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 GNU/Linux and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
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 other systems,
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
3134 that create additional processes using the @code{fork} or @code{vfork}
3135 functions. On @sc{gnu}/Linux platforms, this feature is supported
3136 with 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.
3450 @cindex data breakpoints
3451 @cindex memory tracing
3452 @cindex breakpoint on memory address
3453 @cindex breakpoint on variable modification
3454 A @dfn{watchpoint} is a special breakpoint that stops your program
3455 when the value of an expression changes. The expression may be a value
3456 of a variable, or it could involve values of one or more variables
3457 combined by operators, such as @samp{a + b}. This is sometimes called
3458 @dfn{data breakpoints}. You must use a different command to set
3459 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3460 from that, you can manage a watchpoint like any other breakpoint: you
3461 enable, disable, and delete both breakpoints and watchpoints using the
3464 You can arrange to have values from your program displayed automatically
3465 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3469 @cindex breakpoint on events
3470 A @dfn{catchpoint} is another special breakpoint that stops your program
3471 when a certain kind of event occurs, such as the throwing of a C@t{++}
3472 exception or the loading of a library. As with watchpoints, you use a
3473 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3474 Catchpoints}), but aside from that, you can manage a catchpoint like any
3475 other breakpoint. (To stop when your program receives a signal, use the
3476 @code{handle} command; see @ref{Signals, ,Signals}.)
3478 @cindex breakpoint numbers
3479 @cindex numbers for breakpoints
3480 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3481 catchpoint when you create it; these numbers are successive integers
3482 starting with one. In many of the commands for controlling various
3483 features of breakpoints you use the breakpoint number to say which
3484 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3485 @dfn{disabled}; if disabled, it has no effect on your program until you
3488 @cindex breakpoint ranges
3489 @cindex ranges of breakpoints
3490 Some @value{GDBN} commands accept a range of breakpoints on which to
3491 operate. A breakpoint range is either a single breakpoint number, like
3492 @samp{5}, or two such numbers, in increasing order, separated by a
3493 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3494 all breakpoints in that range are operated on.
3497 * Set Breaks:: Setting breakpoints
3498 * Set Watchpoints:: Setting watchpoints
3499 * Set Catchpoints:: Setting catchpoints
3500 * Delete Breaks:: Deleting breakpoints
3501 * Disabling:: Disabling breakpoints
3502 * Conditions:: Break conditions
3503 * Break Commands:: Breakpoint command lists
3504 * Dynamic Printf:: Dynamic printf
3505 * Save Breakpoints:: How to save breakpoints in a file
3506 * Static Probe Points:: Listing static probe points
3507 * Error in Breakpoints:: ``Cannot insert breakpoints''
3508 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3512 @subsection Setting Breakpoints
3514 @c FIXME LMB what does GDB do if no code on line of breakpt?
3515 @c consider in particular declaration with/without initialization.
3517 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3520 @kindex b @r{(@code{break})}
3521 @vindex $bpnum@r{, convenience variable}
3522 @cindex latest breakpoint
3523 Breakpoints are set with the @code{break} command (abbreviated
3524 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3525 number of the breakpoint you've set most recently; see @ref{Convenience
3526 Vars,, Convenience Variables}, for a discussion of what you can do with
3527 convenience variables.
3530 @item break @var{location}
3531 Set a breakpoint at the given @var{location}, which can specify a
3532 function name, a line number, or an address of an instruction.
3533 (@xref{Specify Location}, for a list of all the possible ways to
3534 specify a @var{location}.) The breakpoint will stop your program just
3535 before it executes any of the code in the specified @var{location}.
3537 When using source languages that permit overloading of symbols, such as
3538 C@t{++}, a function name may refer to more than one possible place to break.
3539 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3542 It is also possible to insert a breakpoint that will stop the program
3543 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3544 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3547 When called without any arguments, @code{break} sets a breakpoint at
3548 the next instruction to be executed in the selected stack frame
3549 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3550 innermost, this makes your program stop as soon as control
3551 returns to that frame. This is similar to the effect of a
3552 @code{finish} command in the frame inside the selected frame---except
3553 that @code{finish} does not leave an active breakpoint. If you use
3554 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3555 the next time it reaches the current location; this may be useful
3558 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3559 least one instruction has been executed. If it did not do this, you
3560 would be unable to proceed past a breakpoint without first disabling the
3561 breakpoint. This rule applies whether or not the breakpoint already
3562 existed when your program stopped.
3564 @item break @dots{} if @var{cond}
3565 Set a breakpoint with condition @var{cond}; evaluate the expression
3566 @var{cond} each time the breakpoint is reached, and stop only if the
3567 value is nonzero---that is, if @var{cond} evaluates as true.
3568 @samp{@dots{}} stands for one of the possible arguments described
3569 above (or no argument) specifying where to break. @xref{Conditions,
3570 ,Break Conditions}, for more information on breakpoint conditions.
3573 @item tbreak @var{args}
3574 Set a breakpoint enabled only for one stop. The @var{args} are the
3575 same as for the @code{break} command, and the breakpoint is set in the same
3576 way, but the breakpoint is automatically deleted after the first time your
3577 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3580 @cindex hardware breakpoints
3581 @item hbreak @var{args}
3582 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3583 @code{break} command and the breakpoint is set in the same way, but the
3584 breakpoint requires hardware support and some target hardware may not
3585 have this support. The main purpose of this is EPROM/ROM code
3586 debugging, so you can set a breakpoint at an instruction without
3587 changing the instruction. This can be used with the new trap-generation
3588 provided by SPARClite DSU and most x86-based targets. These targets
3589 will generate traps when a program accesses some data or instruction
3590 address that is assigned to the debug registers. However the hardware
3591 breakpoint registers can take a limited number of breakpoints. For
3592 example, on the DSU, only two data breakpoints can be set at a time, and
3593 @value{GDBN} will reject this command if more than two are used. Delete
3594 or disable unused hardware breakpoints before setting new ones
3595 (@pxref{Disabling, ,Disabling Breakpoints}).
3596 @xref{Conditions, ,Break Conditions}.
3597 For remote targets, you can restrict the number of hardware
3598 breakpoints @value{GDBN} will use, see @ref{set remote
3599 hardware-breakpoint-limit}.
3602 @item thbreak @var{args}
3603 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3604 are the same as for the @code{hbreak} command and the breakpoint is set in
3605 the same way. However, like the @code{tbreak} command,
3606 the breakpoint is automatically deleted after the
3607 first time your program stops there. Also, like the @code{hbreak}
3608 command, the breakpoint requires hardware support and some target hardware
3609 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3610 See also @ref{Conditions, ,Break Conditions}.
3613 @cindex regular expression
3614 @cindex breakpoints at functions matching a regexp
3615 @cindex set breakpoints in many functions
3616 @item rbreak @var{regex}
3617 Set breakpoints on all functions matching the regular expression
3618 @var{regex}. This command sets an unconditional breakpoint on all
3619 matches, printing a list of all breakpoints it set. Once these
3620 breakpoints are set, they are treated just like the breakpoints set with
3621 the @code{break} command. You can delete them, disable them, or make
3622 them conditional the same way as any other breakpoint.
3624 The syntax of the regular expression is the standard one used with tools
3625 like @file{grep}. Note that this is different from the syntax used by
3626 shells, so for instance @code{foo*} matches all functions that include
3627 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3628 @code{.*} leading and trailing the regular expression you supply, so to
3629 match only functions that begin with @code{foo}, use @code{^foo}.
3631 @cindex non-member C@t{++} functions, set breakpoint in
3632 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3633 breakpoints on overloaded functions that are not members of any special
3636 @cindex set breakpoints on all functions
3637 The @code{rbreak} command can be used to set breakpoints in
3638 @strong{all} the functions in a program, like this:
3641 (@value{GDBP}) rbreak .
3644 @item rbreak @var{file}:@var{regex}
3645 If @code{rbreak} is called with a filename qualification, it limits
3646 the search for functions matching the given regular expression to the
3647 specified @var{file}. This can be used, for example, to set breakpoints on
3648 every function in a given file:
3651 (@value{GDBP}) rbreak file.c:.
3654 The colon separating the filename qualifier from the regex may
3655 optionally be surrounded by spaces.
3657 @kindex info breakpoints
3658 @cindex @code{$_} and @code{info breakpoints}
3659 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3660 @itemx info break @r{[}@var{n}@dots{}@r{]}
3661 Print a table of all breakpoints, watchpoints, and catchpoints set and
3662 not deleted. Optional argument @var{n} means print information only
3663 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3664 For each breakpoint, following columns are printed:
3667 @item Breakpoint Numbers
3669 Breakpoint, watchpoint, or catchpoint.
3671 Whether the breakpoint is marked to be disabled or deleted when hit.
3672 @item Enabled or Disabled
3673 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3674 that are not enabled.
3676 Where the breakpoint is in your program, as a memory address. For a
3677 pending breakpoint whose address is not yet known, this field will
3678 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3679 library that has the symbol or line referred by breakpoint is loaded.
3680 See below for details. A breakpoint with several locations will
3681 have @samp{<MULTIPLE>} in this field---see below for details.
3683 Where the breakpoint is in the source for your program, as a file and
3684 line number. For a pending breakpoint, the original string passed to
3685 the breakpoint command will be listed as it cannot be resolved until
3686 the appropriate shared library is loaded in the future.
3690 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3691 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3692 @value{GDBN} on the host's side. If it is ``target'', then the condition
3693 is evaluated by the target. The @code{info break} command shows
3694 the condition on the line following the affected breakpoint, together with
3695 its condition evaluation mode in between parentheses.
3697 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3698 allowed to have a condition specified for it. The condition is not parsed for
3699 validity until a shared library is loaded that allows the pending
3700 breakpoint to resolve to a valid location.
3703 @code{info break} with a breakpoint
3704 number @var{n} as argument lists only that breakpoint. The
3705 convenience variable @code{$_} and the default examining-address for
3706 the @code{x} command are set to the address of the last breakpoint
3707 listed (@pxref{Memory, ,Examining Memory}).
3710 @code{info break} displays a count of the number of times the breakpoint
3711 has been hit. This is especially useful in conjunction with the
3712 @code{ignore} command. You can ignore a large number of breakpoint
3713 hits, look at the breakpoint info to see how many times the breakpoint
3714 was hit, and then run again, ignoring one less than that number. This
3715 will get you quickly to the last hit of that breakpoint.
3718 For a breakpoints with an enable count (xref) greater than 1,
3719 @code{info break} also displays that count.
3723 @value{GDBN} allows you to set any number of breakpoints at the same place in
3724 your program. There is nothing silly or meaningless about this. When
3725 the breakpoints are conditional, this is even useful
3726 (@pxref{Conditions, ,Break Conditions}).
3728 @cindex multiple locations, breakpoints
3729 @cindex breakpoints, multiple locations
3730 It is possible that a breakpoint corresponds to several locations
3731 in your program. Examples of this situation are:
3735 Multiple functions in the program may have the same name.
3738 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3739 instances of the function body, used in different cases.
3742 For a C@t{++} template function, a given line in the function can
3743 correspond to any number of instantiations.
3746 For an inlined function, a given source line can correspond to
3747 several places where that function is inlined.
3750 In all those cases, @value{GDBN} will insert a breakpoint at all
3751 the relevant locations.
3753 A breakpoint with multiple locations is displayed in the breakpoint
3754 table using several rows---one header row, followed by one row for
3755 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3756 address column. The rows for individual locations contain the actual
3757 addresses for locations, and show the functions to which those
3758 locations belong. The number column for a location is of the form
3759 @var{breakpoint-number}.@var{location-number}.
3764 Num Type Disp Enb Address What
3765 1 breakpoint keep y <MULTIPLE>
3767 breakpoint already hit 1 time
3768 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3769 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3772 Each location can be individually enabled or disabled by passing
3773 @var{breakpoint-number}.@var{location-number} as argument to the
3774 @code{enable} and @code{disable} commands. Note that you cannot
3775 delete the individual locations from the list, you can only delete the
3776 entire list of locations that belong to their parent breakpoint (with
3777 the @kbd{delete @var{num}} command, where @var{num} is the number of
3778 the parent breakpoint, 1 in the above example). Disabling or enabling
3779 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3780 that belong to that breakpoint.
3782 @cindex pending breakpoints
3783 It's quite common to have a breakpoint inside a shared library.
3784 Shared libraries can be loaded and unloaded explicitly,
3785 and possibly repeatedly, as the program is executed. To support
3786 this use case, @value{GDBN} updates breakpoint locations whenever
3787 any shared library is loaded or unloaded. Typically, you would
3788 set a breakpoint in a shared library at the beginning of your
3789 debugging session, when the library is not loaded, and when the
3790 symbols from the library are not available. When you try to set
3791 breakpoint, @value{GDBN} will ask you if you want to set
3792 a so called @dfn{pending breakpoint}---breakpoint whose address
3793 is not yet resolved.
3795 After the program is run, whenever a new shared library is loaded,
3796 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3797 shared library contains the symbol or line referred to by some
3798 pending breakpoint, that breakpoint is resolved and becomes an
3799 ordinary breakpoint. When a library is unloaded, all breakpoints
3800 that refer to its symbols or source lines become pending again.
3802 This logic works for breakpoints with multiple locations, too. For
3803 example, if you have a breakpoint in a C@t{++} template function, and
3804 a newly loaded shared library has an instantiation of that template,
3805 a new location is added to the list of locations for the breakpoint.
3807 Except for having unresolved address, pending breakpoints do not
3808 differ from regular breakpoints. You can set conditions or commands,
3809 enable and disable them and perform other breakpoint operations.
3811 @value{GDBN} provides some additional commands for controlling what
3812 happens when the @samp{break} command cannot resolve breakpoint
3813 address specification to an address:
3815 @kindex set breakpoint pending
3816 @kindex show breakpoint pending
3818 @item set breakpoint pending auto
3819 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3820 location, it queries you whether a pending breakpoint should be created.
3822 @item set breakpoint pending on
3823 This indicates that an unrecognized breakpoint location should automatically
3824 result in a pending breakpoint being created.
3826 @item set breakpoint pending off
3827 This indicates that pending breakpoints are not to be created. Any
3828 unrecognized breakpoint location results in an error. This setting does
3829 not affect any pending breakpoints previously created.
3831 @item show breakpoint pending
3832 Show the current behavior setting for creating pending breakpoints.
3835 The settings above only affect the @code{break} command and its
3836 variants. Once breakpoint is set, it will be automatically updated
3837 as shared libraries are loaded and unloaded.
3839 @cindex automatic hardware breakpoints
3840 For some targets, @value{GDBN} can automatically decide if hardware or
3841 software breakpoints should be used, depending on whether the
3842 breakpoint address is read-only or read-write. This applies to
3843 breakpoints set with the @code{break} command as well as to internal
3844 breakpoints set by commands like @code{next} and @code{finish}. For
3845 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3848 You can control this automatic behaviour with the following commands::
3850 @kindex set breakpoint auto-hw
3851 @kindex show breakpoint auto-hw
3853 @item set breakpoint auto-hw on
3854 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3855 will try to use the target memory map to decide if software or hardware
3856 breakpoint must be used.
3858 @item set breakpoint auto-hw off
3859 This indicates @value{GDBN} should not automatically select breakpoint
3860 type. If the target provides a memory map, @value{GDBN} will warn when
3861 trying to set software breakpoint at a read-only address.
3864 @value{GDBN} normally implements breakpoints by replacing the program code
3865 at the breakpoint address with a special instruction, which, when
3866 executed, given control to the debugger. By default, the program
3867 code is so modified only when the program is resumed. As soon as
3868 the program stops, @value{GDBN} restores the original instructions. This
3869 behaviour guards against leaving breakpoints inserted in the
3870 target should gdb abrubptly disconnect. However, with slow remote
3871 targets, inserting and removing breakpoint can reduce the performance.
3872 This behavior can be controlled with the following commands::
3874 @kindex set breakpoint always-inserted
3875 @kindex show breakpoint always-inserted
3877 @item set breakpoint always-inserted off
3878 All breakpoints, including newly added by the user, are inserted in
3879 the target only when the target is resumed. All breakpoints are
3880 removed from the target when it stops. This is the default mode.
3882 @item set breakpoint always-inserted on
3883 Causes all breakpoints to be inserted in the target at all times. If
3884 the user adds a new breakpoint, or changes an existing breakpoint, the
3885 breakpoints in the target are updated immediately. A breakpoint is
3886 removed from the target only when breakpoint itself is deleted.
3889 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3890 when a breakpoint breaks. If the condition is true, then the process being
3891 debugged stops, otherwise the process is resumed.
3893 If the target supports evaluating conditions on its end, @value{GDBN} may
3894 download the breakpoint, together with its conditions, to it.
3896 This feature can be controlled via the following commands:
3898 @kindex set breakpoint condition-evaluation
3899 @kindex show breakpoint condition-evaluation
3901 @item set breakpoint condition-evaluation host
3902 This option commands @value{GDBN} to evaluate the breakpoint
3903 conditions on the host's side. Unconditional breakpoints are sent to
3904 the target which in turn receives the triggers and reports them back to GDB
3905 for condition evaluation. This is the standard evaluation mode.
3907 @item set breakpoint condition-evaluation target
3908 This option commands @value{GDBN} to download breakpoint conditions
3909 to the target at the moment of their insertion. The target
3910 is responsible for evaluating the conditional expression and reporting
3911 breakpoint stop events back to @value{GDBN} whenever the condition
3912 is true. Due to limitations of target-side evaluation, some conditions
3913 cannot be evaluated there, e.g., conditions that depend on local data
3914 that is only known to the host. Examples include
3915 conditional expressions involving convenience variables, complex types
3916 that cannot be handled by the agent expression parser and expressions
3917 that are too long to be sent over to the target, specially when the
3918 target is a remote system. In these cases, the conditions will be
3919 evaluated by @value{GDBN}.
3921 @item set breakpoint condition-evaluation auto
3922 This is the default mode. If the target supports evaluating breakpoint
3923 conditions on its end, @value{GDBN} will download breakpoint conditions to
3924 the target (limitations mentioned previously apply). If the target does
3925 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3926 to evaluating all these conditions on the host's side.
3930 @cindex negative breakpoint numbers
3931 @cindex internal @value{GDBN} breakpoints
3932 @value{GDBN} itself sometimes sets breakpoints in your program for
3933 special purposes, such as proper handling of @code{longjmp} (in C
3934 programs). These internal breakpoints are assigned negative numbers,
3935 starting with @code{-1}; @samp{info breakpoints} does not display them.
3936 You can see these breakpoints with the @value{GDBN} maintenance command
3937 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3940 @node Set Watchpoints
3941 @subsection Setting Watchpoints
3943 @cindex setting watchpoints
3944 You can use a watchpoint to stop execution whenever the value of an
3945 expression changes, without having to predict a particular place where
3946 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3947 The expression may be as simple as the value of a single variable, or
3948 as complex as many variables combined by operators. Examples include:
3952 A reference to the value of a single variable.
3955 An address cast to an appropriate data type. For example,
3956 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3957 address (assuming an @code{int} occupies 4 bytes).
3960 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3961 expression can use any operators valid in the program's native
3962 language (@pxref{Languages}).
3965 You can set a watchpoint on an expression even if the expression can
3966 not be evaluated yet. For instance, you can set a watchpoint on
3967 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3968 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3969 the expression produces a valid value. If the expression becomes
3970 valid in some other way than changing a variable (e.g.@: if the memory
3971 pointed to by @samp{*global_ptr} becomes readable as the result of a
3972 @code{malloc} call), @value{GDBN} may not stop until the next time
3973 the expression changes.
3975 @cindex software watchpoints
3976 @cindex hardware watchpoints
3977 Depending on your system, watchpoints may be implemented in software or
3978 hardware. @value{GDBN} does software watchpointing by single-stepping your
3979 program and testing the variable's value each time, which is hundreds of
3980 times slower than normal execution. (But this may still be worth it, to
3981 catch errors where you have no clue what part of your program is the
3984 On some systems, such as most PowerPC or x86-based targets,
3985 @value{GDBN} includes support for hardware watchpoints, which do not
3986 slow down the running of your program.
3990 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3991 Set a watchpoint for an expression. @value{GDBN} will break when the
3992 expression @var{expr} is written into by the program and its value
3993 changes. The simplest (and the most popular) use of this command is
3994 to watch the value of a single variable:
3997 (@value{GDBP}) watch foo
4000 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4001 argument, @value{GDBN} breaks only when the thread identified by
4002 @var{threadnum} changes the value of @var{expr}. If any other threads
4003 change the value of @var{expr}, @value{GDBN} will not break. Note
4004 that watchpoints restricted to a single thread in this way only work
4005 with Hardware Watchpoints.
4007 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4008 (see below). The @code{-location} argument tells @value{GDBN} to
4009 instead watch the memory referred to by @var{expr}. In this case,
4010 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4011 and watch the memory at that address. The type of the result is used
4012 to determine the size of the watched memory. If the expression's
4013 result does not have an address, then @value{GDBN} will print an
4016 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4017 of masked watchpoints, if the current architecture supports this
4018 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4019 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4020 to an address to watch. The mask specifies that some bits of an address
4021 (the bits which are reset in the mask) should be ignored when matching
4022 the address accessed by the inferior against the watchpoint address.
4023 Thus, a masked watchpoint watches many addresses simultaneously---those
4024 addresses whose unmasked bits are identical to the unmasked bits in the
4025 watchpoint address. The @code{mask} argument implies @code{-location}.
4029 (@value{GDBP}) watch foo mask 0xffff00ff
4030 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4034 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4035 Set a watchpoint that will break when the value of @var{expr} is read
4039 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4040 Set a watchpoint that will break when @var{expr} is either read from
4041 or written into by the program.
4043 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4044 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4045 This command prints a list of watchpoints, using the same format as
4046 @code{info break} (@pxref{Set Breaks}).
4049 If you watch for a change in a numerically entered address you need to
4050 dereference it, as the address itself is just a constant number which will
4051 never change. @value{GDBN} refuses to create a watchpoint that watches
4052 a never-changing value:
4055 (@value{GDBP}) watch 0x600850
4056 Cannot watch constant value 0x600850.
4057 (@value{GDBP}) watch *(int *) 0x600850
4058 Watchpoint 1: *(int *) 6293584
4061 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4062 watchpoints execute very quickly, and the debugger reports a change in
4063 value at the exact instruction where the change occurs. If @value{GDBN}
4064 cannot set a hardware watchpoint, it sets a software watchpoint, which
4065 executes more slowly and reports the change in value at the next
4066 @emph{statement}, not the instruction, after the change occurs.
4068 @cindex use only software watchpoints
4069 You can force @value{GDBN} to use only software watchpoints with the
4070 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4071 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4072 the underlying system supports them. (Note that hardware-assisted
4073 watchpoints that were set @emph{before} setting
4074 @code{can-use-hw-watchpoints} to zero will still use the hardware
4075 mechanism of watching expression values.)
4078 @item set can-use-hw-watchpoints
4079 @kindex set can-use-hw-watchpoints
4080 Set whether or not to use hardware watchpoints.
4082 @item show can-use-hw-watchpoints
4083 @kindex show can-use-hw-watchpoints
4084 Show the current mode of using hardware watchpoints.
4087 For remote targets, you can restrict the number of hardware
4088 watchpoints @value{GDBN} will use, see @ref{set remote
4089 hardware-breakpoint-limit}.
4091 When you issue the @code{watch} command, @value{GDBN} reports
4094 Hardware watchpoint @var{num}: @var{expr}
4098 if it was able to set a hardware watchpoint.
4100 Currently, the @code{awatch} and @code{rwatch} commands can only set
4101 hardware watchpoints, because accesses to data that don't change the
4102 value of the watched expression cannot be detected without examining
4103 every instruction as it is being executed, and @value{GDBN} does not do
4104 that currently. If @value{GDBN} finds that it is unable to set a
4105 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4106 will print a message like this:
4109 Expression cannot be implemented with read/access watchpoint.
4112 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4113 data type of the watched expression is wider than what a hardware
4114 watchpoint on the target machine can handle. For example, some systems
4115 can only watch regions that are up to 4 bytes wide; on such systems you
4116 cannot set hardware watchpoints for an expression that yields a
4117 double-precision floating-point number (which is typically 8 bytes
4118 wide). As a work-around, it might be possible to break the large region
4119 into a series of smaller ones and watch them with separate watchpoints.
4121 If you set too many hardware watchpoints, @value{GDBN} might be unable
4122 to insert all of them when you resume the execution of your program.
4123 Since the precise number of active watchpoints is unknown until such
4124 time as the program is about to be resumed, @value{GDBN} might not be
4125 able to warn you about this when you set the watchpoints, and the
4126 warning will be printed only when the program is resumed:
4129 Hardware watchpoint @var{num}: Could not insert watchpoint
4133 If this happens, delete or disable some of the watchpoints.
4135 Watching complex expressions that reference many variables can also
4136 exhaust the resources available for hardware-assisted watchpoints.
4137 That's because @value{GDBN} needs to watch every variable in the
4138 expression with separately allocated resources.
4140 If you call a function interactively using @code{print} or @code{call},
4141 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4142 kind of breakpoint or the call completes.
4144 @value{GDBN} automatically deletes watchpoints that watch local
4145 (automatic) variables, or expressions that involve such variables, when
4146 they go out of scope, that is, when the execution leaves the block in
4147 which these variables were defined. In particular, when the program
4148 being debugged terminates, @emph{all} local variables go out of scope,
4149 and so only watchpoints that watch global variables remain set. If you
4150 rerun the program, you will need to set all such watchpoints again. One
4151 way of doing that would be to set a code breakpoint at the entry to the
4152 @code{main} function and when it breaks, set all the watchpoints.
4154 @cindex watchpoints and threads
4155 @cindex threads and watchpoints
4156 In multi-threaded programs, watchpoints will detect changes to the
4157 watched expression from every thread.
4160 @emph{Warning:} In multi-threaded programs, software watchpoints
4161 have only limited usefulness. If @value{GDBN} creates a software
4162 watchpoint, it can only watch the value of an expression @emph{in a
4163 single thread}. If you are confident that the expression can only
4164 change due to the current thread's activity (and if you are also
4165 confident that no other thread can become current), then you can use
4166 software watchpoints as usual. However, @value{GDBN} may not notice
4167 when a non-current thread's activity changes the expression. (Hardware
4168 watchpoints, in contrast, watch an expression in all threads.)
4171 @xref{set remote hardware-watchpoint-limit}.
4173 @node Set Catchpoints
4174 @subsection Setting Catchpoints
4175 @cindex catchpoints, setting
4176 @cindex exception handlers
4177 @cindex event handling
4179 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4180 kinds of program events, such as C@t{++} exceptions or the loading of a
4181 shared library. Use the @code{catch} command to set a catchpoint.
4185 @item catch @var{event}
4186 Stop when @var{event} occurs. The @var{event} can be any of the following:
4189 @item throw @r{[}@var{regexp}@r{]}
4190 @itemx rethrow @r{[}@var{regexp}@r{]}
4191 @itemx catch @r{[}@var{regexp}@r{]}
4193 @kindex catch rethrow
4195 @cindex stop on C@t{++} exceptions
4196 The throwing, re-throwing, or catching of a C@t{++} exception.
4198 If @var{regexp} is given, then only exceptions whose type matches the
4199 regular expression will be caught.
4201 @vindex $_exception@r{, convenience variable}
4202 The convenience variable @code{$_exception} is available at an
4203 exception-related catchpoint, on some systems. This holds the
4204 exception being thrown.
4206 There are currently some limitations to C@t{++} exception handling in
4211 The support for these commands is system-dependent. Currently, only
4212 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4216 The regular expression feature and the @code{$_exception} convenience
4217 variable rely on the presence of some SDT probes in @code{libstdc++}.
4218 If these probes are not present, then these features cannot be used.
4219 These probes were first available in the GCC 4.8 release, but whether
4220 or not they are available in your GCC also depends on how it was
4224 The @code{$_exception} convenience variable is only valid at the
4225 instruction at which an exception-related catchpoint is set.
4228 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4229 location in the system library which implements runtime exception
4230 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4231 (@pxref{Selection}) to get to your code.
4234 If you call a function interactively, @value{GDBN} normally returns
4235 control to you when the function has finished executing. If the call
4236 raises an exception, however, the call may bypass the mechanism that
4237 returns control to you and cause your program either to abort or to
4238 simply continue running until it hits a breakpoint, catches a signal
4239 that @value{GDBN} is listening for, or exits. This is the case even if
4240 you set a catchpoint for the exception; catchpoints on exceptions are
4241 disabled within interactive calls. @xref{Calling}, for information on
4242 controlling this with @code{set unwind-on-terminating-exception}.
4245 You cannot raise an exception interactively.
4248 You cannot install an exception handler interactively.
4252 @kindex catch exception
4253 @cindex Ada exception catching
4254 @cindex catch Ada exceptions
4255 An Ada exception being raised. If an exception name is specified
4256 at the end of the command (eg @code{catch exception Program_Error}),
4257 the debugger will stop only when this specific exception is raised.
4258 Otherwise, the debugger stops execution when any Ada exception is raised.
4260 When inserting an exception catchpoint on a user-defined exception whose
4261 name is identical to one of the exceptions defined by the language, the
4262 fully qualified name must be used as the exception name. Otherwise,
4263 @value{GDBN} will assume that it should stop on the pre-defined exception
4264 rather than the user-defined one. For instance, assuming an exception
4265 called @code{Constraint_Error} is defined in package @code{Pck}, then
4266 the command to use to catch such exceptions is @kbd{catch exception
4267 Pck.Constraint_Error}.
4269 @item exception unhandled
4270 @kindex catch exception unhandled
4271 An exception that was raised but is not handled by the program.
4274 @kindex catch assert
4275 A failed Ada assertion.
4279 @cindex break on fork/exec
4280 A call to @code{exec}.
4283 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4284 @kindex catch syscall
4285 @cindex break on a system call.
4286 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4287 syscall is a mechanism for application programs to request a service
4288 from the operating system (OS) or one of the OS system services.
4289 @value{GDBN} can catch some or all of the syscalls issued by the
4290 debuggee, and show the related information for each syscall. If no
4291 argument is specified, calls to and returns from all system calls
4294 @var{name} can be any system call name that is valid for the
4295 underlying OS. Just what syscalls are valid depends on the OS. On
4296 GNU and Unix systems, you can find the full list of valid syscall
4297 names on @file{/usr/include/asm/unistd.h}.
4299 @c For MS-Windows, the syscall names and the corresponding numbers
4300 @c can be found, e.g., on this URL:
4301 @c http://www.metasploit.com/users/opcode/syscalls.html
4302 @c but we don't support Windows syscalls yet.
4304 Normally, @value{GDBN} knows in advance which syscalls are valid for
4305 each OS, so you can use the @value{GDBN} command-line completion
4306 facilities (@pxref{Completion,, command completion}) to list the
4309 You may also specify the system call numerically. A syscall's
4310 number is the value passed to the OS's syscall dispatcher to
4311 identify the requested service. When you specify the syscall by its
4312 name, @value{GDBN} uses its database of syscalls to convert the name
4313 into the corresponding numeric code, but using the number directly
4314 may be useful if @value{GDBN}'s database does not have the complete
4315 list of syscalls on your system (e.g., because @value{GDBN} lags
4316 behind the OS upgrades).
4318 The example below illustrates how this command works if you don't provide
4322 (@value{GDBP}) catch syscall
4323 Catchpoint 1 (syscall)
4325 Starting program: /tmp/catch-syscall
4327 Catchpoint 1 (call to syscall 'close'), \
4328 0xffffe424 in __kernel_vsyscall ()
4332 Catchpoint 1 (returned from syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Here is an example of catching a system call by name:
4340 (@value{GDBP}) catch syscall chroot
4341 Catchpoint 1 (syscall 'chroot' [61])
4343 Starting program: /tmp/catch-syscall
4345 Catchpoint 1 (call to syscall 'chroot'), \
4346 0xffffe424 in __kernel_vsyscall ()
4350 Catchpoint 1 (returned from syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 An example of specifying a system call numerically. In the case
4356 below, the syscall number has a corresponding entry in the XML
4357 file, so @value{GDBN} finds its name and prints it:
4360 (@value{GDBP}) catch syscall 252
4361 Catchpoint 1 (syscall(s) 'exit_group')
4363 Starting program: /tmp/catch-syscall
4365 Catchpoint 1 (call to syscall 'exit_group'), \
4366 0xffffe424 in __kernel_vsyscall ()
4370 Program exited normally.
4374 However, there can be situations when there is no corresponding name
4375 in XML file for that syscall number. In this case, @value{GDBN} prints
4376 a warning message saying that it was not able to find the syscall name,
4377 but the catchpoint will be set anyway. See the example below:
4380 (@value{GDBP}) catch syscall 764
4381 warning: The number '764' does not represent a known syscall.
4382 Catchpoint 2 (syscall 764)
4386 If you configure @value{GDBN} using the @samp{--without-expat} option,
4387 it will not be able to display syscall names. Also, if your
4388 architecture does not have an XML file describing its system calls,
4389 you will not be able to see the syscall names. It is important to
4390 notice that these two features are used for accessing the syscall
4391 name database. In either case, you will see a warning like this:
4394 (@value{GDBP}) catch syscall
4395 warning: Could not open "syscalls/i386-linux.xml"
4396 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4397 GDB will not be able to display syscall names.
4398 Catchpoint 1 (syscall)
4402 Of course, the file name will change depending on your architecture and system.
4404 Still using the example above, you can also try to catch a syscall by its
4405 number. In this case, you would see something like:
4408 (@value{GDBP}) catch syscall 252
4409 Catchpoint 1 (syscall(s) 252)
4412 Again, in this case @value{GDBN} would not be able to display syscall's names.
4416 A call to @code{fork}.
4420 A call to @code{vfork}.
4422 @item load @r{[}regexp@r{]}
4423 @itemx unload @r{[}regexp@r{]}
4425 @kindex catch unload
4426 The loading or unloading of a shared library. If @var{regexp} is
4427 given, then the catchpoint will stop only if the regular expression
4428 matches one of the affected libraries.
4430 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4431 @kindex catch signal
4432 The delivery of a signal.
4434 With no arguments, this catchpoint will catch any signal that is not
4435 used internally by @value{GDBN}, specifically, all signals except
4436 @samp{SIGTRAP} and @samp{SIGINT}.
4438 With the argument @samp{all}, all signals, including those used by
4439 @value{GDBN}, will be caught. This argument cannot be used with other
4442 Otherwise, the arguments are a list of signal names as given to
4443 @code{handle} (@pxref{Signals}). Only signals specified in this list
4446 One reason that @code{catch signal} can be more useful than
4447 @code{handle} is that you can attach commands and conditions to the
4450 When a signal is caught by a catchpoint, the signal's @code{stop} and
4451 @code{print} settings, as specified by @code{handle}, are ignored.
4452 However, whether the signal is still delivered to the inferior depends
4453 on the @code{pass} setting; this can be changed in the catchpoint's
4458 @item tcatch @var{event}
4460 Set a catchpoint that is enabled only for one stop. The catchpoint is
4461 automatically deleted after the first time the event is caught.
4465 Use the @code{info break} command to list the current catchpoints.
4469 @subsection Deleting Breakpoints
4471 @cindex clearing breakpoints, watchpoints, catchpoints
4472 @cindex deleting breakpoints, watchpoints, catchpoints
4473 It is often necessary to eliminate a breakpoint, watchpoint, or
4474 catchpoint once it has done its job and you no longer want your program
4475 to stop there. This is called @dfn{deleting} the breakpoint. A
4476 breakpoint that has been deleted no longer exists; it is forgotten.
4478 With the @code{clear} command you can delete breakpoints according to
4479 where they are in your program. With the @code{delete} command you can
4480 delete individual breakpoints, watchpoints, or catchpoints by specifying
4481 their breakpoint numbers.
4483 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4484 automatically ignores breakpoints on the first instruction to be executed
4485 when you continue execution without changing the execution address.
4490 Delete any breakpoints at the next instruction to be executed in the
4491 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4492 the innermost frame is selected, this is a good way to delete a
4493 breakpoint where your program just stopped.
4495 @item clear @var{location}
4496 Delete any breakpoints set at the specified @var{location}.
4497 @xref{Specify Location}, for the various forms of @var{location}; the
4498 most useful ones are listed below:
4501 @item clear @var{function}
4502 @itemx clear @var{filename}:@var{function}
4503 Delete any breakpoints set at entry to the named @var{function}.
4505 @item clear @var{linenum}
4506 @itemx clear @var{filename}:@var{linenum}
4507 Delete any breakpoints set at or within the code of the specified
4508 @var{linenum} of the specified @var{filename}.
4511 @cindex delete breakpoints
4513 @kindex d @r{(@code{delete})}
4514 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4515 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4516 ranges specified as arguments. If no argument is specified, delete all
4517 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4518 confirm off}). You can abbreviate this command as @code{d}.
4522 @subsection Disabling Breakpoints
4524 @cindex enable/disable a breakpoint
4525 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4526 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4527 it had been deleted, but remembers the information on the breakpoint so
4528 that you can @dfn{enable} it again later.
4530 You disable and enable breakpoints, watchpoints, and catchpoints with
4531 the @code{enable} and @code{disable} commands, optionally specifying
4532 one or more breakpoint numbers as arguments. Use @code{info break} to
4533 print a list of all breakpoints, watchpoints, and catchpoints if you
4534 do not know which numbers to use.
4536 Disabling and enabling a breakpoint that has multiple locations
4537 affects all of its locations.
4539 A breakpoint, watchpoint, or catchpoint can have any of several
4540 different states of enablement:
4544 Enabled. The breakpoint stops your program. A breakpoint set
4545 with the @code{break} command starts out in this state.
4547 Disabled. The breakpoint has no effect on your program.
4549 Enabled once. The breakpoint stops your program, but then becomes
4552 Enabled for a count. The breakpoint stops your program for the next
4553 N times, then becomes disabled.
4555 Enabled for deletion. The breakpoint stops your program, but
4556 immediately after it does so it is deleted permanently. A breakpoint
4557 set with the @code{tbreak} command starts out in this state.
4560 You can use the following commands to enable or disable breakpoints,
4561 watchpoints, and catchpoints:
4565 @kindex dis @r{(@code{disable})}
4566 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4567 Disable the specified breakpoints---or all breakpoints, if none are
4568 listed. A disabled breakpoint has no effect but is not forgotten. All
4569 options such as ignore-counts, conditions and commands are remembered in
4570 case the breakpoint is enabled again later. You may abbreviate
4571 @code{disable} as @code{dis}.
4574 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4575 Enable the specified breakpoints (or all defined breakpoints). They
4576 become effective once again in stopping your program.
4578 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4579 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4580 of these breakpoints immediately after stopping your program.
4582 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4583 Enable the specified breakpoints temporarily. @value{GDBN} records
4584 @var{count} with each of the specified breakpoints, and decrements a
4585 breakpoint's count when it is hit. When any count reaches 0,
4586 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4587 count (@pxref{Conditions, ,Break Conditions}), that will be
4588 decremented to 0 before @var{count} is affected.
4590 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4591 Enable the specified breakpoints to work once, then die. @value{GDBN}
4592 deletes any of these breakpoints as soon as your program stops there.
4593 Breakpoints set by the @code{tbreak} command start out in this state.
4596 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4597 @c confusing: tbreak is also initially enabled.
4598 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4599 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4600 subsequently, they become disabled or enabled only when you use one of
4601 the commands above. (The command @code{until} can set and delete a
4602 breakpoint of its own, but it does not change the state of your other
4603 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4607 @subsection Break Conditions
4608 @cindex conditional breakpoints
4609 @cindex breakpoint conditions
4611 @c FIXME what is scope of break condition expr? Context where wanted?
4612 @c in particular for a watchpoint?
4613 The simplest sort of breakpoint breaks every time your program reaches a
4614 specified place. You can also specify a @dfn{condition} for a
4615 breakpoint. A condition is just a Boolean expression in your
4616 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4617 a condition evaluates the expression each time your program reaches it,
4618 and your program stops only if the condition is @emph{true}.
4620 This is the converse of using assertions for program validation; in that
4621 situation, you want to stop when the assertion is violated---that is,
4622 when the condition is false. In C, if you want to test an assertion expressed
4623 by the condition @var{assert}, you should set the condition
4624 @samp{! @var{assert}} on the appropriate breakpoint.
4626 Conditions are also accepted for watchpoints; you may not need them,
4627 since a watchpoint is inspecting the value of an expression anyhow---but
4628 it might be simpler, say, to just set a watchpoint on a variable name,
4629 and specify a condition that tests whether the new value is an interesting
4632 Break conditions can have side effects, and may even call functions in
4633 your program. This can be useful, for example, to activate functions
4634 that log program progress, or to use your own print functions to
4635 format special data structures. The effects are completely predictable
4636 unless there is another enabled breakpoint at the same address. (In
4637 that case, @value{GDBN} might see the other breakpoint first and stop your
4638 program without checking the condition of this one.) Note that
4639 breakpoint commands are usually more convenient and flexible than break
4641 purpose of performing side effects when a breakpoint is reached
4642 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4644 Breakpoint conditions can also be evaluated on the target's side if
4645 the target supports it. Instead of evaluating the conditions locally,
4646 @value{GDBN} encodes the expression into an agent expression
4647 (@pxref{Agent Expressions}) suitable for execution on the target,
4648 independently of @value{GDBN}. Global variables become raw memory
4649 locations, locals become stack accesses, and so forth.
4651 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4652 when its condition evaluates to true. This mechanism may provide faster
4653 response times depending on the performance characteristics of the target
4654 since it does not need to keep @value{GDBN} informed about
4655 every breakpoint trigger, even those with false conditions.
4657 Break conditions can be specified when a breakpoint is set, by using
4658 @samp{if} in the arguments to the @code{break} command. @xref{Set
4659 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4660 with the @code{condition} command.
4662 You can also use the @code{if} keyword with the @code{watch} command.
4663 The @code{catch} command does not recognize the @code{if} keyword;
4664 @code{condition} is the only way to impose a further condition on a
4669 @item condition @var{bnum} @var{expression}
4670 Specify @var{expression} as the break condition for breakpoint,
4671 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4672 breakpoint @var{bnum} stops your program only if the value of
4673 @var{expression} is true (nonzero, in C). When you use
4674 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4675 syntactic correctness, and to determine whether symbols in it have
4676 referents in the context of your breakpoint. If @var{expression} uses
4677 symbols not referenced in the context of the breakpoint, @value{GDBN}
4678 prints an error message:
4681 No symbol "foo" in current context.
4686 not actually evaluate @var{expression} at the time the @code{condition}
4687 command (or a command that sets a breakpoint with a condition, like
4688 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4690 @item condition @var{bnum}
4691 Remove the condition from breakpoint number @var{bnum}. It becomes
4692 an ordinary unconditional breakpoint.
4695 @cindex ignore count (of breakpoint)
4696 A special case of a breakpoint condition is to stop only when the
4697 breakpoint has been reached a certain number of times. This is so
4698 useful that there is a special way to do it, using the @dfn{ignore
4699 count} of the breakpoint. Every breakpoint has an ignore count, which
4700 is an integer. Most of the time, the ignore count is zero, and
4701 therefore has no effect. But if your program reaches a breakpoint whose
4702 ignore count is positive, then instead of stopping, it just decrements
4703 the ignore count by one and continues. As a result, if the ignore count
4704 value is @var{n}, the breakpoint does not stop the next @var{n} times
4705 your program reaches it.
4709 @item ignore @var{bnum} @var{count}
4710 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4711 The next @var{count} times the breakpoint is reached, your program's
4712 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4715 To make the breakpoint stop the next time it is reached, specify
4718 When you use @code{continue} to resume execution of your program from a
4719 breakpoint, you can specify an ignore count directly as an argument to
4720 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4721 Stepping,,Continuing and Stepping}.
4723 If a breakpoint has a positive ignore count and a condition, the
4724 condition is not checked. Once the ignore count reaches zero,
4725 @value{GDBN} resumes checking the condition.
4727 You could achieve the effect of the ignore count with a condition such
4728 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4729 is decremented each time. @xref{Convenience Vars, ,Convenience
4733 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4736 @node Break Commands
4737 @subsection Breakpoint Command Lists
4739 @cindex breakpoint commands
4740 You can give any breakpoint (or watchpoint or catchpoint) a series of
4741 commands to execute when your program stops due to that breakpoint. For
4742 example, you might want to print the values of certain expressions, or
4743 enable other breakpoints.
4747 @kindex end@r{ (breakpoint commands)}
4748 @item commands @r{[}@var{range}@dots{}@r{]}
4749 @itemx @dots{} @var{command-list} @dots{}
4751 Specify a list of commands for the given breakpoints. The commands
4752 themselves appear on the following lines. Type a line containing just
4753 @code{end} to terminate the commands.
4755 To remove all commands from a breakpoint, type @code{commands} and
4756 follow it immediately with @code{end}; that is, give no commands.
4758 With no argument, @code{commands} refers to the last breakpoint,
4759 watchpoint, or catchpoint set (not to the breakpoint most recently
4760 encountered). If the most recent breakpoints were set with a single
4761 command, then the @code{commands} will apply to all the breakpoints
4762 set by that command. This applies to breakpoints set by
4763 @code{rbreak}, and also applies when a single @code{break} command
4764 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4768 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4769 disabled within a @var{command-list}.
4771 You can use breakpoint commands to start your program up again. Simply
4772 use the @code{continue} command, or @code{step}, or any other command
4773 that resumes execution.
4775 Any other commands in the command list, after a command that resumes
4776 execution, are ignored. This is because any time you resume execution
4777 (even with a simple @code{next} or @code{step}), you may encounter
4778 another breakpoint---which could have its own command list, leading to
4779 ambiguities about which list to execute.
4782 If the first command you specify in a command list is @code{silent}, the
4783 usual message about stopping at a breakpoint is not printed. This may
4784 be desirable for breakpoints that are to print a specific message and
4785 then continue. If none of the remaining commands print anything, you
4786 see no sign that the breakpoint was reached. @code{silent} is
4787 meaningful only at the beginning of a breakpoint command list.
4789 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4790 print precisely controlled output, and are often useful in silent
4791 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4793 For example, here is how you could use breakpoint commands to print the
4794 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4800 printf "x is %d\n",x
4805 One application for breakpoint commands is to compensate for one bug so
4806 you can test for another. Put a breakpoint just after the erroneous line
4807 of code, give it a condition to detect the case in which something
4808 erroneous has been done, and give it commands to assign correct values
4809 to any variables that need them. End with the @code{continue} command
4810 so that your program does not stop, and start with the @code{silent}
4811 command so that no output is produced. Here is an example:
4822 @node Dynamic Printf
4823 @subsection Dynamic Printf
4825 @cindex dynamic printf
4827 The dynamic printf command @code{dprintf} combines a breakpoint with
4828 formatted printing of your program's data to give you the effect of
4829 inserting @code{printf} calls into your program on-the-fly, without
4830 having to recompile it.
4832 In its most basic form, the output goes to the GDB console. However,
4833 you can set the variable @code{dprintf-style} for alternate handling.
4834 For instance, you can ask to format the output by calling your
4835 program's @code{printf} function. This has the advantage that the
4836 characters go to the program's output device, so they can recorded in
4837 redirects to files and so forth.
4839 If you are doing remote debugging with a stub or agent, you can also
4840 ask to have the printf handled by the remote agent. In addition to
4841 ensuring that the output goes to the remote program's device along
4842 with any other output the program might produce, you can also ask that
4843 the dprintf remain active even after disconnecting from the remote
4844 target. Using the stub/agent is also more efficient, as it can do
4845 everything without needing to communicate with @value{GDBN}.
4849 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4850 Whenever execution reaches @var{location}, print the values of one or
4851 more @var{expressions} under the control of the string @var{template}.
4852 To print several values, separate them with commas.
4854 @item set dprintf-style @var{style}
4855 Set the dprintf output to be handled in one of several different
4856 styles enumerated below. A change of style affects all existing
4857 dynamic printfs immediately. (If you need individual control over the
4858 print commands, simply define normal breakpoints with
4859 explicitly-supplied command lists.)
4862 @kindex dprintf-style gdb
4863 Handle the output using the @value{GDBN} @code{printf} command.
4866 @kindex dprintf-style call
4867 Handle the output by calling a function in your program (normally
4871 @kindex dprintf-style agent
4872 Have the remote debugging agent (such as @code{gdbserver}) handle
4873 the output itself. This style is only available for agents that
4874 support running commands on the target.
4876 @item set dprintf-function @var{function}
4877 Set the function to call if the dprintf style is @code{call}. By
4878 default its value is @code{printf}. You may set it to any expression.
4879 that @value{GDBN} can evaluate to a function, as per the @code{call}
4882 @item set dprintf-channel @var{channel}
4883 Set a ``channel'' for dprintf. If set to a non-empty value,
4884 @value{GDBN} will evaluate it as an expression and pass the result as
4885 a first argument to the @code{dprintf-function}, in the manner of
4886 @code{fprintf} and similar functions. Otherwise, the dprintf format
4887 string will be the first argument, in the manner of @code{printf}.
4889 As an example, if you wanted @code{dprintf} output to go to a logfile
4890 that is a standard I/O stream assigned to the variable @code{mylog},
4891 you could do the following:
4894 (gdb) set dprintf-style call
4895 (gdb) set dprintf-function fprintf
4896 (gdb) set dprintf-channel mylog
4897 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4898 Dprintf 1 at 0x123456: file main.c, line 25.
4900 1 dprintf keep y 0x00123456 in main at main.c:25
4901 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4906 Note that the @code{info break} displays the dynamic printf commands
4907 as normal breakpoint commands; you can thus easily see the effect of
4908 the variable settings.
4910 @item set disconnected-dprintf on
4911 @itemx set disconnected-dprintf off
4912 @kindex set disconnected-dprintf
4913 Choose whether @code{dprintf} commands should continue to run if
4914 @value{GDBN} has disconnected from the target. This only applies
4915 if the @code{dprintf-style} is @code{agent}.
4917 @item show disconnected-dprintf off
4918 @kindex show disconnected-dprintf
4919 Show the current choice for disconnected @code{dprintf}.
4923 @value{GDBN} does not check the validity of function and channel,
4924 relying on you to supply values that are meaningful for the contexts
4925 in which they are being used. For instance, the function and channel
4926 may be the values of local variables, but if that is the case, then
4927 all enabled dynamic prints must be at locations within the scope of
4928 those locals. If evaluation fails, @value{GDBN} will report an error.
4930 @node Save Breakpoints
4931 @subsection How to save breakpoints to a file
4933 To save breakpoint definitions to a file use the @w{@code{save
4934 breakpoints}} command.
4937 @kindex save breakpoints
4938 @cindex save breakpoints to a file for future sessions
4939 @item save breakpoints [@var{filename}]
4940 This command saves all current breakpoint definitions together with
4941 their commands and ignore counts, into a file @file{@var{filename}}
4942 suitable for use in a later debugging session. This includes all
4943 types of breakpoints (breakpoints, watchpoints, catchpoints,
4944 tracepoints). To read the saved breakpoint definitions, use the
4945 @code{source} command (@pxref{Command Files}). Note that watchpoints
4946 with expressions involving local variables may fail to be recreated
4947 because it may not be possible to access the context where the
4948 watchpoint is valid anymore. Because the saved breakpoint definitions
4949 are simply a sequence of @value{GDBN} commands that recreate the
4950 breakpoints, you can edit the file in your favorite editing program,
4951 and remove the breakpoint definitions you're not interested in, or
4952 that can no longer be recreated.
4955 @node Static Probe Points
4956 @subsection Static Probe Points
4958 @cindex static probe point, SystemTap
4959 @cindex static probe point, DTrace
4960 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4961 for Statically Defined Tracing, and the probes are designed to have a tiny
4962 runtime code and data footprint, and no dynamic relocations.
4964 Currently, the following types of probes are supported on
4965 ELF-compatible systems:
4969 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4970 @acronym{SDT} probes@footnote{See
4971 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4972 for more information on how to add @code{SystemTap} @acronym{SDT}
4973 probes in your applications.}. @code{SystemTap} probes are usable
4974 from assembly, C and C@t{++} languages@footnote{See
4975 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4976 for a good reference on how the @acronym{SDT} probes are implemented.}.
4978 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4979 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4983 @cindex semaphores on static probe points
4984 Some @code{SystemTap} probes have an associated semaphore variable;
4985 for instance, this happens automatically if you defined your probe
4986 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4987 @value{GDBN} will automatically enable it when you specify a
4988 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4989 breakpoint at a probe's location by some other method (e.g.,
4990 @code{break file:line}), then @value{GDBN} will not automatically set
4991 the semaphore. @code{DTrace} probes do not support semaphores.
4993 You can examine the available static static probes using @code{info
4994 probes}, with optional arguments:
4998 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4999 If given, @var{type} is either @code{stap} for listing
5000 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5001 probes. If omitted all probes are listed regardless of their types.
5003 If given, @var{provider} is a regular expression used to match against provider
5004 names when selecting which probes to list. If omitted, probes by all
5005 probes from all providers are listed.
5007 If given, @var{name} is a regular expression to match against probe names
5008 when selecting which probes to list. If omitted, probe names are not
5009 considered when deciding whether to display them.
5011 If given, @var{objfile} is a regular expression used to select which
5012 object files (executable or shared libraries) to examine. If not
5013 given, all object files are considered.
5015 @item info probes all
5016 List the available static probes, from all types.
5019 @cindex enabling and disabling probes
5020 Some probe points can be enabled and/or disabled. The effect of
5021 enabling or disabling a probe depends on the type of probe being
5022 handled. Some @code{DTrace} probes can be enabled or
5023 disabled, but @code{SystemTap} probes cannot be disabled.
5025 You can enable (or disable) one or more probes using the following
5026 commands, with optional arguments:
5029 @kindex enable probes
5030 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5031 If given, @var{provider} is a regular expression used to match against
5032 provider names when selecting which probes to enable. If omitted,
5033 all probes from all providers are enabled.
5035 If given, @var{name} is a regular expression to match against probe
5036 names when selecting which probes to enable. If omitted, probe names
5037 are not considered when deciding whether to enable them.
5039 If given, @var{objfile} is a regular expression used to select which
5040 object files (executable or shared libraries) to examine. If not
5041 given, all object files are considered.
5043 @kindex disable probes
5044 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5045 See the @code{enable probes} command above for a description of the
5046 optional arguments accepted by this command.
5049 @vindex $_probe_arg@r{, convenience variable}
5050 A probe may specify up to twelve arguments. These are available at the
5051 point at which the probe is defined---that is, when the current PC is
5052 at the probe's location. The arguments are available using the
5053 convenience variables (@pxref{Convenience Vars})
5054 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5055 probes each probe argument is an integer of the appropriate size;
5056 types are not preserved. In @code{DTrace} probes types are preserved
5057 provided that they are recognized as such by @value{GDBN}; otherwise
5058 the value of the probe argument will be a long integer. The
5059 convenience variable @code{$_probe_argc} holds the number of arguments
5060 at the current probe point.
5062 These variables are always available, but attempts to access them at
5063 any location other than a probe point will cause @value{GDBN} to give
5067 @c @ifclear BARETARGET
5068 @node Error in Breakpoints
5069 @subsection ``Cannot insert breakpoints''
5071 If you request too many active hardware-assisted breakpoints and
5072 watchpoints, you will see this error message:
5074 @c FIXME: the precise wording of this message may change; the relevant
5075 @c source change is not committed yet (Sep 3, 1999).
5077 Stopped; cannot insert breakpoints.
5078 You may have requested too many hardware breakpoints and watchpoints.
5082 This message is printed when you attempt to resume the program, since
5083 only then @value{GDBN} knows exactly how many hardware breakpoints and
5084 watchpoints it needs to insert.
5086 When this message is printed, you need to disable or remove some of the
5087 hardware-assisted breakpoints and watchpoints, and then continue.
5089 @node Breakpoint-related Warnings
5090 @subsection ``Breakpoint address adjusted...''
5091 @cindex breakpoint address adjusted
5093 Some processor architectures place constraints on the addresses at
5094 which breakpoints may be placed. For architectures thus constrained,
5095 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5096 with the constraints dictated by the architecture.
5098 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5099 a VLIW architecture in which a number of RISC-like instructions may be
5100 bundled together for parallel execution. The FR-V architecture
5101 constrains the location of a breakpoint instruction within such a
5102 bundle to the instruction with the lowest address. @value{GDBN}
5103 honors this constraint by adjusting a breakpoint's address to the
5104 first in the bundle.
5106 It is not uncommon for optimized code to have bundles which contain
5107 instructions from different source statements, thus it may happen that
5108 a breakpoint's address will be adjusted from one source statement to
5109 another. Since this adjustment may significantly alter @value{GDBN}'s
5110 breakpoint related behavior from what the user expects, a warning is
5111 printed when the breakpoint is first set and also when the breakpoint
5114 A warning like the one below is printed when setting a breakpoint
5115 that's been subject to address adjustment:
5118 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5121 Such warnings are printed both for user settable and @value{GDBN}'s
5122 internal breakpoints. If you see one of these warnings, you should
5123 verify that a breakpoint set at the adjusted address will have the
5124 desired affect. If not, the breakpoint in question may be removed and
5125 other breakpoints may be set which will have the desired behavior.
5126 E.g., it may be sufficient to place the breakpoint at a later
5127 instruction. A conditional breakpoint may also be useful in some
5128 cases to prevent the breakpoint from triggering too often.
5130 @value{GDBN} will also issue a warning when stopping at one of these
5131 adjusted breakpoints:
5134 warning: Breakpoint 1 address previously adjusted from 0x00010414
5138 When this warning is encountered, it may be too late to take remedial
5139 action except in cases where the breakpoint is hit earlier or more
5140 frequently than expected.
5142 @node Continuing and Stepping
5143 @section Continuing and Stepping
5147 @cindex resuming execution
5148 @dfn{Continuing} means resuming program execution until your program
5149 completes normally. In contrast, @dfn{stepping} means executing just
5150 one more ``step'' of your program, where ``step'' may mean either one
5151 line of source code, or one machine instruction (depending on what
5152 particular command you use). Either when continuing or when stepping,
5153 your program may stop even sooner, due to a breakpoint or a signal. (If
5154 it stops due to a signal, you may want to use @code{handle}, or use
5155 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5156 or you may step into the signal's handler (@pxref{stepping and signal
5161 @kindex c @r{(@code{continue})}
5162 @kindex fg @r{(resume foreground execution)}
5163 @item continue @r{[}@var{ignore-count}@r{]}
5164 @itemx c @r{[}@var{ignore-count}@r{]}
5165 @itemx fg @r{[}@var{ignore-count}@r{]}
5166 Resume program execution, at the address where your program last stopped;
5167 any breakpoints set at that address are bypassed. The optional argument
5168 @var{ignore-count} allows you to specify a further number of times to
5169 ignore a breakpoint at this location; its effect is like that of
5170 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5172 The argument @var{ignore-count} is meaningful only when your program
5173 stopped due to a breakpoint. At other times, the argument to
5174 @code{continue} is ignored.
5176 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5177 debugged program is deemed to be the foreground program) are provided
5178 purely for convenience, and have exactly the same behavior as
5182 To resume execution at a different place, you can use @code{return}
5183 (@pxref{Returning, ,Returning from a Function}) to go back to the
5184 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5185 Different Address}) to go to an arbitrary location in your program.
5187 A typical technique for using stepping is to set a breakpoint
5188 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5189 beginning of the function or the section of your program where a problem
5190 is believed to lie, run your program until it stops at that breakpoint,
5191 and then step through the suspect area, examining the variables that are
5192 interesting, until you see the problem happen.
5196 @kindex s @r{(@code{step})}
5198 Continue running your program until control reaches a different source
5199 line, then stop it and return control to @value{GDBN}. This command is
5200 abbreviated @code{s}.
5203 @c "without debugging information" is imprecise; actually "without line
5204 @c numbers in the debugging information". (gcc -g1 has debugging info but
5205 @c not line numbers). But it seems complex to try to make that
5206 @c distinction here.
5207 @emph{Warning:} If you use the @code{step} command while control is
5208 within a function that was compiled without debugging information,
5209 execution proceeds until control reaches a function that does have
5210 debugging information. Likewise, it will not step into a function which
5211 is compiled without debugging information. To step through functions
5212 without debugging information, use the @code{stepi} command, described
5216 The @code{step} command only stops at the first instruction of a source
5217 line. This prevents the multiple stops that could otherwise occur in
5218 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5219 to stop if a function that has debugging information is called within
5220 the line. In other words, @code{step} @emph{steps inside} any functions
5221 called within the line.
5223 Also, the @code{step} command only enters a function if there is line
5224 number information for the function. Otherwise it acts like the
5225 @code{next} command. This avoids problems when using @code{cc -gl}
5226 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5227 was any debugging information about the routine.
5229 @item step @var{count}
5230 Continue running as in @code{step}, but do so @var{count} times. If a
5231 breakpoint is reached, or a signal not related to stepping occurs before
5232 @var{count} steps, stepping stops right away.
5235 @kindex n @r{(@code{next})}
5236 @item next @r{[}@var{count}@r{]}
5237 Continue to the next source line in the current (innermost) stack frame.
5238 This is similar to @code{step}, but function calls that appear within
5239 the line of code are executed without stopping. Execution stops when
5240 control reaches a different line of code at the original stack level
5241 that was executing when you gave the @code{next} command. This command
5242 is abbreviated @code{n}.
5244 An argument @var{count} is a repeat count, as for @code{step}.
5247 @c FIX ME!! Do we delete this, or is there a way it fits in with
5248 @c the following paragraph? --- Vctoria
5250 @c @code{next} within a function that lacks debugging information acts like
5251 @c @code{step}, but any function calls appearing within the code of the
5252 @c function are executed without stopping.
5254 The @code{next} command only stops at the first instruction of a
5255 source line. This prevents multiple stops that could otherwise occur in
5256 @code{switch} statements, @code{for} loops, etc.
5258 @kindex set step-mode
5260 @cindex functions without line info, and stepping
5261 @cindex stepping into functions with no line info
5262 @itemx set step-mode on
5263 The @code{set step-mode on} command causes the @code{step} command to
5264 stop at the first instruction of a function which contains no debug line
5265 information rather than stepping over it.
5267 This is useful in cases where you may be interested in inspecting the
5268 machine instructions of a function which has no symbolic info and do not
5269 want @value{GDBN} to automatically skip over this function.
5271 @item set step-mode off
5272 Causes the @code{step} command to step over any functions which contains no
5273 debug information. This is the default.
5275 @item show step-mode
5276 Show whether @value{GDBN} will stop in or step over functions without
5277 source line debug information.
5280 @kindex fin @r{(@code{finish})}
5282 Continue running until just after function in the selected stack frame
5283 returns. Print the returned value (if any). This command can be
5284 abbreviated as @code{fin}.
5286 Contrast this with the @code{return} command (@pxref{Returning,
5287 ,Returning from a Function}).
5290 @kindex u @r{(@code{until})}
5291 @cindex run until specified location
5294 Continue running until a source line past the current line, in the
5295 current stack frame, is reached. This command is used to avoid single
5296 stepping through a loop more than once. It is like the @code{next}
5297 command, except that when @code{until} encounters a jump, it
5298 automatically continues execution until the program counter is greater
5299 than the address of the jump.
5301 This means that when you reach the end of a loop after single stepping
5302 though it, @code{until} makes your program continue execution until it
5303 exits the loop. In contrast, a @code{next} command at the end of a loop
5304 simply steps back to the beginning of the loop, which forces you to step
5305 through the next iteration.
5307 @code{until} always stops your program if it attempts to exit the current
5310 @code{until} may produce somewhat counterintuitive results if the order
5311 of machine code does not match the order of the source lines. For
5312 example, in the following excerpt from a debugging session, the @code{f}
5313 (@code{frame}) command shows that execution is stopped at line
5314 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5318 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5320 (@value{GDBP}) until
5321 195 for ( ; argc > 0; NEXTARG) @{
5324 This happened because, for execution efficiency, the compiler had
5325 generated code for the loop closure test at the end, rather than the
5326 start, of the loop---even though the test in a C @code{for}-loop is
5327 written before the body of the loop. The @code{until} command appeared
5328 to step back to the beginning of the loop when it advanced to this
5329 expression; however, it has not really gone to an earlier
5330 statement---not in terms of the actual machine code.
5332 @code{until} with no argument works by means of single
5333 instruction stepping, and hence is slower than @code{until} with an
5336 @item until @var{location}
5337 @itemx u @var{location}
5338 Continue running your program until either the specified @var{location} is
5339 reached, or the current stack frame returns. The location is any of
5340 the forms described in @ref{Specify Location}.
5341 This form of the command uses temporary breakpoints, and
5342 hence is quicker than @code{until} without an argument. The specified
5343 location is actually reached only if it is in the current frame. This
5344 implies that @code{until} can be used to skip over recursive function
5345 invocations. For instance in the code below, if the current location is
5346 line @code{96}, issuing @code{until 99} will execute the program up to
5347 line @code{99} in the same invocation of factorial, i.e., after the inner
5348 invocations have returned.
5351 94 int factorial (int value)
5353 96 if (value > 1) @{
5354 97 value *= factorial (value - 1);
5361 @kindex advance @var{location}
5362 @item advance @var{location}
5363 Continue running the program up to the given @var{location}. An argument is
5364 required, which should be of one of the forms described in
5365 @ref{Specify Location}.
5366 Execution will also stop upon exit from the current stack
5367 frame. This command is similar to @code{until}, but @code{advance} will
5368 not skip over recursive function calls, and the target location doesn't
5369 have to be in the same frame as the current one.
5373 @kindex si @r{(@code{stepi})}
5375 @itemx stepi @var{arg}
5377 Execute one machine instruction, then stop and return to the debugger.
5379 It is often useful to do @samp{display/i $pc} when stepping by machine
5380 instructions. This makes @value{GDBN} automatically display the next
5381 instruction to be executed, each time your program stops. @xref{Auto
5382 Display,, Automatic Display}.
5384 An argument is a repeat count, as in @code{step}.
5388 @kindex ni @r{(@code{nexti})}
5390 @itemx nexti @var{arg}
5392 Execute one machine instruction, but if it is a function call,
5393 proceed until the function returns.
5395 An argument is a repeat count, as in @code{next}.
5399 @anchor{range stepping}
5400 @cindex range stepping
5401 @cindex target-assisted range stepping
5402 By default, and if available, @value{GDBN} makes use of
5403 target-assisted @dfn{range stepping}. In other words, whenever you
5404 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5405 tells the target to step the corresponding range of instruction
5406 addresses instead of issuing multiple single-steps. This speeds up
5407 line stepping, particularly for remote targets. Ideally, there should
5408 be no reason you would want to turn range stepping off. However, it's
5409 possible that a bug in the debug info, a bug in the remote stub (for
5410 remote targets), or even a bug in @value{GDBN} could make line
5411 stepping behave incorrectly when target-assisted range stepping is
5412 enabled. You can use the following command to turn off range stepping
5416 @kindex set range-stepping
5417 @kindex show range-stepping
5418 @item set range-stepping
5419 @itemx show range-stepping
5420 Control whether range stepping is enabled.
5422 If @code{on}, and the target supports it, @value{GDBN} tells the
5423 target to step a range of addresses itself, instead of issuing
5424 multiple single-steps. If @code{off}, @value{GDBN} always issues
5425 single-steps, even if range stepping is supported by the target. The
5426 default is @code{on}.
5430 @node Skipping Over Functions and Files
5431 @section Skipping Over Functions and Files
5432 @cindex skipping over functions and files
5434 The program you are debugging may contain some functions which are
5435 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5436 skip a function or all functions in a file when stepping.
5438 For example, consider the following C function:
5449 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5450 are not interested in stepping through @code{boring}. If you run @code{step}
5451 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5452 step over both @code{foo} and @code{boring}!
5454 One solution is to @code{step} into @code{boring} and use the @code{finish}
5455 command to immediately exit it. But this can become tedious if @code{boring}
5456 is called from many places.
5458 A more flexible solution is to execute @kbd{skip boring}. This instructs
5459 @value{GDBN} never to step into @code{boring}. Now when you execute
5460 @code{step} at line 103, you'll step over @code{boring} and directly into
5463 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5464 example, @code{skip file boring.c}.
5467 @kindex skip function
5468 @item skip @r{[}@var{linespec}@r{]}
5469 @itemx skip function @r{[}@var{linespec}@r{]}
5470 After running this command, the function named by @var{linespec} or the
5471 function containing the line named by @var{linespec} will be skipped over when
5472 stepping. @xref{Specify Location}.
5474 If you do not specify @var{linespec}, the function you're currently debugging
5477 (If you have a function called @code{file} that you want to skip, use
5478 @kbd{skip function file}.)
5481 @item skip file @r{[}@var{filename}@r{]}
5482 After running this command, any function whose source lives in @var{filename}
5483 will be skipped over when stepping.
5485 If you do not specify @var{filename}, functions whose source lives in the file
5486 you're currently debugging will be skipped.
5489 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5490 These are the commands for managing your list of skips:
5494 @item info skip @r{[}@var{range}@r{]}
5495 Print details about the specified skip(s). If @var{range} is not specified,
5496 print a table with details about all functions and files marked for skipping.
5497 @code{info skip} prints the following information about each skip:
5501 A number identifying this skip.
5503 The type of this skip, either @samp{function} or @samp{file}.
5504 @item Enabled or Disabled
5505 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5507 For function skips, this column indicates the address in memory of the function
5508 being skipped. If you've set a function skip on a function which has not yet
5509 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5510 which has the function is loaded, @code{info skip} will show the function's
5513 For file skips, this field contains the filename being skipped. For functions
5514 skips, this field contains the function name and its line number in the file
5515 where it is defined.
5519 @item skip delete @r{[}@var{range}@r{]}
5520 Delete the specified skip(s). If @var{range} is not specified, delete all
5524 @item skip enable @r{[}@var{range}@r{]}
5525 Enable the specified skip(s). If @var{range} is not specified, enable all
5528 @kindex skip disable
5529 @item skip disable @r{[}@var{range}@r{]}
5530 Disable the specified skip(s). If @var{range} is not specified, disable all
5539 A signal is an asynchronous event that can happen in a program. The
5540 operating system defines the possible kinds of signals, and gives each
5541 kind a name and a number. For example, in Unix @code{SIGINT} is the
5542 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5543 @code{SIGSEGV} is the signal a program gets from referencing a place in
5544 memory far away from all the areas in use; @code{SIGALRM} occurs when
5545 the alarm clock timer goes off (which happens only if your program has
5546 requested an alarm).
5548 @cindex fatal signals
5549 Some signals, including @code{SIGALRM}, are a normal part of the
5550 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5551 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5552 program has not specified in advance some other way to handle the signal.
5553 @code{SIGINT} does not indicate an error in your program, but it is normally
5554 fatal so it can carry out the purpose of the interrupt: to kill the program.
5556 @value{GDBN} has the ability to detect any occurrence of a signal in your
5557 program. You can tell @value{GDBN} in advance what to do for each kind of
5560 @cindex handling signals
5561 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5562 @code{SIGALRM} be silently passed to your program
5563 (so as not to interfere with their role in the program's functioning)
5564 but to stop your program immediately whenever an error signal happens.
5565 You can change these settings with the @code{handle} command.
5568 @kindex info signals
5572 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5573 handle each one. You can use this to see the signal numbers of all
5574 the defined types of signals.
5576 @item info signals @var{sig}
5577 Similar, but print information only about the specified signal number.
5579 @code{info handle} is an alias for @code{info signals}.
5581 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5582 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5583 for details about this command.
5586 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5587 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5588 can be the number of a signal or its name (with or without the
5589 @samp{SIG} at the beginning); a list of signal numbers of the form
5590 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5591 known signals. Optional arguments @var{keywords}, described below,
5592 say what change to make.
5596 The keywords allowed by the @code{handle} command can be abbreviated.
5597 Their full names are:
5601 @value{GDBN} should not stop your program when this signal happens. It may
5602 still print a message telling you that the signal has come in.
5605 @value{GDBN} should stop your program when this signal happens. This implies
5606 the @code{print} keyword as well.
5609 @value{GDBN} should print a message when this signal happens.
5612 @value{GDBN} should not mention the occurrence of the signal at all. This
5613 implies the @code{nostop} keyword as well.
5617 @value{GDBN} should allow your program to see this signal; your program
5618 can handle the signal, or else it may terminate if the signal is fatal
5619 and not handled. @code{pass} and @code{noignore} are synonyms.
5623 @value{GDBN} should not allow your program to see this signal.
5624 @code{nopass} and @code{ignore} are synonyms.
5628 When a signal stops your program, the signal is not visible to the
5630 continue. Your program sees the signal then, if @code{pass} is in
5631 effect for the signal in question @emph{at that time}. In other words,
5632 after @value{GDBN} reports a signal, you can use the @code{handle}
5633 command with @code{pass} or @code{nopass} to control whether your
5634 program sees that signal when you continue.
5636 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5637 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5638 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5641 You can also use the @code{signal} command to prevent your program from
5642 seeing a signal, or cause it to see a signal it normally would not see,
5643 or to give it any signal at any time. For example, if your program stopped
5644 due to some sort of memory reference error, you might store correct
5645 values into the erroneous variables and continue, hoping to see more
5646 execution; but your program would probably terminate immediately as
5647 a result of the fatal signal once it saw the signal. To prevent this,
5648 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5651 @cindex stepping and signal handlers
5652 @anchor{stepping and signal handlers}
5654 @value{GDBN} optimizes for stepping the mainline code. If a signal
5655 that has @code{handle nostop} and @code{handle pass} set arrives while
5656 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5657 in progress, @value{GDBN} lets the signal handler run and then resumes
5658 stepping the mainline code once the signal handler returns. In other
5659 words, @value{GDBN} steps over the signal handler. This prevents
5660 signals that you've specified as not interesting (with @code{handle
5661 nostop}) from changing the focus of debugging unexpectedly. Note that
5662 the signal handler itself may still hit a breakpoint, stop for another
5663 signal that has @code{handle stop} in effect, or for any other event
5664 that normally results in stopping the stepping command sooner. Also
5665 note that @value{GDBN} still informs you that the program received a
5666 signal if @code{handle print} is set.
5668 @anchor{stepping into signal handlers}
5670 If you set @code{handle pass} for a signal, and your program sets up a
5671 handler for it, then issuing a stepping command, such as @code{step}
5672 or @code{stepi}, when your program is stopped due to the signal will
5673 step @emph{into} the signal handler (if the target supports that).
5675 Likewise, if you use the @code{queue-signal} command to queue a signal
5676 to be delivered to the current thread when execution of the thread
5677 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5678 stepping command will step into the signal handler.
5680 Here's an example, using @code{stepi} to step to the first instruction
5681 of @code{SIGUSR1}'s handler:
5684 (@value{GDBP}) handle SIGUSR1
5685 Signal Stop Print Pass to program Description
5686 SIGUSR1 Yes Yes Yes User defined signal 1
5690 Program received signal SIGUSR1, User defined signal 1.
5691 main () sigusr1.c:28
5694 sigusr1_handler () at sigusr1.c:9
5698 The same, but using @code{queue-signal} instead of waiting for the
5699 program to receive the signal first:
5704 (@value{GDBP}) queue-signal SIGUSR1
5706 sigusr1_handler () at sigusr1.c:9
5711 @cindex extra signal information
5712 @anchor{extra signal information}
5714 On some targets, @value{GDBN} can inspect extra signal information
5715 associated with the intercepted signal, before it is actually
5716 delivered to the program being debugged. This information is exported
5717 by the convenience variable @code{$_siginfo}, and consists of data
5718 that is passed by the kernel to the signal handler at the time of the
5719 receipt of a signal. The data type of the information itself is
5720 target dependent. You can see the data type using the @code{ptype
5721 $_siginfo} command. On Unix systems, it typically corresponds to the
5722 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5725 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5726 referenced address that raised a segmentation fault.
5730 (@value{GDBP}) continue
5731 Program received signal SIGSEGV, Segmentation fault.
5732 0x0000000000400766 in main ()
5734 (@value{GDBP}) ptype $_siginfo
5741 struct @{...@} _kill;
5742 struct @{...@} _timer;
5744 struct @{...@} _sigchld;
5745 struct @{...@} _sigfault;
5746 struct @{...@} _sigpoll;
5749 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5753 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5754 $1 = (void *) 0x7ffff7ff7000
5758 Depending on target support, @code{$_siginfo} may also be writable.
5761 @section Stopping and Starting Multi-thread Programs
5763 @cindex stopped threads
5764 @cindex threads, stopped
5766 @cindex continuing threads
5767 @cindex threads, continuing
5769 @value{GDBN} supports debugging programs with multiple threads
5770 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5771 are two modes of controlling execution of your program within the
5772 debugger. In the default mode, referred to as @dfn{all-stop mode},
5773 when any thread in your program stops (for example, at a breakpoint
5774 or while being stepped), all other threads in the program are also stopped by
5775 @value{GDBN}. On some targets, @value{GDBN} also supports
5776 @dfn{non-stop mode}, in which other threads can continue to run freely while
5777 you examine the stopped thread in the debugger.
5780 * All-Stop Mode:: All threads stop when GDB takes control
5781 * Non-Stop Mode:: Other threads continue to execute
5782 * Background Execution:: Running your program asynchronously
5783 * Thread-Specific Breakpoints:: Controlling breakpoints
5784 * Interrupted System Calls:: GDB may interfere with system calls
5785 * Observer Mode:: GDB does not alter program behavior
5789 @subsection All-Stop Mode
5791 @cindex all-stop mode
5793 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5794 @emph{all} threads of execution stop, not just the current thread. This
5795 allows you to examine the overall state of the program, including
5796 switching between threads, without worrying that things may change
5799 Conversely, whenever you restart the program, @emph{all} threads start
5800 executing. @emph{This is true even when single-stepping} with commands
5801 like @code{step} or @code{next}.
5803 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5804 Since thread scheduling is up to your debugging target's operating
5805 system (not controlled by @value{GDBN}), other threads may
5806 execute more than one statement while the current thread completes a
5807 single step. Moreover, in general other threads stop in the middle of a
5808 statement, rather than at a clean statement boundary, when the program
5811 You might even find your program stopped in another thread after
5812 continuing or even single-stepping. This happens whenever some other
5813 thread runs into a breakpoint, a signal, or an exception before the
5814 first thread completes whatever you requested.
5816 @cindex automatic thread selection
5817 @cindex switching threads automatically
5818 @cindex threads, automatic switching
5819 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5820 signal, it automatically selects the thread where that breakpoint or
5821 signal happened. @value{GDBN} alerts you to the context switch with a
5822 message such as @samp{[Switching to Thread @var{n}]} to identify the
5825 On some OSes, you can modify @value{GDBN}'s default behavior by
5826 locking the OS scheduler to allow only a single thread to run.
5829 @item set scheduler-locking @var{mode}
5830 @cindex scheduler locking mode
5831 @cindex lock scheduler
5832 Set the scheduler locking mode. It applies to normal execution,
5833 record mode, and replay mode. If it is @code{off}, then there is no
5834 locking and any thread may run at any time. If @code{on}, then only
5835 the current thread may run when the inferior is resumed. The
5836 @code{step} mode optimizes for single-stepping; it prevents other
5837 threads from preempting the current thread while you are stepping, so
5838 that the focus of debugging does not change unexpectedly. Other
5839 threads never get a chance to run when you step, and they are
5840 completely free to run when you use commands like @samp{continue},
5841 @samp{until}, or @samp{finish}. However, unless another thread hits a
5842 breakpoint during its timeslice, @value{GDBN} does not change the
5843 current thread away from the thread that you are debugging. The
5844 @code{replay} mode behaves like @code{off} in record mode and like
5845 @code{on} in replay mode.
5847 @item show scheduler-locking
5848 Display the current scheduler locking mode.
5851 @cindex resume threads of multiple processes simultaneously
5852 By default, when you issue one of the execution commands such as
5853 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5854 threads of the current inferior to run. For example, if @value{GDBN}
5855 is attached to two inferiors, each with two threads, the
5856 @code{continue} command resumes only the two threads of the current
5857 inferior. This is useful, for example, when you debug a program that
5858 forks and you want to hold the parent stopped (so that, for instance,
5859 it doesn't run to exit), while you debug the child. In other
5860 situations, you may not be interested in inspecting the current state
5861 of any of the processes @value{GDBN} is attached to, and you may want
5862 to resume them all until some breakpoint is hit. In the latter case,
5863 you can instruct @value{GDBN} to allow all threads of all the
5864 inferiors to run with the @w{@code{set schedule-multiple}} command.
5867 @kindex set schedule-multiple
5868 @item set schedule-multiple
5869 Set the mode for allowing threads of multiple processes to be resumed
5870 when an execution command is issued. When @code{on}, all threads of
5871 all processes are allowed to run. When @code{off}, only the threads
5872 of the current process are resumed. The default is @code{off}. The
5873 @code{scheduler-locking} mode takes precedence when set to @code{on},
5874 or while you are stepping and set to @code{step}.
5876 @item show schedule-multiple
5877 Display the current mode for resuming the execution of threads of
5882 @subsection Non-Stop Mode
5884 @cindex non-stop mode
5886 @c This section is really only a place-holder, and needs to be expanded
5887 @c with more details.
5889 For some multi-threaded targets, @value{GDBN} supports an optional
5890 mode of operation in which you can examine stopped program threads in
5891 the debugger while other threads continue to execute freely. This
5892 minimizes intrusion when debugging live systems, such as programs
5893 where some threads have real-time constraints or must continue to
5894 respond to external events. This is referred to as @dfn{non-stop} mode.
5896 In non-stop mode, when a thread stops to report a debugging event,
5897 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5898 threads as well, in contrast to the all-stop mode behavior. Additionally,
5899 execution commands such as @code{continue} and @code{step} apply by default
5900 only to the current thread in non-stop mode, rather than all threads as
5901 in all-stop mode. This allows you to control threads explicitly in
5902 ways that are not possible in all-stop mode --- for example, stepping
5903 one thread while allowing others to run freely, stepping
5904 one thread while holding all others stopped, or stepping several threads
5905 independently and simultaneously.
5907 To enter non-stop mode, use this sequence of commands before you run
5908 or attach to your program:
5911 # If using the CLI, pagination breaks non-stop.
5914 # Finally, turn it on!
5918 You can use these commands to manipulate the non-stop mode setting:
5921 @kindex set non-stop
5922 @item set non-stop on
5923 Enable selection of non-stop mode.
5924 @item set non-stop off
5925 Disable selection of non-stop mode.
5926 @kindex show non-stop
5928 Show the current non-stop enablement setting.
5931 Note these commands only reflect whether non-stop mode is enabled,
5932 not whether the currently-executing program is being run in non-stop mode.
5933 In particular, the @code{set non-stop} preference is only consulted when
5934 @value{GDBN} starts or connects to the target program, and it is generally
5935 not possible to switch modes once debugging has started. Furthermore,
5936 since not all targets support non-stop mode, even when you have enabled
5937 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5940 In non-stop mode, all execution commands apply only to the current thread
5941 by default. That is, @code{continue} only continues one thread.
5942 To continue all threads, issue @code{continue -a} or @code{c -a}.
5944 You can use @value{GDBN}'s background execution commands
5945 (@pxref{Background Execution}) to run some threads in the background
5946 while you continue to examine or step others from @value{GDBN}.
5947 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5948 always executed asynchronously in non-stop mode.
5950 Suspending execution is done with the @code{interrupt} command when
5951 running in the background, or @kbd{Ctrl-c} during foreground execution.
5952 In all-stop mode, this stops the whole process;
5953 but in non-stop mode the interrupt applies only to the current thread.
5954 To stop the whole program, use @code{interrupt -a}.
5956 Other execution commands do not currently support the @code{-a} option.
5958 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5959 that thread current, as it does in all-stop mode. This is because the
5960 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5961 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5962 changed to a different thread just as you entered a command to operate on the
5963 previously current thread.
5965 @node Background Execution
5966 @subsection Background Execution
5968 @cindex foreground execution
5969 @cindex background execution
5970 @cindex asynchronous execution
5971 @cindex execution, foreground, background and asynchronous
5973 @value{GDBN}'s execution commands have two variants: the normal
5974 foreground (synchronous) behavior, and a background
5975 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5976 the program to report that some thread has stopped before prompting for
5977 another command. In background execution, @value{GDBN} immediately gives
5978 a command prompt so that you can issue other commands while your program runs.
5980 If the target doesn't support async mode, @value{GDBN} issues an error
5981 message if you attempt to use the background execution commands.
5983 To specify background execution, add a @code{&} to the command. For example,
5984 the background form of the @code{continue} command is @code{continue&}, or
5985 just @code{c&}. The execution commands that accept background execution
5991 @xref{Starting, , Starting your Program}.
5995 @xref{Attach, , Debugging an Already-running Process}.
5999 @xref{Continuing and Stepping, step}.
6003 @xref{Continuing and Stepping, stepi}.
6007 @xref{Continuing and Stepping, next}.
6011 @xref{Continuing and Stepping, nexti}.
6015 @xref{Continuing and Stepping, continue}.
6019 @xref{Continuing and Stepping, finish}.
6023 @xref{Continuing and Stepping, until}.
6027 Background execution is especially useful in conjunction with non-stop
6028 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6029 However, you can also use these commands in the normal all-stop mode with
6030 the restriction that you cannot issue another execution command until the
6031 previous one finishes. Examples of commands that are valid in all-stop
6032 mode while the program is running include @code{help} and @code{info break}.
6034 You can interrupt your program while it is running in the background by
6035 using the @code{interrupt} command.
6042 Suspend execution of the running program. In all-stop mode,
6043 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6044 only the current thread. To stop the whole program in non-stop mode,
6045 use @code{interrupt -a}.
6048 @node Thread-Specific Breakpoints
6049 @subsection Thread-Specific Breakpoints
6051 When your program has multiple threads (@pxref{Threads,, Debugging
6052 Programs with Multiple Threads}), you can choose whether to set
6053 breakpoints on all threads, or on a particular thread.
6056 @cindex breakpoints and threads
6057 @cindex thread breakpoints
6058 @kindex break @dots{} thread @var{threadno}
6059 @item break @var{location} thread @var{threadno}
6060 @itemx break @var{location} thread @var{threadno} if @dots{}
6061 @var{location} specifies source lines; there are several ways of
6062 writing them (@pxref{Specify Location}), but the effect is always to
6063 specify some source line.
6065 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6066 to specify that you only want @value{GDBN} to stop the program when a
6067 particular thread reaches this breakpoint. The @var{threadno} specifier
6068 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6069 in the first column of the @samp{info threads} display.
6071 If you do not specify @samp{thread @var{threadno}} when you set a
6072 breakpoint, the breakpoint applies to @emph{all} threads of your
6075 You can use the @code{thread} qualifier on conditional breakpoints as
6076 well; in this case, place @samp{thread @var{threadno}} before or
6077 after the breakpoint condition, like this:
6080 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6085 Thread-specific breakpoints are automatically deleted when
6086 @value{GDBN} detects the corresponding thread is no longer in the
6087 thread list. For example:
6091 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6094 There are several ways for a thread to disappear, such as a regular
6095 thread exit, but also when you detach from the process with the
6096 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6097 Process}), or if @value{GDBN} loses the remote connection
6098 (@pxref{Remote Debugging}), etc. Note that with some targets,
6099 @value{GDBN} is only able to detect a thread has exited when the user
6100 explictly asks for the thread list with the @code{info threads}
6103 @node Interrupted System Calls
6104 @subsection Interrupted System Calls
6106 @cindex thread breakpoints and system calls
6107 @cindex system calls and thread breakpoints
6108 @cindex premature return from system calls
6109 There is an unfortunate side effect when using @value{GDBN} to debug
6110 multi-threaded programs. If one thread stops for a
6111 breakpoint, or for some other reason, and another thread is blocked in a
6112 system call, then the system call may return prematurely. This is a
6113 consequence of the interaction between multiple threads and the signals
6114 that @value{GDBN} uses to implement breakpoints and other events that
6117 To handle this problem, your program should check the return value of
6118 each system call and react appropriately. This is good programming
6121 For example, do not write code like this:
6127 The call to @code{sleep} will return early if a different thread stops
6128 at a breakpoint or for some other reason.
6130 Instead, write this:
6135 unslept = sleep (unslept);
6138 A system call is allowed to return early, so the system is still
6139 conforming to its specification. But @value{GDBN} does cause your
6140 multi-threaded program to behave differently than it would without
6143 Also, @value{GDBN} uses internal breakpoints in the thread library to
6144 monitor certain events such as thread creation and thread destruction.
6145 When such an event happens, a system call in another thread may return
6146 prematurely, even though your program does not appear to stop.
6149 @subsection Observer Mode
6151 If you want to build on non-stop mode and observe program behavior
6152 without any chance of disruption by @value{GDBN}, you can set
6153 variables to disable all of the debugger's attempts to modify state,
6154 whether by writing memory, inserting breakpoints, etc. These operate
6155 at a low level, intercepting operations from all commands.
6157 When all of these are set to @code{off}, then @value{GDBN} is said to
6158 be @dfn{observer mode}. As a convenience, the variable
6159 @code{observer} can be set to disable these, plus enable non-stop
6162 Note that @value{GDBN} will not prevent you from making nonsensical
6163 combinations of these settings. For instance, if you have enabled
6164 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6165 then breakpoints that work by writing trap instructions into the code
6166 stream will still not be able to be placed.
6171 @item set observer on
6172 @itemx set observer off
6173 When set to @code{on}, this disables all the permission variables
6174 below (except for @code{insert-fast-tracepoints}), plus enables
6175 non-stop debugging. Setting this to @code{off} switches back to
6176 normal debugging, though remaining in non-stop mode.
6179 Show whether observer mode is on or off.
6181 @kindex may-write-registers
6182 @item set may-write-registers on
6183 @itemx set may-write-registers off
6184 This controls whether @value{GDBN} will attempt to alter the values of
6185 registers, such as with assignment expressions in @code{print}, or the
6186 @code{jump} command. It defaults to @code{on}.
6188 @item show may-write-registers
6189 Show the current permission to write registers.
6191 @kindex may-write-memory
6192 @item set may-write-memory on
6193 @itemx set may-write-memory off
6194 This controls whether @value{GDBN} will attempt to alter the contents
6195 of memory, such as with assignment expressions in @code{print}. It
6196 defaults to @code{on}.
6198 @item show may-write-memory
6199 Show the current permission to write memory.
6201 @kindex may-insert-breakpoints
6202 @item set may-insert-breakpoints on
6203 @itemx set may-insert-breakpoints off
6204 This controls whether @value{GDBN} will attempt to insert breakpoints.
6205 This affects all breakpoints, including internal breakpoints defined
6206 by @value{GDBN}. It defaults to @code{on}.
6208 @item show may-insert-breakpoints
6209 Show the current permission to insert breakpoints.
6211 @kindex may-insert-tracepoints
6212 @item set may-insert-tracepoints on
6213 @itemx set may-insert-tracepoints off
6214 This controls whether @value{GDBN} will attempt to insert (regular)
6215 tracepoints at the beginning of a tracing experiment. It affects only
6216 non-fast tracepoints, fast tracepoints being under the control of
6217 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6219 @item show may-insert-tracepoints
6220 Show the current permission to insert tracepoints.
6222 @kindex may-insert-fast-tracepoints
6223 @item set may-insert-fast-tracepoints on
6224 @itemx set may-insert-fast-tracepoints off
6225 This controls whether @value{GDBN} will attempt to insert fast
6226 tracepoints at the beginning of a tracing experiment. It affects only
6227 fast tracepoints, regular (non-fast) tracepoints being under the
6228 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6230 @item show may-insert-fast-tracepoints
6231 Show the current permission to insert fast tracepoints.
6233 @kindex may-interrupt
6234 @item set may-interrupt on
6235 @itemx set may-interrupt off
6236 This controls whether @value{GDBN} will attempt to interrupt or stop
6237 program execution. When this variable is @code{off}, the
6238 @code{interrupt} command will have no effect, nor will
6239 @kbd{Ctrl-c}. It defaults to @code{on}.
6241 @item show may-interrupt
6242 Show the current permission to interrupt or stop the program.
6246 @node Reverse Execution
6247 @chapter Running programs backward
6248 @cindex reverse execution
6249 @cindex running programs backward
6251 When you are debugging a program, it is not unusual to realize that
6252 you have gone too far, and some event of interest has already happened.
6253 If the target environment supports it, @value{GDBN} can allow you to
6254 ``rewind'' the program by running it backward.
6256 A target environment that supports reverse execution should be able
6257 to ``undo'' the changes in machine state that have taken place as the
6258 program was executing normally. Variables, registers etc.@: should
6259 revert to their previous values. Obviously this requires a great
6260 deal of sophistication on the part of the target environment; not
6261 all target environments can support reverse execution.
6263 When a program is executed in reverse, the instructions that
6264 have most recently been executed are ``un-executed'', in reverse
6265 order. The program counter runs backward, following the previous
6266 thread of execution in reverse. As each instruction is ``un-executed'',
6267 the values of memory and/or registers that were changed by that
6268 instruction are reverted to their previous states. After executing
6269 a piece of source code in reverse, all side effects of that code
6270 should be ``undone'', and all variables should be returned to their
6271 prior values@footnote{
6272 Note that some side effects are easier to undo than others. For instance,
6273 memory and registers are relatively easy, but device I/O is hard. Some
6274 targets may be able undo things like device I/O, and some may not.
6276 The contract between @value{GDBN} and the reverse executing target
6277 requires only that the target do something reasonable when
6278 @value{GDBN} tells it to execute backwards, and then report the
6279 results back to @value{GDBN}. Whatever the target reports back to
6280 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6281 assumes that the memory and registers that the target reports are in a
6282 consistant state, but @value{GDBN} accepts whatever it is given.
6285 If you are debugging in a target environment that supports
6286 reverse execution, @value{GDBN} provides the following commands.
6289 @kindex reverse-continue
6290 @kindex rc @r{(@code{reverse-continue})}
6291 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6292 @itemx rc @r{[}@var{ignore-count}@r{]}
6293 Beginning at the point where your program last stopped, start executing
6294 in reverse. Reverse execution will stop for breakpoints and synchronous
6295 exceptions (signals), just like normal execution. Behavior of
6296 asynchronous signals depends on the target environment.
6298 @kindex reverse-step
6299 @kindex rs @r{(@code{step})}
6300 @item reverse-step @r{[}@var{count}@r{]}
6301 Run the program backward until control reaches the start of a
6302 different source line; then stop it, and return control to @value{GDBN}.
6304 Like the @code{step} command, @code{reverse-step} will only stop
6305 at the beginning of a source line. It ``un-executes'' the previously
6306 executed source line. If the previous source line included calls to
6307 debuggable functions, @code{reverse-step} will step (backward) into
6308 the called function, stopping at the beginning of the @emph{last}
6309 statement in the called function (typically a return statement).
6311 Also, as with the @code{step} command, if non-debuggable functions are
6312 called, @code{reverse-step} will run thru them backward without stopping.
6314 @kindex reverse-stepi
6315 @kindex rsi @r{(@code{reverse-stepi})}
6316 @item reverse-stepi @r{[}@var{count}@r{]}
6317 Reverse-execute one machine instruction. Note that the instruction
6318 to be reverse-executed is @emph{not} the one pointed to by the program
6319 counter, but the instruction executed prior to that one. For instance,
6320 if the last instruction was a jump, @code{reverse-stepi} will take you
6321 back from the destination of the jump to the jump instruction itself.
6323 @kindex reverse-next
6324 @kindex rn @r{(@code{reverse-next})}
6325 @item reverse-next @r{[}@var{count}@r{]}
6326 Run backward to the beginning of the previous line executed in
6327 the current (innermost) stack frame. If the line contains function
6328 calls, they will be ``un-executed'' without stopping. Starting from
6329 the first line of a function, @code{reverse-next} will take you back
6330 to the caller of that function, @emph{before} the function was called,
6331 just as the normal @code{next} command would take you from the last
6332 line of a function back to its return to its caller
6333 @footnote{Unless the code is too heavily optimized.}.
6335 @kindex reverse-nexti
6336 @kindex rni @r{(@code{reverse-nexti})}
6337 @item reverse-nexti @r{[}@var{count}@r{]}
6338 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6339 in reverse, except that called functions are ``un-executed'' atomically.
6340 That is, if the previously executed instruction was a return from
6341 another function, @code{reverse-nexti} will continue to execute
6342 in reverse until the call to that function (from the current stack
6345 @kindex reverse-finish
6346 @item reverse-finish
6347 Just as the @code{finish} command takes you to the point where the
6348 current function returns, @code{reverse-finish} takes you to the point
6349 where it was called. Instead of ending up at the end of the current
6350 function invocation, you end up at the beginning.
6352 @kindex set exec-direction
6353 @item set exec-direction
6354 Set the direction of target execution.
6355 @item set exec-direction reverse
6356 @cindex execute forward or backward in time
6357 @value{GDBN} will perform all execution commands in reverse, until the
6358 exec-direction mode is changed to ``forward''. Affected commands include
6359 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6360 command cannot be used in reverse mode.
6361 @item set exec-direction forward
6362 @value{GDBN} will perform all execution commands in the normal fashion.
6363 This is the default.
6367 @node Process Record and Replay
6368 @chapter Recording Inferior's Execution and Replaying It
6369 @cindex process record and replay
6370 @cindex recording inferior's execution and replaying it
6372 On some platforms, @value{GDBN} provides a special @dfn{process record
6373 and replay} target that can record a log of the process execution, and
6374 replay it later with both forward and reverse execution commands.
6377 When this target is in use, if the execution log includes the record
6378 for the next instruction, @value{GDBN} will debug in @dfn{replay
6379 mode}. In the replay mode, the inferior does not really execute code
6380 instructions. Instead, all the events that normally happen during
6381 code execution are taken from the execution log. While code is not
6382 really executed in replay mode, the values of registers (including the
6383 program counter register) and the memory of the inferior are still
6384 changed as they normally would. Their contents are taken from the
6388 If the record for the next instruction is not in the execution log,
6389 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6390 inferior executes normally, and @value{GDBN} records the execution log
6393 The process record and replay target supports reverse execution
6394 (@pxref{Reverse Execution}), even if the platform on which the
6395 inferior runs does not. However, the reverse execution is limited in
6396 this case by the range of the instructions recorded in the execution
6397 log. In other words, reverse execution on platforms that don't
6398 support it directly can only be done in the replay mode.
6400 When debugging in the reverse direction, @value{GDBN} will work in
6401 replay mode as long as the execution log includes the record for the
6402 previous instruction; otherwise, it will work in record mode, if the
6403 platform supports reverse execution, or stop if not.
6405 For architecture environments that support process record and replay,
6406 @value{GDBN} provides the following commands:
6409 @kindex target record
6410 @kindex target record-full
6411 @kindex target record-btrace
6414 @kindex record btrace
6415 @kindex record btrace bts
6416 @kindex record btrace pt
6422 @kindex rec btrace bts
6423 @kindex rec btrace pt
6426 @item record @var{method}
6427 This command starts the process record and replay target. The
6428 recording method can be specified as parameter. Without a parameter
6429 the command uses the @code{full} recording method. The following
6430 recording methods are available:
6434 Full record/replay recording using @value{GDBN}'s software record and
6435 replay implementation. This method allows replaying and reverse
6438 @item btrace @var{format}
6439 Hardware-supported instruction recording. This method does not record
6440 data. Further, the data is collected in a ring buffer so old data will
6441 be overwritten when the buffer is full. It allows limited reverse
6442 execution. Variables and registers are not available during reverse
6445 The recording format can be specified as parameter. Without a parameter
6446 the command chooses the recording format. The following recording
6447 formats are available:
6451 @cindex branch trace store
6452 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6453 this format, the processor stores a from/to record for each executed
6454 branch in the btrace ring buffer.
6457 @cindex Intel(R) Processor Trace
6458 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6459 format, the processor stores the execution trace in a compressed form
6460 that is afterwards decoded by @value{GDBN}.
6462 The trace can be recorded with very low overhead. The compressed
6463 trace format also allows small trace buffers to already contain a big
6464 number of instructions compared to @acronym{BTS}.
6466 Decoding the recorded execution trace, on the other hand, is more
6467 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6468 increased number of instructions to process. You should increase the
6469 buffer-size with care.
6472 Not all recording formats may be available on all processors.
6475 The process record and replay target can only debug a process that is
6476 already running. Therefore, you need first to start the process with
6477 the @kbd{run} or @kbd{start} commands, and then start the recording
6478 with the @kbd{record @var{method}} command.
6480 @cindex displaced stepping, and process record and replay
6481 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6482 will be automatically disabled when process record and replay target
6483 is started. That's because the process record and replay target
6484 doesn't support displaced stepping.
6486 @cindex non-stop mode, and process record and replay
6487 @cindex asynchronous execution, and process record and replay
6488 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6489 the asynchronous execution mode (@pxref{Background Execution}), not
6490 all recording methods are available. The @code{full} recording method
6491 does not support these two modes.
6496 Stop the process record and replay target. When process record and
6497 replay target stops, the entire execution log will be deleted and the
6498 inferior will either be terminated, or will remain in its final state.
6500 When you stop the process record and replay target in record mode (at
6501 the end of the execution log), the inferior will be stopped at the
6502 next instruction that would have been recorded. In other words, if
6503 you record for a while and then stop recording, the inferior process
6504 will be left in the same state as if the recording never happened.
6506 On the other hand, if the process record and replay target is stopped
6507 while in replay mode (that is, not at the end of the execution log,
6508 but at some earlier point), the inferior process will become ``live''
6509 at that earlier state, and it will then be possible to continue the
6510 usual ``live'' debugging of the process from that state.
6512 When the inferior process exits, or @value{GDBN} detaches from it,
6513 process record and replay target will automatically stop itself.
6517 Go to a specific location in the execution log. There are several
6518 ways to specify the location to go to:
6521 @item record goto begin
6522 @itemx record goto start
6523 Go to the beginning of the execution log.
6525 @item record goto end
6526 Go to the end of the execution log.
6528 @item record goto @var{n}
6529 Go to instruction number @var{n} in the execution log.
6533 @item record save @var{filename}
6534 Save the execution log to a file @file{@var{filename}}.
6535 Default filename is @file{gdb_record.@var{process_id}}, where
6536 @var{process_id} is the process ID of the inferior.
6538 This command may not be available for all recording methods.
6540 @kindex record restore
6541 @item record restore @var{filename}
6542 Restore the execution log from a file @file{@var{filename}}.
6543 File must have been created with @code{record save}.
6545 @kindex set record full
6546 @item set record full insn-number-max @var{limit}
6547 @itemx set record full insn-number-max unlimited
6548 Set the limit of instructions to be recorded for the @code{full}
6549 recording method. Default value is 200000.
6551 If @var{limit} is a positive number, then @value{GDBN} will start
6552 deleting instructions from the log once the number of the record
6553 instructions becomes greater than @var{limit}. For every new recorded
6554 instruction, @value{GDBN} will delete the earliest recorded
6555 instruction to keep the number of recorded instructions at the limit.
6556 (Since deleting recorded instructions loses information, @value{GDBN}
6557 lets you control what happens when the limit is reached, by means of
6558 the @code{stop-at-limit} option, described below.)
6560 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6561 delete recorded instructions from the execution log. The number of
6562 recorded instructions is limited only by the available memory.
6564 @kindex show record full
6565 @item show record full insn-number-max
6566 Show the limit of instructions to be recorded with the @code{full}
6569 @item set record full stop-at-limit
6570 Control the behavior of the @code{full} recording method when the
6571 number of recorded instructions reaches the limit. If ON (the
6572 default), @value{GDBN} will stop when the limit is reached for the
6573 first time and ask you whether you want to stop the inferior or
6574 continue running it and recording the execution log. If you decide
6575 to continue recording, each new recorded instruction will cause the
6576 oldest one to be deleted.
6578 If this option is OFF, @value{GDBN} will automatically delete the
6579 oldest record to make room for each new one, without asking.
6581 @item show record full stop-at-limit
6582 Show the current setting of @code{stop-at-limit}.
6584 @item set record full memory-query
6585 Control the behavior when @value{GDBN} is unable to record memory
6586 changes caused by an instruction for the @code{full} recording method.
6587 If ON, @value{GDBN} will query whether to stop the inferior in that
6590 If this option is OFF (the default), @value{GDBN} will automatically
6591 ignore the effect of such instructions on memory. Later, when
6592 @value{GDBN} replays this execution log, it will mark the log of this
6593 instruction as not accessible, and it will not affect the replay
6596 @item show record full memory-query
6597 Show the current setting of @code{memory-query}.
6599 @kindex set record btrace
6600 The @code{btrace} record target does not trace data. As a
6601 convenience, when replaying, @value{GDBN} reads read-only memory off
6602 the live program directly, assuming that the addresses of the
6603 read-only areas don't change. This for example makes it possible to
6604 disassemble code while replaying, but not to print variables.
6605 In some cases, being able to inspect variables might be useful.
6606 You can use the following command for that:
6608 @item set record btrace replay-memory-access
6609 Control the behavior of the @code{btrace} recording method when
6610 accessing memory during replay. If @code{read-only} (the default),
6611 @value{GDBN} will only allow accesses to read-only memory.
6612 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6613 and to read-write memory. Beware that the accessed memory corresponds
6614 to the live target and not necessarily to the current replay
6617 @kindex show record btrace
6618 @item show record btrace replay-memory-access
6619 Show the current setting of @code{replay-memory-access}.
6621 @kindex set record btrace bts
6622 @item set record btrace bts buffer-size @var{size}
6623 @itemx set record btrace bts buffer-size unlimited
6624 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6625 format. Default is 64KB.
6627 If @var{size} is a positive number, then @value{GDBN} will try to
6628 allocate a buffer of at least @var{size} bytes for each new thread
6629 that uses the btrace recording method and the @acronym{BTS} format.
6630 The actually obtained buffer size may differ from the requested
6631 @var{size}. Use the @code{info record} command to see the actual
6632 buffer size for each thread that uses the btrace recording method and
6633 the @acronym{BTS} format.
6635 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6636 allocate a buffer of 4MB.
6638 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6639 also need longer to process the branch trace data before it can be used.
6641 @item show record btrace bts buffer-size @var{size}
6642 Show the current setting of the requested ring buffer size for branch
6643 tracing in @acronym{BTS} format.
6645 @kindex set record btrace pt
6646 @item set record btrace pt buffer-size @var{size}
6647 @itemx set record btrace pt buffer-size unlimited
6648 Set the requested ring buffer size for branch tracing in Intel(R)
6649 Processor Trace format. Default is 16KB.
6651 If @var{size} is a positive number, then @value{GDBN} will try to
6652 allocate a buffer of at least @var{size} bytes for each new thread
6653 that uses the btrace recording method and the Intel(R) Processor Trace
6654 format. The actually obtained buffer size may differ from the
6655 requested @var{size}. Use the @code{info record} command to see the
6656 actual buffer size for each thread.
6658 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6659 allocate a buffer of 4MB.
6661 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6662 also need longer to process the branch trace data before it can be used.
6664 @item show record btrace pt buffer-size @var{size}
6665 Show the current setting of the requested ring buffer size for branch
6666 tracing in Intel(R) Processor Trace format.
6670 Show various statistics about the recording depending on the recording
6675 For the @code{full} recording method, it shows the state of process
6676 record and its in-memory execution log buffer, including:
6680 Whether in record mode or replay mode.
6682 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6684 Highest recorded instruction number.
6686 Current instruction about to be replayed (if in replay mode).
6688 Number of instructions contained in the execution log.
6690 Maximum number of instructions that may be contained in the execution log.
6694 For the @code{btrace} recording method, it shows:
6700 Number of instructions that have been recorded.
6702 Number of blocks of sequential control-flow formed by the recorded
6705 Whether in record mode or replay mode.
6708 For the @code{bts} recording format, it also shows:
6711 Size of the perf ring buffer.
6714 For the @code{pt} recording format, it also shows:
6717 Size of the perf ring buffer.
6721 @kindex record delete
6724 When record target runs in replay mode (``in the past''), delete the
6725 subsequent execution log and begin to record a new execution log starting
6726 from the current address. This means you will abandon the previously
6727 recorded ``future'' and begin recording a new ``future''.
6729 @kindex record instruction-history
6730 @kindex rec instruction-history
6731 @item record instruction-history
6732 Disassembles instructions from the recorded execution log. By
6733 default, ten instructions are disassembled. This can be changed using
6734 the @code{set record instruction-history-size} command. Instructions
6735 are printed in execution order.
6737 It can also print mixed source+disassembly if you specify the the
6738 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6739 as well as in symbolic form by specifying the @code{/r} modifier.
6741 The current position marker is printed for the instruction at the
6742 current program counter value. This instruction can appear multiple
6743 times in the trace and the current position marker will be printed
6744 every time. To omit the current position marker, specify the
6747 To better align the printed instructions when the trace contains
6748 instructions from more than one function, the function name may be
6749 omitted by specifying the @code{/f} modifier.
6751 Speculatively executed instructions are prefixed with @samp{?}. This
6752 feature is not available for all recording formats.
6754 There are several ways to specify what part of the execution log to
6758 @item record instruction-history @var{insn}
6759 Disassembles ten instructions starting from instruction number
6762 @item record instruction-history @var{insn}, +/-@var{n}
6763 Disassembles @var{n} instructions around instruction number
6764 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6765 @var{n} instructions after instruction number @var{insn}. If
6766 @var{n} is preceded with @code{-}, disassembles @var{n}
6767 instructions before instruction number @var{insn}.
6769 @item record instruction-history
6770 Disassembles ten more instructions after the last disassembly.
6772 @item record instruction-history -
6773 Disassembles ten more instructions before the last disassembly.
6775 @item record instruction-history @var{begin}, @var{end}
6776 Disassembles instructions beginning with instruction number
6777 @var{begin} until instruction number @var{end}. The instruction
6778 number @var{end} is included.
6781 This command may not be available for all recording methods.
6784 @item set record instruction-history-size @var{size}
6785 @itemx set record instruction-history-size unlimited
6786 Define how many instructions to disassemble in the @code{record
6787 instruction-history} command. The default value is 10.
6788 A @var{size} of @code{unlimited} means unlimited instructions.
6791 @item show record instruction-history-size
6792 Show how many instructions to disassemble in the @code{record
6793 instruction-history} command.
6795 @kindex record function-call-history
6796 @kindex rec function-call-history
6797 @item record function-call-history
6798 Prints the execution history at function granularity. It prints one
6799 line for each sequence of instructions that belong to the same
6800 function giving the name of that function, the source lines
6801 for this instruction sequence (if the @code{/l} modifier is
6802 specified), and the instructions numbers that form the sequence (if
6803 the @code{/i} modifier is specified). The function names are indented
6804 to reflect the call stack depth if the @code{/c} modifier is
6805 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6809 (@value{GDBP}) @b{list 1, 10}
6820 (@value{GDBP}) @b{record function-call-history /ilc}
6821 1 bar inst 1,4 at foo.c:6,8
6822 2 foo inst 5,10 at foo.c:2,3
6823 3 bar inst 11,13 at foo.c:9,10
6826 By default, ten lines are printed. This can be changed using the
6827 @code{set record function-call-history-size} command. Functions are
6828 printed in execution order. There are several ways to specify what
6832 @item record function-call-history @var{func}
6833 Prints ten functions starting from function number @var{func}.
6835 @item record function-call-history @var{func}, +/-@var{n}
6836 Prints @var{n} functions around function number @var{func}. If
6837 @var{n} is preceded with @code{+}, prints @var{n} functions after
6838 function number @var{func}. If @var{n} is preceded with @code{-},
6839 prints @var{n} functions before function number @var{func}.
6841 @item record function-call-history
6842 Prints ten more functions after the last ten-line print.
6844 @item record function-call-history -
6845 Prints ten more functions before the last ten-line print.
6847 @item record function-call-history @var{begin}, @var{end}
6848 Prints functions beginning with function number @var{begin} until
6849 function number @var{end}. The function number @var{end} is included.
6852 This command may not be available for all recording methods.
6854 @item set record function-call-history-size @var{size}
6855 @itemx set record function-call-history-size unlimited
6856 Define how many lines to print in the
6857 @code{record function-call-history} command. The default value is 10.
6858 A size of @code{unlimited} means unlimited lines.
6860 @item show record function-call-history-size
6861 Show how many lines to print in the
6862 @code{record function-call-history} command.
6867 @chapter Examining the Stack
6869 When your program has stopped, the first thing you need to know is where it
6870 stopped and how it got there.
6873 Each time your program performs a function call, information about the call
6875 That information includes the location of the call in your program,
6876 the arguments of the call,
6877 and the local variables of the function being called.
6878 The information is saved in a block of data called a @dfn{stack frame}.
6879 The stack frames are allocated in a region of memory called the @dfn{call
6882 When your program stops, the @value{GDBN} commands for examining the
6883 stack allow you to see all of this information.
6885 @cindex selected frame
6886 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6887 @value{GDBN} commands refer implicitly to the selected frame. In
6888 particular, whenever you ask @value{GDBN} for the value of a variable in
6889 your program, the value is found in the selected frame. There are
6890 special @value{GDBN} commands to select whichever frame you are
6891 interested in. @xref{Selection, ,Selecting a Frame}.
6893 When your program stops, @value{GDBN} automatically selects the
6894 currently executing frame and describes it briefly, similar to the
6895 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6898 * Frames:: Stack frames
6899 * Backtrace:: Backtraces
6900 * Selection:: Selecting a frame
6901 * Frame Info:: Information on a frame
6902 * Frame Filter Management:: Managing frame filters
6907 @section Stack Frames
6909 @cindex frame, definition
6911 The call stack is divided up into contiguous pieces called @dfn{stack
6912 frames}, or @dfn{frames} for short; each frame is the data associated
6913 with one call to one function. The frame contains the arguments given
6914 to the function, the function's local variables, and the address at
6915 which the function is executing.
6917 @cindex initial frame
6918 @cindex outermost frame
6919 @cindex innermost frame
6920 When your program is started, the stack has only one frame, that of the
6921 function @code{main}. This is called the @dfn{initial} frame or the
6922 @dfn{outermost} frame. Each time a function is called, a new frame is
6923 made. Each time a function returns, the frame for that function invocation
6924 is eliminated. If a function is recursive, there can be many frames for
6925 the same function. The frame for the function in which execution is
6926 actually occurring is called the @dfn{innermost} frame. This is the most
6927 recently created of all the stack frames that still exist.
6929 @cindex frame pointer
6930 Inside your program, stack frames are identified by their addresses. A
6931 stack frame consists of many bytes, each of which has its own address; each
6932 kind of computer has a convention for choosing one byte whose
6933 address serves as the address of the frame. Usually this address is kept
6934 in a register called the @dfn{frame pointer register}
6935 (@pxref{Registers, $fp}) while execution is going on in that frame.
6937 @cindex frame number
6938 @value{GDBN} assigns numbers to all existing stack frames, starting with
6939 zero for the innermost frame, one for the frame that called it,
6940 and so on upward. These numbers do not really exist in your program;
6941 they are assigned by @value{GDBN} to give you a way of designating stack
6942 frames in @value{GDBN} commands.
6944 @c The -fomit-frame-pointer below perennially causes hbox overflow
6945 @c underflow problems.
6946 @cindex frameless execution
6947 Some compilers provide a way to compile functions so that they operate
6948 without stack frames. (For example, the @value{NGCC} option
6950 @samp{-fomit-frame-pointer}
6952 generates functions without a frame.)
6953 This is occasionally done with heavily used library functions to save
6954 the frame setup time. @value{GDBN} has limited facilities for dealing
6955 with these function invocations. If the innermost function invocation
6956 has no stack frame, @value{GDBN} nevertheless regards it as though
6957 it had a separate frame, which is numbered zero as usual, allowing
6958 correct tracing of the function call chain. However, @value{GDBN} has
6959 no provision for frameless functions elsewhere in the stack.
6965 @cindex call stack traces
6966 A backtrace is a summary of how your program got where it is. It shows one
6967 line per frame, for many frames, starting with the currently executing
6968 frame (frame zero), followed by its caller (frame one), and on up the
6971 @anchor{backtrace-command}
6974 @kindex bt @r{(@code{backtrace})}
6977 Print a backtrace of the entire stack: one line per frame for all
6978 frames in the stack.
6980 You can stop the backtrace at any time by typing the system interrupt
6981 character, normally @kbd{Ctrl-c}.
6983 @item backtrace @var{n}
6985 Similar, but print only the innermost @var{n} frames.
6987 @item backtrace -@var{n}
6989 Similar, but print only the outermost @var{n} frames.
6991 @item backtrace full
6993 @itemx bt full @var{n}
6994 @itemx bt full -@var{n}
6995 Print the values of the local variables also. As described above,
6996 @var{n} specifies the number of frames to print.
6998 @item backtrace no-filters
6999 @itemx bt no-filters
7000 @itemx bt no-filters @var{n}
7001 @itemx bt no-filters -@var{n}
7002 @itemx bt no-filters full
7003 @itemx bt no-filters full @var{n}
7004 @itemx bt no-filters full -@var{n}
7005 Do not run Python frame filters on this backtrace. @xref{Frame
7006 Filter API}, for more information. Additionally use @ref{disable
7007 frame-filter all} to turn off all frame filters. This is only
7008 relevant when @value{GDBN} has been configured with @code{Python}
7014 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7015 are additional aliases for @code{backtrace}.
7017 @cindex multiple threads, backtrace
7018 In a multi-threaded program, @value{GDBN} by default shows the
7019 backtrace only for the current thread. To display the backtrace for
7020 several or all of the threads, use the command @code{thread apply}
7021 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7022 apply all backtrace}, @value{GDBN} will display the backtrace for all
7023 the threads; this is handy when you debug a core dump of a
7024 multi-threaded program.
7026 Each line in the backtrace shows the frame number and the function name.
7027 The program counter value is also shown---unless you use @code{set
7028 print address off}. The backtrace also shows the source file name and
7029 line number, as well as the arguments to the function. The program
7030 counter value is omitted if it is at the beginning of the code for that
7033 Here is an example of a backtrace. It was made with the command
7034 @samp{bt 3}, so it shows the innermost three frames.
7038 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7040 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7041 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7043 (More stack frames follow...)
7048 The display for frame zero does not begin with a program counter
7049 value, indicating that your program has stopped at the beginning of the
7050 code for line @code{993} of @code{builtin.c}.
7053 The value of parameter @code{data} in frame 1 has been replaced by
7054 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7055 only if it is a scalar (integer, pointer, enumeration, etc). See command
7056 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7057 on how to configure the way function parameter values are printed.
7059 @cindex optimized out, in backtrace
7060 @cindex function call arguments, optimized out
7061 If your program was compiled with optimizations, some compilers will
7062 optimize away arguments passed to functions if those arguments are
7063 never used after the call. Such optimizations generate code that
7064 passes arguments through registers, but doesn't store those arguments
7065 in the stack frame. @value{GDBN} has no way of displaying such
7066 arguments in stack frames other than the innermost one. Here's what
7067 such a backtrace might look like:
7071 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7073 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7074 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7076 (More stack frames follow...)
7081 The values of arguments that were not saved in their stack frames are
7082 shown as @samp{<optimized out>}.
7084 If you need to display the values of such optimized-out arguments,
7085 either deduce that from other variables whose values depend on the one
7086 you are interested in, or recompile without optimizations.
7088 @cindex backtrace beyond @code{main} function
7089 @cindex program entry point
7090 @cindex startup code, and backtrace
7091 Most programs have a standard user entry point---a place where system
7092 libraries and startup code transition into user code. For C this is
7093 @code{main}@footnote{
7094 Note that embedded programs (the so-called ``free-standing''
7095 environment) are not required to have a @code{main} function as the
7096 entry point. They could even have multiple entry points.}.
7097 When @value{GDBN} finds the entry function in a backtrace
7098 it will terminate the backtrace, to avoid tracing into highly
7099 system-specific (and generally uninteresting) code.
7101 If you need to examine the startup code, or limit the number of levels
7102 in a backtrace, you can change this behavior:
7105 @item set backtrace past-main
7106 @itemx set backtrace past-main on
7107 @kindex set backtrace
7108 Backtraces will continue past the user entry point.
7110 @item set backtrace past-main off
7111 Backtraces will stop when they encounter the user entry point. This is the
7114 @item show backtrace past-main
7115 @kindex show backtrace
7116 Display the current user entry point backtrace policy.
7118 @item set backtrace past-entry
7119 @itemx set backtrace past-entry on
7120 Backtraces will continue past the internal entry point of an application.
7121 This entry point is encoded by the linker when the application is built,
7122 and is likely before the user entry point @code{main} (or equivalent) is called.
7124 @item set backtrace past-entry off
7125 Backtraces will stop when they encounter the internal entry point of an
7126 application. This is the default.
7128 @item show backtrace past-entry
7129 Display the current internal entry point backtrace policy.
7131 @item set backtrace limit @var{n}
7132 @itemx set backtrace limit 0
7133 @itemx set backtrace limit unlimited
7134 @cindex backtrace limit
7135 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7136 or zero means unlimited levels.
7138 @item show backtrace limit
7139 Display the current limit on backtrace levels.
7142 You can control how file names are displayed.
7145 @item set filename-display
7146 @itemx set filename-display relative
7147 @cindex filename-display
7148 Display file names relative to the compilation directory. This is the default.
7150 @item set filename-display basename
7151 Display only basename of a filename.
7153 @item set filename-display absolute
7154 Display an absolute filename.
7156 @item show filename-display
7157 Show the current way to display filenames.
7161 @section Selecting a Frame
7163 Most commands for examining the stack and other data in your program work on
7164 whichever stack frame is selected at the moment. Here are the commands for
7165 selecting a stack frame; all of them finish by printing a brief description
7166 of the stack frame just selected.
7169 @kindex frame@r{, selecting}
7170 @kindex f @r{(@code{frame})}
7173 Select frame number @var{n}. Recall that frame zero is the innermost
7174 (currently executing) frame, frame one is the frame that called the
7175 innermost one, and so on. The highest-numbered frame is the one for
7178 @item frame @var{stack-addr} [ @var{pc-addr} ]
7179 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7180 Select the frame at address @var{stack-addr}. This is useful mainly if the
7181 chaining of stack frames has been damaged by a bug, making it
7182 impossible for @value{GDBN} to assign numbers properly to all frames. In
7183 addition, this can be useful when your program has multiple stacks and
7184 switches between them. The optional @var{pc-addr} can also be given to
7185 specify the value of PC for the stack frame.
7189 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7190 numbers @var{n}, this advances toward the outermost frame, to higher
7191 frame numbers, to frames that have existed longer.
7194 @kindex do @r{(@code{down})}
7196 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7197 positive numbers @var{n}, this advances toward the innermost frame, to
7198 lower frame numbers, to frames that were created more recently.
7199 You may abbreviate @code{down} as @code{do}.
7202 All of these commands end by printing two lines of output describing the
7203 frame. The first line shows the frame number, the function name, the
7204 arguments, and the source file and line number of execution in that
7205 frame. The second line shows the text of that source line.
7213 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7215 10 read_input_file (argv[i]);
7219 After such a printout, the @code{list} command with no arguments
7220 prints ten lines centered on the point of execution in the frame.
7221 You can also edit the program at the point of execution with your favorite
7222 editing program by typing @code{edit}.
7223 @xref{List, ,Printing Source Lines},
7227 @kindex select-frame
7229 The @code{select-frame} command is a variant of @code{frame} that does
7230 not display the new frame after selecting it. This command is
7231 intended primarily for use in @value{GDBN} command scripts, where the
7232 output might be unnecessary and distracting.
7234 @kindex down-silently
7236 @item up-silently @var{n}
7237 @itemx down-silently @var{n}
7238 These two commands are variants of @code{up} and @code{down},
7239 respectively; they differ in that they do their work silently, without
7240 causing display of the new frame. They are intended primarily for use
7241 in @value{GDBN} command scripts, where the output might be unnecessary and
7246 @section Information About a Frame
7248 There are several other commands to print information about the selected
7254 When used without any argument, this command does not change which
7255 frame is selected, but prints a brief description of the currently
7256 selected stack frame. It can be abbreviated @code{f}. With an
7257 argument, this command is used to select a stack frame.
7258 @xref{Selection, ,Selecting a Frame}.
7261 @kindex info f @r{(@code{info frame})}
7264 This command prints a verbose description of the selected stack frame,
7269 the address of the frame
7271 the address of the next frame down (called by this frame)
7273 the address of the next frame up (caller of this frame)
7275 the language in which the source code corresponding to this frame is written
7277 the address of the frame's arguments
7279 the address of the frame's local variables
7281 the program counter saved in it (the address of execution in the caller frame)
7283 which registers were saved in the frame
7286 @noindent The verbose description is useful when
7287 something has gone wrong that has made the stack format fail to fit
7288 the usual conventions.
7290 @item info frame @var{addr}
7291 @itemx info f @var{addr}
7292 Print a verbose description of the frame at address @var{addr}, without
7293 selecting that frame. The selected frame remains unchanged by this
7294 command. This requires the same kind of address (more than one for some
7295 architectures) that you specify in the @code{frame} command.
7296 @xref{Selection, ,Selecting a Frame}.
7300 Print the arguments of the selected frame, each on a separate line.
7304 Print the local variables of the selected frame, each on a separate
7305 line. These are all variables (declared either static or automatic)
7306 accessible at the point of execution of the selected frame.
7310 @node Frame Filter Management
7311 @section Management of Frame Filters.
7312 @cindex managing frame filters
7314 Frame filters are Python based utilities to manage and decorate the
7315 output of frames. @xref{Frame Filter API}, for further information.
7317 Managing frame filters is performed by several commands available
7318 within @value{GDBN}, detailed here.
7321 @kindex info frame-filter
7322 @item info frame-filter
7323 Print a list of installed frame filters from all dictionaries, showing
7324 their name, priority and enabled status.
7326 @kindex disable frame-filter
7327 @anchor{disable frame-filter all}
7328 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7329 Disable a frame filter in the dictionary matching
7330 @var{filter-dictionary} and @var{filter-name}. The
7331 @var{filter-dictionary} may be @code{all}, @code{global},
7332 @code{progspace}, or the name of the object file where the frame filter
7333 dictionary resides. When @code{all} is specified, all frame filters
7334 across all dictionaries are disabled. The @var{filter-name} is the name
7335 of the frame filter and is used when @code{all} is not the option for
7336 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7337 may be enabled again later.
7339 @kindex enable frame-filter
7340 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7341 Enable a frame filter in the dictionary matching
7342 @var{filter-dictionary} and @var{filter-name}. The
7343 @var{filter-dictionary} may be @code{all}, @code{global},
7344 @code{progspace} or the name of the object file where the frame filter
7345 dictionary resides. When @code{all} is specified, all frame filters across
7346 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7347 filter and is used when @code{all} is not the option for
7348 @var{filter-dictionary}.
7353 (gdb) info frame-filter
7355 global frame-filters:
7356 Priority Enabled Name
7357 1000 No PrimaryFunctionFilter
7360 progspace /build/test frame-filters:
7361 Priority Enabled Name
7362 100 Yes ProgspaceFilter
7364 objfile /build/test frame-filters:
7365 Priority Enabled Name
7366 999 Yes BuildProgra Filter
7368 (gdb) disable frame-filter /build/test BuildProgramFilter
7369 (gdb) info frame-filter
7371 global frame-filters:
7372 Priority Enabled Name
7373 1000 No PrimaryFunctionFilter
7376 progspace /build/test frame-filters:
7377 Priority Enabled Name
7378 100 Yes ProgspaceFilter
7380 objfile /build/test frame-filters:
7381 Priority Enabled Name
7382 999 No BuildProgramFilter
7384 (gdb) enable frame-filter global PrimaryFunctionFilter
7385 (gdb) info frame-filter
7387 global frame-filters:
7388 Priority Enabled Name
7389 1000 Yes PrimaryFunctionFilter
7392 progspace /build/test frame-filters:
7393 Priority Enabled Name
7394 100 Yes ProgspaceFilter
7396 objfile /build/test frame-filters:
7397 Priority Enabled Name
7398 999 No BuildProgramFilter
7401 @kindex set frame-filter priority
7402 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7403 Set the @var{priority} of a frame filter in the dictionary matching
7404 @var{filter-dictionary}, and the frame filter name matching
7405 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7406 @code{progspace} or the name of the object file where the frame filter
7407 dictionary resides. The @var{priority} is an integer.
7409 @kindex show frame-filter priority
7410 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7411 Show the @var{priority} of a frame filter in the dictionary matching
7412 @var{filter-dictionary}, and the frame filter name matching
7413 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7414 @code{progspace} or the name of the object file where the frame filter
7420 (gdb) info frame-filter
7422 global frame-filters:
7423 Priority Enabled Name
7424 1000 Yes PrimaryFunctionFilter
7427 progspace /build/test frame-filters:
7428 Priority Enabled Name
7429 100 Yes ProgspaceFilter
7431 objfile /build/test frame-filters:
7432 Priority Enabled Name
7433 999 No BuildProgramFilter
7435 (gdb) set frame-filter priority global Reverse 50
7436 (gdb) info frame-filter
7438 global frame-filters:
7439 Priority Enabled Name
7440 1000 Yes PrimaryFunctionFilter
7443 progspace /build/test frame-filters:
7444 Priority Enabled Name
7445 100 Yes ProgspaceFilter
7447 objfile /build/test frame-filters:
7448 Priority Enabled Name
7449 999 No BuildProgramFilter
7454 @chapter Examining Source Files
7456 @value{GDBN} can print parts of your program's source, since the debugging
7457 information recorded in the program tells @value{GDBN} what source files were
7458 used to build it. When your program stops, @value{GDBN} spontaneously prints
7459 the line where it stopped. Likewise, when you select a stack frame
7460 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7461 execution in that frame has stopped. You can print other portions of
7462 source files by explicit command.
7464 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7465 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7466 @value{GDBN} under @sc{gnu} Emacs}.
7469 * List:: Printing source lines
7470 * Specify Location:: How to specify code locations
7471 * Edit:: Editing source files
7472 * Search:: Searching source files
7473 * Source Path:: Specifying source directories
7474 * Machine Code:: Source and machine code
7478 @section Printing Source Lines
7481 @kindex l @r{(@code{list})}
7482 To print lines from a source file, use the @code{list} command
7483 (abbreviated @code{l}). By default, ten lines are printed.
7484 There are several ways to specify what part of the file you want to
7485 print; see @ref{Specify Location}, for the full list.
7487 Here are the forms of the @code{list} command most commonly used:
7490 @item list @var{linenum}
7491 Print lines centered around line number @var{linenum} in the
7492 current source file.
7494 @item list @var{function}
7495 Print lines centered around the beginning of function
7499 Print more lines. If the last lines printed were printed with a
7500 @code{list} command, this prints lines following the last lines
7501 printed; however, if the last line printed was a solitary line printed
7502 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7503 Stack}), this prints lines centered around that line.
7506 Print lines just before the lines last printed.
7509 @cindex @code{list}, how many lines to display
7510 By default, @value{GDBN} prints ten source lines with any of these forms of
7511 the @code{list} command. You can change this using @code{set listsize}:
7514 @kindex set listsize
7515 @item set listsize @var{count}
7516 @itemx set listsize unlimited
7517 Make the @code{list} command display @var{count} source lines (unless
7518 the @code{list} argument explicitly specifies some other number).
7519 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7521 @kindex show listsize
7523 Display the number of lines that @code{list} prints.
7526 Repeating a @code{list} command with @key{RET} discards the argument,
7527 so it is equivalent to typing just @code{list}. This is more useful
7528 than listing the same lines again. An exception is made for an
7529 argument of @samp{-}; that argument is preserved in repetition so that
7530 each repetition moves up in the source file.
7532 In general, the @code{list} command expects you to supply zero, one or two
7533 @dfn{locations}. Locations specify source lines; there are several ways
7534 of writing them (@pxref{Specify Location}), but the effect is always
7535 to specify some source line.
7537 Here is a complete description of the possible arguments for @code{list}:
7540 @item list @var{location}
7541 Print lines centered around the line specified by @var{location}.
7543 @item list @var{first},@var{last}
7544 Print lines from @var{first} to @var{last}. Both arguments are
7545 locations. When a @code{list} command has two locations, and the
7546 source file of the second location is omitted, this refers to
7547 the same source file as the first location.
7549 @item list ,@var{last}
7550 Print lines ending with @var{last}.
7552 @item list @var{first},
7553 Print lines starting with @var{first}.
7556 Print lines just after the lines last printed.
7559 Print lines just before the lines last printed.
7562 As described in the preceding table.
7565 @node Specify Location
7566 @section Specifying a Location
7567 @cindex specifying location
7569 @cindex source location
7572 * Linespec Locations:: Linespec locations
7573 * Explicit Locations:: Explicit locations
7574 * Address Locations:: Address locations
7577 Several @value{GDBN} commands accept arguments that specify a location
7578 of your program's code. Since @value{GDBN} is a source-level
7579 debugger, a location usually specifies some line in the source code.
7580 Locations may be specified using three different formats:
7581 linespec locations, explicit locations, or address locations.
7583 @node Linespec Locations
7584 @subsection Linespec Locations
7585 @cindex linespec locations
7587 A @dfn{linespec} is a colon-separated list of source location parameters such
7588 as file name, function name, etc. Here are all the different ways of
7589 specifying a linespec:
7593 Specifies the line number @var{linenum} of the current source file.
7596 @itemx +@var{offset}
7597 Specifies the line @var{offset} lines before or after the @dfn{current
7598 line}. For the @code{list} command, the current line is the last one
7599 printed; for the breakpoint commands, this is the line at which
7600 execution stopped in the currently selected @dfn{stack frame}
7601 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7602 used as the second of the two linespecs in a @code{list} command,
7603 this specifies the line @var{offset} lines up or down from the first
7606 @item @var{filename}:@var{linenum}
7607 Specifies the line @var{linenum} in the source file @var{filename}.
7608 If @var{filename} is a relative file name, then it will match any
7609 source file name with the same trailing components. For example, if
7610 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7611 name of @file{/build/trunk/gcc/expr.c}, but not
7612 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7614 @item @var{function}
7615 Specifies the line that begins the body of the function @var{function}.
7616 For example, in C, this is the line with the open brace.
7618 @item @var{function}:@var{label}
7619 Specifies the line where @var{label} appears in @var{function}.
7621 @item @var{filename}:@var{function}
7622 Specifies the line that begins the body of the function @var{function}
7623 in the file @var{filename}. You only need the file name with a
7624 function name to avoid ambiguity when there are identically named
7625 functions in different source files.
7628 Specifies the line at which the label named @var{label} appears
7629 in the function corresponding to the currently selected stack frame.
7630 If there is no current selected stack frame (for instance, if the inferior
7631 is not running), then @value{GDBN} will not search for a label.
7633 @cindex breakpoint at static probe point
7634 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7635 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7636 applications to embed static probes. @xref{Static Probe Points}, for more
7637 information on finding and using static probes. This form of linespec
7638 specifies the location of such a static probe.
7640 If @var{objfile} is given, only probes coming from that shared library
7641 or executable matching @var{objfile} as a regular expression are considered.
7642 If @var{provider} is given, then only probes from that provider are considered.
7643 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7644 each one of those probes.
7647 @node Explicit Locations
7648 @subsection Explicit Locations
7649 @cindex explicit locations
7651 @dfn{Explicit locations} allow the user to directly specify the source
7652 location's parameters using option-value pairs.
7654 Explicit locations are useful when several functions, labels, or
7655 file names have the same name (base name for files) in the program's
7656 sources. In these cases, explicit locations point to the source
7657 line you meant more accurately and unambiguously. Also, using
7658 explicit locations might be faster in large programs.
7660 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7661 defined in the file named @file{foo} or the label @code{bar} in a function
7662 named @code{foo}. @value{GDBN} must search either the file system or
7663 the symbol table to know.
7665 The list of valid explicit location options is summarized in the
7669 @item -source @var{filename}
7670 The value specifies the source file name. To differentiate between
7671 files with the same base name, prepend as many directories as is necessary
7672 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7673 @value{GDBN} will use the first file it finds with the given base
7674 name. This option requires the use of either @code{-function} or @code{-line}.
7676 @item -function @var{function}
7677 The value specifies the name of a function. Operations
7678 on function locations unmodified by other options (such as @code{-label}
7679 or @code{-line}) refer to the line that begins the body of the function.
7680 In C, for example, this is the line with the open brace.
7682 @item -label @var{label}
7683 The value specifies the name of a label. When the function
7684 name is not specified, the label is searched in the function of the currently
7685 selected stack frame.
7687 @item -line @var{number}
7688 The value specifies a line offset for the location. The offset may either
7689 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7690 the command. When specified without any other options, the line offset is
7691 relative to the current line.
7694 Explicit location options may be abbreviated by omitting any non-unique
7695 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7697 @node Address Locations
7698 @subsection Address Locations
7699 @cindex address locations
7701 @dfn{Address locations} indicate a specific program address. They have
7702 the generalized form *@var{address}.
7704 For line-oriented commands, such as @code{list} and @code{edit}, this
7705 specifies a source line that contains @var{address}. For @code{break} and
7706 other breakpoint-oriented commands, this can be used to set breakpoints in
7707 parts of your program which do not have debugging information or
7710 Here @var{address} may be any expression valid in the current working
7711 language (@pxref{Languages, working language}) that specifies a code
7712 address. In addition, as a convenience, @value{GDBN} extends the
7713 semantics of expressions used in locations to cover several situations
7714 that frequently occur during debugging. Here are the various forms
7718 @item @var{expression}
7719 Any expression valid in the current working language.
7721 @item @var{funcaddr}
7722 An address of a function or procedure derived from its name. In C,
7723 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7724 simply the function's name @var{function} (and actually a special case
7725 of a valid expression). In Pascal and Modula-2, this is
7726 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7727 (although the Pascal form also works).
7729 This form specifies the address of the function's first instruction,
7730 before the stack frame and arguments have been set up.
7732 @item '@var{filename}':@var{funcaddr}
7733 Like @var{funcaddr} above, but also specifies the name of the source
7734 file explicitly. This is useful if the name of the function does not
7735 specify the function unambiguously, e.g., if there are several
7736 functions with identical names in different source files.
7740 @section Editing Source Files
7741 @cindex editing source files
7744 @kindex e @r{(@code{edit})}
7745 To edit the lines in a source file, use the @code{edit} command.
7746 The editing program of your choice
7747 is invoked with the current line set to
7748 the active line in the program.
7749 Alternatively, there are several ways to specify what part of the file you
7750 want to print if you want to see other parts of the program:
7753 @item edit @var{location}
7754 Edit the source file specified by @code{location}. Editing starts at
7755 that @var{location}, e.g., at the specified source line of the
7756 specified file. @xref{Specify Location}, for all the possible forms
7757 of the @var{location} argument; here are the forms of the @code{edit}
7758 command most commonly used:
7761 @item edit @var{number}
7762 Edit the current source file with @var{number} as the active line number.
7764 @item edit @var{function}
7765 Edit the file containing @var{function} at the beginning of its definition.
7770 @subsection Choosing your Editor
7771 You can customize @value{GDBN} to use any editor you want
7773 The only restriction is that your editor (say @code{ex}), recognizes the
7774 following command-line syntax:
7776 ex +@var{number} file
7778 The optional numeric value +@var{number} specifies the number of the line in
7779 the file where to start editing.}.
7780 By default, it is @file{@value{EDITOR}}, but you can change this
7781 by setting the environment variable @code{EDITOR} before using
7782 @value{GDBN}. For example, to configure @value{GDBN} to use the
7783 @code{vi} editor, you could use these commands with the @code{sh} shell:
7789 or in the @code{csh} shell,
7791 setenv EDITOR /usr/bin/vi
7796 @section Searching Source Files
7797 @cindex searching source files
7799 There are two commands for searching through the current source file for a
7804 @kindex forward-search
7805 @kindex fo @r{(@code{forward-search})}
7806 @item forward-search @var{regexp}
7807 @itemx search @var{regexp}
7808 The command @samp{forward-search @var{regexp}} checks each line,
7809 starting with the one following the last line listed, for a match for
7810 @var{regexp}. It lists the line that is found. You can use the
7811 synonym @samp{search @var{regexp}} or abbreviate the command name as
7814 @kindex reverse-search
7815 @item reverse-search @var{regexp}
7816 The command @samp{reverse-search @var{regexp}} checks each line, starting
7817 with the one before the last line listed and going backward, for a match
7818 for @var{regexp}. It lists the line that is found. You can abbreviate
7819 this command as @code{rev}.
7823 @section Specifying Source Directories
7826 @cindex directories for source files
7827 Executable programs sometimes do not record the directories of the source
7828 files from which they were compiled, just the names. Even when they do,
7829 the directories could be moved between the compilation and your debugging
7830 session. @value{GDBN} has a list of directories to search for source files;
7831 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7832 it tries all the directories in the list, in the order they are present
7833 in the list, until it finds a file with the desired name.
7835 For example, suppose an executable references the file
7836 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7837 @file{/mnt/cross}. The file is first looked up literally; if this
7838 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7839 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7840 message is printed. @value{GDBN} does not look up the parts of the
7841 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7842 Likewise, the subdirectories of the source path are not searched: if
7843 the source path is @file{/mnt/cross}, and the binary refers to
7844 @file{foo.c}, @value{GDBN} would not find it under
7845 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7847 Plain file names, relative file names with leading directories, file
7848 names containing dots, etc.@: are all treated as described above; for
7849 instance, if the source path is @file{/mnt/cross}, and the source file
7850 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7851 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7852 that---@file{/mnt/cross/foo.c}.
7854 Note that the executable search path is @emph{not} used to locate the
7857 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7858 any information it has cached about where source files are found and where
7859 each line is in the file.
7863 When you start @value{GDBN}, its source path includes only @samp{cdir}
7864 and @samp{cwd}, in that order.
7865 To add other directories, use the @code{directory} command.
7867 The search path is used to find both program source files and @value{GDBN}
7868 script files (read using the @samp{-command} option and @samp{source} command).
7870 In addition to the source path, @value{GDBN} provides a set of commands
7871 that manage a list of source path substitution rules. A @dfn{substitution
7872 rule} specifies how to rewrite source directories stored in the program's
7873 debug information in case the sources were moved to a different
7874 directory between compilation and debugging. A rule is made of
7875 two strings, the first specifying what needs to be rewritten in
7876 the path, and the second specifying how it should be rewritten.
7877 In @ref{set substitute-path}, we name these two parts @var{from} and
7878 @var{to} respectively. @value{GDBN} does a simple string replacement
7879 of @var{from} with @var{to} at the start of the directory part of the
7880 source file name, and uses that result instead of the original file
7881 name to look up the sources.
7883 Using the previous example, suppose the @file{foo-1.0} tree has been
7884 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7885 @value{GDBN} to replace @file{/usr/src} in all source path names with
7886 @file{/mnt/cross}. The first lookup will then be
7887 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7888 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7889 substitution rule, use the @code{set substitute-path} command
7890 (@pxref{set substitute-path}).
7892 To avoid unexpected substitution results, a rule is applied only if the
7893 @var{from} part of the directory name ends at a directory separator.
7894 For instance, a rule substituting @file{/usr/source} into
7895 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7896 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7897 is applied only at the beginning of the directory name, this rule will
7898 not be applied to @file{/root/usr/source/baz.c} either.
7900 In many cases, you can achieve the same result using the @code{directory}
7901 command. However, @code{set substitute-path} can be more efficient in
7902 the case where the sources are organized in a complex tree with multiple
7903 subdirectories. With the @code{directory} command, you need to add each
7904 subdirectory of your project. If you moved the entire tree while
7905 preserving its internal organization, then @code{set substitute-path}
7906 allows you to direct the debugger to all the sources with one single
7909 @code{set substitute-path} is also more than just a shortcut command.
7910 The source path is only used if the file at the original location no
7911 longer exists. On the other hand, @code{set substitute-path} modifies
7912 the debugger behavior to look at the rewritten location instead. So, if
7913 for any reason a source file that is not relevant to your executable is
7914 located at the original location, a substitution rule is the only
7915 method available to point @value{GDBN} at the new location.
7917 @cindex @samp{--with-relocated-sources}
7918 @cindex default source path substitution
7919 You can configure a default source path substitution rule by
7920 configuring @value{GDBN} with the
7921 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7922 should be the name of a directory under @value{GDBN}'s configured
7923 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7924 directory names in debug information under @var{dir} will be adjusted
7925 automatically if the installed @value{GDBN} is moved to a new
7926 location. This is useful if @value{GDBN}, libraries or executables
7927 with debug information and corresponding source code are being moved
7931 @item directory @var{dirname} @dots{}
7932 @item dir @var{dirname} @dots{}
7933 Add directory @var{dirname} to the front of the source path. Several
7934 directory names may be given to this command, separated by @samp{:}
7935 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7936 part of absolute file names) or
7937 whitespace. You may specify a directory that is already in the source
7938 path; this moves it forward, so @value{GDBN} searches it sooner.
7942 @vindex $cdir@r{, convenience variable}
7943 @vindex $cwd@r{, convenience variable}
7944 @cindex compilation directory
7945 @cindex current directory
7946 @cindex working directory
7947 @cindex directory, current
7948 @cindex directory, compilation
7949 You can use the string @samp{$cdir} to refer to the compilation
7950 directory (if one is recorded), and @samp{$cwd} to refer to the current
7951 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7952 tracks the current working directory as it changes during your @value{GDBN}
7953 session, while the latter is immediately expanded to the current
7954 directory at the time you add an entry to the source path.
7957 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7959 @c RET-repeat for @code{directory} is explicitly disabled, but since
7960 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7962 @item set directories @var{path-list}
7963 @kindex set directories
7964 Set the source path to @var{path-list}.
7965 @samp{$cdir:$cwd} are added if missing.
7967 @item show directories
7968 @kindex show directories
7969 Print the source path: show which directories it contains.
7971 @anchor{set substitute-path}
7972 @item set substitute-path @var{from} @var{to}
7973 @kindex set substitute-path
7974 Define a source path substitution rule, and add it at the end of the
7975 current list of existing substitution rules. If a rule with the same
7976 @var{from} was already defined, then the old rule is also deleted.
7978 For example, if the file @file{/foo/bar/baz.c} was moved to
7979 @file{/mnt/cross/baz.c}, then the command
7982 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
7986 will tell @value{GDBN} to replace @samp{/foo/bar} with
7987 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7988 @file{baz.c} even though it was moved.
7990 In the case when more than one substitution rule have been defined,
7991 the rules are evaluated one by one in the order where they have been
7992 defined. The first one matching, if any, is selected to perform
7995 For instance, if we had entered the following commands:
7998 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7999 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8003 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8004 @file{/mnt/include/defs.h} by using the first rule. However, it would
8005 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8006 @file{/mnt/src/lib/foo.c}.
8009 @item unset substitute-path [path]
8010 @kindex unset substitute-path
8011 If a path is specified, search the current list of substitution rules
8012 for a rule that would rewrite that path. Delete that rule if found.
8013 A warning is emitted by the debugger if no rule could be found.
8015 If no path is specified, then all substitution rules are deleted.
8017 @item show substitute-path [path]
8018 @kindex show substitute-path
8019 If a path is specified, then print the source path substitution rule
8020 which would rewrite that path, if any.
8022 If no path is specified, then print all existing source path substitution
8027 If your source path is cluttered with directories that are no longer of
8028 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8029 versions of source. You can correct the situation as follows:
8033 Use @code{directory} with no argument to reset the source path to its default value.
8036 Use @code{directory} with suitable arguments to reinstall the
8037 directories you want in the source path. You can add all the
8038 directories in one command.
8042 @section Source and Machine Code
8043 @cindex source line and its code address
8045 You can use the command @code{info line} to map source lines to program
8046 addresses (and vice versa), and the command @code{disassemble} to display
8047 a range of addresses as machine instructions. You can use the command
8048 @code{set disassemble-next-line} to set whether to disassemble next
8049 source line when execution stops. When run under @sc{gnu} Emacs
8050 mode, the @code{info line} command causes the arrow to point to the
8051 line specified. Also, @code{info line} prints addresses in symbolic form as
8056 @item info line @var{location}
8057 Print the starting and ending addresses of the compiled code for
8058 source line @var{location}. You can specify source lines in any of
8059 the ways documented in @ref{Specify Location}.
8062 For example, we can use @code{info line} to discover the location of
8063 the object code for the first line of function
8064 @code{m4_changequote}:
8066 @c FIXME: I think this example should also show the addresses in
8067 @c symbolic form, as they usually would be displayed.
8069 (@value{GDBP}) info line m4_changequote
8070 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8074 @cindex code address and its source line
8075 We can also inquire (using @code{*@var{addr}} as the form for
8076 @var{location}) what source line covers a particular address:
8078 (@value{GDBP}) info line *0x63ff
8079 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8082 @cindex @code{$_} and @code{info line}
8083 @cindex @code{x} command, default address
8084 @kindex x@r{(examine), and} info line
8085 After @code{info line}, the default address for the @code{x} command
8086 is changed to the starting address of the line, so that @samp{x/i} is
8087 sufficient to begin examining the machine code (@pxref{Memory,
8088 ,Examining Memory}). Also, this address is saved as the value of the
8089 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8094 @cindex assembly instructions
8095 @cindex instructions, assembly
8096 @cindex machine instructions
8097 @cindex listing machine instructions
8099 @itemx disassemble /m
8100 @itemx disassemble /s
8101 @itemx disassemble /r
8102 This specialized command dumps a range of memory as machine
8103 instructions. It can also print mixed source+disassembly by specifying
8104 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8105 as well as in symbolic form by specifying the @code{/r} modifier.
8106 The default memory range is the function surrounding the
8107 program counter of the selected frame. A single argument to this
8108 command is a program counter value; @value{GDBN} dumps the function
8109 surrounding this value. When two arguments are given, they should
8110 be separated by a comma, possibly surrounded by whitespace. The
8111 arguments specify a range of addresses to dump, in one of two forms:
8114 @item @var{start},@var{end}
8115 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8116 @item @var{start},+@var{length}
8117 the addresses from @var{start} (inclusive) to
8118 @code{@var{start}+@var{length}} (exclusive).
8122 When 2 arguments are specified, the name of the function is also
8123 printed (since there could be several functions in the given range).
8125 The argument(s) can be any expression yielding a numeric value, such as
8126 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8128 If the range of memory being disassembled contains current program counter,
8129 the instruction at that location is shown with a @code{=>} marker.
8132 The following example shows the disassembly of a range of addresses of
8133 HP PA-RISC 2.0 code:
8136 (@value{GDBP}) disas 0x32c4, 0x32e4
8137 Dump of assembler code from 0x32c4 to 0x32e4:
8138 0x32c4 <main+204>: addil 0,dp
8139 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8140 0x32cc <main+212>: ldil 0x3000,r31
8141 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8142 0x32d4 <main+220>: ldo 0(r31),rp
8143 0x32d8 <main+224>: addil -0x800,dp
8144 0x32dc <main+228>: ldo 0x588(r1),r26
8145 0x32e0 <main+232>: ldil 0x3000,r31
8146 End of assembler dump.
8149 Here is an example showing mixed source+assembly for Intel x86
8150 with @code{/m} or @code{/s}, when the program is stopped just after
8151 function prologue in a non-optimized function with no inline code.
8154 (@value{GDBP}) disas /m main
8155 Dump of assembler code for function main:
8157 0x08048330 <+0>: push %ebp
8158 0x08048331 <+1>: mov %esp,%ebp
8159 0x08048333 <+3>: sub $0x8,%esp
8160 0x08048336 <+6>: and $0xfffffff0,%esp
8161 0x08048339 <+9>: sub $0x10,%esp
8163 6 printf ("Hello.\n");
8164 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8165 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8169 0x08048348 <+24>: mov $0x0,%eax
8170 0x0804834d <+29>: leave
8171 0x0804834e <+30>: ret
8173 End of assembler dump.
8176 The @code{/m} option is deprecated as its output is not useful when
8177 there is either inlined code or re-ordered code.
8178 The @code{/s} option is the preferred choice.
8179 Here is an example for AMD x86-64 showing the difference between
8180 @code{/m} output and @code{/s} output.
8181 This example has one inline function defined in a header file,
8182 and the code is compiled with @samp{-O2} optimization.
8183 Note how the @code{/m} output is missing the disassembly of
8184 several instructions that are present in the @code{/s} output.
8214 (@value{GDBP}) disas /m main
8215 Dump of assembler code for function main:
8219 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8220 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8224 0x000000000040041d <+29>: xor %eax,%eax
8225 0x000000000040041f <+31>: retq
8226 0x0000000000400420 <+32>: add %eax,%eax
8227 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8229 End of assembler dump.
8230 (@value{GDBP}) disas /s main
8231 Dump of assembler code for function main:
8235 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8239 0x0000000000400406 <+6>: test %eax,%eax
8240 0x0000000000400408 <+8>: js 0x400420 <main+32>
8245 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8246 0x000000000040040d <+13>: test %eax,%eax
8247 0x000000000040040f <+15>: mov $0x1,%eax
8248 0x0000000000400414 <+20>: cmovne %edx,%eax
8252 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8256 0x000000000040041d <+29>: xor %eax,%eax
8257 0x000000000040041f <+31>: retq
8261 0x0000000000400420 <+32>: add %eax,%eax
8262 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8263 End of assembler dump.
8266 Here is another example showing raw instructions in hex for AMD x86-64,
8269 (gdb) disas /r 0x400281,+10
8270 Dump of assembler code from 0x400281 to 0x40028b:
8271 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8272 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8273 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8274 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8275 End of assembler dump.
8278 Addresses cannot be specified as a location (@pxref{Specify Location}).
8279 So, for example, if you want to disassemble function @code{bar}
8280 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8281 and not @samp{disassemble foo.c:bar}.
8283 Some architectures have more than one commonly-used set of instruction
8284 mnemonics or other syntax.
8286 For programs that were dynamically linked and use shared libraries,
8287 instructions that call functions or branch to locations in the shared
8288 libraries might show a seemingly bogus location---it's actually a
8289 location of the relocation table. On some architectures, @value{GDBN}
8290 might be able to resolve these to actual function names.
8293 @kindex set disassembly-flavor
8294 @cindex Intel disassembly flavor
8295 @cindex AT&T disassembly flavor
8296 @item set disassembly-flavor @var{instruction-set}
8297 Select the instruction set to use when disassembling the
8298 program via the @code{disassemble} or @code{x/i} commands.
8300 Currently this command is only defined for the Intel x86 family. You
8301 can set @var{instruction-set} to either @code{intel} or @code{att}.
8302 The default is @code{att}, the AT&T flavor used by default by Unix
8303 assemblers for x86-based targets.
8305 @kindex show disassembly-flavor
8306 @item show disassembly-flavor
8307 Show the current setting of the disassembly flavor.
8311 @kindex set disassemble-next-line
8312 @kindex show disassemble-next-line
8313 @item set disassemble-next-line
8314 @itemx show disassemble-next-line
8315 Control whether or not @value{GDBN} will disassemble the next source
8316 line or instruction when execution stops. If ON, @value{GDBN} will
8317 display disassembly of the next source line when execution of the
8318 program being debugged stops. This is @emph{in addition} to
8319 displaying the source line itself, which @value{GDBN} always does if
8320 possible. If the next source line cannot be displayed for some reason
8321 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8322 info in the debug info), @value{GDBN} will display disassembly of the
8323 next @emph{instruction} instead of showing the next source line. If
8324 AUTO, @value{GDBN} will display disassembly of next instruction only
8325 if the source line cannot be displayed. This setting causes
8326 @value{GDBN} to display some feedback when you step through a function
8327 with no line info or whose source file is unavailable. The default is
8328 OFF, which means never display the disassembly of the next line or
8334 @chapter Examining Data
8336 @cindex printing data
8337 @cindex examining data
8340 The usual way to examine data in your program is with the @code{print}
8341 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8342 evaluates and prints the value of an expression of the language your
8343 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8344 Different Languages}). It may also print the expression using a
8345 Python-based pretty-printer (@pxref{Pretty Printing}).
8348 @item print @var{expr}
8349 @itemx print /@var{f} @var{expr}
8350 @var{expr} is an expression (in the source language). By default the
8351 value of @var{expr} is printed in a format appropriate to its data type;
8352 you can choose a different format by specifying @samp{/@var{f}}, where
8353 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8357 @itemx print /@var{f}
8358 @cindex reprint the last value
8359 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8360 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8361 conveniently inspect the same value in an alternative format.
8364 A more low-level way of examining data is with the @code{x} command.
8365 It examines data in memory at a specified address and prints it in a
8366 specified format. @xref{Memory, ,Examining Memory}.
8368 If you are interested in information about types, or about how the
8369 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8370 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8373 @cindex exploring hierarchical data structures
8375 Another way of examining values of expressions and type information is
8376 through the Python extension command @code{explore} (available only if
8377 the @value{GDBN} build is configured with @code{--with-python}). It
8378 offers an interactive way to start at the highest level (or, the most
8379 abstract level) of the data type of an expression (or, the data type
8380 itself) and explore all the way down to leaf scalar values/fields
8381 embedded in the higher level data types.
8384 @item explore @var{arg}
8385 @var{arg} is either an expression (in the source language), or a type
8386 visible in the current context of the program being debugged.
8389 The working of the @code{explore} command can be illustrated with an
8390 example. If a data type @code{struct ComplexStruct} is defined in your
8400 struct ComplexStruct
8402 struct SimpleStruct *ss_p;
8408 followed by variable declarations as
8411 struct SimpleStruct ss = @{ 10, 1.11 @};
8412 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8416 then, the value of the variable @code{cs} can be explored using the
8417 @code{explore} command as follows.
8421 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8422 the following fields:
8424 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8425 arr = <Enter 1 to explore this field of type `int [10]'>
8427 Enter the field number of choice:
8431 Since the fields of @code{cs} are not scalar values, you are being
8432 prompted to chose the field you want to explore. Let's say you choose
8433 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8434 pointer, you will be asked if it is pointing to a single value. From
8435 the declaration of @code{cs} above, it is indeed pointing to a single
8436 value, hence you enter @code{y}. If you enter @code{n}, then you will
8437 be asked if it were pointing to an array of values, in which case this
8438 field will be explored as if it were an array.
8441 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8442 Continue exploring it as a pointer to a single value [y/n]: y
8443 The value of `*(cs.ss_p)' is a struct/class of type `struct
8444 SimpleStruct' with the following fields:
8446 i = 10 .. (Value of type `int')
8447 d = 1.1100000000000001 .. (Value of type `double')
8449 Press enter to return to parent value:
8453 If the field @code{arr} of @code{cs} was chosen for exploration by
8454 entering @code{1} earlier, then since it is as array, you will be
8455 prompted to enter the index of the element in the array that you want
8459 `cs.arr' is an array of `int'.
8460 Enter the index of the element you want to explore in `cs.arr': 5
8462 `(cs.arr)[5]' is a scalar value of type `int'.
8466 Press enter to return to parent value:
8469 In general, at any stage of exploration, you can go deeper towards the
8470 leaf values by responding to the prompts appropriately, or hit the
8471 return key to return to the enclosing data structure (the @i{higher}
8472 level data structure).
8474 Similar to exploring values, you can use the @code{explore} command to
8475 explore types. Instead of specifying a value (which is typically a
8476 variable name or an expression valid in the current context of the
8477 program being debugged), you specify a type name. If you consider the
8478 same example as above, your can explore the type
8479 @code{struct ComplexStruct} by passing the argument
8480 @code{struct ComplexStruct} to the @code{explore} command.
8483 (gdb) explore struct ComplexStruct
8487 By responding to the prompts appropriately in the subsequent interactive
8488 session, you can explore the type @code{struct ComplexStruct} in a
8489 manner similar to how the value @code{cs} was explored in the above
8492 The @code{explore} command also has two sub-commands,
8493 @code{explore value} and @code{explore type}. The former sub-command is
8494 a way to explicitly specify that value exploration of the argument is
8495 being invoked, while the latter is a way to explicitly specify that type
8496 exploration of the argument is being invoked.
8499 @item explore value @var{expr}
8500 @cindex explore value
8501 This sub-command of @code{explore} explores the value of the
8502 expression @var{expr} (if @var{expr} is an expression valid in the
8503 current context of the program being debugged). The behavior of this
8504 command is identical to that of the behavior of the @code{explore}
8505 command being passed the argument @var{expr}.
8507 @item explore type @var{arg}
8508 @cindex explore type
8509 This sub-command of @code{explore} explores the type of @var{arg} (if
8510 @var{arg} is a type visible in the current context of program being
8511 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8512 is an expression valid in the current context of the program being
8513 debugged). If @var{arg} is a type, then the behavior of this command is
8514 identical to that of the @code{explore} command being passed the
8515 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8516 this command will be identical to that of the @code{explore} command
8517 being passed the type of @var{arg} as the argument.
8521 * Expressions:: Expressions
8522 * Ambiguous Expressions:: Ambiguous Expressions
8523 * Variables:: Program variables
8524 * Arrays:: Artificial arrays
8525 * Output Formats:: Output formats
8526 * Memory:: Examining memory
8527 * Auto Display:: Automatic display
8528 * Print Settings:: Print settings
8529 * Pretty Printing:: Python pretty printing
8530 * Value History:: Value history
8531 * Convenience Vars:: Convenience variables
8532 * Convenience Funs:: Convenience functions
8533 * Registers:: Registers
8534 * Floating Point Hardware:: Floating point hardware
8535 * Vector Unit:: Vector Unit
8536 * OS Information:: Auxiliary data provided by operating system
8537 * Memory Region Attributes:: Memory region attributes
8538 * Dump/Restore Files:: Copy between memory and a file
8539 * Core File Generation:: Cause a program dump its core
8540 * Character Sets:: Debugging programs that use a different
8541 character set than GDB does
8542 * Caching Target Data:: Data caching for targets
8543 * Searching Memory:: Searching memory for a sequence of bytes
8547 @section Expressions
8550 @code{print} and many other @value{GDBN} commands accept an expression and
8551 compute its value. Any kind of constant, variable or operator defined
8552 by the programming language you are using is valid in an expression in
8553 @value{GDBN}. This includes conditional expressions, function calls,
8554 casts, and string constants. It also includes preprocessor macros, if
8555 you compiled your program to include this information; see
8558 @cindex arrays in expressions
8559 @value{GDBN} supports array constants in expressions input by
8560 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8561 you can use the command @code{print @{1, 2, 3@}} to create an array
8562 of three integers. If you pass an array to a function or assign it
8563 to a program variable, @value{GDBN} copies the array to memory that
8564 is @code{malloc}ed in the target program.
8566 Because C is so widespread, most of the expressions shown in examples in
8567 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8568 Languages}, for information on how to use expressions in other
8571 In this section, we discuss operators that you can use in @value{GDBN}
8572 expressions regardless of your programming language.
8574 @cindex casts, in expressions
8575 Casts are supported in all languages, not just in C, because it is so
8576 useful to cast a number into a pointer in order to examine a structure
8577 at that address in memory.
8578 @c FIXME: casts supported---Mod2 true?
8580 @value{GDBN} supports these operators, in addition to those common
8581 to programming languages:
8585 @samp{@@} is a binary operator for treating parts of memory as arrays.
8586 @xref{Arrays, ,Artificial Arrays}, for more information.
8589 @samp{::} allows you to specify a variable in terms of the file or
8590 function where it is defined. @xref{Variables, ,Program Variables}.
8592 @cindex @{@var{type}@}
8593 @cindex type casting memory
8594 @cindex memory, viewing as typed object
8595 @cindex casts, to view memory
8596 @item @{@var{type}@} @var{addr}
8597 Refers to an object of type @var{type} stored at address @var{addr} in
8598 memory. The address @var{addr} may be any expression whose value is
8599 an integer or pointer (but parentheses are required around binary
8600 operators, just as in a cast). This construct is allowed regardless
8601 of what kind of data is normally supposed to reside at @var{addr}.
8604 @node Ambiguous Expressions
8605 @section Ambiguous Expressions
8606 @cindex ambiguous expressions
8608 Expressions can sometimes contain some ambiguous elements. For instance,
8609 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8610 a single function name to be defined several times, for application in
8611 different contexts. This is called @dfn{overloading}. Another example
8612 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8613 templates and is typically instantiated several times, resulting in
8614 the same function name being defined in different contexts.
8616 In some cases and depending on the language, it is possible to adjust
8617 the expression to remove the ambiguity. For instance in C@t{++}, you
8618 can specify the signature of the function you want to break on, as in
8619 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8620 qualified name of your function often makes the expression unambiguous
8623 When an ambiguity that needs to be resolved is detected, the debugger
8624 has the capability to display a menu of numbered choices for each
8625 possibility, and then waits for the selection with the prompt @samp{>}.
8626 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8627 aborts the current command. If the command in which the expression was
8628 used allows more than one choice to be selected, the next option in the
8629 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8632 For example, the following session excerpt shows an attempt to set a
8633 breakpoint at the overloaded symbol @code{String::after}.
8634 We choose three particular definitions of that function name:
8636 @c FIXME! This is likely to change to show arg type lists, at least
8639 (@value{GDBP}) b String::after
8642 [2] file:String.cc; line number:867
8643 [3] file:String.cc; line number:860
8644 [4] file:String.cc; line number:875
8645 [5] file:String.cc; line number:853
8646 [6] file:String.cc; line number:846
8647 [7] file:String.cc; line number:735
8649 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8650 Breakpoint 2 at 0xb344: file String.cc, line 875.
8651 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8652 Multiple breakpoints were set.
8653 Use the "delete" command to delete unwanted
8660 @kindex set multiple-symbols
8661 @item set multiple-symbols @var{mode}
8662 @cindex multiple-symbols menu
8664 This option allows you to adjust the debugger behavior when an expression
8667 By default, @var{mode} is set to @code{all}. If the command with which
8668 the expression is used allows more than one choice, then @value{GDBN}
8669 automatically selects all possible choices. For instance, inserting
8670 a breakpoint on a function using an ambiguous name results in a breakpoint
8671 inserted on each possible match. However, if a unique choice must be made,
8672 then @value{GDBN} uses the menu to help you disambiguate the expression.
8673 For instance, printing the address of an overloaded function will result
8674 in the use of the menu.
8676 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8677 when an ambiguity is detected.
8679 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8680 an error due to the ambiguity and the command is aborted.
8682 @kindex show multiple-symbols
8683 @item show multiple-symbols
8684 Show the current value of the @code{multiple-symbols} setting.
8688 @section Program Variables
8690 The most common kind of expression to use is the name of a variable
8693 Variables in expressions are understood in the selected stack frame
8694 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8698 global (or file-static)
8705 visible according to the scope rules of the
8706 programming language from the point of execution in that frame
8709 @noindent This means that in the function
8724 you can examine and use the variable @code{a} whenever your program is
8725 executing within the function @code{foo}, but you can only use or
8726 examine the variable @code{b} while your program is executing inside
8727 the block where @code{b} is declared.
8729 @cindex variable name conflict
8730 There is an exception: you can refer to a variable or function whose
8731 scope is a single source file even if the current execution point is not
8732 in this file. But it is possible to have more than one such variable or
8733 function with the same name (in different source files). If that
8734 happens, referring to that name has unpredictable effects. If you wish,
8735 you can specify a static variable in a particular function or file by
8736 using the colon-colon (@code{::}) notation:
8738 @cindex colon-colon, context for variables/functions
8740 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8741 @cindex @code{::}, context for variables/functions
8744 @var{file}::@var{variable}
8745 @var{function}::@var{variable}
8749 Here @var{file} or @var{function} is the name of the context for the
8750 static @var{variable}. In the case of file names, you can use quotes to
8751 make sure @value{GDBN} parses the file name as a single word---for example,
8752 to print a global value of @code{x} defined in @file{f2.c}:
8755 (@value{GDBP}) p 'f2.c'::x
8758 The @code{::} notation is normally used for referring to
8759 static variables, since you typically disambiguate uses of local variables
8760 in functions by selecting the appropriate frame and using the
8761 simple name of the variable. However, you may also use this notation
8762 to refer to local variables in frames enclosing the selected frame:
8771 process (a); /* Stop here */
8782 For example, if there is a breakpoint at the commented line,
8783 here is what you might see
8784 when the program stops after executing the call @code{bar(0)}:
8789 (@value{GDBP}) p bar::a
8792 #2 0x080483d0 in foo (a=5) at foobar.c:12
8795 (@value{GDBP}) p bar::a
8799 @cindex C@t{++} scope resolution
8800 These uses of @samp{::} are very rarely in conflict with the very
8801 similar use of the same notation in C@t{++}. When they are in
8802 conflict, the C@t{++} meaning takes precedence; however, this can be
8803 overridden by quoting the file or function name with single quotes.
8805 For example, suppose the program is stopped in a method of a class
8806 that has a field named @code{includefile}, and there is also an
8807 include file named @file{includefile} that defines a variable,
8811 (@value{GDBP}) p includefile
8813 (@value{GDBP}) p includefile::some_global
8814 A syntax error in expression, near `'.
8815 (@value{GDBP}) p 'includefile'::some_global
8819 @cindex wrong values
8820 @cindex variable values, wrong
8821 @cindex function entry/exit, wrong values of variables
8822 @cindex optimized code, wrong values of variables
8824 @emph{Warning:} Occasionally, a local variable may appear to have the
8825 wrong value at certain points in a function---just after entry to a new
8826 scope, and just before exit.
8828 You may see this problem when you are stepping by machine instructions.
8829 This is because, on most machines, it takes more than one instruction to
8830 set up a stack frame (including local variable definitions); if you are
8831 stepping by machine instructions, variables may appear to have the wrong
8832 values until the stack frame is completely built. On exit, it usually
8833 also takes more than one machine instruction to destroy a stack frame;
8834 after you begin stepping through that group of instructions, local
8835 variable definitions may be gone.
8837 This may also happen when the compiler does significant optimizations.
8838 To be sure of always seeing accurate values, turn off all optimization
8841 @cindex ``No symbol "foo" in current context''
8842 Another possible effect of compiler optimizations is to optimize
8843 unused variables out of existence, or assign variables to registers (as
8844 opposed to memory addresses). Depending on the support for such cases
8845 offered by the debug info format used by the compiler, @value{GDBN}
8846 might not be able to display values for such local variables. If that
8847 happens, @value{GDBN} will print a message like this:
8850 No symbol "foo" in current context.
8853 To solve such problems, either recompile without optimizations, or use a
8854 different debug info format, if the compiler supports several such
8855 formats. @xref{Compilation}, for more information on choosing compiler
8856 options. @xref{C, ,C and C@t{++}}, for more information about debug
8857 info formats that are best suited to C@t{++} programs.
8859 If you ask to print an object whose contents are unknown to
8860 @value{GDBN}, e.g., because its data type is not completely specified
8861 by the debug information, @value{GDBN} will say @samp{<incomplete
8862 type>}. @xref{Symbols, incomplete type}, for more about this.
8864 If you append @kbd{@@entry} string to a function parameter name you get its
8865 value at the time the function got called. If the value is not available an
8866 error message is printed. Entry values are available only with some compilers.
8867 Entry values are normally also printed at the function parameter list according
8868 to @ref{set print entry-values}.
8871 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8877 (gdb) print i@@entry
8881 Strings are identified as arrays of @code{char} values without specified
8882 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8883 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8884 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8885 defines literal string type @code{"char"} as @code{char} without a sign.
8890 signed char var1[] = "A";
8893 You get during debugging
8898 $2 = @{65 'A', 0 '\0'@}
8902 @section Artificial Arrays
8904 @cindex artificial array
8906 @kindex @@@r{, referencing memory as an array}
8907 It is often useful to print out several successive objects of the
8908 same type in memory; a section of an array, or an array of
8909 dynamically determined size for which only a pointer exists in the
8912 You can do this by referring to a contiguous span of memory as an
8913 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8914 operand of @samp{@@} should be the first element of the desired array
8915 and be an individual object. The right operand should be the desired length
8916 of the array. The result is an array value whose elements are all of
8917 the type of the left argument. The first element is actually the left
8918 argument; the second element comes from bytes of memory immediately
8919 following those that hold the first element, and so on. Here is an
8920 example. If a program says
8923 int *array = (int *) malloc (len * sizeof (int));
8927 you can print the contents of @code{array} with
8933 The left operand of @samp{@@} must reside in memory. Array values made
8934 with @samp{@@} in this way behave just like other arrays in terms of
8935 subscripting, and are coerced to pointers when used in expressions.
8936 Artificial arrays most often appear in expressions via the value history
8937 (@pxref{Value History, ,Value History}), after printing one out.
8939 Another way to create an artificial array is to use a cast.
8940 This re-interprets a value as if it were an array.
8941 The value need not be in memory:
8943 (@value{GDBP}) p/x (short[2])0x12345678
8944 $1 = @{0x1234, 0x5678@}
8947 As a convenience, if you leave the array length out (as in
8948 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8949 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8951 (@value{GDBP}) p/x (short[])0x12345678
8952 $2 = @{0x1234, 0x5678@}
8955 Sometimes the artificial array mechanism is not quite enough; in
8956 moderately complex data structures, the elements of interest may not
8957 actually be adjacent---for example, if you are interested in the values
8958 of pointers in an array. One useful work-around in this situation is
8959 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8960 Variables}) as a counter in an expression that prints the first
8961 interesting value, and then repeat that expression via @key{RET}. For
8962 instance, suppose you have an array @code{dtab} of pointers to
8963 structures, and you are interested in the values of a field @code{fv}
8964 in each structure. Here is an example of what you might type:
8974 @node Output Formats
8975 @section Output Formats
8977 @cindex formatted output
8978 @cindex output formats
8979 By default, @value{GDBN} prints a value according to its data type. Sometimes
8980 this is not what you want. For example, you might want to print a number
8981 in hex, or a pointer in decimal. Or you might want to view data in memory
8982 at a certain address as a character string or as an instruction. To do
8983 these things, specify an @dfn{output format} when you print a value.
8985 The simplest use of output formats is to say how to print a value
8986 already computed. This is done by starting the arguments of the
8987 @code{print} command with a slash and a format letter. The format
8988 letters supported are:
8992 Regard the bits of the value as an integer, and print the integer in
8996 Print as integer in signed decimal.
8999 Print as integer in unsigned decimal.
9002 Print as integer in octal.
9005 Print as integer in binary. The letter @samp{t} stands for ``two''.
9006 @footnote{@samp{b} cannot be used because these format letters are also
9007 used with the @code{x} command, where @samp{b} stands for ``byte'';
9008 see @ref{Memory,,Examining Memory}.}
9011 @cindex unknown address, locating
9012 @cindex locate address
9013 Print as an address, both absolute in hexadecimal and as an offset from
9014 the nearest preceding symbol. You can use this format used to discover
9015 where (in what function) an unknown address is located:
9018 (@value{GDBP}) p/a 0x54320
9019 $3 = 0x54320 <_initialize_vx+396>
9023 The command @code{info symbol 0x54320} yields similar results.
9024 @xref{Symbols, info symbol}.
9027 Regard as an integer and print it as a character constant. This
9028 prints both the numerical value and its character representation. The
9029 character representation is replaced with the octal escape @samp{\nnn}
9030 for characters outside the 7-bit @sc{ascii} range.
9032 Without this format, @value{GDBN} displays @code{char},
9033 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9034 constants. Single-byte members of vectors are displayed as integer
9038 Regard the bits of the value as a floating point number and print
9039 using typical floating point syntax.
9042 @cindex printing strings
9043 @cindex printing byte arrays
9044 Regard as a string, if possible. With this format, pointers to single-byte
9045 data are displayed as null-terminated strings and arrays of single-byte data
9046 are displayed as fixed-length strings. Other values are displayed in their
9049 Without this format, @value{GDBN} displays pointers to and arrays of
9050 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9051 strings. Single-byte members of a vector are displayed as an integer
9055 Like @samp{x} formatting, the value is treated as an integer and
9056 printed as hexadecimal, but leading zeros are printed to pad the value
9057 to the size of the integer type.
9060 @cindex raw printing
9061 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9062 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9063 Printing}). This typically results in a higher-level display of the
9064 value's contents. The @samp{r} format bypasses any Python
9065 pretty-printer which might exist.
9068 For example, to print the program counter in hex (@pxref{Registers}), type
9075 Note that no space is required before the slash; this is because command
9076 names in @value{GDBN} cannot contain a slash.
9078 To reprint the last value in the value history with a different format,
9079 you can use the @code{print} command with just a format and no
9080 expression. For example, @samp{p/x} reprints the last value in hex.
9083 @section Examining Memory
9085 You can use the command @code{x} (for ``examine'') to examine memory in
9086 any of several formats, independently of your program's data types.
9088 @cindex examining memory
9090 @kindex x @r{(examine memory)}
9091 @item x/@var{nfu} @var{addr}
9094 Use the @code{x} command to examine memory.
9097 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9098 much memory to display and how to format it; @var{addr} is an
9099 expression giving the address where you want to start displaying memory.
9100 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9101 Several commands set convenient defaults for @var{addr}.
9104 @item @var{n}, the repeat count
9105 The repeat count is a decimal integer; the default is 1. It specifies
9106 how much memory (counting by units @var{u}) to display.
9107 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9110 @item @var{f}, the display format
9111 The display format is one of the formats used by @code{print}
9112 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9113 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9114 The default is @samp{x} (hexadecimal) initially. The default changes
9115 each time you use either @code{x} or @code{print}.
9117 @item @var{u}, the unit size
9118 The unit size is any of
9124 Halfwords (two bytes).
9126 Words (four bytes). This is the initial default.
9128 Giant words (eight bytes).
9131 Each time you specify a unit size with @code{x}, that size becomes the
9132 default unit the next time you use @code{x}. For the @samp{i} format,
9133 the unit size is ignored and is normally not written. For the @samp{s} format,
9134 the unit size defaults to @samp{b}, unless it is explicitly given.
9135 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9136 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9137 Note that the results depend on the programming language of the
9138 current compilation unit. If the language is C, the @samp{s}
9139 modifier will use the UTF-16 encoding while @samp{w} will use
9140 UTF-32. The encoding is set by the programming language and cannot
9143 @item @var{addr}, starting display address
9144 @var{addr} is the address where you want @value{GDBN} to begin displaying
9145 memory. The expression need not have a pointer value (though it may);
9146 it is always interpreted as an integer address of a byte of memory.
9147 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9148 @var{addr} is usually just after the last address examined---but several
9149 other commands also set the default address: @code{info breakpoints} (to
9150 the address of the last breakpoint listed), @code{info line} (to the
9151 starting address of a line), and @code{print} (if you use it to display
9152 a value from memory).
9155 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9156 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9157 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9158 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9159 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9161 Since the letters indicating unit sizes are all distinct from the
9162 letters specifying output formats, you do not have to remember whether
9163 unit size or format comes first; either order works. The output
9164 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9165 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9167 Even though the unit size @var{u} is ignored for the formats @samp{s}
9168 and @samp{i}, you might still want to use a count @var{n}; for example,
9169 @samp{3i} specifies that you want to see three machine instructions,
9170 including any operands. For convenience, especially when used with
9171 the @code{display} command, the @samp{i} format also prints branch delay
9172 slot instructions, if any, beyond the count specified, which immediately
9173 follow the last instruction that is within the count. The command
9174 @code{disassemble} gives an alternative way of inspecting machine
9175 instructions; see @ref{Machine Code,,Source and Machine Code}.
9177 All the defaults for the arguments to @code{x} are designed to make it
9178 easy to continue scanning memory with minimal specifications each time
9179 you use @code{x}. For example, after you have inspected three machine
9180 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9181 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9182 the repeat count @var{n} is used again; the other arguments default as
9183 for successive uses of @code{x}.
9185 When examining machine instructions, the instruction at current program
9186 counter is shown with a @code{=>} marker. For example:
9189 (@value{GDBP}) x/5i $pc-6
9190 0x804837f <main+11>: mov %esp,%ebp
9191 0x8048381 <main+13>: push %ecx
9192 0x8048382 <main+14>: sub $0x4,%esp
9193 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9194 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9197 @cindex @code{$_}, @code{$__}, and value history
9198 The addresses and contents printed by the @code{x} command are not saved
9199 in the value history because there is often too much of them and they
9200 would get in the way. Instead, @value{GDBN} makes these values available for
9201 subsequent use in expressions as values of the convenience variables
9202 @code{$_} and @code{$__}. After an @code{x} command, the last address
9203 examined is available for use in expressions in the convenience variable
9204 @code{$_}. The contents of that address, as examined, are available in
9205 the convenience variable @code{$__}.
9207 If the @code{x} command has a repeat count, the address and contents saved
9208 are from the last memory unit printed; this is not the same as the last
9209 address printed if several units were printed on the last line of output.
9211 @anchor{addressable memory unit}
9212 @cindex addressable memory unit
9213 Most targets have an addressable memory unit size of 8 bits. This means
9214 that to each memory address are associated 8 bits of data. Some
9215 targets, however, have other addressable memory unit sizes.
9216 Within @value{GDBN} and this document, the term
9217 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9218 when explicitly referring to a chunk of data of that size. The word
9219 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9220 the addressable memory unit size of the target. For most systems,
9221 addressable memory unit is a synonym of byte.
9223 @cindex remote memory comparison
9224 @cindex target memory comparison
9225 @cindex verify remote memory image
9226 @cindex verify target memory image
9227 When you are debugging a program running on a remote target machine
9228 (@pxref{Remote Debugging}), you may wish to verify the program's image
9229 in the remote machine's memory against the executable file you
9230 downloaded to the target. Or, on any target, you may want to check
9231 whether the program has corrupted its own read-only sections. The
9232 @code{compare-sections} command is provided for such situations.
9235 @kindex compare-sections
9236 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9237 Compare the data of a loadable section @var{section-name} in the
9238 executable file of the program being debugged with the same section in
9239 the target machine's memory, and report any mismatches. With no
9240 arguments, compares all loadable sections. With an argument of
9241 @code{-r}, compares all loadable read-only sections.
9243 Note: for remote targets, this command can be accelerated if the
9244 target supports computing the CRC checksum of a block of memory
9245 (@pxref{qCRC packet}).
9249 @section Automatic Display
9250 @cindex automatic display
9251 @cindex display of expressions
9253 If you find that you want to print the value of an expression frequently
9254 (to see how it changes), you might want to add it to the @dfn{automatic
9255 display list} so that @value{GDBN} prints its value each time your program stops.
9256 Each expression added to the list is given a number to identify it;
9257 to remove an expression from the list, you specify that number.
9258 The automatic display looks like this:
9262 3: bar[5] = (struct hack *) 0x3804
9266 This display shows item numbers, expressions and their current values. As with
9267 displays you request manually using @code{x} or @code{print}, you can
9268 specify the output format you prefer; in fact, @code{display} decides
9269 whether to use @code{print} or @code{x} depending your format
9270 specification---it uses @code{x} if you specify either the @samp{i}
9271 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9275 @item display @var{expr}
9276 Add the expression @var{expr} to the list of expressions to display
9277 each time your program stops. @xref{Expressions, ,Expressions}.
9279 @code{display} does not repeat if you press @key{RET} again after using it.
9281 @item display/@var{fmt} @var{expr}
9282 For @var{fmt} specifying only a display format and not a size or
9283 count, add the expression @var{expr} to the auto-display list but
9284 arrange to display it each time in the specified format @var{fmt}.
9285 @xref{Output Formats,,Output Formats}.
9287 @item display/@var{fmt} @var{addr}
9288 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9289 number of units, add the expression @var{addr} as a memory address to
9290 be examined each time your program stops. Examining means in effect
9291 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9294 For example, @samp{display/i $pc} can be helpful, to see the machine
9295 instruction about to be executed each time execution stops (@samp{$pc}
9296 is a common name for the program counter; @pxref{Registers, ,Registers}).
9299 @kindex delete display
9301 @item undisplay @var{dnums}@dots{}
9302 @itemx delete display @var{dnums}@dots{}
9303 Remove items from the list of expressions to display. Specify the
9304 numbers of the displays that you want affected with the command
9305 argument @var{dnums}. It can be a single display number, one of the
9306 numbers shown in the first field of the @samp{info display} display;
9307 or it could be a range of display numbers, as in @code{2-4}.
9309 @code{undisplay} does not repeat if you press @key{RET} after using it.
9310 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9312 @kindex disable display
9313 @item disable display @var{dnums}@dots{}
9314 Disable the display of item numbers @var{dnums}. A disabled display
9315 item is not printed automatically, but is not forgotten. It may be
9316 enabled again later. Specify the numbers of the displays that you
9317 want affected with the command argument @var{dnums}. It can be a
9318 single display number, one of the numbers shown in the first field of
9319 the @samp{info display} display; or it could be a range of display
9320 numbers, as in @code{2-4}.
9322 @kindex enable display
9323 @item enable display @var{dnums}@dots{}
9324 Enable display of item numbers @var{dnums}. It becomes effective once
9325 again in auto display of its expression, until you specify otherwise.
9326 Specify the numbers of the displays that you want affected with the
9327 command argument @var{dnums}. It can be a single display number, one
9328 of the numbers shown in the first field of the @samp{info display}
9329 display; or it could be a range of display numbers, as in @code{2-4}.
9332 Display the current values of the expressions on the list, just as is
9333 done when your program stops.
9335 @kindex info display
9337 Print the list of expressions previously set up to display
9338 automatically, each one with its item number, but without showing the
9339 values. This includes disabled expressions, which are marked as such.
9340 It also includes expressions which would not be displayed right now
9341 because they refer to automatic variables not currently available.
9344 @cindex display disabled out of scope
9345 If a display expression refers to local variables, then it does not make
9346 sense outside the lexical context for which it was set up. Such an
9347 expression is disabled when execution enters a context where one of its
9348 variables is not defined. For example, if you give the command
9349 @code{display last_char} while inside a function with an argument
9350 @code{last_char}, @value{GDBN} displays this argument while your program
9351 continues to stop inside that function. When it stops elsewhere---where
9352 there is no variable @code{last_char}---the display is disabled
9353 automatically. The next time your program stops where @code{last_char}
9354 is meaningful, you can enable the display expression once again.
9356 @node Print Settings
9357 @section Print Settings
9359 @cindex format options
9360 @cindex print settings
9361 @value{GDBN} provides the following ways to control how arrays, structures,
9362 and symbols are printed.
9365 These settings are useful for debugging programs in any language:
9369 @item set print address
9370 @itemx set print address on
9371 @cindex print/don't print memory addresses
9372 @value{GDBN} prints memory addresses showing the location of stack
9373 traces, structure values, pointer values, breakpoints, and so forth,
9374 even when it also displays the contents of those addresses. The default
9375 is @code{on}. For example, this is what a stack frame display looks like with
9376 @code{set print address on}:
9381 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9383 530 if (lquote != def_lquote)
9387 @item set print address off
9388 Do not print addresses when displaying their contents. For example,
9389 this is the same stack frame displayed with @code{set print address off}:
9393 (@value{GDBP}) set print addr off
9395 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9396 530 if (lquote != def_lquote)
9400 You can use @samp{set print address off} to eliminate all machine
9401 dependent displays from the @value{GDBN} interface. For example, with
9402 @code{print address off}, you should get the same text for backtraces on
9403 all machines---whether or not they involve pointer arguments.
9406 @item show print address
9407 Show whether or not addresses are to be printed.
9410 When @value{GDBN} prints a symbolic address, it normally prints the
9411 closest earlier symbol plus an offset. If that symbol does not uniquely
9412 identify the address (for example, it is a name whose scope is a single
9413 source file), you may need to clarify. One way to do this is with
9414 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9415 you can set @value{GDBN} to print the source file and line number when
9416 it prints a symbolic address:
9419 @item set print symbol-filename on
9420 @cindex source file and line of a symbol
9421 @cindex symbol, source file and line
9422 Tell @value{GDBN} to print the source file name and line number of a
9423 symbol in the symbolic form of an address.
9425 @item set print symbol-filename off
9426 Do not print source file name and line number of a symbol. This is the
9429 @item show print symbol-filename
9430 Show whether or not @value{GDBN} will print the source file name and
9431 line number of a symbol in the symbolic form of an address.
9434 Another situation where it is helpful to show symbol filenames and line
9435 numbers is when disassembling code; @value{GDBN} shows you the line
9436 number and source file that corresponds to each instruction.
9438 Also, you may wish to see the symbolic form only if the address being
9439 printed is reasonably close to the closest earlier symbol:
9442 @item set print max-symbolic-offset @var{max-offset}
9443 @itemx set print max-symbolic-offset unlimited
9444 @cindex maximum value for offset of closest symbol
9445 Tell @value{GDBN} to only display the symbolic form of an address if the
9446 offset between the closest earlier symbol and the address is less than
9447 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9448 to always print the symbolic form of an address if any symbol precedes
9449 it. Zero is equivalent to @code{unlimited}.
9451 @item show print max-symbolic-offset
9452 Ask how large the maximum offset is that @value{GDBN} prints in a
9456 @cindex wild pointer, interpreting
9457 @cindex pointer, finding referent
9458 If you have a pointer and you are not sure where it points, try
9459 @samp{set print symbol-filename on}. Then you can determine the name
9460 and source file location of the variable where it points, using
9461 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9462 For example, here @value{GDBN} shows that a variable @code{ptt} points
9463 at another variable @code{t}, defined in @file{hi2.c}:
9466 (@value{GDBP}) set print symbol-filename on
9467 (@value{GDBP}) p/a ptt
9468 $4 = 0xe008 <t in hi2.c>
9472 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9473 does not show the symbol name and filename of the referent, even with
9474 the appropriate @code{set print} options turned on.
9477 You can also enable @samp{/a}-like formatting all the time using
9478 @samp{set print symbol on}:
9481 @item set print symbol on
9482 Tell @value{GDBN} to print the symbol corresponding to an address, if
9485 @item set print symbol off
9486 Tell @value{GDBN} not to print the symbol corresponding to an
9487 address. In this mode, @value{GDBN} will still print the symbol
9488 corresponding to pointers to functions. This is the default.
9490 @item show print symbol
9491 Show whether @value{GDBN} will display the symbol corresponding to an
9495 Other settings control how different kinds of objects are printed:
9498 @item set print array
9499 @itemx set print array on
9500 @cindex pretty print arrays
9501 Pretty print arrays. This format is more convenient to read,
9502 but uses more space. The default is off.
9504 @item set print array off
9505 Return to compressed format for arrays.
9507 @item show print array
9508 Show whether compressed or pretty format is selected for displaying
9511 @cindex print array indexes
9512 @item set print array-indexes
9513 @itemx set print array-indexes on
9514 Print the index of each element when displaying arrays. May be more
9515 convenient to locate a given element in the array or quickly find the
9516 index of a given element in that printed array. The default is off.
9518 @item set print array-indexes off
9519 Stop printing element indexes when displaying arrays.
9521 @item show print array-indexes
9522 Show whether the index of each element is printed when displaying
9525 @item set print elements @var{number-of-elements}
9526 @itemx set print elements unlimited
9527 @cindex number of array elements to print
9528 @cindex limit on number of printed array elements
9529 Set a limit on how many elements of an array @value{GDBN} will print.
9530 If @value{GDBN} is printing a large array, it stops printing after it has
9531 printed the number of elements set by the @code{set print elements} command.
9532 This limit also applies to the display of strings.
9533 When @value{GDBN} starts, this limit is set to 200.
9534 Setting @var{number-of-elements} to @code{unlimited} or zero means
9535 that the number of elements to print is unlimited.
9537 @item show print elements
9538 Display the number of elements of a large array that @value{GDBN} will print.
9539 If the number is 0, then the printing is unlimited.
9541 @item set print frame-arguments @var{value}
9542 @kindex set print frame-arguments
9543 @cindex printing frame argument values
9544 @cindex print all frame argument values
9545 @cindex print frame argument values for scalars only
9546 @cindex do not print frame argument values
9547 This command allows to control how the values of arguments are printed
9548 when the debugger prints a frame (@pxref{Frames}). The possible
9553 The values of all arguments are printed.
9556 Print the value of an argument only if it is a scalar. The value of more
9557 complex arguments such as arrays, structures, unions, etc, is replaced
9558 by @code{@dots{}}. This is the default. Here is an example where
9559 only scalar arguments are shown:
9562 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9567 None of the argument values are printed. Instead, the value of each argument
9568 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9571 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9576 By default, only scalar arguments are printed. This command can be used
9577 to configure the debugger to print the value of all arguments, regardless
9578 of their type. However, it is often advantageous to not print the value
9579 of more complex parameters. For instance, it reduces the amount of
9580 information printed in each frame, making the backtrace more readable.
9581 Also, it improves performance when displaying Ada frames, because
9582 the computation of large arguments can sometimes be CPU-intensive,
9583 especially in large applications. Setting @code{print frame-arguments}
9584 to @code{scalars} (the default) or @code{none} avoids this computation,
9585 thus speeding up the display of each Ada frame.
9587 @item show print frame-arguments
9588 Show how the value of arguments should be displayed when printing a frame.
9590 @item set print raw frame-arguments on
9591 Print frame arguments in raw, non pretty-printed, form.
9593 @item set print raw frame-arguments off
9594 Print frame arguments in pretty-printed form, if there is a pretty-printer
9595 for the value (@pxref{Pretty Printing}),
9596 otherwise print the value in raw form.
9597 This is the default.
9599 @item show print raw frame-arguments
9600 Show whether to print frame arguments in raw form.
9602 @anchor{set print entry-values}
9603 @item set print entry-values @var{value}
9604 @kindex set print entry-values
9605 Set printing of frame argument values at function entry. In some cases
9606 @value{GDBN} can determine the value of function argument which was passed by
9607 the function caller, even if the value was modified inside the called function
9608 and therefore is different. With optimized code, the current value could be
9609 unavailable, but the entry value may still be known.
9611 The default value is @code{default} (see below for its description). Older
9612 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9613 this feature will behave in the @code{default} setting the same way as with the
9616 This functionality is currently supported only by DWARF 2 debugging format and
9617 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9618 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9621 The @var{value} parameter can be one of the following:
9625 Print only actual parameter values, never print values from function entry
9629 #0 different (val=6)
9630 #0 lost (val=<optimized out>)
9632 #0 invalid (val=<optimized out>)
9636 Print only parameter values from function entry point. The actual parameter
9637 values are never printed.
9639 #0 equal (val@@entry=5)
9640 #0 different (val@@entry=5)
9641 #0 lost (val@@entry=5)
9642 #0 born (val@@entry=<optimized out>)
9643 #0 invalid (val@@entry=<optimized out>)
9647 Print only parameter values from function entry point. If value from function
9648 entry point is not known while the actual value is known, print the actual
9649 value for such parameter.
9651 #0 equal (val@@entry=5)
9652 #0 different (val@@entry=5)
9653 #0 lost (val@@entry=5)
9655 #0 invalid (val@@entry=<optimized out>)
9659 Print actual parameter values. If actual parameter value is not known while
9660 value from function entry point is known, print the entry point value for such
9664 #0 different (val=6)
9665 #0 lost (val@@entry=5)
9667 #0 invalid (val=<optimized out>)
9671 Always print both the actual parameter value and its value from function entry
9672 point, even if values of one or both are not available due to compiler
9675 #0 equal (val=5, val@@entry=5)
9676 #0 different (val=6, val@@entry=5)
9677 #0 lost (val=<optimized out>, val@@entry=5)
9678 #0 born (val=10, val@@entry=<optimized out>)
9679 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9683 Print the actual parameter value if it is known and also its value from
9684 function entry point if it is known. If neither is known, print for the actual
9685 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9686 values are known and identical, print the shortened
9687 @code{param=param@@entry=VALUE} notation.
9689 #0 equal (val=val@@entry=5)
9690 #0 different (val=6, val@@entry=5)
9691 #0 lost (val@@entry=5)
9693 #0 invalid (val=<optimized out>)
9697 Always print the actual parameter value. Print also its value from function
9698 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9699 if both values are known and identical, print the shortened
9700 @code{param=param@@entry=VALUE} notation.
9702 #0 equal (val=val@@entry=5)
9703 #0 different (val=6, val@@entry=5)
9704 #0 lost (val=<optimized out>, val@@entry=5)
9706 #0 invalid (val=<optimized out>)
9710 For analysis messages on possible failures of frame argument values at function
9711 entry resolution see @ref{set debug entry-values}.
9713 @item show print entry-values
9714 Show the method being used for printing of frame argument values at function
9717 @item set print repeats @var{number-of-repeats}
9718 @itemx set print repeats unlimited
9719 @cindex repeated array elements
9720 Set the threshold for suppressing display of repeated array
9721 elements. When the number of consecutive identical elements of an
9722 array exceeds the threshold, @value{GDBN} prints the string
9723 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9724 identical repetitions, instead of displaying the identical elements
9725 themselves. Setting the threshold to @code{unlimited} or zero will
9726 cause all elements to be individually printed. The default threshold
9729 @item show print repeats
9730 Display the current threshold for printing repeated identical
9733 @item set print null-stop
9734 @cindex @sc{null} elements in arrays
9735 Cause @value{GDBN} to stop printing the characters of an array when the first
9736 @sc{null} is encountered. This is useful when large arrays actually
9737 contain only short strings.
9740 @item show print null-stop
9741 Show whether @value{GDBN} stops printing an array on the first
9742 @sc{null} character.
9744 @item set print pretty on
9745 @cindex print structures in indented form
9746 @cindex indentation in structure display
9747 Cause @value{GDBN} to print structures in an indented format with one member
9748 per line, like this:
9763 @item set print pretty off
9764 Cause @value{GDBN} to print structures in a compact format, like this:
9768 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9769 meat = 0x54 "Pork"@}
9774 This is the default format.
9776 @item show print pretty
9777 Show which format @value{GDBN} is using to print structures.
9779 @item set print sevenbit-strings on
9780 @cindex eight-bit characters in strings
9781 @cindex octal escapes in strings
9782 Print using only seven-bit characters; if this option is set,
9783 @value{GDBN} displays any eight-bit characters (in strings or
9784 character values) using the notation @code{\}@var{nnn}. This setting is
9785 best if you are working in English (@sc{ascii}) and you use the
9786 high-order bit of characters as a marker or ``meta'' bit.
9788 @item set print sevenbit-strings off
9789 Print full eight-bit characters. This allows the use of more
9790 international character sets, and is the default.
9792 @item show print sevenbit-strings
9793 Show whether or not @value{GDBN} is printing only seven-bit characters.
9795 @item set print union on
9796 @cindex unions in structures, printing
9797 Tell @value{GDBN} to print unions which are contained in structures
9798 and other unions. This is the default setting.
9800 @item set print union off
9801 Tell @value{GDBN} not to print unions which are contained in
9802 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9805 @item show print union
9806 Ask @value{GDBN} whether or not it will print unions which are contained in
9807 structures and other unions.
9809 For example, given the declarations
9812 typedef enum @{Tree, Bug@} Species;
9813 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9814 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9825 struct thing foo = @{Tree, @{Acorn@}@};
9829 with @code{set print union on} in effect @samp{p foo} would print
9832 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9836 and with @code{set print union off} in effect it would print
9839 $1 = @{it = Tree, form = @{...@}@}
9843 @code{set print union} affects programs written in C-like languages
9849 These settings are of interest when debugging C@t{++} programs:
9852 @cindex demangling C@t{++} names
9853 @item set print demangle
9854 @itemx set print demangle on
9855 Print C@t{++} names in their source form rather than in the encoded
9856 (``mangled'') form passed to the assembler and linker for type-safe
9857 linkage. The default is on.
9859 @item show print demangle
9860 Show whether C@t{++} names are printed in mangled or demangled form.
9862 @item set print asm-demangle
9863 @itemx set print asm-demangle on
9864 Print C@t{++} names in their source form rather than their mangled form, even
9865 in assembler code printouts such as instruction disassemblies.
9868 @item show print asm-demangle
9869 Show whether C@t{++} names in assembly listings are printed in mangled
9872 @cindex C@t{++} symbol decoding style
9873 @cindex symbol decoding style, C@t{++}
9874 @kindex set demangle-style
9875 @item set demangle-style @var{style}
9876 Choose among several encoding schemes used by different compilers to
9877 represent C@t{++} names. The choices for @var{style} are currently:
9881 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9882 This is the default.
9885 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9888 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9891 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9894 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9895 @strong{Warning:} this setting alone is not sufficient to allow
9896 debugging @code{cfront}-generated executables. @value{GDBN} would
9897 require further enhancement to permit that.
9900 If you omit @var{style}, you will see a list of possible formats.
9902 @item show demangle-style
9903 Display the encoding style currently in use for decoding C@t{++} symbols.
9905 @item set print object
9906 @itemx set print object on
9907 @cindex derived type of an object, printing
9908 @cindex display derived types
9909 When displaying a pointer to an object, identify the @emph{actual}
9910 (derived) type of the object rather than the @emph{declared} type, using
9911 the virtual function table. Note that the virtual function table is
9912 required---this feature can only work for objects that have run-time
9913 type identification; a single virtual method in the object's declared
9914 type is sufficient. Note that this setting is also taken into account when
9915 working with variable objects via MI (@pxref{GDB/MI}).
9917 @item set print object off
9918 Display only the declared type of objects, without reference to the
9919 virtual function table. This is the default setting.
9921 @item show print object
9922 Show whether actual, or declared, object types are displayed.
9924 @item set print static-members
9925 @itemx set print static-members on
9926 @cindex static members of C@t{++} objects
9927 Print static members when displaying a C@t{++} object. The default is on.
9929 @item set print static-members off
9930 Do not print static members when displaying a C@t{++} object.
9932 @item show print static-members
9933 Show whether C@t{++} static members are printed or not.
9935 @item set print pascal_static-members
9936 @itemx set print pascal_static-members on
9937 @cindex static members of Pascal objects
9938 @cindex Pascal objects, static members display
9939 Print static members when displaying a Pascal object. The default is on.
9941 @item set print pascal_static-members off
9942 Do not print static members when displaying a Pascal object.
9944 @item show print pascal_static-members
9945 Show whether Pascal static members are printed or not.
9947 @c These don't work with HP ANSI C++ yet.
9948 @item set print vtbl
9949 @itemx set print vtbl on
9950 @cindex pretty print C@t{++} virtual function tables
9951 @cindex virtual functions (C@t{++}) display
9952 @cindex VTBL display
9953 Pretty print C@t{++} virtual function tables. The default is off.
9954 (The @code{vtbl} commands do not work on programs compiled with the HP
9955 ANSI C@t{++} compiler (@code{aCC}).)
9957 @item set print vtbl off
9958 Do not pretty print C@t{++} virtual function tables.
9960 @item show print vtbl
9961 Show whether C@t{++} virtual function tables are pretty printed, or not.
9964 @node Pretty Printing
9965 @section Pretty Printing
9967 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9968 Python code. It greatly simplifies the display of complex objects. This
9969 mechanism works for both MI and the CLI.
9972 * Pretty-Printer Introduction:: Introduction to pretty-printers
9973 * Pretty-Printer Example:: An example pretty-printer
9974 * Pretty-Printer Commands:: Pretty-printer commands
9977 @node Pretty-Printer Introduction
9978 @subsection Pretty-Printer Introduction
9980 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9981 registered for the value. If there is then @value{GDBN} invokes the
9982 pretty-printer to print the value. Otherwise the value is printed normally.
9984 Pretty-printers are normally named. This makes them easy to manage.
9985 The @samp{info pretty-printer} command will list all the installed
9986 pretty-printers with their names.
9987 If a pretty-printer can handle multiple data types, then its
9988 @dfn{subprinters} are the printers for the individual data types.
9989 Each such subprinter has its own name.
9990 The format of the name is @var{printer-name};@var{subprinter-name}.
9992 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9993 Typically they are automatically loaded and registered when the corresponding
9994 debug information is loaded, thus making them available without having to
9995 do anything special.
9997 There are three places where a pretty-printer can be registered.
10001 Pretty-printers registered globally are available when debugging
10005 Pretty-printers registered with a program space are available only
10006 when debugging that program.
10007 @xref{Progspaces In Python}, for more details on program spaces in Python.
10010 Pretty-printers registered with an objfile are loaded and unloaded
10011 with the corresponding objfile (e.g., shared library).
10012 @xref{Objfiles In Python}, for more details on objfiles in Python.
10015 @xref{Selecting Pretty-Printers}, for further information on how
10016 pretty-printers are selected,
10018 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10021 @node Pretty-Printer Example
10022 @subsection Pretty-Printer Example
10024 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10027 (@value{GDBP}) print s
10029 static npos = 4294967295,
10031 <std::allocator<char>> = @{
10032 <__gnu_cxx::new_allocator<char>> = @{
10033 <No data fields>@}, <No data fields>
10035 members of std::basic_string<char, std::char_traits<char>,
10036 std::allocator<char> >::_Alloc_hider:
10037 _M_p = 0x804a014 "abcd"
10042 With a pretty-printer for @code{std::string} only the contents are printed:
10045 (@value{GDBP}) print s
10049 @node Pretty-Printer Commands
10050 @subsection Pretty-Printer Commands
10051 @cindex pretty-printer commands
10054 @kindex info pretty-printer
10055 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10056 Print the list of installed pretty-printers.
10057 This includes disabled pretty-printers, which are marked as such.
10059 @var{object-regexp} is a regular expression matching the objects
10060 whose pretty-printers to list.
10061 Objects can be @code{global}, the program space's file
10062 (@pxref{Progspaces In Python}),
10063 and the object files within that program space (@pxref{Objfiles In Python}).
10064 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10065 looks up a printer from these three objects.
10067 @var{name-regexp} is a regular expression matching the name of the printers
10070 @kindex disable pretty-printer
10071 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10072 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10073 A disabled pretty-printer is not forgotten, it may be enabled again later.
10075 @kindex enable pretty-printer
10076 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10077 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10082 Suppose we have three pretty-printers installed: one from library1.so
10083 named @code{foo} that prints objects of type @code{foo}, and
10084 another from library2.so named @code{bar} that prints two types of objects,
10085 @code{bar1} and @code{bar2}.
10088 (gdb) info pretty-printer
10095 (gdb) info pretty-printer library2
10100 (gdb) disable pretty-printer library1
10102 2 of 3 printers enabled
10103 (gdb) info pretty-printer
10110 (gdb) disable pretty-printer library2 bar:bar1
10112 1 of 3 printers enabled
10113 (gdb) info pretty-printer library2
10120 (gdb) disable pretty-printer library2 bar
10122 0 of 3 printers enabled
10123 (gdb) info pretty-printer library2
10132 Note that for @code{bar} the entire printer can be disabled,
10133 as can each individual subprinter.
10135 @node Value History
10136 @section Value History
10138 @cindex value history
10139 @cindex history of values printed by @value{GDBN}
10140 Values printed by the @code{print} command are saved in the @value{GDBN}
10141 @dfn{value history}. This allows you to refer to them in other expressions.
10142 Values are kept until the symbol table is re-read or discarded
10143 (for example with the @code{file} or @code{symbol-file} commands).
10144 When the symbol table changes, the value history is discarded,
10145 since the values may contain pointers back to the types defined in the
10150 @cindex history number
10151 The values printed are given @dfn{history numbers} by which you can
10152 refer to them. These are successive integers starting with one.
10153 @code{print} shows you the history number assigned to a value by
10154 printing @samp{$@var{num} = } before the value; here @var{num} is the
10157 To refer to any previous value, use @samp{$} followed by the value's
10158 history number. The way @code{print} labels its output is designed to
10159 remind you of this. Just @code{$} refers to the most recent value in
10160 the history, and @code{$$} refers to the value before that.
10161 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10162 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10163 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10165 For example, suppose you have just printed a pointer to a structure and
10166 want to see the contents of the structure. It suffices to type
10172 If you have a chain of structures where the component @code{next} points
10173 to the next one, you can print the contents of the next one with this:
10180 You can print successive links in the chain by repeating this
10181 command---which you can do by just typing @key{RET}.
10183 Note that the history records values, not expressions. If the value of
10184 @code{x} is 4 and you type these commands:
10192 then the value recorded in the value history by the @code{print} command
10193 remains 4 even though the value of @code{x} has changed.
10196 @kindex show values
10198 Print the last ten values in the value history, with their item numbers.
10199 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10200 values} does not change the history.
10202 @item show values @var{n}
10203 Print ten history values centered on history item number @var{n}.
10205 @item show values +
10206 Print ten history values just after the values last printed. If no more
10207 values are available, @code{show values +} produces no display.
10210 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10211 same effect as @samp{show values +}.
10213 @node Convenience Vars
10214 @section Convenience Variables
10216 @cindex convenience variables
10217 @cindex user-defined variables
10218 @value{GDBN} provides @dfn{convenience variables} that you can use within
10219 @value{GDBN} to hold on to a value and refer to it later. These variables
10220 exist entirely within @value{GDBN}; they are not part of your program, and
10221 setting a convenience variable has no direct effect on further execution
10222 of your program. That is why you can use them freely.
10224 Convenience variables are prefixed with @samp{$}. Any name preceded by
10225 @samp{$} can be used for a convenience variable, unless it is one of
10226 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10227 (Value history references, in contrast, are @emph{numbers} preceded
10228 by @samp{$}. @xref{Value History, ,Value History}.)
10230 You can save a value in a convenience variable with an assignment
10231 expression, just as you would set a variable in your program.
10235 set $foo = *object_ptr
10239 would save in @code{$foo} the value contained in the object pointed to by
10242 Using a convenience variable for the first time creates it, but its
10243 value is @code{void} until you assign a new value. You can alter the
10244 value with another assignment at any time.
10246 Convenience variables have no fixed types. You can assign a convenience
10247 variable any type of value, including structures and arrays, even if
10248 that variable already has a value of a different type. The convenience
10249 variable, when used as an expression, has the type of its current value.
10252 @kindex show convenience
10253 @cindex show all user variables and functions
10254 @item show convenience
10255 Print a list of convenience variables used so far, and their values,
10256 as well as a list of the convenience functions.
10257 Abbreviated @code{show conv}.
10259 @kindex init-if-undefined
10260 @cindex convenience variables, initializing
10261 @item init-if-undefined $@var{variable} = @var{expression}
10262 Set a convenience variable if it has not already been set. This is useful
10263 for user-defined commands that keep some state. It is similar, in concept,
10264 to using local static variables with initializers in C (except that
10265 convenience variables are global). It can also be used to allow users to
10266 override default values used in a command script.
10268 If the variable is already defined then the expression is not evaluated so
10269 any side-effects do not occur.
10272 One of the ways to use a convenience variable is as a counter to be
10273 incremented or a pointer to be advanced. For example, to print
10274 a field from successive elements of an array of structures:
10278 print bar[$i++]->contents
10282 Repeat that command by typing @key{RET}.
10284 Some convenience variables are created automatically by @value{GDBN} and given
10285 values likely to be useful.
10288 @vindex $_@r{, convenience variable}
10290 The variable @code{$_} is automatically set by the @code{x} command to
10291 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10292 commands which provide a default address for @code{x} to examine also
10293 set @code{$_} to that address; these commands include @code{info line}
10294 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10295 except when set by the @code{x} command, in which case it is a pointer
10296 to the type of @code{$__}.
10298 @vindex $__@r{, convenience variable}
10300 The variable @code{$__} is automatically set by the @code{x} command
10301 to the value found in the last address examined. Its type is chosen
10302 to match the format in which the data was printed.
10305 @vindex $_exitcode@r{, convenience variable}
10306 When the program being debugged terminates normally, @value{GDBN}
10307 automatically sets this variable to the exit code of the program, and
10308 resets @code{$_exitsignal} to @code{void}.
10311 @vindex $_exitsignal@r{, convenience variable}
10312 When the program being debugged dies due to an uncaught signal,
10313 @value{GDBN} automatically sets this variable to that signal's number,
10314 and resets @code{$_exitcode} to @code{void}.
10316 To distinguish between whether the program being debugged has exited
10317 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10318 @code{$_exitsignal} is not @code{void}), the convenience function
10319 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10320 Functions}). For example, considering the following source code:
10323 #include <signal.h>
10326 main (int argc, char *argv[])
10333 A valid way of telling whether the program being debugged has exited
10334 or signalled would be:
10337 (@value{GDBP}) define has_exited_or_signalled
10338 Type commands for definition of ``has_exited_or_signalled''.
10339 End with a line saying just ``end''.
10340 >if $_isvoid ($_exitsignal)
10341 >echo The program has exited\n
10343 >echo The program has signalled\n
10349 Program terminated with signal SIGALRM, Alarm clock.
10350 The program no longer exists.
10351 (@value{GDBP}) has_exited_or_signalled
10352 The program has signalled
10355 As can be seen, @value{GDBN} correctly informs that the program being
10356 debugged has signalled, since it calls @code{raise} and raises a
10357 @code{SIGALRM} signal. If the program being debugged had not called
10358 @code{raise}, then @value{GDBN} would report a normal exit:
10361 (@value{GDBP}) has_exited_or_signalled
10362 The program has exited
10366 The variable @code{$_exception} is set to the exception object being
10367 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10370 @itemx $_probe_arg0@dots{}$_probe_arg11
10371 Arguments to a static probe. @xref{Static Probe Points}.
10374 @vindex $_sdata@r{, inspect, convenience variable}
10375 The variable @code{$_sdata} contains extra collected static tracepoint
10376 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10377 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10378 if extra static tracepoint data has not been collected.
10381 @vindex $_siginfo@r{, convenience variable}
10382 The variable @code{$_siginfo} contains extra signal information
10383 (@pxref{extra signal information}). Note that @code{$_siginfo}
10384 could be empty, if the application has not yet received any signals.
10385 For example, it will be empty before you execute the @code{run} command.
10388 @vindex $_tlb@r{, convenience variable}
10389 The variable @code{$_tlb} is automatically set when debugging
10390 applications running on MS-Windows in native mode or connected to
10391 gdbserver that supports the @code{qGetTIBAddr} request.
10392 @xref{General Query Packets}.
10393 This variable contains the address of the thread information block.
10397 @node Convenience Funs
10398 @section Convenience Functions
10400 @cindex convenience functions
10401 @value{GDBN} also supplies some @dfn{convenience functions}. These
10402 have a syntax similar to convenience variables. A convenience
10403 function can be used in an expression just like an ordinary function;
10404 however, a convenience function is implemented internally to
10407 These functions do not require @value{GDBN} to be configured with
10408 @code{Python} support, which means that they are always available.
10412 @item $_isvoid (@var{expr})
10413 @findex $_isvoid@r{, convenience function}
10414 Return one if the expression @var{expr} is @code{void}. Otherwise it
10417 A @code{void} expression is an expression where the type of the result
10418 is @code{void}. For example, you can examine a convenience variable
10419 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10423 (@value{GDBP}) print $_exitcode
10425 (@value{GDBP}) print $_isvoid ($_exitcode)
10428 Starting program: ./a.out
10429 [Inferior 1 (process 29572) exited normally]
10430 (@value{GDBP}) print $_exitcode
10432 (@value{GDBP}) print $_isvoid ($_exitcode)
10436 In the example above, we used @code{$_isvoid} to check whether
10437 @code{$_exitcode} is @code{void} before and after the execution of the
10438 program being debugged. Before the execution there is no exit code to
10439 be examined, therefore @code{$_exitcode} is @code{void}. After the
10440 execution the program being debugged returned zero, therefore
10441 @code{$_exitcode} is zero, which means that it is not @code{void}
10444 The @code{void} expression can also be a call of a function from the
10445 program being debugged. For example, given the following function:
10454 The result of calling it inside @value{GDBN} is @code{void}:
10457 (@value{GDBP}) print foo ()
10459 (@value{GDBP}) print $_isvoid (foo ())
10461 (@value{GDBP}) set $v = foo ()
10462 (@value{GDBP}) print $v
10464 (@value{GDBP}) print $_isvoid ($v)
10470 These functions require @value{GDBN} to be configured with
10471 @code{Python} support.
10475 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10476 @findex $_memeq@r{, convenience function}
10477 Returns one if the @var{length} bytes at the addresses given by
10478 @var{buf1} and @var{buf2} are equal.
10479 Otherwise it returns zero.
10481 @item $_regex(@var{str}, @var{regex})
10482 @findex $_regex@r{, convenience function}
10483 Returns one if the string @var{str} matches the regular expression
10484 @var{regex}. Otherwise it returns zero.
10485 The syntax of the regular expression is that specified by @code{Python}'s
10486 regular expression support.
10488 @item $_streq(@var{str1}, @var{str2})
10489 @findex $_streq@r{, convenience function}
10490 Returns one if the strings @var{str1} and @var{str2} are equal.
10491 Otherwise it returns zero.
10493 @item $_strlen(@var{str})
10494 @findex $_strlen@r{, convenience function}
10495 Returns the length of string @var{str}.
10497 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10498 @findex $_caller_is@r{, convenience function}
10499 Returns one if the calling function's name is equal to @var{name}.
10500 Otherwise it returns zero.
10502 If the optional argument @var{number_of_frames} is provided,
10503 it is the number of frames up in the stack to look.
10511 at testsuite/gdb.python/py-caller-is.c:21
10512 #1 0x00000000004005a0 in middle_func ()
10513 at testsuite/gdb.python/py-caller-is.c:27
10514 #2 0x00000000004005ab in top_func ()
10515 at testsuite/gdb.python/py-caller-is.c:33
10516 #3 0x00000000004005b6 in main ()
10517 at testsuite/gdb.python/py-caller-is.c:39
10518 (gdb) print $_caller_is ("middle_func")
10520 (gdb) print $_caller_is ("top_func", 2)
10524 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10525 @findex $_caller_matches@r{, convenience function}
10526 Returns one if the calling function's name matches the regular expression
10527 @var{regexp}. Otherwise it returns zero.
10529 If the optional argument @var{number_of_frames} is provided,
10530 it is the number of frames up in the stack to look.
10533 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10534 @findex $_any_caller_is@r{, convenience function}
10535 Returns one if any calling function's name is equal to @var{name}.
10536 Otherwise it returns zero.
10538 If the optional argument @var{number_of_frames} is provided,
10539 it is the number of frames up in the stack to look.
10542 This function differs from @code{$_caller_is} in that this function
10543 checks all stack frames from the immediate caller to the frame specified
10544 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10545 frame specified by @var{number_of_frames}.
10547 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10548 @findex $_any_caller_matches@r{, convenience function}
10549 Returns one if any calling function's name matches the regular expression
10550 @var{regexp}. Otherwise it returns zero.
10552 If the optional argument @var{number_of_frames} is provided,
10553 it is the number of frames up in the stack to look.
10556 This function differs from @code{$_caller_matches} in that this function
10557 checks all stack frames from the immediate caller to the frame specified
10558 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10559 frame specified by @var{number_of_frames}.
10563 @value{GDBN} provides the ability to list and get help on
10564 convenience functions.
10567 @item help function
10568 @kindex help function
10569 @cindex show all convenience functions
10570 Print a list of all convenience functions.
10577 You can refer to machine register contents, in expressions, as variables
10578 with names starting with @samp{$}. The names of registers are different
10579 for each machine; use @code{info registers} to see the names used on
10583 @kindex info registers
10584 @item info registers
10585 Print the names and values of all registers except floating-point
10586 and vector registers (in the selected stack frame).
10588 @kindex info all-registers
10589 @cindex floating point registers
10590 @item info all-registers
10591 Print the names and values of all registers, including floating-point
10592 and vector registers (in the selected stack frame).
10594 @item info registers @var{regname} @dots{}
10595 Print the @dfn{relativized} value of each specified register @var{regname}.
10596 As discussed in detail below, register values are normally relative to
10597 the selected stack frame. The @var{regname} may be any register name valid on
10598 the machine you are using, with or without the initial @samp{$}.
10601 @anchor{standard registers}
10602 @cindex stack pointer register
10603 @cindex program counter register
10604 @cindex process status register
10605 @cindex frame pointer register
10606 @cindex standard registers
10607 @value{GDBN} has four ``standard'' register names that are available (in
10608 expressions) on most machines---whenever they do not conflict with an
10609 architecture's canonical mnemonics for registers. The register names
10610 @code{$pc} and @code{$sp} are used for the program counter register and
10611 the stack pointer. @code{$fp} is used for a register that contains a
10612 pointer to the current stack frame, and @code{$ps} is used for a
10613 register that contains the processor status. For example,
10614 you could print the program counter in hex with
10621 or print the instruction to be executed next with
10628 or add four to the stack pointer@footnote{This is a way of removing
10629 one word from the stack, on machines where stacks grow downward in
10630 memory (most machines, nowadays). This assumes that the innermost
10631 stack frame is selected; setting @code{$sp} is not allowed when other
10632 stack frames are selected. To pop entire frames off the stack,
10633 regardless of machine architecture, use @code{return};
10634 see @ref{Returning, ,Returning from a Function}.} with
10640 Whenever possible, these four standard register names are available on
10641 your machine even though the machine has different canonical mnemonics,
10642 so long as there is no conflict. The @code{info registers} command
10643 shows the canonical names. For example, on the SPARC, @code{info
10644 registers} displays the processor status register as @code{$psr} but you
10645 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10646 is an alias for the @sc{eflags} register.
10648 @value{GDBN} always considers the contents of an ordinary register as an
10649 integer when the register is examined in this way. Some machines have
10650 special registers which can hold nothing but floating point; these
10651 registers are considered to have floating point values. There is no way
10652 to refer to the contents of an ordinary register as floating point value
10653 (although you can @emph{print} it as a floating point value with
10654 @samp{print/f $@var{regname}}).
10656 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10657 means that the data format in which the register contents are saved by
10658 the operating system is not the same one that your program normally
10659 sees. For example, the registers of the 68881 floating point
10660 coprocessor are always saved in ``extended'' (raw) format, but all C
10661 programs expect to work with ``double'' (virtual) format. In such
10662 cases, @value{GDBN} normally works with the virtual format only (the format
10663 that makes sense for your program), but the @code{info registers} command
10664 prints the data in both formats.
10666 @cindex SSE registers (x86)
10667 @cindex MMX registers (x86)
10668 Some machines have special registers whose contents can be interpreted
10669 in several different ways. For example, modern x86-based machines
10670 have SSE and MMX registers that can hold several values packed
10671 together in several different formats. @value{GDBN} refers to such
10672 registers in @code{struct} notation:
10675 (@value{GDBP}) print $xmm1
10677 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10678 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10679 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10680 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10681 v4_int32 = @{0, 20657912, 11, 13@},
10682 v2_int64 = @{88725056443645952, 55834574859@},
10683 uint128 = 0x0000000d0000000b013b36f800000000
10688 To set values of such registers, you need to tell @value{GDBN} which
10689 view of the register you wish to change, as if you were assigning
10690 value to a @code{struct} member:
10693 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10696 Normally, register values are relative to the selected stack frame
10697 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10698 value that the register would contain if all stack frames farther in
10699 were exited and their saved registers restored. In order to see the
10700 true contents of hardware registers, you must select the innermost
10701 frame (with @samp{frame 0}).
10703 @cindex caller-saved registers
10704 @cindex call-clobbered registers
10705 @cindex volatile registers
10706 @cindex <not saved> values
10707 Usually ABIs reserve some registers as not needed to be saved by the
10708 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10709 registers). It may therefore not be possible for @value{GDBN} to know
10710 the value a register had before the call (in other words, in the outer
10711 frame), if the register value has since been changed by the callee.
10712 @value{GDBN} tries to deduce where the inner frame saved
10713 (``callee-saved'') registers, from the debug info, unwind info, or the
10714 machine code generated by your compiler. If some register is not
10715 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10716 its own knowledge of the ABI, or because the debug/unwind info
10717 explicitly says the register's value is undefined), @value{GDBN}
10718 displays @w{@samp{<not saved>}} as the register's value. With targets
10719 that @value{GDBN} has no knowledge of the register saving convention,
10720 if a register was not saved by the callee, then its value and location
10721 in the outer frame are assumed to be the same of the inner frame.
10722 This is usually harmless, because if the register is call-clobbered,
10723 the caller either does not care what is in the register after the
10724 call, or has code to restore the value that it does care about. Note,
10725 however, that if you change such a register in the outer frame, you
10726 may also be affecting the inner frame. Also, the more ``outer'' the
10727 frame is you're looking at, the more likely a call-clobbered
10728 register's value is to be wrong, in the sense that it doesn't actually
10729 represent the value the register had just before the call.
10731 @node Floating Point Hardware
10732 @section Floating Point Hardware
10733 @cindex floating point
10735 Depending on the configuration, @value{GDBN} may be able to give
10736 you more information about the status of the floating point hardware.
10741 Display hardware-dependent information about the floating
10742 point unit. The exact contents and layout vary depending on the
10743 floating point chip. Currently, @samp{info float} is supported on
10744 the ARM and x86 machines.
10748 @section Vector Unit
10749 @cindex vector unit
10751 Depending on the configuration, @value{GDBN} may be able to give you
10752 more information about the status of the vector unit.
10755 @kindex info vector
10757 Display information about the vector unit. The exact contents and
10758 layout vary depending on the hardware.
10761 @node OS Information
10762 @section Operating System Auxiliary Information
10763 @cindex OS information
10765 @value{GDBN} provides interfaces to useful OS facilities that can help
10766 you debug your program.
10768 @cindex auxiliary vector
10769 @cindex vector, auxiliary
10770 Some operating systems supply an @dfn{auxiliary vector} to programs at
10771 startup. This is akin to the arguments and environment that you
10772 specify for a program, but contains a system-dependent variety of
10773 binary values that tell system libraries important details about the
10774 hardware, operating system, and process. Each value's purpose is
10775 identified by an integer tag; the meanings are well-known but system-specific.
10776 Depending on the configuration and operating system facilities,
10777 @value{GDBN} may be able to show you this information. For remote
10778 targets, this functionality may further depend on the remote stub's
10779 support of the @samp{qXfer:auxv:read} packet, see
10780 @ref{qXfer auxiliary vector read}.
10785 Display the auxiliary vector of the inferior, which can be either a
10786 live process or a core dump file. @value{GDBN} prints each tag value
10787 numerically, and also shows names and text descriptions for recognized
10788 tags. Some values in the vector are numbers, some bit masks, and some
10789 pointers to strings or other data. @value{GDBN} displays each value in the
10790 most appropriate form for a recognized tag, and in hexadecimal for
10791 an unrecognized tag.
10794 On some targets, @value{GDBN} can access operating system-specific
10795 information and show it to you. The types of information available
10796 will differ depending on the type of operating system running on the
10797 target. The mechanism used to fetch the data is described in
10798 @ref{Operating System Information}. For remote targets, this
10799 functionality depends on the remote stub's support of the
10800 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10804 @item info os @var{infotype}
10806 Display OS information of the requested type.
10808 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10810 @anchor{linux info os infotypes}
10812 @kindex info os cpus
10814 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10815 the available fields from /proc/cpuinfo. For each supported architecture
10816 different fields are available. Two common entries are processor which gives
10817 CPU number and bogomips; a system constant that is calculated during
10818 kernel initialization.
10820 @kindex info os files
10822 Display the list of open file descriptors on the target. For each
10823 file descriptor, @value{GDBN} prints the identifier of the process
10824 owning the descriptor, the command of the owning process, the value
10825 of the descriptor, and the target of the descriptor.
10827 @kindex info os modules
10829 Display the list of all loaded kernel modules on the target. For each
10830 module, @value{GDBN} prints the module name, the size of the module in
10831 bytes, the number of times the module is used, the dependencies of the
10832 module, the status of the module, and the address of the loaded module
10835 @kindex info os msg
10837 Display the list of all System V message queues on the target. For each
10838 message queue, @value{GDBN} prints the message queue key, the message
10839 queue identifier, the access permissions, the current number of bytes
10840 on the queue, the current number of messages on the queue, the processes
10841 that last sent and received a message on the queue, the user and group
10842 of the owner and creator of the message queue, the times at which a
10843 message was last sent and received on the queue, and the time at which
10844 the message queue was last changed.
10846 @kindex info os processes
10848 Display the list of processes on the target. For each process,
10849 @value{GDBN} prints the process identifier, the name of the user, the
10850 command corresponding to the process, and the list of processor cores
10851 that the process is currently running on. (To understand what these
10852 properties mean, for this and the following info types, please consult
10853 the general @sc{gnu}/Linux documentation.)
10855 @kindex info os procgroups
10857 Display the list of process groups on the target. For each process,
10858 @value{GDBN} prints the identifier of the process group that it belongs
10859 to, the command corresponding to the process group leader, the process
10860 identifier, and the command line of the process. The list is sorted
10861 first by the process group identifier, then by the process identifier,
10862 so that processes belonging to the same process group are grouped together
10863 and the process group leader is listed first.
10865 @kindex info os semaphores
10867 Display the list of all System V semaphore sets on the target. For each
10868 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10869 set identifier, the access permissions, the number of semaphores in the
10870 set, the user and group of the owner and creator of the semaphore set,
10871 and the times at which the semaphore set was operated upon and changed.
10873 @kindex info os shm
10875 Display the list of all System V shared-memory regions on the target.
10876 For each shared-memory region, @value{GDBN} prints the region key,
10877 the shared-memory identifier, the access permissions, the size of the
10878 region, the process that created the region, the process that last
10879 attached to or detached from the region, the current number of live
10880 attaches to the region, and the times at which the region was last
10881 attached to, detach from, and changed.
10883 @kindex info os sockets
10885 Display the list of Internet-domain sockets on the target. For each
10886 socket, @value{GDBN} prints the address and port of the local and
10887 remote endpoints, the current state of the connection, the creator of
10888 the socket, the IP address family of the socket, and the type of the
10891 @kindex info os threads
10893 Display the list of threads running on the target. For each thread,
10894 @value{GDBN} prints the identifier of the process that the thread
10895 belongs to, the command of the process, the thread identifier, and the
10896 processor core that it is currently running on. The main thread of a
10897 process is not listed.
10901 If @var{infotype} is omitted, then list the possible values for
10902 @var{infotype} and the kind of OS information available for each
10903 @var{infotype}. If the target does not return a list of possible
10904 types, this command will report an error.
10907 @node Memory Region Attributes
10908 @section Memory Region Attributes
10909 @cindex memory region attributes
10911 @dfn{Memory region attributes} allow you to describe special handling
10912 required by regions of your target's memory. @value{GDBN} uses
10913 attributes to determine whether to allow certain types of memory
10914 accesses; whether to use specific width accesses; and whether to cache
10915 target memory. By default the description of memory regions is
10916 fetched from the target (if the current target supports this), but the
10917 user can override the fetched regions.
10919 Defined memory regions can be individually enabled and disabled. When a
10920 memory region is disabled, @value{GDBN} uses the default attributes when
10921 accessing memory in that region. Similarly, if no memory regions have
10922 been defined, @value{GDBN} uses the default attributes when accessing
10925 When a memory region is defined, it is given a number to identify it;
10926 to enable, disable, or remove a memory region, you specify that number.
10930 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10931 Define a memory region bounded by @var{lower} and @var{upper} with
10932 attributes @var{attributes}@dots{}, and add it to the list of regions
10933 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10934 case: it is treated as the target's maximum memory address.
10935 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10938 Discard any user changes to the memory regions and use target-supplied
10939 regions, if available, or no regions if the target does not support.
10942 @item delete mem @var{nums}@dots{}
10943 Remove memory regions @var{nums}@dots{} from the list of regions
10944 monitored by @value{GDBN}.
10946 @kindex disable mem
10947 @item disable mem @var{nums}@dots{}
10948 Disable monitoring of memory regions @var{nums}@dots{}.
10949 A disabled memory region is not forgotten.
10950 It may be enabled again later.
10953 @item enable mem @var{nums}@dots{}
10954 Enable monitoring of memory regions @var{nums}@dots{}.
10958 Print a table of all defined memory regions, with the following columns
10962 @item Memory Region Number
10963 @item Enabled or Disabled.
10964 Enabled memory regions are marked with @samp{y}.
10965 Disabled memory regions are marked with @samp{n}.
10968 The address defining the inclusive lower bound of the memory region.
10971 The address defining the exclusive upper bound of the memory region.
10974 The list of attributes set for this memory region.
10979 @subsection Attributes
10981 @subsubsection Memory Access Mode
10982 The access mode attributes set whether @value{GDBN} may make read or
10983 write accesses to a memory region.
10985 While these attributes prevent @value{GDBN} from performing invalid
10986 memory accesses, they do nothing to prevent the target system, I/O DMA,
10987 etc.@: from accessing memory.
10991 Memory is read only.
10993 Memory is write only.
10995 Memory is read/write. This is the default.
10998 @subsubsection Memory Access Size
10999 The access size attribute tells @value{GDBN} to use specific sized
11000 accesses in the memory region. Often memory mapped device registers
11001 require specific sized accesses. If no access size attribute is
11002 specified, @value{GDBN} may use accesses of any size.
11006 Use 8 bit memory accesses.
11008 Use 16 bit memory accesses.
11010 Use 32 bit memory accesses.
11012 Use 64 bit memory accesses.
11015 @c @subsubsection Hardware/Software Breakpoints
11016 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11017 @c will use hardware or software breakpoints for the internal breakpoints
11018 @c used by the step, next, finish, until, etc. commands.
11022 @c Always use hardware breakpoints
11023 @c @item swbreak (default)
11026 @subsubsection Data Cache
11027 The data cache attributes set whether @value{GDBN} will cache target
11028 memory. While this generally improves performance by reducing debug
11029 protocol overhead, it can lead to incorrect results because @value{GDBN}
11030 does not know about volatile variables or memory mapped device
11035 Enable @value{GDBN} to cache target memory.
11037 Disable @value{GDBN} from caching target memory. This is the default.
11040 @subsection Memory Access Checking
11041 @value{GDBN} can be instructed to refuse accesses to memory that is
11042 not explicitly described. This can be useful if accessing such
11043 regions has undesired effects for a specific target, or to provide
11044 better error checking. The following commands control this behaviour.
11047 @kindex set mem inaccessible-by-default
11048 @item set mem inaccessible-by-default [on|off]
11049 If @code{on} is specified, make @value{GDBN} treat memory not
11050 explicitly described by the memory ranges as non-existent and refuse accesses
11051 to such memory. The checks are only performed if there's at least one
11052 memory range defined. If @code{off} is specified, make @value{GDBN}
11053 treat the memory not explicitly described by the memory ranges as RAM.
11054 The default value is @code{on}.
11055 @kindex show mem inaccessible-by-default
11056 @item show mem inaccessible-by-default
11057 Show the current handling of accesses to unknown memory.
11061 @c @subsubsection Memory Write Verification
11062 @c The memory write verification attributes set whether @value{GDBN}
11063 @c will re-reads data after each write to verify the write was successful.
11067 @c @item noverify (default)
11070 @node Dump/Restore Files
11071 @section Copy Between Memory and a File
11072 @cindex dump/restore files
11073 @cindex append data to a file
11074 @cindex dump data to a file
11075 @cindex restore data from a file
11077 You can use the commands @code{dump}, @code{append}, and
11078 @code{restore} to copy data between target memory and a file. The
11079 @code{dump} and @code{append} commands write data to a file, and the
11080 @code{restore} command reads data from a file back into the inferior's
11081 memory. Files may be in binary, Motorola S-record, Intel hex,
11082 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11083 append to binary files, and cannot read from Verilog Hex files.
11088 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11089 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11090 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11091 or the value of @var{expr}, to @var{filename} in the given format.
11093 The @var{format} parameter may be any one of:
11100 Motorola S-record format.
11102 Tektronix Hex format.
11104 Verilog Hex format.
11107 @value{GDBN} uses the same definitions of these formats as the
11108 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11109 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11113 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11114 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11115 Append the contents of memory from @var{start_addr} to @var{end_addr},
11116 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11117 (@value{GDBN} can only append data to files in raw binary form.)
11120 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11121 Restore the contents of file @var{filename} into memory. The
11122 @code{restore} command can automatically recognize any known @sc{bfd}
11123 file format, except for raw binary. To restore a raw binary file you
11124 must specify the optional keyword @code{binary} after the filename.
11126 If @var{bias} is non-zero, its value will be added to the addresses
11127 contained in the file. Binary files always start at address zero, so
11128 they will be restored at address @var{bias}. Other bfd files have
11129 a built-in location; they will be restored at offset @var{bias}
11130 from that location.
11132 If @var{start} and/or @var{end} are non-zero, then only data between
11133 file offset @var{start} and file offset @var{end} will be restored.
11134 These offsets are relative to the addresses in the file, before
11135 the @var{bias} argument is applied.
11139 @node Core File Generation
11140 @section How to Produce a Core File from Your Program
11141 @cindex dump core from inferior
11143 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11144 image of a running process and its process status (register values
11145 etc.). Its primary use is post-mortem debugging of a program that
11146 crashed while it ran outside a debugger. A program that crashes
11147 automatically produces a core file, unless this feature is disabled by
11148 the user. @xref{Files}, for information on invoking @value{GDBN} in
11149 the post-mortem debugging mode.
11151 Occasionally, you may wish to produce a core file of the program you
11152 are debugging in order to preserve a snapshot of its state.
11153 @value{GDBN} has a special command for that.
11157 @kindex generate-core-file
11158 @item generate-core-file [@var{file}]
11159 @itemx gcore [@var{file}]
11160 Produce a core dump of the inferior process. The optional argument
11161 @var{file} specifies the file name where to put the core dump. If not
11162 specified, the file name defaults to @file{core.@var{pid}}, where
11163 @var{pid} is the inferior process ID.
11165 Note that this command is implemented only for some systems (as of
11166 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11168 On @sc{gnu}/Linux, this command can take into account the value of the
11169 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11170 dump (@pxref{set use-coredump-filter}).
11172 @kindex set use-coredump-filter
11173 @anchor{set use-coredump-filter}
11174 @item set use-coredump-filter on
11175 @itemx set use-coredump-filter off
11176 Enable or disable the use of the file
11177 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11178 files. This file is used by the Linux kernel to decide what types of
11179 memory mappings will be dumped or ignored when generating a core dump
11180 file. @var{pid} is the process ID of a currently running process.
11182 To make use of this feature, you have to write in the
11183 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11184 which is a bit mask representing the memory mapping types. If a bit
11185 is set in the bit mask, then the memory mappings of the corresponding
11186 types will be dumped; otherwise, they will be ignored. This
11187 configuration is inherited by child processes. For more information
11188 about the bits that can be set in the
11189 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11190 manpage of @code{core(5)}.
11192 By default, this option is @code{on}. If this option is turned
11193 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11194 and instead uses the same default value as the Linux kernel in order
11195 to decide which pages will be dumped in the core dump file. This
11196 value is currently @code{0x33}, which means that bits @code{0}
11197 (anonymous private mappings), @code{1} (anonymous shared mappings),
11198 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11199 This will cause these memory mappings to be dumped automatically.
11202 @node Character Sets
11203 @section Character Sets
11204 @cindex character sets
11206 @cindex translating between character sets
11207 @cindex host character set
11208 @cindex target character set
11210 If the program you are debugging uses a different character set to
11211 represent characters and strings than the one @value{GDBN} uses itself,
11212 @value{GDBN} can automatically translate between the character sets for
11213 you. The character set @value{GDBN} uses we call the @dfn{host
11214 character set}; the one the inferior program uses we call the
11215 @dfn{target character set}.
11217 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11218 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11219 remote protocol (@pxref{Remote Debugging}) to debug a program
11220 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11221 then the host character set is Latin-1, and the target character set is
11222 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11223 target-charset EBCDIC-US}, then @value{GDBN} translates between
11224 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11225 character and string literals in expressions.
11227 @value{GDBN} has no way to automatically recognize which character set
11228 the inferior program uses; you must tell it, using the @code{set
11229 target-charset} command, described below.
11231 Here are the commands for controlling @value{GDBN}'s character set
11235 @item set target-charset @var{charset}
11236 @kindex set target-charset
11237 Set the current target character set to @var{charset}. To display the
11238 list of supported target character sets, type
11239 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11241 @item set host-charset @var{charset}
11242 @kindex set host-charset
11243 Set the current host character set to @var{charset}.
11245 By default, @value{GDBN} uses a host character set appropriate to the
11246 system it is running on; you can override that default using the
11247 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11248 automatically determine the appropriate host character set. In this
11249 case, @value{GDBN} uses @samp{UTF-8}.
11251 @value{GDBN} can only use certain character sets as its host character
11252 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11253 @value{GDBN} will list the host character sets it supports.
11255 @item set charset @var{charset}
11256 @kindex set charset
11257 Set the current host and target character sets to @var{charset}. As
11258 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11259 @value{GDBN} will list the names of the character sets that can be used
11260 for both host and target.
11263 @kindex show charset
11264 Show the names of the current host and target character sets.
11266 @item show host-charset
11267 @kindex show host-charset
11268 Show the name of the current host character set.
11270 @item show target-charset
11271 @kindex show target-charset
11272 Show the name of the current target character set.
11274 @item set target-wide-charset @var{charset}
11275 @kindex set target-wide-charset
11276 Set the current target's wide character set to @var{charset}. This is
11277 the character set used by the target's @code{wchar_t} type. To
11278 display the list of supported wide character sets, type
11279 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11281 @item show target-wide-charset
11282 @kindex show target-wide-charset
11283 Show the name of the current target's wide character set.
11286 Here is an example of @value{GDBN}'s character set support in action.
11287 Assume that the following source code has been placed in the file
11288 @file{charset-test.c}:
11294 = @{72, 101, 108, 108, 111, 44, 32, 119,
11295 111, 114, 108, 100, 33, 10, 0@};
11296 char ibm1047_hello[]
11297 = @{200, 133, 147, 147, 150, 107, 64, 166,
11298 150, 153, 147, 132, 90, 37, 0@};
11302 printf ("Hello, world!\n");
11306 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11307 containing the string @samp{Hello, world!} followed by a newline,
11308 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11310 We compile the program, and invoke the debugger on it:
11313 $ gcc -g charset-test.c -o charset-test
11314 $ gdb -nw charset-test
11315 GNU gdb 2001-12-19-cvs
11316 Copyright 2001 Free Software Foundation, Inc.
11321 We can use the @code{show charset} command to see what character sets
11322 @value{GDBN} is currently using to interpret and display characters and
11326 (@value{GDBP}) show charset
11327 The current host and target character set is `ISO-8859-1'.
11331 For the sake of printing this manual, let's use @sc{ascii} as our
11332 initial character set:
11334 (@value{GDBP}) set charset ASCII
11335 (@value{GDBP}) show charset
11336 The current host and target character set is `ASCII'.
11340 Let's assume that @sc{ascii} is indeed the correct character set for our
11341 host system --- in other words, let's assume that if @value{GDBN} prints
11342 characters using the @sc{ascii} character set, our terminal will display
11343 them properly. Since our current target character set is also
11344 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11347 (@value{GDBP}) print ascii_hello
11348 $1 = 0x401698 "Hello, world!\n"
11349 (@value{GDBP}) print ascii_hello[0]
11354 @value{GDBN} uses the target character set for character and string
11355 literals you use in expressions:
11358 (@value{GDBP}) print '+'
11363 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11366 @value{GDBN} relies on the user to tell it which character set the
11367 target program uses. If we print @code{ibm1047_hello} while our target
11368 character set is still @sc{ascii}, we get jibberish:
11371 (@value{GDBP}) print ibm1047_hello
11372 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11373 (@value{GDBP}) print ibm1047_hello[0]
11378 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11379 @value{GDBN} tells us the character sets it supports:
11382 (@value{GDBP}) set target-charset
11383 ASCII EBCDIC-US IBM1047 ISO-8859-1
11384 (@value{GDBP}) set target-charset
11387 We can select @sc{ibm1047} as our target character set, and examine the
11388 program's strings again. Now the @sc{ascii} string is wrong, but
11389 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11390 target character set, @sc{ibm1047}, to the host character set,
11391 @sc{ascii}, and they display correctly:
11394 (@value{GDBP}) set target-charset IBM1047
11395 (@value{GDBP}) show charset
11396 The current host character set is `ASCII'.
11397 The current target character set is `IBM1047'.
11398 (@value{GDBP}) print ascii_hello
11399 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11400 (@value{GDBP}) print ascii_hello[0]
11402 (@value{GDBP}) print ibm1047_hello
11403 $8 = 0x4016a8 "Hello, world!\n"
11404 (@value{GDBP}) print ibm1047_hello[0]
11409 As above, @value{GDBN} uses the target character set for character and
11410 string literals you use in expressions:
11413 (@value{GDBP}) print '+'
11418 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11421 @node Caching Target Data
11422 @section Caching Data of Targets
11423 @cindex caching data of targets
11425 @value{GDBN} caches data exchanged between the debugger and a target.
11426 Each cache is associated with the address space of the inferior.
11427 @xref{Inferiors and Programs}, about inferior and address space.
11428 Such caching generally improves performance in remote debugging
11429 (@pxref{Remote Debugging}), because it reduces the overhead of the
11430 remote protocol by bundling memory reads and writes into large chunks.
11431 Unfortunately, simply caching everything would lead to incorrect results,
11432 since @value{GDBN} does not necessarily know anything about volatile
11433 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11434 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11436 Therefore, by default, @value{GDBN} only caches data
11437 known to be on the stack@footnote{In non-stop mode, it is moderately
11438 rare for a running thread to modify the stack of a stopped thread
11439 in a way that would interfere with a backtrace, and caching of
11440 stack reads provides a significant speed up of remote backtraces.} or
11441 in the code segment.
11442 Other regions of memory can be explicitly marked as
11443 cacheable; @pxref{Memory Region Attributes}.
11446 @kindex set remotecache
11447 @item set remotecache on
11448 @itemx set remotecache off
11449 This option no longer does anything; it exists for compatibility
11452 @kindex show remotecache
11453 @item show remotecache
11454 Show the current state of the obsolete remotecache flag.
11456 @kindex set stack-cache
11457 @item set stack-cache on
11458 @itemx set stack-cache off
11459 Enable or disable caching of stack accesses. When @code{on}, use
11460 caching. By default, this option is @code{on}.
11462 @kindex show stack-cache
11463 @item show stack-cache
11464 Show the current state of data caching for memory accesses.
11466 @kindex set code-cache
11467 @item set code-cache on
11468 @itemx set code-cache off
11469 Enable or disable caching of code segment accesses. When @code{on},
11470 use caching. By default, this option is @code{on}. This improves
11471 performance of disassembly in remote debugging.
11473 @kindex show code-cache
11474 @item show code-cache
11475 Show the current state of target memory cache for code segment
11478 @kindex info dcache
11479 @item info dcache @r{[}line@r{]}
11480 Print the information about the performance of data cache of the
11481 current inferior's address space. The information displayed
11482 includes the dcache width and depth, and for each cache line, its
11483 number, address, and how many times it was referenced. This
11484 command is useful for debugging the data cache operation.
11486 If a line number is specified, the contents of that line will be
11489 @item set dcache size @var{size}
11490 @cindex dcache size
11491 @kindex set dcache size
11492 Set maximum number of entries in dcache (dcache depth above).
11494 @item set dcache line-size @var{line-size}
11495 @cindex dcache line-size
11496 @kindex set dcache line-size
11497 Set number of bytes each dcache entry caches (dcache width above).
11498 Must be a power of 2.
11500 @item show dcache size
11501 @kindex show dcache size
11502 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11504 @item show dcache line-size
11505 @kindex show dcache line-size
11506 Show default size of dcache lines.
11510 @node Searching Memory
11511 @section Search Memory
11512 @cindex searching memory
11514 Memory can be searched for a particular sequence of bytes with the
11515 @code{find} command.
11519 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11520 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11521 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11522 etc. The search begins at address @var{start_addr} and continues for either
11523 @var{len} bytes or through to @var{end_addr} inclusive.
11526 @var{s} and @var{n} are optional parameters.
11527 They may be specified in either order, apart or together.
11530 @item @var{s}, search query size
11531 The size of each search query value.
11537 halfwords (two bytes)
11541 giant words (eight bytes)
11544 All values are interpreted in the current language.
11545 This means, for example, that if the current source language is C/C@t{++}
11546 then searching for the string ``hello'' includes the trailing '\0'.
11548 If the value size is not specified, it is taken from the
11549 value's type in the current language.
11550 This is useful when one wants to specify the search
11551 pattern as a mixture of types.
11552 Note that this means, for example, that in the case of C-like languages
11553 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11554 which is typically four bytes.
11556 @item @var{n}, maximum number of finds
11557 The maximum number of matches to print. The default is to print all finds.
11560 You can use strings as search values. Quote them with double-quotes
11562 The string value is copied into the search pattern byte by byte,
11563 regardless of the endianness of the target and the size specification.
11565 The address of each match found is printed as well as a count of the
11566 number of matches found.
11568 The address of the last value found is stored in convenience variable
11570 A count of the number of matches is stored in @samp{$numfound}.
11572 For example, if stopped at the @code{printf} in this function:
11578 static char hello[] = "hello-hello";
11579 static struct @{ char c; short s; int i; @}
11580 __attribute__ ((packed)) mixed
11581 = @{ 'c', 0x1234, 0x87654321 @};
11582 printf ("%s\n", hello);
11587 you get during debugging:
11590 (gdb) find &hello[0], +sizeof(hello), "hello"
11591 0x804956d <hello.1620+6>
11593 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11594 0x8049567 <hello.1620>
11595 0x804956d <hello.1620+6>
11597 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11598 0x8049567 <hello.1620>
11600 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11601 0x8049560 <mixed.1625>
11603 (gdb) print $numfound
11606 $2 = (void *) 0x8049560
11609 @node Optimized Code
11610 @chapter Debugging Optimized Code
11611 @cindex optimized code, debugging
11612 @cindex debugging optimized code
11614 Almost all compilers support optimization. With optimization
11615 disabled, the compiler generates assembly code that corresponds
11616 directly to your source code, in a simplistic way. As the compiler
11617 applies more powerful optimizations, the generated assembly code
11618 diverges from your original source code. With help from debugging
11619 information generated by the compiler, @value{GDBN} can map from
11620 the running program back to constructs from your original source.
11622 @value{GDBN} is more accurate with optimization disabled. If you
11623 can recompile without optimization, it is easier to follow the
11624 progress of your program during debugging. But, there are many cases
11625 where you may need to debug an optimized version.
11627 When you debug a program compiled with @samp{-g -O}, remember that the
11628 optimizer has rearranged your code; the debugger shows you what is
11629 really there. Do not be too surprised when the execution path does not
11630 exactly match your source file! An extreme example: if you define a
11631 variable, but never use it, @value{GDBN} never sees that
11632 variable---because the compiler optimizes it out of existence.
11634 Some things do not work as well with @samp{-g -O} as with just
11635 @samp{-g}, particularly on machines with instruction scheduling. If in
11636 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11637 please report it to us as a bug (including a test case!).
11638 @xref{Variables}, for more information about debugging optimized code.
11641 * Inline Functions:: How @value{GDBN} presents inlining
11642 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11645 @node Inline Functions
11646 @section Inline Functions
11647 @cindex inline functions, debugging
11649 @dfn{Inlining} is an optimization that inserts a copy of the function
11650 body directly at each call site, instead of jumping to a shared
11651 routine. @value{GDBN} displays inlined functions just like
11652 non-inlined functions. They appear in backtraces. You can view their
11653 arguments and local variables, step into them with @code{step}, skip
11654 them with @code{next}, and escape from them with @code{finish}.
11655 You can check whether a function was inlined by using the
11656 @code{info frame} command.
11658 For @value{GDBN} to support inlined functions, the compiler must
11659 record information about inlining in the debug information ---
11660 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11661 other compilers do also. @value{GDBN} only supports inlined functions
11662 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11663 do not emit two required attributes (@samp{DW_AT_call_file} and
11664 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11665 function calls with earlier versions of @value{NGCC}. It instead
11666 displays the arguments and local variables of inlined functions as
11667 local variables in the caller.
11669 The body of an inlined function is directly included at its call site;
11670 unlike a non-inlined function, there are no instructions devoted to
11671 the call. @value{GDBN} still pretends that the call site and the
11672 start of the inlined function are different instructions. Stepping to
11673 the call site shows the call site, and then stepping again shows
11674 the first line of the inlined function, even though no additional
11675 instructions are executed.
11677 This makes source-level debugging much clearer; you can see both the
11678 context of the call and then the effect of the call. Only stepping by
11679 a single instruction using @code{stepi} or @code{nexti} does not do
11680 this; single instruction steps always show the inlined body.
11682 There are some ways that @value{GDBN} does not pretend that inlined
11683 function calls are the same as normal calls:
11687 Setting breakpoints at the call site of an inlined function may not
11688 work, because the call site does not contain any code. @value{GDBN}
11689 may incorrectly move the breakpoint to the next line of the enclosing
11690 function, after the call. This limitation will be removed in a future
11691 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11692 or inside the inlined function instead.
11695 @value{GDBN} cannot locate the return value of inlined calls after
11696 using the @code{finish} command. This is a limitation of compiler-generated
11697 debugging information; after @code{finish}, you can step to the next line
11698 and print a variable where your program stored the return value.
11702 @node Tail Call Frames
11703 @section Tail Call Frames
11704 @cindex tail call frames, debugging
11706 Function @code{B} can call function @code{C} in its very last statement. In
11707 unoptimized compilation the call of @code{C} is immediately followed by return
11708 instruction at the end of @code{B} code. Optimizing compiler may replace the
11709 call and return in function @code{B} into one jump to function @code{C}
11710 instead. Such use of a jump instruction is called @dfn{tail call}.
11712 During execution of function @code{C}, there will be no indication in the
11713 function call stack frames that it was tail-called from @code{B}. If function
11714 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11715 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11716 some cases @value{GDBN} can determine that @code{C} was tail-called from
11717 @code{B}, and it will then create fictitious call frame for that, with the
11718 return address set up as if @code{B} called @code{C} normally.
11720 This functionality is currently supported only by DWARF 2 debugging format and
11721 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11722 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11725 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11726 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11730 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11732 Stack level 1, frame at 0x7fffffffda30:
11733 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11734 tail call frame, caller of frame at 0x7fffffffda30
11735 source language c++.
11736 Arglist at unknown address.
11737 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11740 The detection of all the possible code path executions can find them ambiguous.
11741 There is no execution history stored (possible @ref{Reverse Execution} is never
11742 used for this purpose) and the last known caller could have reached the known
11743 callee by multiple different jump sequences. In such case @value{GDBN} still
11744 tries to show at least all the unambiguous top tail callers and all the
11745 unambiguous bottom tail calees, if any.
11748 @anchor{set debug entry-values}
11749 @item set debug entry-values
11750 @kindex set debug entry-values
11751 When set to on, enables printing of analysis messages for both frame argument
11752 values at function entry and tail calls. It will show all the possible valid
11753 tail calls code paths it has considered. It will also print the intersection
11754 of them with the final unambiguous (possibly partial or even empty) code path
11757 @item show debug entry-values
11758 @kindex show debug entry-values
11759 Show the current state of analysis messages printing for both frame argument
11760 values at function entry and tail calls.
11763 The analysis messages for tail calls can for example show why the virtual tail
11764 call frame for function @code{c} has not been recognized (due to the indirect
11765 reference by variable @code{x}):
11768 static void __attribute__((noinline, noclone)) c (void);
11769 void (*x) (void) = c;
11770 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11771 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11772 int main (void) @{ x (); return 0; @}
11774 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11775 DW_TAG_GNU_call_site 0x40039a in main
11777 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11780 #1 0x000000000040039a in main () at t.c:5
11783 Another possibility is an ambiguous virtual tail call frames resolution:
11787 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11788 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11789 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11790 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11791 static void __attribute__((noinline, noclone)) b (void)
11792 @{ if (i) c (); else e (); @}
11793 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11794 int main (void) @{ a (); return 0; @}
11796 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11797 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11798 tailcall: reduced: 0x4004d2(a) |
11801 #1 0x00000000004004d2 in a () at t.c:8
11802 #2 0x0000000000400395 in main () at t.c:9
11805 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11806 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11808 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11809 @ifset HAVE_MAKEINFO_CLICK
11810 @set ARROW @click{}
11811 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11812 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11814 @ifclear HAVE_MAKEINFO_CLICK
11816 @set CALLSEQ1B @value{CALLSEQ1A}
11817 @set CALLSEQ2B @value{CALLSEQ2A}
11820 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11821 The code can have possible execution paths @value{CALLSEQ1B} or
11822 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11824 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11825 has found. It then finds another possible calling sequcen - that one is
11826 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11827 printed as the @code{reduced:} calling sequence. That one could have many
11828 futher @code{compare:} and @code{reduced:} statements as long as there remain
11829 any non-ambiguous sequence entries.
11831 For the frame of function @code{b} in both cases there are different possible
11832 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11833 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11834 therefore this one is displayed to the user while the ambiguous frames are
11837 There can be also reasons why printing of frame argument values at function
11842 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11843 static void __attribute__((noinline, noclone)) a (int i);
11844 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11845 static void __attribute__((noinline, noclone)) a (int i)
11846 @{ if (i) b (i - 1); else c (0); @}
11847 int main (void) @{ a (5); return 0; @}
11850 #0 c (i=i@@entry=0) at t.c:2
11851 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11852 function "a" at 0x400420 can call itself via tail calls
11853 i=<optimized out>) at t.c:6
11854 #2 0x000000000040036e in main () at t.c:7
11857 @value{GDBN} cannot find out from the inferior state if and how many times did
11858 function @code{a} call itself (via function @code{b}) as these calls would be
11859 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11860 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11861 prints @code{<optimized out>} instead.
11864 @chapter C Preprocessor Macros
11866 Some languages, such as C and C@t{++}, provide a way to define and invoke
11867 ``preprocessor macros'' which expand into strings of tokens.
11868 @value{GDBN} can evaluate expressions containing macro invocations, show
11869 the result of macro expansion, and show a macro's definition, including
11870 where it was defined.
11872 You may need to compile your program specially to provide @value{GDBN}
11873 with information about preprocessor macros. Most compilers do not
11874 include macros in their debugging information, even when you compile
11875 with the @option{-g} flag. @xref{Compilation}.
11877 A program may define a macro at one point, remove that definition later,
11878 and then provide a different definition after that. Thus, at different
11879 points in the program, a macro may have different definitions, or have
11880 no definition at all. If there is a current stack frame, @value{GDBN}
11881 uses the macros in scope at that frame's source code line. Otherwise,
11882 @value{GDBN} uses the macros in scope at the current listing location;
11885 Whenever @value{GDBN} evaluates an expression, it always expands any
11886 macro invocations present in the expression. @value{GDBN} also provides
11887 the following commands for working with macros explicitly.
11891 @kindex macro expand
11892 @cindex macro expansion, showing the results of preprocessor
11893 @cindex preprocessor macro expansion, showing the results of
11894 @cindex expanding preprocessor macros
11895 @item macro expand @var{expression}
11896 @itemx macro exp @var{expression}
11897 Show the results of expanding all preprocessor macro invocations in
11898 @var{expression}. Since @value{GDBN} simply expands macros, but does
11899 not parse the result, @var{expression} need not be a valid expression;
11900 it can be any string of tokens.
11903 @item macro expand-once @var{expression}
11904 @itemx macro exp1 @var{expression}
11905 @cindex expand macro once
11906 @i{(This command is not yet implemented.)} Show the results of
11907 expanding those preprocessor macro invocations that appear explicitly in
11908 @var{expression}. Macro invocations appearing in that expansion are
11909 left unchanged. This command allows you to see the effect of a
11910 particular macro more clearly, without being confused by further
11911 expansions. Since @value{GDBN} simply expands macros, but does not
11912 parse the result, @var{expression} need not be a valid expression; it
11913 can be any string of tokens.
11916 @cindex macro definition, showing
11917 @cindex definition of a macro, showing
11918 @cindex macros, from debug info
11919 @item info macro [-a|-all] [--] @var{macro}
11920 Show the current definition or all definitions of the named @var{macro},
11921 and describe the source location or compiler command-line where that
11922 definition was established. The optional double dash is to signify the end of
11923 argument processing and the beginning of @var{macro} for non C-like macros where
11924 the macro may begin with a hyphen.
11926 @kindex info macros
11927 @item info macros @var{location}
11928 Show all macro definitions that are in effect at the location specified
11929 by @var{location}, and describe the source location or compiler
11930 command-line where those definitions were established.
11932 @kindex macro define
11933 @cindex user-defined macros
11934 @cindex defining macros interactively
11935 @cindex macros, user-defined
11936 @item macro define @var{macro} @var{replacement-list}
11937 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11938 Introduce a definition for a preprocessor macro named @var{macro},
11939 invocations of which are replaced by the tokens given in
11940 @var{replacement-list}. The first form of this command defines an
11941 ``object-like'' macro, which takes no arguments; the second form
11942 defines a ``function-like'' macro, which takes the arguments given in
11945 A definition introduced by this command is in scope in every
11946 expression evaluated in @value{GDBN}, until it is removed with the
11947 @code{macro undef} command, described below. The definition overrides
11948 all definitions for @var{macro} present in the program being debugged,
11949 as well as any previous user-supplied definition.
11951 @kindex macro undef
11952 @item macro undef @var{macro}
11953 Remove any user-supplied definition for the macro named @var{macro}.
11954 This command only affects definitions provided with the @code{macro
11955 define} command, described above; it cannot remove definitions present
11956 in the program being debugged.
11960 List all the macros defined using the @code{macro define} command.
11963 @cindex macros, example of debugging with
11964 Here is a transcript showing the above commands in action. First, we
11965 show our source files:
11970 #include "sample.h"
11973 #define ADD(x) (M + x)
11978 printf ("Hello, world!\n");
11980 printf ("We're so creative.\n");
11982 printf ("Goodbye, world!\n");
11989 Now, we compile the program using the @sc{gnu} C compiler,
11990 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11991 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11992 and @option{-gdwarf-4}; we recommend always choosing the most recent
11993 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11994 includes information about preprocessor macros in the debugging
11998 $ gcc -gdwarf-2 -g3 sample.c -o sample
12002 Now, we start @value{GDBN} on our sample program:
12006 GNU gdb 2002-05-06-cvs
12007 Copyright 2002 Free Software Foundation, Inc.
12008 GDB is free software, @dots{}
12012 We can expand macros and examine their definitions, even when the
12013 program is not running. @value{GDBN} uses the current listing position
12014 to decide which macro definitions are in scope:
12017 (@value{GDBP}) list main
12020 5 #define ADD(x) (M + x)
12025 10 printf ("Hello, world!\n");
12027 12 printf ("We're so creative.\n");
12028 (@value{GDBP}) info macro ADD
12029 Defined at /home/jimb/gdb/macros/play/sample.c:5
12030 #define ADD(x) (M + x)
12031 (@value{GDBP}) info macro Q
12032 Defined at /home/jimb/gdb/macros/play/sample.h:1
12033 included at /home/jimb/gdb/macros/play/sample.c:2
12035 (@value{GDBP}) macro expand ADD(1)
12036 expands to: (42 + 1)
12037 (@value{GDBP}) macro expand-once ADD(1)
12038 expands to: once (M + 1)
12042 In the example above, note that @code{macro expand-once} expands only
12043 the macro invocation explicit in the original text --- the invocation of
12044 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12045 which was introduced by @code{ADD}.
12047 Once the program is running, @value{GDBN} uses the macro definitions in
12048 force at the source line of the current stack frame:
12051 (@value{GDBP}) break main
12052 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12054 Starting program: /home/jimb/gdb/macros/play/sample
12056 Breakpoint 1, main () at sample.c:10
12057 10 printf ("Hello, world!\n");
12061 At line 10, the definition of the macro @code{N} at line 9 is in force:
12064 (@value{GDBP}) info macro N
12065 Defined at /home/jimb/gdb/macros/play/sample.c:9
12067 (@value{GDBP}) macro expand N Q M
12068 expands to: 28 < 42
12069 (@value{GDBP}) print N Q M
12074 As we step over directives that remove @code{N}'s definition, and then
12075 give it a new definition, @value{GDBN} finds the definition (or lack
12076 thereof) in force at each point:
12079 (@value{GDBP}) next
12081 12 printf ("We're so creative.\n");
12082 (@value{GDBP}) info macro N
12083 The symbol `N' has no definition as a C/C++ preprocessor macro
12084 at /home/jimb/gdb/macros/play/sample.c:12
12085 (@value{GDBP}) next
12087 14 printf ("Goodbye, world!\n");
12088 (@value{GDBP}) info macro N
12089 Defined at /home/jimb/gdb/macros/play/sample.c:13
12091 (@value{GDBP}) macro expand N Q M
12092 expands to: 1729 < 42
12093 (@value{GDBP}) print N Q M
12098 In addition to source files, macros can be defined on the compilation command
12099 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12100 such a way, @value{GDBN} displays the location of their definition as line zero
12101 of the source file submitted to the compiler.
12104 (@value{GDBP}) info macro __STDC__
12105 Defined at /home/jimb/gdb/macros/play/sample.c:0
12112 @chapter Tracepoints
12113 @c This chapter is based on the documentation written by Michael
12114 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12116 @cindex tracepoints
12117 In some applications, it is not feasible for the debugger to interrupt
12118 the program's execution long enough for the developer to learn
12119 anything helpful about its behavior. If the program's correctness
12120 depends on its real-time behavior, delays introduced by a debugger
12121 might cause the program to change its behavior drastically, or perhaps
12122 fail, even when the code itself is correct. It is useful to be able
12123 to observe the program's behavior without interrupting it.
12125 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12126 specify locations in the program, called @dfn{tracepoints}, and
12127 arbitrary expressions to evaluate when those tracepoints are reached.
12128 Later, using the @code{tfind} command, you can examine the values
12129 those expressions had when the program hit the tracepoints. The
12130 expressions may also denote objects in memory---structures or arrays,
12131 for example---whose values @value{GDBN} should record; while visiting
12132 a particular tracepoint, you may inspect those objects as if they were
12133 in memory at that moment. However, because @value{GDBN} records these
12134 values without interacting with you, it can do so quickly and
12135 unobtrusively, hopefully not disturbing the program's behavior.
12137 The tracepoint facility is currently available only for remote
12138 targets. @xref{Targets}. In addition, your remote target must know
12139 how to collect trace data. This functionality is implemented in the
12140 remote stub; however, none of the stubs distributed with @value{GDBN}
12141 support tracepoints as of this writing. The format of the remote
12142 packets used to implement tracepoints are described in @ref{Tracepoint
12145 It is also possible to get trace data from a file, in a manner reminiscent
12146 of corefiles; you specify the filename, and use @code{tfind} to search
12147 through the file. @xref{Trace Files}, for more details.
12149 This chapter describes the tracepoint commands and features.
12152 * Set Tracepoints::
12153 * Analyze Collected Data::
12154 * Tracepoint Variables::
12158 @node Set Tracepoints
12159 @section Commands to Set Tracepoints
12161 Before running such a @dfn{trace experiment}, an arbitrary number of
12162 tracepoints can be set. A tracepoint is actually a special type of
12163 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12164 standard breakpoint commands. For instance, as with breakpoints,
12165 tracepoint numbers are successive integers starting from one, and many
12166 of the commands associated with tracepoints take the tracepoint number
12167 as their argument, to identify which tracepoint to work on.
12169 For each tracepoint, you can specify, in advance, some arbitrary set
12170 of data that you want the target to collect in the trace buffer when
12171 it hits that tracepoint. The collected data can include registers,
12172 local variables, or global data. Later, you can use @value{GDBN}
12173 commands to examine the values these data had at the time the
12174 tracepoint was hit.
12176 Tracepoints do not support every breakpoint feature. Ignore counts on
12177 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12178 commands when they are hit. Tracepoints may not be thread-specific
12181 @cindex fast tracepoints
12182 Some targets may support @dfn{fast tracepoints}, which are inserted in
12183 a different way (such as with a jump instead of a trap), that is
12184 faster but possibly restricted in where they may be installed.
12186 @cindex static tracepoints
12187 @cindex markers, static tracepoints
12188 @cindex probing markers, static tracepoints
12189 Regular and fast tracepoints are dynamic tracing facilities, meaning
12190 that they can be used to insert tracepoints at (almost) any location
12191 in the target. Some targets may also support controlling @dfn{static
12192 tracepoints} from @value{GDBN}. With static tracing, a set of
12193 instrumentation points, also known as @dfn{markers}, are embedded in
12194 the target program, and can be activated or deactivated by name or
12195 address. These are usually placed at locations which facilitate
12196 investigating what the target is actually doing. @value{GDBN}'s
12197 support for static tracing includes being able to list instrumentation
12198 points, and attach them with @value{GDBN} defined high level
12199 tracepoints that expose the whole range of convenience of
12200 @value{GDBN}'s tracepoints support. Namely, support for collecting
12201 registers values and values of global or local (to the instrumentation
12202 point) variables; tracepoint conditions and trace state variables.
12203 The act of installing a @value{GDBN} static tracepoint on an
12204 instrumentation point, or marker, is referred to as @dfn{probing} a
12205 static tracepoint marker.
12207 @code{gdbserver} supports tracepoints on some target systems.
12208 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12210 This section describes commands to set tracepoints and associated
12211 conditions and actions.
12214 * Create and Delete Tracepoints::
12215 * Enable and Disable Tracepoints::
12216 * Tracepoint Passcounts::
12217 * Tracepoint Conditions::
12218 * Trace State Variables::
12219 * Tracepoint Actions::
12220 * Listing Tracepoints::
12221 * Listing Static Tracepoint Markers::
12222 * Starting and Stopping Trace Experiments::
12223 * Tracepoint Restrictions::
12226 @node Create and Delete Tracepoints
12227 @subsection Create and Delete Tracepoints
12230 @cindex set tracepoint
12232 @item trace @var{location}
12233 The @code{trace} command is very similar to the @code{break} command.
12234 Its argument @var{location} can be any valid location.
12235 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12236 which is a point in the target program where the debugger will briefly stop,
12237 collect some data, and then allow the program to continue. Setting a tracepoint
12238 or changing its actions takes effect immediately if the remote stub
12239 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12241 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12242 these changes don't take effect until the next @code{tstart}
12243 command, and once a trace experiment is running, further changes will
12244 not have any effect until the next trace experiment starts. In addition,
12245 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12246 address is not yet resolved. (This is similar to pending breakpoints.)
12247 Pending tracepoints are not downloaded to the target and not installed
12248 until they are resolved. The resolution of pending tracepoints requires
12249 @value{GDBN} support---when debugging with the remote target, and
12250 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12251 tracing}), pending tracepoints can not be resolved (and downloaded to
12252 the remote stub) while @value{GDBN} is disconnected.
12254 Here are some examples of using the @code{trace} command:
12257 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12259 (@value{GDBP}) @b{trace +2} // 2 lines forward
12261 (@value{GDBP}) @b{trace my_function} // first source line of function
12263 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12265 (@value{GDBP}) @b{trace *0x2117c4} // an address
12269 You can abbreviate @code{trace} as @code{tr}.
12271 @item trace @var{location} if @var{cond}
12272 Set a tracepoint with condition @var{cond}; evaluate the expression
12273 @var{cond} each time the tracepoint is reached, and collect data only
12274 if the value is nonzero---that is, if @var{cond} evaluates as true.
12275 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12276 information on tracepoint conditions.
12278 @item ftrace @var{location} [ if @var{cond} ]
12279 @cindex set fast tracepoint
12280 @cindex fast tracepoints, setting
12282 The @code{ftrace} command sets a fast tracepoint. For targets that
12283 support them, fast tracepoints will use a more efficient but possibly
12284 less general technique to trigger data collection, such as a jump
12285 instruction instead of a trap, or some sort of hardware support. It
12286 may not be possible to create a fast tracepoint at the desired
12287 location, in which case the command will exit with an explanatory
12290 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12293 On 32-bit x86-architecture systems, fast tracepoints normally need to
12294 be placed at an instruction that is 5 bytes or longer, but can be
12295 placed at 4-byte instructions if the low 64K of memory of the target
12296 program is available to install trampolines. Some Unix-type systems,
12297 such as @sc{gnu}/Linux, exclude low addresses from the program's
12298 address space; but for instance with the Linux kernel it is possible
12299 to let @value{GDBN} use this area by doing a @command{sysctl} command
12300 to set the @code{mmap_min_addr} kernel parameter, as in
12303 sudo sysctl -w vm.mmap_min_addr=32768
12307 which sets the low address to 32K, which leaves plenty of room for
12308 trampolines. The minimum address should be set to a page boundary.
12310 @item strace @var{location} [ if @var{cond} ]
12311 @cindex set static tracepoint
12312 @cindex static tracepoints, setting
12313 @cindex probe static tracepoint marker
12315 The @code{strace} command sets a static tracepoint. For targets that
12316 support it, setting a static tracepoint probes a static
12317 instrumentation point, or marker, found at @var{location}. It may not
12318 be possible to set a static tracepoint at the desired location, in
12319 which case the command will exit with an explanatory message.
12321 @value{GDBN} handles arguments to @code{strace} exactly as for
12322 @code{trace}, with the addition that the user can also specify
12323 @code{-m @var{marker}} as @var{location}. This probes the marker
12324 identified by the @var{marker} string identifier. This identifier
12325 depends on the static tracepoint backend library your program is
12326 using. You can find all the marker identifiers in the @samp{ID} field
12327 of the @code{info static-tracepoint-markers} command output.
12328 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12329 Markers}. For example, in the following small program using the UST
12335 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12340 the marker id is composed of joining the first two arguments to the
12341 @code{trace_mark} call with a slash, which translates to:
12344 (@value{GDBP}) info static-tracepoint-markers
12345 Cnt Enb ID Address What
12346 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12352 so you may probe the marker above with:
12355 (@value{GDBP}) strace -m ust/bar33
12358 Static tracepoints accept an extra collect action --- @code{collect
12359 $_sdata}. This collects arbitrary user data passed in the probe point
12360 call to the tracing library. In the UST example above, you'll see
12361 that the third argument to @code{trace_mark} is a printf-like format
12362 string. The user data is then the result of running that formating
12363 string against the following arguments. Note that @code{info
12364 static-tracepoint-markers} command output lists that format string in
12365 the @samp{Data:} field.
12367 You can inspect this data when analyzing the trace buffer, by printing
12368 the $_sdata variable like any other variable available to
12369 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12372 @cindex last tracepoint number
12373 @cindex recent tracepoint number
12374 @cindex tracepoint number
12375 The convenience variable @code{$tpnum} records the tracepoint number
12376 of the most recently set tracepoint.
12378 @kindex delete tracepoint
12379 @cindex tracepoint deletion
12380 @item delete tracepoint @r{[}@var{num}@r{]}
12381 Permanently delete one or more tracepoints. With no argument, the
12382 default is to delete all tracepoints. Note that the regular
12383 @code{delete} command can remove tracepoints also.
12388 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12390 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12394 You can abbreviate this command as @code{del tr}.
12397 @node Enable and Disable Tracepoints
12398 @subsection Enable and Disable Tracepoints
12400 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12403 @kindex disable tracepoint
12404 @item disable tracepoint @r{[}@var{num}@r{]}
12405 Disable tracepoint @var{num}, or all tracepoints if no argument
12406 @var{num} is given. A disabled tracepoint will have no effect during
12407 a trace experiment, but it is not forgotten. You can re-enable
12408 a disabled tracepoint using the @code{enable tracepoint} command.
12409 If the command is issued during a trace experiment and the debug target
12410 has support for disabling tracepoints during a trace experiment, then the
12411 change will be effective immediately. Otherwise, it will be applied to the
12412 next trace experiment.
12414 @kindex enable tracepoint
12415 @item enable tracepoint @r{[}@var{num}@r{]}
12416 Enable tracepoint @var{num}, or all tracepoints. If this command is
12417 issued during a trace experiment and the debug target supports enabling
12418 tracepoints during a trace experiment, then the enabled tracepoints will
12419 become effective immediately. Otherwise, they will become effective the
12420 next time a trace experiment is run.
12423 @node Tracepoint Passcounts
12424 @subsection Tracepoint Passcounts
12428 @cindex tracepoint pass count
12429 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12430 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12431 automatically stop a trace experiment. If a tracepoint's passcount is
12432 @var{n}, then the trace experiment will be automatically stopped on
12433 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12434 @var{num} is not specified, the @code{passcount} command sets the
12435 passcount of the most recently defined tracepoint. If no passcount is
12436 given, the trace experiment will run until stopped explicitly by the
12442 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12443 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12445 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12446 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12447 (@value{GDBP}) @b{trace foo}
12448 (@value{GDBP}) @b{pass 3}
12449 (@value{GDBP}) @b{trace bar}
12450 (@value{GDBP}) @b{pass 2}
12451 (@value{GDBP}) @b{trace baz}
12452 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12453 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12454 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12455 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12459 @node Tracepoint Conditions
12460 @subsection Tracepoint Conditions
12461 @cindex conditional tracepoints
12462 @cindex tracepoint conditions
12464 The simplest sort of tracepoint collects data every time your program
12465 reaches a specified place. You can also specify a @dfn{condition} for
12466 a tracepoint. A condition is just a Boolean expression in your
12467 programming language (@pxref{Expressions, ,Expressions}). A
12468 tracepoint with a condition evaluates the expression each time your
12469 program reaches it, and data collection happens only if the condition
12472 Tracepoint conditions can be specified when a tracepoint is set, by
12473 using @samp{if} in the arguments to the @code{trace} command.
12474 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12475 also be set or changed at any time with the @code{condition} command,
12476 just as with breakpoints.
12478 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12479 the conditional expression itself. Instead, @value{GDBN} encodes the
12480 expression into an agent expression (@pxref{Agent Expressions})
12481 suitable for execution on the target, independently of @value{GDBN}.
12482 Global variables become raw memory locations, locals become stack
12483 accesses, and so forth.
12485 For instance, suppose you have a function that is usually called
12486 frequently, but should not be called after an error has occurred. You
12487 could use the following tracepoint command to collect data about calls
12488 of that function that happen while the error code is propagating
12489 through the program; an unconditional tracepoint could end up
12490 collecting thousands of useless trace frames that you would have to
12494 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12497 @node Trace State Variables
12498 @subsection Trace State Variables
12499 @cindex trace state variables
12501 A @dfn{trace state variable} is a special type of variable that is
12502 created and managed by target-side code. The syntax is the same as
12503 that for GDB's convenience variables (a string prefixed with ``$''),
12504 but they are stored on the target. They must be created explicitly,
12505 using a @code{tvariable} command. They are always 64-bit signed
12508 Trace state variables are remembered by @value{GDBN}, and downloaded
12509 to the target along with tracepoint information when the trace
12510 experiment starts. There are no intrinsic limits on the number of
12511 trace state variables, beyond memory limitations of the target.
12513 @cindex convenience variables, and trace state variables
12514 Although trace state variables are managed by the target, you can use
12515 them in print commands and expressions as if they were convenience
12516 variables; @value{GDBN} will get the current value from the target
12517 while the trace experiment is running. Trace state variables share
12518 the same namespace as other ``$'' variables, which means that you
12519 cannot have trace state variables with names like @code{$23} or
12520 @code{$pc}, nor can you have a trace state variable and a convenience
12521 variable with the same name.
12525 @item tvariable $@var{name} [ = @var{expression} ]
12527 The @code{tvariable} command creates a new trace state variable named
12528 @code{$@var{name}}, and optionally gives it an initial value of
12529 @var{expression}. The @var{expression} is evaluated when this command is
12530 entered; the result will be converted to an integer if possible,
12531 otherwise @value{GDBN} will report an error. A subsequent
12532 @code{tvariable} command specifying the same name does not create a
12533 variable, but instead assigns the supplied initial value to the
12534 existing variable of that name, overwriting any previous initial
12535 value. The default initial value is 0.
12537 @item info tvariables
12538 @kindex info tvariables
12539 List all the trace state variables along with their initial values.
12540 Their current values may also be displayed, if the trace experiment is
12543 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12544 @kindex delete tvariable
12545 Delete the given trace state variables, or all of them if no arguments
12550 @node Tracepoint Actions
12551 @subsection Tracepoint Action Lists
12555 @cindex tracepoint actions
12556 @item actions @r{[}@var{num}@r{]}
12557 This command will prompt for a list of actions to be taken when the
12558 tracepoint is hit. If the tracepoint number @var{num} is not
12559 specified, this command sets the actions for the one that was most
12560 recently defined (so that you can define a tracepoint and then say
12561 @code{actions} without bothering about its number). You specify the
12562 actions themselves on the following lines, one action at a time, and
12563 terminate the actions list with a line containing just @code{end}. So
12564 far, the only defined actions are @code{collect}, @code{teval}, and
12565 @code{while-stepping}.
12567 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12568 Commands, ,Breakpoint Command Lists}), except that only the defined
12569 actions are allowed; any other @value{GDBN} command is rejected.
12571 @cindex remove actions from a tracepoint
12572 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12573 and follow it immediately with @samp{end}.
12576 (@value{GDBP}) @b{collect @var{data}} // collect some data
12578 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12580 (@value{GDBP}) @b{end} // signals the end of actions.
12583 In the following example, the action list begins with @code{collect}
12584 commands indicating the things to be collected when the tracepoint is
12585 hit. Then, in order to single-step and collect additional data
12586 following the tracepoint, a @code{while-stepping} command is used,
12587 followed by the list of things to be collected after each step in a
12588 sequence of single steps. The @code{while-stepping} command is
12589 terminated by its own separate @code{end} command. Lastly, the action
12590 list is terminated by an @code{end} command.
12593 (@value{GDBP}) @b{trace foo}
12594 (@value{GDBP}) @b{actions}
12595 Enter actions for tracepoint 1, one per line:
12598 > while-stepping 12
12599 > collect $pc, arr[i]
12604 @kindex collect @r{(tracepoints)}
12605 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12606 Collect values of the given expressions when the tracepoint is hit.
12607 This command accepts a comma-separated list of any valid expressions.
12608 In addition to global, static, or local variables, the following
12609 special arguments are supported:
12613 Collect all registers.
12616 Collect all function arguments.
12619 Collect all local variables.
12622 Collect the return address. This is helpful if you want to see more
12626 Collects the number of arguments from the static probe at which the
12627 tracepoint is located.
12628 @xref{Static Probe Points}.
12630 @item $_probe_arg@var{n}
12631 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12632 from the static probe at which the tracepoint is located.
12633 @xref{Static Probe Points}.
12636 @vindex $_sdata@r{, collect}
12637 Collect static tracepoint marker specific data. Only available for
12638 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12639 Lists}. On the UST static tracepoints library backend, an
12640 instrumentation point resembles a @code{printf} function call. The
12641 tracing library is able to collect user specified data formatted to a
12642 character string using the format provided by the programmer that
12643 instrumented the program. Other backends have similar mechanisms.
12644 Here's an example of a UST marker call:
12647 const char master_name[] = "$your_name";
12648 trace_mark(channel1, marker1, "hello %s", master_name)
12651 In this case, collecting @code{$_sdata} collects the string
12652 @samp{hello $yourname}. When analyzing the trace buffer, you can
12653 inspect @samp{$_sdata} like any other variable available to
12657 You can give several consecutive @code{collect} commands, each one
12658 with a single argument, or one @code{collect} command with several
12659 arguments separated by commas; the effect is the same.
12661 The optional @var{mods} changes the usual handling of the arguments.
12662 @code{s} requests that pointers to chars be handled as strings, in
12663 particular collecting the contents of the memory being pointed at, up
12664 to the first zero. The upper bound is by default the value of the
12665 @code{print elements} variable; if @code{s} is followed by a decimal
12666 number, that is the upper bound instead. So for instance
12667 @samp{collect/s25 mystr} collects as many as 25 characters at
12670 The command @code{info scope} (@pxref{Symbols, info scope}) is
12671 particularly useful for figuring out what data to collect.
12673 @kindex teval @r{(tracepoints)}
12674 @item teval @var{expr1}, @var{expr2}, @dots{}
12675 Evaluate the given expressions when the tracepoint is hit. This
12676 command accepts a comma-separated list of expressions. The results
12677 are discarded, so this is mainly useful for assigning values to trace
12678 state variables (@pxref{Trace State Variables}) without adding those
12679 values to the trace buffer, as would be the case if the @code{collect}
12682 @kindex while-stepping @r{(tracepoints)}
12683 @item while-stepping @var{n}
12684 Perform @var{n} single-step instruction traces after the tracepoint,
12685 collecting new data after each step. The @code{while-stepping}
12686 command is followed by the list of what to collect while stepping
12687 (followed by its own @code{end} command):
12690 > while-stepping 12
12691 > collect $regs, myglobal
12697 Note that @code{$pc} is not automatically collected by
12698 @code{while-stepping}; you need to explicitly collect that register if
12699 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12702 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12703 @kindex set default-collect
12704 @cindex default collection action
12705 This variable is a list of expressions to collect at each tracepoint
12706 hit. It is effectively an additional @code{collect} action prepended
12707 to every tracepoint action list. The expressions are parsed
12708 individually for each tracepoint, so for instance a variable named
12709 @code{xyz} may be interpreted as a global for one tracepoint, and a
12710 local for another, as appropriate to the tracepoint's location.
12712 @item show default-collect
12713 @kindex show default-collect
12714 Show the list of expressions that are collected by default at each
12719 @node Listing Tracepoints
12720 @subsection Listing Tracepoints
12723 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12724 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12725 @cindex information about tracepoints
12726 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12727 Display information about the tracepoint @var{num}. If you don't
12728 specify a tracepoint number, displays information about all the
12729 tracepoints defined so far. The format is similar to that used for
12730 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12731 command, simply restricting itself to tracepoints.
12733 A tracepoint's listing may include additional information specific to
12738 its passcount as given by the @code{passcount @var{n}} command
12741 the state about installed on target of each location
12745 (@value{GDBP}) @b{info trace}
12746 Num Type Disp Enb Address What
12747 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12749 collect globfoo, $regs
12754 2 tracepoint keep y <MULTIPLE>
12756 2.1 y 0x0804859c in func4 at change-loc.h:35
12757 installed on target
12758 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12759 installed on target
12760 2.3 y <PENDING> set_tracepoint
12761 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12762 not installed on target
12767 This command can be abbreviated @code{info tp}.
12770 @node Listing Static Tracepoint Markers
12771 @subsection Listing Static Tracepoint Markers
12774 @kindex info static-tracepoint-markers
12775 @cindex information about static tracepoint markers
12776 @item info static-tracepoint-markers
12777 Display information about all static tracepoint markers defined in the
12780 For each marker, the following columns are printed:
12784 An incrementing counter, output to help readability. This is not a
12787 The marker ID, as reported by the target.
12788 @item Enabled or Disabled
12789 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12790 that are not enabled.
12792 Where the marker is in your program, as a memory address.
12794 Where the marker is in the source for your program, as a file and line
12795 number. If the debug information included in the program does not
12796 allow @value{GDBN} to locate the source of the marker, this column
12797 will be left blank.
12801 In addition, the following information may be printed for each marker:
12805 User data passed to the tracing library by the marker call. In the
12806 UST backend, this is the format string passed as argument to the
12808 @item Static tracepoints probing the marker
12809 The list of static tracepoints attached to the marker.
12813 (@value{GDBP}) info static-tracepoint-markers
12814 Cnt ID Enb Address What
12815 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12816 Data: number1 %d number2 %d
12817 Probed by static tracepoints: #2
12818 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12824 @node Starting and Stopping Trace Experiments
12825 @subsection Starting and Stopping Trace Experiments
12828 @kindex tstart [ @var{notes} ]
12829 @cindex start a new trace experiment
12830 @cindex collected data discarded
12832 This command starts the trace experiment, and begins collecting data.
12833 It has the side effect of discarding all the data collected in the
12834 trace buffer during the previous trace experiment. If any arguments
12835 are supplied, they are taken as a note and stored with the trace
12836 experiment's state. The notes may be arbitrary text, and are
12837 especially useful with disconnected tracing in a multi-user context;
12838 the notes can explain what the trace is doing, supply user contact
12839 information, and so forth.
12841 @kindex tstop [ @var{notes} ]
12842 @cindex stop a running trace experiment
12844 This command stops the trace experiment. If any arguments are
12845 supplied, they are recorded with the experiment as a note. This is
12846 useful if you are stopping a trace started by someone else, for
12847 instance if the trace is interfering with the system's behavior and
12848 needs to be stopped quickly.
12850 @strong{Note}: a trace experiment and data collection may stop
12851 automatically if any tracepoint's passcount is reached
12852 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12855 @cindex status of trace data collection
12856 @cindex trace experiment, status of
12858 This command displays the status of the current trace data
12862 Here is an example of the commands we described so far:
12865 (@value{GDBP}) @b{trace gdb_c_test}
12866 (@value{GDBP}) @b{actions}
12867 Enter actions for tracepoint #1, one per line.
12868 > collect $regs,$locals,$args
12869 > while-stepping 11
12873 (@value{GDBP}) @b{tstart}
12874 [time passes @dots{}]
12875 (@value{GDBP}) @b{tstop}
12878 @anchor{disconnected tracing}
12879 @cindex disconnected tracing
12880 You can choose to continue running the trace experiment even if
12881 @value{GDBN} disconnects from the target, voluntarily or
12882 involuntarily. For commands such as @code{detach}, the debugger will
12883 ask what you want to do with the trace. But for unexpected
12884 terminations (@value{GDBN} crash, network outage), it would be
12885 unfortunate to lose hard-won trace data, so the variable
12886 @code{disconnected-tracing} lets you decide whether the trace should
12887 continue running without @value{GDBN}.
12890 @item set disconnected-tracing on
12891 @itemx set disconnected-tracing off
12892 @kindex set disconnected-tracing
12893 Choose whether a tracing run should continue to run if @value{GDBN}
12894 has disconnected from the target. Note that @code{detach} or
12895 @code{quit} will ask you directly what to do about a running trace no
12896 matter what this variable's setting, so the variable is mainly useful
12897 for handling unexpected situations, such as loss of the network.
12899 @item show disconnected-tracing
12900 @kindex show disconnected-tracing
12901 Show the current choice for disconnected tracing.
12905 When you reconnect to the target, the trace experiment may or may not
12906 still be running; it might have filled the trace buffer in the
12907 meantime, or stopped for one of the other reasons. If it is running,
12908 it will continue after reconnection.
12910 Upon reconnection, the target will upload information about the
12911 tracepoints in effect. @value{GDBN} will then compare that
12912 information to the set of tracepoints currently defined, and attempt
12913 to match them up, allowing for the possibility that the numbers may
12914 have changed due to creation and deletion in the meantime. If one of
12915 the target's tracepoints does not match any in @value{GDBN}, the
12916 debugger will create a new tracepoint, so that you have a number with
12917 which to specify that tracepoint. This matching-up process is
12918 necessarily heuristic, and it may result in useless tracepoints being
12919 created; you may simply delete them if they are of no use.
12921 @cindex circular trace buffer
12922 If your target agent supports a @dfn{circular trace buffer}, then you
12923 can run a trace experiment indefinitely without filling the trace
12924 buffer; when space runs out, the agent deletes already-collected trace
12925 frames, oldest first, until there is enough room to continue
12926 collecting. This is especially useful if your tracepoints are being
12927 hit too often, and your trace gets terminated prematurely because the
12928 buffer is full. To ask for a circular trace buffer, simply set
12929 @samp{circular-trace-buffer} to on. You can set this at any time,
12930 including during tracing; if the agent can do it, it will change
12931 buffer handling on the fly, otherwise it will not take effect until
12935 @item set circular-trace-buffer on
12936 @itemx set circular-trace-buffer off
12937 @kindex set circular-trace-buffer
12938 Choose whether a tracing run should use a linear or circular buffer
12939 for trace data. A linear buffer will not lose any trace data, but may
12940 fill up prematurely, while a circular buffer will discard old trace
12941 data, but it will have always room for the latest tracepoint hits.
12943 @item show circular-trace-buffer
12944 @kindex show circular-trace-buffer
12945 Show the current choice for the trace buffer. Note that this may not
12946 match the agent's current buffer handling, nor is it guaranteed to
12947 match the setting that might have been in effect during a past run,
12948 for instance if you are looking at frames from a trace file.
12953 @item set trace-buffer-size @var{n}
12954 @itemx set trace-buffer-size unlimited
12955 @kindex set trace-buffer-size
12956 Request that the target use a trace buffer of @var{n} bytes. Not all
12957 targets will honor the request; they may have a compiled-in size for
12958 the trace buffer, or some other limitation. Set to a value of
12959 @code{unlimited} or @code{-1} to let the target use whatever size it
12960 likes. This is also the default.
12962 @item show trace-buffer-size
12963 @kindex show trace-buffer-size
12964 Show the current requested size for the trace buffer. Note that this
12965 will only match the actual size if the target supports size-setting,
12966 and was able to handle the requested size. For instance, if the
12967 target can only change buffer size between runs, this variable will
12968 not reflect the change until the next run starts. Use @code{tstatus}
12969 to get a report of the actual buffer size.
12973 @item set trace-user @var{text}
12974 @kindex set trace-user
12976 @item show trace-user
12977 @kindex show trace-user
12979 @item set trace-notes @var{text}
12980 @kindex set trace-notes
12981 Set the trace run's notes.
12983 @item show trace-notes
12984 @kindex show trace-notes
12985 Show the trace run's notes.
12987 @item set trace-stop-notes @var{text}
12988 @kindex set trace-stop-notes
12989 Set the trace run's stop notes. The handling of the note is as for
12990 @code{tstop} arguments; the set command is convenient way to fix a
12991 stop note that is mistaken or incomplete.
12993 @item show trace-stop-notes
12994 @kindex show trace-stop-notes
12995 Show the trace run's stop notes.
12999 @node Tracepoint Restrictions
13000 @subsection Tracepoint Restrictions
13002 @cindex tracepoint restrictions
13003 There are a number of restrictions on the use of tracepoints. As
13004 described above, tracepoint data gathering occurs on the target
13005 without interaction from @value{GDBN}. Thus the full capabilities of
13006 the debugger are not available during data gathering, and then at data
13007 examination time, you will be limited by only having what was
13008 collected. The following items describe some common problems, but it
13009 is not exhaustive, and you may run into additional difficulties not
13015 Tracepoint expressions are intended to gather objects (lvalues). Thus
13016 the full flexibility of GDB's expression evaluator is not available.
13017 You cannot call functions, cast objects to aggregate types, access
13018 convenience variables or modify values (except by assignment to trace
13019 state variables). Some language features may implicitly call
13020 functions (for instance Objective-C fields with accessors), and therefore
13021 cannot be collected either.
13024 Collection of local variables, either individually or in bulk with
13025 @code{$locals} or @code{$args}, during @code{while-stepping} may
13026 behave erratically. The stepping action may enter a new scope (for
13027 instance by stepping into a function), or the location of the variable
13028 may change (for instance it is loaded into a register). The
13029 tracepoint data recorded uses the location information for the
13030 variables that is correct for the tracepoint location. When the
13031 tracepoint is created, it is not possible, in general, to determine
13032 where the steps of a @code{while-stepping} sequence will advance the
13033 program---particularly if a conditional branch is stepped.
13036 Collection of an incompletely-initialized or partially-destroyed object
13037 may result in something that @value{GDBN} cannot display, or displays
13038 in a misleading way.
13041 When @value{GDBN} displays a pointer to character it automatically
13042 dereferences the pointer to also display characters of the string
13043 being pointed to. However, collecting the pointer during tracing does
13044 not automatically collect the string. You need to explicitly
13045 dereference the pointer and provide size information if you want to
13046 collect not only the pointer, but the memory pointed to. For example,
13047 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13051 It is not possible to collect a complete stack backtrace at a
13052 tracepoint. Instead, you may collect the registers and a few hundred
13053 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13054 (adjust to use the name of the actual stack pointer register on your
13055 target architecture, and the amount of stack you wish to capture).
13056 Then the @code{backtrace} command will show a partial backtrace when
13057 using a trace frame. The number of stack frames that can be examined
13058 depends on the sizes of the frames in the collected stack. Note that
13059 if you ask for a block so large that it goes past the bottom of the
13060 stack, the target agent may report an error trying to read from an
13064 If you do not collect registers at a tracepoint, @value{GDBN} can
13065 infer that the value of @code{$pc} must be the same as the address of
13066 the tracepoint and use that when you are looking at a trace frame
13067 for that tracepoint. However, this cannot work if the tracepoint has
13068 multiple locations (for instance if it was set in a function that was
13069 inlined), or if it has a @code{while-stepping} loop. In those cases
13070 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13075 @node Analyze Collected Data
13076 @section Using the Collected Data
13078 After the tracepoint experiment ends, you use @value{GDBN} commands
13079 for examining the trace data. The basic idea is that each tracepoint
13080 collects a trace @dfn{snapshot} every time it is hit and another
13081 snapshot every time it single-steps. All these snapshots are
13082 consecutively numbered from zero and go into a buffer, and you can
13083 examine them later. The way you examine them is to @dfn{focus} on a
13084 specific trace snapshot. When the remote stub is focused on a trace
13085 snapshot, it will respond to all @value{GDBN} requests for memory and
13086 registers by reading from the buffer which belongs to that snapshot,
13087 rather than from @emph{real} memory or registers of the program being
13088 debugged. This means that @strong{all} @value{GDBN} commands
13089 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13090 behave as if we were currently debugging the program state as it was
13091 when the tracepoint occurred. Any requests for data that are not in
13092 the buffer will fail.
13095 * tfind:: How to select a trace snapshot
13096 * tdump:: How to display all data for a snapshot
13097 * save tracepoints:: How to save tracepoints for a future run
13101 @subsection @code{tfind @var{n}}
13104 @cindex select trace snapshot
13105 @cindex find trace snapshot
13106 The basic command for selecting a trace snapshot from the buffer is
13107 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13108 counting from zero. If no argument @var{n} is given, the next
13109 snapshot is selected.
13111 Here are the various forms of using the @code{tfind} command.
13115 Find the first snapshot in the buffer. This is a synonym for
13116 @code{tfind 0} (since 0 is the number of the first snapshot).
13119 Stop debugging trace snapshots, resume @emph{live} debugging.
13122 Same as @samp{tfind none}.
13125 No argument means find the next trace snapshot.
13128 Find the previous trace snapshot before the current one. This permits
13129 retracing earlier steps.
13131 @item tfind tracepoint @var{num}
13132 Find the next snapshot associated with tracepoint @var{num}. Search
13133 proceeds forward from the last examined trace snapshot. If no
13134 argument @var{num} is given, it means find the next snapshot collected
13135 for the same tracepoint as the current snapshot.
13137 @item tfind pc @var{addr}
13138 Find the next snapshot associated with the value @var{addr} of the
13139 program counter. Search proceeds forward from the last examined trace
13140 snapshot. If no argument @var{addr} is given, it means find the next
13141 snapshot with the same value of PC as the current snapshot.
13143 @item tfind outside @var{addr1}, @var{addr2}
13144 Find the next snapshot whose PC is outside the given range of
13145 addresses (exclusive).
13147 @item tfind range @var{addr1}, @var{addr2}
13148 Find the next snapshot whose PC is between @var{addr1} and
13149 @var{addr2} (inclusive).
13151 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13152 Find the next snapshot associated with the source line @var{n}. If
13153 the optional argument @var{file} is given, refer to line @var{n} in
13154 that source file. Search proceeds forward from the last examined
13155 trace snapshot. If no argument @var{n} is given, it means find the
13156 next line other than the one currently being examined; thus saying
13157 @code{tfind line} repeatedly can appear to have the same effect as
13158 stepping from line to line in a @emph{live} debugging session.
13161 The default arguments for the @code{tfind} commands are specifically
13162 designed to make it easy to scan through the trace buffer. For
13163 instance, @code{tfind} with no argument selects the next trace
13164 snapshot, and @code{tfind -} with no argument selects the previous
13165 trace snapshot. So, by giving one @code{tfind} command, and then
13166 simply hitting @key{RET} repeatedly you can examine all the trace
13167 snapshots in order. Or, by saying @code{tfind -} and then hitting
13168 @key{RET} repeatedly you can examine the snapshots in reverse order.
13169 The @code{tfind line} command with no argument selects the snapshot
13170 for the next source line executed. The @code{tfind pc} command with
13171 no argument selects the next snapshot with the same program counter
13172 (PC) as the current frame. The @code{tfind tracepoint} command with
13173 no argument selects the next trace snapshot collected by the same
13174 tracepoint as the current one.
13176 In addition to letting you scan through the trace buffer manually,
13177 these commands make it easy to construct @value{GDBN} scripts that
13178 scan through the trace buffer and print out whatever collected data
13179 you are interested in. Thus, if we want to examine the PC, FP, and SP
13180 registers from each trace frame in the buffer, we can say this:
13183 (@value{GDBP}) @b{tfind start}
13184 (@value{GDBP}) @b{while ($trace_frame != -1)}
13185 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13186 $trace_frame, $pc, $sp, $fp
13190 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13191 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13192 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13193 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13194 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13195 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13196 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13197 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13198 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13199 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13200 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13203 Or, if we want to examine the variable @code{X} at each source line in
13207 (@value{GDBP}) @b{tfind start}
13208 (@value{GDBP}) @b{while ($trace_frame != -1)}
13209 > printf "Frame %d, X == %d\n", $trace_frame, X
13219 @subsection @code{tdump}
13221 @cindex dump all data collected at tracepoint
13222 @cindex tracepoint data, display
13224 This command takes no arguments. It prints all the data collected at
13225 the current trace snapshot.
13228 (@value{GDBP}) @b{trace 444}
13229 (@value{GDBP}) @b{actions}
13230 Enter actions for tracepoint #2, one per line:
13231 > collect $regs, $locals, $args, gdb_long_test
13234 (@value{GDBP}) @b{tstart}
13236 (@value{GDBP}) @b{tfind line 444}
13237 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13239 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13241 (@value{GDBP}) @b{tdump}
13242 Data collected at tracepoint 2, trace frame 1:
13243 d0 0xc4aa0085 -995491707
13247 d4 0x71aea3d 119204413
13250 d7 0x380035 3670069
13251 a0 0x19e24a 1696330
13252 a1 0x3000668 50333288
13254 a3 0x322000 3284992
13255 a4 0x3000698 50333336
13256 a5 0x1ad3cc 1758156
13257 fp 0x30bf3c 0x30bf3c
13258 sp 0x30bf34 0x30bf34
13260 pc 0x20b2c8 0x20b2c8
13264 p = 0x20e5b4 "gdb-test"
13271 gdb_long_test = 17 '\021'
13276 @code{tdump} works by scanning the tracepoint's current collection
13277 actions and printing the value of each expression listed. So
13278 @code{tdump} can fail, if after a run, you change the tracepoint's
13279 actions to mention variables that were not collected during the run.
13281 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13282 uses the collected value of @code{$pc} to distinguish between trace
13283 frames that were collected at the tracepoint hit, and frames that were
13284 collected while stepping. This allows it to correctly choose whether
13285 to display the basic list of collections, or the collections from the
13286 body of the while-stepping loop. However, if @code{$pc} was not collected,
13287 then @code{tdump} will always attempt to dump using the basic collection
13288 list, and may fail if a while-stepping frame does not include all the
13289 same data that is collected at the tracepoint hit.
13290 @c This is getting pretty arcane, example would be good.
13292 @node save tracepoints
13293 @subsection @code{save tracepoints @var{filename}}
13294 @kindex save tracepoints
13295 @kindex save-tracepoints
13296 @cindex save tracepoints for future sessions
13298 This command saves all current tracepoint definitions together with
13299 their actions and passcounts, into a file @file{@var{filename}}
13300 suitable for use in a later debugging session. To read the saved
13301 tracepoint definitions, use the @code{source} command (@pxref{Command
13302 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13303 alias for @w{@code{save tracepoints}}
13305 @node Tracepoint Variables
13306 @section Convenience Variables for Tracepoints
13307 @cindex tracepoint variables
13308 @cindex convenience variables for tracepoints
13311 @vindex $trace_frame
13312 @item (int) $trace_frame
13313 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13314 snapshot is selected.
13316 @vindex $tracepoint
13317 @item (int) $tracepoint
13318 The tracepoint for the current trace snapshot.
13320 @vindex $trace_line
13321 @item (int) $trace_line
13322 The line number for the current trace snapshot.
13324 @vindex $trace_file
13325 @item (char []) $trace_file
13326 The source file for the current trace snapshot.
13328 @vindex $trace_func
13329 @item (char []) $trace_func
13330 The name of the function containing @code{$tracepoint}.
13333 Note: @code{$trace_file} is not suitable for use in @code{printf},
13334 use @code{output} instead.
13336 Here's a simple example of using these convenience variables for
13337 stepping through all the trace snapshots and printing some of their
13338 data. Note that these are not the same as trace state variables,
13339 which are managed by the target.
13342 (@value{GDBP}) @b{tfind start}
13344 (@value{GDBP}) @b{while $trace_frame != -1}
13345 > output $trace_file
13346 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13352 @section Using Trace Files
13353 @cindex trace files
13355 In some situations, the target running a trace experiment may no
13356 longer be available; perhaps it crashed, or the hardware was needed
13357 for a different activity. To handle these cases, you can arrange to
13358 dump the trace data into a file, and later use that file as a source
13359 of trace data, via the @code{target tfile} command.
13364 @item tsave [ -r ] @var{filename}
13365 @itemx tsave [-ctf] @var{dirname}
13366 Save the trace data to @var{filename}. By default, this command
13367 assumes that @var{filename} refers to the host filesystem, so if
13368 necessary @value{GDBN} will copy raw trace data up from the target and
13369 then save it. If the target supports it, you can also supply the
13370 optional argument @code{-r} (``remote'') to direct the target to save
13371 the data directly into @var{filename} in its own filesystem, which may be
13372 more efficient if the trace buffer is very large. (Note, however, that
13373 @code{target tfile} can only read from files accessible to the host.)
13374 By default, this command will save trace frame in tfile format.
13375 You can supply the optional argument @code{-ctf} to save date in CTF
13376 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13377 that can be shared by multiple debugging and tracing tools. Please go to
13378 @indicateurl{http://www.efficios.com/ctf} to get more information.
13380 @kindex target tfile
13384 @item target tfile @var{filename}
13385 @itemx target ctf @var{dirname}
13386 Use the file named @var{filename} or directory named @var{dirname} as
13387 a source of trace data. Commands that examine data work as they do with
13388 a live target, but it is not possible to run any new trace experiments.
13389 @code{tstatus} will report the state of the trace run at the moment
13390 the data was saved, as well as the current trace frame you are examining.
13391 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13395 (@value{GDBP}) target ctf ctf.ctf
13396 (@value{GDBP}) tfind
13397 Found trace frame 0, tracepoint 2
13398 39 ++a; /* set tracepoint 1 here */
13399 (@value{GDBP}) tdump
13400 Data collected at tracepoint 2, trace frame 0:
13404 c = @{"123", "456", "789", "123", "456", "789"@}
13405 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13413 @chapter Debugging Programs That Use Overlays
13416 If your program is too large to fit completely in your target system's
13417 memory, you can sometimes use @dfn{overlays} to work around this
13418 problem. @value{GDBN} provides some support for debugging programs that
13422 * How Overlays Work:: A general explanation of overlays.
13423 * Overlay Commands:: Managing overlays in @value{GDBN}.
13424 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13425 mapped by asking the inferior.
13426 * Overlay Sample Program:: A sample program using overlays.
13429 @node How Overlays Work
13430 @section How Overlays Work
13431 @cindex mapped overlays
13432 @cindex unmapped overlays
13433 @cindex load address, overlay's
13434 @cindex mapped address
13435 @cindex overlay area
13437 Suppose you have a computer whose instruction address space is only 64
13438 kilobytes long, but which has much more memory which can be accessed by
13439 other means: special instructions, segment registers, or memory
13440 management hardware, for example. Suppose further that you want to
13441 adapt a program which is larger than 64 kilobytes to run on this system.
13443 One solution is to identify modules of your program which are relatively
13444 independent, and need not call each other directly; call these modules
13445 @dfn{overlays}. Separate the overlays from the main program, and place
13446 their machine code in the larger memory. Place your main program in
13447 instruction memory, but leave at least enough space there to hold the
13448 largest overlay as well.
13450 Now, to call a function located in an overlay, you must first copy that
13451 overlay's machine code from the large memory into the space set aside
13452 for it in the instruction memory, and then jump to its entry point
13455 @c NB: In the below the mapped area's size is greater or equal to the
13456 @c size of all overlays. This is intentional to remind the developer
13457 @c that overlays don't necessarily need to be the same size.
13461 Data Instruction Larger
13462 Address Space Address Space Address Space
13463 +-----------+ +-----------+ +-----------+
13465 +-----------+ +-----------+ +-----------+<-- overlay 1
13466 | program | | main | .----| overlay 1 | load address
13467 | variables | | program | | +-----------+
13468 | and heap | | | | | |
13469 +-----------+ | | | +-----------+<-- overlay 2
13470 | | +-----------+ | | | load address
13471 +-----------+ | | | .-| overlay 2 |
13473 mapped --->+-----------+ | | +-----------+
13474 address | | | | | |
13475 | overlay | <-' | | |
13476 | area | <---' +-----------+<-- overlay 3
13477 | | <---. | | load address
13478 +-----------+ `--| overlay 3 |
13485 @anchor{A code overlay}A code overlay
13489 The diagram (@pxref{A code overlay}) shows a system with separate data
13490 and instruction address spaces. To map an overlay, the program copies
13491 its code from the larger address space to the instruction address space.
13492 Since the overlays shown here all use the same mapped address, only one
13493 may be mapped at a time. For a system with a single address space for
13494 data and instructions, the diagram would be similar, except that the
13495 program variables and heap would share an address space with the main
13496 program and the overlay area.
13498 An overlay loaded into instruction memory and ready for use is called a
13499 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13500 instruction memory. An overlay not present (or only partially present)
13501 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13502 is its address in the larger memory. The mapped address is also called
13503 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13504 called the @dfn{load memory address}, or @dfn{LMA}.
13506 Unfortunately, overlays are not a completely transparent way to adapt a
13507 program to limited instruction memory. They introduce a new set of
13508 global constraints you must keep in mind as you design your program:
13513 Before calling or returning to a function in an overlay, your program
13514 must make sure that overlay is actually mapped. Otherwise, the call or
13515 return will transfer control to the right address, but in the wrong
13516 overlay, and your program will probably crash.
13519 If the process of mapping an overlay is expensive on your system, you
13520 will need to choose your overlays carefully to minimize their effect on
13521 your program's performance.
13524 The executable file you load onto your system must contain each
13525 overlay's instructions, appearing at the overlay's load address, not its
13526 mapped address. However, each overlay's instructions must be relocated
13527 and its symbols defined as if the overlay were at its mapped address.
13528 You can use GNU linker scripts to specify different load and relocation
13529 addresses for pieces of your program; see @ref{Overlay Description,,,
13530 ld.info, Using ld: the GNU linker}.
13533 The procedure for loading executable files onto your system must be able
13534 to load their contents into the larger address space as well as the
13535 instruction and data spaces.
13539 The overlay system described above is rather simple, and could be
13540 improved in many ways:
13545 If your system has suitable bank switch registers or memory management
13546 hardware, you could use those facilities to make an overlay's load area
13547 contents simply appear at their mapped address in instruction space.
13548 This would probably be faster than copying the overlay to its mapped
13549 area in the usual way.
13552 If your overlays are small enough, you could set aside more than one
13553 overlay area, and have more than one overlay mapped at a time.
13556 You can use overlays to manage data, as well as instructions. In
13557 general, data overlays are even less transparent to your design than
13558 code overlays: whereas code overlays only require care when you call or
13559 return to functions, data overlays require care every time you access
13560 the data. Also, if you change the contents of a data overlay, you
13561 must copy its contents back out to its load address before you can copy a
13562 different data overlay into the same mapped area.
13567 @node Overlay Commands
13568 @section Overlay Commands
13570 To use @value{GDBN}'s overlay support, each overlay in your program must
13571 correspond to a separate section of the executable file. The section's
13572 virtual memory address and load memory address must be the overlay's
13573 mapped and load addresses. Identifying overlays with sections allows
13574 @value{GDBN} to determine the appropriate address of a function or
13575 variable, depending on whether the overlay is mapped or not.
13577 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13578 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13583 Disable @value{GDBN}'s overlay support. When overlay support is
13584 disabled, @value{GDBN} assumes that all functions and variables are
13585 always present at their mapped addresses. By default, @value{GDBN}'s
13586 overlay support is disabled.
13588 @item overlay manual
13589 @cindex manual overlay debugging
13590 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13591 relies on you to tell it which overlays are mapped, and which are not,
13592 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13593 commands described below.
13595 @item overlay map-overlay @var{overlay}
13596 @itemx overlay map @var{overlay}
13597 @cindex map an overlay
13598 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13599 be the name of the object file section containing the overlay. When an
13600 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13601 functions and variables at their mapped addresses. @value{GDBN} assumes
13602 that any other overlays whose mapped ranges overlap that of
13603 @var{overlay} are now unmapped.
13605 @item overlay unmap-overlay @var{overlay}
13606 @itemx overlay unmap @var{overlay}
13607 @cindex unmap an overlay
13608 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13609 must be the name of the object file section containing the overlay.
13610 When an overlay is unmapped, @value{GDBN} assumes it can find the
13611 overlay's functions and variables at their load addresses.
13614 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13615 consults a data structure the overlay manager maintains in the inferior
13616 to see which overlays are mapped. For details, see @ref{Automatic
13617 Overlay Debugging}.
13619 @item overlay load-target
13620 @itemx overlay load
13621 @cindex reloading the overlay table
13622 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13623 re-reads the table @value{GDBN} automatically each time the inferior
13624 stops, so this command should only be necessary if you have changed the
13625 overlay mapping yourself using @value{GDBN}. This command is only
13626 useful when using automatic overlay debugging.
13628 @item overlay list-overlays
13629 @itemx overlay list
13630 @cindex listing mapped overlays
13631 Display a list of the overlays currently mapped, along with their mapped
13632 addresses, load addresses, and sizes.
13636 Normally, when @value{GDBN} prints a code address, it includes the name
13637 of the function the address falls in:
13640 (@value{GDBP}) print main
13641 $3 = @{int ()@} 0x11a0 <main>
13644 When overlay debugging is enabled, @value{GDBN} recognizes code in
13645 unmapped overlays, and prints the names of unmapped functions with
13646 asterisks around them. For example, if @code{foo} is a function in an
13647 unmapped overlay, @value{GDBN} prints it this way:
13650 (@value{GDBP}) overlay list
13651 No sections are mapped.
13652 (@value{GDBP}) print foo
13653 $5 = @{int (int)@} 0x100000 <*foo*>
13656 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13660 (@value{GDBP}) overlay list
13661 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13662 mapped at 0x1016 - 0x104a
13663 (@value{GDBP}) print foo
13664 $6 = @{int (int)@} 0x1016 <foo>
13667 When overlay debugging is enabled, @value{GDBN} can find the correct
13668 address for functions and variables in an overlay, whether or not the
13669 overlay is mapped. This allows most @value{GDBN} commands, like
13670 @code{break} and @code{disassemble}, to work normally, even on unmapped
13671 code. However, @value{GDBN}'s breakpoint support has some limitations:
13675 @cindex breakpoints in overlays
13676 @cindex overlays, setting breakpoints in
13677 You can set breakpoints in functions in unmapped overlays, as long as
13678 @value{GDBN} can write to the overlay at its load address.
13680 @value{GDBN} can not set hardware or simulator-based breakpoints in
13681 unmapped overlays. However, if you set a breakpoint at the end of your
13682 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13683 you are using manual overlay management), @value{GDBN} will re-set its
13684 breakpoints properly.
13688 @node Automatic Overlay Debugging
13689 @section Automatic Overlay Debugging
13690 @cindex automatic overlay debugging
13692 @value{GDBN} can automatically track which overlays are mapped and which
13693 are not, given some simple co-operation from the overlay manager in the
13694 inferior. If you enable automatic overlay debugging with the
13695 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13696 looks in the inferior's memory for certain variables describing the
13697 current state of the overlays.
13699 Here are the variables your overlay manager must define to support
13700 @value{GDBN}'s automatic overlay debugging:
13704 @item @code{_ovly_table}:
13705 This variable must be an array of the following structures:
13710 /* The overlay's mapped address. */
13713 /* The size of the overlay, in bytes. */
13714 unsigned long size;
13716 /* The overlay's load address. */
13719 /* Non-zero if the overlay is currently mapped;
13721 unsigned long mapped;
13725 @item @code{_novlys}:
13726 This variable must be a four-byte signed integer, holding the total
13727 number of elements in @code{_ovly_table}.
13731 To decide whether a particular overlay is mapped or not, @value{GDBN}
13732 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13733 @code{lma} members equal the VMA and LMA of the overlay's section in the
13734 executable file. When @value{GDBN} finds a matching entry, it consults
13735 the entry's @code{mapped} member to determine whether the overlay is
13738 In addition, your overlay manager may define a function called
13739 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13740 will silently set a breakpoint there. If the overlay manager then
13741 calls this function whenever it has changed the overlay table, this
13742 will enable @value{GDBN} to accurately keep track of which overlays
13743 are in program memory, and update any breakpoints that may be set
13744 in overlays. This will allow breakpoints to work even if the
13745 overlays are kept in ROM or other non-writable memory while they
13746 are not being executed.
13748 @node Overlay Sample Program
13749 @section Overlay Sample Program
13750 @cindex overlay example program
13752 When linking a program which uses overlays, you must place the overlays
13753 at their load addresses, while relocating them to run at their mapped
13754 addresses. To do this, you must write a linker script (@pxref{Overlay
13755 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13756 since linker scripts are specific to a particular host system, target
13757 architecture, and target memory layout, this manual cannot provide
13758 portable sample code demonstrating @value{GDBN}'s overlay support.
13760 However, the @value{GDBN} source distribution does contain an overlaid
13761 program, with linker scripts for a few systems, as part of its test
13762 suite. The program consists of the following files from
13763 @file{gdb/testsuite/gdb.base}:
13767 The main program file.
13769 A simple overlay manager, used by @file{overlays.c}.
13774 Overlay modules, loaded and used by @file{overlays.c}.
13777 Linker scripts for linking the test program on the @code{d10v-elf}
13778 and @code{m32r-elf} targets.
13781 You can build the test program using the @code{d10v-elf} GCC
13782 cross-compiler like this:
13785 $ d10v-elf-gcc -g -c overlays.c
13786 $ d10v-elf-gcc -g -c ovlymgr.c
13787 $ d10v-elf-gcc -g -c foo.c
13788 $ d10v-elf-gcc -g -c bar.c
13789 $ d10v-elf-gcc -g -c baz.c
13790 $ d10v-elf-gcc -g -c grbx.c
13791 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13792 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13795 The build process is identical for any other architecture, except that
13796 you must substitute the appropriate compiler and linker script for the
13797 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13801 @chapter Using @value{GDBN} with Different Languages
13804 Although programming languages generally have common aspects, they are
13805 rarely expressed in the same manner. For instance, in ANSI C,
13806 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13807 Modula-2, it is accomplished by @code{p^}. Values can also be
13808 represented (and displayed) differently. Hex numbers in C appear as
13809 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13811 @cindex working language
13812 Language-specific information is built into @value{GDBN} for some languages,
13813 allowing you to express operations like the above in your program's
13814 native language, and allowing @value{GDBN} to output values in a manner
13815 consistent with the syntax of your program's native language. The
13816 language you use to build expressions is called the @dfn{working
13820 * Setting:: Switching between source languages
13821 * Show:: Displaying the language
13822 * Checks:: Type and range checks
13823 * Supported Languages:: Supported languages
13824 * Unsupported Languages:: Unsupported languages
13828 @section Switching Between Source Languages
13830 There are two ways to control the working language---either have @value{GDBN}
13831 set it automatically, or select it manually yourself. You can use the
13832 @code{set language} command for either purpose. On startup, @value{GDBN}
13833 defaults to setting the language automatically. The working language is
13834 used to determine how expressions you type are interpreted, how values
13837 In addition to the working language, every source file that
13838 @value{GDBN} knows about has its own working language. For some object
13839 file formats, the compiler might indicate which language a particular
13840 source file is in. However, most of the time @value{GDBN} infers the
13841 language from the name of the file. The language of a source file
13842 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13843 show each frame appropriately for its own language. There is no way to
13844 set the language of a source file from within @value{GDBN}, but you can
13845 set the language associated with a filename extension. @xref{Show, ,
13846 Displaying the Language}.
13848 This is most commonly a problem when you use a program, such
13849 as @code{cfront} or @code{f2c}, that generates C but is written in
13850 another language. In that case, make the
13851 program use @code{#line} directives in its C output; that way
13852 @value{GDBN} will know the correct language of the source code of the original
13853 program, and will display that source code, not the generated C code.
13856 * Filenames:: Filename extensions and languages.
13857 * Manually:: Setting the working language manually
13858 * Automatically:: Having @value{GDBN} infer the source language
13862 @subsection List of Filename Extensions and Languages
13864 If a source file name ends in one of the following extensions, then
13865 @value{GDBN} infers that its language is the one indicated.
13883 C@t{++} source file
13889 Objective-C source file
13893 Fortran source file
13896 Modula-2 source file
13900 Assembler source file. This actually behaves almost like C, but
13901 @value{GDBN} does not skip over function prologues when stepping.
13904 In addition, you may set the language associated with a filename
13905 extension. @xref{Show, , Displaying the Language}.
13908 @subsection Setting the Working Language
13910 If you allow @value{GDBN} to set the language automatically,
13911 expressions are interpreted the same way in your debugging session and
13914 @kindex set language
13915 If you wish, you may set the language manually. To do this, issue the
13916 command @samp{set language @var{lang}}, where @var{lang} is the name of
13917 a language, such as
13918 @code{c} or @code{modula-2}.
13919 For a list of the supported languages, type @samp{set language}.
13921 Setting the language manually prevents @value{GDBN} from updating the working
13922 language automatically. This can lead to confusion if you try
13923 to debug a program when the working language is not the same as the
13924 source language, when an expression is acceptable to both
13925 languages---but means different things. For instance, if the current
13926 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13934 might not have the effect you intended. In C, this means to add
13935 @code{b} and @code{c} and place the result in @code{a}. The result
13936 printed would be the value of @code{a}. In Modula-2, this means to compare
13937 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13939 @node Automatically
13940 @subsection Having @value{GDBN} Infer the Source Language
13942 To have @value{GDBN} set the working language automatically, use
13943 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13944 then infers the working language. That is, when your program stops in a
13945 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13946 working language to the language recorded for the function in that
13947 frame. If the language for a frame is unknown (that is, if the function
13948 or block corresponding to the frame was defined in a source file that
13949 does not have a recognized extension), the current working language is
13950 not changed, and @value{GDBN} issues a warning.
13952 This may not seem necessary for most programs, which are written
13953 entirely in one source language. However, program modules and libraries
13954 written in one source language can be used by a main program written in
13955 a different source language. Using @samp{set language auto} in this
13956 case frees you from having to set the working language manually.
13959 @section Displaying the Language
13961 The following commands help you find out which language is the
13962 working language, and also what language source files were written in.
13965 @item show language
13966 @anchor{show language}
13967 @kindex show language
13968 Display the current working language. This is the
13969 language you can use with commands such as @code{print} to
13970 build and compute expressions that may involve variables in your program.
13973 @kindex info frame@r{, show the source language}
13974 Display the source language for this frame. This language becomes the
13975 working language if you use an identifier from this frame.
13976 @xref{Frame Info, ,Information about a Frame}, to identify the other
13977 information listed here.
13980 @kindex info source@r{, show the source language}
13981 Display the source language of this source file.
13982 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13983 information listed here.
13986 In unusual circumstances, you may have source files with extensions
13987 not in the standard list. You can then set the extension associated
13988 with a language explicitly:
13991 @item set extension-language @var{ext} @var{language}
13992 @kindex set extension-language
13993 Tell @value{GDBN} that source files with extension @var{ext} are to be
13994 assumed as written in the source language @var{language}.
13996 @item info extensions
13997 @kindex info extensions
13998 List all the filename extensions and the associated languages.
14002 @section Type and Range Checking
14004 Some languages are designed to guard you against making seemingly common
14005 errors through a series of compile- and run-time checks. These include
14006 checking the type of arguments to functions and operators and making
14007 sure mathematical overflows are caught at run time. Checks such as
14008 these help to ensure a program's correctness once it has been compiled
14009 by eliminating type mismatches and providing active checks for range
14010 errors when your program is running.
14012 By default @value{GDBN} checks for these errors according to the
14013 rules of the current source language. Although @value{GDBN} does not check
14014 the statements in your program, it can check expressions entered directly
14015 into @value{GDBN} for evaluation via the @code{print} command, for example.
14018 * Type Checking:: An overview of type checking
14019 * Range Checking:: An overview of range checking
14022 @cindex type checking
14023 @cindex checks, type
14024 @node Type Checking
14025 @subsection An Overview of Type Checking
14027 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14028 arguments to operators and functions have to be of the correct type,
14029 otherwise an error occurs. These checks prevent type mismatch
14030 errors from ever causing any run-time problems. For example,
14033 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14035 (@value{GDBP}) print obj.my_method (0)
14038 (@value{GDBP}) print obj.my_method (0x1234)
14039 Cannot resolve method klass::my_method to any overloaded instance
14042 The second example fails because in C@t{++} the integer constant
14043 @samp{0x1234} is not type-compatible with the pointer parameter type.
14045 For the expressions you use in @value{GDBN} commands, you can tell
14046 @value{GDBN} to not enforce strict type checking or
14047 to treat any mismatches as errors and abandon the expression;
14048 When type checking is disabled, @value{GDBN} successfully evaluates
14049 expressions like the second example above.
14051 Even if type checking is off, there may be other reasons
14052 related to type that prevent @value{GDBN} from evaluating an expression.
14053 For instance, @value{GDBN} does not know how to add an @code{int} and
14054 a @code{struct foo}. These particular type errors have nothing to do
14055 with the language in use and usually arise from expressions which make
14056 little sense to evaluate anyway.
14058 @value{GDBN} provides some additional commands for controlling type checking:
14060 @kindex set check type
14061 @kindex show check type
14063 @item set check type on
14064 @itemx set check type off
14065 Set strict type checking on or off. If any type mismatches occur in
14066 evaluating an expression while type checking is on, @value{GDBN} prints a
14067 message and aborts evaluation of the expression.
14069 @item show check type
14070 Show the current setting of type checking and whether @value{GDBN}
14071 is enforcing strict type checking rules.
14074 @cindex range checking
14075 @cindex checks, range
14076 @node Range Checking
14077 @subsection An Overview of Range Checking
14079 In some languages (such as Modula-2), it is an error to exceed the
14080 bounds of a type; this is enforced with run-time checks. Such range
14081 checking is meant to ensure program correctness by making sure
14082 computations do not overflow, or indices on an array element access do
14083 not exceed the bounds of the array.
14085 For expressions you use in @value{GDBN} commands, you can tell
14086 @value{GDBN} to treat range errors in one of three ways: ignore them,
14087 always treat them as errors and abandon the expression, or issue
14088 warnings but evaluate the expression anyway.
14090 A range error can result from numerical overflow, from exceeding an
14091 array index bound, or when you type a constant that is not a member
14092 of any type. Some languages, however, do not treat overflows as an
14093 error. In many implementations of C, mathematical overflow causes the
14094 result to ``wrap around'' to lower values---for example, if @var{m} is
14095 the largest integer value, and @var{s} is the smallest, then
14098 @var{m} + 1 @result{} @var{s}
14101 This, too, is specific to individual languages, and in some cases
14102 specific to individual compilers or machines. @xref{Supported Languages, ,
14103 Supported Languages}, for further details on specific languages.
14105 @value{GDBN} provides some additional commands for controlling the range checker:
14107 @kindex set check range
14108 @kindex show check range
14110 @item set check range auto
14111 Set range checking on or off based on the current working language.
14112 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14115 @item set check range on
14116 @itemx set check range off
14117 Set range checking on or off, overriding the default setting for the
14118 current working language. A warning is issued if the setting does not
14119 match the language default. If a range error occurs and range checking is on,
14120 then a message is printed and evaluation of the expression is aborted.
14122 @item set check range warn
14123 Output messages when the @value{GDBN} range checker detects a range error,
14124 but attempt to evaluate the expression anyway. Evaluating the
14125 expression may still be impossible for other reasons, such as accessing
14126 memory that the process does not own (a typical example from many Unix
14130 Show the current setting of the range checker, and whether or not it is
14131 being set automatically by @value{GDBN}.
14134 @node Supported Languages
14135 @section Supported Languages
14137 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14138 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14139 @c This is false ...
14140 Some @value{GDBN} features may be used in expressions regardless of the
14141 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14142 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14143 ,Expressions}) can be used with the constructs of any supported
14146 The following sections detail to what degree each source language is
14147 supported by @value{GDBN}. These sections are not meant to be language
14148 tutorials or references, but serve only as a reference guide to what the
14149 @value{GDBN} expression parser accepts, and what input and output
14150 formats should look like for different languages. There are many good
14151 books written on each of these languages; please look to these for a
14152 language reference or tutorial.
14155 * C:: C and C@t{++}
14158 * Objective-C:: Objective-C
14159 * OpenCL C:: OpenCL C
14160 * Fortran:: Fortran
14162 * Modula-2:: Modula-2
14167 @subsection C and C@t{++}
14169 @cindex C and C@t{++}
14170 @cindex expressions in C or C@t{++}
14172 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14173 to both languages. Whenever this is the case, we discuss those languages
14177 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14178 @cindex @sc{gnu} C@t{++}
14179 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14180 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14181 effectively, you must compile your C@t{++} programs with a supported
14182 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14183 compiler (@code{aCC}).
14186 * C Operators:: C and C@t{++} operators
14187 * C Constants:: C and C@t{++} constants
14188 * C Plus Plus Expressions:: C@t{++} expressions
14189 * C Defaults:: Default settings for C and C@t{++}
14190 * C Checks:: C and C@t{++} type and range checks
14191 * Debugging C:: @value{GDBN} and C
14192 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14193 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14197 @subsubsection C and C@t{++} Operators
14199 @cindex C and C@t{++} operators
14201 Operators must be defined on values of specific types. For instance,
14202 @code{+} is defined on numbers, but not on structures. Operators are
14203 often defined on groups of types.
14205 For the purposes of C and C@t{++}, the following definitions hold:
14210 @emph{Integral types} include @code{int} with any of its storage-class
14211 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14214 @emph{Floating-point types} include @code{float}, @code{double}, and
14215 @code{long double} (if supported by the target platform).
14218 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14221 @emph{Scalar types} include all of the above.
14226 The following operators are supported. They are listed here
14227 in order of increasing precedence:
14231 The comma or sequencing operator. Expressions in a comma-separated list
14232 are evaluated from left to right, with the result of the entire
14233 expression being the last expression evaluated.
14236 Assignment. The value of an assignment expression is the value
14237 assigned. Defined on scalar types.
14240 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14241 and translated to @w{@code{@var{a} = @var{a op b}}}.
14242 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14243 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14244 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14247 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14248 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14249 should be of an integral type.
14252 Logical @sc{or}. Defined on integral types.
14255 Logical @sc{and}. Defined on integral types.
14258 Bitwise @sc{or}. Defined on integral types.
14261 Bitwise exclusive-@sc{or}. Defined on integral types.
14264 Bitwise @sc{and}. Defined on integral types.
14267 Equality and inequality. Defined on scalar types. The value of these
14268 expressions is 0 for false and non-zero for true.
14270 @item <@r{, }>@r{, }<=@r{, }>=
14271 Less than, greater than, less than or equal, greater than or equal.
14272 Defined on scalar types. The value of these expressions is 0 for false
14273 and non-zero for true.
14276 left shift, and right shift. Defined on integral types.
14279 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14282 Addition and subtraction. Defined on integral types, floating-point types and
14285 @item *@r{, }/@r{, }%
14286 Multiplication, division, and modulus. Multiplication and division are
14287 defined on integral and floating-point types. Modulus is defined on
14291 Increment and decrement. When appearing before a variable, the
14292 operation is performed before the variable is used in an expression;
14293 when appearing after it, the variable's value is used before the
14294 operation takes place.
14297 Pointer dereferencing. Defined on pointer types. Same precedence as
14301 Address operator. Defined on variables. Same precedence as @code{++}.
14303 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14304 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14305 to examine the address
14306 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14310 Negative. Defined on integral and floating-point types. Same
14311 precedence as @code{++}.
14314 Logical negation. Defined on integral types. Same precedence as
14318 Bitwise complement operator. Defined on integral types. Same precedence as
14323 Structure member, and pointer-to-structure member. For convenience,
14324 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14325 pointer based on the stored type information.
14326 Defined on @code{struct} and @code{union} data.
14329 Dereferences of pointers to members.
14332 Array indexing. @code{@var{a}[@var{i}]} is defined as
14333 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14336 Function parameter list. Same precedence as @code{->}.
14339 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14340 and @code{class} types.
14343 Doubled colons also represent the @value{GDBN} scope operator
14344 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14348 If an operator is redefined in the user code, @value{GDBN} usually
14349 attempts to invoke the redefined version instead of using the operator's
14350 predefined meaning.
14353 @subsubsection C and C@t{++} Constants
14355 @cindex C and C@t{++} constants
14357 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14362 Integer constants are a sequence of digits. Octal constants are
14363 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14364 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14365 @samp{l}, specifying that the constant should be treated as a
14369 Floating point constants are a sequence of digits, followed by a decimal
14370 point, followed by a sequence of digits, and optionally followed by an
14371 exponent. An exponent is of the form:
14372 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14373 sequence of digits. The @samp{+} is optional for positive exponents.
14374 A floating-point constant may also end with a letter @samp{f} or
14375 @samp{F}, specifying that the constant should be treated as being of
14376 the @code{float} (as opposed to the default @code{double}) type; or with
14377 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14381 Enumerated constants consist of enumerated identifiers, or their
14382 integral equivalents.
14385 Character constants are a single character surrounded by single quotes
14386 (@code{'}), or a number---the ordinal value of the corresponding character
14387 (usually its @sc{ascii} value). Within quotes, the single character may
14388 be represented by a letter or by @dfn{escape sequences}, which are of
14389 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14390 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14391 @samp{@var{x}} is a predefined special character---for example,
14392 @samp{\n} for newline.
14394 Wide character constants can be written by prefixing a character
14395 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14396 form of @samp{x}. The target wide character set is used when
14397 computing the value of this constant (@pxref{Character Sets}).
14400 String constants are a sequence of character constants surrounded by
14401 double quotes (@code{"}). Any valid character constant (as described
14402 above) may appear. Double quotes within the string must be preceded by
14403 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14406 Wide string constants can be written by prefixing a string constant
14407 with @samp{L}, as in C. The target wide character set is used when
14408 computing the value of this constant (@pxref{Character Sets}).
14411 Pointer constants are an integral value. You can also write pointers
14412 to constants using the C operator @samp{&}.
14415 Array constants are comma-separated lists surrounded by braces @samp{@{}
14416 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14417 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14418 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14421 @node C Plus Plus Expressions
14422 @subsubsection C@t{++} Expressions
14424 @cindex expressions in C@t{++}
14425 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14427 @cindex debugging C@t{++} programs
14428 @cindex C@t{++} compilers
14429 @cindex debug formats and C@t{++}
14430 @cindex @value{NGCC} and C@t{++}
14432 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14433 the proper compiler and the proper debug format. Currently,
14434 @value{GDBN} works best when debugging C@t{++} code that is compiled
14435 with the most recent version of @value{NGCC} possible. The DWARF
14436 debugging format is preferred; @value{NGCC} defaults to this on most
14437 popular platforms. Other compilers and/or debug formats are likely to
14438 work badly or not at all when using @value{GDBN} to debug C@t{++}
14439 code. @xref{Compilation}.
14444 @cindex member functions
14446 Member function calls are allowed; you can use expressions like
14449 count = aml->GetOriginal(x, y)
14452 @vindex this@r{, inside C@t{++} member functions}
14453 @cindex namespace in C@t{++}
14455 While a member function is active (in the selected stack frame), your
14456 expressions have the same namespace available as the member function;
14457 that is, @value{GDBN} allows implicit references to the class instance
14458 pointer @code{this} following the same rules as C@t{++}. @code{using}
14459 declarations in the current scope are also respected by @value{GDBN}.
14461 @cindex call overloaded functions
14462 @cindex overloaded functions, calling
14463 @cindex type conversions in C@t{++}
14465 You can call overloaded functions; @value{GDBN} resolves the function
14466 call to the right definition, with some restrictions. @value{GDBN} does not
14467 perform overload resolution involving user-defined type conversions,
14468 calls to constructors, or instantiations of templates that do not exist
14469 in the program. It also cannot handle ellipsis argument lists or
14472 It does perform integral conversions and promotions, floating-point
14473 promotions, arithmetic conversions, pointer conversions, conversions of
14474 class objects to base classes, and standard conversions such as those of
14475 functions or arrays to pointers; it requires an exact match on the
14476 number of function arguments.
14478 Overload resolution is always performed, unless you have specified
14479 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14480 ,@value{GDBN} Features for C@t{++}}.
14482 You must specify @code{set overload-resolution off} in order to use an
14483 explicit function signature to call an overloaded function, as in
14485 p 'foo(char,int)'('x', 13)
14488 The @value{GDBN} command-completion facility can simplify this;
14489 see @ref{Completion, ,Command Completion}.
14491 @cindex reference declarations
14493 @value{GDBN} understands variables declared as C@t{++} references; you can use
14494 them in expressions just as you do in C@t{++} source---they are automatically
14497 In the parameter list shown when @value{GDBN} displays a frame, the values of
14498 reference variables are not displayed (unlike other variables); this
14499 avoids clutter, since references are often used for large structures.
14500 The @emph{address} of a reference variable is always shown, unless
14501 you have specified @samp{set print address off}.
14504 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14505 expressions can use it just as expressions in your program do. Since
14506 one scope may be defined in another, you can use @code{::} repeatedly if
14507 necessary, for example in an expression like
14508 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14509 resolving name scope by reference to source files, in both C and C@t{++}
14510 debugging (@pxref{Variables, ,Program Variables}).
14513 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14518 @subsubsection C and C@t{++} Defaults
14520 @cindex C and C@t{++} defaults
14522 If you allow @value{GDBN} to set range checking automatically, it
14523 defaults to @code{off} whenever the working language changes to
14524 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14525 selects the working language.
14527 If you allow @value{GDBN} to set the language automatically, it
14528 recognizes source files whose names end with @file{.c}, @file{.C}, or
14529 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14530 these files, it sets the working language to C or C@t{++}.
14531 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14532 for further details.
14535 @subsubsection C and C@t{++} Type and Range Checks
14537 @cindex C and C@t{++} checks
14539 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14540 checking is used. However, if you turn type checking off, @value{GDBN}
14541 will allow certain non-standard conversions, such as promoting integer
14542 constants to pointers.
14544 Range checking, if turned on, is done on mathematical operations. Array
14545 indices are not checked, since they are often used to index a pointer
14546 that is not itself an array.
14549 @subsubsection @value{GDBN} and C
14551 The @code{set print union} and @code{show print union} commands apply to
14552 the @code{union} type. When set to @samp{on}, any @code{union} that is
14553 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14554 appears as @samp{@{...@}}.
14556 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14557 with pointers and a memory allocation function. @xref{Expressions,
14560 @node Debugging C Plus Plus
14561 @subsubsection @value{GDBN} Features for C@t{++}
14563 @cindex commands for C@t{++}
14565 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14566 designed specifically for use with C@t{++}. Here is a summary:
14569 @cindex break in overloaded functions
14570 @item @r{breakpoint menus}
14571 When you want a breakpoint in a function whose name is overloaded,
14572 @value{GDBN} has the capability to display a menu of possible breakpoint
14573 locations to help you specify which function definition you want.
14574 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14576 @cindex overloading in C@t{++}
14577 @item rbreak @var{regex}
14578 Setting breakpoints using regular expressions is helpful for setting
14579 breakpoints on overloaded functions that are not members of any special
14581 @xref{Set Breaks, ,Setting Breakpoints}.
14583 @cindex C@t{++} exception handling
14585 @itemx catch rethrow
14587 Debug C@t{++} exception handling using these commands. @xref{Set
14588 Catchpoints, , Setting Catchpoints}.
14590 @cindex inheritance
14591 @item ptype @var{typename}
14592 Print inheritance relationships as well as other information for type
14594 @xref{Symbols, ,Examining the Symbol Table}.
14596 @item info vtbl @var{expression}.
14597 The @code{info vtbl} command can be used to display the virtual
14598 method tables of the object computed by @var{expression}. This shows
14599 one entry per virtual table; there may be multiple virtual tables when
14600 multiple inheritance is in use.
14602 @cindex C@t{++} demangling
14603 @item demangle @var{name}
14604 Demangle @var{name}.
14605 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14607 @cindex C@t{++} symbol display
14608 @item set print demangle
14609 @itemx show print demangle
14610 @itemx set print asm-demangle
14611 @itemx show print asm-demangle
14612 Control whether C@t{++} symbols display in their source form, both when
14613 displaying code as C@t{++} source and when displaying disassemblies.
14614 @xref{Print Settings, ,Print Settings}.
14616 @item set print object
14617 @itemx show print object
14618 Choose whether to print derived (actual) or declared types of objects.
14619 @xref{Print Settings, ,Print Settings}.
14621 @item set print vtbl
14622 @itemx show print vtbl
14623 Control the format for printing virtual function tables.
14624 @xref{Print Settings, ,Print Settings}.
14625 (The @code{vtbl} commands do not work on programs compiled with the HP
14626 ANSI C@t{++} compiler (@code{aCC}).)
14628 @kindex set overload-resolution
14629 @cindex overloaded functions, overload resolution
14630 @item set overload-resolution on
14631 Enable overload resolution for C@t{++} expression evaluation. The default
14632 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14633 and searches for a function whose signature matches the argument types,
14634 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14635 Expressions, ,C@t{++} Expressions}, for details).
14636 If it cannot find a match, it emits a message.
14638 @item set overload-resolution off
14639 Disable overload resolution for C@t{++} expression evaluation. For
14640 overloaded functions that are not class member functions, @value{GDBN}
14641 chooses the first function of the specified name that it finds in the
14642 symbol table, whether or not its arguments are of the correct type. For
14643 overloaded functions that are class member functions, @value{GDBN}
14644 searches for a function whose signature @emph{exactly} matches the
14647 @kindex show overload-resolution
14648 @item show overload-resolution
14649 Show the current setting of overload resolution.
14651 @item @r{Overloaded symbol names}
14652 You can specify a particular definition of an overloaded symbol, using
14653 the same notation that is used to declare such symbols in C@t{++}: type
14654 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14655 also use the @value{GDBN} command-line word completion facilities to list the
14656 available choices, or to finish the type list for you.
14657 @xref{Completion,, Command Completion}, for details on how to do this.
14660 @node Decimal Floating Point
14661 @subsubsection Decimal Floating Point format
14662 @cindex decimal floating point format
14664 @value{GDBN} can examine, set and perform computations with numbers in
14665 decimal floating point format, which in the C language correspond to the
14666 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14667 specified by the extension to support decimal floating-point arithmetic.
14669 There are two encodings in use, depending on the architecture: BID (Binary
14670 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14671 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14674 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14675 to manipulate decimal floating point numbers, it is not possible to convert
14676 (using a cast, for example) integers wider than 32-bit to decimal float.
14678 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14679 point computations, error checking in decimal float operations ignores
14680 underflow, overflow and divide by zero exceptions.
14682 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14683 to inspect @code{_Decimal128} values stored in floating point registers.
14684 See @ref{PowerPC,,PowerPC} for more details.
14690 @value{GDBN} can be used to debug programs written in D and compiled with
14691 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14692 specific feature --- dynamic arrays.
14697 @cindex Go (programming language)
14698 @value{GDBN} can be used to debug programs written in Go and compiled with
14699 @file{gccgo} or @file{6g} compilers.
14701 Here is a summary of the Go-specific features and restrictions:
14704 @cindex current Go package
14705 @item The current Go package
14706 The name of the current package does not need to be specified when
14707 specifying global variables and functions.
14709 For example, given the program:
14713 var myglob = "Shall we?"
14719 When stopped inside @code{main} either of these work:
14723 (gdb) p main.myglob
14726 @cindex builtin Go types
14727 @item Builtin Go types
14728 The @code{string} type is recognized by @value{GDBN} and is printed
14731 @cindex builtin Go functions
14732 @item Builtin Go functions
14733 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14734 function and handles it internally.
14736 @cindex restrictions on Go expressions
14737 @item Restrictions on Go expressions
14738 All Go operators are supported except @code{&^}.
14739 The Go @code{_} ``blank identifier'' is not supported.
14740 Automatic dereferencing of pointers is not supported.
14744 @subsection Objective-C
14746 @cindex Objective-C
14747 This section provides information about some commands and command
14748 options that are useful for debugging Objective-C code. See also
14749 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14750 few more commands specific to Objective-C support.
14753 * Method Names in Commands::
14754 * The Print Command with Objective-C::
14757 @node Method Names in Commands
14758 @subsubsection Method Names in Commands
14760 The following commands have been extended to accept Objective-C method
14761 names as line specifications:
14763 @kindex clear@r{, and Objective-C}
14764 @kindex break@r{, and Objective-C}
14765 @kindex info line@r{, and Objective-C}
14766 @kindex jump@r{, and Objective-C}
14767 @kindex list@r{, and Objective-C}
14771 @item @code{info line}
14776 A fully qualified Objective-C method name is specified as
14779 -[@var{Class} @var{methodName}]
14782 where the minus sign is used to indicate an instance method and a
14783 plus sign (not shown) is used to indicate a class method. The class
14784 name @var{Class} and method name @var{methodName} are enclosed in
14785 brackets, similar to the way messages are specified in Objective-C
14786 source code. For example, to set a breakpoint at the @code{create}
14787 instance method of class @code{Fruit} in the program currently being
14791 break -[Fruit create]
14794 To list ten program lines around the @code{initialize} class method,
14798 list +[NSText initialize]
14801 In the current version of @value{GDBN}, the plus or minus sign is
14802 required. In future versions of @value{GDBN}, the plus or minus
14803 sign will be optional, but you can use it to narrow the search. It
14804 is also possible to specify just a method name:
14810 You must specify the complete method name, including any colons. If
14811 your program's source files contain more than one @code{create} method,
14812 you'll be presented with a numbered list of classes that implement that
14813 method. Indicate your choice by number, or type @samp{0} to exit if
14816 As another example, to clear a breakpoint established at the
14817 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14820 clear -[NSWindow makeKeyAndOrderFront:]
14823 @node The Print Command with Objective-C
14824 @subsubsection The Print Command With Objective-C
14825 @cindex Objective-C, print objects
14826 @kindex print-object
14827 @kindex po @r{(@code{print-object})}
14829 The print command has also been extended to accept methods. For example:
14832 print -[@var{object} hash]
14835 @cindex print an Objective-C object description
14836 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14838 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14839 and print the result. Also, an additional command has been added,
14840 @code{print-object} or @code{po} for short, which is meant to print
14841 the description of an object. However, this command may only work
14842 with certain Objective-C libraries that have a particular hook
14843 function, @code{_NSPrintForDebugger}, defined.
14846 @subsection OpenCL C
14849 This section provides information about @value{GDBN}s OpenCL C support.
14852 * OpenCL C Datatypes::
14853 * OpenCL C Expressions::
14854 * OpenCL C Operators::
14857 @node OpenCL C Datatypes
14858 @subsubsection OpenCL C Datatypes
14860 @cindex OpenCL C Datatypes
14861 @value{GDBN} supports the builtin scalar and vector datatypes specified
14862 by OpenCL 1.1. In addition the half- and double-precision floating point
14863 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14864 extensions are also known to @value{GDBN}.
14866 @node OpenCL C Expressions
14867 @subsubsection OpenCL C Expressions
14869 @cindex OpenCL C Expressions
14870 @value{GDBN} supports accesses to vector components including the access as
14871 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14872 supported by @value{GDBN} can be used as well.
14874 @node OpenCL C Operators
14875 @subsubsection OpenCL C Operators
14877 @cindex OpenCL C Operators
14878 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14882 @subsection Fortran
14883 @cindex Fortran-specific support in @value{GDBN}
14885 @value{GDBN} can be used to debug programs written in Fortran, but it
14886 currently supports only the features of Fortran 77 language.
14888 @cindex trailing underscore, in Fortran symbols
14889 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14890 among them) append an underscore to the names of variables and
14891 functions. When you debug programs compiled by those compilers, you
14892 will need to refer to variables and functions with a trailing
14896 * Fortran Operators:: Fortran operators and expressions
14897 * Fortran Defaults:: Default settings for Fortran
14898 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14901 @node Fortran Operators
14902 @subsubsection Fortran Operators and Expressions
14904 @cindex Fortran operators and expressions
14906 Operators must be defined on values of specific types. For instance,
14907 @code{+} is defined on numbers, but not on characters or other non-
14908 arithmetic types. Operators are often defined on groups of types.
14912 The exponentiation operator. It raises the first operand to the power
14916 The range operator. Normally used in the form of array(low:high) to
14917 represent a section of array.
14920 The access component operator. Normally used to access elements in derived
14921 types. Also suitable for unions. As unions aren't part of regular Fortran,
14922 this can only happen when accessing a register that uses a gdbarch-defined
14926 @node Fortran Defaults
14927 @subsubsection Fortran Defaults
14929 @cindex Fortran Defaults
14931 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14932 default uses case-insensitive matches for Fortran symbols. You can
14933 change that with the @samp{set case-insensitive} command, see
14934 @ref{Symbols}, for the details.
14936 @node Special Fortran Commands
14937 @subsubsection Special Fortran Commands
14939 @cindex Special Fortran commands
14941 @value{GDBN} has some commands to support Fortran-specific features,
14942 such as displaying common blocks.
14945 @cindex @code{COMMON} blocks, Fortran
14946 @kindex info common
14947 @item info common @r{[}@var{common-name}@r{]}
14948 This command prints the values contained in the Fortran @code{COMMON}
14949 block whose name is @var{common-name}. With no argument, the names of
14950 all @code{COMMON} blocks visible at the current program location are
14957 @cindex Pascal support in @value{GDBN}, limitations
14958 Debugging Pascal programs which use sets, subranges, file variables, or
14959 nested functions does not currently work. @value{GDBN} does not support
14960 entering expressions, printing values, or similar features using Pascal
14963 The Pascal-specific command @code{set print pascal_static-members}
14964 controls whether static members of Pascal objects are displayed.
14965 @xref{Print Settings, pascal_static-members}.
14968 @subsection Modula-2
14970 @cindex Modula-2, @value{GDBN} support
14972 The extensions made to @value{GDBN} to support Modula-2 only support
14973 output from the @sc{gnu} Modula-2 compiler (which is currently being
14974 developed). Other Modula-2 compilers are not currently supported, and
14975 attempting to debug executables produced by them is most likely
14976 to give an error as @value{GDBN} reads in the executable's symbol
14979 @cindex expressions in Modula-2
14981 * M2 Operators:: Built-in operators
14982 * Built-In Func/Proc:: Built-in functions and procedures
14983 * M2 Constants:: Modula-2 constants
14984 * M2 Types:: Modula-2 types
14985 * M2 Defaults:: Default settings for Modula-2
14986 * Deviations:: Deviations from standard Modula-2
14987 * M2 Checks:: Modula-2 type and range checks
14988 * M2 Scope:: The scope operators @code{::} and @code{.}
14989 * GDB/M2:: @value{GDBN} and Modula-2
14993 @subsubsection Operators
14994 @cindex Modula-2 operators
14996 Operators must be defined on values of specific types. For instance,
14997 @code{+} is defined on numbers, but not on structures. Operators are
14998 often defined on groups of types. For the purposes of Modula-2, the
14999 following definitions hold:
15004 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15008 @emph{Character types} consist of @code{CHAR} and its subranges.
15011 @emph{Floating-point types} consist of @code{REAL}.
15014 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15018 @emph{Scalar types} consist of all of the above.
15021 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15024 @emph{Boolean types} consist of @code{BOOLEAN}.
15028 The following operators are supported, and appear in order of
15029 increasing precedence:
15033 Function argument or array index separator.
15036 Assignment. The value of @var{var} @code{:=} @var{value} is
15040 Less than, greater than on integral, floating-point, or enumerated
15044 Less than or equal to, greater than or equal to
15045 on integral, floating-point and enumerated types, or set inclusion on
15046 set types. Same precedence as @code{<}.
15048 @item =@r{, }<>@r{, }#
15049 Equality and two ways of expressing inequality, valid on scalar types.
15050 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15051 available for inequality, since @code{#} conflicts with the script
15055 Set membership. Defined on set types and the types of their members.
15056 Same precedence as @code{<}.
15059 Boolean disjunction. Defined on boolean types.
15062 Boolean conjunction. Defined on boolean types.
15065 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15068 Addition and subtraction on integral and floating-point types, or union
15069 and difference on set types.
15072 Multiplication on integral and floating-point types, or set intersection
15076 Division on floating-point types, or symmetric set difference on set
15077 types. Same precedence as @code{*}.
15080 Integer division and remainder. Defined on integral types. Same
15081 precedence as @code{*}.
15084 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15087 Pointer dereferencing. Defined on pointer types.
15090 Boolean negation. Defined on boolean types. Same precedence as
15094 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15095 precedence as @code{^}.
15098 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15101 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15105 @value{GDBN} and Modula-2 scope operators.
15109 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15110 treats the use of the operator @code{IN}, or the use of operators
15111 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15112 @code{<=}, and @code{>=} on sets as an error.
15116 @node Built-In Func/Proc
15117 @subsubsection Built-in Functions and Procedures
15118 @cindex Modula-2 built-ins
15120 Modula-2 also makes available several built-in procedures and functions.
15121 In describing these, the following metavariables are used:
15126 represents an @code{ARRAY} variable.
15129 represents a @code{CHAR} constant or variable.
15132 represents a variable or constant of integral type.
15135 represents an identifier that belongs to a set. Generally used in the
15136 same function with the metavariable @var{s}. The type of @var{s} should
15137 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15140 represents a variable or constant of integral or floating-point type.
15143 represents a variable or constant of floating-point type.
15149 represents a variable.
15152 represents a variable or constant of one of many types. See the
15153 explanation of the function for details.
15156 All Modula-2 built-in procedures also return a result, described below.
15160 Returns the absolute value of @var{n}.
15163 If @var{c} is a lower case letter, it returns its upper case
15164 equivalent, otherwise it returns its argument.
15167 Returns the character whose ordinal value is @var{i}.
15170 Decrements the value in the variable @var{v} by one. Returns the new value.
15172 @item DEC(@var{v},@var{i})
15173 Decrements the value in the variable @var{v} by @var{i}. Returns the
15176 @item EXCL(@var{m},@var{s})
15177 Removes the element @var{m} from the set @var{s}. Returns the new
15180 @item FLOAT(@var{i})
15181 Returns the floating point equivalent of the integer @var{i}.
15183 @item HIGH(@var{a})
15184 Returns the index of the last member of @var{a}.
15187 Increments the value in the variable @var{v} by one. Returns the new value.
15189 @item INC(@var{v},@var{i})
15190 Increments the value in the variable @var{v} by @var{i}. Returns the
15193 @item INCL(@var{m},@var{s})
15194 Adds the element @var{m} to the set @var{s} if it is not already
15195 there. Returns the new set.
15198 Returns the maximum value of the type @var{t}.
15201 Returns the minimum value of the type @var{t}.
15204 Returns boolean TRUE if @var{i} is an odd number.
15207 Returns the ordinal value of its argument. For example, the ordinal
15208 value of a character is its @sc{ascii} value (on machines supporting
15209 the @sc{ascii} character set). The argument @var{x} must be of an
15210 ordered type, which include integral, character and enumerated types.
15212 @item SIZE(@var{x})
15213 Returns the size of its argument. The argument @var{x} can be a
15214 variable or a type.
15216 @item TRUNC(@var{r})
15217 Returns the integral part of @var{r}.
15219 @item TSIZE(@var{x})
15220 Returns the size of its argument. The argument @var{x} can be a
15221 variable or a type.
15223 @item VAL(@var{t},@var{i})
15224 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15228 @emph{Warning:} Sets and their operations are not yet supported, so
15229 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15233 @cindex Modula-2 constants
15235 @subsubsection Constants
15237 @value{GDBN} allows you to express the constants of Modula-2 in the following
15243 Integer constants are simply a sequence of digits. When used in an
15244 expression, a constant is interpreted to be type-compatible with the
15245 rest of the expression. Hexadecimal integers are specified by a
15246 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15249 Floating point constants appear as a sequence of digits, followed by a
15250 decimal point and another sequence of digits. An optional exponent can
15251 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15252 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15253 digits of the floating point constant must be valid decimal (base 10)
15257 Character constants consist of a single character enclosed by a pair of
15258 like quotes, either single (@code{'}) or double (@code{"}). They may
15259 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15260 followed by a @samp{C}.
15263 String constants consist of a sequence of characters enclosed by a
15264 pair of like quotes, either single (@code{'}) or double (@code{"}).
15265 Escape sequences in the style of C are also allowed. @xref{C
15266 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15270 Enumerated constants consist of an enumerated identifier.
15273 Boolean constants consist of the identifiers @code{TRUE} and
15277 Pointer constants consist of integral values only.
15280 Set constants are not yet supported.
15284 @subsubsection Modula-2 Types
15285 @cindex Modula-2 types
15287 Currently @value{GDBN} can print the following data types in Modula-2
15288 syntax: array types, record types, set types, pointer types, procedure
15289 types, enumerated types, subrange types and base types. You can also
15290 print the contents of variables declared using these type.
15291 This section gives a number of simple source code examples together with
15292 sample @value{GDBN} sessions.
15294 The first example contains the following section of code:
15303 and you can request @value{GDBN} to interrogate the type and value of
15304 @code{r} and @code{s}.
15307 (@value{GDBP}) print s
15309 (@value{GDBP}) ptype s
15311 (@value{GDBP}) print r
15313 (@value{GDBP}) ptype r
15318 Likewise if your source code declares @code{s} as:
15322 s: SET ['A'..'Z'] ;
15326 then you may query the type of @code{s} by:
15329 (@value{GDBP}) ptype s
15330 type = SET ['A'..'Z']
15334 Note that at present you cannot interactively manipulate set
15335 expressions using the debugger.
15337 The following example shows how you might declare an array in Modula-2
15338 and how you can interact with @value{GDBN} to print its type and contents:
15342 s: ARRAY [-10..10] OF CHAR ;
15346 (@value{GDBP}) ptype s
15347 ARRAY [-10..10] OF CHAR
15350 Note that the array handling is not yet complete and although the type
15351 is printed correctly, expression handling still assumes that all
15352 arrays have a lower bound of zero and not @code{-10} as in the example
15355 Here are some more type related Modula-2 examples:
15359 colour = (blue, red, yellow, green) ;
15360 t = [blue..yellow] ;
15368 The @value{GDBN} interaction shows how you can query the data type
15369 and value of a variable.
15372 (@value{GDBP}) print s
15374 (@value{GDBP}) ptype t
15375 type = [blue..yellow]
15379 In this example a Modula-2 array is declared and its contents
15380 displayed. Observe that the contents are written in the same way as
15381 their @code{C} counterparts.
15385 s: ARRAY [1..5] OF CARDINAL ;
15391 (@value{GDBP}) print s
15392 $1 = @{1, 0, 0, 0, 0@}
15393 (@value{GDBP}) ptype s
15394 type = ARRAY [1..5] OF CARDINAL
15397 The Modula-2 language interface to @value{GDBN} also understands
15398 pointer types as shown in this example:
15402 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15409 and you can request that @value{GDBN} describes the type of @code{s}.
15412 (@value{GDBP}) ptype s
15413 type = POINTER TO ARRAY [1..5] OF CARDINAL
15416 @value{GDBN} handles compound types as we can see in this example.
15417 Here we combine array types, record types, pointer types and subrange
15428 myarray = ARRAY myrange OF CARDINAL ;
15429 myrange = [-2..2] ;
15431 s: POINTER TO ARRAY myrange OF foo ;
15435 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15439 (@value{GDBP}) ptype s
15440 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15443 f3 : ARRAY [-2..2] OF CARDINAL;
15448 @subsubsection Modula-2 Defaults
15449 @cindex Modula-2 defaults
15451 If type and range checking are set automatically by @value{GDBN}, they
15452 both default to @code{on} whenever the working language changes to
15453 Modula-2. This happens regardless of whether you or @value{GDBN}
15454 selected the working language.
15456 If you allow @value{GDBN} to set the language automatically, then entering
15457 code compiled from a file whose name ends with @file{.mod} sets the
15458 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15459 Infer the Source Language}, for further details.
15462 @subsubsection Deviations from Standard Modula-2
15463 @cindex Modula-2, deviations from
15465 A few changes have been made to make Modula-2 programs easier to debug.
15466 This is done primarily via loosening its type strictness:
15470 Unlike in standard Modula-2, pointer constants can be formed by
15471 integers. This allows you to modify pointer variables during
15472 debugging. (In standard Modula-2, the actual address contained in a
15473 pointer variable is hidden from you; it can only be modified
15474 through direct assignment to another pointer variable or expression that
15475 returned a pointer.)
15478 C escape sequences can be used in strings and characters to represent
15479 non-printable characters. @value{GDBN} prints out strings with these
15480 escape sequences embedded. Single non-printable characters are
15481 printed using the @samp{CHR(@var{nnn})} format.
15484 The assignment operator (@code{:=}) returns the value of its right-hand
15488 All built-in procedures both modify @emph{and} return their argument.
15492 @subsubsection Modula-2 Type and Range Checks
15493 @cindex Modula-2 checks
15496 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15499 @c FIXME remove warning when type/range checks added
15501 @value{GDBN} considers two Modula-2 variables type equivalent if:
15505 They are of types that have been declared equivalent via a @code{TYPE
15506 @var{t1} = @var{t2}} statement
15509 They have been declared on the same line. (Note: This is true of the
15510 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15513 As long as type checking is enabled, any attempt to combine variables
15514 whose types are not equivalent is an error.
15516 Range checking is done on all mathematical operations, assignment, array
15517 index bounds, and all built-in functions and procedures.
15520 @subsubsection The Scope Operators @code{::} and @code{.}
15522 @cindex @code{.}, Modula-2 scope operator
15523 @cindex colon, doubled as scope operator
15525 @vindex colon-colon@r{, in Modula-2}
15526 @c Info cannot handle :: but TeX can.
15529 @vindex ::@r{, in Modula-2}
15532 There are a few subtle differences between the Modula-2 scope operator
15533 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15538 @var{module} . @var{id}
15539 @var{scope} :: @var{id}
15543 where @var{scope} is the name of a module or a procedure,
15544 @var{module} the name of a module, and @var{id} is any declared
15545 identifier within your program, except another module.
15547 Using the @code{::} operator makes @value{GDBN} search the scope
15548 specified by @var{scope} for the identifier @var{id}. If it is not
15549 found in the specified scope, then @value{GDBN} searches all scopes
15550 enclosing the one specified by @var{scope}.
15552 Using the @code{.} operator makes @value{GDBN} search the current scope for
15553 the identifier specified by @var{id} that was imported from the
15554 definition module specified by @var{module}. With this operator, it is
15555 an error if the identifier @var{id} was not imported from definition
15556 module @var{module}, or if @var{id} is not an identifier in
15560 @subsubsection @value{GDBN} and Modula-2
15562 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15563 Five subcommands of @code{set print} and @code{show print} apply
15564 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15565 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15566 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15567 analogue in Modula-2.
15569 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15570 with any language, is not useful with Modula-2. Its
15571 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15572 created in Modula-2 as they can in C or C@t{++}. However, because an
15573 address can be specified by an integral constant, the construct
15574 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15576 @cindex @code{#} in Modula-2
15577 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15578 interpreted as the beginning of a comment. Use @code{<>} instead.
15584 The extensions made to @value{GDBN} for Ada only support
15585 output from the @sc{gnu} Ada (GNAT) compiler.
15586 Other Ada compilers are not currently supported, and
15587 attempting to debug executables produced by them is most likely
15591 @cindex expressions in Ada
15593 * Ada Mode Intro:: General remarks on the Ada syntax
15594 and semantics supported by Ada mode
15596 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15597 * Additions to Ada:: Extensions of the Ada expression syntax.
15598 * Overloading support for Ada:: Support for expressions involving overloaded
15600 * Stopping Before Main Program:: Debugging the program during elaboration.
15601 * Ada Exceptions:: Ada Exceptions
15602 * Ada Tasks:: Listing and setting breakpoints in tasks.
15603 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15604 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15606 * Ada Glitches:: Known peculiarities of Ada mode.
15609 @node Ada Mode Intro
15610 @subsubsection Introduction
15611 @cindex Ada mode, general
15613 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15614 syntax, with some extensions.
15615 The philosophy behind the design of this subset is
15619 That @value{GDBN} should provide basic literals and access to operations for
15620 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15621 leaving more sophisticated computations to subprograms written into the
15622 program (which therefore may be called from @value{GDBN}).
15625 That type safety and strict adherence to Ada language restrictions
15626 are not particularly important to the @value{GDBN} user.
15629 That brevity is important to the @value{GDBN} user.
15632 Thus, for brevity, the debugger acts as if all names declared in
15633 user-written packages are directly visible, even if they are not visible
15634 according to Ada rules, thus making it unnecessary to fully qualify most
15635 names with their packages, regardless of context. Where this causes
15636 ambiguity, @value{GDBN} asks the user's intent.
15638 The debugger will start in Ada mode if it detects an Ada main program.
15639 As for other languages, it will enter Ada mode when stopped in a program that
15640 was translated from an Ada source file.
15642 While in Ada mode, you may use `@t{--}' for comments. This is useful
15643 mostly for documenting command files. The standard @value{GDBN} comment
15644 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15645 middle (to allow based literals).
15647 @node Omissions from Ada
15648 @subsubsection Omissions from Ada
15649 @cindex Ada, omissions from
15651 Here are the notable omissions from the subset:
15655 Only a subset of the attributes are supported:
15659 @t{'First}, @t{'Last}, and @t{'Length}
15660 on array objects (not on types and subtypes).
15663 @t{'Min} and @t{'Max}.
15666 @t{'Pos} and @t{'Val}.
15672 @t{'Range} on array objects (not subtypes), but only as the right
15673 operand of the membership (@code{in}) operator.
15676 @t{'Access}, @t{'Unchecked_Access}, and
15677 @t{'Unrestricted_Access} (a GNAT extension).
15685 @code{Characters.Latin_1} are not available and
15686 concatenation is not implemented. Thus, escape characters in strings are
15687 not currently available.
15690 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15691 equality of representations. They will generally work correctly
15692 for strings and arrays whose elements have integer or enumeration types.
15693 They may not work correctly for arrays whose element
15694 types have user-defined equality, for arrays of real values
15695 (in particular, IEEE-conformant floating point, because of negative
15696 zeroes and NaNs), and for arrays whose elements contain unused bits with
15697 indeterminate values.
15700 The other component-by-component array operations (@code{and}, @code{or},
15701 @code{xor}, @code{not}, and relational tests other than equality)
15702 are not implemented.
15705 @cindex array aggregates (Ada)
15706 @cindex record aggregates (Ada)
15707 @cindex aggregates (Ada)
15708 There is limited support for array and record aggregates. They are
15709 permitted only on the right sides of assignments, as in these examples:
15712 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15713 (@value{GDBP}) set An_Array := (1, others => 0)
15714 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15715 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15716 (@value{GDBP}) set A_Record := (1, "Peter", True);
15717 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15721 discriminant's value by assigning an aggregate has an
15722 undefined effect if that discriminant is used within the record.
15723 However, you can first modify discriminants by directly assigning to
15724 them (which normally would not be allowed in Ada), and then performing an
15725 aggregate assignment. For example, given a variable @code{A_Rec}
15726 declared to have a type such as:
15729 type Rec (Len : Small_Integer := 0) is record
15731 Vals : IntArray (1 .. Len);
15735 you can assign a value with a different size of @code{Vals} with two
15739 (@value{GDBP}) set A_Rec.Len := 4
15740 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15743 As this example also illustrates, @value{GDBN} is very loose about the usual
15744 rules concerning aggregates. You may leave out some of the
15745 components of an array or record aggregate (such as the @code{Len}
15746 component in the assignment to @code{A_Rec} above); they will retain their
15747 original values upon assignment. You may freely use dynamic values as
15748 indices in component associations. You may even use overlapping or
15749 redundant component associations, although which component values are
15750 assigned in such cases is not defined.
15753 Calls to dispatching subprograms are not implemented.
15756 The overloading algorithm is much more limited (i.e., less selective)
15757 than that of real Ada. It makes only limited use of the context in
15758 which a subexpression appears to resolve its meaning, and it is much
15759 looser in its rules for allowing type matches. As a result, some
15760 function calls will be ambiguous, and the user will be asked to choose
15761 the proper resolution.
15764 The @code{new} operator is not implemented.
15767 Entry calls are not implemented.
15770 Aside from printing, arithmetic operations on the native VAX floating-point
15771 formats are not supported.
15774 It is not possible to slice a packed array.
15777 The names @code{True} and @code{False}, when not part of a qualified name,
15778 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15780 Should your program
15781 redefine these names in a package or procedure (at best a dubious practice),
15782 you will have to use fully qualified names to access their new definitions.
15785 @node Additions to Ada
15786 @subsubsection Additions to Ada
15787 @cindex Ada, deviations from
15789 As it does for other languages, @value{GDBN} makes certain generic
15790 extensions to Ada (@pxref{Expressions}):
15794 If the expression @var{E} is a variable residing in memory (typically
15795 a local variable or array element) and @var{N} is a positive integer,
15796 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15797 @var{N}-1 adjacent variables following it in memory as an array. In
15798 Ada, this operator is generally not necessary, since its prime use is
15799 in displaying parts of an array, and slicing will usually do this in
15800 Ada. However, there are occasional uses when debugging programs in
15801 which certain debugging information has been optimized away.
15804 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15805 appears in function or file @var{B}.'' When @var{B} is a file name,
15806 you must typically surround it in single quotes.
15809 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15810 @var{type} that appears at address @var{addr}.''
15813 A name starting with @samp{$} is a convenience variable
15814 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15817 In addition, @value{GDBN} provides a few other shortcuts and outright
15818 additions specific to Ada:
15822 The assignment statement is allowed as an expression, returning
15823 its right-hand operand as its value. Thus, you may enter
15826 (@value{GDBP}) set x := y + 3
15827 (@value{GDBP}) print A(tmp := y + 1)
15831 The semicolon is allowed as an ``operator,'' returning as its value
15832 the value of its right-hand operand.
15833 This allows, for example,
15834 complex conditional breaks:
15837 (@value{GDBP}) break f
15838 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15842 Rather than use catenation and symbolic character names to introduce special
15843 characters into strings, one may instead use a special bracket notation,
15844 which is also used to print strings. A sequence of characters of the form
15845 @samp{["@var{XX}"]} within a string or character literal denotes the
15846 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15847 sequence of characters @samp{["""]} also denotes a single quotation mark
15848 in strings. For example,
15850 "One line.["0a"]Next line.["0a"]"
15853 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15857 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15858 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15862 (@value{GDBP}) print 'max(x, y)
15866 When printing arrays, @value{GDBN} uses positional notation when the
15867 array has a lower bound of 1, and uses a modified named notation otherwise.
15868 For example, a one-dimensional array of three integers with a lower bound
15869 of 3 might print as
15876 That is, in contrast to valid Ada, only the first component has a @code{=>}
15880 You may abbreviate attributes in expressions with any unique,
15881 multi-character subsequence of
15882 their names (an exact match gets preference).
15883 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15884 in place of @t{a'length}.
15887 @cindex quoting Ada internal identifiers
15888 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15889 to lower case. The GNAT compiler uses upper-case characters for
15890 some of its internal identifiers, which are normally of no interest to users.
15891 For the rare occasions when you actually have to look at them,
15892 enclose them in angle brackets to avoid the lower-case mapping.
15895 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15899 Printing an object of class-wide type or dereferencing an
15900 access-to-class-wide value will display all the components of the object's
15901 specific type (as indicated by its run-time tag). Likewise, component
15902 selection on such a value will operate on the specific type of the
15907 @node Overloading support for Ada
15908 @subsubsection Overloading support for Ada
15909 @cindex overloading, Ada
15911 The debugger supports limited overloading. Given a subprogram call in which
15912 the function symbol has multiple definitions, it will use the number of
15913 actual parameters and some information about their types to attempt to narrow
15914 the set of definitions. It also makes very limited use of context, preferring
15915 procedures to functions in the context of the @code{call} command, and
15916 functions to procedures elsewhere.
15918 If, after narrowing, the set of matching definitions still contains more than
15919 one definition, @value{GDBN} will display a menu to query which one it should
15923 (@value{GDBP}) print f(1)
15924 Multiple matches for f
15926 [1] foo.f (integer) return boolean at foo.adb:23
15927 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15931 In this case, just select one menu entry either to cancel expression evaluation
15932 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
15933 instance (type the corresponding number and press @key{RET}).
15935 Here are a couple of commands to customize @value{GDBN}'s behavior in this
15940 @kindex set ada print-signatures
15941 @item set ada print-signatures
15942 Control whether parameter types and return types are displayed in overloads
15943 selection menus. It is @code{on} by default.
15944 @xref{Overloading support for Ada}.
15946 @kindex show ada print-signatures
15947 @item show ada print-signatures
15948 Show the current setting for displaying parameter types and return types in
15949 overloads selection menu.
15950 @xref{Overloading support for Ada}.
15954 @node Stopping Before Main Program
15955 @subsubsection Stopping at the Very Beginning
15957 @cindex breakpointing Ada elaboration code
15958 It is sometimes necessary to debug the program during elaboration, and
15959 before reaching the main procedure.
15960 As defined in the Ada Reference
15961 Manual, the elaboration code is invoked from a procedure called
15962 @code{adainit}. To run your program up to the beginning of
15963 elaboration, simply use the following two commands:
15964 @code{tbreak adainit} and @code{run}.
15966 @node Ada Exceptions
15967 @subsubsection Ada Exceptions
15969 A command is provided to list all Ada exceptions:
15972 @kindex info exceptions
15973 @item info exceptions
15974 @itemx info exceptions @var{regexp}
15975 The @code{info exceptions} command allows you to list all Ada exceptions
15976 defined within the program being debugged, as well as their addresses.
15977 With a regular expression, @var{regexp}, as argument, only those exceptions
15978 whose names match @var{regexp} are listed.
15981 Below is a small example, showing how the command can be used, first
15982 without argument, and next with a regular expression passed as an
15986 (@value{GDBP}) info exceptions
15987 All defined Ada exceptions:
15988 constraint_error: 0x613da0
15989 program_error: 0x613d20
15990 storage_error: 0x613ce0
15991 tasking_error: 0x613ca0
15992 const.aint_global_e: 0x613b00
15993 (@value{GDBP}) info exceptions const.aint
15994 All Ada exceptions matching regular expression "const.aint":
15995 constraint_error: 0x613da0
15996 const.aint_global_e: 0x613b00
15999 It is also possible to ask @value{GDBN} to stop your program's execution
16000 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16003 @subsubsection Extensions for Ada Tasks
16004 @cindex Ada, tasking
16006 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16007 @value{GDBN} provides the following task-related commands:
16012 This command shows a list of current Ada tasks, as in the following example:
16019 (@value{GDBP}) info tasks
16020 ID TID P-ID Pri State Name
16021 1 8088000 0 15 Child Activation Wait main_task
16022 2 80a4000 1 15 Accept Statement b
16023 3 809a800 1 15 Child Activation Wait a
16024 * 4 80ae800 3 15 Runnable c
16029 In this listing, the asterisk before the last task indicates it to be the
16030 task currently being inspected.
16034 Represents @value{GDBN}'s internal task number.
16040 The parent's task ID (@value{GDBN}'s internal task number).
16043 The base priority of the task.
16046 Current state of the task.
16050 The task has been created but has not been activated. It cannot be
16054 The task is not blocked for any reason known to Ada. (It may be waiting
16055 for a mutex, though.) It is conceptually "executing" in normal mode.
16058 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16059 that were waiting on terminate alternatives have been awakened and have
16060 terminated themselves.
16062 @item Child Activation Wait
16063 The task is waiting for created tasks to complete activation.
16065 @item Accept Statement
16066 The task is waiting on an accept or selective wait statement.
16068 @item Waiting on entry call
16069 The task is waiting on an entry call.
16071 @item Async Select Wait
16072 The task is waiting to start the abortable part of an asynchronous
16076 The task is waiting on a select statement with only a delay
16079 @item Child Termination Wait
16080 The task is sleeping having completed a master within itself, and is
16081 waiting for the tasks dependent on that master to become terminated or
16082 waiting on a terminate Phase.
16084 @item Wait Child in Term Alt
16085 The task is sleeping waiting for tasks on terminate alternatives to
16086 finish terminating.
16088 @item Accepting RV with @var{taskno}
16089 The task is accepting a rendez-vous with the task @var{taskno}.
16093 Name of the task in the program.
16097 @kindex info task @var{taskno}
16098 @item info task @var{taskno}
16099 This command shows detailled informations on the specified task, as in
16100 the following example:
16105 (@value{GDBP}) info tasks
16106 ID TID P-ID Pri State Name
16107 1 8077880 0 15 Child Activation Wait main_task
16108 * 2 807c468 1 15 Runnable task_1
16109 (@value{GDBP}) info task 2
16110 Ada Task: 0x807c468
16113 Parent: 1 (main_task)
16119 @kindex task@r{ (Ada)}
16120 @cindex current Ada task ID
16121 This command prints the ID of the current task.
16127 (@value{GDBP}) info tasks
16128 ID TID P-ID Pri State Name
16129 1 8077870 0 15 Child Activation Wait main_task
16130 * 2 807c458 1 15 Runnable t
16131 (@value{GDBP}) task
16132 [Current task is 2]
16135 @item task @var{taskno}
16136 @cindex Ada task switching
16137 This command is like the @code{thread @var{threadno}}
16138 command (@pxref{Threads}). It switches the context of debugging
16139 from the current task to the given task.
16145 (@value{GDBP}) info tasks
16146 ID TID P-ID Pri State Name
16147 1 8077870 0 15 Child Activation Wait main_task
16148 * 2 807c458 1 15 Runnable t
16149 (@value{GDBP}) task 1
16150 [Switching to task 1]
16151 #0 0x8067726 in pthread_cond_wait ()
16153 #0 0x8067726 in pthread_cond_wait ()
16154 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16155 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16156 #3 0x806153e in system.tasking.stages.activate_tasks ()
16157 #4 0x804aacc in un () at un.adb:5
16160 @item break @var{location} task @var{taskno}
16161 @itemx break @var{location} task @var{taskno} if @dots{}
16162 @cindex breakpoints and tasks, in Ada
16163 @cindex task breakpoints, in Ada
16164 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16165 These commands are like the @code{break @dots{} thread @dots{}}
16166 command (@pxref{Thread Stops}). The
16167 @var{location} argument specifies source lines, as described
16168 in @ref{Specify Location}.
16170 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16171 to specify that you only want @value{GDBN} to stop the program when a
16172 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16173 numeric task identifiers assigned by @value{GDBN}, shown in the first
16174 column of the @samp{info tasks} display.
16176 If you do not specify @samp{task @var{taskno}} when you set a
16177 breakpoint, the breakpoint applies to @emph{all} tasks of your
16180 You can use the @code{task} qualifier on conditional breakpoints as
16181 well; in this case, place @samp{task @var{taskno}} before the
16182 breakpoint condition (before the @code{if}).
16190 (@value{GDBP}) info tasks
16191 ID TID P-ID Pri State Name
16192 1 140022020 0 15 Child Activation Wait main_task
16193 2 140045060 1 15 Accept/Select Wait t2
16194 3 140044840 1 15 Runnable t1
16195 * 4 140056040 1 15 Runnable t3
16196 (@value{GDBP}) b 15 task 2
16197 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16198 (@value{GDBP}) cont
16203 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16205 (@value{GDBP}) info tasks
16206 ID TID P-ID Pri State Name
16207 1 140022020 0 15 Child Activation Wait main_task
16208 * 2 140045060 1 15 Runnable t2
16209 3 140044840 1 15 Runnable t1
16210 4 140056040 1 15 Delay Sleep t3
16214 @node Ada Tasks and Core Files
16215 @subsubsection Tasking Support when Debugging Core Files
16216 @cindex Ada tasking and core file debugging
16218 When inspecting a core file, as opposed to debugging a live program,
16219 tasking support may be limited or even unavailable, depending on
16220 the platform being used.
16221 For instance, on x86-linux, the list of tasks is available, but task
16222 switching is not supported.
16224 On certain platforms, the debugger needs to perform some
16225 memory writes in order to provide Ada tasking support. When inspecting
16226 a core file, this means that the core file must be opened with read-write
16227 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16228 Under these circumstances, you should make a backup copy of the core
16229 file before inspecting it with @value{GDBN}.
16231 @node Ravenscar Profile
16232 @subsubsection Tasking Support when using the Ravenscar Profile
16233 @cindex Ravenscar Profile
16235 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16236 specifically designed for systems with safety-critical real-time
16240 @kindex set ravenscar task-switching on
16241 @cindex task switching with program using Ravenscar Profile
16242 @item set ravenscar task-switching on
16243 Allows task switching when debugging a program that uses the Ravenscar
16244 Profile. This is the default.
16246 @kindex set ravenscar task-switching off
16247 @item set ravenscar task-switching off
16248 Turn off task switching when debugging a program that uses the Ravenscar
16249 Profile. This is mostly intended to disable the code that adds support
16250 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16251 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16252 To be effective, this command should be run before the program is started.
16254 @kindex show ravenscar task-switching
16255 @item show ravenscar task-switching
16256 Show whether it is possible to switch from task to task in a program
16257 using the Ravenscar Profile.
16262 @subsubsection Known Peculiarities of Ada Mode
16263 @cindex Ada, problems
16265 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16266 we know of several problems with and limitations of Ada mode in
16268 some of which will be fixed with planned future releases of the debugger
16269 and the GNU Ada compiler.
16273 Static constants that the compiler chooses not to materialize as objects in
16274 storage are invisible to the debugger.
16277 Named parameter associations in function argument lists are ignored (the
16278 argument lists are treated as positional).
16281 Many useful library packages are currently invisible to the debugger.
16284 Fixed-point arithmetic, conversions, input, and output is carried out using
16285 floating-point arithmetic, and may give results that only approximate those on
16289 The GNAT compiler never generates the prefix @code{Standard} for any of
16290 the standard symbols defined by the Ada language. @value{GDBN} knows about
16291 this: it will strip the prefix from names when you use it, and will never
16292 look for a name you have so qualified among local symbols, nor match against
16293 symbols in other packages or subprograms. If you have
16294 defined entities anywhere in your program other than parameters and
16295 local variables whose simple names match names in @code{Standard},
16296 GNAT's lack of qualification here can cause confusion. When this happens,
16297 you can usually resolve the confusion
16298 by qualifying the problematic names with package
16299 @code{Standard} explicitly.
16302 Older versions of the compiler sometimes generate erroneous debugging
16303 information, resulting in the debugger incorrectly printing the value
16304 of affected entities. In some cases, the debugger is able to work
16305 around an issue automatically. In other cases, the debugger is able
16306 to work around the issue, but the work-around has to be specifically
16309 @kindex set ada trust-PAD-over-XVS
16310 @kindex show ada trust-PAD-over-XVS
16313 @item set ada trust-PAD-over-XVS on
16314 Configure GDB to strictly follow the GNAT encoding when computing the
16315 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16316 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16317 a complete description of the encoding used by the GNAT compiler).
16318 This is the default.
16320 @item set ada trust-PAD-over-XVS off
16321 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16322 sometimes prints the wrong value for certain entities, changing @code{ada
16323 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16324 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16325 @code{off}, but this incurs a slight performance penalty, so it is
16326 recommended to leave this setting to @code{on} unless necessary.
16330 @cindex GNAT descriptive types
16331 @cindex GNAT encoding
16332 Internally, the debugger also relies on the compiler following a number
16333 of conventions known as the @samp{GNAT Encoding}, all documented in
16334 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16335 how the debugging information should be generated for certain types.
16336 In particular, this convention makes use of @dfn{descriptive types},
16337 which are artificial types generated purely to help the debugger.
16339 These encodings were defined at a time when the debugging information
16340 format used was not powerful enough to describe some of the more complex
16341 types available in Ada. Since DWARF allows us to express nearly all
16342 Ada features, the long-term goal is to slowly replace these descriptive
16343 types by their pure DWARF equivalent. To facilitate that transition,
16344 a new maintenance option is available to force the debugger to ignore
16345 those descriptive types. It allows the user to quickly evaluate how
16346 well @value{GDBN} works without them.
16350 @kindex maint ada set ignore-descriptive-types
16351 @item maintenance ada set ignore-descriptive-types [on|off]
16352 Control whether the debugger should ignore descriptive types.
16353 The default is not to ignore descriptives types (@code{off}).
16355 @kindex maint ada show ignore-descriptive-types
16356 @item maintenance ada show ignore-descriptive-types
16357 Show if descriptive types are ignored by @value{GDBN}.
16361 @node Unsupported Languages
16362 @section Unsupported Languages
16364 @cindex unsupported languages
16365 @cindex minimal language
16366 In addition to the other fully-supported programming languages,
16367 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16368 It does not represent a real programming language, but provides a set
16369 of capabilities close to what the C or assembly languages provide.
16370 This should allow most simple operations to be performed while debugging
16371 an application that uses a language currently not supported by @value{GDBN}.
16373 If the language is set to @code{auto}, @value{GDBN} will automatically
16374 select this language if the current frame corresponds to an unsupported
16378 @chapter Examining the Symbol Table
16380 The commands described in this chapter allow you to inquire about the
16381 symbols (names of variables, functions and types) defined in your
16382 program. This information is inherent in the text of your program and
16383 does not change as your program executes. @value{GDBN} finds it in your
16384 program's symbol table, in the file indicated when you started @value{GDBN}
16385 (@pxref{File Options, ,Choosing Files}), or by one of the
16386 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16388 @cindex symbol names
16389 @cindex names of symbols
16390 @cindex quoting names
16391 Occasionally, you may need to refer to symbols that contain unusual
16392 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16393 most frequent case is in referring to static variables in other
16394 source files (@pxref{Variables,,Program Variables}). File names
16395 are recorded in object files as debugging symbols, but @value{GDBN} would
16396 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16397 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16398 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16405 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16408 @cindex case-insensitive symbol names
16409 @cindex case sensitivity in symbol names
16410 @kindex set case-sensitive
16411 @item set case-sensitive on
16412 @itemx set case-sensitive off
16413 @itemx set case-sensitive auto
16414 Normally, when @value{GDBN} looks up symbols, it matches their names
16415 with case sensitivity determined by the current source language.
16416 Occasionally, you may wish to control that. The command @code{set
16417 case-sensitive} lets you do that by specifying @code{on} for
16418 case-sensitive matches or @code{off} for case-insensitive ones. If
16419 you specify @code{auto}, case sensitivity is reset to the default
16420 suitable for the source language. The default is case-sensitive
16421 matches for all languages except for Fortran, for which the default is
16422 case-insensitive matches.
16424 @kindex show case-sensitive
16425 @item show case-sensitive
16426 This command shows the current setting of case sensitivity for symbols
16429 @kindex set print type methods
16430 @item set print type methods
16431 @itemx set print type methods on
16432 @itemx set print type methods off
16433 Normally, when @value{GDBN} prints a class, it displays any methods
16434 declared in that class. You can control this behavior either by
16435 passing the appropriate flag to @code{ptype}, or using @command{set
16436 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16437 display the methods; this is the default. Specifying @code{off} will
16438 cause @value{GDBN} to omit the methods.
16440 @kindex show print type methods
16441 @item show print type methods
16442 This command shows the current setting of method display when printing
16445 @kindex set print type typedefs
16446 @item set print type typedefs
16447 @itemx set print type typedefs on
16448 @itemx set print type typedefs off
16450 Normally, when @value{GDBN} prints a class, it displays any typedefs
16451 defined in that class. You can control this behavior either by
16452 passing the appropriate flag to @code{ptype}, or using @command{set
16453 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16454 display the typedef definitions; this is the default. Specifying
16455 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16456 Note that this controls whether the typedef definition itself is
16457 printed, not whether typedef names are substituted when printing other
16460 @kindex show print type typedefs
16461 @item show print type typedefs
16462 This command shows the current setting of typedef display when
16465 @kindex info address
16466 @cindex address of a symbol
16467 @item info address @var{symbol}
16468 Describe where the data for @var{symbol} is stored. For a register
16469 variable, this says which register it is kept in. For a non-register
16470 local variable, this prints the stack-frame offset at which the variable
16473 Note the contrast with @samp{print &@var{symbol}}, which does not work
16474 at all for a register variable, and for a stack local variable prints
16475 the exact address of the current instantiation of the variable.
16477 @kindex info symbol
16478 @cindex symbol from address
16479 @cindex closest symbol and offset for an address
16480 @item info symbol @var{addr}
16481 Print the name of a symbol which is stored at the address @var{addr}.
16482 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16483 nearest symbol and an offset from it:
16486 (@value{GDBP}) info symbol 0x54320
16487 _initialize_vx + 396 in section .text
16491 This is the opposite of the @code{info address} command. You can use
16492 it to find out the name of a variable or a function given its address.
16494 For dynamically linked executables, the name of executable or shared
16495 library containing the symbol is also printed:
16498 (@value{GDBP}) info symbol 0x400225
16499 _start + 5 in section .text of /tmp/a.out
16500 (@value{GDBP}) info symbol 0x2aaaac2811cf
16501 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16506 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16507 Demangle @var{name}.
16508 If @var{language} is provided it is the name of the language to demangle
16509 @var{name} in. Otherwise @var{name} is demangled in the current language.
16511 The @samp{--} option specifies the end of options,
16512 and is useful when @var{name} begins with a dash.
16514 The parameter @code{demangle-style} specifies how to interpret the kind
16515 of mangling used. @xref{Print Settings}.
16518 @item whatis[/@var{flags}] [@var{arg}]
16519 Print the data type of @var{arg}, which can be either an expression
16520 or a name of a data type. With no argument, print the data type of
16521 @code{$}, the last value in the value history.
16523 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16524 is not actually evaluated, and any side-effecting operations (such as
16525 assignments or function calls) inside it do not take place.
16527 If @var{arg} is a variable or an expression, @code{whatis} prints its
16528 literal type as it is used in the source code. If the type was
16529 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16530 the data type underlying the @code{typedef}. If the type of the
16531 variable or the expression is a compound data type, such as
16532 @code{struct} or @code{class}, @code{whatis} never prints their
16533 fields or methods. It just prints the @code{struct}/@code{class}
16534 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16535 such a compound data type, use @code{ptype}.
16537 If @var{arg} is a type name that was defined using @code{typedef},
16538 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16539 Unrolling means that @code{whatis} will show the underlying type used
16540 in the @code{typedef} declaration of @var{arg}. However, if that
16541 underlying type is also a @code{typedef}, @code{whatis} will not
16544 For C code, the type names may also have the form @samp{class
16545 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16546 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16548 @var{flags} can be used to modify how the type is displayed.
16549 Available flags are:
16553 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16554 parameters and typedefs defined in a class when printing the class'
16555 members. The @code{/r} flag disables this.
16558 Do not print methods defined in the class.
16561 Print methods defined in the class. This is the default, but the flag
16562 exists in case you change the default with @command{set print type methods}.
16565 Do not print typedefs defined in the class. Note that this controls
16566 whether the typedef definition itself is printed, not whether typedef
16567 names are substituted when printing other types.
16570 Print typedefs defined in the class. This is the default, but the flag
16571 exists in case you change the default with @command{set print type typedefs}.
16575 @item ptype[/@var{flags}] [@var{arg}]
16576 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16577 detailed description of the type, instead of just the name of the type.
16578 @xref{Expressions, ,Expressions}.
16580 Contrary to @code{whatis}, @code{ptype} always unrolls any
16581 @code{typedef}s in its argument declaration, whether the argument is
16582 a variable, expression, or a data type. This means that @code{ptype}
16583 of a variable or an expression will not print literally its type as
16584 present in the source code---use @code{whatis} for that. @code{typedef}s at
16585 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16586 fields, methods and inner @code{class typedef}s of @code{struct}s,
16587 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16589 For example, for this variable declaration:
16592 typedef double real_t;
16593 struct complex @{ real_t real; double imag; @};
16594 typedef struct complex complex_t;
16596 real_t *real_pointer_var;
16600 the two commands give this output:
16604 (@value{GDBP}) whatis var
16606 (@value{GDBP}) ptype var
16607 type = struct complex @{
16611 (@value{GDBP}) whatis complex_t
16612 type = struct complex
16613 (@value{GDBP}) whatis struct complex
16614 type = struct complex
16615 (@value{GDBP}) ptype struct complex
16616 type = struct complex @{
16620 (@value{GDBP}) whatis real_pointer_var
16622 (@value{GDBP}) ptype real_pointer_var
16628 As with @code{whatis}, using @code{ptype} without an argument refers to
16629 the type of @code{$}, the last value in the value history.
16631 @cindex incomplete type
16632 Sometimes, programs use opaque data types or incomplete specifications
16633 of complex data structure. If the debug information included in the
16634 program does not allow @value{GDBN} to display a full declaration of
16635 the data type, it will say @samp{<incomplete type>}. For example,
16636 given these declarations:
16640 struct foo *fooptr;
16644 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16647 (@value{GDBP}) ptype foo
16648 $1 = <incomplete type>
16652 ``Incomplete type'' is C terminology for data types that are not
16653 completely specified.
16656 @item info types @var{regexp}
16658 Print a brief description of all types whose names match the regular
16659 expression @var{regexp} (or all types in your program, if you supply
16660 no argument). Each complete typename is matched as though it were a
16661 complete line; thus, @samp{i type value} gives information on all
16662 types in your program whose names include the string @code{value}, but
16663 @samp{i type ^value$} gives information only on types whose complete
16664 name is @code{value}.
16666 This command differs from @code{ptype} in two ways: first, like
16667 @code{whatis}, it does not print a detailed description; second, it
16668 lists all source files where a type is defined.
16670 @kindex info type-printers
16671 @item info type-printers
16672 Versions of @value{GDBN} that ship with Python scripting enabled may
16673 have ``type printers'' available. When using @command{ptype} or
16674 @command{whatis}, these printers are consulted when the name of a type
16675 is needed. @xref{Type Printing API}, for more information on writing
16678 @code{info type-printers} displays all the available type printers.
16680 @kindex enable type-printer
16681 @kindex disable type-printer
16682 @item enable type-printer @var{name}@dots{}
16683 @item disable type-printer @var{name}@dots{}
16684 These commands can be used to enable or disable type printers.
16687 @cindex local variables
16688 @item info scope @var{location}
16689 List all the variables local to a particular scope. This command
16690 accepts a @var{location} argument---a function name, a source line, or
16691 an address preceded by a @samp{*}, and prints all the variables local
16692 to the scope defined by that location. (@xref{Specify Location}, for
16693 details about supported forms of @var{location}.) For example:
16696 (@value{GDBP}) @b{info scope command_line_handler}
16697 Scope for command_line_handler:
16698 Symbol rl is an argument at stack/frame offset 8, length 4.
16699 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16700 Symbol linelength is in static storage at address 0x150a1c, length 4.
16701 Symbol p is a local variable in register $esi, length 4.
16702 Symbol p1 is a local variable in register $ebx, length 4.
16703 Symbol nline is a local variable in register $edx, length 4.
16704 Symbol repeat is a local variable at frame offset -8, length 4.
16708 This command is especially useful for determining what data to collect
16709 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16712 @kindex info source
16714 Show information about the current source file---that is, the source file for
16715 the function containing the current point of execution:
16718 the name of the source file, and the directory containing it,
16720 the directory it was compiled in,
16722 its length, in lines,
16724 which programming language it is written in,
16726 if the debug information provides it, the program that compiled the file
16727 (which may include, e.g., the compiler version and command line arguments),
16729 whether the executable includes debugging information for that file, and
16730 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16732 whether the debugging information includes information about
16733 preprocessor macros.
16737 @kindex info sources
16739 Print the names of all source files in your program for which there is
16740 debugging information, organized into two lists: files whose symbols
16741 have already been read, and files whose symbols will be read when needed.
16743 @kindex info functions
16744 @item info functions
16745 Print the names and data types of all defined functions.
16747 @item info functions @var{regexp}
16748 Print the names and data types of all defined functions
16749 whose names contain a match for regular expression @var{regexp}.
16750 Thus, @samp{info fun step} finds all functions whose names
16751 include @code{step}; @samp{info fun ^step} finds those whose names
16752 start with @code{step}. If a function name contains characters
16753 that conflict with the regular expression language (e.g.@:
16754 @samp{operator*()}), they may be quoted with a backslash.
16756 @kindex info variables
16757 @item info variables
16758 Print the names and data types of all variables that are defined
16759 outside of functions (i.e.@: excluding local variables).
16761 @item info variables @var{regexp}
16762 Print the names and data types of all variables (except for local
16763 variables) whose names contain a match for regular expression
16766 @kindex info classes
16767 @cindex Objective-C, classes and selectors
16769 @itemx info classes @var{regexp}
16770 Display all Objective-C classes in your program, or
16771 (with the @var{regexp} argument) all those matching a particular regular
16774 @kindex info selectors
16775 @item info selectors
16776 @itemx info selectors @var{regexp}
16777 Display all Objective-C selectors in your program, or
16778 (with the @var{regexp} argument) all those matching a particular regular
16782 This was never implemented.
16783 @kindex info methods
16785 @itemx info methods @var{regexp}
16786 The @code{info methods} command permits the user to examine all defined
16787 methods within C@t{++} program, or (with the @var{regexp} argument) a
16788 specific set of methods found in the various C@t{++} classes. Many
16789 C@t{++} classes provide a large number of methods. Thus, the output
16790 from the @code{ptype} command can be overwhelming and hard to use. The
16791 @code{info-methods} command filters the methods, printing only those
16792 which match the regular-expression @var{regexp}.
16795 @cindex opaque data types
16796 @kindex set opaque-type-resolution
16797 @item set opaque-type-resolution on
16798 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16799 declared as a pointer to a @code{struct}, @code{class}, or
16800 @code{union}---for example, @code{struct MyType *}---that is used in one
16801 source file although the full declaration of @code{struct MyType} is in
16802 another source file. The default is on.
16804 A change in the setting of this subcommand will not take effect until
16805 the next time symbols for a file are loaded.
16807 @item set opaque-type-resolution off
16808 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16809 is printed as follows:
16811 @{<no data fields>@}
16814 @kindex show opaque-type-resolution
16815 @item show opaque-type-resolution
16816 Show whether opaque types are resolved or not.
16818 @kindex set print symbol-loading
16819 @cindex print messages when symbols are loaded
16820 @item set print symbol-loading
16821 @itemx set print symbol-loading full
16822 @itemx set print symbol-loading brief
16823 @itemx set print symbol-loading off
16824 The @code{set print symbol-loading} command allows you to control the
16825 printing of messages when @value{GDBN} loads symbol information.
16826 By default a message is printed for the executable and one for each
16827 shared library, and normally this is what you want. However, when
16828 debugging apps with large numbers of shared libraries these messages
16830 When set to @code{brief} a message is printed for each executable,
16831 and when @value{GDBN} loads a collection of shared libraries at once
16832 it will only print one message regardless of the number of shared
16833 libraries. When set to @code{off} no messages are printed.
16835 @kindex show print symbol-loading
16836 @item show print symbol-loading
16837 Show whether messages will be printed when a @value{GDBN} command
16838 entered from the keyboard causes symbol information to be loaded.
16840 @kindex maint print symbols
16841 @cindex symbol dump
16842 @kindex maint print psymbols
16843 @cindex partial symbol dump
16844 @kindex maint print msymbols
16845 @cindex minimal symbol dump
16846 @item maint print symbols @var{filename}
16847 @itemx maint print psymbols @var{filename}
16848 @itemx maint print msymbols @var{filename}
16849 Write a dump of debugging symbol data into the file @var{filename}.
16850 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16851 symbols with debugging data are included. If you use @samp{maint print
16852 symbols}, @value{GDBN} includes all the symbols for which it has already
16853 collected full details: that is, @var{filename} reflects symbols for
16854 only those files whose symbols @value{GDBN} has read. You can use the
16855 command @code{info sources} to find out which files these are. If you
16856 use @samp{maint print psymbols} instead, the dump shows information about
16857 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16858 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16859 @samp{maint print msymbols} dumps just the minimal symbol information
16860 required for each object file from which @value{GDBN} has read some symbols.
16861 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16862 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16864 @kindex maint info symtabs
16865 @kindex maint info psymtabs
16866 @cindex listing @value{GDBN}'s internal symbol tables
16867 @cindex symbol tables, listing @value{GDBN}'s internal
16868 @cindex full symbol tables, listing @value{GDBN}'s internal
16869 @cindex partial symbol tables, listing @value{GDBN}'s internal
16870 @item maint info symtabs @r{[} @var{regexp} @r{]}
16871 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16873 List the @code{struct symtab} or @code{struct partial_symtab}
16874 structures whose names match @var{regexp}. If @var{regexp} is not
16875 given, list them all. The output includes expressions which you can
16876 copy into a @value{GDBN} debugging this one to examine a particular
16877 structure in more detail. For example:
16880 (@value{GDBP}) maint info psymtabs dwarf2read
16881 @{ objfile /home/gnu/build/gdb/gdb
16882 ((struct objfile *) 0x82e69d0)
16883 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16884 ((struct partial_symtab *) 0x8474b10)
16887 text addresses 0x814d3c8 -- 0x8158074
16888 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16889 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16890 dependencies (none)
16893 (@value{GDBP}) maint info symtabs
16897 We see that there is one partial symbol table whose filename contains
16898 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16899 and we see that @value{GDBN} has not read in any symtabs yet at all.
16900 If we set a breakpoint on a function, that will cause @value{GDBN} to
16901 read the symtab for the compilation unit containing that function:
16904 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16905 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16907 (@value{GDBP}) maint info symtabs
16908 @{ objfile /home/gnu/build/gdb/gdb
16909 ((struct objfile *) 0x82e69d0)
16910 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16911 ((struct symtab *) 0x86c1f38)
16914 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16915 linetable ((struct linetable *) 0x8370fa0)
16916 debugformat DWARF 2
16922 @kindex maint set symbol-cache-size
16923 @cindex symbol cache size
16924 @item maint set symbol-cache-size @var{size}
16925 Set the size of the symbol cache to @var{size}.
16926 The default size is intended to be good enough for debugging
16927 most applications. This option exists to allow for experimenting
16928 with different sizes.
16930 @kindex maint show symbol-cache-size
16931 @item maint show symbol-cache-size
16932 Show the size of the symbol cache.
16934 @kindex maint print symbol-cache
16935 @cindex symbol cache, printing its contents
16936 @item maint print symbol-cache
16937 Print the contents of the symbol cache.
16938 This is useful when debugging symbol cache issues.
16940 @kindex maint print symbol-cache-statistics
16941 @cindex symbol cache, printing usage statistics
16942 @item maint print symbol-cache-statistics
16943 Print symbol cache usage statistics.
16944 This helps determine how well the cache is being utilized.
16946 @kindex maint flush-symbol-cache
16947 @cindex symbol cache, flushing
16948 @item maint flush-symbol-cache
16949 Flush the contents of the symbol cache, all entries are removed.
16950 This command is useful when debugging the symbol cache.
16951 It is also useful when collecting performance data.
16956 @chapter Altering Execution
16958 Once you think you have found an error in your program, you might want to
16959 find out for certain whether correcting the apparent error would lead to
16960 correct results in the rest of the run. You can find the answer by
16961 experiment, using the @value{GDBN} features for altering execution of the
16964 For example, you can store new values into variables or memory
16965 locations, give your program a signal, restart it at a different
16966 address, or even return prematurely from a function.
16969 * Assignment:: Assignment to variables
16970 * Jumping:: Continuing at a different address
16971 * Signaling:: Giving your program a signal
16972 * Returning:: Returning from a function
16973 * Calling:: Calling your program's functions
16974 * Patching:: Patching your program
16975 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16979 @section Assignment to Variables
16982 @cindex setting variables
16983 To alter the value of a variable, evaluate an assignment expression.
16984 @xref{Expressions, ,Expressions}. For example,
16991 stores the value 4 into the variable @code{x}, and then prints the
16992 value of the assignment expression (which is 4).
16993 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16994 information on operators in supported languages.
16996 @kindex set variable
16997 @cindex variables, setting
16998 If you are not interested in seeing the value of the assignment, use the
16999 @code{set} command instead of the @code{print} command. @code{set} is
17000 really the same as @code{print} except that the expression's value is
17001 not printed and is not put in the value history (@pxref{Value History,
17002 ,Value History}). The expression is evaluated only for its effects.
17004 If the beginning of the argument string of the @code{set} command
17005 appears identical to a @code{set} subcommand, use the @code{set
17006 variable} command instead of just @code{set}. This command is identical
17007 to @code{set} except for its lack of subcommands. For example, if your
17008 program has a variable @code{width}, you get an error if you try to set
17009 a new value with just @samp{set width=13}, because @value{GDBN} has the
17010 command @code{set width}:
17013 (@value{GDBP}) whatis width
17015 (@value{GDBP}) p width
17017 (@value{GDBP}) set width=47
17018 Invalid syntax in expression.
17022 The invalid expression, of course, is @samp{=47}. In
17023 order to actually set the program's variable @code{width}, use
17026 (@value{GDBP}) set var width=47
17029 Because the @code{set} command has many subcommands that can conflict
17030 with the names of program variables, it is a good idea to use the
17031 @code{set variable} command instead of just @code{set}. For example, if
17032 your program has a variable @code{g}, you run into problems if you try
17033 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17034 the command @code{set gnutarget}, abbreviated @code{set g}:
17038 (@value{GDBP}) whatis g
17042 (@value{GDBP}) set g=4
17046 The program being debugged has been started already.
17047 Start it from the beginning? (y or n) y
17048 Starting program: /home/smith/cc_progs/a.out
17049 "/home/smith/cc_progs/a.out": can't open to read symbols:
17050 Invalid bfd target.
17051 (@value{GDBP}) show g
17052 The current BFD target is "=4".
17057 The program variable @code{g} did not change, and you silently set the
17058 @code{gnutarget} to an invalid value. In order to set the variable
17062 (@value{GDBP}) set var g=4
17065 @value{GDBN} allows more implicit conversions in assignments than C; you can
17066 freely store an integer value into a pointer variable or vice versa,
17067 and you can convert any structure to any other structure that is the
17068 same length or shorter.
17069 @comment FIXME: how do structs align/pad in these conversions?
17070 @comment /doc@cygnus.com 18dec1990
17072 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17073 construct to generate a value of specified type at a specified address
17074 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17075 to memory location @code{0x83040} as an integer (which implies a certain size
17076 and representation in memory), and
17079 set @{int@}0x83040 = 4
17083 stores the value 4 into that memory location.
17086 @section Continuing at a Different Address
17088 Ordinarily, when you continue your program, you do so at the place where
17089 it stopped, with the @code{continue} command. You can instead continue at
17090 an address of your own choosing, with the following commands:
17094 @kindex j @r{(@code{jump})}
17095 @item jump @var{location}
17096 @itemx j @var{location}
17097 Resume execution at @var{location}. Execution stops again immediately
17098 if there is a breakpoint there. @xref{Specify Location}, for a description
17099 of the different forms of @var{location}. It is common
17100 practice to use the @code{tbreak} command in conjunction with
17101 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17103 The @code{jump} command does not change the current stack frame, or
17104 the stack pointer, or the contents of any memory location or any
17105 register other than the program counter. If @var{location} is in
17106 a different function from the one currently executing, the results may
17107 be bizarre if the two functions expect different patterns of arguments or
17108 of local variables. For this reason, the @code{jump} command requests
17109 confirmation if the specified line is not in the function currently
17110 executing. However, even bizarre results are predictable if you are
17111 well acquainted with the machine-language code of your program.
17114 On many systems, you can get much the same effect as the @code{jump}
17115 command by storing a new value into the register @code{$pc}. The
17116 difference is that this does not start your program running; it only
17117 changes the address of where it @emph{will} run when you continue. For
17125 makes the next @code{continue} command or stepping command execute at
17126 address @code{0x485}, rather than at the address where your program stopped.
17127 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17129 The most common occasion to use the @code{jump} command is to back
17130 up---perhaps with more breakpoints set---over a portion of a program
17131 that has already executed, in order to examine its execution in more
17136 @section Giving your Program a Signal
17137 @cindex deliver a signal to a program
17141 @item signal @var{signal}
17142 Resume execution where your program is stopped, but immediately give it the
17143 signal @var{signal}. The @var{signal} can be the name or the number of a
17144 signal. For example, on many systems @code{signal 2} and @code{signal
17145 SIGINT} are both ways of sending an interrupt signal.
17147 Alternatively, if @var{signal} is zero, continue execution without
17148 giving a signal. This is useful when your program stopped on account of
17149 a signal and would ordinarily see the signal when resumed with the
17150 @code{continue} command; @samp{signal 0} causes it to resume without a
17153 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17154 delivered to the currently selected thread, not the thread that last
17155 reported a stop. This includes the situation where a thread was
17156 stopped due to a signal. So if you want to continue execution
17157 suppressing the signal that stopped a thread, you should select that
17158 same thread before issuing the @samp{signal 0} command. If you issue
17159 the @samp{signal 0} command with another thread as the selected one,
17160 @value{GDBN} detects that and asks for confirmation.
17162 Invoking the @code{signal} command is not the same as invoking the
17163 @code{kill} utility from the shell. Sending a signal with @code{kill}
17164 causes @value{GDBN} to decide what to do with the signal depending on
17165 the signal handling tables (@pxref{Signals}). The @code{signal} command
17166 passes the signal directly to your program.
17168 @code{signal} does not repeat when you press @key{RET} a second time
17169 after executing the command.
17171 @kindex queue-signal
17172 @item queue-signal @var{signal}
17173 Queue @var{signal} to be delivered immediately to the current thread
17174 when execution of the thread resumes. The @var{signal} can be the name or
17175 the number of a signal. For example, on many systems @code{signal 2} and
17176 @code{signal SIGINT} are both ways of sending an interrupt signal.
17177 The handling of the signal must be set to pass the signal to the program,
17178 otherwise @value{GDBN} will report an error.
17179 You can control the handling of signals from @value{GDBN} with the
17180 @code{handle} command (@pxref{Signals}).
17182 Alternatively, if @var{signal} is zero, any currently queued signal
17183 for the current thread is discarded and when execution resumes no signal
17184 will be delivered. This is useful when your program stopped on account
17185 of a signal and would ordinarily see the signal when resumed with the
17186 @code{continue} command.
17188 This command differs from the @code{signal} command in that the signal
17189 is just queued, execution is not resumed. And @code{queue-signal} cannot
17190 be used to pass a signal whose handling state has been set to @code{nopass}
17195 @xref{stepping into signal handlers}, for information on how stepping
17196 commands behave when the thread has a signal queued.
17199 @section Returning from a Function
17202 @cindex returning from a function
17205 @itemx return @var{expression}
17206 You can cancel execution of a function call with the @code{return}
17207 command. If you give an
17208 @var{expression} argument, its value is used as the function's return
17212 When you use @code{return}, @value{GDBN} discards the selected stack frame
17213 (and all frames within it). You can think of this as making the
17214 discarded frame return prematurely. If you wish to specify a value to
17215 be returned, give that value as the argument to @code{return}.
17217 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17218 Frame}), and any other frames inside of it, leaving its caller as the
17219 innermost remaining frame. That frame becomes selected. The
17220 specified value is stored in the registers used for returning values
17223 The @code{return} command does not resume execution; it leaves the
17224 program stopped in the state that would exist if the function had just
17225 returned. In contrast, the @code{finish} command (@pxref{Continuing
17226 and Stepping, ,Continuing and Stepping}) resumes execution until the
17227 selected stack frame returns naturally.
17229 @value{GDBN} needs to know how the @var{expression} argument should be set for
17230 the inferior. The concrete registers assignment depends on the OS ABI and the
17231 type being returned by the selected stack frame. For example it is common for
17232 OS ABI to return floating point values in FPU registers while integer values in
17233 CPU registers. Still some ABIs return even floating point values in CPU
17234 registers. Larger integer widths (such as @code{long long int}) also have
17235 specific placement rules. @value{GDBN} already knows the OS ABI from its
17236 current target so it needs to find out also the type being returned to make the
17237 assignment into the right register(s).
17239 Normally, the selected stack frame has debug info. @value{GDBN} will always
17240 use the debug info instead of the implicit type of @var{expression} when the
17241 debug info is available. For example, if you type @kbd{return -1}, and the
17242 function in the current stack frame is declared to return a @code{long long
17243 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17244 into a @code{long long int}:
17247 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17249 (@value{GDBP}) return -1
17250 Make func return now? (y or n) y
17251 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17252 43 printf ("result=%lld\n", func ());
17256 However, if the selected stack frame does not have a debug info, e.g., if the
17257 function was compiled without debug info, @value{GDBN} has to find out the type
17258 to return from user. Specifying a different type by mistake may set the value
17259 in different inferior registers than the caller code expects. For example,
17260 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17261 of a @code{long long int} result for a debug info less function (on 32-bit
17262 architectures). Therefore the user is required to specify the return type by
17263 an appropriate cast explicitly:
17266 Breakpoint 2, 0x0040050b in func ()
17267 (@value{GDBP}) return -1
17268 Return value type not available for selected stack frame.
17269 Please use an explicit cast of the value to return.
17270 (@value{GDBP}) return (long long int) -1
17271 Make selected stack frame return now? (y or n) y
17272 #0 0x00400526 in main ()
17277 @section Calling Program Functions
17280 @cindex calling functions
17281 @cindex inferior functions, calling
17282 @item print @var{expr}
17283 Evaluate the expression @var{expr} and display the resulting value.
17284 The expression may include calls to functions in the program being
17288 @item call @var{expr}
17289 Evaluate the expression @var{expr} without displaying @code{void}
17292 You can use this variant of the @code{print} command if you want to
17293 execute a function from your program that does not return anything
17294 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17295 with @code{void} returned values that @value{GDBN} will otherwise
17296 print. If the result is not void, it is printed and saved in the
17300 It is possible for the function you call via the @code{print} or
17301 @code{call} command to generate a signal (e.g., if there's a bug in
17302 the function, or if you passed it incorrect arguments). What happens
17303 in that case is controlled by the @code{set unwindonsignal} command.
17305 Similarly, with a C@t{++} program it is possible for the function you
17306 call via the @code{print} or @code{call} command to generate an
17307 exception that is not handled due to the constraints of the dummy
17308 frame. In this case, any exception that is raised in the frame, but has
17309 an out-of-frame exception handler will not be found. GDB builds a
17310 dummy-frame for the inferior function call, and the unwinder cannot
17311 seek for exception handlers outside of this dummy-frame. What happens
17312 in that case is controlled by the
17313 @code{set unwind-on-terminating-exception} command.
17316 @item set unwindonsignal
17317 @kindex set unwindonsignal
17318 @cindex unwind stack in called functions
17319 @cindex call dummy stack unwinding
17320 Set unwinding of the stack if a signal is received while in a function
17321 that @value{GDBN} called in the program being debugged. If set to on,
17322 @value{GDBN} unwinds the stack it created for the call and restores
17323 the context to what it was before the call. If set to off (the
17324 default), @value{GDBN} stops in the frame where the signal was
17327 @item show unwindonsignal
17328 @kindex show unwindonsignal
17329 Show the current setting of stack unwinding in the functions called by
17332 @item set unwind-on-terminating-exception
17333 @kindex set unwind-on-terminating-exception
17334 @cindex unwind stack in called functions with unhandled exceptions
17335 @cindex call dummy stack unwinding on unhandled exception.
17336 Set unwinding of the stack if a C@t{++} exception is raised, but left
17337 unhandled while in a function that @value{GDBN} called in the program being
17338 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17339 it created for the call and restores the context to what it was before
17340 the call. If set to off, @value{GDBN} the exception is delivered to
17341 the default C@t{++} exception handler and the inferior terminated.
17343 @item show unwind-on-terminating-exception
17344 @kindex show unwind-on-terminating-exception
17345 Show the current setting of stack unwinding in the functions called by
17350 @cindex weak alias functions
17351 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17352 for another function. In such case, @value{GDBN} might not pick up
17353 the type information, including the types of the function arguments,
17354 which causes @value{GDBN} to call the inferior function incorrectly.
17355 As a result, the called function will function erroneously and may
17356 even crash. A solution to that is to use the name of the aliased
17360 @section Patching Programs
17362 @cindex patching binaries
17363 @cindex writing into executables
17364 @cindex writing into corefiles
17366 By default, @value{GDBN} opens the file containing your program's
17367 executable code (or the corefile) read-only. This prevents accidental
17368 alterations to machine code; but it also prevents you from intentionally
17369 patching your program's binary.
17371 If you'd like to be able to patch the binary, you can specify that
17372 explicitly with the @code{set write} command. For example, you might
17373 want to turn on internal debugging flags, or even to make emergency
17379 @itemx set write off
17380 If you specify @samp{set write on}, @value{GDBN} opens executable and
17381 core files for both reading and writing; if you specify @kbd{set write
17382 off} (the default), @value{GDBN} opens them read-only.
17384 If you have already loaded a file, you must load it again (using the
17385 @code{exec-file} or @code{core-file} command) after changing @code{set
17386 write}, for your new setting to take effect.
17390 Display whether executable files and core files are opened for writing
17391 as well as reading.
17394 @node Compiling and Injecting Code
17395 @section Compiling and injecting code in @value{GDBN}
17396 @cindex injecting code
17397 @cindex writing into executables
17398 @cindex compiling code
17400 @value{GDBN} supports on-demand compilation and code injection into
17401 programs running under @value{GDBN}. GCC 5.0 or higher built with
17402 @file{libcc1.so} must be installed for this functionality to be enabled.
17403 This functionality is implemented with the following commands.
17406 @kindex compile code
17407 @item compile code @var{source-code}
17408 @itemx compile code -raw @var{--} @var{source-code}
17409 Compile @var{source-code} with the compiler language found as the current
17410 language in @value{GDBN} (@pxref{Languages}). If compilation and
17411 injection is not supported with the current language specified in
17412 @value{GDBN}, or the compiler does not support this feature, an error
17413 message will be printed. If @var{source-code} compiles and links
17414 successfully, @value{GDBN} will load the object-code emitted,
17415 and execute it within the context of the currently selected inferior.
17416 It is important to note that the compiled code is executed immediately.
17417 After execution, the compiled code is removed from @value{GDBN} and any
17418 new types or variables you have defined will be deleted.
17420 The command allows you to specify @var{source-code} in two ways.
17421 The simplest method is to provide a single line of code to the command.
17425 compile code printf ("hello world\n");
17428 If you specify options on the command line as well as source code, they
17429 may conflict. The @samp{--} delimiter can be used to separate options
17430 from actual source code. E.g.:
17433 compile code -r -- printf ("hello world\n");
17436 Alternatively you can enter source code as multiple lines of text. To
17437 enter this mode, invoke the @samp{compile code} command without any text
17438 following the command. This will start the multiple-line editor and
17439 allow you to type as many lines of source code as required. When you
17440 have completed typing, enter @samp{end} on its own line to exit the
17445 >printf ("hello\n");
17446 >printf ("world\n");
17450 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17451 provided @var{source-code} in a callable scope. In this case, you must
17452 specify the entry point of the code by defining a function named
17453 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17454 inferior. Using @samp{-raw} option may be needed for example when
17455 @var{source-code} requires @samp{#include} lines which may conflict with
17456 inferior symbols otherwise.
17458 @kindex compile file
17459 @item compile file @var{filename}
17460 @itemx compile file -raw @var{filename}
17461 Like @code{compile code}, but take the source code from @var{filename}.
17464 compile file /home/user/example.c
17469 @item compile print @var{expr}
17470 @itemx compile print /@var{f} @var{expr}
17471 Compile and execute @var{expr} with the compiler language found as the
17472 current language in @value{GDBN} (@pxref{Languages}). By default the
17473 value of @var{expr} is printed in a format appropriate to its data type;
17474 you can choose a different format by specifying @samp{/@var{f}}, where
17475 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17478 @item compile print
17479 @itemx compile print /@var{f}
17480 @cindex reprint the last value
17481 Alternatively you can enter the expression (source code producing it) as
17482 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17483 command without any text following the command. This will start the
17484 multiple-line editor.
17488 The process of compiling and injecting the code can be inspected using:
17491 @anchor{set debug compile}
17492 @item set debug compile
17493 @cindex compile command debugging info
17494 Turns on or off display of @value{GDBN} process of compiling and
17495 injecting the code. The default is off.
17497 @item show debug compile
17498 Displays the current state of displaying @value{GDBN} process of
17499 compiling and injecting the code.
17502 @subsection Compilation options for the @code{compile} command
17504 @value{GDBN} needs to specify the right compilation options for the code
17505 to be injected, in part to make its ABI compatible with the inferior
17506 and in part to make the injected code compatible with @value{GDBN}'s
17510 The options used, in increasing precedence:
17513 @item target architecture and OS options (@code{gdbarch})
17514 These options depend on target processor type and target operating
17515 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17516 (@code{-m64}) compilation option.
17518 @item compilation options recorded in the target
17519 @value{NGCC} (since version 4.7) stores the options used for compilation
17520 into @code{DW_AT_producer} part of DWARF debugging information according
17521 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17522 explicitly specify @code{-g} during inferior compilation otherwise
17523 @value{NGCC} produces no DWARF. This feature is only relevant for
17524 platforms where @code{-g} produces DWARF by default, otherwise one may
17525 try to enforce DWARF by using @code{-gdwarf-4}.
17527 @item compilation options set by @code{set compile-args}
17531 You can override compilation options using the following command:
17534 @item set compile-args
17535 @cindex compile command options override
17536 Set compilation options used for compiling and injecting code with the
17537 @code{compile} commands. These options override any conflicting ones
17538 from the target architecture and/or options stored during inferior
17541 @item show compile-args
17542 Displays the current state of compilation options override.
17543 This does not show all the options actually used during compilation,
17544 use @ref{set debug compile} for that.
17547 @subsection Caveats when using the @code{compile} command
17549 There are a few caveats to keep in mind when using the @code{compile}
17550 command. As the caveats are different per language, the table below
17551 highlights specific issues on a per language basis.
17554 @item C code examples and caveats
17555 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17556 attempt to compile the source code with a @samp{C} compiler. The source
17557 code provided to the @code{compile} command will have much the same
17558 access to variables and types as it normally would if it were part of
17559 the program currently being debugged in @value{GDBN}.
17561 Below is a sample program that forms the basis of the examples that
17562 follow. This program has been compiled and loaded into @value{GDBN},
17563 much like any other normal debugging session.
17566 void function1 (void)
17569 printf ("function 1\n");
17572 void function2 (void)
17587 For the purposes of the examples in this section, the program above has
17588 been compiled, loaded into @value{GDBN}, stopped at the function
17589 @code{main}, and @value{GDBN} is awaiting input from the user.
17591 To access variables and types for any program in @value{GDBN}, the
17592 program must be compiled and packaged with debug information. The
17593 @code{compile} command is not an exception to this rule. Without debug
17594 information, you can still use the @code{compile} command, but you will
17595 be very limited in what variables and types you can access.
17597 So with that in mind, the example above has been compiled with debug
17598 information enabled. The @code{compile} command will have access to
17599 all variables and types (except those that may have been optimized
17600 out). Currently, as @value{GDBN} has stopped the program in the
17601 @code{main} function, the @code{compile} command would have access to
17602 the variable @code{k}. You could invoke the @code{compile} command
17603 and type some source code to set the value of @code{k}. You can also
17604 read it, or do anything with that variable you would normally do in
17605 @code{C}. Be aware that changes to inferior variables in the
17606 @code{compile} command are persistent. In the following example:
17609 compile code k = 3;
17613 the variable @code{k} is now 3. It will retain that value until
17614 something else in the example program changes it, or another
17615 @code{compile} command changes it.
17617 Normal scope and access rules apply to source code compiled and
17618 injected by the @code{compile} command. In the example, the variables
17619 @code{j} and @code{k} are not accessible yet, because the program is
17620 currently stopped in the @code{main} function, where these variables
17621 are not in scope. Therefore, the following command
17624 compile code j = 3;
17628 will result in a compilation error message.
17630 Once the program is continued, execution will bring these variables in
17631 scope, and they will become accessible; then the code you specify via
17632 the @code{compile} command will be able to access them.
17634 You can create variables and types with the @code{compile} command as
17635 part of your source code. Variables and types that are created as part
17636 of the @code{compile} command are not visible to the rest of the program for
17637 the duration of its run. This example is valid:
17640 compile code int ff = 5; printf ("ff is %d\n", ff);
17643 However, if you were to type the following into @value{GDBN} after that
17644 command has completed:
17647 compile code printf ("ff is %d\n'', ff);
17651 a compiler error would be raised as the variable @code{ff} no longer
17652 exists. Object code generated and injected by the @code{compile}
17653 command is removed when its execution ends. Caution is advised
17654 when assigning to program variables values of variables created by the
17655 code submitted to the @code{compile} command. This example is valid:
17658 compile code int ff = 5; k = ff;
17661 The value of the variable @code{ff} is assigned to @code{k}. The variable
17662 @code{k} does not require the existence of @code{ff} to maintain the value
17663 it has been assigned. However, pointers require particular care in
17664 assignment. If the source code compiled with the @code{compile} command
17665 changed the address of a pointer in the example program, perhaps to a
17666 variable created in the @code{compile} command, that pointer would point
17667 to an invalid location when the command exits. The following example
17668 would likely cause issues with your debugged program:
17671 compile code int ff = 5; p = &ff;
17674 In this example, @code{p} would point to @code{ff} when the
17675 @code{compile} command is executing the source code provided to it.
17676 However, as variables in the (example) program persist with their
17677 assigned values, the variable @code{p} would point to an invalid
17678 location when the command exists. A general rule should be followed
17679 in that you should either assign @code{NULL} to any assigned pointers,
17680 or restore a valid location to the pointer before the command exits.
17682 Similar caution must be exercised with any structs, unions, and typedefs
17683 defined in @code{compile} command. Types defined in the @code{compile}
17684 command will no longer be available in the next @code{compile} command.
17685 Therefore, if you cast a variable to a type defined in the
17686 @code{compile} command, care must be taken to ensure that any future
17687 need to resolve the type can be achieved.
17690 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17691 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17692 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17693 Compilation failed.
17694 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17698 Variables that have been optimized away by the compiler are not
17699 accessible to the code submitted to the @code{compile} command.
17700 Access to those variables will generate a compiler error which @value{GDBN}
17701 will print to the console.
17704 @subsection Compiler search for the @code{compile} command
17706 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17707 may not be obvious for remote targets of different architecture than where
17708 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17709 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17710 command @code{set environment}). @xref{Environment}. @code{PATH} on
17711 @value{GDBN} host is searched for @value{NGCC} binary matching the
17712 target architecture and operating system.
17714 Specifically @code{PATH} is searched for binaries matching regular expression
17715 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17716 debugged. @var{arch} is processor name --- multiarch is supported, so for
17717 example both @code{i386} and @code{x86_64} targets look for pattern
17718 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17719 for pattern @code{s390x?}. @var{os} is currently supported only for
17720 pattern @code{linux(-gnu)?}.
17723 @chapter @value{GDBN} Files
17725 @value{GDBN} needs to know the file name of the program to be debugged,
17726 both in order to read its symbol table and in order to start your
17727 program. To debug a core dump of a previous run, you must also tell
17728 @value{GDBN} the name of the core dump file.
17731 * Files:: Commands to specify files
17732 * File Caching:: Information about @value{GDBN}'s file caching
17733 * Separate Debug Files:: Debugging information in separate files
17734 * MiniDebugInfo:: Debugging information in a special section
17735 * Index Files:: Index files speed up GDB
17736 * Symbol Errors:: Errors reading symbol files
17737 * Data Files:: GDB data files
17741 @section Commands to Specify Files
17743 @cindex symbol table
17744 @cindex core dump file
17746 You may want to specify executable and core dump file names. The usual
17747 way to do this is at start-up time, using the arguments to
17748 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17749 Out of @value{GDBN}}).
17751 Occasionally it is necessary to change to a different file during a
17752 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17753 specify a file you want to use. Or you are debugging a remote target
17754 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17755 Program}). In these situations the @value{GDBN} commands to specify
17756 new files are useful.
17759 @cindex executable file
17761 @item file @var{filename}
17762 Use @var{filename} as the program to be debugged. It is read for its
17763 symbols and for the contents of pure memory. It is also the program
17764 executed when you use the @code{run} command. If you do not specify a
17765 directory and the file is not found in the @value{GDBN} working directory,
17766 @value{GDBN} uses the environment variable @code{PATH} as a list of
17767 directories to search, just as the shell does when looking for a program
17768 to run. You can change the value of this variable, for both @value{GDBN}
17769 and your program, using the @code{path} command.
17771 @cindex unlinked object files
17772 @cindex patching object files
17773 You can load unlinked object @file{.o} files into @value{GDBN} using
17774 the @code{file} command. You will not be able to ``run'' an object
17775 file, but you can disassemble functions and inspect variables. Also,
17776 if the underlying BFD functionality supports it, you could use
17777 @kbd{gdb -write} to patch object files using this technique. Note
17778 that @value{GDBN} can neither interpret nor modify relocations in this
17779 case, so branches and some initialized variables will appear to go to
17780 the wrong place. But this feature is still handy from time to time.
17783 @code{file} with no argument makes @value{GDBN} discard any information it
17784 has on both executable file and the symbol table.
17787 @item exec-file @r{[} @var{filename} @r{]}
17788 Specify that the program to be run (but not the symbol table) is found
17789 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17790 if necessary to locate your program. Omitting @var{filename} means to
17791 discard information on the executable file.
17793 @kindex symbol-file
17794 @item symbol-file @r{[} @var{filename} @r{]}
17795 Read symbol table information from file @var{filename}. @code{PATH} is
17796 searched when necessary. Use the @code{file} command to get both symbol
17797 table and program to run from the same file.
17799 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17800 program's symbol table.
17802 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17803 some breakpoints and auto-display expressions. This is because they may
17804 contain pointers to the internal data recording symbols and data types,
17805 which are part of the old symbol table data being discarded inside
17808 @code{symbol-file} does not repeat if you press @key{RET} again after
17811 When @value{GDBN} is configured for a particular environment, it
17812 understands debugging information in whatever format is the standard
17813 generated for that environment; you may use either a @sc{gnu} compiler, or
17814 other compilers that adhere to the local conventions.
17815 Best results are usually obtained from @sc{gnu} compilers; for example,
17816 using @code{@value{NGCC}} you can generate debugging information for
17819 For most kinds of object files, with the exception of old SVR3 systems
17820 using COFF, the @code{symbol-file} command does not normally read the
17821 symbol table in full right away. Instead, it scans the symbol table
17822 quickly to find which source files and which symbols are present. The
17823 details are read later, one source file at a time, as they are needed.
17825 The purpose of this two-stage reading strategy is to make @value{GDBN}
17826 start up faster. For the most part, it is invisible except for
17827 occasional pauses while the symbol table details for a particular source
17828 file are being read. (The @code{set verbose} command can turn these
17829 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17830 Warnings and Messages}.)
17832 We have not implemented the two-stage strategy for COFF yet. When the
17833 symbol table is stored in COFF format, @code{symbol-file} reads the
17834 symbol table data in full right away. Note that ``stabs-in-COFF''
17835 still does the two-stage strategy, since the debug info is actually
17839 @cindex reading symbols immediately
17840 @cindex symbols, reading immediately
17841 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17842 @itemx file @r{[} -readnow @r{]} @var{filename}
17843 You can override the @value{GDBN} two-stage strategy for reading symbol
17844 tables by using the @samp{-readnow} option with any of the commands that
17845 load symbol table information, if you want to be sure @value{GDBN} has the
17846 entire symbol table available.
17848 @c FIXME: for now no mention of directories, since this seems to be in
17849 @c flux. 13mar1992 status is that in theory GDB would look either in
17850 @c current dir or in same dir as myprog; but issues like competing
17851 @c GDB's, or clutter in system dirs, mean that in practice right now
17852 @c only current dir is used. FFish says maybe a special GDB hierarchy
17853 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17857 @item core-file @r{[}@var{filename}@r{]}
17859 Specify the whereabouts of a core dump file to be used as the ``contents
17860 of memory''. Traditionally, core files contain only some parts of the
17861 address space of the process that generated them; @value{GDBN} can access the
17862 executable file itself for other parts.
17864 @code{core-file} with no argument specifies that no core file is
17867 Note that the core file is ignored when your program is actually running
17868 under @value{GDBN}. So, if you have been running your program and you
17869 wish to debug a core file instead, you must kill the subprocess in which
17870 the program is running. To do this, use the @code{kill} command
17871 (@pxref{Kill Process, ,Killing the Child Process}).
17873 @kindex add-symbol-file
17874 @cindex dynamic linking
17875 @item add-symbol-file @var{filename} @var{address}
17876 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17877 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17878 The @code{add-symbol-file} command reads additional symbol table
17879 information from the file @var{filename}. You would use this command
17880 when @var{filename} has been dynamically loaded (by some other means)
17881 into the program that is running. The @var{address} should give the memory
17882 address at which the file has been loaded; @value{GDBN} cannot figure
17883 this out for itself. You can additionally specify an arbitrary number
17884 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17885 section name and base address for that section. You can specify any
17886 @var{address} as an expression.
17888 The symbol table of the file @var{filename} is added to the symbol table
17889 originally read with the @code{symbol-file} command. You can use the
17890 @code{add-symbol-file} command any number of times; the new symbol data
17891 thus read is kept in addition to the old.
17893 Changes can be reverted using the command @code{remove-symbol-file}.
17895 @cindex relocatable object files, reading symbols from
17896 @cindex object files, relocatable, reading symbols from
17897 @cindex reading symbols from relocatable object files
17898 @cindex symbols, reading from relocatable object files
17899 @cindex @file{.o} files, reading symbols from
17900 Although @var{filename} is typically a shared library file, an
17901 executable file, or some other object file which has been fully
17902 relocated for loading into a process, you can also load symbolic
17903 information from relocatable @file{.o} files, as long as:
17907 the file's symbolic information refers only to linker symbols defined in
17908 that file, not to symbols defined by other object files,
17910 every section the file's symbolic information refers to has actually
17911 been loaded into the inferior, as it appears in the file, and
17913 you can determine the address at which every section was loaded, and
17914 provide these to the @code{add-symbol-file} command.
17918 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17919 relocatable files into an already running program; such systems
17920 typically make the requirements above easy to meet. However, it's
17921 important to recognize that many native systems use complex link
17922 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17923 assembly, for example) that make the requirements difficult to meet. In
17924 general, one cannot assume that using @code{add-symbol-file} to read a
17925 relocatable object file's symbolic information will have the same effect
17926 as linking the relocatable object file into the program in the normal
17929 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17931 @kindex remove-symbol-file
17932 @item remove-symbol-file @var{filename}
17933 @item remove-symbol-file -a @var{address}
17934 Remove a symbol file added via the @code{add-symbol-file} command. The
17935 file to remove can be identified by its @var{filename} or by an @var{address}
17936 that lies within the boundaries of this symbol file in memory. Example:
17939 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17940 add symbol table from file "/home/user/gdb/mylib.so" at
17941 .text_addr = 0x7ffff7ff9480
17943 Reading symbols from /home/user/gdb/mylib.so...done.
17944 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17945 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17950 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17952 @kindex add-symbol-file-from-memory
17953 @cindex @code{syscall DSO}
17954 @cindex load symbols from memory
17955 @item add-symbol-file-from-memory @var{address}
17956 Load symbols from the given @var{address} in a dynamically loaded
17957 object file whose image is mapped directly into the inferior's memory.
17958 For example, the Linux kernel maps a @code{syscall DSO} into each
17959 process's address space; this DSO provides kernel-specific code for
17960 some system calls. The argument can be any expression whose
17961 evaluation yields the address of the file's shared object file header.
17962 For this command to work, you must have used @code{symbol-file} or
17963 @code{exec-file} commands in advance.
17966 @item section @var{section} @var{addr}
17967 The @code{section} command changes the base address of the named
17968 @var{section} of the exec file to @var{addr}. This can be used if the
17969 exec file does not contain section addresses, (such as in the
17970 @code{a.out} format), or when the addresses specified in the file
17971 itself are wrong. Each section must be changed separately. The
17972 @code{info files} command, described below, lists all the sections and
17976 @kindex info target
17979 @code{info files} and @code{info target} are synonymous; both print the
17980 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17981 including the names of the executable and core dump files currently in
17982 use by @value{GDBN}, and the files from which symbols were loaded. The
17983 command @code{help target} lists all possible targets rather than
17986 @kindex maint info sections
17987 @item maint info sections
17988 Another command that can give you extra information about program sections
17989 is @code{maint info sections}. In addition to the section information
17990 displayed by @code{info files}, this command displays the flags and file
17991 offset of each section in the executable and core dump files. In addition,
17992 @code{maint info sections} provides the following command options (which
17993 may be arbitrarily combined):
17997 Display sections for all loaded object files, including shared libraries.
17998 @item @var{sections}
17999 Display info only for named @var{sections}.
18000 @item @var{section-flags}
18001 Display info only for sections for which @var{section-flags} are true.
18002 The section flags that @value{GDBN} currently knows about are:
18005 Section will have space allocated in the process when loaded.
18006 Set for all sections except those containing debug information.
18008 Section will be loaded from the file into the child process memory.
18009 Set for pre-initialized code and data, clear for @code{.bss} sections.
18011 Section needs to be relocated before loading.
18013 Section cannot be modified by the child process.
18015 Section contains executable code only.
18017 Section contains data only (no executable code).
18019 Section will reside in ROM.
18021 Section contains data for constructor/destructor lists.
18023 Section is not empty.
18025 An instruction to the linker to not output the section.
18026 @item COFF_SHARED_LIBRARY
18027 A notification to the linker that the section contains
18028 COFF shared library information.
18030 Section contains common symbols.
18033 @kindex set trust-readonly-sections
18034 @cindex read-only sections
18035 @item set trust-readonly-sections on
18036 Tell @value{GDBN} that readonly sections in your object file
18037 really are read-only (i.e.@: that their contents will not change).
18038 In that case, @value{GDBN} can fetch values from these sections
18039 out of the object file, rather than from the target program.
18040 For some targets (notably embedded ones), this can be a significant
18041 enhancement to debugging performance.
18043 The default is off.
18045 @item set trust-readonly-sections off
18046 Tell @value{GDBN} not to trust readonly sections. This means that
18047 the contents of the section might change while the program is running,
18048 and must therefore be fetched from the target when needed.
18050 @item show trust-readonly-sections
18051 Show the current setting of trusting readonly sections.
18054 All file-specifying commands allow both absolute and relative file names
18055 as arguments. @value{GDBN} always converts the file name to an absolute file
18056 name and remembers it that way.
18058 @cindex shared libraries
18059 @anchor{Shared Libraries}
18060 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18061 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18062 DSBT (TIC6X) shared libraries.
18064 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18065 shared libraries. @xref{Expat}.
18067 @value{GDBN} automatically loads symbol definitions from shared libraries
18068 when you use the @code{run} command, or when you examine a core file.
18069 (Before you issue the @code{run} command, @value{GDBN} does not understand
18070 references to a function in a shared library, however---unless you are
18071 debugging a core file).
18073 @c FIXME: some @value{GDBN} release may permit some refs to undef
18074 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18075 @c FIXME...lib; check this from time to time when updating manual
18077 There are times, however, when you may wish to not automatically load
18078 symbol definitions from shared libraries, such as when they are
18079 particularly large or there are many of them.
18081 To control the automatic loading of shared library symbols, use the
18085 @kindex set auto-solib-add
18086 @item set auto-solib-add @var{mode}
18087 If @var{mode} is @code{on}, symbols from all shared object libraries
18088 will be loaded automatically when the inferior begins execution, you
18089 attach to an independently started inferior, or when the dynamic linker
18090 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18091 is @code{off}, symbols must be loaded manually, using the
18092 @code{sharedlibrary} command. The default value is @code{on}.
18094 @cindex memory used for symbol tables
18095 If your program uses lots of shared libraries with debug info that
18096 takes large amounts of memory, you can decrease the @value{GDBN}
18097 memory footprint by preventing it from automatically loading the
18098 symbols from shared libraries. To that end, type @kbd{set
18099 auto-solib-add off} before running the inferior, then load each
18100 library whose debug symbols you do need with @kbd{sharedlibrary
18101 @var{regexp}}, where @var{regexp} is a regular expression that matches
18102 the libraries whose symbols you want to be loaded.
18104 @kindex show auto-solib-add
18105 @item show auto-solib-add
18106 Display the current autoloading mode.
18109 @cindex load shared library
18110 To explicitly load shared library symbols, use the @code{sharedlibrary}
18114 @kindex info sharedlibrary
18116 @item info share @var{regex}
18117 @itemx info sharedlibrary @var{regex}
18118 Print the names of the shared libraries which are currently loaded
18119 that match @var{regex}. If @var{regex} is omitted then print
18120 all shared libraries that are loaded.
18123 @item info dll @var{regex}
18124 This is an alias of @code{info sharedlibrary}.
18126 @kindex sharedlibrary
18128 @item sharedlibrary @var{regex}
18129 @itemx share @var{regex}
18130 Load shared object library symbols for files matching a
18131 Unix regular expression.
18132 As with files loaded automatically, it only loads shared libraries
18133 required by your program for a core file or after typing @code{run}. If
18134 @var{regex} is omitted all shared libraries required by your program are
18137 @item nosharedlibrary
18138 @kindex nosharedlibrary
18139 @cindex unload symbols from shared libraries
18140 Unload all shared object library symbols. This discards all symbols
18141 that have been loaded from all shared libraries. Symbols from shared
18142 libraries that were loaded by explicit user requests are not
18146 Sometimes you may wish that @value{GDBN} stops and gives you control
18147 when any of shared library events happen. The best way to do this is
18148 to use @code{catch load} and @code{catch unload} (@pxref{Set
18151 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18152 command for this. This command exists for historical reasons. It is
18153 less useful than setting a catchpoint, because it does not allow for
18154 conditions or commands as a catchpoint does.
18157 @item set stop-on-solib-events
18158 @kindex set stop-on-solib-events
18159 This command controls whether @value{GDBN} should give you control
18160 when the dynamic linker notifies it about some shared library event.
18161 The most common event of interest is loading or unloading of a new
18164 @item show stop-on-solib-events
18165 @kindex show stop-on-solib-events
18166 Show whether @value{GDBN} stops and gives you control when shared
18167 library events happen.
18170 Shared libraries are also supported in many cross or remote debugging
18171 configurations. @value{GDBN} needs to have access to the target's libraries;
18172 this can be accomplished either by providing copies of the libraries
18173 on the host system, or by asking @value{GDBN} to automatically retrieve the
18174 libraries from the target. If copies of the target libraries are
18175 provided, they need to be the same as the target libraries, although the
18176 copies on the target can be stripped as long as the copies on the host are
18179 @cindex where to look for shared libraries
18180 For remote debugging, you need to tell @value{GDBN} where the target
18181 libraries are, so that it can load the correct copies---otherwise, it
18182 may try to load the host's libraries. @value{GDBN} has two variables
18183 to specify the search directories for target libraries.
18186 @cindex prefix for executable and shared library file names
18187 @cindex system root, alternate
18188 @kindex set solib-absolute-prefix
18189 @kindex set sysroot
18190 @item set sysroot @var{path}
18191 Use @var{path} as the system root for the program being debugged. Any
18192 absolute shared library paths will be prefixed with @var{path}; many
18193 runtime loaders store the absolute paths to the shared library in the
18194 target program's memory. When starting processes remotely, and when
18195 attaching to already-running processes (local or remote), their
18196 executable filenames will be prefixed with @var{path} if reported to
18197 @value{GDBN} as absolute by the operating system. If you use
18198 @code{set sysroot} to find executables and shared libraries, they need
18199 to be laid out in the same way that they are on the target, with
18200 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18203 If @var{path} starts with the sequence @file{target:} and the target
18204 system is remote then @value{GDBN} will retrieve the target binaries
18205 from the remote system. This is only supported when using a remote
18206 target that supports the @code{remote get} command (@pxref{File
18207 Transfer,,Sending files to a remote system}). The part of @var{path}
18208 following the initial @file{target:} (if present) is used as system
18209 root prefix on the remote file system. If @var{path} starts with the
18210 sequence @file{remote:} this is converted to the sequence
18211 @file{target:} by @code{set sysroot}@footnote{Historically the
18212 functionality to retrieve binaries from the remote system was
18213 provided by prefixing @var{path} with @file{remote:}}. If you want
18214 to specify a local system root using a directory that happens to be
18215 named @file{target:} or @file{remote:}, you need to use some
18216 equivalent variant of the name like @file{./target:}.
18218 For targets with an MS-DOS based filesystem, such as MS-Windows and
18219 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18220 absolute file name with @var{path}. But first, on Unix hosts,
18221 @value{GDBN} converts all backslash directory separators into forward
18222 slashes, because the backslash is not a directory separator on Unix:
18225 c:\foo\bar.dll @result{} c:/foo/bar.dll
18228 Then, @value{GDBN} attempts prefixing the target file name with
18229 @var{path}, and looks for the resulting file name in the host file
18233 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18236 If that does not find the binary, @value{GDBN} tries removing
18237 the @samp{:} character from the drive spec, both for convenience, and,
18238 for the case of the host file system not supporting file names with
18242 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18245 This makes it possible to have a system root that mirrors a target
18246 with more than one drive. E.g., you may want to setup your local
18247 copies of the target system shared libraries like so (note @samp{c} vs
18251 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18252 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18253 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18257 and point the system root at @file{/path/to/sysroot}, so that
18258 @value{GDBN} can find the correct copies of both
18259 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18261 If that still does not find the binary, @value{GDBN} tries
18262 removing the whole drive spec from the target file name:
18265 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18268 This last lookup makes it possible to not care about the drive name,
18269 if you don't want or need to.
18271 The @code{set solib-absolute-prefix} command is an alias for @code{set
18274 @cindex default system root
18275 @cindex @samp{--with-sysroot}
18276 You can set the default system root by using the configure-time
18277 @samp{--with-sysroot} option. If the system root is inside
18278 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18279 @samp{--exec-prefix}), then the default system root will be updated
18280 automatically if the installed @value{GDBN} is moved to a new
18283 @kindex show sysroot
18285 Display the current executable and shared library prefix.
18287 @kindex set solib-search-path
18288 @item set solib-search-path @var{path}
18289 If this variable is set, @var{path} is a colon-separated list of
18290 directories to search for shared libraries. @samp{solib-search-path}
18291 is used after @samp{sysroot} fails to locate the library, or if the
18292 path to the library is relative instead of absolute. If you want to
18293 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18294 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18295 finding your host's libraries. @samp{sysroot} is preferred; setting
18296 it to a nonexistent directory may interfere with automatic loading
18297 of shared library symbols.
18299 @kindex show solib-search-path
18300 @item show solib-search-path
18301 Display the current shared library search path.
18303 @cindex DOS file-name semantics of file names.
18304 @kindex set target-file-system-kind (unix|dos-based|auto)
18305 @kindex show target-file-system-kind
18306 @item set target-file-system-kind @var{kind}
18307 Set assumed file system kind for target reported file names.
18309 Shared library file names as reported by the target system may not
18310 make sense as is on the system @value{GDBN} is running on. For
18311 example, when remote debugging a target that has MS-DOS based file
18312 system semantics, from a Unix host, the target may be reporting to
18313 @value{GDBN} a list of loaded shared libraries with file names such as
18314 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18315 drive letters, so the @samp{c:\} prefix is not normally understood as
18316 indicating an absolute file name, and neither is the backslash
18317 normally considered a directory separator character. In that case,
18318 the native file system would interpret this whole absolute file name
18319 as a relative file name with no directory components. This would make
18320 it impossible to point @value{GDBN} at a copy of the remote target's
18321 shared libraries on the host using @code{set sysroot}, and impractical
18322 with @code{set solib-search-path}. Setting
18323 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18324 to interpret such file names similarly to how the target would, and to
18325 map them to file names valid on @value{GDBN}'s native file system
18326 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18327 to one of the supported file system kinds. In that case, @value{GDBN}
18328 tries to determine the appropriate file system variant based on the
18329 current target's operating system (@pxref{ABI, ,Configuring the
18330 Current ABI}). The supported file system settings are:
18334 Instruct @value{GDBN} to assume the target file system is of Unix
18335 kind. Only file names starting the forward slash (@samp{/}) character
18336 are considered absolute, and the directory separator character is also
18340 Instruct @value{GDBN} to assume the target file system is DOS based.
18341 File names starting with either a forward slash, or a drive letter
18342 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18343 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18344 considered directory separators.
18347 Instruct @value{GDBN} to use the file system kind associated with the
18348 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18349 This is the default.
18353 @cindex file name canonicalization
18354 @cindex base name differences
18355 When processing file names provided by the user, @value{GDBN}
18356 frequently needs to compare them to the file names recorded in the
18357 program's debug info. Normally, @value{GDBN} compares just the
18358 @dfn{base names} of the files as strings, which is reasonably fast
18359 even for very large programs. (The base name of a file is the last
18360 portion of its name, after stripping all the leading directories.)
18361 This shortcut in comparison is based upon the assumption that files
18362 cannot have more than one base name. This is usually true, but
18363 references to files that use symlinks or similar filesystem
18364 facilities violate that assumption. If your program records files
18365 using such facilities, or if you provide file names to @value{GDBN}
18366 using symlinks etc., you can set @code{basenames-may-differ} to
18367 @code{true} to instruct @value{GDBN} to completely canonicalize each
18368 pair of file names it needs to compare. This will make file-name
18369 comparisons accurate, but at a price of a significant slowdown.
18372 @item set basenames-may-differ
18373 @kindex set basenames-may-differ
18374 Set whether a source file may have multiple base names.
18376 @item show basenames-may-differ
18377 @kindex show basenames-may-differ
18378 Show whether a source file may have multiple base names.
18382 @section File Caching
18383 @cindex caching of opened files
18384 @cindex caching of bfd objects
18386 To speed up file loading, and reduce memory usage, @value{GDBN} will
18387 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18388 BFD, bfd, The Binary File Descriptor Library}. The following commands
18389 allow visibility and control of the caching behavior.
18392 @kindex maint info bfds
18393 @item maint info bfds
18394 This prints information about each @code{bfd} object that is known to
18397 @kindex maint set bfd-sharing
18398 @kindex maint show bfd-sharing
18399 @kindex bfd caching
18400 @item maint set bfd-sharing
18401 @item maint show bfd-sharing
18402 Control whether @code{bfd} objects can be shared. When sharing is
18403 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18404 than reopening the same file. Turning sharing off does not cause
18405 already shared @code{bfd} objects to be unshared, but all future files
18406 that are opened will create a new @code{bfd} object. Similarly,
18407 re-enabling sharing does not cause multiple existing @code{bfd}
18408 objects to be collapsed into a single shared @code{bfd} object.
18410 @kindex set debug bfd-cache @var{level}
18411 @kindex bfd caching
18412 @item set debug bfd-cache @var{level}
18413 Turns on debugging of the bfd cache, setting the level to @var{level}.
18415 @kindex show debug bfd-cache
18416 @kindex bfd caching
18417 @item show debug bfd-cache
18418 Show the current debugging level of the bfd cache.
18421 @node Separate Debug Files
18422 @section Debugging Information in Separate Files
18423 @cindex separate debugging information files
18424 @cindex debugging information in separate files
18425 @cindex @file{.debug} subdirectories
18426 @cindex debugging information directory, global
18427 @cindex global debugging information directories
18428 @cindex build ID, and separate debugging files
18429 @cindex @file{.build-id} directory
18431 @value{GDBN} allows you to put a program's debugging information in a
18432 file separate from the executable itself, in a way that allows
18433 @value{GDBN} to find and load the debugging information automatically.
18434 Since debugging information can be very large---sometimes larger
18435 than the executable code itself---some systems distribute debugging
18436 information for their executables in separate files, which users can
18437 install only when they need to debug a problem.
18439 @value{GDBN} supports two ways of specifying the separate debug info
18444 The executable contains a @dfn{debug link} that specifies the name of
18445 the separate debug info file. The separate debug file's name is
18446 usually @file{@var{executable}.debug}, where @var{executable} is the
18447 name of the corresponding executable file without leading directories
18448 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18449 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18450 checksum for the debug file, which @value{GDBN} uses to validate that
18451 the executable and the debug file came from the same build.
18454 The executable contains a @dfn{build ID}, a unique bit string that is
18455 also present in the corresponding debug info file. (This is supported
18456 only on some operating systems, when using the ELF or PE file formats
18457 for binary files and the @sc{gnu} Binutils.) For more details about
18458 this feature, see the description of the @option{--build-id}
18459 command-line option in @ref{Options, , Command Line Options, ld.info,
18460 The GNU Linker}. The debug info file's name is not specified
18461 explicitly by the build ID, but can be computed from the build ID, see
18465 Depending on the way the debug info file is specified, @value{GDBN}
18466 uses two different methods of looking for the debug file:
18470 For the ``debug link'' method, @value{GDBN} looks up the named file in
18471 the directory of the executable file, then in a subdirectory of that
18472 directory named @file{.debug}, and finally under each one of the global debug
18473 directories, in a subdirectory whose name is identical to the leading
18474 directories of the executable's absolute file name.
18477 For the ``build ID'' method, @value{GDBN} looks in the
18478 @file{.build-id} subdirectory of each one of the global debug directories for
18479 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18480 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18481 are the rest of the bit string. (Real build ID strings are 32 or more
18482 hex characters, not 10.)
18485 So, for example, suppose you ask @value{GDBN} to debug
18486 @file{/usr/bin/ls}, which has a debug link that specifies the
18487 file @file{ls.debug}, and a build ID whose value in hex is
18488 @code{abcdef1234}. If the list of the global debug directories includes
18489 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18490 debug information files, in the indicated order:
18494 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18496 @file{/usr/bin/ls.debug}
18498 @file{/usr/bin/.debug/ls.debug}
18500 @file{/usr/lib/debug/usr/bin/ls.debug}.
18503 @anchor{debug-file-directory}
18504 Global debugging info directories default to what is set by @value{GDBN}
18505 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18506 you can also set the global debugging info directories, and view the list
18507 @value{GDBN} is currently using.
18511 @kindex set debug-file-directory
18512 @item set debug-file-directory @var{directories}
18513 Set the directories which @value{GDBN} searches for separate debugging
18514 information files to @var{directory}. Multiple path components can be set
18515 concatenating them by a path separator.
18517 @kindex show debug-file-directory
18518 @item show debug-file-directory
18519 Show the directories @value{GDBN} searches for separate debugging
18524 @cindex @code{.gnu_debuglink} sections
18525 @cindex debug link sections
18526 A debug link is a special section of the executable file named
18527 @code{.gnu_debuglink}. The section must contain:
18531 A filename, with any leading directory components removed, followed by
18534 zero to three bytes of padding, as needed to reach the next four-byte
18535 boundary within the section, and
18537 a four-byte CRC checksum, stored in the same endianness used for the
18538 executable file itself. The checksum is computed on the debugging
18539 information file's full contents by the function given below, passing
18540 zero as the @var{crc} argument.
18543 Any executable file format can carry a debug link, as long as it can
18544 contain a section named @code{.gnu_debuglink} with the contents
18547 @cindex @code{.note.gnu.build-id} sections
18548 @cindex build ID sections
18549 The build ID is a special section in the executable file (and in other
18550 ELF binary files that @value{GDBN} may consider). This section is
18551 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18552 It contains unique identification for the built files---the ID remains
18553 the same across multiple builds of the same build tree. The default
18554 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18555 content for the build ID string. The same section with an identical
18556 value is present in the original built binary with symbols, in its
18557 stripped variant, and in the separate debugging information file.
18559 The debugging information file itself should be an ordinary
18560 executable, containing a full set of linker symbols, sections, and
18561 debugging information. The sections of the debugging information file
18562 should have the same names, addresses, and sizes as the original file,
18563 but they need not contain any data---much like a @code{.bss} section
18564 in an ordinary executable.
18566 The @sc{gnu} binary utilities (Binutils) package includes the
18567 @samp{objcopy} utility that can produce
18568 the separated executable / debugging information file pairs using the
18569 following commands:
18572 @kbd{objcopy --only-keep-debug foo foo.debug}
18577 These commands remove the debugging
18578 information from the executable file @file{foo} and place it in the file
18579 @file{foo.debug}. You can use the first, second or both methods to link the
18584 The debug link method needs the following additional command to also leave
18585 behind a debug link in @file{foo}:
18588 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18591 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18592 a version of the @code{strip} command such that the command @kbd{strip foo -f
18593 foo.debug} has the same functionality as the two @code{objcopy} commands and
18594 the @code{ln -s} command above, together.
18597 Build ID gets embedded into the main executable using @code{ld --build-id} or
18598 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18599 compatibility fixes for debug files separation are present in @sc{gnu} binary
18600 utilities (Binutils) package since version 2.18.
18605 @cindex CRC algorithm definition
18606 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18607 IEEE 802.3 using the polynomial:
18609 @c TexInfo requires naked braces for multi-digit exponents for Tex
18610 @c output, but this causes HTML output to barf. HTML has to be set using
18611 @c raw commands. So we end up having to specify this equation in 2
18616 <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>
18617 + <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
18623 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18624 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18628 The function is computed byte at a time, taking the least
18629 significant bit of each byte first. The initial pattern
18630 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18631 the final result is inverted to ensure trailing zeros also affect the
18634 @emph{Note:} This is the same CRC polynomial as used in handling the
18635 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18636 However in the case of the Remote Serial Protocol, the CRC is computed
18637 @emph{most} significant bit first, and the result is not inverted, so
18638 trailing zeros have no effect on the CRC value.
18640 To complete the description, we show below the code of the function
18641 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18642 initially supplied @code{crc} argument means that an initial call to
18643 this function passing in zero will start computing the CRC using
18646 @kindex gnu_debuglink_crc32
18649 gnu_debuglink_crc32 (unsigned long crc,
18650 unsigned char *buf, size_t len)
18652 static const unsigned long crc32_table[256] =
18654 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18655 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18656 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18657 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18658 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18659 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18660 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18661 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18662 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18663 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18664 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18665 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18666 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18667 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18668 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18669 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18670 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18671 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18672 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18673 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18674 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18675 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18676 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18677 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18678 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18679 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18680 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18681 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18682 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18683 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18684 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18685 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18686 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18687 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18688 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18689 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18690 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18691 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18692 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18693 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18694 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18695 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18696 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18697 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18698 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18699 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18700 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18701 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18702 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18703 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18704 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18707 unsigned char *end;
18709 crc = ~crc & 0xffffffff;
18710 for (end = buf + len; buf < end; ++buf)
18711 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18712 return ~crc & 0xffffffff;
18717 This computation does not apply to the ``build ID'' method.
18719 @node MiniDebugInfo
18720 @section Debugging information in a special section
18721 @cindex separate debug sections
18722 @cindex @samp{.gnu_debugdata} section
18724 Some systems ship pre-built executables and libraries that have a
18725 special @samp{.gnu_debugdata} section. This feature is called
18726 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18727 is used to supply extra symbols for backtraces.
18729 The intent of this section is to provide extra minimal debugging
18730 information for use in simple backtraces. It is not intended to be a
18731 replacement for full separate debugging information (@pxref{Separate
18732 Debug Files}). The example below shows the intended use; however,
18733 @value{GDBN} does not currently put restrictions on what sort of
18734 debugging information might be included in the section.
18736 @value{GDBN} has support for this extension. If the section exists,
18737 then it is used provided that no other source of debugging information
18738 can be found, and that @value{GDBN} was configured with LZMA support.
18740 This section can be easily created using @command{objcopy} and other
18741 standard utilities:
18744 # Extract the dynamic symbols from the main binary, there is no need
18745 # to also have these in the normal symbol table.
18746 nm -D @var{binary} --format=posix --defined-only \
18747 | awk '@{ print $1 @}' | sort > dynsyms
18749 # Extract all the text (i.e. function) symbols from the debuginfo.
18750 # (Note that we actually also accept "D" symbols, for the benefit
18751 # of platforms like PowerPC64 that use function descriptors.)
18752 nm @var{binary} --format=posix --defined-only \
18753 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18756 # Keep all the function symbols not already in the dynamic symbol
18758 comm -13 dynsyms funcsyms > keep_symbols
18760 # Separate full debug info into debug binary.
18761 objcopy --only-keep-debug @var{binary} debug
18763 # Copy the full debuginfo, keeping only a minimal set of symbols and
18764 # removing some unnecessary sections.
18765 objcopy -S --remove-section .gdb_index --remove-section .comment \
18766 --keep-symbols=keep_symbols debug mini_debuginfo
18768 # Drop the full debug info from the original binary.
18769 strip --strip-all -R .comment @var{binary}
18771 # Inject the compressed data into the .gnu_debugdata section of the
18774 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18778 @section Index Files Speed Up @value{GDBN}
18779 @cindex index files
18780 @cindex @samp{.gdb_index} section
18782 When @value{GDBN} finds a symbol file, it scans the symbols in the
18783 file in order to construct an internal symbol table. This lets most
18784 @value{GDBN} operations work quickly---at the cost of a delay early
18785 on. For large programs, this delay can be quite lengthy, so
18786 @value{GDBN} provides a way to build an index, which speeds up
18789 The index is stored as a section in the symbol file. @value{GDBN} can
18790 write the index to a file, then you can put it into the symbol file
18791 using @command{objcopy}.
18793 To create an index file, use the @code{save gdb-index} command:
18796 @item save gdb-index @var{directory}
18797 @kindex save gdb-index
18798 Create an index file for each symbol file currently known by
18799 @value{GDBN}. Each file is named after its corresponding symbol file,
18800 with @samp{.gdb-index} appended, and is written into the given
18804 Once you have created an index file you can merge it into your symbol
18805 file, here named @file{symfile}, using @command{objcopy}:
18808 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18809 --set-section-flags .gdb_index=readonly symfile symfile
18812 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18813 sections that have been deprecated. Usually they are deprecated because
18814 they are missing a new feature or have performance issues.
18815 To tell @value{GDBN} to use a deprecated index section anyway
18816 specify @code{set use-deprecated-index-sections on}.
18817 The default is @code{off}.
18818 This can speed up startup, but may result in some functionality being lost.
18819 @xref{Index Section Format}.
18821 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18822 must be done before gdb reads the file. The following will not work:
18825 $ gdb -ex "set use-deprecated-index-sections on" <program>
18828 Instead you must do, for example,
18831 $ gdb -iex "set use-deprecated-index-sections on" <program>
18834 There are currently some limitation on indices. They only work when
18835 for DWARF debugging information, not stabs. And, they do not
18836 currently work for programs using Ada.
18838 @node Symbol Errors
18839 @section Errors Reading Symbol Files
18841 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18842 such as symbol types it does not recognize, or known bugs in compiler
18843 output. By default, @value{GDBN} does not notify you of such problems, since
18844 they are relatively common and primarily of interest to people
18845 debugging compilers. If you are interested in seeing information
18846 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18847 only one message about each such type of problem, no matter how many
18848 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18849 to see how many times the problems occur, with the @code{set
18850 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18853 The messages currently printed, and their meanings, include:
18856 @item inner block not inside outer block in @var{symbol}
18858 The symbol information shows where symbol scopes begin and end
18859 (such as at the start of a function or a block of statements). This
18860 error indicates that an inner scope block is not fully contained
18861 in its outer scope blocks.
18863 @value{GDBN} circumvents the problem by treating the inner block as if it had
18864 the same scope as the outer block. In the error message, @var{symbol}
18865 may be shown as ``@code{(don't know)}'' if the outer block is not a
18868 @item block at @var{address} out of order
18870 The symbol information for symbol scope blocks should occur in
18871 order of increasing addresses. This error indicates that it does not
18874 @value{GDBN} does not circumvent this problem, and has trouble
18875 locating symbols in the source file whose symbols it is reading. (You
18876 can often determine what source file is affected by specifying
18877 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18880 @item bad block start address patched
18882 The symbol information for a symbol scope block has a start address
18883 smaller than the address of the preceding source line. This is known
18884 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18886 @value{GDBN} circumvents the problem by treating the symbol scope block as
18887 starting on the previous source line.
18889 @item bad string table offset in symbol @var{n}
18892 Symbol number @var{n} contains a pointer into the string table which is
18893 larger than the size of the string table.
18895 @value{GDBN} circumvents the problem by considering the symbol to have the
18896 name @code{foo}, which may cause other problems if many symbols end up
18899 @item unknown symbol type @code{0x@var{nn}}
18901 The symbol information contains new data types that @value{GDBN} does
18902 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18903 uncomprehended information, in hexadecimal.
18905 @value{GDBN} circumvents the error by ignoring this symbol information.
18906 This usually allows you to debug your program, though certain symbols
18907 are not accessible. If you encounter such a problem and feel like
18908 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18909 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18910 and examine @code{*bufp} to see the symbol.
18912 @item stub type has NULL name
18914 @value{GDBN} could not find the full definition for a struct or class.
18916 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18917 The symbol information for a C@t{++} member function is missing some
18918 information that recent versions of the compiler should have output for
18921 @item info mismatch between compiler and debugger
18923 @value{GDBN} could not parse a type specification output by the compiler.
18928 @section GDB Data Files
18930 @cindex prefix for data files
18931 @value{GDBN} will sometimes read an auxiliary data file. These files
18932 are kept in a directory known as the @dfn{data directory}.
18934 You can set the data directory's name, and view the name @value{GDBN}
18935 is currently using.
18938 @kindex set data-directory
18939 @item set data-directory @var{directory}
18940 Set the directory which @value{GDBN} searches for auxiliary data files
18941 to @var{directory}.
18943 @kindex show data-directory
18944 @item show data-directory
18945 Show the directory @value{GDBN} searches for auxiliary data files.
18948 @cindex default data directory
18949 @cindex @samp{--with-gdb-datadir}
18950 You can set the default data directory by using the configure-time
18951 @samp{--with-gdb-datadir} option. If the data directory is inside
18952 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18953 @samp{--exec-prefix}), then the default data directory will be updated
18954 automatically if the installed @value{GDBN} is moved to a new
18957 The data directory may also be specified with the
18958 @code{--data-directory} command line option.
18959 @xref{Mode Options}.
18962 @chapter Specifying a Debugging Target
18964 @cindex debugging target
18965 A @dfn{target} is the execution environment occupied by your program.
18967 Often, @value{GDBN} runs in the same host environment as your program;
18968 in that case, the debugging target is specified as a side effect when
18969 you use the @code{file} or @code{core} commands. When you need more
18970 flexibility---for example, running @value{GDBN} on a physically separate
18971 host, or controlling a standalone system over a serial port or a
18972 realtime system over a TCP/IP connection---you can use the @code{target}
18973 command to specify one of the target types configured for @value{GDBN}
18974 (@pxref{Target Commands, ,Commands for Managing Targets}).
18976 @cindex target architecture
18977 It is possible to build @value{GDBN} for several different @dfn{target
18978 architectures}. When @value{GDBN} is built like that, you can choose
18979 one of the available architectures with the @kbd{set architecture}
18983 @kindex set architecture
18984 @kindex show architecture
18985 @item set architecture @var{arch}
18986 This command sets the current target architecture to @var{arch}. The
18987 value of @var{arch} can be @code{"auto"}, in addition to one of the
18988 supported architectures.
18990 @item show architecture
18991 Show the current target architecture.
18993 @item set processor
18995 @kindex set processor
18996 @kindex show processor
18997 These are alias commands for, respectively, @code{set architecture}
18998 and @code{show architecture}.
19002 * Active Targets:: Active targets
19003 * Target Commands:: Commands for managing targets
19004 * Byte Order:: Choosing target byte order
19007 @node Active Targets
19008 @section Active Targets
19010 @cindex stacking targets
19011 @cindex active targets
19012 @cindex multiple targets
19014 There are multiple classes of targets such as: processes, executable files or
19015 recording sessions. Core files belong to the process class, making core file
19016 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19017 on multiple active targets, one in each class. This allows you to (for
19018 example) start a process and inspect its activity, while still having access to
19019 the executable file after the process finishes. Or if you start process
19020 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19021 presented a virtual layer of the recording target, while the process target
19022 remains stopped at the chronologically last point of the process execution.
19024 Use the @code{core-file} and @code{exec-file} commands to select a new core
19025 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19026 specify as a target a process that is already running, use the @code{attach}
19027 command (@pxref{Attach, ,Debugging an Already-running Process}).
19029 @node Target Commands
19030 @section Commands for Managing Targets
19033 @item target @var{type} @var{parameters}
19034 Connects the @value{GDBN} host environment to a target machine or
19035 process. A target is typically a protocol for talking to debugging
19036 facilities. You use the argument @var{type} to specify the type or
19037 protocol of the target machine.
19039 Further @var{parameters} are interpreted by the target protocol, but
19040 typically include things like device names or host names to connect
19041 with, process numbers, and baud rates.
19043 The @code{target} command does not repeat if you press @key{RET} again
19044 after executing the command.
19046 @kindex help target
19048 Displays the names of all targets available. To display targets
19049 currently selected, use either @code{info target} or @code{info files}
19050 (@pxref{Files, ,Commands to Specify Files}).
19052 @item help target @var{name}
19053 Describe a particular target, including any parameters necessary to
19056 @kindex set gnutarget
19057 @item set gnutarget @var{args}
19058 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19059 knows whether it is reading an @dfn{executable},
19060 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19061 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19062 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19065 @emph{Warning:} To specify a file format with @code{set gnutarget},
19066 you must know the actual BFD name.
19070 @xref{Files, , Commands to Specify Files}.
19072 @kindex show gnutarget
19073 @item show gnutarget
19074 Use the @code{show gnutarget} command to display what file format
19075 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19076 @value{GDBN} will determine the file format for each file automatically,
19077 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19080 @cindex common targets
19081 Here are some common targets (available, or not, depending on the GDB
19086 @item target exec @var{program}
19087 @cindex executable file target
19088 An executable file. @samp{target exec @var{program}} is the same as
19089 @samp{exec-file @var{program}}.
19091 @item target core @var{filename}
19092 @cindex core dump file target
19093 A core dump file. @samp{target core @var{filename}} is the same as
19094 @samp{core-file @var{filename}}.
19096 @item target remote @var{medium}
19097 @cindex remote target
19098 A remote system connected to @value{GDBN} via a serial line or network
19099 connection. This command tells @value{GDBN} to use its own remote
19100 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19102 For example, if you have a board connected to @file{/dev/ttya} on the
19103 machine running @value{GDBN}, you could say:
19106 target remote /dev/ttya
19109 @code{target remote} supports the @code{load} command. This is only
19110 useful if you have some other way of getting the stub to the target
19111 system, and you can put it somewhere in memory where it won't get
19112 clobbered by the download.
19114 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19115 @cindex built-in simulator target
19116 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19124 works; however, you cannot assume that a specific memory map, device
19125 drivers, or even basic I/O is available, although some simulators do
19126 provide these. For info about any processor-specific simulator details,
19127 see the appropriate section in @ref{Embedded Processors, ,Embedded
19130 @item target native
19131 @cindex native target
19132 Setup for local/native process debugging. Useful to make the
19133 @code{run} command spawn native processes (likewise @code{attach},
19134 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19135 (@pxref{set auto-connect-native-target}).
19139 Different targets are available on different configurations of @value{GDBN};
19140 your configuration may have more or fewer targets.
19142 Many remote targets require you to download the executable's code once
19143 you've successfully established a connection. You may wish to control
19144 various aspects of this process.
19149 @kindex set hash@r{, for remote monitors}
19150 @cindex hash mark while downloading
19151 This command controls whether a hash mark @samp{#} is displayed while
19152 downloading a file to the remote monitor. If on, a hash mark is
19153 displayed after each S-record is successfully downloaded to the
19157 @kindex show hash@r{, for remote monitors}
19158 Show the current status of displaying the hash mark.
19160 @item set debug monitor
19161 @kindex set debug monitor
19162 @cindex display remote monitor communications
19163 Enable or disable display of communications messages between
19164 @value{GDBN} and the remote monitor.
19166 @item show debug monitor
19167 @kindex show debug monitor
19168 Show the current status of displaying communications between
19169 @value{GDBN} and the remote monitor.
19174 @kindex load @var{filename}
19175 @item load @var{filename}
19177 Depending on what remote debugging facilities are configured into
19178 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19179 is meant to make @var{filename} (an executable) available for debugging
19180 on the remote system---by downloading, or dynamic linking, for example.
19181 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19182 the @code{add-symbol-file} command.
19184 If your @value{GDBN} does not have a @code{load} command, attempting to
19185 execute it gets the error message ``@code{You can't do that when your
19186 target is @dots{}}''
19188 The file is loaded at whatever address is specified in the executable.
19189 For some object file formats, you can specify the load address when you
19190 link the program; for other formats, like a.out, the object file format
19191 specifies a fixed address.
19192 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19194 Depending on the remote side capabilities, @value{GDBN} may be able to
19195 load programs into flash memory.
19197 @code{load} does not repeat if you press @key{RET} again after using it.
19201 @section Choosing Target Byte Order
19203 @cindex choosing target byte order
19204 @cindex target byte order
19206 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19207 offer the ability to run either big-endian or little-endian byte
19208 orders. Usually the executable or symbol will include a bit to
19209 designate the endian-ness, and you will not need to worry about
19210 which to use. However, you may still find it useful to adjust
19211 @value{GDBN}'s idea of processor endian-ness manually.
19215 @item set endian big
19216 Instruct @value{GDBN} to assume the target is big-endian.
19218 @item set endian little
19219 Instruct @value{GDBN} to assume the target is little-endian.
19221 @item set endian auto
19222 Instruct @value{GDBN} to use the byte order associated with the
19226 Display @value{GDBN}'s current idea of the target byte order.
19230 Note that these commands merely adjust interpretation of symbolic
19231 data on the host, and that they have absolutely no effect on the
19235 @node Remote Debugging
19236 @chapter Debugging Remote Programs
19237 @cindex remote debugging
19239 If you are trying to debug a program running on a machine that cannot run
19240 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19241 For example, you might use remote debugging on an operating system kernel,
19242 or on a small system which does not have a general purpose operating system
19243 powerful enough to run a full-featured debugger.
19245 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19246 to make this work with particular debugging targets. In addition,
19247 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19248 but not specific to any particular target system) which you can use if you
19249 write the remote stubs---the code that runs on the remote system to
19250 communicate with @value{GDBN}.
19252 Other remote targets may be available in your
19253 configuration of @value{GDBN}; use @code{help target} to list them.
19256 * Connecting:: Connecting to a remote target
19257 * File Transfer:: Sending files to a remote system
19258 * Server:: Using the gdbserver program
19259 * Remote Configuration:: Remote configuration
19260 * Remote Stub:: Implementing a remote stub
19264 @section Connecting to a Remote Target
19266 @value{GDBN} needs an unstripped copy of your program to access symbol
19267 and debugging information. Some remote targets (@pxref{qXfer
19268 executable filename read}, and @pxref{Host I/O Packets}) allow
19269 @value{GDBN} to access program files over the same connection used to
19270 communicate with @value{GDBN}. With such a target, if the remote
19271 program is unstripped, the only command you need is @code{target
19272 remote}. Otherwise, start up @value{GDBN} using the name of the local
19273 unstripped copy of your program as the first argument, or use the
19274 @code{file} command.
19276 @cindex @code{target remote}
19277 @value{GDBN} can communicate with the target over a serial line, or
19278 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19279 each case, @value{GDBN} uses the same protocol for debugging your
19280 program; only the medium carrying the debugging packets varies. The
19281 @code{target remote} command establishes a connection to the target.
19282 Its arguments indicate which medium to use:
19286 @item target remote @var{serial-device}
19287 @cindex serial line, @code{target remote}
19288 Use @var{serial-device} to communicate with the target. For example,
19289 to use a serial line connected to the device named @file{/dev/ttyb}:
19292 target remote /dev/ttyb
19295 If you're using a serial line, you may want to give @value{GDBN} the
19296 @samp{--baud} option, or use the @code{set serial baud} command
19297 (@pxref{Remote Configuration, set serial baud}) before the
19298 @code{target} command.
19300 @item target remote @code{@var{host}:@var{port}}
19301 @itemx target remote @code{tcp:@var{host}:@var{port}}
19302 @cindex @acronym{TCP} port, @code{target remote}
19303 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19304 The @var{host} may be either a host name or a numeric @acronym{IP}
19305 address; @var{port} must be a decimal number. The @var{host} could be
19306 the target machine itself, if it is directly connected to the net, or
19307 it might be a terminal server which in turn has a serial line to the
19310 For example, to connect to port 2828 on a terminal server named
19314 target remote manyfarms:2828
19317 If your remote target is actually running on the same machine as your
19318 debugger session (e.g.@: a simulator for your target running on the
19319 same host), you can omit the hostname. For example, to connect to
19320 port 1234 on your local machine:
19323 target remote :1234
19327 Note that the colon is still required here.
19329 @item target remote @code{udp:@var{host}:@var{port}}
19330 @cindex @acronym{UDP} port, @code{target remote}
19331 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19332 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19335 target remote udp:manyfarms:2828
19338 When using a @acronym{UDP} connection for remote debugging, you should
19339 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19340 can silently drop packets on busy or unreliable networks, which will
19341 cause havoc with your debugging session.
19343 @item target remote | @var{command}
19344 @cindex pipe, @code{target remote} to
19345 Run @var{command} in the background and communicate with it using a
19346 pipe. The @var{command} is a shell command, to be parsed and expanded
19347 by the system's command shell, @code{/bin/sh}; it should expect remote
19348 protocol packets on its standard input, and send replies on its
19349 standard output. You could use this to run a stand-alone simulator
19350 that speaks the remote debugging protocol, to make net connections
19351 using programs like @code{ssh}, or for other similar tricks.
19353 If @var{command} closes its standard output (perhaps by exiting),
19354 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19355 program has already exited, this will have no effect.)
19359 Once the connection has been established, you can use all the usual
19360 commands to examine and change data. The remote program is already
19361 running; you can use @kbd{step} and @kbd{continue}, and you do not
19362 need to use @kbd{run}.
19364 @cindex interrupting remote programs
19365 @cindex remote programs, interrupting
19366 Whenever @value{GDBN} is waiting for the remote program, if you type the
19367 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19368 program. This may or may not succeed, depending in part on the hardware
19369 and the serial drivers the remote system uses. If you type the
19370 interrupt character once again, @value{GDBN} displays this prompt:
19373 Interrupted while waiting for the program.
19374 Give up (and stop debugging it)? (y or n)
19377 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19378 (If you decide you want to try again later, you can use @samp{target
19379 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19380 goes back to waiting.
19383 @kindex detach (remote)
19385 When you have finished debugging the remote program, you can use the
19386 @code{detach} command to release it from @value{GDBN} control.
19387 Detaching from the target normally resumes its execution, but the results
19388 will depend on your particular remote stub. After the @code{detach}
19389 command, @value{GDBN} is free to connect to another target.
19393 The @code{disconnect} command behaves like @code{detach}, except that
19394 the target is generally not resumed. It will wait for @value{GDBN}
19395 (this instance or another one) to connect and continue debugging. After
19396 the @code{disconnect} command, @value{GDBN} is again free to connect to
19399 @cindex send command to remote monitor
19400 @cindex extend @value{GDBN} for remote targets
19401 @cindex add new commands for external monitor
19403 @item monitor @var{cmd}
19404 This command allows you to send arbitrary commands directly to the
19405 remote monitor. Since @value{GDBN} doesn't care about the commands it
19406 sends like this, this command is the way to extend @value{GDBN}---you
19407 can add new commands that only the external monitor will understand
19411 @node File Transfer
19412 @section Sending files to a remote system
19413 @cindex remote target, file transfer
19414 @cindex file transfer
19415 @cindex sending files to remote systems
19417 Some remote targets offer the ability to transfer files over the same
19418 connection used to communicate with @value{GDBN}. This is convenient
19419 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19420 running @code{gdbserver} over a network interface. For other targets,
19421 e.g.@: embedded devices with only a single serial port, this may be
19422 the only way to upload or download files.
19424 Not all remote targets support these commands.
19428 @item remote put @var{hostfile} @var{targetfile}
19429 Copy file @var{hostfile} from the host system (the machine running
19430 @value{GDBN}) to @var{targetfile} on the target system.
19433 @item remote get @var{targetfile} @var{hostfile}
19434 Copy file @var{targetfile} from the target system to @var{hostfile}
19435 on the host system.
19437 @kindex remote delete
19438 @item remote delete @var{targetfile}
19439 Delete @var{targetfile} from the target system.
19444 @section Using the @code{gdbserver} Program
19447 @cindex remote connection without stubs
19448 @code{gdbserver} is a control program for Unix-like systems, which
19449 allows you to connect your program with a remote @value{GDBN} via
19450 @code{target remote}---but without linking in the usual debugging stub.
19452 @code{gdbserver} is not a complete replacement for the debugging stubs,
19453 because it requires essentially the same operating-system facilities
19454 that @value{GDBN} itself does. In fact, a system that can run
19455 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19456 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19457 because it is a much smaller program than @value{GDBN} itself. It is
19458 also easier to port than all of @value{GDBN}, so you may be able to get
19459 started more quickly on a new system by using @code{gdbserver}.
19460 Finally, if you develop code for real-time systems, you may find that
19461 the tradeoffs involved in real-time operation make it more convenient to
19462 do as much development work as possible on another system, for example
19463 by cross-compiling. You can use @code{gdbserver} to make a similar
19464 choice for debugging.
19466 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19467 or a TCP connection, using the standard @value{GDBN} remote serial
19471 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19472 Do not run @code{gdbserver} connected to any public network; a
19473 @value{GDBN} connection to @code{gdbserver} provides access to the
19474 target system with the same privileges as the user running
19478 @subsection Running @code{gdbserver}
19479 @cindex arguments, to @code{gdbserver}
19480 @cindex @code{gdbserver}, command-line arguments
19482 Run @code{gdbserver} on the target system. You need a copy of the
19483 program you want to debug, including any libraries it requires.
19484 @code{gdbserver} does not need your program's symbol table, so you can
19485 strip the program if necessary to save space. @value{GDBN} on the host
19486 system does all the symbol handling.
19488 To use the server, you must tell it how to communicate with @value{GDBN};
19489 the name of your program; and the arguments for your program. The usual
19493 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19496 @var{comm} is either a device name (to use a serial line), or a TCP
19497 hostname and portnumber, or @code{-} or @code{stdio} to use
19498 stdin/stdout of @code{gdbserver}.
19499 For example, to debug Emacs with the argument
19500 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19504 target> gdbserver /dev/com1 emacs foo.txt
19507 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19510 To use a TCP connection instead of a serial line:
19513 target> gdbserver host:2345 emacs foo.txt
19516 The only difference from the previous example is the first argument,
19517 specifying that you are communicating with the host @value{GDBN} via
19518 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19519 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19520 (Currently, the @samp{host} part is ignored.) You can choose any number
19521 you want for the port number as long as it does not conflict with any
19522 TCP ports already in use on the target system (for example, @code{23} is
19523 reserved for @code{telnet}).@footnote{If you choose a port number that
19524 conflicts with another service, @code{gdbserver} prints an error message
19525 and exits.} You must use the same port number with the host @value{GDBN}
19526 @code{target remote} command.
19528 The @code{stdio} connection is useful when starting @code{gdbserver}
19532 (gdb) target remote | ssh -T hostname gdbserver - hello
19535 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19536 and we don't want escape-character handling. Ssh does this by default when
19537 a command is provided, the flag is provided to make it explicit.
19538 You could elide it if you want to.
19540 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19541 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19542 display through a pipe connected to gdbserver.
19543 Both @code{stdout} and @code{stderr} use the same pipe.
19545 @subsubsection Attaching to a Running Program
19546 @cindex attach to a program, @code{gdbserver}
19547 @cindex @option{--attach}, @code{gdbserver} option
19549 On some targets, @code{gdbserver} can also attach to running programs.
19550 This is accomplished via the @code{--attach} argument. The syntax is:
19553 target> gdbserver --attach @var{comm} @var{pid}
19556 @var{pid} is the process ID of a currently running process. It isn't necessary
19557 to point @code{gdbserver} at a binary for the running process.
19560 You can debug processes by name instead of process ID if your target has the
19561 @code{pidof} utility:
19564 target> gdbserver --attach @var{comm} `pidof @var{program}`
19567 In case more than one copy of @var{program} is running, or @var{program}
19568 has multiple threads, most versions of @code{pidof} support the
19569 @code{-s} option to only return the first process ID.
19571 @subsubsection Multi-Process Mode for @code{gdbserver}
19572 @cindex @code{gdbserver}, multiple processes
19573 @cindex multiple processes with @code{gdbserver}
19575 When you connect to @code{gdbserver} using @code{target remote},
19576 @code{gdbserver} debugs the specified program only once. When the
19577 program exits, or you detach from it, @value{GDBN} closes the connection
19578 and @code{gdbserver} exits.
19580 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19581 enters multi-process mode. When the debugged program exits, or you
19582 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19583 though no program is running. The @code{run} and @code{attach}
19584 commands instruct @code{gdbserver} to run or attach to a new program.
19585 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19586 remote exec-file}) to select the program to run. Command line
19587 arguments are supported, except for wildcard expansion and I/O
19588 redirection (@pxref{Arguments}).
19590 @cindex @option{--multi}, @code{gdbserver} option
19591 To start @code{gdbserver} without supplying an initial command to run
19592 or process ID to attach, use the @option{--multi} command line option.
19593 Then you can connect using @kbd{target extended-remote} and start
19594 the program you want to debug.
19596 In multi-process mode @code{gdbserver} does not automatically exit unless you
19597 use the option @option{--once}. You can terminate it by using
19598 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19599 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19600 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19601 @option{--multi} option to @code{gdbserver} has no influence on that.
19603 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19605 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19607 @code{gdbserver} normally terminates after all of its debugged processes have
19608 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19609 extended-remote}, @code{gdbserver} stays running even with no processes left.
19610 @value{GDBN} normally terminates the spawned debugged process on its exit,
19611 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19612 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19613 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19614 stays running even in the @kbd{target remote} mode.
19616 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19617 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19618 completeness, at most one @value{GDBN} can be connected at a time.
19620 @cindex @option{--once}, @code{gdbserver} option
19621 By default, @code{gdbserver} keeps the listening TCP port open, so that
19622 subsequent connections are possible. However, if you start @code{gdbserver}
19623 with the @option{--once} option, it will stop listening for any further
19624 connection attempts after connecting to the first @value{GDBN} session. This
19625 means no further connections to @code{gdbserver} will be possible after the
19626 first one. It also means @code{gdbserver} will terminate after the first
19627 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19628 connections and even in the @kbd{target extended-remote} mode. The
19629 @option{--once} option allows reusing the same port number for connecting to
19630 multiple instances of @code{gdbserver} running on the same host, since each
19631 instance closes its port after the first connection.
19633 @anchor{Other Command-Line Arguments for gdbserver}
19634 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19636 @cindex @option{--debug}, @code{gdbserver} option
19637 The @option{--debug} option tells @code{gdbserver} to display extra
19638 status information about the debugging process.
19639 @cindex @option{--remote-debug}, @code{gdbserver} option
19640 The @option{--remote-debug} option tells @code{gdbserver} to display
19641 remote protocol debug output. These options are intended for
19642 @code{gdbserver} development and for bug reports to the developers.
19644 @cindex @option{--debug-format}, @code{gdbserver} option
19645 The @option{--debug-format=option1[,option2,...]} option tells
19646 @code{gdbserver} to include additional information in each output.
19647 Possible options are:
19651 Turn off all extra information in debugging output.
19653 Turn on all extra information in debugging output.
19655 Include a timestamp in each line of debugging output.
19658 Options are processed in order. Thus, for example, if @option{none}
19659 appears last then no additional information is added to debugging output.
19661 @cindex @option{--wrapper}, @code{gdbserver} option
19662 The @option{--wrapper} option specifies a wrapper to launch programs
19663 for debugging. The option should be followed by the name of the
19664 wrapper, then any command-line arguments to pass to the wrapper, then
19665 @kbd{--} indicating the end of the wrapper arguments.
19667 @code{gdbserver} runs the specified wrapper program with a combined
19668 command line including the wrapper arguments, then the name of the
19669 program to debug, then any arguments to the program. The wrapper
19670 runs until it executes your program, and then @value{GDBN} gains control.
19672 You can use any program that eventually calls @code{execve} with
19673 its arguments as a wrapper. Several standard Unix utilities do
19674 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19675 with @code{exec "$@@"} will also work.
19677 For example, you can use @code{env} to pass an environment variable to
19678 the debugged program, without setting the variable in @code{gdbserver}'s
19682 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19685 @subsection Connecting to @code{gdbserver}
19687 Run @value{GDBN} on the host system.
19689 First make sure you have the necessary symbol files. Load symbols for
19690 your application using the @code{file} command before you connect. Use
19691 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19692 was compiled with the correct sysroot using @code{--with-sysroot}).
19694 The symbol file and target libraries must exactly match the executable
19695 and libraries on the target, with one exception: the files on the host
19696 system should not be stripped, even if the files on the target system
19697 are. Mismatched or missing files will lead to confusing results
19698 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19699 files may also prevent @code{gdbserver} from debugging multi-threaded
19702 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19703 For TCP connections, you must start up @code{gdbserver} prior to using
19704 the @code{target remote} command. Otherwise you may get an error whose
19705 text depends on the host system, but which usually looks something like
19706 @samp{Connection refused}. Don't use the @code{load}
19707 command in @value{GDBN} when using @code{gdbserver}, since the program is
19708 already on the target.
19710 @subsection Monitor Commands for @code{gdbserver}
19711 @cindex monitor commands, for @code{gdbserver}
19712 @anchor{Monitor Commands for gdbserver}
19714 During a @value{GDBN} session using @code{gdbserver}, you can use the
19715 @code{monitor} command to send special requests to @code{gdbserver}.
19716 Here are the available commands.
19720 List the available monitor commands.
19722 @item monitor set debug 0
19723 @itemx monitor set debug 1
19724 Disable or enable general debugging messages.
19726 @item monitor set remote-debug 0
19727 @itemx monitor set remote-debug 1
19728 Disable or enable specific debugging messages associated with the remote
19729 protocol (@pxref{Remote Protocol}).
19731 @item monitor set debug-format option1@r{[},option2,...@r{]}
19732 Specify additional text to add to debugging messages.
19733 Possible options are:
19737 Turn off all extra information in debugging output.
19739 Turn on all extra information in debugging output.
19741 Include a timestamp in each line of debugging output.
19744 Options are processed in order. Thus, for example, if @option{none}
19745 appears last then no additional information is added to debugging output.
19747 @item monitor set libthread-db-search-path [PATH]
19748 @cindex gdbserver, search path for @code{libthread_db}
19749 When this command is issued, @var{path} is a colon-separated list of
19750 directories to search for @code{libthread_db} (@pxref{Threads,,set
19751 libthread-db-search-path}). If you omit @var{path},
19752 @samp{libthread-db-search-path} will be reset to its default value.
19754 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19755 not supported in @code{gdbserver}.
19758 Tell gdbserver to exit immediately. This command should be followed by
19759 @code{disconnect} to close the debugging session. @code{gdbserver} will
19760 detach from any attached processes and kill any processes it created.
19761 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19762 of a multi-process mode debug session.
19766 @subsection Tracepoints support in @code{gdbserver}
19767 @cindex tracepoints support in @code{gdbserver}
19769 On some targets, @code{gdbserver} supports tracepoints, fast
19770 tracepoints and static tracepoints.
19772 For fast or static tracepoints to work, a special library called the
19773 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19774 This library is built and distributed as an integral part of
19775 @code{gdbserver}. In addition, support for static tracepoints
19776 requires building the in-process agent library with static tracepoints
19777 support. At present, the UST (LTTng Userspace Tracer,
19778 @url{http://lttng.org/ust}) tracing engine is supported. This support
19779 is automatically available if UST development headers are found in the
19780 standard include path when @code{gdbserver} is built, or if
19781 @code{gdbserver} was explicitly configured using @option{--with-ust}
19782 to point at such headers. You can explicitly disable the support
19783 using @option{--with-ust=no}.
19785 There are several ways to load the in-process agent in your program:
19788 @item Specifying it as dependency at link time
19790 You can link your program dynamically with the in-process agent
19791 library. On most systems, this is accomplished by adding
19792 @code{-linproctrace} to the link command.
19794 @item Using the system's preloading mechanisms
19796 You can force loading the in-process agent at startup time by using
19797 your system's support for preloading shared libraries. Many Unixes
19798 support the concept of preloading user defined libraries. In most
19799 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19800 in the environment. See also the description of @code{gdbserver}'s
19801 @option{--wrapper} command line option.
19803 @item Using @value{GDBN} to force loading the agent at run time
19805 On some systems, you can force the inferior to load a shared library,
19806 by calling a dynamic loader function in the inferior that takes care
19807 of dynamically looking up and loading a shared library. On most Unix
19808 systems, the function is @code{dlopen}. You'll use the @code{call}
19809 command for that. For example:
19812 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19815 Note that on most Unix systems, for the @code{dlopen} function to be
19816 available, the program needs to be linked with @code{-ldl}.
19819 On systems that have a userspace dynamic loader, like most Unix
19820 systems, when you connect to @code{gdbserver} using @code{target
19821 remote}, you'll find that the program is stopped at the dynamic
19822 loader's entry point, and no shared library has been loaded in the
19823 program's address space yet, including the in-process agent. In that
19824 case, before being able to use any of the fast or static tracepoints
19825 features, you need to let the loader run and load the shared
19826 libraries. The simplest way to do that is to run the program to the
19827 main procedure. E.g., if debugging a C or C@t{++} program, start
19828 @code{gdbserver} like so:
19831 $ gdbserver :9999 myprogram
19834 Start GDB and connect to @code{gdbserver} like so, and run to main:
19838 (@value{GDBP}) target remote myhost:9999
19839 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19840 (@value{GDBP}) b main
19841 (@value{GDBP}) continue
19844 The in-process tracing agent library should now be loaded into the
19845 process; you can confirm it with the @code{info sharedlibrary}
19846 command, which will list @file{libinproctrace.so} as loaded in the
19847 process. You are now ready to install fast tracepoints, list static
19848 tracepoint markers, probe static tracepoints markers, and start
19851 @node Remote Configuration
19852 @section Remote Configuration
19855 @kindex show remote
19856 This section documents the configuration options available when
19857 debugging remote programs. For the options related to the File I/O
19858 extensions of the remote protocol, see @ref{system,
19859 system-call-allowed}.
19862 @item set remoteaddresssize @var{bits}
19863 @cindex address size for remote targets
19864 @cindex bits in remote address
19865 Set the maximum size of address in a memory packet to the specified
19866 number of bits. @value{GDBN} will mask off the address bits above
19867 that number, when it passes addresses to the remote target. The
19868 default value is the number of bits in the target's address.
19870 @item show remoteaddresssize
19871 Show the current value of remote address size in bits.
19873 @item set serial baud @var{n}
19874 @cindex baud rate for remote targets
19875 Set the baud rate for the remote serial I/O to @var{n} baud. The
19876 value is used to set the speed of the serial port used for debugging
19879 @item show serial baud
19880 Show the current speed of the remote connection.
19882 @item set serial parity @var{parity}
19883 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19884 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19886 @item show serial parity
19887 Show the current parity of the serial port.
19889 @item set remotebreak
19890 @cindex interrupt remote programs
19891 @cindex BREAK signal instead of Ctrl-C
19892 @anchor{set remotebreak}
19893 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19894 when you type @kbd{Ctrl-c} to interrupt the program running
19895 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19896 character instead. The default is off, since most remote systems
19897 expect to see @samp{Ctrl-C} as the interrupt signal.
19899 @item show remotebreak
19900 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19901 interrupt the remote program.
19903 @item set remoteflow on
19904 @itemx set remoteflow off
19905 @kindex set remoteflow
19906 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19907 on the serial port used to communicate to the remote target.
19909 @item show remoteflow
19910 @kindex show remoteflow
19911 Show the current setting of hardware flow control.
19913 @item set remotelogbase @var{base}
19914 Set the base (a.k.a.@: radix) of logging serial protocol
19915 communications to @var{base}. Supported values of @var{base} are:
19916 @code{ascii}, @code{octal}, and @code{hex}. The default is
19919 @item show remotelogbase
19920 Show the current setting of the radix for logging remote serial
19923 @item set remotelogfile @var{file}
19924 @cindex record serial communications on file
19925 Record remote serial communications on the named @var{file}. The
19926 default is not to record at all.
19928 @item show remotelogfile.
19929 Show the current setting of the file name on which to record the
19930 serial communications.
19932 @item set remotetimeout @var{num}
19933 @cindex timeout for serial communications
19934 @cindex remote timeout
19935 Set the timeout limit to wait for the remote target to respond to
19936 @var{num} seconds. The default is 2 seconds.
19938 @item show remotetimeout
19939 Show the current number of seconds to wait for the remote target
19942 @cindex limit hardware breakpoints and watchpoints
19943 @cindex remote target, limit break- and watchpoints
19944 @anchor{set remote hardware-watchpoint-limit}
19945 @anchor{set remote hardware-breakpoint-limit}
19946 @item set remote hardware-watchpoint-limit @var{limit}
19947 @itemx set remote hardware-breakpoint-limit @var{limit}
19948 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19949 watchpoints. A limit of -1, the default, is treated as unlimited.
19951 @cindex limit hardware watchpoints length
19952 @cindex remote target, limit watchpoints length
19953 @anchor{set remote hardware-watchpoint-length-limit}
19954 @item set remote hardware-watchpoint-length-limit @var{limit}
19955 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19956 a remote hardware watchpoint. A limit of -1, the default, is treated
19959 @item show remote hardware-watchpoint-length-limit
19960 Show the current limit (in bytes) of the maximum length of
19961 a remote hardware watchpoint.
19963 @item set remote exec-file @var{filename}
19964 @itemx show remote exec-file
19965 @anchor{set remote exec-file}
19966 @cindex executable file, for remote target
19967 Select the file used for @code{run} with @code{target
19968 extended-remote}. This should be set to a filename valid on the
19969 target system. If it is not set, the target will use a default
19970 filename (e.g.@: the last program run).
19972 @item set remote interrupt-sequence
19973 @cindex interrupt remote programs
19974 @cindex select Ctrl-C, BREAK or BREAK-g
19975 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19976 @samp{BREAK-g} as the
19977 sequence to the remote target in order to interrupt the execution.
19978 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19979 is high level of serial line for some certain time.
19980 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19981 It is @code{BREAK} signal followed by character @code{g}.
19983 @item show interrupt-sequence
19984 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19985 is sent by @value{GDBN} to interrupt the remote program.
19986 @code{BREAK-g} is BREAK signal followed by @code{g} and
19987 also known as Magic SysRq g.
19989 @item set remote interrupt-on-connect
19990 @cindex send interrupt-sequence on start
19991 Specify whether interrupt-sequence is sent to remote target when
19992 @value{GDBN} connects to it. This is mostly needed when you debug
19993 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19994 which is known as Magic SysRq g in order to connect @value{GDBN}.
19996 @item show interrupt-on-connect
19997 Show whether interrupt-sequence is sent
19998 to remote target when @value{GDBN} connects to it.
20002 @item set tcp auto-retry on
20003 @cindex auto-retry, for remote TCP target
20004 Enable auto-retry for remote TCP connections. This is useful if the remote
20005 debugging agent is launched in parallel with @value{GDBN}; there is a race
20006 condition because the agent may not become ready to accept the connection
20007 before @value{GDBN} attempts to connect. When auto-retry is
20008 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20009 to establish the connection using the timeout specified by
20010 @code{set tcp connect-timeout}.
20012 @item set tcp auto-retry off
20013 Do not auto-retry failed TCP connections.
20015 @item show tcp auto-retry
20016 Show the current auto-retry setting.
20018 @item set tcp connect-timeout @var{seconds}
20019 @itemx set tcp connect-timeout unlimited
20020 @cindex connection timeout, for remote TCP target
20021 @cindex timeout, for remote target connection
20022 Set the timeout for establishing a TCP connection to the remote target to
20023 @var{seconds}. The timeout affects both polling to retry failed connections
20024 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20025 that are merely slow to complete, and represents an approximate cumulative
20026 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20027 @value{GDBN} will keep attempting to establish a connection forever,
20028 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20030 @item show tcp connect-timeout
20031 Show the current connection timeout setting.
20034 @cindex remote packets, enabling and disabling
20035 The @value{GDBN} remote protocol autodetects the packets supported by
20036 your debugging stub. If you need to override the autodetection, you
20037 can use these commands to enable or disable individual packets. Each
20038 packet can be set to @samp{on} (the remote target supports this
20039 packet), @samp{off} (the remote target does not support this packet),
20040 or @samp{auto} (detect remote target support for this packet). They
20041 all default to @samp{auto}. For more information about each packet,
20042 see @ref{Remote Protocol}.
20044 During normal use, you should not have to use any of these commands.
20045 If you do, that may be a bug in your remote debugging stub, or a bug
20046 in @value{GDBN}. You may want to report the problem to the
20047 @value{GDBN} developers.
20049 For each packet @var{name}, the command to enable or disable the
20050 packet is @code{set remote @var{name}-packet}. The available settings
20053 @multitable @columnfractions 0.28 0.32 0.25
20056 @tab Related Features
20058 @item @code{fetch-register}
20060 @tab @code{info registers}
20062 @item @code{set-register}
20066 @item @code{binary-download}
20068 @tab @code{load}, @code{set}
20070 @item @code{read-aux-vector}
20071 @tab @code{qXfer:auxv:read}
20072 @tab @code{info auxv}
20074 @item @code{symbol-lookup}
20075 @tab @code{qSymbol}
20076 @tab Detecting multiple threads
20078 @item @code{attach}
20079 @tab @code{vAttach}
20082 @item @code{verbose-resume}
20084 @tab Stepping or resuming multiple threads
20090 @item @code{software-breakpoint}
20094 @item @code{hardware-breakpoint}
20098 @item @code{write-watchpoint}
20102 @item @code{read-watchpoint}
20106 @item @code{access-watchpoint}
20110 @item @code{pid-to-exec-file}
20111 @tab @code{qXfer:exec-file:read}
20112 @tab @code{attach}, @code{run}
20114 @item @code{target-features}
20115 @tab @code{qXfer:features:read}
20116 @tab @code{set architecture}
20118 @item @code{library-info}
20119 @tab @code{qXfer:libraries:read}
20120 @tab @code{info sharedlibrary}
20122 @item @code{memory-map}
20123 @tab @code{qXfer:memory-map:read}
20124 @tab @code{info mem}
20126 @item @code{read-sdata-object}
20127 @tab @code{qXfer:sdata:read}
20128 @tab @code{print $_sdata}
20130 @item @code{read-spu-object}
20131 @tab @code{qXfer:spu:read}
20132 @tab @code{info spu}
20134 @item @code{write-spu-object}
20135 @tab @code{qXfer:spu:write}
20136 @tab @code{info spu}
20138 @item @code{read-siginfo-object}
20139 @tab @code{qXfer:siginfo:read}
20140 @tab @code{print $_siginfo}
20142 @item @code{write-siginfo-object}
20143 @tab @code{qXfer:siginfo:write}
20144 @tab @code{set $_siginfo}
20146 @item @code{threads}
20147 @tab @code{qXfer:threads:read}
20148 @tab @code{info threads}
20150 @item @code{get-thread-local-@*storage-address}
20151 @tab @code{qGetTLSAddr}
20152 @tab Displaying @code{__thread} variables
20154 @item @code{get-thread-information-block-address}
20155 @tab @code{qGetTIBAddr}
20156 @tab Display MS-Windows Thread Information Block.
20158 @item @code{search-memory}
20159 @tab @code{qSearch:memory}
20162 @item @code{supported-packets}
20163 @tab @code{qSupported}
20164 @tab Remote communications parameters
20166 @item @code{pass-signals}
20167 @tab @code{QPassSignals}
20168 @tab @code{handle @var{signal}}
20170 @item @code{program-signals}
20171 @tab @code{QProgramSignals}
20172 @tab @code{handle @var{signal}}
20174 @item @code{hostio-close-packet}
20175 @tab @code{vFile:close}
20176 @tab @code{remote get}, @code{remote put}
20178 @item @code{hostio-open-packet}
20179 @tab @code{vFile:open}
20180 @tab @code{remote get}, @code{remote put}
20182 @item @code{hostio-pread-packet}
20183 @tab @code{vFile:pread}
20184 @tab @code{remote get}, @code{remote put}
20186 @item @code{hostio-pwrite-packet}
20187 @tab @code{vFile:pwrite}
20188 @tab @code{remote get}, @code{remote put}
20190 @item @code{hostio-unlink-packet}
20191 @tab @code{vFile:unlink}
20192 @tab @code{remote delete}
20194 @item @code{hostio-readlink-packet}
20195 @tab @code{vFile:readlink}
20198 @item @code{hostio-fstat-packet}
20199 @tab @code{vFile:fstat}
20202 @item @code{hostio-setfs-packet}
20203 @tab @code{vFile:setfs}
20206 @item @code{noack-packet}
20207 @tab @code{QStartNoAckMode}
20208 @tab Packet acknowledgment
20210 @item @code{osdata}
20211 @tab @code{qXfer:osdata:read}
20212 @tab @code{info os}
20214 @item @code{query-attached}
20215 @tab @code{qAttached}
20216 @tab Querying remote process attach state.
20218 @item @code{trace-buffer-size}
20219 @tab @code{QTBuffer:size}
20220 @tab @code{set trace-buffer-size}
20222 @item @code{trace-status}
20223 @tab @code{qTStatus}
20224 @tab @code{tstatus}
20226 @item @code{traceframe-info}
20227 @tab @code{qXfer:traceframe-info:read}
20228 @tab Traceframe info
20230 @item @code{install-in-trace}
20231 @tab @code{InstallInTrace}
20232 @tab Install tracepoint in tracing
20234 @item @code{disable-randomization}
20235 @tab @code{QDisableRandomization}
20236 @tab @code{set disable-randomization}
20238 @item @code{conditional-breakpoints-packet}
20239 @tab @code{Z0 and Z1}
20240 @tab @code{Support for target-side breakpoint condition evaluation}
20242 @item @code{multiprocess-extensions}
20243 @tab @code{multiprocess extensions}
20244 @tab Debug multiple processes and remote process PID awareness
20246 @item @code{swbreak-feature}
20247 @tab @code{swbreak stop reason}
20250 @item @code{hwbreak-feature}
20251 @tab @code{hwbreak stop reason}
20254 @item @code{fork-event-feature}
20255 @tab @code{fork stop reason}
20258 @item @code{vfork-event-feature}
20259 @tab @code{vfork stop reason}
20262 @item @code{exec-event-feature}
20263 @tab @code{exec stop reason}
20266 @item @code{thread-events}
20267 @tab @code{QThreadEvents}
20268 @tab Tracking thread lifetime.
20270 @item @code{no-resumed-stop-reply}
20271 @tab @code{no resumed thread left stop reply}
20272 @tab Tracking thread lifetime.
20277 @section Implementing a Remote Stub
20279 @cindex debugging stub, example
20280 @cindex remote stub, example
20281 @cindex stub example, remote debugging
20282 The stub files provided with @value{GDBN} implement the target side of the
20283 communication protocol, and the @value{GDBN} side is implemented in the
20284 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20285 these subroutines to communicate, and ignore the details. (If you're
20286 implementing your own stub file, you can still ignore the details: start
20287 with one of the existing stub files. @file{sparc-stub.c} is the best
20288 organized, and therefore the easiest to read.)
20290 @cindex remote serial debugging, overview
20291 To debug a program running on another machine (the debugging
20292 @dfn{target} machine), you must first arrange for all the usual
20293 prerequisites for the program to run by itself. For example, for a C
20298 A startup routine to set up the C runtime environment; these usually
20299 have a name like @file{crt0}. The startup routine may be supplied by
20300 your hardware supplier, or you may have to write your own.
20303 A C subroutine library to support your program's
20304 subroutine calls, notably managing input and output.
20307 A way of getting your program to the other machine---for example, a
20308 download program. These are often supplied by the hardware
20309 manufacturer, but you may have to write your own from hardware
20313 The next step is to arrange for your program to use a serial port to
20314 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20315 machine). In general terms, the scheme looks like this:
20319 @value{GDBN} already understands how to use this protocol; when everything
20320 else is set up, you can simply use the @samp{target remote} command
20321 (@pxref{Targets,,Specifying a Debugging Target}).
20323 @item On the target,
20324 you must link with your program a few special-purpose subroutines that
20325 implement the @value{GDBN} remote serial protocol. The file containing these
20326 subroutines is called a @dfn{debugging stub}.
20328 On certain remote targets, you can use an auxiliary program
20329 @code{gdbserver} instead of linking a stub into your program.
20330 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20333 The debugging stub is specific to the architecture of the remote
20334 machine; for example, use @file{sparc-stub.c} to debug programs on
20337 @cindex remote serial stub list
20338 These working remote stubs are distributed with @value{GDBN}:
20343 @cindex @file{i386-stub.c}
20346 For Intel 386 and compatible architectures.
20349 @cindex @file{m68k-stub.c}
20350 @cindex Motorola 680x0
20352 For Motorola 680x0 architectures.
20355 @cindex @file{sh-stub.c}
20358 For Renesas SH architectures.
20361 @cindex @file{sparc-stub.c}
20363 For @sc{sparc} architectures.
20365 @item sparcl-stub.c
20366 @cindex @file{sparcl-stub.c}
20369 For Fujitsu @sc{sparclite} architectures.
20373 The @file{README} file in the @value{GDBN} distribution may list other
20374 recently added stubs.
20377 * Stub Contents:: What the stub can do for you
20378 * Bootstrapping:: What you must do for the stub
20379 * Debug Session:: Putting it all together
20382 @node Stub Contents
20383 @subsection What the Stub Can Do for You
20385 @cindex remote serial stub
20386 The debugging stub for your architecture supplies these three
20390 @item set_debug_traps
20391 @findex set_debug_traps
20392 @cindex remote serial stub, initialization
20393 This routine arranges for @code{handle_exception} to run when your
20394 program stops. You must call this subroutine explicitly in your
20395 program's startup code.
20397 @item handle_exception
20398 @findex handle_exception
20399 @cindex remote serial stub, main routine
20400 This is the central workhorse, but your program never calls it
20401 explicitly---the setup code arranges for @code{handle_exception} to
20402 run when a trap is triggered.
20404 @code{handle_exception} takes control when your program stops during
20405 execution (for example, on a breakpoint), and mediates communications
20406 with @value{GDBN} on the host machine. This is where the communications
20407 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20408 representative on the target machine. It begins by sending summary
20409 information on the state of your program, then continues to execute,
20410 retrieving and transmitting any information @value{GDBN} needs, until you
20411 execute a @value{GDBN} command that makes your program resume; at that point,
20412 @code{handle_exception} returns control to your own code on the target
20416 @cindex @code{breakpoint} subroutine, remote
20417 Use this auxiliary subroutine to make your program contain a
20418 breakpoint. Depending on the particular situation, this may be the only
20419 way for @value{GDBN} to get control. For instance, if your target
20420 machine has some sort of interrupt button, you won't need to call this;
20421 pressing the interrupt button transfers control to
20422 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20423 simply receiving characters on the serial port may also trigger a trap;
20424 again, in that situation, you don't need to call @code{breakpoint} from
20425 your own program---simply running @samp{target remote} from the host
20426 @value{GDBN} session gets control.
20428 Call @code{breakpoint} if none of these is true, or if you simply want
20429 to make certain your program stops at a predetermined point for the
20430 start of your debugging session.
20433 @node Bootstrapping
20434 @subsection What You Must Do for the Stub
20436 @cindex remote stub, support routines
20437 The debugging stubs that come with @value{GDBN} are set up for a particular
20438 chip architecture, but they have no information about the rest of your
20439 debugging target machine.
20441 First of all you need to tell the stub how to communicate with the
20445 @item int getDebugChar()
20446 @findex getDebugChar
20447 Write this subroutine to read a single character from the serial port.
20448 It may be identical to @code{getchar} for your target system; a
20449 different name is used to allow you to distinguish the two if you wish.
20451 @item void putDebugChar(int)
20452 @findex putDebugChar
20453 Write this subroutine to write a single character to the serial port.
20454 It may be identical to @code{putchar} for your target system; a
20455 different name is used to allow you to distinguish the two if you wish.
20458 @cindex control C, and remote debugging
20459 @cindex interrupting remote targets
20460 If you want @value{GDBN} to be able to stop your program while it is
20461 running, you need to use an interrupt-driven serial driver, and arrange
20462 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20463 character). That is the character which @value{GDBN} uses to tell the
20464 remote system to stop.
20466 Getting the debugging target to return the proper status to @value{GDBN}
20467 probably requires changes to the standard stub; one quick and dirty way
20468 is to just execute a breakpoint instruction (the ``dirty'' part is that
20469 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20471 Other routines you need to supply are:
20474 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20475 @findex exceptionHandler
20476 Write this function to install @var{exception_address} in the exception
20477 handling tables. You need to do this because the stub does not have any
20478 way of knowing what the exception handling tables on your target system
20479 are like (for example, the processor's table might be in @sc{rom},
20480 containing entries which point to a table in @sc{ram}).
20481 The @var{exception_number} specifies the exception which should be changed;
20482 its meaning is architecture-dependent (for example, different numbers
20483 might represent divide by zero, misaligned access, etc). When this
20484 exception occurs, control should be transferred directly to
20485 @var{exception_address}, and the processor state (stack, registers,
20486 and so on) should be just as it is when a processor exception occurs. So if
20487 you want to use a jump instruction to reach @var{exception_address}, it
20488 should be a simple jump, not a jump to subroutine.
20490 For the 386, @var{exception_address} should be installed as an interrupt
20491 gate so that interrupts are masked while the handler runs. The gate
20492 should be at privilege level 0 (the most privileged level). The
20493 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20494 help from @code{exceptionHandler}.
20496 @item void flush_i_cache()
20497 @findex flush_i_cache
20498 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20499 instruction cache, if any, on your target machine. If there is no
20500 instruction cache, this subroutine may be a no-op.
20502 On target machines that have instruction caches, @value{GDBN} requires this
20503 function to make certain that the state of your program is stable.
20507 You must also make sure this library routine is available:
20510 @item void *memset(void *, int, int)
20512 This is the standard library function @code{memset} that sets an area of
20513 memory to a known value. If you have one of the free versions of
20514 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20515 either obtain it from your hardware manufacturer, or write your own.
20518 If you do not use the GNU C compiler, you may need other standard
20519 library subroutines as well; this varies from one stub to another,
20520 but in general the stubs are likely to use any of the common library
20521 subroutines which @code{@value{NGCC}} generates as inline code.
20524 @node Debug Session
20525 @subsection Putting it All Together
20527 @cindex remote serial debugging summary
20528 In summary, when your program is ready to debug, you must follow these
20533 Make sure you have defined the supporting low-level routines
20534 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20536 @code{getDebugChar}, @code{putDebugChar},
20537 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20541 Insert these lines in your program's startup code, before the main
20542 procedure is called:
20549 On some machines, when a breakpoint trap is raised, the hardware
20550 automatically makes the PC point to the instruction after the
20551 breakpoint. If your machine doesn't do that, you may need to adjust
20552 @code{handle_exception} to arrange for it to return to the instruction
20553 after the breakpoint on this first invocation, so that your program
20554 doesn't keep hitting the initial breakpoint instead of making
20558 For the 680x0 stub only, you need to provide a variable called
20559 @code{exceptionHook}. Normally you just use:
20562 void (*exceptionHook)() = 0;
20566 but if before calling @code{set_debug_traps}, you set it to point to a
20567 function in your program, that function is called when
20568 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20569 error). The function indicated by @code{exceptionHook} is called with
20570 one parameter: an @code{int} which is the exception number.
20573 Compile and link together: your program, the @value{GDBN} debugging stub for
20574 your target architecture, and the supporting subroutines.
20577 Make sure you have a serial connection between your target machine and
20578 the @value{GDBN} host, and identify the serial port on the host.
20581 @c The "remote" target now provides a `load' command, so we should
20582 @c document that. FIXME.
20583 Download your program to your target machine (or get it there by
20584 whatever means the manufacturer provides), and start it.
20587 Start @value{GDBN} on the host, and connect to the target
20588 (@pxref{Connecting,,Connecting to a Remote Target}).
20592 @node Configurations
20593 @chapter Configuration-Specific Information
20595 While nearly all @value{GDBN} commands are available for all native and
20596 cross versions of the debugger, there are some exceptions. This chapter
20597 describes things that are only available in certain configurations.
20599 There are three major categories of configurations: native
20600 configurations, where the host and target are the same, embedded
20601 operating system configurations, which are usually the same for several
20602 different processor architectures, and bare embedded processors, which
20603 are quite different from each other.
20608 * Embedded Processors::
20615 This section describes details specific to particular native
20619 * BSD libkvm Interface:: Debugging BSD kernel memory images
20620 * SVR4 Process Information:: SVR4 process information
20621 * DJGPP Native:: Features specific to the DJGPP port
20622 * Cygwin Native:: Features specific to the Cygwin port
20623 * Hurd Native:: Features specific to @sc{gnu} Hurd
20624 * Darwin:: Features specific to Darwin
20627 @node BSD libkvm Interface
20628 @subsection BSD libkvm Interface
20631 @cindex kernel memory image
20632 @cindex kernel crash dump
20634 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20635 interface that provides a uniform interface for accessing kernel virtual
20636 memory images, including live systems and crash dumps. @value{GDBN}
20637 uses this interface to allow you to debug live kernels and kernel crash
20638 dumps on many native BSD configurations. This is implemented as a
20639 special @code{kvm} debugging target. For debugging a live system, load
20640 the currently running kernel into @value{GDBN} and connect to the
20644 (@value{GDBP}) @b{target kvm}
20647 For debugging crash dumps, provide the file name of the crash dump as an
20651 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20654 Once connected to the @code{kvm} target, the following commands are
20660 Set current context from the @dfn{Process Control Block} (PCB) address.
20663 Set current context from proc address. This command isn't available on
20664 modern FreeBSD systems.
20667 @node SVR4 Process Information
20668 @subsection SVR4 Process Information
20670 @cindex examine process image
20671 @cindex process info via @file{/proc}
20673 Many versions of SVR4 and compatible systems provide a facility called
20674 @samp{/proc} that can be used to examine the image of a running
20675 process using file-system subroutines.
20677 If @value{GDBN} is configured for an operating system with this
20678 facility, the command @code{info proc} is available to report
20679 information about the process running your program, or about any
20680 process running on your system. This includes, as of this writing,
20681 @sc{gnu}/Linux and Solaris, for example.
20683 This command may also work on core files that were created on a system
20684 that has the @samp{/proc} facility.
20690 @itemx info proc @var{process-id}
20691 Summarize available information about any running process. If a
20692 process ID is specified by @var{process-id}, display information about
20693 that process; otherwise display information about the program being
20694 debugged. The summary includes the debugged process ID, the command
20695 line used to invoke it, its current working directory, and its
20696 executable file's absolute file name.
20698 On some systems, @var{process-id} can be of the form
20699 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20700 within a process. If the optional @var{pid} part is missing, it means
20701 a thread from the process being debugged (the leading @samp{/} still
20702 needs to be present, or else @value{GDBN} will interpret the number as
20703 a process ID rather than a thread ID).
20705 @item info proc cmdline
20706 @cindex info proc cmdline
20707 Show the original command line of the process. This command is
20708 specific to @sc{gnu}/Linux.
20710 @item info proc cwd
20711 @cindex info proc cwd
20712 Show the current working directory of the process. This command is
20713 specific to @sc{gnu}/Linux.
20715 @item info proc exe
20716 @cindex info proc exe
20717 Show the name of executable of the process. This command is specific
20720 @item info proc mappings
20721 @cindex memory address space mappings
20722 Report the memory address space ranges accessible in the program, with
20723 information on whether the process has read, write, or execute access
20724 rights to each range. On @sc{gnu}/Linux systems, each memory range
20725 includes the object file which is mapped to that range, instead of the
20726 memory access rights to that range.
20728 @item info proc stat
20729 @itemx info proc status
20730 @cindex process detailed status information
20731 These subcommands are specific to @sc{gnu}/Linux systems. They show
20732 the process-related information, including the user ID and group ID;
20733 how many threads are there in the process; its virtual memory usage;
20734 the signals that are pending, blocked, and ignored; its TTY; its
20735 consumption of system and user time; its stack size; its @samp{nice}
20736 value; etc. For more information, see the @samp{proc} man page
20737 (type @kbd{man 5 proc} from your shell prompt).
20739 @item info proc all
20740 Show all the information about the process described under all of the
20741 above @code{info proc} subcommands.
20744 @comment These sub-options of 'info proc' were not included when
20745 @comment procfs.c was re-written. Keep their descriptions around
20746 @comment against the day when someone finds the time to put them back in.
20747 @kindex info proc times
20748 @item info proc times
20749 Starting time, user CPU time, and system CPU time for your program and
20752 @kindex info proc id
20754 Report on the process IDs related to your program: its own process ID,
20755 the ID of its parent, the process group ID, and the session ID.
20758 @item set procfs-trace
20759 @kindex set procfs-trace
20760 @cindex @code{procfs} API calls
20761 This command enables and disables tracing of @code{procfs} API calls.
20763 @item show procfs-trace
20764 @kindex show procfs-trace
20765 Show the current state of @code{procfs} API call tracing.
20767 @item set procfs-file @var{file}
20768 @kindex set procfs-file
20769 Tell @value{GDBN} to write @code{procfs} API trace to the named
20770 @var{file}. @value{GDBN} appends the trace info to the previous
20771 contents of the file. The default is to display the trace on the
20774 @item show procfs-file
20775 @kindex show procfs-file
20776 Show the file to which @code{procfs} API trace is written.
20778 @item proc-trace-entry
20779 @itemx proc-trace-exit
20780 @itemx proc-untrace-entry
20781 @itemx proc-untrace-exit
20782 @kindex proc-trace-entry
20783 @kindex proc-trace-exit
20784 @kindex proc-untrace-entry
20785 @kindex proc-untrace-exit
20786 These commands enable and disable tracing of entries into and exits
20787 from the @code{syscall} interface.
20790 @kindex info pidlist
20791 @cindex process list, QNX Neutrino
20792 For QNX Neutrino only, this command displays the list of all the
20793 processes and all the threads within each process.
20796 @kindex info meminfo
20797 @cindex mapinfo list, QNX Neutrino
20798 For QNX Neutrino only, this command displays the list of all mapinfos.
20802 @subsection Features for Debugging @sc{djgpp} Programs
20803 @cindex @sc{djgpp} debugging
20804 @cindex native @sc{djgpp} debugging
20805 @cindex MS-DOS-specific commands
20808 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20809 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20810 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20811 top of real-mode DOS systems and their emulations.
20813 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20814 defines a few commands specific to the @sc{djgpp} port. This
20815 subsection describes those commands.
20820 This is a prefix of @sc{djgpp}-specific commands which print
20821 information about the target system and important OS structures.
20824 @cindex MS-DOS system info
20825 @cindex free memory information (MS-DOS)
20826 @item info dos sysinfo
20827 This command displays assorted information about the underlying
20828 platform: the CPU type and features, the OS version and flavor, the
20829 DPMI version, and the available conventional and DPMI memory.
20834 @cindex segment descriptor tables
20835 @cindex descriptor tables display
20837 @itemx info dos ldt
20838 @itemx info dos idt
20839 These 3 commands display entries from, respectively, Global, Local,
20840 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20841 tables are data structures which store a descriptor for each segment
20842 that is currently in use. The segment's selector is an index into a
20843 descriptor table; the table entry for that index holds the
20844 descriptor's base address and limit, and its attributes and access
20847 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20848 segment (used for both data and the stack), and a DOS segment (which
20849 allows access to DOS/BIOS data structures and absolute addresses in
20850 conventional memory). However, the DPMI host will usually define
20851 additional segments in order to support the DPMI environment.
20853 @cindex garbled pointers
20854 These commands allow to display entries from the descriptor tables.
20855 Without an argument, all entries from the specified table are
20856 displayed. An argument, which should be an integer expression, means
20857 display a single entry whose index is given by the argument. For
20858 example, here's a convenient way to display information about the
20859 debugged program's data segment:
20862 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20863 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20867 This comes in handy when you want to see whether a pointer is outside
20868 the data segment's limit (i.e.@: @dfn{garbled}).
20870 @cindex page tables display (MS-DOS)
20872 @itemx info dos pte
20873 These two commands display entries from, respectively, the Page
20874 Directory and the Page Tables. Page Directories and Page Tables are
20875 data structures which control how virtual memory addresses are mapped
20876 into physical addresses. A Page Table includes an entry for every
20877 page of memory that is mapped into the program's address space; there
20878 may be several Page Tables, each one holding up to 4096 entries. A
20879 Page Directory has up to 4096 entries, one each for every Page Table
20880 that is currently in use.
20882 Without an argument, @kbd{info dos pde} displays the entire Page
20883 Directory, and @kbd{info dos pte} displays all the entries in all of
20884 the Page Tables. An argument, an integer expression, given to the
20885 @kbd{info dos pde} command means display only that entry from the Page
20886 Directory table. An argument given to the @kbd{info dos pte} command
20887 means display entries from a single Page Table, the one pointed to by
20888 the specified entry in the Page Directory.
20890 @cindex direct memory access (DMA) on MS-DOS
20891 These commands are useful when your program uses @dfn{DMA} (Direct
20892 Memory Access), which needs physical addresses to program the DMA
20895 These commands are supported only with some DPMI servers.
20897 @cindex physical address from linear address
20898 @item info dos address-pte @var{addr}
20899 This command displays the Page Table entry for a specified linear
20900 address. The argument @var{addr} is a linear address which should
20901 already have the appropriate segment's base address added to it,
20902 because this command accepts addresses which may belong to @emph{any}
20903 segment. For example, here's how to display the Page Table entry for
20904 the page where a variable @code{i} is stored:
20907 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20908 @exdent @code{Page Table entry for address 0x11a00d30:}
20909 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20913 This says that @code{i} is stored at offset @code{0xd30} from the page
20914 whose physical base address is @code{0x02698000}, and shows all the
20915 attributes of that page.
20917 Note that you must cast the addresses of variables to a @code{char *},
20918 since otherwise the value of @code{__djgpp_base_address}, the base
20919 address of all variables and functions in a @sc{djgpp} program, will
20920 be added using the rules of C pointer arithmetics: if @code{i} is
20921 declared an @code{int}, @value{GDBN} will add 4 times the value of
20922 @code{__djgpp_base_address} to the address of @code{i}.
20924 Here's another example, it displays the Page Table entry for the
20928 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20929 @exdent @code{Page Table entry for address 0x29110:}
20930 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20934 (The @code{+ 3} offset is because the transfer buffer's address is the
20935 3rd member of the @code{_go32_info_block} structure.) The output
20936 clearly shows that this DPMI server maps the addresses in conventional
20937 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20938 linear (@code{0x29110}) addresses are identical.
20940 This command is supported only with some DPMI servers.
20943 @cindex DOS serial data link, remote debugging
20944 In addition to native debugging, the DJGPP port supports remote
20945 debugging via a serial data link. The following commands are specific
20946 to remote serial debugging in the DJGPP port of @value{GDBN}.
20949 @kindex set com1base
20950 @kindex set com1irq
20951 @kindex set com2base
20952 @kindex set com2irq
20953 @kindex set com3base
20954 @kindex set com3irq
20955 @kindex set com4base
20956 @kindex set com4irq
20957 @item set com1base @var{addr}
20958 This command sets the base I/O port address of the @file{COM1} serial
20961 @item set com1irq @var{irq}
20962 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20963 for the @file{COM1} serial port.
20965 There are similar commands @samp{set com2base}, @samp{set com3irq},
20966 etc.@: for setting the port address and the @code{IRQ} lines for the
20969 @kindex show com1base
20970 @kindex show com1irq
20971 @kindex show com2base
20972 @kindex show com2irq
20973 @kindex show com3base
20974 @kindex show com3irq
20975 @kindex show com4base
20976 @kindex show com4irq
20977 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20978 display the current settings of the base address and the @code{IRQ}
20979 lines used by the COM ports.
20982 @kindex info serial
20983 @cindex DOS serial port status
20984 This command prints the status of the 4 DOS serial ports. For each
20985 port, it prints whether it's active or not, its I/O base address and
20986 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20987 counts of various errors encountered so far.
20991 @node Cygwin Native
20992 @subsection Features for Debugging MS Windows PE Executables
20993 @cindex MS Windows debugging
20994 @cindex native Cygwin debugging
20995 @cindex Cygwin-specific commands
20997 @value{GDBN} supports native debugging of MS Windows programs, including
20998 DLLs with and without symbolic debugging information.
21000 @cindex Ctrl-BREAK, MS-Windows
21001 @cindex interrupt debuggee on MS-Windows
21002 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21003 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21004 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21005 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21006 sequence, which can be used to interrupt the debuggee even if it
21009 There are various additional Cygwin-specific commands, described in
21010 this section. Working with DLLs that have no debugging symbols is
21011 described in @ref{Non-debug DLL Symbols}.
21016 This is a prefix of MS Windows-specific commands which print
21017 information about the target system and important OS structures.
21019 @item info w32 selector
21020 This command displays information returned by
21021 the Win32 API @code{GetThreadSelectorEntry} function.
21022 It takes an optional argument that is evaluated to
21023 a long value to give the information about this given selector.
21024 Without argument, this command displays information
21025 about the six segment registers.
21027 @item info w32 thread-information-block
21028 This command displays thread specific information stored in the
21029 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21030 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21032 @kindex set cygwin-exceptions
21033 @cindex debugging the Cygwin DLL
21034 @cindex Cygwin DLL, debugging
21035 @item set cygwin-exceptions @var{mode}
21036 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21037 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21038 @value{GDBN} will delay recognition of exceptions, and may ignore some
21039 exceptions which seem to be caused by internal Cygwin DLL
21040 ``bookkeeping''. This option is meant primarily for debugging the
21041 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21042 @value{GDBN} users with false @code{SIGSEGV} signals.
21044 @kindex show cygwin-exceptions
21045 @item show cygwin-exceptions
21046 Displays whether @value{GDBN} will break on exceptions that happen
21047 inside the Cygwin DLL itself.
21049 @kindex set new-console
21050 @item set new-console @var{mode}
21051 If @var{mode} is @code{on} the debuggee will
21052 be started in a new console on next start.
21053 If @var{mode} is @code{off}, the debuggee will
21054 be started in the same console as the debugger.
21056 @kindex show new-console
21057 @item show new-console
21058 Displays whether a new console is used
21059 when the debuggee is started.
21061 @kindex set new-group
21062 @item set new-group @var{mode}
21063 This boolean value controls whether the debuggee should
21064 start a new group or stay in the same group as the debugger.
21065 This affects the way the Windows OS handles
21068 @kindex show new-group
21069 @item show new-group
21070 Displays current value of new-group boolean.
21072 @kindex set debugevents
21073 @item set debugevents
21074 This boolean value adds debug output concerning kernel events related
21075 to the debuggee seen by the debugger. This includes events that
21076 signal thread and process creation and exit, DLL loading and
21077 unloading, console interrupts, and debugging messages produced by the
21078 Windows @code{OutputDebugString} API call.
21080 @kindex set debugexec
21081 @item set debugexec
21082 This boolean value adds debug output concerning execute events
21083 (such as resume thread) seen by the debugger.
21085 @kindex set debugexceptions
21086 @item set debugexceptions
21087 This boolean value adds debug output concerning exceptions in the
21088 debuggee seen by the debugger.
21090 @kindex set debugmemory
21091 @item set debugmemory
21092 This boolean value adds debug output concerning debuggee memory reads
21093 and writes by the debugger.
21097 This boolean values specifies whether the debuggee is called
21098 via a shell or directly (default value is on).
21102 Displays if the debuggee will be started with a shell.
21107 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21110 @node Non-debug DLL Symbols
21111 @subsubsection Support for DLLs without Debugging Symbols
21112 @cindex DLLs with no debugging symbols
21113 @cindex Minimal symbols and DLLs
21115 Very often on windows, some of the DLLs that your program relies on do
21116 not include symbolic debugging information (for example,
21117 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21118 symbols in a DLL, it relies on the minimal amount of symbolic
21119 information contained in the DLL's export table. This section
21120 describes working with such symbols, known internally to @value{GDBN} as
21121 ``minimal symbols''.
21123 Note that before the debugged program has started execution, no DLLs
21124 will have been loaded. The easiest way around this problem is simply to
21125 start the program --- either by setting a breakpoint or letting the
21126 program run once to completion.
21128 @subsubsection DLL Name Prefixes
21130 In keeping with the naming conventions used by the Microsoft debugging
21131 tools, DLL export symbols are made available with a prefix based on the
21132 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21133 also entered into the symbol table, so @code{CreateFileA} is often
21134 sufficient. In some cases there will be name clashes within a program
21135 (particularly if the executable itself includes full debugging symbols)
21136 necessitating the use of the fully qualified name when referring to the
21137 contents of the DLL. Use single-quotes around the name to avoid the
21138 exclamation mark (``!'') being interpreted as a language operator.
21140 Note that the internal name of the DLL may be all upper-case, even
21141 though the file name of the DLL is lower-case, or vice-versa. Since
21142 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21143 some confusion. If in doubt, try the @code{info functions} and
21144 @code{info variables} commands or even @code{maint print msymbols}
21145 (@pxref{Symbols}). Here's an example:
21148 (@value{GDBP}) info function CreateFileA
21149 All functions matching regular expression "CreateFileA":
21151 Non-debugging symbols:
21152 0x77e885f4 CreateFileA
21153 0x77e885f4 KERNEL32!CreateFileA
21157 (@value{GDBP}) info function !
21158 All functions matching regular expression "!":
21160 Non-debugging symbols:
21161 0x6100114c cygwin1!__assert
21162 0x61004034 cygwin1!_dll_crt0@@0
21163 0x61004240 cygwin1!dll_crt0(per_process *)
21167 @subsubsection Working with Minimal Symbols
21169 Symbols extracted from a DLL's export table do not contain very much
21170 type information. All that @value{GDBN} can do is guess whether a symbol
21171 refers to a function or variable depending on the linker section that
21172 contains the symbol. Also note that the actual contents of the memory
21173 contained in a DLL are not available unless the program is running. This
21174 means that you cannot examine the contents of a variable or disassemble
21175 a function within a DLL without a running program.
21177 Variables are generally treated as pointers and dereferenced
21178 automatically. For this reason, it is often necessary to prefix a
21179 variable name with the address-of operator (``&'') and provide explicit
21180 type information in the command. Here's an example of the type of
21184 (@value{GDBP}) print 'cygwin1!__argv'
21189 (@value{GDBP}) x 'cygwin1!__argv'
21190 0x10021610: "\230y\""
21193 And two possible solutions:
21196 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21197 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21201 (@value{GDBP}) x/2x &'cygwin1!__argv'
21202 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21203 (@value{GDBP}) x/x 0x10021608
21204 0x10021608: 0x0022fd98
21205 (@value{GDBP}) x/s 0x0022fd98
21206 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21209 Setting a break point within a DLL is possible even before the program
21210 starts execution. However, under these circumstances, @value{GDBN} can't
21211 examine the initial instructions of the function in order to skip the
21212 function's frame set-up code. You can work around this by using ``*&''
21213 to set the breakpoint at a raw memory address:
21216 (@value{GDBP}) break *&'python22!PyOS_Readline'
21217 Breakpoint 1 at 0x1e04eff0
21220 The author of these extensions is not entirely convinced that setting a
21221 break point within a shared DLL like @file{kernel32.dll} is completely
21225 @subsection Commands Specific to @sc{gnu} Hurd Systems
21226 @cindex @sc{gnu} Hurd debugging
21228 This subsection describes @value{GDBN} commands specific to the
21229 @sc{gnu} Hurd native debugging.
21234 @kindex set signals@r{, Hurd command}
21235 @kindex set sigs@r{, Hurd command}
21236 This command toggles the state of inferior signal interception by
21237 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21238 affected by this command. @code{sigs} is a shorthand alias for
21243 @kindex show signals@r{, Hurd command}
21244 @kindex show sigs@r{, Hurd command}
21245 Show the current state of intercepting inferior's signals.
21247 @item set signal-thread
21248 @itemx set sigthread
21249 @kindex set signal-thread
21250 @kindex set sigthread
21251 This command tells @value{GDBN} which thread is the @code{libc} signal
21252 thread. That thread is run when a signal is delivered to a running
21253 process. @code{set sigthread} is the shorthand alias of @code{set
21256 @item show signal-thread
21257 @itemx show sigthread
21258 @kindex show signal-thread
21259 @kindex show sigthread
21260 These two commands show which thread will run when the inferior is
21261 delivered a signal.
21264 @kindex set stopped@r{, Hurd command}
21265 This commands tells @value{GDBN} that the inferior process is stopped,
21266 as with the @code{SIGSTOP} signal. The stopped process can be
21267 continued by delivering a signal to it.
21270 @kindex show stopped@r{, Hurd command}
21271 This command shows whether @value{GDBN} thinks the debuggee is
21274 @item set exceptions
21275 @kindex set exceptions@r{, Hurd command}
21276 Use this command to turn off trapping of exceptions in the inferior.
21277 When exception trapping is off, neither breakpoints nor
21278 single-stepping will work. To restore the default, set exception
21281 @item show exceptions
21282 @kindex show exceptions@r{, Hurd command}
21283 Show the current state of trapping exceptions in the inferior.
21285 @item set task pause
21286 @kindex set task@r{, Hurd commands}
21287 @cindex task attributes (@sc{gnu} Hurd)
21288 @cindex pause current task (@sc{gnu} Hurd)
21289 This command toggles task suspension when @value{GDBN} has control.
21290 Setting it to on takes effect immediately, and the task is suspended
21291 whenever @value{GDBN} gets control. Setting it to off will take
21292 effect the next time the inferior is continued. If this option is set
21293 to off, you can use @code{set thread default pause on} or @code{set
21294 thread pause on} (see below) to pause individual threads.
21296 @item show task pause
21297 @kindex show task@r{, Hurd commands}
21298 Show the current state of task suspension.
21300 @item set task detach-suspend-count
21301 @cindex task suspend count
21302 @cindex detach from task, @sc{gnu} Hurd
21303 This command sets the suspend count the task will be left with when
21304 @value{GDBN} detaches from it.
21306 @item show task detach-suspend-count
21307 Show the suspend count the task will be left with when detaching.
21309 @item set task exception-port
21310 @itemx set task excp
21311 @cindex task exception port, @sc{gnu} Hurd
21312 This command sets the task exception port to which @value{GDBN} will
21313 forward exceptions. The argument should be the value of the @dfn{send
21314 rights} of the task. @code{set task excp} is a shorthand alias.
21316 @item set noninvasive
21317 @cindex noninvasive task options
21318 This command switches @value{GDBN} to a mode that is the least
21319 invasive as far as interfering with the inferior is concerned. This
21320 is the same as using @code{set task pause}, @code{set exceptions}, and
21321 @code{set signals} to values opposite to the defaults.
21323 @item info send-rights
21324 @itemx info receive-rights
21325 @itemx info port-rights
21326 @itemx info port-sets
21327 @itemx info dead-names
21330 @cindex send rights, @sc{gnu} Hurd
21331 @cindex receive rights, @sc{gnu} Hurd
21332 @cindex port rights, @sc{gnu} Hurd
21333 @cindex port sets, @sc{gnu} Hurd
21334 @cindex dead names, @sc{gnu} Hurd
21335 These commands display information about, respectively, send rights,
21336 receive rights, port rights, port sets, and dead names of a task.
21337 There are also shorthand aliases: @code{info ports} for @code{info
21338 port-rights} and @code{info psets} for @code{info port-sets}.
21340 @item set thread pause
21341 @kindex set thread@r{, Hurd command}
21342 @cindex thread properties, @sc{gnu} Hurd
21343 @cindex pause current thread (@sc{gnu} Hurd)
21344 This command toggles current thread suspension when @value{GDBN} has
21345 control. Setting it to on takes effect immediately, and the current
21346 thread is suspended whenever @value{GDBN} gets control. Setting it to
21347 off will take effect the next time the inferior is continued.
21348 Normally, this command has no effect, since when @value{GDBN} has
21349 control, the whole task is suspended. However, if you used @code{set
21350 task pause off} (see above), this command comes in handy to suspend
21351 only the current thread.
21353 @item show thread pause
21354 @kindex show thread@r{, Hurd command}
21355 This command shows the state of current thread suspension.
21357 @item set thread run
21358 This command sets whether the current thread is allowed to run.
21360 @item show thread run
21361 Show whether the current thread is allowed to run.
21363 @item set thread detach-suspend-count
21364 @cindex thread suspend count, @sc{gnu} Hurd
21365 @cindex detach from thread, @sc{gnu} Hurd
21366 This command sets the suspend count @value{GDBN} will leave on a
21367 thread when detaching. This number is relative to the suspend count
21368 found by @value{GDBN} when it notices the thread; use @code{set thread
21369 takeover-suspend-count} to force it to an absolute value.
21371 @item show thread detach-suspend-count
21372 Show the suspend count @value{GDBN} will leave on the thread when
21375 @item set thread exception-port
21376 @itemx set thread excp
21377 Set the thread exception port to which to forward exceptions. This
21378 overrides the port set by @code{set task exception-port} (see above).
21379 @code{set thread excp} is the shorthand alias.
21381 @item set thread takeover-suspend-count
21382 Normally, @value{GDBN}'s thread suspend counts are relative to the
21383 value @value{GDBN} finds when it notices each thread. This command
21384 changes the suspend counts to be absolute instead.
21386 @item set thread default
21387 @itemx show thread default
21388 @cindex thread default settings, @sc{gnu} Hurd
21389 Each of the above @code{set thread} commands has a @code{set thread
21390 default} counterpart (e.g., @code{set thread default pause}, @code{set
21391 thread default exception-port}, etc.). The @code{thread default}
21392 variety of commands sets the default thread properties for all
21393 threads; you can then change the properties of individual threads with
21394 the non-default commands.
21401 @value{GDBN} provides the following commands specific to the Darwin target:
21404 @item set debug darwin @var{num}
21405 @kindex set debug darwin
21406 When set to a non zero value, enables debugging messages specific to
21407 the Darwin support. Higher values produce more verbose output.
21409 @item show debug darwin
21410 @kindex show debug darwin
21411 Show the current state of Darwin messages.
21413 @item set debug mach-o @var{num}
21414 @kindex set debug mach-o
21415 When set to a non zero value, enables debugging messages while
21416 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21417 file format used on Darwin for object and executable files.) Higher
21418 values produce more verbose output. This is a command to diagnose
21419 problems internal to @value{GDBN} and should not be needed in normal
21422 @item show debug mach-o
21423 @kindex show debug mach-o
21424 Show the current state of Mach-O file messages.
21426 @item set mach-exceptions on
21427 @itemx set mach-exceptions off
21428 @kindex set mach-exceptions
21429 On Darwin, faults are first reported as a Mach exception and are then
21430 mapped to a Posix signal. Use this command to turn on trapping of
21431 Mach exceptions in the inferior. This might be sometimes useful to
21432 better understand the cause of a fault. The default is off.
21434 @item show mach-exceptions
21435 @kindex show mach-exceptions
21436 Show the current state of exceptions trapping.
21441 @section Embedded Operating Systems
21443 This section describes configurations involving the debugging of
21444 embedded operating systems that are available for several different
21447 @value{GDBN} includes the ability to debug programs running on
21448 various real-time operating systems.
21450 @node Embedded Processors
21451 @section Embedded Processors
21453 This section goes into details specific to particular embedded
21456 @cindex send command to simulator
21457 Whenever a specific embedded processor has a simulator, @value{GDBN}
21458 allows to send an arbitrary command to the simulator.
21461 @item sim @var{command}
21462 @kindex sim@r{, a command}
21463 Send an arbitrary @var{command} string to the simulator. Consult the
21464 documentation for the specific simulator in use for information about
21465 acceptable commands.
21471 * M32R/SDI:: Renesas M32R/SDI
21472 * M68K:: Motorola M68K
21473 * MicroBlaze:: Xilinx MicroBlaze
21474 * MIPS Embedded:: MIPS Embedded
21475 * PowerPC Embedded:: PowerPC Embedded
21478 * Super-H:: Renesas Super-H
21484 @value{GDBN} provides the following ARM-specific commands:
21487 @item set arm disassembler
21489 This commands selects from a list of disassembly styles. The
21490 @code{"std"} style is the standard style.
21492 @item show arm disassembler
21494 Show the current disassembly style.
21496 @item set arm apcs32
21497 @cindex ARM 32-bit mode
21498 This command toggles ARM operation mode between 32-bit and 26-bit.
21500 @item show arm apcs32
21501 Display the current usage of the ARM 32-bit mode.
21503 @item set arm fpu @var{fputype}
21504 This command sets the ARM floating-point unit (FPU) type. The
21505 argument @var{fputype} can be one of these:
21509 Determine the FPU type by querying the OS ABI.
21511 Software FPU, with mixed-endian doubles on little-endian ARM
21514 GCC-compiled FPA co-processor.
21516 Software FPU with pure-endian doubles.
21522 Show the current type of the FPU.
21525 This command forces @value{GDBN} to use the specified ABI.
21528 Show the currently used ABI.
21530 @item set arm fallback-mode (arm|thumb|auto)
21531 @value{GDBN} uses the symbol table, when available, to determine
21532 whether instructions are ARM or Thumb. This command controls
21533 @value{GDBN}'s default behavior when the symbol table is not
21534 available. The default is @samp{auto}, which causes @value{GDBN} to
21535 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21538 @item show arm fallback-mode
21539 Show the current fallback instruction mode.
21541 @item set arm force-mode (arm|thumb|auto)
21542 This command overrides use of the symbol table to determine whether
21543 instructions are ARM or Thumb. The default is @samp{auto}, which
21544 causes @value{GDBN} to use the symbol table and then the setting
21545 of @samp{set arm fallback-mode}.
21547 @item show arm force-mode
21548 Show the current forced instruction mode.
21550 @item set debug arm
21551 Toggle whether to display ARM-specific debugging messages from the ARM
21552 target support subsystem.
21554 @item show debug arm
21555 Show whether ARM-specific debugging messages are enabled.
21559 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21560 The @value{GDBN} ARM simulator accepts the following optional arguments.
21563 @item --swi-support=@var{type}
21564 Tell the simulator which SWI interfaces to support. The argument
21565 @var{type} may be a comma separated list of the following values.
21566 The default value is @code{all}.
21579 @subsection Renesas M32R/SDI
21581 The following commands are available for M32R/SDI:
21586 @cindex reset SDI connection, M32R
21587 This command resets the SDI connection.
21591 This command shows the SDI connection status.
21594 @kindex debug_chaos
21595 @cindex M32R/Chaos debugging
21596 Instructs the remote that M32R/Chaos debugging is to be used.
21598 @item use_debug_dma
21599 @kindex use_debug_dma
21600 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21603 @kindex use_mon_code
21604 Instructs the remote to use the MON_CODE method of accessing memory.
21607 @kindex use_ib_break
21608 Instructs the remote to set breakpoints by IB break.
21610 @item use_dbt_break
21611 @kindex use_dbt_break
21612 Instructs the remote to set breakpoints by DBT.
21618 The Motorola m68k configuration includes ColdFire support.
21621 @subsection MicroBlaze
21622 @cindex Xilinx MicroBlaze
21623 @cindex XMD, Xilinx Microprocessor Debugger
21625 The MicroBlaze is a soft-core processor supported on various Xilinx
21626 FPGAs, such as Spartan or Virtex series. Boards with these processors
21627 usually have JTAG ports which connect to a host system running the Xilinx
21628 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21629 This host system is used to download the configuration bitstream to
21630 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21631 communicates with the target board using the JTAG interface and
21632 presents a @code{gdbserver} interface to the board. By default
21633 @code{xmd} uses port @code{1234}. (While it is possible to change
21634 this default port, it requires the use of undocumented @code{xmd}
21635 commands. Contact Xilinx support if you need to do this.)
21637 Use these GDB commands to connect to the MicroBlaze target processor.
21640 @item target remote :1234
21641 Use this command to connect to the target if you are running @value{GDBN}
21642 on the same system as @code{xmd}.
21644 @item target remote @var{xmd-host}:1234
21645 Use this command to connect to the target if it is connected to @code{xmd}
21646 running on a different system named @var{xmd-host}.
21649 Use this command to download a program to the MicroBlaze target.
21651 @item set debug microblaze @var{n}
21652 Enable MicroBlaze-specific debugging messages if non-zero.
21654 @item show debug microblaze @var{n}
21655 Show MicroBlaze-specific debugging level.
21658 @node MIPS Embedded
21659 @subsection @acronym{MIPS} Embedded
21661 @cindex @acronym{MIPS} boards
21662 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21663 @acronym{MIPS} board attached to a serial line. This is available when
21664 you configure @value{GDBN} with @samp{--target=mips-elf}.
21667 Use these @value{GDBN} commands to specify the connection to your target board:
21670 @item target mips @var{port}
21671 @kindex target mips @var{port}
21672 To run a program on the board, start up @code{@value{GDBP}} with the
21673 name of your program as the argument. To connect to the board, use the
21674 command @samp{target mips @var{port}}, where @var{port} is the name of
21675 the serial port connected to the board. If the program has not already
21676 been downloaded to the board, you may use the @code{load} command to
21677 download it. You can then use all the usual @value{GDBN} commands.
21679 For example, this sequence connects to the target board through a serial
21680 port, and loads and runs a program called @var{prog} through the
21684 host$ @value{GDBP} @var{prog}
21685 @value{GDBN} is free software and @dots{}
21686 (@value{GDBP}) target mips /dev/ttyb
21687 (@value{GDBP}) load @var{prog}
21691 @item target mips @var{hostname}:@var{portnumber}
21692 On some @value{GDBN} host configurations, you can specify a TCP
21693 connection (for instance, to a serial line managed by a terminal
21694 concentrator) instead of a serial port, using the syntax
21695 @samp{@var{hostname}:@var{portnumber}}.
21697 @item target pmon @var{port}
21698 @kindex target pmon @var{port}
21701 @item target ddb @var{port}
21702 @kindex target ddb @var{port}
21703 NEC's DDB variant of PMON for Vr4300.
21705 @item target lsi @var{port}
21706 @kindex target lsi @var{port}
21707 LSI variant of PMON.
21713 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21716 @item set mipsfpu double
21717 @itemx set mipsfpu single
21718 @itemx set mipsfpu none
21719 @itemx set mipsfpu auto
21720 @itemx show mipsfpu
21721 @kindex set mipsfpu
21722 @kindex show mipsfpu
21723 @cindex @acronym{MIPS} remote floating point
21724 @cindex floating point, @acronym{MIPS} remote
21725 If your target board does not support the @acronym{MIPS} floating point
21726 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21727 need this, you may wish to put the command in your @value{GDBN} init
21728 file). This tells @value{GDBN} how to find the return value of
21729 functions which return floating point values. It also allows
21730 @value{GDBN} to avoid saving the floating point registers when calling
21731 functions on the board. If you are using a floating point coprocessor
21732 with only single precision floating point support, as on the @sc{r4650}
21733 processor, use the command @samp{set mipsfpu single}. The default
21734 double precision floating point coprocessor may be selected using
21735 @samp{set mipsfpu double}.
21737 In previous versions the only choices were double precision or no
21738 floating point, so @samp{set mipsfpu on} will select double precision
21739 and @samp{set mipsfpu off} will select no floating point.
21741 As usual, you can inquire about the @code{mipsfpu} variable with
21742 @samp{show mipsfpu}.
21744 @item set timeout @var{seconds}
21745 @itemx set retransmit-timeout @var{seconds}
21746 @itemx show timeout
21747 @itemx show retransmit-timeout
21748 @cindex @code{timeout}, @acronym{MIPS} protocol
21749 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21750 @kindex set timeout
21751 @kindex show timeout
21752 @kindex set retransmit-timeout
21753 @kindex show retransmit-timeout
21754 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21755 remote protocol, with the @code{set timeout @var{seconds}} command. The
21756 default is 5 seconds. Similarly, you can control the timeout used while
21757 waiting for an acknowledgment of a packet with the @code{set
21758 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21759 You can inspect both values with @code{show timeout} and @code{show
21760 retransmit-timeout}. (These commands are @emph{only} available when
21761 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21763 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21764 is waiting for your program to stop. In that case, @value{GDBN} waits
21765 forever because it has no way of knowing how long the program is going
21766 to run before stopping.
21768 @item set syn-garbage-limit @var{num}
21769 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21770 @cindex synchronize with remote @acronym{MIPS} target
21771 Limit the maximum number of characters @value{GDBN} should ignore when
21772 it tries to synchronize with the remote target. The default is 10
21773 characters. Setting the limit to -1 means there's no limit.
21775 @item show syn-garbage-limit
21776 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21777 Show the current limit on the number of characters to ignore when
21778 trying to synchronize with the remote system.
21780 @item set monitor-prompt @var{prompt}
21781 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21782 @cindex remote monitor prompt
21783 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21784 remote monitor. The default depends on the target:
21794 @item show monitor-prompt
21795 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21796 Show the current strings @value{GDBN} expects as the prompt from the
21799 @item set monitor-warnings
21800 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21801 Enable or disable monitor warnings about hardware breakpoints. This
21802 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21803 display warning messages whose codes are returned by the @code{lsi}
21804 PMON monitor for breakpoint commands.
21806 @item show monitor-warnings
21807 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21808 Show the current setting of printing monitor warnings.
21810 @item pmon @var{command}
21811 @kindex pmon@r{, @acronym{MIPS} remote}
21812 @cindex send PMON command
21813 This command allows sending an arbitrary @var{command} string to the
21814 monitor. The monitor must be in debug mode for this to work.
21817 @node PowerPC Embedded
21818 @subsection PowerPC Embedded
21820 @cindex DVC register
21821 @value{GDBN} supports using the DVC (Data Value Compare) register to
21822 implement in hardware simple hardware watchpoint conditions of the form:
21825 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21826 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21829 The DVC register will be automatically used when @value{GDBN} detects
21830 such pattern in a condition expression, and the created watchpoint uses one
21831 debug register (either the @code{exact-watchpoints} option is on and the
21832 variable is scalar, or the variable has a length of one byte). This feature
21833 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21836 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21837 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21838 in which case watchpoints using only one debug register are created when
21839 watching variables of scalar types.
21841 You can create an artificial array to watch an arbitrary memory
21842 region using one of the following commands (@pxref{Expressions}):
21845 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21846 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21849 PowerPC embedded processors support masked watchpoints. See the discussion
21850 about the @code{mask} argument in @ref{Set Watchpoints}.
21852 @cindex ranged breakpoint
21853 PowerPC embedded processors support hardware accelerated
21854 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21855 the inferior whenever it executes an instruction at any address within
21856 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21857 use the @code{break-range} command.
21859 @value{GDBN} provides the following PowerPC-specific commands:
21862 @kindex break-range
21863 @item break-range @var{start-location}, @var{end-location}
21864 Set a breakpoint for an address range given by
21865 @var{start-location} and @var{end-location}, which can specify a function name,
21866 a line number, an offset of lines from the current line or from the start
21867 location, or an address of an instruction (see @ref{Specify Location},
21868 for a list of all the possible ways to specify a @var{location}.)
21869 The breakpoint will stop execution of the inferior whenever it
21870 executes an instruction at any address within the specified range,
21871 (including @var{start-location} and @var{end-location}.)
21873 @kindex set powerpc
21874 @item set powerpc soft-float
21875 @itemx show powerpc soft-float
21876 Force @value{GDBN} to use (or not use) a software floating point calling
21877 convention. By default, @value{GDBN} selects the calling convention based
21878 on the selected architecture and the provided executable file.
21880 @item set powerpc vector-abi
21881 @itemx show powerpc vector-abi
21882 Force @value{GDBN} to use the specified calling convention for vector
21883 arguments and return values. The valid options are @samp{auto};
21884 @samp{generic}, to avoid vector registers even if they are present;
21885 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21886 registers. By default, @value{GDBN} selects the calling convention
21887 based on the selected architecture and the provided executable file.
21889 @item set powerpc exact-watchpoints
21890 @itemx show powerpc exact-watchpoints
21891 Allow @value{GDBN} to use only one debug register when watching a variable
21892 of scalar type, thus assuming that the variable is accessed through the
21893 address of its first byte.
21898 @subsection Atmel AVR
21901 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21902 following AVR-specific commands:
21905 @item info io_registers
21906 @kindex info io_registers@r{, AVR}
21907 @cindex I/O registers (Atmel AVR)
21908 This command displays information about the AVR I/O registers. For
21909 each register, @value{GDBN} prints its number and value.
21916 When configured for debugging CRIS, @value{GDBN} provides the
21917 following CRIS-specific commands:
21920 @item set cris-version @var{ver}
21921 @cindex CRIS version
21922 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21923 The CRIS version affects register names and sizes. This command is useful in
21924 case autodetection of the CRIS version fails.
21926 @item show cris-version
21927 Show the current CRIS version.
21929 @item set cris-dwarf2-cfi
21930 @cindex DWARF-2 CFI and CRIS
21931 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21932 Change to @samp{off} when using @code{gcc-cris} whose version is below
21935 @item show cris-dwarf2-cfi
21936 Show the current state of using DWARF-2 CFI.
21938 @item set cris-mode @var{mode}
21940 Set the current CRIS mode to @var{mode}. It should only be changed when
21941 debugging in guru mode, in which case it should be set to
21942 @samp{guru} (the default is @samp{normal}).
21944 @item show cris-mode
21945 Show the current CRIS mode.
21949 @subsection Renesas Super-H
21952 For the Renesas Super-H processor, @value{GDBN} provides these
21956 @item set sh calling-convention @var{convention}
21957 @kindex set sh calling-convention
21958 Set the calling-convention used when calling functions from @value{GDBN}.
21959 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21960 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21961 convention. If the DWARF-2 information of the called function specifies
21962 that the function follows the Renesas calling convention, the function
21963 is called using the Renesas calling convention. If the calling convention
21964 is set to @samp{renesas}, the Renesas calling convention is always used,
21965 regardless of the DWARF-2 information. This can be used to override the
21966 default of @samp{gcc} if debug information is missing, or the compiler
21967 does not emit the DWARF-2 calling convention entry for a function.
21969 @item show sh calling-convention
21970 @kindex show sh calling-convention
21971 Show the current calling convention setting.
21976 @node Architectures
21977 @section Architectures
21979 This section describes characteristics of architectures that affect
21980 all uses of @value{GDBN} with the architecture, both native and cross.
21987 * HPPA:: HP PA architecture
21988 * SPU:: Cell Broadband Engine SPU architecture
21994 @subsection AArch64
21995 @cindex AArch64 support
21997 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21998 following special commands:
22001 @item set debug aarch64
22002 @kindex set debug aarch64
22003 This command determines whether AArch64 architecture-specific debugging
22004 messages are to be displayed.
22006 @item show debug aarch64
22007 Show whether AArch64 debugging messages are displayed.
22012 @subsection x86 Architecture-specific Issues
22015 @item set struct-convention @var{mode}
22016 @kindex set struct-convention
22017 @cindex struct return convention
22018 @cindex struct/union returned in registers
22019 Set the convention used by the inferior to return @code{struct}s and
22020 @code{union}s from functions to @var{mode}. Possible values of
22021 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22022 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22023 are returned on the stack, while @code{"reg"} means that a
22024 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22025 be returned in a register.
22027 @item show struct-convention
22028 @kindex show struct-convention
22029 Show the current setting of the convention to return @code{struct}s
22034 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22035 @cindex Intel(R) Memory Protection Extensions (MPX).
22037 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22038 @footnote{The register named with capital letters represent the architecture
22039 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22040 which are the lower bound and upper bound. Bounds are effective addresses or
22041 memory locations. The upper bounds are architecturally represented in 1's
22042 complement form. A bound having lower bound = 0, and upper bound = 0
22043 (1's complement of all bits set) will allow access to the entire address space.
22045 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22046 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22047 display the upper bound performing the complement of one operation on the
22048 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22049 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22050 can also be noted that the upper bounds are inclusive.
22052 As an example, assume that the register BND0 holds bounds for a pointer having
22053 access allowed for the range between 0x32 and 0x71. The values present on
22054 bnd0raw and bnd registers are presented as follows:
22057 bnd0raw = @{0x32, 0xffffffff8e@}
22058 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22061 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22062 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22063 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22064 Python, the display includes the memory size, in bits, accessible to
22067 Bounds can also be stored in bounds tables, which are stored in
22068 application memory. These tables store bounds for pointers by specifying
22069 the bounds pointer's value along with its bounds. Evaluating and changing
22070 bounds located in bound tables is therefore interesting while investigating
22071 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22074 @item show mpx bound @var{pointer}
22075 @kindex show mpx bound
22076 Display bounds of the given @var{pointer}.
22078 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22079 @kindex set mpx bound
22080 Set the bounds of a pointer in the bound table.
22081 This command takes three parameters: @var{pointer} is the pointers
22082 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22083 for lower and upper bounds respectively.
22089 See the following section.
22092 @subsection @acronym{MIPS}
22094 @cindex stack on Alpha
22095 @cindex stack on @acronym{MIPS}
22096 @cindex Alpha stack
22097 @cindex @acronym{MIPS} stack
22098 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22099 sometimes requires @value{GDBN} to search backward in the object code to
22100 find the beginning of a function.
22102 @cindex response time, @acronym{MIPS} debugging
22103 To improve response time (especially for embedded applications, where
22104 @value{GDBN} may be restricted to a slow serial line for this search)
22105 you may want to limit the size of this search, using one of these
22109 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22110 @item set heuristic-fence-post @var{limit}
22111 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22112 search for the beginning of a function. A value of @var{0} (the
22113 default) means there is no limit. However, except for @var{0}, the
22114 larger the limit the more bytes @code{heuristic-fence-post} must search
22115 and therefore the longer it takes to run. You should only need to use
22116 this command when debugging a stripped executable.
22118 @item show heuristic-fence-post
22119 Display the current limit.
22123 These commands are available @emph{only} when @value{GDBN} is configured
22124 for debugging programs on Alpha or @acronym{MIPS} processors.
22126 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22130 @item set mips abi @var{arg}
22131 @kindex set mips abi
22132 @cindex set ABI for @acronym{MIPS}
22133 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22134 values of @var{arg} are:
22138 The default ABI associated with the current binary (this is the
22148 @item show mips abi
22149 @kindex show mips abi
22150 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22152 @item set mips compression @var{arg}
22153 @kindex set mips compression
22154 @cindex code compression, @acronym{MIPS}
22155 Tell @value{GDBN} which @acronym{MIPS} compressed
22156 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22157 inferior. @value{GDBN} uses this for code disassembly and other
22158 internal interpretation purposes. This setting is only referred to
22159 when no executable has been associated with the debugging session or
22160 the executable does not provide information about the encoding it uses.
22161 Otherwise this setting is automatically updated from information
22162 provided by the executable.
22164 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22165 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22166 executables containing @acronym{MIPS16} code frequently are not
22167 identified as such.
22169 This setting is ``sticky''; that is, it retains its value across
22170 debugging sessions until reset either explicitly with this command or
22171 implicitly from an executable.
22173 The compiler and/or assembler typically add symbol table annotations to
22174 identify functions compiled for the @acronym{MIPS16} or
22175 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22176 are present, @value{GDBN} uses them in preference to the global
22177 compressed @acronym{ISA} encoding setting.
22179 @item show mips compression
22180 @kindex show mips compression
22181 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22182 @value{GDBN} to debug the inferior.
22185 @itemx show mipsfpu
22186 @xref{MIPS Embedded, set mipsfpu}.
22188 @item set mips mask-address @var{arg}
22189 @kindex set mips mask-address
22190 @cindex @acronym{MIPS} addresses, masking
22191 This command determines whether the most-significant 32 bits of 64-bit
22192 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22193 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22194 setting, which lets @value{GDBN} determine the correct value.
22196 @item show mips mask-address
22197 @kindex show mips mask-address
22198 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22201 @item set remote-mips64-transfers-32bit-regs
22202 @kindex set remote-mips64-transfers-32bit-regs
22203 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22204 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22205 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22206 and 64 bits for other registers, set this option to @samp{on}.
22208 @item show remote-mips64-transfers-32bit-regs
22209 @kindex show remote-mips64-transfers-32bit-regs
22210 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22212 @item set debug mips
22213 @kindex set debug mips
22214 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22215 target code in @value{GDBN}.
22217 @item show debug mips
22218 @kindex show debug mips
22219 Show the current setting of @acronym{MIPS} debugging messages.
22225 @cindex HPPA support
22227 When @value{GDBN} is debugging the HP PA architecture, it provides the
22228 following special commands:
22231 @item set debug hppa
22232 @kindex set debug hppa
22233 This command determines whether HPPA architecture-specific debugging
22234 messages are to be displayed.
22236 @item show debug hppa
22237 Show whether HPPA debugging messages are displayed.
22239 @item maint print unwind @var{address}
22240 @kindex maint print unwind@r{, HPPA}
22241 This command displays the contents of the unwind table entry at the
22242 given @var{address}.
22248 @subsection Cell Broadband Engine SPU architecture
22249 @cindex Cell Broadband Engine
22252 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22253 it provides the following special commands:
22256 @item info spu event
22258 Display SPU event facility status. Shows current event mask
22259 and pending event status.
22261 @item info spu signal
22262 Display SPU signal notification facility status. Shows pending
22263 signal-control word and signal notification mode of both signal
22264 notification channels.
22266 @item info spu mailbox
22267 Display SPU mailbox facility status. Shows all pending entries,
22268 in order of processing, in each of the SPU Write Outbound,
22269 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22272 Display MFC DMA status. Shows all pending commands in the MFC
22273 DMA queue. For each entry, opcode, tag, class IDs, effective
22274 and local store addresses and transfer size are shown.
22276 @item info spu proxydma
22277 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22278 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22279 and local store addresses and transfer size are shown.
22283 When @value{GDBN} is debugging a combined PowerPC/SPU application
22284 on the Cell Broadband Engine, it provides in addition the following
22288 @item set spu stop-on-load @var{arg}
22290 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22291 will give control to the user when a new SPE thread enters its @code{main}
22292 function. The default is @code{off}.
22294 @item show spu stop-on-load
22296 Show whether to stop for new SPE threads.
22298 @item set spu auto-flush-cache @var{arg}
22299 Set whether to automatically flush the software-managed cache. When set to
22300 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22301 cache to be flushed whenever SPE execution stops. This provides a consistent
22302 view of PowerPC memory that is accessed via the cache. If an application
22303 does not use the software-managed cache, this option has no effect.
22305 @item show spu auto-flush-cache
22306 Show whether to automatically flush the software-managed cache.
22311 @subsection PowerPC
22312 @cindex PowerPC architecture
22314 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22315 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22316 numbers stored in the floating point registers. These values must be stored
22317 in two consecutive registers, always starting at an even register like
22318 @code{f0} or @code{f2}.
22320 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22321 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22322 @code{f2} and @code{f3} for @code{$dl1} and so on.
22324 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22325 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22328 @subsection Nios II
22329 @cindex Nios II architecture
22331 When @value{GDBN} is debugging the Nios II architecture,
22332 it provides the following special commands:
22336 @item set debug nios2
22337 @kindex set debug nios2
22338 This command turns on and off debugging messages for the Nios II
22339 target code in @value{GDBN}.
22341 @item show debug nios2
22342 @kindex show debug nios2
22343 Show the current setting of Nios II debugging messages.
22346 @node Controlling GDB
22347 @chapter Controlling @value{GDBN}
22349 You can alter the way @value{GDBN} interacts with you by using the
22350 @code{set} command. For commands controlling how @value{GDBN} displays
22351 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22356 * Editing:: Command editing
22357 * Command History:: Command history
22358 * Screen Size:: Screen size
22359 * Numbers:: Numbers
22360 * ABI:: Configuring the current ABI
22361 * Auto-loading:: Automatically loading associated files
22362 * Messages/Warnings:: Optional warnings and messages
22363 * Debugging Output:: Optional messages about internal happenings
22364 * Other Misc Settings:: Other Miscellaneous Settings
22372 @value{GDBN} indicates its readiness to read a command by printing a string
22373 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22374 can change the prompt string with the @code{set prompt} command. For
22375 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22376 the prompt in one of the @value{GDBN} sessions so that you can always tell
22377 which one you are talking to.
22379 @emph{Note:} @code{set prompt} does not add a space for you after the
22380 prompt you set. This allows you to set a prompt which ends in a space
22381 or a prompt that does not.
22385 @item set prompt @var{newprompt}
22386 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22388 @kindex show prompt
22390 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22393 Versions of @value{GDBN} that ship with Python scripting enabled have
22394 prompt extensions. The commands for interacting with these extensions
22398 @kindex set extended-prompt
22399 @item set extended-prompt @var{prompt}
22400 Set an extended prompt that allows for substitutions.
22401 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22402 substitution. Any escape sequences specified as part of the prompt
22403 string are replaced with the corresponding strings each time the prompt
22409 set extended-prompt Current working directory: \w (gdb)
22412 Note that when an extended-prompt is set, it takes control of the
22413 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22415 @kindex show extended-prompt
22416 @item show extended-prompt
22417 Prints the extended prompt. Any escape sequences specified as part of
22418 the prompt string with @code{set extended-prompt}, are replaced with the
22419 corresponding strings each time the prompt is displayed.
22423 @section Command Editing
22425 @cindex command line editing
22427 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22428 @sc{gnu} library provides consistent behavior for programs which provide a
22429 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22430 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22431 substitution, and a storage and recall of command history across
22432 debugging sessions.
22434 You may control the behavior of command line editing in @value{GDBN} with the
22435 command @code{set}.
22438 @kindex set editing
22441 @itemx set editing on
22442 Enable command line editing (enabled by default).
22444 @item set editing off
22445 Disable command line editing.
22447 @kindex show editing
22449 Show whether command line editing is enabled.
22452 @ifset SYSTEM_READLINE
22453 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22455 @ifclear SYSTEM_READLINE
22456 @xref{Command Line Editing},
22458 for more details about the Readline
22459 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22460 encouraged to read that chapter.
22462 @node Command History
22463 @section Command History
22464 @cindex command history
22466 @value{GDBN} can keep track of the commands you type during your
22467 debugging sessions, so that you can be certain of precisely what
22468 happened. Use these commands to manage the @value{GDBN} command
22471 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22472 package, to provide the history facility.
22473 @ifset SYSTEM_READLINE
22474 @xref{Using History Interactively, , , history, GNU History Library},
22476 @ifclear SYSTEM_READLINE
22477 @xref{Using History Interactively},
22479 for the detailed description of the History library.
22481 To issue a command to @value{GDBN} without affecting certain aspects of
22482 the state which is seen by users, prefix it with @samp{server }
22483 (@pxref{Server Prefix}). This
22484 means that this command will not affect the command history, nor will it
22485 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22486 pressed on a line by itself.
22488 @cindex @code{server}, command prefix
22489 The server prefix does not affect the recording of values into the value
22490 history; to print a value without recording it into the value history,
22491 use the @code{output} command instead of the @code{print} command.
22493 Here is the description of @value{GDBN} commands related to command
22497 @cindex history substitution
22498 @cindex history file
22499 @kindex set history filename
22500 @cindex @env{GDBHISTFILE}, environment variable
22501 @item set history filename @var{fname}
22502 Set the name of the @value{GDBN} command history file to @var{fname}.
22503 This is the file where @value{GDBN} reads an initial command history
22504 list, and where it writes the command history from this session when it
22505 exits. You can access this list through history expansion or through
22506 the history command editing characters listed below. This file defaults
22507 to the value of the environment variable @code{GDBHISTFILE}, or to
22508 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22511 @cindex save command history
22512 @kindex set history save
22513 @item set history save
22514 @itemx set history save on
22515 Record command history in a file, whose name may be specified with the
22516 @code{set history filename} command. By default, this option is disabled.
22518 @item set history save off
22519 Stop recording command history in a file.
22521 @cindex history size
22522 @kindex set history size
22523 @cindex @env{GDBHISTSIZE}, environment variable
22524 @item set history size @var{size}
22525 @itemx set history size unlimited
22526 Set the number of commands which @value{GDBN} keeps in its history list.
22527 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22528 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22529 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22530 either a negative number or the empty string, then the number of commands
22531 @value{GDBN} keeps in the history list is unlimited.
22533 @cindex remove duplicate history
22534 @kindex set history remove-duplicates
22535 @item set history remove-duplicates @var{count}
22536 @itemx set history remove-duplicates unlimited
22537 Control the removal of duplicate history entries in the command history list.
22538 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22539 history entries and remove the first entry that is a duplicate of the current
22540 entry being added to the command history list. If @var{count} is
22541 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22542 removal of duplicate history entries is disabled.
22544 Only history entries added during the current session are considered for
22545 removal. This option is set to 0 by default.
22549 History expansion assigns special meaning to the character @kbd{!}.
22550 @ifset SYSTEM_READLINE
22551 @xref{Event Designators, , , history, GNU History Library},
22553 @ifclear SYSTEM_READLINE
22554 @xref{Event Designators},
22558 @cindex history expansion, turn on/off
22559 Since @kbd{!} is also the logical not operator in C, history expansion
22560 is off by default. If you decide to enable history expansion with the
22561 @code{set history expansion on} command, you may sometimes need to
22562 follow @kbd{!} (when it is used as logical not, in an expression) with
22563 a space or a tab to prevent it from being expanded. The readline
22564 history facilities do not attempt substitution on the strings
22565 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22567 The commands to control history expansion are:
22570 @item set history expansion on
22571 @itemx set history expansion
22572 @kindex set history expansion
22573 Enable history expansion. History expansion is off by default.
22575 @item set history expansion off
22576 Disable history expansion.
22579 @kindex show history
22581 @itemx show history filename
22582 @itemx show history save
22583 @itemx show history size
22584 @itemx show history expansion
22585 These commands display the state of the @value{GDBN} history parameters.
22586 @code{show history} by itself displays all four states.
22591 @kindex show commands
22592 @cindex show last commands
22593 @cindex display command history
22594 @item show commands
22595 Display the last ten commands in the command history.
22597 @item show commands @var{n}
22598 Print ten commands centered on command number @var{n}.
22600 @item show commands +
22601 Print ten commands just after the commands last printed.
22605 @section Screen Size
22606 @cindex size of screen
22607 @cindex screen size
22610 @cindex pauses in output
22612 Certain commands to @value{GDBN} may produce large amounts of
22613 information output to the screen. To help you read all of it,
22614 @value{GDBN} pauses and asks you for input at the end of each page of
22615 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22616 to discard the remaining output. Also, the screen width setting
22617 determines when to wrap lines of output. Depending on what is being
22618 printed, @value{GDBN} tries to break the line at a readable place,
22619 rather than simply letting it overflow onto the following line.
22621 Normally @value{GDBN} knows the size of the screen from the terminal
22622 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22623 together with the value of the @code{TERM} environment variable and the
22624 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22625 you can override it with the @code{set height} and @code{set
22632 @kindex show height
22633 @item set height @var{lpp}
22634 @itemx set height unlimited
22636 @itemx set width @var{cpl}
22637 @itemx set width unlimited
22639 These @code{set} commands specify a screen height of @var{lpp} lines and
22640 a screen width of @var{cpl} characters. The associated @code{show}
22641 commands display the current settings.
22643 If you specify a height of either @code{unlimited} or zero lines,
22644 @value{GDBN} does not pause during output no matter how long the
22645 output is. This is useful if output is to a file or to an editor
22648 Likewise, you can specify @samp{set width unlimited} or @samp{set
22649 width 0} to prevent @value{GDBN} from wrapping its output.
22651 @item set pagination on
22652 @itemx set pagination off
22653 @kindex set pagination
22654 Turn the output pagination on or off; the default is on. Turning
22655 pagination off is the alternative to @code{set height unlimited}. Note that
22656 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22657 Options, -batch}) also automatically disables pagination.
22659 @item show pagination
22660 @kindex show pagination
22661 Show the current pagination mode.
22666 @cindex number representation
22667 @cindex entering numbers
22669 You can always enter numbers in octal, decimal, or hexadecimal in
22670 @value{GDBN} by the usual conventions: octal numbers begin with
22671 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22672 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22673 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22674 10; likewise, the default display for numbers---when no particular
22675 format is specified---is base 10. You can change the default base for
22676 both input and output with the commands described below.
22679 @kindex set input-radix
22680 @item set input-radix @var{base}
22681 Set the default base for numeric input. Supported choices
22682 for @var{base} are decimal 8, 10, or 16. The base must itself be
22683 specified either unambiguously or using the current input radix; for
22687 set input-radix 012
22688 set input-radix 10.
22689 set input-radix 0xa
22693 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22694 leaves the input radix unchanged, no matter what it was, since
22695 @samp{10}, being without any leading or trailing signs of its base, is
22696 interpreted in the current radix. Thus, if the current radix is 16,
22697 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22700 @kindex set output-radix
22701 @item set output-radix @var{base}
22702 Set the default base for numeric display. Supported choices
22703 for @var{base} are decimal 8, 10, or 16. The base must itself be
22704 specified either unambiguously or using the current input radix.
22706 @kindex show input-radix
22707 @item show input-radix
22708 Display the current default base for numeric input.
22710 @kindex show output-radix
22711 @item show output-radix
22712 Display the current default base for numeric display.
22714 @item set radix @r{[}@var{base}@r{]}
22718 These commands set and show the default base for both input and output
22719 of numbers. @code{set radix} sets the radix of input and output to
22720 the same base; without an argument, it resets the radix back to its
22721 default value of 10.
22726 @section Configuring the Current ABI
22728 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22729 application automatically. However, sometimes you need to override its
22730 conclusions. Use these commands to manage @value{GDBN}'s view of the
22736 @cindex Newlib OS ABI and its influence on the longjmp handling
22738 One @value{GDBN} configuration can debug binaries for multiple operating
22739 system targets, either via remote debugging or native emulation.
22740 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22741 but you can override its conclusion using the @code{set osabi} command.
22742 One example where this is useful is in debugging of binaries which use
22743 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22744 not have the same identifying marks that the standard C library for your
22747 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22748 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22749 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22750 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22754 Show the OS ABI currently in use.
22757 With no argument, show the list of registered available OS ABI's.
22759 @item set osabi @var{abi}
22760 Set the current OS ABI to @var{abi}.
22763 @cindex float promotion
22765 Generally, the way that an argument of type @code{float} is passed to a
22766 function depends on whether the function is prototyped. For a prototyped
22767 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22768 according to the architecture's convention for @code{float}. For unprototyped
22769 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22770 @code{double} and then passed.
22772 Unfortunately, some forms of debug information do not reliably indicate whether
22773 a function is prototyped. If @value{GDBN} calls a function that is not marked
22774 as prototyped, it consults @kbd{set coerce-float-to-double}.
22777 @kindex set coerce-float-to-double
22778 @item set coerce-float-to-double
22779 @itemx set coerce-float-to-double on
22780 Arguments of type @code{float} will be promoted to @code{double} when passed
22781 to an unprototyped function. This is the default setting.
22783 @item set coerce-float-to-double off
22784 Arguments of type @code{float} will be passed directly to unprototyped
22787 @kindex show coerce-float-to-double
22788 @item show coerce-float-to-double
22789 Show the current setting of promoting @code{float} to @code{double}.
22793 @kindex show cp-abi
22794 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22795 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22796 used to build your application. @value{GDBN} only fully supports
22797 programs with a single C@t{++} ABI; if your program contains code using
22798 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22799 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22800 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22801 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22802 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22803 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22808 Show the C@t{++} ABI currently in use.
22811 With no argument, show the list of supported C@t{++} ABI's.
22813 @item set cp-abi @var{abi}
22814 @itemx set cp-abi auto
22815 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22819 @section Automatically loading associated files
22820 @cindex auto-loading
22822 @value{GDBN} sometimes reads files with commands and settings automatically,
22823 without being explicitly told so by the user. We call this feature
22824 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22825 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22826 results or introduce security risks (e.g., if the file comes from untrusted
22830 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22831 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22833 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22834 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22837 There are various kinds of files @value{GDBN} can automatically load.
22838 In addition to these files, @value{GDBN} supports auto-loading code written
22839 in various extension languages. @xref{Auto-loading extensions}.
22841 Note that loading of these associated files (including the local @file{.gdbinit}
22842 file) requires accordingly configured @code{auto-load safe-path}
22843 (@pxref{Auto-loading safe path}).
22845 For these reasons, @value{GDBN} includes commands and options to let you
22846 control when to auto-load files and which files should be auto-loaded.
22849 @anchor{set auto-load off}
22850 @kindex set auto-load off
22851 @item set auto-load off
22852 Globally disable loading of all auto-loaded files.
22853 You may want to use this command with the @samp{-iex} option
22854 (@pxref{Option -init-eval-command}) such as:
22856 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22859 Be aware that system init file (@pxref{System-wide configuration})
22860 and init files from your home directory (@pxref{Home Directory Init File})
22861 still get read (as they come from generally trusted directories).
22862 To prevent @value{GDBN} from auto-loading even those init files, use the
22863 @option{-nx} option (@pxref{Mode Options}), in addition to
22864 @code{set auto-load no}.
22866 @anchor{show auto-load}
22867 @kindex show auto-load
22868 @item show auto-load
22869 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22873 (gdb) show auto-load
22874 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22875 libthread-db: Auto-loading of inferior specific libthread_db is on.
22876 local-gdbinit: Auto-loading of .gdbinit script from current directory
22878 python-scripts: Auto-loading of Python scripts is on.
22879 safe-path: List of directories from which it is safe to auto-load files
22880 is $debugdir:$datadir/auto-load.
22881 scripts-directory: List of directories from which to load auto-loaded scripts
22882 is $debugdir:$datadir/auto-load.
22885 @anchor{info auto-load}
22886 @kindex info auto-load
22887 @item info auto-load
22888 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22892 (gdb) info auto-load
22895 Yes /home/user/gdb/gdb-gdb.gdb
22896 libthread-db: No auto-loaded libthread-db.
22897 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22901 Yes /home/user/gdb/gdb-gdb.py
22905 These are @value{GDBN} control commands for the auto-loading:
22907 @multitable @columnfractions .5 .5
22908 @item @xref{set auto-load off}.
22909 @tab Disable auto-loading globally.
22910 @item @xref{show auto-load}.
22911 @tab Show setting of all kinds of files.
22912 @item @xref{info auto-load}.
22913 @tab Show state of all kinds of files.
22914 @item @xref{set auto-load gdb-scripts}.
22915 @tab Control for @value{GDBN} command scripts.
22916 @item @xref{show auto-load gdb-scripts}.
22917 @tab Show setting of @value{GDBN} command scripts.
22918 @item @xref{info auto-load gdb-scripts}.
22919 @tab Show state of @value{GDBN} command scripts.
22920 @item @xref{set auto-load python-scripts}.
22921 @tab Control for @value{GDBN} Python scripts.
22922 @item @xref{show auto-load python-scripts}.
22923 @tab Show setting of @value{GDBN} Python scripts.
22924 @item @xref{info auto-load python-scripts}.
22925 @tab Show state of @value{GDBN} Python scripts.
22926 @item @xref{set auto-load guile-scripts}.
22927 @tab Control for @value{GDBN} Guile scripts.
22928 @item @xref{show auto-load guile-scripts}.
22929 @tab Show setting of @value{GDBN} Guile scripts.
22930 @item @xref{info auto-load guile-scripts}.
22931 @tab Show state of @value{GDBN} Guile scripts.
22932 @item @xref{set auto-load scripts-directory}.
22933 @tab Control for @value{GDBN} auto-loaded scripts location.
22934 @item @xref{show auto-load scripts-directory}.
22935 @tab Show @value{GDBN} auto-loaded scripts location.
22936 @item @xref{add-auto-load-scripts-directory}.
22937 @tab Add directory for auto-loaded scripts location list.
22938 @item @xref{set auto-load local-gdbinit}.
22939 @tab Control for init file in the current directory.
22940 @item @xref{show auto-load local-gdbinit}.
22941 @tab Show setting of init file in the current directory.
22942 @item @xref{info auto-load local-gdbinit}.
22943 @tab Show state of init file in the current directory.
22944 @item @xref{set auto-load libthread-db}.
22945 @tab Control for thread debugging library.
22946 @item @xref{show auto-load libthread-db}.
22947 @tab Show setting of thread debugging library.
22948 @item @xref{info auto-load libthread-db}.
22949 @tab Show state of thread debugging library.
22950 @item @xref{set auto-load safe-path}.
22951 @tab Control directories trusted for automatic loading.
22952 @item @xref{show auto-load safe-path}.
22953 @tab Show directories trusted for automatic loading.
22954 @item @xref{add-auto-load-safe-path}.
22955 @tab Add directory trusted for automatic loading.
22958 @node Init File in the Current Directory
22959 @subsection Automatically loading init file in the current directory
22960 @cindex auto-loading init file in the current directory
22962 By default, @value{GDBN} reads and executes the canned sequences of commands
22963 from init file (if any) in the current working directory,
22964 see @ref{Init File in the Current Directory during Startup}.
22966 Note that loading of this local @file{.gdbinit} file also requires accordingly
22967 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22970 @anchor{set auto-load local-gdbinit}
22971 @kindex set auto-load local-gdbinit
22972 @item set auto-load local-gdbinit [on|off]
22973 Enable or disable the auto-loading of canned sequences of commands
22974 (@pxref{Sequences}) found in init file in the current directory.
22976 @anchor{show auto-load local-gdbinit}
22977 @kindex show auto-load local-gdbinit
22978 @item show auto-load local-gdbinit
22979 Show whether auto-loading of canned sequences of commands from init file in the
22980 current directory is enabled or disabled.
22982 @anchor{info auto-load local-gdbinit}
22983 @kindex info auto-load local-gdbinit
22984 @item info auto-load local-gdbinit
22985 Print whether canned sequences of commands from init file in the
22986 current directory have been auto-loaded.
22989 @node libthread_db.so.1 file
22990 @subsection Automatically loading thread debugging library
22991 @cindex auto-loading libthread_db.so.1
22993 This feature is currently present only on @sc{gnu}/Linux native hosts.
22995 @value{GDBN} reads in some cases thread debugging library from places specific
22996 to the inferior (@pxref{set libthread-db-search-path}).
22998 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22999 without checking this @samp{set auto-load libthread-db} switch as system
23000 libraries have to be trusted in general. In all other cases of
23001 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23002 auto-load libthread-db} is enabled before trying to open such thread debugging
23005 Note that loading of this debugging library also requires accordingly configured
23006 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23009 @anchor{set auto-load libthread-db}
23010 @kindex set auto-load libthread-db
23011 @item set auto-load libthread-db [on|off]
23012 Enable or disable the auto-loading of inferior specific thread debugging library.
23014 @anchor{show auto-load libthread-db}
23015 @kindex show auto-load libthread-db
23016 @item show auto-load libthread-db
23017 Show whether auto-loading of inferior specific thread debugging library is
23018 enabled or disabled.
23020 @anchor{info auto-load libthread-db}
23021 @kindex info auto-load libthread-db
23022 @item info auto-load libthread-db
23023 Print the list of all loaded inferior specific thread debugging libraries and
23024 for each such library print list of inferior @var{pid}s using it.
23027 @node Auto-loading safe path
23028 @subsection Security restriction for auto-loading
23029 @cindex auto-loading safe-path
23031 As the files of inferior can come from untrusted source (such as submitted by
23032 an application user) @value{GDBN} does not always load any files automatically.
23033 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23034 directories trusted for loading files not explicitly requested by user.
23035 Each directory can also be a shell wildcard pattern.
23037 If the path is not set properly you will see a warning and the file will not
23042 Reading symbols from /home/user/gdb/gdb...done.
23043 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23044 declined by your `auto-load safe-path' set
23045 to "$debugdir:$datadir/auto-load".
23046 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23047 declined by your `auto-load safe-path' set
23048 to "$debugdir:$datadir/auto-load".
23052 To instruct @value{GDBN} to go ahead and use the init files anyway,
23053 invoke @value{GDBN} like this:
23056 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23059 The list of trusted directories is controlled by the following commands:
23062 @anchor{set auto-load safe-path}
23063 @kindex set auto-load safe-path
23064 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23065 Set the list of directories (and their subdirectories) trusted for automatic
23066 loading and execution of scripts. You can also enter a specific trusted file.
23067 Each directory can also be a shell wildcard pattern; wildcards do not match
23068 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23069 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23070 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23071 its default value as specified during @value{GDBN} compilation.
23073 The list of directories uses path separator (@samp{:} on GNU and Unix
23074 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23075 to the @env{PATH} environment variable.
23077 @anchor{show auto-load safe-path}
23078 @kindex show auto-load safe-path
23079 @item show auto-load safe-path
23080 Show the list of directories trusted for automatic loading and execution of
23083 @anchor{add-auto-load-safe-path}
23084 @kindex add-auto-load-safe-path
23085 @item add-auto-load-safe-path
23086 Add an entry (or list of entries) to the list of directories trusted for
23087 automatic loading and execution of scripts. Multiple entries may be delimited
23088 by the host platform path separator in use.
23091 This variable defaults to what @code{--with-auto-load-dir} has been configured
23092 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23093 substitution applies the same as for @ref{set auto-load scripts-directory}.
23094 The default @code{set auto-load safe-path} value can be also overriden by
23095 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23097 Setting this variable to @file{/} disables this security protection,
23098 corresponding @value{GDBN} configuration option is
23099 @option{--without-auto-load-safe-path}.
23100 This variable is supposed to be set to the system directories writable by the
23101 system superuser only. Users can add their source directories in init files in
23102 their home directories (@pxref{Home Directory Init File}). See also deprecated
23103 init file in the current directory
23104 (@pxref{Init File in the Current Directory during Startup}).
23106 To force @value{GDBN} to load the files it declined to load in the previous
23107 example, you could use one of the following ways:
23110 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23111 Specify this trusted directory (or a file) as additional component of the list.
23112 You have to specify also any existing directories displayed by
23113 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23115 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23116 Specify this directory as in the previous case but just for a single
23117 @value{GDBN} session.
23119 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23120 Disable auto-loading safety for a single @value{GDBN} session.
23121 This assumes all the files you debug during this @value{GDBN} session will come
23122 from trusted sources.
23124 @item @kbd{./configure --without-auto-load-safe-path}
23125 During compilation of @value{GDBN} you may disable any auto-loading safety.
23126 This assumes all the files you will ever debug with this @value{GDBN} come from
23130 On the other hand you can also explicitly forbid automatic files loading which
23131 also suppresses any such warning messages:
23134 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23135 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23137 @item @file{~/.gdbinit}: @samp{set auto-load no}
23138 Disable auto-loading globally for the user
23139 (@pxref{Home Directory Init File}). While it is improbable, you could also
23140 use system init file instead (@pxref{System-wide configuration}).
23143 This setting applies to the file names as entered by user. If no entry matches
23144 @value{GDBN} tries as a last resort to also resolve all the file names into
23145 their canonical form (typically resolving symbolic links) and compare the
23146 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23147 own before starting the comparison so a canonical form of directories is
23148 recommended to be entered.
23150 @node Auto-loading verbose mode
23151 @subsection Displaying files tried for auto-load
23152 @cindex auto-loading verbose mode
23154 For better visibility of all the file locations where you can place scripts to
23155 be auto-loaded with inferior --- or to protect yourself against accidental
23156 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23157 all the files attempted to be loaded. Both existing and non-existing files may
23160 For example the list of directories from which it is safe to auto-load files
23161 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23162 may not be too obvious while setting it up.
23165 (gdb) set debug auto-load on
23166 (gdb) file ~/src/t/true
23167 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23168 for objfile "/tmp/true".
23169 auto-load: Updating directories of "/usr:/opt".
23170 auto-load: Using directory "/usr".
23171 auto-load: Using directory "/opt".
23172 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23173 by your `auto-load safe-path' set to "/usr:/opt".
23177 @anchor{set debug auto-load}
23178 @kindex set debug auto-load
23179 @item set debug auto-load [on|off]
23180 Set whether to print the filenames attempted to be auto-loaded.
23182 @anchor{show debug auto-load}
23183 @kindex show debug auto-load
23184 @item show debug auto-load
23185 Show whether printing of the filenames attempted to be auto-loaded is turned
23189 @node Messages/Warnings
23190 @section Optional Warnings and Messages
23192 @cindex verbose operation
23193 @cindex optional warnings
23194 By default, @value{GDBN} is silent about its inner workings. If you are
23195 running on a slow machine, you may want to use the @code{set verbose}
23196 command. This makes @value{GDBN} tell you when it does a lengthy
23197 internal operation, so you will not think it has crashed.
23199 Currently, the messages controlled by @code{set verbose} are those
23200 which announce that the symbol table for a source file is being read;
23201 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23204 @kindex set verbose
23205 @item set verbose on
23206 Enables @value{GDBN} output of certain informational messages.
23208 @item set verbose off
23209 Disables @value{GDBN} output of certain informational messages.
23211 @kindex show verbose
23213 Displays whether @code{set verbose} is on or off.
23216 By default, if @value{GDBN} encounters bugs in the symbol table of an
23217 object file, it is silent; but if you are debugging a compiler, you may
23218 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23223 @kindex set complaints
23224 @item set complaints @var{limit}
23225 Permits @value{GDBN} to output @var{limit} complaints about each type of
23226 unusual symbols before becoming silent about the problem. Set
23227 @var{limit} to zero to suppress all complaints; set it to a large number
23228 to prevent complaints from being suppressed.
23230 @kindex show complaints
23231 @item show complaints
23232 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23236 @anchor{confirmation requests}
23237 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23238 lot of stupid questions to confirm certain commands. For example, if
23239 you try to run a program which is already running:
23243 The program being debugged has been started already.
23244 Start it from the beginning? (y or n)
23247 If you are willing to unflinchingly face the consequences of your own
23248 commands, you can disable this ``feature'':
23252 @kindex set confirm
23254 @cindex confirmation
23255 @cindex stupid questions
23256 @item set confirm off
23257 Disables confirmation requests. Note that running @value{GDBN} with
23258 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23259 automatically disables confirmation requests.
23261 @item set confirm on
23262 Enables confirmation requests (the default).
23264 @kindex show confirm
23266 Displays state of confirmation requests.
23270 @cindex command tracing
23271 If you need to debug user-defined commands or sourced files you may find it
23272 useful to enable @dfn{command tracing}. In this mode each command will be
23273 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23274 quantity denoting the call depth of each command.
23277 @kindex set trace-commands
23278 @cindex command scripts, debugging
23279 @item set trace-commands on
23280 Enable command tracing.
23281 @item set trace-commands off
23282 Disable command tracing.
23283 @item show trace-commands
23284 Display the current state of command tracing.
23287 @node Debugging Output
23288 @section Optional Messages about Internal Happenings
23289 @cindex optional debugging messages
23291 @value{GDBN} has commands that enable optional debugging messages from
23292 various @value{GDBN} subsystems; normally these commands are of
23293 interest to @value{GDBN} maintainers, or when reporting a bug. This
23294 section documents those commands.
23297 @kindex set exec-done-display
23298 @item set exec-done-display
23299 Turns on or off the notification of asynchronous commands'
23300 completion. When on, @value{GDBN} will print a message when an
23301 asynchronous command finishes its execution. The default is off.
23302 @kindex show exec-done-display
23303 @item show exec-done-display
23304 Displays the current setting of asynchronous command completion
23307 @cindex ARM AArch64
23308 @item set debug aarch64
23309 Turns on or off display of debugging messages related to ARM AArch64.
23310 The default is off.
23312 @item show debug aarch64
23313 Displays the current state of displaying debugging messages related to
23315 @cindex gdbarch debugging info
23316 @cindex architecture debugging info
23317 @item set debug arch
23318 Turns on or off display of gdbarch debugging info. The default is off
23319 @item show debug arch
23320 Displays the current state of displaying gdbarch debugging info.
23321 @item set debug aix-solib
23322 @cindex AIX shared library debugging
23323 Control display of debugging messages from the AIX shared library
23324 support module. The default is off.
23325 @item show debug aix-thread
23326 Show the current state of displaying AIX shared library debugging messages.
23327 @item set debug aix-thread
23328 @cindex AIX threads
23329 Display debugging messages about inner workings of the AIX thread
23331 @item show debug aix-thread
23332 Show the current state of AIX thread debugging info display.
23333 @item set debug check-physname
23335 Check the results of the ``physname'' computation. When reading DWARF
23336 debugging information for C@t{++}, @value{GDBN} attempts to compute
23337 each entity's name. @value{GDBN} can do this computation in two
23338 different ways, depending on exactly what information is present.
23339 When enabled, this setting causes @value{GDBN} to compute the names
23340 both ways and display any discrepancies.
23341 @item show debug check-physname
23342 Show the current state of ``physname'' checking.
23343 @item set debug coff-pe-read
23344 @cindex COFF/PE exported symbols
23345 Control display of debugging messages related to reading of COFF/PE
23346 exported symbols. The default is off.
23347 @item show debug coff-pe-read
23348 Displays the current state of displaying debugging messages related to
23349 reading of COFF/PE exported symbols.
23350 @item set debug dwarf-die
23352 Dump DWARF DIEs after they are read in.
23353 The value is the number of nesting levels to print.
23354 A value of zero turns off the display.
23355 @item show debug dwarf-die
23356 Show the current state of DWARF DIE debugging.
23357 @item set debug dwarf-line
23358 @cindex DWARF Line Tables
23359 Turns on or off display of debugging messages related to reading
23360 DWARF line tables. The default is 0 (off).
23361 A value of 1 provides basic information.
23362 A value greater than 1 provides more verbose information.
23363 @item show debug dwarf-line
23364 Show the current state of DWARF line table debugging.
23365 @item set debug dwarf-read
23366 @cindex DWARF Reading
23367 Turns on or off display of debugging messages related to reading
23368 DWARF debug info. The default is 0 (off).
23369 A value of 1 provides basic information.
23370 A value greater than 1 provides more verbose information.
23371 @item show debug dwarf-read
23372 Show the current state of DWARF reader debugging.
23373 @item set debug displaced
23374 @cindex displaced stepping debugging info
23375 Turns on or off display of @value{GDBN} debugging info for the
23376 displaced stepping support. The default is off.
23377 @item show debug displaced
23378 Displays the current state of displaying @value{GDBN} debugging info
23379 related to displaced stepping.
23380 @item set debug event
23381 @cindex event debugging info
23382 Turns on or off display of @value{GDBN} event debugging info. The
23384 @item show debug event
23385 Displays the current state of displaying @value{GDBN} event debugging
23387 @item set debug expression
23388 @cindex expression debugging info
23389 Turns on or off display of debugging info about @value{GDBN}
23390 expression parsing. The default is off.
23391 @item show debug expression
23392 Displays the current state of displaying debugging info about
23393 @value{GDBN} expression parsing.
23394 @item set debug frame
23395 @cindex frame debugging info
23396 Turns on or off display of @value{GDBN} frame debugging info. The
23398 @item show debug frame
23399 Displays the current state of displaying @value{GDBN} frame debugging
23401 @item set debug gnu-nat
23402 @cindex @sc{gnu}/Hurd debug messages
23403 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23404 @item show debug gnu-nat
23405 Show the current state of @sc{gnu}/Hurd debugging messages.
23406 @item set debug infrun
23407 @cindex inferior debugging info
23408 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23409 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23410 for implementing operations such as single-stepping the inferior.
23411 @item show debug infrun
23412 Displays the current state of @value{GDBN} inferior debugging.
23413 @item set debug jit
23414 @cindex just-in-time compilation, debugging messages
23415 Turns on or off debugging messages from JIT debug support.
23416 @item show debug jit
23417 Displays the current state of @value{GDBN} JIT debugging.
23418 @item set debug lin-lwp
23419 @cindex @sc{gnu}/Linux LWP debug messages
23420 @cindex Linux lightweight processes
23421 Turns on or off debugging messages from the Linux LWP debug support.
23422 @item show debug lin-lwp
23423 Show the current state of Linux LWP debugging messages.
23424 @item set debug linux-namespaces
23425 @cindex @sc{gnu}/Linux namespaces debug messages
23426 Turns on or off debugging messages from the Linux namespaces debug support.
23427 @item show debug linux-namespaces
23428 Show the current state of Linux namespaces debugging messages.
23429 @item set debug mach-o
23430 @cindex Mach-O symbols processing
23431 Control display of debugging messages related to Mach-O symbols
23432 processing. The default is off.
23433 @item show debug mach-o
23434 Displays the current state of displaying debugging messages related to
23435 reading of COFF/PE exported symbols.
23436 @item set debug notification
23437 @cindex remote async notification debugging info
23438 Turns on or off debugging messages about remote async notification.
23439 The default is off.
23440 @item show debug notification
23441 Displays the current state of remote async notification debugging messages.
23442 @item set debug observer
23443 @cindex observer debugging info
23444 Turns on or off display of @value{GDBN} observer debugging. This
23445 includes info such as the notification of observable events.
23446 @item show debug observer
23447 Displays the current state of observer debugging.
23448 @item set debug overload
23449 @cindex C@t{++} overload debugging info
23450 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23451 info. This includes info such as ranking of functions, etc. The default
23453 @item show debug overload
23454 Displays the current state of displaying @value{GDBN} C@t{++} overload
23456 @cindex expression parser, debugging info
23457 @cindex debug expression parser
23458 @item set debug parser
23459 Turns on or off the display of expression parser debugging output.
23460 Internally, this sets the @code{yydebug} variable in the expression
23461 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23462 details. The default is off.
23463 @item show debug parser
23464 Show the current state of expression parser debugging.
23465 @cindex packets, reporting on stdout
23466 @cindex serial connections, debugging
23467 @cindex debug remote protocol
23468 @cindex remote protocol debugging
23469 @cindex display remote packets
23470 @item set debug remote
23471 Turns on or off display of reports on all packets sent back and forth across
23472 the serial line to the remote machine. The info is printed on the
23473 @value{GDBN} standard output stream. The default is off.
23474 @item show debug remote
23475 Displays the state of display of remote packets.
23476 @item set debug serial
23477 Turns on or off display of @value{GDBN} serial debugging info. The
23479 @item show debug serial
23480 Displays the current state of displaying @value{GDBN} serial debugging
23482 @item set debug solib-frv
23483 @cindex FR-V shared-library debugging
23484 Turns on or off debugging messages for FR-V shared-library code.
23485 @item show debug solib-frv
23486 Display the current state of FR-V shared-library code debugging
23488 @item set debug symbol-lookup
23489 @cindex symbol lookup
23490 Turns on or off display of debugging messages related to symbol lookup.
23491 The default is 0 (off).
23492 A value of 1 provides basic information.
23493 A value greater than 1 provides more verbose information.
23494 @item show debug symbol-lookup
23495 Show the current state of symbol lookup debugging messages.
23496 @item set debug symfile
23497 @cindex symbol file functions
23498 Turns on or off display of debugging messages related to symbol file functions.
23499 The default is off. @xref{Files}.
23500 @item show debug symfile
23501 Show the current state of symbol file debugging messages.
23502 @item set debug symtab-create
23503 @cindex symbol table creation
23504 Turns on or off display of debugging messages related to symbol table creation.
23505 The default is 0 (off).
23506 A value of 1 provides basic information.
23507 A value greater than 1 provides more verbose information.
23508 @item show debug symtab-create
23509 Show the current state of symbol table creation debugging.
23510 @item set debug target
23511 @cindex target debugging info
23512 Turns on or off display of @value{GDBN} target debugging info. This info
23513 includes what is going on at the target level of GDB, as it happens. The
23514 default is 0. Set it to 1 to track events, and to 2 to also track the
23515 value of large memory transfers.
23516 @item show debug target
23517 Displays the current state of displaying @value{GDBN} target debugging
23519 @item set debug timestamp
23520 @cindex timestampping debugging info
23521 Turns on or off display of timestamps with @value{GDBN} debugging info.
23522 When enabled, seconds and microseconds are displayed before each debugging
23524 @item show debug timestamp
23525 Displays the current state of displaying timestamps with @value{GDBN}
23527 @item set debug varobj
23528 @cindex variable object debugging info
23529 Turns on or off display of @value{GDBN} variable object debugging
23530 info. The default is off.
23531 @item show debug varobj
23532 Displays the current state of displaying @value{GDBN} variable object
23534 @item set debug xml
23535 @cindex XML parser debugging
23536 Turns on or off debugging messages for built-in XML parsers.
23537 @item show debug xml
23538 Displays the current state of XML debugging messages.
23541 @node Other Misc Settings
23542 @section Other Miscellaneous Settings
23543 @cindex miscellaneous settings
23546 @kindex set interactive-mode
23547 @item set interactive-mode
23548 If @code{on}, forces @value{GDBN} to assume that GDB was started
23549 in a terminal. In practice, this means that @value{GDBN} should wait
23550 for the user to answer queries generated by commands entered at
23551 the command prompt. If @code{off}, forces @value{GDBN} to operate
23552 in the opposite mode, and it uses the default answers to all queries.
23553 If @code{auto} (the default), @value{GDBN} tries to determine whether
23554 its standard input is a terminal, and works in interactive-mode if it
23555 is, non-interactively otherwise.
23557 In the vast majority of cases, the debugger should be able to guess
23558 correctly which mode should be used. But this setting can be useful
23559 in certain specific cases, such as running a MinGW @value{GDBN}
23560 inside a cygwin window.
23562 @kindex show interactive-mode
23563 @item show interactive-mode
23564 Displays whether the debugger is operating in interactive mode or not.
23567 @node Extending GDB
23568 @chapter Extending @value{GDBN}
23569 @cindex extending GDB
23571 @value{GDBN} provides several mechanisms for extension.
23572 @value{GDBN} also provides the ability to automatically load
23573 extensions when it reads a file for debugging. This allows the
23574 user to automatically customize @value{GDBN} for the program
23578 * Sequences:: Canned Sequences of @value{GDBN} Commands
23579 * Python:: Extending @value{GDBN} using Python
23580 * Guile:: Extending @value{GDBN} using Guile
23581 * Auto-loading extensions:: Automatically loading extensions
23582 * Multiple Extension Languages:: Working with multiple extension languages
23583 * Aliases:: Creating new spellings of existing commands
23586 To facilitate the use of extension languages, @value{GDBN} is capable
23587 of evaluating the contents of a file. When doing so, @value{GDBN}
23588 can recognize which extension language is being used by looking at
23589 the filename extension. Files with an unrecognized filename extension
23590 are always treated as a @value{GDBN} Command Files.
23591 @xref{Command Files,, Command files}.
23593 You can control how @value{GDBN} evaluates these files with the following
23597 @kindex set script-extension
23598 @kindex show script-extension
23599 @item set script-extension off
23600 All scripts are always evaluated as @value{GDBN} Command Files.
23602 @item set script-extension soft
23603 The debugger determines the scripting language based on filename
23604 extension. If this scripting language is supported, @value{GDBN}
23605 evaluates the script using that language. Otherwise, it evaluates
23606 the file as a @value{GDBN} Command File.
23608 @item set script-extension strict
23609 The debugger determines the scripting language based on filename
23610 extension, and evaluates the script using that language. If the
23611 language is not supported, then the evaluation fails.
23613 @item show script-extension
23614 Display the current value of the @code{script-extension} option.
23619 @section Canned Sequences of Commands
23621 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23622 Command Lists}), @value{GDBN} provides two ways to store sequences of
23623 commands for execution as a unit: user-defined commands and command
23627 * Define:: How to define your own commands
23628 * Hooks:: Hooks for user-defined commands
23629 * Command Files:: How to write scripts of commands to be stored in a file
23630 * Output:: Commands for controlled output
23631 * Auto-loading sequences:: Controlling auto-loaded command files
23635 @subsection User-defined Commands
23637 @cindex user-defined command
23638 @cindex arguments, to user-defined commands
23639 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23640 which you assign a new name as a command. This is done with the
23641 @code{define} command. User commands may accept up to 10 arguments
23642 separated by whitespace. Arguments are accessed within the user command
23643 via @code{$arg0@dots{}$arg9}. A trivial example:
23647 print $arg0 + $arg1 + $arg2
23652 To execute the command use:
23659 This defines the command @code{adder}, which prints the sum of
23660 its three arguments. Note the arguments are text substitutions, so they may
23661 reference variables, use complex expressions, or even perform inferior
23664 @cindex argument count in user-defined commands
23665 @cindex how many arguments (user-defined commands)
23666 In addition, @code{$argc} may be used to find out how many arguments have
23667 been passed. This expands to a number in the range 0@dots{}10.
23672 print $arg0 + $arg1
23675 print $arg0 + $arg1 + $arg2
23683 @item define @var{commandname}
23684 Define a command named @var{commandname}. If there is already a command
23685 by that name, you are asked to confirm that you want to redefine it.
23686 The argument @var{commandname} may be a bare command name consisting of letters,
23687 numbers, dashes, and underscores. It may also start with any predefined
23688 prefix command. For example, @samp{define target my-target} creates
23689 a user-defined @samp{target my-target} command.
23691 The definition of the command is made up of other @value{GDBN} command lines,
23692 which are given following the @code{define} command. The end of these
23693 commands is marked by a line containing @code{end}.
23696 @kindex end@r{ (user-defined commands)}
23697 @item document @var{commandname}
23698 Document the user-defined command @var{commandname}, so that it can be
23699 accessed by @code{help}. The command @var{commandname} must already be
23700 defined. This command reads lines of documentation just as @code{define}
23701 reads the lines of the command definition, ending with @code{end}.
23702 After the @code{document} command is finished, @code{help} on command
23703 @var{commandname} displays the documentation you have written.
23705 You may use the @code{document} command again to change the
23706 documentation of a command. Redefining the command with @code{define}
23707 does not change the documentation.
23709 @kindex dont-repeat
23710 @cindex don't repeat command
23712 Used inside a user-defined command, this tells @value{GDBN} that this
23713 command should not be repeated when the user hits @key{RET}
23714 (@pxref{Command Syntax, repeat last command}).
23716 @kindex help user-defined
23717 @item help user-defined
23718 List all user-defined commands and all python commands defined in class
23719 COMAND_USER. The first line of the documentation or docstring is
23724 @itemx show user @var{commandname}
23725 Display the @value{GDBN} commands used to define @var{commandname} (but
23726 not its documentation). If no @var{commandname} is given, display the
23727 definitions for all user-defined commands.
23728 This does not work for user-defined python commands.
23730 @cindex infinite recursion in user-defined commands
23731 @kindex show max-user-call-depth
23732 @kindex set max-user-call-depth
23733 @item show max-user-call-depth
23734 @itemx set max-user-call-depth
23735 The value of @code{max-user-call-depth} controls how many recursion
23736 levels are allowed in user-defined commands before @value{GDBN} suspects an
23737 infinite recursion and aborts the command.
23738 This does not apply to user-defined python commands.
23741 In addition to the above commands, user-defined commands frequently
23742 use control flow commands, described in @ref{Command Files}.
23744 When user-defined commands are executed, the
23745 commands of the definition are not printed. An error in any command
23746 stops execution of the user-defined command.
23748 If used interactively, commands that would ask for confirmation proceed
23749 without asking when used inside a user-defined command. Many @value{GDBN}
23750 commands that normally print messages to say what they are doing omit the
23751 messages when used in a user-defined command.
23754 @subsection User-defined Command Hooks
23755 @cindex command hooks
23756 @cindex hooks, for commands
23757 @cindex hooks, pre-command
23760 You may define @dfn{hooks}, which are a special kind of user-defined
23761 command. Whenever you run the command @samp{foo}, if the user-defined
23762 command @samp{hook-foo} exists, it is executed (with no arguments)
23763 before that command.
23765 @cindex hooks, post-command
23767 A hook may also be defined which is run after the command you executed.
23768 Whenever you run the command @samp{foo}, if the user-defined command
23769 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23770 that command. Post-execution hooks may exist simultaneously with
23771 pre-execution hooks, for the same command.
23773 It is valid for a hook to call the command which it hooks. If this
23774 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23776 @c It would be nice if hookpost could be passed a parameter indicating
23777 @c if the command it hooks executed properly or not. FIXME!
23779 @kindex stop@r{, a pseudo-command}
23780 In addition, a pseudo-command, @samp{stop} exists. Defining
23781 (@samp{hook-stop}) makes the associated commands execute every time
23782 execution stops in your program: before breakpoint commands are run,
23783 displays are printed, or the stack frame is printed.
23785 For example, to ignore @code{SIGALRM} signals while
23786 single-stepping, but treat them normally during normal execution,
23791 handle SIGALRM nopass
23795 handle SIGALRM pass
23798 define hook-continue
23799 handle SIGALRM pass
23803 As a further example, to hook at the beginning and end of the @code{echo}
23804 command, and to add extra text to the beginning and end of the message,
23812 define hookpost-echo
23816 (@value{GDBP}) echo Hello World
23817 <<<---Hello World--->>>
23822 You can define a hook for any single-word command in @value{GDBN}, but
23823 not for command aliases; you should define a hook for the basic command
23824 name, e.g.@: @code{backtrace} rather than @code{bt}.
23825 @c FIXME! So how does Joe User discover whether a command is an alias
23827 You can hook a multi-word command by adding @code{hook-} or
23828 @code{hookpost-} to the last word of the command, e.g.@:
23829 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23831 If an error occurs during the execution of your hook, execution of
23832 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23833 (before the command that you actually typed had a chance to run).
23835 If you try to define a hook which does not match any known command, you
23836 get a warning from the @code{define} command.
23838 @node Command Files
23839 @subsection Command Files
23841 @cindex command files
23842 @cindex scripting commands
23843 A command file for @value{GDBN} is a text file made of lines that are
23844 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23845 also be included. An empty line in a command file does nothing; it
23846 does not mean to repeat the last command, as it would from the
23849 You can request the execution of a command file with the @code{source}
23850 command. Note that the @code{source} command is also used to evaluate
23851 scripts that are not Command Files. The exact behavior can be configured
23852 using the @code{script-extension} setting.
23853 @xref{Extending GDB,, Extending GDB}.
23857 @cindex execute commands from a file
23858 @item source [-s] [-v] @var{filename}
23859 Execute the command file @var{filename}.
23862 The lines in a command file are generally executed sequentially,
23863 unless the order of execution is changed by one of the
23864 @emph{flow-control commands} described below. The commands are not
23865 printed as they are executed. An error in any command terminates
23866 execution of the command file and control is returned to the console.
23868 @value{GDBN} first searches for @var{filename} in the current directory.
23869 If the file is not found there, and @var{filename} does not specify a
23870 directory, then @value{GDBN} also looks for the file on the source search path
23871 (specified with the @samp{directory} command);
23872 except that @file{$cdir} is not searched because the compilation directory
23873 is not relevant to scripts.
23875 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23876 on the search path even if @var{filename} specifies a directory.
23877 The search is done by appending @var{filename} to each element of the
23878 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23879 and the search path contains @file{/home/user} then @value{GDBN} will
23880 look for the script @file{/home/user/mylib/myscript}.
23881 The search is also done if @var{filename} is an absolute path.
23882 For example, if @var{filename} is @file{/tmp/myscript} and
23883 the search path contains @file{/home/user} then @value{GDBN} will
23884 look for the script @file{/home/user/tmp/myscript}.
23885 For DOS-like systems, if @var{filename} contains a drive specification,
23886 it is stripped before concatenation. For example, if @var{filename} is
23887 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23888 will look for the script @file{c:/tmp/myscript}.
23890 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23891 each command as it is executed. The option must be given before
23892 @var{filename}, and is interpreted as part of the filename anywhere else.
23894 Commands that would ask for confirmation if used interactively proceed
23895 without asking when used in a command file. Many @value{GDBN} commands that
23896 normally print messages to say what they are doing omit the messages
23897 when called from command files.
23899 @value{GDBN} also accepts command input from standard input. In this
23900 mode, normal output goes to standard output and error output goes to
23901 standard error. Errors in a command file supplied on standard input do
23902 not terminate execution of the command file---execution continues with
23906 gdb < cmds > log 2>&1
23909 (The syntax above will vary depending on the shell used.) This example
23910 will execute commands from the file @file{cmds}. All output and errors
23911 would be directed to @file{log}.
23913 Since commands stored on command files tend to be more general than
23914 commands typed interactively, they frequently need to deal with
23915 complicated situations, such as different or unexpected values of
23916 variables and symbols, changes in how the program being debugged is
23917 built, etc. @value{GDBN} provides a set of flow-control commands to
23918 deal with these complexities. Using these commands, you can write
23919 complex scripts that loop over data structures, execute commands
23920 conditionally, etc.
23927 This command allows to include in your script conditionally executed
23928 commands. The @code{if} command takes a single argument, which is an
23929 expression to evaluate. It is followed by a series of commands that
23930 are executed only if the expression is true (its value is nonzero).
23931 There can then optionally be an @code{else} line, followed by a series
23932 of commands that are only executed if the expression was false. The
23933 end of the list is marked by a line containing @code{end}.
23937 This command allows to write loops. Its syntax is similar to
23938 @code{if}: the command takes a single argument, which is an expression
23939 to evaluate, and must be followed by the commands to execute, one per
23940 line, terminated by an @code{end}. These commands are called the
23941 @dfn{body} of the loop. The commands in the body of @code{while} are
23942 executed repeatedly as long as the expression evaluates to true.
23946 This command exits the @code{while} loop in whose body it is included.
23947 Execution of the script continues after that @code{while}s @code{end}
23950 @kindex loop_continue
23951 @item loop_continue
23952 This command skips the execution of the rest of the body of commands
23953 in the @code{while} loop in whose body it is included. Execution
23954 branches to the beginning of the @code{while} loop, where it evaluates
23955 the controlling expression.
23957 @kindex end@r{ (if/else/while commands)}
23959 Terminate the block of commands that are the body of @code{if},
23960 @code{else}, or @code{while} flow-control commands.
23965 @subsection Commands for Controlled Output
23967 During the execution of a command file or a user-defined command, normal
23968 @value{GDBN} output is suppressed; the only output that appears is what is
23969 explicitly printed by the commands in the definition. This section
23970 describes three commands useful for generating exactly the output you
23975 @item echo @var{text}
23976 @c I do not consider backslash-space a standard C escape sequence
23977 @c because it is not in ANSI.
23978 Print @var{text}. Nonprinting characters can be included in
23979 @var{text} using C escape sequences, such as @samp{\n} to print a
23980 newline. @strong{No newline is printed unless you specify one.}
23981 In addition to the standard C escape sequences, a backslash followed
23982 by a space stands for a space. This is useful for displaying a
23983 string with spaces at the beginning or the end, since leading and
23984 trailing spaces are otherwise trimmed from all arguments.
23985 To print @samp{@w{ }and foo =@w{ }}, use the command
23986 @samp{echo \@w{ }and foo = \@w{ }}.
23988 A backslash at the end of @var{text} can be used, as in C, to continue
23989 the command onto subsequent lines. For example,
23992 echo This is some text\n\
23993 which is continued\n\
23994 onto several lines.\n
23997 produces the same output as
24000 echo This is some text\n
24001 echo which is continued\n
24002 echo onto several lines.\n
24006 @item output @var{expression}
24007 Print the value of @var{expression} and nothing but that value: no
24008 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24009 value history either. @xref{Expressions, ,Expressions}, for more information
24012 @item output/@var{fmt} @var{expression}
24013 Print the value of @var{expression} in format @var{fmt}. You can use
24014 the same formats as for @code{print}. @xref{Output Formats,,Output
24015 Formats}, for more information.
24018 @item printf @var{template}, @var{expressions}@dots{}
24019 Print the values of one or more @var{expressions} under the control of
24020 the string @var{template}. To print several values, make
24021 @var{expressions} be a comma-separated list of individual expressions,
24022 which may be either numbers or pointers. Their values are printed as
24023 specified by @var{template}, exactly as a C program would do by
24024 executing the code below:
24027 printf (@var{template}, @var{expressions}@dots{});
24030 As in @code{C} @code{printf}, ordinary characters in @var{template}
24031 are printed verbatim, while @dfn{conversion specification} introduced
24032 by the @samp{%} character cause subsequent @var{expressions} to be
24033 evaluated, their values converted and formatted according to type and
24034 style information encoded in the conversion specifications, and then
24037 For example, you can print two values in hex like this:
24040 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24043 @code{printf} supports all the standard @code{C} conversion
24044 specifications, including the flags and modifiers between the @samp{%}
24045 character and the conversion letter, with the following exceptions:
24049 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24052 The modifier @samp{*} is not supported for specifying precision or
24056 The @samp{'} flag (for separation of digits into groups according to
24057 @code{LC_NUMERIC'}) is not supported.
24060 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24064 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24067 The conversion letters @samp{a} and @samp{A} are not supported.
24071 Note that the @samp{ll} type modifier is supported only if the
24072 underlying @code{C} implementation used to build @value{GDBN} supports
24073 the @code{long long int} type, and the @samp{L} type modifier is
24074 supported only if @code{long double} type is available.
24076 As in @code{C}, @code{printf} supports simple backslash-escape
24077 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24078 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24079 single character. Octal and hexadecimal escape sequences are not
24082 Additionally, @code{printf} supports conversion specifications for DFP
24083 (@dfn{Decimal Floating Point}) types using the following length modifiers
24084 together with a floating point specifier.
24089 @samp{H} for printing @code{Decimal32} types.
24092 @samp{D} for printing @code{Decimal64} types.
24095 @samp{DD} for printing @code{Decimal128} types.
24098 If the underlying @code{C} implementation used to build @value{GDBN} has
24099 support for the three length modifiers for DFP types, other modifiers
24100 such as width and precision will also be available for @value{GDBN} to use.
24102 In case there is no such @code{C} support, no additional modifiers will be
24103 available and the value will be printed in the standard way.
24105 Here's an example of printing DFP types using the above conversion letters:
24107 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24111 @item eval @var{template}, @var{expressions}@dots{}
24112 Convert the values of one or more @var{expressions} under the control of
24113 the string @var{template} to a command line, and call it.
24117 @node Auto-loading sequences
24118 @subsection Controlling auto-loading native @value{GDBN} scripts
24119 @cindex native script auto-loading
24121 When a new object file is read (for example, due to the @code{file}
24122 command, or because the inferior has loaded a shared library),
24123 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24124 @xref{Auto-loading extensions}.
24126 Auto-loading can be enabled or disabled,
24127 and the list of auto-loaded scripts can be printed.
24130 @anchor{set auto-load gdb-scripts}
24131 @kindex set auto-load gdb-scripts
24132 @item set auto-load gdb-scripts [on|off]
24133 Enable or disable the auto-loading of canned sequences of commands scripts.
24135 @anchor{show auto-load gdb-scripts}
24136 @kindex show auto-load gdb-scripts
24137 @item show auto-load gdb-scripts
24138 Show whether auto-loading of canned sequences of commands scripts is enabled or
24141 @anchor{info auto-load gdb-scripts}
24142 @kindex info auto-load gdb-scripts
24143 @cindex print list of auto-loaded canned sequences of commands scripts
24144 @item info auto-load gdb-scripts [@var{regexp}]
24145 Print the list of all canned sequences of commands scripts that @value{GDBN}
24149 If @var{regexp} is supplied only canned sequences of commands scripts with
24150 matching names are printed.
24152 @c Python docs live in a separate file.
24153 @include python.texi
24155 @c Guile docs live in a separate file.
24156 @include guile.texi
24158 @node Auto-loading extensions
24159 @section Auto-loading extensions
24160 @cindex auto-loading extensions
24162 @value{GDBN} provides two mechanisms for automatically loading extensions
24163 when a new object file is read (for example, due to the @code{file}
24164 command, or because the inferior has loaded a shared library):
24165 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24166 section of modern file formats like ELF.
24169 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24170 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24171 * Which flavor to choose?::
24174 The auto-loading feature is useful for supplying application-specific
24175 debugging commands and features.
24177 Auto-loading can be enabled or disabled,
24178 and the list of auto-loaded scripts can be printed.
24179 See the @samp{auto-loading} section of each extension language
24180 for more information.
24181 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24182 For Python files see @ref{Python Auto-loading}.
24184 Note that loading of this script file also requires accordingly configured
24185 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24187 @node objfile-gdbdotext file
24188 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24189 @cindex @file{@var{objfile}-gdb.gdb}
24190 @cindex @file{@var{objfile}-gdb.py}
24191 @cindex @file{@var{objfile}-gdb.scm}
24193 When a new object file is read, @value{GDBN} looks for a file named
24194 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24195 where @var{objfile} is the object file's name and
24196 where @var{ext} is the file extension for the extension language:
24199 @item @file{@var{objfile}-gdb.gdb}
24200 GDB's own command language
24201 @item @file{@var{objfile}-gdb.py}
24203 @item @file{@var{objfile}-gdb.scm}
24207 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24208 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24209 components, and appending the @file{-gdb.@var{ext}} suffix.
24210 If this file exists and is readable, @value{GDBN} will evaluate it as a
24211 script in the specified extension language.
24213 If this file does not exist, then @value{GDBN} will look for
24214 @var{script-name} file in all of the directories as specified below.
24216 Note that loading of these files requires an accordingly configured
24217 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24219 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24220 scripts normally according to its @file{.exe} filename. But if no scripts are
24221 found @value{GDBN} also tries script filenames matching the object file without
24222 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24223 is attempted on any platform. This makes the script filenames compatible
24224 between Unix and MS-Windows hosts.
24227 @anchor{set auto-load scripts-directory}
24228 @kindex set auto-load scripts-directory
24229 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24230 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24231 may be delimited by the host platform path separator in use
24232 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24234 Each entry here needs to be covered also by the security setting
24235 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24237 @anchor{with-auto-load-dir}
24238 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24239 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24240 configuration option @option{--with-auto-load-dir}.
24242 Any reference to @file{$debugdir} will get replaced by
24243 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24244 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24245 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24246 @file{$datadir} must be placed as a directory component --- either alone or
24247 delimited by @file{/} or @file{\} directory separators, depending on the host
24250 The list of directories uses path separator (@samp{:} on GNU and Unix
24251 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24252 to the @env{PATH} environment variable.
24254 @anchor{show auto-load scripts-directory}
24255 @kindex show auto-load scripts-directory
24256 @item show auto-load scripts-directory
24257 Show @value{GDBN} auto-loaded scripts location.
24259 @anchor{add-auto-load-scripts-directory}
24260 @kindex add-auto-load-scripts-directory
24261 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24262 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24263 Multiple entries may be delimited by the host platform path separator in use.
24266 @value{GDBN} does not track which files it has already auto-loaded this way.
24267 @value{GDBN} will load the associated script every time the corresponding
24268 @var{objfile} is opened.
24269 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24270 is evaluated more than once.
24272 @node dotdebug_gdb_scripts section
24273 @subsection The @code{.debug_gdb_scripts} section
24274 @cindex @code{.debug_gdb_scripts} section
24276 For systems using file formats like ELF and COFF,
24277 when @value{GDBN} loads a new object file
24278 it will look for a special section named @code{.debug_gdb_scripts}.
24279 If this section exists, its contents is a list of null-terminated entries
24280 specifying scripts to load. Each entry begins with a non-null prefix byte that
24281 specifies the kind of entry, typically the extension language and whether the
24282 script is in a file or inlined in @code{.debug_gdb_scripts}.
24284 The following entries are supported:
24287 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24288 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24289 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24290 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24293 @subsubsection Script File Entries
24295 If the entry specifies a file, @value{GDBN} will look for the file first
24296 in the current directory and then along the source search path
24297 (@pxref{Source Path, ,Specifying Source Directories}),
24298 except that @file{$cdir} is not searched, since the compilation
24299 directory is not relevant to scripts.
24301 File entries can be placed in section @code{.debug_gdb_scripts} with,
24302 for example, this GCC macro for Python scripts.
24305 /* Note: The "MS" section flags are to remove duplicates. */
24306 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24308 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24309 .byte 1 /* Python */\n\
24310 .asciz \"" script_name "\"\n\
24316 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24317 Then one can reference the macro in a header or source file like this:
24320 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24323 The script name may include directories if desired.
24325 Note that loading of this script file also requires accordingly configured
24326 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24328 If the macro invocation is put in a header, any application or library
24329 using this header will get a reference to the specified script,
24330 and with the use of @code{"MS"} attributes on the section, the linker
24331 will remove duplicates.
24333 @subsubsection Script Text Entries
24335 Script text entries allow to put the executable script in the entry
24336 itself instead of loading it from a file.
24337 The first line of the entry, everything after the prefix byte and up to
24338 the first newline (@code{0xa}) character, is the script name, and must not
24339 contain any kind of space character, e.g., spaces or tabs.
24340 The rest of the entry, up to the trailing null byte, is the script to
24341 execute in the specified language. The name needs to be unique among
24342 all script names, as @value{GDBN} executes each script only once based
24345 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24349 #include "symcat.h"
24350 #include "gdb/section-scripts.h"
24352 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24353 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24354 ".ascii \"gdb.inlined-script\\n\"\n"
24355 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24356 ".ascii \" def __init__ (self):\\n\"\n"
24357 ".ascii \" super (test_cmd, self).__init__ ("
24358 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24359 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24360 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24361 ".ascii \"test_cmd ()\\n\"\n"
24367 Loading of inlined scripts requires a properly configured
24368 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24369 The path to specify in @code{auto-load safe-path} is the path of the file
24370 containing the @code{.debug_gdb_scripts} section.
24372 @node Which flavor to choose?
24373 @subsection Which flavor to choose?
24375 Given the multiple ways of auto-loading extensions, it might not always
24376 be clear which one to choose. This section provides some guidance.
24379 Benefits of the @file{-gdb.@var{ext}} way:
24383 Can be used with file formats that don't support multiple sections.
24386 Ease of finding scripts for public libraries.
24388 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24389 in the source search path.
24390 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24391 isn't a source directory in which to find the script.
24394 Doesn't require source code additions.
24398 Benefits of the @code{.debug_gdb_scripts} way:
24402 Works with static linking.
24404 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24405 trigger their loading. When an application is statically linked the only
24406 objfile available is the executable, and it is cumbersome to attach all the
24407 scripts from all the input libraries to the executable's
24408 @file{-gdb.@var{ext}} script.
24411 Works with classes that are entirely inlined.
24413 Some classes can be entirely inlined, and thus there may not be an associated
24414 shared library to attach a @file{-gdb.@var{ext}} script to.
24417 Scripts needn't be copied out of the source tree.
24419 In some circumstances, apps can be built out of large collections of internal
24420 libraries, and the build infrastructure necessary to install the
24421 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24422 cumbersome. It may be easier to specify the scripts in the
24423 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24424 top of the source tree to the source search path.
24427 @node Multiple Extension Languages
24428 @section Multiple Extension Languages
24430 The Guile and Python extension languages do not share any state,
24431 and generally do not interfere with each other.
24432 There are some things to be aware of, however.
24434 @subsection Python comes first
24436 Python was @value{GDBN}'s first extension language, and to avoid breaking
24437 existing behaviour Python comes first. This is generally solved by the
24438 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24439 extension languages, and when it makes a call to an extension language,
24440 (say to pretty-print a value), it tries each in turn until an extension
24441 language indicates it has performed the request (e.g., has returned the
24442 pretty-printed form of a value).
24443 This extends to errors while performing such requests: If an error happens
24444 while, for example, trying to pretty-print an object then the error is
24445 reported and any following extension languages are not tried.
24448 @section Creating new spellings of existing commands
24449 @cindex aliases for commands
24451 It is often useful to define alternate spellings of existing commands.
24452 For example, if a new @value{GDBN} command defined in Python has
24453 a long name to type, it is handy to have an abbreviated version of it
24454 that involves less typing.
24456 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24457 of the @samp{step} command even though it is otherwise an ambiguous
24458 abbreviation of other commands like @samp{set} and @samp{show}.
24460 Aliases are also used to provide shortened or more common versions
24461 of multi-word commands. For example, @value{GDBN} provides the
24462 @samp{tty} alias of the @samp{set inferior-tty} command.
24464 You can define a new alias with the @samp{alias} command.
24469 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24473 @var{ALIAS} specifies the name of the new alias.
24474 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24477 @var{COMMAND} specifies the name of an existing command
24478 that is being aliased.
24480 The @samp{-a} option specifies that the new alias is an abbreviation
24481 of the command. Abbreviations are not shown in command
24482 lists displayed by the @samp{help} command.
24484 The @samp{--} option specifies the end of options,
24485 and is useful when @var{ALIAS} begins with a dash.
24487 Here is a simple example showing how to make an abbreviation
24488 of a command so that there is less to type.
24489 Suppose you were tired of typing @samp{disas}, the current
24490 shortest unambiguous abbreviation of the @samp{disassemble} command
24491 and you wanted an even shorter version named @samp{di}.
24492 The following will accomplish this.
24495 (gdb) alias -a di = disas
24498 Note that aliases are different from user-defined commands.
24499 With a user-defined command, you also need to write documentation
24500 for it with the @samp{document} command.
24501 An alias automatically picks up the documentation of the existing command.
24503 Here is an example where we make @samp{elms} an abbreviation of
24504 @samp{elements} in the @samp{set print elements} command.
24505 This is to show that you can make an abbreviation of any part
24509 (gdb) alias -a set print elms = set print elements
24510 (gdb) alias -a show print elms = show print elements
24511 (gdb) set p elms 20
24513 Limit on string chars or array elements to print is 200.
24516 Note that if you are defining an alias of a @samp{set} command,
24517 and you want to have an alias for the corresponding @samp{show}
24518 command, then you need to define the latter separately.
24520 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24521 @var{ALIAS}, just as they are normally.
24524 (gdb) alias -a set pr elms = set p ele
24527 Finally, here is an example showing the creation of a one word
24528 alias for a more complex command.
24529 This creates alias @samp{spe} of the command @samp{set print elements}.
24532 (gdb) alias spe = set print elements
24537 @chapter Command Interpreters
24538 @cindex command interpreters
24540 @value{GDBN} supports multiple command interpreters, and some command
24541 infrastructure to allow users or user interface writers to switch
24542 between interpreters or run commands in other interpreters.
24544 @value{GDBN} currently supports two command interpreters, the console
24545 interpreter (sometimes called the command-line interpreter or @sc{cli})
24546 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24547 describes both of these interfaces in great detail.
24549 By default, @value{GDBN} will start with the console interpreter.
24550 However, the user may choose to start @value{GDBN} with another
24551 interpreter by specifying the @option{-i} or @option{--interpreter}
24552 startup options. Defined interpreters include:
24556 @cindex console interpreter
24557 The traditional console or command-line interpreter. This is the most often
24558 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24559 @value{GDBN} will use this interpreter.
24562 @cindex mi interpreter
24563 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24564 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24565 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24569 @cindex mi2 interpreter
24570 The current @sc{gdb/mi} interface.
24573 @cindex mi1 interpreter
24574 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24578 @cindex invoke another interpreter
24579 The interpreter being used by @value{GDBN} may not be dynamically
24580 switched at runtime. Although possible, this could lead to a very
24581 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24582 enters the command "interpreter-set console" in a console view,
24583 @value{GDBN} would switch to using the console interpreter, rendering
24584 the IDE inoperable!
24586 @kindex interpreter-exec
24587 Although you may only choose a single interpreter at startup, you may execute
24588 commands in any interpreter from the current interpreter using the appropriate
24589 command. If you are running the console interpreter, simply use the
24590 @code{interpreter-exec} command:
24593 interpreter-exec mi "-data-list-register-names"
24596 @sc{gdb/mi} has a similar command, although it is only available in versions of
24597 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24600 @chapter @value{GDBN} Text User Interface
24602 @cindex Text User Interface
24605 * TUI Overview:: TUI overview
24606 * TUI Keys:: TUI key bindings
24607 * TUI Single Key Mode:: TUI single key mode
24608 * TUI Commands:: TUI-specific commands
24609 * TUI Configuration:: TUI configuration variables
24612 The @value{GDBN} Text User Interface (TUI) is a terminal
24613 interface which uses the @code{curses} library to show the source
24614 file, the assembly output, the program registers and @value{GDBN}
24615 commands in separate text windows. The TUI mode is supported only
24616 on platforms where a suitable version of the @code{curses} library
24619 The TUI mode is enabled by default when you invoke @value{GDBN} as
24620 @samp{@value{GDBP} -tui}.
24621 You can also switch in and out of TUI mode while @value{GDBN} runs by
24622 using various TUI commands and key bindings, such as @command{tui
24623 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24624 @ref{TUI Keys, ,TUI Key Bindings}.
24627 @section TUI Overview
24629 In TUI mode, @value{GDBN} can display several text windows:
24633 This window is the @value{GDBN} command window with the @value{GDBN}
24634 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24635 managed using readline.
24638 The source window shows the source file of the program. The current
24639 line and active breakpoints are displayed in this window.
24642 The assembly window shows the disassembly output of the program.
24645 This window shows the processor registers. Registers are highlighted
24646 when their values change.
24649 The source and assembly windows show the current program position
24650 by highlighting the current line and marking it with a @samp{>} marker.
24651 Breakpoints are indicated with two markers. The first marker
24652 indicates the breakpoint type:
24656 Breakpoint which was hit at least once.
24659 Breakpoint which was never hit.
24662 Hardware breakpoint which was hit at least once.
24665 Hardware breakpoint which was never hit.
24668 The second marker indicates whether the breakpoint is enabled or not:
24672 Breakpoint is enabled.
24675 Breakpoint is disabled.
24678 The source, assembly and register windows are updated when the current
24679 thread changes, when the frame changes, or when the program counter
24682 These windows are not all visible at the same time. The command
24683 window is always visible. The others can be arranged in several
24694 source and assembly,
24697 source and registers, or
24700 assembly and registers.
24703 A status line above the command window shows the following information:
24707 Indicates the current @value{GDBN} target.
24708 (@pxref{Targets, ,Specifying a Debugging Target}).
24711 Gives the current process or thread number.
24712 When no process is being debugged, this field is set to @code{No process}.
24715 Gives the current function name for the selected frame.
24716 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24717 When there is no symbol corresponding to the current program counter,
24718 the string @code{??} is displayed.
24721 Indicates the current line number for the selected frame.
24722 When the current line number is not known, the string @code{??} is displayed.
24725 Indicates the current program counter address.
24729 @section TUI Key Bindings
24730 @cindex TUI key bindings
24732 The TUI installs several key bindings in the readline keymaps
24733 @ifset SYSTEM_READLINE
24734 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24736 @ifclear SYSTEM_READLINE
24737 (@pxref{Command Line Editing}).
24739 The following key bindings are installed for both TUI mode and the
24740 @value{GDBN} standard mode.
24749 Enter or leave the TUI mode. When leaving the TUI mode,
24750 the curses window management stops and @value{GDBN} operates using
24751 its standard mode, writing on the terminal directly. When reentering
24752 the TUI mode, control is given back to the curses windows.
24753 The screen is then refreshed.
24757 Use a TUI layout with only one window. The layout will
24758 either be @samp{source} or @samp{assembly}. When the TUI mode
24759 is not active, it will switch to the TUI mode.
24761 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24765 Use a TUI layout with at least two windows. When the current
24766 layout already has two windows, the next layout with two windows is used.
24767 When a new layout is chosen, one window will always be common to the
24768 previous layout and the new one.
24770 Think of it as the Emacs @kbd{C-x 2} binding.
24774 Change the active window. The TUI associates several key bindings
24775 (like scrolling and arrow keys) with the active window. This command
24776 gives the focus to the next TUI window.
24778 Think of it as the Emacs @kbd{C-x o} binding.
24782 Switch in and out of the TUI SingleKey mode that binds single
24783 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24786 The following key bindings only work in the TUI mode:
24791 Scroll the active window one page up.
24795 Scroll the active window one page down.
24799 Scroll the active window one line up.
24803 Scroll the active window one line down.
24807 Scroll the active window one column left.
24811 Scroll the active window one column right.
24815 Refresh the screen.
24818 Because the arrow keys scroll the active window in the TUI mode, they
24819 are not available for their normal use by readline unless the command
24820 window has the focus. When another window is active, you must use
24821 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24822 and @kbd{C-f} to control the command window.
24824 @node TUI Single Key Mode
24825 @section TUI Single Key Mode
24826 @cindex TUI single key mode
24828 The TUI also provides a @dfn{SingleKey} mode, which binds several
24829 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24830 switch into this mode, where the following key bindings are used:
24833 @kindex c @r{(SingleKey TUI key)}
24837 @kindex d @r{(SingleKey TUI key)}
24841 @kindex f @r{(SingleKey TUI key)}
24845 @kindex n @r{(SingleKey TUI key)}
24849 @kindex q @r{(SingleKey TUI key)}
24851 exit the SingleKey mode.
24853 @kindex r @r{(SingleKey TUI key)}
24857 @kindex s @r{(SingleKey TUI key)}
24861 @kindex u @r{(SingleKey TUI key)}
24865 @kindex v @r{(SingleKey TUI key)}
24869 @kindex w @r{(SingleKey TUI key)}
24874 Other keys temporarily switch to the @value{GDBN} command prompt.
24875 The key that was pressed is inserted in the editing buffer so that
24876 it is possible to type most @value{GDBN} commands without interaction
24877 with the TUI SingleKey mode. Once the command is entered the TUI
24878 SingleKey mode is restored. The only way to permanently leave
24879 this mode is by typing @kbd{q} or @kbd{C-x s}.
24883 @section TUI-specific Commands
24884 @cindex TUI commands
24886 The TUI has specific commands to control the text windows.
24887 These commands are always available, even when @value{GDBN} is not in
24888 the TUI mode. When @value{GDBN} is in the standard mode, most
24889 of these commands will automatically switch to the TUI mode.
24891 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24892 terminal, or @value{GDBN} has been started with the machine interface
24893 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24894 these commands will fail with an error, because it would not be
24895 possible or desirable to enable curses window management.
24900 Activate TUI mode. The last active TUI window layout will be used if
24901 TUI mode has prevsiouly been used in the current debugging session,
24902 otherwise a default layout is used.
24905 @kindex tui disable
24906 Disable TUI mode, returning to the console interpreter.
24910 List and give the size of all displayed windows.
24912 @item layout @var{name}
24914 Changes which TUI windows are displayed. In each layout the command
24915 window is always displayed, the @var{name} parameter controls which
24916 additional windows are displayed, and can be any of the following:
24920 Display the next layout.
24923 Display the previous layout.
24926 Display the source and command windows.
24929 Display the assembly and command windows.
24932 Display the source, assembly, and command windows.
24935 When in @code{src} layout display the register, source, and command
24936 windows. When in @code{asm} or @code{split} layout display the
24937 register, assembler, and command windows.
24940 @item focus @var{name}
24942 Changes which TUI window is currently active for scrolling. The
24943 @var{name} parameter can be any of the following:
24947 Make the next window active for scrolling.
24950 Make the previous window active for scrolling.
24953 Make the source window active for scrolling.
24956 Make the assembly window active for scrolling.
24959 Make the register window active for scrolling.
24962 Make the command window active for scrolling.
24967 Refresh the screen. This is similar to typing @kbd{C-L}.
24969 @item tui reg @var{group}
24971 Changes the register group displayed in the tui register window to
24972 @var{group}. If the register window is not currently displayed this
24973 command will cause the register window to be displayed. The list of
24974 register groups, as well as their order is target specific. The
24975 following groups are available on most targets:
24978 Repeatedly selecting this group will cause the display to cycle
24979 through all of the available register groups.
24982 Repeatedly selecting this group will cause the display to cycle
24983 through all of the available register groups in the reverse order to
24987 Display the general registers.
24989 Display the floating point registers.
24991 Display the system registers.
24993 Display the vector registers.
24995 Display all registers.
25000 Update the source window and the current execution point.
25002 @item winheight @var{name} +@var{count}
25003 @itemx winheight @var{name} -@var{count}
25005 Change the height of the window @var{name} by @var{count}
25006 lines. Positive counts increase the height, while negative counts
25007 decrease it. The @var{name} parameter can be one of @code{src} (the
25008 source window), @code{cmd} (the command window), @code{asm} (the
25009 disassembly window), or @code{regs} (the register display window).
25011 @item tabset @var{nchars}
25013 Set the width of tab stops to be @var{nchars} characters. This
25014 setting affects the display of TAB characters in the source and
25018 @node TUI Configuration
25019 @section TUI Configuration Variables
25020 @cindex TUI configuration variables
25022 Several configuration variables control the appearance of TUI windows.
25025 @item set tui border-kind @var{kind}
25026 @kindex set tui border-kind
25027 Select the border appearance for the source, assembly and register windows.
25028 The possible values are the following:
25031 Use a space character to draw the border.
25034 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25037 Use the Alternate Character Set to draw the border. The border is
25038 drawn using character line graphics if the terminal supports them.
25041 @item set tui border-mode @var{mode}
25042 @kindex set tui border-mode
25043 @itemx set tui active-border-mode @var{mode}
25044 @kindex set tui active-border-mode
25045 Select the display attributes for the borders of the inactive windows
25046 or the active window. The @var{mode} can be one of the following:
25049 Use normal attributes to display the border.
25055 Use reverse video mode.
25058 Use half bright mode.
25060 @item half-standout
25061 Use half bright and standout mode.
25064 Use extra bright or bold mode.
25066 @item bold-standout
25067 Use extra bright or bold and standout mode.
25072 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25075 @cindex @sc{gnu} Emacs
25076 A special interface allows you to use @sc{gnu} Emacs to view (and
25077 edit) the source files for the program you are debugging with
25080 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25081 executable file you want to debug as an argument. This command starts
25082 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25083 created Emacs buffer.
25084 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25086 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25091 All ``terminal'' input and output goes through an Emacs buffer, called
25094 This applies both to @value{GDBN} commands and their output, and to the input
25095 and output done by the program you are debugging.
25097 This is useful because it means that you can copy the text of previous
25098 commands and input them again; you can even use parts of the output
25101 All the facilities of Emacs' Shell mode are available for interacting
25102 with your program. In particular, you can send signals the usual
25103 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25107 @value{GDBN} displays source code through Emacs.
25109 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25110 source file for that frame and puts an arrow (@samp{=>}) at the
25111 left margin of the current line. Emacs uses a separate buffer for
25112 source display, and splits the screen to show both your @value{GDBN} session
25115 Explicit @value{GDBN} @code{list} or search commands still produce output as
25116 usual, but you probably have no reason to use them from Emacs.
25119 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25120 a graphical mode, enabled by default, which provides further buffers
25121 that can control the execution and describe the state of your program.
25122 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25124 If you specify an absolute file name when prompted for the @kbd{M-x
25125 gdb} argument, then Emacs sets your current working directory to where
25126 your program resides. If you only specify the file name, then Emacs
25127 sets your current working directory to the directory associated
25128 with the previous buffer. In this case, @value{GDBN} may find your
25129 program by searching your environment's @code{PATH} variable, but on
25130 some operating systems it might not find the source. So, although the
25131 @value{GDBN} input and output session proceeds normally, the auxiliary
25132 buffer does not display the current source and line of execution.
25134 The initial working directory of @value{GDBN} is printed on the top
25135 line of the GUD buffer and this serves as a default for the commands
25136 that specify files for @value{GDBN} to operate on. @xref{Files,
25137 ,Commands to Specify Files}.
25139 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25140 need to call @value{GDBN} by a different name (for example, if you
25141 keep several configurations around, with different names) you can
25142 customize the Emacs variable @code{gud-gdb-command-name} to run the
25145 In the GUD buffer, you can use these special Emacs commands in
25146 addition to the standard Shell mode commands:
25150 Describe the features of Emacs' GUD Mode.
25153 Execute to another source line, like the @value{GDBN} @code{step} command; also
25154 update the display window to show the current file and location.
25157 Execute to next source line in this function, skipping all function
25158 calls, like the @value{GDBN} @code{next} command. Then update the display window
25159 to show the current file and location.
25162 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25163 display window accordingly.
25166 Execute until exit from the selected stack frame, like the @value{GDBN}
25167 @code{finish} command.
25170 Continue execution of your program, like the @value{GDBN} @code{continue}
25174 Go up the number of frames indicated by the numeric argument
25175 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25176 like the @value{GDBN} @code{up} command.
25179 Go down the number of frames indicated by the numeric argument, like the
25180 @value{GDBN} @code{down} command.
25183 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25184 tells @value{GDBN} to set a breakpoint on the source line point is on.
25186 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25187 separate frame which shows a backtrace when the GUD buffer is current.
25188 Move point to any frame in the stack and type @key{RET} to make it
25189 become the current frame and display the associated source in the
25190 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25191 selected frame become the current one. In graphical mode, the
25192 speedbar displays watch expressions.
25194 If you accidentally delete the source-display buffer, an easy way to get
25195 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25196 request a frame display; when you run under Emacs, this recreates
25197 the source buffer if necessary to show you the context of the current
25200 The source files displayed in Emacs are in ordinary Emacs buffers
25201 which are visiting the source files in the usual way. You can edit
25202 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25203 communicates with Emacs in terms of line numbers. If you add or
25204 delete lines from the text, the line numbers that @value{GDBN} knows cease
25205 to correspond properly with the code.
25207 A more detailed description of Emacs' interaction with @value{GDBN} is
25208 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25212 @chapter The @sc{gdb/mi} Interface
25214 @unnumberedsec Function and Purpose
25216 @cindex @sc{gdb/mi}, its purpose
25217 @sc{gdb/mi} is a line based machine oriented text interface to
25218 @value{GDBN} and is activated by specifying using the
25219 @option{--interpreter} command line option (@pxref{Mode Options}). It
25220 is specifically intended to support the development of systems which
25221 use the debugger as just one small component of a larger system.
25223 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25224 in the form of a reference manual.
25226 Note that @sc{gdb/mi} is still under construction, so some of the
25227 features described below are incomplete and subject to change
25228 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25230 @unnumberedsec Notation and Terminology
25232 @cindex notational conventions, for @sc{gdb/mi}
25233 This chapter uses the following notation:
25237 @code{|} separates two alternatives.
25240 @code{[ @var{something} ]} indicates that @var{something} is optional:
25241 it may or may not be given.
25244 @code{( @var{group} )*} means that @var{group} inside the parentheses
25245 may repeat zero or more times.
25248 @code{( @var{group} )+} means that @var{group} inside the parentheses
25249 may repeat one or more times.
25252 @code{"@var{string}"} means a literal @var{string}.
25256 @heading Dependencies
25260 * GDB/MI General Design::
25261 * GDB/MI Command Syntax::
25262 * GDB/MI Compatibility with CLI::
25263 * GDB/MI Development and Front Ends::
25264 * GDB/MI Output Records::
25265 * GDB/MI Simple Examples::
25266 * GDB/MI Command Description Format::
25267 * GDB/MI Breakpoint Commands::
25268 * GDB/MI Catchpoint Commands::
25269 * GDB/MI Program Context::
25270 * GDB/MI Thread Commands::
25271 * GDB/MI Ada Tasking Commands::
25272 * GDB/MI Program Execution::
25273 * GDB/MI Stack Manipulation::
25274 * GDB/MI Variable Objects::
25275 * GDB/MI Data Manipulation::
25276 * GDB/MI Tracepoint Commands::
25277 * GDB/MI Symbol Query::
25278 * GDB/MI File Commands::
25280 * GDB/MI Kod Commands::
25281 * GDB/MI Memory Overlay Commands::
25282 * GDB/MI Signal Handling Commands::
25284 * GDB/MI Target Manipulation::
25285 * GDB/MI File Transfer Commands::
25286 * GDB/MI Ada Exceptions Commands::
25287 * GDB/MI Support Commands::
25288 * GDB/MI Miscellaneous Commands::
25291 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25292 @node GDB/MI General Design
25293 @section @sc{gdb/mi} General Design
25294 @cindex GDB/MI General Design
25296 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25297 parts---commands sent to @value{GDBN}, responses to those commands
25298 and notifications. Each command results in exactly one response,
25299 indicating either successful completion of the command, or an error.
25300 For the commands that do not resume the target, the response contains the
25301 requested information. For the commands that resume the target, the
25302 response only indicates whether the target was successfully resumed.
25303 Notifications is the mechanism for reporting changes in the state of the
25304 target, or in @value{GDBN} state, that cannot conveniently be associated with
25305 a command and reported as part of that command response.
25307 The important examples of notifications are:
25311 Exec notifications. These are used to report changes in
25312 target state---when a target is resumed, or stopped. It would not
25313 be feasible to include this information in response of resuming
25314 commands, because one resume commands can result in multiple events in
25315 different threads. Also, quite some time may pass before any event
25316 happens in the target, while a frontend needs to know whether the resuming
25317 command itself was successfully executed.
25320 Console output, and status notifications. Console output
25321 notifications are used to report output of CLI commands, as well as
25322 diagnostics for other commands. Status notifications are used to
25323 report the progress of a long-running operation. Naturally, including
25324 this information in command response would mean no output is produced
25325 until the command is finished, which is undesirable.
25328 General notifications. Commands may have various side effects on
25329 the @value{GDBN} or target state beyond their official purpose. For example,
25330 a command may change the selected thread. Although such changes can
25331 be included in command response, using notification allows for more
25332 orthogonal frontend design.
25336 There's no guarantee that whenever an MI command reports an error,
25337 @value{GDBN} or the target are in any specific state, and especially,
25338 the state is not reverted to the state before the MI command was
25339 processed. Therefore, whenever an MI command results in an error,
25340 we recommend that the frontend refreshes all the information shown in
25341 the user interface.
25345 * Context management::
25346 * Asynchronous and non-stop modes::
25350 @node Context management
25351 @subsection Context management
25353 @subsubsection Threads and Frames
25355 In most cases when @value{GDBN} accesses the target, this access is
25356 done in context of a specific thread and frame (@pxref{Frames}).
25357 Often, even when accessing global data, the target requires that a thread
25358 be specified. The CLI interface maintains the selected thread and frame,
25359 and supplies them to target on each command. This is convenient,
25360 because a command line user would not want to specify that information
25361 explicitly on each command, and because user interacts with
25362 @value{GDBN} via a single terminal, so no confusion is possible as
25363 to what thread and frame are the current ones.
25365 In the case of MI, the concept of selected thread and frame is less
25366 useful. First, a frontend can easily remember this information
25367 itself. Second, a graphical frontend can have more than one window,
25368 each one used for debugging a different thread, and the frontend might
25369 want to access additional threads for internal purposes. This
25370 increases the risk that by relying on implicitly selected thread, the
25371 frontend may be operating on a wrong one. Therefore, each MI command
25372 should explicitly specify which thread and frame to operate on. To
25373 make it possible, each MI command accepts the @samp{--thread} and
25374 @samp{--frame} options, the value to each is @value{GDBN} identifier
25375 for thread and frame to operate on.
25377 Usually, each top-level window in a frontend allows the user to select
25378 a thread and a frame, and remembers the user selection for further
25379 operations. However, in some cases @value{GDBN} may suggest that the
25380 current thread be changed. For example, when stopping on a breakpoint
25381 it is reasonable to switch to the thread where breakpoint is hit. For
25382 another example, if the user issues the CLI @samp{thread} command via
25383 the frontend, it is desirable to change the frontend's selected thread to the
25384 one specified by user. @value{GDBN} communicates the suggestion to
25385 change current thread using the @samp{=thread-selected} notification.
25386 No such notification is available for the selected frame at the moment.
25388 Note that historically, MI shares the selected thread with CLI, so
25389 frontends used the @code{-thread-select} to execute commands in the
25390 right context. However, getting this to work right is cumbersome. The
25391 simplest way is for frontend to emit @code{-thread-select} command
25392 before every command. This doubles the number of commands that need
25393 to be sent. The alternative approach is to suppress @code{-thread-select}
25394 if the selected thread in @value{GDBN} is supposed to be identical to the
25395 thread the frontend wants to operate on. However, getting this
25396 optimization right can be tricky. In particular, if the frontend
25397 sends several commands to @value{GDBN}, and one of the commands changes the
25398 selected thread, then the behaviour of subsequent commands will
25399 change. So, a frontend should either wait for response from such
25400 problematic commands, or explicitly add @code{-thread-select} for
25401 all subsequent commands. No frontend is known to do this exactly
25402 right, so it is suggested to just always pass the @samp{--thread} and
25403 @samp{--frame} options.
25405 @subsubsection Language
25407 The execution of several commands depends on which language is selected.
25408 By default, the current language (@pxref{show language}) is used.
25409 But for commands known to be language-sensitive, it is recommended
25410 to use the @samp{--language} option. This option takes one argument,
25411 which is the name of the language to use while executing the command.
25415 -data-evaluate-expression --language c "sizeof (void*)"
25420 The valid language names are the same names accepted by the
25421 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25422 @samp{local} or @samp{unknown}.
25424 @node Asynchronous and non-stop modes
25425 @subsection Asynchronous command execution and non-stop mode
25427 On some targets, @value{GDBN} is capable of processing MI commands
25428 even while the target is running. This is called @dfn{asynchronous
25429 command execution} (@pxref{Background Execution}). The frontend may
25430 specify a preferrence for asynchronous execution using the
25431 @code{-gdb-set mi-async 1} command, which should be emitted before
25432 either running the executable or attaching to the target. After the
25433 frontend has started the executable or attached to the target, it can
25434 find if asynchronous execution is enabled using the
25435 @code{-list-target-features} command.
25438 @item -gdb-set mi-async on
25439 @item -gdb-set mi-async off
25440 Set whether MI is in asynchronous mode.
25442 When @code{off}, which is the default, MI execution commands (e.g.,
25443 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25444 for the program to stop before processing further commands.
25446 When @code{on}, MI execution commands are background execution
25447 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25448 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25449 MI commands even while the target is running.
25451 @item -gdb-show mi-async
25452 Show whether MI asynchronous mode is enabled.
25455 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25456 @code{target-async} instead of @code{mi-async}, and it had the effect
25457 of both putting MI in asynchronous mode and making CLI background
25458 commands possible. CLI background commands are now always possible
25459 ``out of the box'' if the target supports them. The old spelling is
25460 kept as a deprecated alias for backwards compatibility.
25462 Even if @value{GDBN} can accept a command while target is running,
25463 many commands that access the target do not work when the target is
25464 running. Therefore, asynchronous command execution is most useful
25465 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25466 it is possible to examine the state of one thread, while other threads
25469 When a given thread is running, MI commands that try to access the
25470 target in the context of that thread may not work, or may work only on
25471 some targets. In particular, commands that try to operate on thread's
25472 stack will not work, on any target. Commands that read memory, or
25473 modify breakpoints, may work or not work, depending on the target. Note
25474 that even commands that operate on global state, such as @code{print},
25475 @code{set}, and breakpoint commands, still access the target in the
25476 context of a specific thread, so frontend should try to find a
25477 stopped thread and perform the operation on that thread (using the
25478 @samp{--thread} option).
25480 Which commands will work in the context of a running thread is
25481 highly target dependent. However, the two commands
25482 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25483 to find the state of a thread, will always work.
25485 @node Thread groups
25486 @subsection Thread groups
25487 @value{GDBN} may be used to debug several processes at the same time.
25488 On some platfroms, @value{GDBN} may support debugging of several
25489 hardware systems, each one having several cores with several different
25490 processes running on each core. This section describes the MI
25491 mechanism to support such debugging scenarios.
25493 The key observation is that regardless of the structure of the
25494 target, MI can have a global list of threads, because most commands that
25495 accept the @samp{--thread} option do not need to know what process that
25496 thread belongs to. Therefore, it is not necessary to introduce
25497 neither additional @samp{--process} option, nor an notion of the
25498 current process in the MI interface. The only strictly new feature
25499 that is required is the ability to find how the threads are grouped
25502 To allow the user to discover such grouping, and to support arbitrary
25503 hierarchy of machines/cores/processes, MI introduces the concept of a
25504 @dfn{thread group}. Thread group is a collection of threads and other
25505 thread groups. A thread group always has a string identifier, a type,
25506 and may have additional attributes specific to the type. A new
25507 command, @code{-list-thread-groups}, returns the list of top-level
25508 thread groups, which correspond to processes that @value{GDBN} is
25509 debugging at the moment. By passing an identifier of a thread group
25510 to the @code{-list-thread-groups} command, it is possible to obtain
25511 the members of specific thread group.
25513 To allow the user to easily discover processes, and other objects, he
25514 wishes to debug, a concept of @dfn{available thread group} is
25515 introduced. Available thread group is an thread group that
25516 @value{GDBN} is not debugging, but that can be attached to, using the
25517 @code{-target-attach} command. The list of available top-level thread
25518 groups can be obtained using @samp{-list-thread-groups --available}.
25519 In general, the content of a thread group may be only retrieved only
25520 after attaching to that thread group.
25522 Thread groups are related to inferiors (@pxref{Inferiors and
25523 Programs}). Each inferior corresponds to a thread group of a special
25524 type @samp{process}, and some additional operations are permitted on
25525 such thread groups.
25527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25528 @node GDB/MI Command Syntax
25529 @section @sc{gdb/mi} Command Syntax
25532 * GDB/MI Input Syntax::
25533 * GDB/MI Output Syntax::
25536 @node GDB/MI Input Syntax
25537 @subsection @sc{gdb/mi} Input Syntax
25539 @cindex input syntax for @sc{gdb/mi}
25540 @cindex @sc{gdb/mi}, input syntax
25542 @item @var{command} @expansion{}
25543 @code{@var{cli-command} | @var{mi-command}}
25545 @item @var{cli-command} @expansion{}
25546 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25547 @var{cli-command} is any existing @value{GDBN} CLI command.
25549 @item @var{mi-command} @expansion{}
25550 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25551 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25553 @item @var{token} @expansion{}
25554 "any sequence of digits"
25556 @item @var{option} @expansion{}
25557 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25559 @item @var{parameter} @expansion{}
25560 @code{@var{non-blank-sequence} | @var{c-string}}
25562 @item @var{operation} @expansion{}
25563 @emph{any of the operations described in this chapter}
25565 @item @var{non-blank-sequence} @expansion{}
25566 @emph{anything, provided it doesn't contain special characters such as
25567 "-", @var{nl}, """ and of course " "}
25569 @item @var{c-string} @expansion{}
25570 @code{""" @var{seven-bit-iso-c-string-content} """}
25572 @item @var{nl} @expansion{}
25581 The CLI commands are still handled by the @sc{mi} interpreter; their
25582 output is described below.
25585 The @code{@var{token}}, when present, is passed back when the command
25589 Some @sc{mi} commands accept optional arguments as part of the parameter
25590 list. Each option is identified by a leading @samp{-} (dash) and may be
25591 followed by an optional argument parameter. Options occur first in the
25592 parameter list and can be delimited from normal parameters using
25593 @samp{--} (this is useful when some parameters begin with a dash).
25600 We want easy access to the existing CLI syntax (for debugging).
25603 We want it to be easy to spot a @sc{mi} operation.
25606 @node GDB/MI Output Syntax
25607 @subsection @sc{gdb/mi} Output Syntax
25609 @cindex output syntax of @sc{gdb/mi}
25610 @cindex @sc{gdb/mi}, output syntax
25611 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25612 followed, optionally, by a single result record. This result record
25613 is for the most recent command. The sequence of output records is
25614 terminated by @samp{(gdb)}.
25616 If an input command was prefixed with a @code{@var{token}} then the
25617 corresponding output for that command will also be prefixed by that same
25621 @item @var{output} @expansion{}
25622 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25624 @item @var{result-record} @expansion{}
25625 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25627 @item @var{out-of-band-record} @expansion{}
25628 @code{@var{async-record} | @var{stream-record}}
25630 @item @var{async-record} @expansion{}
25631 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25633 @item @var{exec-async-output} @expansion{}
25634 @code{[ @var{token} ] "*" @var{async-output nl}}
25636 @item @var{status-async-output} @expansion{}
25637 @code{[ @var{token} ] "+" @var{async-output nl}}
25639 @item @var{notify-async-output} @expansion{}
25640 @code{[ @var{token} ] "=" @var{async-output nl}}
25642 @item @var{async-output} @expansion{}
25643 @code{@var{async-class} ( "," @var{result} )*}
25645 @item @var{result-class} @expansion{}
25646 @code{"done" | "running" | "connected" | "error" | "exit"}
25648 @item @var{async-class} @expansion{}
25649 @code{"stopped" | @var{others}} (where @var{others} will be added
25650 depending on the needs---this is still in development).
25652 @item @var{result} @expansion{}
25653 @code{ @var{variable} "=" @var{value}}
25655 @item @var{variable} @expansion{}
25656 @code{ @var{string} }
25658 @item @var{value} @expansion{}
25659 @code{ @var{const} | @var{tuple} | @var{list} }
25661 @item @var{const} @expansion{}
25662 @code{@var{c-string}}
25664 @item @var{tuple} @expansion{}
25665 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25667 @item @var{list} @expansion{}
25668 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25669 @var{result} ( "," @var{result} )* "]" }
25671 @item @var{stream-record} @expansion{}
25672 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25674 @item @var{console-stream-output} @expansion{}
25675 @code{"~" @var{c-string nl}}
25677 @item @var{target-stream-output} @expansion{}
25678 @code{"@@" @var{c-string nl}}
25680 @item @var{log-stream-output} @expansion{}
25681 @code{"&" @var{c-string nl}}
25683 @item @var{nl} @expansion{}
25686 @item @var{token} @expansion{}
25687 @emph{any sequence of digits}.
25695 All output sequences end in a single line containing a period.
25698 The @code{@var{token}} is from the corresponding request. Note that
25699 for all async output, while the token is allowed by the grammar and
25700 may be output by future versions of @value{GDBN} for select async
25701 output messages, it is generally omitted. Frontends should treat
25702 all async output as reporting general changes in the state of the
25703 target and there should be no need to associate async output to any
25707 @cindex status output in @sc{gdb/mi}
25708 @var{status-async-output} contains on-going status information about the
25709 progress of a slow operation. It can be discarded. All status output is
25710 prefixed by @samp{+}.
25713 @cindex async output in @sc{gdb/mi}
25714 @var{exec-async-output} contains asynchronous state change on the target
25715 (stopped, started, disappeared). All async output is prefixed by
25719 @cindex notify output in @sc{gdb/mi}
25720 @var{notify-async-output} contains supplementary information that the
25721 client should handle (e.g., a new breakpoint information). All notify
25722 output is prefixed by @samp{=}.
25725 @cindex console output in @sc{gdb/mi}
25726 @var{console-stream-output} is output that should be displayed as is in the
25727 console. It is the textual response to a CLI command. All the console
25728 output is prefixed by @samp{~}.
25731 @cindex target output in @sc{gdb/mi}
25732 @var{target-stream-output} is the output produced by the target program.
25733 All the target output is prefixed by @samp{@@}.
25736 @cindex log output in @sc{gdb/mi}
25737 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25738 instance messages that should be displayed as part of an error log. All
25739 the log output is prefixed by @samp{&}.
25742 @cindex list output in @sc{gdb/mi}
25743 New @sc{gdb/mi} commands should only output @var{lists} containing
25749 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25750 details about the various output records.
25752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25753 @node GDB/MI Compatibility with CLI
25754 @section @sc{gdb/mi} Compatibility with CLI
25756 @cindex compatibility, @sc{gdb/mi} and CLI
25757 @cindex @sc{gdb/mi}, compatibility with CLI
25759 For the developers convenience CLI commands can be entered directly,
25760 but there may be some unexpected behaviour. For example, commands
25761 that query the user will behave as if the user replied yes, breakpoint
25762 command lists are not executed and some CLI commands, such as
25763 @code{if}, @code{when} and @code{define}, prompt for further input with
25764 @samp{>}, which is not valid MI output.
25766 This feature may be removed at some stage in the future and it is
25767 recommended that front ends use the @code{-interpreter-exec} command
25768 (@pxref{-interpreter-exec}).
25770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25771 @node GDB/MI Development and Front Ends
25772 @section @sc{gdb/mi} Development and Front Ends
25773 @cindex @sc{gdb/mi} development
25775 The application which takes the MI output and presents the state of the
25776 program being debugged to the user is called a @dfn{front end}.
25778 Although @sc{gdb/mi} is still incomplete, it is currently being used
25779 by a variety of front ends to @value{GDBN}. This makes it difficult
25780 to introduce new functionality without breaking existing usage. This
25781 section tries to minimize the problems by describing how the protocol
25784 Some changes in MI need not break a carefully designed front end, and
25785 for these the MI version will remain unchanged. The following is a
25786 list of changes that may occur within one level, so front ends should
25787 parse MI output in a way that can handle them:
25791 New MI commands may be added.
25794 New fields may be added to the output of any MI command.
25797 The range of values for fields with specified values, e.g.,
25798 @code{in_scope} (@pxref{-var-update}) may be extended.
25800 @c The format of field's content e.g type prefix, may change so parse it
25801 @c at your own risk. Yes, in general?
25803 @c The order of fields may change? Shouldn't really matter but it might
25804 @c resolve inconsistencies.
25807 If the changes are likely to break front ends, the MI version level
25808 will be increased by one. This will allow the front end to parse the
25809 output according to the MI version. Apart from mi0, new versions of
25810 @value{GDBN} will not support old versions of MI and it will be the
25811 responsibility of the front end to work with the new one.
25813 @c Starting with mi3, add a new command -mi-version that prints the MI
25816 The best way to avoid unexpected changes in MI that might break your front
25817 end is to make your project known to @value{GDBN} developers and
25818 follow development on @email{gdb@@sourceware.org} and
25819 @email{gdb-patches@@sourceware.org}.
25820 @cindex mailing lists
25822 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25823 @node GDB/MI Output Records
25824 @section @sc{gdb/mi} Output Records
25827 * GDB/MI Result Records::
25828 * GDB/MI Stream Records::
25829 * GDB/MI Async Records::
25830 * GDB/MI Breakpoint Information::
25831 * GDB/MI Frame Information::
25832 * GDB/MI Thread Information::
25833 * GDB/MI Ada Exception Information::
25836 @node GDB/MI Result Records
25837 @subsection @sc{gdb/mi} Result Records
25839 @cindex result records in @sc{gdb/mi}
25840 @cindex @sc{gdb/mi}, result records
25841 In addition to a number of out-of-band notifications, the response to a
25842 @sc{gdb/mi} command includes one of the following result indications:
25846 @item "^done" [ "," @var{results} ]
25847 The synchronous operation was successful, @code{@var{results}} are the return
25852 This result record is equivalent to @samp{^done}. Historically, it
25853 was output instead of @samp{^done} if the command has resumed the
25854 target. This behaviour is maintained for backward compatibility, but
25855 all frontends should treat @samp{^done} and @samp{^running}
25856 identically and rely on the @samp{*running} output record to determine
25857 which threads are resumed.
25861 @value{GDBN} has connected to a remote target.
25863 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25865 The operation failed. The @code{msg=@var{c-string}} variable contains
25866 the corresponding error message.
25868 If present, the @code{code=@var{c-string}} variable provides an error
25869 code on which consumers can rely on to detect the corresponding
25870 error condition. At present, only one error code is defined:
25873 @item "undefined-command"
25874 Indicates that the command causing the error does not exist.
25879 @value{GDBN} has terminated.
25883 @node GDB/MI Stream Records
25884 @subsection @sc{gdb/mi} Stream Records
25886 @cindex @sc{gdb/mi}, stream records
25887 @cindex stream records in @sc{gdb/mi}
25888 @value{GDBN} internally maintains a number of output streams: the console, the
25889 target, and the log. The output intended for each of these streams is
25890 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25892 Each stream record begins with a unique @dfn{prefix character} which
25893 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25894 Syntax}). In addition to the prefix, each stream record contains a
25895 @code{@var{string-output}}. This is either raw text (with an implicit new
25896 line) or a quoted C string (which does not contain an implicit newline).
25899 @item "~" @var{string-output}
25900 The console output stream contains text that should be displayed in the
25901 CLI console window. It contains the textual responses to CLI commands.
25903 @item "@@" @var{string-output}
25904 The target output stream contains any textual output from the running
25905 target. This is only present when GDB's event loop is truly
25906 asynchronous, which is currently only the case for remote targets.
25908 @item "&" @var{string-output}
25909 The log stream contains debugging messages being produced by @value{GDBN}'s
25913 @node GDB/MI Async Records
25914 @subsection @sc{gdb/mi} Async Records
25916 @cindex async records in @sc{gdb/mi}
25917 @cindex @sc{gdb/mi}, async records
25918 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25919 additional changes that have occurred. Those changes can either be a
25920 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25921 target activity (e.g., target stopped).
25923 The following is the list of possible async records:
25927 @item *running,thread-id="@var{thread}"
25928 The target is now running. The @var{thread} field tells which
25929 specific thread is now running, and can be @samp{all} if all threads
25930 are running. The frontend should assume that no interaction with a
25931 running thread is possible after this notification is produced.
25932 The frontend should not assume that this notification is output
25933 only once for any command. @value{GDBN} may emit this notification
25934 several times, either for different threads, because it cannot resume
25935 all threads together, or even for a single thread, if the thread must
25936 be stepped though some code before letting it run freely.
25938 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25939 The target has stopped. The @var{reason} field can have one of the
25943 @item breakpoint-hit
25944 A breakpoint was reached.
25945 @item watchpoint-trigger
25946 A watchpoint was triggered.
25947 @item read-watchpoint-trigger
25948 A read watchpoint was triggered.
25949 @item access-watchpoint-trigger
25950 An access watchpoint was triggered.
25951 @item function-finished
25952 An -exec-finish or similar CLI command was accomplished.
25953 @item location-reached
25954 An -exec-until or similar CLI command was accomplished.
25955 @item watchpoint-scope
25956 A watchpoint has gone out of scope.
25957 @item end-stepping-range
25958 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25959 similar CLI command was accomplished.
25960 @item exited-signalled
25961 The inferior exited because of a signal.
25963 The inferior exited.
25964 @item exited-normally
25965 The inferior exited normally.
25966 @item signal-received
25967 A signal was received by the inferior.
25969 The inferior has stopped due to a library being loaded or unloaded.
25970 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25971 set or when a @code{catch load} or @code{catch unload} catchpoint is
25972 in use (@pxref{Set Catchpoints}).
25974 The inferior has forked. This is reported when @code{catch fork}
25975 (@pxref{Set Catchpoints}) has been used.
25977 The inferior has vforked. This is reported in when @code{catch vfork}
25978 (@pxref{Set Catchpoints}) has been used.
25979 @item syscall-entry
25980 The inferior entered a system call. This is reported when @code{catch
25981 syscall} (@pxref{Set Catchpoints}) has been used.
25982 @item syscall-return
25983 The inferior returned from a system call. This is reported when
25984 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25986 The inferior called @code{exec}. This is reported when @code{catch exec}
25987 (@pxref{Set Catchpoints}) has been used.
25990 The @var{id} field identifies the thread that directly caused the stop
25991 -- for example by hitting a breakpoint. Depending on whether all-stop
25992 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25993 stop all threads, or only the thread that directly triggered the stop.
25994 If all threads are stopped, the @var{stopped} field will have the
25995 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25996 field will be a list of thread identifiers. Presently, this list will
25997 always include a single thread, but frontend should be prepared to see
25998 several threads in the list. The @var{core} field reports the
25999 processor core on which the stop event has happened. This field may be absent
26000 if such information is not available.
26002 @item =thread-group-added,id="@var{id}"
26003 @itemx =thread-group-removed,id="@var{id}"
26004 A thread group was either added or removed. The @var{id} field
26005 contains the @value{GDBN} identifier of the thread group. When a thread
26006 group is added, it generally might not be associated with a running
26007 process. When a thread group is removed, its id becomes invalid and
26008 cannot be used in any way.
26010 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26011 A thread group became associated with a running program,
26012 either because the program was just started or the thread group
26013 was attached to a program. The @var{id} field contains the
26014 @value{GDBN} identifier of the thread group. The @var{pid} field
26015 contains process identifier, specific to the operating system.
26017 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26018 A thread group is no longer associated with a running program,
26019 either because the program has exited, or because it was detached
26020 from. The @var{id} field contains the @value{GDBN} identifier of the
26021 thread group. The @var{code} field is the exit code of the inferior; it exists
26022 only when the inferior exited with some code.
26024 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26025 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26026 A thread either was created, or has exited. The @var{id} field
26027 contains the @value{GDBN} identifier of the thread. The @var{gid}
26028 field identifies the thread group this thread belongs to.
26030 @item =thread-selected,id="@var{id}"
26031 Informs that the selected thread was changed as result of the last
26032 command. This notification is not emitted as result of @code{-thread-select}
26033 command but is emitted whenever an MI command that is not documented
26034 to change the selected thread actually changes it. In particular,
26035 invoking, directly or indirectly (via user-defined command), the CLI
26036 @code{thread} command, will generate this notification.
26038 We suggest that in response to this notification, front ends
26039 highlight the selected thread and cause subsequent commands to apply to
26042 @item =library-loaded,...
26043 Reports that a new library file was loaded by the program. This
26044 notification has 4 fields---@var{id}, @var{target-name},
26045 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26046 opaque identifier of the library. For remote debugging case,
26047 @var{target-name} and @var{host-name} fields give the name of the
26048 library file on the target, and on the host respectively. For native
26049 debugging, both those fields have the same value. The
26050 @var{symbols-loaded} field is emitted only for backward compatibility
26051 and should not be relied on to convey any useful information. The
26052 @var{thread-group} field, if present, specifies the id of the thread
26053 group in whose context the library was loaded. If the field is
26054 absent, it means the library was loaded in the context of all present
26057 @item =library-unloaded,...
26058 Reports that a library was unloaded by the program. This notification
26059 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26060 the same meaning as for the @code{=library-loaded} notification.
26061 The @var{thread-group} field, if present, specifies the id of the
26062 thread group in whose context the library was unloaded. If the field is
26063 absent, it means the library was unloaded in the context of all present
26066 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26067 @itemx =traceframe-changed,end
26068 Reports that the trace frame was changed and its new number is
26069 @var{tfnum}. The number of the tracepoint associated with this trace
26070 frame is @var{tpnum}.
26072 @item =tsv-created,name=@var{name},initial=@var{initial}
26073 Reports that the new trace state variable @var{name} is created with
26074 initial value @var{initial}.
26076 @item =tsv-deleted,name=@var{name}
26077 @itemx =tsv-deleted
26078 Reports that the trace state variable @var{name} is deleted or all
26079 trace state variables are deleted.
26081 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26082 Reports that the trace state variable @var{name} is modified with
26083 the initial value @var{initial}. The current value @var{current} of
26084 trace state variable is optional and is reported if the current
26085 value of trace state variable is known.
26087 @item =breakpoint-created,bkpt=@{...@}
26088 @itemx =breakpoint-modified,bkpt=@{...@}
26089 @itemx =breakpoint-deleted,id=@var{number}
26090 Reports that a breakpoint was created, modified, or deleted,
26091 respectively. Only user-visible breakpoints are reported to the MI
26094 The @var{bkpt} argument is of the same form as returned by the various
26095 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26096 @var{number} is the ordinal number of the breakpoint.
26098 Note that if a breakpoint is emitted in the result record of a
26099 command, then it will not also be emitted in an async record.
26101 @item =record-started,thread-group="@var{id}"
26102 @itemx =record-stopped,thread-group="@var{id}"
26103 Execution log recording was either started or stopped on an
26104 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26105 group corresponding to the affected inferior.
26107 @item =cmd-param-changed,param=@var{param},value=@var{value}
26108 Reports that a parameter of the command @code{set @var{param}} is
26109 changed to @var{value}. In the multi-word @code{set} command,
26110 the @var{param} is the whole parameter list to @code{set} command.
26111 For example, In command @code{set check type on}, @var{param}
26112 is @code{check type} and @var{value} is @code{on}.
26114 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26115 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26116 written in an inferior. The @var{id} is the identifier of the
26117 thread group corresponding to the affected inferior. The optional
26118 @code{type="code"} part is reported if the memory written to holds
26122 @node GDB/MI Breakpoint Information
26123 @subsection @sc{gdb/mi} Breakpoint Information
26125 When @value{GDBN} reports information about a breakpoint, a
26126 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26131 The breakpoint number. For a breakpoint that represents one location
26132 of a multi-location breakpoint, this will be a dotted pair, like
26136 The type of the breakpoint. For ordinary breakpoints this will be
26137 @samp{breakpoint}, but many values are possible.
26140 If the type of the breakpoint is @samp{catchpoint}, then this
26141 indicates the exact type of catchpoint.
26144 This is the breakpoint disposition---either @samp{del}, meaning that
26145 the breakpoint will be deleted at the next stop, or @samp{keep},
26146 meaning that the breakpoint will not be deleted.
26149 This indicates whether the breakpoint is enabled, in which case the
26150 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26151 Note that this is not the same as the field @code{enable}.
26154 The address of the breakpoint. This may be a hexidecimal number,
26155 giving the address; or the string @samp{<PENDING>}, for a pending
26156 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26157 multiple locations. This field will not be present if no address can
26158 be determined. For example, a watchpoint does not have an address.
26161 If known, the function in which the breakpoint appears.
26162 If not known, this field is not present.
26165 The name of the source file which contains this function, if known.
26166 If not known, this field is not present.
26169 The full file name of the source file which contains this function, if
26170 known. If not known, this field is not present.
26173 The line number at which this breakpoint appears, if known.
26174 If not known, this field is not present.
26177 If the source file is not known, this field may be provided. If
26178 provided, this holds the address of the breakpoint, possibly followed
26182 If this breakpoint is pending, this field is present and holds the
26183 text used to set the breakpoint, as entered by the user.
26186 Where this breakpoint's condition is evaluated, either @samp{host} or
26190 If this is a thread-specific breakpoint, then this identifies the
26191 thread in which the breakpoint can trigger.
26194 If this breakpoint is restricted to a particular Ada task, then this
26195 field will hold the task identifier.
26198 If the breakpoint is conditional, this is the condition expression.
26201 The ignore count of the breakpoint.
26204 The enable count of the breakpoint.
26206 @item traceframe-usage
26209 @item static-tracepoint-marker-string-id
26210 For a static tracepoint, the name of the static tracepoint marker.
26213 For a masked watchpoint, this is the mask.
26216 A tracepoint's pass count.
26218 @item original-location
26219 The location of the breakpoint as originally specified by the user.
26220 This field is optional.
26223 The number of times the breakpoint has been hit.
26226 This field is only given for tracepoints. This is either @samp{y},
26227 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26231 Some extra data, the exact contents of which are type-dependent.
26235 For example, here is what the output of @code{-break-insert}
26236 (@pxref{GDB/MI Breakpoint Commands}) might be:
26239 -> -break-insert main
26240 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26241 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26242 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26247 @node GDB/MI Frame Information
26248 @subsection @sc{gdb/mi} Frame Information
26250 Response from many MI commands includes an information about stack
26251 frame. This information is a tuple that may have the following
26256 The level of the stack frame. The innermost frame has the level of
26257 zero. This field is always present.
26260 The name of the function corresponding to the frame. This field may
26261 be absent if @value{GDBN} is unable to determine the function name.
26264 The code address for the frame. This field is always present.
26267 The name of the source files that correspond to the frame's code
26268 address. This field may be absent.
26271 The source line corresponding to the frames' code address. This field
26275 The name of the binary file (either executable or shared library) the
26276 corresponds to the frame's code address. This field may be absent.
26280 @node GDB/MI Thread Information
26281 @subsection @sc{gdb/mi} Thread Information
26283 Whenever @value{GDBN} has to report an information about a thread, it
26284 uses a tuple with the following fields:
26288 The numeric id assigned to the thread by @value{GDBN}. This field is
26292 Target-specific string identifying the thread. This field is always present.
26295 Additional information about the thread provided by the target.
26296 It is supposed to be human-readable and not interpreted by the
26297 frontend. This field is optional.
26300 Either @samp{stopped} or @samp{running}, depending on whether the
26301 thread is presently running. This field is always present.
26304 The value of this field is an integer number of the processor core the
26305 thread was last seen on. This field is optional.
26308 @node GDB/MI Ada Exception Information
26309 @subsection @sc{gdb/mi} Ada Exception Information
26311 Whenever a @code{*stopped} record is emitted because the program
26312 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26313 @value{GDBN} provides the name of the exception that was raised via
26314 the @code{exception-name} field.
26316 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26317 @node GDB/MI Simple Examples
26318 @section Simple Examples of @sc{gdb/mi} Interaction
26319 @cindex @sc{gdb/mi}, simple examples
26321 This subsection presents several simple examples of interaction using
26322 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26323 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26324 the output received from @sc{gdb/mi}.
26326 Note the line breaks shown in the examples are here only for
26327 readability, they don't appear in the real output.
26329 @subheading Setting a Breakpoint
26331 Setting a breakpoint generates synchronous output which contains detailed
26332 information of the breakpoint.
26335 -> -break-insert main
26336 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26337 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26338 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26343 @subheading Program Execution
26345 Program execution generates asynchronous records and MI gives the
26346 reason that execution stopped.
26352 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26353 frame=@{addr="0x08048564",func="main",
26354 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26355 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26360 <- *stopped,reason="exited-normally"
26364 @subheading Quitting @value{GDBN}
26366 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26374 Please note that @samp{^exit} is printed immediately, but it might
26375 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26376 performs necessary cleanups, including killing programs being debugged
26377 or disconnecting from debug hardware, so the frontend should wait till
26378 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26379 fails to exit in reasonable time.
26381 @subheading A Bad Command
26383 Here's what happens if you pass a non-existent command:
26387 <- ^error,msg="Undefined MI command: rubbish"
26392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26393 @node GDB/MI Command Description Format
26394 @section @sc{gdb/mi} Command Description Format
26396 The remaining sections describe blocks of commands. Each block of
26397 commands is laid out in a fashion similar to this section.
26399 @subheading Motivation
26401 The motivation for this collection of commands.
26403 @subheading Introduction
26405 A brief introduction to this collection of commands as a whole.
26407 @subheading Commands
26409 For each command in the block, the following is described:
26411 @subsubheading Synopsis
26414 -command @var{args}@dots{}
26417 @subsubheading Result
26419 @subsubheading @value{GDBN} Command
26421 The corresponding @value{GDBN} CLI command(s), if any.
26423 @subsubheading Example
26425 Example(s) formatted for readability. Some of the described commands have
26426 not been implemented yet and these are labeled N.A.@: (not available).
26429 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26430 @node GDB/MI Breakpoint Commands
26431 @section @sc{gdb/mi} Breakpoint Commands
26433 @cindex breakpoint commands for @sc{gdb/mi}
26434 @cindex @sc{gdb/mi}, breakpoint commands
26435 This section documents @sc{gdb/mi} commands for manipulating
26438 @subheading The @code{-break-after} Command
26439 @findex -break-after
26441 @subsubheading Synopsis
26444 -break-after @var{number} @var{count}
26447 The breakpoint number @var{number} is not in effect until it has been
26448 hit @var{count} times. To see how this is reflected in the output of
26449 the @samp{-break-list} command, see the description of the
26450 @samp{-break-list} command below.
26452 @subsubheading @value{GDBN} Command
26454 The corresponding @value{GDBN} command is @samp{ignore}.
26456 @subsubheading Example
26461 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26462 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26463 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26471 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26478 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26479 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26480 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26485 @subheading The @code{-break-catch} Command
26486 @findex -break-catch
26489 @subheading The @code{-break-commands} Command
26490 @findex -break-commands
26492 @subsubheading Synopsis
26495 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26498 Specifies the CLI commands that should be executed when breakpoint
26499 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26500 are the commands. If no command is specified, any previously-set
26501 commands are cleared. @xref{Break Commands}. Typical use of this
26502 functionality is tracing a program, that is, printing of values of
26503 some variables whenever breakpoint is hit and then continuing.
26505 @subsubheading @value{GDBN} Command
26507 The corresponding @value{GDBN} command is @samp{commands}.
26509 @subsubheading Example
26514 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26515 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26516 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26519 -break-commands 1 "print v" "continue"
26524 @subheading The @code{-break-condition} Command
26525 @findex -break-condition
26527 @subsubheading Synopsis
26530 -break-condition @var{number} @var{expr}
26533 Breakpoint @var{number} will stop the program only if the condition in
26534 @var{expr} is true. The condition becomes part of the
26535 @samp{-break-list} output (see the description of the @samp{-break-list}
26538 @subsubheading @value{GDBN} Command
26540 The corresponding @value{GDBN} command is @samp{condition}.
26542 @subsubheading Example
26546 -break-condition 1 1
26550 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26551 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26552 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26553 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26554 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26555 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26556 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26557 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26558 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26559 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26563 @subheading The @code{-break-delete} Command
26564 @findex -break-delete
26566 @subsubheading Synopsis
26569 -break-delete ( @var{breakpoint} )+
26572 Delete the breakpoint(s) whose number(s) are specified in the argument
26573 list. This is obviously reflected in the breakpoint list.
26575 @subsubheading @value{GDBN} Command
26577 The corresponding @value{GDBN} command is @samp{delete}.
26579 @subsubheading Example
26587 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26588 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26589 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26590 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26591 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26592 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26593 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26598 @subheading The @code{-break-disable} Command
26599 @findex -break-disable
26601 @subsubheading Synopsis
26604 -break-disable ( @var{breakpoint} )+
26607 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26608 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26610 @subsubheading @value{GDBN} Command
26612 The corresponding @value{GDBN} command is @samp{disable}.
26614 @subsubheading Example
26622 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26623 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26624 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26625 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26626 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26627 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26628 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26629 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26630 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26631 line="5",thread-groups=["i1"],times="0"@}]@}
26635 @subheading The @code{-break-enable} Command
26636 @findex -break-enable
26638 @subsubheading Synopsis
26641 -break-enable ( @var{breakpoint} )+
26644 Enable (previously disabled) @var{breakpoint}(s).
26646 @subsubheading @value{GDBN} Command
26648 The corresponding @value{GDBN} command is @samp{enable}.
26650 @subsubheading Example
26658 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26659 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26660 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26661 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26662 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26663 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26664 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26665 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26666 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26667 line="5",thread-groups=["i1"],times="0"@}]@}
26671 @subheading The @code{-break-info} Command
26672 @findex -break-info
26674 @subsubheading Synopsis
26677 -break-info @var{breakpoint}
26681 Get information about a single breakpoint.
26683 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26684 Information}, for details on the format of each breakpoint in the
26687 @subsubheading @value{GDBN} Command
26689 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26691 @subsubheading Example
26694 @subheading The @code{-break-insert} Command
26695 @findex -break-insert
26696 @anchor{-break-insert}
26698 @subsubheading Synopsis
26701 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26702 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26703 [ -p @var{thread-id} ] [ @var{location} ]
26707 If specified, @var{location}, can be one of:
26710 @item linespec location
26711 A linespec location. @xref{Linespec Locations}.
26713 @item explicit location
26714 An explicit location. @sc{gdb/mi} explicit locations are
26715 analogous to the CLI's explicit locations using the option names
26716 listed below. @xref{Explicit Locations}.
26719 @item --source @var{filename}
26720 The source file name of the location. This option requires the use
26721 of either @samp{--function} or @samp{--line}.
26723 @item --function @var{function}
26724 The name of a function or method.
26726 @item --label @var{label}
26727 The name of a label.
26729 @item --line @var{lineoffset}
26730 An absolute or relative line offset from the start of the location.
26733 @item address location
26734 An address location, *@var{address}. @xref{Address Locations}.
26738 The possible optional parameters of this command are:
26742 Insert a temporary breakpoint.
26744 Insert a hardware breakpoint.
26746 If @var{location} cannot be parsed (for example if it
26747 refers to unknown files or functions), create a pending
26748 breakpoint. Without this flag, @value{GDBN} will report
26749 an error, and won't create a breakpoint, if @var{location}
26752 Create a disabled breakpoint.
26754 Create a tracepoint. @xref{Tracepoints}. When this parameter
26755 is used together with @samp{-h}, a fast tracepoint is created.
26756 @item -c @var{condition}
26757 Make the breakpoint conditional on @var{condition}.
26758 @item -i @var{ignore-count}
26759 Initialize the @var{ignore-count}.
26760 @item -p @var{thread-id}
26761 Restrict the breakpoint to the specified @var{thread-id}.
26764 @subsubheading Result
26766 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26767 resulting breakpoint.
26769 Note: this format is open to change.
26770 @c An out-of-band breakpoint instead of part of the result?
26772 @subsubheading @value{GDBN} Command
26774 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26775 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26777 @subsubheading Example
26782 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26783 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26786 -break-insert -t foo
26787 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26788 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26792 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26793 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26794 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26795 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26796 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26797 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26798 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26799 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26800 addr="0x0001072c", func="main",file="recursive2.c",
26801 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26803 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26804 addr="0x00010774",func="foo",file="recursive2.c",
26805 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26808 @c -break-insert -r foo.*
26809 @c ~int foo(int, int);
26810 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26811 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26816 @subheading The @code{-dprintf-insert} Command
26817 @findex -dprintf-insert
26819 @subsubheading Synopsis
26822 -dprintf-insert [ -t ] [ -f ] [ -d ]
26823 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26824 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26829 If supplied, @var{location} may be specified the same way as for
26830 the @code{-break-insert} command. @xref{-break-insert}.
26832 The possible optional parameters of this command are:
26836 Insert a temporary breakpoint.
26838 If @var{location} cannot be parsed (for example, if it
26839 refers to unknown files or functions), create a pending
26840 breakpoint. Without this flag, @value{GDBN} will report
26841 an error, and won't create a breakpoint, if @var{location}
26844 Create a disabled breakpoint.
26845 @item -c @var{condition}
26846 Make the breakpoint conditional on @var{condition}.
26847 @item -i @var{ignore-count}
26848 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26849 to @var{ignore-count}.
26850 @item -p @var{thread-id}
26851 Restrict the breakpoint to the specified @var{thread-id}.
26854 @subsubheading Result
26856 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26857 resulting breakpoint.
26859 @c An out-of-band breakpoint instead of part of the result?
26861 @subsubheading @value{GDBN} Command
26863 The corresponding @value{GDBN} command is @samp{dprintf}.
26865 @subsubheading Example
26869 4-dprintf-insert foo "At foo entry\n"
26870 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26871 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26872 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26873 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26874 original-location="foo"@}
26876 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26877 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26878 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26879 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26880 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26881 original-location="mi-dprintf.c:26"@}
26885 @subheading The @code{-break-list} Command
26886 @findex -break-list
26888 @subsubheading Synopsis
26894 Displays the list of inserted breakpoints, showing the following fields:
26898 number of the breakpoint
26900 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26902 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26905 is the breakpoint enabled or no: @samp{y} or @samp{n}
26907 memory location at which the breakpoint is set
26909 logical location of the breakpoint, expressed by function name, file
26911 @item Thread-groups
26912 list of thread groups to which this breakpoint applies
26914 number of times the breakpoint has been hit
26917 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26918 @code{body} field is an empty list.
26920 @subsubheading @value{GDBN} Command
26922 The corresponding @value{GDBN} command is @samp{info break}.
26924 @subsubheading Example
26929 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26930 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26931 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26932 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26933 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26934 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26935 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26936 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26937 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26939 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26940 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26941 line="13",thread-groups=["i1"],times="0"@}]@}
26945 Here's an example of the result when there are no breakpoints:
26950 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26961 @subheading The @code{-break-passcount} Command
26962 @findex -break-passcount
26964 @subsubheading Synopsis
26967 -break-passcount @var{tracepoint-number} @var{passcount}
26970 Set the passcount for tracepoint @var{tracepoint-number} to
26971 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26972 is not a tracepoint, error is emitted. This corresponds to CLI
26973 command @samp{passcount}.
26975 @subheading The @code{-break-watch} Command
26976 @findex -break-watch
26978 @subsubheading Synopsis
26981 -break-watch [ -a | -r ]
26984 Create a watchpoint. With the @samp{-a} option it will create an
26985 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26986 read from or on a write to the memory location. With the @samp{-r}
26987 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26988 trigger only when the memory location is accessed for reading. Without
26989 either of the options, the watchpoint created is a regular watchpoint,
26990 i.e., it will trigger when the memory location is accessed for writing.
26991 @xref{Set Watchpoints, , Setting Watchpoints}.
26993 Note that @samp{-break-list} will report a single list of watchpoints and
26994 breakpoints inserted.
26996 @subsubheading @value{GDBN} Command
26998 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27001 @subsubheading Example
27003 Setting a watchpoint on a variable in the @code{main} function:
27008 ^done,wpt=@{number="2",exp="x"@}
27013 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27014 value=@{old="-268439212",new="55"@},
27015 frame=@{func="main",args=[],file="recursive2.c",
27016 fullname="/home/foo/bar/recursive2.c",line="5"@}
27020 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27021 the program execution twice: first for the variable changing value, then
27022 for the watchpoint going out of scope.
27027 ^done,wpt=@{number="5",exp="C"@}
27032 *stopped,reason="watchpoint-trigger",
27033 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27034 frame=@{func="callee4",args=[],
27035 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27036 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27041 *stopped,reason="watchpoint-scope",wpnum="5",
27042 frame=@{func="callee3",args=[@{name="strarg",
27043 value="0x11940 \"A string argument.\""@}],
27044 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27045 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27049 Listing breakpoints and watchpoints, at different points in the program
27050 execution. Note that once the watchpoint goes out of scope, it is
27056 ^done,wpt=@{number="2",exp="C"@}
27059 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27060 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27061 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27062 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27063 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27064 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27065 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27066 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27067 addr="0x00010734",func="callee4",
27068 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27069 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27071 bkpt=@{number="2",type="watchpoint",disp="keep",
27072 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27077 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27078 value=@{old="-276895068",new="3"@},
27079 frame=@{func="callee4",args=[],
27080 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27081 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27084 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27085 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27086 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27087 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27088 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27089 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27090 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27091 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27092 addr="0x00010734",func="callee4",
27093 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27094 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27096 bkpt=@{number="2",type="watchpoint",disp="keep",
27097 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27101 ^done,reason="watchpoint-scope",wpnum="2",
27102 frame=@{func="callee3",args=[@{name="strarg",
27103 value="0x11940 \"A string argument.\""@}],
27104 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27105 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27108 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27109 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27110 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27111 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27112 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27113 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27114 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27115 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27116 addr="0x00010734",func="callee4",
27117 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27118 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27119 thread-groups=["i1"],times="1"@}]@}
27124 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27125 @node GDB/MI Catchpoint Commands
27126 @section @sc{gdb/mi} Catchpoint Commands
27128 This section documents @sc{gdb/mi} commands for manipulating
27132 * Shared Library GDB/MI Catchpoint Commands::
27133 * Ada Exception GDB/MI Catchpoint Commands::
27136 @node Shared Library GDB/MI Catchpoint Commands
27137 @subsection Shared Library @sc{gdb/mi} Catchpoints
27139 @subheading The @code{-catch-load} Command
27140 @findex -catch-load
27142 @subsubheading Synopsis
27145 -catch-load [ -t ] [ -d ] @var{regexp}
27148 Add a catchpoint for library load events. If the @samp{-t} option is used,
27149 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27150 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27151 in a disabled state. The @samp{regexp} argument is a regular
27152 expression used to match the name of the loaded library.
27155 @subsubheading @value{GDBN} Command
27157 The corresponding @value{GDBN} command is @samp{catch load}.
27159 @subsubheading Example
27162 -catch-load -t foo.so
27163 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27164 what="load of library matching foo.so",catch-type="load",times="0"@}
27169 @subheading The @code{-catch-unload} Command
27170 @findex -catch-unload
27172 @subsubheading Synopsis
27175 -catch-unload [ -t ] [ -d ] @var{regexp}
27178 Add a catchpoint for library unload events. If the @samp{-t} option is
27179 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27180 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27181 created in a disabled state. The @samp{regexp} argument is a regular
27182 expression used to match the name of the unloaded library.
27184 @subsubheading @value{GDBN} Command
27186 The corresponding @value{GDBN} command is @samp{catch unload}.
27188 @subsubheading Example
27191 -catch-unload -d bar.so
27192 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27193 what="load of library matching bar.so",catch-type="unload",times="0"@}
27197 @node Ada Exception GDB/MI Catchpoint Commands
27198 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27200 The following @sc{gdb/mi} commands can be used to create catchpoints
27201 that stop the execution when Ada exceptions are being raised.
27203 @subheading The @code{-catch-assert} Command
27204 @findex -catch-assert
27206 @subsubheading Synopsis
27209 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27212 Add a catchpoint for failed Ada assertions.
27214 The possible optional parameters for this command are:
27217 @item -c @var{condition}
27218 Make the catchpoint conditional on @var{condition}.
27220 Create a disabled catchpoint.
27222 Create a temporary catchpoint.
27225 @subsubheading @value{GDBN} Command
27227 The corresponding @value{GDBN} command is @samp{catch assert}.
27229 @subsubheading Example
27233 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27234 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27235 thread-groups=["i1"],times="0",
27236 original-location="__gnat_debug_raise_assert_failure"@}
27240 @subheading The @code{-catch-exception} Command
27241 @findex -catch-exception
27243 @subsubheading Synopsis
27246 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27250 Add a catchpoint stopping when Ada exceptions are raised.
27251 By default, the command stops the program when any Ada exception
27252 gets raised. But it is also possible, by using some of the
27253 optional parameters described below, to create more selective
27256 The possible optional parameters for this command are:
27259 @item -c @var{condition}
27260 Make the catchpoint conditional on @var{condition}.
27262 Create a disabled catchpoint.
27263 @item -e @var{exception-name}
27264 Only stop when @var{exception-name} is raised. This option cannot
27265 be used combined with @samp{-u}.
27267 Create a temporary catchpoint.
27269 Stop only when an unhandled exception gets raised. This option
27270 cannot be used combined with @samp{-e}.
27273 @subsubheading @value{GDBN} Command
27275 The corresponding @value{GDBN} commands are @samp{catch exception}
27276 and @samp{catch exception unhandled}.
27278 @subsubheading Example
27281 -catch-exception -e Program_Error
27282 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27283 enabled="y",addr="0x0000000000404874",
27284 what="`Program_Error' Ada exception", thread-groups=["i1"],
27285 times="0",original-location="__gnat_debug_raise_exception"@}
27289 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27290 @node GDB/MI Program Context
27291 @section @sc{gdb/mi} Program Context
27293 @subheading The @code{-exec-arguments} Command
27294 @findex -exec-arguments
27297 @subsubheading Synopsis
27300 -exec-arguments @var{args}
27303 Set the inferior program arguments, to be used in the next
27306 @subsubheading @value{GDBN} Command
27308 The corresponding @value{GDBN} command is @samp{set args}.
27310 @subsubheading Example
27314 -exec-arguments -v word
27321 @subheading The @code{-exec-show-arguments} Command
27322 @findex -exec-show-arguments
27324 @subsubheading Synopsis
27327 -exec-show-arguments
27330 Print the arguments of the program.
27332 @subsubheading @value{GDBN} Command
27334 The corresponding @value{GDBN} command is @samp{show args}.
27336 @subsubheading Example
27341 @subheading The @code{-environment-cd} Command
27342 @findex -environment-cd
27344 @subsubheading Synopsis
27347 -environment-cd @var{pathdir}
27350 Set @value{GDBN}'s working directory.
27352 @subsubheading @value{GDBN} Command
27354 The corresponding @value{GDBN} command is @samp{cd}.
27356 @subsubheading Example
27360 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27366 @subheading The @code{-environment-directory} Command
27367 @findex -environment-directory
27369 @subsubheading Synopsis
27372 -environment-directory [ -r ] [ @var{pathdir} ]+
27375 Add directories @var{pathdir} to beginning of search path for source files.
27376 If the @samp{-r} option is used, the search path is reset to the default
27377 search path. If directories @var{pathdir} are supplied in addition to the
27378 @samp{-r} option, the search path is first reset and then addition
27380 Multiple directories may be specified, separated by blanks. Specifying
27381 multiple directories in a single command
27382 results in the directories added to the beginning of the
27383 search path in the same order they were presented in the command.
27384 If blanks are needed as
27385 part of a directory name, double-quotes should be used around
27386 the name. In the command output, the path will show up separated
27387 by the system directory-separator character. The directory-separator
27388 character must not be used
27389 in any directory name.
27390 If no directories are specified, the current search path is displayed.
27392 @subsubheading @value{GDBN} Command
27394 The corresponding @value{GDBN} command is @samp{dir}.
27396 @subsubheading Example
27400 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27401 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27403 -environment-directory ""
27404 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27406 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27407 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27409 -environment-directory -r
27410 ^done,source-path="$cdir:$cwd"
27415 @subheading The @code{-environment-path} Command
27416 @findex -environment-path
27418 @subsubheading Synopsis
27421 -environment-path [ -r ] [ @var{pathdir} ]+
27424 Add directories @var{pathdir} to beginning of search path for object files.
27425 If the @samp{-r} option is used, the search path is reset to the original
27426 search path that existed at gdb start-up. If directories @var{pathdir} are
27427 supplied in addition to the
27428 @samp{-r} option, the search path is first reset and then addition
27430 Multiple directories may be specified, separated by blanks. Specifying
27431 multiple directories in a single command
27432 results in the directories added to the beginning of the
27433 search path in the same order they were presented in the command.
27434 If blanks are needed as
27435 part of a directory name, double-quotes should be used around
27436 the name. In the command output, the path will show up separated
27437 by the system directory-separator character. The directory-separator
27438 character must not be used
27439 in any directory name.
27440 If no directories are specified, the current path is displayed.
27443 @subsubheading @value{GDBN} Command
27445 The corresponding @value{GDBN} command is @samp{path}.
27447 @subsubheading Example
27452 ^done,path="/usr/bin"
27454 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27455 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27457 -environment-path -r /usr/local/bin
27458 ^done,path="/usr/local/bin:/usr/bin"
27463 @subheading The @code{-environment-pwd} Command
27464 @findex -environment-pwd
27466 @subsubheading Synopsis
27472 Show the current working directory.
27474 @subsubheading @value{GDBN} Command
27476 The corresponding @value{GDBN} command is @samp{pwd}.
27478 @subsubheading Example
27483 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27488 @node GDB/MI Thread Commands
27489 @section @sc{gdb/mi} Thread Commands
27492 @subheading The @code{-thread-info} Command
27493 @findex -thread-info
27495 @subsubheading Synopsis
27498 -thread-info [ @var{thread-id} ]
27501 Reports information about either a specific thread, if
27502 the @var{thread-id} parameter is present, or about all
27503 threads. When printing information about all threads,
27504 also reports the current thread.
27506 @subsubheading @value{GDBN} Command
27508 The @samp{info thread} command prints the same information
27511 @subsubheading Result
27513 The result is a list of threads. The following attributes are
27514 defined for a given thread:
27518 This field exists only for the current thread. It has the value @samp{*}.
27521 The identifier that @value{GDBN} uses to refer to the thread.
27524 The identifier that the target uses to refer to the thread.
27527 Extra information about the thread, in a target-specific format. This
27531 The name of the thread. If the user specified a name using the
27532 @code{thread name} command, then this name is given. Otherwise, if
27533 @value{GDBN} can extract the thread name from the target, then that
27534 name is given. If @value{GDBN} cannot find the thread name, then this
27538 The stack frame currently executing in the thread.
27541 The thread's state. The @samp{state} field may have the following
27546 The thread is stopped. Frame information is available for stopped
27550 The thread is running. There's no frame information for running
27556 If @value{GDBN} can find the CPU core on which this thread is running,
27557 then this field is the core identifier. This field is optional.
27561 @subsubheading Example
27566 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27567 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27568 args=[]@},state="running"@},
27569 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27570 frame=@{level="0",addr="0x0804891f",func="foo",
27571 args=[@{name="i",value="10"@}],
27572 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27573 state="running"@}],
27574 current-thread-id="1"
27578 @subheading The @code{-thread-list-ids} Command
27579 @findex -thread-list-ids
27581 @subsubheading Synopsis
27587 Produces a list of the currently known @value{GDBN} thread ids. At the
27588 end of the list it also prints the total number of such threads.
27590 This command is retained for historical reasons, the
27591 @code{-thread-info} command should be used instead.
27593 @subsubheading @value{GDBN} Command
27595 Part of @samp{info threads} supplies the same information.
27597 @subsubheading Example
27602 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27603 current-thread-id="1",number-of-threads="3"
27608 @subheading The @code{-thread-select} Command
27609 @findex -thread-select
27611 @subsubheading Synopsis
27614 -thread-select @var{threadnum}
27617 Make @var{threadnum} the current thread. It prints the number of the new
27618 current thread, and the topmost frame for that thread.
27620 This command is deprecated in favor of explicitly using the
27621 @samp{--thread} option to each command.
27623 @subsubheading @value{GDBN} Command
27625 The corresponding @value{GDBN} command is @samp{thread}.
27627 @subsubheading Example
27634 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27635 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27639 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27640 number-of-threads="3"
27643 ^done,new-thread-id="3",
27644 frame=@{level="0",func="vprintf",
27645 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27646 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27651 @node GDB/MI Ada Tasking Commands
27652 @section @sc{gdb/mi} Ada Tasking Commands
27654 @subheading The @code{-ada-task-info} Command
27655 @findex -ada-task-info
27657 @subsubheading Synopsis
27660 -ada-task-info [ @var{task-id} ]
27663 Reports information about either a specific Ada task, if the
27664 @var{task-id} parameter is present, or about all Ada tasks.
27666 @subsubheading @value{GDBN} Command
27668 The @samp{info tasks} command prints the same information
27669 about all Ada tasks (@pxref{Ada Tasks}).
27671 @subsubheading Result
27673 The result is a table of Ada tasks. The following columns are
27674 defined for each Ada task:
27678 This field exists only for the current thread. It has the value @samp{*}.
27681 The identifier that @value{GDBN} uses to refer to the Ada task.
27684 The identifier that the target uses to refer to the Ada task.
27687 The identifier of the thread corresponding to the Ada task.
27689 This field should always exist, as Ada tasks are always implemented
27690 on top of a thread. But if @value{GDBN} cannot find this corresponding
27691 thread for any reason, the field is omitted.
27694 This field exists only when the task was created by another task.
27695 In this case, it provides the ID of the parent task.
27698 The base priority of the task.
27701 The current state of the task. For a detailed description of the
27702 possible states, see @ref{Ada Tasks}.
27705 The name of the task.
27709 @subsubheading Example
27713 ^done,tasks=@{nr_rows="3",nr_cols="8",
27714 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27715 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27716 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27717 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27718 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27719 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27720 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27721 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27722 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27723 state="Child Termination Wait",name="main_task"@}]@}
27727 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27728 @node GDB/MI Program Execution
27729 @section @sc{gdb/mi} Program Execution
27731 These are the asynchronous commands which generate the out-of-band
27732 record @samp{*stopped}. Currently @value{GDBN} only really executes
27733 asynchronously with remote targets and this interaction is mimicked in
27736 @subheading The @code{-exec-continue} Command
27737 @findex -exec-continue
27739 @subsubheading Synopsis
27742 -exec-continue [--reverse] [--all|--thread-group N]
27745 Resumes the execution of the inferior program, which will continue
27746 to execute until it reaches a debugger stop event. If the
27747 @samp{--reverse} option is specified, execution resumes in reverse until
27748 it reaches a stop event. Stop events may include
27751 breakpoints or watchpoints
27753 signals or exceptions
27755 the end of the process (or its beginning under @samp{--reverse})
27757 the end or beginning of a replay log if one is being used.
27759 In all-stop mode (@pxref{All-Stop
27760 Mode}), may resume only one thread, or all threads, depending on the
27761 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27762 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27763 ignored in all-stop mode. If the @samp{--thread-group} options is
27764 specified, then all threads in that thread group are resumed.
27766 @subsubheading @value{GDBN} Command
27768 The corresponding @value{GDBN} corresponding is @samp{continue}.
27770 @subsubheading Example
27777 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27778 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27784 @subheading The @code{-exec-finish} Command
27785 @findex -exec-finish
27787 @subsubheading Synopsis
27790 -exec-finish [--reverse]
27793 Resumes the execution of the inferior program until the current
27794 function is exited. Displays the results returned by the function.
27795 If the @samp{--reverse} option is specified, resumes the reverse
27796 execution of the inferior program until the point where current
27797 function was called.
27799 @subsubheading @value{GDBN} Command
27801 The corresponding @value{GDBN} command is @samp{finish}.
27803 @subsubheading Example
27805 Function returning @code{void}.
27812 *stopped,reason="function-finished",frame=@{func="main",args=[],
27813 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27817 Function returning other than @code{void}. The name of the internal
27818 @value{GDBN} variable storing the result is printed, together with the
27825 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27826 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27827 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27828 gdb-result-var="$1",return-value="0"
27833 @subheading The @code{-exec-interrupt} Command
27834 @findex -exec-interrupt
27836 @subsubheading Synopsis
27839 -exec-interrupt [--all|--thread-group N]
27842 Interrupts the background execution of the target. Note how the token
27843 associated with the stop message is the one for the execution command
27844 that has been interrupted. The token for the interrupt itself only
27845 appears in the @samp{^done} output. If the user is trying to
27846 interrupt a non-running program, an error message will be printed.
27848 Note that when asynchronous execution is enabled, this command is
27849 asynchronous just like other execution commands. That is, first the
27850 @samp{^done} response will be printed, and the target stop will be
27851 reported after that using the @samp{*stopped} notification.
27853 In non-stop mode, only the context thread is interrupted by default.
27854 All threads (in all inferiors) will be interrupted if the
27855 @samp{--all} option is specified. If the @samp{--thread-group}
27856 option is specified, all threads in that group will be interrupted.
27858 @subsubheading @value{GDBN} Command
27860 The corresponding @value{GDBN} command is @samp{interrupt}.
27862 @subsubheading Example
27873 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27874 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27875 fullname="/home/foo/bar/try.c",line="13"@}
27880 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27884 @subheading The @code{-exec-jump} Command
27887 @subsubheading Synopsis
27890 -exec-jump @var{location}
27893 Resumes execution of the inferior program at the location specified by
27894 parameter. @xref{Specify Location}, for a description of the
27895 different forms of @var{location}.
27897 @subsubheading @value{GDBN} Command
27899 The corresponding @value{GDBN} command is @samp{jump}.
27901 @subsubheading Example
27904 -exec-jump foo.c:10
27905 *running,thread-id="all"
27910 @subheading The @code{-exec-next} Command
27913 @subsubheading Synopsis
27916 -exec-next [--reverse]
27919 Resumes execution of the inferior program, stopping when the beginning
27920 of the next source line is reached.
27922 If the @samp{--reverse} option is specified, resumes reverse execution
27923 of the inferior program, stopping at the beginning of the previous
27924 source line. If you issue this command on the first line of a
27925 function, it will take you back to the caller of that function, to the
27926 source line where the function was called.
27929 @subsubheading @value{GDBN} Command
27931 The corresponding @value{GDBN} command is @samp{next}.
27933 @subsubheading Example
27939 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27944 @subheading The @code{-exec-next-instruction} Command
27945 @findex -exec-next-instruction
27947 @subsubheading Synopsis
27950 -exec-next-instruction [--reverse]
27953 Executes one machine instruction. If the instruction is a function
27954 call, continues until the function returns. If the program stops at an
27955 instruction in the middle of a source line, the address will be
27958 If the @samp{--reverse} option is specified, resumes reverse execution
27959 of the inferior program, stopping at the previous instruction. If the
27960 previously executed instruction was a return from another function,
27961 it will continue to execute in reverse until the call to that function
27962 (from the current stack frame) is reached.
27964 @subsubheading @value{GDBN} Command
27966 The corresponding @value{GDBN} command is @samp{nexti}.
27968 @subsubheading Example
27972 -exec-next-instruction
27976 *stopped,reason="end-stepping-range",
27977 addr="0x000100d4",line="5",file="hello.c"
27982 @subheading The @code{-exec-return} Command
27983 @findex -exec-return
27985 @subsubheading Synopsis
27991 Makes current function return immediately. Doesn't execute the inferior.
27992 Displays the new current frame.
27994 @subsubheading @value{GDBN} Command
27996 The corresponding @value{GDBN} command is @samp{return}.
27998 @subsubheading Example
28002 200-break-insert callee4
28003 200^done,bkpt=@{number="1",addr="0x00010734",
28004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28009 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28010 frame=@{func="callee4",args=[],
28011 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28012 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28018 111^done,frame=@{level="0",func="callee3",
28019 args=[@{name="strarg",
28020 value="0x11940 \"A string argument.\""@}],
28021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28027 @subheading The @code{-exec-run} Command
28030 @subsubheading Synopsis
28033 -exec-run [ --all | --thread-group N ] [ --start ]
28036 Starts execution of the inferior from the beginning. The inferior
28037 executes until either a breakpoint is encountered or the program
28038 exits. In the latter case the output will include an exit code, if
28039 the program has exited exceptionally.
28041 When neither the @samp{--all} nor the @samp{--thread-group} option
28042 is specified, the current inferior is started. If the
28043 @samp{--thread-group} option is specified, it should refer to a thread
28044 group of type @samp{process}, and that thread group will be started.
28045 If the @samp{--all} option is specified, then all inferiors will be started.
28047 Using the @samp{--start} option instructs the debugger to stop
28048 the execution at the start of the inferior's main subprogram,
28049 following the same behavior as the @code{start} command
28050 (@pxref{Starting}).
28052 @subsubheading @value{GDBN} Command
28054 The corresponding @value{GDBN} command is @samp{run}.
28056 @subsubheading Examples
28061 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28066 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28067 frame=@{func="main",args=[],file="recursive2.c",
28068 fullname="/home/foo/bar/recursive2.c",line="4"@}
28073 Program exited normally:
28081 *stopped,reason="exited-normally"
28086 Program exited exceptionally:
28094 *stopped,reason="exited",exit-code="01"
28098 Another way the program can terminate is if it receives a signal such as
28099 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28103 *stopped,reason="exited-signalled",signal-name="SIGINT",
28104 signal-meaning="Interrupt"
28108 @c @subheading -exec-signal
28111 @subheading The @code{-exec-step} Command
28114 @subsubheading Synopsis
28117 -exec-step [--reverse]
28120 Resumes execution of the inferior program, stopping when the beginning
28121 of the next source line is reached, if the next source line is not a
28122 function call. If it is, stop at the first instruction of the called
28123 function. If the @samp{--reverse} option is specified, resumes reverse
28124 execution of the inferior program, stopping at the beginning of the
28125 previously executed source line.
28127 @subsubheading @value{GDBN} Command
28129 The corresponding @value{GDBN} command is @samp{step}.
28131 @subsubheading Example
28133 Stepping into a function:
28139 *stopped,reason="end-stepping-range",
28140 frame=@{func="foo",args=[@{name="a",value="10"@},
28141 @{name="b",value="0"@}],file="recursive2.c",
28142 fullname="/home/foo/bar/recursive2.c",line="11"@}
28152 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28157 @subheading The @code{-exec-step-instruction} Command
28158 @findex -exec-step-instruction
28160 @subsubheading Synopsis
28163 -exec-step-instruction [--reverse]
28166 Resumes the inferior which executes one machine instruction. If the
28167 @samp{--reverse} option is specified, resumes reverse execution of the
28168 inferior program, stopping at the previously executed instruction.
28169 The output, once @value{GDBN} has stopped, will vary depending on
28170 whether we have stopped in the middle of a source line or not. In the
28171 former case, the address at which the program stopped will be printed
28174 @subsubheading @value{GDBN} Command
28176 The corresponding @value{GDBN} command is @samp{stepi}.
28178 @subsubheading Example
28182 -exec-step-instruction
28186 *stopped,reason="end-stepping-range",
28187 frame=@{func="foo",args=[],file="try.c",
28188 fullname="/home/foo/bar/try.c",line="10"@}
28190 -exec-step-instruction
28194 *stopped,reason="end-stepping-range",
28195 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28196 fullname="/home/foo/bar/try.c",line="10"@}
28201 @subheading The @code{-exec-until} Command
28202 @findex -exec-until
28204 @subsubheading Synopsis
28207 -exec-until [ @var{location} ]
28210 Executes the inferior until the @var{location} specified in the
28211 argument is reached. If there is no argument, the inferior executes
28212 until a source line greater than the current one is reached. The
28213 reason for stopping in this case will be @samp{location-reached}.
28215 @subsubheading @value{GDBN} Command
28217 The corresponding @value{GDBN} command is @samp{until}.
28219 @subsubheading Example
28223 -exec-until recursive2.c:6
28227 *stopped,reason="location-reached",frame=@{func="main",args=[],
28228 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28233 @subheading -file-clear
28234 Is this going away????
28237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28238 @node GDB/MI Stack Manipulation
28239 @section @sc{gdb/mi} Stack Manipulation Commands
28241 @subheading The @code{-enable-frame-filters} Command
28242 @findex -enable-frame-filters
28245 -enable-frame-filters
28248 @value{GDBN} allows Python-based frame filters to affect the output of
28249 the MI commands relating to stack traces. As there is no way to
28250 implement this in a fully backward-compatible way, a front end must
28251 request that this functionality be enabled.
28253 Once enabled, this feature cannot be disabled.
28255 Note that if Python support has not been compiled into @value{GDBN},
28256 this command will still succeed (and do nothing).
28258 @subheading The @code{-stack-info-frame} Command
28259 @findex -stack-info-frame
28261 @subsubheading Synopsis
28267 Get info on the selected frame.
28269 @subsubheading @value{GDBN} Command
28271 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28272 (without arguments).
28274 @subsubheading Example
28279 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28280 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28281 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28285 @subheading The @code{-stack-info-depth} Command
28286 @findex -stack-info-depth
28288 @subsubheading Synopsis
28291 -stack-info-depth [ @var{max-depth} ]
28294 Return the depth of the stack. If the integer argument @var{max-depth}
28295 is specified, do not count beyond @var{max-depth} frames.
28297 @subsubheading @value{GDBN} Command
28299 There's no equivalent @value{GDBN} command.
28301 @subsubheading Example
28303 For a stack with frame levels 0 through 11:
28310 -stack-info-depth 4
28313 -stack-info-depth 12
28316 -stack-info-depth 11
28319 -stack-info-depth 13
28324 @anchor{-stack-list-arguments}
28325 @subheading The @code{-stack-list-arguments} Command
28326 @findex -stack-list-arguments
28328 @subsubheading Synopsis
28331 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28332 [ @var{low-frame} @var{high-frame} ]
28335 Display a list of the arguments for the frames between @var{low-frame}
28336 and @var{high-frame} (inclusive). If @var{low-frame} and
28337 @var{high-frame} are not provided, list the arguments for the whole
28338 call stack. If the two arguments are equal, show the single frame
28339 at the corresponding level. It is an error if @var{low-frame} is
28340 larger than the actual number of frames. On the other hand,
28341 @var{high-frame} may be larger than the actual number of frames, in
28342 which case only existing frames will be returned.
28344 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28345 the variables; if it is 1 or @code{--all-values}, print also their
28346 values; and if it is 2 or @code{--simple-values}, print the name,
28347 type and value for simple data types, and the name and type for arrays,
28348 structures and unions. If the option @code{--no-frame-filters} is
28349 supplied, then Python frame filters will not be executed.
28351 If the @code{--skip-unavailable} option is specified, arguments that
28352 are not available are not listed. Partially available arguments
28353 are still displayed, however.
28355 Use of this command to obtain arguments in a single frame is
28356 deprecated in favor of the @samp{-stack-list-variables} command.
28358 @subsubheading @value{GDBN} Command
28360 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28361 @samp{gdb_get_args} command which partially overlaps with the
28362 functionality of @samp{-stack-list-arguments}.
28364 @subsubheading Example
28371 frame=@{level="0",addr="0x00010734",func="callee4",
28372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28373 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28374 frame=@{level="1",addr="0x0001076c",func="callee3",
28375 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28376 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28377 frame=@{level="2",addr="0x0001078c",func="callee2",
28378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28379 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28380 frame=@{level="3",addr="0x000107b4",func="callee1",
28381 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28382 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28383 frame=@{level="4",addr="0x000107e0",func="main",
28384 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28385 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28387 -stack-list-arguments 0
28390 frame=@{level="0",args=[]@},
28391 frame=@{level="1",args=[name="strarg"]@},
28392 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28393 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28394 frame=@{level="4",args=[]@}]
28396 -stack-list-arguments 1
28399 frame=@{level="0",args=[]@},
28401 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28402 frame=@{level="2",args=[
28403 @{name="intarg",value="2"@},
28404 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28405 @{frame=@{level="3",args=[
28406 @{name="intarg",value="2"@},
28407 @{name="strarg",value="0x11940 \"A string argument.\""@},
28408 @{name="fltarg",value="3.5"@}]@},
28409 frame=@{level="4",args=[]@}]
28411 -stack-list-arguments 0 2 2
28412 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28414 -stack-list-arguments 1 2 2
28415 ^done,stack-args=[frame=@{level="2",
28416 args=[@{name="intarg",value="2"@},
28417 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28421 @c @subheading -stack-list-exception-handlers
28424 @anchor{-stack-list-frames}
28425 @subheading The @code{-stack-list-frames} Command
28426 @findex -stack-list-frames
28428 @subsubheading Synopsis
28431 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28434 List the frames currently on the stack. For each frame it displays the
28439 The frame number, 0 being the topmost frame, i.e., the innermost function.
28441 The @code{$pc} value for that frame.
28445 File name of the source file where the function lives.
28446 @item @var{fullname}
28447 The full file name of the source file where the function lives.
28449 Line number corresponding to the @code{$pc}.
28451 The shared library where this function is defined. This is only given
28452 if the frame's function is not known.
28455 If invoked without arguments, this command prints a backtrace for the
28456 whole stack. If given two integer arguments, it shows the frames whose
28457 levels are between the two arguments (inclusive). If the two arguments
28458 are equal, it shows the single frame at the corresponding level. It is
28459 an error if @var{low-frame} is larger than the actual number of
28460 frames. On the other hand, @var{high-frame} may be larger than the
28461 actual number of frames, in which case only existing frames will be
28462 returned. If the option @code{--no-frame-filters} is supplied, then
28463 Python frame filters will not be executed.
28465 @subsubheading @value{GDBN} Command
28467 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28469 @subsubheading Example
28471 Full stack backtrace:
28477 [frame=@{level="0",addr="0x0001076c",func="foo",
28478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28479 frame=@{level="1",addr="0x000107a4",func="foo",
28480 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28481 frame=@{level="2",addr="0x000107a4",func="foo",
28482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28483 frame=@{level="3",addr="0x000107a4",func="foo",
28484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28485 frame=@{level="4",addr="0x000107a4",func="foo",
28486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28487 frame=@{level="5",addr="0x000107a4",func="foo",
28488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28489 frame=@{level="6",addr="0x000107a4",func="foo",
28490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28491 frame=@{level="7",addr="0x000107a4",func="foo",
28492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28493 frame=@{level="8",addr="0x000107a4",func="foo",
28494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28495 frame=@{level="9",addr="0x000107a4",func="foo",
28496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28497 frame=@{level="10",addr="0x000107a4",func="foo",
28498 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28499 frame=@{level="11",addr="0x00010738",func="main",
28500 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28504 Show frames between @var{low_frame} and @var{high_frame}:
28508 -stack-list-frames 3 5
28510 [frame=@{level="3",addr="0x000107a4",func="foo",
28511 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28512 frame=@{level="4",addr="0x000107a4",func="foo",
28513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28514 frame=@{level="5",addr="0x000107a4",func="foo",
28515 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28519 Show a single frame:
28523 -stack-list-frames 3 3
28525 [frame=@{level="3",addr="0x000107a4",func="foo",
28526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28531 @subheading The @code{-stack-list-locals} Command
28532 @findex -stack-list-locals
28533 @anchor{-stack-list-locals}
28535 @subsubheading Synopsis
28538 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28541 Display the local variable names for the selected frame. If
28542 @var{print-values} is 0 or @code{--no-values}, print only the names of
28543 the variables; if it is 1 or @code{--all-values}, print also their
28544 values; and if it is 2 or @code{--simple-values}, print the name,
28545 type and value for simple data types, and the name and type for arrays,
28546 structures and unions. In this last case, a frontend can immediately
28547 display the value of simple data types and create variable objects for
28548 other data types when the user wishes to explore their values in
28549 more detail. If the option @code{--no-frame-filters} is supplied, then
28550 Python frame filters will not be executed.
28552 If the @code{--skip-unavailable} option is specified, local variables
28553 that are not available are not listed. Partially available local
28554 variables are still displayed, however.
28556 This command is deprecated in favor of the
28557 @samp{-stack-list-variables} command.
28559 @subsubheading @value{GDBN} Command
28561 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28563 @subsubheading Example
28567 -stack-list-locals 0
28568 ^done,locals=[name="A",name="B",name="C"]
28570 -stack-list-locals --all-values
28571 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28572 @{name="C",value="@{1, 2, 3@}"@}]
28573 -stack-list-locals --simple-values
28574 ^done,locals=[@{name="A",type="int",value="1"@},
28575 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28579 @anchor{-stack-list-variables}
28580 @subheading The @code{-stack-list-variables} Command
28581 @findex -stack-list-variables
28583 @subsubheading Synopsis
28586 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28589 Display the names of local variables and function arguments for the selected frame. If
28590 @var{print-values} is 0 or @code{--no-values}, print only the names of
28591 the variables; if it is 1 or @code{--all-values}, print also their
28592 values; and if it is 2 or @code{--simple-values}, print the name,
28593 type and value for simple data types, and the name and type for arrays,
28594 structures and unions. If the option @code{--no-frame-filters} is
28595 supplied, then Python frame filters will not be executed.
28597 If the @code{--skip-unavailable} option is specified, local variables
28598 and arguments that are not available are not listed. Partially
28599 available arguments and local variables are still displayed, however.
28601 @subsubheading Example
28605 -stack-list-variables --thread 1 --frame 0 --all-values
28606 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28611 @subheading The @code{-stack-select-frame} Command
28612 @findex -stack-select-frame
28614 @subsubheading Synopsis
28617 -stack-select-frame @var{framenum}
28620 Change the selected frame. Select a different frame @var{framenum} on
28623 This command in deprecated in favor of passing the @samp{--frame}
28624 option to every command.
28626 @subsubheading @value{GDBN} Command
28628 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28629 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28631 @subsubheading Example
28635 -stack-select-frame 2
28640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28641 @node GDB/MI Variable Objects
28642 @section @sc{gdb/mi} Variable Objects
28646 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28648 For the implementation of a variable debugger window (locals, watched
28649 expressions, etc.), we are proposing the adaptation of the existing code
28650 used by @code{Insight}.
28652 The two main reasons for that are:
28656 It has been proven in practice (it is already on its second generation).
28659 It will shorten development time (needless to say how important it is
28663 The original interface was designed to be used by Tcl code, so it was
28664 slightly changed so it could be used through @sc{gdb/mi}. This section
28665 describes the @sc{gdb/mi} operations that will be available and gives some
28666 hints about their use.
28668 @emph{Note}: In addition to the set of operations described here, we
28669 expect the @sc{gui} implementation of a variable window to require, at
28670 least, the following operations:
28673 @item @code{-gdb-show} @code{output-radix}
28674 @item @code{-stack-list-arguments}
28675 @item @code{-stack-list-locals}
28676 @item @code{-stack-select-frame}
28681 @subheading Introduction to Variable Objects
28683 @cindex variable objects in @sc{gdb/mi}
28685 Variable objects are "object-oriented" MI interface for examining and
28686 changing values of expressions. Unlike some other MI interfaces that
28687 work with expressions, variable objects are specifically designed for
28688 simple and efficient presentation in the frontend. A variable object
28689 is identified by string name. When a variable object is created, the
28690 frontend specifies the expression for that variable object. The
28691 expression can be a simple variable, or it can be an arbitrary complex
28692 expression, and can even involve CPU registers. After creating a
28693 variable object, the frontend can invoke other variable object
28694 operations---for example to obtain or change the value of a variable
28695 object, or to change display format.
28697 Variable objects have hierarchical tree structure. Any variable object
28698 that corresponds to a composite type, such as structure in C, has
28699 a number of child variable objects, for example corresponding to each
28700 element of a structure. A child variable object can itself have
28701 children, recursively. Recursion ends when we reach
28702 leaf variable objects, which always have built-in types. Child variable
28703 objects are created only by explicit request, so if a frontend
28704 is not interested in the children of a particular variable object, no
28705 child will be created.
28707 For a leaf variable object it is possible to obtain its value as a
28708 string, or set the value from a string. String value can be also
28709 obtained for a non-leaf variable object, but it's generally a string
28710 that only indicates the type of the object, and does not list its
28711 contents. Assignment to a non-leaf variable object is not allowed.
28713 A frontend does not need to read the values of all variable objects each time
28714 the program stops. Instead, MI provides an update command that lists all
28715 variable objects whose values has changed since the last update
28716 operation. This considerably reduces the amount of data that must
28717 be transferred to the frontend. As noted above, children variable
28718 objects are created on demand, and only leaf variable objects have a
28719 real value. As result, gdb will read target memory only for leaf
28720 variables that frontend has created.
28722 The automatic update is not always desirable. For example, a frontend
28723 might want to keep a value of some expression for future reference,
28724 and never update it. For another example, fetching memory is
28725 relatively slow for embedded targets, so a frontend might want
28726 to disable automatic update for the variables that are either not
28727 visible on the screen, or ``closed''. This is possible using so
28728 called ``frozen variable objects''. Such variable objects are never
28729 implicitly updated.
28731 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28732 fixed variable object, the expression is parsed when the variable
28733 object is created, including associating identifiers to specific
28734 variables. The meaning of expression never changes. For a floating
28735 variable object the values of variables whose names appear in the
28736 expressions are re-evaluated every time in the context of the current
28737 frame. Consider this example:
28742 struct work_state state;
28749 If a fixed variable object for the @code{state} variable is created in
28750 this function, and we enter the recursive call, the variable
28751 object will report the value of @code{state} in the top-level
28752 @code{do_work} invocation. On the other hand, a floating variable
28753 object will report the value of @code{state} in the current frame.
28755 If an expression specified when creating a fixed variable object
28756 refers to a local variable, the variable object becomes bound to the
28757 thread and frame in which the variable object is created. When such
28758 variable object is updated, @value{GDBN} makes sure that the
28759 thread/frame combination the variable object is bound to still exists,
28760 and re-evaluates the variable object in context of that thread/frame.
28762 The following is the complete set of @sc{gdb/mi} operations defined to
28763 access this functionality:
28765 @multitable @columnfractions .4 .6
28766 @item @strong{Operation}
28767 @tab @strong{Description}
28769 @item @code{-enable-pretty-printing}
28770 @tab enable Python-based pretty-printing
28771 @item @code{-var-create}
28772 @tab create a variable object
28773 @item @code{-var-delete}
28774 @tab delete the variable object and/or its children
28775 @item @code{-var-set-format}
28776 @tab set the display format of this variable
28777 @item @code{-var-show-format}
28778 @tab show the display format of this variable
28779 @item @code{-var-info-num-children}
28780 @tab tells how many children this object has
28781 @item @code{-var-list-children}
28782 @tab return a list of the object's children
28783 @item @code{-var-info-type}
28784 @tab show the type of this variable object
28785 @item @code{-var-info-expression}
28786 @tab print parent-relative expression that this variable object represents
28787 @item @code{-var-info-path-expression}
28788 @tab print full expression that this variable object represents
28789 @item @code{-var-show-attributes}
28790 @tab is this variable editable? does it exist here?
28791 @item @code{-var-evaluate-expression}
28792 @tab get the value of this variable
28793 @item @code{-var-assign}
28794 @tab set the value of this variable
28795 @item @code{-var-update}
28796 @tab update the variable and its children
28797 @item @code{-var-set-frozen}
28798 @tab set frozeness attribute
28799 @item @code{-var-set-update-range}
28800 @tab set range of children to display on update
28803 In the next subsection we describe each operation in detail and suggest
28804 how it can be used.
28806 @subheading Description And Use of Operations on Variable Objects
28808 @subheading The @code{-enable-pretty-printing} Command
28809 @findex -enable-pretty-printing
28812 -enable-pretty-printing
28815 @value{GDBN} allows Python-based visualizers to affect the output of the
28816 MI variable object commands. However, because there was no way to
28817 implement this in a fully backward-compatible way, a front end must
28818 request that this functionality be enabled.
28820 Once enabled, this feature cannot be disabled.
28822 Note that if Python support has not been compiled into @value{GDBN},
28823 this command will still succeed (and do nothing).
28825 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28826 may work differently in future versions of @value{GDBN}.
28828 @subheading The @code{-var-create} Command
28829 @findex -var-create
28831 @subsubheading Synopsis
28834 -var-create @{@var{name} | "-"@}
28835 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28838 This operation creates a variable object, which allows the monitoring of
28839 a variable, the result of an expression, a memory cell or a CPU
28842 The @var{name} parameter is the string by which the object can be
28843 referenced. It must be unique. If @samp{-} is specified, the varobj
28844 system will generate a string ``varNNNNNN'' automatically. It will be
28845 unique provided that one does not specify @var{name} of that format.
28846 The command fails if a duplicate name is found.
28848 The frame under which the expression should be evaluated can be
28849 specified by @var{frame-addr}. A @samp{*} indicates that the current
28850 frame should be used. A @samp{@@} indicates that a floating variable
28851 object must be created.
28853 @var{expression} is any expression valid on the current language set (must not
28854 begin with a @samp{*}), or one of the following:
28858 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28861 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28864 @samp{$@var{regname}} --- a CPU register name
28867 @cindex dynamic varobj
28868 A varobj's contents may be provided by a Python-based pretty-printer. In this
28869 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28870 have slightly different semantics in some cases. If the
28871 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28872 will never create a dynamic varobj. This ensures backward
28873 compatibility for existing clients.
28875 @subsubheading Result
28877 This operation returns attributes of the newly-created varobj. These
28882 The name of the varobj.
28885 The number of children of the varobj. This number is not necessarily
28886 reliable for a dynamic varobj. Instead, you must examine the
28887 @samp{has_more} attribute.
28890 The varobj's scalar value. For a varobj whose type is some sort of
28891 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28892 will not be interesting.
28895 The varobj's type. This is a string representation of the type, as
28896 would be printed by the @value{GDBN} CLI. If @samp{print object}
28897 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28898 @emph{actual} (derived) type of the object is shown rather than the
28899 @emph{declared} one.
28902 If a variable object is bound to a specific thread, then this is the
28903 thread's identifier.
28906 For a dynamic varobj, this indicates whether there appear to be any
28907 children available. For a non-dynamic varobj, this will be 0.
28910 This attribute will be present and have the value @samp{1} if the
28911 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28912 then this attribute will not be present.
28915 A dynamic varobj can supply a display hint to the front end. The
28916 value comes directly from the Python pretty-printer object's
28917 @code{display_hint} method. @xref{Pretty Printing API}.
28920 Typical output will look like this:
28923 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28924 has_more="@var{has_more}"
28928 @subheading The @code{-var-delete} Command
28929 @findex -var-delete
28931 @subsubheading Synopsis
28934 -var-delete [ -c ] @var{name}
28937 Deletes a previously created variable object and all of its children.
28938 With the @samp{-c} option, just deletes the children.
28940 Returns an error if the object @var{name} is not found.
28943 @subheading The @code{-var-set-format} Command
28944 @findex -var-set-format
28946 @subsubheading Synopsis
28949 -var-set-format @var{name} @var{format-spec}
28952 Sets the output format for the value of the object @var{name} to be
28955 @anchor{-var-set-format}
28956 The syntax for the @var{format-spec} is as follows:
28959 @var{format-spec} @expansion{}
28960 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
28963 The natural format is the default format choosen automatically
28964 based on the variable type (like decimal for an @code{int}, hex
28965 for pointers, etc.).
28967 The zero-hexadecimal format has a representation similar to hexadecimal
28968 but with padding zeroes to the left of the value. For example, a 32-bit
28969 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
28970 zero-hexadecimal format.
28972 For a variable with children, the format is set only on the
28973 variable itself, and the children are not affected.
28975 @subheading The @code{-var-show-format} Command
28976 @findex -var-show-format
28978 @subsubheading Synopsis
28981 -var-show-format @var{name}
28984 Returns the format used to display the value of the object @var{name}.
28987 @var{format} @expansion{}
28992 @subheading The @code{-var-info-num-children} Command
28993 @findex -var-info-num-children
28995 @subsubheading Synopsis
28998 -var-info-num-children @var{name}
29001 Returns the number of children of a variable object @var{name}:
29007 Note that this number is not completely reliable for a dynamic varobj.
29008 It will return the current number of children, but more children may
29012 @subheading The @code{-var-list-children} Command
29013 @findex -var-list-children
29015 @subsubheading Synopsis
29018 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29020 @anchor{-var-list-children}
29022 Return a list of the children of the specified variable object and
29023 create variable objects for them, if they do not already exist. With
29024 a single argument or if @var{print-values} has a value of 0 or
29025 @code{--no-values}, print only the names of the variables; if
29026 @var{print-values} is 1 or @code{--all-values}, also print their
29027 values; and if it is 2 or @code{--simple-values} print the name and
29028 value for simple data types and just the name for arrays, structures
29031 @var{from} and @var{to}, if specified, indicate the range of children
29032 to report. If @var{from} or @var{to} is less than zero, the range is
29033 reset and all children will be reported. Otherwise, children starting
29034 at @var{from} (zero-based) and up to and excluding @var{to} will be
29037 If a child range is requested, it will only affect the current call to
29038 @code{-var-list-children}, but not future calls to @code{-var-update}.
29039 For this, you must instead use @code{-var-set-update-range}. The
29040 intent of this approach is to enable a front end to implement any
29041 update approach it likes; for example, scrolling a view may cause the
29042 front end to request more children with @code{-var-list-children}, and
29043 then the front end could call @code{-var-set-update-range} with a
29044 different range to ensure that future updates are restricted to just
29047 For each child the following results are returned:
29052 Name of the variable object created for this child.
29055 The expression to be shown to the user by the front end to designate this child.
29056 For example this may be the name of a structure member.
29058 For a dynamic varobj, this value cannot be used to form an
29059 expression. There is no way to do this at all with a dynamic varobj.
29061 For C/C@t{++} structures there are several pseudo children returned to
29062 designate access qualifiers. For these pseudo children @var{exp} is
29063 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29064 type and value are not present.
29066 A dynamic varobj will not report the access qualifying
29067 pseudo-children, regardless of the language. This information is not
29068 available at all with a dynamic varobj.
29071 Number of children this child has. For a dynamic varobj, this will be
29075 The type of the child. If @samp{print object}
29076 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29077 @emph{actual} (derived) type of the object is shown rather than the
29078 @emph{declared} one.
29081 If values were requested, this is the value.
29084 If this variable object is associated with a thread, this is the thread id.
29085 Otherwise this result is not present.
29088 If the variable object is frozen, this variable will be present with a value of 1.
29091 A dynamic varobj can supply a display hint to the front end. The
29092 value comes directly from the Python pretty-printer object's
29093 @code{display_hint} method. @xref{Pretty Printing API}.
29096 This attribute will be present and have the value @samp{1} if the
29097 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29098 then this attribute will not be present.
29102 The result may have its own attributes:
29106 A dynamic varobj can supply a display hint to the front end. The
29107 value comes directly from the Python pretty-printer object's
29108 @code{display_hint} method. @xref{Pretty Printing API}.
29111 This is an integer attribute which is nonzero if there are children
29112 remaining after the end of the selected range.
29115 @subsubheading Example
29119 -var-list-children n
29120 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29121 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29123 -var-list-children --all-values n
29124 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29125 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29129 @subheading The @code{-var-info-type} Command
29130 @findex -var-info-type
29132 @subsubheading Synopsis
29135 -var-info-type @var{name}
29138 Returns the type of the specified variable @var{name}. The type is
29139 returned as a string in the same format as it is output by the
29143 type=@var{typename}
29147 @subheading The @code{-var-info-expression} Command
29148 @findex -var-info-expression
29150 @subsubheading Synopsis
29153 -var-info-expression @var{name}
29156 Returns a string that is suitable for presenting this
29157 variable object in user interface. The string is generally
29158 not valid expression in the current language, and cannot be evaluated.
29160 For example, if @code{a} is an array, and variable object
29161 @code{A} was created for @code{a}, then we'll get this output:
29164 (gdb) -var-info-expression A.1
29165 ^done,lang="C",exp="1"
29169 Here, the value of @code{lang} is the language name, which can be
29170 found in @ref{Supported Languages}.
29172 Note that the output of the @code{-var-list-children} command also
29173 includes those expressions, so the @code{-var-info-expression} command
29176 @subheading The @code{-var-info-path-expression} Command
29177 @findex -var-info-path-expression
29179 @subsubheading Synopsis
29182 -var-info-path-expression @var{name}
29185 Returns an expression that can be evaluated in the current
29186 context and will yield the same value that a variable object has.
29187 Compare this with the @code{-var-info-expression} command, which
29188 result can be used only for UI presentation. Typical use of
29189 the @code{-var-info-path-expression} command is creating a
29190 watchpoint from a variable object.
29192 This command is currently not valid for children of a dynamic varobj,
29193 and will give an error when invoked on one.
29195 For example, suppose @code{C} is a C@t{++} class, derived from class
29196 @code{Base}, and that the @code{Base} class has a member called
29197 @code{m_size}. Assume a variable @code{c} is has the type of
29198 @code{C} and a variable object @code{C} was created for variable
29199 @code{c}. Then, we'll get this output:
29201 (gdb) -var-info-path-expression C.Base.public.m_size
29202 ^done,path_expr=((Base)c).m_size)
29205 @subheading The @code{-var-show-attributes} Command
29206 @findex -var-show-attributes
29208 @subsubheading Synopsis
29211 -var-show-attributes @var{name}
29214 List attributes of the specified variable object @var{name}:
29217 status=@var{attr} [ ( ,@var{attr} )* ]
29221 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29223 @subheading The @code{-var-evaluate-expression} Command
29224 @findex -var-evaluate-expression
29226 @subsubheading Synopsis
29229 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29232 Evaluates the expression that is represented by the specified variable
29233 object and returns its value as a string. The format of the string
29234 can be specified with the @samp{-f} option. The possible values of
29235 this option are the same as for @code{-var-set-format}
29236 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29237 the current display format will be used. The current display format
29238 can be changed using the @code{-var-set-format} command.
29244 Note that one must invoke @code{-var-list-children} for a variable
29245 before the value of a child variable can be evaluated.
29247 @subheading The @code{-var-assign} Command
29248 @findex -var-assign
29250 @subsubheading Synopsis
29253 -var-assign @var{name} @var{expression}
29256 Assigns the value of @var{expression} to the variable object specified
29257 by @var{name}. The object must be @samp{editable}. If the variable's
29258 value is altered by the assign, the variable will show up in any
29259 subsequent @code{-var-update} list.
29261 @subsubheading Example
29269 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29273 @subheading The @code{-var-update} Command
29274 @findex -var-update
29276 @subsubheading Synopsis
29279 -var-update [@var{print-values}] @{@var{name} | "*"@}
29282 Reevaluate the expressions corresponding to the variable object
29283 @var{name} and all its direct and indirect children, and return the
29284 list of variable objects whose values have changed; @var{name} must
29285 be a root variable object. Here, ``changed'' means that the result of
29286 @code{-var-evaluate-expression} before and after the
29287 @code{-var-update} is different. If @samp{*} is used as the variable
29288 object names, all existing variable objects are updated, except
29289 for frozen ones (@pxref{-var-set-frozen}). The option
29290 @var{print-values} determines whether both names and values, or just
29291 names are printed. The possible values of this option are the same
29292 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29293 recommended to use the @samp{--all-values} option, to reduce the
29294 number of MI commands needed on each program stop.
29296 With the @samp{*} parameter, if a variable object is bound to a
29297 currently running thread, it will not be updated, without any
29300 If @code{-var-set-update-range} was previously used on a varobj, then
29301 only the selected range of children will be reported.
29303 @code{-var-update} reports all the changed varobjs in a tuple named
29306 Each item in the change list is itself a tuple holding:
29310 The name of the varobj.
29313 If values were requested for this update, then this field will be
29314 present and will hold the value of the varobj.
29317 @anchor{-var-update}
29318 This field is a string which may take one of three values:
29322 The variable object's current value is valid.
29325 The variable object does not currently hold a valid value but it may
29326 hold one in the future if its associated expression comes back into
29330 The variable object no longer holds a valid value.
29331 This can occur when the executable file being debugged has changed,
29332 either through recompilation or by using the @value{GDBN} @code{file}
29333 command. The front end should normally choose to delete these variable
29337 In the future new values may be added to this list so the front should
29338 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29341 This is only present if the varobj is still valid. If the type
29342 changed, then this will be the string @samp{true}; otherwise it will
29345 When a varobj's type changes, its children are also likely to have
29346 become incorrect. Therefore, the varobj's children are automatically
29347 deleted when this attribute is @samp{true}. Also, the varobj's update
29348 range, when set using the @code{-var-set-update-range} command, is
29352 If the varobj's type changed, then this field will be present and will
29355 @item new_num_children
29356 For a dynamic varobj, if the number of children changed, or if the
29357 type changed, this will be the new number of children.
29359 The @samp{numchild} field in other varobj responses is generally not
29360 valid for a dynamic varobj -- it will show the number of children that
29361 @value{GDBN} knows about, but because dynamic varobjs lazily
29362 instantiate their children, this will not reflect the number of
29363 children which may be available.
29365 The @samp{new_num_children} attribute only reports changes to the
29366 number of children known by @value{GDBN}. This is the only way to
29367 detect whether an update has removed children (which necessarily can
29368 only happen at the end of the update range).
29371 The display hint, if any.
29374 This is an integer value, which will be 1 if there are more children
29375 available outside the varobj's update range.
29378 This attribute will be present and have the value @samp{1} if the
29379 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29380 then this attribute will not be present.
29383 If new children were added to a dynamic varobj within the selected
29384 update range (as set by @code{-var-set-update-range}), then they will
29385 be listed in this attribute.
29388 @subsubheading Example
29395 -var-update --all-values var1
29396 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29397 type_changed="false"@}]
29401 @subheading The @code{-var-set-frozen} Command
29402 @findex -var-set-frozen
29403 @anchor{-var-set-frozen}
29405 @subsubheading Synopsis
29408 -var-set-frozen @var{name} @var{flag}
29411 Set the frozenness flag on the variable object @var{name}. The
29412 @var{flag} parameter should be either @samp{1} to make the variable
29413 frozen or @samp{0} to make it unfrozen. If a variable object is
29414 frozen, then neither itself, nor any of its children, are
29415 implicitly updated by @code{-var-update} of
29416 a parent variable or by @code{-var-update *}. Only
29417 @code{-var-update} of the variable itself will update its value and
29418 values of its children. After a variable object is unfrozen, it is
29419 implicitly updated by all subsequent @code{-var-update} operations.
29420 Unfreezing a variable does not update it, only subsequent
29421 @code{-var-update} does.
29423 @subsubheading Example
29427 -var-set-frozen V 1
29432 @subheading The @code{-var-set-update-range} command
29433 @findex -var-set-update-range
29434 @anchor{-var-set-update-range}
29436 @subsubheading Synopsis
29439 -var-set-update-range @var{name} @var{from} @var{to}
29442 Set the range of children to be returned by future invocations of
29443 @code{-var-update}.
29445 @var{from} and @var{to} indicate the range of children to report. If
29446 @var{from} or @var{to} is less than zero, the range is reset and all
29447 children will be reported. Otherwise, children starting at @var{from}
29448 (zero-based) and up to and excluding @var{to} will be reported.
29450 @subsubheading Example
29454 -var-set-update-range V 1 2
29458 @subheading The @code{-var-set-visualizer} command
29459 @findex -var-set-visualizer
29460 @anchor{-var-set-visualizer}
29462 @subsubheading Synopsis
29465 -var-set-visualizer @var{name} @var{visualizer}
29468 Set a visualizer for the variable object @var{name}.
29470 @var{visualizer} is the visualizer to use. The special value
29471 @samp{None} means to disable any visualizer in use.
29473 If not @samp{None}, @var{visualizer} must be a Python expression.
29474 This expression must evaluate to a callable object which accepts a
29475 single argument. @value{GDBN} will call this object with the value of
29476 the varobj @var{name} as an argument (this is done so that the same
29477 Python pretty-printing code can be used for both the CLI and MI).
29478 When called, this object must return an object which conforms to the
29479 pretty-printing interface (@pxref{Pretty Printing API}).
29481 The pre-defined function @code{gdb.default_visualizer} may be used to
29482 select a visualizer by following the built-in process
29483 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29484 a varobj is created, and so ordinarily is not needed.
29486 This feature is only available if Python support is enabled. The MI
29487 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29488 can be used to check this.
29490 @subsubheading Example
29492 Resetting the visualizer:
29496 -var-set-visualizer V None
29500 Reselecting the default (type-based) visualizer:
29504 -var-set-visualizer V gdb.default_visualizer
29508 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29509 can be used to instantiate this class for a varobj:
29513 -var-set-visualizer V "lambda val: SomeClass()"
29517 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29518 @node GDB/MI Data Manipulation
29519 @section @sc{gdb/mi} Data Manipulation
29521 @cindex data manipulation, in @sc{gdb/mi}
29522 @cindex @sc{gdb/mi}, data manipulation
29523 This section describes the @sc{gdb/mi} commands that manipulate data:
29524 examine memory and registers, evaluate expressions, etc.
29526 For details about what an addressable memory unit is,
29527 @pxref{addressable memory unit}.
29529 @c REMOVED FROM THE INTERFACE.
29530 @c @subheading -data-assign
29531 @c Change the value of a program variable. Plenty of side effects.
29532 @c @subsubheading GDB Command
29534 @c @subsubheading Example
29537 @subheading The @code{-data-disassemble} Command
29538 @findex -data-disassemble
29540 @subsubheading Synopsis
29544 [ -s @var{start-addr} -e @var{end-addr} ]
29545 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29553 @item @var{start-addr}
29554 is the beginning address (or @code{$pc})
29555 @item @var{end-addr}
29557 @item @var{filename}
29558 is the name of the file to disassemble
29559 @item @var{linenum}
29560 is the line number to disassemble around
29562 is the number of disassembly lines to be produced. If it is -1,
29563 the whole function will be disassembled, in case no @var{end-addr} is
29564 specified. If @var{end-addr} is specified as a non-zero value, and
29565 @var{lines} is lower than the number of disassembly lines between
29566 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29567 displayed; if @var{lines} is higher than the number of lines between
29568 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29573 @item 0 disassembly only
29574 @item 1 mixed source and disassembly (deprecated)
29575 @item 2 disassembly with raw opcodes
29576 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29577 @item 4 mixed source and disassembly
29578 @item 5 mixed source and disassembly with raw opcodes
29581 Modes 1 and 3 are deprecated. The output is ``source centric''
29582 which hasn't proved useful in practice.
29583 @xref{Machine Code}, for a discussion of the difference between
29584 @code{/m} and @code{/s} output of the @code{disassemble} command.
29587 @subsubheading Result
29589 The result of the @code{-data-disassemble} command will be a list named
29590 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29591 used with the @code{-data-disassemble} command.
29593 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29598 The address at which this instruction was disassembled.
29601 The name of the function this instruction is within.
29604 The decimal offset in bytes from the start of @samp{func-name}.
29607 The text disassembly for this @samp{address}.
29610 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29611 bytes for the @samp{inst} field.
29615 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29616 @samp{src_and_asm_line}, each of which has the following fields:
29620 The line number within @samp{file}.
29623 The file name from the compilation unit. This might be an absolute
29624 file name or a relative file name depending on the compile command
29628 Absolute file name of @samp{file}. It is converted to a canonical form
29629 using the source file search path
29630 (@pxref{Source Path, ,Specifying Source Directories})
29631 and after resolving all the symbolic links.
29633 If the source file is not found this field will contain the path as
29634 present in the debug information.
29636 @item line_asm_insn
29637 This is a list of tuples containing the disassembly for @samp{line} in
29638 @samp{file}. The fields of each tuple are the same as for
29639 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29640 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29645 Note that whatever included in the @samp{inst} field, is not
29646 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29649 @subsubheading @value{GDBN} Command
29651 The corresponding @value{GDBN} command is @samp{disassemble}.
29653 @subsubheading Example
29655 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29659 -data-disassemble -s $pc -e "$pc + 20" -- 0
29662 @{address="0x000107c0",func-name="main",offset="4",
29663 inst="mov 2, %o0"@},
29664 @{address="0x000107c4",func-name="main",offset="8",
29665 inst="sethi %hi(0x11800), %o2"@},
29666 @{address="0x000107c8",func-name="main",offset="12",
29667 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29668 @{address="0x000107cc",func-name="main",offset="16",
29669 inst="sethi %hi(0x11800), %o2"@},
29670 @{address="0x000107d0",func-name="main",offset="20",
29671 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29675 Disassemble the whole @code{main} function. Line 32 is part of
29679 -data-disassemble -f basics.c -l 32 -- 0
29681 @{address="0x000107bc",func-name="main",offset="0",
29682 inst="save %sp, -112, %sp"@},
29683 @{address="0x000107c0",func-name="main",offset="4",
29684 inst="mov 2, %o0"@},
29685 @{address="0x000107c4",func-name="main",offset="8",
29686 inst="sethi %hi(0x11800), %o2"@},
29688 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29689 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29693 Disassemble 3 instructions from the start of @code{main}:
29697 -data-disassemble -f basics.c -l 32 -n 3 -- 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"@}]
29708 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29712 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29714 src_and_asm_line=@{line="31",
29715 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29716 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29717 line_asm_insn=[@{address="0x000107bc",
29718 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29719 src_and_asm_line=@{line="32",
29720 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29721 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29722 line_asm_insn=[@{address="0x000107c0",
29723 func-name="main",offset="4",inst="mov 2, %o0"@},
29724 @{address="0x000107c4",func-name="main",offset="8",
29725 inst="sethi %hi(0x11800), %o2"@}]@}]
29730 @subheading The @code{-data-evaluate-expression} Command
29731 @findex -data-evaluate-expression
29733 @subsubheading Synopsis
29736 -data-evaluate-expression @var{expr}
29739 Evaluate @var{expr} as an expression. The expression could contain an
29740 inferior function call. The function call will execute synchronously.
29741 If the expression contains spaces, it must be enclosed in double quotes.
29743 @subsubheading @value{GDBN} Command
29745 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29746 @samp{call}. In @code{gdbtk} only, there's a corresponding
29747 @samp{gdb_eval} command.
29749 @subsubheading Example
29751 In the following example, the numbers that precede the commands are the
29752 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29753 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29757 211-data-evaluate-expression A
29760 311-data-evaluate-expression &A
29761 311^done,value="0xefffeb7c"
29763 411-data-evaluate-expression A+3
29766 511-data-evaluate-expression "A + 3"
29772 @subheading The @code{-data-list-changed-registers} Command
29773 @findex -data-list-changed-registers
29775 @subsubheading Synopsis
29778 -data-list-changed-registers
29781 Display a list of the registers that have changed.
29783 @subsubheading @value{GDBN} Command
29785 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29786 has the corresponding command @samp{gdb_changed_register_list}.
29788 @subsubheading Example
29790 On a PPC MBX board:
29798 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29799 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29802 -data-list-changed-registers
29803 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29804 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29805 "24","25","26","27","28","30","31","64","65","66","67","69"]
29810 @subheading The @code{-data-list-register-names} Command
29811 @findex -data-list-register-names
29813 @subsubheading Synopsis
29816 -data-list-register-names [ ( @var{regno} )+ ]
29819 Show a list of register names for the current target. If no arguments
29820 are given, it shows a list of the names of all the registers. If
29821 integer numbers are given as arguments, it will print a list of the
29822 names of the registers corresponding to the arguments. To ensure
29823 consistency between a register name and its number, the output list may
29824 include empty register names.
29826 @subsubheading @value{GDBN} Command
29828 @value{GDBN} does not have a command which corresponds to
29829 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29830 corresponding command @samp{gdb_regnames}.
29832 @subsubheading Example
29834 For the PPC MBX board:
29837 -data-list-register-names
29838 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29839 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29840 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29841 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29842 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29843 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29844 "", "pc","ps","cr","lr","ctr","xer"]
29846 -data-list-register-names 1 2 3
29847 ^done,register-names=["r1","r2","r3"]
29851 @subheading The @code{-data-list-register-values} Command
29852 @findex -data-list-register-values
29854 @subsubheading Synopsis
29857 -data-list-register-values
29858 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29861 Display the registers' contents. The format according to which the
29862 registers' contents are to be returned is given by @var{fmt}, followed
29863 by an optional list of numbers specifying the registers to display. A
29864 missing list of numbers indicates that the contents of all the
29865 registers must be returned. The @code{--skip-unavailable} option
29866 indicates that only the available registers are to be returned.
29868 Allowed formats for @var{fmt} are:
29885 @subsubheading @value{GDBN} Command
29887 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29888 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29890 @subsubheading Example
29892 For a PPC MBX board (note: line breaks are for readability only, they
29893 don't appear in the actual output):
29897 -data-list-register-values r 64 65
29898 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29899 @{number="65",value="0x00029002"@}]
29901 -data-list-register-values x
29902 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29903 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29904 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29905 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29906 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29907 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29908 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29909 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29910 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29911 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29912 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29913 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29914 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29915 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29916 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29917 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29918 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29919 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29920 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29921 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29922 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29923 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29924 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29925 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29926 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29927 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29928 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29929 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29930 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29931 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29932 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29933 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29934 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29935 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29936 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29937 @{number="69",value="0x20002b03"@}]
29942 @subheading The @code{-data-read-memory} Command
29943 @findex -data-read-memory
29945 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29947 @subsubheading Synopsis
29950 -data-read-memory [ -o @var{byte-offset} ]
29951 @var{address} @var{word-format} @var{word-size}
29952 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29959 @item @var{address}
29960 An expression specifying the address of the first memory word to be
29961 read. Complex expressions containing embedded white space should be
29962 quoted using the C convention.
29964 @item @var{word-format}
29965 The format to be used to print the memory words. The notation is the
29966 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29969 @item @var{word-size}
29970 The size of each memory word in bytes.
29972 @item @var{nr-rows}
29973 The number of rows in the output table.
29975 @item @var{nr-cols}
29976 The number of columns in the output table.
29979 If present, indicates that each row should include an @sc{ascii} dump. The
29980 value of @var{aschar} is used as a padding character when a byte is not a
29981 member of the printable @sc{ascii} character set (printable @sc{ascii}
29982 characters are those whose code is between 32 and 126, inclusively).
29984 @item @var{byte-offset}
29985 An offset to add to the @var{address} before fetching memory.
29988 This command displays memory contents as a table of @var{nr-rows} by
29989 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29990 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29991 (returned as @samp{total-bytes}). Should less than the requested number
29992 of bytes be returned by the target, the missing words are identified
29993 using @samp{N/A}. The number of bytes read from the target is returned
29994 in @samp{nr-bytes} and the starting address used to read memory in
29997 The address of the next/previous row or page is available in
29998 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30001 @subsubheading @value{GDBN} Command
30003 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30004 @samp{gdb_get_mem} memory read command.
30006 @subsubheading Example
30008 Read six bytes of memory starting at @code{bytes+6} but then offset by
30009 @code{-6} bytes. Format as three rows of two columns. One byte per
30010 word. Display each word in hex.
30014 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30015 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30016 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30017 prev-page="0x0000138a",memory=[
30018 @{addr="0x00001390",data=["0x00","0x01"]@},
30019 @{addr="0x00001392",data=["0x02","0x03"]@},
30020 @{addr="0x00001394",data=["0x04","0x05"]@}]
30024 Read two bytes of memory starting at address @code{shorts + 64} and
30025 display as a single word formatted in decimal.
30029 5-data-read-memory shorts+64 d 2 1 1
30030 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30031 next-row="0x00001512",prev-row="0x0000150e",
30032 next-page="0x00001512",prev-page="0x0000150e",memory=[
30033 @{addr="0x00001510",data=["128"]@}]
30037 Read thirty two bytes of memory starting at @code{bytes+16} and format
30038 as eight rows of four columns. Include a string encoding with @samp{x}
30039 used as the non-printable character.
30043 4-data-read-memory bytes+16 x 1 8 4 x
30044 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30045 next-row="0x000013c0",prev-row="0x0000139c",
30046 next-page="0x000013c0",prev-page="0x00001380",memory=[
30047 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30048 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30049 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30050 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30051 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30052 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30053 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30054 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30058 @subheading The @code{-data-read-memory-bytes} Command
30059 @findex -data-read-memory-bytes
30061 @subsubheading Synopsis
30064 -data-read-memory-bytes [ -o @var{offset} ]
30065 @var{address} @var{count}
30072 @item @var{address}
30073 An expression specifying the address of the first addressable memory unit
30074 to be read. Complex expressions containing embedded white space should be
30075 quoted using the C convention.
30078 The number of addressable memory units to read. This should be an integer
30082 The offset relative to @var{address} at which to start reading. This
30083 should be an integer literal. This option is provided so that a frontend
30084 is not required to first evaluate address and then perform address
30085 arithmetics itself.
30089 This command attempts to read all accessible memory regions in the
30090 specified range. First, all regions marked as unreadable in the memory
30091 map (if one is defined) will be skipped. @xref{Memory Region
30092 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30093 regions. For each one, if reading full region results in an errors,
30094 @value{GDBN} will try to read a subset of the region.
30096 In general, every single memory unit in the region may be readable or not,
30097 and the only way to read every readable unit is to try a read at
30098 every address, which is not practical. Therefore, @value{GDBN} will
30099 attempt to read all accessible memory units at either beginning or the end
30100 of the region, using a binary division scheme. This heuristic works
30101 well for reading accross a memory map boundary. Note that if a region
30102 has a readable range that is neither at the beginning or the end,
30103 @value{GDBN} will not read it.
30105 The result record (@pxref{GDB/MI Result Records}) that is output of
30106 the command includes a field named @samp{memory} whose content is a
30107 list of tuples. Each tuple represent a successfully read memory block
30108 and has the following fields:
30112 The start address of the memory block, as hexadecimal literal.
30115 The end address of the memory block, as hexadecimal literal.
30118 The offset of the memory block, as hexadecimal literal, relative to
30119 the start address passed to @code{-data-read-memory-bytes}.
30122 The contents of the memory block, in hex.
30128 @subsubheading @value{GDBN} Command
30130 The corresponding @value{GDBN} command is @samp{x}.
30132 @subsubheading Example
30136 -data-read-memory-bytes &a 10
30137 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30139 contents="01000000020000000300"@}]
30144 @subheading The @code{-data-write-memory-bytes} Command
30145 @findex -data-write-memory-bytes
30147 @subsubheading Synopsis
30150 -data-write-memory-bytes @var{address} @var{contents}
30151 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30158 @item @var{address}
30159 An expression specifying the address of the first addressable memory unit
30160 to be written. Complex expressions containing embedded white space should
30161 be quoted using the C convention.
30163 @item @var{contents}
30164 The hex-encoded data to write. It is an error if @var{contents} does
30165 not represent an integral number of addressable memory units.
30168 Optional argument indicating the number of addressable memory units to be
30169 written. If @var{count} is greater than @var{contents}' length,
30170 @value{GDBN} will repeatedly write @var{contents} until it fills
30171 @var{count} memory units.
30175 @subsubheading @value{GDBN} Command
30177 There's no corresponding @value{GDBN} command.
30179 @subsubheading Example
30183 -data-write-memory-bytes &a "aabbccdd"
30190 -data-write-memory-bytes &a "aabbccdd" 16e
30195 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30196 @node GDB/MI Tracepoint Commands
30197 @section @sc{gdb/mi} Tracepoint Commands
30199 The commands defined in this section implement MI support for
30200 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30202 @subheading The @code{-trace-find} Command
30203 @findex -trace-find
30205 @subsubheading Synopsis
30208 -trace-find @var{mode} [@var{parameters}@dots{}]
30211 Find a trace frame using criteria defined by @var{mode} and
30212 @var{parameters}. The following table lists permissible
30213 modes and their parameters. For details of operation, see @ref{tfind}.
30218 No parameters are required. Stops examining trace frames.
30221 An integer is required as parameter. Selects tracepoint frame with
30224 @item tracepoint-number
30225 An integer is required as parameter. Finds next
30226 trace frame that corresponds to tracepoint with the specified number.
30229 An address is required as parameter. Finds
30230 next trace frame that corresponds to any tracepoint at the specified
30233 @item pc-inside-range
30234 Two addresses are required as parameters. Finds next trace
30235 frame that corresponds to a tracepoint at an address inside the
30236 specified range. Both bounds are considered to be inside the range.
30238 @item pc-outside-range
30239 Two addresses are required as parameters. Finds
30240 next trace frame that corresponds to a tracepoint at an address outside
30241 the specified range. Both bounds are considered to be inside the range.
30244 Line specification is required as parameter. @xref{Specify Location}.
30245 Finds next trace frame that corresponds to a tracepoint at
30246 the specified location.
30250 If @samp{none} was passed as @var{mode}, the response does not
30251 have fields. Otherwise, the response may have the following fields:
30255 This field has either @samp{0} or @samp{1} as the value, depending
30256 on whether a matching tracepoint was found.
30259 The index of the found traceframe. This field is present iff
30260 the @samp{found} field has value of @samp{1}.
30263 The index of the found tracepoint. This field is present iff
30264 the @samp{found} field has value of @samp{1}.
30267 The information about the frame corresponding to the found trace
30268 frame. This field is present only if a trace frame was found.
30269 @xref{GDB/MI Frame Information}, for description of this field.
30273 @subsubheading @value{GDBN} Command
30275 The corresponding @value{GDBN} command is @samp{tfind}.
30277 @subheading -trace-define-variable
30278 @findex -trace-define-variable
30280 @subsubheading Synopsis
30283 -trace-define-variable @var{name} [ @var{value} ]
30286 Create trace variable @var{name} if it does not exist. If
30287 @var{value} is specified, sets the initial value of the specified
30288 trace variable to that value. Note that the @var{name} should start
30289 with the @samp{$} character.
30291 @subsubheading @value{GDBN} Command
30293 The corresponding @value{GDBN} command is @samp{tvariable}.
30295 @subheading The @code{-trace-frame-collected} Command
30296 @findex -trace-frame-collected
30298 @subsubheading Synopsis
30301 -trace-frame-collected
30302 [--var-print-values @var{var_pval}]
30303 [--comp-print-values @var{comp_pval}]
30304 [--registers-format @var{regformat}]
30305 [--memory-contents]
30308 This command returns the set of collected objects, register names,
30309 trace state variable names, memory ranges and computed expressions
30310 that have been collected at a particular trace frame. The optional
30311 parameters to the command affect the output format in different ways.
30312 See the output description table below for more details.
30314 The reported names can be used in the normal manner to create
30315 varobjs and inspect the objects themselves. The items returned by
30316 this command are categorized so that it is clear which is a variable,
30317 which is a register, which is a trace state variable, which is a
30318 memory range and which is a computed expression.
30320 For instance, if the actions were
30322 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30323 collect *(int*)0xaf02bef0@@40
30327 the object collected in its entirety would be @code{myVar}. The
30328 object @code{myArray} would be partially collected, because only the
30329 element at index @code{myIndex} would be collected. The remaining
30330 objects would be computed expressions.
30332 An example output would be:
30336 -trace-frame-collected
30338 explicit-variables=[@{name="myVar",value="1"@}],
30339 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30340 @{name="myObj.field",value="0"@},
30341 @{name="myPtr->field",value="1"@},
30342 @{name="myCount + 2",value="3"@},
30343 @{name="$tvar1 + 1",value="43970027"@}],
30344 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30345 @{number="1",value="0x0"@},
30346 @{number="2",value="0x4"@},
30348 @{number="125",value="0x0"@}],
30349 tvars=[@{name="$tvar1",current="43970026"@}],
30350 memory=[@{address="0x0000000000602264",length="4"@},
30351 @{address="0x0000000000615bc0",length="4"@}]
30358 @item explicit-variables
30359 The set of objects that have been collected in their entirety (as
30360 opposed to collecting just a few elements of an array or a few struct
30361 members). For each object, its name and value are printed.
30362 The @code{--var-print-values} option affects how or whether the value
30363 field is output. If @var{var_pval} is 0, then print only the names;
30364 if it is 1, print also their values; and if it is 2, print the name,
30365 type and value for simple data types, and the name and type for
30366 arrays, structures and unions.
30368 @item computed-expressions
30369 The set of computed expressions that have been collected at the
30370 current trace frame. The @code{--comp-print-values} option affects
30371 this set like the @code{--var-print-values} option affects the
30372 @code{explicit-variables} set. See above.
30375 The registers that have been collected at the current trace frame.
30376 For each register collected, the name and current value are returned.
30377 The value is formatted according to the @code{--registers-format}
30378 option. See the @command{-data-list-register-values} command for a
30379 list of the allowed formats. The default is @samp{x}.
30382 The trace state variables that have been collected at the current
30383 trace frame. For each trace state variable collected, the name and
30384 current value are returned.
30387 The set of memory ranges that have been collected at the current trace
30388 frame. Its content is a list of tuples. Each tuple represents a
30389 collected memory range and has the following fields:
30393 The start address of the memory range, as hexadecimal literal.
30396 The length of the memory range, as decimal literal.
30399 The contents of the memory block, in hex. This field is only present
30400 if the @code{--memory-contents} option is specified.
30406 @subsubheading @value{GDBN} Command
30408 There is no corresponding @value{GDBN} command.
30410 @subsubheading Example
30412 @subheading -trace-list-variables
30413 @findex -trace-list-variables
30415 @subsubheading Synopsis
30418 -trace-list-variables
30421 Return a table of all defined trace variables. Each element of the
30422 table has the following fields:
30426 The name of the trace variable. This field is always present.
30429 The initial value. This is a 64-bit signed integer. This
30430 field is always present.
30433 The value the trace variable has at the moment. This is a 64-bit
30434 signed integer. This field is absent iff current value is
30435 not defined, for example if the trace was never run, or is
30440 @subsubheading @value{GDBN} Command
30442 The corresponding @value{GDBN} command is @samp{tvariables}.
30444 @subsubheading Example
30448 -trace-list-variables
30449 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30450 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30451 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30452 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30453 body=[variable=@{name="$trace_timestamp",initial="0"@}
30454 variable=@{name="$foo",initial="10",current="15"@}]@}
30458 @subheading -trace-save
30459 @findex -trace-save
30461 @subsubheading Synopsis
30464 -trace-save [-r ] @var{filename}
30467 Saves the collected trace data to @var{filename}. Without the
30468 @samp{-r} option, the data is downloaded from the target and saved
30469 in a local file. With the @samp{-r} option the target is asked
30470 to perform the save.
30472 @subsubheading @value{GDBN} Command
30474 The corresponding @value{GDBN} command is @samp{tsave}.
30477 @subheading -trace-start
30478 @findex -trace-start
30480 @subsubheading Synopsis
30486 Starts a tracing experiments. The result of this command does not
30489 @subsubheading @value{GDBN} Command
30491 The corresponding @value{GDBN} command is @samp{tstart}.
30493 @subheading -trace-status
30494 @findex -trace-status
30496 @subsubheading Synopsis
30502 Obtains the status of a tracing experiment. The result may include
30503 the following fields:
30508 May have a value of either @samp{0}, when no tracing operations are
30509 supported, @samp{1}, when all tracing operations are supported, or
30510 @samp{file} when examining trace file. In the latter case, examining
30511 of trace frame is possible but new tracing experiement cannot be
30512 started. This field is always present.
30515 May have a value of either @samp{0} or @samp{1} depending on whether
30516 tracing experiement is in progress on target. This field is present
30517 if @samp{supported} field is not @samp{0}.
30520 Report the reason why the tracing was stopped last time. This field
30521 may be absent iff tracing was never stopped on target yet. The
30522 value of @samp{request} means the tracing was stopped as result of
30523 the @code{-trace-stop} command. The value of @samp{overflow} means
30524 the tracing buffer is full. The value of @samp{disconnection} means
30525 tracing was automatically stopped when @value{GDBN} has disconnected.
30526 The value of @samp{passcount} means tracing was stopped when a
30527 tracepoint was passed a maximal number of times for that tracepoint.
30528 This field is present if @samp{supported} field is not @samp{0}.
30530 @item stopping-tracepoint
30531 The number of tracepoint whose passcount as exceeded. This field is
30532 present iff the @samp{stop-reason} field has the value of
30536 @itemx frames-created
30537 The @samp{frames} field is a count of the total number of trace frames
30538 in the trace buffer, while @samp{frames-created} is the total created
30539 during the run, including ones that were discarded, such as when a
30540 circular trace buffer filled up. Both fields are optional.
30544 These fields tell the current size of the tracing buffer and the
30545 remaining space. These fields are optional.
30548 The value of the circular trace buffer flag. @code{1} means that the
30549 trace buffer is circular and old trace frames will be discarded if
30550 necessary to make room, @code{0} means that the trace buffer is linear
30554 The value of the disconnected tracing flag. @code{1} means that
30555 tracing will continue after @value{GDBN} disconnects, @code{0} means
30556 that the trace run will stop.
30559 The filename of the trace file being examined. This field is
30560 optional, and only present when examining a trace file.
30564 @subsubheading @value{GDBN} Command
30566 The corresponding @value{GDBN} command is @samp{tstatus}.
30568 @subheading -trace-stop
30569 @findex -trace-stop
30571 @subsubheading Synopsis
30577 Stops a tracing experiment. The result of this command has the same
30578 fields as @code{-trace-status}, except that the @samp{supported} and
30579 @samp{running} fields are not output.
30581 @subsubheading @value{GDBN} Command
30583 The corresponding @value{GDBN} command is @samp{tstop}.
30586 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30587 @node GDB/MI Symbol Query
30588 @section @sc{gdb/mi} Symbol Query Commands
30592 @subheading The @code{-symbol-info-address} Command
30593 @findex -symbol-info-address
30595 @subsubheading Synopsis
30598 -symbol-info-address @var{symbol}
30601 Describe where @var{symbol} is stored.
30603 @subsubheading @value{GDBN} Command
30605 The corresponding @value{GDBN} command is @samp{info address}.
30607 @subsubheading Example
30611 @subheading The @code{-symbol-info-file} Command
30612 @findex -symbol-info-file
30614 @subsubheading Synopsis
30620 Show the file for the symbol.
30622 @subsubheading @value{GDBN} Command
30624 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30625 @samp{gdb_find_file}.
30627 @subsubheading Example
30631 @subheading The @code{-symbol-info-function} Command
30632 @findex -symbol-info-function
30634 @subsubheading Synopsis
30637 -symbol-info-function
30640 Show which function the symbol lives in.
30642 @subsubheading @value{GDBN} Command
30644 @samp{gdb_get_function} in @code{gdbtk}.
30646 @subsubheading Example
30650 @subheading The @code{-symbol-info-line} Command
30651 @findex -symbol-info-line
30653 @subsubheading Synopsis
30659 Show the core addresses of the code for a source line.
30661 @subsubheading @value{GDBN} Command
30663 The corresponding @value{GDBN} command is @samp{info line}.
30664 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30666 @subsubheading Example
30670 @subheading The @code{-symbol-info-symbol} Command
30671 @findex -symbol-info-symbol
30673 @subsubheading Synopsis
30676 -symbol-info-symbol @var{addr}
30679 Describe what symbol is at location @var{addr}.
30681 @subsubheading @value{GDBN} Command
30683 The corresponding @value{GDBN} command is @samp{info symbol}.
30685 @subsubheading Example
30689 @subheading The @code{-symbol-list-functions} Command
30690 @findex -symbol-list-functions
30692 @subsubheading Synopsis
30695 -symbol-list-functions
30698 List the functions in the executable.
30700 @subsubheading @value{GDBN} Command
30702 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30703 @samp{gdb_search} in @code{gdbtk}.
30705 @subsubheading Example
30710 @subheading The @code{-symbol-list-lines} Command
30711 @findex -symbol-list-lines
30713 @subsubheading Synopsis
30716 -symbol-list-lines @var{filename}
30719 Print the list of lines that contain code and their associated program
30720 addresses for the given source filename. The entries are sorted in
30721 ascending PC order.
30723 @subsubheading @value{GDBN} Command
30725 There is no corresponding @value{GDBN} command.
30727 @subsubheading Example
30730 -symbol-list-lines basics.c
30731 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30737 @subheading The @code{-symbol-list-types} Command
30738 @findex -symbol-list-types
30740 @subsubheading Synopsis
30746 List all the type names.
30748 @subsubheading @value{GDBN} Command
30750 The corresponding commands are @samp{info types} in @value{GDBN},
30751 @samp{gdb_search} in @code{gdbtk}.
30753 @subsubheading Example
30757 @subheading The @code{-symbol-list-variables} Command
30758 @findex -symbol-list-variables
30760 @subsubheading Synopsis
30763 -symbol-list-variables
30766 List all the global and static variable names.
30768 @subsubheading @value{GDBN} Command
30770 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30772 @subsubheading Example
30776 @subheading The @code{-symbol-locate} Command
30777 @findex -symbol-locate
30779 @subsubheading Synopsis
30785 @subsubheading @value{GDBN} Command
30787 @samp{gdb_loc} in @code{gdbtk}.
30789 @subsubheading Example
30793 @subheading The @code{-symbol-type} Command
30794 @findex -symbol-type
30796 @subsubheading Synopsis
30799 -symbol-type @var{variable}
30802 Show type of @var{variable}.
30804 @subsubheading @value{GDBN} Command
30806 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30807 @samp{gdb_obj_variable}.
30809 @subsubheading Example
30814 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30815 @node GDB/MI File Commands
30816 @section @sc{gdb/mi} File Commands
30818 This section describes the GDB/MI commands to specify executable file names
30819 and to read in and obtain symbol table information.
30821 @subheading The @code{-file-exec-and-symbols} Command
30822 @findex -file-exec-and-symbols
30824 @subsubheading Synopsis
30827 -file-exec-and-symbols @var{file}
30830 Specify the executable file to be debugged. This file is the one from
30831 which the symbol table is also read. If no file is specified, the
30832 command clears the executable and symbol information. If breakpoints
30833 are set when using this command with no arguments, @value{GDBN} will produce
30834 error messages. Otherwise, no output is produced, except a completion
30837 @subsubheading @value{GDBN} Command
30839 The corresponding @value{GDBN} command is @samp{file}.
30841 @subsubheading Example
30845 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30851 @subheading The @code{-file-exec-file} Command
30852 @findex -file-exec-file
30854 @subsubheading Synopsis
30857 -file-exec-file @var{file}
30860 Specify the executable file to be debugged. Unlike
30861 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30862 from this file. If used without argument, @value{GDBN} clears the information
30863 about the executable file. No output is produced, except a completion
30866 @subsubheading @value{GDBN} Command
30868 The corresponding @value{GDBN} command is @samp{exec-file}.
30870 @subsubheading Example
30874 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30881 @subheading The @code{-file-list-exec-sections} Command
30882 @findex -file-list-exec-sections
30884 @subsubheading Synopsis
30887 -file-list-exec-sections
30890 List the sections of the current executable file.
30892 @subsubheading @value{GDBN} Command
30894 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30895 information as this command. @code{gdbtk} has a corresponding command
30896 @samp{gdb_load_info}.
30898 @subsubheading Example
30903 @subheading The @code{-file-list-exec-source-file} Command
30904 @findex -file-list-exec-source-file
30906 @subsubheading Synopsis
30909 -file-list-exec-source-file
30912 List the line number, the current source file, and the absolute path
30913 to the current source file for the current executable. The macro
30914 information field has a value of @samp{1} or @samp{0} depending on
30915 whether or not the file includes preprocessor macro information.
30917 @subsubheading @value{GDBN} Command
30919 The @value{GDBN} equivalent is @samp{info source}
30921 @subsubheading Example
30925 123-file-list-exec-source-file
30926 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30931 @subheading The @code{-file-list-exec-source-files} Command
30932 @findex -file-list-exec-source-files
30934 @subsubheading Synopsis
30937 -file-list-exec-source-files
30940 List the source files for the current executable.
30942 It will always output both the filename and fullname (absolute file
30943 name) of a source file.
30945 @subsubheading @value{GDBN} Command
30947 The @value{GDBN} equivalent is @samp{info sources}.
30948 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30950 @subsubheading Example
30953 -file-list-exec-source-files
30955 @{file=foo.c,fullname=/home/foo.c@},
30956 @{file=/home/bar.c,fullname=/home/bar.c@},
30957 @{file=gdb_could_not_find_fullpath.c@}]
30962 @subheading The @code{-file-list-shared-libraries} Command
30963 @findex -file-list-shared-libraries
30965 @subsubheading Synopsis
30968 -file-list-shared-libraries
30971 List the shared libraries in the program.
30973 @subsubheading @value{GDBN} Command
30975 The corresponding @value{GDBN} command is @samp{info shared}.
30977 @subsubheading Example
30981 @subheading The @code{-file-list-symbol-files} Command
30982 @findex -file-list-symbol-files
30984 @subsubheading Synopsis
30987 -file-list-symbol-files
30992 @subsubheading @value{GDBN} Command
30994 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30996 @subsubheading Example
31001 @subheading The @code{-file-symbol-file} Command
31002 @findex -file-symbol-file
31004 @subsubheading Synopsis
31007 -file-symbol-file @var{file}
31010 Read symbol table info from the specified @var{file} argument. When
31011 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31012 produced, except for a completion notification.
31014 @subsubheading @value{GDBN} Command
31016 The corresponding @value{GDBN} command is @samp{symbol-file}.
31018 @subsubheading Example
31022 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31028 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31029 @node GDB/MI Memory Overlay Commands
31030 @section @sc{gdb/mi} Memory Overlay Commands
31032 The memory overlay commands are not implemented.
31034 @c @subheading -overlay-auto
31036 @c @subheading -overlay-list-mapping-state
31038 @c @subheading -overlay-list-overlays
31040 @c @subheading -overlay-map
31042 @c @subheading -overlay-off
31044 @c @subheading -overlay-on
31046 @c @subheading -overlay-unmap
31048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31049 @node GDB/MI Signal Handling Commands
31050 @section @sc{gdb/mi} Signal Handling Commands
31052 Signal handling commands are not implemented.
31054 @c @subheading -signal-handle
31056 @c @subheading -signal-list-handle-actions
31058 @c @subheading -signal-list-signal-types
31062 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31063 @node GDB/MI Target Manipulation
31064 @section @sc{gdb/mi} Target Manipulation Commands
31067 @subheading The @code{-target-attach} Command
31068 @findex -target-attach
31070 @subsubheading Synopsis
31073 -target-attach @var{pid} | @var{gid} | @var{file}
31076 Attach to a process @var{pid} or a file @var{file} outside of
31077 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31078 group, the id previously returned by
31079 @samp{-list-thread-groups --available} must be used.
31081 @subsubheading @value{GDBN} Command
31083 The corresponding @value{GDBN} command is @samp{attach}.
31085 @subsubheading Example
31089 =thread-created,id="1"
31090 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31096 @subheading The @code{-target-compare-sections} Command
31097 @findex -target-compare-sections
31099 @subsubheading Synopsis
31102 -target-compare-sections [ @var{section} ]
31105 Compare data of section @var{section} on target to the exec file.
31106 Without the argument, all sections are compared.
31108 @subsubheading @value{GDBN} Command
31110 The @value{GDBN} equivalent is @samp{compare-sections}.
31112 @subsubheading Example
31117 @subheading The @code{-target-detach} Command
31118 @findex -target-detach
31120 @subsubheading Synopsis
31123 -target-detach [ @var{pid} | @var{gid} ]
31126 Detach from the remote target which normally resumes its execution.
31127 If either @var{pid} or @var{gid} is specified, detaches from either
31128 the specified process, or specified thread group. There's no output.
31130 @subsubheading @value{GDBN} Command
31132 The corresponding @value{GDBN} command is @samp{detach}.
31134 @subsubheading Example
31144 @subheading The @code{-target-disconnect} Command
31145 @findex -target-disconnect
31147 @subsubheading Synopsis
31153 Disconnect from the remote target. There's no output and the target is
31154 generally not resumed.
31156 @subsubheading @value{GDBN} Command
31158 The corresponding @value{GDBN} command is @samp{disconnect}.
31160 @subsubheading Example
31170 @subheading The @code{-target-download} Command
31171 @findex -target-download
31173 @subsubheading Synopsis
31179 Loads the executable onto the remote target.
31180 It prints out an update message every half second, which includes the fields:
31184 The name of the section.
31186 The size of what has been sent so far for that section.
31188 The size of the section.
31190 The total size of what was sent so far (the current and the previous sections).
31192 The size of the overall executable to download.
31196 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31197 @sc{gdb/mi} Output Syntax}).
31199 In addition, it prints the name and size of the sections, as they are
31200 downloaded. These messages include the following fields:
31204 The name of the section.
31206 The size of the section.
31208 The size of the overall executable to download.
31212 At the end, a summary is printed.
31214 @subsubheading @value{GDBN} Command
31216 The corresponding @value{GDBN} command is @samp{load}.
31218 @subsubheading Example
31220 Note: each status message appears on a single line. Here the messages
31221 have been broken down so that they can fit onto a page.
31226 +download,@{section=".text",section-size="6668",total-size="9880"@}
31227 +download,@{section=".text",section-sent="512",section-size="6668",
31228 total-sent="512",total-size="9880"@}
31229 +download,@{section=".text",section-sent="1024",section-size="6668",
31230 total-sent="1024",total-size="9880"@}
31231 +download,@{section=".text",section-sent="1536",section-size="6668",
31232 total-sent="1536",total-size="9880"@}
31233 +download,@{section=".text",section-sent="2048",section-size="6668",
31234 total-sent="2048",total-size="9880"@}
31235 +download,@{section=".text",section-sent="2560",section-size="6668",
31236 total-sent="2560",total-size="9880"@}
31237 +download,@{section=".text",section-sent="3072",section-size="6668",
31238 total-sent="3072",total-size="9880"@}
31239 +download,@{section=".text",section-sent="3584",section-size="6668",
31240 total-sent="3584",total-size="9880"@}
31241 +download,@{section=".text",section-sent="4096",section-size="6668",
31242 total-sent="4096",total-size="9880"@}
31243 +download,@{section=".text",section-sent="4608",section-size="6668",
31244 total-sent="4608",total-size="9880"@}
31245 +download,@{section=".text",section-sent="5120",section-size="6668",
31246 total-sent="5120",total-size="9880"@}
31247 +download,@{section=".text",section-sent="5632",section-size="6668",
31248 total-sent="5632",total-size="9880"@}
31249 +download,@{section=".text",section-sent="6144",section-size="6668",
31250 total-sent="6144",total-size="9880"@}
31251 +download,@{section=".text",section-sent="6656",section-size="6668",
31252 total-sent="6656",total-size="9880"@}
31253 +download,@{section=".init",section-size="28",total-size="9880"@}
31254 +download,@{section=".fini",section-size="28",total-size="9880"@}
31255 +download,@{section=".data",section-size="3156",total-size="9880"@}
31256 +download,@{section=".data",section-sent="512",section-size="3156",
31257 total-sent="7236",total-size="9880"@}
31258 +download,@{section=".data",section-sent="1024",section-size="3156",
31259 total-sent="7748",total-size="9880"@}
31260 +download,@{section=".data",section-sent="1536",section-size="3156",
31261 total-sent="8260",total-size="9880"@}
31262 +download,@{section=".data",section-sent="2048",section-size="3156",
31263 total-sent="8772",total-size="9880"@}
31264 +download,@{section=".data",section-sent="2560",section-size="3156",
31265 total-sent="9284",total-size="9880"@}
31266 +download,@{section=".data",section-sent="3072",section-size="3156",
31267 total-sent="9796",total-size="9880"@}
31268 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31275 @subheading The @code{-target-exec-status} Command
31276 @findex -target-exec-status
31278 @subsubheading Synopsis
31281 -target-exec-status
31284 Provide information on the state of the target (whether it is running or
31285 not, for instance).
31287 @subsubheading @value{GDBN} Command
31289 There's no equivalent @value{GDBN} command.
31291 @subsubheading Example
31295 @subheading The @code{-target-list-available-targets} Command
31296 @findex -target-list-available-targets
31298 @subsubheading Synopsis
31301 -target-list-available-targets
31304 List the possible targets to connect to.
31306 @subsubheading @value{GDBN} Command
31308 The corresponding @value{GDBN} command is @samp{help target}.
31310 @subsubheading Example
31314 @subheading The @code{-target-list-current-targets} Command
31315 @findex -target-list-current-targets
31317 @subsubheading Synopsis
31320 -target-list-current-targets
31323 Describe the current target.
31325 @subsubheading @value{GDBN} Command
31327 The corresponding information is printed by @samp{info file} (among
31330 @subsubheading Example
31334 @subheading The @code{-target-list-parameters} Command
31335 @findex -target-list-parameters
31337 @subsubheading Synopsis
31340 -target-list-parameters
31346 @subsubheading @value{GDBN} Command
31350 @subsubheading Example
31354 @subheading The @code{-target-select} Command
31355 @findex -target-select
31357 @subsubheading Synopsis
31360 -target-select @var{type} @var{parameters @dots{}}
31363 Connect @value{GDBN} to the remote target. This command takes two args:
31367 The type of target, for instance @samp{remote}, etc.
31368 @item @var{parameters}
31369 Device names, host names and the like. @xref{Target Commands, ,
31370 Commands for Managing Targets}, for more details.
31373 The output is a connection notification, followed by the address at
31374 which the target program is, in the following form:
31377 ^connected,addr="@var{address}",func="@var{function name}",
31378 args=[@var{arg list}]
31381 @subsubheading @value{GDBN} Command
31383 The corresponding @value{GDBN} command is @samp{target}.
31385 @subsubheading Example
31389 -target-select remote /dev/ttya
31390 ^connected,addr="0xfe00a300",func="??",args=[]
31394 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31395 @node GDB/MI File Transfer Commands
31396 @section @sc{gdb/mi} File Transfer Commands
31399 @subheading The @code{-target-file-put} Command
31400 @findex -target-file-put
31402 @subsubheading Synopsis
31405 -target-file-put @var{hostfile} @var{targetfile}
31408 Copy file @var{hostfile} from the host system (the machine running
31409 @value{GDBN}) to @var{targetfile} on the target system.
31411 @subsubheading @value{GDBN} Command
31413 The corresponding @value{GDBN} command is @samp{remote put}.
31415 @subsubheading Example
31419 -target-file-put localfile remotefile
31425 @subheading The @code{-target-file-get} Command
31426 @findex -target-file-get
31428 @subsubheading Synopsis
31431 -target-file-get @var{targetfile} @var{hostfile}
31434 Copy file @var{targetfile} from the target system to @var{hostfile}
31435 on the host system.
31437 @subsubheading @value{GDBN} Command
31439 The corresponding @value{GDBN} command is @samp{remote get}.
31441 @subsubheading Example
31445 -target-file-get remotefile localfile
31451 @subheading The @code{-target-file-delete} Command
31452 @findex -target-file-delete
31454 @subsubheading Synopsis
31457 -target-file-delete @var{targetfile}
31460 Delete @var{targetfile} from the target system.
31462 @subsubheading @value{GDBN} Command
31464 The corresponding @value{GDBN} command is @samp{remote delete}.
31466 @subsubheading Example
31470 -target-file-delete remotefile
31476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31477 @node GDB/MI Ada Exceptions Commands
31478 @section Ada Exceptions @sc{gdb/mi} Commands
31480 @subheading The @code{-info-ada-exceptions} Command
31481 @findex -info-ada-exceptions
31483 @subsubheading Synopsis
31486 -info-ada-exceptions [ @var{regexp}]
31489 List all Ada exceptions defined within the program being debugged.
31490 With a regular expression @var{regexp}, only those exceptions whose
31491 names match @var{regexp} are listed.
31493 @subsubheading @value{GDBN} Command
31495 The corresponding @value{GDBN} command is @samp{info exceptions}.
31497 @subsubheading Result
31499 The result is a table of Ada exceptions. The following columns are
31500 defined for each exception:
31504 The name of the exception.
31507 The address of the exception.
31511 @subsubheading Example
31514 -info-ada-exceptions aint
31515 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31516 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31517 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31518 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31519 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31522 @subheading Catching Ada Exceptions
31524 The commands describing how to ask @value{GDBN} to stop when a program
31525 raises an exception are described at @ref{Ada Exception GDB/MI
31526 Catchpoint Commands}.
31529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31530 @node GDB/MI Support Commands
31531 @section @sc{gdb/mi} Support Commands
31533 Since new commands and features get regularly added to @sc{gdb/mi},
31534 some commands are available to help front-ends query the debugger
31535 about support for these capabilities. Similarly, it is also possible
31536 to query @value{GDBN} about target support of certain features.
31538 @subheading The @code{-info-gdb-mi-command} Command
31539 @cindex @code{-info-gdb-mi-command}
31540 @findex -info-gdb-mi-command
31542 @subsubheading Synopsis
31545 -info-gdb-mi-command @var{cmd_name}
31548 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31550 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31551 is technically not part of the command name (@pxref{GDB/MI Input
31552 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31553 for ease of use, this command also accepts the form with the leading
31556 @subsubheading @value{GDBN} Command
31558 There is no corresponding @value{GDBN} command.
31560 @subsubheading Result
31562 The result is a tuple. There is currently only one field:
31566 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31567 @code{"false"} otherwise.
31571 @subsubheading Example
31573 Here is an example where the @sc{gdb/mi} command does not exist:
31576 -info-gdb-mi-command unsupported-command
31577 ^done,command=@{exists="false"@}
31581 And here is an example where the @sc{gdb/mi} command is known
31585 -info-gdb-mi-command symbol-list-lines
31586 ^done,command=@{exists="true"@}
31589 @subheading The @code{-list-features} Command
31590 @findex -list-features
31591 @cindex supported @sc{gdb/mi} features, list
31593 Returns a list of particular features of the MI protocol that
31594 this version of gdb implements. A feature can be a command,
31595 or a new field in an output of some command, or even an
31596 important bugfix. While a frontend can sometimes detect presence
31597 of a feature at runtime, it is easier to perform detection at debugger
31600 The command returns a list of strings, with each string naming an
31601 available feature. Each returned string is just a name, it does not
31602 have any internal structure. The list of possible feature names
31608 (gdb) -list-features
31609 ^done,result=["feature1","feature2"]
31612 The current list of features is:
31615 @item frozen-varobjs
31616 Indicates support for the @code{-var-set-frozen} command, as well
31617 as possible presense of the @code{frozen} field in the output
31618 of @code{-varobj-create}.
31619 @item pending-breakpoints
31620 Indicates support for the @option{-f} option to the @code{-break-insert}
31623 Indicates Python scripting support, Python-based
31624 pretty-printing commands, and possible presence of the
31625 @samp{display_hint} field in the output of @code{-var-list-children}
31627 Indicates support for the @code{-thread-info} command.
31628 @item data-read-memory-bytes
31629 Indicates support for the @code{-data-read-memory-bytes} and the
31630 @code{-data-write-memory-bytes} commands.
31631 @item breakpoint-notifications
31632 Indicates that changes to breakpoints and breakpoints created via the
31633 CLI will be announced via async records.
31634 @item ada-task-info
31635 Indicates support for the @code{-ada-task-info} command.
31636 @item language-option
31637 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31638 option (@pxref{Context management}).
31639 @item info-gdb-mi-command
31640 Indicates support for the @code{-info-gdb-mi-command} command.
31641 @item undefined-command-error-code
31642 Indicates support for the "undefined-command" error code in error result
31643 records, produced when trying to execute an undefined @sc{gdb/mi} command
31644 (@pxref{GDB/MI Result Records}).
31645 @item exec-run-start-option
31646 Indicates that the @code{-exec-run} command supports the @option{--start}
31647 option (@pxref{GDB/MI Program Execution}).
31650 @subheading The @code{-list-target-features} Command
31651 @findex -list-target-features
31653 Returns a list of particular features that are supported by the
31654 target. Those features affect the permitted MI commands, but
31655 unlike the features reported by the @code{-list-features} command, the
31656 features depend on which target GDB is using at the moment. Whenever
31657 a target can change, due to commands such as @code{-target-select},
31658 @code{-target-attach} or @code{-exec-run}, the list of target features
31659 may change, and the frontend should obtain it again.
31663 (gdb) -list-target-features
31664 ^done,result=["async"]
31667 The current list of features is:
31671 Indicates that the target is capable of asynchronous command
31672 execution, which means that @value{GDBN} will accept further commands
31673 while the target is running.
31676 Indicates that the target is capable of reverse execution.
31677 @xref{Reverse Execution}, for more information.
31681 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31682 @node GDB/MI Miscellaneous Commands
31683 @section Miscellaneous @sc{gdb/mi} Commands
31685 @c @subheading -gdb-complete
31687 @subheading The @code{-gdb-exit} Command
31690 @subsubheading Synopsis
31696 Exit @value{GDBN} immediately.
31698 @subsubheading @value{GDBN} Command
31700 Approximately corresponds to @samp{quit}.
31702 @subsubheading Example
31712 @subheading The @code{-exec-abort} Command
31713 @findex -exec-abort
31715 @subsubheading Synopsis
31721 Kill the inferior running program.
31723 @subsubheading @value{GDBN} Command
31725 The corresponding @value{GDBN} command is @samp{kill}.
31727 @subsubheading Example
31732 @subheading The @code{-gdb-set} Command
31735 @subsubheading Synopsis
31741 Set an internal @value{GDBN} variable.
31742 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31744 @subsubheading @value{GDBN} Command
31746 The corresponding @value{GDBN} command is @samp{set}.
31748 @subsubheading Example
31758 @subheading The @code{-gdb-show} Command
31761 @subsubheading Synopsis
31767 Show the current value of a @value{GDBN} variable.
31769 @subsubheading @value{GDBN} Command
31771 The corresponding @value{GDBN} command is @samp{show}.
31773 @subsubheading Example
31782 @c @subheading -gdb-source
31785 @subheading The @code{-gdb-version} Command
31786 @findex -gdb-version
31788 @subsubheading Synopsis
31794 Show version information for @value{GDBN}. Used mostly in testing.
31796 @subsubheading @value{GDBN} Command
31798 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31799 default shows this information when you start an interactive session.
31801 @subsubheading Example
31803 @c This example modifies the actual output from GDB to avoid overfull
31809 ~Copyright 2000 Free Software Foundation, Inc.
31810 ~GDB is free software, covered by the GNU General Public License, and
31811 ~you are welcome to change it and/or distribute copies of it under
31812 ~ certain conditions.
31813 ~Type "show copying" to see the conditions.
31814 ~There is absolutely no warranty for GDB. Type "show warranty" for
31816 ~This GDB was configured as
31817 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31822 @subheading The @code{-list-thread-groups} Command
31823 @findex -list-thread-groups
31825 @subheading Synopsis
31828 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31831 Lists thread groups (@pxref{Thread groups}). When a single thread
31832 group is passed as the argument, lists the children of that group.
31833 When several thread group are passed, lists information about those
31834 thread groups. Without any parameters, lists information about all
31835 top-level thread groups.
31837 Normally, thread groups that are being debugged are reported.
31838 With the @samp{--available} option, @value{GDBN} reports thread groups
31839 available on the target.
31841 The output of this command may have either a @samp{threads} result or
31842 a @samp{groups} result. The @samp{thread} result has a list of tuples
31843 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31844 Information}). The @samp{groups} result has a list of tuples as value,
31845 each tuple describing a thread group. If top-level groups are
31846 requested (that is, no parameter is passed), or when several groups
31847 are passed, the output always has a @samp{groups} result. The format
31848 of the @samp{group} result is described below.
31850 To reduce the number of roundtrips it's possible to list thread groups
31851 together with their children, by passing the @samp{--recurse} option
31852 and the recursion depth. Presently, only recursion depth of 1 is
31853 permitted. If this option is present, then every reported thread group
31854 will also include its children, either as @samp{group} or
31855 @samp{threads} field.
31857 In general, any combination of option and parameters is permitted, with
31858 the following caveats:
31862 When a single thread group is passed, the output will typically
31863 be the @samp{threads} result. Because threads may not contain
31864 anything, the @samp{recurse} option will be ignored.
31867 When the @samp{--available} option is passed, limited information may
31868 be available. In particular, the list of threads of a process might
31869 be inaccessible. Further, specifying specific thread groups might
31870 not give any performance advantage over listing all thread groups.
31871 The frontend should assume that @samp{-list-thread-groups --available}
31872 is always an expensive operation and cache the results.
31876 The @samp{groups} result is a list of tuples, where each tuple may
31877 have the following fields:
31881 Identifier of the thread group. This field is always present.
31882 The identifier is an opaque string; frontends should not try to
31883 convert it to an integer, even though it might look like one.
31886 The type of the thread group. At present, only @samp{process} is a
31890 The target-specific process identifier. This field is only present
31891 for thread groups of type @samp{process} and only if the process exists.
31894 The exit code of this group's last exited thread, formatted in octal.
31895 This field is only present for thread groups of type @samp{process} and
31896 only if the process is not running.
31899 The number of children this thread group has. This field may be
31900 absent for an available thread group.
31903 This field has a list of tuples as value, each tuple describing a
31904 thread. It may be present if the @samp{--recurse} option is
31905 specified, and it's actually possible to obtain the threads.
31908 This field is a list of integers, each identifying a core that one
31909 thread of the group is running on. This field may be absent if
31910 such information is not available.
31913 The name of the executable file that corresponds to this thread group.
31914 The field is only present for thread groups of type @samp{process},
31915 and only if there is a corresponding executable file.
31919 @subheading Example
31923 -list-thread-groups
31924 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31925 -list-thread-groups 17
31926 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31927 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31928 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31929 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31930 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31931 -list-thread-groups --available
31932 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31933 -list-thread-groups --available --recurse 1
31934 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31935 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31936 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31937 -list-thread-groups --available --recurse 1 17 18
31938 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31939 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31940 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31943 @subheading The @code{-info-os} Command
31946 @subsubheading Synopsis
31949 -info-os [ @var{type} ]
31952 If no argument is supplied, the command returns a table of available
31953 operating-system-specific information types. If one of these types is
31954 supplied as an argument @var{type}, then the command returns a table
31955 of data of that type.
31957 The types of information available depend on the target operating
31960 @subsubheading @value{GDBN} Command
31962 The corresponding @value{GDBN} command is @samp{info os}.
31964 @subsubheading Example
31966 When run on a @sc{gnu}/Linux system, the output will look something
31972 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31973 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31974 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31975 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31976 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31978 item=@{col0="files",col1="Listing of all file descriptors",
31979 col2="File descriptors"@},
31980 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31981 col2="Kernel modules"@},
31982 item=@{col0="msg",col1="Listing of all message queues",
31983 col2="Message queues"@},
31984 item=@{col0="processes",col1="Listing of all processes",
31985 col2="Processes"@},
31986 item=@{col0="procgroups",col1="Listing of all process groups",
31987 col2="Process groups"@},
31988 item=@{col0="semaphores",col1="Listing of all semaphores",
31989 col2="Semaphores"@},
31990 item=@{col0="shm",col1="Listing of all shared-memory regions",
31991 col2="Shared-memory regions"@},
31992 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31994 item=@{col0="threads",col1="Listing of all threads",
31998 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31999 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32000 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32001 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32002 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32003 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32004 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32005 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32007 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32008 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32012 (Note that the MI output here includes a @code{"Title"} column that
32013 does not appear in command-line @code{info os}; this column is useful
32014 for MI clients that want to enumerate the types of data, such as in a
32015 popup menu, but is needless clutter on the command line, and
32016 @code{info os} omits it.)
32018 @subheading The @code{-add-inferior} Command
32019 @findex -add-inferior
32021 @subheading Synopsis
32027 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32028 inferior is not associated with any executable. Such association may
32029 be established with the @samp{-file-exec-and-symbols} command
32030 (@pxref{GDB/MI File Commands}). The command response has a single
32031 field, @samp{inferior}, whose value is the identifier of the
32032 thread group corresponding to the new inferior.
32034 @subheading Example
32039 ^done,inferior="i3"
32042 @subheading The @code{-interpreter-exec} Command
32043 @findex -interpreter-exec
32045 @subheading Synopsis
32048 -interpreter-exec @var{interpreter} @var{command}
32050 @anchor{-interpreter-exec}
32052 Execute the specified @var{command} in the given @var{interpreter}.
32054 @subheading @value{GDBN} Command
32056 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32058 @subheading Example
32062 -interpreter-exec console "break main"
32063 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32064 &"During symbol reading, bad structure-type format.\n"
32065 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32070 @subheading The @code{-inferior-tty-set} Command
32071 @findex -inferior-tty-set
32073 @subheading Synopsis
32076 -inferior-tty-set /dev/pts/1
32079 Set terminal for future runs of the program being debugged.
32081 @subheading @value{GDBN} Command
32083 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32085 @subheading Example
32089 -inferior-tty-set /dev/pts/1
32094 @subheading The @code{-inferior-tty-show} Command
32095 @findex -inferior-tty-show
32097 @subheading Synopsis
32103 Show terminal for future runs of program being debugged.
32105 @subheading @value{GDBN} Command
32107 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32109 @subheading Example
32113 -inferior-tty-set /dev/pts/1
32117 ^done,inferior_tty_terminal="/dev/pts/1"
32121 @subheading The @code{-enable-timings} Command
32122 @findex -enable-timings
32124 @subheading Synopsis
32127 -enable-timings [yes | no]
32130 Toggle the printing of the wallclock, user and system times for an MI
32131 command as a field in its output. This command is to help frontend
32132 developers optimize the performance of their code. No argument is
32133 equivalent to @samp{yes}.
32135 @subheading @value{GDBN} Command
32139 @subheading Example
32147 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32148 addr="0x080484ed",func="main",file="myprog.c",
32149 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32151 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32159 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32160 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32161 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32162 fullname="/home/nickrob/myprog.c",line="73"@}
32167 @chapter @value{GDBN} Annotations
32169 This chapter describes annotations in @value{GDBN}. Annotations were
32170 designed to interface @value{GDBN} to graphical user interfaces or other
32171 similar programs which want to interact with @value{GDBN} at a
32172 relatively high level.
32174 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32178 This is Edition @value{EDITION}, @value{DATE}.
32182 * Annotations Overview:: What annotations are; the general syntax.
32183 * Server Prefix:: Issuing a command without affecting user state.
32184 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32185 * Errors:: Annotations for error messages.
32186 * Invalidation:: Some annotations describe things now invalid.
32187 * Annotations for Running::
32188 Whether the program is running, how it stopped, etc.
32189 * Source Annotations:: Annotations describing source code.
32192 @node Annotations Overview
32193 @section What is an Annotation?
32194 @cindex annotations
32196 Annotations start with a newline character, two @samp{control-z}
32197 characters, and the name of the annotation. If there is no additional
32198 information associated with this annotation, the name of the annotation
32199 is followed immediately by a newline. If there is additional
32200 information, the name of the annotation is followed by a space, the
32201 additional information, and a newline. The additional information
32202 cannot contain newline characters.
32204 Any output not beginning with a newline and two @samp{control-z}
32205 characters denotes literal output from @value{GDBN}. Currently there is
32206 no need for @value{GDBN} to output a newline followed by two
32207 @samp{control-z} characters, but if there was such a need, the
32208 annotations could be extended with an @samp{escape} annotation which
32209 means those three characters as output.
32211 The annotation @var{level}, which is specified using the
32212 @option{--annotate} command line option (@pxref{Mode Options}), controls
32213 how much information @value{GDBN} prints together with its prompt,
32214 values of expressions, source lines, and other types of output. Level 0
32215 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32216 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32217 for programs that control @value{GDBN}, and level 2 annotations have
32218 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32219 Interface, annotate, GDB's Obsolete Annotations}).
32222 @kindex set annotate
32223 @item set annotate @var{level}
32224 The @value{GDBN} command @code{set annotate} sets the level of
32225 annotations to the specified @var{level}.
32227 @item show annotate
32228 @kindex show annotate
32229 Show the current annotation level.
32232 This chapter describes level 3 annotations.
32234 A simple example of starting up @value{GDBN} with annotations is:
32237 $ @kbd{gdb --annotate=3}
32239 Copyright 2003 Free Software Foundation, Inc.
32240 GDB is free software, covered by the GNU General Public License,
32241 and you are welcome to change it and/or distribute copies of it
32242 under certain conditions.
32243 Type "show copying" to see the conditions.
32244 There is absolutely no warranty for GDB. Type "show warranty"
32246 This GDB was configured as "i386-pc-linux-gnu"
32257 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32258 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32259 denotes a @samp{control-z} character) are annotations; the rest is
32260 output from @value{GDBN}.
32262 @node Server Prefix
32263 @section The Server Prefix
32264 @cindex server prefix
32266 If you prefix a command with @samp{server } then it will not affect
32267 the command history, nor will it affect @value{GDBN}'s notion of which
32268 command to repeat if @key{RET} is pressed on a line by itself. This
32269 means that commands can be run behind a user's back by a front-end in
32270 a transparent manner.
32272 The @code{server } prefix does not affect the recording of values into
32273 the value history; to print a value without recording it into the
32274 value history, use the @code{output} command instead of the
32275 @code{print} command.
32277 Using this prefix also disables confirmation requests
32278 (@pxref{confirmation requests}).
32281 @section Annotation for @value{GDBN} Input
32283 @cindex annotations for prompts
32284 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32285 to know when to send output, when the output from a given command is
32288 Different kinds of input each have a different @dfn{input type}. Each
32289 input type has three annotations: a @code{pre-} annotation, which
32290 denotes the beginning of any prompt which is being output, a plain
32291 annotation, which denotes the end of the prompt, and then a @code{post-}
32292 annotation which denotes the end of any echo which may (or may not) be
32293 associated with the input. For example, the @code{prompt} input type
32294 features the following annotations:
32302 The input types are
32305 @findex pre-prompt annotation
32306 @findex prompt annotation
32307 @findex post-prompt annotation
32309 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32311 @findex pre-commands annotation
32312 @findex commands annotation
32313 @findex post-commands annotation
32315 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32316 command. The annotations are repeated for each command which is input.
32318 @findex pre-overload-choice annotation
32319 @findex overload-choice annotation
32320 @findex post-overload-choice annotation
32321 @item overload-choice
32322 When @value{GDBN} wants the user to select between various overloaded functions.
32324 @findex pre-query annotation
32325 @findex query annotation
32326 @findex post-query annotation
32328 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32330 @findex pre-prompt-for-continue annotation
32331 @findex prompt-for-continue annotation
32332 @findex post-prompt-for-continue annotation
32333 @item prompt-for-continue
32334 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32335 expect this to work well; instead use @code{set height 0} to disable
32336 prompting. This is because the counting of lines is buggy in the
32337 presence of annotations.
32342 @cindex annotations for errors, warnings and interrupts
32344 @findex quit annotation
32349 This annotation occurs right before @value{GDBN} responds to an interrupt.
32351 @findex error annotation
32356 This annotation occurs right before @value{GDBN} responds to an error.
32358 Quit and error annotations indicate that any annotations which @value{GDBN} was
32359 in the middle of may end abruptly. For example, if a
32360 @code{value-history-begin} annotation is followed by a @code{error}, one
32361 cannot expect to receive the matching @code{value-history-end}. One
32362 cannot expect not to receive it either, however; an error annotation
32363 does not necessarily mean that @value{GDBN} is immediately returning all the way
32366 @findex error-begin annotation
32367 A quit or error annotation may be preceded by
32373 Any output between that and the quit or error annotation is the error
32376 Warning messages are not yet annotated.
32377 @c If we want to change that, need to fix warning(), type_error(),
32378 @c range_error(), and possibly other places.
32381 @section Invalidation Notices
32383 @cindex annotations for invalidation messages
32384 The following annotations say that certain pieces of state may have
32388 @findex frames-invalid annotation
32389 @item ^Z^Zframes-invalid
32391 The frames (for example, output from the @code{backtrace} command) may
32394 @findex breakpoints-invalid annotation
32395 @item ^Z^Zbreakpoints-invalid
32397 The breakpoints may have changed. For example, the user just added or
32398 deleted a breakpoint.
32401 @node Annotations for Running
32402 @section Running the Program
32403 @cindex annotations for running programs
32405 @findex starting annotation
32406 @findex stopping annotation
32407 When the program starts executing due to a @value{GDBN} command such as
32408 @code{step} or @code{continue},
32414 is output. When the program stops,
32420 is output. Before the @code{stopped} annotation, a variety of
32421 annotations describe how the program stopped.
32424 @findex exited annotation
32425 @item ^Z^Zexited @var{exit-status}
32426 The program exited, and @var{exit-status} is the exit status (zero for
32427 successful exit, otherwise nonzero).
32429 @findex signalled annotation
32430 @findex signal-name annotation
32431 @findex signal-name-end annotation
32432 @findex signal-string annotation
32433 @findex signal-string-end annotation
32434 @item ^Z^Zsignalled
32435 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32436 annotation continues:
32442 ^Z^Zsignal-name-end
32446 ^Z^Zsignal-string-end
32451 where @var{name} is the name of the signal, such as @code{SIGILL} or
32452 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32453 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32454 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32455 user's benefit and have no particular format.
32457 @findex signal annotation
32459 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32460 just saying that the program received the signal, not that it was
32461 terminated with it.
32463 @findex breakpoint annotation
32464 @item ^Z^Zbreakpoint @var{number}
32465 The program hit breakpoint number @var{number}.
32467 @findex watchpoint annotation
32468 @item ^Z^Zwatchpoint @var{number}
32469 The program hit watchpoint number @var{number}.
32472 @node Source Annotations
32473 @section Displaying Source
32474 @cindex annotations for source display
32476 @findex source annotation
32477 The following annotation is used instead of displaying source code:
32480 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32483 where @var{filename} is an absolute file name indicating which source
32484 file, @var{line} is the line number within that file (where 1 is the
32485 first line in the file), @var{character} is the character position
32486 within the file (where 0 is the first character in the file) (for most
32487 debug formats this will necessarily point to the beginning of a line),
32488 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32489 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32490 @var{addr} is the address in the target program associated with the
32491 source which is being displayed. The @var{addr} is in the form @samp{0x}
32492 followed by one or more lowercase hex digits (note that this does not
32493 depend on the language).
32495 @node JIT Interface
32496 @chapter JIT Compilation Interface
32497 @cindex just-in-time compilation
32498 @cindex JIT compilation interface
32500 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32501 interface. A JIT compiler is a program or library that generates native
32502 executable code at runtime and executes it, usually in order to achieve good
32503 performance while maintaining platform independence.
32505 Programs that use JIT compilation are normally difficult to debug because
32506 portions of their code are generated at runtime, instead of being loaded from
32507 object files, which is where @value{GDBN} normally finds the program's symbols
32508 and debug information. In order to debug programs that use JIT compilation,
32509 @value{GDBN} has an interface that allows the program to register in-memory
32510 symbol files with @value{GDBN} at runtime.
32512 If you are using @value{GDBN} to debug a program that uses this interface, then
32513 it should work transparently so long as you have not stripped the binary. If
32514 you are developing a JIT compiler, then the interface is documented in the rest
32515 of this chapter. At this time, the only known client of this interface is the
32518 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32519 JIT compiler communicates with @value{GDBN} by writing data into a global
32520 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32521 attaches, it reads a linked list of symbol files from the global variable to
32522 find existing code, and puts a breakpoint in the function so that it can find
32523 out about additional code.
32526 * Declarations:: Relevant C struct declarations
32527 * Registering Code:: Steps to register code
32528 * Unregistering Code:: Steps to unregister code
32529 * Custom Debug Info:: Emit debug information in a custom format
32533 @section JIT Declarations
32535 These are the relevant struct declarations that a C program should include to
32536 implement the interface:
32546 struct jit_code_entry
32548 struct jit_code_entry *next_entry;
32549 struct jit_code_entry *prev_entry;
32550 const char *symfile_addr;
32551 uint64_t symfile_size;
32554 struct jit_descriptor
32557 /* This type should be jit_actions_t, but we use uint32_t
32558 to be explicit about the bitwidth. */
32559 uint32_t action_flag;
32560 struct jit_code_entry *relevant_entry;
32561 struct jit_code_entry *first_entry;
32564 /* GDB puts a breakpoint in this function. */
32565 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32567 /* Make sure to specify the version statically, because the
32568 debugger may check the version before we can set it. */
32569 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32572 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32573 modifications to this global data properly, which can easily be done by putting
32574 a global mutex around modifications to these structures.
32576 @node Registering Code
32577 @section Registering Code
32579 To register code with @value{GDBN}, the JIT should follow this protocol:
32583 Generate an object file in memory with symbols and other desired debug
32584 information. The file must include the virtual addresses of the sections.
32587 Create a code entry for the file, which gives the start and size of the symbol
32591 Add it to the linked list in the JIT descriptor.
32594 Point the relevant_entry field of the descriptor at the entry.
32597 Set @code{action_flag} to @code{JIT_REGISTER} and call
32598 @code{__jit_debug_register_code}.
32601 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32602 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32603 new code. However, the linked list must still be maintained in order to allow
32604 @value{GDBN} to attach to a running process and still find the symbol files.
32606 @node Unregistering Code
32607 @section Unregistering Code
32609 If code is freed, then the JIT should use the following protocol:
32613 Remove the code entry corresponding to the code from the linked list.
32616 Point the @code{relevant_entry} field of the descriptor at the code entry.
32619 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32620 @code{__jit_debug_register_code}.
32623 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32624 and the JIT will leak the memory used for the associated symbol files.
32626 @node Custom Debug Info
32627 @section Custom Debug Info
32628 @cindex custom JIT debug info
32629 @cindex JIT debug info reader
32631 Generating debug information in platform-native file formats (like ELF
32632 or COFF) may be an overkill for JIT compilers; especially if all the
32633 debug info is used for is displaying a meaningful backtrace. The
32634 issue can be resolved by having the JIT writers decide on a debug info
32635 format and also provide a reader that parses the debug info generated
32636 by the JIT compiler. This section gives a brief overview on writing
32637 such a parser. More specific details can be found in the source file
32638 @file{gdb/jit-reader.in}, which is also installed as a header at
32639 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32641 The reader is implemented as a shared object (so this functionality is
32642 not available on platforms which don't allow loading shared objects at
32643 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32644 @code{jit-reader-unload} are provided, to be used to load and unload
32645 the readers from a preconfigured directory. Once loaded, the shared
32646 object is used the parse the debug information emitted by the JIT
32650 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32651 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32654 @node Using JIT Debug Info Readers
32655 @subsection Using JIT Debug Info Readers
32656 @kindex jit-reader-load
32657 @kindex jit-reader-unload
32659 Readers can be loaded and unloaded using the @code{jit-reader-load}
32660 and @code{jit-reader-unload} commands.
32663 @item jit-reader-load @var{reader}
32664 Load the JIT reader named @var{reader}, which is a shared
32665 object specified as either an absolute or a relative file name. In
32666 the latter case, @value{GDBN} will try to load the reader from a
32667 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32668 system (here @var{libdir} is the system library directory, often
32669 @file{/usr/local/lib}).
32671 Only one reader can be active at a time; trying to load a second
32672 reader when one is already loaded will result in @value{GDBN}
32673 reporting an error. A new JIT reader can be loaded by first unloading
32674 the current one using @code{jit-reader-unload} and then invoking
32675 @code{jit-reader-load}.
32677 @item jit-reader-unload
32678 Unload the currently loaded JIT reader.
32682 @node Writing JIT Debug Info Readers
32683 @subsection Writing JIT Debug Info Readers
32684 @cindex writing JIT debug info readers
32686 As mentioned, a reader is essentially a shared object conforming to a
32687 certain ABI. This ABI is described in @file{jit-reader.h}.
32689 @file{jit-reader.h} defines the structures, macros and functions
32690 required to write a reader. It is installed (along with
32691 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32692 the system include directory.
32694 Readers need to be released under a GPL compatible license. A reader
32695 can be declared as released under such a license by placing the macro
32696 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32698 The entry point for readers is the symbol @code{gdb_init_reader},
32699 which is expected to be a function with the prototype
32701 @findex gdb_init_reader
32703 extern struct gdb_reader_funcs *gdb_init_reader (void);
32706 @cindex @code{struct gdb_reader_funcs}
32708 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32709 functions. These functions are executed to read the debug info
32710 generated by the JIT compiler (@code{read}), to unwind stack frames
32711 (@code{unwind}) and to create canonical frame IDs
32712 (@code{get_Frame_id}). It also has a callback that is called when the
32713 reader is being unloaded (@code{destroy}). The struct looks like this
32716 struct gdb_reader_funcs
32718 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32719 int reader_version;
32721 /* For use by the reader. */
32724 gdb_read_debug_info *read;
32725 gdb_unwind_frame *unwind;
32726 gdb_get_frame_id *get_frame_id;
32727 gdb_destroy_reader *destroy;
32731 @cindex @code{struct gdb_symbol_callbacks}
32732 @cindex @code{struct gdb_unwind_callbacks}
32734 The callbacks are provided with another set of callbacks by
32735 @value{GDBN} to do their job. For @code{read}, these callbacks are
32736 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32737 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32738 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32739 files and new symbol tables inside those object files. @code{struct
32740 gdb_unwind_callbacks} has callbacks to read registers off the current
32741 frame and to write out the values of the registers in the previous
32742 frame. Both have a callback (@code{target_read}) to read bytes off the
32743 target's address space.
32745 @node In-Process Agent
32746 @chapter In-Process Agent
32747 @cindex debugging agent
32748 The traditional debugging model is conceptually low-speed, but works fine,
32749 because most bugs can be reproduced in debugging-mode execution. However,
32750 as multi-core or many-core processors are becoming mainstream, and
32751 multi-threaded programs become more and more popular, there should be more
32752 and more bugs that only manifest themselves at normal-mode execution, for
32753 example, thread races, because debugger's interference with the program's
32754 timing may conceal the bugs. On the other hand, in some applications,
32755 it is not feasible for the debugger to interrupt the program's execution
32756 long enough for the developer to learn anything helpful about its behavior.
32757 If the program's correctness depends on its real-time behavior, delays
32758 introduced by a debugger might cause the program to fail, even when the
32759 code itself is correct. It is useful to be able to observe the program's
32760 behavior without interrupting it.
32762 Therefore, traditional debugging model is too intrusive to reproduce
32763 some bugs. In order to reduce the interference with the program, we can
32764 reduce the number of operations performed by debugger. The
32765 @dfn{In-Process Agent}, a shared library, is running within the same
32766 process with inferior, and is able to perform some debugging operations
32767 itself. As a result, debugger is only involved when necessary, and
32768 performance of debugging can be improved accordingly. Note that
32769 interference with program can be reduced but can't be removed completely,
32770 because the in-process agent will still stop or slow down the program.
32772 The in-process agent can interpret and execute Agent Expressions
32773 (@pxref{Agent Expressions}) during performing debugging operations. The
32774 agent expressions can be used for different purposes, such as collecting
32775 data in tracepoints, and condition evaluation in breakpoints.
32777 @anchor{Control Agent}
32778 You can control whether the in-process agent is used as an aid for
32779 debugging with the following commands:
32782 @kindex set agent on
32784 Causes the in-process agent to perform some operations on behalf of the
32785 debugger. Just which operations requested by the user will be done
32786 by the in-process agent depends on the its capabilities. For example,
32787 if you request to evaluate breakpoint conditions in the in-process agent,
32788 and the in-process agent has such capability as well, then breakpoint
32789 conditions will be evaluated in the in-process agent.
32791 @kindex set agent off
32792 @item set agent off
32793 Disables execution of debugging operations by the in-process agent. All
32794 of the operations will be performed by @value{GDBN}.
32798 Display the current setting of execution of debugging operations by
32799 the in-process agent.
32803 * In-Process Agent Protocol::
32806 @node In-Process Agent Protocol
32807 @section In-Process Agent Protocol
32808 @cindex in-process agent protocol
32810 The in-process agent is able to communicate with both @value{GDBN} and
32811 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32812 used for communications between @value{GDBN} or GDBserver and the IPA.
32813 In general, @value{GDBN} or GDBserver sends commands
32814 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32815 in-process agent replies back with the return result of the command, or
32816 some other information. The data sent to in-process agent is composed
32817 of primitive data types, such as 4-byte or 8-byte type, and composite
32818 types, which are called objects (@pxref{IPA Protocol Objects}).
32821 * IPA Protocol Objects::
32822 * IPA Protocol Commands::
32825 @node IPA Protocol Objects
32826 @subsection IPA Protocol Objects
32827 @cindex ipa protocol objects
32829 The commands sent to and results received from agent may contain some
32830 complex data types called @dfn{objects}.
32832 The in-process agent is running on the same machine with @value{GDBN}
32833 or GDBserver, so it doesn't have to handle as much differences between
32834 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32835 However, there are still some differences of two ends in two processes:
32839 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32840 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32842 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32843 GDBserver is compiled with one, and in-process agent is compiled with
32847 Here are the IPA Protocol Objects:
32851 agent expression object. It represents an agent expression
32852 (@pxref{Agent Expressions}).
32853 @anchor{agent expression object}
32855 tracepoint action object. It represents a tracepoint action
32856 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32857 memory, static trace data and to evaluate expression.
32858 @anchor{tracepoint action object}
32860 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32861 @anchor{tracepoint object}
32865 The following table describes important attributes of each IPA protocol
32868 @multitable @columnfractions .30 .20 .50
32869 @headitem Name @tab Size @tab Description
32870 @item @emph{agent expression object} @tab @tab
32871 @item length @tab 4 @tab length of bytes code
32872 @item byte code @tab @var{length} @tab contents of byte code
32873 @item @emph{tracepoint action for collecting memory} @tab @tab
32874 @item 'M' @tab 1 @tab type of tracepoint action
32875 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32876 address of the lowest byte to collect, otherwise @var{addr} is the offset
32877 of @var{basereg} for memory collecting.
32878 @item len @tab 8 @tab length of memory for collecting
32879 @item basereg @tab 4 @tab the register number containing the starting
32880 memory address for collecting.
32881 @item @emph{tracepoint action for collecting registers} @tab @tab
32882 @item 'R' @tab 1 @tab type of tracepoint action
32883 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32884 @item 'L' @tab 1 @tab type of tracepoint action
32885 @item @emph{tracepoint action for expression evaluation} @tab @tab
32886 @item 'X' @tab 1 @tab type of tracepoint action
32887 @item agent expression @tab length of @tab @ref{agent expression object}
32888 @item @emph{tracepoint object} @tab @tab
32889 @item number @tab 4 @tab number of tracepoint
32890 @item address @tab 8 @tab address of tracepoint inserted on
32891 @item type @tab 4 @tab type of tracepoint
32892 @item enabled @tab 1 @tab enable or disable of tracepoint
32893 @item step_count @tab 8 @tab step
32894 @item pass_count @tab 8 @tab pass
32895 @item numactions @tab 4 @tab number of tracepoint actions
32896 @item hit count @tab 8 @tab hit count
32897 @item trace frame usage @tab 8 @tab trace frame usage
32898 @item compiled_cond @tab 8 @tab compiled condition
32899 @item orig_size @tab 8 @tab orig size
32900 @item condition @tab 4 if condition is NULL otherwise length of
32901 @ref{agent expression object}
32902 @tab zero if condition is NULL, otherwise is
32903 @ref{agent expression object}
32904 @item actions @tab variable
32905 @tab numactions number of @ref{tracepoint action object}
32908 @node IPA Protocol Commands
32909 @subsection IPA Protocol Commands
32910 @cindex ipa protocol commands
32912 The spaces in each command are delimiters to ease reading this commands
32913 specification. They don't exist in real commands.
32917 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32918 Installs a new fast tracepoint described by @var{tracepoint_object}
32919 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32920 head of @dfn{jumppad}, which is used to jump to data collection routine
32925 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32926 @var{target_address} is address of tracepoint in the inferior.
32927 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32928 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32929 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32930 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32937 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32938 is about to kill inferiors.
32946 @item probe_marker_at:@var{address}
32947 Asks in-process agent to probe the marker at @var{address}.
32954 @item unprobe_marker_at:@var{address}
32955 Asks in-process agent to unprobe the marker at @var{address}.
32959 @chapter Reporting Bugs in @value{GDBN}
32960 @cindex bugs in @value{GDBN}
32961 @cindex reporting bugs in @value{GDBN}
32963 Your bug reports play an essential role in making @value{GDBN} reliable.
32965 Reporting a bug may help you by bringing a solution to your problem, or it
32966 may not. But in any case the principal function of a bug report is to help
32967 the entire community by making the next version of @value{GDBN} work better. Bug
32968 reports are your contribution to the maintenance of @value{GDBN}.
32970 In order for a bug report to serve its purpose, you must include the
32971 information that enables us to fix the bug.
32974 * Bug Criteria:: Have you found a bug?
32975 * Bug Reporting:: How to report bugs
32979 @section Have You Found a Bug?
32980 @cindex bug criteria
32982 If you are not sure whether you have found a bug, here are some guidelines:
32985 @cindex fatal signal
32986 @cindex debugger crash
32987 @cindex crash of debugger
32989 If the debugger gets a fatal signal, for any input whatever, that is a
32990 @value{GDBN} bug. Reliable debuggers never crash.
32992 @cindex error on valid input
32994 If @value{GDBN} produces an error message for valid input, that is a
32995 bug. (Note that if you're cross debugging, the problem may also be
32996 somewhere in the connection to the target.)
32998 @cindex invalid input
33000 If @value{GDBN} does not produce an error message for invalid input,
33001 that is a bug. However, you should note that your idea of
33002 ``invalid input'' might be our idea of ``an extension'' or ``support
33003 for traditional practice''.
33006 If you are an experienced user of debugging tools, your suggestions
33007 for improvement of @value{GDBN} are welcome in any case.
33010 @node Bug Reporting
33011 @section How to Report Bugs
33012 @cindex bug reports
33013 @cindex @value{GDBN} bugs, reporting
33015 A number of companies and individuals offer support for @sc{gnu} products.
33016 If you obtained @value{GDBN} from a support organization, we recommend you
33017 contact that organization first.
33019 You can find contact information for many support companies and
33020 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33022 @c should add a web page ref...
33025 @ifset BUGURL_DEFAULT
33026 In any event, we also recommend that you submit bug reports for
33027 @value{GDBN}. The preferred method is to submit them directly using
33028 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33029 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33032 @strong{Do not send bug reports to @samp{info-gdb}, or to
33033 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33034 not want to receive bug reports. Those that do have arranged to receive
33037 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33038 serves as a repeater. The mailing list and the newsgroup carry exactly
33039 the same messages. Often people think of posting bug reports to the
33040 newsgroup instead of mailing them. This appears to work, but it has one
33041 problem which can be crucial: a newsgroup posting often lacks a mail
33042 path back to the sender. Thus, if we need to ask for more information,
33043 we may be unable to reach you. For this reason, it is better to send
33044 bug reports to the mailing list.
33046 @ifclear BUGURL_DEFAULT
33047 In any event, we also recommend that you submit bug reports for
33048 @value{GDBN} to @value{BUGURL}.
33052 The fundamental principle of reporting bugs usefully is this:
33053 @strong{report all the facts}. If you are not sure whether to state a
33054 fact or leave it out, state it!
33056 Often people omit facts because they think they know what causes the
33057 problem and assume that some details do not matter. Thus, you might
33058 assume that the name of the variable you use in an example does not matter.
33059 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33060 stray memory reference which happens to fetch from the location where that
33061 name is stored in memory; perhaps, if the name were different, the contents
33062 of that location would fool the debugger into doing the right thing despite
33063 the bug. Play it safe and give a specific, complete example. That is the
33064 easiest thing for you to do, and the most helpful.
33066 Keep in mind that the purpose of a bug report is to enable us to fix the
33067 bug. It may be that the bug has been reported previously, but neither
33068 you nor we can know that unless your bug report is complete and
33071 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33072 bell?'' Those bug reports are useless, and we urge everyone to
33073 @emph{refuse to respond to them} except to chide the sender to report
33076 To enable us to fix the bug, you should include all these things:
33080 The version of @value{GDBN}. @value{GDBN} announces it if you start
33081 with no arguments; you can also print it at any time using @code{show
33084 Without this, we will not know whether there is any point in looking for
33085 the bug in the current version of @value{GDBN}.
33088 The type of machine you are using, and the operating system name and
33092 The details of the @value{GDBN} build-time configuration.
33093 @value{GDBN} shows these details if you invoke it with the
33094 @option{--configuration} command-line option, or if you type
33095 @code{show configuration} at @value{GDBN}'s prompt.
33098 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33099 ``@value{GCC}--2.8.1''.
33102 What compiler (and its version) was used to compile the program you are
33103 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33104 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33105 to get this information; for other compilers, see the documentation for
33109 The command arguments you gave the compiler to compile your example and
33110 observe the bug. For example, did you use @samp{-O}? To guarantee
33111 you will not omit something important, list them all. A copy of the
33112 Makefile (or the output from make) is sufficient.
33114 If we were to try to guess the arguments, we would probably guess wrong
33115 and then we might not encounter the bug.
33118 A complete input script, and all necessary source files, that will
33122 A description of what behavior you observe that you believe is
33123 incorrect. For example, ``It gets a fatal signal.''
33125 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33126 will certainly notice it. But if the bug is incorrect output, we might
33127 not notice unless it is glaringly wrong. You might as well not give us
33128 a chance to make a mistake.
33130 Even if the problem you experience is a fatal signal, you should still
33131 say so explicitly. Suppose something strange is going on, such as, your
33132 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33133 the C library on your system. (This has happened!) Your copy might
33134 crash and ours would not. If you told us to expect a crash, then when
33135 ours fails to crash, we would know that the bug was not happening for
33136 us. If you had not told us to expect a crash, then we would not be able
33137 to draw any conclusion from our observations.
33140 @cindex recording a session script
33141 To collect all this information, you can use a session recording program
33142 such as @command{script}, which is available on many Unix systems.
33143 Just run your @value{GDBN} session inside @command{script} and then
33144 include the @file{typescript} file with your bug report.
33146 Another way to record a @value{GDBN} session is to run @value{GDBN}
33147 inside Emacs and then save the entire buffer to a file.
33150 If you wish to suggest changes to the @value{GDBN} source, send us context
33151 diffs. If you even discuss something in the @value{GDBN} source, refer to
33152 it by context, not by line number.
33154 The line numbers in our development sources will not match those in your
33155 sources. Your line numbers would convey no useful information to us.
33159 Here are some things that are not necessary:
33163 A description of the envelope of the bug.
33165 Often people who encounter a bug spend a lot of time investigating
33166 which changes to the input file will make the bug go away and which
33167 changes will not affect it.
33169 This is often time consuming and not very useful, because the way we
33170 will find the bug is by running a single example under the debugger
33171 with breakpoints, not by pure deduction from a series of examples.
33172 We recommend that you save your time for something else.
33174 Of course, if you can find a simpler example to report @emph{instead}
33175 of the original one, that is a convenience for us. Errors in the
33176 output will be easier to spot, running under the debugger will take
33177 less time, and so on.
33179 However, simplification is not vital; if you do not want to do this,
33180 report the bug anyway and send us the entire test case you used.
33183 A patch for the bug.
33185 A patch for the bug does help us if it is a good one. But do not omit
33186 the necessary information, such as the test case, on the assumption that
33187 a patch is all we need. We might see problems with your patch and decide
33188 to fix the problem another way, or we might not understand it at all.
33190 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33191 construct an example that will make the program follow a certain path
33192 through the code. If you do not send us the example, we will not be able
33193 to construct one, so we will not be able to verify that the bug is fixed.
33195 And if we cannot understand what bug you are trying to fix, or why your
33196 patch should be an improvement, we will not install it. A test case will
33197 help us to understand.
33200 A guess about what the bug is or what it depends on.
33202 Such guesses are usually wrong. Even we cannot guess right about such
33203 things without first using the debugger to find the facts.
33206 @c The readline documentation is distributed with the readline code
33207 @c and consists of the two following files:
33210 @c Use -I with makeinfo to point to the appropriate directory,
33211 @c environment var TEXINPUTS with TeX.
33212 @ifclear SYSTEM_READLINE
33213 @include rluser.texi
33214 @include hsuser.texi
33218 @appendix In Memoriam
33220 The @value{GDBN} project mourns the loss of the following long-time
33225 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33226 to Free Software in general. Outside of @value{GDBN}, he was known in
33227 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33229 @item Michael Snyder
33230 Michael was one of the Global Maintainers of the @value{GDBN} project,
33231 with contributions recorded as early as 1996, until 2011. In addition
33232 to his day to day participation, he was a large driving force behind
33233 adding Reverse Debugging to @value{GDBN}.
33236 Beyond their technical contributions to the project, they were also
33237 enjoyable members of the Free Software Community. We will miss them.
33239 @node Formatting Documentation
33240 @appendix Formatting Documentation
33242 @cindex @value{GDBN} reference card
33243 @cindex reference card
33244 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33245 for printing with PostScript or Ghostscript, in the @file{gdb}
33246 subdirectory of the main source directory@footnote{In
33247 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33248 release.}. If you can use PostScript or Ghostscript with your printer,
33249 you can print the reference card immediately with @file{refcard.ps}.
33251 The release also includes the source for the reference card. You
33252 can format it, using @TeX{}, by typing:
33258 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33259 mode on US ``letter'' size paper;
33260 that is, on a sheet 11 inches wide by 8.5 inches
33261 high. You will need to specify this form of printing as an option to
33262 your @sc{dvi} output program.
33264 @cindex documentation
33266 All the documentation for @value{GDBN} comes as part of the machine-readable
33267 distribution. The documentation is written in Texinfo format, which is
33268 a documentation system that uses a single source file to produce both
33269 on-line information and a printed manual. You can use one of the Info
33270 formatting commands to create the on-line version of the documentation
33271 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33273 @value{GDBN} includes an already formatted copy of the on-line Info
33274 version of this manual in the @file{gdb} subdirectory. The main Info
33275 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33276 subordinate files matching @samp{gdb.info*} in the same directory. If
33277 necessary, you can print out these files, or read them with any editor;
33278 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33279 Emacs or the standalone @code{info} program, available as part of the
33280 @sc{gnu} Texinfo distribution.
33282 If you want to format these Info files yourself, you need one of the
33283 Info formatting programs, such as @code{texinfo-format-buffer} or
33286 If you have @code{makeinfo} installed, and are in the top level
33287 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33288 version @value{GDBVN}), you can make the Info file by typing:
33295 If you want to typeset and print copies of this manual, you need @TeX{},
33296 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33297 Texinfo definitions file.
33299 @TeX{} is a typesetting program; it does not print files directly, but
33300 produces output files called @sc{dvi} files. To print a typeset
33301 document, you need a program to print @sc{dvi} files. If your system
33302 has @TeX{} installed, chances are it has such a program. The precise
33303 command to use depends on your system; @kbd{lpr -d} is common; another
33304 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33305 require a file name without any extension or a @samp{.dvi} extension.
33307 @TeX{} also requires a macro definitions file called
33308 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33309 written in Texinfo format. On its own, @TeX{} cannot either read or
33310 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33311 and is located in the @file{gdb-@var{version-number}/texinfo}
33314 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33315 typeset and print this manual. First switch to the @file{gdb}
33316 subdirectory of the main source directory (for example, to
33317 @file{gdb-@value{GDBVN}/gdb}) and type:
33323 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33325 @node Installing GDB
33326 @appendix Installing @value{GDBN}
33327 @cindex installation
33330 * Requirements:: Requirements for building @value{GDBN}
33331 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33332 * Separate Objdir:: Compiling @value{GDBN} in another directory
33333 * Config Names:: Specifying names for hosts and targets
33334 * Configure Options:: Summary of options for configure
33335 * System-wide configuration:: Having a system-wide init file
33339 @section Requirements for Building @value{GDBN}
33340 @cindex building @value{GDBN}, requirements for
33342 Building @value{GDBN} requires various tools and packages to be available.
33343 Other packages will be used only if they are found.
33345 @heading Tools/Packages Necessary for Building @value{GDBN}
33347 @item ISO C90 compiler
33348 @value{GDBN} is written in ISO C90. It should be buildable with any
33349 working C90 compiler, e.g.@: GCC.
33353 @heading Tools/Packages Optional for Building @value{GDBN}
33357 @value{GDBN} can use the Expat XML parsing library. This library may be
33358 included with your operating system distribution; if it is not, you
33359 can get the latest version from @url{http://expat.sourceforge.net}.
33360 The @file{configure} script will search for this library in several
33361 standard locations; if it is installed in an unusual path, you can
33362 use the @option{--with-libexpat-prefix} option to specify its location.
33368 Remote protocol memory maps (@pxref{Memory Map Format})
33370 Target descriptions (@pxref{Target Descriptions})
33372 Remote shared library lists (@xref{Library List Format},
33373 or alternatively @pxref{Library List Format for SVR4 Targets})
33375 MS-Windows shared libraries (@pxref{Shared Libraries})
33377 Traceframe info (@pxref{Traceframe Info Format})
33379 Branch trace (@pxref{Branch Trace Format},
33380 @pxref{Branch Trace Configuration Format})
33384 @cindex compressed debug sections
33385 @value{GDBN} will use the @samp{zlib} library, if available, to read
33386 compressed debug sections. Some linkers, such as GNU gold, are capable
33387 of producing binaries with compressed debug sections. If @value{GDBN}
33388 is compiled with @samp{zlib}, it will be able to read the debug
33389 information in such binaries.
33391 The @samp{zlib} library is likely included with your operating system
33392 distribution; if it is not, you can get the latest version from
33393 @url{http://zlib.net}.
33396 @value{GDBN}'s features related to character sets (@pxref{Character
33397 Sets}) require a functioning @code{iconv} implementation. If you are
33398 on a GNU system, then this is provided by the GNU C Library. Some
33399 other systems also provide a working @code{iconv}.
33401 If @value{GDBN} is using the @code{iconv} program which is installed
33402 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33403 This is done with @option{--with-iconv-bin} which specifies the
33404 directory that contains the @code{iconv} program.
33406 On systems without @code{iconv}, you can install GNU Libiconv. If you
33407 have previously installed Libiconv, you can use the
33408 @option{--with-libiconv-prefix} option to configure.
33410 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33411 arrange to build Libiconv if a directory named @file{libiconv} appears
33412 in the top-most source directory. If Libiconv is built this way, and
33413 if the operating system does not provide a suitable @code{iconv}
33414 implementation, then the just-built library will automatically be used
33415 by @value{GDBN}. One easy way to set this up is to download GNU
33416 Libiconv, unpack it, and then rename the directory holding the
33417 Libiconv source code to @samp{libiconv}.
33420 @node Running Configure
33421 @section Invoking the @value{GDBN} @file{configure} Script
33422 @cindex configuring @value{GDBN}
33423 @value{GDBN} comes with a @file{configure} script that automates the process
33424 of preparing @value{GDBN} for installation; you can then use @code{make} to
33425 build the @code{gdb} program.
33427 @c irrelevant in info file; it's as current as the code it lives with.
33428 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33429 look at the @file{README} file in the sources; we may have improved the
33430 installation procedures since publishing this manual.}
33433 The @value{GDBN} distribution includes all the source code you need for
33434 @value{GDBN} in a single directory, whose name is usually composed by
33435 appending the version number to @samp{gdb}.
33437 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33438 @file{gdb-@value{GDBVN}} directory. That directory contains:
33441 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33442 script for configuring @value{GDBN} and all its supporting libraries
33444 @item gdb-@value{GDBVN}/gdb
33445 the source specific to @value{GDBN} itself
33447 @item gdb-@value{GDBVN}/bfd
33448 source for the Binary File Descriptor library
33450 @item gdb-@value{GDBVN}/include
33451 @sc{gnu} include files
33453 @item gdb-@value{GDBVN}/libiberty
33454 source for the @samp{-liberty} free software library
33456 @item gdb-@value{GDBVN}/opcodes
33457 source for the library of opcode tables and disassemblers
33459 @item gdb-@value{GDBVN}/readline
33460 source for the @sc{gnu} command-line interface
33462 @item gdb-@value{GDBVN}/glob
33463 source for the @sc{gnu} filename pattern-matching subroutine
33465 @item gdb-@value{GDBVN}/mmalloc
33466 source for the @sc{gnu} memory-mapped malloc package
33469 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33470 from the @file{gdb-@var{version-number}} source directory, which in
33471 this example is the @file{gdb-@value{GDBVN}} directory.
33473 First switch to the @file{gdb-@var{version-number}} source directory
33474 if you are not already in it; then run @file{configure}. Pass the
33475 identifier for the platform on which @value{GDBN} will run as an
33481 cd gdb-@value{GDBVN}
33482 ./configure @var{host}
33487 where @var{host} is an identifier such as @samp{sun4} or
33488 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33489 (You can often leave off @var{host}; @file{configure} tries to guess the
33490 correct value by examining your system.)
33492 Running @samp{configure @var{host}} and then running @code{make} builds the
33493 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33494 libraries, then @code{gdb} itself. The configured source files, and the
33495 binaries, are left in the corresponding source directories.
33498 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33499 system does not recognize this automatically when you run a different
33500 shell, you may need to run @code{sh} on it explicitly:
33503 sh configure @var{host}
33506 If you run @file{configure} from a directory that contains source
33507 directories for multiple libraries or programs, such as the
33508 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33510 creates configuration files for every directory level underneath (unless
33511 you tell it not to, with the @samp{--norecursion} option).
33513 You should run the @file{configure} script from the top directory in the
33514 source tree, the @file{gdb-@var{version-number}} directory. If you run
33515 @file{configure} from one of the subdirectories, you will configure only
33516 that subdirectory. That is usually not what you want. In particular,
33517 if you run the first @file{configure} from the @file{gdb} subdirectory
33518 of the @file{gdb-@var{version-number}} directory, you will omit the
33519 configuration of @file{bfd}, @file{readline}, and other sibling
33520 directories of the @file{gdb} subdirectory. This leads to build errors
33521 about missing include files such as @file{bfd/bfd.h}.
33523 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33524 However, you should make sure that the shell on your path (named by
33525 the @samp{SHELL} environment variable) is publicly readable. Remember
33526 that @value{GDBN} uses the shell to start your program---some systems refuse to
33527 let @value{GDBN} debug child processes whose programs are not readable.
33529 @node Separate Objdir
33530 @section Compiling @value{GDBN} in Another Directory
33532 If you want to run @value{GDBN} versions for several host or target machines,
33533 you need a different @code{gdb} compiled for each combination of
33534 host and target. @file{configure} is designed to make this easy by
33535 allowing you to generate each configuration in a separate subdirectory,
33536 rather than in the source directory. If your @code{make} program
33537 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33538 @code{make} in each of these directories builds the @code{gdb}
33539 program specified there.
33541 To build @code{gdb} in a separate directory, run @file{configure}
33542 with the @samp{--srcdir} option to specify where to find the source.
33543 (You also need to specify a path to find @file{configure}
33544 itself from your working directory. If the path to @file{configure}
33545 would be the same as the argument to @samp{--srcdir}, you can leave out
33546 the @samp{--srcdir} option; it is assumed.)
33548 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33549 separate directory for a Sun 4 like this:
33553 cd gdb-@value{GDBVN}
33556 ../gdb-@value{GDBVN}/configure sun4
33561 When @file{configure} builds a configuration using a remote source
33562 directory, it creates a tree for the binaries with the same structure
33563 (and using the same names) as the tree under the source directory. In
33564 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33565 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33566 @file{gdb-sun4/gdb}.
33568 Make sure that your path to the @file{configure} script has just one
33569 instance of @file{gdb} in it. If your path to @file{configure} looks
33570 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33571 one subdirectory of @value{GDBN}, not the whole package. This leads to
33572 build errors about missing include files such as @file{bfd/bfd.h}.
33574 One popular reason to build several @value{GDBN} configurations in separate
33575 directories is to configure @value{GDBN} for cross-compiling (where
33576 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33577 programs that run on another machine---the @dfn{target}).
33578 You specify a cross-debugging target by
33579 giving the @samp{--target=@var{target}} option to @file{configure}.
33581 When you run @code{make} to build a program or library, you must run
33582 it in a configured directory---whatever directory you were in when you
33583 called @file{configure} (or one of its subdirectories).
33585 The @code{Makefile} that @file{configure} generates in each source
33586 directory also runs recursively. If you type @code{make} in a source
33587 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33588 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33589 will build all the required libraries, and then build GDB.
33591 When you have multiple hosts or targets configured in separate
33592 directories, you can run @code{make} on them in parallel (for example,
33593 if they are NFS-mounted on each of the hosts); they will not interfere
33597 @section Specifying Names for Hosts and Targets
33599 The specifications used for hosts and targets in the @file{configure}
33600 script are based on a three-part naming scheme, but some short predefined
33601 aliases are also supported. The full naming scheme encodes three pieces
33602 of information in the following pattern:
33605 @var{architecture}-@var{vendor}-@var{os}
33608 For example, you can use the alias @code{sun4} as a @var{host} argument,
33609 or as the value for @var{target} in a @code{--target=@var{target}}
33610 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33612 The @file{configure} script accompanying @value{GDBN} does not provide
33613 any query facility to list all supported host and target names or
33614 aliases. @file{configure} calls the Bourne shell script
33615 @code{config.sub} to map abbreviations to full names; you can read the
33616 script, if you wish, or you can use it to test your guesses on
33617 abbreviations---for example:
33620 % sh config.sub i386-linux
33622 % sh config.sub alpha-linux
33623 alpha-unknown-linux-gnu
33624 % sh config.sub hp9k700
33626 % sh config.sub sun4
33627 sparc-sun-sunos4.1.1
33628 % sh config.sub sun3
33629 m68k-sun-sunos4.1.1
33630 % sh config.sub i986v
33631 Invalid configuration `i986v': machine `i986v' not recognized
33635 @code{config.sub} is also distributed in the @value{GDBN} source
33636 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33638 @node Configure Options
33639 @section @file{configure} Options
33641 Here is a summary of the @file{configure} options and arguments that
33642 are most often useful for building @value{GDBN}. @file{configure} also has
33643 several other options not listed here. @inforef{What Configure
33644 Does,,configure.info}, for a full explanation of @file{configure}.
33647 configure @r{[}--help@r{]}
33648 @r{[}--prefix=@var{dir}@r{]}
33649 @r{[}--exec-prefix=@var{dir}@r{]}
33650 @r{[}--srcdir=@var{dirname}@r{]}
33651 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33652 @r{[}--target=@var{target}@r{]}
33657 You may introduce options with a single @samp{-} rather than
33658 @samp{--} if you prefer; but you may abbreviate option names if you use
33663 Display a quick summary of how to invoke @file{configure}.
33665 @item --prefix=@var{dir}
33666 Configure the source to install programs and files under directory
33669 @item --exec-prefix=@var{dir}
33670 Configure the source to install programs under directory
33673 @c avoid splitting the warning from the explanation:
33675 @item --srcdir=@var{dirname}
33676 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33677 @code{make} that implements the @code{VPATH} feature.}@*
33678 Use this option to make configurations in directories separate from the
33679 @value{GDBN} source directories. Among other things, you can use this to
33680 build (or maintain) several configurations simultaneously, in separate
33681 directories. @file{configure} writes configuration-specific files in
33682 the current directory, but arranges for them to use the source in the
33683 directory @var{dirname}. @file{configure} creates directories under
33684 the working directory in parallel to the source directories below
33687 @item --norecursion
33688 Configure only the directory level where @file{configure} is executed; do not
33689 propagate configuration to subdirectories.
33691 @item --target=@var{target}
33692 Configure @value{GDBN} for cross-debugging programs running on the specified
33693 @var{target}. Without this option, @value{GDBN} is configured to debug
33694 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33696 There is no convenient way to generate a list of all available targets.
33698 @item @var{host} @dots{}
33699 Configure @value{GDBN} to run on the specified @var{host}.
33701 There is no convenient way to generate a list of all available hosts.
33704 There are many other options available as well, but they are generally
33705 needed for special purposes only.
33707 @node System-wide configuration
33708 @section System-wide configuration and settings
33709 @cindex system-wide init file
33711 @value{GDBN} can be configured to have a system-wide init file;
33712 this file will be read and executed at startup (@pxref{Startup, , What
33713 @value{GDBN} does during startup}).
33715 Here is the corresponding configure option:
33718 @item --with-system-gdbinit=@var{file}
33719 Specify that the default location of the system-wide init file is
33723 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33724 it may be subject to relocation. Two possible cases:
33728 If the default location of this init file contains @file{$prefix},
33729 it will be subject to relocation. Suppose that the configure options
33730 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33731 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33732 init file is looked for as @file{$install/etc/gdbinit} instead of
33733 @file{$prefix/etc/gdbinit}.
33736 By contrast, if the default location does not contain the prefix,
33737 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33738 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33739 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33740 wherever @value{GDBN} is installed.
33743 If the configured location of the system-wide init file (as given by the
33744 @option{--with-system-gdbinit} option at configure time) is in the
33745 data-directory (as specified by @option{--with-gdb-datadir} at configure
33746 time) or in one of its subdirectories, then @value{GDBN} will look for the
33747 system-wide init file in the directory specified by the
33748 @option{--data-directory} command-line option.
33749 Note that the system-wide init file is only read once, during @value{GDBN}
33750 initialization. If the data-directory is changed after @value{GDBN} has
33751 started with the @code{set data-directory} command, the file will not be
33755 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33758 @node System-wide Configuration Scripts
33759 @subsection Installed System-wide Configuration Scripts
33760 @cindex system-wide configuration scripts
33762 The @file{system-gdbinit} directory, located inside the data-directory
33763 (as specified by @option{--with-gdb-datadir} at configure time) contains
33764 a number of scripts which can be used as system-wide init files. To
33765 automatically source those scripts at startup, @value{GDBN} should be
33766 configured with @option{--with-system-gdbinit}. Otherwise, any user
33767 should be able to source them by hand as needed.
33769 The following scripts are currently available:
33772 @item @file{elinos.py}
33774 @cindex ELinOS system-wide configuration script
33775 This script is useful when debugging a program on an ELinOS target.
33776 It takes advantage of the environment variables defined in a standard
33777 ELinOS environment in order to determine the location of the system
33778 shared libraries, and then sets the @samp{solib-absolute-prefix}
33779 and @samp{solib-search-path} variables appropriately.
33781 @item @file{wrs-linux.py}
33782 @pindex wrs-linux.py
33783 @cindex Wind River Linux system-wide configuration script
33784 This script is useful when debugging a program on a target running
33785 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33786 the host-side sysroot used by the target system.
33790 @node Maintenance Commands
33791 @appendix Maintenance Commands
33792 @cindex maintenance commands
33793 @cindex internal commands
33795 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33796 includes a number of commands intended for @value{GDBN} developers,
33797 that are not documented elsewhere in this manual. These commands are
33798 provided here for reference. (For commands that turn on debugging
33799 messages, see @ref{Debugging Output}.)
33802 @kindex maint agent
33803 @kindex maint agent-eval
33804 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33805 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33806 Translate the given @var{expression} into remote agent bytecodes.
33807 This command is useful for debugging the Agent Expression mechanism
33808 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33809 expression useful for data collection, such as by tracepoints, while
33810 @samp{maint agent-eval} produces an expression that evaluates directly
33811 to a result. For instance, a collection expression for @code{globa +
33812 globb} will include bytecodes to record four bytes of memory at each
33813 of the addresses of @code{globa} and @code{globb}, while discarding
33814 the result of the addition, while an evaluation expression will do the
33815 addition and return the sum.
33816 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33817 If not, generate remote agent bytecode for current frame PC address.
33819 @kindex maint agent-printf
33820 @item maint agent-printf @var{format},@var{expr},...
33821 Translate the given format string and list of argument expressions
33822 into remote agent bytecodes and display them as a disassembled list.
33823 This command is useful for debugging the agent version of dynamic
33824 printf (@pxref{Dynamic Printf}).
33826 @kindex maint info breakpoints
33827 @item @anchor{maint info breakpoints}maint info breakpoints
33828 Using the same format as @samp{info breakpoints}, display both the
33829 breakpoints you've set explicitly, and those @value{GDBN} is using for
33830 internal purposes. Internal breakpoints are shown with negative
33831 breakpoint numbers. The type column identifies what kind of breakpoint
33836 Normal, explicitly set breakpoint.
33839 Normal, explicitly set watchpoint.
33842 Internal breakpoint, used to handle correctly stepping through
33843 @code{longjmp} calls.
33845 @item longjmp resume
33846 Internal breakpoint at the target of a @code{longjmp}.
33849 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33852 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33855 Shared library events.
33859 @kindex maint info btrace
33860 @item maint info btrace
33861 Pint information about raw branch tracing data.
33863 @kindex maint btrace packet-history
33864 @item maint btrace packet-history
33865 Print the raw branch trace packets that are used to compute the
33866 execution history for the @samp{record btrace} command. Both the
33867 information and the format in which it is printed depend on the btrace
33872 For the BTS recording format, print a list of blocks of sequential
33873 code. For each block, the following information is printed:
33877 Newer blocks have higher numbers. The oldest block has number zero.
33878 @item Lowest @samp{PC}
33879 @item Highest @samp{PC}
33883 For the Intel(R) Processor Trace recording format, print a list of
33884 Intel(R) Processor Trace packets. For each packet, the following
33885 information is printed:
33888 @item Packet number
33889 Newer packets have higher numbers. The oldest packet has number zero.
33891 The packet's offset in the trace stream.
33892 @item Packet opcode and payload
33896 @kindex maint btrace clear-packet-history
33897 @item maint btrace clear-packet-history
33898 Discards the cached packet history printed by the @samp{maint btrace
33899 packet-history} command. The history will be computed again when
33902 @kindex maint btrace clear
33903 @item maint btrace clear
33904 Discard the branch trace data. The data will be fetched anew and the
33905 branch trace will be recomputed when needed.
33907 This implicitly truncates the branch trace to a single branch trace
33908 buffer. When updating branch trace incrementally, the branch trace
33909 available to @value{GDBN} may be bigger than a single branch trace
33912 @kindex maint set btrace pt skip-pad
33913 @item maint set btrace pt skip-pad
33914 @kindex maint show btrace pt skip-pad
33915 @item maint show btrace pt skip-pad
33916 Control whether @value{GDBN} will skip PAD packets when computing the
33919 @kindex set displaced-stepping
33920 @kindex show displaced-stepping
33921 @cindex displaced stepping support
33922 @cindex out-of-line single-stepping
33923 @item set displaced-stepping
33924 @itemx show displaced-stepping
33925 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33926 if the target supports it. Displaced stepping is a way to single-step
33927 over breakpoints without removing them from the inferior, by executing
33928 an out-of-line copy of the instruction that was originally at the
33929 breakpoint location. It is also known as out-of-line single-stepping.
33932 @item set displaced-stepping on
33933 If the target architecture supports it, @value{GDBN} will use
33934 displaced stepping to step over breakpoints.
33936 @item set displaced-stepping off
33937 @value{GDBN} will not use displaced stepping to step over breakpoints,
33938 even if such is supported by the target architecture.
33940 @cindex non-stop mode, and @samp{set displaced-stepping}
33941 @item set displaced-stepping auto
33942 This is the default mode. @value{GDBN} will use displaced stepping
33943 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33944 architecture supports displaced stepping.
33947 @kindex maint check-psymtabs
33948 @item maint check-psymtabs
33949 Check the consistency of currently expanded psymtabs versus symtabs.
33950 Use this to check, for example, whether a symbol is in one but not the other.
33952 @kindex maint check-symtabs
33953 @item maint check-symtabs
33954 Check the consistency of currently expanded symtabs.
33956 @kindex maint expand-symtabs
33957 @item maint expand-symtabs [@var{regexp}]
33958 Expand symbol tables.
33959 If @var{regexp} is specified, only expand symbol tables for file
33960 names matching @var{regexp}.
33962 @kindex maint set catch-demangler-crashes
33963 @kindex maint show catch-demangler-crashes
33964 @cindex demangler crashes
33965 @item maint set catch-demangler-crashes [on|off]
33966 @itemx maint show catch-demangler-crashes
33967 Control whether @value{GDBN} should attempt to catch crashes in the
33968 symbol name demangler. The default is to attempt to catch crashes.
33969 If enabled, the first time a crash is caught, a core file is created,
33970 the offending symbol is displayed and the user is presented with the
33971 option to terminate the current session.
33973 @kindex maint cplus first_component
33974 @item maint cplus first_component @var{name}
33975 Print the first C@t{++} class/namespace component of @var{name}.
33977 @kindex maint cplus namespace
33978 @item maint cplus namespace
33979 Print the list of possible C@t{++} namespaces.
33981 @kindex maint deprecate
33982 @kindex maint undeprecate
33983 @cindex deprecated commands
33984 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33985 @itemx maint undeprecate @var{command}
33986 Deprecate or undeprecate the named @var{command}. Deprecated commands
33987 cause @value{GDBN} to issue a warning when you use them. The optional
33988 argument @var{replacement} says which newer command should be used in
33989 favor of the deprecated one; if it is given, @value{GDBN} will mention
33990 the replacement as part of the warning.
33992 @kindex maint dump-me
33993 @item maint dump-me
33994 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33995 Cause a fatal signal in the debugger and force it to dump its core.
33996 This is supported only on systems which support aborting a program
33997 with the @code{SIGQUIT} signal.
33999 @kindex maint internal-error
34000 @kindex maint internal-warning
34001 @kindex maint demangler-warning
34002 @cindex demangler crashes
34003 @item maint internal-error @r{[}@var{message-text}@r{]}
34004 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34005 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34007 Cause @value{GDBN} to call the internal function @code{internal_error},
34008 @code{internal_warning} or @code{demangler_warning} and hence behave
34009 as though an internal problem has been detected. In addition to
34010 reporting the internal problem, these functions give the user the
34011 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34012 and @code{internal_warning}) create a core file of the current
34013 @value{GDBN} session.
34015 These commands take an optional parameter @var{message-text} that is
34016 used as the text of the error or warning message.
34018 Here's an example of using @code{internal-error}:
34021 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34022 @dots{}/maint.c:121: internal-error: testing, 1, 2
34023 A problem internal to GDB has been detected. Further
34024 debugging may prove unreliable.
34025 Quit this debugging session? (y or n) @kbd{n}
34026 Create a core file? (y or n) @kbd{n}
34030 @cindex @value{GDBN} internal error
34031 @cindex internal errors, control of @value{GDBN} behavior
34032 @cindex demangler crashes
34034 @kindex maint set internal-error
34035 @kindex maint show internal-error
34036 @kindex maint set internal-warning
34037 @kindex maint show internal-warning
34038 @kindex maint set demangler-warning
34039 @kindex maint show demangler-warning
34040 @item maint set internal-error @var{action} [ask|yes|no]
34041 @itemx maint show internal-error @var{action}
34042 @itemx maint set internal-warning @var{action} [ask|yes|no]
34043 @itemx maint show internal-warning @var{action}
34044 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34045 @itemx maint show demangler-warning @var{action}
34046 When @value{GDBN} reports an internal problem (error or warning) it
34047 gives the user the opportunity to both quit @value{GDBN} and create a
34048 core file of the current @value{GDBN} session. These commands let you
34049 override the default behaviour for each particular @var{action},
34050 described in the table below.
34054 You can specify that @value{GDBN} should always (yes) or never (no)
34055 quit. The default is to ask the user what to do.
34058 You can specify that @value{GDBN} should always (yes) or never (no)
34059 create a core file. The default is to ask the user what to do. Note
34060 that there is no @code{corefile} option for @code{demangler-warning}:
34061 demangler warnings always create a core file and this cannot be
34065 @kindex maint packet
34066 @item maint packet @var{text}
34067 If @value{GDBN} is talking to an inferior via the serial protocol,
34068 then this command sends the string @var{text} to the inferior, and
34069 displays the response packet. @value{GDBN} supplies the initial
34070 @samp{$} character, the terminating @samp{#} character, and the
34073 @kindex maint print architecture
34074 @item maint print architecture @r{[}@var{file}@r{]}
34075 Print the entire architecture configuration. The optional argument
34076 @var{file} names the file where the output goes.
34078 @kindex maint print c-tdesc
34079 @item maint print c-tdesc
34080 Print the current target description (@pxref{Target Descriptions}) as
34081 a C source file. The created source file can be used in @value{GDBN}
34082 when an XML parser is not available to parse the description.
34084 @kindex maint print dummy-frames
34085 @item maint print dummy-frames
34086 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34089 (@value{GDBP}) @kbd{b add}
34091 (@value{GDBP}) @kbd{print add(2,3)}
34092 Breakpoint 2, add (a=2, b=3) at @dots{}
34094 The program being debugged stopped while in a function called from GDB.
34096 (@value{GDBP}) @kbd{maint print dummy-frames}
34097 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34101 Takes an optional file parameter.
34103 @kindex maint print registers
34104 @kindex maint print raw-registers
34105 @kindex maint print cooked-registers
34106 @kindex maint print register-groups
34107 @kindex maint print remote-registers
34108 @item maint print registers @r{[}@var{file}@r{]}
34109 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34110 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34111 @itemx maint print register-groups @r{[}@var{file}@r{]}
34112 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34113 Print @value{GDBN}'s internal register data structures.
34115 The command @code{maint print raw-registers} includes the contents of
34116 the raw register cache; the command @code{maint print
34117 cooked-registers} includes the (cooked) value of all registers,
34118 including registers which aren't available on the target nor visible
34119 to user; the command @code{maint print register-groups} includes the
34120 groups that each register is a member of; and the command @code{maint
34121 print remote-registers} includes the remote target's register numbers
34122 and offsets in the `G' packets.
34124 These commands take an optional parameter, a file name to which to
34125 write the information.
34127 @kindex maint print reggroups
34128 @item maint print reggroups @r{[}@var{file}@r{]}
34129 Print @value{GDBN}'s internal register group data structures. The
34130 optional argument @var{file} tells to what file to write the
34133 The register groups info looks like this:
34136 (@value{GDBP}) @kbd{maint print reggroups}
34149 This command forces @value{GDBN} to flush its internal register cache.
34151 @kindex maint print objfiles
34152 @cindex info for known object files
34153 @item maint print objfiles @r{[}@var{regexp}@r{]}
34154 Print a dump of all known object files.
34155 If @var{regexp} is specified, only print object files whose names
34156 match @var{regexp}. For each object file, this command prints its name,
34157 address in memory, and all of its psymtabs and symtabs.
34159 @kindex maint print user-registers
34160 @cindex user registers
34161 @item maint print user-registers
34162 List all currently available @dfn{user registers}. User registers
34163 typically provide alternate names for actual hardware registers. They
34164 include the four ``standard'' registers @code{$fp}, @code{$pc},
34165 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34166 registers can be used in expressions in the same way as the canonical
34167 register names, but only the latter are listed by the @code{info
34168 registers} and @code{maint print registers} commands.
34170 @kindex maint print section-scripts
34171 @cindex info for known .debug_gdb_scripts-loaded scripts
34172 @item maint print section-scripts [@var{regexp}]
34173 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34174 If @var{regexp} is specified, only print scripts loaded by object files
34175 matching @var{regexp}.
34176 For each script, this command prints its name as specified in the objfile,
34177 and the full path if known.
34178 @xref{dotdebug_gdb_scripts section}.
34180 @kindex maint print statistics
34181 @cindex bcache statistics
34182 @item maint print statistics
34183 This command prints, for each object file in the program, various data
34184 about that object file followed by the byte cache (@dfn{bcache})
34185 statistics for the object file. The objfile data includes the number
34186 of minimal, partial, full, and stabs symbols, the number of types
34187 defined by the objfile, the number of as yet unexpanded psym tables,
34188 the number of line tables and string tables, and the amount of memory
34189 used by the various tables. The bcache statistics include the counts,
34190 sizes, and counts of duplicates of all and unique objects, max,
34191 average, and median entry size, total memory used and its overhead and
34192 savings, and various measures of the hash table size and chain
34195 @kindex maint print target-stack
34196 @cindex target stack description
34197 @item maint print target-stack
34198 A @dfn{target} is an interface between the debugger and a particular
34199 kind of file or process. Targets can be stacked in @dfn{strata},
34200 so that more than one target can potentially respond to a request.
34201 In particular, memory accesses will walk down the stack of targets
34202 until they find a target that is interested in handling that particular
34205 This command prints a short description of each layer that was pushed on
34206 the @dfn{target stack}, starting from the top layer down to the bottom one.
34208 @kindex maint print type
34209 @cindex type chain of a data type
34210 @item maint print type @var{expr}
34211 Print the type chain for a type specified by @var{expr}. The argument
34212 can be either a type name or a symbol. If it is a symbol, the type of
34213 that symbol is described. The type chain produced by this command is
34214 a recursive definition of the data type as stored in @value{GDBN}'s
34215 data structures, including its flags and contained types.
34217 @kindex maint set dwarf always-disassemble
34218 @kindex maint show dwarf always-disassemble
34219 @item maint set dwarf always-disassemble
34220 @item maint show dwarf always-disassemble
34221 Control the behavior of @code{info address} when using DWARF debugging
34224 The default is @code{off}, which means that @value{GDBN} should try to
34225 describe a variable's location in an easily readable format. When
34226 @code{on}, @value{GDBN} will instead display the DWARF location
34227 expression in an assembly-like format. Note that some locations are
34228 too complex for @value{GDBN} to describe simply; in this case you will
34229 always see the disassembly form.
34231 Here is an example of the resulting disassembly:
34234 (gdb) info addr argc
34235 Symbol "argc" is a complex DWARF expression:
34239 For more information on these expressions, see
34240 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34242 @kindex maint set dwarf max-cache-age
34243 @kindex maint show dwarf max-cache-age
34244 @item maint set dwarf max-cache-age
34245 @itemx maint show dwarf max-cache-age
34246 Control the DWARF compilation unit cache.
34248 @cindex DWARF compilation units cache
34249 In object files with inter-compilation-unit references, such as those
34250 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34251 reader needs to frequently refer to previously read compilation units.
34252 This setting controls how long a compilation unit will remain in the
34253 cache if it is not referenced. A higher limit means that cached
34254 compilation units will be stored in memory longer, and more total
34255 memory will be used. Setting it to zero disables caching, which will
34256 slow down @value{GDBN} startup, but reduce memory consumption.
34258 @kindex maint set profile
34259 @kindex maint show profile
34260 @cindex profiling GDB
34261 @item maint set profile
34262 @itemx maint show profile
34263 Control profiling of @value{GDBN}.
34265 Profiling will be disabled until you use the @samp{maint set profile}
34266 command to enable it. When you enable profiling, the system will begin
34267 collecting timing and execution count data; when you disable profiling or
34268 exit @value{GDBN}, the results will be written to a log file. Remember that
34269 if you use profiling, @value{GDBN} will overwrite the profiling log file
34270 (often called @file{gmon.out}). If you have a record of important profiling
34271 data in a @file{gmon.out} file, be sure to move it to a safe location.
34273 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34274 compiled with the @samp{-pg} compiler option.
34276 @kindex maint set show-debug-regs
34277 @kindex maint show show-debug-regs
34278 @cindex hardware debug registers
34279 @item maint set show-debug-regs
34280 @itemx maint show show-debug-regs
34281 Control whether to show variables that mirror the hardware debug
34282 registers. Use @code{on} to enable, @code{off} to disable. If
34283 enabled, the debug registers values are shown when @value{GDBN} inserts or
34284 removes a hardware breakpoint or watchpoint, and when the inferior
34285 triggers a hardware-assisted breakpoint or watchpoint.
34287 @kindex maint set show-all-tib
34288 @kindex maint show show-all-tib
34289 @item maint set show-all-tib
34290 @itemx maint show show-all-tib
34291 Control whether to show all non zero areas within a 1k block starting
34292 at thread local base, when using the @samp{info w32 thread-information-block}
34295 @kindex maint set target-async
34296 @kindex maint show target-async
34297 @item maint set target-async
34298 @itemx maint show target-async
34299 This controls whether @value{GDBN} targets operate in synchronous or
34300 asynchronous mode (@pxref{Background Execution}). Normally the
34301 default is asynchronous, if it is available; but this can be changed
34302 to more easily debug problems occurring only in synchronous mode.
34304 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34305 @kindex maint show target-non-stop
34306 @item maint set target-non-stop
34307 @itemx maint show target-non-stop
34309 This controls whether @value{GDBN} targets always operate in non-stop
34310 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34311 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34312 if supported by the target.
34315 @item maint set target-non-stop auto
34316 This is the default mode. @value{GDBN} controls the target in
34317 non-stop mode if the target supports it.
34319 @item maint set target-non-stop on
34320 @value{GDBN} controls the target in non-stop mode even if the target
34321 does not indicate support.
34323 @item maint set target-non-stop off
34324 @value{GDBN} does not control the target in non-stop mode even if the
34325 target supports it.
34328 @kindex maint set per-command
34329 @kindex maint show per-command
34330 @item maint set per-command
34331 @itemx maint show per-command
34332 @cindex resources used by commands
34334 @value{GDBN} can display the resources used by each command.
34335 This is useful in debugging performance problems.
34338 @item maint set per-command space [on|off]
34339 @itemx maint show per-command space
34340 Enable or disable the printing of the memory used by GDB for each command.
34341 If enabled, @value{GDBN} will display how much memory each command
34342 took, following the command's own output.
34343 This can also be requested by invoking @value{GDBN} with the
34344 @option{--statistics} command-line switch (@pxref{Mode Options}).
34346 @item maint set per-command time [on|off]
34347 @itemx maint show per-command time
34348 Enable or disable the printing of the execution time of @value{GDBN}
34350 If enabled, @value{GDBN} will display how much time it
34351 took to execute each command, following the command's own output.
34352 Both CPU time and wallclock time are printed.
34353 Printing both is useful when trying to determine whether the cost is
34354 CPU or, e.g., disk/network latency.
34355 Note that the CPU time printed is for @value{GDBN} only, it does not include
34356 the execution time of the inferior because there's no mechanism currently
34357 to compute how much time was spent by @value{GDBN} and how much time was
34358 spent by the program been debugged.
34359 This can also be requested by invoking @value{GDBN} with the
34360 @option{--statistics} command-line switch (@pxref{Mode Options}).
34362 @item maint set per-command symtab [on|off]
34363 @itemx maint show per-command symtab
34364 Enable or disable the printing of basic symbol table statistics
34366 If enabled, @value{GDBN} will display the following information:
34370 number of symbol tables
34372 number of primary symbol tables
34374 number of blocks in the blockvector
34378 @kindex maint space
34379 @cindex memory used by commands
34380 @item maint space @var{value}
34381 An alias for @code{maint set per-command space}.
34382 A non-zero value enables it, zero disables it.
34385 @cindex time of command execution
34386 @item maint time @var{value}
34387 An alias for @code{maint set per-command time}.
34388 A non-zero value enables it, zero disables it.
34390 @kindex maint translate-address
34391 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34392 Find the symbol stored at the location specified by the address
34393 @var{addr} and an optional section name @var{section}. If found,
34394 @value{GDBN} prints the name of the closest symbol and an offset from
34395 the symbol's location to the specified address. This is similar to
34396 the @code{info address} command (@pxref{Symbols}), except that this
34397 command also allows to find symbols in other sections.
34399 If section was not specified, the section in which the symbol was found
34400 is also printed. For dynamically linked executables, the name of
34401 executable or shared library containing the symbol is printed as well.
34405 The following command is useful for non-interactive invocations of
34406 @value{GDBN}, such as in the test suite.
34409 @item set watchdog @var{nsec}
34410 @kindex set watchdog
34411 @cindex watchdog timer
34412 @cindex timeout for commands
34413 Set the maximum number of seconds @value{GDBN} will wait for the
34414 target operation to finish. If this time expires, @value{GDBN}
34415 reports and error and the command is aborted.
34417 @item show watchdog
34418 Show the current setting of the target wait timeout.
34421 @node Remote Protocol
34422 @appendix @value{GDBN} Remote Serial Protocol
34427 * Stop Reply Packets::
34428 * General Query Packets::
34429 * Architecture-Specific Protocol Details::
34430 * Tracepoint Packets::
34431 * Host I/O Packets::
34433 * Notification Packets::
34434 * Remote Non-Stop::
34435 * Packet Acknowledgment::
34437 * File-I/O Remote Protocol Extension::
34438 * Library List Format::
34439 * Library List Format for SVR4 Targets::
34440 * Memory Map Format::
34441 * Thread List Format::
34442 * Traceframe Info Format::
34443 * Branch Trace Format::
34444 * Branch Trace Configuration Format::
34450 There may be occasions when you need to know something about the
34451 protocol---for example, if there is only one serial port to your target
34452 machine, you might want your program to do something special if it
34453 recognizes a packet meant for @value{GDBN}.
34455 In the examples below, @samp{->} and @samp{<-} are used to indicate
34456 transmitted and received data, respectively.
34458 @cindex protocol, @value{GDBN} remote serial
34459 @cindex serial protocol, @value{GDBN} remote
34460 @cindex remote serial protocol
34461 All @value{GDBN} commands and responses (other than acknowledgments
34462 and notifications, see @ref{Notification Packets}) are sent as a
34463 @var{packet}. A @var{packet} is introduced with the character
34464 @samp{$}, the actual @var{packet-data}, and the terminating character
34465 @samp{#} followed by a two-digit @var{checksum}:
34468 @code{$}@var{packet-data}@code{#}@var{checksum}
34472 @cindex checksum, for @value{GDBN} remote
34474 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34475 characters between the leading @samp{$} and the trailing @samp{#} (an
34476 eight bit unsigned checksum).
34478 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34479 specification also included an optional two-digit @var{sequence-id}:
34482 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34485 @cindex sequence-id, for @value{GDBN} remote
34487 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34488 has never output @var{sequence-id}s. Stubs that handle packets added
34489 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34491 When either the host or the target machine receives a packet, the first
34492 response expected is an acknowledgment: either @samp{+} (to indicate
34493 the package was received correctly) or @samp{-} (to request
34497 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34502 The @samp{+}/@samp{-} acknowledgments can be disabled
34503 once a connection is established.
34504 @xref{Packet Acknowledgment}, for details.
34506 The host (@value{GDBN}) sends @var{command}s, and the target (the
34507 debugging stub incorporated in your program) sends a @var{response}. In
34508 the case of step and continue @var{command}s, the response is only sent
34509 when the operation has completed, and the target has again stopped all
34510 threads in all attached processes. This is the default all-stop mode
34511 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34512 execution mode; see @ref{Remote Non-Stop}, for details.
34514 @var{packet-data} consists of a sequence of characters with the
34515 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34518 @cindex remote protocol, field separator
34519 Fields within the packet should be separated using @samp{,} @samp{;} or
34520 @samp{:}. Except where otherwise noted all numbers are represented in
34521 @sc{hex} with leading zeros suppressed.
34523 Implementors should note that prior to @value{GDBN} 5.0, the character
34524 @samp{:} could not appear as the third character in a packet (as it
34525 would potentially conflict with the @var{sequence-id}).
34527 @cindex remote protocol, binary data
34528 @anchor{Binary Data}
34529 Binary data in most packets is encoded either as two hexadecimal
34530 digits per byte of binary data. This allowed the traditional remote
34531 protocol to work over connections which were only seven-bit clean.
34532 Some packets designed more recently assume an eight-bit clean
34533 connection, and use a more efficient encoding to send and receive
34536 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34537 as an escape character. Any escaped byte is transmitted as the escape
34538 character followed by the original character XORed with @code{0x20}.
34539 For example, the byte @code{0x7d} would be transmitted as the two
34540 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34541 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34542 @samp{@}}) must always be escaped. Responses sent by the stub
34543 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34544 is not interpreted as the start of a run-length encoded sequence
34547 Response @var{data} can be run-length encoded to save space.
34548 Run-length encoding replaces runs of identical characters with one
34549 instance of the repeated character, followed by a @samp{*} and a
34550 repeat count. The repeat count is itself sent encoded, to avoid
34551 binary characters in @var{data}: a value of @var{n} is sent as
34552 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34553 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34554 code 32) for a repeat count of 3. (This is because run-length
34555 encoding starts to win for counts 3 or more.) Thus, for example,
34556 @samp{0* } is a run-length encoding of ``0000'': the space character
34557 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34560 The printable characters @samp{#} and @samp{$} or with a numeric value
34561 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34562 seven repeats (@samp{$}) can be expanded using a repeat count of only
34563 five (@samp{"}). For example, @samp{00000000} can be encoded as
34566 The error response returned for some packets includes a two character
34567 error number. That number is not well defined.
34569 @cindex empty response, for unsupported packets
34570 For any @var{command} not supported by the stub, an empty response
34571 (@samp{$#00}) should be returned. That way it is possible to extend the
34572 protocol. A newer @value{GDBN} can tell if a packet is supported based
34575 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34576 commands for register access, and the @samp{m} and @samp{M} commands
34577 for memory access. Stubs that only control single-threaded targets
34578 can implement run control with the @samp{c} (continue), and @samp{s}
34579 (step) commands. Stubs that support multi-threading targets should
34580 support the @samp{vCont} command. All other commands are optional.
34585 The following table provides a complete list of all currently defined
34586 @var{command}s and their corresponding response @var{data}.
34587 @xref{File-I/O Remote Protocol Extension}, for details about the File
34588 I/O extension of the remote protocol.
34590 Each packet's description has a template showing the packet's overall
34591 syntax, followed by an explanation of the packet's meaning. We
34592 include spaces in some of the templates for clarity; these are not
34593 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34594 separate its components. For example, a template like @samp{foo
34595 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34596 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34597 @var{baz}. @value{GDBN} does not transmit a space character between the
34598 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34601 @cindex @var{thread-id}, in remote protocol
34602 @anchor{thread-id syntax}
34603 Several packets and replies include a @var{thread-id} field to identify
34604 a thread. Normally these are positive numbers with a target-specific
34605 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34606 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34609 In addition, the remote protocol supports a multiprocess feature in
34610 which the @var{thread-id} syntax is extended to optionally include both
34611 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34612 The @var{pid} (process) and @var{tid} (thread) components each have the
34613 format described above: a positive number with target-specific
34614 interpretation formatted as a big-endian hex string, literal @samp{-1}
34615 to indicate all processes or threads (respectively), or @samp{0} to
34616 indicate an arbitrary process or thread. Specifying just a process, as
34617 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34618 error to specify all processes but a specific thread, such as
34619 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34620 for those packets and replies explicitly documented to include a process
34621 ID, rather than a @var{thread-id}.
34623 The multiprocess @var{thread-id} syntax extensions are only used if both
34624 @value{GDBN} and the stub report support for the @samp{multiprocess}
34625 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34628 Note that all packet forms beginning with an upper- or lower-case
34629 letter, other than those described here, are reserved for future use.
34631 Here are the packet descriptions.
34636 @cindex @samp{!} packet
34637 @anchor{extended mode}
34638 Enable extended mode. In extended mode, the remote server is made
34639 persistent. The @samp{R} packet is used to restart the program being
34645 The remote target both supports and has enabled extended mode.
34649 @cindex @samp{?} packet
34651 Indicate the reason the target halted. The reply is the same as for
34652 step and continue. This packet has a special interpretation when the
34653 target is in non-stop mode; see @ref{Remote Non-Stop}.
34656 @xref{Stop Reply Packets}, for the reply specifications.
34658 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34659 @cindex @samp{A} packet
34660 Initialized @code{argv[]} array passed into program. @var{arglen}
34661 specifies the number of bytes in the hex encoded byte stream
34662 @var{arg}. See @code{gdbserver} for more details.
34667 The arguments were set.
34673 @cindex @samp{b} packet
34674 (Don't use this packet; its behavior is not well-defined.)
34675 Change the serial line speed to @var{baud}.
34677 JTC: @emph{When does the transport layer state change? When it's
34678 received, or after the ACK is transmitted. In either case, there are
34679 problems if the command or the acknowledgment packet is dropped.}
34681 Stan: @emph{If people really wanted to add something like this, and get
34682 it working for the first time, they ought to modify ser-unix.c to send
34683 some kind of out-of-band message to a specially-setup stub and have the
34684 switch happen "in between" packets, so that from remote protocol's point
34685 of view, nothing actually happened.}
34687 @item B @var{addr},@var{mode}
34688 @cindex @samp{B} packet
34689 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34690 breakpoint at @var{addr}.
34692 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34693 (@pxref{insert breakpoint or watchpoint packet}).
34695 @cindex @samp{bc} packet
34698 Backward continue. Execute the target system in reverse. No parameter.
34699 @xref{Reverse Execution}, for more information.
34702 @xref{Stop Reply Packets}, for the reply specifications.
34704 @cindex @samp{bs} packet
34707 Backward single step. Execute one instruction in reverse. No parameter.
34708 @xref{Reverse Execution}, for more information.
34711 @xref{Stop Reply Packets}, for the reply specifications.
34713 @item c @r{[}@var{addr}@r{]}
34714 @cindex @samp{c} packet
34715 Continue at @var{addr}, which is the address to resume. If @var{addr}
34716 is omitted, resume at current address.
34718 This packet is deprecated for multi-threading support. @xref{vCont
34722 @xref{Stop Reply Packets}, for the reply specifications.
34724 @item C @var{sig}@r{[};@var{addr}@r{]}
34725 @cindex @samp{C} packet
34726 Continue with signal @var{sig} (hex signal number). If
34727 @samp{;@var{addr}} is omitted, resume at same address.
34729 This packet is deprecated for multi-threading support. @xref{vCont
34733 @xref{Stop Reply Packets}, for the reply specifications.
34736 @cindex @samp{d} packet
34739 Don't use this packet; instead, define a general set packet
34740 (@pxref{General Query Packets}).
34744 @cindex @samp{D} packet
34745 The first form of the packet is used to detach @value{GDBN} from the
34746 remote system. It is sent to the remote target
34747 before @value{GDBN} disconnects via the @code{detach} command.
34749 The second form, including a process ID, is used when multiprocess
34750 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34751 detach only a specific process. The @var{pid} is specified as a
34752 big-endian hex string.
34762 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34763 @cindex @samp{F} packet
34764 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34765 This is part of the File-I/O protocol extension. @xref{File-I/O
34766 Remote Protocol Extension}, for the specification.
34769 @anchor{read registers packet}
34770 @cindex @samp{g} packet
34771 Read general registers.
34775 @item @var{XX@dots{}}
34776 Each byte of register data is described by two hex digits. The bytes
34777 with the register are transmitted in target byte order. The size of
34778 each register and their position within the @samp{g} packet are
34779 determined by the @value{GDBN} internal gdbarch functions
34780 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34781 specification of several standard @samp{g} packets is specified below.
34783 When reading registers from a trace frame (@pxref{Analyze Collected
34784 Data,,Using the Collected Data}), the stub may also return a string of
34785 literal @samp{x}'s in place of the register data digits, to indicate
34786 that the corresponding register has not been collected, thus its value
34787 is unavailable. For example, for an architecture with 4 registers of
34788 4 bytes each, the following reply indicates to @value{GDBN} that
34789 registers 0 and 2 have not been collected, while registers 1 and 3
34790 have been collected, and both have zero value:
34794 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34801 @item G @var{XX@dots{}}
34802 @cindex @samp{G} packet
34803 Write general registers. @xref{read registers packet}, for a
34804 description of the @var{XX@dots{}} data.
34814 @item H @var{op} @var{thread-id}
34815 @cindex @samp{H} packet
34816 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34817 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34818 should be @samp{c} for step and continue operations (note that this
34819 is deprecated, supporting the @samp{vCont} command is a better
34820 option), and @samp{g} for other operations. The thread designator
34821 @var{thread-id} has the format and interpretation described in
34822 @ref{thread-id syntax}.
34833 @c 'H': How restrictive (or permissive) is the thread model. If a
34834 @c thread is selected and stopped, are other threads allowed
34835 @c to continue to execute? As I mentioned above, I think the
34836 @c semantics of each command when a thread is selected must be
34837 @c described. For example:
34839 @c 'g': If the stub supports threads and a specific thread is
34840 @c selected, returns the register block from that thread;
34841 @c otherwise returns current registers.
34843 @c 'G' If the stub supports threads and a specific thread is
34844 @c selected, sets the registers of the register block of
34845 @c that thread; otherwise sets current registers.
34847 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34848 @anchor{cycle step packet}
34849 @cindex @samp{i} packet
34850 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34851 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34852 step starting at that address.
34855 @cindex @samp{I} packet
34856 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34860 @cindex @samp{k} packet
34863 The exact effect of this packet is not specified.
34865 For a bare-metal target, it may power cycle or reset the target
34866 system. For that reason, the @samp{k} packet has no reply.
34868 For a single-process target, it may kill that process if possible.
34870 A multiple-process target may choose to kill just one process, or all
34871 that are under @value{GDBN}'s control. For more precise control, use
34872 the vKill packet (@pxref{vKill packet}).
34874 If the target system immediately closes the connection in response to
34875 @samp{k}, @value{GDBN} does not consider the lack of packet
34876 acknowledgment to be an error, and assumes the kill was successful.
34878 If connected using @kbd{target extended-remote}, and the target does
34879 not close the connection in response to a kill request, @value{GDBN}
34880 probes the target state as if a new connection was opened
34881 (@pxref{? packet}).
34883 @item m @var{addr},@var{length}
34884 @cindex @samp{m} packet
34885 Read @var{length} addressable memory units starting at address @var{addr}
34886 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34887 any particular boundary.
34889 The stub need not use any particular size or alignment when gathering
34890 data from memory for the response; even if @var{addr} is word-aligned
34891 and @var{length} is a multiple of the word size, the stub is free to
34892 use byte accesses, or not. For this reason, this packet may not be
34893 suitable for accessing memory-mapped I/O devices.
34894 @cindex alignment of remote memory accesses
34895 @cindex size of remote memory accesses
34896 @cindex memory, alignment and size of remote accesses
34900 @item @var{XX@dots{}}
34901 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
34902 The reply may contain fewer addressable memory units than requested if the
34903 server was able to read only part of the region of memory.
34908 @item M @var{addr},@var{length}:@var{XX@dots{}}
34909 @cindex @samp{M} packet
34910 Write @var{length} addressable memory units starting at address @var{addr}
34911 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
34912 byte is transmitted as a two-digit hexadecimal number.
34919 for an error (this includes the case where only part of the data was
34924 @cindex @samp{p} packet
34925 Read the value of register @var{n}; @var{n} is in hex.
34926 @xref{read registers packet}, for a description of how the returned
34927 register value is encoded.
34931 @item @var{XX@dots{}}
34932 the register's value
34936 Indicating an unrecognized @var{query}.
34939 @item P @var{n@dots{}}=@var{r@dots{}}
34940 @anchor{write register packet}
34941 @cindex @samp{P} packet
34942 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34943 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34944 digits for each byte in the register (target byte order).
34954 @item q @var{name} @var{params}@dots{}
34955 @itemx Q @var{name} @var{params}@dots{}
34956 @cindex @samp{q} packet
34957 @cindex @samp{Q} packet
34958 General query (@samp{q}) and set (@samp{Q}). These packets are
34959 described fully in @ref{General Query Packets}.
34962 @cindex @samp{r} packet
34963 Reset the entire system.
34965 Don't use this packet; use the @samp{R} packet instead.
34968 @cindex @samp{R} packet
34969 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34970 This packet is only available in extended mode (@pxref{extended mode}).
34972 The @samp{R} packet has no reply.
34974 @item s @r{[}@var{addr}@r{]}
34975 @cindex @samp{s} packet
34976 Single step, resuming at @var{addr}. If
34977 @var{addr} is omitted, resume at same address.
34979 This packet is deprecated for multi-threading support. @xref{vCont
34983 @xref{Stop Reply Packets}, for the reply specifications.
34985 @item S @var{sig}@r{[};@var{addr}@r{]}
34986 @anchor{step with signal packet}
34987 @cindex @samp{S} packet
34988 Step with signal. This is analogous to the @samp{C} packet, but
34989 requests a single-step, rather than a normal resumption of execution.
34991 This packet is deprecated for multi-threading support. @xref{vCont
34995 @xref{Stop Reply Packets}, for the reply specifications.
34997 @item t @var{addr}:@var{PP},@var{MM}
34998 @cindex @samp{t} packet
34999 Search backwards starting at address @var{addr} for a match with pattern
35000 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35001 There must be at least 3 digits in @var{addr}.
35003 @item T @var{thread-id}
35004 @cindex @samp{T} packet
35005 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35010 thread is still alive
35016 Packets starting with @samp{v} are identified by a multi-letter name,
35017 up to the first @samp{;} or @samp{?} (or the end of the packet).
35019 @item vAttach;@var{pid}
35020 @cindex @samp{vAttach} packet
35021 Attach to a new process with the specified process ID @var{pid}.
35022 The process ID is a
35023 hexadecimal integer identifying the process. In all-stop mode, all
35024 threads in the attached process are stopped; in non-stop mode, it may be
35025 attached without being stopped if that is supported by the target.
35027 @c In non-stop mode, on a successful vAttach, the stub should set the
35028 @c current thread to a thread of the newly-attached process. After
35029 @c attaching, GDB queries for the attached process's thread ID with qC.
35030 @c Also note that, from a user perspective, whether or not the
35031 @c target is stopped on attach in non-stop mode depends on whether you
35032 @c use the foreground or background version of the attach command, not
35033 @c on what vAttach does; GDB does the right thing with respect to either
35034 @c stopping or restarting threads.
35036 This packet is only available in extended mode (@pxref{extended mode}).
35042 @item @r{Any stop packet}
35043 for success in all-stop mode (@pxref{Stop Reply Packets})
35045 for success in non-stop mode (@pxref{Remote Non-Stop})
35048 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35049 @cindex @samp{vCont} packet
35050 @anchor{vCont packet}
35051 Resume the inferior, specifying different actions for each thread.
35052 If an action is specified with no @var{thread-id}, then it is applied to any
35053 threads that don't have a specific action specified; if no default action is
35054 specified then other threads should remain stopped in all-stop mode and
35055 in their current state in non-stop mode.
35056 Specifying multiple
35057 default actions is an error; specifying no actions is also an error.
35058 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35060 Currently supported actions are:
35066 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35070 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35073 @item r @var{start},@var{end}
35074 Step once, and then keep stepping as long as the thread stops at
35075 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35076 The remote stub reports a stop reply when either the thread goes out
35077 of the range or is stopped due to an unrelated reason, such as hitting
35078 a breakpoint. @xref{range stepping}.
35080 If the range is empty (@var{start} == @var{end}), then the action
35081 becomes equivalent to the @samp{s} action. In other words,
35082 single-step once, and report the stop (even if the stepped instruction
35083 jumps to @var{start}).
35085 (A stop reply may be sent at any point even if the PC is still within
35086 the stepping range; for example, it is valid to implement this packet
35087 in a degenerate way as a single instruction step operation.)
35091 The optional argument @var{addr} normally associated with the
35092 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35093 not supported in @samp{vCont}.
35095 The @samp{t} action is only relevant in non-stop mode
35096 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35097 A stop reply should be generated for any affected thread not already stopped.
35098 When a thread is stopped by means of a @samp{t} action,
35099 the corresponding stop reply should indicate that the thread has stopped with
35100 signal @samp{0}, regardless of whether the target uses some other signal
35101 as an implementation detail.
35103 The stub must support @samp{vCont} if it reports support for
35104 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35105 this case @samp{vCont} actions can be specified to apply to all threads
35106 in a process by using the @samp{p@var{pid}.-1} form of the
35110 @xref{Stop Reply Packets}, for the reply specifications.
35113 @cindex @samp{vCont?} packet
35114 Request a list of actions supported by the @samp{vCont} packet.
35118 @item vCont@r{[};@var{action}@dots{}@r{]}
35119 The @samp{vCont} packet is supported. Each @var{action} is a supported
35120 command in the @samp{vCont} packet.
35122 The @samp{vCont} packet is not supported.
35125 @anchor{vCtrlC packet}
35127 @cindex @samp{vCtrlC} packet
35128 Interrupt remote target as if a control-C was pressed on the remote
35129 terminal. This is the equivalent to reacting to the @code{^C}
35130 (@samp{\003}, the control-C character) character in all-stop mode
35131 while the target is running, except this works in non-stop mode.
35132 @xref{interrupting remote targets}, for more info on the all-stop
35143 @item vFile:@var{operation}:@var{parameter}@dots{}
35144 @cindex @samp{vFile} packet
35145 Perform a file operation on the target system. For details,
35146 see @ref{Host I/O Packets}.
35148 @item vFlashErase:@var{addr},@var{length}
35149 @cindex @samp{vFlashErase} packet
35150 Direct the stub to erase @var{length} bytes of flash starting at
35151 @var{addr}. The region may enclose any number of flash blocks, but
35152 its start and end must fall on block boundaries, as indicated by the
35153 flash block size appearing in the memory map (@pxref{Memory Map
35154 Format}). @value{GDBN} groups flash memory programming operations
35155 together, and sends a @samp{vFlashDone} request after each group; the
35156 stub is allowed to delay erase operation until the @samp{vFlashDone}
35157 packet is received.
35167 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35168 @cindex @samp{vFlashWrite} packet
35169 Direct the stub to write data to flash address @var{addr}. The data
35170 is passed in binary form using the same encoding as for the @samp{X}
35171 packet (@pxref{Binary Data}). The memory ranges specified by
35172 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35173 not overlap, and must appear in order of increasing addresses
35174 (although @samp{vFlashErase} packets for higher addresses may already
35175 have been received; the ordering is guaranteed only between
35176 @samp{vFlashWrite} packets). If a packet writes to an address that was
35177 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35178 target-specific method, the results are unpredictable.
35186 for vFlashWrite addressing non-flash memory
35192 @cindex @samp{vFlashDone} packet
35193 Indicate to the stub that flash programming operation is finished.
35194 The stub is permitted to delay or batch the effects of a group of
35195 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35196 @samp{vFlashDone} packet is received. The contents of the affected
35197 regions of flash memory are unpredictable until the @samp{vFlashDone}
35198 request is completed.
35200 @item vKill;@var{pid}
35201 @cindex @samp{vKill} packet
35202 @anchor{vKill packet}
35203 Kill the process with the specified process ID @var{pid}, which is a
35204 hexadecimal integer identifying the process. This packet is used in
35205 preference to @samp{k} when multiprocess protocol extensions are
35206 supported; see @ref{multiprocess extensions}.
35216 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35217 @cindex @samp{vRun} packet
35218 Run the program @var{filename}, passing it each @var{argument} on its
35219 command line. The file and arguments are hex-encoded strings. If
35220 @var{filename} is an empty string, the stub may use a default program
35221 (e.g.@: the last program run). The program is created in the stopped
35224 @c FIXME: What about non-stop mode?
35226 This packet is only available in extended mode (@pxref{extended mode}).
35232 @item @r{Any stop packet}
35233 for success (@pxref{Stop Reply Packets})
35237 @cindex @samp{vStopped} packet
35238 @xref{Notification Packets}.
35240 @item X @var{addr},@var{length}:@var{XX@dots{}}
35242 @cindex @samp{X} packet
35243 Write data to memory, where the data is transmitted in binary.
35244 Memory is specified by its address @var{addr} and number of addressable memory
35245 units @var{length} (@pxref{addressable memory unit});
35246 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35256 @item z @var{type},@var{addr},@var{kind}
35257 @itemx Z @var{type},@var{addr},@var{kind}
35258 @anchor{insert breakpoint or watchpoint packet}
35259 @cindex @samp{z} packet
35260 @cindex @samp{Z} packets
35261 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35262 watchpoint starting at address @var{address} of kind @var{kind}.
35264 Each breakpoint and watchpoint packet @var{type} is documented
35267 @emph{Implementation notes: A remote target shall return an empty string
35268 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35269 remote target shall support either both or neither of a given
35270 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35271 avoid potential problems with duplicate packets, the operations should
35272 be implemented in an idempotent way.}
35274 @item z0,@var{addr},@var{kind}
35275 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35276 @cindex @samp{z0} packet
35277 @cindex @samp{Z0} packet
35278 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35279 @var{addr} of type @var{kind}.
35281 A memory breakpoint is implemented by replacing the instruction at
35282 @var{addr} with a software breakpoint or trap instruction. The
35283 @var{kind} is target-specific and typically indicates the size of
35284 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35285 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35286 architectures have additional meanings for @var{kind};
35287 @var{cond_list} is an optional list of conditional expressions in bytecode
35288 form that should be evaluated on the target's side. These are the
35289 conditions that should be taken into consideration when deciding if
35290 the breakpoint trigger should be reported back to @var{GDBN}.
35292 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35293 for how to best report a memory breakpoint event to @value{GDBN}.
35295 The @var{cond_list} parameter is comprised of a series of expressions,
35296 concatenated without separators. Each expression has the following form:
35300 @item X @var{len},@var{expr}
35301 @var{len} is the length of the bytecode expression and @var{expr} is the
35302 actual conditional expression in bytecode form.
35306 The optional @var{cmd_list} parameter introduces commands that may be
35307 run on the target, rather than being reported back to @value{GDBN}.
35308 The parameter starts with a numeric flag @var{persist}; if the flag is
35309 nonzero, then the breakpoint may remain active and the commands
35310 continue to be run even when @value{GDBN} disconnects from the target.
35311 Following this flag is a series of expressions concatenated with no
35312 separators. Each expression has the following form:
35316 @item X @var{len},@var{expr}
35317 @var{len} is the length of the bytecode expression and @var{expr} is the
35318 actual conditional expression in bytecode form.
35322 see @ref{Architecture-Specific Protocol Details}.
35324 @emph{Implementation note: It is possible for a target to copy or move
35325 code that contains memory breakpoints (e.g., when implementing
35326 overlays). The behavior of this packet, in the presence of such a
35327 target, is not defined.}
35339 @item z1,@var{addr},@var{kind}
35340 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35341 @cindex @samp{z1} packet
35342 @cindex @samp{Z1} packet
35343 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35344 address @var{addr}.
35346 A hardware breakpoint is implemented using a mechanism that is not
35347 dependant on being able to modify the target's memory. The @var{kind}
35348 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35350 @emph{Implementation note: A hardware breakpoint is not affected by code
35363 @item z2,@var{addr},@var{kind}
35364 @itemx Z2,@var{addr},@var{kind}
35365 @cindex @samp{z2} packet
35366 @cindex @samp{Z2} packet
35367 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35368 The number of bytes to watch is specified by @var{kind}.
35380 @item z3,@var{addr},@var{kind}
35381 @itemx Z3,@var{addr},@var{kind}
35382 @cindex @samp{z3} packet
35383 @cindex @samp{Z3} packet
35384 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35385 The number of bytes to watch is specified by @var{kind}.
35397 @item z4,@var{addr},@var{kind}
35398 @itemx Z4,@var{addr},@var{kind}
35399 @cindex @samp{z4} packet
35400 @cindex @samp{Z4} packet
35401 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35402 The number of bytes to watch is specified by @var{kind}.
35416 @node Stop Reply Packets
35417 @section Stop Reply Packets
35418 @cindex stop reply packets
35420 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35421 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35422 receive any of the below as a reply. Except for @samp{?}
35423 and @samp{vStopped}, that reply is only returned
35424 when the target halts. In the below the exact meaning of @dfn{signal
35425 number} is defined by the header @file{include/gdb/signals.h} in the
35426 @value{GDBN} source code.
35428 As in the description of request packets, we include spaces in the
35429 reply templates for clarity; these are not part of the reply packet's
35430 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35436 The program received signal number @var{AA} (a two-digit hexadecimal
35437 number). This is equivalent to a @samp{T} response with no
35438 @var{n}:@var{r} pairs.
35440 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35441 @cindex @samp{T} packet reply
35442 The program received signal number @var{AA} (a two-digit hexadecimal
35443 number). This is equivalent to an @samp{S} response, except that the
35444 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35445 and other information directly in the stop reply packet, reducing
35446 round-trip latency. Single-step and breakpoint traps are reported
35447 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35451 If @var{n} is a hexadecimal number, it is a register number, and the
35452 corresponding @var{r} gives that register's value. The data @var{r} is a
35453 series of bytes in target byte order, with each byte given by a
35454 two-digit hex number.
35457 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35458 the stopped thread, as specified in @ref{thread-id syntax}.
35461 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35462 the core on which the stop event was detected.
35465 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35466 specific event that stopped the target. The currently defined stop
35467 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35468 signal. At most one stop reason should be present.
35471 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35472 and go on to the next; this allows us to extend the protocol in the
35476 The currently defined stop reasons are:
35482 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35485 @cindex shared library events, remote reply
35487 The packet indicates that the loaded libraries have changed.
35488 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35489 list of loaded libraries. The @var{r} part is ignored.
35491 @cindex replay log events, remote reply
35493 The packet indicates that the target cannot continue replaying
35494 logged execution events, because it has reached the end (or the
35495 beginning when executing backward) of the log. The value of @var{r}
35496 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35497 for more information.
35500 @anchor{swbreak stop reason}
35501 The packet indicates a memory breakpoint instruction was executed,
35502 irrespective of whether it was @value{GDBN} that planted the
35503 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35504 part must be left empty.
35506 On some architectures, such as x86, at the architecture level, when a
35507 breakpoint instruction executes the program counter points at the
35508 breakpoint address plus an offset. On such targets, the stub is
35509 responsible for adjusting the PC to point back at the breakpoint
35512 This packet should not be sent by default; older @value{GDBN} versions
35513 did not support it. @value{GDBN} requests it, by supplying an
35514 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35515 remote stub must also supply the appropriate @samp{qSupported} feature
35516 indicating support.
35518 This packet is required for correct non-stop mode operation.
35521 The packet indicates the target stopped for a hardware breakpoint.
35522 The @var{r} part must be left empty.
35524 The same remarks about @samp{qSupported} and non-stop mode above
35527 @cindex fork events, remote reply
35529 The packet indicates that @code{fork} was called, and @var{r}
35530 is the thread ID of the new child process. Refer to
35531 @ref{thread-id syntax} for the format of the @var{thread-id}
35532 field. This packet is only applicable to targets that support
35535 This packet should not be sent by default; older @value{GDBN} versions
35536 did not support it. @value{GDBN} requests it, by supplying an
35537 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35538 remote stub must also supply the appropriate @samp{qSupported} feature
35539 indicating support.
35541 @cindex vfork events, remote reply
35543 The packet indicates that @code{vfork} was called, and @var{r}
35544 is the thread ID of the new child process. Refer to
35545 @ref{thread-id syntax} for the format of the @var{thread-id}
35546 field. This packet is only applicable to targets that support
35549 This packet should not be sent by default; older @value{GDBN} versions
35550 did not support it. @value{GDBN} requests it, by supplying an
35551 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35552 remote stub must also supply the appropriate @samp{qSupported} feature
35553 indicating support.
35555 @cindex vforkdone events, remote reply
35557 The packet indicates that a child process created by a vfork
35558 has either called @code{exec} or terminated, so that the
35559 address spaces of the parent and child process are no longer
35560 shared. The @var{r} part is ignored. This packet is only
35561 applicable to targets that support vforkdone events.
35563 This packet should not be sent by default; older @value{GDBN} versions
35564 did not support it. @value{GDBN} requests it, by supplying an
35565 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35566 remote stub must also supply the appropriate @samp{qSupported} feature
35567 indicating support.
35569 @cindex exec events, remote reply
35571 The packet indicates that @code{execve} was called, and @var{r}
35572 is the absolute pathname of the file that was executed, in hex.
35573 This packet is only applicable to targets that support exec events.
35575 This packet should not be sent by default; older @value{GDBN} versions
35576 did not support it. @value{GDBN} requests it, by supplying an
35577 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35578 remote stub must also supply the appropriate @samp{qSupported} feature
35579 indicating support.
35581 @cindex thread create event, remote reply
35582 @anchor{thread create event}
35584 The packet indicates that the thread was just created. The new thread
35585 is stopped until @value{GDBN} sets it running with a resumption packet
35586 (@pxref{vCont packet}). This packet should not be sent by default;
35587 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35588 also the @samp{w} (@ref{thread exit event}) remote reply below.
35593 @itemx W @var{AA} ; process:@var{pid}
35594 The process exited, and @var{AA} is the exit status. This is only
35595 applicable to certain targets.
35597 The second form of the response, including the process ID of the exited
35598 process, can be used only when @value{GDBN} has reported support for
35599 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35600 The @var{pid} is formatted as a big-endian hex string.
35603 @itemx X @var{AA} ; process:@var{pid}
35604 The process terminated with signal @var{AA}.
35606 The second form of the response, including the process ID of the
35607 terminated process, can be used only when @value{GDBN} has reported
35608 support for multiprocess protocol extensions; see @ref{multiprocess
35609 extensions}. The @var{pid} is formatted as a big-endian hex string.
35611 @anchor{thread exit event}
35612 @cindex thread exit event, remote reply
35613 @item w @var{AA} ; @var{tid}
35615 The thread exited, and @var{AA} is the exit status. This response
35616 should not be sent by default; @value{GDBN} requests it with the
35617 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35620 There are no resumed threads left in the target. In other words, even
35621 though the process is alive, the last resumed thread has exited. For
35622 example, say the target process has two threads: thread 1 and thread
35623 2. The client leaves thread 1 stopped, and resumes thread 2, which
35624 subsequently exits. At this point, even though the process is still
35625 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35626 executing either. The @samp{N} stop reply thus informs the client
35627 that it can stop waiting for stop replies. This packet should not be
35628 sent by default; older @value{GDBN} versions did not support it.
35629 @value{GDBN} requests it, by supplying an appropriate
35630 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35631 also supply the appropriate @samp{qSupported} feature indicating
35634 @item O @var{XX}@dots{}
35635 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35636 written as the program's console output. This can happen at any time
35637 while the program is running and the debugger should continue to wait
35638 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35640 @item F @var{call-id},@var{parameter}@dots{}
35641 @var{call-id} is the identifier which says which host system call should
35642 be called. This is just the name of the function. Translation into the
35643 correct system call is only applicable as it's defined in @value{GDBN}.
35644 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35647 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35648 this very system call.
35650 The target replies with this packet when it expects @value{GDBN} to
35651 call a host system call on behalf of the target. @value{GDBN} replies
35652 with an appropriate @samp{F} packet and keeps up waiting for the next
35653 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35654 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35655 Protocol Extension}, for more details.
35659 @node General Query Packets
35660 @section General Query Packets
35661 @cindex remote query requests
35663 Packets starting with @samp{q} are @dfn{general query packets};
35664 packets starting with @samp{Q} are @dfn{general set packets}. General
35665 query and set packets are a semi-unified form for retrieving and
35666 sending information to and from the stub.
35668 The initial letter of a query or set packet is followed by a name
35669 indicating what sort of thing the packet applies to. For example,
35670 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35671 definitions with the stub. These packet names follow some
35676 The name must not contain commas, colons or semicolons.
35678 Most @value{GDBN} query and set packets have a leading upper case
35681 The names of custom vendor packets should use a company prefix, in
35682 lower case, followed by a period. For example, packets designed at
35683 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35684 foos) or @samp{Qacme.bar} (for setting bars).
35687 The name of a query or set packet should be separated from any
35688 parameters by a @samp{:}; the parameters themselves should be
35689 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35690 full packet name, and check for a separator or the end of the packet,
35691 in case two packet names share a common prefix. New packets should not begin
35692 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35693 packets predate these conventions, and have arguments without any terminator
35694 for the packet name; we suspect they are in widespread use in places that
35695 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35696 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35699 Like the descriptions of the other packets, each description here
35700 has a template showing the packet's overall syntax, followed by an
35701 explanation of the packet's meaning. We include spaces in some of the
35702 templates for clarity; these are not part of the packet's syntax. No
35703 @value{GDBN} packet uses spaces to separate its components.
35705 Here are the currently defined query and set packets:
35711 Turn on or off the agent as a helper to perform some debugging operations
35712 delegated from @value{GDBN} (@pxref{Control Agent}).
35714 @item QAllow:@var{op}:@var{val}@dots{}
35715 @cindex @samp{QAllow} packet
35716 Specify which operations @value{GDBN} expects to request of the
35717 target, as a semicolon-separated list of operation name and value
35718 pairs. Possible values for @var{op} include @samp{WriteReg},
35719 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35720 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35721 indicating that @value{GDBN} will not request the operation, or 1,
35722 indicating that it may. (The target can then use this to set up its
35723 own internals optimally, for instance if the debugger never expects to
35724 insert breakpoints, it may not need to install its own trap handler.)
35727 @cindex current thread, remote request
35728 @cindex @samp{qC} packet
35729 Return the current thread ID.
35733 @item QC @var{thread-id}
35734 Where @var{thread-id} is a thread ID as documented in
35735 @ref{thread-id syntax}.
35736 @item @r{(anything else)}
35737 Any other reply implies the old thread ID.
35740 @item qCRC:@var{addr},@var{length}
35741 @cindex CRC of memory block, remote request
35742 @cindex @samp{qCRC} packet
35743 @anchor{qCRC packet}
35744 Compute the CRC checksum of a block of memory using CRC-32 defined in
35745 IEEE 802.3. The CRC is computed byte at a time, taking the most
35746 significant bit of each byte first. The initial pattern code
35747 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35749 @emph{Note:} This is the same CRC used in validating separate debug
35750 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35751 Files}). However the algorithm is slightly different. When validating
35752 separate debug files, the CRC is computed taking the @emph{least}
35753 significant bit of each byte first, and the final result is inverted to
35754 detect trailing zeros.
35759 An error (such as memory fault)
35760 @item C @var{crc32}
35761 The specified memory region's checksum is @var{crc32}.
35764 @item QDisableRandomization:@var{value}
35765 @cindex disable address space randomization, remote request
35766 @cindex @samp{QDisableRandomization} packet
35767 Some target operating systems will randomize the virtual address space
35768 of the inferior process as a security feature, but provide a feature
35769 to disable such randomization, e.g.@: to allow for a more deterministic
35770 debugging experience. On such systems, this packet with a @var{value}
35771 of 1 directs the target to disable address space randomization for
35772 processes subsequently started via @samp{vRun} packets, while a packet
35773 with a @var{value} of 0 tells the target to enable address space
35776 This packet is only available in extended mode (@pxref{extended mode}).
35781 The request succeeded.
35784 An error occurred. The error number @var{nn} is given as hex digits.
35787 An empty reply indicates that @samp{QDisableRandomization} is not supported
35791 This packet is not probed by default; the remote stub must request it,
35792 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35793 This should only be done on targets that actually support disabling
35794 address space randomization.
35797 @itemx qsThreadInfo
35798 @cindex list active threads, remote request
35799 @cindex @samp{qfThreadInfo} packet
35800 @cindex @samp{qsThreadInfo} packet
35801 Obtain a list of all active thread IDs from the target (OS). Since there
35802 may be too many active threads to fit into one reply packet, this query
35803 works iteratively: it may require more than one query/reply sequence to
35804 obtain the entire list of threads. The first query of the sequence will
35805 be the @samp{qfThreadInfo} query; subsequent queries in the
35806 sequence will be the @samp{qsThreadInfo} query.
35808 NOTE: This packet replaces the @samp{qL} query (see below).
35812 @item m @var{thread-id}
35814 @item m @var{thread-id},@var{thread-id}@dots{}
35815 a comma-separated list of thread IDs
35817 (lower case letter @samp{L}) denotes end of list.
35820 In response to each query, the target will reply with a list of one or
35821 more thread IDs, separated by commas.
35822 @value{GDBN} will respond to each reply with a request for more thread
35823 ids (using the @samp{qs} form of the query), until the target responds
35824 with @samp{l} (lower-case ell, for @dfn{last}).
35825 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35828 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35829 initial connection with the remote target, and the very first thread ID
35830 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35831 message. Therefore, the stub should ensure that the first thread ID in
35832 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35834 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35835 @cindex get thread-local storage address, remote request
35836 @cindex @samp{qGetTLSAddr} packet
35837 Fetch the address associated with thread local storage specified
35838 by @var{thread-id}, @var{offset}, and @var{lm}.
35840 @var{thread-id} is the thread ID associated with the
35841 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35843 @var{offset} is the (big endian, hex encoded) offset associated with the
35844 thread local variable. (This offset is obtained from the debug
35845 information associated with the variable.)
35847 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35848 load module associated with the thread local storage. For example,
35849 a @sc{gnu}/Linux system will pass the link map address of the shared
35850 object associated with the thread local storage under consideration.
35851 Other operating environments may choose to represent the load module
35852 differently, so the precise meaning of this parameter will vary.
35856 @item @var{XX}@dots{}
35857 Hex encoded (big endian) bytes representing the address of the thread
35858 local storage requested.
35861 An error occurred. The error number @var{nn} is given as hex digits.
35864 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35867 @item qGetTIBAddr:@var{thread-id}
35868 @cindex get thread information block address
35869 @cindex @samp{qGetTIBAddr} packet
35870 Fetch address of the Windows OS specific Thread Information Block.
35872 @var{thread-id} is the thread ID associated with the thread.
35876 @item @var{XX}@dots{}
35877 Hex encoded (big endian) bytes representing the linear address of the
35878 thread information block.
35881 An error occured. This means that either the thread was not found, or the
35882 address could not be retrieved.
35885 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35888 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35889 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35890 digit) is one to indicate the first query and zero to indicate a
35891 subsequent query; @var{threadcount} (two hex digits) is the maximum
35892 number of threads the response packet can contain; and @var{nextthread}
35893 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35894 returned in the response as @var{argthread}.
35896 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35900 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35901 Where: @var{count} (two hex digits) is the number of threads being
35902 returned; @var{done} (one hex digit) is zero to indicate more threads
35903 and one indicates no further threads; @var{argthreadid} (eight hex
35904 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35905 is a sequence of thread IDs, @var{threadid} (eight hex
35906 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35910 @cindex section offsets, remote request
35911 @cindex @samp{qOffsets} packet
35912 Get section offsets that the target used when relocating the downloaded
35917 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35918 Relocate the @code{Text} section by @var{xxx} from its original address.
35919 Relocate the @code{Data} section by @var{yyy} from its original address.
35920 If the object file format provides segment information (e.g.@: @sc{elf}
35921 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35922 segments by the supplied offsets.
35924 @emph{Note: while a @code{Bss} offset may be included in the response,
35925 @value{GDBN} ignores this and instead applies the @code{Data} offset
35926 to the @code{Bss} section.}
35928 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35929 Relocate the first segment of the object file, which conventionally
35930 contains program code, to a starting address of @var{xxx}. If
35931 @samp{DataSeg} is specified, relocate the second segment, which
35932 conventionally contains modifiable data, to a starting address of
35933 @var{yyy}. @value{GDBN} will report an error if the object file
35934 does not contain segment information, or does not contain at least
35935 as many segments as mentioned in the reply. Extra segments are
35936 kept at fixed offsets relative to the last relocated segment.
35939 @item qP @var{mode} @var{thread-id}
35940 @cindex thread information, remote request
35941 @cindex @samp{qP} packet
35942 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35943 encoded 32 bit mode; @var{thread-id} is a thread ID
35944 (@pxref{thread-id syntax}).
35946 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35949 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35953 @cindex non-stop mode, remote request
35954 @cindex @samp{QNonStop} packet
35956 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35957 @xref{Remote Non-Stop}, for more information.
35962 The request succeeded.
35965 An error occurred. The error number @var{nn} is given as hex digits.
35968 An empty reply indicates that @samp{QNonStop} is not supported by
35972 This packet is not probed by default; the remote stub must request it,
35973 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35974 Use of this packet is controlled by the @code{set non-stop} command;
35975 @pxref{Non-Stop Mode}.
35977 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35978 @cindex pass signals to inferior, remote request
35979 @cindex @samp{QPassSignals} packet
35980 @anchor{QPassSignals}
35981 Each listed @var{signal} should be passed directly to the inferior process.
35982 Signals are numbered identically to continue packets and stop replies
35983 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35984 strictly greater than the previous item. These signals do not need to stop
35985 the inferior, or be reported to @value{GDBN}. All other signals should be
35986 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35987 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35988 new list. This packet improves performance when using @samp{handle
35989 @var{signal} nostop noprint pass}.
35994 The request succeeded.
35997 An error occurred. The error number @var{nn} is given as hex digits.
36000 An empty reply indicates that @samp{QPassSignals} is not supported by
36004 Use of this packet is controlled by the @code{set remote pass-signals}
36005 command (@pxref{Remote Configuration, set remote pass-signals}).
36006 This packet is not probed by default; the remote stub must request it,
36007 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36009 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36010 @cindex signals the inferior may see, remote request
36011 @cindex @samp{QProgramSignals} packet
36012 @anchor{QProgramSignals}
36013 Each listed @var{signal} may be delivered to the inferior process.
36014 Others should be silently discarded.
36016 In some cases, the remote stub may need to decide whether to deliver a
36017 signal to the program or not without @value{GDBN} involvement. One
36018 example of that is while detaching --- the program's threads may have
36019 stopped for signals that haven't yet had a chance of being reported to
36020 @value{GDBN}, and so the remote stub can use the signal list specified
36021 by this packet to know whether to deliver or ignore those pending
36024 This does not influence whether to deliver a signal as requested by a
36025 resumption packet (@pxref{vCont packet}).
36027 Signals are numbered identically to continue packets and stop replies
36028 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36029 strictly greater than the previous item. Multiple
36030 @samp{QProgramSignals} packets do not combine; any earlier
36031 @samp{QProgramSignals} list is completely replaced by the new list.
36036 The request succeeded.
36039 An error occurred. The error number @var{nn} is given as hex digits.
36042 An empty reply indicates that @samp{QProgramSignals} is not supported
36046 Use of this packet is controlled by the @code{set remote program-signals}
36047 command (@pxref{Remote Configuration, set remote program-signals}).
36048 This packet is not probed by default; the remote stub must request it,
36049 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36051 @anchor{QThreadEvents}
36052 @item QThreadEvents:1
36053 @itemx QThreadEvents:0
36054 @cindex thread create/exit events, remote request
36055 @cindex @samp{QThreadEvents} packet
36057 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36058 reporting of thread create and exit events. @xref{thread create
36059 event}, for the reply specifications. For example, this is used in
36060 non-stop mode when @value{GDBN} stops a set of threads and
36061 synchronously waits for the their corresponding stop replies. Without
36062 exit events, if one of the threads exits, @value{GDBN} would hang
36063 forever not knowing that it should no longer expect a stop for that
36064 same thread. @value{GDBN} does not enable this feature unless the
36065 stub reports that it supports it by including @samp{QThreadEvents+} in
36066 its @samp{qSupported} reply.
36071 The request succeeded.
36074 An error occurred. The error number @var{nn} is given as hex digits.
36077 An empty reply indicates that @samp{QThreadEvents} is not supported by
36081 Use of this packet is controlled by the @code{set remote thread-events}
36082 command (@pxref{Remote Configuration, set remote thread-events}).
36084 @item qRcmd,@var{command}
36085 @cindex execute remote command, remote request
36086 @cindex @samp{qRcmd} packet
36087 @var{command} (hex encoded) is passed to the local interpreter for
36088 execution. Invalid commands should be reported using the output
36089 string. Before the final result packet, the target may also respond
36090 with a number of intermediate @samp{O@var{output}} console output
36091 packets. @emph{Implementors should note that providing access to a
36092 stubs's interpreter may have security implications}.
36097 A command response with no output.
36099 A command response with the hex encoded output string @var{OUTPUT}.
36101 Indicate a badly formed request.
36103 An empty reply indicates that @samp{qRcmd} is not recognized.
36106 (Note that the @code{qRcmd} packet's name is separated from the
36107 command by a @samp{,}, not a @samp{:}, contrary to the naming
36108 conventions above. Please don't use this packet as a model for new
36111 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36112 @cindex searching memory, in remote debugging
36114 @cindex @samp{qSearch:memory} packet
36116 @cindex @samp{qSearch memory} packet
36117 @anchor{qSearch memory}
36118 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36119 Both @var{address} and @var{length} are encoded in hex;
36120 @var{search-pattern} is a sequence of bytes, also hex encoded.
36125 The pattern was not found.
36127 The pattern was found at @var{address}.
36129 A badly formed request or an error was encountered while searching memory.
36131 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36134 @item QStartNoAckMode
36135 @cindex @samp{QStartNoAckMode} packet
36136 @anchor{QStartNoAckMode}
36137 Request that the remote stub disable the normal @samp{+}/@samp{-}
36138 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36143 The stub has switched to no-acknowledgment mode.
36144 @value{GDBN} acknowledges this reponse,
36145 but neither the stub nor @value{GDBN} shall send or expect further
36146 @samp{+}/@samp{-} acknowledgments in the current connection.
36148 An empty reply indicates that the stub does not support no-acknowledgment mode.
36151 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36152 @cindex supported packets, remote query
36153 @cindex features of the remote protocol
36154 @cindex @samp{qSupported} packet
36155 @anchor{qSupported}
36156 Tell the remote stub about features supported by @value{GDBN}, and
36157 query the stub for features it supports. This packet allows
36158 @value{GDBN} and the remote stub to take advantage of each others'
36159 features. @samp{qSupported} also consolidates multiple feature probes
36160 at startup, to improve @value{GDBN} performance---a single larger
36161 packet performs better than multiple smaller probe packets on
36162 high-latency links. Some features may enable behavior which must not
36163 be on by default, e.g.@: because it would confuse older clients or
36164 stubs. Other features may describe packets which could be
36165 automatically probed for, but are not. These features must be
36166 reported before @value{GDBN} will use them. This ``default
36167 unsupported'' behavior is not appropriate for all packets, but it
36168 helps to keep the initial connection time under control with new
36169 versions of @value{GDBN} which support increasing numbers of packets.
36173 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36174 The stub supports or does not support each returned @var{stubfeature},
36175 depending on the form of each @var{stubfeature} (see below for the
36178 An empty reply indicates that @samp{qSupported} is not recognized,
36179 or that no features needed to be reported to @value{GDBN}.
36182 The allowed forms for each feature (either a @var{gdbfeature} in the
36183 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36187 @item @var{name}=@var{value}
36188 The remote protocol feature @var{name} is supported, and associated
36189 with the specified @var{value}. The format of @var{value} depends
36190 on the feature, but it must not include a semicolon.
36192 The remote protocol feature @var{name} is supported, and does not
36193 need an associated value.
36195 The remote protocol feature @var{name} is not supported.
36197 The remote protocol feature @var{name} may be supported, and
36198 @value{GDBN} should auto-detect support in some other way when it is
36199 needed. This form will not be used for @var{gdbfeature} notifications,
36200 but may be used for @var{stubfeature} responses.
36203 Whenever the stub receives a @samp{qSupported} request, the
36204 supplied set of @value{GDBN} features should override any previous
36205 request. This allows @value{GDBN} to put the stub in a known
36206 state, even if the stub had previously been communicating with
36207 a different version of @value{GDBN}.
36209 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36214 This feature indicates whether @value{GDBN} supports multiprocess
36215 extensions to the remote protocol. @value{GDBN} does not use such
36216 extensions unless the stub also reports that it supports them by
36217 including @samp{multiprocess+} in its @samp{qSupported} reply.
36218 @xref{multiprocess extensions}, for details.
36221 This feature indicates that @value{GDBN} supports the XML target
36222 description. If the stub sees @samp{xmlRegisters=} with target
36223 specific strings separated by a comma, it will report register
36227 This feature indicates whether @value{GDBN} supports the
36228 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36229 instruction reply packet}).
36232 This feature indicates whether @value{GDBN} supports the swbreak stop
36233 reason in stop replies. @xref{swbreak stop reason}, for details.
36236 This feature indicates whether @value{GDBN} supports the hwbreak stop
36237 reason in stop replies. @xref{swbreak stop reason}, for details.
36240 This feature indicates whether @value{GDBN} supports fork event
36241 extensions to the remote protocol. @value{GDBN} does not use such
36242 extensions unless the stub also reports that it supports them by
36243 including @samp{fork-events+} in its @samp{qSupported} reply.
36246 This feature indicates whether @value{GDBN} supports vfork event
36247 extensions to the remote protocol. @value{GDBN} does not use such
36248 extensions unless the stub also reports that it supports them by
36249 including @samp{vfork-events+} in its @samp{qSupported} reply.
36252 This feature indicates whether @value{GDBN} supports exec event
36253 extensions to the remote protocol. @value{GDBN} does not use such
36254 extensions unless the stub also reports that it supports them by
36255 including @samp{exec-events+} in its @samp{qSupported} reply.
36257 @item vContSupported
36258 This feature indicates whether @value{GDBN} wants to know the
36259 supported actions in the reply to @samp{vCont?} packet.
36262 Stubs should ignore any unknown values for
36263 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36264 packet supports receiving packets of unlimited length (earlier
36265 versions of @value{GDBN} may reject overly long responses). Additional values
36266 for @var{gdbfeature} may be defined in the future to let the stub take
36267 advantage of new features in @value{GDBN}, e.g.@: incompatible
36268 improvements in the remote protocol---the @samp{multiprocess} feature is
36269 an example of such a feature. The stub's reply should be independent
36270 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36271 describes all the features it supports, and then the stub replies with
36272 all the features it supports.
36274 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36275 responses, as long as each response uses one of the standard forms.
36277 Some features are flags. A stub which supports a flag feature
36278 should respond with a @samp{+} form response. Other features
36279 require values, and the stub should respond with an @samp{=}
36282 Each feature has a default value, which @value{GDBN} will use if
36283 @samp{qSupported} is not available or if the feature is not mentioned
36284 in the @samp{qSupported} response. The default values are fixed; a
36285 stub is free to omit any feature responses that match the defaults.
36287 Not all features can be probed, but for those which can, the probing
36288 mechanism is useful: in some cases, a stub's internal
36289 architecture may not allow the protocol layer to know some information
36290 about the underlying target in advance. This is especially common in
36291 stubs which may be configured for multiple targets.
36293 These are the currently defined stub features and their properties:
36295 @multitable @columnfractions 0.35 0.2 0.12 0.2
36296 @c NOTE: The first row should be @headitem, but we do not yet require
36297 @c a new enough version of Texinfo (4.7) to use @headitem.
36299 @tab Value Required
36303 @item @samp{PacketSize}
36308 @item @samp{qXfer:auxv:read}
36313 @item @samp{qXfer:btrace:read}
36318 @item @samp{qXfer:btrace-conf:read}
36323 @item @samp{qXfer:exec-file:read}
36328 @item @samp{qXfer:features:read}
36333 @item @samp{qXfer:libraries:read}
36338 @item @samp{qXfer:libraries-svr4:read}
36343 @item @samp{augmented-libraries-svr4-read}
36348 @item @samp{qXfer:memory-map:read}
36353 @item @samp{qXfer:sdata:read}
36358 @item @samp{qXfer:spu:read}
36363 @item @samp{qXfer:spu:write}
36368 @item @samp{qXfer:siginfo:read}
36373 @item @samp{qXfer:siginfo:write}
36378 @item @samp{qXfer:threads:read}
36383 @item @samp{qXfer:traceframe-info:read}
36388 @item @samp{qXfer:uib:read}
36393 @item @samp{qXfer:fdpic:read}
36398 @item @samp{Qbtrace:off}
36403 @item @samp{Qbtrace:bts}
36408 @item @samp{Qbtrace:pt}
36413 @item @samp{Qbtrace-conf:bts:size}
36418 @item @samp{Qbtrace-conf:pt:size}
36423 @item @samp{QNonStop}
36428 @item @samp{QPassSignals}
36433 @item @samp{QStartNoAckMode}
36438 @item @samp{multiprocess}
36443 @item @samp{ConditionalBreakpoints}
36448 @item @samp{ConditionalTracepoints}
36453 @item @samp{ReverseContinue}
36458 @item @samp{ReverseStep}
36463 @item @samp{TracepointSource}
36468 @item @samp{QAgent}
36473 @item @samp{QAllow}
36478 @item @samp{QDisableRandomization}
36483 @item @samp{EnableDisableTracepoints}
36488 @item @samp{QTBuffer:size}
36493 @item @samp{tracenz}
36498 @item @samp{BreakpointCommands}
36503 @item @samp{swbreak}
36508 @item @samp{hwbreak}
36513 @item @samp{fork-events}
36518 @item @samp{vfork-events}
36523 @item @samp{exec-events}
36528 @item @samp{QThreadEvents}
36533 @item @samp{no-resumed}
36540 These are the currently defined stub features, in more detail:
36543 @cindex packet size, remote protocol
36544 @item PacketSize=@var{bytes}
36545 The remote stub can accept packets up to at least @var{bytes} in
36546 length. @value{GDBN} will send packets up to this size for bulk
36547 transfers, and will never send larger packets. This is a limit on the
36548 data characters in the packet, including the frame and checksum.
36549 There is no trailing NUL byte in a remote protocol packet; if the stub
36550 stores packets in a NUL-terminated format, it should allow an extra
36551 byte in its buffer for the NUL. If this stub feature is not supported,
36552 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36554 @item qXfer:auxv:read
36555 The remote stub understands the @samp{qXfer:auxv:read} packet
36556 (@pxref{qXfer auxiliary vector read}).
36558 @item qXfer:btrace:read
36559 The remote stub understands the @samp{qXfer:btrace:read}
36560 packet (@pxref{qXfer btrace read}).
36562 @item qXfer:btrace-conf:read
36563 The remote stub understands the @samp{qXfer:btrace-conf:read}
36564 packet (@pxref{qXfer btrace-conf read}).
36566 @item qXfer:exec-file:read
36567 The remote stub understands the @samp{qXfer:exec-file:read} packet
36568 (@pxref{qXfer executable filename read}).
36570 @item qXfer:features:read
36571 The remote stub understands the @samp{qXfer:features:read} packet
36572 (@pxref{qXfer target description read}).
36574 @item qXfer:libraries:read
36575 The remote stub understands the @samp{qXfer:libraries:read} packet
36576 (@pxref{qXfer library list read}).
36578 @item qXfer:libraries-svr4:read
36579 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36580 (@pxref{qXfer svr4 library list read}).
36582 @item augmented-libraries-svr4-read
36583 The remote stub understands the augmented form of the
36584 @samp{qXfer:libraries-svr4:read} packet
36585 (@pxref{qXfer svr4 library list read}).
36587 @item qXfer:memory-map:read
36588 The remote stub understands the @samp{qXfer:memory-map:read} packet
36589 (@pxref{qXfer memory map read}).
36591 @item qXfer:sdata:read
36592 The remote stub understands the @samp{qXfer:sdata:read} packet
36593 (@pxref{qXfer sdata read}).
36595 @item qXfer:spu:read
36596 The remote stub understands the @samp{qXfer:spu:read} packet
36597 (@pxref{qXfer spu read}).
36599 @item qXfer:spu:write
36600 The remote stub understands the @samp{qXfer:spu:write} packet
36601 (@pxref{qXfer spu write}).
36603 @item qXfer:siginfo:read
36604 The remote stub understands the @samp{qXfer:siginfo:read} packet
36605 (@pxref{qXfer siginfo read}).
36607 @item qXfer:siginfo:write
36608 The remote stub understands the @samp{qXfer:siginfo:write} packet
36609 (@pxref{qXfer siginfo write}).
36611 @item qXfer:threads:read
36612 The remote stub understands the @samp{qXfer:threads:read} packet
36613 (@pxref{qXfer threads read}).
36615 @item qXfer:traceframe-info:read
36616 The remote stub understands the @samp{qXfer:traceframe-info:read}
36617 packet (@pxref{qXfer traceframe info read}).
36619 @item qXfer:uib:read
36620 The remote stub understands the @samp{qXfer:uib:read}
36621 packet (@pxref{qXfer unwind info block}).
36623 @item qXfer:fdpic:read
36624 The remote stub understands the @samp{qXfer:fdpic:read}
36625 packet (@pxref{qXfer fdpic loadmap read}).
36628 The remote stub understands the @samp{QNonStop} packet
36629 (@pxref{QNonStop}).
36632 The remote stub understands the @samp{QPassSignals} packet
36633 (@pxref{QPassSignals}).
36635 @item QStartNoAckMode
36636 The remote stub understands the @samp{QStartNoAckMode} packet and
36637 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36640 @anchor{multiprocess extensions}
36641 @cindex multiprocess extensions, in remote protocol
36642 The remote stub understands the multiprocess extensions to the remote
36643 protocol syntax. The multiprocess extensions affect the syntax of
36644 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36645 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36646 replies. Note that reporting this feature indicates support for the
36647 syntactic extensions only, not that the stub necessarily supports
36648 debugging of more than one process at a time. The stub must not use
36649 multiprocess extensions in packet replies unless @value{GDBN} has also
36650 indicated it supports them in its @samp{qSupported} request.
36652 @item qXfer:osdata:read
36653 The remote stub understands the @samp{qXfer:osdata:read} packet
36654 ((@pxref{qXfer osdata read}).
36656 @item ConditionalBreakpoints
36657 The target accepts and implements evaluation of conditional expressions
36658 defined for breakpoints. The target will only report breakpoint triggers
36659 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36661 @item ConditionalTracepoints
36662 The remote stub accepts and implements conditional expressions defined
36663 for tracepoints (@pxref{Tracepoint Conditions}).
36665 @item ReverseContinue
36666 The remote stub accepts and implements the reverse continue packet
36670 The remote stub accepts and implements the reverse step packet
36673 @item TracepointSource
36674 The remote stub understands the @samp{QTDPsrc} packet that supplies
36675 the source form of tracepoint definitions.
36678 The remote stub understands the @samp{QAgent} packet.
36681 The remote stub understands the @samp{QAllow} packet.
36683 @item QDisableRandomization
36684 The remote stub understands the @samp{QDisableRandomization} packet.
36686 @item StaticTracepoint
36687 @cindex static tracepoints, in remote protocol
36688 The remote stub supports static tracepoints.
36690 @item InstallInTrace
36691 @anchor{install tracepoint in tracing}
36692 The remote stub supports installing tracepoint in tracing.
36694 @item EnableDisableTracepoints
36695 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36696 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36697 to be enabled and disabled while a trace experiment is running.
36699 @item QTBuffer:size
36700 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36701 packet that allows to change the size of the trace buffer.
36704 @cindex string tracing, in remote protocol
36705 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36706 See @ref{Bytecode Descriptions} for details about the bytecode.
36708 @item BreakpointCommands
36709 @cindex breakpoint commands, in remote protocol
36710 The remote stub supports running a breakpoint's command list itself,
36711 rather than reporting the hit to @value{GDBN}.
36714 The remote stub understands the @samp{Qbtrace:off} packet.
36717 The remote stub understands the @samp{Qbtrace:bts} packet.
36720 The remote stub understands the @samp{Qbtrace:pt} packet.
36722 @item Qbtrace-conf:bts:size
36723 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36725 @item Qbtrace-conf:pt:size
36726 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36729 The remote stub reports the @samp{swbreak} stop reason for memory
36733 The remote stub reports the @samp{hwbreak} stop reason for hardware
36737 The remote stub reports the @samp{fork} stop reason for fork events.
36740 The remote stub reports the @samp{vfork} stop reason for vfork events
36741 and vforkdone events.
36744 The remote stub reports the @samp{exec} stop reason for exec events.
36746 @item vContSupported
36747 The remote stub reports the supported actions in the reply to
36748 @samp{vCont?} packet.
36750 @item QThreadEvents
36751 The remote stub understands the @samp{QThreadEvents} packet.
36754 The remote stub reports the @samp{N} stop reply.
36759 @cindex symbol lookup, remote request
36760 @cindex @samp{qSymbol} packet
36761 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36762 requests. Accept requests from the target for the values of symbols.
36767 The target does not need to look up any (more) symbols.
36768 @item qSymbol:@var{sym_name}
36769 The target requests the value of symbol @var{sym_name} (hex encoded).
36770 @value{GDBN} may provide the value by using the
36771 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36775 @item qSymbol:@var{sym_value}:@var{sym_name}
36776 Set the value of @var{sym_name} to @var{sym_value}.
36778 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36779 target has previously requested.
36781 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36782 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36788 The target does not need to look up any (more) symbols.
36789 @item qSymbol:@var{sym_name}
36790 The target requests the value of a new symbol @var{sym_name} (hex
36791 encoded). @value{GDBN} will continue to supply the values of symbols
36792 (if available), until the target ceases to request them.
36797 @itemx QTDisconnected
36804 @itemx qTMinFTPILen
36806 @xref{Tracepoint Packets}.
36808 @item qThreadExtraInfo,@var{thread-id}
36809 @cindex thread attributes info, remote request
36810 @cindex @samp{qThreadExtraInfo} packet
36811 Obtain from the target OS a printable string description of thread
36812 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36813 for the forms of @var{thread-id}. This
36814 string may contain anything that the target OS thinks is interesting
36815 for @value{GDBN} to tell the user about the thread. The string is
36816 displayed in @value{GDBN}'s @code{info threads} display. Some
36817 examples of possible thread extra info strings are @samp{Runnable}, or
36818 @samp{Blocked on Mutex}.
36822 @item @var{XX}@dots{}
36823 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36824 comprising the printable string containing the extra information about
36825 the thread's attributes.
36828 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36829 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36830 conventions above. Please don't use this packet as a model for new
36849 @xref{Tracepoint Packets}.
36851 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36852 @cindex read special object, remote request
36853 @cindex @samp{qXfer} packet
36854 @anchor{qXfer read}
36855 Read uninterpreted bytes from the target's special data area
36856 identified by the keyword @var{object}. Request @var{length} bytes
36857 starting at @var{offset} bytes into the data. The content and
36858 encoding of @var{annex} is specific to @var{object}; it can supply
36859 additional details about what data to access.
36861 Here are the specific requests of this form defined so far. All
36862 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36863 formats, listed below.
36866 @item qXfer:auxv:read::@var{offset},@var{length}
36867 @anchor{qXfer auxiliary vector read}
36868 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36869 auxiliary vector}. Note @var{annex} must be empty.
36871 This packet is not probed by default; the remote stub must request it,
36872 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36874 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36875 @anchor{qXfer btrace read}
36877 Return a description of the current branch trace.
36878 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36879 packet may have one of the following values:
36883 Returns all available branch trace.
36886 Returns all available branch trace if the branch trace changed since
36887 the last read request.
36890 Returns the new branch trace since the last read request. Adds a new
36891 block to the end of the trace that begins at zero and ends at the source
36892 location of the first branch in the trace buffer. This extra block is
36893 used to stitch traces together.
36895 If the trace buffer overflowed, returns an error indicating the overflow.
36898 This packet is not probed by default; the remote stub must request it
36899 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36901 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36902 @anchor{qXfer btrace-conf read}
36904 Return a description of the current branch trace configuration.
36905 @xref{Branch Trace Configuration Format}.
36907 This packet is not probed by default; the remote stub must request it
36908 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36910 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36911 @anchor{qXfer executable filename read}
36912 Return the full absolute name of the file that was executed to create
36913 a process running on the remote system. The annex specifies the
36914 numeric process ID of the process to query, encoded as a hexadecimal
36915 number. If the annex part is empty the remote stub should return the
36916 filename corresponding to the currently executing process.
36918 This packet is not probed by default; the remote stub must request it,
36919 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36921 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36922 @anchor{qXfer target description read}
36923 Access the @dfn{target description}. @xref{Target Descriptions}. The
36924 annex specifies which XML document to access. The main description is
36925 always loaded from the @samp{target.xml} annex.
36927 This packet is not probed by default; the remote stub must request it,
36928 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36930 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36931 @anchor{qXfer library list read}
36932 Access the target's list of loaded libraries. @xref{Library List Format}.
36933 The annex part of the generic @samp{qXfer} packet must be empty
36934 (@pxref{qXfer read}).
36936 Targets which maintain a list of libraries in the program's memory do
36937 not need to implement this packet; it is designed for platforms where
36938 the operating system manages the list of loaded libraries.
36940 This packet is not probed by default; the remote stub must request it,
36941 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36943 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36944 @anchor{qXfer svr4 library list read}
36945 Access the target's list of loaded libraries when the target is an SVR4
36946 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36947 of the generic @samp{qXfer} packet must be empty unless the remote
36948 stub indicated it supports the augmented form of this packet
36949 by supplying an appropriate @samp{qSupported} response
36950 (@pxref{qXfer read}, @ref{qSupported}).
36952 This packet is optional for better performance on SVR4 targets.
36953 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36955 This packet is not probed by default; the remote stub must request it,
36956 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36958 If the remote stub indicates it supports the augmented form of this
36959 packet then the annex part of the generic @samp{qXfer} packet may
36960 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36961 arguments. The currently supported arguments are:
36964 @item start=@var{address}
36965 A hexadecimal number specifying the address of the @samp{struct
36966 link_map} to start reading the library list from. If unset or zero
36967 then the first @samp{struct link_map} in the library list will be
36968 chosen as the starting point.
36970 @item prev=@var{address}
36971 A hexadecimal number specifying the address of the @samp{struct
36972 link_map} immediately preceding the @samp{struct link_map}
36973 specified by the @samp{start} argument. If unset or zero then
36974 the remote stub will expect that no @samp{struct link_map}
36975 exists prior to the starting point.
36979 Arguments that are not understood by the remote stub will be silently
36982 @item qXfer:memory-map:read::@var{offset},@var{length}
36983 @anchor{qXfer memory map read}
36984 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36985 annex part of the generic @samp{qXfer} packet must be empty
36986 (@pxref{qXfer read}).
36988 This packet is not probed by default; the remote stub must request it,
36989 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36991 @item qXfer:sdata:read::@var{offset},@var{length}
36992 @anchor{qXfer sdata read}
36994 Read contents of the extra collected static tracepoint marker
36995 information. The annex part of the generic @samp{qXfer} packet must
36996 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36999 This packet is not probed by default; the remote stub must request it,
37000 by supplying an appropriate @samp{qSupported} response
37001 (@pxref{qSupported}).
37003 @item qXfer:siginfo:read::@var{offset},@var{length}
37004 @anchor{qXfer siginfo read}
37005 Read contents of the extra signal information on the target
37006 system. The annex part of the generic @samp{qXfer} packet must be
37007 empty (@pxref{qXfer read}).
37009 This packet is not probed by default; the remote stub must request it,
37010 by supplying an appropriate @samp{qSupported} response
37011 (@pxref{qSupported}).
37013 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37014 @anchor{qXfer spu read}
37015 Read contents of an @code{spufs} file on the target system. The
37016 annex specifies which file to read; it must be of the form
37017 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37018 in the target process, and @var{name} identifes the @code{spufs} file
37019 in that context to be accessed.
37021 This packet is not probed by default; the remote stub must request it,
37022 by supplying an appropriate @samp{qSupported} response
37023 (@pxref{qSupported}).
37025 @item qXfer:threads:read::@var{offset},@var{length}
37026 @anchor{qXfer threads read}
37027 Access the list of threads on target. @xref{Thread List Format}. The
37028 annex part of the generic @samp{qXfer} packet must be empty
37029 (@pxref{qXfer read}).
37031 This packet is not probed by default; the remote stub must request it,
37032 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37034 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37035 @anchor{qXfer traceframe info read}
37037 Return a description of the current traceframe's contents.
37038 @xref{Traceframe Info Format}. The annex part of the generic
37039 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37041 This packet is not probed by default; the remote stub must request it,
37042 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37044 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37045 @anchor{qXfer unwind info block}
37047 Return the unwind information block for @var{pc}. This packet is used
37048 on OpenVMS/ia64 to ask the kernel unwind information.
37050 This packet is not probed by default.
37052 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37053 @anchor{qXfer fdpic loadmap read}
37054 Read contents of @code{loadmap}s on the target system. The
37055 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37056 executable @code{loadmap} or interpreter @code{loadmap} to read.
37058 This packet is not probed by default; the remote stub must request it,
37059 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37061 @item qXfer:osdata:read::@var{offset},@var{length}
37062 @anchor{qXfer osdata read}
37063 Access the target's @dfn{operating system information}.
37064 @xref{Operating System Information}.
37071 Data @var{data} (@pxref{Binary Data}) has been read from the
37072 target. There may be more data at a higher address (although
37073 it is permitted to return @samp{m} even for the last valid
37074 block of data, as long as at least one byte of data was read).
37075 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37079 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37080 There is no more data to be read. It is possible for @var{data} to
37081 have fewer bytes than the @var{length} in the request.
37084 The @var{offset} in the request is at the end of the data.
37085 There is no more data to be read.
37088 The request was malformed, or @var{annex} was invalid.
37091 The offset was invalid, or there was an error encountered reading the data.
37092 The @var{nn} part is a hex-encoded @code{errno} value.
37095 An empty reply indicates the @var{object} string was not recognized by
37096 the stub, or that the object does not support reading.
37099 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37100 @cindex write data into object, remote request
37101 @anchor{qXfer write}
37102 Write uninterpreted bytes into the target's special data area
37103 identified by the keyword @var{object}, starting at @var{offset} bytes
37104 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37105 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37106 is specific to @var{object}; it can supply additional details about what data
37109 Here are the specific requests of this form defined so far. All
37110 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37111 formats, listed below.
37114 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37115 @anchor{qXfer siginfo write}
37116 Write @var{data} to the extra signal information on the target system.
37117 The annex part of the generic @samp{qXfer} packet must be
37118 empty (@pxref{qXfer write}).
37120 This packet is not probed by default; the remote stub must request it,
37121 by supplying an appropriate @samp{qSupported} response
37122 (@pxref{qSupported}).
37124 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37125 @anchor{qXfer spu write}
37126 Write @var{data} to an @code{spufs} file on the target system. The
37127 annex specifies which file to write; it must be of the form
37128 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37129 in the target process, and @var{name} identifes the @code{spufs} file
37130 in that context to be accessed.
37132 This packet is not probed by default; the remote stub must request it,
37133 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37139 @var{nn} (hex encoded) is the number of bytes written.
37140 This may be fewer bytes than supplied in the request.
37143 The request was malformed, or @var{annex} was invalid.
37146 The offset was invalid, or there was an error encountered writing the data.
37147 The @var{nn} part is a hex-encoded @code{errno} value.
37150 An empty reply indicates the @var{object} string was not
37151 recognized by the stub, or that the object does not support writing.
37154 @item qXfer:@var{object}:@var{operation}:@dots{}
37155 Requests of this form may be added in the future. When a stub does
37156 not recognize the @var{object} keyword, or its support for
37157 @var{object} does not recognize the @var{operation} keyword, the stub
37158 must respond with an empty packet.
37160 @item qAttached:@var{pid}
37161 @cindex query attached, remote request
37162 @cindex @samp{qAttached} packet
37163 Return an indication of whether the remote server attached to an
37164 existing process or created a new process. When the multiprocess
37165 protocol extensions are supported (@pxref{multiprocess extensions}),
37166 @var{pid} is an integer in hexadecimal format identifying the target
37167 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37168 the query packet will be simplified as @samp{qAttached}.
37170 This query is used, for example, to know whether the remote process
37171 should be detached or killed when a @value{GDBN} session is ended with
37172 the @code{quit} command.
37177 The remote server attached to an existing process.
37179 The remote server created a new process.
37181 A badly formed request or an error was encountered.
37185 Enable branch tracing for the current thread using Branch Trace Store.
37190 Branch tracing has been enabled.
37192 A badly formed request or an error was encountered.
37196 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37201 Branch tracing has been enabled.
37203 A badly formed request or an error was encountered.
37207 Disable branch tracing for the current thread.
37212 Branch tracing has been disabled.
37214 A badly formed request or an error was encountered.
37217 @item Qbtrace-conf:bts:size=@var{value}
37218 Set the requested ring buffer size for new threads that use the
37219 btrace recording method in bts format.
37224 The ring buffer size has been set.
37226 A badly formed request or an error was encountered.
37229 @item Qbtrace-conf:pt:size=@var{value}
37230 Set the requested ring buffer size for new threads that use the
37231 btrace recording method in pt format.
37236 The ring buffer size has been set.
37238 A badly formed request or an error was encountered.
37243 @node Architecture-Specific Protocol Details
37244 @section Architecture-Specific Protocol Details
37246 This section describes how the remote protocol is applied to specific
37247 target architectures. Also see @ref{Standard Target Features}, for
37248 details of XML target descriptions for each architecture.
37251 * ARM-Specific Protocol Details::
37252 * MIPS-Specific Protocol Details::
37255 @node ARM-Specific Protocol Details
37256 @subsection @acronym{ARM}-specific Protocol Details
37259 * ARM Breakpoint Kinds::
37262 @node ARM Breakpoint Kinds
37263 @subsubsection @acronym{ARM} Breakpoint Kinds
37264 @cindex breakpoint kinds, @acronym{ARM}
37266 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37271 16-bit Thumb mode breakpoint.
37274 32-bit Thumb mode (Thumb-2) breakpoint.
37277 32-bit @acronym{ARM} mode breakpoint.
37281 @node MIPS-Specific Protocol Details
37282 @subsection @acronym{MIPS}-specific Protocol Details
37285 * MIPS Register packet Format::
37286 * MIPS Breakpoint Kinds::
37289 @node MIPS Register packet Format
37290 @subsubsection @acronym{MIPS} Register Packet Format
37291 @cindex register packet format, @acronym{MIPS}
37293 The following @code{g}/@code{G} packets have previously been defined.
37294 In the below, some thirty-two bit registers are transferred as
37295 sixty-four bits. Those registers should be zero/sign extended (which?)
37296 to fill the space allocated. Register bytes are transferred in target
37297 byte order. The two nibbles within a register byte are transferred
37298 most-significant -- least-significant.
37303 All registers are transferred as thirty-two bit quantities in the order:
37304 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37305 registers; fsr; fir; fp.
37308 All registers are transferred as sixty-four bit quantities (including
37309 thirty-two bit registers such as @code{sr}). The ordering is the same
37314 @node MIPS Breakpoint Kinds
37315 @subsubsection @acronym{MIPS} Breakpoint Kinds
37316 @cindex breakpoint kinds, @acronym{MIPS}
37318 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37323 16-bit @acronym{MIPS16} mode breakpoint.
37326 16-bit @acronym{microMIPS} mode breakpoint.
37329 32-bit standard @acronym{MIPS} mode breakpoint.
37332 32-bit @acronym{microMIPS} mode breakpoint.
37336 @node Tracepoint Packets
37337 @section Tracepoint Packets
37338 @cindex tracepoint packets
37339 @cindex packets, tracepoint
37341 Here we describe the packets @value{GDBN} uses to implement
37342 tracepoints (@pxref{Tracepoints}).
37346 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37347 @cindex @samp{QTDP} packet
37348 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37349 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37350 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37351 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37352 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37353 the number of bytes that the target should copy elsewhere to make room
37354 for the tracepoint. If an @samp{X} is present, it introduces a
37355 tracepoint condition, which consists of a hexadecimal length, followed
37356 by a comma and hex-encoded bytes, in a manner similar to action
37357 encodings as described below. If the trailing @samp{-} is present,
37358 further @samp{QTDP} packets will follow to specify this tracepoint's
37364 The packet was understood and carried out.
37366 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37368 The packet was not recognized.
37371 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37372 Define actions to be taken when a tracepoint is hit. The @var{n} and
37373 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37374 this tracepoint. This packet may only be sent immediately after
37375 another @samp{QTDP} packet that ended with a @samp{-}. If the
37376 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37377 specifying more actions for this tracepoint.
37379 In the series of action packets for a given tracepoint, at most one
37380 can have an @samp{S} before its first @var{action}. If such a packet
37381 is sent, it and the following packets define ``while-stepping''
37382 actions. Any prior packets define ordinary actions --- that is, those
37383 taken when the tracepoint is first hit. If no action packet has an
37384 @samp{S}, then all the packets in the series specify ordinary
37385 tracepoint actions.
37387 The @samp{@var{action}@dots{}} portion of the packet is a series of
37388 actions, concatenated without separators. Each action has one of the
37394 Collect the registers whose bits are set in @var{mask},
37395 a hexadecimal number whose @var{i}'th bit is set if register number
37396 @var{i} should be collected. (The least significant bit is numbered
37397 zero.) Note that @var{mask} may be any number of digits long; it may
37398 not fit in a 32-bit word.
37400 @item M @var{basereg},@var{offset},@var{len}
37401 Collect @var{len} bytes of memory starting at the address in register
37402 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37403 @samp{-1}, then the range has a fixed address: @var{offset} is the
37404 address of the lowest byte to collect. The @var{basereg},
37405 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37406 values (the @samp{-1} value for @var{basereg} is a special case).
37408 @item X @var{len},@var{expr}
37409 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37410 it directs. The agent expression @var{expr} is as described in
37411 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37412 two-digit hex number in the packet; @var{len} is the number of bytes
37413 in the expression (and thus one-half the number of hex digits in the
37418 Any number of actions may be packed together in a single @samp{QTDP}
37419 packet, as long as the packet does not exceed the maximum packet
37420 length (400 bytes, for many stubs). There may be only one @samp{R}
37421 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37422 actions. Any registers referred to by @samp{M} and @samp{X} actions
37423 must be collected by a preceding @samp{R} action. (The
37424 ``while-stepping'' actions are treated as if they were attached to a
37425 separate tracepoint, as far as these restrictions are concerned.)
37430 The packet was understood and carried out.
37432 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37434 The packet was not recognized.
37437 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37438 @cindex @samp{QTDPsrc} packet
37439 Specify a source string of tracepoint @var{n} at address @var{addr}.
37440 This is useful to get accurate reproduction of the tracepoints
37441 originally downloaded at the beginning of the trace run. The @var{type}
37442 is the name of the tracepoint part, such as @samp{cond} for the
37443 tracepoint's conditional expression (see below for a list of types), while
37444 @var{bytes} is the string, encoded in hexadecimal.
37446 @var{start} is the offset of the @var{bytes} within the overall source
37447 string, while @var{slen} is the total length of the source string.
37448 This is intended for handling source strings that are longer than will
37449 fit in a single packet.
37450 @c Add detailed example when this info is moved into a dedicated
37451 @c tracepoint descriptions section.
37453 The available string types are @samp{at} for the location,
37454 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37455 @value{GDBN} sends a separate packet for each command in the action
37456 list, in the same order in which the commands are stored in the list.
37458 The target does not need to do anything with source strings except
37459 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37462 Although this packet is optional, and @value{GDBN} will only send it
37463 if the target replies with @samp{TracepointSource} @xref{General
37464 Query Packets}, it makes both disconnected tracing and trace files
37465 much easier to use. Otherwise the user must be careful that the
37466 tracepoints in effect while looking at trace frames are identical to
37467 the ones in effect during the trace run; even a small discrepancy
37468 could cause @samp{tdump} not to work, or a particular trace frame not
37471 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37472 @cindex define trace state variable, remote request
37473 @cindex @samp{QTDV} packet
37474 Create a new trace state variable, number @var{n}, with an initial
37475 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37476 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37477 the option of not using this packet for initial values of zero; the
37478 target should simply create the trace state variables as they are
37479 mentioned in expressions. The value @var{builtin} should be 1 (one)
37480 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37481 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37482 @samp{qTsV} packet had it set. The contents of @var{name} is the
37483 hex-encoded name (without the leading @samp{$}) of the trace state
37486 @item QTFrame:@var{n}
37487 @cindex @samp{QTFrame} packet
37488 Select the @var{n}'th tracepoint frame from the buffer, and use the
37489 register and memory contents recorded there to answer subsequent
37490 request packets from @value{GDBN}.
37492 A successful reply from the stub indicates that the stub has found the
37493 requested frame. The response is a series of parts, concatenated
37494 without separators, describing the frame we selected. Each part has
37495 one of the following forms:
37499 The selected frame is number @var{n} in the trace frame buffer;
37500 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37501 was no frame matching the criteria in the request packet.
37504 The selected trace frame records a hit of tracepoint number @var{t};
37505 @var{t} is a hexadecimal number.
37509 @item QTFrame:pc:@var{addr}
37510 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37511 currently selected frame whose PC is @var{addr};
37512 @var{addr} is a hexadecimal number.
37514 @item QTFrame:tdp:@var{t}
37515 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37516 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37517 is a hexadecimal number.
37519 @item QTFrame:range:@var{start}:@var{end}
37520 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37521 currently selected frame whose PC is between @var{start} (inclusive)
37522 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37525 @item QTFrame:outside:@var{start}:@var{end}
37526 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37527 frame @emph{outside} the given range of addresses (exclusive).
37530 @cindex @samp{qTMinFTPILen} packet
37531 This packet requests the minimum length of instruction at which a fast
37532 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37533 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37534 it depends on the target system being able to create trampolines in
37535 the first 64K of memory, which might or might not be possible for that
37536 system. So the reply to this packet will be 4 if it is able to
37543 The minimum instruction length is currently unknown.
37545 The minimum instruction length is @var{length}, where @var{length}
37546 is a hexadecimal number greater or equal to 1. A reply
37547 of 1 means that a fast tracepoint may be placed on any instruction
37548 regardless of size.
37550 An error has occurred.
37552 An empty reply indicates that the request is not supported by the stub.
37556 @cindex @samp{QTStart} packet
37557 Begin the tracepoint experiment. Begin collecting data from
37558 tracepoint hits in the trace frame buffer. This packet supports the
37559 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37560 instruction reply packet}).
37563 @cindex @samp{QTStop} packet
37564 End the tracepoint experiment. Stop collecting trace frames.
37566 @item QTEnable:@var{n}:@var{addr}
37568 @cindex @samp{QTEnable} packet
37569 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37570 experiment. If the tracepoint was previously disabled, then collection
37571 of data from it will resume.
37573 @item QTDisable:@var{n}:@var{addr}
37575 @cindex @samp{QTDisable} packet
37576 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37577 experiment. No more data will be collected from the tracepoint unless
37578 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37581 @cindex @samp{QTinit} packet
37582 Clear the table of tracepoints, and empty the trace frame buffer.
37584 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37585 @cindex @samp{QTro} packet
37586 Establish the given ranges of memory as ``transparent''. The stub
37587 will answer requests for these ranges from memory's current contents,
37588 if they were not collected as part of the tracepoint hit.
37590 @value{GDBN} uses this to mark read-only regions of memory, like those
37591 containing program code. Since these areas never change, they should
37592 still have the same contents they did when the tracepoint was hit, so
37593 there's no reason for the stub to refuse to provide their contents.
37595 @item QTDisconnected:@var{value}
37596 @cindex @samp{QTDisconnected} packet
37597 Set the choice to what to do with the tracing run when @value{GDBN}
37598 disconnects from the target. A @var{value} of 1 directs the target to
37599 continue the tracing run, while 0 tells the target to stop tracing if
37600 @value{GDBN} is no longer in the picture.
37603 @cindex @samp{qTStatus} packet
37604 Ask the stub if there is a trace experiment running right now.
37606 The reply has the form:
37610 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37611 @var{running} is a single digit @code{1} if the trace is presently
37612 running, or @code{0} if not. It is followed by semicolon-separated
37613 optional fields that an agent may use to report additional status.
37617 If the trace is not running, the agent may report any of several
37618 explanations as one of the optional fields:
37623 No trace has been run yet.
37625 @item tstop[:@var{text}]:0
37626 The trace was stopped by a user-originated stop command. The optional
37627 @var{text} field is a user-supplied string supplied as part of the
37628 stop command (for instance, an explanation of why the trace was
37629 stopped manually). It is hex-encoded.
37632 The trace stopped because the trace buffer filled up.
37634 @item tdisconnected:0
37635 The trace stopped because @value{GDBN} disconnected from the target.
37637 @item tpasscount:@var{tpnum}
37638 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37640 @item terror:@var{text}:@var{tpnum}
37641 The trace stopped because tracepoint @var{tpnum} had an error. The
37642 string @var{text} is available to describe the nature of the error
37643 (for instance, a divide by zero in the condition expression); it
37647 The trace stopped for some other reason.
37651 Additional optional fields supply statistical and other information.
37652 Although not required, they are extremely useful for users monitoring
37653 the progress of a trace run. If a trace has stopped, and these
37654 numbers are reported, they must reflect the state of the just-stopped
37659 @item tframes:@var{n}
37660 The number of trace frames in the buffer.
37662 @item tcreated:@var{n}
37663 The total number of trace frames created during the run. This may
37664 be larger than the trace frame count, if the buffer is circular.
37666 @item tsize:@var{n}
37667 The total size of the trace buffer, in bytes.
37669 @item tfree:@var{n}
37670 The number of bytes still unused in the buffer.
37672 @item circular:@var{n}
37673 The value of the circular trace buffer flag. @code{1} means that the
37674 trace buffer is circular and old trace frames will be discarded if
37675 necessary to make room, @code{0} means that the trace buffer is linear
37678 @item disconn:@var{n}
37679 The value of the disconnected tracing flag. @code{1} means that
37680 tracing will continue after @value{GDBN} disconnects, @code{0} means
37681 that the trace run will stop.
37685 @item qTP:@var{tp}:@var{addr}
37686 @cindex tracepoint status, remote request
37687 @cindex @samp{qTP} packet
37688 Ask the stub for the current state of tracepoint number @var{tp} at
37689 address @var{addr}.
37693 @item V@var{hits}:@var{usage}
37694 The tracepoint has been hit @var{hits} times so far during the trace
37695 run, and accounts for @var{usage} in the trace buffer. Note that
37696 @code{while-stepping} steps are not counted as separate hits, but the
37697 steps' space consumption is added into the usage number.
37701 @item qTV:@var{var}
37702 @cindex trace state variable value, remote request
37703 @cindex @samp{qTV} packet
37704 Ask the stub for the value of the trace state variable number @var{var}.
37709 The value of the variable is @var{value}. This will be the current
37710 value of the variable if the user is examining a running target, or a
37711 saved value if the variable was collected in the trace frame that the
37712 user is looking at. Note that multiple requests may result in
37713 different reply values, such as when requesting values while the
37714 program is running.
37717 The value of the variable is unknown. This would occur, for example,
37718 if the user is examining a trace frame in which the requested variable
37723 @cindex @samp{qTfP} packet
37725 @cindex @samp{qTsP} packet
37726 These packets request data about tracepoints that are being used by
37727 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37728 of data, and multiple @code{qTsP} to get additional pieces. Replies
37729 to these packets generally take the form of the @code{QTDP} packets
37730 that define tracepoints. (FIXME add detailed syntax)
37733 @cindex @samp{qTfV} packet
37735 @cindex @samp{qTsV} packet
37736 These packets request data about trace state variables that are on the
37737 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37738 and multiple @code{qTsV} to get additional variables. Replies to
37739 these packets follow the syntax of the @code{QTDV} packets that define
37740 trace state variables.
37746 @cindex @samp{qTfSTM} packet
37747 @cindex @samp{qTsSTM} packet
37748 These packets request data about static tracepoint markers that exist
37749 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37750 first piece of data, and multiple @code{qTsSTM} to get additional
37751 pieces. Replies to these packets take the following form:
37755 @item m @var{address}:@var{id}:@var{extra}
37757 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37758 a comma-separated list of markers
37760 (lower case letter @samp{L}) denotes end of list.
37762 An error occurred. The error number @var{nn} is given as hex digits.
37764 An empty reply indicates that the request is not supported by the
37768 The @var{address} is encoded in hex;
37769 @var{id} and @var{extra} are strings encoded in hex.
37771 In response to each query, the target will reply with a list of one or
37772 more markers, separated by commas. @value{GDBN} will respond to each
37773 reply with a request for more markers (using the @samp{qs} form of the
37774 query), until the target responds with @samp{l} (lower-case ell, for
37777 @item qTSTMat:@var{address}
37779 @cindex @samp{qTSTMat} packet
37780 This packets requests data about static tracepoint markers in the
37781 target program at @var{address}. Replies to this packet follow the
37782 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37783 tracepoint markers.
37785 @item QTSave:@var{filename}
37786 @cindex @samp{QTSave} packet
37787 This packet directs the target to save trace data to the file name
37788 @var{filename} in the target's filesystem. The @var{filename} is encoded
37789 as a hex string; the interpretation of the file name (relative vs
37790 absolute, wild cards, etc) is up to the target.
37792 @item qTBuffer:@var{offset},@var{len}
37793 @cindex @samp{qTBuffer} packet
37794 Return up to @var{len} bytes of the current contents of trace buffer,
37795 starting at @var{offset}. The trace buffer is treated as if it were
37796 a contiguous collection of traceframes, as per the trace file format.
37797 The reply consists as many hex-encoded bytes as the target can deliver
37798 in a packet; it is not an error to return fewer than were asked for.
37799 A reply consisting of just @code{l} indicates that no bytes are
37802 @item QTBuffer:circular:@var{value}
37803 This packet directs the target to use a circular trace buffer if
37804 @var{value} is 1, or a linear buffer if the value is 0.
37806 @item QTBuffer:size:@var{size}
37807 @anchor{QTBuffer-size}
37808 @cindex @samp{QTBuffer size} packet
37809 This packet directs the target to make the trace buffer be of size
37810 @var{size} if possible. A value of @code{-1} tells the target to
37811 use whatever size it prefers.
37813 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37814 @cindex @samp{QTNotes} packet
37815 This packet adds optional textual notes to the trace run. Allowable
37816 types include @code{user}, @code{notes}, and @code{tstop}, the
37817 @var{text} fields are arbitrary strings, hex-encoded.
37821 @subsection Relocate instruction reply packet
37822 When installing fast tracepoints in memory, the target may need to
37823 relocate the instruction currently at the tracepoint address to a
37824 different address in memory. For most instructions, a simple copy is
37825 enough, but, for example, call instructions that implicitly push the
37826 return address on the stack, and relative branches or other
37827 PC-relative instructions require offset adjustment, so that the effect
37828 of executing the instruction at a different address is the same as if
37829 it had executed in the original location.
37831 In response to several of the tracepoint packets, the target may also
37832 respond with a number of intermediate @samp{qRelocInsn} request
37833 packets before the final result packet, to have @value{GDBN} handle
37834 this relocation operation. If a packet supports this mechanism, its
37835 documentation will explicitly say so. See for example the above
37836 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37837 format of the request is:
37840 @item qRelocInsn:@var{from};@var{to}
37842 This requests @value{GDBN} to copy instruction at address @var{from}
37843 to address @var{to}, possibly adjusted so that executing the
37844 instruction at @var{to} has the same effect as executing it at
37845 @var{from}. @value{GDBN} writes the adjusted instruction to target
37846 memory starting at @var{to}.
37851 @item qRelocInsn:@var{adjusted_size}
37852 Informs the stub the relocation is complete. The @var{adjusted_size} is
37853 the length in bytes of resulting relocated instruction sequence.
37855 A badly formed request was detected, or an error was encountered while
37856 relocating the instruction.
37859 @node Host I/O Packets
37860 @section Host I/O Packets
37861 @cindex Host I/O, remote protocol
37862 @cindex file transfer, remote protocol
37864 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37865 operations on the far side of a remote link. For example, Host I/O is
37866 used to upload and download files to a remote target with its own
37867 filesystem. Host I/O uses the same constant values and data structure
37868 layout as the target-initiated File-I/O protocol. However, the
37869 Host I/O packets are structured differently. The target-initiated
37870 protocol relies on target memory to store parameters and buffers.
37871 Host I/O requests are initiated by @value{GDBN}, and the
37872 target's memory is not involved. @xref{File-I/O Remote Protocol
37873 Extension}, for more details on the target-initiated protocol.
37875 The Host I/O request packets all encode a single operation along with
37876 its arguments. They have this format:
37880 @item vFile:@var{operation}: @var{parameter}@dots{}
37881 @var{operation} is the name of the particular request; the target
37882 should compare the entire packet name up to the second colon when checking
37883 for a supported operation. The format of @var{parameter} depends on
37884 the operation. Numbers are always passed in hexadecimal. Negative
37885 numbers have an explicit minus sign (i.e.@: two's complement is not
37886 used). Strings (e.g.@: filenames) are encoded as a series of
37887 hexadecimal bytes. The last argument to a system call may be a
37888 buffer of escaped binary data (@pxref{Binary Data}).
37892 The valid responses to Host I/O packets are:
37896 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37897 @var{result} is the integer value returned by this operation, usually
37898 non-negative for success and -1 for errors. If an error has occured,
37899 @var{errno} will be included in the result specifying a
37900 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37901 operations which return data, @var{attachment} supplies the data as a
37902 binary buffer. Binary buffers in response packets are escaped in the
37903 normal way (@pxref{Binary Data}). See the individual packet
37904 documentation for the interpretation of @var{result} and
37908 An empty response indicates that this operation is not recognized.
37912 These are the supported Host I/O operations:
37915 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37916 Open a file at @var{filename} and return a file descriptor for it, or
37917 return -1 if an error occurs. The @var{filename} is a string,
37918 @var{flags} is an integer indicating a mask of open flags
37919 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37920 of mode bits to use if the file is created (@pxref{mode_t Values}).
37921 @xref{open}, for details of the open flags and mode values.
37923 @item vFile:close: @var{fd}
37924 Close the open file corresponding to @var{fd} and return 0, or
37925 -1 if an error occurs.
37927 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37928 Read data from the open file corresponding to @var{fd}. Up to
37929 @var{count} bytes will be read from the file, starting at @var{offset}
37930 relative to the start of the file. The target may read fewer bytes;
37931 common reasons include packet size limits and an end-of-file
37932 condition. The number of bytes read is returned. Zero should only be
37933 returned for a successful read at the end of the file, or if
37934 @var{count} was zero.
37936 The data read should be returned as a binary attachment on success.
37937 If zero bytes were read, the response should include an empty binary
37938 attachment (i.e.@: a trailing semicolon). The return value is the
37939 number of target bytes read; the binary attachment may be longer if
37940 some characters were escaped.
37942 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37943 Write @var{data} (a binary buffer) to the open file corresponding
37944 to @var{fd}. Start the write at @var{offset} from the start of the
37945 file. Unlike many @code{write} system calls, there is no
37946 separate @var{count} argument; the length of @var{data} in the
37947 packet is used. @samp{vFile:write} returns the number of bytes written,
37948 which may be shorter than the length of @var{data}, or -1 if an
37951 @item vFile:fstat: @var{fd}
37952 Get information about the open file corresponding to @var{fd}.
37953 On success the information is returned as a binary attachment
37954 and the return value is the size of this attachment in bytes.
37955 If an error occurs the return value is -1. The format of the
37956 returned binary attachment is as described in @ref{struct stat}.
37958 @item vFile:unlink: @var{filename}
37959 Delete the file at @var{filename} on the target. Return 0,
37960 or -1 if an error occurs. The @var{filename} is a string.
37962 @item vFile:readlink: @var{filename}
37963 Read value of symbolic link @var{filename} on the target. Return
37964 the number of bytes read, or -1 if an error occurs.
37966 The data read should be returned as a binary attachment on success.
37967 If zero bytes were read, the response should include an empty binary
37968 attachment (i.e.@: a trailing semicolon). The return value is the
37969 number of target bytes read; the binary attachment may be longer if
37970 some characters were escaped.
37972 @item vFile:setfs: @var{pid}
37973 Select the filesystem on which @code{vFile} operations with
37974 @var{filename} arguments will operate. This is required for
37975 @value{GDBN} to be able to access files on remote targets where
37976 the remote stub does not share a common filesystem with the
37979 If @var{pid} is nonzero, select the filesystem as seen by process
37980 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37981 the remote stub. Return 0 on success, or -1 if an error occurs.
37982 If @code{vFile:setfs:} indicates success, the selected filesystem
37983 remains selected until the next successful @code{vFile:setfs:}
37989 @section Interrupts
37990 @cindex interrupts (remote protocol)
37991 @anchor{interrupting remote targets}
37993 In all-stop mode, when a program on the remote target is running,
37994 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
37995 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
37996 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37998 The precise meaning of @code{BREAK} is defined by the transport
37999 mechanism and may, in fact, be undefined. @value{GDBN} does not
38000 currently define a @code{BREAK} mechanism for any of the network
38001 interfaces except for TCP, in which case @value{GDBN} sends the
38002 @code{telnet} BREAK sequence.
38004 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38005 transport mechanisms. It is represented by sending the single byte
38006 @code{0x03} without any of the usual packet overhead described in
38007 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38008 transmitted as part of a packet, it is considered to be packet data
38009 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38010 (@pxref{X packet}), used for binary downloads, may include an unescaped
38011 @code{0x03} as part of its packet.
38013 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38014 When Linux kernel receives this sequence from serial port,
38015 it stops execution and connects to gdb.
38017 In non-stop mode, because packet resumptions are asynchronous
38018 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38019 command to the remote stub, even when the target is running. For that
38020 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38021 packet}) with the usual packet framing instead of the single byte
38024 Stubs are not required to recognize these interrupt mechanisms and the
38025 precise meaning associated with receipt of the interrupt is
38026 implementation defined. If the target supports debugging of multiple
38027 threads and/or processes, it should attempt to interrupt all
38028 currently-executing threads and processes.
38029 If the stub is successful at interrupting the
38030 running program, it should send one of the stop
38031 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38032 of successfully stopping the program in all-stop mode, and a stop reply
38033 for each stopped thread in non-stop mode.
38034 Interrupts received while the
38035 program is stopped are discarded.
38037 @node Notification Packets
38038 @section Notification Packets
38039 @cindex notification packets
38040 @cindex packets, notification
38042 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38043 packets that require no acknowledgment. Both the GDB and the stub
38044 may send notifications (although the only notifications defined at
38045 present are sent by the stub). Notifications carry information
38046 without incurring the round-trip latency of an acknowledgment, and so
38047 are useful for low-impact communications where occasional packet loss
38050 A notification packet has the form @samp{% @var{data} #
38051 @var{checksum}}, where @var{data} is the content of the notification,
38052 and @var{checksum} is a checksum of @var{data}, computed and formatted
38053 as for ordinary @value{GDBN} packets. A notification's @var{data}
38054 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38055 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38056 to acknowledge the notification's receipt or to report its corruption.
38058 Every notification's @var{data} begins with a name, which contains no
38059 colon characters, followed by a colon character.
38061 Recipients should silently ignore corrupted notifications and
38062 notifications they do not understand. Recipients should restart
38063 timeout periods on receipt of a well-formed notification, whether or
38064 not they understand it.
38066 Senders should only send the notifications described here when this
38067 protocol description specifies that they are permitted. In the
38068 future, we may extend the protocol to permit existing notifications in
38069 new contexts; this rule helps older senders avoid confusing newer
38072 (Older versions of @value{GDBN} ignore bytes received until they see
38073 the @samp{$} byte that begins an ordinary packet, so new stubs may
38074 transmit notifications without fear of confusing older clients. There
38075 are no notifications defined for @value{GDBN} to send at the moment, but we
38076 assume that most older stubs would ignore them, as well.)
38078 Each notification is comprised of three parts:
38080 @item @var{name}:@var{event}
38081 The notification packet is sent by the side that initiates the
38082 exchange (currently, only the stub does that), with @var{event}
38083 carrying the specific information about the notification, and
38084 @var{name} specifying the name of the notification.
38086 The acknowledge sent by the other side, usually @value{GDBN}, to
38087 acknowledge the exchange and request the event.
38090 The purpose of an asynchronous notification mechanism is to report to
38091 @value{GDBN} that something interesting happened in the remote stub.
38093 The remote stub may send notification @var{name}:@var{event}
38094 at any time, but @value{GDBN} acknowledges the notification when
38095 appropriate. The notification event is pending before @value{GDBN}
38096 acknowledges. Only one notification at a time may be pending; if
38097 additional events occur before @value{GDBN} has acknowledged the
38098 previous notification, they must be queued by the stub for later
38099 synchronous transmission in response to @var{ack} packets from
38100 @value{GDBN}. Because the notification mechanism is unreliable,
38101 the stub is permitted to resend a notification if it believes
38102 @value{GDBN} may not have received it.
38104 Specifically, notifications may appear when @value{GDBN} is not
38105 otherwise reading input from the stub, or when @value{GDBN} is
38106 expecting to read a normal synchronous response or a
38107 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38108 Notification packets are distinct from any other communication from
38109 the stub so there is no ambiguity.
38111 After receiving a notification, @value{GDBN} shall acknowledge it by
38112 sending a @var{ack} packet as a regular, synchronous request to the
38113 stub. Such acknowledgment is not required to happen immediately, as
38114 @value{GDBN} is permitted to send other, unrelated packets to the
38115 stub first, which the stub should process normally.
38117 Upon receiving a @var{ack} packet, if the stub has other queued
38118 events to report to @value{GDBN}, it shall respond by sending a
38119 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38120 packet to solicit further responses; again, it is permitted to send
38121 other, unrelated packets as well which the stub should process
38124 If the stub receives a @var{ack} packet and there are no additional
38125 @var{event} to report, the stub shall return an @samp{OK} response.
38126 At this point, @value{GDBN} has finished processing a notification
38127 and the stub has completed sending any queued events. @value{GDBN}
38128 won't accept any new notifications until the final @samp{OK} is
38129 received . If further notification events occur, the stub shall send
38130 a new notification, @value{GDBN} shall accept the notification, and
38131 the process shall be repeated.
38133 The process of asynchronous notification can be illustrated by the
38136 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38139 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38141 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38146 The following notifications are defined:
38147 @multitable @columnfractions 0.12 0.12 0.38 0.38
38156 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38157 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38158 for information on how these notifications are acknowledged by
38160 @tab Report an asynchronous stop event in non-stop mode.
38164 @node Remote Non-Stop
38165 @section Remote Protocol Support for Non-Stop Mode
38167 @value{GDBN}'s remote protocol supports non-stop debugging of
38168 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38169 supports non-stop mode, it should report that to @value{GDBN} by including
38170 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38172 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38173 establishing a new connection with the stub. Entering non-stop mode
38174 does not alter the state of any currently-running threads, but targets
38175 must stop all threads in any already-attached processes when entering
38176 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38177 probe the target state after a mode change.
38179 In non-stop mode, when an attached process encounters an event that
38180 would otherwise be reported with a stop reply, it uses the
38181 asynchronous notification mechanism (@pxref{Notification Packets}) to
38182 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38183 in all processes are stopped when a stop reply is sent, in non-stop
38184 mode only the thread reporting the stop event is stopped. That is,
38185 when reporting a @samp{S} or @samp{T} response to indicate completion
38186 of a step operation, hitting a breakpoint, or a fault, only the
38187 affected thread is stopped; any other still-running threads continue
38188 to run. When reporting a @samp{W} or @samp{X} response, all running
38189 threads belonging to other attached processes continue to run.
38191 In non-stop mode, the target shall respond to the @samp{?} packet as
38192 follows. First, any incomplete stop reply notification/@samp{vStopped}
38193 sequence in progress is abandoned. The target must begin a new
38194 sequence reporting stop events for all stopped threads, whether or not
38195 it has previously reported those events to @value{GDBN}. The first
38196 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38197 subsequent stop replies are sent as responses to @samp{vStopped} packets
38198 using the mechanism described above. The target must not send
38199 asynchronous stop reply notifications until the sequence is complete.
38200 If all threads are running when the target receives the @samp{?} packet,
38201 or if the target is not attached to any process, it shall respond
38204 If the stub supports non-stop mode, it should also support the
38205 @samp{swbreak} stop reason if software breakpoints are supported, and
38206 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38207 (@pxref{swbreak stop reason}). This is because given the asynchronous
38208 nature of non-stop mode, between the time a thread hits a breakpoint
38209 and the time the event is finally processed by @value{GDBN}, the
38210 breakpoint may have already been removed from the target. Due to
38211 this, @value{GDBN} needs to be able to tell whether a trap stop was
38212 caused by a delayed breakpoint event, which should be ignored, as
38213 opposed to a random trap signal, which should be reported to the user.
38214 Note the @samp{swbreak} feature implies that the target is responsible
38215 for adjusting the PC when a software breakpoint triggers, if
38216 necessary, such as on the x86 architecture.
38218 @node Packet Acknowledgment
38219 @section Packet Acknowledgment
38221 @cindex acknowledgment, for @value{GDBN} remote
38222 @cindex packet acknowledgment, for @value{GDBN} remote
38223 By default, when either the host or the target machine receives a packet,
38224 the first response expected is an acknowledgment: either @samp{+} (to indicate
38225 the package was received correctly) or @samp{-} (to request retransmission).
38226 This mechanism allows the @value{GDBN} remote protocol to operate over
38227 unreliable transport mechanisms, such as a serial line.
38229 In cases where the transport mechanism is itself reliable (such as a pipe or
38230 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38231 It may be desirable to disable them in that case to reduce communication
38232 overhead, or for other reasons. This can be accomplished by means of the
38233 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38235 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38236 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38237 and response format still includes the normal checksum, as described in
38238 @ref{Overview}, but the checksum may be ignored by the receiver.
38240 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38241 no-acknowledgment mode, it should report that to @value{GDBN}
38242 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38243 @pxref{qSupported}.
38244 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38245 disabled via the @code{set remote noack-packet off} command
38246 (@pxref{Remote Configuration}),
38247 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38248 Only then may the stub actually turn off packet acknowledgments.
38249 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38250 response, which can be safely ignored by the stub.
38252 Note that @code{set remote noack-packet} command only affects negotiation
38253 between @value{GDBN} and the stub when subsequent connections are made;
38254 it does not affect the protocol acknowledgment state for any current
38256 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38257 new connection is established,
38258 there is also no protocol request to re-enable the acknowledgments
38259 for the current connection, once disabled.
38264 Example sequence of a target being re-started. Notice how the restart
38265 does not get any direct output:
38270 @emph{target restarts}
38273 <- @code{T001:1234123412341234}
38277 Example sequence of a target being stepped by a single instruction:
38280 -> @code{G1445@dots{}}
38285 <- @code{T001:1234123412341234}
38289 <- @code{1455@dots{}}
38293 @node File-I/O Remote Protocol Extension
38294 @section File-I/O Remote Protocol Extension
38295 @cindex File-I/O remote protocol extension
38298 * File-I/O Overview::
38299 * Protocol Basics::
38300 * The F Request Packet::
38301 * The F Reply Packet::
38302 * The Ctrl-C Message::
38304 * List of Supported Calls::
38305 * Protocol-specific Representation of Datatypes::
38307 * File-I/O Examples::
38310 @node File-I/O Overview
38311 @subsection File-I/O Overview
38312 @cindex file-i/o overview
38314 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38315 target to use the host's file system and console I/O to perform various
38316 system calls. System calls on the target system are translated into a
38317 remote protocol packet to the host system, which then performs the needed
38318 actions and returns a response packet to the target system.
38319 This simulates file system operations even on targets that lack file systems.
38321 The protocol is defined to be independent of both the host and target systems.
38322 It uses its own internal representation of datatypes and values. Both
38323 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38324 translating the system-dependent value representations into the internal
38325 protocol representations when data is transmitted.
38327 The communication is synchronous. A system call is possible only when
38328 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38329 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38330 the target is stopped to allow deterministic access to the target's
38331 memory. Therefore File-I/O is not interruptible by target signals. On
38332 the other hand, it is possible to interrupt File-I/O by a user interrupt
38333 (@samp{Ctrl-C}) within @value{GDBN}.
38335 The target's request to perform a host system call does not finish
38336 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38337 after finishing the system call, the target returns to continuing the
38338 previous activity (continue, step). No additional continue or step
38339 request from @value{GDBN} is required.
38342 (@value{GDBP}) continue
38343 <- target requests 'system call X'
38344 target is stopped, @value{GDBN} executes system call
38345 -> @value{GDBN} returns result
38346 ... target continues, @value{GDBN} returns to wait for the target
38347 <- target hits breakpoint and sends a Txx packet
38350 The protocol only supports I/O on the console and to regular files on
38351 the host file system. Character or block special devices, pipes,
38352 named pipes, sockets or any other communication method on the host
38353 system are not supported by this protocol.
38355 File I/O is not supported in non-stop mode.
38357 @node Protocol Basics
38358 @subsection Protocol Basics
38359 @cindex protocol basics, file-i/o
38361 The File-I/O protocol uses the @code{F} packet as the request as well
38362 as reply packet. Since a File-I/O system call can only occur when
38363 @value{GDBN} is waiting for a response from the continuing or stepping target,
38364 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38365 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38366 This @code{F} packet contains all information needed to allow @value{GDBN}
38367 to call the appropriate host system call:
38371 A unique identifier for the requested system call.
38374 All parameters to the system call. Pointers are given as addresses
38375 in the target memory address space. Pointers to strings are given as
38376 pointer/length pair. Numerical values are given as they are.
38377 Numerical control flags are given in a protocol-specific representation.
38381 At this point, @value{GDBN} has to perform the following actions.
38385 If the parameters include pointer values to data needed as input to a
38386 system call, @value{GDBN} requests this data from the target with a
38387 standard @code{m} packet request. This additional communication has to be
38388 expected by the target implementation and is handled as any other @code{m}
38392 @value{GDBN} translates all value from protocol representation to host
38393 representation as needed. Datatypes are coerced into the host types.
38396 @value{GDBN} calls the system call.
38399 It then coerces datatypes back to protocol representation.
38402 If the system call is expected to return data in buffer space specified
38403 by pointer parameters to the call, the data is transmitted to the
38404 target using a @code{M} or @code{X} packet. This packet has to be expected
38405 by the target implementation and is handled as any other @code{M} or @code{X}
38410 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38411 necessary information for the target to continue. This at least contains
38418 @code{errno}, if has been changed by the system call.
38425 After having done the needed type and value coercion, the target continues
38426 the latest continue or step action.
38428 @node The F Request Packet
38429 @subsection The @code{F} Request Packet
38430 @cindex file-i/o request packet
38431 @cindex @code{F} request packet
38433 The @code{F} request packet has the following format:
38436 @item F@var{call-id},@var{parameter@dots{}}
38438 @var{call-id} is the identifier to indicate the host system call to be called.
38439 This is just the name of the function.
38441 @var{parameter@dots{}} are the parameters to the system call.
38442 Parameters are hexadecimal integer values, either the actual values in case
38443 of scalar datatypes, pointers to target buffer space in case of compound
38444 datatypes and unspecified memory areas, or pointer/length pairs in case
38445 of string parameters. These are appended to the @var{call-id} as a
38446 comma-delimited list. All values are transmitted in ASCII
38447 string representation, pointer/length pairs separated by a slash.
38453 @node The F Reply Packet
38454 @subsection The @code{F} Reply Packet
38455 @cindex file-i/o reply packet
38456 @cindex @code{F} reply packet
38458 The @code{F} reply packet has the following format:
38462 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38464 @var{retcode} is the return code of the system call as hexadecimal value.
38466 @var{errno} is the @code{errno} set by the call, in protocol-specific
38468 This parameter can be omitted if the call was successful.
38470 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38471 case, @var{errno} must be sent as well, even if the call was successful.
38472 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38479 or, if the call was interrupted before the host call has been performed:
38486 assuming 4 is the protocol-specific representation of @code{EINTR}.
38491 @node The Ctrl-C Message
38492 @subsection The @samp{Ctrl-C} Message
38493 @cindex ctrl-c message, in file-i/o protocol
38495 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38496 reply packet (@pxref{The F Reply Packet}),
38497 the target should behave as if it had
38498 gotten a break message. The meaning for the target is ``system call
38499 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38500 (as with a break message) and return to @value{GDBN} with a @code{T02}
38503 It's important for the target to know in which
38504 state the system call was interrupted. There are two possible cases:
38508 The system call hasn't been performed on the host yet.
38511 The system call on the host has been finished.
38515 These two states can be distinguished by the target by the value of the
38516 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38517 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38518 on POSIX systems. In any other case, the target may presume that the
38519 system call has been finished --- successfully or not --- and should behave
38520 as if the break message arrived right after the system call.
38522 @value{GDBN} must behave reliably. If the system call has not been called
38523 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38524 @code{errno} in the packet. If the system call on the host has been finished
38525 before the user requests a break, the full action must be finished by
38526 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38527 The @code{F} packet may only be sent when either nothing has happened
38528 or the full action has been completed.
38531 @subsection Console I/O
38532 @cindex console i/o as part of file-i/o
38534 By default and if not explicitly closed by the target system, the file
38535 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38536 on the @value{GDBN} console is handled as any other file output operation
38537 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38538 by @value{GDBN} so that after the target read request from file descriptor
38539 0 all following typing is buffered until either one of the following
38544 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38546 system call is treated as finished.
38549 The user presses @key{RET}. This is treated as end of input with a trailing
38553 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38554 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38558 If the user has typed more characters than fit in the buffer given to
38559 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38560 either another @code{read(0, @dots{})} is requested by the target, or debugging
38561 is stopped at the user's request.
38564 @node List of Supported Calls
38565 @subsection List of Supported Calls
38566 @cindex list of supported file-i/o calls
38583 @unnumberedsubsubsec open
38584 @cindex open, file-i/o system call
38589 int open(const char *pathname, int flags);
38590 int open(const char *pathname, int flags, mode_t mode);
38594 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38597 @var{flags} is the bitwise @code{OR} of the following values:
38601 If the file does not exist it will be created. The host
38602 rules apply as far as file ownership and time stamps
38606 When used with @code{O_CREAT}, if the file already exists it is
38607 an error and open() fails.
38610 If the file already exists and the open mode allows
38611 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38612 truncated to zero length.
38615 The file is opened in append mode.
38618 The file is opened for reading only.
38621 The file is opened for writing only.
38624 The file is opened for reading and writing.
38628 Other bits are silently ignored.
38632 @var{mode} is the bitwise @code{OR} of the following values:
38636 User has read permission.
38639 User has write permission.
38642 Group has read permission.
38645 Group has write permission.
38648 Others have read permission.
38651 Others have write permission.
38655 Other bits are silently ignored.
38658 @item Return value:
38659 @code{open} returns the new file descriptor or -1 if an error
38666 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38669 @var{pathname} refers to a directory.
38672 The requested access is not allowed.
38675 @var{pathname} was too long.
38678 A directory component in @var{pathname} does not exist.
38681 @var{pathname} refers to a device, pipe, named pipe or socket.
38684 @var{pathname} refers to a file on a read-only filesystem and
38685 write access was requested.
38688 @var{pathname} is an invalid pointer value.
38691 No space on device to create the file.
38694 The process already has the maximum number of files open.
38697 The limit on the total number of files open on the system
38701 The call was interrupted by the user.
38707 @unnumberedsubsubsec close
38708 @cindex close, file-i/o system call
38717 @samp{Fclose,@var{fd}}
38719 @item Return value:
38720 @code{close} returns zero on success, or -1 if an error occurred.
38726 @var{fd} isn't a valid open file descriptor.
38729 The call was interrupted by the user.
38735 @unnumberedsubsubsec read
38736 @cindex read, file-i/o system call
38741 int read(int fd, void *buf, unsigned int count);
38745 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38747 @item Return value:
38748 On success, the number of bytes read is returned.
38749 Zero indicates end of file. If count is zero, read
38750 returns zero as well. On error, -1 is returned.
38756 @var{fd} is not a valid file descriptor or is not open for
38760 @var{bufptr} is an invalid pointer value.
38763 The call was interrupted by the user.
38769 @unnumberedsubsubsec write
38770 @cindex write, file-i/o system call
38775 int write(int fd, const void *buf, unsigned int count);
38779 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38781 @item Return value:
38782 On success, the number of bytes written are returned.
38783 Zero indicates nothing was written. On error, -1
38790 @var{fd} is not a valid file descriptor or is not open for
38794 @var{bufptr} is an invalid pointer value.
38797 An attempt was made to write a file that exceeds the
38798 host-specific maximum file size allowed.
38801 No space on device to write the data.
38804 The call was interrupted by the user.
38810 @unnumberedsubsubsec lseek
38811 @cindex lseek, file-i/o system call
38816 long lseek (int fd, long offset, int flag);
38820 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38822 @var{flag} is one of:
38826 The offset is set to @var{offset} bytes.
38829 The offset is set to its current location plus @var{offset}
38833 The offset is set to the size of the file plus @var{offset}
38837 @item Return value:
38838 On success, the resulting unsigned offset in bytes from
38839 the beginning of the file is returned. Otherwise, a
38840 value of -1 is returned.
38846 @var{fd} is not a valid open file descriptor.
38849 @var{fd} is associated with the @value{GDBN} console.
38852 @var{flag} is not a proper value.
38855 The call was interrupted by the user.
38861 @unnumberedsubsubsec rename
38862 @cindex rename, file-i/o system call
38867 int rename(const char *oldpath, const char *newpath);
38871 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38873 @item Return value:
38874 On success, zero is returned. On error, -1 is returned.
38880 @var{newpath} is an existing directory, but @var{oldpath} is not a
38884 @var{newpath} is a non-empty directory.
38887 @var{oldpath} or @var{newpath} is a directory that is in use by some
38891 An attempt was made to make a directory a subdirectory
38895 A component used as a directory in @var{oldpath} or new
38896 path is not a directory. Or @var{oldpath} is a directory
38897 and @var{newpath} exists but is not a directory.
38900 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38903 No access to the file or the path of the file.
38907 @var{oldpath} or @var{newpath} was too long.
38910 A directory component in @var{oldpath} or @var{newpath} does not exist.
38913 The file is on a read-only filesystem.
38916 The device containing the file has no room for the new
38920 The call was interrupted by the user.
38926 @unnumberedsubsubsec unlink
38927 @cindex unlink, file-i/o system call
38932 int unlink(const char *pathname);
38936 @samp{Funlink,@var{pathnameptr}/@var{len}}
38938 @item Return value:
38939 On success, zero is returned. On error, -1 is returned.
38945 No access to the file or the path of the file.
38948 The system does not allow unlinking of directories.
38951 The file @var{pathname} cannot be unlinked because it's
38952 being used by another process.
38955 @var{pathnameptr} is an invalid pointer value.
38958 @var{pathname} was too long.
38961 A directory component in @var{pathname} does not exist.
38964 A component of the path is not a directory.
38967 The file is on a read-only filesystem.
38970 The call was interrupted by the user.
38976 @unnumberedsubsubsec stat/fstat
38977 @cindex fstat, file-i/o system call
38978 @cindex stat, file-i/o system call
38983 int stat(const char *pathname, struct stat *buf);
38984 int fstat(int fd, struct stat *buf);
38988 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38989 @samp{Ffstat,@var{fd},@var{bufptr}}
38991 @item Return value:
38992 On success, zero is returned. On error, -1 is returned.
38998 @var{fd} is not a valid open file.
39001 A directory component in @var{pathname} does not exist or the
39002 path is an empty string.
39005 A component of the path is not a directory.
39008 @var{pathnameptr} is an invalid pointer value.
39011 No access to the file or the path of the file.
39014 @var{pathname} was too long.
39017 The call was interrupted by the user.
39023 @unnumberedsubsubsec gettimeofday
39024 @cindex gettimeofday, file-i/o system call
39029 int gettimeofday(struct timeval *tv, void *tz);
39033 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39035 @item Return value:
39036 On success, 0 is returned, -1 otherwise.
39042 @var{tz} is a non-NULL pointer.
39045 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39051 @unnumberedsubsubsec isatty
39052 @cindex isatty, file-i/o system call
39057 int isatty(int fd);
39061 @samp{Fisatty,@var{fd}}
39063 @item Return value:
39064 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39070 The call was interrupted by the user.
39075 Note that the @code{isatty} call is treated as a special case: it returns
39076 1 to the target if the file descriptor is attached
39077 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39078 would require implementing @code{ioctl} and would be more complex than
39083 @unnumberedsubsubsec system
39084 @cindex system, file-i/o system call
39089 int system(const char *command);
39093 @samp{Fsystem,@var{commandptr}/@var{len}}
39095 @item Return value:
39096 If @var{len} is zero, the return value indicates whether a shell is
39097 available. A zero return value indicates a shell is not available.
39098 For non-zero @var{len}, the value returned is -1 on error and the
39099 return status of the command otherwise. Only the exit status of the
39100 command is returned, which is extracted from the host's @code{system}
39101 return value by calling @code{WEXITSTATUS(retval)}. In case
39102 @file{/bin/sh} could not be executed, 127 is returned.
39108 The call was interrupted by the user.
39113 @value{GDBN} takes over the full task of calling the necessary host calls
39114 to perform the @code{system} call. The return value of @code{system} on
39115 the host is simplified before it's returned
39116 to the target. Any termination signal information from the child process
39117 is discarded, and the return value consists
39118 entirely of the exit status of the called command.
39120 Due to security concerns, the @code{system} call is by default refused
39121 by @value{GDBN}. The user has to allow this call explicitly with the
39122 @code{set remote system-call-allowed 1} command.
39125 @item set remote system-call-allowed
39126 @kindex set remote system-call-allowed
39127 Control whether to allow the @code{system} calls in the File I/O
39128 protocol for the remote target. The default is zero (disabled).
39130 @item show remote system-call-allowed
39131 @kindex show remote system-call-allowed
39132 Show whether the @code{system} calls are allowed in the File I/O
39136 @node Protocol-specific Representation of Datatypes
39137 @subsection Protocol-specific Representation of Datatypes
39138 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39141 * Integral Datatypes::
39143 * Memory Transfer::
39148 @node Integral Datatypes
39149 @unnumberedsubsubsec Integral Datatypes
39150 @cindex integral datatypes, in file-i/o protocol
39152 The integral datatypes used in the system calls are @code{int},
39153 @code{unsigned int}, @code{long}, @code{unsigned long},
39154 @code{mode_t}, and @code{time_t}.
39156 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39157 implemented as 32 bit values in this protocol.
39159 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39161 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39162 in @file{limits.h}) to allow range checking on host and target.
39164 @code{time_t} datatypes are defined as seconds since the Epoch.
39166 All integral datatypes transferred as part of a memory read or write of a
39167 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39170 @node Pointer Values
39171 @unnumberedsubsubsec Pointer Values
39172 @cindex pointer values, in file-i/o protocol
39174 Pointers to target data are transmitted as they are. An exception
39175 is made for pointers to buffers for which the length isn't
39176 transmitted as part of the function call, namely strings. Strings
39177 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39184 which is a pointer to data of length 18 bytes at position 0x1aaf.
39185 The length is defined as the full string length in bytes, including
39186 the trailing null byte. For example, the string @code{"hello world"}
39187 at address 0x123456 is transmitted as
39193 @node Memory Transfer
39194 @unnumberedsubsubsec Memory Transfer
39195 @cindex memory transfer, in file-i/o protocol
39197 Structured data which is transferred using a memory read or write (for
39198 example, a @code{struct stat}) is expected to be in a protocol-specific format
39199 with all scalar multibyte datatypes being big endian. Translation to
39200 this representation needs to be done both by the target before the @code{F}
39201 packet is sent, and by @value{GDBN} before
39202 it transfers memory to the target. Transferred pointers to structured
39203 data should point to the already-coerced data at any time.
39207 @unnumberedsubsubsec struct stat
39208 @cindex struct stat, in file-i/o protocol
39210 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39211 is defined as follows:
39215 unsigned int st_dev; /* device */
39216 unsigned int st_ino; /* inode */
39217 mode_t st_mode; /* protection */
39218 unsigned int st_nlink; /* number of hard links */
39219 unsigned int st_uid; /* user ID of owner */
39220 unsigned int st_gid; /* group ID of owner */
39221 unsigned int st_rdev; /* device type (if inode device) */
39222 unsigned long st_size; /* total size, in bytes */
39223 unsigned long st_blksize; /* blocksize for filesystem I/O */
39224 unsigned long st_blocks; /* number of blocks allocated */
39225 time_t st_atime; /* time of last access */
39226 time_t st_mtime; /* time of last modification */
39227 time_t st_ctime; /* time of last change */
39231 The integral datatypes conform to the definitions given in the
39232 appropriate section (see @ref{Integral Datatypes}, for details) so this
39233 structure is of size 64 bytes.
39235 The values of several fields have a restricted meaning and/or
39241 A value of 0 represents a file, 1 the console.
39244 No valid meaning for the target. Transmitted unchanged.
39247 Valid mode bits are described in @ref{Constants}. Any other
39248 bits have currently no meaning for the target.
39253 No valid meaning for the target. Transmitted unchanged.
39258 These values have a host and file system dependent
39259 accuracy. Especially on Windows hosts, the file system may not
39260 support exact timing values.
39263 The target gets a @code{struct stat} of the above representation and is
39264 responsible for coercing it to the target representation before
39267 Note that due to size differences between the host, target, and protocol
39268 representations of @code{struct stat} members, these members could eventually
39269 get truncated on the target.
39271 @node struct timeval
39272 @unnumberedsubsubsec struct timeval
39273 @cindex struct timeval, in file-i/o protocol
39275 The buffer of type @code{struct timeval} used by the File-I/O protocol
39276 is defined as follows:
39280 time_t tv_sec; /* second */
39281 long tv_usec; /* microsecond */
39285 The integral datatypes conform to the definitions given in the
39286 appropriate section (see @ref{Integral Datatypes}, for details) so this
39287 structure is of size 8 bytes.
39290 @subsection Constants
39291 @cindex constants, in file-i/o protocol
39293 The following values are used for the constants inside of the
39294 protocol. @value{GDBN} and target are responsible for translating these
39295 values before and after the call as needed.
39306 @unnumberedsubsubsec Open Flags
39307 @cindex open flags, in file-i/o protocol
39309 All values are given in hexadecimal representation.
39321 @node mode_t Values
39322 @unnumberedsubsubsec mode_t Values
39323 @cindex mode_t values, in file-i/o protocol
39325 All values are given in octal representation.
39342 @unnumberedsubsubsec Errno Values
39343 @cindex errno values, in file-i/o protocol
39345 All values are given in decimal representation.
39370 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39371 any error value not in the list of supported error numbers.
39374 @unnumberedsubsubsec Lseek Flags
39375 @cindex lseek flags, in file-i/o protocol
39384 @unnumberedsubsubsec Limits
39385 @cindex limits, in file-i/o protocol
39387 All values are given in decimal representation.
39390 INT_MIN -2147483648
39392 UINT_MAX 4294967295
39393 LONG_MIN -9223372036854775808
39394 LONG_MAX 9223372036854775807
39395 ULONG_MAX 18446744073709551615
39398 @node File-I/O Examples
39399 @subsection File-I/O Examples
39400 @cindex file-i/o examples
39402 Example sequence of a write call, file descriptor 3, buffer is at target
39403 address 0x1234, 6 bytes should be written:
39406 <- @code{Fwrite,3,1234,6}
39407 @emph{request memory read from target}
39410 @emph{return "6 bytes written"}
39414 Example sequence of a read call, file descriptor 3, buffer is at target
39415 address 0x1234, 6 bytes should be read:
39418 <- @code{Fread,3,1234,6}
39419 @emph{request memory write to target}
39420 -> @code{X1234,6:XXXXXX}
39421 @emph{return "6 bytes read"}
39425 Example sequence of a read call, call fails on the host due to invalid
39426 file descriptor (@code{EBADF}):
39429 <- @code{Fread,3,1234,6}
39433 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39437 <- @code{Fread,3,1234,6}
39442 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39446 <- @code{Fread,3,1234,6}
39447 -> @code{X1234,6:XXXXXX}
39451 @node Library List Format
39452 @section Library List Format
39453 @cindex library list format, remote protocol
39455 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39456 same process as your application to manage libraries. In this case,
39457 @value{GDBN} can use the loader's symbol table and normal memory
39458 operations to maintain a list of shared libraries. On other
39459 platforms, the operating system manages loaded libraries.
39460 @value{GDBN} can not retrieve the list of currently loaded libraries
39461 through memory operations, so it uses the @samp{qXfer:libraries:read}
39462 packet (@pxref{qXfer library list read}) instead. The remote stub
39463 queries the target's operating system and reports which libraries
39466 The @samp{qXfer:libraries:read} packet returns an XML document which
39467 lists loaded libraries and their offsets. Each library has an
39468 associated name and one or more segment or section base addresses,
39469 which report where the library was loaded in memory.
39471 For the common case of libraries that are fully linked binaries, the
39472 library should have a list of segments. If the target supports
39473 dynamic linking of a relocatable object file, its library XML element
39474 should instead include a list of allocated sections. The segment or
39475 section bases are start addresses, not relocation offsets; they do not
39476 depend on the library's link-time base addresses.
39478 @value{GDBN} must be linked with the Expat library to support XML
39479 library lists. @xref{Expat}.
39481 A simple memory map, with one loaded library relocated by a single
39482 offset, looks like this:
39486 <library name="/lib/libc.so.6">
39487 <segment address="0x10000000"/>
39492 Another simple memory map, with one loaded library with three
39493 allocated sections (.text, .data, .bss), looks like this:
39497 <library name="sharedlib.o">
39498 <section address="0x10000000"/>
39499 <section address="0x20000000"/>
39500 <section address="0x30000000"/>
39505 The format of a library list is described by this DTD:
39508 <!-- library-list: Root element with versioning -->
39509 <!ELEMENT library-list (library)*>
39510 <!ATTLIST library-list version CDATA #FIXED "1.0">
39511 <!ELEMENT library (segment*, section*)>
39512 <!ATTLIST library name CDATA #REQUIRED>
39513 <!ELEMENT segment EMPTY>
39514 <!ATTLIST segment address CDATA #REQUIRED>
39515 <!ELEMENT section EMPTY>
39516 <!ATTLIST section address CDATA #REQUIRED>
39519 In addition, segments and section descriptors cannot be mixed within a
39520 single library element, and you must supply at least one segment or
39521 section for each library.
39523 @node Library List Format for SVR4 Targets
39524 @section Library List Format for SVR4 Targets
39525 @cindex library list format, remote protocol
39527 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39528 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39529 shared libraries. Still a special library list provided by this packet is
39530 more efficient for the @value{GDBN} remote protocol.
39532 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39533 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39534 target, the following parameters are reported:
39538 @code{name}, the absolute file name from the @code{l_name} field of
39539 @code{struct link_map}.
39541 @code{lm} with address of @code{struct link_map} used for TLS
39542 (Thread Local Storage) access.
39544 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39545 @code{struct link_map}. For prelinked libraries this is not an absolute
39546 memory address. It is a displacement of absolute memory address against
39547 address the file was prelinked to during the library load.
39549 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39552 Additionally the single @code{main-lm} attribute specifies address of
39553 @code{struct link_map} used for the main executable. This parameter is used
39554 for TLS access and its presence is optional.
39556 @value{GDBN} must be linked with the Expat library to support XML
39557 SVR4 library lists. @xref{Expat}.
39559 A simple memory map, with two loaded libraries (which do not use prelink),
39563 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39564 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39566 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39568 </library-list-svr>
39571 The format of an SVR4 library list is described by this DTD:
39574 <!-- library-list-svr4: Root element with versioning -->
39575 <!ELEMENT library-list-svr4 (library)*>
39576 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39577 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39578 <!ELEMENT library EMPTY>
39579 <!ATTLIST library name CDATA #REQUIRED>
39580 <!ATTLIST library lm CDATA #REQUIRED>
39581 <!ATTLIST library l_addr CDATA #REQUIRED>
39582 <!ATTLIST library l_ld CDATA #REQUIRED>
39585 @node Memory Map Format
39586 @section Memory Map Format
39587 @cindex memory map format
39589 To be able to write into flash memory, @value{GDBN} needs to obtain a
39590 memory map from the target. This section describes the format of the
39593 The memory map is obtained using the @samp{qXfer:memory-map:read}
39594 (@pxref{qXfer memory map read}) packet and is an XML document that
39595 lists memory regions.
39597 @value{GDBN} must be linked with the Expat library to support XML
39598 memory maps. @xref{Expat}.
39600 The top-level structure of the document is shown below:
39603 <?xml version="1.0"?>
39604 <!DOCTYPE memory-map
39605 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39606 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39612 Each region can be either:
39617 A region of RAM starting at @var{addr} and extending for @var{length}
39621 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39626 A region of read-only memory:
39629 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39634 A region of flash memory, with erasure blocks @var{blocksize}
39638 <memory type="flash" start="@var{addr}" length="@var{length}">
39639 <property name="blocksize">@var{blocksize}</property>
39645 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39646 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39647 packets to write to addresses in such ranges.
39649 The formal DTD for memory map format is given below:
39652 <!-- ................................................... -->
39653 <!-- Memory Map XML DTD ................................ -->
39654 <!-- File: memory-map.dtd .............................. -->
39655 <!-- .................................... .............. -->
39656 <!-- memory-map.dtd -->
39657 <!-- memory-map: Root element with versioning -->
39658 <!ELEMENT memory-map (memory | property)>
39659 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39660 <!ELEMENT memory (property)>
39661 <!-- memory: Specifies a memory region,
39662 and its type, or device. -->
39663 <!ATTLIST memory type CDATA #REQUIRED
39664 start CDATA #REQUIRED
39665 length CDATA #REQUIRED
39666 device CDATA #IMPLIED>
39667 <!-- property: Generic attribute tag -->
39668 <!ELEMENT property (#PCDATA | property)*>
39669 <!ATTLIST property name CDATA #REQUIRED>
39672 @node Thread List Format
39673 @section Thread List Format
39674 @cindex thread list format
39676 To efficiently update the list of threads and their attributes,
39677 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39678 (@pxref{qXfer threads read}) and obtains the XML document with
39679 the following structure:
39682 <?xml version="1.0"?>
39684 <thread id="id" core="0" name="name">
39685 ... description ...
39690 Each @samp{thread} element must have the @samp{id} attribute that
39691 identifies the thread (@pxref{thread-id syntax}). The
39692 @samp{core} attribute, if present, specifies which processor core
39693 the thread was last executing on. The @samp{name} attribute, if
39694 present, specifies the human-readable name of the thread. The content
39695 of the of @samp{thread} element is interpreted as human-readable
39696 auxiliary information.
39698 @node Traceframe Info Format
39699 @section Traceframe Info Format
39700 @cindex traceframe info format
39702 To be able to know which objects in the inferior can be examined when
39703 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39704 memory ranges, registers and trace state variables that have been
39705 collected in a traceframe.
39707 This list is obtained using the @samp{qXfer:traceframe-info:read}
39708 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39710 @value{GDBN} must be linked with the Expat library to support XML
39711 traceframe info discovery. @xref{Expat}.
39713 The top-level structure of the document is shown below:
39716 <?xml version="1.0"?>
39717 <!DOCTYPE traceframe-info
39718 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39719 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39725 Each traceframe block can be either:
39730 A region of collected memory starting at @var{addr} and extending for
39731 @var{length} bytes from there:
39734 <memory start="@var{addr}" length="@var{length}"/>
39738 A block indicating trace state variable numbered @var{number} has been
39742 <tvar id="@var{number}"/>
39747 The formal DTD for the traceframe info format is given below:
39750 <!ELEMENT traceframe-info (memory | tvar)* >
39751 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39753 <!ELEMENT memory EMPTY>
39754 <!ATTLIST memory start CDATA #REQUIRED
39755 length CDATA #REQUIRED>
39757 <!ATTLIST tvar id CDATA #REQUIRED>
39760 @node Branch Trace Format
39761 @section Branch Trace Format
39762 @cindex branch trace format
39764 In order to display the branch trace of an inferior thread,
39765 @value{GDBN} needs to obtain the list of branches. This list is
39766 represented as list of sequential code blocks that are connected via
39767 branches. The code in each block has been executed sequentially.
39769 This list is obtained using the @samp{qXfer:btrace:read}
39770 (@pxref{qXfer btrace read}) packet and is an XML document.
39772 @value{GDBN} must be linked with the Expat library to support XML
39773 traceframe info discovery. @xref{Expat}.
39775 The top-level structure of the document is shown below:
39778 <?xml version="1.0"?>
39780 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39781 "http://sourceware.org/gdb/gdb-btrace.dtd">
39790 A block of sequentially executed instructions starting at @var{begin}
39791 and ending at @var{end}:
39794 <block begin="@var{begin}" end="@var{end}"/>
39799 The formal DTD for the branch trace format is given below:
39802 <!ELEMENT btrace (block* | pt) >
39803 <!ATTLIST btrace version CDATA #FIXED "1.0">
39805 <!ELEMENT block EMPTY>
39806 <!ATTLIST block begin CDATA #REQUIRED
39807 end CDATA #REQUIRED>
39809 <!ELEMENT pt (pt-config?, raw?)>
39811 <!ELEMENT pt-config (cpu?)>
39813 <!ELEMENT cpu EMPTY>
39814 <!ATTLIST cpu vendor CDATA #REQUIRED
39815 family CDATA #REQUIRED
39816 model CDATA #REQUIRED
39817 stepping CDATA #REQUIRED>
39819 <!ELEMENT raw (#PCDATA)>
39822 @node Branch Trace Configuration Format
39823 @section Branch Trace Configuration Format
39824 @cindex branch trace configuration format
39826 For each inferior thread, @value{GDBN} can obtain the branch trace
39827 configuration using the @samp{qXfer:btrace-conf:read}
39828 (@pxref{qXfer btrace-conf read}) packet.
39830 The configuration describes the branch trace format and configuration
39831 settings for that format. The following information is described:
39835 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39838 The size of the @acronym{BTS} ring buffer in bytes.
39841 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39845 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39849 @value{GDBN} must be linked with the Expat library to support XML
39850 branch trace configuration discovery. @xref{Expat}.
39852 The formal DTD for the branch trace configuration format is given below:
39855 <!ELEMENT btrace-conf (bts?, pt?)>
39856 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39858 <!ELEMENT bts EMPTY>
39859 <!ATTLIST bts size CDATA #IMPLIED>
39861 <!ELEMENT pt EMPTY>
39862 <!ATTLIST pt size CDATA #IMPLIED>
39865 @include agentexpr.texi
39867 @node Target Descriptions
39868 @appendix Target Descriptions
39869 @cindex target descriptions
39871 One of the challenges of using @value{GDBN} to debug embedded systems
39872 is that there are so many minor variants of each processor
39873 architecture in use. It is common practice for vendors to start with
39874 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39875 and then make changes to adapt it to a particular market niche. Some
39876 architectures have hundreds of variants, available from dozens of
39877 vendors. This leads to a number of problems:
39881 With so many different customized processors, it is difficult for
39882 the @value{GDBN} maintainers to keep up with the changes.
39884 Since individual variants may have short lifetimes or limited
39885 audiences, it may not be worthwhile to carry information about every
39886 variant in the @value{GDBN} source tree.
39888 When @value{GDBN} does support the architecture of the embedded system
39889 at hand, the task of finding the correct architecture name to give the
39890 @command{set architecture} command can be error-prone.
39893 To address these problems, the @value{GDBN} remote protocol allows a
39894 target system to not only identify itself to @value{GDBN}, but to
39895 actually describe its own features. This lets @value{GDBN} support
39896 processor variants it has never seen before --- to the extent that the
39897 descriptions are accurate, and that @value{GDBN} understands them.
39899 @value{GDBN} must be linked with the Expat library to support XML
39900 target descriptions. @xref{Expat}.
39903 * Retrieving Descriptions:: How descriptions are fetched from a target.
39904 * Target Description Format:: The contents of a target description.
39905 * Predefined Target Types:: Standard types available for target
39907 * Standard Target Features:: Features @value{GDBN} knows about.
39910 @node Retrieving Descriptions
39911 @section Retrieving Descriptions
39913 Target descriptions can be read from the target automatically, or
39914 specified by the user manually. The default behavior is to read the
39915 description from the target. @value{GDBN} retrieves it via the remote
39916 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39917 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39918 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39919 XML document, of the form described in @ref{Target Description
39922 Alternatively, you can specify a file to read for the target description.
39923 If a file is set, the target will not be queried. The commands to
39924 specify a file are:
39927 @cindex set tdesc filename
39928 @item set tdesc filename @var{path}
39929 Read the target description from @var{path}.
39931 @cindex unset tdesc filename
39932 @item unset tdesc filename
39933 Do not read the XML target description from a file. @value{GDBN}
39934 will use the description supplied by the current target.
39936 @cindex show tdesc filename
39937 @item show tdesc filename
39938 Show the filename to read for a target description, if any.
39942 @node Target Description Format
39943 @section Target Description Format
39944 @cindex target descriptions, XML format
39946 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39947 document which complies with the Document Type Definition provided in
39948 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39949 means you can use generally available tools like @command{xmllint} to
39950 check that your feature descriptions are well-formed and valid.
39951 However, to help people unfamiliar with XML write descriptions for
39952 their targets, we also describe the grammar here.
39954 Target descriptions can identify the architecture of the remote target
39955 and (for some architectures) provide information about custom register
39956 sets. They can also identify the OS ABI of the remote target.
39957 @value{GDBN} can use this information to autoconfigure for your
39958 target, or to warn you if you connect to an unsupported target.
39960 Here is a simple target description:
39963 <target version="1.0">
39964 <architecture>i386:x86-64</architecture>
39969 This minimal description only says that the target uses
39970 the x86-64 architecture.
39972 A target description has the following overall form, with [ ] marking
39973 optional elements and @dots{} marking repeatable elements. The elements
39974 are explained further below.
39977 <?xml version="1.0"?>
39978 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39979 <target version="1.0">
39980 @r{[}@var{architecture}@r{]}
39981 @r{[}@var{osabi}@r{]}
39982 @r{[}@var{compatible}@r{]}
39983 @r{[}@var{feature}@dots{}@r{]}
39988 The description is generally insensitive to whitespace and line
39989 breaks, under the usual common-sense rules. The XML version
39990 declaration and document type declaration can generally be omitted
39991 (@value{GDBN} does not require them), but specifying them may be
39992 useful for XML validation tools. The @samp{version} attribute for
39993 @samp{<target>} may also be omitted, but we recommend
39994 including it; if future versions of @value{GDBN} use an incompatible
39995 revision of @file{gdb-target.dtd}, they will detect and report
39996 the version mismatch.
39998 @subsection Inclusion
39999 @cindex target descriptions, inclusion
40002 @cindex <xi:include>
40005 It can sometimes be valuable to split a target description up into
40006 several different annexes, either for organizational purposes, or to
40007 share files between different possible target descriptions. You can
40008 divide a description into multiple files by replacing any element of
40009 the target description with an inclusion directive of the form:
40012 <xi:include href="@var{document}"/>
40016 When @value{GDBN} encounters an element of this form, it will retrieve
40017 the named XML @var{document}, and replace the inclusion directive with
40018 the contents of that document. If the current description was read
40019 using @samp{qXfer}, then so will be the included document;
40020 @var{document} will be interpreted as the name of an annex. If the
40021 current description was read from a file, @value{GDBN} will look for
40022 @var{document} as a file in the same directory where it found the
40023 original description.
40025 @subsection Architecture
40026 @cindex <architecture>
40028 An @samp{<architecture>} element has this form:
40031 <architecture>@var{arch}</architecture>
40034 @var{arch} is one of the architectures from the set accepted by
40035 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40038 @cindex @code{<osabi>}
40040 This optional field was introduced in @value{GDBN} version 7.0.
40041 Previous versions of @value{GDBN} ignore it.
40043 An @samp{<osabi>} element has this form:
40046 <osabi>@var{abi-name}</osabi>
40049 @var{abi-name} is an OS ABI name from the same selection accepted by
40050 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40052 @subsection Compatible Architecture
40053 @cindex @code{<compatible>}
40055 This optional field was introduced in @value{GDBN} version 7.0.
40056 Previous versions of @value{GDBN} ignore it.
40058 A @samp{<compatible>} element has this form:
40061 <compatible>@var{arch}</compatible>
40064 @var{arch} is one of the architectures from the set accepted by
40065 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40067 A @samp{<compatible>} element is used to specify that the target
40068 is able to run binaries in some other than the main target architecture
40069 given by the @samp{<architecture>} element. For example, on the
40070 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40071 or @code{powerpc:common64}, but the system is able to run binaries
40072 in the @code{spu} architecture as well. The way to describe this
40073 capability with @samp{<compatible>} is as follows:
40076 <architecture>powerpc:common</architecture>
40077 <compatible>spu</compatible>
40080 @subsection Features
40083 Each @samp{<feature>} describes some logical portion of the target
40084 system. Features are currently used to describe available CPU
40085 registers and the types of their contents. A @samp{<feature>} element
40089 <feature name="@var{name}">
40090 @r{[}@var{type}@dots{}@r{]}
40096 Each feature's name should be unique within the description. The name
40097 of a feature does not matter unless @value{GDBN} has some special
40098 knowledge of the contents of that feature; if it does, the feature
40099 should have its standard name. @xref{Standard Target Features}.
40103 Any register's value is a collection of bits which @value{GDBN} must
40104 interpret. The default interpretation is a two's complement integer,
40105 but other types can be requested by name in the register description.
40106 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40107 Target Types}), and the description can define additional composite types.
40109 Each type element must have an @samp{id} attribute, which gives
40110 a unique (within the containing @samp{<feature>}) name to the type.
40111 Types must be defined before they are used.
40114 Some targets offer vector registers, which can be treated as arrays
40115 of scalar elements. These types are written as @samp{<vector>} elements,
40116 specifying the array element type, @var{type}, and the number of elements,
40120 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40124 If a register's value is usefully viewed in multiple ways, define it
40125 with a union type containing the useful representations. The
40126 @samp{<union>} element contains one or more @samp{<field>} elements,
40127 each of which has a @var{name} and a @var{type}:
40130 <union id="@var{id}">
40131 <field name="@var{name}" type="@var{type}"/>
40137 If a register's value is composed from several separate values, define
40138 it with a structure type. There are two forms of the @samp{<struct>}
40139 element; a @samp{<struct>} element must either contain only bitfields
40140 or contain no bitfields. If the structure contains only bitfields,
40141 its total size in bytes must be specified, each bitfield must have an
40142 explicit start and end, and bitfields are automatically assigned an
40143 integer type. The field's @var{start} should be less than or
40144 equal to its @var{end}, and zero represents the least significant bit.
40147 <struct id="@var{id}" size="@var{size}">
40148 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40153 If the structure contains no bitfields, then each field has an
40154 explicit type, and no implicit padding is added.
40157 <struct id="@var{id}">
40158 <field name="@var{name}" type="@var{type}"/>
40164 If a register's value is a series of single-bit flags, define it with
40165 a flags type. The @samp{<flags>} element has an explicit @var{size}
40166 and contains one or more @samp{<field>} elements. Each field has a
40167 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40171 <flags id="@var{id}" size="@var{size}">
40172 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40177 @subsection Registers
40180 Each register is represented as an element with this form:
40183 <reg name="@var{name}"
40184 bitsize="@var{size}"
40185 @r{[}regnum="@var{num}"@r{]}
40186 @r{[}save-restore="@var{save-restore}"@r{]}
40187 @r{[}type="@var{type}"@r{]}
40188 @r{[}group="@var{group}"@r{]}/>
40192 The components are as follows:
40197 The register's name; it must be unique within the target description.
40200 The register's size, in bits.
40203 The register's number. If omitted, a register's number is one greater
40204 than that of the previous register (either in the current feature or in
40205 a preceding feature); the first register in the target description
40206 defaults to zero. This register number is used to read or write
40207 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40208 packets, and registers appear in the @code{g} and @code{G} packets
40209 in order of increasing register number.
40212 Whether the register should be preserved across inferior function
40213 calls; this must be either @code{yes} or @code{no}. The default is
40214 @code{yes}, which is appropriate for most registers except for
40215 some system control registers; this is not related to the target's
40219 The type of the register. It may be a predefined type, a type
40220 defined in the current feature, or one of the special types @code{int}
40221 and @code{float}. @code{int} is an integer type of the correct size
40222 for @var{bitsize}, and @code{float} is a floating point type (in the
40223 architecture's normal floating point format) of the correct size for
40224 @var{bitsize}. The default is @code{int}.
40227 The register group to which this register belongs. It must
40228 be either @code{general}, @code{float}, or @code{vector}. If no
40229 @var{group} is specified, @value{GDBN} will not display the register
40230 in @code{info registers}.
40234 @node Predefined Target Types
40235 @section Predefined Target Types
40236 @cindex target descriptions, predefined types
40238 Type definitions in the self-description can build up composite types
40239 from basic building blocks, but can not define fundamental types. Instead,
40240 standard identifiers are provided by @value{GDBN} for the fundamental
40241 types. The currently supported types are:
40250 Signed integer types holding the specified number of bits.
40257 Unsigned integer types holding the specified number of bits.
40261 Pointers to unspecified code and data. The program counter and
40262 any dedicated return address register may be marked as code
40263 pointers; printing a code pointer converts it into a symbolic
40264 address. The stack pointer and any dedicated address registers
40265 may be marked as data pointers.
40268 Single precision IEEE floating point.
40271 Double precision IEEE floating point.
40274 The 12-byte extended precision format used by ARM FPA registers.
40277 The 10-byte extended precision format used by x87 registers.
40280 32bit @sc{eflags} register used by x86.
40283 32bit @sc{mxcsr} register used by x86.
40287 @node Standard Target Features
40288 @section Standard Target Features
40289 @cindex target descriptions, standard features
40291 A target description must contain either no registers or all the
40292 target's registers. If the description contains no registers, then
40293 @value{GDBN} will assume a default register layout, selected based on
40294 the architecture. If the description contains any registers, the
40295 default layout will not be used; the standard registers must be
40296 described in the target description, in such a way that @value{GDBN}
40297 can recognize them.
40299 This is accomplished by giving specific names to feature elements
40300 which contain standard registers. @value{GDBN} will look for features
40301 with those names and verify that they contain the expected registers;
40302 if any known feature is missing required registers, or if any required
40303 feature is missing, @value{GDBN} will reject the target
40304 description. You can add additional registers to any of the
40305 standard features --- @value{GDBN} will display them just as if
40306 they were added to an unrecognized feature.
40308 This section lists the known features and their expected contents.
40309 Sample XML documents for these features are included in the
40310 @value{GDBN} source tree, in the directory @file{gdb/features}.
40312 Names recognized by @value{GDBN} should include the name of the
40313 company or organization which selected the name, and the overall
40314 architecture to which the feature applies; so e.g.@: the feature
40315 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40317 The names of registers are not case sensitive for the purpose
40318 of recognizing standard features, but @value{GDBN} will only display
40319 registers using the capitalization used in the description.
40322 * AArch64 Features::
40325 * MicroBlaze Features::
40328 * Nios II Features::
40329 * PowerPC Features::
40330 * S/390 and System z Features::
40335 @node AArch64 Features
40336 @subsection AArch64 Features
40337 @cindex target descriptions, AArch64 features
40339 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40340 targets. It should contain registers @samp{x0} through @samp{x30},
40341 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40343 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40344 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40348 @subsection ARM Features
40349 @cindex target descriptions, ARM features
40351 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40353 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40354 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40356 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40357 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40358 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40361 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40362 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40364 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40365 it should contain at least registers @samp{wR0} through @samp{wR15} and
40366 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40367 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40369 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40370 should contain at least registers @samp{d0} through @samp{d15}. If
40371 they are present, @samp{d16} through @samp{d31} should also be included.
40372 @value{GDBN} will synthesize the single-precision registers from
40373 halves of the double-precision registers.
40375 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40376 need to contain registers; it instructs @value{GDBN} to display the
40377 VFP double-precision registers as vectors and to synthesize the
40378 quad-precision registers from pairs of double-precision registers.
40379 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40380 be present and include 32 double-precision registers.
40382 @node i386 Features
40383 @subsection i386 Features
40384 @cindex target descriptions, i386 features
40386 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40387 targets. It should describe the following registers:
40391 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40393 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40395 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40396 @samp{fs}, @samp{gs}
40398 @samp{st0} through @samp{st7}
40400 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40401 @samp{foseg}, @samp{fooff} and @samp{fop}
40404 The register sets may be different, depending on the target.
40406 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40407 describe registers:
40411 @samp{xmm0} through @samp{xmm7} for i386
40413 @samp{xmm0} through @samp{xmm15} for amd64
40418 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40419 @samp{org.gnu.gdb.i386.sse} feature. It should
40420 describe the upper 128 bits of @sc{ymm} registers:
40424 @samp{ymm0h} through @samp{ymm7h} for i386
40426 @samp{ymm0h} through @samp{ymm15h} for amd64
40429 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40430 Memory Protection Extension (MPX). It should describe the following registers:
40434 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40436 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40439 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40440 describe a single register, @samp{orig_eax}.
40442 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40443 @samp{org.gnu.gdb.i386.avx} feature. It should
40444 describe additional @sc{xmm} registers:
40448 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40451 It should describe the upper 128 bits of additional @sc{ymm} registers:
40455 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40459 describe the upper 256 bits of @sc{zmm} registers:
40463 @samp{zmm0h} through @samp{zmm7h} for i386.
40465 @samp{zmm0h} through @samp{zmm15h} for amd64.
40469 describe the additional @sc{zmm} registers:
40473 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40476 @node MicroBlaze Features
40477 @subsection MicroBlaze Features
40478 @cindex target descriptions, MicroBlaze features
40480 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40481 targets. It should contain registers @samp{r0} through @samp{r31},
40482 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40483 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40484 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40486 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40487 If present, it should contain registers @samp{rshr} and @samp{rslr}
40489 @node MIPS Features
40490 @subsection @acronym{MIPS} Features
40491 @cindex target descriptions, @acronym{MIPS} features
40493 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40494 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40495 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40498 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40499 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40500 registers. They may be 32-bit or 64-bit depending on the target.
40502 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40503 it may be optional in a future version of @value{GDBN}. It should
40504 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40505 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40507 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40508 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40509 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40510 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40512 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40513 contain a single register, @samp{restart}, which is used by the
40514 Linux kernel to control restartable syscalls.
40516 @node M68K Features
40517 @subsection M68K Features
40518 @cindex target descriptions, M68K features
40521 @item @samp{org.gnu.gdb.m68k.core}
40522 @itemx @samp{org.gnu.gdb.coldfire.core}
40523 @itemx @samp{org.gnu.gdb.fido.core}
40524 One of those features must be always present.
40525 The feature that is present determines which flavor of m68k is
40526 used. The feature that is present should contain registers
40527 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40528 @samp{sp}, @samp{ps} and @samp{pc}.
40530 @item @samp{org.gnu.gdb.coldfire.fp}
40531 This feature is optional. If present, it should contain registers
40532 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40536 @node Nios II Features
40537 @subsection Nios II Features
40538 @cindex target descriptions, Nios II features
40540 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40541 targets. It should contain the 32 core registers (@samp{zero},
40542 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40543 @samp{pc}, and the 16 control registers (@samp{status} through
40546 @node PowerPC Features
40547 @subsection PowerPC Features
40548 @cindex target descriptions, PowerPC features
40550 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40551 targets. It should contain registers @samp{r0} through @samp{r31},
40552 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40553 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40555 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40556 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40558 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40559 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40562 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40563 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40564 will combine these registers with the floating point registers
40565 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40566 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40567 through @samp{vs63}, the set of vector registers for POWER7.
40569 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40570 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40571 @samp{spefscr}. SPE targets should provide 32-bit registers in
40572 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40573 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40574 these to present registers @samp{ev0} through @samp{ev31} to the
40577 @node S/390 and System z Features
40578 @subsection S/390 and System z Features
40579 @cindex target descriptions, S/390 features
40580 @cindex target descriptions, System z features
40582 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40583 System z targets. It should contain the PSW and the 16 general
40584 registers. In particular, System z targets should provide the 64-bit
40585 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40586 S/390 targets should provide the 32-bit versions of these registers.
40587 A System z target that runs in 31-bit addressing mode should provide
40588 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40589 register's upper halves @samp{r0h} through @samp{r15h}, and their
40590 lower halves @samp{r0l} through @samp{r15l}.
40592 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40593 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40596 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40597 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40599 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40600 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40601 targets and 32-bit otherwise. In addition, the feature may contain
40602 the @samp{last_break} register, whose width depends on the addressing
40603 mode, as well as the @samp{system_call} register, which is always
40606 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40607 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40608 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40610 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40611 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40612 combined by @value{GDBN} with the floating point registers @samp{f0}
40613 through @samp{f15} to present the 128-bit wide vector registers
40614 @samp{v0} through @samp{v15}. In addition, this feature should
40615 contain the 128-bit wide vector registers @samp{v16} through
40618 @node TIC6x Features
40619 @subsection TMS320C6x Features
40620 @cindex target descriptions, TIC6x features
40621 @cindex target descriptions, TMS320C6x features
40622 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40623 targets. It should contain registers @samp{A0} through @samp{A15},
40624 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40626 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40627 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40628 through @samp{B31}.
40630 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40631 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40633 @node Operating System Information
40634 @appendix Operating System Information
40635 @cindex operating system information
40641 Users of @value{GDBN} often wish to obtain information about the state of
40642 the operating system running on the target---for example the list of
40643 processes, or the list of open files. This section describes the
40644 mechanism that makes it possible. This mechanism is similar to the
40645 target features mechanism (@pxref{Target Descriptions}), but focuses
40646 on a different aspect of target.
40648 Operating system information is retrived from the target via the
40649 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40650 read}). The object name in the request should be @samp{osdata}, and
40651 the @var{annex} identifies the data to be fetched.
40654 @appendixsection Process list
40655 @cindex operating system information, process list
40657 When requesting the process list, the @var{annex} field in the
40658 @samp{qXfer} request should be @samp{processes}. The returned data is
40659 an XML document. The formal syntax of this document is defined in
40660 @file{gdb/features/osdata.dtd}.
40662 An example document is:
40665 <?xml version="1.0"?>
40666 <!DOCTYPE target SYSTEM "osdata.dtd">
40667 <osdata type="processes">
40669 <column name="pid">1</column>
40670 <column name="user">root</column>
40671 <column name="command">/sbin/init</column>
40672 <column name="cores">1,2,3</column>
40677 Each item should include a column whose name is @samp{pid}. The value
40678 of that column should identify the process on the target. The
40679 @samp{user} and @samp{command} columns are optional, and will be
40680 displayed by @value{GDBN}. The @samp{cores} column, if present,
40681 should contain a comma-separated list of cores that this process
40682 is running on. Target may provide additional columns,
40683 which @value{GDBN} currently ignores.
40685 @node Trace File Format
40686 @appendix Trace File Format
40687 @cindex trace file format
40689 The trace file comes in three parts: a header, a textual description
40690 section, and a trace frame section with binary data.
40692 The header has the form @code{\x7fTRACE0\n}. The first byte is
40693 @code{0x7f} so as to indicate that the file contains binary data,
40694 while the @code{0} is a version number that may have different values
40697 The description section consists of multiple lines of @sc{ascii} text
40698 separated by newline characters (@code{0xa}). The lines may include a
40699 variety of optional descriptive or context-setting information, such
40700 as tracepoint definitions or register set size. @value{GDBN} will
40701 ignore any line that it does not recognize. An empty line marks the end
40704 @c FIXME add some specific types of data
40706 The trace frame section consists of a number of consecutive frames.
40707 Each frame begins with a two-byte tracepoint number, followed by a
40708 four-byte size giving the amount of data in the frame. The data in
40709 the frame consists of a number of blocks, each introduced by a
40710 character indicating its type (at least register, memory, and trace
40711 state variable). The data in this section is raw binary, not a
40712 hexadecimal or other encoding; its endianness matches the target's
40715 @c FIXME bi-arch may require endianness/arch info in description section
40718 @item R @var{bytes}
40719 Register block. The number and ordering of bytes matches that of a
40720 @code{g} packet in the remote protocol. Note that these are the
40721 actual bytes, in target order and @value{GDBN} register order, not a
40722 hexadecimal encoding.
40724 @item M @var{address} @var{length} @var{bytes}...
40725 Memory block. This is a contiguous block of memory, at the 8-byte
40726 address @var{address}, with a 2-byte length @var{length}, followed by
40727 @var{length} bytes.
40729 @item V @var{number} @var{value}
40730 Trace state variable block. This records the 8-byte signed value
40731 @var{value} of trace state variable numbered @var{number}.
40735 Future enhancements of the trace file format may include additional types
40738 @node Index Section Format
40739 @appendix @code{.gdb_index} section format
40740 @cindex .gdb_index section format
40741 @cindex index section format
40743 This section documents the index section that is created by @code{save
40744 gdb-index} (@pxref{Index Files}). The index section is
40745 DWARF-specific; some knowledge of DWARF is assumed in this
40748 The mapped index file format is designed to be directly
40749 @code{mmap}able on any architecture. In most cases, a datum is
40750 represented using a little-endian 32-bit integer value, called an
40751 @code{offset_type}. Big endian machines must byte-swap the values
40752 before using them. Exceptions to this rule are noted. The data is
40753 laid out such that alignment is always respected.
40755 A mapped index consists of several areas, laid out in order.
40759 The file header. This is a sequence of values, of @code{offset_type}
40760 unless otherwise noted:
40764 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40765 Version 4 uses a different hashing function from versions 5 and 6.
40766 Version 6 includes symbols for inlined functions, whereas versions 4
40767 and 5 do not. Version 7 adds attributes to the CU indices in the
40768 symbol table. Version 8 specifies that symbols from DWARF type units
40769 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40770 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40772 @value{GDBN} will only read version 4, 5, or 6 indices
40773 by specifying @code{set use-deprecated-index-sections on}.
40774 GDB has a workaround for potentially broken version 7 indices so it is
40775 currently not flagged as deprecated.
40778 The offset, from the start of the file, of the CU list.
40781 The offset, from the start of the file, of the types CU list. Note
40782 that this area can be empty, in which case this offset will be equal
40783 to the next offset.
40786 The offset, from the start of the file, of the address area.
40789 The offset, from the start of the file, of the symbol table.
40792 The offset, from the start of the file, of the constant pool.
40796 The CU list. This is a sequence of pairs of 64-bit little-endian
40797 values, sorted by the CU offset. The first element in each pair is
40798 the offset of a CU in the @code{.debug_info} section. The second
40799 element in each pair is the length of that CU. References to a CU
40800 elsewhere in the map are done using a CU index, which is just the
40801 0-based index into this table. Note that if there are type CUs, then
40802 conceptually CUs and type CUs form a single list for the purposes of
40806 The types CU list. This is a sequence of triplets of 64-bit
40807 little-endian values. In a triplet, the first value is the CU offset,
40808 the second value is the type offset in the CU, and the third value is
40809 the type signature. The types CU list is not sorted.
40812 The address area. The address area consists of a sequence of address
40813 entries. Each address entry has three elements:
40817 The low address. This is a 64-bit little-endian value.
40820 The high address. This is a 64-bit little-endian value. Like
40821 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40824 The CU index. This is an @code{offset_type} value.
40828 The symbol table. This is an open-addressed hash table. The size of
40829 the hash table is always a power of 2.
40831 Each slot in the hash table consists of a pair of @code{offset_type}
40832 values. The first value is the offset of the symbol's name in the
40833 constant pool. The second value is the offset of the CU vector in the
40836 If both values are 0, then this slot in the hash table is empty. This
40837 is ok because while 0 is a valid constant pool index, it cannot be a
40838 valid index for both a string and a CU vector.
40840 The hash value for a table entry is computed by applying an
40841 iterative hash function to the symbol's name. Starting with an
40842 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40843 the string is incorporated into the hash using the formula depending on the
40848 The formula is @code{r = r * 67 + c - 113}.
40850 @item Versions 5 to 7
40851 The formula is @code{r = r * 67 + tolower (c) - 113}.
40854 The terminating @samp{\0} is not incorporated into the hash.
40856 The step size used in the hash table is computed via
40857 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40858 value, and @samp{size} is the size of the hash table. The step size
40859 is used to find the next candidate slot when handling a hash
40862 The names of C@t{++} symbols in the hash table are canonicalized. We
40863 don't currently have a simple description of the canonicalization
40864 algorithm; if you intend to create new index sections, you must read
40868 The constant pool. This is simply a bunch of bytes. It is organized
40869 so that alignment is correct: CU vectors are stored first, followed by
40872 A CU vector in the constant pool is a sequence of @code{offset_type}
40873 values. The first value is the number of CU indices in the vector.
40874 Each subsequent value is the index and symbol attributes of a CU in
40875 the CU list. This element in the hash table is used to indicate which
40876 CUs define the symbol and how the symbol is used.
40877 See below for the format of each CU index+attributes entry.
40879 A string in the constant pool is zero-terminated.
40882 Attributes were added to CU index values in @code{.gdb_index} version 7.
40883 If a symbol has multiple uses within a CU then there is one
40884 CU index+attributes value for each use.
40886 The format of each CU index+attributes entry is as follows
40892 This is the index of the CU in the CU list.
40894 These bits are reserved for future purposes and must be zero.
40896 The kind of the symbol in the CU.
40900 This value is reserved and should not be used.
40901 By reserving zero the full @code{offset_type} value is backwards compatible
40902 with previous versions of the index.
40904 The symbol is a type.
40906 The symbol is a variable or an enum value.
40908 The symbol is a function.
40910 Any other kind of symbol.
40912 These values are reserved.
40916 This bit is zero if the value is global and one if it is static.
40918 The determination of whether a symbol is global or static is complicated.
40919 The authorative reference is the file @file{dwarf2read.c} in
40920 @value{GDBN} sources.
40924 This pseudo-code describes the computation of a symbol's kind and
40925 global/static attributes in the index.
40928 is_external = get_attribute (die, DW_AT_external);
40929 language = get_attribute (cu_die, DW_AT_language);
40932 case DW_TAG_typedef:
40933 case DW_TAG_base_type:
40934 case DW_TAG_subrange_type:
40938 case DW_TAG_enumerator:
40940 is_static = (language != CPLUS && language != JAVA);
40942 case DW_TAG_subprogram:
40944 is_static = ! (is_external || language == ADA);
40946 case DW_TAG_constant:
40948 is_static = ! is_external;
40950 case DW_TAG_variable:
40952 is_static = ! is_external;
40954 case DW_TAG_namespace:
40958 case DW_TAG_class_type:
40959 case DW_TAG_interface_type:
40960 case DW_TAG_structure_type:
40961 case DW_TAG_union_type:
40962 case DW_TAG_enumeration_type:
40964 is_static = (language != CPLUS && language != JAVA);
40972 @appendix Manual pages
40976 * gdb man:: The GNU Debugger man page
40977 * gdbserver man:: Remote Server for the GNU Debugger man page
40978 * gcore man:: Generate a core file of a running program
40979 * gdbinit man:: gdbinit scripts
40985 @c man title gdb The GNU Debugger
40987 @c man begin SYNOPSIS gdb
40988 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40989 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40990 [@option{-b}@w{ }@var{bps}]
40991 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40992 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40993 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40994 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40995 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40998 @c man begin DESCRIPTION gdb
40999 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41000 going on ``inside'' another program while it executes -- or what another
41001 program was doing at the moment it crashed.
41003 @value{GDBN} can do four main kinds of things (plus other things in support of
41004 these) to help you catch bugs in the act:
41008 Start your program, specifying anything that might affect its behavior.
41011 Make your program stop on specified conditions.
41014 Examine what has happened, when your program has stopped.
41017 Change things in your program, so you can experiment with correcting the
41018 effects of one bug and go on to learn about another.
41021 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41024 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41025 commands from the terminal until you tell it to exit with the @value{GDBN}
41026 command @code{quit}. You can get online help from @value{GDBN} itself
41027 by using the command @code{help}.
41029 You can run @code{gdb} with no arguments or options; but the most
41030 usual way to start @value{GDBN} is with one argument or two, specifying an
41031 executable program as the argument:
41037 You can also start with both an executable program and a core file specified:
41043 You can, instead, specify a process ID as a second argument, if you want
41044 to debug a running process:
41052 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41053 named @file{1234}; @value{GDBN} does check for a core file first).
41054 With option @option{-p} you can omit the @var{program} filename.
41056 Here are some of the most frequently needed @value{GDBN} commands:
41058 @c pod2man highlights the right hand side of the @item lines.
41060 @item break [@var{file}:]@var{functiop}
41061 Set a breakpoint at @var{function} (in @var{file}).
41063 @item run [@var{arglist}]
41064 Start your program (with @var{arglist}, if specified).
41067 Backtrace: display the program stack.
41069 @item print @var{expr}
41070 Display the value of an expression.
41073 Continue running your program (after stopping, e.g. at a breakpoint).
41076 Execute next program line (after stopping); step @emph{over} any
41077 function calls in the line.
41079 @item edit [@var{file}:]@var{function}
41080 look at the program line where it is presently stopped.
41082 @item list [@var{file}:]@var{function}
41083 type the text of the program in the vicinity of where it is presently stopped.
41086 Execute next program line (after stopping); step @emph{into} any
41087 function calls in the line.
41089 @item help [@var{name}]
41090 Show information about @value{GDBN} command @var{name}, or general information
41091 about using @value{GDBN}.
41094 Exit from @value{GDBN}.
41098 For full details on @value{GDBN},
41099 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41100 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41101 as the @code{gdb} entry in the @code{info} program.
41105 @c man begin OPTIONS gdb
41106 Any arguments other than options specify an executable
41107 file and core file (or process ID); that is, the first argument
41108 encountered with no
41109 associated option flag is equivalent to a @option{-se} option, and the second,
41110 if any, is equivalent to a @option{-c} option if it's the name of a file.
41112 both long and short forms; both are shown here. The long forms are also
41113 recognized if you truncate them, so long as enough of the option is
41114 present to be unambiguous. (If you prefer, you can flag option
41115 arguments with @option{+} rather than @option{-}, though we illustrate the
41116 more usual convention.)
41118 All the options and command line arguments you give are processed
41119 in sequential order. The order makes a difference when the @option{-x}
41125 List all options, with brief explanations.
41127 @item -symbols=@var{file}
41128 @itemx -s @var{file}
41129 Read symbol table from file @var{file}.
41132 Enable writing into executable and core files.
41134 @item -exec=@var{file}
41135 @itemx -e @var{file}
41136 Use file @var{file} as the executable file to execute when
41137 appropriate, and for examining pure data in conjunction with a core
41140 @item -se=@var{file}
41141 Read symbol table from file @var{file} and use it as the executable
41144 @item -core=@var{file}
41145 @itemx -c @var{file}
41146 Use file @var{file} as a core dump to examine.
41148 @item -command=@var{file}
41149 @itemx -x @var{file}
41150 Execute @value{GDBN} commands from file @var{file}.
41152 @item -ex @var{command}
41153 Execute given @value{GDBN} @var{command}.
41155 @item -directory=@var{directory}
41156 @itemx -d @var{directory}
41157 Add @var{directory} to the path to search for source files.
41160 Do not execute commands from @file{~/.gdbinit}.
41164 Do not execute commands from any @file{.gdbinit} initialization files.
41168 ``Quiet''. Do not print the introductory and copyright messages. These
41169 messages are also suppressed in batch mode.
41172 Run in batch mode. Exit with status @code{0} after processing all the command
41173 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41174 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41175 commands in the command files.
41177 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41178 download and run a program on another computer; in order to make this
41179 more useful, the message
41182 Program exited normally.
41186 (which is ordinarily issued whenever a program running under @value{GDBN} control
41187 terminates) is not issued when running in batch mode.
41189 @item -cd=@var{directory}
41190 Run @value{GDBN} using @var{directory} as its working directory,
41191 instead of the current directory.
41195 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41196 @value{GDBN} to output the full file name and line number in a standard,
41197 recognizable fashion each time a stack frame is displayed (which
41198 includes each time the program stops). This recognizable format looks
41199 like two @samp{\032} characters, followed by the file name, line number
41200 and character position separated by colons, and a newline. The
41201 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41202 characters as a signal to display the source code for the frame.
41205 Set the line speed (baud rate or bits per second) of any serial
41206 interface used by @value{GDBN} for remote debugging.
41208 @item -tty=@var{device}
41209 Run using @var{device} for your program's standard input and output.
41213 @c man begin SEEALSO gdb
41215 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41216 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41217 documentation are properly installed at your site, the command
41224 should give you access to the complete manual.
41226 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41227 Richard M. Stallman and Roland H. Pesch, July 1991.
41231 @node gdbserver man
41232 @heading gdbserver man
41234 @c man title gdbserver Remote Server for the GNU Debugger
41236 @c man begin SYNOPSIS gdbserver
41237 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41239 gdbserver --attach @var{comm} @var{pid}
41241 gdbserver --multi @var{comm}
41245 @c man begin DESCRIPTION gdbserver
41246 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41247 than the one which is running the program being debugged.
41250 @subheading Usage (server (target) side)
41253 Usage (server (target) side):
41256 First, you need to have a copy of the program you want to debug put onto
41257 the target system. The program can be stripped to save space if needed, as
41258 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41259 the @value{GDBN} running on the host system.
41261 To use the server, you log on to the target system, and run the @command{gdbserver}
41262 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41263 your program, and (c) its arguments. The general syntax is:
41266 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41269 For example, using a serial port, you might say:
41273 @c @file would wrap it as F</dev/com1>.
41274 target> gdbserver /dev/com1 emacs foo.txt
41277 target> gdbserver @file{/dev/com1} emacs foo.txt
41281 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41282 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41283 waits patiently for the host @value{GDBN} to communicate with it.
41285 To use a TCP connection, you could say:
41288 target> gdbserver host:2345 emacs foo.txt
41291 This says pretty much the same thing as the last example, except that we are
41292 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41293 that we are expecting to see a TCP connection from @code{host} to local TCP port
41294 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41295 want for the port number as long as it does not conflict with any existing TCP
41296 ports on the target system. This same port number must be used in the host
41297 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41298 you chose a port number that conflicts with another service, @command{gdbserver} will
41299 print an error message and exit.
41301 @command{gdbserver} can also attach to running programs.
41302 This is accomplished via the @option{--attach} argument. The syntax is:
41305 target> gdbserver --attach @var{comm} @var{pid}
41308 @var{pid} is the process ID of a currently running process. It isn't
41309 necessary to point @command{gdbserver} at a binary for the running process.
41311 To start @code{gdbserver} without supplying an initial command to run
41312 or process ID to attach, use the @option{--multi} command line option.
41313 In such case you should connect using @kbd{target extended-remote} to start
41314 the program you want to debug.
41317 target> gdbserver --multi @var{comm}
41321 @subheading Usage (host side)
41327 You need an unstripped copy of the target program on your host system, since
41328 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41329 would, with the target program as the first argument. (You may need to use the
41330 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41331 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41332 new command you need to know about is @code{target remote}
41333 (or @code{target extended-remote}). Its argument is either
41334 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41335 descriptor. For example:
41339 @c @file would wrap it as F</dev/ttyb>.
41340 (gdb) target remote /dev/ttyb
41343 (gdb) target remote @file{/dev/ttyb}
41348 communicates with the server via serial line @file{/dev/ttyb}, and:
41351 (gdb) target remote the-target:2345
41355 communicates via a TCP connection to port 2345 on host `the-target', where
41356 you previously started up @command{gdbserver} with the same port number. Note that for
41357 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41358 command, otherwise you may get an error that looks something like
41359 `Connection refused'.
41361 @command{gdbserver} can also debug multiple inferiors at once,
41364 the @value{GDBN} manual in node @code{Inferiors and Programs}
41365 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41368 @ref{Inferiors and Programs}.
41370 In such case use the @code{extended-remote} @value{GDBN} command variant:
41373 (gdb) target extended-remote the-target:2345
41376 The @command{gdbserver} option @option{--multi} may or may not be used in such
41380 @c man begin OPTIONS gdbserver
41381 There are three different modes for invoking @command{gdbserver}:
41386 Debug a specific program specified by its program name:
41389 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41392 The @var{comm} parameter specifies how should the server communicate
41393 with @value{GDBN}; it is either a device name (to use a serial line),
41394 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41395 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41396 debug in @var{prog}. Any remaining arguments will be passed to the
41397 program verbatim. When the program exits, @value{GDBN} will close the
41398 connection, and @code{gdbserver} will exit.
41401 Debug a specific program by specifying the process ID of a running
41405 gdbserver --attach @var{comm} @var{pid}
41408 The @var{comm} parameter is as described above. Supply the process ID
41409 of a running program in @var{pid}; @value{GDBN} will do everything
41410 else. Like with the previous mode, when the process @var{pid} exits,
41411 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41414 Multi-process mode -- debug more than one program/process:
41417 gdbserver --multi @var{comm}
41420 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41421 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41422 close the connection when a process being debugged exits, so you can
41423 debug several processes in the same session.
41426 In each of the modes you may specify these options:
41431 List all options, with brief explanations.
41434 This option causes @command{gdbserver} to print its version number and exit.
41437 @command{gdbserver} will attach to a running program. The syntax is:
41440 target> gdbserver --attach @var{comm} @var{pid}
41443 @var{pid} is the process ID of a currently running process. It isn't
41444 necessary to point @command{gdbserver} at a binary for the running process.
41447 To start @code{gdbserver} without supplying an initial command to run
41448 or process ID to attach, use this command line option.
41449 Then you can connect using @kbd{target extended-remote} and start
41450 the program you want to debug. The syntax is:
41453 target> gdbserver --multi @var{comm}
41457 Instruct @code{gdbserver} to display extra status information about the debugging
41459 This option is intended for @code{gdbserver} development and for bug reports to
41462 @item --remote-debug
41463 Instruct @code{gdbserver} to display remote protocol debug output.
41464 This option is intended for @code{gdbserver} development and for bug reports to
41467 @item --debug-format=option1@r{[},option2,...@r{]}
41468 Instruct @code{gdbserver} to include extra information in each line
41469 of debugging output.
41470 @xref{Other Command-Line Arguments for gdbserver}.
41473 Specify a wrapper to launch programs
41474 for debugging. The option should be followed by the name of the
41475 wrapper, then any command-line arguments to pass to the wrapper, then
41476 @kbd{--} indicating the end of the wrapper arguments.
41479 By default, @command{gdbserver} keeps the listening TCP port open, so that
41480 additional connections are possible. However, if you start @code{gdbserver}
41481 with the @option{--once} option, it will stop listening for any further
41482 connection attempts after connecting to the first @value{GDBN} session.
41484 @c --disable-packet is not documented for users.
41486 @c --disable-randomization and --no-disable-randomization are superseded by
41487 @c QDisableRandomization.
41492 @c man begin SEEALSO gdbserver
41494 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41495 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41496 documentation are properly installed at your site, the command
41502 should give you access to the complete manual.
41504 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41505 Richard M. Stallman and Roland H. Pesch, July 1991.
41512 @c man title gcore Generate a core file of a running program
41515 @c man begin SYNOPSIS gcore
41516 gcore [-o @var{filename}] @var{pid}
41520 @c man begin DESCRIPTION gcore
41521 Generate a core dump of a running program with process ID @var{pid}.
41522 Produced file is equivalent to a kernel produced core file as if the process
41523 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41524 limit). Unlike after a crash, after @command{gcore} the program remains
41525 running without any change.
41528 @c man begin OPTIONS gcore
41530 @item -o @var{filename}
41531 The optional argument
41532 @var{filename} specifies the file name where to put the core dump.
41533 If not specified, the file name defaults to @file{core.@var{pid}},
41534 where @var{pid} is the running program process ID.
41538 @c man begin SEEALSO gcore
41540 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41541 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41542 documentation are properly installed at your site, the command
41549 should give you access to the complete manual.
41551 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41552 Richard M. Stallman and Roland H. Pesch, July 1991.
41559 @c man title gdbinit GDB initialization scripts
41562 @c man begin SYNOPSIS gdbinit
41563 @ifset SYSTEM_GDBINIT
41564 @value{SYSTEM_GDBINIT}
41573 @c man begin DESCRIPTION gdbinit
41574 These files contain @value{GDBN} commands to automatically execute during
41575 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41578 the @value{GDBN} manual in node @code{Sequences}
41579 -- shell command @code{info -f gdb -n Sequences}.
41585 Please read more in
41587 the @value{GDBN} manual in node @code{Startup}
41588 -- shell command @code{info -f gdb -n Startup}.
41595 @ifset SYSTEM_GDBINIT
41596 @item @value{SYSTEM_GDBINIT}
41598 @ifclear SYSTEM_GDBINIT
41599 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41601 System-wide initialization file. It is executed unless user specified
41602 @value{GDBN} option @code{-nx} or @code{-n}.
41605 the @value{GDBN} manual in node @code{System-wide configuration}
41606 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41609 @ref{System-wide configuration}.
41613 User initialization file. It is executed unless user specified
41614 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41617 Initialization file for current directory. It may need to be enabled with
41618 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41621 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41622 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41625 @ref{Init File in the Current Directory}.
41630 @c man begin SEEALSO gdbinit
41632 gdb(1), @code{info -f gdb -n Startup}
41634 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41635 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41636 documentation are properly installed at your site, the command
41642 should give you access to the complete manual.
41644 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41645 Richard M. Stallman and Roland H. Pesch, July 1991.
41651 @node GNU Free Documentation License
41652 @appendix GNU Free Documentation License
41655 @node Concept Index
41656 @unnumbered Concept Index
41660 @node Command and Variable Index
41661 @unnumbered Command, Variable, and Function Index
41666 % I think something like @@colophon should be in texinfo. In the
41668 \long\def\colophon{\hbox to0pt{}\vfill
41669 \centerline{The body of this manual is set in}
41670 \centerline{\fontname\tenrm,}
41671 \centerline{with headings in {\bf\fontname\tenbf}}
41672 \centerline{and examples in {\tt\fontname\tentt}.}
41673 \centerline{{\it\fontname\tenit\/},}
41674 \centerline{{\bf\fontname\tenbf}, and}
41675 \centerline{{\sl\fontname\tensl\/}}
41676 \centerline{are used for emphasis.}\vfill}
41678 % Blame: doc@@cygnus.com, 1991.