30231 modes and their parameters. For details of operation, see @ref{tfind}.
30236 No parameters are required. Stops examining trace frames.
30239 An integer is required as parameter. Selects tracepoint frame with
30242 @item tracepoint-number
30243 An integer is required as parameter. Finds next
30244 trace frame that corresponds to tracepoint with the specified number.
30247 An address is required as parameter. Finds
30248 next trace frame that corresponds to any tracepoint at the specified
30251 @item pc-inside-range
30252 Two addresses are required as parameters. Finds next trace
30253 frame that corresponds to a tracepoint at an address inside the
30254 specified range. Both bounds are considered to be inside the range.
30256 @item pc-outside-range
30257 Two addresses are required as parameters. Finds
30258 next trace frame that corresponds to a tracepoint at an address outside
30259 the specified range. Both bounds are considered to be inside the range.
30262 Line specification is required as parameter. @xref{Specify Location}.
30263 Finds next trace frame that corresponds to a tracepoint at
30264 the specified location.
30268 If @samp{none} was passed as @var{mode}, the response does not
30269 have fields. Otherwise, the response may have the following fields:
30273 This field has either @samp{0} or @samp{1} as the value, depending
30274 on whether a matching tracepoint was found.
30277 The index of the found traceframe. This field is present iff
30278 the @samp{found} field has value of @samp{1}.
30281 The index of the found tracepoint. This field is present iff
30282 the @samp{found} field has value of @samp{1}.
30285 The information about the frame corresponding to the found trace
30286 frame. This field is present only if a trace frame was found.
30287 @xref{GDB/MI Frame Information}, for description of this field.
30291 @subsubheading @value{GDBN} Command
30293 The corresponding @value{GDBN} command is @samp{tfind}.
30295 @subheading -trace-define-variable
30296 @findex -trace-define-variable
30298 @subsubheading Synopsis
30301 -trace-define-variable @var{name} [ @var{value} ]
30304 Create trace variable @var{name} if it does not exist. If
30305 @var{value} is specified, sets the initial value of the specified
30306 trace variable to that value. Note that the @var{name} should start
30307 with the @samp{$} character.
30309 @subsubheading @value{GDBN} Command
30311 The corresponding @value{GDBN} command is @samp{tvariable}.
30313 @subheading The @code{-trace-frame-collected} Command
30314 @findex -trace-frame-collected
30316 @subsubheading Synopsis
30319 -trace-frame-collected
30320 [--var-print-values @var{var_pval}]
30321 [--comp-print-values @var{comp_pval}]
30322 [--registers-format @var{regformat}]
30323 [--memory-contents]
30326 This command returns the set of collected objects, register names,
30327 trace state variable names, memory ranges and computed expressions
30328 that have been collected at a particular trace frame. The optional
30329 parameters to the command affect the output format in different ways.
30330 See the output description table below for more details.
30332 The reported names can be used in the normal manner to create
30333 varobjs and inspect the objects themselves. The items returned by
30334 this command are categorized so that it is clear which is a variable,
30335 which is a register, which is a trace state variable, which is a
30336 memory range and which is a computed expression.
30338 For instance, if the actions were
30340 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30341 collect *(int*)0xaf02bef0@@40
30345 the object collected in its entirety would be @code{myVar}. The
30346 object @code{myArray} would be partially collected, because only the
30347 element at index @code{myIndex} would be collected. The remaining
30348 objects would be computed expressions.
30350 An example output would be:
30354 -trace-frame-collected
30356 explicit-variables=[@{name="myVar",value="1"@}],
30357 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30358 @{name="myObj.field",value="0"@},
30359 @{name="myPtr->field",value="1"@},
30360 @{name="myCount + 2",value="3"@},
30361 @{name="$tvar1 + 1",value="43970027"@}],
30362 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30363 @{number="1",value="0x0"@},
30364 @{number="2",value="0x4"@},
30366 @{number="125",value="0x0"@}],
30367 tvars=[@{name="$tvar1",current="43970026"@}],
30368 memory=[@{address="0x0000000000602264",length="4"@},
30369 @{address="0x0000000000615bc0",length="4"@}]
30376 @item explicit-variables
30377 The set of objects that have been collected in their entirety (as
30378 opposed to collecting just a few elements of an array or a few struct
30379 members). For each object, its name and value are printed.
30380 The @code{--var-print-values} option affects how or whether the value
30381 field is output. If @var{var_pval} is 0, then print only the names;
30382 if it is 1, print also their values; and if it is 2, print the name,
30383 type and value for simple data types, and the name and type for
30384 arrays, structures and unions.
30386 @item computed-expressions
30387 The set of computed expressions that have been collected at the
30388 current trace frame. The @code{--comp-print-values} option affects
30389 this set like the @code{--var-print-values} option affects the
30390 @code{explicit-variables} set. See above.
30393 The registers that have been collected at the current trace frame.
30394 For each register collected, the name and current value are returned.
30395 The value is formatted according to the @code{--registers-format}
30396 option. See the @command{-data-list-register-values} command for a
30397 list of the allowed formats. The default is @samp{x}.
30400 The trace state variables that have been collected at the current
30401 trace frame. For each trace state variable collected, the name and
30402 current value are returned.
30405 The set of memory ranges that have been collected at the current trace
30406 frame. Its content is a list of tuples. Each tuple represents a
30407 collected memory range and has the following fields:
30411 The start address of the memory range, as hexadecimal literal.
30414 The length of the memory range, as decimal literal.
30417 The contents of the memory block, in hex. This field is only present
30418 if the @code{--memory-contents} option is specified.
30424 @subsubheading @value{GDBN} Command
30426 There is no corresponding @value{GDBN} command.
30428 @subsubheading Example
30430 @subheading -trace-list-variables
30431 @findex -trace-list-variables
30433 @subsubheading Synopsis
30436 -trace-list-variables
30439 Return a table of all defined trace variables. Each element of the
30440 table has the following fields:
30444 The name of the trace variable. This field is always present.
30447 The initial value. This is a 64-bit signed integer. This
30448 field is always present.
30451 The value the trace variable has at the moment. This is a 64-bit
30452 signed integer. This field is absent iff current value is
30453 not defined, for example if the trace was never run, or is
30458 @subsubheading @value{GDBN} Command
30460 The corresponding @value{GDBN} command is @samp{tvariables}.
30462 @subsubheading Example
30466 -trace-list-variables
30467 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30468 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30469 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30470 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30471 body=[variable=@{name="$trace_timestamp",initial="0"@}
30472 variable=@{name="$foo",initial="10",current="15"@}]@}
30476 @subheading -trace-save
30477 @findex -trace-save
30479 @subsubheading Synopsis
30482 -trace-save [-r ] @var{filename}
30485 Saves the collected trace data to @var{filename}. Without the
30486 @samp{-r} option, the data is downloaded from the target and saved
30487 in a local file. With the @samp{-r} option the target is asked
30488 to perform the save.
30490 @subsubheading @value{GDBN} Command
30492 The corresponding @value{GDBN} command is @samp{tsave}.
30495 @subheading -trace-start
30496 @findex -trace-start
30498 @subsubheading Synopsis
30504 Starts a tracing experiments. The result of this command does not
30507 @subsubheading @value{GDBN} Command
30509 The corresponding @value{GDBN} command is @samp{tstart}.
30511 @subheading -trace-status
30512 @findex -trace-status
30514 @subsubheading Synopsis
30520 Obtains the status of a tracing experiment. The result may include
30521 the following fields:
30526 May have a value of either @samp{0}, when no tracing operations are
30527 supported, @samp{1}, when all tracing operations are supported, or
30528 @samp{file} when examining trace file. In the latter case, examining
30529 of trace frame is possible but new tracing experiement cannot be
30530 started. This field is always present.
30533 May have a value of either @samp{0} or @samp{1} depending on whether
30534 tracing experiement is in progress on target. This field is present
30535 if @samp{supported} field is not @samp{0}.
30538 Report the reason why the tracing was stopped last time. This field
30539 may be absent iff tracing was never stopped on target yet. The
30540 value of @samp{request} means the tracing was stopped as result of
30541 the @code{-trace-stop} command. The value of @samp{overflow} means
30542 the tracing buffer is full. The value of @samp{disconnection} means
30543 tracing was automatically stopped when @value{GDBN} has disconnected.
30544 The value of @samp{passcount} means tracing was stopped when a
30545 tracepoint was passed a maximal number of times for that tracepoint.
30546 This field is present if @samp{supported} field is not @samp{0}.
30548 @item stopping-tracepoint
30549 The number of tracepoint whose passcount as exceeded. This field is
30550 present iff the @samp{stop-reason} field has the value of
30554 @itemx frames-created
30555 The @samp{frames} field is a count of the total number of trace frames
30556 in the trace buffer, while @samp{frames-created} is the total created
30557 during the run, including ones that were discarded, such as when a
30558 circular trace buffer filled up. Both fields are optional.
30562 These fields tell the current size of the tracing buffer and the
30563 remaining space. These fields are optional.
30566 The value of the circular trace buffer flag. @code{1} means that the
30567 trace buffer is circular and old trace frames will be discarded if
30568 necessary to make room, @code{0} means that the trace buffer is linear
30572 The value of the disconnected tracing flag. @code{1} means that
30573 tracing will continue after @value{GDBN} disconnects, @code{0} means
30574 that the trace run will stop.
30577 The filename of the trace file being examined. This field is
30578 optional, and only present when examining a trace file.
30582 @subsubheading @value{GDBN} Command
30584 The corresponding @value{GDBN} command is @samp{tstatus}.
30586 @subheading -trace-stop
30587 @findex -trace-stop
30589 @subsubheading Synopsis
30595 Stops a tracing experiment. The result of this command has the same
30596 fields as @code{-trace-status}, except that the @samp{supported} and
30597 @samp{running} fields are not output.
30599 @subsubheading @value{GDBN} Command
30601 The corresponding @value{GDBN} command is @samp{tstop}.
30604 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30605 @node GDB/MI Symbol Query
30606 @section @sc{gdb/mi} Symbol Query Commands
30610 @subheading The @code{-symbol-info-address} Command
30611 @findex -symbol-info-address
30613 @subsubheading Synopsis
30616 -symbol-info-address @var{symbol}
30619 Describe where @var{symbol} is stored.
30621 @subsubheading @value{GDBN} Command
30623 The corresponding @value{GDBN} command is @samp{info address}.
30625 @subsubheading Example
30629 @subheading The @code{-symbol-info-file} Command
30630 @findex -symbol-info-file
30632 @subsubheading Synopsis
30638 Show the file for the symbol.
30640 @subsubheading @value{GDBN} Command
30642 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30643 @samp{gdb_find_file}.
30645 @subsubheading Example
30649 @subheading The @code{-symbol-info-function} Command
30650 @findex -symbol-info-function
30652 @subsubheading Synopsis
30655 -symbol-info-function
30658 Show which function the symbol lives in.
30660 @subsubheading @value{GDBN} Command
30662 @samp{gdb_get_function} in @code{gdbtk}.
30664 @subsubheading Example
30668 @subheading The @code{-symbol-info-line} Command
30669 @findex -symbol-info-line
30671 @subsubheading Synopsis
30677 Show the core addresses of the code for a source line.
30679 @subsubheading @value{GDBN} Command
30681 The corresponding @value{GDBN} command is @samp{info line}.
30682 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30684 @subsubheading Example
30688 @subheading The @code{-symbol-info-symbol} Command
30689 @findex -symbol-info-symbol
30691 @subsubheading Synopsis
30694 -symbol-info-symbol @var{addr}
30697 Describe what symbol is at location @var{addr}.
30699 @subsubheading @value{GDBN} Command
30701 The corresponding @value{GDBN} command is @samp{info symbol}.
30703 @subsubheading Example
30707 @subheading The @code{-symbol-list-functions} Command
30708 @findex -symbol-list-functions
30710 @subsubheading Synopsis
30713 -symbol-list-functions
30716 List the functions in the executable.
30718 @subsubheading @value{GDBN} Command
30720 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30721 @samp{gdb_search} in @code{gdbtk}.
30723 @subsubheading Example
30728 @subheading The @code{-symbol-list-lines} Command
30729 @findex -symbol-list-lines
30731 @subsubheading Synopsis
30734 -symbol-list-lines @var{filename}
30737 Print the list of lines that contain code and their associated program
30738 addresses for the given source filename. The entries are sorted in
30739 ascending PC order.
30741 @subsubheading @value{GDBN} Command
30743 There is no corresponding @value{GDBN} command.
30745 @subsubheading Example
30748 -symbol-list-lines basics.c
30749 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30755 @subheading The @code{-symbol-list-types} Command
30756 @findex -symbol-list-types
30758 @subsubheading Synopsis
30764 List all the type names.
30766 @subsubheading @value{GDBN} Command
30768 The corresponding commands are @samp{info types} in @value{GDBN},
30769 @samp{gdb_search} in @code{gdbtk}.
30771 @subsubheading Example
30775 @subheading The @code{-symbol-list-variables} Command
30776 @findex -symbol-list-variables
30778 @subsubheading Synopsis
30781 -symbol-list-variables
30784 List all the global and static variable names.
30786 @subsubheading @value{GDBN} Command
30788 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30790 @subsubheading Example
30794 @subheading The @code{-symbol-locate} Command
30795 @findex -symbol-locate
30797 @subsubheading Synopsis
30803 @subsubheading @value{GDBN} Command
30805 @samp{gdb_loc} in @code{gdbtk}.
30807 @subsubheading Example
30811 @subheading The @code{-symbol-type} Command
30812 @findex -symbol-type
30814 @subsubheading Synopsis
30817 -symbol-type @var{variable}
30820 Show type of @var{variable}.
30822 @subsubheading @value{GDBN} Command
30824 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30825 @samp{gdb_obj_variable}.
30827 @subsubheading Example
30832 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30833 @node GDB/MI File Commands
30834 @section @sc{gdb/mi} File Commands
30836 This section describes the GDB/MI commands to specify executable file names
30837 and to read in and obtain symbol table information.
30839 @subheading The @code{-file-exec-and-symbols} Command
30840 @findex -file-exec-and-symbols
30842 @subsubheading Synopsis
30845 -file-exec-and-symbols @var{file}
30848 Specify the executable file to be debugged. This file is the one from
30849 which the symbol table is also read. If no file is specified, the
30850 command clears the executable and symbol information. If breakpoints
30851 are set when using this command with no arguments, @value{GDBN} will produce
30852 error messages. Otherwise, no output is produced, except a completion
30855 @subsubheading @value{GDBN} Command
30857 The corresponding @value{GDBN} command is @samp{file}.
30859 @subsubheading Example
30863 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30869 @subheading The @code{-file-exec-file} Command
30870 @findex -file-exec-file
30872 @subsubheading Synopsis
30875 -file-exec-file @var{file}
30878 Specify the executable file to be debugged. Unlike
30879 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30880 from this file. If used without argument, @value{GDBN} clears the information
30881 about the executable file. No output is produced, except a completion
30884 @subsubheading @value{GDBN} Command
30886 The corresponding @value{GDBN} command is @samp{exec-file}.
30888 @subsubheading Example
30892 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30899 @subheading The @code{-file-list-exec-sections} Command
30900 @findex -file-list-exec-sections
30902 @subsubheading Synopsis
30905 -file-list-exec-sections
30908 List the sections of the current executable file.
30910 @subsubheading @value{GDBN} Command
30912 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30913 information as this command. @code{gdbtk} has a corresponding command
30914 @samp{gdb_load_info}.
30916 @subsubheading Example
30921 @subheading The @code{-file-list-exec-source-file} Command
30922 @findex -file-list-exec-source-file
30924 @subsubheading Synopsis
30927 -file-list-exec-source-file
30930 List the line number, the current source file, and the absolute path
30931 to the current source file for the current executable. The macro
30932 information field has a value of @samp{1} or @samp{0} depending on
30933 whether or not the file includes preprocessor macro information.
30935 @subsubheading @value{GDBN} Command
30937 The @value{GDBN} equivalent is @samp{info source}
30939 @subsubheading Example
30943 123-file-list-exec-source-file
30944 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30949 @subheading The @code{-file-list-exec-source-files} Command
30950 @findex -file-list-exec-source-files
30952 @subsubheading Synopsis
30955 -file-list-exec-source-files
30958 List the source files for the current executable.
30960 It will always output both the filename and fullname (absolute file
30961 name) of a source file.
30963 @subsubheading @value{GDBN} Command
30965 The @value{GDBN} equivalent is @samp{info sources}.
30966 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30968 @subsubheading Example
30971 -file-list-exec-source-files
30973 @{file=foo.c,fullname=/home/foo.c@},
30974 @{file=/home/bar.c,fullname=/home/bar.c@},
30975 @{file=gdb_could_not_find_fullpath.c@}]
30980 @subheading The @code{-file-list-shared-libraries} Command
30981 @findex -file-list-shared-libraries
30983 @subsubheading Synopsis
30986 -file-list-shared-libraries
30989 List the shared libraries in the program.
30991 @subsubheading @value{GDBN} Command
30993 The corresponding @value{GDBN} command is @samp{info shared}.
30995 @subsubheading Example
30999 @subheading The @code{-file-list-symbol-files} Command
31000 @findex -file-list-symbol-files
31002 @subsubheading Synopsis
31005 -file-list-symbol-files
31010 @subsubheading @value{GDBN} Command
31012 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31014 @subsubheading Example
31019 @subheading The @code{-file-symbol-file} Command
31020 @findex -file-symbol-file
31022 @subsubheading Synopsis
31025 -file-symbol-file @var{file}
31028 Read symbol table info from the specified @var{file} argument. When
31029 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31030 produced, except for a completion notification.
31032 @subsubheading @value{GDBN} Command
31034 The corresponding @value{GDBN} command is @samp{symbol-file}.
31036 @subsubheading Example
31040 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31047 @node GDB/MI Memory Overlay Commands
31048 @section @sc{gdb/mi} Memory Overlay Commands
31050 The memory overlay commands are not implemented.
31052 @c @subheading -overlay-auto
31054 @c @subheading -overlay-list-mapping-state
31056 @c @subheading -overlay-list-overlays
31058 @c @subheading -overlay-map
31060 @c @subheading -overlay-off
31062 @c @subheading -overlay-on
31064 @c @subheading -overlay-unmap
31066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31067 @node GDB/MI Signal Handling Commands
31068 @section @sc{gdb/mi} Signal Handling Commands
31070 Signal handling commands are not implemented.
31072 @c @subheading -signal-handle
31074 @c @subheading -signal-list-handle-actions
31076 @c @subheading -signal-list-signal-types
31080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31081 @node GDB/MI Target Manipulation
31082 @section @sc{gdb/mi} Target Manipulation Commands
31085 @subheading The @code{-target-attach} Command
31086 @findex -target-attach
31088 @subsubheading Synopsis
31091 -target-attach @var{pid} | @var{gid} | @var{file}
31094 Attach to a process @var{pid} or a file @var{file} outside of
31095 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31096 group, the id previously returned by
31097 @samp{-list-thread-groups --available} must be used.
31099 @subsubheading @value{GDBN} Command
31101 The corresponding @value{GDBN} command is @samp{attach}.
31103 @subsubheading Example
31107 =thread-created,id="1"
31108 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31114 @subheading The @code{-target-compare-sections} Command
31115 @findex -target-compare-sections
31117 @subsubheading Synopsis
31120 -target-compare-sections [ @var{section} ]
31123 Compare data of section @var{section} on target to the exec file.
31124 Without the argument, all sections are compared.
31126 @subsubheading @value{GDBN} Command
31128 The @value{GDBN} equivalent is @samp{compare-sections}.
31130 @subsubheading Example
31135 @subheading The @code{-target-detach} Command
31136 @findex -target-detach
31138 @subsubheading Synopsis
31141 -target-detach [ @var{pid} | @var{gid} ]
31144 Detach from the remote target which normally resumes its execution.
31145 If either @var{pid} or @var{gid} is specified, detaches from either
31146 the specified process, or specified thread group. There's no output.
31148 @subsubheading @value{GDBN} Command
31150 The corresponding @value{GDBN} command is @samp{detach}.
31152 @subsubheading Example
31162 @subheading The @code{-target-disconnect} Command
31163 @findex -target-disconnect
31165 @subsubheading Synopsis
31171 Disconnect from the remote target. There's no output and the target is
31172 generally not resumed.
31174 @subsubheading @value{GDBN} Command
31176 The corresponding @value{GDBN} command is @samp{disconnect}.
31178 @subsubheading Example
31188 @subheading The @code{-target-download} Command
31189 @findex -target-download
31191 @subsubheading Synopsis
31197 Loads the executable onto the remote target.
31198 It prints out an update message every half second, which includes the fields:
31202 The name of the section.
31204 The size of what has been sent so far for that section.
31206 The size of the section.
31208 The total size of what was sent so far (the current and the previous sections).
31210 The size of the overall executable to download.
31214 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31215 @sc{gdb/mi} Output Syntax}).
31217 In addition, it prints the name and size of the sections, as they are
31218 downloaded. These messages include the following fields:
31222 The name of the section.
31224 The size of the section.
31226 The size of the overall executable to download.
31230 At the end, a summary is printed.
31232 @subsubheading @value{GDBN} Command
31234 The corresponding @value{GDBN} command is @samp{load}.
31236 @subsubheading Example
31238 Note: each status message appears on a single line. Here the messages
31239 have been broken down so that they can fit onto a page.
31244 +download,@{section=".text",section-size="6668",total-size="9880"@}
31245 +download,@{section=".text",section-sent="512",section-size="6668",
31246 total-sent="512",total-size="9880"@}
31247 +download,@{section=".text",section-sent="1024",section-size="6668",
31248 total-sent="1024",total-size="9880"@}
31249 +download,@{section=".text",section-sent="1536",section-size="6668",
31250 total-sent="1536",total-size="9880"@}
31251 +download,@{section=".text",section-sent="2048",section-size="6668",
31252 total-sent="2048",total-size="9880"@}
31253 +download,@{section=".text",section-sent="2560",section-size="6668",
31254 total-sent="2560",total-size="9880"@}
31255 +download,@{section=".text",section-sent="3072",section-size="6668",
31256 total-sent="3072",total-size="9880"@}
31257 +download,@{section=".text",section-sent="3584",section-size="6668",
31258 total-sent="3584",total-size="9880"@}
31259 +download,@{section=".text",section-sent="4096",section-size="6668",
31260 total-sent="4096",total-size="9880"@}
31261 +download,@{section=".text",section-sent="4608",section-size="6668",
31262 total-sent="4608",total-size="9880"@}
31263 +download,@{section=".text",section-sent="5120",section-size="6668",
31264 total-sent="5120",total-size="9880"@}
31265 +download,@{section=".text",section-sent="5632",section-size="6668",
31266 total-sent="5632",total-size="9880"@}
31267 +download,@{section=".text",section-sent="6144",section-size="6668",
31268 total-sent="6144",total-size="9880"@}
31269 +download,@{section=".text",section-sent="6656",section-size="6668",
31270 total-sent="6656",total-size="9880"@}
31271 +download,@{section=".init",section-size="28",total-size="9880"@}
31272 +download,@{section=".fini",section-size="28",total-size="9880"@}
31273 +download,@{section=".data",section-size="3156",total-size="9880"@}
31274 +download,@{section=".data",section-sent="512",section-size="3156",
31275 total-sent="7236",total-size="9880"@}
31276 +download,@{section=".data",section-sent="1024",section-size="3156",
31277 total-sent="7748",total-size="9880"@}
31278 +download,@{section=".data",section-sent="1536",section-size="3156",
31279 total-sent="8260",total-size="9880"@}
31280 +download,@{section=".data",section-sent="2048",section-size="3156",
31281 total-sent="8772",total-size="9880"@}
31282 +download,@{section=".data",section-sent="2560",section-size="3156",
31283 total-sent="9284",total-size="9880"@}
31284 +download,@{section=".data",section-sent="3072",section-size="3156",
31285 total-sent="9796",total-size="9880"@}
31286 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31293 @subheading The @code{-target-exec-status} Command
31294 @findex -target-exec-status
31296 @subsubheading Synopsis
31299 -target-exec-status
31302 Provide information on the state of the target (whether it is running or
31303 not, for instance).
31305 @subsubheading @value{GDBN} Command
31307 There's no equivalent @value{GDBN} command.
31309 @subsubheading Example
31313 @subheading The @code{-target-list-available-targets} Command
31314 @findex -target-list-available-targets
31316 @subsubheading Synopsis
31319 -target-list-available-targets
31322 List the possible targets to connect to.
31324 @subsubheading @value{GDBN} Command
31326 The corresponding @value{GDBN} command is @samp{help target}.
31328 @subsubheading Example
31332 @subheading The @code{-target-list-current-targets} Command
31333 @findex -target-list-current-targets
31335 @subsubheading Synopsis
31338 -target-list-current-targets
31341 Describe the current target.
31343 @subsubheading @value{GDBN} Command
31345 The corresponding information is printed by @samp{info file} (among
31348 @subsubheading Example
31352 @subheading The @code{-target-list-parameters} Command
31353 @findex -target-list-parameters
31355 @subsubheading Synopsis
31358 -target-list-parameters
31364 @subsubheading @value{GDBN} Command
31368 @subsubheading Example
31372 @subheading The @code{-target-select} Command
31373 @findex -target-select
31375 @subsubheading Synopsis
31378 -target-select @var{type} @var{parameters @dots{}}
31381 Connect @value{GDBN} to the remote target. This command takes two args:
31385 The type of target, for instance @samp{remote}, etc.
31386 @item @var{parameters}
31387 Device names, host names and the like. @xref{Target Commands, ,
31388 Commands for Managing Targets}, for more details.
31391 The output is a connection notification, followed by the address at
31392 which the target program is, in the following form:
31395 ^connected,addr="@var{address}",func="@var{function name}",
31396 args=[@var{arg list}]
31399 @subsubheading @value{GDBN} Command
31401 The corresponding @value{GDBN} command is @samp{target}.
31403 @subsubheading Example
31407 -target-select remote /dev/ttya
31408 ^connected,addr="0xfe00a300",func="??",args=[]
31412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31413 @node GDB/MI File Transfer Commands
31414 @section @sc{gdb/mi} File Transfer Commands
31417 @subheading The @code{-target-file-put} Command
31418 @findex -target-file-put
31420 @subsubheading Synopsis
31423 -target-file-put @var{hostfile} @var{targetfile}
31426 Copy file @var{hostfile} from the host system (the machine running
31427 @value{GDBN}) to @var{targetfile} on the target system.
31429 @subsubheading @value{GDBN} Command
31431 The corresponding @value{GDBN} command is @samp{remote put}.
31433 @subsubheading Example
31437 -target-file-put localfile remotefile
31443 @subheading The @code{-target-file-get} Command
31444 @findex -target-file-get
31446 @subsubheading Synopsis
31449 -target-file-get @var{targetfile} @var{hostfile}
31452 Copy file @var{targetfile} from the target system to @var{hostfile}
31453 on the host system.
31455 @subsubheading @value{GDBN} Command
31457 The corresponding @value{GDBN} command is @samp{remote get}.
31459 @subsubheading Example
31463 -target-file-get remotefile localfile
31469 @subheading The @code{-target-file-delete} Command
31470 @findex -target-file-delete
31472 @subsubheading Synopsis
31475 -target-file-delete @var{targetfile}
31478 Delete @var{targetfile} from the target system.
31480 @subsubheading @value{GDBN} Command
31482 The corresponding @value{GDBN} command is @samp{remote delete}.
31484 @subsubheading Example
31488 -target-file-delete remotefile
31494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31495 @node GDB/MI Ada Exceptions Commands
31496 @section Ada Exceptions @sc{gdb/mi} Commands
31498 @subheading The @code{-info-ada-exceptions} Command
31499 @findex -info-ada-exceptions
31501 @subsubheading Synopsis
31504 -info-ada-exceptions [ @var{regexp}]
31507 List all Ada exceptions defined within the program being debugged.
31508 With a regular expression @var{regexp}, only those exceptions whose
31509 names match @var{regexp} are listed.
31511 @subsubheading @value{GDBN} Command
31513 The corresponding @value{GDBN} command is @samp{info exceptions}.
31515 @subsubheading Result
31517 The result is a table of Ada exceptions. The following columns are
31518 defined for each exception:
31522 The name of the exception.
31525 The address of the exception.
31529 @subsubheading Example
31532 -info-ada-exceptions aint
31533 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31534 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31535 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31536 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31537 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31540 @subheading Catching Ada Exceptions
31542 The commands describing how to ask @value{GDBN} to stop when a program
31543 raises an exception are described at @ref{Ada Exception GDB/MI
31544 Catchpoint Commands}.
31547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31548 @node GDB/MI Support Commands
31549 @section @sc{gdb/mi} Support Commands
31551 Since new commands and features get regularly added to @sc{gdb/mi},
31552 some commands are available to help front-ends query the debugger
31553 about support for these capabilities. Similarly, it is also possible
31554 to query @value{GDBN} about target support of certain features.
31556 @subheading The @code{-info-gdb-mi-command} Command
31557 @cindex @code{-info-gdb-mi-command}
31558 @findex -info-gdb-mi-command
31560 @subsubheading Synopsis
31563 -info-gdb-mi-command @var{cmd_name}
31566 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31568 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31569 is technically not part of the command name (@pxref{GDB/MI Input
31570 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31571 for ease of use, this command also accepts the form with the leading
31574 @subsubheading @value{GDBN} Command
31576 There is no corresponding @value{GDBN} command.
31578 @subsubheading Result
31580 The result is a tuple. There is currently only one field:
31584 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31585 @code{"false"} otherwise.
31589 @subsubheading Example
31591 Here is an example where the @sc{gdb/mi} command does not exist:
31594 -info-gdb-mi-command unsupported-command
31595 ^done,command=@{exists="false"@}
31599 And here is an example where the @sc{gdb/mi} command is known
31603 -info-gdb-mi-command symbol-list-lines
31604 ^done,command=@{exists="true"@}
31607 @subheading The @code{-list-features} Command
31608 @findex -list-features
31609 @cindex supported @sc{gdb/mi} features, list
31611 Returns a list of particular features of the MI protocol that
31612 this version of gdb implements. A feature can be a command,
31613 or a new field in an output of some command, or even an
31614 important bugfix. While a frontend can sometimes detect presence
31615 of a feature at runtime, it is easier to perform detection at debugger
31618 The command returns a list of strings, with each string naming an
31619 available feature. Each returned string is just a name, it does not
31620 have any internal structure. The list of possible feature names
31626 (gdb) -list-features
31627 ^done,result=["feature1","feature2"]
31630 The current list of features is:
31633 @item frozen-varobjs
31634 Indicates support for the @code{-var-set-frozen} command, as well
31635 as possible presense of the @code{frozen} field in the output
31636 of @code{-varobj-create}.
31637 @item pending-breakpoints
31638 Indicates support for the @option{-f} option to the @code{-break-insert}
31641 Indicates Python scripting support, Python-based
31642 pretty-printing commands, and possible presence of the
31643 @samp{display_hint} field in the output of @code{-var-list-children}
31645 Indicates support for the @code{-thread-info} command.
31646 @item data-read-memory-bytes
31647 Indicates support for the @code{-data-read-memory-bytes} and the
31648 @code{-data-write-memory-bytes} commands.
31649 @item breakpoint-notifications
31650 Indicates that changes to breakpoints and breakpoints created via the
31651 CLI will be announced via async records.
31652 @item ada-task-info
31653 Indicates support for the @code{-ada-task-info} command.
31654 @item language-option
31655 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31656 option (@pxref{Context management}).
31657 @item info-gdb-mi-command
31658 Indicates support for the @code{-info-gdb-mi-command} command.
31659 @item undefined-command-error-code
31660 Indicates support for the "undefined-command" error code in error result
31661 records, produced when trying to execute an undefined @sc{gdb/mi} command
31662 (@pxref{GDB/MI Result Records}).
31663 @item exec-run-start-option
31664 Indicates that the @code{-exec-run} command supports the @option{--start}
31665 option (@pxref{GDB/MI Program Execution}).
31668 @subheading The @code{-list-target-features} Command
31669 @findex -list-target-features
31671 Returns a list of particular features that are supported by the
31672 target. Those features affect the permitted MI commands, but
31673 unlike the features reported by the @code{-list-features} command, the
31674 features depend on which target GDB is using at the moment. Whenever
31675 a target can change, due to commands such as @code{-target-select},
31676 @code{-target-attach} or @code{-exec-run}, the list of target features
31677 may change, and the frontend should obtain it again.
31681 (gdb) -list-target-features
31682 ^done,result=["async"]
31685 The current list of features is:
31689 Indicates that the target is capable of asynchronous command
31690 execution, which means that @value{GDBN} will accept further commands
31691 while the target is running.
31694 Indicates that the target is capable of reverse execution.
31695 @xref{Reverse Execution}, for more information.
31699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31700 @node GDB/MI Miscellaneous Commands
31701 @section Miscellaneous @sc{gdb/mi} Commands
31703 @c @subheading -gdb-complete
31705 @subheading The @code{-gdb-exit} Command
31708 @subsubheading Synopsis
31714 Exit @value{GDBN} immediately.
31716 @subsubheading @value{GDBN} Command
31718 Approximately corresponds to @samp{quit}.
31720 @subsubheading Example
31730 @subheading The @code{-exec-abort} Command
31731 @findex -exec-abort
31733 @subsubheading Synopsis
31739 Kill the inferior running program.
31741 @subsubheading @value{GDBN} Command
31743 The corresponding @value{GDBN} command is @samp{kill}.
31745 @subsubheading Example
31750 @subheading The @code{-gdb-set} Command
31753 @subsubheading Synopsis
31759 Set an internal @value{GDBN} variable.
31760 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31762 @subsubheading @value{GDBN} Command
31764 The corresponding @value{GDBN} command is @samp{set}.
31766 @subsubheading Example
31776 @subheading The @code{-gdb-show} Command
31779 @subsubheading Synopsis
31785 Show the current value of a @value{GDBN} variable.
31787 @subsubheading @value{GDBN} Command
31789 The corresponding @value{GDBN} command is @samp{show}.
31791 @subsubheading Example
31800 @c @subheading -gdb-source
31803 @subheading The @code{-gdb-version} Command
31804 @findex -gdb-version
31806 @subsubheading Synopsis
31812 Show version information for @value{GDBN}. Used mostly in testing.
31814 @subsubheading @value{GDBN} Command
31816 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31817 default shows this information when you start an interactive session.
31819 @subsubheading Example
31821 @c This example modifies the actual output from GDB to avoid overfull
31827 ~Copyright 2000 Free Software Foundation, Inc.
31828 ~GDB is free software, covered by the GNU General Public License, and
31829 ~you are welcome to change it and/or distribute copies of it under
31830 ~ certain conditions.
31831 ~Type "show copying" to see the conditions.
31832 ~There is absolutely no warranty for GDB. Type "show warranty" for
31834 ~This GDB was configured as
31835 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31840 @subheading The @code{-list-thread-groups} Command
31841 @findex -list-thread-groups
31843 @subheading Synopsis
31846 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31849 Lists thread groups (@pxref{Thread groups}). When a single thread
31850 group is passed as the argument, lists the children of that group.
31851 When several thread group are passed, lists information about those
31852 thread groups. Without any parameters, lists information about all
31853 top-level thread groups.
31855 Normally, thread groups that are being debugged are reported.
31856 With the @samp{--available} option, @value{GDBN} reports thread groups
31857 available on the target.
31859 The output of this command may have either a @samp{threads} result or
31860 a @samp{groups} result. The @samp{thread} result has a list of tuples
31861 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31862 Information}). The @samp{groups} result has a list of tuples as value,
31863 each tuple describing a thread group. If top-level groups are
31864 requested (that is, no parameter is passed), or when several groups
31865 are passed, the output always has a @samp{groups} result. The format
31866 of the @samp{group} result is described below.
31868 To reduce the number of roundtrips it's possible to list thread groups
31869 together with their children, by passing the @samp{--recurse} option
31870 and the recursion depth. Presently, only recursion depth of 1 is
31871 permitted. If this option is present, then every reported thread group
31872 will also include its children, either as @samp{group} or
31873 @samp{threads} field.
31875 In general, any combination of option and parameters is permitted, with
31876 the following caveats:
31880 When a single thread group is passed, the output will typically
31881 be the @samp{threads} result. Because threads may not contain
31882 anything, the @samp{recurse} option will be ignored.
31885 When the @samp{--available} option is passed, limited information may
31886 be available. In particular, the list of threads of a process might
31887 be inaccessible. Further, specifying specific thread groups might
31888 not give any performance advantage over listing all thread groups.
31889 The frontend should assume that @samp{-list-thread-groups --available}
31890 is always an expensive operation and cache the results.
31894 The @samp{groups} result is a list of tuples, where each tuple may
31895 have the following fields:
31899 Identifier of the thread group. This field is always present.
31900 The identifier is an opaque string; frontends should not try to
31901 convert it to an integer, even though it might look like one.
31904 The type of the thread group. At present, only @samp{process} is a
31908 The target-specific process identifier. This field is only present
31909 for thread groups of type @samp{process} and only if the process exists.
31912 The exit code of this group's last exited thread, formatted in octal.
31913 This field is only present for thread groups of type @samp{process} and
31914 only if the process is not running.
31917 The number of children this thread group has. This field may be
31918 absent for an available thread group.
31921 This field has a list of tuples as value, each tuple describing a
31922 thread. It may be present if the @samp{--recurse} option is
31923 specified, and it's actually possible to obtain the threads.
31926 This field is a list of integers, each identifying a core that one
31927 thread of the group is running on. This field may be absent if
31928 such information is not available.
31931 The name of the executable file that corresponds to this thread group.
31932 The field is only present for thread groups of type @samp{process},
31933 and only if there is a corresponding executable file.
31937 @subheading Example
31941 -list-thread-groups
31942 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31943 -list-thread-groups 17
31944 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31945 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31946 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31947 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31948 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31949 -list-thread-groups --available
31950 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31951 -list-thread-groups --available --recurse 1
31952 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31953 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31954 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31955 -list-thread-groups --available --recurse 1 17 18
31956 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31957 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31958 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31961 @subheading The @code{-info-os} Command
31964 @subsubheading Synopsis
31967 -info-os [ @var{type} ]
31970 If no argument is supplied, the command returns a table of available
31971 operating-system-specific information types. If one of these types is
31972 supplied as an argument @var{type}, then the command returns a table
31973 of data of that type.
31975 The types of information available depend on the target operating
31978 @subsubheading @value{GDBN} Command
31980 The corresponding @value{GDBN} command is @samp{info os}.
31982 @subsubheading Example
31984 When run on a @sc{gnu}/Linux system, the output will look something
31990 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31991 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31992 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31993 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31994 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31996 item=@{col0="files",col1="Listing of all file descriptors",
31997 col2="File descriptors"@},
31998 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31999 col2="Kernel modules"@},
32000 item=@{col0="msg",col1="Listing of all message queues",
32001 col2="Message queues"@},
32002 item=@{col0="processes",col1="Listing of all processes",
32003 col2="Processes"@},
32004 item=@{col0="procgroups",col1="Listing of all process groups",
32005 col2="Process groups"@},
32006 item=@{col0="semaphores",col1="Listing of all semaphores",
32007 col2="Semaphores"@},
32008 item=@{col0="shm",col1="Listing of all shared-memory regions",
32009 col2="Shared-memory regions"@},
32010 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32012 item=@{col0="threads",col1="Listing of all threads",
32016 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32017 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32018 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32019 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32020 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32021 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32022 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32023 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32025 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32026 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32030 (Note that the MI output here includes a @code{"Title"} column that
32031 does not appear in command-line @code{info os}; this column is useful
32032 for MI clients that want to enumerate the types of data, such as in a
32033 popup menu, but is needless clutter on the command line, and
32034 @code{info os} omits it.)
32036 @subheading The @code{-add-inferior} Command
32037 @findex -add-inferior
32039 @subheading Synopsis
32045 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32046 inferior is not associated with any executable. Such association may
32047 be established with the @samp{-file-exec-and-symbols} command
32048 (@pxref{GDB/MI File Commands}). The command response has a single
32049 field, @samp{inferior}, whose value is the identifier of the
32050 thread group corresponding to the new inferior.
32052 @subheading Example
32057 ^done,inferior="i3"
32060 @subheading The @code{-interpreter-exec} Command
32061 @findex -interpreter-exec
32063 @subheading Synopsis
32066 -interpreter-exec @var{interpreter} @var{command}
32068 @anchor{-interpreter-exec}
32070 Execute the specified @var{command} in the given @var{interpreter}.
32072 @subheading @value{GDBN} Command
32074 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32076 @subheading Example
32080 -interpreter-exec console "break main"
32081 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32082 &"During symbol reading, bad structure-type format.\n"
32083 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32088 @subheading The @code{-inferior-tty-set} Command
32089 @findex -inferior-tty-set
32091 @subheading Synopsis
32094 -inferior-tty-set /dev/pts/1
32097 Set terminal for future runs of the program being debugged.
32099 @subheading @value{GDBN} Command
32101 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32103 @subheading Example
32107 -inferior-tty-set /dev/pts/1
32112 @subheading The @code{-inferior-tty-show} Command
32113 @findex -inferior-tty-show
32115 @subheading Synopsis
32121 Show terminal for future runs of program being debugged.
32123 @subheading @value{GDBN} Command
32125 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32127 @subheading Example
32131 -inferior-tty-set /dev/pts/1
32135 ^done,inferior_tty_terminal="/dev/pts/1"
32139 @subheading The @code{-enable-timings} Command
32140 @findex -enable-timings
32142 @subheading Synopsis
32145 -enable-timings [yes | no]
32148 Toggle the printing of the wallclock, user and system times for an MI
32149 command as a field in its output. This command is to help frontend
32150 developers optimize the performance of their code. No argument is
32151 equivalent to @samp{yes}.
32153 @subheading @value{GDBN} Command
32157 @subheading Example
32165 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32166 addr="0x080484ed",func="main",file="myprog.c",
32167 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32169 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32177 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32178 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32179 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32180 fullname="/home/nickrob/myprog.c",line="73"@}
32185 @chapter @value{GDBN} Annotations
32187 This chapter describes annotations in @value{GDBN}. Annotations were
32188 designed to interface @value{GDBN} to graphical user interfaces or other
32189 similar programs which want to interact with @value{GDBN} at a
32190 relatively high level.
32192 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32196 This is Edition @value{EDITION}, @value{DATE}.
32200 * Annotations Overview:: What annotations are; the general syntax.
32201 * Server Prefix:: Issuing a command without affecting user state.
32202 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32203 * Errors:: Annotations for error messages.
32204 * Invalidation:: Some annotations describe things now invalid.
32205 * Annotations for Running::
32206 Whether the program is running, how it stopped, etc.
32207 * Source Annotations:: Annotations describing source code.
32210 @node Annotations Overview
32211 @section What is an Annotation?
32212 @cindex annotations
32214 Annotations start with a newline character, two @samp{control-z}
32215 characters, and the name of the annotation. If there is no additional
32216 information associated with this annotation, the name of the annotation
32217 is followed immediately by a newline. If there is additional
32218 information, the name of the annotation is followed by a space, the
32219 additional information, and a newline. The additional information
32220 cannot contain newline characters.
32222 Any output not beginning with a newline and two @samp{control-z}
32223 characters denotes literal output from @value{GDBN}. Currently there is
32224 no need for @value{GDBN} to output a newline followed by two
32225 @samp{control-z} characters, but if there was such a need, the
32226 annotations could be extended with an @samp{escape} annotation which
32227 means those three characters as output.
32229 The annotation @var{level}, which is specified using the
32230 @option{--annotate} command line option (@pxref{Mode Options}), controls
32231 how much information @value{GDBN} prints together with its prompt,
32232 values of expressions, source lines, and other types of output. Level 0
32233 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32234 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32235 for programs that control @value{GDBN}, and level 2 annotations have
32236 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32237 Interface, annotate, GDB's Obsolete Annotations}).
32240 @kindex set annotate
32241 @item set annotate @var{level}
32242 The @value{GDBN} command @code{set annotate} sets the level of
32243 annotations to the specified @var{level}.
32245 @item show annotate
32246 @kindex show annotate
32247 Show the current annotation level.
32250 This chapter describes level 3 annotations.
32252 A simple example of starting up @value{GDBN} with annotations is:
32255 $ @kbd{gdb --annotate=3}
32257 Copyright 2003 Free Software Foundation, Inc.
32258 GDB is free software, covered by the GNU General Public License,
32259 and you are welcome to change it and/or distribute copies of it
32260 under certain conditions.
32261 Type "show copying" to see the conditions.
32262 There is absolutely no warranty for GDB. Type "show warranty"
32264 This GDB was configured as "i386-pc-linux-gnu"
32275 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32276 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32277 denotes a @samp{control-z} character) are annotations; the rest is
32278 output from @value{GDBN}.
32280 @node Server Prefix
32281 @section The Server Prefix
32282 @cindex server prefix
32284 If you prefix a command with @samp{server } then it will not affect
32285 the command history, nor will it affect @value{GDBN}'s notion of which
32286 command to repeat if @key{RET} is pressed on a line by itself. This
32287 means that commands can be run behind a user's back by a front-end in
32288 a transparent manner.
32290 The @code{server } prefix does not affect the recording of values into
32291 the value history; to print a value without recording it into the
32292 value history, use the @code{output} command instead of the
32293 @code{print} command.
32295 Using this prefix also disables confirmation requests
32296 (@pxref{confirmation requests}).
32299 @section Annotation for @value{GDBN} Input
32301 @cindex annotations for prompts
32302 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32303 to know when to send output, when the output from a given command is
32306 Different kinds of input each have a different @dfn{input type}. Each
32307 input type has three annotations: a @code{pre-} annotation, which
32308 denotes the beginning of any prompt which is being output, a plain
32309 annotation, which denotes the end of the prompt, and then a @code{post-}
32310 annotation which denotes the end of any echo which may (or may not) be
32311 associated with the input. For example, the @code{prompt} input type
32312 features the following annotations:
32320 The input types are
32323 @findex pre-prompt annotation
32324 @findex prompt annotation
32325 @findex post-prompt annotation
32327 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32329 @findex pre-commands annotation
32330 @findex commands annotation
32331 @findex post-commands annotation
32333 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32334 command. The annotations are repeated for each command which is input.
32336 @findex pre-overload-choice annotation
32337 @findex overload-choice annotation
32338 @findex post-overload-choice annotation
32339 @item overload-choice
32340 When @value{GDBN} wants the user to select between various overloaded functions.
32342 @findex pre-query annotation
32343 @findex query annotation
32344 @findex post-query annotation
32346 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32348 @findex pre-prompt-for-continue annotation
32349 @findex prompt-for-continue annotation
32350 @findex post-prompt-for-continue annotation
32351 @item prompt-for-continue
32352 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32353 expect this to work well; instead use @code{set height 0} to disable
32354 prompting. This is because the counting of lines is buggy in the
32355 presence of annotations.
32360 @cindex annotations for errors, warnings and interrupts
32362 @findex quit annotation
32367 This annotation occurs right before @value{GDBN} responds to an interrupt.
32369 @findex error annotation
32374 This annotation occurs right before @value{GDBN} responds to an error.
32376 Quit and error annotations indicate that any annotations which @value{GDBN} was
32377 in the middle of may end abruptly. For example, if a
32378 @code{value-history-begin} annotation is followed by a @code{error}, one
32379 cannot expect to receive the matching @code{value-history-end}. One
32380 cannot expect not to receive it either, however; an error annotation
32381 does not necessarily mean that @value{GDBN} is immediately returning all the way
32384 @findex error-begin annotation
32385 A quit or error annotation may be preceded by
32391 Any output between that and the quit or error annotation is the error
32394 Warning messages are not yet annotated.
32395 @c If we want to change that, need to fix warning(), type_error(),
32396 @c range_error(), and possibly other places.
32399 @section Invalidation Notices
32401 @cindex annotations for invalidation messages
32402 The following annotations say that certain pieces of state may have
32406 @findex frames-invalid annotation
32407 @item ^Z^Zframes-invalid
32409 The frames (for example, output from the @code{backtrace} command) may
32412 @findex breakpoints-invalid annotation
32413 @item ^Z^Zbreakpoints-invalid
32415 The breakpoints may have changed. For example, the user just added or
32416 deleted a breakpoint.
32419 @node Annotations for Running
32420 @section Running the Program
32421 @cindex annotations for running programs
32423 @findex starting annotation
32424 @findex stopping annotation
32425 When the program starts executing due to a @value{GDBN} command such as
32426 @code{step} or @code{continue},
32432 is output. When the program stops,
32438 is output. Before the @code{stopped} annotation, a variety of
32439 annotations describe how the program stopped.
32442 @findex exited annotation
32443 @item ^Z^Zexited @var{exit-status}
32444 The program exited, and @var{exit-status} is the exit status (zero for
32445 successful exit, otherwise nonzero).
32447 @findex signalled annotation
32448 @findex signal-name annotation
32449 @findex signal-name-end annotation
32450 @findex signal-string annotation
32451 @findex signal-string-end annotation
32452 @item ^Z^Zsignalled
32453 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32454 annotation continues:
32460 ^Z^Zsignal-name-end
32464 ^Z^Zsignal-string-end
32469 where @var{name} is the name of the signal, such as @code{SIGILL} or
32470 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32471 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32472 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32473 user's benefit and have no particular format.
32475 @findex signal annotation
32477 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32478 just saying that the program received the signal, not that it was
32479 terminated with it.
32481 @findex breakpoint annotation
32482 @item ^Z^Zbreakpoint @var{number}
32483 The program hit breakpoint number @var{number}.
32485 @findex watchpoint annotation
32486 @item ^Z^Zwatchpoint @var{number}
32487 The program hit watchpoint number @var{number}.
32490 @node Source Annotations
32491 @section Displaying Source
32492 @cindex annotations for source display
32494 @findex source annotation
32495 The following annotation is used instead of displaying source code:
32498 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32501 where @var{filename} is an absolute file name indicating which source
32502 file, @var{line} is the line number within that file (where 1 is the
32503 first line in the file), @var{character} is the character position
32504 within the file (where 0 is the first character in the file) (for most
32505 debug formats this will necessarily point to the beginning of a line),
32506 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32507 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32508 @var{addr} is the address in the target program associated with the
32509 source which is being displayed. The @var{addr} is in the form @samp{0x}
32510 followed by one or more lowercase hex digits (note that this does not
32511 depend on the language).
32513 @node JIT Interface
32514 @chapter JIT Compilation Interface
32515 @cindex just-in-time compilation
32516 @cindex JIT compilation interface
32518 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32519 interface. A JIT compiler is a program or library that generates native
32520 executable code at runtime and executes it, usually in order to achieve good
32521 performance while maintaining platform independence.
32523 Programs that use JIT compilation are normally difficult to debug because
32524 portions of their code are generated at runtime, instead of being loaded from
32525 object files, which is where @value{GDBN} normally finds the program's symbols
32526 and debug information. In order to debug programs that use JIT compilation,
32527 @value{GDBN} has an interface that allows the program to register in-memory
32528 symbol files with @value{GDBN} at runtime.
32530 If you are using @value{GDBN} to debug a program that uses this interface, then
32531 it should work transparently so long as you have not stripped the binary. If
32532 you are developing a JIT compiler, then the interface is documented in the rest
32533 of this chapter. At this time, the only known client of this interface is the
32536 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32537 JIT compiler communicates with @value{GDBN} by writing data into a global
32538 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32539 attaches, it reads a linked list of symbol files from the global variable to
32540 find existing code, and puts a breakpoint in the function so that it can find
32541 out about additional code.
32544 * Declarations:: Relevant C struct declarations
32545 * Registering Code:: Steps to register code
32546 * Unregistering Code:: Steps to unregister code
32547 * Custom Debug Info:: Emit debug information in a custom format
32551 @section JIT Declarations
32553 These are the relevant struct declarations that a C program should include to
32554 implement the interface:
32564 struct jit_code_entry
32566 struct jit_code_entry *next_entry;
32567 struct jit_code_entry *prev_entry;
32568 const char *symfile_addr;
32569 uint64_t symfile_size;
32572 struct jit_descriptor
32575 /* This type should be jit_actions_t, but we use uint32_t
32576 to be explicit about the bitwidth. */
32577 uint32_t action_flag;
32578 struct jit_code_entry *relevant_entry;
32579 struct jit_code_entry *first_entry;
32582 /* GDB puts a breakpoint in this function. */
32583 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32585 /* Make sure to specify the version statically, because the
32586 debugger may check the version before we can set it. */
32587 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32590 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32591 modifications to this global data properly, which can easily be done by putting
32592 a global mutex around modifications to these structures.
32594 @node Registering Code
32595 @section Registering Code
32597 To register code with @value{GDBN}, the JIT should follow this protocol:
32601 Generate an object file in memory with symbols and other desired debug
32602 information. The file must include the virtual addresses of the sections.
32605 Create a code entry for the file, which gives the start and size of the symbol
32609 Add it to the linked list in the JIT descriptor.
32612 Point the relevant_entry field of the descriptor at the entry.
32615 Set @code{action_flag} to @code{JIT_REGISTER} and call
32616 @code{__jit_debug_register_code}.
32619 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32620 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32621 new code. However, the linked list must still be maintained in order to allow
32622 @value{GDBN} to attach to a running process and still find the symbol files.
32624 @node Unregistering Code
32625 @section Unregistering Code
32627 If code is freed, then the JIT should use the following protocol:
32631 Remove the code entry corresponding to the code from the linked list.
32634 Point the @code{relevant_entry} field of the descriptor at the code entry.
32637 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32638 @code{__jit_debug_register_code}.
32641 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32642 and the JIT will leak the memory used for the associated symbol files.
32644 @node Custom Debug Info
32645 @section Custom Debug Info
32646 @cindex custom JIT debug info
32647 @cindex JIT debug info reader
32649 Generating debug information in platform-native file formats (like ELF
32650 or COFF) may be an overkill for JIT compilers; especially if all the
32651 debug info is used for is displaying a meaningful backtrace. The
32652 issue can be resolved by having the JIT writers decide on a debug info
32653 format and also provide a reader that parses the debug info generated
32654 by the JIT compiler. This section gives a brief overview on writing
32655 such a parser. More specific details can be found in the source file
32656 @file{gdb/jit-reader.in}, which is also installed as a header at
32657 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32659 The reader is implemented as a shared object (so this functionality is
32660 not available on platforms which don't allow loading shared objects at
32661 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32662 @code{jit-reader-unload} are provided, to be used to load and unload
32663 the readers from a preconfigured directory. Once loaded, the shared
32664 object is used the parse the debug information emitted by the JIT
32668 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32669 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32672 @node Using JIT Debug Info Readers
32673 @subsection Using JIT Debug Info Readers
32674 @kindex jit-reader-load
32675 @kindex jit-reader-unload
32677 Readers can be loaded and unloaded using the @code{jit-reader-load}
32678 and @code{jit-reader-unload} commands.
32681 @item jit-reader-load @var{reader}
32682 Load the JIT reader named @var{reader}, which is a shared
32683 object specified as either an absolute or a relative file name. In
32684 the latter case, @value{GDBN} will try to load the reader from a
32685 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32686 system (here @var{libdir} is the system library directory, often
32687 @file{/usr/local/lib}).
32689 Only one reader can be active at a time; trying to load a second
32690 reader when one is already loaded will result in @value{GDBN}
32691 reporting an error. A new JIT reader can be loaded by first unloading
32692 the current one using @code{jit-reader-unload} and then invoking
32693 @code{jit-reader-load}.
32695 @item jit-reader-unload
32696 Unload the currently loaded JIT reader.
32700 @node Writing JIT Debug Info Readers
32701 @subsection Writing JIT Debug Info Readers
32702 @cindex writing JIT debug info readers
32704 As mentioned, a reader is essentially a shared object conforming to a
32705 certain ABI. This ABI is described in @file{jit-reader.h}.
32707 @file{jit-reader.h} defines the structures, macros and functions
32708 required to write a reader. It is installed (along with
32709 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32710 the system include directory.
32712 Readers need to be released under a GPL compatible license. A reader
32713 can be declared as released under such a license by placing the macro
32714 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32716 The entry point for readers is the symbol @code{gdb_init_reader},
32717 which is expected to be a function with the prototype
32719 @findex gdb_init_reader
32721 extern struct gdb_reader_funcs *gdb_init_reader (void);
32724 @cindex @code{struct gdb_reader_funcs}
32726 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32727 functions. These functions are executed to read the debug info
32728 generated by the JIT compiler (@code{read}), to unwind stack frames
32729 (@code{unwind}) and to create canonical frame IDs
32730 (@code{get_Frame_id}). It also has a callback that is called when the
32731 reader is being unloaded (@code{destroy}). The struct looks like this
32734 struct gdb_reader_funcs
32736 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32737 int reader_version;
32739 /* For use by the reader. */
32742 gdb_read_debug_info *read;
32743 gdb_unwind_frame *unwind;
32744 gdb_get_frame_id *get_frame_id;
32745 gdb_destroy_reader *destroy;
32749 @cindex @code{struct gdb_symbol_callbacks}
32750 @cindex @code{struct gdb_unwind_callbacks}
32752 The callbacks are provided with another set of callbacks by
32753 @value{GDBN} to do their job. For @code{read}, these callbacks are
32754 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32755 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32756 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32757 files and new symbol tables inside those object files. @code{struct
32758 gdb_unwind_callbacks} has callbacks to read registers off the current
32759 frame and to write out the values of the registers in the previous
32760 frame. Both have a callback (@code{target_read}) to read bytes off the
32761 target's address space.
32763 @node In-Process Agent
32764 @chapter In-Process Agent
32765 @cindex debugging agent
32766 The traditional debugging model is conceptually low-speed, but works fine,
32767 because most bugs can be reproduced in debugging-mode execution. However,
32768 as multi-core or many-core processors are becoming mainstream, and
32769 multi-threaded programs become more and more popular, there should be more
32770 and more bugs that only manifest themselves at normal-mode execution, for
32771 example, thread races, because debugger's interference with the program's
32772 timing may conceal the bugs. On the other hand, in some applications,
32773 it is not feasible for the debugger to interrupt the program's execution
32774 long enough for the developer to learn anything helpful about its behavior.
32775 If the program's correctness depends on its real-time behavior, delays
32776 introduced by a debugger might cause the program to fail, even when the
32777 code itself is correct. It is useful to be able to observe the program's
32778 behavior without interrupting it.
32780 Therefore, traditional debugging model is too intrusive to reproduce
32781 some bugs. In order to reduce the interference with the program, we can
32782 reduce the number of operations performed by debugger. The
32783 @dfn{In-Process Agent}, a shared library, is running within the same
32784 process with inferior, and is able to perform some debugging operations
32785 itself. As a result, debugger is only involved when necessary, and
32786 performance of debugging can be improved accordingly. Note that
32787 interference with program can be reduced but can't be removed completely,
32788 because the in-process agent will still stop or slow down the program.
32790 The in-process agent can interpret and execute Agent Expressions
32791 (@pxref{Agent Expressions}) during performing debugging operations. The
32792 agent expressions can be used for different purposes, such as collecting
32793 data in tracepoints, and condition evaluation in breakpoints.
32795 @anchor{Control Agent}
32796 You can control whether the in-process agent is used as an aid for
32797 debugging with the following commands:
32800 @kindex set agent on
32802 Causes the in-process agent to perform some operations on behalf of the
32803 debugger. Just which operations requested by the user will be done
32804 by the in-process agent depends on the its capabilities. For example,
32805 if you request to evaluate breakpoint conditions in the in-process agent,
32806 and the in-process agent has such capability as well, then breakpoint
32807 conditions will be evaluated in the in-process agent.
32809 @kindex set agent off
32810 @item set agent off
32811 Disables execution of debugging operations by the in-process agent. All
32812 of the operations will be performed by @value{GDBN}.
32816 Display the current setting of execution of debugging operations by
32817 the in-process agent.
32821 * In-Process Agent Protocol::
32824 @node In-Process Agent Protocol
32825 @section In-Process Agent Protocol
32826 @cindex in-process agent protocol
32828 The in-process agent is able to communicate with both @value{GDBN} and
32829 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32830 used for communications between @value{GDBN} or GDBserver and the IPA.
32831 In general, @value{GDBN} or GDBserver sends commands
32832 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32833 in-process agent replies back with the return result of the command, or
32834 some other information. The data sent to in-process agent is composed
32835 of primitive data types, such as 4-byte or 8-byte type, and composite
32836 types, which are called objects (@pxref{IPA Protocol Objects}).
32839 * IPA Protocol Objects::
32840 * IPA Protocol Commands::
32843 @node IPA Protocol Objects
32844 @subsection IPA Protocol Objects
32845 @cindex ipa protocol objects
32847 The commands sent to and results received from agent may contain some
32848 complex data types called @dfn{objects}.
32850 The in-process agent is running on the same machine with @value{GDBN}
32851 or GDBserver, so it doesn't have to handle as much differences between
32852 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32853 However, there are still some differences of two ends in two processes:
32857 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32858 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32860 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32861 GDBserver is compiled with one, and in-process agent is compiled with
32865 Here are the IPA Protocol Objects:
32869 agent expression object. It represents an agent expression
32870 (@pxref{Agent Expressions}).
32871 @anchor{agent expression object}
32873 tracepoint action object. It represents a tracepoint action
32874 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32875 memory, static trace data and to evaluate expression.
32876 @anchor{tracepoint action object}
32878 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32879 @anchor{tracepoint object}
32883 The following table describes important attributes of each IPA protocol
32886 @multitable @columnfractions .30 .20 .50
32887 @headitem Name @tab Size @tab Description
32888 @item @emph{agent expression object} @tab @tab
32889 @item length @tab 4 @tab length of bytes code
32890 @item byte code @tab @var{length} @tab contents of byte code
32891 @item @emph{tracepoint action for collecting memory} @tab @tab
32892 @item 'M' @tab 1 @tab type of tracepoint action
32893 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32894 address of the lowest byte to collect, otherwise @var{addr} is the offset
32895 of @var{basereg} for memory collecting.
32896 @item len @tab 8 @tab length of memory for collecting
32897 @item basereg @tab 4 @tab the register number containing the starting
32898 memory address for collecting.
32899 @item @emph{tracepoint action for collecting registers} @tab @tab
32900 @item 'R' @tab 1 @tab type of tracepoint action
32901 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32902 @item 'L' @tab 1 @tab type of tracepoint action
32903 @item @emph{tracepoint action for expression evaluation} @tab @tab
32904 @item 'X' @tab 1 @tab type of tracepoint action
32905 @item agent expression @tab length of @tab @ref{agent expression object}
32906 @item @emph{tracepoint object} @tab @tab
32907 @item number @tab 4 @tab number of tracepoint
32908 @item address @tab 8 @tab address of tracepoint inserted on
32909 @item type @tab 4 @tab type of tracepoint
32910 @item enabled @tab 1 @tab enable or disable of tracepoint
32911 @item step_count @tab 8 @tab step
32912 @item pass_count @tab 8 @tab pass
32913 @item numactions @tab 4 @tab number of tracepoint actions
32914 @item hit count @tab 8 @tab hit count
32915 @item trace frame usage @tab 8 @tab trace frame usage
32916 @item compiled_cond @tab 8 @tab compiled condition
32917 @item orig_size @tab 8 @tab orig size
32918 @item condition @tab 4 if condition is NULL otherwise length of
32919 @ref{agent expression object}
32920 @tab zero if condition is NULL, otherwise is
32921 @ref{agent expression object}
32922 @item actions @tab variable
32923 @tab numactions number of @ref{tracepoint action object}
32926 @node IPA Protocol Commands
32927 @subsection IPA Protocol Commands
32928 @cindex ipa protocol commands
32930 The spaces in each command are delimiters to ease reading this commands
32931 specification. They don't exist in real commands.
32935 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32936 Installs a new fast tracepoint described by @var{tracepoint_object}
32937 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32938 head of @dfn{jumppad}, which is used to jump to data collection routine
32943 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32944 @var{target_address} is address of tracepoint in the inferior.
32945 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32946 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32947 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32948 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32955 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32956 is about to kill inferiors.
32964 @item probe_marker_at:@var{address}
32965 Asks in-process agent to probe the marker at @var{address}.
32972 @item unprobe_marker_at:@var{address}
32973 Asks in-process agent to unprobe the marker at @var{address}.
32977 @chapter Reporting Bugs in @value{GDBN}
32978 @cindex bugs in @value{GDBN}
32979 @cindex reporting bugs in @value{GDBN}
32981 Your bug reports play an essential role in making @value{GDBN} reliable.
32983 Reporting a bug may help you by bringing a solution to your problem, or it
32984 may not. But in any case the principal function of a bug report is to help
32985 the entire community by making the next version of @value{GDBN} work better. Bug
32986 reports are your contribution to the maintenance of @value{GDBN}.
32988 In order for a bug report to serve its purpose, you must include the
32989 information that enables us to fix the bug.
32992 * Bug Criteria:: Have you found a bug?
32993 * Bug Reporting:: How to report bugs
32997 @section Have You Found a Bug?
32998 @cindex bug criteria
33000 If you are not sure whether you have found a bug, here are some guidelines:
33003 @cindex fatal signal
33004 @cindex debugger crash
33005 @cindex crash of debugger
33007 If the debugger gets a fatal signal, for any input whatever, that is a
33008 @value{GDBN} bug. Reliable debuggers never crash.
33010 @cindex error on valid input
33012 If @value{GDBN} produces an error message for valid input, that is a
33013 bug. (Note that if you're cross debugging, the problem may also be
33014 somewhere in the connection to the target.)
33016 @cindex invalid input
33018 If @value{GDBN} does not produce an error message for invalid input,
33019 that is a bug. However, you should note that your idea of
33020 ``invalid input'' might be our idea of ``an extension'' or ``support
33021 for traditional practice''.
33024 If you are an experienced user of debugging tools, your suggestions
33025 for improvement of @value{GDBN} are welcome in any case.
33028 @node Bug Reporting
33029 @section How to Report Bugs
33030 @cindex bug reports
33031 @cindex @value{GDBN} bugs, reporting
33033 A number of companies and individuals offer support for @sc{gnu} products.
33034 If you obtained @value{GDBN} from a support organization, we recommend you
33035 contact that organization first.
33037 You can find contact information for many support companies and
33038 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33040 @c should add a web page ref...
33043 @ifset BUGURL_DEFAULT
33044 In any event, we also recommend that you submit bug reports for
33045 @value{GDBN}. The preferred method is to submit them directly using
33046 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33047 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33050 @strong{Do not send bug reports to @samp{info-gdb}, or to
33051 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33052 not want to receive bug reports. Those that do have arranged to receive
33055 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33056 serves as a repeater. The mailing list and the newsgroup carry exactly
33057 the same messages. Often people think of posting bug reports to the
33058 newsgroup instead of mailing them. This appears to work, but it has one
33059 problem which can be crucial: a newsgroup posting often lacks a mail
33060 path back to the sender. Thus, if we need to ask for more information,
33061 we may be unable to reach you. For this reason, it is better to send
33062 bug reports to the mailing list.
33064 @ifclear BUGURL_DEFAULT
33065 In any event, we also recommend that you submit bug reports for
33066 @value{GDBN} to @value{BUGURL}.
33070 The fundamental principle of reporting bugs usefully is this:
33071 @strong{report all the facts}. If you are not sure whether to state a
33072 fact or leave it out, state it!
33074 Often people omit facts because they think they know what causes the
33075 problem and assume that some details do not matter. Thus, you might
33076 assume that the name of the variable you use in an example does not matter.
33077 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33078 stray memory reference which happens to fetch from the location where that
33079 name is stored in memory; perhaps, if the name were different, the contents
33080 of that location would fool the debugger into doing the right thing despite
33081 the bug. Play it safe and give a specific, complete example. That is the
33082 easiest thing for you to do, and the most helpful.
33084 Keep in mind that the purpose of a bug report is to enable us to fix the
33085 bug. It may be that the bug has been reported previously, but neither
33086 you nor we can know that unless your bug report is complete and
33089 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33090 bell?'' Those bug reports are useless, and we urge everyone to
33091 @emph{refuse to respond to them} except to chide the sender to report
33094 To enable us to fix the bug, you should include all these things:
33098 The version of @value{GDBN}. @value{GDBN} announces it if you start
33099 with no arguments; you can also print it at any time using @code{show
33102 Without this, we will not know whether there is any point in looking for
33103 the bug in the current version of @value{GDBN}.
33106 The type of machine you are using, and the operating system name and
33110 The details of the @value{GDBN} build-time configuration.
33111 @value{GDBN} shows these details if you invoke it with the
33112 @option{--configuration} command-line option, or if you type
33113 @code{show configuration} at @value{GDBN}'s prompt.
33116 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33117 ``@value{GCC}--2.8.1''.
33120 What compiler (and its version) was used to compile the program you are
33121 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33122 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33123 to get this information; for other compilers, see the documentation for
33127 The command arguments you gave the compiler to compile your example and
33128 observe the bug. For example, did you use @samp{-O}? To guarantee
33129 you will not omit something important, list them all. A copy of the
33130 Makefile (or the output from make) is sufficient.
33132 If we were to try to guess the arguments, we would probably guess wrong
33133 and then we might not encounter the bug.
33136 A complete input script, and all necessary source files, that will
33140 A description of what behavior you observe that you believe is
33141 incorrect. For example, ``It gets a fatal signal.''
33143 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33144 will certainly notice it. But if the bug is incorrect output, we might
33145 not notice unless it is glaringly wrong. You might as well not give us
33146 a chance to make a mistake.
33148 Even if the problem you experience is a fatal signal, you should still
33149 say so explicitly. Suppose something strange is going on, such as, your
33150 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33151 the C library on your system. (This has happened!) Your copy might
33152 crash and ours would not. If you told us to expect a crash, then when
33153 ours fails to crash, we would know that the bug was not happening for
33154 us. If you had not told us to expect a crash, then we would not be able
33155 to draw any conclusion from our observations.
33158 @cindex recording a session script
33159 To collect all this information, you can use a session recording program
33160 such as @command{script}, which is available on many Unix systems.
33161 Just run your @value{GDBN} session inside @command{script} and then
33162 include the @file{typescript} file with your bug report.
33164 Another way to record a @value{GDBN} session is to run @value{GDBN}
33165 inside Emacs and then save the entire buffer to a file.
33168 If you wish to suggest changes to the @value{GDBN} source, send us context
33169 diffs. If you even discuss something in the @value{GDBN} source, refer to
33170 it by context, not by line number.
33172 The line numbers in our development sources will not match those in your
33173 sources. Your line numbers would convey no useful information to us.
33177 Here are some things that are not necessary:
33181 A description of the envelope of the bug.
33183 Often people who encounter a bug spend a lot of time investigating
33184 which changes to the input file will make the bug go away and which
33185 changes will not affect it.
33187 This is often time consuming and not very useful, because the way we
33188 will find the bug is by running a single example under the debugger
33189 with breakpoints, not by pure deduction from a series of examples.
33190 We recommend that you save your time for something else.
33192 Of course, if you can find a simpler example to report @emph{instead}
33193 of the original one, that is a convenience for us. Errors in the
33194 output will be easier to spot, running under the debugger will take
33195 less time, and so on.
33197 However, simplification is not vital; if you do not want to do this,
33198 report the bug anyway and send us the entire test case you used.
33201 A patch for the bug.
33203 A patch for the bug does help us if it is a good one. But do not omit
33204 the necessary information, such as the test case, on the assumption that
33205 a patch is all we need. We might see problems with your patch and decide
33206 to fix the problem another way, or we might not understand it at all.
33208 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33209 construct an example that will make the program follow a certain path
33210 through the code. If you do not send us the example, we will not be able
33211 to construct one, so we will not be able to verify that the bug is fixed.
33213 And if we cannot understand what bug you are trying to fix, or why your
33214 patch should be an improvement, we will not install it. A test case will
33215 help us to understand.
33218 A guess about what the bug is or what it depends on.
33220 Such guesses are usually wrong. Even we cannot guess right about such
33221 things without first using the debugger to find the facts.
33224 @c The readline documentation is distributed with the readline code
33225 @c and consists of the two following files:
33228 @c Use -I with makeinfo to point to the appropriate directory,
33229 @c environment var TEXINPUTS with TeX.
33230 @ifclear SYSTEM_READLINE
33231 @include rluser.texi
33232 @include hsuser.texi
33236 @appendix In Memoriam
33238 The @value{GDBN} project mourns the loss of the following long-time
33243 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33244 to Free Software in general. Outside of @value{GDBN}, he was known in
33245 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33247 @item Michael Snyder
33248 Michael was one of the Global Maintainers of the @value{GDBN} project,
33249 with contributions recorded as early as 1996, until 2011. In addition
33250 to his day to day participation, he was a large driving force behind
33251 adding Reverse Debugging to @value{GDBN}.
33254 Beyond their technical contributions to the project, they were also
33255 enjoyable members of the Free Software Community. We will miss them.
33257 @node Formatting Documentation
33258 @appendix Formatting Documentation
33260 @cindex @value{GDBN} reference card
33261 @cindex reference card
33262 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33263 for printing with PostScript or Ghostscript, in the @file{gdb}
33264 subdirectory of the main source directory@footnote{In
33265 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33266 release.}. If you can use PostScript or Ghostscript with your printer,
33267 you can print the reference card immediately with @file{refcard.ps}.
33269 The release also includes the source for the reference card. You
33270 can format it, using @TeX{}, by typing:
33276 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33277 mode on US ``letter'' size paper;
33278 that is, on a sheet 11 inches wide by 8.5 inches
33279 high. You will need to specify this form of printing as an option to
33280 your @sc{dvi} output program.
33282 @cindex documentation
33284 All the documentation for @value{GDBN} comes as part of the machine-readable
33285 distribution. The documentation is written in Texinfo format, which is
33286 a documentation system that uses a single source file to produce both
33287 on-line information and a printed manual. You can use one of the Info
33288 formatting commands to create the on-line version of the documentation
33289 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33291 @value{GDBN} includes an already formatted copy of the on-line Info
33292 version of this manual in the @file{gdb} subdirectory. The main Info
33293 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33294 subordinate files matching @samp{gdb.info*} in the same directory. If
33295 necessary, you can print out these files, or read them with any editor;
33296 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33297 Emacs or the standalone @code{info} program, available as part of the
33298 @sc{gnu} Texinfo distribution.
33300 If you want to format these Info files yourself, you need one of the
33301 Info formatting programs, such as @code{texinfo-format-buffer} or
33304 If you have @code{makeinfo} installed, and are in the top level
33305 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33306 version @value{GDBVN}), you can make the Info file by typing:
33313 If you want to typeset and print copies of this manual, you need @TeX{},
33314 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33315 Texinfo definitions file.
33317 @TeX{} is a typesetting program; it does not print files directly, but
33318 produces output files called @sc{dvi} files. To print a typeset
33319 document, you need a program to print @sc{dvi} files. If your system
33320 has @TeX{} installed, chances are it has such a program. The precise
33321 command to use depends on your system; @kbd{lpr -d} is common; another
33322 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33323 require a file name without any extension or a @samp{.dvi} extension.
33325 @TeX{} also requires a macro definitions file called
33326 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33327 written in Texinfo format. On its own, @TeX{} cannot either read or
33328 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33329 and is located in the @file{gdb-@var{version-number}/texinfo}
33332 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33333 typeset and print this manual. First switch to the @file{gdb}
33334 subdirectory of the main source directory (for example, to
33335 @file{gdb-@value{GDBVN}/gdb}) and type:
33341 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33343 @node Installing GDB
33344 @appendix Installing @value{GDBN}
33345 @cindex installation
33348 * Requirements:: Requirements for building @value{GDBN}
33349 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33350 * Separate Objdir:: Compiling @value{GDBN} in another directory
33351 * Config Names:: Specifying names for hosts and targets
33352 * Configure Options:: Summary of options for configure
33353 * System-wide configuration:: Having a system-wide init file
33357 @section Requirements for Building @value{GDBN}
33358 @cindex building @value{GDBN}, requirements for
33360 Building @value{GDBN} requires various tools and packages to be available.
33361 Other packages will be used only if they are found.
33363 @heading Tools/Packages Necessary for Building @value{GDBN}
33365 @item ISO C90 compiler
33366 @value{GDBN} is written in ISO C90. It should be buildable with any
33367 working C90 compiler, e.g.@: GCC.
33371 @heading Tools/Packages Optional for Building @value{GDBN}
33375 @value{GDBN} can use the Expat XML parsing library. This library may be
33376 included with your operating system distribution; if it is not, you
33377 can get the latest version from @url{http://expat.sourceforge.net}.
33378 The @file{configure} script will search for this library in several
33379 standard locations; if it is installed in an unusual path, you can
33380 use the @option{--with-libexpat-prefix} option to specify its location.
33386 Remote protocol memory maps (@pxref{Memory Map Format})
33388 Target descriptions (@pxref{Target Descriptions})
33390 Remote shared library lists (@xref{Library List Format},
33391 or alternatively @pxref{Library List Format for SVR4 Targets})
33393 MS-Windows shared libraries (@pxref{Shared Libraries})
33395 Traceframe info (@pxref{Traceframe Info Format})
33397 Branch trace (@pxref{Branch Trace Format},
33398 @pxref{Branch Trace Configuration Format})
33402 @cindex compressed debug sections
33403 @value{GDBN} will use the @samp{zlib} library, if available, to read
33404 compressed debug sections. Some linkers, such as GNU gold, are capable
33405 of producing binaries with compressed debug sections. If @value{GDBN}
33406 is compiled with @samp{zlib}, it will be able to read the debug
33407 information in such binaries.
33409 The @samp{zlib} library is likely included with your operating system
33410 distribution; if it is not, you can get the latest version from
33411 @url{http://zlib.net}.
33414 @value{GDBN}'s features related to character sets (@pxref{Character
33415 Sets}) require a functioning @code{iconv} implementation. If you are
33416 on a GNU system, then this is provided by the GNU C Library. Some
33417 other systems also provide a working @code{iconv}.
33419 If @value{GDBN} is using the @code{iconv} program which is installed
33420 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33421 This is done with @option{--with-iconv-bin} which specifies the
33422 directory that contains the @code{iconv} program.
33424 On systems without @code{iconv}, you can install GNU Libiconv. If you
33425 have previously installed Libiconv, you can use the
33426 @option{--with-libiconv-prefix} option to configure.
33428 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33429 arrange to build Libiconv if a directory named @file{libiconv} appears
33430 in the top-most source directory. If Libiconv is built this way, and
33431 if the operating system does not provide a suitable @code{iconv}
33432 implementation, then the just-built library will automatically be used
33433 by @value{GDBN}. One easy way to set this up is to download GNU
33434 Libiconv, unpack it, and then rename the directory holding the
33435 Libiconv source code to @samp{libiconv}.
33438 @node Running Configure
33439 @section Invoking the @value{GDBN} @file{configure} Script
33440 @cindex configuring @value{GDBN}
33441 @value{GDBN} comes with a @file{configure} script that automates the process
33442 of preparing @value{GDBN} for installation; you can then use @code{make} to
33443 build the @code{gdb} program.
33445 @c irrelevant in info file; it's as current as the code it lives with.
33446 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33447 look at the @file{README} file in the sources; we may have improved the
33448 installation procedures since publishing this manual.}
33451 The @value{GDBN} distribution includes all the source code you need for
33452 @value{GDBN} in a single directory, whose name is usually composed by
33453 appending the version number to @samp{gdb}.
33455 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33456 @file{gdb-@value{GDBVN}} directory. That directory contains:
33459 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33460 script for configuring @value{GDBN} and all its supporting libraries
33462 @item gdb-@value{GDBVN}/gdb
33463 the source specific to @value{GDBN} itself
33465 @item gdb-@value{GDBVN}/bfd
33466 source for the Binary File Descriptor library
33468 @item gdb-@value{GDBVN}/include
33469 @sc{gnu} include files
33471 @item gdb-@value{GDBVN}/libiberty
33472 source for the @samp{-liberty} free software library
33474 @item gdb-@value{GDBVN}/opcodes
33475 source for the library of opcode tables and disassemblers
33477 @item gdb-@value{GDBVN}/readline
33478 source for the @sc{gnu} command-line interface
33480 @item gdb-@value{GDBVN}/glob
33481 source for the @sc{gnu} filename pattern-matching subroutine
33483 @item gdb-@value{GDBVN}/mmalloc
33484 source for the @sc{gnu} memory-mapped malloc package
33487 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33488 from the @file{gdb-@var{version-number}} source directory, which in
33489 this example is the @file{gdb-@value{GDBVN}} directory.
33491 First switch to the @file{gdb-@var{version-number}} source directory
33492 if you are not already in it; then run @file{configure}. Pass the
33493 identifier for the platform on which @value{GDBN} will run as an
33499 cd gdb-@value{GDBVN}
33500 ./configure @var{host}
33505 where @var{host} is an identifier such as @samp{sun4} or
33506 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33507 (You can often leave off @var{host}; @file{configure} tries to guess the
33508 correct value by examining your system.)
33510 Running @samp{configure @var{host}} and then running @code{make} builds the
33511 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33512 libraries, then @code{gdb} itself. The configured source files, and the
33513 binaries, are left in the corresponding source directories.
33516 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33517 system does not recognize this automatically when you run a different
33518 shell, you may need to run @code{sh} on it explicitly:
33521 sh configure @var{host}
33524 If you run @file{configure} from a directory that contains source
33525 directories for multiple libraries or programs, such as the
33526 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33528 creates configuration files for every directory level underneath (unless
33529 you tell it not to, with the @samp{--norecursion} option).
33531 You should run the @file{configure} script from the top directory in the
33532 source tree, the @file{gdb-@var{version-number}} directory. If you run
33533 @file{configure} from one of the subdirectories, you will configure only
33534 that subdirectory. That is usually not what you want. In particular,
33535 if you run the first @file{configure} from the @file{gdb} subdirectory
33536 of the @file{gdb-@var{version-number}} directory, you will omit the
33537 configuration of @file{bfd}, @file{readline}, and other sibling
33538 directories of the @file{gdb} subdirectory. This leads to build errors
33539 about missing include files such as @file{bfd/bfd.h}.
33541 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33542 However, you should make sure that the shell on your path (named by
33543 the @samp{SHELL} environment variable) is publicly readable. Remember
33544 that @value{GDBN} uses the shell to start your program---some systems refuse to
33545 let @value{GDBN} debug child processes whose programs are not readable.
33547 @node Separate Objdir
33548 @section Compiling @value{GDBN} in Another Directory
33550 If you want to run @value{GDBN} versions for several host or target machines,
33551 you need a different @code{gdb} compiled for each combination of
33552 host and target. @file{configure} is designed to make this easy by
33553 allowing you to generate each configuration in a separate subdirectory,
33554 rather than in the source directory. If your @code{make} program
33555 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33556 @code{make} in each of these directories builds the @code{gdb}
33557 program specified there.
33559 To build @code{gdb} in a separate directory, run @file{configure}
33560 with the @samp{--srcdir} option to specify where to find the source.
33561 (You also need to specify a path to find @file{configure}
33562 itself from your working directory. If the path to @file{configure}
33563 would be the same as the argument to @samp{--srcdir}, you can leave out
33564 the @samp{--srcdir} option; it is assumed.)
33566 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33567 separate directory for a Sun 4 like this:
33571 cd gdb-@value{GDBVN}
33574 ../gdb-@value{GDBVN}/configure sun4
33579 When @file{configure} builds a configuration using a remote source
33580 directory, it creates a tree for the binaries with the same structure
33581 (and using the same names) as the tree under the source directory. In
33582 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33583 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33584 @file{gdb-sun4/gdb}.
33586 Make sure that your path to the @file{configure} script has just one
33587 instance of @file{gdb} in it. If your path to @file{configure} looks
33588 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33589 one subdirectory of @value{GDBN}, not the whole package. This leads to
33590 build errors about missing include files such as @file{bfd/bfd.h}.
33592 One popular reason to build several @value{GDBN} configurations in separate
33593 directories is to configure @value{GDBN} for cross-compiling (where
33594 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33595 programs that run on another machine---the @dfn{target}).
33596 You specify a cross-debugging target by
33597 giving the @samp{--target=@var{target}} option to @file{configure}.
33599 When you run @code{make} to build a program or library, you must run
33600 it in a configured directory---whatever directory you were in when you
33601 called @file{configure} (or one of its subdirectories).
33603 The @code{Makefile} that @file{configure} generates in each source
33604 directory also runs recursively. If you type @code{make} in a source
33605 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33606 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33607 will build all the required libraries, and then build GDB.
33609 When you have multiple hosts or targets configured in separate
33610 directories, you can run @code{make} on them in parallel (for example,
33611 if they are NFS-mounted on each of the hosts); they will not interfere
33615 @section Specifying Names for Hosts and Targets
33617 The specifications used for hosts and targets in the @file{configure}
33618 script are based on a three-part naming scheme, but some short predefined
33619 aliases are also supported. The full naming scheme encodes three pieces
33620 of information in the following pattern:
33623 @var{architecture}-@var{vendor}-@var{os}
33626 For example, you can use the alias @code{sun4} as a @var{host} argument,
33627 or as the value for @var{target} in a @code{--target=@var{target}}
33628 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33630 The @file{configure} script accompanying @value{GDBN} does not provide
33631 any query facility to list all supported host and target names or
33632 aliases. @file{configure} calls the Bourne shell script
33633 @code{config.sub} to map abbreviations to full names; you can read the
33634 script, if you wish, or you can use it to test your guesses on
33635 abbreviations---for example:
33638 % sh config.sub i386-linux
33640 % sh config.sub alpha-linux
33641 alpha-unknown-linux-gnu
33642 % sh config.sub hp9k700
33644 % sh config.sub sun4
33645 sparc-sun-sunos4.1.1
33646 % sh config.sub sun3
33647 m68k-sun-sunos4.1.1
33648 % sh config.sub i986v
33649 Invalid configuration `i986v': machine `i986v' not recognized
33653 @code{config.sub} is also distributed in the @value{GDBN} source
33654 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33656 @node Configure Options
33657 @section @file{configure} Options
33659 Here is a summary of the @file{configure} options and arguments that
33660 are most often useful for building @value{GDBN}. @file{configure} also has
33661 several other options not listed here. @inforef{What Configure
33662 Does,,configure.info}, for a full explanation of @file{configure}.
33665 configure @r{[}--help@r{]}
33666 @r{[}--prefix=@var{dir}@r{]}
33667 @r{[}--exec-prefix=@var{dir}@r{]}
33668 @r{[}--srcdir=@var{dirname}@r{]}
33669 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33670 @r{[}--target=@var{target}@r{]}
33675 You may introduce options with a single @samp{-} rather than
33676 @samp{--} if you prefer; but you may abbreviate option names if you use
33681 Display a quick summary of how to invoke @file{configure}.
33683 @item --prefix=@var{dir}
33684 Configure the source to install programs and files under directory
33687 @item --exec-prefix=@var{dir}
33688 Configure the source to install programs under directory
33691 @c avoid splitting the warning from the explanation:
33693 @item --srcdir=@var{dirname}
33694 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33695 @code{make} that implements the @code{VPATH} feature.}@*
33696 Use this option to make configurations in directories separate from the
33697 @value{GDBN} source directories. Among other things, you can use this to
33698 build (or maintain) several configurations simultaneously, in separate
33699 directories. @file{configure} writes configuration-specific files in
33700 the current directory, but arranges for them to use the source in the
33701 directory @var{dirname}. @file{configure} creates directories under
33702 the working directory in parallel to the source directories below
33705 @item --norecursion
33706 Configure only the directory level where @file{configure} is executed; do not
33707 propagate configuration to subdirectories.
33709 @item --target=@var{target}
33710 Configure @value{GDBN} for cross-debugging programs running on the specified
33711 @var{target}. Without this option, @value{GDBN} is configured to debug
33712 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33714 There is no convenient way to generate a list of all available targets.
33716 @item @var{host} @dots{}
33717 Configure @value{GDBN} to run on the specified @var{host}.
33719 There is no convenient way to generate a list of all available hosts.
33722 There are many other options available as well, but they are generally
33723 needed for special purposes only.
33725 @node System-wide configuration
33726 @section System-wide configuration and settings
33727 @cindex system-wide init file
33729 @value{GDBN} can be configured to have a system-wide init file;
33730 this file will be read and executed at startup (@pxref{Startup, , What
33731 @value{GDBN} does during startup}).
33733 Here is the corresponding configure option:
33736 @item --with-system-gdbinit=@var{file}
33737 Specify that the default location of the system-wide init file is
33741 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33742 it may be subject to relocation. Two possible cases:
33746 If the default location of this init file contains @file{$prefix},
33747 it will be subject to relocation. Suppose that the configure options
33748 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33749 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33750 init file is looked for as @file{$install/etc/gdbinit} instead of
33751 @file{$prefix/etc/gdbinit}.
33754 By contrast, if the default location does not contain the prefix,
33755 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33756 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33757 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33758 wherever @value{GDBN} is installed.
33761 If the configured location of the system-wide init file (as given by the
33762 @option{--with-system-gdbinit} option at configure time) is in the
33763 data-directory (as specified by @option{--with-gdb-datadir} at configure
33764 time) or in one of its subdirectories, then @value{GDBN} will look for the
33765 system-wide init file in the directory specified by the
33766 @option{--data-directory} command-line option.
33767 Note that the system-wide init file is only read once, during @value{GDBN}
33768 initialization. If the data-directory is changed after @value{GDBN} has
33769 started with the @code{set data-directory} command, the file will not be
33773 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33776 @node System-wide Configuration Scripts
33777 @subsection Installed System-wide Configuration Scripts
33778 @cindex system-wide configuration scripts
33780 The @file{system-gdbinit} directory, located inside the data-directory
33781 (as specified by @option{--with-gdb-datadir} at configure time) contains
33782 a number of scripts which can be used as system-wide init files. To
33783 automatically source those scripts at startup, @value{GDBN} should be
33784 configured with @option{--with-system-gdbinit}. Otherwise, any user
33785 should be able to source them by hand as needed.
33787 The following scripts are currently available:
33790 @item @file{elinos.py}
33792 @cindex ELinOS system-wide configuration script
33793 This script is useful when debugging a program on an ELinOS target.
33794 It takes advantage of the environment variables defined in a standard
33795 ELinOS environment in order to determine the location of the system
33796 shared libraries, and then sets the @samp{solib-absolute-prefix}
33797 and @samp{solib-search-path} variables appropriately.
33799 @item @file{wrs-linux.py}
33800 @pindex wrs-linux.py
33801 @cindex Wind River Linux system-wide configuration script
33802 This script is useful when debugging a program on a target running
33803 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33804 the host-side sysroot used by the target system.
33808 @node Maintenance Commands
33809 @appendix Maintenance Commands
33810 @cindex maintenance commands
33811 @cindex internal commands
33813 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33814 includes a number of commands intended for @value{GDBN} developers,
33815 that are not documented elsewhere in this manual. These commands are
33816 provided here for reference. (For commands that turn on debugging
33817 messages, see @ref{Debugging Output}.)
33820 @kindex maint agent
33821 @kindex maint agent-eval
33822 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33823 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33824 Translate the given @var{expression} into remote agent bytecodes.
33825 This command is useful for debugging the Agent Expression mechanism
33826 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33827 expression useful for data collection, such as by tracepoints, while
33828 @samp{maint agent-eval} produces an expression that evaluates directly
33829 to a result. For instance, a collection expression for @code{globa +
33830 globb} will include bytecodes to record four bytes of memory at each
33831 of the addresses of @code{globa} and @code{globb}, while discarding
33832 the result of the addition, while an evaluation expression will do the
33833 addition and return the sum.
33834 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33835 If not, generate remote agent bytecode for current frame PC address.
33837 @kindex maint agent-printf
33838 @item maint agent-printf @var{format},@var{expr},...
33839 Translate the given format string and list of argument expressions
33840 into remote agent bytecodes and display them as a disassembled list.
33841 This command is useful for debugging the agent version of dynamic
33842 printf (@pxref{Dynamic Printf}).
33844 @kindex maint info breakpoints
33845 @item @anchor{maint info breakpoints}maint info breakpoints
33846 Using the same format as @samp{info breakpoints}, display both the
33847 breakpoints you've set explicitly, and those @value{GDBN} is using for
33848 internal purposes. Internal breakpoints are shown with negative
33849 breakpoint numbers. The type column identifies what kind of breakpoint
33854 Normal, explicitly set breakpoint.
33857 Normal, explicitly set watchpoint.
33860 Internal breakpoint, used to handle correctly stepping through
33861 @code{longjmp} calls.
33863 @item longjmp resume
33864 Internal breakpoint at the target of a @code{longjmp}.
33867 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33870 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33873 Shared library events.
33877 @kindex maint info btrace
33878 @item maint info btrace
33879 Pint information about raw branch tracing data.
33881 @kindex maint btrace packet-history
33882 @item maint btrace packet-history
33883 Print the raw branch trace packets that are used to compute the
33884 execution history for the @samp{record btrace} command. Both the
33885 information and the format in which it is printed depend on the btrace
33890 For the BTS recording format, print a list of blocks of sequential
33891 code. For each block, the following information is printed:
33895 Newer blocks have higher numbers. The oldest block has number zero.
33896 @item Lowest @samp{PC}
33897 @item Highest @samp{PC}
33901 For the Intel(R) Processor Trace recording format, print a list of
33902 Intel(R) Processor Trace packets. For each packet, the following
33903 information is printed:
33906 @item Packet number
33907 Newer packets have higher numbers. The oldest packet has number zero.
33909 The packet's offset in the trace stream.
33910 @item Packet opcode and payload
33914 @kindex maint btrace clear-packet-history
33915 @item maint btrace clear-packet-history
33916 Discards the cached packet history printed by the @samp{maint btrace
33917 packet-history} command. The history will be computed again when
33920 @kindex maint btrace clear
33921 @item maint btrace clear
33922 Discard the branch trace data. The data will be fetched anew and the
33923 branch trace will be recomputed when needed.
33925 This implicitly truncates the branch trace to a single branch trace
33926 buffer. When updating branch trace incrementally, the branch trace
33927 available to @value{GDBN} may be bigger than a single branch trace
33930 @kindex maint set btrace pt skip-pad
33931 @item maint set btrace pt skip-pad
33932 @kindex maint show btrace pt skip-pad
33933 @item maint show btrace pt skip-pad
33934 Control whether @value{GDBN} will skip PAD packets when computing the
33937 @kindex set displaced-stepping
33938 @kindex show displaced-stepping
33939 @cindex displaced stepping support
33940 @cindex out-of-line single-stepping
33941 @item set displaced-stepping
33942 @itemx show displaced-stepping
33943 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33944 if the target supports it. Displaced stepping is a way to single-step
33945 over breakpoints without removing them from the inferior, by executing
33946 an out-of-line copy of the instruction that was originally at the
33947 breakpoint location. It is also known as out-of-line single-stepping.
33950 @item set displaced-stepping on
33951 If the target architecture supports it, @value{GDBN} will use
33952 displaced stepping to step over breakpoints.
33954 @item set displaced-stepping off
33955 @value{GDBN} will not use displaced stepping to step over breakpoints,
33956 even if such is supported by the target architecture.
33958 @cindex non-stop mode, and @samp{set displaced-stepping}
33959 @item set displaced-stepping auto
33960 This is the default mode. @value{GDBN} will use displaced stepping
33961 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33962 architecture supports displaced stepping.
33965 @kindex maint check-psymtabs
33966 @item maint check-psymtabs
33967 Check the consistency of currently expanded psymtabs versus symtabs.
33968 Use this to check, for example, whether a symbol is in one but not the other.
33970 @kindex maint check-symtabs
33971 @item maint check-symtabs
33972 Check the consistency of currently expanded symtabs.
33974 @kindex maint expand-symtabs
33975 @item maint expand-symtabs [@var{regexp}]
33976 Expand symbol tables.
33977 If @var{regexp} is specified, only expand symbol tables for file
33978 names matching @var{regexp}.
33980 @kindex maint set catch-demangler-crashes
33981 @kindex maint show catch-demangler-crashes
33982 @cindex demangler crashes
33983 @item maint set catch-demangler-crashes [on|off]
33984 @itemx maint show catch-demangler-crashes
33985 Control whether @value{GDBN} should attempt to catch crashes in the
33986 symbol name demangler. The default is to attempt to catch crashes.
33987 If enabled, the first time a crash is caught, a core file is created,
33988 the offending symbol is displayed and the user is presented with the
33989 option to terminate the current session.
33991 @kindex maint cplus first_component
33992 @item maint cplus first_component @var{name}
33993 Print the first C@t{++} class/namespace component of @var{name}.
33995 @kindex maint cplus namespace
33996 @item maint cplus namespace
33997 Print the list of possible C@t{++} namespaces.
33999 @kindex maint deprecate
34000 @kindex maint undeprecate
34001 @cindex deprecated commands
34002 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34003 @itemx maint undeprecate @var{command}
34004 Deprecate or undeprecate the named @var{command}. Deprecated commands
34005 cause @value{GDBN} to issue a warning when you use them. The optional
34006 argument @var{replacement} says which newer command should be used in
34007 favor of the deprecated one; if it is given, @value{GDBN} will mention
34008 the replacement as part of the warning.
34010 @kindex maint dump-me
34011 @item maint dump-me
34012 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34013 Cause a fatal signal in the debugger and force it to dump its core.
34014 This is supported only on systems which support aborting a program
34015 with the @code{SIGQUIT} signal.
34017 @kindex maint internal-error
34018 @kindex maint internal-warning
34019 @kindex maint demangler-warning
34020 @cindex demangler crashes
34021 @item maint internal-error @r{[}@var{message-text}@r{]}
34022 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34023 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34025 Cause @value{GDBN} to call the internal function @code{internal_error},
34026 @code{internal_warning} or @code{demangler_warning} and hence behave
34027 as though an internal problem has been detected. In addition to
34028 reporting the internal problem, these functions give the user the
34029 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34030 and @code{internal_warning}) create a core file of the current
34031 @value{GDBN} session.
34033 These commands take an optional parameter @var{message-text} that is
34034 used as the text of the error or warning message.
34036 Here's an example of using @code{internal-error}:
34039 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34040 @dots{}/maint.c:121: internal-error: testing, 1, 2
34041 A problem internal to GDB has been detected. Further
34042 debugging may prove unreliable.
34043 Quit this debugging session? (y or n) @kbd{n}
34044 Create a core file? (y or n) @kbd{n}
34048 @cindex @value{GDBN} internal error
34049 @cindex internal errors, control of @value{GDBN} behavior
34050 @cindex demangler crashes
34052 @kindex maint set internal-error
34053 @kindex maint show internal-error
34054 @kindex maint set internal-warning
34055 @kindex maint show internal-warning
34056 @kindex maint set demangler-warning
34057 @kindex maint show demangler-warning
34058 @item maint set internal-error @var{action} [ask|yes|no]
34059 @itemx maint show internal-error @var{action}
34060 @itemx maint set internal-warning @var{action} [ask|yes|no]
34061 @itemx maint show internal-warning @var{action}
34062 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34063 @itemx maint show demangler-warning @var{action}
34064 When @value{GDBN} reports an internal problem (error or warning) it
34065 gives the user the opportunity to both quit @value{GDBN} and create a
34066 core file of the current @value{GDBN} session. These commands let you
34067 override the default behaviour for each particular @var{action},
34068 described in the table below.
34072 You can specify that @value{GDBN} should always (yes) or never (no)
34073 quit. The default is to ask the user what to do.
34076 You can specify that @value{GDBN} should always (yes) or never (no)
34077 create a core file. The default is to ask the user what to do. Note
34078 that there is no @code{corefile} option for @code{demangler-warning}:
34079 demangler warnings always create a core file and this cannot be
34083 @kindex maint packet
34084 @item maint packet @var{text}
34085 If @value{GDBN} is talking to an inferior via the serial protocol,
34086 then this command sends the string @var{text} to the inferior, and
34087 displays the response packet. @value{GDBN} supplies the initial
34088 @samp{$} character, the terminating @samp{#} character, and the
34091 @kindex maint print architecture
34092 @item maint print architecture @r{[}@var{file}@r{]}
34093 Print the entire architecture configuration. The optional argument
34094 @var{file} names the file where the output goes.
34096 @kindex maint print c-tdesc
34097 @item maint print c-tdesc
34098 Print the current target description (@pxref{Target Descriptions}) as
34099 a C source file. The created source file can be used in @value{GDBN}
34100 when an XML parser is not available to parse the description.
34102 @kindex maint print dummy-frames
34103 @item maint print dummy-frames
34104 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34107 (@value{GDBP}) @kbd{b add}
34109 (@value{GDBP}) @kbd{print add(2,3)}
34110 Breakpoint 2, add (a=2, b=3) at @dots{}
34112 The program being debugged stopped while in a function called from GDB.
34114 (@value{GDBP}) @kbd{maint print dummy-frames}
34115 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34119 Takes an optional file parameter.
34121 @kindex maint print registers
34122 @kindex maint print raw-registers
34123 @kindex maint print cooked-registers
34124 @kindex maint print register-groups
34125 @kindex maint print remote-registers
34126 @item maint print registers @r{[}@var{file}@r{]}
34127 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34128 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34129 @itemx maint print register-groups @r{[}@var{file}@r{]}
34130 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34131 Print @value{GDBN}'s internal register data structures.
34133 The command @code{maint print raw-registers} includes the contents of
34134 the raw register cache; the command @code{maint print
34135 cooked-registers} includes the (cooked) value of all registers,
34136 including registers which aren't available on the target nor visible
34137 to user; the command @code{maint print register-groups} includes the
34138 groups that each register is a member of; and the command @code{maint
34139 print remote-registers} includes the remote target's register numbers
34140 and offsets in the `G' packets.
34142 These commands take an optional parameter, a file name to which to
34143 write the information.
34145 @kindex maint print reggroups
34146 @item maint print reggroups @r{[}@var{file}@r{]}
34147 Print @value{GDBN}'s internal register group data structures. The
34148 optional argument @var{file} tells to what file to write the
34151 The register groups info looks like this:
34154 (@value{GDBP}) @kbd{maint print reggroups}
34167 This command forces @value{GDBN} to flush its internal register cache.
34169 @kindex maint print objfiles
34170 @cindex info for known object files
34171 @item maint print objfiles @r{[}@var{regexp}@r{]}
34172 Print a dump of all known object files.
34173 If @var{regexp} is specified, only print object files whose names
34174 match @var{regexp}. For each object file, this command prints its name,
34175 address in memory, and all of its psymtabs and symtabs.
34177 @kindex maint print user-registers
34178 @cindex user registers
34179 @item maint print user-registers
34180 List all currently available @dfn{user registers}. User registers
34181 typically provide alternate names for actual hardware registers. They
34182 include the four ``standard'' registers @code{$fp}, @code{$pc},
34183 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34184 registers can be used in expressions in the same way as the canonical
34185 register names, but only the latter are listed by the @code{info
34186 registers} and @code{maint print registers} commands.
34188 @kindex maint print section-scripts
34189 @cindex info for known .debug_gdb_scripts-loaded scripts
34190 @item maint print section-scripts [@var{regexp}]
34191 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34192 If @var{regexp} is specified, only print scripts loaded by object files
34193 matching @var{regexp}.
34194 For each script, this command prints its name as specified in the objfile,
34195 and the full path if known.
34196 @xref{dotdebug_gdb_scripts section}.
34198 @kindex maint print statistics
34199 @cindex bcache statistics
34200 @item maint print statistics
34201 This command prints, for each object file in the program, various data
34202 about that object file followed by the byte cache (@dfn{bcache})
34203 statistics for the object file. The objfile data includes the number
34204 of minimal, partial, full, and stabs symbols, the number of types
34205 defined by the objfile, the number of as yet unexpanded psym tables,
34206 the number of line tables and string tables, and the amount of memory
34207 used by the various tables. The bcache statistics include the counts,
34208 sizes, and counts of duplicates of all and unique objects, max,
34209 average, and median entry size, total memory used and its overhead and
34210 savings, and various measures of the hash table size and chain
34213 @kindex maint print target-stack
34214 @cindex target stack description
34215 @item maint print target-stack
34216 A @dfn{target} is an interface between the debugger and a particular
34217 kind of file or process. Targets can be stacked in @dfn{strata},
34218 so that more than one target can potentially respond to a request.
34219 In particular, memory accesses will walk down the stack of targets
34220 until they find a target that is interested in handling that particular
34223 This command prints a short description of each layer that was pushed on
34224 the @dfn{target stack}, starting from the top layer down to the bottom one.
34226 @kindex maint print type
34227 @cindex type chain of a data type
34228 @item maint print type @var{expr}
34229 Print the type chain for a type specified by @var{expr}. The argument
34230 can be either a type name or a symbol. If it is a symbol, the type of
34231 that symbol is described. The type chain produced by this command is
34232 a recursive definition of the data type as stored in @value{GDBN}'s
34233 data structures, including its flags and contained types.
34235 @kindex maint set dwarf always-disassemble
34236 @kindex maint show dwarf always-disassemble
34237 @item maint set dwarf always-disassemble
34238 @item maint show dwarf always-disassemble
34239 Control the behavior of @code{info address} when using DWARF debugging
34242 The default is @code{off}, which means that @value{GDBN} should try to
34243 describe a variable's location in an easily readable format. When
34244 @code{on}, @value{GDBN} will instead display the DWARF location
34245 expression in an assembly-like format. Note that some locations are
34246 too complex for @value{GDBN} to describe simply; in this case you will
34247 always see the disassembly form.
34249 Here is an example of the resulting disassembly:
34252 (gdb) info addr argc
34253 Symbol "argc" is a complex DWARF expression:
34257 For more information on these expressions, see
34258 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34260 @kindex maint set dwarf max-cache-age
34261 @kindex maint show dwarf max-cache-age
34262 @item maint set dwarf max-cache-age
34263 @itemx maint show dwarf max-cache-age
34264 Control the DWARF compilation unit cache.
34266 @cindex DWARF compilation units cache
34267 In object files with inter-compilation-unit references, such as those
34268 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34269 reader needs to frequently refer to previously read compilation units.
34270 This setting controls how long a compilation unit will remain in the
34271 cache if it is not referenced. A higher limit means that cached
34272 compilation units will be stored in memory longer, and more total
34273 memory will be used. Setting it to zero disables caching, which will
34274 slow down @value{GDBN} startup, but reduce memory consumption.
34276 @kindex maint set profile
34277 @kindex maint show profile
34278 @cindex profiling GDB
34279 @item maint set profile
34280 @itemx maint show profile
34281 Control profiling of @value{GDBN}.
34283 Profiling will be disabled until you use the @samp{maint set profile}
34284 command to enable it. When you enable profiling, the system will begin
34285 collecting timing and execution count data; when you disable profiling or
34286 exit @value{GDBN}, the results will be written to a log file. Remember that
34287 if you use profiling, @value{GDBN} will overwrite the profiling log file
34288 (often called @file{gmon.out}). If you have a record of important profiling
34289 data in a @file{gmon.out} file, be sure to move it to a safe location.
34291 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34292 compiled with the @samp{-pg} compiler option.
34294 @kindex maint set show-debug-regs
34295 @kindex maint show show-debug-regs
34296 @cindex hardware debug registers
34297 @item maint set show-debug-regs
34298 @itemx maint show show-debug-regs
34299 Control whether to show variables that mirror the hardware debug
34300 registers. Use @code{on} to enable, @code{off} to disable. If
34301 enabled, the debug registers values are shown when @value{GDBN} inserts or
34302 removes a hardware breakpoint or watchpoint, and when the inferior
34303 triggers a hardware-assisted breakpoint or watchpoint.
34305 @kindex maint set show-all-tib
34306 @kindex maint show show-all-tib
34307 @item maint set show-all-tib
34308 @itemx maint show show-all-tib
34309 Control whether to show all non zero areas within a 1k block starting
34310 at thread local base, when using the @samp{info w32 thread-information-block}
34313 @kindex maint set target-async
34314 @kindex maint show target-async
34315 @item maint set target-async
34316 @itemx maint show target-async
34317 This controls whether @value{GDBN} targets operate in synchronous or
34318 asynchronous mode (@pxref{Background Execution}). Normally the
34319 default is asynchronous, if it is available; but this can be changed
34320 to more easily debug problems occurring only in synchronous mode.
34322 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34323 @kindex maint show target-non-stop
34324 @item maint set target-non-stop
34325 @itemx maint show target-non-stop
34327 This controls whether @value{GDBN} targets always operate in non-stop
34328 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34329 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34330 if supported by the target.
34333 @item maint set target-non-stop auto
34334 This is the default mode. @value{GDBN} controls the target in
34335 non-stop mode if the target supports it.
34337 @item maint set target-non-stop on
34338 @value{GDBN} controls the target in non-stop mode even if the target
34339 does not indicate support.
34341 @item maint set target-non-stop off
34342 @value{GDBN} does not control the target in non-stop mode even if the
34343 target supports it.
34346 @kindex maint set per-command
34347 @kindex maint show per-command
34348 @item maint set per-command
34349 @itemx maint show per-command
34350 @cindex resources used by commands
34352 @value{GDBN} can display the resources used by each command.
34353 This is useful in debugging performance problems.
34356 @item maint set per-command space [on|off]
34357 @itemx maint show per-command space
34358 Enable or disable the printing of the memory used by GDB for each command.
34359 If enabled, @value{GDBN} will display how much memory each command
34360 took, following the command's own output.
34361 This can also be requested by invoking @value{GDBN} with the
34362 @option{--statistics} command-line switch (@pxref{Mode Options}).
34364 @item maint set per-command time [on|off]
34365 @itemx maint show per-command time
34366 Enable or disable the printing of the execution time of @value{GDBN}
34368 If enabled, @value{GDBN} will display how much time it
34369 took to execute each command, following the command's own output.
34370 Both CPU time and wallclock time are printed.
34371 Printing both is useful when trying to determine whether the cost is
34372 CPU or, e.g., disk/network latency.
34373 Note that the CPU time printed is for @value{GDBN} only, it does not include
34374 the execution time of the inferior because there's no mechanism currently
34375 to compute how much time was spent by @value{GDBN} and how much time was
34376 spent by the program been debugged.
34377 This can also be requested by invoking @value{GDBN} with the
34378 @option{--statistics} command-line switch (@pxref{Mode Options}).
34380 @item maint set per-command symtab [on|off]
34381 @itemx maint show per-command symtab
34382 Enable or disable the printing of basic symbol table statistics
34384 If enabled, @value{GDBN} will display the following information:
34388 number of symbol tables
34390 number of primary symbol tables
34392 number of blocks in the blockvector
34396 @kindex maint space
34397 @cindex memory used by commands
34398 @item maint space @var{value}
34399 An alias for @code{maint set per-command space}.
34400 A non-zero value enables it, zero disables it.
34403 @cindex time of command execution
34404 @item maint time @var{value}
34405 An alias for @code{maint set per-command time}.
34406 A non-zero value enables it, zero disables it.
34408 @kindex maint translate-address
34409 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34410 Find the symbol stored at the location specified by the address
34411 @var{addr} and an optional section name @var{section}. If found,
34412 @value{GDBN} prints the name of the closest symbol and an offset from
34413 the symbol's location to the specified address. This is similar to
34414 the @code{info address} command (@pxref{Symbols}), except that this
34415 command also allows to find symbols in other sections.
34417 If section was not specified, the section in which the symbol was found
34418 is also printed. For dynamically linked executables, the name of
34419 executable or shared library containing the symbol is printed as well.
34423 The following command is useful for non-interactive invocations of
34424 @value{GDBN}, such as in the test suite.
34427 @item set watchdog @var{nsec}
34428 @kindex set watchdog
34429 @cindex watchdog timer
34430 @cindex timeout for commands
34431 Set the maximum number of seconds @value{GDBN} will wait for the
34432 target operation to finish. If this time expires, @value{GDBN}
34433 reports and error and the command is aborted.
34435 @item show watchdog
34436 Show the current setting of the target wait timeout.
34439 @node Remote Protocol
34440 @appendix @value{GDBN} Remote Serial Protocol
34445 * Stop Reply Packets::
34446 * General Query Packets::
34447 * Architecture-Specific Protocol Details::
34448 * Tracepoint Packets::
34449 * Host I/O Packets::
34451 * Notification Packets::
34452 * Remote Non-Stop::
34453 * Packet Acknowledgment::
34455 * File-I/O Remote Protocol Extension::
34456 * Library List Format::
34457 * Library List Format for SVR4 Targets::
34458 * Memory Map Format::
34459 * Thread List Format::
34460 * Traceframe Info Format::
34461 * Branch Trace Format::
34462 * Branch Trace Configuration Format::
34468 There may be occasions when you need to know something about the
34469 protocol---for example, if there is only one serial port to your target
34470 machine, you might want your program to do something special if it
34471 recognizes a packet meant for @value{GDBN}.
34473 In the examples below, @samp{->} and @samp{<-} are used to indicate
34474 transmitted and received data, respectively.
34476 @cindex protocol, @value{GDBN} remote serial
34477 @cindex serial protocol, @value{GDBN} remote
34478 @cindex remote serial protocol
34479 All @value{GDBN} commands and responses (other than acknowledgments
34480 and notifications, see @ref{Notification Packets}) are sent as a
34481 @var{packet}. A @var{packet} is introduced with the character
34482 @samp{$}, the actual @var{packet-data}, and the terminating character
34483 @samp{#} followed by a two-digit @var{checksum}:
34486 @code{$}@var{packet-data}@code{#}@var{checksum}
34490 @cindex checksum, for @value{GDBN} remote
34492 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34493 characters between the leading @samp{$} and the trailing @samp{#} (an
34494 eight bit unsigned checksum).
34496 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34497 specification also included an optional two-digit @var{sequence-id}:
34500 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34503 @cindex sequence-id, for @value{GDBN} remote
34505 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34506 has never output @var{sequence-id}s. Stubs that handle packets added
34507 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34509 When either the host or the target machine receives a packet, the first
34510 response expected is an acknowledgment: either @samp{+} (to indicate
34511 the package was received correctly) or @samp{-} (to request
34515 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34520 The @samp{+}/@samp{-} acknowledgments can be disabled
34521 once a connection is established.
34522 @xref{Packet Acknowledgment}, for details.
34524 The host (@value{GDBN}) sends @var{command}s, and the target (the
34525 debugging stub incorporated in your program) sends a @var{response}. In
34526 the case of step and continue @var{command}s, the response is only sent
34527 when the operation has completed, and the target has again stopped all
34528 threads in all attached processes. This is the default all-stop mode
34529 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34530 execution mode; see @ref{Remote Non-Stop}, for details.
34532 @var{packet-data} consists of a sequence of characters with the
34533 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34536 @cindex remote protocol, field separator
34537 Fields within the packet should be separated using @samp{,} @samp{;} or
34538 @samp{:}. Except where otherwise noted all numbers are represented in
34539 @sc{hex} with leading zeros suppressed.
34541 Implementors should note that prior to @value{GDBN} 5.0, the character
34542 @samp{:} could not appear as the third character in a packet (as it
34543 would potentially conflict with the @var{sequence-id}).
34545 @cindex remote protocol, binary data
34546 @anchor{Binary Data}
34547 Binary data in most packets is encoded either as two hexadecimal
34548 digits per byte of binary data. This allowed the traditional remote
34549 protocol to work over connections which were only seven-bit clean.
34550 Some packets designed more recently assume an eight-bit clean
34551 connection, and use a more efficient encoding to send and receive
34554 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34555 as an escape character. Any escaped byte is transmitted as the escape
34556 character followed by the original character XORed with @code{0x20}.
34557 For example, the byte @code{0x7d} would be transmitted as the two
34558 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34559 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34560 @samp{@}}) must always be escaped. Responses sent by the stub
34561 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34562 is not interpreted as the start of a run-length encoded sequence
34565 Response @var{data} can be run-length encoded to save space.
34566 Run-length encoding replaces runs of identical characters with one
34567 instance of the repeated character, followed by a @samp{*} and a
34568 repeat count. The repeat count is itself sent encoded, to avoid
34569 binary characters in @var{data}: a value of @var{n} is sent as
34570 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34571 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34572 code 32) for a repeat count of 3. (This is because run-length
34573 encoding starts to win for counts 3 or more.) Thus, for example,
34574 @samp{0* } is a run-length encoding of ``0000'': the space character
34575 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34578 The printable characters @samp{#} and @samp{$} or with a numeric value
34579 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34580 seven repeats (@samp{$}) can be expanded using a repeat count of only
34581 five (@samp{"}). For example, @samp{00000000} can be encoded as
34584 The error response returned for some packets includes a two character
34585 error number. That number is not well defined.
34587 @cindex empty response, for unsupported packets
34588 For any @var{command} not supported by the stub, an empty response
34589 (@samp{$#00}) should be returned. That way it is possible to extend the
34590 protocol. A newer @value{GDBN} can tell if a packet is supported based
34593 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34594 commands for register access, and the @samp{m} and @samp{M} commands
34595 for memory access. Stubs that only control single-threaded targets
34596 can implement run control with the @samp{c} (continue), and @samp{s}
34597 (step) commands. Stubs that support multi-threading targets should
34598 support the @samp{vCont} command. All other commands are optional.
34603 The following table provides a complete list of all currently defined
34604 @var{command}s and their corresponding response @var{data}.
34605 @xref{File-I/O Remote Protocol Extension}, for details about the File
34606 I/O extension of the remote protocol.
34608 Each packet's description has a template showing the packet's overall
34609 syntax, followed by an explanation of the packet's meaning. We
34610 include spaces in some of the templates for clarity; these are not
34611 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34612 separate its components. For example, a template like @samp{foo
34613 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34614 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34615 @var{baz}. @value{GDBN} does not transmit a space character between the
34616 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34619 @cindex @var{thread-id}, in remote protocol
34620 @anchor{thread-id syntax}
34621 Several packets and replies include a @var{thread-id} field to identify
34622 a thread. Normally these are positive numbers with a target-specific
34623 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34624 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34627 In addition, the remote protocol supports a multiprocess feature in
34628 which the @var{thread-id} syntax is extended to optionally include both
34629 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34630 The @var{pid} (process) and @var{tid} (thread) components each have the
34631 format described above: a positive number with target-specific
34632 interpretation formatted as a big-endian hex string, literal @samp{-1}
34633 to indicate all processes or threads (respectively), or @samp{0} to
34634 indicate an arbitrary process or thread. Specifying just a process, as
34635 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34636 error to specify all processes but a specific thread, such as
34637 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34638 for those packets and replies explicitly documented to include a process
34639 ID, rather than a @var{thread-id}.
34641 The multiprocess @var{thread-id} syntax extensions are only used if both
34642 @value{GDBN} and the stub report support for the @samp{multiprocess}
34643 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34646 Note that all packet forms beginning with an upper- or lower-case
34647 letter, other than those described here, are reserved for future use.
34649 Here are the packet descriptions.
34654 @cindex @samp{!} packet
34655 @anchor{extended mode}
34656 Enable extended mode. In extended mode, the remote server is made
34657 persistent. The @samp{R} packet is used to restart the program being
34663 The remote target both supports and has enabled extended mode.
34667 @cindex @samp{?} packet
34669 Indicate the reason the target halted. The reply is the same as for
34670 step and continue. This packet has a special interpretation when the
34671 target is in non-stop mode; see @ref{Remote Non-Stop}.
34674 @xref{Stop Reply Packets}, for the reply specifications.
34676 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34677 @cindex @samp{A} packet
34678 Initialized @code{argv[]} array passed into program. @var{arglen}
34679 specifies the number of bytes in the hex encoded byte stream
34680 @var{arg}. See @code{gdbserver} for more details.
34685 The arguments were set.
34691 @cindex @samp{b} packet
34692 (Don't use this packet; its behavior is not well-defined.)
34693 Change the serial line speed to @var{baud}.
34695 JTC: @emph{When does the transport layer state change? When it's
34696 received, or after the ACK is transmitted. In either case, there are
34697 problems if the command or the acknowledgment packet is dropped.}
34699 Stan: @emph{If people really wanted to add something like this, and get
34700 it working for the first time, they ought to modify ser-unix.c to send
34701 some kind of out-of-band message to a specially-setup stub and have the
34702 switch happen "in between" packets, so that from remote protocol's point
34703 of view, nothing actually happened.}
34705 @item B @var{addr},@var{mode}
34706 @cindex @samp{B} packet
34707 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34708 breakpoint at @var{addr}.
34710 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34711 (@pxref{insert breakpoint or watchpoint packet}).
34713 @cindex @samp{bc} packet
34716 Backward continue. Execute the target system in reverse. No parameter.
34717 @xref{Reverse Execution}, for more information.
34720 @xref{Stop Reply Packets}, for the reply specifications.
34722 @cindex @samp{bs} packet
34725 Backward single step. Execute one instruction in reverse. No parameter.
34726 @xref{Reverse Execution}, for more information.
34729 @xref{Stop Reply Packets}, for the reply specifications.
34731 @item c @r{[}@var{addr}@r{]}
34732 @cindex @samp{c} packet
34733 Continue at @var{addr}, which is the address to resume. If @var{addr}
34734 is omitted, resume at current address.
34736 This packet is deprecated for multi-threading support. @xref{vCont
34740 @xref{Stop Reply Packets}, for the reply specifications.
34742 @item C @var{sig}@r{[};@var{addr}@r{]}
34743 @cindex @samp{C} packet
34744 Continue with signal @var{sig} (hex signal number). If
34745 @samp{;@var{addr}} is omitted, resume at same address.
34747 This packet is deprecated for multi-threading support. @xref{vCont
34751 @xref{Stop Reply Packets}, for the reply specifications.
34754 @cindex @samp{d} packet
34757 Don't use this packet; instead, define a general set packet
34758 (@pxref{General Query Packets}).
34762 @cindex @samp{D} packet
34763 The first form of the packet is used to detach @value{GDBN} from the
34764 remote system. It is sent to the remote target
34765 before @value{GDBN} disconnects via the @code{detach} command.
34767 The second form, including a process ID, is used when multiprocess
34768 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34769 detach only a specific process. The @var{pid} is specified as a
34770 big-endian hex string.
34780 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34781 @cindex @samp{F} packet
34782 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34783 This is part of the File-I/O protocol extension. @xref{File-I/O
34784 Remote Protocol Extension}, for the specification.
34787 @anchor{read registers packet}
34788 @cindex @samp{g} packet
34789 Read general registers.
34793 @item @var{XX@dots{}}
34794 Each byte of register data is described by two hex digits. The bytes
34795 with the register are transmitted in target byte order. The size of
34796 each register and their position within the @samp{g} packet are
34797 determined by the @value{GDBN} internal gdbarch functions
34798 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34799 specification of several standard @samp{g} packets is specified below.
34801 When reading registers from a trace frame (@pxref{Analyze Collected
34802 Data,,Using the Collected Data}), the stub may also return a string of
34803 literal @samp{x}'s in place of the register data digits, to indicate
34804 that the corresponding register has not been collected, thus its value
34805 is unavailable. For example, for an architecture with 4 registers of
34806 4 bytes each, the following reply indicates to @value{GDBN} that
34807 registers 0 and 2 have not been collected, while registers 1 and 3
34808 have been collected, and both have zero value:
34812 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34819 @item G @var{XX@dots{}}
34820 @cindex @samp{G} packet
34821 Write general registers. @xref{read registers packet}, for a
34822 description of the @var{XX@dots{}} data.
34832 @item H @var{op} @var{thread-id}
34833 @cindex @samp{H} packet
34834 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34835 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34836 should be @samp{c} for step and continue operations (note that this
34837 is deprecated, supporting the @samp{vCont} command is a better
34838 option), and @samp{g} for other operations. The thread designator
34839 @var{thread-id} has the format and interpretation described in
34840 @ref{thread-id syntax}.
34851 @c 'H': How restrictive (or permissive) is the thread model. If a
34852 @c thread is selected and stopped, are other threads allowed
34853 @c to continue to execute? As I mentioned above, I think the
34854 @c semantics of each command when a thread is selected must be
34855 @c described. For example:
34857 @c 'g': If the stub supports threads and a specific thread is
34858 @c selected, returns the register block from that thread;
34859 @c otherwise returns current registers.
34861 @c 'G' If the stub supports threads and a specific thread is
34862 @c selected, sets the registers of the register block of
34863 @c that thread; otherwise sets current registers.
34865 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34866 @anchor{cycle step packet}
34867 @cindex @samp{i} packet
34868 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34869 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34870 step starting at that address.
34873 @cindex @samp{I} packet
34874 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34878 @cindex @samp{k} packet
34881 The exact effect of this packet is not specified.
34883 For a bare-metal target, it may power cycle or reset the target
34884 system. For that reason, the @samp{k} packet has no reply.
34886 For a single-process target, it may kill that process if possible.
34888 A multiple-process target may choose to kill just one process, or all
34889 that are under @value{GDBN}'s control. For more precise control, use
34890 the vKill packet (@pxref{vKill packet}).
34892 If the target system immediately closes the connection in response to
34893 @samp{k}, @value{GDBN} does not consider the lack of packet
34894 acknowledgment to be an error, and assumes the kill was successful.
34896 If connected using @kbd{target extended-remote}, and the target does
34897 not close the connection in response to a kill request, @value{GDBN}
34898 probes the target state as if a new connection was opened
34899 (@pxref{? packet}).
34901 @item m @var{addr},@var{length}
34902 @cindex @samp{m} packet
34903 Read @var{length} addressable memory units starting at address @var{addr}
34904 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34905 any particular boundary.
34907 The stub need not use any particular size or alignment when gathering
34908 data from memory for the response; even if @var{addr} is word-aligned
34909 and @var{length} is a multiple of the word size, the stub is free to
34910 use byte accesses, or not. For this reason, this packet may not be
34911 suitable for accessing memory-mapped I/O devices.
34912 @cindex alignment of remote memory accesses
34913 @cindex size of remote memory accesses
34914 @cindex memory, alignment and size of remote accesses
34918 @item @var{XX@dots{}}
34919 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
34920 The reply may contain fewer addressable memory units than requested if the
34921 server was able to read only part of the region of memory.
34926 @item M @var{addr},@var{length}:@var{XX@dots{}}
34927 @cindex @samp{M} packet
34928 Write @var{length} addressable memory units starting at address @var{addr}
34929 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
34930 byte is transmitted as a two-digit hexadecimal number.
34937 for an error (this includes the case where only part of the data was
34942 @cindex @samp{p} packet
34943 Read the value of register @var{n}; @var{n} is in hex.
34944 @xref{read registers packet}, for a description of how the returned
34945 register value is encoded.
34949 @item @var{XX@dots{}}
34950 the register's value
34954 Indicating an unrecognized @var{query}.
34957 @item P @var{n@dots{}}=@var{r@dots{}}
34958 @anchor{write register packet}
34959 @cindex @samp{P} packet
34960 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34961 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34962 digits for each byte in the register (target byte order).
34972 @item q @var{name} @var{params}@dots{}
34973 @itemx Q @var{name} @var{params}@dots{}
34974 @cindex @samp{q} packet
34975 @cindex @samp{Q} packet
34976 General query (@samp{q}) and set (@samp{Q}). These packets are
34977 described fully in @ref{General Query Packets}.
34980 @cindex @samp{r} packet
34981 Reset the entire system.
34983 Don't use this packet; use the @samp{R} packet instead.
34986 @cindex @samp{R} packet
34987 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34988 This packet is only available in extended mode (@pxref{extended mode}).
34990 The @samp{R} packet has no reply.
34992 @item s @r{[}@var{addr}@r{]}
34993 @cindex @samp{s} packet
34994 Single step, resuming at @var{addr}. If
34995 @var{addr} is omitted, resume at same address.
34997 This packet is deprecated for multi-threading support. @xref{vCont
35001 @xref{Stop Reply Packets}, for the reply specifications.
35003 @item S @var{sig}@r{[};@var{addr}@r{]}
35004 @anchor{step with signal packet}
35005 @cindex @samp{S} packet
35006 Step with signal. This is analogous to the @samp{C} packet, but
35007 requests a single-step, rather than a normal resumption of execution.
35009 This packet is deprecated for multi-threading support. @xref{vCont
35013 @xref{Stop Reply Packets}, for the reply specifications.
35015 @item t @var{addr}:@var{PP},@var{MM}
35016 @cindex @samp{t} packet
35017 Search backwards starting at address @var{addr} for a match with pattern
35018 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35019 There must be at least 3 digits in @var{addr}.
35021 @item T @var{thread-id}
35022 @cindex @samp{T} packet
35023 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35028 thread is still alive
35034 Packets starting with @samp{v} are identified by a multi-letter name,
35035 up to the first @samp{;} or @samp{?} (or the end of the packet).
35037 @item vAttach;@var{pid}
35038 @cindex @samp{vAttach} packet
35039 Attach to a new process with the specified process ID @var{pid}.
35040 The process ID is a
35041 hexadecimal integer identifying the process. In all-stop mode, all
35042 threads in the attached process are stopped; in non-stop mode, it may be
35043 attached without being stopped if that is supported by the target.
35045 @c In non-stop mode, on a successful vAttach, the stub should set the
35046 @c current thread to a thread of the newly-attached process. After
35047 @c attaching, GDB queries for the attached process's thread ID with qC.
35048 @c Also note that, from a user perspective, whether or not the
35049 @c target is stopped on attach in non-stop mode depends on whether you
35050 @c use the foreground or background version of the attach command, not
35051 @c on what vAttach does; GDB does the right thing with respect to either
35052 @c stopping or restarting threads.
35054 This packet is only available in extended mode (@pxref{extended mode}).
35060 @item @r{Any stop packet}
35061 for success in all-stop mode (@pxref{Stop Reply Packets})
35063 for success in non-stop mode (@pxref{Remote Non-Stop})
35066 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35067 @cindex @samp{vCont} packet
35068 @anchor{vCont packet}
35069 Resume the inferior, specifying different actions for each thread.
35070 If an action is specified with no @var{thread-id}, then it is applied to any
35071 threads that don't have a specific action specified; if no default action is
35072 specified then other threads should remain stopped in all-stop mode and
35073 in their current state in non-stop mode.
35074 Specifying multiple
35075 default actions is an error; specifying no actions is also an error.
35076 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35078 Currently supported actions are:
35084 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35088 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35091 @item r @var{start},@var{end}
35092 Step once, and then keep stepping as long as the thread stops at
35093 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35094 The remote stub reports a stop reply when either the thread goes out
35095 of the range or is stopped due to an unrelated reason, such as hitting
35096 a breakpoint. @xref{range stepping}.
35098 If the range is empty (@var{start} == @var{end}), then the action
35099 becomes equivalent to the @samp{s} action. In other words,
35100 single-step once, and report the stop (even if the stepped instruction
35101 jumps to @var{start}).
35103 (A stop reply may be sent at any point even if the PC is still within
35104 the stepping range; for example, it is valid to implement this packet
35105 in a degenerate way as a single instruction step operation.)
35109 The optional argument @var{addr} normally associated with the
35110 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35111 not supported in @samp{vCont}.
35113 The @samp{t} action is only relevant in non-stop mode
35114 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35115 A stop reply should be generated for any affected thread not already stopped.
35116 When a thread is stopped by means of a @samp{t} action,
35117 the corresponding stop reply should indicate that the thread has stopped with
35118 signal @samp{0}, regardless of whether the target uses some other signal
35119 as an implementation detail.
35121 The stub must support @samp{vCont} if it reports support for
35122 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35123 this case @samp{vCont} actions can be specified to apply to all threads
35124 in a process by using the @samp{p@var{pid}.-1} form of the
35128 @xref{Stop Reply Packets}, for the reply specifications.
35131 @cindex @samp{vCont?} packet
35132 Request a list of actions supported by the @samp{vCont} packet.
35136 @item vCont@r{[};@var{action}@dots{}@r{]}
35137 The @samp{vCont} packet is supported. Each @var{action} is a supported
35138 command in the @samp{vCont} packet.
35140 The @samp{vCont} packet is not supported.
35143 @anchor{vCtrlC packet}
35145 @cindex @samp{vCtrlC} packet
35146 Interrupt remote target as if a control-C was pressed on the remote
35147 terminal. This is the equivalent to reacting to the @code{^C}
35148 (@samp{\003}, the control-C character) character in all-stop mode
35149 while the target is running, except this works in non-stop mode.
35150 @xref{interrupting remote targets}, for more info on the all-stop
35161 @item vFile:@var{operation}:@var{parameter}@dots{}
35162 @cindex @samp{vFile} packet
35163 Perform a file operation on the target system. For details,
35164 see @ref{Host I/O Packets}.
35166 @item vFlashErase:@var{addr},@var{length}
35167 @cindex @samp{vFlashErase} packet
35168 Direct the stub to erase @var{length} bytes of flash starting at
35169 @var{addr}. The region may enclose any number of flash blocks, but
35170 its start and end must fall on block boundaries, as indicated by the
35171 flash block size appearing in the memory map (@pxref{Memory Map
35172 Format}). @value{GDBN} groups flash memory programming operations
35173 together, and sends a @samp{vFlashDone} request after each group; the
35174 stub is allowed to delay erase operation until the @samp{vFlashDone}
35175 packet is received.
35185 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35186 @cindex @samp{vFlashWrite} packet
35187 Direct the stub to write data to flash address @var{addr}. The data
35188 is passed in binary form using the same encoding as for the @samp{X}
35189 packet (@pxref{Binary Data}). The memory ranges specified by
35190 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35191 not overlap, and must appear in order of increasing addresses
35192 (although @samp{vFlashErase} packets for higher addresses may already
35193 have been received; the ordering is guaranteed only between
35194 @samp{vFlashWrite} packets). If a packet writes to an address that was
35195 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35196 target-specific method, the results are unpredictable.
35204 for vFlashWrite addressing non-flash memory
35210 @cindex @samp{vFlashDone} packet
35211 Indicate to the stub that flash programming operation is finished.
35212 The stub is permitted to delay or batch the effects of a group of
35213 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35214 @samp{vFlashDone} packet is received. The contents of the affected
35215 regions of flash memory are unpredictable until the @samp{vFlashDone}
35216 request is completed.
35218 @item vKill;@var{pid}
35219 @cindex @samp{vKill} packet
35220 @anchor{vKill packet}
35221 Kill the process with the specified process ID @var{pid}, which is a
35222 hexadecimal integer identifying the process. This packet is used in
35223 preference to @samp{k} when multiprocess protocol extensions are
35224 supported; see @ref{multiprocess extensions}.
35234 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35235 @cindex @samp{vRun} packet
35236 Run the program @var{filename}, passing it each @var{argument} on its
35237 command line. The file and arguments are hex-encoded strings. If
35238 @var{filename} is an empty string, the stub may use a default program
35239 (e.g.@: the last program run). The program is created in the stopped
35242 @c FIXME: What about non-stop mode?
35244 This packet is only available in extended mode (@pxref{extended mode}).
35250 @item @r{Any stop packet}
35251 for success (@pxref{Stop Reply Packets})
35255 @cindex @samp{vStopped} packet
35256 @xref{Notification Packets}.
35258 @item X @var{addr},@var{length}:@var{XX@dots{}}
35260 @cindex @samp{X} packet
35261 Write data to memory, where the data is transmitted in binary.
35262 Memory is specified by its address @var{addr} and number of addressable memory
35263 units @var{length} (@pxref{addressable memory unit});
35264 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35274 @item z @var{type},@var{addr},@var{kind}
35275 @itemx Z @var{type},@var{addr},@var{kind}
35276 @anchor{insert breakpoint or watchpoint packet}
35277 @cindex @samp{z} packet
35278 @cindex @samp{Z} packets
35279 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35280 watchpoint starting at address @var{address} of kind @var{kind}.
35282 Each breakpoint and watchpoint packet @var{type} is documented
35285 @emph{Implementation notes: A remote target shall return an empty string
35286 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35287 remote target shall support either both or neither of a given
35288 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35289 avoid potential problems with duplicate packets, the operations should
35290 be implemented in an idempotent way.}
35292 @item z0,@var{addr},@var{kind}
35293 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35294 @cindex @samp{z0} packet
35295 @cindex @samp{Z0} packet
35296 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35297 @var{addr} of type @var{kind}.
35299 A memory breakpoint is implemented by replacing the instruction at
35300 @var{addr} with a software breakpoint or trap instruction. The
35301 @var{kind} is target-specific and typically indicates the size of
35302 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35303 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35304 architectures have additional meanings for @var{kind};
35305 @var{cond_list} is an optional list of conditional expressions in bytecode
35306 form that should be evaluated on the target's side. These are the
35307 conditions that should be taken into consideration when deciding if
35308 the breakpoint trigger should be reported back to @var{GDBN}.
35310 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35311 for how to best report a memory breakpoint event to @value{GDBN}.
35313 The @var{cond_list} parameter is comprised of a series of expressions,
35314 concatenated without separators. Each expression has the following form:
35318 @item X @var{len},@var{expr}
35319 @var{len} is the length of the bytecode expression and @var{expr} is the
35320 actual conditional expression in bytecode form.
35324 The optional @var{cmd_list} parameter introduces commands that may be
35325 run on the target, rather than being reported back to @value{GDBN}.
35326 The parameter starts with a numeric flag @var{persist}; if the flag is
35327 nonzero, then the breakpoint may remain active and the commands
35328 continue to be run even when @value{GDBN} disconnects from the target.
35329 Following this flag is a series of expressions concatenated with no
35330 separators. Each expression has the following form:
35334 @item X @var{len},@var{expr}
35335 @var{len} is the length of the bytecode expression and @var{expr} is the
35336 actual conditional expression in bytecode form.
35340 see @ref{Architecture-Specific Protocol Details}.
35342 @emph{Implementation note: It is possible for a target to copy or move
35343 code that contains memory breakpoints (e.g., when implementing
35344 overlays). The behavior of this packet, in the presence of such a
35345 target, is not defined.}
35357 @item z1,@var{addr},@var{kind}
35358 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35359 @cindex @samp{z1} packet
35360 @cindex @samp{Z1} packet
35361 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35362 address @var{addr}.
35364 A hardware breakpoint is implemented using a mechanism that is not
35365 dependant on being able to modify the target's memory. The @var{kind}
35366 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35368 @emph{Implementation note: A hardware breakpoint is not affected by code
35381 @item z2,@var{addr},@var{kind}
35382 @itemx Z2,@var{addr},@var{kind}
35383 @cindex @samp{z2} packet
35384 @cindex @samp{Z2} packet
35385 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35386 The number of bytes to watch is specified by @var{kind}.
35398 @item z3,@var{addr},@var{kind}
35399 @itemx Z3,@var{addr},@var{kind}
35400 @cindex @samp{z3} packet
35401 @cindex @samp{Z3} packet
35402 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35403 The number of bytes to watch is specified by @var{kind}.
35415 @item z4,@var{addr},@var{kind}
35416 @itemx Z4,@var{addr},@var{kind}
35417 @cindex @samp{z4} packet
35418 @cindex @samp{Z4} packet
35419 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35420 The number of bytes to watch is specified by @var{kind}.
35434 @node Stop Reply Packets
35435 @section Stop Reply Packets
35436 @cindex stop reply packets
35438 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35439 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35440 receive any of the below as a reply. Except for @samp{?}
35441 and @samp{vStopped}, that reply is only returned
35442 when the target halts. In the below the exact meaning of @dfn{signal
35443 number} is defined by the header @file{include/gdb/signals.h} in the
35444 @value{GDBN} source code.
35446 As in the description of request packets, we include spaces in the
35447 reply templates for clarity; these are not part of the reply packet's
35448 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35454 The program received signal number @var{AA} (a two-digit hexadecimal
35455 number). This is equivalent to a @samp{T} response with no
35456 @var{n}:@var{r} pairs.
35458 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35459 @cindex @samp{T} packet reply
35460 The program received signal number @var{AA} (a two-digit hexadecimal
35461 number). This is equivalent to an @samp{S} response, except that the
35462 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35463 and other information directly in the stop reply packet, reducing
35464 round-trip latency. Single-step and breakpoint traps are reported
35465 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35469 If @var{n} is a hexadecimal number, it is a register number, and the
35470 corresponding @var{r} gives that register's value. The data @var{r} is a
35471 series of bytes in target byte order, with each byte given by a
35472 two-digit hex number.
35475 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35476 the stopped thread, as specified in @ref{thread-id syntax}.
35479 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35480 the core on which the stop event was detected.
35483 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35484 specific event that stopped the target. The currently defined stop
35485 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35486 signal. At most one stop reason should be present.
35489 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35490 and go on to the next; this allows us to extend the protocol in the
35494 The currently defined stop reasons are:
35500 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35503 @cindex shared library events, remote reply
35505 The packet indicates that the loaded libraries have changed.
35506 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35507 list of loaded libraries. The @var{r} part is ignored.
35509 @cindex replay log events, remote reply
35511 The packet indicates that the target cannot continue replaying
35512 logged execution events, because it has reached the end (or the
35513 beginning when executing backward) of the log. The value of @var{r}
35514 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35515 for more information.
35518 @anchor{swbreak stop reason}
35519 The packet indicates a memory breakpoint instruction was executed,
35520 irrespective of whether it was @value{GDBN} that planted the
35521 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35522 part must be left empty.
35524 On some architectures, such as x86, at the architecture level, when a
35525 breakpoint instruction executes the program counter points at the
35526 breakpoint address plus an offset. On such targets, the stub is
35527 responsible for adjusting the PC to point back at the breakpoint
35530 This packet should not be sent by default; older @value{GDBN} versions
35531 did not support it. @value{GDBN} requests it, by supplying an
35532 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35533 remote stub must also supply the appropriate @samp{qSupported} feature
35534 indicating support.
35536 This packet is required for correct non-stop mode operation.
35539 The packet indicates the target stopped for a hardware breakpoint.
35540 The @var{r} part must be left empty.
35542 The same remarks about @samp{qSupported} and non-stop mode above
35545 @cindex fork events, remote reply
35547 The packet indicates that @code{fork} was called, and @var{r}
35548 is the thread ID of the new child process. Refer to
35549 @ref{thread-id syntax} for the format of the @var{thread-id}
35550 field. This packet is only applicable to targets that support
35553 This packet should not be sent by default; older @value{GDBN} versions
35554 did not support it. @value{GDBN} requests it, by supplying an
35555 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35556 remote stub must also supply the appropriate @samp{qSupported} feature
35557 indicating support.
35559 @cindex vfork events, remote reply
35561 The packet indicates that @code{vfork} was called, and @var{r}
35562 is the thread ID of the new child process. Refer to
35563 @ref{thread-id syntax} for the format of the @var{thread-id}
35564 field. This packet is only applicable to targets that support
35567 This packet should not be sent by default; older @value{GDBN} versions
35568 did not support it. @value{GDBN} requests it, by supplying an
35569 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35570 remote stub must also supply the appropriate @samp{qSupported} feature
35571 indicating support.
35573 @cindex vforkdone events, remote reply
35575 The packet indicates that a child process created by a vfork
35576 has either called @code{exec} or terminated, so that the
35577 address spaces of the parent and child process are no longer
35578 shared. The @var{r} part is ignored. This packet is only
35579 applicable to targets that support vforkdone events.
35581 This packet should not be sent by default; older @value{GDBN} versions
35582 did not support it. @value{GDBN} requests it, by supplying an
35583 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35584 remote stub must also supply the appropriate @samp{qSupported} feature
35585 indicating support.
35587 @cindex exec events, remote reply
35589 The packet indicates that @code{execve} was called, and @var{r}
35590 is the absolute pathname of the file that was executed, in hex.
35591 This packet is only applicable to targets that support exec events.
35593 This packet should not be sent by default; older @value{GDBN} versions
35594 did not support it. @value{GDBN} requests it, by supplying an
35595 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35596 remote stub must also supply the appropriate @samp{qSupported} feature
35597 indicating support.
35599 @cindex thread create event, remote reply
35600 @anchor{thread create event}
35602 The packet indicates that the thread was just created. The new thread
35603 is stopped until @value{GDBN} sets it running with a resumption packet
35604 (@pxref{vCont packet}). This packet should not be sent by default;
35605 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35606 also the @samp{w} (@ref{thread exit event}) remote reply below.
35611 @itemx W @var{AA} ; process:@var{pid}
35612 The process exited, and @var{AA} is the exit status. This is only
35613 applicable to certain targets.
35615 The second form of the response, including the process ID of the exited
35616 process, can be used only when @value{GDBN} has reported support for
35617 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35618 The @var{pid} is formatted as a big-endian hex string.
35621 @itemx X @var{AA} ; process:@var{pid}
35622 The process terminated with signal @var{AA}.
35624 The second form of the response, including the process ID of the
35625 terminated process, can be used only when @value{GDBN} has reported
35626 support for multiprocess protocol extensions; see @ref{multiprocess
35627 extensions}. The @var{pid} is formatted as a big-endian hex string.
35629 @anchor{thread exit event}
35630 @cindex thread exit event, remote reply
35631 @item w @var{AA} ; @var{tid}
35633 The thread exited, and @var{AA} is the exit status. This response
35634 should not be sent by default; @value{GDBN} requests it with the
35635 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35638 There are no resumed threads left in the target. In other words, even
35639 though the process is alive, the last resumed thread has exited. For
35640 example, say the target process has two threads: thread 1 and thread
35641 2. The client leaves thread 1 stopped, and resumes thread 2, which
35642 subsequently exits. At this point, even though the process is still
35643 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35644 executing either. The @samp{N} stop reply thus informs the client
35645 that it can stop waiting for stop replies. This packet should not be
35646 sent by default; older @value{GDBN} versions did not support it.
35647 @value{GDBN} requests it, by supplying an appropriate
35648 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35649 also supply the appropriate @samp{qSupported} feature indicating
35652 @item O @var{XX}@dots{}
35653 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35654 written as the program's console output. This can happen at any time
35655 while the program is running and the debugger should continue to wait
35656 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35658 @item F @var{call-id},@var{parameter}@dots{}
35659 @var{call-id} is the identifier which says which host system call should
35660 be called. This is just the name of the function. Translation into the
35661 correct system call is only applicable as it's defined in @value{GDBN}.
35662 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35665 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35666 this very system call.
35668 The target replies with this packet when it expects @value{GDBN} to
35669 call a host system call on behalf of the target. @value{GDBN} replies
35670 with an appropriate @samp{F} packet and keeps up waiting for the next
35671 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35672 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35673 Protocol Extension}, for more details.
35677 @node General Query Packets
35678 @section General Query Packets
35679 @cindex remote query requests
35681 Packets starting with @samp{q} are @dfn{general query packets};
35682 packets starting with @samp{Q} are @dfn{general set packets}. General
35683 query and set packets are a semi-unified form for retrieving and
35684 sending information to and from the stub.
35686 The initial letter of a query or set packet is followed by a name
35687 indicating what sort of thing the packet applies to. For example,
35688 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35689 definitions with the stub. These packet names follow some
35694 The name must not contain commas, colons or semicolons.
35696 Most @value{GDBN} query and set packets have a leading upper case
35699 The names of custom vendor packets should use a company prefix, in
35700 lower case, followed by a period. For example, packets designed at
35701 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35702 foos) or @samp{Qacme.bar} (for setting bars).
35705 The name of a query or set packet should be separated from any
35706 parameters by a @samp{:}; the parameters themselves should be
35707 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35708 full packet name, and check for a separator or the end of the packet,
35709 in case two packet names share a common prefix. New packets should not begin
35710 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35711 packets predate these conventions, and have arguments without any terminator
35712 for the packet name; we suspect they are in widespread use in places that
35713 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35714 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35717 Like the descriptions of the other packets, each description here
35718 has a template showing the packet's overall syntax, followed by an
35719 explanation of the packet's meaning. We include spaces in some of the
35720 templates for clarity; these are not part of the packet's syntax. No
35721 @value{GDBN} packet uses spaces to separate its components.
35723 Here are the currently defined query and set packets:
35729 Turn on or off the agent as a helper to perform some debugging operations
35730 delegated from @value{GDBN} (@pxref{Control Agent}).
35732 @item QAllow:@var{op}:@var{val}@dots{}
35733 @cindex @samp{QAllow} packet
35734 Specify which operations @value{GDBN} expects to request of the
35735 target, as a semicolon-separated list of operation name and value
35736 pairs. Possible values for @var{op} include @samp{WriteReg},
35737 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35738 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35739 indicating that @value{GDBN} will not request the operation, or 1,
35740 indicating that it may. (The target can then use this to set up its
35741 own internals optimally, for instance if the debugger never expects to
35742 insert breakpoints, it may not need to install its own trap handler.)
35745 @cindex current thread, remote request
35746 @cindex @samp{qC} packet
35747 Return the current thread ID.
35751 @item QC @var{thread-id}
35752 Where @var{thread-id} is a thread ID as documented in
35753 @ref{thread-id syntax}.
35754 @item @r{(anything else)}
35755 Any other reply implies the old thread ID.
35758 @item qCRC:@var{addr},@var{length}
35759 @cindex CRC of memory block, remote request
35760 @cindex @samp{qCRC} packet
35761 @anchor{qCRC packet}
35762 Compute the CRC checksum of a block of memory using CRC-32 defined in
35763 IEEE 802.3. The CRC is computed byte at a time, taking the most
35764 significant bit of each byte first. The initial pattern code
35765 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35767 @emph{Note:} This is the same CRC used in validating separate debug
35768 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35769 Files}). However the algorithm is slightly different. When validating
35770 separate debug files, the CRC is computed taking the @emph{least}
35771 significant bit of each byte first, and the final result is inverted to
35772 detect trailing zeros.
35777 An error (such as memory fault)
35778 @item C @var{crc32}
35779 The specified memory region's checksum is @var{crc32}.
35782 @item QDisableRandomization:@var{value}
35783 @cindex disable address space randomization, remote request
35784 @cindex @samp{QDisableRandomization} packet
35785 Some target operating systems will randomize the virtual address space
35786 of the inferior process as a security feature, but provide a feature
35787 to disable such randomization, e.g.@: to allow for a more deterministic
35788 debugging experience. On such systems, this packet with a @var{value}
35789 of 1 directs the target to disable address space randomization for
35790 processes subsequently started via @samp{vRun} packets, while a packet
35791 with a @var{value} of 0 tells the target to enable address space
35794 This packet is only available in extended mode (@pxref{extended mode}).
35799 The request succeeded.
35802 An error occurred. The error number @var{nn} is given as hex digits.
35805 An empty reply indicates that @samp{QDisableRandomization} is not supported
35809 This packet is not probed by default; the remote stub must request it,
35810 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35811 This should only be done on targets that actually support disabling
35812 address space randomization.
35815 @itemx qsThreadInfo
35816 @cindex list active threads, remote request
35817 @cindex @samp{qfThreadInfo} packet
35818 @cindex @samp{qsThreadInfo} packet
35819 Obtain a list of all active thread IDs from the target (OS). Since there
35820 may be too many active threads to fit into one reply packet, this query
35821 works iteratively: it may require more than one query/reply sequence to
35822 obtain the entire list of threads. The first query of the sequence will
35823 be the @samp{qfThreadInfo} query; subsequent queries in the
35824 sequence will be the @samp{qsThreadInfo} query.
35826 NOTE: This packet replaces the @samp{qL} query (see below).
35830 @item m @var{thread-id}
35832 @item m @var{thread-id},@var{thread-id}@dots{}
35833 a comma-separated list of thread IDs
35835 (lower case letter @samp{L}) denotes end of list.
35838 In response to each query, the target will reply with a list of one or
35839 more thread IDs, separated by commas.
35840 @value{GDBN} will respond to each reply with a request for more thread
35841 ids (using the @samp{qs} form of the query), until the target responds
35842 with @samp{l} (lower-case ell, for @dfn{last}).
35843 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35846 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35847 initial connection with the remote target, and the very first thread ID
35848 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35849 message. Therefore, the stub should ensure that the first thread ID in
35850 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35852 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35853 @cindex get thread-local storage address, remote request
35854 @cindex @samp{qGetTLSAddr} packet
35855 Fetch the address associated with thread local storage specified
35856 by @var{thread-id}, @var{offset}, and @var{lm}.
35858 @var{thread-id} is the thread ID associated with the
35859 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35861 @var{offset} is the (big endian, hex encoded) offset associated with the
35862 thread local variable. (This offset is obtained from the debug
35863 information associated with the variable.)
35865 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35866 load module associated with the thread local storage. For example,
35867 a @sc{gnu}/Linux system will pass the link map address of the shared
35868 object associated with the thread local storage under consideration.
35869 Other operating environments may choose to represent the load module
35870 differently, so the precise meaning of this parameter will vary.
35874 @item @var{XX}@dots{}
35875 Hex encoded (big endian) bytes representing the address of the thread
35876 local storage requested.
35879 An error occurred. The error number @var{nn} is given as hex digits.
35882 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35885 @item qGetTIBAddr:@var{thread-id}
35886 @cindex get thread information block address
35887 @cindex @samp{qGetTIBAddr} packet
35888 Fetch address of the Windows OS specific Thread Information Block.
35890 @var{thread-id} is the thread ID associated with the thread.
35894 @item @var{XX}@dots{}
35895 Hex encoded (big endian) bytes representing the linear address of the
35896 thread information block.
35899 An error occured. This means that either the thread was not found, or the
35900 address could not be retrieved.
35903 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35906 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35907 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35908 digit) is one to indicate the first query and zero to indicate a
35909 subsequent query; @var{threadcount} (two hex digits) is the maximum
35910 number of threads the response packet can contain; and @var{nextthread}
35911 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35912 returned in the response as @var{argthread}.
35914 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35918 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35919 Where: @var{count} (two hex digits) is the number of threads being
35920 returned; @var{done} (one hex digit) is zero to indicate more threads
35921 and one indicates no further threads; @var{argthreadid} (eight hex
35922 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35923 is a sequence of thread IDs, @var{threadid} (eight hex
35924 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35928 @cindex section offsets, remote request
35929 @cindex @samp{qOffsets} packet
35930 Get section offsets that the target used when relocating the downloaded
35935 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35936 Relocate the @code{Text} section by @var{xxx} from its original address.
35937 Relocate the @code{Data} section by @var{yyy} from its original address.
35938 If the object file format provides segment information (e.g.@: @sc{elf}
35939 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35940 segments by the supplied offsets.
35942 @emph{Note: while a @code{Bss} offset may be included in the response,
35943 @value{GDBN} ignores this and instead applies the @code{Data} offset
35944 to the @code{Bss} section.}
35946 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35947 Relocate the first segment of the object file, which conventionally
35948 contains program code, to a starting address of @var{xxx}. If
35949 @samp{DataSeg} is specified, relocate the second segment, which
35950 conventionally contains modifiable data, to a starting address of
35951 @var{yyy}. @value{GDBN} will report an error if the object file
35952 does not contain segment information, or does not contain at least
35953 as many segments as mentioned in the reply. Extra segments are
35954 kept at fixed offsets relative to the last relocated segment.
35957 @item qP @var{mode} @var{thread-id}
35958 @cindex thread information, remote request
35959 @cindex @samp{qP} packet
35960 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35961 encoded 32 bit mode; @var{thread-id} is a thread ID
35962 (@pxref{thread-id syntax}).
35964 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35967 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35971 @cindex non-stop mode, remote request
35972 @cindex @samp{QNonStop} packet
35974 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35975 @xref{Remote Non-Stop}, for more information.
35980 The request succeeded.
35983 An error occurred. The error number @var{nn} is given as hex digits.
35986 An empty reply indicates that @samp{QNonStop} is not supported by
35990 This packet is not probed by default; the remote stub must request it,
35991 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35992 Use of this packet is controlled by the @code{set non-stop} command;
35993 @pxref{Non-Stop Mode}.
35995 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35996 @cindex pass signals to inferior, remote request
35997 @cindex @samp{QPassSignals} packet
35998 @anchor{QPassSignals}
35999 Each listed @var{signal} should be passed directly to the inferior process.
36000 Signals are numbered identically to continue packets and stop replies
36001 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36002 strictly greater than the previous item. These signals do not need to stop
36003 the inferior, or be reported to @value{GDBN}. All other signals should be
36004 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36005 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36006 new list. This packet improves performance when using @samp{handle
36007 @var{signal} nostop noprint pass}.
36012 The request succeeded.
36015 An error occurred. The error number @var{nn} is given as hex digits.
36018 An empty reply indicates that @samp{QPassSignals} is not supported by
36022 Use of this packet is controlled by the @code{set remote pass-signals}
36023 command (@pxref{Remote Configuration, set remote pass-signals}).
36024 This packet is not probed by default; the remote stub must request it,
36025 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36027 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36028 @cindex signals the inferior may see, remote request
36029 @cindex @samp{QProgramSignals} packet
36030 @anchor{QProgramSignals}
36031 Each listed @var{signal} may be delivered to the inferior process.
36032 Others should be silently discarded.
36034 In some cases, the remote stub may need to decide whether to deliver a
36035 signal to the program or not without @value{GDBN} involvement. One
36036 example of that is while detaching --- the program's threads may have
36037 stopped for signals that haven't yet had a chance of being reported to
36038 @value{GDBN}, and so the remote stub can use the signal list specified
36039 by this packet to know whether to deliver or ignore those pending
36042 This does not influence whether to deliver a signal as requested by a
36043 resumption packet (@pxref{vCont packet}).
36045 Signals are numbered identically to continue packets and stop replies
36046 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36047 strictly greater than the previous item. Multiple
36048 @samp{QProgramSignals} packets do not combine; any earlier
36049 @samp{QProgramSignals} list is completely replaced by the new list.
36054 The request succeeded.
36057 An error occurred. The error number @var{nn} is given as hex digits.
36060 An empty reply indicates that @samp{QProgramSignals} is not supported
36064 Use of this packet is controlled by the @code{set remote program-signals}
36065 command (@pxref{Remote Configuration, set remote program-signals}).
36066 This packet is not probed by default; the remote stub must request it,
36067 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36069 @anchor{QThreadEvents}
36070 @item QThreadEvents:1
36071 @itemx QThreadEvents:0
36072 @cindex thread create/exit events, remote request
36073 @cindex @samp{QThreadEvents} packet
36075 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36076 reporting of thread create and exit events. @xref{thread create
36077 event}, for the reply specifications. For example, this is used in
36078 non-stop mode when @value{GDBN} stops a set of threads and
36079 synchronously waits for the their corresponding stop replies. Without
36080 exit events, if one of the threads exits, @value{GDBN} would hang
36081 forever not knowing that it should no longer expect a stop for that
36082 same thread. @value{GDBN} does not enable this feature unless the
36083 stub reports that it supports it by including @samp{QThreadEvents+} in
36084 its @samp{qSupported} reply.
36089 The request succeeded.
36092 An error occurred. The error number @var{nn} is given as hex digits.
36095 An empty reply indicates that @samp{QThreadEvents} is not supported by
36099 Use of this packet is controlled by the @code{set remote thread-events}
36100 command (@pxref{Remote Configuration, set remote thread-events}).
36102 @item qRcmd,@var{command}
36103 @cindex execute remote command, remote request
36104 @cindex @samp{qRcmd} packet
36105 @var{command} (hex encoded) is passed to the local interpreter for
36106 execution. Invalid commands should be reported using the output
36107 string. Before the final result packet, the target may also respond
36108 with a number of intermediate @samp{O@var{output}} console output
36109 packets. @emph{Implementors should note that providing access to a
36110 stubs's interpreter may have security implications}.
36115 A command response with no output.
36117 A command response with the hex encoded output string @var{OUTPUT}.
36119 Indicate a badly formed request.
36121 An empty reply indicates that @samp{qRcmd} is not recognized.
36124 (Note that the @code{qRcmd} packet's name is separated from the
36125 command by a @samp{,}, not a @samp{:}, contrary to the naming
36126 conventions above. Please don't use this packet as a model for new
36129 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36130 @cindex searching memory, in remote debugging
36132 @cindex @samp{qSearch:memory} packet
36134 @cindex @samp{qSearch memory} packet
36135 @anchor{qSearch memory}
36136 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36137 Both @var{address} and @var{length} are encoded in hex;
36138 @var{search-pattern} is a sequence of bytes, also hex encoded.
36143 The pattern was not found.
36145 The pattern was found at @var{address}.
36147 A badly formed request or an error was encountered while searching memory.
36149 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36152 @item QStartNoAckMode
36153 @cindex @samp{QStartNoAckMode} packet
36154 @anchor{QStartNoAckMode}
36155 Request that the remote stub disable the normal @samp{+}/@samp{-}
36156 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36161 The stub has switched to no-acknowledgment mode.
36162 @value{GDBN} acknowledges this reponse,
36163 but neither the stub nor @value{GDBN} shall send or expect further
36164 @samp{+}/@samp{-} acknowledgments in the current connection.
36166 An empty reply indicates that the stub does not support no-acknowledgment mode.
36169 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36170 @cindex supported packets, remote query
36171 @cindex features of the remote protocol
36172 @cindex @samp{qSupported} packet
36173 @anchor{qSupported}
36174 Tell the remote stub about features supported by @value{GDBN}, and
36175 query the stub for features it supports. This packet allows
36176 @value{GDBN} and the remote stub to take advantage of each others'
36177 features. @samp{qSupported} also consolidates multiple feature probes
36178 at startup, to improve @value{GDBN} performance---a single larger
36179 packet performs better than multiple smaller probe packets on
36180 high-latency links. Some features may enable behavior which must not
36181 be on by default, e.g.@: because it would confuse older clients or
36182 stubs. Other features may describe packets which could be
36183 automatically probed for, but are not. These features must be
36184 reported before @value{GDBN} will use them. This ``default
36185 unsupported'' behavior is not appropriate for all packets, but it
36186 helps to keep the initial connection time under control with new
36187 versions of @value{GDBN} which support increasing numbers of packets.
36191 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36192 The stub supports or does not support each returned @var{stubfeature},
36193 depending on the form of each @var{stubfeature} (see below for the
36196 An empty reply indicates that @samp{qSupported} is not recognized,
36197 or that no features needed to be reported to @value{GDBN}.
36200 The allowed forms for each feature (either a @var{gdbfeature} in the
36201 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36205 @item @var{name}=@var{value}
36206 The remote protocol feature @var{name} is supported, and associated
36207 with the specified @var{value}. The format of @var{value} depends
36208 on the feature, but it must not include a semicolon.
36210 The remote protocol feature @var{name} is supported, and does not
36211 need an associated value.
36213 The remote protocol feature @var{name} is not supported.
36215 The remote protocol feature @var{name} may be supported, and
36216 @value{GDBN} should auto-detect support in some other way when it is
36217 needed. This form will not be used for @var{gdbfeature} notifications,
36218 but may be used for @var{stubfeature} responses.
36221 Whenever the stub receives a @samp{qSupported} request, the
36222 supplied set of @value{GDBN} features should override any previous
36223 request. This allows @value{GDBN} to put the stub in a known
36224 state, even if the stub had previously been communicating with
36225 a different version of @value{GDBN}.
36227 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36232 This feature indicates whether @value{GDBN} supports multiprocess
36233 extensions to the remote protocol. @value{GDBN} does not use such
36234 extensions unless the stub also reports that it supports them by
36235 including @samp{multiprocess+} in its @samp{qSupported} reply.
36236 @xref{multiprocess extensions}, for details.
36239 This feature indicates that @value{GDBN} supports the XML target
36240 description. If the stub sees @samp{xmlRegisters=} with target
36241 specific strings separated by a comma, it will report register
36245 This feature indicates whether @value{GDBN} supports the
36246 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36247 instruction reply packet}).
36250 This feature indicates whether @value{GDBN} supports the swbreak stop
36251 reason in stop replies. @xref{swbreak stop reason}, for details.
36254 This feature indicates whether @value{GDBN} supports the hwbreak stop
36255 reason in stop replies. @xref{swbreak stop reason}, for details.
36258 This feature indicates whether @value{GDBN} supports fork event
36259 extensions to the remote protocol. @value{GDBN} does not use such
36260 extensions unless the stub also reports that it supports them by
36261 including @samp{fork-events+} in its @samp{qSupported} reply.
36264 This feature indicates whether @value{GDBN} supports vfork event
36265 extensions to the remote protocol. @value{GDBN} does not use such
36266 extensions unless the stub also reports that it supports them by
36267 including @samp{vfork-events+} in its @samp{qSupported} reply.
36270 This feature indicates whether @value{GDBN} supports exec event
36271 extensions to the remote protocol. @value{GDBN} does not use such
36272 extensions unless the stub also reports that it supports them by
36273 including @samp{exec-events+} in its @samp{qSupported} reply.
36275 @item vContSupported
36276 This feature indicates whether @value{GDBN} wants to know the
36277 supported actions in the reply to @samp{vCont?} packet.
36280 Stubs should ignore any unknown values for
36281 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36282 packet supports receiving packets of unlimited length (earlier
36283 versions of @value{GDBN} may reject overly long responses). Additional values
36284 for @var{gdbfeature} may be defined in the future to let the stub take
36285 advantage of new features in @value{GDBN}, e.g.@: incompatible
36286 improvements in the remote protocol---the @samp{multiprocess} feature is
36287 an example of such a feature. The stub's reply should be independent
36288 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36289 describes all the features it supports, and then the stub replies with
36290 all the features it supports.
36292 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36293 responses, as long as each response uses one of the standard forms.
36295 Some features are flags. A stub which supports a flag feature
36296 should respond with a @samp{+} form response. Other features
36297 require values, and the stub should respond with an @samp{=}
36300 Each feature has a default value, which @value{GDBN} will use if
36301 @samp{qSupported} is not available or if the feature is not mentioned
36302 in the @samp{qSupported} response. The default values are fixed; a
36303 stub is free to omit any feature responses that match the defaults.
36305 Not all features can be probed, but for those which can, the probing
36306 mechanism is useful: in some cases, a stub's internal
36307 architecture may not allow the protocol layer to know some information
36308 about the underlying target in advance. This is especially common in
36309 stubs which may be configured for multiple targets.
36311 These are the currently defined stub features and their properties:
36313 @multitable @columnfractions 0.35 0.2 0.12 0.2
36314 @c NOTE: The first row should be @headitem, but we do not yet require
36315 @c a new enough version of Texinfo (4.7) to use @headitem.
36317 @tab Value Required
36321 @item @samp{PacketSize}
36326 @item @samp{qXfer:auxv:read}
36331 @item @samp{qXfer:btrace:read}
36336 @item @samp{qXfer:btrace-conf:read}
36341 @item @samp{qXfer:exec-file:read}
36346 @item @samp{qXfer:features:read}
36351 @item @samp{qXfer:libraries:read}
36356 @item @samp{qXfer:libraries-svr4:read}
36361 @item @samp{augmented-libraries-svr4-read}
36366 @item @samp{qXfer:memory-map:read}
36371 @item @samp{qXfer:sdata:read}
36376 @item @samp{qXfer:spu:read}
36381 @item @samp{qXfer:spu:write}
36386 @item @samp{qXfer:siginfo:read}
36391 @item @samp{qXfer:siginfo:write}
36396 @item @samp{qXfer:threads:read}
36401 @item @samp{qXfer:traceframe-info:read}
36406 @item @samp{qXfer:uib:read}
36411 @item @samp{qXfer:fdpic:read}
36416 @item @samp{Qbtrace:off}
36421 @item @samp{Qbtrace:bts}
36426 @item @samp{Qbtrace:pt}
36431 @item @samp{Qbtrace-conf:bts:size}
36436 @item @samp{Qbtrace-conf:pt:size}
36441 @item @samp{QNonStop}
36446 @item @samp{QPassSignals}
36451 @item @samp{QStartNoAckMode}
36456 @item @samp{multiprocess}
36461 @item @samp{ConditionalBreakpoints}
36466 @item @samp{ConditionalTracepoints}
36471 @item @samp{ReverseContinue}
36476 @item @samp{ReverseStep}
36481 @item @samp{TracepointSource}
36486 @item @samp{QAgent}
36491 @item @samp{QAllow}
36496 @item @samp{QDisableRandomization}
36501 @item @samp{EnableDisableTracepoints}
36506 @item @samp{QTBuffer:size}
36511 @item @samp{tracenz}
36516 @item @samp{BreakpointCommands}
36521 @item @samp{swbreak}
36526 @item @samp{hwbreak}
36531 @item @samp{fork-events}
36536 @item @samp{vfork-events}
36541 @item @samp{exec-events}
36546 @item @samp{QThreadEvents}
36551 @item @samp{no-resumed}
36558 These are the currently defined stub features, in more detail:
36561 @cindex packet size, remote protocol
36562 @item PacketSize=@var{bytes}
36563 The remote stub can accept packets up to at least @var{bytes} in
36564 length. @value{GDBN} will send packets up to this size for bulk
36565 transfers, and will never send larger packets. This is a limit on the
36566 data characters in the packet, including the frame and checksum.
36567 There is no trailing NUL byte in a remote protocol packet; if the stub
36568 stores packets in a NUL-terminated format, it should allow an extra
36569 byte in its buffer for the NUL. If this stub feature is not supported,
36570 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36572 @item qXfer:auxv:read
36573 The remote stub understands the @samp{qXfer:auxv:read} packet
36574 (@pxref{qXfer auxiliary vector read}).
36576 @item qXfer:btrace:read
36577 The remote stub understands the @samp{qXfer:btrace:read}
36578 packet (@pxref{qXfer btrace read}).
36580 @item qXfer:btrace-conf:read
36581 The remote stub understands the @samp{qXfer:btrace-conf:read}
36582 packet (@pxref{qXfer btrace-conf read}).
36584 @item qXfer:exec-file:read
36585 The remote stub understands the @samp{qXfer:exec-file:read} packet
36586 (@pxref{qXfer executable filename read}).
36588 @item qXfer:features:read
36589 The remote stub understands the @samp{qXfer:features:read} packet
36590 (@pxref{qXfer target description read}).
36592 @item qXfer:libraries:read
36593 The remote stub understands the @samp{qXfer:libraries:read} packet
36594 (@pxref{qXfer library list read}).
36596 @item qXfer:libraries-svr4:read
36597 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36598 (@pxref{qXfer svr4 library list read}).
36600 @item augmented-libraries-svr4-read
36601 The remote stub understands the augmented form of the
36602 @samp{qXfer:libraries-svr4:read} packet
36603 (@pxref{qXfer svr4 library list read}).
36605 @item qXfer:memory-map:read
36606 The remote stub understands the @samp{qXfer:memory-map:read} packet
36607 (@pxref{qXfer memory map read}).
36609 @item qXfer:sdata:read
36610 The remote stub understands the @samp{qXfer:sdata:read} packet
36611 (@pxref{qXfer sdata read}).
36613 @item qXfer:spu:read
36614 The remote stub understands the @samp{qXfer:spu:read} packet
36615 (@pxref{qXfer spu read}).
36617 @item qXfer:spu:write
36618 The remote stub understands the @samp{qXfer:spu:write} packet
36619 (@pxref{qXfer spu write}).
36621 @item qXfer:siginfo:read
36622 The remote stub understands the @samp{qXfer:siginfo:read} packet
36623 (@pxref{qXfer siginfo read}).
36625 @item qXfer:siginfo:write
36626 The remote stub understands the @samp{qXfer:siginfo:write} packet
36627 (@pxref{qXfer siginfo write}).
36629 @item qXfer:threads:read
36630 The remote stub understands the @samp{qXfer:threads:read} packet
36631 (@pxref{qXfer threads read}).
36633 @item qXfer:traceframe-info:read
36634 The remote stub understands the @samp{qXfer:traceframe-info:read}
36635 packet (@pxref{qXfer traceframe info read}).
36637 @item qXfer:uib:read
36638 The remote stub understands the @samp{qXfer:uib:read}
36639 packet (@pxref{qXfer unwind info block}).
36641 @item qXfer:fdpic:read
36642 The remote stub understands the @samp{qXfer:fdpic:read}
36643 packet (@pxref{qXfer fdpic loadmap read}).
36646 The remote stub understands the @samp{QNonStop} packet
36647 (@pxref{QNonStop}).
36650 The remote stub understands the @samp{QPassSignals} packet
36651 (@pxref{QPassSignals}).
36653 @item QStartNoAckMode
36654 The remote stub understands the @samp{QStartNoAckMode} packet and
36655 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36658 @anchor{multiprocess extensions}
36659 @cindex multiprocess extensions, in remote protocol
36660 The remote stub understands the multiprocess extensions to the remote
36661 protocol syntax. The multiprocess extensions affect the syntax of
36662 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36663 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36664 replies. Note that reporting this feature indicates support for the
36665 syntactic extensions only, not that the stub necessarily supports
36666 debugging of more than one process at a time. The stub must not use
36667 multiprocess extensions in packet replies unless @value{GDBN} has also
36668 indicated it supports them in its @samp{qSupported} request.
36670 @item qXfer:osdata:read
36671 The remote stub understands the @samp{qXfer:osdata:read} packet
36672 ((@pxref{qXfer osdata read}).
36674 @item ConditionalBreakpoints
36675 The target accepts and implements evaluation of conditional expressions
36676 defined for breakpoints. The target will only report breakpoint triggers
36677 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36679 @item ConditionalTracepoints
36680 The remote stub accepts and implements conditional expressions defined
36681 for tracepoints (@pxref{Tracepoint Conditions}).
36683 @item ReverseContinue
36684 The remote stub accepts and implements the reverse continue packet
36688 The remote stub accepts and implements the reverse step packet
36691 @item TracepointSource
36692 The remote stub understands the @samp{QTDPsrc} packet that supplies
36693 the source form of tracepoint definitions.
36696 The remote stub understands the @samp{QAgent} packet.
36699 The remote stub understands the @samp{QAllow} packet.
36701 @item QDisableRandomization
36702 The remote stub understands the @samp{QDisableRandomization} packet.
36704 @item StaticTracepoint
36705 @cindex static tracepoints, in remote protocol
36706 The remote stub supports static tracepoints.
36708 @item InstallInTrace
36709 @anchor{install tracepoint in tracing}
36710 The remote stub supports installing tracepoint in tracing.
36712 @item EnableDisableTracepoints
36713 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36714 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36715 to be enabled and disabled while a trace experiment is running.
36717 @item QTBuffer:size
36718 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36719 packet that allows to change the size of the trace buffer.
36722 @cindex string tracing, in remote protocol
36723 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36724 See @ref{Bytecode Descriptions} for details about the bytecode.
36726 @item BreakpointCommands
36727 @cindex breakpoint commands, in remote protocol
36728 The remote stub supports running a breakpoint's command list itself,
36729 rather than reporting the hit to @value{GDBN}.
36732 The remote stub understands the @samp{Qbtrace:off} packet.
36735 The remote stub understands the @samp{Qbtrace:bts} packet.
36738 The remote stub understands the @samp{Qbtrace:pt} packet.
36740 @item Qbtrace-conf:bts:size
36741 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36743 @item Qbtrace-conf:pt:size
36744 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36747 The remote stub reports the @samp{swbreak} stop reason for memory
36751 The remote stub reports the @samp{hwbreak} stop reason for hardware
36755 The remote stub reports the @samp{fork} stop reason for fork events.
36758 The remote stub reports the @samp{vfork} stop reason for vfork events
36759 and vforkdone events.
36762 The remote stub reports the @samp{exec} stop reason for exec events.
36764 @item vContSupported
36765 The remote stub reports the supported actions in the reply to
36766 @samp{vCont?} packet.
36768 @item QThreadEvents
36769 The remote stub understands the @samp{QThreadEvents} packet.
36772 The remote stub reports the @samp{N} stop reply.
36777 @cindex symbol lookup, remote request
36778 @cindex @samp{qSymbol} packet
36779 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36780 requests. Accept requests from the target for the values of symbols.
36785 The target does not need to look up any (more) symbols.
36786 @item qSymbol:@var{sym_name}
36787 The target requests the value of symbol @var{sym_name} (hex encoded).
36788 @value{GDBN} may provide the value by using the
36789 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36793 @item qSymbol:@var{sym_value}:@var{sym_name}
36794 Set the value of @var{sym_name} to @var{sym_value}.
36796 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36797 target has previously requested.
36799 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36800 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36806 The target does not need to look up any (more) symbols.
36807 @item qSymbol:@var{sym_name}
36808 The target requests the value of a new symbol @var{sym_name} (hex
36809 encoded). @value{GDBN} will continue to supply the values of symbols
36810 (if available), until the target ceases to request them.
36815 @itemx QTDisconnected
36822 @itemx qTMinFTPILen
36824 @xref{Tracepoint Packets}.
36826 @item qThreadExtraInfo,@var{thread-id}
36827 @cindex thread attributes info, remote request
36828 @cindex @samp{qThreadExtraInfo} packet
36829 Obtain from the target OS a printable string description of thread
36830 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36831 for the forms of @var{thread-id}. This
36832 string may contain anything that the target OS thinks is interesting
36833 for @value{GDBN} to tell the user about the thread. The string is
36834 displayed in @value{GDBN}'s @code{info threads} display. Some
36835 examples of possible thread extra info strings are @samp{Runnable}, or
36836 @samp{Blocked on Mutex}.
36840 @item @var{XX}@dots{}
36841 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36842 comprising the printable string containing the extra information about
36843 the thread's attributes.
36846 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36847 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36848 conventions above. Please don't use this packet as a model for new
36867 @xref{Tracepoint Packets}.
36869 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36870 @cindex read special object, remote request
36871 @cindex @samp{qXfer} packet
36872 @anchor{qXfer read}
36873 Read uninterpreted bytes from the target's special data area
36874 identified by the keyword @var{object}. Request @var{length} bytes
36875 starting at @var{offset} bytes into the data. The content and
36876 encoding of @var{annex} is specific to @var{object}; it can supply
36877 additional details about what data to access.
36879 Here are the specific requests of this form defined so far. All
36880 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36881 formats, listed below.
36884 @item qXfer:auxv:read::@var{offset},@var{length}
36885 @anchor{qXfer auxiliary vector read}
36886 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36887 auxiliary vector}. Note @var{annex} must be empty.
36889 This packet is not probed by default; the remote stub must request it,
36890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36892 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36893 @anchor{qXfer btrace read}
36895 Return a description of the current branch trace.
36896 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36897 packet may have one of the following values:
36901 Returns all available branch trace.
36904 Returns all available branch trace if the branch trace changed since
36905 the last read request.
36908 Returns the new branch trace since the last read request. Adds a new
36909 block to the end of the trace that begins at zero and ends at the source
36910 location of the first branch in the trace buffer. This extra block is
36911 used to stitch traces together.
36913 If the trace buffer overflowed, returns an error indicating the overflow.
36916 This packet is not probed by default; the remote stub must request it
36917 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36919 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36920 @anchor{qXfer btrace-conf read}
36922 Return a description of the current branch trace configuration.
36923 @xref{Branch Trace Configuration Format}.
36925 This packet is not probed by default; the remote stub must request it
36926 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36928 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36929 @anchor{qXfer executable filename read}
36930 Return the full absolute name of the file that was executed to create
36931 a process running on the remote system. The annex specifies the
36932 numeric process ID of the process to query, encoded as a hexadecimal
36933 number. If the annex part is empty the remote stub should return the
36934 filename corresponding to the currently executing process.
36936 This packet is not probed by default; the remote stub must request it,
36937 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36939 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36940 @anchor{qXfer target description read}
36941 Access the @dfn{target description}. @xref{Target Descriptions}. The
36942 annex specifies which XML document to access. The main description is
36943 always loaded from the @samp{target.xml} annex.
36945 This packet is not probed by default; the remote stub must request it,
36946 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36948 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36949 @anchor{qXfer library list read}
36950 Access the target's list of loaded libraries. @xref{Library List Format}.
36951 The annex part of the generic @samp{qXfer} packet must be empty
36952 (@pxref{qXfer read}).
36954 Targets which maintain a list of libraries in the program's memory do
36955 not need to implement this packet; it is designed for platforms where
36956 the operating system manages the list of loaded libraries.
36958 This packet is not probed by default; the remote stub must request it,
36959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36961 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36962 @anchor{qXfer svr4 library list read}
36963 Access the target's list of loaded libraries when the target is an SVR4
36964 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36965 of the generic @samp{qXfer} packet must be empty unless the remote
36966 stub indicated it supports the augmented form of this packet
36967 by supplying an appropriate @samp{qSupported} response
36968 (@pxref{qXfer read}, @ref{qSupported}).
36970 This packet is optional for better performance on SVR4 targets.
36971 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36973 This packet is not probed by default; the remote stub must request it,
36974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36976 If the remote stub indicates it supports the augmented form of this
36977 packet then the annex part of the generic @samp{qXfer} packet may
36978 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36979 arguments. The currently supported arguments are:
36982 @item start=@var{address}
36983 A hexadecimal number specifying the address of the @samp{struct
36984 link_map} to start reading the library list from. If unset or zero
36985 then the first @samp{struct link_map} in the library list will be
36986 chosen as the starting point.
36988 @item prev=@var{address}
36989 A hexadecimal number specifying the address of the @samp{struct
36990 link_map} immediately preceding the @samp{struct link_map}
36991 specified by the @samp{start} argument. If unset or zero then
36992 the remote stub will expect that no @samp{struct link_map}
36993 exists prior to the starting point.
36997 Arguments that are not understood by the remote stub will be silently
37000 @item qXfer:memory-map:read::@var{offset},@var{length}
37001 @anchor{qXfer memory map read}
37002 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37003 annex part of the generic @samp{qXfer} packet must be empty
37004 (@pxref{qXfer read}).
37006 This packet is not probed by default; the remote stub must request it,
37007 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37009 @item qXfer:sdata:read::@var{offset},@var{length}
37010 @anchor{qXfer sdata read}
37012 Read contents of the extra collected static tracepoint marker
37013 information. The annex part of the generic @samp{qXfer} packet must
37014 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37017 This packet is not probed by default; the remote stub must request it,
37018 by supplying an appropriate @samp{qSupported} response
37019 (@pxref{qSupported}).
37021 @item qXfer:siginfo:read::@var{offset},@var{length}
37022 @anchor{qXfer siginfo read}
37023 Read contents of the extra signal information on the target
37024 system. The annex part of the generic @samp{qXfer} packet must be
37025 empty (@pxref{qXfer read}).
37027 This packet is not probed by default; the remote stub must request it,
37028 by supplying an appropriate @samp{qSupported} response
37029 (@pxref{qSupported}).
37031 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37032 @anchor{qXfer spu read}
37033 Read contents of an @code{spufs} file on the target system. The
37034 annex specifies which file to read; it must be of the form
37035 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37036 in the target process, and @var{name} identifes the @code{spufs} file
37037 in that context to be accessed.
37039 This packet is not probed by default; the remote stub must request it,
37040 by supplying an appropriate @samp{qSupported} response
37041 (@pxref{qSupported}).
37043 @item qXfer:threads:read::@var{offset},@var{length}
37044 @anchor{qXfer threads read}
37045 Access the list of threads on target. @xref{Thread List Format}. The
37046 annex part of the generic @samp{qXfer} packet must be empty
37047 (@pxref{qXfer read}).
37049 This packet is not probed by default; the remote stub must request it,
37050 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37052 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37053 @anchor{qXfer traceframe info read}
37055 Return a description of the current traceframe's contents.
37056 @xref{Traceframe Info Format}. The annex part of the generic
37057 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37059 This packet is not probed by default; the remote stub must request it,
37060 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37062 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37063 @anchor{qXfer unwind info block}
37065 Return the unwind information block for @var{pc}. This packet is used
37066 on OpenVMS/ia64 to ask the kernel unwind information.
37068 This packet is not probed by default.
37070 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37071 @anchor{qXfer fdpic loadmap read}
37072 Read contents of @code{loadmap}s on the target system. The
37073 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37074 executable @code{loadmap} or interpreter @code{loadmap} to read.
37076 This packet is not probed by default; the remote stub must request it,
37077 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37079 @item qXfer:osdata:read::@var{offset},@var{length}
37080 @anchor{qXfer osdata read}
37081 Access the target's @dfn{operating system information}.
37082 @xref{Operating System Information}.
37089 Data @var{data} (@pxref{Binary Data}) has been read from the
37090 target. There may be more data at a higher address (although
37091 it is permitted to return @samp{m} even for the last valid
37092 block of data, as long as at least one byte of data was read).
37093 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37097 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37098 There is no more data to be read. It is possible for @var{data} to
37099 have fewer bytes than the @var{length} in the request.
37102 The @var{offset} in the request is at the end of the data.
37103 There is no more data to be read.
37106 The request was malformed, or @var{annex} was invalid.
37109 The offset was invalid, or there was an error encountered reading the data.
37110 The @var{nn} part is a hex-encoded @code{errno} value.
37113 An empty reply indicates the @var{object} string was not recognized by
37114 the stub, or that the object does not support reading.
37117 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37118 @cindex write data into object, remote request
37119 @anchor{qXfer write}
37120 Write uninterpreted bytes into the target's special data area
37121 identified by the keyword @var{object}, starting at @var{offset} bytes
37122 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37123 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37124 is specific to @var{object}; it can supply additional details about what data
37127 Here are the specific requests of this form defined so far. All
37128 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37129 formats, listed below.
37132 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37133 @anchor{qXfer siginfo write}
37134 Write @var{data} to the extra signal information on the target system.
37135 The annex part of the generic @samp{qXfer} packet must be
37136 empty (@pxref{qXfer write}).
37138 This packet is not probed by default; the remote stub must request it,
37139 by supplying an appropriate @samp{qSupported} response
37140 (@pxref{qSupported}).
37142 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37143 @anchor{qXfer spu write}
37144 Write @var{data} to an @code{spufs} file on the target system. The
37145 annex specifies which file to write; it must be of the form
37146 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37147 in the target process, and @var{name} identifes the @code{spufs} file
37148 in that context to be accessed.
37150 This packet is not probed by default; the remote stub must request it,
37151 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37157 @var{nn} (hex encoded) is the number of bytes written.
37158 This may be fewer bytes than supplied in the request.
37161 The request was malformed, or @var{annex} was invalid.
37164 The offset was invalid, or there was an error encountered writing the data.
37165 The @var{nn} part is a hex-encoded @code{errno} value.
37168 An empty reply indicates the @var{object} string was not
37169 recognized by the stub, or that the object does not support writing.
37172 @item qXfer:@var{object}:@var{operation}:@dots{}
37173 Requests of this form may be added in the future. When a stub does
37174 not recognize the @var{object} keyword, or its support for
37175 @var{object} does not recognize the @var{operation} keyword, the stub
37176 must respond with an empty packet.
37178 @item qAttached:@var{pid}
37179 @cindex query attached, remote request
37180 @cindex @samp{qAttached} packet
37181 Return an indication of whether the remote server attached to an
37182 existing process or created a new process. When the multiprocess
37183 protocol extensions are supported (@pxref{multiprocess extensions}),
37184 @var{pid} is an integer in hexadecimal format identifying the target
37185 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37186 the query packet will be simplified as @samp{qAttached}.
37188 This query is used, for example, to know whether the remote process
37189 should be detached or killed when a @value{GDBN} session is ended with
37190 the @code{quit} command.
37195 The remote server attached to an existing process.
37197 The remote server created a new process.
37199 A badly formed request or an error was encountered.
37203 Enable branch tracing for the current thread using Branch Trace Store.
37208 Branch tracing has been enabled.
37210 A badly formed request or an error was encountered.
37214 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37219 Branch tracing has been enabled.
37221 A badly formed request or an error was encountered.
37225 Disable branch tracing for the current thread.
37230 Branch tracing has been disabled.
37232 A badly formed request or an error was encountered.
37235 @item Qbtrace-conf:bts:size=@var{value}
37236 Set the requested ring buffer size for new threads that use the
37237 btrace recording method in bts format.
37242 The ring buffer size has been set.
37244 A badly formed request or an error was encountered.
37247 @item Qbtrace-conf:pt:size=@var{value}
37248 Set the requested ring buffer size for new threads that use the
37249 btrace recording method in pt format.
37254 The ring buffer size has been set.
37256 A badly formed request or an error was encountered.
37261 @node Architecture-Specific Protocol Details
37262 @section Architecture-Specific Protocol Details
37264 This section describes how the remote protocol is applied to specific
37265 target architectures. Also see @ref{Standard Target Features}, for
37266 details of XML target descriptions for each architecture.
37269 * ARM-Specific Protocol Details::
37270 * MIPS-Specific Protocol Details::
37273 @node ARM-Specific Protocol Details
37274 @subsection @acronym{ARM}-specific Protocol Details
37277 * ARM Breakpoint Kinds::
37280 @node ARM Breakpoint Kinds
37281 @subsubsection @acronym{ARM} Breakpoint Kinds
37282 @cindex breakpoint kinds, @acronym{ARM}
37284 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37289 16-bit Thumb mode breakpoint.
37292 32-bit Thumb mode (Thumb-2) breakpoint.
37295 32-bit @acronym{ARM} mode breakpoint.
37299 @node MIPS-Specific Protocol Details
37300 @subsection @acronym{MIPS}-specific Protocol Details
37303 * MIPS Register packet Format::
37304 * MIPS Breakpoint Kinds::
37307 @node MIPS Register packet Format
37308 @subsubsection @acronym{MIPS} Register Packet Format
37309 @cindex register packet format, @acronym{MIPS}
37311 The following @code{g}/@code{G} packets have previously been defined.
37312 In the below, some thirty-two bit registers are transferred as
37313 sixty-four bits. Those registers should be zero/sign extended (which?)
37314 to fill the space allocated. Register bytes are transferred in target
37315 byte order. The two nibbles within a register byte are transferred
37316 most-significant -- least-significant.
37321 All registers are transferred as thirty-two bit quantities in the order:
37322 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37323 registers; fsr; fir; fp.
37326 All registers are transferred as sixty-four bit quantities (including
37327 thirty-two bit registers such as @code{sr}). The ordering is the same
37332 @node MIPS Breakpoint Kinds
37333 @subsubsection @acronym{MIPS} Breakpoint Kinds
37334 @cindex breakpoint kinds, @acronym{MIPS}
37336 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37341 16-bit @acronym{MIPS16} mode breakpoint.
37344 16-bit @acronym{microMIPS} mode breakpoint.
37347 32-bit standard @acronym{MIPS} mode breakpoint.
37350 32-bit @acronym{microMIPS} mode breakpoint.
37354 @node Tracepoint Packets
37355 @section Tracepoint Packets
37356 @cindex tracepoint packets
37357 @cindex packets, tracepoint
37359 Here we describe the packets @value{GDBN} uses to implement
37360 tracepoints (@pxref{Tracepoints}).
37364 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37365 @cindex @samp{QTDP} packet
37366 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37367 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37368 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37369 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37370 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37371 the number of bytes that the target should copy elsewhere to make room
37372 for the tracepoint. If an @samp{X} is present, it introduces a
37373 tracepoint condition, which consists of a hexadecimal length, followed
37374 by a comma and hex-encoded bytes, in a manner similar to action
37375 encodings as described below. If the trailing @samp{-} is present,
37376 further @samp{QTDP} packets will follow to specify this tracepoint's
37382 The packet was understood and carried out.
37384 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37386 The packet was not recognized.
37389 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37390 Define actions to be taken when a tracepoint is hit. The @var{n} and
37391 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37392 this tracepoint. This packet may only be sent immediately after
37393 another @samp{QTDP} packet that ended with a @samp{-}. If the
37394 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37395 specifying more actions for this tracepoint.
37397 In the series of action packets for a given tracepoint, at most one
37398 can have an @samp{S} before its first @var{action}. If such a packet
37399 is sent, it and the following packets define ``while-stepping''
37400 actions. Any prior packets define ordinary actions --- that is, those
37401 taken when the tracepoint is first hit. If no action packet has an
37402 @samp{S}, then all the packets in the series specify ordinary
37403 tracepoint actions.
37405 The @samp{@var{action}@dots{}} portion of the packet is a series of
37406 actions, concatenated without separators. Each action has one of the
37412 Collect the registers whose bits are set in @var{mask},
37413 a hexadecimal number whose @var{i}'th bit is set if register number
37414 @var{i} should be collected. (The least significant bit is numbered
37415 zero.) Note that @var{mask} may be any number of digits long; it may
37416 not fit in a 32-bit word.
37418 @item M @var{basereg},@var{offset},@var{len}
37419 Collect @var{len} bytes of memory starting at the address in register
37420 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37421 @samp{-1}, then the range has a fixed address: @var{offset} is the
37422 address of the lowest byte to collect. The @var{basereg},
37423 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37424 values (the @samp{-1} value for @var{basereg} is a special case).
37426 @item X @var{len},@var{expr}
37427 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37428 it directs. The agent expression @var{expr} is as described in
37429 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37430 two-digit hex number in the packet; @var{len} is the number of bytes
37431 in the expression (and thus one-half the number of hex digits in the
37436 Any number of actions may be packed together in a single @samp{QTDP}
37437 packet, as long as the packet does not exceed the maximum packet
37438 length (400 bytes, for many stubs). There may be only one @samp{R}
37439 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37440 actions. Any registers referred to by @samp{M} and @samp{X} actions
37441 must be collected by a preceding @samp{R} action. (The
37442 ``while-stepping'' actions are treated as if they were attached to a
37443 separate tracepoint, as far as these restrictions are concerned.)
37448 The packet was understood and carried out.
37450 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37452 The packet was not recognized.
37455 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37456 @cindex @samp{QTDPsrc} packet
37457 Specify a source string of tracepoint @var{n} at address @var{addr}.
37458 This is useful to get accurate reproduction of the tracepoints
37459 originally downloaded at the beginning of the trace run. The @var{type}
37460 is the name of the tracepoint part, such as @samp{cond} for the
37461 tracepoint's conditional expression (see below for a list of types), while
37462 @var{bytes} is the string, encoded in hexadecimal.
37464 @var{start} is the offset of the @var{bytes} within the overall source
37465 string, while @var{slen} is the total length of the source string.
37466 This is intended for handling source strings that are longer than will
37467 fit in a single packet.
37468 @c Add detailed example when this info is moved into a dedicated
37469 @c tracepoint descriptions section.
37471 The available string types are @samp{at} for the location,
37472 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37473 @value{GDBN} sends a separate packet for each command in the action
37474 list, in the same order in which the commands are stored in the list.
37476 The target does not need to do anything with source strings except
37477 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37480 Although this packet is optional, and @value{GDBN} will only send it
37481 if the target replies with @samp{TracepointSource} @xref{General
37482 Query Packets}, it makes both disconnected tracing and trace files
37483 much easier to use. Otherwise the user must be careful that the
37484 tracepoints in effect while looking at trace frames are identical to
37485 the ones in effect during the trace run; even a small discrepancy
37486 could cause @samp{tdump} not to work, or a particular trace frame not
37489 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37490 @cindex define trace state variable, remote request
37491 @cindex @samp{QTDV} packet
37492 Create a new trace state variable, number @var{n}, with an initial
37493 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37494 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37495 the option of not using this packet for initial values of zero; the
37496 target should simply create the trace state variables as they are
37497 mentioned in expressions. The value @var{builtin} should be 1 (one)
37498 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37499 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37500 @samp{qTsV} packet had it set. The contents of @var{name} is the
37501 hex-encoded name (without the leading @samp{$}) of the trace state
37504 @item QTFrame:@var{n}
37505 @cindex @samp{QTFrame} packet
37506 Select the @var{n}'th tracepoint frame from the buffer, and use the
37507 register and memory contents recorded there to answer subsequent
37508 request packets from @value{GDBN}.
37510 A successful reply from the stub indicates that the stub has found the
37511 requested frame. The response is a series of parts, concatenated
37512 without separators, describing the frame we selected. Each part has
37513 one of the following forms:
37517 The selected frame is number @var{n} in the trace frame buffer;
37518 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37519 was no frame matching the criteria in the request packet.
37522 The selected trace frame records a hit of tracepoint number @var{t};
37523 @var{t} is a hexadecimal number.
37527 @item QTFrame:pc:@var{addr}
37528 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37529 currently selected frame whose PC is @var{addr};
37530 @var{addr} is a hexadecimal number.
37532 @item QTFrame:tdp:@var{t}
37533 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37534 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37535 is a hexadecimal number.
37537 @item QTFrame:range:@var{start}:@var{end}
37538 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37539 currently selected frame whose PC is between @var{start} (inclusive)
37540 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37543 @item QTFrame:outside:@var{start}:@var{end}
37544 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37545 frame @emph{outside} the given range of addresses (exclusive).
37548 @cindex @samp{qTMinFTPILen} packet
37549 This packet requests the minimum length of instruction at which a fast
37550 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37551 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37552 it depends on the target system being able to create trampolines in
37553 the first 64K of memory, which might or might not be possible for that
37554 system. So the reply to this packet will be 4 if it is able to
37561 The minimum instruction length is currently unknown.
37563 The minimum instruction length is @var{length}, where @var{length}
37564 is a hexadecimal number greater or equal to 1. A reply
37565 of 1 means that a fast tracepoint may be placed on any instruction
37566 regardless of size.
37568 An error has occurred.
37570 An empty reply indicates that the request is not supported by the stub.
37574 @cindex @samp{QTStart} packet
37575 Begin the tracepoint experiment. Begin collecting data from
37576 tracepoint hits in the trace frame buffer. This packet supports the
37577 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37578 instruction reply packet}).
37581 @cindex @samp{QTStop} packet
37582 End the tracepoint experiment. Stop collecting trace frames.
37584 @item QTEnable:@var{n}:@var{addr}
37586 @cindex @samp{QTEnable} packet
37587 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37588 experiment. If the tracepoint was previously disabled, then collection
37589 of data from it will resume.
37591 @item QTDisable:@var{n}:@var{addr}
37593 @cindex @samp{QTDisable} packet
37594 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37595 experiment. No more data will be collected from the tracepoint unless
37596 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37599 @cindex @samp{QTinit} packet
37600 Clear the table of tracepoints, and empty the trace frame buffer.
37602 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37603 @cindex @samp{QTro} packet
37604 Establish the given ranges of memory as ``transparent''. The stub
37605 will answer requests for these ranges from memory's current contents,
37606 if they were not collected as part of the tracepoint hit.
37608 @value{GDBN} uses this to mark read-only regions of memory, like those
37609 containing program code. Since these areas never change, they should
37610 still have the same contents they did when the tracepoint was hit, so
37611 there's no reason for the stub to refuse to provide their contents.
37613 @item QTDisconnected:@var{value}
37614 @cindex @samp{QTDisconnected} packet
37615 Set the choice to what to do with the tracing run when @value{GDBN}
37616 disconnects from the target. A @var{value} of 1 directs the target to
37617 continue the tracing run, while 0 tells the target to stop tracing if
37618 @value{GDBN} is no longer in the picture.
37621 @cindex @samp{qTStatus} packet
37622 Ask the stub if there is a trace experiment running right now.
37624 The reply has the form:
37628 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37629 @var{running} is a single digit @code{1} if the trace is presently
37630 running, or @code{0} if not. It is followed by semicolon-separated
37631 optional fields that an agent may use to report additional status.
37635 If the trace is not running, the agent may report any of several
37636 explanations as one of the optional fields:
37641 No trace has been run yet.
37643 @item tstop[:@var{text}]:0
37644 The trace was stopped by a user-originated stop command. The optional
37645 @var{text} field is a user-supplied string supplied as part of the
37646 stop command (for instance, an explanation of why the trace was
37647 stopped manually). It is hex-encoded.
37650 The trace stopped because the trace buffer filled up.
37652 @item tdisconnected:0
37653 The trace stopped because @value{GDBN} disconnected from the target.
37655 @item tpasscount:@var{tpnum}
37656 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37658 @item terror:@var{text}:@var{tpnum}
37659 The trace stopped because tracepoint @var{tpnum} had an error. The
37660 string @var{text} is available to describe the nature of the error
37661 (for instance, a divide by zero in the condition expression); it
37665 The trace stopped for some other reason.
37669 Additional optional fields supply statistical and other information.
37670 Although not required, they are extremely useful for users monitoring
37671 the progress of a trace run. If a trace has stopped, and these
37672 numbers are reported, they must reflect the state of the just-stopped
37677 @item tframes:@var{n}
37678 The number of trace frames in the buffer.
37680 @item tcreated:@var{n}
37681 The total number of trace frames created during the run. This may
37682 be larger than the trace frame count, if the buffer is circular.
37684 @item tsize:@var{n}
37685 The total size of the trace buffer, in bytes.
37687 @item tfree:@var{n}
37688 The number of bytes still unused in the buffer.
37690 @item circular:@var{n}
37691 The value of the circular trace buffer flag. @code{1} means that the
37692 trace buffer is circular and old trace frames will be discarded if
37693 necessary to make room, @code{0} means that the trace buffer is linear
37696 @item disconn:@var{n}
37697 The value of the disconnected tracing flag. @code{1} means that
37698 tracing will continue after @value{GDBN} disconnects, @code{0} means
37699 that the trace run will stop.
37703 @item qTP:@var{tp}:@var{addr}
37704 @cindex tracepoint status, remote request
37705 @cindex @samp{qTP} packet
37706 Ask the stub for the current state of tracepoint number @var{tp} at
37707 address @var{addr}.
37711 @item V@var{hits}:@var{usage}
37712 The tracepoint has been hit @var{hits} times so far during the trace
37713 run, and accounts for @var{usage} in the trace buffer. Note that
37714 @code{while-stepping} steps are not counted as separate hits, but the
37715 steps' space consumption is added into the usage number.
37719 @item qTV:@var{var}
37720 @cindex trace state variable value, remote request
37721 @cindex @samp{qTV} packet
37722 Ask the stub for the value of the trace state variable number @var{var}.
37727 The value of the variable is @var{value}. This will be the current
37728 value of the variable if the user is examining a running target, or a
37729 saved value if the variable was collected in the trace frame that the
37730 user is looking at. Note that multiple requests may result in
37731 different reply values, such as when requesting values while the
37732 program is running.
37735 The value of the variable is unknown. This would occur, for example,
37736 if the user is examining a trace frame in which the requested variable
37741 @cindex @samp{qTfP} packet
37743 @cindex @samp{qTsP} packet
37744 These packets request data about tracepoints that are being used by
37745 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37746 of data, and multiple @code{qTsP} to get additional pieces. Replies
37747 to these packets generally take the form of the @code{QTDP} packets
37748 that define tracepoints. (FIXME add detailed syntax)
37751 @cindex @samp{qTfV} packet
37753 @cindex @samp{qTsV} packet
37754 These packets request data about trace state variables that are on the
37755 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37756 and multiple @code{qTsV} to get additional variables. Replies to
37757 these packets follow the syntax of the @code{QTDV} packets that define
37758 trace state variables.
37764 @cindex @samp{qTfSTM} packet
37765 @cindex @samp{qTsSTM} packet
37766 These packets request data about static tracepoint markers that exist
37767 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37768 first piece of data, and multiple @code{qTsSTM} to get additional
37769 pieces. Replies to these packets take the following form:
37773 @item m @var{address}:@var{id}:@var{extra}
37775 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37776 a comma-separated list of markers
37778 (lower case letter @samp{L}) denotes end of list.
37780 An error occurred. The error number @var{nn} is given as hex digits.
37782 An empty reply indicates that the request is not supported by the
37786 The @var{address} is encoded in hex;
37787 @var{id} and @var{extra} are strings encoded in hex.
37789 In response to each query, the target will reply with a list of one or
37790 more markers, separated by commas. @value{GDBN} will respond to each
37791 reply with a request for more markers (using the @samp{qs} form of the
37792 query), until the target responds with @samp{l} (lower-case ell, for
37795 @item qTSTMat:@var{address}
37797 @cindex @samp{qTSTMat} packet
37798 This packets requests data about static tracepoint markers in the
37799 target program at @var{address}. Replies to this packet follow the
37800 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37801 tracepoint markers.
37803 @item QTSave:@var{filename}
37804 @cindex @samp{QTSave} packet
37805 This packet directs the target to save trace data to the file name
37806 @var{filename} in the target's filesystem. The @var{filename} is encoded
37807 as a hex string; the interpretation of the file name (relative vs
37808 absolute, wild cards, etc) is up to the target.
37810 @item qTBuffer:@var{offset},@var{len}
37811 @cindex @samp{qTBuffer} packet
37812 Return up to @var{len} bytes of the current contents of trace buffer,
37813 starting at @var{offset}. The trace buffer is treated as if it were
37814 a contiguous collection of traceframes, as per the trace file format.
37815 The reply consists as many hex-encoded bytes as the target can deliver
37816 in a packet; it is not an error to return fewer than were asked for.
37817 A reply consisting of just @code{l} indicates that no bytes are
37820 @item QTBuffer:circular:@var{value}
37821 This packet directs the target to use a circular trace buffer if
37822 @var{value} is 1, or a linear buffer if the value is 0.
37824 @item QTBuffer:size:@var{size}
37825 @anchor{QTBuffer-size}
37826 @cindex @samp{QTBuffer size} packet
37827 This packet directs the target to make the trace buffer be of size
37828 @var{size} if possible. A value of @code{-1} tells the target to
37829 use whatever size it prefers.
37831 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37832 @cindex @samp{QTNotes} packet
37833 This packet adds optional textual notes to the trace run. Allowable
37834 types include @code{user}, @code{notes}, and @code{tstop}, the
37835 @var{text} fields are arbitrary strings, hex-encoded.
37839 @subsection Relocate instruction reply packet
37840 When installing fast tracepoints in memory, the target may need to
37841 relocate the instruction currently at the tracepoint address to a
37842 different address in memory. For most instructions, a simple copy is
37843 enough, but, for example, call instructions that implicitly push the
37844 return address on the stack, and relative branches or other
37845 PC-relative instructions require offset adjustment, so that the effect
37846 of executing the instruction at a different address is the same as if
37847 it had executed in the original location.
37849 In response to several of the tracepoint packets, the target may also
37850 respond with a number of intermediate @samp{qRelocInsn} request
37851 packets before the final result packet, to have @value{GDBN} handle
37852 this relocation operation. If a packet supports this mechanism, its
37853 documentation will explicitly say so. See for example the above
37854 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37855 format of the request is:
37858 @item qRelocInsn:@var{from};@var{to}
37860 This requests @value{GDBN} to copy instruction at address @var{from}
37861 to address @var{to}, possibly adjusted so that executing the
37862 instruction at @var{to} has the same effect as executing it at
37863 @var{from}. @value{GDBN} writes the adjusted instruction to target
37864 memory starting at @var{to}.
37869 @item qRelocInsn:@var{adjusted_size}
37870 Informs the stub the relocation is complete. The @var{adjusted_size} is
37871 the length in bytes of resulting relocated instruction sequence.
37873 A badly formed request was detected, or an error was encountered while
37874 relocating the instruction.
37877 @node Host I/O Packets
37878 @section Host I/O Packets
37879 @cindex Host I/O, remote protocol
37880 @cindex file transfer, remote protocol
37882 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37883 operations on the far side of a remote link. For example, Host I/O is
37884 used to upload and download files to a remote target with its own
37885 filesystem. Host I/O uses the same constant values and data structure
37886 layout as the target-initiated File-I/O protocol. However, the
37887 Host I/O packets are structured differently. The target-initiated
37888 protocol relies on target memory to store parameters and buffers.
37889 Host I/O requests are initiated by @value{GDBN}, and the
37890 target's memory is not involved. @xref{File-I/O Remote Protocol
37891 Extension}, for more details on the target-initiated protocol.
37893 The Host I/O request packets all encode a single operation along with
37894 its arguments. They have this format:
37898 @item vFile:@var{operation}: @var{parameter}@dots{}
37899 @var{operation} is the name of the particular request; the target
37900 should compare the entire packet name up to the second colon when checking
37901 for a supported operation. The format of @var{parameter} depends on
37902 the operation. Numbers are always passed in hexadecimal. Negative
37903 numbers have an explicit minus sign (i.e.@: two's complement is not
37904 used). Strings (e.g.@: filenames) are encoded as a series of
37905 hexadecimal bytes. The last argument to a system call may be a
37906 buffer of escaped binary data (@pxref{Binary Data}).
37910 The valid responses to Host I/O packets are:
37914 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37915 @var{result} is the integer value returned by this operation, usually
37916 non-negative for success and -1 for errors. If an error has occured,
37917 @var{errno} will be included in the result specifying a
37918 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37919 operations which return data, @var{attachment} supplies the data as a
37920 binary buffer. Binary buffers in response packets are escaped in the
37921 normal way (@pxref{Binary Data}). See the individual packet
37922 documentation for the interpretation of @var{result} and
37926 An empty response indicates that this operation is not recognized.
37930 These are the supported Host I/O operations:
37933 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37934 Open a file at @var{filename} and return a file descriptor for it, or
37935 return -1 if an error occurs. The @var{filename} is a string,
37936 @var{flags} is an integer indicating a mask of open flags
37937 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37938 of mode bits to use if the file is created (@pxref{mode_t Values}).
37939 @xref{open}, for details of the open flags and mode values.
37941 @item vFile:close: @var{fd}
37942 Close the open file corresponding to @var{fd} and return 0, or
37943 -1 if an error occurs.
37945 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37946 Read data from the open file corresponding to @var{fd}. Up to
37947 @var{count} bytes will be read from the file, starting at @var{offset}
37948 relative to the start of the file. The target may read fewer bytes;
37949 common reasons include packet size limits and an end-of-file
37950 condition. The number of bytes read is returned. Zero should only be
37951 returned for a successful read at the end of the file, or if
37952 @var{count} was zero.
37954 The data read should be returned as a binary attachment on success.
37955 If zero bytes were read, the response should include an empty binary
37956 attachment (i.e.@: a trailing semicolon). The return value is the
37957 number of target bytes read; the binary attachment may be longer if
37958 some characters were escaped.
37960 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37961 Write @var{data} (a binary buffer) to the open file corresponding
37962 to @var{fd}. Start the write at @var{offset} from the start of the
37963 file. Unlike many @code{write} system calls, there is no
37964 separate @var{count} argument; the length of @var{data} in the
37965 packet is used. @samp{vFile:write} returns the number of bytes written,
37966 which may be shorter than the length of @var{data}, or -1 if an
37969 @item vFile:fstat: @var{fd}
37970 Get information about the open file corresponding to @var{fd}.
37971 On success the information is returned as a binary attachment
37972 and the return value is the size of this attachment in bytes.
37973 If an error occurs the return value is -1. The format of the
37974 returned binary attachment is as described in @ref{struct stat}.
37976 @item vFile:unlink: @var{filename}
37977 Delete the file at @var{filename} on the target. Return 0,
37978 or -1 if an error occurs. The @var{filename} is a string.
37980 @item vFile:readlink: @var{filename}
37981 Read value of symbolic link @var{filename} on the target. Return
37982 the number of bytes read, or -1 if an error occurs.
37984 The data read should be returned as a binary attachment on success.
37985 If zero bytes were read, the response should include an empty binary
37986 attachment (i.e.@: a trailing semicolon). The return value is the
37987 number of target bytes read; the binary attachment may be longer if
37988 some characters were escaped.
37990 @item vFile:setfs: @var{pid}
37991 Select the filesystem on which @code{vFile} operations with
37992 @var{filename} arguments will operate. This is required for
37993 @value{GDBN} to be able to access files on remote targets where
37994 the remote stub does not share a common filesystem with the
37997 If @var{pid} is nonzero, select the filesystem as seen by process
37998 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37999 the remote stub. Return 0 on success, or -1 if an error occurs.
38000 If @code{vFile:setfs:} indicates success, the selected filesystem
38001 remains selected until the next successful @code{vFile:setfs:}
38007 @section Interrupts
38008 @cindex interrupts (remote protocol)
38009 @anchor{interrupting remote targets}
38011 In all-stop mode, when a program on the remote target is running,
38012 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38013 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38014 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38016 The precise meaning of @code{BREAK} is defined by the transport
38017 mechanism and may, in fact, be undefined. @value{GDBN} does not
38018 currently define a @code{BREAK} mechanism for any of the network
38019 interfaces except for TCP, in which case @value{GDBN} sends the
38020 @code{telnet} BREAK sequence.
38022 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38023 transport mechanisms. It is represented by sending the single byte
38024 @code{0x03} without any of the usual packet overhead described in
38025 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38026 transmitted as part of a packet, it is considered to be packet data
38027 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38028 (@pxref{X packet}), used for binary downloads, may include an unescaped
38029 @code{0x03} as part of its packet.
38031 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38032 When Linux kernel receives this sequence from serial port,
38033 it stops execution and connects to gdb.
38035 In non-stop mode, because packet resumptions are asynchronous
38036 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38037 command to the remote stub, even when the target is running. For that
38038 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38039 packet}) with the usual packet framing instead of the single byte
38042 Stubs are not required to recognize these interrupt mechanisms and the
38043 precise meaning associated with receipt of the interrupt is
38044 implementation defined. If the target supports debugging of multiple
38045 threads and/or processes, it should attempt to interrupt all
38046 currently-executing threads and processes.
38047 If the stub is successful at interrupting the
38048 running program, it should send one of the stop
38049 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38050 of successfully stopping the program in all-stop mode, and a stop reply
38051 for each stopped thread in non-stop mode.
38052 Interrupts received while the
38053 program is stopped are discarded.
38055 @node Notification Packets
38056 @section Notification Packets
38057 @cindex notification packets
38058 @cindex packets, notification
38060 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38061 packets that require no acknowledgment. Both the GDB and the stub
38062 may send notifications (although the only notifications defined at
38063 present are sent by the stub). Notifications carry information
38064 without incurring the round-trip latency of an acknowledgment, and so
38065 are useful for low-impact communications where occasional packet loss
38068 A notification packet has the form @samp{% @var{data} #
38069 @var{checksum}}, where @var{data} is the content of the notification,
38070 and @var{checksum} is a checksum of @var{data}, computed and formatted
38071 as for ordinary @value{GDBN} packets. A notification's @var{data}
38072 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38073 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38074 to acknowledge the notification's receipt or to report its corruption.
38076 Every notification's @var{data} begins with a name, which contains no
38077 colon characters, followed by a colon character.
38079 Recipients should silently ignore corrupted notifications and
38080 notifications they do not understand. Recipients should restart
38081 timeout periods on receipt of a well-formed notification, whether or
38082 not they understand it.
38084 Senders should only send the notifications described here when this
38085 protocol description specifies that they are permitted. In the
38086 future, we may extend the protocol to permit existing notifications in
38087 new contexts; this rule helps older senders avoid confusing newer
38090 (Older versions of @value{GDBN} ignore bytes received until they see
38091 the @samp{$} byte that begins an ordinary packet, so new stubs may
38092 transmit notifications without fear of confusing older clients. There
38093 are no notifications defined for @value{GDBN} to send at the moment, but we
38094 assume that most older stubs would ignore them, as well.)
38096 Each notification is comprised of three parts:
38098 @item @var{name}:@var{event}
38099 The notification packet is sent by the side that initiates the
38100 exchange (currently, only the stub does that), with @var{event}
38101 carrying the specific information about the notification, and
38102 @var{name} specifying the name of the notification.
38104 The acknowledge sent by the other side, usually @value{GDBN}, to
38105 acknowledge the exchange and request the event.
38108 The purpose of an asynchronous notification mechanism is to report to
38109 @value{GDBN} that something interesting happened in the remote stub.
38111 The remote stub may send notification @var{name}:@var{event}
38112 at any time, but @value{GDBN} acknowledges the notification when
38113 appropriate. The notification event is pending before @value{GDBN}
38114 acknowledges. Only one notification at a time may be pending; if
38115 additional events occur before @value{GDBN} has acknowledged the
38116 previous notification, they must be queued by the stub for later
38117 synchronous transmission in response to @var{ack} packets from
38118 @value{GDBN}. Because the notification mechanism is unreliable,
38119 the stub is permitted to resend a notification if it believes
38120 @value{GDBN} may not have received it.
38122 Specifically, notifications may appear when @value{GDBN} is not
38123 otherwise reading input from the stub, or when @value{GDBN} is
38124 expecting to read a normal synchronous response or a
38125 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38126 Notification packets are distinct from any other communication from
38127 the stub so there is no ambiguity.
38129 After receiving a notification, @value{GDBN} shall acknowledge it by
38130 sending a @var{ack} packet as a regular, synchronous request to the
38131 stub. Such acknowledgment is not required to happen immediately, as
38132 @value{GDBN} is permitted to send other, unrelated packets to the
38133 stub first, which the stub should process normally.
38135 Upon receiving a @var{ack} packet, if the stub has other queued
38136 events to report to @value{GDBN}, it shall respond by sending a
38137 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38138 packet to solicit further responses; again, it is permitted to send
38139 other, unrelated packets as well which the stub should process
38142 If the stub receives a @var{ack} packet and there are no additional
38143 @var{event} to report, the stub shall return an @samp{OK} response.
38144 At this point, @value{GDBN} has finished processing a notification
38145 and the stub has completed sending any queued events. @value{GDBN}
38146 won't accept any new notifications until the final @samp{OK} is
38147 received . If further notification events occur, the stub shall send
38148 a new notification, @value{GDBN} shall accept the notification, and
38149 the process shall be repeated.
38151 The process of asynchronous notification can be illustrated by the
38154 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38157 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38159 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38164 The following notifications are defined:
38165 @multitable @columnfractions 0.12 0.12 0.38 0.38
38174 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38175 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38176 for information on how these notifications are acknowledged by
38178 @tab Report an asynchronous stop event in non-stop mode.
38182 @node Remote Non-Stop
38183 @section Remote Protocol Support for Non-Stop Mode
38185 @value{GDBN}'s remote protocol supports non-stop debugging of
38186 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38187 supports non-stop mode, it should report that to @value{GDBN} by including
38188 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38190 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38191 establishing a new connection with the stub. Entering non-stop mode
38192 does not alter the state of any currently-running threads, but targets
38193 must stop all threads in any already-attached processes when entering
38194 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38195 probe the target state after a mode change.
38197 In non-stop mode, when an attached process encounters an event that
38198 would otherwise be reported with a stop reply, it uses the
38199 asynchronous notification mechanism (@pxref{Notification Packets}) to
38200 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38201 in all processes are stopped when a stop reply is sent, in non-stop
38202 mode only the thread reporting the stop event is stopped. That is,
38203 when reporting a @samp{S} or @samp{T} response to indicate completion
38204 of a step operation, hitting a breakpoint, or a fault, only the
38205 affected thread is stopped; any other still-running threads continue
38206 to run. When reporting a @samp{W} or @samp{X} response, all running
38207 threads belonging to other attached processes continue to run.
38209 In non-stop mode, the target shall respond to the @samp{?} packet as
38210 follows. First, any incomplete stop reply notification/@samp{vStopped}
38211 sequence in progress is abandoned. The target must begin a new
38212 sequence reporting stop events for all stopped threads, whether or not
38213 it has previously reported those events to @value{GDBN}. The first
38214 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38215 subsequent stop replies are sent as responses to @samp{vStopped} packets
38216 using the mechanism described above. The target must not send
38217 asynchronous stop reply notifications until the sequence is complete.
38218 If all threads are running when the target receives the @samp{?} packet,
38219 or if the target is not attached to any process, it shall respond
38222 If the stub supports non-stop mode, it should also support the
38223 @samp{swbreak} stop reason if software breakpoints are supported, and
38224 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38225 (@pxref{swbreak stop reason}). This is because given the asynchronous
38226 nature of non-stop mode, between the time a thread hits a breakpoint
38227 and the time the event is finally processed by @value{GDBN}, the
38228 breakpoint may have already been removed from the target. Due to
38229 this, @value{GDBN} needs to be able to tell whether a trap stop was
38230 caused by a delayed breakpoint event, which should be ignored, as
38231 opposed to a random trap signal, which should be reported to the user.
38232 Note the @samp{swbreak} feature implies that the target is responsible
38233 for adjusting the PC when a software breakpoint triggers, if
38234 necessary, such as on the x86 architecture.
38236 @node Packet Acknowledgment
38237 @section Packet Acknowledgment
38239 @cindex acknowledgment, for @value{GDBN} remote
38240 @cindex packet acknowledgment, for @value{GDBN} remote
38241 By default, when either the host or the target machine receives a packet,
38242 the first response expected is an acknowledgment: either @samp{+} (to indicate
38243 the package was received correctly) or @samp{-} (to request retransmission).
38244 This mechanism allows the @value{GDBN} remote protocol to operate over
38245 unreliable transport mechanisms, such as a serial line.
38247 In cases where the transport mechanism is itself reliable (such as a pipe or
38248 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38249 It may be desirable to disable them in that case to reduce communication
38250 overhead, or for other reasons. This can be accomplished by means of the
38251 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38253 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38254 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38255 and response format still includes the normal checksum, as described in
38256 @ref{Overview}, but the checksum may be ignored by the receiver.
38258 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38259 no-acknowledgment mode, it should report that to @value{GDBN}
38260 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38261 @pxref{qSupported}.
38262 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38263 disabled via the @code{set remote noack-packet off} command
38264 (@pxref{Remote Configuration}),
38265 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38266 Only then may the stub actually turn off packet acknowledgments.
38267 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38268 response, which can be safely ignored by the stub.
38270 Note that @code{set remote noack-packet} command only affects negotiation
38271 between @value{GDBN} and the stub when subsequent connections are made;
38272 it does not affect the protocol acknowledgment state for any current
38274 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38275 new connection is established,
38276 there is also no protocol request to re-enable the acknowledgments
38277 for the current connection, once disabled.
38282 Example sequence of a target being re-started. Notice how the restart
38283 does not get any direct output:
38288 @emph{target restarts}
38291 <- @code{T001:1234123412341234}
38295 Example sequence of a target being stepped by a single instruction:
38298 -> @code{G1445@dots{}}
38303 <- @code{T001:1234123412341234}
38307 <- @code{1455@dots{}}
38311 @node File-I/O Remote Protocol Extension
38312 @section File-I/O Remote Protocol Extension
38313 @cindex File-I/O remote protocol extension
38316 * File-I/O Overview::
38317 * Protocol Basics::
38318 * The F Request Packet::
38319 * The F Reply Packet::
38320 * The Ctrl-C Message::
38322 * List of Supported Calls::
38323 * Protocol-specific Representation of Datatypes::
38325 * File-I/O Examples::
38328 @node File-I/O Overview
38329 @subsection File-I/O Overview
38330 @cindex file-i/o overview
38332 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38333 target to use the host's file system and console I/O to perform various
38334 system calls. System calls on the target system are translated into a
38335 remote protocol packet to the host system, which then performs the needed
38336 actions and returns a response packet to the target system.
38337 This simulates file system operations even on targets that lack file systems.
38339 The protocol is defined to be independent of both the host and target systems.
38340 It uses its own internal representation of datatypes and values. Both
38341 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38342 translating the system-dependent value representations into the internal
38343 protocol representations when data is transmitted.
38345 The communication is synchronous. A system call is possible only when
38346 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38347 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38348 the target is stopped to allow deterministic access to the target's
38349 memory. Therefore File-I/O is not interruptible by target signals. On
38350 the other hand, it is possible to interrupt File-I/O by a user interrupt
38351 (@samp{Ctrl-C}) within @value{GDBN}.
38353 The target's request to perform a host system call does not finish
38354 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38355 after finishing the system call, the target returns to continuing the
38356 previous activity (continue, step). No additional continue or step
38357 request from @value{GDBN} is required.
38360 (@value{GDBP}) continue
38361 <- target requests 'system call X'
38362 target is stopped, @value{GDBN} executes system call
38363 -> @value{GDBN} returns result
38364 ... target continues, @value{GDBN} returns to wait for the target
38365 <- target hits breakpoint and sends a Txx packet
38368 The protocol only supports I/O on the console and to regular files on
38369 the host file system. Character or block special devices, pipes,
38370 named pipes, sockets or any other communication method on the host
38371 system are not supported by this protocol.
38373 File I/O is not supported in non-stop mode.
38375 @node Protocol Basics
38376 @subsection Protocol Basics
38377 @cindex protocol basics, file-i/o
38379 The File-I/O protocol uses the @code{F} packet as the request as well
38380 as reply packet. Since a File-I/O system call can only occur when
38381 @value{GDBN} is waiting for a response from the continuing or stepping target,
38382 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38383 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38384 This @code{F} packet contains all information needed to allow @value{GDBN}
38385 to call the appropriate host system call:
38389 A unique identifier for the requested system call.
38392 All parameters to the system call. Pointers are given as addresses
38393 in the target memory address space. Pointers to strings are given as
38394 pointer/length pair. Numerical values are given as they are.
38395 Numerical control flags are given in a protocol-specific representation.
38399 At this point, @value{GDBN} has to perform the following actions.
38403 If the parameters include pointer values to data needed as input to a
38404 system call, @value{GDBN} requests this data from the target with a
38405 standard @code{m} packet request. This additional communication has to be
38406 expected by the target implementation and is handled as any other @code{m}
38410 @value{GDBN} translates all value from protocol representation to host
38411 representation as needed. Datatypes are coerced into the host types.
38414 @value{GDBN} calls the system call.
38417 It then coerces datatypes back to protocol representation.
38420 If the system call is expected to return data in buffer space specified
38421 by pointer parameters to the call, the data is transmitted to the
38422 target using a @code{M} or @code{X} packet. This packet has to be expected
38423 by the target implementation and is handled as any other @code{M} or @code{X}
38428 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38429 necessary information for the target to continue. This at least contains
38436 @code{errno}, if has been changed by the system call.
38443 After having done the needed type and value coercion, the target continues
38444 the latest continue or step action.
38446 @node The F Request Packet
38447 @subsection The @code{F} Request Packet
38448 @cindex file-i/o request packet
38449 @cindex @code{F} request packet
38451 The @code{F} request packet has the following format:
38454 @item F@var{call-id},@var{parameter@dots{}}
38456 @var{call-id} is the identifier to indicate the host system call to be called.
38457 This is just the name of the function.
38459 @var{parameter@dots{}} are the parameters to the system call.
38460 Parameters are hexadecimal integer values, either the actual values in case
38461 of scalar datatypes, pointers to target buffer space in case of compound
38462 datatypes and unspecified memory areas, or pointer/length pairs in case
38463 of string parameters. These are appended to the @var{call-id} as a
38464 comma-delimited list. All values are transmitted in ASCII
38465 string representation, pointer/length pairs separated by a slash.
38471 @node The F Reply Packet
38472 @subsection The @code{F} Reply Packet
38473 @cindex file-i/o reply packet
38474 @cindex @code{F} reply packet
38476 The @code{F} reply packet has the following format:
38480 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38482 @var{retcode} is the return code of the system call as hexadecimal value.
38484 @var{errno} is the @code{errno} set by the call, in protocol-specific
38486 This parameter can be omitted if the call was successful.
38488 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38489 case, @var{errno} must be sent as well, even if the call was successful.
38490 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38497 or, if the call was interrupted before the host call has been performed:
38504 assuming 4 is the protocol-specific representation of @code{EINTR}.
38509 @node The Ctrl-C Message
38510 @subsection The @samp{Ctrl-C} Message
38511 @cindex ctrl-c message, in file-i/o protocol
38513 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38514 reply packet (@pxref{The F Reply Packet}),
38515 the target should behave as if it had
38516 gotten a break message. The meaning for the target is ``system call
38517 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38518 (as with a break message) and return to @value{GDBN} with a @code{T02}
38521 It's important for the target to know in which
38522 state the system call was interrupted. There are two possible cases:
38526 The system call hasn't been performed on the host yet.
38529 The system call on the host has been finished.
38533 These two states can be distinguished by the target by the value of the
38534 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38535 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38536 on POSIX systems. In any other case, the target may presume that the
38537 system call has been finished --- successfully or not --- and should behave
38538 as if the break message arrived right after the system call.
38540 @value{GDBN} must behave reliably. If the system call has not been called
38541 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38542 @code{errno} in the packet. If the system call on the host has been finished
38543 before the user requests a break, the full action must be finished by
38544 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38545 The @code{F} packet may only be sent when either nothing has happened
38546 or the full action has been completed.
38549 @subsection Console I/O
38550 @cindex console i/o as part of file-i/o
38552 By default and if not explicitly closed by the target system, the file
38553 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38554 on the @value{GDBN} console is handled as any other file output operation
38555 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38556 by @value{GDBN} so that after the target read request from file descriptor
38557 0 all following typing is buffered until either one of the following
38562 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38564 system call is treated as finished.
38567 The user presses @key{RET}. This is treated as end of input with a trailing
38571 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38572 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38576 If the user has typed more characters than fit in the buffer given to
38577 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38578 either another @code{read(0, @dots{})} is requested by the target, or debugging
38579 is stopped at the user's request.
38582 @node List of Supported Calls
38583 @subsection List of Supported Calls
38584 @cindex list of supported file-i/o calls
38601 @unnumberedsubsubsec open
38602 @cindex open, file-i/o system call
38607 int open(const char *pathname, int flags);
38608 int open(const char *pathname, int flags, mode_t mode);
38612 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38615 @var{flags} is the bitwise @code{OR} of the following values:
38619 If the file does not exist it will be created. The host
38620 rules apply as far as file ownership and time stamps
38624 When used with @code{O_CREAT}, if the file already exists it is
38625 an error and open() fails.
38628 If the file already exists and the open mode allows
38629 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38630 truncated to zero length.
38633 The file is opened in append mode.
38636 The file is opened for reading only.
38639 The file is opened for writing only.
38642 The file is opened for reading and writing.
38646 Other bits are silently ignored.
38650 @var{mode} is the bitwise @code{OR} of the following values:
38654 User has read permission.
38657 User has write permission.
38660 Group has read permission.
38663 Group has write permission.
38666 Others have read permission.
38669 Others have write permission.
38673 Other bits are silently ignored.
38676 @item Return value:
38677 @code{open} returns the new file descriptor or -1 if an error
38684 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38687 @var{pathname} refers to a directory.
38690 The requested access is not allowed.
38693 @var{pathname} was too long.
38696 A directory component in @var{pathname} does not exist.
38699 @var{pathname} refers to a device, pipe, named pipe or socket.
38702 @var{pathname} refers to a file on a read-only filesystem and
38703 write access was requested.
38706 @var{pathname} is an invalid pointer value.
38709 No space on device to create the file.
38712 The process already has the maximum number of files open.
38715 The limit on the total number of files open on the system
38719 The call was interrupted by the user.
38725 @unnumberedsubsubsec close
38726 @cindex close, file-i/o system call
38735 @samp{Fclose,@var{fd}}
38737 @item Return value:
38738 @code{close} returns zero on success, or -1 if an error occurred.
38744 @var{fd} isn't a valid open file descriptor.
38747 The call was interrupted by the user.
38753 @unnumberedsubsubsec read
38754 @cindex read, file-i/o system call
38759 int read(int fd, void *buf, unsigned int count);
38763 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38765 @item Return value:
38766 On success, the number of bytes read is returned.
38767 Zero indicates end of file. If count is zero, read
38768 returns zero as well. On error, -1 is returned.
38774 @var{fd} is not a valid file descriptor or is not open for
38778 @var{bufptr} is an invalid pointer value.
38781 The call was interrupted by the user.
38787 @unnumberedsubsubsec write
38788 @cindex write, file-i/o system call
38793 int write(int fd, const void *buf, unsigned int count);
38797 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38799 @item Return value:
38800 On success, the number of bytes written are returned.
38801 Zero indicates nothing was written. On error, -1
38808 @var{fd} is not a valid file descriptor or is not open for
38812 @var{bufptr} is an invalid pointer value.
38815 An attempt was made to write a file that exceeds the
38816 host-specific maximum file size allowed.
38819 No space on device to write the data.
38822 The call was interrupted by the user.
38828 @unnumberedsubsubsec lseek
38829 @cindex lseek, file-i/o system call
38834 long lseek (int fd, long offset, int flag);
38838 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38840 @var{flag} is one of:
38844 The offset is set to @var{offset} bytes.
38847 The offset is set to its current location plus @var{offset}
38851 The offset is set to the size of the file plus @var{offset}
38855 @item Return value:
38856 On success, the resulting unsigned offset in bytes from
38857 the beginning of the file is returned. Otherwise, a
38858 value of -1 is returned.
38864 @var{fd} is not a valid open file descriptor.
38867 @var{fd} is associated with the @value{GDBN} console.
38870 @var{flag} is not a proper value.
38873 The call was interrupted by the user.
38879 @unnumberedsubsubsec rename
38880 @cindex rename, file-i/o system call
38885 int rename(const char *oldpath, const char *newpath);
38889 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38891 @item Return value:
38892 On success, zero is returned. On error, -1 is returned.
38898 @var{newpath} is an existing directory, but @var{oldpath} is not a
38902 @var{newpath} is a non-empty directory.
38905 @var{oldpath} or @var{newpath} is a directory that is in use by some
38909 An attempt was made to make a directory a subdirectory
38913 A component used as a directory in @var{oldpath} or new
38914 path is not a directory. Or @var{oldpath} is a directory
38915 and @var{newpath} exists but is not a directory.
38918 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38921 No access to the file or the path of the file.
38925 @var{oldpath} or @var{newpath} was too long.
38928 A directory component in @var{oldpath} or @var{newpath} does not exist.
38931 The file is on a read-only filesystem.
38934 The device containing the file has no room for the new
38938 The call was interrupted by the user.
38944 @unnumberedsubsubsec unlink
38945 @cindex unlink, file-i/o system call
38950 int unlink(const char *pathname);
38954 @samp{Funlink,@var{pathnameptr}/@var{len}}
38956 @item Return value:
38957 On success, zero is returned. On error, -1 is returned.
38963 No access to the file or the path of the file.
38966 The system does not allow unlinking of directories.
38969 The file @var{pathname} cannot be unlinked because it's
38970 being used by another process.
38973 @var{pathnameptr} is an invalid pointer value.
38976 @var{pathname} was too long.
38979 A directory component in @var{pathname} does not exist.
38982 A component of the path is not a directory.
38985 The file is on a read-only filesystem.
38988 The call was interrupted by the user.
38994 @unnumberedsubsubsec stat/fstat
38995 @cindex fstat, file-i/o system call
38996 @cindex stat, file-i/o system call
39001 int stat(const char *pathname, struct stat *buf);
39002 int fstat(int fd, struct stat *buf);
39006 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39007 @samp{Ffstat,@var{fd},@var{bufptr}}
39009 @item Return value:
39010 On success, zero is returned. On error, -1 is returned.
39016 @var{fd} is not a valid open file.
39019 A directory component in @var{pathname} does not exist or the
39020 path is an empty string.
39023 A component of the path is not a directory.
39026 @var{pathnameptr} is an invalid pointer value.
39029 No access to the file or the path of the file.
39032 @var{pathname} was too long.
39035 The call was interrupted by the user.
39041 @unnumberedsubsubsec gettimeofday
39042 @cindex gettimeofday, file-i/o system call
39047 int gettimeofday(struct timeval *tv, void *tz);
39051 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39053 @item Return value:
39054 On success, 0 is returned, -1 otherwise.
39060 @var{tz} is a non-NULL pointer.
39063 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39069 @unnumberedsubsubsec isatty
39070 @cindex isatty, file-i/o system call
39075 int isatty(int fd);
39079 @samp{Fisatty,@var{fd}}
39081 @item Return value:
39082 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39088 The call was interrupted by the user.
39093 Note that the @code{isatty} call is treated as a special case: it returns
39094 1 to the target if the file descriptor is attached
39095 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39096 would require implementing @code{ioctl} and would be more complex than
39101 @unnumberedsubsubsec system
39102 @cindex system, file-i/o system call
39107 int system(const char *command);
39111 @samp{Fsystem,@var{commandptr}/@var{len}}
39113 @item Return value:
39114 If @var{len} is zero, the return value indicates whether a shell is
39115 available. A zero return value indicates a shell is not available.
39116 For non-zero @var{len}, the value returned is -1 on error and the
39117 return status of the command otherwise. Only the exit status of the
39118 command is returned, which is extracted from the host's @code{system}
39119 return value by calling @code{WEXITSTATUS(retval)}. In case
39120 @file{/bin/sh} could not be executed, 127 is returned.
39126 The call was interrupted by the user.
39131 @value{GDBN} takes over the full task of calling the necessary host calls
39132 to perform the @code{system} call. The return value of @code{system} on
39133 the host is simplified before it's returned
39134 to the target. Any termination signal information from the child process
39135 is discarded, and the return value consists
39136 entirely of the exit status of the called command.
39138 Due to security concerns, the @code{system} call is by default refused
39139 by @value{GDBN}. The user has to allow this call explicitly with the
39140 @code{set remote system-call-allowed 1} command.
39143 @item set remote system-call-allowed
39144 @kindex set remote system-call-allowed
39145 Control whether to allow the @code{system} calls in the File I/O
39146 protocol for the remote target. The default is zero (disabled).
39148 @item show remote system-call-allowed
39149 @kindex show remote system-call-allowed
39150 Show whether the @code{system} calls are allowed in the File I/O
39154 @node Protocol-specific Representation of Datatypes
39155 @subsection Protocol-specific Representation of Datatypes
39156 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39159 * Integral Datatypes::
39161 * Memory Transfer::
39166 @node Integral Datatypes
39167 @unnumberedsubsubsec Integral Datatypes
39168 @cindex integral datatypes, in file-i/o protocol
39170 The integral datatypes used in the system calls are @code{int},
39171 @code{unsigned int}, @code{long}, @code{unsigned long},
39172 @code{mode_t}, and @code{time_t}.
39174 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39175 implemented as 32 bit values in this protocol.
39177 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39179 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39180 in @file{limits.h}) to allow range checking on host and target.
39182 @code{time_t} datatypes are defined as seconds since the Epoch.
39184 All integral datatypes transferred as part of a memory read or write of a
39185 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39188 @node Pointer Values
39189 @unnumberedsubsubsec Pointer Values
39190 @cindex pointer values, in file-i/o protocol
39192 Pointers to target data are transmitted as they are. An exception
39193 is made for pointers to buffers for which the length isn't
39194 transmitted as part of the function call, namely strings. Strings
39195 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39202 which is a pointer to data of length 18 bytes at position 0x1aaf.
39203 The length is defined as the full string length in bytes, including
39204 the trailing null byte. For example, the string @code{"hello world"}
39205 at address 0x123456 is transmitted as
39211 @node Memory Transfer
39212 @unnumberedsubsubsec Memory Transfer
39213 @cindex memory transfer, in file-i/o protocol
39215 Structured data which is transferred using a memory read or write (for
39216 example, a @code{struct stat}) is expected to be in a protocol-specific format
39217 with all scalar multibyte datatypes being big endian. Translation to
39218 this representation needs to be done both by the target before the @code{F}
39219 packet is sent, and by @value{GDBN} before
39220 it transfers memory to the target. Transferred pointers to structured
39221 data should point to the already-coerced data at any time.
39225 @unnumberedsubsubsec struct stat
39226 @cindex struct stat, in file-i/o protocol
39228 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39229 is defined as follows:
39233 unsigned int st_dev; /* device */
39234 unsigned int st_ino; /* inode */
39235 mode_t st_mode; /* protection */
39236 unsigned int st_nlink; /* number of hard links */
39237 unsigned int st_uid; /* user ID of owner */
39238 unsigned int st_gid; /* group ID of owner */
39239 unsigned int st_rdev; /* device type (if inode device) */
39240 unsigned long st_size; /* total size, in bytes */
39241 unsigned long st_blksize; /* blocksize for filesystem I/O */
39242 unsigned long st_blocks; /* number of blocks allocated */
39243 time_t st_atime; /* time of last access */
39244 time_t st_mtime; /* time of last modification */
39245 time_t st_ctime; /* time of last change */
39249 The integral datatypes conform to the definitions given in the
39250 appropriate section (see @ref{Integral Datatypes}, for details) so this
39251 structure is of size 64 bytes.
39253 The values of several fields have a restricted meaning and/or
39259 A value of 0 represents a file, 1 the console.
39262 No valid meaning for the target. Transmitted unchanged.
39265 Valid mode bits are described in @ref{Constants}. Any other
39266 bits have currently no meaning for the target.
39271 No valid meaning for the target. Transmitted unchanged.
39276 These values have a host and file system dependent
39277 accuracy. Especially on Windows hosts, the file system may not
39278 support exact timing values.
39281 The target gets a @code{struct stat} of the above representation and is
39282 responsible for coercing it to the target representation before
39285 Note that due to size differences between the host, target, and protocol
39286 representations of @code{struct stat} members, these members could eventually
39287 get truncated on the target.
39289 @node struct timeval
39290 @unnumberedsubsubsec struct timeval
39291 @cindex struct timeval, in file-i/o protocol
39293 The buffer of type @code{struct timeval} used by the File-I/O protocol
39294 is defined as follows:
39298 time_t tv_sec; /* second */
39299 long tv_usec; /* microsecond */
39303 The integral datatypes conform to the definitions given in the
39304 appropriate section (see @ref{Integral Datatypes}, for details) so this
39305 structure is of size 8 bytes.
39308 @subsection Constants
39309 @cindex constants, in file-i/o protocol
39311 The following values are used for the constants inside of the
39312 protocol. @value{GDBN} and target are responsible for translating these
39313 values before and after the call as needed.
39324 @unnumberedsubsubsec Open Flags
39325 @cindex open flags, in file-i/o protocol
39327 All values are given in hexadecimal representation.
39339 @node mode_t Values
39340 @unnumberedsubsubsec mode_t Values
39341 @cindex mode_t values, in file-i/o protocol
39343 All values are given in octal representation.
39360 @unnumberedsubsubsec Errno Values
39361 @cindex errno values, in file-i/o protocol
39363 All values are given in decimal representation.
39388 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39389 any error value not in the list of supported error numbers.
39392 @unnumberedsubsubsec Lseek Flags
39393 @cindex lseek flags, in file-i/o protocol
39402 @unnumberedsubsubsec Limits
39403 @cindex limits, in file-i/o protocol
39405 All values are given in decimal representation.
39408 INT_MIN -2147483648
39410 UINT_MAX 4294967295
39411 LONG_MIN -9223372036854775808
39412 LONG_MAX 9223372036854775807
39413 ULONG_MAX 18446744073709551615
39416 @node File-I/O Examples
39417 @subsection File-I/O Examples
39418 @cindex file-i/o examples
39420 Example sequence of a write call, file descriptor 3, buffer is at target
39421 address 0x1234, 6 bytes should be written:
39424 <- @code{Fwrite,3,1234,6}
39425 @emph{request memory read from target}
39428 @emph{return "6 bytes written"}
39432 Example sequence of a read call, file descriptor 3, buffer is at target
39433 address 0x1234, 6 bytes should be read:
39436 <- @code{Fread,3,1234,6}
39437 @emph{request memory write to target}
39438 -> @code{X1234,6:XXXXXX}
39439 @emph{return "6 bytes read"}
39443 Example sequence of a read call, call fails on the host due to invalid
39444 file descriptor (@code{EBADF}):
39447 <- @code{Fread,3,1234,6}
39451 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39455 <- @code{Fread,3,1234,6}
39460 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39464 <- @code{Fread,3,1234,6}
39465 -> @code{X1234,6:XXXXXX}
39469 @node Library List Format
39470 @section Library List Format
39471 @cindex library list format, remote protocol
39473 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39474 same process as your application to manage libraries. In this case,
39475 @value{GDBN} can use the loader's symbol table and normal memory
39476 operations to maintain a list of shared libraries. On other
39477 platforms, the operating system manages loaded libraries.
39478 @value{GDBN} can not retrieve the list of currently loaded libraries
39479 through memory operations, so it uses the @samp{qXfer:libraries:read}
39480 packet (@pxref{qXfer library list read}) instead. The remote stub
39481 queries the target's operating system and reports which libraries
39484 The @samp{qXfer:libraries:read} packet returns an XML document which
39485 lists loaded libraries and their offsets. Each library has an
39486 associated name and one or more segment or section base addresses,
39487 which report where the library was loaded in memory.
39489 For the common case of libraries that are fully linked binaries, the
39490 library should have a list of segments. If the target supports
39491 dynamic linking of a relocatable object file, its library XML element
39492 should instead include a list of allocated sections. The segment or
39493 section bases are start addresses, not relocation offsets; they do not
39494 depend on the library's link-time base addresses.
39496 @value{GDBN} must be linked with the Expat library to support XML
39497 library lists. @xref{Expat}.
39499 A simple memory map, with one loaded library relocated by a single
39500 offset, looks like this:
39504 <library name="/lib/libc.so.6">
39505 <segment address="0x10000000"/>
39510 Another simple memory map, with one loaded library with three
39511 allocated sections (.text, .data, .bss), looks like this:
39515 <library name="sharedlib.o">
39516 <section address="0x10000000"/>
39517 <section address="0x20000000"/>
39518 <section address="0x30000000"/>
39523 The format of a library list is described by this DTD:
39526 <!-- library-list: Root element with versioning -->
39527 <!ELEMENT library-list (library)*>
39528 <!ATTLIST library-list version CDATA #FIXED "1.0">
39529 <!ELEMENT library (segment*, section*)>
39530 <!ATTLIST library name CDATA #REQUIRED>
39531 <!ELEMENT segment EMPTY>
39532 <!ATTLIST segment address CDATA #REQUIRED>
39533 <!ELEMENT section EMPTY>
39534 <!ATTLIST section address CDATA #REQUIRED>
39537 In addition, segments and section descriptors cannot be mixed within a
39538 single library element, and you must supply at least one segment or
39539 section for each library.
39541 @node Library List Format for SVR4 Targets
39542 @section Library List Format for SVR4 Targets
39543 @cindex library list format, remote protocol
39545 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39546 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39547 shared libraries. Still a special library list provided by this packet is
39548 more efficient for the @value{GDBN} remote protocol.
39550 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39551 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39552 target, the following parameters are reported:
39556 @code{name}, the absolute file name from the @code{l_name} field of
39557 @code{struct link_map}.
39559 @code{lm} with address of @code{struct link_map} used for TLS
39560 (Thread Local Storage) access.
39562 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39563 @code{struct link_map}. For prelinked libraries this is not an absolute
39564 memory address. It is a displacement of absolute memory address against
39565 address the file was prelinked to during the library load.
39567 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39570 Additionally the single @code{main-lm} attribute specifies address of
39571 @code{struct link_map} used for the main executable. This parameter is used
39572 for TLS access and its presence is optional.
39574 @value{GDBN} must be linked with the Expat library to support XML
39575 SVR4 library lists. @xref{Expat}.
39577 A simple memory map, with two loaded libraries (which do not use prelink),
39581 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39582 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39584 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39586 </library-list-svr>
39589 The format of an SVR4 library list is described by this DTD:
39592 <!-- library-list-svr4: Root element with versioning -->
39593 <!ELEMENT library-list-svr4 (library)*>
39594 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39595 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39596 <!ELEMENT library EMPTY>
39597 <!ATTLIST library name CDATA #REQUIRED>
39598 <!ATTLIST library lm CDATA #REQUIRED>
39599 <!ATTLIST library l_addr CDATA #REQUIRED>
39600 <!ATTLIST library l_ld CDATA #REQUIRED>
39603 @node Memory Map Format
39604 @section Memory Map Format
39605 @cindex memory map format
39607 To be able to write into flash memory, @value{GDBN} needs to obtain a
39608 memory map from the target. This section describes the format of the
39611 The memory map is obtained using the @samp{qXfer:memory-map:read}
39612 (@pxref{qXfer memory map read}) packet and is an XML document that
39613 lists memory regions.
39615 @value{GDBN} must be linked with the Expat library to support XML
39616 memory maps. @xref{Expat}.
39618 The top-level structure of the document is shown below:
39621 <?xml version="1.0"?>
39622 <!DOCTYPE memory-map
39623 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39624 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39630 Each region can be either:
39635 A region of RAM starting at @var{addr} and extending for @var{length}
39639 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39644 A region of read-only memory:
39647 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39652 A region of flash memory, with erasure blocks @var{blocksize}
39656 <memory type="flash" start="@var{addr}" length="@var{length}">
39657 <property name="blocksize">@var{blocksize}</property>
39663 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39664 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39665 packets to write to addresses in such ranges.
39667 The formal DTD for memory map format is given below:
39670 <!-- ................................................... -->
39671 <!-- Memory Map XML DTD ................................ -->
39672 <!-- File: memory-map.dtd .............................. -->
39673 <!-- .................................... .............. -->
39674 <!-- memory-map.dtd -->
39675 <!-- memory-map: Root element with versioning -->
39676 <!ELEMENT memory-map (memory | property)>
39677 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39678 <!ELEMENT memory (property)>
39679 <!-- memory: Specifies a memory region,
39680 and its type, or device. -->
39681 <!ATTLIST memory type CDATA #REQUIRED
39682 start CDATA #REQUIRED
39683 length CDATA #REQUIRED
39684 device CDATA #IMPLIED>
39685 <!-- property: Generic attribute tag -->
39686 <!ELEMENT property (#PCDATA | property)*>
39687 <!ATTLIST property name CDATA #REQUIRED>
39690 @node Thread List Format
39691 @section Thread List Format
39692 @cindex thread list format
39694 To efficiently update the list of threads and their attributes,
39695 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39696 (@pxref{qXfer threads read}) and obtains the XML document with
39697 the following structure:
39700 <?xml version="1.0"?>
39702 <thread id="id" core="0" name="name">
39703 ... description ...
39708 Each @samp{thread} element must have the @samp{id} attribute that
39709 identifies the thread (@pxref{thread-id syntax}). The
39710 @samp{core} attribute, if present, specifies which processor core
39711 the thread was last executing on. The @samp{name} attribute, if
39712 present, specifies the human-readable name of the thread. The content
39713 of the of @samp{thread} element is interpreted as human-readable
39714 auxiliary information.
39716 @node Traceframe Info Format
39717 @section Traceframe Info Format
39718 @cindex traceframe info format
39720 To be able to know which objects in the inferior can be examined when
39721 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39722 memory ranges, registers and trace state variables that have been
39723 collected in a traceframe.
39725 This list is obtained using the @samp{qXfer:traceframe-info:read}
39726 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39728 @value{GDBN} must be linked with the Expat library to support XML
39729 traceframe info discovery. @xref{Expat}.
39731 The top-level structure of the document is shown below:
39734 <?xml version="1.0"?>
39735 <!DOCTYPE traceframe-info
39736 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39737 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39743 Each traceframe block can be either:
39748 A region of collected memory starting at @var{addr} and extending for
39749 @var{length} bytes from there:
39752 <memory start="@var{addr}" length="@var{length}"/>
39756 A block indicating trace state variable numbered @var{number} has been
39760 <tvar id="@var{number}"/>
39765 The formal DTD for the traceframe info format is given below:
39768 <!ELEMENT traceframe-info (memory | tvar)* >
39769 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39771 <!ELEMENT memory EMPTY>
39772 <!ATTLIST memory start CDATA #REQUIRED
39773 length CDATA #REQUIRED>
39775 <!ATTLIST tvar id CDATA #REQUIRED>
39778 @node Branch Trace Format
39779 @section Branch Trace Format
39780 @cindex branch trace format
39782 In order to display the branch trace of an inferior thread,
39783 @value{GDBN} needs to obtain the list of branches. This list is
39784 represented as list of sequential code blocks that are connected via
39785 branches. The code in each block has been executed sequentially.
39787 This list is obtained using the @samp{qXfer:btrace:read}
39788 (@pxref{qXfer btrace read}) packet and is an XML document.
39790 @value{GDBN} must be linked with the Expat library to support XML
39791 traceframe info discovery. @xref{Expat}.
39793 The top-level structure of the document is shown below:
39796 <?xml version="1.0"?>
39798 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39799 "http://sourceware.org/gdb/gdb-btrace.dtd">
39808 A block of sequentially executed instructions starting at @var{begin}
39809 and ending at @var{end}:
39812 <block begin="@var{begin}" end="@var{end}"/>
39817 The formal DTD for the branch trace format is given below:
39820 <!ELEMENT btrace (block* | pt) >
39821 <!ATTLIST btrace version CDATA #FIXED "1.0">
39823 <!ELEMENT block EMPTY>
39824 <!ATTLIST block begin CDATA #REQUIRED
39825 end CDATA #REQUIRED>
39827 <!ELEMENT pt (pt-config?, raw?)>
39829 <!ELEMENT pt-config (cpu?)>
39831 <!ELEMENT cpu EMPTY>
39832 <!ATTLIST cpu vendor CDATA #REQUIRED
39833 family CDATA #REQUIRED
39834 model CDATA #REQUIRED
39835 stepping CDATA #REQUIRED>
39837 <!ELEMENT raw (#PCDATA)>
39840 @node Branch Trace Configuration Format
39841 @section Branch Trace Configuration Format
39842 @cindex branch trace configuration format
39844 For each inferior thread, @value{GDBN} can obtain the branch trace
39845 configuration using the @samp{qXfer:btrace-conf:read}
39846 (@pxref{qXfer btrace-conf read}) packet.
39848 The configuration describes the branch trace format and configuration
39849 settings for that format. The following information is described:
39853 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39856 The size of the @acronym{BTS} ring buffer in bytes.
39859 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39863 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39867 @value{GDBN} must be linked with the Expat library to support XML
39868 branch trace configuration discovery. @xref{Expat}.
39870 The formal DTD for the branch trace configuration format is given below:
39873 <!ELEMENT btrace-conf (bts?, pt?)>
39874 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39876 <!ELEMENT bts EMPTY>
39877 <!ATTLIST bts size CDATA #IMPLIED>
39879 <!ELEMENT pt EMPTY>
39880 <!ATTLIST pt size CDATA #IMPLIED>
39883 @include agentexpr.texi
39885 @node Target Descriptions
39886 @appendix Target Descriptions
39887 @cindex target descriptions
39889 One of the challenges of using @value{GDBN} to debug embedded systems
39890 is that there are so many minor variants of each processor
39891 architecture in use. It is common practice for vendors to start with
39892 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39893 and then make changes to adapt it to a particular market niche. Some
39894 architectures have hundreds of variants, available from dozens of
39895 vendors. This leads to a number of problems:
39899 With so many different customized processors, it is difficult for
39900 the @value{GDBN} maintainers to keep up with the changes.
39902 Since individual variants may have short lifetimes or limited
39903 audiences, it may not be worthwhile to carry information about every
39904 variant in the @value{GDBN} source tree.
39906 When @value{GDBN} does support the architecture of the embedded system
39907 at hand, the task of finding the correct architecture name to give the
39908 @command{set architecture} command can be error-prone.
39911 To address these problems, the @value{GDBN} remote protocol allows a
39912 target system to not only identify itself to @value{GDBN}, but to
39913 actually describe its own features. This lets @value{GDBN} support
39914 processor variants it has never seen before --- to the extent that the
39915 descriptions are accurate, and that @value{GDBN} understands them.
39917 @value{GDBN} must be linked with the Expat library to support XML
39918 target descriptions. @xref{Expat}.
39921 * Retrieving Descriptions:: How descriptions are fetched from a target.
39922 * Target Description Format:: The contents of a target description.
39923 * Predefined Target Types:: Standard types available for target
39925 * Standard Target Features:: Features @value{GDBN} knows about.
39928 @node Retrieving Descriptions
39929 @section Retrieving Descriptions
39931 Target descriptions can be read from the target automatically, or
39932 specified by the user manually. The default behavior is to read the
39933 description from the target. @value{GDBN} retrieves it via the remote
39934 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39935 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39936 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39937 XML document, of the form described in @ref{Target Description
39940 Alternatively, you can specify a file to read for the target description.
39941 If a file is set, the target will not be queried. The commands to
39942 specify a file are:
39945 @cindex set tdesc filename
39946 @item set tdesc filename @var{path}
39947 Read the target description from @var{path}.
39949 @cindex unset tdesc filename
39950 @item unset tdesc filename
39951 Do not read the XML target description from a file. @value{GDBN}
39952 will use the description supplied by the current target.
39954 @cindex show tdesc filename
39955 @item show tdesc filename
39956 Show the filename to read for a target description, if any.
39960 @node Target Description Format
39961 @section Target Description Format
39962 @cindex target descriptions, XML format
39964 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39965 document which complies with the Document Type Definition provided in
39966 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39967 means you can use generally available tools like @command{xmllint} to
39968 check that your feature descriptions are well-formed and valid.
39969 However, to help people unfamiliar with XML write descriptions for
39970 their targets, we also describe the grammar here.
39972 Target descriptions can identify the architecture of the remote target
39973 and (for some architectures) provide information about custom register
39974 sets. They can also identify the OS ABI of the remote target.
39975 @value{GDBN} can use this information to autoconfigure for your
39976 target, or to warn you if you connect to an unsupported target.
39978 Here is a simple target description:
39981 <target version="1.0">
39982 <architecture>i386:x86-64</architecture>
39987 This minimal description only says that the target uses
39988 the x86-64 architecture.
39990 A target description has the following overall form, with [ ] marking
39991 optional elements and @dots{} marking repeatable elements. The elements
39992 are explained further below.
39995 <?xml version="1.0"?>
39996 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39997 <target version="1.0">
39998 @r{[}@var{architecture}@r{]}
39999 @r{[}@var{osabi}@r{]}
40000 @r{[}@var{compatible}@r{]}
40001 @r{[}@var{feature}@dots{}@r{]}
40006 The description is generally insensitive to whitespace and line
40007 breaks, under the usual common-sense rules. The XML version
40008 declaration and document type declaration can generally be omitted
40009 (@value{GDBN} does not require them), but specifying them may be
40010 useful for XML validation tools. The @samp{version} attribute for
40011 @samp{<target>} may also be omitted, but we recommend
40012 including it; if future versions of @value{GDBN} use an incompatible
40013 revision of @file{gdb-target.dtd}, they will detect and report
40014 the version mismatch.
40016 @subsection Inclusion
40017 @cindex target descriptions, inclusion
40020 @cindex <xi:include>
40023 It can sometimes be valuable to split a target description up into
40024 several different annexes, either for organizational purposes, or to
40025 share files between different possible target descriptions. You can
40026 divide a description into multiple files by replacing any element of
40027 the target description with an inclusion directive of the form:
40030 <xi:include href="@var{document}"/>
40034 When @value{GDBN} encounters an element of this form, it will retrieve
40035 the named XML @var{document}, and replace the inclusion directive with
40036 the contents of that document. If the current description was read
40037 using @samp{qXfer}, then so will be the included document;
40038 @var{document} will be interpreted as the name of an annex. If the
40039 current description was read from a file, @value{GDBN} will look for
40040 @var{document} as a file in the same directory where it found the
40041 original description.
40043 @subsection Architecture
40044 @cindex <architecture>
40046 An @samp{<architecture>} element has this form:
40049 <architecture>@var{arch}</architecture>
40052 @var{arch} is one of the architectures from the set accepted by
40053 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40056 @cindex @code{<osabi>}
40058 This optional field was introduced in @value{GDBN} version 7.0.
40059 Previous versions of @value{GDBN} ignore it.
40061 An @samp{<osabi>} element has this form:
40064 <osabi>@var{abi-name}</osabi>
40067 @var{abi-name} is an OS ABI name from the same selection accepted by
40068 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40070 @subsection Compatible Architecture
40071 @cindex @code{<compatible>}
40073 This optional field was introduced in @value{GDBN} version 7.0.
40074 Previous versions of @value{GDBN} ignore it.
40076 A @samp{<compatible>} element has this form:
40079 <compatible>@var{arch}</compatible>
40082 @var{arch} is one of the architectures from the set accepted by
40083 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40085 A @samp{<compatible>} element is used to specify that the target
40086 is able to run binaries in some other than the main target architecture
40087 given by the @samp{<architecture>} element. For example, on the
40088 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40089 or @code{powerpc:common64}, but the system is able to run binaries
40090 in the @code{spu} architecture as well. The way to describe this
40091 capability with @samp{<compatible>} is as follows:
40094 <architecture>powerpc:common</architecture>
40095 <compatible>spu</compatible>
40098 @subsection Features
40101 Each @samp{<feature>} describes some logical portion of the target
40102 system. Features are currently used to describe available CPU
40103 registers and the types of their contents. A @samp{<feature>} element
40107 <feature name="@var{name}">
40108 @r{[}@var{type}@dots{}@r{]}
40114 Each feature's name should be unique within the description. The name
40115 of a feature does not matter unless @value{GDBN} has some special
40116 knowledge of the contents of that feature; if it does, the feature
40117 should have its standard name. @xref{Standard Target Features}.
40121 Any register's value is a collection of bits which @value{GDBN} must
40122 interpret. The default interpretation is a two's complement integer,
40123 but other types can be requested by name in the register description.
40124 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40125 Target Types}), and the description can define additional composite types.
40127 Each type element must have an @samp{id} attribute, which gives
40128 a unique (within the containing @samp{<feature>}) name to the type.
40129 Types must be defined before they are used.
40132 Some targets offer vector registers, which can be treated as arrays
40133 of scalar elements. These types are written as @samp{<vector>} elements,
40134 specifying the array element type, @var{type}, and the number of elements,
40138 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40142 If a register's value is usefully viewed in multiple ways, define it
40143 with a union type containing the useful representations. The
40144 @samp{<union>} element contains one or more @samp{<field>} elements,
40145 each of which has a @var{name} and a @var{type}:
40148 <union id="@var{id}">
40149 <field name="@var{name}" type="@var{type}"/>
40155 If a register's value is composed from several separate values, define
40156 it with a structure type. There are two forms of the @samp{<struct>}
40157 element; a @samp{<struct>} element must either contain only bitfields
40158 or contain no bitfields. If the structure contains only bitfields,
40159 its total size in bytes must be specified, each bitfield must have an
40160 explicit start and end, and bitfields are automatically assigned an
40161 integer type. The field's @var{start} should be less than or
40162 equal to its @var{end}, and zero represents the least significant bit.
40165 <struct id="@var{id}" size="@var{size}">
40166 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40171 If the structure contains no bitfields, then each field has an
40172 explicit type, and no implicit padding is added.
40175 <struct id="@var{id}">
40176 <field name="@var{name}" type="@var{type}"/>
40182 If a register's value is a series of single-bit flags, define it with
40183 a flags type. The @samp{<flags>} element has an explicit @var{size}
40184 and contains one or more @samp{<field>} elements. Each field has a
40185 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40189 <flags id="@var{id}" size="@var{size}">
40190 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40195 @subsection Registers
40198 Each register is represented as an element with this form:
40201 <reg name="@var{name}"
40202 bitsize="@var{size}"
40203 @r{[}regnum="@var{num}"@r{]}
40204 @r{[}save-restore="@var{save-restore}"@r{]}
40205 @r{[}type="@var{type}"@r{]}
40206 @r{[}group="@var{group}"@r{]}/>
40210 The components are as follows:
40215 The register's name; it must be unique within the target description.
40218 The register's size, in bits.
40221 The register's number. If omitted, a register's number is one greater
40222 than that of the previous register (either in the current feature or in
40223 a preceding feature); the first register in the target description
40224 defaults to zero. This register number is used to read or write
40225 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40226 packets, and registers appear in the @code{g} and @code{G} packets
40227 in order of increasing register number.
40230 Whether the register should be preserved across inferior function
40231 calls; this must be either @code{yes} or @code{no}. The default is
40232 @code{yes}, which is appropriate for most registers except for
40233 some system control registers; this is not related to the target's
40237 The type of the register. It may be a predefined type, a type
40238 defined in the current feature, or one of the special types @code{int}
40239 and @code{float}. @code{int} is an integer type of the correct size
40240 for @var{bitsize}, and @code{float} is a floating point type (in the
40241 architecture's normal floating point format) of the correct size for
40242 @var{bitsize}. The default is @code{int}.
40245 The register group to which this register belongs. It must
40246 be either @code{general}, @code{float}, or @code{vector}. If no
40247 @var{group} is specified, @value{GDBN} will not display the register
40248 in @code{info registers}.
40252 @node Predefined Target Types
40253 @section Predefined Target Types
40254 @cindex target descriptions, predefined types
40256 Type definitions in the self-description can build up composite types
40257 from basic building blocks, but can not define fundamental types. Instead,
40258 standard identifiers are provided by @value{GDBN} for the fundamental
40259 types. The currently supported types are:
40268 Signed integer types holding the specified number of bits.
40275 Unsigned integer types holding the specified number of bits.
40279 Pointers to unspecified code and data. The program counter and
40280 any dedicated return address register may be marked as code
40281 pointers; printing a code pointer converts it into a symbolic
40282 address. The stack pointer and any dedicated address registers
40283 may be marked as data pointers.
40286 Single precision IEEE floating point.
40289 Double precision IEEE floating point.
40292 The 12-byte extended precision format used by ARM FPA registers.
40295 The 10-byte extended precision format used by x87 registers.
40298 32bit @sc{eflags} register used by x86.
40301 32bit @sc{mxcsr} register used by x86.
40305 @node Standard Target Features
40306 @section Standard Target Features
40307 @cindex target descriptions, standard features
40309 A target description must contain either no registers or all the
40310 target's registers. If the description contains no registers, then
40311 @value{GDBN} will assume a default register layout, selected based on
40312 the architecture. If the description contains any registers, the
40313 default layout will not be used; the standard registers must be
40314 described in the target description, in such a way that @value{GDBN}
40315 can recognize them.
40317 This is accomplished by giving specific names to feature elements
40318 which contain standard registers. @value{GDBN} will look for features
40319 with those names and verify that they contain the expected registers;
40320 if any known feature is missing required registers, or if any required
40321 feature is missing, @value{GDBN} will reject the target
40322 description. You can add additional registers to any of the
40323 standard features --- @value{GDBN} will display them just as if
40324 they were added to an unrecognized feature.
40326 This section lists the known features and their expected contents.
40327 Sample XML documents for these features are included in the
40328 @value{GDBN} source tree, in the directory @file{gdb/features}.
40330 Names recognized by @value{GDBN} should include the name of the
40331 company or organization which selected the name, and the overall
40332 architecture to which the feature applies; so e.g.@: the feature
40333 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40335 The names of registers are not case sensitive for the purpose
40336 of recognizing standard features, but @value{GDBN} will only display
40337 registers using the capitalization used in the description.
40340 * AArch64 Features::
40343 * MicroBlaze Features::
40346 * Nios II Features::
40347 * PowerPC Features::
40348 * S/390 and System z Features::
40353 @node AArch64 Features
40354 @subsection AArch64 Features
40355 @cindex target descriptions, AArch64 features
40357 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40358 targets. It should contain registers @samp{x0} through @samp{x30},
40359 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40361 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40362 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40366 @subsection ARM Features
40367 @cindex target descriptions, ARM features
40369 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40371 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40372 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40374 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40375 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40376 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40379 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40380 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40382 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40383 it should contain at least registers @samp{wR0} through @samp{wR15} and
40384 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40385 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40387 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40388 should contain at least registers @samp{d0} through @samp{d15}. If
40389 they are present, @samp{d16} through @samp{d31} should also be included.
40390 @value{GDBN} will synthesize the single-precision registers from
40391 halves of the double-precision registers.
40393 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40394 need to contain registers; it instructs @value{GDBN} to display the
40395 VFP double-precision registers as vectors and to synthesize the
40396 quad-precision registers from pairs of double-precision registers.
40397 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40398 be present and include 32 double-precision registers.
40400 @node i386 Features
40401 @subsection i386 Features
40402 @cindex target descriptions, i386 features
40404 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40405 targets. It should describe the following registers:
40409 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40411 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40413 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40414 @samp{fs}, @samp{gs}
40416 @samp{st0} through @samp{st7}
40418 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40419 @samp{foseg}, @samp{fooff} and @samp{fop}
40422 The register sets may be different, depending on the target.
40424 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40425 describe registers:
40429 @samp{xmm0} through @samp{xmm7} for i386
40431 @samp{xmm0} through @samp{xmm15} for amd64
40436 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40437 @samp{org.gnu.gdb.i386.sse} feature. It should
40438 describe the upper 128 bits of @sc{ymm} registers:
40442 @samp{ymm0h} through @samp{ymm7h} for i386
40444 @samp{ymm0h} through @samp{ymm15h} for amd64
40447 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40448 Memory Protection Extension (MPX). It should describe the following registers:
40452 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40454 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40457 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40458 describe a single register, @samp{orig_eax}.
40460 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40461 @samp{org.gnu.gdb.i386.avx} feature. It should
40462 describe additional @sc{xmm} registers:
40466 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40469 It should describe the upper 128 bits of additional @sc{ymm} registers:
40473 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40477 describe the upper 256 bits of @sc{zmm} registers:
40481 @samp{zmm0h} through @samp{zmm7h} for i386.
40483 @samp{zmm0h} through @samp{zmm15h} for amd64.
40487 describe the additional @sc{zmm} registers:
40491 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40494 @node MicroBlaze Features
40495 @subsection MicroBlaze Features
40496 @cindex target descriptions, MicroBlaze features
40498 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40499 targets. It should contain registers @samp{r0} through @samp{r31},
40500 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40501 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40502 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40504 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40505 If present, it should contain registers @samp{rshr} and @samp{rslr}
40507 @node MIPS Features
40508 @subsection @acronym{MIPS} Features
40509 @cindex target descriptions, @acronym{MIPS} features
40511 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40512 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40513 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40516 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40517 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40518 registers. They may be 32-bit or 64-bit depending on the target.
40520 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40521 it may be optional in a future version of @value{GDBN}. It should
40522 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40523 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40525 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40526 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40527 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40528 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40530 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40531 contain a single register, @samp{restart}, which is used by the
40532 Linux kernel to control restartable syscalls.
40534 @node M68K Features
40535 @subsection M68K Features
40536 @cindex target descriptions, M68K features
40539 @item @samp{org.gnu.gdb.m68k.core}
40540 @itemx @samp{org.gnu.gdb.coldfire.core}
40541 @itemx @samp{org.gnu.gdb.fido.core}
40542 One of those features must be always present.
40543 The feature that is present determines which flavor of m68k is
40544 used. The feature that is present should contain registers
40545 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40546 @samp{sp}, @samp{ps} and @samp{pc}.
40548 @item @samp{org.gnu.gdb.coldfire.fp}
40549 This feature is optional. If present, it should contain registers
40550 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40554 @node Nios II Features
40555 @subsection Nios II Features
40556 @cindex target descriptions, Nios II features
40558 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40559 targets. It should contain the 32 core registers (@samp{zero},
40560 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40561 @samp{pc}, and the 16 control registers (@samp{status} through
40564 @node PowerPC Features
40565 @subsection PowerPC Features
40566 @cindex target descriptions, PowerPC features
40568 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40569 targets. It should contain registers @samp{r0} through @samp{r31},
40570 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40571 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40573 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40574 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40576 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40577 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40580 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40581 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40582 will combine these registers with the floating point registers
40583 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40584 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40585 through @samp{vs63}, the set of vector registers for POWER7.
40587 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40588 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40589 @samp{spefscr}. SPE targets should provide 32-bit registers in
40590 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40591 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40592 these to present registers @samp{ev0} through @samp{ev31} to the
40595 @node S/390 and System z Features
40596 @subsection S/390 and System z Features
40597 @cindex target descriptions, S/390 features
40598 @cindex target descriptions, System z features
40600 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40601 System z targets. It should contain the PSW and the 16 general
40602 registers. In particular, System z targets should provide the 64-bit
40603 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40604 S/390 targets should provide the 32-bit versions of these registers.
40605 A System z target that runs in 31-bit addressing mode should provide
40606 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40607 register's upper halves @samp{r0h} through @samp{r15h}, and their
40608 lower halves @samp{r0l} through @samp{r15l}.
40610 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40611 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40614 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40615 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40617 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40618 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40619 targets and 32-bit otherwise. In addition, the feature may contain
40620 the @samp{last_break} register, whose width depends on the addressing
40621 mode, as well as the @samp{system_call} register, which is always
40624 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40625 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40626 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40628 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40629 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40630 combined by @value{GDBN} with the floating point registers @samp{f0}
40631 through @samp{f15} to present the 128-bit wide vector registers
40632 @samp{v0} through @samp{v15}. In addition, this feature should
40633 contain the 128-bit wide vector registers @samp{v16} through
40636 @node TIC6x Features
40637 @subsection TMS320C6x Features
40638 @cindex target descriptions, TIC6x features
40639 @cindex target descriptions, TMS320C6x features
40640 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40641 targets. It should contain registers @samp{A0} through @samp{A15},
40642 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40644 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40645 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40646 through @samp{B31}.
40648 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40649 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40651 @node Operating System Information
40652 @appendix Operating System Information
40653 @cindex operating system information
40659 Users of @value{GDBN} often wish to obtain information about the state of
40660 the operating system running on the target---for example the list of
40661 processes, or the list of open files. This section describes the
40662 mechanism that makes it possible. This mechanism is similar to the
40663 target features mechanism (@pxref{Target Descriptions}), but focuses
40664 on a different aspect of target.
40666 Operating system information is retrived from the target via the
40667 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40668 read}). The object name in the request should be @samp{osdata}, and
40669 the @var{annex} identifies the data to be fetched.
40672 @appendixsection Process list
40673 @cindex operating system information, process list
40675 When requesting the process list, the @var{annex} field in the
40676 @samp{qXfer} request should be @samp{processes}. The returned data is
40677 an XML document. The formal syntax of this document is defined in
40678 @file{gdb/features/osdata.dtd}.
40680 An example document is:
40683 <?xml version="1.0"?>
40684 <!DOCTYPE target SYSTEM "osdata.dtd">
40685 <osdata type="processes">
40687 <column name="pid">1</column>
40688 <column name="user">root</column>
40689 <column name="command">/sbin/init</column>
40690 <column name="cores">1,2,3</column>
40695 Each item should include a column whose name is @samp{pid}. The value
40696 of that column should identify the process on the target. The
40697 @samp{user} and @samp{command} columns are optional, and will be
40698 displayed by @value{GDBN}. The @samp{cores} column, if present,
40699 should contain a comma-separated list of cores that this process
40700 is running on. Target may provide additional columns,
40701 which @value{GDBN} currently ignores.
40703 @node Trace File Format
40704 @appendix Trace File Format
40705 @cindex trace file format
40707 The trace file comes in three parts: a header, a textual description
40708 section, and a trace frame section with binary data.
40710 The header has the form @code{\x7fTRACE0\n}. The first byte is
40711 @code{0x7f} so as to indicate that the file contains binary data,
40712 while the @code{0} is a version number that may have different values
40715 The description section consists of multiple lines of @sc{ascii} text
40716 separated by newline characters (@code{0xa}). The lines may include a
40717 variety of optional descriptive or context-setting information, such
40718 as tracepoint definitions or register set size. @value{GDBN} will
40719 ignore any line that it does not recognize. An empty line marks the end
40722 @c FIXME add some specific types of data
40724 The trace frame section consists of a number of consecutive frames.
40725 Each frame begins with a two-byte tracepoint number, followed by a
40726 four-byte size giving the amount of data in the frame. The data in
40727 the frame consists of a number of blocks, each introduced by a
40728 character indicating its type (at least register, memory, and trace
40729 state variable). The data in this section is raw binary, not a
40730 hexadecimal or other encoding; its endianness matches the target's
40733 @c FIXME bi-arch may require endianness/arch info in description section
40736 @item R @var{bytes}
40737 Register block. The number and ordering of bytes matches that of a
40738 @code{g} packet in the remote protocol. Note that these are the
40739 actual bytes, in target order and @value{GDBN} register order, not a
40740 hexadecimal encoding.
40742 @item M @var{address} @var{length} @var{bytes}...
40743 Memory block. This is a contiguous block of memory, at the 8-byte
40744 address @var{address}, with a 2-byte length @var{length}, followed by
40745 @var{length} bytes.
40747 @item V @var{number} @var{value}
40748 Trace state variable block. This records the 8-byte signed value
40749 @var{value} of trace state variable numbered @var{number}.
40753 Future enhancements of the trace file format may include additional types
40756 @node Index Section Format
40757 @appendix @code{.gdb_index} section format
40758 @cindex .gdb_index section format
40759 @cindex index section format
40761 This section documents the index section that is created by @code{save
40762 gdb-index} (@pxref{Index Files}). The index section is
40763 DWARF-specific; some knowledge of DWARF is assumed in this
40766 The mapped index file format is designed to be directly
40767 @code{mmap}able on any architecture. In most cases, a datum is
40768 represented using a little-endian 32-bit integer value, called an
40769 @code{offset_type}. Big endian machines must byte-swap the values
40770 before using them. Exceptions to this rule are noted. The data is
40771 laid out such that alignment is always respected.
40773 A mapped index consists of several areas, laid out in order.
40777 The file header. This is a sequence of values, of @code{offset_type}
40778 unless otherwise noted:
40782 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40783 Version 4 uses a different hashing function from versions 5 and 6.
40784 Version 6 includes symbols for inlined functions, whereas versions 4
40785 and 5 do not. Version 7 adds attributes to the CU indices in the
40786 symbol table. Version 8 specifies that symbols from DWARF type units
40787 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40788 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40790 @value{GDBN} will only read version 4, 5, or 6 indices
40791 by specifying @code{set use-deprecated-index-sections on}.
40792 GDB has a workaround for potentially broken version 7 indices so it is
40793 currently not flagged as deprecated.
40796 The offset, from the start of the file, of the CU list.
40799 The offset, from the start of the file, of the types CU list. Note
40800 that this area can be empty, in which case this offset will be equal
40801 to the next offset.
40804 The offset, from the start of the file, of the address area.
40807 The offset, from the start of the file, of the symbol table.
40810 The offset, from the start of the file, of the constant pool.
40814 The CU list. This is a sequence of pairs of 64-bit little-endian
40815 values, sorted by the CU offset. The first element in each pair is
40816 the offset of a CU in the @code{.debug_info} section. The second
40817 element in each pair is the length of that CU. References to a CU
40818 elsewhere in the map are done using a CU index, which is just the
40819 0-based index into this table. Note that if there are type CUs, then
40820 conceptually CUs and type CUs form a single list for the purposes of
40824 The types CU list. This is a sequence of triplets of 64-bit
40825 little-endian values. In a triplet, the first value is the CU offset,
40826 the second value is the type offset in the CU, and the third value is
40827 the type signature. The types CU list is not sorted.
40830 The address area. The address area consists of a sequence of address
40831 entries. Each address entry has three elements:
40835 The low address. This is a 64-bit little-endian value.
40838 The high address. This is a 64-bit little-endian value. Like
40839 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40842 The CU index. This is an @code{offset_type} value.
40846 The symbol table. This is an open-addressed hash table. The size of
40847 the hash table is always a power of 2.
40849 Each slot in the hash table consists of a pair of @code{offset_type}
40850 values. The first value is the offset of the symbol's name in the
40851 constant pool. The second value is the offset of the CU vector in the
40854 If both values are 0, then this slot in the hash table is empty. This
40855 is ok because while 0 is a valid constant pool index, it cannot be a
40856 valid index for both a string and a CU vector.
40858 The hash value for a table entry is computed by applying an
40859 iterative hash function to the symbol's name. Starting with an
40860 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40861 the string is incorporated into the hash using the formula depending on the
40866 The formula is @code{r = r * 67 + c - 113}.
40868 @item Versions 5 to 7
40869 The formula is @code{r = r * 67 + tolower (c) - 113}.
40872 The terminating @samp{\0} is not incorporated into the hash.
40874 The step size used in the hash table is computed via
40875 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40876 value, and @samp{size} is the size of the hash table. The step size
40877 is used to find the next candidate slot when handling a hash
40880 The names of C@t{++} symbols in the hash table are canonicalized. We
40881 don't currently have a simple description of the canonicalization
40882 algorithm; if you intend to create new index sections, you must read
40886 The constant pool. This is simply a bunch of bytes. It is organized
40887 so that alignment is correct: CU vectors are stored first, followed by
40890 A CU vector in the constant pool is a sequence of @code{offset_type}
40891 values. The first value is the number of CU indices in the vector.
40892 Each subsequent value is the index and symbol attributes of a CU in
40893 the CU list. This element in the hash table is used to indicate which
40894 CUs define the symbol and how the symbol is used.
40895 See below for the format of each CU index+attributes entry.
40897 A string in the constant pool is zero-terminated.
40900 Attributes were added to CU index values in @code{.gdb_index} version 7.
40901 If a symbol has multiple uses within a CU then there is one
40902 CU index+attributes value for each use.
40904 The format of each CU index+attributes entry is as follows
40910 This is the index of the CU in the CU list.
40912 These bits are reserved for future purposes and must be zero.
40914 The kind of the symbol in the CU.
40918 This value is reserved and should not be used.
40919 By reserving zero the full @code{offset_type} value is backwards compatible
40920 with previous versions of the index.
40922 The symbol is a type.
40924 The symbol is a variable or an enum value.
40926 The symbol is a function.
40928 Any other kind of symbol.
40930 These values are reserved.
40934 This bit is zero if the value is global and one if it is static.
40936 The determination of whether a symbol is global or static is complicated.
40937 The authorative reference is the file @file{dwarf2read.c} in
40938 @value{GDBN} sources.
40942 This pseudo-code describes the computation of a symbol's kind and
40943 global/static attributes in the index.
40946 is_external = get_attribute (die, DW_AT_external);
40947 language = get_attribute (cu_die, DW_AT_language);
40950 case DW_TAG_typedef:
40951 case DW_TAG_base_type:
40952 case DW_TAG_subrange_type:
40956 case DW_TAG_enumerator:
40958 is_static = (language != CPLUS && language != JAVA);
40960 case DW_TAG_subprogram:
40962 is_static = ! (is_external || language == ADA);
40964 case DW_TAG_constant:
40966 is_static = ! is_external;
40968 case DW_TAG_variable:
40970 is_static = ! is_external;
40972 case DW_TAG_namespace:
40976 case DW_TAG_class_type:
40977 case DW_TAG_interface_type:
40978 case DW_TAG_structure_type:
40979 case DW_TAG_union_type:
40980 case DW_TAG_enumeration_type:
40982 is_static = (language != CPLUS && language != JAVA);
40990 @appendix Manual pages
40994 * gdb man:: The GNU Debugger man page
40995 * gdbserver man:: Remote Server for the GNU Debugger man page
40996 * gcore man:: Generate a core file of a running program
40997 * gdbinit man:: gdbinit scripts
41003 @c man title gdb The GNU Debugger
41005 @c man begin SYNOPSIS gdb
41006 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41007 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41008 [@option{-b}@w{ }@var{bps}]
41009 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41010 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41011 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41012 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41013 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41016 @c man begin DESCRIPTION gdb
41017 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41018 going on ``inside'' another program while it executes -- or what another
41019 program was doing at the moment it crashed.
41021 @value{GDBN} can do four main kinds of things (plus other things in support of
41022 these) to help you catch bugs in the act:
41026 Start your program, specifying anything that might affect its behavior.
41029 Make your program stop on specified conditions.
41032 Examine what has happened, when your program has stopped.
41035 Change things in your program, so you can experiment with correcting the
41036 effects of one bug and go on to learn about another.
41039 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41042 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41043 commands from the terminal until you tell it to exit with the @value{GDBN}
41044 command @code{quit}. You can get online help from @value{GDBN} itself
41045 by using the command @code{help}.
41047 You can run @code{gdb} with no arguments or options; but the most
41048 usual way to start @value{GDBN} is with one argument or two, specifying an
41049 executable program as the argument:
41055 You can also start with both an executable program and a core file specified:
41061 You can, instead, specify a process ID as a second argument, if you want
41062 to debug a running process:
41070 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41071 named @file{1234}; @value{GDBN} does check for a core file first).
41072 With option @option{-p} you can omit the @var{program} filename.
41074 Here are some of the most frequently needed @value{GDBN} commands:
41076 @c pod2man highlights the right hand side of the @item lines.
41078 @item break [@var{file}:]@var{functiop}
41079 Set a breakpoint at @var{function} (in @var{file}).
41081 @item run [@var{arglist}]
41082 Start your program (with @var{arglist}, if specified).
41085 Backtrace: display the program stack.
41087 @item print @var{expr}
41088 Display the value of an expression.
41091 Continue running your program (after stopping, e.g. at a breakpoint).
41094 Execute next program line (after stopping); step @emph{over} any
41095 function calls in the line.
41097 @item edit [@var{file}:]@var{function}
41098 look at the program line where it is presently stopped.
41100 @item list [@var{file}:]@var{function}
41101 type the text of the program in the vicinity of where it is presently stopped.
41104 Execute next program line (after stopping); step @emph{into} any
41105 function calls in the line.
41107 @item help [@var{name}]
41108 Show information about @value{GDBN} command @var{name}, or general information
41109 about using @value{GDBN}.
41112 Exit from @value{GDBN}.
41116 For full details on @value{GDBN},
41117 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41118 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41119 as the @code{gdb} entry in the @code{info} program.
41123 @c man begin OPTIONS gdb
41124 Any arguments other than options specify an executable
41125 file and core file (or process ID); that is, the first argument
41126 encountered with no
41127 associated option flag is equivalent to a @option{-se} option, and the second,
41128 if any, is equivalent to a @option{-c} option if it's the name of a file.
41130 both long and short forms; both are shown here. The long forms are also
41131 recognized if you truncate them, so long as enough of the option is
41132 present to be unambiguous. (If you prefer, you can flag option
41133 arguments with @option{+} rather than @option{-}, though we illustrate the
41134 more usual convention.)
41136 All the options and command line arguments you give are processed
41137 in sequential order. The order makes a difference when the @option{-x}
41143 List all options, with brief explanations.
41145 @item -symbols=@var{file}
41146 @itemx -s @var{file}
41147 Read symbol table from file @var{file}.
41150 Enable writing into executable and core files.
41152 @item -exec=@var{file}
41153 @itemx -e @var{file}
41154 Use file @var{file} as the executable file to execute when
41155 appropriate, and for examining pure data in conjunction with a core
41158 @item -se=@var{file}
41159 Read symbol table from file @var{file} and use it as the executable
41162 @item -core=@var{file}
41163 @itemx -c @var{file}
41164 Use file @var{file} as a core dump to examine.
41166 @item -command=@var{file}
41167 @itemx -x @var{file}
41168 Execute @value{GDBN} commands from file @var{file}.
41170 @item -ex @var{command}
41171 Execute given @value{GDBN} @var{command}.
41173 @item -directory=@var{directory}
41174 @itemx -d @var{directory}
41175 Add @var{directory} to the path to search for source files.
41178 Do not execute commands from @file{~/.gdbinit}.
41182 Do not execute commands from any @file{.gdbinit} initialization files.
41186 ``Quiet''. Do not print the introductory and copyright messages. These
41187 messages are also suppressed in batch mode.
41190 Run in batch mode. Exit with status @code{0} after processing all the command
41191 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41192 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41193 commands in the command files.
41195 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41196 download and run a program on another computer; in order to make this
41197 more useful, the message
41200 Program exited normally.
41204 (which is ordinarily issued whenever a program running under @value{GDBN} control
41205 terminates) is not issued when running in batch mode.
41207 @item -cd=@var{directory}
41208 Run @value{GDBN} using @var{directory} as its working directory,
41209 instead of the current directory.
41213 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41214 @value{GDBN} to output the full file name and line number in a standard,
41215 recognizable fashion each time a stack frame is displayed (which
41216 includes each time the program stops). This recognizable format looks
41217 like two @samp{\032} characters, followed by the file name, line number
41218 and character position separated by colons, and a newline. The
41219 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41220 characters as a signal to display the source code for the frame.
41223 Set the line speed (baud rate or bits per second) of any serial
41224 interface used by @value{GDBN} for remote debugging.
41226 @item -tty=@var{device}
41227 Run using @var{device} for your program's standard input and output.
41231 @c man begin SEEALSO gdb
41233 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41234 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41235 documentation are properly installed at your site, the command
41242 should give you access to the complete manual.
41244 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41245 Richard M. Stallman and Roland H. Pesch, July 1991.
41249 @node gdbserver man
41250 @heading gdbserver man
41252 @c man title gdbserver Remote Server for the GNU Debugger
41254 @c man begin SYNOPSIS gdbserver
41255 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41257 gdbserver --attach @var{comm} @var{pid}
41259 gdbserver --multi @var{comm}
41263 @c man begin DESCRIPTION gdbserver
41264 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41265 than the one which is running the program being debugged.
41268 @subheading Usage (server (target) side)
41271 Usage (server (target) side):
41274 First, you need to have a copy of the program you want to debug put onto
41275 the target system. The program can be stripped to save space if needed, as
41276 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41277 the @value{GDBN} running on the host system.
41279 To use the server, you log on to the target system, and run the @command{gdbserver}
41280 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41281 your program, and (c) its arguments. The general syntax is:
41284 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41287 For example, using a serial port, you might say:
41291 @c @file would wrap it as F</dev/com1>.
41292 target> gdbserver /dev/com1 emacs foo.txt
41295 target> gdbserver @file{/dev/com1} emacs foo.txt
41299 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41300 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41301 waits patiently for the host @value{GDBN} to communicate with it.
41303 To use a TCP connection, you could say:
41306 target> gdbserver host:2345 emacs foo.txt
41309 This says pretty much the same thing as the last example, except that we are
41310 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41311 that we are expecting to see a TCP connection from @code{host} to local TCP port
41312 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41313 want for the port number as long as it does not conflict with any existing TCP
41314 ports on the target system. This same port number must be used in the host
41315 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41316 you chose a port number that conflicts with another service, @command{gdbserver} will
41317 print an error message and exit.
41319 @command{gdbserver} can also attach to running programs.
41320 This is accomplished via the @option{--attach} argument. The syntax is:
41323 target> gdbserver --attach @var{comm} @var{pid}
41326 @var{pid} is the process ID of a currently running process. It isn't
41327 necessary to point @command{gdbserver} at a binary for the running process.
41329 To start @code{gdbserver} without supplying an initial command to run
41330 or process ID to attach, use the @option{--multi} command line option.
41331 In such case you should connect using @kbd{target extended-remote} to start
41332 the program you want to debug.
41335 target> gdbserver --multi @var{comm}
41339 @subheading Usage (host side)
41345 You need an unstripped copy of the target program on your host system, since
41346 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41347 would, with the target program as the first argument. (You may need to use the
41348 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41349 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41350 new command you need to know about is @code{target remote}
41351 (or @code{target extended-remote}). Its argument is either
41352 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41353 descriptor. For example:
41357 @c @file would wrap it as F</dev/ttyb>.
41358 (gdb) target remote /dev/ttyb
41361 (gdb) target remote @file{/dev/ttyb}
41366 communicates with the server via serial line @file{/dev/ttyb}, and:
41369 (gdb) target remote the-target:2345
41373 communicates via a TCP connection to port 2345 on host `the-target', where
41374 you previously started up @command{gdbserver} with the same port number. Note that for
41375 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41376 command, otherwise you may get an error that looks something like
41377 `Connection refused'.
41379 @command{gdbserver} can also debug multiple inferiors at once,
41382 the @value{GDBN} manual in node @code{Inferiors and Programs}
41383 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41386 @ref{Inferiors and Programs}.
41388 In such case use the @code{extended-remote} @value{GDBN} command variant:
41391 (gdb) target extended-remote the-target:2345
41394 The @command{gdbserver} option @option{--multi} may or may not be used in such
41398 @c man begin OPTIONS gdbserver
41399 There are three different modes for invoking @command{gdbserver}:
41404 Debug a specific program specified by its program name:
41407 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41410 The @var{comm} parameter specifies how should the server communicate
41411 with @value{GDBN}; it is either a device name (to use a serial line),
41412 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41413 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41414 debug in @var{prog}. Any remaining arguments will be passed to the
41415 program verbatim. When the program exits, @value{GDBN} will close the
41416 connection, and @code{gdbserver} will exit.
41419 Debug a specific program by specifying the process ID of a running
41423 gdbserver --attach @var{comm} @var{pid}
41426 The @var{comm} parameter is as described above. Supply the process ID
41427 of a running program in @var{pid}; @value{GDBN} will do everything
41428 else. Like with the previous mode, when the process @var{pid} exits,
41429 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41432 Multi-process mode -- debug more than one program/process:
41435 gdbserver --multi @var{comm}
41438 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41439 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41440 close the connection when a process being debugged exits, so you can
41441 debug several processes in the same session.
41444 In each of the modes you may specify these options:
41449 List all options, with brief explanations.
41452 This option causes @command{gdbserver} to print its version number and exit.
41455 @command{gdbserver} will attach to a running program. The syntax is:
41458 target> gdbserver --attach @var{comm} @var{pid}
41461 @var{pid} is the process ID of a currently running process. It isn't
41462 necessary to point @command{gdbserver} at a binary for the running process.
41465 To start @code{gdbserver} without supplying an initial command to run
41466 or process ID to attach, use this command line option.
41467 Then you can connect using @kbd{target extended-remote} and start
41468 the program you want to debug. The syntax is:
41471 target> gdbserver --multi @var{comm}
41475 Instruct @code{gdbserver} to display extra status information about the debugging
41477 This option is intended for @code{gdbserver} development and for bug reports to
41480 @item --remote-debug
41481 Instruct @code{gdbserver} to display remote protocol debug output.
41482 This option is intended for @code{gdbserver} development and for bug reports to
41485 @item --debug-format=option1@r{[},option2,...@r{]}
41486 Instruct @code{gdbserver} to include extra information in each line
41487 of debugging output.
41488 @xref{Other Command-Line Arguments for gdbserver}.
41491 Specify a wrapper to launch programs
41492 for debugging. The option should be followed by the name of the
41493 wrapper, then any command-line arguments to pass to the wrapper, then
41494 @kbd{--} indicating the end of the wrapper arguments.
41497 By default, @command{gdbserver} keeps the listening TCP port open, so that
41498 additional connections are possible. However, if you start @code{gdbserver}
41499 with the @option{--once} option, it will stop listening for any further
41500 connection attempts after connecting to the first @value{GDBN} session.
41502 @c --disable-packet is not documented for users.
41504 @c --disable-randomization and --no-disable-randomization are superseded by
41505 @c QDisableRandomization.
41510 @c man begin SEEALSO gdbserver
41512 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41513 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41514 documentation are properly installed at your site, the command
41520 should give you access to the complete manual.
41522 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41523 Richard M. Stallman and Roland H. Pesch, July 1991.
41530 @c man title gcore Generate a core file of a running program
41533 @c man begin SYNOPSIS gcore
41534 gcore [-o @var{filename}] @var{pid}
41538 @c man begin DESCRIPTION gcore
41539 Generate a core dump of a running program with process ID @var{pid}.
41540 Produced file is equivalent to a kernel produced core file as if the process
41541 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41542 limit). Unlike after a crash, after @command{gcore} the program remains
41543 running without any change.
41546 @c man begin OPTIONS gcore
41548 @item -o @var{filename}
41549 The optional argument
41550 @var{filename} specifies the file name where to put the core dump.
41551 If not specified, the file name defaults to @file{core.@var{pid}},
41552 where @var{pid} is the running program process ID.
41556 @c man begin SEEALSO gcore
41558 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41559 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41560 documentation are properly installed at your site, the command
41567 should give you access to the complete manual.
41569 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41570 Richard M. Stallman and Roland H. Pesch, July 1991.
41577 @c man title gdbinit GDB initialization scripts
41580 @c man begin SYNOPSIS gdbinit
41581 @ifset SYSTEM_GDBINIT
41582 @value{SYSTEM_GDBINIT}
41591 @c man begin DESCRIPTION gdbinit
41592 These files contain @value{GDBN} commands to automatically execute during
41593 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41596 the @value{GDBN} manual in node @code{Sequences}
41597 -- shell command @code{info -f gdb -n Sequences}.
41603 Please read more in
41605 the @value{GDBN} manual in node @code{Startup}
41606 -- shell command @code{info -f gdb -n Startup}.
41613 @ifset SYSTEM_GDBINIT
41614 @item @value{SYSTEM_GDBINIT}
41616 @ifclear SYSTEM_GDBINIT
41617 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41619 System-wide initialization file. It is executed unless user specified
41620 @value{GDBN} option @code{-nx} or @code{-n}.
41623 the @value{GDBN} manual in node @code{System-wide configuration}
41624 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41627 @ref{System-wide configuration}.
41631 User initialization file. It is executed unless user specified
41632 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41635 Initialization file for current directory. It may need to be enabled with
41636 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41639 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41640 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41643 @ref{Init File in the Current Directory}.
41648 @c man begin SEEALSO gdbinit
41650 gdb(1), @code{info -f gdb -n Startup}
41652 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41653 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41654 documentation are properly installed at your site, the command
41660 should give you access to the complete manual.
41662 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41663 Richard M. Stallman and Roland H. Pesch, July 1991.
41669 @node GNU Free Documentation License
41670 @appendix GNU Free Documentation License
41673 @node Concept Index
41674 @unnumbered Concept Index
41678 @node Command and Variable Index
41679 @unnumbered Command, Variable, and Function Index
41684 % I think something like @@colophon should be in texinfo. In the
41686 \long\def\colophon{\hbox to0pt{}\vfill
41687 \centerline{The body of this manual is set in}
41688 \centerline{\fontname\tenrm,}
41689 \centerline{with headings in {\bf\fontname\tenbf}}
41690 \centerline{and examples in {\tt\fontname\tentt}.}
41691 \centerline{{\it\fontname\tenit\/},}
41692 \centerline{{\bf\fontname\tenbf}, and}
41693 \centerline{{\sl\fontname\tensl\/}}
41694 \centerline{are used for emphasis.}\vfill}
41696 % Blame: doc@@cygnus.com, 1991.